Base station device of cellular communication network for performing relay communication, terminal device, and control method thereof

Abstract

A base station apparatus of a cellular communication network for performing relay communication, a terminal apparatus, and control methods thereof are provided. The base station apparatus is configured to establish a wireless link for a backhaul line between the base station apparatus and a relay apparatus, and provide a first time period in which a radio resource is used for the backhaul line by the base station apparatus and a second time period in which the radio resource is not used for the backhaul line.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980013594.0, filed on February 14, 2019, entitled “Base station apparatus, terminal apparatus and control method thereof for cellular communication network for relay communication”. Technical Field

[0002] This invention relates to base station devices, terminal devices, and control methods thereof, and more particularly, to control technology for relay communication in wireless communication networks. Background Technology

[0003] The 3rd Generation Partnership Project (3GPP) discusses relay communication technologies that enable communication between base station equipment and remote terminals (see Non-Patent Documents 1 and 2). In relay communication, one or more relay devices are included between the base station equipment and the terminal in the communication path. These relay devices receive signals transmitted from the base station equipment and forward them to the terminal equipment; additionally, they receive signals transmitted from the terminal equipment and forward them to the base station equipment.

[0004] Existing technical documents

[0005] Non-patent literature

[0006] Non-patent document 1: 3GPP TR 36.806, V9.0.0, March 2010

[0007] Non-patent document 2: 3GPP TR 36.826, V11.0.0, September 2012 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In relay communication, some problems may arise as a wireless link is established between base station equipment and relay equipment.

[0010] means for solving problems

[0011] The present invention provides a technique for solving at least one of the problems in relay communication.

[0012] According to one aspect of the present invention, a base station device is configured to establish a wireless link for a backhaul line between the base station device and a relay device, and to provide a first time period in which the wireless resources are used by the base station device for the backhaul line and a second time period in which the wireless resources are not used for the backhaul line.

[0013] Furthermore, according to another aspect of the present invention, the terminal device is configured to request a connection to an access line from the base station device during a second time period provided by the base station device, wherein the base station device is configured to establish a wireless link for a backhaul line between the base station device and a relay device, and to provide a first time period in which the wireless resources are used by the base station device for the backhaul line and the second time period in which the wireless resources are not used for the backhaul line.

[0014] Invention Effects

[0015] According to the present invention, at least one of the problems in relay communication can be solved.

[0016] Other features and advantages of the invention will become apparent from the following description with reference to the accompanying drawings. Furthermore, in the drawings, the same or identical components are labeled with the same reference numerals. Attached Figure Description

[0017] The accompanying drawings are included in and form a part of this specification. The drawings illustrate embodiments of the invention and, together with the description of the embodiments, serve to explain the principles of the invention.

[0018] Figure 1 This is a diagram illustrating an example configuration of a wireless communication system with accompanying relay transmission according to Embodiment 1.

[0019] Figure 2 This is a diagram illustrating an example of the hardware configuration of the control device according to Embodiment 1.

[0020] Figure 3 This is a diagram illustrating an example of the functional configuration of the control device involved in Embodiment 1.

[0021] Figure 4 This is a diagram illustrating an example of the functional configuration of the relay device according to Embodiment 1.

[0022] Figure 5 This is a diagram illustrating an example of the processing flow performed in the wireless communication system according to Embodiment 1.

[0023] Figure 6 This is a diagram illustrating a configuration example of a wireless communication system with accompanying relay transmission according to Embodiment 2.

[0024] Figure 7 This is a diagram illustrating an example of the functional configuration of the base station device according to Embodiment 2.

[0025] Figure 8 This is a diagram illustrating an example of the functional configuration of the terminal device according to Embodiment 2.

[0026] Figure 9This is a diagram illustrating the first example of the processing flow involved in Implementation Method 2.

[0027] Figure 10 This is a diagram illustrating a second example of the processing flow involved in Implementation Method 2.

[0028] Figure 11 This is a diagram illustrating a third example of the processing flow involved in Implementation Method 2. Detailed Implementation

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0030] <Implementation Method 1>

[0031] In the following embodiments, a case is discussed where relay communication is performed using a communication path that includes multiple relay devices and spans multiple wireless links. In such relay communication, if a portion of the span is interrupted, the communication device (base station device or relay device) forming the wireless link in that span can recognize the interruption, but other communication devices on the communication path cannot. Therefore, although a portion of the communication path is interrupted, the communication devices that cannot recognize the interruption attempt to perform relay communication, potentially wasting wireless resources and consuming power. Furthermore, if the control device managing the communication path cannot recognize the interruption, the communication path cannot be rebuilt, potentially resulting in prolonged periods of communication downtime. This embodiment presents a solution to this problem.

[0032] (System Composition)

[0033] Figure 1 This illustrates an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system is configured to include a base station device 101, multiple relay devices 102-104, and a terminal device 105. Figure 1 In this example, communication between base station device 101 and terminal device 105 is relayed by relay devices 102-104. Furthermore, Figure 1 As an example, the number of relay devices that relay communication between base station device 101 and terminal device 105 is not limited to three. Furthermore, in Figure 1This diagram only shows the communication link between base station device 101 and terminal device 105, but different communication links can be configured for multiple terminal devices. In this embodiment, a tree-like network topology with base station device 101 as the vertices is used. Furthermore, the multiple segments 111 constituting the communication link are formed, for example, by fifth-generation cellular communication (NR, New Radio). In addition to the relay-related communication link, a Long Term Evolution (LTE) based wireless communication line 112 can be used between each relay device and base station device 101. For example, each relay device can be configured to conduct control communication with base station device 101 via LTE-based wireless communication line 112 and transmit user data using NR.

[0034] Here, if the wireless link between relay device 102 and relay device 103 is unintentionally severed, base station device 101 and relay device 104 cannot recognize the severed link. Therefore, although the wireless link between relay device 102 and relay device 103 is severed, relay device 104 continues to relay data from terminal device 105, or base station device 101 continues to send data destined for terminal device 105 to relay device 102. In use Figure 1 In such a tree-like network topology, communication between base station device 101 and terminal device 105 is interrupted because no communication path is provided to allow the interrupted segment to detour. Furthermore, base station device 101, for example, cannot receive an acknowledgment response from terminal device 105, and therefore can only recognize that a certain segment of the communication link has been interrupted. Thus, besides the time spent recognizing the interruption, base station device 101 cannot identify which segment of the communication link has been interrupted. In contrast, for example, relay device 103 notifies relay device 104 that the communication segment between it and relay device 102 has been interrupted, and relay device 102 can then notify base station device 101 of the interruption. However, in this case, for example, if a relay path based on multiple relay devices (not shown) is further established at the distance from relay device 104, the interruption of the segment between relay device 102 and relay device 103 must be notified to these relay devices sequentially. Furthermore, if the interrupted segment is located far from base station device 101, the interruption notification must be transmitted in multiple segments to reach base station device 101. That is, if a segment of a relay-based communication link is interrupted, notifying the interruption along the communication link sometimes wastes radio resources allocated separately for each segment. Additionally, regarding notifications along the communication link, the longer the communication link, the longer the notification process takes.

[0035] Therefore, in this embodiment, for example, if the wireless link in the communication interval between relay device 102 and relay device 103 is cut off, relay device 103 uses the LTE wireless communication line 112 to notify base station device 101 that the cutoff has been detected. That is, if a portion of the communication link between base station device 101 and terminal device 105 is cut off, the downstream relay device among the relay devices communicating in that interval, as observed from base station device 101, uses a wireless communication line capable of direct communication with base station device 101 to notify base station device 101 of the cutoff. Alternatively, the upstream relay device (e.g., relay device 102) as observed from base station device 101 may also notify base station device 101 of this notification. When base station device 101 receives this notification, it uses the LTE wireless communication line 112 to compare the downstream relay device of the relay device that sent the notification and notifies the upstream relay device that the wireless link in the communication interval has been cut off. In this case, if there are multiple relay devices performing relay operations in sections downstream of the cut-off section, the cut-off notification can be sent to all of these relay devices simultaneously. Therefore, compared to sequential cut-off notifications via relay-based communication links, this reduces the waste of wireless resources and shortens the notification completion time.

[0036] Furthermore, when the base station device 101 receives a disconnection notification from the relay device, it can receive the reason for the disconnection, either included in or separately from the notification. Therefore, the base station device 101 can perform various controls to maintain the communication link with the terminal device 105 based on the reason for the disconnection.

[0037] For example, if the reason for notification is the degradation of the wireless quality of the wireless link in the severed section, the base station device 101 can send an instruction signal to the relay device forming the wireless link in that section to increase the transmission power of the signal to rebuild the wireless link in that section. That is, if a notification is received from the relay device that the wireless link in the communication section established by the relay device has been severed due to the degradation of the wireless quality, the base station device 101 may send an instruction signal to at least one of the relay device and the target devices of the relay devices in that communication section to increase the transmission power to re-establish the wireless link. In the case of re-establishing the communication link in the severed section by improving the degradation of the wireless quality by increasing the transmission power, the previously established communication link between the base station device 101 and the terminal device 105 can be maintained.

[0038] Furthermore, if the reason for notification is the degradation of the wireless quality of the wireless link in the severed section, the base station device 101 can send an instruction signal to the relay device forming the wireless link in that section to change the operating frequency or communication timing and to rebuild the wireless link in that section. That is, when the wireless quality in the frequency channel and time slot used for communication in the severed section deteriorates due to interference or frequency-selective transmission paths, there is a possibility that changing the operating frequency or communication timing can improve the wireless quality. Therefore, the base station device 101 instructs at least one of the relay device and its target device constituting the wireless link in the severed communication section to change the operating frequency or communication timing to initiate a trial of rebuilding the wireless link in that communication section. Through such a change in operating frequency and communication timing, the degradation of wireless quality is improved, and when the wireless link in the severed section is rebuilt, the previously established communication link between the base station device 101 and the terminal device 105 can be maintained.

[0039] Furthermore, when a wireless link is disconnected, the base station device 101 can receive information from the relay device constituting the disconnected wireless link, including the reason for the disconnection and information indicating the operating frequency or communication timing at the time of disconnection. Then, if the reason for disconnection is a degradation of wireless quality, the base station device 101 can send an indication signal indicating the use of a frequency or timing different from the operating frequency or communication timing at the time of disconnection to at least one of the relay device and its target device constituting the wireless link in the disconnected communication segment. Thus, the base station device 101 can specify unused frequencies and communication timings in other wireless links surrounding the disconnected communication segment, thereby increasing the probability of successful wireless link reconstruction.

[0040] On the other hand, if the reason for the disconnection of the wireless link notified by the relay device is a failure of the target device that established the wireless link with the relay device, the base station device 101 can send an instruction to the relay device to establish a communication link with the terminal device 105 without including the target device. Upon receiving this instruction, the relay device can, for example, measure the wireless quality with surrounding relay devices to search for a connection destination. Furthermore, the base station device 101 can send the instruction including information about other relay devices present in the vicinity of the relay device. Additionally, the base station device 101 can send information about devices among the other relay devices present in the vicinity of the relay device whose hop count (number of relays) in the communication interval with the base station device 101 is less than a predetermined number. This predetermined number could, for example, be a number corresponding to the number of hops from the base station device 101 to the disconnected interval. This prevents excessive hop counts in the communication link after handover. Upon receiving information about other surrounding relay devices, the relay device can search for other relay devices with good wireless quality from the other relay devices indicated by this information, establish a wireless link with the discovered other relay devices, and reconstruct the communication link.

[0041] Furthermore, the base station device 101 can, for example, send an indication signal for reconfiguring the communication link to all of the multiple relay devices constituting the communication link. For example, if the wireless link in a predetermined number or more segments within the communication link is severed, the base station device 101 can send an indication signal for reconfiguring the communication link. Thus, in cases where improving only a part of the communication link is insufficient, or where communication quality deteriorates when switching a part of the communication link path to another path, the communication link can be reconfigured by resetting it, resulting in an optimized communication link. Furthermore, in this case, the base station device 101 can determine the communication link (communication path) it should construct by receiving reports of wireless quality between the base station device and other surrounding relay devices or between the base station device 101 and all relay devices. At this time, the base station device 101 can obtain information about the location and communication capabilities of each relay device in advance, select relay devices to constitute the communication link based on this information, and send an indication signal for reconfiguring the communication link to the selected relay devices. For example, the base station device 101 can notify each relay device of the target device it should connect to. In this case, the communication link from base station device 101 to terminal device 105 is reconstructed by establishing a wireless link with the target device that has been notified of the relay device. Furthermore, the communication capability information may include at least one of a corresponding frequency and a corresponding communication mode. For example, it can be said that the more corresponding frequencies there are, the better the interference with other surrounding devices can be suppressed, and the better the wireless quality can be improved even if the wireless quality of the wireless link formed by the relay device deteriorates. Additionally, by specifying the corresponding communication mode, it is possible to determine whether a connection with other devices can be established, or whether high-speed communication can be handled. Based on this information, base station device 101 can appropriately establish a relay-based communication link.

[0042] When reconstructing a communication link, the base station device 101 can further transmit timing information for the reconstruction. Thus, each relay device performs the communication link switching operation at an independent timing, allowing two devices in each interval to perform wireless link establishment processing at a shared timing, enabling reliable communication link reconstruction. Furthermore, by using such a shared timing, events such as some intervals corresponding to the reconstructed communication link while other intervals correspond to the unreconstructed communication link can be prevented.

[0043] Furthermore, in this embodiment, the base station device 101 operates as a control device for managing the communication link between the base station device 101 and the terminal device 105, but is not limited thereto. For example, a network node that can be wired to the base station device 101 can also function as a control device for managing the communication link between the base station device 101 and the terminal device 105.

[0044] Hereinafter, examples of the configuration of such a base station device 101 (control device) and relay device, as well as examples of the processing flow performed by these devices, will be described.

[0045] (Hardware Components)

[0046] Figure 2 This section illustrates an example of the hardware configuration of base station device 101 and relay devices 102-104. In one example, base station device 101 and relay devices 102-104 have... Figure 2 The hardware configuration shown includes, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication circuit 205. In the base station device 101 and the relay devices 102-104, for example, the CPU 201 executes a program recorded in, for example, any one of the ROM 202, RAM 203, and external storage device 204, which implements the functions of the base station device 101 and the relay devices 102-104 as described above.

[0047] Then, the base station device 101 and relay devices 102-104 communicate with other devices, for example, through the communication circuit 205 controlled by the CPU 201. Furthermore, the communication circuit 205 of the base station device 101 can communicate with other base station devices and other network nodes (e.g., external processing device 131) via wired lines. Additionally, the communication circuit 205 of the base station device 101 can form one or more beams to conduct LTE- and NR-based wireless communication with the relay devices 102-104. The base station device 101 can communicate with any relay device (in LTE) via both NR and LTE. Figure 1 In the example, relay device 102) is connected, and connections are established between other relay devices that perform relaying within a portion of a communication link formed by relaying based on this relay device via LTE. That is, base station device 101 establishes a direct LTE connection and a direct NR connection with the relay device at the initial first hop of the relay-based communication link, and establishes direct LTE connections and indirect NR-based relay link connections with relay devices after the second hop. Furthermore, in Figure 2 The diagram shown illustrates a base station device 101 and relay devices 102-104 with a single communication circuit 205, but multiple communication circuits may be included. For example, base station device 101 may have a first communication circuit for wired communication, a second communication circuit for wireless communication under NR, and a third communication circuit for wireless communication under LTE. Similarly, relay devices 102-104 may have a first communication circuit for NR and a second communication circuit for LTE, for example.

[0048] Furthermore, the base station device 101 and the relay devices 102-104 may have dedicated hardware to perform each function, or some functions may be performed by hardware while others are performed by a computer that activates the program. Alternatively, all functions may be performed by a computer and a program.

[0049] (Functional Composition)

[0050] Figure 3 This illustrates a functional configuration example of a base station device 101. The base station device 101 includes, for example, a first communication unit 301, a second communication unit 302, and a communication link management and control unit 303. The first communication unit 301 performs wireless communication, for example, using a wireless communication protocol conforming to the NR standard. The second communication unit 302 performs wireless communication, for example, using a wireless communication protocol conforming to the LTE standard. The communication link management and control unit 303 uses the second communication unit 302 to manage and control a relay link formed by one or more relay devices used in communication based on the first communication unit 301.

[0051] The communication link management and control unit 303, for example, stores and manages information about the relay devices constituting the relay link when a communication link is established. For example, when a communication link is constituted by more than one relay device, the communication link management and control unit 303 can store information identifying the communication link in association with information identifying the relay devices. Furthermore, for example, if the wireless link is disconnected in at least a portion of the relay link, the communication link management and control unit 303 receives a notification of disconnection detection from the relay device that established the wireless link via the second communication unit 302. When the communication link management and control unit 303 receives the notification of wireless link disconnection detection, it can control the first communication unit 301 accordingly to suppress communication in the relay link containing the wireless link. For example, the communication link management and control unit 303 controls the first communication unit 301 to stop sending data to a terminal device connected to a relay device downstream of the disconnected wireless link. For example, the communication link management and control unit 303 can determine the relay device downstream of the cut wireless link and the terminal device connected to the relay device based on the information of the relay device constituting the communication link stored when the communication link is established, without sending the prescribed signal to the terminal device through the first communication unit 301.

[0052] Furthermore, when the communication link management and control unit 303 receives a notification that a wireless link has been disconnected, it can receive information indicating the reason for the disconnection via the second communication unit 302 through the notification or a signal different from the notification. Then, the communication link management and control unit 303 can also send an indication signal via the second communication unit 302 to maintain or reconstruct the communication link based on the received reason. In addition, at this time, the communication link management and control unit 303 can, for example, determine the relay device that, along with the source of the notification, established the disconnected wireless link and should send the indication signal based on information about the relay devices constituting the communication link stored when the communication link was established. For example, if the reason for the disconnection is a degradation of wireless quality, the communication link management and control unit 303 can instruct an increase in transmission power, change the operating frequency, or change the communication timing to rebuild the wireless link, thereby maintaining the established communication link. At this time, the communication link management and control unit 303 can also generate and send an indication signal containing information specifying a frequency and time slot different from the frequency and time slot used at the time of disconnection as the frequency and time slot to be used. In this case, the communication link management and control unit 303 can also acquire information about the frequency and time slot used during the disconnection of the wireless link, for example, when the wireless link is established or when the wireless link is disconnected. Furthermore, if the reason for disconnection is a relay device malfunction, the communication link management and control unit 303 can reconstruct the communication link without including that relay device. Further, the communication link management and control unit 303 can also send an instruction via the second communication unit 302 to reconstruct the communication link for all relay devices forming the communication link, based on situations such as a predetermined number or more intervals in the communication link being disconnected. For example, the communication link management and control unit 303 can determine the relay devices constituting the communication link based on information stored when the communication link is established, and send an instruction to reconstruct the communication link for all determined relay devices. In this case, the communication link management and control unit 303 can send timing information for reconstructing the communication link via the second communication unit 302. Furthermore, the communication link management and control unit 303 can collect information in advance about the location and communication capabilities of each of the multiple relay devices. Based on this information, it selects the relay devices to form the reconstructed communication link and sends a communication link reconstruction instruction signal to these relay devices. In addition, the communication capabilities may include, for example, at least one of a corresponding frequency and a corresponding communication mode. Thus, communication link reconstruction can be appropriately performed based on the location and capabilities of the multiple relay devices.

[0053] then, Figure 4This section describes an example of the functional configuration of relay devices 102-104. In one example, each relay device includes a first communication unit 401, a second communication unit 402, a disconnection detection unit 403, and a disconnection reason determination unit 404. The first communication unit 401 performs wireless communication, for example, using a wireless communication protocol following the NR standard. For example, in a relay-based communication link, the first communication unit 401 establishes a wireless link with a device (base station device 101 or other relay device) on the upstream side of base station device 101, and establishes a wireless link with a relay device on the opposite side of base station device 101 as long as it is not the end of the communication link, and performs communication relay. In addition, the first communication unit 401 can communicate with the terminal device 105. The second communication unit 402 performs wireless communication with base station device 101, for example, using a wireless communication protocol following the LTE standard. The disconnection detection unit 403 performs this detection, for example, when the upstream wireless link in the wireless link established by this device in a relay-based communication link is disconnected. Furthermore, the disconnection detection unit 403 can also detect the disconnection of the downstream wireless link. When a disconnection is detected, the disconnection detection unit 403 notifies the base station device 101 of the wireless link disconnection via the second communication unit 402. Alternatively, when a disconnection of a downstream wireless link is detected, the disconnection detection unit 403 can also notify the base station device 101 via the unbroken communication link section using the first communication unit 401. When a wireless link established between this device and other devices is disconnected, the disconnection reason determination unit 404 can determine the reason for the wireless link disconnection and include the determination result in the wireless link disconnection notification, or notify the base station device 101 via a different signal. Furthermore, the disconnection detection unit 403 or the disconnection reason determination unit 404 can also notify the base station device 101 of the frequency and time slot used during the disconnection. Additionally, the second communication unit 402 can also notify the base station device 101 of the corresponding frequency and corresponding communication mode of the first communication unit 401.

[0054] (Processing flow)

[0055] Next, use Figure 5 For Figure 1 An example of the processing flow performed in a wireless communication system is given to illustrate this. Furthermore, Figure 5 The processing example is one example; it's possible to execute only a portion of these processes, add other processes based on these processes, and also rearrange the order of the processes. Furthermore, in... Figure 5 In this context, a communication method conforming to the NR standard is used in relay communication, while a wireless communication line different from the NR standard used to directly connect each relay device and base station device 101 is established using a communication method conforming to the LTE standard. Furthermore, in... Figure 5In the text, “NR” and “LTE”, indicated by parentheses, indicate that the signal is transmitted and received through either the NR or LTE wireless communication line.

[0056] First, a relay communication link using NR is established in a manner that enables communication between base station device 101 and terminal device 105 (S501). For example, when data destined for terminal device 105 is generated in base station device 101, or when terminal device 105 accesses base station device 101 using, for example, an LTE line, the processing in S501 is executed. Alternatively, the processing in S501 can be performed in advance. That is, for example, the NR-based relay communication link can be pre-set based on the geographical distribution of the generated traffic and the location distribution of relay devices, as in S501. Furthermore, the communication link using the relay communication link between base station device 101 and terminal device 105 can be established at least based on the fact that terminal device 105 enters the service area of ​​each relay device (in this case, relay device 104). If the NR-based relay communication link is established, data transmission and reception between base station device 101 and terminal device 105 can be performed (S502).

[0057] Then, for example, suppose the wireless link between relay device 102 and relay device 103 in the relay communication link is cut off (S503). Relay device 103 then detects the cutoff and notifies base station device 101 of the detected cutoff via LTE (S504). Then, base station device 101 notifies relay device 104, which is downstream of relay devices 102 and 103 in the relay communication link, via LTE that the relay communication link has been cut off upstream (S505). Thus, base station device 101 and downstream relay device 104 can know that the relay communication link is unusable at that moment. Therefore, base station device 101 can, for example, transmit data to terminal device 105 without using NR (not shown), if there is data to be transmitted (e.g., data to be transmitted to terminal device 105). Furthermore, relay device 102 can also detect the cutoff of the wireless link and notify base station device 101 of the cutoff. In this case, relay device 102 can notify base station device 101 of the detected cutoff via LTE, or it can use NR instead of LTE. This is because relay device 102 is the relay device on the base station device 101 side of the two relay devices that build a cut wireless link in the relay communication link, and therefore can send information to base station device 101 via NR.

[0058] Furthermore, relay device 103 (relay device 102) can notify base station device 101 of the reason for disconnection along with or separately from the disconnection notification in S504 (S506). Additionally, relay device 103 (relay device 102) can, for example, notify base station device 101 of at least one of the usage frequency and usage time slot at the time of disconnection during the timing of S504 or S506. Furthermore, for example, when establishing a relay communication link in S501, this information can also be notified to base station device 101 from each relay device. When base station device 101 receives the reason for disconnection, it sends a reconstruction instruction corresponding to the reason to relay devices 102 and 103 (S507). The reconstruction instructions corresponding to each reason are as described above and will not be described here. Then, relay devices 102 and 103 perform NR-based wireless link reconstruction (S508). Through this wireless link reconstruction, NR-based communication between base station device 101 and terminal device 105 is possible. Furthermore, for example, in the event of a failure of relay device 102, base station device 101 can send an indication signal to relay device 103, either via a relay device different from relay device 102 or directly, to establish a communication link with base station device 101. In this case, relay device 103 establishes a wireless link, for example, with other relay devices or base station device 101 directly or indirectly connected to base station device 101. Thus, base station device 101 can perform NR-based communication with terminal device 105 via a communication link that does not include relay device 102. Furthermore, hereinafter, it is assumed that the wireless link between relay device 102 and relay device 103 has been rebuilt.

[0059] Next, the disconnection of the wireless link between relay device 102 and relay device 103 and the disconnection of the wireless link between relay device 103 and relay device 104 are performed concurrently (S509). Then, for example, the downstream relay devices (relay device 103 and relay device 104) in each wireless link send a notification of the wireless link being disconnected to the base station device 101 via LTE (S510). In this example, since there is no relay device downstream of relay device 104, no notification of disconnection to the downstream relay devices is sent from the base station device 101. The base station device 101 decides to rebuild the communication link based on the number (e.g., 2) or more wireless links being disconnected. At this time, the base station device 101 determines, for example, the topology for establishing the communication link based on information such as the location and communication capabilities of each relay device. Here, for example, the base station device 101 decides to establish the communication link established between relay device 102 and relay device 104 (S511). In this case, the base station device 101 sends an indication signal for establishing a wireless link to the relay devices 102 and 104 to reconstruct the relay communication link (S512). Furthermore, the indication signal may also include timing information for the reconstructing of the relay communication link. Alternatively, the timing information for the reconstructing can be sent separately. By reconstructing the relay communication link, data communication between the base station device 101 and the terminal device 105 can be performed.

[0060] Based on the above configuration, when a section of the relay communication link is interrupted, the base station device 101 and the relay device that has established a wireless link downstream of that section can identify the interruption of the relay communication link. Furthermore, the base station device 101 can instruct the reconstruction of the wireless link in the interrupted section and the overall reconfiguration of the relay communication link based on the reason for the interruption and the number of interrupted sections, thereby restarting NR-based communication between the base station device 101 and the terminal device 105.

[0061] Thus, according to this embodiment, the state of the communication path in relay communication can be properly managed.

[0062] <Implementation Method 2>

[0063] In relay communication, the frequency bands available for the backhaul line established between the base station device (donor node) and the relay device (relay node) and the access line used to connect the terminal device to the base station device, etc., can be the same. Furthermore, the establishment of the connection between the base station device and the relay device can be performed in the same manner as the conventional steps for connecting a terminal device to a base station device.

[0064] When a common frequency band is used in the backhaul and access lines, the terminal device may sometimes unintentionally attempt to connect to the base station device during or after the establishment of the backhaul line between the base station and the relay device. That is, the base station device sends synchronization and reporting signals periodically to enable the establishment of the backhaul line when the relay device starts up / restarts. However, since the connection sequence is common in both the backhaul and access lines, the terminal device can attempt to access the base station device based on these synchronization and reporting signals. The base station device can also establish a connection with the terminal device, but if such unnecessarily attempted access based on the terminal device is performed, sufficient communication speed may not be achieved in the backhaul line. In this embodiment, a method for addressing this problem is discussed.

[0065] (System Composition)

[0066] Figure 6 This illustrates an example configuration of the wireless communication system according to this embodiment. This wireless communication system is configured with relay transmission; in one example, it is configured to include a base station device 601, a relay device 602, and terminal devices 603 and 604. Furthermore, in... Figure 1 The document describes a base station device 601, a relay device 602, and two terminal devices 603 and 604, but multiple base station devices, relay devices, and terminal devices may also exist. Additionally, in... Figure 1 In this system, a single-hop relay path is formed by one relay device 602, but multiple relay devices can also form a multi-hop relay path. Furthermore, in... Figure 1 In this system, a relay path is formed by one relay device 602, but multiple relay paths can also be formed by multiple relay devices. Alternatively, for example, relay device 602 can be connected to multiple relay devices to form relay paths branching within relay device 602. That is, there is no particular limitation on the topology of the relay paths, and any configuration can be used. Furthermore, while this wireless communication system is designed to communicate according to the 5th generation NR (New Radio) standard, the following discussion can also be applied when communicating according to standards prior to 5th generation such as LTE, or future standards that have not yet been established.

[0067] Base station device 601 can form one or more beams 621 and 622, using at least one of them (in Figure 1In the case of beam 621, a wireless link 611 for the backhaul line is established between the relay device 602 and the base station device 601. The relay device 602 then relays communications performed by the base station device 601 (e.g., communications between the terminal device 603 and the base station device 601). The relay device 602 is, in one example, a fixed station that does not move, but it could also be a mobile station depending on the situation. However, in this embodiment, assuming that the wireless link between the base station device 601 and the relay device 602 can ensure sufficiently good wireless quality, this wireless link between the base station device 601 and the relay device 602 is referred to as the backhaul line (backhaul link).

[0068] The backhaul line is established through the same steps as the access line established between the terminal device and the base station device. That is, the relay device 602 establishes synchronization using a synchronization signal sent by the base station device 601, and, based on various information obtained through report signals, begins communication by performing processes such as establishing a Radio Resource Control (RRC) connection with the base station device 601. At this time, for example, if the relay device 602 is fixed, the wireless communication environment is stable, so the base station device 601 can use a longer transmission period for the synchronization signal and report signal used to establish the backhaul line than for establishing the access line. However, since these synchronization signals and report signals are not stopped being transmitted, it is conceivable that, for example, the terminal device 604 can attempt to establish the access line based on these synchronization signals and report signals. Backhaul lines are generally used to relay communication between multiple terminal devices and the base station device 601, so it is often necessary to ensure sufficient communication capacity. However, when the access line is established together with the backhaul line, ensuring the communication capacity of the backhaul line becomes more difficult because a portion of the communication capacity is allocated to the access line. Furthermore, the base station device 601 can also reject the establishment of a wireless link in response to a signal attempting to establish an access link from a terminal device. However, it is conceivable that such rejection would result in a waste of wireless or computing resources, or interference with the backhaul line from the terminal device. Therefore, it is particularly important to eliminate the need for such access link establishment attempts from terminal devices.

[0069] In this embodiment, the base station device 601, during or after establishing a backhaul line, transmits a report signal containing information indicating that radio resources are being used for the backhaul line, in a trial manner where the establishment of an access line is not required. For example, the report signal includes a specified field (e.g., 1 bit) whose bits (bit column) constitute information indicating whether the base station device transmitting the report signal is using radio resources for the backhaul line. Furthermore, while the case of a report signal containing "information indicating whether radio resources are being used for the backhaul line" has been described here, this information could also be any information indicating whether a request to establish a connection based on a terminal device is restricted. In one example, this information can be reported via the Master Information Block (MIB) in the Physical Reporting Channel (PBCH). Thus, a synchronized terminal device can identify whether radio resources in the base station device are being used for the backhaul line without connecting to the base station device. Alternatively, this information can also be reported via the System Information Block (SIB) in the Physical Downlink Shared Channel (PDSCH).

[0070] When terminal device 604 receives such a report signal, it identifies whether the base station device that sent the report signal is using the radio resources that sent the report signal for a backhaul line. Then, for example, if the radio resources are being used for a backhaul line, terminal device 604 decides not to attempt to establish an access line using those radio resources, that is, it decides not to request a connection from the base station device that sent the report signal. On the other hand, for example, if the radio resources are not being used for a backhaul line, terminal device 604 decides to request a connection with the base station device that sent the report signal. In this way, terminal device 604 does not attempt to establish an access line using radio resources used in a backhaul line, thus easily ensuring the communication capacity of the backhaul line.

[0071] Furthermore, when the base station device 601 forms multiple beams 621 and 622 as described above, and each can provide an individual wireless link, it can also transmit a report signal containing the information described above to each of the multiple beams. For example, in Figure 1In the example, although a backhaul link is established for beam 621, no backhaul link is established for beam 622. In this case, base station device 601 sends a report signal in beam 621 containing information indicating that radio resources are being used for the backhaul link, and sends a report signal in beam 622 containing information indicating that radio resources are not being used for the backhaul link. In this case, terminal device 604 receives the report signal via at least one of these beams and determines whether to request a connection with base station device 601 based on the report signal. For example, if terminal device 604 can receive the report signals from both beams 621 and 622, since radio resources in beam 621 are used for the backhaul link, it determines that it will not request the establishment of a connection via beam 621 from base station device 601. On the other hand, since radio resources in beam 622 are not used for the backhaul link, terminal device 604 can request the establishment of a connection with base station device 601 via beam 622.

[0072] Additionally, base station device 601 can further transmit information indicating whether other base station devices within a defined range from its location are using radio resources for backhaul. Here, the defined range can be defined as the area where base station devices that a terminal device capable of receiving a report signal from base station device 601 can connect to are distributed. In one example, the defined range can be defined as a circle centered on base station device 601 with a radius twice the receivable distance of the signal transmitted by base station device 601. Furthermore, this information can also be transmitted via MIB, SIB, etc. Upon receiving this information, terminal device 604 can determine the base station device to request connection based on this information. That is, terminal device 604 can select a base station device that is not using radio resources for backhaul (or whose base station device can provide a beam for a radio link) and request connection establishment from that base station device. This avoids the terminal device attempting to establish an access line using radio resources for backhaul.

[0073] Furthermore, the terminal device 604 can exclude base station devices or beams that indicate the use of radio resources for the backhaul line from the targets of radio quality measurement for a certain period of time through the aforementioned reporting signal. Therefore, the terminal device 604 does not measure base station devices or beams that utilize radio resources in the backhaul line for a certain period of time, and thus does not request connection establishment.

[0074] The base station device 601 may further transmit conditions allowing the use of radio resources as an access line, for example. In one example, these conditions may also be transmitted via MIB, SIB, etc. The terminal device 604, upon meeting the notified conditions, can request connection establishment even if the radio resources are used for the backhaul. Here, in one example, the conditions may include at least one of the following: the amount of data transmitted or the speed of the requested data communication is below a specified value, or an emergency call. Thus, even if the radio resources are used for the backhaul, the base station device can establish a connection with the terminal device if the communication capacity of the backhaul is not significantly reduced, or in cases requiring urgent communication such as an emergency call. Furthermore, if all received report signals indicate that the radio resources are used for the backhaul, i.e., there are no radio resources in the vicinity not used for the backhaul, the terminal device can also connect to the base station device (or beam) using radio resources in the backhaul. In this case, the terminal device may also be configured to send a connection establishment request signal along with information indicating that there are no base station devices (or beams) in the vicinity not using radio resources in the backhaul. In addition, base station equipment can also allocate wireless resources to such terminal equipment without significantly reducing the communication capacity of the backhaul line.

[0075] If the usage of radio resources used for backhaul (e.g., cumulative usage over a certain period) exceeds a predetermined amount, the base station device 601 may also send a report signal containing information indicating that radio resources have been used for backhaul. That is, even if the base station device 601 is configured to use radio resources for backhaul, but its usage is below a predetermined amount, it can still send a report signal containing information indicating that no radio resources have been used for backhaul. Therefore, the base station device can allow connection establishment requests based on terminal devices when the amount of radio resources used for backhaul is low and communication capacity is sufficient. Furthermore, the base station device 601 can periodically count the usage of radio resources based on backhaul and periodically update the information in the report signal.

[0076] Furthermore, during a period corresponding to the amount of radio resources used for the backhaul, the base station device 601 can also send a report signal containing information indicating that radio resources have been used for the backhaul. For example, if the usage of radio resources for the backhaul is 30%, the base station device 601 can send a report signal containing first information indicating that radio resources have been used for the backhaul during a period of 30+α% (α≥0) of the total period. On the other hand, in this case, during the remaining 70–α% of the period, the base station device 601 can send a report signal containing second information indicating that radio resources have not been used for the backhaul. Thus, upon receiving the report signal containing the second information, the terminal device 604 can request a connection from the base station device 601. That is, through this method, the base station device can allow connection establishment requests based on the terminal device when the amount of radio resources used for the backhaul is small and the communication capacity is sufficient.

[0077] Hereinafter, examples of the configuration of the base station device and the terminal device performing the above-described processing and the processing flow will be described. Furthermore, the base station device described above can also be replaced by a relay device. For example, the relay device can transmit a report signal containing the above-described information to the wireless link formed by this device. That is, when a communication link is established including two or more relay devices, the relay device connected to other relay devices can transmit the above-described information in the report signal regarding the backhaul line established between these relay devices. In other words, the relay device according to this embodiment and the appended claims can be processed as the base station device described above.

[0078] (Device Composition)

[0079] The configuration of the base station device 601 and the terminal device 604 according to this embodiment will be described below. Furthermore, the hardware configuration of these devices is set to be the same as that of Embodiment 1. In addition, the communication circuit 205 of the base station device 101 can form one or more beams to wirelessly communicate with the relay device 602 and the terminal device 604. Furthermore, in this case, the communication circuit 205 of the terminal device 604 is configured to connect to the base station device 601 via at least one of the beams formed by the communication circuit 205 of the base station device 601, and via the relay device 602 (the beam formed by the relay device 602 as appropriate), and is configured to communicate with the base station device 601 through this connection. Furthermore, the base station device 601 may, for example, have a first communication circuit for wired communication with other base station devices 601, and a second communication circuit for wireless communication with the relay device 602 and the terminal device 604. In addition, the terminal device 604 may also have, for example, a first communication circuit for NR and a first communication circuit for LTE (Long Term Evolution). In addition, the terminal device 604 may also have wireless communication circuits related to standards other than cellular, such as wireless LAN, and may further have wired communication circuits used for wired connections, such as those based on USB connections.

[0080] Figure 7 This section describes a functional configuration example of a base station device 601. As an example, the base station device 601 includes a communication unit 701, a BH line usage determination unit 702, a report signal generation unit 703, a other base station information acquisition unit 704, and a condition storage unit 705. Furthermore, this functional configuration example is just one illustration; the base station device 601 may have other functions typical of base station devices, or it may not include these functions. Figure 7 Part of the functionality or, depending on the circumstances, not possessing it. Figure 7 All of its functions.

[0081] The communication unit 701 can wirelessly communicate with the relay device 602 and, depending on the situation, wirelessly communicate between the terminal devices 603 and 604. The communication unit 701 can, for example, follow the NR (New Radio) standard, a 5th generation communication standard, or LTE and other previous generation communication standards for wireless communication. Furthermore, the communication unit 701 can, for example, use an antenna array containing multiple antenna elements to form one or more beams with variable directional characteristics, but is not limited to this. For example, the communication unit 701 may not use an omnidirectional antenna to form a beam, or it may use an antenna with a fixed directional direction, such as a parabolic antenna, for communication. Depending on the situation, the communication unit 701 may also use a parabolic antenna to connect to the relay device 602, or use an omnidirectional antenna or antenna array to connect to surrounding terminal devices. Even in such cases, the terminal device 604 may receive signals transmitted from the beam radiated from the parabolic antenna, thus enabling it to perform the processing described in this embodiment.

[0082] The BH line usage determination unit 702 determines whether the base station device 601 uses radio resources for backhaul. In one example, the BH line usage determination unit 702 determines that radio resources are used for backhaul based on the establishment of a backhaul between the communication unit 701 and the relay device 602. Furthermore, the BH line usage determination unit 702 determines that radio resources are used for backhaul based on the establishment of a backhaul between the communication unit 701 and the relay device 602 in the first of the multiple formed beams. In addition, in this case, the BH line usage determination unit 702 can determine that radio resources are not used for backhaul for a second beam, which is different from the first beam, as long as no backhaul has been established with other relay devices. Furthermore, the BH line usage determination unit 702 can monitor the actual usage of radio resources in the established backhaul and determine that radio resources are used for backhaul if the usage exceeds a predetermined amount. In this case, the BH line usage determination unit 702 can determine that the radio resources are not used for the backhaul when the usage is below a predetermined amount, or when the usage is below a second predetermined amount that is even smaller than the predetermined amount. Furthermore, when using the second predetermined amount, or when the usage is below but exceeds the predetermined amount, the BH line usage determination unit 702 can also determine whether the radio resources are used for the backhaul within a period corresponding to the usage amount. Moreover, the period corresponding to the usage amount can be a length that has a positive correlation with, for example, proportionality, to the ratio of the amount of usable radio resources to the actual usage. In this case, the BH line usage determination unit 702 outputs a determination result indicating that the radio resources are used for the backhaul within the period corresponding to the usage amount, and outputs a determination result indicating that the radio resources are not used for the backhaul during other periods. Additionally, even when the usage exceeds the predetermined amount or is below the second predetermined amount, the BH line usage determination unit 702 can still determine whether the radio resources are used for the backhaul within the period corresponding to the usage amount. That is, the BH line usage determination unit 702 can decide that the radio resources are used for the backhaul line for the entire period if the usage exceeds the aforementioned predetermined amount, or it can decide that the radio resources are used for the backhaul line for a period of length corresponding to the usage without setting an upper limit such as the predetermined amount. Similarly, the BH line usage determination unit 702 can decide that the radio resources are not used for the backhaul line for the entire period if the usage is below the second predetermined amount, or it can decide not to set a lower limit such as the second predetermined amount.

[0083] The report signal generation unit 703 uses the determination result of the BH line usage determination unit 702 to set the value of a field indicating whether radio resources are used for backhaul, and generates a report signal. For example, the report signal generation unit 703 sets the value of this field to "1" based on the determination result that radio resources are used for backhaul, and sets the value of this field to "0" based on the determination result that radio resources are not used for backhaul. Alternatively, the value of this field can be "0" to indicate that radio resources are not used for backhaul. When multiple beams are formed in the communication unit 701, the report signal generation unit 703 can generate a separate report signal for each beam, and can set the field indicating whether radio resources are used for backhaul for each beam. Furthermore, the report signal generation unit 703 can also include information acquired by the other base station information acquisition unit 704 (described later) regarding whether radio resources are used for backhaul in other base station devices (and beams formed by those base station devices) in the report signal. In this case, the report signal generation unit 703 may include only information about other base station devices / beams whose radio resources are not used for the backhaul line in the report signal, or it may include only information about other base station devices / beams whose radio resources are used for the backhaul line in the report signal. Alternatively, the report signal generation unit 703 may also include the conditions stored in the condition storage unit 705 (described later) that allow the terminal device to request a connection to radio resources used for the backhaul line in the report signal.

[0084] The other base station information acquisition unit 704 acquires information from other base station devices within a predetermined range from the base station device 601 regarding whether radio resources are used for backhaul. For example, the other base station information acquisition unit 704 receives information from other base station devices via wired or wireless communication using an X2 or Xn interface regarding whether radio resources are used for backhaul in that base station device (or the beam formed by that base station device). Furthermore, the other base station information acquisition unit 704 can acquire, for example, at least one of the identification information of the base station device using radio resources for backhaul and the identification information of the beam. Additionally, the base station device 601 itself can also transmit information to other base station devices regarding whether it uses radio resources for backhaul or its own identification information. Furthermore, when the base station device 601 forms multiple beams, it can transmit identification information of the beams using radio resources for backhaul. Moreover, the predetermined range can be, for example, a circle centered on the base station device 601 with a radius equal to twice the receivable distance of the signal transmitted by the base station device 601. Alternatively, the defined range may be set as a range from the location where the base station device 601 can receive signals transmitted in a beam using radio resources for backhaul, to a location far away from a predetermined distance determined by the power that a typical base station device can use when transmitting signals. Alternatively, the defined range may be the range of cells registered as adjacent to the base station device 601 (or the formed beam). In this case, the other base station information acquisition unit 704 can acquire some or all of the aforementioned information from the base station devices corresponding to the cells registered in the neighboring cell list.

[0085] The other base station information acquisition unit 704 can acquire the aforementioned information by requesting information from other base station devices within a specified range, or it can receive information periodically sent from other base station devices without making a request. Information related to these other base station devices is input to the report signal generation unit 703, which can generate a report signal based on this information. At this time, the report signal generation unit 703 can generate a report signal, thereby sending general information about other base station devices located far from base station device 601, and detailed information about other base station devices located near base station device 601. For example, for information about other base station devices located near base station device 601, information about each of the beams formed by these base station devices can be included in the report signal. On the other hand, for distant base station devices, if any one of the multiple beams uses radio resources for backhaul, information indicating that radio resources are used for backhaul in that base station device can be included in the report signal. Thus, the information sent can differ depending on the distance from base station device 601. Furthermore, information about other base station devices is not necessary, and the other base station information acquisition unit 704 can be omitted.

[0086] When the radio resources are used for the backhaul, the condition storage unit 705 stores conditions that allow the radio resources to be used as access lines. These conditions may include, for example, at least one of the following: the data transmission volume or the requested data communication speed is below a specified value, or it may be an emergency call. That is, conditions may include communication that does not strain the communication capacity of the backhaul, or a situation requiring an emergency connection. Furthermore, the conditions may be appropriately set by the communication operator managing the base station device 601, and conditions other than data volume / communication speed and whether it is an emergency call may also be set. The report signal generation unit 703 can generate a report signal containing information about the conditions stored in the condition storage unit 705 as needed. Furthermore, if specific conditions such as emergency calls are set commonly by all communication operators, these common conditions may not be included in the report signal. This is because such conditions can be preset in the terminal device. Additionally, the base station device 601 may also refuse all connection requests to the radio resources used for the backhaul without using the aforementioned conditions; in this case, the condition storage unit 705 can be omitted.

[0087] Next, use Figure 8An example of the functional configuration of the terminal device 604 will be described. In one example, the terminal device 604 includes a communication unit 801, a connection determination unit 802, and a connection destination determination unit 803. Furthermore, this functional configuration is just one example; the terminal device 604 may have other functions typical of a terminal device, or it may not have these functions. Figure 8 Part of the functionality or, depending on the circumstances, not possessing it. Figure 8 All of its functions. Furthermore, the terminal device 603 may also have the same functional configuration.

[0088] Communication unit 801 communicates wirelessly with base station device 601 and relay device 602. Communication unit 701 can, for example, communicate wirelessly according to NR (New Radio) standard, which is a 5th generation communication standard, LTE, and other previous generation communication standards.

[0089] The connectivity determination unit 802 analyzes the report signal received via the communication unit 801 and determines whether the radio resource that sent the report signal is used for backhaul. For example, the connectivity determination unit 802 can identify a specific field within the report signal and make the determination based on which bit ("0" or "1") is set in that field. Furthermore, when the base station device 601 receives report signals through multiple beams and receives at least a portion of these report signals, the connectivity determination unit 802 determines whether the radio resource for each beam is used for backhaul. Then, for example, the connectivity determination unit 802 does not request the establishment of an access line for the base station device or beam whose radio resource is used for backhaul.

[0090] Furthermore, if the report signal describes the conditions for requesting the establishment of an access line, the connectivity determination unit 802 acquires and saves the information of those conditions. Then, when the terminal device 604 attempts to connect to the network, the connectivity determination unit 802 determines whether the conditions obtained through communication performed via that connection are met. The connectivity determination unit 802 can then be configured not to request the establishment of an access line from a base station device or beam whose radio resources are used for backhaul, if the communication performed by the terminal device 604 does not meet the conditions. On the other hand, the connectivity determination unit 802 determines that, for a base station device or beam whose radio resources are used for backhaul, the communication performed by the terminal device 604 meets the conditions, and allows the request to establish an access line from that base station device or beam. Here, as described above, the conditions may include, for example, data volume, communication speed, emergency calls, etc.

[0091] Furthermore, in one example, the connectivity determination unit 802 may exclude base station devices or beams that do not request the establishment of access lines from the targets of wireless quality measurement for a certain period of time. This is because the terminal device 604 does not request connection for base station devices or beams excluded from the targets of wireless quality measurement.

[0092] If the connection destination determination unit 803 receives a report signal from base station device 601 (or the beam formed by base station device 601) containing information about whether radio resources in other base station devices are used for backhaul, it acquires and stores this information. Then, based on this acquired information about other base station devices, the connection destination determination unit 803 determines the base station device or beam from which the establishment of the access line (connection destination) is requested. The connection destination determination unit 803 may be configured not to request the establishment of an access line for, for example, other base station devices whose radio resources are used for backhaul or beams formed by those base station devices. That is, the connection destination determination unit 803 can determine the connection destination from base station devices or beams whose radio resources are not used for backhaul, for example, based on radio quality. Therefore, the terminal device 604 can select surrounding base station devices or beams formed by these base station devices that are not used for backhaul and request the establishment of an access line for that selected target.

[0093] Furthermore, if no other base station devices or relay devices are available for connection to the surrounding area, the terminal device 604 may request a connection from a base station device whose radio resources are being used for backhaul. In this case, the terminal device 604 may, for example, include information indicating that no devices are available for connection to the surrounding area in the connection request signal. The base station device 601 may allow the terminal device 604 to connect to the terminal device 604 containing such information. However, the base station device 601 may also prioritize backhaul or may be configured to provide communication services to the terminal device 604 using radio resources not used in the backhaul.

[0094] (Processing flow)

[0095] Next, several examples of the processing flow performed in the wireless communication system according to this embodiment will be described. Furthermore, in the following examples, the reporting signal is provided with a 1-bit "BH Usage" field indicating whether wireless resources are used for backhaul, and the value of this field is "1" to indicate that wireless resources are used for backhaul.

[0096] Figure 9This is a first example of the process flow executed in the wireless communication system according to this embodiment. In this process, the base station device 601 establishes a backhaul line with the relay device 602 (S901). In this case, the base station device 601 periodically sends a report signal in which the "BH Usage" field is set to "1" (S902). This report signal is received by some or all of the communication devices (e.g., the relay device 602 and the terminal device 604) capable of receiving signals sent from the base station device 601. Furthermore, in the case of forming multiple beams, the base station device 601 can independently send a report signal in each of the multiple beams to determine whether wireless resources are used for the backhaul line. In addition, the base station device 601 can set the "BH Usage" field to "1" from the moment the process for establishing the backhaul line begins, or it can set the "BH Usage" field to "1" after the process ends and the backhaul line is established. When the terminal device 604 receives the report signal, it extracts the value set in the "BH Usage" field. Furthermore, in this case, since "1" is set, the terminal device 604 can determine that the radio resources are used for the backhaul line from the source of the report signal (i.e., the base station device 601). Then, based on this determination, the terminal device 604 decides not to make a connection request to the base station device 601 (S903).

[0097] Subsequently, the base station device 601 is configured to disconnect the backhaul line established with the relay device 602 (S904). Based on the disconnection of the backhaul line, the base station device 601 sets the "BH Usage" field in the report signal to "0". Alternatively, the base station device 601 may set the "BH Usage" field to "0" at the moment the backhaul line disconnection process begins. The base station device 601 sends a report signal indicating that the "BH Usage" field is set to "0" (S905). Upon receiving this report signal, the terminal device 604 extracts the value set in the "BH Usage" field. Then, in this case, since it is set to "0", the terminal device 604 can determine from the source of the report signal (i.e., the base station device 601) that the radio resources are not being used for the backhaul line. Based on this determination, the terminal device 604 decides to allow the base station device 601 to request the establishment of an access line (S906). Then, the terminal device 604 may request a connection to the base station device 601 whose radio resources are not used for the backhaul line as needed (S907).

[0098] Furthermore, the base station device 601 can also send a report signal setting the "BH Usage" field to "0" while maintaining the established backhaul link with the relay device 602. For example, the base station device 601 monitors the actual traffic volume on the established backhaul link, and if the traffic volume is less than a predetermined amount, it can set the "BH Usage" field to "0". Additionally, the base station device 601 can set the period for setting the "BH Usage" field to "0" and the period for setting it to "1" according to a time ratio corresponding to the traffic volume. That is, the base station device 601 can set a period for accepting connection requests from terminal devices and a period for not accepting them based on the actual traffic volume on the backhaul link. In this case, the terminal device 604 can determine whether to set the connection destination as the base station device 601 or another base station device or relay device based on the value of the "BH Usage" field in the report signal received during the period when the access link should be established. According to this method, based on the utilization rate of the backhaul line in the base station device 601, an appropriate number of terminal devices can be allowed to access the system without generating an unnecessary large number of terminal devices accessing the system.

[0099] In this way, the terminal device 604 can identify whether the base station device 601 is using radio resources for backhaul by monitoring the specified fields of the report signal sent by the base station device 601. Furthermore, since the terminal device 604 does not request a connection while the base station device 601 is using radio resources for backhaul, it can prevent the communication capacity of the backhaul from being reduced due to the establishment of the access line. Additionally, because the terminal device 604 does not make connection requests, the processing burden in the base station device 601 can also be reduced.

[0100] Next, use Figure 10The following is a second example illustrating the processing flow performed in a wireless communication system. In this example, the report signal, based on information that wireless resources are used for backhaul, also notifies the conditions under which a connection request is permitted. Furthermore, for example, multiple conditions can be predefined, and if any one of these conditions is met, information regarding whether a connection request is permitted can be included in the report signal. For example, a three-bit condition specification field can be prepared in the report signal: a "1" in the first bit if the amount of data to be communicated is below a specified value; a "1" in the second bit if the requested communication speed is below a specified value; and a "1" in the third bit if an emergency call is present. In this case, setting a "0" indicates that the connection request is not permitted even if the condition corresponding to the bit with the "0" set is met. For example, setting this field to "011" indicates that the connection request is not permitted even with a small amount of data, but is permitted when the communication speed is below a specified value or in the case of an emergency call. Furthermore, the specified values ​​related to the amount of data and the communication speed can be either predetermined fixed values ​​or specified in other fields within the report signal. For example, after the aforementioned three-bit field, a field indicating the amount of data in bits or the communication speed can also be set. Furthermore, in this case, if the amount of data or the communication speed is not used as a condition, the field indicating the amount of data or the communication speed can be omitted.

[0101] exist Figure 10 In, with Figure 9 Similarly, a backhaul line is established between base station device 601 and relay device 602 (S901). In this case, base station device 601 sets the aforementioned "BH usage" field to "1" and sends a report signal containing information on the conditions for allowing a connection request (S1001). When terminal device 604 receives this report signal, it first checks the "BH usage" field, and if the value of this field is "0", it determines that the connection request is allowed. On the other hand, in Figure 10 In this case, since the value of the "BH usage" field is set to "1", the terminal device 604 then obtains information on the conditions for allowing the connection request. Then, when requesting the establishment of an access line, the terminal device 604 determines whether the obtained conditions are met (S1002). If the conditions are met, it can request a connection to the base station device 601. Furthermore, if the conditions are not met, the terminal device 604 is configured not to make such a connection request to the base station device 601, but instead to make a connection request to, for example, other base station devices or relay devices. Thus, for terminal devices 604 that meet the limiting conditions such as situations that do not significantly affect the communication capacity of the backhaul line or emergency calls, the connection is allowed, thereby providing necessary communication services to the terminal device while maintaining the quality of the backhaul line.

[0102] Next, use Figure 11 The following is a third example of the processing flow performed in a wireless communication system. In this example, the base station device 601 transmits information in its reporting signal, including whether wireless resources are used for backhaul, not only in its own device but also in other surrounding base station devices (relay devices, depending on the situation) (S1101). Based on this information, the terminal device 604 determines the base station device or relay device as the connection destination (S1102). For example, the terminal device 604 can determine a device among the surrounding base station devices or relay devices that does not use wireless resources for backhaul and whose wireless quality is above a specified value as the connection destination. In this case, for example, regarding devices that use wireless resources for backhaul, by excluding them from the wireless quality measurement targets, unnecessary measurements of beams that do not allow connection requests are not required, thus reducing power consumption and processing load.

[0103] As described above, the base station device 601 sends a report signal indicating whether radio resources are being used for the backhaul, eliminating the need for the terminal device 604 to make unnecessary connection requests to the base station device 601. Therefore, the communication capacity and quality of the backhaul can be maintained at a high level. Furthermore, "whether radio resources are being used for the backhaul" can also be expressed as "whether connection requests based on the terminal device 604 are allowed," and the primary reason for allowing a connection request is not necessarily whether it is used in the backhaul. That is, the above-described configuration and processing can be applied in all situations where it is necessary to avoid unnecessary connection requests based on the terminal device 604.

[0104] According to this embodiment, it is possible to prevent the terminal device from making unnecessary access to the backhaul line between the base station device and the relay device.

[0105] The above describes representative configurations and processing flows involved in this embodiment. However, these are merely examples, and various modifications and variations of the embodiments described in this specification within the scope of the claims are naturally included within the scope of the present invention.

[0106] This invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, in order to disclose the scope of the invention, the following claims are appended.

[0107] This application claims priority based on Japanese Patent Application No. 2018-029466, filed on February 22, 2018, and Japanese Patent Application No. 2018-054512, filed on March 22, 2018, the entire contents of which are incorporated herein by reference.

Claims

1. A first relay device that is a first relay device in a wireless communication system including a control device, a first relay device, and a second relay device, characterized by, the first relay device and the second relay device performing relaying between at least a part of a communication link involved in communication performed by the control device, the first relay device performing relaying between at least a part of the communication link between the control device and the second relay device in the communication link, the first relay device transmitting, to the control device, information indicating a case where disconnection of at least a part of an interval between the control device and the first relay device in the communication link is detected.

2. The first relay device according to claim 1, characterized by, the first relay device transmitting the information to the control device through a wireless communication line different from the communication link.

3. The first relay device according to claim 2, characterized by, the second relay device receiving, from the control device, a signal indicating reconfiguration of the communication link of the interval in the communication link where disconnection is detected, through a wireless communication line different from the communication link.

4. The first relay device according to claim 1, characterized by, the control device transmitting the information received from the first relay device to another relay device different from the first relay device.

5. The first relay device according to claim 1, characterized by, the control device transmitting the information indicating the case where disconnection of a communication interval with the first relay device is detected to the second relay device.

6. The first relay device according to claim 2, characterized by, the first relay device transmitting the information to the control device using a communication line of long term evolution.

7. A communication method performed by a first relay device in a wireless communication system including a control device, the first relay device, and a second relay device, characterized by, the first relay device and the second relay device performing relaying between at least a part of a communication link involved in communication performed by the control device, the first relay device performing relaying between at least a part of the communication link between the control device and the second relay device in the communication link, the communication method including: the first relay device transmitting, to the control device, information indicating a case where disconnection of at least a part of an interval between the control device and the first relay device in the communication link is detected.

8. A storage medium storing a program for causing a computer to function as the first relay device according to any one of claims 1 to 6.

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