WO2009131156A1 - 無線通信システム、送信装置、受信装置及び通信方法 - Google Patents
無線通信システム、送信装置、受信装置及び通信方法 Download PDFInfo
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- WO2009131156A1 WO2009131156A1 PCT/JP2009/058013 JP2009058013W WO2009131156A1 WO 2009131156 A1 WO2009131156 A1 WO 2009131156A1 JP 2009058013 W JP2009058013 W JP 2009058013W WO 2009131156 A1 WO2009131156 A1 WO 2009131156A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
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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
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03828—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties
- H04L25/03834—Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties using pulse shaping
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
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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
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
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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
- H04W52/30—TPC using constraints in the total amount of available transmission power
- H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
- H04W52/346—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading distributing total power among users or channels
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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
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
Definitions
- the present invention relates to a radio communication system that performs communication using a frequency-spread signal such as SC-FDMA system, a radio communication system that controls the rate of clipping in spectrum shaping according to a propagation path, a transmitter, a receiver, and It relates to a communication method.
- a frequency-spread signal such as SC-FDMA system
- each cell uses the same frequency band, so that each cell is allocated to the system.
- a one-frequency repetitive cellular system that can be used as a whole has been proposed.
- OFDMA Orthogonal Frequency Division Multiple Access
- communication is performed by applying different modulation methods to information data according to reception conditions such as 64-QAM (64-ary Quadrature Amplitude Modulation) and BPSK (Binary Phase Shift Keying).
- 64-QAM 64-ary Quadrature Amplitude Modulation
- BPSK Binary Phase Shift Keying
- the PAPR Peak to Average Power Ratio
- the PAPR Peak to Average Power Ratio
- the high peak power is a downlink with a relatively large margin for the transmission power amplification function.
- SC-FDMA which converts a single carrier signal on the time axis into a frequency signal by time-frequency conversion such as Discrete Fourier Transform (DFT), and maps the frequency signal to a part of a frequency band with good reception conditions.
- DFT Discrete Fourier Transform
- the Single Carrier-Frequency Division Multiple Access method is adopted as an uplink transmission method in a next-generation cellular system called LTE (Long Term Evolution).
- a signal that is blocked for time-frequency conversion (hereinafter referred to as a frame in this specification) in a radio propagation path.
- a partial waveform behind the frame having a length equal to or longer than the maximum delay time of the delay wave is added as a CP (Cyclic Prefix) at the head of the frame, and the CP is removed by the receiving device, so that the delay wave in the propagation path The effect can be cycled within the received frame.
- the impulse response in the radio propagation path can be equivalently expressed as cyclic convolution, and the value of the discrete frequency signal obtained by DFT can be signal-processed independently.
- the water injection theorem is widely known in the field of information theory and the like as a spectrum shaping technique for maximizing the reception energy in the receiver.
- FIG. 8 shows the concept of the water injection theorem.
- the received noise-to-signal power ratio which is the reciprocal of the received signal-to-noise power ratio
- the area below the straight line P and surrounded by the noise signal power ratio and the straight line P (the shaded area in FIG. 5B) is set to be the transmission power Q.
- the transmission power assigned to each frequency can be determined as shown in FIG. This is an optimal transmission power distribution in which an amount of water corresponding to the transmission power is poured from the top with respect to the noise signal power ratio in FIG. Because there is, it is called the water injection theorem.
- nonlinear iterative equalization with excellent interference suppression function represented by turbo equalization is premised on error correction coding and improves the reliability of transmitted bits by removing distortion caused by propagation path. And the decoding that improves the reliability of the transmitted bits by error correction processing, improve the reliability, and pass this improved reliability information between the equalization-decoders as prior information and repeat it Thus, complete equalization is realized even for the signal whose spectrum has been shaped by the water injection theorem.
- the spectrum shaping technique using the turbo equalization technique can completely suppress the intersymbol interference due to the spectrum shaping and the radio propagation path by the turbo equalization if the iterative process is converged, and on the time axis.
- the spread delayed wave component can be synthesized, and the received energy maximized by the water injection theorem can be used effectively (for example, Non-Patent Document 2).
- the convergence state of the iterative process refers to a state in which transmission bit information can be completely grasped without stopping improvement in reliability by equalization and improvement in reliability by decoding.
- FIG. 9 shows the concept of spectrum shaping by clipping when two transmitters communicate with a base station.
- FIG. 4A shows an example of a primary spectrum shaping that maximizes received energy
- FIG. 5B shows an example of a concept of secondary spectrum shaping for multiplexing signals from a plurality of transmission apparatuses.
- each transmitting apparatus performs spectrum shaping based on a water injection theorem that can maximize received energy (overlapping spectrum B101).
- the secondary spectrum shaping in FIG. 5B the clipped spectrum C101
- Clipping in the secondary spectrum shaping is performed on the spectrum notified from the base station apparatus.
- the base station selects the frequency to be used for transmission alternately from the highest of the gains of the propagation path among the discrete frequencies that overlap between transmitters (so as to avoid spectral overlap between users), and a predetermined band.
- Scheduling is performed to clip the remaining frequencies, and the scheduling result is notified to each transmitter.
- the signal of the transmitter when the signal of the transmitter is multiplexed with the frequency, it cannot be used for transmission using a frequency with a good propagation condition for a certain user, and therefore, further spectrum shaping is performed for the optimal water injection theorem. Therefore, it can be considered that both suboptimal spectrum shaping and signal frequency multiplexing are realized.
- FIG. 10 shows a block diagram of the analysis model
- FIG. 11A shows an example of the convergence state
- FIG. 11B shows an example of the non-convergence state.
- the analysis model includes an equalizer 1101 and a decoder 1102, and is a model that delivers improved reliability to each other.
- the received signal and propagation path characteristics, the average received signal-to-noise power ratio, and the reliability obtained from the decoder 1102 are required for the equalization processing.
- the reliability of the transmission bits obtained from the equalizer 1101 is input, and improved reliability is output by performing error correction processing.
- MI mutual information
- FIGS. 11A and 11B These are shown as input / output characteristics of the equalizer 1101 and the decoder 1102 in FIGS. 11A and 11B.
- the horizontal axis represents the input MI of the equalizer
- the vertical axis represents the output MI of the equalizer. This is because, in turbo equalization, the equalizer output MI becomes the input MI of the decoder, so the input / output MI characteristics of the decoder are reversed in the same graph as the input / output MI characteristics of the equalizer. It also means that.
- FIG. 11A shows the convergence state of the iterative process
- L1101 shows the input / output characteristics of the equalizer
- L1102 shows the input / output characteristics of the decoder.
- the MI starts from the origin and is equalized by the equalization processing as in A1101.
- the MI obtained by the equalization process becomes the input MI of the decoder
- the process proceeds horizontally as in A1102, and improvement by error correction is obtained.
- the trajectories are drawn in the order of A1103 and A1104
- the input / output characteristics of the respective lines do not intersect with each other, so that 1 is finally obtained at the decoder output MI, and the transmission bit can be completely grasped.
- FIG. 11B the input / output characteristics of each other intersect, and when the locus is drawn, the improvement is not made at the intersection.
- This state is called a stack, and no matter how many times it is repeated based on the turbo principle, no detection error is lost, and the iterative process becomes a non-convergent state.
- Non-Patent Document 4 An adaptive coding modulation method that adaptively selects a combination of the coding rate and the coding rate has also been proposed (for example, Non-Patent Document 4).
- the adaptive coding and modulation method is a method in which the number of bits transmitted for each frame changes, and the transmission rate is unstable because the amount of information that can be transmitted is reduced particularly in a poor channel condition. There was a problem of becoming.
- the present invention has been made in view of such circumstances, and an object of the present invention is to improve transmission characteristics by controlling the ratio of clipping in spectrum shaping according to a propagation path, and perform wireless communication at a stable transmission rate.
- a communication system, a transmission device, a reception device, and a communication method are provided.
- the present invention has been made in order to solve the above-described problem.
- the spectrum shaping includes frequency-spreading a transmission signal, assigning the frequency-spread signal to a discrete frequency, and including at least clipping with respect to the assigned signal.
- a wireless communication system comprising a plurality of transmission devices that perform transmission and a reception device that receives the transmission signal, Based on the transmission signal, the reception apparatus performs transmission path information regarding propagation path characteristics between all the transmission apparatuses and reception apparatuses, and clipping regarding a clipping ratio of a spectrum adaptively controlled according to the propagation path characteristics. Information is generated and fed back to the transmitting device, and the transmitting device determines the clipping ratio based on the fed back transmission path information and the clipping information between all the transmitting devices and the receiving device. It is characterized in that spectrum shaping is performed adaptively according to the characteristics, and multiplexing is performed at a frequency.
- the present invention also includes a plurality of transmission apparatuses that frequency-spread a transmission signal, assign the frequency-spread signal to a discrete frequency, perform spectrum shaping including at least clipping on the assigned signal, and transmit the spectrum signal.
- a wireless communication system comprising a receiving device for receiving the transmission signal,
- the reception apparatus is a spectrum that is adaptively controlled according to transmission path information related to propagation path characteristics between all the transmission apparatuses and the reception apparatuses, and the coding characteristics of the propagation path characteristics and error correction codes of received signals.
- Clipping information related to the clipping ratio and coding information related to the coding rate are generated and fed back to the transmission device, and the transmission device is based on the feedback channel information, the clipping information, and the coding information.
- the clipping ratio is adaptively controlled according to the propagation path characteristics between all the transmission apparatuses and the receiving apparatuses, and the coding rate of the error correction code in the transmission apparatus is controlled according to the clipping ratio. It is characterized by spectrum shaping and multiplexing by frequency.
- the wireless communication system of the present invention is any one of the wireless communication systems described above, wherein the transmitting device does not overlap the spectrum by clipping with respect to the transmission signal of another transmitting device.
- the radio communication system according to the present invention is any one of the radio communication systems described above, wherein the transmission device overlaps a part of a spectrum by clipping a transmission signal of another transmission device. .
- the radio communication system of the present invention is any one of the radio communication systems described above, wherein the transmission device distributes power so that received energy is increased based on the propagation path characteristic information. And a secondary spectrum shaping unit that performs at least clipping based on the clipping information,
- the receiving apparatus determines a channel estimation unit that estimates a channel characteristic that is a frequency response characteristic of a channel from the transmitting apparatus to the receiving apparatus, and determines the clipping ratio in each transmitting apparatus based on the channel characteristic.
- a transmission unit that extracts a frequency-spread signal from each of the transmission devices based on the spectrum allocation information from the received signal, and a replica of the transmission signal from the signal extracted by the spectrum extraction unit.
- a soft cancel unit that cancels at least the signal, an equalization unit that detects a transmission signal transmitted from the transmission apparatus with respect to an output from the soft cancel unit, and a demodulation unit that extracts information about code data from the detected signal Then, error correction processing is performed on the information regarding the extracted code data, and the information is updated.
- a decoding unit, a soft replica generation unit that generates a replica of the transmission signal from information on the updated code data, and a reception signal replica as a propagation path characteristic that is also the effect of spectrum shaping performed by the transmission device An equivalent channel characteristic multiplying unit, a channel information related to the channel characteristic estimated by the channel estimation unit, and an information generation unit that generates clipping information related to the clipping ratio determined by the scheduling unit and feeds back to the transmission device It is characterized by comprising.
- the wireless communication system of the present invention is the above-described wireless communication system, wherein the transmission device is based on the channel characteristic information and an encoding unit that encodes a transmission signal based on the encoding information.
- a primary spectrum shaping unit that distributes power so as to increase received energy, and a secondary spectrum shaping unit that performs at least clipping based on the clipping information,
- the receiving apparatus includes: a propagation path estimation unit that estimates a propagation path characteristic that is a frequency response characteristic of a propagation path from the transmission apparatus to the receiving apparatus; and an error correction code of a received signal based on the propagation path characteristic.
- a coding rate a scheduling unit that determines the clipping ratio in each transmission device according to the coding rate, and a spectrum from which each of the transmission devices extracts a frequency-spread signal based on the spectrum allocation information from the received signal
- An extraction unit a soft cancellation unit that at least cancels a replica of the transmission signal from the signal extracted by the spectrum extraction unit, and a transmission signal transmitted by the transmission device with respect to an output from the soft cancellation unit, etc.
- a demodulator that extracts information on code data from the detected signal, and the extracted code An error correction process is performed on the information on the data, and the decoding unit that updates the information, the soft replica generation unit that generates a replica of the transmission signal from the information on the updated code data, and the transmission device
- the effect of the shaped spectrum is also the equivalent channel characteristic multiplier that generates a received signal replica as the channel characteristic, the channel information related to the channel characteristic estimated by the channel estimator, and the encoding determined by the scheduling unit
- an information generating unit that generates coding information related to a rate and clipping information related to a clipping ratio and feeds back to the transmitting apparatus.
- the wireless communication system of the present invention is the above-described wireless communication system, wherein the scheduling unit determines a coding rate according to a decoding characteristic of the decoding unit based on a coding rate.
- the wireless communication system of the present invention is any one of the wireless communication systems described above, wherein the scheduling unit calculates the clipping ratio based on a mutual information amount of input / output characteristics of the equalization unit. It is determined based on a chart.
- the wireless communication system of the present invention is the above-described wireless communication system, wherein the scheduling unit is connected to the first transmission device among equalization characteristics between at least two transmission devices and at least one reception device.
- the difference between the mutual information is obtained using the first equalization characteristic and the second equalization characteristic, If the difference is positive, increase the clipping ratio of the second transmission apparatus or decrease the clipping ratio of the first transmission apparatus. If the difference is negative, decrease the clipping ratio of the second transmission apparatus. Or increasing the clipping ratio of the first transmitter.
- the present invention also provides a plurality of transmission devices that frequency-spread a transmission signal, assign the frequency-spread signal to discrete frequencies, perform spectrum shaping on the assigned signal, and transmit the spectrum to a reception device.
- a primary spectrum shaping unit that distributes power so that reception energy is increased according to transmission path information related to propagation path characteristics between the transmission apparatus and the reception apparatus fed back from the reception apparatus, and fed back from the reception apparatus
- a secondary spectrum shaping unit that performs at least clipping based on clipping information relating to a clipping ratio of the spectrum that is adaptively controlled in accordance with propagation path characteristics, and the spectrum shaping is performed on all the transmission devices and the reception devices. It is characterized in that it is adaptively applied according to the propagation path characteristic between and multiplexed by frequency.
- the present invention also provides a plurality of transmission devices that frequency-spread a transmission signal, assign the frequency-spread signal to discrete frequencies, perform spectrum shaping on the assigned signal, and transmit the spectrum to a reception device.
- a primary spectrum shaping unit that distributes power so that received energy is increased based on transmission path information relating to propagation path characteristics between the transmission apparatus and the reception apparatus fed back from the reception apparatus, and from the reception apparatus
- a secondary spectrum shaping unit that performs at least clipping based on the clipping information on the clipping ratio of the spectrum that is adaptively controlled according to the feedback channel characteristics and the coding rate of the error correction code of the received signal;
- the spectrum shaping is adaptively performed according to propagation path characteristics and coding rates between all the transmission apparatuses and the reception apparatuses, and multiplexed in frequency.
- the present invention also includes a primary spectrum shaping unit that distributes power so that received energy is increased, and a secondary spectrum shaping unit that performs at least clipping, and assigns a frequency-spread signal to discrete frequencies,
- a receiving device that receives a signal from a transmitting device that performs spectrum shaping on the assigned signal and transmits the signal,
- a propagation path estimation unit that estimates a propagation path characteristic that is a frequency response characteristic of a propagation path from the transmission apparatus to the reception apparatus; a scheduling unit that determines the clipping ratio in each transmission apparatus based on the propagation path characteristic;
- each of the transmission devices extracts a spectrum spread signal, and software for canceling at least a replica of the transmission signal from the signal extracted by the spectrum extraction unit
- a cancellation unit an equalization unit that detects a transmission signal transmitted by the transmission apparatus with respect to an output from the soft cancellation unit;
- a demodulation unit that extracts information about code data from the detected signal;
- a decoding unit that performs error correction processing on the information about the
- the present invention also includes a primary spectrum shaping unit that distributes power so that received energy is increased, and a secondary spectrum shaping unit that performs at least clipping, and assigns a frequency-spread signal to discrete frequencies,
- a receiving device that receives a signal from a transmitting device that performs spectrum shaping on the assigned signal and transmits the signal,
- a propagation path estimation unit that estimates a propagation path characteristic that is a frequency response characteristic of a propagation path from the transmission apparatus to the reception apparatus, and an encoding rate of an error correction code of a received signal based on the propagation path characteristic;
- a scheduling unit that determines the clipping ratio in each transmission device according to the coding rate;
- a spectrum extraction unit that extracts a frequency-spread signal from each of the transmission devices based on the spectrum allocation information from the received signal; From the signal extracted by the spectrum extraction unit, a soft cancellation unit that at least cancels the replica of the transmission signal, an equalization unit that detects the transmission signal transmitted by the transmission device, with respect to the
- the effect of spectrum shaping is also related to the equivalent channel characteristic multiplier that generates a received signal replica as the channel characteristic, the channel information related to the channel characteristic estimated by the channel estimator, and the coding rate determined by the scheduling unit. And an information generation unit that generates encoding information and clipping information related to a clipping ratio and feeds back to the transmission apparatus.
- the receiving apparatus is any of the above-described receiving apparatuses, wherein the scheduling unit determines the clipping ratio based on an EXIT chart calculated from the propagation path characteristics. To do.
- the receiving apparatus of the present invention is the above-described receiving apparatus, wherein the scheduling unit calculates a difference in mutual information amount in an initial state of an EXIT chart calculated from propagation path characteristics and an initial value of a clipping ratio.
- a means for determining whether the difference is positive a means for increasing the clipping ratio if the difference is positive, a means for decreasing the clipping ratio if the difference is negative, and a
- the present invention also includes a plurality of transmission apparatuses that frequency-spread a transmission signal, assign the frequency-spread signal to a discrete frequency, perform spectrum shaping including at least clipping on the assigned signal, and transmit the spectrum signal.
- a communication method of a wireless communication system comprising a receiving device for receiving the transmission signal, Based on the transmission signal, the reception apparatus performs transmission path information related to propagation path characteristics between all the transmission apparatuses and reception apparatuses, and clipping related to a spectrum clipping ratio adaptively controlled according to the propagation path characteristics. Information is generated and fed back to the transmitter, and the clipping ratio is set to a propagation path between all the transmitters and receivers based on the transmission path information and the clipping information fed back by the transmitter. It is characterized in that spectrum shaping is performed adaptively according to the characteristics, and multiplexing is performed at a frequency.
- the present invention also includes a plurality of transmission apparatuses that frequency-spread a transmission signal, assign the frequency-spread signal to a discrete frequency, perform spectrum shaping including at least clipping on the assigned signal, and transmit the spectrum signal.
- a communication method of a wireless communication system comprising a receiving device for receiving the transmission signal, Spectrum that is adaptively controlled by the receiving apparatus according to transmission path information related to propagation path characteristics between all the transmission apparatuses and the receiving apparatuses, and the coding characteristics of the propagation path characteristics and error correction codes of received signals. Clipping information related to the clipping ratio and coding information related to the coding rate are generated and fed back to the transmission device.
- the clipping ratio is adaptively controlled according to the propagation path characteristics between all the transmission apparatuses and the receiving apparatuses, and the coding rate of the error correction code in the transmission apparatus is controlled according to the clipping ratio. It is characterized by spectrum shaping and multiplexing by frequency.
- the communication method of the present invention is any one of the communication methods described above, wherein the transmission device does not overlap the spectrum by clipping the transmission signal of another transmission device.
- the communication method of the present invention is any one of the communication methods described above, wherein a part of spectrum is overlapped by clipping the transmission signal of another transmission device by the transmission device.
- the communication method of the present invention is any one of the communication methods described above, wherein the clipping ratio is determined based on an EXIT chart calculated from propagation path characteristics.
- the communication method of the present invention is the communication method described above, wherein the clipping ratio is calculated based on the EXIT chart calculated from the propagation path characteristics and the initial value of the clipping ratio. Calculating the difference between the two, determining whether the difference is positive, increasing the clipping percentage if the difference is positive, and decreasing the clipping ratio if the difference is negative.
- a step of setting a difference in mutual information amount in the state before transition and a difference in mutual information amount in the state after transition and comparing the magnitudes If the difference in mutual information in the previous state is smaller, the state before transition is set as the optimal clipping ratio, while the state in the state after transition is When towards each other the information amount of the difference is large, the state before transition the state after transition, characterized in that it comprises the steps of: returning to the step of determining the difference in the mutual information again.
- the convergence rate of repetitive control is ensured by increasing the clipping ratio according to the propagation path that changes every moment, or by reducing the clipping ratio by assigning the clipped frequency to the transmission. It is possible to transmit information at a stable transmission rate while increasing the amount of energy transmission.
- a part of the spectrum can be overlapped, not only can transmission be performed using a frequency with a better reception situation, but also a large amount of information can be obtained with less frequency resources by overlapping. Can be transmitted.
- FIG. 1 It is a block diagram which shows 1st Embodiment of the transmitter which concerns on this invention. It is a block diagram which shows 1st Embodiment of the receiver which concerns on this invention. It is a figure which shows the input-output characteristic of an equalizer and a decoder, (a) shows the example of the EXIT chart in the received signal of each transmission apparatus when a spectrum is clipped in the ratio of 50% by secondary spectrum shaping. (B) shows the example of the EXIT chart in the received signal when the clipping ratio is changed between the signal of the transmitting apparatus 1 and the signal of the transmitting apparatus 2 to obtain the optimum clipping ratio. It is a figure which shows the concept of the setting method of the ratio of clipping using an EXIT chart.
- FIG. 1 shows an example of a transmission apparatus (mobile station apparatus).
- the transmission apparatus includes a coding unit 1, an interleaver 2, a modulation unit 3, a DFT unit 4, a propagation path information detection unit 5, a primary spectrum shaping unit 6, a clipping information detection unit 7, a secondary spectrum shaping unit 8, an IDFT (Inverse (DFT) unit 9, pilot signal generation unit 10, pilot signal multiplexing unit 11, CP insertion unit 12, radio unit 13, and transmission antenna 14.
- DFT Inverse
- the information bits are subjected to error correction coding in the coding unit 1, and the obtained code bits are rearranged in the interleaver 2.
- the modulation unit 3 modulates the interleaved code bits, and the DFT unit 4 converts the code bits into frequency signals.
- the channel characteristic is detected by the channel information detecting unit 5 for detecting the channel characteristic information (channel information) fed back from the base station apparatus (receiving apparatus), and propagated by the primary spectrum shaping unit 6.
- the water injection theorem for allocating energy according to the road characteristics is applied to the transmission spectrum obtained from the DFT unit 4.
- clipping information in the secondary spectrum shaping determined by the scheduling of the base station apparatus fed back from the base station apparatus is detected by the clipping information detection unit 7 and the secondary spectrum shaping unit 8 performs the secondary spectrum shaping. .
- the signal is converted again into a time signal by the IDFT unit 9.
- a pilot signal for estimating the propagation path characteristic is generated by the pilot signal generation unit 10 and multiplexed with the time signal output from the IDFT unit 9 by the pilot signal multiplexing unit 11.
- a CP is added to the multiplexed transmission signal by the CP insertion unit 12, up-converted to a radio frequency by the radio unit 13, and transmitted from the transmission antenna 14. This is the same for each transmitter.
- the case of the water injection theorem in the primary spectrum shaping unit 6 has been described, but the shaping that increases the received energy is essentially the same technique, and is not limited to the water injection theorem.
- FIG. 2 shows an example of a receiving device.
- the reception apparatus includes a reception antenna 21, a radio unit 22, a CP removal unit 23, a pilot separation unit 24, a first propagation path estimation unit 25-1, a second propagation path estimation unit 25-2, a scheduling unit 26, a propagation path Information generation unit / clipping information generation unit 27, buffer 28, first DFT unit 29, spectrum extraction unit 30, soft cancellation units 31-1, 31-2, equalization units 32-1, 32-2, IDFT unit 33 -1, 33-2, demodulation units 34-1 and 34-2, deinterleavers 35-1 and 35-2, decoding units 36-1 and 36-2, interleavers 37-1 and 37-2, and soft replicas It includes generation units 38-1 and 38-2, second DFT units 39-1 and 39-2, equivalent channel multiplication units 40-1 and 40-2, and determination units 41-1 and 41-2.
- the block 50-1 is a block for detecting only the signal from the first transmitter
- the block 50-2 is a block for detecting only the signal from the second transmitter.
- the received signals transmitted from the two transmitting devices are simultaneously received by the receiving antenna 21 and are down-converted from the radio frequency to the baseband by the radio unit 22.
- CP is removed by the CP removal unit 23 and input to the pilot separation unit 24.
- the pilot separation unit 24 separates the pilot signal and the data signal from each transmission device from the received signal, and the separated pilot signal is used as the first propagation path estimation unit 25-1 and the second propagation path estimation unit 25-2.
- the frequency response of the propagation path from each transmitting device to the receiving device is estimated.
- the scheduling unit 26 determines the water injection theorem and the clipping ratio in each transmission device based on the estimated values of the propagation channel estimation units 25-1 and 25-2, and the propagation channel information generation unit / clipping information generation unit 27 performs propagation.
- Information relating to the path characteristics and information relating to the clipping ratio are generated, converted into signals for feedback to the respective transmission devices, and transmitted to the transmission devices.
- the information on the propagation path characteristics and the information on the clipping ratio are stored in the buffer 28 for use in detecting the signal of the next frame.
- the transmission power assigned to the kth discrete frequency in the uth transmission apparatus is expressed by Expression (1).
- ⁇ u (k) is the real transmission power assigned to the k-th discrete frequency
- N 0 is the noise power density
- ⁇ u (k) is the complex gain of the propagation path at the k-th discrete frequency
- ⁇ * u ( k) is the complex conjugate of u u (k).
- ⁇ is a value common to all discrete frequencies used for transmission determined by the total transmission power
- (x) + is a clipping that outputs 0 when x is smaller than 0 and outputs x when x is 0 or more. It is an operator.
- Further clipping is performed on the transmission power of each frequency thus obtained in the secondary spectrum shaping unit so as not to overlap between the transmission apparatuses.
- the clipping is performed alternately from the overlapping discrete frequencies having the smallest propagation path gain.
- the gain for the frequency signal applied by the spectrum shaping process is regarded as a gain by the propagation path in the base station apparatus and the reception process is performed. At this time, the gain of the propagation path is regarded as zero for the clipped discrete frequency signal.
- the data signal separated by the pilot separation unit 24 is converted into a frequency signal by the first DFT unit 29, and information regarding the clipping ratio in the previous frame stored in the buffer 28 by the spectrum extraction unit 30 is obtained.
- the separated signals from the transmitters are respectively input to soft cancel sections 31-1 and 31-2, and the received signal replicas output from equivalent channel multiplication sections 40-1 and 40-2 described later are canceled. .
- a received signal replica is not obtained at the first time, nothing is canceled.
- the respective signals output from the soft cancellation units 31-1 and 31-2 are subjected to frequency domain equalization in the equalization units 32-1 and 32-2, and the equalized reception signals are output.
- the equalized signals in IDFT units 33-1 and 33-2 are converted into time domains, input to demodulation units 34-1 and 34-2, and decomposed into LLRs of code bits.
- the obtained LLR is restored to the original LLR arrangement of the code bits by the deinterleavers 35-1 and 35-2, and subjected to error correction processing by the decoding units 36-1 and 36-2, thereby improving reliability. LLR is output.
- the output LLRs are rearranged again by interleavers 37-1 and 37-2, and replicas of transmission signals having amplitudes proportional to the reliability are generated by soft replica generation units 38-1 and 38-2.
- the modulation method is quaternary phase shift keying (QPSK) and the LLRs of the first and second bits of the code bits constituting the QPSK symbol are ⁇ 1 and ⁇ 2 respectively
- the soft replica s “soft” is expressed by Expression (2).
- the soft replica obtained as in equation (2) is necessary for calculation of the received signal after equalization, it is input to the equalization units 32-1 and 32-2, and the soft cancellation is performed. Therefore, they are input to the second DFT units 39-1 and 39-2, respectively.
- a gain for the transmission signal including spectrum shaping by the equivalent propagation path multipliers 40-1 and 40-2 is defined as an equivalent propagation path, and a reception signal replica is generated by multiplying the gain.
- the gain of the equivalent propagation path in which the gain by spectrum shaping on the transmission apparatus side is also regarded as the propagation path is expressed by, for example, the expression (3) in the case of the transmission apparatus 1.
- Equation (3) ⁇ 1 (k) is the equivalent channel gain at the k-th discrete frequency represented by a complex number, and m 1 (k) is the spectrum shaping at the k-th discrete frequency calculated by Equation (1). ⁇ 1 (k) is a complex channel gain at the kth discrete frequency.
- the equivalent channel gain expressed by the equation (3) is multiplied by the transmission signal replica on the frequency axis, and again transmitted to the soft cancellation units 31-1 and 31-2. Enter and repeat. This process is repeated a predetermined number of times or until there is no error, and finally the information bits are determined by the determination units 41-1 and 41-2. In this way, even inter-symbol interference generated by spectrum shaping is considered and suppressed as inter-symbol interference due to the propagation path, information bits can be detected with high energy, and missing spectrum due to clipping can be reproduced.
- the scheduling unit 26 changes the overlapping spectrum when the primary spectrum shaping is performed to use a frequency that is not used by any other transmission apparatus.
- a propagation path that is converted every moment is different for each transmission apparatus. Since it is independent, it is important not to clip the signal of each transmitting apparatus uniformly but to make the ratio of clipping adaptive to each transmitting terminal so as to keep the convergence state of all transmitting apparatuses.
- An EXIT chart is used as a method for realizing this.
- FIG. 3 shows an example in which clipping is performed uniformly when the number of transmitting terminals is two.
- FIG. 6A shows the EXIT in the received signal of each transmitter when the spectrum is clipped at a rate of 50% by the secondary spectrum shaping including the clipping by the primary spectrum shaping (water injection theorem) shown as the prior art.
- An example of a chart is shown.
- L31 is the input / output characteristic of the MI of the equalization unit 32-1 that detects the signal of the transmission apparatus 1
- L32 is the input / output characteristic of the MI of the equalization unit 32-2 that detects the signal of the transmission apparatus 2
- L33 is the decoding unit
- the input / output characteristics of MI in 36-1 and 36-2 are shown.
- L31 is in a non-convergent state, but L31 is a decoding unit 36-1, 36. This means that there is a distance for the characteristic ⁇ 2, and that the capacity that can be supported by the propagation path is redundant with respect to the transmission rate of the error correction code.
- FIG. 4B shows a case where the clipping ratio is changed between the signal from the transmission apparatus 1 and the signal from the transmission apparatus 2 to obtain an optimum clipping ratio.
- L34 is the input / output characteristic of the MI of the equalization unit 32-1 that detects the signal of the transmission apparatus 1
- L35 is the input / output characteristic of the MI of the equalization part 32-2 that detects the signal of the transmission apparatus 2
- L36 is the decoding unit
- the input / output characteristics of MI in 36-1 and 36-2 are shown, which are the same as those in L33.
- the transmitter 2 is not subjected to much clipping, and the clipping ratio is reduced.
- the clipping ratio is set to more than 50%. By doing so, the difference in the input / output characteristics of the MI of the equalization unit in each transmission apparatus is reduced, and control is performed so that the convergence state can be easily maintained.
- FIG. 4 shows a concept of a clipping ratio setting method using the EXIT chart.
- L41 is the input / output characteristic of the MI of the equalizer 32-1 for detecting the signal of the transmitting apparatus 1 in the initial state s
- L42 is the input / output of the MI of the equalizer 32-2 for detecting the signal of the transmitting apparatus 2
- Characteristic L43 represents the MI input / output characteristics of the decoders 36-1 and 36-2, which are the same as L31, L32 and L33, respectively.
- the equalization unit outputs MI for detecting the signals of the transmission apparatuses 1 and 2 in the initial state ⁇ are I 1 start (s) and I 2 start (s), and the end points are I 1 end (s) and I Let 2 end (s).
- the received signal-to-noise power ratio of the equalizer output at the start point and the end point of the transmission apparatus 1 is expressed by the following equation.
- ⁇ 1 start and ⁇ 1 end are real numbers in the transmission apparatus 1 represented by the following equations, respectively.
- the output MI at the start point and the end point is expressed by the following equation in the case of QPSK.
- Equations (8) and (9) are applicable in the case of BPSK or QPSK, and in the case of other multilevel modulation schemes, 4SNR 1 start and 4SNR 1 end constant multiple 4 differ depending on the modulation scheme.
- Equation (8) and Equation (9) are 3.2 in Layer 1 and 3.2 Becomes 0.8.
- the equation (12) is an equalization unit for signal detection of the transmission device 2 from the output of the equalization unit for signal detection of the transmission device 1 represented by the equations (10) and (11). Represents the sum of output differences. If this value is positive, it means that the characteristic of the equalizer 32-1 for signal detection of the transmission apparatus 1 is higher in FIG. In the case of FIG. 4, the ratio of the equalizing unit 32-2 for detection is higher. Therefore, if this value is positive, the signal clipping ratio of the transmission apparatus 1 is increased and the signal clipping ratio of the transmission apparatus 2 is decreased. On the other hand, if negative, the reverse is done.
- the spectrum shaping at the time of the primary spectrum shaping is stored, and clipping is provisionally performed to calculate the start point and the end point.
- clipping is provisionally performed to calculate the start point and the end point.
- the signals of both transmitters are clipped by 50%, the overlapping spectrum is alternately clipped from the one with the poor reception status.
- the ratio of clipping to the signal of each transmitting terminal is different between 60% and 40%, the transmission apparatus that performs clipping up to 40% alternately and the 60% to be clipped is the remaining overlap. Clip all spectra. Note that when both transmitters clip the same frequency in primary spectrum shaping, the result may not be exactly the same as the set ratio, but it is possible to assume that it should not overlap.
- the increase / decrease of the clipping ratio may be changed for each discrete frequency, but it becomes complicated as the number of DFT points increases, so the combinations of ratios as shown in Table 1 are preliminarily stored in the LUT (Look Up Table). And may be changed according to the value of Expression (12).
- FIG. 5 shows a flowchart of the processing of the scheduling unit 26 described above.
- step S1 a mutual information amount difference ⁇ I (s) in the initial state s is calculated, and in step S2, it is determined whether or not it is positive. If ⁇ I (s) is positive, one shift is made in the direction of + (plus) in Table 1 in step S3, and if negative, shift is made in the ⁇ (minus) direction in step S4.
- step S5 ⁇ I (s + p) in the state s + p before the transition and ⁇ I (s + n) in the state s + n after the transition are set for the combination of the clipping ratios in the next state determined in this way, and in step S6. Compare their sizes.
- ⁇ I (s + p) in the state before transition is smaller, it can be considered that the difference has begun to increase, so the state in state ⁇ I (s + p) before transition is set as the optimum clipping ratio.
- ⁇ I (s + p) is larger, the difference in the input / output characteristics of the equalizer MI may still be reduced, so s is replaced with s + n, and the process returns to step S2 to repeat.
- a stable transmission rate can be achieved by controlling the clipping ratio so that the convergence state is adaptively maintained for a propagation path that changes every moment.
- the reception apparatus base station apparatus
- the reception apparatus has an interference suppression function. Therefore, even if they are overlapped, even signals from other transmitters are input to the canceller that detects the intersymbol interference component in the signal of each transmitter with respect to the overlapping spectrum, and canceled together. Then, the signal can be completely separated.
- FIG. 6 shows the concept of primary spectrum shaping and secondary spectrum shaping in the case where signal duplication of each transmitting apparatus is allowed.
- FIG. 5A shows the concept of primary spectrum shaping (overlapping spectrum B1), and the control is based on the same water injection theorem as in the first embodiment, and thus the description thereof is omitted.
- FIG. 6B shows the concept of secondary spectrum shaping, and since overlapping is allowed (overlapping spectrum B2), clipping is performed at a certain ratio in order from the poorest propagation path state (clipped). Spectrum C1). Therefore, as shown in the figure, some of the spectrum overlaps, but the receiving device (base station device) may demodulate the signals from both transmitting devices, so only intersymbol interference can be used in interference suppression. In addition, if the interference of signals between transmitters is also suppressed in a lump, the signals can be completely separated, and this method can obtain the maximum transmission characteristics.
- FIG. 7 shows an example of a receiving device (base station device).
- the reception apparatus includes a reception antenna 101, a radio unit 102, a CP removal unit 103, a pilot separation unit 104, a first propagation path estimation unit 105-1, a second propagation path estimation unit 105-2, a scheduling unit 106, a propagation path Information generation unit / clipping information generation unit 107, buffer 108, first DFT unit 109, spectrum extraction unit 110, soft cancellation units 111-1, 111-2, equalization units 112-1, 112-2, IDFT 113-1 113-2, demodulation units 114-1 and 114-2, deinterleavers 115-1 and 115-2, decoding units 116-1 and 116-2, interleavers 117-1 and 117-2, a soft replica generation unit 118-1, 118-2, second DFT units 119-1, 119-2, equivalent channel multiplication units 120-1, 120-2, interference extraction unit 121- , 121-2, and a determination unit 122-1, 122-2.
- the block 150-1 is a block for detecting only the signal from the first transmitter
- the block 150-2 is a block for detecting only the signal from the second transmitter.
- the interference extraction units 121-1 and 121-2 extract only overlapping interference from signals from other transmission apparatuses, and are canceled by the soft cancellation units 111-1 and 111-2, respectively.
- the scheduling unit 106 determines a ratio of clipping a spectrum having a low channel gain frequency in the primary spectrum shaping and the secondary spectrum shaping shown in FIG. 6 according to the channel variation.
- the method for determining the clipping ratio is the same as that in the first embodiment. However, in this case, since signals from other transmission apparatuses remain as interference, Expression (6) representing the reception signal-to-noise power ratio at the starting point in the transmission apparatus 1 is expressed by the following Expression (13).
- u represents the index of the transmitting apparatus
- U represents the total number of transmitting apparatuses multiplexed simultaneously.
- the received signal-to-noise power ratio is calculated by equation (4).
- ⁇ ′ u (k) is an equivalent channel gain obtained by extracting only the frequency overlapping with the signal from the transmitter 1 in the equivalent channel gain including the spectrum shaping effect of the signal of the u th transmitter. It is.
- duplication not only duplication is allowed and multiplexing is performed, but also scheduling is simplified, and a large number of transmission devices can be accommodated with less frequency, and empty spectrum can be created by allowing duplication. Multiple devices can also be multiplexed.
- FIG. 12 shows coding rates 1/8, 1/7, 1/6, 1/5, 1/4, 1/3, 1/2, 2/3, 3 when the error correction code is a convolutional code.
- the input / output characteristics of the mutual information amount of the decoder in the case of / 4, 4/5, 5/6, 6/7, and 7/8 are shown.
- 201 represents a decoder characteristic with a coding rate of 1/8
- similarly 202 to 212 represent decoder characteristics with a coding rate in the above-described order.
- the vertical axis represents the decoder input mutual information amount
- the horizontal axis represents the decoder output mutual information amount. Since this input / output characteristic is uniquely determined by the structure of the code, each transmission opportunity is determined. It is not necessary to perform the calculation, and it may be stored in a memory or the like. In this way, the lower the coding rate, the more redundant bits, and the stronger the error correction, the lower the input mutual information amount necessary to achieve the same output mutual information amount. In this way, the clipping and the coding rate are optimized together by utilizing the fact that the characteristics are different at each coding rate.
- FIG. 13 shows an example of an EXIT chart for optimization in the present embodiment.
- the viewpoints of the transmission apparatus optimized in the first embodiment or the second embodiment are I 1 start (s ′) and I 2 start (s ′), and the end points are I 1 end (s ′) and I 2.
- 301 is an input / output characteristic of the mutual information amount of the equalization unit obtained by connecting the start point and end point values optimized in the transmission apparatus 1 with a straight line
- 302 is a start point and end point value optimized in the transmission apparatus 2.
- the receiving apparatus performs processing for determining the clipping ratio and the coding rate by the scheduling unit 26 in FIG. 2 and the scheduling unit 106 in FIG. 7, and sends the coding information related to the determined coding rate to the transmitting device. (Propagation path information, clipping information) and the transmission path information generation unit / clipping information generation units 27 and 107 transmit the result.
- the encoded information fed back from the receiving apparatus is received by the transmitting apparatus in FIG. 1, detected by an encoded information detecting unit (not shown), and encoded by the encoding unit 1 at the encoding rate of the encoded information. Turn into.
- a convolutional code for example, an error correction code such as a turbo code or a low density parity check (LDPC: Low Density Parity Check) code may be used.
- LDPC Low Density Parity Check
- a predetermined threshold is provided to set the input / output characteristics of the equalization unit.
- a coding rate larger than the width and closest to the input / output characteristic of the equalization unit may be selected at the point where the input / output characteristic of the decoding unit is closest.
Abstract
Description
前記受信装置は、前記送信信号に基づいて、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報及び該伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報を生成して、前記送信装置にフィードバックし、前記送信装置は、フィードバックされた前記伝送路情報及び前記クリッピング情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御してスペクトル整形を施し、周波数で多重することを特徴とする。
前記受信装置は、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報、該伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報及びその符号化率に関する符号化情報を生成して、前記送信装置にフィードバックし、前記送信装置は、フィードバックされた前記伝送路情報、前記クリッピング情報及び符号化情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御し、前記クリッピングの割合に応じて前記送信装置における誤り訂正符号の符号化率を制御してスペクトル整形を施し、周波数で多重することを特徴とする。
前記受信装置は、前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、前記伝搬路特性に基づいて各送信装置における前記クリッピング割合を決定するスケジューリング部と、受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、前記検出された信号から符号データに関する情報を抽出する復調部と、前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定したクリッピング割合に関するクリッピング情報を生成して前記送信装置にフィードバックする情報生成部と、を具備することを特徴とする。
前記受信装置は、前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、前記伝搬路特性に基づいて、受信した信号の誤り訂正符号の符号化率と、その符号化率による各送信装置における前記クリッピング割合を決定するスケジューリング部と、受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、前記検出された信号から符号データに関する情報を抽出する復調部と、前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定した符号化率に関する符号化情報及びクリッピング割合に関するクリッピング情報とを生成して前記送信装置にフィードバックする情報生成部と、を具備することを特徴とする。
前記受信装置からフィードバックされた前記送信装置と前記受信装置の間の伝搬路特性に関する伝送路情報により受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、前記受信装置からフィードバックされた伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報に基づいて少なくともクリッピングを施す2次スペクトル整形部と、を具備し、前記スペクトル整形を、前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に施し、周波数で多重することを特徴とする。
前記受信装置からフィードバックされた前記送信装置と前記受信装置の間の伝搬路特性に関する伝送路情報に基づいて、受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、前記受信装置からフィードバックされた前記伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報に基づいて、少なくともクリッピングを施す2次スペクトル整形部と、を具備し、前記スペクトル整形を、前記スペクトル整形を前記全ての送信装置と受信装置の間の伝搬路特性と符号化率に応じて適応的に施し、周波数で多重することを特徴とする。
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、前記伝搬路特性に基づいて各送信装置における前記クリッピング割合を決定するスケジューリング部と、受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、前記検出された信号から符号データに関する情報を抽出する復調部と、前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定したクリッピング割合に関するクリッピング情報を生成して前記送信装置にフィードバックする情報生成部と、を具備することを特徴とする。
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、前記伝搬路特性に基づいて、受信した信号の誤り訂正符号の符号化率と、その符号化率による各送信装置における前記クリッピング割合を決定するスケジューリング部と、受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、前記検出された信号から符号データに関する情報を抽出する復調部と、前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定した符号化率に関する符号化情報及びクリッピング割合に関するクリッピング情報とを生成して前記送信装置にフィードバックする情報生成部と、を具備することを特徴とする。
前記受信装置により、前記送信信号に基づいて、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報及び該伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報を生成して、前記送信装置にフィードバックし、前記送信装置により、フィードバックされた前記伝送路情報及び前記クリッピング情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御してスペクトル整形を施し、周波数で多重することを特徴とする。
前記受信装置により、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報、該伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報及びその符号化率に関する符号化情報を生成して、前記送信装置にフィードバックし、前記送信装置により、フィードバックされた前記伝送路情報、前記クリッピング情報及び符号化情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御し、前記クリッピングの割合に応じて前記送信装置における誤り訂正符号の符号化率を制御してスペクトル整形を施し、周波数で多重することを特徴とする。
以下の実施形態では、多重される送信装置数を2として説明する。以下に示す実施形態においては、特に断りのない限り、一般的に言われる移動局から基地局への通信である上りリンクでの通信を対象としているが、本発明の対象とする通信は、これに限定されない。なお、移動局は前述の送信装置を表している。また、干渉抑圧機能を有する非線形繰り返し等化技術として周波数領域SC/MMSE(Soft Canceller with Minimum Mean Square Error)ターボ等化を用いるものとするが、干渉抑圧機能を有する非線形繰り返し等化であれば本質的に同一であるため、これに限定されない。
第1の実施形態として、重複を許容せずにスペクトルをクリッピングさせる割合を適応的に制御する場合について説明する。図1に送信装置(移動局装置)の一例を示す。送信装置は、符号部1、インターリーバ2、変調部3、DFT部4、伝搬路情報検出部5、1次スペクトル整形部6、クリッピング情報検出部7、2次スペクトル整形部8、IDFT(Inverse DFT)部9、パイロット信号生成部10、パイロット信号多重部11、CP挿入部12、無線部13、送信アンテナ14から構成されている。
第1の実施形態では、重複させることを許容せず、周波数軸上で全送信装置からの信号を直交させる場合について説明したが、干渉抑圧機能を受信装置(基地局装置)が有しているので、例え重複させたとしても、重複しているスペクトルに対して各送信装置の信号における符号間干渉成分を検出するキャンセラに対して他の送信装置からの信号までも入力し、一括してキャンセルすれば信号を完全に分離することができる。
第3の実施形態として、これまでの実施形態は全送信装置の符号化率が同一である場合を示したが、本実施形態は各送信装置が適用する誤り訂正符号の符号化率も併せて制御することができる。図12に、誤り訂正符号が畳み込み符号である場合の符号化率1/8、1/7、1/6、1/5、1/4、1/3、1/2、2/3、3/4、4/5、5/6、6/7、7/8の場合の復号器の相互情報量の入出力特性を示す。同図において、201は符号化率1/8の復号器特性を表し、同様に202~212はそれぞれ上述の順の符号化率の復号器特性を示している。また、図11と同様に縦軸が復号器入力相互情報量、横軸が復号器出力相互情報量を表しており、この入出力特性は符号の構造により一意に決定されるため、伝送機会毎に計算する必要はなく、メモリなどに保存しておいても良い。このように、符号化率が低いほど冗長ビットが多いため、誤り訂正が強いので同じ出力相互情報量を達成するために必要な入力相互情報量は低くなる。このように、各符号化率で特性が異なることを利用してクリッピングと符号化率を一括して最適化する。
また、これらの実施形態はシングルキャリア伝送方式で記載したが、伝送可能な周波数帯が信号の帯域幅より広い場合には各離散スペクトルを受信状況の良好な周波数に割り当て、受信側で元の並びに戻すダイナミックスペクトル制御に関しても、伝搬路の周波数特性を、信号を割り当てた周波数から抽出して再構成すればシングルキャリア方式に帰着されるため、適用可能である。
さらに、シングルキャリア伝送は周波数拡散を施したマルチキャリア方式とも考えることができるため、DFTの代わりに拡散符号を用いたマルチキャリア方式であるMC-CDM(Multi-Carrier Code Division Multiplexing)にも適用可能である。
2 インターリーバ
3 変調部
4 DFT部
5 伝搬路情報検出部
6 1次スペクトル整形部
7 クリッピング情報検出部
8 2次スペクトル整形部
9 IDFT部
10 パイロット信号生成部
11 パイロット信号多重部
12 CP挿入部
13 無線部
14 送信アンテナ
21 受信アンテナ
22 無線部
23 CP除去部
24 パイロット分離部
25-1 第1の伝搬路推定部
25-2 第2の伝搬路推定部
26 スケジューリング部
27 伝搬路情報生成部・クリッピング情報生成部
28 バッファ
29 第1のDFT部
30 スペクトル抽出部
31-1,31-2 ソフトキャンセル部
32-1,32-2 等化部
33-1、33-2 IDFT部
34-1,34-2 復調部
35-1,35-2 デインターリーバ
36-1,36-2 復号部
37-1,37-2 インターリーバ
38-1,38-2 ソフトレプリカ生成部
39-1,39-2 第2のDFT部
40-1,40-2 等価伝搬路乗算部
41-1,41-2 判定部
101 受信アンテナ
102 無線部
103 CP除去部
104 パイロット分離部
105 伝搬路推定部
105-1 第1の伝搬路推定部
105-2 第2の伝搬路推定部
106 スケジューリング部
107 伝搬路情報生成部・クリッピング情報生成部
108 バッファ
109 第1のDFT部
110 スペクトル抽出部
111-1,111-2 ソフトキャンセル部
112-1,112-2 等化部
113-1、113-2 IDFT部
114-1,114-2 復調部
115-1,115-2 デインターリーバ
116-1,116-2 復号部
117-1,117-2 インターリーバ
118-1,118-2 ソフトレプリカ生成部
119-1,119-2 第2のDFT部
120-1,120-2 等価伝搬路乗算部
121-1,121-2 干渉抽出部
122-1,122-2 判定部
Claims (21)
- 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対して少なくともクリッピングを含むスペクトル整形を施して送信する複数の送信装置と、
前記送信信号を受信する受信装置と、
を具備する無線通信システムであって、
前記受信装置は、前記送信信号に基づいて、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報及び該伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報を生成して、前記送信装置にフィードバックし、
前記送信装置は、フィードバックされた前記伝送路情報及び前記クリッピング情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御してスペクトル整形を施し、周波数で多重することを特徴とする無線通信システム。 - 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対して少なくともクリッピングを含むスペクトル整形を施して送信する複数の送信装置と、
前記送信信号を受信する受信装置と、
を具備する無線通信システムであって、
前記受信装置は、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報、該伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報及びその符号化率に関する符号化情報を生成して、前記送信装置にフィードバックし、
前記送信装置は、フィードバックされた前記伝送路情報、前記クリッピング情報及び符号化情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御し、前記クリッピングの割合に応じて前記送信装置における誤り訂正符号の符号化率を制御してスペクトル整形を施し、周波数で多重することを特徴とする無線通信システム。 - 前記送信装置は、他の送信装置の送信信号に対しクリッピングによりスペクトルを重複させないことを特徴とする請求項1又は2に記載の無線通信システム。
- 前記送信装置は、他の送信装置の送信信号に対しクリッピングにより一部のスペクトルを重複させることを特徴とする請求項1又は2に記載の無線通信システム。
- 前記送信装置は、
前記伝搬路特性情報に基づいて受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、
前記クリッピング情報に基づいて少なくともクリッピングを施す2次スペクトル整形部と、
を具備し、
前記受信装置は、
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、
前記伝搬路特性に基づいて各送信装置における前記クリッピング割合を決定するスケジューリング部と、
受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、
前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、
前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、
前記検出された信号から符号データに関する情報を抽出する復調部と、
前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、
前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、
前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、
前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定したクリッピング割合に関するクリッピング情報を生成して前記送信装置にフィードバックする情報生成部と、
を具備することを特徴とする請求項1に記載の無線通信システム。 - 前記送信装置は、
前記符号化情報に基づいて送信信号を符号化する符号化部と、
前記伝搬路特性情報に基づいて受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、
前記クリッピング情報に基づいて少なくともクリッピングを施す2次スペクトル整形部と、
を具備し、
前記受信装置は、
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、
前記伝搬路特性に基づいて、受信した信号の誤り訂正符号の符号化率と、その符号化率による各送信装置における前記クリッピング割合を決定するスケジューリング部と、
受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、
前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、
前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、
前記検出された信号から符号データに関する情報を抽出する復調部と、
前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、
前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、
前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、
前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定した符号化率に関する符号化情報及びクリッピング割合に関するクリッピング情報とを生成して前記送信装置にフィードバックする情報生成部と、
を具備することを特徴とする請求項2に記載の無線通信システム。 - 前記スケジューリング部は、符号化率による前記復号部の復号特性に応じて符号化率を決定することを特徴とする請求項6に記載の無線通信システム。
- 前記スケジューリング部は、前記クリッピングの割合を、前記等化部の入出力特性の相互情報量により算出されるEXITチャートに基づいて決定することを特徴とする請求項5乃至7のいずれかに記載の無線通信システム。
- 前記スケジューリング部は、
少なくとも2つの送信装置と少なくとも1つの受信装置間の等化特性のうち、第一の送信装置との間の第一の等化特性と第二の送信装置との間の第二の等化特性において、第一の等化特性と第二の等化特性を用いて相互情報量の差をとり、差異が正であれば、第二の送信装置のクリッピング割合を大きくするか、または第一の送信装置のクリッピング割合を小さくし、差異が負であれば、第二の送信装置のクリッピング割合を小さくするか、または第一の送信装置のクリッピング割合を大きくすることを特徴とする請求項8に記載の無線通信システム。 - 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対してスペクトル整形を施して受信装置に送信する複数の送信装置であって、
前記受信装置からフィードバックされた前記送信装置と前記受信装置の間の伝搬路特性に関する伝送路情報により受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、
前記受信装置からフィードバックされた伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報に基づいて少なくともクリッピングを施す2次スペクトル整形部と、
を具備し、
前記スペクトル整形を、前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に施し、周波数で多重することを特徴とする送信装置。 - 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対してスペクトル整形を施して受信装置に送信する複数の送信装置であって、
前記受信装置からフィードバックされた前記送信装置と前記受信装置の間の伝搬路特性に関する伝送路情報に基づいて、受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、
前記受信装置からフィードバックされた前記伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報に基づいて、少なくともクリッピングを施す2次スペクトル整形部と、
を具備し、
前記スペクトル整形を、前記スペクトル整形を前記全ての送信装置と受信装置の間の伝搬路特性と符号化率に応じて適応的に施し、周波数で多重することを特徴とする送信装置。 - 受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、少なくともクリッピングを施す2次スペクトル整形部とを具備して、周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対してスペクトル整形を施して送信する送信装置からの信号を受信する受信装置であって、
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、
前記伝搬路特性に基づいて各送信装置における前記クリッピング割合を決定するスケジューリング部と、
受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、
前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、
前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、
前記検出された信号から符号データに関する情報を抽出する復調部と、
前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、
前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、
前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、
前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定したクリッピング割合に関するクリッピング情報を生成して前記送信装置にフィードバックする情報生成部と、
を具備することを特徴とする受信装置。 - 受信エネルギーが大きくなるように電力を配分する1次スペクトル整形部と、少なくともクリッピングを施す2次スペクトル整形部とを具備して、周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対してスペクトル整形を施して送信する送信装置からの信号を受信する受信装置であって、
前記送信装置から前記受信装置までの伝搬路の周波数応答特性である伝搬路特性を推定する伝搬路推定部と、
前記伝搬路特性に基づいて、受信した信号の誤り訂正符号の符号化率と、その符号化率による各送信装置における前記クリッピング割合を決定するスケジューリング部と、
受信した信号から、前記スペクトル割当情報に基づき、前記送信装置各々が周波数拡散された信号を抽出するスペクトル抽出部と、
前記スペクトル抽出部が抽出した信号から、前記送信信号のレプリカを少なくともキャンセルするソフトキャンセル部と、
前記ソフトキャンセル部からの出力に対し、前記送信装置が送信した送信信号を検出する等化部と、
前記検出された信号から符号データに関する情報を抽出する復調部と、
前記抽出された符号データに関する情報に対し、誤り訂正処理を行い、該情報を更新する復号部と、
前記更新された符号データに関する情報から、前記送信信号のレプリカを生成するソフトレプリカ生成部と、
前記送信装置で施されたスペクトル整形の効果も伝搬路特性として受信信号レプリカを生成する等価伝搬路特性乗算部と、
前記伝搬路推定部により推定した伝搬路特性に関する伝搬路情報と、前記スケジューリング部により決定した符号化率に関する符号化情報及びクリッピング割合に関するクリッピング情報とを生成して前記送信装置にフィードバックする情報生成部と、
を具備することを特徴とする受信装置。 - 前記スケジューリング部は、前記クリッピングの割合を、前記伝搬路特性から算出されるEXITチャートに基づいて決定することを特徴とする請求項12又は13に記載の受信装置。
- 前記スケジューリング部は、
伝搬路特性とクリッピングの割合の初期値から算出されるEXITチャートの初期状態における相互情報量の差異を計算し、その差異が正かどうかを判断する手段と、
差異が正であれば、クリッピングの割合を増加させ、差異が負であれば、クリッピングの割合を減少させる手段と、
決定された次の状態のクリッピングの割合の組み合わせに対し、変移前の状態における相互情報量の差異と、変移後の状態における相互情報量の差異を設定して、その大きさを比較する手段と、
もし変移前の状態における相互情報量の差異の方が小さい場合は、変移前の状態を最適なクリッピングの割合として設定し、一方、変移後の状態における相互情報量の差異の方が大きい場合には、変移後の状態を変移前の状態として、再び相互情報量の差異を判断して処理を繰り返す手段と、
を備えることを特徴とする請求項14に記載の受信装置。 - 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対して少なくともクリッピングを含むスペクトル整形を施して送信する複数の送信装置と、前記送信信号を受信する受信装置とを具備する無線通信システムの通信方法であって、
前記受信装置により、前記送信信号に基づいて、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報及び該伝搬路特性に応じて適応的に制御されたスペクトルのクリッピング割合に関するクリッピング情報を生成して、前記送信装置にフィードバックし、
前記送信装置により、フィードバックされた前記伝送路情報及び前記クリッピング情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御してスペクトル整形を施し、周波数で多重することを特徴とする通信方法。 - 送信信号を周波数拡散し、前記周波数拡散された信号を離散周波数に割り当て、前記割り当てられた信号に対して少なくともクリッピングを含むスペクトル整形を施して送信する複数の送信装置と、前記送信信号を受信する受信装置とを具備する無線通信システムの通信方法であって、
前記受信装置により、前記全ての送信装置と受信装置の間の伝搬路特性に関する伝送路情報、該伝搬路特性と受信した信号の誤り訂正符号の符号化率に応じて適応的に制御されるスペクトルのクリッピング割合に関するクリッピング情報及びその符号化率に関する符号化情報を生成して、前記送信装置にフィードバックし、
前記送信装置により、フィードバックされた前記伝送路情報、前記クリッピング情報及び符号化情報に基づいて、前記クリッピング割合を前記全ての送信装置と受信装置の間の伝搬路特性に応じて適応的に制御し、前記クリッピングの割合に応じて前記送信装置における誤り訂正符号の符号化率を制御してスペクトル整形を施し、周波数で多重することを特徴とする通信方法。 - 前記送信装置により、他の送信装置の送信信号に対しクリッピングによりスペクトルを重複させないことを特徴とする請求項16又は17に記載の通信方法。
- 前記送信装置により、他の送信装置の送信信号に対しクリッピングにより一部のスペクトルを重複させることを特徴とする請求項16又は17に記載の通信方法。
- 前記クリッピングの割合は、伝搬路特性から算出されるEXITチャートに基づいて決定されることを特徴とする請求項16または請求項17に記載の通信方法。
- 前記クリッピングの割合は、前記伝搬路特性とクリッピングの割合の初期値からから算出されるEXITチャートを用いて初期状態における相互情報量の差異を計算し、その差異が正かどうかを判断するステップと、
差異が正であれば、クリッピングの割合を増加させ、差異が負であれば、クリッピングの割合を減少させるステップと、
決定された次の状態のクリッピングの割合の組み合わせに対し、変移前の状態における相互情報量の差異と、変移後の状態における相互情報量の差異を設定して、その大きさを比較するステップと、
変移前の状態における相互情報量の差異の方が小さい場合は、変移前の状態を最適なクリッピングの割合として設定し、一方、変移後の状態における相互情報量の差異の方が大きい場合には、変移後の状態を変移前の状態として、再び相互情報量の差異を判断するステップに戻るステップと、
を備えることを特徴とする請求項20に記載の通信方法。
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