Relay selection or reselection method, device and system

Abstract

An embodiment of the present invention provides a relay selection or reselection method, device and system, which includes, in a UE-to-UE relay scenario, a first terminal device triggers a relay selection or reselection in at least one of the following situations: a PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold, the first terminal device detects a radio link failure of a PC5 interface between the first terminal device and the second relay device, an indication of an upper layer, an indication of a first relay device, a PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold, the first terminal device receives a PC5-S link release message from a second relay device, the first terminal device detects a radio link failure of a PC5 interface between the first terminal device and the second relay device, an indication of a second relay device, an indication of a third relay device, an indication of a second terminal device, and a PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold.

Description

[Technical Field]

[0001] The present invention relates to the field of communications. [Background technology]

[0002] Release 17 considers UE-to-UE relay, which can extend the coverage of sidelink transmissions between two sidelink UEs and save power.

[0003] Figure 1 is a schematic diagram of a UE-to-UE relay scenario. As shown in Figure 1, in one scenario, all UEs (including source UE 11, relay UE 12, and destination UE 13) are within the network coverage, and in another scenario, all UEs are out of the network coverage. In yet another scenario, at least one UE is within the network coverage and at least one UE is out of the network coverage, which is also referred to as a partial coverage scenario. Figure 2 is a schematic diagram of the network architecture for the scenario shown in Figure 1.

[0004] The above description of the background art is merely for the purpose of explaining the configuration of the present invention more clearly and completely, and is provided for the understanding of those skilled in the art. These configurations described in the background art of the present invention should not be construed as being well known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0005] According to the discovery of the present inventors, the prior art only specifies the circumstances in which a remote UE triggers relay selection or reselection in a UE-to-Network relay scenario, and some circumstances in which a relay selection or reselection is triggered in the prior art do not apply to triggering relay selection or reselection by a source UE and / or a destination UE in a UE-to-UE relay scenario, because the UE-to-UE relay scenario is not related to the signal strength of the Uu interface or communication with the network.

[0006] To solve the above-mentioned problems and other similar problems, embodiments of the present invention provide a relay selection or reselection method, apparatus and system. [Means for solving the problem]

[0007] In one aspect of an embodiment of the present invention, a relay selection or reselection device configured in a first terminal device, in a UE-to-UE relay scenario, includes: a PC5 signal strength between the first terminal device and a second terminal device is lower than a first signal strength threshold; the first terminal device has detected a radio link failure (RLF) of the PC5 interface between the first terminal device and the second terminal device; an instruction from an upper layer; an instruction from the first relay device; the PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold; the first terminal device has received a PC5-S link release message from the second relay device; the first terminal device has detected a radio link failure (RLF) of the PC5 interface between the first terminal device and the second relay device; The present invention provides an apparatus including a trigger unit that triggers the selection or reselection of a relay device in at least one of the following situations: an instruction from a second relay device, an instruction from a third relay device, an instruction from a second terminal device, and a PC5 signal strength between a first terminal device and a third relay device is higher than a seventh signal strength threshold; the first relay device is a candidate relay device; the second relay device is a current relay device via which the first terminal device communicates with the second terminal device; and the third relay device is another relay device other than the current relay device via which the first terminal device communicates with the second terminal device.

[0008] In another aspect of the embodiment of the present invention, there is provided a relay selection or reselection device, configured in a relay device, for UE-to-UE relay (UE-to-UEIn a scenario of a relay, the PC5 signal strength between the relay device and a first terminal device is higher than a third signal strength threshold, and the relay device is a candidate relay device; the PC5 signal strength between the relay device and a second terminal device is higher than a fourth signal strength threshold, and the relay device is a candidate relay device; the relay device detects an RLF of the PC5 interface or PC5-RRC connection between the relay device and the second terminal device, and the relay device is a current relay device through which the first terminal device communicates with the second terminal device; and the second terminal device is lower than a fifth signal strength threshold, the relay device is the current relay device through which the first terminal device communicates with the second terminal device, the relay device has determined that the second terminal device is performing or will perform relay device reselection, the relay device is the current relay device through which the first terminal device communicates with the second terminal device, the PC5-S link between the relay device and the first terminal device is released, and the relay device has determined that the first terminal device is performing or will perform relay device reselection. the relay device is the current relay device via which the first terminal device communicates with the second terminal device; the PC5-S link between the relay device and the second terminal device is released, and the relay device is the current relay device via which the first terminal device communicates with the second terminal device; the relay device has determined that the PC5 signal strength between another relay device and the second terminal device is higher than a sixth signal strength threshold, and the relay device is the current relay device via which the first terminal device communicates with the second terminal device; the PC5 signal strength between the relay device and the first terminal device is and an instruction unit that instructs the first terminal device to trigger or perform relay selection or reselection in at least one of the following situations: the PC5 signal strength between the relay device and the second terminal device is higher than a seventh signal strength threshold and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device; and the PC5 signal strength between the relay device and the second terminal device is higher than a sixth signal strength threshold and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0009] Another aspect of an embodiment of the present invention provides a relay selection or reselection device configured in a second terminal device, the relay selection or reselection device including an instruction unit that instructs the first terminal device to trigger or perform relay selection or reselection in at least one of the following situations in a UE-to-UE relay scenario: an end-to-end PC5-RRC connection or PC5 link between a first terminal device and a second terminal device is released, the second terminal device is performing or about to perform relay device selection or reselection, and the PC5 signal strength between a third relay device and the second terminal device is higher than a sixth signal strength threshold, and the third relay device is another relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0010] One of the advantageous effects of the embodiments of the present invention is as follows: In a UE-to-UE relay scenario, the embodiments of the present invention solve the problem of how a source UE and / or a destination UE triggers relay selection or reselection, and can guarantee the radio signal quality between the source UE or the destination UE and the relay UE, and ensure that the service quality requirements are met.

[0011] As shown in the following description and drawings, specific embodiments of the present invention are disclosed in detail to illustrate ways in which the principles of the present invention can be employed. However, the scope of the present invention is not limited to these embodiments. The present invention encompasses all modifications, alterations, and equivalents within the spirit and scope of the appended claims.

[0012] Features described and / or shown in one embodiment may be used in the same or similar manner in one or more other embodiments, may be combined with features in other embodiments, or may be substituted for features in other embodiments.

[0013] It should be noted that in this text, the term "comprise / have" means the presence of a feature, element, step or component, and does not exclude the presence or addition of one or more other features, elements, steps or components. [Brief explanation of the drawings]

[0014] Elements and features depicted in one drawing and one embodiment of an example of the invention may be combined with elements and features shown in one or more drawings or embodiments, and in the drawings, like reference numerals may indicate corresponding elements in multiple drawings and may indicate corresponding elements used in more than one embodiment.

[0015] The drawings included are used to further understand the embodiments of the present invention, constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the written description, explain the principles of the present invention. Note that the drawings described below are merely some examples of the present invention, and those skilled in the art can easily imagine other drawings based on these drawings. [Figure 1] FIG. 1 is a schematic diagram of a UE-to-UE relay scenario. [Figure 2] FIG. 2 is a schematic diagram of the network architecture of the scenario shown in FIG. 1. [Figure 3] FIG. 1 is a schematic diagram of a UE-to-Network relay scenario. [Figure 4] 2 is a schematic diagram of an example of a relay selection or reselection method according to an embodiment of the present invention; [Figure 5] FIG. 10 is a schematic diagram of another example of a relay selection or reselection method according to an embodiment of the present invention; [Figure 6] FIG. 10 is a schematic diagram of another example of a relay selection or reselection method according to an embodiment of the present invention; [Figure 7] 1 is a schematic diagram of an example of a relay selection or reselection device according to an embodiment of the present invention; [Figure 8] 10 is a schematic diagram of another example of a relay selection or reselection device according to an embodiment of the present invention; [Figure 9]10 is a schematic diagram of another example of a relay selection or reselection device according to an embodiment of the present invention; [Figure 10] 1 is a schematic diagram of a communication system according to an embodiment of the present invention; [Figure 11] FIG. 1 is a schematic diagram of a terminal device according to an embodiment of the present invention. [Figure 12] 1 is a schematic diagram of a relay device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0016] The above and other features of the present invention will become apparent from the following description. In the specification and drawings, specific embodiments of the present invention are disclosed in detail, and some of the embodiments in which the principles of the present invention can be adopted are shown. However, the present invention is not limited to the described embodiments. The present invention includes all modifications, variations, and equivalents within the scope of the appended claims. Below, various embodiments of the present invention will be described with reference to the drawings. These embodiments are merely illustrative and do not limit the present invention.

[0017] In embodiments of the present invention, the terms "first," "second," etc. are used in titles to distinguish between different elements, but do not represent the spatial arrangement or temporal order of these elements, and these elements are not limited to these terms. The term "and / or" includes any and all combinations of one or more of the terms listed in the associated list. The terms "comprise," "include," "have," etc. refer to the presence of listed features, elements, elements, or components, but do not exclude the presence or addition of one or more other features, elements, elements, or components.

[0018] In the embodiments of the present invention, the singular forms "one," "the," etc., include the plural and should be understood broadly as "one kind" or "one class," and are not limited to "one." Furthermore, the term "said" should be understood to include both the singular and the plural, unless the context clearly indicates otherwise. Furthermore, the term "described in" should be understood to mean "described at least in part," and the term "based on" should be understood to mean "based at least in part," unless the context clearly indicates otherwise.

[0019] In embodiments of the present invention, the terms "communication network" or "wireless communication network" may refer to a network conforming to any communication standard, such as, for example, Long Term Evolution (LTE), Long Term Evolution Advanced (LTE-A, LTE-Advanced), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), etc.

[0020] Additionally, communications between devices in a communications system may occur according to any stage of communications protocol, including, but not limited to, 1G (generation), 2G, 2.5G, 2.75G, 3G, 4G, 4.5G, and future 5G, New Radio (NR), etc., and / or other currently known or future developed communications protocols.

[0021] In an embodiment of the present invention, the term "network device" refers to a device in a communication system that allows a terminal device to access the communication system and provides a service to the terminal device, and may include, but is not limited to, a base station (BS), an access point (AP), a transmission reception point (TRP), a broadcast transmitter, a mobility management entity (MME), a gateway, a server, a radio network controller (RNC), a base station controller (BSC), etc.

[0022] A base station may include, but is not limited to, a Node B (NodeB or NB), evolved Node B (eNodeB or eNB), 5G base station (gNB), etc., as well as a remote radio head (RRH), a remote radio unit (RRU), a relay, or a low power node (e.g., femto, pico, etc.). Also, the term "base station" may include some or all of these functionalities, and each base station may provide communication coverage for a particular geographic area. The term "cell" may refer to a base station and / or its coverage area, depending on the context in which the term is used.

[0023] In the embodiments of the present invention, the term "User Equipment" (UE) or "Terminal Equipment" (TE) refers to a device that accesses a communication network and receives network services via, for example, a network device. The terminal device may be fixed or mobile, and may also be referred to as a mobile station (MS), a terminal, a subscriber station (SS), an access terminal (AT), a station, etc.

[0024] The terminal device may include, but is not limited to, a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a machine-type communication device, a laptop computer, a cordless phone, a smartphone, a smart watch, a digital camera, and the like.

[0025] Also, for example, in a scenario such as the Internet of Things (IoT), the user equipment may be a monitoring or measuring device or apparatus, and may include, but is not limited to, a Machine Type Communication (MTC) terminal, an in-vehicle communication terminal, a Device to Device (D2D) terminal, a Machine to Machine (M2M) terminal, etc.

[0026] Figure 3 is a schematic diagram of UE-to-Network relay scenarios. As shown in Figure 3, in Scenario 1, the remote UE 31 is out of the coverage range of the network and the relay UE 32 is within the coverage range of the network, in Scenario 2, the remote UE 31 and the relay UE 32 are both within the coverage range of the network, and in Scenario 3, the remote UE 31 and the relay UE 32 are within the coverage range of different cells.

[0027] In Release 17 UE-to-Network relay, the remote UE triggers relay selection when:

[0028] The current serving cell's direct Uu signal strength is lower than the configured signal strength threshold Upper layer (ProSe layer) instructions In Release 17 UE-to-Network relay, the remote UE triggers relay reselection when:

[0029] · The current relay UE's PC5 signal strength is lower than the (pre-)configured signal strength threshold The relay UE indicates cell selection / reselection, handover or Uu interface radio link failure (RLF) via the PC5-RRC connection. When the remote UE receives a PC5-S link release message from the relay UE When the remote UE detects an RLF on the PC5 interface Upper layer (ProSe layer) instructions The prior art only specifies the circumstances under which a remote UE triggers relay selection or reselection in a UE-to-Network relay scenario. Because the UE-to-UE relay scenario is not related to the signal strength of the Uu interface or communication with the network, the prior art does not apply some circumstances under which relay selection or reselection is triggered by a source UE and / or a destination UE in a UE-to-UE relay scenario.

[0030] In view of the above problems, the present invention has been proposed. Various embodiments of the present invention will be described below with reference to the drawings. These embodiments are merely illustrative and do not limit the present invention.

[0031] Example 1 An embodiment of the present invention provides a relay selection or reselection method, which is explained from the first terminal device side.

[0032] 4 is a schematic diagram of an example of a relay selection or reselection method according to an embodiment of the present invention. As shown in FIG. 4, the method includes the following steps:

[0033] Step 401: In a UE-to-UE relay scenario, the first terminal device: The PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second terminal device; Higher-level instructions, an instruction from the first relay device; The PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold; The first terminal device receives a PC5-S link release message from the second relay device; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second relay device; An instruction to the second relay device; instructions for the third relay device; An instruction of the second terminal device; and Triggering relay device selection or reselection in at least one of the following situations: the PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold.

[0034] In an embodiment of the present invention, the first terminal device may be a source UE in a UE-to-UE relay scenario, such as a first remote UE or the source UE 11 in the scenario shown in Fig. 1, or a destination UE in a UE-to-UE relay scenario, such as a second remote UE or the destination UE 13 in the scenario shown in Fig. 1. Accordingly, when the first terminal device is a source UE in a UE-to-UE relay scenario, the second terminal device is a destination UE in the UE-to-UE relay scenario, and when the first terminal device is a destination UE in the UE-to-UE relay scenario, the second terminal device is a source UE in the UE-to-UE relay scenario.

[0035] According to an embodiment of the present invention, trigger conditions for relay selection or reselection by a source UE and / or a destination UE in a UE-to-UE relay scenario are defined, and the problem of how a source UE and / or a destination UE in a UE-to-UE relay scenario triggers relay selection or reselection is solved.

[0036] In some embodiments, in a UE-to-UE relay scenario, the first terminal device: The PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second terminal device; Higher layer instructions, and At least one condition of the indication of the first relay device triggers the selection of the relay device.

[0037] In the above embodiment, in one situation, the first terminal device triggers the selection of a relay device when it detects that the PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold. Here, the first signal strength threshold may be pre-configured, configured by a network device, or pre-defined, but the present invention is not limited thereto. Furthermore, the PC5 signal strength between the first terminal device and the second terminal device, i.e., the signal strength of the PC5 interface between the first terminal device and the second terminal device, may be the SL-RSRP (Sidelink Reference Received Power) and / or SD-RSRP (Sidelink Discovery Message Reference Signal Received Power) of the second terminal device of the PC5 interface measured by the first terminal device.

[0038] In the above embodiment, in one situation, the first terminal device triggers the selection of a relay device when it detects a radio link failure (RLF) of the PC5 interface between the first terminal device and the second terminal device. For example, the second terminal device has one or more destinations, destination IDs, or L2 IDs, and determines that an RLF has occurred in the PC5 interface between the first terminal device and the second terminal device when the sidelink RLC entity of the first terminal device indicates that the maximum number of retransmissions of the destination to the second terminal device has been reached. Alternatively, it determines that an RLF has occurred in the PC5 interface between the first terminal device and the second terminal device when the T400 timer in the first terminal device for the destination of the second terminal device has timed out. Alternatively, it determines that an RLF has occurred in the PC5 interface between the first terminal device and the second terminal device when the media access control (MAC) entity of the first terminal device indicates that the maximum number of consecutive HARQ DTXs (discontinuous transmissions) to the destination of the second terminal device has been reached. Alternatively, if the sidelink PDCP (Packet Data Convergence Protocol) entity of the first terminal device indicates that the integrity verification of the SL-SRB2 or SL-SRB3 for the destination of the second terminal device has failed, it is determined that an RLF has occurred on the PC5 interface between the first terminal device and the second terminal device.

[0039] In the above embodiment, in one situation, the first terminal device triggers the selection of a relay device when receiving an instruction from a higher layer, where the higher layer refers to a layer higher than the RRC (Radio Resource Control), PDCP, or MAC of the first terminal device, and may be, for example, a Non-Access stratum (NAS), a V2X (Vehicle-to-Everything layer: a vehicle-to-everything / road-to-vehicle communication layer, which can provide functions related to communication between vehicles and other things), or a Proximity-based Services layer (ProSe layer: a Proximity-based Services layer, which can provide functions related to services between nearby terminal devices).

[0040] In the above embodiment, in one situation, the first terminal device triggers the selection of a relay device when receiving an instruction from the first relay device, where the first relay device is a candidate relay device, for example, the relay device may have the ability to relay a service from a source UE to a destination UE, where the instruction from the first relay device includes, for example, that the PC5 signal strength between the first relay device and the first terminal device is higher than a third signal strength threshold and / or that the PC5 signal strength between the first relay device and the second terminal device is higher than a fourth signal strength threshold.

[0041] That is, if the PC5 signal strength between the first relay device and the first terminal device is higher than the third signal strength threshold, or if the PC5 signal strength between the first relay device and the second terminal device is higher than the fourth signal strength threshold, the first relay device sends an instruction to the first terminal device, and the first terminal device triggers the selection of a relay device upon receiving the instruction from the first relay device. Here, the PC5 signal strength may be the SL-RSRP and / or SD-RSRP of the first or second terminal device of the PC5 interface measured by the first relay device. The third and fourth signal strength thresholds may be pre-configured, configured by a network device, or pre-defined, and the present invention is not limited thereto.

[0042] In the above embodiment, the instruction from the first relay device may be transmitted via a discovery-related message, a PC5 direct communication-related message, or a PC5-RRC message, but the present invention is not limited thereto. The PC5-RRC message is a message transmitted after the first terminal device establishes a PC5 connection with the first relay device.

[0043] In some other embodiments, in a UE-to-UE relay scenario, the first terminal device: The PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold; The first terminal device receives a PC5-S link release message from the second relay device; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second relay device; Higher-level instructions, An instruction to the second relay device; instructions for the third relay device; An instruction of the second terminal device; and Trigger a reselection of the relay device in at least one of the following situations: the PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold.

[0044] In the above embodiment, in one situation, the first terminal device triggers a reselection of a relay device when it detects that the PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold. Here, the second relay device is the current relay device through which the first terminal device communicates with the second terminal device. Here, the second signal strength threshold may be pre-configured, configured by a network device, or pre-defined, and the present invention is not limited thereto. Furthermore, the PC5 signal strength between the first terminal device and the second relay device, i.e., the signal strength of the PC5 interface between the first terminal device and the second relay device, may be the SL-RSRP and / or SD-RSRP of the second relay device of the PC5 interface measured by the first terminal device.

[0045] In the above embodiment, in one situation, when the first terminal device receives a PC5-S (PC5-Signaling) link release message from the second terminal device, it triggers reselection of the relay device. For example, when the second terminal device releases the PC5-S link between the first terminal device and the second terminal device, it sends a PC5-S link release message (e.g., a Disconnect Request message) to the first terminal device. When the first terminal device receives this message, it triggers reselection of the relay device. Alternatively, the first terminal device may trigger reselection of the relay device when it sends a link release response message (e.g., a Disconnect Response message).

[0046] In the above embodiment, in one situation, the first terminal device triggers relay device reselection when it detects that a radio link failure (RLF) has occurred on the PC5 interface between the first terminal device and the second relay device. For example, the second relay device has one or more destinations, destination IDs, or L2 IDs, and determines that an RLF has occurred on the PC5 interface between the first terminal device and the second relay device when the sidelink RLC entity of the first terminal device indicates that the maximum number of retransmissions for the destination to the second relay device has been reached. Alternatively, determines that an RLF has occurred on the PC5 interface between the first terminal device and the second relay device when the T400 timer of the first terminal device for the destination of the second relay device has timed out. Alternatively, determines that an RLF has occurred on the PC5 interface between the first terminal device and the second relay device when the MAC entity of the first terminal device indicates that the maximum number of consecutive HARQ DTXs (discontinuous transmissions) for the destination of the second relay device has been reached. Alternatively, if the sidelink PDCP entity of the first terminal device indicates that integrity verification of SL-SRB2 or SL-SRB3 for the destination of the second relay device has failed, it is determined that an RLF has occurred on the PC5 interface between the first terminal device and the second relay device.

[0047] In the above embodiment, in one situation, the first terminal device triggers reselection of a relay device when receiving an instruction from a higher layer, where the higher layer means a layer higher than the RRC, PDCP, or MAC of the first terminal device, such as a non-access layer, a V2X layer, or a ProSe layer.

[0048] In the above embodiment, in one situation, the first terminal device triggers the reselection of a relay device when receiving an instruction from the second relay device, where the instruction from the second relay device is, for example: The second relay device detects an RLF of the PC5 interface or PC5-RRC connection between the second relay device and the second terminal device; The PC5 signal strength between the second relay device and the second terminal device is lower than a fifth signal strength threshold; the second terminal device is performing or about to perform a relay device reselection; The PC5-S link between the second relay device and the second terminal device is released; and The PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

[0049] In the above embodiment, in one situation, when the second relay device detects that an RLF has occurred in the PC5 interface or the PC5-RRC connection between the second terminal device and the second terminal device, the second relay device sends an indication to the first terminal device. Upon receiving this indication, the first terminal device triggers relay device reselection. For example, the second terminal device determines that an RLF has occurred in the PC5 interface or the PC5-RRC connection between the second relay device and the second terminal device if the second relay device has one or more destinations, destination IDs, or L2 IDs, and the sidelink RLC entity of the second relay device indicates that the maximum number of retransmissions for the destination to the second terminal device has been reached. Alternatively, the second relay device determines that an RLF has occurred in the PC5 interface or the PC5-RRC connection between the second relay device and the second terminal device if the T400 timer of the second relay device for the destination of the second terminal device times out. Alternatively, if the MAC (media access control) entity of the second relay device indicates the maximum number of continuous HARQ DTX (discontinuous transmission) to the destination of the second terminal device, it is determined that an RLF has occurred on the PC5 interface or destination connection between the second relay device and the second terminal device. Alternatively, if the sidelink PDCP (destination ID: packet data aggregation protocol) entity of the second relay device indicates that the integrity verification of the SL-SRB2 or SL-SRB3 for the destination of the second terminal device has failed, it is determined that an RLF has occurred on the PC5 interface or destination connection between the second relay device and the second terminal device.

[0050] In the above embodiment, in one situation, if the second relay device detects that the PC5 signal strength between the second relay device and the second terminal device is lower than a fifth signal strength threshold, the second relay device sends an instruction to the first terminal device. Upon receiving this instruction, the first terminal device triggers reselection of a relay device. Here, the fifth signal strength threshold may be pre-configured and pre-defined by the network device, but the present invention is not limited thereto. Furthermore, the PC5 signal strength between the second relay device and the second terminal device, i.e., the signal strength of the PC5 interface between the second relay device and the second terminal device, may be the SL-RSRP and / or SD-RSRP of the second terminal device of the PC5 interface measured by the second relay device.

[0051] In the above embodiment, in one situation, when the second terminal device is performing or about to perform relay device reselection, it may notify the second relay device of this situation via a PC5-RRC message or PC5-S signaling. Upon receiving the notification from the second terminal device, the second relay device sends an instruction to the first terminal device. Upon receiving the instruction, the first terminal device triggers relay device reselection.

[0052] In the above embodiment, in one situation, when the second relay device releases the PC5-S link between the second terminal device and the first terminal device, the second relay device sends an instruction to the first terminal device. When the first terminal device receives this instruction, the second relay device triggers reselection of a relay device. For example, the second relay device sends a PC5-S link release message (e.g., a Disconnect Request message) to the second terminal device and then sends the above instruction to the first terminal device. Alternatively, the second relay device sends the above instruction to the first terminal device when or after receiving a link release response message (e.g., a Disconnect Response message) from the second terminal device.

[0053] In the above embodiment, in one situation, if the third relay device detects that the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold, the third relay device may notify the second relay device of this situation. Upon receiving the notification from the third relay device, the second relay device sends an instruction to the first terminal device. Upon receiving the instruction, the first terminal device triggers reselection of a relay device. Here, the sixth signal strength threshold may be pre-configured, configured by a network device, or pre-defined, but the present invention is not limited thereto. Furthermore, the PC5 signal strength between the third relay device and the second terminal device, i.e., the signal strength of the PC5 interface between the third relay device and the second terminal device, may be the SL-RSRP and / or SD-RSRP of the second terminal device of the PC5 interface measured by the third relay device.

[0054] In the above embodiment, the third relay device may report the above situation to the first terminal device in another manner, for example, the third relay device may notify the second terminal device of the above situation, and the second terminal device may instruct the first terminal device.

[0055] In the above embodiment, the indication of the second relay device may be sent via at least one of a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE (media access control element) and a sidelink relay adaptation layer (SRAP) control PDU (Protocol Data Unit), but the present invention is not limited thereto.

[0056] In the above embodiment, in one situation, the first terminal device triggers a reselection of a relay device when receiving an instruction from a third relay device, the third relay device being another relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0057] Here, the instruction from the third relay device may include, for example, that the PC5 signal strength between the third relay device and the first terminal device is higher than the seventh signal strength threshold and / or that the PC5 signal strength between the third relay device and the second terminal device is higher than the sixth signal strength threshold. That is, if the PC5 signal strength between the third relay device and the first terminal device is higher than the seventh signal strength threshold and / or that the PC5 signal strength between the third relay device and the second terminal device is higher than the sixth signal strength threshold, the third relay device sends an instruction to the first terminal device. Upon receiving the instruction from the third relay device, the first terminal device triggers the selection of a relay device. Here, the sixth signal strength threshold and the seventh signal strength threshold may be pre-configured, configured by a network device, or pre-defined, but the present invention is not limited thereto. Furthermore, the PC5 signal strength between the third relay device and the first terminal device, i.e., the signal strength of the PC5 interface between the third relay device and the first terminal device, may be the SL-RSRP and / or SD-RSRP of the first terminal device of the PC5 interface measured by the third relay device.

[0058] In the above embodiment, the instruction from the third relay device may be sent via a discovery-related message, a PC5 direct communication-related message, or a PC5-RRC message, but the present invention is not limited thereto. The PC5-RRC message is a message sent after the first terminal device establishes a PC5 connection with the third relay device.

[0059] In the above embodiment, in one situation, the first terminal device triggers the reselection of a relay device when receiving an instruction from the second terminal device, where the instruction from the second terminal device is, for example: The end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; The second terminal device is performing or about to perform a relay device selection or reselection; and The PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

[0060] In the above embodiment, in one situation, when the end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released, the second terminal device sends an indication to the first terminal device, and upon receiving the indication, the first terminal device triggers the reselection of a relay device.

[0061] In the above embodiment, in one situation, when the second terminal device is performing or about to perform relay device selection or reselection, it may indicate this situation to the first terminal device, and upon receiving this indication, the first terminal device triggers relay device reselection.

[0062] In the above embodiment, in one situation, if the second terminal device detects that the PC5 signal strength between the second terminal device and the third relay device is higher than the configured sixth signal strength threshold, the second terminal device may indicate this situation to the first terminal device. Upon receiving this indication, the first terminal device triggers a relay device reselection. Here, the PC5 signal strength between the second terminal device and the third relay device, i.e., the signal strength of the PC5 interface between the second terminal device and the third relay device, may be the SL-RSRP and / or SD-RSRP of the third relay device of the PC5 interface measured by the second terminal device.

[0063] In the above embodiment, the indication of the second terminal device may be sent via an end-to-end PC5-RRC message or PC5-S signaling, but the present invention is not limited thereto.

[0064] In the above embodiment, in one situation, the first terminal device triggers reselection of a relay device when it detects that the PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold, where the PC5 signal strength between the first terminal device and the third relay device, i.e., the signal strength of the PC5 interface between the first terminal device and the third relay device, may be the SL-RSRP and / or SD-RSRP of the third relay device of the PC5 interface measured by the first terminal device.

[0065] In each of the above embodiments, the first terminal device triggers the reselection of a relay device, that is, does not use the second relay device as the relay device through which to communicate with the second terminal device.

[0066] In each of the above embodiments, when relay device selection or reselection is triggered, the first terminal device and / or the second terminal device may select or reselect a relay device using upper layer criteria. During the relay device selection or reselection process, the first terminal device and / or the second terminal device may determine that one of the relay devices is suitable if it detects that the PC5 signal strength between the first terminal device and / or the second terminal device is higher than an eighth signal strength threshold, which may be pre-configured or configured by the network. The first terminal device and / or the second terminal device may search for a suitable relay device that meets the access stratum criteria and / or the upper layer criteria. If there are multiple suitable relay devices that meet the access stratum criteria and the upper layer criteria, the first terminal device and / or the second terminal device may select one relay device from among them.

[0067] In the above embodiments, the trigger conditions of the embodiments of the present invention are merely described as examples, but the present invention is not limited thereto and may be appropriately modified based on the above embodiments. For example, the trigger conditions of the above embodiments may be used alone, or one or more of the trigger conditions of the above embodiments may be used in combination.

[0068] In some aspects of the present invention, the first terminal device may notify the second terminal device of a situation that triggers the selection of a relay device, or may notify the current relay device (second relay device) and / or the second terminal device of a situation that triggers the reselection of a relay device, thereby allowing the current relay device and / or the second terminal device to know that the first terminal device has triggered the selection / reselection of a relay device.

[0069] In some aspects of the present invention, the first terminal device may establish a connection with the second terminal device via the selected or reselected relay device, but the present invention is not limited to the method and process of establishing the connection.

[0070] In the embodiment of the present invention, there is no limitation on the value of each signal strength threshold, and different signal strength thresholds may be the same or different.

[0071] According to the method of the embodiment of the present invention, the conditions under which a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario are defined, and the problem of how a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario is solved.

[0072] <Example 2> The embodiment of the present invention provides a relay selection or reselection method, and will be explained from the relay device side. Explanation of the same content as in the first embodiment will be omitted.

[0073] 5 is a schematic diagram of another example of a relay selection or reselection method according to an embodiment of the present invention. As shown in FIG. 5, the method includes the following steps:

[0074] Step 501: In a UE-to-UE relay scenario, relay selection is The PC5 signal strength between the relay device and the first terminal device is higher than a third signal strength threshold, and the relay device is a candidate relay device (first relay device); The PC5 signal strength between the relay device and the second terminal device is higher than a fourth signal strength threshold, and the relay device is a candidate relay device (first relay device); The relay device detects the RLF of the PC5 interface or PC5-RRC connection between the second terminal device and the relay device, and the relay device is the current relay device (second relay device) through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the second terminal device is lower than a fifth signal strength threshold, and the relay device is the current relay device (second relay device) through which the first terminal device communicates with the second terminal device; The relay device is a current relay device (second relay device) through which the second terminal device communicates with the second terminal device, and the second terminal device is currently performing or has determined that the second terminal device is about to perform a reselection of the relay device; The PC5-S link between the relay device and the first terminal device is released, and the relay device is the current relay device (second relay device) through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the second terminal device is released, and the relay device is the current relay device (second relay device) through which the first terminal device communicates with the second terminal device; The relay device determines that the PC5 signal strength between another relay device (a third relay device) and the second terminal device is higher than a sixth signal strength threshold, and the relay device is the current relay device (a second relay device) through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the first terminal device is higher than the seventh signal strength threshold, and the relay device is a relay device (third relay device) other than the current relay device through which the first terminal device communicates with the second terminal device; and In at least one of the following situations: the PC5 signal strength between the relay device and the second terminal device is higher than a sixth signal strength threshold; and the relay device is another relay device (third relay device) other than the current relay device through which the first terminal device communicates with the second terminal device, the first terminal device is instructed to trigger or perform relay selection or reselection.

[0075] For example, if the PC5 signal strength between a relay device (first relay device) and a first terminal device is higher than a third signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs the selection of a relay device according to the instruction.

[0076] Also, for example, when the PC5 signal strength between a relay device (first relay device) and a second terminal device is higher than a fourth signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or executes the selection of a relay device according to the instruction.

[0077] Also, for example, when a relay device (second relay device) detects an RLF of the PC5 interface or PC5-RRC connection between the second terminal device, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs reselection of the relay device according to the instruction.

[0078] Also, for example, if the PC5 signal strength between the relay device (second relay device) and the second terminal device is lower than the fifth signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or executes reselection of the relay device according to the instruction.

[0079] Also, for example, when a relay device (second relay device) determines that the second terminal device is performing or is about to perform a reselection of a relay device, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs a reselection of a relay device in accordance with the instruction.

[0080] Also, for example, when the PC5-S link between a relay device (second relay device) and a first terminal device is released, the relay device sends a PC5-S link release message (e.g., a Disconnect Request message) to the first terminal device, and via this message instructs the first terminal device to trigger reselection of the relay device, and when the first terminal device receives this message, it triggers reselection of the relay device, or when the first terminal device responds to a PC5-S link release response message (e.g., a Disconnect Response message), it triggers reselection of the relay device.

[0081] Also, for example, when the PC5-S link between the relay device (second relay device) and the second terminal device is released, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or executes reselection of the relay device in accordance with the instruction.

[0082] Also, for example, if a relay device (second relay device) determines that the PC5 signal strength between another relay device (third relay device) and the second terminal device is higher than the sixth signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs reselection of a relay device in accordance with the instruction.

[0083] Also, for example, if the PC5 signal strength between the relay device (third relay device) and the first terminal device is higher than the seventh signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs reselection of the relay device according to the instruction.

[0084] Also, for example, if the PC5 signal strength between the relay device (third relay device) and the second terminal device is higher than the sixth signal strength threshold, the relay device sends an instruction to the first terminal device, and the first terminal device triggers or performs reselection of the relay device according to the instruction.

[0085] In some embodiments, the relay device instruction is transmitted via at least one of a discovery-related message, a PC5 direct communication-related message, a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and a SRAP control PDU, where different instructions may be transmitted via the same or different messages / signaling, as specifically exemplified in Example 1, and the description thereof will be omitted here.

[0086] In some embodiments, the relay device may receive information (referred to as first information) from the second terminal device and, based on the first information, determine that the second terminal device has performed or is about to perform a reselection of the relay device.

[0087] In the above embodiment, the first information may be sent by the second terminal device to the relay device via a PC5-RRC message or PC5-S signaling, but the present invention is not limited thereto.

[0088] In some embodiments, a relay device (second relay device) may receive information (referred to as second information) from another relay device (third relay device) or a second terminal device, and based on the second information, determine that the PC5 signal strength between the other relay device and the second terminal device is higher than a sixth signal strength threshold.

[0089] In an embodiment of the present invention, the above-mentioned signal strength thresholds may be pre-configured, configured by a network device, or pre-defined, and the present invention is not limited thereto, and the values ​​of the signal strength thresholds may be the same or different.

[0090] The above-mentioned embodiments are merely illustrative of the embodiments of the present invention, but the present invention is not limited thereto and may be appropriately modified based on the above-mentioned embodiments. For example, the above-mentioned embodiments may be used alone or in combination with one or more of them.

[0091] According to the method of the embodiment of the present invention, the conditions under which a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario are defined, and the problem of how a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario is solved.

[0092] Example 3 The embodiment of the present invention provides a relay selection or reselection method, and will be described from the perspective of the second terminal device. Description of the same content as in the first embodiment will be omitted.

[0093] 6 is a schematic diagram of another example of a relay selection or reselection method according to an embodiment of the present invention. As shown in FIG. 6, the method includes the following steps:

[0094] Step 601: In a UE-to-UE relay scenario, the second terminal device: The end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; The second terminal device is performing or about to perform a relay device selection or reselection; and In at least one situation where the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold, the first terminal device instructs the first terminal device to trigger or perform relay selection or reselection. Here, the third relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0095] For example, when an end-to-end PC5-RRC connection or PC5 link between a first terminal device and a second terminal device is released, the second terminal device sends an instruction to the first terminal device, and the first terminal device triggers or performs selection or reselection of a relay device according to the instruction.

[0096] Also, for example, when a second terminal device is performing or is about to perform selection or reselection of a relay device, the second terminal device sends an instruction to the first terminal device, and the first terminal device triggers or performs selection or reselection of a relay device in accordance with the instruction.

[0097] Also, for example, if the PC5 signal strength between the third relay device and the second terminal device is higher than the sixth signal strength threshold, the second terminal device sends an instruction to the first terminal device, and the first terminal device triggers or performs the selection or reselection of a relay device according to the instruction.

[0098] In some embodiments, the sixth signal strength threshold is pre-configured, configured by the network device, or pre-defined.

[0099] In some embodiments, the indication of the second terminal device may be sent via a PC5-RRC message or PC5-S signaling.

[0100] In some embodiments, the second terminal device may receive information (referred to as third information) transmitted by the first terminal device, the third information instructing the first terminal device to trigger selection or reselection of a relay device.

[0101] In some embodiments, the second terminal device may establish a connection with the first terminal device via a selected or reselected relay device, but the present invention is not limited to the method and process of establishing the connection.

[0102] The above-mentioned embodiments are merely illustrative of the embodiments of the present invention, but the present invention is not limited thereto and may be appropriately modified based on the above-mentioned embodiments. For example, the above-mentioned embodiments may be used alone or in combination with one or more of them.

[0103] According to the method of the embodiment of the present invention, the conditions under which a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario are defined, and the problem of how a source UE and / or a destination UE triggers relay selection or reselection in a UE-to-UE relay scenario is solved.

[0104] Example 4 An embodiment of the present invention provides a relay selection or reselection device.

[0105] 7 is a schematic diagram of an example of a relay selection or reselection device according to an embodiment of the present invention. The device may be, for example, a terminal device, or a component configured in the terminal device. For convenience of explanation, the terminal device is referred to as a first terminal device. Since the problem-solving principle of the device is similar to that of the method of the first embodiment, the specific implementation of the device may refer to the implementation of the method of the first embodiment, and the overlapping content will not be described again.

[0106] As shown in FIG. 7, a relay selection or reselection device 700 according to an embodiment of the present invention includes the following units:

[0107] The trigger unit 701, in a UE-to-UE relay scenario, The PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second terminal device; Higher-level instructions, an instruction from the first relay device; The PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold; The first terminal device receives a PC5-S link release message from the second relay device; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second relay device; An instruction to the second relay device; instructions for the third relay device; An instruction of the second terminal device; and Triggering relay device selection or reselection in at least one of the following situations: the PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold.

[0108] Here, the first relay device is a candidate relay device, the second relay device is a current relay device through which the first terminal device communicates with the second terminal device, and the third relay device is another relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0109] In some embodiments, the indication from the first relay device includes that the PC5 signal strength between the first relay device and the first terminal device is higher than a third signal strength threshold, and / or that the PC5 signal strength between the first relay device and the second terminal device is higher than a fourth signal strength threshold.

[0110] In some embodiments, the indication of the first relay device may be transmitted via a discovery related message, a PC5 direct communication related message, or a PC5-RRC message.

[0111] In some embodiments, the second relay device's instructions include: The second relay device detects an RLF of the PC5 interface or PC5-RRC connection between the second relay device and the second terminal device; The PC5 signal strength between the second relay device and the second terminal device is lower than a fifth signal strength threshold; the second terminal device is performing or about to perform a relay device reselection; The PC5-S link between the second relay device and the second terminal device is released; and The PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

[0112] In some embodiments, the indication of the second relay device may be sent via at least one of a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and a SRAP control PDU.

[0113] In some embodiments, the indication from the third relay device includes that the PC5 signal strength between the third relay device and the first terminal device is higher than a seventh signal strength threshold, and / or that the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

[0114] In some embodiments, the indication of the third relay device may be transmitted via a discovery related message, a PC5 direct communication related message, or a PC5-RRC message.

[0115] In some embodiments, the second terminal device instruction includes: The end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; The second terminal device is performing or about to perform a relay device selection or reselection; and The PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

[0116] In some embodiments, the indication of the second terminal device may be sent via an end-to-end PC5-RRC message or PC5-S signaling.

[0117] In some embodiments, as shown in FIG. 7, the relay selection or reselection device 700 may further include the following units:

[0118] The transmitter 702 notifies the second terminal device of a situation that triggers the selection of a relay device, or notifies the current relay device and / or the second terminal device of a situation that triggers the reselection of a relay device.

[0119] In some embodiments, as shown in FIG. 7, the relay selection or reselection device 700 may further include the following units:

[0120] The processing unit 703 establishes a connection with the second terminal device via the selected or reselected relay device.

[0121] In some embodiments, the signal strength threshold is pre-configured, configured by the network device, or pre-defined.

[0122] In some embodiments, the upper layer is a non-access stratum of the first terminal device.

[0123] 8 is a schematic diagram of another example of a relay selection or reselection device according to an embodiment of the present invention. The device may be, for example, a relay device, or a component configured in a relay device. Since the problem-solving principle of the device is similar to that of the method of the second embodiment, the specific implementation of the device may refer to the implementation of the method of the second embodiment, and the overlapping content will not be described again.

[0124] As shown in FIG. 8, a relay selection or reselection device 800 according to an embodiment of the present invention includes the following units:

[0125] The instruction unit 801, in a UE-to-UE relay scenario, The PC5 signal strength between the relay device and the first terminal device is higher than a third signal strength threshold, and the relay device is a candidate relay device; The PC5 signal strength between the relay device and the second terminal device is higher than a fourth signal strength threshold, and the relay device is a candidate relay device; The relay device detects an RLF of the PC5 interface or PC5-RRC connection between the second terminal device and the relay device, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the second terminal device is lower than a fifth signal strength threshold, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; the relay device determines that the second terminal device is performing or will perform a relay device reselection, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the first terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the second terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; the relay device determines that the PC5 signal strength between the other relay device and the second terminal device is higher than a sixth signal strength threshold, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the first terminal device is higher than a seventh signal strength threshold, and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device; and In at least one of the following situations: the PC5 signal strength between the relay device and the second terminal device is higher than a sixth signal strength threshold, and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device, the first terminal device is instructed to trigger or perform relay selection or reselection.

[0126] In some embodiments, the relay indication is sent via at least one of a discovery related message, a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and a SRAP control PDU.

[0127] In some embodiments, as shown in FIG. 8, the relay selection or reselection device 800 further includes the following units:

[0128] The first receiver 802 receives first information from the second terminal device and determines, based on the first information, that the second terminal device has performed or is about to perform reselection of a relay device.

[0129] In some embodiments, the first information may be sent by the second terminal device to the relay device via a PC5-RRC message or PC5-S signaling.

[0130] In some embodiments, as shown in FIG. 8, the relay selection or reselection device 800 further includes the following units:

[0131] The second receiving unit 803 receives second information from another relay device or a second terminal device, and determines, based on the second information, that the PC5 signal strength between the other relay device and the second terminal device is higher than a sixth signal strength threshold.

[0132] In some embodiments, the signal strength threshold is pre-configured, configured by the network device, or pre-defined.

[0133] 9 is a schematic diagram of another example of a relay selection or reselection device according to an embodiment of the present invention. The device may be, for example, a terminal device, or a component configured in the terminal device. For convenience of explanation, the terminal device is referred to as a second terminal device. Since the problem-solving principle of the device is similar to that of the method of the third embodiment, the specific implementation of the device may refer to the implementation of the method of the third embodiment, and the overlapping content will not be described again.

[0134] As shown in FIG. 9, a relay selection or reselection device 900 according to an embodiment of the present invention includes the following units:

[0135] The instruction unit 901, in a UE-to-UE relay scenario, The end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; The second terminal device is performing or about to perform a relay device selection or reselection; and In at least one situation where the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold, the first terminal device is instructed to trigger or perform relay selection or reselection.

[0136] Here, the third relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device.

[0137] In some embodiments, the sixth signal strength threshold is pre-configured, configured by the network device, or pre-defined.

[0138] In some embodiments, the indication of the second terminal device is sent via a PC5-RRC message or PC5-S signaling.

[0139] In some embodiments, as shown in FIG. 9, the relay selection or reselection device 900 further includes the following units:

[0140] The receiving unit 902 receives third information transmitted by the first terminal device to the second terminal device, the third information instructing the first terminal device to trigger selection or reselection of a relay device.

[0141] In some embodiments, as shown in FIG. 9, the relay selection or reselection device 900 device further includes the following units:

[0142] The processing unit 903 establishes a connection with the first terminal device via the selected or reselected relay device.

[0143] Although the above description is limited to the components or modules related to the present invention, the present invention is not limited thereto. The relay selection or reselection devices 700 to 900 according to the embodiments of the present invention may include other components or modules, and reference may be made to related art for specific details of these components or modules.

[0144] 7 to 9 only show exemplary connections or signal flows between the respective components or modules, but those skilled in the art may employ various related technologies such as bus connections. The various components or modules described above may be implemented by hardware devices such as a processor, memory, transmitter, and receiver, but the present invention is not limited to these.

[0145] According to the device of the embodiment of the present invention, the conditions under which the source UE and / or the destination UE triggers relay selection or reselection in a UE-to-UE relay scenario are specified, and the problem of how the source UE and / or the destination UE triggers relay selection or reselection in a UE-to-UE relay scenario is solved.

[0146] <Example 5> An embodiment of the present invention provides a communication system. Fig. 10 is a schematic diagram showing a communication system according to an embodiment of the present invention. As shown in Fig. 10, a communication system 1000 includes a first terminal device 1001, a second terminal device 1002, and a relay device 1003. For convenience of explanation, Fig. 10 illustrates an example in which only one first terminal device, one second terminal device, and one relay device are included, but the embodiment of the present invention is not limited thereto.

[0147] In the embodiment of the present invention, the first terminal device 1001, the second terminal device 1002 and the relay device 1003 are in a UE-to-UE relay scenario.

[0148] In the embodiments of the present invention, a first terminal device 1001 is configured to execute the method described in embodiment 1, a second terminal device 1002 is configured to execute the method described in embodiment 3, and a relay device 1003 is configured to execute the method described in embodiment 2. Since each method is described in detail in embodiments 1 to 3, the contents thereof are incorporated herein by reference and the description thereof is omitted.

[0149] An embodiment of the present invention further provides a terminal device, which may be, for example, a source UE in a UE-to-UE relay scenario or a destination UE in a UE-to-UE relay scenario, but the present invention is not limited thereto and may be other devices.

[0150] 11 is a schematic diagram illustrating a terminal device according to an embodiment of the present invention. As shown in FIG. 11, the terminal device 1100 may include a processor 1101 and a memory 1102. The memory 1102 stores data and programs and is connected to the processor 1101. It should be noted that this diagram is merely an example, and other types of structures may be used to supplement or replace this structure to realize communication functions or other functions.

[0151] For example, the processor 1101 may be configured to execute a program to implement the method described in the first or third embodiment.

[0152] As shown in Fig. 11, the terminal device 1100 may further include a communication module 1103, an input unit 1104, a display 1105, and a power source 1106. Note that the terminal device 1100 does not need to include all of the units shown in Fig. 11. Furthermore, the terminal device 1100 may further include units not shown in Fig. 11, and prior art may be referred to.

[0153] An embodiment of the present invention further provides a relay device, which may be, for example, a relay UE in a UE-to-UE relay scenario, but the present invention is not limited thereto and may be other devices.

[0154] 12 is a schematic diagram illustrating a relay device according to an embodiment of the present invention. As shown in FIG. 12, the relay device 1200 may include a processor 1201 and a memory 1202. The memory 1202 stores data and programs and is connected to the processor 1201. Note that this diagram is for illustrative purposes only, and other types of structures may be used to supplement or replace this structure to achieve communication functions or other functions.

[0155] For example, the processor 1201 may be configured to execute a program to implement the method described in the second embodiment.

[0156] As shown in Fig. 12, the relay device 1200 may further include a communication module 1203, an input unit 1204, a display 1205, and a power supply 1206. Note that the relay device 1200 does not need to include all of the units shown in Fig. 12. Furthermore, the relay device 1200 may further include units not shown in Fig. 12, and prior art may be referred to.

[0157] In an embodiment of the present invention, there is further provided a computer-readable program, which, when executed on a terminal device, causes a computer to execute the method described in the above embodiment 1 or embodiment 3 on the terminal device.

[0158] An embodiment of the present invention further provides a storage medium having a computer-readable program stored therein, the program, when executed, causing a computer to perform the method described in the above embodiment 1 or embodiment 3 on a terminal device.

[0159] An embodiment of the present invention further provides a computer-readable program, which, when executed in a relay device, causes a computer to execute the method described in the above embodiment 2 in the relay device.

[0160] An embodiment of the present invention further provides a storage medium having a computer-readable program stored therein, the program, when executed, causing a computer to perform the method described in the above embodiment 2 in a relay device.

[0161] The above-described apparatus and methods of the present invention may be realized by hardware or a combination of hardware and software. The present invention relates to a computer-readable program that, when executed by a logic unit, causes the logic unit to implement the above-described apparatus or components, or to implement the above-described various methods or steps. The logic unit may be, for example, a field programmable logic unit, a microprocessor, or a processor used in a computer. The present invention also relates to a storage medium for storing the above-described program, for example, a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0162] Each processing method in each device described with reference to the embodiments of the present invention may be implemented by hardware, a software module executed by a processor, or a combination of both. For example, one or more of the functional block diagrams shown in the drawings, or one or more combinations of the functional block diagrams, may correspond to each software module in a computer program flow or each hardware module. These software modules may correspond to each step shown in the drawings. These hardware modules may be implemented by implementing these software modules in hardware, for example, using a field programmable gate array (FPGA).

[0163] The software module may be located in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, mobile hard disk, CD-ROM, or any other form of storage medium known to those skilled in the art. The storage medium may be connected to the processor so that the processor reads information from or writes information to the storage medium, or the storage medium may be a component of the processor. The processor and the storage medium may be located in an ASIC. The software module may be stored in the memory of the mobile terminal or in a memory card inserted into the mobile terminal. For example, if a device (e.g., a mobile terminal) uses a relatively large-capacity MEGA-SIM card or a large-capacity flash memory device, the software module may be stored in the MEGA-SIM card or the large-capacity flash memory device.

[0164] One or more functional blocks and / or one or more combinations of functional blocks in the functional block diagrams set forth in the figures may be implemented with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or any suitable combination thereof to perform the functions described herein. One or more functional blocks and / or one or more combinations of functional blocks in the functional block diagrams set forth in the figures may be implemented with, for example, a combination of computing devices, such as a combination of a DSP and a microprocessor, a combination of multiple microprocessors, one or more microprocessors in combination with a DSP communication, or any other configuration.

[0165] Although the present invention has been described above with reference to specific embodiments, the above description is merely illustrative and does not limit the scope of protection of the present invention. Various modifications and changes may be made to the present invention without departing from the spirit and principles of the present invention, and these modifications and changes are also within the scope of the present invention.

[0166] Furthermore, the following supplementary notes are disclosed regarding the embodiments including the above examples. (Appendix 1) 1. A relay selection or reselection method, comprising: In a UE-to-UE relay scenario, a first terminal device: The PC5 signal strength between the first terminal device and the second terminal device is lower than a first signal strength threshold; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second terminal device; Higher-level instructions, an instruction from the first relay device; The PC5 signal strength between the first terminal device and the second relay device is lower than a second signal strength threshold; The first terminal device receives a PC5-S link release message from the second relay device; The first terminal device detects a radio link failure (RLF) of a PC5 interface between the first terminal device and the second relay device; An instruction to the second relay device; instructions for the third relay device; An instruction of the second terminal device; and triggering a selection or reselection of a relay device in at least one situation where a PC5 signal strength between the first terminal device and the third relay device is higher than a seventh signal strength threshold; A method in which the first relay device is a candidate relay device, the second relay device is a current relay device through which the first terminal device communicates with the second terminal device, and the third relay device is another relay device other than the current relay device through which the first terminal device communicates with the second terminal device. (Appendix 2) The instruction from the first relay device is The method described in Appendix 1, including the PC5 signal strength between the first relay device and the first terminal device being higher than a third signal strength threshold, and / or the PC5 signal strength between the first relay device and the second terminal device being higher than a fourth signal strength threshold. (Appendix 3) The method of claim 2, wherein the indication of the first relay device is transmitted via a discovery-related message, a PC5 direct communication-related message, or a PC5-RRC message. (Appendix 4) The instruction from the second relay device is The second relay device detects an RLF of the PC5 interface or PC5-RRC connection between the second relay device and the second terminal device; The PC5 signal strength between the second relay device and the second terminal device is lower than a fifth signal strength threshold; the second terminal device is performing or about to perform a relay device reselection; The PC5-S link between the second relay device and the second terminal device is released; and 2. The method of claim 1, including at least one of: the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold. (Appendix 5) 5. The method of claim 1 or 4, wherein the indication of the second relay device is sent via at least one of a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and a SRAP control PDU. (Appendix 6) The instruction from the third relay device is The method described in Appendix 1, including the PC5 signal strength between the third relay device and the first terminal device being higher than a seventh signal strength threshold, and / or the PC5 signal strength between the third relay device and the second terminal device being higher than a sixth signal strength threshold. (Appendix 7) 7. The method of claim 1 or 6, wherein the indication of the third relay device is transmitted via a discovery related message, a PC5 direct communication related message or a PC5-RRC message. (Appendix 8) The instruction of the second terminal device is An end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; the second terminal device is performing or about to perform relay device selection or reselection; and 2. The method of claim 1, including at least one of: the PC5 signal strength between the third relay device and the second terminal device is higher than a sixth signal strength threshold. (Appendix 9) The method according to any one of Supplementary Note 1 to 8, wherein the instruction of the second terminal device is sent via an end-to-end PC5-RRC message or PC5-S signaling. (Appendix 10) A method as described in any of Supplementary Notes 1 to 9, further comprising a step in which the first terminal device notifies the second terminal device of a situation that triggers the selection of a relay device, or notifies the current relay device and / or the second terminal device of a situation that triggers the reselection of a relay device. (Appendix 11) 10. The method of any one of Supplementary Notes 1 to 9, further comprising a step of the first terminal device establishing a connection with the second terminal device via the selected or reselected relay device. (Appendix 12) 12. The method of any of claims 1 to 11, wherein the signal strength threshold is pre-configured, configured by a network device, or pre-defined. (Appendix 13) 12. A method according to any one of Supplementary Notes 1 to 11, wherein the upper layer is a non-access stratum of the first terminal device. (Appendix 14) 1. A relay selection or reselection method, comprising: In a UE-to-UE relay scenario, the relay device: The PC5 signal strength between the relay device and the first terminal device is higher than a third signal strength threshold, and the relay device is a candidate relay device; The PC5 signal strength between the relay device and a second terminal device is higher than a fourth signal strength threshold, and the relay device is a candidate relay device; The relay device detects an RLF of the PC5 interface or PC5-RRC connection between the first terminal device and the second terminal device, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the second terminal device is lower than a fifth signal strength threshold, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The relay device determines that the second terminal device is performing or will perform a relay device reselection, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the first terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the second terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The relay device determines that the PC5 signal strength between another relay device and the second terminal device is higher than a sixth signal strength threshold, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the first terminal device is higher than a seventh signal strength threshold, and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device; and A method comprising a step of instructing the first terminal device to trigger or perform relay selection or reselection in at least one of the following situations: the PC5 signal strength between the relay device and the second terminal device is higher than a sixth signal strength threshold, and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device. (Appendix 15) 15. The method of claim 14, wherein the instruction of the relay device is sent via at least one of a discovery related message, a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and a SRAP control PDU. (Appendix 16) 15. The method of claim 14, further comprising: the relay device receiving first information from the second terminal device; and determining, based on the first information, that the second terminal device will perform or attempt to perform relay device reselection. (Appendix 17) 17. The method of claim 16, wherein the first information is transmitted by the second terminal device to the relay device via a PC5-RRC message or PC5-S signaling. (Appendix 18) The method of claim 14, further comprising the step of: the relay device receiving second information from another relay device or the second terminal device; and determining, based on the second information, that the PC5 signal strength between the other relay device and the second terminal device is higher than a sixth signal strength threshold. (Appendix 19) 19. The method of any of claims 14 to 18, wherein the signal strength threshold is pre-configured, configured by a network device, or pre-defined. (Appendix 20) 1. A relay selection or reselection method, comprising: In a UE-to-UE relay scenario, the second terminal device: The end-to-end PC5-RRC connection or PC5 link between the first terminal device and the second terminal device is released; the second terminal device is performing or about to perform relay device selection or reselection; and In at least one situation where a PC5 signal strength between a third relay device and the second terminal device is higher than a sixth signal strength threshold, instructing the first terminal device to trigger or perform relay selection or reselection; A method, wherein the third relay device is another relay device other than the current relay device through which the first terminal device communicates with the second terminal device. (Appendix 21) 21. The method of claim 20, wherein the sixth signal strength threshold is pre-configured, configured by a network device, or pre-defined. (Appendix 22) 22. The method of claim 20 or 21, wherein the instruction of the second terminal device is sent via a PC5-RRC message or PC5-S signaling. (Appendix 23) 23. A method as described in any of Supplementary Notes 20 to 22, further comprising a step in which the second terminal device receives third information transmitted by the first terminal device, the third information instructing the first terminal device to trigger selection or reselection of a relay device. (Appendix 24) 24. A method as claimed in any one of appendices 20 to 23, further comprising the step of the second terminal device establishing a connection with the first terminal device via the selected or reselected relay device. (Appendix 25) 25. A terminal device comprising: a memory having a computer program stored therein; and a processor, the processor configured to execute the computer program to implement a method according to any one of claims 1 to 13 and 20 to 24. (Appendix 26) 20. A network device comprising: a memory having a computer program stored therein; and a processor, the processor configured to execute the computer program to implement a method according to any one of claims 14 to 19. (Appendix 27) A communication system including a first terminal device, a second terminal device, and a relay device, the first terminal device is configured to perform a method according to any one of Supplementary Notes 1 to 13; the relay device is configured to perform a method according to any one of claims 14 to 19; 25. A communication system, wherein the second terminal device is configured to perform a method according to any one of Supplementary Notes 20 to 24.

Claims

1. An apparatus configured in a first terminal device, comprising: a communication unit that communicates with a second terminal device via a relay device; The processing unit detects a radio link failure (RLF) of PC5 between the first terminal device and the second terminal device; a processing unit that triggers a selection process of the relay device when at least one condition is satisfied: the signal strength of the PC5 between the first terminal device and the second terminal device is lower than a first signal strength threshold; The device, wherein the processing unit triggers a reselection process of the relay device when the communication unit receives a PC5-S link release message from a second relay device.

2. that a higher layer instruction has been received; 2. The device of claim 1, wherein the processing unit triggers a selection process for the relay device when at least one of the following conditions is met: an indication of a first relay device is received, and the first relay device is a candidate relay device.

3. The instruction from the first relay device is The device of claim 2, including: the signal strength of PC5 between the first relay device and the first terminal device is higher than a third signal strength threshold; and / or the signal strength of PC5 between the first relay device and the second terminal device is higher than a fourth signal strength threshold.

4. The device according to claim 1 , wherein the processing unit establishes a connection with the second terminal device via a selected relay device.

5. The device according to claim 2 , wherein the higher layer is a layer higher than an RRC of the first terminal device and includes at least one of a non-access layer, a V2X layer, and a proximity service layer.

6. The preprocessing unit detects a radio link failure (RLF) of PC5 between the first terminal device and the second relay device; Higher-level instructions, an instruction from the second relay device; An instruction of the third relay device; an instruction of the second terminal device; The signal strength of PC5 between the first terminal device and the third relay device is higher than a seventh signal strength threshold; and When at least one condition is satisfied: the signal strength of the PC5 between the first terminal device and the second relay device is lower than a second signal strength threshold, the processing unit triggers a reselection process of the relay device; The device according to claim 1 , wherein the second relay device is a current relay device through which the communication unit communicates with the second terminal device.

7. The instruction from the second relay device is The second relay device detects an RLF in the PC5 or PC5-RRC connection between the second relay device and the second terminal device; the signal strength of PC5 between the second relay device and the second terminal device is lower than a fifth signal strength threshold; the second terminal device is performing or about to perform a relay device reselection; The PC5-S link between the second relay device and the second terminal device is released; and The device of claim 6 , including at least one of: a signal strength of a PC5 between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

8. 7. The apparatus of claim 6, wherein the indication of the second relay device is sent via at least one of a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and an SRAP control PDU.

9. The instruction from the third relay device is The device described in claim 6, including: the signal strength of PC5 between the third relay device and the first terminal device is higher than a seventh signal strength threshold; and / or the signal strength of PC5 between the third relay device and the second terminal device is higher than a sixth signal strength threshold.

10. The device according to claim 6 , wherein the communication unit is configured to notify a current relay device and / or the second terminal device to trigger a reselection process of the relay device.

11. The device according to claim 6 , wherein the processing unit establishes a connection with the second terminal device via the reselected relay device.

12. The device of claim 6 , wherein the second signal strength threshold is configured by a network device.

13. The device according to claim 6 , wherein the third relay device is a relay device other than the current relay device through which the communication unit communicates with the second terminal device.

14. A device configured as a relay device, The PC5-S link between the relay device and the first terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5-S link between the relay device and the second terminal device is released, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the first terminal device is higher than a seventh signal strength threshold, and the relay device is a relay device other than the current relay device through which the first terminal device communicates with the second terminal device; and a processing unit that instructs the first terminal device to trigger or perform relay selection or relay reselection in a UE-to-UE relay scenario when at least one of the following conditions is met: a PC5 signal strength between the relay device and the second terminal device is higher than a sixth signal strength threshold; and the relay device is a relay device other than a current relay device through which the first terminal device communicates with the second terminal device.

15. A PC5 signal strength between the relay device and a first terminal device is higher than a third signal strength threshold, and the relay device is a candidate relay device; The PC5 signal strength between the relay device and a second terminal device is higher than a fourth signal strength threshold, and the relay device is a candidate relay device; The relay device detects an RLF in the PC5 interface or PC5-RRC connection between the first terminal device and the second terminal device, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; The PC5 signal strength between the relay device and the second terminal device is lower than a fifth signal strength threshold, and the relay device is a current relay device through which the first terminal device communicates with the second terminal device; the relay device determines that the second terminal device is performing or will perform a relay device reselection, and the relay device is the current relay device through which the first terminal device communicates with the second terminal device; 15. The apparatus of claim 14, wherein, when at least one of the following conditions is satisfied: the relay device determines that a PC5 signal strength between another relay device and the second terminal device is higher than a sixth signal strength threshold; and the relay device is a current relay device through which the first terminal device communicates with the second terminal device, the processing unit instructs the first terminal device to trigger or perform relay selection or relay reselection in a UE-to-UE relay scenario.

16. 16. The apparatus of claim 15, wherein the indication of the relay device is sent via at least one of a discovery related message, a PC5-RRC message, a PC5-S signaling, a sidelink MAC CE, and an SRAP control PDU.

17. a receiving unit that receives first information from the second terminal device, The apparatus of claim 15 , wherein the processing unit determines, based on the first information, that the second terminal device has performed or is about to perform a relay device reselection.

18. The device according to claim 17, wherein the first information is transmitted by the second terminal device to the relay device via a PC5-RRC message or PC5-S signaling.

19. a receiving unit that receives second information from another relay device or the second terminal device; The device of claim 15 , wherein the processing unit determines, based on the second information, that a PC5 signal strength between the other relay device and the second terminal device is higher than a sixth signal strength threshold.

20. 16. The device of claim 15, wherein the signal strength threshold is pre-configured, configured by a network device, or pre-defined.

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