Relay terminal, base station, communication method, and program

Abstract

Disclosed is a relay terminal having a Sidelink relay function for relaying communication between a base station and a remote terminal in Sidelink. The relay terminal is characterized by having a setting means for setting a priority when the relay terminal operates as a Sidelink relay terminal, and a transmission means for transmitting a message including information relating to the priority to the base station, wherein the transmission means transmits the message every time the priority is updated or periodically.

Description

Relay terminal, base station, communication method and program

[0001] The present disclosure relates to a relay terminal, a base station, a communication method, and a program.

[0002] In recent years, the 3rd Generation Partnership Project (3GPP) (registered trademark) has been formulating specifications for LTE (Long Term Evolution) and next-generation (NR: New Radio) technologies. Among these, a standard specification called Sidelink communication (hereinafter also referred to as "Sidelink") has been formulated. This specification realizes direct wireless communication between devices using an interface called PC5, without going through a mobile communication network (core network).

[0003] Furthermore, 3GPP is currently developing specifications to expand the communication range of Sidelink by using a Sidelink relay function that relays Sidelink communication via a relay device (relay UE (User Equipment)). For example, one of the operations of Sidelink communication specifies a procedure for switching from a direct path, in which a remote UE directly communicates with a base station, to an indirect path, in which the remote UE indirectly communicates with the base station via a relay UE. By following this procedure, even if communication via a direct path becomes difficult due to the remote UE moving away from the base station, communication with the base station can be continued via the relay UE.

[0004] Patent Document 1 proposes a means for a remote UE to switch from a direct path to an indirect path.

[0005] U.S. Patent Publication No. 2022 / 0377822

[0006] Since the relay UE also handles data transfer for the remote UE, an increase in communication traffic of the remote UE will constrict the communication bandwidth between the relay UE and the base station. Furthermore, when the communication bandwidth is constricted, the communication speed of services such as video viewing and file transfer provided by the relay UE itself is also affected. Therefore, when connecting a remote UE to a relay UE, it is necessary to consider the communication status of the relay UE.

[0007] The present invention has been made in consideration of the above-mentioned problems, and an object of one aspect of the present invention is to provide a mechanism that enables control of a communication path of a remote UE based on the state of a relay UE.

[0008] A terminal according to one aspect of the present invention is a relay terminal having a Sidelink relay function that relays communication between a base station and a remote terminal in Sidelink, and is characterized in that it has a setting means for setting a priority when operating as a Sidelink relay terminal, and a transmission means for transmitting a message including information about the priority to the base station, and the transmission means transmits the message each time the priority is updated or periodically.

[0009] According to one aspect of the present invention, it is possible to provide a mechanism that enables control of a communication path of a remote UE based on the state of a relay UE.

[0010] FIG. 1 is a diagram illustrating a configuration of a communication system in the present embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of a relay UE in the present embodiment. FIG. 3 is a block diagram illustrating an example of a functional configuration of a base station in the present embodiment. FIG. 4 is a sequence diagram illustrating processing performed by a communication system in the present embodiment. FIG. 5 is a flowchart illustrating processing by a relay UE in the present embodiment. FIG. 6 is a flowchart illustrating processing by a base station in the present embodiment. FIG. 7 is a flowchart illustrating a base station in the case where the priority of a relay UE in the present embodiment is high. FIG. 8 is a flowchart illustrating a base station in the case where the priority of a relay UE in the present embodiment is low. FIG. 9 is an explanatory diagram of a message format of SidelinkUEInformationNR in the present embodiment. FIG. 10 is a sequence diagram illustrating processing performed by a communication system in the present embodiment.

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference symbols are used for the same or similar components, and redundant explanations will be omitted.

[0012] <First embodiment> [System configuration] Fig. 1 is a diagram showing an example of the configuration of a communication system according to this embodiment. The communication system is composed of UE A101, UE B102, UE C104, and one or more base stations 103. The communication system according to this embodiment can be applied not only to LTE and 5G (NR) but also to communication systems of 6G and beyond. In the following description, when there is no need to distinguish between UE A101, UE B102, and UE C104, they will be referred to as UEs. The UEs may also be referred to as terminals. The base stations may also be referred to as eNBs (enhanced NodeBs) or gNBs (gNodeBs).

[0013] UE A101 has a Sidelink relay function and operates as a relay UE that relays communication between UE A101 and the base station 103. A relay UE may also be called a Sidelink relay UE. A relay UE refers to a UE that provides a function to support remote UEs in connecting to a network. UE B102 has a Sidelink communication function and is a remote UE that communicates with the base station 103 via UE A101. A remote UE refers to a UE that communicates with the network via a relay UE. UE C104 has a Sidelink relay function. UE C104 is a relay UE candidate for UE B102. A remote UE is an example of a remote terminal. A relay UE is also an example of a relay terminal.

[0014] The base station 103 generates a base station communication area 105 and communicates with UEs located within the base station communication area 105. The base station communication area 105 is also called a cell.

[0015] In Fig. 1, UE A101 and UE C104 are located within a base station communication area 105. UE B102 may also be located within the base station communication area 105 as it moves. UEs can perform sidelink communication with each other regardless of whether they are located within the base station communication area 105. Also, UEs can perform uplink / downlink communication with a base station 103.

[0016] [Functional Configuration of the Device] Next, an example of the functional configuration of a UE will be described. Note that the configuration of the functional blocks described below is merely an example. Some or all of the functional blocks described below may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or additional functional blocks may be added. Furthermore, one functional block shown in the following description may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block.

[0017] 2 is a block diagram showing an example of the functional configuration of a UE, in which a communication system according to this embodiment will be described using UE A101.

[0018] The control unit 201 controls each unit of the UE A101 according to input signals and a program described later. Note that instead of the control unit 201 controlling the entire UE, the entire UE may be controlled by multiple hardware devices sharing the processing. The control unit 201 also controls the communication establishment means.

[0019] The storage unit 202 stores a control program executed by the control unit 201, information related to communication, parameter values ​​for determining whether or not a UE can operate as a relay UE, etc. The control unit 201 executes the control program stored in the storage unit 202 to perform various operations described below.

[0020] The RRC message generation processing unit 203 generates messages used in RRC (Radio Resource Control), which is a protocol used for control signals between the base station 103 and the UE. The RRC message generation processing unit 203 also generates messages such as DedicatedSIBRequest and SidelinkUEInformationNR, which will be described later.

[0021] The RRC message analysis processing unit 204 analyzes an RRC message received from the base station 103. For example, the RRC message analysis processing unit 204 analyzes a message including SIB12 information, which will be described later. SIB stands for System Information Block, and the SIB12 information includes information such as emergency information from the Commercial Mobile Alerting System (CMAS).

[0022] The bandwidth management unit 205 manages whether a sufficient communication bandwidth is secured for services requiring communication functions, such as applications running on the device itself, to operate normally in communication processing performed by the communication unit 207 (described later). The services refer to functions that the UE provides to the user who owns the UE, such as video viewing, web browsing, sending and receiving XR (Extended Reality / Cross Reality) content data, and file transfer. The bandwidth management unit 205 sets a priority when operating as a relay UE. The bandwidth management unit 205 is an example of a setting means.

[0023] The Sidelink Relay processing unit 206 performs processing to relay communication between the remote UE and the base station 103 by connecting to the remote UE via a PC5 interface.

[0024] The communication unit 207 is an interface for communicating with external devices including UEs and base stations 103, and receives signals from the external devices and transmits signals to the external devices. Specifically, the communication unit 207 may use a PC5 interface (sidelink communication) or a Uu interface (uplink / downlink communication) conforming to the 3GPP standard. Furthermore, when the communication unit 207 receives communication from an external device including a UE or base station 103, it can measure the signal strength associated with the communication. The signal strength may be, for example, RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), or the like. The measurement result of the signal strength measured by the communication unit 207 is notified to the control unit 201. Furthermore, the measurement result of the signal strength measured by the communication unit 207 may be reported to the base station 103 by an RRC message. Furthermore, the communication unit 207 performs transmission processing of messages generated by the RRC message generation processing unit 203, reception processing of RRC messages transmitted from the base station 103 and the UE, and transmission and reception processing of other necessary radio signals. Furthermore, the communication unit 207 transmits to the base station 130 a message including information regarding the priority when the UE operates as a relay UE. Furthermore, the communication unit 207 transmits to the base station 130 a message including information regarding the priority every time the priority is updated or periodically. The communication unit 207 is an example of a transmitting means and a receiving means.

[0025] Furthermore, when the communication bandwidth used for communication with the base station 10 exceeds a predetermined threshold, the communication unit 207 notifies the user that the communication bandwidth has exceeded the predetermined threshold. The communication unit 207 is an example of a notification means.

[0026] FIG. 3 is a block diagram showing an example of the functional configuration of the base station 103.

[0027] The control unit 301 controls the operation of the base station 103 in accordance with the input signals and a program described below. Note that instead of the control unit 301 controlling the entire device, the entire device may be controlled by having multiple pieces of hardware share the processing. The control unit 301 also controls the communication establishment means. The control unit 301 is an example of a control means.

[0028] Furthermore, the control unit 301 controls the communication path of the remote UE based on information about the priority when the UE operates as a relay UE and the measurement result of the signal strength notified from the UE.

[0029] The storage unit 302 is a storage unit that stores the control program executed by the control unit 301 and information related to communication as the base station 103. The various operations described below are performed by the control unit 301 executing the control program stored in the storage unit 302.

[0030] The RRC message generation processing unit 303 generates messages used in the RRC, which is a protocol used for control signals between the base station 103 and the UE.

[0031] The RRC message analysis processing unit 304 analyzes RRC messages received from the UE, and also processes RRC messages related to DedicatedSIBRequest, SidelinkUEInformationNR, and Measurement Configuration and Reporting, which will be described later.

[0032] The UE management unit 305 manages UE information of UEs present within the base station communication area 105 and maintains a management table that stores UE information for each subordinate UE. The management table also stores identification information for each subordinate UE and measurement result information (such as signal strength) reported from the UE. The management table also manages the operating status of UEs present within the base station communication area 105, such as whether the UE is operating as a relay UE or a remote UE. The management table also manages information notified by SidelinkUEInformationNR. The UE management unit 305 also uses the management table to manage information regarding the priority of the UE when operating as a relay UE, which is transmitted from the relay UE. The UE management unit 305 also uses the management table to manage signal strength measurement results reported from the remote UE when the base station 103 is communicating with the remote UE via the relay UE. The UE management unit 305 is an example of a first management means and a second management means.

[0033] The determination unit 306 determines whether to perform indirect connection processing via a relay UE or direct connection processing with the base station 103 for a UE managed in the management table of the UE management unit 305 .

[0034] The communication unit 307 is an interface for communicating with UEs communicating with the base station 103, other base stations, and external devices such as core network devices. Specifically, the interface includes a Uu interface (uplink / downlink communication), an Xn interface (inter-base station communication), and an NG interface (inter-base station and core network communication). Furthermore, when the communication unit 307 receives communication from an external device such as a UE or another base station, it can measure the signal strength associated with the communication. The signal strength may be, for example, RSRP, RSRQ, RSRI, etc. The measurement result of the signal strength measured by the communication unit 307 is notified to the control unit 301. Furthermore, the communication unit 307 performs transmission processing of messages generated by the RRC message generation processing unit 303, reception processing of RRC messages transmitted from the UE, and transmission and reception processing of other necessary radio signals.

[0035] The control unit 201 (and the control unit 301) described above is configured with one or more processors, such as a CPU or an MPU. The control unit 201 controls the entire UE A101 by executing a control program read into the RAM, which is the storage unit 202. Note that the processes performed by the control units 201 and 301 described in the flowcharts described below can also be realized using various hardware circuits. The various hardware circuits include an ASIC (Application Specific Integrated Circuit) and an FPGA (Field Programmable Gate Array). Furthermore, the processes described in the flowcharts described below can also be realized by having the hardware circuits cooperate with a processor, such as a CPU or an MPU.

[0036] The storage unit 202 and the storage unit 302 may include a main storage unit and an auxiliary storage unit. The main storage unit may be, for example, a read-only memory (ROM) or a random access memory (RAM). The main storage unit may store or temporarily store programs and data such as an operating system (OS), which is basic software executed by the control unit 201, and application software. The auxiliary storage unit may be, for example, a hard disk drive (HDD) or a solid state drive (SSD), and may store data related to application software.

[0037] For example, the control program stored in the non-volatile storage area is expanded into a RAM (Random Access Memory) and executed by a processor constituting the control unit 201. In this way, the control unit 201 and the storage unit 202 may function as a so-called computer.

[0038] The storage unit 202 may include a recording medium that stores a predetermined program. The program stored in this recording medium may be installed via a drive device or the like, and the installed predetermined program may be executable by the control unit 201. Various types of recording media can be used as the recording medium. For example, the recording medium may be a recording medium that records information optically, electrically, or magnetically, such as a CD (Compact Disc)-ROM, a flexible disk, or a magneto-optical disk. The recording medium may also be a semiconductor memory that records information electrically, such as a ROM or a flash memory. Note that the recording medium does not include a carrier wave.

[0039] The above is an example of a block diagram showing an example of the functional configuration of a communication device according to this embodiment. Note that this embodiment has been described using UE A101, but UE B101 and UE C104 may also have a similar configuration.

[0040] [Processing Example] An example of the operation of this embodiment will be described using the operation sequence example shown in FIG. 4 and the flowchart examples shown in FIGS. 5, 6 and 8.

[0041] 4 shows the processing performed when the base station 103 receives SidelinkUEInformationNR from UE A101 and a message related to Measurement Configuration and Reporting from UE B102. Here, it is assumed that the signal strength measured by UE B102 between UE A101, UE C104, and the base station 103 is the strongest for UE A101.

[0042] Even in such a case, UE B102 switches from Sidelink Relay, which uses UE A101 as a relay UE to direct communication with base station 103, depending on the communication state of UE A101. This will be explained below.

[0043] UE A101 performs uplink / downlink communication with the base station 103 in response to a user's use of a service (e.g., web browsing) (F401). Furthermore, UE A101 acts as a relay UE and is responsible for relaying uplink / downlink communication of UE B102 acting as a remote UE (F402, S501).

[0044] Now, suppose that the user of UE A101 starts using an additional service (e.g., music streaming) on ​​UE A101. As a result, the amount of traffic in uplink or downlink communication increases, and the bandwidth management unit 205 detects that the increased communication bandwidth may hinder the normal implementation of the service. In this case, the bandwidth management unit 205 notifies the control unit 201 of this fact (S502-YES). The control unit 201 generates a DedicatedSIBRequest in the RRC message generation processing unit 203 and transmits it to the base station 103 via the communication unit 207 (F403, S503).

[0045] The base station 103 receives the DedicatedSIBRequest from UE A101 at the communication unit 307 and analyzes it at the RRC message analysis processing unit 304. Furthermore, the base station 103 generates a message including SIB12 information at the RRC message generation processing unit 303 and transmits the message to UE A101 via the communication unit 307 (F404).

[0046] The communication unit 207 of UE A101 receives SIB12 information (system information related to Sidelink) from the base station 103 and analyzes it in the RRC message analysis processing unit 204 (S504). Furthermore, when the SIB12 information is received, the communication unit 207 transmits SidelinkUEInformationNR (a message including information related to priority) including ue-Relay-Type to the base station 103 (F405, S505).

[0047] The message format of SidelinkUEInformationNR is shown in Figure 9. In this embodiment, a new information element called ue-Relay-Type is added to SidelinkUEInformationNR. ue-Relay-Type indicates the priority when operating as a relay UE. This priority means whether the UE is in a state where it can operate as a relay UE (i.e., a state where the priority when operating as a relay UE is high) or in a state where it is better not to operate as a relay UE (i.e., a state where the priority when operating as a relay UE is low). As an example, if the UE is in a state where it can operate as a relay UE, it may be set to Positive, and if it is in a state where it is better not to operate as a relay UE, it may be set to Negative.

[0048] UE A101 may determine the priority of operating as a relay UE based on the communication bandwidth between UE A101 and the base station 103, which is detected by the bandwidth management unit 205. For example, the bandwidth management unit 205 may set Negative if the communication bandwidth in use between UE A101 and the base station 103 is equal to or greater than a predetermined threshold, and may set Positive if the communication bandwidth in use between UE A101 and the base station 103 is less than the predetermined threshold. Note that the communication bandwidth in use between UE A101 and the base station 103 may be an average downlink communication speed and / or an average uplink communication speed during a predetermined communication time.

[0049] UE A101 may determine the priority of operating as a relay UE based on the total value of the communication bandwidth in use with each remote UE detected by the bandwidth management unit 205. For example, the bandwidth management unit 205 may set the total value of the communication bandwidth in use with each remote UE to Negative if the total value of the communication bandwidth in use with each remote UE is equal to or greater than a predetermined threshold, and may set the total value of the communication bandwidth in use with each remote UE to Positive if the total value is less than the predetermined threshold. Note that the total value of the communication bandwidth in use with each remote UE may be the total value of the average downlink communication speed and / or the average uplink communication speed measured for each remote UE during a predetermined communication time.

[0050] Furthermore, the bandwidth management unit 205 may set ue-Relay-Type as a priority when operating as a relay UE based on the number of remote UEs for which the UE is relaying communication. For example, if the number of remote UEs connected to the UE is equal to or greater than a predetermined threshold, the bandwidth management unit 205 may set ue-Relay-Type as Negative, and if the number is less than the predetermined threshold, the bandwidth management unit 205 may set ue-Relay-Type as Positive.

[0051] Furthermore, the priority when operating as a relay UE may be divided into three or more levels. For example, ue-Relay-Type may be able to express three or more levels such as High / Middle / Low instead of two levels of Positive / Negative.

[0052] In addition, the priority when operating as a relay UE may be set based on a user instruction.

[0053] UE A101 detects in the bandwidth management unit 205 that it is in a state where it is better not to operate as a relay UE. In this case, the RRC message generation processing unit 203 generates an RRC message in which ue-Relay-Type is set to Negative. This message is then transmitted to the base station 103 via the communication unit 307 (F405, S505).

[0054] The base station 103 receives SidelinkUEInformationNR from UE A101 via the communication unit 307 and analyzes it via the RRC message analysis processing unit 304 (S601). Next, the control unit 301 checks the priority of UE A101 when it operates as a relay UE (S602). Here, the control unit 301 checks that Negative is set in the ue-Relay-Type of SidelinkUEInformationNR. The information analyzed by the RRC message analysis processing unit 304 (information that UE A101 is Negative) is managed in the UE management unit 205 in the management information of UE A101.

[0055] The same process is also performed periodically in UE C104, and is reflected in the management information of UE B101 in UE management section 205 (F406 to F408).

[0056] Note that UE A101 and UE C104 may omit the transmission of DedicatedSIBRequest in F403 and F406 when receiving SIB12 from the base station 103. This is because SIB12 is periodically transmitted from the base station 103, and therefore, depending on the timing, SIB12 can be received without transmitting DedicatedSIBRequest.

[0057] UE B102 is in uplink / downlink communication with UE A101 operating as a relay UE, and periodically notifies the base station 103 of communication information around the UE itself using a mechanism of Measurement Configuration and Reporting. Specifically, UE B102 notifies the base station 103 of the cells, base stations, and relay UE information that the UE itself can detect, as well as their signal strengths, etc. (F409).

[0058] Here, the mechanism of Measurement Configuration and Reporting will be described. The base station 103 sets a Measurement Object in the UE, which indicates the frequency and / or cell identifier of the target for signal strength measurement. Based on the Measurement Object set by the base station 103, the UE measures the signal strength of radio waves transmitted from one or more base stations present around the UE and radio waves transmitted from relay UEs, and notifies (reports) the base station 103.

[0059] When the base station 103 receives the Measurement Reports transmitted from UE B102 at the communication unit 307, the base station 103 analyzes the Measurement Reports at the RRC message analysis processing unit 304. The peripheral device information of UE B102 and their signal strength information included in the Measurement Reports analyzed by the RRC message analysis processing unit 304 are managed as management information of UE B102 in the UE management unit 205 (S603).

[0060] Here, the determination unit 306 of the base station 103 examines the switching of the connection mode of UE B102 based on the management information of UE A101, UE B102 and UE C104 managed by the UE management unit 205 (F410, S604).

[0061] The following describes how the connection topology is considered for switching based on the signal strengths of the base station 103, UE A101, and UE C104, and the ue-Relay-Type information of UE A101 and UE C104.

[0062] In this embodiment, as described above, the ue-Relay-Type of UE A101 is Negative, that is, UE A101 is in a state where it is better not to operate as a relay UE (S606). The processing procedure in this case will be described with reference to the flowchart in FIG.

[0063] The determination unit 306 analyzes whether the base station 103 has the strongest signal strength in the vicinity of the UE B 102 (S801).

[0064] Here, although it is different from the situation in this embodiment, a case where the signal strength of the base station 103 is the highest in the vicinity of UE B102 will be mentioned. In this case, the determination unit 306 determines that UE B102 should change the communication mode from a connection using UE A101 as a relay UE to a communication mode where UE B102 is directly connected to the base station 103. The base station 103 notifies UE B102 of switching from a connection state path via UE A101 to a state where UE B102 is directly connected to the base station 103. Upon receiving this notification, UE B102 performs handover to the base station 103 (S802).

[0065] Next, the case where UE A101 has the highest signal strength in the vicinity of UE B102 (S803-YES) will be described. First, the determination unit 306 checks the device with the second best signal strength after UE A101 (S804). If the device with the second best signal strength after UE A101 is the base station 103 (S804-YES), the base station 103 determines that UE B102 should switch from a connection state in which UE A101 is the relay UE to a state in which it is directly connected to the base station 103 (F411, S802). The base station 103 notifies UE B102 of the determination result. Upon receiving the notification, UE B102 performs a switch from a connection state in which UE A101 is the relay UE to a state in which it is directly connected to the base station 103 in accordance with a predetermined procedure.

[0066] If the device with the second best signal strength after UE A101 is not the base station 103 (S804-NO), the determination unit 306 determines that the device with the second best signal strength is UE C104 (S805). Then, the determination unit 306 determines whether UE C104 can operate as a relay UE (S806). If the setting of the ue-Relay-Type information in UE C104 is Negative (S806-NO), the determination unit 306 determines that there is no valid candidate for switching the connection destination, and does not perform any switching process (S807).

[0067] Finally, if the highest signal strength is not the base station 103 nor UE A101 but UE C104 (S808), the determination unit 306 compares the ue-Relay-Type information of UE A101 and UE C104 (S809). First, if the setting of the ue-Relay-Type information of UE C104 is Positive (S809-YES), the determination unit 306 determines to switch from the connection state in which UE A101 is the relay UE to the connection state in which UE C104 is the relay UE (S811). Furthermore, the base station 103 notifies UE B102 of the determination result (F411). Upon receiving the notification, UE B102 switches from a connection state in which UE A101 is the relay UE to a connection state in which UE C104 is the relay UE in accordance with a predetermined procedure.

[0068] On the other hand, if the setting of the ue-Relay-Type information of UE C104 is Negative (S809-NO), the device with the next best signal strength after UE A101 is checked (S810). If the base station 103 has the next best signal strength after UE C101 (S809-YES), the base station 103 determines that UE B102 should switch to a state in which it is directly connected to the base station 103. The base station 103 notifies UE B102 of the determination result (F411). Upon receiving the notification, UE B102 performs a switchover from a connection state in which UE A101 is the relay UE to a state in which it is directly connected to the base station 103 in accordance with a predetermined procedure (S802).

[0069] On the other hand, let us consider the case where UE A101 has the second best signal strength after UE C104. In this case, the ue-Relay-Type information for both UE A101 and UE C104 is Negative. Therefore, the base station 103 determines to switch from the connection state path with UE A101 as the relay UE to a connection state with UE C104, which has better signal strength, as the relay UE. The base station 103 notifies UE B102 of the result of this determination (F411). Upon receiving this notification, UE B102 performs a switch to a connection state with UE C104 as the relay UE in accordance with a predetermined procedure (S811).

[0070] As described above, when the continuation of the service being provided by the UE is likely to be affected, the bandwidth management unit 205 determines that it is better not to operate as a relay UE. The relay UE can immediately notify the base station 103 to that effect.

[0071] The base station 103 can resolve the above concerns regarding service continuity by reviewing the connection status of the remote UE based on information about peripheral devices of the remote UE and information about relay UEs that are in a state where it is better not to operate as relay UEs.

[0072] Second Embodiment In this embodiment, a case will be described in which UE A101 is in a state where it is possible to operate as a relay UE, and UE C104 is in a state where it is better not to operate as a relay UE.

[0073] The system configuration in this embodiment is the same as that shown in FIG. 1, and the configurations of the devices that make up the system are also the same as those shown in FIGS.

[0074] (Processing Example) An example of the operation of this embodiment will be described using the operation sequence example shown in FIG. 10 and the flowchart examples shown in FIGS. 5, 6 and 7.

[0075] 10 shows the process when the base station 103 receives SidelinkUEInformationNR from UE A101 and receives a message related to Measurement Configuration and Reporting from UE B102 in this embodiment. Here, the signal strength of UE C104 measured by UE B102 is better than the signal strength of UE A101 measured by UE B102. Also, the signal strength of the base station measured by UE B102 is worse than the signal strength of UE A101 and UE C104 measured by UE B102. In this embodiment, even in such a case, UE B102 continues Sidelink Relay, relaying UE A101 as a relay UE.

[0076] As in the first embodiment, UE A101 is connected to the base station 103, and uplink / downlink communication is occurring as a result of the user executing an application (F1001). UE A101 also functions as a relay UE, and is responsible for relaying uplink / downlink communication of UE B102, which functions as a remote UE (F1002, S501).

[0077] UE A101 communicates with the base station 103 by executing applications on its own device and relaying communications of the relay UE, but it is assumed that there is sufficient communication bandwidth between UE A101 and the base station 103.

[0078] The base station 103 periodically generates a message including SIB12 information in the RRC message generation processing unit 303 and transmits the message to the UE A101 via the communication unit 307 (F1004).

[0079] UE A101 receives a message including SIB12 information from UE A101 at the communication unit 207 and analyzes it at the RRC message analysis processing unit 204 (S504). Also, SidelinkUEInformationNR is generated at the RRC message generation processing unit 203 and transmitted to UE A101 via the communication unit 207 (F1005). Note that the message format of SidelinkUEInformationNR is the same as that of the first embodiment, and therefore description thereof will be omitted here.

[0080] In this embodiment, it is assumed that UE A101 is in a state where it can operate as a relay UE. Therefore, the RRC message generation processing unit 203 of UE A101 generates a message (SidelinkUEInformationNR) with ue-Relay-Type set to Positive. Furthermore, this message is transmitted to the base station 103 via the communication unit 307 (F1005, S505).

[0081] The processing performed by the base station 103 when SidelinkUEInformationNR is received is the same as in the first embodiment, and therefore will not be described here (S601, S602).

[0082] In this embodiment, it is assumed that UE C104 is in a state where it is better not to operate as a relay UE. Here, the same process as that described in the first embodiment is performed, and information that UE C104 is in a state where it is better not to operate as a relay UE is reflected in the management information of UE B101 in the UE management unit 205 (F1006 to F1008).

[0083] UE B102 is in uplink / downlink communication with UE A101 as a relay UE, and periodically notifies the base station 103 of communication information around the UE itself using a mechanism of Measurement Configuration and Reporting. Specifically, this information includes the signal strength between the UE B102 and the base station 103, the signal strength between the UE B102 and the relay UE, etc. (F1009).

[0084] The processing performed by the base station 103 when receiving a message related to Measurement Configuration and Reporting is the same as that in the first embodiment, and therefore will not be described here (F1010, S603).

[0085] The following describes how the base station 103 switches the connection topology of UE B101 based on the signal strengths of the base station 103, UE A101, and UE C104, and the ue-Relay-Type information of UE A101 and UE C104 (S604).

[0086] In this embodiment, as described above, the processing procedure when the UE-Relay-Type of UE A101 is Positive, that is, when UE A101 is in a state where it can operate as a relay UE (S605), will be described with reference to the flowchart of FIG.

[0087] As described above, the UE-Relay-Type of UE A101 is Positive, that is, there is no problem with UE A101 operating as a relay UE.

[0088] As in the first embodiment, the determination unit 306 first analyzes whether the base station 103 has the best signal strength between UE B102 and the base station 103 (S701). Here, although different from the situation assumed in the embodiment, a case will be mentioned in which the signal strength of the base station 103 measured by UE B102 is better than the signal strength measured by UE B102 for other UEs. In this case, the determination unit 306 determines that UE B102 should change its communication mode from a connection using UE A101 as a relay UE to a direct connection with the base station 103. The base station 103 notifies UE B102 of a switch from a connection state path via UE A101 to a state in which UE B102 is directly connected to the base station 103 (S706).

[0089] Next, assume that the UE with the best signal strength between UE B102 and UE A101, not base station 103 (S702). This case is different from the situation assumed in this embodiment, but it is worth mentioning. In this case, determination unit 306 determines that UE B102 should continue the connection state with UE A101 as the relay UE, and does not perform any particular switching process (S707).

[0090] Finally, assume that the signal strength between UE B102 and UE C104 is not the base station 103 or UE A101, but UE C104 (S703). The determination unit 306 compares the ue-Relay-Type information of UE A101 and UE C104 (S704). In this embodiment, it is assumed that the ue-Relay-Type information settings of UE A101 and UE C104 are Negative. In this case, the signal strength of the base station 103 is then confirmed (S705). In this embodiment, since the signal strength of the base station 103 is the worst, it is recognized that the signal strength next to UE C104 is UE A101. Although the signal strength of UE A101 is weaker than that of UE C104, since the ue-Relay-Type information of UE A101 is set to Positive, no particular switching process is performed.

[0091] Note that the case where the base station 103 has the second best signal strength after UE C 104 will also be mentioned. The base station 103 determines that UE B 102 should switch from a connection state in which UE A 101 is a relay UE to a state in which UE B 102 is directly connected to the base station 103 (S706).

[0092] Although this is different from the situation assumed in this embodiment, the case where the setting of the ue-Relay-Type information of UE C104 is the same as Positive will also be mentioned. In this case, the base station 103 notifies UE B102 that it will switch to UE C104, which has better signal strength (S708).

[0093] As described above, if there is a relay UE candidate other than the own device and the signal strength of the candidate is better than that of the own device, but it is better for the relay UE candidate not to operate as a relay UE, it is possible to suppress switching of relay UEs.

[0094] In the first embodiment, whether or not a relay UE can operate as a relay UE has been described based on the increase in communication bandwidth caused by activating a service at the relay UE. However, the present invention is not limited to this regarding whether or not a relay UE can operate as a relay UE.

[0095] For example, whether or not a relay UE can operate as a relay UE may be intentionally set by the relay UE user. Also, when the communication bandwidth of the relay terminal exceeds a predetermined threshold, the user may be notified of this, and the relay UE user may be able to set a priority at that time.

[0096] Furthermore, the priority of the relay UE when it operates as a relay UE may be set based on the device characteristics of the relay UE. For example, in the case of a device that runs various services, such as a smartphone, it is preferable that the relay UE does not operate as a relay UE.

[0097] On the other hand, it is desirable to actively use a communication relay device or a communication auxiliary device that is installed on a road or the like to support a communication device that is outside the communication range of the base station 103 as a relay UE. Therefore, in this case, it is preferable to set the device so that it does not interfere with the operation as a relay UE.

[0098] In the above example, the remote UE that uses a smartphone as a relay UE can detect communication relay devices, communication auxiliary devices, etc. installed on the road, etc., thereby enabling a smooth transition of the relay UE.

[0099] In this embodiment, too, if a terminal currently operating as a relay UE is about to encounter problems in continuing to operate as a relay UE, it is possible to prompt the terminal to change its connection destination to another relay UE or base station via the base station.

[0100] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0101] This application claims priority based on Japanese Patent Application No. 2023-121207, filed on July 26, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A relay terminal having a Sidelink relay function that relays communications between a base station and a remote terminal in a Sidelink, comprising: a receiving means for receiving a signal from the base station; and a transmitting means for transmitting a message to the base station that includes information regarding a priority when operating as a Sidelink relay terminal, wherein the transmitting means transmits the message each time the priority is updated or periodically.

2. The relay terminal according to claim 1, further comprising a setting means for setting the priority by comparing a communication band used in communication with the base station with a predetermined threshold value.

3. The relay terminal according to claim 1, further comprising a setting means for setting the priority based on an instruction from a user.

4. A relay terminal as claimed in any one of claims 1 to 3, further comprising a notification means for, when a communication band used for communication with the base station exceeds a predetermined threshold, notifying a user that the communication band has exceeded a predetermined threshold.

5. The relay terminal according to any one of claims 1 to 4, further comprising a setting means for setting the priority based on device characteristics of the relay terminal.

6. The relay terminal according to any one of claims 1 to 5, further comprising a setting means for setting the priority based on the number of remote terminals currently relaying communication.

7. A relay terminal according to any one of claims 1 to 6, wherein the receiving means receives system information regarding Sidelink from the base station, and the transmitting means, when receiving the system information, transmits a message including information regarding the priority to the base station.

8. A base station that communicates with a remote terminal in Sidelink via a relay terminal having a Sidelink relay function, comprising: a first management means for managing information regarding the priority when operating as a Sidelink relay terminal, transmitted from the relay terminal; a second management means for managing measurement results of signal strength reported from the remote terminal when communicating with the remote terminal via the relay terminal; and a control means for controlling the communication path of the remote terminal based on the information regarding the priority and the measurement results.

9. A communication method executed by a relay terminal having a Sidelink relay function that relays communications between a base station and a remote terminal in Sidelink, comprising: a step of receiving a signal from the base station; and a step of transmitting a message including information regarding priority when operating as a Sidelink relay terminal to the base station, wherein the transmitting step transmits the message each time the priority is updated or periodically.

10. A communication method executed by a base station that communicates with a remote terminal in Sidelink via a relay terminal having a Sidelink relay function, comprising: a step of managing information regarding the priority when operating as a Sidelink relay terminal, transmitted from the relay terminal; a step of managing measurement results of signal strength reported from the remote terminal when communicating with the remote terminal via the relay terminal; and a step of controlling the communication path of the remote terminal based on the information regarding the priority and the measurement results.

11. A program for causing a relay terminal having a Sidelink relay function that relays communications between a base station and a remote terminal in Sidelink to execute the steps of receiving a signal from the base station and transmitting a message including information regarding the priority when operating as a Sidelink relay terminal to the base station, wherein the transmitting step transmits the message each time the priority is updated or periodically.

12. A program for causing a base station that communicates with a remote terminal in Sidelink via a relay terminal having a Sidelink relay function to execute the following steps: managing information regarding the priority when operating as a Sidelink relay terminal, which is transmitted from the relay terminal; managing measurement results of signal strength reported from the remote terminal when communicating with the remote terminal via the relay terminal; and controlling the communication path of the remote terminal based on the information regarding the priority and the measurement results.

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