Communication relay device and program

Abstract

To provide a communication relay device and a computer program that contribute to improving communication quality in a system that relays between a base station and a mobile station.SOLUTION: A communication relay device according to an embodiment includes a detection unit and a control unit. The detection unit detects a mobile station located within a coverage area formed by a plurality of slave units. The control unit controls communication resources used by the slave units to communicate with the mobile station on the basis of a detection result by the detection unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication relay device and a program. [Background technology]

[0002] Commercial mobile phone services using 5G (5th generation mobile communications system) were launched in Japan in 2020. One of the technologies attracting attention in 5G is beamforming. This is a function that expands coverage and cell capacity by simultaneously communicating with multiple users by coordinating the operation of multiple antenna elements on a single antenna to form a radio wave beam in any direction, and is generally achieved in combination with a massively multi-element antenna (Massive MIMO).

[0003] Incidentally, even before 5G, there was a Distributed Antenna System (DAS) system as a measure to improve indoor coverage for mobile communication systems. The DAS system relays signals between mobile stations and base stations, and consists of a master unit and multiple slave units that are distributed. The master unit distributes the signal from one base station to multiple slave units, and each slave unit outputs the same downlink signal from its respective antenna, thereby creating an area as one cell.

[0004] If a DAS system is simply applied to a 5G system, as mentioned above, the same signal is output from each slave unit, so the beams formed by the distributed slave units do not necessarily point in the direction of the mobile station within the coverage area. In addition, the master unit combines the uplink signals from all slave units and transmits them to the base station, which causes degradation of the Noise Figure (NF). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6567438 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a communication relay device and a program that contribute to improving communication quality. [Means for solving the problem]

[0007] A communication relay device according to an embodiment includes a receiving unit, an adding unit, and a control unit. The receiving unit receives signals transmitted from a plurality of child devices. The adding unit adds the signals received by the receiving unit to generate a signal to be transmitted to a base station. The control unit controls the adding unit not to add signals not used for communication among the signals received by the receiving unit, assigns streams corresponding to each beam of beamforming, and performs an adding process on the assigned streams. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows a mobile communication system including a communication relay system. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of the parent unit shown in FIG. 1; [Diagram 3] 3 is a diagram showing an example of the configuration of a UL signal processing unit shown in FIG. 2; [Figure 4] FIG. 4 is a diagram showing a configuration example of the UL MUX SW shown in FIG. 3. [Diagram 5] 2 is a diagram showing an example of the configuration of a DL signal processing unit shown in FIG. 1; [Figure 6] FIG. 6 is a diagram showing an example of the configuration of the DL MUX SW shown in FIG. 5. [Figure 7] 4 is a flowchart for explaining the process of the parent unit shown in FIG. 1 . [Figure 8] FIG. 1 is a diagram for explaining an operation example of the distributed antenna system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A communication relay system according to an embodiment will be described below with reference to the drawings. FIG. 1 shows a part of a fifth generation mobile communication system, so-called 5G. This mobile communication system includes a 5G core network 5GC (5th Generation Core network) and a radio access network NR (New radio). In the example of FIG. 1, a communication relay system is included in the radio access network NR.

[0010] The 5G core network 5GC controls the radio access network NR, bundles traffic and communicates with external networks (Internet IN, external telephone network EN, etc.), and has a core device C as its central device. The core device C performs, for example, authentication and security management, session management, policy control, packet forwarding, etc.

[0011] Meanwhile, the radio access network NR includes a plurality of base station devices (for example, gNB (gNodeB) 1 and gNB 2 in FIG. 1). The base station devices gNB 1 and gNB 2 are controlled by a core device C, and each of them forms a wireless communication area (so-called a cell) capable of communicating with a mobile station UE (User Equipment).

[0012] More specifically, the base station device gNB1 wirelessly communicates with the mobile station UE through an antenna device AN installed on the rooftop of a building or on a dedicated tower, and connects the mobile station UE to the 5G core network 5GC through a core device C. The base station device gNB1 also performs beamforming using Massive MIMO, which controls the phase of signals in multiple antenna elements on the antenna device AN, thereby contributing to an increase in communication capacity.

[0013] The base station device gNB2 has the same functions as the base station device gNB1, but communicates wirelessly with the mobile station UE through a distributed antenna system DAS instead of the antenna device AN, and connects the mobile station UE to the 5G core network 5GC through the core device C.

[0014] The distributed antenna system DAS is used to form a wireless communication area that is relatively small compared to the antenna device AN in special locations (for example, inside buildings, underground shopping malls, and other structures, depopulated or overpopulated areas, areas where it is difficult or limited to construct towers, event venues, and other temporary locations for the antenna device AN), and as shown in Figure 1, it comprises a master unit MU (Master Unit), remote units RU (Remote Units) 1 to RU3, and antennas AN1 to AN3.

[0015] The master unit MU controls each unit of the distributed antenna system DAS and serves as a communication relay device that enables the mobile station UE to communicate with the base station apparatus gNB2 via the antennas (AN1 to AN3) and slave units (RU1 to RU3). When the master unit MU is connected to each of the slave units RU1 to RU3 by optical communication lines, it is generally referred to as an optical repeater.

[0016] Antennas AN1 to AN3 are connected one-to-one to their corresponding slave units RU1 to RU3, each consisting of a large number of antenna elements, and compatible with Massive MIMO, in which directivity is controlled (beamforming) by phase adjustment of the transmitted RF signal and / or received RF signal.

[0017] In this embodiment, for the sake of simplicity, each of the antennas AN1 to AN3 will be described as performing beamforming to simultaneously form up to four beams in any direction, and for the sake of simplicity, the parent unit MU, which will be described in detail later, will also be described as processing (relaying) up to four streams simultaneously corresponding to the above four beams.

[0018] In an actual device, the number is not limited to a maximum of four, and may be three or less, or five or more. Also, the number of beams formed by each of the antennas AN1 to AN3 is not fixed, and may be dynamically changed by varying the number of antenna elements used.

[0019] The slave units RU1 to RU3 are connected one-to-one to the corresponding antennas AN1 to AN3, respectively, and can be connected to the master unit MU so as to be able to communicate with the master unit MU via an optical communication line. The slave units RU1 to RU3 can perform beamforming by phase adjustment for the corresponding antennas AN1 to AN3, respectively, and can detect (search) the direction in which the mobile station UE is located by measuring the reception strength and performing beamforming.

[0020] More specifically, for the uplink, the slave units RU1 to RU3 perform phase adjustment (beamforming) on ​​the RF signals obtained by the corresponding antennas AN1 to AN3, and obtain received RF signals corresponding to up to four beams. Note that in the beamforming in the slave units RU1 to RU3, a beam corresponding to the number of streams assigned to each mobile station UE by the master unit MU is formed, out of the up to four beams, toward the mobile station UE.

[0021] The slave units RU1 to RU3 then down-convert the received RF signals corresponding to each beam, and simultaneously demodulate them into four received signals corresponding to up to four beams. The slave units RU1 to RU3 then serially bundle the demodulated received signals, convert them from electrical signals to optical signals (modulate the optical carrier), and transmit them to the master unit MU via the optical communication line. The stream included in the received signals is referred to as a UL stream signal.

[0022] On the other hand, for the downlink, the slave units RU1 to RU3 convert the optical signals transmitted from the master unit MU over the optical communication line into electrical signals and simultaneously demodulate them into signals corresponding respectively to a maximum of four streams (hereinafter referred to as DL stream signals).

[0023] The slave units RU1 to RU3 then generate transmission RF signals by modulating a carrier wave using the DL stream signals, and output these transmission RF signals to the connected antennas AN1 to AN3, respectively, for emission into space. Each of the slave units RU1 to RU3 is capable of beamforming, which forms up to four beams simultaneously, and forms a beam for each DL stream signal for transmission. In other words, when four DL stream signals are obtained by demodulation, four beams are formed, and each beam transmits one DL stream signal.

[0024] Next, the master unit MU will be described in detail. Fig. 2 shows an example of the configuration of the master unit MU. That is, the master unit MU includes ports P1 to P3, a transmission unit 10, a UL (Up Link) signal processing unit 20, a DL (Down Link) signal processing unit 30, and a control unit 100. The ports P1 to P3 correspond to the slave units RU1 to RU3, respectively, and are connectable one-to-one to an optical communication line.

[0025] For the uplink, ports P1-P3 convert the optical signals sent from the corresponding slave units RU1-RU3 into electrical signals, demodulate them into up to four received signals (received signals of each beam demodulated by slave units RU1-RU3) corresponding to the beams, and output them in parallel. Each demodulated received signal is output to UL signal processor 20.

[0026] The ports P1 to P3 also function as information acquisition units that acquire information sent from the slave units RU1 to RU3 from each received signal, monitor each demodulated received signal, and detect a communication start request (PRACH) from the mobile station UE contained in the received signal and a stream ID assigned to each received signal (UL stream signal). The ports P1 to P3 also function as position detection units that detect the presence of a mobile station UE located within the coverage area formed by each slave unit RU1 to RU3 from the detection results. These detection results are notified to the control unit 100.

[0027] On the other hand, for the downlink, up to four DL stream signals are simultaneously input to each of the ports P1 to P3 from the DL signal processing unit 30. Then, the ports P1 to P3 serially bundle the input DL stream signals, convert them from electrical signals to optical signals (modulate the optical carrier), and transmit them to the corresponding slave units RU1 to RU3 via the optical communication lines.

[0028] The transmission unit 10 accommodates a communication line connected to the base station device gNB2, and communicates with the base station device gNB2 through this communication line. Specifically, for the uplink, the transmission unit 10 transmits UL signals (up to four at a time) input from the UL signal processing unit 20 to the base station device gNB2. On the other hand, for the downlink, the transmission unit 10 receives DL signals (up to four at a time) transmitted from the base station device gNB2 through the above-mentioned communication line, and outputs them to the DL signal processing unit 30.

[0029] The UL signal processing unit 20, under the control of the control unit 100, performs signal addition processing to selectively add the reception signals of each beam input from ports P1 to P3, and outputs the result as a UL signal to the transmission unit 10. The above signal addition processing will be described in detail later.

[0030] The DL signal processing unit 30 performs signal distribution processing to selectively distribute and output the DL signal input from the transmission unit 10 to the ports P1 to P3 under the control of the control unit 100. The above signal distribution processing will be described in detail later.

[0031] The control unit 100 is a control center that controls each part of the master unit MU and includes a memory (not shown) that stores control programs and control data, and a processor (not shown) that executes processing based on the control programs and the control data, thereby achieving various control functions. Details of the control will be described later in the explanation of the operation.

[0032] Next, a configuration example of the UL signal processing unit 20 will be described with reference to FIG. The UL signal processing unit 20 includes uplink multiplexer switches (UL MUX SW) 211-213 and addition processing units 221-224.

[0033] UL MUX SW211-213 correspond one-to-one to ports P1-P3, respectively, and receive up to four received signals output from ports P1-P3, and selectively multiplex and output these signals in accordance with UL switching signals α, β, γ from the control unit 100.

[0034] Here, a configuration example of the UL MUX SW 211 will be described with reference to Fig. 4. Note that the configurations of the UL MUX SWs 212 and 213 are similar, so descriptions thereof will be omitted. However, the UL switching signals α, β, and γ may be different from one another. The UL MUX SW 211 includes a switching control section 2110, multiplexers 2111 to 2114, and an output switch 2115.

[0035] Each of the multiplexers 2111 to 2114 has four input terminals, and receives up to four received signals output from port P1. Then, in accordance with an instruction from the switching control unit 2110, the multiplexers 2111 to 2114 selectively multiplex the input received signals and output the multiplexed received signal to the output switch 2115.

[0036] The output switch 2115 includes four independent switches corresponding to the multiplexers 2111-2114, and each switch receives a multiplexed received signal from the corresponding multiplexer 2111-2114. Then, in accordance with an instruction from the switching control unit 2110, the multiplexed received signal is output from an output terminal of the switch. This output terminal is the output terminal of the UL MUX SW 211.

[0037] The switching control unit 2110 controls the multiplexers 2111-2114 and the output switch 2115 in accordance with the UL switching signal α from the control unit 100, and controls multiplexing and output. That is, by control in accordance with the UL switching signal α, up to four received signals output from port P1 are selectively multiplexed, and the output and output destination of the multiplexed received signal are controlled.

[0038] 3 again. Each of the addition processing units 221-224 has three input terminals and is connected to one of the four output terminals of the UL MUX SWs 211-213, and the multiplexed received signals are input to the three input terminals. The addition processing units 221-224 add (combine) up to three multiplexed received signals and output the added multiplexed received signal to the transmission unit 10 as a UL signal.

[0039] Next, a configuration example of the DL signal processing unit 30 will be described with reference to FIG. The DL signal processing unit 30 includes downlink multiplexer switches (DL MUX SW) 311 to 313.

[0040] DL MUX SW311-313 correspond one-to-one to ports P1-P3, respectively, and receive up to four DL signals output from the transmission unit 10, selectively multiplexing these DL signals in accordance with DL switching signals χ, ψ, ω from the control unit 100, and outputting the signals to the corresponding ports P1-P3. Note that it is also possible to output the signals without multiplexing.

[0041] Here, a configuration example of the DL MUX SW 311 will be described with reference to Fig. 6. Note that the DL MUX SWs 312 and 313 have the same configuration, so a description thereof will be omitted. However, the DL switching signals χ, ψ, and ω may be different from one another. The DL MUX SW 311 includes a switching control unit 3110 and multiplexers 3111 to 3114.

[0042] The multiplexers 3111-3114 each have four input terminals, and receive a maximum of four distributed DL signals output from the transmission unit 10. Then, in accordance with instructions from the switching control unit 2110, the multiplexers 3111-3114 selectively multiplex the input DL signals and output them as one signal. Each of the multiplexers 3111-3114 also has a one-to-one correspondence with one of the four input terminals of the port P1, and outputs the signal obtained by the above multiplexing to the corresponding input terminal of the port P1.

[0043] The switching control unit 3110 controls the multiplexers 3111-3114 and controls multiplexing and output according to the DL switching signal χ from the control unit 100. That is, under the control of the switching control unit 3110 according to the DL switching signal χ, a maximum of four DL signals can be selectively multiplexed and output to any or all of the four input terminals of the port P1.

[0044] Next, the operation of the communication relay system will be described. In the following description, the operation of the distributed antenna system DAS will be particularly described. Figure 7 is a flow chart for explaining the control flow of the control unit 100 of the master unit MU.

[0045] 7, monitors the detection results notified from the ports P1-P3, and monitors the communications (communication start, communication in progress, communication end) through the slave units RU1-RU3. That is, it monitors and waits for a communication start request from a mobile station UE present in the coverage area formed by the slave units RU1-RU3, and for the end of a communication session being performed by a mobile station UE within the coverage area.

[0046] For example, if a mobile station UE present in the coverage area of ​​the slave unit RU1 transmits a communication start request, the communication start request is received by the antenna AN1 and the slave unit RU1, and reaches the port P1 of the master unit MU via an optical communication line. An example of the communication start request is a signal such as a Physical Random Access Channel (PRACH).

[0047] Port P1 to which the communication start request has arrived detects the occurrence of the communication start request and notifies the control unit 100 of this fact. In response, the control unit 100 recognizes that the port that has sent the notification is P1, and the process proceeds to step 701.

[0048] The above describes an example of detecting a communication start request through slave unit RU1, but a similar operation is performed for slave unit RU2 (or RU3) as well, whereby a notification is sent from port P2 (or P3), and the control unit 100 recognizes that a notification has been received from P2 (or P3).

[0049] In the initial state of operation of the distributed antenna system DAS, the master unit MU distributes and outputs the DL signal from the base station apparatus gNB2 to each of the slave units RU1 to RU3 for the downlink stream. In addition, in the initial state, the slave units RU1 to RU3 form beams in the same direction according to the same algorithm and transmit DL signals. However, it is also possible to apply different settings to the slave units RU1 to RU3 as an initial setting so that they form beams in predetermined directions.

[0050] In step 701, the control unit 100 acquires detection results from all of the ports P1 to P3, and counts the number of mobile stations UE in communication from the detection results for each of the slave units RU1 to RU3.

[0051] As a method for counting the number of mobile stations UE in communication, for example, the ports P1 to P3 or the control unit 100 may monitor the PRACH transmitted from the mobile stations UE to the base station apparatus gNB2, and the number may be counted for each of the slave units RU1 to RU3 by distinguishing the mobile stations UE.

[0052] In step 702, the control unit 100 executes a stream allocation process, and proceeds to step 703. Specifically, the control unit 100 allocates stream IDs 1 to ID 4 to the mobile station UE that has requested to start communication and the mobile station UE that is already in communication, according to a predetermined stream allocation algorithm, and proceeds to step 703. Note that for the mobile station UE that is already in communication, the stream IDs to be allocated will be reviewed, but it is also possible not to change them.

[0053] The above stream allocation algorithm may take into account various factors, and the stream ID to be allocated to each mobile station UE is determined based on, for example, the number of streams that the parent unit MU can process (four in this example), the number of child units accommodated by the parent unit MU (three, RU1 to RU3 in this example), the number of mobile stations UE present within the coverage area of ​​each child unit RU1 to RU3 (for example, the number of PRACHs recognized by the control unit 100), the maximum number of streams between the parent unit MU and each child unit RU1 to RU3 (four in this example), the maximum number of streams between each child unit RU1 to RU3 and the mobile station UE (four in this example), the communication quality of each resource, the type of communication used by the mobile station UE, the communication capabilities of the mobile station UE, etc.

[0054] Of these pieces of information, the information relating to the master unit MU and slave units RU1-RU3 may be stored in advance in a storage unit (not shown) of the master unit MU. Also, the information relating to the slave units RU1-RU3 and the mobile station UE may be dynamically acquired by the control unit 100 from the slave units RU1-RU3 and the mobile station UE via ports P1-P3.

[0055] In step 703, the control unit 100 notifies each of the slave units RU1 to RU3 of the stream ID assigned to the mobile station UE in step 702, and proceeds to step 704. Specifically, for example, the control unit 100 notifies each of the slave units RU1 to RU3 of the identification information of the mobile station UE and the assigned stream ID in association with each other.

[0056] Furthermore, each of the slave units RU1 to RU3 that has received the notification secures communication resources for each mobile station UE according to the number of notified stream IDs, and establishes a communication link with each mobile station UE according to a predetermined procedure.

[0057] In step 704, the control unit 100 performs signal addition processing on the four signals output from each of the ports P1 to P3 based on the stream ID assigned to the mobile station UE in step 702, thereby generating four UL signals, and proceeds to step 705.

[0058] In this signal addition process, four signals output from each of the ports P1 to P3 are selectively added to generate four UL signals, and the addition process is performed after excluding some or all of the signals that do not include the stream sent from the mobile station UE. As a result, at least the signal that includes the stream sent from the mobile station UE is included in one of the four UL signals.

[0059] More specifically, based on the stream ID assigned to the mobile station UE in step 702, the control unit 100 generates UL switching signals α, β, and γ for adding up the signals corresponding to the assigned stream IDs among the four signals output from each of the ports P1 to P3, and controls the signal adding process of the UL signal processing unit 20.

[0060] In step 705, the control unit 100 controls the UL signal processing unit 20 and the transmission unit 10 to start transmitting the four UL signals obtained by the signal addition processing of the UL signal processing unit 20 to the base station device gNB2 via the transmission unit 10, and then terminates the processing.

[0061] 7 again, monitors the detection results notified from ports P1-P3, and monitors communication (communication start, communication in progress, communication end) for each of the slave units RU1-RU3. When a communication start request is issued from a mobile station UE present in the coverage area formed by each of the slave units RU1-RU3, or when a communication session being performed by a mobile station UE within the coverage area ends, the control unit 100 executes the processing from step 701 onwards again.

[0062] Next, the operation will be described with a specific example with reference to FIG. As shown in FIG. 8(a), consider the case where a mobile station UE1 requesting communication is present only in the coverage area of ​​handset RU1 among handset RU1 to RU3, that is, the case where a communication start request is transmitted from mobile station UE1, and no mobile station is present in the coverage areas of the other handset units RU2 and RU3.

[0063] In this case, the control unit 100 recognizes from the detection results of each of the ports P1 to P3 obtained in step 701 that the mobile station UE1 is present only in the coverage area of ​​the child unit RU1, and, using the above-mentioned stream allocation algorithm in step 702, assigns, for example, all four streams ID1 to ID4 to the child unit RU1, and assigns 0 stream to the remaining child units RU2 and RU3.

[0064] As a result, in step 703, the slave unit RU1 notifies the mobile station UE1 that stream IDs 1 to 4 are assigned, and secures communication resources for the four streams (UL stream signals), and establishes a communication link with the mobile station UE1 for communication using the four streams according to a predetermined procedure. More specifically, in order to receive the four UL stream signals, all four beams that can be formed by the antenna AN1, i.e., beams corresponding to the streams IDs 1 to ID4 respectively, are formed toward the mobile station UE1.

[0065] Meanwhile, in the parent unit MU, the control unit 100 recognizes that, based on the stream IDs ID1 to ID4 assigned to the mobile station UE1 in step 702, the streams assigned to the child unit RU1 are ID1 to ID4, and the number of streams assigned to the remaining child units RU2 and RU3 is zero, and generates UL switching signals α, β, and γ for adding signals corresponding to the assigned stream IDs.

[0066] At this time, the UL switching signal α is a signal that instructs the UL MUX SW 211 to output the four signals input from the port P1, which correspond respectively to the four beams of the slave unit RU1, to the corresponding addition processing units 221 to 224.

[0067] On the other hand, the UL switching signal β is a signal that instructs the UL MUX SW 212 not to output some or all of the four signals input from port P2 and corresponding to the four beams of the slave unit RU2 to the addition processing units 221 to 224.

[0068] Similarly, the UL switching signal γ is a signal that instructs the UL MUX SW 213 not to output to the addition processing units 221-224 some or all of the four signals input from port P3 and corresponding to the four beams of the slave RU3.

[0069] As a result, the addition processing units 221-224 output the signals of the four streams ID1-ID4 of the slave unit RU1 input from port P1 to the transmission unit 10, with little or no addition of signals from the other slave units RU2, Ru3. In this way, the addition processing units 221-224 prevent signals that are not expected to be used for communication from being added to signals that are actually used for communication.

[0070] Next, the example shown in FIG. 8(b) will be described. In this example, one mobile station UE (UE1, UE2, UE3) exists in each of the cover areas of the slave units RU1 to RU3. Alternatively, it may be considered that the mobile stations UE2 and UE3 have moved from the state shown in Fig. 7(a) (where only the mobile station UE1 exists) to the cover areas of the slave units RU2 and RU3, respectively (or that the mobile stations UE2 and UE3, originally existing in the cover areas of the slave units RU2 and RU3, respectively, have made a communication start request from a state where they were not communicating).

[0071] In this case, the control unit 100 recognizes from the detection results of the ports P1-P3 obtained in step 701 that one mobile station UE (UE1, UE2, UE3) exists in each of the cover areas of the slave units RU1-RU3, and that each of the three mobile stations is requesting communication. Then, the control unit 100 assigns, for example, two streams ID1 and ID2 to the slave unit RU1, and assigns one stream ID3 and ID4 to the remaining slave units RU2 and RU3, respectively, according to the stream assignment algorithm in step 702.

[0072] There are various possible reasons why the number of allocated streams is greater for the slave unit RU1 than for the slave units RU2 and RU3, such as (1) when the mobile station UE1 has already been in communication before the mobile stations UE2 and UE3, (2) when the wireless transmission path environment is better (or worse) for the mobile station UE1 than for the mobile stations UE2 and UE3, (3) when the type of communication is such that the mobile station UE1 requires more resources than the mobile stations UE2 and UE3, (4) when the mobile station UE1 is a device that has priority over the mobile stations UE2 and UE3 (administrator, user of a special service, etc.), and (5) when the mobile station UE1 has higher communication performance than the mobile stations UE2 and UE3 (for example, the mobile stations UE2 and UE3 do not have the ability to use two streams). It is possible to perform the stream allocation process of step 702 by weighting the priority of these various conditions.

[0073] As a result, in step 703, the slave unit RU1 notifies the mobile station UE1 that stream IDs 1 and 2 are assigned, and the slave unit RU1 secures communication resources for the two streams (UL stream signals), and establishes a communication link with the mobile station UE1 for communication using the two streams according to a predetermined procedure. More specifically, in order to receive the two UL stream signals, two beams out of four beams that can be formed by the antenna AN1, that is, beams corresponding to streams IDs 1 and ID2, respectively, are formed toward the mobile station UE1.

[0074] Similarly, in step 703, the slave unit RU2 notifies the mobile station UE2 of the allocation of stream ID3, reserves communication resources for one stream (UL stream signal), and establishes a communication link with the mobile station UE2 for communication with the one stream according to a predetermined procedure. More specifically, in order to receive one UL stream signal, one of four beams that can be formed by the antenna AN2, i.e., a beam corresponding to stream ID3, is formed toward the mobile station UE2.

[0075] Similarly, in step 703, the slave unit RU3 notifies the mobile station UE3 of the allocation of stream ID4, reserves communication resources for one stream (UL stream signal), and establishes a communication link with the mobile station UE3 for communication with the one stream according to a predetermined procedure. More specifically, in order to receive one UL stream signal, one of four beams that can be formed by the antenna AN3, i.e., a beam corresponding to stream ID4, is formed toward the mobile station UE3.

[0076] Meanwhile, in the parent unit MU, the control unit 100 generates UL switching signals α, β, and γ based on the assignment in step 702 of two streams ID1 and ID2 to the mobile station UE1 and one stream ID3 and ID4 to the mobile stations UE2 and UE3, respectively.

[0077] At this time, the UL switching signal α is a signal that instructs the UL MUX SW211 to output to the addition processing units 221 and 222 the signals corresponding to streams ID1 and ID2 out of the four signals input from port P1 and corresponding respectively to the four beams of the child unit RU1.

[0078] On the other hand, the UL switching signal β is an instruction signal to UL MUX SW212 to make sure that, of the four signals input from port P2 corresponding to the four beams of child unit RU2, the signal corresponding to stream ID3 is output to addition processing unit 223, and that the remaining three signals are not output in whole or in part to addition processing units 221 to 224.

[0079] Similarly, the UL switching signal γ is an instruction signal to UL MUX SW213 to make sure that, of the four signals input from port P3 corresponding to the four beams of child unit RU3, the signal corresponding to stream ID4 is output to addition processing unit 223, and that the remaining three signals are not output in whole or in part to addition processing units 221 to 224. That is, the UL switching signals α, β, and γ are signals including instructions to cause the addition processing units 221 to 224 not to output some or all of the signals not being used for communication.

[0080] As a result, the addition processing units 221 and 222 output the two streams ID1 and ID2 of the slave unit RU1 input from port P1 to the transmission unit 10, respectively, with little or no addition of signals from the other slave units RU2 and RU3.

[0081] Similarly, the addition processing unit 223 outputs the signal of stream ID3 of slave unit RU2 input from port P2 to the transmission unit 10 with little or no addition of signals from the other slave units RU1 and RU3.

[0082] Similarly, the addition processing unit 224 outputs the signal of stream ID4 of slave unit RU3 input from port P3 to the transmission unit 10 with little or no addition of signals from the other slave units RU1 and RU2. That is, in the addition processing units 221 to 224, signals not used in communication (signals not expected for communication) are prevented from being added to signals actually used in communication.

[0083] As described above, in the communication relay system having the above configuration, in the distributed antenna system DAS having multiple slave units RU1 to RU3, the necessary streams are autonomously assigned to each slave unit, and each slave unit autonomously performs beamforming on the assigned stream.

[0084] Therefore, according to the communication relay system having the above configuration, communication resources are allocated to each slave unit depending on the presence of a mobile station, so that communication resources in the distributed antenna system DAS can be utilized efficiently, which ultimately contributes to improving communication quality.

[0085] Furthermore, in the communication relay system configured as described above, when the master unit MU, which connects the multiple slave units RU1-RU3 to the base station apparatus gNB2, adds (combines) the signals received by the slave units RU1-RU3 and transmits them to the base station apparatus gNB2, some or all of the signals not used for communication (signals for which communication is not expected) are not added.

[0086] Therefore, according to the communication relay system configured as above, the addition of unnecessary signal components to the signal transmitted from the master unit MU to the base station apparatus gNB2 is suppressed, thereby improving the degradation of the NF and contributing to improved communication quality.

[0087] It should be noted that the present invention is not limited to the above-described embodiment as it is, and in the implementation stage, the components can be modified and embodied without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiment. For example, a configuration in which some components are deleted from all the components shown in the embodiment can also be considered. Furthermore, the components described in different embodiments may be appropriately combined.

[0088] For example, in the above embodiment, an example has been described in which the base station device gNB2 is directly connected to the distributed antenna system DAS, but a repeater for increasing the number of distributions may be provided between the base station device gNB2 and the distributed antenna system DAS, and multiple distributed antenna systems DAS may be connected to the base station device gNB2.

[0089] In the above embodiment, the control unit 100 of the master unit MU determines the streams to be assigned to each of the slave units RU1 to RU3, but this is not limiting. For example, the control units of the slave units RU1 to RU3 may determine the number of streams to be used by themselves based on the number of mobile stations UE present in their coverage areas or the number of free streams notified by the master unit MU. Alternatively, the repeater described above may perform the same process as the control unit 100, and assign streams to each distributed antenna system DAS.

[0090] In the above embodiment, it has been explained that in the initial control state shown in FIG. 7, for the downlink stream, the master unit MU distributes and outputs the DL signal from the base station apparatus gNB2 to each of the slave units RU1-RU3. However, as shown in FIGS. 5 and 6, the master unit MU has a function of selectively outputting up to four DL signals sent from the base station apparatus gNB2 to any of the ports P1-P3 in accordance with DL switching signals χ, ψ, ω from the control unit 100.

[0091] Therefore, for example, after uplink stream allocation is performed by the stream allocation process of step 702, the result of this allocation may be referenced, and the same number of downlink streams may be allocated to the child units (RU1 to RU3) to which the uplink streams were allocated, and each child unit RU1 to RU3 may be caused to transmit the corresponding downlink streams. It goes without saying that various modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0092] 10...transmission unit, 20...UL signal processing unit, 30...DL signal processing unit, 100...control unit, 211-213...UL MUX SW, 221-224...addition processing units, 311-313...DL MUX SW, 2110...switching control unit, 2111-2114...multiplexer, 2115...output switch, 3110...switching control unit, 3111-3114...multiplexer, 5GC...G core network, AN1-AN3...antennas, MU...parent unit, P1-P3...ports, RU1-RU3...child units, UE...mobile station, UE1-UE3...mobile station, gNB1...base station apparatus, gNB2...base station apparatus.

Claims

1. A communication relay device capable of connecting a plurality of slave units that wirelessly communicate with a mobile station and transmitting a signal transmitted from the mobile station through the slave unit to a base station, comprising: a receiving unit for receiving signals transmitted from each of the plurality of slave units; an adder unit that adds up the signals received by the receiver unit to generate a signal to be transmitted to the base station; a control unit that controls the adding unit not to add signals not used for communication among the signals received by the receiving unit, assigns streams corresponding to each beam of beamforming, and performs an addition process on the assigned streams; A communication relay device comprising:

2. Further, an acquisition unit for acquiring information from the child device is provided, The control unit controls the adding unit not to add signals that are not used for communication among the signals received by the receiving unit, based on the information acquired by the acquiring unit. The communication relay device according to claim 1 .

3. A computer used in a communication relay device capable of connecting a plurality of slave units that wirelessly communicate with a mobile station and transmitting a signal transmitted from the mobile station through the slave unit to a base station, A receiving unit that receives signals transmitted from each of the plurality of slave units; an adder unit that adds up the signals received by the receiver unit to generate a signal to be transmitted to the base station; a control unit that controls the adding unit not to add signals not used for communication among the signals received by the receiving unit, assigns streams corresponding to each beam of beamforming, and performs an addition process on the assigned streams; A program that makes things work.

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