Communication device, control device, control method, and program enabling efficient operation of relay transmission system

Abstract

To enable advanced and efficient control of a mesh network followed by relay transmission of a layer 1.SOLUTION: In a relay communication system in which multiple radio repeaters receive radio signals from a base station device by forming beams and amplify and transfer the received radio signals, a communication device that has a function of the radio repeater receives information that indicates a first candidate of the direction of the beam and a second candidate of the direction of the beam different from the first candidate and an interval value that indicates the time to wait before switching the direction of the beam between the first candidate and the second candidate from a control device that controls the relay communication system, and controls the beam so that the beam is directed in the direction indicated by the second candidate after waiting for the time indicated by the interval value when the signal transmitted from the base station device cannot be detected from the base station device or another communication device at prescribed timing while directing the beam in the direction indicated by the first candidate.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to an operation technique for an efficient relay transmission system.

Background Art

[0002] In a cellular communication system, a technique for relaying communication between a base station device and a terminal device is known. For example, Patent Document 1 describes a relay communication system using Integrated Access and Backhaul (IAB). Also, as a mode of relay communication, a mesh network is known. In a mesh network, when a failure occurs in some links in a set communication path, another communication path that does not pass through that link can be set, thereby enabling communication to continue.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a relay communication system using IAB, it is necessary to demodulate routing information between relay devices in the media access control (MAC) layer (layer 2). By performing this demodulation, a certain processing delay occurs, and it is assumed that, for example, control such as rapid path switching cannot be performed. Also, since a device cost related to the function for the layer 2 demodulation process is required, the cost may increase when constructing a network by preparing a large number of relay devices. On the other hand, by configuring a mesh network using a wireless repeater that relays at the physical layer (layer 1), no processing delay related to the layer 2 demodulation process occurs, and the network configuration cost can be reduced. However, in a mesh network using a layer 1 relay device, it is important to efficiently operate the network.

Means for Solving the Problem

[0005] The present invention provides an efficient operation technique for a mesh network using a layer 1 relay device.

[0006] A communication device according to an aspect of the present invention is a communication device having the function of the wireless repeater in a relay communication system configured such that a plurality of wireless repeaters receive a wireless signal from a base station device by forming a beam, amplify the received wireless signal, and transfer it, and includes: receiving means for receiving, from a control device that controls the relay communication system, information indicating a first candidate of the direction of the beam and a second candidate of the direction of the beam different from the first candidate, and an interval value indicating a time to wait before switching the direction of the beam between the first candidate and the second candidate; and control means for controlling the beam to direct the beam in the direction indicated by the second candidate after waiting for the time indicated by the interval value when a signal transmitted from the base station device cannot be detected at a predetermined timing while the beam is directed in the direction indicated by the first candidate by the base station device or another communication device.

[0007] A control device according to an aspect of the present invention controls a relay communication system configured such that a plurality of radio repeaters receive a radio signal from a base station device by forming beams, amplify the received radio signal, and transfer it. The control device is configured to, based on the radio quality, which is the result of measuring the radio signal from the base station device or another radio repeater using the beams that can be formed in each of the plurality of radio repeaters, identify a relay communication path to be used between the base station device and the plurality of radio repeaters, and a plurality of alternative communication paths to be used when each of the radio links included in the relay communication path becomes unavailable; determine a first candidate for the direction of the beam to be set in each of the plurality of radio repeaters based on the relay communication path; determine a second candidate for the direction of the beam to be switched from the first candidate in each of the plurality of radio repeaters based on the plurality of alternative communication paths; determine an interval value indicating the time to wait before the radio repeater switches the beam; and notify each of the plurality of radio repeaters of the information on the first candidate and the second candidate and the interval value.

Effect of the Invention

[0008] According to the present invention, a mesh network using a layer 1 relay device can be efficiently operated.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of the features described in the embodiments are essential for the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Also, the same or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] (System Configuration) Fig. 1 shows a configuration example of a wireless communication system according to this embodiment. The wireless communication system is a wireless mesh network, and in one example, it includes a base station device 101 and a plurality of communication devices (communication devices 111 to 116). The base station device 101 is a base station device that performs wireless communication compliant with, for example, the 5th generation (5G) cellular communication standard or its successor standard, and is configured to establish a connection with a terminal device and perform wireless communication. The communication devices 111 to 116 can be, for example, communication devices capable of establishing a connection with a terminal device and performing wireless communication, similar to the base station device. However, in this embodiment, the communication devices 111 to 116 have a function as a wireless repeater that relays a signal transmitted from the base station device 101 at the physical layer (layer 1). Also, the communication devices 111 to 116 can be configured as a single device having, for example, a function as a layer 1 wireless repeater and a function for communicating with other communication devices and a control device 121 described later, but are not limited thereto. For example, the communication devices 111 to 116 may be realized as an aggregate of devices in which these functions are implemented as separate devices. Note that between the base station device 101 and each of the communication devices 111 to 116, signals are transmitted using a frequency band capable of high-capacity communication such as millimeter waves, and a backhaul link is constructed by wireless communication. The radio waves in the frequency band for the backhaul link transmitted from the base station device 101 are amplified and output by a communication device (for example, communication device 111) that receives the radio waves. Also, the amplified and output radio waves are received by another communication device, and that other communication device amplifies and outputs the radio waves. In this way, a relay communication path is established through a plurality of communication devices.

[0012] When a signal addressed to a terminal device under its own control arrives at the communication device, the communication device demodulates the signal, converts it into a signal in a format that the terminal device can receive, and transmits it to the terminal device. Also, the communication device converts the signal received from the terminal device into a format that can be transmitted over a backhaul line and transmits it to another communication device or a base station device. Note that this is just an example, and the communication device may have a function as a general wireless repeater. That is, it has a function of amplifying and outputting radio waves arriving from a base station device, a terminal device, or another communication device (wireless repeater), and for example, it may not have functions such as converting a signal received from a base station device or another communication device into a wireless signal in a format that the terminal device can process, or converting a signal received from the terminal device into a format for flowing to a backhaul line. Note that hereinafter, the description will focus on the relaying communication function in the communication device.

[0013] Generally, in a communication system using a wireless repeater that performs relaying at layer 1, a wireless repeater is placed at a pre-planned position, and the coverage area is improved by simply amplifying and outputting the radio waves received by the wireless repeater. In such a configuration, the wireless repeater only radiates radio waves in a pre-set direction, and it is not easy to perform flexible communication such as switching the relaying path in a mesh network. On the other hand, in recent years, there are wireless repeaters configured to be able to set beams in multiple patterns and perform relaying using a beam in any of those patterns. In such a wireless repeater, for example, by using a beam of a pattern that can detect a signal with the maximum received power, a relaying path with good wireless quality can be selectively used.

[0014] The control device 121 controls the wireless relay network by the communication device as described above. The control device 121 specifies the order relationship of the relay communications formed by each communication device based on the position information of each communication device and the beam pointing direction when receiving radio waves. Then, the control device 121 forms routing information for forming a relay communication path. The control device 121 forms the setting information for the relay process in each communication device for forming a relay communication path as routing information and can notify the formed routing information to each communication device. Note that each communication device may communicate with the control device 121 using, for example, a wired communication line, or may communicate with the control device 121 via, for example, the base station device 101. Further, the communication device may be capable of wireless communication by a legacy communication method such as Long Term Evolution (LTE), 5th Generation (5G) cellular communication system, Wireless LAN, Bluetooth (registered trademark) Low Energy (BLE), etc., and may perform control communication with the control device 121 by such wireless communication.

[0015] (Specification of Relay Communication Path) In the configuration as described above, the control device 121 first specifies what kind of relay communication path is configured by the base station device 101 and the communication devices 111 to 116. In the present embodiment, the control device 121 specifies the direction in which each communication device can receive a wireless signal with a power equal to or higher than a predetermined power level. Then, based on the specified direction, the control device 121 specifies from which of the base station device or other communication devices each communication device can receive the wireless signal. When a communication device can receive a wireless signal from the base station device or other communication devices with a power equal to or higher than a predetermined power level, the control device 121 can determine that a relay communication link can be formed between this communication device and the base station device or other communication devices.

[0016] Each communication device executes a wireless signal detection process using, for example, a plurality of beam patterns that can be used for signal reception. The communication device identifies a predetermined number (e.g., one) of beams from the ones with stronger received power of the wireless signal or one or more beams in which the wireless signal is received with power equal to or higher than a predetermined value, and notifies the control device 121 of information indicating the beam. For example, in the example of FIG. 2, the communication device 202 measures the wireless signal transmitted from the base station device or the communication device 201 in each pattern of beams 211 to 215. Then, the communication device 202 notifies the control device 121 of, for example, the position of its own device and information on the beam 212 (direction of orientation) in which the wireless signal is received with power equal to or higher than a predetermined level. Note that the communication device 201 may form a plurality of beams when outputting the wireless signal. In this case, the communication device 201 may be configured to amplify the wireless signal received from, for example, the base station device and output it from at least a part (in one example, all) of the plurality of beams. Then, the communication device 202 may be configured to detect the wireless signal transmitted from any of the one or more beams. Note that the communication device 201 may be capable of forming only one beam, and in that case, it is configured to output the amplified wireless signal using that beam.

[0017] Note that the information on the beam 212 may include, for example, the posture (antenna arrangement) of the communication device 202 and information on the antenna weights. In this case, the control device 121 can identify the antenna pattern from the information on the antenna weights and can identify the direction of orientation of the beam 212 based on the pattern and the posture information. Note that this is only an example, and the communication device 202 itself may identify the direction of orientation of the beam 212 from its own antenna weights and antenna pattern and notify the control device 121 of the identified information. Also, the communication device 202 may notify the control device 121 of information indicating which of the plurality of fixed directional antennas detected the wireless signal with sufficient power.

[0018] Note that the control device 121 may have in advance information regarding the relationship between each antenna pattern and its pointing direction and the corresponding index. In this case, the communication device 202 can notify the control device 121 of the index information indicating in which antenna pattern the radio signal was detected with sufficient power. Thereby, the control device 121 can identify the antenna pattern corresponding to the index and identify in which direction the communication device 202 detected the incoming radio wave with sufficient power. Note that the communication device 202 may notify the control device 121, for example, when it is installed, of the information indicating the antenna pattern and the information indicating the index that can identify the antenna pattern. Also, for example, such information may be input by the communication carrier to the communication device 202 and the control device 121 before the operation of the communication device 202 is actually started. Further, when the communication device is installed, the position information of the communication device may be input to the control device 121. In this case, the control device 121 may be configured to acquire only the information that can identify in which antenna pattern each communication device detected a radio signal with sufficient power.

[0019] When the control device 121 acquires the position of a communication device and the reception direction of radio waves from each communication device, it identifies the node that output the radio waves received by that communication device. For example, as shown in FIG. 3, the control device 121 identifies a base station device or another communication device existing in the direction corresponding to the beam 212 from the position of the communication device 202 based on the information received from the communication device 202. The control device 121 acquires, for example, the information on the direction of the beam used when detecting the position information and the radio signal for the communication device 201 and the communication device 203 as well. Also, the control device 121 is assumed to hold, for example, the information on the position of the base station device 101. Here, the candidates for the source of the radio signal received by the communication device 202 are devices other than the communication device 202. Therefore, the control device 121 determines whether the positions of the base station device 101, the communication device 201, and the communication device 203 exist in the direction corresponding to the beam 212 with respect to the position of the communication device 202 as a reference. Thereby, the control device 121 identifies, for example, that the source of the radio signal detected at the communication device 202 is the communication device 201. Also, the control device 121 can similarly identify that the source of the radio signal detected by the communication device 201 is the base station device 101. Then, the control device 121 can identify from these identification results that there is a relay communication path through which the radio signal is relayed in the order of the base station device 101, the communication device 201, and the communication device 202.

[0020] Similarly, the control device 121 identifies all available relay communication paths. For example, in the example of FIG. 1, as the path from the base station device 101 to the communication device 116, (1) the path via the base station device 101, the communication device 111, the communication device 114, and the communication device 115, (2) the path via the base station device 101, the communication device 111, and the communication device 115, (3) the path via the base station device 101, the communication device 111, the communication device 112, and the communication device 115, (4) the path via the base station device 101, the communication device 112, and the communication device 115, (5) the path via the base station device 101, the communication device 111, and the communication device 112, (6) the path via the base station device 101 and the communication device 112, (7) the path via the base station device 101, the communication device 111, the communication device 112, and the communication device 113, (8) the path via the base station device 101, the communication device 112, and the communication device 113, and (9) the path via the base station device 101 and the communication device 113 can be identified. In this way, the control device 121 can identify all relay communication paths that can be set in the relay network composed of the base station device 101 and the communication devices 111 to 116 in FIG. 1, for example. Note that the method for identifying the relay communication path is not limited to this, and the relay communication path may be identified by other methods.

[0021] (Setting of Usage Path) The control device 121 notifies each communication device of the information on the relay communication path specified as above as routing information. In one example, the control device 121 notifies each communication device of information that can identify the relay communication path in which the communication device is involved. For example, in the system of FIG. 1, with respect to the communication device 115, as the information on the relay communication path from the base station device 101 to the communication device 115, the paths consisting of (10) the base station device 101, the communication device 111, the communication device 114, and the communication device 115, (11) the base station device 101, the communication device 111, and the communication device 115, (12) the base station device 101, the communication device 111, the communication device 112, and the communication device 115, and (13) the base station device 101, the communication device 112, and the communication device 115 are notified. Also, as the communication paths in which the communication device 115 is involved, the above-mentioned paths (1) to (4) which are the communication paths between the base station device 101 and the communication device 116 are notified to the communication device 115. Each communication device can operate so as to use any of the paths (10) to (13) above when, for example, the control device 121 or the base station device 101 instructs that the path from the base station device 101 to the communication device 115 should be used. Note that when the path from the base station device 101 to the communication device 116 should be used, each communication device can operate so as to use any of the paths (1) to (9) above.

[0022] In addition, as routing information, the control device 121 can notify one or more beam patterns that each communication device should use. For example, the control device 121 can notify the communication device 115 that it should use a beam directed in the direction of the communication device 114 for the path (10), a beam directed in the direction of the communication device 112 for the path (11), and a beam directed in the direction of the communication device 114 for the paths (12) and (13). Note that the information indicating the above-described paths may not be notified, and only the information of the beam capable of relaying the radio signal transmitted from the base station device 101 may be notified. Further, the control device 121 may include, as routing information, the beam pattern that each communication device should use when outputting a signal. That is, the control device 121 can identify, for example, the beam pattern for transmission or reception of each communication device to be used for forming each relay communication path, and provide the information of the beam pattern to each communication device.

[0023] The control device 121 can determine which of the configurable relay communication paths should be used based on various criteria. For example, when the delay until the signal transmitted from the base station device 101 reaches the terminal device exceeds the length of the cyclic prefix (CP), at the terminal device, the signal received via the relay communication path may become non-orthogonal to, for example, the signal directly arriving from the base station device 101. For this reason, the control device 121 can select the relay communication path to be used so that the relay delay in the relay communication path is equal to or less than a predetermined value. Further, the control device 121 can select the relay communication path to be used based on, for example, the radio quality and the number of hops of the relay communication path (the number of links between the base station device 101 and the terminal communication device (relay device)). Note that when the radio quality is used in the selection of the relay communication path, each communication device can notify the control device 121 by associating the information indicating the radio quality of the radio signal with the beam when notifying the information regarding the beam when detecting the radio signal at a predetermined power or more. The information indicating the radio quality can be, for example, the reference signal received power (RSRP), the reference signal received quality (RSRQ), the signal-to-noise ratio (SNR), or the like.

[0024] The control device 121 can determine a relay communication path to be used by using a model with the base station device and each communication device that performs relaying as nodes. FIG. 4 is a diagram modeling the relay communication network of FIG. 1. The circles in FIG. 4 indicate the base station device or communication devices, and the numbers shown inside the circles indicate which base station device or communication device it is. That is, the circle marked "101" indicates the base station device 101, and the circles marked "111" to "116" indicate the communication devices 111 to 116, respectively. The arrow connecting two circles indicates that the radio signal sent from the device on the starting side of the arrow can reach the device on the ending side of the arrow with sufficient power, and a path for relay communication can be formed between the two devices. Note that the arrow indicates how the radio signal is relayed when starting from the base station device 101. That is, when a radio signal is sent from the base station device 101, relay communication is performed along the arrow, indicating that the radio signal is not transmitted in the direction opposite to the direction indicated by the arrow. Note that the model when a signal is transmitted to the base station device 101 may be created separately, or a model with the direction of the arrow in FIG. 4 reversed may be used.

[0025] In FIG. 4, the numbers attached to the arrows (for example, "1" between the base station device 101 and the communication device 111, "6" between the base station device 101 and the communication device 113, etc.) correspond to the "cost" when using that link. The "cost" here corresponds to, for example, propagation delay or radio quality. The lower the cost value, the more advantageous it is to use that link, such as a smaller propagation delay or higher radio quality. The cost of the relay communication path is the sum of the costs of all the links included in that relay communication path. For example, in FIG. 4, the cost of the relay communication path consisting of the base station device 101, the communication device 112, and the communication device 116 is "6", which is obtained by adding the cost "3" of the link between the base station device 101 and the communication device 112 to the cost "3" of the link between the communication device 112 and the communication device 116.

[0026] In this embodiment, the control device 121 selects a relay communication path so that the number of hops is sufficiently suppressed in order to shorten the time until a radio signal reaches the terminal device from the base station device 101, for example.

[0027] The control device 121 preferentially selects, for example, a relay communication path with a smaller number of hops as the relay communication path to be used. For example, in FIG. 4, among the relay communication paths that can be formed up to the communication device 116 from the base station device 101, either the path (A) consisting of the base station device 101, the communication device 112, and the communication device 116, which can be reached in two hops, or the path (B) consisting of the base station device 101, the communication device 113, and the communication device 116 can be preferentially selected as the relay communication path to be used. Also, at this time, when there are a plurality of paths with the same number of hops, the path with the smaller cost can be preferentially selected. That is, since the cost of the above path (A) is 6 and the cost of the path (B) is 8, the control device 121 can preferentially select the path (A) between the path (A) and the path (B). Note that the control device 121 can select, for each of the communication devices 111 to 116, the relay communication path with the minimum number of hops from the base station device 101 as the relay communication path to be used as described above. Also, when there are a plurality of paths with the minimum number of hops for each of the communication devices 111 to 116, the control device 121 can select the path with the minimum cost among the plurality of paths as the relay communication path to be used.

[0028] Further, on the premise that the number of hops is equal to or less than a predetermined number, the control device 121 may preferentially select a path with a smaller cost as the relay communication path to be used. For example, when the predetermined number is 3, among the paths from the base station device 101 to the communication device 116, the path (C) consisting of the base station device 101, the communication device 111, the communication device 114, the communication device 115, and the communication device 116, the path (D) consisting of the base station device 101, the communication device 111, the communication device 112, the communication device 115, and the communication device 116, and the path (E) consisting of the base station device 101, the communication device 111, the communication device 112, the communication device 113, and the communication device 116 are not selected because the number of hops is 4. On the other hand, among the above paths (A) and (B), the path (F) consisting of the base station device 101, the communication device 111, the communication device 112, and the communication device 116, the path (G) consisting of the base station device 101, the communication device 111, the communication device 115, and the communication device 116, the path (H) consisting of the base station device 101, the communication device 112, the communication device 115, and the communication device 116, and the path (I) consisting of the base station device 101, the communication device 112, the communication device 113, and the communication device 116 have a number of hops of 3 or less. Therefore, the control device 121 can select the path with the minimum cost among these paths as the relay communication path to be used. For example, the cost of path (A) is 6, the cost of path (B) is 8, the cost of path (F) is 5, the cost of path (G) is 5, the cost of path (H) is 6, and the cost of path (I) is 7. Therefore, the control device 121 can select path (F) or path (G) as the relay communication path to be used. In this way, the control device 121 can, for example, extract all relay communication paths within the range of the hop number limit, and preferentially select the path with a smaller cost as the relay communication path to be used from among the extracted relay communication paths.

[0029] Incidentally, the above example described the procedure for selecting individual relay communication paths from the base station apparatus 101 to the communication apparatuses 111 to 116 based on cost. According to this procedure, for example, when the communication apparatuses 111 to 116 can decode the control information part of the signal arriving from the base station apparatus 101 and can switch the relay destination according to the destination of the signal, relay communication can be performed via an appropriate path. On the other hand, when the communication apparatuses 111 to 116 cannot decode the control information part of the received signal, the transfer destination of the radio signal cannot be changed according to the destination of the signal.

[0030] Therefore, the relay communication path may be specified so as to determine the signal transfer direction in each communication apparatus to one based on the total cost regarding the relay communication path in the entire system. To explain this relay communication path specifying method, FIGS. 5(A) to 5(D), which are models with the number of nodes reduced to simplify the explanation, will be used to explain the case where the maximum number of hops is 3 as an example. In FIGS. 5(A) to 5(D), the node 501 corresponds to, for example, a base station apparatus, and the nodes 502 to 505 correspond to, for example, communication apparatuses including radio repeaters. Here, as shown in FIG. 5(A), the node 501 can form links with the node 502 and the node 503. Note that "can form a link" here means that the radio signal transmitted from the node 501 is received at the nodes 502 and 503 with power equal to or higher than a predetermined level (using at least one beam pattern). Also, the cost of each link is represented by the number attached to the link. For example, the cost of the link from the node 501 to the node 502 is 1, and the cost of the link from the node 501 to the node 503 is 4. The node 502 can form a link with the node 503, and the node 503 can form links with the node 504 and the node 505. Further, the node 504 can form a link with the node 505.

[0031] In such a configuration, only one relay communication path is set and used between the node 501 and all of the nodes 502 to 505. That is, focusing on the node 503, there are a path directly reaching from the node 501 to the node 503 and a path reaching from the node 501 to the node 503 via the node 502, but not both of them are used. Instead, only one of them is used. Also, as described above, since the relay communication path is selected so that the maximum hop count is 3, a 4-hop path connecting in the order of the nodes 501, 502, 503, 504, 505 is not selected. For this reason, in the configuration as shown in FIG. 5(A), the selectable paths are only the three patterns shown in FIGS. 5(B) to 5(D). Here, the pattern of FIG. 5(B) will be described. In this pattern, the path to the node 502 is the path directly reaching from the node 501 to the node 502, and the cost is 1. The path to the node 503 is the path reaching from the node 501 to the node 503 via the node 502, and the cost is 1 + 2 = 3. The path to the node 504 is the path from the node 501 to the node 503 with the path between the nodes 503 and 504 added, and the cost is 1 + 2 + 1 = 4. And the path to the node 505 is the path from the node 501 to the node 503 with the path between the nodes 503 and 505 added, and the cost is 1 + 2 + 2 = 5. Therefore, the total cost in the pattern of FIG. 5(B) is 1 + 3 + 4 + 5 = 13.

[0032] Similarly, in FIG. 5(C), the cost to reach node 502 is 1, the cost to reach node 503 is 4, the cost to reach node 504 is 4 + 1 = 5, and the cost to reach node 505 is 4 + 1 + 2 = 7. Therefore, the total cost in the pattern of FIG. 5(C) is 1 + 4 + 5 + 7 = 17. Also, in FIG. 5(D), the cost to reach node 502 is 1, the cost to reach node 503 is 4, the cost to reach node 504 is 4 + 1 = 5, and the cost to reach node 505 is 4 + 2 = 6. Therefore, the total cost in the pattern of FIG. 5(D) is 1 + 4 + 5 + 6 = 16. Therefore, among the relay communication paths such as those in FIGS. 5(B) to 5(D), the relay communication path in FIG. 5(B) has the minimum total cost. For this reason, when it is possible to form links between nodes as in FIG. 5(A), it can be determined that the relay communication path in FIG. 5(B) will be used. Also, when a wireless link failure or the like occurs in the relay communication path of FIG. 5(B), processing is performed such that the relay communication path in FIG. 5(D) with the next lowest cost is used. When neither the relay communication paths in FIGS. 5(B) and 5(D) can be used, processing may be performed such that the relay communication path in FIG. 5(C) is used. However, this is just an example, and an alternative relay communication path for cases such as when a wireless link failure occurs may be determined according to the procedure described later. For example, when a relay communication path such as that in FIG. 5(B) or 5(D) is set, node 503 will transfer the signal received from node 501 in two directions, the direction towards node 504 and the direction towards node 505. In this case, node 503 may disperse power and transfer the signal in multiple directions compared to when transferring the signal in one direction. Therefore, it can be assumed that the wireless quality of the signal transmitted from node 503 and received at node 504 in the cases of FIGS. 5(B) and 5(D) will be lower than in the case of FIG. 5(C). For this reason, when the cost corresponds to the wireless quality, it may be set to different values for the cases of FIGS. 5(B) and 5(D) and the case of FIG. 5(C).Incidentally, when the cost corresponds to the distance between nodes, there is no change in the distance between nodes whether the signal is transmitted to a plurality of nodes or to a single node, so the cost does not change.

[0033] (Relay communication path switching) When a radio link included in the relay communication path set as described above becomes unusable due to the occurrence of a radio link failure or the like, the control device 121 can pre-set an alternative relay communication path (hereinafter, this path may be referred to as an "alternative communication path"). For example, in the configuration of FIG. 1, assume that a relay communication path as shown in FIG. 6(A) is set as the path to be used. That is, six paths are set: the path from the base station device 101 to the communication device 111, the path from the base station device 101 to the communication device 112 via the communication device 111, the path from the base station device 101 to the communication device 113 via the communication devices 111 and 112, the path from the base station device 101 to the communication device 114 via the communication device 111, the path from the base station device 101 to the communication device 115 via the communication device 111, and the path from the base station device 101 to the communication device 116 via the communication devices 111 and 115. And these paths are constituted by six radio links: (1) the radio link between the base station device 101 and the communication device 111, (2) the radio link between the communication device 111 and the communication device 112, (3) the radio link between the communication device 112 and the communication device 113, (4) the radio link between the communication device 111 and the communication device 114, (5) the radio link between the communication device 111 and the communication device 115, and (6) the radio link between the communication device 115 and the communication device 116. The control device 121 can, for example, pre-set alternative communication paths when these radio links are each disconnected.

[0034] For example, when the wireless link between the communication device 111 and the communication device 112 described above is disconnected, all of the relay communication paths via the communication device 112 among the relay communication paths in Fig. 6(A) become unavailable. Therefore, the communication device 112 can perform settings for switching the direction of the beam from the direction of the communication device 111 to the direction of the base station device 101. In this setting, as shown in Fig. 6(B), the wireless link between the communication device 111 and the communication device 112 is not used, and the wireless link between the base station device 101 and the communication device 112 is used. In this case, a relay communication path between the base station device 101 and the communication device 113 can be set using the wireless link between the base station device 101 and the communication device 112 and the wireless link between the communication device 112 and the communication device 113. However, it is not limited to this. For example, a path directly reaching from the base station device 101 to the communication device 113 may be used. The control device 121 can determine which of these paths to set as the alternative communication path based on, for example, the above-described cost value. Here, it is assumed that the control device 121 has set the communication path in Fig. 6(B) as the alternative communication path.

[0035] The control device 121 performs such alternative communication path setting processing for all cases where one or more wireless links cannot be used. Fig. 6(C) shows an example of an alternative communication path when the wireless link between the communication device 111 and the communication device 115 becomes unusable. In this case, for example, as the path to the communication device 115, a path from the base station device 101 via the communication device 111 and the communication device 114 to the communication device 115 can be selected. On the other hand, when such a path is used, the path to the communication device 116 via the communication device 115 has a hop count of 4, so it cannot be used due to the hop count limit. Therefore, as the path to the communication device 116, a path from the base station device 101 via the communication device 111 and the communication device 112 to the communication device 116 can be selected. Although other alternative communication paths can be selected depending on the cost of each wireless link, for example, it is assumed here that the alternative communication path in Fig. 6(C) is selected. Similarly, when the wireless link between the communication device 115 and the communication device 116 becomes unusable, for example, based on the cost of each wireless link, the alternative communication path in Fig. 6(D) is selected, and when the wireless link between the communication device 112 and the communication device 113 becomes unusable, for example, based on the cost of each wireless link, it is assumed that the alternative communication path in Fig. 6(E) is selected.

[0036] Also, Fig. 6(F) and Fig. 6(G) show alternative communication paths when the wireless link between the base station device 101 and the communication device 111 becomes unusable and when the wireless link between the communication device 111 and the communication device 114 becomes unusable, respectively. When the wireless link between the base station device 101 and the communication device 111 becomes unusable, a relay communication path to the communication device 111 and the communication device 114 cannot be set, so in this case, no path to the communication device 111 and the communication device 114 is set. Similarly, when the wireless link between the communication device 111 and the communication device 114 becomes unusable, no path to the communication device 114 is set. Note that this is only an example of the configuration as shown in Fig. 1, and in reality, alternative communication paths to these communication devices can naturally be set by using other communication devices.

[0037] Note that, although the examples in FIGS. 6(B) to 6(G) illustrate the case where one radio link becomes unavailable, an alternative communication path may be set when multiple radio links become unavailable. In this case, for each case where all combinations of the multiple radio links become unavailable, an alternative communication path can be specified.

[0038] Based on the alternative communication path specified in this way, the control device 121 aggregates the directions of the beams after change when the radio signal from the base station device 101 cannot reach each communication device. Then, based on the aggregation result for each communication device, the control device 121 sets the direction of the beam with a high usage frequency in the alternative communication path as a candidate for the direction of the beam after change of that communication device. Then, the control device 121 notifies each communication device that the direction of the beam in the relay communication path to be used is the first candidate, and the direction of a beam different from the first candidate with the highest usage frequency in the alternative communication path is the second candidate. Note that, the direction of a beam different from the first candidate and the second candidate with the next highest usage frequency in the alternative communication path may be notified to each communication device as the third candidate.

[0039] For example, as shown in FIG. 6(A), the communication device 112 directs a beam toward the communication device 111 in the relay communication path to be used. Here, when the radio signal from the base station device 101 cannot reach the communication device 112 from the communication device 111, an alternative communication path in which the communication device 112 is involved is set. The alternative communication path in which the communication device 112 is involved is set as shown in FIGS. 6(B) and 6(F), and in these cases, the beam is directed toward the base station device 101 in the alternative communication path. That is, the communication device 112 directs the beam toward the base station device 101 in both of the two alternative communication paths. Therefore, the communication device 112 is notified that the direction of the communication device 111 used in the initially used relay communication path is the first candidate for the direction of the beam, and the direction of the base station device 101 used in the alternative communication path is the second candidate for the direction of the beam.

[0040] Also, as shown in FIG. 6(A), the communication device 113 directs a beam toward the communication device 112 in the relay communication path to be used. Here, when the radio signal from the base station device 101 cannot reach the communication device 113 from the communication device 112, an alternative communication path involving the communication device 113 is set. The alternative communication path involving the communication device 113 is set as shown in FIGS. 6(B), 6(E), and 6(F). Here, in the cases of FIGS. 6(B) and 6(F), the communication device 113 does not need to change the direction of the beam. That is, in the cases of FIGS. 6(B) and 6(F), since the direction of the beam is switched in the communication device 112 on the upstream side (the side of the base station device 101), the radio signal from the base station device 101 can be supplied to the communication device 113, so there is no need to change the direction of the beam of the communication device 113. On the other hand, in the case of FIG. 6(E), the communication device 113 directs the beam toward the base station device 101 in the alternative communication path. That is, the communication device 113 does not switch the direction of the beam in two alternative communication paths, and changes the direction of the beam toward the base station device 101 in one alternative communication path. Therefore, the direction of the communication device 112 is notified to the communication device 113 as the first candidate for the direction of the beam, and the direction of the base station device 101 is notified as the second candidate for the direction of the beam.

[0041] As shown in Fig. 6(A), the communication device 115 directs a beam in the direction of the communication device 111 in the relay communication path to be used. Here, when the radio signal from the base station device 101 cannot reach the communication device 111, an alternative communication path involving the communication device 115 is set. The communication device 115 changes the beam direction to the direction of the communication device 114 in the case of Fig. 6(C) and changes the beam direction to the direction of the communication device 112 in the case of Fig. 6(F). Therefore, in the alternative communication path involving the communication device 115, two directions, namely the direction of the communication device 112 and the direction of the communication device 114, become the destinations for changing the beam direction of the communication device 115 with the same frequency. In this case, for example, the direction corresponding to a lower-cost alternative communication path for the entire system can be notified to the communication device 115 as the second candidate for the beam direction. Note that this is just an example, and the second candidate for the beam direction may be determined based on other criteria. For example, when the radio link between the base station device 101 and the communication device 111 becomes unavailable, even if the communication device 115 directs the beam in the direction of the communication device 114, communication cannot be resumed. On the other hand, by directing the beam in the direction of the communication device 112, the communication device 115 can resume communication even if either the radio link between the base station device 101 and the communication device 111 or the radio link between the communication device 111 and the communication device 112 becomes unavailable (for example, when the communication device 112 changes the beam direction). Therefore, the direction of the communication device 112 may be prioritized as the destination for changing the beam direction. In view of such circumstances, here, it is assumed that the direction of the communication device 112 is selected as the second candidate for the beam direction. In this case, the direction of the communication device 111 is notified to the communication device 115 as the first candidate for the beam direction, the direction of the communication device 112 is notified as the second candidate for the beam direction, and if necessary, the direction of the communication device 114 is notified as the third candidate for the beam direction.

[0042] As shown in Fig. 6(A), the communication device 116 directs a beam toward the communication device 115 in the relay communication path to be used. Here, when the radio signal from the base station device 101 cannot reach the communication device 115, an alternative communication path involving the communication device 116 is set. The communication device 116 changes the direction of the beam toward the communication device 112 in the cases of Figs. 6(C) and 6(D), and does not change the direction of the beam in the case of Fig. 6(F). For this reason, the direction of the communication device 115 is notified to the communication device 116 as the first candidate for the direction of the beam, and the direction of the communication device 112 is notified as the second candidate for the direction of the beam.

[0043] Note that in the configuration as shown in Fig. 6(A), the communication devices 111 and 114 do not have an alternative communication path to be switched when they can no longer receive the radio signal from the base station device 101. For this reason, the control device 121 can notify only the first candidate for the direction of the beam.

[0044] Each communication device, as an initial state, forms a beam in the direction of the first candidate notified as described above, receives the radio signal from the base station device 101, (forms a transmission beam if necessary) amplifies the radio signal, and transfers it. Then, when the radio signal from the base station device 101 has not been received for a certain period of time, each communication device switches the direction of the beam to the second candidate, switches to an alternative communication path where the radio signal can be received, and continues the relay communication.

[0045] On the other hand, if each communication device immediately switches to an alternative communication path in response to the loss of detection of the radio signal from the base station device 101, the relay communication path that is assumed to be used in each communication device may shift. That is, for example, when the radio link between communication device 111 and communication device 112 becomes unavailable, communication device 112 can resume communication in the entire system by changing the beam direction as shown in Fig. 6(B), while communication device 113 may also change the beam direction as shown in Fig. 6(E). That is, even when communication device 113 no longer detects the radio signal from base station device 101, it may change the beam direction even though communication can be resumed by simply waiting. As a result, for example, a communication path that is highly costly and inefficient may be used.

[0046] In view of such circumstances, in this embodiment, when the control device 121 notifies each communication device of the first candidate and the second candidate for the beam direction as described above, it sets an interval value (waiting time) during which the beam direction is not changed and the device waits without changing the beam direction from the time when the radio signal from the base station device 101 is no longer detected until the beam direction is changed. This interval value is set shorter, for example, for communication devices on the upstream side (the side closer to the base station device 101). In one example, the interval value is set to 0 for a communication device in which the beam direction in the alternative communication path is uniquely determined. For example, when either the radio link between the base station device 101 and the communication device 111 or the radio link between the communication device 111 and the communication device 112 becomes unavailable, communication device 112 no longer detects the radio signal from the base station device 101. However, in either of Figs. 6(B) and 6(F), which are the alternative communication paths in this case, the beam direction is changed toward the base station device 101. Therefore, the control device 121 can notify communication device 112 that the interval value is 0, for example, in parallel with notifying the above-described first candidate and second candidate.

[0047] On one hand, for example, when any one of the radio links between the base station device 101 and the communication device 111, between the communication device 111 and the communication device 112, or between the communication device 112 and the communication device 113 becomes unavailable, the radio signal from the base station device 101 cannot be detected. The alternative communication path at this time is any one of FIGS. 6(B), 6(E), and 6(F). In the case of FIG. 6(E), the direction of the beam is changed to the direction of the base station device 101, but in the cases of FIGS. 6(B) and 6(F), the direction of the beam is not changed. That is, the direction of the beam in the alternative communication path is not uniquely determined. Therefore, the control device 121 can notify the communication device 113 of an interval value greater than 0.

[0048] Note that, for a communication device in which the direction of the beam in the alternative communication path is not uniquely determined, the control device 121 can notify an interval value of a length corresponding to the number of hops from the base station device 101 to the communication device in the relay communication path (by the first candidate of the beam direction) to be used. For example, the communication device 115 exists at a position reachable from the base station device 101 in two hops in the relay communication path of FIG. 6(A), and the communication device 116 exists at a position reachable from the base station device 101 in three hops in the relay communication path. Therefore, the control device 121 can notify the communication device 115 of an interval value shorter than that of the communication device 116. That is, a shorter interval value is notified to a communication device on the upstream side (the side closer to the base station device 101). According to this, when the relay communication can be restarted by changing the beam direction in the communication device on the upstream side, it is possible to prevent the communication device on the downstream side from unnecessarily changing the beam direction. Note that the method for determining the interval value is not limited to the above example. For example, the interval value may be determined based only on the number of hops from the base station device 101 in the relay communication path to be used. That is, even if the direction of the beam in the alternative communication path is not uniquely determined, the interval value may be set to 0 for a communication device reachable from the base station device 101 in one hop, and then, as the number of hops increases by one, the interval value may be increased by a predetermined value (Δx). In this case, the interval value of the communication device reaching the nth hop from the base station device 101 in the initial relay communication path (the relay communication path set to be used with the highest priority) can be determined as (n - 1)×Δx. Also, as described above, the interval value may be determined according to the number of hops starting from a communication device in which the direction of the beam in the alternative communication path is uniquely determined. In this case, when the number of hops from the starting point is m, it can be determined as m×Δx.

[0049] Note that the communication device 116 can receive a radio signal from the base station device 101 when, for example, the communication device 115 directs the beam toward the communication device 114 as shown in FIG. 6(C). However, in this case, the number of hops increases, and it is assumed that it takes time for the radio signal to reach the communication device 116. For this reason, the communication device 116 may not be able to receive the radio signal at the timing when the radio signal should be received, and it may be determined that communication cannot be resumed normally. As a result, the communication device 116 may change the direction of the beam to the second candidate direction (the direction of the communication device 112). Thereby, when the communication device 115 directs the beam toward the communication device 114, a relay communication path as shown in FIG. 6(C) is used.

[0050] Note that each communication device may periodically notify the control device 121 of information on the direction in which the device itself is directing the beam. Then, for example, when there is a path whose hop count exceeds a predetermined number (3 in the above example) used as a limit in determining the relay communication path, the control device 121 may instruct a specific communication device to change the direction of the beam so that such a path disappears. For example, when the communication device 115 directs the beam toward the communication device 114, and the radio signal from the base station device 101 reaches the communication device 116 at a predetermined timing and the communication device 116 maintains the direction of the beam in the direction of the communication device 115, the control device 121 may instruct the communication device 116 to direct the beam in the direction of the communication device 112. Note that as long as the radio signal from the base station device 101 arrives at a certain timing, it may be allowed that the hop count in the used relay communication path exceeds the predetermined number.

[0051] Note that "not detecting the radio signal from the base station apparatus 101" in the above-described embodiment corresponds to the case where the synchronization signal and the notification signal periodically transmitted from the base station apparatus 101 are not received at a predetermined timing. That is, when there is a signal-free section in the case where the radio signal is intermittently transmitted from the base station apparatus 101, even if the signal-free section exists, as long as the radio signal periodically transmitted is detected, it is not determined that "the radio signal from the base station apparatus 101 is not detected". This is because there is simply no radio signal transmitted from the base station apparatus 101 in the first place, and there is no problem with the radio link.

[0052] Note that the communication apparatuses 111 to 116 can periodically observe radio signals in a plurality of configurable beams and notify the control apparatus 121 of the observation results. Further, the communication apparatuses 111 to 116 can notify the control apparatus 121 of the information on the beam currently being used, together with or separately from the observation results of the radio signals. Based on the received information, the control apparatus 121 can identify, for example, whether the communication apparatuses 111 to 116 are using the initially set relay communication path or an alternative communication path. Then, when it is determined that the alternative communication path is being used and the initially set relay communication path has become available (for example, due to an improvement in radio quality), the control apparatus 121 can notify each communication apparatus to switch the beam setting from the alternative communication path to the initial communication path. Further, the control apparatus 121 can identify the relay communication path and the alternative communication path to be used based on the radio quality information received periodically, and based on the identification result, notify each communication apparatus of the information on the direction of the beam to be set and the interval value.

[0053] (Device Configuration) With reference to FIG. 7, a hardware configuration example of the control device and the communication device will be described. In one example, the control device and the communication device are configured to include a processor 701, a ROM 702, a RAM 703, a storage device 704, and a communication circuit 705. The processor 701 is a computer including one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and reads and executes programs stored in the ROM 702 and the storage device 704 to execute the overall processing of the device and each of the above-described processes. The ROM 702 is a read-only memory that stores information such as programs and various parameters related to the processes executed by the control device and the communication device. The RAM 703 functions as a workspace when the processor 701 executes a program, and is a random access memory that stores temporary information. The storage device 704 is configured by, for example, a removable external storage device or the like.

[0054] The communication circuit 705 of the communication device has a function of amplifying and outputting a radio signal transmitted by, for example, a base station device or another communication device. Note that the communication circuit 705 of the communication device may be configured to form an antenna weight for signal reception by setting an antenna weight corresponding to each of a plurality of antennas. Note that the communication circuit 705 of the communication device may further be configured to form an antenna weight for signal transmission. Also, the communication circuit 705 of the communication device may be connected to a plurality of directional antennas and may be configured to use at least one of them. Further, the communication circuit 705 of the communication device may be separately prepared for each of a plurality of beam patterns, and the communication circuit 705 corresponding to a beam pattern other than the beam to be used may be configured to be turned off. Also, the communication circuit 705 of the communication device may have a communication function for notifying the control device of at least any one of information capable of specifying a beam that has detected a radio signal at a predetermined power or higher, the reception quality of the radio signal in each beam, the position information of the communication device, and the like. In one example, the communication circuit 705 of the communication device may be configured to notify the base station device of the information via, for example, a relay communication path. In this case, the base station device may transfer the information to the control device. Also, the communication circuit 705 of the communication device may have a function of directly notifying the control device of the information using a legacy communication method or a wired communication method. Also, the communication circuit 705 of the communication device may be configured to receive information on candidates for the direction of a beam corresponding to a relay communication path generated by the control device via, for example, a relay communication path or directly from the control device.

[0055] The communication circuit 705 of the control device may have any communication function capable of acquiring information from the communication device and transmitting information to the communication device. The communication circuit 705 of the control device may be configured to establish a connection using a wired communication method between, for example, a base station device and the communication device and transmit and receive information. Also, the communication circuit 705 of the control device may have a configuration capable of communicating using a legacy communication method and may be configured to perform wireless communication with the communication device using the communication method.

[0056] FIG. 8 is a diagram showing a functional configuration example of a control device. As its functions, the control device has, for example, an information acquisition unit 801, a route identification unit 802, a beam setting notification unit 803, and an interval information notification unit 804. Note that the functional blocks in FIG. 8 are schematically shown, and each functional block may be integrated and realized, or may be further subdivided. Also, each function in FIG. 8 may be realized, for example, by a processor 701 executing a program stored in a ROM 702 or a storage device 704, or may be realized, for example, by a processor existing inside a communication circuit 705 executing predetermined software. Note that details of the processing executed by each functional unit will not be described here, and only a general overview of its major functions will be outlined.

[0057] The information acquisition unit 801 acquires at least any one of information that can identify the beam of a communication device that has received a radio signal from a communication device at a power equal to or higher than a predetermined power, the reception quality of the radio signal in each beam, information that can identify the position information of the communication device, and the like, from the communication device. Based on the information acquired by the information acquisition unit 801, the route identification unit 802 identifies, for example, as described above, which device's signal each communication device amplifies and outputs, and identifies a relay communication route. For example, the route identification unit 802 identifies a configurable communication route as described with reference to FIGS. 2 and 3. Then, the route identification unit 802 identifies, for example, that a communication route as shown in FIG. 1 can be set between the base station device 101 and the communication devices 111 to 116. The route identification unit 802 further determines an actual relay communication route to be used and an alternative relay communication route among the configurable communication routes. Then, the route identification unit 802 determines one or more candidates for the direction of the beam to be set by each communication device. The beam setting notification unit 803 notifies each communication device of information on one or more candidates for the direction of the beam identified by the route identification unit 802. The interval information notification unit 804 notifies the communication device of information on the time (interval value) from the timing when the communication device becomes in a non-detection state of a radio signal from the base station device until the direction of the beam is changed.

[0058] FIG. 9 is a diagram showing a functional configuration example of a communication device. The communication device has, as its functions, for example, a measurement unit 901, an information notification unit 902, and a beam control unit 903. Note that the functional blocks in FIG. 9 are schematically shown, and each functional block may be integrated and realized, or may be further subdivided. Also, each function in FIG. 9 may be realized, for example, by a processor 701 executing a program stored in a ROM 702 or a storage device 704, or may be realized, for example, by a processor existing inside a communication circuit 705 executing predetermined software. Note that the details of the processing executed by each functional unit are not described here, and only the general functions are outlined.

[0059] The measurement unit 901 receives a radio signal arriving from another communication device or a base station device with each of a plurality of beams that can be set, for example, and specifies whether the radio signal is detected with a power equal to or higher than a predetermined power when any of the beams is used. The information notification unit 902 notifies the control device of information on the beam specified by the measurement unit 901, information such as the reception quality of the radio signal when that beam is used, and the like. The information notification unit 902 can notify the control device, for example, of an index pre-assigned to the beam as information on the beam for reception. Also, the information notification unit 902 can notify the control device of the position information of its own device. The beam control unit 903 acquires, from the control device, information on candidates for the direction of the beam determined by the control device based on the information notified by the information notification unit 902, and sets a beam to be used for communication based on that information.

[0060] When no radio signal from the base station apparatus is detected, the beam control unit 903 switches the beam in the direction corresponding to the alternative communication path. At this time, the beam control unit 903 can switch the direction of the beam after waiting for a period corresponding to the interval value notified from the control device from the timing when the radio signal from the base station apparatus was not detected at the timing when the radio signal from the base station apparatus should have been received. Note that if the beam control unit 903 can detect a radio signal from the base station apparatus during the period corresponding to the notified interval value, it can maintain the direction of the beam without switching. According to this, by switching the direction of the beam in the upstream communication device, the relay communication path is reconfigured, and thus it becomes possible to resume normal communication.

[0061] Also, during the execution of the relay communication, the measurement unit 901 may periodically measure radio signals from the base station apparatus or other communication devices for each of the configurable beams, and the information notification unit 902 may notify the control device of the measurement results. Note that the information notification unit 902 may notify the control device 121 of information indicating the currently used beam periodically, together with or separately from the measurement results.

[0062] (Flow of processing) Subsequently, an example of the flow of processing when the control device identifies the relay communication path and the alternative communication path and notifies the setting information to each communication device will be described with reference to FIG. 10. Note that FIG. 10 is merely a diagram for outlining the processing executed by the control device. For example, one processing step may be divided into a plurality of processing steps, or a plurality of processing steps may be integrated into one processing step. Also, within the scope not departing from the gist described in this embodiment, the order of processing may be changed, or a part of the processing may be omitted.

[0063] First, the control device acquires information that can identify a configurable communication path, such as measurement results (radio quality) of radio signals arriving from each communication device from the base station device or other communication devices, and information on the position of the communication device (S1001). Then, based on the acquired information, the control device identifies the positional relationship between the base station device and each communication device and identifies a configurable radio link (S1002). For example, the control device identifies the positional relationship and the configurable radio link and generates a model as shown in FIG. 4. Then, based on the model, the control device identifies the relay communication path to be used and an alternative communication path when a part of the radio links in the relay communication path becomes unusable (S1003). For example, the control device identifies the relay communication path to be used as shown in FIG. 6(A) and identifies the alternative communication paths as shown in FIGS. 6(B) to 6(G). Then, based on the identified relay communication path to be used, the control device determines a first candidate for the beam direction of each communication device, and further, based on the alternative communication path, determines a second candidate for the beam direction for the communication devices where the alternative communication path exists (S1004). Note that the control device may determine three or more candidates for one or more communication devices. The control device further determines, for example, whether the direction of the beam in the alternative communication path is uniquely determined, and based on the number of hops from the base station device to the communication device for the communication devices whose direction is not uniquely determined, determines the waiting time (interval value) until the beam direction is switched when the radio signal from the base station device cannot be detected in the used beam (S1005). Then, the control device notifies each communication device of the candidate for the beam direction and the interval value determined individually for each communication device (S1006).

[0064] Next, after the control device individually determines the beam direction candidates and interval values for each communication device, an example of the processing flow executed in the wireless communication system will be described with reference to FIG. 11. Here, in the system of FIG. 1, it is assumed that the control device 121 determines the beam direction candidates and interval values for the communication devices 111 to 116 based on the relay communication path as shown in FIG. 6(A) and the alternative communication paths as shown in FIGS. 6(B) to 6(G).

[0065] The control device 121 notifies the communication device 111 of information indicating the direction of the base station device 101 as the first candidate for the beam direction (S1101). Note that it is sufficient for the control device 121 to notify information that can identify the beam to be used by the communication device 111. For example, the control device 121 can notify the communication device 111 of a beam ID such that, as a result, the beam is directed toward the base station device 101. That is, the communication device 111 does not need to know in which direction the base station device 101 exists as seen from its own device. The same applies to other communication devices. In the example of FIG. 1, there is no beam switching destination for the communication device 111. That is, even if the communication device 111 cannot detect the radio signal from the base station device 101, it can operate so as not to change the beam direction. For this reason, the control device 121 does not notify the communication device 111 of information on the second candidate for the beam direction, nor does it notify the interval value. This is because the interval value cannot be used since beam switching does not occur.

[0066] The control device 121 notifies the communication device 112 of information indicating the direction of the communication device 111 as the first candidate for the beam direction and the direction of the base station device 101 as the second candidate for the beam direction (S1102). Further, the control device 121 may notify information setting the interval value for waiting before switching from the first candidate to the second candidate to "0". This is because, in the alternative communication path used when the radio signal from the base station device 101 cannot reach from the communication device 111, the communication device 112 always directs the beam toward the base station device 101, so there is no need to wait at the time of beam switching. Note that the communication device 112 immediately switches the beam direction to the direction of the base station device 101, for example, when it cannot detect a radio signal at the timing when a radio signal from the base station device 101 should reach from the communication device 111. However, this is just an example, and the communication device 112 may switch the beam direction when it fails to detect a radio signal continuously a predetermined number of times at an opportunity when a radio signal from the base station device 101 should be received. Also, in other communication devices, when a radio signal from the base station device 101 fails to be detected continuously a predetermined number of times at an opportunity when the radio signal should be received, the beam direction may be changed after waiting for a period corresponding to the interval value.

[0067] The control device 121 notifies the communication device 113 of information indicating the direction of the communication device 112 as the first candidate for the beam direction and the direction of the base station device 101 as the second candidate for the beam direction (S1103). Further, the control device 121 may notify information setting the interval value for waiting before switching from the first candidate to the second candidate to "2Δx". Here, this interval value (2Δx) can be, for example, a value set for the communication device at the third hop from the base station device 101 in the initial relay communication path when the direction in which the beam should be directed in the alternative communication path is not uniquely determined. The communication device 113 maintains the beam direction in the direction of the communication device 112 in a part of the alternative communication path and changes the beam direction to the direction of the base station device 101 in another alternative communication path, so the beam direction is not uniquely determined. For this reason, a non-zero interval value "2Δx" is notified to the communication device 112. Note that an interval value of (n - 1)×Δx is set for the communication device at the nth hop from the base station device 101 in the initial relay communication path. Here, an example is shown in which "2Δx" is notified as the interval value determined by the hop count from the base station device 101, but the interval value may be determined based on the hop count from the communication device 111 for which the interval value is 0 in the initial relay communication path. That is, an interval value of "Δx" may be notified to the communication device 113. Note that an example is shown in which the interval value increases by Δx according to the hop count, but it is not limited to this. That is, a value that increases but is not proportional according to the increase in the hop count may be used as the interval value.

[0068] The control device 121 notifies the communication device 114 of information indicating the direction of the communication device 111 as the first candidate for the beam direction (S1104). Similar to the communication device 111, there is no beam switching destination for the communication device 114. That is, the communication device 114 can operate so as not to change the beam direction even if it cannot detect the radio signal from the base station device 101. Therefore, the control device 121 does not notify the communication device 114 of the information on the second candidate for the beam direction, nor does it notify the interval value.

[0069] In the same manner as the above-described processing, the control device 121 notifies the communication device 115 of the direction of the communication device 111 as the first candidate for the beam direction, the direction of the communication device 112 as the second candidate, and notifies "Δx" as the interval value (S1105). This is because the communication device 115 can be reached from the base station device 101 in two hops in the initial relay communication path. Further, the control device 121 notifies the communication device 116 of the direction of the communication device 115 as the first candidate for the beam direction, the direction of the communication device 112 as the second candidate, and notifies "2Δx", which is longer than "Δx", as the interval value (S1106). This is because the communication device 116 can be reached from the base station device 101 in three hops in the initial relay communication path.

[0070] Communication devices 111 to 116 form a beam in the direction of the notified first candidate to receive a radio signal. As a result, an initial relay communication path as shown in Fig. 6(A) is formed by the base station device 101 and the communication devices 111 to 116. In this situation, when the base station device 101 transmits a radio signal (S1107), the radio signal is received by the communication device 111, and the communication device 111 amplifies and transfers the radio signal. Then, when the communication devices 112, 114, and 115 receive this radio signal, they amplify and transfer the radio signal. Then, when the communication device 113 receives the radio signal from the communication device 112 and the communication device 116 receives the radio signal from the communication device 115, they amplify and transfer the radio signal. In this way, the radio signal is transferred among the communication devices 111 to 116 (S1108). Note that the radio signal transferred from each communication device is received by a terminal device (not shown) existing around the communication device, and communication between the base station device 101 and the terminal device is performed based on the radio signal.

[0071] After that, for example, assume that the base station device 101 transmits a radio signal (S1109), and although the communication device 111 amplifies and transfers the radio signal, the radio signal does not reach the communication device 112 (S1110). In this case, the radio signal also does not reach the communication device 113. It is assumed that the radio signal reaches other communication devices (S1111). At this time, since the interval value "0" is notified to the communication device 112, without waiting, the communication device 112 switches the beam direction from the first candidate (the direction of the communication device 111) to the second candidate (the direction of the base station device 101) (S1112). On the other hand, the communication device 113 waits for a period corresponding to the notified interval value "2Δx" according to the value (S1113). In this case, when a radio signal is transmitted from the base station device 101 (S1114), the communication device 112 can receive this radio signal using the beam with the changed direction (S1115). As a result, the communication device 113 can receive the radio signal without changing the beam direction and amplify and transfer the radio signal. On the other hand, other communication devices can receive the radio signal as it is and amplify and transfer the radio signal (S1116).

[0072] For example, the communication device 112 may measure whether a radio signal from the communication device 111 arrives periodically, and switch the beam direction back to the direction of the communication device 111 in response to the radio link with the communication device 111 returning to an available state. Thereby, it becomes possible to preferentially use a relay communication path that is excellent from the perspective of cost, for example. Also, when the communication device 112 cannot receive a radio signal while the beam is directed toward the base station device 101, it may return the beam direction to the direction of the communication device 111. Note that the communication device 112 may return the beam direction from the direction of the base station device 101 to the direction of the communication device 111 without a waiting time according to the above-described interval value. Note that an interval value for returning the beam direction may be prepared separately. Also, when the communication device 112 cannot receive a radio signal while the beam is directed toward the base station device 101, it may stop relaying the radio signal. In this case, until the control device 121 receives the beam setting information again, the beam direction may be directed toward the communication device 111, or the relaying of the radio signal may be stopped. The same applies to other communication devices. Note that each communication device can measure the radio quality of the radio signal transmitted from the base station device 101 during communication (after the start of amplification and transfer of the radio signal after the completion of the setting of the above-described relay communication path) and notify the control device 121. Note that each communication device can measure the radio signal arriving from the base station device 101 or another communication device using each of the plurality of beams that can be formed. That is, not only the beams in the directions used in the relay communication path and the alternative communication path but also the measurement with the beams in the directions not used for communication can be performed. Then, the control device 121 can re-set the relay communication path and the alternative communication path and set the beams in each communication device based on those paths. When each communication device receives the beam setting information from the control device 121 again, it updates the setting in its own device and can change the beam direction if necessary as a result of the update.

[0073] As described above, in the relay communication system using the wireless repeater, it becomes possible to maintain and operate the relay communication while efficiently switching between the relay communication path and the alternative communication path. Therefore, it becomes possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0074] The invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the invention.

Claims

1. A communication device having the function of the wireless repeater in a relay communication system configured such that a plurality of wireless repeaters receive a wireless signal from a base station device by forming a beam, amplify the received wireless signal, and transfer it, a receiving means for receiving, from a control device that controls the relay communication system, information indicating a first candidate of the direction of the beam and a second candidate of the direction of the beam different from the first candidate, and an interval value indicating a time to wait before switching the direction of the beam between the first candidate and the second candidate; a control means for controlling the beam to be directed in the direction indicated by the second candidate after waiting for the time indicated by the interval value when a signal transmitted from the base station device cannot be detected at a predetermined timing while the beam is directed in the direction indicated by the first candidate; The communication device characterized by comprising the above.

2. The control means controls the beam so as not to change the direction of the beam from the direction indicated by the first candidate when the signal transmitted from the base station device cannot be detected at the predetermined timing while the beam is directed in the direction indicated by the first candidate, and the signal can be detected during the time indicated by the interval value. The communication device according to Claim 1, characterized by this.

3. The receiving means acquires the information indicating the first candidate and the second candidate and the interval value by communicating with the control device by a predetermined communication method, The wireless repeater is configured to amplify and transfer a wireless signal of a communication method different from the predetermined communication method. The communication device according to Claim 1, characterized by this.

4. measuring means for measuring a signal transmitted from the base station device in a plurality of configurable beams; notification means for notifying the control device of the result of the measurement; The communication device according to Claim 1, further characterized by comprising the above.

5. A control device for controlling a relay communication system configured such that a plurality of wireless repeaters receive a wireless signal from a base station device by forming a beam, amplify the received wireless signal, and transfer it, Based on the radio quality which is the result of measuring the radio signal from the base station device or another radio repeater using the beams that can be formed in each of the plurality of radio repeaters, a relay communication path to be used in the base station device and the plurality of radio repeaters, and a plurality of alternative communication paths to be used when each of the radio links included in the relay communication path becomes unusable, a specifying means for specifying; Determining a first candidate for the direction of the beam to be set in each of the plurality of radio repeaters based on the relay communication path, and determining a second candidate for the direction of the beam to be switched from the first candidate in each of the plurality of radio repeaters based on the plurality of alternative communication paths, and a determining means for determining an interval value indicating the time to wait before the radio repeater switches the beam; A notifying means for notifying each of the plurality of radio repeaters of the information on the first candidate and the second candidate and the interval value; A control device characterized by comprising the above.

6. The determining means determines the interval value for each of the plurality of radio repeaters such that the interval value becomes longer as the number of hops from the base station device to the radio repeater in the relay communication path is larger. The control device according to claim 5, characterized in that.

7. The determining means sets the interval value for a radio repeater in which the direction to which the beam should be directed in the plurality of alternative communication paths is uniquely determined to 0. The control device according to claim 5, characterized in that.

8. The determining means determines the interval value for a first radio repeater in which the direction to which the beam should be directed in the plurality of alternative communication paths is not uniquely determined such that the interval value becomes longer as the number of hops from a second radio repeater in which the direction to which the beam should be directed in the plurality of alternative paths is uniquely determined to the first radio repeater in the relay communication path is larger. The control device according to claim 7, characterized in that.

9. The notifying means notifies the information indicating the first candidate and the second candidate and the interval value by communicating with each of the plurality of radio repeaters by a predetermined communication method. The radio repeater is configured to amplify and transfer a radio signal of a communication method different from the predetermined communication method. The control device according to claim 5, characterized in that.

10. In a relay communication system configured such that a plurality of radio repeaters receive a radio signal from a base station device by forming a beam, amplify the received radio signal, and transfer it, a control method executed by a communication device having the function of the radio repeater, Receiving, from a control device that controls the relay communication system, information indicating a first candidate for the direction of the beam and a second candidate for the direction of the beam different from the first candidate, and an interval value indicating a time to wait before switching the direction of the beam between the first candidate and the second candidate; When a signal transmitted from the base station device cannot be detected at a predetermined timing while the beam is directed in the direction indicated by the first candidate by the base station device or another communication device, waiting for the time indicated by the interval value and then controlling the beam to be directed in the direction indicated by the second candidate; A control method characterized by including.

11. A control method executed by a control device that controls a relay communication system configured such that a plurality of radio repeaters receive a radio signal from a base station device by forming a beam, amplify the received radio signal, and transfer it, Based on the radio quality, which is the result of measuring a radio signal from the base station device or another radio repeater using a beam that can be formed in each of the plurality of radio repeaters, identifying a relay communication path to be used between the base station device and the plurality of radio repeaters, and a plurality of alternative communication paths to be used when each of the radio links included in the relay communication path becomes unusable; Determining a first candidate for the direction of the beam to be set in each of the plurality of radio repeaters based on the relay communication path, determining a second candidate for the direction of the beam to be switched from the first candidate in each of the plurality of radio repeaters based on the plurality of alternative communication paths, and determining an interval value indicating a time to wait before the radio repeater switches the beam; Notifying each of the plurality of radio repeaters of the information on the first candidate and the second candidate and the interval value; A control method characterized by including.

12. In a relay communication system configured such that a plurality of radio repeaters receive a radio signal from a base station apparatus by forming a beam, amplify the received radio signal, and transfer it, a communication apparatus having the function of the radio repeater and provided in a computer, receives from a control apparatus that controls the relay communication system, information indicating a first candidate of the direction of the beam and a second candidate of the direction of the beam different from the first candidate, and an interval value indicating a time to wait before switching the direction of the beam between the first candidate and the second candidate, controls the beam so that when a signal transmitted from the base station apparatus cannot be detected at a predetermined timing while the beam is directed in the direction indicated by the first candidate from the base station apparatus or another communication apparatus, after waiting for the time indicated by the interval value, the beam is directed in the direction indicated by the second candidate, a program for.

13. In a computer provided in a control apparatus that controls a relay communication system configured such that a plurality of radio repeaters receive a radio signal from a base station apparatus by forming a beam, amplify the received radio signal, and transfer it, based on the radio quality, which is the result of measuring a radio signal from the base station apparatus or another radio repeater using a beam that can be formed in each of the plurality of radio repeaters, identify a relay communication path to be used between the base station apparatus and the plurality of radio repeaters, and a plurality of alternative communication paths to be used when each of the radio links included in the relay communication path becomes unusable, determine a first candidate of the direction of the beam to be set in each of the plurality of radio repeaters based on the relay communication path, determine a second candidate of the direction of the beam to be switched from the first candidate in each of the plurality of radio repeaters based on the plurality of alternative communication paths, and determine an interval value indicating a time to wait before the radio repeater switches the beam, notify each of the plurality of radio repeaters of information on the first candidate and the second candidate and the interval value, a program for.

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