Wireless communication system, control device, wireless communication method, and wireless communication program

Abstract

To improve the communication quality of a radio communication system by determining a relay path in multi-hop relay and determining a beam direction in a radio relay station.SOLUTION: A radio communication system includes: a plurality of radio relay stations each of which performs a beam direction control by an antenna including a variable phase shifter; a first base station; a second base station; and a control device. The control device determines a relay station that performs relay from the first base station to a terminal from among the plurality of radio relay stations, based on position information of the terminal; and determines a relay path. The second base station notifies information of the relay path to a relay station used for the relay path. The relay station used for the relay path forms a beam in a determined direction based on the relay path; and relays radio waves. At least one of the control device and the relay station used for the relay path determines a beam direction. The first base station performs radio communication with the terminal via the relay path.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system that relays radio waves, a control device, a wireless communication method, and a wireless communication program. [Background Art]

[0002] In a wireless relay station that relays radio waves, a technique for improving gain by using analog beamforming is known. This makes it possible to improve communication quality even in non-line-of-sight communication where millimeter wave quality degrades, or in long-distance communication.

[0003] Furthermore, in recent years, adaptively performing beamforming even for wireless relay stations constituting backhaul makes it possible to adaptively change the relay path from a transmitting station to a receiving station, and further improvement in communication quality is expected (see, for example, Non-Patent Document 1). [Prior Art Documents] [Non-Patent Documents]

[0004] [Non-Patent Document 1] Yoneda, Sakaguchi, Iwabuchi, Murakami, "Study on Millimeter Wave Multi-hop Analog Relay Single-User MIMO", SRW2020-83, March 2021 [Non-Patent Document 2] H.Abbas and K. Hamdi, "Millimeter wave communications over relay networks", IEEE WCNC, April 2018 [Non-Patent Document 3] Iwabuchi, Murakami, Ogawa, Takatori, Yoneda, Sakaguchi, "A Study on Relay Beam Control Method Using Terminal Position Information in Multiple Analog Relay Systems", 2021 IEICE Society Conference, B-5-50, September 2021 [Summary of Invention] [Problem to be Solved by the Invention]

[0005] However, when using repeaters or other devices that do not have signal processing functions such as demodulation of radio waves as wireless relay stations, the challenge was how to determine the relay path and beam direction for moving terminals (see, for example, Non-Patent Document 2). Although beam control methods have been proposed for single-hop relays (see, for example, Non-Patent Document 3), beam control methods for multi-hop relays remain a challenge.

[0006] The primary objective of this disclosure is to provide a wireless communication system that can improve communication quality by determining the relay path and the beam direction at wireless relay stations, even in multi-hop relays, in order to solve the aforementioned problems.

[0007] Furthermore, a second objective of this disclosure is to provide a control device that can determine the relay path and improve communication quality even in multi-hop relay.

[0008] Furthermore, a third objective of this disclosure is to provide a wireless communication method that can improve communication quality by determining the relay path and the beam direction at the wireless relay station, even in multi-hop relay.

[0009] Furthermore, a fourth objective of this disclosure is to provide a wireless communication program that can determine the relay path and improve communication quality even in multi-hop relay. [Means for solving the problem]

[0010] A first aspect of this disclosure is a wireless communication system for relaying radio waves, Multiple radio relay stations that transmit and receive radio waves use antennas equipped with variable phase shifters to control the direction of the beam, The first base station and A second base station that receives location information from the terminal, Control device and Equipped with, The control device is The process of receiving the location information from the second base station, Based on the location information, a relay path determination process is performed to determine which wireless relay station will wirelessly relay from the first base station to the terminal from among the plurality of wireless relay stations, and to determine the relay path. The process of notifying the second base station of the relay path information, It is configured to perform, The aforementioned second base station is The system is configured to perform a notification process to notify each of the wireless relay stations used in the relay path of information about the relay path. The wireless relay stations used in the aforementioned relay path are: The process of receiving information about the relay route, Based on the aforementioned relay path, a relay process is performed to form a beam in a direction determined based on the position of the relaying partner and the position of the own station, and relay radio waves. It is configured to perform, At least one of the control device and the wireless relay station used in the relay path performs a direction determination process to determine the direction of the beam. The aforementioned first base station is It is preferable to perform wireless communication with the terminal via the relay path.

[0011] Furthermore, a second aspect of this disclosure is a control device for controlling a plurality of radio relay stations that control the direction of a beam using an antenna equipped with a variable phase meter, The process of receiving location information from the device, Based on the location information, a relay path determination process is performed to determine which wireless relay station will wirelessly relay the signal from the terminal to the base station that will wirelessly relay the signal from the terminal to the terminal, and to determine the relay path, from among the plurality of wireless relay stations. The process of notifying each of the wireless relay stations used in the relay path of the relay path information, It is preferable to configure it to perform the following:

[0012] A third aspect of the present disclosure is a wireless communication method using a plurality of wireless relay stations that perform beam direction control with an antenna including a variable phase shifter, the method comprising: receiving location information of a terminal; based on the location information, determining, from among the plurality of wireless relay stations, a wireless relay station that wirelessly relays communication from a first base station to the terminal, and performing relay route determination processing for determining a relay route; notifying each of the wireless relay stations used for the relay route of information on the relay route; based on the relay route, performing direction determination processing for determining a beam direction of the wireless relay station used for the relay route from the position of one wireless station connecting the relay and the position of the other wireless station connecting the relay; the wireless relay station used for the relay route receiving the information on the relay route; the wireless relay station used for the relay route forming a beam based on a result of the direction determination processing by the antenna, and performing relay processing for relaying wireless radio waves; and preferably, the method further comprises the first base station performing wireless communication with the terminal via the relay route.

[0013] A fourth aspect of the present disclosure is a program for wireless communication that is caused to be executed by a control device that controls a plurality of wireless relay stations that perform beam direction control with an antenna including a variable phase shifter, the program comprising: processing for receiving location information of a terminal; based on the location information, relay route determination processing for determining, from among a plurality of wireless relay stations, a wireless relay station that wirelessly relays communication from a base station to the terminal, and determining a relay route; processing for notifying each of the wireless relay stations used for the relay route of information on the relay route; and preferably, the program comprises a program that causes the above processes to be executed. Effects of the Invention

[0014] According to the first to fourth aspects of this disclosure, it is possible to provide a wireless communication system, control device, wireless communication method, and wireless communication program that can improve communication quality by determining the relay path and the direction of the beam at the wireless relay station, even in multi-hop relay. [Brief explanation of the drawing]

[0015] [Figure 1] This is an example of the configuration of a wireless communication system relating to the comparative example of this disclosure. [Figure 2] This is an example of the configuration of a wireless communication system according to Embodiment 1 of the present disclosure. [Figure 3] This is a functional block diagram of the control device according to Embodiment 1 of the present disclosure. [Figure 4] This is a functional block diagram of a relay station according to Embodiment 1 of the present disclosure. [Figure 5] This figure illustrates the candidate determination process performed by the control device according to Embodiment 1 of the present disclosure. [Figure 6] This diagram illustrates the grouping process performed by the control device according to Embodiment 1 of the present disclosure. [Figure 7] This figure illustrates the route candidate calculation process performed by the control device according to Embodiment 1 of the present disclosure. [Figure 8] This figure illustrates the relay path determination process and relay node type determination process performed by the control device according to Embodiment 1 of the present disclosure. [Figure 9] This diagram illustrates the direction determination process performed by the beam control unit of a relay station classified as a backhaul relay node. [Figure 10] This diagram illustrates the direction determination process performed by the beam control unit of a relay station classified as an edge relay node. [Figure 11] This is a flowchart of the processing performed by the control device according to Embodiment 1 of the present disclosure. [Figure 12] This is a flowchart of the processing performed by the relay node type determination unit of the control device according to Embodiment 1 of the present disclosure. [Figure 13]This is a flowchart of the processes performed by relay stations classified as backhaul relay nodes. [Figure 14] This is a flowchart of the processes performed by relay stations classified as edge relay nodes. [Modes for carrying out the invention]

[0016] Comparative Example Here, we will first describe a comparative example of prior art. Figure 1 shows an example configuration of a wireless communication system related to the comparative example of this disclosure. The wireless communication system 100 includes a transmitting station, a wireless base station (hereinafter referred to as "base station") 110, and a receiving station, a wireless terminal (hereinafter referred to as "terminal") 120. Furthermore, it includes a plurality of wireless relay stations (hereinafter referred to as "relay stations") 130 that receive radio waves from the base station 110 and retransmit them to the terminal 120. In other words, single-hop relay is assumed here.

[0017] Base station 110 is a base station that communicates wirelessly with terminal 120 via relay station 130. Base station 110 acquires location information of terminal 120. Furthermore, based on the acquired location information, it generates a beam 140 whose direction is selected by beamforming and transmits it to relay station 130.

[0018] Relay station 130 is a relay station such as a repeater. Relay station 130, such as a repeater, amplifies radio waves but does not have complex signal processing functions such as demodulation, so it can be deployed at low cost.

[0019] Multiple relay stations 130 exist within a range 150 where their distance from terminal 120 is below a predetermined value. Of the multiple relay stations 130, relay station 130(1), which is particularly close to terminal 120, receives the direction-selected beam 140 transmitted from base station 110 at a high reception level. Relay stations 130(2) and 130(3) are also close to terminal 120 and receive the direction-selected beam 140.

[0020] Relay stations 130(1), 130(2), and 130(3), upon receiving the direction-selected beam 140, amplify the radio waves and retransmit them to terminal 120. The strength of the retransmitted radio waves depends on the strength of the radio waves received.

[0021] Terminal 120 is, for example, a smartphone. Terminal 120 receives radio waves transmitted at high intensity from relay station 130(1). Furthermore, it receives radio waves from relay stations 130(2) and 130(3).

[0022] As explained above, in the conventional wireless communication system 100, the base station 110 performs beamforming and adaptively controls the direction of the beam. By relaying the direction-selected beam 140 to the relay station 130, it becomes possible to relay from the base station 110 to the terminal 120 via a short relay path. In other words, the loss of radio waves during propagation is suppressed, and wireless communication with high gain becomes possible.

[0023] While Figure 1 illustrates the case where the base station 110 performs beamforming, Non-Patent Literature 2, for example, discloses a technique in which the relay station 130 also adaptively controls the beam direction through beamforming. This enables wireless communication with even higher gain. However, the relay method in that case is assumed to be single-hop relay.

[0024] As mentioned above, in multi-hop relay, the technology for determining the relay path from base station 110 to terminal 120 and for relay station 130 to adaptively control the beam direction by beamforming had not been established.

[0025] Embodiment 1 Figure 2 shows an example configuration of a wireless communication system according to Embodiment 1 of this disclosure. The wireless communication system 200 includes a first base station 211, a second base station 212, a plurality of terminals 220, a plurality of relay stations 230, and a control device 240. In this case, the relay stations 130 are assumed to transmit and receive radio waves from each other. That is, multi-hop relay is assumed to be performed.

[0026] The first base station 211 uses high-frequency radio waves to perform high-capacity wireless communication (hereinafter referred to as data communication) with the terminal 220 and the relay station 230. The high-frequency band is, for example, the millimeter-wave band.

[0027] The second base station 212 receives terminal environment information transmitted from terminal 220. Furthermore, it notifies the control unit 240 of the received terminal environment information. Here, terminal environment information includes location information and other sensing information of each terminal 220.

[0028] Furthermore, the second base station 212 receives information about the relay route determined by the control device 240 based on terminal environment information from the control device 240. It then transmits this relay route information to each relay station 230 as a second base station notification signal 251.

[0029] The transmission of the second base station notification signal 251 uses radio waves in a lower frequency band than the high-frequency band radio waves mentioned above. This allows the signal to be transmitted without placing a load on the data communication exchanged between the first base station 211, the relay station 230, and the terminal 220.

[0030] Terminal 220 is a device such as a smartphone, similar to the example. Terminal 220 performs wireless communication with the first base station 211 using the high-frequency band described above. Furthermore, it performs wireless communication with the second base station 212 using the low-frequency radio waves described above to notify terminal environment information.

[0031] Terminal environment information can be generated, for example, by acquiring the device's own location information using GPS, LiDAR, etc. Terminal 220 periodically transmits the generated terminal environment information as a terminal notification signal 252 to the second base station 212 and the relay station 230. Low-frequency radio waves are used to transmit the terminal notification signal 252.

[0032] Relay station 230, like the comparative example, is a repeater or similar relay station that amplifies signals but does not have signal processing functions such as demodulation. Relay station 230 has a receiving antenna that forms an analog beam for receiving and a transmitting antenna that forms an analog beam for transmitting.

[0033] The receiving and transmitting antennas are each equipped with variable phase shifters. This allows for phase control of the analog beam during radio wave transmission and reception, enabling beamforming, which dynamically switches the direction of the beam.

[0034] Furthermore, when the relay station 230 receives the second base station notification signal 251 from the second base station 212, it performs a process (hereinafter referred to as the direction determination process) to determine the direction of the beam based on the relay path information contained in the second base station notification signal 251, and the position of the relaying partner and the position of the relay station. In addition, it performs a process (hereinafter referred to as the relay process) to form a beam in that direction using the receiving antenna and transmitting antenna described above and relay radio waves for data communication.

[0035] The control device 240 acquires terminal environment information of terminal 220 via the second base station 212. Furthermore, based on the acquired terminal environment information, it determines which relay station 230 will relay the signal from the first base station 211 to terminal 220 from among multiple relay stations 230, and executes a process to determine the relay route (hereinafter referred to as the relay route determination process).

[0036] Furthermore, the control device 240 classifies the relay stations 230 adopted in the relay path according to the determined relay path into backhaul relay nodes or edge relay nodes, and performs a process to determine the relay node type (hereinafter referred to as the relay node type determination process). Here, an edge relay node is a relay station 230 among the relay stations 230 adopted in the relay path that directly communicates wirelessly with the terminal 220. A backhaul relay node is a relay station 230 among the relay stations 230 adopted in the relay path that is not an edge relay node.

[0037] Furthermore, the control device 240 notifies the second base station 212 of the determined relay route and information including the relay node type.

[0038] As described above, in the wireless communication system 200 of this disclosure, the control device 240 determines the relay path based on terminal environment information transmitted from the terminal 220. Furthermore, based on the determined relay path, the relay station 230 determines the beam direction and adaptively controls the beam direction by beamforming. This enables high-gain wireless communication even in multi-hop relays.

[0039] In this case, if the relay path is determined by autonomous control at each relay station 230, it may not be possible to obtain location information at relay stations 230 that are far from the terminal, and a proper communication path may not be formed. In this disclosure, the control device 240 centrally determines the relay path, thereby eliminating such possibilities and ensuring that the relay path is reliably determined.

[0040] Furthermore, in the wireless communication system 200 of this disclosure, the second base station 212 receives location information acquired by the terminal using GPS, LiDAR, etc. Since the second base station 212 does not need to measure location information from the state of radio waves emitted from the terminal 220, the amount of communication required for feedback can be reduced.

[0041] Figure 3 is a functional block diagram of the control device according to Embodiment 1 of the present disclosure. The communication unit 241 of the control device 240 is the part that communicates with the second base station 212 and receives terminal environment information of the terminal 220. The relay node type determination unit 242 is the part that performs the relay route determination process described above. Furthermore, it is the part that executes the relay node type determination process described above according to the determined relay route.

[0042] The relay route determination process performed by the relay node type determination unit 242 further includes candidate determination processing, grouping processing, and route candidate calculation processing, but the details will be described later.

[0043] The notification information generation unit 243 is responsible for summarizing the relay route information and relay node type information determined by the relay node type determination unit 242 and generating information for notification to the relay station 230 (hereinafter referred to as relay node notification information). The generated relay node notification information is notified from the communication unit 241 to the second base station 212, and then distributed from the second base station 212 to the relay station 230 selected for the relay route as a second base station notification signal 251.

[0044] Thus, in the wireless communication system 200 of this disclosure, the control device 240 determines the relay path and the relay node type of the relay station 230 based on terminal environment information acquired by the terminal 220.

[0045] Figure 4 is a functional block diagram of a relay station according to Embodiment 1 of the present disclosure. The first communication unit 231 of the relay station 230 is the part that receives the second base station notification signal 251 from the second base station 212.

[0046] The relay node type management unit 232 is the part that extracts information about the relay node type of its own station from the received second base station notification signal 251.

[0047] The relay node type management unit 232, when its own relay node type is designated as a backhaul relay node, instructs the beam control unit 233 to perform direction determination processing as a backhaul relay node. On the other hand, when its own relay node type is designated as an edge relay node, it instructs the beam control unit 233 to perform direction determination processing as an edge relay node.

[0048] The beam control unit 233 is the part that performs the direction determination process described above. The relay station 230 has multiple candidates with different beam directions, and in the direction determination process, it selects from among the candidates the beam that is closest to the beam direction calculated based on the position of the relay partner and the position of the own station.

[0049] When performing direction determination processing as a backhaul relay node, the beam control unit 233 calculates the beam direction based on its own position and the positions of other relay stations 230 or the first base station 211 that connect it to the relay. The positions of the other relay stations 230 and the first base station 211 are known by means of notification, for example, by the second base station notification signal 251.

[0050] On the other hand, when performing direction determination processing as an edge relay node, the beam control unit 233 calculates the beam direction based on its own position and the position of the terminal 220 connecting it to the relay. In obtaining the position of the terminal 220, the relay station 230 autonomously acquires terminal environment information.

[0051] The beam control unit 233 further performs a process of notifying the base station side antenna unit 234 and the terminal relay side antenna unit 235 of the result of the direction determination process.

[0052] The base station antenna unit 234 is the receiving antenna described above. Based on the result of the direction determination process performed by the beam control unit 233, the base station antenna unit 234 performs beamforming and forms a beam in the determined direction.

[0053] The amplification unit 236 is the part that amplifies the received radio waves. In the amplification process, the power may be amplified at the same frequency as the radio wave received by the base station antenna unit 234, or it may be converted to a different frequency before amplification.

[0054] The terminal relay antenna section 235 is the transmitting antenna described above, which retransmits the radio waves amplified by the amplification section 236 to another relay station 230 or terminal 220. In the terminal relay antenna section 235 as well, beamforming is performed based on the result of the selection process performed by the beam control section 233, and a beam is formed in the determined direction.

[0055] The second communication unit 237 is the part that receives the terminal notification signal 252 from the terminal 220 as radio waves.

[0056] As described above, the relay station 130 of this disclosure determines the beam direction based on the relay path and relay node type information determined by the control device 240. If the relay node type of the station is designated as an edge relay node, the relay station 130 acquires the terminal 220 location information itself and determines the beam direction. This allows the beam direction to be determined in a shorter time compared to acquiring the location information via the control device 240.

[0057] <Variations> Furthermore, the First Communications Unit 231 and the Second Communications Unit 237 do not necessarily need to be separate.

[0058] Figure 5 is a diagram illustrating the candidate determination process performed by the control device according to Embodiment 1 of the present disclosure. The control device 240 has location information for the first base station 211, the second base station 212, and each relay station 230. Based on the location information of the terminal 220, the control device 240 executes a process (hereinafter referred to as the candidate determination process) to designate relay stations 230 whose distance from the terminal 220 is less than or equal to a predetermined value as edge relay node candidates 260.

[0059] For example, if terminals 220(1), 220(2), and 220(3) are located as shown in Figure 5, the relay stations 230 located inside a circle of a predetermined radius centered on each terminal 220 will be edge relay node candidates 260(1), 260(2), and 260(3), respectively.

[0060] Thus, in the wireless communication system 200 of this disclosure, the control device 240 determines a relay station 230 whose distance from the terminal 220 is less than or equal to a predetermined value as a candidate for an edge relay node.

[0061] Figure 6 is a diagram illustrating the grouping process performed by the control device according to Embodiment 1 of this disclosure. In Figure 6, the positions of the first base station 211, relay station 230, terminal 220(1), terminal 220(2), and terminal 220(3) are assumed to be the same as in Figure 5. Furthermore, the edge relay node candidate 260 is assumed to have been determined as described in Figure 5.

[0062] In the grouping process, the control device 240 groups relay stations 230 located within a certain distance from the first base station 211 as Tier #1. Furthermore, relay stations 230 located within a certain distance from each of the relay stations 230 belonging to Tier #1 are grouped as Tier #2. This process is repeated up to Tier #n to group the relay stations 230. Here, n is a predetermined number of hops. Note that the Tier is not updated for relay stations 230 that have already been grouped.

[0063] Furthermore, in the grouping process, the process of finding the next Tier is not performed from the edge relay node candidate 260. For example, in Figure 6, Tier #2 group includes two relay stations 230 belonging to edge relay node candidate 260(3). The process of finding the next Tier is not performed from these relay stations 230.

[0064] In Figure 6, all relay stations 230 belonging to Tier #4 become relay stations 230 belonging to the edge relay node candidate 260, so the grouping process ends here.

[0065] Furthermore, the control device 240 excludes the relay station 230 that was not classified into any group during the grouping process as an excluded relay station 270 from the list of candidates for use in the relay route. In Figure 6, the relay station 230 enclosed by the dashed line is the excluded relay station 270.

[0066] Thus, the control device 240 of this disclosure performs a grouping process to divide the relay stations 230 into n groups according to their distance from the first base station 211, from the Tier#1 group, which has the shortest distance to the first base station, to the Tier#n group, which includes the edge relay node candidate 260 and has the furthest distance to the first base station.

[0067] Figure 7 is a diagram illustrating the route candidate calculation process performed by the control device according to Embodiment 1 of this disclosure. However, in Figure 7, Tier #1 to Tier #4 groups are assumed to be as determined in Figure 6.

[0068] In the route candidate calculation process, the control device 240 considers all routes connecting the first base station 211 and each relay station 230 belonging to Tier#1 as candidate relay routes from the first base station 211 to Tier#1. Furthermore, it considers all routes connecting each relay station 230 belonging to Tier#1 to each relay station 230 belonging to Tier#2 as candidate relay routes from Tier#1 to Tier#2.

[0069] In this way, all routes from each relay station 230 belonging to Tier#(n-1) to each relay station 230 belonging to Tier#n are considered as relay route candidates. However, relay route candidates are not calculated between tiers where n is 2 or more apart. Furthermore, relay route candidates are not calculated within the same tier.

[0070] Furthermore, in the route candidate calculation process, all routes connecting each relay station 230 belonging to the edge relay node candidate 260 and the terminal 220 that is the relay destination of said relay station 230 are further processed to be considered as relay route candidates.

[0071] As a result of the route candidate calculation process described above, all relay route candidates from the first base station 211 to each terminal 220 are calculated as shown in Figure 7.

[0072] Figure 8 is a diagram illustrating the relay path determination process and relay node type determination process performed by the control device according to Embodiment 1 of this disclosure. However, in Figure 8, the relay path candidates are assumed to be as determined in Figure 7.

[0073] In the relay path determination process, the control device 240 selects the relay path with the shortest relay path length from among the relay path candidates. In this process, it determines the relay path from terminal 220 to the first base station 211.

[0074] Furthermore, if relay routes for multiple terminals 220 must be determined in a single relay route determination process, the relay routes will be determined starting with the terminals 220 with the fewest relay stations 230 included in the edge relay node candidate 260 (hereinafter referred to as the number of candidates). If the number of candidates is the same, the relay routes will be determined first for the terminals 220 that are farther from the first base station 211.

[0075] Furthermore, the relay station 230, which was adopted for the relay path between terminal 220 and the first base station 211 for which the relay path was determined earlier, is excluded from the relay path to terminal 220 later. This allows the relay station 230 to perform beamforming corresponding to terminal 220 for which the relay path was determined earlier.

[0076] In the example shown in Figure 8, the control device 240 must determine the relay routes for terminals 220(1), 220(2), and 220(3) in a single relay route determination process. In this case, the relay route for terminal 220(1), which has one candidate, is determined first. Furthermore, although terminals 220(2) and 220(3) both have two candidate routes, the relay route for terminal 220(2) is determined first because it is further away from the first base station 211.

[0077] As a result of the relay route determination process described above, the relay routes 280 from the first base station 211 to each terminal 220 are determined as shown in Figure 8. Relay routes 280(1), 280(2), and 280(3) are relay routes from the first base station 211 to terminals 220(1), 220(2), and 220(3), respectively.

[0078] Next, the control device 240 performs relay node type determination processing based on the results of the relay path determination processing. In this process, relay stations 230 that directly transmit radio waves to each terminal 220 in the relay path 280 to each terminal 220 are classified as edge relay nodes 282. On the other hand, in the relay path 280 to each terminal 220, the relay stations 230 excluding the edge relay nodes 282 are classified as backhaul relay nodes 281.

[0079] As a result of the relay node type determination process described above, the relay station 230 is classified as shown in Figure 8, and backhaul relay nodes 281 and edge relay nodes 282 are determined. Relay stations 230 that do not belong to either category are shown as unused relay nodes 283.

[0080] As described above, the control device 240 of this disclosure selects the relay path from among the relay path candidates that has the shortest distance from the first base station 211 to the terminal 220. This reduces the propagation loss of radio waves during relaying and enables high-quality wireless communication.

[0081] <Variations> In the relay route determination process described above, it was explained that a relay station 230 used for relaying to a terminal 220 for which a relay route has been determined earlier is excluded from the relay route to subsequent terminals 220. However, the same relay station 230 may be used for relaying to multiple terminals 220. This function can be achieved by linking with the scheduling information of the first base station 211 and notifying the relay station 230 of the scheduling information in advance.

[0082] The relay station 230 switches beam directions based on scheduling information. For example, if it is scheduled to communicate with terminal 220(1) at time t1 and with terminal 220(2) at time t2, it will form a beam constituting the relay path 280(1) to terminal 220(1) at time t1. Then, at time t2, it will operate to form a beam constituting the relay path 280(2) to terminal 220(2).

[0083] Figure 9 illustrates the direction determination process performed by the beam control unit of a relay station classified as a backhaul relay node. Here, to clarify that the two relay stations 230 are backhaul relay nodes, they are labeled as backhaul relay node 281(1) and backhaul relay node 281(1). It is also assumed that, as a result of the relay path determination process, a relay path has been selected to connect these stations.

[0084] Furthermore, Figure 9 shows two backhaul relay nodes 281 as viewed from above. We will explain the case where the antennas of the two backhaul relay nodes 281 are installed at the same height and beams are formed in a two-dimensional direction on the plane of the paper. Note that the antennas referred to here are the base station side antenna section 234 or the terminal relay side antenna section 235.

[0085] At each backhaul relay node 281, the location of its own station and the location of the connected station are known, for example, by a method such as notification from a second base station notification signal 251 from a second base station 212. The location of each backhaul relay node 281 is shown in two-dimensional coordinates.

[0086] First, the backhaul relay node 281(1) geometrically calculates the direction φ1 of the beam that should be directed towards the backhaul relay node 281(2). The following equation (Equation 1) is used for this purpose. TIFF0007912264000001.tif12132

[0087] Here, (x0, y0) is the position of backhaul relay node 281(1), and (x1, y1) is the position of backhaul relay node (2). Also, φ0 is the antenna installation angle of backhaul relay node 281(1), and is the angle formed by the axis 290(1) which is horizontal to the x-axis and the normal vector 291(1) which indicates the front direction of the antenna. The domain is 0 ≤ φ0 < 2π.

[0088] Here, the beam direction φ1 is given as the angle from the normal vector 291(1) which indicates the front direction of the antenna. The domain is (-(π / 2)≦φ1<(π / 2)).

[0089] As mentioned above, the relay station 230 has multiple beam candidates with different directions. The backhaul relay node 281(1) selects from these candidates the beam having the transmission direction closest to the calculated beam direction φ1. There, the beam that satisfies the following (Equation 2) is selected. TIFF0007912264000002.tif11112

[0090] However, n is a number assigned to the beam candidate, where n=1, 2, ... Also, φ with a hat symbol. n is a unit vector indicating the beam direction of the nth beam candidate, and is shown as an angle from the normal 291(1) which indicates the front direction of the antenna.

[0091] For backhaul relay node 281(2), the direction Φ2 of the beam that should be directed towards backhaul relay node 281(1) is calculated in the same way. The following (Equation 3) is used there. TIFF0007912264000003.tif12143

[0092] Here, Φ'0 is the antenna installation angle of backhaul relay node 281(2), and the method of defining the angle and the definition range are the same as in the case of backhaul relay node 281(1).

[0093] Furthermore, for the backhaul relay node 281(2), the beam with the transmission direction closest to the calculated beam direction Φ2 is selected from the candidates. There, as in the previous case, the beam that satisfies the following (Equation 4) is selected. TIFF0007912264000004.tif12113

[0094] In this way, the beam control unit 233 of the relay station 230, which is classified as a backhaul relay node, calculates the beam direction based on its own position and the positions of other relay stations 230 that connect it to the relay. Furthermore, it determines the direction closest to the calculated beam direction from among the candidates.

[0095] <Variations> Figure 9 illustrates the direction determination process when transmitting and receiving beams between two backhaul relay nodes 281, but one of them may be the first base station 211. In that case as well, the backhaul relay node 281 can perform beam direction determination.

[0096] Figure 10 illustrates the direction determination process performed by the beam control unit of a relay station classified as an edge relay node. Here, to clarify that relay station 230 is an edge relay node 282, it is labeled as edge relay node 282. It is also assumed that, as a result of the relay path determination process, the relay path is determined to connect edge relay node 282 and terminal 220.

[0097] Furthermore, Figure 10, like Figure 9, shows the edge relay node 282 and terminal 220 as a top view. Here, for the sake of explanation, we will assume that the antenna of the edge relay node 282 and the terminal 220 are at the same installation height, and we will explain the case where a beam is formed in a two-dimensional direction on the plane of the paper. Note that the antenna refers to the base station side antenna unit 234 or the terminal relay side antenna unit 235. Note that at the edge relay node 282, the location information of terminal 220 is assumed to be known from the terminal environment information.

[0098] The edge relay node 282 geometrically calculates the direction φ1 of the beam that should be directed towards the terminal 220. Here, as in Figure 9, the following (Equation 1) is used. TIFF0007912264000005.tif12144

[0099] However, (x0, y0) is the location of edge relay node 282, and (x1, y1) is the location of terminal 220. Also, φ0 is the antenna installation angle of edge relay node 282.

[0100] Furthermore, the edge relay node 282 selects a beam from the candidates that has the transmission direction closest to the calculated beam direction φ1. There, as in Figure 9, a beam that satisfies the following (Equation 2) is selected. TIFF0007912264000006.tif12105

[0101] In this way, the beam control unit 233 of the relay station 230, which is classified as an edge relay node, calculates the beam direction based on its own position and the position of the terminal 220 connecting it to the relay. Furthermore, it determines the direction closest to the calculated beam direction from among the candidates.

[0102] Figure 11 is a flowchart of the processing performed by the control device according to Embodiment 1 of this disclosure. First, terminal environment information is acquired (step S110). Next, the relay route determination process described in Figure 8 is executed (step S111). Furthermore, the relay node type determination process described in Figure 8 is executed (step S112). Finally, relay node notification information is generated (step S113).

[0103] Figure 12 is a flowchart of the processing performed by the relay node type determination unit of the control device according to Embodiment 1 of this disclosure. First, the candidate determination process described in Figure 5 is executed (step S120). Next, the grouping process described in Figure 6 is executed (step S121). Next, the route candidate calculation process described in Figure 7 is executed (step S122). Next, the relay route determination process described in Figure 8 is executed (step S123). Finally, the relay node type determination process described in Figure 8 is executed (step S124).

[0104] Figure 13 is a flowchart of the processing performed by a relay station classified as a backhaul relay node. First, it receives the second base station notification signal 251 (step S130). Next, it performs direction determination processing for the first beam (step S131). Here, the first beam is the beam directed towards relay station 230 or the first base station 211, which belongs to a Tier group that is one Tier smaller than the Tier group to which the station belongs, among the connection partners specified in the relay path. Next, it performs direction determination processing for the second beam (step S132). Here, the second beam is the beam directed towards relay station 230, which belongs to a Tier group that is one Tier larger than the Tier group to which the station belongs, among the connection partners specified in the relay path.

[0105] Figure 14 is a flowchart of the processes performed by relay stations classified as edge relay nodes. The following is performed. First, the second base station notification signal 251 is received (step S140). Next, direction determination processing for the first beam is performed (step S141). Next, terminal environment information is acquired (step S142). Next, direction determination processing for the second beam is performed (step S143). However, the second beam here refers to the beam directed towards the terminal 220 of the connection partner specified in the relay path.

[0106] Furthermore, the processing performed by the control device 240 and relay station 230 in this disclosure may be executed by a program using a computer equipped with a CPU and memory, in which the program is stored in memory. Alternatively, the processing may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program may be provided by recording it on a storage medium or by providing it via a network.

[0107] As described above, this disclosure provides a wireless communication system 200 and a wireless communication method that can improve communication quality by determining the relay path and the direction of the beam at the wireless relay station, even in multi-hop relay.

[0108] Furthermore, this disclosure provides a control device 240 and a wireless communication program that can determine a relay path and improve communication quality even in multi-hop relay.

[0109] <Variations> This disclosure primarily describes the case where data is transmitted from the first base station 211 to the terminal 220. However, it is also applicable when data is transmitted from the terminal 220 to the first base station. In that case as well, the same effects as described above can be obtained.

[0110] Furthermore, although this disclosure describes a configuration in which the control device 240 and the second base station 212 are separate, the functions of the control device 240 may also be provided by the second base station 212.

[0111] Furthermore, although this disclosure describes a case where the first base station 211 performs wireless communication using high-frequency radio waves and the second base station performs wireless communication using lower-frequency radio waves, the frequency band of the radio waves is not necessarily limited.

[0112] Furthermore, although this disclosure describes a case where the direction determination process is performed by the relay station 230, the direction determination process may be performed by the control device 240 for relay stations 230 belonging to a backhaul relay node. In this case, the information on the beam direction for each backhaul relay node determined by the control device 240 is included in the relay node notification information described above and notified to the second base station 212. As a result, the relay station 230 adopted as a backhaul relay node can perform relay processing based on the beam in the determined direction.

[0113] <Correspondence with terms used in claims> In the grouping process explained in Figure 6, Tier #1 group, Tier #2 group, ... Tier #n group are referred to as the 1st group, 2nd group, ... nth group in the claims.

[0114] Furthermore, in the direction determination process described in this disclosure, the relay station 230 connects with any of the first base station 211, the relay station 230, or the terminal 220, but in the claims, these are collectively referred to as radio stations. [Explanation of Symbols]

[0115] Wireless communication system 100; base station 110; wireless terminal 120; relay station 130; direction-selected beam 140, range 150; wireless communication system 200; first base station 211, second base station 212; terminal 220; relay station 230; first communication unit 231; relay node type management unit 232; beam control unit 233; base station side antenna unit 234; terminal relay side antenna unit 235; amplification unit 236; second communication unit 237; control device 240; communication unit 241; relay node type determination unit 242; notification information generation unit 243; second base station notification signal 251; terminal notification signal 252; edge relay node candidate 260; ineligible relay station 270; relay path 280; backhaul relay node 281; edge relay node 282; unused relay node 283; axis 290; normal 291

Claims

1. A wireless communication system that relays radio waves, Multiple radio relay stations that transmit and receive radio waves use antennas equipped with variable phase shifters to control the direction of the beam, The first base station and A second base station that receives location information from the terminal, Control device and Equipped with, The control device is The process of receiving the location information from the second base station, Based on the location information, a relay path determination process is performed to determine which wireless relay station will wirelessly relay from the first base station to the terminal from among the plurality of wireless relay stations, and to determine the relay path. The process of notifying the second base station of the relay path information, It is configured to perform, The aforementioned second base station is The system is configured to perform a notification process to notify each of the wireless relay stations used in the relay path of information about the relay path. The wireless relay stations used in the aforementioned relay path are: The process of receiving information about the relay route, Based on the aforementioned relay path, a relay process is performed to form a beam in a direction determined based on the position of the relaying partner and the position of the own station, and relay radio waves. It is configured to perform, At least one of the control device and the wireless relay station used in the relay path performs a direction determination process to determine the direction of the beam. The aforementioned first base station is A wireless communication system that performs wireless communication with the terminal via the relay path.

2. In the relay route determination process, Based on the location information, a candidate determination process is performed to select from the plurality of wireless relay stations that are less than or equal to a predetermined value in distance from the terminal as candidate edge relay nodes. A grouping process that divides the plurality of wireless relay stations into n groups according to their distance from the first base station, from the first group having the shortest distance to the first base station to the nth group including the edge relay node candidate and having the farthest distance to the first base station, A route candidate calculation process that calculates all routes connecting the first base station and each of the radio relay stations included in the first group, routes connecting radio relay stations that are in groups where n is different by one in the n groups, and routes connecting each of the radio relay stations included in the n group and the terminal, and designates these as relay route candidates. The wireless communication system according to claim 1, wherein the relay route is determined to be the route with the shortest distance from the first base station to the terminal, selected from the relay route candidates.

3. If multiple of the aforementioned terminals are provided, In the relay path determination process, relay paths are determined in order from the terminals with the fewest candidate edge relay nodes among the terminals, The wireless communication system according to claim 2, wherein if the number of candidate edge relay nodes is the same, the relay path is determined starting with the terminal that is further away from the first base station.

4. The location information is transmitted from the terminal using radio waves in a lower frequency band than the radio waves transmitted and received between the first base station and the terminal. The aforementioned second base station is The wireless communication system according to claim 1, wherein in the notification process, information about the relay path is notified using the low-frequency radio waves.

5. The aforementioned plurality of wireless relay stations include a plurality of candidates with different beam directions in the beam direction control, The direction determination process further includes a process of determining the direction closest to the determined beam direction from among the candidates, The wireless relay stations used in the aforementioned relay path are: The wireless communication system according to claim 1, wherein the relay processing is performed using a beam selected from the candidates.

6. A control device for controlling multiple radio relay stations that control the direction of a beam using an antenna equipped with a variable phase meter, The process of receiving terminal location information from the second base station, Based on the location information, a relay path determination process is performed to determine which wireless relay station will wirelessly relay the signal from the terminal to the first base station that communicates wirelessly with the terminal, and to determine the relay path, from among the plurality of wireless relay stations. The process involves notifying the second base station of the relay route information, and via the second base station, notifying each of the radio relay stations used in the relay route of the relay route information, A control device configured to perform the following actions.

7. A wireless communication method using multiple wireless relay stations that control the direction of a beam using antennas equipped with variable phase shifters, The control device that controls the aforementioned plurality of wireless relay stations receives terminal location information from the second base station, The control device performs a relay path determination process that determines, based on the location information, which wireless relay station will wirelessly relay from the first base station to the terminal from among the plurality of wireless relay stations, and determines the relay path. The control device notifies the second base station of the relay path information, and via the second base station, notifies each of the radio relay stations used in the relay path of the relay path information. The wireless relay station used in the relay path receives information about the relay path from the second base station, The wireless relay station used in the relay path performs a direction determination process to determine the direction of the beam of the wireless relay station used in the relay path, based on the information of the relay path, from the position of one of the connecting wireless stations and the position of the other connecting wireless station. The wireless relay station used in the relay path performs relay processing to form a beam with the antenna based on the result of the direction determination process and relay radio waves, A wireless communication method comprising the first base station performing wireless communication with the terminal via the relay path.

8. A wireless communication program to be executed by a control device that controls multiple wireless relay stations that control the direction of a beam using an antenna equipped with a variable phase meter, The process of receiving terminal location information from the second base station, Based on the location information, a relay path determination process is performed to determine which wireless relay station will wirelessly relay the signal from the terminal to the first base station that communicates wirelessly with the terminal, and to determine the relay path, from among the plurality of wireless relay stations. The process involves notifying the second base station of the relay route information, and via the second base station, notifying each of the radio relay stations used in the relay route of the relay route information, A wireless communication program including a program that causes the control device to execute the above.

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