Relay control system, relay device, and relay control method

Abstract

The present invention relates to a relay control system that uses a dynamic reflection plate as a relay for wireless communication, and the purpose of the present invention is to, by appropriately controlling the beam width of a reflection wave by a relay device, improve the reception quality at a reception point while achieving a reduction of overhead required for beam search. A reflection unit 40 of a relay device 30 includes a plurality of reflecting elements each of which is capable of imparting mutually independent phase shifts to incoming waves from a transmission point 10. The distance between the relay device 30 and a reception point 20 is estimated on the basis of terminal information issued from the reception point 20. A division number for grouping the plurality of reflecting elements is determined on the basis of the distance. The plurality of reflecting elements are grouped into one or more reflecting element groups in accordance with the division number. The position of the reception point 20 is estimated on the basis of the terminal information. A phase weight is given to each of the reflecting elements so that each of the reflecting element groups produces a beam directed to the position of the reception point 20.

Description

[Technical field]

[0001] The present disclosure relates to a relay control system, a relay device, and a relay control method, and more particularly to a relay control system, a relay device, and a relay control method that use a dynamic reflector as a wireless communication relay. [Background technology]

[0002] The following Non-Patent Document 1 discloses a beam tracking method in millimeter wave communication. More specifically, Non-Patent Document 1 discloses a method for appropriately controlling the beam width in beam tracking in order to prevent the performance of wireless communication from deteriorating due to a combination of high mobility and narrow beam width.

[0003] Furthermore, Non-Patent Documents 2 and 3 below disclose a technique for improving the coverage of a transmission point by using a dynamic reflector (RIS: Reconfigurable Intelligent Surface) as a relay device for wireless communication. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Adaptive Beamwidth Control for mmWave Beam Tracking, Hyeonjin Chung, Jeongwan Kang, Hyowon Kim, Young Mi Park, and Sunwoo Kim, p137-141, IEEE COMMUNICATIONS LETTERS, VOL. 25, NO. 1, January 2021 [Non-Patent Document 2] Wireless Communications Through Reconfigurable Intelligent Surfaces, ERTUGRUL BASAR, MARCO DI RENZO, JULIEN DE ROSNY, MEROUANE DEBBAH, MOHAMED-SLIM ALOUINI, RUI ZHANG, p116753-116773, VOLUME 7, 2019, IEEE Access, August 13, 2019 [Non-Patent Document 3] Intelligent Reflecting Surface Enhanced Wireless Network via Joint Active and Passive Beamforming, Qingqing Wu, Rui Zhang, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, p5394-5409, VOL. 18, NO. 11, November 2019 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned RIS is equipped with many reflecting elements arranged two-dimensionally to obtain gain by reflection. The RIS can dynamically control the direction of the reflected wave by controlling the phase that each reflecting element adds to the incoming wave. In this case, channel information between the transmitting point and the receiving point that exchange radio signals via the RIS is used to determine the phase that each reflecting element adds.

[0006] The aforementioned channel information needs to be acquired for each reflecting element. Therefore, in a relay control system using a RIS, the overhead required to acquire channel information tends to be large, which is an issue. To address this issue, a method of sweeping the reflection direction without acquiring channel information can be considered. However, because the width of the beam formed by reflection at the RIS is very narrow, the overhead required for sweeping also becomes large.

[0007] In order to reduce the overhead, it is possible to determine the reflection method using the position information of the transmitting and receiving points. However, since the position information contains estimation errors and the beam width of the RIS is very narrow, this method has the problem that it is difficult to keep the wireless terminals that constitute the receiving points within the coverage of the beam.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and has a first objective to provide a relay control system that can improve reception quality at the receiving point while reducing overhead associated with beam search by appropriately controlling the beam width of a reflected wave by a relay device.

[0009] A second object of the present disclosure is to provide a relay device that can improve the reception quality at a reception point while reducing the overhead required for beam search by appropriately controlling the beam width of a reflected wave heading toward the reception point.

[0010] In addition, a third object of the present disclosure is to provide a relay control method that can improve the reception quality at the receiving point while reducing the overhead required for beam search by appropriately controlling the beam width of the reflected wave by the relay device. [Means for solving the problem]

[0011] In order to achieve the above object, a first aspect is a relay control system using a relay device having a plurality of reflecting elements capable of imparting independent phase shifts to waves arriving from a transmitting point, the relay control system comprising: A process of estimating a distance between the relay device and the reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflecting elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; A process of estimating a position of the reception point based on the terminal information; a phase control process for giving a phase weight to each of the reflecting elements so that each of the reflecting elements generates a beam directed toward the position of the receiving point; Preferably, the system is configured to execute:

[0012] A second aspect is a relay device, The antenna includes a plurality of reflecting elements each capable of imparting an independent phase shift to an incoming wave from a transmitting point, A process of estimating a distance to a reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflecting elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; A process of estimating a position of the reception point based on the terminal information; It is preferable that each of the group of reflecting elements is configured to perform a process of applying a phase weight to each of the reflecting elements so as to generate a beam directed toward the position of the receiving point.

[0013] A third aspect is a relay control method using a relay device having a plurality of reflecting elements capable of imparting independent phase shifts to waves arriving from a transmitting point, the method comprising the steps of: estimating a distance between the relay device and the reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflective elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; estimating a position of the reception point based on the terminal information; providing a phase weight to each of the reflecting elements such that each of the reflecting elements generates a beam directed toward the position of the receiving point; It is preferable that the present invention includes the following: Effect of the Invention

[0014] According to the first to third aspects, the beam of the reflected wave from the relay device can be given an appropriate width and intensity to cover the receiving point. Therefore, according to these aspects, the overhead required for beam search can be reduced and the receiving quality at the receiving point can be improved. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram for explaining a configuration of a relay control system according to a first embodiment of the present disclosure. [Diagram 2] 2 is a block diagram for explaining the configuration of a relay device shown in FIG. 1. [Diagram 3] 3 is a diagram for explaining the configuration of a reflector included in the relay device shown in FIGS. 1 and 2. FIG. [Figure 4] 1 is a diagram for explaining the influence of the distance between a relay device (RIS) and a receiving point (UE) on the received power and the tolerance to position error. [Figure 5A] 1 is a diagram showing how a reflecting section of a relay device generates a single beam with a beam width θ by reflection over a total area S. [Figure 5B] FIG. 13 is a diagram showing how the reflecting section of the repeater generates two beams with a beam width of 2θ by reflecting light from half its area S / 2. [Figure 5C] FIG. 13 is a diagram showing how the reflecting section of the repeater generates four beams with a beam width of 4θ by reflecting light from each of its quarter areas, S / 4. [Figure 6] 4 is a flowchart illustrating an operation of the relay control system according to the first embodiment of the present disclosure. [Figure 7] 11 is a flowchart for explaining an operation of an active determination process executed by a relay device according to the first embodiment of the present disclosure. [Figure 8] 13 shows a table that defines the relationship between the distance between a repeater and a receiving point and the number of reflecting element groups to be formed in a reflecting portion. [Figure 9]11 is a flowchart illustrating a process flow executed by the relay device according to the first embodiment of the present disclosure to control a beam width. [Figure 10] An example of a specific allocation of reflective elements corresponding to the grouping method shown in FIG. 5B is shown. [Figure 11] Another example of dividing the reflective elements into two groups is shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Embodiment 1 [Configuration of the first embodiment] Fig. 1 shows a configuration of a relay control system according to a first embodiment of the present disclosure. The system shown in Fig. 1 includes a transmission point 10, a reception point 20, and a relay device 30. The transmission point 10 is configured with a wireless base station or the like under the management of a telecommunications carrier. Meanwhile, the reception point 20 is configured with a user equipment (UE) such as a smartphone. If the reception point 20 belongs to the communication area of ​​the transmission point 10 and there is no obstacle or the like between them, the reception point 20 can directly communicate with the transmission point 10.

[0017] The relay device 30 is configured by a dynamic reflector, that is, a RIS (Reconfigurable Intelligent Surface). The relay device 30 is disposed to relay a wireless signal between the transmission point 10 and the reception point 20. Even if the reception point 20 cannot directly communicate with the transmission point 10, it may be possible for the reception point 20 to communicate with the transmission point 10 via the relay device 30.

[0018] Fig. 2 is a block diagram for explaining the configuration of the relay device 30 in this embodiment. As shown in Fig. 2, the relay device 30 includes a communication unit 32. The communication unit 32 is a block for transmitting and receiving control information between the transmission point 10 and the reception point 20 for use in controlling the relay device 30. The control information acquired by the communication unit 32 is provided to a storage unit 34 and a beam control unit 36.

[0019] The control information includes, for example, position information of the user terminal constituting the reception point 20, information on the reception power at the reception point 20, and the like. The beam control unit 36 ​​judges, based on the information, what kind of beam is appropriate for the relay device 30 to form. More specifically, it judges whether a beam with a wide coverage even if the power reaching the reception point 20 is weak is appropriate, or whether a beam with a narrow beam width but strong power reaching the reception point is appropriate. Then, it specifies the characteristics of the beam to be formed, and provides the result to the phase control unit 38.

[0020] The phase control unit 38 calculates phase weights necessary for generating a beam having an appropriate width and directed in an appropriate direction, based on the control information read from the storage unit 34 and the information provided by the beam control unit 36. The information on the phase weights calculated by the phase control unit 38 is provided to the reflecting unit 40.

[0021] FIG. 3 is a diagram for explaining the configuration of the reflecting unit 40. As shown in FIG. 3, the reflecting unit 40 includes a plurality of reflecting elements 42. The reflecting elements 42 are regularly arranged at equal intervals in a two-dimensional manner. Each of the reflecting elements 42 has a mechanism for reflecting or transmitting the radio wave emitted from the transmission point 10. An individual ID is assigned to each of the reflecting elements 42, and they can be controlled independently of each other. More specifically, each of the reflecting elements 42 can add a desired phase weight to an incoming wave to generate a reflected wave with a desired phase shift.

[0022] The phase shift can be generated, for example, by connecting a variable phase shifter that gives an arbitrary phase shift to each reflecting element 42. Alternatively, the phase shift may be generated using a device that can control the phase in two values ​​by turning a switch on and off. Also, the phase of the incoming wave reflected by the reflecting element 42 may be shifted by other methods.

[0023] The description will be continued with reference to Fig. 2 again. A control signal for each of the reflecting elements 42 is provided to the reflecting unit 40 from the phase control unit 38. This control signal includes a phase weight command for each of the reflecting elements 42. The phase weight can be calculated, for example, by a method of performing channel estimation, a method using position information (see, for example, Japanese Patent No. 5200090), or other known methods.

[0024] [Features of the first embodiment] The process executed by the relay device 40 will be described in more detail below with reference to FIGS.

[0025] Fig. 4 shows the effect of the distance between the relay device 30 and the reception point 20 (hereinafter referred to as the "RIS-UE distance") on the "received power" and "position error tolerance" at the reception point 20. The strength of the beam heading toward the reception point 20 attenuates during the propagation process. For this reason, as shown by the solid line in Fig. 4, the "received power" at the reception point 20 decreases as the RIS-UE distance increases.

[0026] "Position error tolerance" refers to the tolerance of coverage to errors contained in the "position information" of the reception point 20. Generally, "position information" contains errors. For this reason, the reflected wave beam generated by the relay device 40 does not necessarily head accurately toward the reception point 20. On the other hand, the reflected wave beam tends to become wider as the propagation distance increases. And the wider the beam width, the easier it is for the beam to cover the reception point 20. For this reason, the "position error tolerance" becomes better as the RIS-UE distance becomes longer, as shown by the dashed line in FIG. 4.

[0027] 4, strong reception power is obtained but the tolerance to position errors is low. Therefore, in order to establish first contact with a reception point 20 located in such an area, the transmission power does not need to be very strong, but it is desirable to ensure a large beam width.

[0028] In the medium distance area indicated by reference numeral 46 in Fig. 4, both the reception power and the position error tolerance are moderate. Therefore, in order to establish first contact with the reception point 20 located in such an area 46, it is desirable to generate a beam with a good balance between the transmission power and the beam width.

[0029] 4, high position error tolerance is obtained, but the received power is weak. Therefore, in order to establish first contact with the receiving point 20 located in such an area 48, it is desirable to narrow the beam width and generate a beam with high power.

[0030] 5A shows a state in which the reflecting section 40 of the repeater 30 uses all of the reflecting elements 42, i.e., the entire area S, to generate a beam 50 of width θ. The power of the beam increases as the number of reflecting elements 42 used to generate the beam increases. Therefore, in the state shown in FIG. 5A, a beam 50 with a narrow width θ and high power can be generated.

[0031] Figure 5B shows the state where the reflector 40 divides the area S in two to generate two beams 52 with width θ. In this case, depending on the number of reflecting elements 42 used for generation, the power of each of the beams 52 is approximately half that of the beam 50 shown in Figure 5A. However, since two beams are generated, the width they cover can be approximately twice as wide as in the case shown in Figure 5A.

[0032] Figure 5C shows the reflector 40 dividing the area S into four to generate four beams 54 of width θ. In this case, depending on the number of reflector elements 42 used, each of the beams 54 will have approximately one-quarter the power of the beam 50 shown in Figure 5A. However, since four beams are generated, the width they cover can be approximately four times that of the case shown in Figure 5A.

[0033] In this way, according to the relay device 30, it is possible to create either a narrow beam 50 with high power or a wide beam 54 with low power, depending on how the multiple reflecting elements 42 of the reflecting section 40 are grouped. Then, for example, by using the narrow and high-power beam 50 for a distant receiving point 20 and the wide and low-power beam 54 for a nearby receiving point 20, it becomes possible to relatively easily establish first contact with the receiving point 20 regardless of the presence of a position error.

[0034] Therefore, in this embodiment, when it becomes necessary to newly establish communication with the reception point 20, the first step is to first have the relay device 30 execute the following process to establish first contact. (1) Determine the distance to the receiving point 20. (2) Determine the grouping of reflective elements 42 to generate a beam suitable for covering receiving point 20 located at the above distance. (3) In accordance with the above grouping, a phase weight for generating a beam toward the receiving point 20 is assigned to each of the reflecting elements 42.

[0035] In addition, after the relay device 30 of this embodiment has established first contact with the receiving point 20, as a second step, the relay device 30 changes the beam characteristics in order to improve communication quality. Specifically, the beam width is gradually narrowed while correcting the position information within a range in which the receiving point 20 does not fall out of the beam coverage. In other words, the number of groups of the reflecting elements 42 that form the beam is reduced. As a result, the beam generated by the relay device 30 gradually changes to one that has high intensity and is narrow but accurately covers the receiving point 20. As a result, the communication quality between the relay device 30 and the receiving point 20 is improved.

[0036] The above-mentioned first and second steps can be performed without requiring a huge amount of overhead. Therefore, according to the system of the present embodiment, it is possible to provide the reception point 20 with good reception quality while reducing the overhead required for beam search.

[0037] Fig. 6 is a flow chart for explaining the operation of the relay control system of this embodiment. In the example shown in Fig. 6, first, a reference signal is transmitted from a transmission point 10 (step 100). The reference signal is a signal for measuring communication quality and channel conditions, and is received by a reception point 20.

[0038] At the reception point 20, communication quality is measured based on the received reference signal (step 102). More specifically, here, for example, received power, signal-to-interference power, signal-to-interference-plus-noise power, and signal-to-noise power are measured as communication quality. Channel state information may be estimated together with the communication quality.

[0039] Next, at the reception point 20, a process for estimating its own position is performed (step 104). The position estimation can be performed, for example, by using a cellular system or a wireless LAN access point. More specifically, it can be realized by three-point positioning using the reception power, the arrival time, and the arrival time difference, or by beacon positioning using BLE (Bluetooth Low Energy). Alternatively, PDR (Pedestrian Dead Reckoning) may be used, which estimates relative position information using sensors (acceleration sensor, gyro sensor, magnetic sensor) mounted on the user terminal UE (reception point 20). Furthermore, the self-position may be estimated by GPS positioning, sonic wave / geomagnetic / UWB positioning, or a combination of these. Furthermore, height information may be included in the self-position.

[0040] After the above process is completed, the reception point 20 performs broadcast processing (step 106). Specifically, in addition to the communication quality and position estimation information acquired by the reception point 20 through the processes of steps 102 and 104, the identification number of the reception point 20 is transmitted by a broadcast method. Hereinafter, the information transmitted in this manner is referred to as "terminal information." The broadcast method may be a multicast method or a group cast method.

[0041] The relay device 30 stores the terminal information transmitted from the reception point 20 in the storage unit 34 (step 108). Here, the reception time of the terminal information and other information may be recorded in the storage unit 34 together with the terminal information.

[0042] In parallel with the above process, the relay device 30 estimates the distance between the relay device 30 and the reception point 20, that is, the RIS-UE distance, based on the terminal information (step 110). Specifically, when the relay device 30 receives the terminal information from the reception point 20, it determines whether or not activation is required for the reception point 20. If it is determined that activation is required, the relay device 30 calculates the RIS-UE distance using the location information of the reception point 20 included in the terminal information and its own location information that has been acquired and registered in advance.

[0043] 7 is a flowchart for explaining the flow of processing executed by relay device 30 to determine whether activation is required. Hereinafter, the explanation of the flowchart shown in FIG. 6 will be temporarily interrupted to explain the flow of processing for determining activation.

[0044] 7 is repeatedly started at regular time intervals in the relay device 30. When this routine is started, it is first determined whether or not the current state is idle (step 120).

[0045] When it is determined by the above process that the current state is idle, it is then determined whether or not terminal information has been received from any of the reception points 20 (step 122).

[0046] As a result, if reception of the terminal information is confirmed, it is determined whether or not the communication quality at the reception point 20 that transmitted the terminal information is equal to or lower than a threshold based on the "communication quality" included in the terminal information (step 124). This threshold is a value determined for determining whether or not the current communication quality is a desired quality.

[0047] Therefore, if it is determined in step 124 that the communication quality is equal to or lower than the threshold, it can be determined that the desired communication cannot be established with the signal that the reception point 20 receives directly from the transmission point 10. In this case, the relay device 30 is activated for the reception point 20 (step 126).

[0048] After the process of step 126 is completed, it is then determined whether or not a certain period of time has elapsed since the relay device 30 was activated (step 128).

[0049] If it is determined that the certain period of time has not yet elapsed, the active state continues (step 130). Thereafter, steps 126 to 128 are repeated until it is determined that the certain period of time has elapsed.

[0050] Then, when it is determined that the time since becoming active has reached a certain period of time, the state of the relay device 30 is returned to the idle state (step 132).

[0051] According to the above process, after receiving terminal information from a reception point 20 with poor reception quality, the relay device 30 maintains an active state for a certain period of time and then returns to an idle state. If the reception point 20 still needs the relay device 30 after returning to the idle state, the processes of steps 122 to 126 are repeated and the relay device 30 is activated again. Also, if another reception point 20 other than the reception point 20 needs the relay device 30, the relay device 30 becomes active for that reception point 20. Therefore, if the state of the relay device 30 is controlled by the process shown in FIG. 7, a single relay device 30 can efficiently support a plurality of reception points 20.

[0052] Referring again to Fig. 6, the operation of the relay control system of this embodiment will be described. As shown in Fig. 6, after completing the process of step 110, the relay device 30 next determines the division number of the reflecting element 42 (step 140). Specifically, here, based on the RIS-UE distance estimated in step 110, the number of groups to be applied to the reflecting element 42 in order to establish first contact with the receiving point 20 to be activated is determined.

[0053] Fig. 8 shows an example of a table that relay device 30 refers to in the process of step 140. However, the table that is referred to here is not limited to the table shown in Fig. 8, and any table that associates the RIS-UE distance with the number of groups of reflecting elements 42 can be used.

[0054] The table shown in Fig. 8 indicates that when the RIS-UE distance is less than AAm, the reflective elements 42 are divided into eight groups. It also indicates that as the RIS-UE distance increases, the number of groups decreases from 8 to 4 to 2 to 1. In step 140 above, in accordance with the table shown in Fig. 8, the shorter the RIS-UE distance, the larger the number of groups of the reflective elements 42 is set to, and when the RIS-UE distance is CCm or more, the number of groups is set to the minimum value "1".

[0055] In the flowchart shown in FIG. 6, following the process of step 140, the relay device 30 estimates the direction of the reception point 20 to be activated (step 142). Specifically, the direction of the reception point 20 as seen from the relay device 30 is estimated based on the position information of the reception point 20 stored in the process of step 108 and its own position information acquired in advance. For the relay device 30, the direction of the reception point 20 is the direction in which the incoming wave from the transmission point 10 should be reflected. How the incoming wave is reflected is a function of the installation angle of the relay device 30, more strictly, the installation angle of the reflecting unit 40. For this reason, in this step 142, the installation angle of the reflecting unit 40 acquired in advance may be reflected in the direction of the reception point 20.

[0056] Next, the relay device 30 determines a beam reflection method for each divided group (step 146). Specifically, an offset angle that differs for each group of the reflecting elements 42 is added to the direction of the receiving point 20 estimated in step 142. The offset angle is preset for the relay device 30, and is adjusted so that the beams for each group are adjacent to each other to form a single coherent beam, as shown in FIG. 5B or 5C.

[0057] After the above processing is completed, when a reference signal is transmitted from the transmission point 10 (step 148), this signal passes through the relay device 30 and reaches the reception point 20 in the form of a beam characterized by the processing of steps 140 to 146 above. This beam is given a width and intensity suitable for covering the position of the reception point 20. Therefore, according to the above processing, first contact with the reception point 20 can be easily established without requiring a large amount of overhead.

[0058] Thereafter, the above-mentioned processes of steps 102, 104 and 106 are executed again at the reception point 20. As a result, the communication quality is measured and the position of the reception point 20 is estimated based on the information received in the form of a beam via the relay device 30. Then, the terminal information including the communication quality and the position information is transmitted by a broadcast method.

[0059] When the relay device 30 receives the terminal information, it again executes the processes of steps 108 and 142. That is, it stores the received terminal information in the storage unit 34, and estimates the direction of the reception point 20 based on the position information with improved accuracy.

[0060] Next, the relay device 30 starts the second step of processing to improve the communication quality. Specifically, first, the number of groups of the reflection elements 42 is updated (step 150). The processing of step 150 is executed based on a comparison between the communication quality received last time and the communication quality received this time.

[0061] For example, if the communication quality received this time is better than the communication quality received last time, it can be estimated that the current beam covers the reception point 20. If the current beam covers the reception point 20, the communication quality may be further improved by correcting the direction, narrowing the beam width and increasing the beam intensity. Therefore, if the communication quality has improved from the previous time to the current time, in the above step 150, the number of groups of reflective elements 42 is reduced to further narrow the beam width.

[0062] On the other hand, if the communication quality received this time is equal to or lower than the communication quality received last time, it can be estimated that the current beam may not adequately cover the reception point 20. In this case, it is appropriate to widen the beam width to improve the coverage. Therefore, if the communication quality has not improved from the previous time to the current time, in the above step 150, the number of groups of the reflecting elements 42 is increased to widen the beam width by one step.

[0063] Thereafter, the relay device 30 updates the reflection direction of the beam based on the number of groups determined in step 150 and the direction estimated in the most recent step 142 (step 152). Specifically, the direction of the reception point 20 is re-estimated using the latest position information on the reception point 20. Then, the updated number of reflecting element groups is applied to the newly estimated terminal direction, and the same process as in step 146 is performed. Note that when re-estimating the direction of the reception point 20, past position information of the same reception point 20 obtained up to now may be used.

[0064] 9 is a flowchart for explaining the flow of processing executed by the relay device 30 so that the relay control system of the present embodiment realizes the above-mentioned functions. Note that the routine shown in FIG. 9 shows the flow of processing after the relay device 30 is activated for a specific reception point 20.

[0065] In the routine shown in FIG. 9, first, location information and communication quality are acquired from the terminal information received from the reception point 20 (step 160).

[0066] The direction of the receiving point 20 is then estimated (162) based on the position information.

[0067] In addition to estimating the direction, the relay device 30 estimates the distance to the reception point 20 based on the position information (step 164).

[0068] Next, by referring to the table shown in the above figure or by other methods, the number of groups of reflecting elements 42 for forming a beam appropriate for covering the position of receiving point 20 is selected (step 166).

[0069] Next, a phase weight to be given to each of the reflecting elements 42 is set (step 168). More specifically, the reflecting elements 42 are divided into one or more groups based on the number of groups selected in step 166. Then, a phase weight for each of the reflecting elements 42 is calculated so that the reflecting elements 42 belonging to each group form the beam that each group should form.

[0070] After completing the above process, when the relay device 30 receives a reference signal from the transmitting point 10, it adds the above phase weight to the signal to form a beam toward the receiving point 20. When the receiving point 20 receives the beam, it again transmits the terminal information.

[0071] As shown in FIG. 9, when relay device 30 receives the terminal information transmitted in this manner, it again acquires location information and communication quality therefrom (step 170).

[0072] The relay device 30 determines whether the communication quality thus acquired is improved from the communication quality previously acquired (step 172).

[0073] As a result, if an improvement in quality is observed, it can be determined that the current beam adequately covers the reception point 20. If such a determination is made, the relay device 30 updates the direction of the reception point 20 based on the newly acquired position information (step 174).

[0074] Furthermore, in order to increase the intensity of the beam and further improve the communication quality, the repeater 30 reduces the number of groups of the reflecting elements 42 so as to reduce the reflection width (step 176). After that, the repeater 30 returns to step 170 and repeats the above process.

[0075] If it is determined in step 172 that no improvement in communication quality has been observed, it can be estimated that the current beam may not adequately cover the receiving point 20. In this case, the relay device 30 determines whether the current reflection width is maximum or not (step 178).

[0076] If it is determined that the current reflection width is not the maximum, it can be determined that there is still room to improve coverage by widening the reflection width. In this case, the relay device 30 first updates the direction of the receiving point 20 based on the latest position information acquired by the process of step 170 (step 180).

[0077] Next, the repeater 30 attempts to expand the reflection width in order to improve coverage. Specifically, the number of groups of the reflecting elements 42 is increased so as to expand the reflection width (step 182). After that, the repeater 30 returns to step 170 and repeats the above process.

[0078] If it is determined in step 178 that the reflection width is already at its maximum, it can be determined that there is no room left to improve coverage by widening the reflection width. In this case, the relay device 30 returns to step 160 and executes the above process again to re-establish contact with the receiving point 20 from the beginning.

[0079] As described above, according to the relay control system of the present embodiment, the characteristics of the beam generated by the relay device 30 can be made to correspond to the RIS-UE distance. As a result, it is possible to quickly establish first contact for beam search while solving the overhead problem.

[0080] In addition, according to the relay control system of this embodiment, it is possible to adjust the beam characteristics so as to improve the communication quality after the relay device 30 establishes first contact with the receiving point 20. Therefore, according to this embodiment, it is possible to efficiently improve the communication quality after the communication via the relay device 30 is established.

[0081] Incidentally, in the above-mentioned embodiment 1, as shown in Fig. 5B or 5C, the reflecting elements 42 are grouped so that the reflecting elements 42 belonging to the same group form one block. However, the method of grouping the reflecting elements 42 is not limited to this. As long as there is no significant bias in the number of reflecting elements 42 belonging to each group, the allocation of which reflecting elements 42 to which which group is to be assigned can be freely set, including random combinations.

[0082] For reference, a specific example of allocation of reflective elements 42 corresponding to the grouping method shown in Fig. 5B is shown in Fig. 10. Here, the reflecting section 40 is divided into a group of reflective elements 42-1 belonging to the left half block and a group of reflective elements 42-2 belonging to the right half block.

[0083] Another example of dividing the reflective elements 42 into two groups is shown in Fig. 11. Here, the reflective elements 42-1 belonging to the first group and the reflective elements 42-2 belonging to the second group are arranged alternately. According to the method shown in Fig. 11, the number of the reflective elements 42-1 belonging to the first group is the same as the number of the reflective elements 42-2 belonging to the second group. As a result, it is possible to form a beam substantially similar to that in the case of using the method shown in Fig. 10. [Explanation of symbols]

[0084] 10 Transmission Point 20 Receiving point 30 Relay Device 32 Communications Department 34 Storage section 36 Beam control section 38 Phase control section 40 Reflector 42 Reflective elements 50, 52, 54 Beam

Claims

1. A relay control system using a relay device having a plurality of reflecting elements capable of imparting independent phase shifts to waves arriving from a transmitting point, comprising: A process of estimating a distance between the relay device and the reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflecting elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; A process of estimating a position of the reception point based on the terminal information; a phase control process for giving a phase weight to each of the reflecting elements so that each of the reflecting elements generates a beam directed toward the position of the receiving point; A relay control system configured to:

2. The phase control process includes: A process of setting an angle toward the position of the receiving point; setting an offset angle for each of the reflective element groups; determining a direction of travel of a beam generated by each of the reflective elements by adding the offset angle to the angle; The relay control system according to claim 1 ,

3. 3. The relay control system according to claim 2, wherein the offset angle is set so that the beams generated by the respective reflecting elements are adjacent to each other to form a single coherent beam.

4. The terminal information includes communication quality at the reception point, A process of reducing the number of divisions when an improvement in the communication quality is recognized; increasing the number of divisions when no improvement in the communication quality is observed; 4. The relay control system according to claim 1, further configured to:

5. 5. The relay control system according to claim 1, wherein the relay device is configured to activate the relay device for the reception point when the communication quality of the signal received by the reception point directly from the transmission point is below a threshold.

6. The relay control system according to claim 5 , wherein the relay device is configured to cancel activation for the reception point when a certain time has elapsed after activation for the reception point.

7. The antenna includes a plurality of reflecting elements each capable of imparting an independent phase shift to an incoming wave from a transmitting point, A process of estimating a distance to a reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflecting elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; A process of estimating a position of the reception point based on the terminal information; a process of providing a phase weight to each of the reflecting elements so that each of the reflecting elements generates a beam directed toward the position of the receiving point; 23. A relay device configured to execute the steps of:

8. A relay control method using a relay device having a plurality of reflecting elements capable of imparting independent phase shifts to waves arriving from a transmitting point, comprising the steps of: estimating a distance between the relay device and the reception point based on terminal information transmitted from the reception point; determining a number of divisions for dividing the plurality of reflective elements into groups based on the distance; grouping the plurality of reflective elements into one or more reflective element groups according to the division number; estimating a position of the reception point based on the terminal information; providing a phase weight to each of the reflecting elements such that each of the reflecting elements generates a beam directed toward the position of the receiving point; A relay control method comprising:

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