Communication device, base station, control method, and program

Abstract

Disclosed is a communication device comprising a sidelink relay means that relays communication between a base station and remote user equipment (UE), a generation means that generates a SRAP control PDU, which is a sidelink adaptation protocol (SRAP) PDU, and a transmission means that transmits the SRAP control PDU generated by the generation means, wherein when a prescribed condition is fulfilled while relaying by the sidelink relay means is being performed, the generation means stores stopping-related information regarding stopping the relaying by the sidelink relay means in the SRAP control PDU.

Description

Communication device, base station, control method, and program

[0001] The present disclosure relates to a communication device, a base station, a control 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) standards. Among these, a standard specification called Sidelink communication 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 (registered trademark) is currently developing specifications to extend the Sidelink communication range by using a Sidelink relay function that relays Sidelink communication via a relay device (relay UE). The specifications define a means for a communication terminal (remote UE) that has the function of connecting to a base station through the Sidelink relay function to switch from an indirect path. Specifically, the specifications define a means for switching from communication connecting to a base station via a relay UE (indirect path) to direct communication with the base station (direct path) without disconnecting the service, and a means for switching from a direct path to an indirect path without disconnecting the service.

[0004] Patent Document 1 proposes a means for a remote UE to switch from an indirect path to a direct path without disconnecting the service.

[0005] US Patent Application Publication No. 2022 / 0377822

[0006] The decision to switch paths is made mainly based on the signal strength between the remote UE and the relay UE and the signal strength between the remote UE and the base station, without taking into consideration the internal circumstances of the relay UE. Internal circumstances of the relay UE may include, for example, the remaining battery life of the relay UE or a fail-soft function due to the loss of some processes. Currently, there is no mechanism to inform the base station that the relay function cannot continue if it cannot continue due to internal circumstances of the relay UE. In this case, if the relay function of the relay UE suddenly stops, a sequence of reconnection to the base station will be executed, which may reduce service continuity.

[0007] The present invention has been made in consideration of at least one of the above-mentioned problems, and an object of the present invention is to provide a mechanism that enables a base station to use information regarding the suspension of a relay function of a relay UE.

[0008] According to one aspect of the present invention, a base station includes: a communication means for communicating with a remote UE via a relay UE (User Equipment); a receiving means for receiving an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU, from the relay UE; and a control means for, when the receiving means receives the SRAP control PDU storing stop-related information related to stop of relaying via the relay UE, executing communication control for the communication means based on the stop-related information.

[0009] According to one aspect of the present invention, it is possible to provide a mechanism that enables the base station to use information regarding the suspension of the relay function of a relay UE.

[0010] FIG. 1 is a diagram illustrating a configuration of a communication device in this embodiment. FIG. 2 is a block diagram illustrating an example of a functional configuration of a base station in this embodiment. FIG. 3 is a block diagram illustrating an example of a functional configuration of a relay UE in this embodiment. FIG. 4 is a diagram illustrating an example of a configuration of a relay function non-continuation notification in the first embodiment. FIG. 5 is a diagram illustrating an example of a configuration of a relay function non-continuation notification in the first embodiment. FIG. 6 is a flowchart between communication devices in the first embodiment. FIG. 7 is a diagram illustrating an example of a configuration of a relay function non-continuation notification in the second embodiment. FIG. 8 is a flowchart between communication devices in the second embodiment.

[0011] Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant description may be omitted.

[0012] First Embodiment Fig. 1 is a diagram showing an example of the configuration of a system according to this embodiment. In Fig. 1, UE A (101) and UE B (102) are located within a communication area 104 of a base station 103.

[0013] In this embodiment, the UE (User Equipment) is assumed to be a terminal compatible with Sidelink relay communication. Specifically, the UE is assumed to be a smartphone or the like, but is not limited to this. For example, the UE may be a communication terminal such as a tablet terminal or a PC, a wearable terminal such as a smart watch or a head-mounted display, or a car navigation device installed in an automobile.

[0014] In Fig. 1, UE A (101) operates as a remote UE and communicates with a base station 103 using Sidelink relay communication. UE B (102) operates as a relay UE and relays communication between UE A (101) and the base station 103 using the Sidelink relay function. That is, UE A (101) is transmitting and receiving data to and from the base station on an indirect path with UE B (102).

[0015] FIG. 2 is a block diagram showing an example of the functional configuration of the base station 103 in this embodiment.

[0016] Note that some or all of the functional blocks described in FIG. 2 (as well as FIG. 3 described later) may be replaced with other functional blocks that perform similar functions, or some functional blocks may be omitted. Also, new functional blocks may be added. Furthermore, one functional block described below may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block.

[0017] In the example shown in FIG. 2, the base station 103 includes a control unit 201, a storage unit 202, a UE management unit 203, a path switching processing unit 204, an SRAP PDU generation processing unit 205, an SRAP PDU analysis processing unit 206, and a radio communication unit 207.

[0018] The control unit 201 controls the operation of the base station 103. The control unit 201 is configured with one or more processors such as a CPU or an MPU, and controls the entire communication device by executing a control program read into the RAM, which is the storage unit 202. Note that each process performed by the control unit 201, which will be described in the flowcharts below, can also be realized using a hardware circuit such as an ASIC or an FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit, and FPGA is an abbreviation for Field Programmable Gate Array. Furthermore, the processes described in the flowcharts below can also be realized by using a hardware circuit in cooperation with a processor such as a CPU or an MPU.

[0019] The memory unit 202 stores information used by the control unit 201 for control and information related to communication. The memory unit 202 may include a main memory unit and an auxiliary memory unit. The main memory unit is, for example, a read-only memory (ROM) or a random access memory (RAM). The main memory 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 memory unit is, for example, a hard disk drive (HDD) or a solid state drive (SSD), and may store data related to application software. For example, a control program stored in a non-volatile memory area is expanded into a random access memory (RAM) 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.

[0020] 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.

[0021] The recording medium does not include a carrier wave.

[0022] The UE management unit 203 manages UE information within the base station area, including the IDs of the subordinate UEs and measurement results reported from the subordinate UEs (such as the signal strength of the Uu link, which will be described later).

[0023] Based on the UE information managed by the UE management unit 203, the path switching processing unit 204 determines whether the UE under its management should be connected via an indirect path or a direct path.

[0024] The SRAP PDU generation processing unit 205 generates a message used to instruct path switching. In this embodiment, the SRAP PDU generation processing unit 205 generates a PDU (SRAP PDU) used in the Sidelink Adaptation Protocol (SRAP). SRAP is a protocol used in the NR (New Radio) Sidelink relay function.

[0025] The SRAP PDU analysis processing unit 206 analyzes the SRAP PDU received from a subordinate relay UE (hereinafter also referred to as a "subordinate relay UE").

[0026] The functions corresponding to the UE management unit 203, the path switching processing unit 204 and / or the SRAP PDU generation processing unit 205 may be realized as software modules implemented by the control unit 201.

[0027] The wireless communication unit 207 transmits and receives information to and from the subordinate UEs via wireless communication. For example, the wireless communication unit 207 performs processing such as transmitting a message generated by the SRAP PDU generation processing unit 205, receiving an SRAP PDU from the subordinate UEs, and receiving other necessary wireless signals.

[0028] FIG. 3 is a block diagram showing an example of the functional configuration of the relay UE (102) in this embodiment.

[0029] In the example shown in FIG. 3 , the relay UE ( 102 ) includes a control unit 301 , a storage unit 302 , a signal strength measurement unit 303 , a Sidelink Relay processing unit 304 , an SRAP PDU generation processing unit 305 , an SRAP PDU analysis processing unit 306 , and a wireless communication unit 307 .

[0030] The control unit 301 controls the operation of the relay UE (102). The control unit 301 is configured with one or more processors such as a CPU or an MPU, and controls the entire communication device by executing a control program read into the RAM, which is the storage unit 302. Note that each process performed by the control unit 301, which will be described in the flowcharts below, can also be realized using a hardware circuit such as an ASIC or an FPGA. Furthermore, the processes described in the flowcharts below can also be realized by cooperation between the hardware circuit and a processor such as a CPU or an MPU.

[0031] The storage unit 302 stores information used by the control unit 301 for control and information related to communication.

[0032] The signal strength measurement unit 303 measures the "signal strength between remote UEs (PC5 link)" and the "signal strength between base stations (Uu link)" as seen from the relay UE (102).

[0033] The Sidelink Relay processing unit 304 establishes a Sidelink connection with the remote UE. This enables the Sidelink Relay processing unit 304 to relay communication between the remote UE and the base station 103 via the NR Sidelink relay function of the relay UE (i.e., an indirect path). Note that, hereinafter, the NR Sidelink relay function is also simply referred to as the Sidelink relay function.

[0034] The SRAP PDU generation processing unit 305 is a SRAP PDU generation unit similar to the SRAP PDU generation processing unit 205 of the base station 103 described above. In this embodiment, when the relay UE determines that its own NR Sidelink relay function cannot be continued, the SRAP PDU generation processing unit 305 generates a PDU (an example of stop-related information) for notifying the base station 103 that the relay function cannot be continued. Details of the PDU for notifying the base station 103 that the relay function cannot be continued will be described later with reference to FIG. 4.

[0035] The SRAP PDU analysis processing unit 306 analyzes the SRAP PDU received from the remote UE and the base station 103 .

[0036] The wireless communication unit 307 transmits and receives information via wireless communication with the remote UE and the base station 103. The wireless communication unit 307 performs transmission processing of the SRAP PDU generated by the SRAP PDU generation processing unit 305, reception processing of the SRAP PDU from the remote UE and the base station 103, and other necessary wireless communication reception processing.

[0037] FIG. 4 shows an example of the structure of a PDU indicating that the relay function cannot be continued.

[0038] In a SRAP PDU, when one bit of the D / C field 401 has a value of 0, this indicates that the PDU is data (i.e., an SRAP DATA PDU). Also, when one bit of the D / C field 401 has a value of 1, this indicates that the PDU is a control message (i.e., an SRAP Control PDU). In a PDU indicating that the relay function cannot be continued, a value of 1 is set in the D / C field 401. In this embodiment, when the D / C field 401 has a value indicating an SRAP Control PDU, a 4-bit PDU type field 402 and a 3-bit Reserved field 403 are added. Also, when the D / C field 401 has a value indicating an SRAP Control PDU, the fields following the Reserved field 403 are configured as optional fields.

[0039] The PDU type field 402 indicates whether the relay function cannot be continued when the PDU is an SRAP Control PDU. In this embodiment, a value of 0000 in the PDU type field 402 indicates "relay function cannot be continued." Note that the value 0000 is just an example, and any other value may be used as long as it does not overlap with values ​​of other PDU types.

[0040] In this embodiment, an SRAP Control PDU including a value corresponding to "relay function cannot be continued" is used as an example of the stoppage-related information, but the stoppage-related information is not limited to this. Any value indicating that relaying cannot be continued / that operation as a relay will not be continued may be used. Furthermore, for example, a value corresponding to a relay RLF (Radio Link Failure), which indicates that a problem has occurred with the radio link for relaying, may be used as the stoppage-related information. In other words, the stoppage-related information of this embodiment can be modified in any way as long as it can notify the base station that communication may be interrupted. That is, the above specific example is merely an example of the stoppage-related information, and it should be noted that the actual name and the specific format for notifying the information are not limited to the above specific example.

[0041] The Reserved field 403 is an unused field.

[0042] Option field 1 (indicated by reference numeral 404) is a field for storing additional information, and uses the fields from the second octet onwards of the PDU. In this embodiment, the additional information stores the remaining time that the relay UE can continue to function as a relay. Note that this is just an example, and other appropriate configurations may also be used. For example, in addition to the remaining time for continuing the relay function, a field indicating the reason why the relay UE cannot continue to function as a relay may be added.

[0043] Fig. 5 shows an example of the structure of a PDU indicating that the relay function cannot be continued, which adds the reason why the relay UE cannot continue the relay function. In Fig. 5, an option field 2 (indicated by reference numeral 504) is added to the format shown in Fig. 4. Option field 2 stores a value indicating the reason why the relay function cannot be continued. The reason why the relay function cannot be continued will be described later.

[0044] Next, the operation of this embodiment will be described with reference to FIG.

[0045] 6 is an example of a flowchart showing a notification by a relay UE that the relay function cannot be continued, and a process by the base station 103 that receives the notification and determines whether to switch from an indirect path to a direct path, in this embodiment. The process shown in the flowchart can be realized in the base station 103 by the control unit 201 executing a control program stored in the storage unit 202, thereby calculating and processing information and controlling each piece of hardware. Also, in UE B (102), the process can be realized by the control unit 301 executing a control program stored in the storage unit 302, thereby calculating and processing information and controlling each piece of hardware.

[0046] In this embodiment, the relay UE UE B (102) performs relay using the Sidelink Relay processing unit 304. That is, the UE B (102) relays communication of user data (such as streaming data) between the remote UE UE A (101) and the base station 103 via an indirect path (S601).

[0047] The control unit 301 of UE B (102) determines whether or not it is impossible to continue the relay function of its own terminal (S602). If the control unit 301 of UE B (102) determines that it is impossible to continue the relay function of its own terminal, it notifies the Sidelink Relay processing unit 304 that it is impossible to continue the relay function. Here, the control unit 301 may determine that it is impossible to continue the relay function of its own terminal if a predetermined condition is satisfied. In this case, the predetermined condition may be a condition related to the state (device state or communication state) of the relay UE. For example, it may determine that it is impossible to continue the relay function of its own terminal if any one of the following conditions (1) to (7) is satisfied: Condition (1) The remaining battery power of the own terminal falls below a threshold; Condition (2) A hardware failure is detected; Condition (3) Some processes (e.g., processes operating to implement the signal strength measurement unit 303) are lost. Condition (4) When the user or user application turns off the NR Sidelink Relay function. Condition (5) When the user turns off the power or resets the power. Condition (6) When the signal strength of the PC5 link falls below the threshold. Condition (7) When the signal strength of the Uu link falls below the threshold.

[0048] Alternatively, the control unit 301 may determine that the relay function of the own terminal cannot be continued when any combination of two or more of the above conditions (1) to (7) is satisfied. Furthermore, among the above conditions (1) to (7), condition (1) and the like may be determined in a manner that includes prediction. For example, regarding condition (1), it may be determined that condition (1) is not satisfied when the remaining battery charge of the own terminal is below a threshold but is currently being charged or is scheduled to be charged in a short time. Furthermore, regarding condition (1), when the battery charge of the own terminal is also used for purposes other than communication (e.g., transportation), the remaining battery charge of the own terminal may only refer to the remaining battery charge available for communication.

[0049] In another embodiment, in addition to the above conditions (1) to (7), the following condition (8) may be determined: Condition (8) The temperature of the terminal (own device) exceeds the upper limit temperature.

[0050] Upon receiving the notification from the control unit 301, the Sidelink Relay processing unit 304 creates an SRAP control PDU indicating that the relay function cannot be continued via the SRAP PDU generation processing unit 305 (S603). Hereinafter, the SRAP control PDU indicating that the relay function cannot be continued may be referred to as a relay function continuation disable notification. Here, the SRAP PDU generation processing unit 305 stores the time until the relay function is stopped, calculated by the control unit 301, in option field 1 (404). In this embodiment, the option field is 2 bytes long and stores a value between 0 and 65535. The unit is seconds, and if the calculation is impossible (N / A), 0 is stored (S604). Also, as an option, an option field 2 (504) may be added and values ​​corresponding to the above-mentioned conditions (1) to (8) may be stored. In this embodiment, the following values ​​can be set. In this case, the base station 103 can determine the reason for stopping the relay function in the relay UE. 0 Low battery level (set when condition (1) is met) 1 Fault (hardware cause) (set when condition (2) is met) 2 Fault (software cause) (set when condition (3) is met) 3 Side link relay function off (set when condition (4) is met) 4 Power off or power reset (set when condition (5) is met) 5 Decrease in PC5 link signal strength (set when condition (6) is met) 6 Decrease in Uu link signal strength (set when condition (7) is met) 7 Rise in terminal temperature (set when condition (8) is met)

[0051] The Sidelink Relay processing unit 304 sends a notification to the base station 103 via the wireless communication unit 307 that the relay function cannot be continued (S605). If the time until the relay function is stopped calculated in S604 has elapsed, the control unit 301 stops the function of the Sidelink Relay processing unit 304. If the calculation is not possible, the Sidelink Relay processing unit 304 stops its function when the time set as the initial value (e.g., 60 seconds) has elapsed (S606). In a modified example, the Sidelink Relay processing unit 304 may stop its function before the predetermined time has elapsed.

[0052] When the radio communication unit 207 in the base station 103 receives the SRAP PDU, the SRAP PDU analysis processing unit 206 analyzes the contents of the received SRAP PDU (S607).

[0053] The analysis determines whether the D / C field 401 has a value indicating "SRAP Control PDU" and whether the PDU type field 402 indicates "relay function cannot be continued" (S608). If the D / C field 401 has a value indicating "SRAP Control PDU" and the PDU type field 402 indicates "relay function cannot be continued" (i.e., the above-mentioned "relay function cannot be continued notification"), the process proceeds to S609. In S609, the SRAP PDU analysis processing unit 206 determines that the SRAP PDU is a relay function cannot be continued notification. The SRAP PDU analysis processing unit 206 then interprets the value stored in option field 1 (404) as the time until the relay function is stopped and acquires the value. Based on the analysis result by the SRAP PDU analysis processing unit 206, the control unit 201 determines that it is difficult for UE B (102) to continue the relay function. In this case, the control unit 201 requests the path switching processing unit 204 to switch the path of UE A (101) within the time until the relay function is stopped (immediately if N / A). The path switching processing unit 204 switches UE A (101) from the indirect path to the direct path. If the received SRAP PDU is not a notification that the relay function cannot be continued, the process corresponding to the other SRAP PDU is carried out (S610).

[0054] By the above flow, when UE B (102) cannot continue relaying, UE B (102) and base station 103 can switch from an indirect path to a direct path in UE A (101) without disconnecting the service.

[0055] In this way, according to this embodiment, it is possible to provide a mechanism that enables the base station 103 to acquire information (notification that relay function cannot be continued) regarding the stop of the relay function of the relay UE (102). As a result, based on the notification that relay function cannot be continued, the base station 103 can switch from an indirect path to a direct path in the UE A (101) while maintaining the service in the UE A (101).

[0056] According to this embodiment, the relay UE (102) can include information about the time until the relay function is stopped in the notification of the inability to continue the relay function. In this case, the base station 103 can switch the UE A (101) from the indirect path to the direct path at an appropriate timing based on the time information.

[0057] Second Embodiment The configuration of a communication device (FIG. 1) and the functional configuration of a communication device (FIGS. 2 and 3) in a second embodiment are the same as those in the first embodiment.

[0058] In the first embodiment, an example was described in which the base station 103 can perform path switching for the remote UE without disconnecting the service when the NR Sidelink Relay function in the relay UE cannot be continued. In the second embodiment, an example is described in which the NR Sidelink Relay function of the relay UE is interrupted. For example, when a program that occupies the CPU utilization rate or network bandwidth is executed in the relay UE, the NR Sidelink Relay function becomes unavailable until the program is completed. Such a program is, for example, a throughput measurement application, but is not limited to this.

[0059] In this embodiment, as a second predetermined condition, when a relay UE suspends its own NR Sidelink relay function, the NR Sidelink relay function is suspended and stopped. Specifically, when a relay UE suspends its own NR Sidelink relay function, the SRAP PDU generation processing unit 305 generates a PDU for notifying the base station of the suspension of the relay function. An example of the configuration of a PDU indicating suspension of the relay function (an example of suspension-related information) is shown in FIG. 7.

[0060] The D / C field 401 has a value of 1, i.e., a value indicating an SRAP Control PDU, followed by a 4-bit PDU type field 402 and a 3-bit Reserved field 403. The configuration followed by an options field is the same as in FIGS.

[0061] In this embodiment, if the PDU type field 402 has a value of 0001, it indicates "relay function suspended." This SRAP Control PDU is hereinafter referred to as a "relay function suspended notification." The relay function suspended notification has option field 1 704 set to 4 bytes and option field 2 705 set to 2 bytes.

[0062] Option field 1 704 stores the planned time for relay interruption. As shown in 706 in FIG. 7, the values ​​that can be set in the 4 bytes are as follows: MSB bits 0 to 6 represent the year, with 2023 being 0 and up to 127 (2150) being possible to store. The following bits 7 to 10 represent the month and may store values ​​1 to 12. Bits 11 to 15 represent the day and may store values ​​1 to 31. Bits 16 to 20 represent the hour and may store values ​​0-23. Bits 21 to 26 represent the minute and may store values ​​0 to 59. Finally, bits 27 to 31 represent the second and may specify values ​​0 to 29 in 2-second increments.

[0063] The recovery time of the relay function after interruption is stored in the option field 2 705. In this embodiment, the recovery time can be set to 1 to 65535 seconds.

[0064] Next, the operation of this embodiment will be described with reference to FIG.

[0065] FIG. 8 is an example of a flowchart showing a process of notifying a relay function interruption notification by a relay UE and a process of determining switching from an indirect path to a direct path by a base station that has received the notification, in this embodiment.

[0066] In the second embodiment, UE B (102), which is a relay UE, performs relay using the Sidelink Relay processing unit 304. That is, UE B (102) relays communication of user data (such as streaming data) between UE A (101), which is a remote UE, and the base station 103 via an indirect path (S801).

[0067] The control unit 301 of the UE B (102) determines whether or not it is necessary to suspend the relay function of the own terminal (S802). If it is determined that it is necessary to suspend the relay function of the own terminal, the process proceeds to S803 and subsequent steps to notify the Sidelink Relay processing unit 304 of the suspension of the relay function.

[0068] Upon receiving the notification from the control unit 301, the Sidelink Relay processing unit 304 creates a PDU indicating the interruption of the relay function (hereinafter referred to as a relay function interruption notification) via the SRAP PDU generation processing unit 305 (S803). Here, the SRAP PDU generation processing unit 305 stores the time until the relay function is interrupted, calculated by the control unit 301, in the option field 1 704. Also, the SRAP PDU generation processing unit 305 stores the time until the relay function is restored, calculated by the control unit 301, in the option field 2 705 (S804).

[0069] The Sidelink Relay processing unit 304 sends a relay function interruption notification to the base station 103 via the wireless communication unit 307 (S805).

[0070] When the relay interruption time calculated in S804 is reached, the control unit 301 stops the function of the Sidelink Relay processing unit 304. When the recovery time calculated in S804 has elapsed since the interruption time, the control unit 301 resumes the Sidelink Relay processing unit 304 (S806).

[0071] When the radio communication unit 207 in the base station 103 receives the SRAP PDU, the SRAP PDU analysis processing unit 206 analyzes the contents of the received SRAP PDU (S807).

[0072] Next, the SRAP PDU analysis processor 206 determines whether the D / C field 401 has a value indicating "SRAP Control PDU" and whether the PDU type field 402 indicates "relay function cannot be continued" (S808). If the D / C field 401 has a value indicating "SRAP Control PDU" and the PDU type field 402 indicates "relay function cannot be continued" (i.e., the above-mentioned "relay function cannot be continued notification"), the following occurs: The SRAP PDU analysis processor 206 determines that the SRAP PDU is a relay function cannot be continued notification (FIGS. 4 and 5), and proceeds to S609 according to STEP 1 of FIG. 6 in the first embodiment (S809).

[0073] When the D / C field 401 has a value indicating "SRAP Control PDU" and the PDU type field 402 indicates "relay function interruption" (i.e., the aforementioned "relay function interruption notification"), the following occurs: SRAP PDU analysis processing unit 206 determines that the SRAP PDU is a relay function interruption notification, interprets the value stored in option field 1 704 as the time until the relay function is interrupted, and acquires that value. Also, it interprets the value stored in option field 2 705 as the time until the relay function is restored after being interrupted, and acquires that value.

[0074] Based on the analysis result of the SRAP PDU analysis processing unit 206, the control unit 201 recognizes that UE B (102) will suspend the relay function, and requests the path switching processing unit 204 to switch the path of UE A (101) within the time until the relay function is suspended. The path switching processing unit 204 switches UE A (101) from the indirect path to the direct path (S811, S812). If the received SRAP PDU is not a relay function suspension notification, it performs processing corresponding to other SRAP PDUs (S813).

[0075] After the relay function recovery time of UE B (102) acquired in S810 has elapsed, the control unit 201 acquires the signal strength with UE A (101) switched in S812 and the signal strength with UE B (102) from the UE management unit 203 and compares them. If the signal strength with UE B (102) is greater than the signal strength with UE A, it determines to switch to the original indirect path (i.e., the system configuration shown in FIG. 1) and causes the path switching processing unit 204 to execute path switching (S814, S815, S816).

[0076] By the above flow, when UE B (102) discontinues the relaying continuation, UE B (102) and base station 103 can switch UE A (101) from the indirect path to the direct path without interrupting the service.

[0077] In this embodiment, the base station 103 takes into consideration the possibility that both the relay function non-continuation notification and the relay function interruption notification will be received. However, a configuration is also possible in which only the relay function interruption notification is used out of the relay function non-continuation notification and the relay function interruption notification. In this case, steps S808 and S809 may be omitted from the flow shown in FIG. 8 .

[0078] Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments.

[0079] For example, in the above-described embodiment, switching from an indirect path to a direct path is performed based on a notification that the relay function cannot be continued or a notification that the relay function is suspended, but this is not limited to this. For example, switching from an indirect path to another indirect path using another relay UE may be realized based on a notification that the relay function cannot be continued or a notification that the relay function is suspended. For example, if the signal strength between UE A (101) and the base station 103 is lower than the signal strength between UE A (101) and another UE (UE other than UE B (102)), switching to an indirect path via the other UE may be realized.

[0080] In addition, in the above-described embodiment, instead of SRAP, a method may be used to notify the gNB that the relay function cannot be continued or interrupted by using the RRC connection between the base station and the relay UE.

[0081] 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.

[0082] This application claims priority based on Japanese Patent Application No. 2023-096727, filed on June 13, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A communications device comprising: a Sidelink relay means for relaying communications between a base station and a remote UE (User Equipment); a generation means for generating an SRAP control PDU, which is a PDU (Protocol Data Unit) of a Sidelink Adaptation Protocol (SRAP); and a transmission means for transmitting the SRAP control PDU generated by the generation means, wherein the generation means stores stop-related information regarding the stop of relaying by the Sidelink relay means in the SRAP control PDU when a predetermined condition is satisfied under a situation in which relaying by the Sidelink relay means is being performed.

2. The communication device according to claim 1, wherein the predetermined condition relates to a state of the device itself.

3. A communication device as described in claim 1 or 2, further comprising a first detection means for detecting a remaining charge of a battery that supplies power to the device, and the specified condition is satisfied when the remaining charge of the battery detected by the first detection means falls below a threshold value.

4. A communication device as described in any one of claims 1 to 3, further comprising a second detection means for detecting a specified abnormality in the device itself, wherein the specified condition is satisfied when the specified abnormality is detected by the second detection means.

5. The communication device according to claim 4, wherein the specified abnormality includes at least one of a hardware failure of the device itself and a disappearance of a process in software implemented in the device itself.

6. A communication device according to any one of claims 1 to 5, wherein the predetermined condition is satisfied when a function relating to the Sidelink relay means is turned off.

7. A communication device according to any one of claims 1 to 6, wherein the predetermined condition is satisfied when the power of the device itself is turned off or reset.

8. A communications device according to any one of claims 1 to 7, further comprising first measuring means for measuring a signal strength of a signal received from said remote UE, said predetermined condition being met when said signal strength falls below a threshold value.

9. A communications device according to any one of claims 1 to 8, further comprising second measuring means for measuring a signal strength of a signal received from said base station, said predetermined condition being met when said signal strength is below a threshold value.

10. The communication device according to any one of claims 1 to 9, wherein said generating means stores a value meaning "SRAP control PDU" in a D / C field of said SRAP control PDU.

11. The communication device according to claim 1, wherein the generating means stores the stop-related information in a PDU type field of the SRAP control PDU.

12. A communication device as claimed in any one of claims 1 to 11, wherein the stop-related information includes at least one of information indicating a stop of a function related to the Sidelink relay means, information indicating the time until the stop, information indicating the cause of the stop, and information indicating the time until resumption after the stop.

13. A base station comprising: a communication means for communicating with a remote UE via a relay UE (User Equipment); a receiving means for receiving an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU, from the relay UE; and a control means for, when the receiving means receives an SRAP control PDU storing stop-related information regarding stop of relaying via the relay UE, executing communication control related to the communication means based on the stop-related information.

14. The base station according to claim 13, wherein said control means executes said communication control based on said stop-related information stored in a PDU type field of said SRAP control PDU when a value meaning "SRAP control PDU" is stored in a D / C field of said SRAP control PDU.

15. The base station according to claim 13, wherein the communication control includes instructing the remote UE to switch from an indirect path via the relay UE to another path based on the outage-related information.

16. The base station according to claim 15, wherein the suspension-related information includes at least one of information indicating suspension of the function of relaying to a remote UE via the relay UE, information indicating the time until the suspension, information indicating the cause of the suspension, and information indicating the time until resumption after the suspension.

17. The base station according to claim 16, wherein said communication control includes instructing said switching within said time remaining until said stoppage, based on information indicating the time remaining until said stoppage.

18. A base station according to claim 16 or 17, wherein the communication control includes instructing switching from the different path after switching to the indirect path based on information indicating the time until resumption after the suspension.

19. A control method for controlling communications, comprising: a relaying step of relaying communications between a base station and a remote UE (User Equipment); a generating step of generating an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU; and a transmitting step of transmitting the SRAP control PDU generated by the generating step, wherein the generating step includes storing stop-related information regarding stop of relaying by the relaying step in the SRAP control PDU when a predetermined condition is satisfied under a situation in which relaying by the relaying step is being performed.

20. A program that causes a computer to execute a relaying step of relaying communication between a base station and a remote UE (User Equipment); a generating step of generating an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU; and a transmitting step of transmitting the SRAP control PDU generated by the generating step, wherein the generating step includes storing stop-related information regarding the stop of relaying by the relaying step in the SRAP control PDU when a predetermined condition is satisfied under a situation in which relaying by the relaying step is being performed.

21. A control method comprising: a communication step of communicating with a remote UE via a relay UE (User Equipment); a receiving step of receiving an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU, from the relay UE; and a control step of, when the receiving step receives an SRAP control PDU storing stop-related information regarding the stop of relaying via the relay UE, executing communication control related to the communication step based on the stop-related information.

22. A program causing a computer to execute the following steps: a communication step of communicating with a remote UE via a relay UE (User Equipment); a receiving step of receiving an SRAP control PDU, which is a Sidelink Adaptation Protocol (SRAP) PDU, from the relay UE; and a control step of, when an SRAP control PDU storing stop-related information regarding the stop of relaying via the relay UE is received in the receiving step, executing communication control related to the communication step based on the stop-related information.

23. A communication device comprising: a Sidelink relay means for relaying communication between a base station and a remote UE (User Equipment); and a notification means for notifying the base station of stop-related information regarding the stop of relaying by the Sidelink relay means when a predetermined condition is satisfied under a situation in which relaying by the Sidelink relay means is being performed.

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