Relay device, control method, and program

Abstract

This invention provides technology for properly performing relay communication using relay devices. [Solution] A relay device that communicates with a first communication device and a second communication device includes: a receiving means for receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device; a first determination means for determining the usage status of the communication path based on the first message; and a transmitting means for transmitting a second message to the second communication device according to the usage status.

Description

Technical Field

[0001] The present disclosure relates to a relay device, a control method, and a program.

Background Art

[0002] In the 3rd Generation Partnership Project (3GPP (registered trademark): 3rd Generation Partnership Project), cellular communication standards (also referred to as 3GPP standards) have been established. In recent years, the specifications of LTE (Long Term Evolution) and NR (New Radio) of 3GPP have been in progress. Among these, a standard specification called sidelink communication (hereinafter, simply referred to as sidelink) has been established. This specification realizes direct wireless communication between communication terminals using an interface called PC5. Communication terminals are also referred to as terminal devices, terminals, user devices, UEs (User Equipment), etc.

[0003] In ProSe (Proximity based Services), which is the communication standard for NR sidelink, the standardization of 5G ProSe UE-to-UE Relay is in progress. UE-to-UE Relay is a mechanism in sidelink communication where two communication terminals (End UEs) directly communicate without going through a base station, and a relay device (also described as Relay) relays the communication between wireless terminals. By relaying the communication, it becomes possible to extend the communication distance between communication terminals.

[0004] The UE-to-UE Relay standard is described in Non-Patent Document 1. By 3GPP Release 18 (Rel-18), link release and link changes for single-hop UE-to-UE Relay using one relay device have been standardized. Discussions are now underway for Release 19 (Rel-19) regarding functional enhancements to single-hop UE-to-UE Relay using one relay device, and for UE-to-UE Relay using multiple relay devices (also called multi-hop UE-to-UE Relay). In this specification and drawings, release may be replaced with disconnection. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS 23.304, Proximity based Services (ProSe) in the 5G System (5GS) [Overview of the project] [Problems that the invention aims to solve]

[0006] Existing standards specify the following regarding link release processing in UE-to-UE Relay: Specifically, in link release processing, a relay device that receives a Disconnect Request modifies the message it sends depending on the usage status of the link it forms (or establishes or constructs) with the destination End UE. If only the End UE that sent the Disconnect Request is using the link, the relay device sends a Disconnect Request. If other End UEs are also using the link, the relay device sends a Link Modification Request. In this specification and drawings, "Disconnect Request" and "Disconnect Request Message" are used interchangeably, and "Link Modification Request" and "Link Modification Request Message" are used interchangeably. The same applies to other messages.

[0007] When the above process is implemented in a multi-hop UE-to-UE Relay, the second relay device receives messages sent by the first relay device according to the link usage status. In this case, the behavior of the relay device when it receives a link change request during the UE-to-UE Relay's link release process is not specified and is not clearly defined. If this behavior is not clearly defined, it may not be possible to properly perform relay communication using relay devices.

[0008] One aspect of this disclosure, in view of the above, aims to provide a technology for appropriately performing relay communication using a relay device. [Means for solving the problem]

[0009] A relay device according to one aspect of the present disclosure is a relay device that communicates with a first communication device and a second communication device, and includes: receiving means for receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device; first determination means for determining the usage status of the communication path based on the first message; and transmitting means for transmitting a second message to the second communication device according to the usage status. [Effects of the Invention]

[0010] According to one aspect of this disclosure, relay communication using a relay device can be performed appropriately. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing an example of the hardware configuration of a relay device according to an embodiment. [Figure 2] This is a block diagram showing an example of the functional configuration of a relay device according to an embodiment. [Figure 3] This is a diagram showing an example configuration of a communication system according to the embodiment. [Figure 4]This is a sequence diagram showing an example of the link release process for a multi-hop UE-to-UE Relay according to the first embodiment. [Figure 5] This figure shows an example of processing by the relay device according to the first embodiment. [Figure 6] This figure shows an example of processing by a relay device according to the second embodiment. [Modes for carrying out the invention]

[0012] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the scope of the claims. While the embodiments describe multiple features, not all of these features are essential to this disclosure, and the features may be combined in any way. Furthermore, in the attached drawings, the same or similar configurations may be given the same reference numeral, and redundant descriptions may be omitted. Also, the technical scope of this disclosure is determined by the claims and is not limited by the following individual embodiments.

[0013] [Summary of the Embodiment] As described in detail below, the relay device communicates (e.g., sidelink communication) with a first communication device (e.g., End UE) and a second communication device (e.g., another relay device). The relay device receives a first message (e.g., Link Modification Request) from the first communication device requesting a change in the communication path between the first communication device and the second communication device (via the relay device). The relay device determines the usage status of the communication path (e.g., based on the virtual transmission path included in the communication path (e.g., QoS (Quality of Service) flow)). The relay device sends a second message (e.g., Link Modification Request or Disconnect Request) to the second communication device according to the determined usage status. In this way, the relay device can properly perform relay communication by sending a second message according to the usage status of the communication path when it receives a first message requesting a change in the communication path.

[0014] [First Embodiment] This embodiment describes the message transmission process of the relay device in the link release sequence of a multi-hop UE-to-UE Relay.

[0015] (Configuration of the relay device) Figure 1 is a block diagram showing an example of the hardware configuration of the relay device according to this embodiment. The relay device according to this embodiment is a relay device (relay terminal) that relays sidelink communication between terminals to extend the coverage of sidelink communication.

[0016] As shown in Figure 1, the hardware configuration 101 of the relay device includes, for example, a control unit 102, a storage unit 103, a wireless communication unit 104, a communication antenna control unit 105, a GPS communication unit 106, and a GPS antenna control unit 107.

[0017] The control unit 102 is composed of, for example, one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 102 controls the entire relay device by executing, for example, a control program stored in the storage unit 103 (the control program read into the RAM (Random Access Memory)). Each process performed by the control unit 102 described later using the flowchart can also be realized using a hardware circuit such as an ASIC or an FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit, and FPGA is an abbreviation for Field Programmable Gate Array. Also, by the cooperation of the hardware circuit and processors such as the CPU and MPU, the processes described later using the flowchart can be realized.

[0018] The storage unit 103 stores the control program executed by the control unit 102 and various types of information such as cell information and connection terminal information. The storage unit 103 may include a main storage unit and an auxiliary storage unit. The main storage unit is, for example, a ROM (Read Only Memory), a RAM, etc. The main storage unit may store or temporarily store programs and data such as an OS (Operating System), which is basic software executed by the control unit 102, and application software. The auxiliary storage unit is, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), etc., and may store data related to application software, etc. For example, a control program stored in a non-volatile storage area is expanded into the RAM and executed by a processor constituting the control unit 102. Thus, the control unit 102 and the storage unit 103 may function as a so-called computer.

[0019] The wireless communication unit 104 performs cellular communications such as LTE (Long Term Evolution) and 5G (NR) compliant with the 3GPP standard. In various embodiments including this embodiment, 5G will be described. However, the present disclosure is also applicable to those other than 5G (for example, next-generation mobile communication systems such as 5G Advanced and 6G, LTE, LTE-Advanced, combinations thereof, etc.).

[0020] The communication antenna control unit 105 controls the antennas for wireless communication performed by the wireless communication unit 104. For example, the communication antenna control unit 105 controls the antennas so as to switch the directivity direction of the antennas.

[0021] The GPS communication unit 106 receives satellite signals from GPS (Global Positioning System) satellites and acquires position information of the current position including position identification information such as longitude and latitude information, current time information, etc. Note that the GPS communication unit 106 may have a function of measuring (positioning) the current position based on the satellite signals. Note that, instead of or in addition to GPS, other GNSS (Global Navigation Satellite System) may be used.

[0022] The GPS antenna control unit 107 controls the antennas for GPS communication performed by the GPS communication unit 106.

[0023] FIG. 2 is a block diagram showing a functional configuration example of the relay device according to this embodiment. The functional blocks shown in FIG. 2 are realized by software.

[0024] The software function 200 shown in FIG. 2 includes a signal transmission unit 201, a signal reception unit 202, a data storage unit 203, a connection control unit 204, a message type determination unit 205, a link usage status determination unit 206, a transmission message determination unit 207, and a relay end determination unit 208.

[0025] The signal transmitting unit 201 and the signal receiving unit 202 perform cellular communication such as LTE and 5G (NR) in accordance with 3GPP standards with the communication device. Link release request messages and link change request messages, which will be described later, are transmitted and received by the signal transmitting unit 201 and the signal receiving unit 202. The signal transmitting unit 201 and the signal receiving unit 202 may also be called the (signal) transmitting / receiving unit, the (signal) communication unit, etc.

[0026] The data storage unit 203 stores and retains information about the software (program) and the connected terminal.

[0027] The connection control unit 204 controls side link connections, relay connections, etc., with other communication devices.

[0028] The message type determination unit 205 determines the message type of the link change request received from the communication device forming the UE-to-UE Relay.

[0029] The link usage determination unit 206 determines the usage status of the link (in other words, the communication path) with the communication device forming the UE-to-UE Relay. The method for determining the link usage status will be described later.

[0030] When the message sending determination unit 207 receives a link change request message (or a link release request message), it determines the message to send based on the determinations of the message type determination unit 205 and the link usage status determination unit 206.

[0031] The relay termination decision unit 208 decides whether or not to terminate the UE-to-UE Relay relay based on the determination of the link usage status determination unit 206. The conditions for determining the termination of the relay will be described in the second embodiment.

[0032] Furthermore, some (or sometimes all) of the described functional blocks may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or further functional blocks may be added. Also, one functional block may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block. In addition, only some of the functional blocks may be configured in hardware, with the remaining functions configured in software. When a functional block is configured in software, the processor constituting the control unit 102 shown in Figure 1 executes a control program to realize the function stored in the storage unit 103 shown in Figure 1. This provides the function of that functional block.

[0033] Figure 3 shows an example configuration of the communication system according to this embodiment. In the example shown in Figure 3, each of the two End UEs (the pair of End UE301 and End UE302, and the pair of End UE305 and End UE306) forms two UE-to-UE Relays using a common relay device.

[0034] End UE301 and End UE302 form a UE-to-UE Relay via relay devices 303 and 304. This UE-to-UE Relay is connected by a single QoS flow. A QoS flow is a virtual transmission path generated for each QoS unit. A QoS flow is identified by identification information or an identifier called QFI (QoS Flow Identifier). Here, the QFI of this QoS flow is set to 1.

[0035] End UE305 and End UE306 form a UE-to-UE Relay via relay devices 303 and 304. This UE-to-UE Relay is connected by two QoS flows. The QFIs of these QoS flows are set to 2 and 3.

[0036] The communication path between relay device 303 and relay device 304 includes the QoS flows (QFI=1~3) of these two UE-to-UE Relays.

[0037] Next, we will explain the Link Modification Request message. The Link Modification Request message is an example of a message that requests a change in the communication path.

[0038] The Link Modification Request message format used in this embodiment is the message format specified in TS 24.554. Specifically, the Link Modification Request includes a Link modification operation code information element, a PC5 QoS flow descriptions information element, and the like.

[0039] A Link Modification Request is used to add a QoS flow to an existing link, or to modify or delete an existing QoS flow. These additions, modifications, and deletions are distinguished by specifying the message type. The message type is specified in the Link modification operation code field of the Link modification operation code information element. For example, when End UE deletes a QoS flow, it specifies a value indicating the deletion of the QoS flow (5 (decimal):0101 (binary)) as the message type. Then, End UE stores the QFI of the QoS flow to be deleted in the PQFI field of the PC5 QoS flow description in the PC5 QoS flow descriptions information element. PQFI is an abbreviation for PC5 QoS Flow Identifier. A relay device that receives a Link Modification Request message can determine from the message type and PQFI contained in the message that a deletion of a QoS flow is being requested, and which QFI to be deleted.

[0040] Next, we will explain how the relay device determines the link usage status and decides what to do with the link.

[0041] The link usage status is determined (or judged) by the link usage status determination unit 206 based on the QoS flow included in the link and the QFI to be deleted specified in the link change request message.

[0042] If only the QoS flow that was requested to be deleted in the link change request exists on the link, the relay device can determine that there are no other End UEs using this link other than the End UE that issued the link change request. In this case, the relay device decides to release the link and sends a link release request message to the communication devices forming the link.

[0043] If a link change request includes both a QoS flow that has been requested to be deleted and other QoS flows, the relay device can determine that there are other End UEs using the link besides the End UE that issued the link change request. In this case, the relay device decides not to release the link and to delete only the specified QoS flow. The relay device sends a link change request message to the communication devices that form the link.

[0044] If the QoS flow requested to be deleted in a link change request does not exist on the link, the relay device can determine that the End UE that issued the link change request is not using this link. In this case, the relay device decides not to take any special action on this link. The relay device does not send a message to the communication devices that form the link.

[0045] The relay device can also handle the situation similarly when the End UE sends a link release request message. However, in this case, all QoS flows included in the link will be deleted. A link release request message is an example of a message requesting the disconnection of the communication path.

[0046] Next, Figure 3 will be used to illustrate an example of the process flow for releasing links in a multi-hop UE-to-UE Relay.

[0047] First, we will explain the case where End UE301 sends a link release request to relay device 303.

[0048] As described above, in a link release request, all QoS flows included in the link are subject to deletion. The relay device 303 obtains the QFI (QFI=1) to be deleted.

[0049] Next, the relay device 303 checks the usage status of the links it forms with End UE 305 and the links it forms with relay device 304.

[0050] Since the link formed with End UE305 does not contain the QFI to be deleted, relay device 303 decides not to process this link. Therefore, relay device 303 does not send a message to End UE305.

[0051] Since the link formed with relay device 304 includes both the QFI to be deleted and the other QFIs, relay device 303 decides not to release the link and to delete only the QFI to be deleted. Therefore, relay device 303 sends a link change request message (Type: QoS flow deletion, PQFI: 1) to relay device 304.

[0052] Upon receiving a link change request message, relay device 304 obtains the message type and the QFI to be deleted (QFI=1) from the received message. Then, relay device 304 checks the usage status of the links it forms with End UE 302 and End UE 306.

[0053] Since the link formed with End UE302 contains only the QFI to be deleted, relay device 304 decides to release this link. Therefore, relay device 304 sends a link release request message to End UE302.

[0054] Since the link formed with End UE306 does not contain the QFI to be deleted, relay device 304 decides not to process this link. Therefore, relay device 304 does not send a message to End UE306.

[0055] Next, we will describe the case where End UE305 sends a link change request (Type: QoS flow deletion, PQFI: 2) to relay device 303.

[0056] The relay device 303 obtains the message type and the QFI to be deleted (QFI=2) from the received message. Then, the relay device 303 checks the usage status of the links it forms with End UE 301 and the links it forms with relay device 304.

[0057] Since the link formed with End UE301 does not contain the QFI to be deleted, relay device 303 decides not to process this link. Therefore, relay device 303 does not send a message to End UE301.

[0058] Since the link formed with relay device 304 includes both the QFI to be deleted and the other QFIs, relay device 303 decides not to release the link and to delete only the QFI to be deleted. Therefore, relay device 303 sends a link change request message (Type: QoS flow deletion, PQFI: 2) to relay device 304.

[0059] Upon receiving a link change request message, relay device 304 obtains the message type and the QFI to be deleted (QFI=2) from the received message. Then, relay device 304 checks the usage status of the links it forms with End UE 302 and End UE 306.

[0060] Since the link formed with End UE302 does not contain the QFI to be deleted, relay device 304 decides not to process this link. Therefore, relay device 304 does not send a message to End UE302.

[0061] Since the link formed with End UE306 includes both the QFI to be deleted and the other QFIs, relay device 304 decides not to release the link and to delete only the QFI to be deleted. Therefore, relay device 304 sends a link change request message (Type: QoS flow deletion, PQFI: 2) to End UE306.

[0062] Figure 4 is a sequence diagram showing an example of the link release process for a multi-hop UE-to-UE Relay according to this embodiment.

[0063] End UE301 and relay device 303 form a unicast link (400a). Relay device 303 and relay device 304 form a unicast link (400b). Relay device 304 and End UE302 form a unicast link (400c).

[0064] End UE301 sends a Disconnect Request message to relay device 303 (S401).

[0065] When relay device 303 receives a Disconnect Request, it responds with a Disconnect Response and deletes all context data associated with the unicast link (400a) (S402). The Disconnect Response may also be called a link release response or link release response message.

[0066] Next, the relay device 303 checks the usage status of the unicast link (400b) it has formed with the relay device 304.

[0067] If other UEs are not using a unicast link (400b), relay device 303 sends a Disconnect Request message to relay device 304 (S403a).

[0068] When relay device 304 receives a Disconnect Request, it responds with a Disconnect Response and deletes all context data associated with the unicast link (400b) (S404a).

[0069] Next, the relay device 304 checks the usage status of the unicast link (400c) it has formed with End UE 302.

[0070] If other UEs are not using a unicast link (400c), the relay device 304 sends a Disconnect Request message to End UE 302 (S405a).

[0071] When End UE302 receives a Disconnect Request, it responds with a Disconnect Response, deleting all context data associated with the unicast link (400c) (S406a).

[0072] If another UE is using a unicast link (400c), the relay device 304 sends a Link Modification Request to End UE 302 (S405b).

[0073] When End UE302 receives a Link Modification Request, it checks the message type. If the message type indicates QoS flow deletion, End UE302 responds with Link Modification Accept and deletes all context data associated with the unicast link (400c) (S406b).

[0074] If another UE is using a unicast link (400b), relay device 303 sends a Link Modification Request to relay device 304 (S403b).

[0075] When relay device 304 receives a Link Modification Request, it checks the message type. If the message type indicates QoS flow deletion, relay device 304 checks the usage status of the unicast link (400c) it has formed with End UE 302.

[0076] If other UEs are not using a unicast link (400c), the relay device 304 sends a Disconnect Request to End UE 302 (S405a).

[0077] When End UE302 receives a Disconnect Request, it responds with a Disconnect Response, deleting all context data associated with the unicast link (400c) (S406a).

[0078] If another UE is using a unicast link (400c), the relay device 304 sends a Link Modification Request to End UE 302 (S405b).

[0079] When End UE302 receives a Link Modification Request, it checks the message type. If the message type indicates QoS flow deletion, End UE302 responds with Link Modification Accept and deletes all context data associated with the unicast link (400c) (S406b).

[0080] When relay device 304 receives Link Modification Accept, it responds to relay device 303 with Link Modification Accept (S404b). Then, relay device 304 deletes all context data associated with the unicast link (S404b).

[0081] Next, we will describe an example of a processing flow in which a relay device selects a message to send to the next communication device when it receives a Link Modification Request.

[0082] Figure 5 shows an example of processing by a relay device according to this embodiment. More specifically, Figure 5 shows an example of processing by the relay device from the time it receives a Link Modification Request from the first communication device until it sends a message to the second communication device. In this embodiment, it is assumed that the first communication device is an End UE and the second communication device is a relay device, or that the first communication device is a relay device and the second communication device is either a relay device or an End UE.

[0083] First, the relay device receives a Link Modification Request from the first communication device (S501) and checks the message type (S502).

[0084] If the message type does not indicate QoS flow deletion (No in S502), the relay device sends a Link Modification Request to the second communication device (S508) and terminates processing.

[0085] On the other hand, if the message type indicates QoS flow deletion (Yes in S502), the relay device operates as follows: The relay device obtains the identifier (QFI) of the QoS flow to be deleted (S503) and checks the QoS flow included in the link it is forming with the second communication device (S504). As mentioned above, the relay device determines the link usage status based on the QoS flow included in the link.

[0086] First, the relay device checks whether the link contains the QoS flow to be deleted (S505).

[0087] If the link does not contain the QoS flow to be deleted (No in S505), the relay device determines (or determines) that the End UE that issued the QoS flow deletion request is not using this link and does not change the link. In this case, the relay device completes processing without sending a message to the second communication device.

[0088] On the other hand, if the link contains a QoS flow to be deleted (Yes in S505), the relay device checks whether the link contains any QoS flows other than those to be deleted (S506).

[0089] If the link does not contain any QoS flows other than those to be deleted (No in S506), the relay device determines (or determines) that only the End UE that issued the QoS flow deletion request is using this link and releases the link. In this case, the relay device sends a Disconnect Request to the second communication device (S507) and finishes processing.

[0090] On the other hand, if the link contains QoS flows other than those to be deleted (Yes in S506), the relay device determines (or determines) that other End UEs besides the End UE that issued the QoS flow deletion request are also using this link. Therefore, the relay device leaves the link and deletes only the specific QoS flow in question. In this case, the relay device sends a Link Modification Request to the second communication device (S508) and completes the process.

[0091] In addition, while the above explains that a Disconnect Request is sent as the message to send when it is decided to release a link, a Link Modification Request may also be sent. In this case, the QoS flows to be deleted in the Link Modification Request will be all QoS flows included in the link.

[0092] In this embodiment, the processing when a relay device forming a UE-to-UE Relay receives a Link Modification Request has been described. In this embodiment, the relay device determines the processing to be performed on the link based on the message type of the received message and the link usage status, and sends a message accordingly. In this way, by clarifying the behavior of the relay device that receives a link modification request in the link release processing of a UE-to-UE Relay, it becomes possible to realize the link release processing of a multi-hop UE-to-UE Relay. Therefore, relay communication using relay devices can be performed appropriately.

[0093] [Second Embodiment] In the first embodiment, the processing when a relay device forming a UE-to-UE Relay receives a Link Modification Request was clarified, and the link release process for a multi-hop UE-to-UE Relay was described.

[0094] More specifically, in the first embodiment, the link usage status was determined based on the QoS flow included in the link, and the link was not released if it was in use. However, even if the link is in use, there are use cases where it is desirable to prioritize releasing the link depending on the application (for example, when the termination conditions for the relay process described below are met). Therefore, in this embodiment, we will describe an example in the UE-to-UE Relay link release process in which the relay device decides to terminate the relay based on the link usage status and releases the link.

[0095] In the following, we will omit descriptions of configurations and processes that are the same as or similar to those in the first embodiment, and will focus on describing configurations and processes that differ from those in the first embodiment.

[0096] Figure 6 shows an example of processing by a relay device according to this embodiment. More specifically, Figure 6 shows an example of processing from when the relay device receives a Link Modification Request from the first communication device until it sends a message to the second communication device. In this embodiment, it is assumed that the first communication device is an End UE and the second communication device is a relay device, or that the first communication device is a relay device and the second communication device is either a relay device or an End UE.

[0097] The process from when the relay device receives a Link Modification Request from the first communication device until it confirms the link with the second communication device (S501-S504) is the same as in the first embodiment, so the explanation is omitted.

[0098] The relay device checks whether the conditions for determining the termination of relaying (referred to as the termination conditions for relaying) have been met, based on the QFI to be deleted obtained from the received message and the QFI included in the link with the second communication device (S601).

[0099] The termination condition for relay processing refers to the conditions under which the relay device decides to terminate the UE-to-UE Relay process. When this condition is met, the relay device sends a link release request message to the connected communication device, thereby terminating the UE-to-UE Relay.

[0100] An example of a termination condition for relay processing is the deletion of a specific QFI (for example, the termination of a specific service resulting in the deletion of a specific QoS flow associated with that service). If a relay device is required to operate as a relay device for a specific UE-to-UE Relay, it should terminate its relay processing when that specific UE-to-UE Relay terminates its communication. If the relay device has sufficient resources and is also operating as a relay device for other UE-to-UE Relays, it cannot terminate its relay processing even if the specific UE-to-UE Relay requests link release. This is because other UE-to-UE Relays are using the link. Therefore, the relay device monitors the specific QFI used by the specific UE-to-UE Relay and determines (or decides) to terminate its relay processing when the specific QFI is no longer included in the link. Additionally or alternatively, the termination condition may be that a specific QFI becomes subject to deletion.

[0101] Another example of a condition for terminating relay processing is when the priority of the QoS flows included in the link falls below (or becomes below) a threshold. In 5G (NR), QoS characteristics are standardized for each service (Section 5.7.4 of TS 23.501), and each QoS characteristic has a priority assigned to it. If the QoS flows included in the link consist only of low-priority QoS flows (below or below the threshold) (i.e., only low-priority QoS flows are in use), the relay device decides to terminate relay processing.

[0102] If the conditions for terminating the relay process are met (Yes in S601), the relay device sends a Disconnect Request to the connected communication device (S602) and terminates the process.

[0103] On the other hand, if the termination conditions for relay processing are not met (No in S601), the relay device continues processing to change the message to be transmitted according to the link usage status (S505-S508). These processes are the same as in the first embodiment, so their explanation is omitted.

[0104] In this embodiment as well, if the relay device decides to terminate the relay process, it may send a Link Modification Request instead of a Disconnect Request. In this case, the QoS flows to be deleted in the Link Modification Request will be all QoS flows included in the link.

[0105] In this embodiment, the processing when a relay device forming a UE-to-UE Relay receives a Link Modification Request has been described. In this embodiment, the relay device decides whether or not to terminate the relay process based on the link usage status, and sends a link release request if it decides to terminate the relay process. In this way, by clarifying the behavior of the relay device that receives a link modification request in the link release process of a UE-to-UE Relay, it becomes possible to realize the link release process of a multi-hop UE-to-UE Relay. Therefore, relay communication using relay devices can be performed appropriately.

[0106] [Other embodiments] Although a multi-hop UE-to-UE relay has been described above, this disclosure may also be applied to a single-hop UE-to-UE relay. That is, both the first communication device and the second communication device described using Figures 5 and 6 may be End UEs.

[0107] Regarding the second embodiment, the above describes the conditions under which the relay device decides to terminate the relay process (termination conditions). However, conditions other than those described above may be used as termination conditions. For example, if the QoS flows included in the link consist only of QoS flows with a large delay time set in the QoS characteristics (only QoS flows with a delay time less than or equal to the threshold are in use), the relay device may decide to terminate the relay process. Also, for example, the relay device may decide to terminate the relay process if it detects that the link or the QoS flows included in the link are being used due to unauthorized access. Furthermore, the termination conditions may be any combination of the termination conditions described in the second embodiment and the termination conditions described here.

[0108] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the embodiments described above to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. Furthermore, this disclosure can also be implemented by a circuit (e.g., an ASIC or FPGA) that implements one or more functions.

[0109] This disclosure is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of this disclosure.

[0110] The names of the functional units, messages, parameters, fields, etc., described in the embodiments described above are examples and may be changed to other names.

[0111] The matters described in the above-described embodiments may be incorporated into other embodiments, insofar as they do not contradict each other.

[0112] Furthermore, the following additional information is disclosed regarding the above embodiments.

[0113] [Note 1] A relay device that communicates with the first communication device and the second communication device, Receiving means for receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device, A first determination means for determining the usage status of the communication path based on the first message, A transmission means for transmitting a second message corresponding to the usage status to the second communication device, A relay device having the following features.

[0114] [Note 2] The system further comprises a second determination means for determining the message type of the first message, The aforementioned communication path includes the communication path between the relay device and the second communication device. The relay device described in Appendix 1, wherein the second message is a message corresponding to the usage status of the communication path between the relay device and the second communication device and the type of message.

[0115] [Note 3] The relay device as described in Appendix 2, wherein the first determination means determines the usage status of the communication path between the relay device and the second communication device based on a first QoS flow included in the communication path between the relay device and the second communication device.

[0116] [Note 4] The relay device as described in Appendix 3, wherein, if the message type indicates the deletion of the first QoS flow, and the communication path between the relay device and the second communication device includes only the first QoS flow, the transmitting means sends a message to the second communication device as the second message requesting the disconnection of the communication path between the relay device and the second communication device.

[0117] [Note 5] The relay device according to Appendix 3, wherein the message type indicates the deletion of the first QoS flow, and the communication path between the relay device and the second communication device includes the first QoS flow and a second QoS flow other than the first QoS flow, the transmitting means transmits a message to the second communication device requesting a change in the communication path between the relay device and the second communication device as the second message.

[0118] [Note 6] The relay device as described in Appendix 3, wherein if the message type does not indicate the deletion of the first QoS flow, and the first QoS flow is included in the communication path between the relay device and the second communication device, the transmitting means transmits to the second communication device a message requesting a change in the communication path between the relay device and the second communication device as the second message.

[0119] [Note 7] The relay device according to any one of appendices 3 to 6, wherein if the communication path between the relay device and the second communication device does not include the first QoS flow, the transmitting means does not transmit a message to the second communication device.

[0120] [Note 8] The aforementioned communication path includes the communication path between the relay device and the second communication device. The relay device further includes a determination means for determining whether or not to disconnect the communication path between the relay device and the second communication device based on the usage status of the communication path between the relay device and the second communication device. The relay device according to any one of the appendices 1 to 7, wherein, in response to the determination means determining to disconnect the communication path between the relay device and the second communication device, the transmission means transmits a message to the second communication device requesting the disconnection of the communication path between the relay device and the second communication device as the second message.

[0121] [Note 9] The relay device according to Appendix 8, wherein the determination means determines whether or not to disconnect the communication path between the relay device and the second communication device based on the usage status of the QoS flow included in the communication path between the relay device and the second communication device.

[0122] [Note 10] The relay device according to Appendix 9, wherein the determination means determines to disconnect the communication path between the relay device and the second communication device in response to a specific QoS flow being removed from the communication path between the relay device and the second communication device.

[0123] [Note 11] The relay device according to Appendix 9, wherein the determination means determines to disconnect the communication path between the relay device and the second communication device when there are no QoS flows with a priority above a threshold in the communication path between the relay device and the second communication device.

[0124] [Note 12] A control method for a relay device that communicates with a first communication device and a second communication device, The process includes receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device, A step of determining the usage status of the communication path based on the first message, A step of transmitting a second message corresponding to the usage status to the second communication device, A control method including

[0125] [Note 13] A program to cause the relay device's computer to execute the control method described in Appendix 12. [Explanation of symbols]

[0126] 102 Control Unit 103 Storage section 201 Signal Transmission Unit 202 Signal Receiving Unit 203 Data Storage Unit 205 Message Type Determination Unit 206 Link Usage Determination Unit 207 Message Determination Unit 208 Broadcast termination decision section 301, 302, 305, 306 End UE 303, 304 Relay (relay device)

Claims

1. A relay device that communicates with the first communication device and the second communication device, Receiving means for receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device, A first determination means for determining the usage status of the communication path based on the first message, A transmission means for transmitting a second message corresponding to the usage status to the second communication device, A relay device having the following features.

2. The system further includes a second determination means for determining the message type of the first message, The aforementioned communication path includes the communication path between the relay device and the second communication device. The relay device according to claim 1, wherein the second message is a message corresponding to the usage status of the communication path between the relay device and the second communication device and the type of message.

3. The relay device according to claim 2, wherein the first determination means determines the usage status of the communication path between the relay device and the second communication device based on a first QoS flow included in the communication path between the relay device and the second communication device.

4. The relay device according to claim 3, wherein if the message type indicates the deletion of the first QoS flow and the communication path between the relay device and the second communication device includes only the first QoS flow, the transmitting means transmits to the second communication device a message requesting the disconnection of the communication path between the relay device and the second communication device as the second message.

5. The relay device according to claim 3, wherein if the message type indicates the deletion of the first QoS flow, and the communication path between the relay device and the second communication device includes the first QoS flow and a second QoS flow other than the first QoS flow, the transmitting means transmits to the second communication device a message requesting a change in the communication path between the relay device and the second communication device as the second message.

6. If the message type does not indicate the deletion of the first QoS flow, and the communication path between the relay device and the second communication device includes the first QoS flow, the transmitting means transmits to the second communication device a message requesting a change in the communication path between the relay device and the second communication device as the second message, the relay device according to claim 3.

7. The relay device according to claim 3, wherein if the communication path between the relay device and the second communication device does not include the first QoS flow, the transmitting means does not transmit a message to the second communication device.

8. The aforementioned communication path includes the communication path between the relay device and the second communication device. The relay device further includes a determination means for determining whether or not to disconnect the communication path between the relay device and the second communication device based on the usage status of the communication path between the relay device and the second communication device. The relay device according to claim 1, wherein, in response to the determination means determining to disconnect the communication path between the relay device and the second communication device, the transmission means transmits to the second communication device a message requesting the disconnection of the communication path between the relay device and the second communication device as the second message.

9. The relay device according to claim 8, wherein the determination means determines whether or not to disconnect the communication path between the relay device and the second communication device based on the usage status of the QoS flow included in the communication path between the relay device and the second communication device.

10. The relay device according to claim 9, wherein the determination means determines to disconnect the communication path between the relay device and the second communication device in response to a specific QoS flow being removed from the communication path between the relay device and the second communication device.

11. The relay device according to claim 9, wherein the determination means determines to disconnect the communication path between the relay device and the second communication device when there are no more QoS flows with a priority of a threshold or higher in the communication path between the relay device and the second communication device.

12. A control method for a relay device that communicates with a first communication device and a second communication device, The process includes receiving a first message from the first communication device requesting a change in the communication path between the first communication device and the second communication device, A step of determining the usage status of the communication path based on the first message, A step of transmitting a second message corresponding to the usage status to the second communication device, A control method including

13. A program for causing the computer of a relay device to execute the control method described in claim 12.

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