WO2009096145A1 - Dispositif de radiocommunication, système de radiocommunication et procédé de radiocommunication - Google Patents

Dispositif de radiocommunication, système de radiocommunication et procédé de radiocommunication Download PDF

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Publication number
WO2009096145A1
WO2009096145A1 PCT/JP2009/000149 JP2009000149W WO2009096145A1 WO 2009096145 A1 WO2009096145 A1 WO 2009096145A1 JP 2009000149 W JP2009000149 W JP 2009000149W WO 2009096145 A1 WO2009096145 A1 WO 2009096145A1
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Prior art keywords
precoding
wireless communication
codewords
codeword
power
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PCT/JP2009/000149
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English (en)
Japanese (ja)
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Rong Hong Mo
Qian Yu
Masayuki Hoshino
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Panasonic Corporation
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0426—Power distribution
    • H04B7/0434—Power distribution using multiple eigenmodes
    • H04B7/0443—Power distribution using multiple eigenmodes utilizing "waterfilling" technique
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/1893—Physical mapping arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Definitions

  • the present invention relates to a wireless communication apparatus, a wireless communication system, and a wireless communication method applicable to a MIMO (Multiple Input Multiple Output) system that performs communication using a plurality of antennas.
  • MIMO Multiple Input Multiple Output
  • hybrid ARQ Hybrid Automatic Repeat Re- Quest
  • a transmitter transmits each data packet with a cyclic redundancy check (CRC) bit for error detection.
  • CRC cyclic redundancy check
  • the receiver receives each data packet transmitted from the transmitter, and checks the contents of these data packets through the CRC. If the received data packet fails the CRC check, the receiver returns a NACK (Negative Acknowledgment) signal to the transmitter and requests retransmission.
  • NACK Negative Acknowledgment
  • the receiver decodes the retransmitted data packet together with the previous reception failure data packet to improve the decoding performance.
  • the receiver if the received data packet passes the CRC check, the receiver returns an ACK (Acknowledgement) signal to the transmitter and acknowledges the successful reception and decoding of the data packet.
  • ACK Acknowledgement
  • MIMO Multiple Input Multiple Output
  • MIMO technology uses multiple antennas for both transmission and reception, and simultaneously transmits individual data streams via multiple antennas (spatial multiplexing transmission), thereby improving frequency utilization efficiency without additional bandwidth and power consumption.
  • Promising in terms of improvement That is, by applying MIMO, the transmission capacity can be improved without expanding time / frequency resources. If the channel information is known at both the transmitter and receiver, the capacity of the MIMO system increases linearly with the minimum number of antennas implemented in the transmitter and receiver.
  • SCW single codeword
  • MCW multiple codeword
  • the input information bit sequence is CRC-encoded, channel-encoded, and mapped to data symbols to form a data packet.
  • the data packets are then segmented into multiple (spatial) data streams and transmitted in parallel via multiple transmit antennas.
  • all detected data space streams are multiplexed into a single data packet and channel decoding and CRC checking are performed through the channel decoder and CRC checking module, respectively.
  • an ACK / NACK signal is transmitted to the transmitter according to the CRC check result, and the reception quality of the transmission data packet is acknowledged.
  • the input information bit sequence is CRC encoded, channel encoded, and individually mapped to data symbols to form a plurality of data packets. Then, a multi-input information bit sequence using a plurality of data packets is transmitted in parallel via a plurality of antennas. The receiver first reconstructs a plurality of data packets using the detected data space stream, and independently performs channel decoding and CRC check for each data packet. Subsequently, a plurality of ACK / NACK signals are fed back to the transmitter according to the CRC check result for each data packet, and the reception quality of the plurality of data packets is acknowledged.
  • precoding In precoding, in order to reflect the observation status (propagation channel status) of the received signal at the receiving point, a feedback signal including beam information is transmitted from the receiver to the transmitter, and the transmitter controls the beam using the feedback signal. To do.
  • a right matrix of singular value decomposition (SVD) of the MIMO channel in the transmitter that is, a precoding matrix obtained from the right singular matrix
  • SVD singular value decomposition
  • a more efficient method predetermines a codebook consisting of precoding sets that are optimally designed to reflect the statistics of the MIMO fading channel.
  • the precoding matrix is selected from a codebook based on channel conditions and some predetermined criteria.
  • the receiver transmits an index corresponding to the selected precoding matrix to the transmitter. This requires very few bits for signaling the index of the precoding matrix to the transmitter. If the precoding matrix set (codebook) is optimally designed, capacity loss can be achieved at an acceptable level.
  • Precoding can be used for both SCW transmission and MCW transmission.
  • MCW transmission when precoding is applied at the transmitter, data packets from different codewords contribute to signals transmitted via multiple antennas with different weight values. For this reason, each codeword has different link conditions. As a result, the decoding quality varies with the codeword. In the MCW type MIMO system, some codewords are correctly decoded and pass the CRC check, while others are not decoded correctly and are likely to require retransmission.
  • the retransmission codeword has higher transmission quality requirements as opposed to initial communication where the codeword has the same requirements and transmission quality.
  • a precoding design for retransmission must address the challenges of higher transmission quality requirements in order to reduce the number of retransmissions and improve system capacity.
  • Non-Patent Document 1 As a prior art for adapting precoding to retransmission, as disclosed in Non-Patent Document 1, there is a method in which precoding vectors used for MCW codewords are replaced during retransmission. 3GPP TSG RAN WG1 # 49, R1-072384, Nortel, "HARQ performance enhancement", May 7th-11th, 2007
  • Non-Patent Document 1 simply replacing the precoding vector used for each codeword at the time of retransmission cannot guarantee whether sufficient transmission quality requirements can be obtained at each codeword at the time of retransmission.
  • the temporal change of the propagation path condition does not occur very much (when the temporal channel correlation is high)
  • the improvement of the reception quality in each codeword cannot be expected.
  • the newly transmitted codeword fails to be decoded (decoding result) May be NACK).
  • the present invention has been made in view of the above circumstances, and a radio communication apparatus, a radio communication system, and a radio communication capable of improving the transmission quality of each codeword at the time of retransmission when precoding is employed in MIMO. It aims to provide a method.
  • the present invention provides, as a first aspect, a wireless communication apparatus that performs communication using a plurality of codewords using a plurality of antennas, and that receives a signal of a plurality of codewords transmitted from a plurality of antennas of a transmission apparatus
  • a decoding unit that decodes each of the received multiple codewords, a channel estimation unit that estimates a propagation state of each of the received multiple codewords, and a future transmission based on the propagation state of each codeword
  • a precoding matrix selection unit for selecting a precoding matrix for beam forming by precoding and a decoding result of each of the decoded codewords to adjust the power of each codeword in the precoding matrix
  • a parameter determination unit for determining the parameters of each of the codewords Issue result, the feedback information including the information for specifying the precoding matrix and the parameter, to provide a radio communication apparatus and a feedback information output unit to be transmitted to the transmission device.
  • the present invention provides, as a second aspect, the wireless communication apparatus described above, wherein the parameter determination unit adjusts the power of each codeword as the parameter while keeping the power of all codewords constant. Includes those that calculate offset values.
  • the present invention provides, as a third aspect, the above wireless communication apparatus, wherein the parameter determination unit converts a code word that needs to be retransmitted when the decoding result is negative based on the decoding result of each code word. Including those that determine parameters to allocate more power to.
  • the parameter determination unit determines whether a codeword that needs to be retransmitted based on a decoding result of each codeword is negative.
  • a parameter for allocating more power to codewords having poor decoding reliability is included.
  • the present invention provides, as a fifth aspect, the above-described wireless communication device, wherein the parameter determination unit is configured to detect an antenna having a good channel condition based on a channel condition for each of a plurality of antennas of the transmission device. To determine parameters to allocate more power.
  • the present invention provides, as a sixth aspect, the wireless communication apparatus described above, wherein the parameter determination unit needs to retransmit based on the decoding result and the number of retransmissions of each codeword, with no decoding result This includes determining a parameter for assigning more power to a large codeword as the number of retransmissions increases.
  • the present invention provides, as a seventh aspect, the above wireless communication apparatus, wherein the parameter determination unit calculates a decoding quality of each codeword, and a codeword that needs to be retransmitted because the decoding result is negative
  • the parameter determination unit calculates a decoding quality of each codeword, and a codeword that needs to be retransmitted because the decoding result is negative
  • a parameter for adaptively allocating power so as to obtain the best decoding quality is included.
  • the present invention provides, as an eighth aspect, a wireless communication apparatus that performs communication using a plurality of codewords using a plurality of antennas, and an encoding unit that encodes a plurality of codewords to be transmitted to a receiving apparatus;
  • a precoding processing unit that performs precoding to form a predetermined beam by weighting signals output to a plurality of antennas for a plurality of encoded codewords, and a signal after the precoding processing via a plurality of antennas
  • a transmitter for transmitting to the receiver, and the precoding processor includes a precoding matrix for the precoding included in feedback information from the receiver and each codeword in the precoding matrix. Based on the information that specifies the parameters for adjusting the power, To provide a radio communication apparatus for performing the loading.
  • the present invention provides, as a ninth aspect, the above wireless communication apparatus, wherein the precoding processing unit uses each codeword as a parameter in the precoding matrix while maintaining the power of all codewords constant. Including pre-coding using an offset value for adjusting the power of.
  • the present invention provides, as a tenth aspect, the wireless communication apparatus described above, wherein the precoding processing unit needs to retransmit based on a decoding result of each of the plurality of codewords with no decoding result. This includes precoding that allocates more power to codewords.
  • the present invention provides, as an eleventh aspect, the wireless communication apparatus described above, wherein the precoding processing unit needs to retransmit based on a decoding result of each of the plurality of codewords with no decoding result.
  • precoding in which more power is allocated to codewords having poor decoding reliability in these codewords is included.
  • the present invention provides, as a twelfth aspect, the wireless communication apparatus described above, wherein the precoding processing unit is based on a channel condition for each of the plurality of antennas and has an excellent channel condition. This includes precoding that allocates a lot of power.
  • the precoding processing unit re-determines whether the decoding result is negative based on each decoding result and the number of retransmissions of the plurality of codewords. This includes codewords that need to be transmitted and that perform precoding with more power allocated as the number of retransmissions increases.
  • the present invention provides, as a fourteenth aspect, the wireless communication apparatus described above, wherein the precoding processing unit needs to retransmit based on the decoding quality of each of the plurality of codewords with no decoding result.
  • This includes codewords that are precoded with adaptively assigned power so that the decoding quality is best.
  • this invention provides a radio
  • a wireless communication system that performs communication using a plurality of codewords using a plurality of antennas, and receives a plurality of codeword signals transmitted from a plurality of antennas of a transmission apparatus.
  • a receiving unit a decoding unit that decodes each of the received multiple codewords, a channel estimation unit that estimates the propagation status of each of the received multiple codewords, and a future based on the propagation status of each codeword
  • a precoding matrix selection unit for selecting a precoding matrix for beam forming by precoding in transmission, and adjusting the power of each codeword in the precoding matrix based on the decoding result of each of the decoded codewords
  • a parameter determining unit for determining a parameter for performing the reception
  • An encoding unit for encoding a plurality of codewords to be transmitted to a device, and forming a predetermined beam by weighting signals output to a plurality of antennas based on the precoding matrix and the parameters for the encoded plurality of codewords
  • a wireless communication system comprising: a precoding processing unit that performs precoding to transmit; and a transmission unit that transmits a signal after the precoding processing to the reception device via a plurality of antennas.
  • a wireless communication method in a wireless communication system that performs communication using a plurality of codewords using a plurality of antennas, wherein a plurality of codewords transmitted from a plurality of antennas of a transmission apparatus are transmitted.
  • a wireless communication method is provided.
  • the power of the precoding matrix is adjusted so that more power is allocated to the retransmission codeword when retransmission occurs based on the decoding result of each of the multiple codewords. It becomes possible to do. Thereby, it is possible to improve the transmission quality of each codeword at the time of retransmission.
  • the present invention it is possible to provide a radio communication apparatus, a radio communication system, and a radio communication method that can improve the transmission quality of each codeword at the time of retransmission when precoding is employed in MIMO.
  • Block diagram illustrating a configuration of a transmitter for MCW MIMO precoding system Block diagram illustrating the configuration of a receiver for MCW MIMO precoding system
  • a diagram illustrating a more efficient way to achieve precoding in a MIMO system under limited feedback The figure which shows the relationship of parameter (DELTA) i and (delta) i determined based on the signaling condition of ACK / NACK, the channel conditions of a transmission antenna, and decoding reliability
  • DELTA parameter
  • delta delta
  • a block diagram showing a configuration of a receiver for an MCW MIMO precoding system according to the present embodiment Block diagram showing the configuration of a transmitter for the MCW MIMO precoding system according to the present embodiment
  • Precoding processing unit 122, 124 Transmitting antenna 202, 204 Receiving antenna 214, 216 Demapping and decoding unit 218, 220 CRC checking unit 602 Channel estimation unit 604 Parameter selection unit 606 Precoding matrix selection unit
  • the wireless communication system in a wireless communication system employing MIMO, precoding is performed by weighting a plurality of antennas to form a beam.
  • a configuration example in the case of performing is shown.
  • the transmission device and the reception device perform signal transmission using a plurality of CWs using a plurality of antennas, and perform retransmission control (adaptive retransmission control) using HARQ in MCW.
  • a signal is transmitted from a base station to a user terminal, and ACK / NACK indicating whether reception is possible is fed back from the user terminal to the base station.
  • the base station (wireless communication base station device) becomes a transmitting device (wireless communication device having a transmitter function), and the user terminal (wireless communication mobile station device) is a receiving device (wireless communication device having a receiver function).
  • the following embodiment is an example for description, and the present invention is not limited to this.
  • a precoding method capable of improving the transmission quality of a spatial stream at the time of retransmission when MCW is simultaneously transmitted in a MIMO system and retransmission control by HARQ is performed is presented.
  • the transmission quality of the retransmission data stream can be improved.
  • the input power of the precoding matrix is adjusted while keeping the transmission power of all the codewords and the physical antenna constant.
  • the receiver first decodes the initial transmission codeword. If there is a codeword that fails the CRC check and needs to be retransmitted, the receiver will, for each input of the precoding matrix included in the codeword for initial transmission, based on the ACK / NACK signal and / or the decoding quality We will add an offset value. This offset value will be used to allocate more power retransmission codewords for antennas with good channel conditions and less power for antennas with poor channel conditions.
  • the transmission quality of the retransmission codeword is improved as compared with the precoding method that does not use input adjustment of the precoding matrix while keeping the transmission power of the codeword and the physical antenna constant. Then, the receiver feeds back the offset value together with the precoding matrix to the transmitter.
  • This offset value can be either predetermined based on channel statistics or adaptively determined based on instantaneous channel conditions.
  • a set of offset values with respect to a precoding matrix input for retransmission is expressed as ACK / NACK.
  • the signal is determined in advance according to the case, and the index of the offset value set to be used next time is fed back to the transmitter for notification from the receiver according to the ACK / NACK signal.
  • the offset value determination method in the dynamic adjustment method adaptively determined based on the instantaneous channel condition, the offset value for the input of the precoding matrix is adapted based on the decoding quality at the receiver. To be determined and fed back to the transmitter for notification.
  • a new codeword refers to a codeword that has not been transmitted before
  • a retransmission codeword refers to a codeword that is retransmitted based on the previous transmission codeword.
  • FIG. 1 is a block diagram illustrating the configuration of a transmitter for an MCW MIMO precoding system having two transmission antennas and two reception antennas.
  • a precoding matrix is applied at the transmitter, and a beam of a data sequence corresponding to each codeword is formed by precoding.
  • Each block shown in the following drawings has a function realized by a hardware circuit in the wireless communication apparatus or a software program operating on the processor.
  • the CRC encoding units 106 and 108 perform CRC encoding on the input bit sequences CW1 (102) and CW2 (104), respectively.
  • Channel coding and symbol mapping sections 110 and 112 perform channel coding and symbol mapping for the respective input bit sequences CW1 and CW2, and generate two codewords s 1 (114) and s 2 (116).
  • the precoding processing unit 130 receives data symbols from two code words, multiplies the weights specified by the precoding matrix, and outputs an output signal x 1 (118) which is a weighted sum of the code words s 1 and s 2. ) And x 2 (120). These output signals x 1 and x 2 are transmitted via physical transmission antennas Tx1 (122) and Tx2 (124). At this time, the transmitter performs retransmission control by HARQ based on the ACK / NACK signal fed back from the receiver, and retransmits the codeword notified of NACK.
  • the output signals x 1 and x 2 are mathematically expressed by the following formula (1).
  • the signal transmitted via the antenna Tx1 and the antenna Tx2 is given by the following formula (2).
  • N S and N T are the number of codewords and the number of transmission antennas, respectively, N S ⁇ min (N T , N R ), and N R is the number of reception antennas.
  • the transmission power of the data symbol s j distributed to the antenna Txi is expressed by the following mathematical formula (3).
  • the contribution of the code word s j to the signal transmitted via the i-th antenna Txi is defined by the weight value
  • transmitter output signals x 1 and x 2 propagate through a MIMO channel given by a matrix of N R rows and N T columns to reach the receiver.
  • the input / output relationship of the precoding MIMO channel is given by the following equation (5).
  • r, H, and n represent a received signal vector, a channel matrix, and an additive white Gaussian noise (AWGN) vector, respectively.
  • AWGN additive white Gaussian noise
  • FIG. 2 is a block diagram illustrating a configuration of a receiver for an MCW MIMO precoding system having two transmission antennas and two reception antennas.
  • Reception signals r 1 (206) and r 2 (208) received by reception antennas Rx1 (202) and Rx2 (204) are input to MIMO detection section 208, respectively.
  • the MIMO detection unit 208 separates the independent data symbols and generates codewords s 1 (210) and s 2 (212).
  • the MIMO detection unit 208 uses a known detection system, such as a linear least mean square error (LMMSE) decoder (not shown), and the precoding matrix C is known at the receiver through signaling transmission (not shown).
  • LMMSE linear least mean square error
  • Demapping and decoding sections 214 and 216 receive detected codewords s 1 and s 2 and perform symbol demapping and channel decoding, respectively.
  • the CRC checkers 218 and 220 perform CRC check on the decoded codewords.
  • two output bit sequences CW1 (222) and CW2 (224) are output.
  • the matrix C is first quantized and then immediately fed back to the transmitter via the uplink. Because of the irregular characteristics of the MIMO channel, the right singular matrix changes every moment. In this case, since a huge signaling overhead is caused, it is not practical to feed back a strict right singular matrix.
  • FIG. 3 is a diagram illustrating a more efficient method of implementing precoding in a MIMO system under limited feedback.
  • FIG. 3 shows a precoding matrix output procedure.
  • the codebook 304 consisting of a finite set of precoding matrices is predetermined based on MIMO channel characteristics using some known techniques (for example, linear interpolation not shown).
  • the size of the codebook ⁇ is defined by N c (number of codes or number of antennas). The number of binary bits of log 2 N c characterizes the codebook ⁇ (i) as a whole.
  • one precoding matrix C is selected from the codebook for each transmission, and a metric (for example, capacity or SNR (Signal to Noise ratio, Signal-to-noise ratio)) is maximized (306). Then, as an example of information specifying the selected precoding matrix C, an index of the precoding matrix C is fed back to the transmitter 310 via the uplink of the wireless communication system (308).
  • a metric for example, capacity or SNR (Signal to Noise ratio, Signal-to-noise ratio)
  • the precoding matrix is represented by, for example, the unitary shown in Equation (7) below. Must be a matrix.
  • the above precoding design is mainly for initial transmission where two transmission codewords become new codewords.
  • the codeword whose decoding result is NACK is retransmitted according to a specific HARQ scheme (Chase scheme or IR (incremental redundancy) scheme, not shown).
  • the retransmitted codeword is combined with the initial transmission codeword to obtain retransmission composite gain and improve decoding performance.
  • the retransmission codeword requires higher transmission quality than the new codeword in order to improve the decoding performance after retransmission synthesis.
  • the precoding scheme for retransmission needs to be designed to meet this requirement.
  • the present embodiment proposes a precoding design method by adjusting the input power of the precoding matrix in the codebook based on the ACK / NACK signal or the decoding quality that achieves this goal.
  • the codeword s 2 Since a signal obtained by combining the above signals is observed at the receiver, the codeword s 2 actually interferes with the retransmission codeword s 1 .
  • the received signal power from the transmission antenna Tx2 of the retransmission codeword s 1 is given by the following formula (11).
  • Interference power from new codeword s 2 transmitted via the transmission antennas Tx1 to retransmission codeword s 1, that is, the reception signal power from the transmission antenna Tx1 new codeword s 2 is given by the following equation (12) It is done.
  • the interference power from the new codeword s 2 transmitted to the retransmission codeword s 1 via the transmission antenna Tx 2 that is, the received signal power from the transmission antenna Tx 2 of the new codeword s 2 is expressed by the following equation (13). Given in.
  • the fading gain of a given MIMO channel for example, i ⁇ ⁇ 1, ⁇ , N R ⁇ i ⁇ in ⁇ 1, ⁇ , N T ⁇ to h ij of
  • the precoding matrix c pq of q ⁇ ⁇ 1,..., N S ⁇ with p ⁇ ⁇ 1,..., N T ⁇ determines the power of the codeword transmitted through the transmitting antenna.
  • the channel conditions of the transmission antenna Tx1 and the transmission antenna Tx2 are given by the following equations (14) and (15), respectively.
  • A can be a real value or an imaginary value.
  • the first column of the precoding matrix is the weight coefficient of the code word s 1 through the transmission antenna, and the second column of the precoding matrix is the weight coefficient of the code word s 2 through the transmission antenna.
  • the structure of the precoding matrix in the codebook ensures unitarity of the precoding matrix.
  • the decoding quality varies with the codeword. For 2 rows by 2 columns (2 ⁇ 2) MIMO using two codewords, the following four cases occur. (1) When both transmission antennas Tx1 and Tx2 have good channel conditions sufficient for correct decoding and both codewords s 1 and s 2 are ACK (2) Both transmission antennas Tx1 and Tx2 are correct decoding the has a poor channel condition can not be performed, the code word s 1, s 2 if both the NACK (3) transmit antennas Tx1, codewords s 1 of the signal power from Tx2 codeword s 2 and additive white When the code word s 1 becomes NACK and the code word s 2 becomes ACK when the interference power from the Gaussian noise AWGN is not sufficient, (4) The signal power of the code word s 2 from the transmission antennas Tx1 and Tx2 is codewords s 1 and additive not sufficient to counteract the interference power from white Gaussian noise AWGN, codeword s 1 is ACK next code If the word s 1,
  • codebook ⁇ (i) is designed as equation (17) below.
  • ⁇ i and ⁇ i are real numbers and satisfy 0 ⁇ ⁇ i , ⁇ i ⁇
  • Equation (17) The structure of the precoding matrix in Equation (17) continues to have unitary nature of the precoding matrix given by Equation (16).
  • the purpose of introducing the parameters ⁇ i and ⁇ i is to adjust the power of each input of the precoding matrix in retransmission.
  • ⁇ i > ⁇ i means that more power of the codeword s 1 is assigned to the transmission antenna Tx1, and less power is assigned to the transmission antenna Tx2.
  • ⁇ i ⁇ i means that more power of the codeword s 2 is assigned to the transmission antenna Tx1, and less power is assigned to the transmission antenna Tx2.
  • ⁇ i ⁇ i indicates that the equal power of both codewords s 1 and s 2 is assigned to the transmitting antenna, where ⁇ i and ⁇ i provide the difference between the initial transmission and the retransmission. It is only used for.
  • the first column A + ⁇ i , A + ⁇ i of the matrix is related to the weight of the code word s 1
  • the second column A + ⁇ i , ⁇ (A + ⁇ i ) of the matrix is related to the weight of the code word s 2.
  • the first row of the matrix is related to the weight of the transmission antenna Tx1
  • the second row is related to the weight of the transmission antenna Tx2.
  • the magnitude relationship between the parameters ⁇ i and ⁇ i is determined according to the condition of the ACK / NACK signal and the channel condition of the transmitting antenna.
  • the parameters ⁇ i and ⁇ i are adjusted according to the decoding reliability, which is one of decoding quality.
  • FIG. 4 is a diagram showing the relationship between the ACK / NACK signaling of the decoding result of each codeword, the channel condition of the transmitting antenna, and the parameters ⁇ i and ⁇ i determined based on the decoding reliability.
  • the parameter is set to ⁇ i > ⁇ i ⁇ 0 when the transmission antenna Tx1 has better channel conditions than the transmission antenna Tx2. Also, when the channel condition of the transmission antenna Tx2 is better than that of the transmission antenna Tx1, ⁇ i > ⁇ i ⁇ 0 is set.
  • the parameter is set to ⁇ i > ⁇ i ⁇ 0 when the transmission antenna Tx1 has better channel conditions than the transmission antenna Tx2. Further, when the channel condition of the transmission antenna Tx2 is better than that of the transmission antenna Tx1, ⁇ i > ⁇ i ⁇ 0 is set. That is, the power distribution is adjusted so that more power is allocated to the code word that needs to be retransmitted because the decoding result is NACK. At this time, a lot of power is allocated to the antenna having a good channel condition.
  • Decoding reliability is one metric that indicates decoding quality, and each codeword is measured by comparing the average LLR (Log Likelihood Ratio) or SNR of decoded bits with each other for comparison.
  • LLR Log Likelihood Ratio
  • the parameter is set to ⁇ i > ⁇ i ⁇ 0.
  • ⁇ i > ⁇ i ⁇ 0 is set.
  • the parameter is set to ⁇ i > ⁇ i ⁇ 0 when the transmission antenna Tx1 has better channel conditions than the transmission antenna Tx2. Further, when the channel condition of the transmission antenna Tx2 is better than that of the transmission antenna Tx1, ⁇ i > ⁇ i ⁇ 0 is set. That is, the power distribution is adjusted so that more power is allocated to the codeword having the lower decoding reliability.
  • FIG. 5 is a flowchart showing a procedure for determining the parameters ⁇ i and ⁇ i shown in FIG.
  • the receiver determines whether codeword s 1 has a NACK signal (506). If the code word s 1 is NACK, it is determined whether the code word s 2 has a NACK signal (514). If the code word s 1 is ACK, that is, the code word s 1 is ACK and the code word s 2 is NACK. In this case, the channel conditions of the two transmission antennas Tx1 and Tx2 are determined (508).
  • step 508 if the transmission antenna Tx1 has better channel conditions than the transmission antenna Tx2, the parameter is set to ⁇ i > ⁇ i ⁇ 0 and more of the power of the codeword s 2 is assigned to the antenna Tx1 (510). If the channel condition of the transmission antenna Tx2 is better than that of the transmission antenna Tx1, the parameter is set to ⁇ i > ⁇ i ⁇ 0, and more power of the codeword s 2 is assigned to the antenna Tx2 (512).
  • the decoding reliability determined by the average LLR or SNR of the decoded bits is determined.
  • the processing of steps 508, 510, and 512 is performed, and the transmission antenna Tx 1 has better channel conditions than the transmission antenna Tx 2.
  • the parameter is set to ⁇ i > ⁇ i ⁇ 0, and the parameter is set to ⁇ i > ⁇ i ⁇ 0 when the transmission antenna Tx2 has better channel conditions than the transmission antenna Tx1.
  • the process proceeds to step 516.
  • the code word s 2 is not NACK in step 514, that is, if the code word s 1 is NACK and the code word s 2 is ACK, channel conditions of the two transmission antennas Tx1 and Tx2 are determined (516). If the transmit antenna Tx1 has better channel conditions than the transmit antenna Tx2 at step 516, the parameter is set to ⁇ i > ⁇ i ⁇ 0 and more of the power of the codeword s 1 is assigned to the antenna Tx1 (518). If the channel condition of the transmission antenna Tx2 is better than that of the transmission antenna Tx1, the parameter is set to ⁇ i > ⁇ i ⁇ 0, and more power of the codeword s 1 is allocated to the antenna Tx2 (520).
  • ⁇ i and ⁇ i are based on ACK / NACK signaling, decoding reliability information (average LLR and SNR of decoded bits), and channel conditions of the transmitting antenna given by equations (14) and (15). Based on this, it is determined by either a static adjustment method or a dynamic adjustment method described later.
  • FIG. 6 is a block diagram showing a configuration of a receiver for the MCW type MIMO precoding system according to the present embodiment.
  • FIG. 6 is an example in which constituent elements characteristic to the present embodiment are added to the configuration of FIG.
  • the receiver includes a channel estimation unit 602, a parameter selection unit 604, and a precoding matrix selection unit 606.
  • a transmission unit 608 including a transmission signal processing unit for transmitting feedback information, a transmission RF unit, and the like is provided. Others are the same as FIG.
  • the channel estimation unit 602 performs channel estimation based on the received signals r 1 (206) and r 2 (208) received by the receiving antennas Rx1 (202) and Rx2 (204), and a channel matrix H corresponding to the channel estimation result Is output.
  • the parameter selection unit 604 receives the channel matrix H and the ACK / NACK signal output according to the CRC check result of each codeword decoded in the CRC check units 218 and 220.
  • the parameter selection unit 604 selects and determines the parameters ⁇ i and ⁇ i as described above based on the channel matrix H and the ACK / NACK signal.
  • the precoding matrix selection unit 606 selects and determines the precoding matrix C based on the channel matrix H and the parameters ⁇ i and ⁇ i .
  • the receiver feeds back the index information specifying the determined parameters ⁇ i and ⁇ i and the precoding matrix C to the transmitter via the transmitter 608 together with the ACK / NACK signal of each codeword.
  • the receiving antennas 202 and 204 and a receiving RF unit (not shown) realize the function of the receiving unit.
  • the MIMO detection unit 208 and the demapping and decoding units 214 and 216 realize the function of the decoding unit.
  • the parameter selection unit 604 implements the function of the parameter determination unit.
  • the transmission unit 608 and the transmission antenna (usually also serving as a reception antenna) implement the function of the feedback information output unit.
  • FIG. 7 is a block diagram illustrating a configuration of a transmitter for the MCW MIMO precoding system according to the present embodiment.
  • FIG. 7 is an example in which components characteristic to the present embodiment are added to the configuration of FIG.
  • the transmitter has a characteristic function in the precoding processing unit 730.
  • a reception unit 710 including a reception RF unit for receiving feedback information, a reception signal processing unit, and the like is provided.
  • the transmitter acquires the precoding matrix C fed back from the receiver and the index information of the parameters ⁇ i and ⁇ i via the receiving unit 710.
  • Pre-encoding processor 730 uses the precoding matrix C and the parameter delta i, the index information of [delta] i, determining the precoding matrix C after power adjustment, pre for the two codewords s 1, s 2 Perform the coding process.
  • the code words s 1 and s 2 are respectively multiplied by the weights specified by the precoding matrix C and the parameters ⁇ i and ⁇ i to generate output signals x 1 and x 2 .
  • the CRC encoding units 106 and 108 and the channel encoding and symbol mapping units 110 and 112 realize the function of the encoding unit.
  • the transmission antennas 122 and 124 and a transmission RF unit (not shown) realize the function of the transmission unit.
  • the reception unit 710 and the reception antenna (usually also serving as the transmission antenna) realize the function of the feedback information reception unit.
  • a parameter set ⁇ i , ⁇ i ⁇ is defined based on the number of retransmissions of two codewords and ACK / NACK signaling.
  • the coefficient b is a positive value parameter and can be determined in advance from a simulation based on the channel statistics and the quality of service (QOS) of the data packet.
  • the parameter set ⁇ i , ⁇ i ⁇ is one of the sets given on the right side of Equation (18) based on the number of retransmissions of two codewords and ACK / NACK signaling. I will take.
  • the first parameter set given on the right side of Equation (18) indicates that more power of codeword s 1 will be allocated to transmit antenna Tx1.
  • the second parameter set also indicates that more power of codeword s 2 will be allocated to transmit antenna Tx1.
  • a codeword having a larger number of retransmissions must have higher requirements regarding transmission quality. For this reason, in the code word having the larger number of retransmissions, more power of the code word is allocated to the transmission antenna having better channel conditions. As w increases or as the difference in the number of retransmissions of two codewords increases, codewords having a larger number of retransmissions have even higher retransmission quality requirements. For this reason, in the codeword to be retransmitted, it is necessary to allocate much greater power of the codeword to the transmit antenna with better channel conditions. Accordingly, as the number of retransmissions increases, the power distribution is made to differ between codewords.
  • FIG. 8 is a diagram illustrating a method for obtaining the coefficient b in the equation (18) by simulation.
  • the coefficient b is determined based on a given MIMO channel statistic and packet error rate (PER: PacketPackError Rate) performance.
  • PER PacketPackError Rate
  • random coefficients b are generated irregularly according to a uniform distribution in the range of b ⁇
  • the decoding bits of the codeword that has passed the CRC check (becomes ACK) at the receiver are collected (814). Thereafter, the procedure between steps 804 to 814 is repeated until the MIMO channel is sufficiently simulated in this simulation. Next, the average throughput for a given coefficient b is calculated using the decoded information pits collected in step 814 (816). Thereafter, the procedure between steps 802 to 816 is repeated in this simulation to obtain an average throughput for different coefficients b. The coefficient b that provides the best average throughput is the final selection result.
  • FIG. 9 is a diagram showing a processing procedure for static parameter adjustment.
  • the receiver first detects and decodes the received signal (902). Then, based on the given MIMO channel estimation result, the channel conditions of the transmission antennas Tx1 and Tx2 are calculated from the equations (14) and (15) (904). Next, w is acquired based on the CRC check result of the current transmission and the number of retransmissions of all codewords (906). Then, a parameter set ⁇ i , ⁇ i ⁇ given by Equation (18) is selected as power adjustment parameters ⁇ i , ⁇ i to be used for the next transmission based on ACK / NACK signaling of two code words. (908). The index of the selected parameter set ⁇ i , ⁇ i ⁇ is fed back to the transmitter via the uplink.
  • FIG. 10 is a diagram illustrating a processing procedure for dynamic parameter adjustment.
  • the receiver first detects and decodes the received signal (1002).
  • the decoding failure to a mean LLR of decoded bits of the code word becomes NACK, is calculated by D r (1004).
  • Dr is obtained by the following equation (19).
  • 0) represent information probabilities to be decoded as 1 and 0, respectively.
  • the required average LLR corresponding to the required PER is calculated based on the relationship between the average LLR and PER defined in advance (1006). Based on the relationship between the SNR and the average LLR, the required SNR for the next retransmission credit is extracted (1008). Subsequently, a parameter set ⁇ i , ⁇ i ⁇ is determined by solving the following mathematical formulas (20), (21), and (22) based on the required SNR (1010). The index of the selected parameter set ⁇ i , ⁇ i ⁇ is fed back to the transmitter via the uplink.
  • a combination of parameters ⁇ i , ⁇ i (for example, four ways) is temporarily set. Then, the precoding matrix C based on the temporarily set parameters ⁇ i and ⁇ i is substituted into the equations (20), (21), and (22), and the SNR for each parameter ⁇ i and ⁇ i is calculated. Thereafter, the parameter delta i, the parameter set of the largest SNR from the combinations of ⁇ i ⁇ i, ⁇ i ⁇ selects.
  • the SNR calculated here can be used as the decoding reliability at the time of parameter determination in FIGS. 4 and 5 described above.
  • retransmission of a plurality of codewords is required according to ACK / NACK of each codeword.
  • a precoding matrix is determined so that more power is allocated to a simple codeword and more power is allocated to a high quality antenna among a plurality of antennas.
  • each functional block used in the description of each of the above embodiments is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.
  • the name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.
  • the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible.
  • An FPGA Field Programmable Gate Array
  • a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.
  • the present invention has an effect of improving the transmission quality of each codeword at the time of retransmission when precoding is employed in MIMO, and is applied to a MIMO system that performs communication using a plurality of antennas. It is useful as an applicable wireless communication device, wireless communication system, wireless communication method, and the like.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Radio Transmission System (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)

Abstract

Selon l'invention, il est possible d'améliorer la qualité de transmission de mots de code lors d'une retransmission lorsqu'un précodage est employé dans le système entrée multiple/sortie multiple (MIMO). Un récepteur pour un système de précodage MIMO de type MCW comprend : une unité de sélection de paramètre (604) qui sélectionne des paramètres Δi, δi pour régler une valeur de décalage d'ajustement de puissance de chaque mot de code conformément à une matrice de canal H sur la base d'un résultat d'estimation de canal et d'un signal ACK/NACK de chaque mot de code ; et une unité de sélection de matrice de précodage (606) qui sélectionne et décide une matrice de précodage C pour une formation de faisceau de précodage conformément à la matrice de canal H et aux paramètres Δi, δi. Le récepteur renvoie et rapporte à l'émetteur les informations d'index spécifiant les paramètres Δi, δi et la matrice de précodage C conjointement avec le signal ACK/NACK de chaque mot de code.
PCT/JP2009/000149 2008-01-29 2009-01-16 Dispositif de radiocommunication, système de radiocommunication et procédé de radiocommunication WO2009096145A1 (fr)

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JP2013502766A (ja) * 2009-08-17 2013-01-24 富士通株式会社 プリコーディング行列コードブックグループを生成する方法及び装置
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CN104253967A (zh) * 2014-09-26 2014-12-31 厦门亿联网络技术股份有限公司 一种实时视频通信传输控制方法
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JP2011014979A (ja) * 2009-06-30 2011-01-20 Fujitsu Ltd 無線通信システム、無線通信装置及び制御装置
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CN104253967A (zh) * 2014-09-26 2014-12-31 厦门亿联网络技术股份有限公司 一种实时视频通信传输控制方法

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