WO2004019532A1 - Ofdm−cdma送信装置及びofdm−cdma送信方法 - Google Patents
Ofdm−cdma送信装置及びofdm−cdma送信方法 Download PDFInfo
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- WO2004019532A1 WO2004019532A1 PCT/JP2003/010202 JP0310202W WO2004019532A1 WO 2004019532 A1 WO2004019532 A1 WO 2004019532A1 JP 0310202 W JP0310202 W JP 0310202W WO 2004019532 A1 WO2004019532 A1 WO 2004019532A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/38—TPC being performed in particular situations
- H04W52/42—TPC being performed in particular situations in systems with time, space, frequency or polarisation diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1829—Arrangements specially adapted for the receiver end
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- 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
- H04L5/026—Multiplexing of multicarrier modulation signals using code division
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/7103—Interference-related aspects the interference being multiple access interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
- H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
- H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
- H04B2201/7097—Direct sequence modulation interference
- H04B2201/709709—Methods of preventing interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L2001/0092—Error control systems characterised by the topology of the transmission link
- H04L2001/0096—Channel splitting in point-to-point links
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
Definitions
- OFDM-C DMA transmission device and OFDM-C DMA transmission method
- the present invention is suitable for application to an OFDM-CDMA transmitting apparatus or a CDMA transmitting apparatus that spreads a transmission symbol, allocates the spread chips to subcarriers orthogonal to each other, and performs radio transmission.
- a plurality of symbols are arranged in the same frequency band and transmitted by code division multiplexing of transmission symbols.
- the receiving side can separate and restore a plurality of multiplexed symbols.
- OFDM-CDMA systems are broadly divided into time-domain spreading and frequency-domain spreading.
- time domain spreading method each spread data spread in chip units by a spreading code is arranged in the same subcarrier in the time direction.
- frequency domain spreading method each spread data spread on a chip basis is allocated to different subcarriers and arranged.
- Fig. 1 shows a configuration example of a conventional OFDM-CDMA communication device.
- OFDM-CDMA communication apparatus 1 converts a plurality of transmission signals l to k,, (4 k + 1) to 5 k
- the signals are input to spreaders A 1 to A (5 k) which use different spreading codes to spread in chip units.
- the spread signals are added by adders C1 to C5 to obtain code division multiplexed signals.
- adders C1 to C5 In the case of FIG. 1, in each of the adders C1 to C5, spread signals corresponding to k transmission signals are multiplexed.
- the code division multiplexed signals output from the adders C1 to C5 are parallel-serial converted by a parallel / serial converter (P / S) 4, and then inverse fast Fourier transform circuits (IFFT) 5 By being converted, orthogonal frequency division multiplexing is performed.
- the OFDM-CDMA communication device 1 is a radio reception unit (RF) that performs a radio reception process such as an antenna AN and an Xanaguchi digital conversion process of the OFDM-C DMA signal transmitted from the OFDM-CDMA communication device having the same configuration.
- RF radio reception unit
- FFT fast Fourier transform circuit
- the FFT 6 performs a fast Fourier transform process on the input signal to obtain a code division multiplexed signal transmitted by each subcarrier.
- the propagation path compensating circuit 7 compensates for phase fluctuations and the like generated in the propagation path based on known signals such as a propagation path estimation briamble included in the signal.
- the signal after propagation path compensation is despread by despreader 8, whereby a received signal addressed to the own station is extracted from a plurality of transmission signals.
- FIG. 2 shows a signal arrangement of OFDM-CDMA signals formed by conventional OFDM-CDMA communication apparatus 1.
- the number of transmission signals is 5 k and the spreading ratio is m
- the number of subcarriers is the same as the spreading ratio m.
- the following signals are allocated to each subcarrier. That is, on the first subcarrier # 1, the first spread signal (chip) of the multiplexed transmission signals l to k is arranged, The second spread signal (chip) of the signal obtained by multiplexing the transmission signals 1 to k is arranged in the second subcarrier, and the transmission signal (4 k + l) The m-th spread signal among the signals multiplexing ⁇ 5k is arranged.
- the number of subcarriers and the spreading ratio do not always have to match.
- the diffusion ratio m is set to 1/5 of the number of subcarriers is shown (the diffusion ratio is not limited to this case, and it goes without saying that the diffusion ratio can be set arbitrarily).
- the communication device using the conventional code division multiplexing method has a problem that it is difficult to achieve both frequency utilization efficiency and error rate characteristics. This also applies to a communication device of the CDMA system which is not as remarkable as the OFDM-CDMA system. Disclosure of the invention
- An object of the present invention is to provide a wireless transmission device and a wireless transmission method of an OFDM-CDMA system that can achieve both frequency use efficiency and error rate characteristics.
- This object is achieved by selecting the number of multiplexes (that is, the number of code multiplexes) for each symbol in code division multiplexing of transmission symbols.
- this is achieved by selecting a spreading ratio for each symbol when code division multiplexing transmission symbols.
- FIG. 1 is a block diagram showing the configuration of a conventional OFDM-CDMA communication device
- FIG. 2 is a diagram showing a signal arrangement example of a conventional OFDM-CDMA signal
- FIG. 3 is a block diagram showing a configuration of an OFDM-CDMA transmitting apparatus according to Embodiment 1 of the present invention
- FIG. 4 is a diagram showing a signal arrangement example of an OFDM-CDMA signal transmitted by the OFDM-CDMA transmitting apparatus according to the first embodiment
- FIG. 5 is a block diagram showing another configuration example of the OFDM-CDMA transmitting apparatus according to the first embodiment
- FIG. 6 is a block diagram showing the configuration of the OFDM-CDMA transmitting apparatus according to the second embodiment
- FIG. 7 is a block diagram showing the configuration of the 0 F DM-C DMA receiving apparatus according to the second embodiment
- Fig. 8 is a diagram showing an example of the signal arrangement of OFDM-CDMA signals for explaining two-dimensional spreading
- FIG. 9 is a block diagram showing a configuration of the OFDM-CDMA transmitting apparatus according to the third embodiment.
- FIG. 10 is a block diagram showing the configuration of the OFDM-CDMA transmitting apparatus according to the fourth embodiment.
- FIG. 11 is a block diagram illustrating a configuration of an OFDM-CDMA transmitting apparatus according to a fifth embodiment
- FIG. 12 is a block diagram illustrating a configuration of a CDMA transmitting apparatus according to Embodiment 6;
- FIG. 13 is a block diagram illustrating a configuration of a CDMA transmitting apparatus according to Embodiment 7;
- FIG. 14 is a block diagram showing the configuration of the CDMA receiving apparatus according to the seventh embodiment;
- FIG. 15 is a block diagram showing the configuration of the OFDM-CDMA transmitting apparatus according to the eighth embodiment;
- FIG. 16 is a block diagram showing a configuration of a CDMA transmitting apparatus according to Embodiment 9;
- FIG. 17 is a block diagram showing the configuration of the CDMA transmission apparatus according to the tenth embodiment.
- FIG. 3 shows a schematic configuration of an OFDM-CDMA transmitting apparatus according to Embodiment 1 of the present invention.
- the FDM—CDMA transmitting apparatus 100 performs code division multiplexing on a plurality of transmission signals 1 to 5 k using different spreading codes, and distributes the code division multiplexed spreading signals to a plurality of subcarriers orthogonal to each other. Thus, transmission of the OFDM-CDMA method is performed.
- the OFDM-C DMA transmitting apparatus 100 uses a plurality of transmission signals 1 to k,, (4 k + 1) to 5 k via buffers Z 1 to Z (5 k) and chips using different spreading codes. Input to diffusers A 1 to A (5 k) that spread to units.
- the spread signals are collectively input to the selection units B1, B5 in a plurality of systems. Specifically, k spread signals for the transmission signals l to k are input to the selection unit B1, and k spread signals for the transmission signals (4k + l) to 5k are selected by the selection unit B5.
- each of the transmission signals l to k,, (4k + 1) to 5k is a signal that has been subjected to QPSK (Quadrature Phase Shift Keying) modulation processing or 16-level QAM modulation processing by a modulation unit (not shown). It is.
- the selection units B1 to B5 have a function as multiplex number selection means for selecting a multiplex number for each transmission symbol. In the case of this embodiment, the selection units B1 to B5 The number of multiplexes is selected based on the information from the state detection unit 111. Specifically, the line status sent from each user is detected by the line status detection unit 111 via the antenna AN and the reception radio unit (RF) 110, and the user is determined according to the line status of each user. Select the multiplex number for each.
- RF reception radio unit
- each adder C 1 -C 5 forms a code division multiplexed signal by multiplexing the spread symbols selected by the selectors B 1 -B 5.
- the code division multiplexed signals output from the adders C1 to C5 are parallel-serial converted by a parallel serial conversion unit (PZS) 101, and then inverse fast Fourier conversion units (IFFT) 102. By being converted, orthogonal frequency division multiplexing is performed.
- PZS parallel serial conversion unit
- IFFT inverse fast Fourier conversion units
- This forms an OFDM-CDMA signal in which the spread chips are distributed to a plurality of orthogonal subcarriers, and the OFDM-CDMA signal performs radio transmission processing such as digital-to-analog conversion processing and signal amplification.
- the signal is transmitted via the transmission unit (RF) 103 and the antenna AN.
- FIG. 4 shows a frame format of an OFDM-CDMA signal transmitted by OFDM-CDMA transmitting apparatus 100.
- OF DM—CDMA transmitter 100 sets the spreading ratio to 1/5 of the number of subcarriers and sets all subcarriers to 5 subcarrier groups # l to #m, # m + l to # 2m, # 2m + l to # 3m, # 3 m + l ⁇ # 4m, divided into # 4m + l ⁇ # 5 m.
- a code division multiplexed signal obtained by each of the adders C1 to C5 is arranged.
- the code division multiplexed signal obtained by the adder C1 is allocated to the subcarrier groups # 1 to #m and allocated to the subcarriers in the frequency axis direction, and the subcarrier groups # 4m + 1 to # 5m are allocated to the subcarrier groups # 1 to # 5m.
- the code division multiplexed signal obtained by the adder C5 is allocated to the subcarriers in the frequency axis direction and arranged.
- the OFDM-CDMA transmitter 100 is, as apparent from FIG.
- transmission is performed with the number of multiplexed transmission signals reduced (multiplexing number n ⁇ k), and time t2 to time t3 and time t3 to time t In one burst period of 4, transmission is performed with the number of multiplexed transmission signals increased (multiplex number k).
- transmission is performed by reducing the number of multiplexes for the symbol of the user with poor round / line state.
- a signal (symbol) of a user having a poor line condition is transmitted with a reduced number of multiplexes.
- the OFDM-CDMA transmitting apparatus 100 detects the line state with each user by the line state detecting unit 111 and sends it to the selecting units B1 to B5.
- the selection units B1 to B5 reduce the number of multiplexes for symbols addressed to users with poor line conditions.
- the code division multiplexed signal whose number of multiplexes is appropriately selected in this way is distributed to a plurality of mutually orthogonal subcarriers by IFFT 102 as orthogonal frequency division multiplexing means (that is, frequency axis spread to a plurality of subcarriers). ) And OFDM-CDMA signal.
- an OFDM-CDMA transmission apparatus 100 capable of achieving both frequency utilization efficiency and error rate characteristics can be realized by reducing the number of multiplexes of symbols transmitted to users with poor line conditions. .
- the present invention is not limited to this. It can be widely applied when the number of multiplexed transmission symbols is smaller than the number of multiplexed other transmission symbols.
- the overall error rate characteristics and the error rate characteristics of the information that greatly affect the transmission efficiency can be maintained without significantly reducing the overall frequency use efficiency. Can be improved.
- the selecting sections B1 to B5 based on a control signal designating a specific symbol from the controlling section 151. What is necessary is just to reduce the multiplexing number of a specific symbol.
- the diffusion ratio is set to 1Z5, the number of subcarriers, has been described.
- the diffusion ratio is not limited to 1/5 but can be set arbitrarily.
- the diffusion ratio of each subcarrier group does not necessarily have to be the same, but can be set arbitrarily.
- the present invention is not limited to the case where the subcarriers are grouped as in the embodiment, and the spread signals may be arranged on all the subcarriers.
- FIG. 4 shows a case where the number of multiplexed signals (n ⁇ k) in all subcarrier groups is reduced during a certain burst period (time points tl to t2).
- the present invention is not limited to this. It is sufficient to appropriately reduce only the number of multiplexed specific symbols, and is not limited to the frame format as shown in FIG.
- DS-CDMA direct spreading CDMA
- the method of the present embodiment in which the multiplexing number of a specific symbol is made smaller than the multiplexing number of other symbols is effective even when applied to the DS-CDMA method. When applied, the effect is even more pronounced.
- the diffusion ratio of a particular symbol is larger than that of another symbol.
- the quality when a specific symbol is despread on the receiving side can be made better than other symbols.
- the spreading ratio is increased, the frequency use efficiency decreases, but the spread ratio is increased only for specific symbols, so that the frequency use efficiency does not need to be reduced much.
- the symbol for increasing the spreading ratio is better than other symbols, such as a symbol transmitted to a user with poor line conditions and a symbol indicating control information or retransmission information. It is preferable to select a symbol that requires high quality.
- FIG. 6 shows a schematic configuration of an OFDM-CDMA transmitting apparatus according to this embodiment.
- OFDM—CDMA transmitting apparatus 200 makes the spreading ratio of retransmission signals 1 to ⁇ larger than the spreading ratios of other transmission signals. It is supposed to.
- spreading sections A (5k + 1) to A (5k + n) for spreading retransmission signals 1 to ⁇ have a larger spreading ratio than other spreading sections A1 to A (5k).
- the retransmission signals 1 to n are spread using a spreading code.
- the spread signal is multiplexed by an adder C6 and then input to a parallel-serial conversion unit (P / S) 201.
- P / S parallel-serial conversion unit
- the parallel serial conversion section 201 of the OFDM-CDMA transmission apparatus 200 includes the parallel-serial conversion section 101 of the OFDM-CDMA transmission apparatus 100 described in the first embodiment. More than one adder units C1 to C6, and one more code division multiplexed signal is input for one system, and this code division multiplexed signal has a spreading ratio greater than that of the other systems. The chip rate is high because it is large.
- the frequency band of the spread symbol becomes large.
- a method of changing the subcarrier group to which the spread signal is assigned, or a method of arranging the spread signal on both the frequency subcarrier and the time subcarrier are used. Just fine.
- the spreading ratio of retransmission signals 1 to n is set to twice that of other transmission signals 1 to 5 k
- one group of subcarriers is supported for the same number of transmission signals.
- two groups of sub-carriers may be used.
- the association between the code division signals and the subcarrier groups is determined by the parallel / serial conversion unit (P / S) 201 in which order the code division multiplex signals obtained by the adders C1 to C6 are assigned. This can be realized by appropriately setting whether to output to the inverse Fourier transform unit (IFFT) 102.
- IFFT inverse Fourier transform unit
- FIG. 7 shows a configuration of an OFDM-CDMA receiving apparatus 300 that receives and demodulates an OFDM-CDMA signal transmitted from FDM_CDMA transmitting apparatus 200.
- the OFDM-C DMA receiving device 300 includes a radio receiving unit (RF) 301 that performs a radio receiving process such as an antenna AN and an analog digital conversion process on the OFDM-CDMA signal transmitted from the OFDM-C DMA transmitting device 200.
- RF radio receiving unit
- FFT Fast Fourier Transform
- the propagation path compensating section 303 compensates for phase fluctuations or the like generated in the propagation path based on a known signal such as a propagation path estimation preamble included in the signal.
- the signals after propagation path compensation are input to despreading sections 304 and 305 having different numbers of taps.
- the number of taps of despreading section 305 for despreading the transmission signal is such that the normal transmission signal is despread. Twice as large as the despreading section 304. This makes it possible to recover both the normal transmission signal and the retransmission signal.
- the spreading ratio of a symbol required to have better quality than other symbols is determined by the other symbol.
- an OFDM-CDMA transmitting apparatus 200 that can achieve both frequency utilization efficiency and error rate characteristics can be realized.
- the spread signal is arranged in the frequency direction, so that the error rate characteristic deterioration with respect to time variations such as frequency offset and fading does not increase. Therefore, the method of this embodiment in which the spreading ratio of a specific symbol is made larger than the spreading ratio of other symbols is effective even when applied to the DS-C DMA system, but OFDM-C When applied to the DMA system, a more remarkable effect appears.
- the method of the present embodiment in which the spreading ratio of a specific symbol is made larger than that of another symbol, is used when the multiplexing number of a specific symbol in the first embodiment is made smaller than the multiplexing number of other symbols.
- the frequency utilization efficiency and the error rate characteristics can be more compatible.
- This embodiment proposes to reduce the number of multiplexed known signals or increase the spreading ratio when transmitting a known signal for cell identification. As a result, a known signal for cell identification can be transmitted with high quality, so that the probability of a communication partner erroneously recognizing a cell can be reduced.
- a transmission signal including a known signal for cell identification is transmitted to a communication terminal that is a transmission destination station.
- the cell to which the own station belongs is recognized.
- cell identification becomes possible by the wireless base station transmitting a known signal corresponding to each cell and the communication terminal identifying the type of base signal received.
- This embodiment is intended to improve the cell discrimination characteristics without lowering the frequency use efficiency.
- FIG. 9 shows the configuration of the OFDM-CDMA transmitting apparatus 400 of this embodiment.
- OFDM—CDMA transmitting apparatus 400 transmits a known signal for cell identification to spreading section A (5 k + n + 1). Input.
- the spreading ratio of spreading section A (5k + n + 1) spreads retransmission signals l to n.
- the spreading ratios are set to be larger than the spreading ratios for the other transmission signals 1 to 5k. This can improve the error rate characteristics on the receiving side of the known signal for cell identification.
- the number of multiplexes multiplexed by the adder C6 is smaller than the number of multiplexes multiplexed by the other adders C1 to C5. . That is, the number (n + 1) obtained by adding the known signals to the retransmission signals l to n input to the adder C6 is equal to the transmission signals l to k, 4 input to the other adders C1 to C5. k + 1-5k is less than the number k. As a result, the error rate characteristics of the known signal and the retransmission signal are further improved.
- the number of multiplexed known signals for cell identification is made smaller than the number of multiplexed other transmitted signals, and / or the spreading ratio is made larger.
- An OFDM-CDMA transmission apparatus 400 capable of causing a communication terminal to accurately perform cell identification without significantly lowering the frequency use efficiency can be realized.
- the present invention is not limited to this, and only the number of multiplexed signals may be reduced or only the spreading ratio may be increased.
- This embodiment proposes that, when a known signal for frame synchronization is arranged at the beginning of a frame and transmitted, the number of multiplexed signals of the known signal is reduced and / or the spreading ratio is increased. As a result, a known signal for frame synchronization can be transmitted with high quality, and the communication partner can perform frame synchronization with high accuracy.
- a known signal for frame synchronization may be arranged at the beginning of a transmission frame and transmitted. Then, the communication terminal detects the known signal to obtain a frame. Synchronization is performed. This embodiment is intended to improve the accuracy of frame synchronization without lowering the frequency use efficiency.
- FIG. 1 ⁇ shows a schematic configuration of the OFDM-CDMA transmitting apparatus of this embodiment.
- OFDM-CDM A transmitting apparatus 500 inputs a known signal for frame synchronization to spreading section A (5 k + n + 1).
- the spreading ratio of spreading section A (5 k + n + 1) is the same as that of spreading sections A (5 k + 1) to A (5 k + n), which spread retransmission signals 1 to n. It is set to be larger than the diffusion ratio of k. As a result, it is possible to improve the error rate characteristics on the receiving side of the known signal for frame synchronization.
- the OFDM-CDMA transmitting apparatus 500 has a smaller number of multiplexes multiplexed by the adder C6 than a number of multiplexes multiplexed by the other adders C1 to C5. That is, the number (n + 1) power S obtained by adding the known signals to the retransmission signals l to n input to the adder C6, the transmission signals l to k, input to the other adders C1 to C5, 4 k + 1 to 5 k is less than the number k. As a result, the error rate characteristics of the known signal and the retransmission signal for frame synchronization are further improved.
- the parallel / serial conversion unit (P / S) 201 in addition to the code division multiplexed signals obtained by the adders C1 to C6, a signal indicating the head of the frame from a control unit (not shown) is input. You.
- the parallel-to-serial converter 201 outputs the code division multiplexed signal input from the adder C6 at the timing when the signal indicating the head of the frame is input.
- the code division multiplexed known signal can be arranged at the beginning of the frame of the OFDM-CDMA signal.
- the number of multiplexed known signals for frame synchronization is made smaller and the spreading ratio is made larger than the number of multiplexed other transmitted signals, thereby increasing the frequency utilization efficiency.
- OFDM-CDMA transmitting apparatus 500 that can improve the frame synchronization accuracy of a communication terminal without significantly lowering the frequency.
- the number of multiplexed known signals for frame synchronization is reduced as compared with the number of multiplexed other transmitted signals, and the spreading ratio is increased.
- the present invention is not limited to this, and only the number of multiplexed signals may be reduced or only the spreading ratio may be increased.
- This embodiment proposes to reduce the number of multiplexed retransmission signals and / or increase the spreading ratio as the number of retransmissions increases. This makes it possible to prevent an increase in the number of retransmissions while suppressing a decrease in frequency use efficiency.
- An increase in the number of retransmissions means an increase in the delay between data transmission and reception. In other words, the amount of data transmitted per time decreases, and the transmission efficiency deteriorates.
- the number of code multiplexes is reduced or the spreading ratio is increased, thereby improving the effect of improving the error rate characteristics as the number of retransmissions increases. . This can prevent an increase in the number of retransmissions.
- the number of retransmissions can be reduced effectively without wasting the transmission data amount. .
- the number of code multiplexes in the retransmission signal is unnecessarily reduced or the spreading ratio is unnecessarily increased just because the retransmission request has been issued, the amount of transmitted data decreases, so the number of retransmissions increases.
- FIG. 11 shows a schematic configuration of an OFDM-CDMA transmitting apparatus according to this embodiment.
- OFDM—CDM A transmitting apparatus 600 retransmits signals to selecting sections B 1 to B 5 that select the number of multiplexed transmission signals. Enter information indicating the number. Information indicating the number of retransmissions is output from a control unit (not shown).
- the selection units B1 to B5 determine whether the number of retransmissions is large in the input spread signal and based on the information indicating the number of retransmissions. , The number of multiplexed signals to be multiplexed on the signal is reduced. This will be specifically described. For example, when all the transmission signals l to k are the first transmissions, the selection unit B1 selects and outputs all the input transmission signals l to k. As a result, in the power P calculator C1, a code division multiplexed signal having k signal multiplexes is obtained.
- the selection unit B1 includes the transmission signal 1 among the input transmission signals l to k (k-1 ) Transmission signals are selected and output.
- adder C1 a code division multiplexed signal having a signal multiplexing number (k ⁇ 1) including transmission signal 1 as the first retransmission signal is obtained.
- the selection unit B 1 selects (k ⁇ 1 2) of the input transmission signals 1 to k including the transmission signal 1. Select and output the transmission signal.
- adder C1 a code division multiplexed signal having a signal multiplexing number (k-1 2) including transmission signal 1 as the second retransmission signal is obtained.
- the frequency An OFDM-CDMA transmitting apparatus 600 that can achieve both usage efficiency and error rate characteristics can be realized.
- FIG. 11 describes a configuration in which the number of multiplexed signals for a retransmission signal is reduced as the number of retransmissions increases, the retransmission signal with a higher number of retransmissions has a higher spreading factor according to the information indicating the number of retransmissions. The same effect can be obtained even if is increased.
- the fifth embodiment a case has been described where the method of reducing the number of multiplexed retransmission signals and / or increasing the spreading ratio as the number of retransmissions increases is applied to the OFDM-CDMA wireless transmission apparatus.
- this method it is proposed that this method be applied to a DS-CDMA DMA transmission apparatus.
- the OFDM-CDMA system since a signal spread in the frequency direction is arranged, the reception level of all the chips of the spreading code does not drop, so that a frequency diversity effect can be obtained. Therefore, even under a multipath environment, the effect of improving the error rate is large.
- the OFDM-CDMA system is multi-carrier transmission, the peak power becomes large and the power consumption of the entire device becomes large.
- the DS-C DMA method can reduce the peak power compared to the OFDM-C DMA method, so that the power consumption of the entire device can be suppressed. Therefore, considering that the power consumption of the entire device is kept low, the DS-CDMA system is more advantageous. Considering this point, this embodiment proposes to apply the present invention to a DS-CDMA wireless transmission apparatus.
- FIG. 12 shows a schematic configuration of a CDMA transmitting apparatus according to this embodiment.
- the CDM transmitting apparatus 700 of FIG. It has the same configuration as.
- the OFDM-CDMA transmitting apparatus according to the fifth embodiment except that the process of reducing the number of code multiplexes of the retransmission signal and / or increasing the spreading ratio is applied to the DS-CDMA transmission. Same as 600.
- the process of reducing the number of code multiplexes of retransmission signals and / or increasing the spreading ratio is performed by using the HSDPA (High Speed Downlink Packet Access) method of transmitting data using a high-speed downlink channel. If used in this type of wireless transmission device, the number of retransmissions can be effectively reduced without significantly reducing the frequency use efficiency.
- HSDPA High Speed Downlink Packet Access
- Embodiments 7 to 10 provide a radio transmission apparatus of the CDMA system and the OFDM-CDMA system and a method thereof that can effectively reduce the number of retransmissions without substantially reducing the error rate.
- Embodiments 7 to 10 The concept common to the following Embodiments 7 to 10 is to increase the number of spreading codes assigned to retransmission signals as the number of retransmissions increases. That is, one retransmission signal is code-division multiplexed using a plurality of spreading codes according to the number of retransmissions and transmitted.
- the error rate characteristics of the retransmitted signal can be improved. As a result, it is possible to prevent the number of retransmissions from being excessively increased without substantially reducing the transmission efficiency.
- FIG. 13 shows a schematic configuration of CDMA transmitting apparatus 1100 according to the seventh embodiment.
- the CDMA transmitting apparatus 1100 inputs the modulated transmission signal to the control unit 1102 of the code division multiplexing unit 1101.
- Control section 1102 transmits the input transmission signal to a plurality of spreading sections 1103 to 1106 that perform spreading processing using different spreading codes at predetermined timing.
- each of the spreading units 1103 to 1106 performs a spreading process using a spreading code that is orthogonal to each other (that is, a spreading code whose mutual correlation is “0”).
- the spread signal obtained by spreading section 1103 is transmitted to selecting section 1109.
- the spread signals obtained by spreading sections 1104, 1105, and 1106 are sent to selecting section 1107.
- Selection section 1107 selectively outputs a spread signal based on a signal from control section 1102 indicating the number of retransmissions. Specifically, at the time of the first retransmission, only the spread signal from spreading section 1104 is selectively output, and at the time of the second retransmission, the spread signals from spreading section 1104 and spreading section 1105 are selectively output. At the time of retransmission for the first time, spread signals from all spreading sections 1104, 1105, and 1106 are selectively output.
- Adder 1108 adds the spread signals output from selector 1107. As a result, a code division multiplex signal is obtained.
- the selection unit 1109 determines whether only the signal from the spreading unit 1103 or the spreading unit 1103 and the addition unit based on the signal indicating whether the signal to be transmitted this time is a retransmission signal from the control unit 1102 or not. Selectively outputs both signals of unit 1 108. Specifically, only signals from spreading section 1103 are selected and output at the time of initial transmission, and both signals of spreading section 1103 and adding section 1108 are selected and output at the time of retransmission.
- the output of the selection unit 1109 is transmitted via a radio transmission unit (RF) 110 and an antenna 111, which are provided as transmission means and perform radio transmission processing such as digital-to-analog conversion processing and signal amplification. You.
- RF radio transmission unit
- the receiving system of the CDMA transmitting apparatus 1100 is a radio receiving unit (R) that performs radio receiving processing such as analog-to-digital conversion processing of the CDMA signal received by the antenna 1 1 1 1 F)
- the signal is input to the despreading unit 1113 via 1112.
- the signal despread by despreading section 113 is output as a received signal and sent to retransmission request detection section 114.
- Retransmission request detecting section 111 detects a retransmission request signal included in the received signal, and sends the detection result to control section 1102.
- the control unit 1102 is provided with a buffer, and when there is a retransmission request, outputs a previously transmitted transmission signal stored in the buffer as a retransmission signal. Control section 1102 also controls the transmission timing of the retransmission signal and the like.
- FIG. 9 shows a schematic configuration of a wireless receiving apparatus that receives a CDMA signal transmitted from CDMA transmitting apparatus 1100.
- the CDMA receiving apparatus 1200 is input to a plurality of despreading sections 1203 to 1206 via a radio receiving section (RF) 1202 which performs a radio receiving process such as an analog-to-digital conversion process on a CDMA signal received by the antenna 1200.
- RF radio receiving section
- each despreading unit 1203, 1204, 1205, 1206 receives using the same spreading code as the spreading code used in each spreading unit 1103, 1104, 1105, 1106 of the CDMA transmitting apparatus 1100. It is designed to despread CDMA signals.
- the despread result obtained by the despreading units 1203 to 1206 is input to the selection unit 1207.
- the selection unit 1207 selects a despread result having the largest correlation power from each despread result. Then, the selected despread result is sent to error detecting section 1208.
- Error detection section 1208 detects whether or not an error has occurred in the result of the despreading, and outputs no input signal as a received signal when no error has been detected. On the other hand, when an error is detected, it notifies retransmission request signal forming section 1209 of the fact. Incidentally, here, in order to simplify the explanation, an error is directly detected from the despread result. However, in practice, the error is detected by demodulating and decoding the despread result. Retransmission request signal forming section 1209 forms a retransmission request signal, when an error is detected. The retransmission request signal is transmitted to the radio transmitter (RF) 1210 and antenna 120 It is transmitted to CDMA transmitting apparatus 1100 via 1.
- RF radio transmitter
- selecting section 1109 selects and transmits the transmission signal spread by spreading section 1103.
- CDMA receiving apparatus 1200 Upon receiving the first transmission signal, CDMA receiving apparatus 1200 outputs the result of despreading in despreading section 1203 to error detecting section 1208, and when error detecting section 1208 detects an error, it transmits a CDMA signal.
- a retransmission request signal is transmitted to device 1 100.
- the CDMA transmitting apparatus 1100 selects only the spread signal from the spreading section 1104 by the selecting section 1107, and further selects the spread signal from the spreading section 1103 and the adding section 1108 in the selecting section 1109. Select output from. As a result, the CDMA transmitting apparatus 1100 transmits a two-code multiplexed retransmission signal.
- CDMA receiving apparatus 1200 selects the despread signal having the larger correlation power from the despread results from despreading section 1203 and despreading section 1204 by selecting section 1207. And sends it to the error detection unit 1208.
- error detecting section 1208 transmits a retransmission request signal to CDMA transmitting apparatus 1100 again.
- CDMA transmitting apparatus 1100 selects a spreading signal from spreading section 1104 and spreading section 1105 by selecting section 1107, and further selects a spreading signal from spreading section 1103 and adding section by selecting section 1109. 1 Select the output from 108.
- a retransmission signal multiplexed with three codes is transmitted from CDMA transmitting apparatus 1100.
- CDMA receiving apparatus 1200 selects the despread signal having the highest correlation power from the despread results from despreading sections 1203, 1204, and 1205 by selecting section 1207.
- the error is sent to the error detector 1208.
- error detecting section 1208 transmits a retransmission request signal to CDMA transmitting apparatus 1100 again.
- C DMA transmitting apparatus 1100 selects spread signals from spreading sections 1104, 1105, and 1106 by selecting section 1107, and further selects In 1109, the spread signal from spreading section 1103 and the output from addition section 1108 are selected. As a result, a retransmission signal multiplexed with four codes is transmitted from CDMA transmitting apparatus 1100.
- selecting section 1207 selects the despread signal having the largest correlation power from the despread results from despreading sections 1203, 1204, 205, and 1206. I do.
- the number of spreading codes assigned to retransmission signals is increased.
- the effect of improving the error rate can be enhanced as the number of retransmissions increases.
- the number of retransmissions can be effectively reduced without lowering the error rate characteristics.
- the number of spreading codes assigned to the retransmission signal is increased, so that the number of retransmissions can be effectively reduced without substantially reducing the error rate characteristic. 1 100 can be realized.
- the configuration of each of the spreading units A1 to A (5k) and A (5k + 1) to A (5k + n) shown in FIG. 2 may be changed to a code division multiplex unit 1101 in FIG.
- the effects of the above-described first to sixth embodiments can be obtained.
- the present invention is not limited to this. To combine multiple despread results May be used to obtain a received signal.
- a retransmission signal is multiplexed with two codes at the time of the first retransmission, multiplexed with three codes at the time of the second retransmission, and multiplexed with four codes at the time of the third retransmission
- the present invention is not limited to this. In short, it is only necessary to increase the number of code multiplexes as the number of retransmissions increases.
- the number of spread signals corresponding to the number of retransmissions is selected by selection section 1107.
- the case of selection is described, but the point is that the code multiplexing number of the transmission signal should be increased as the number of retransmissions increases.For example, the number of spreading units to be turned on according to the number of retransmissions is increased.
- the output may be multiplexed.
- transmission to one transmission destination (user) has been described for simplicity of description. However, similar processing is performed on signals addressed to a plurality of users, and those signals are subjected to code division. Of course, it can be multiplexed and transmitted.
- the code division multiplexing unit 1101 shown in FIG. 13 may be provided only for the user, and the signals output from the respective selectors 111 may be multiplexed and transmitted.
- Embodiment 7 a case will be described in which the technology described in Embodiment 7 is applied to an OFDM-CDMA wireless transmission device.
- the interference between preceding and following codes in a multipath environment can be removed by the guard interval, so the technology that increased the number of spreading codes assigned to retransmission signals as the number of retransmissions increased increases.
- the error rate performance in a multipath environment can be further improved, and the effect of suppressing the number of retransmissions can be increased.
- the ⁇ F DM-C DMA transmitting apparatus 130 of this embodiment includes a parallel-serial conversion circuit and a serial-parallel conversion circuit. And a reordering unit 1303 for reordering spread signals, and performing inverse fast Fourier transform processing on the reordered spread signals. Accordingly, the configuration is the same as that of the CDMA transmitting apparatus 1100 in FIG. 13 except that an inverse fast Fourier transform unit (IFFT) 1302 in which the spread chips are arranged in a plurality of subcarriers orthogonal to each other is provided. .
- IFFT inverse fast Fourier transform unit
- a transmission signal spread to a plurality of users is input to reordering section 1301. Then, according to the processing of the reordering unit 1301, the OFDM-CDMA transmitting apparatus 1300 spreads each spread chip in the frequency axis direction, spreads it in the time axis direction, or spreads the frequency axis and the time axis. It can be spread to both.
- the receiving system is omitted in FIG. 15, it has a configuration for receiving a retransmission request signal from a transmission partner as in FIG.
- the number of spreading codes assigned to the retransmission signal is increased as the number of retransmissions increases, so that multipath It is possible to realize an OFDM-CDMA transmitter 1300 that can further improve the error rate characteristics under the environment and further reduce the number of retransmissions.
- the code division multiplex unit 1101 is divided into the spreading units A 1 to A (5 k) and A (5 k) shown in FIG. 1, FIG. 3, FIG. 5, FIG. 6, FIG. 9, FIG.
- k + 1) to A (5k + n) are used, the effects of the first to fifth embodiments described above can be obtained in addition to the effects of the present embodiment.
- This embodiment proposes that the number of spreading codes assigned to a retransmission signal be changed according to the code multiplexing number of the entire transmission signal.
- the number of code multiplexes to be finally transmitted after code division multiplexing is not limited to a signal addressed to one user, but also includes a signal addressed to another user.
- the number of spreading codes assigned to the retransmission signal is changed.
- the CDMA transmitting apparatus 1400 in the state has code division multiplexing units 401-1 to 401-n for the number of users (n).
- the code division multiplex units 1401-12-1 to 1401-1n have the same configuration as the code division multiplex unit 1401-1-1, the configuration of the code division multiplex unit 1401-1_1 will be described below.
- the selection unit 141 1 of the code division multiplexing unit 1401-1 is determined by the total number of code multiplexes transmitted from the CDMA transmitting apparatus 1400, that is, the number of code division multiplexed signals added by the addition unit 141 3 If the number of code multiplexes is equal to or more than a predetermined number, only one of the two spread signals input is output. On the other hand, if the number of code multiplexes is less than the predetermined number, both of the two input spread signals are output. The other code division multiplexing units 1401-2 to 1401-n perform the same processing as this processing. Then, the outputs of the selection units 1109 provided in the respective code division multiplexing units 1401-1-1 to 1401-1n are multiplexed by the addition unit 1413.
- control unit 1410 of the code division multiplexing unit 1401-1 receives a signal indicating the number of code multiplexes of the entire CDMA transmission device 1400 from an upper control unit (not shown) of the CDMA transmission device 1400, This is sent to the selector 141 1.
- FIG. 16 for simplification of the drawing, the configuration of a receiving system for detecting a retransmission request signal is omitted, but a receiving system similar to that in FIG. 13 is provided.
- CDMA transmitting apparatus 1400 selects and transmits the transmission signal spread by spreading section 1103 in selecting section 1109 at the time of initial transmission. Also, at the time of the first retransmission, selecting section 1412 selects only the spread signal by spreading section 1104, and selecting section 1109 selects the spread signal from spreading section 1103 and the output from adding section 1108. As a result, retransmission signal multiplexed with two codes is output from selection section 110.
- C DMA transmitting apparatus 1400 selects spreading signals output from spreading section 1104 and selecting section 141 1 by selecting section 141 2 and adds These spread signals are multiplexed by 1 108.
- the selection unit 1411 outputs one spread signal when the number of code multiplexes in the entire CDMA transmitter 1400 is large, and outputs two spread signals when the number of code multiplexes is small. Since a signal is output, as a result, two or three spread signals are multiplexed in the adder 144. As a result, a retransmission signal multiplexed with 3 codes or 4 codes is output from the selection unit 1109.
- the C DMA transmitting apparatus 1400 selects the spread signals output from the spreading section 1 104 and the selecting section 1 4 1 1 by the selecting section 1 4 1 2 and the adding section 1 1 0 8 multiplexes these spread signals.
- the selection unit 1411 outputs one spread signal when the number of code multiplexes in the entire CDMA transmitter 1400 is large, and outputs two spread signals when the number of code multiplexes is small. Since a signal is output, as a result, two or three spread signals are multiplexed in the adder 144. As a result, a retransmission signal multiplexed with 3 codes or 4 codes is output from the selection unit 1109.
- the CDMA transmitting apparatus 1400 does not simply increase the number of spreading codes assigned to the retransmission signal as the number of retransmissions increases, but instead addresses other users who are code division multiplexed with the retransmission signal.
- the number of spreading codes to be assigned to the retransmission signal is determined by taking into account the total number of code multiplexes including the number of retransmission signals, and the error rate characteristics of the retransmission signal can be further improved. It becomes possible to reduce it step by step.
- the number of spreading codes assigned to one retransmission signal is increased, a plurality of spreading signals are formed for one retransmission signal, multiplexed and transmitted, and the reception side selects the one having the largest correlation coefficient.
- the more spreading codes are assigned to one retransmission signal the better the error rate performance will be.
- the number of spreading codes assigned to the retransmission signal is changed according to the number of code multiplexes, thereby further improving the error rate characteristic of the retransmission signal as compared with the seventh embodiment. Therefore, it is possible to realize a CDMA transmitting apparatus 1400 capable of further reducing the number of retransmissions.
- the configuration of each of the spreading units A 1 to A (5 k) and A (5 k + 1) to A (5 k + n) shown in FIG. 12 is shown in the code division multiplex unit 1 401 of FIG. What should I do?
- the effects of the above-described first to sixth embodiments can be obtained.
- the retransmission signal is multiplexed by two codes at the time of the first retransmission, and is multiplexed by 3 codes or 4 codes at the time of the second and third retransmissions.
- the code multiplex number is not limited to this.
- a case has been described in which the features of the present embodiment are applied to a CDMA transmission apparatus 1400 of the CDMA communication system, but the present embodiment is applied to a radio transmission apparatus of the OFDM-CDMA communication system. You can also.
- a rearrangement unit consisting of a parallel-serial conversion unit and a serial-parallel conversion unit may be provided instead of the addition unit 14 13, and inverse Fourier transform processing may be performed on the rearranged signals. .
- This embodiment proposes, in addition to the configurations of Embodiments 7 and 9, to increase the transmission power of a retransmission signal as the number of retransmissions increases. As a result, the error rate characteristics of the retransmitted signal are further improved as compared with Embodiments 7 and 9. Since it can be improved, the number of retransmissions can be further reduced.
- the code division multiplexing unit 150 0 1—1 of the CDMA transmitting apparatus 150 of this embodiment has a calorie calculation. Except for having a multiplication unit 1503 as transmission power control means and a selection unit 1502 for selecting a multiplication coefficient to be multiplied by the multiplication unit 1503 after the unit 111 It has a configuration similar to that of the CDMA transmitter 140 in FIG. Selection section 1502 selects a coefficient according to a signal indicating the number of retransmissions from control section 1410.
- the signal from the adder 1108 is output at the same signal level from the multiplier 1503 at the first retransmission, and the signal from the adder 1108 is output at the second retransmission. Is output at a double signal level, and at the third retransmission, the signal from the adder 110 is output at a triple signal level.
- the number of spreading codes assigned to the retransmission signal increases, and the transmission power of the retransmission signal increases.
- transmission is performed with the same transmission power as the signal addressed to other users, and at the time of the first retransmission, the retransmission signal is transmitted at twice the transmission power of the signal destined for other users.
- the signal is transmitted at three times the transmission power of the signal addressed to other users, and at the third retransmission, the signal is transmitted at four times the transmission power of the signal addressed to other users.
- the transmission power of the retransmission signal is increased as the number of retransmissions increases. Since the error rate characteristic of the retransmission signal can be further improved, it is possible to realize a CDMA transmission apparatus 1500 capable of further reducing the number of retransmissions.
- the set value of the transmission power described in this embodiment is an example, and the present invention is not limited to this, and the point is that the transmission power of the retransmission signal may be increased as the number of retransmissions increases. It is also effective to change the transmission power of the retransmission signal according to the total number of code multiplexes transmitted from the CDMA transmitter. Specifically, when the number of users performing communication is small, the number of code multiplexes is naturally small. In this case, it is possible to improve the quality of the retransmitting user by further increasing the transmission power of the retransmission signal. become able to.
- the seventh, ninth, and tenth embodiments described above mainly the description has been given of the CDMA transmitting apparatus.
- the configuration of the seventh, ninth, and tenth embodiments is applied to the OFDM-CDMA transmitting apparatus.
- the same effects as in the seventh, ninth, and tenth embodiments can be obtained.
- the spread signal is distributed to a plurality of subcarriers, so that the degree of freedom in the arrangement of the spread signal can be increased as compared to the CDMA method.
- time-domain spreading in which spread signals are arranged in the time direction of the same subcarrier frequency-domain spreading in which spread signals are arranged in different subcarriers (that is, in the frequency direction), and in both the time direction and the frequency direction
- Two-dimensional diffusion to be arranged can be set.
- the spreading signal can be transmitted to multiple subcarriers. Since it is possible to arrange and transmit signals with a certain degree of freedom, it is possible to transmit a spread signal effectively in a plurality of subcarriers even when the number of chips increases.
- the case where the number of multiplexed specific symbols is reduced and / or the diffusion ratio is increased has been described. If is made smaller than the modulation level of other symbols, the error rate characteristics can be further improved without significantly lowering the frequency utilization efficiency. In other words, if modulation processing of other symbols is performed by 16-value QAM, but modulation processing of specific symbols is performed by QPSK, QPSK has better error rate characteristics than 16-value QAM. Improved error rate performance Up.
- power information described by taking control information or retransmission information as an example of a specific symbol for reducing the number of multiplexing and / or increasing the spreading ratio The present invention is not limited to this. May be selected as the channel estimation preamble. In other words, if the number of code multiplexes of the channel estimation preamble is reduced and / or the spreading ratio is increased and periodically inserted into the transmission signal, the channel estimation preamble can be transmitted with good quality. If the propagation path estimation result is updated using the propagation path estimation preamble in the propagation path capturing unit 303 shown in the figure, highly accurate propagation path estimation can be performed.
- the number of multiplexes of a specific symbol may be smaller than the number of multiplexes of other symbols, and the number of multiplexes is not particularly limited. It can be transmitted without using. That is, it is preferable to select a multiplex number of “1” for a symbol that is particularly important among the specific symbols and transmit the symbol.
- the spreading ratio of a particular symbol may be larger than the spreading ratio of other symbols, and the value of the spreading ratio is not particularly limited. It may be.
- setting the spreading ratio to “1” means that there is no spreading, so in the case of OFDM-CDMA, a specific symbol is transmitted by OFDM. As a result, a specific symbol can be transmitted at high quality and at high speed.
- the multiplexed spread signal when distributed to a plurality of subcarriers orthogonal to each other by the orthogonal frequency division multiplexing means, the subcarriers in the frequency axis direction or the subcarriers in the frequency axis direction and the time axis direction are used.
- (2D spreading) has been described, but the present invention is not limited to this, and a chip of a specific symbol with a reduced number of multiplexing or a chip of a specific symbol with a large spreading ratio is allocated only to subcarriers in the time axis direction. It may be. In this case, for example, the reception level is lowered due to frequency selective fading.
- the error rate characteristics of the specific symbol can be further improved. This method is suitable when the moving speed of the communication terminal is low and the time variation of fading is small.
- An OFDM-CDMA transmitting apparatus comprises: a spreading means for spreading transmission symbols; a multiplex number selecting means for selecting a multiplex number for each transmission symbol; and a spread signal of each transmission symbol with the selected multiplex number.
- a configuration including multiplexing means for multiplexing, and orthogonal frequency division multiplexing means for distributing the multiplexed spread signal to a plurality of subcarriers is adopted.
- the multiplex number selection means since the number of multiplexes for each transmission symbol is selected by the multiplex number selection means, it becomes possible to select the intersymbol interference at the time of transmission of the code division multiplexed signal for each symbol, thereby improving the error rate characteristics.
- the evil can be selected for each symbol.
- the error rate characteristics can be improved without significantly reducing the frequency characteristics.
- An OFDM-CDMA transmitting apparatus includes: a spreading unit that selects a spreading ratio for each transmission symbol to spread a transmission symbol; a multiplexing unit that multiplexes a spread signal of each transmission symbol; Orthogonal frequency division multiplexing means for distributing the spread signal to a plurality of subcarriers.
- the spread ratio of each spread signal forming the code division multiplexed signal is selected for each symbol, so that the quality of the error rate characteristic can be selected for each symbol.
- the error rate characteristics can be improved without significantly reducing the frequency characteristics.
- the OFDM-CDMA transmitting apparatus of the present invention is a specific symbol having a reduced number of multiplexes.
- a specific symbol with a large spreading factor is placed at the beginning of the frame. According to this configuration, when frame synchronization is performed on the receiving side based on the specific symbol at the head of the frame, the specific symbol for frame synchronization is transmitted with high quality. Can be performed with high accuracy.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the number of multiplexes of retransmission symbols is reduced as the number of retransmissions is increased or the spreading ratio of retransmission symbols is increased as the number of retransmissions is increased.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the modulation level of a specific symbol with a reduced number of multiplexes or a specific symbol with an increased spreading ratio is smaller than the modulation level of another transmission symbol. .
- the error rate characteristic of the specific symbol can be further improved without significantly reducing the frequency use efficiency.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which a specific symbol with a reduced multiplexing number or a specific symbol with a large spreading ratio is periodically inserted.
- An OFDM-CDMA receiving apparatus of the present invention is an OFDM-CDMA receiving apparatus that receives and demodulates a signal transmitted from the OFDM-CDMA transmitting apparatus.
- a configuration is adopted in which the propagation path estimation result is updated using the reduced specific symbol or the specific symbol with a higher spreading ratio.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the number of multiplexed specific symbols whose number of multiplexes is reduced is “1”.
- the specific symbol whose multiplex number is “1” is transmitted without any intersymbol interference. Therefore, the symbol rate of a particularly important symbol can be further improved by selecting the multiplex number to be “1” and transmitting the symbol that is particularly important among the specific symbols.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the spreading means sets the spreading factor of the specific symbol whose multiplex number is reduced to “1”.
- setting the spreading ratio to "1" means that spreading is not performed, so that specific symbols can be transmitted at high speed. Therefore, a specific symbol can be transmitted at high quality and at high speed.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the orthogonal frequency division multiplexing means distributes chips of a specific symbol having a reduced number of multiplexing or an increased spreading ratio only in the time axis direction.
- the error rate characteristics of a specific symbol can be further improved. become able to. Particularly, it is suitable when the time variation of fading is small.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration in which the spreading means multicode-multiplexes the retransmission signal by increasing the number of spreading codes assigned to the retransmission signal as the number of retransmissions increases.
- the retransmission signal is transmitted after being subjected to code division multiplexing (multi-code multiplexing) using a plurality of spreading codes. If the code is used for despreading, and the result of the despreading with the largest correlation power is selected or combined, the error rate characteristics of the retransmitted signal are improved. Since the number of code division multiplexes increases as the number of retransmissions increases, the error rate characteristics of the retransmission signal can be improved without unnecessary reduction in frequency use efficiency. Can be improved. As a result, the number of retransmissions can be effectively reduced without substantially reducing the error rate.
- the spreading means determines the number of spreading codes assigned to the retransmission signal in accordance with the number of other code division multiplexed signals multiplexed on the retransmission signal after multicode multiplexing. Change, adopt a configuration.
- the number of code division multiplexing of retransmission signals is determined in consideration of the number of code division multiplexing of all transmitted signals including the code division multiplexing signal addressed to other users, so that inter-code interference is suppressed. Is done.
- the error rate characteristics of the retransmission signal can be further improved, and the number of retransmissions can be further reduced.
- the OFDM-CDMA transmitting apparatus of the present invention employs a configuration that further includes transmission power control means for increasing the transmission power of a retransmission signal that has been multiplexed as the number of retransmissions increases.
- the error rate characteristic of the retransmission signal can be improved as the number of retransmissions increases, so that the number of retransmissions can be further reduced. Also, it is possible to prevent unnecessary interference with other signals as compared with the case where the transmission power is controlled to be high when the number of retransmissions is small.
- the transmission power control means changes the transmission power according to the number of other code division multiplexed signals multiplexed on the retransmitted signal after multicode multiplexing. Take.
- the transmission power is increased, and if the number is large, the transmission power is not increased, thereby further reducing the influence on other signals.
- the error rate characteristics of the retransmission signal can be effectively improved.
- the number of multiplexing (that is, the number of code multiplexing) is selected for each symbol, and / or the spreading ratio is selected for each symbol, so that the frequency use efficiency is improved.
- OFDM-CDMA system and a wireless transmission device and a wireless transmission method of the CDMA system which are compatible with the error rate characteristics.
- the number of spreading codes assigned to the retransmission signal is increased, so that the number of retransmissions can be effectively reduced without substantially reducing the error rate.
- the present invention is suitable for application to an OFDM_CDMA system or a CDMA system wireless transmission device that requires both improvement in frequency use efficiency and improvement in error rate characteristics.
Abstract
Description
Claims
Priority Applications (3)
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EP03792665A EP1531568A4 (en) | 2002-08-23 | 2003-08-11 | ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING TRANSMISSION DEVICE AND CODE DIVISION MULTIPLE ACCESS AND OPTICAL FREQUENCY MULTIPLEXING TRANSMISSION METHOD AND CODE DIVISION MULTIPLE ACCESS |
US10/502,091 US7616608B2 (en) | 2002-08-23 | 2003-08-11 | OFDM-CDMA transmission device and OFDM-CDMA transmission method |
AU2003254932A AU2003254932A1 (en) | 2002-08-23 | 2003-08-11 | Ofdm-cdma transmission device and ofdm-cdma transmission method |
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JP2002/244310 | 2002-08-23 | ||
JP2002244309A JP4142917B2 (ja) | 2002-08-23 | 2002-08-23 | Cdma送信装置及びofdm−cdma送信装置 |
JP2002/244309 | 2002-08-23 | ||
JP2002244310A JP4146689B2 (ja) | 2002-08-23 | 2002-08-23 | Ofdm−cdma送信装置 |
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Also Published As
Publication number | Publication date |
---|---|
CN100579309C (zh) | 2010-01-06 |
CN1650555A (zh) | 2005-08-03 |
US20050163082A1 (en) | 2005-07-28 |
EP1531568A1 (en) | 2005-05-18 |
AU2003254932A1 (en) | 2004-03-11 |
EP1531568A4 (en) | 2011-10-26 |
US7616608B2 (en) | 2009-11-10 |
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