Relay terminal, base station, communication method, and program

Abstract

To provide a mechanism that enables control of the communication path of remote UE based on the state of relay UE.SOLUTION: A relay terminal is disclosed that has a sidelink relay function for relaying communication between a base station and a remote terminal in a sidelink. The relay terminal includes setting means for setting a priority when operating as a sidelink relay terminal, and transmitting means for transmitting a message including information regarding the priority to the base station. The transmitting means transmits the message each time the priority is updated or periodically.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In recent years, the 3GPP (3rd Generation Partnership Project) (registered trademark) has been formulating specifications for LTE (Long Term Evolution) and next-generation (NR: New Radio) standards. 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 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, as one of the operations of Sidelink communication, 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 is specified. By following this procedure, for example, even if communication via a direct path becomes difficult because the remote UE is 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Publication No. 2022 / 0377822 Summary of the Invention [Problem to be solved by the invention]

[0006] Since the relay UE also handles data transfer for remote UEs, an increase in the communication traffic of the remote UE will put a strain on the communication bandwidth between the relay UE and the base station. In addition, if the communication bandwidth is compressed, the communication speed of the services provided by the relay UE itself, such as video viewing and file transfer, will also be affected. Therefore, when connecting a remote UE to a relay UE, it is necessary to take into account the communication status of the relay UE.

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

[0008] A terminal according to one aspect of the present invention is a relay terminal having a sidelink relay function for relaying communications between a base station and a remote terminal in a 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 regarding the priority to the base station, and the transmission means transmits the message each time the priority is updated or periodically. Effect of the Invention

[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. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention; [Diagram 2] 2 is a block diagram showing an example of a functional configuration of a relay UE in the present embodiment. FIG. [Diagram 3]2 is a block diagram showing an example of a functional configuration of a base station according to the present embodiment. FIG. [Figure 4] FIG. 2 is a sequence diagram showing a process performed by the communication system according to the present embodiment. [Diagram 5] 13 is a flowchart showing a process of a relay UE according to the present embodiment. [Figure 6] 6 is a flowchart showing a process of a base station according to the present embodiment. [Figure 7] 13 is a flowchart of a base station when a relay UE has a high priority in the present embodiment. [Figure 8] 13 is a flowchart of the base station when the priority of a relay UE is low in the present embodiment. [Figure 9] 1 is an explanatory diagram of a message format of SidelinkUEInformationNR in this embodiment. [Figure 10] FIG. 2 is a sequence diagram showing a process performed by the communication system according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference symbols are used for the same or similar configurations, and duplicated descriptions are omitted. <First embodiment>

[0012] [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 are referred to as UEs. The UEs may be referred to as terminals. The base stations may 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 base station 103. The relay UE may be called a sidelink relay UE. The relay UE means a UE that provides a function to support a remote UE to connect 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. The remote UE means 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. The remote UE is an example of a remote terminal. Also, the relay UE is 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. Also, UE B102 may be located within the base station communication area 105 as it moves. Regardless of whether the UE is located within the base station communication area 105 or not, the UEs can perform sidelink communication with each other. Also, the UEs can perform uplink / downlink communication with the base station 103.

[0016] [Functional configuration of the device] Next, a functional configuration example of the 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 further functional blocks may be added. In addition, 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 a functional configuration of a UE. Here, the communication system of the present embodiment will be described using a UE A101.

[0018] The control unit 201 controls each unit of the UE A101 according to the input signal and a program described later. 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, a parameter value 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 processor 204 analyzes an RRC message received from the base station 103. For example, the RRC message analysis processor 204 analyzes a message including SIB12 information, which will be described later. SIB is an abbreviation for System Information Block, and the SIB12 information includes information such as emergency information of a Commercial Mobile Alerting System (CMAS).

[0022] The bandwidth management unit 205 manages whether or not a sufficient communication bandwidth is secured for services requiring communication functions such as applications implemented in the device itself to operate normally in communication processing implemented by the communication unit 207 described later. Note that the service means a function that the UE provides to the user who possesses 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 an external device including a UE and the base station 103, and receives a signal from the external device and transmits a signal to the external device. Specifically, the communication unit 207 may include a PC5 interface (Sidelink communication) and a Uu interface (Uplink / Downlink communication) conforming to the 3GPP standard. When the communication unit 207 receives a communication from an external device including a UE and the base station 103, the communication unit 207 may measure the signal strength related to the communication. The signal strength may be, for example, RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), etc. The measurement result of the signal strength measured by the communication unit 207 is notified to the control unit 201. 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. The communication unit 207 also performs a transmission process of a message generated by the RRC message generation processing unit 203, a reception process of an RRC message transmitted from the base station 103 and the UE, and other necessary transmission and reception processes of radio signals. Furthermore, the communication unit 207 transmits a message including information regarding the priority when the UE operates as a relay UE to the base station 130. Furthermore, the communication unit 207 transmits a message including information regarding the priority to the base station 130 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 band used in communication with the base station 10 exceeds a predetermined threshold, the communication unit 207 notifies the user that the communication band 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 according to the input signal and a program described later. Instead of the control unit 301 controlling the entire device, the entire device may be controlled by having a plurality of hardware devices 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] In addition, the control unit 301 performs control regarding the communication path of the remote UE based on information regarding 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 control unit 301 executes the control program stored in the storage unit 302 to perform various operations described below.

[0030] The RRC message generation processing unit 303 generates messages used in 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 an RRC message received from the UE. The RRC message analysis processing unit 304 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 existing within the base station communication area 105, and holds 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 (signal strength, etc.) reported from the UE. The management table also manages the operation state of the UE existing within the base station communication area 105, such as whether the UE is operating as a relay UE or a remote UE. Furthermore, the management table also manages information notified by SidelinkUEInformationNR. The UE management unit 305 also uses the management table to manage information on the priority 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 the measurement result of the signal strength 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 the UE managed in the management table of the UE management unit 305 .

[0034] The communication unit 307 is an interface for communicating with an external device such as a UE communicating with the base station 103, another base station, and a core network device. 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). When the communication unit 307 receives communication from an external device such as a UE or another base station, the communication unit 307 can measure the signal strength related to 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. The communication unit 307 also performs a transmission process of a message generated by the RRC message generation processing unit 303, a reception process of an RRC message transmitted from the UE, and a transmission / reception process of other necessary radio signals.

[0035] The control unit 201 (the same applies to 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, which will be described in the flowcharts 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 below can also be realized by having the hardware circuits cooperate with a processor, such as a CPU or an MPU.

[0036] Moreover, the storage unit 202 and the storage unit 302 may include a main storage unit and an auxiliary storage unit. The main storage unit is, 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 is, for example, a Hard Disk Drive (HDD) or a Solid State Drive (SSD), and may store data related to application software and the like.

[0037] For example, a control program stored in a non-volatile storage area is expanded in a RAM (Random Access Memory) and executed by a processor constituting the control unit 201. In this manner, 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 for storing 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. The recording medium may be of various types. 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 the same configuration.

[0040] [Processing example] An example of the operation of this embodiment will be described with reference to an example of an operation sequence shown in FIG. 4 and example flowcharts shown in FIGS.

[0041] 4 shows 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 among 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, in which UE A101 serves as a relay UE, to direct communication with base station 103, depending on the communication state of UE A101. This will be described below.

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

[0044] Here, it is assumed that the user of UE A101 starts using an additional service (e.g., streaming music) 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 increase in communication bandwidth may hinder normal execution 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 Dedicated SIB Request from the UE A101 at the communication unit 307, and analyzes it at the RRC message analysis processing unit 304. Furthermore, the RRC message generation processing unit 303 generates a message including SIB12 information, and transmits it to the UE A101 via the communication unit 307 (F404).

[0046] The communication unit 207 of the 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 (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 Fig. 9. In this embodiment, an information element called ue-Relay-Type is newly added to SidelinkUEInformationNR. ue-Relay-Type indicates the priority when operating as a relay UE. The 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, when the UE is in a state where it can operate as a relay UE, Positive may be set, and when it is better not to operate as a relay UE, Negative may be set.

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

[0049] UE A101 may determine the priority when 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 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 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] In addition, the bandwidth management unit 205 may set the priority of the UE-Relay-Type 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 the UE-Relay-Type to Negative, and if the number is less than the predetermined threshold, the bandwidth management unit 205 may set the UE-Relay-Type to Positive.

[0051] In addition, the priority when operating as a relay UE may be divided into three or more stages. For example, the UE-Relay-Type may be capable of expressing three or more stages such as High / Middle / Low instead of two stages 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 that it is better not to operate as a relay UE in the bandwidth management unit 205. In this case, the RRC message generation processing unit 203 generates an RRC message with ue-Relay-Type set to Negative. Furthermore, this message is transmitted to the base station 103 via the communication unit 307 (F405, S505).

[0054] The base station 103 receives SidelinkUEInformationNR from UE A101 at the communication unit 307, and analyzes it at 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 ue-Relay-Type of SidelinkUEInformationNR is set to Negative. The information analyzed by the RRC message analysis processing unit 304 (information that UE A101 is Negative) is managed in the management information of UE A101 in the UE management unit 205.

[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] When UE A101 and UE C104 receive SIB12 from the base station 103, they may omit the transmission of DedicatedSIBRequest in F403 and F406. Since SIB12 is periodically transmitted from the base station 103, depending on the timing, it is possible to receive SIB12 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 B102 using the mechanism of Measurement Configuration and Reporting. Specifically, UE B102 notifies the base station 103 of cells, base stations, and relay UE information that the UE B102 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, in the UE, a Measurement Object that indicates the frequency and / or cell identifier of the target for which the signal strength is to be measured. 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 existing around the UE and radio waves transmitted from a relay UE, 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 the signal strength information thereof, which are included in the Measurement Reports analyzed by the RRC message analysis processing unit 304, are managed in the management information of UE B102 in the UE management unit 205 (S603).

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

[0061] The following describes how switching of the connection mode is considered based on the signal strengths of 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 in which 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 or not the base station with the strongest signal strength in the vicinity of the UE B 102 is the base station 103 (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 form to a direct connection with the base station 103, instead of a connection using UE A101 as a relay UE. The base station 103 notifies UE B102 of switching from a connection state path via UE A101 to a state of direct connection to the base station 103. UE B102 that has received the notification performs handover to the base station 103 (S802).

[0065] Next, a 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 a relay UE to a state in which the UE 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 switching from a connection state in which UE A101 is a relay UE to a state in which the UE is directly connected to the base station 103 according to 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 ue-Relay-Type information in UE C104 is Negative (S806-NO), the determination unit 306 determines that there is no appropriate candidate for switching the connection destination, and does not perform switching processing (S807).

[0067] Finally, if the highest signal strength is not the base station 103 nor the UE A101 but the UE C104 (S808), the determination unit 306 compares the ue-Relay-Type information of the UE A101 and the UE C104 (S809). First, if the setting of the ue-Relay-Type information of the UE C104 is Positive (S809-YES), the determination unit 306 determines to switch from a connection state in which the UE A101 is the relay UE to a connection state in which the UE C104 is the relay UE (S811). Furthermore, the base station 103 notifies the UE B102 of the determination result (F411). The UE B102 that receives the notification performs switching from a connection state in which the UE A101 is the relay UE to a connection state in which the UE C104 is the relay UE according to 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 second best signal strength after UE A101 is checked (S810). If the base station 103 has the second best signal strength after UE C101 (S809-YES), the base station 103 judges 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 judgment result (F411). Having received the notice, UE B102 follows a predetermined procedure to switch from a connection state in which UE A101 is a relay UE to a state in which it is directly connected to the base station 103 (S802).

[0069] On the other hand, a case where UE A101 has the second best signal strength after UE C104 will be described. Here, the ue-Relay-Type information of both UE A101 and UE C104 is Negative. Therefore, it is determined 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 determination result (F411). Having received the notification, UE B102 performs switching 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 hindered, 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-mentioned concerns regarding service continuity by reviewing the connection status of the remote UE based on information on peripheral devices of the remote UE and information on 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 capable of operating as a relay UE, and UE C104 is in a state in which it is better not to operate as a relay UE.

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

[0074] (Processing example) An example of the operation of this embodiment will be described with reference to an example of an operation sequence shown in FIG. 10 and example flowcharts shown in FIGS.

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

[0076] As in the first embodiment, UE A101 is connected to the base station 103, and uplink / downlink communication occurs as a result of the execution of an application by a user (F1001). Also, UE A101 operates as a relay UE, and is responsible for relaying uplink / downlink communication of UE B102 operating as a remote UE (F1002, S501).

[0077] UE A101 communicates with the base station 103 by executing applications 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 the message 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 capable of operating 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, the message is transmitted to the base station 103 via the communication unit 307 (F1005, S505).

[0081] The process performed by the base station 103 when receiving the SidelinkUEInformationNR is the same as that in the first embodiment, and therefore the description thereof will be omitted 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 the method 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 management information of UE B101 in UE management section 205 (F1006 to F1008).

[0083] UE B102 is performing uplink / downlink communication with UE A101 as a relay UE, and periodically notifies the base station 103 of communication information around the own device by a mechanism of Measurement Configuration and Reporting. Specifically, the 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 similar to that in the first embodiment, and therefore will not be described here (F1010, S603).

[0085] The following describes how base station 103 switches UE B101 to a connection mode based on the signal strengths of 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, the processing procedure when the UE-Relay-Type of UE A101 is Positive, that is, when UE A101 is in a state capable of operating 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 it 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 the UE B102 and the base station 103 (S701). Here, although it is different from the situation assumed in the embodiment, a case will be mentioned where the signal strength of the base station 103 measured by the UE B102 is the best compared to the signal strength measured by the UE B102 for other UEs. In this case, the determination unit 306 determines that the UE B102 should change the communication form to a direct connection with the base station 103, instead of a connection with the UE A101 as a relay UE. The base station 103 notifies the UE B102 of switching from a connection state path via the UE A101 to a state of direct connection to the base station 103 (S706).

[0089] Next, assume that the UE with the best signal strength between UE B102 is not the base station 103 but the UE A101 (S702). This case is also different from the situation assumed in this embodiment, but it is worth mentioning. In this case, the 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, it is assumed that the strongest signal between UE B102 is not the base station 103 nor the UE A101, but the 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 of UE A101 and UE C104 is set to Negative. In this case, the signal strength of the base station 103 is checked (S705). In this embodiment, since the signal strength of the base station 103 is the worst, it is recognized that the UE A101 has the second best signal strength after UE C104. Although the signal strength of UE A101 is inferior to that of UE C104, since the ue-Relay-Type information of UE A101 is set to Positive, no 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 to switch UE B 102 from a connection state in which UE A 101 is the relay UE to a state in which UE B 102 is directly connected to the base station 103 (S706).

[0092] Although this embodiment assumes a different situation, the case where the setting of the ue-Relay-Type information of UE C104 is Positive will be mentioned. In this case, the base station 103 notifies the UE B102 that the UE B102 will be switched to the UE C104 with better signal strength (S708).

[0093] As described above, when 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, if it is better for the relay UE candidate not to operate as a relay UE, it is possible to suppress switching of the relay UE. <Other embodiments> In the first embodiment, the operation of a relay UE is explained based on an increase in communication bandwidth caused by activating a service in the relay UE. However, the present invention is not limited to this regarding the operation of a relay UE.

[0094] For example, the relay UE user may be able to intentionally set whether or not to operate as a relay UE. In addition, 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 the priority at that time.

[0095] Furthermore, the priority of the 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 device does not operate as a relay UE.

[0096] On the other hand, in the case of a communication relay device or a communication auxiliary device that is installed on the road or the like to support a communication device that is outside the communication range of the base station 103, it is desirable to actively use it as a relay UE. Therefore, in this case, it is preferable to set it so that there is no problem with its operation as a relay UE.

[0097] In the above example, the remote UE, which uses a smartphone as a relay UE, can detect communication relay devices and communication auxiliary devices installed on the road, etc., enabling a smooth transition of the relay UE.

[0098] In this embodiment as well, when a terminal operating as a relay UE is about to encounter a problem 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 a base station via the base station.

[0099] In addition, the following supplementary notes are disclosed regarding the above embodiment.

[0100] (Appendix 1) A relay terminal having a sidelink relay function for relaying communication between a base station and a remote terminal in a sidelink, a receiving means for receiving a signal from the base station; A transmitting means for transmitting a message including information regarding a priority when operating as a Sidelink relay terminal to the base station, The relay terminal according to claim 1, wherein the transmitting means transmits the message every time the priority is updated or periodically.

[0101] (Appendix 2) A setting means for setting the priority by comparing a communication band used in communication with the base station with a predetermined threshold value, 2. A relay terminal as described in Appendix 1.

[0102] (Appendix 3) A setting means for setting the priority based on an instruction from a user, 2. A relay terminal as described in Appendix 1.

[0103] (Appendix 4) a notification means for notifying a user that a communication band used in communication with the base station has exceeded a predetermined threshold when the communication band has exceeded the predetermined threshold; 4. The relay terminal according to claim 1,

[0104] (Appendix 5) A setting means for setting the priority based on device characteristics of the relay terminal. 5. The relay terminal according to claim 1,

[0105] (Appendix 6) A setting means for setting the priority based on the number of remote terminals currently relaying communication. 6. The relay terminal according to claim 1,

[0106] (Appendix 7) The receiving means receives system information regarding a sidelink from the base station, When the transmitting means receives the system information, the transmitting means transmits a message including information regarding the priority to the base station. 7. The relay terminal according to claim 1, [Explanation of symbols]

[0107] 101UEA 102UEB 103 Base station 104UEC 201 Control section 202 Storage section 203 RRC message generation processing unit 204 RRC message analysis processing unit 205 Bandwidth Management Unit 206 SidelinkRelay processing unit 207 Communications Department 301 Control Unit 302 Storage section 303 RRC message generation processing unit 304 RRC message analysis processing unit 305 UE Management Department 306 Judgment section 307 Communications Department

Claims

1. A relay terminal having a Sidelink relay function for relaying communication between a base station and a remote terminal in Sidelink, a receiving means for receiving a signal from the base station; A transmitting means for transmitting a message including information regarding a priority when operating as a Sidelink relay terminal to the base station, The relay terminal according to claim 1, wherein the transmitting means transmits the message every time the priority is updated or periodically.

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

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

4. a notification means for notifying a user that a communication band used in communication with the base station has exceeded a predetermined threshold when the communication band has exceeded the predetermined threshold; The relay terminal according to any one of claims 1 to 3.

5. A setting means for setting the priority based on device characteristics of the relay terminal. The relay terminal according to claim 1.

6. A setting means for setting the priority based on the number of remote terminals currently relaying communication. The relay terminal according to claim 1.

7. The receiving means receives system information regarding Sidelink from the base station, When the transmitting means receives the system information, the transmitting means transmits a message including information regarding the priority to the base station. The relay terminal according to claim 1.

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

9. A communication method implemented by a relay terminal having a Sidelink relay function that relays communication between a base station and a remote terminal in Sidelink, comprising: receiving a signal from the base station; Sending a message to the base station including information regarding the priority of operating as a Sidelink relay terminal; A communication method, wherein the sending step sends the message every 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: Managing information regarding priority when operating as a Sidelink relay terminal, the information being transmitted from the relay terminal; managing a signal strength measurement result reported from the remote terminal when the remote terminal is communicating with the relay terminal; performing control regarding a communication path of the remote terminal based on the information regarding the priority and the measurement result; A communication method comprising:

11. A relay terminal having a Sidelink relay function for relaying communication between a base station and a remote terminal in Sidelink, receiving a signal from the base station; transmitting a message including information regarding the priority of operating as a Sidelink relay terminal to the base station; The program, wherein the sending step sends the message every time the priority is updated or periodically.

12. A base station that communicates with a remote terminal in Sidelink via a relay terminal having a Sidelink relay function, Managing information regarding priority when operating as a Sidelink relay terminal, the information being transmitted from the relay terminal; managing a signal strength measurement result reported from the remote terminal when the remote terminal is communicating with the relay terminal; performing control regarding a communication path of the remote terminal based on the information regarding the priority and the measurement result; A program for executing the above.

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