WO2012023516A1 - 通信制御方法、基地局装置及び移動局装置 - Google Patents
通信制御方法、基地局装置及び移動局装置 Download PDFInfo
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- WO2012023516A1 WO2012023516A1 PCT/JP2011/068458 JP2011068458W WO2012023516A1 WO 2012023516 A1 WO2012023516 A1 WO 2012023516A1 JP 2011068458 W JP2011068458 W JP 2011068458W WO 2012023516 A1 WO2012023516 A1 WO 2012023516A1
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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
- H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B7/0478—Special codebook structures directed to feedback optimisation
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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
- H04B7/06—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
- H04B7/0652—Feedback error handling
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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
- H04B7/06—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
- H04B7/0621—Feedback content
- H04B7/063—Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
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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
- H04B7/06—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 communication control method, a base station apparatus, and a mobile station apparatus, and more particularly to a communication control method, base station apparatus, and mobile station apparatus that support multi-antenna transmission.
- HSDPA High Speed Packet Access Access
- HSUPA High SpeckWed SpeckWed
- CDMA Wideband Code Division Multiple Access
- LTE Long Term Evolution
- the third generation system can achieve a maximum transmission rate of about 2 Mbps on the downlink using generally a fixed bandwidth of 5 MHz.
- a maximum transmission rate of about 300 Mbps on the downlink and about 75 Mbps on the uplink can be realized using a variable band of 1.4 MHz to 20 MHz.
- LTE-A LTE Advanced
- LTE-A LTE Advanced
- a MIMO (Multi Input Multi Output) system has been proposed as a wireless communication technology that improves the data rate (frequency utilization efficiency) by transmitting and receiving data with a plurality of antennas (for example, non-patent) Reference 1).
- a MIMO system a plurality of transmission / reception antennas are prepared in a transmitter / receiver, and different transmission information sequences are transmitted simultaneously from different transmission antennas.
- the data rate (frequency utilization efficiency) is increased by separating and detecting simultaneously transmitted information sequences using the fact that different fading fluctuations occur between transmission / reception antennas. Is possible.
- transmission information sequences transmitted simultaneously from different transmission antennas are all transmitted from a single user MIMO (SU-MIMO (Single User MIMO)), which is for the same user, and multi-information is transmitted from different users.
- SU-MIMO Single User MIMO
- MU-MIMO Multiple User MIMO
- a phase / amplitude control amount (precoding matrix (precoding weight)) to be set in the antenna of the transmitter on the receiver side and the precoding matrix are assigned.
- the optimal PMI from the codebook that defines multiple PMIs (Precoding Matrix Indicators) for each rank and feed back to the transmitter, and select the RI (Rank Indicator) indicating the optimal rank and feed back to the transmitter .
- the precoding weight for each transmission antenna is specified from the codebook based on the PMI and RI fed back from the receiver, and the transmission information sequence is transmitted by performing precoding.
- the throughput characteristics of the entire system largely depend on the precoding weights defined in the codebook. That is, the directivity of the transmission beam that transmits the transmission information sequence from the transmitter side to the receiver is determined by these precoding weights. For this reason, when the optimal precoding weight is not selected, it becomes difficult to form a transmission beam having effective directivity with respect to the receiver. Such a transmission beam causes an erroneous detection of a received signal in the receiver and causes a reduction in throughput. As a result, a situation occurs in which the throughput characteristics of the entire MIMO system deteriorate.
- the present invention has been made in view of such circumstances, and provides a communication control method, a base station apparatus, and a mobile station apparatus that can suppress degradation of throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- the purpose is to provide.
- a plurality of precoding weights and PMIs (Precoding Matrix Indicators) assigned to the precoding weights are determined, and the bit information of the PMI assigned to the precoding weights is transmitted from the first communication device.
- PMIs Precoding Matrix Indicators
- a communication control method using a code book adjusted so as to suppress the influence of the feedback error of the PMI, the step of feeding back the PMI selected from the code book to the second communication device, and the fed back PMI Comprises precoding a transmission signal based on the precoding weight allocated on the codebook, and transmitting the transmission signal to the first communication device.
- the base station apparatus of the present invention includes: a selection unit that selects the precoding weight from a code book that defines a plurality of precoding weights and PMIs assigned to the precoding weight; and the precoding weight selected by the selection unit.
- Precoding means for precoding the transmission signal based on the transmission signal, and transmission means for transmitting the transmission signal precoded by the precoding means to a mobile station apparatus, and the precoding in the codebook The PMI bit information allocated to the weight is adjusted so as to suppress the influence of the feedback error from the mobile station apparatus.
- the mobile station apparatus of the present invention includes: a selection unit that selects the PMI from a code book that defines a plurality of precoding weights and PMIs assigned to the precoding weight; and the PMI selected by the selection unit Feedback means for feeding back to the base station apparatus, and the bit information of the PMI allocated to the precoding weight in the codebook is adjusted so as to suppress the influence of the feedback error on the base station apparatus.
- the PMI bit information allocated to the precoding weight is adjusted in the codebook so as to suppress the influence of feedback error from the mobile station apparatus (feedback error for the base station apparatus). Yes. For this reason, even when a feedback error from the mobile station apparatus occurs, it is possible to avoid that precoding is performed with a precoding weight extremely different from the original precoding weight. As a result, it is possible to prevent a situation in which the throughput of the mobile station apparatus is remarkably lowered, and thus it is possible to suppress deterioration of throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- the present invention it is possible to suppress degradation of throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- FIG. 1 is a conceptual diagram of a MIMO system to which a communication control method according to the present invention is applied. It is explanatory drawing of the structure of the transmission beam transmitted with respect to a user apparatus from a base station apparatus in downlink MIMO transmission. It is explanatory drawing of the structure of the transmission beam formed by the precoding weight defined by the general codebook used by downlink MIMO transmission, and these precoding weights. It is explanatory drawing of the structural example of the transmission beam when a transmission error generate
- FIG. 1 is a conceptual diagram of a MIMO system to which a communication control method according to the present invention is applied.
- the base station apparatus eNodeB and the user apparatus UE are each provided with four antennas.
- the user apparatus UE measures the channel fluctuation amount using the received signal from each antenna, and based on the measured channel fluctuation quantity, the base station apparatus eNodeB Select PMI (Precoding Matrix Indicator) and RI (Rank Indicator) according to the phase / amplitude control amount (precoding weight) that maximizes the throughput (or reception SINR) after combining the transmission data from each transmit antenna To do. Then, the selected PMI and RI are fed back to the base station apparatus eNodeB on the uplink. In the base station apparatus eNodeB, after precoding transmission data based on the PMI and RI fed back from the user apparatus UE, information transmission is performed from each antenna.
- PMI Precoding Matrix Indicator
- RI Rank Indicator
- the signal separation / decoding unit 11 separates and decodes the control channel signal and the data channel signal included in the reception signals received via the reception antennas RX # 1 to RX # 4.
- the signal separation / decoding unit 11 performs a decoding process to reproduce a data channel signal for the user apparatus UE.
- the PMI selection unit 12 selects a PMI according to the channel state estimated by a channel estimation unit (not shown). At this time, the PMI selection unit 12 assigns N precoding weights (hereinafter, appropriately referred to as “weights”) known to both the user apparatus UE and the base station apparatus eNodeB and the PMIs assigned to the weights for each rank. An optimum PMI is selected from a plurality of codebooks 13 determined.
- the RI selection unit 14 selects an RI according to the channel state estimated by the channel estimation unit. These PMI and RI are transmitted as feedback information to the base station apparatus eNodeB.
- the precoding weight selection unit 21 selects or selects a weight for each transmission antenna from the codebook 22 based on PMI and RI fed back from the user apparatus UE.
- a weight suitable for the user apparatus UE is generated from the obtained weight.
- the precoding multiplication unit 23 multiplies the transmission signal parallel-converted by the serial / parallel conversion unit (S / P) 24 by a weight, thereby controlling the phase and amplitude for each of the transmission antennas TX # 1 to TX # 4. (shift.
- the phase / amplitude-shifted transmission data is transmitted from the four transmission antennas TX # 1 to TX # 4.
- a transmission beam having effective directivity toward the user apparatus UE is formed by performing the phase / amplitude shift of the transmission data with the weight based on PMI and RI fed back from the user apparatus UE.
- FIG. 2 is an explanatory diagram of a configuration of a transmission beam transmitted from the base station apparatus eNodeB to the user apparatus UE in downlink MIMO transmission.
- the right side and the left side shown in the figure are 0 degrees and 180 degrees, respectively, and the upper side and the lower side are 90 degrees and 270 degrees, respectively. Shall be shown.
- FIG. 2 with the base station apparatus eNodeB as the center, the right side and the left side shown in the figure are 0 degrees and 180 degrees, respectively, and the upper side and the lower side are 90 degrees and 270 degrees, respectively. Shall be shown.
- FIG. 2 is an explanatory diagram of a configuration of a transmission beam transmitted from the base station apparatus eNodeB to the user apparatus UE in downlink MIMO transmission.
- the user apparatus UE # 1 is located in the vicinity of the 0-degree direction from the base station apparatus eNodeB, and the user apparatus UE # 2 is located in the vicinity of the 60-degree direction from the base station apparatus eNodeB.
- the precoding weight selection unit 21 sets a weight for forming a transmission beam having directivity as indicated by a solid line in FIG. 22 is selected and precoding is performed.
- the base station apparatus eNodeB selects a weight for forming a transmission beam having directivity as indicated by a broken line in FIG. Do coding.
- FIG. 3A shows weights defined in a general codebook used in downlink MIMO transmission and PMIs assigned to these weights.
- FIG. 3B shows the configuration of the transmission beam formed by the weight shown in FIG. 3A.
- FIG. 3A shows a part of a code book to which an 8 ⁇ 8 DFT (Discrete Fourier Transform) matrix is applied (upper four rows for application to four transmission antennas).
- Each row illustrated in FIG. 3A corresponds to each transmission antenna included in the base station device eNodeB
- each column illustrated in FIG. 3A corresponds to a transmission stream from the base station device eNodeB.
- a set of weights corresponding to each column is referred to as “f 0 ” to “f 7 ”.
- weights f 0 to f 7 are each assigned a PMI composed of 3-bit bit information. That is, the weights f 0 is assigned "000”, the weight f 1 is assigned “001”, the weight f 2 is assigned “010”, the weight f 3 is assigned “011” Yes. Further, the weight f 4 is assigned “100”, the weight f 5 is assigned “101”, the weight f 6 are assigned the “110”, the weight f 7 is assigned "111” Yes.
- the transmission beam formed by the base station apparatus eNodeB with the weights f 0 to f 7 has directivity as shown in FIG. 3B, for example. That is, when the weight f 0 is used, a transmission beam having directivity mainly in the 0 degree direction and the 180 degree direction is formed (indicated by a thin solid line in FIG. 3B). When the weight f 1 is used, a transmission beam having directivity mainly in the 15-degree direction and the 165-degree direction is formed (indicated by a thin broken line in FIG. 3B). When using weights f 2 (shown by a chain line a thin one-dot in FIG. 3B) mainly 30 degree direction and the transmission beam is formed to have directivity in the 150 degree direction.
- weights f 3 When using weights f 3 (shown by a thin two-dot chain line in FIG. 3B) mainly 50 degree direction and transmit beam is formed having directivity in the 130 degree direction.
- a transmission beam having directivity mainly in the 90-degree direction and the 270-degree direction is formed (indicated by a thick solid line in FIG. 3B).
- weights f 5 which transmit beam is formed mainly directed against 230-degree direction and the 310 ° direction.
- weight f 6 When using the weight f 6 (shown by a thick one-dot chain line in FIG. 3B) primarily 210 ° direction and the transmission beam having directivity in a 330 degree direction is formed.
- weights f 7 When using weights f 7 (shown in bold in Figure 3B two-dot chain line) which mainly transmit beam having a directivity in 195 ° direction and the 345 ° direction is formed.
- the weights used for forming these transmission beams are selected or generated in the base station apparatus eNodeB based on the PMI fed back from the user apparatus UE. For this reason, when a transmission error occurs in bit information (hereinafter referred to as “PMI bit information” as appropriate) constituting the PMI from the user apparatus UE (that is, when a feedback error occurs in the PMI), transmission having a desired directivity is performed. A situation in which the beam cannot be formed may occur.
- the PMI is fed back from the user apparatus UE using PUCCH (Physical Uplink Control CHannel), but error detection using CRC (Cyclic Redundancy Check) is not performed on this PUCCH. For this reason, the PMI in which the feedback error has occurred is processed in the base station apparatus eNodeB in a state including erroneous bit information.
- PUCCH Physical Uplink Control CHannel
- CRC Cyclic Redundancy Check
- FIG. 4 is an explanatory diagram of a configuration example of a transmission beam when a transmission error occurs in PMI bit information fed back from the user apparatus UE using a general code book.
- the transmission beam formed by the weight f 0 is a desired transmission beam.
- PMI bit information of “000” is assigned to the weight f 0 .
- a transmission beam formed when a 1-bit transmission error occurs in PMI bit information “000” assigned to weight f 0 will be described. If a transmission error occurs in the bit on the right side, the PMI bit information becomes “001”, and a transmission beam corresponding to the transmission beam originally formed by the weight f 1 is formed. When a transmission error occurs in the center bit, the PMI bit information becomes “010”, and a transmission beam corresponding to the transmission beam originally formed by the weight f 2 is formed. Further, when a transmission error occurs in the left bit, the PMI bit information becomes “100”, and a transmission beam corresponding to the transmission beam originally formed by the weight f 4 is formed.
- a transmission beam having directivity is formed in the vicinity of the desired transmission beam.
- the false detection rate is low and can be accommodated with a certain decrease in throughput.
- a transmission beam having a directivity different from the desired transmission beam is formed.
- Such a transmission beam causes erroneous detection of a received signal in a desired user apparatus UE (user apparatus UE located in the vicinity of the 0-degree direction from the base station apparatus eNodeB) and causes a reduction in throughput.
- such a transmission beam does not have effective directivity with respect to a desired user apparatus UE, and reception power (gain) necessary for appropriately demodulating a reception signal may be insufficient.
- reception power (gain) necessary for appropriately demodulating a reception signal may be insufficient.
- the received signal cannot be demodulated appropriately, and as a result of erroneously detecting the received signal, the throughput decreases.
- the throughput characteristics of the entire MIMO system are deteriorated.
- This situation largely depends on the arrangement of the PMI bit information assigned to the weight. That is, in a general code book, the PMI bit information assigned to the weights is assigned to the respective weights so as to form an ascending order by a so-called binary system as shown in FIG. 3A.
- PMI bit information is assigned in this way, a 1-bit transmission error causes a reduction in throughput in a desired user apparatus UE.
- the present inventor has paid attention to the fact that the arrangement of the PMI bit information assigned to the weight in this way causes deterioration of the throughput characteristics in the MIMO system, and has come to the present invention.
- the PMI bit information allocated to the weight is adjusted from the user apparatus UE to the base station apparatus eNodeB using a code book adjusted so as to suppress the influence due to the feedback error from the user apparatus UE. Feedback and precoding of a transmission signal from the base station apparatus eNodeB to the user apparatus UE.
- this communication control method even when a feedback error from the user apparatus UE occurs, it is possible to avoid precoding with a weight extremely different from the original weight. As a result, it is possible to prevent a situation in which the throughput of the user apparatus UE is significantly reduced, and thus it is possible to suppress degradation of the throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- the bit information of the PMI assigned to the weight in the codebook is adjusted so as to suppress the influence of the transmission beam formed based on the PMI in which the feedback error has occurred.
- FIG. 5 is an explanatory diagram showing an example of the configuration of the weights defined in the codebook used in the communication control method according to the first aspect of the present invention and the PMI (PMI bit information) assigned to these weights.
- 5 shows PMI (PMI bit information) in the general code book shown in FIG. 3 for convenience of explanation.
- FIG. 5 shows an example of a code book used in the communication control method according to the present invention, and the present invention is not limited to this.
- the PMI bit information is configured in an ascending order by a so-called binary system.
- the gray coding is a coding method in which adjacent values (that is, PMI bit information) are arranged so that the Hamming distance is always 1.
- weights PMI bits information f 2 assigns a PMI bit information "011” of the weight f 3 shown in FIG. 3, PMI bits Weight f 3
- the PMI bit information “010” of the weight f 2 shown in FIG. 3 is assigned to the information.
- the PMI bit information of the weight f 4 allocates the PMI bit information "110” of the weight f 6 shown in FIG. 3, the PMI bit information of the weight f 5, PMI bit information weights f 7 shown in FIG. 3 " 111 "is assigned.
- the PMI bit information of the weight f 6 assigns a PMI bit information "101" of the weight f 5 shown in FIG.
- FIG. 6 is an explanatory diagram of a configuration example of a transmission beam when a transmission error occurs in PMI bit information fed back from the user apparatus UE using the code book according to the first aspect.
- the transmission beam formed by the weight f 0 is a desired transmission beam.
- the code book according to the first aspect when used, it is formed with the original weight f 0 even when a transmission error occurs in the PMI bit information, compared to the case where the code book shown in FIG. 3 is used. It is possible to avoid the formation of a transmission beam having a directivity extremely different from that of the transmission beam. Thereby, since the ratio of the erroneous detection of the received signal in the desired user apparatus UE (the user apparatus UE located near the 0-degree direction from the base station apparatus eNodeB) can be reduced, the throughput in the user apparatus UE can be reduced. Can be suppressed. As a result, it is possible to suppress a situation in which the throughput characteristic of the entire MIMO system deteriorates.
- the user apparatus UE and the base station apparatus eNodeB both have two codebooks (hereinafter referred to as “double codebook” as appropriate), and consider a method of feeding back feedback information including PMI at different periods for different communication bands. Has been.
- codebook W1 a first codebook for long period / wideband
- codebook W2 a second codebook for narrowband
- a plurality of weights known to both the user apparatus UE and the base station apparatus eNodeB and the weights are assigned to the weights, as in a general code book (for example, the code book shown in FIG. 3).
- PMI is included.
- the weight for each transmission antenna is selected from the codebooks W1 and W2 based on the PMI fed back from the user apparatus UE, and after precoding transmission data using this weight, Information is transmitted from the antenna.
- the base station apparatus eNodeB has a PMI selected from the codebook W1 (hereinafter referred to as “PMI 1 ”) and a PMI selected from the codebook W2 (hereinafter referred to as “PMI 2 ”).
- PMI 1 a PMI selected from the codebook W1
- PMI 2 a PMI selected from the codebook W2
- the code book according to the first aspect can also be applied to such a double code book.
- a specific example in which the code book according to the first aspect is applied to a double code book will be described.
- the codebook W1 includes a set of N weights (hereinafter referred to as “weight subset”) known to both the user apparatus UE and the base station apparatus eNodeB, and PMI 1 assigned to the weight subset.
- weight subset a weight having an effect of selecting and phase-controlling a specific weight in the weight subset defined in the code book W1 and a PMI 2 assigned to the weight are defined. It shall be.
- the weight subset is obtained by grouping all weights defined in the code book W1 into a predetermined number of groups.
- a weight subset is selected based on PMI 1 fed back from the user apparatus UE in a long cycle, and is optimal from the weight subsets according to PMI 2 fed back in a short cycle.
- a proper weight can be selected and phase controlled.
- FIG. 7 is an explanatory diagram of a configuration example of a transmission beam formed by the weight subset selected from the first codebook W1.
- FIG. 7 shows a case where a weight subset is configured by dividing all (in this case, 16) weights defined in the codebook W1 into eight groups. Note that adjacent weight subsets include two overlapping weights.
- 7A to 7H show transmission beams formed by the respective weight subsets selected from the code book W1.
- the transmission beam formed by each weight subset includes transmission beams having four directivities.
- the weight subsets shown in FIGS. 7A to 7H are referred to as “fs 0 ” to “fs 7 ”.
- base station apparatus eNodeB selects a weight subset that forms a transmission beam shown in any of FIGS. 7A to 7H. Then, when the PMI 2 selected from the code book W2 is fed back from the user apparatus UE, the base station apparatus eNodeB selects an optimal weight from these weight subsets. For example, when PMI 2 is fed back after PMI 1 corresponding to the weight subset forming the transmission beam shown in FIG. 7C is fed back, the weight forming one of the transmission beams shown in FIG. 7C is selected. It becomes.
- PMI bit information is assigned to each weight subset of the code book W1 so as to form an ascending order by a so-called binary system
- PMI bit information as shown in FIG. 8 is assigned. That is, the weight subset fs 0 is assigned "000”, weights to a subset fs 1 is assigned “001”, the weight subset fs 2 is assigned “010”, the weight subset fs 3 "011” Is assigned.
- the weight subset fs 4 is assigned "100”
- the weight subset fs 5 is assigned "101"
- "110” is assigned to the weight subset fs 6
- 111" is assigned to the weight subset fs 7 It has been.
- weight subset fs 0 is a desired weight subset. Also, a description will be given of a transmission beam formed when a 1-bit transmission error occurs in PMI bit information “000” assigned to weight subset fs 0 .
- the PMI bit information becomes “001”, and a transmission beam corresponding to the transmission beam originally formed by the weight subset fs 1 is formed. . If a transmission error occurs in the central bit, the PMI bit information becomes “010”, and a transmission beam corresponding to the transmission beam originally formed by the weight subset fs 2 is formed. Further, when a transmission error occurs in the left bit, the PMI bit information is “100”, and a transmission beam corresponding to the transmission beam originally formed by the weight subset fs 4 is formed. .
- PMI bit information is assigned to the weight subsets fs 0 to fs 7 defined in the code book W1 used in the communication control method according to the first aspect. Allocation of these PMI bit information is performed by gray coding as in the case shown in FIG. That is, the weight subset fs 2 to PMI bits of information, assigns the "011" PMI bit information of the weight subset fs 3 shown in FIG. 8, the PMI bit information of the weight subset fs 3, wait subset fs 2 shown in FIG. 8 PMI bit information “010” is assigned. Moreover, the PMI bit information Wait subset fs 4, allocates the PMI bit information "110" of the weight subset fs 6 shown in FIG.
- the PMI bit information Wait subset fs 5, weight subset fs 7 shown in FIG. 8 PMI bit information “111” is assigned.
- the weight subset fs 6 to PMI bits of information assigns the "101" PMI bits information Wait subset fs 5 shown in FIG. 8, the PMI bit information Wait subset fs 7, wait subset fs 4 shown in FIG. 8 PMI bit information “100” is assigned.
- the weight subsets fs 0 and fs 1 are assigned the same PMI bit information “000” and “001” as the weight subsets fs 0 and fs 1 shown in FIG.
- the code book W1 according to the first aspect when used, it is formed by the original weight subset f S0 when a transmission error occurs in the PMI bit information, compared to the case where the code book shown in FIG. 8 is used. It is possible to reduce the rate at which a transmission beam having a directivity extremely different from that of the transmission beam is formed. Thereby, since the ratio of the erroneous detection of the received signal in the desired user apparatus UE can be reduced, it is possible to suppress a decrease in throughput in the user apparatus UE. As a result, it is possible to suppress a situation in which the throughput characteristic of the entire MIMO system deteriorates.
- the PMI bit information is assigned to each weight of the code book W2 so as to form an ascending order by a so-called binary system
- the PMI bit information as shown in FIG. 10 is assigned. That is, the weight f 10 is assigned "00", the weight f 11 is assigned “01”, the weight f 12 is assigned “10”, the weight f 13 is assigned "11" Yes.
- weight f 11 is the desired weight. Further, a description will be given of the transmission beam transmission error of one bit PMI bit information allocated to the weight f 11 "01" is formed in the event of.
- the PMI bit information becomes “00”, and a transmission beam corresponding to the transmission beam originally formed by the weight f 10 is formed.
- the PMI bit information becomes “11”, and a transmission beam corresponding to the transmission beam originally formed by the weight subset f 13 is formed. .
- PMI bit information is assigned to the weights f 10 to f 13 defined in the code book W2 used in the communication control method according to the first aspect. Allocation of these PMI bit information is performed by gray coding as in the case shown in FIGS. That is, the bit information of the weight f 12, allocates the bit information "11" weights f 13 shown in FIG. 10A, the bit information of the weight f 13, the "10" bit information weights f 12 shown in FIG. 10A assignment ing. By assigning bit information to weights f 10 to f 13 in this manner, the Hamming distance of PMI bit information assigned to adjacent weights is always 1.
- PMI bit information is assigned to weights (weight subsets) by gray coding.
- the PMI is composed of more bit information of 3 bits or more, there is a situation in which the assignment of PMI bit information weights by Gray coding cannot optimally suppress the degradation of the throughput characteristics of the entire system. Can do.
- code book used in the communication control method according to the second aspect of the present invention (code book according to the second aspect) it is selected when a transmission error occurs in the PMI bit information fed back from the user apparatus UE.
- the PMI bit information is assigned to the weights so that the sum of the angular differences of the transmission beams formed by the obtained weights (hereinafter referred to as “transmission beam based on transmission error”) is minimized.
- transmission beam based on transmission error allocation of PMI bit information in the code book according to the second aspect will be described using a specific example. In the following description, for convenience of explanation, a description will be given using a transmission beam formed by weights corresponding to PMI bit information in the codebook.
- FIG. 11 is a diagram for explaining assignment of PMI bit information in the code book according to the second mode.
- produces in the PMI bit information fed back from the user apparatus UE using the general code book is shown.
- transmission beam B 0 a transmission beam formed by the weight f 0
- transmission beam B 0 a transmission beam formed by the weight f 0
- transmission beam B ′ 1 the transmission beam originally formed by the weights f 1 , f 2 and f 4 (hereinafter referred to as “transmission beam B ′ 1 ”, “transmission beam B ′ 2 ” and “transmission beam B ′ 4 ”, respectively).
- transmission beams B ′ 1 , B ′ 2 and B ′ 4 constitute a transmission beam based on a transmission error.
- the transmission beam B'1 has a transmission beam B 0 and the angle difference delta 0, 1
- transmitted beam B'2 has a transmission beam B 0 and the angle difference delta 0, 2
- transmit beam B ' 4 has an angular difference ⁇ 0,3 with the transmission beam B 0 .
- the sum of the angular differences between the transmission beam B 0 and the transmission beams (transmission beams B ′ 1 , B ′ 2 and B ′ 4 ) based on these transmission errors is PMI bit information is assigned to a weight so as to be minimized.
- Equation 1 The sum of the angular errors between the transmission beam B 0 and these transmission beams B ′ 1 , B ′ 2 and B ′ 4 is obtained by (Equation 1) shown below.
- Equation 1 “i” indicates PMI bit information of a desired transmission beam, and “j” indicates PMI bit information of the transmission beam based on a transmission error.
- “ ⁇ i, j ” is a function for calculating the sum of angle differences from the PMI bit information of the desired transmission beam and the PMI bit information of the transmission beam based on the transmission error.
- the transmission beam based on the transmission error can be brought close to the desired transmission beam.
- the ratio of the erroneous detection of the received signal in the desired user apparatus UE can be reduced, it is possible to suppress a decrease in throughput in the user apparatus UE.
- the PMI bit information is assigned to the weight so that the sum of the angular differences of the transmission beams based on the transmission error is minimized, regardless of the number of bits of the PMI bit information, Since the transmission beam based on these transmission errors can be brought close to the desired transmission beam, even when the PMI is composed of bit information of 3 bits or more, it effectively effectively degrades the throughput characteristics of the entire system. It becomes possible to suppress.
- the communication control method using the code book according to the second aspect can be applied to the MIMO system using the double code book described above.
- the feedback information from the user apparatus UE includes CQI (Channel Quality Indicator) corresponding to this PMI in addition to the PMI.
- CQI Channel Quality Indicator
- the CQI when the user apparatus UE feeds back a PMI whose PMI bit information is “000”, the CQI when the weight corresponding to the PMI is used is notified to the base station apparatus eNodeB. Therefore, if the PMI is erroneously selected in the base station apparatus eNodeB, the value becomes lower than the CQI fed back at the time of actual data reception, and the false detection rate of the received signal increases.
- the value of the transmission array gain (array gain) has the most influence on the CQI value measured by the user apparatus UE during actual data reception.
- the transmission array gain is a gain obtained by using a plurality of transmission antenna elements (arrays) and effectively adding power of radio waves transmitted from each array by the user apparatus UE.
- transmission occurs when a transmission error occurs in the PMI bit information fed back from the user apparatus UE.
- the PMI bit information is assigned to the weight so that the sum of the array gains in the transmission beam based on the error is maximized.
- allocation of PMI bit information in the codebook according to the third aspect will be described using an example shown in FIG.
- the PMI bit is set so that the sum of the array gains in the transmission beams (transmission beams B ′ 1 , B ′ 2 and B ′ 4 ) based on these transmission errors is maximized. Assign information to weights.
- Equation 2 The sum of the array gains of the transmission beams based on the transmission error can be obtained by (Equation 2) shown below.
- Equation 2 Here, “i” indicates PMI bit information of a desired transmission beam, and “j” indicates PMI bit information of the transmission beam based on a transmission error.
- F j H f i is a function for calculating the sum of array gains from PMI bit information of a desired transmission beam and PMI bit information of the transmission beam based on a transmission error.
- the code book according to the third aspect when used, even when a transmission error occurs in the PMI bit information, the reception gain in the user apparatus UE based on the transmission beam based on the transmission error can be ensured. Thereby, since the ratio of the erroneous detection of the received signal in the desired user apparatus UE can be reduced, it is possible to suppress a decrease in throughput in the user apparatus UE. As a result, it is possible to suppress a situation in which the throughput characteristic of the entire MIMO system deteriorates.
- the PMI bit information is assigned to the weight so that the sum of the array gains of the transmission beams based on the transmission error is maximized, regardless of the number of bits of the PMI bit information, Since the transmission beam based on these transmission errors can be brought close to the desired transmission beam, even when the PMI is composed of bit information of 4 bits or more, it effectively effectively degrades the throughput characteristics of the entire system. It becomes possible to suppress.
- the communication control method using the code book according to the third aspect can also be applied to the MIMO system using the above-described double code book.
- PMI bit information is assigned to weights so as to minimize the sum of angle differences or maximize the sum of array gains.
- These techniques are suitable for improving on average the adverse effects on the transmit beam based on all transmission errors in the codebook.
- the allocation of PMI bit information is not limited to these methods, and can be changed as appropriate. For example, among the transmission beams based on the transmission error, only the transmission beam having the most adverse effect (for example, the transmission beam B ′ 4 shown in FIG. 11) may be noticed, and this adverse effect may be improved.
- the communication control method it is conceivable to assign the PMI bit information to the weight so as to minimize the angle error of the transmission beam having the maximum angle error.
- the communication control method it is conceivable to assign the PMI bit information to the weight so as to maximize the reception gain of the transmission beam having the smallest reception gain.
- FIG. 12 is a diagram for explaining the configuration of the mobile communication system 1 including the mobile station apparatus 10 and the base station apparatus 20 according to an embodiment of the present invention.
- the mobile communication system 1 shown in FIG. 12 is a system including, for example, an LTE system or SUPER 3G.
- the mobile communication system 1 may be called IMT-Advanced or 4G.
- the mobile communication system 1 includes a base station device 20 and a plurality of mobile station devices 10 (10 1 , 10 2 , 10 3 ,... 10 n , n communicating with the base station device 20. Is an integer of n> 0).
- the base station apparatus 20 is connected to the higher station apparatus 30, and the higher station apparatus 30 is connected to the core network 40.
- the mobile station device 10 communicates with the base station device 20 in the cell 50.
- the upper station device 30 includes, for example, an access gateway device, a radio network controller (RNC), a mobility management entity (MME), and the like, but is not limited thereto.
- RNC radio network controller
- MME mobility management entity
- each mobile station apparatus (10 1 , 10 2 , 10 3 ,... 10 n ) has the same configuration, function, and state, the following description will be given as the mobile station apparatus 10 unless otherwise noted. Proceed. For convenience of explanation, it is assumed that the mobile station device 10 is in radio communication with the base station device 20, but more generally, user equipment (UE: User Equipment) including both the mobile station device and the fixed terminal device. It's okay.
- UE User Equipment
- OFDMA Orthogonal Frequency Division Multiple Access
- SC-FDMA Single Carrier Frequency Division Multiple Access
- OFDMA is a multi-carrier transmission scheme that performs communication by dividing a frequency band into a plurality of narrow frequency bands (subcarriers) and mapping data to each subcarrier.
- SC-FDMA is a single carrier transmission method that reduces interference between terminals by dividing a system band into bands each consisting of one or continuous resource blocks for each terminal, and a plurality of terminals using different bands. .
- PDSCH Physical Downlink Shared CHannel
- PDCCH Physical Downlink Control CHannel
- PCFICH Physical Control Format Indicator CHannel
- PHICH Physical Hybrid-ARQ Indicator CHannel
- User data that is, a normal data signal is transmitted by this PDSCH. Transmission data is included in this user data.
- the component carrier CC and scheduling information allocated to the mobile station device 10 by the base station device 20 are notified to the mobile station device 10 through the L1 / L2 control channel.
- PUSCH Physical Uplink Shared CHannel
- PUCCH Physical Uplink Control CHannel
- User data is transmitted by this PUSCH.
- downlink radio quality information CQI: Channel Quality Indicator
- CQI Channel Quality Indicator
- FIG. 13 is a block diagram showing a configuration of mobile station apparatus 10 according to the present embodiment.
- FIG. 14 is a block diagram showing a configuration of base station apparatus 20 according to the present embodiment. Note that the configurations of the mobile station apparatus 10 and the base station apparatus 20 shown in FIGS. 13 and 14 are simplified for explaining the present invention, and the configurations of the normal mobile station apparatus and the base station apparatus are as follows. It shall be provided.
- the transmission signals transmitted from the base station apparatus 20 are received by the receiving antennas RX # 1 to RX # N, and are transmitted by the duplexers 101 # 1 to 101 # N. And the receiving path are output to the RF receiving circuits 102 # 1 to 102 # N. Then, the RF receiving circuits 102 # 1 to 102 # N perform frequency conversion processing for converting radio frequency signals into baseband signals.
- the baseband signal subjected to the frequency conversion processing is subjected to cyclic prefix (CP) removal units 103 # 1 to 103 # N after the CP is removed, and then to a fast Fourier transform unit (FFT unit) 104 # 1 to 104. Is output to #N.
- CP cyclic prefix
- FFT unit fast Fourier transform unit
- the reception timing estimation unit 105 estimates the reception timing from the reference signal included in the reception signal, and notifies the CP removal units 103 # 1 to 103 # N of the estimation result.
- the FFT units 104 # 1 to 104 # N perform a Fourier transform on the input received signals, and convert the time series signals into frequency domain signals. Thereafter, the data channel signal included in the received signal is output to data channel signal demodulation section 106.
- the data channel signal demodulator 106 uses, for example, the mean square error minimum (MMSE: Minimum Mean Squared Error) or maximum likelihood estimation detection (MLD: Maximum) for the data channel signals input from the FFT units 104 # 1 to 104 # N. Likelihood Detection) Separation by signal separation method. As a result, the data channel signal arriving from the base station apparatus 20 is separated into data channel signals relating to the users # 1 to #k, and the data channel signal relating to the user of the mobile station apparatus 10 (here, referred to as the user k) is Extracted.
- MMSE Minimum Mean Squared Error
- MLD Maximum
- Channel estimation section 107 estimates the channel fluctuation amount in the channel propagation path from the reference signal included in the received signals output from FFT sections 104 # 1 to 104 # N, and uses the estimated channel fluctuation quantity as data channel signal demodulation section 106. And a channel quality measurement unit 109 and a rank / precoding weight selection unit 110 to be described later.
- the data channel signal demodulator 106 separates the data channel signal by the MLD signal separation method described above based on the notified channel fluctuation amount. Thereby, the received signal regarding the user k is demodulated.
- the extracted data channel signal related to the user k Prior to demodulation processing by the data channel signal demodulating unit 106, the extracted data channel signal related to the user k is demapped by a subcarrier demapping unit (not shown) and returned to a time-series signal. To do.
- the data channel signal relating to user k demodulated by data channel signal demodulating section 106 is output to channel decoding section 108. Then, a channel decoding process is performed by the channel decoding unit 108 to reproduce a transmission signal for the user k (hereinafter referred to as “transmission signal #k”).
- the channel quality (CQI) measurement unit 109 measures the channel quality (CQI) based on the channel fluctuation amount notified from the channel estimation unit 107.
- Channel quality (CQI) measurement section 109 notifies CQI as a measurement result to rank / precoding weight selection section 110 and feedback control signal generation section 111.
- Rank / precoding weight selection section 110 constitutes selection means, and selects rank (RI) and precoding weight (PMI) from the codebook based on the channel fluctuation amount notified from channel estimation section 107. . Then, the selected precoding weight (PMI) is notified to the precoding multiplier 114, and the selected rank (RI) and precoding weight (PMI) are notified to the feedback control signal generator 111.
- the rank / precoding weight selection unit 110 uses the weight (from the code book in which the PMI bit information is assigned to the weight by Gray coding ( PMI) is selected. Further, when the communication control method according to the second aspect is applied, the weight (PMI) from the code book in which the PMI bit information is assigned to the weight so that the sum of the angle errors of the transmission beam based on the transmission error is minimized. Select. Further, when the communication control method according to the third aspect is applied, the weight (PMI) from the code book in which the PMI bit information is assigned to the weight so that the sum of the array gains in the transmission beam based on the transmission error is maximized. Select. When the mobile communication system is configured by a MIMO system using a double codebook, rank / precoding weight selection section 110 receives weight (PMI 1 ) and weight (PMI 2 ) from codebooks W1 and W2 described above. ) Is selected.
- PMI Gray coding
- feedback control signal generation section 111 feedback information is fed back to base station apparatus 20 based on CQI, PMI and RI notified from channel quality (CQI) measurement section 109 and rank / precoding weight selection section 110.
- a control signal including PUCCH (for example, PUCCH) is generated.
- the control signal generated by the feedback control signal generation unit 111 is output to the multiplexer (MUX) 115.
- MUX multiplexer
- transmission data #k related to user #k sent from the upper layer is channel-encoded by channel encoder 112, then subcarrier-modulated by data modulator 113, and output to precoding multiplier 114.
- the Reference signal #k related to user #k generated by a reference signal generator (not shown) is input to precoding multiplier 114.
- the precoding multiplication unit 114 Based on the weight obtained from the PMI selected by the rank / precoding weight selection unit 110, the precoding multiplication unit 114 converts the transmission data #k and the reference signal for each of the reception antennas RX # 1 to RX # N and the phase and / or reference signal. Or amplitude shift.
- the phase and / or amplitude-shifted transmission data #k and the reference signal are output to the multiplexer (MUX) 115.
- MUX multiplexer
- the multiplexer (MUX) 115 the transmission data #k and the reference signal #k that have been phase-shifted and / or amplitude-shifted and the control signal generated by the feedback control signal generation unit 111 are combined and received by the receiving antennas RX # 1 ⁇ RX # 1.
- a transmission signal is generated for each RX # N.
- the transmission signal generated by the multiplexer (MUX) 115 is subjected to discrete Fourier transform by the discrete Fourier transform units (DFT) 116 # 1 to 116 # N, and each transmission signal sequence has a transmission bandwidth (DFT size) in the frequency domain. Diffused.
- DFT discrete Fourier transform unit
- the inverse fast Fourier transform units (IFFT) 117 # 1 to 117 # N perform inverse fast Fourier transform to convert the frequency domain signal into the time domain signal, and then add the CP adding units 118 # 1 to 118 # N. Then, the CP is added and output to the RF transmission circuits 119 # 1 to 119 # N. Then, after frequency conversion processing for conversion into a radio frequency band is performed by the RF transmission circuits 119 # 1 to 119 # N, the reception antennas RX # 1 to RX # are passed through the duplexers 101 # 1 to 101 # N. N is output from the reception antennas RX # 1 to RX # N to the base station apparatus 20 via the uplink.
- These transmission system processing units constitute feedback means for feeding back feedback information to the base station apparatus 20.
- PMI is selected from the codebooks according to the first to third aspects, and feedback information including this PMI is fed back to base station apparatus 20. Therefore, the PMI bit information adjusted so as to suppress the influence of the feedback error on the base station apparatus 20 can be fed back to the base station apparatus 20.
- the transmission signal transmitted from the mobile station apparatus 10 is received by the transmission antennas TX # 1 to TX # N, and is transmitted by the duplexers 201 # 1 to 201 # N. And the reception path are output to the RF reception circuits 202 # 1 to 202 # N. Then, frequency conversion processing for converting a radio frequency signal into a baseband signal is performed in the RF reception circuits 202 # 1 to 202 # N.
- the baseband signal that has been subjected to frequency conversion processing is subjected to CP removal by cyclic prefix (CP) removal sections 203 # 1 to 203 # N, and then fast Fourier transform sections (FFT sections) 204 # 1 to 204. Is output to #N.
- CP cyclic prefix
- Reception timing estimation section 205 estimates reception timing from a reference signal included in the reception signal, and notifies the CP removal sections 203 # 1 to 203 # N of the estimation result.
- the FFT units 204 # 1 to 204 # N perform Fourier transform on the input received signals, and convert the time-series signals into frequency domain signals.
- the received signal converted into the frequency domain signal is subjected to inverse discrete Fourier transform by inverse discrete Fourier transform units (IDFT) 206 # 1 to 206 # N and despread into a time domain signal. Thereafter, the data channel signal included in the received signal is output to data channel signal demodulation sections 207 # 1 to 207 # N.
- IDFT inverse discrete Fourier transform units
- Data channel signal demodulation sections 207 # 1 to 207 # k use the data channel signals input from IDFT sections 206 # 1 to 206 # N, for example, mean square error minimum (MMSE) or maximum likelihood estimation detection (MLD). Separate by signal separation method. As a result, the data channel signals coming from the mobile station apparatus 10 are separated into data channel signals related to the users # 1 to #k, and the data channel signals related to the respective mobile station apparatuses 10 are extracted.
- MMSE mean square error minimum
- MLD maximum likelihood estimation detection
- Channel estimation sections 208 # 1 to 208 # k estimate channel fluctuation amounts from reference signals included in the received signals output from IDFT sections 206 # 1 to 206 # N, and the estimated channel fluctuation amounts are demodulated as data channel signals.
- Data channel signal demodulation sections 207 # 1 to #k separate the data channel signal by the MLD signal separation method described above based on the notified channel fluctuation amount. Thereby, the received signal regarding each mobile station apparatus 10 is demodulated.
- the extracted data channel signals relating to each mobile station apparatus 10 are demapped by a subcarrier demapping unit (not shown) and returned to a time-series signal. It shall be.
- the data channel signals related to the respective mobile station apparatuses 10 demodulated by the data channel signal demodulation units 207 # 1 to 207 # k are output to the channel decoding units 209 # 1 to 209 # k.
- parallel / serial conversion is performed by parallel / serial conversion section (P / S) 210, whereby each mobile station apparatus 10 Data channel signals (data signals) are reproduced.
- Control channel signal demodulation sections 211 # 1 to 211 # k demodulate control channel signals (for example, PDSCH) included in the received signals input from IDFT sections 206 # 1 to 206 # k. At this time, control channel signal demodulation sections 211 # 1 to 211 # k demodulate control channel signals based on the channel fluctuation amounts notified from channel estimation sections 208 # 1 to #k.
- the control channel signal includes feedback information from the mobile station apparatus 10. This feedback information includes RI, PMI, and CQI selected by the mobile station apparatus 10.
- the control channel signals demodulated by control channel signal demodulation sections 211 # 1 to 211 # k are output to rank / MCS selection sections 214 # 1 to 214 # k and precoding weight selection section 213, which will be described later.
- the fading correlation estimation unit 212 estimates the fading correlation value of the channel propagation path based on the channel fluctuation amount notified from the channel estimation units 208 # 1 to 208 # k. Then, fading correlation estimation section 212 notifies precoding weight selection section 213 of the estimated fading correlation value.
- Precoding weight selection section 213 constitutes selection means, and is notified from feedback information (RI and PMI) output from control channel signal demodulation sections 211 # 1 to 211 # k and from fading correlation estimation section 212. A rank (RI) and a weight (PMI) are selected from the codebook based on the fading correlation value. Then, the precoding weight selection unit 213 notifies the precoding weight generation unit 215 of the selected rank (RI) and weight (PMI).
- the precoding weight selection unit 213 uses the weight (PMI) from the codebook in which the PMI bit information is assigned to the weight by gray coding. Select. Further, when the communication control method according to the second aspect is applied, the weight (PMI) from the code book in which the PMI bit information is assigned to the weight so that the sum of the angle errors of the transmission beam based on the transmission error is minimized. Select. Further, when the communication control method according to the third aspect is applied, the weight (PMI) from the code book in which the PMI bit information is assigned to the weight so that the sum of the array gains in the transmission beam based on the transmission error is maximized. Select. When the mobile communication system is configured with a MIMO system using a double codebook, the precoding weight selection unit 213 obtains weights (PMI 1 ) and weights (PMI 2 ) from the codebooks W1 and W2, respectively. select.
- Rank / MCS Modulation and Coding Scheme selection sections 214 # 1 to 214 # k select rank / MCS based on the control channel signals notified from control channel signal demodulation sections 211 # 1 to 211 # k.
- the selected rank / MCS is output to channel coding sections 217 # 1 to 217 # k and data modulation sections 218 # 1 to 218 # k, which will be described later.
- the precoding weight generation unit 215 generates a weight for actually performing precoding on transmission data based on the rank (RI) and weight (PMI) notified from the precoding weight selection unit 213. For example, the precoding weight generation unit 215 generates a weight in consideration of zero-forcing for removing interference. The selected weight is output to precoding multiplication sections 220 # 1 to 220 # k described later.
- transmission data # 1 to #k for users # 1 to #k are output to serial / parallel converter (S / P) 216, and after serial / parallel conversion, correspond to each user # 1 to #k. Output to channel coding sections 217 # 1 to 217 # k.
- the serial / parallel conversion in the serial / parallel converter (S / P) 216 is performed based on the number of multiple users notified from a scheduler (not shown).
- the rank / MCS notified from the rank / MCS selection units 214 # 1 to 214 # k is referred to.
- the serial / parallel converted transmission data # 1 to #k are channel-encoded by the channel encoders 217 # 1 to 217 # k and then output to the data modulators 218 # 1 to 218 # k for data modulation. Is done. At this time, channel coding and data modulation are performed based on MCS given from rank / MCS selection sections 214 # 1 to 214 # k. Transmission data # 1 to #k data-modulated by data modulators 218 # 1 to 218 # k are subjected to inverse Fourier transform by a discrete Fourier transform unit (not shown), and converted from a time-series signal to a frequency domain signal. It is output to the subcarrier mapping unit 219.
- the subcarrier mapping unit 219 maps the transmission data # 1 to #k to subcarriers according to schedule information given from a scheduler (not shown). At this time, subcarrier mapping section 219 maps (multiplexes) reference signals # 1 to #k input from a reference signal generation section (not shown) to subcarriers together with transmission data # 1 to #k. Transmission data # 1 to #k mapped to subcarriers in this way are output to precoding multipliers 220 # 1 to 220 # k.
- Precoding multipliers 220 # 1 to 220 # k constitute precoding means, and transmit data for each of transmission antennas TX # 1 to TX # N based on the weight given from precoding weight generator 215. # 1 to #k are phase and / or amplitude shifted (weighting of transmission antennas TX # 1 to TX # N by precoding). Then, the transmission data # 1 to #k shifted in phase and / or amplitude by the precoding multiplier 220 are output to the multiplexer (MUX) 221.
- MUX multiplexer
- the multiplexer (MUX) 221 combines the transmission data # 1 to #k shifted in phase and / or amplitude, and generates transmission signals for the transmission antennas TX # 1 to TX # N.
- the transmission signal generated by the multiplexer (MUX) 221 is subjected to inverse fast Fourier transform by inverse fast Fourier transform units (IFFT) 222 # 1 to 222 # N, and converted from a frequency domain signal to a time domain signal. Then, after the CPs are added by the cyclic prefix (CP) adding units 223 # 1 to 223 # N, they are output to the RF transmission circuits 224 # 1 to 224 # N.
- IFFT inverse fast Fourier transform units
- the transmission antennas TX # 1 to TX # are transmitted via the duplexers 201 # 1 to 201 # N.
- N is transmitted to the mobile station apparatus 10 via the downlink from the transmission antennas TX # 1 to TX # N.
- these transmission system processing units constitute transmission means for transmitting a transmission signal to the mobile station apparatus 10.
- PMI is selected from the codebook used in the communication control method according to the first to third aspects, and the base station apparatus 20 responds to the weight generated based on this PMI. Therefore, even when a feedback error from the mobile station apparatus 10 occurs, it is possible to avoid precoding with a weight that is extremely different from the original weight. . As a result, it is possible to prevent a situation in which the throughput in the mobile station apparatus 10 is significantly reduced, and thus it is possible to suppress deterioration in throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- the PMI bit information allocated to the weight is adjusted in the codebook so as to suppress the influence of the feedback error from the mobile station apparatus 10. For this reason, even when a feedback error from the mobile station apparatus 10 occurs, it is possible to avoid precoding with a weight that is extremely different from the original weight. As a result, it is possible to prevent a situation in which the throughput in the mobile station apparatus 10 is significantly reduced, and thus it is possible to suppress deterioration in throughput characteristics of the entire system in a mobile communication system that performs MIMO transmission.
- the adjustment method when allocating PMI bit information to weights is not limited to this, and it is affected by feedback errors from mobile station apparatus 10 (including errors other than PMI bit information transmission errors). Arbitrary adjustment methods for suppressing the above are included.
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Abstract
Description
(式1)
ここで、「i」は所望の送信ビームのPMIビット情報を示し、「j」は、送信エラーに基づく送信ビームのPMIビット情報を示している。また、「Δi,j」は、所望の送信ビームのPMIビット情報と、送信エラーに基づく送信ビームのPMIビット情報とから角度差の総和を算出するための関数である。
(式2)
ここで、「i」は所望の送信ビームのPMIビット情報を示し、「j」は、送信エラーに基づく送信ビームのPMIビット情報を示している。また、「fj Hfi」は、所望の送信ビームのPMIビット情報と、送信エラーに基づく送信ビームのPMIビット情報とからアレイ利得の総和を算出するための関数である。
Claims (11)
- プリコーディングウェイトと当該プリコーディングウェイトに割り当てられるPMI(Precoding Matrix Indicator)とを複数定め、前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、第1の通信装置からのフィードバックエラーによる影響を抑制するように調整したコードブックを用いた通信制御方法であって、
前記コードブックから選択された前記PMIを第2の通信装置にフィードバックするステップと、フィードバックされた前記PMIが前記コードブック上で割り当てられた前記プリコーディングウェイトに基づいて送信信号のプリコーディングを行うステップと、前記送信信号を前記第1の通信装置に送信するステップとを具備することを特徴とする通信制御方法。 - 前記コードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される送信ビームの影響を抑制するように調整したことを特徴とする請求項1記載の通信制御方法。
- 前記コードブックに定められた隣り合う前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、互いのビット情報同士のハミング距離が常に1になるようにグレイコーディングにより配列したことを特徴とする請求項2記載の通信制御方法。
- 前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される複数の送信ビームと所望の送信ビームとの角度差の総和が最小化するように調整したことを特徴とする請求項2記載の通信制御方法。
- 前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される複数の送信ビームにおけるアレイ利得の総和が最大化するように調整したことを特徴とする請求項2記載の通信制御方法。
- 前記コードブックを、第1のコードブック及び第2のコードブックで構成し、前記第1のコードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される送信ビームの影響を抑制するように調整したことを特徴とする請求項2記載の通信制御方法。
- 前記コードブックを、第1のコードブック及び第2のコードブックで構成し、前記第2のコードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される送信ビームの影響を抑制するように調整したことを特徴とする請求項2記載の通信制御方法。
- プリコーディングウェイトと当該プリコーディングウェイトに割り当てられるPMI(Precoding Matrix Indicator)とを複数定めたコードブックから前記プリコーディングウェイトを選択する選択手段と、前記選択手段で選択された前記プリコーディングウェイトに基づいて送信信号のプリコーディングを行うプリコーディング手段と、前記プリコーディング手段でプリコーディングが行われた前記送信信号を移動局装置に送信する送信手段とを具備し、
前記コードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、前記移動局装置からのフィードバックエラーによる影響を抑制するように調整したことを特徴とする基地局装置。 - 前記コードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される送信ビームの影響を抑制するように調整したことを特徴とする請求項8記載の基地局装置。
- プリコーディングウェイトと当該プリコーディングウェイトに割り当てられるPMI(Precoding Matrix Indicator)とを複数定めたコードブックから前記PMIを選択する選択手段と、前記選択手段で選択された前記PMIを基地局装置にフィードバックするフィードバック手段とを具備し、
前記コードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、前記基地局装置に対するフィードバックエラーによる影響を抑制するように調整したことを特徴とする移動局装置。 - 前記コードブックにおける前記プリコーディングウェイトに割り当てられる前記PMIのビット情報を、フィードバックエラーが発生した前記PMIに基づいて形成される送信ビームの影響を抑制するように調整したことを特徴とする請求項10記載の移動局装置。
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