JP2011014979A - Radio communication system, radio communication device, and control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption associated with operation processing for obtaining identification information used for precoding processing in radio communication devices.SOLUTION: The radio communication device transmits the identification information on a weight matrix used for the precoding processing of a transmission signal to another radio communication device, and receives a signal subjected to the precoding processing for transmission by the identification information from another radio communication device. The radio communication device is equipped with: an operation section for computing a prescribed evaluation index by a channel estimated value between a transmission side antenna of the other radio communication device estimated from a pilot signal included in a reception signal and a reception side antenna of an own device, and for selecting the identification information based on the computed result; and a stop control section for stopping the operation processing being performed in the operation section when the retransmission state of the reception signal meets prescribed conditions.

Description

  The present disclosure relates to a wireless communication system that performs precoding processing, a wireless communication device that configures the wireless communication system, and a control device thereof.

  MIMO technology is a wireless communication system that uses a plurality of antennas to transmit and receive wireless signals. MIMO is an abbreviation for Multi-Input Multi-Output. In radio signal transmission by MIMO, transmission data is parallelized and transmitted from a plurality of antennas, so that multiple transmissions corresponding to the number of antennas are possible, and an increase in data rate can be achieved. Further, in radio signal transmission by MIMO, a reception diversity effect can be obtained by receiving the same data by a plurality of antennas. Moreover, the transmission diversity effect can be obtained by transmitting the same data from a plurality of antennas on the transmission side.

  MIMO technology is applied to LTE systems, which are next-generation wireless communication systems. LTE is an abbreviation for Long Term Evolution. The LTE system is a high-speed data communication standard of W-CDMA, which is a third generation wireless communication method, and adopts OFDM as a transmission method. W-CDMA is an abbreviation for Wideband Code Division Multiple Access, and OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. The OFDM transmission system in wireless communication is a system that performs high-frequency transmission with high frequency utilization efficiency because signal transmission is performed using a plurality of orthogonalized subcarriers. The transmission OFDM symbol sequence is divided and distributed to a number of subcarriers and transmitted in parallel. For this reason, the transmission rate per one subcarrier can be reduced, and the delay interference characteristic in multipath can be improved. The LTE system is standardized by 3GPP TS36 series. 3GPP is an abbreviation for 3rd Generation Partnership Project.

  In the MIMO technique, a precoding process is performed by a transmission apparatus (Japanese Patent Laid-Open No. 2008-104193). Transmission signals are transmitted from a plurality of antennas, and transmission signals from the respective antennas are received by a plurality of antennas. That is, the transmission signal reaches each receiving antenna via a plurality of channels between a plurality of transmitting antennas and a plurality of receiving antennas. Hereinafter, the channel may be referred to as a propagation path. The receiver performs channel estimation processing to estimate the characteristics of each channel between the transmitting antenna and the receiving antenna based on the known pilot signal included in the received signal in order to synthesize and demodulate the received signals. To do. In addition, the received signal has a waveform in which the amplitude and phase are distorted due to multipath fading and the like in each channel, and reception characteristics may deteriorate.

  The precoding process in the transmission device is performed based on the channel estimation value obtained on the reception side, and the propagation path characteristics are set for the transmission data in the transmission device so that the reception characteristics in the reception device are the best. This is a process of multiplying a weight matrix in advance to cancel out. For example, precoding processing in the LTE system is defined in 3GPP TS 36.211 V8.5.0 (2008-12) 6.3.4 Precoding. The type of weight matrix is determined in advance according to the number of antennas, and the transmission apparatus and the reception apparatus hold a weight matrix table and a precoding matrix indicator table for identifying the index. Hereinafter, the precoding matrix indicator is referred to as PMI or identification information. The weight matrix table is a code table, for example. The receiving device performs an operation for obtaining an optimum PMI based on the channel estimation value obtained from the received signal, and feeds back the PMI to the transmitting device. The PMI required by the receiving apparatus also changes in accordance with the change in the propagation path characteristics, and the receiving apparatus can always obtain the optimum receiving characteristics by feeding back the PMI to the transmitting apparatus. This feedback control is called closed loop control.

  In the LTE system, a radio base station apparatus on the transmission side transmits an OFDM signal in which a user channel for transmitting user data and a reference signal known on the reception side are multiplexed as a downlink signal. Hereinafter, the user channel is referred to as SCH, and the reference signal is referred to as RS (Reference Signal, also referred to as pilot signal). The radio base station apparatus on the transmission side performs precoding processing only on the SCH and does not perform precoding processing on the RS. The mobile terminal on the receiving side obtains the characteristics of the propagation path based on the comparison between the known RS and the received RS, and obtains the PMI by calculation. The relationship between the transmission SCH (SCHtx) and the reception SCH (SCHrx) and the relationship between the transmission RS (RStx) and the reception RS (RSrx) are expressed by the following equations (1) and (2), respectively.

  Hch is a propagation matrix representing the characteristics of the propagation path (hereinafter referred to as channel estimation value), Wi is a weight matrix, i is PMI, and N is noise. In the equation (1), ideally, the best reception characteristics can be obtained by canceling the channel estimation value Hch and the weight matrix Wi. Further, by not performing the precoding process using the weight matrix Wi on the transmission RStx, the mobile terminal on the reception side can obtain the channel estimation value Hch.

JP 2008-104193 A

3GPP TS 36.211 V8.5.0 (2008-12) 6.3.4 Precoding

  The mobile terminal on the receiving side performs maximum ratio combining processing on each channel estimation value H as many as the number of receiving antennas, and calculates an evaluation index for each PMI in units of subbands that are frequency bands of multiple adjacent subcarriers. Then, all the calculation results are stored. Then, the mobile terminal selects an optimal PMI based on the calculation result. An example metric Mi of the evaluation index is shown in equation (3).

All the metrics M _i are obtained for the number of PMIs, and i when the maximum M _i is reached is the optimum PMI. H is the channel estimate

, () ^H represents conjugate transposition, sc represents an OFDM subcarrier, and Nsc represents the number of OFDM subcarriers.

  If the mobile terminal on the receiving side continues to perform the calculation process for obtaining this PMI during communication, the calculation of the above equation (3) is carried out in a large amount, so that power consumption increases.

  Accordingly, an object of the present disclosure is to reduce power consumption associated with a calculation process for obtaining identification information used for a precoding process in a wireless communication apparatus.

  The wireless communication device of the present disclosure transmits identification information about a weight matrix used for precoding processing of a transmission signal to another wireless communication device, and is precoded using the identification information by the other wireless communication device. In a wireless communication apparatus that receives a signal transmitted in a predetermined manner, a predetermined value is determined using a channel estimation value between the transmission-side antenna of the other wireless communication apparatus and the reception-side antenna of the own apparatus estimated from a pilot signal included in the reception signal A calculation unit that calculates the evaluation index of the received signal, and selects the identification information based on the calculation result, and a stop control unit that stops the calculation process performed by the calculation unit when the retransmission state of the received signal satisfies a predetermined condition And comprising.

  Further, the stop control unit may perform control to stop the calculation process performed by the PMI calculation unit based on the power ratio (SIR) between the data signal component and the interference signal component.

  According to the wireless communication device of the present disclosure, it is possible to reduce power consumption associated with arithmetic processing for obtaining identification information used for precoding processing.

It is a figure which shows the principal part structural example of the radio | wireless communications system in this Embodiment. 7 is a diagram illustrating a configuration example of a PMI calculation unit 207. FIG. 3 is a diagram illustrating a configuration example of a HARQ combining unit 208 and a HARQ combining control unit 209. FIG. FIG. 7 is a diagram for explaining a first stop control process of a stop control unit 211. 7 is a diagram for explaining a second stop control process of the stop control unit 211. FIG. FIG. 10 is a diagram for explaining a third stop control process of the stop control unit 211.

  Embodiments of the present invention will be described below with reference to the drawings. However, this embodiment does not limit the technical scope of the present invention.

  In the present embodiment, the radio communication apparatus temporarily stops the PMI estimation process when the propagation path condition is poor and the noise included in the received signal is large. PMI is an abbreviation for Precoding Matrix Indicator. When the noise is large, the probability of the estimated PMI decreases. Even if PMI with low probability is fed back to another wireless communication device on the transmission side, and the other wireless communication device performs precoding processing based on the PMI, the reception characteristics of the wireless communication device on the reception side No improvement can be expected. The wireless communication device determines whether or not the propagation path is deteriorated to such an extent that reception characteristics cannot be improved even if PMI calculation processing is performed. Stop temporarily. Thereby, the power consumption of the wireless communication device can be reduced. In particular, when the wireless communication device is a mobile terminal, the limited power capacity of the on-board battery can be used effectively, and the battery life can be extended.

  In the present embodiment, the radio communication apparatus determines whether or not the propagation path is deteriorated so that reception characteristics cannot be improved even if the PMI calculation process is performed based on the retransmission state in the retransmission control. The retransmission control may be referred to as ARQ. ARQ is an abbreviation for Automatic Repeat reQuest.

  The retransmission control is a control method in which the transmission side transmits the same data again when the transmission side cannot normally decode the data transmitted from the transmission side. For example, CRC is used as the error detection method. CRC is an abbreviation for Cyclic Redundancy Check. On the receiving side, if the data cannot be decoded normally, NACK information is notified to the transmitting side to request retransmission of the data. When receiving normally, ACK information is notified.

  Retransmission of data frequently occurs when the condition of the propagation path is bad and noise is large. Therefore, the PMI calculation stop control unit monitors whether or not retransmissions are frequently occurring, and determines that the probability of PMI required by the calculation is low when data retransmissions occur above a certain level. Then, the calculation process for obtaining the PMI is stopped.

  A HARQ scheme that combines retransmission control and error correction coding processing is also realized. HARQ is an abbreviation for Hybrid Automatic Repeat reQuest. In this embodiment, an example in which HARQ processing is applied as retransmission control will be described. Of course, the present embodiment can also be applied to a wireless communication system employing ARQ processing.

  FIG. 1 is a diagram illustrating a configuration example of a main part of a wireless communication system according to the present embodiment. The radio communication system illustrated in FIG. 1 is an LTE system that employs, for example, MIMO technology, and includes a radio base station 100 that is a transmission side and a mobile terminal 200 that is a reception side. Radio base station 100 includes modulation section 101, precoding processing section 102, multiplexing section 103, S / P section 104, IFFT section 105, GI addition section 106, radio section 107, and HARQ control section 108. And a plurality of antennas 109-1 to 109-n. When the antennas 109-1 to 109-n are not distinguished, they are collectively referred to as the antenna 109. The mobile terminal 200 includes a radio unit 201, a symbol extraction unit 202, an FFT unit 203, a demodulation unit 204, a channel estimation unit 205, an SIR estimation unit 206, a PMI calculation unit 207, a HARQ synthesis unit 208, HARQ synthesis control section 209, decoding section 210, stop control section 211, and antennas 212-1 to 212-n are provided. When the antennas 212-1 to 212-n are not distinguished, they are collectively referred to as the antenna 212.

  The configuration of radio base station 100 will be described. Modulation section 101 modulates an encoded sequence of user data that has been subjected to predetermined error correction encoding processing such as turbo encoding, using a predetermined modulation scheme, and generates data symbols having in-phase components and quadrature components. The modulation method is, for example, QPSK or 16QAM. QPSK is an abbreviation for Quadrature Phase Shift Keying, and 16QAM is an abbreviation for 16 Quadrature Amplitude Modulation. For example, a CRC code is added to the user data as an error detection code. CRC is an abbreviation for Cyclic Redundancy Check.

  Precoding processing section 102 stores weight matrix information corresponding to PMI, and precodes data symbols using a weight matrix corresponding to PMI designated by mobile terminal 200.

  Multiplexing section 103 multiplexes pilot signals RS and various control signals known to both radio base station 100 and mobile terminal 200 on the precoded data symbols. S / P section 104 converts the multiplexed symbols into parallel data and outputs subcarrier samples (in the figure, description of parallel data is omitted). IFFT section 105 combines each subcarrier sample by performing IFFT processing, and outputs an OFDM signal. A guard interval (GI) insertion unit 106 inserts a guard interval between OFDM signals. IFFT is an abbreviation for Inverse Fast Fourier Transform. The Guard Institute and other bars are sometimes referred to as GI.

  Radio section 107 performs D / A conversion on the OFDM signal in which the GI is inserted, converts the baseband frequency to the radio frequency, and transmits the downlink signal from antenna 109. Radio section 107 receives an uplink signal from mobile terminal 200 received by antenna 109. The uplink signal in the present embodiment includes a response signal ACK / NACK indicating whether or not decoding by decoding section 210 in mobile terminal 200 and PMI obtained by PMI calculation section 207 described later. The uplink signal received by the radio unit 107 is converted from a radio frequency to a baseband frequency and A / D converted. Although the demodulation process of the radio base station 100 is not described in detail, the principle is the same as the demodulation process in the mobile terminal 200 described later. The PMI included in the uplink signal from the mobile terminal 200 is input to the precoding processing unit 102 and designates a weight matrix used in the precoding processing unit 102. The ACK / NACK included in the uplink signal from the mobile terminal 200 is input to the HARQ processing unit 108. The HARQ control unit 108 determines whether or not data retransmission is necessary based on the ACK / NACK signal from the mobile terminal 200. When receiving the NACK signal, the HARQ control unit 108 outputs user data corresponding to the NACK signal for retransmission.

  A configuration of the mobile terminal 200 will be described. The radio unit 201 converts the downlink signal received from the antenna 212 from the radio base station 100 from a radio frequency to a baseband frequency, and performs A / D conversion. The symbol extraction unit 202 removes the guard interval and extracts a symbol based on the reception timing at the beginning of each symbol obtained by a predetermined timing detection process using a known pilot signal.

  The FFT unit 203 performs FFT processing on the input symbol and converts it into subcarrier samples. Channel estimation section 205 calculates the correlation between the received pilot signal and the known pilot signal, and calculates a channel estimation value for each subcarrier. Demodulation section 204 demodulates the data symbol using the channel estimation value for each subcarrier. By multiplying each subcarrier by the complex conjugate number of each channel estimation value, signal distortion in the propagation path due to multipath fading or the like is compensated. The PMI calculation unit 207 calculates PMI according to the above-described equation (3) using the obtained channel estimation value.

  FIG. 2 is a diagram illustrating a configuration example of the PMI calculation unit 207. The PMI calculation unit 207 includes a metric calculation unit 207a and a storage / selection unit 207b. The channel estimation values H corresponding to the number of reception antennas obtained by the channel estimation unit 205 and all weight matrices W for each PMI are input to the metric calculation unit 207a. Metric calculation unit 207a performs maximum ratio combining (Maximum Ratio Combining) on each channel estimation value H for the number of reception antennas. Then, the metric calculation unit 207a calculates the metric Mi exemplified by the above equation (3) for each PMI in units of subbands that are frequency bands of a plurality of adjacent subcarriers. The storage / selection unit 207b stores the metric Mi for each PMI, selects and outputs the PMI corresponding to the weight matrix that gives the maximum metric.

  The PMI selected by the PMI calculation unit 207 is output to the stop control unit 211, and the PMI is transmitted to the radio base station 100 as an uplink signal according to the control of the stop control unit 211. The operation of the stop control unit 211 will be described later.

  SIR estimating section 206 obtains an SIR estimated value by a known method using the received pilot signal and its conjugate complex number. SIR is the ratio between desired signal power and interference signal power in the received signal, and is an abbreviation for Signal to Interference Ratio. The reception level of the received signal at the antenna 212 varies for each antenna 212. Since the radio unit 201 performs AGC control so that each received signal has a certain appropriate level, the amplification factor of each received signal differs depending on the received level, and therefore, the noise that is an interference signal component included in the received signal The level is also different for each received signal. AGC is an abbreviation for Auto Gain Control. When the demodulator 204 performs, for example, maximum likelihood demodulation, the level of the desired signal component affects the accuracy of likelihood determination, so the demodulator 204 normalizes the symbol based on the SIR estimation value. As a result, the noise component level in each symbol becomes constant, the level difference of each symbol becomes the level difference of the desired wave component, and accurate demodulation is realized.

  HARQ combining section 208 combines with the original data stored in the internal memory when the demodulated data is retransmission data. The original data is data transmitted before the current retransmission. HARQ combining control section 209 determines whether or not the demodulated data is retransmission data. If HARQ combining control section 209 determines that the demodulated data is retransmission data, HARQ combining section 208 controls retransmission data and original data to be combined.

  The decoding unit 210 decodes the encoded data, and further executes error detection processing using a CRC code. Information of decoding success / decoding failure, which is an error detection processing result, is input to the HARQ synthesis control unit 210. HARQ synthesis control section 209 generates an ACK / NACK signal based on the error detection processing result. The ACK / NACK signal is transmitted to radio base station 100 as an uplink signal. Although the transmission process of the mobile terminal 200 is not described in detail, the principle is the same as the transmission process in the radio base station 100 described above.

  FIG. 3 is a diagram illustrating a configuration example of the HARQ combining unit 208 and the HARQ combining control unit 209. The HARQ synthesis control unit 209 includes a received signal information management unit 2091 and a standby state management unit 2092. The received signal information management unit 2091 is configured to determine, from the control signal demodulated by the demodulation unit 204, the process number of the user data corresponding to the control signal and whether the user data of the process number is retransmission data or new data. / Retransmit identification information is extracted and stored.

  When the user data is retransmission data, received signal information management section 2091 instructs reading section 2082 of HARQ combining section 208 to read the original data of the retransmission data from data memory 2084. The reading unit 2082 reads the original data from the data memory 2084, and the adding unit 2081 combines the demodulated retransmission data and the read original data. For example, when original data is not read from the data memory 2084 as in the case of new data, the adder 2081 outputs the demodulated data as it is. When the writing unit 2083 acquires data from the adding unit 2081 and receives a write instruction from the standby state management unit 2092 of the HARQ synthesis control unit 209, the writing unit 2083 writes the data into the data memory 2084.

  The standby state management unit 2092 of the HARQ synthesis control unit 209 includes a process number of user data, expected mode information indicating whether the user data of the process number should be new data or retransmission data, and retransmission data. The number of retransmissions in a certain case is stored. The initial value of the expected mode information for each process number is “new”. The standby state management unit 2092 updates the expected mode information and the number of retransmissions based on the error detection processing result from the decoding unit 210. For example, upon receiving the error detection processing result of decoding failure, the standby state management unit 2092 sets the expected mode information of the process number to the “waiting for retransmission” state, and sends the data of the process number to the writing unit 2083. Instructs writing to the data memory 2084. In addition, the standby state management unit 2092 counts the number of times “wait for retransmission” is set, and increments the number of retransmissions. Further, ACK / NACK generation unit 2092A of standby state management unit 2092 generates a NACK signal and transmits it to radio base station 100 when receiving the error detection processing result of decoding failure. The ACK / NACK generation unit 2092A of the standby state management unit 2092 generates an ACK signal and transmits it to the radio base station 100 when it receives the error detection processing result of the decoding success. The received signal information management unit 2091 compares the new / retransmission identification information of each process number obtained from the control signal with the expected mode information registered in the standby state management unit 2092 so that they match. Confirm.

  The stop control unit 211 determines whether to stop the calculation process of the PMI calculation unit 207 based on the expected mode information of each process number monitored by the standby state management unit 2092 of the HARQ synthesis control unit 209. When the determination is made, stop control for stopping the calculation process of the PMI calculation unit 207 is executed. The stop control of the stop control unit 211 will be described.

(First stop control method)
FIG. 4 is a diagram for explaining the first stop control process of the stop control unit 211. As an example, the HARQ synthesis control unit 209 monitors the retransmission status of a maximum of eight process numbers retroactively from the latest process number (monitored process number Np_max = 8). In the first stop control process, the stop control unit 211 stops the calculation process of the PMI calculation unit 207 when all the expected mode information of the process number to be monitored is “waiting for retransmission”. FIG. 4A is a diagram showing a change example of the process number and the number of retransmissions. When the number of retransmissions is 1 or more, the expected mode information is “retransmission”. Therefore, in the example of FIG. 4A, when the PMI operation unit 207 receives the error detection processing result of the decoding failure for the process number 13, the expected mode information of all eight monitored process numbers is “waiting for retransmission”. Therefore, the calculation processing operation of the PMI calculation unit 207 is stopped at that timing.

  FIG. 4B is a flowchart of the first stop control process. The stop control unit 211 determines whether the expected mode information of all the monitoring target process numbers of the HARQ synthesis control unit 209 is “waiting for retransmission” (S100). When the expected mode information of all process numbers is “waiting for retransmission”, the stop control unit 211 stops the calculation process of the PMI calculation unit 207 (PMI calculation OFF) (S101), and sets a predetermined fixed PMI. Transmit to the radio base station 100 (S102). When the arithmetic processing is stopped, the stop is maintained. When the expected mode information of all process numbers is not “wait for retransmission”, the calculation processing operation of the PMI calculation unit 207 is continued (PMI calculation ON) (S103), and the PMI selected based on the calculation result is transmitted to the radio base station 100. Transmit (S104). When the calculation processing operation of the PMI calculation unit 207 is stopped, the calculation processing operation of the stop control unit PMI calculation unit 207 is resumed.

  The fixed PMI transmitted in S102 may be a plurality of different PMIs for each subband, or may be a single PMI common to all subbands. Hereinafter, also in the second stop control process and the third stop control process, which will be described later, the fixed PMI determined in advance may be a plurality of PMIs different for each subband, or may be common to all subbands. There may be two PMIs.

(Second stop control method)
FIG. 5 is a diagram for explaining the second stop control process of the stop control unit 211. In the second stop control process, when the expected mode information of the last B (B <Np_max) process numbers out of the number of monitored processes Np_max = 8 is “waiting for retransmission”, the stop control unit 211 The calculation process 207 is stopped. FIG. 5A is a diagram showing an example of changes in the process number and the number of retransmissions as in FIG. 4A. When the number of retransmissions is 1 or more, the expected mode information is “retransmission”. In the case of B = 3, in the example of FIG. 5A, when the PMI operation unit 207 receives the error detection processing result of the decoding failure for the process number 8, the expected mode information of the latest three monitored process numbers is “Resend”. “Waiting”, the calculation processing operation of the PMI calculation unit 207 is stopped at that timing.

  FIG. 5B is a flowchart of the second stop control process. The stop control unit 211 determines whether the expected mode information of the last B process numbers is “waiting for retransmission” from the latest number among the process number monitored by the HARQ synthesis control unit 209 (S200). When the expected mode information of the last B process numbers is “waiting for retransmission”, the stop control unit 211 stops the calculation process of the PMI calculation unit 207 (PMI calculation OFF) (S201), and is fixed in advance. PMI is transmitted to the radio base station 100 (S202). When the arithmetic processing is stopped, the stop is maintained. If the expected mode information of the last B process numbers is not “wait for retransmission”, the calculation processing operation of the PMI calculation unit 207 is continued (PMI calculation ON) (S203), and the PMI selected based on the calculation result is Transmit to the station 100 (S204). When the calculation processing operation of the PMI calculation unit 207 is stopped, the calculation processing operation of the stop control unit PMI calculation unit 207 is resumed.

(Third stop control method)
FIG. 6 is a diagram for explaining the third stop control process of the stop control unit 211. In the third stop control process, the stop control unit 211 indicates that the expected mode information of C (C <Np_max) process numbers in the number of monitored processes Np_max = 8 is “waiting for retransmission” and the number of retransmissions Is equal to or greater than the threshold value D, the calculation process of the PMI calculation unit 207 is stopped. In this case, C may not be the latest number of processes. FIG. 6A is a diagram showing a change example of the process number and the number of retransmissions as in FIG. 4A. When the number of retransmissions is 1 or more, the expected mode information is “retransmission”. In the case of C = 3 and D = 2, in the example of FIG. 6A, when the PMI calculation unit 207 receives the error detection processing result of the decoding failure for the process number 16, C out of the number of monitored processes Np_max = 8. Since the expected mode information of (C <Np_max) process numbers is “waiting for retransmission” and the number of retransmissions is two or more, the calculation processing operation of the PMI calculation unit 207 is stopped at that timing.

  FIG. 6B is a flowchart of the third stop control process. The stop control unit 211 determines whether or not the expected mode information of the C process numbers among the monitoring target process numbers of the HARQ synthesis control unit 209 is “waiting for retransmission” and the number of retransmissions is greater than or equal to the threshold value D ( S300). When the expected mode information of the C process numbers is “waiting for retransmission” and the number of retransmissions is greater than or equal to the threshold D, the stop control unit 211 stops the calculation process of the PMI calculation unit 207 (PMI calculation OFF) ( (S301), a predetermined fixed PMI is transmitted to the radio base station 100 (S302). When the arithmetic processing is stopped, the stop is maintained. When the expected mode information of the C process numbers is “waiting for retransmission” and the number of retransmissions is not greater than or equal to the threshold value D, the calculation processing operation of the PMI calculation unit 207 is continued (PMI calculation ON) (S303), The selected PMI is transmitted to the radio base station 100 (S304). When the calculation processing operation of the PMI calculation unit 207 is stopped, the calculation processing operation of the stop control unit PMI calculation unit 207 is resumed.

  As a modification of the first to third stop control methods described above, the stop control unit 211 may not transmit a fixed PMI to the radio base station 100. In this case, a predetermined fixed PMI is registered in the precoding processing unit 102 of the radio base station 100, the precoding processing unit 102 determines whether to receive PMI from the mobile terminal 200, and at a timing when it does not receive The precoding process may be performed based on a fixed PMI registered in advance. The fixed PMI set in the precoding processing unit 102 may be a plurality of PMIs different for each subband, or may be a single PMI common to all subbands. Since the mobile terminal 200 does not transmit a fixed PMI, it is possible to reduce the transmission power for that purpose and to further reduce the power consumption.

  In the above-described embodiment, the stop control unit 211 has been described with respect to an example in which the PMI calculation stop control is performed based on the retransmission status of the received signal, but instead of the retransmission status, the PMI calculation is performed based on the SIR estimation value. Computation stop control may be performed. Since the SIR estimated value represents the noise ratio included in the received signal, the probability of PMI decreases as the noise ratio increases.

  The stop control unit 211 determines whether or not the SIR estimation value obtained by the SIR estimation unit 206 is equal to or greater than a predetermined threshold value, and if it is equal to or greater than the threshold value, stops the calculation process of the PMI calculation unit 207 and is determined in advance. The fixed PMI is transmitted to the radio base station 100. Alternatively, the stop control unit 211 stops the calculation process of the PMI calculation unit 207 and stops the transmission of the PMI to the radio base station 100 when the SIR estimation value is greater than or equal to a predetermined threshold value. When the precoding processing unit 102 of the radio base station 100 does not receive PMI from the mobile terminal 200, the precoding processing unit 102 performs precoding processing using a predetermined fixed PMI set in the precoding processing unit 102. When the estimated SIR value is less than the predetermined threshold, stop control unit 211 causes PMI calculation unit 207 to perform calculation processing, and transmits PMI selected based on the calculation result to radio base station 100.

  The radio communication apparatus according to the present embodiment has been described using mobile terminal 200 as an example, but can also be applied to radio base station apparatus 100.

  In the above description, the PMI calculation stop control process applied to the LTE system has been described. However, the wireless communication apparatus that performs the PMI calculation stop control process is not limited to the radio reception apparatus of the LTE system. The PMI calculation stop control process of the present embodiment is applicable to a wireless communication apparatus of another communication system that employs closed loop control in which precoding processing is performed on the transmission side and PMI is fed back from the reception side.

  Moreover, the precoding process by closed loop control is applicable to the radio | wireless communications system in which a some channel is defined between transmission / reception antennas. Therefore, the present embodiment is not limited to the MIMO system, and can also be applied to a wireless communication system in which a plurality of channels are defined between transmission and reception antennas, such as a SIMO system and a MISO system. SIMO is an abbreviation for Single-Input Multi-Output, and MISO is an abbreviation for Multi-Input Single-Output.

  The main technical features of the embodiment described above are as follows.

(Appendix 1)
Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In a wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
A wireless communication apparatus comprising:

(Appendix 2)
In the wireless communication device of appendix 1,
The stop control unit transmits a predetermined fixed identification information to the other communication device when the calculation process performed by the calculation unit is stopped.

(Appendix 3)
In the wireless communication device of appendix 1,
The said stop control part will stop transmission of the said identification information to said other communication apparatus, if the arithmetic processing currently performed by the said calculating part is stopped.

(Appendix 4)
In the wireless communication device of appendix 1,
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose retransmission state is waiting for retransmission is equal to or greater than a predetermined number.

(Appendix 5)
In the wireless communication device of appendix 1,
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose retransmission state is awaiting retransmission is a predetermined number or more retroactively from the latest received signal.

(Appendix 6)
In the wireless communication device of appendix 1,
The retransmission state includes the number of retransmissions when each received signal is waiting for retransmission,
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose number of retransmissions is equal to or greater than a predetermined threshold is equal to or greater than a predetermined number.

(Appendix 7)
Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In a wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the power ratio between the data signal component and the interference signal component included in the received signal is equal to or less than a predetermined value, a stop control unit that stops the arithmetic processing performed in the arithmetic unit;
A wireless communication apparatus comprising:

(Appendix 8)
In the wireless communication device of appendix 7,
The stop control unit transmits a predetermined fixed identification information to the other communication device when the calculation process performed by the calculation unit is stopped.

(Appendix 9)
In the wireless communication device of appendix 7,
The said stop control part will stop transmission of the said identification information to said other communication apparatus, if the arithmetic processing currently performed by the said calculating part is stopped.

(Appendix 10)
In the wireless communication device according to any one of appendices 1 to 9,
The wireless communication apparatus is a mobile terminal and receives a signal from a wireless base station which is another communication apparatus.

(Appendix 11)
In the wireless communication device according to any one of appendices 1 to 10,
A wireless communication apparatus having a plurality of receiving antennas, each receiving a signal transmitted from a plurality of transmitting antennas.

(Appendix 12)
A first wireless communication apparatus that transmits identification information about a weight matrix used for precoding processing of a transmission signal; and the identification information from the first wireless communication apparatus is received, and precoding is performed using the identification information In a wireless communication system comprising a second wireless communication device that transmits a processed signal,
The first wireless communication device is:
A channel estimation value between the transmitting antenna of the other wireless communication apparatus and the receiving antenna of the own apparatus, which is estimated from a pilot signal included in the received signal after receiving a signal transmitted from the second wireless communication apparatus A calculation unit that calculates a predetermined evaluation index using and selects the identification information based on the calculation result;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
With
The second wireless communication device is:
A wireless communication system, comprising: a precoding processing unit that performs precoding processing using predetermined fixed identification information when the identification information is not received from the first wireless communication device.

(Appendix 13)
Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another communication device, and a signal transmitted by precoding processing using the identification information by the other communication device is transmitted by a receiving antenna. In the control device of the receiving wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
A control device comprising:

(Appendix 14)
Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In the control device of the wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the power ratio between the data signal component and the interference signal component included in the received signal is equal to or less than a predetermined value, a stop control unit that stops the arithmetic processing performed in the arithmetic unit;
A control device comprising:

  100: Radio base station, 101: Modulation unit, 102: Precoding processing unit, 103: Multiplexing unit, 104: S / P unit, 105: IFFT unit, 106: GI addition unit, 107: Radio unit, 108: HARQ control 109: Antenna 200: Mobile terminal 201: Radio unit 202: Symbol extraction unit 203: FFT unit 204: Demodulation unit 205: Channel estimation unit 206: SIR estimation unit 207: PMI calculation unit 208: HARQ synthesis unit, 209: HARQ synthesis control unit, 201: decoding unit, 211: stop control unit, 212: antenna, 2081: adder, 2082: read unit, 2083: write unit, 2084: data memory, 2091: Received signal information manager, 2092: Standby state manager, 2092A: ACK / NACK generator

Claims (10)

Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In a wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
A wireless communication apparatus comprising: The wireless communication device according to claim 1.
The stop control unit transmits a predetermined fixed PMI to the other communication device when the calculation process performed by the PMI calculation unit is stopped. The wireless communication device according to claim 1.
The wireless communication device, wherein the stop control unit stops transmission of PMI to the other communication device when the arithmetic processing performed in the PMI arithmetic unit is stopped. The wireless communication device according to claim 1.
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose retransmission state is waiting for retransmission is equal to or greater than a predetermined number. The wireless communication device according to claim 1.
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose retransmission state is awaiting retransmission is a predetermined number or more retroactively from the latest received signal. The wireless communication device according to claim 1.
The retransmission state includes the number of retransmissions when each received signal is waiting for retransmission,
The wireless communication apparatus according to claim 1, wherein the predetermined condition is that the number of received signals whose number of retransmissions is equal to or greater than a predetermined threshold is equal to or greater than a predetermined number. Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In a wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the power ratio between the data signal component and the interference signal component included in the received signal is equal to or less than a predetermined value, a stop control unit that stops the arithmetic processing performed in the arithmetic unit;
A wireless communication apparatus comprising: A first wireless communication device that transmits identification information about a weight matrix used for precoding processing, and a signal that has received the identification information from the first wireless communication device and has performed precoding processing using the identification information In a wireless communication system comprising a second wireless communication device for transmitting
The first wireless communication device is:
Channel estimation value between the transmitting antenna of the other wireless communication device and the receiving antenna of the own device estimated from the pilot signal included in the received signal after receiving the signal transmitted from the second wireless communication device A calculation unit that calculates a predetermined evaluation index using and selects the identification information based on a calculation result;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
With
The second wireless communication device is:
A wireless communication system, comprising: a precoding processing unit that performs precoding processing using predetermined fixed identification information when the identification information is not received from the first wireless communication device. Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In the control device of the wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the retransmission state of the received signal satisfies a predetermined condition, a stop control unit that stops the arithmetic processing performed in the arithmetic unit,
A control device comprising: Identification information about a weight matrix used for precoding processing of a transmission signal is transmitted to another wireless communication device, and a signal transmitted by precoding processing using the identification information by the other wireless communication device is received. In the control device of the wireless communication device,
A predetermined evaluation index is calculated using a channel estimation value between the transmission-side antenna of the other radio communication apparatus and the reception-side antenna of the own apparatus, which is estimated from a pilot signal included in the reception signal, and based on the calculation result, A calculation unit for selecting identification information;
When the power ratio between the data signal component and the interference signal component included in the received signal is equal to or less than a predetermined value, a stop control unit that stops the arithmetic processing performed in the arithmetic unit;
A control device comprising: