JP5004982B2 - Multi-carrier wireless communication system and multi-carrier wireless communication method - Google Patents

Description

  The present invention relates to a multi-carrier wireless communication system and a multi-carrier wireless communication method that perform superimposed transmission.

  In recent years, the problem of depletion of finite frequency resources has become serious in the field of wireless communication, and improvement in frequency utilization efficiency is desired. As a technique for improving frequency utilization efficiency, a method of superimposing a signal using a guard band has been proposed (see Non-Patent Document 1).

  A method of superimposing a radio signal between a first system that transmits a radio signal with high power and a second system that transmits a radio signal with low power has also been proposed (see Non-Patent Document 2). In this method, the receiving device of the first system decodes as it is, the receiving device of the second system decodes the radio signal of the first system to generate a replica signal, and removes the replica signal from the received signal. Detect and decode system radio signals.

Takatoshi Sugiyama, 3 others, “Staggered Superposition Transmission Method for Narrow Bandwidth SSMA Signals and Multiple High Speed Signals”, IEICE Transactions B-II, IEICE, November 1994, Vol. J77-B-II, No. 11, p. 674-680 Jun Naganaga, 2 others, “Modulation method that does not require channel information for superimposition communication by cognitive radio”, IEICE Communication Society Conference, IEICE Communication Conference 1, IEICE, September 2008, B- 17-9, p. 452

  However, the method using the guard band has a problem that the frequency band of the guard band is greatly limited and it may be difficult to superimpose. Also, in the method of generating the replica signal, the quality of the generated replica signal is deteriorated depending on the accuracy of decoding and the accuracy of channel estimation, and the receiving quality of the second system cannot be correctly decoded and the reception quality is deteriorated. There was a problem that. In view of the above circumstances, an object of the present invention is to provide a multi-carrier wireless communication system and a multi-carrier wireless communication method capable of performing superimposed transmission while suppressing a decrease in reception quality.

  [1] According to one aspect of the present invention, a first transmission device and a first reception device that transmit and receive radio signals composed of a plurality of subcarriers, a second transmission device that transmits and receives radio signals composed of a plurality of subcarriers, and a second transmission device A first transmission device that performs error correction coding on first data to be transmitted and generates error correction coded bits. An error correction encoding unit, a first modulation unit for a first transmission device that modulates error correction encoding bits to generate a plurality of modulation symbols, and a part of amplitude values of the plurality of modulation symbols become zero A block encoding unit that performs effective block encoding, a second modulation unit for a first transmission device that generates a modulation signal by arranging the block-coded modulation symbols on each subcarrier, and a first transmission signal from the modulation signal. A transmission unit for a first transmission device that generates and transmits the second transmission device, wherein the second transmission device performs error correction coding on the second data to be transmitted and generates error correction coded bits. An error correction coding unit for the device, a first modulation unit for the second transmission device that modulates the error correction coded bits to generate a plurality of modulation symbols, and a modulation symbol having an amplitude value of zero in the first transmission signal A second modulation unit for a second transmission device that generates a modulation signal arranged on a subcarrier in a frequency band, and a transmission unit for a second transmission device that generates and transmits a second transmission signal from the modulation signal, The first receiver includes a first receiver for receiving the first transmission signal and the second transmission signal, and a second demodulator for the first receiver that acquires a symbol for each subcarrier from the received signal. And the symbol A first decoding device block decoding unit that performs block decoding according to the block coding of the block coding unit, and the first decoding unit modulation unit for modulating the block decoded symbol A first demodulating unit for the first receiving device that performs the corresponding demodulation, and an error correction process and a decoding process corresponding to the error correction coding of the error correcting coding unit for the first transmitting device using the demodulated value An error correction decoding unit for the first receiving device that generates the first data, and the second receiving device receives the first transmission signal and the second transmission signal. A second demodulator for a second receiver that obtains a symbol for each subcarrier from the received signal, and a second that performs block decoding on the symbol according to block coding of the block encoder Blower for receiver A first decoding unit for a second receiving device that performs demodulation according to the modulation of the first modulating unit for the first transmitting device, and a demodulated value for the symbol subjected to block decoding A first error correction decoding unit for the second receiving device that generates the first data by performing error correction processing and decoding processing according to error correction coding of the error correction coding unit for the first transmission device using A determination unit that determines a frequency band of a subcarrier whose amplitude value is zero in the first transmission signal based on the first data, and among the received signals, the amplitude value is zero in the first transmission signal. A symbol is obtained from a signal in the frequency band of the subcarrier, and a subcarrier selection unit that performs demodulation according to the modulation of the first modulation unit for the second transmission device, and a value after demodulation by the subcarrier selection unit is used. The first A second error correction decoding unit for the second receiving device that generates the second data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding unit for the transmission device. Features.

  [2] One aspect of the present invention is the multicarrier wireless communication system described above, wherein the first transmission device includes subcarriers in which modulation symbols whose amplitude values are zeroed by the block encoder are arranged. A null subcarrier information notification unit for notifying the second transmission device of information, and the second modulation unit for the second transmission device has an amplitude value in the first transmission signal according to the null subcarrier information. A modulation symbol is arranged on a subcarrier in a frequency band that becomes zero.

  [3] One aspect of the present invention is the multicarrier wireless communication system described above, in which the second transmission device includes a first reception device reception unit that receives the first transmission signal and the second transmission signal. A second demodulator for a first receiver that obtains a symbol for each subcarrier from the received signal, and a first receiver that performs block decoding on the symbol according to block coding of the block encoder A block decoding unit for the first receiver, a first demodulating unit for the first receiving device that performs demodulation in accordance with the modulation of the first modulation unit for the first transmitting device, and the demodulated value for the symbol subjected to the block decoding An error correction decoding unit for the first receiving device that generates the first data by performing an error correction process and a decoding process according to the error correction coding of the error correction coding unit for the first transmission device, and Based on first data And a null subcarrier determining unit that detects information on a subcarrier in which a modulation symbol having an amplitude value of zero by the block encoding unit is arranged, and the second modulation unit for the second transmission device includes: According to the null subcarrier information, modulation symbols are arranged on subcarriers in a frequency band in which the amplitude value is zero in the first transmission signal.

  [4] According to one aspect of the present invention, a first transmission device and a first reception device that transmit and receive a radio signal including a plurality of subcarriers, a second transmission device and a second transmission device that transmit and receive a radio signal including a plurality of subcarriers. A multicarrier wireless communication method performed by a multicarrier wireless communication system including a receiving device, wherein the first transmitting device performs error correction coding on the first data to be transmitted and sets error correction coded bits. A first error correction coding step for the first transmission device to be generated, a first modulation step for the first transmission device that modulates the error correction coded bits to generate a plurality of modulation symbols, and a part of the modulation symbols. A block coding step for performing block coding such that the amplitude value becomes zero, and a modulation signal generated by arranging the block-coded modulation symbols on each subcarrier. A second modulation step for the transmission device, a transmission step for the first transmission device that generates and transmits a first transmission signal from the modulated signal, and the second transmission device performs error correction coding on the second data to be transmitted An error correction coding step for the second transmission device that generates error correction coding bits, a first modulation step for the second transmission device that modulates the error correction coding bits and generates a plurality of modulation symbols, and modulation A second modulation step for a second transmission device for generating a modulation signal by arranging a symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal, and generating a second transmission signal from the modulation signal A second transmitting device transmitting step for transmitting, a first receiving device receiving step for receiving the first transmitting signal and the second transmitting signal, and a sub key from the received signal. A second demodulating step for the first receiving device for obtaining a symbol for each rear, and a block decoding step for the first receiving device for performing block decoding according to block coding of the block coding step for the symbol; A first demodulation step for a first receiving device that performs demodulation according to the modulation of the first modulation step for the first transmitting device with respect to the block-decoded symbol, and the first transmission using the demodulated value An error correction decoding step for the first receiving device that generates the first data by performing an error correction process and a decoding process according to the error correction coding of the device error correction coding step, and the second receiving device, A second receiving device receiving step for receiving the first transmission signal and the second transmission signal; and a second receiving device for obtaining a symbol for each subcarrier from the received signal. A second demodulation step, a second decoding device block decoding step for performing block decoding on the symbol in accordance with block encoding in the block encoding step, and a block decoding for the symbol, A first demodulating step for the second receiving device that performs demodulation according to the modulation of the first modulating step for one transmitting device, and an error correction coding of the error correcting coding step for the first transmitting device using the demodulated value And a first error correction decoding step for the second receiving device that generates the first data by performing error correction processing and decoding processing according to the above, and an amplitude value in the first transmission signal based on the first data A determination step of determining a frequency band of a subcarrier that becomes zero, and a frequency of a subcarrier that has an amplitude value of zero in the first transmission signal among the received signals. A symbol is obtained from a signal of several bands, a subcarrier selection step for performing demodulation according to the modulation of the first modulation step for the second transmission device, and a value after demodulation by the subcarrier selection step, A second error correction decoding step for the second receiving device that generates the second data by performing an error correction process and a decoding process according to the error correction encoding of the error correction encoding step for the two transmission devices, It is characterized by that.

  [5] One aspect of the present invention is the multicarrier wireless communication method according to the above, wherein the first transmission device has a subcarrier in which a modulation symbol whose amplitude value becomes zero by the block encoding step is arranged. A null subcarrier information notifying step for notifying the second transmitting device of information, and in the second modulating step for the second transmitting device, the second transmitting device performs the first transmission according to the null subcarrier information. A modulation symbol is arranged on a subcarrier in a frequency band in which an amplitude value is zero in a transmission signal.

  [6] One aspect of the present invention is the above-described multicarrier wireless communication method, wherein the second transmission device receives the first transmission signal and the second transmission signal. A second demodulating step for a first receiving device that acquires a symbol for each subcarrier from the received signal, and a first receiving device that performs block decoding on the symbol according to block coding in the block coding step A block decoding step for the first receiver, a first demodulation step for the first receiver for performing demodulation in accordance with the modulation of the first modulation step for the first transmitter for the block decoded symbol, and a value after demodulation A first receiving device for generating the first data by performing error correction processing and decoding processing according to error correction coding in the error correction coding step for the first transmission device An error correction decoding step, and a null subcarrier determination step of detecting information on a subcarrier in which a modulation symbol having an amplitude value of zero in the block encoding step is arranged based on the first data, In the second modulation step for the second transmission device, the second transmission device arranges a modulation symbol on a subcarrier in a frequency band in which the amplitude value is zero in the first transmission signal, according to the null subcarrier information. It is characterized by that.

  According to the present invention, the second transmission signal is configured such that the amplitude is given only to the subcarrier in the frequency band in which the amplitude value is zero in the first transmission signal, and the first transmission signal and the second transmission signal are superimposed. Is done. Therefore, the influence of the interference of the first transmission signal with respect to the second transmission signal is small. The first transmission signal can eliminate the influence of the second transmission signal superimposed by block decoding and error correction decoding. Therefore, it is possible to perform superimposed transmission while suppressing a decrease in reception quality.

It is the schematic showing the outline of the radio | wireless communications system which is 1st embodiment of the radio | wireless communications system which transmits / receives a signal by multicarrier transmission. It is a block diagram showing the function structure of a 1st transmitter. It is the schematic showing the appearance probability of each constellation point after block coding. It is the schematic showing the outline of a 1st transmission signal. It is a flowchart which shows the procedure of the transmission process of a 1st transmitter. It is a block diagram showing the function structure of a 1st receiver. It is a flowchart which shows the procedure of the reception process of a 1st receiver. It is a block diagram showing the function structure of a 2nd transmitter. It is the schematic showing the outline of a transmission signal. It is a flowchart which shows the procedure of the transmission process of a 2nd transmitter. It is a block diagram showing the function structure of a 2nd receiver. It is a flowchart which shows the procedure of the reception process of a 2nd receiver. It is the schematic showing the outline of the modification of a radio | wireless communications system. It is the schematic showing the outline of the radio | wireless communications system a which is 2nd embodiment of the radio | wireless communications system which transmits / receives a signal by multicarrier transmission. It is a block diagram showing the function structure of a 1st transmitter. It is a flowchart which shows the procedure of the transmission process of the 1st transmission apparatus of 2nd embodiment. It is a block diagram showing the function structure of a 2nd transmitter. It is a flowchart which shows the procedure of the transmission process of the 2nd transmission apparatus of 2nd embodiment.

[First embodiment]
FIG. 1 is a schematic diagram illustrating an outline of a wireless communication system 10 that is a first embodiment of a wireless communication system that transmits and receives signals by multicarrier transmission. The wireless communication system 10 includes a first transmission device 1, a first reception device 2, a second transmission device 3, and a second reception device 4. The first transmitter 1 transmits a radio signal to the first receiver 2, and the second transmitter 3 transmits a radio signal to the second receiver 4. Note that the number of the first transmission device 1, the first reception device 2, the second transmission device 3, and the second reception device 4 included in the wireless communication system 10 is not limited to one as shown in FIG. Multiple units may be included. In FIG. 1, the first transmission device 1 and the second transmission device 3 are base station devices, and the first reception device 2 and the second reception device 4 are wireless communication terminals. The second transmission device 3 may be a wireless communication terminal, and the first reception device 2 and the second reception device 4 may be base station devices.

  A wireless communication terminal is a terminal device that performs wireless communication with a base station device, such as a mobile phone, a wireless LAN (Local Area Network) terminal, or a WiMAX (registered trademark) (Worldwide Interoperability for Microwave Access) terminal. is there. The base station device is a device that performs wireless communication with a plurality of wireless communication terminals, such as a base station device in a mobile phone network, a wireless LAN router, or a WiMAX (registered trademark) base station. The first transmission device 1, the first reception device 2, the second transmission device 3, and the second reception device 4 perform wireless communication by a multicarrier transmission method (for example, OFDM (Orthogonal frequency division multiplex)). .

  FIG. 2 is a block diagram illustrating a functional configuration of the first transmission device 1. As shown in the figure, the first transmission device 1 includes an FEC encoding unit 101, a first modulation unit 102, a block encoding unit 103, a serial-parallel conversion unit 104, a second modulation unit 105, a transmission unit 106, an antenna 107, and a null. A subcarrier information notification unit 108 is provided.

The FEC encoding unit 101 encodes a bit string of first data to be transmitted according to FEC (Forward Error Correction) to generate error correction encoded bits.
The first modulation unit 102 generates a plurality of modulation symbols by performing modulation processing (mapping processing) on the error correction coded bits. Specifically, the first modulation unit 102 performs modulation processing by a modulation scheme such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), or 8PSK (Octuple Phase Shift Keying), and performs error correction coding. A combination of amplitude value and phase value (modulation symbol) corresponding to the bit is generated.

The block encoding unit 103 performs block encoding processing on the plurality of modulation symbols generated by the first modulation unit 102. The block encoding unit 103 is applied with a block encoding method that can perform a lossless operation (block decoding) and that the amplitude value of a part of the symbol after the block encoding becomes zero. For example, the block encoding unit 103 performs block encoding processing using a Hadamard matrix that is a kind of orthogonal matrix such as Equation 1. In Equation 1, d ₁ and d ₂ represent modulation symbols, respectively, and b ₁ and b ₂ represent modulation symbols after block coding (block coded modulation symbols), respectively. The block encoding unit 103 is not limited to the Hadamard matrix, and may use an M sequence or a scramble code.

FIG. 3 is a schematic diagram showing the appearance probability of each constellation point after block coding. The vertical axis Q represents a quadrature component and the horizontal axis I represents an in-phase component. FIG. 3 shows an example in which a modulation symbol modulated by equal power QPSK (4 constellation points) is block-coded by a 2 × 2 Hadamard matrix. In this case, there are 16 combinations of modulation symbols d ₁ and d ₂ . Further, there are nine constellation points of the block coded modulation symbols b ₁ and b ₂ , and the appearance probability of the constellation point (I, Q) = (0, 0) at which the amplitude is zero is 4/16 ( 25%).

  Returning to FIG. 2, the description of the first transmission device 1 will be continued. The serial / parallel conversion unit 104 performs serial / parallel conversion (serial / parallel conversion) on the plurality of block-coded modulation symbols generated by the block coding unit 103.

  The second modulation unit 105 arranges each block-coded modulation symbol parallelized by the serial-parallel conversion unit 104 in each subcarrier, and performs IFFT (Inverse Fast Fourier Transform) or parallel-serial conversion (parallel / serial). Conversion) and insertion of a guard interval to generate a modulated signal.

The transmission unit 106 generates a transmission signal by performing processing such as digital / analog conversion, power amplification, and up-conversion on the modulated signal.
The antenna 107 transmits the transmission signal generated by the transmission unit 106 by radio. Hereinafter, the transmission signal transmitted by the first transmission device 1 is referred to as “first transmission signal”.

  Null subcarrier information notifying section 108 is a subcarrier to which a block-coded modulation symbol having an amplitude value of zero is allocated based on the result of block coding processing by block coding section 103, in other words, the amplitude is zero. Null subcarrier information representing the number of subcarriers (hereinafter, such subcarriers are referred to as “null subcarriers”) and frequency bands (hereinafter, the frequency band of null subcarriers is referred to as “null frequency bands”) is generated. Then, the null subcarrier information notification unit 108 notifies the second transmission device 3 of null subcarrier information. At this time, the null subcarrier information notification unit 108 may notify via a wired network such as a LAN, may notify via a wireless network such as a wireless LAN or Bluetooth (registered trademark), or USB. You may notify via cables, such as (Universal Serial Bus).

  FIG. 4 is a schematic diagram illustrating an outline of the first transmission signal. In FIG. 4, the horizontal axis represents frequency and the vertical axis represents amplitude. FIG. 4A shows a transmission signal generated according to a conventional multicarrier scheme (QPSK modulation, OFDM), and FIG. 4B shows a first transmission signal generated by the first transmission device 1. In FIG. 4A, the amplitude of each of the plurality of subcarriers is a1 and uniform, and there is no null subcarrier. On the other hand, in FIG. 4B, there are subcarriers having a relatively large amplitude a2, subcarriers having a relatively small amplitude a1, and null subcarriers having an amplitude of zero. Null subcarriers are subcarriers that exist in the frequency band indicated by the upward arrow in FIG. 4B and in which block-coded modulation symbols having an amplitude value of zero are arranged.

Next, the operation and processing procedure of the first transmission device 1 will be described. FIG. 5 is a flowchart showing the procedure of the transmission process of the first transmission device 1.
As shown in FIG. 5, first, the FEC encoder 101 performs error correction encoding on the bit string of the first data to be transmitted in accordance with FEC to generate error correction encoded bits (step S101). Next, the first modulation unit 102 modulates the error correction coded bits to generate a modulation symbol (step S102). Next, the block coding unit 103 performs block coding processing on the modulation symbols (step S103). Next, the null subcarrier information notification unit 108 notifies null subcarrier information based on the result of the block encoding process (step S104). Next, the serial-parallel conversion unit 104 performs serial-parallel conversion on the block-coded modulation symbol (step S105). Next, the second modulation unit 105 performs IFFT processing (step S106), and performs parallel-serial conversion and insertion of a guard interval (step S107). Next, the transmission part 106 produces | generates a 1st transmission signal (step S108). Then, the antenna 107 transmits the first transmission signal wirelessly (step S109), and the transmission process shown in this flowchart ends.

Next, the functional configuration of the first receiving device 2 will be described.
FIG. 6 is a block diagram illustrating a functional configuration of the first receiving device 2. As illustrated, the first receiving device 2 includes an antenna 201, a receiving unit 202, a second demodulating unit 203, a parallel-serial converting unit 204, a block decoding unit 205, a first demodulating unit 206, and an FEC decoding unit 207.

The antenna 201 receives a signal obtained by combining the first transmission signal transmitted by the first transmission device 1 and the signal transmitted by the second transmission device 3.
The receiving unit 202 down-converts the received signal, further performs analog / digital conversion, and generates a modulated signal.

The second demodulator 203 removes a plurality of symbols by performing guard interval removal, serial parallel conversion, FFT (Fast Fourier Transform), frequency domain equalization processing using preamble information, and the like on the modulated signal. Generate.
The parallel-serial converter 204 performs parallel-serial conversion on a plurality of symbols arranged in parallel.

  The block decoding unit 205 performs a block decoding process corresponding to the block encoding process by the block encoding unit 103 of the first transmission device 1 on each symbol to generate a modulation symbol. For example, when the block encoding unit 103 performs block encoding processing using a Hadamard matrix like Equation 1, the block decoding unit 205 uses a inverse matrix of Hadamard matrix like Equation 2 to perform block decoding processing. I do.

The first demodulation unit 206 generates an error correction coded bit by performing demodulation processing (demapping processing) on the modulation symbol in accordance with the modulation processing by the first modulation unit 102 of the first transmission device 1.
The FEC decoding unit 207 performs error correction processing and decoding processing corresponding to the error correction coding processing by the FEC coding unit 101 of the first transmission device 1 on the error correction coded bits, thereby obtaining the first transmission device 1. The first data that was the transmission target is generated.

Next, the operation and processing procedure of the first receiving device 2 will be described. FIG. 7 is a flowchart showing the procedure of the reception process of the first receiving device 2.
As shown in FIG. 7, the antenna 201 first receives a signal (step S201), and the receiving unit 202 generates a modulated signal from the received signal (step S202). Next, the second demodulation unit 203 performs guard interval removal and serial-parallel conversion on the modulated signal (step S203). Next, the second demodulator 203 performs a FFT to generate a plurality of symbols (step S204). Next, the parallel / serial conversion unit 204 performs parallel / serial conversion on a plurality of symbols (step S205). Next, the block decoding unit 205 generates a modulation symbol by performing a block decoding process on each symbol (step S206). Next, the first demodulator 206 demodulates the modulation symbols to generate error correction coded bits (step S207). Next, the FEC decoding unit 207 generates first data by performing error correction decoding on the error correction encoded bits (step S208), and the reception process shown in this flowchart ends.

  FIG. 8 is a block diagram illustrating a functional configuration of the second transmission device 3. As illustrated, the second transmission device 3 includes a rate adjustment buffer 301, an FEC encoding unit 302, a first modulation unit 303, a serial-parallel conversion unit 304, a subcarrier selection unit 305, a second modulation unit 306, and a transmission unit 307. The antenna 308 is provided.

  The rate adjustment buffer 301 buffers the second data to be transmitted, and outputs the number of bits to the FEC encoding unit 302 according to the number of null subcarriers indicated by the null subcarrier information notified from the first transmission device 1 Adjust. That is, since the second transmission device 3 performs radio communication using only the subcarriers in the null frequency band of the first transmission signal, the rate adjustment buffer 301 can transmit with one transmission signal according to the number of null subcarriers. Only the second data of the number of bits is output to the FEC encoding unit 302, and the remaining second data is buffered until the next transmission timing.

The FEC encoding unit 302 encodes the bit string of the second data output from the rate adjustment buffer 301 according to FEC, and generates error correction encoded bits.
The first modulation unit 303 generates a plurality of modulation symbols by performing modulation processing on the error correction coded bits. Specifically, the first modulation unit 303 performs modulation processing using a modulation scheme such as BPSK, QPSK, or 8PSK, for example, and generates a combination (modulation symbol) of an amplitude value and a phase value corresponding to the error correction coding bits. . Note that the first modulation unit 303 may perform modulation processing by the same modulation method as the first modulation unit 102 of the first transmission device 1, or may perform modulation processing by a different modulation method.

The serial / parallel converter 304 performs serial / parallel conversion on the plurality of modulation symbols generated by the first modulator 303.
The subcarrier selection unit 305 arranges the modulation symbol generated by the first modulation unit 303 according to the frequency band of the null subcarrier indicated by the null subcarrier information notified from the first transmission device 1. Select the band. Specifically, subcarrier selecting section 305 instructs second modulating section 306 to arrange a modulation symbol on a subcarrier located in the frequency band of the notified null subcarrier.

  The second modulation unit 306 places each modulation symbol parallelized by the serial-parallel conversion unit 304 on each subcarrier selected by the subcarrier selection unit 305, and performs IFFT, parallel-serial conversion, and insertion of a guard interval. Thus, a modulation signal is generated.

The transmission unit 307 generates a transmission signal by performing processing such as digital / analog conversion, power amplification, and up-conversion on the modulated signal.
The antenna 308 wirelessly transmits the transmission signal generated by the transmission unit 307. Hereinafter, the transmission signal transmitted by the second transmission device 3 is referred to as “second transmission signal”.

  FIG. 9 is a schematic diagram illustrating an outline of a transmission signal. In FIG. 9, the horizontal axis represents frequency, and the vertical axis represents amplitude. FIG. 9A represents a first transmission signal generated by the first transmission device 1, and FIG. 9B represents a second transmission signal generated by the second transmission device 3. As shown in the figure, the second transmission signal is composed only of subcarriers in the frequency band of the null subcarrier of the first transmission signal, and modulation symbols are arranged only in these subcarriers. Further, as illustrated in FIG. 9, the amplitude a0 of the second transmission signal is desirably smaller than the two amplitudes a1 and a2 of the first transmission signal.

Next, the operation and processing procedure of the second transmission device 3 will be described. FIG. 10 is a flowchart showing the procedure of the transmission process of the second transmission device 3.
As shown in FIG. 10, first, the rate adjustment buffer 301 determines the number of bits that can be transmitted based on the null subcarrier information, and outputs second data to be transmitted according to the number of bits (step S301). Next, the FEC encoding unit 302 performs error correction encoding on the bit string of the second data to be transmitted according to FEC to generate error correction encoded bits (step S302). Next, the first modulation unit 303 modulates the error correction coded bits to generate a modulation symbol (step S303). Next, the serial / parallel conversion unit 304 performs serial / parallel conversion on the modulation symbol (step S304). Next, subcarrier selecting section 305 selects the frequency of the subcarrier on which the modulation symbol is arranged based on the null subcarrier information (step S305). Next, second modulation section 306 arranges modulation symbols for the subcarriers of the frequency selected by subcarrier selection section 305 (step S306). Next, the second modulation unit 306 performs IFFT processing (step S307), and performs parallel-serial conversion and insertion of guard intervals (step S308). Next, the transmission unit 307 generates a second transmission signal (step S309). Then, the antenna 308 transmits the second transmission signal wirelessly (step S310), and the transmission process shown in this flowchart ends.

Next, the functional configuration of the second receiving device 4 will be described.
FIG. 11 is a block diagram illustrating a functional configuration of the second receiving device 4. As illustrated, the second receiving device 4 includes an antenna 401, a receiving unit 402, a second demodulating unit 403, a parallel-serial converting unit 404, a block decoding unit 405, a first demodulating unit 406, a first FEC decoding unit 407, a null. A subcarrier determination unit 408, a subcarrier selection unit 409, and a second FEC decoding unit 410 are provided.

The antenna 401 receives a signal obtained by combining the first transmission signal transmitted by the first transmission device 1 and the second transmission signal transmitted by the second transmission device 3.
The receiving unit 402 performs down-conversion on the received signal, further performs analog / digital conversion, and generates a modulated signal.

The second demodulator 403 generates a plurality of symbols by performing guard interval removal, serial / parallel conversion, frequency domain equalization processing using FFT and preamble information, and the like on the modulated signal.
The parallel / serial conversion unit 404 performs parallel / serial conversion on a plurality of symbols arranged in parallel.

  The block decoding unit 405 performs a block decoding process corresponding to the block encoding process by the block encoding unit 103 of the first transmission device 1 on each symbol to generate a modulation symbol. For example, when the block encoding unit 103 performs block encoding processing using a Hadamard matrix such as Equation 1, the block decoding unit 405 uses an inverse matrix of the Hadamard matrix such as Equation 2 above. Perform block decoding.

The first demodulating unit 406 generates an error correction coded bit by performing demodulation processing (demapping processing) on the modulation symbol in accordance with the modulation processing by the first modulation unit 102 of the first transmission device 1.
The first FEC decoding unit 407 performs the first transmission by performing error correction processing and decoding processing corresponding to the error correction coding processing by the FEC coding unit 101 of the first transmission device 1 on the error correction coded bits. The first data that is the transmission target in the device 1 is generated.

  The null subcarrier determination unit 408 determines a null frequency band in the first transmission signal of the first transmission device 1. Specifically, the null subcarrier determination unit 408 performs, on the first data generated by the first FEC decoding unit 407, the FEC encoding unit 101, the first modulation unit 102, and the block encoding of the first transmission device 1. A replica signal is generated by performing the same processing as unit 103, and a null frequency band in which null subcarriers are arranged is determined.

  The subcarrier selection unit 409 acquires only the symbols of the subcarriers in the null frequency band determined by the null subcarrier determination unit 408 among the symbols generated by the second demodulation unit 403. That is, the subcarrier selection unit 409 acquires the modulation symbol only from the subcarrier on which the modulation symbol is arranged by the second transmission device 3. Then, the subcarrier selecting unit 409 performs error correction coding of the second data by performing demodulation processing corresponding to the modulation processing by the first modulation unit 303 of the second transmission device 3 on each acquired modulation symbol. Generate bits.

  The second FEC decoding unit 410 performs error correction processing and decoding according to the error correction coding processing by the FEC coding unit 302 of the second transmission device 3 for the error correction coded bits generated by the subcarrier selection unit 409. By performing the conversion processing, second data that has been a transmission target in the second transmission device 3 is generated.

Next, the operation and processing procedure of the second receiving device 4 will be described. FIG. 12 is a flowchart illustrating the procedure of the reception process of the second reception device 4.
As shown in FIG. 12, the antenna 401 first receives a signal (step S401), and the reception unit 402 generates a modulated signal from the received signal (step S402). Next, the second demodulator 403 performs guard interval removal and serial / parallel conversion on the modulated signal (step S403). Next, the second demodulator 403 performs FFT to generate a plurality of symbols (step S404). Next, the parallel / serial conversion unit 404 performs parallel / serial conversion on the symbol (step S405). Next, the block decoding unit 405 generates a modulation symbol by performing a block decoding process on each symbol (step S406). Next, the first demodulator 406 demodulates the modulation symbol to generate error correction coded bits (step S407). Next, the first FEC decoding unit 407 generates first data by performing error correction decoding on the error correction encoded bits (step S408).

  Next, the null subcarrier determination unit 408 generates a replica signal (step S409) and determines a null frequency band (step S410). Next, the subcarrier selection unit 409 obtains a modulation symbol from the subcarrier in the null frequency band and demodulates it to generate error correction coded bits of the second data (step S411). Then, the second FEC encoding unit 410 generates second data by performing error correction decoding on the error correction encoded bits (step S412), and the transmission process illustrated in this flowchart ends.

  The first receiving device 2 and the second receiving device 4 of the wireless communication system 10 configured as described above receive a signal obtained by combining the first transmission signal and the second transmission signal. However, since the first transmission signal has noise tolerance by FEC and block coding processing, if the amplitude a0 of the second transmission device is equal to or smaller than the amplitude a1 of the first transmission signal, the first reception device 2 and the second transmission device The receiving device 4 can correctly generate the first data. Then, the second receiver 4 correctly generates the first data in this way, thereby accurately determining the null frequency band, selecting the subcarrier of the second transmission signal arranged in the null frequency band, Two data can be generated correctly. That is, the wireless communication system 10 can perform superposition transmission without using a guard band.

  Moreover, the 1st transmitter 1 can generate the null subcarrier which has a part of 1st data, without providing the null subcarrier which does not contain transmission data arbitrarily by performing a block encoding process. . Therefore, the first transmission signal having a null subcarrier can be generated without reducing the amount of data included in the first transmission signal. Since the second transmission signal is configured by giving amplitude only to the subcarriers in the null frequency band of the first transmission signal, the influence of interference by the first transmission signal is small. With the above configuration, it is possible to realize superposition transmission in which the reception quality of the second transmission signal is improved as compared with the conventional one while suppressing a decrease in data transmission efficiency (communication speed) due to the first transmission signal.

In the first transmission signal, null subcarriers are generated with a certain probability (25% in the case of FIG. 3). For this reason, the symbol rate of the second transmission signal settles to a substantially constant value, and the second transmission signal can be transmitted stably.
Compared with the prior art, it is possible to reduce the amount of calculation for subtraction processing for removing the replica signal from the received signal.

<Modification>
FIG. 13 is a schematic diagram illustrating an outline of a modified example of the wireless communication system 10. As illustrated, the first transmission device 1 and the second transmission device 3 of the wireless communication system 10 may be configured as a single transmission device. In this case, the null subcarrier notification unit 108 may be configured to notify the null subcarrier information to the rate adjustment buffer 301 and the subcarrier selection unit 305 connected by wiring. In this case, the first transmission signal and the second transmission signal may be transmitted from different antennas, or a signal obtained by combining the first transmission signal and the second transmission signal in advance may be transmitted from the antenna. good.

In addition, from the viewpoint of interference with the first transmission signal, the signal format (subcarrier interval, symbol rate, etc.) of the second transmission signal is preferably equal to that of the first transmission signal.
In addition, it is desirable that the transmission power spectral density of the second transmission signal is suppressed to an extent that does not hinder block decoding processing by the block decoding unit 205.
Moreover, each said structure may be comprised by the single carrier transmission system instead of a multicarrier transmission system. In that case, a time slot with zero amplitude is generated instead of a subcarrier with zero amplitude. That is, the wireless communication system 10 according to the single carrier transmission scheme can be configured by replacing the concept related to the subcarriers in the frequency direction with time slots in the time direction.

[Second Embodiment]
FIG. 14 is a schematic diagram illustrating an outline of a wireless communication system 10a which is a second embodiment of a wireless communication system that transmits and receives signals by multicarrier transmission. The radio communication system 10a of the second embodiment differs from the radio communication system 10 of the first embodiment in that the first transmission device 1a does not notify the second transmission device 3a of null subcarrier information. And the structure of the 2nd receiver 4 is the same as 1st embodiment. Hereinafter, the difference between the wireless communication system 10a of the second embodiment and the wireless communication system 10 of the first embodiment will be described.

FIG. 15 is a block diagram illustrating a functional configuration of the first transmission device 1a. In FIG. 15, the same components as those of the first transmission device 1 of the first embodiment are denoted by the same reference numerals as those in FIG.
The first transmission device 1 a is different from the first transmission device 1 in that the null subcarrier information notification unit 108 is not provided, and the other configuration is the same as that of the first transmission device 1. Therefore, the description about each structure of the 1st transmitter 1a is abbreviate | omitted.

  FIG. 16 is a flowchart showing the procedure of the transmission process of the first transmission device 1a of the second embodiment. The same processes as those in FIG. 5 are denoted by the same reference numerals as those in FIG. 5 in FIG. As shown in the figure, the procedure of the transmission process of the second embodiment is the same as the procedure of the transmission process of the first embodiment in that the serial / parallel converter 104 performs serial / parallel conversion (step S105) after the process of step S103. Differently, other procedures are the same as in the first embodiment.

  FIG. 17 is a block diagram illustrating a functional configuration of the second transmission device 3a. 17, the same configuration as that of the second transmission device 3 of the first embodiment is denoted by the same reference numerals as those in FIG. 8 in FIG. 17, and description thereof is omitted.

  The second transmission device 3a further includes an antenna 311, a reception unit 312, a second demodulation unit 313, a parallel-serial conversion unit 314, a block decoding unit 315, a first demodulation unit 316, an FEC decoding unit 317, and a null subcarrier determination unit 318. Unlike the second transmission device 3, the other configurations are the same as those of the second transmission device 3.

  The rate adjustment buffer 301 and the subcarrier selection unit 305 of the second transmission device 3a operate based on the determination result of the null subcarrier determination unit 318, not the null subcarrier information notified from the first transmission device 1a. Although different from the first embodiment, the other operations are the same as those of the first embodiment, and thus the description thereof is omitted. In addition, the FEC encoding unit 302, the first modulation unit 303, the serial-parallel conversion unit 304, the second modulation unit 306, the transmission unit 307, and the antenna 308 have the same configurations as those in the first embodiment, and thus description thereof is omitted.

  In addition, the antenna 311, the reception unit 312, the second demodulation unit 313, the parallel-serial conversion unit 314, the block decoding unit 315, the first demodulation unit 316, and the FEC decoding unit 317 are respectively the antenna 201 and the reception unit of the first reception device 2. 202, the second demodulator 203, the parallel-serial converter 204, the block decoder 205, the first demodulator 206, and the FEC decoder 207 are configured in the same manner, and the description thereof is omitted.

  The null subcarrier determination unit 318 performs the same process as the FEC encoding unit 101, the first modulation unit 102, and the block encoding unit 103 of the first transmission device 1a on the first data generated by the FEC decoding unit 317. By performing this, a replica signal is generated, and the number of null subcarriers and the null frequency band are determined.

  FIG. 18 is a flowchart illustrating a procedure of transmission processing of the second transmission device 3a of the second embodiment. The same processes as those in FIG. 10 are denoted by the same reference numerals as those in FIG. 10 in FIG. As shown in the figure, first, the antenna 311 receives a signal (step S311), and the receiving unit 312 generates a modulated signal from the received signal (step S312). Next, the second demodulator 313 performs guard interval removal and serial-parallel conversion on the modulated signal (step S313). Next, the second demodulator 313 performs FFT to generate a plurality of symbols (step S314). Next, the parallel / serial conversion unit 314 performs parallel / serial conversion on a plurality of symbols (step S315). Next, the block decoding unit 315 generates a modulation symbol by performing a block decoding process on each symbol (step S316). Next, the first demodulator 316 demodulates the modulation symbols to generate error correction coded bits (step S317). Next, the FEC decoding unit 317 generates first data by decoding the error correction encoded bits (step S318).

  Next, the null subcarrier determination unit 318 generates a replica signal (step S319), and determines the number of null subcarriers and the null frequency band (step S320). Thereafter, the second transmission device 3a performs the processing of step S301 to step S310 as in the first embodiment, and the transmission processing represented in this flowchart ends.

In the wireless communication system 10a of the second embodiment configured as described above, the second transmission device 3a determines the number of null subcarriers and the null frequency band without receiving notification of null subcarrier information from the first transmission device 1a. To detect. Therefore, it becomes possible to install the 1st transmitter 1a and the 2nd transmitter 3a in the position physically separated. For example, the first transmission device 1a may be configured as a relay device having a wide communication range, and the second transmission device 3a may be configured as a base station device having a narrower communication range.
Moreover, the radio | wireless communications system 10a of 2nd embodiment is the modification except that the 1st transmission device 1a and the 2nd transmission device 3a are comprised as one apparatus among the modifications of 1st embodiment. Similarly, it may be modified.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... 1st transmission apparatus, 101 ... FEC encoding part, 102 ... 1st modulation part, 103 ... Block encoding part, 104 ... Serial-parallel conversion part, 105 ... 2nd modulation part, 106 ... Transmission part, 107 ... Antenna 2 ... 1st receiver, 201 ... antenna, 202 ... receiver, 203 ... second demodulator, 204 ... parallel-serial converter, 205 ... block decoder, 206 ... first demodulator, 207 ... FEC decoder, DESCRIPTION OF SYMBOLS 3 ... 2nd transmitter, 301 ... Rate adjustment buffer, 302 ... FEC encoding part, 303 ... 1st modulation | alteration part, 304 ... Serial-parallel conversion part, 305 ... Subcarrier selection part, 306 ... 2nd modulation | alteration part, 307 ... Transmitter, 308 ... antenna, 311 ... antenna, 312 ... receiver, 313 ... second demodulator, 314 ... parallel-serial converter, 315 ... block decoder, 316 ... 1 demodulator, 317 ... FEC decoder, 318 ... null subcarrier determination unit, 4 ... second receiver, 401 ... antenna, 402 ... receiver, 403 ... second demodulator, 404 ... parallel-serial converter, 405 ... Block decoding unit, 406 ... first demodulation unit, 407 ... FEC decoding unit, 408 ... null subcarrier determination unit, 409 ... subcarrier selection unit, 410 ... second FEC decoding unit, 10 ... wireless communication system

Claims (6)

Multi-carrier wireless communication including a first transmission device and a first reception device that transmit and receive wireless signals composed of a plurality of subcarriers, and a second transmission device and a second reception device that transmit and receive wireless signals composed of a plurality of subcarriers A system,
The first transmitter is
Performing error correction encoding on the first data to be transmitted, and generating an error correction encoded bit;
A first modulation unit for a first transmission device that modulates error correction coded bits and generates a plurality of modulation symbols;
A block encoding unit that performs block encoding such that some amplitude values are zero for a plurality of modulation symbols;
A second modulation unit for the first transmission device that arranges block-coded modulation symbols on each subcarrier and generates a modulation signal;
A transmitter for a first transmitter that generates and transmits a first transmission signal from the modulated signal;
With
The second transmitter is
Performing error correction encoding on the second data to be transmitted, and generating an error correction encoded bit;
A first modulation unit for a second transmission device that modulates error correction coded bits and generates a plurality of modulation symbols;
A second modulation unit for a second transmission device that generates a modulation signal by arranging a modulation symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal;
A second transmission device transmitter for generating and transmitting a second transmission signal from the modulated signal;
With
The first receiving device is
A receiver for a first receiver that receives the first transmission signal and the second transmission signal;
A second demodulator for a first receiver that acquires a symbol for each subcarrier from the received signal;
A block decoding unit for a first receiving device that performs block decoding according to block coding of the block coding unit for the symbol;
A first demodulator for a first receiver that performs demodulation according to the modulation of the first modulator for the first transmitter on the block-decoded symbol;
Error correction for the first receiving device that generates the first data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding unit for the first transmission device using the demodulated value A decryption unit;
With
The second receiving device is
A receiver for a second receiver that receives the first transmission signal and the second transmission signal;
A second demodulator for a second receiver that acquires symbols for each subcarrier from the received signal;
A block decoding unit for a second receiving device that performs block decoding according to block coding of the block coding unit for the symbol;
A first demodulator for a second receiver that performs demodulation in accordance with the modulation of the first modulator for the first transmitter with respect to the block-decoded symbol;
The first for the second receiving device that generates the first data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding unit for the first transmission device using the demodulated value An error correction decoding unit;
A determination unit for determining a frequency band of a subcarrier having an amplitude value of zero in the first transmission signal based on the first data;
Among the received signals, a sub is obtained from a signal in a frequency band of a subcarrier having an amplitude value of zero in the first transmission signal, and demodulated according to the modulation of the first modulation unit for the second transmission device. A carrier selection section;
Using the value demodulated by the subcarrier selection unit, the second data is generated by performing error correction processing and decoding processing according to error correction coding of the error correction coding unit for the second transmission device A second error correction decoding unit for the second receiving device;
A multi-carrier wireless communication system comprising: The first transmission device further includes a null subcarrier information notification unit for notifying the second transmission device of information on a subcarrier in which a modulation symbol whose amplitude value becomes zero by the block encoding unit is arranged,
The second modulation unit for the second transmission device arranges a modulation symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal, according to the null subcarrier information. Item 4. The multicarrier wireless communication system according to Item 1. The second transmitter is
A receiver for a first receiver that receives the first transmission signal and the second transmission signal;
A second demodulator for a first receiver that acquires a symbol for each subcarrier from the received signal;
A block decoding unit for a first receiving device that performs block decoding according to block coding of the block coding unit for the symbol;
A first demodulator for a first receiver that performs demodulation according to the modulation of the first modulator for the first transmitter on the block-decoded symbol;
Error correction for the first receiving device that generates the first data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding unit for the first transmission device using the demodulated value A decryption unit;
Based on the first data, further comprising: a null subcarrier determination unit that detects information on a subcarrier in which a modulation symbol having an amplitude value of zero by the block encoding unit is arranged;
The second modulation unit for the second transmission device arranges a modulation symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal according to the information on the null subcarrier. The multicarrier wireless communication system according to claim 1. Multi-carrier wireless communication including a first transmission device and a first reception device that transmit and receive wireless signals composed of a plurality of subcarriers, and a second transmission device and a second reception device that transmit and receive wireless signals composed of a plurality of subcarriers A multi-carrier wireless communication method performed by a system,
The first transmission device is
Performing error correction encoding on the first data to be transmitted and generating error correction encoded bits;
A first modulation step for a first transmission device that modulates error correction coded bits to generate a plurality of modulation symbols;
A block encoding step for performing block encoding such that some amplitude values are zero for a plurality of modulation symbols;
A second modulation step for the first transmission device that places a block-coded modulation symbol on each subcarrier to generate a modulated signal;
A transmission step for a first transmission device that generates and transmits a first transmission signal from the modulated signal;
The second transmission device is
An encoding step for a second transmitting device that performs error correction encoding on the second data to be transmitted and generates error correction encoded bits;
A first modulation step for a second transmission device that modulates error correction coded bits to generate a plurality of modulation symbols;
A second modulation step for a second transmission device that generates a modulation signal by arranging a modulation symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal;
A transmission step for a second transmission device that generates and transmits a second transmission signal from the modulated signal;
The first receiving device is
A first receiving device receiving step for receiving the first transmission signal and the second transmission signal;
A second demodulation step for the first receiving device for obtaining a symbol for each subcarrier from the received signal;
A block decoding step for a first receiver that performs block decoding according to the block encoding of the block encoding step for the symbol;
A first demodulating step for a first receiving device that performs demodulation according to the modulation of the first modulating step for the first transmitting device on the block-decoded symbols;
Error correction for the first receiving device that generates the first data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding step for the first transmission device using the demodulated value A decryption step;
The second receiving device is
A second receiving device receiving step for receiving the first transmission signal and the second transmission signal;
A second demodulation step for the second receiving device for obtaining a symbol for each subcarrier from the received signal;
A block decoding step for a second receiver that performs block decoding according to block encoding of the block encoding step for the symbol;
A first demodulating step for a second receiving device that performs demodulation in accordance with the modulation of the first modulating step for the first transmitting device, with respect to the block-decoded symbol;
First for second receiving device that generates the first data by performing error correction processing and decoding processing according to error correction coding in the error correction coding step for first transmitting device using the demodulated value An error correction decoding step;
A determination step of determining a frequency band of a subcarrier having an amplitude value of zero in the first transmission signal based on the first data;
Among the received signals, a sub is obtained from a signal in a frequency band of a subcarrier having an amplitude value of zero in the first transmission signal, and demodulated according to the modulation in the first modulation step for the second transmission device. Career selection step;
Using the value demodulated in the subcarrier selection step, the second data is generated by performing error correction processing and decoding processing according to error correction coding in the error correction coding step for the second transmission device A second error correction decoding step for the second receiving device;
A multi-carrier wireless communication method comprising: The first transmission device further includes a null subcarrier information notification step of notifying the second transmission device of information on subcarriers in which modulation symbols whose amplitude values have become zero by the block encoding step are arranged,
In the second modulation step for the second transmission device, the second transmission device arranges a modulation symbol on a subcarrier in a frequency band in which an amplitude value is zero in the first transmission signal, according to the null subcarrier information. The multi-carrier radio communication method according to claim 4. The second transmission device is
A first receiving device receiving step for receiving the first transmission signal and the second transmission signal;
A second demodulation step for the first receiving device for obtaining a symbol for each subcarrier from the received signal;
A block decoding step for a first receiver that performs block decoding according to the block encoding of the block encoding step for the symbol;
A first demodulating step for a first receiving device that performs demodulation according to the modulation of the first modulating step for the first transmitting device on the block-decoded symbols;
Error correction for the first receiving device that generates the first data by performing error correction processing and decoding processing according to the error correction coding of the error correction coding step for the first transmission device using the demodulated value A decryption step;
Based on the first data, further comprising a null subcarrier determination step of detecting information on subcarriers in which modulation symbols having amplitude values of zero in the block encoding step are arranged,
In the second modulation step for the second transmission device, the second transmission device arranges a modulation symbol on a subcarrier in a frequency band in which the amplitude value is zero in the first transmission signal in accordance with the null subcarrier information. The multicarrier wireless communication method according to claim 4, wherein:

Images