RU2791991C2 - Beamformer for through beamforming communication system - Google Patents

Abstract

FIELD: wireless communication system.

SUBSTANCE: technical result is achieved due to the fact that end-to-end beamforming systems (500) include end-to-end repeaters (503, 1202, 3403) and terrestrial networks (502) to provide communication with user terminals (517) located in coverage areas (519) of user beams, the ground segment may include geographically distributed access nodes (515) and a central data processing system (505); wherein the reverse uplink signals (525) transmitted from user terminals have multipath propagation induced by a plurality of signal receiving/transmitting paths (1702) in the end-to-end repeater, and are transmitted to the terrestrial network, terrestrial network using shapers (513, 531) beamformers recovers user data streams transmitted by user terminals from reverse downlink signals (527), the terrestrial network using beamformers (513, 529) generates forward uplink signals (521) from appropriately weighted combinations of user data streams that after relaying, downlink direct signals (522) are generated by the end-to-end relay, which are combined to form user beams.

EFFECT: equalization of delays and elimination of distortions in the feeder communication line.

33 cl, 56 dwg

Description

FIELD OF TECHNOLOGY

The disclosed systems, methods, and apparatuses relate to end-to-end beamforming in a system using an end-to-end repeater.

BACKGROUND OF THE INVENTION

Wireless communication systems, such as satellite communication systems, provide a means by which data, including audio, video, and various other types of data, can be transmitted from one location to another. The information originates from a first station, such as a first ground station, and is transmitted to a wireless relay, such as a communications satellite. The information received by the wireless repeater is retransmitted to a second station, such as a second ground station. In some relay wireless communication systems, the first or second station (or both) is mounted on a vehicle, such as an aircraft, vessel, or land vehicle. The information may be transmitted in only one direction (eg, only from the first ground station to the second ground station) or may be transmitted in both directions (eg, also from the second ground station to the first ground station).

In a wireless relay system in which the wireless repeater is a satellite, the satellite may be a geostationary satellite, in which case the orbit of the satellite is synchronized with the rotation of the Earth while the coverage area of the satellite remains substantially stationary with respect to the Earth. In other cases, the satellite is in orbit around the Earth, and this results in the satellite's coverage area moving across the surface of the Earth as the satellite crosses its orbital path laterally.

Signals directed to or from the first station may be directed using an antenna that is shaped to focus the signal into a narrow beam. Such antennas usually have a parabolic reflector to focus the beam.

In some cases, the beam may be shaped electronically by adjusting the gain and phase (or time delay) of signals transmitted, received, or transmitted and received by multiple elements of a phased array antenna. The beam can be directed by properly selecting the relative phase and amplifying the signals transmitted and/or received by each element of the phased array antenna. In most cases, all of the energy transmitted from the ground station is intended to be received by a single wireless repeater. Similarly, information received by the second station is typically received from one wireless repeater at a time. Thus, in general, the transmit beam formed to transmit information to the wireless repeater (either using electronic beamforming or using a profiled reflector antenna) is relatively narrow to ensure that as much of the transmitted energy as possible is directed to the wireless repeater. Similarly, the receive beam formed to receive information from the wireless repeater is typically narrow to collect energy from the direction of the wireless repeater with minimal interference from other sources.

In many cases under consideration, the signals transmitted from the wireless repeater to the first and second stations are not directed to the same station. In contrast, a wireless repeater is capable of transmitting signals over a relatively large geographic area. For example, in one satellite communications system, a satellite can serve the entire continental United States. In such a case, the satellite is said to have a satellite coverage area that includes the entire continental United States. However, to increase the amount of data that can be transmitted via a satellite, the energy transmitted by the satellite is focused into beams. The beams can be directed to geographic areas on Earth.

BRIEF DESCRIPTION OF THE FIGURES

The drawings are for illustrative purposes only and simply represent examples. These drawings are provided to facilitate the reader's understanding of the disclosed method and apparatus. They do not limit the scope, scope or applicability of the claimed invention. For clarity and ease of illustration, these drawings are not necessarily drawn to scale.

FIG. 1 is an illustration of an example satellite communication system.

FIG. 2 is a diagram showing an example of a beam pattern covering the continental United States.

FIG. 3 is an illustration of an example forward link of a satellite communication system in which the satellite has a phased array with multiple links per beam to enable beamforming on board.

FIG. 4 is an illustration of an example forward link of a satellite communication system including a terrestrial beamformer.

FIG. 5 is an illustration of an example of an end-to-end beamforming system.

FIG. 6 is an illustration of an example signal paths for signals traveling in the reverse direction.

FIG. 7 is an illustration of an example signal paths in the reverse direction from the user terminal.

FIG. 8 is a simplified illustration of an example reverse channel end-to-end matrix model.

FIG. 9 is an illustration of an example forward signal paths.

FIG. 10 is an illustration of an example forward signal paths to a user terminal located within the user beam coverage area.

FIG. 11 is a simplified illustration of an example forward channel through-matrix model.

FIG. 12 is an illustration of an example of an end-to-end relay satellite supporting forward and backward data transmission.

FIG. 13 is an illustration of an example of an uplink frequency band divided into two parts.

FIG. 14 is an illustration of an example of end-to-end relay with time multiplexing between forward and reverse data.

FIG. 15 is a block diagram of the components of an example end-to-end relay system implemented as a satellite.

FIG. 16 is a block diagram of an example of a transponder containing a phase shifter.

FIG. 17 is a graph of an example signal power diagrams of several antenna elements.

FIG. 18 is an illustration of an example of 3 dB signal power contours for several antenna elements.

FIG. 19 is an illustration of an example of overlapping signal strength patterns of multiple antenna elements.

FIG. 20A-20E are illustrations of examples of 3 dB signal power loop overlap for multiple antenna elements.

FIG. 21 is an illustration of an example of numbering 16 antenna elements and overlapping their 3 dB signal power contours.

FIG. 22 is a table showing an example of the correspondences of receive antenna elements and transmit antenna elements over 16 transponders.

FIG. 23 is a cross-sectional illustration of a parabolic reflector antenna and an array of elements centered at the focal point of the parabola.

FIG. 24 is a cross-sectional illustration of a parabolic reflector antenna and an array of elements located at a distance from the focal point of the parabola.

FIG. 25 is an illustration of an example of a repeater coverage area (shown with single cross hatching) and an area (shown with double cross hatching) defined by points located within the coverage area of the repeater, which are also contained within the coverage areas of the six antenna elements.

FIG. 26 shows an example of a repeater antenna pattern in which all points within the coverage area of the repeater are also contained within the coverage areas of at least four antenna elements.

FIG. 27 is an illustration of an example distribution of access nodes (ANs) and user beam coverage areas.

FIG. 28 is an example plot of normalized forward and reverse link throughput versus number of deployed ANs.

FIG. 29 is a block diagram of an example ground segment 502 for an end-to-end beamforming system.

FIG. 30 is a block diagram of an example forward/reverse beamformer.

FIG. 31 is a block diagram of an example of a forward beamformer including a plurality of time-sliced reverse directional beamformers with demultiplexing and time domain multiplexing.

FIG. 32 is an illustration of a simplified example of a ground segment showing the operation of a time sliced forward beamformer (TSBF).

FIG. 33 is a block diagram of an example of a return beamformer including a plurality of time sliced return beamformers with demultiplexing and time domain multiplexing.

FIG. 34 is an illustration of a simplified example of a ground segment showing the operation of a return beamformer that employs time domain multiplexing.

FIG. 35 is a block diagram of an example of a multiband forward/reverse beamformer using demultiplexing and subband multiplexing.

FIG. 36 and FIG. 37 is an illustration of an example clock for the forward link.

FIG. 38 is a block diagram of an example Access Node (AN).

FIG. 39 is a block diagram of a portion of the AN example.

FIG. 40 is a block diagram of an example of AN 515 in which processing on multiple subbands is performed separately.

FIG. 41 is an illustration of an example of an end-to-end beamforming system to provide coverage of different user link and feeder link coverage areas.

FIG. 42 is an illustration of an example signal path model for signals carrying reverse data on a reverse link end-to-end.

FIG. 43 is an illustration of an example signal path model for signals carrying direct data over a forward link end-to-end.

FIG. 44A and 44B are illustrations of examples of a forward signal path and a reverse signal path, respectively.

FIG. 45 is an illustration of an example of the visible Earth coverage of an end-to-end repeater.

FIG. 46 is an illustration of an example of the North American coverage area of an end-to-end repeater.

FIG. 47A and 47B are block diagrams of examples of a forward signal path and a reverse signal path, respectively, each of which selectively activates a plurality of user link antenna subsystems.

FIG. 48A and 48B illustrate an example of an end-to-end repeater coverage area that includes a plurality of selectively activated user coverage areas.

FIG. 49 is a block diagram of an example of a forward signal path that provides for selective activation of multiple user link antenna subsystems and multiple feeder link antenna subsystems.

Reference symbols (eg, 100) are used herein to refer to aspects of the drawings. Similar or similar aspects are generally shown using the same numbers. A group of like or similar elements may be designated with a single reference symbol (eg 200) and individual elements of the group may be designated with a supplemental reference symbol (eg 200a, 200b).

The figures are not intended to be exhaustive or to limit the claimed invention to the exact form disclosed. The disclosed method and apparatus may be practiced with modification and variation, and the present invention is limited only by the claims and their equivalents.

DETAILED DESCRIPTION

This detailed description is organized as follows. First, an introduction to relay wireless communication systems using satellite communications and beamforming is described. Second, end-to-end beamforming in general and at the system level is described using end-to-end beamforming by satellite as an example, although the application of end-to-end beamforming is not limited to satellite communications. Third, forward and backward data handling is described in the context of end-to-end beamforming. Fourth, end-to-end repeaters and their antennas are described using a communications satellite as an example. The following describes terrestrial networks for end-to-end beamforming, including related aspects such as delay equalization, feed-link distortion, and beam weight calculation. Finally, end-to-end beamforming with separate user link and feeder link coverage areas, as well as systems with multiple coverage areas, is described.

Satellite connection

FIG. 1 is an illustration of an example fan structure of a satellite communication system 100. A satellite is used as an example of a wireless repeater. While many examples are described throughout the text of this disclosure in the context of a satellite or satellite communications system, it is intended that such examples are not limited to a satellite; any other suitable wireless repeater that can operate in a similar manner may be used. System 100 includes a ground station 101 on Earth, a communications satellite 103, and a terrestrial transmission source on Earth, such as a user terminal 105. Satellite coverage can be broadly defined as the area from and/or to which a transmission source on Earth or a receiver on earth, such as a ground station on earth or a user terminal, may communicate via satellite. In some systems, the coverage areas for each link (eg, forward uplink coverage area, forward downlink coverage area, reverse uplink coverage area, and reverse downlink coverage area) may differ. The forward uplink coverage area and the reverse uplink coverage area are collectively referred to as the uplink coverage area of the satellite. Similarly, the forward downlink coverage area and the reverse downlink coverage area are collectively referred to as the downlink coverage area of the satellite. Although the satellite coverage area is only active for a satellite that is in service (e.g., in an operational orbit), the satellite can be considered to have (e.g., it can be configured to have) a satellite antenna pattern that is independent of the relative the position of the satellite relative to the earth. This means that the satellite antenna radiation pattern is the distribution pattern of the energy transmitted from the satellite antenna (transmitted from the satellite antenna or received by the satellite antenna). The radiation pattern of a satellite dish corresponds to the irradiation (transmitting into or receiving from it) of a particular satellite coverage area when the satellite is in an operational orbit. The coverage area of a satellite is determined by the radiation pattern of the satellite dish, the orbital position and spatial position for which the satellite is intended, as well as a given antenna gain threshold. In general, the intersection of the antenna pattern (at a particular antenna gain, e.g. 3 dB, 4 dB, 6 dB, 10 dB of maximum gain) with the specific physical area under consideration (e.g., an area on or near the surface of the Earth) defines the area antenna covers. Antennas may be configured to provide a particular antenna pattern (and/or coverage area), and such antenna patterns may be determined by calculation (eg, analysis or simulation) and/or by performing experimental measurements (eg, at a test site for antenna testing or in actual use).

Although only one user terminal 105 is shown in the drawing for simplicity, a system typically contains a plurality of user terminals 105. The satellite communication system 100 functions as a point in a multipoint system. This means that a station 101 on Earth within the coverage area of the satellite can send information to and receive information from any of the user terminals 105 within the coverage area of the satellite. However, user terminals 105 only communicate with station 101 on Earth. Earth station 101 receives live data from communications network 107, modulates the data with feeder link modem 109, and transmits the data to satellite 103 on a direct uplink feeder link 111. Satellite 103 relays this live data to user terminals 105 on a direct user downlink communication (sometimes referred to as direct operational downlink) 113. In some cases, data transmission in the forward direction from the station 101 on Earth is intended for several of the user terminals 105 (for example, the information is multicast to user terminals 105). In some cases, the forward data transmission from station 101 on Earth is for only one user terminal 105 (eg, unicast for a particular user terminal 105). User terminals 105 transmit data back to satellite 103 on a reverse user uplink (sometimes referred to as reverse operational uplink) 115. Satellite 103 relays the return data to station 101 on Earth on a reverse feeder downlink 117. Feederlink modem 109 demodulates return data that is transmitted to the communication network 107 . This feedback capability is essentially used by a number of user terminals 105.

FIG. 2 is a diagram showing an example of one configuration of satellite beam coverage areas for serving the continental United States. The configuration example shows seventy beams. The first beam 201 covers approximately two-thirds of the state of Washington. The second beam 203 next to the first beam 201 covers the area immediately east of the first beam 201. The third beam 205 approximately covers Oregon south of the first beam 201. The fourth beam 207 covers the area located approximately southeast of the first beam 201. Typically, there is some overlap between adjacent beams. In some cases, a multi-color (eg, two-, three-, or four-color reusable radiation pattern) is used. In an example of a four-color radiation pattern, beams 201, 203, 205, 207 individually define a unique combination of frequency (e.g., frequency band or bands, or one or more channels) and/or antenna polarization (e.g., in some cases, the antenna may be configured to right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) signals; other polarization techniques are available). Accordingly, relatively little mutual interference can occur between signals transmitted in different beams 201, 203, 205, 207. These combinations of frequency and antenna polarization can then be reused in a repeating non-overlapping "four-color" reusable radiation pattern. In some situations, the desired communication throughput can be achieved using a single color. In some cases, time separation of beams and/or other interference suppression techniques may be used.

To some extent, focusing the beams into smaller areas, and thus increasing the number of beams, can increase the data throughput of the satellite, providing more opportunities for frequency reuse. However, as the number of beams increases, the level of system complexity, and in many cases the level of complexity of the satellite, can also increase.

The increasing complexity of the satellite design, as a rule, leads to an increase in its size, mass and power consumption. Putting satellites into orbit is expensive. The cost of launching a satellite is partly determined by its mass and size. In addition, there are absolute limits on the mass and size of a satellite if launched using currently available rocket technology. This necessitates the choice of the optimal ratio between the features that can characterize the satellite. Moreover, the amount of electricity that can be supplied to the components of the satellite is limited. Therefore, mass, size and power consumption are parameters that must be taken into account when designing a satellite.

In the text of this disclosure, the term "receiving antenna element" refers to a physical transducer that converts an electromagnetic signal into an electrical signal, and the term "transmitting antenna element" refers to a physical transducer that outputs an electromagnetic signal when excited by an electrical signal. The antenna element may include a horn, a baffled polarized horn (e.g., which can function as two combined elements with different polarizations), a multi-port multi-band horn (e.g., a dual-band 20 GHz/30 GHz LHCP/RHCP dual polarization), a resonator slot antenna, F-type inverted antenna, slotted waveguide, plane traveling wave antenna, helical, loop, rectangular microstrip antenna, antenna element of any other configuration, or a combination of interconnected sub-elements. An antenna element has a corresponding antenna pattern that describes how the antenna gain varies with direction (or angle). The antenna element also has a coverage area, which corresponds to the area (eg, part of the Earth's surface) or volume (eg, part of the Earth's surface with airspace above the surface) in which the antenna element provides the desired level of gain (eg, within 3 dB, 6 dB , 10 dB or other value relative to the maximum gain of the antenna element). The coverage area of the antenna element can be modified with various structures such as reflector, frequency selective surface, lens antenna, radome, and the like. Some satellites, including those described herein, may contain multiple transponders, each capable of independently receiving and transmitting signals. Each transponder is connected to antenna elements (for example, a receiving element and a transmitting element) to form a signal receive / transmit path, which has a radiation pattern (antenna pattern) different from the radiation patterns of other signal receive / transmit paths, to create unique beams, which can be distributed over different beam coverage areas. As a rule, one signal receiving/transmitting path is common for multiple beams due to the use of input and/or output multiplexers. In both cases, the number of beams that can be formed simultaneously is essentially limited by the number of signal receive/transmit paths deployed on the satellite.

Beamforming

Beamforming for the link may be performed by adjusting the signal phase (or time delay) and sometimes the signal amplitude for signals transmitted and/or received by multiple elements of one or more antenna arrays with overlapping coverage areas. In some cases, some or all of the antenna elements are arranged as an array of constituent receive and/or transmit elements that cooperate to provide end-to-end beamforming, as described below. For transmissions (from the transmitting elements of one or more antenna arrays), the relative phases and sometimes the amplitudes of the transmitted signals are adjusted so that the energy transmitted by the transmitting antenna elements is structurally superimposed at the desired location. This phase/amplitude adjustment is commonly referred to as "applying beam weights" to the transmitted signals. For reception (receiving elements of one or more antenna arrays), the relative phases and sometimes the amplitudes of the received signals are adjusted (i.e., the same or different beam weights are applied) so that the energy received by the receiving antenna elements from the desired location is structurally superimposed on these receiving antenna elements. In some cases, the beamformer calculates the desired antenna element beam weights. In some cases, the term "beamforming" may refer to the application of beam weights. Adaptive beamformers have a function to dynamically calculate beam weights. The calculation of the beam weights may require direct or indirect characterization of the link. The processes of calculating the beam weights and applying the beam weights may be performed in the same or different system elements.

Antenna beams can be steered, selectively shaped and/or otherwise reconfigured by applying different beam weights. For example, the number of active beams, the coverage area of the beams, the sizes of the beams, the relative gain of the beams, and other parameters can be changed over time. This flexibility is required in some situations. Beamforming antennas can substantially form relatively narrow beams. Narrow beams may allow signals transmitted via one beam to be separated from signals transmitted via other beams (eg, to avoid interference). Accordingly, narrow beams may allow frequency and polarization reuse to a greater extent than when forming large beams. For example, beams that are narrowly shaped can provide two non-contiguous coverage areas that do not overlap. Each beam can use either right-hand polarization or left-hand polarization. Repeated use may result in an increase in the amount of data transmitted and/or received.

Some satellites use on-board beamforming (OBBF) to electronically control the array of antenna elements. FIG. 3 is an illustration of a satellite system 300 in which the satellite 302 has a phased array with multiple feeder links per beam (MFPB) for on-board beamforming capability. In this example, the beam weights are computed at the ground computer center and then transmitted to or pre-stored on the satellite for use (not shown). FIG. 3 shows a forward link, although this architecture can be used for forward links, reverse links, or both forward and reverse links. Beamforming may be applied to the user link, feeder link, or both. The illustrated forward link is a signal path from one of a plurality of gateways (GWs) 304 to one or more of a plurality of user terminals within one or more beam spot coverage areas 306. The satellite 302 includes a receive antenna array 307, a transmit antenna array 309, a downconverter (D/C) and a gain module 311, a receive array beamformer 313, and a transmit array beamformer 315. Satellite 302 can form beams on both feeder link 308 and user link 310. Each of the L elements of the receiving array 307 receives K signals from K GWs 304. For each of the K generated feeder link beams (e.g., one beam per GW 304) apply a different beam weight (eg, adjust phase/amplitude) by the receive array beamformer 313 for each signal received by each of the L elements of the receive array (receiver array 307). Accordingly, for K beams generated using a receive antenna array 307 comprising L receive antenna elements, K different beam weight vectors of length L are applied to the L signals received by the L receive antenna array elements. A receive array beamformer 313 in satellite 302 adjusts the phase/amplitude of the signals received by the L receive array elements to produce K received beam signals. Each of the K received beams is focused to receive a signal from one GW 304. Accordingly, the receive array beamformer 313 outputs the K received beam signals to the D/C and the gain module 311. One such received beam signal is generated for the signal received from each transmitting GW 304.

The D/C and gain unit 311 downconverts each of the K received beam signals and adjusts the gain accordingly. The K signals output by the D/C and gain module 311 are transmitted to the beamformer 315 of the transmitting antenna array. Transmit array beamformer 315 applies a vector of L weights to each of the K signals for a total of L x K transmit beam weights to form K beams on user downlink 310.

In some cases, a satellite may require significant processing power to control the phase and gain of each antenna element used for beamforming. The use of such processing power leads to an increase in the level of complexity of the satellite. In some cases, satellites may operate with terrestrial beamforming (GBBF) to reduce satellite complexity while maintaining the benefits of electronic narrow beamforming.

FIG. 4 is an illustration of one example of a satellite communication system 400 containing a direct GBBF. The GBBF is conducted on the forward user link 317 via an array of L elements similar to those described above. The phases/amplitudes of the signals transmitted over the user link 317 are weighted to form beams. Feeder link 319 uses a single feed per beam (SFPB) scheme in which each receive and transmit antenna element of antenna 324 is dedicated to one feeder link beam.

Before transmission from one GW or several GW 304 to each ofKforward feed link beamformer 321 transmitting antenna array beamformer applies the corresponding one ofK beam weight vectors, each of lengthL, to each ofKtransmitted signals. DefinitionK vectorsL weighting coefficients and their application to signals allows you to form on the groundKdirect beams for the forward user downlink 317. In the uplink feeder link 319, each ofLdifferent signals is multiplexed to obtain a frequency division multiplexed (FDM) signal using a multiplexer 323 (or the like). Each FDM signal is transmitted by GW 304 to one of the receive antenna elements in antenna 324 via feeder link 319. FDM receiver 325 at satellite 327 receives signals from antenna 324. An analog-to-digital (A/D) converter 326 converts the received analog signals to digital signals. The digital channel processor 328 demultiplexes the FDM signals, each of which has been appropriately weighted by the beamformer 321 for transmission through one of theLarray elements of the transmit antenna elements of the transmit antenna 329. The digital channel processor 328 outputs the signals to a digital-to-analog converter (D/A) 331 for conversion back to analog form. The analog D/A output signals 331 are upconverted and amplified with a boost converter (U/C) and gain stage 330, and then transmitted with a corresponding transmit antenna element 329. The corresponding process is reversed for return beams. It should be noted that this type of FDM feeder link system requiresL times the bandwidth because user beams make it unusable in systems with large data bandwidths or in systems that contain a large number of elementsL.

Through beamforming systems

The end-to-end beamforming systems described herein form end-to-end beams through an end-to-end repeater. An end-to-end beamforming system may connect user terminals to data sources/sinks. In contrast to the beamforming systems described above, in a central data processing system (CPS) end-to-end beamforming system, beam weights are calculated and end-to-end beam weights are applied within the terrestrial network (and not at the satellite). Through-beam signals are transmitted and received at an array of Access Nodes (ANs), which may be a Satellite Access Node (SAN). As described above, any suitable type of end-to-end relays may be used in an end-to-end beamforming system, and different types of ANs may be used to communicate with different types of end-to-end relays. The term "central" refers to the fact that the CPS is available to the ANs that are involved in transmitting and/or receiving the signal, and does not refer to the specific geographic location where the CPS is located. The beamformer within the CPS calculates one set of end-to-end beam weights that takes into account: (1) uplink wireless signal paths to the end-to-end repeater; (2) paths for receiving/transmitting a signal through an end-to-end repeater; and (3) downlink wireless signal paths from the end-to-end repeater. Beam weights can be mathematically represented as a matrix. As described above, OBBF and GBBF satellite systems have beam weight vector sizes determined by the number of antenna elements on the satellite. In contrast, end-to-end beam weight vectors have sizes determined by the number of ANs and not by the number of elements on the end-to-end relay. In general, the number of ANs does not match the number of antenna elements on the end-to-end repeater. The additionally formed through beams do not terminate either at the transmitting or receiving antenna elements of the end-to-end repeater. On the contrary, efficient retransmission of shaped end-to-end beamformers occurs because the end-to-end beamforming systems comprise uplink signal paths, repeater signal paths (via satellite or other suitable end-to-end repeater), and downlink signal paths.

Since end-to-end beamforming considers both the user link and the feeder link (as well as the end-to-end repeater), only one set of beam weights is needed to form the required end-to-end user beams in a particular direction (eg, forward user beams or return user beams). Thus, one set of end-to-end forward beam weights (hereinafter referred to simply as forward beam weights) causes the signals transmitted from the AN through the direct uplink, through the end-to-end repeater, and also through the direct downlink to form end-to-end direct user beams. (hereinafter referred to as direct user beams). Conversely, signals transmitted back from users through the reverse uplink, through the end-to-end repeater, and the reverse downlink have end-to-end return beam weights (hereinafter referred to as return beam weights), are applied to form end-to-end return user beams (hereinafter referred to as return custom rays). Under some conditions, it may be very difficult or impossible to distinguish between uplink and downlink characteristics. Accordingly, feedlink shaped beams, user shaped beam gain, and intrinsic carrier-to-interference (C/I) ratios for uplink and downlink may no longer have their traditional role in system design, and signal ratio concepts /noise (Es/No) and end-to-end C/I for uplink and downlink may still be relevant.

FIG. 5 is an illustration of an example of an end-to-end beamforming system 500. System 500 includes: ground segment 502; end-to-end relay 503; and a plurality of user terminals 517. Ground segment 502 contains M ANs 515 geographically distributed over the coverage area of the ANs. ANs 515 and user terminals 517 may be collectively referred to as terrestrial receivers, terrestrial transmitters, or terrestrial transceivers, depending on the particular functionality in question, as they are located on or near the earth and both transmit and receive signals. In some instances, user terminals 517 and/or ANs 515 may be located on an aircraft, a floating craft, or mounted on a ground vehicle, etc. In some cases, user terminals 517 may be geographically distributed. AN 515 may be geographically distributed. The ANs 515 provide signals through the distribution network 518 to the CPS 505 within the ground segment 502. The CPS 505 is connected to a data source (not shown) such as the Internet, a video headend, or other such facility.

User terminals 517 may be grouped with other adjacent user terminals 517 (eg, as illustrated by user terminals 517a and 517b). In some cases, such groups of user terminals 517 are served by the same user beam and therefore are within the same geographic coverage area 519 of the forward and/or return user beams. A user terminal 517 is within a user beam if the user terminal 517 is within the coverage area served by that user beam. Although in FIG. 5 shows only one such user beam coverage area 519 that contains more than one user terminal 517, in some cases, user beam coverage area 519 may contain any suitable number of user terminals 517. Moreover, the image in FIG. 5 is not intended to indicate the relative size of the different user beam coverage areas 519. This means that all user beam coverage areas 519 may be approximately the same size. Alternatively, user beam coverage areas 519 can be of various sizes, with some user beam coverage areas 519 being much larger than others. In some cases, the number of ANs 515 is not equal to the number of user beam coverage areas 519.

End-to-end relay 503 relays signals wirelessly between user terminals 517 and a number of network access nodes, such as ANs 515 shown in FIG. 5. End-to-end repeater 503 includes a plurality of signal paths. For example, each signal path may include at least one receive antenna element, at least one transmit antenna element, and at least one transponder (as detailed below). In some cases, a plurality of receiving antenna elements are arranged to receive signals reflected by the receiving reflector to form a receiving antenna array. In some cases, a plurality of transmit antenna elements are arranged to transmit signals to thereby form a transmit antenna array.

In some cases, an end-to-end relay 503 is provided on the satellite. In other cases, the end-to-end repeater 503 is provided on an aircraft, airship, tower, underwater structure, or any other suitable structure or vehicle in which the end-to-end repeater 503 may be located. In some cases, the system uses different frequency bands (in the same or in different frequency bands) for uplinks and downlinks. In some cases, the feeder links and user links are in different frequency bands. In some cases, the end-to-end repeater 503 acts as a passive or active reflector.

As described herein, the various functions of the end-to-end repeater 503 provide end-to-end beamforming. One function is that the end-to-end relay 503 includes a plurality of transponders that, in the context of end-to-end beamforming systems, induce multipath propagation between the AN 515 and user terminals 517. Another function is that the antennas (e.g., one or more antenna subsystems ) of the end-to-end repeater 503 participate in end-to-end beamforming such that when correctly weighted beam signals are transmitted over the multipath path induced by the end-to-end repeater 503, forward and/or return user beams are formed. For example, in feed-forward, each of a plurality of transponders receives superimposed combined (beam-weighted) uplink direct signals 521 from a plurality (e.g., all) of the ANs 515 (referred to herein as combined direct input signals) and the transponders output the corresponding composite signals (referred to herein as direct downlink signals). Each of the direct downlink signals may be a unique combination of beam-weighted direct uplink signals 521 which, when transmitted by the end-to-end repeater transmit antenna elements 503, are superimposed to form user beams 519 at desired locations (e.g., in this case, at recovery locations within direct user beams). The reverse end-to-end beamforming capability is provided in a similar manner. Thus, the end-to-end relay 503 can cause multiple overlaps, thus enabling end-to-end beamforming over the induced multipath channels.

Feedback data

FIG. 6 is an illustration of an example of a signal path model for signals carrying reverse data on a reverse link end-to-end. The feedback data is data passing from the user terminals 517 to the AN 515. The signals in FIG. 6 pass from right to left. Signals originate from user terminals 517. User terminals 517 transmit return uplink signals 525 (which contain reverse user data streams) up to end-to-end relay 503. Return uplink signals 525 from user terminals 517 in K user beam coverage areas 519 are received in an array L paths 1702 receive/transmit a signal. In some cases, the uplink coverage area for end-to-end relay 503 is defined by a set of points from which all of the L receive antenna elements 406 can receive signals. In other cases, the coverage area of the repeater is defined by such a set of points from which a subset (eg, the required number that is greater than 1, but less) L receive antenna elements 406 can receive signals. Similarly, in some cases, the downlink coverage area is defined by the set of points to which all of the L transmit antenna elements 409 can reliably send signals. In other cases, the downlink coverage area for end-to-end relay 503 is defined by a set of points to which a subset of transmit antenna elements 409 can reliably send signals. In some cases, the size of the subset of receive antenna elements 406 or transmit antenna elements 409 is at least four. In other cases, the subset size is 6, 10, 20, 100, or any other number that provides the required system performance.

For simplicity, some examples are described and/or illustrated such that all L receive antenna elements 406 receive signals from all points in the uplink coverage area and/or all L transmit antenna elements 409 transmit to all points in the downlink coverage area. It is contemplated that such descriptions do not require all L elements to receive and/or transmit signals at a significant signal level. For example, in some cases, the L subset of receive antenna elements 406 receives an uplink signal (e.g., reverse uplink signal 525 from user terminal 517 or forward uplink signal 521 from AN 515), so that subset of receive antenna elements 406 receives the signal uplink at a signal level close to the peak level of the received uplink signal (eg, substantially not less than the signal level corresponding to the uplink signal having the highest signal level); others of the L non-subset receive antenna elements 406 receive the uplink signal at a significantly lower level (eg, well below the peak level of the received uplink signal). In some cases, the uplink signal received by each receive antenna element of the subset is at a signal level within 10 dB of the maximum signal level received by any of the receive antenna elements 406. In some cases, the subset includes at least 10% of the receive antenna elements elements 406. In some cases, the subset includes at least 10 receive antenna elements 406.

Similarly, on the transmit side, a L subset of transmit antenna elements 409 transmits a downlink signal to a receiver on Earth (e.g., return downlink signal 527 to AN 515 or forward downlink signal 522 to user terminal 517), such that the subset of transmitters antenna elements 409 transmits the downlink signal to the receiver at a received signal level close to the peak level of the transmitted downlink signal (eg, substantially not lower than the signal level corresponding to the downlink signal having the highest received signal level); others of the L transmit antenna elements 409 not in the subset transmit the downlink signal such that it is received at a significantly lower level (eg, well below the maximum downlink transmitted signal level). In some cases, the signal level is within 3 dB of the signal level corresponding to the maximum gain of the transmitting antenna elements 409. In other cases, the signal level is within 6 dB of the signal level corresponding to the maximum gain of the transmitting antenna elements 409. In the third cases, the level signal is within 10 dB of the signal level corresponding to the maximum gain of the transmitting antenna elements 409.

In some cases, the signal received by each receive antenna element 406 originates from the same source (eg, one of the user terminals 517) due to the overlap of the receive antenna pattern of each receive antenna element. However, in some cases, within the coverage area of the end-to-end repeater, there may be points where the user terminal is located and from which not all of the receiving antenna elements can receive a signal. In some of these cases, there may be a significant number of receive antenna elements that do not (or cannot) receive a signal from user terminals located within the coverage area of the end-to-end repeater. However, as described herein, end-to-end repeater 503 induction of multipath may rely on signal reception by at least two receiver elements.

As shown in FIG. 6 and described in more detail below, in some cases, the receive/transmit signal path 1702 includes a receive antenna element 406, a transponder 410, and a transmit antenna element 409. In such cases, each of the plurality of transponders 410 receives return uplink signals 525 via a respective receive antenna element. 406. The output of each signal receive/transmit path 1702 is a downlink return signal 527 associated with the corresponding combination of received uplink return signals. The reverse downlink signal is generated by the signal receiving/transmitting path 1702. The reverse downlink signal 527 is transmitted to an array of M ANs 515. In some cases, ANs 515 are placed at geographically dispersed locations (eg, receive or recovery locations) throughout the end-to-end repeater coverage area. In some cases, each transponder 410 connects a respective one of the receive antenna elements 406 to a respective one of the transmit antenna elements 409. Accordingly, there are L different signal paths from a user terminal 517 located in the user beam coverage area 519 to a particular AN 515. This creates L paths between user terminal 517 and AN 515. L paths between one user terminal 517 and one AN 515 are collectively referred to as end-to-end reverse multipath 1908 (see FIG. 8). Accordingly, the reception of an uplink return signal 525 from a transmission location within the user beam coverage area 519 through L transponders 410 generates L return downlink signals 527, each of which is transmitted from one of the transponders 410 (i.e., through L co-located communications tracts). Each end-to-end reverse multipath channel 1908 is associated with a vector in the uplink emission matrix A _r , a payload matrix E , and a vector in the downlink emission matrix C _t . It should be noted that considering the antenna element coverage patterns, in some cases some of the L paths may have relatively low energy (e.g. 6 dB, 10 dB, 20 dB, 30 dB or any other suitable power factor that is lower than other paths). ). Downlink reverse signal 527 overlay 1706 is received at each of the ANs 515 (eg, at M geographically dispersed receive or recovery locations). Each downlink return signal 527 comprises an overlay of a plurality of transmitted downlink return signals 527 resulting in a corresponding combined return signal. The respective combined returns are connected to a return beam generator 531 (see FIGS. 5 and 29).

FIG. 7 illustrates an example of an end-to-end reverse link 523 from a single user terminal 517 located within user beam coverage area 519 to an AN 515. An uplink return signal 525 transmitted from a user terminal 517 is received by an array of L receive antenna elements 406 at the end-to-end. relay 503 (eg, or is received by a subset L of receive antenna elements 406).

Ar is an L x K reverse uplink emission matrix. The reverse uplink emission matrix values model the signal path from the reference location in the user beam coverage area 519 to the end-to-end repeater receiving antenna elements 406. For example, Ar _L,1 represents the value of one element of the reverse uplink emission matrix (ie, path amplitude and phase) from the reference location in the 1st user beam coverage area 519 to the L th receive antenna element. In some cases, all of the values of the reverse uplink emission matrix Ar may be non-zero (eg, there is a significant signaling path from the reference location to each of the receive antenna elements of the receive antenna array).

E (of size L x L ) is a payload matrix and provides a model (amplitude and phase) of the paths from the receive antenna elements 406 to the transmit antenna elements 409. For the purposes of this document, the “payload” of an end-to-end repeater 503 essentially includes a set of components end-to-end relay 503 that affect and/or are affected by communication signals as they are received, relayed through, and transmitted from the end-to-end relay 503. For example, the end-to-end relay payload may include antenna elements, reflectors, transponders, etc.; but the end-to-end repeater may further include batteries, solar cells, sensors, and/or other components not considered herein as part of the payload (because they do not interfere with signals during normal operation). Considering a set of components as a payload allows the overall impact of an end-to-end relay to be mathematically modeled as a single payload matrix E. The dominant path from each receive antenna element 406 to each respective transmit antenna element 409 is modeled by a value lying on the diagonal of the payload matrix E. Assuming that there is no crosstalk between the receive/transmit signal paths, the off-diagonal values of the payload matrix are zero. In some cases, crosstalk may not be zero. Isolation of signal transmission paths from each other allows to reduce crosstalk to a minimum. In some cases, since crosstalk is negligible, the payload matrix E can be estimated using a diagonal matrix. In some cases, the off-diagonal values (or any other suitable values) of the payload matrix may be interpreted as zero even when there is some influence on the signal corresponding to these values, to reduce mathematical complexity and/or for other reasons.

Ct is an M x L reverse downlink emission matrix. The reverse downlink emission matrix values model the signal paths from the transmit antenna elements 409 to AN 515. For example, Ct _3,2 is the reverse downlink emission matrix value (eg, gain and path phase) from the second transmit antenna element 409 _b to the third AN 515 _c . In some cases, all of the values of the downlink emission matrix Ct may be non-zero. In some cases, some of the values of the downlink emission matrix Ct are essentially zero (e.g., the antenna pattern produced by the respective transmit antenna elements 409 of the transmit antenna array is such that the transmit antenna element 409 does not transmit useful signals to some of the ANs 515) .

As can be seen in FIG. 7, the end-to-end reverse multipath from a user terminal 517 in a particular user beam coverage area 519 to a particular AN 515 is the sum of L different paths. The end-to-end reverse multipath has multipath induced by L unique paths through transponders 410 in the end-to-end repeater. As is the case with many multipath channels, the amplitudes and phases of the paths can add up favorably (constructively) to a high end-to-end gain definition, or unfavorably (destructively) to a low end-to-end gain definition. With a large number of different paths L between the user terminal and the AN, the end-to-end gain may have a Rayleigh amplitude distribution. With this allocation, it often happens that the gains of some end-to-end channels from a particular user terminal 517 to a particular AN 515 are 20 dB or more below the average channel gain level from the user terminal 517 to AN 515. This end-to-end beamforming system specifically induces a multipath environment for end-to-end path from any user terminal to any AN.

FIG. 8 is a simplified illustration of an example model of all end-to-end reverse multipath channels from user beam coverage areas 519 to AN 515. ). Channels 1908 connect user terminals in the same user beam coverage area 519 to one AN 515 over L different receive/transmit paths 1702, with each path passing through a different one of the L receive/transmit signal paths (and associated transponders) of the repeater. Although this effect is referred to as "multipath" in this document, this multipath is different from conventional multipath (e.g., in a mobile radio system or a multi-input-multi-output (MIMO) system) because the multipath paths in the present invention are intentionally induced ( and, as described herein, are affected by) L signal receiving/transmitting paths. Each of the M x K end-to-end reverse multipaths originating from a user terminal 517 within a particular user beam coverage area 519 may be modeled by an end-to-end reverse multipath. Each such end-to-end reverse multipath path extends from a reference location (or recovery location) within a particular user beam coverage area 519 to one of the ANs 515.

Each ofMxK end-to-end reverse multipath channels 1908 can be individually modeled to calculate the corresponding elementM xKmatricesHret return channels. MatrixHret reverse channels hasK vectors, each of which has a dimension equal toM, so that each vector models the end-to-end reverse channel gains for multipath communication between the reference location at one of the respectiveK coverage areas of user beams andM AN 515: Each end-to-end return multipath link connects one ofM AN 515 with a reference location in one ofK return user beams throughL transponders 410 (see FIG. 7). In some cases, only a subsetL The transponders 410 on the end-to-end repeater 503 are used to create an end-to-end reverse multipath (eg, only a subset is considered to be in the signaling path given significant energy input into the end-to-end reverse multipath). In some cases, the number of custom beamsK more transpondersLincluded in the signal transmission path of the end-to-end reverse multipath channel. Moreover, in some cases the number ANM more transpondersL, included in the signaling path of the end-to-end reverse multipath channel 1908. In one example, the elementHret _4.2 matricesHret the return channel is connected to the channel from the reference location in the second user beam coverage area 1903 to the fourth AN 1901. MatrixHret models the end-to-end channel as a product of matricesCt xE xAr (see FIG. 6). Each element inHret models the end-to-end gain of one end-to-end reverse multipath channel 1908. Due to the multipath nature of the channel, it may be subject to deep fading. The user return beams may be generated by the CPS 505. The CPS 505 calculates the return beam weights based on a model of theseM xK paths and generates return user beams by applying return beam weights to a plurality of combined return signals, with each weight calculated for each end-to-end reverse multipath connecting user terminals 517 in the same user beam coverage area to one of the plurality of ANs 515. In some cases, the return beam weights are computed prior to receiving the combined return signal. There is one end-to-end return link from each of theK 519 user beam coverage zones up toM AN 515: Weighting (i.e., complex relative phase/amplitude assignment) of each of the signals receivedM AN 515 allows these signals to be combined to form a return user beam using the CPS 505's beamforming capability within the ground segment 502. A beam weight matrix calculation is used to determine how to weight each end-to-end return multipath channel 1908 to form a set of return user beams, as described in more detail below. User beams are not generated by directly adjusting the relative phase and amplitude of signals transmitted by one end-to-end repeater antenna element relative to the phase and amplitude of signals transmitted by other end-to-end repeater antenna elements. Instead, user beams are formed by applying weights associated with a channel matrixMxK, ToM AN signals. It is the plurality of ANs that allows the reception of path diversity signals from one transmitter (user terminal) to multiple receivers (ANs), ensuring successful transmission of information from any user terminal in the presence of a specially induced multipath channel.

Direct connection data

FIG. 9 is an illustration of an example signal path model for signals carrying forward data over the forward link end-to-end 501. The forward data is the data transmitted from the AN 515 to the user terminals 517. The signals in this figure travel from right to left. The signals originate from M AN 515, which are located in the coverage area of the end-to-end repeater 503. There are K user beam coverage areas 519. Signals from each AN 515 are relayed by L paths 2001 of signal reception/transmission.

The signal receiving/transmitting paths 2001 transmit the relayed signal to user terminals 517 in user beam coverage areas 519. Accordingly, there may be L different signal paths from a particular AN 515 to a user terminal 517 located in the user beam coverage area 519. This creates L paths between each AN 515 and each user terminal 517. It should be noted that due to antenna element coverage patterns, some of the L paths may have less energy than other paths.

FIG. 10 illustrates an example of an end-to-end forward link 501 connecting multiple access points at geographically dispersed locations to a user terminal 517 in a user beam (eg, located at a recovery location within user beam coverage area 519) via an end-to-end relay 503. In some cases, a direct data signal is received at the beamformer prior to generating direct uplink signals. A plurality of direct uplink signals are generated at the beamformer and transmitted to a plurality of ANs 515. For example, each AN 515 receives a unique (beam-weighted) direct uplink signal generated according to the beam weights corresponding to that AN 515. Each AN 515 has a terminal transmitting a direct uplink signal via one of the M uplinks. Each direct uplink signal contains a direct data signal associated with a direct user beam. The direct data signal is "associated with" the direct user beam because it is intended to be received by user terminals 517 served by the user beam. In some cases, the direct data signal contains two or more user data streams. The user data streams may be multiplexed together by time division multiplexing or frequency division multiplexing, and so on. In some cases, each user data stream is intended to be transmitted to one or more of a plurality of user terminals in a single forward user beam.

As described in more detail below, each direct uplink signal is transmitted in time synchronization by its respective transmit AN 515. The forward uplink signals 521 transmitted from AN 515 are received by multiple transponders 410 at the end-to-end relay 503 via receive antenna elements 406 at the end-to-end. repeater 503. The overlay 550 of direct uplink signals 521 received from geographically dispersed locations creates a combined direct input signal 545. Each transponder 410 simultaneously receives a combined direct input signal 545. However, each transponder 410 will receive signals with slightly different timing due to differences in the location of the receive antenna elements 406 associated with each transponder 401.

Cr is an L x M forward uplink emission matrix. The forward uplink emission matrix values model the signal path (amplitude and phase) from the AN 515 to the receive antenna elements 406. E is an L x L payload matrix and provides a model of the transponder signal paths from the receive antenna elements 406 to the transmit antenna elements 409. The forward path gain from each receive antenna element 406 through a respective one of the plurality of transponders to each respective transmit antenna element 409 is modeled by the diagonal values of the payload matrix. As noted above for the reverse link, assuming no crosstalk between antenna elements, the off-diagonal payload matrix values are zero. In some cases, crosstalk may not be zero. Isolation of signal transmission paths from each other allows to reduce crosstalk to a minimum. In this example, each of the transponders 410 connects a respective one of the receive antenna elements 406 to a respective one of the transmit antenna elements 409. Accordingly, a direct downlink signal 522 output from each of the transponders 410 is transmitted by each of the plurality of transponders 410 (see FIG. 9) through the transmit antenna elements 409 so that the direct downlink signals 522 form a forward user beam (by performing constructive and destructive overlap at the desired beamforming recovery geographic locations). In some cases, multiple user beams are generated, each corresponding to a geographic user beam coverage area 519 serving a respective set of user terminals 517 within the user beam coverage area 519 . The path from the first transmitting antenna element 409a (see FIG. 10) to the reference location (or allocation location) in the first user beam coverage area 519 is given by the value At ₁₁ of the forward downlink emission matrix. As noted with respect to the reverse link, this end-to-end beamforming system specifically induces a multipath environment for the end-to-end path from any AN 515 to any user terminal 517. to the user terminal 517. The user terminal 517 (or, more generally, a foothold or recovery location in the user beam coverage area 519 for reception and/or recovery) receives a plurality of direct downlink signals 522 and recovers at least a portion direct data signal from the received set of direct signals 522 downlink. The transmitted direct downlink signals 522 can be received by the user terminal 517 at a signal level within 10 dB of the maximum signal level of any other signals transmitted by the transmitting antenna elements 409 within the subset. In some cases, the subset of transmit antenna elements includes at least 10% of the plurality of transmit antenna elements present in the end-to-end relay 503. In some cases, the subset of transmit antenna elements includes at least 10 transmit antenna elements, no matter how many transmit antenna elements elements 409 are present in the end-to-end relay 503. In one case, receiving a plurality of direct downlink signals includes receiving an overlay 551 of a plurality of direct downlink signals.

FIG. 11 is a simplified illustration of a model of all end-to-end direct multipath channels 2208 from M AN 515 to K user beam coverage areas 519. As shown in FIG. 11, there is an end-to-end forward multipath link 2208 that connects each AN 515 to each user beam coverage area 519. Each channel 2208 from one AN 515 to one user beam coverage area 519 has multipath induced by passing L unique paths from the AN 515 through multiple transponders to the user beam coverage area 519. Thus, the K x M multipath channels 2208 can be individually modeled and the model of each is used as an element of the K x M forward channel matrix Hfwd . The forward channel matrix Hfwd has M vectors, each of dimension equal to K , such that each vector models the end-to-end forward multipath gains between the corresponding one of the M AN 515 and the reference locations (or restoration locations) in the K forward user coverage areas. rays. Each end-to-end direct multipath channel connects one of the M ANs 515 to user terminals 517 served by one of the K direct user beams via L transponders 410 (see FIG. 10). In some cases, only the L subset of transponders 410 on the end-to-end repeater 503 is used to create an end-to-end direct multipath channel (ie, transponders included in the signal path of the end-to-end direct multipath channel). In some cases, the number of user paths K is greater than the number of transponders L included in the signal path of the end-to-end direct multipath channel. Moreover, in some cases, the number AN M is greater than the number of transponders L included in the signal path of the end-to-end direct multipath channel.

H-fwd may be an end-to-end direct link in the form of a product of matrices A t x E x Cr . Each element in Hfwd is an end-to-end direct gain due to the multipath nature of the path and may be subject to deep fading. A suitable beam weight may be computed for each of the multiple end-to-end direct multipath channels 2208 by the CPS 505 within the ground segment 502 to generate direct user beams from the M AN set 515 to each user beam coverage area 519. Multiple ANs 515 enable multi-transmitter (AN) path diversity signaling to a single receiver (user terminal), ensuring successful transmission of information to any user terminal 517 in the presence of a specially induced multipath channel.

Combined feed-forward and feedback data

FIG. 12 illustrates an example of an end-to-end repeater that supports both forward and reverse communication. In some cases, the same end-to-end relay signal paths (eg, a set of receive antenna elements, transponders, and transmit antenna elements) may be used for both the end-to-end forward link 501 and the end-to-end reverse link 523. Some other cases include forward link transponders and reverse link transponders, which may or may not share receive and transmit antenna elements. In some cases, system 1200 has multiple ANs and user terminals located in the same geographic region 1208 (which may be, for example, a specific state, an entire country, a region, an entire visible area, or any other suitable geographic region 1208). A single end-to-end relay 1202 (located on satellite or any other suitable end-to-end relay) receives direct uplink signals 521 from the AN and transmits direct downlink signals 522 to user terminals. At different times or frequencies, end-to-end relay 1202 also receives uplink return signals 525 from user terminals and transmits downlink return signals 527 to the AN. In some cases, the end-to-end relay 1202 is shared between forward and reverse data using techniques such as time domain duplexing, frequency domain duplexing, and the like. same frequency range: forward data is transmitted in time intervals that are different (non-overlapping) from those used for return data transmission. In some cases, frequency domain duplexing uses different frequencies for forward and reverse data, thus providing simultaneous, non-interfering transmission of forward and reverse data.

FIG. 13 is an illustration of an uplink frequency band divided into two parts. The low frequency (left) part of the band is allocated to the forward uplink, and the high frequency (right) part of the band is allocated to the reverse uplink. The uplink range may be divided into multiple portions of either forward or reverse data.

FIG. 14 is an illustration of forward data and reverse data subjected to time division multiplexing. A data frame period is shown in which forward data transmission occurs in the first time slot of the frame and reverse data transmission occurs in the last time slot of the frame. The end-to-end relay receives a signal from one or more access nodes in a first (forward) receive time slot and from one or more of the user terminals in a second (reverse) receive time slot that does not overlap with the first receive time slot. The end-to-end relay transmits a signal to one or more user terminals in a first (forward) transmission time slot and to one or more access nodes in a second (reverse) transmission time interval that does not overlap with the first transmission time interval. The data frame may be repeated or may change dynamically. The frame may be divided into multiple (eg, non-contiguous) parts for forward and reverse data.

Satellites for end-to-end beamforming

In some cases, end-to-end relay 503 is implemented on a satellite such that the satellite is used to relay signals from ANs (which in such cases may be referred to as Satellite Access Nodes (SANs)) to user terminals and vice versa. In some cases, the satellite is in geostationary orbit. An example satellite operating as an end-to-end relay has an array of receive antenna elements, an array of transmit antenna elements, and a number of transponders that couple the receive antenna elements to the transmit antenna elements. The arrays contain a large number of antenna elements with overlapping antenna element coverage areas similar to traditional single link phased array antennas. It is the overlapping antenna element coverage areas on both the transmit antenna elements and the receive antenna elements that create the previously described multipath environment. In some cases, the antenna patterns generated by the respective antenna elements and the patterns resulting from overlapping coverage areas of the antenna elements (eg, overlapping patterns of a composite directional antenna) are identical. For the purposes of this disclosure, the term "identical" means that they have substantially the same power distribution over a given set of points in space, using the antenna element as a reference point for locating the points in space. It is very difficult to ensure complete identity. Thus, radiation patterns with relatively small deviations from each other are included in the concept of "identical" radiation patterns. In other cases, the radiation patterns of a receive composite directional antenna may not be identical, and in fact may differ significantly. Such antenna patterns may still result in overlapping coverage areas of the antenna elements, however the resulting coverage areas will not be identical.

Antenna types include, without limitation, array-radiator reflectors, confocal arrays, direct-radiating arrays, and other forms of antenna arrays. Each antenna may be a system that includes additional optical components to help receive and/or transmit signals, such as one or more reflectors. In some cases, the satellite includes components to assist in system clocking and beamforming calibration.

FIG. 15 is a diagram of an example satellite 1502 that can be used as an end-to-end relay 503. In some cases, satellite 1502 has a transmit antenna 401 having an array reflector and a receive antenna 402 having an array reflector. The receive antenna 402 includes a receive reflector (not shown) and an array of receive antenna elements 406. The receive antenna elements 406 are irradiated by the receive reflector. The transmit antenna 401 includes a transmit reflector (not shown) and an array of transmit antenna elements 409. The transmit antenna elements 409 are arranged to irradiate the transmit reflector. In some cases, a single reflector is used for both reception and transmission. In some cases, one port of the antenna element is used for reception and the other port for transmission. Some antennas have the ability to distinguish between signals of different polarizations. For example, the antenna element may include four waveguide ports for right-hand circular polarization (RHCP) signal reception, left-hand circular polarization (LHCP) signal reception, RHCP signal transmission, and LHCP signal transmission, respectively. In some cases, dual polarization can be used to increase system throughput. In other cases, a single polarization may be used to reduce interference (eg, with other systems that use a different polarization).

The example satellite 1502 also contains a plurality of transponders 410. Transponder 410 couples the output of one receive antenna element 406 to the input of a transmit antenna element 409. In some cases, transponder 410 amplifies the received signal. Each receive antenna element outputs a unique received signal. In some cases, a subset of receive antenna elements 406 receives a signal from a terrestrial transmitter, such as a user terminal 517 in the case of a reverse link signal, or an AN 515 in the case of a forward link signal. In some of these cases, the gain of each receive antenna element in the subset for the received signal is within a relatively small range. In some cases, the range is 3 dB. Otherwise, the range is 6 dB. In still other cases, the range is 10 dB. Accordingly, at each of the plurality of satellite receive antenna elements 406, it will receive a communication signal originating from a terrestrial transmitter such that a subset of receive antenna elements 406 receive the communication signal at a signal level substantially greater than or equal to the signal level corresponding to the maximum gain of the receive antenna element 406 .

In some cases, at least 10 transponders 410 are provided on satellite 1502. In another case, at least 100 transponders 410 are provided on satellite 1502. In another case, the number of transponders per polarity may be in the range of 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, or may be between or above the numbers indicated. In some cases, the transponder 410 includes a low noise amplifier (LNA) 412, a frequency converter and associated filters 414, and a power amplifier (PA) 420. In some cases, when the uplink frequency and the downlink frequency are the same, the transponder does not contain frequency converter. In other cases, a plurality of receive antenna elements operate at the first frequency. Each receive antenna element 406 is associated with one transponder 410. The receive antenna element 406 is connected to the input of the LNA 412. Accordingly, the LNA independently amplifies the unique received signal provided by the receive antenna element associated with the transponder 410. In some cases, the output of the LNA 412 is coupled to a frequency converter. 414. Frequency converter 414 converts the amplified signal to a second frequency.

The output of the transponder is connected to the corresponding one of the transmitting antenna elements. In these examples, there is a one-to-one correspondence between transponder 410, corresponding receive antenna element 406, and corresponding transmit antenna element 409 such that the output of each receive antenna element 406 is connected to the input of one and only one transponder, and the output of that transponder is connected to the input of one and only only one transmitting antenna element.

FIG. 16 is an illustration of an example transponder 410. Transponder 410 may be an example of an end-to-end relay 503 transponder as described above (eg, satellite 1502 in FIG. 15). In this example, the transponder includes a phase shifter 418 in addition to a low noise amplifier (LNA) 412, a frequency converter and associated filters 414, and a transponder power amplifier (PA) 410. As illustrated in FIG. 16, an example transponder 410 may also be connected to a phase shift controller 427. For example, the phase shift controller 427 may be connected (directly or indirectly) to each of some or all of the transponders of the end-to-end repeater 503 such that the phase shift controller 427 may individually set the phases for each transponder. Phase shifters can be useful in calibration, for example as described below.

Antennas

To create a multipath environment, antenna element coverage areas may overlap with antenna element coverage areas of at least one other antenna element of the same polarity, frequency, and type (transmitting or receiving, respectively). In some cases, a plurality of receive composite directional antenna patterns operating at the same receive polarization and receive frequency (eg, having at least a portion of a common receive frequency) overlap with each other. For example, in some cases, at least 25% of the receive composite directional antenna patterns operating at the same receive polarization and receive frequency (e.g., having at least a common receive frequency region) overlap with at least five other receive composite directional antenna patterns. antennas of receiving antenna elements. Similarly, in some cases, at least 25% of the transmitting composite directional antenna patterns operating at the same polarization and transmit frequency (e.g., having at least a common transmit frequency portion) overlap with at least five other transmitting composite directional antenna patterns. antennas. The amount of overlap varies from system to system. In some cases, at least one of the receive antenna elements 406 has composite directional antenna patterns that overlap with those of other receive antenna elements 406 operating at the same receive frequency (e.g., having at least a common receive frequency region) and the same the same polarization of reception. Thus, at least some of the plurality of receive antenna elements are capable of receiving the same signals from the same source. In some instances, at least one of the transmit antenna elements 409 has a composite directional antenna pattern that overlaps with those of other transmit antenna elements 409 operating at the same transmit frequency (e.g., having at least a common transmit frequency region) and the same the same transmission polarization. Thus, at least some of the plurality of transmit antenna elements are capable of transmitting signals having the same frequency at the same polarization to the same receiver. In some cases, the overlapping radiation patterns of a composite directional antenna may have gains that differ by less than 3 dB (or any other suitable value) over a common geographic area. Antenna elements, whether transmitting or receiving, may have a wide radiation pattern of a composite directional antenna and thus a relatively wide coverage area of the antenna element. In some cases, signals transmitted by a terrestrial transmitter, such as user terminal 517 or access node 515, are received by all of the receive antenna elements 406 of an end-to-end relay (eg, satellite). In some cases, a subset of elements 406 receives signals from a terrestrial transmitter. In some cases, the subset includes at least 50% of the receive antenna elements. In other cases, the subset includes at least 75% of the receive antenna elements. In still other cases, the subset includes at least 90% (eg, up to and including all) of the receive antenna elements. Different subsets of receive antenna elements 406 may receive signals from different terrestrial transmitters. Similarly, in some cases, the subset of elements 409 transmits signals that can be received by the user terminal 517. In some cases, the subset includes at least 50% of the transmit antenna elements. In other cases, the subset includes at least 75% of the transmit antenna elements. In still other cases, the subset includes at least 90% (eg, up to and including all) of the transmit antenna elements. Different subsets of elements 409 may transmit signals that may be received by different user terminals. Moreover, user terminals may be within multiple user beam coverage areas 519 formed. For the purpose of this disclosure, the antenna pattern is the distribution pattern of the energy transmitted or received by the antenna. In some cases, energy may be directly radiated from and to the antenna element. In other cases, energy from one or more transmit antenna elements may be reflected by one or more reflectors forming the antenna element's beam pattern. Similarly, the receiving element may receive energy directly or after the energy has been reflected from one or more reflectors. In some cases, antennas may be composed of multiple elements, each of which has a composite directional antenna pattern that establishes a respective coverage area of the antenna element. Similarly, all or a subset of the receive or transmit antenna elements that receive and transmit signals on the AN 515 may overlap such that a plurality of receive antenna elements receive signals from the same AN 515 and/or a plurality of transmit antenna elements transmit signals to one and the same AN 515.

FIG. 17 is an illustration of the radiation patterns of a composite directional antenna produced by multiple antenna elements (either receive antenna elements 406 or transmit antenna elements 409) that intersect at 3 dB points. The radiation pattern 1301 of the composite directional antenna of the first antenna element has a maximum gain of the composite directional antenna along the electrical axis 1303 of the directional antenna. As shown, the composite directional antenna pattern 1301 attenuates approximately 3 dB before it intersects with the composite directional antenna pattern 1305. Since the overlap of each pair of two adjacent composite directional antenna patterns occurs along the 3 dB line 1307 for only a relatively small portion of the composite directional antenna patterns, the antenna elements producing these composite directional antenna patterns are considered to be non-overlapping.

FIG. 18 shows idealized 3 dB antenna pattern contours 3901, 3902, 3903 of several elements 406, 409 with maximum gain indicated by "x". The contours 3901, 3902, 3903 are referred to herein as "idealized" because the contours are shown as circular for simplicity. However, the contours 3901, 3902, 3903 need not be circular. Each loop indicates the location where the transmitted or received signal power is 3 dB below the maximum level. Outside the loop, the signal is more than 3 dB below maximum. Inside the loop, the signal is less than 3 dB below the maximum (i.e., within 3 dB of the maximum). In a system where the receive composite directional antenna pattern coverage covers all points for which the receive composite directional antenna gain is within 3 dB of the maximum receive composite directional antenna gain, the area within the contour is referred to as the "antenna element coverage area". The 3 dB antenna pattern contour for each element 406, 409 does not overlap. This means that only a relatively small portion of the area within the 3 dB antenna pattern contour 3901 overlaps with the area that lies within the adjacent 3 dB antenna pattern contours 3902, 3903.

FIG. 19 is an illustration of antenna patterns 1411, 1413, 1415 of multiple antenna elements (either receive antenna elements 406 or transmit antenna elements 409). In contrast to the radiation patterns of the composite directional antenna in FIG. 17, the radiation patterns of the composite directional antenna shown in FIG. 19 intersect 1417 in the region above the 3 dB line 1307.

FIG. 20A-20E illustrate 3 dB antenna contours for multiple antenna elements 406, 409 with the center point of the beam (maximum gain) labeled "x". FIG. 20A shows a specific antenna pattern 1411 of the first antenna element 406. In FIG. 20B shows 3 dB antenna pattern contours 1411, 1413 for two specific elements 406. In FIG. 20C shows 3 dB antenna contours for three elements 406. FIG. 20D shows 3 dB antenna contours for four elements 406. FIG. 20E shows 3 dB antenna contours for an array of 16 antenna elements 406. 3 dB antenna contours are shown overlapping in region 1418 (e.g., 16 3 dB antenna contours are shown). The antenna elements in either the receive or transmit antenna may be placed in any of several different configurations. For example, if the cells have a substantially circular horn feed, they can be placed in a honeycomb configuration to tightly pack the cells in a small amount of space. In some cases, the antenna elements are aligned in horizontal rows and vertical columns.

FIG. 21 is an exemplary illustration of the relative positions of the 3 dB receive antenna footprints associated with the receive antenna elements 406. The beam centers of element 406 are numbered 1 to 16, with element ₄₀₆₄ identified by the number "4" at the top left assigned to the indicator "x". beam center. In some cases, there may be more than 16 receive antenna elements 406. However, for simplicity, FIG. Only 16 are shown in FIG. 21. Thus, for simplicity, only the array of receive antenna elements 406 is shown. Zone 2101 in the center is the area where all antenna element coverage areas overlap.

In some cases, at least one point within the coverage area of a repeater (e.g., the coverage area of a satellite) is within the 3 dB antenna pattern contour of the partial beams of multiple antenna elements 406. In one such case, at least one point is within 3 dB antenna contours of at least 100 different antenna elements 406. Alternatively, at least 10% of the repeater coverage area is within the 3 dB antenna contours of at least 30 different antenna elements. In another case, at least 20% of the repeater coverage area is within 3 dB antenna contours of at least 20 different antenna elements. In another case, at least 30% of the repeater coverage area is within 3 dB antenna contours of at least 10 different antenna elements. Alternatively, at least 40% of the repeater coverage area is within 3 dB antenna contours of at least eight different antenna elements. Alternatively, at least 50% of the repeater coverage area is within 3 dB antenna contours of at least four different antenna elements. However, in some cases more than one of these relationships may be valid.

In some cases, the end-to-end repeater has a repeater coverage area (e.g., satellite coverage area) in which at least 25% of the points in the uplink repeater coverage area are within (e.g., span) overlapping coverage areas of at least six receive antenna elements 406. In some cases, 25% of the points within the coverage area of an uplink repeater are within (e.g., span) overlapping coverage areas of at least four receive antenna elements 406. In some cases, an end-to-end repeater has a coverage area in which at least 25% of the points within the downlink repeater coverage area are within (e.g., span) overlapping coverage areas of at least six transmit antenna elements 409. In some cases, 25% of the points within the downlink repeater coverage area are within (e.g., cover) overlapping coverage areas n at least four transmit antenna elements 409.

In some cases, the receive antenna 402 may be pointed to approximately the same coverage area as the transmit antenna 401, so that some receive antenna element coverage areas may naturally correspond to specific transmit antenna element coverage areas. In these cases, receive antenna elements 406 can be mapped to respective transmit antenna elements 409 via transponders 410, creating similar transmit and receive antenna element coverage for each receive/transmit signal path. However, in some cases it may be advantageous to associate receive antenna elements 406 with transmit antenna elements 409 that do not correspond to the same partial beam coverage area. Accordingly, the order of assignment of the elements 406 of the receive antenna 402 to the elements 409 of the transmit antenna 401 may vary randomly (or otherwise). Such permutation includes the case that results in receive antenna elements 406 not being aligned with transmit antenna elements 409 that are in the same relative location within the array or have the same coverage area. For example, each receive antenna element 406 within the receive antenna element array may be associated with the same transponder 410 as the transmit antenna element 409 located at the mirror location of the transmit antenna element array. Any other permutation may be used to match the receive antenna elements 406 with the transmit antenna elements 409 according to the permutation (e.g., pairing each receive antenna element 406 with the same transponder to which the corresponding transmit antenna element 409 is connected according to the particular permutation of the receive antenna element 406 and transmitting antenna element 409).

FIG. 22 is a table 4200 showing an example of the correspondences of receive antenna elements 406 and transmit antenna elements 409 over 16 transponders 410. Each transponder 410 has an input connected exclusively to the corresponding receive antenna element 406 and an output connected exclusively to the corresponding transmit antenna element 409 (for example, , there is a one-to-one correspondence between each receive antenna element 406, one transponder 410, and one transmit antenna element 409). In some cases, the end-to-end repeater (eg, satellite) may have other receive antenna elements, transponders, and transmit antenna elements that are not one-to-one (and do not operate as part of an end-to-end beamforming system).

The first column 4202 of table 4200 identifies the transponder 410. The second column 4204 identifies the receive antenna element 406 to which the transponder 410 from the first column is connected. The third column 4206 of table 4200 identifies the associated transmit antenna element 409 to which the output of the transponder 410 is connected. Each receive antenna element 406 is connected to the input of the transponder 410 identified in the same row of table 4200. Similarly, each transmit antenna element 409 is connected to the output of the transponder 410 identified in the same row of table 4200. The third column of table 4200 shows an example of a direct mapping in which each receive antenna element 406 of the receive antenna array is connected to the same transponder 410 as the transmit antenna element 409 at the same relative location. within the transmitting antenna array. The fourth column 4208 of table 4200 shows an example of interleaved matching, in which the first receive antenna element 406 is connected to the first transponder 410 and the tenth transmit antenna element 409. The second receive antenna element 406 is connected to the second transponder 410 and the ninth transmit antenna element 409, and so on. In some cases, other permutations are used, including random matching, in which the particular pairing of the receive antenna element 406 and the transmitting element 409 with the transponder 410 is chosen at random.

Direct matching, which seeks to keep the coverage areas of the receive and transmit antenna elements as close as possible for each receive/transmit signal path, essentially creates the highest overall system throughput. Random and interleaved permutations essentially give slightly less capacity, but provide a more robust system in the event of AN outages, failure of terrestrial fibers, or loss of receive/transmit signal paths due to electronic failures at the end-to-end repeater (for example, in one or more transponders ). Random and interleaved permutations enable the use of less expensive non-redundant ANs. The random and interleaved permutations also provide a smaller spread between the throughput in the most efficient path and the throughput in the least efficient path. Random and interleaved permutations may also be more useful early on in a system with only a portion of the AN, whereby only a fraction of the total bandwidth will be available, but without reducing the coverage area. An example of this is the phased deployment of ANs, where the system initially works with only 50% of the deployed ANs. This can provide throughput that is less than full capacity while still allowing operation over the entire coverage area. As demand increases, more ANs are deployed to increase throughput until full throughput is reached where all ANs are active. In some cases, changing the composition of the AN causes the beam weights to be recalculated. Changing the composition may include changing the number or characteristics of one or more ANs. This may require recalculation of the forward and/or reverse end-to-end gains.

In some cases, the antenna is a reflector antenna with a multi-element feed and a parabolic reflector. In other cases, the reflector does not have a parabolic shape. An array of receive antenna elements 406 may be arranged to receive signals reflected by the reflector. Similarly, an array of transmit antenna elements 409 may be arranged to form an array to irradiate the reflector. One way to provide elements with overlapping radiation patterns of a composite directional antenna is to defocus (defocus) elements 406, 409 due to the fact that the focal plane of the reflector is located behind (or in front of) the array of elements 406, 409 (i.e., the receiving antenna array is located outside focal plane of the receiving reflector).

FIG. 23 is an illustration of a parabolic reflector 1521 with a central feed in cross section. The focal point 1523 lies in a focal plane 1525 perpendicular to the central axis 1527 of the reflector 1521. Received signals that reach the reflector 1521 while moving parallel to the central axis 1527 are focused at the focal point 1523. Similarly, signals that are transmitted from an antenna element located at the focal point and reach the reflector 1521 will be reflected off the reflector 1521 to form a focused beam parallel to the center axis 1527. This arrangement is often used in "one feed per beam" systems to maximize the directivity of each beam and minimize overlap with beams formed by adjacent feeds .

FIG. 24 is an illustration of another parabolic reflector 1621. When placing antenna elements 1629 (either receive antenna elements or transmit antenna elements 406, 409, 3416, 3419, 3426, 3429) outside the focal plane (for example, in front of the focal plane 1625 of the reflector 1621), the path of the transmitted signals 1631 that reach the reflector 1621 will not be parallel to each other when they are reflected from the reflector 1621, resulting in an increase in beam width compared to a focused beam. In some cases, reflectors have shapes other than parabolic. Such reflectors can also lead to defocusing of the antenna. An end-to-end beamforming system can use this type of defocused antenna to create overlap in the coverage area of adjacent antenna elements and thus provide a large number of useful receive/transmit paths for given beam locations in the repeater coverage area.

In one case, a repeater coverage area is established where 25% of the points within the repeater coverage area are within antenna element coverage areas of at least six composite directional antenna patterns when an end-to-end repeater is deployed (e.g., an end-to-end satellite repeater is in operational orbit). Alternatively, 25% of the points within the coverage area of the repeater are within the coverage areas of at least four receive antenna elements. FIG. 25 is an illustration of an example of a repeater coverage area 3201 (for an end-to-end satellite repeater, also referred to as a satellite coverage area) (shown in single cross hatching) and an area 3203 (shown in double cross hatching) defined by points within the repeater coverage area 3201 that are also contained within zones 3205, 3207, 3209, 3211, 3213, 3215 covering six antenna elements. Coverage area 3201 and antenna element coverage areas 3205, 3207, 3209, 3211, 3213, 3215 may be either receive antenna element coverage areas or transmit antenna element coverage areas and may be associated with the forward link only or the reverse link only. The size of the coverage zones 3205, 3207, 3209, 3211, 3213, 3215 of the antenna elements is determined by the required performance to be provided by the system. A more robust system may have larger antenna element coverage areas than a less robust system. In some cases, each antenna element coverage area 3205, 3207, 3209, 3211, 3213, 3215 covers all points for which the composite directional antenna gain is within 10 dB of the maximum composite directional antenna gain for the antenna element that defines the composite beam pattern. directional antenna. Otherwise, each antenna element coverage area 3205, 3207, 3209, 3211, 3213, 3215 covers all points for which the composite directional antenna gain is within 6 dB of the maximum composite directional antenna gain. In the third case, each antenna element coverage area 3205, 3207, 3209, 3211, 3213, 3215 covers all points for which the composite directional antenna gain is within 3 dB of the maximum composite directional antenna gain. Even when the end-to-end relay has not yet been deployed (eg, the end-to-end satellite relay is not in an operational orbit), the end-to-end relay still has composite directional antenna patterns that meet the definition above. This means that the antenna element coverage areas corresponding to an end-to-end repeater in orbit can be calculated from the radiation patterns of a composite directional antenna even when the end-to-end repeater is not in operational orbit. The end-to-end repeater may include additional antenna elements that do not participate in beamforming and thus may not have the above characteristics.

FIG. 26 is an illustration of an end-to-end repeater (e.g., satellite) antenna pattern 3300 in which all of the points that are within the coverage area 3301 of the repeater (e.g., satellite coverage area) are also contained within the coverage areas 3303, 3305, 3307, 3309 of the at least four antenna elements. There may be other antenna elements on the end-to-end repeater, which may have antenna element coverage areas 3311 that do not contain all points that are within the coverage area 3301 of the repeater.

The system can operate in any suitable spectrum. For example, the end-to-end beamforming system may operate in C, L, S, X, V, Ka, Ku, or other suitable band or bands. In some such systems, the receiving means operates in C, L, S, X, V, Ka, Ku, or other suitable band or bands. In some cases, the forward uplink and reverse uplink may operate in the same frequency range (eg, around 30 GHz); and the forward downlink and reverse downlink may operate in a non-overlapping frequency range (eg, around 20 GHz). The end-to-end system may use any suitable bandwidth (eg, 500 MHz, 1 GHz, 2 GHz, 3.5 GHz, etc.). In some cases, the forward and reverse links use the same transponders.

In order to promote system clock synchronization, the lengths of the paths L of the transponders are set so that in some cases they correspond to the propagation time delays of the signals, for example, by selecting an appropriate cable length. An end-to-end repeater (eg, satellite) in some cases has a repeater (eg, satellite beacon) beacon generator 426 within the calibration support module 424 (see FIG. 15). The beacon generator 426 generates a repeater beacon signal. The end-to-end repeater broadcasts the repeater beacon signal to further assist system clock synchronization as well as maintain feeder link calibration. In some cases, the repeater beacon signal is a pseudo-random (known as PN) sequence, such as a PN direct sequence code spread spectrum signal, that travels at a high chip rate (e.g., 100, 200, 400, or 800 Mchips per second (Mchip/s) or any other suitable value). In some cases, a linearly polarized transponder (e.g., satellite) beacon broadcasts the signals received by the RHCP and LHCP antennas over a wide coverage area with an antenna, such as a horn antenna (not shown), or is coupled to one or more transponders 410 for transmission via an associated transmitter. antenna element 409. In one system example, beams are formed in a plurality of 500 MHz bandwidth channels in Ka-band, and the 400 Mchip/s PN code is filtered or pulse-shaped to fit into a 500 MHz bandwidth channel. When multiple channels are used, the same PN code may be transmitted on each of the channels. The system may use one beacon for each channel, or one beacon for two or more channels.

Since there may be a large number of signal receiving/transmitting paths in an end-to-end repeater, redundancy of individual signal receiving/transmitting paths may not be required. In the event of a failure of the receive/transmit signal path, the system may still operate at a performance level very close to its previous level, although a modification of the beamforming factors may be applied to account for losses.

Terrestrial networks

The terrestrial network of an exemplary end-to-end beamforming system comprises a number of geographically dispersed access node (AN) ground stations pointed to a common end-to-end repeater. Considering the forward link first, note that the central data processing system (CPS) calculates the beam weights for transmitting user data and communicates with the AN via a distribution network. The CPS also interacts with data sources provided to user terminals. The distribution network can be implemented in various ways, for example, using a fiber optic cable infrastructure. Synchronization between the CPS and the SAN may be deterministic (eg, using switched circuits) or non-deterministic (eg, using a packet-switched network). In some cases, the CPS is implemented at a single point, such as using application specific integrated circuits (ASICs) to control signal processing. In some cases, the CPS is implemented in a distributed manner, such as using cloud computing techniques.

As shown in the example in FIG. 5, CPS 505 may include a plurality of feeder link modems 507. For the forward link, each of the feeder link modems 507 receives live user data streams 509 from various data sources such as the Internet, a video headend (not shown), and so on. Received direct user data streams 509 are modulated by modems 507 to form K direct beam signals 511. In some cases, K may be in the range 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, or numbers in between or greater. Each of the K direct beam signals carries direct user data streams to be transmitted by one of the K direct user beams. Accordingly, if K = 400, then there are 400 direct beam signals 511, each transmitted on a respective one of the 400 direct user beams to the direct user beam coverage area 519. K direct beam signals 511 are connected to the direct beamformer.

If M ANs 515 are present in ground segment 502, the direct beamformer output is M access point specific direct signals 516, each containing weighted direct beam signals corresponding to some or all of the K direct beam signals 511. The direct beamformer may generate M access point-specific direct signals 516 based on the matrix product of the K x M matrix of direct beam weights by the K direct data signals. Distribution network 518 distributes each of the M access point-specific direct signals to a corresponding one of the M ANs 515. Each AN 515 transmits an uplink direct signal 521 containing a corresponding access node-specific direct signal 516. Each AN 515 transmits its respective direct signal 521 uplink for a repeater to one or more (eg, up to and including all) direct user beam coverage areas over one or more (eg, up to and including all) end-to-end repeater direct signal receive/transmit paths. The transponders 410, 411 within the end-to-end repeater 503 receive a combined direct signal input comprising an overlay 550 of direct uplink signals 521 transmitted by multiple (eg, up to and including all) ANs 515. Each transponder (eg, each signal receive/transmit path through relay) relays the combined input direct signal as the corresponding direct downlink signal to the user terminal 517 in the downlink in the forward direction.

FIG. 27 is an illustration of an example of an AN 515 distribution. Each of the smaller numbered circles represents the location of the AN 515. Each of the larger circles indicates a user beam coverage area 519. In some cases, the AN 515s are spaced approximately evenly across the coverage area of the end-to-end repeater 503. In other cases, the ANs 515 may be unevenly distributed across the entire coverage area. In still other cases, the AN 515s may be evenly or unevenly distributed over one or more sub-areas of the repeater's coverage area. Typically, system performance is highest when AN 515s are evenly distributed throughout the coverage area. However, factors may cause trade-offs in AN placement. For example, AN 515 can be placed based on the amount of interference, rain or other environmental conditions, property value, distribution network access, and so on. For example, for a rain-sensitive satellite-based end-to-end relay system, more ANs 515 can be placed in areas that are less likely to experience rain-induced fading (eg, the western US). As another example, AN 515s can be placed more densely in rainy areas (eg, the southeastern United States) to provide some diversity gain to counteract rain-induced fading effects. AN 515s can be placed along fiber paths to reduce distribution costs associated with AN 515s.

The number AN 515 M may be a selectable parameter that may be selected based on several criteria. Fewer ANs can result in a simpler and less costly ground segment and lower operating costs for the distribution network. With more ANs, the system will have better performance. FIG. 28 shows a simulation of the normalized throughput of the forward and reverse links as a function of the number of ANs deployed in the example system. The normalized throughput is the throughput at M AN divided by the throughput obtained at the largest number of ANs in the simulation. Throughput increases as the number of ANs increases, but does not increase indefinitely. The throughput of both the forward and reverse links approaches the asymptotic limit as the number of ANs increases. This simulation was performed with L = 517 transmit and receive antenna elements and with AN distributed uniformly over the coverage area, but this asymptotic behavior of the throughput can be observed for other values of L and other spatial distributions of AN. Curves similar to those shown in FIG. 28 can be useful in choosing M , the number of ANs to be deployed, and in understanding how system capacity can be brought into use as ANs are phased in as described previously.

FIG. 29 is a block diagram of an example ground segment 502 for an end-to-end beamforming system. FIG. 29 can be illustrated, for example, ground segment 502 of FIG. 5. Ground segment 502 includes a CPS 505, a distribution network 518, and an AN 515. CPS 505 includes a beam signal interface 524, a forward/reverse beamformer 513, a distribution interface 536, and a beam weight generator 910.

For the forward link, the beam signal interface 524 receives forward beam signals (FBS) 511 associated with each of the forward user beams. Beam signal interface 524 may include a forward beam data multiplexer 526 and a forward beam data stream modulator 528 . Forward beam data multiplexer 526 may receive forward user data streams 509 containing direct data for transmission to user terminals 517. Forward user data streams 509 may contain, for example, data packets (e.g., TCP packets, UDP packets, etc.). ) for transmission to user terminals 517 via end-to-end beamforming system 500 in FIG. 5. The forward beam data mux 526 groups (eg, multiplexes) the forward user data streams 509 into their respective forward user beam coverage areas to obtain the forward beam data streams 532. Forward beam data multiplexer 526 may use, for example, time domain multiplexing, frequency domain multiplexing, or a combination of multiplexing techniques to generate forward beam data streams 532. The forward beam data stream modulator 528 may modulate the forward beam data streams 532 according to one or more modulation schemes (eg, mapping data bits to modulation symbols) to create forward beam signals 511 that are applied to the forward/reverse beamformer 513. In some cases, modulator 528 may frequency multiplex multiple modulated signals to create a multi-carrier signal 511. Beam signal interface 524 may, for example, implement the functionality of feeder link modems 507 described with reference to FIG. 5.

The forward/reverse beamformer 513 may include a forward beamformer 529 and a backward beamformer 531. A beam weight generator 910 generates a matrix 918 of M x K forward beam weights. Techniques for generating a matrix 918 of M x K forward beam weights are described in more detail below. Forward beamformer 529 may include a matrix multiplier that calculates M access node-specific forward signals 516 (ANFS). For example, this calculation may be based on the matrix product of a matrix 918 of M x K direct beam weights and a vector of K direct beam signals 511. In some examples, each of the K forward beam signals 511 may be associated with one of the F subbands in the forward direction. In this case, forward beamformer 529 may generate samples for M access node-specific forward signals 516 for each of the F forward subbands (e.g., effectively performing a matrix product operation for each of the F subbands for respective subsets of the K forward beam signals 511 ). Distribution interface 536 distributes (eg, via distribution network 518) M access node-specific direct signals 516 to respective ANs 515.

For the reverse link, distribution interface 536 receives combined feedback signals 907 from AN 515 (eg, via distribution network 518). Each return data signal from user terminals 517 may be included in a plurality of (eg, up to and including all) combined return signals 907. A beam weight generator 910 generates a matrix 937 of K x M return beam weights. Techniques for generating a matrix 937 of K x M back-beam weights are described in more detail below. A return beam generator 531 calculates K return beam signals 915 for the K return user beam coverage areas. For example, this calculation may be based on the matrix product of a matrix 937 of the return beam weights and a vector of the respective combined return signals 907. The beam signal interface 524 may include a return beam signal demodulator 552 and a return beam data demultiplexer 554. The return beam signal demodulator 552 may demodulate each of the return beam signals to obtain K return beam data streams 534 associated with the K return user beam coverage areas. The return beam data stream demultiplexer 554 may demultiplex each of the K return beam data streams 534 into respective return user data streams 535 associated with return data signals transmitted from user terminals 517. In some examples, each of the return user beams may be associated with one of R subbands in the reverse direction. In this case, the return beamformer 531 may generate respective subsets of the return beam signals 915 associated with each of the R subbands in the reverse direction (e.g., effectively performing a matrix product operation for each of the R subbands in the return direction for the respective subsets of the return beam signals 915 ).

FIG. 30 is a block diagram of an example of forward/reverse beamformer 513. The forward/reverse beamformer 513 includes a forward beamformer 529, a forward sync module 945, a reverse beamformer 531, and a sync module 947. The forward timing module 945 associates each of the M access point-specific direct signals 516 with a timestamp (e.g., multiplexes the timestamp with the access point-specific direct signal to form a multiplexed access point-specific direct signal) that indicates when the signal should reach the end-to-end repeater. Thus, the data of K direct beam signals 511 that are separated in the separation unit 904 within the direct beam generator 529 can be transmitted at the appropriate time to each of the ANs 515. The synchronization unit 947 arranges the received signals based on timestamps. M samples of combined AN return signals (CRS) 907 are associated with timestamps indicating when particular samples were transmitted from the end-to-end relay. Synchronization issues and timestamp generation are described in more detail below.

Direct beamformer 529 includes data input 925, beam weight input 920, and access node output 923. Forward beamformer 529 applies the M x K values of the beam weight matrix to each of the K direct data signals 511 to generate M access point-specific direct signals 521, each containing K weighted direct beam signals. Direct beamformer 529 may comprise a separation module 904 and M direct weighting and summing modules 533 . Separation module 904 separates (eg, duplicates) each of the K direct beam signals 511 into M groups 906 of K direct beam signals, one group 906 for each of the M direct weighting and summing modules 533. Accordingly, each direct weighting and summing module 533 receives all K direct data signals 511 .

The forward beam weight generator 917 generates an M x K forward beam weight matrix 918 . In some cases, forward beam weight matrix 918 is generated based on a channel matrix whose elements are end-to-end direct gain estimates for each of the K x M end-to-end direct multipath channels to form a forward channel matrix, as further described below. End-to-end direct gain estimates are obtained from channel estimation module 919 . In some cases, the channel estimator includes a channel data store 921 that stores data related to various end-to-end multipath channel parameters, as described in more detail below. The channel estimator 919 outputs the estimated end-to-end gain signal to cause forward beam weight generator 917 to generate a forward beam weight matrix 918 . Each of the weighting and summing modules 533 is connected to receive respective beamforming weight vectors from the direct beam weight matrix 918 (only one such connection is shown in FIG. 30 for simplicity). The first weighting and summing module 533 applies a weight equal to the M x K element value of 1.1 M x K of the direct beam weight matrix 918 to the first of the K direct beam signals 511 (described in more detail below). A weighting factor equal to the value of element 1.2 M x K of the direct beam weight matrix 918 is applied to the second of the K direct beam signals 511. The other matrix weights are similarly applied to the K-th direct beam signal 511, which is weighted using a value equal to element 1, K M x K of the direct beam weight matrix 918 . Then, each of the K weighted direct beam signals 903 are summed and output from the first weighting and summing module 533 as an access point specific direct signal 516. Then, the access point specific direct signal 516 output by the first weighting and summing module 533, transmitted to the module 945 synchronization. Synchronization module 945 outputs the access node-specific direct signal 516 to the first AN 515 via distribution network 518 (see FIG. 5). Similarly, each of the other weighting and summing modules 533 receives the K direct beam signals 511 and performs the weighting and summing of the K direct beam signals 511. The output signals from each of the M weighting and summing modules 533 are transmitted through the distribution network 518 to the associated M ANs 515 so that the output signal from the m th weighting and summing module is transmitted to the m th AN 515. In some cases, the timing module 945 handles jittery timings and uneven distribution network delays, as well as some other timing issues, by associating a timestamp with the data. Details of an example timing technique are provided below with respect to FIG. 36 and 37.

As a result of the application of the beam weights by the forward beamformer 529 in the ground segment 502, the signals transmitted from the AN 515 through the end-to-end repeater 503 form user beams. The size and location of the beams that can be formed may depend on the number of deployed ANs 515, the number and patterns of repeater antenna elements through which the signal passes, the location of the end-to-end repeater 503, and/or the geographic separation of the ANs 515.

With regard to the end-to-end reverse link 523 shown in FIG. 5, then a user terminal 517 within one of the user beam coverage areas 519 transmits signals up to an end-to-end repeater 503. The signals are then relayed down to the ground segment 502. The signals are received by the AN 515.

As also shown in FIG. thirty,M downlink feedback signals 527 are received usingM AN 515, and are transmitted as combined return signals 907 fromM AN 515 through the distribution network 518, and are received at the input 931 of the access node shaper 531 return beams. The 947 timing module builds the combined feedback signals fromM AN 515 with each other and outputs time-synchronized signals to the return beam generator 531. Back-beam weight generator 935 generates back-beam weights in the formK xM matrices 937 return beam weights based on information stored in the channel data store 941 within the channel estimation module 943 . The return beamformer 531 includes a beam weight input 939 through which the return beamformer 531 receives a return beam weight matrix 937 . Each ofM combined feedback signals 907 AN is transmitted to the corresponding one ofM splitter modules 539 and assigning a weighting factor within the return beam generator 531 . Each splitter and weighting module 539 splits the time-synchronized signal intoK copies 909. The splitter and weighting module 539 assigns a weighting factor to each ofK copies 909 using itemk, m K xM a return beam weight matrix 937 . More information regardingK x M the return beam weight matrix is given below. Then each set ofK weighted combined feedback signals 911 is transmitted to the module 913 combining. In some cases, the merge module 913 combineskth weighted combined feedback signal 911 output from each splitter module 539 and weight assignment. The return beamformer 531 includes a data return output 933 that outputsK return beam signals 915, each containing samples associated with one ofK return user beams 519 (for example, samples received through each ofM AN). Each ofK return beam signals 915 may comprise samples from one or more user terminals 517.K of the combined and aligned formed return beam signals 915 is transmitted to the feeder link modems 507 (see FIG. 5). It should be noted that the back-timing adjustment may be performed after splitting and weighting. Similarly, for the forward link, the forward timing adjustment may be performed prior to beamforming.

As described above, direct beamformer 529 may perform matrix product operations on the input samples of the K direct beam signals 511 to calculate M access point specific direct beam signals 516 in real time. As the beamwidth increases (eg, to support a shorter symbol span) and/or the values of K and M become large, the matrix product operation is computationally time-consuming and expensive, and the amount of computation required may exceed the capacity of a single compute node (eg, one computing server, etc.). The operations of the return beam generator 531 are similar in computational intensity. Various approaches can be used to partition the computing resources of the multiple computing nodes in the forward/reverse beamformer 513. In one example, direct beam generator 529 in FIG. 30 may be divided into separate weighting and summing modules 533 for each of the M ANs 515, which may be distributed to different computing nodes. As such, implementation considerations include cost, power consumption, scalability with respect to K , M , and bandwidth, system availability (eg, due to node failure, etc.), system upgradeability, and system delays. The above example is for a row (or column). The reverse is also possible. Other ways of grouping matrix operations can be considered (for example, division by four with [1,1 for K /2, M /2], […] computed separately and summable).

In some cases, forward/reverse beamformer 513 may include a time domain multiplexing architecture to handle beam weighting operations by time sliced beamformers. FIG. 31 is a block diagram of an example of a direct beamformer 529 comprising a plurality of time-sliced direct beamformers with demultiplexing and time domain multiplexing. The forward beamformer 529 includes a direct beamformer 3002, N time sliced direct beamformers 3006, and an access point forward multiplexer 3010.

The forward beam signal demultiplexer 3002 receives the direct beam signals 511 and demultiplexes the K direct beam signals 511 to form time sliced direct beam inputs (FTSI) 3004 for input to the N time sliced direct beamformers 3006 . For example, the forward beam signal demultiplexer 3002 routes the first subset in the time domain of samples for the K forward beam signals 511 to the first time sliced direct beamformer 3006, which generates the samples associated with the M access point specific direct signals corresponding to the first subset in the time domain. samples. The forward time sliced beamformer 3006 outputs samples corresponding to the M access point specific direct signals for the first subset in the time domain of samples by its forward time sliced beam (FTSO) output 3008 to the access point forward multiplexer 3010. The forward time sliced beamformer 3006 can output samples associated with each of the M access point specific direct signals with synchronization time information (e.g., corresponding time slice index, etc.) used by the access nodes to provide synchronization (e.g., , by pre-correction) of the corresponding access point-specific direct signals when received by the end-to-end repeater. The direct access point multiplexer 3010 multiplexes the time domain subsets of the M access point specific direct signals received via the N time sliced direct beam outputs 3008 to generate the M access point specific direct signals 516. Each of the direct beamformers 3006 with may include a data buffer, a beam matrix buffer, and a processor for beam weights that performs a matrix product operation. This means that each of the forward time sliced beamformers 3006 can perform calculations mathematically equivalent to those performed by the branching module 904 and direct weighting and summing modules 533 shown for the forward beamformer 529 in FIG. 30 during processing of samples of one time slicing index. Updating the beam weight matrix may be performed in steps. For example, the beamweight matrix buffers for the time-slice direct beamformers can be updated during off-load period by changing interval slotting indices t across the N time-slice direct beamformers 3006 . Alternatively, each time sliced forward beamformer may comprise two buffers that may be used in a ping-pong configuration (eg, one may be updated when the other is used). In some cases, multiple buffers may be used to store beam weights corresponding to multiple user beam patterns (eg, multiple user coverage areas). The beamweight buffers and data buffers for the time sliced direct beamformers 3006 may be implemented as any type of memory or storage, including dynamic or static random access memory (RAM). The beam weight processing may be implemented in an application specific integrated circuit (ASIC) and/or a user programmable gate array (FPGA) and may include one or more processor cores (eg, in a cloud computing environment). Additionally or alternatively, the beamweight buffer, the data buffer, and the processor for the beamweights may be integrated into one component.

FIG. 32 illustrates a simplified example of a ground segment showing the operation of a time sliced direct beamformer 529. In the example of FIG. 32, the forward beamformer 529 receives four direct beamformers (eg, K = 4), generates access node-specific direct signals for five ANs (eg, M = 5), and contains three time-sliced direct beamformers (eg, N = 3 ). Forward beam signals are denoted FB k : t , where k is the index of the direct beam signal and t is the time slicing index (eg, corresponding to a subset in the time domain of the samples). The forward beam signal demultiplexer 3002 receives the four time-domain subsets of the direct beam signal samples associated with the four direct user beams, and demultiplexes each direct beam signal such that one time sliced direct beam input signal 3004 includes for a particular quantization index t time subset in the time domain of samples from each of the forward beam signals 511. For example, time domain subsets may be a single sample, a contiguous block of samples, or a non-continuous (eg, interleaved) block of samples, as described below. The forward time sliced beamformers 3006 generate (eg, based on the forward beam signals 511 and forward beam weight matrix 918) each of the M access point specific direct signals for a time slice index t , which is denoted AF m : t . For example, the time-domain subsets of samples FB1 : 0, FB2 : 0, FB3 : 0, and FB4 : 0 for time slice index t = 0 are input to the first time sliced direct beamformer TSBF[1] 3006 that generates the respective samples of the access node-specific direct signals AF1 : 0, AF2 : 0, AF3 : 0, AF4 : 0 and AF5 : 0 at the direct beam output 3008 with time slice. For subsequent index values t = 1, 2, the time-slices of the time-domain subset of the samples of the direct beam signals 511 are demultiplexed by the direct beam signal demultiplexer 3002 for input to the second and third time-sliced direct beamformers 3006, which generate access node-specific direct signals. associated with the respective time slice indices t to the time slice direct beam outputs 3008 . FIG. 32 also shows that with a time slice index value t = 3, the first time slice direct beamformer generates access node-specific direct signals associated with the corresponding time slice index 3 . The matrix product operation performed by each time-slice forward beamformer 3006 for one time-slice index value t may take longer than the actual time of a subset in the time-domain of samples (e.g., the number of samples S times the sample interval t _S ). However, each time sliced direct beamformer 3006 can process only one time-domain subset of samples for each of the N time slice indices t . The direct access node multiplexer 3010 receives the direct time sliced output data 3030 from each of the time sliced forward beamformers 3006 and multiplexes the time domain subsets of samples to generate M access node specific direct signals 516 for distribution to the respective ANs.

FIG. 33 is a block diagram of an example of a return beamformer 531 comprising a plurality of time sliced return beamformers with demultiplexing and time domain multiplexing. The return beamformer 531 includes a reverse combined signal demultiplexer 3012, N time sliced return beamformers 3016, and a return beam signal multiplexer 3020. The reverse combined signal demultiplexer 3012 receives the M combined reverse signals 907 (eg, from M AN) and demultiplexes the M combined reverse signals 907 into time sliced reverse beam (RTSI) input signals 3014 for input to the N time sliced return beamformers 3016. Each of the time sliced return beamers 3016 outputs the samples associated with the K return beam signals 915 for respective subsets in the sample time domain via respective time sliced return beam (RTSO) outputs 3018 to the return beam multiplexer 3020. The return beam multiplexer 3020 multiplexes the time domain subsets of the samples for the K return beam signals received by the N time sliced return beam outputs 3018 to generate the K return beam signals 915. Each of the time sliced return beamformers 3016 may include a data buffer, a beam matrix buffer, and a beam weight processor performing a matrix product operation. This means that each of the time sliced return beamformers 3016 can perform calculations mathematically equivalent to those performed by the splitter and weight module 539 and the combiner 913 shown with the return beamformer 531 in FIG. 30 during processing of samples for one time slice index. As described above with respect to time-sliced direct beamformers, updating the beamweight matrix may be performed incrementally using a ping-pong beamweight buffer configuration (eg, one may be updated while the other is in use). In some cases, multiple buffers may be used to store beam weights corresponding to multiple user beam patterns (eg, multiple user coverage areas). The beamweight buffers and data buffers for the time sliced return beamformers 3016 may be implemented as any type of memory or storage, including dynamic or static random access memory (RAM). The beam weight processing may be implemented in an application specific integrated circuit (ASIC) and/or a user programmable gate array (FPGA) and may include one or more processor cores. Additionally or alternatively, the beamweight buffer, the data buffer, and the processor for the beamweights may be integrated into one component.

FIG. 34 illustrates a simplified example of a ground segment showing the operation of a return beamformer 531 that employs time domain multiplexing. In the example of FIG. 33, a return beamformer 531 receives five combined returns (eg, M = 5), generates return beam signals (RBS) for four user returns (eg, K = 5), and contains three time-sliced return beamformers (eg, N = 3). The combined feedback signals are denoted RC m : t , where m is the AN index and t is the time slicing index (eg, corresponding to a subset in the time domain of the samples). The de-combined signal demultiplexer 3012 receives the four time-domain subsets of the combined return signals from the five ANs and demultiplexes each combined return signal such that one time-sliced return-beam input 3014 includes, for a particular time-slice index t, the corresponding time-slice subsets. sample areas from each of the combined feedback signals 907. For example, time domain subsets can be a single sample, a contiguous block of samples, or a non-continuous (eg, interleaved) block of samples, as described below. The time sliced return beamformers 3016 generate (eg, based on the combined returns 907 and the return beam weight matrix 937) each of the K return beam signals for time slice index t , which denote RB k : t . For example, the time-domain subsets of samples RC1 : 0, RC2 : 0, RC3 : 0, RC4 : 0, and RC5 : 0 for the time slice index t = 0 are input to the first time sliced return beamformer 3016, which generates the corresponding samples of the return beam signals RB1 : 0, RB2 : 0, RB3 : 0 and RB4 : 0 to the time sliced return beam output 3018. For subsequent index values t = 1, 2, the time-slicing subsets of the time-domain subsets of the combined return signal samples 907 are demultiplexed by the inverse combined signal demultiplexer 3012 for input to second and third time-slice return beamformers 3016, respectively, which generate samples for the return beam signals. associated with the respective time slice indices t to the time slice return beam outputs 3018. FIG. 34 also shows that, at a value of t =3 of the time slice index, the first time slice return beamformer generates samples of the return beam signals associated with the corresponding time slice index 3 . The matrix product operation performed by each time-slice return beamformer 3016 for one time-slice index value t may take longer than the real time of a subset in the time-domain of samples (e.g., number of samples S times sample interval t _S ). However, each time sliced return beamer 3016 can process only one subset in the time domain of samples of each of the N time slice indices t . The return beam multiplexer 3020 receives the time sliced return beam outputs 3018 from each of the time sliced return beam generators 3016 and multiplexes the time domain subsets of the samples to generate K return beam signals 915.

Although FIG. 31-34 illustrate the same number N of time sliced forward beamformers 3006 and time sliced return beamformers 3016, some implementations may use more or fewer time sliced forward beamformers 3006 than time sliced return beamformers 3016. In some examples, the forward beamformer 529 and/or the return beamformer 531 may have a bandwidth reserve to provide node resiliency. For example, if each direct time slicer 3006 spends t _FTS processing one set of samples for a time slice index t having a real time slice duration t _D , where t _FTS = N ∙ t _D , the forward beam generator 529 may comprise N + E shapers 3006 direct beams with time slicing. In some examples, each of the N+E direct time sliced beamformers 3006 is used in operation, with each direct time sliced beamformer 3006 having an effective additional power of E / N . If one direct time sliced beamformer 3006 fails, operations can be transferred to another direct time sliced beamformer 3006 (e.g., by adjusting the routing of time domain samples (or groups of samples) through demultiplexing and time domain multiplexing) . Thus, the direct beamformer 529 can be fault tolerant of up to E of the time sliced direct beamformers 3006 before it starts to affect system performance. In addition, the extra power allows time sliced beamformers to be maintained and upgraded while the system is running. For example, upgrading time sliced beamformers can be done incrementally as the system can operate with time sliced beamformers of varying performance. The data samples associated with the time slicing index t may be interleaved. For example, the first time slicing index t ₀ may be associated with samples 0, P, 2P. . . (S - 1) * P, and the second time slicing index t ₁ can be associated with samples 1, P + 1, 2P + 1. . . (S - 1) * P + 1, etc., where S is the number of samples in each set of samples and P is the duration of the interleave. Also, interleaving can make the system more robust to time sliced beamformer failures because each block of time sliced beamformer samples is separated in time such that errors due to a missing block are distributed over time, which is similar to the benefit of using forward equalization interleaving. errors. In fact, the distributed errors caused by the failure of the time sliced beamformer may cause noise-like effects and not lead to any errors in the user data, especially if direct error coding is applied. Although examples have been illustrated where N = 3, other values of N may be used, and N does not necessarily have any particular relationship to K or M.

As described above, the forward beamformer 529 and the return beamformer 531 illustrated in FIG. 31 and 33, respectively, can perform demultiplexing and time domain multiplexing for time sliced beamforming for one channel or subband. By using an additional subband multiplexing/demultiplexing switching layer, a plurality of subbands can be processed independently. FIG. 35 is a block diagram of an example of a multiband forward/reverse beamformer 513 that uses demultiplexing and subband multiplexing. The multiband forward/reverse beamformer 513 may support F forward subbands and R reverse subbands.

The multi-band forward/reverse beamformer 513 comprises F forward subband beamformers 3026, R reverse subband beamformers 3036, and a subband multiplexer/demultiplexer 3030. For example, direct beam signals 511 may be divided into F direct subbands. Each of the F forward subbands may be associated with a subset of the K direct user beam coverage areas. This means that the K direct user beam coverage areas may include a plurality of subsets of direct user beam coverage areas associated with different (e.g., different frequency and/or polarization, etc.) subbands, where the direct user beam coverage areas within each of the subsets may be non-overlapping (eg, in 3 dB signal contours, etc.). Thus, each of the direct subband beamformer inputs 3024 may include a subset K ₁ of the direct beam signals 511. Each of the F direct beamformers 3026 may have the functionality of a direct beamformer 529, generating direct subband beamformer outputs 3028 that contain M access node-specific direct signals associated with a subset of forward beam signals 511 (e.g., a matrix product of K ₁ signals direct beam and M x K ₁ direct beam weight matrix). Thus, each of the ANs 515 can receive a plurality of access node-specific direct signals associated with different subbands (eg, for each of the F direct subbands). ANs may combine (eg, sum) signals in different subbands in direct uplink signals, as described in more detail below. Similarly, ANs 515 may generate multiple combined return signals 907 for R different reverse subbands. Each of the R return subbands may be associated with a subset of the K return user beam coverage areas. This means that the K return user beam coverage areas may include a plurality of subsets of return user beam coverage areas associated with different frequency subbands, where the return user beam coverage areas within each of the subsets may be non-overlapping (e.g., in signal level contours 3 dB, etc.). The subband multiplexer/demultiplexer 3030 may separate the combined return signals 907 into R input signals 3034 of the reverse subband beamformer. Then, each of the reverse subband beamformers 3036 may generate a reverse subband beamformer output 3038, which may include return beam signals 915 for a subset of return user beams (e.g., for feeder link modems 507 or a return beam signal demodulator, etc.). .). In some examples, the multiband forward/return beamformer 513 may support multiple types of polarization (eg, right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), etc.), which in some cases may actually double the number of subbands.

In some cases, time-slice multiplexing and demultiplexing for forward beamformer 529 and return beamformer 531 (e.g., using forward beam signal demultiplexer 3002, access point direct signal multiplexer 3010, reverse combined signal demultiplexer 3012, return beam signal multiplexer 3020), and subband multiplexing/demultiplexing (subband multiplexer/demultiplexer 3030) can be performed by packet switching (eg, by switching in an Ethernet network, etc.). In some cases, time-slicing and sub-band switching may be performed in the same switching nodes or in a different order. For example, a switching matrix architecture may be used, where each node of the switching matrix may be connected to a subset of ANs 515, forward time sliced beamformers 3006, reverse time sliced beamformers 3016, or feeder link modems 507. The switch fabric architecture may allow, for example, any AN to be connected (eg, via switches and/or switch matrix backplane) to any forward time sliced beamformer or backward time sliced beamformer in a low latency hierarchical flat architecture. In one example, a system supporting bandwidths K ≤ 600, M ≤ 600, and 500 MHz (eg, per subband) with fourteen subbands for the forward or reverse links can be implemented using a commercially available 2048-port 10GigE switching platform.

Delay Correction

In some cases, the differences in propagation delays along each path between end-to-end relay 503 and CPS 505 are not significant. For example, on the reverse link, when the same signal (eg, data transmitted to or from a particular user) is received by multiple ANs 515, each signal instance may arrive at the CPS being substantially consistent with every other signal instance. Similarly, when the same signal is transmitted to a user terminal 517 across multiple ANs 515, each signal instance may arrive at the user terminal 517 substantially consistent with every other signal instance. In other words, the signals can be phase- and time-matched with sufficient accuracy that the signals are coherently combined such that the propagation delay and beamforming effects are small relative to the symbol rate. As an illustrative example, if the difference in signal propagation delay is 10 microseconds, the beamforming bandwidth can be in the order of tens of kHz, and a narrowband signal, for example ≈ 10 kbit/s, can be used, with possible slight performance degradation. A signal rate of 10 kbps corresponds to a symbol length of 100 microseconds, and a delay spread of 10 microseconds is only one tenth of the symbol length. In these cases, for purposes of system analysis, it can be assumed that signals received by the end-to-end relay at one point in time will be relayed and transmitted at essentially the same time, as described previously.

In other cases, there may be a significant difference in propagation delay with respect to the transmission interval (transmitted symbol length) of the signals transmitted by the transmitting antenna elements 409 to the AN 515. Significant delay variations may occur as the signals from each AN 515 travel through the distribution network 518. . In these cases, a delay correction can be applied to match the propagation delay values.

The end-to-end reverse link signals received by CPS 505 via distribution network 518 can be time-aligned using a relay beacon transmitted from an end-to-end relay, such as a PN beacon, as described previously. Each AN 515 can create a timestamp of the combined return signal using the repeater beacon signal as a reference. Thus, different ANs 515 may receive the same signal at different times, but the signals received at each AN 515 may be timestamped to allow CPS 505 to correlate them in time. The CPS 505 may buffer the signals such that beamforming is performed by combining signals having the same timestamp.

As shown in FIG. 33 and 34, delay correction for the reverse link may be performed by demultiplexing the combined return signals for the time sliced return beamformers 3016. For example, each AN may partition the combined feedback into sets of samples associated with time slice indices t , which may include interleaved samples of the combined feedback. The time slicing indices t may be determined based on the repeater beacon signal. The ANs may send subsets of samples multiplexed with respective time slice indices t (eg, as a multiplexed combined return signal) to the return beamformer 531, which may be used as reverse link timing information. Subsets of samples from each AN may be demultiplexed (eg, by switching), and one time sliced return beamformer 3016 may receive subsets of samples from each AN for time slice index t (in some cases, for one of the multiple subbands). By performing a matrix product operation on the return beam weight matrix and a subset of samples from each of the M combined return signals associated with the time slice index t, the time slice return beam generator 3016 can at the same time match the signals relayed by the end-to-end relay to apply return beam weight matrices.

For the forward link, the beamformer 513 within the CPS 505 may generate a timestamp that indicates when each access node-specific forward signal transmitted by the AN 515 should reach the end-to-end relay 503. Each AN 515 may transmit the access node beacon signal 2530, for example looped PN signal. Each such signal may be looped back to the AN 515 by the end-to-end relay 503. The ANs 515 may receive both the relay beacon signal and relayed (loopback) access node beacon signals from any or all of the ANs. The received access point beacon timing relative to the repeater beacon timing indicates when the access point beacon has reached the end-to-end repeater. If you adjust the timing of the access point beacon signal so that, after being relayed by the end-to-end repeater, it reaches the AN at the same time as the beacon signal reaches the AN repeater, the access point beacon signal will arrive at the end-to-end repeater in synchronism with the repeater beacon signal. After performing this function on all ANs, all access node beacon signals will arrive at the end-to-end repeater in synchronism with the repeater beacon signal. The final step in the process is for each AN to transmit its access node-specific direct signals in synchronization with its access node beacon signal. This can be done with timestamps, as described later. Alternatively, the CPS may control the delay correction by sending appropriate access node-specific forward signals, offset by appropriate time domain offsets, to the AN (eg, if the synchronization via distribution network is deterministic).

FIG. 36 is an illustration of the PN sequences used to map timing in the system. The horizontal axis on the figure reflects time. PN sequence 2301 AN ₁ of chips 2303 is transmitted in the access node beacon signal from the first AN. The relative time this sequence reaches the end-to-end relay is shown by the PN sequence 2305. There is a time offset of the PN sequence 2305 relative to the AN ₁ PN sequence 2301 due to propagation delay from the AN to the end-to-end relay. The relay beacon PN sequence 2307 is generated within the end-to-end relay and transmitted from it in the relay beacon signal. The PN signal element of the PN sequence 2307 of the relay beacon at time T ₀ 2315 is matched with the PN signal element 2316 of the PN received signal 2305 AN ₁ at time T ₀ . The PN signal element 2316 of the PN received signal 2305 AN ₁ is matched with the PN signal element 2315 of the PN sequence 2307 of the repeater beacon when the correct transmission time value for AN ₁ is adjusted. The PN sequence 2305 is looped back from the end-to-end relay and the PN sequence 2317 is received on AN ₁ . The PN sequence 2319 transmitted from the end-to-end relay in the relay beacon PN sequence is received at AN ₁ . Note that the PN sequences 2317, 2319 on AN ₁ are matched, indicating that they have been matched at the end-to-end relay.

FIG. 37 shows an example of an AN ₂ where the timing of the PN sequence generated in AN ₂ is incorrectly adjusted. It should be noted that the PN sequence 2311 generated at the AN ₂ is received at the end-to-end relay, which is shown as a sequence 2309 offset by dt from the PN sequence 2307 of the repeater beacon. This offset is related to the timing error that is used to generate the sequence in AN ₂ . It should also be noted that the arrival of AN ₂ by AN ₂ PN sequence 2321 is offset relative to reaching AN ₂ 2323 by the repeater beacon PN sequence by the same amount of dt . The signal processing at AN ₂ will detect this error and correct the transmission timing by adjusting the timing by dt to match the PN sequences 2321, 2323.

FIG. 36 and 37, the same PN chip rate is used for the repeater beacon PN sequence and all (loopbacked) of the AN PN signals for ease of illustration of the concept. The concepts of the same timing can be applied at different values of the PN-chip repetition rate. As shown in FIG. 31 and 32, the time slice indices t may be used to synchronize the access node-specific forward signals received by the end-to-end relay from each of the ANs. For example, time slice indices t may be multiplexed with access node-specific direct signals 516. Each AN may transmit samples of the access node-specific direct signals with a particular time slice index t consistent with the corresponding timing information in the PN-sequence of chips transmitted in the corresponding beacon signals of the access point. Since the respective access node beacon signals have been corrected to compensate for the respective propagation delays and phase shifts between the AN and the end-to-end relay, the samples associated with the time slice index t will arrive at the end-to-end relay time-synchronized and correctly phase-matched relative to each other.

In cases where the AN receives its own access point beacon signals, it is possible to loop back the access node beacon signals using the same end-to-end relay communication equipment that also carries data in the forward direction. In these cases, the relative gains and/or phases of the transponders in the end-to-end repeater can be adjusted as described later.

FIG. 38 is a block diagram of an example AN 515. AN 515 includes a receiver 4002, a receive timing and phase adjuster 4024, a repeater beacon demodulator 2511, a multiplexer 4004, a network interface 4006, a controller 2523, a demultiplexer 4060, a transmit timing and phase canceler 4020, and transmitter 4012. Network interface 4006 may be connected to, for example, CPS 505 via network port 4008.

On the reverse link, the receiver 4002 receives the reverse downlink signal 527. The reverse downlink signal 527 may include, for example, a combination of the reverse uplink signals relayed by the end-to-end relay (eg, through multiple receive/transmit signal paths, etc.) and the repeater beacon signal. The receiver 4002 may perform downconversion and sampling, for example. The relay beacon demodulator 2511 may demodulate the relay beacon signal into a digitized composite return signal 907 to obtain relay timing information 2520. For example, the relay beacon demodulator 2511 may perform demodulation to recover the chip timing associated with the relay PN code and generate timestamps corresponding to the transmission time from the end-to-end relay for samples of the digitized combined return signal 527. The multiplexer 4004 may multiplex the timing information 2520 rebroadcast with samples of the digitized combined return signal (eg, to form a multiplexed combined return signal) to be routed to the CPS 505 (eg, via the network interface 4006). Multiplexing the relay timing information 2520 may include generating subsets of samples corresponding to time slice indices t for routing to CPS 505. For example, multiplexer 4004 may output subsets of samples associated with each time slice index t for input to the back beamforming architecture. time-slicing described above with reference to FIG. 33, 34, and 35. In some cases, multiplexer 4004 may include an interleaver 4044 to interleave samples for each subset of samples.

On the forward link, network interface 4006 may receive AN input 4014 (eg, via network port 4008). The demultiplexer 4060 may demultiplex the AN input signal 4014 to obtain the access point-specific direct signal 516 and forward signal transmission timing information 4016 indicating the transmission time for the access point-specific direct signal 516. For example, the access point-specific direct signal 516 may contain information about the timing of the transmission of the direct signal (for example, multiplexed with data samples, etc.). In one example, the access node-specific direct signal 516 contains sets of samples (eg, in data packets), where each set of samples is associated with a time slice index t . For example, each set of samples may be samples of the access node-specific direct signal 516 generated in accordance with the time sliced direct beamforming architecture described above with reference to FIG. 31, 32, and 35. Demultiplexer 4060 may include a de-interleaver 4050 for de-interleaving samples associated with time slicing indices t .

The transmit timing and phase canceler 4020 may receive and buffer the access node specific direct signal 516 and output direct uplink signal samples 4022 for transmission by transmitter 4012 at the appropriate time as direct uplink signal 521. The transmitter 4012 may perform digital-to-analog and up-conversion to output the direct uplink signal 521. The forward uplink signal samples 4022 may include an access node-specific forward signal 516 and an access node beacon signal 2530 (e.g., a looped PN signal), which may include transmission timing information (e.g., chip timing information with PN code, frame timing information, etc.). The transmit timing and phase compensator 4020 may multiplex the access node-specific direct signal 516 with the access node beacon signal 2530 such that the forward timing and phase information 4016 is synchronized with the corresponding transmit timing and phase information in the beacon signal 2530. access node.

In some examples, the generation of the access node beacon signal 2530 is performed locally in the AN 515 (eg, in the access node beacon generator 2529). Alternatively, the access node beacon signal 2530 may be generated in a separate component (eg, CPS 505) and routed to the AN 515 (eg, via network interface 4006). As described above, the access node beacon signal 2530 may be used to compensate for the forward uplink signal 521 to account for propagation differences and phase shifts between the AN and the end-to-end relay. For example, the access node beacon signal 2530 may be transmitted on the forward uplink signal 521 and relayed by the end-to-end relay, and then received again by the receiver 4002. The controller 2523 may compare the relayed transmission timing and phase information 4026 obtained (e.g., from demodulation, etc.). .d.) from the relayed beacon signal of the access point with information 4028 about the timing and phase when received, obtained (for example, during demodulation, etc.) from the beacon signal of the repeater. The controller 2523 may generate a timing and phase adjustment signal 2524 for input to the transmit timing and phase equalizer 4020 to correct the access node beacon signal 2530 to compensate for propagation delay and phase shifts. For example, access node beacon signal 2530 may contain a PN code and frame timing information (eg, one or more frame number bits, etc.). The transmit timing and phase compensator 4020 may, for example, adjust frame timing information to roughly compensate for signal propagation delay (e.g., output frame timing information in the access point beacon signal such that the relayed access point beacon signal will contain relayed frame timing information). in transmission, coarsely matched to the corresponding frame timing information in the relay beacon signal, on change of which the PN code element is considered as the least significant bit (LSB), etc.). Additionally or alternatively, the transmit timing and phase canceler 4020 may perform timing and phase adjustment on the direct uplink signal samples 4022 to compensate for the difference in timing or phase between the transmitted timing and phase information 4026 and the timing and phase information 4028. reception. For example, where the access node beacon signal 2530 is generated based on a local oscillator, timing or phase differences between the local oscillator signals and the received repeater beacon signal can be corrected by adjusting the timing and phase for the direct uplink signal samples 4022. In some examples, access node beacon demodulation is performed locally at the AN 515 (eg, by access node beacon demodulator 2519). Alternatively, demodulation of the access node's beacon signal may be performed in a separate component (eg, CPS 505) and relayed transmission timing and phase information 4026 may be obtained in another transmission (eg, via network interface 4006). For example, deep fading can make it difficult to receive and demodulate the AN's own relayed beacon signal unless the transmission is at a higher power than another signal transmission, which can result in lower power budget for communication signals. Thus, combining the reception of the relayed access point beacon signal from multiple ANs 515 can increase the effective received power and demodulation accuracy for the relayed access point beacon signal. Thus, demodulation of the access point beacon signal from one AN 515 may be performed using downlink signals received at multiple ANs 515. Demodulation of the access point beacon signal may be performed at CPS 505 based on combined return signals 907, which may also contain about the signal for access point beacon signals from most or all AN 515. If necessary, end-to-end beamforming for access point beacon signals can be performed considering access point beacon uplinks (eg, C _r ), repeater loopback (eg, E ), and /or access node beacon downlinks (eg, C _t ).

Elimination of distortion in the feeder line

In addition to delay correction in the signal paths to the end-to-end repeater from all ANs, phase shifts induced by the feeder links can be eliminated before beamforming. The phase shift of each of the links between the end-to-end repeater and M AN will be different. Reasons for different phase shifts for each link include, without limitation, signal path length, atmospheric conditions such as scintillation, Doppler frequency shift, and different AN oscillator errors. These phase shifts are essentially different for each AN and change over time (due to scintillation, Doppler shift and different AN oscillator errors). By eliminating dynamic distortion in the feeder link, the rate of adaptation of the beam weights can be slower than in the alternative where the adaptation of the beam weights is fast enough to track the dynamics of the feeder link.

In the reverse direction, downlink distortion at the AN is common to both the repeater beacon PN and user data signals (eg, reverse downlink signals). In some cases, coherent PN demodulation of the repeater beacon provides channel information that is used to eliminate most or all of these distortions from the return data signal. In some cases, the PN signal of the relay beacon is a known PN sequence that is constantly transmitted and is within the range of the data sessions. The equivalent (or effective) isotropically radiated power (EIRP) of this in-band PN signal is set so that the interference in these communications does not exceed the maximum allowable level. In some cases, the feeder link debuffing process for the reverse link includes coherent demodulation and tracking the timing and phase of the received repeater beacon PN signal. For example, the repeater beacon demodulator 2511 may determine receive timing and phase adjustments 2512 to compensate for feeder link distortion based on a comparison of the repeater beacon PN signal with a local reference signal (eg, local oscillator or PLL). The resulting timing and phase differences in the reverse downlink signal are then eliminated (eg, by the receive timing and phase adjuster 4024), thereby removing feeder link distortion from the communication signal (eg, reverse downlink signals 527). After feeder link distortion is removed, the reverse link signals from the beam will have a common frequency error across all ANs and are thus suitable for beamforming. The total frequency error may include, without limitation, user terminal frequency error fractions, user terminal uplink Doppler shift, end-to-end repeater frequency conversion error, and repeater beacon frequency error PN.

In the forward direction, the access point beacon signal from each AN may be used to provide uplink de-aliasing. The uplink distortion will be superimposed on the forward link data (eg, access point-specific signal) as well as the access point beacon signal. Coherent demodulation of the access point beacon signal can be used to obtain timing and phase differences of the access point beacon signal (eg, relative to the repeater beacon signal). The resulting timing and phase differences are then removed from the transmitted beacon signal of the access point so that the received beacon signal of the access point is in phase with the beacon signal of the repeater.

In some cases, the forward link de-distortion process is a phase locked loop (PLL) system with a propagation delay from the AN to the end-to-end repeater and back within the loopback design. In some cases, the round trip delay from the AN to the end-to-end repeater and back to the AN can be significant. For example, a geosynchronous satellite operating as an end-to-end relay will generate a round trip delay of approximately 250 milliseconds (ms). A very narrow loop bandwidth can be used to keep this loop stable in the presence of a large delay. With a delay of 250 ms, the PLL closed-loop bandwidth can typically be less than one Hz. In such cases, high stability oscillators at both the satellite and the AN can be used to maintain reliable phase lock, as indicated by block 2437 in FIG. 39 (see below).

In some cases, the access point beacon signal is a burst signal that is transmitted only during calibration intervals. No session data is transmitted during the calibration interval to eliminate this interference in the access point's beacon signal. Since no session data is transmitted during the calibration interval, the transmit power of the access node's beacon signal may be high compared to what would be needed when the session data was transmitted. This is because there is no problem of interfering with the session data (there is no session data at this time). This technique provides a high signal-to-noise ratio (SNR) for the access point beacon signal when it is transmitted during the calibration interval. The frequency of use of calibration intervals is the reciprocal of the time elapsed between calibration intervals. Because each calibration interval provides a phase sample for the PLL, this calibration frequency is the sample rate of that discrete-time PLL. In some cases, the sampling rate is high enough to maintain the bandwidth of a closed PLL with little information distortion. The product of the calibration frequency (loop sampling rate) and the calibration interval is the fraction of time that the end-to-end repeater cannot be used for these communications without additional interference from the channel probe signal. In some cases, values less than 0.1 are used, and in some cases values less than 0.01 are used.

FIG. 39 is a block diagram of an example 2409 AN transceiver. Input 2408 of AN transceiver 2409 receives reverse link end-to-end signals received by AN 515 (eg, for one of a plurality of subbands). Input 2408 is connected to input 2501 of downconverter (D/C) 2503. Output D/C 2503 is connected to analog-to-digital converter (A/D) 2509. Output A/D 2509 is connected to time controller 2515 when receiving Rx and/or regulator 2517 phase Rx. The Rx receive timing controller 2515 and the Rx phase controller 2517 can illustrate aspects of the timing and phase controller 4024 in FIG. 38. The D/C 2503 is a quadrature buck converter. Accordingly, the D/C 2503 provides in-phase and quadrature output signals to the A/D 2509. The received signals may include communication signals (eg, a combination of reverse uplink signals transmitted by user terminals), access point beacon signals (eg, transmitted by those same AN and/or other ANs) and the repeater beacon signal. The digital samples are transmitted to the demodulator 2511 of the repeater beacon signals. The relay beacon demodulator 2511 demodulates the relay beacon signal. In addition, the relay beacon demodulator 2511 generates a time control signal 2513 and a phase control signal 2514 to eliminate distortion in the feeder link based on the received relay beacon signal. Such distortions include Doppler shift, AN frequency error, scintillation effects, changes in signal path length, and so on. When performing coherent demodulation of the repeater beacon signal, a phase locked loop (PLL) system can be used to eliminate most or all of these errors. Error correction in the repeater beacon signal also corrects the corresponding errors in the communication and access point beacon signals on the feeder link (eg, because such errors are common to the repeater beacon signal, access point beacon signals, and communication signals). After the feed-link distortion has been removed, the end-to-end reverse link communication signal from the user terminal 517 nominally has the same frequency error at each of the M ANs 515. This total error includes the user terminal frequency error, user link Doppler, end-to-end repeater frequency conversion error and the frequency error of the repeater beacon signals.

The digital samples that have the feeder link distortion removed are passed to multiplexer 2518, which may be an example of multiplexer 4004 in FIG. 38. Multiplexer 2518 associates (eg, via timestamps) the samples with relay timing information 2520 from relay beacon demodulator 2511. The output of the multiplexer 2518 is connected to the output port 2410 of the transceiver 2409 AN. Output port 2410 is connected to multiplexer 2413 and through interface 2415 (see FIG. 40) to CPS 505. CPS 505 can then use the timestamps associated with the received digital samples to match the digital samples received from each of the ANs 515. Additionally, or alternatively, feeder link de-aliasing can be performed at CPS 505. For example, digital samples of reverse link end-to-end signals with repeater beacon turned on can be routed from AN 515 to CPS 505, and CPS 505 can use timing information (e.g., on repeater beacon signal) in each of the combined return signals to determine appropriate adjustments for the respective combined return signals to compensate for downlink channel impairment.

The access node beacon signal 2530 may be generated locally by the access node beacon generator 2529 . The access node beacon demodulator 2519 demodulates the access node beacon signal received by the AN 515 (eg, after being relayed by the end-to-end relay and received at input 2408). The relay beacon demodulator 2511 transmits the received relay timing and phase information signal 2521 to the controller 2523. The controller 2523 also receives a relayed signal 2525 with timing and phase information when transmitted from the access node beacon demodulator 2519. The controller 2523 compares the received relay timing and phase information with the relayed transmission timing and phase information and generates a coarse timing signal 2527 . The coarse time signal 2527 is transmitted to the beacon generator 2529 of the access node. The access point beacon generator 2529 generates an access point beacon signal 2530 with embedded transmission timing information to be transmitted from the AN 515 to the end-to-end repeater 503. As mentioned in the description above, the difference between the timing information and the phase of the repeater (included in the beacon signal repeater) and transmission time and phase information (included in the access point beacon signal) are used to correct the transmission timing and phase information to synchronize the relayed transmission timing and phase information with the received timing and phase information of the repeater. The coarse time is corrected by a signal 2527 to the access node beacon generator 2529, and the fine time is corrected by a signal 2540 to the transmit time (Tx) controller 2539. Using the relayed timing and phase information 2525, when transmitted from the access node beacon demodulator 2519, synchronized with the received repeater timing and phase information 2521, the access node beacon generator 2529 generates timestamps 2531 that facilitate synchronization of the access node beacon signal 2530 and transmitted access point-specific direct signal from the CPS 505. This means that the data samples from the CPS 505 are received on the input port 2423 along with timestamps 2535 that indicate when the associated data samples should reach the end-to-end relay 503. Buffering module 2537, time synchronization and summation buffers the data samples transmitted from the CPS 505 and sums them with the samples from the access node beacon generator 2529 based on time stamps 2535, 2531. PN samples and session data samples with identical time values, denoted by timestamps, are added to each other. In this example, the multiple beam signals (x _k (n) * b _k ) are added to each other in the CPS 505, and the access node-specific direct signal containing the combination of the multiple beam signals is sent to the AN by the CPS 505.

When the data samples are properly matched at the AN, they arrive at the end-to-end relay 503 at the required time (eg, at the same time that the same data samples are received from other ANs). The controller 2539 time when transmitting performs adjustments to the exact time based on the output signal 2540 controller of the exact time from the module 2523 time controller. The phase adjuster 2541 during transmission performs signal phase adjustments in response to the phase control signal 2542 generated by the beacon demodulator 2519 of the access node. The transmit timing adjuster 2539 and transmit phase adjuster 2541 may illustrate, for example, aspects of the timing and transmit phase compensator 4020 in FIG. 38.

The output of the transmit phase controller 2541 is connected to the input of a digital-to-analog converter (D/A) 2543. The quadrature analog output from D/A 2543 is connected to a boost converter (U/C) 2545 to be transmitted by the HPA 2433 (see FIG. 40) to the end-to-end repeater 503. The amplitude control signal 2547 provided by the access point beacon demodulator 2519 provides amplitude feedback at U/C 2545 to compensate for phenomena such as uplink signal fading due to rain.

In some cases, the PN code used by each AN for the access node beacon signal 2530 is different from the code used by each other AN. In some cases, each of the PN codes in the access point beacon signals is different from the repeater PN code used in the repeater beacon signal. Accordingly, each AN 515 may be able to distinguish its own access point beacon signal from those of other ANs 515. ANs 515 may be able to distinguish between their own access point beacon signal and the repeater beacon signal.

As previously described, an end-to-end gain link from anywhere in the coverage area to any other point in the coverage area is a multipath channel with L different paths, which can result in very deep signal fading for some point-to-point channels. Transmit (forward link) diversity and receive (reverse link) diversity are very effective in reducing deep signal fading and maintaining communication system performance. However, there is no transmit/receive diversity for access node beacon signals. As a result, the point-to-point link of the looped signal, which is the signal transmitted from the AN back to the same AN, can have end-to-end gains that are much lower than average. Values 20 dB below average can occur in a large number of signal paths ( L ). These slightly lower end-to-end gains result in reduced SNR for these ANs and can make link connection difficult. Accordingly, in some cases, higher gain antennas are used in the AN. Alternatively, as shown in the example of the transponder in FIG. 16, a phase adjuster 418 may be included in each of the signal receive/transmit paths. The phase controller 418 may be independently controlled by a phase shift controller 427 (eg, controlled via a telemetry, tracking and control (TT&C) link from a ground control center). Relative phase correction can be effective in increasing the end-to-end gains of low-gain looped paths. For example, the goal may be to select phase shift settings to increase the loopback gain value corresponding to the most severe conditions (gain from AN and back). It should be noted that phase selection does not substantially change the distribution of gains when estimating all points in the coverage area to all other points in the coverage area, but may increase the gains in low gain looped paths.

To work this out, consider a set of gains from each of the M AN 515s to all the other AN 515s. There are M ² gains, only M of which are looped paths. Consider two options for the distribution of gains, the first is the overall distribution for all paths ( M ² ), which can be estimated by compiling a histogram for all M ² paths. For ANs uniformly distributed throughout the coverage area, this distribution can be indicative of the distribution of end-to-end gain from any point to any other point in the coverage area. The second distribution is the loopback gain distribution (ring distribution), which can be estimated by plotting a histogram for only the M looped paths. In many cases, the user's choice of phase parameters of the receive/transmit signal path (and optional gain settings) does not provide a significant change in the overall distribution. This is especially the case for random or interleaved transmission-to-receiver mappings. However, in most cases, the ring distribution can be improved with user-selectable (as opposed to random) phase (and optionally gain) settings. This is because the set of ring gain values consists of M paths (as opposed to the total number of M ² paths), and the number of degrees of freedom in phase and gain correction is L . Often, L is of the same order as M , which allows for much higher loop gains with low gains through custom phase selection. Another way of looking at this is that choosing a custom phase does not necessarily eliminate low end-to-end gain values, but instead moves them from a ring gain set ( M elements in the set) to a non-ring gain set ( M ² - M elements). For non-trivial values of M, the larger set is often much larger than the first.

AN 515 may handle one or more subbands. FIG. 40 is a block diagram of an example of AN 515 in which processing on multiple subbands is performed separately. On the end-to-end reverse link 523 (see FIG. 5), the AN 515 receives reverse downlink signals 527 from the end-to-end repeater 503 through a low noise amplifier (LNA) 2401. The amplified signals are transmitted from the LNA 2401 to a power divider 2403. The power divider 2403 divides the signal into multiple output signals. Each signal is output to one of the output ports 2405, 2407 of the power divider 2403. One of the output ports 2407 can be used as a test port. Other ports 2405 are connected to the input 2408 of the corresponding one of the many transceivers 2409 AN (only one shown). AN transceivers 2409 process the signals received in the respective subbands. The 2409 AN transceiver performs several functions detailed above. The outputs 2410 of the transceivers 2409 AN are connected to the input ports 2411 of the multiplexer 2413 subband. The outputs are combined in a sub-band multiplexer 2413 and output to a distribution network interface 2415. Interface 2415 provides an interface for data to or from the AN 515 and to or from the CPS 505 over the distribution network (see FIG. 5). Subband processing may have the advantage of reducing the performance requirements for the RF components used to implement the end-to-end repeater and AN. For example, when dividing the 3.5 GHz bandwidth (which, for example, may be used in a Ka-band system) into seven sub-bands, each sub-band is only 500 MHz wide. This means that each of the access point-specific direct signals may include multiple sub-signals associated with different sub-bands (e.g., associated with different subsets of direct user beam coverage areas), and the AN transceivers 2409 may up-convert the sub-signals for different carrier frequencies. This division of the bandwidth may allow the use of components with a tighter tolerance, since fluctuations in amplitude and phase in different subbands can be compensated for with separate beamforming, calibration, etc. weights. for different subbands. Of course, other systems may use a different number of subbands and/or test ports. In some cases, a single subband may be used and some components shown herein may be missing (eg, power divider 2403 and multiplexer 2413 may be omitted).

On the through forward link 501, data is received from the CPS 505 via an interface 2415. The received data is passed to an input 2417 of a subband demultiplexer 2419. The subband demultiplexer 2419 separates the data into multiple data signals. The data signals are applied from the output ports 2421 of the subband demultiplexer 2419 to the input ports 2423 of the transceivers 2409 AN. The output ports 2425 transceivers 2409 AN connected to the input ports 2427 module 2429 summation. Module 2429 summation sums the signals issued by the seven transceivers 2409 AN. From the output port 2431 of the summing module 2429, the output signal of the summing module 2429 is transmitted to the input port 2433 of the high power amplifier 2435 (HPA). The output of the HPA 2435 is connected to an antenna (not shown) that provides output signals to an end-to-end repeater 503. In some cases, an ultra stable oscillator 2437 is connected to the AN transceivers 2409 to provide a stable frequency reference source.

Beam Weight Calculation

As shown in FIG. 8, which is an example of the description of signals on the reverse link, the mathematical model of the end-to-end reverse link can be used to describe the communication link as follows:

УР. 1,

UR. 1,

Where

x is the K x 1 column vectors of the transmitted signal. In some cases, the square of the magnitude of each element in x is defined as one (same transmit power). In some cases, this may not be the case.

y is the K x 1 column vectors of the received signal after beamforming.

Ar is an L x K reverse uplink emission matrix. Element a _lk contains the gain and phase of the path from the reference location located in beam K to the l th (letter "el") receive antenna element 406 in the Rx array. In some cases, reverse uplink emission matrix values are stored in channel data store 941 (see FIG. 30).

E is an L x L payload matrix. Element e _ij determines the gain and phase of the signal from the j antenna element 406 in the receiving array to the i antenna element 409 in the transmitting array. In some cases, in addition to cases with random crosstalk between paths (due to the limited isolation of the electronics), the matrix E is a diagonal matrix. The matrix E can be normalized such that the sum of the squared magnitude of all elements in the matrix is L . In some cases, the payload matrix values are stored in the channel data store 941 (see FIG. 29).

Ct is an M x L reverse downlink emission matrix. Element c _ml contains the gain and phase of the path from the l th (letter "el") antenna element in the Tx matrix to the m th AN 515 among M AN 515. In some cases, the values of the reverse downlink radiation matrix are stored in the data store 941 channel (see FIG. 29).

Hret is a reverse channel matrix M x K equal to the product Ct x E x Ar .

представляет собой единичную матрицу L x L. n _ul represents noise vectorLx 1 complex Gaussian noise. Uplink noise covariance

is the identity matrixL x L.

испытано в восходящей линии связи, а

испытано в нисходящей линии связи.σ ² represents the change in noise.

tested in the uplink, and

tested in the downlink.

представляет собой единичную матрицу M x M. n _dl is the noise vector M x 1 of complex Gaussian noise. Downlink noise covariance

is the identity matrix M x M .

Bret is a K x M matrix of end-to-end reverse link beam weights.

The examples are essentially described above (eg, with reference to FIGS. 6-11) in a manner that suggests some similarities between forward and reverse end-to-end multipath channels. For example, the forward and reverse channel matrices are described above with reference essentially to M , K , E and other models. However, such descriptions are only intended to simplify the description for greater clarity and are not intended to limit the examples to only cases with identical forward and reverse configurations. For example, in some cases the same transponders are used for both forward and return traffic, and the payload matrix E may be the same for both forward and return end-to-end beamforming (and associated beam weight calculations) respectively. In other cases, different transponders are used for forward and reverse traffic, and different matrices may be used to model the respective end-to-end multipath channels and calculate the respective path weights - the payload matrix ( Efwd ) in the forward direction and the payload matrix ( Eret ) in the reverse direction. . Similarly, in some cases, the same M AN 515 and K user terminals 517 are considered part of both forward and reverse end-to-end multipath channels. In other cases, the M and K values may refer to different subsets of ANs 515 and/or user terminals 517 and/or different numbers of ANs 515 and/or user terminals 517 in the forward and reverse directions.

Beam weights can be calculated in a variety of ways to meet system requirements. In some cases, they are calculated after the end-to-end relay is deployed. In some cases, the payload matrix E is created prior to deployment. In some cases, beam weights are calculated to increase the signal-to-interference-to-noise ratio (SINR) for each beam, and they can be calculated as follows:

УР. 2, 3,

UR. 2, 3,

WhereR is the covariance of the received signal, and( * ) ^H represents the adjoint (Hermitian) operator of the transposition operation.

The k , m element of the K x M return beam weight matrix Bret provides the weights for beamforming at the m-th AN 515 from the user terminal in the k -th user beam. Accordingly, in some cases, each of the return beam weights used to generate the return user beams is calculated by estimating the end-to-end return gain factors (i.e., channel matrix elements Hret ) for each of the end-to-end multipath channels (e.g., each of the end-to-end return multipath channels).

UR. 2 will be true, where R is the received signal covariance as provided in the UR. 3. Thus, when all of the SD matrices are known. 1, 2, and 3, the beam weights used to form the through beams can be directly determined.

This set of beam weights allows you to reduce the standard error between x and y . It also makes it possible to increase the end-to-end signal-to-interference-to-noise ratio (SINR) for each of the K end-to-end reverse link signals 525 (derived from each of the K beams).

в УР. 3 представляет собой ковариацию шума нисходящей линии связи (которая некоррелирована). Второй член

в УР. 3 представляет собой ковариацию шума восходящей линии связи (которая коррелирована на AN). Третий член HH ^H в УР. 3 представляет собой ковариацию сигнала. Установка дисперсии шума восходящей линии связи в нуль и опускание последнего члена (HH ^H ) приводит к получению набора весовых коэффициентов, которые увеличивают отношение сигнал/шум в нисходящей линии связи путем согласования фазы принимаемых сигналов на каждом из M AN 515. Установка дисперсии шума нисходящей линии связи в нуль и опускание 3 члена приводит к получению набора весовых коэффициентов, что увеличивает SINR для восходящей линии связи. Установка дисперсии шумов как в восходящей линии связи, так и в нисходящей линии связи в нуль приводит к декорреляции при приеме, что увеличивает отношение мощности сигнала на несущей к помехе (C/I).First Member

in UR. 3 is the downlink noise covariance (which is uncorrelated). Second term

in UR. 3 is the uplink noise covariance (which is correlated on the AN). The third member of HH ^H in UR. 3 represents the signal covariance. Setting the uplink noise variance to zero and omitting the last term ( HH ^H ) results in a set of weights that increase the downlink signal-to-noise ratio by matching the phase of the received signals at each of the M AN 515. Setting the downlink noise variance link to zero and dropping 3 terms results in a set of weights that increases the SINR for the uplink. Setting both the uplink and downlink noise variance to zero results in decorrelation in reception, which increases the carrier-to-interference ratio (C/I).

In some cases, the beam weights are normalized so that the sum of the square of the magnitude of any Bret row is equal to one.

In some cases, the decision of the UR. 2 is determined by the presence of a priori information about the matrices Ar , Ct and E , as well as the dispersions of the noise vectors n _ul and n _dl . Information about the values of the matrix elements can be obtained from measurements performed during the manufacture and testing of the corresponding components of the end-to-end repeater. This may work in systems where the values in the matrices do not change significantly while the system is running. However, for some systems, especially those operating in high frequency bands, this possibility may not exist. In such cases, the Ar , Ct , and E matrices can be estimated after the deployment of the carrier (such as a satellite) hosting the end-to-end repeater.

In some cases, where a priori information is not used to set the weights, the decision of the UR. 2 can be determined by evaluating the R and H values. In some cases, assigned user terminals 517 at the center of each user beam coverage area 519 transmit known x signals during calibration periods. Vector adopted in AN 515:

u = H x + Ct E n _ul + n _dl 4

In one example, CPS 505 estimates R and H values based on the following relationships:

представляет собой оценку ковариационной матрицы

представляет собой оценку матрицы H канала, а

k представляет собой оценку вектора корреляции,

представляет собой сопряженное число k-го компонента вектора передачи с частотной ошибкой, возникающей при передаче в восходящей линии связи. В некоторых случаях в период калибровки обратные данные сеанса связи не передаются. Это означает, что в период калибровки по сквозной обратной линии связи передаются лишь калибровочные сигналы, которые известны AN, для обеспечения определения значения

из принятого вектора u с использованием уравнения выше. Это, в свою очередь, позволяет определить значение

. Как оценку ковариационной матрицы

, так и оценку матрицы

канала получают на основе сигналов, принятых в период калибровки.

is an estimate of the covariance matrix

is an estimate of the matrix H of the channel, and

k is the estimate of the correlation vector,

is the conjugate of the k th component of the transmission vector with the frequency error occurring in the uplink transmission. In some cases, no reverse session data is transmitted during the calibration period. This means that during the calibration period, only calibration signals that are known to the AN are transmitted on the reverse link end-to-end to ensure that the value

from the received vector u using the equation above. This, in turn, makes it possible to determine the value

. How to estimate the covariance matrix

, and an estimate of the matrix

the channel is obtained based on the signals received during the calibration period.

при наличии данных сеанса связи (например, даже если x неизвестно). Это может быть обусловлено тем фактом, что

определяется только на основе принимаемого сигнала u. Тем не менее, значение

оценивается на основе сигналов, принятых в период калибровки, в который передаются лишь калибровочные сигналы по обратной линии связи.In some cases, the CPS 505 may evaluate the covariance matrix

in the presence of session data (eg, even if x is unknown). This may be due to the fact that

is determined only on the basis of the received signal u . However, the value

is estimated based on the signals received during the calibration period, in which only calibration signals are transmitted on the reverse link.

канала, так ковариационной матрицы

выполняются, когда данные сеанса связи передаются по обратной линии связи. В этом случае ковариационную матрицу

оценивают так, как упомянуто выше. Однако значение x определяется путем демодуляции принятого сигнала. После того, как значение x стало известно, можно оценить матрицу канала, как упомянуто выше в УР. 6 и УР. 7.In some cases, estimates as matrices

channel, so the covariance matrix

are performed when session data is transmitted on the reverse link. In this case, the covariance matrix

evaluated as mentioned above. However, the value of x is determined by demodulating the received signal. Once the value of x is known, the channel matrix can be estimated as mentioned above in the EP. 6 and UR. 7.

The signal and noise components of the signal after beamforming are contained in the vector Bret H x . The signal and interference powers for each of the beams are contained in the K x K matrix Bret H . The power in the kth diagonal element Bret H is the required signal power from the beam k . The sum of the squares of the values of all elements in row k , excluding the diagonal element, is the interference power in beam k . Therefore, C/I for ray k is:

УР. 8,

UR. 8,

. k-й диагональный элемент ковариационной матрицы содержит мощность шума восходящей линии связи в луче k. Тогда отношение сигнал/шум восходящей линии связи для луча k вычисляется следующим образом:where s _kj are elements of Bret H . The uplink noise is contained in the vector Bret Ct En _ul , which corresponds to the K x K covariance matrix

. The k th diagonal element of the covariance matrix contains the uplink noise power in beam k . Then the uplink signal-to-noise ratio for path k is calculated as follows:

УР. 9,

UR. 9,

, основанная на нормализованных весовых коэффициентах лучей. Следовательно, отношение сигнал/шум для нисходящей линии связи следующее:where t _kk is the k th diagonal element of the uplink covariance matrix. The downlink noise is contained in the vector Bret n _dl , which corresponds to the covariance

, based on normalized beam weights. Therefore, the signal-to-noise ratio for the downlink is:

УР. 10

UR. 10

End-to-end SINR is a combination of UR. 8-10:

УР. 11

UR. eleven

The equations above describe how the end-to-end SINR is calculated given the payload matrix E. The payload matrix can be constructed by rationally choosing the gain and phases for each of the E elements. The gain and phase of the diagonal E elements that optimize some auxiliary metric (which is essentially a function of the SINR K of the beam according to the calculation above) can be chosen and implemented by adjusting the phase shifter 418 in each of the L transponders 411. Functions of interest include, without limitation, the sum of SINR _k (total SINR), the sum of Log(1 + SINR _k ) (proportional to the total bandwidth), or the total power in the channel matrix H. In some cases, the improvement of the auxiliary function by adjusting the gains and phases is very small and negligible. This is sometimes the case when random or interleaved antenna element mappings are used. In some cases, the auxiliary function can be improved with a non-trivial amount by user selection of the gain and phase of the received/transmitted signal.

As shown in FIG. 9, a mathematical model of the end-to-end forward link 501 may be used to describe the link 501 as follows:

УР. 12,

UR. 12,

Where

x is the K x 1 column vectors of the transmitted signal. The square of the magnitude of each element in x is defined as one (same signal strength). In some cases, unequal transmit power can be achieved by choosing forward beam weights.

y is the K x 1 column vectors of the received signal.

Cr is an L x M forward uplink emission matrix. Element c _lm contains the gain and phase of the path 2002 from the m th AN 515 to the l th (letter "el") receive antenna element 406 of the Rx array of the antenna at the end-to-end repeater 503. In some cases, the forward uplink emission matrix values are stored in channel data store 921 (see FIG. 29).

E is an L x L payload matrix. Element e _ij determines the gain and phase of the signal from the j-th element of the receiving antenna array to the i -th antenna element of the transmitting array. In all cases, with the exception of cases with random crosstalk between paths (due to the limited isolation of the electronics), the matrix E is a diagonal matrix. In some cases, the matrix E is normalized so that the sum of the squared magnitude of all elements in the matrix is equal to L . In some cases, the payload matrix values are stored in the channel data store 921 (see FIG. 29).

At is the K x L emission matrix of the forward downlink. Element a _kl contains the gain and phase of the path from the antenna element L (letter "el") in the Tx lattice of the end-to-end repeater 503 to the reference location in the user beam k . In some cases, the forward downlink emission matrix values are stored in the channel data store 921 (see FIG. 29).

Hfwd is a K x M forward channel matrix equal to the product of A _t EC _r .

n _ul is the noise vector L x 1 of complex Gaussian noise. The uplink noise covariance is:

,

,

where I _L is the L x L identity matrix.

n _dl is the noise vectorKx 1 complex Gaussian noise. The downlink noise covariance is:

,

,

where I _K is the K x K identity matrix.

Bfwd is an M x K beamweight matrix of end-to-end forward link beamweights.

The beam weights for user beam k are the entries in column k Bfwd . Unlike the reverse link, the C/I for path k is not determined using the beam weights for path k . The weights for path k determine the uplink signal-to-noise ratio (SNR) and downlink SNR, as well as the carrier power (C) in C/I. However, the interference power in beam k is determined based on the beam weights for all other beams except beam k . In some cases, the beam weight for beam k is chosen to increase the SNR. Such beam weights also increase the C/I for path k as C increases. However, interference to other beams may be generated. Thus, unlike the reverse link case, optimal beam weights are not calculated based on two beams (independently of the other beams).

In some cases, the beam weights (including the radiation and payload matrices used to calculate them) are determined after the end-to-end relay has been deployed. In some cases, the payload matrix E is created prior to deployment. In some cases, it is possible to compute a set of beam weights using interference from other beams on path k and take it as interference on path k . Although this approach does not calculate the optimal beam weights, it can be used to simplify the calculation. This allows you to define a set of weights for each beam independently of all other beams. The resulting forward beam weights are then computed similarly to the back beam weights:

, где УР. 13

, where UR. 13

УР. 14

UR. 14

в УР. 14 представляет собой ковариацию шума нисходящей линии связи (некоррелированную). Второй член

представляет собой ковариацию шума восходящей линии связи (которая коррелирована на AN). Третий член HH ^H представляет собой ковариацию сигнала. Настройка дисперсии шума восходящей линии связи в нуль и опускание последнего члена (HH ^H ) позволяют получить набор весовых коэффициентов, которые увеличивают отношение сигнал/шум в нисходящей линии связи путем согласования фазы принимаемых сигналов на M AN 515. Настройка дисперсии шума нисходящей линии связи в нуль и опускание 3 члена приводят к получению набора весовых коэффициентов, что увеличивает SINR для восходящей линии связи. Настройка дисперсии шумов как в восходящей линии связи, так и в нисходящей линии связи в нуль приводит к декорреляции при приеме, в результате чего увеличивается отношение C/I. В прямой линии связи по существу преобладают шум и помехи нисходящей линии связи. Таким образом, эти члены по существу можно использовать для вычисления весового коэффициента луча. В некоторых случаях второй член в УР. 14 (шум восходящей линии связи) незначителен по сравнению с первым членом (шум нисходящей линии связи). В таких случаях второй член может быть опущен в ковариационных расчетах, что еще больше упрощает расчет, но при этом позволяет получать набор весовых коэффициентов луча, которые увеличивают сквозное SINR.First Member

in UR. 14 is the downlink noise covariance (uncorrelated). Second member

is the uplink noise covariance (which is correlated on the AN). The third term HH ^H is the signal covariance. Setting the uplink noise variance to zero and omitting the last term ( HH ^H ) results in a set of weights that increase the downlink signal-to-noise ratio by phase-matching the received signals at M AN 515. Setting the downlink noise variance to zero and omitting 3 terms results in a set of weights that increases the SINR for the uplink. Setting the noise variance in both the uplink and downlink to zero results in receive decorrelation, resulting in an increase in C/I. The forward link is substantially dominated by downlink noise and interference. Thus, these terms can essentially be used to calculate the beam weight. In some cases, the second term in the ur. 14 (uplink noise) is negligible compared to the first term (downlink noise). In such cases, the second term can be omitted from the covariance calculations, which further simplifies the calculation while still allowing a set of beam weights that increase the end-to-end SINR.

As with the reverse link, the beam weights can be normalized. For transmitter weights distributed with the same power across all K forward link signals, each Bfwd column can be scaled such that the sum of the squared values of all elements in any column is equal to one. With equal power distribution, each of the signals has the same share of the total power AN (total power from all ANs assigned to the signal x _k ). In some cases, forward links implement unequal power distribution between the forward link signals. Accordingly, in some cases, some beam signals have a power that is greater than an equal part of the total power AN. This fact can be used to equalize the SINR across all beams, or to provide a larger SINR for more important beams than less important beams. To obtain the beam weights for unequal power distribution M x K , the beam weight matrix for equal powers Bfwd is multiplied by the K x K diagonal matrix P . Thus, the new matrix Bfwd = Bfwd P . Let's pretend that

then the square of the valuek-th diagonal element represents the power allocated to the user signal x_k. MatrixP power distribution is normalized such that the sum or square of the diagonal elements is (equal to)K (off-diagonal elements are equal to zero).

In some cases, the decision of the UR. 13 is determined by the presence of a priori information about the matrices At , Cr and E , as well as the dispersions of the noise vectors n _ul and n _dl . In some cases, information about the values of the matrix elements can be obtained from measurements performed during the manufacture and testing of the corresponding components of the end-to-end repeater. This can work well in systems where there is no significant change in the values in the matrices compared to the values measured while the system is running. However, in some systems, especially those operating in the high frequency bands, this may not be the case.

In some cases, where a priori information is not used to specify the weighting factors, the R and H values for the forward link can be estimated to determine the UR solution. 13. In some cases, a channel sounding signal is transmitted during AN calibration periods. The channel sounding signals may be of many different types of signals. In one case, each AN transmits different orthogonal and known PN sequences. The channel sounding signals may be pre-corrected in time, frequency, and/or phase to eliminate distortion on the feeder link (as described further below). During the calibration interval, all session data may be omitted to reduce interference in the channel sounding signals. In some cases, the channel sounding signals may be the same as the signals used to de-alias the feeder link.

. С использованием измерений от всех K назначенных терминалов получается оценка всей матрицы канала. Во многих случаях для улучшения оценки матрицы канала целесообразно комбинировать результаты измерений за множество интервалов калибровки. После того как получена оценка матрицы канала, оценку ковариационной матрицы

можно получить из УР. 14 с использованием значения 0 для второго члена. Эта оценка ковариационной матрицы может быть очень точной, если шум восходящей линии связи (второй член в УР. 14) пренебрежимо мал по отношению к шуму нисходящей линии связи (первый член в УР. 14). После этого весовые коэффициенты луча прямой линии связи можно вычислить с использованием оценок матрицы канала и ковариационной матрицы в УР. 13. Соответственно, в некоторых случаях вычисление весовых коэффициентов луча включает в себя оценку коэффициентов сквозного прямого усиления (т.е. значений элементов матрицы Hfwd канала) для каждого из сквозных прямых многолучевых каналов между AN 515 и опорным местоположением в зоне покрытия пользовательских лучей. В других случаях вычисление весовых коэффициентов луча включает в себя оценку коэффициентов сквозного прямого усиления для K x M сквозных прямых многолучевых каналов от M AN 515 до опорных местоположений, размещенных в пределах K зон покрытия пользовательских лучей.In a calibration interval, a terminal may be assigned at the center of each beam to receive and process channel sounding signals. Vector K x 1 u of signals received during the calibration period: u = H x + At E n _ul + n _dl , where x is the M x 1 vector of channel sounding signals transmitted. In some cases, each assigned terminal first removes the spurious frequency error (caused by Doppler and terminal oscillator error) and then correlates the received signal with each of the M known orthogonal PN sequences. The results of these correlations are M complex numbers (amplitude and phase) for each terminal, and these results are fed back to the CPS via the reverse link. The M complex numbers computed by the terminal at the center of the kth beam may be used to form the kth row of the channel matrix estimate

. Using the measurements from all K assigned terminals, an estimate of the entire channel matrix is obtained. In many cases, to improve the estimate of the channel matrix, it is advisable to combine the results of measurements over multiple calibration intervals. After the channel matrix estimate is obtained, the covariance matrix estimate

can be obtained from UR. 14 using the value 0 for the second term. This estimate of the covariance matrix can be very accurate if the uplink noise (second term in EL.14) is negligible relative to the downlink noise (first term in EL.14). Thereafter, the forward link beam weights can be computed using the estimates of the channel matrix and the covariance matrix in the UR. 13. Accordingly, in some cases, the calculation of the beam weights includes estimating the end-to-end direct gain factors (i.e., channel matrix Hfwd values) for each of the end-to-end direct multipath channels between the AN 515 and a reference location in the user beam coverage area. In other cases, the calculation of the beam weights includes estimating the end-to-end direct gains for the K x M end-to-end direct multipath channels from M AN 515 to the reference locations located within the K user beam coverage areas.

The signal and noise components of the signal after beamforming are contained in the vector H Bfwd x (the product of H , Bfwd , x ) . The signal strength and interference values for each of the beams are contained in the K x K matrix H Bfwd . The power at the k th diagonal element H Bfwd is the required signal power for beam k . The sum of the squares of the values of all elements in row k , excluding the diagonal element, is the interference power in beam k . Therefore, C/I for ray k is:

УР. 15

UR. 15

. k-й диагональный элемент ковариационной матрицы содержит мощность шума восходящей линии связи в луче k. Тогда отношение сигнал/шум восходящей линии связи для луча k вычисляется следующим образом:where s _kj are elements of HB fwd . The uplink noise is contained in the vector A _t E n _ul , which corresponds to the K x K covariance matrix

. The k th diagonal element of the covariance matrix contains the uplink noise power in beam k . Then the uplink signal-to-noise ratio for path k is calculated as follows:

УР. 16

UR. 16

. Следовательно, отношение сигнал/шум для нисходящей линии связи следующее:where t _kk is the k th diagonal element of the uplink covariance matrix. The downlink noise is contained in the vector n _dl , which corresponds to the covariance

. Therefore, the signal-to-noise ratio for the downlink is:

УР. 17

UR. 17

End-to-end SINR is a combination of UR. 15-UR. 17:

УР. 18

UR. 18

The equations above describe how the end-to-end SINR is calculated given the payload matrix E. The payload matrix can be constructed by rationally choosing the gain and phases of each of the E elements. The gain and phase of the diagonal elements E that optimize some auxiliary measure (which is essentially a function of the SINR K of the beam in accordance with the calculation above) can be selected and implemented by installing a phase shifter 418 in each of the L transponders 411. Functions of interest include, without limitation, the sum of SINR _k (total SINR), the sum of Log(1 + SINR _k ) (proportional to the total bandwidth), or the total power in the channel matrix H. In some cases, improving the auxiliary function by adjusting the gains and phases very few and insignificant. This is sometimes the case when random or interleaved antenna element mappings are used. In some cases, the auxiliary function can be improved with a non-trivial amount by user selection of the gain and phase of the received/transmitted signal.

Separate coverage areas

In some of the examples described above, we assume that the end-to-end relay 503 is configured to serve a single coverage area shared by both user terminals 517 and AN 515. satellite coverage, and both ANs and user terminals are geographically distributed throughout the satellite coverage area (eg, as in FIG. 27). The number of beams that can be formed in the satellite coverage area, as well as the dimensions (beam coverage areas) of these beams, can be affected by aspects of the design of the antenna system, such as the number and placement of antenna elements, reflector size, and so on. For example, a very high throughput implementation may involve deploying a large number of ANs (eg, hundreds) with sufficient distance between the ANs to allow end-to-end beamforming. For example, as mentioned above with reference to FIG. 28, an increase in the number of ANs can increase system capacity, although the return decreases as the number increases. When a single antenna system serves both user terminals and ANs, performing such a deployment with sufficient distance between the ANs can result in a very wide geographic distribution of the ANs (eg, over the entire satellite coverage area, as in FIG. 27). In practice, the implementation of such allocation may include placing ANs in undesirable locations, such as areas with poor access to high speed network (eg, poor fiber infrastructure back to CPS 505, crossing one or more oceans, etc.), many jurisdictions, location in expensive and/or densely populated areas, etc. Accordingly, the placement of the AN is often associated with various compromises.

Some examples of end-to-end repeater 503 are constructed with multiple antenna systems, thus providing separate service to two or more distinct coverage areas with a single end-to-end repeater 503. As described below, end-to-end repeater 503 may include at least a first antenna system that serves a coverage area. AN, and at least a second antenna system that serves the coverage area of the user. Because the user terminal and AN coverage areas are served by different antenna systems, each antenna system can be configured to conform to different design parameters, and each coverage area can be at least partially distinct (e.g., by geography, beam size, and/or beam density, frequency band, etc.). For example, using such a multi-antenna system approach may allow user terminals distributed over a relatively large geographic area (eg, throughout the US) to be served by a large number of ANs distributed over a relatively small geographic area (eg, the eastern US). For example, the AN coverage area may represent some fraction (eg, less than half, less than one quarter, less than one fifth, less than one tenth) of the user's coverage area by physical area.

FIG. 41 is an illustration of an example of an end-to-end beamforming system 3400. System 3400 is an end-to-end beamforming system that includes: a plurality of geographically distributed access nodes (ANs) 515; end-to-end repeater 3403); and a plurality of user terminals 517. The end-to-end relay 3403 may be an example of the end-to-end relay 503 described herein. ANs 515 are geographically distributed in AN coverage area 3450, and user terminals 517 are geographically distributed in user coverage area 3460. Both of the AN coverage area 3450 and the user coverage area 3460 are within the coverage area of the end-to-end repeater 3403, but the AN coverage area 3450 is different from the user coverage area 3460. In other words, the AN area is not the same as the user coverage area, but is a significant (non-trivial) area (eg, more than one quarter, half, etc. of the AN coverage area) that does not overlap with the user coverage area. For example, in some cases, at least half of the coverage area of the user does not overlap the coverage area of the AN. As described above (eg, in FIG. 5), ANs 515 may provide signals through distribution network 518 to CPS 505 within ground segment 502, and CPS 505 may be connected to a data source.

The end-to-end repeater 3403 includes a separate feeder link antenna subsystem 3410 and a user link antenna subsystem 3420. The feeder link antenna subsystem 3410 and the user link antenna subsystem 3420 are each capable of supporting end-to-end beamforming. For example, as described below, each antenna subsystem may contain its own array(s) of cooperating antenna elements, its own reflector(s), and so on. Antenna subsystem 3410 feeder link may contain an array of interacting components of the receiving elements 3416 feeder links and an array of interacting components of the transmitting elements 3419 feeder links. The user link antenna subsystem 3420 may comprise an array of user link receiving element cooperating components 3426 and an array of user link cooperating transmitter element 3429 components. The constituent elements "interact" in the sense that an array of such constituent elements has characteristics that make their respective antenna subsystem suitable for use in a beamforming system. For example, a given user link constituent receiver element 3426 may receive superimposed combined uplink return signals from multiple (eg, all) user beam coverage areas 519 in a manner that facilitates the formation of return user beams. A given user link component transmitter element 3429 may transmit a direct downlink signal such that it is superimposed on corresponding signals transmitted by other user link component transmitter elements 3429 to form some or all of the forward user beams. This constituent feederlink receiver element 3416 can receive superimposed combined direct uplink signals from multiple (eg, all) ANs 515 in a manner that facilitates direct user beams (eg, by induction of multipath at end-to-end repeater 3403). A given feederlink component transmitter element 3419 may transmit a return downlink signal such that it is superimposed on corresponding transmissions from other feederlink component transmitter elements 3419, facilitating the formation of some or all of the return user beams (e.g., by providing reception at the AN 515 combined returns that can be assigned beam weights to form user return beams).

An example of an end-to-end relay 3403 includes a plurality of forward link transponders 3430 and a plurality of reverse link transponders 3440. The transponders may be any suitable type of direct relay signal path between antenna subsystems. Each forward link transponder 3430 connects a respective one of the feeder link constituent receive elements 3416 to a respective one of the user link constituent transmit elements 3429. Each reverse link transponder 3440 connects a respective one of the user link constituent receive elements 3426 to a respective one of the feeder link constituent transmit elements 3419. For example, as described, in some examples, there is a one-to-one correspondence between each user link constituent receive element 3426 and the corresponding feeder link constituent transmit element 3419 (or vice versa), or each user link constituent receive element 3426 is connected to "one and only one"constituent transmission element 3419 of the feeder line (or vice versa), or the like. In some such cases, one side of each transponder is connected to one receive element and the other side of the transponder is connected to one transmit element. In other such cases, one or both sides of the transponder may be selectively connected (eg, by a switch or other means described below) to one of a plurality of elements. For example, end-to-end relay 3403 may include one feeder link antenna subsystem 3410 and two user link antenna subsystems 3420; and each transponder can be connected on one side to one feeder link element, and on the other side selectively connected to either one user link element of the first user link antenna subsystem 3420 or one user link element of the second user link antenna subsystem 3420 connections. In such selective connection cases, each side of each transponder at any given time may still be considered (eg, for a particular signal-related transaction) to be associated with "one and only one" element or the like.

For direct communication sessions, transmission signals from the AN 515 may be received (via feeder uplinks 521) by feeder link component receive elements 3416, relayed by forward link transponders 3430 to user link component transmitter elements 3429, and transmitted by user link component transmitter elements 3429 communications to user terminals 517 in user coverage area 3460. For feedback sessions, transmission signals from user terminals 517 may be received by user link component receiver elements, relayed by reverse link transponders 3440 to feeder link component transmitter elements 3419, and transmitted by feeder link component transmitter elements 3419 to ANs 515 in coverage area 3450 AN (via feeder downlink signals 527). The complete signal path from the AN 515 to the user terminal 517 via the end-to-end relay 3403 is referred to as the end-to-end forward link 501; and the complete signal path from the user terminal 517 to the AN 515 via the end-to-end repeater 3403 is referred to as the end-to-end reverse link 523. As described herein, the end-to-end forward link 501 and the end-to-end reverse link 523 may each contain a plurality of multipath channels for forward and reverse sessions.

In some cases, each of a plurality of geographically dispersed access nodes (eg, AN 515) contains an output of end-to-end beam-weighted direct uplink signals. An end-to-end relay (eg, end-to-end relay 3403) includes an array of cooperating feeder link receiver elements 3416 in wireless communication with distributed access nodes, an array of cooperating user link transmitter elements 3419 in wireless communication with a plurality of user terminals 517, and a plurality of forward link transponders 3430. The forward link transponders 3430 are direct relay (or no processing) transponders such that each transponder outputs a signal that matches the signal it receives with little or no processing. For example, each forward link transponder 3430 can amplify and/or frequency convert the signal it receives, but not perform more complex processing (eg, cannot demodulate and/or modulate, onboard beamforming, etc.). In some cases, each forward link transponder 3430 receives an input signal in a first frequency band (eg, 30 GHz, LHCP) and outputs in a second frequency band (eg, 20 GHz, RHCP), and each reverse link transponder 3440 receives an input signal in the first frequency band (eg 30 GHz, RHCP) and outputs in the second frequency band (eg 20 GHz, LHCP). Any suitable combination of frequency and/or polarization may be used, and the same or different frequency bands may be used for the user link and feeder link. Each forward link transponder 3430 is coupled between a respective one of the feeder link constituent receive elements 3416 and a respective one of the user link constituent transmit elements 3419 (eg, in a one-to-one correspondence). The forward link transponders 3430 convert the overlays of multiple beam-weighted direct uplink signals via the feeder link constituent receive elements 3416 into direct downlink signals (eg, combined input direct signals). The transmission of direct downlink signals by user-link component transmitter elements 3429 contributes to the formation of a direct user beam serving at least some of the plurality of user terminals 517. As described herein, direct uplink signals can be weighted across the end-to-end beam and synchronized (eg, phase-locked and optionally time-synchronized) prior to transmission from the AN 515, which can provide the desired overlap of these signals in the feeder link constituent receive elements 3416.

The transmission facilitates forward user beamforming in the sense that beamforming is end-to-end, as described herein; beamforming is the result of a variety of steps, including calculating and applying appropriate weights to direct uplink signals prior to transmission to the repeater from the AN 515, multipath induction with multiple forward link transponders 3430 of the end-to-end repeater 3403, and transmitting direct downlink signals from using the antenna array of the user's communication line. However, for purposes of simplification, some descriptions may define a direct beam as being formed by superimposing the transmitted direct downlink signals. In some instances, each of the plurality of user terminals 517 is in wireless communication with an array of cooperating user link transmitter elements 3429 to receive combined (eg, superimposed) transmitted direct downlink signals.

In some cases, the end-to-end relay 3403 further comprises an array of user link component receiver elements 3426 in wireless communication with user terminals 517, an array of cooperating feeder link transmitter element components 3419 in wireless communication with distributed ANs 515, and a plurality of reverse transponders 3440. communication lines. The reverse link transponders 3440 may be similar or identical to the forward link transponder 3430 (e.g., forward relay transponders), except that they are each connected between a respective one of the constituent receive elements 3426 of the user link and a corresponding one of the constituent transmit elements. elements 3419 feeder line. When reverse uplink signals are received by the array of cooperating user-link receiver elements 3426, reverse downlink signals are generated in reverse link transponders 3440. In some cases, each return downlink signal is a corresponding overlay of return uplink signals received by the user link constituent receiver element 3426 from a plurality of user terminals 517 (eg, from a plurality of user beam coverage areas 519). In some cases, each of the plurality of user terminals is in wireless communication with an array of cooperating user link receiver elements 3426 to transmit a corresponding reverse uplink signal to the plurality of user link receiver elements 3426.

In some instances, downlink return signals are transmitted by feeder link component transmitter element 3419 to geographically dispersed AN 515s. As described herein, each AN 515 can receive superimposed downlink composite return signals transmitted from feeder link component transmitter elements 3419. links (ie, which correspond to the return signals of the downlink). The received downlink return signals (referred to as combined receive signals) may be passed to a return beamformer, which may combine, synchronize, apply beam weights, and perform any other suitable processing. For example, the return beamformer may apply weights to the received downlink return overlays 1706 (ie, apply return beam weights to the combined returns) prior to combining the signals. The return beamformer may also synchronize the combined return signals prior to combining the signals to account for at least the appropriate propagation delay differences between the 3403 end-to-end repeater and the AN 515. from AN 515).

Due to the end-to-end nature of beamforming, the correct application of the return beamweights by the return beamformer allows return user beams to be generated even though the return beamformer may be connected to the feeder link side of end-to-end multipath channels and the user beams may be formed on the user line side. communication of end-to-end multipath channels. Accordingly, the return beamformer may be referred to as enabling user return beamforming (a number of other aspects of system 3400 also facilitate end-to-end return beamforming, such as multipath induction with reverse link transponders 3440 of end-to-end repeater 3403). However, the return beamformer may be referred to as a user return beamformer for simplicity.

In some cases, the end-to-end relay 3403 further comprises a feeder link antenna subsystem 3410 for emitting within an access node coverage area (AN coverage area 3450) within which a plurality of distributed access nodes are located. Antenna subsystem 3410 feeder link contains an array of interacting components of the receiving elements 3416 feeder link. In some cases, the end-to-end relay 3403 also includes a user link antenna subsystem 3420 for emitting in a user coverage area 3460 within which a plurality of user terminals 517 are geographically distributed (eg, in a plurality of user beam coverage areas 519). Antenna subsystem 3420 user link contains an array of interacting components of the transmitting elements 3429 user link. In some cases, the user-link antenna subsystem 3420 comprises a user-link receive array and a user-link transmit array (eg, separate half-duplex arrays of cooperating user-link constituent elements). The user link receive array and the user link transmit array may be spatially interleaved (eg, to point to the same reflector), spatially separated (eg, to point to receive and transmit reflectors, respectively), or placed in any other suitable manner. In other cases, the user link antenna subsystem 3420 comprises full duplex elements (eg, each user link component transmitter element 3429 shares a radiating design with a corresponding user link component receiver element 3426). Similarly, in some instances, the feederlink antenna subsystem 3410 comprises a feederlink receive array and a feederlink transmit array that may be spatially coupled in any suitable manner and may directly radiate, be directed to a single reflector, be directed to separate transmitters, and receiving reflectors, etc. In other cases, the feeder link antenna subsystem 3410 contains full duplex elements. The feeder link antenna subsystem 3410 and the user link antenna subsystem 3420 may have the same or different aperture sizes. In some cases, feeder link antenna subsystem 3410 and user link antenna subsystem 3420 operate in the same frequency band (eg, Ka-band, etc.). In some cases, feeder link antenna subsystem 3410 and user link antenna subsystem 3420 operate in different frequency bands (eg, feeder link uses V-band, user link uses Ka-band, etc.).

In examples, such as those illustrated in FIG. 41, AN coverage area 3450 is different from user coverage area 3460. The AN coverage area 3450 may be a single continuous coverage area or a plurality of disconnected coverage areas. Similarly (and regardless of whether the AN's coverage area is single or composed of multiple parts), the user coverage area 3460 may be a single continuous coverage area or a plurality of disconnected coverage areas. In some cases, the AN coverage area 3450 is a subset of the user's coverage area 3460. In some cases, at least half of the user coverage area 3460 does not overlap the AN coverage area 3450. As described below, in some instances, feeder link antenna subsystem 3410 further comprises one or more feeder link reflectors, and user link antenna subsystem 3420 further comprises one or more user link reflectors. In some cases, the feeder link reflector is significantly larger (e.g., at least twice as large, at least five times as large, ten times as large, fifty times as large, eighty times as large in physical area, etc.). ) than the user link reflector. In some cases, the feeder link reflector has approximately the same physical area (eg, within 5%, 10%, 25%) as the user link reflector.

In some cases, the system 3400 operates in the context of terrestrial network functions, as described with reference to FIG. 5. For example, end-to-end relay 3403 communicates with ANs 515, which communicate with CPS 505 via distribution network 518. In some cases, CPS 505 includes a forward beamformer 529 and/or a return beamformer 531, for example, as described with reference to FIG. 29. As described above, forward beamformer 529 can participate in direct through beamforming by applying calculated forward beam weights (eg, provided by forward beam weight generator 918) to forward link signals; and the return beam generator 531 may participate in the formation of return through beams by applying the calculated return beam weights (eg, provided by the return beam weight generator 935) to the reverse link signals. As described above, the end-to-end forward beam weights and/or the set of end-to-end return beam weights may be calculated in accordance with the estimated end-to-end gain factors for the end-to-end multipath channels, with each end-to-end multipath channel communicatively connecting a respective one of the allocated ANs 515 to a respective location. in a user coverage area (eg, user terminal 517 or any suitable reference location) through a respective set of forward link relay transponders 3430 and/or through a respective set of forward link relay transponders 3440. In some cases, although not shown, the end-to-end relay 3403 includes a beacon transmitter. The beacon transmitter may be implemented as described above with reference to the beacon signal generator and calibration support module 424 in FIG. 15. In some cases, a generated beacon signal may be used such that a plurality of distributed ANs 515 are connected via time synchronized wireless communication with an end-to-end repeater 3403 (e.g., via a plurality of constituent feederlink receiver elements 3416 in accordance with the beacon signal).

In some cases, the system 3400 includes a system for generating multiple direct user beams using end-to-end beamforming. In such cases, means are used to transmit a plurality of direct uplink signals from a plurality of geographically dispersed locations, wherein the plurality of direct uplink signals are formed from a weighted combination of a plurality of user beam signals, and each user beam signal corresponding to one and only one user beam. For example, the plurality of geographically distributed locations may include a plurality of ANs 515, and the means for transmitting the plurality of direct uplink signals may include some or all of the forward beamformers 529, distribution network 518, and geographically distributed ANs 515 (in communication with end-to-end repeater 3403). In such cases, means for relaying a plurality of direct uplink signals to generate a plurality of direct downlink signals may also be used. Each direct downlink signal is created by amplifying a unique overlay of a plurality of direct uplink signals, and a plurality of direct downlink signals are superimposed to form a plurality of user beams, with each user beam signal predominating within the respective user beam. For example, means for relaying a plurality of direct uplink signals to generate a plurality of direct downlink signals may include an end-to-end relay 3403 (in communication with one or more user terminals in user beam coverage areas 519) with its co-located multiple signal paths. , which may include forward link transponders 3430 and reverse link transponders 3440.

In some such cases, first means are used to receive the first overlay of a plurality of forward downlink signals and recover the first of the plurality of user beam signals. Such first means may include a user terminal 517 (eg, including a user terminal antenna and a modem or other components for recovering user beam signals from forward downlink signals). In some such cases, second means (eg, including the second user terminal 517) are also used to receive a second overlay of the plurality of direct downlink signals and recover a second one of the plurality of user beam signals. For example, the first receiving means is located within the first user beam and the second receiving means is located within the second user beam.

FIG. 42 is an illustration of an example signal path model for signals carrying reverse data on the reverse link end-to-end 523. The example model may operate similarly to the model described with reference to FIG. 6-8, except that the end-to-end relay 3403 includes reverse link signal paths 3502 for reverse link communication. Each reverse link signal path 3502 may include a reverse link transponder 3440 coupled between a user link constituent receive element 3426 and a feeder link constituent transmit element 3419. Signals originating from user terminals 517 in K user beam coverage areas 519 are transmitted (as return uplink signals 525) to an end-to-end repeater 3403, received by an array of L reverse link signal paths 3502, transmitted during a session via L transponders 3440 reverse link to L respective constituent feeder link transmission elements 3419 and are transmitted by each of the L constituent feeder link transmission elements 3419 to some or all of the M AN 515 (similar to that shown in FIG. 7). Thus, a plurality of reverse link signal paths 3502 (eg, reverse link transponders 3440) induce multipath during reverse link communication. For example, the output of each reverse link signal path 3502 is a downlink return signal 527 related to the corresponding one of the received uplink return signals 525 (e.g., related to the received combined uplink return signals 525 transmitted from a plurality of user beam coverage areas 519) and is transmitted on downlink return signals 527 to M ANs 515 (eg, geographically distributed across AN coverage area 3450). As described above, there are L (or up to L ) different ways to receive a signal from a user terminal 517 located in the user beam coverage area 519 to a particular AN 515. Thus, the end-to-end relay 3403 creates L paths between the user terminal 517 and the AN 515, collectively referred to as end-to-end reverse multipath 1908 (eg, similar to FIG. 8).

End-to-end reverse multipath channels may be modeled in a manner similar to that described above. For example, Ar is an L x K reverse uplink emission matrix, Ct is an M x L reverse downlink emission matrix, and Eret is an L x L reverse payload matrix for paths from user link constituent receive elements 3426 communication to the components of the transmission elements 3419 feeder line. As described above, the end-to-end reverse multipath channel from a user terminal 517 in a particular user beam coverage area 519 to a particular AN 515 is characterized by the network effect of L different signal paths induced by L unique reverse link signal paths 3502 through the end-to-end repeater 3403. With K user beam coverage areas 519 and M AN 515 may be provided with M x K induced end-to-end reverse multipath channels in the end-to-end reverse link 523 (via the end-to-end repeater 3403), and each may be individually modeled to calculate the corresponding M x K element of the reverse channel matrix Hret ( C _t x Eret x Ar ). As mentioned above (eg, with reference to FIGS. 6-8), not all ANs 515, user beam coverage areas 519, and/or reverse link transponders 3440 need to be part of the end-to-end reverse multipath channels. In some cases, the number of user beams K is greater than the number of transponders L in the end-to-end reverse multipath signal path and/or the number AN M is greater than the number of transponders L in the end-to-end reverse multipath signal path. As described with reference to FIG. 5, CPS 505 can provide user return beamforming by applying return beam weights to received downlink return signals 527 (received signals after AN reception are referred to as combined return signals 907, as further explained below). The return beam weights may be computed based on the M x K model of signal paths for each end-to-end reverse multipath that connects user terminals 517 in one user beam coverage area 519 to one of the plurality of ANs 515.

FIG. 43 is an illustration of an example signal path model for signals carrying direct data over the forward link 501. The example model may operate similarly to the model described with reference to FIG. 9-11, except that the end-to-end relay 3403 includes forward link signal paths 3602 for forward link sessions. Each forward link signal path 3602 may include a forward link transponder 3430 coupled between a feeder link constituent receive element 3416 and a user link constituent transmit element 3429. As described above, each direct uplink signal 521 is assigned a beamweight (eg, in the forward beamformer 515 in the CPS 505 of ground segment 502) prior to transmission from the AN 515. Each AN 515 receives a unique forward uplink signal 521 and transmits a unique direct uplink signal 521 via one of the M uplinks (eg, time synchronized). Direct uplink signals 521 are received from geographically dispersed locations (e.g., from AN 515) using some or all of the forward link transponders 3430 in a superimposed manner that allows the creation of combined direct input signals 545. Each forward link transponder 3430 simultaneously receives a combined input forward signal 545, albeit slightly different in timing due to differences in the locations of each component feeder link receiver element 3416 associated with each forward link transponder 3430. For example, although each constituent feederlink receiver element 3416 may receive a combination of the same plurality of direct uplink signals 521, the combined input direct signals 545 received may differ slightly. The combined direct input signals 545 are received by L forward link transponders 3430 via respective feeder link component receive elements 3416, transmitted during a session via L forward link transponders 3430 to L respective user link component transmitter elements 3429, and transmitted by L components by user link transmitting elements 3429 to one or more of the K user beam coverage areas 519 (eg, as a downlink direct signal 522, each associated with a respective one of the received combined direct input signals 521). Thus, a plurality of forward link signal paths 3602 (eg, forward link transponders 3430) induce multipath in forward link sessions. As described above, there are L different ways to obtain a signal from the AN 515 to a particular user terminal 517 in the user beam coverage area 519. Thus, end-to-end relay 3403 induces a plurality (eg, up to L ) of signal paths between one AN 515 and one user terminal 517 (or one user beam coverage area 519), which may be referred to collectively as an end-to-end direct multipath channel 2208 (eg, similarly FIG 10).

End-to-end forward multipath channels 2208 may be modeled in a manner similar to that described above. For example, Cr is the L x M forward uplink emission matrix, At is the K x L forward downlink emission matrix, and Efwd is the L x L forward payload matrix for paths from feeder link constituent receiving elements 3416 communication to the constituent transmitting elements 3429 of the user link. In some cases, the forward payload matrix Efwd and the reverse payload matrix Eret may be different to reflect differences between the forward link signal paths 3602 and the reverse link signal paths 3502. As described above, the end-to-end direct multipath channel from a particular AN 515 to a user terminal 517 in a particular user beam coverage area 519 is characterized by the network effect of L different signal paths induced by L unique forward link signal paths 3602 through the end-to-end repeater 3403. With K user beam coverage areas 519 and M AN 515 may be provided with M x K induced end-to-end direct multipath channels in the end-to-end forward link 501, and each of these may be individually modeled to compute a corresponding M x K element of the forward channel matrix Hfwd ( At x Efwd x Cr ). As mentioned above with reference to the reverse direction, not all ANs 515, user beam coverage areas 519, and/or forward link transponders 3430 need to be part of end-to-end forward multipath channels. In some cases, the number of user beams K is greater than the number of transponders L in the end-to-end direct multipath signal path, and/or the number AN M is greater than the number of transponders L in the end-to-end direct multipath signal path. As described with reference to FIG. 5, an appropriate beam weight may be computed for each of the plurality of end-to-end direct multipath channels by CPS 505 to generate direct user beams. The use of multiple transmitters (AN 515) with a single receiver (user terminal 517) can provide path diversity to ensure successful transmission of information to any user terminal 517 in the presence of a specially induced multipath channel.

FIG. 41-43 depict end-to-end repeaters 3403 implemented with separate forward link transponders 3430 and reverse link transponders 3440. FIG. 44A and 44B are illustrations of examples of forward signal path 3700 (similar to forward signal path 3602 in FIG. 43) and reverse signal path 3750 (similar to reverse signal path 3502 in FIG. 42), respectively. As described above, the direct signal path 3700 includes a forward link transponder 3430 coupled between a feeder link component receiving element 3416 and a user link component transmitting element 3429. The reverse signal path 3750 includes a reverse link transponder 3440 coupled between a user link component receiver element 3426 and a feeder link component transmitter 3419. In some cases, each forward link transponder 3430 and each reverse link transponder 3440 are cross-pole transponders. For example, the forward link transponder 3430 receives a direct uplink signal at a left-hand circular polarization (LHCP) uplink frequency and outputs a forward downlink signal at a right-hand circular polarization (RHCP) downlink frequency, and each reverse transponder 3440 The communication line receives the return uplink signal at the uplink frequency of right circular polarization (RHCP) and outputs the return signal of the downlink at the frequency of the downlink left circular polarization (LHCP). One such case (ie, with the polarizations described in the previous example) is illustrated only by solid lines in FIG. 44A and 44B, and another such case (ie, with opposite polarizations compared to those described in the previous example) is illustrated only by dotted lines in FIG. 44A and 44B. In other cases, some or all of the transponders may provide a two-pole pair of signal paths. For example, if one follows both the solid and dashed lines in FIG. 44A and 44B, forward link transponders 3430 and reverse link transponders 3440 can receive direct uplink signals on the uplink frequency or another frequency with both types of polarization (LHCP and RHCP) and can simultaneously output direct downlink signals to downlink frequency or on another frequency with both types of polarization (RHCP and LHCP). For example, such cases may allow multiple systems to operate in parallel using any suitable type of interference suppression techniques (eg, using time division, frequency division, etc.). In some cases, the end-to-end relay 3403 contains a large number of transponders, such as 512 forward link transponders 3430 and 512 reverse link transponders 3440 (eg, a total of 1024 transponders). Other implementations may use smaller numbers of transponders, such as 10 or any other suitable number. In some cases, antenna elements are implemented as full duplex designs such that each receive antenna element shares the design with a corresponding transmit antenna element. For example, each illustrated antenna element may be implemented as two of four waveguide ports of a radiating structure capable of both transmitting and receiving signals. In some cases, only feeder link elements or only user link elements are full duplex. Other implementations may use different types of polarization. For example, in some implementations, transponders may be connected between the receive antenna element and the transmit antenna element with the same polarity.

Both the example forward link transponder 3430 and the example reverse link transponder 3440 may comprise low noise amplifiers (LNAs) 3705, frequency converters and associated filters 3710, channel amplifiers 3715, phase shifters 3720, power amplifiers 3725 (e.g., power amplifiers 3725). traveling wave tube (TWTA), solid state power amplifiers (SSPA), etc.) and 3730 harmonic filters (HF). In bipolar implementations, as shown, each pole has its own signal path with its own set of transponder components. Some implementations may use more or fewer components. For example, frequency converters and their associated filters 3710 may be useful in cases where the uplink and downlink frequencies are different. As one example, each forward link transponder 3430 may receive an input in a first frequency band and may output signals in a second frequency band, and each reverse link transponder 3440 may receive an input in a first frequency band and may output signals in a second frequency band. .

In some cases, multiple subbands are used (e.g., seven 500 MHz subbands as described above. For example, in some cases, transponders can be provided that operate on the same subbands used in implementing a terrestrial network with multiple subbands, essentially allowing for multiple independent and parallel end-to-end beamforming systems via a single end-to-end repeater (each end-to-end beamforming system operates in a different subband) In other cases, a wideband end-to-end beamforming system may use multiple subbands in the terrestrial network, but transmit one or more (or all) subbands via wideband transponders (e.g. 7 sub-bands, each 500 MHz wide, transmitted over 3.5 GHz bandwidth transponders) In such cases, each transponder may contain multiple frequency converters and associated 3710 filters and/or other components designed to process one or more more subband.). The use of multiple subbands may allow for less stringent transponder amplitude and phase requirements since the terrestrial network can individually determine the beam weights used in each of the subbands, effectively calibrating the amplitude and phase variation of the transponder bandwidth. For example, in the case of separate forward and reverse transponders and using 7 subbands for each beam, a total of 14 different beam weights could be used, i.e. 7 subbands * 2 directions (forward and reverse). In some cases, each transponder path contains only LNA 3705, channel amplifier 3715, and power amplifier 3725. Some implementations of the end-to-end repeater 3403 use phase shift controllers and/or other controllers that can individually set the phases and/or other characteristics of each transponder, as described above.

The antenna elements may transmit and/or receive signals in any suitable manner. In some cases, the end-to-end repeater 3403 includes one or more reflectors with a radiator in the form of an antenna array. For example, the feeder link antenna subsystem 3410 may comprise a feeder link reflector for both transmit and receive, or a separate feeder link transmit reflector and a separate feeder link receive reflector. Similarly, the user link antenna subsystem 3420 may comprise a user link reflector for both transmitting and receiving, or a separate user link transmit reflector and a separate user link receive reflector. In one example, the feeder link antenna subsystem 3410 comprises an array of radiating structures, and each radiating structure includes a feeder link component receiving element 3416 and a feeder link component transmitting element 3419. In such a case, the feeder link antenna subsystem 3410 may also include a feeder link reflector that irradiates feeder link component receive elements 3416 and is irradiated by feeder link component transmitter elements 3419. In some cases, the reflector is implemented as a plurality of reflectors, which may have different shapes, sizes, orientations, and so on. In other cases, the feeder link antenna subsystem 3410 and/or the user link antenna subsystem 3420 is implemented without reflectors, such as a direct radiating array.

As mentioned above, the separation of the feeder link antenna subsystem 3410 and the user link antenna subsystem 3420 can serve one or more AN coverage areas 3450 that are different from one or more user coverage areas 3460. For example, the feeder link antenna subsystem 3410 may be implemented with a reflector having a significantly larger physical area than the user coverage area reflector 3460. A larger reflector can provide a geographic distribution of a large number of ANs 515 in a much smaller AN coverage area 3450, such as a small subset of a user's coverage area 3460. Some examples are shown in FIG. 45 and 46.

FIG. 45 shows an example of the visible area 3800 of Earth coverage of an end-to-end repeater 3403 (eg, a satellite). In the example of the end-to-end repeater 3403, feeder-link antenna subsystem 3410 includes an 18-meter feeder-link reflector, and user-link antenna subsystem 3420 includes a 2-meter user-link reflector (e.g., feeder-link reflector area of approximately eighty times the reflector area of the user link). Each antenna subsystem also includes an array of 512 cooperating transmit/receive elements. For example, an example of an end-to-end relay 3403 may include 512 forward link transponders 3430 (eg, generating 512 forward paths 3700 as shown in FIG. 44A) and 512 reverse link transponders 3440 (eg, generating 512 reverse paths 3750). signal as shown in Fig. 44B). User coverage area 3460 includes 625 user beam coverage areas 519 . The small shaded area in the eastern United States represents an AN coverage area 3450 that includes 597 AN 515s distributed across it. AN 515. Such a relatively dense AN coverage area 3450 is referred to herein as an "AN pool".

FIG. 46 shows an example of a Continental United States (CONUS) coverage 3900 by an end-to-end repeater 3403 (eg, satellite). An example of an end-to-end repeater 3403 is similar to the example shown in FIG. 45, except that the user-link antenna subsystem 3420 includes a 5-meter user-link reflector (eg, the feeder-link reflector is approximately four times the size of the user-link reflector). User coverage area 3460 includes 523 user beam coverage areas 519 . AN coverage area 3450 (AN pool) is the same as in FIG. 45: An area in the eastern US containing 597 AN 515s distributed within it, which is a small subset of the user's coverage area 3460.

Multiple coverage areas

In the end-to-end repeater example 3403 described above, the user link antenna subsystem 3420 is described as a single antenna subsystem (e.g., single user link reflector), and the feeder link antenna subsystem 3410 is described as a single antenna subsystem (e.g., single feeder link reflector). communication lines). In some cases, user link antenna subsystem 3420 may include one or more antenna subsystems (e.g., two or more antenna element subarrays) associated with one or more user link reflectors, and feeder link antenna subsystem 3410 may include one or more antenna subsystems associated with one or more feeder link reflectors. For example, some end-to-end relays 3403 may include a user-link antenna subsystem 3420 that includes a first set of user-link receive/transmit elements associated with a first user-link reflector (e.g., each element is positioned to irradiate the first user-link reflector communication and/or exposure to the first user-link reflector), and a second set of user-link receiving/transmitting elements associated with the second user-link reflector. In some cases, the two user link reflectors have approximately the same physical area (eg, within 5%, 10%, 25%, 50%) of each other. In some cases, one user-link reflector is significantly larger (eg, at least twice the physical area) of the other. Each set of constituent user-link receiver/transmit elements and associated user-link reflector can radiate in a respective user-separated coverage area. For example, areas of multiple user coverage areas may be non-overlapping, partially overlapping, fully overlapping (eg, a smaller user coverage area may be contained within a larger user coverage area), and so on. In some cases, multiple user coverage areas may be active (exposed) at the same time. In other cases, as described below, it may be possible to selectively activate different portions of the constituent receive/transmit elements of the user link, thus activating different user coverage areas at different points in time. Switching between areas from multiple coverage areas can be coordinated with the CPS. For example, beamforming calibration, beamweight calculation, and beamweight application may occur in two parallel beamformers, one for each of two different coverage areas. The use of appropriate weighting factors in the beamformers can be synchronized to match the operation of the end-to-end repeater. In some cases, the beam weights may have changed with time slicing in case of using time slicing beamformers.

FIG. 47A and 47B show an example of a forward signal path 4000 and a reverse signal path 4050, respectively, each of which selectively activates a plurality of user link antenna subsystems 3420. Each signal path includes a transponder connected between the constituent antenna elements. As shown in FIG. 47A, forward link transponder 3430 is similar to that described with reference to FIG. 44A, except that the output side of the forward link transponder 3430 is selectively coupled to one of two constituent user-link transmission elements 3429, each of which is part of a separate user-link antenna subsystem 3420 (e.g., each of which is part of a separate user-link array). interacting components of the user link transmission elements 3429). As described above, the forward link transponder 3430 may include some or all of the LNA 3705, frequency converters and associated filters 3710, channel amplifiers 3715, phase shifters 3720, power amplifiers 3725, and harmonic filters 3730.

The forward link transponder 3430 of FIG. 47A further comprises switches 4010 (forward link switches) that selectively couple the transponder to either the first user link component transmitter element 3429a (the first user link antenna subsystem 3420) via a first set of power amplifiers 3725 and harmonic filters 3730, or to a second component transmitting user link element 3429b (second user link antenna subsystem 3420) via a second set of power amplifiers 3725 and harmonic filters 3730. For example, in the first switching mode, the forward link transponder 3430 actually forms a signal path between the feeder link component receive element 3416 and the first user link component transmitter element 3429, and in the second switch mode, the forward link transponder 3430 actually forms the signal path between the same constituent receiving element 3416 of the feeder link and the second constituent transmitting element 3429 of the user link. Switches 4010 (SW) may be implemented using any suitable switching means such as an electromechanical switch, relay, transistor, etc. Although shown as switches 4010, other implementations may use any other suitable means to selectively connect the input of the forward link transponder 3430 to multiple outputs. For example, power amplifiers 3725 (eg, providing high gain in the on position and zero (or negative) gain in the off position) can be used as switches.

As shown in FIG. 47B, the reverse link transponder 3440 functionally replicates the forward link transponder 3430 in FIG. 47A. Instead of selectively connecting the output side of the transponder, as is the case with the forward link in FIG. 47A, the input side of the reverse link transponder 3440 of FIG. 47B is selectively coupled to one of two constituent user link receiver elements 3426. Again, each user link constituent receiver element 3426 may be part of a separate user link antenna subsystem 3420 (eg, each part of a separate array of cooperating user link receiver elements 3426). As described above (e.g., in FIG. 44B), the reverse link transponder 3440 may include some or all of the LNA 3705, frequency converters and associated filters 3710, channel amplifiers 3715, phase shifters 3720, power amplifiers 3725, and harmonic filters 3730. .

The reverse link transponder 3440 in FIG. 47B further includes switches 4010 (reverse link switches) that selectively couple the transponder to either the first user-link receiver element 3426 (the first user-link antenna subsystem 3420) via the first set of LNA 3705 or the second user-link receiver element 3426 communication (second user link antenna subsystem 3420) via the second set of LNA 3705. For example, in the first switching mode, the reverse link transponder 3440 actually forms a signal path between the first user link constituent receiver element 3426 and the feeder link constituent transmitter element 3419; and in the second switching mode, the reverse link transponder 3440 essentially forms a signal path between the second user link receiver element 3426 and the same feeder link transmitter element 3419. Switches 4010 may be implemented using any suitable switching means such as an electromechanical switch, relay, transistor, etc. Although shown as switches 4010, other implementations may use any other suitable means to selectively connect the input of the forward link transponder 3430 to multiple outputs. For example, 3705 amplifiers (eg, providing high gain in the on position and zero (or negative) gain in the off position) can be used as switches.

Examples of end-to-end relay 3403 may include a switch controller 4070 to selectively switch some or all of the switches 4010 (or other suitable selective connection means) in accordance with a switch program. For example, the switch program may be stored on the on-board storage device of the end-to-end relay 3403. In some cases, the switch program actually selects which user link antenna subsystem 3420 to activate (e.g., which set of user beams to emit) at each of a plurality of time intervals (e.g., time slots ). In some cases, switching is allocated an equal amount of time for multiple subscriber link antenna subsystems 3420 (eg, each of the two subsystems is activated for approximately half of this time). In other cases, switching may be used to achieve bandwidth allocation goals. For example, one user-link antenna subsystem 3420 may be associated with users with a higher number of requests and may be allocated most of the program time, while another user-link antenna subsystem 3420 may be associated with users with fewer requests, and a smaller part of the time in the program can be allocated for it.

FIG. 48A and 48B show an example of coverage areas 4100 and 4150 of end-to-end repeater 3403, which include a plurality of selectively activated user coverage areas 3460a, 3460b. An example of an end-to-end repeater 503 is similar to the end-to-end repeaters shown in FIG. 38 and 39, except for different antenna subsystems. In this example, the user-link antenna subsystem 3420 includes two 9-meter user-link reflectors, and the transponders are configured to selectively activate only half of the user-beams at any given time (e.g., the transponders are implemented as shown in FIG. 47A and 47B). For example, in the first time interval, as shown in FIG. 48A, user coverage area 3460a includes five hundred and ninety active user beam coverage areas 519. User beam coverage active areas 519 actually cover the western half of the US. AN coverage area 3450 (AN pool) is the same as in FIG. 38 and 39: an area in the eastern US containing 597 ANs 515 distributed therein. In the first time interval, the AN coverage area 3450 does not overlap with the user's active coverage area 3460. In the second time interval, as shown in FIG. 48B, user coverage area 3460b includes another five hundred and ninety active user beam coverage areas 519. The active user beam coverage areas 519 in the second time slot actually cover the eastern half of the US. The AN coverage area 3450 does not change. However, in the second time interval, the AN coverage area 3450 is completely covered by the user's active coverage area 3460 (represents a subset of it). Capacity can be flexibly allocated to different areas (eg, between east and west user coverage areas) by dynamically adjusting the ratio of time allocated to the respective user link antenna subsystems.

Although the previous example illustrates two user coverage areas with the same dimensions, a different number of user coverage areas (e.g., three or more) may be provided and they may have different sizes (e.g., coverage of the entire surface of the Earth, continental US only, US only, only region, etc.). In cases with multiple user coverage areas 3460, user coverage areas 3460 may have any suitable geographic relationship. In some cases, the first and second user coverage areas 3460 partially overlap (eg, as shown in FIGS. 48A and 48B). In other cases, the second user coverage area 3460 may be a subset of the first user coverage area 3460 (eg, as shown in FIGS. 45 and 46). In other cases, the first and second user coverage areas do not overlap (eg, are heterogeneous).

FIG. 47A-47B describe user link side signal path selection. However, in some cases, alternatively or additionally, switching of the signal path from the feeder link side is used. FIG. 49 shows an example of a forward signal path 4200 that selectively activates multiple user link antenna subsystems 3420 and multiple feeder link antenna subsystems 3410. The signal path includes a forward link transponder 3430 coupled between the constituent antenna elements. As described above, the forward link transponder 3430 may include some or all of the LNA 3705, frequency converters and associated filters 3710, channel amplifiers 3715, phase shifters 3720, power amplifiers 3725, and harmonic filters 3730. The input side of the forward link transponder 3430 is selectively coupled to one of the two constituent feeder link receiver elements 3416 (eg, using switches 4010a and 4010b or any other suitable path selection means). Each component feeder link receiver element 3416 may be part of a separate feeder link antenna subsystem 3410 (eg, each part of a separate array of cooperating feeder link receiver elements 3416). The output side of the forward link transponder 3430 is selectively coupled to one of the two constituent user link transmission elements 3429 (eg, using switches 4010c and 4010d or any other suitable path selection means). Each user link component transmitter element 3429 may be part of a separate user link antenna subsystem 3420 (eg, each part of a separate array of cooperating user link component transmitter elements 3429). One or more switch controllers (not shown) may be included in the end-to-end relay 3403 to select between some or all of the four possible signal paths provided by the forward link transponder 3430. The transponders in FIG. 47A, 47B and 49 are only intended to illustrate a few of the many possible cases. Moreover, path selection between more than two user link antenna subsystems 3420 and/or more than two feeder link antenna subsystems 3410 may be used in some cases. Similarly, selection of an additional path may be possible in cases where the user link antenna subsystem 3420 and/or feeder link constituent receive element 3416 have separate reflectors for transmit and receive, or the like.

Similarly, a plurality of AN coverage areas may also be provided. As one example, it may be desirable to stop the traffic of specific geographic areas in their respective areas. For example, an end-to-end repeater 3403 with or without paired transponders as illustrated in FIG. 49 can serve a first AN coverage area 3450 and a first user coverage area 3460, both in North America, and a second AN coverage area 3450 and a second user coverage area 3460, both in South America. In the case of path selection (eg, switching) in the transponders, one end-to-end repeater 3403 (eg, one satellite) can serve traffic associated with a user coverage area 3460 in North America using AN 515 in an AN coverage area 3450 in North America and serve traffic associated with user coverage area 3460 in South America using AN 515 in AN coverage area 3450 in South America. Bandwidth can be flexibly allocated to different areas (eg, between user coverage areas in the Americas) by dynamically adjusting the ratio of time allocated to the respective antenna subsystems.

In general, the characteristics of the end-to-end repeater 3403 described in FIG. 41 allow at least one user beam coverage area 519 other than at least one AN coverage area 3450 to be served. In some cases, siloed coverage area service may enable the use of AN pools to provide high throughput for a large user coverage area 3460 . FIG. 45, 46, 48A and 48B show various examples of such AN pool implementations. Deploying a large number of AN 515s in a relatively small geographic area can provide a number of characteristics. For example, it may be easier to ensure that more (or even all) AN 515s are deployed closer to a high speed network (e.g., in a region with good fiber connectivity to CPS 505) within the borders of the same country or region, on land, etc. with less deviation from the ideal distribution of AN 515. Implementation of separate service coverage areas with path selection (eg, as in FIGS. 47A-47B) may provide additional performance. For example, as described above, one AN pool (and one end-to-end repeater 3403) can be used to selectively serve multiple user coverage areas 3460 . Likewise, a single end-to-end relay 3403 may be used to differentiate and serve traffic across regions.

In some cases, separate path selection coverage area services may provide different interference management and/or bandwidth management functions. For example, as shown in FIG. 48A and 48B, four categories of links can be considered: forward link communication from the AN pool to the western user coverage core 3460 in FIG. 48A ("Link A"); direct link communication from the AN pool to the eastern core 3460 of user coverage in FIG. 48B ("link B"); reverse link communication from the western core 3460 of user coverage in FIG. 48A to pool AN ("link C"); and reverse link communication from the east core 3460 of user coverage in FIG. 48V to AN pool ("link D"). In the first time interval, the eastern user coverage area 3460 in FIG. 48B such that communication occurs over link B and link D. Since there is complete overlap between AN coverage area 3450 and east user coverage area 3460, interference can potentially occur between links B and D. Accordingly, in the first time slot, link B may be allocated a first portion of the bandwidth (eg, 2 GHz), and link D may be allocated a second portion of the bandwidth (eg, 1.5 GHz). In the first second interval, the western user coverage area 3460 of FIG. 48A so that communication is on link A and link C. Since there is no overlap between AN coverage area 3450 and user coverage area 3460 west, the full bandwidth can be used in the second slot between links A and C (e.g., 3, 5 GHz) of the end-to-end relay 3403. For example, in a first time slot, forward uplink signals may be received using a first frequency band, and return uplink signals may be received using a second frequency band different from the first frequency band; and in the second time slot, forward uplink signals and reverse uplink signals may be received using the same frequency band (eg, first, second, or other frequency band). In some cases, frequency reuse may be implemented in both the first and second time slots using other first time slot interference suppression techniques. In some cases, path selection timing may be chosen to compensate for such differences in bandwidth allocation over different time slots. For example, the first time slot may be longer than the second time slot so that links B and D are allocated less bandwidth for a longer period of time to at least partially offset the allocation of more bandwidth to links A and C for a shorter time period. period of time.

In some cases, the first reverse uplink signals are received in a first time slot by a plurality of cooperating user link receiver elements 3426a from a first portion of a plurality of user terminals 517 geographically distributed throughout the first user coverage area (e.g., east user coverage area 3460) or some portion thereof, and the second uplink return signals are received in a second time interval by a plurality of cooperating user link receiver elements 3426b from a second portion of a plurality of user terminals 517 geographically distributed throughout a second user coverage area (e.g., the western area 3460 user coverage) or some part of it. When the AN coverage area (AN pool) 3450 is a subset of the first user coverage area (eg, as illustrated in FIGS. 48A and 48B), the AN timing can be calibrated by the end-to-end relay 3403 in the first time slot (eg, when there is overlap between user coverage area 3460 and AN coverage area 3450).

As described above, some cases may include determining an appropriate relative timing adjustment for each of the plurality of ANs 515 such that the associated transmissions from the plurality of ANs 515 reach the end-to-end relay 3403 in synchrony (e.g., with a sufficient degree of coordinated timing relative to the symbol duration that, as typically represents a fraction of the duration of the symbol, such as 10%, 5%, 2%, or other suitable value). In such cases, direct uplink signals are transmitted by multiple ANs 515 according to respective relative timing adjustments. In some such cases, a beacon timing signal (e.g., a PN signal generated by a beacon generator as described above) is received by at least some of the plurality of ANs 515 from the end-to-end relay 3403, and the corresponding relative timing adjustments are determined in accordance with the beacon timing signal. In other such cases, some or all of the ANs 515 may receive loopback transmissions from the end-to-end relay 3403, and the appropriate relative timing adjustments are determined in accordance with the loopback transmissions. The use of different approaches to AN 515 calibration may depend on the ability of the AN 515 to communicate with the end-to-end repeater 3403. Accordingly, in some cases, the AN 515 calibration can only be performed at time intervals during which the corresponding coverage areas are illuminated. For example, loopback transmissions may only be used during time slots during which there is some overlap between AN coverage area 3450 and user coverage area 3460 (e.g., ANs 515 communicate over a looped beam that can use both feeder link antenna subsystem 3410 and and the end-to-end repeater user-link antenna subsystem 3420 3403). In some cases, correct calibration may further depend on some overlap between the feeder downlink frequency band and the user downlink frequency band.

Conclusion

Although the disclosed method and apparatus have been described above in the context of various examples, cases, and implementations, it should be understood that the specific features, aspects, and functionality described in one or more of the individual examples may be applicable to other examples. Thus, the scope and scope of the claimed invention is not limited to any of the above examples, but is defined by the claims.

Terms and phrases used in this document, as well as their variations, unless expressly stated otherwise, should be considered non-limiting and not limiting. As examples of the above: the term "including" is used to mean "including, without limitation" or the like; the term "example" is used to provide examples of the implementation of the description element, but not an exhaustive or limiting list; terms in the singular are used to mean "at least one", "one or more", or the like.

In the text of the description, the term "connect" or "connected" is used in a broad sense to refer to either a physical or electrical (including wireless) connection between components. In some cases, the first component may be connected to the second component through an intermediate third component placed between the first and second components. For example, components can be connected via direct connections, matching circuits, amplifiers, attenuators, filters, DC blocks, AC blocks, and so on.

If a group of objects is connected by the conjunction "and", this does not mean that all and each of these objects must be present in the group, but means that the group includes all objects or any subset of them, unless otherwise expressly indicated. Similarly, a group of objects linked by "or" should not be interpreted as requiring mutual exclusivity of the objects in the group, but should be interpreted as including all or any subset of the objects unless expressly stated otherwise. Moreover, while the objects, elements, or components of the disclosed method and apparatus may be described or claimed in the singular, the plural is intended to be included within their scope unless limited to the singular is explicitly stated.

The presence of expanding words and phrases such as "one or more", "at least" or other similar phrases in some cases does not mean that, in cases where such expanding phrases may be absent, a narrower meaning is assumed or required.

Although reference numerals may be included in the claims, they are provided solely for the function of facilitating the understanding of the claims, and the inclusion (or exclusion) of reference numerals should not be construed as limiting the scope of the subject matter covered by the claims.

Claims (42)

1. A method for providing a communication service to user terminals (517) distributed over a user coverage area (3460) by means of an end-to-end repeater (503, 1202, 1502, 3403) containing a plurality of paths (1702) for receiving/transmitting a reverse signal, the method including: myself: receiving at a plurality of access nodes (515) at geographically dispersed locations respective reverse downlink signals (527) from an end-to-end relay, each of the respective reverse downlink signals comprising reverse user data streams (535) transmitted from a plurality of user terminals and relayed end-to-end repeater, to form a combined return signal (907); determining a matrix (937) of return beam weights for end-to-end beamforming transmitted from a plurality of return user beam coverage areas (519) to a plurality of access nodes via an end-to-end repeater; applying to each of the respective combined returns signals respective beamforming weights from the return beam weight matrix to obtain a respective set of weighted combined returns (911) associated with each of the plurality of return user beam coverage areas; And combining, for each of the plurality of return user beam coverage areas, a respective plurality of weighted combined returns to obtain a return beam signal (915) associated with each of the plurality of return user beam coverage areas, wherein the corresponding set of weighted combined returns are adjusted to compensate for the respective propagation delays signal and phase shifts between the end-to-end repeater and multiple access nodes prior to combining. 2. The method of claim 1, further comprising: receiving, at a plurality of access points, a relay beacon signal transmitted from an end-to-end relay; And demodulating the respective received repeater beacon signals to obtain the appropriate receive timing information (2520), wherein the correction of the respective propagation delays is based at least in part on the respective receive timing information. 3. The method of claim 2, which further includes: determining, for the plurality of access nodes, respective receive timing adjustment (2512, 2513) and corresponding receive phase adjustment (2512, 2514) to compensate for downlink channel distortion over based at least in part on a comparison of the respective received relay beacon signals with the respective local reference signals. 4. The method of claim 3, further comprising: adjusting the timing of the respective combined return signals based on the respective receive timing adjustment values. 5. The method of claim 3 or 4, further comprising: adjusting the phase of the respective combined return signals based on the respective receive phase adjustment values. 6. The method according to any one of paragraphs. 2-5, in which demodulation is performed on a plurality of access nodes. 7. The method according to any one of paragraphs. 2-6, in which the repeater beacon signal contains a pseudonoise (PN) code (2307). 8. The method according to any one of paragraphs. 2-7, in which the repeater beacon signal contains frame timing information. 9. The method according to any one of paragraphs. 1-8, further comprising: multiplexing at a plurality of access nodes the respective combined reverse signals and the corresponding timing information to obtain the respective multiplexed combined reverse signals; And directing from the plurality of access nodes the respective multiplexed combined return signals to the return beam generator (531) for application. 10. The method according to any one of paragraphs. 1-9, wherein correcting the respective propagation delays and phase shifts includes matching portions of the respective combined reverse downlink signals with the same timing on transmission from the end-to-end repeater prior to application. 11. The method according to any one of paragraphs. 1-10, wherein correcting the respective propagation delays and phase shifts includes negotiating, for each of the plurality of return user beam coverage areas, portions of the respective plurality of weighted combined returns with the same timing from the end-to-end relay prior to combining. 12. The method according to any one of paragraphs. 1-11, further including: demodulating each of the return beam signals to obtain a return beam data stream (534) associated with each of the plurality of return user beam coverage areas. 13. The method of claim 12, further comprising: demultiplexing each of the return beam data streams into respective reverse user data streams (535) associated with respective return uplink signals (525) transmitted from a plurality of user terminals. 14. The method according to any one of paragraphs. 1-13, in which each of the return uplink signals from a plurality of user terminals is included in a set of corresponding return downlink signals. 15. The method according to any one of paragraphs. 1-14, wherein each of the plurality of user terminals transmits a respective uplink return signal via a plurality of end-to-end relay return signal receive/transmit paths. 16. The method according to any one of paragraphs. 1-15, wherein a plurality of access nodes are distributed over the coverage area (3450) of the access node corresponding to the coverage area of the feeder link antenna of the end-to-end repeater. 17. The method of claim 16, wherein the plurality of return user beam coverage areas comprise a user coverage area, and wherein the access node coverage area at least partially overlaps with the user coverage area. 18. The method according to any one of paragraphs. 1-17, wherein two or more of the plurality of access nodes are located within one of the plurality of return user beam coverage areas. 19. The method according to any one of paragraphs. 1-18, wherein at least one of the plurality of return user beam coverage areas covers an area in which no access point is located. 20. The method according to any one of paragraphs. 1-19, in which the plurality of access nodes contains the first number of access nodes, and the end-to-end relay contains the second number of paths for receiving/transmitting the return signal, the first number being different from the second number. 21. The method of claim 20, wherein the first number is greater than the second number. 22. The method of claim 20 or 21, wherein the plurality of return user beam coverage areas comprises a third number of return user beam coverage areas, and wherein the third number is different from the first number. 23. The method according to any one of paragraphs. 1-22, in which the plurality of user terminals transmits reverse uplink signals in the reverse uplink frequency band, and the end-to-end relay relays the reverse uplink signals via reverse signal transmission/reception paths to the plurality of access nodes using the reverse uplink frequency band. downlink, and wherein the reverse downlink frequency band is different from the reverse uplink frequency band. 24. The method according to any one of paragraphs. 1-23, in which the end-to-end relay is a satellite. 25. The method according to any one of paragraphs. 1-24, wherein the respective combined reverse link signals comprise a plurality of modulated signals received on different subbands. 26. The method of claim 25, wherein the plurality of return user beam coverage areas comprises a plurality of subsets of return user beam coverage areas associated with different frequency subbands. 27. The method of claim 26, wherein each of the plurality of subsets of return user beam coverage areas comprises a plurality of non-overlapping return user beam coverage areas. 28. The method of claim 25 or 26, wherein the bandwidth for each of the different subbands is greater than or equal to 500 MHz. 29. The method according to any one of paragraphs. 1-28, wherein the return beam weight matrix has dimensions corresponding to the number of the set of return user beam coverage areas and the number of the set of access nodes. 30. The method according to any one of paragraphs. 1-29, wherein the return beam weight matrix is determined based on a reverse uplink emission matrix having dimensions corresponding to the number of a plurality of reverse user beam coverage areas and the number of a plurality of reverse signal receive/transmit paths, and a reverse downlink emission matrix, having dimensions corresponding to the number of multiple paths for receiving/transmitting the return signal and the number of multiple access nodes. 31. The method of claim 30, wherein the return beam weight matrix is determined based on the end-to-end relay return payload matrix having dimensions corresponding to the number of a plurality of return signal receive/transmit paths. 32. The method of claim 31, wherein the return beam weight matrix is defined as the product of the reverse uplink emission matrix, the reverse payload matrix, and the reverse downlink emission matrix. 33. The method of claim 31, wherein the reverse payload matrix comprises a diagonal matrix.

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