Relay station, information processing device, and method

Abstract

To provide stable non-regenerative relay even when a terminal station moves.SOLUTION: A relay station includes a plurality of first antennas used for communication with a terminal station, one or more second antennas used for communication with a base station, and a radio device performing non-regenerative relay. The relay station transmits a first beam pattern with the maximum SINR of a received signal from the terminal station, the received signal including at least a part of self-interference and measured in a first slot of a wireless frame. An information processing apparatus acquires a beam pattern set based on the first beam pattern and transmits it to the relay station. In a second slot, based on SINRs of received signals from the terminal station measured for each of beam patterns included in the beam pattern set in a plurality of symbols, the relay station selects a second beam pattern from the beam pattern set, and updates a beam pattern to be used by the first antennas to the second beam pattern.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a relay station, an information processing device, and a method. [Background technology]

[0002] Wireless communications such as the 5th Generation Mobile Communication System (5G) are expected to achieve ultra-low latency communications of sub-milliseconds or less. On the other hand, from the perspective of improving communication services, it is desirable to expand the coverage area of ​​cells, and relay communication via relay stations is an effective way to achieve this. Therefore, wireless communication methods have been proposed in which the terminal station that performs wireless communication acts as the relay station. Furthermore, as a relay technology with low latency, non-regenerative relaying is desirable, in which the relay station does not perform demodulation or decoding, but instead performs signal amplification and simple filtering. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP TS 38.174 V17.0.0 (2022-03) [Non-patent document 2] 3GPP TS 38.106 V1.0.0 (2022-03) Summary of the Invention [Problem to be solved by the invention]

[0004] Communication quality can be improved by using beamforming, which uses multiple antenna elements to increase antenna gain toward a terminal station. The direction in which radio waves are concentrated by beamforming using multiple antenna elements is set by a beam pattern. In other words, beamforming can increase antenna gain toward a terminal station according to the movement of the terminal station by switching the beam pattern.

[0005] When a terminal station moves at high speed, the optimal beam pattern of the antenna at the relay station directed at the terminal station changes in slot or symbol units. Therefore, unless the relay station updates the beam pattern in accordance with the high-speed movement of the terminal station, the SINR (Signal to Interference and Noise power Ratio) of the relayed signal may decrease, potentially making it impossible to continue non-regenerative relay. Note that high-speed movement of a terminal station may be, for example, movement by Shinkansen at speeds of 200 km / h to 300 km / h. However, this is not limited to this, and the speed at which high-speed movement of a terminal station is considered to vary depending on the frequency band used in wireless communication.

[0006] One aspect of the present disclosure is to provide a relay station, an information processing device, and a method that can provide stable communication by non-regenerative relay even when a terminal station moves at high speed. [Means for solving the problem]

[0007] One aspect of the present disclosure is a plurality of first antennas used for communication with mobile terminal stations, the beam directions of which are controlled in accordance with a predetermined beam pattern to enhance the antenna gain; one or more second antennas used for communication with a base station; a radio device that performs non-regenerative relay between the base station and the terminal station, relaying a signal without demodulating or decoding it; and acquiring information on a set of beam patterns acquired based on a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal from the terminal station, the received signal being measured in a first slot of a radio frame and including at least a portion of self-interference occurring between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative repeating. And, In a second slot subsequent to the first slot, selecting a second beam pattern from a plurality of beam patterns included in the set of beam patterns based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols for each of the plurality of beam patterns; updating beam patterns used by the plurality of first antennas to the second beam pattern in a next symbol of the one or a plurality of consecutive symbols; a control unit that executes the above; It is a relay station equipped with:

[0008] Another aspect of the present disclosure is receiving a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal measured in a first slot of a radio frame from a relay station including a plurality of first antennas used for communication with a mobile terminal station, the first antennas having a beam direction that increases antenna gain and is controlled according to a predetermined beam pattern, one or more second antennas used for communication with a base station, and a radio device that performs non-regenerative relay, which relays signals between the base station and the terminal station without demodulating or decoding them; the first beam pattern being a received signal measured in a first slot of a radio frame from the terminal station, the received signal including at least a portion of self-interference that occurs between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative relay; Obtaining information about a set of beam patterns based on the first beam pattern, and transmitting the information about the set of beam patterns to the relay station; a control unit that executes An information processing device comprising: The relay station In a second slot subsequent to the first slot, for each of a plurality of beam patterns included in the set of beam patterns, a second beam pattern is selected from the plurality of beam patterns based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols; updating the beam patterns used by the plurality of first antennas to the second beam pattern in a next symbol of the one or a plurality of consecutive symbols; It is an information processing device.

[0009] Another aspect of the present disclosure is a plurality of first antennas used for communication with mobile terminal stations, the beam directions of which are controlled in accordance with a predetermined beam pattern to enhance the antenna gain; one or more second antennas used for communication with a base station; a relay station including a radio device that performs non-regenerative relay, which relays a signal between the base station and the terminal station without demodulating or decoding the signal; transmitting a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal from the terminal station, the received signal being measured in a first slot of a radio frame and including at least a portion of self-interference occurring between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative relaying; The information processing device receiving the first beam pattern from the relay station; obtaining information about a set of beam patterns based on the first beam pattern; transmitting information about the set of beam patterns to the relay station; The relay station: In a second slot subsequent to the first slot, selecting a second beam pattern from a plurality of beam patterns included in the set of beam patterns based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols for each of the plurality of beam patterns; updating beam patterns used by the plurality of first antennas to the second beam pattern in a next symbol of the one or a plurality of consecutive symbols; The method includes:

[0010] According to one aspect of the present disclosure, stable non-regenerative relay communication can be provided even when a terminal station moves at high speed. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a system configuration of a communication system according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a system configuration of a communication system. [Figure 3] FIG. 3 is a diagram showing an example of a processing sequence related to updating a beam pattern of a relay station in the communication system according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a hardware configuration of a relay station. [Figure 5] FIG. 5 is a diagram illustrating an example of a hardware configuration of the control device. [Figure 6] FIG. 6 is an example of a flowchart of a beam pattern selection process in a relay station. [Figure 7] FIG. 7 is a diagram showing an example of the relationship between a plurality of beam patterns included in a beam pattern set assigned to a relay station in the first embodiment. [Figure 8] FIG. 8 is an example of a flowchart of the beam pattern set determination process of the control device 1 in the first embodiment. [Figure 9]FIG. 9 is an example of a flowchart of a beam pattern update process of a relay station in the first embodiment. [Figure 10] FIG. 10 is a flowchart of (1) the beam pattern determination process when a moving average window is used. [Figure 11] FIG. 11 is a flowchart of the beam pattern determination process when (2) switch-and-stay is used. [Figure 12] FIG. 12 shows an example of a simulation result of the beam pattern update process in the communication system according to the first embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a processing sequence related to updating a beam pattern of a relay station in the communication system according to the second embodiment. [Figure 14] FIG. 14 is an example of a flowchart of a beam pattern update process of a relay station in the second embodiment. [Figure 15] FIG. 15 is a diagram showing an example of the relationship between a plurality of beam patterns used in the update process of the beam pattern set in the second embodiment. [Figure 16] FIG. 16 is a diagram showing an example of a time chart in the update process of the beam pattern set in the second embodiment. [Figure 17] FIG. 17 is an example of a flowchart of a beam pattern set update process performed by the control device in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] In one aspect of the present disclosure, a relay station is assigned multiple beam patterns that are expected to maximize the SINR of the received signal from a terminal station, and updates the beam pattern to be used from the multiple beam patterns every one or more symbols. This makes it possible to provide stable communication through non-regenerative relay even when the terminal is moving at high speed.

[0013] More specifically, one aspect of the present disclosure is a relay station. The relay station includes a plurality of first antennas used for communication with mobile terminal stations, one or more second antennas used for communication with a base station, a radio device that performs non-regenerative relay by relaying signals between the base station and the terminal stations without demodulating or decoding them, and a control unit. The beam directions of the plurality of first antennas, which are directions in which antenna gain is increased, are controlled according to a predetermined beam pattern.

[0014] The relay station may be, for example, a base station, a small base station, a mobile base station, a smartphone, an in-vehicle device, etc. The control unit may be, for example, a computer, a CPU (Central Processing Unit), a D These are processors such as SP (Digital Signal Processor) and GPU (Graphics Processing Unit), and arithmetic circuits such as FPGA (Field Programmable Gate Array).

[0015] The multiple first antennas and one or more second antennas provided in the relay station are, for example, adaptive array antennas. An adaptive array antenna is an array antenna in which multiple antenna elements are arranged. An adaptive array antenna can electrically change its directivity by adaptively controlling the weighting of each antenna element according to the propagation environment. A beam pattern represents the angular dependency of the receiving sensitivity with respect to the main axis of the antenna. In beamforming, the main axis of the antenna is the direction in which the antenna gain of multiple antenna elements is increased. In other words, the beam pattern changes depending on the direction in which the antenna gain is increased. Hereinafter, the direction in which the antenna gain from multiple first antennas is increased will be referred to as of This is called the beam direction.

[0016] The control unit acquires information about a set of beam patterns acquired based on a first beam pattern that maximizes the SINR of a received signal from a terminal station, the received signal including at least a portion of self-interference, measured in a first slot of a radio frame. The power due to self-interference is generated between signals transmitted and received by multiple first antennas and signals transmitted and received by one or more second antennas by non-regenerative repeating. The control unit selects a second beam pattern from the multiple beam patterns in the second slot based on the SINR of a received signal from the terminal station, including at least a portion of self-interference, measured in one or multiple consecutive symbols for each of the multiple beam patterns included in the set of beam patterns. The control unit also updates the beam pattern used by the multiple first antennas to the second beam pattern in a symbol next to one or multiple consecutive symbols.

[0017] A radio frame has a time length of 10 milliseconds. One radio frame contains 10 slots. A slot is the basic transmission unit for modulation and demodulation. Each slot is assigned to either the uplink or downlink. Uplink communication is performed during the slot assigned to the uplink. Downlink communication is performed during the slot assigned to the downlink. The first and second slots are, for example, uplink slots. One slot contains a predetermined number of symbols. A symbol is a period during which one set of phase and amplitude state continues in a modulated signal. In other words, the beam pattern used by the antenna can be updated when switching slots. For example, in Orthogonal Frequency Division Multiple Access (OFDM), a modulation method adopted in 5G, the number of symbols contained in one slot varies depending on the subcarrier spacing. For example, if the subcarrier spacing is 15 kHz in OFDM modulation, one slot contains 14 symbols.

[0018] In one aspect of the present disclosure, the relay station determines a beam pattern to be used in the next slot from a set of beam patterns based on the SINR of each beam pattern in one or more symbols. The SINR is calculated taking into consideration that the received signal from the terminal station contains at least a portion of self-interference at the relay station due to non-regenerative relaying. Furthermore, the set of beam patterns is determined based on the beam pattern that maximizes the SINR in the first slot. This allows the beam pattern to be switched to one that does not cause the SINR to become so low that communication cannot be continued, even when the terminal station is moving at high speed, and provides stable non-regenerative relay communication.

[0019] In one aspect of the present disclosure, the information regarding the set of beam patterns may include information regarding a third beam pattern obtained based on the first beam pattern and information regarding multiple beam patterns whose beam directions are within a first range of beam directions defined by a first angle relative to the beam direction of the third beam pattern. That is, the set of beam patterns assigned to the relay station is not composed of multiple beam patterns with different beam directions, but of multiple beam patterns whose beam directions are all within the first range. The third beam pattern is obtained based on the first beam pattern that maximizes the SINR in the first slot, and the first range of beam directions is defined based on the third beam pattern. Therefore, the set of beam patterns assigned to the relay station includes multiple beam patterns that are likely to maximize the SINR in a slot or symbol after the first slot. By selecting a beam pattern to be used by the multiple first antennas from the set of beam patterns, it is possible to switch to a beam pattern that does not cause the SINR to become so low that communication cannot be continued. The first angle may be an angle in the azimuth or elevation direction of the first antenna, an angle in a three-dimensional coordinate space formed by the azimuth and elevation directions of the first antenna, or an angle represented by the azimuth and elevation angles of the first antenna.

[0020] In one aspect of the present disclosure, the plurality of beam patterns included in the set of beam patterns may be arranged so that their beam directions are equally spaced apart by a second angle. Furthermore, the information regarding the plurality of beam patterns may include at least a first angle and a second angle. Like the first angle, the second angle may be an angle in the azimuth or elevation direction of the first antenna, an angle in a three-dimensional coordinate space formed by the azimuth and elevation directions of the first antenna, or an angle represented by the azimuth and elevation angles of the first antenna. By assigning a set of beam patterns to a relay station to a plurality of beam patterns arranged so that their beam directions are equally spaced apart by the second angle, the beam directions of the beam patterns can be dispersed within the first range. This allows for more comprehensive searching of optimal beam patterns within the first range.

[0021] In one aspect of the present disclosure, the first range may have a width of a first angle in the positive and negative directions centered on the beam direction of the third beam pattern. In this case, the third beam pattern may be set to the first beam pattern. Furthermore, the first angle and the second angle may each be set to a predetermined value. When the third beam pattern, the first angle, and the second angle are acquired according to predefined settings, complex processing is not performed, thereby reducing the processing load of a device that generates information about a set of beam patterns. The device that generates information about a set of beam patterns may be, for example, a relay station, a control device, or a base station.

[0022] In one aspect of the present disclosure, the control unit may acquire, at a predetermined timing, a first beam pattern that maximizes the SINR of a received signal from a terminal station that includes at least a portion of self-interference. The predetermined timing may be, for example, a predetermined symbol in an uplink slot. In this case, the third beam pattern may be set to the first beam pattern acquired in the first slot. The first angle is estimated from a first change in beam direction from the first beam pattern in the third slot acquired one slot before the first slot to the first beam pattern in the first slot, and is set to the first angle in the first slot of the beam pattern that maximizes the SINR in a fourth slot that is to be acquired after the first slot. The second angle may be set to a first change in the angle of the beam direction from the first beam pattern, and the second angle may be set to a second change in the angle of the beam direction per symbol between the acquisition timings of the first beam pattern in the first slot and the beam pattern with the maximum SINR in the fourth slot, estimated from the first change.

[0023] That is, the first angle and the second angle are obtained based on changes in the optimal beam pattern to be used by the multiple first antennas, which change in response to the movement of the terminal station. For example, the faster the moving speed of the terminal station, the larger the first angle and the larger the first range. Furthermore, since the first angle (first change amount) can take a positive or negative value depending on the moving direction of the terminal station, the first range is set to face the moving direction of the terminal station in the fourth slot. Therefore, by setting the third beam pattern, the first angle, and the second angle in consideration of the movement of the terminal station, it is possible to obtain a first range that more accurately captures the position of the terminal station in the fourth slot. This allows the beam directions of the beam patterns of the multiple first antennas to be more accurately directed toward the position of the terminal station.

[0024] In one aspect of the present disclosure, the control unit may receive information regarding the set of beam patterns from a first device located upstream. That is, the information regarding the set of beam patterns may be generated by the first device. The first device may be, for example, a control device or a base station. This allows the first device to centrally control the beam patterns used by each relay station in the entire wireless network system. Note that the information regarding the set of beam patterns may be generated by the relay station itself. In this case, there is no communication delay in obtaining the information regarding the set of beam patterns, and the beam pattern can be updated to an optimal beam pattern according to the movement of the terminal station more quickly. Note that, in the present disclosure, an optimal beam pattern refers to a beam pattern that provides the highest SINR.

[0025] Furthermore, when information regarding the set of beam patterns is received from the first device, the third beam pattern may be set to a beam pattern obtained by changing the beam direction from the first beam pattern acquired in the first slot by a third change in the angle of the beam direction from the first beam pattern in the first slot to the beam pattern estimated to have the maximum SINR in the second slot, the change being in accordance with the time difference from the first slot to the second slot at which the information regarding the set of beam patterns begins to be used in the relay station, as estimated from the first change. That is, the third change in angle is an angular offset that takes into account the time difference until the information regarding the set of beam patterns begins to be used in the relay station. This allows the relay station to assign a set of beam patterns that more accurately captures the location of the terminal station in the second slot at which the information regarding the set of beam patterns is used. The relay station can update the beam patterns used by the multiple first antennas to a beam pattern with a larger maximum SINR, i.e., a beam pattern whose beam direction is more accurately directed toward the location of the terminal station.

[0026] Another aspect of the present disclosure can be identified as an information processing device that acquires information about the set of beam patterns and transmits it to a relay station. Furthermore, another aspect of the present disclosure can be identified as a method in which the information processing device executes a process of acquiring information about the set of beam patterns and a process in which the relay station selects and updates a beam pattern to be used from the set of beam patterns. Specifically, the method includes a relay station including: a plurality of first antennas used for communication with a mobile terminal station, the beam direction of which is a direction in which antenna gain is increased, controlled according to a predetermined beam pattern; one or more second antennas used for communication with a base station; and a radio device that performs non-regenerative relay, which relays signals between the base station and the terminal station without demodulating or decoding, and the relay station measures received signals measured in a first slot of a radio frame, the received signals being at least a fraction of self-interference occurring between signals transmitted and received by the plurality of first antennas via non-regenerative relay and signals transmitted and received by the one or more second antennas. the relay station, in a second slot after the first slot, for each of the plurality of beam patterns included in the set of beam patterns, selecting a second beam pattern from the plurality of beam patterns based on the SINR of the received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols; and updating the beam pattern used in the plurality of first antennas to the second beam pattern in the symbol next to the one or a plurality of consecutive symbols.

[0027] Another aspect can be specified as a program for causing a relay station or an information processing device to execute the method, and a computer-readable non-transitory storage medium on which the program is recorded.

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The configurations of the following embodiments are examples, and the present disclosure is not limited to the configurations of the embodiments.

[0029] First Embodiment FIG. 1 is a diagram showing an example of the system configuration of a communication system 100A according to the first embodiment. The communication system 100A includes a control device 1, a base station 2, relay stations 3 (3-1, ..., 3-M), and a terminal station 4. The control device 1 is a device on a core network to which the base station 2 is connected. However, the control device 1 can also be considered to be the core network itself, or a system included in the core network. The core network includes, for example, an optical fiber network. The control device 1 controls the base station 2, relay stations 3, and terminal station 4, and provides communication services to the terminal station 4.

[0030] The base station 2 provides a wireless access network to the terminal station 4. An area where wireless communication is possible in the wireless access network is also called a cell. In the first embodiment, the base station 2 has one or more antennas (for example, #1), a radio 21 connected to the one or more antennas, and a control circuit 22. The control circuit 22 has, for example, a processor and a memory. The processor controls communication with the control device 1 and wireless communication with the relay station 3 and the terminal station 4 using a computer program on the memory.

[0031] The terminal station 4 is, for example, a mobile station such as a smartphone, a tablet terminal, a wearable terminal, or an in-vehicle data communication device. However, the present invention is not limited to this, and the terminal station 4 may be a stationary terminal device. For example, the terminal device connects to a wireless access network within the range of a cell provided by the base station 2. The relay station 3 relays wireless communication between the base station 2 and the terminal station 4. The relay station 3 is, for example, a small base station, a mobile base station, an in-vehicle device, or a smartphone. In the first embodiment, the relay station 3 is a device selected as a relay station by the control device 1 from devices having a configuration capable of non-regenerative relaying.

[0032] When a connection request is generated from a terminal station 4, the control device 1 selects one or more devices located within the range of the cell provided by the base station 2 as relay stations 3 and instructs them to relay wireless communication. In the first embodiment, when multiple relay stations 3 are to be individually distinguished, they are assigned sub-numbers such as relay station 3-1, ..., 3-M. Here, the sub-number M is an integer indicating the number of relay stations 3. In FIG. 1, relay stations 3-1 and 3-M are illustrated as examples. However, when relay stations 3-1, ..., 3-M are collectively referred to, they are simply referred to as relay station 3.

[0033] The relay station 3 has a plurality of antennas (for example, #1, ..., #G) and The relay station 3 includes a radio 31 connected thereto and a control unit 32. Although the relay station 3 is shown in Fig. 1 as including one radio 31, the present invention is not limited to this, and the relay station 3 may include multiple radios 31, one for each antenna.

[0034] The terminal station 4 has one or more antennas (for example, #1), a radio 41 connected to the one or more antennas, and a control circuit 42. For example, a mobile station within a cell requests the base station 2 to connect to the radio access network, and when connected, the mobile station operates as the terminal station 4. The mobile station within the cell may request the base station 2 directly to connect to the radio access network. Alternatively, the mobile station within the cell may request the base station 2 to connect to the radio access network via a device operating as a relay station 3 within the cell. The terminal station 4 can be said to be a station that can communicate with the base station 2 via one or more relay stations 3 or without via any of the one or more relay stations 3.

[0035] FIG. 2 is a diagram illustrating an example of the system configuration of a communication system 100B. In the first embodiment, the system configuration may be the communication system 100B. Compared to the communication system 100A in FIG. 1, the communication system 100B has a central base station 2A and one or more distributed base stations 2B instead of the base station 2. When one or more distributed base stations 2B are to be individually distinguished, a subnumber is assigned, such as distributed base stations 2B-1, ..., 2B-S. Here, the subnumber S is an integer indicating the number of distributed base stations. In FIG. 2, distributed base stations 2B-1 and 2B-S are illustrated as examples. However, when the distributed base stations 2B-1, ..., 2B-S are collectively referred to, they are simply referred to as distributed base station 2B.

[0036] The central base station 2A has a control circuit 22A. Furthermore, the distributed base station 2B has a radio 21B. The control circuit 22A of the central base station 2A and the radio 21B of the distributed base station 2B are connected by, for example, an optical fiber C1 or a wireless network. The topology of the optical fiber C1 connecting the central base station 2A and multiple distributed base stations 2B is not limited to a specific topology. For example, the topology of the optical fiber C1 may be a one-to-one connection between nodes, a network that branches with increasing distance from the central base station 2A, a star network, a ring network, or the like. Furthermore, when connecting the control circuit 22A of the central base station 2A and the radio 21B of the distributed base station 2B by a wireless network, the standard and protocol of the wireless network employed are not limited to specific ones.

[0037] 1, the control circuit 22A has a processor and a memory. The processor controls communication with the control device 1 and wireless communication with the relay station 3 and terminal station 4 using a computer program stored in the memory. That is, the control circuit 22A controls wireless communication with the relay station 3 and terminal station 4 via the radio 21B of one or more distributed base stations 2B.

[0038] In the communication systems 100A and 100B, the control unit 32 of the relay station may include an antenna for the control channel in addition to the antennas #1 to #G. Hereinafter, when there is no need to distinguish between the communication systems 100A and 100B, they will simply be referred to as the communication systems 100.

[0039] In the first embodiment, it is assumed that the following is adopted in the communication system 100. In the communication system 100, the same frequency channel is used in the uplink and downlink by time division multiplexing. Furthermore, the slot timing of radio frames is synchronized between the base station 2, relay station 3, and terminal station 4. In the communication system 100, a block transmission method with a cyclic prefix such as CP-OFDM (Cyclic Prefix - Orthogonal Frequency Division Multiplexing) is adopted as the radio modulation method. Furthermore, the relay station 3 shares resource block information used in the uplink and downlink by the terminal station 4 to be relayed. Note that the uplink is used for communication in the direction from the terminal station 4 to the base station 2. The downlink is a communication link in the direction from the base station 2 to the terminal station 4. Hereinafter, the downlink direction may be referred to as the down direction, and the uplink direction may be referred to as the up direction.

[0040] In the first embodiment, the relay station 3 receives a set of beam patterns from the control device 1, and selects and updates the beam pattern that maximizes the SINR from among the multiple beam patterns included in the set. The SINR of the received signal from the terminal station 4 is calculated taking into account the effect of self-interference due to non-regenerative relaying. This allows the relay station to update the beam pattern at intervals shorter than the radio frame, and can provide stable non-regenerative relay communications even when the terminal station 4 is moving at high speed.

[0041] 3 is a diagram showing an example of a processing sequence related to updating the beam pattern of the relay station 3 in the communication system 100 according to the first embodiment. In FIG. 3, the processing flow from S1 to S3 is shown, and the details of each processing will be described later.

[0042] In S1, the relay station 3 executes a beam pattern selection process in a predetermined uplink slot in the radio frame. In the beam pattern selection process in S1, the relay station 3 selects a beam pattern from a set of preset beam patterns that maximizes the SINR of the signal received from the terminal station 4, and notifies the control device 1 of that beam pattern and the maximum SINR of that beam pattern. Hereinafter, when simply referring to SINR, it will refer to the SINR of the signal received from the terminal station 4.

[0043] In S2, the control device 1 executes a beam pattern set determination process to determine a set of beam patterns to be assigned to the relay station 3. In the beam pattern set determination process in S2, the control device 1 determines a beam pattern set to be assigned to the relay station 3 based on the beam patterns notified from the relay station 3, and notifies the relay station 3.

[0044] The relay station 3 performs non-regenerative relay using a beam pattern included in the beam pattern set notified by the control device 1. At the same time, in S3, the relay station 3 performs a beam pattern update process. In the beam pattern update process in S3, the relay station 3 monitors the SINR on a symbol-by-symbol basis for each beam pattern included in the beam pattern set, selects the beam pattern that maximizes the SINR, and updates the beam pattern. Note that in FIG. 3, the control device 1 performs the beam pattern set determination process in S2, but the base station 2 may also perform it.

[0045] FIG. 4 is a diagram showing an example of the hardware configuration of relay station 3. Relay station 3 includes radio units 31-1 and 31-2, a control unit 32, a self-interference cancellation unit 33, and a baseband circuit 34. Radio unit 31-1 is connected to antennas #1 to #N for communication with the terminal station. Radio unit 31-2 is connected to one or more antennas for communication with control device 1. Note that radio units 31-1 and 31-2 have the same configuration. When radio units 31-1 and 31-2 are collectively referred to, they are simply described as radio unit 31. Note that the total of the number N of antennas for communication with the terminal station and the number of one or more antennas for communication with control device 1 is the number G of antennas held by relay station 3. That is, N < G. Hereinafter, radio unit 31-1 connected to antennas #1 to #N for communication with the terminal station will be described as a representative example.

[0046] Radio unit 31-1 includes a transmit / receive switch 311, a transmitter 312, a receiver 313, and other multipliers and adders. Transmit / receive switch 311 is a switch that switches the transmission or reception of antennas #1 to #N. Transmit / receive switch 311 is connected to either transmitter 312 or receiver 313. When transmit / receive switch 311 is connected to transmitter 312, the antenna and transmitter 312 are connected, and the antenna operates as a transmit antenna. When transmit / receive switch 311 is connected to receiver 313, the antenna and receiver 313 are connected, and the antenna operates as a receive antenna. The switching of the connection of transmit / receive switch 311 in radio unit 31-1 is performed according to an instruction from control unit 32.

[0047] Receiver 313 receives a received signal from the antenna when connected to the antenna by transmit / receive switch 311. Receiver 313 has a quadrature detection circuit and an analog-to-digital (AD) converter. Receiver 313 down-converts the received signal by the quadrature detection circuit and further converts it into digital data by the AD converter to obtain a baseband signal. Receiver 313 outputs the obtained baseband signal to self-interference cancellation unit 33.

[0048] Here, the antenna for communication with the terminal station connected to the radio 31-1 operates as a receiving antenna that receives signals from the terminal station 4 in communication in the uplink direction. On the other hand, the antenna for communication with the base station 2 connected to the radio 31-2 operates as a transmitting antenna that transmits signals to the base station 2 in communication in the uplink direction. The antenna for communication with the terminal station connected to the radio 31-1 operates as a transmitting antenna that transmits signals to the terminal station 4 in communication in the downlink direction. On the other hand, the antenna for communication with the base station 2 connected to the radio 31-2 operates as a receiving antenna that receives signals from the base station 2 in communication in the downlink direction.

[0049] The power difference between the transmission signal and the reception signal of an antenna is, for example, about 100 dB. Therefore, between the antenna for communication with the terminal station and the antenna for communication with the base station 2, a part of the transmission signal interferes with the reception signal. The interference between a part of the transmission signal and the reception signal at the relay station 3 is called self-interference. Because the transmission signal has a higher power than the reception signal, the effect of self-interference of the reception signal on the transmission signal is negligibly small. However, the effect of self-interference of a part of the transmission signal on the radio signal cannot be ignored, and this part of the transmission signal becomes an interference signal for the reception signal. Therefore, the part of the transmission signal that becomes an interference signal due to self-interference on the reception signal will self-interfere with the radio frequency (RF) analog filter in the quadrature detection circuit in the receiver 313. The interference is suppressed by using the FIR filter in the interference canceller 33 in combination.

[0050] The self-interference cancellation unit 33 has an FIR filter. The self-interference cancellation unit 33 uses the FIR filter to suppress a part of the transmission signal that is mixed into and interfering with the received signal. The self-interference cancellation unit 33 outputs the received signal filtered by the FIR filter to the baseband circuit 34.

[0051] The received signals output from the self-interference canceller 33 are weighted by a weight w_(curt,n) corresponding to each antenna #n by a receiver-side multiplier, which generates the beam pattern p_(j,curt) currently in use for that antenna #n. n is a variable indicating the antenna. n takes values ​​of 1,...,N. N is the number of antennas used for communication with the terminal station 4. p_(j,curt) indicates the beam pattern currently in use (current, abbreviated as curt) at relay station j. w_(curt,n) indicates the weight corresponding to antenna #n in the beam pattern p_(j,curt). The weight w is a complex number. The letters in parentheses following the underline following the letters indicating the beam pattern, weight, etc. are shown as subscripts in the figure. The received signals from antennas #1 to #N, weighted by each weight, are then added by an adder and output to the baseband circuit 34.

[0052] The baseband circuit 34 normally performs demodulation, decoding, etc. on the received signal, which is a baseband signal, but in non-regenerative relay, the received signal, which is a baseband signal, is output as is to the radio 31 connected to the transmitting antenna. For example, the received signal received from the antenna for communication with the terminal station is output by the baseband circuit 34 to the radio 31-2 connected to the antenna for communication with the base station 2. For example, the received signal received from the antenna for communication with the base station 2 is output by the baseband circuit 34 to the radio 31-3 connected to the antenna for communication with the terminal station. The signal is output to the radio 31-1.

[0053] Next, the transmission side of the radio 31-1 will be described. A signal received from an antenna for communication with the base station 2 is output by the baseband circuit 34 to the radio 31-1 connected to the antenna for communication with the terminal station, and is then transmitted from the relay station 3 as a transmission signal. The transmission signal output from the baseband circuit 34 is branched and weighted by a transmission-side multiplier corresponding to each antenna #n with a weight w_(curt,n) that generates the beam pattern p_(j,curt) currently in use for that antenna #n. Each transmission signal weighted by each weight is then output to the transmitter 312. Note that, for convenience, in FIG. 4, the transmission signal is output from the transmission-side multiplier to the transmitter 312 via the self-interference canceller 33, but in reality, self-interference suppression is not performed on the transmission signal.

[0054] The transmitter 312 has a digital-to-analog (DA) converter, a modulation circuit, and an amplifier circuit. When the transmitter 312 is connected to an antenna by a switch, it receives a transmission signal from the baseband circuit 34 via a transmission-side multiplier and a self-interference canceller 33. The transmitter 312 converts the transmission signal into an analog signal and generates an RF signal using the modulation circuit. The transmitter 312 also amplifies the power (amplitude) of the RF signal using the amplifier circuit. The transmitter 312 transmits the RF signal as a relay signal from the antenna connected by the transmit / receive switch 311.

[0055] The control unit 32 is, for example, a processor such as a CPU or a DSP (Digital Signal Processor), or an arithmetic circuit such as an FPGA. The control unit 32 controls the non-regenerative relay processing. More specifically, the control unit 32 measures the radio wave propagation characteristics of the propagation path, calculates the SINR for each beam pattern, notifies the control device 1 of the beam pattern and its SINR via a control channel, and updates the beam pattern. The control unit 32 is an example of the "control unit" of the "relay station."

[0056] The hardware configuration of relay station 3 is not limited to that shown in Fig. 4. For example, in Fig. 4, relay station 3 includes an antenna for a control channel connected to control unit 32, separate from antennas #1 to #N for communication with terminal stations and one or more antennas for communication with base stations, but this is not limiting. For example, relay station 3 may not include an antenna for a control channel in control unit 32, and may use any of antennas #1 to #G as the antenna for the control channel.

[0057] FIG. 5 is a diagram illustrating an example of the hardware configuration of the control device 1. The control device 1 has a CPU 11, a main memory device 12, and external devices, and executes communication processing and information processing using a computer program. The CPU 11 is also called a processor. The CPU 11 is not limited to a single processor, and may have a multi-processor configuration. The CPU 11 may also include a graphics processing unit (GPU), a digital signal processor (DSP), etc. The CPU 11 may also include a field programmable gate array (F The external device may be linked to a hardware circuit such as a PGA. Examples of the external device include an external storage device 13, an output device 14, an operation device 15, and a communication device 16.

[0058] The CPU 11 executes a computer program that has been loaded in an executable manner into the main memory device 12, and provides processing for the control device 1. The main memory device 12 stores the computer program executed by the CPU 11, data processed by the CPU 11, etc. The main memory device 12 may be a dynamic random access memory (DRAM), a static random access memory (SRAM), etc. , Read Only Memory (ROM), etc. Furthermore, the external storage device 13 is used, for example, as a storage area that assists the main storage device 12, and stores computer programs executed by the CPU 11, data processed by the CPU 11, etc. The external storage device 13 is a hard disk The control device 1 may be a hard disk drive, a solid state drive (SSD), or the like. A drive unit for a removable storage medium may be connected. Examples of removable storage media include a Blu-ray disc, a Digital Versatile Disc (DVD), a Compact Disc (CD), a flash memory card, etc. The CPU 11 is an example of a "control unit" of an "information processing device."

[0059] The output device 14 is, for example, a display device such as a liquid crystal display or an electroluminescence panel. However, the output device 14 may also include a speaker or other device for outputting sound. The operation device 15 is, for example, a touch panel with a touch sensor superimposed on a display. The communication device 16 communicates with the base station 2 and an external network such as the Internet via, for example, optical fiber. The communication device 16 is, for example, a gateway connected to the base station 2 and a gateway that communicates with an external network such as the Internet. The communication device 16 may be a single device or a combination of multiple devices. The hardware configuration of the control device 1 is not limited to that shown in FIG. 5.

[0060] (Selection process of beam pattern with maximum SINR at relay station 3) Fig. 6 is an example of a flowchart of the beam pattern selection process in the relay station 3. The beam pattern selection process in the relay station 3 corresponds to the process executed in S1 in Fig. 3. The process shown in Fig. 6 is repeatedly executed at a predetermined cycle when an instruction to relay to the terminal station 4 is received from the control device 1 via a control channel.

[0061] In OP11, the control unit 32 determines whether it is time to measure self-interference. The timing to measure self-interference is notified from the control device 1, for example, via a control channel. If it is time to measure self-interference (OP11: YES), the process proceeds to OP12. If it is not time to measure self-interference (OP11: NO), the process shown in FIG. 6 ends.

[0062] In OP12, the control unit 32 transmits a reference signal from either the antenna for communication with the terminal station 4 connected to the wireless device 31-1 or the antenna for communication with the base station 2 connected to the wireless device 31-2. In OP13, the control unit 32 receives the reference signal transmitted in OP12 with the antenna for communication with the base station 2 connected to the wireless device 31-2 or the antenna for communication with the terminal station 4 connected to the wireless device 31-1, and measures the propagation characteristics between the antenna for communication with the terminal station 4 and the antenna for communication with the base station 2.

[0063] The processes of OP12 and OP13 may be performed for all beam patterns included in the beam pattern set P_(j) of the antenna for communication with the terminal station 4, or may be performed for some of the beam patterns. The beam pattern set P_(j) may be held in advance by the control unit 32, or may be notified in advance by the control device 1. When the processes of OP12 and OP13 are performed for some of the beam patterns, the propagation characteristics between the antenna for communication with the terminal station 4 and the antenna for communication with the base station 2 for the other beam patterns are complemented using the propagation characteristics of the measured beam patterns. For example, if the angular difference in beam direction between beam pattern A and beam pattern B is less than a predetermined value and the propagation characteristics of beam pattern A have been measured, the propagation characteristics of beam pattern B may be approximated by the propagation characteristics of beam pattern A.

[0064] In OP14, the control unit 32 determines whether or not it is the s-th uplink slot period specified by the control device 1. If it is the s-th uplink slot period (OP14: YES), the process proceeds to OP15. The control unit 32 remains in a standby state until the s-th uplink slot period begins (OP14: NO).

[0065] In OP15, the control unit 32 converts the reference signal from the terminal station 4 into a beam pattern p_( The received signal vector Rx_(j,0)={rx_(1),...,rx_(N)} when received at antenna #n is recorded. rx(j,n) is the received signal of antenna #n. The beam pattern p_(j,0) is a beam pattern that is held in advance by the control unit 32 or notified by the control device 1. The received signal rx_(n) is a measurement of the received signal output from the self-interference cancellation unit 33. Therefore, the power of the received signal rx_(n) is a value from which the amount of self-interference suppression by the self-interference cancellation unit 33 has been removed.

[0066] In OP16, the SINR is calculated for each beam pattern p_(j,d) included in the beam pattern set P_(j). d is a variable indicating the beam pattern. d takes the value d=1,...,D. D is the number of beam patterns included in the beam pattern set P_(j). SINR Γ_(j,k)(p_(j,d)) for beam pattern p_(j,d) is calculated by the following equation 1: k is a variable indicating the terminal station 4.

number

[0067] W_(j) is the noise power at the relay station 3. I_(j)(p_(j,d)) is the self-interference power remaining in the received signal. The self-interference power is represented by the propagation characteristics between the antenna for communication with the terminal station 4 and the antenna for communication with the base station 2. Furthermore, the amount of self-interference suppression by the self-interference canceller 33 can be considered a fixed value. Therefore, the self-interference power remaining in the received signal can also be considered as interference between the input signal (transmitted signal) to the self-interference canceller 33 and the output signal (received signal) from the self-interference canceller 33, between the baseband circuit 34 and the self-interference canceller 33. In this case, if the propagation characteristics indicating the coupling between the input signal (transmitted signal) to the self-interference canceller 33 (transmitted signal) and the output signal (received signal) from the self-interference canceller 33 in the beam pattern p_(j,d) are represented as H_(R→R)(p_(j,d)), I_(j)(p_(j,d)) is expressed by the following equation 2. Note that H_(R→R)(p_(j,d)) can be calculated from the propagation characteristics between the antenna for communication with the terminal station 4 and the antenna for communication with the base station 2 in the beam pattern p_(j,d) and the amount of self-interference suppression by the self-interference removal unit 33.

number

[0068] In OP17, the control unit 32 notifies the control device 1 of the beam pattern p_(j,max)(s) having the maximum SINR among the multiple beam patterns p_(j,d) included in the beam pattern set P_(j) found in OP16, along with the SINR. s is a variable indicating a slot in a radio frame. Thereafter, the processing shown in FIG. 6 ends. Note that the beam pattern selection processing of the relay station 3 shown in FIG. 6 is an example, and the beam pattern selection processing of the relay station 3 is not limited to the processing shown in FIG. 6. For example, the SINR for each beam pattern may be calculated using the received signal of antenna #n, the propagation characteristics between the antenna for communication with the terminal station 4 and the antenna for communication with the base station 2 in that beam pattern, the amount of self-interference suppression by the self-interference canceller 33, and the noise power W_(j) at the relay station 3.

[0069] (Processing of determining a set of beam patterns to be assigned to relay station 3 in control device 1) Fig. 7 is a diagram showing an example of the relationship between a plurality of beam patterns included in a beam pattern set assigned to the relay station 3 in the first embodiment. The example shown in Fig. 7 shows beam patterns in the azimuth angle direction.

[0070] In the first embodiment, the beam pattern set P_(j,R)(s) assigned to the relay station 3 is defined by a central beam pattern p_(j,R)(s), θ_(j,R) that defines the range of angles of the beam direction in the positive and negative directions centered on the beam direction of the beam pattern p_(j,R)(s), and a step width Δθ_(j,R) between the beam patterns. That is, in the first embodiment, the beam pattern set P_(j,R)(s) assigned to the relay station 3 includes θ_(j,R) / Δθ_(j,R) × 2 beam patterns. The beam direction of a beam pattern refers to the direction in which radio waves are collected and antenna gain is increased when the beam pattern is applied to an antenna.

[0071] The central beam pattern p_(j,R)(s) of the beam pattern set P_(j,R)(s) is set to the beam pattern p_(j,max)(s) notified by the relay station 3. The angle range ±θ_(j,R) of the beam direction and the step width Δθ_(j,R) are each set to a preset value. In this way, by setting the multiple beam patterns included in the beam pattern set P_(j,R)(s) so that the beam directions are at equal angle intervals with a step width Δθ_(j,R), the relay station 3 can thoroughly search for better beam patterns within the angle range ±θ_(j,R).

[0072] Fig. 8 is an example of a flowchart of the beam pattern set determination process of the control device 1 in the first embodiment. The process shown in Fig. 8 is repeatedly executed at a predetermined cycle. The process shown in Fig. 8 is executed mainly by the CPU 11 of the control device 1, but for convenience, the process will be described mainly by the control device 1.

[0073] In OP21, the control device 1 determines whether or not it has received notification of the beam pattern p_(j,max)(s) and the SINR for that beam pattern p_(j,max)(s) from the relay station 3. If notification of the beam pattern p_(j,max)(s) and the SINR for that beam pattern p_(j,max)(s) has been received from the relay station 3 (OP21: YES), the processing proceeds to OP22. If notification of the beam pattern p_(j,max)(s) and the SINR for that beam pattern p_(j,max)(s) has not been received from the relay station 3 (OP21: NO), the processing shown in FIG. 8 ends.

[0074] In OP22, the control device 1 determines whether the SINR notified from the relay station 3 is equal to or greater than a threshold. This threshold is used to determine whether the relay station 3 should continue non-regenerative relaying to the terminal station 4. If the SINR notified from the relay station 3 is equal to or greater than the threshold (OP22: YES), the process proceeds to OP23. If the SINR notified from the relay station 3 is less than the threshold (OP22: NO), it is determined that the relay station 3 cannot continue non-regenerative relaying to the terminal station 4 regardless of which beam pattern included in the beam pattern set P_(j) is used, and the process shown in FIG. 8 ends.

[0075] In OP23, the control device 1 determines the beam pattern set P_(j,R)(s) to be assigned to the relay station 3. The control device 1 sets the central beam pattern p_(j,R)(s) to p_(j,max)(s). The control device 1 sets the beam direction angle range ±θ_(j,R) and the step width Δθ_(j,R) to predetermined fixed values.

[0076] In OP24, the control device 1 notifies the relay station 3 of information about the beam pattern set P_(j,R)(s). The information about the beam pattern set P_(j,R)(s) may include, for example, For example, the information includes a central beam pattern p_(j,R)(s), a beam direction angle range ±θ_(j,R), and a step width Δθ_(j,R). Then, the processing shown in FIG. 8 ends. Information about the beam pattern set P_(j,R)(s) is an example of "information about a set of beam patterns." Beam pattern p_(j,max)(s) is an example of a "first beam pattern." Beam pattern p_(j,R)(s) is an example of a "third beam pattern." The beam direction angle range is an example of a "first range." θ_(j,R), which defines the beam direction angle range, is an example of a "first angle." The step width Δθ_(j,R) is an example of a "second angle."

[0077] 7 and 8 are merely examples, and the definition of the beam pattern set P_(j,R)(s) is not limited to the example shown in FIG. 7. For example, the beam pattern set P_(j,R)(s) may be determined by randomly determining a predetermined number of beam patterns whose beam directions fall within the beam direction angle range ±θ_(j,R). In this case, the information about the beam pattern set P_(j,R)(s) may include the beam pattern p_(j,R)(s) and the predetermined number of beam patterns included in the beam pattern set P_(j,R)(s). Also, as shown in Figure 7, even when a beam pattern set P_(j,R)(s) to be notified to relay station 3 is defined, the information regarding the beam pattern set P_(j,R)(s) to be notified to relay station 3 may include, for example, beam pattern p_(j,R)(s) and multiple beam patterns with a step width Δθ_(j,R) whose beam direction falls within the beam direction angle range ±θ_(j,R).

[0078] (Beam pattern update process at relay station 3) Fig. 9 is an example of a flowchart of the beam pattern update process of the relay station 3 in the first embodiment. The process shown in Fig. 9 is the process executed in S3 of Fig. 3. The process shown in Fig. 9 is repeatedly executed at a predetermined period. The process shown in Fig. 9 may be started, for example, after notifying the control device 1 in the beam pattern selection process of the beam pattern p_(j,max)(s) having the maximum SINR among the multiple beam patterns p_(j,d) included in the beam pattern set P_(j) and the SINR.

[0079] In OP31, the control unit 32 determines whether or not the beam pattern set P_(j,R)(s) has been received from the control device 1. If the beam pattern set P_(j,R)(s) has been received from the control device 1 (OP31: YES), the processing proceeds to OP32. If the beam pattern set P_(j,R)(s) has not been received from the control device 1 (OP31: NO), the processing shown in FIG. 9 ends.

[0080] In OP32, the control unit 32 determines whether or not a symbol change has occurred. If a symbol change has occurred (OP32: YES), the process proceeds to OP33. If a symbol change has not occurred (OP32: NO), the control unit 32 enters a standby state.

[0081] In OP33, the control unit 32 updates the beam pattern p_(j,curt) currently in use by the antenna for communication with the terminal station 4 to beam pattern p_(j,next) and starts non-regenerative relay. The initial value of p_(j,curt) is p_(j,0). The initial value of p_(j,next) is the beam pattern p_(j,R)(s) included in the beam pattern set P_(j,R)(s).

[0082] In OP34, the control unit 32 determines whether or not it is an uplink slot period. If it is an uplink slot period (OP34: YES), the process proceeds to OP35. If it is not an uplink slot period, that is, if it is a downlink slot period (OP34: NO), the process proceeds to OP38.

[0083] The processes from OP35 to OP37 are executed when it is the period of the uplink slot. In OP35, the control unit 32 records the received signal vector Rx_(j,curt)={rx_(1),...,rx_(N)} when the relay signal (data signal) from the terminal station 4 is received with the beam pattern p_(j,curt). In OP36, the SINR is calculated for each beam pattern p_(j,d) included in the beam pattern set P_(j,R). The SINR Γ_(j,k)(p_(j,d)) in the beam pattern p_(j,d) is calculated using the above formula 1. The weight vector W_(j,d)={w_(j,1),...,w_(j,n)} that generates each beam pattern p_(j,d) included in the beam pattern set P_(j,R) is obtained by determining the angle of the beam direction of the beam pattern p_(j,d). The beam direction of each beam pattern p_(j,d) included in the beam pattern set P_(j,R) can be obtained by the beam pattern p_(j,R)(s), the beam direction angle range ±θ_(j,R), and the step width Δθ_(j,R).

[0084] In OP37, the control unit 32 executes a beam pattern determination process to determine the beam pattern p_(j,next) to be used in the next symbol based on the SINR of each beam pattern p_(j,d) calculated in OP 36. The details of the beam pattern determination process will be described later.

[0085] In OP38, the control unit 32 determines whether or not the termination condition for the beam pattern update process is satisfied. Update process The termination condition of this is, for example, one or all of the following: the period in the radio frame specified by the control device 1 has ended; and an instruction to stop non-regenerative repeating to the terminal station 4 has been received from the control device 1 via the control channel. If the termination condition of the beam pattern update process is met (OP38: YES), the process shown in FIG. 9 ends.

[0086] If the termination condition for the beam pattern update process is not satisfied (OP38: NO), the process proceeds to OP32, where the beam pattern p_(j,curt) used for each symbol is updated to p_(j,next) (OP33). During the uplink slot, the SINR is calculated for each beam pattern p_(j,d) included in the beam pattern set P_(j,R) for each symbol (OP36), and the beam pattern p_(j,next) is determined (OP37). During the downlink slot, the processes from OP35 to OP37 are not executed, and the beam pattern p_(j,next) determined for the last symbol in the immediately preceding uplink slot is used for non-regenerative relaying.

[0087] The beam pattern determination process in OP 37 includes (1) a method using a moving average window and (2) a method using a switch-and-stay. The administrator of communication system 100 can arbitrarily set which of (1) the method using a moving average window and (2) the method using a switch-and-stay is to be used.

[0088] 10 is a flowchart of (1) the beam pattern determination process when a moving average window is used. The process shown in FIG. 10 is one of the processes executed in OP37 in FIG.

[0089] In OP3711, the control unit 32 acquires the moving average value W_(MA)(θ_(j,max)(h-Lw+1:h)) of the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that has the maximum SINR among the multiple beam patterns included in the beam pattern set P_(j,R) for each of the multiple symbols included in the moving average window W_(MA). h is a variable indicating the symbol. Lw is the number of symbols in the moving average window. For example, if Lw=3, and the current symbol is #h, then the beam patterns that have the maximum SINR for each of the symbols #h-2 to #h are acquired. The average value of the beam directions θ_(j,max)(h-2), θ_(j,max)(h-1), and θ_(j,max)(h) is calculated as the moving average value W_(MA)(θ_(j,max)(h-Lw+1:h)).

[0090] In OP3712, the control unit 32 selects the beam pattern p_(j,near_maxθ) from the beam pattern set P_(j,R) that provides the closest beam direction to the moving average value W_(MA)(θ_(j,max)(h-Lw+1:h)).

[0091] In OP3713, the control unit 32 sets the beam pattern p_(j,near_maxθ) that provides the beam direction closest to the moving average value W_(MA)(θ_(j,max)(h-Lw+1:h)) as the beam pattern p_(j,next) to be used in the next symbol. After that, the process proceeds to OP38 in FIG. 9.

[0092] For example, when Lw = 3, assume that the beam pattern that maximizes the SINR in each of the symbols from symbol #h-2 to symbol #h+2 is beam pattern p_(j,D). In this case, beam pattern p_(j,D) is the beam pattern p_(j,curt) used for the three symbols from symbol #h+1 to symbol #h+3. Also, even in a situation where the beam pattern that maximizes the SINR changes for each symbol, if beam pattern p_(j,near_maxθ) that provides the closest beam direction to the moving average value W_(MA)(θ_(j,max)(h-Lw+1:h)) from symbol #h-2 to symbol #h+2 is beam pattern p_(j,D), then beam pattern p_(j,D) is the beam pattern p_(j,curt) used for the three symbols from symbol #h+1 to symbol #h+3. In this way, by using a moving average window, it is possible to prevent the period in which the beam pattern p_(j,curt) used changes from becoming too short.

[0093] Figure 11 is a flowchart of the beam pattern determination process when (2) switch and stay is used. In the beam pattern determination process when (2) switch and stay is used, when the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that results in the maximum SINR becomes positive or negative for Lss consecutive symbols with respect to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt), p_(j,next) is updated to a beam pattern whose beam direction is moved in a consecutive positive or negative direction. The process shown in Figure 11 is one of the processes executed in OP37 of Figure 9.

[0094] In OP3721, the control unit 32 records the value obtained by subtracting the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) from the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that results in the maximum SINR in the current symbol #h. 72 In 1, it is recorded whether the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that results in the maximum SINR in the current symbol #h is positive or negative relative to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt).

[0095] In operation OP3722, the control unit 32 determines whether θ_(j,max)(h)−θ_(j,curt) is positive or negative. If θ_(j,max)(h)−θ_(j,curt) is positive (OP3722: YES), the processing proceeds to operation OP3723.

[0096] In OP3723, the control unit 32 determines whether the beam direction θ_(j,max)(h-1) of the beam pattern p_(j,max)(h-1) that results in the maximum SINR with respect to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) is positive or not, even in the symbol #h-1 immediately preceding the current symbol #h. -1) If there is no record of -θ_(j,curt), OP3723 will result in a negative judgment.

[0097] If θ_(j,max)(h-1)-θ_(j,curt) is positive (OP3723: YES), the processing proceeds to OP3724. In OP3724, the control unit 32 increments the variable q by 1. The variable q is a variable for counting the number of times that the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that has the maximum SINR for the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) is consecutively positive or negative. The initial value of q is 0, and the value is cleared when the beam pattern update processing of Figure 9 is completed.

[0098] In operation OP3725, the control unit 32 determines whether the value of q is equal to or greater than Lss, that is, whether the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that has the maximum SINR for the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) has been positive Lss times or more in a row. If the value of q is equal to or greater than Lss (OP3725: YES), the process proceeds to operation OP3726. If the value of q is less than Lss (OP3725: NO), p_(j,next) is not updated, the process shown in FIG. 11 ends, and the process proceeds to operation OP38 in FIG. 9.

[0099] In OP3726, the control unit 32 sets p_(j,next) to a beam pattern whose beam direction is the direction obtained by adding the step width Δθ_(j,R) to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt). After that, the processing shown in Fig. 11 ends, and the processing proceeds to OP38 in Fig. 9.

[0100] Next, if θ_(j,max)(h)-θ_(j,curt) is negative or 0 (OP3722: NO), the processing proceeds to OP3727. In OP3727, the control unit 32 determines whether the beam direction θ_(j,max)(h-1) of the beam pattern p_(j,max)(h-1) that results in the maximum SINR relative to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) is negative for the symbol #h-1 immediately preceding the current symbol #h. If there is no record of θ_(j,max)(h-1)-θ_(j,curt), OP3727 results in a negative determination.

[0101] If θ_(j,max)(h−1)−θ_(j,curt) is negative (OP3727: YES), the processing proceeds to OP3728. In OP3728, the control unit 32 increments the variable q by 1.

[0102] In operation OP3729, the control unit 32 determines whether the value of q is equal to or greater than Lss, that is, whether the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that has the maximum SINR for the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) has been negative Lss times or more consecutively. If the value of q is equal to or greater than Lss (OP3729: YES), the process proceeds to operation OP3730. If the value of q is less than Lss (OP3729: NO), p_(j,next) is not updated, the process shown in FIG. 11 ends, and the process proceeds to operation OP38 in FIG. 9.

[0103] In OP3730, the control unit 32 sets p_(j,next) to a beam pattern whose beam direction is the direction obtained by subtracting the step width Δθ_(j,R) from the beam direction θ_(j,curt) of the current beam pattern p_(j,curt). After that, the processing shown in Fig. 11 ends, and the processing proceeds to OP38 in Fig. 9.

[0104] In OP3723, if θ_(j,max)(h-1)-θ_(j,curt) is negative or 0 (OP3723:NO), and in OP3727, if θ_(j,ma If x)(h-1)-θ_(j,curt) is positive or 0 (OP3727: NO), the process proceeds to OP3731. In OP3731, the control unit 32 sets q to the initial value of 0. In this case, p_(j,next) is not updated, the process shown in FIG. 11 ends, and the process proceeds to OP38 in FIG. 9.

[0105] If the beam direction θ_(j,max)(h) of the beam pattern p_(j,max)(h) that results in the maximum SINR relative to the beam direction θ_(j,curt) of the current beam pattern p_(j,curt) becomes positive or negative Lss times or more consecutively, it indicates that the terminal station 4 is moving at high speed. In this case, by updating the beam pattern p_(j,next) by moving the beam direction of the beam pattern p_(j,curt) by Δθ_(j,R) in the positive or negative direction, it is possible to update to a more optimal beam pattern that corresponds to the high-speed movement of the terminal station 4.

[0106] The beam pattern update process of the relay station 3 is not limited to (1) the method using a moving average window or (2) the method using switch-and-stay. For example, the beam pattern p_(j,curt) to be used may be updated for each symbol to the beam pattern included in the beam pattern set P_(j,R) that results in the maximum SINR.

[0107] (How to determine Lw and Lss) Methods for determining (1) the size Lw of the moving average window W_(MA) in the beam pattern update process using a moving average window, and (2) Lss in the beam pattern update process using switch and stay, include, for example, the following (A)-(C).

[0108] (A) Set to a predetermined fixed value. For example, Lw and Lss are set to 3 symbols. (B) Set to the maximum number of symbols that is equal to or less than the coherent time Tc (the time length over which the characteristics of the propagation path can be considered to be the same). For example, let Lw and Lss be the quotients obtained by dividing the coherent time by the symbol time length. The coherent time Tc is calculated from the moving speed v_(UE) of the terminal station 4 and the frequency used. Note that the moving speed v_(UE) of the terminal station 4 may be a predetermined value, or may be calculated as an estimated value from the cyclic prefix of the received signal in the immediately preceding uplink slot from the terminal station 4, or a value collected from the terminal station 4 by the 5G core network via a predetermined application may be acquired and used.

[0109] (C) Using a regression equation that predicts the beam direction that results in the maximum SINR, the beam direction θ_(j,max)(h) obtained on a symbol-by-symbol basis at relay station 3 is set based on the deviation σ_(beam) from the beam direction obtained by the regression equation and the target deviation σ_(error). This regression equation uses the beam direction θ_(j,max)(h) of the beam pattern that results in the maximum SINR in one symbol as the objective variable and the symbol number h of that symbol as the explanatory variable. In addition, this regression equation is fitted using a set of the beam direction θ_(j,max)(h) obtained for each symbol during the beam pattern update process using moving average or switch-and-stay in the immediately preceding uplink slot and the symbol number h of each symbol in the immediately preceding uplink slot (the coefficients of each term are calculated). Lw and Lss are calculated based on the deviation (square root of mean square error) σ_(beam) between the beam direction output value when the symbol number h of the current symbol in the current slot is input to the regression equation and the beam direction θ_(j,max)(h) obtained for the current symbol. Lw and Lss may be updated for each symbol by, for example, multiplying the current Lw and Lss values ​​by the square of the quotient obtained by dividing σ_(beam) by σ_(error).

[0110] Lw and Lss are parameters that affect the interval (or frequency) of updating the beam pattern used by the antenna for communication with the terminal station 4. If Lw and Lss are too small, For example, by taking into consideration the moving speed of the terminal station 4, or the beam pattern with the maximum SINR acquired on a symbol-by-symbol basis and the SINR in that beam pattern, Lw and Lss can be set to appropriate values, thereby providing stable communication.

[0111] Fig. 12 is an example of a simulation result of the beam pattern update process in the communication system 100 according to the first embodiment. In the graph shown in Fig. 12, the horizontal axis represents symbols (time) and the vertical axis represents the angle of the beam direction of the beam pattern that maximizes the SINR for each symbol. The example shown in Fig. 12 shows the angle of the beam direction for each symbol relative to the position of the terminal station 4, the angle of the beam direction of the beam pattern in use when the beam pattern is updated to the beam pattern with the maximum SINR on a symbol-by-symbol basis, (1) the angle of the beam direction of the beam pattern in use when the beam pattern is updated using a method that uses a moving average window, and (2) the angle of the beam direction of the beam pattern in use when the beam pattern is updated using a method that uses a switch-and-stay.

[0112] In the simulation of beam pattern update using either method, the conditions such as the moving speed and route of the terminal station 4, the transmission power of the relay station 3, and the propagation path characteristics between the terminal station 4 and the relay station 3 are the same.

[0113] The average error in the angle for each symbol using each beam pattern update method, relative to the beam direction angle of the beam pattern used when updating the beam pattern on a symbol-by-symbol basis, was 4.75 degrees when updating to the beam pattern with the maximum SINR on a symbol-by-symbol basis, 2.32 degrees when updating the beam pattern with (1) the method using a moving average window, and 2.53 degrees when updating the beam pattern with (2) the method using switch-and-stay. Therefore, updating the beam pattern with (1) the method using a moving average window and (2) the method using switch-and-stay has a smaller average beam direction error than updating to the beam pattern with the maximum SINR on a symbol-by-symbol basis, enabling non-regenerative relay communications to be provided with more stable quality.

[0114] <Effects of the First Embodiment> According to the first embodiment, the beam patterns of the multiple antennas of the relay station 3 used for communication with the terminal station 4 can be updated in units of one or more symbols. This makes it possible to provide stable non-regenerative relay communication even when the terminal station 4 is moving at high speed. Furthermore, the beam pattern is updated based on the SINR for each beam pattern included in the beam pattern set P_(j,R) calculated in units of symbols. Furthermore, the beam pattern set P_(j,R) is obtained based on the beam pattern that provides the maximum SINR in a certain slot. The SINR in the beam pattern is calculated taking into account the effect of self-interference caused by non-regenerative relaying in the relay station 3. Therefore, according to the first embodiment, the effect of self-interference caused by non-regenerative relaying in the relay station 3 is also taken into account, making it possible to obtain a more accurate SINR in the beam pattern. This makes it possible to update the beam pattern in use to a beam pattern that ensures that an SINR is obtained that allows stable continued communication.

[0115] Second Embodiment In the first embodiment, after receiving notification of the beam pattern set P_(j,R) from the control device 1, the relay station 3 executes the beam pattern update process using the notified beam pattern set P_(j,R) until a termination condition is satisfied. In the second embodiment, the beam pattern set P_(j,R) assigned to the relay station 3 is updated based on the beam pattern with the maximum SINR among the beam patterns included in the beam pattern set P_(j,R), which is calculated on a symbol-by-symbol basis. In the second embodiment, explanations common to the first embodiment will be omitted. do.

[0116] FIG. 13 is a diagram showing an example of a processing sequence related to updating a beam pattern of a relay station 3 in a communication system 100 according to the second embodiment. In the second embodiment, the system configuration of the communication system 100, the configuration of the control device 1, the base station 2, the relay station 3, and the terminal station 4 are the same as those in the first embodiment. In the second embodiment, the beam pattern that maximizes the SINR by the relay station 3 in S1 is updated. Selection The process is the same as in the first embodiment until the control device 1 executes the process of determining a set of beam patterns to be assigned to the relay station 3 in S2.

[0117] In the second embodiment, after the control device 1 notifies the relay station 3 of the beam pattern set, in S3-1 the relay station 3 executes a beam pattern update process and notifies the control device 1 of the beam pattern with the maximum SINR at a predetermined timing. In S4, the control device 1 executes a beam pattern set update process to update the beam pattern set to be assigned to the relay station 3 based on the beam pattern with the maximum SINR notified by the relay station 3. In the second embodiment, the processes of S3-1 and S4 are repeatedly performed by the relay station 3 and the control device 1 until the termination condition for the beam pattern update process is satisfied.

[0118] Fig. 14 is an example of a flowchart of the beam pattern update process of the relay station 3 in the second embodiment. The process shown in Fig. 14 is the process executed in S3-1 of Fig. 13. The process shown in Fig. 14 is repeatedly executed at a predetermined period. In Fig. 14, the same processes as those in the beam pattern update process in the first embodiment of Fig. 9 are assigned the same reference numerals.

[0119] The process from OP31 to OP37 of receiving the beam pattern set P_(j,R)(s) from the control device 1, calculating the SINR for each beam pattern included in the beam pattern set P_(j,R)(s) for each symbol of the uplink slot, and determining the next beam pattern p_(j,next) to be used is the same as in the first embodiment.

[0120] In operation OP311, the control unit 32 determines whether or not the symbol is the end of the uplink slot. If it is the end of the uplink slot (OP311: YES), the process proceeds to operation OP312. If it is not the end of the uplink slot (OP311: NO), the process proceeds to operation OP32.

[0121] In OP312, the control unit 32 notifies the control device 1 of the beam pattern p_(j,max)(s) that has the highest number of times (or frequency) of reaching the maximum SINR among the beam patterns included in the beam pattern set P_(j,R)(s) for each symbol in the uplink slot, and the maximum SINR for that beam pattern.

[0122] In OP313, the control unit 32 determines whether or not the beam pattern set P_(j,R)(s) has been received from the control device 1. If the beam pattern set P_(j,R)(s) has been received from the control device 1 (OP313: YES), the process proceeds to OP314. If the beam pattern set P_(j,R)(s) has not been received from the control device 1 (OP313: NO), the control unit 32 enters a standby state. For example, if the beam pattern set P_(j,R)(s) has not been received from the control device 1 even after a predetermined time has elapsed, the control unit 32 may proceed with the process to OP32.

[0123] In OP314, the control unit 32 updates the beam pattern set P_(j,R)(s) to the beam pattern set P_(j,R)(s) received from the control device 1. Also, the control unit 32 updates the beam pattern p_(j,next) to be used in the next symbol to the beam pattern p_(j,R)(s) included in the beam pattern set P_(j,R)(s) received from the control device 1. Thereafter, the processing proceeds to OP38.

[0124] If the termination condition is not met (OP38: NO), the beam pattern p_(j,curt) used at the start of the next symbol is changed to the value specified in OP31. 3 The beam pattern is updated to the beam pattern p_(j,R)(s) included in the beam pattern set P_(j,R)(s) received by , and non-regenerative relaying is performed. Note that the beam pattern update process of the relay station 3 in the second embodiment shown in Figure 14 is an example and is not limited to this. For example, the beam pattern notified to the control device 1 in OP312 may be a beam pattern that results in the maximum SINR in the last symbol of the uplink slot.

[0125] (Updating process of the beam pattern set assigned to the relay station 3 in the control device 1) Fig. 15 is a diagram showing an example of the relationship between a plurality of beam patterns used in the update process of the beam pattern set in Embodiment 2. The example shown in Fig. 15 shows beam patterns in the azimuth angle direction.

[0126] In Figure 15, it is assumed that the control device 1 receives notification of the beam pattern p_(j,max)(s) that results in the maximum SINR from the relay station 3 in the sth slot. It is assumed that the previous notification occurred in the s-Δs1th slot. It is also assumed that the next notification is scheduled to occur in the s+Δs2th slot. The beam pattern notified in the s-Δs1th slot is assumed to be p_(j,max)(s-Δs1). The beam pattern notified in the s+Δs2th slot is assumed to be p_(j,max)(s+Δs2).

[0127] In the second embodiment, the control device 1 sets the central beam pattern p_(j,R)(s), θ_(j,R) that defines the angular range of the beam direction, and the step width Δθ_(j,R) between beam patterns based on the change from beam pattern p_(j,max)(s-Δs1) to beam pattern p_(j,max)(s). Since the control device 1 instructs the relay station 3 on the notification timing of the beam pattern that will result in the maximum SINR, it knows the slot in which the notification will be made.

[0128] First, let Δφ_(j,m) be the change in the angle of the beam direction from beam pattern p_(j,max)(s-Δs1) to beam pattern p_(j,max)(s). Let ΔT_(j,m) be the time length from the s-Δs1th slot to the sth slot. Dividing Δφ_(j,m) by ΔT_(j,m) gives the change per unit time in the beam direction of the beam pattern resulting in the maximum SINR. Multiplying the change per unit time in the beam direction of the beam pattern resulting in the maximum SINR by ΔT_(j,e), the time length from the sth slot to the s+Δs2th slot, gives an estimate of the change in the angle of the beam direction from beam pattern p_(j,max)(s) to beam pattern p_(j,max)(s+Δs2). In the second embodiment, the range in which the beam direction of the beam pattern with the maximum SINR is estimated to change between the sth slot and the s+Δs2th slot is set as θ_(j,R), which defines the angle range of the beam direction. That is, in the second embodiment, θ_(j,R) can be calculated using the following equation 3.

number

[0129] The multiple beam patterns included in the beam pattern set P_(j,R)(s) are set so that the beam directions are evenly spaced within the beam direction angle range θ_(j,R). Therefore, the step width Δθ_(j,R) can be calculated by dividing θ_(j,R) by the number of symbols Nsym included between the sth slot and the s+Δs2th slot, as shown in Equation 4 below.

number

[0130] The central beam pattern p_(j,R)(s) is calculated by taking into account the predicted change in the angle of the beam direction of the beam pattern that results in the maximum SINR during the time from when the beam pattern p_(j,max)(s) is notified from the relay station 3 until when the control device 1 notifies the relay station 3 of information about the beam pattern set P_(j,R)(s) and the relay station 3 uses it for beam pattern update processing. The beam pattern is notified from the relay station 3 to the control device 1 using the uplink, but the information about the beam pattern set P_(j,R)(s) is notified from the control device 1 to the relay station 3 using the downlink. Therefore, the slot in which the control device 1 notifies the relay station 3 of information about the beam pattern set P_(j,R)(s) is the first downlink slot after the sth slot in which the beam pattern is notified from the relay station 3. This downlink slot is assumed to be the s+Δs3th slot. The amount of change in the angle of the beam direction of the beam pattern predicted to change from the sth slot to the s+Δs3th slot can also be considered an offset when using beam pattern p_(j,max)(s) as the beam pattern predicted to have the maximum SINR at the s+Δs3th slot. If the amount of change in the angle of the beam direction of the beam pattern predicted to change from the sth slot to the s+Δs3th slot is Δθoffset(s+Δs3), Δθoffset(s+Δs3) is expressed by the following equation 5, using the amount of change per unit time in the beam direction of the beam pattern that will have the maximum SINR. Tslot is the time length of one slot.

number

[0131] Then, the beam pattern with the maximum SINR in the s+Δs3th slot is the beam pattern p_(j,max)(s) with the maximum SINR in the sth slot. The beam pattern is predicted by shifting the beam direction by Δθoffset(s+Δs3). Therefore, in the second embodiment, the beam pattern predicted to maximize the SINR in the s+Δs3th slot is defined as the central beam pattern p_(j,R)(s). The central beam pattern p_(j,R)(s) in the second embodiment is expressed by the following equation 6:

number

[0132] Fig. 16 is a diagram showing an example of a time chart in the update process of the beam pattern set in the second embodiment. Fig. 16 shows an example of allocation of slots to uplink and downlink. In Fig. 16, "U" indicates that the slot is an uplink slot. "D" indicates that the slot is a downlink slot.

[0133] The s-Δs1th, sth, s+Δs3th, and s+Δs2th slots in the time chart shown in Figure 16 correspond to the slots described in Figure 15. The time length of one slot is Tslot. The time length ΔT_(j,m) from the s-Δs1th slot to the sth slot is calculated by the number of slots Δs1 × Tslot. The time length ΔT_(j,e) from the sth slot to the s+Δs3th slot is calculated by the number of slots Δs2 × Tslot.

[0134] The sth slot is an uplink slot. In the sth slot, the relay station 3 acquires the beam pattern p_(j,max)(s) with the maximum SINR from among the beam patterns included in the beam pattern set P_(j,R)(s-Δs1) based on the received signal from the terminal station 4, and notifies the control device 1 (OP312 in FIG. 14). The control device 1 acquires the beam pattern set P_(j,R)(s) from the beam pattern p_(j,max)(s-Δs1) and beam pattern p_(j,max)(s) notified by the relay station 3 in the s-Δs1th uplink slot before the sth, as described in FIG. 15.

[0135] The downlink slot after the sth slot is the s+Δs3th slot. In the s+Δs3th downlink slot, the control device 1 notifies the relay station 3 of information related to the beam pattern set P_(j,R)(s). The relay station 3 receives the beam pattern set P_(j,R)(s) from the control device 1 (OP313 in FIG. 14), updates the beam pattern set (OP314 in FIG. 14), and executes the beam pattern update process.

[0136] In FIG. 14, the relay station 3 notifies the user of the beam pattern that will provide the maximum SINR at the end of each uplink slot. of However, the timing of the notification of the beam pattern from the relay station 3 is not limited to this. The timing of the notification of the beam pattern from the relay station 3 does not have to be at the end of each uplink slot. , B The method of setting the beam pattern p_(j,R)(s), the beam direction angle range θ_(j,R), and the step size Δθ_(j,R) is merely an example and is not limited to the examples shown in Figures 15 and 16. For example, the beam pattern p_(j,R)(s) may be set to the beam pattern p_(j,max)(s) notified by the relay station 3 in the sth slot, without adding Δθoffset to the beam direction angle.

[0137] FIG. 17 is an example of a flowchart of the beam pattern set update process of the control device 1 in the second embodiment. The process shown in FIG. 17 is repeatedly executed at a predetermined cycle. The main body that executes the process shown in FIG. 17 is the CPU 11 of the control device 1. However, for convenience, the control device 1 The explanation will be centered around the above.

[0138] In OP41, the control device 1 determines whether or not it has received notification from the relay station 3 of the beam pattern p_(j,max)(s) that provides the maximum SINR in the sth uplink slot in the radio frame and the SINR for that beam pattern p_(j,max)(s). If notification of the beam pattern p_(j,max)(s) and the SINR for that beam pattern p_(j,max)(s) has been received from the relay station 3 (OP41: YES), the process proceeds to OP42. If notification of the beam pattern p_(j,max)(s) and the SINR for that beam pattern p_(j,max)(s) has not been received from the relay station 3 (OP41: NO), the process shown in FIG. 17 ends.

[0139] In OP42, the control device 1 determines whether the SINR notified from the relay station 3 is equal to or greater than a threshold. If the SINR notified from the relay station 3 is equal to or greater than the threshold (OP42: YES), the process proceeds to OP43. If the SINR notified from the relay station 3 is less than the threshold (OP42: NO), the process shown in FIG. 17 ends.

[0140] In OP43, the control device 1 obtains the angular range θ_(j,R) of the beam direction according to Equation 3. In OP44, the control device 1 obtains the step width Δθ_(j,R) according to Equation 4. In OP45, the control device 1 obtains the offset Δθoffset according to Equation 5. In OP46, the control device 1 obtains the beam pattern p_(j,R)(s) according to Equation 6.

[0141] In OP47, the control device 1 notifies the relay station 3 of information about the beam pattern set P_(j,R). The information about the beam pattern set P_(j,R) includes the beam pattern p_(j,R)(s), the beam direction angle range θ_(j,R), and the step width Δθ_(j,R). Then, the processing shown in FIG. 17 ends.

[0142] In the second embodiment, the control device 1 updates the beam pattern set P_(j,R) to be assigned to the relay station 3 based on changes in the beam pattern with the maximum SINR notified from the relay station 3. As a result, the multiple beam patterns included in the beam pattern set P_(j,R) to be assigned to the relay station 3 are also updated in accordance with the movement of the terminal station 4. Since the used beam pattern p_(j,curt) is updated with a beam pattern selected from the beam pattern set P_(j,R), by using the updated used beam pattern p_(j,curt), it is possible to provide more stable communication with a larger SINR value in accordance with changes in the position of the terminal station 4 due to movement.

[0143] Furthermore, in the second embodiment, the beam pattern p_(j,R)(s) included in the beam pattern set P_(j,R) is acquired using an offset Δθoffset, taking into account the time difference due to notification from the control device 1 to the relay station 3. After receiving the beam pattern set P_(j,R), the relay station 3 performs non-regenerative relaying using the beam pattern p_(j,R)(s), which increases the likelihood that the SINR in the non-regenerative relaying will be maximized, making it possible to provide communications of higher quality.

[0144] <Other embodiments> The above-described embodiment is merely an example, and the present disclosure can be implemented with appropriate modifications within the scope that does not deviate from the gist of the disclosure.

[0145] In the first and second embodiments, the control device 1 determines the set of beam patterns to be assigned to the relay station 3. Alternatively, the base station 2 may determine the set of beam patterns to be assigned to the relay station 3. In this case, the base station 2 determines the set of beam patterns to be assigned to the relay station 3 in the same manner as in the first and second embodiments. The relay station 3 performs the processing that the control device 1 performs instead of the control device 1. Alternatively, the relay station 3 may determine the beam pattern set by itself and update the beam pattern. In this case, the relay station 3 also performs processing other than the processing related to communication with the control device 1, for example, as shown in FIG. 8 or FIG. 17. When the relay station 3 determines the beam pattern set by itself, no communication delay occurs between the relay station 3 and the control device 1, so the relay station 3 can obtain the beam pattern set more quickly.

[0146] In the first and second embodiments, the angle of the beam direction of the beam pattern of the antenna for communication between the relay station 3 and the terminal station 4 is handled only in the azimuth direction, but the angle of the beam direction may be handled in two directions, the azimuth direction and the elevation direction. In this case, in addition to the azimuth angle θ, the elevation angle φ is also used as a parameter indicating the angle of the beam direction. Note that even if the elevation angle φ is added to the angle of the beam direction, there is no change in the logic described in the first and second embodiments.

[0147] In the first and second embodiments, a relay station equipped with a plurality of antenna elements that perform electrical beamforming by using variable weights is assumed as the relay station 3. However, the present invention is not limited to this, and for example, if it is possible to physically change the direction in units of one or more symbols, it is also possible to adopt a relay station equipped with an antenna that can change its direction mechanically as the relay station 3.

[0148] Furthermore, the processes and means described in this disclosure can be freely combined and implemented as long as no technical contradictions arise.

[0149] Furthermore, a process described as being performed by one device may be shared and executed by multiple devices. Alternatively, a process described as being performed by different devices may be executed by one device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0150] The present disclosure can also be realized by providing a computer program implementing the functions described in the above embodiments to a computer, and having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer via a non-transitory computer-readable storage medium connectable to the computer's system bus or via a network. Non-transitory computer-readable storage media include any type of medium suitable for storing electronic instructions, such as any type of disk, including magnetic disks (e.g., floppy disks, hard disk drives (HDDs), etc.), optical disks (e.g., CD-ROMs, DVDs, Blu-ray disks), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic cards, flash memory, or optical cards. [Explanation of symbols]

[0151] 1. Control device 2...Base station 3. Relay Station 4. Terminal station 11. CPU 12...Main memory 13...External storage device 16. Communication equipment 21. Radio 22 Control circuit 31. Radio 32 Control section 33. Self-interference removal section 34 Baseband circuit 41 Radio 42 Control circuit 100 Communication Systems 311··Transmit / Receive Switch 312 Transmitter 313··Receiver

Claims

1. a plurality of first antennas used for communication with mobile terminal stations, the beam directions of which are controlled in accordance with predetermined beam patterns to enhance antenna gain; one or more second antennas used for communication with a base station; a radio device that performs non-regenerative relay between the base station and the terminal station, relaying a signal without demodulating or decoding it; acquiring information on a set of beam patterns acquired based on a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal from the terminal station, the received signal being measured in a first slot of a radio frame and including at least a portion of self-interference occurring between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative relay; In a second slot subsequent to the first slot, selecting a second beam pattern from a plurality of beam patterns included in the set of beam patterns based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols for each of the plurality of beam patterns; updating beam patterns used by the plurality of first antennas to the second beam pattern in a next symbol of the one or a plurality of consecutive symbols; a control unit that executes the above; A relay station comprising:

2. the information on the set of beam patterns includes information on a third beam pattern acquired based on the first beam pattern, and information on the plurality of beam patterns whose beam directions are within a first range of beam directions defined by a first angle with respect to the beam direction of the third beam pattern; The relay station according to claim 1 .

3. the plurality of beam patterns are arranged such that the beam directions of the respective beams are equally spaced at a second angle; the information about the plurality of beam patterns includes at least the first angle and the second angle; The relay station according to claim 2 .

4. the first range has a width of the first angle in positive and negative directions centered on the beam direction of the third beam pattern, the third beam pattern is set to the first beam pattern, The first angle and the second angle are each set to a predetermined value. The relay station according to claim 3 .

5. the control unit acquires, at a predetermined timing, the first beam pattern that maximizes the SINR of a received signal from the terminal station that includes at least a portion of the self-interference; the third beam pattern is set to the first beam pattern acquired in the first slot; the first angle is set to a first change amount of a beam direction angle of a beam pattern having a maximum SINR in a fourth slot to be acquired next to the first slot, from a first beam pattern in the first slot, estimated from a first change in beam direction from a first beam pattern in a third slot acquired one slot before the first slot to the first beam pattern in the first slot; the second angle is set to a second change amount of the angle of the beam direction per symbol between acquisition timings of the first beam pattern in the first slot and the beam pattern with the maximum SINR in the fourth slot, estimated from the first change; The relay station according to claim 3 .

6. the control unit receives information about the set of beam patterns from an upstream first device; the third beam pattern is set to a beam pattern obtained by changing the beam direction from the first beam pattern acquired in the first slot by a third change amount of the angle of the beam direction from the first beam pattern in the first slot to the beam pattern estimated to have the maximum SINR in the second slot, the third change amount corresponding to the time difference, estimated from the first change, from the first slot to the second slot at which information on the set of beam patterns begins to be used in the relay station; The relay station according to claim 5 .

7. The control unit receives information about the set of beam patterns from an upstream first device. A relay station according to any one of claims 1 to 5.

8. the control unit selects, as the second beam pattern, a beam pattern that provides a beam direction closest to a moving average value of beam directions of beam patterns that maximize SINR for each symbol included in a moving average window that includes the current symbol and has a window size equal to the first number of symbols in the second slot; The relay station according to claim 1 .

9. The control unit controls the number of first antennas in use in the second slot. when the beam direction of the beam pattern having the maximum SINR changes in a positive or negative direction for a second number of consecutive symbols with respect to the beam direction of the beam pattern currently in use, a beam pattern whose beam direction has changed in a positive or negative direction by a predetermined angle from the beam direction of the beam pattern currently in use is selected as the second beam pattern. The relay station according to claim 1 .

10. the control unit sets the first number of symbols to a maximum number of symbols equal to or less than a coherent time in a frequency used for a first moving speed of the terminal station. The relay station according to claim 8.

11. the control unit calculates a first moving speed of the terminal station from a cyclic prefix of a received signal in an uplink slot immediately before the second slot; The relay station of claim 10.

12. The control unit acquires a first moving speed of the terminal station from a core network. The relay station of claim 10.

13. The control unit determining, for each of a plurality of symbols included in an uplink slot immediately preceding the second slot, one or more coefficients of explanatory variables in a predetermined regression model equation having a symbol number of one symbol in one slot as an explanatory variable and a beam direction of a beam pattern that gives the maximum SINR in the one symbol as an objective function, based on a symbol number in the immediately preceding uplink slot and a beam direction of a beam pattern that gives the maximum SINR in the one symbol; determining the number of first symbols based on a deviation of a value of a response variable from a beam direction of a beam pattern that provides a maximum SINR for one symbol when a symbol number of the one symbol is input as an explanatory variable of the predetermined regression model equation to which the one or more coefficients are applied, and a target deviation; The relay station according to claim 8.

14. receiving a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal measured in a first slot of a radio frame from a relay station including a plurality of first antennas used for communication with a mobile terminal station, the first antennas having a beam direction, which is a direction in which antenna gain is increased, controlled according to a predetermined beam pattern, one or more second antennas used for communication with a base station, and a radio device that performs non-regenerative relay, which relays signals between the base station and the terminal station without demodulating or decoding them; the first beam pattern being a received signal measured in a first slot of a radio frame from the terminal station, the received signal including at least a portion of self-interference generated between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative relay; obtaining information about a set of beam patterns based on the first beam pattern; transmitting information about the set of beam patterns to the relay station; a control unit that executes An information processing device comprising: The relay station In a second slot subsequent to the first slot, for each of a plurality of beam patterns included in the set of beam patterns, a second beam pattern is selected based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols; In the next symbol of the one or a plurality of consecutive symbols, updating the beam pattern used in the scanner to the second beam pattern; Information processing device.

15. the control unit acquires information about the set of beam patterns, including information about a third beam pattern acquired based on the first beam pattern, and information about the plurality of beam patterns whose beam directions are within a first range of beam directions defined by a first angle with respect to the beam direction of the third beam pattern. The information processing device according to claim 14.

16. The control unit setting the plurality of beam patterns to a plurality of beam patterns arranged such that the beam directions of the respective beams are equally spaced at a second angle; The information about the plurality of beam patterns includes at least the first angle and the second angle. The information processing device according to claim 15.

17. The control unit setting the first range to a range having a width of the first angle in positive and negative directions centered on the beam direction of the third beam pattern; setting the third beam pattern to the first beam pattern; The information processing apparatus according to claim 16 , wherein the first angle and the second angle are each set to a predetermined value.

18. the relay station acquires, at a predetermined timing, the first beam pattern that maximizes the SINR of a received signal from the terminal station that includes at least a portion of the self-interference; The control unit setting the third beam pattern to the first beam pattern acquired in the first slot; setting the first angle to a first change amount of a beam direction angle from a first beam pattern in a third slot acquired immediately before the first slot, of a beam pattern that maximizes SINR in a fourth slot to be acquired after the first slot, estimated from a first change in beam direction from a first beam pattern in the third slot acquired immediately before the first slot to the first beam pattern in the first slot; setting the second angle to a second change amount of the angle of the beam direction per symbol between acquisition timings of the first beam pattern in the first slot and the beam pattern with the maximum SINR in the fourth slot, estimated from the first change; The information processing device according to claim 16.

19. the control unit sets the third beam pattern to a beam pattern obtained by changing the beam direction from the first beam pattern acquired in the first slot by a third change amount in the angle of the beam direction from the first beam pattern in the first slot to the beam pattern estimated to maximize SINR in the second slot, the third change amount corresponding to the time difference, estimated from the first change, from the first slot to the second slot until information on the set of beam patterns is applied at the relay station. The information processing device according to claim 18.

20. a plurality of first antennas used for communication with mobile terminal stations, the beam directions of which are controlled in accordance with predetermined beam patterns to enhance antenna gain; one or more second antennas used for communication with a base station; A non-regenerative relay is performed between the base station and the terminal station, in which a signal is relayed without being demodulated or decoded. a relay station including a radio transmitting a first beam pattern that maximizes the SINR (Signal to Interference and Noise power Ratio) of a received signal from the terminal station, the received signal being measured in a first slot of a radio frame and including at least a portion of self-interference occurring between signals transmitted and received by the plurality of first antennas and signals transmitted and received by the one or more second antennas due to the non-regenerative relaying; The information processing device receiving the first beam pattern from the relay station; obtaining information about a set of beam patterns based on the first beam pattern; transmitting information about the set of beam patterns to the relay station; The relay station: In a second slot subsequent to the first slot, selecting a second beam pattern from a plurality of beam patterns included in the set of beam patterns based on an SINR of a received signal from the terminal station including at least a portion of the self-interference measured in one or a plurality of consecutive symbols for each of the plurality of beam patterns; updating beam patterns used by the plurality of first antennas to the second beam pattern in a next symbol of the one or a plurality of consecutive symbols; A method comprising:

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