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WO1988001392A2 - Systeme de telemetrie et de traitement par satellite pour surveillance mobile et transmission de donnees - Google Patents

Systeme de telemetrie et de traitement par satellite pour surveillance mobile et transmission de donnees Download PDF

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Publication number
WO1988001392A2
WO1988001392A2 PCT/US1987/002059 US8702059W WO8801392A2 WO 1988001392 A2 WO1988001392 A2 WO 1988001392A2 US 8702059 W US8702059 W US 8702059W WO 8801392 A2 WO8801392 A2 WO 8801392A2
Authority
WO
WIPO (PCT)
Prior art keywords
satellite
satellites
mobile units
mobile
control facilities
Prior art date
Application number
PCT/US1987/002059
Other languages
English (en)
Other versions
WO1988001392A3 (fr
Inventor
Ronald Braff
Original Assignee
The Mitre Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Mitre Corporation filed Critical The Mitre Corporation
Publication of WO1988001392A2 publication Critical patent/WO1988001392A2/fr
Publication of WO1988001392A3 publication Critical patent/WO1988001392A3/fr
Priority to DK211788A priority Critical patent/DK211788A/da
Priority to KR1019880700437A priority patent/KR880701891A/ko

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
    • G01S13/878—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/76—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted
    • G01S13/78—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/003—Transmission of data between radar, sonar or lidar systems and remote stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1853—Satellite systems for providing telephony service to a mobile station, i.e. mobile satellite service
    • H04B7/18545—Arrangements for managing station mobility, i.e. for station registration or localisation
    • H04B7/18547—Arrangements for managing station mobility, i.e. for station registration or localisation for geolocalisation of a station
    • H04B7/18554—Arrangements for managing station mobility, i.e. for station registration or localisation for geolocalisation of a station using the position provided by an existing geolocalisation system

Definitions

  • the present invention relates to a satellite surveillance and data link system. More particularly, it relates to a system for determining the range from a satellite to a plurality of mobile units, for storing uploaded commands to poll mobile units until the poll is scheduled to be transmitted, and for acquiring mobile units that request entry into the system, all through satellite on-board computing capability.
  • Satellites have been in successful operation for ship-to-shore communications for several years through a service provided by the international consortium, INMARSAT. Recently, the aviation community has rapidly begun to renew its interest for the use . of satellites for air traffic control, airline operational control and public correspondence.
  • Still another object of the invention is a satellite system including the use of cross-link communications between the satellites to provide for on-board satellite position determination and for on-board acquisition of mobile units into the system.
  • Yet another object of the invention is a system in which the on-board processing involves not only signal regeneration and beam switching capability, but also digital data processing of messages, for storage of poll commands, generation of polls to mobile units according to a schedule, storage of replies to polls, and formatting of messages.
  • a ranging and processing satellite system for data communication and surveillance of mobile units from multiple control facilities including at least two satellites adapted for polling individual mobile units requested by one or more of the control facilities and for receiving replies from the mobile units including the mobile units' altitude, such as an aircraft's barometric altitude.
  • a cross-link communication path is provided between the satellites.
  • the satellites include processing apparatus to compute the ranges between the mobile unit and each of the satellites using the replies from the mobile units; the satellites further include apparatus for transmitting the computer ranges to at least one control facility, and for computing the mobile unit's position for acquisition.
  • the control facilities employ TDMA (time division multiple access) or FDMA (frequency division multiple access) multiplexed channels as uplinks to the satellites.
  • Fig. 1 is a schematic illustration of the RAPSAT external data flow
  • Fig. 2 is a diagram of the overall RAPSAT system architecture employing two geostationary satellites as an example
  • Fig. 3a illustrates an upload of poll commands from ten control facilities to a RAPSAT satellite
  • Fig. 3b illustrates the geographical coverage area of a pair of control facilities
  • FIG. 4a illustrates a prior art polling sequence
  • Fig. 4b illustrates the polling sequence disclosed herein;
  • Fig. 5 illustrates the multiple access system of the present invention
  • Fig. 6 is an illustrative diagram of the RAPSAT on-board processing top-level data flow
  • Fig. 7 is an illustrative block diagram of the RAPSAT forward link.
  • Fig. 8 is an illustrative block diagram of the RAPSAT return link.
  • the ranging and processing satellite system has been designed to provide multiple access for both mobile unit users and their control facilities (such as those operated by air traffic control, marine traffic regulation, and commercial transportation companies).
  • the ground control facilities obtain access to the satellite via terrestrial links to large central earth stations.
  • the on-board processing of the present invention makes it readily possible for a number of control facilities to gain access to the satellite directly from their premises via TDMA or FDMA channel uplinks as illustrated in Fig. 1.
  • a RAPSAT satellite 10 includes an on-board processor which provides the logic and memory functions to be described hereinafter.
  • Satellite access for multiple mobile units is accomplished through a polling scheme that is Initiated at the satellite 10 under the control of on-board processing, based on poll commands from the control facilities.
  • the replies from the mobile units 12 to the polling commands (or polls) from the satellite 10 are processed on-board the satellite 10; such processing includes two-way range determination to the mobile unit.
  • the resulting data is transmitted via a time-division multiplexed (TDM) down-link broadcast to control facilities 16.
  • TDM time-division multiplexed
  • Fig. 2 is an overall diagram of the RAPSAT system architecture employing, as an example, two geostationary satellites 18 and 20, each handling one-half of the mobile units 22 and 24.
  • the two satellites 18 and 20 are used for the purposes of sharing the processing load and for mobile unit position determination. Position determination is accomplished by range-range measurements and transmitted altitude information included in a mobile unit's reply to a poll addressed to that unit.
  • Each of the satellites 18 and 20 individually polls those mobile units that are under the control of the control facilities 26 and 28 having access to that satellite.
  • the replies to the polls are received by both satellites for position determination.
  • the satellite 20 transmits a poll to a mobile unit 24, with a reply being received both by the polling satellite 20 and the receive-only satellite 18.
  • the receive-only satellite 18 transmits to satellite 20 by communications path 30 a message containing the time satellite 18 received the reply to the poll originated by satellite 20; this information is processed by the satellite 20 and eventually is transmitted to the ground control facilities 28.
  • Satellites 18 and 20 simultaneously use the same frequency spectrum; thus, a two-fold frequency reuse is employed for spectral efficiency. This is accomplished by spot beam technology. Furthermore, the coverage of each satellite is partitioned into two areas for the purpose of filling the garbling guard times that must be placed between individual polls from the satellite when operating in a multi-satellite ranging mode. Garbling refers to an interfering overlap of replies at a received satellite. See B.D. Elrod, "Aircraft Interrogation Scheduling with ASTRO-DABS", Mitre Technical Report, MTR-6368, March 30, 1973. The filling of the garbling guard time — made readily possible by on-board processing — gives RAPSAT almost twice the capacity of previously proposed discrete address polling type satellite systems. See B.D.
  • the RAPSAT system disclosed herein is designed such that a number of control facilities such as 26 and 28 can each directly access a satellite from earth stations located on their premises. Mobile units such as 22 and 24 achieve access for data link service and surveillance service by replying to periodic polls addressed to them from the satellites 18 and 20. Such polls have been previously uploaded by the control facilities 26 or 28 and stored on-board the satellite in a computer. The methods of access will now be described in conjunction with Figs. 3, 4, and 5.
  • TDMA TDMA channel upload of poll commands from ten control facilities to one of the satellites 18 or 20 of Fig. 2.
  • the control facility uploads in Fig. 3a are labeled as the five pairs (Al, A2) , (Bl, B2), (Cl, C2) , (Dl, D2), and (El, E2) .
  • Each control facility is assigned a geographical area of responsibility and loads its poll commands into the uplink channel during its assigned time slot. Since ten control facilities are assumed in this example, ten time slots are allocated each frame. If frame duration is assumed to be four seconds, then each time slot is approximately 0.4 seconds. Each satellite's coverage area is divided in half. Thus, RAPSAT, as illustrated in this example, consists of our major coverage sub-areas, or two quadrants per satellite. Each member of a pair of control facilities (for example, El, E2) is assigned a geographical coverage area within a different quadrant, as illustrated in Fig. 3b. The geographical areas are sufficiently separated that poll replies from each area can be readily separated by spot beam receive antennas on the satellite. The order of the uplink poll command loading time sequence is synchronized to the order of polling of the area covered by each control facility in a pair as will be shown hereinbelow.
  • the multiple access of mobile units is designed to account for the guard time that should be inserted between polls to prevent garbling of replies when the poll replies are to be received by more than one satellite. If the polls are to be received by only one satellite, then garbling can be precluded by polling the mobile units in ascending order of range from the satellite, and by using a guard time between polls if a reply burst from a mobile unit is of greater duration than the next poll burst transmitted from the satellite.
  • B.D. Elrod in the 1973 report referred to above has shown that garbling can also be precluded when replies are to be received by more than one satellite if the guard time satisfies the following inequality:
  • Trl burst duration of reply to first poll and ? t2 burst duration of the next poll transmission.
  • Elrod divided the coverage area of the polling satellite into solid hexagonal cells of three-dimension diameter cT .
  • these cells will be called range ordering cells (ROC) or range ordering subvolum.es to emphasize that they are different from the common frequency reuse cells used in mobile telephone systems.
  • ROC range ordering cells
  • T guard time
  • the forward link can be fully utilized if mobile units are alternately polled as illustrated in Fig. 4b.
  • mobile units from a pair of control facilities are alternately polled by the on-board processor which has the poll commands stored in its memory. For example, referring to Fig. 5, a mooile unit under Control Facility (El) is polled, the next poll is for a mobile unit under Control Facility ( ⁇ 2), then a mobile unit under Control Facility (El) and so on.
  • each control facility pair occupies the two uplink time slots occurring prior to the alternating polling of their respective coverage areas. That is, control facilities (Al) and (A2) start their uplink slots every four seconds and complete them just prior to the alternating polling of their coverage areas. This allows the controlling authority on the ground the maximum amount of time (about three seconds for this example) to prepare and send an advisory or request data link message during the next poll.
  • On-board processing allows the range from satellite to mobile unit to be determined ar the satellite.
  • the on-board processor records the time the poll is transmitted.
  • the time when the reply to the poll is received is also determined to derive range to the mobile unit as is done in conventional radar systems. That is, the total round trip time is an indication of range from the mobile unit to the satellite.
  • Aircraft geocentric altitude can be estimated from the sum of transmitted baroaltimeter-derived altitude with proper corrections applied to it and the local earth radius.
  • the system of the present invention derives a cooperative position determination by this method for the surveillance function. Referring again to Fig. 2, a reply to a satellite's poll is received at both satellites 18 and 20. The time the mobile unit 24 transmitted the reply can be calculated at the polling satellite 20 to be
  • T time when mobile units replies to poll
  • T_ __C_L time when polling satellite initiates poll to mobile unit
  • R, range to second satellite
  • T , time when mobile unit's reply is received at second satellite.
  • the second satellite 18 transmits its poll-received time (T , ) to the polling satellite 20 via the cross ⁇ link 30.
  • the clocks on both satellites are synchronized; therefore, the polling satellite uses the above equations to calculate the range between the second satellite and the mobile unit.
  • the two ranges and received altitude (in the case of an aircraft) become part of the mobile unit's down-link message to the control facility and are used on-board the satellite to compute position for acquisition of mobile units entering the system. Garbling between replies to polls initiated by both satellites is precluded by directional receive antennas on the satellites.
  • the acquisition of mobile units according to the present invention can also be accomplished by on-board processing. Periodically, for example, every two seconds, a broadcast message is transmitted by the satellite for the purpose of requesting acquisition. Those mobile units seeking acquisition will reply. Based on a mobile unit's reply (including altitude for the case of an aircraft), the polling satellite can calculate the mobile unit's position as described above, and, thus, identify the ROC where the mobile unit is located. During the next sweep of this ROC, the mobile unit is polled. This reply is then processed as any other reply. The efficiency of this method is decreased by the absence of garbling protection. However, if the acquisition reply message length is kept at a minimum (e.g., identification, range code and abbreviated position information from the mobile unit navigation system) then the probability of garbling is minimized.
  • a minimum e.g., identification, range code and abbreviated position information from the mobile unit navigation system
  • RAPSAT Concept according to the present invention centers around the use of large scale on-board processing.
  • the operational on-board processing features of RAPSAT are:
  • Fig. 6 is a top-level data flow chart of RAPSAT on-board processing.
  • the processing is divided into forward processing and return processing.
  • the forward front end processing block 40 (a) scans a poll request buffer for decoded poll request messages from the control facilities, (b) checks the messages for completeness and consistency, and (c) controls the message flow to the poll-initiate processing block 42 to ensure that the poll request messages from a control facility reach the poll-initiate processing block 42 in time for the scan of the control facility's coverage area.
  • the poll-initiate processing block 42 (a) interprets the poll request messages from the control facilities, (b) formats them into poll messages to the mobile units, (c) controls the scanning of the coverage area of each control facility by controlling the switching to the corresponding spot beam,
  • a return front end processing block 46 scans the poll reply buffer for decoded replies from mobile units, associates replies with their receive times, checks replies for completeness and consistency, and controls the reply flow to the return correlation processing block 44. It detects and counters external interfering signals in the return link by identifying and evaluating the interference, initiating an alert message to satellite ground control for action, attempting to reject the interference through signal processing and, if necessary, closing the beam through which the interference is present. It also similarly processes buffered decoded reply data received from the other satellite.
  • the return correlation processing block 44 (a) correlates a reply message to the corresponding poll intiation message, (b) pairs the poll intiation time and poll receive times at its satellite and at the other satellite for range determination, (c) performs the two-way ranging computation for each satellite,
  • the forward functions (ground to mobile unit) of the satellite receive and process the poll request messages from the control facilities and initiate the polls.
  • the return functions receive and process the replies from the mobile units, correlate them with the poll initiations, determine range to the mobile unit, and generate the TDM down ⁇ link to the control facilities.
  • Fig. 7 is an exemplary top-level block diagram of the satellite forward functions.
  • the receiver 50 includes an up-link antenna assembly, low-noise front end, down converter and demodulator.
  • a decoder 52 digitizes and formats the demodulated poll request messages to make them suitable for digital processing.
  • a buffer 54 stores the digitized poll request messages until they are accessed by a forward processing block 56 as described above for Fig. 6.
  • An encoder 58 transforms the poll bit streams into a waveform that is suitable for modulating the carrier.
  • a transmitter 60 contains a modulator, up converter, power amplifier and spot beam antenna assembly. Since only one poll is transmitted at a time, the power amplifier can be operated at full power capability without generating intermodulation products, a significant advantage that is often stated for TDMA.
  • Fig. 8 is a top-level block diagram of the satellite return functions.
  • Receivers 62 and 64 representing multiple parallel receivers, consist of spot beam receive antenna assemblies, low noise front ends, down converters and demodulators. This figure illustrates parallel receivers in a functional sense. A common receiver can also be used with appropriate beam switching. However, the parallel approach would allow a less complicated operation since the poll- transmit and reply-receive functions would not have to be synchronized for receive beam switching.
  • the data decoders 66 and 68 digitize, apply forward error correction, and format the demodulated replies into a format suitable for digital processing.
  • the demodulated replies are also rerouted to reply timing blocks 70 and 72 where the reply arrival time is determined based upon the satellite time reference.
  • a return link buffer 74 stores the digitized reply messages and arrival time until they are accessed by the return processing block 76.
  • a cross-link buffer 78 stores the digitized reply messages received from the other satellite until accessed by the return processing block 76 which has been described above in conjunction with Fig. 6.
  • a down-link includes a down-link transmitter 80 and provides a TMD stream of processed replies. Each control facility processes those replies that are of interest to it. This provides a backup capability in the event a control facility has an outage. In that case, another control facility(ies) would be assigned the failed control facility's TDMA uplink slot and would receive the corresponding replies on the TDM down-link.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Relay Systems (AREA)

Abstract

Un système de satellites comprend au moins deux satellites ayant à bord des installations de traitement qui permettent l'échange de messages de données et la détermination de la position d'unités mobiles avec un accès direct depuis des installations multiples de commande au sol. Les satellites transmettent des données et interrogent des unités mobiles individuelles selon des instructions reçues d'une ou plusieurs installations de commande et reçoivent des réponses des unités mobiles, y compris leur altitude et d'autres données d'intérêt pour l'installation de comande. Au moins deux satellites communiquent l'un avec l'autre par une voie de communication croisée. Les satellites comprennent des appareils de traitement par ordinateur pour calculer les distances entre les unités mobiles et chaque satellite sur la base des réponses reçues des unités mobiles, pour enregistrer et traiter des messages. Les informations concernant la position et les messages sont transmises à au moins une des installations de commande. De préférence les installations de commande utilisent des protocoles d'accès multiple par partage dans le temps (TDMA) ou d'accès multiple par partage des fréquences (FDMA) pour communiquer avec les satellites. Le traitement à bord permet aisément à une pluralité d'installations de commande d'avoir directement accès aux statellites plutôt que de passer par une station centrale au sol et d'augmenter la capacité d'un système d'interrogation d'adresses individuelles sur un spectre donné de fréquences radio attribuées. Un système d'interrogation d'adresses individuelles est un système dans lequel chaque unité mobile est individuellement interrogée et répond seulement à des interrogations qui l'identifient expressément.
PCT/US1987/002059 1986-08-20 1987-08-20 Systeme de telemetrie et de traitement par satellite pour surveillance mobile et transmission de donnees WO1988001392A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DK211788A DK211788A (da) 1986-08-20 1988-04-19 Satellitovervaagningssystem
KR1019880700437A KR880701891A (ko) 1986-08-20 1988-04-20 이동감시 및 데이터 링크를 위한 범위지정 및 처리 위성시스템

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US89819686A 1986-08-20 1986-08-20
US898,196 1986-08-20

Publications (2)

Publication Number Publication Date
WO1988001392A2 true WO1988001392A2 (fr) 1988-02-25
WO1988001392A3 WO1988001392A3 (fr) 1988-03-10

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PCT/US1987/002059 WO1988001392A2 (fr) 1986-08-20 1987-08-20 Systeme de telemetrie et de traitement par satellite pour surveillance mobile et transmission de donnees

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KR (1) KR880701891A (fr)
AU (1) AU7915987A (fr)
DK (1) DK211788A (fr)
WO (1) WO1988001392A2 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0310939A3 (en) * 1987-09-30 1990-04-04 Nec Corporation Satellite-based vehicle communication/position determination system
WO1998014795A1 (fr) * 1996-09-30 1998-04-09 Qualcomm Incorporated Determination d'une position au moyen d'un satellite sur orbite basse terrestre
WO1998014796A3 (fr) * 1996-09-30 1998-06-18 Qualcomm Inc Determination passive de position au moyen de deux satellites sur orbite terrestre basse
GB2320992A (en) * 1997-01-03 1998-07-08 Motorola Inc Communicating between aircraft and flight control centre using satellites
WO1998028634A3 (fr) * 1996-12-04 1998-08-27 Olivetti Res Ltd Systeme de detection permettant de determiner la position d'objets et de recueillir toute autre information les concernant
US6137441A (en) * 1998-09-09 2000-10-24 Qualcomm Incorporated Accurate range and range rate determination in a satellite communications system
US6298238B1 (en) 1998-09-09 2001-10-02 Qualcomm Incorporated Fast user terminal position determination in a satellite communications system
US6369754B1 (en) 1999-04-02 2002-04-09 Qualcomm Inc. Fine positioning of a user terminal in a satellite communication system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100425246B1 (ko) * 2001-05-04 2004-03-30 이지로보틱스 주식회사 무선조작 로봇 제어 시스템

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1591517B1 (de) * 1967-07-21 1971-08-05 Siemens Ag Funk-Ortungsverfahren durch Laufzeitmessung zu Fahrzeugen mit Transpondern ueber Erdsatelliten
US3665464A (en) * 1969-05-01 1972-05-23 Goodyear Aerospace Corp Method and apparatus for high speed vehicle position acquisition
US3750166A (en) * 1971-06-11 1973-07-31 J Dearth Pilot data system
US4359733A (en) * 1980-09-23 1982-11-16 Neill Gerard K O Satellite-based vehicle position determining system

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0310939A3 (en) * 1987-09-30 1990-04-04 Nec Corporation Satellite-based vehicle communication/position determination system
US6107959A (en) * 1996-09-30 2000-08-22 Qualcomm Incorporated Positioning determination using one low-Earth orbit satellite
WO1998014795A1 (fr) * 1996-09-30 1998-04-09 Qualcomm Incorporated Determination d'une position au moyen d'un satellite sur orbite basse terrestre
WO1998014796A3 (fr) * 1996-09-30 1998-06-18 Qualcomm Inc Determination passive de position au moyen de deux satellites sur orbite terrestre basse
EP1199579A1 (fr) * 1996-09-30 2002-04-24 QUALCOMM Incorporated Détermination passive de position au moyen de deux satellites sur orbite terrestre basse
US6078284A (en) * 1996-09-30 2000-06-20 Qualcomm Incorporated Passive position determination using two low-earth orbit satellites
WO1998028634A3 (fr) * 1996-12-04 1998-08-27 Olivetti Res Ltd Systeme de detection permettant de determiner la position d'objets et de recueillir toute autre information les concernant
GB2320992A (en) * 1997-01-03 1998-07-08 Motorola Inc Communicating between aircraft and flight control centre using satellites
GB2320992B (en) * 1997-01-03 2001-11-21 Motorola Inc Global aviation communication system
FR2758224A1 (fr) * 1997-01-03 1998-07-10 Motorola Inc Systeme mondial de telecommunications pour l'aviation
US6137441A (en) * 1998-09-09 2000-10-24 Qualcomm Incorporated Accurate range and range rate determination in a satellite communications system
US6298238B1 (en) 1998-09-09 2001-10-02 Qualcomm Incorporated Fast user terminal position determination in a satellite communications system
US6369754B1 (en) 1999-04-02 2002-04-09 Qualcomm Inc. Fine positioning of a user terminal in a satellite communication system

Also Published As

Publication number Publication date
DK211788D0 (da) 1988-04-19
KR880701891A (ko) 1988-11-05
WO1988001392A3 (fr) 1988-03-10
AU7915987A (en) 1988-03-08
DK211788A (da) 1988-05-11

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