JP2007081625A - Device and method for multiantenna radio communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve quality in reception and throughput in a system by using a different communication channel in retransmission for transmission in an MIMO transmission system. <P>SOLUTION: There are provided a plurality of antennas for receiving a plurality of demodulation signals transmitted from the plurality of antennas simultaneously, a retransmission request detector for detecting a retransmission request included in a reception signal, a data selector for selecting data to be retransmitted by using the retransmission request, and a radio unit for changing the communication channel of the data to be retransmitted to the communication channel CH2 different from the previous one CH1 to transmit the data to be retransmitted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method, and is particularly applicable to a case where a modulated signal is transmitted using a plurality of antennas.

  Conventionally, as in a transmission method called MIMO (Multi-Input Multi-Output) described in Non-Patent Document 1, for example, different modulation signals are transmitted from a plurality of antennas, and are simultaneously transmitted from each antenna on the receiving side. There has been proposed a method of improving the transmission rate without expanding the frequency band by separating and demodulating the modulation signal.

  This method will be briefly described. As shown in FIG. 33, modulated signals A and B are simultaneously transmitted from two antennas B (Base station) -AN1 and B-AN2, respectively, and are transmitted by two antennas T (Terminal) -AN1 and T-AN2. Consider a case where modulated signals A and B are received. In this case, it is necessary to estimate four channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t) on the receiving side.

Therefore, as shown in FIG. 33, pilot symbols (for radio wave propagation environment estimation) for estimating channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t) in modulated signals A and B. Symbols) 01, 02, 03, 04 are arranged. The known signal here the pilot symbols 01, 03 are transmitted simultaneously complex C, and the known signal of -C Pilot symbol 02 ^*, and sends a known signal of the pilot symbol 04 ^{C *.} Incidentally, * indicates a conjugate complex number. In addition, data symbols other than pilot symbols 01, 02, 03, 04 are arranged in both modulation signal A and modulation signal B.

  As described above, in a radio transmission apparatus that transmits different modulation signals from multiple antennas simultaneously, by embedding a pilot symbol in the modulation signal transmitted from each antenna, the modulation signal synthesized on the propagation path is good on the receiving side. Can be separated and demodulated. As described above, the transmission rate can be improved without expanding the frequency band.

  In MIMO transmission, the quality of the received signal (data error rate) varies greatly depending on the propagation environment (multipath state formed by the reception power of the direct wave, reflected wave, delay wave, arrival angle, delay time, etc.) In general, the more scattered the propagation channel (also called multipath rich, rich scattering, random propagation channel, etc.), the more suitable the propagation channel for the MIMO transmission system, that is, the larger the transmission capacity, the separation on the receiving side It is known that it becomes a propagation channel that is easy to transmit and has high reception quality.

  However, as disclosed in Non-Patent Document 2, there is a wave having a dominant power component (which is often a direct wave), particularly in a LOS (Line-Of-Sight) environment. Even when the reception field strength is sufficient, good reception quality may not be obtained.

  As a remarkable example, when the transceiver is fixed, the direct wave becomes a stable component with small time fluctuation, and therefore has a large power compared to the scattered wave, and h11 (t) and h12 (t). , H21 (t), h22 (t), the smaller the phase difference of the direct wave components, that is, the larger the value generally expressed as channel correlation or propagation channel correlation, the more difficult the separation becomes, and the state continues. .

  In addition, studies are also being conducted in the case where a scheme defined in a wireless communication standard (3GPP, 3GPP2, IEEE 802.11, etc.) is applied to the MIMO transmission method. In Patent Document 1, HARQ (Hybrid Automatic Repeat request) A mechanism for applying the scheme is being studied.

  This method will be briefly described. FIG. 34 shows a transmitter configuration of the wireless communication system disclosed in Patent Document 1. In FIG. The information to be transmitted is divided into two parts after being subjected to CRC (Cyclic Redundancy Check) coding for detecting a transmission signal frame error, and they are named as a first part and a second part, respectively. The information after the CRC encoding divided into two is subjected to error correction encoding by an encoder 52 and an encoder 53, respectively. The error-corrected code bits are modulated by modulator 54 and modulator 55, respectively, and the modulated signals are output from antenna 56 and antenna 57, respectively.

At this time, if the first part and / or the second part has an error on the reception side, the reception side issues a retransmission request to the transmission side. At this time, by adding “swapping” signal information to the retransmission request, it is possible to retransmit using a different antenna from the previous one. In the case of FIG. 34, in the previous transmission, the first part is transmitted by the antenna 56, the second part is transmitted by the antenna 57, and the transmitted first part and / or second part is accompanied by an error. When received, the second part is transmitted by the antenna 56 and the first part is transmitted by the antenna 57 at the time of retransmission. By retransmitting in this way, since the first part and / or the second part passes through a propagation channel different from the previous transmission, the possibility of removing the error is improved.
“Proposal of SDM-COFDM system for wideband mobile communication realizing 100Mbit / s by MIMO channel” IEICE, RCS-2001-135, October 2001 "Analysis of MIMO system in rice fading" IEICE, RCS2003-90, July 2003 JP 2004-135304 A

  However, even when the antenna used for retransmission is different from the previous transmission as in the MIMO-HARQ scheme disclosed in Patent Document 1, if the same communication channel is used, the improvement in reception quality is small. There is. Here, the communication channel is a frequency band (not limited to one) assigned at the time of communication. As an example, FIG. 35 shows eight communications assigned for wireless LAN in Japan and the United States. The channel (there is a frequency band assigned to the wireless LAN other than this communication channel) is shown. Here, the communication channel names CH1, CH2,..., CH8 are names given in this specification, and are not formal names.

  In the MIMO transmission system, as described above, it is known that the ease of separation (in other words, the reception quality of the received digital signal) differs depending on the propagation environment.

  At this time, as shown in Patent Document 1, even if the transmission antenna is changed at the time of retransmission, if retransmission is continued on the same communication channel, a wave having a dominant power component as in the above-described LOS environment is generated. If present, the reception quality improvement may be small.

  The present invention has been made in view of the above points, and in the MIMO transmission method, a radio transmission apparatus capable of improving reception quality and system throughput by transmitting using a different communication channel during retransmission. It is another object of the present invention to provide a wireless transmission method. This is based on the property that the multipath state for each communication channel is different because the relationship (position, time variation, etc.) of the transmitter / receiver and the reflector is different.

  The present invention for solving this problem includes a plurality of antennas that receive a plurality of modulated signals transmitted simultaneously from a plurality of antennas, a retransmission request detection unit that detects a retransmission request included in the received signal, and the retransmission Using a request, a data selection unit that selects data to be retransmitted, and when the retransmission request is detected, the communication channel of the data to be retransmitted is changed to a communication channel different from the previous communication channel, and the retransmission is performed. And a wireless unit that transmits data.

  According to this configuration, since the multipath state is different for each communication channel, the transmission signal data requested to be retransmitted because an error has occurred can be retransmitted using a communication channel different from the previous one. Even when it is difficult to separate signals multiplexed using the MIMO transmission method on the same communication channel, the reception quality of received signals is improved, transmission signal frame errors are reduced, and system throughput is improved. Can be made. Also, frame errors can be reduced with a simple configuration in which the communication channel is simply changed during retransmission.

  The present invention for solving such a problem, a plurality of antennas that receive a plurality of modulated signals transmitted simultaneously from a plurality of antennas, a reception confirmation response detection unit that detects a reception confirmation response included in the received signal, A data selection unit that selects data to be retransmitted using the reception confirmation response, and the communication channel of the data to be retransmitted is changed to a communication channel different from the previous communication channel when the reception confirmation response is detected. And a radio unit that transmits the data to be retransmitted.

  According to this configuration, since the multipath state differs for each communication channel, the transmission signal frame in which an error has occurred can be retransmitted using a communication channel different from the previous one. Even when it is difficult to separate signals multiplexed using the MIMO transmission method, it is possible to improve reception quality of received signals, reduce transmission signal frame errors, and improve system throughput. Further, at the time of retransmission, transmission signal frame errors can be reduced with a simple configuration in which the communication channel is simply changed.

  The wireless transmission device of the present invention has a communication channel change request detection unit, and adopts a configuration for setting a communication channel based on communication channel information returned from the receiver to the transmitter.

  According to this configuration, when an error occurs in a transmission signal frame, it is used for retransmission according to not only the presence / absence of a frame error but also the communication channel status, multipath status, received field strength, etc. that can be used by the system. Since the communication channel is set, the communication channel can be changed based on more reliable information. As a result, the reception quality of the received signal is improved, the transmission signal frame error is reduced, and the system throughput is improved. Can do. Further, at the time of retransmission, transmission signal frame errors can be reduced with a simple configuration in which the communication channel is simply changed.

  As described above, according to the present invention, in the MIMO transmission scheme in which different modulation signals are transmitted from a plurality of antennas, the reception quality of the reception signal is improved and the transmission signal frame error is reduced by using different communication channels at the time of retransmission. System throughput can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The gist of the present invention is to change a communication channel used at the time of retransmission based on a transmission signal frame error detected on the receiving side in a wireless transmission device capable of using a plurality of communication channels.

  At this time, there are two basic methods for changing the communication channel at the time of retransmission based on the transmission signal frame error.

  First, the communication channel is changed at the time of retransmission based on retransmission request information from the receiving side. This is a system generally known as ARQ, and requests transmission of a corresponding frame when a transmission signal frame error occurs.

  Second, the communication channel is changed at the time of retransmission based on the reception confirmation response from the reception side. This is a system generally known as ACK (ACKnowledgement), and when a transmission signal frame error does not occur, it notifies that reception has been successful.

  In this embodiment, a base station (Base Station) is assumed as a transmitting side (wireless transmitting apparatus) and a terminal (Terminal) is assumed as a receiving side, but the present invention is referred to as a base station-terminal. The present invention is not limited to the system, and can be applied in the same manner as long as it is between wireless communication devices such as between base stations, between terminals, and an access point (AP) -wireless LAN card.

  Further, the modulation signal used in the present embodiment is a technical term generally used in wireless communication. However, in this embodiment, the type of the modulation signal is not limited unless otherwise specified. Therefore, BPSK, QPSK, 16QAM, 64QAM, 128QAM, 256QAM, GMSK, π / 4 shift QPSK, etc. can be used as the modulation signal.

  In the following embodiments, a 2 × 2 MIMO transmission system that uses two antennas for transmission and reception will be described as a MIMO transmission system, but there is no limitation on the number of antennas in the application of the present invention.

(Embodiment 1)
A feature of the present embodiment is that a retransmission request information is transmitted from a reception side to a transmission side based on a transmission signal frame error detected at the reception side, and a communication channel used at the time of retransmission based on the retransmission request information on the transmission side. Is to change. As a result, even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel, the multiplexed signal can be separated by changing the communication channel, and the received signal can be separated. The reception quality can be improved, the transmission signal frame error can be reduced, and the system throughput can be improved.

  As in the 2 × 2 MIMO transmission system shown in FIG. 1, the modulated signal A and the modulated signal B are transmitted from the two antennas B (Base Station) -AN1 and B-AN2, respectively, and the two antennas T (Terminal) -AN1, T A case will be described in which a signal obtained by combining modulated signals A and B by -AN2 is received, and these signals are separated and demodulated.

  In this case, the receiving side needs to demodulate each modulated signal by estimating four channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t). Here, t indicates time. Therefore, the preambles used for signal detection, timing detection, AGC (Automatic Gain Control) control, frequency offset estimation, modulation scheme / coding rate and other transmission method information, propagation channel estimation, etc. are required in modulated signals A and B. It is necessary to provide it accordingly.

  Incidentally, the symbols necessary for demodulation described above can be collectively referred to as pilot symbols, unique words, preambles, and the like. Call. The channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t) are estimated using channel estimation symbols.

  FIG. 2 shows an example of a detailed configuration on the time axis of one frame in a signal transmitted by the base station.

  Control symbols 201-1 and 201-2 are transmitted with modulated signals A and B, symbols for AGC control, frequency offset, and the like, transmission method information (including information on whether it is a retransmission symbol), etc. Is a symbol for.

  Here, the control symbols 201-1 and 201-2 are not necessarily transmitted from a plurality of antennas, and may be transmitted from a single antenna. In that case, the control symbol 201-2 is deleted. As an advantage of transmitting from one antenna, transmission is possible with a simple configuration. Also, a terminal that assumes transmission from a single antenna can receive and decode the control symbol. In addition, a reception path diversity gain can be obtained by combining signals received by a plurality of antennas to improve reception quality.

  Further, as an advantage of transmitting from a plurality of antennas, a transmission path diversity gain can be obtained. In addition, the maximum value of the signal amplifier of the transmitter can be reduced (this advantage can be similarly enjoyed in other embodiments).

  The channel estimation symbol 202-1 of the modulation signal A and the channel estimation symbol 202-2 of the modulation signal B are transmitted, for example, at the same time, and the receiver uses each symbol for each channel by fading or the like. Estimate channel variation.

  1 corresponds to the control symbols 201-1 and 201-2 and the channel estimation symbols 202-1 and 202-2 described above. The data symbol 203-1 of the modulation signal A and the data symbol 203-2 of the modulation signal B are transmitted, for example, at the same time, and data is transmitted. It is assumed that FCS (Frame Check Sequence) 204-1 of modulated signal A and FCS 204-2 of modulated signal B are transmitted at the same time, for example.

  Here, FCS is a general term for error detection codes for checking whether received data is correct, and is sometimes called a checksum, a parity sum, or the like. As a specific example, there is a CRC (Cyclic Redundancy Check). Then, the receiver can check whether there is an error in the data transmitted with the modulated signal A by inspecting the FCS 204-1. Similarly, by checking the FCS 204-2, it is possible to confirm whether or not there is an error in the data transmitted by the modulation signal B.

  FIG. 3 shows an example of a configuration of terminal-side radio transmission apparatus 300 in the present embodiment. Error determination section 301-1 receives as input digital data of modulated signal A obtained by demodulating the signal transmitted by the base station, and uses FCS 204-1 in FIG. Output error information of A. Similarly, error determination section 301-2 receives received digital data of modulated signal B obtained by demodulating the signal transmitted by the base station, and uses FCS 204-2 in FIG. As information, error presence / absence information of the modulation signal B is output.

  Retransmission requesting section 302 receives error presence / absence information of modulated signals A and B, determines whether or not to request retransmission, and requests retransmission information (for example, bit “1” as ACK if there is no error). When an error occurs, bit “0”) is output as NACK.

  The data generation unit 303 receives retransmission request information and transmission digital data, generates a transmission digital signal, and outputs it.

  The transmission unit 304 receives the transmission digital signal, generates and outputs a modulated signal, and outputs the modulated signal as a radio wave from the antennas T-AN1 and T-AN2.

  FIG. 4 shows an example of the frame structure of the modulated signal transmitted by the terminal. Control symbols 401-1 and 401-2 are symbols for AGC control, frequency offset, etc., transmission method information, etc., transmitted by modulated signals A and B, respectively. Channel estimation symbols 402-1 and 402-2 are channel estimation symbols transmitted from transmission antennas T-AN1 and T-AN2, respectively, and the base station (receiver) performs channel estimation using these symbols. . Data symbols 403-1 and 403-2 are data symbols transmitted from transmission antennas T-AN1 and T-AN2, respectively, and transmit data. Retransmission request information symbols 404-1 and 404-2 are retransmission request information symbols transmitted from transmission antennas T-AN 1 and T-AN 2, respectively, and are information output from retransmission request section 302 in FIG. 3 transmits a modulated signal according to the frame configuration of FIG.

  FIG. 5 shows an example of the configuration of the base station side radio apparatus 500.

  The receiving unit 552 receives a received signal received by the receiving antenna 551, performs processing such as frequency conversion, demodulates, and outputs received digital data. Here, each of the reception digital data, which is an output signal from the reception antenna 551, the reception unit 552, and the reception unit 552, is illustrated as one, but this is for the sake of simplicity and is configured by a plurality of each. May be. In short, it is only necessary to receive a transmission signal from the terminal-side wireless transmission device 300 of FIG. 3 and to decode the transmission signal frame of the terminal shown in FIG.

  The retransmission request detection unit 553 receives the received digital data, extracts the retransmission request information 554, and outputs it. At this time, information on whether to retransmit modulated signal A or retransmit modulated signal B is included in retransmission request information 554 along with the presence or absence of a retransmission request. In addition, retransmission request information 554 also includes communication channel change information indicating whether to change the communication channel at the time of retransmission. Here, the communication channel change information does not necessarily need to be included when communication channel assignment at the time of retransmission is set in advance, such as when the system is set when the communication channel is always switched at the time of retransmission.

  In the operation related to the transmitter described below, it is assumed that information on whether to switch the communication channel at the time of retransmission is set in advance, and based on feedback information (communication channel information) from the terminal at the time of retransmission, The operation for switching the communication channel will be described in the operation related to the transmission unit in FIG. 13 based on the communication channel information symbols 1101-1 and 1101-2.

  The operation related to the transmission unit in FIG. 5 will be described in detail.

  Transmission data storage section 501-1 receives transmission digital data A of modulated signal A as input, and stores the data. The accumulated data is used at the time of retransmission. This data is named transmission digital data of the accumulated modulation signal A, and is output from the data accumulation unit 501-1 as a transmission digital signal 509-1 of the accumulated modulation signal A.

  Similarly, transmission data storage section 501-2 receives transmission digital data of modulated signal B as input, and stores the data. The accumulated data is used at the time of retransmission. This data is named transmission digital data of the accumulated modulation signal B, and is output from the data accumulation unit 501-2 as a transmission digital signal 509-2 of the accumulated modulation signal B.

  Frame configuration signal generation section 507 receives retransmission request information 554 as input, determines the frame configuration, and outputs frame configuration signal 508. An example of a frame configuration determination method will be described later with reference to FIG.

  The data selection unit 502 includes transmission digital data of the modulation signal A, transmission digital signal 509-1 of the modulation signal A accumulated, transmission digital data of the modulation signal B, transmission digital data 509-2 of the modulation signal B accumulated, When retransmission request information 554 is input, and retransmission request information 554 requests retransmission, and when retransmission of modulated signal A is requested, transmission digital signal 509-1 of accumulated modulated signal A is transmitted digitally. Output as a signal. When retransmission request information 554 requests retransmission and requests retransmission of modulated signal B, accumulated transmission digital data 509-2 of modulated signal B is output as a transmission digital signal.

  Further, the data selection unit 502 outputs the transmission digital data of the modulation signal A and the transmission digital data of the modulation signal B as transmission digital signals regardless of whether or not the retransmission request information 554 requests retransmission. From which communication channel transmission digital data of modulation signal A, transmission digital signal 509-1 of accumulated modulation signal A, transmission digital data of modulation signal B, and transmission digital data 509-2 of modulation signal B are stored. The method for transmission will be described later with reference to FIG. 6 showing the flow of transmission signals of the base station and the terminal.

  Encoding sections 503-1 and 503-2 receive transmission digital data A and transmission digital data B as input, and in accordance with frame configuration signal 508 from frame configuration signal generation section 507, errors are detected in transmission digital data A and transmission digital data B. Encoded data is formed by performing a correction encoding process, and this is output to the modulation | alteration part 504-1 and 504-2. Here, the error correction code used for the error correction coding process is not limited, and convolutional code, Reed-Solomon code, turbo code, LDPC (Low Density Parity Check) code, and the like are used.

  Modulation sections 504-1 and 504-2 perform modulation processing such as BPSK, QPSK, and 16QAM on the encoded data from encoding sections 503-1 and 503-2, and at the timing according to frame configuration signal 508. Then, a baseband signal is formed by inserting a symbol for channel estimation and transmitted to an IFFT (Inverse Fast Fourier Transform) unit.

  IFFT sections 505-1 and 505-2 send OFDM (Orthogonal Frequency Division Multiplexing) modulation signals obtained by performing IFFT operations on the baseband signals to radio sections 506-1 and 506-2. The IFFT part includes an S / P (Serial-Parallel) part. The IFFT calculation is an example of a method for realizing IDFT (Inverse Discrete Fourier Transform) at high speed and with a low calculation amount.

  The radio units 506-1 and 506-2 form transmission signals by performing radio processing such as up-conversion and amplification on the IFFT signals from the IFFT units 505-1 and 505-2, respectively, and antenna B- Supply to AN1 and B-AN2.

  Thus, different signals are transmitted simultaneously from the antennas AN1 and AN2.

  FIG. 6 shows the flow of transmission signals between the base station and the terminal in the present embodiment. At this time, the signal transmitted by the base station is shown in units of one frame, and is composed of control information symbols, channel estimation symbols, data symbols, FCS, and the like.

  The signal flow is as follows. The odd periods of TA1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TA2, 4, 6,.

  First, in the period TA1, the base station transmits data 1A and data 1B.

  Next, in the period TA2, since the error determination unit 301 confirms that no error has occurred from the received data 1A and data 1B, the retransmission request unit 302 does not make a retransmission request.

  Next, in the period TA3, the base station transmits data 2A and data 2B.

  Next, in the period TA4, since the error determination unit 301 confirms that an error has occurred in the data 2A from the received data 2A and data 2B, the retransmission request unit 302 retransmits the data 2A. Request.

  At this time, the retransmission request unit 302 can improve the reception quality of the data 2A to be retransmitted by including an instruction to change the communication channel from CH1 to CH2 in the retransmission request.

  This is because, in general, different communication channels have different communication channel states and multipath states. In addition, since no signal is transmitted from CH2 of modulated signal B at the time when data 2A to be retransmitted is transmitted from CH2 of modulated signal A, reception diversity gain (ideally transmission 1, reception 2 on the receiving side) The reception quality can be improved by obtaining the maximum ratio combination.

  Next, in period TA5, the base station transmits data 3A and data 3B using CH1 and retransmits data 2A using CH2 based on the request from the terminal in period TA4. At this time, since the data 3A can be transmitted together with the retransmission of the data 2A as the modulated signal A, the transmission rate can be maintained.

  Next, in the period TA6, since the error determination unit 301 confirms that no error has occurred in the received data 3A, data 3B, and data 2A, the retransmission request unit 302 does not make a retransmission request.

  Next, in the period TA7, the base station transmits data 4A and data 4B.

  Next, in the period TA8, the terminal determines that the error determination unit 301 has generated an error in the data 4B from the received data 4A and data 4B, so that the retransmission request unit 302 retransmits the modulated signal B. Make a request. At this time, retransmission request section 302 compares the received electric field strength of modulated signal A with the received electric field strength of modulated signal B, detects that the received electric field strength of modulated signal B is low, and makes a retransmission request for modulated signal B. This method can also be realized. The advantages are as described above.

  Next, in the period TA9, the base station retransmits the data 4B based on the retransmission request in the period TA8. At this time, the base station changes the communication channel of data 4B from CH1 to CH2, transmits data 5A and data 5B using CH1, and retransmits data 4B using CH2. Thereby, the reception quality of the data 4B to be retransmitted can be improved. The reason is the same as that in the retransmission during the period TA5, and thus description thereof is omitted here.

  Next, in the period TA10, since the error determination unit 301 confirms that an error has occurred in the data 4B again in the period TA10, the retransmission request unit 302 requests retransmission again, but at this time, the communication channel Is changed from CH2 of modulated signal B to CH2 of modulated signal A. By doing so, it is possible to eliminate the influence of the communication channel and improve the reception quality. That is, the data 4B retransmitted for the first time was transmitted so as to have excellent reception quality in the period TA10, but an error still occurred. Therefore, it is preferable to re-transmit again using a communication channel different from the first one.

  Next, in period TA11, the base station retransmits data 4B from CH2 of modulated signal A.

  As described above, the configuration of changing the communication channel and transmitting at the time of retransmission is a feature of the present embodiment.

  When the received electric field strength of the modulated signal A is compared with the received electric field strength of the modulated signal B at the time of retransmission such as the period TA4, if the received electric field strength of the modulated signal A is detected to be low, There is also a method of requesting retransmission of signal A. This is because the reception quality of the modulation signal having a low reception electric field strength is lower than that of the modulation signal having a low reception electric field strength.

  FIG. 7 shows an example of the configuration of terminal-side radio reception apparatus 700 in the present embodiment.

  Received signals received by the antennas T-AN1 and T-AN2 are supplied to the radio units 701-1 and 701-2, respectively. Radio units 701-1 and 701-2 obtain baseband signals by subjecting received signals to radio processing such as down-conversion and orthogonal demodulation, and obtain the obtained baseband signals as FFT units 702-1 and 702. To -2.

  The FFT unit 702-1 performs an FFT operation corresponding to the IFFT operation used in the IFFT units 505-1 and 50-2 of FIG. 5 on the baseband signal output from the wireless unit 701-1, thereby performing the post-FFT operation. A baseband signal is obtained, and the obtained baseband signal after FFT is sent to the channel estimation unit 703-1 for the modulated signal A, the channel estimation unit 703-2 for the modulated signal B, and the signal processing unit 704. Here, the FFT operation according to the IFFT operation is an operation generally referred to as OFDM demodulation processing, which is processing for obtaining a signal before IFFT.

  Similarly, the baseband signal after FFT output from FFT section 702-2 is sent to channel estimation section 703-3 for modulated signal A, channel estimation section 703-4 for modulated signal B, and signal processing section 704.

  The channel estimation unit 703-1 for the modulated signal A estimates the channel fluctuation of the modulated signal A (the modulated signal A transmitted from the antenna B-AN1 of the base station) based on the channel estimation symbol, thereby obtaining the channel estimation value h11. obtain. Thereby, the channel fluctuation between the antenna B-AN1 of the base station and the antenna T-AN1 of the terminal is estimated.

  The channel estimation unit 703-2 for the modulated signal B estimates the channel fluctuation of the modulated signal B (the modulated signal B transmitted from the antenna B-AN2 of the base station) based on the channel estimation symbol, thereby obtaining the channel estimated value h12. obtain. Thereby, the channel fluctuation between the antenna B-AN2 of the base station and the antenna T-AN1 of the terminal is estimated.

  Similarly to the channel estimation unit 703-1, the channel estimation unit 703-3 for the modulated signal A estimates the channel fluctuation of the modulated signal A to obtain the channel estimation value h21. Thereby, the channel fluctuation between the antenna B-AN1 of the base station and the antenna T-AN2 of the terminal is estimated.

  Similarly to the channel estimation unit 703-2, the channel estimation unit 703-4 of the modulation signal B estimates the channel fluctuation of the modulation signal B, thereby obtaining the channel estimation value h22. Thereby, the channel fluctuation between the antenna B-AN2 of the base station and the antenna T-AN2 of the terminal is estimated.

  The signal processing unit 704 receives the channel fluctuation estimation values h11, h21, h12, h22 and transmission method information 707 (described in the description of the control information detection unit 705 below) in addition to the baseband signal after the FFT, and receives it. Digital data A and B are output. Here, when the transmission method information 707 indicates a transmission method in which the modulated signals A and B are transmitted at the same time, the baseband signal is detected using the channel fluctuation estimation values h11, h21, h12, and h22. By performing decoding or the like, reception digital data A and reception digital data B corresponding to transmission digital data A and transmission digital data B are output.

  Frame errors based on the received digital data A and the received digital data B output from the signal processing unit 704 are detected by error determination units 301-1 and 301-2 in FIG. 3, respectively. If an error occurs, a retransmission request is sent to the base station (transmission side) as described above.

  Note that the detection method used for the signal processing unit 704 is not limited, and includes ICD (Inverse Channel Detection, also called ZF (Zero Forcing)), MMSE (Minimum), which performs an inverse matrix operation of a channel estimation matrix composed of channel estimation values. Mean square error (Mean Square Error), MLD (Maximum Likelihood Detection), etc. are used.

  The control information detection unit 705 receives the baseband signal after the FFT operation, detects the control information symbols 201-1 and 201-2 in the transmission signal frame configuration of FIG. 2 transmitted by the base station, and indicates the transmission method In the case of information or a retransmitted signal, information indicating whether the retransmitted signal is the modulation signal A or B or the communication channel CH1 or CH2 is detected, and these information are transmitted as transmission method information. 707 is output.

  The transmission method indicates a modulation scheme, an error correction code coding rate, diversity transmission (space-time code, spatial spreading), signal point arrangement, and the like.

  Retransmission information processing section 706 receives, as input, channel fluctuation estimation values h11, h12, h21, h22, baseband signals after FFT, and transmission method information 707 output from channel estimation sections 703-1 to 703-4, and retransmits received digital information. Data A and B are output.

  Note that the retransmission information processing unit 706 indicates that the transmission method information 707 indicates a retransmitted signal, and that the modulation signal A indicates that the retransmitted modulation signal is the modulation signal A. The received digital data of the modulated signal A is output. Similarly, if the transmission method information 707 indicates a retransmitted signal and the retransmitted modulated signal indicates a modulated signal B, the modulated signal B is demodulated and modulated. The received digital data of signal B is output. This operation is performed, for example, during the periods TA5, TA9, and TA11 in FIG.

  Here, in the terminal-side radio receiving apparatus 700 shown in FIG. 7, the processing in the retransmission signal processing unit 706 has been described as a processing unit different from the signal processing unit 704 in order to clearly describe the processing. Even if the signal processing unit 706 is included in the signal processing unit 704, the same processing can be performed. The configuration in this case is shown in FIG. Since the operations in FIG. 8 other than the signal processing unit 704 described above are the same as those in FIG.

  FIG. 9 shows another example of the flow of transmission signals between the base station and the terminal in the present embodiment described in FIG. The difference from FIG. 6 is that communication channels CH1 and CH2 are used at times other than retransmission, and FIG. 6 shows that communication channels CH1 and CH2 are always used.

  The signal flow is as follows. The odd periods TB1, 3, 5,... Are periods during which the base station can transmit, and the even periods TB2, 4, 6,.

  First, in period TB1, the base station transmits data 1A from CH1 of modulated signal A, data 2A from CH2, and data 1B from CH1 of modulated signal B, and data 2B from CH2.

  Next, in the period TB2, the terminal confirms that the error determination unit 301 has not generated an error from the received data 1A, data 2A, data 1B, and data 2B. Do not do.

  Next, in period TB3, the base station transmits data 3A and data 2A from CH1 of modulated signal A, data 4A from CH1 of modulated signal B, and data 4B from CH2.

  Next, in the period TB4, the terminal confirms that the error determination unit 301 has an error in the data 3A from the received data 3A, data 4A, data 3B, and data 4B. , Request retransmission of data 3A. At this time, the communication channel is changed from CH1 to CH2. Thereby, the reception quality of the data 2A to be retransmitted can be improved. The reason is as described in the explanation of FIG.

  Next, in period TB5, the base station performs transmission of data 5A, data 5B, and data 6B and retransmission of data 3A based on the retransmission request in period TB4.

  Next, in the period TB6, the terminal confirms that the error determination unit 301 does not generate an error in the received data 5A, data 5B, data 6B, and data 3A, so the retransmission request unit 302 does not make a retransmission request. .

  Next, in period TB7, the base station transmits data 6A from CH1 of modulated signal A, data 7A from CH2, and data 7B from CH1 of modulated signal B, and data 8B from CH2.

  Next, in the period TB8, the terminal checks that the error determination unit 301 has an error in the data 7B from the received data 6A, data 7A, data 7B, and data 8B. , Request retransmission of data 7B.

  Next, in the period TB9, the base station retransmits the data 7B. At this time, the communication channel is changed from CH1 to CH2. Thereby, the reception quality of the data 7B to be retransmitted can be improved. The reason is as described in the explanation of FIG. The transmission data of other communication channels is retransmitted from CH1 of modulated signal A to data 8A, CH2 to data 9A, CH1 of modulated signal B to data 9B, and CH2 to data 7B.

  Next, in the period TB10, since the error determination unit 301 confirms the occurrence of an error again in the data 7B, the retransmission request unit 302 requests retransmission again, but at this time, the terminal determines the communication channel of the modulation signal B. Change from CH2 to CH2 of modulated signal A. By doing so, the reception quality is improved. That is, the data 7B retransmitted for the first time was transmitted as much as possible with a reception quality superior to that of the period TB9, but an error still occurred. Therefore, it is preferable to re-transmit again using a communication channel different from the first one.

  Next, in period TB11, the base station retransmits data 7B from CH2 of modulated signal A.

  As described above, the configuration of changing the communication channel and transmitting at the time of retransmission is a feature of this embodiment.

  Thus, the retransmission request information is transmitted from the reception side to the transmission side based on the transmission signal frame error detected at the reception side, and the transmission side changes the communication channel used at the time of retransmission based on the retransmission request information. Even when it is difficult to separate signals multiplexed using the MIMO transmission method in the communication channels of the above, since the multipath state differs for each communication channel, the reception quality of the received signal is improved and the transmission signal frame is improved. Errors can be reduced and system throughput can be improved.

(Embodiment 2)
The feature of this embodiment is that the reception quality of the received signal is further improved from that of the first embodiment by feeding back communication channel information from the receiving side to the transmitting side with respect to the method described in the first embodiment. It is possible to reduce transmission signal frame errors and improve system throughput.

  In the following description, the contents described in the first embodiment are omitted.

  FIG. 10 shows an example of the configuration of the terminal-side radio transmission apparatus 1000, and parts that operate in the same way as in FIG. 3 are given the same reference numerals and explanations thereof are omitted.

  Retransmission requesting section 1001 receives error presence / absence information and communication channel information of modulated signals A and B, determines whether or not to make a retransmission request based on the error presence / absence information, and sends retransmission request information and communication channel information symbols. Output.

  Data generation section 1002 receives retransmission request information symbols, communication channel information symbols, and transmission digital data symbols, generates a transmission digital signal, and outputs it.

  FIG. 11 shows an example of the frame configuration of the modulated signal transmitted by the terminal. The same reference numerals are given to the parts that operate in the same way as in FIG. 4, and the following description is omitted. Communication channel information symbols 1101-1 and 1101-2 of modulated signal A and modulated signal B indicate communication channel information symbols of modulated signal A and modulated signal B, respectively. Here, the communication channel information symbol is information for determining whether the communication channel is suitable for the wireless communication. Each of the modulation signal A and the modulation signal B includes a received CNR (Carrier to Noise Ratio) or SNR (Signal). to Noise Ratio), multipath state of the propagation channel, RSSI for each receiving antenna, and the like.

  An example of a method for calculating the reception CNR and the reception SNR is a method based on an inverse matrix of a propagation channel matrix described in Non-Patent Document 1, and a method based on an eigenvalue of a propagation channel matrix described in Non-Patent Document 2. It is done. Examples of the method for calculating the multipath state of the propagation channel include a method based on the inverse matrix of the channel matrix described in Non-Patent Document 1 and the propagation channel described in Non-Patent Document 2. In the propagation channel from the transmitting antenna to the receiving antenna formed by the eigenvalue-based method, the correlation matrix of the propagation channel matrix, the direct wave, the reflected wave, the delayed wave, etc. There is a method to calculate "power of".

  10 transmits a modulated signal according to the frame configuration of FIG.

  FIG. 12 shows an example of the configuration of the base station-side radio apparatus 1200, and parts that operate in the same way as in FIG.

  The receiving unit 1203 receives a received signal received by the receiving antenna 551, performs processing such as frequency conversion, demodulates, and outputs received digital data and communication channel information data.

  Communication channel change request detection section 1201 receives communication channel information data demodulated from the received signal, extracts communication channel change request signal 1202 and outputs it.

  Retransmission request detection section 1204 receives received digital data, extracts retransmission request information 554, and outputs it. At this time, information on whether to retransmit modulated signal A or retransmit modulated signal B is included in retransmission request information 554 along with the presence or absence of a retransmission request. In FIG. 5, it is assumed that information on whether to change the communication channel at the time of retransmission is included in retransmission request information 554, but in FIG. 12, the communication channel is changed based on the communication channel information data output from receiving section 1203. It is decided whether to do. Here, the characteristics of the communication channel switching methods described so far are summarized below.

  The first switching method changes the communication channel based on a preset method at the time of retransmission. It can be changed with the simplest configuration. However, when the retransmission frame can be transmitted without error without actually being changed (for example, when HARQ (Hybrid ARQ) such as Chase Combining is used), the change is unnecessary. In addition, the structure of the terminal side radio | wireless receiving apparatus in this case is shown in FIG.

  The second switching method is changed based on communication channel switching information determined by the terminal at the time of retransmission. Since switching is performed based on the state of the communication channel, it is possible to change the communication channel with higher accuracy than in the first switching method. Also, as compared with the third switching method, only the information that determines whether or not to change the communication channel needs to be fed back, so that only a small amount of feedback data is required. However, loads (power consumption, memory area consumption, calculation must be completed within a certain time, etc.) are applied to terminals that are generally smaller in size than base stations and have low cost requirements.

  In the third switching method, at the time of retransmission, the base station determines and changes based on communication channel information from the terminal. Since switching is performed based on the state of the communication channel, it is possible to change the communication channel with higher accuracy than in the first switching method. In addition, since the base station performs calculations based on communication channel information, adaptive control technology (modulation method, coding rate, signal point arrangement, number of transmission antennas, etc., combined frames addressed to multiple users are combined into one frame. As a result, the communication channel can be changed with high accuracy. In general, the size of the apparatus is larger than that of the terminal, and the calculation is performed at the base station having a sufficient cost requirement. Therefore, it is easy to absorb the load.

  In addition, as an example of a method for obtaining the communication channel information before changing the communication channel, a control signal (beacon signal) used for confirming a channel usage state before communication, By using the communication channel information estimated at the time of performing communication before the start of data frame communication, the communication channel can be changed more efficiently and accurately.

  In FIG. 12, the operation related to the transmitter based on the communication channel information symbol will be described in detail. Here, parts that operate in the same manner as in FIG. 5 are given the same reference numerals, and descriptions thereof are omitted.

  Frame configuration signal generation section 1205 receives retransmission request information 554 and communication channel change request signal 1202 as input, determines the frame configuration, and outputs frame configuration signal 508. An example of the frame configuration determination method will be described later with reference to FIG.

  The radio units 1206-1 and 1206-2 respectively perform transmission processing such as up-conversion and amplification on the IFFT signals from the IFFT units 505-1 and 505-2, thereby forming transmission signals, respectively. -Supply to AN1 and B-AN2. Further, the communication channel is changed based on the communication channel change request signal 1202. Details of the changing method will be described with reference to FIG.

  Thus, different signals are transmitted simultaneously from the antennas AN1 and AN2.

  FIG. 13 shows the flow of transmission signals between the base station and the terminal in this embodiment, and the description of the parts that operate in the same way as in FIG. 6 is simplified or omitted. The signal flow is as follows. The odd period of TC1, 3, 5,... Is a period during which the base station can transmit, and the even period of TC2, 4, 6,.

  First, in the period TC1, the base station transmits data 1A and data 1B.

  Next, in the period TC2, since the error determination unit 301 confirms that no error has occurred from the received data 1A and data 1B, the retransmission request unit 1001 does not make a retransmission request.

  Next, in the period TC3, the base station transmits data 2A and data 2B.

  Next, in the period TC4, since the error determination unit 301 has confirmed that an error has occurred in the data 2A from the received data 2A and data 2B, the retransmission request unit 1001 retransmits the data 2A. Request. At this time, since there is no communication channel change request, the communication channel is not changed and is retransmitted using CH1. This is because, depending on the retransmission algorithm, it is possible to eliminate errors in the retransmission frame without changing the communication channel. An example is the Chase Combining algorithm in HARQ as described above.

  Next, in period TC5, the base station performs transmission of data 3B and retransmission of data 2A based on the retransmission request in period TC4.

  Next, in the period TC6, since the error determination unit 301 confirms that no error has occurred in the data 2A and the data 3B, the retransmission request unit 1001 does not make a retransmission request.

  Next, in the period TC7, the base station transmits data 3A and data 4B.

  Next, in the period TC8, since the error determination unit 301 confirmed that an error has occurred in the data 4B from the received data 3A and data 4B, the retransmission request unit 1001 performs a retransmission request for the data 4B. I do. Since the communication channel change request is valid, the communication channel is changed from CH1 to CH2 and retransmitted. The reception quality can be improved by changing the communication channel. At this time, since the signal is not transmitted from CH2 of modulated signal A during the time when data 4B to be retransmitted is transmitted from CH2 of modulated signal B, the reception diversity gain (ideally transmission 1) , The maximum ratio combining of reception 2), the reception quality can be improved.

  Next, in the period TC9, the base station performs transmission of the data 4A and 5B and retransmission of the data 4B based on the retransmission request in the period TC8.

  Next, in the period TC10, since the error determination unit 301 confirms that no error has occurred in the data 4A, the data 5B, and the retransmitted data 4B, the retransmission request unit 1001 does not make a retransmission request.

  Next, in the period TC11, the base station transmits data 5A and data 6B as the next data.

  Thus, at the time of retransmission, the configuration in which the communication channel is changed and transmitted based on the communication channel information is the difference from the first embodiment, that is, the feature of the present embodiment.

  FIG. 14 shows an example of the configuration of terminal-side radio reception apparatus 1400 in the present embodiment, and portions that operate in the same way as in FIG.

  Channel estimation values h11, h12, h21, h22 output from channel information / received signal storage unit 1401, channel estimation units 703-1, 703-2, 703-3, and 703-4 and baseband signals after FFT are input. The information is accumulated.

  Further, the channel information / reception signal storage unit 1401 receives the transmission method information 707, and when the transmission method information 707 indicates that this received signal is a retransmitted signal, the channel estimation value stored. , Communication channel information to output baseband signal after FFT and feed back to base station (correlation matrix of propagation channel matrix, CNR and SNR of modulation signal A and modulation signal B, RSSI for each receiving antenna, propagation Output the channel estimate itself).

  The retransmission signal processing unit 1402 receives the accumulated channel estimation value, the baseband signal after FFT, the channel estimation value of the signal received this time, the baseband signal after FFT, and the transmission method information 707 as input, and the transmission method information 707. Indicates that the received signal is a retransmitted signal, the same detection / decoding processing as the signal processing unit 704 is performed. At this time, reception quality can be further improved by detecting and decoding using the accumulated value and the current value, such as the above-described HARQ Chase Combining algorithm.

  Note that in this embodiment, when a radio access scheme for communication using the same communication channel for transmission and reception is applied (for example, TDD (Time Division Duplex) scheme), communication channel information symbols are not fed back and a received signal arrives. The communication channel information can be obtained based on the desired propagation channel estimation value.

  Thus, based on the transmission signal frame error detected on the receiving side, retransmission request information is transmitted from the receiving side to the transmitting side, and communication channel information is fed back from the receiving side to the transmitting side. Even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel by changing the communication channel used at the time of retransmission based on the communication channel information, reception of received signals Quality can be improved, transmission signal frame errors can be reduced, and system throughput can be improved.

(Embodiment 3)
A feature of the present embodiment is that a reception confirmation response is transmitted from the reception side to the transmission side based on the reception confirmation response of the transmission signal frame detected on the reception side, and the transmission side uses the retransmission confirmation frame based on the reception confirmation response. To change the communication channel. As a result, even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel, the reception quality of the received signal is improved, the transmission signal frame error is reduced, and the system throughput is reduced. Can be improved.

  In the present embodiment, the basic configuration is the same as the method for switching the communication channel during retransmission based on the retransmission request information described in the first and second embodiments. Below, it demonstrates centering around the difference with Embodiment 1 and Embodiment 2. FIG.

  FIG. 15 shows an example of the configuration of terminal-side radio transmission apparatus 1500 according to the present embodiment, and parts that operate in the same way as in FIG. The difference from FIG. 3 is that the retransmission request unit 302 in FIG. 3 is replaced with a reception confirmation response signal generation unit 1501. Here, the reception confirmation response method used in the reception confirmation response signal generation unit 1501 is described at the beginning of the embodiment, but when there is no error in the received transmission signal frame, the fact is fed back to the transmission side. IEEE 802.11 is an example of a standard that uses this method.

  The reception confirmation response signal generation unit 1501 receives the error presence / absence information of the modulated signals A and B output from the error determination units 301-1 and 301-2, and if there is no error in the modulation signals A and B, the reception confirmation response A signal (a response signal generally called ACK and a signal notifying that when there is no frame error) is output. Also, nothing is output when an error occurs in the modulation signals A and B.

  The data generation unit 1502 receives the reception confirmation response signal and the transmission digital data, generates a transmission digital signal, and outputs it.

  Transmitting section 304 receives transmission digital data as input, generates and outputs a modulated signal according to the transmission signal frame configuration (details will be described later) of the terminal shown in FIG. 16, and outputs the modulated signal as a radio wave from antennas T-AN1 and T-AN2.

  FIG. 16 shows an example of the frame configuration of the modulated signal transmitted by the terminal-side radio transmission apparatus 1500. Portions that operate in the same manner as in FIG.

  Reception confirmation response symbols 1601-1 and 160-2 are reception confirmation response symbols transmitted from transmission antennas T-AN1 and T-AN2, and are information output from reception confirmation response signal generation section 1501 in FIG.

  FIG. 17 shows an example of the base station-side radio apparatus 1700, and parts that operate in the same way as in FIG.

  The reception confirmation response detection unit 1701 receives the reception digital data received by the reception unit 552, extracts the reception confirmation response information 1702 from the reception confirmation response symbols 1601-1 and 160-2, and outputs it. At this time, information (ACK) indicating whether modulated signal A was received without error or modulated signal B was received without error is included in reception acknowledgment information 1702.

  Also, information on whether or not to change the communication channel at the time of retransmission is included in the reception confirmation response information 1702. Here, the information on whether or not to change the communication channel at the time of retransmission is not necessarily an acknowledgment when the communication channel assignment at the time of retransmission is set in advance, such as when the system is set to always switch the communication channel at the time of retransmission. The information 1702 need not be included.

  In the operation related to the transmission unit described below, description will be made assuming that information on whether to switch the communication channel at the time of retransmission is set in advance. Further, the operation of switching the communication channel based on feedback information (communication channel information) from the terminal at the time of retransmission will be described in the operation related to the transmission unit in FIG. 22 based on communication channel information symbols 1101-1 and 1101-2. To do.

  The operation related to the transmission unit in FIG. 17 will be described in detail.

  Frame configuration signal generation section 507 receives reception confirmation response information 1702 as input, determines the frame configuration, and outputs frame configuration signal 508. An example of a frame configuration determination method will be described later with reference to FIG.

  The data selection unit 1703 includes transmission digital data of the modulation signal A, transmission digital signal 509-1 of the modulation signal A accumulated, transmission digital data of the modulation signal B, transmission digital signal 509-2 of the modulation signal B accumulated, When the reception confirmation response signal 1702 is input and the reception confirmation response signal 1702 does not include the reception confirmation response of the modulation signal A, or when the reception confirmation response signal of the modulation signal A cannot be confirmed at a certain time. The transmission digital signal 509-1 of the accumulated modulation signal A is output as a transmission digital signal.

  Here, the fixed time is generally defined for each communication standard. For example, in IEEE802.11, it is defined as SIFS (Short InterFrame Space) 16 μs.

  Further, when the reception confirmation response signal 1702 does not include the reception confirmation response of the modulation signal B, or when the reception confirmation response signal of the modulation signal B cannot be confirmed at a certain time, the stored modulation signal B The transmission digital signal 509-2 is output as a transmission digital signal.

  The data selection unit 1703 transmits the transmission digital data of the modulation signal A and the transmission digital data of the modulation signal B regardless of whether the reception confirmation response signal 1702 includes or does not include the reception confirmation responses of the modulation signals A and B. Output as. Further, when the reception confirmation response signal 1702 includes both reception confirmation responses of the modulation signals A and B, the data selection unit 1703-2 outputs the transmission digital data of the modulation signal B as the selected transmission digital signal.

  Next, the transmission digital data of modulation signal A, the transmission digital signal 509-1 of modulated signal A, the transmission digital data of modulation signal B, and the transmission digital data 509-2 of modulation signal B are selected. A method for transmitting from a communication channel will be described with reference to FIG. 18 showing a flow of transmission signals of a base station and a terminal.

  FIG. 18 shows the flow of transmission signals between the base station and the terminal in the present embodiment, and parts that operate in the same manner as in FIG. At this time, the signal transmitted by the base station is shown in units of one frame, and is composed of control information symbols, channel estimation symbols, data symbols, FCS, and the like.

  The signal flow is as follows. The odd periods of TD1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TD2, 4, 6,.

  First, in the period TD1, the base station transmits data 1A and data 1B.

  Next, in the period TD2, since the error determination unit 301 confirmed that no error has occurred from the received data 1A and data 1B, the reception confirmation response signal generation unit 1501 receives the data 1A and data 1B. Send an acknowledgment of receipt.

  Next, in the period TD3, the base station transmits data 2A and data 2B as data next.

  Next, in the period TD4, since the error determination unit 301 has confirmed that an error has occurred in the data 2A from the received data 2A and data 2B, the reception confirmation response signal generation unit 1501 receives the data 2B. Send only the receipt confirmation response.

  Next, in the period TD5, the base station does not receive the reception confirmation response for the data 2A, so changes the communication channel from CH1 to CH2 and retransmits the data 2A. Thereby, the reception quality of the data 2A to be retransmitted can be improved. The reason is as described in FIG. 6 of the first embodiment. In addition, since no signal is transmitted from CH2 of modulated signal B at the time when data 2A to be retransmitted is transmitted from CH2 of modulated signal A, reception diversity gain (ideally transmission 1, reception 2 on the receiving side) The reception quality can be improved by obtaining the maximum ratio combination.

  Note that the base station transmits data 3A and data 3B and retransmits data 2A based on the reception confirmation response in the period TD4. At this time, since the data 3A and the data 3B can be transmitted together with the retransmission of the data 2A, the transmission rate can be maintained.

  Next, in the period TD6, since the error determination unit 301 has confirmed that no error has occurred in the data 3A, the data 3B, and the retransmitted data 2A, the reception confirmation response signal generation unit 1501 receives the data 3A, The reception confirmation response of data 3B and data 2A is transmitted.

  Next, in the period TD7, the base station transmits data 4A and data 4B as the next data.

  Next, in the period TD8, since the error determination unit 301 confirmed that an error has occurred in the data 4B from the received data 4A and data 4B, the reception confirmation response signal generation unit 1501 receives the data 4A. Send only the receipt confirmation response.

  Next, in the period TD9, the base station retransmits the data 4B. At this time, the communication channel is changed from CH1 to CH2. Thereby, the reception quality of the data 4B to be retransmitted can be improved. The reason is as described in FIG.

  The base station transmits data 5A and 5B and retransmits data 4B based on the reception confirmation response in period TD8.

  Next, in the period TD10, since the error determination unit 301 confirms that an error has occurred again in the data 4B, the terminal confirms that the reception confirmation response signal generation unit 1501 receives only the reception confirmation responses for the data 5A and the data 5B. Send. At this time, the communication channel for retransmitting the data 4B is changed from CH2 of the modulation signal B to CH2 of the modulation signal A. By doing so, the reception quality is improved. That is, the data 4B retransmitted for the first time was transmitted so as to have better reception quality in the period TD9, but an error still occurred. Therefore, it is preferable to send the data again through a communication channel different from the first one.

  Next, in period TD11, the base station retransmits data 4B from CH2 of modulated signal A.

  As described above, the configuration of changing the communication channel and transmitting at the time of retransmission is a feature of this embodiment.

  Further, although not shown in FIG. 18, when reception of all data fails (when an error occurs in all frames), the reception confirmation response signal is not transmitted. If the reception acknowledgment signal is not received after waiting for a certain time (for example, SIFS time) in the base station, the reception quality can be improved by switching the communication channel used last time to another communication channel. . For example, if reception of both data 1A and data 1B in the period TD1 fails, the communication channel is changed from CH1 to CH2 for both data 1A and data 1B during retransmission.

  Note that an example of the configuration of the terminal-side radio reception apparatus according to the present embodiment is the same as that of terminal-side radio reception apparatus 700 shown in FIG. 7, and thus description thereof is omitted here.

  FIG. 19 shows another example of the flow of transmission signals between the base station and the terminal in the present embodiment described in FIG. 9 and FIG. A difference from FIG. 18 is that communication channels CH1 and CH2 are used at times other than retransmission, and FIG. 19 shows that communication channels CH1 and CH2 are always used.

  The signal flow is as follows. The odd periods of TE1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TE2, 4, 6,.

  First, in period TE1, the base station transmits data 1A from CH1 of modulated signal A, data 2A from CH2, and data 1B from CH1 of modulated signal B, and data 2B from CH2.

  Next, in the period TE2, since the error determination unit 301 confirmed that no error has occurred from the received data 1A, data 2A, data 1B, and data 2B, the terminal determines data 1A, data 2A, and data 1A. , The reception confirmation response of data 1B is transmitted.

  Next, in period TE3, the base station transmits data 3A and data 2A of CH2 from CH1 of modulated signal A, data 3B from CH1 of modulated signal B, and data 4B from CH2.

  Next, in the period TE4, the terminal determines that an error has occurred in the data 3A from the received data 3A, data 4A, data 3B, and data 4B. Unit 1501 transmits only reception confirmation responses for data 3B, data 4A, and data 4B. At this time, the communication channel for retransmitting the data 3A is changed from CH1 to CH2. Thereby, the reception quality of the data 3A to be retransmitted can be improved. The reason is as described in FIG.

  Next, in period TE5, the base station performs transmission of data 5A, data 5B, and data 6B and retransmission of data 3A based on the reception confirmation response in period TE4.

  Next, in the period TE6, since the error determination unit 301 confirmed that no error occurred in the data 5A, the data 5B, the data 6B, and the retransmitted data 3A, the reception confirmation response signal generation unit 1501 The reception confirmation response of data 5A, data 5B, data 6B, and retransmitted data 3A is transmitted.

  Next, in the period TE7, the base station transmits data 6A and data 2A of CH2 from CH1 of the modulated signal A, data 7B from CH1 of modulated signal B, and data 8B from CH2.

  Next, in the period TE8, since the error determination unit 301 confirms that an error has occurred in the data 7B, the terminal confirms that the reception confirmation response signal generation unit 1501 receives only the data 6A, the data 7A, and the data 8B. Send an acknowledgment.

  Next, in the period TE9, the base station retransmits the data 7B. At this time, the communication channel is changed from CH1 to CH2. Thereby, the reception quality of the data 7B to be retransmitted can be improved. The reason is as described in FIG.

  Note that the base station retransmits data 8A from CH1 to data 9A, data 9A from CH2 to data 9B, data 9B from CH1 to data 9B, and data 7B from CH2 based on the reception confirmation response in period TE8.

  Next, in the period TE10, since the error determination unit 301 confirms that the error has occurred again in the data 7B, the terminal confirms that the reception confirmation response signal generation unit 1501 includes only the data 8A, the data 9A, and the data 9B. Send receipt acknowledgment.

  Next, in period TE11, the base station retransmits data 7B from CH2 of modulated signal A. By doing so, the reception quality is improved. That is, the data 7B retransmitted for the first time was transmitted as much as possible in the period TE9 so as to obtain excellent reception quality, but an error still occurred. Therefore, it is preferable to send the data again through a communication channel different from the first one.

  As described above, the configuration of changing the communication channel and transmitting at the time of retransmission is a feature of this embodiment.

  Although not shown in FIG. 19, as described in the description of FIG. 18, when reception of all data fails (when an error occurs in all frames), the reception confirmation response signal is not transmitted. If the reception acknowledgment signal is not received after waiting for a certain time (for example, SIFS time) in the base station, the reception quality can be improved by switching the communication channel used last time to another communication channel. . For example, if reception of both data 1A and data 1B in period TE1 fails, at the time of retransmission in period TE3, the communication channel for both data 1A and data 1B is changed from CH1 to CH2.

  Thus, the reception confirmation response is transmitted from the reception side to the transmission side based on the reception confirmation response of the transmission signal frame detected on the reception side, and the transmission side changes the communication channel used at the time of retransmission based on the reception confirmation response. It is. As a result, even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel, the reception quality of the received signal is improved, the transmission signal frame error is reduced, and the system throughput is reduced. Can be improved.

(Embodiment 4)
The feature of the present embodiment is that the reception quality of the received signal is further improved compared to the third embodiment by feeding back the communication channel information from the receiving side to the transmitting side with respect to the method described in the third embodiment. Transmission signal frame errors can be reduced, and system throughput can be improved.

  FIG. 20 shows an example of a frame configuration of a modulated signal transmitted by the terminal. Each part of FIG. 20 is composed of parts that operate in the same manner as in FIGS. 4, 11, and 16, and only the combinations are different from those of FIGS.

  21 transmits a modulated signal according to the frame configuration of FIG. 21, parts that operate in the same manner as in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  The reception confirmation response signal generation unit 2101 receives the error presence / absence information of the modulation signals A and B and the communication channel width change signal output from the error determination units 301-1 and 301-2, and there is no error in the modulation signals A and B Includes a reception confirmation response signal (a response signal generally called ACK and a signal notifying that when there is no frame error) and communication channel information. Also, nothing is output when an error occurs in the modulation signals A and B.

  The data generation unit 2102 receives the reception confirmation response signal, communication channel information, and transmission digital data, and generates and outputs a transmission digital signal.

  FIG. 22 shows an example of the configuration of the base station-side radio apparatus 2200, which is configured with parts that operate in the same manner as in FIGS. 5, 12, and 17, and is combined with FIGS. Are different, and the description is omitted.

  In FIG. 17, information indicating whether or not to change the communication channel at the time of retransmission is included in the reception confirmation response information 1702, but in FIG. 22, communication is performed based on communication channel information data fed back from the reception side to the transmission side. It is determined whether to change the channel.

  The features of the communication channel switching method based on the communication channel information data have been described in the second embodiment, and are omitted here. Hereinafter, the flow of transmission signals of the base station and the terminal in the present embodiment using FIG. Will be explained.

  An example of a method for obtaining the communication channel information before changing the communication channel has been described in the second embodiment, and is omitted here.

  FIG. 23 shows the flow of transmission signals between the base station and the terminal in the present embodiment, and description of parts that operate in the same manner as in FIGS. 6 and 18 is simplified or omitted.

  The signal flow is as follows. The odd periods of TF1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TF2, 4, 6,.

  First, in the period TF1, the base station transmits data 1A and data 1B.

  Next, in the period TF2, since the error determination unit 301 has confirmed that no error has occurred from the received data 1A and data 1B, the reception confirmation response signal generation unit 2101 has received data 1A and data 1B. Send an acknowledgment of receipt.

  In the period TF3, the base station transmits data 2A and data 2B as data.

  Next, in the period TF4, since the error determination unit 301 has confirmed that an error has occurred in the data 2A from the received data 2A and data 2B, the reception confirmation response signal generation unit 2101 receives the data 2B. Send only the receipt confirmation response.

  Next, in period TF5, since the base station did not receive the acknowledgment of data 2A, the base station changes the communication channel from CH1 to CH2, retransmits data 2A by CH1, and transmits data 3B by CH2. Thereby, the reception quality of the data 2A to be retransmitted can be improved. The reason is as described in FIG. 6 of the first embodiment.

  Next, in the period TF6, since the error determination unit 301 has confirmed that no error has occurred in the data 3B and the retransmitted data 2A, the reception confirmation response signal generation unit 2101 has received the data data 3B and the data 2A. Send an acknowledgment of receipt.

  Note that in this embodiment, when a radio access scheme for communication using the same communication channel for transmission and reception is applied (for example, TDD (Time Division Duplex) scheme), communication channel information symbols are not fed back and a received signal arrives. The communication channel information can be obtained based on the desired propagation channel estimation value.

  Thus, a reception confirmation response is transmitted from the reception side to the transmission side based on the transmission signal frame error detected at the reception side, and communication channel information is fed back from the reception side to the transmission side. Even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel by changing the communication channel used at the time of retransmission based on the communication channel information, reception of received signals Quality can be improved, transmission signal frame errors can be reduced, and system throughput can be improved.

  Next, in the period TF7, the base station transmits data 3A and data 4B.

  Next, in the period TF8, since the error determination unit 301 has confirmed that an error has occurred in the data 4B from the received data 3A and data 4B, the reception confirmation response signal generation unit 2101 has received the data 3A. Send only the receipt confirmation response. Since the communication channel change request is valid, at the time of retransmission, the communication channel is changed from CH1 to CH2 and transmitted. The reception quality can be improved by changing the communication channel. At this time, since the signal is not transmitted from CH2 of modulated signal A during the time when data 4B to be retransmitted is transmitted from CH2 of modulated signal B, the reception diversity gain (ideally transmission 1) , The maximum ratio combining of reception 2), the reception quality can be improved.

  Next, in the period TF9, the base station performs transmission of the data 4A and 5B and retransmission of the data 4B based on the reception confirmation response and the communication channel change request in the period TF8.

  Next, in the period TF10, since the error determination unit 301 has confirmed that no error has occurred in the data 4A, the data 5B, and the retransmitted data 4B, the reception confirmation response signal generation unit 2101 receives the data 4A, The reception confirmation response of data 5B and data 4B is transmitted.

  Next, in the period TF11, the base station transmits data 5A and data 6B as the next data.

  Thus, at the time of retransmission, the configuration in which the communication channel is changed and transmitted based on the communication channel information is the difference from the first embodiment, that is, the feature of the present embodiment.

(Embodiment 5)
A feature of the present embodiment is that a retransmission request information is transmitted from a reception side to a transmission side based on a transmission signal frame error detected on the reception side, and a communication channel used at the time of retransmission is transmitted based on the retransmission request information on the transmission side. It is to change the width. As a result, even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel and good reception quality cannot be obtained, the reception quality of the reception signal is improved, and the transmission signal frame is improved. Errors can be reduced and system throughput can be improved.

  In the present embodiment, a method for changing the communication channel width in the method for changing a communication channel based on retransmission request information described in the first and second embodiments will be described.

  FIG. 24 shows an example of terminal-side radio transmission apparatus 2400 in the present embodiment, and parts that operate in the same way as in FIG. 3 are given the same reference numerals and explanations thereof are omitted.

  The retransmission request unit 2401 determines whether to perform retransmission based on the error presence / absence information of the modulation signal A from the error determination unit 301-1 and the error presence / absence information of the modulation signal B from the error determination unit 301-2. Whether to change the communication channel width is determined based on the communication channel width change signal, and is output as retransmission request information and communication channel width change request information, respectively.

  Data generation section 2402 receives retransmission request information, communication channel width change request information, and transmission digital data, generates a transmission digital signal, and outputs it.

  FIG. 25 shows the frame configuration of the modulated signal transmitted by the terminal in the present embodiment, and the same reference numerals are given to portions that operate in the same manner as in FIG.

  Communication channel width change request information 2501-1 and 2501-2 are communication channel width change request information of modulated signal A and modulated signal B, and are signals output from retransmission request section 2401 in FIG. 24 transmits a modulated signal in accordance with the frame of FIG.

  FIG. 26 shows an example of the configuration of base station-side radio apparatus 2600 in the present embodiment, and the same reference numerals are given to portions that operate in the same manner as in FIG. 5, and description thereof will be omitted.

  A communication channel width change request detection unit 2601 receives the received digital data output from the reception unit 552, extracts communication channel width change request information, and outputs a communication channel width change request signal 2602.

  Frame configuration signal generation section 2603 receives retransmission request signal and communication channel width change request signal 2602 and outputs a frame configuration signal.

  Here, an advantage of changing the communication channel width will be described. In general, the wider the signal, the more the variation in the frequency domain can be used as the frequency gain. For example, the spreading gain when a time domain signal is spread into a frequency domain signal is large. Conversely, the narrower the signal, the lower the degradation due to fluctuations in the time domain. An example of this is a countermeasure against delayed waves by OFDM modulation. In addition, as an example seen from the viewpoint of interleaving used in error correction codes and the like, in the case of an OFDM modulated signal, interleaving is performed between more subcarriers (wider frequency band) by widening the communication channel width. Therefore, it is easy to obtain a frequency gain. As described above, since the time / frequency band occupied by the signal is changed by changing the communication channel width, the reception quality also changes accordingly. At this time, it is possible to obtain better reception quality by the method as in the above example.

  FIG. 27 shows the flow of transmission signals between the base station and the terminal in the present embodiment, and the description of the parts that operate in the same way as in FIG. 6 will be simplified or omitted.

  The signal flow is as follows. The odd periods of TG1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TG2, 4, 6,.

  First, in the period TG1, the base station transmits data 1A and data 1B.

  Next, in the period TG2, since the error determination unit 301 confirms that an error has occurred in the data 1A from the received data 1A and data 1B, the retransmission request unit 2401 performs a retransmission request for the data 1A. And a communication channel change (the method described in the first embodiment).

  Next, in the period TG3, the base station transmits data 1A (changes the communication channel from CH1 to CH2), data 2A, and data 2B.

  Next, in the period TG4, since the error determination unit 301 confirms that an error has occurred again in the data 1A from the received data 1A, data 2A, and data 2B, the retransmission request unit 2401 Request retransmission of 1A.

  As an example of such an event, there is a case where the data 1A uses a large multi-level modulation as compared with other data. For example, data 1A is 256QAM, and other data is 16QAM.

  Next, in period TG5, the base station performs transmission of data 3A and data 3B and retransmission of data 1A based on the request in period TG4. At this time, since the communication channel is changed, the communication channel of data 1A to be retransmitted is changed from CH2 of modulated signal A to CH2 of modulated signal B.

  Next, in the period TG6, since the error determination unit 301 also detects an error in the data 1A this time, the retransmission request unit 2401 requests retransmission of the data 1A and a change in communication channel width.

  Next, in the period TG7, the base station changes the communication channel width of the data 1A to 2 times (CH1 and CH2), and the data 4A and the data 4B also transmit on the communication channels having the communication channel width doubled, respectively. To do.

  At this time, as a configuration example of the data 1A, a configuration in which the number of subcarriers in OFDM modulation is doubled and every other subcarrier is used can be considered. As a result, the correlation of the propagation channel between subcarriers on which data is carried is lowered, and a frequency diversity effect can be obtained. Further, the reception quality is improved by doubling the number of subcarriers for OFDM modulation and setting the modulation multi-level number for each subcarrier to ½ (for example, 16QAM is changed to QPSK). Further, a configuration that lowers the coding rate of the error correction code can be considered. As a result, the reception quality is improved. In addition, it should be noted that the above-described configuration example of the data 1A can also obtain the frequency diversity effect obtained by performing interleaving between a larger number of subcarriers (a wider frequency band).

  In addition, as an example of the configuration of data 4A and data 4B, there is a configuration in which the number of subcarriers for OFDM modulation is doubled, data 4A is allocated to the subcarrier located in CH1, and data 4B is allocated to the subcarrier located in CH2. Conceivable. By arranging in this way, it is possible to provide compatibility with the transmission on the original communication channel (CH1 or CH2) (processing before IFFT and after FFT has the same configuration). Alternatively, the data 4A and the data 4B may be mixed with OFDM-modulated subcarriers in which the number of subcarriers is doubled and transmitted. In this case, the above-described frequency diversity effect can be obtained.

  Next, in the period TG8, since the error determination unit 301 confirms that no error has occurred in the data 4A, the data 4B, and the retransmitted data 1A, the retransmission request unit 2401 does not make a retransmission request.

  Thus, at the time of retransmission, the configuration in which the communication channel width is changed and transmitted is the difference from Embodiment 1, that is, the feature of this embodiment.

  Note that an example of the terminal-side radio reception apparatus in this embodiment has been described with reference to FIG. 7 (Embodiment 1) and FIG. 14 (Embodiment 2), and thus description thereof is omitted here.

  In the present embodiment, it is determined whether the communication channel width is changed on the terminal side and notified to the base station side, but the configuration determined on the base station side can be similarly implemented. Moreover, it can also be set as the structure which issues the request | requirement which changes a communication channel width from the base station side to the terminal side.

  Further, the configuration in which the communication channel information described in the second embodiment and the fourth embodiment is added as a determination element for determining the communication channel width can be similarly implemented. At this time, since it is based on the communication channel, more A communication channel width change can be performed with high reliability (the reception quality is likely to improve after the communication channel width change).

  In the present embodiment, the communication channel width to be changed has been described as being doubled. However, other values, for example, triple, 1/2 times, 1/3, 1/4, 1/8 times, etc., are similarly used. (Effects are described above in this embodiment).

  Thus, based on the transmission signal frame error detected on the receiving side, retransmission request information is transmitted from the receiving side to the transmitting side, a communication channel change request is transmitted, and the communication channel width used at the time of retransmission is changed. Even when it is difficult to separate signals multiplexed using the MIMO transmission method on the same communication channel, the reception quality of received signals is improved, transmission signal frame errors are reduced, and system throughput is improved. Can be made.

(Embodiment 6)
A feature of the present embodiment is that a transmission confirmation frame is transmitted from the reception side to the transmission side based on a transmission signal frame error detected on the reception side, and a communication channel used at the time of retransmission is transmitted based on the reception confirmation response on the transmission side. It is to change the width. As a result, even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel and good reception quality cannot be obtained, the reception quality of the reception signal is improved, and the transmission signal frame is improved. Errors can be reduced and system throughput can be improved.

  The difference from the fifth embodiment is that the retransmission request information detection unit is changed to a reception confirmation response detection unit.

  In the present embodiment, a method of changing the communication channel width in the method of changing the communication channel based on the reception confirmation response described in the third and fourth embodiments will be described.

  Since the method for changing the communication channel change width has been described in the fifth embodiment, it will be simplified or omitted here and a specific example of the method for changing the communication channel change width will be described.

  FIG. 28 shows an example of terminal-side radio transmission apparatus 2800 in the present embodiment. Portions that operate in the same manner as in FIG. 3 are assigned the same reference numerals, and descriptions thereof are omitted.

  The reception confirmation response signal generation unit 2801 determines whether to perform retransmission based on the error presence / absence information of the modulation signal A from the error determination unit 301-1 and the error presence / absence information of the modulation signal B from the error determination unit 301-2. Further, it is determined whether or not to change the communication channel width based on the communication channel width change signal, and is output as a reception confirmation response and communication channel width change request information, respectively.

  The data generation unit 2802 receives the reception confirmation response, communication channel width change request information, and transmission digital data, generates a transmission digital signal, and outputs it.

  FIG. 29 shows the frame structure of the modulated signal transmitted by the terminal in this embodiment, and is composed of the parts described in FIG. 4, FIG. 16, and FIG. Is omitted, but the configuration is different from that of FIGS.

  FIG. 30 shows an example of the configuration of base station-side radio apparatus 3000 in the present embodiment, which is configured with the parts described in FIG. 5, FIG. 17, and FIG. The description of the parts that operate in the same manner is omitted.

  Frame configuration signal generation section 2603 receives reception confirmation response and communication channel width change request signal 2602 and outputs a frame configuration signal.

  The advantage of changing the communication channel width has been described in the fifth embodiment, and will not be described.

  FIG. 31 shows the flow of transmission signals between the base station and the terminal in the present embodiment, and description of parts that operate in the same manner as in FIGS. 6 and 27 will be simplified or omitted.

  The signal flow is as follows. The odd periods of TH1, 3, 5,... Are periods in which the base station can transmit, and the even periods of TH2, 4, 6,.

  First, in the period TH1, the base station transmits data 1A and data 1B.

  Next, in the period TH2, since the error determination unit 301 confirmed that an error has occurred in the data 1A from the received data 1A and data 1B, the reception confirmation response signal generation unit 2801 The communication channel change (the method described in the third embodiment) is requested in the reception confirmation response and retransmission of data 1A.

  Next, in the period TH3, the base station transmits data 1A (changes the communication channel from CH1 to CH2), data 2A, and data 2B.

  Next, in period TH4, the terminal confirms that error has occurred again in data 1A from received data 1A, data 2A, and data 2B, so that reception confirmation response signal generation unit 2801 Transmits acknowledgments for receiving data 2A and data 2B.

  Next, in period TH5, the base station performs transmission of data 3A and data 3B and retransmission of data 1A based on the request in period TH4. At this time, since the communication channel is changed, the communication channel of data 1A to be retransmitted is changed from CH2 of modulated signal A to CH2 of modulated signal B.

  Next, in the period TH6, since the error determination unit 301 has detected an error in the data 1A this time, the reception confirmation response signal generation unit 2801 receives the reception confirmation response of the data 3A and data 3B and the communication channel width change request. Send.

  Next, in period TH7, the base station changes the communication channel width of data 1A to twice (CH1 and CH2), and data 4A and data 4B also transmit on the communication channel with the communication channel width doubled, respectively. To do.

  Next, in the period TH8, since the error determination unit 301 has confirmed that no error has occurred in the data 4A, the data 4B, and the retransmitted data 1A, the reception confirmation response signal generation unit 2801 The reception confirmation response of data 4B and data 1A is transmitted.

  Thus, at the time of retransmission, the configuration in which the communication channel width is changed and transmitted is the difference from Embodiment 1, that is, the feature of this embodiment.

  FIG. 32 describes an example of this embodiment, a specific method for changing the communication channel width.

  FIG. 32 shows a procedure for securing a communication channel based on RTS (Request to Send) and CTS (Clear to Send) adopted in the IEEE 802.11 standard. Further, 20 MHz shown in the conventional example 3 is set as one communication channel width.

  Here, the case where the base station A and the terminal A want to perform communication will be described.

  First, one (for example, base station A) transmits RTS using communication channel CH1. Devices other than the terminal A that has received this RTS do not transmit during the NAV (Network Allocation Vector) period set in the RTS.

  Next, the other (terminal A) transmits a CTS using the communication channel CH2. A device other than the base station A that has received this CTS does not transmit during the NAV period set in the CTS.

  Therefore, the base station A and the terminal A can perform 40 MHz transmission during the period (40 MHz frame exchange in the figure) set in the RTS (or CTS).

  As described above, the communication channel width can be changed. Here, the method for changing the communication channel width is just an example. When the communication channel width is changed, there are other restrictions such as waiting for the digital circuit and analog circuit to respond. However, the present embodiment is not limited to these restrictions. Also, the communication channel width change in the fifth embodiment can be performed in the same manner as the method described in FIG.

  Note that an example of the terminal-side radio reception apparatus in this embodiment has been described with reference to FIG. 7 (Embodiment 1) and FIG. 14 (Embodiment 2), and thus description thereof is omitted here.

  In the present embodiment, it is determined whether to change the communication channel width on the terminal side and notify the base station side, but the configuration determined on the base station side can be similarly implemented. Moreover, it can also be set as the structure which issues the request | requirement which changes a communication channel width from the base station side to the terminal side. Further, the configuration in which the communication channel information described in the second embodiment and the fourth embodiment is added as a determination element for determining the communication channel width can be similarly implemented. At this time, since it is based on the communication channel, more A communication channel width change can be performed with high reliability (the reception quality is likely to improve after the communication channel width change).

  Further, in this embodiment, the communication channel width is changed based on the reception confirmation response from the terminal side and the communication channel width change request. However, based on the communication channel width change rule at the time of retransmission determined in advance by the base station side. The configuration can be similarly implemented by changing the communication channel width. For example, a method of increasing the communication channel width that can be used by the system at the time of retransmission to 2, 3, 4,..., A method of doubling at the time of retransmission, and the like can be considered.

  This is because in the case of a system using a reception confirmation response, if an error occurs in all frames, the reception confirmation response is not transmitted, and therefore a communication channel width change signal cannot be obtained. Even in such a system, better reception quality can be obtained by changing the communication channel width based on the above-described rules and the like.

  In the present embodiment, the communication channel width to be changed has been described as being doubled, but other values, for example, triple, 1/2 times, 1/3, 1/4, 1/8 times, and the like are similarly used. (Effects are described above in this embodiment).

  Thus, by transmitting a reception confirmation response from the reception side to the transmission side based on the transmission signal frame error detected on the reception side, transmitting a communication channel change request, and changing the communication channel width used at the time of retransmission, Even when it is difficult to separate signals multiplexed using the MIMO transmission method in the same communication channel, the reception quality of received signals is improved, transmission signal frame errors are reduced, and the system throughput is improved. be able to.

(Embodiment 7)
In the embodiment described above, after switching the communication channel at the time of retransmission, the subsequent data has been described as being transmitted on the communication channel before switching, but may be transmitted on the communication channel after switching. This determination includes a method of setting as a system in advance, and based on the determination result when determining whether to switch communication channels based on communication channel information. In general, when the time variation of a communication channel is small, it is better to use the communication channel after switching for subsequent data transmission.

  In the above-described embodiment, the example applied to the OFDM system has been described. However, the present invention is not limited to this, and can be applied to, for example, a single carrier system or a spread spectrum communication system. In the case of a single carrier system, the IFFT unit and the FFT unit are not provided. In the case of the spread spectrum communication system, the IFFT unit and the FFT unit become a spreading unit and a despreading unit, respectively. The same can be applied to the case where the multicarrier scheme and the spread spectrum communication scheme are used together (for example, OFDM-CDMA scheme).

  In the above-described embodiment, the communication channel to be changed is also referred to as an own channel (also referred to as a control channel or a control channel) to an adjacent channel (CH1 and CH3 for CH2 in the conventional example in FIG. 3, an extension channel, an extension channel, or the like). However, the present invention is not limited to this, and the present invention can be similarly implemented even if the communication channel is changed to one or more communication channels (CH4 with respect to CH2, etc.). In general, as the communication channels become farther apart, the correlation between the communication channels becomes lower, so that better reception quality can be obtained by changing the communication channel, but the circuit configuration such as an analog filter can be complicated.

  Further, in the above-described embodiment, the order of the parts of the transmission signal frame configuration (for example, FIG. 4) from the base station and the terminal is not limited to this, and for example, retransmission request information symbol 404-1 in FIG. May be positioned before data symbol 403-1. In short, any configuration may be used as long as processing necessary for reception such as synchronization, propagation channel estimation, frequency offset correction, and the like is performed in the preamble, and subsequent symbols can be demodulated and decoded using these.

  In addition, the retransmission method using the retransmission request information, the reception confirmation response, the communication channel information, and the communication channel width change request information described in the above embodiment is not limited to the above embodiment, It can be realized by combining the embodiments. For example, the second embodiment does not describe the case where two communication channels are always used as described with reference to FIG. 9 in the first embodiment. This can be realized by the combination of FIG.

  In the above-described embodiment, a group of a plurality of parts is named a frame, but the present invention can be similarly applied to other names such as packets and units.

  Further, in the above-described embodiment, it can be carried out even when space-time coding is performed, and the document “Space-Time Block Codes from Orthogonal Design” IEEE Transactions on Information Theory, pp.1456-1467, vol.45, no.5, July 1999 Space-Time Block Codes, literature “Space-Time Block Codes for High Data Rate Wireless Communication: Performance Criterion and Code Construction” IEEE Transactions on Information Theory, pp.744-765, vol. Even if the spatio-temporal trellis code shown in 44, no. 2, March 1998 is applied, it can be similarly implemented.

  The present invention relates to a wireless transmission device and a wireless transmission method, and particularly to a wireless communication system intended to improve system throughput in the case of using a plurality of communication channels using a method of transmitting different modulation signals from a plurality of antennas. And suitable.

The figure which shows the structure of the 2 * 2 MIMO transmission system in Embodiment 1 of this invention. The figure which shows the structure of the transmission signal frame from the base station in Embodiment 1 of this invention. The figure which shows the structure of the terminal side radio | wireless transmitter in Embodiment 1 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 1 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 1 of this invention. The figure which shows the flow of the transmission signal of 2 * 2 MIMO transmission system in Embodiment 1 of this invention. The figure which shows the structure of the terminal side radio | wireless receiving apparatus in Embodiment 1 of this invention. The figure which shows the structure of the terminal side radio | wireless receiving apparatus in Embodiment 1 of this invention. The figure which shows the flow of the transmission signal of 2 * 2 MIMO transmission system in Embodiment 1 of this invention. The figure which shows the structure of the terminal side radio | wireless transmitter in Embodiment 2 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 2 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 2 of this invention. The figure which shows the flow of the transmission signal of the 2 * 2 MIMO transmission system in Embodiment 2 of this invention. The figure which shows the structure of the terminal side radio | wireless receiving apparatus in Embodiment 2 of this invention. The figure which shows the structure of the terminal side radio | wireless transmitter in Embodiment 3 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 3 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 3 of this invention. The figure which shows the flow of the transmission signal of the 2 * 2 MIMO transmission system in Embodiment 3 of this invention. The figure which shows the flow of the transmission signal of the 2 * 2 MIMO transmission system in Embodiment 3 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 4 of this invention. The figure which shows the structure of the terminal side radio | wireless receiving apparatus in Embodiment 4 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 4 of this invention. The figure which shows the flow of the transmission signal of 2 * 2 MIMO transmission system in Embodiment 4 of this invention. The figure which shows the structure of the terminal side radio | wireless transmitter in Embodiment 5 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 5 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 5 of this invention. The figure which shows the flow of the transmission signal of 2 * 2 MIMO transmission system in Embodiment 5 of this invention. The figure which shows the structure of the terminal side radio | wireless transmitter in Embodiment 6 of this invention. The figure which shows the structure of the transmission signal frame of the terminal in Embodiment 6 of this invention. The figure which shows the structure of the base station side radio | wireless apparatus in Embodiment 6 of this invention. The figure which shows the flow of the transmission signal of the 2 * 2 MIMO transmission system in Embodiment 6 of this invention. The figure which shows the flow of a communication channel width change of the 2 * 2 MIMO transmission system in Embodiment 6 of this invention. The figure which shows the structure of the conventional 2x2 MIMO transmission system. The figure which shows the structure of the conventional radio | wireless transmitter. The figure which shows arrangement of the conventional wireless communication channel

Explanation of symbols

201, 401 Control information symbol 202, 402 Channel estimation symbol 203, 403 Data symbol 204, 405 FCS
301 Error judgment unit 302, 1001, 2401 Retransmission request unit 303, 1002, 1502, 2102, 2402, 2802 Data generation unit 304 Transmission unit 404 Retransmission request information symbol 500, 1200, 1700, 2600 Base station side radio apparatus 501 Transmission data storage Unit 502 data selection unit 503 encoding unit 504 modulation unit 505 IFFT unit 506, 701, 1206 radio unit 507 frame configuration signal generation unit 508 frame configuration signal 509 transmission digital signal 551 reception antenna 552, 1203 reception unit 553, 1204 retransmission request detection Section 554 Retransmission request information 700, 800, 1400 Terminal side wireless reception device 702 FFT section 703 Channel estimation section 704, 801 Signal processing section 705 Control information detection section 706 Retransmission information processing section 707 Transmission Method information 1000, 1500, 2400, 2800 Terminal side wireless transmission device 1101 Communication channel information symbol 1201 Communication channel change request detection unit 1202 Communication channel change request signal 1205, 2603 Frame configuration signal generation unit 1401 Channel information / received signal storage unit 1402 Retransmission Signal processing unit 1501, 2101, 2801 Reception confirmation response signal generation unit 1601 Reception confirmation response symbol 1701 Reception confirmation response detection unit 1702 Reception confirmation response information 2501 Communication channel width change request information 2601 Communication channel width change request detection unit 2602 Communication channel width change Request signal

Claims (12)

A plurality of antennas for receiving a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A retransmission request detection unit for detecting a retransmission request included in the received signal;
A data selection unit for selecting data to be retransmitted using the retransmission request;
When the retransmission request is detected, the communication channel of the data to be retransmitted is changed to a communication channel different from the previous communication channel, and a radio unit for transmitting the data to be retransmitted;
A multi-antenna wireless communication device. A plurality of antennas for receiving a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A retransmission request detection unit for detecting a retransmission request included in the received signal;
A communication channel change request detecting unit for detecting a communication channel change request signal included in the received signal;
A data selection unit for selecting data to be retransmitted using the retransmission request;
Using the communication channel change request signal, changing a communication channel of the data to be retransmitted and transmitting the data to be retransmitted;
A multi-antenna wireless communication device. A plurality of antennas for receiving a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A reception confirmation response detecting unit for detecting a reception confirmation response included in the received signal;
A data selection unit that selects data to be retransmitted using the reception confirmation response;
A radio unit for changing the communication channel of the data to be retransmitted to a communication channel different from the previous communication channel and transmitting the data to be retransmitted when the reception acknowledgment is detected;
A multi-antenna wireless communication device. A plurality of antennas for receiving a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A reception confirmation response detecting unit for detecting a reception confirmation response included in the received signal;
A communication channel change request detecting unit for detecting a communication channel change request signal included in the received signal;
A data selection unit that selects data to be retransmitted using the reception confirmation response;
Using the communication channel change request signal, changing a communication channel of the data to be retransmitted and transmitting the data to be retransmitted;
A multi-antenna wireless communication device. The multi-antenna wireless communication device according to claim 1, wherein the wireless unit changes a communication channel to an adjacent channel. The multi-antenna wireless communication apparatus according to any one of claims 1 to 4, wherein the wireless unit changes a communication channel width to a local channel and an adjacent channel. A first step of receiving at a plurality of antennas a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A second step of detecting a retransmission request included in the received signal;
A third step of selecting data to be retransmitted using the retransmission request;
A fourth step of changing the communication channel of the data to be retransmitted to a communication channel different from the previous communication channel and transmitting the data to be retransmitted when the retransmission request is detected;
A multi-antenna wireless communication method comprising: A first step of receiving at a plurality of antennas a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A second step of detecting a retransmission request included in the received signal;
A third step of detecting a communication channel change request signal included in the received signal;
A fourth step of selecting data to be retransmitted using the retransmission request;
A fifth step of changing the communication channel of the data to be retransmitted using the communication channel change request signal and transmitting the data to be retransmitted;
A multi-antenna wireless communication method comprising: A first step of receiving at a plurality of antennas a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A second step of detecting a reception confirmation response included in the received signal;
A third step of selecting data to be retransmitted using the acknowledgment response;
A fourth step of changing the communication channel of the data to be retransmitted to a communication channel different from the previous communication channel and transmitting the data to be retransmitted when the reception acknowledgment is detected;
A multi-antenna wireless communication method comprising: A first step of receiving at a plurality of antennas a plurality of modulated signals transmitted simultaneously from a plurality of antennas;
A second step of detecting a reception confirmation response included in the received signal;
A third step of detecting a communication channel change request signal included in the received signal;
A fourth step of selecting data to be retransmitted using the acknowledgment response;
A fifth step of changing the communication channel of the data to be retransmitted using the communication channel change request signal and transmitting the data to be retransmitted;
A multi-antenna wireless communication method comprising: The multi-antenna wireless communication method according to claim 7, wherein the communication channel is changed to an adjacent channel. The multi-antenna wireless communication method according to any one of claims 7 to 10, wherein the communication channel changes a communication channel width to a local channel and an adjacent channel.

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