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WO2003003611A2 - Procede permettant d'ameliorer l'utilisation des bandes de communication radio, et systeme de communication utilisant ce procede - Google Patents

Procede permettant d'ameliorer l'utilisation des bandes de communication radio, et systeme de communication utilisant ce procede Download PDF

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Publication number
WO2003003611A2
WO2003003611A2 PCT/IL2002/000520 IL0200520W WO03003611A2 WO 2003003611 A2 WO2003003611 A2 WO 2003003611A2 IL 0200520 W IL0200520 W IL 0200520W WO 03003611 A2 WO03003611 A2 WO 03003611A2
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WIPO (PCT)
Prior art keywords
sub
cell
carriers
phase
receiver
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PCT/IL2002/000520
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English (en)
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WO2003003611A3 (fr
Inventor
Michael Bank
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Strathmore Ltd.
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Publication date
Application filed by Strathmore Ltd. filed Critical Strathmore Ltd.
Priority to AU2002345325A priority Critical patent/AU2002345325A1/en
Publication of WO2003003611A2 publication Critical patent/WO2003003611A2/fr
Publication of WO2003003611A3 publication Critical patent/WO2003003611A3/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0491—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas using two or more sectors, i.e. sector diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/023—Multiplexing of multicarrier modulation signals, e.g. multi-user orthogonal frequency division multiple access [OFDMA]
    • H04L5/026—Multiplexing of multicarrier modulation signals, e.g. multi-user orthogonal frequency division multiple access [OFDMA] using code division

Definitions

  • the present invention relates to the field of wireless communication systems. More particularly, the invention relates to a method and system for increasing the number of communication channels that can be simultaneously established within a cell, by using essentially the same set of radio frequency (RF) sub-carriers for transmitting the data that corresponds to each communication channel.
  • RF radio frequency
  • conventional systems such as GSM
  • the number of people that may simultaneously use their cellular phones in a crowded place is rather small.
  • the number of users may be as high as 160.
  • This drawback is due to the limited maximum bandwidth that is allowed for each sector in each cell. The bandwidth allowed for each sector is limited in order to minimize the interference between each two adjacent sectors. Consequently, the number of channels that might be utilized by a sector in a cell is rather low.
  • channels are allocated to sectors in a cell according to the number of users in the sectors, namely channels are allocated to more 'busy' sectors on the expanse of less busy sectors.
  • there is a maximum number of channels that can be utilized by a specific sector which is rather low (e.g. 15-20 channels per sector).
  • 8 data sources e.g. 8 data sources
  • Other RF systems are also used to allocate to sectors in a cell according to the number of users in the sectors, namely channels are allocated to more 'busy' sectors on the expanse of less busy sectors.
  • there is a maximum number of channels that can be utilized by a specific sector which is rather low (e.g. 15-20 channels per sector).
  • one sector's communication band which comprises e.g. 20 channels
  • COFDM Coded Orthogonal Frequency Division Multiplexing
  • a communication channel comprises m orthogonal carriers, and the data to be transmitted is distributed between these carriers.
  • Using multi-carriers according to this technique allows reducing the symbol (i.e. a set of logic '0' and ' 1') transmission rate at each carrier, and using the orthogonality property significantly reduces inter-symbol interference.
  • the essence of this technique is keeping high symbol/data rate transmission. It does not solve the problem of efficiently allocating Radio Frequency bands.
  • Multi-carrier' is a Radio Frequency (RF) signal comprising a set of m
  • + ⁇ is a group of ⁇ t , wherein each ⁇ represents a different symbol; e.g.
  • + ⁇ j ⁇ +10°,+100 o ,-170 o ,-80° ⁇ , wherein + 10° may represent a symbol '00',
  • + 100° may represent symbol '01' etc.
  • This group may be also called a 'positive symbol scheme'.
  • a sub-carrier may be modulated by such positive symbol scheme in which case it is said that the sub-carrier is assigned a positive symbol scheme.
  • - ⁇ is a group of ⁇ t , wherein each symbol is represented by the respective negative phase as appears in group + ⁇ ,- .
  • the symbol '00' for example, is represented in group - ⁇ j by -10° .
  • This group i.e. - ⁇ j
  • This group may be also called a 'negative symbol scheme'.
  • a sub-carrier may be modulated by a negative symbol scheme in which case it is said that the sub-carrier is assigned a negative symbol scheme.
  • 'Inversion rule' is a rule applied by a receiver on the received signal, determining which of the sub-carriers' schemes should be inverted from negative scheme (- ⁇ j) to positive scheme ( + ⁇ j ).
  • 'Composite-carrier' is a multi-carrier signal, wherein every sub-carrier
  • the multi-carrier signal is phase-modulated by either a positive or a
  • each said scheme modulates a different sub-carrier in a specific multi-carrier signal.
  • a schemes combination may be (SQ) wherein ft through / are the sub-carriers of a specific composite carrier, which are modulated by positive and negative symbols schemes as specified (i.e. ft by + ⁇ j etc.).
  • SC 2 ⁇ / 1 : + ⁇ 2 , 2 : - ⁇ 2 , 3 : - ⁇ 2 > 4 : + ⁇ 2 ⁇ .
  • each cell has a unique schemes combination SC t , since it is assigned a unique
  • 'Communication channel' is a wireless connection established between a (base) station and an end-user using a mobile, or stationary, transceiver.
  • the new system which comprises a transmitter, wherein, and from which, the above-mentioned composite carrier is generated and transmitted, and a receiver that applies the inversion rule as specified above, is hereinafter referred to as the Frequency Bank System (FBS).
  • FBS Frequency Bank System
  • the transmitter and receiver may be a base station and a mobile, or a stationary, receiver of a cellular system, respectively.
  • the transmitter may be a local TV or Radio station and the receiver is a mobile, or a stationary, TV receiver or Radio receiver, respectively.
  • the digital modulation may be carried out by phase-shifting the sub-carriers' RF frequencies, such that the phases being uniformly spaced on a O ⁇ 360° circle and representing digital symbols.
  • the modulation method may be selected from the group of: BPSK, DBPSK, QPSK, DQPSK, MSK, MPSK, DMPSK.
  • the data may consist of digital symbols.
  • a guard interval may be added to each symbol before transmission of the symbol, for reducing the effect of transient interference in the receiver, that can be later identifying and removing.
  • Fig. 1A Schematically illustrates one CDMA cell (prior art).
  • Fig. IB Schematically illustrates three .CDMA cells (prior art).
  • FIG. 2A Schematically illustrates a TDMA cellular system (GSM, AMPS, DAMPS), in which seven adjacent cells have different frequencies to eliminate mutual RF interference (prior art);
  • Fig. 2B Schematically illustrates a TDMA cellular system (GSM, AMPS, DAMPS), using the 'Tree Sector Cell' technique (prior art);
  • Fig. 2C Schematically illustrates a TDMA cellular system (GSM, AMPS, DAMPS), using the 'Six Sector Cells' technique (prior art);
  • Fig. 3A Schematically illustrates the minimal critical area(s) in conventional systems
  • Fig. 3B Schematically illustrates the absence of critical area, according to a preferred embodiment of the invention.
  • FIG. 4 Schematically illustrates mutual interference between two communication systems using essentially the same RF channels (prior art).
  • Fig. 5A Schematically illustrates applying an inversion rule in a simplified case (i.e. two cells), according to a preferred embodiment of the invention
  • Fig. 5B Schematically illustrates applying an inversion rule in a more practical case (i.e. three cells), according to a preferred embodiment of the invention
  • Fig. 6 Schematically illustrates transmitting exemplary training signals from cells using essentially the same four sub-carriers, according to a preferred embodiment of the invention
  • FIG. 7A Schematically illustrates a block diagram of a transmitter, according to a preferred embodiment of the invention
  • Fig. 7B Schematically illustrates a block diagram of a receiver, according to a preferred embodiment of the invention
  • Fig. 7C Schematically illustrates a two-cell model having exemplary schemes combinations, according to a preferred embodiment of the invention.
  • Fig. 8 is a flowchart of a process by which the data is interpreted by a receiver, according to a preferred embodiment of the invention.
  • the present invention is directed to a method and system for increasing the number of communication channels that can be simultaneously established within a cell.
  • a signal which is transmitted from a cell in cellular systems, or from local radio and television stations, comprises m sub-carriers spaced uniformly throughout allocated frequency band.
  • the preferred number of sub-carriers in the multi-carrier signal is m-4.
  • ⁇ t ⁇ is determined by the data and the digital modulation scheme (e.g.
  • a receiver receives all transmissions carried by all sub-carriers and obtain, by summing the corresponding phases, the total phase ⁇ ; of all the received signals at frequency ft .
  • the receiver changes the sign of the total phase ⁇ ; - for all i values that correspond to negative elements in the corresponding row of the cell.
  • the phase ⁇ t is obtained in the receiver, by summing the values of the total phase ⁇ , , after changing phase sign, and dividing the result of the summation by a number determined according to m and/or the ratio between the magnitudes of the sub -carriers within a cell, and the sub -carriers within its neighboring/overlapping cells.
  • each of the m sub-carriers carries simultaneously (i.e. modulated by) the same data (i.e. digital symbols).
  • the sub-carriers in a multi-carrier signal are uniformly spaced throughout a selected frequency band, and the spacing is inversly related to the symbol duration T s .
  • a minimal system comprising three cells, each cell having a unique
  • SC 3 ⁇ j : + ⁇ 3 , ft : - ⁇ 3 , ft : - ⁇ 3 , ft : + ⁇ 3 ⁇ , for a third transmission point.
  • orthogonal serials/codes are selected from the known Walsh-Hadamard matrix, which is used to generate orthogonal codes.
  • Walsh-Hadamard orthogonal codes i.e. serials
  • serials are generated recursively by:
  • each row i.e. code/serial
  • every other row zero cross-correlation
  • is multiplied by SQ '.
  • cell 1 is assigned a basic symbol scheme
  • a Walsh-Hadamard matrix of higher order should be considered, in order to generate more orthogonal codes to chose from.
  • the receiver has three sets of modified carriers, one of which is a set of 'all positive' symbol schemes, belonging to the selected transmission point, and the other two sets of symbol schemes, belonging to the adjacent/interfering cells, each one having at least one negative phase scheme.
  • the receiver sums-up the 'phase contribution' of every sub-carrier, from every adjacent transmission point.
  • each one of the sub-carrier has, therefore, three phases contributions.
  • sub-carrier ft contributes (to the summation) + ⁇ 1 from cell A, + ⁇ 2 from cell B and - ⁇ 3 from cell C.
  • ft x through ft contribute their respective phases.
  • the selected composite carrier comprises sub-carriers that are modulated by the same data, the data can be extracted from either one of the sub-carriers.
  • the data extraction is relatively easy, because, as is mentioned before, the sub-carriers in the multi-carrier signal are orthogonal, which provides for clear separation of the modulation signals of the sub-carriers in the receiver.
  • Guard interval is a technique of which purpose is to ehminate transient effects due to multi-path receptions, doppler effect and other factors. During the guard interval the receiver does not interpret the transmitted signal. This technique will not be further discussed, as it is well known in the art of wireless communication systems, such as Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB-T) terrestrial systems that use COFDM techniques. Whether guard intervals should be used in the invention depend on the signal's delay and the symbol(s) duration. If the signal's delay is ⁇ t and the symbol duration is T s , the duration of the guard interval At g must comply with the rule ⁇ t ⁇ At g ⁇ (0.1 ⁇ 02) * T s .
  • the symbol transmission rate is reduced to allow a longer symbol duration, into which a guard interval of adequate duration can be affiliated.
  • the symbol rate can be doubled by doubling the number of the sub-carriers (e.g. from four to eight) while still maintaining the principle of having different scheme combinations in each group of sub-carriers in adjacent cells, which is the essence of this invention. Utihzing eight sub-carriers instead of four doubles the bandwidth of the channel. However, the channel's capacity is doubled as well, thereby maintaining the efficiency of the channel.
  • S/N Signal to Noise ratio
  • each of the sub-carriers transmitted power density is lower than the transmitted power density of a conventional system.
  • the basis of the (FBS) cellular system is formed from a cluster having three adjacent cells (each cell having a different composite carrier), of which pattern repeats itself as required without interference between two adjacent cells within the same cluster of cells, or between cells in adjacent clusters.
  • Synphase interference is essentially ehminated in a FBS systems, since, according to the present invention, FBS system involves inverting half of the sub-carriers' phases, thereby causing to 'self-canceling' of such interference. Adjacent cells transmitting signals with high magnitudes
  • each sub-carrier is modulated by digital symbols.
  • a digital modulation technique known in the art as Quadrature Phase Shift Keying (QPSK) is referred to.
  • the sub -carriers of the FBS system can be modulated by utihzing other currently known digital modulation techniques, such as Binary PSK (BPSK), Differential Binary PSK (DBQPSK), Differential QPSK (DQPSK), Minimum Shift Keying (MSK) , Minimum Phase Shift Keying (MPSK), Differential Minimum Phase Shift Keying (DMPSK) etc.
  • BPSK Binary PSK
  • DBQPSK Differential Binary PSK
  • DQPSK Differential QPSK
  • MSK Minimum Shift Keying
  • MPSK Minimum Phase Shift Keying
  • DMPSK Differential Minimum Phase Shift Keying
  • the same set of m sub-carriers can be used by any number of adjacent transmission points without cross interference, due to the unique phases arrangements.
  • the schemes combinations are changed from one point/area to another adjacent point/area.
  • the essence of the present invention is that instead of reusing frequencies, as is the case in conventional systems, substantially only schemes combinations are reused, thus efficiently utilizing frequency bands.
  • the invention makes use of a communication technique known in the art as COFDM.
  • COFDM communication technique
  • the present invention makes use of some features of this technique; namely m orthogonal sub-carriers are also used, but unlike in the conventional COFDM systems, each of the m sub-carriers (simultaneously) transmits the same data.
  • every transmission point transmits the same m sub-carriers.
  • each transmission point has a different schemes combination. Consequently, the same channel, comprising the same m sub-carriers, may be used by several adjacent transmission points without cross interference. A mobile receiver which is tuned to one transmission point is not affected, therefore, by other transmitting points.
  • each transmission point comprises the same four sub-carriers (i.e. ft through ft) but different schemes combination (SQ and SC 2 ).
  • ft has a negative symbol scheme (501a) in cell A (- ⁇ j ) and a positive symbol scheme (502a) in cell B (+ ⁇ 2 ) .
  • f has a positive symbol scheme (503a) in cell A (+ ⁇ t ) and negative symbol scheme (504a) in cell B (- ⁇ 2 ) .
  • a mobile phone might be located at a critical area between cells A and B (507a), and receive a signal b(t) described by Equation 1. This is the worst case since the magnitude of the interfering signal is as high as the selected signal. However, due to the phases arrangement (i.e. each transmission point having a unique schemes combination), the receiver can cancel out any interference of that kind.
  • 'A' - denotes the sub-carriers magnitudes in both cells (i.e. A and B) in the worst case; that is when the interfering signal(s) is the strongest.
  • the interfering signal has smaller magnitude (i.e. ⁇ 'A').
  • the receiver is capable of changing its inversion rule according to a specific transmission point which is to be received.
  • the mobile receiver receives a slightly stronger signal from cell A, it is set to mode 'receiver A', which means that the receiver is programmed to invert the symbol scheme of carriers ft 2 and ft 3 in order to get 'all positive' phases (508a). Additionally, the symbol schemes of ft and ft 3 , which are received from cell B, are also inverted according to the same inversion rule. The significance of this symbol scheme inversion process will be understood by further inspecting the various phases in Equation 2. The phases of the received four carriers, before applying the inversion rule, are:
  • the mobile receiver Since the mobile receiver is programmed, according to this example, to apply the inversion rule that allows it to receive signals from cell A, the resultant signal phase depends only on the phase of the sub-carriers in cell A (i.e. ⁇ ), while it is not affected by (any of the sub-carriers of) the signal transmitted from cell B. Similarly, if the receiver's mode is switched to receive signals from cell B, after inverting ft 2 and ft 4 the resultant phase is (4* ⁇ 2 )l2.
  • the resultant divisor in Eq. 3 is a private case, where the sub-carriers have the same magnitude 'A' (see Eq. 1).
  • the result of Eq. 3 is (4 * ⁇ )l q ('q' : a real number).
  • a training signal is transmitted from each cell's base station, of which magnitude is measured by/in a receiver.
  • Fig. 5B illustrates a more realistic example of three cells (i.e. A, B and C) in a cellular system
  • each cell uses the same four sub-carriers (i.e. ft through f A ) but with different symbol schemes, thus creating three distinguished sets of multi-carriers.
  • sub-carriers ft l and ft have a symbol scheme + ⁇
  • sub -carriers ft and ft have a symbol scheme - ⁇ A
  • sub -carriers ft and ft have a symbol scheme - ⁇ A
  • sub -carriers f x and ft have a symbol scheme + ⁇ #
  • sub -carriers f 2 and f 4 have a symbol scheme ⁇ # .
  • sub-carriers f[ and f 4 have a symbol scheme + ⁇
  • sub-carriers ft and ft have a symbol scheme - ⁇ .
  • receiver 501b may be switched over three modes of operations in order to allow it to receive signal coming from either cell (i.e. A, B or C).
  • the decision to which cell it will be tuned to is taken according to the strongest signal, which is received in the receiver.
  • a mobile phone is closer to cell A, its receiver is forced by the transmitter in cell A to switch to 'receiver A' mode; namely receiver A is programmed to invert the phases of carriers ft and ft to yield 'all positive' phases (502b). Since transmission points B and C are allowed, according to the invention, to be rather close to transmission point A, receiver A detects their signal, which is almost as strong as the signal coming from point A.
  • receiver A since receiver A is programmed to invert ft and ft (i.e. to yield 'all positive' symbol schemes), it also inverts ft and ft 4 in signals which are received from cells B and C. Inverting signal B by receiver A results in negative symbol schemes (504b), and the same applies to signal C whenever received by receiver A (503b).
  • Fig. 6 illustrates one exemplary method for measuring the magnitude of representative sub-carriers; i.e. one representative carrier from each transmission point (cell).
  • a cell e.g. cell A
  • transmits only one (non- modulated) sub-carrier e.g. f[) from the set of m available sub-carriers, which is received in a receiver.
  • the magnitude of the received signal is measured and recorded in a memory in the receiver, while the phases, which are embedded in the transmitted signal(s), are 'known' to the receiver; i.e. the receiver 'knows' what phases it expects to receive.
  • Sub-carrier ft is used to measure the signal propagation delays, after which a further adjustment can be made, in the receiver, to the interpreted signal. Measuring the changes in the phases of the four sub-carriers, as compared to the 'known'/expected phases, allows the receiver to calculate multi-path propagation, as well as propagation delays.
  • Fig. 7A illustrates a block diagram of a transmitter, according to a preferred embodiment of the invention.
  • the output of an analog source 601 is sampled and digitized by an Analog-to-Digital (A/D) converter 602.
  • the stream of binary bits enters a Digital Signal Processor (DSP), which is comprised of two main elements.
  • the first element (604) is a module which assembles a predefined constant portion of the digital data stream into symbols.
  • the symbols are the data by which the 'n' RF sub-carriers 603 are modulated, for example, in a technique known as Quadrature Phase Shift Keying (QPSK).
  • QPSK Quadrature Phase Shift Keying
  • the second element of the DSP is the Inverse Fast Fourier Transform (IFFT) 605.
  • IFFT Inverse Fast Fourier Transform
  • the analog signal comprises a multi-carrier signal, which comprises m sub-carriers, each sub-carrier phase changes according to the changes in the stream of bits (i.e. changing symbols).
  • the modulated multi-carrier i.e.
  • composite signal) signal is then 'up-shifted' in frequency (607); i.e. from Intermediate Frequency (IF) to the final/transmitted frequency, and transmitted by antenna 608.
  • IF Intermediate Frequency
  • the result of the IFFT 605a could be achieved by applying any type of 'frequency-domain' to 'time-domain' transformation.
  • Fig. 7B illustrates a block diagram of a receiver, according to a preferred embodiment of the invention.
  • the received analog signal (by antenna 609) is 'down-shifted' (610) in frequency to IF frequency and digitized by A/D converter 611.
  • the inversion rule of the receiver is implemented, for example, by FFT (612) in the DSP module, after which the phases of the received sub -carriers (from the selected transmission point and from other adjacent transmission points) are summed-up to cancel out the interfering sub -carriers from adjacent cells.
  • the symbols i.e. data
  • a digital signal decompression feature is also included in the receiver, although not shown in Fig. 7B. .
  • the result of the FFT 612 could be achieved by applying any type of to 'time-domain' to 'frequency-domain' transformation.
  • This figure further illustrates an example of two schemes combinations. Additionally, symbols comprising two binary bits are predefined. Therefore, four distinguished symbols are possible in such a system (i.e. '00', '01', '10' and '11').
  • f[ (in cell A) has a positive symbol scheme + ⁇ .
  • the practical implication in this case is that whenever sub-carrier ft is to be modulated by e.g. symbol [00] it is phase-shifted by +10° . However, whenever sub-carrier ft ⁇ is to be modulated by symbol [11], it is phase-shifted by -170° etc.
  • f 3 and ft have negative symbols schemes (- ⁇ i). For example, whenever symbol [00] is the modulating data, a phase shift of. -10° is added to ft and ft . Similarly, whenever symbol [10] is the modulating data, a phase shift of + 80° is added to ft 3 and ft 4 .
  • each transmission point has a different basic symbol scheme.
  • cell B has a different basic symbol scheme (i.e.
  • the same negation principle is applied to ft through ft . For example, whenever the symbol [00] is the modulation data, a phase of (-70) degrees is added to 2 and ft 3 .
  • each data/symbol (e.g. in cell A) simultaneously modulates ft ⁇ through ft .
  • Fig. 8 illustrates a flow chart of the receiving steps. This figure references a typical case of three transmission cells, each cell uses a multi-carrier signal comprising four sub-carriers. Since the received multi-carrier signal is digitally modulated, a synchronization function (801) must be apphed on it. If a guard interval is added to the transmitted signal, this block (i.e. 802) is required in order to identify it and to allow the receiver to extract the actual/effective data. The guard interval is used as recovery time, and the receiver regards as effective data only the signal that is received between two consecutive guard intervals.
  • each cell transmits a training signal.
  • cell A may use for this purpose sub-carrier /j , cell B sub-carrier ft etc.
  • each cell uses ft 4 to transmit a training signal for measuring the signal propagation delay (s).
  • the required compensation factors i.e. At,A ⁇ ,q ) are calculated (803). The usage of them is described hereinafter.
  • phase' corrections There are two types of phases' corrections that must be carried out in the receiver. The first one is due to signal propagation delay during normal operation (i.e. whenever an actual data is received)- ⁇ t (804) is used to make the necessary phases adjustments (807) in that respect. The second type of phases corrections is due to the variance in the sub-carriers magnitudes- 'g' (806) is used to make these necessary corrections.
  • the FFT (808) is apphed on the phase-corrected signal (807), in order to calculate the multi-carriers magnitudes 810 and phases 809 in the received signal.
  • the phases are summed up (811) to cancel out any interfering sub-carriers in a way that is described before.
  • the resulting sum of phases (811) is erroneous due to the differences in the various sub-carriers magnitudes. Therefore, after measurements of the magnitudes have been made (803), and the correction factor 'g' has been calculated (805), based on these measurements, 'g' is used (806) to make the necessary phases corrections (812).
  • Phase ⁇ (812) represents, therefore, the calculated phase(s) representing symbols which are received from a selected transmitter (i.e. a base station in a cell). Together with ⁇ , the calculated magnitudes (810) are used to correct errors in the stream of incoming digital bits, by applying a 'Soft Decision' technique (813), which is a technique well known in the art of decoding of digital data, and therefore will not be further described.
  • each sub-carrier is modulated by shifting its phase by a different shift (e.g. ⁇ in cell A and ⁇ 2 in cell B), we get the following composite signal:
  • the Soft Decision Decoder After the Soft Decision Decoder (813) tests each symbol, it disassembles the symbols, to provide the corresponding reconstructed binary digits (814), after which they are converted to analog signal by a Digital-to-Analog converter.
  • Combination number 0 is impractical since there is nothing advantageous about this combination; i.e. a receiver is not required to apply any Inversion Rule.
  • the number of sub-carriers may be increased
  • CDMA Coded Division Multi-Access
  • CDMA systems are the more advanced systems that are widely used today. However, the present invention presents a significant advantage over CDMA systems, as is demonstrated in the following example.
  • CDMA systems have minimal 15 users per MHz per cell (see J. Gardiner, B. West, Personal Communication Systems and Technologies, Artech House, Boston). Consequently, a 25 MHz frequency band can serve up to 375 Voice Connections.
  • a bit rate of 20 kbit/s like in CDMA-900
  • QPSK- FBS signals of 0.5 bit/Hz
  • the Bit Rate (BR) for each Voice Connection (VC) is 22.8 kbits/s. Assuming there are a maximum of 20 channels in each sector of a cell, each channel having 8 Voice Connection (VC), a maximum of 160 VC can be utilized in this system.
  • the channel bit rate is 200 kbits/s. Since according to present invention the frequency efficiency in the QPSK-FBS signal is 0.5 bit/Hz, the actual frequency channel occupies 400 kHz.
  • Transmission point Si is assumed to be the selected point from which the transmission is to be received, while S2 and S3 are the interfering transmission points.
  • a phase representing the original symbol, as is transmitted by point Si is calculated.
  • the present invention improves performance over other wireless communication systems, due to its new type of composite carrier.
  • the main advantage of the present invention is that the communication capacity of the existing frequency range is significantly increased.
  • Other advantages, that result from the main advantage, are:
  • DAB Digital Audio Broadcasting
  • DVD-T Digital Video Broadcasting

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Abstract

L'invention concerne un procédé et un système permettant d'augmenter le nombre des canaux de communication pouvant être simultanément mis en place dans une cellule contenue dans un groupe de cellules. Une bande de fréquence devant être utilisée par chaque cellule du groupe est obtenue, puis, le nombre de m=2n (n=1, 2,...,) sous-porteuses orthogonales identiques f1, f2, fm, sur lesquelles des données individuelles sont transmises dans chaque canal de communication est déterminé pour toutes les cellules du groupe. Une phase ζ¿i? est attribuée à chaque sous-porteuse fi (i=1, 2,..., m) dans une cellule, de telle sorte que la valeur absolue |ζi| soit déterminée par les données transmises et par le modèle de modulation numérique, et que cette valeur absolue soit identique pour toutes les fi dans la cellule, et que le signe de chaque ζi dans la cellule soit identique au signe d'un élément correspondant choisi dans une rangée dans une matrice Walsh-Hadamard mxm correspondant à la cellule, de sorte que les cellules avoisinantes/chevauchantes utilisent différentes rangées. Les données contenues dans chaque cellule sont transmises sur les sous-porteuses et sur leurs phases correspondantes. Toutes les transmissions effectuées par toutes les sous-porteuses sont reçues, et la phase totale ζi de tous les signaux reçus à la fréquence fi sont obtenus. Le signe de la phase totale ζi est modifié pour chaque cellule pour toutes les valeurs i correspondant aux éléments négatifs contenus dans la rangée correspondante de la cellule. La phase ζi de n'importe quelle sous-porteuse fi transmise est obtenue par addition des valeurs de la phase totale ζi, après modification des signes de phase, puis, division du résultat de l'addition par un nombre déterminé en fonction de m et/ou du rapport entre les magnitudes des sous-porteuses dans une cellule et les magnitudes des sous-porteuses dans les cellules avoisinantes/chevauchantes.
PCT/IL2002/000520 2001-06-28 2002-06-27 Procede permettant d'ameliorer l'utilisation des bandes de communication radio, et systeme de communication utilisant ce procede WO2003003611A2 (fr)

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AU2002345325A AU2002345325A1 (en) 2001-06-28 2002-06-27 Cellular communication system which uses multicarrier spread-spectrum transmission

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IL144068 2001-06-28
IL14406801A IL144068A0 (en) 2001-06-28 2001-06-28 A method for improving the utilization of radio communication bands, and a communication system using the method

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007020626A1 (fr) * 2005-08-18 2007-02-22 Hill, Hanit Selecter Systeme mobile de communications sans fil sans signaux pilotes
EP1762013B1 (fr) * 2005-04-08 2010-08-11 Panasonic Corporation Appareil de communication et méthode de communication associée

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5282222A (en) * 1992-03-31 1994-01-25 Michel Fattouche Method and apparatus for multiple access between transceivers in wireless communications using OFDM spread spectrum
US5970053A (en) * 1996-12-24 1999-10-19 Rdl, Inc. Method and apparatus for controlling peak factor of coherent frequency-division-multiplexed systems

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1762013B1 (fr) * 2005-04-08 2010-08-11 Panasonic Corporation Appareil de communication et méthode de communication associée
WO2007020626A1 (fr) * 2005-08-18 2007-02-22 Hill, Hanit Selecter Systeme mobile de communications sans fil sans signaux pilotes

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AU2002345325A1 (en) 2003-03-03
IL144068A0 (en) 2002-04-21
WO2003003611A3 (fr) 2004-03-11

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