Base station device, wireless terminal device, wireless communication system, and communication control method

Abstract

Provided are a base station device, a wireless terminal device, a wireless communication system, and a communication control method with which uplink communication performance is improved. The base station device has a plurality of RUs (20). The RUs (20) each have the following components. A reception BB processing unit (221) and a MIMO processing unit (222) receive signals transmitted from each of a plurality of wireless terminal devices that cooperatively transmit transmission data. A control unit (224) selects a reference wireless station from the RU (20), determines the phase of transmission data for each wireless terminal device in the selected reference wireless station, and notifies each wireless terminal device.

Description

[Technical Field]

[0001] The present invention relates to a base station device, a wireless terminal device, a wireless communication system, and a communication control method. [Background technology]

[0002] The 3GPP (registered trademark) (3rd Generation Partnership Project), which develops wireless communication standards, is currently conducting technical studies on communication standards for fifth-generation mobile communications (5G or NR (New Radio)). In the current networks targeted by fifth-generation mobile communications, traffic from mobile devices such as smartphones and feature phones accounts for the majority of network resources. Furthermore, the traffic used by mobile devices is expected to continue to expand in the future.

[0003] On the other hand, with the development of IoT (Internet of Things) services, etc., it is necessary to support services with a wide variety of requirements. Therefore, in the communication standards for 5th generation mobile communications, technologies that achieve even higher data rates, larger capacity, and lower latency will be important.

[0004] In particular, the communication performance of the uplink from a wireless terminal device to a base station device can be a serious bottleneck in the wireless system in NR. Therefore, NR requires higher uplink communication performance in terms of coverage, throughput, service continuity, etc. For example, improvements in uplink communication capacity and transmission signal quality are required to enable users to transmit information using various wireless terminal devices and to upload rich content such as video and virtual reality (VR) from various wireless terminal devices.

[0005] Demand for improved communication efficiency, including improvements in communication capacity and reduced power consumption as described above, is expected to increase further in the next generation of communication systems known as sixth generation mobile communication systems (6G) and Beyond 5G.

[0006] Here, as a technology for improving communication performance between a wireless terminal device and a base station, a technology has been proposed in which UE (User Equipment) configuration related to carrier aggregation and NR band processing combination is received from the base station and communication is performed according to the received UE configuration. Also, a technology has been proposed in which signals addressed to multiple wireless terminal devices are multiplexed into a frame and transmitted. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2021-505029 [Patent Document 2] Japanese Patent Application Publication No. 2018-170797 Summary of the Invention [Problem to be solved by the invention]

[0008] However, wireless terminal devices are subject to significant constraints, such as the number of antennas mounted and the maximum transmission power, which are determined by the size of the housing. These constraints on wireless terminal devices are a major bottleneck in uplink communication performance. While relaxing the constraints on the number of antennas and other aspects to improve uplink communication performance is conceivable, this would result in an increase in the size of the wireless terminal device. For wireless terminal devices that are required to be small and lightweight, increasing the size is not realistic, and it is difficult to improve uplink communication performance by relaxing the constraints on the wireless terminal device itself.

[0009] Furthermore, a technology that allows a UE to receive UE configuration related to carrier aggregation or NR band processing combination from a base station and then communicate with the UE can realize efficient communication related to control signals between a wireless terminal device and a base station, but it is difficult to improve the uplink communication performance itself. Furthermore, a technology that multiplexes signals addressed to multiple wireless terminal devices into a frame and transmits them is a technology for improving the transmission efficiency of downlink communication, but it is difficult to improve the uplink communication performance.

[0010] The disclosed technology has been made in view of the above, and aims to provide a base station device, a wireless terminal device, a wireless communication system, and a communication control method that improve uplink communication performance. [Means for solving the problem]

[0011] In one aspect of the base station device, wireless terminal device, wireless communication system, and communication control method disclosed herein, the base station device has a plurality of wireless stations. The wireless stations have the following units: a receiving unit receives signals transmitted from each of a plurality of wireless terminal devices that cooperatively transmit transmission data; a control unit selects a reference wireless station from the plurality of wireless stations, determines the phase of the transmission data for each of the wireless terminal devices at the selected reference wireless station, and notifies each of the wireless terminal devices of the phase. [Effects of the Invention]

[0012] According to one aspect of the base station device, the wireless terminal device, the wireless communication system, and the communication control method disclosed in the present application, it is possible to achieve an effect of improving communication performance in the uplink direction. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a wireless communication system. [Figure 2] FIG. 2 is a diagram illustrating another example of the configuration of a wireless communication system. [Figure 3] FIG. 3 is a block diagram of the wireless terminal device according to the first embodiment. [Figure 4] FIG. 4 is a block diagram of an RU, which is a radio station. [Figure 5] FIG. 5 is a block diagram related to reception quality measurement in the reception processing of an RU. [Figure 6] FIG. 6 is a diagram for explaining the separation of the reference signal. [Figure 7] FIG. 7 is a diagram for explaining acquisition of a received signal for each wireless terminal device. [Figure 8] FIG. 8 is a diagram for explaining propagation path compensation and combining. [Figure 9] FIG. 9 is a diagram illustrating an example of weighting. [Figure 10] FIG. 10 is a sequence diagram of an uplink data transmission process performed by the wireless communication system according to the first embodiment. [Figure 11] FIG. 11 is a flowchart of an uplink data transmission process performed by the wireless terminal device according to the first embodiment. [Figure 12] FIG. 12 is a flowchart of an uplink data reception process by an RU according to the first embodiment. [Figure 13] FIG. 13 is a block diagram of a wireless terminal device using a different relay method. [Figure 14] FIG. 14 is a diagram illustrating an example of data distribution according to the second embodiment. [Figure 15] FIG. 15 is a diagram illustrating an example of a hardware configuration of a wireless terminal device. [Figure 16] FIG. 16 illustrates an example of the hardware configuration of an RU. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following describes in detail exemplary embodiments of a base station device, a wireless terminal device, a wireless communication system, and a communication control method disclosed herein with reference to the accompanying drawings. Note that the base station device, the wireless terminal device, the wireless communication system, and the communication control method disclosed herein are not limited to the following exemplary embodiments. [Example]

[0015] 1 is a diagram illustrating the configuration of a wireless communication system. The wireless communication system 1 according to this embodiment includes a plurality of wireless terminal devices 10 that perform coordinated transmission for transmitting data in a coordinated manner, a plurality of RUs (Remote Units or Radio Units) 20, DUs (Distributed Units) 30, CUs (Central Units) 40, and a CN (Core Network) 50. The RUs 20, DUs 30, and CUs 40 are base station devices.

[0016] The CN 50 is a network located above the base station equipment.

[0017] The DU 30 and CU 40 perform the baseband functions of the base station device. The CU 40 is connected to the CN 50. The CU 40 is also connected to the DU 30. A plurality of RUs 20 are connected to the DU 30. The number of RUs 20 connected to the DU 30 does not necessarily have to be two or more; it may be one.

[0018] More specifically, the DU 30 performs baseband processing of the physical layer and the L2 layer. For example, the DU 30 receives uplink data, which is data in the uplink direction, transmitted from the wireless terminal device 10. Then, the DU 30 performs baseband processing of the physical layer and the L2 layer on the received uplink data, and transmits the data to the CU 40.

[0019] The CU 40 performs baseband processing of the L2 layer, which is higher than the function assigned to the DU 30. For example, the CU 40 receives, from the DU 30, uplink data that has been subjected to baseband processing of the physical layer and the L2 layer assigned to the DU 30. Then, the CU 40 performs baseband processing of the L2 layer, which is higher than the function assigned to the DU 30, on the received uplink data, and transmits the data to the CN 50.

[0020] Here, in FIG. 1, the DU 30 and the CU 40 are shown as separate devices, but the DU 30 and the CU 40 do not have to be separate devices, and the functions of both may be integrated into one device.

[0021] The RU 20 is a radio station of a base station device. The RU 20 is connected to the DU 30. The RU 20 receives reference signals cooperatively transmitted from each of the multiple wireless terminal devices 10. The RU 20 then selects appropriate weights for the reference signals transmitted from each of the wireless terminal devices 10, weights them, and combines them to generate a combined signal. Here, the weights have amplitudes and phases corresponding to the reception results of the signals transmitted from each of the wireless terminal devices 10, and are preferably set so as to maximize the quality of the received signal after combination. Next, the RU 20 measures the reception quality of the generated combined signal.

[0022] Each RU 20 then transmits the measurement results of reception quality to a specific RU 20 that is predetermined as the device that selects the RU 20 that will be the reference for data transmission in cooperative transmission. The specific RU 20 compares the measurement results of reception quality from each RU 20 and determines the RU 20 with the best reception quality as the reference RU 20. The destination of the measurement results of reception quality and the comparison of the measurement results to determine the reference RU 20 may be determined by the DU 30 or CU 40 instead of by the specific RU 20. Hereinafter, the RU 20 that will be the reference for data transmission in cooperative transmission is referred to as the "reference radio station." The RU 20 selected as the reference radio station then determines the phase setting of the transmission data in the wireless terminal device 10 so that the reception quality is optimal. The RU 20 selected as the reference radio station then transmits and notifies each wireless terminal device 10 of its respective phase setting.

[0023] Thereafter, each RU 20 receives uplink data that has been phase-controlled using the notified phase setting from each radio terminal device 10. Then, each RU 20 transmits the received uplink data to the DU 30.

[0024] FIG. 1 shows three wireless terminal devices 10. One of the wireless terminal devices 10 is, for example, a smartphone. Another of the wireless terminal devices 10 is, for example, a smartwatch. The remaining wireless terminal device 10 is, for example, an eyeglass-type communication device. The three wireless terminal devices 10 shown in FIG. 1 perform cooperative transmission to transmit uplink data to the RU 20. That is, the multiple wireless terminal devices 10 are each treated as a MIMO antenna and perform MIMO transmission of the uplink data. For example, a wireless terminal device 10 that is a smartphone generates uplink data and transmits data to be cooperatively transmitted from the generated uplink data to the other wireless terminal devices 10. Then, the three wireless terminal devices 10 transmit the data they have received as their own uplink data to the RU 20.

[0025] Here, the three wireless terminal devices 10 may transmit the same transmission data or may each transmit different transmission data obtained by dividing one transmission data. The case where the same transmission data is transmitted is called MIMO diversity, and the case where one transmission data is divided and each transmits different transmission data is called MIMO multiplexing. In the case of MIMO diversity, the three wireless terminal devices 10 transmit transmission data in cooperation with each other, thereby increasing the total transmission power of the transmission data. Furthermore, in the case of MIMO multiplexing, the three wireless terminal devices 10 transmit transmission data in cooperation with each other, thereby shortening the transmission time of one transmission data or increasing the amount of data transmitted in a certain period of time, thereby improving communication speed.

[0026] The wireless terminal device 10 transmits a reference signal to each RU 20. After that, the wireless terminal device 10 receives information on the phase setting for transmitting uplink data to the wireless terminal device 10 from the RU 20, which is the reference wireless station. The wireless terminal device 10 then transmits the uplink data to each RU 20 using the notified phase setting.

[0027] While this embodiment illustrates a configuration in which a DU 30 and a CU 40 have a one-to-one relationship, the wireless communication system 1 may have other configurations. FIG. 2 illustrates another example of the configuration of a wireless communication system. As illustrated in FIG. 2, a configuration may be adopted in which multiple DUs 30 are connected to one CU 40, and multiple RUs 20 are placed under each DU 30. In this case, the combination of RUs 20 to be selected as reference radio stations is not limited to RUs 20 under the same DU 30, and the reference radio station may be selected from RUs 20 connected to different DUs 30. Furthermore, although not illustrated, a configuration in which one RU 20 is placed under one DU 30 in FIG. 2 may also be adopted.

[0028] The operation of the RU 20 and the wireless terminal device 10 in transmitting uplink data will be described in detail below. Fig. 3 is a block diagram of a wireless terminal device according to a first embodiment. When cooperatively transmitting uplink data with another wireless terminal device 10, the wireless terminal device 10 shown in Fig. 3 can forward data transmitted from the other wireless terminal device 10 to the RU 20. As a relay technique used in this case, the wireless terminal device 10 shown in Fig. 3 uses a technique called DF (Decode and Forward), which encodes decoded data and transmits it from the antenna 104. The wireless terminal device 10 will be described with reference to Fig. 3.

[0029] The wireless terminal device 10 includes a wireless communication circuit 101 , a processing unit 102 , a storage unit 103 and an antenna 104 .

[0030] The wireless communication circuit 101 receives a wireless signal transmitted from the RU 20 via the antenna 104. The wireless communication circuit 101 then performs processing such as down-conversion (frequency conversion) and A / D (Analog / Digital) conversion on the received wireless signal to convert it into a baseband signal. The wireless communication circuit 101 then outputs the baseband signal to the processing unit 102.

[0031] The wireless communication circuit 101 also receives a baseband signal as input from the processing unit 102. Next, the wireless communication circuit 101 converts the acquired baseband signal into a wireless signal by performing processes such as D / A conversion and up-conversion (frequency conversion). The wireless communication circuit 101 then transmits the wireless signal to the RU 20 via the antenna 104.

[0032] The storage unit 103 temporarily stores data when the processing unit 102 performs various processes on the baseband signal.

[0033] The processing unit 102 performs processing on the baseband signal. As shown in FIG. 3 , the processing unit 102 includes a reception BB (Base Band) processing unit 121, a decoding unit 122, a relay unit 123, a transmission data processing unit 124, and a transmission BB processing unit 125.

[0034] The reception BB processing unit 121 acquires the baseband signal input from the wireless communication circuit 101. Then, the reception BB processing unit 121 performs processing such as channel estimation, channel compensation, and demodulation on the acquired baseband signal to convert it into soft decision information before decoding. Thereafter, the reception BB processing unit 121 outputs the processed baseband signal to the decoding unit 122.

[0035] The decoding unit 122 receives an input of a baseband signal converted into soft decision information from the reception BB processing unit 121. Then, the decoding unit 122 performs error correction decoding, such as Viterbi decoding or turbo decoding, on the acquired baseband signal. Here, the decoding method corresponds to the coding method implemented on the transmitting side and is not limited to the above example. Thereafter, in the case of data reception, the decoding unit 122 passes the decoded data to an application (not shown) that performs processing on an upper layer. For example, the application provides the acquired data to a user by displaying it on a screen. Furthermore, in the case of signal relay in cooperative transmission, the decoding unit 122 outputs the decoded data to the relay unit 123.

[0036] Furthermore, if the data is control information that notifies the phase of the uplink data, the decoding unit 122 outputs the decoded data to the control unit 126 .

[0037] The relay unit 123 operates when relaying a signal in cooperative transmission. The relay unit 123 acquires the decoded data from the decoding unit 122. Then, the relay unit 123 transfers the acquired data to the transmission data processing unit 124.

[0038] When performing communication, the control unit 126 instructs the transmission data processing unit 124 to transmit a reference signal. Thereafter, the control unit 126 receives an input of a control signal notifying the phase of the uplink data from the decoding unit 122. Then, the control unit 126 notifies the transmission BB processing unit 125 of the phase of the uplink data specified by the control signal.

[0039] At the start of communication, the transmission data processing unit 124 receives an instruction to transmit a reference signal from the control unit 126. Then, the transmission data processing unit 124 generates a reference signal and outputs it to the transmission BB processing unit 125.

[0040] Furthermore, when transmitting data, the transmission data processing unit 124 receives input of data to be transmitted from an application that performs processing in an upper layer, etc. Furthermore, in the case of signal relay in cooperative transmission, the transmission data processing unit 124 receives input of data from the relay unit 123. Then, the transmission data processing unit 124 performs processing such as encoding on the acquired data. Thereafter, the transmission data processing unit 124 outputs the encoded data to the transmission BB processing unit 125.

[0041] The transmission BB processing unit 125 receives an input of a reference signal generated at the start of communication from the transmission data processing unit 124. Then, the transmission BB processing unit 125 performs modulation on the reference signal, mapping to time resources and frequency resources, etc. Thereafter, the transmission BB processing unit 125 outputs the processed reference signal to the wireless communication circuit 101.

[0042] The transmission BB processing unit 125 also receives input of encoded data from the transmission data processing unit 124. The transmission BB processing unit 125 then performs modulation on the acquired data, mapping to time resources and frequency resources, etc. The transmission BB processing unit 125 then outputs the processed data to the wireless communication circuit 101.

[0043] Fig. 4 is a block diagram of an RU, which is a radio station. Next, the RU 20 will be described with reference to Fig. 4. As shown in Fig. 4, the RU 20 has a radio communication circuit 201, a processing unit 202, a storage unit 203, and an antenna 204.

[0044] The wireless communication circuit 201 receives a wireless signal transmitted from the wireless terminal device 10 via the antenna 204. Then, the wireless communication circuit 201 converts the received wireless signal into a baseband signal by performing processing such as down-conversion (frequency conversion) and A / D conversion. The wireless communication circuit 201 then outputs the baseband signal to the processing unit 202.

[0045] Furthermore, the wireless communication circuit 201 receives an input of a baseband signal received from the DU 30 from the processing unit 202. Next, the wireless communication circuit 201 performs processing such as D / A conversion and up-conversion (frequency conversion) on the acquired baseband signal to convert it into a wireless signal. Then, the wireless communication circuit 201 transmits the wireless signal to the wireless terminal device 10 via the antenna 204.

[0046] The storage unit 203 temporarily stores data when the processing unit 202 performs various processes on the baseband signal.

[0047] The processing unit 202 performs processing on the baseband signal. The processing unit 202 also adds and combines weight candidates for the reference signal and determines the weight that provides the best quality. As shown in FIG. 4 , the processing unit 202 has a reception BB processing unit 221, a MIMO processing unit 222, a decoding unit 223, a control unit 224, a transmission data processing unit 225, and a transmission BB processing unit 226.

[0048] The reception BB processing unit 221 acquires the baseband signal input from the wireless communication circuit 201. Then, the reception BB processing unit 221 performs processing such as channel estimation and channel compensation. Here, the reception BB processing unit 221 has a plurality of weight candidates to be added to each wireless terminal device 10. In the case of a reference signal, the reception BB processing unit 221 selects an appropriate weight for each wireless terminal device 10 according to the received reference signal and the MIMO system, and performs channel compensation by adding the weight to the reference signal. Thereafter, the reception BB processing unit 221 outputs the processed baseband signal to the MIMO processing unit 222.

[0049] The MIMO processing unit 222 receives baseband signals as input from the reception BB processing unit 221. The MIMO processing unit 222 then performs MIMO reception processing on the acquired baseband signals to combine the baseband signals and generate a combined signal. Furthermore, the MIMO processing unit 222 performs demodulation and the like on the combined baseband signal to convert it into soft decision information before decoding.

[0050] Thereafter, if the data is uplink data transmitted from the wireless terminal devices 10, the MIMO processing unit 222 outputs a baseband signal that is a combined signal that has been subjected to MIMO reception processing to the decoding unit 223. If the data is a reference signal, the MIMO processing unit 222 outputs a baseband signal that is a combined signal obtained by combining the reference signals transmitted from the wireless terminal devices 10 to the control unit 224.

[0051] The above-described reception BB processing unit 221 and MIMO processing unit 222 are an example of a “reception unit.” That is, the reception BB processing unit 221 and the MIMO processing unit 222 receive signals transmitted from each of the multiple wireless terminal devices 10 that cooperatively transmit transmission data.

[0052] The decoding unit 223 receives an input of the baseband signal that has been subjected to MIMO reception processing from the MIMO processing unit 222. Then, the decoding unit 223 performs error correction decoding. After that, the decoding unit 223 transmits the decoded baseband signal to the DU 30.

[0053] The control unit 224 receives an input of a combined signal obtained by combining reference signals transmitted from each wireless terminal device 10 from the MIMO processing unit 222. Next, the control unit 224 measures the reception quality of the acquired combined signal. Specifically, the control unit 224 measures the reception quality by calculating the signal-to-noise ratio (SN (Signal Noise) ratio) of the received baseband signal and the transmission capacity available for transmission between the wireless terminal device 10 and the RU 20.

[0054] If the RU 20 is not a specific RU 20 that has been predetermined as a device for selecting a reference radio station, the control unit 224 transmits the measurement results of the reception quality to the specific RU 20. At this time, for example, if there is a network for communication between RUs 20, the control unit 224 uses that network to transmit the information to the other RU 20. Alternatively, the control unit 224 may transmit the information to the other RU 20 via the DU 30.

[0055] On the other hand, if the RU 20 is a specific RU, the control unit 224 acquires the measurement results of the reception quality transmitted from each of the other RUs 20. The control unit 224 then compares the reception quality transmitted from each RU 20 and selects the RU 20 with the best reception quality as the reference radio station. The control unit 224 then notifies the selected RU 20 that it is the reference radio station.

[0056] In this embodiment, the measurement results of reception quality are transmitted from other RUs 20 to a specific RU 20, and the specific RU 20 selects a reference radio station. However, the method of selecting a reference radio station is not limited to this. For example, all RUs 20 may acquire the measurement results of reception quality of each RU 20 and individually select a reference radio station. In this method, the measurement results of reception quality used by each RU 20 are the same, so all RUs 20 can select the same reference radio station. In this case, the RU 20 selected as the reference radio station can confirm for itself that it is the reference radio station, and therefore does not need to be notified that it is the reference radio station.

[0057] The control unit 224 in the RU 20 selected as the reference radio station receives notification from the specific RU 20 that it is the reference radio station. The control unit 224 then determines a phase setting for each wireless terminal device 10 so as to optimize the reception quality of uplink data cooperatively transmitted from each wireless terminal device 10. For example, the control unit 224 may determine a phase setting for each wireless terminal device 10 from a weight selected as an optimal weight from among weight candidates by the reception BB processing unit 221. The control unit 224 then instructs the transmission data processing unit 225 to transmit control information that notifies each wireless terminal device 10 of the phase setting determined for that wireless terminal device 10.

[0058] In this embodiment, the RU 20 that has become the reference radio station transmits the phase setting of the uplink data for each wireless terminal device 10, but the method of notifying the phase setting is not limited to this. For example, another RU 20, such as a specific RU 20, may obtain information about the phase setting of the RU 20 selected as the reference radio station and notify each wireless terminal device 10.

[0059] In the case of downlink data transmission, the transmission data processing unit 225 receives data to be transmitted from the DU 30. The transmission data processing unit 225 also receives from the control unit 224 a transmission instruction for control information that notifies each wireless terminal device 10 of the phase setting determined for each wireless terminal device 10.

[0060] Then, the transmission data processing unit 225 performs processing such as encoding on the received data, and then outputs the encoded baseband signal to the transmission BB processing unit 226.

[0061] The transmission BB processing unit 226 receives an input of an encoded baseband signal from the transmission data processing unit 225. Then, the transmission BB processing unit 226 performs processing on the received baseband signal, such as modulation and mapping to time resources and frequency resources. Thereafter, the transmission BB processing unit 226 outputs the processed baseband signal to the wireless communication circuit 201.

[0062] Here, the reference signal reception processing by the RU 20 will be explained in more detail. Fig. 5 is a block diagram related to reception quality measurement in the reception processing of the RU. Here, there are three wireless terminal devices 10, wireless terminal devices 10a to 10c, each having one antenna 104. Furthermore, the RU 20 has three receiving antennas Rx1 to Rx3 for reception as antenna 204. However, the number of antennas 104 and 204 is just an example and is not limited to this.

[0063] Each of the wireless terminal devices 10a to 10c transmits a reference signal to the receiving antennas Rx1 to Rx3 of the RU 20 (step S200).

[0064] Here, reference signals for uplink data transmitted by radio terminal devices 10a to 10c are reference signals s1 to s3, respectively, and signals received by receiving antennas Rx1 to Rx3 of RU 20, respectively, are received signals r1 to r3.

[0065] Here, the channel matrix (H) representing the characteristics of the channel is expressed by the following equation (1).

[0066]

number

[0067] The first argument (x) of each component (hxy) in the propagation path matrix (H) represents the number of the receiving antennas Rx1 to Rx3, and the second argument (y) represents the number of the transmitting antenna. Here, the receiving antenna number is the last number of each of the receiving antennas Rx1 to Rx3. The transmitting antenna number is a number where the antenna 104 of the wireless terminal device 10a is number 1, the antenna 104 of the wireless terminal device 10b is number 2, and the antenna 104 of the wireless terminal device 10c is number 3. For example, h13 is a complex number representing the change in phase and magnitude that a signal undergoes when a radio wave propagates from the antenna 104 of the wireless terminal device 10c to the receiving antenna Rx1. That is, the propagation paths between each of the wireless terminal devices 10a to 10c and each of the receiving antennas Rx1 to Rx3 have propagation path states h11 to h33, as shown in FIG. 5.

[0068] In this case, the received signals r1 to r3 are expressed by the following equation (2): where n1 to n3 represent noise.

[0069]

number

[0070] That is, the received signals received by each of the receiving antennas Rx1 to Rx3 are expressed by the following equation (3).

[0071]

number

[0072] Next, the RU 20 performs signal separation for each of the wireless terminal devices 10a to 10c for the signals received by the receiving antenna Rx1 (step S201). The RU 20 also performs signal separation for each of the wireless terminal devices 10a to 10c for the signals received by each of the receiving antennas Rx2 (step S202). The RU 20 also performs signal separation for each of the wireless terminal devices 10a to 10c for the signals received by the receiving antenna Rx3 (step S203). For example, the reception BB processing unit 221 executes the processes of steps S201 to S203.

[0073] Each of the reference signals s1 to s3 is transmitted by each of the wireless terminal devices 10a to 10c using a different time component, a different frequency component, or a different signal sequence pattern, or a combination of these methods, so that the receiving RU 20 can separate the reference signals s1 to s3 transmitted from each of the wireless terminal devices 10a to 10c.

[0074] Fig. 6 is a diagram for explaining separation of reference signals. In each of graphs 21 to 23 in Fig. 6, the horizontal axis represents the passage of time and the vertical axis represents frequency. Graph 21 shows an example where reference signals s1 to s3 are transmitted using different time components. Graph 22 shows an example where reference signals s1 to s3 are transmitted using different frequency components. Graph 23 shows an example where reference signals s1 to s3 are transmitted using different signal sequence patterns. In the case of graph 23, each of wireless terminal devices 10a to 10c transmits reference signals s1 to s3 using common time components and frequency components.

[0075] As shown in graph 21, when wireless terminal devices 10a to 10c transmit their respective reference signals s1 to s3 using different time components, RU 20 can separate and extract the reference signals s1 to s3 for each of wireless terminal devices 10a to 10c by extracting each time component.

[0076] As shown in graph 22, when wireless terminal devices 10a to 10c transmit their respective reference signals s1 to s3 using different frequency components, RU 20 can separate and extract the reference signals s1 to s3 for each of wireless terminal devices 10a to 10c by extracting each frequency component.

[0077] Furthermore, in the case of graph 23, wireless terminal devices 10a to 10c transmit reference signals s1 to s3 using the signal sequence patterns of reference signals s1 to s3 shown in graph 23. Each reference signal s1 to s3 is transmitted with a value corresponding to time T1 to T4 shown in graph 23. In this case, RU 20 multiplies each of wireless terminal devices 10a to 10c by the complex conjugate of the signal sequence and then adds the results of each multiplication, thereby removing or reducing and extracting the components of the other wireless terminal devices 10a to 10c.

[0078] For example, signal separation in the case shown in graph 23 will be described in more detail. When extracting a reference signal from the wireless terminal device 10a that has arrived at the receiving antenna Rx1, the RU 20 performs the following process. At each of times T1 to T4, the RU 20 multiplies the received signal including reference signals s1 to s3 by the complex conjugate of the signal sequence pattern of the reference signal s1 of the wireless terminal device 10a, thereby obtaining equation 24 shown in FIG. 7. FIG. 7 is a diagram for explaining how the received signal is obtained for each wireless terminal device. In equation 24, "si(t) * " represents the complex conjugate of "si(t)".

[0079] RU 20 then adds each equation in Equation 24. In this case, component 241 in the first term of each equation is added in phase with reference signal s1 from wireless terminal device 10a, leaving component (h11) of the propagation path characteristics. However, in this case, RU 20 assumes that fluctuations in nearby propagation paths are negligibly small in the time domain and frequency domain, as shown in graph 23.

[0080] Furthermore, when the signal sequence patterns of reference signal s2 and reference signal s1 are orthogonal, component 242 in the second term of each equation is summed to remove the component of reference signal s2 from wireless terminal device 10b. The component of reference signal s3 from wireless terminal device 10c in the third term is similarly removed. Furthermore, the noise component in the fourth term is randomly added and remains as noise.

[0081] In this case, the RU 20 calculates the following equation (4) as the result of extracting the reference signal s1 from the wireless terminal device 10a received by the receiving antenna Rx1.

[0082]

number

[0083] Similarly, the RU 20 calculates the following equations (5) and (6) as the extraction result of the reference signal s1 received from the wireless terminal device 10a by the receiving antennas Rx2 and Rx3.

[0084]

number

number

[0085] The RU 20 performs the same calculation for all combinations of receiving antennas Rx1 to Rx3 and wireless terminal devices 10a to 10c. Then, the RU 20 estimates the propagation path conditions (h11 to h33) between the receiving antennas Rx1 to Rx3 from the reference signals s1 to s3 received by each of the receiving antennas Rx1 to Rx3 (steps S204 to S206). For example, the reception BB processing unit 221 executes the processes of steps S204 to S206.

[0086] Next, the RU 20 uses the reference signals s1 to s3 obtained by the receiving antennas Rx1 to Rx3 for each of the wireless terminal devices 10a to 10c, weights them using the complex conjugate of the channel state, and then combines them. This allows the RU 20 to generate a combined signal as a received signal combined using maximum ratio combining. For example, the receiving BB processing unit 221 performs the weighting process, and the MIMO processing unit 222 performs the combining process.

[0087] 8 is a diagram for explaining propagation path compensation and combining. For example, the RU 20 receives a signal r which is a reference signal s1 received by the receiving antenna Rx1 and is obtained by signal separation using the formulas (4) to (6). 1,MS1The RU 20 performs the following process to compensate the propagation path for the signal r 1,MS1 Similarly, the RU 20 weights the signal r 2,MS1 The RU 20 weights the signal r, which is the reference signal s1 received by the receiving antenna Rx3, with the complex conjugate of the state h21 of the propagation path between the wireless terminal device 10a and the receiving antenna Rx2. 3,MS1 The RU 20 weights each signal r after the propagation path compensation by the complex conjugate of the state h31 of the propagation path between the wireless terminal device 10a and the receiving antenna Rx3. 1,MS1 ~r 3,MS1 and combine them to obtain the reference signal s1 from the wireless terminal device 10a (step S207).

[0088] Similarly, the RU 20 acquires the reference signal s2 from the wireless terminal device 10b (step S208), and the RU 20 acquires the reference signal s3 from the wireless terminal device 10c (step S209).

[0089] Next, in the case of MIMO diversity in which each of the wireless terminal devices 10a to 10c transmits the same data, the RU 20 combines the received signals from the wireless terminal devices 10a to 10c by adding them together to obtain reference signals s1 to s3 after diversity combining (step S210).

[0090] On the other hand, in the case of MIMO multiplexing in which one piece of data is divided and the radio terminal devices 10a to 10c each transmit different divided data, the RU 20 uses the signals of the radio terminal devices 10a to 10c as reference signals s1 to s3.

[0091] Thereafter, the RU 20 measures the reception quality according to the MIMO system by calculating the reception quality of each of the wireless terminal devices 10a to 10c or the combined reference signals s1 to s3 (step S211). For example, the control unit 224 executes the process of step S211.

[0092] For example, in the case of MIMO multiplexing, the RU 20 can measure the SNR from the time and frequency average of multiple reference signals s1 to s3 in the signal for each of the wireless terminal devices 10a to 10c and the variance thereof. Also, in the case of MIMO diversity, the RU 20 can measure the SNR by calculating the average value and variance of the combined signal after combining the reference signals s1 to s3 from each of the wireless terminal devices 10a to 10c.

[0093] As described above, the RU 20 uses a reference signal on the receiving side to determine the propagation path characteristics between each wireless terminal device 10, performs compensation using the propagation path characteristics, and then combines the same compensated signals to extract the received signal and measure its quality.

[0094] Although the above describes the reception of reference signals, the RU 20 can also obtain received signals for uplink data by performing similar processing. That is, the RU 20 weights the received signals r1 to r3 from the receiving antennas Rx1 to Rx3 using the complex conjugate of the propagation path state, and then combines them to obtain a received signal after combining using maximum ratio combining.

[0095] For example, let us consider a case where the signal components of the wireless terminal devices 10a to 10c are s01 to s03, respectively, and the channel matrix (H) is given by Equation (1). In this case, the RU 20 calculates the following Equation (7) by weighting and combining the received signals r1 to r3 with the complex conjugates of the channel states h11, h21, and h31.

[0096]

number

[0097] In equation (7), the coefficients applied to the signal components s02 and s03 of the wireless terminal devices 10b and 10c have random phases, so they cancel each other out and the remaining components become interference, resulting in a combined received signal from the wireless terminal device 10a.

[0098] Similarly, the RU 20 can obtain the combined received signal from the wireless terminal device 10b and the combined received signal from the wireless terminal device 10c, which are expressed by the following equations (8) and (9).

[0099]

number

number

[0100] Next, we will explain how the RU 20 weights the reference signals. The RU 20 has several weight candidates as weights for each transmitting wireless terminal device 10. The RU 20 then selects the optimal weight from the weight candidates according to the MIMO system.

[0101] For example, in the case of MIMO diversity, the RU 20 assigns weights to each wireless terminal device 10 such that the signals transmitted from the transmitting wireless terminal device 10 are as in-phase as possible, i.e., have a constructive phase, at the antenna 204 of the RU 20. In contrast, in the case of MIMO multiplexing, the RU 20 assigns weights to each wireless terminal device 10 such that the signals are as orthogonal as possible at the antenna 204.

[0102] Fig. 9 is a diagram showing an example of weighting. With reference to Fig. 9, weighting of signals will be described using an example in which wireless terminal devices 10a to 10c and receiving antennas Rx1 to Rx3 exist.

[0103] 9, the transmission paths between wireless terminal devices 10a to 10c at receiving antenna Rx1 are in states 41 to 43. In this case, RU 20 has weights W1 to W4 as weight candidates. RU 20 determines to add weight W1, represented by arrow 31, to the signal from wireless terminal device 10a.

[0104] In the case of MIMO diversity, RU 20 assigns weights to the signals from wireless terminal device 10b and 10c so that they mutually reinforce each other as much as possible. In this case, RU 20 assigns weight W4, represented by arrow 32, to the signal from wireless terminal device 10b, and weight W4, represented by arrow 33, to the signal from wireless terminal device 10c. As a result, as shown in state 51 representing the weighted signals, RU 20 can adjust the weighted signals so that they mutually reinforce each other.

[0105] In contrast, in the case of MIMO multiplexing, RU 20 assigns weights to the signals from wireless terminal device 10b and 10c so that they are as orthogonal as possible. In this case, RU 20 assigns weight W1, indicated by arrow 34, to the signal from wireless terminal device 10b, and weight W2, indicated by arrow 35, to the signal from wireless terminal device 10c. As a result, as shown in state 52 representing the weighted signals, RU 20 can adjust the weighted signals so that they are as orthogonal as possible to each other. RU 20 also takes into consideration the reception states of receive antennas Rx2 and Rx3, and determines weights that will maximize the reception quality of the signal combining the received signals from receive antennas Rx1 to Rx3.

[0106] Fig. 10 is a sequence diagram of an uplink data transmission process by the wireless communication system according to the embodiment 1. The flow of the uplink data transmission process by the wireless communication system 1 according to the embodiment will be described with reference to Fig. 10. Here, the case where the wireless terminal devices 10a to 10c perform coordinated transmission of signals to the RUs 20a to 20c will be described.

[0107] The wireless terminal device 10a transmits uplink data to the wireless terminal devices 10b and 10c to share the uplink data (step S1). At this time, in the case of MIMO diversity, the wireless terminal device 10a transmits the same data as its own transmission data to the wireless terminal devices 10b and 10c. In the case of MIMO multiplexing, the wireless terminal device 10a divides the transmission data and transmits to the wireless terminal devices 10b and 10c a portion of the data that does not overlap with the data it transmits, without overlapping. However, step S1 may be performed between steps S12 and S13. In this case, the wireless station RU 20 may also notify the division method (division ratio to each terminal device, data type, etc.) when notifying the phase setting, and the divided data can be shared according to that division method.

[0108] Next, radio terminal device 10a transmits a reference signal to RUs 20a to 20c (step S2). Radio terminal device 10b also transmits a reference signal to RUs 20a to 20c (step S3). Radio terminal device 10c also transmits a reference signal to RUs 20a to 20c (step S4). These reference signals are transmitted using time multiplexing, frequency multiplexing, multiplexing using a signal sequence pattern, or the like.

[0109] RU 20a receives the reference signals, weights and combines them to generate a combined signal, and estimates the reception quality (step S5). Similarly, RU 20b receives the reference signals, weights and combines them to generate a combined signal, and estimates the reception quality (step S6). RU 20c receives the reference signals, weights and combines them to generate a combined signal, and estimates the reception quality (step S7).

[0110] Here, it is assumed that the RU 20b is the specific RU 20 that determines the reference radio station. The RU 20a transmits the estimation result of the reception quality to the RU 20b (step S8). The RU 20c also transmits the estimation result of the reception quality to the RU 20b (step S9).

[0111] The RU 20b receives the estimation results of the reception qualities of the RUs 20a and 20c. The RU 20b then compares the estimation results of the reception qualities of the RUs 20a to 20c and determines the RU 20 with the best reception quality among the RUs 20a to 20c as the reference radio station (step S10). Here, we will explain the case where the RU 20b is selected as the reference radio station.

[0112] Next, the RU 20b determines the setting of the phase (or weight having phase and amplitude) of each of the wireless terminal devices 10a to 10c from the weight assigned to each of the wireless terminal devices 10a to 10c (step S11).

[0113] Next, the RU 20b notifies each of the wireless terminal devices 10a to 10c of the phase setting (possibly weight setting) for each of the wireless terminal devices 10a to 10c (step S12).

[0114] The wireless terminal device 10a receives a notification of the phase setting from the RU 20b. Then, the wireless terminal device 10a transmits uplink data to the RUs 20a to 20c at the set phase (step S13). Similarly, the wireless terminal device 10b also receives a notification of the phase setting from the RU 20b. Then, the wireless terminal device 10b transmits the shared uplink data to the RUs 20a to 20c at the set phase (step S14). Similarly, the wireless terminal device 10c also receives a notification of the phase setting from the RU 20b. Then, the wireless terminal device 10c transmits the shared uplink data to the RUs 20a to 20c at the set phase (step S15).

[0115] The RU 20a receives uplink data transmitted from each of the wireless terminal devices 10a to 10c. Then, the RU 20a generates a baseband signal by performing decoding, demodulation, MIMO combining, etc. Then, the RU 20a transfers the baseband signal to the DU 30 (step S16).

[0116] The RU 20b also receives the uplink data transmitted from each of the wireless terminal devices 10a to 10c. Then, the RU 20b generates a baseband signal by performing decoding, demodulation, MIMO combining, etc. Then, the RU 20b transfers the baseband signal to the DU 30 (step S17).

[0117] The RU 20c also receives the uplink data transmitted from each of the wireless terminal devices 10a to 10c. Then, the RU 20c generates a baseband signal by performing decoding, demodulation, MIMO combining, etc. Then, the RU 20c transfers the baseband signal to the DU 30 (step S18).

[0118] The DU 30 receives baseband signals from each of the RUs 20a to 20c. Then, the DU 30 performs baseband processing on the received baseband signals and transfers them to the CU 40 (step S19). Here, the uplink data transmitted from each of the wireless terminal devices 10a to 10c may be combined by the DU 30 or the CU 40.

[0119] 11 is a flowchart of the uplink data transmission process by the wireless terminal device according to the embodiment 1. Next, the flow of the uplink data transmission process by the wireless terminal device 10 according to the embodiment 1 will be described with reference to FIG.

[0120] The wireless terminal device 10 shares uplink data with other wireless terminal devices 10 that perform coordinated transmission. Then, the control unit 126 of the wireless terminal device 10 transmits a reference signal to the RUs 20a to 20c (step S101).

[0121] Thereafter, the control unit 126 of the wireless terminal device 10 receives information on the setting of the phase of the uplink data (or a weight having a phase and an amplitude) from the reference wireless station RU 20 (step S102). Then, the control unit 126 instructs the transmission BB processing unit 125 to transmit the uplink data with the set phase.

[0122] Then, the transmission BB processing unit 125 of the wireless terminal device 10 transmits the uplink data to the RU 20 at the set phase (step S103).

[0123] 12 is a flowchart of an uplink data reception process by the RU according to embodiment 1. Next, the flow of the uplink data reception process by the RU 20 according to embodiment 1 will be described with reference to FIG.

[0124] The reception BB processing unit 221 receives the reference signal converted into a baseband signal (step S111).

[0125] Then, the reception BB processing unit 221 performs channel estimation on the reference signal and determines an appropriate weight for each wireless terminal device 10 from among the weight candidates (step S112).

[0126] Next, the reception BB processing unit 221 performs channel compensation by applying a weight to the reference signal for each wireless terminal device 10. Next, the reception BB processing unit 221 outputs the reference signal after channel estimation and channel compensation to the MIMO processing unit 222. The MIMO processing unit 222 combines the reference signals received from the reception BB processing unit 221 to obtain a received signal (step S113). Thereafter, the MIMO processing unit 222 outputs the received signal to the control unit 224.

[0127] The control unit 224 measures the reception quality of the received signal received from the MIMO processing unit 222 (step S114).

[0128] Next, the control unit 224 determines whether the own device is a specific RU 20 that will select a reference radio station (step S115).

[0129] If it is not a specific RU 20 (step S115: No), the control unit 224 transmits the measurement result of the reception quality to the specific RU 20 (step S116).

[0130] On the other hand, if it is a specific RU 20 (step S115: Yes), the control unit 224 receives the measurement results of the reception quality in the other RUs 20 (step S117).

[0131] Next, the control unit 224 compares the measurement results of the reception quality of each RU 20 and selects the RU 20 with the best reception quality as the reference radio station. Then, the control unit 224 notifies the selected RU 20 that it is the reference radio station (step S118).

[0132] Thereafter, the control unit 224 determines whether or not the own device has been selected as the reference radio station (step S119). If the own device is not the reference radio station (step S119: No), the uplink data reception process proceeds to step S121.

[0133] On the other hand, if the wireless terminal device is the reference wireless station (step S119: Yes), the control unit 224 sets the phase of the uplink data (or a weight having a phase and amplitude) for each wireless terminal device 10 from the weight assigned to each wireless terminal device 10. Then, the control unit 224 instructs the transmission data processing unit 225 to notify the phase set for each wireless terminal device 10. The transmission data processing unit 225 notifies the phase set for each wireless terminal device 10 (step S120).

[0134] Thereafter, the MIMO processing unit 222 receives the uplink data transmitted at the set phase via the antenna 204, the wireless communication circuit 201, and the reception BB processing unit 221 (step S121). Then, the MIMO processing unit 222 performs MIMO reception processing on the received uplink data and outputs the result to the decoding unit 223.

[0135] The decoding unit 223 decodes the uplink data and transfers it to the DU 30 (step S122).

[0136] As described above, the RU according to this embodiment generates received signals by assigning appropriate weights to reference signals from each wireless terminal device, measures the reception quality of the generated received signals, and selects the RU with the best reception quality among the multiple RUs as a reference wireless station. Furthermore, the RU selected as the reference wireless station determines the phase setting for uplink data in each wireless terminal device based on the weights assigned to each reference signal, and notifies each wireless terminal device of the set phase. The wireless terminal device transmits uplink data to the RU using the notified phase.

[0137] As a result, a wireless terminal device that performs coordinated transmission can improve the reception quality of uplink data at an RU by appropriately adjusting the phase of each uplink data and performing MIMO transmission. Furthermore, by selecting an RU with high reception quality from among multiple RUs as a reference wireless station, the reception quality of coordinatedly transmitted uplink data can be improved. This achieves MIMO effects such as improved transmission capacity or reduced required transmission power. Furthermore, it becomes possible to improve the transmission rate. Therefore, uplink communication performance can be improved.

[0138] (Variation) In the first embodiment, the wireless terminal device 10 relays data received from other wireless terminal devices 10 by DF when transmitting the data to the RU 20 by cooperative transmission. However, the present invention is not limited to this example, and the wireless communication system 1 according to the embodiment can improve the uplink communication performance in the same way even for wireless terminal devices 10 that employ other relaying methods.

[0139] 13 is a block diagram of a wireless terminal device using a different relay method. The wireless terminal device 10 shown in FIG. 13 relays signals using AF (Amplify and Forward), which amplifies the received wireless signal as is and transmits it from the antenna 104.

[0140] 13, in transmitting uplink data, the relay unit 123 receives the uplink data converted into a baseband signal from the wireless communication circuit 101. Then, the relay unit 123 outputs the acquired baseband signal of the uplink data to the transmission BB processing unit 125.

[0141] The transmission BB processing unit 125 receives a baseband signal of uplink data that has not been demodulated or decoded from the relay unit 123. Then, the transmission BB processing unit 125 performs phase control of the uplink data so that the phase becomes the set phase. Thereafter, the transmission BB processing unit 125 outputs the phase-controlled baseband signal of the uplink data to the wireless communication circuit 101.

[0142] In this case, too, RU20 measures the reception quality of the reference signal transmitted from each wireless terminal device 10, selects the RU20 with the best reception quality as the reference wireless station, and notifies each wireless terminal device 10 of the phase setting obtained from the weight assigned by RU20 of the reference wireless station.

[0143] As described above, even in the case of a wireless terminal device that relays signals using AF, a wireless terminal device that performs cooperative transmission can improve the reception quality of uplink data at an RU by appropriately adjusting the phase of each uplink data and performing MIMO transmission. Furthermore, by selecting an RU with high reception quality from among multiple RUs as a reference wireless station, the reception quality of cooperatively transmitted uplink data can be improved. This achieves MIMO effects such as improved transmission capacity or reduced required transmission power. Furthermore, it becomes possible to improve the transmission rate. Therefore, uplink communication performance can be improved. [Example]

[0144] Next, a second embodiment will be described. In the case of MIMO multiplexing, the RU 20 according to this embodiment determines distribution data to be distributed to each wireless terminal device 10 according to the reception quality between each wireless terminal device 10 and the RU 20, and causes each wireless terminal device 10 to transmit uplink data. The RU 20 according to this embodiment is also shown in the block diagram of FIG. 4. In the following description, description of the operation of each unit similar to that of the first embodiment will be omitted.

[0145] After determining the reference radio station, the control unit 224 in the RU 20 selected as the reference base station compares the reception quality of the reference signal from each wireless terminal device 10. Then, the control unit 224 determines the amount of distribution data to be distributed to each wireless terminal device 10 according to the reception quality. Thereafter, the control unit 224 instructs the transmission data processing unit 225 to notify the wireless terminal device 10, which is the source of the uplink data, of the determined amount of distribution data to be distributed to each wireless terminal device 10.

[0146] Fig. 14 is a diagram illustrating an example of data distribution according to the second embodiment. For example, the following description will be given assuming that the wireless terminal devices 10a to 10c perform coordinated transmission and that the reception quality of the wireless terminal device 10a is the highest, the reception quality of the wireless terminal device 10b is the second highest, and the reception quality of the wireless terminal device 10c is the lowest, as shown in table 101 in Fig. 14. In addition, here, the source of uplink data is assumed to be the wireless terminal device 10a.

[0147] In this case, the control unit 224 assigns the maximum amount of data to be distributed to the wireless terminal device 10a as "large," the next largest amount of data to be distributed to the wireless terminal device 10b as "medium," and the minimum amount of data to be distributed to the wireless terminal device 10c as "small," as shown in Table 101. The control unit 224 then notifies the wireless terminal device 10a of the information on the determined amount of data to be distributed to each of the wireless terminal devices 10a to 10c.

[0148] The control unit 126 of the wireless terminal device 10a receives notification of the information on the amount of data to be distributed and determines the uplink data to be transmitted from the wireless terminal device 10a, the uplink data to be transmitted to the wireless terminal device 10b, and the uplink data to be transmitted to the wireless terminal device 10c according to the distribution of the notified amount of data.

[0149] Thereafter, the control unit 126 instructs the transmission data processing unit 124 to transmit uplink data to be transmitted from its own device to the RU 20. The control unit 126 also instructs the transmission data processing unit 124 to transmit uplink data to be transmitted by wireless terminal device 10b to wireless terminal device 10b. The control unit 126 also instructs the transmission data processing unit 124 to transmit uplink data to be transmitted by wireless terminal device 10c to wireless terminal device 10c.

[0150] (Variation) Alternatively, the control unit 224 of the RU 20 may determine the type of data to be distributed to each wireless terminal device 10 according to the result of comparing the reception qualities. In this case, the control unit 224 instructs the transmission data processing unit 225 to notify the wireless terminal device 10, which is the source of the uplink data, of the type of distribution data to be distributed to each wireless terminal device 10 that has been determined.

[0151] For example, the following description will be given assuming that wireless terminal devices 10a to 10c perform cooperative transmission and that the reception quality of wireless terminal device 10a is the highest, that of wireless terminal device 10b is the second highest, and that of wireless terminal device 10c is the lowest, as shown in table 102 of Fig. 14. Also, here again, the source of uplink data is assumed to be wireless terminal device 10a.

[0152] The control unit 224 determines the large-sized "video" data to be distributed to the wireless terminal device 10a, the medium-sized "audio" data to be distributed to the wireless terminal device 10b, and the small-sized "text" data to be distributed to the wireless terminal device 10c, as shown in Table 102. The control unit 224 then notifies the wireless terminal device 10a of information on the type of distribution data to be distributed to each of the determined wireless terminal devices 10a to 10c.

[0153] The control unit 126 of the wireless terminal device 10a receives notification of information on the type of distribution data to be distributed. Then, in accordance with the notified distribution of the type of distribution data, the control unit 126 sets the uplink data to be transmitted from the wireless terminal device 10a to video, the uplink data to be transmitted to the wireless terminal device 10b to audio, and the uplink data to be transmitted to the wireless terminal device 10c to text. The control unit 126 then transmits the audio data and text data to be transmitted to the wireless terminal devices 10b and 10c, respectively. The control unit 126 also causes the transmission data processing unit 124 to transmit the video data.

[0154] As described above, the RU according to this embodiment and its modifications determines the distribution data to be distributed to each wireless terminal device according to the reception quality of each wireless terminal device at the reference wireless station, and notifies the wireless terminal device that is the source of the uplink data. Upon receiving the notification, the wireless terminal device performs cooperative transmission of the uplink data together with the other wireless terminal devices in accordance with the specified distribution.

[0155] As a result, the higher the reception quality, the more uplink data can be transmitted from the wireless terminal device, and the transmission rate can be further improved. In other words, in the case of MIMO multiplexing, by improving the reception quality in the RU of the signal transmitted from each wireless terminal device and optimizing the amount of transmission data distributed to each terminal according to that quality, it is possible to improve the transmission capacity and reduce the transmission power of the terminal. Therefore, it is possible to improve the communication performance in the uplink direction.

[0156] (Hardware configuration) Fig. 15 is a diagram showing an example of the hardware configuration of a wireless terminal device. For example, as shown in Fig. 15, the wireless terminal device 10 has a processor 91, a wireless communication circuit 92, a storage device 93, and a memory 94. The processor 91 is connected to the wireless communication circuit 92, the storage device 93, and the memory 94 via a bus.

[0157] The storage device 93 is, for example, a hard disk, and stores various programs including a program that realizes the processes executed by the processor 91.

[0158] The memory 94 realizes the function of the storage unit 103. For example, the memory 94 temporarily stores signals in the middle of processing.

[0159] The processor 91 reads and executes various programs stored in the storage device 93, thereby realizing functions such as a receiving BB processing unit 121, a decoding unit 122, a relay unit 123 in the case of DF, a transmitting data processing unit 124, a transmitting BB processing unit 125, and a control unit 126.

[0160] The wireless communication circuit 92 realizes, for example, the functions of the wireless communication circuit 101 and the relay unit 123 in the case of AF.

[0161] Fig. 16 is a diagram showing an example of the hardware configuration of an RU. For example, as shown in Fig. 16, the RU 20 has a processor 95, a wireless communication circuit 96, a storage device 97, and a memory 98. The processor 95 is connected to the wireless communication circuit 96, the storage device 97, and the memory 98 via a bus.

[0162] The storage device 97 is, for example, a hard disk, and stores various programs including a program that realizes the processes executed by the processor 95.

[0163] The memory 98 realizes the function of the storage unit 203. For example, the memory 98 temporarily stores signals in the middle of processing.

[0164] The processor 95 reads and executes various programs stored in the storage device 97, thereby realizing functions such as the receiving BB processing unit 221, the MIMO processing unit 222, the decoding unit 223, the control unit 224, the transmitting data processing unit 225, and the transmitting BB processing unit 226.

[0165] The wireless communication circuit 96 realizes the functions of the wireless communication circuit 201, for example. [Explanation of symbols]

[0166] 1. Wireless communication systems 10, 10a to 10c Wireless terminal device 20, 20a~20c RU (radio station) 30 DU 40 CU 50CN 101 Wireless communication circuit 102 Processing section 103 Storage section 104 Antenna 121 Receiving BB processing unit 122 Decoding unit 123 Relay Section 124 Transmission data processing unit 125 Transmission BB processing unit 126 Control Unit 201 Wireless communication circuit 202 Processing section 203 Storage section 204 Antenna 221 Receiving BB processing unit 222 MIMO processing unit 223 Decoding Unit 224 Control Unit 225 Transmission data processing unit 226 Transmission BB processing unit

Claims

1. A base station device having a plurality of radio stations, The radio station a receiving unit that receives signals transmitted from each of a plurality of wireless terminal devices that cooperatively transmit transmission data; a control unit that selects a reference radio station from the plurality of radio stations, determines the phase of the transmission data for each of the radio terminal devices at the selected reference radio station, and notifies each of the radio terminal devices of the phase; A base station device comprising:

2. 2. The base station device according to claim 1, wherein the control unit selects the reference radio station from among the plurality of radio stations based on reception quality of a signal received by the receiving unit.

3. 3. The base station device according to claim 1, wherein the control unit determines a phase of the transmission data for each of the wireless terminal devices based on reception quality at the selected reference wireless station.

4. the receiving unit receives a reference signal from each of the wireless terminal devices; The control unit measures the reception quality of the reference signal and selects the reference radio station based on the measurement result.

3. The base station device according to claim 1, wherein the base station device is a communication device.

5. The base station apparatus according to claim 4 , wherein the control unit performs weighted combining on the reference signal to generate a combined signal, measures reception quality of the combined signal, and sets the measured reception quality as the reference signal.

6. The base station apparatus according to claim 5 , wherein the control unit selects the reference radio station from among the radio stations having the highest reception quality of the reference signal.

7. 2. The base station device according to claim 1, wherein the control unit determines the phase of the transmission data for each of the wireless terminal devices so as to maximize reception quality at the reference wireless station.

8. The base station device according to claim 1, characterized in that the control unit determines distribution data to be distributed to each of the wireless terminal devices from the transmission data that is cooperatively transmitted based on the reception quality at the reference wireless station for each of the wireless terminal devices, and notifies the wireless terminal devices of the distribution data for each of the wireless terminal devices.

9. A plurality of wireless terminal devices that cooperatively transmit transmission data, a control unit that selects a reference radio station from among a plurality of radio stations included in a base station device, and receives a setting of the phase of the transmission data determined by the selected reference radio station; a transmitting unit that performs phase control based on the phase setting received by the control unit and transmits the transmission data; A wireless terminal device comprising:

10. The wireless terminal device according to claim 9, characterized in that the control unit receives a setting of the phase of the transmission data determined in the reference wireless station selected from among the plurality of wireless stations based on the reception quality of the signals sent from each of the wireless terminal devices.

11. 11. The wireless terminal device according to claim 9, wherein the control unit receives a setting for the phase of the transmission data that is determined based on reception quality at the selected reference wireless station.

12. A wireless communication system having a base station device including a plurality of wireless terminal devices that cooperatively transmit transmission data, and a plurality of wireless stations that receive the transmission data cooperatively transmitted from the plurality of wireless terminal devices, Each of the radio stations a receiving unit for receiving a signal transmitted from each of the wireless terminal devices; a first control unit that selects a reference radio station from the radio stations, determines a phase of the transmission data for each of the radio terminal devices at the selected reference radio station, and notifies each of the radio terminal devices of the phase of the transmission data; Each of the wireless terminal devices a second control unit that receives a setting for the phase of the transmission data from the reference radio station; a transmitting unit that performs phase control based on the setting of the phase received by the second control unit and transmits the transmission data. A wireless communication system comprising:

13. 13. The wireless communication system according to claim 12, wherein the first control unit selects the reference wireless station from among the plurality of wireless stations based on reception quality of a signal received by the receiving unit.

14. 14. The wireless communication system according to claim 12, wherein the first control unit determines a phase of the transmission data for each of the wireless terminal devices based on reception quality at the selected reference wireless station.

15. A communication control method for communication between a plurality of wireless terminal devices that cooperatively transmit transmission data and a base station device having a plurality of wireless stations that receive the transmission data cooperatively transmitted from the plurality of wireless terminal devices, comprising: causing the radio station to select a reference radio station from among the plurality of radio stations; causing the radio station to determine a phase of the transmission data for each of the radio terminal devices at the reference radio station and notify each of the radio terminal devices; Each of the wireless terminal devices receives a phase setting of the transmission data from the wireless station, and transmits the transmission data by performing phase control based on the received phase setting. A communication control method comprising:

16. 16. The communication control method according to claim 15, wherein the radio station is caused to select the reference radio station from among a plurality of the radio stations based on reception quality of signals transmitted from each of the radio terminal devices.

17. 17. The communication control method according to claim 15, wherein the radio station determines a phase of the transmission data for each of the radio terminal devices based on reception quality at the selected reference radio station.

Images