JP5999099B2 - Wireless communication system, wireless communication method, and wireless communication apparatus - Google Patents

Description

  The present invention relates to a wireless communication system, a wireless communication method, and a wireless communication apparatus.

  In recent years, in order to further increase the speed and capacity of wireless communication in a wireless communication system such as a mobile phone system, the next generation wireless communication technology has been discussed. For example, 3GPP (3rd Generation Partnership Project), a standardization organization, proposes a communication standard called LTE (Long Term Evolution) and a communication standard called LTE-A (LTE-Advanced) based on LTE wireless communication technology. Has been.

  In an LTE-A system or the like, multipoint coordinated (Coordinated MultiPoint, hereinafter also referred to as CoMP) communication is being studied in order to reduce inter-cell interference and improve received signal strength. In multipoint cooperative communication, a plurality of geographically distant points cooperate to perform communication. Each point corresponds to, for example, a base station, an antenna, or a cell formed by these. Thereby, dynamic adjustment of transmission or reception between multiple points is performed. For example, in uplink multipoint cooperative communication, a method of combining signals while receiving signals received in a plurality of cells is being studied.

3GPP TS36.211 V10.2.0 (2011-06) 3GPP TR36.814 V9.0.0 (2010-03)

  However, in order to reduce inter-cell interference and improve received signal strength through multipoint coordinated communication, appropriate adjustments between cells are necessary in consideration of control delay and increased signaling. . For example, in uplink multipoint cooperative communication, it is assumed that the timing for receiving a signal transmitted from a terminal is different for each cell. At this time, depending on the reception timing between the cells, there is a possibility that the influence of inter-symbol interference increases and the improvement of the reception characteristics may be hindered by the combination processing of uplink multipoint cooperative communication.

  The disclosed technology has been made in view of the above, and an object thereof is to provide a wireless communication system, a wireless communication apparatus, and a wireless communication method capable of improving reception characteristics in multipoint cooperative communication. .

  In order to solve the above-described problems and achieve the object, in one aspect, a wireless communication system disclosed in the present application is a plurality of first wireless communication devices that transmit data transmitted from a second wireless communication device. Receive. A first transmission unit that transmits information related to transmission timing based on information about the plurality of first wireless communication devices to the second wireless communication device, and the plurality of first wireless communication devices from the second wireless communication device. A second transmission unit that transmits the data at the transmission timing.

  According to one aspect of the wireless communication system disclosed in the present case, it is possible to improve reception characteristics in uplink multipoint cooperative communication.

FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to the first embodiment. FIG. 2 is a sequence diagram for explaining the operation of the wireless communication system. FIG. 3 is a diagram for explaining the reception timing in the wireless communication apparatus. FIG. 4 is a diagram for explaining reception characteristics in the wireless communication device. FIG. 5 is a diagram illustrating a configuration of a wireless communication system according to the second embodiment. FIG. 6 is a diagram illustrating a functional configuration of the base station. FIG. 7 is a diagram illustrating a functional configuration of the mobile station. FIG. 8 is a diagram illustrating a hardware configuration of the base station. FIG. 9 is a diagram illustrating a hardware configuration of the mobile station. FIG. 10 is a sequence diagram for explaining the operation of the wireless communication system. FIG. 11 is a sequence diagram for explaining the operation of the wireless communication system. FIG. 12 is a diagram for explaining the reception timing at the base station. FIG. 13 is a diagram for explaining reception characteristics at the base station. FIG. 14 is a diagram illustrating a configuration of a wireless communication system according to the third embodiment. FIG. 15 is a diagram illustrating a functional configuration of an RRH (Remote Radio Head). FIG. 16 is a diagram illustrating a configuration of a wireless communication system according to the fourth embodiment.

Embodiments of a wireless communication system, a wireless communication method, and a wireless communication apparatus disclosed in the present application will be described below with reference to the drawings. Note that the wireless communication system, the wireless communication method, and the wireless communication device disclosed in the present application are not limited by the following embodiments.
[First Embodiment]
FIG. 1 shows a configuration of a wireless communication system 1 according to the first embodiment. As shown in FIG. 1, the wireless communication system 1 includes a plurality of wireless communication devices 10 and 20 and a wireless communication device 30. For example, the wireless communication system 1 can be realized by using the wireless communication devices 10 and 20 as a base station and the wireless communication device 30 as a mobile station. The wireless communication devices 10 and 20 form cells C1 and C2, respectively, and the wireless communication device 30 is located in the cell C1. The wireless communication devices 10 and 20 perform communication between the wireless communication devices 10 and 20 via wired connection or wireless connection, and perform CoMP communication with the wireless communication device 30. The radio communication devices 10 and 20 perform uplink CoMP communication, receive data transmitted by the radio communication device 30 by the radio communication devices 10 and 20, and synthesize a reception signal between the radio communication devices 10 and 20. Process. In this way, by combining received signals between the radio communication devices 10 and 20, inter-cell interference is reduced and received signal strength is improved to improve reception characteristics.

  As illustrated in FIG. 1, the wireless communication device 10 includes an antenna 11, a transmission unit 12, a reception unit 13, and a control unit 14 as a functional configuration. Each of these components is connected so that signals and data can be input and output in one direction or in both directions. The component parts 21 to 24 of the wireless communication device 20 are the same as the component parts 11 to 14 of the wireless communication device 10.

  The control unit 14 acquires information and signals from the wireless communication device 20 via a wired connection or a wireless connection. The control unit 14 determines information related to transmission timing that is a reference when data is transmitted from the wireless communication device 30 based on the information related to the wireless communication devices 10 and 20. The information related to the wireless communication devices 10 and 20 includes, for example, information related to reception quality at the wireless communication devices 10 and 20 measured by the wireless communication devices 10 and 20 and distribution of reception timings at the wireless communication devices 10 and 20. Contains information about. The reception quality is, for example, SIR (Signal to Interference Ratio), SINR (Signal to Interference and Noise Ratio), RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Power) (= received power value / total power value). Including. The control unit 14 combines the signal received by the wireless communication device 10 and the signal received by the wireless communication device 20 to execute a decoding process or the like, and acquires data transmitted from the wireless communication device 30. The control unit 14 determines a transmission timing serving as an uplink reference so that information regarding the wireless communication apparatuses 10 and 20 satisfies a predetermined condition. For example, the control unit 14 determines a transmission timing serving as an uplink reference so that the reception quality of the combined signal is the highest. The control unit 14 corresponds to an example of a determination unit and a processing unit in this case. The information related to the wireless communication devices 10 and 20 can include various information related to the wireless communication devices 10 and 20 such as the type, installation position, arrangement relationship, or operation status of each wireless communication device 10 and 20.

  The transmission unit 12 transmits information related to transmission timing serving as an uplink reference to the wireless communication device 30 via the antenna 11. The receiving unit 13 receives data transmitted from the wireless communication device 30 at a reference transmission timing via the antenna 11. The antenna 11 may be separated for transmission and reception.

  The wireless communication device 10 includes, for example, a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), a memory, and an RF (Radio Frequency) circuit including an antenna as hardware components. The memory includes, for example, RAM such as SDRAM (Synchronous Dynamic Random Access Memory), ROM (Read Only Memory), and flash memory, and stores programs, control information, and data. The transmission unit 12 and the reception unit 13 are realized by, for example, an RF circuit. The control unit 14 is realized by an integrated circuit such as a DSP or FPGA. The hardware configuration of the wireless communication device 20 is the same as that of the wireless communication device 10.

  As shown in FIG. 1, the wireless communication device 30 includes an antenna 31, a transmission unit 32, a reception unit 33, and a control unit 34 as functional configurations. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

  The receiving unit 33 receives information related to the reference transmission timing from the wireless communication device 10. The control unit 34 performs processing such as encoding of data to be transmitted. The transmission unit 32 transmits data to the wireless communication devices 10 and 20 at a reference transmission timing. The antenna 31 may be separated for transmission and reception.

  The wireless communication device 30 includes, for example, a CPU (Central Processing Unit), a memory, and an RF circuit including an antenna as hardware components. The memory includes RAM such as SDRAM, ROM, and flash memory, for example, and stores programs, control information, and data. The transmission unit 32 and the reception unit 33 are realized by, for example, an RF circuit. The control unit 34 is realized by an integrated circuit such as a CPU, for example.

  Next, the operation of the wireless communication system 1 in the first embodiment will be described. FIG. 2 is a sequence diagram for explaining an operation related to timing control of the wireless communication system 1. As a premise, in the wireless communication system 1, the wireless communication devices 10 and 20 each perform reception processing at the control timing of its own device, and the timing synchronization between the reception signal and the reception processing is performed by the uplink from the wireless communication device 30. It has been established by adjusting the transmission timing. For example, when uplink CoMP communication is not performed, the timing synchronization between the radio communication device 30 and the radio communication device 10 corresponding to the serving cell C1 indicates that the uplink transmission timing from the radio communication device 30 is the same as the radio communication device. It is established by adjusting to match the timing of 10 reception processes. Such adjustment is executed, for example, by transmitting a command for adjusting the uplink transmission timing from the wireless communication device 10 to the wireless communication device 30 and performing the next transmission by the wireless communication device 10 in response to this command. Is done.

  When performing uplink CoMP communication, the wireless communication device 30 transmits data to the wireless communication devices 10 and 20 using the same channel at the same transmission timing. At this time, depending on the transmission timing serving as an uplink reference, the influence of inter-symbol interference due to the timing difference between the received signal and the reception process may increase, thereby hindering improvement in reception characteristics. The timing difference between the received signal and the received process is, for example, the position on the time axis of an OFDM (Orthogonal Frequency Division Multiplexing) symbol included in the received signal and the position on the time axis of an FFT (Fast Fourier Transform) window used in the received process Is the difference. Therefore, in the wireless communication system 1, when performing uplink CoMP communication, timing control is performed as follows.

  As shown in FIG. 2, the wireless communication devices 10 and 20 obtain information related to the wireless communication devices 10 and 20 in cooperation (S1). For example, the wireless communication device 10 measures reception quality at the wireless communication device 10. In addition, the wireless communication device 10 acquires information such as reception quality measured by the wireless communication device 20 from the wireless communication device 20.

  The wireless communication devices 10 and 20 work together to determine information related to transmission timing that serves as an uplink reference when data is transmitted from the wireless communication device 30 (S2). For example, the wireless communication device 10 uses the information related to the reception quality of the wireless communication devices 10 and 20 to transmit the information related to the transmission timing serving as the uplink reference so that the reception quality of the combined signal satisfies the predetermined condition. decide. The information regarding the transmission timing used as a reference | standard contains the information which shows the wireless communication apparatus used as the reference | standard among the wireless communication apparatuses 10 and 20, for example. Note that the wireless communication device 10 may determine a reference transmission timing and transmit the reference transmission timing itself to the wireless communication device 30 as information on the reference transmission timing. Further, based on information transmitted from the wireless communication device 10, the wireless communication device 30 may determine a transmission timing that serves as a reference. Thereby, the transmission timing used as the reference | standard of an uplink is adjusted between the radio | wireless communication apparatuses 10 and 20, and is determined appropriately.

  The wireless communication device 10 transmits information related to the reference transmission timing to the wireless communication device 30 (S3). For example, the wireless communication device 10 transmits identification information (cell ID or the like) of a wireless communication device serving as a reference among the wireless communication devices 10 and 20 as information related to a transmission timing serving as a reference. The wireless communication device 30 receives information related to the reference transmission timing, and transmits data to the wireless communication devices 10 and 20 at the reference transmission timing (S4). For example, data is transmitted to the wireless communication devices 10 and 20 at a predetermined transmission timing with respect to the reference wireless communication device. As a result, data is transmitted at an appropriate transmission timing adjusted between the wireless communication devices 10 and 20. The data transmitted from the wireless communication device 10 is received by the wireless communication devices 10 and 20, respectively.

  The wireless communication devices 10 and 20 cooperate to synthesize the signal received by the wireless communication device 10 and the signal received by the wireless communication device 20 to acquire data (S5). For example, the wireless communication device 10 acquires a signal received by the wireless communication device 20 and combines it with the signal received by the wireless communication device 10 to acquire data. Since data is transmitted at the transmission timing adjusted between the radio communication apparatuses 10 and 20, the influence of intersymbol interference in the combined signal is reduced, and reception characteristics are improved.

  The above operation will be described with reference to the examples of FIGS. FIG. 3 is a diagram for explaining the reception timing in the wireless communication apparatus. In the example of FIG. 3, an OFDM signal is received and processed using an FFT window. 3A and 3B, time is shown in the horizontal direction, and OFDM symbol reception timing in the wireless communication apparatuses 10 and 20 is shown in order from the top.

  In the state of FIG. 3A, the transmission timing is determined so that the received OFDM symbol of the wireless communication apparatus 10 fits in the received FFT window. At this time, in the wireless communication device 20, the received OFDM symbol does not fit in the received FFT window, and intersymbol interference occurs in the region A.

  In the state of FIG. 3 (B), the transmission timing is determined so that the transmission timing is earlier than the state of FIG. 3 (A), and the received OFDM symbol of the wireless communication apparatus 20 falls within the reception FFT window. At this time, in the wireless communication apparatus 10, the received OFDM symbol does not fit in the received FFT window, and intersymbol interference occurs in the region B.

  FIG. 4 is a diagram for explaining reception characteristics in the radio communication apparatuses 10 and 20. In the example of FIG. 4, SINR is used as the reception quality. In FIG. 4, the vertical axis represents SINR, and the horizontal axis represents reception timing. The timing is shown as a relative value when the effective OFDM symbol length is 1 and the timing T1 in the state where the received OFDM symbol is within the reception FFT window in the wireless communication apparatus 10 is 0. The wireless communication device 20 is in a state where the received OFDM symbol is within the reception FFT window at the timing T2 = 0.2.

  FIG. 4 shows the SINR (indicated by “□” in FIG. 4) of the signal received by the wireless communication device 10 when the transmission timing is changed from the state M to the state N. The SINR of the signal (indicated by “Δ” in FIG. 4) and the SINR of the combined received signal (indicated by “◯” in FIG. 4) are shown. Note that the SINR of each of the wireless communication devices 10 and 20 is measured in a state in which the received OFDM symbol is controlled to be within the reception FFT window by timing control for each of the wireless communication devices 10 and 20.

  As shown in FIG. 4, the SINR of the wireless communication apparatus 10 becomes a value R1 in the state of FIG. 3A in which the received OFDM symbol at the timing T1 is within the reception FFT window, and is illustrated from the state of FIG. As the state changes to 3 (B), SINR decreases due to an increase in intersymbol interference. On the other hand, the SINR of the wireless communication device 20 becomes the value R2 (<R1) in the state of FIG. 3B in which the received OFDM symbol at the timing T2 is within the reception FFT window, and from the state of FIG. As the state changes to (A), the RINR decreases due to an increase in intersymbol interference. At this time, the SINR of the combined received signal takes the maximum value R3 in the state of FIG. 3A at timing T1.

  At this time, for example, the wireless communication device 10 with the highest reception quality among the wireless communication devices 10 and 20 is determined as the reference wireless communication device as the transmission timing that maximizes the reception quality of the combined received signal. .

Note that the wireless communication device with the highest reception quality is obtained, for example, by obtaining the SINR in each wireless communication device and adding it to all the wireless communication devices. Further, the SINR of each of the wireless communication devices 10 and 20 is, for example, the following equation (1), where S is a signal, N is a noise, and α is a rate at which the timing of the received signal protrudes from the FFT window.
SINR = S × (1−α) / (N + S × α) (1)
Can be used to calculate.

  Then, the cell ID of the wireless communication device 10 is transmitted to the wireless communication device 30 as a reference wireless communication device, and a predetermined transmission from the wireless communication device 30 to the wireless communication device 10 as a reference transmission timing. Data is transmitted to the wireless communication devices 10 and 20 at the timing. As a result, when the signals received by the wireless communication devices 10 and 20 are combined to acquire data, the influence of intersymbol interference is reduced in the combined received signal, and reception characteristics are improved.

As described above, according to the first embodiment, it is possible to improve reception characteristics in the wireless communication system 1 that performs uplink CoMP communication.
[Second Embodiment]
FIG. 5 is a diagram illustrating a configuration of a wireless communication system 50 according to the second embodiment. As shown in FIG. 5, the wireless communication system 50 includes a plurality of base stations 60, 80, 90 and a mobile station 100. The base stations 60, 80, and 90 form cells C11, C12, and C13, respectively, and the mobile station 100 is located in the cell C11. Base stations 60, 80, and 90 communicate with each other and perform CoMP communication with mobile station 100. Base station 60 is a serving base station, and base stations 80 and 90 are cooperative base stations. The base stations 60, 80, and 90 perform uplink CoMP communication, and perform processing of receiving and combining the data transmitted by the mobile station 100 in cooperation with the base stations 60, 80, and 90.

  FIG. 6 is a diagram illustrating a functional configuration of the base station 60. As shown in FIG. 6, the base station 60 includes a receiving antenna 61, a data receiving unit 62, a RACH (Random Access Channel) receiving unit 63, and an SRS (Sounding Reference Signal) receiving unit 64. The base station 60 includes a transmission antenna 65, a control channel transmission unit 66, and a data channel transmission unit 67. The base station 60 includes a data demodulator 68, a data decoder 69, a reception buffer 70, and a transmission buffer 71. In addition, the base station 60 includes a timing detection unit 72, a reception quality measurement unit 73, a scheduler unit 74, a UL grant (UpLink grant) generation unit 75, and a TA (Timing Advance) command / RAR (Random Access Response) generation. Part 76. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

  The data reception unit 62 receives uplink data transmitted from the mobile station 100 via the reception antenna 61. For example, uplink data is transmitted from the mobile station 100 using PUSCH (Physical Uplink Shared CHannel).

  The RACH receiving unit 63 receives a random access signal transmitted from the mobile station 100 using the RACH via the receiving antenna 61. Random access is a procedure for transmitting data from one wireless communication device (for example, a mobile station) to the other wireless communication device (for example, a base station) from a state where wireless resources used for data transmission are not allocated. It is. The base station 60 establishes synchronization with the mobile station 100 by receiving the random access signal.

  The SRS receiving unit 64 receives SRS from the mobile station 100 via the receiving antenna 61. The SRS is a known signal transmitted by the mobile station 100, and the base station 60 grasps the channel quality and the like by receiving the SRS. Moreover, the base station 60 determines the transmission timing from the mobile station 100 to the base station 60 by receiving SRS.

  The data demodulator 68 receives the received data from the data receiver 62 and performs demodulation processing. In the demodulation processing, for example, data received from the mobile station 100 is demodulated based on a channel estimation result for PUSCH estimated using DM-RS (DeModulation RS) transmitted from the mobile station 100 as a reference signal.

  The data decoder 69 receives the data demodulated by the data demodulator 68, performs a decoding process, and stores the acquired data in the reception buffer 70.

  The timing detector 72 detects the current reception timing of the local station based on the random access signal received by the RACH receiver 63. The timing detection unit 72 detects the current reception timing of the local station based on the SRS received by the SRS reception unit 64. In addition, the timing detection unit 72 acquires timing information of the base stations 80 and 90 from the base stations 80 and 90. For example, the timing detector 72 acquires timing information detected by the timing detectors of the base stations 80 and 90 based on the SRS received by the SRS receivers of the base stations 80 and 90.

  The reception quality measurement unit 73 measures the reception quality of the local station using the SRS received by the SRS reception unit 64. Further, the reception quality measuring unit 73 acquires information indicating the reception quality measured by the reception quality measuring unit of the base stations 80 and 90 from the base stations 80 and 90.

  The scheduler unit 74 performs scheduling processing such as resource allocation based on the reception quality and timing information of the base stations 60, 80, and 90. For example, the scheduler unit 74 determines SRS resource allocation information for transmitting SRS from the mobile station 100 to the base station 60. For example, the scheduler unit 74 acquires SRS resource allocation information for transmitting SRS from the mobile station 100 to the base stations 80 and 90. The SRS resource allocation information includes, for example, time and frequency at which SRS can be transmitted, and SRS data series information. The scheduler unit 74 may adjust the SRS resource allocation information of the base stations 60, 80, 90 so that the SRSs of the base stations 60, 80, 90 do not collide. Further, for example, the scheduler unit 74 determines a transmission timing serving as an uplink reference from the mobile station 100 to the base stations 60, 80, and 90 during CoMP communication.

  The UL grant generation unit 75 generates UL grant indicating a control signal for allocating uplink resources based on the scheduling information by the scheduler unit 74. The UL grant includes SRS resource allocation information from the mobile station 100 to the base stations 60, 80, 90. The UL grant includes information indicating transmission timing that is a reference from the mobile station 100 to the base stations 60, 80, and 90. In the second embodiment, the cell ID of the reference base station is used as the information indicating the reference transmission timing.

  The TA command / RAR generator 76 generates a random access response RAR based on the reception result of the random access signal. The RAR includes timing adjustment information based on the timing information detected by the timing detection unit 72 according to the random access signal. The timing adjustment information includes, for example, the transmission timing of the mobile station 100 from the current time so that the timing at which the signal transmitted from the mobile station 100 is received by the base station 60 is within a predetermined reception window of the base station 60. Indicates whether to make it early or late. Further, the TA command / RAR generator 76 generates a TA command based on the timing information detected by the timing detector 72 according to the SRS received by the SRS receiver 64. The TA command indicates how much the transmission timing from the mobile station 100 should be made earlier or later than the current transmission timing. For example, the base station 60 determines at which timing position in the reception window the SRS is received, and determines the TA command to return to the window center when the reception timing position of the SRS is likely to protrude from the reception window. To do.

  The control channel transmission unit 66 transmits control information to the mobile station 100 using the control channel via the transmission antenna 65. The control channel includes a PDCCH (Physical Downlink Control CHannel). The control information includes a UL grant generated by the UL grant generation unit 75.

  The data channel transmission unit 17 transmits data to the mobile station 100 through the transmission antenna 65 using the data channel. The data channel includes PDSCH (Physical Downlink Shared CHannel). The transmission data includes data stored in the transmission buffer 71 and TA command / RAR generated by the TA command / RAR generation unit 76.

  In addition, when CoMP communication is performed between the base stations 60, 80, 90 and the mobile station 100 regarding the downlink, data and control information are directly transmitted from the base stations 60, 80, 90 to the mobile station 100. Is possible. In this case, the SRS resource allocation information and the TA command may be transmitted from the base stations 80 and 90 to the mobile station 100 instead of from the base station 60.

  FIG. 7 is a diagram illustrating a functional configuration of the mobile station 100. As illustrated in FIG. 7, the mobile station 100 includes a transmission antenna 101, a data transmission unit 102, an SRS transmission unit 103, and a RACH transmission unit 104. In addition, the mobile station 100 includes a reception antenna 105, a control channel reception unit 106, and a data channel reception unit 107. The mobile station 100 includes application processing units 109 and 110, a transmission buffer 108, and a reception buffer 111. In addition, the mobile station 100 includes a data sequence generation unit 112, a transmission timing control unit 113, a UL grant analysis unit 114, and a higher layer control information analysis unit 115. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

  The control channel receiving unit 106 receives control information transmitted from the base station 60 using the control channel via the reception antenna 105. The control channel includes a PDCCH (Physical Downlink Control CHannel). The control information includes UL grant.

  The data channel receiving unit 107 receives data transmitted from the base station 60 using the data channel via the receiving antenna 105. The data channel includes PDSCH (Physical Downlink Shared CHannel). The data channel receiving unit 107 uses the control information received by the control channel 106 to perform demodulation processing, decoding processing, and the like of the received data, and stores in the reception buffer 110 and inputs to the higher layer control information analysis unit 115 I do.

  Upper layer control information analysis section 115 acquires upper layer control information received by data channel receiving section 107. Upper layer control information includes RACH resource allocation information, SRS resource allocation information, and TA commands. For example, the TA command is included in the header area of the decoded received data.

  The UL grant analysis unit 114 analyzes the UL grant received by the control channel reception unit 106 and acquires information. The acquired information includes information regarding the transmission timing used as a reference.

  The transmission timing control unit 113 performs transmission via the RACH based on the TA command acquired by the higher layer control information analysis unit 115 and information on the transmission timing used as a reference acquired by the UL grant analysis unit 114, and SRS The transmission timing of data transmission and data transmission is controlled.

  The data sequence generation unit 112 generates a data sequence used for a random access preamble and SRS based on the RACH resource allocation information and the SRS resource allocation information.

  The data transmission unit 102 transmits the data stored in the transmission buffer 108 to the base stations 60, 80, 90 via the transmission antenna 101. The transmission data is transmitted using, for example, PUSCH.

  The SRS transmission unit 103 transmits the SRS to the base stations 60, 80, 90 using the transmission timing set in the transmission timing control unit 113.

  The RACH transmission unit 104 transmits a signal using the RACH using the transmission timing set in the transmission timing control unit 113.

  The application processing unit 109 generates data to be transmitted and stores it in the transmission buffer 108. In addition, the application processing unit 110 acquires and processes the reception data stored in the reception buffer 111.

  FIG. 8 is a diagram illustrating a hardware configuration of the base station 60. As illustrated in FIG. 8, the base station 60 includes, as hardware components, for example, a DSP 60A, an FPGA 60B, a memory 60C, an RF circuit 60D including an antenna A1, and a network IF 60E. The DSP 60A and the FPGA 60B are connected so that various signals and data can be input / output via a network IF 60E such as a switch. The memory 60C includes, for example, a RAM such as an SDRAM, a ROM, and a flash memory, and stores programs, control information, and data. The data demodulating unit 68, the data decoding unit 69, the timing detecting unit 72, the reception quality measuring unit 73, the scheduler unit 74, the UL grant generating unit 75, and the TA command / RAR generating unit 76 are, for example, integrated circuits such as a DSP 60A and FPGA 60B. Realized. The data receiving unit 62, the RACH receiving unit 63, the SRS receiving unit 64, the control channel transmitting unit 66, and the data channel transmitting unit 67 are realized by, for example, the RF circuit 60D. The reception buffer 70 and the transmission buffer 71 are realized by the memory 60C, for example. Although the hardware configuration of the base station 60 has been described above, the hardware configuration of the other base stations 80 and 90 is the same as that of the base station 60, and thus detailed description thereof is omitted.

  The mobile station 100 is realized by a mobile terminal such as a mobile phone. FIG. 9 is a diagram illustrating a hardware configuration of the mobile station 100. As shown in FIG. 9, the mobile station 100 includes, as hardware components, for example, a CPU 100A, a memory 100B, an RF circuit 100C including an antenna A2, and a display device 100D such as an LCD (Liquid Crystal Display). Have. The memory 100B includes, for example, a RAM such as an SDRAM, a ROM, and a flash memory, and stores programs, control information, and data. The data transmission unit 102, SRS transmission unit 103, RACH transmission unit 104, control channel reception unit 106, and data channel reception unit 107 are realized by, for example, the RF circuit 100C. Further, the application processing units 109 and 110, the data series generation unit 112, the transmission timing control unit 113, the UL grant analysis unit 114, and the upper layer control information analysis unit 115 are realized by an integrated circuit such as the CPU 100A, for example. The transmission buffer 108 and the reception buffer 111 are realized by the memory 100B, for example.

  Next, the operation of the wireless communication system 50 according to the second embodiment will be described. 10 and 11 are sequence diagrams for explaining the operation of the wireless communication system 50.

  As shown in FIG. 10, the mobile station 100 transmits a random access signal for initial synchronization to the base station 60 (S11). For example, the mobile station 100 uses, as a random access preamble, a signal sequence randomly selected from a plurality of signal sequences by the data sequence generation unit 112 based on system information transmitted using BCH (Broadcast CHannel). Transmit to the base station 60. A signal transmitted via the RACH is set to have a long CP length, and the allowable range of the reception timing deviation is relatively large. Therefore, it is possible to receive even when the initial timing control is not performed. ing. The base station 60 can grasp the current reception timing of its own station by receiving the random access signal.

  The base station 60 transmits RAR as a response to the received random access signal (S12). RAR includes timing adjustment information of uplink transmission timing. The mobile station 100 determines the next transmission timing based on this timing adjustment information. As a result, synchronization is established between the base station 60 and the mobile station 100.

  The base station 60 transmits a message for starting CoMP communication to the mobile station 100 (S13). This message includes cell ID allocation information of the cooperative base stations 80 and 90, for example. The base station 60 notifies the base stations 80 and 90 of information necessary for CoMP communication. Note that the process of selecting a cooperative base station may be performed by the mobile station 100.

  Hereinafter, the mobile station 100 establishes synchronization with the cooperative base stations 80 and 90 (S14 to S17). The mobile station 100 performs random access transmission for initial synchronization to the base station 80 (S14). The RACH resource allocation information uses BCH or PUCCH, and the base station 80 transmits an RAR including uplink transmission timing adjustment information as a response to the received random access preamble (S15). In addition, the mobile station 100 performs random access transmission for initial synchronization to the base station 90 (S16). The base station 90 transmits an RAR including uplink transmission timing adjustment information to the base station 90 as a response to the received random access preamble (S17). Thereby, initial synchronization of transmission timing is performed between the mobile station 100 and each base station 60, 80, 90, and the initial value of the transmission timing to each base station 60, 80, 90 is stored.

  The base station 80 notifies the SRS resource allocation information to the base station 60 (S18). Further, the base station 90 notifies the SRS resource allocation information to the base station 60 (S19). The base station 60 transmits the SRS resource allocation information of the base stations 60, 80, 90 to the mobile station 100 (S20). In addition, when the base stations 60, 80, 90 perform downlink CoMP communication, the SRS resource allocation information may be directly transmitted from the base stations 60, 80, 90 to the mobile station 100.

  Hereinafter, the base stations 60, 80, and 90 periodically repeat uplink transmission timing update processing in order (S21 to S28). The uplink transmission timing update process is performed in the transmission cycle of the upper layer control information using the data channel. The upper layer control information is transmitted at a period of 80 [ms], 160 [ms], or 320 [ms], for example.

  The mobile station 100 transmits SRS to the base station 60 (S21), and the base station 60 generates a TA command and transmits it to the mobile station 100 (S22). Further, the mobile station 100 transmits an SRS to the base station 80 (S23), the base station 80 generates a TA command and notifies the base station 60 (S24), and the base station 60 transmits the notified TA command. It transmits to the mobile station 100 (S25). Also, the mobile station 100 transmits an SRS to the base station 90 (S26), generates a TA command and notifies the base station 60 (S27), and the base station 60 transmits the notified TA command to the mobile station 100. (S28). The mobile station 100 updates the stored transmission timing to each of the base stations 60, 80, 90 in accordance with the received TA command. The mobile station 100 performs the next transmission to the base stations 60, 80, and 90 using the updated transmission timing. When the base stations 60, 80, 90 perform downlink CoMP communication, the TA commands may be directly transmitted from the base stations 60, 80, 90 to the mobile station 100.

  Next, as shown in FIG. 11, when starting uplink data transmission, the mobile station 100 transmits SRSs to the base stations 60, 80, and 90, respectively (S29 to S31). The base stations 60, 80, 90 cooperate to measure and acquire the reception quality (S32). For example, the base stations 60, 80, and 90 measure the reception quality using the received SRS as a reference signal. The base station 60 acquires information on the reception quality of the base stations 80 and 90 and timing information from the base stations 80 and 90.

  The base stations 60, 80, and 90 determine information related to transmission timing that is a reference when data is transmitted from the mobile station 100 (S33). For example, the base station 60 determines a base station serving as a reference for transmission timing based on the information regarding the reception quality of the base stations 60, 80, 90 and the timing information (S33). Thereby, the reference transmission timing is adjusted between the base stations 60, 80, and 90 and appropriately determined.

  The base station 60 transmits information related to the reference transmission timing to the mobile station 100 (S34). For example, the base station 60 generates a UL grant including the cell ID of the base station serving as a reference, and transmits the generated UL grant to the mobile station 100. Note that UL grant transmission using the control channel is performed in a shorter cycle than transmission of higher layer control information. For example, UL grant is transmitted at a cycle of 1 [ms]. Since the transmission timing is controlled in such a relatively short cycle, uplink transmission can be performed at a transmission timing that appropriately follows changes in the propagation environment.

  The mobile station 100 transmits data to the base stations 60, 80, 90 at the received transmission timing as a reference (S35). Thereby, data is transmitted at an appropriate transmission timing adjusted between the base stations 60, 80 and 90. Data transmitted from the mobile station 100 is received by the base stations 60, 80, and 90, respectively.

  The base stations 60, 80, 90 cooperate to synthesize signals received at the base stations 60, 80, 90 to acquire data (S36). For example, the base station 60 acquires signals received by the base stations 80 and 90, and combines the signals received by the base stations 60, 80, and 90 to acquire data. Since data is transmitted at the transmission timing adjusted between the base stations 60, 80, 90, the influence of intersymbol interference is reduced in the combined received signal, and reception characteristics are improved.

  The above operation will be described with reference to the examples of FIGS. FIG. 12 is a diagram for explaining reception timings at the base stations 60, 80, 90. In the example of FIG. 12, an OFDM signal is received and processed using an FFT window. In each of FIGS. 12A, 12B, and 12C, the horizontal direction indicates time, and the OFDM symbol reception timing in the base stations 60, 80, and 90 in order from the top.

  In the state of FIG. 12A, the transmission timing is determined so that the received OFDM symbol of the base station 60 fits in the received FFT window. At this time, in the base stations 80 and 90, the received OFDM symbols do not fit in the received FFT window, and intersymbol interference occurs in the regions C and D.

  In the state of FIG. 12 (B), the transmission timing is determined so that the transmission timing is earlier than the state of FIG. 12 (A) and the received OFDM symbol of the base station 80 fits in the reception FFT window. At this time, in the base stations 60 and 90, the received OFDM symbols do not fit in the received FFT window, and intersymbol interference occurs in the regions E and F.

  In the state of FIG. 12C, the transmission timing is determined so that the transmission timing is advanced from the state of FIG. 12B, and the received OFDM symbol of the base station 90 fits in the reception FFT window. At this time, in the base station 60, the received OFDM symbol does not fit in the received FFT window, and intersymbol interference occurs in the region G.

  FIG. 13 is a diagram for explaining reception characteristics at the base stations 60, 80, and 90. In the example of FIG. 13, SINR is used as the reception quality. In FIG. 13, the vertical axis represents SINR, and the horizontal axis represents reception timing. The timing is a relative value when the effective OFDM symbol length is 1, and the timing T3 in the state where the received OFDM symbol is within the received FFT window at the base station 60 is 0. The base station 80 enters a state where the received OFDM symbol at the base station 80 is within the received FFT window at timing T4 = 0.18. The base station 90 enters a state in which the received OFDM symbol at the base station 90 is within the received FFT window at timing T5 = 0.2.

  FIG. 13 illustrates the SINR (indicated by “□” in FIG. 13) of the signal received by the base station 60 and the SINR of the signal received by the base station 80 when the transmission timing is changed from the state P to the state R. 13, the SINR of the signal received by the base station 90 (indicated by “X” in FIG. 13), and the SINR of the combined received signal (indicated by “◯” in FIG. 13). ). The SINR of each of the base stations 60, 80, 90 is measured in a state where the received OFDM symbols are controlled to be within the reception FFT window by the timing control for each of the base stations 60, 80, 90.

  As shown in FIG. 13, the SINR of the base station 60 becomes the value R4 in the state of FIG. 12A where the received OFDM symbol at the timing T3 is within the received FFT window, and from the state of FIG. As the state changes to (C), the SINR decreases due to the increase in intersymbol interference. The SINR of the base station 80 is the maximum value R5 (<R4) in the state of FIG. 12B in which the received OFDM symbol at the timing T4 is within the received FFT window. The SINR of the base station 90 is a value R6 (<R5) in the state of FIG. 12C in which the received OFDM symbol at timing T5 is within the received FFT window. At this time, the SINR of the combined received signal is the maximum value R7 in the state of FIG. 12B at timing T4.

  At this time, the base station 80 of the base stations 60, 80, and 90 is determined as a reference base station as the transmission timing that maximizes the reception quality of the combined received signal. In this case, considering the reception quality and the distribution of the reception timing, it is more possible to make the symbol closer to the timing of the base stations 80 and 90 where the reception timing is densely distributed than to match the timing of the base station 60 having the highest reception quality. The effect of reducing the influence of interfering interference is great.

  Then, the cell ID of the base station 80 is transmitted as the reference base station to the mobile station 100, and the mobile station 100 transmits the reference transmission timing to the base station 80 at a predetermined transmission timing as the reference transmission timing. Data is transmitted from 100 to the base stations 60, 80, 90. Thereby, when data is acquired by combining the signals received by the base stations 60, 80, 90, the influence of intersymbol interference is reduced in the combined received signal, and reception characteristics are improved.

  As described above, according to the second embodiment, it is possible to improve reception characteristics in the radio communication system 50 that performs uplink CoMP communication.

As another embodiment, when determining the reference transmission timing, a value obtained by correcting the reception quality with a predetermined value corresponding to the distribution of the reception timing is used as an index value. The transmission timing may be determined. For example, the reception quality is multiplied by a coefficient corresponding to the relative value based on the median or average value of the reception timing, or an offset value corresponding to the relative value based on the median or average value of the reception timing is added to the reception quality. You may do it. Also, for example, the reception quality is multiplied by a coefficient according to the order close to the median or average value of the reception timing, or an offset value according to the order close to the median or average value of the reception timing is added to the reception quality. May be. Further, for example, the base station closest to the median or average value of the reception timing may be selected, or the nearest base station may be multiplied by a predetermined coefficient or a predetermined offset value may be added.
[Third Embodiment]
FIG. 14 is a diagram illustrating a configuration of a wireless communication system 200 according to the third embodiment. As illustrated in FIG. 14, the wireless communication system 200 includes a mobile station 100 and base stations that form a cell. The base station includes a plurality of RRHs (Remote Radio Heads) 230A to 230C and a BBU (BaseBand Unit) 220. Each of the RRHs 230A to 230C has an antenna (point) and is disposed at a distant point to form cover areas E21, 22, and 23. The cell of the base station is formed by the cover areas E21, 22 and 23. The BBU 220 is disposed at a point distant from the RRHs 230A to 230C, and is connected to the RRHs 230A to 230C by wired connection. The mobile station 100 is located in the cover area E21 of the RRH 230A. RRHs 230 </ b> A to 230 </ b> C correspond to an example of a first wireless communication device, and perform communication with each other and perform CoMP communication with mobile station 100. Cover area E21 of RRH 230A is used as a serving cell, and cover areas E22 and E23 of RRH 230B and 230C are used as cooperative cells. The RRHs 230A to 230C perform uplink CoMP communication, and perform processing of receiving and combining data transmitted by the mobile station 100 in cooperation with the RRHs 230A to 230C. Since the configuration and operation of the mobile station 100 are the same as those of the mobile station 100 of the second embodiment, the same reference numerals are given and description thereof is omitted.

  FIG. 15 is a diagram illustrating a functional configuration of the RRHs 230A to 230C and the BBU 220 of the base station 210. As illustrated in FIG. 15, the RRH 230A of the base station 210 includes a reception antenna 231A, a transmission antenna 232A, and a radio unit 233A. The radio unit 233A includes a data receiver 234A, a RACH receiver 235A, an SRS receiver 236A, a control channel transmitter 237A, and a data channel transmitter 238A. The BBU 220 includes a data demodulator 240, a data decoder 241, a timing detector 243, a reception buffer 242, a reception quality measurement unit 244, a scheduler unit 245, a UL grant generation unit 246, a TA command A RAR generator 247 and a transmission buffer 248 are provided. Details of the components of the RRH 230A and the BBU 220 are the same as those of the components of the base station 60 of the second embodiment.

  The RRH 230B includes a reception antenna 231B, a transmission antenna 232B, and a radio unit 233B. The radio unit 233B includes a data reception unit 234B, a RACH reception unit 235B, an SRS reception unit 236B, a control channel transmission unit 237B, and a data channel transmission unit 238A. Details of each component of the RRH 230B are the same as each component of the RRH 230A.

  The RRH 230C includes a reception antenna 231C, a transmission antenna 232C, and a radio unit 233C. The radio unit 233C includes a data reception unit 234C, a RACH reception unit 235C, an SRS reception unit 236C, a control channel transmission unit 237C, and a data channel transmission unit 238C. Details of each component of the RRH 230C are the same as each component of the RRH 230A.

  Next, the operation of the wireless communication system 200 will be described. The operation of the radio communication system 200 is basically a transmission / reception operation of the base stations 60, 80, 90 of the second embodiment as an operation of the RRHs 230A to 230C. Is the operation of the BBU 220. However, in the second embodiment, the base station 60 takes the initiative to acquire information from the base stations 80 and 90 and perform cooperative processing (S32, S33, S36), whereas in the third embodiment, the BBU 220 performs information processing. Aggregate and perform cooperative processing.

  In the timing control operation of the wireless communication system 200, timing control is executed in the same manner as in the description of FIG. 13 of the second embodiment. For example, for RRHs 230A to 230C that perform uplink CoMP communication, a reference transmission timing is determined as the transmission timing that maximizes the reception quality of the combined received signal.

According to the third embodiment, similarly to the second embodiment, reception characteristics can be improved in the wireless communication system 200 that performs uplink CoMP communication.
[Fourth Embodiment]
FIG. 16 is a diagram illustrating a configuration of a wireless communication system 300 according to the fourth embodiment. In the wireless communication system 300, base stations 310, 320, and 330 and RRHs 340A to 340L are mixed as an example of a first wireless communication apparatus, and at least a part of these perform cooperative communication.

  As shown in FIG. 16, in the wireless communication system 300, a plurality of base stations 310, 320, and 330 form a plurality of cells C31, C32, and C33. In each cell C31, C32, C33, a plurality of RRHs 340A to 340L having antennas (points) are arranged. RRHs 340A to 340L each have an antenna and a radio unit, and BBUs including a baseband processing unit and the like are arranged at different positions. RRHs 340A to 340l are arranged at the ends of cells C31, C32, and C33 of base stations 310, 320, and 330, respectively. RRHs 340A to 340l form cover areas E41A to E41L, respectively. The BBUs connected to the RRHs 340A to 340L are arranged at substantially the same positions as the base stations 310, 320, and 330, respectively. The BBUs corresponding to the RRHs 340A to 340L are connected or integrated with the base stations 310, 320, and 330 forming the cells C31, C32, and C33 that are in the area, and between the base stations 310, 320, and 330. Collaborative scheduling is possible. In the fourth embodiment, it is assumed that the mobile station 100 is located in the cover area E340A of the RRH 340A under the base station 310. Since the configuration and operation of the mobile station 100 are the same as those of the mobile station 100 of the second embodiment, the same reference numerals are given and description thereof is omitted.

  The functional configurations and operations of the base stations 310, 320, and 330 are the same as those of the base station 60 of the second embodiment. The functional configurations and operations of the RRHs 340A to 340L are the same as those of the RRH 230A of the third embodiment.

  In the timing control operation of the wireless communication system 300, timing control is executed in the same manner as in the description of FIG. 13 of the second embodiment. For example, for at least a part of base stations 310, 320, and 330 that perform uplink CoMP communication and RRHs 340A to 340L, a transmission timing that serves as a reference is used as a transmission timing that maximizes the reception quality of the combined received signal. It is determined.

  According to the fourth embodiment, similarly to the second and third embodiments, reception characteristics can be improved in the wireless communication system 300 that performs uplink CoMP communication.

  Although the fourth embodiment has been described on the assumption that the cover area of each RRH exists in the same cell, the cover area of each RRH may exist across different cells.

  Moreover, the radio | wireless communications system of 1st-4th embodiment is realizable as a LTE-A system, for example. In addition, it is also possible to apply to the radio | wireless communications system using communication systems other than LTE-A.

  Further, as a wireless communication system, for example, it is also possible to apply to a heterogeneous network in which base stations having different transmission powers are mixed or wireless communication devices using different types of communication methods are mixed. .

  In the first to fourth embodiments, the condition for determining the reference transmission timing is the installation position of each device (wireless communication device, base station, RRH, antenna, etc.), the arrangement relationship with other devices, or They can be updated as appropriate according to the changing factors such as the operation status and radio wave condition of each device.

  The first to fourth embodiments can be applied to mobile terminals such as mobile phones, smartphones, and PDAs (Personal Digital Assistants) as mobile stations. In addition, the first to fourth embodiments can be applied to various communication devices that communicate with a base station such as a mobile relay station.

  The first to fourth embodiments can be applied to base stations of various scales such as a macro base station and a femto base station as base stations. In addition, the first to fourth embodiments can be applied to various communication devices that perform communication with a mobile station such as a relay station.

  In addition, the specific mode of distribution / integration of each component of the base station and mobile station is not limited to the mode of the first to fourth embodiments, and all or a part thereof can be used for various loads, usage conditions, etc. Accordingly, it may be configured to be functionally or physically distributed / integrated in an arbitrary unit. For example, the memory may be connected via a network or a cable as an external device of the base station or mobile station.

1, 50, 200, 300 Wireless communication system 10, 20, 30 Wireless communication device 11, 21, 31 Antenna 12, 22, 32 Transmitter 13, 23, 33 Receiver 14, 24, 34 Controller 60, 80, 90 , 310, 320, 330 Base station 60A DSP
60B FPGA
60C memory 60D RF circuit 60E network IF
61 reception antenna 62,234A data reception unit 63,235A RACH reception unit 64,236A SRS reception unit 65 transmission antenna 66,237A control channel transmission unit 67,238A data channel transmission unit 68,240 data demodulation unit 69,241 data decoding unit 70,242 Reception buffer 71,248 Transmission buffer 72,243 Timing detection unit 73,244 Reception quality measurement unit 74,245 Scheduler unit 75,246 UL grant generation unit 76,247 TA command / RAR generation unit 100 Mobile station 100A CPU
100B memory 100C RF circuit 100D display device 101 transmitting antenna 102 data transmitting unit 103 SRS transmitting unit 104 RACH transmitting unit 105 receiving antenna 106 control channel receiving unit 107 data channel receiving unit 108 transmission buffer 109, 110 application processing unit 111 receiving buffer 112 data Sequence generation unit 113 Transmission timing control unit 114 UL grant analysis unit 115 Upper layer control information analysis unit 220 BBU
230A-230C, 340A-340L RRH
231A to 231C Receiving antenna 232A to 232C Transmitting antenna 233A to 233C Radio unit C1, C2, C11, C12, C13, C31, C32, C33 cells E21 to E23, E41A to E41L RRH cover area

Claims (10)

In a wireless communication system in which a plurality of first wireless communication devices receive data transmitted from a second wireless communication device in parallel , and synthesize and decode the received plurality of data .
A first transmission unit configured to transmit, to the second wireless communication device, information related to the optimal transmission timing based on the information related to the plurality of first wireless communication devices;
A second transmission unit that transmits the data at the transmission timing from the second wireless communication device to the plurality of first wireless communication devices;
A wireless communication system comprising: The information regarding the transmission timing is information indicating a predetermined first wireless communication device among the plurality of first wireless communication devices,
The second transmission unit transmits the data to the plurality of first wireless communication devices at a transmission timing to the predetermined first wireless communication device among a plurality of transmission timings to the plurality of first wireless communication devices. Send to the wireless communication device,
The wireless communication system according to claim 1. At least one of the plurality of first wireless communication devices is
The wireless communication system according to claim 1, further comprising: a determination unit that determines information related to the transmission timing from information related to the plurality of first wireless communication devices. A wireless communication method in which a plurality of first wireless communication devices receive data transmitted from a second wireless communication device in parallel , synthesize and decode the received plurality of data ,
Based on the information on the plurality of first wireless communication devices, information on the optimal transmission timing for combining is transmitted to the second wireless communication device,
Transmitting the data from the second wireless communication device to the plurality of first wireless communication devices at the transmission timing;
A wireless communication method. The information related to the transmission timing is information related to a predetermined first wireless communication device among the plurality of first wireless communication devices,
Among the plurality of transmission timings to the plurality of first wireless communication devices, the data is transmitted from the second wireless communication device to the plurality of first timings at the transmission timing to the predetermined first wireless communication device. Send to the wireless communication device,
The wireless communication method according to claim 4. At least one of the plurality of first wireless communication devices determines information related to the transmission timing from information related to the plurality of first wireless communication devices.
The wireless communication method according to claim 4. In a wireless communication device that receives data transmitted from the second wireless communication device in parallel in cooperation with another wireless communication device, combines and decodes the received plurality of data ,
A transmission unit configured to transmit information related to optimal transmission timing to the second wireless communication device based on information related to the wireless communication device and the other wireless communication device;
A receiver for receiving data transmitted from the second wireless communication device at the transmission timing;
A wireless communication apparatus comprising: The information on the transmission timing is information indicating a predetermined wireless communication device among the wireless communication device and the other wireless communication device,
The receiving unit receives data transmitted from the second wireless communication device at a transmission timing to the predetermined wireless communication device among a plurality of transmission timings to the wireless communication device and the other wireless communication device. The wireless communication apparatus according to claim 7, wherein the wireless communication apparatus receives the wireless communication apparatus. A wireless communication device,
Based on information on a plurality of first wireless communication devices that receive data transmitted from the wireless communication device in parallel , combine and decode the received plurality of data, information on the optimal transmission timing for combining , A receiving unit for receiving from at least one of the plurality of first wireless communication devices;
A transmitter that transmits data to the plurality of first wireless communication devices at the transmission timing;
A wireless communication apparatus comprising: The information related to the transmission timing is information related to a predetermined first wireless communication device among the plurality of first wireless communication devices,
The transmission unit transmits the data to the plurality of first wireless communication devices at a transmission timing to the predetermined first wireless communication device among a plurality of transmission timings to the plurality of first wireless communication devices. Send to
The wireless communication apparatus according to claim 9.

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