WO2022037456A1 - 一种中继ue重选方法、介质及设备 - Google Patents

一种中继ue重选方法、介质及设备 Download PDF

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Publication number
WO2022037456A1
WO2022037456A1 PCT/CN2021/112084 CN2021112084W WO2022037456A1 WO 2022037456 A1 WO2022037456 A1 WO 2022037456A1 CN 2021112084 W CN2021112084 W CN 2021112084W WO 2022037456 A1 WO2022037456 A1 WO 2022037456A1
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Prior art keywords
relay
remote
threshold
measurement result
message
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PCT/CN2021/112084
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English (en)
French (fr)
Inventor
才宇
徐海博
姚楚婷
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华为技术有限公司
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Publication of WO2022037456A1 publication Critical patent/WO2022037456A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/14—Direct-mode setup
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user

Definitions

  • One or more embodiments of the present application generally relate to the field of communications, and specifically relate to a method, medium, and device for relay UE reselection.
  • D2D Device-to-Device
  • Proximity Service Proximity Service
  • 3GPP 3rd Generation Partnership Project
  • UE User Equipment
  • Remote UE Remote UE
  • a UE that provides a network connection function for a remote UE is also called a relay UE (UE-to-Network Relay, Relay UE).
  • the remote UE may perform relay UE reselection, thereby Select to establish direct communication with other relay UEs and maintain connection to the network through the selected other relay UEs.
  • the remote UE will periodically measure the signal strength of the discovery message sent by the relay UE, so as to perform relay reselection.
  • the embodiments of the present application provide a method for reselection of a relay UE (relay UE).
  • the method is used for a remote UE (remote UE), including: discovering a first relay UE and selecting and selecting the first relay UE.
  • a relay UE establishes a first direct link for direct communication between the remote UE and the first relay UE; and measures incoming data received over the first direct link from The signal of the first relay UE is obtained, and a measurement result of the signal is obtained; in the case that the measurement result is less than the first threshold, relay UE reselection is performed.
  • a request message for establishing the first direct link is sent to the first relay UE, and sending and/or receiving of the discovery message is stopped.
  • the signals include reference signals associated with a Physical Sidelink Shared Channel (PSSCH) and/or a Physical Sidelink Control Channel (PSCCH).
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • the measurement result includes at least one of the following parameters: received power of a reference signal associated with the Physical Sidelink Shared Channel (PSSCH) or Physical Sidelink Control Channel (PSCCH), received quality, strength.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • performing relay UE reselection under the condition that the measurement result is smaller than the first threshold value includes, under the condition that the measurement result is smaller than the first threshold value, sending and/or receiving the Discover news.
  • performing relay UE reselection when the measurement result is less than a first threshold including sending and/or receiving the discovery message when the measurement result is less than a second threshold , and if the measurement result is less than the first threshold, perform relay UE reselection, where the second threshold is greater than the first threshold.
  • the discovery message is sent and/or received upon receipt of a rejection message (Direct Communication Reject) from the first relay UE, wherein the rejection message is used to reject the remote UE A request sent by the UE to the first relay UE for establishing the first direct link.
  • a rejection message Direct Communication Reject
  • a sidelink discovery reference signal (Sidelink Discovery Reference Signal) from the first relay UE is measured, and when the measurement result of the sidelink discovery reference signal is greater than or equal to a third threshold, Stop sending and/or stop receiving discovery messages.
  • the measurement result of the side link discovery reference signal includes: received power (SD-RSRP) of the side link discovery reference signal, at least one of reception quality and strength.
  • SD-RSRP received power
  • the measurement result is greater than or equal to a fourth threshold, measuring the signal received from the first relay UE through the first direct link at a first period; and In the case where the measurement result is less than the fourth threshold, measure the signal from the first relay UE received through the first direct link with a second period, wherein the second period is less than the first period cycle.
  • the remote UE in the RRC-CONNECTED state, measuring a signal received from the first relay UE over the first direct link at a third period; and at all In the case where the remote UE is in the RRC-IDLE or RRC-INACTIVE state, the signal received from the first relay UE through the first direct link is measured with a fourth period, wherein the fourth period greater than the third period.
  • the discovery message includes at least one of the following messages: a broadcast message (Announcement) for the relay UE to discover the remote UE, an announcement message for the remote UE to discover the relay UE A request message (Solicitation) and a response message (Response) of the relay UE to the request.
  • the embodiments of the present application provide a machine-readable medium, on which instructions are stored, and when the instructions are executed on the machine, cause the machine to execute the process described in the first aspect. method.
  • embodiments of the present application provide a device, including: a processor; and a memory, where instructions are stored on the memory, and when the instructions are executed by the processor, the user equipment is made to execute the first The method described in one aspect.
  • the measurement result is smaller than the first
  • restarting the direct discovery process and reselection of the relay UE can reduce the waste of UE power consumption.
  • FIG. 1 is a schematic diagram of an application scenario according to an embodiment of the present application.
  • FIG. 2 is a schematic flowchart of interaction between a remote UE and a relay UE according to an embodiment of the present application
  • FIG. 3 is a flowchart of a method for reselection of a relay UE according to an embodiment of the present application
  • FIG. 4 is a flowchart of a method for reselection of a relay UE according to another embodiment of the present application.
  • FIG. 5 is a block diagram of a user equipment according to an embodiment of the present application.
  • first, second, etc. may be used herein to describe various elements or data, these elements or data should not be limited by these terms. These terms are used only to distinguish one feature from another. For example, a first feature could be termed a second feature, and, similarly, a second feature could be termed a first feature, without departing from the scope of example embodiments.
  • FIG. 1 is a schematic diagram of an application scenario according to an embodiment of the present application, and the scenario includes user equipments 11 , 12 and 13 and a network device 2 .
  • User equipment also known as terminal and terminal equipment, is a device that provides voice and/or data connectivity to users.
  • Mobile internet devices MIDs
  • wearable devices such as smart watches, smart bracelets, pedometers, etc.
  • personal digital assistants portable media players, navigation devices, video game devices, set-top boxes, virtual Reality and/or augmented reality devices, IoT devices, industrial control devices, streaming media client devices, e-books, reading devices, POS machines, V2X (Vehicle to Everything, vehicle-to-the-world information exchange) terminal devices, SL (Sidelink) , side link)/ProSe terminal equipment, roadside unit (Road Site Unit, RSU) and other equipment.
  • MIDs Mobile internet devices
  • wearable devices such as smart watches, smart bracelets, pedometers, etc.
  • personal digital assistants portable media players
  • navigation devices video game devices
  • set-top boxes set-top boxes
  • virtual Reality and/or augmented reality devices IoT devices
  • IoT devices IoT devices
  • Network equipment also known as Radio Access Network (RAN) equipment
  • RAN Radio Access Network
  • RAN Radio Access Network
  • the network equipment includes network equipment of various frequency systems, for example, including but not limited to: low-frequency network equipment and high-frequency network equipment.
  • the UE12 and the UE13 implement communication connection with the network device 2 through the Uu interface.
  • the communication between them can be based on, but not limited to, the third generation (3rd-Generation, 3G) mobile communication system, the fourth generation (4th-Generation, 4G) mobile communication system, the fifth generation (5th generation, 5G) system , a new radio (NR) system or a communication system with the same architecture as the 5G system and other subsequent mobile communication systems.
  • the UE11 can access the network through the network device 2 by establishing a direct link with the UE12 or the UE13.
  • the UE11 is referred to as a remote UE (Remote UE)
  • the UE12 and UE13 that provide the remote UE11 with a function of supporting its connection to the network are referred to as relay UEs (UE-to-Network Relay, Relay UE).
  • the remote UE accesses the network through the network device via the relay UE, and the technical solutions of the present application are also applicable to the case where the remote UE communicates with another remote UE via the relay UE.
  • Relay UEs are also known as UE-to-UE Relays (UE-to-UE Relays).
  • both the UE12 and the UE13 shown in FIG. 1 access the network device 2, but those skilled in the art can understand that the UE12 and the UE13 may also access different network devices.
  • a remote UE eg UE11
  • a relay UE eg UE12 or UE13
  • UE11 can discover UE12 or UE13
  • Either UE12 or UE13 can discover UE11
  • E-UTRA Evolved-UMTS Terrestrial Radio Access, Evolved UMTS Terrestrial Radio Access
  • WLAN Wireless Local Area Network, Wireless Local Area Network
  • the direct discovery process of proximity services is simply referred to as a direct discovery process.
  • the direct discovery process includes two modes, namely, mode A and mode B.
  • the relay UE sends a broadcast message for direct discovery (UE-to-Network Relay Discovery Announcement message), and the remote UE monitors the broadcast message.
  • UE-to-Network Relay Discovery Announcement message UE-to-Network Relay Discovery Announcement message
  • the remote UE sends a request message for direct discovery (UE-to-Network Relay Discovery Solicitation message).
  • the relay UE that matches the relay service code (Relay Service Code) contained in the request message sends a response message (UE-to-Network Relay Discovery Response message) to the remote UE.
  • the remote UE After the remote UE detects and discovers one or more candidate relay UEs (candidate relay UE) through the above-mentioned direct discovery process, it selects a relay UE that meets the conditions to establish a direct link. For example, in the scenario shown in FIG. 1 , the UE11 detects and discovers the relay UE12 and the relay UE13 through direct discovery, and selects the UE12 that satisfies the conditions to establish the direct link.
  • the conditions here may include, but are not limited to: satisfying ProSe layer criteria, satisfying access layer criteria, and the like.
  • the candidate relay with the highest ranking of the access stratum criteria is selected UE.
  • the communication between the remote UE11 and the relay UE12 can be one-to-one ProSe Direct Communication (One-to-one ProSe Direct Communication), or V2X (Vehicle To Everything) communication (defined in 3GPP TS 23.285) and direct communication between two or other types of wireless communication between adjacent user equipments.
  • the communication link between the remote UE11 and the relay UE12 may be referred to as a direct link (Direct Link), a layer-2 link (Layer-2 link), a PC5 unicast link (unicast link) or a side link (Sidelink) ), the communication interface is PC5 interface.
  • the remote UE11 can communicate with the network through the relay UE12.
  • the remote UE initiates a UE-to-network relay reselection procedure to reselect the relay UE.
  • the remote UE11 when the conditions for relay UE reselection are met, the remote UE11 will initiate the relay UE reselection process. After the relay UE reselection, the remote UE11 may finally select the relay UE13. And establish a direct link with it, and then access the network.
  • the standard of the low protocol layer specified in the above standard may include that the received power (Sidelink Discovery Reference Signal Received Power, SD-RSRP) of the side link reference signal of the relay UE is lower than the threshold q-RxLevMin.
  • SD-RSRP is the received power of the demodulation reference signal associated with the Physical Sidelink Discovery Channel (PSDCH). This requires that the remote UE and the relay UE still need to perform direct discovery after establishing the direct link, and periodically measure the received power of the discovery signal, that is, the above-mentioned SD-RSRP.
  • the direct discovery process still needs to be performed in the form of the above-mentioned mode A or mode B, Therefore, the power consumption of the remote UE will be wasted.
  • FIG. 2 is a schematic diagram of interaction between a remote UE and a relay UE according to an embodiment of the present application.
  • step 201 the above-mentioned direct discovery process of mode A or mode B is performed between the remote UE and the relay UE.
  • the direct discovery process is not limited to the above-mentioned Mode A or Mode B, and may also be other discovery processes.
  • a request message for establishing a direct link for example, a direct communication request message (Direct Communication Request) is sent to the relay UE.
  • a direct communication request message (Direct Communication Request)
  • the relay UE sends a message for indicating acceptance of the direct link establishment to the remote UE, for example, a direct communication accept message (Direct Communication Accept).
  • a direct communication accept message Direct Communication Accept
  • the relay UE sends the message to the remote UE, it can be considered that the direct link between the remote UE and the relay UE is successfully established.
  • the remote UE receives the message, it can be considered that the direct link between the remote UE and the relay UE is successfully established.
  • the relay UE can check the user information (User Info) and IP address configuration (IP Address Config) contained in the above-mentioned request message for establishing the direct link, and after completing the authentication and successfully establishing the security association, send the message to the remote UE. Message used to indicate acceptance of direct link establishment.
  • the direct discovery process between the remote UE and the relay UE can be stopped and/or the measurement of other intermediate UEs can be stopped. following the UE to reduce waste of power consumption.
  • stopping the direct discovery process and/or stopping the measurement of other relay UEs can be performed after step 203, that is, the remote UE and the relay UE establish a direct After the link (option 1).
  • step 202 it is also possible to stop the direct discovery process and/or stop measuring other relay UEs after the remote UE sends a request message for establishing a direct link to the relay UE in step 202 (option). 2).
  • stopping the direct discovery process and/or stopping measuring other relay UEs earlier can save more power consumption of the UE.
  • the above process of stopping direct discovery includes, but is not limited to, stopping the remote UE from sending and/or receiving discovery messages.
  • the discovery message includes, but is not limited to, messages sent/received in the two direct discovery modes specified in the 3GPP standard TS23.303, for example, the above-mentioned direct discovery broadcast message (UE-to-Network Relay Discovery Announcement message) , the above-mentioned direct discovery request message (UE-to-Network Relay Discovery Solicitation message), the above-mentioned response message (UE-to-Network Relay Discovery Response message), and/or other information sent/received in the direct discovery process.
  • the stopping of receiving the discovery message mentioned here may also mean stopping the monitoring of the discovery message.
  • the above-mentioned stopping the direct discovery process may refer to stopping the discovery process between the remote UE and the relay UE, including that the remote UE stops sending discovery messages to the relay UE, or the relay UE stops receiving discovery messages sent by the remote UE, Or the relay UE stops sending the discovery message to the remote UE. If the relay UE still needs to discover other UEs or is discovered by other UEs, the relay UE may still perform a discovery process, including receiving and/or sending a discovery message.
  • FIG. 3 is a flowchart of a method for reselection of a relay UE according to an embodiment of the present application.
  • a remote UE discovers and selects a first relay UE (eg, UE12).
  • the remote UE may discover one or more candidates of relay UEs through Mode A or Mode B of the above-mentioned direct discovery procedure.
  • the remote UE selects the relay UE; if there are multiple relay UE candidates all meeting the condition, it can be selected from multiple relay UE candidates.
  • a relay UE with the highest ranking is selected among the relay UE candidates.
  • the ranking mentioned here may be based on, for example, the measurement result of the signal from the relay UE measured by the remote UE.
  • it may be a reference signal associated with a Physical Sidelink Discovery Channel (PSDCH), or a reference signal associated with a Physical Sidelink Shared Channel (PSSCH), or a Physical Sidelink Control Channel (PSCCH).
  • PSDCH Physical Sidelink Discovery Channel
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • Reference signals associated with PSSCH or PSCCH may be used when discovery messages are transmitted over PSSCH. Therefore, measuring the signal from the relay UE may be measuring the reference signal of the PSSCH carrying the discovery message from the relay UE, and/or the reference signal of the PSSCH on which the PSSCH is scheduled.
  • a reference signal associated with a channel may be understood as the reference signal used to demodulate the channel, and may also be understood as the reference signal transmitted on the channel.
  • the reference signal may be a demodulation reference signal.
  • the measurement result of the signal may be at least one of the received power of the signal, the received quality of the signal, or the strength of the signal.
  • a threshold for measuring the measurement result of the signal may be pre-configured or configured by the network device, and the relay UE is selected by using the threshold. For example, select a UE whose measurement result is higher than or equal to the above threshold as the relay UE; or, if the signal measurement results of multiple relay UE candidates are all higher than the above threshold, select the UE with the largest measurement result as the relay UE and so on.
  • the above-mentioned threshold may be the minimum value (q-RxLevMin) of the received power required for relay UE reselection specified in the 3GPP standard, or the sum of the minimum value and minHyst, where minHyst represents a hysteresis parameter ,etc.
  • the remote UE After the remote UE discovers and selects the first relay UE in step 301, in step 302, the remote UE establishes a first direct link with the selected first relay UE, so that the remote UE passes the first direct link Directly communicate with the first relay UE, so as to connect with the network (UE-To-Network Relay) or with another remote UE (UE-To-UE Relay) through the first relay UE.
  • the network UE-To-Network Relay
  • UE-To-UE Relay another remote UE
  • the remote UE After the remote UE discovers and selects the first relay UE through the direct discovery process, it will send a request message for establishing a direct link, for example, a direct communication request message, to the first relay UE.
  • a request message for establishing a direct link for example, a direct communication request message
  • the first relay UE will check the user information (User Info) and IP address configuration (IP Address Config) contained in the above-mentioned direct communication request message (Direct Communication Request), after completing the mutual authentication procedure and successfully establishing the After the security association, the first relay UE will send to the remote UE a message indicating acceptance of the establishment of the direct link, for example, a direct communication accept message (Direct Communication Accept). link establishment.
  • User Info user information
  • IP Address Config IP Address Config
  • the remote UE in the next step 303, in order to reduce the waste of power consumption of the UE, the remote UE will stop the direct discovery process and/or stop measuring other relay UEs.
  • the process of stopping the direct discovery by the remote UE may be stopping sending discovery messages, stopping receiving discovery messages, or stopping sending and receiving discovery messages at the same time.
  • the discovery message refers to a broadcast message (UE-to-Network Relay Discovery Announcement message) from the relay UE.
  • the discovery message refers to the request message for direct discovery (UE-to-Network Relay Discovery Solicitation message), and the response to the request message from the relay UE (UE-to-Network Relay Discovery Response message).
  • the remote UE may only stop receiving the discovery message, that is, not receive broadcasts or responses from the relay UE; it may also only stop sending the discovery message, that is, not send the request message; or it may stop at the same time Receive and stop sending discovery messages.
  • the remote UE stops the direct discovery process and/or stops measuring other relay UEs, and does not receive or send relevant information, the power consumption of the UE can be reduced.
  • stopping the direct discovery process can also be represented by sending a related instruction message, for example, a request message (ProSe Direct Discovery Close Request) indicating to close the ProSe Direct Discovery and the like.
  • a request message ProSe Direct Discovery Close Request
  • the remote UE receives signals from the first relay UE and measures these signals to obtain measurement results in order to trigger relay UE reselection by the remote UE.
  • the remote UE since the remote UE stops the direct discovery process and cannot receive and measure the reference signal associated with the discovery message from the relay UE, it is necessary to trigger the relay UE reselection in other ways.
  • the remote UE and the first relay UE may transmit PC5 signaling and PC5 user plane data on the first direct link.
  • PC5 signaling and PC5 user plane data on the first direct link can be transmitted through side chain communication.
  • the PSSCH can carry PC5 signaling and PC5 user plane data.
  • the first relay UE sends PC5 user plane data or PC5 signaling to the remote UE
  • the first relay UE needs to send the PSSCH carrying the data or signaling to the remote UE, and the first relay UE can also send the PSCCH to the remote UE .
  • the PSCCH is associated with the PSSCH, the PSCCH is used for scheduling the PSSCH, or the PSCCH is used to indicate the resources for transmitting the PSSCH.
  • PSSCH can also carry PC5RRC signaling.
  • the remote UE may receive signals from the first relay UE via the first direct link and measure these signals to obtain measurement results. Or the remote UE may receive signals from the first relay UE via sidechain communication and measure these signals to obtain the measurements.
  • the remote UE may initiate a keep-alive process, that is, the remote UE sends a keep-alive message to the first relay UE. After receiving the keep-alive message, the first relay UE sends a keep-alive Ack message to the remote UE. Keep-alive messages and keep-alive Ack messages can be sent over PSSCH. Therefore, the remote UE can measure the received power of the associated reference signal of the PSSCH carrying the keep-alive Ack message, which is used for relay UE reselection or triggering the remote UE to perform a discovery process.
  • the first relay UE if the first relay UE does not send PC5 user plane data or PC5 signaling to the remote UE, the first relay UE initiates a keep-alive process, that is, the first relay UE sends a keep-alive message to the remote UE. Therefore, the remote UE can measure the received power of the associated reference signal of the PSSCH carrying the keep-alive Ack message, which is used for relay UE reselection or triggering the remote UE to perform a discovery process. After receiving the keep-alive message, the remote UE sends a keep-alive Ack message to the first relay UE.
  • the signals from the first relay UE measured by the remote UE may include sidelink signals, where the sidelink signals may include sidechain communication signals, sidelink reference signals, such as sidechains associated with PSSCH at least one of a channel reference signal and a sidelink reference signal associated with the PSCCH.
  • the above measurement results may include, but are not limited to, received power, received quality, signal strength of the signal, and/or other information indicative of the quality of communication between the remote UE and the relay UE.
  • the received power of the reference signal associated with the PSSCH, or the reference signal strength associated with the PSCCH, or any combination of different measurements of different reference signals, such as the received quality of the reference signal associated with the PSSCH and the reference signal associated with the PSCCH The received power of the associated reference signal.
  • step 302 the remote UE measures the signal from the relay UE and obtains the measurement result after stopping the direct discovery process
  • step 302 Once the remote UE establishes the first direct link with the first relay UE, it can measure the signal from the first relay UE through the first direct link and obtain the measurement result, so step 303 and step 304 may also occur simultaneously
  • this application does not specifically limit this.
  • the direct discovery process may be stopped at other time points.
  • the remote UE sends a direct communication request message (Direct Communication Request) for establishing a direct link to the first relay UE. ) and before the remote UE establishes the first direct link with the first relay UE.
  • Direct Communication Request direct communication request message
  • step 305 it is determined whether the measurement result of the signal in the above-mentioned step 304 is less than the first threshold. If the measurement result of the signal is greater than or equal to the first threshold, it indicates that the current first relay UE is still suitable, and the remote UE continues to measure the signal of the first relay UE.
  • step 306 is executed.
  • the remote UE performs a direct discovery process so as to perform the reselection of the relay UE, and/or measure other relay UEs.
  • the method of measuring other relay UEs may be the same as the method of measuring the signals of the relay UEs in step 301 .
  • the first threshold may be preconfigured or configured by the network device.
  • the first threshold can be set to meet the minimum value (q-RxLevMin) of the received power required for the reselection of the relay UE specified in the 3GPP standard, or it can be equal to the above step 301 in which the remote UE discovers and selects the first threshold through the direct discovery process. Threshold used by relay UEs.
  • the measurement result of the signal is used to compare with the first threshold, but those skilled in the art can understand that the value determined based on the measurement result of the signal may also be used to compare with the first threshold. For example, a measurement of the signal plus a power value is compared to a first threshold. The power value may be indicated by the first relay UE to the remote UE.
  • it may be based on a value determined by the received power of the reference signal, eg, a result obtained via a related mathematical calculation is compared with a first threshold value.
  • the remote UE when some other conditions are met, even if the measurement result of the signal determined in the above step 305 is greater than or equal to the first threshold, the remote UE will be triggered to perform the direct discovery process so as to proceed. Re-selection of the relay UE, and/or measurement of other relay UEs.
  • these other conditions may be, for example, that the remote UE receives a message from the relay UE for refusing to establish the first direct link, for example, a Direct Communication Reject message, or the remote UE receives a message from the relay UE A message for releasing the first direct link, for example, a release message for releasing direct communication (Direct Communication Release), or a request message for establishing a direct link, or a direct communication setup (Direct Communication Setup) or direct communication guarantee.
  • the remote UE does not receive any response from the relay UE, or the PC5 Discovery message (PC5 Discovery) is retransmitted M consecutive times to trigger the communication between the remote UE and the relay UE.
  • PC5 Discovery PC5 Discovery
  • the remote UE After the signal strength measurement, the remote UE does not receive any response from the relay UE, or the remote UE detects a sidelink radio link failure, etc.
  • the direct communication rejection message is used to instruct the relay UE to reject the request for establishing direct communication proposed by the remote UE, and the direct communication release message is used to instruct the relay UE to request the release of the direct communication with the remote UE.
  • the remote UE performs a direct discovery process. Specifically, the remote UE receives and/or sends a discovery message. For example, it may restart to receive broadcast messages for direct discovery (UE-to- Network Relay Discovery Announcement message), or the remote UE restarts sending the request message for direct discovery (UE-to-Network Relay Discovery Solicitation message), or the remote UE restarts receiving the response to the request message from the relay UE (UE-to-Network Relay Discovery Response message).
  • UE-to- Network Relay Discovery Announcement message UE-to- Network Relay Discovery Announcement message
  • the remote UE restarts sending the request message for direct discovery (UE-to-Network Relay Discovery Solicitation message)
  • UE-to-Network Relay Discovery Response message UE-to-Network Relay Discovery Response message
  • the remote UE discovers and selects a second relay UE, eg UE13.
  • the second relay UE discovered by the remote UE may also be one or more cases.
  • the process of discovering and selecting the second relay UE by the remote UE through the direct discovery process is the same as the process of discovering and selecting the first relay UE in the above step 301, for example, it can be performed based on the measurement result of the signal from the second relay UE selection, the threshold value of the signal measurement result, etc. can also be set, which will not be repeated here.
  • the threshold value of the measurement result may be the first threshold value, or the first threshold value plus an offset value.
  • a certain condition is satisfied between the measurement result of the second relay UE and the measurement result of the first relay UE. For example, the measurement result of the second relay UE is greater than the measurement result of the first relay UE. Alternatively, the measurement result of the second relay UE is greater than the measurement result of the first relay UE plus an offset value.
  • step 308 when it is determined that the second relay UE meets the conditions, the remote UE will select the second relay UE and establish a direct link therewith.
  • the remote UE establishes a second direct link with the selected second relay UE.
  • the remote UE when it discovers and selects the second relay UE through the direct discovery process, it will send a direct communication request message (Direct Communication Request) for establishing a direct link to the second relay UE to Trigger mutual authentication.
  • the second relay UE After completing the mutual authentication procedure and successfully establishing the security association, the second relay UE will send a Direct Communication Accept message (Direct Communication Accept) to the remote UE to indicate that the direct link is successfully established.
  • the establishment of the direct link with the second relay UE is completed. So far, the remote UE has completed the relay UE reselection.
  • the remote UE after the remote UE establishes a direct link with the relay UE, it stops the direct discovery process, and when the remote UE measures When the measurement result of the signal from the first relay UE received by the link is smaller than the first threshold, the direct discovery process is restarted and the relay UE reselection is performed, thereby reducing the waste of UE power consumption.
  • the direct discovery process is performed when it is determined that the measurement result of the signal received through the first direct link is less than the first threshold, those skilled in the art should understand that other conditions can also be satisfied. , for a direct discovery process.
  • the direct discovery procedure is performed, and/or other relay UEs are measured, wherein the second threshold is greater than the first threshold.
  • the direct discovery process can be restarted earlier in this way, and/or other relay UEs can be measured for faster completion Relay UE reselection.
  • the above step compares the measurement result of the signal received via the first direct link with the second threshold
  • those skilled in the art will understand that such a comparison can also be performed between the value determined based on the measurement result of the signal and the second threshold.
  • the second threshold is compared. For example, a measurement of the signal plus a power value is compared to a second threshold.
  • the power value may be indicated by the first relay UE to the remote UE.
  • the measured received power of the reference signal associated with the PSSCH may be compared with the second threshold, or the value determined by the received power of the reference signal, for example, the result obtained through the relevant mathematical calculation may be compared with the second threshold. Threshold comparison.
  • the remote UE continues to measure over the first relay UE For the signal received by the direct link from the first relay UE, when the measurement result is less than the first threshold, the relay UE reselection is performed.
  • the second threshold may also be preconfigured or configured by the network device.
  • the second threshold may be the sum of the first threshold and minHyst, where minHyst represents a hysteresis parameter.
  • the threshold for the remote UE to select the second relay UE may be the threshold in step 301, or equal to the first threshold or the second threshold.
  • the direct discovery process of the remote UE to the relay UE can be started earlier, and the signal quality of the relay UE can be measured. , so that the relay UE reselection can be completed faster when the relay UE reselection condition is satisfied.
  • FIG. 4 is a flowchart of a method for reselection of a relay UE according to another embodiment of the present application. Different from the embodiment shown in FIG. 3 above, in the embodiment shown in FIG. 4 , the remote UE stops the direct discovery process earlier, thereby saving more power consumption of the UE.
  • step 401 the remote UE discovers and selects the first relay UE through the direct discovery process, and in step 402, the remote UE sends a direct communication request message (Direct Communication Request) to the first relay UE for Request to establish a direct link with the first relay UE.
  • a direct communication request message Direct Communication Request
  • step 401 and step 402 reference may be made to step 301 in the aforementioned FIG. 3 , and details are not repeated here.
  • the remote UE After the remote UE sends a direct communication request message (Direct Communication Request), in step 403, the remote UE stops the direct discovery process.
  • the remote UE may also stop the direct discovery process at the same time as sending the direct communication request message, which is not specifically limited in the embodiments of the present application.
  • the remote UE can stop receiving broadcast messages for direct discovery (UE-to-Network Relay Discovery Announcement messages) from relay UEs, or stop sending request messages for direct discovery (UE-to-Network Relay Discovery Solicitation). message), it can also be that the remote UE stops receiving the response to the request message from the relay UE (UE-to-Network Relay Discovery Response message), or it can also be represented by sending a related instruction message, such as indicating to close the proximity For the request message (ProSe Direct Discovery Close Request) of the service direct connection discovery, for details, refer to the aforementioned step 303, which will not be repeated here.
  • step 404 the determination in step 404 is yes.
  • step 405 is performed next.
  • the remote UE receives signals from the relay UE, and measures these signals to obtain measurement results in order to trigger the remote UE to perform relay UE reselection.
  • step 406 it is determined whether the measurement result of the signal in the above-mentioned step 405 is less than the first threshold. If the measurement result of the signal is greater than or equal to the first threshold, it indicates that the current relay UE is still suitable, and the remote UE continues to measure the signal of the first relay UE.
  • step 407 is executed.
  • the remote UE restarts the direct discovery process to perform relay UE reselection.
  • step 407 the remote UE restarts direct discovery.
  • step 408 the remote UE rediscovers and selects the second relay UE through the direct discovery procedure.
  • step 409 when it is determined that the second relay UE meets the conditions, the remote UE will select the second relay UE and establish a direct link with it.
  • step 404 if the determination in step 404 is no, it means that the first relay UE sends a direct communication rejection message (Direct Communication Reject) to the remote UE, and the remote UE does not communicate with the first relay.
  • the UE successfully establishes the first direct link.
  • the method flow goes to step 407, that is, the remote UE restarts the direct discovery, so as to discover other suitable relay UEs.
  • the remote UE stops the direct discovery process before establishing a direct link with the relay UE.
  • the embodiment can further reduce the waste of UE power consumption.
  • the direct discovery process can be stopped earlier to further save the power consumption of the remote UE.
  • the difference from the embodiment shown in FIG. 4 is that the direct discovery process is stopped after the remote UE discovers a relay UE that satisfies the conditions through the direct discovery process.
  • the condition mentioned here can be the case where the signal quality from the relay UE is good, for example, the remote UE discovers the relay UE through the direct discovery process, and measures the measurement result of the reference signal of the channel carrying the discovery message from the relay UE When the value is greater than the third threshold, the direct discovery process is stopped.
  • the measurement result mentioned here may be the received power of the signal, or at least one of the received quality of the signal and the strength of the signal.
  • the third threshold may be pre-configured or configured through a network device, and may be greater than or equal to the first threshold or the second threshold, which is not specifically limited in this embodiment of the present application.
  • the power consumption of the remote UE can be further saved.
  • the direct discovery process is not stopped immediately after the remote UE establishes the direct link with the relay UE. Instead, when the quality of the signal from the relay UE is good, for example, when the measurement result of the remote UE by measuring the signal from the relay UE is greater than the third threshold, the direct discovery process is stopped.
  • the signal mentioned here may be the above-mentioned reference signal associated with the Physical Sidelink Discovery Channel (PSDCH), or may be the Physical Sidelink Shared Channel (PSSCH), or the Physical Sidelink Control Channel (PSCCH) associated reference signal.
  • the measurement result of the signal may be the received power of the signal, or at least one of the received quality of the signal and the strength of the signal.
  • the third threshold may be pre-configured or configured through a network device, and may be greater than or equal to the first threshold or the second threshold, which is not specifically limited in this embodiment of the present application.
  • steps 307 and 308 in FIG. 3 and steps 408 and 409 in FIG. 4 only the process of the remote UE discovering and selecting the second relay UE to establish the second direct link is shown, but the technical The skilled person can understand that the method for reselection of the relay UE according to the present application as shown in FIG. 3 or FIG. 4 can also be performed in the process of the remote UE discovering and selecting the second relay UE to establish the second direct link.
  • the relay UE reselection method according to the present application is described in detail above with reference to FIG. 3 and FIG. 4 , and the remote UE can save UE power consumption by stopping the direct discovery process at different times.
  • the power consumption of the UE can be further saved in other ways.
  • the remote UE can choose whether to perform a direct discovery process or measure the signal quality of the relay UE according to its own state.
  • the remote UE when the remote UE is in the RRC-CONNECTED state, data transmission needs to be performed on the direct link between the remote UE and the relay UE, and the remote UE can perform a direct discovery process or measure the signal of the relay UE in order to When the relay UE is no longer suitable, relay UE reselection is performed.
  • a direct link between the remote UE and the relay UE will be performed.
  • Link keepalive (keepalive) process When no keep-alive message (Direct Communication Keepalive) or keep-alive response message (Direct Communication Keepalive ACK) is received from the relay UE, the remote UE restarts the direct discovery process and performs relay UE reselection.
  • the power consumption of the UE can be further saved.
  • the remote UE may measure the signal from the relay UE (eg, the first relay UE, or the second relay UE), and adjust the measurement period according to the measurement result of the signal.
  • the measurement of the signal from the relay UE shows that the communication quality between the remote UE and the relay UE is better (eg, higher signal strength, higher received power, better reception quality, etc.), the above the longer the measurement period. In this way, the power consumption of the UE can be further reduced.
  • the measurement result of the signal from the relay UE measured by the remote UE is greater than or equal to the fourth threshold
  • the measurement of the signal is performed in the first cycle.
  • the measurement result is smaller than the fourth threshold
  • the measurement of the signal is performed in the second cycle.
  • the second period is smaller than the first period.
  • the fourth threshold may be pre-configured or configured through a network device, and may also be equal to the first threshold or the second threshold in the above-mentioned embodiment, or any value, and so on.
  • the signal measurement is performed in a longer period, which can further save the power consumption of the remote UE.
  • the purpose of saving power consumption can also be achieved by changing the signal measurement period.
  • the signal from the relay UE is measured at the third cycle; when the remote UE is in the RRC-IDLE or RRC-INACTIVE state, the signal from the relay is measured at the fourth cycle The signal of the UE, wherein the fourth period is greater than the third period.
  • first cycle, second cycle, third cycle, and fourth cycle may be pre-configured or configured through network devices, and the length of the cycle may be adjusted according to actual needs.
  • the embodiments of the present application This is not specifically limited.
  • the power of the UE to send PSSCH/PSCCH may be determined by the channel conditions of the side chain, for example, according to the path loss between the two UEs. For example, the larger the path loss is, the larger the transmission power is, and the smaller the path loss is, the smaller the transmission power is. Since the transmit power of the signal is determined according to the channel condition of the side link, the received power of the signal may not necessarily reflect the channel condition between the two UEs. For the relay scenario, after the remote UE establishes the first direct link with the first relay UE, the PC5RRC connection between the remote UE and the first relay UE is also considered to be established.
  • the power of the PSSCH/PSCCH (including the PSSCH reference signal/PSCCH reference signal) sent by the first relay UE to the remote UE may be determined according to the channel conditions of the side link.
  • the channel conditions may include path loss between the first relay UE and the remote UE.
  • the remote UE may not necessarily determine the channel condition with the first relay UE according to the received power of the PSSCH/PSCCH reference signal. Therefore, the remote UE determines whether to trigger the reselection of the relay UE and/or measure other relay UEs and/or perform the discovery process according to the received power is not accurate enough.
  • the remote UE In order for the remote UE to perform relay UE reselection and/or to measure other relay UEs and/or to perform a discovery process according to the measurement result reflecting the channel situation more accurately, the following methods may be adopted.
  • the remote UE determines the first received power of the signal sent by the first relay UE.
  • the signal sent by the first relay UE may include PSSCH and/or PSCCH reference signals.
  • the power at which the first relay UE sends the signal is the first transmission power
  • the first transmission power is the transmission of the signal determined by the first relay UE considering the side chain channel situation between the remote UE and the first relay UE power.
  • the first transmit power is determined according to side chain channel conditions between the remote UE and the first relay UE. Sidechain channel conditions include path loss.
  • the remote UE establishes a side chain unicast link, or a PC5 unicast link, or a PC5 RRC connection, or a direct link, or a layer 2 link with the first relay UE.
  • the first relay UE sends first power indication information to the remote UE, which is used to indicate the first power.
  • the first power may be a transmit power headroom of a signal of the first relay UE.
  • the first relay UE may determine the first power according to side chain channel conditions between the remote UE and the first relay UE.
  • the first power is equal to the second transmit power minus the first transmit power.
  • the second transmit power is the transmit power of the signal when the first relay UE does not consider the side chain channel situation between the remote UE and the first relay UE. That is to say, the second transmit power is independent of the side chain channel situation between the remote UE and the first relay UE.
  • the second transmit power is determined according to the downlink path loss and/or the maximum transmit power of the first relay UE.
  • the second transmission power is the power at which the first relay UE sends the discovery message.
  • the power for sending the discovery message may be understood as the power for sending the reference signal of the channel carrying the discovery message.
  • the channel carrying the discovery message
  • the remote UE determines, according to the first received power and the first power, whether to trigger the reselection of the relay UE and/or measure other relay UEs and/or perform a discovery procedure.
  • the remote UE may perform relay UE reselection according to the first received power and the first power. For example, if the first received power plus the first power is less than or equal to a preset threshold, the relay UE is triggered to reselection and/or measure other relay UEs and/or perform a discovery process.
  • Another method is that after the remote UE and the first relay UE establish a side chain unicast link, or a PC5 unicast link, or a PC5 RRC connection, or a direct link, or a layer 2 link, the first relay UE sends a
  • the signal sent by the remote UE for the measurement of the remote UE does not consider the side chain channel situation between the remote UE and the first relay UE.
  • the signal used for remote UE measurements may be the reference signal of the channel carrying the discovery message.
  • the channel carrying the discovery message can be PSSCH or PSDCH.
  • the UE includes corresponding hardware structures and/or software modules for executing each function.
  • Those skilled in the art should easily realize that the present application can be implemented in hardware or a combination of hardware and computer software with the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein. Whether a function is performed by hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Skilled artisans may implement the described functionality using different methods for each particular application, but such implementations should not be considered beyond the scope of this application.
  • each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module.
  • the above-mentioned integrated modules can be implemented in the form of hardware, and can also be implemented in the form of software function modules. It should be noted that, the division of modules in the embodiments of the present application is schematic, and is only a logical function division, and there may be other division manners in actual implementation.
  • User equipment 500 may include one or more processors 502 , system control logic 508 connected to at least one of processors 502 , system memory 504 connected to system control logic 508 , non-volatile memory 504 connected to system control logic 508 Memory (NVM) 506 , and network interface 510 to system control logic 508 .
  • processors 502 may include one or more processors 502 , system control logic 508 connected to at least one of processors 502 , system memory 504 connected to system control logic 508 , non-volatile memory 504 connected to system control logic 508 Memory (NVM) 506 , and network interface 510 to system control logic 508 .
  • NVM system control logic 508 Memory
  • Processor 502 may include one or more single-core or multi-core processors.
  • Processor 502 may include any combination of general-purpose processors and special-purpose processors (eg, graphics processors, application processors, baseband processors, etc.).
  • the processor 502 may be configured to perform one or more embodiments in accordance with the various embodiments shown in Figures 2-4.
  • system control logic 508 may include any suitable interface controller to provide any suitable interface to at least one of processors 502 and/or any suitable device or component in communication with system control logic 508 .
  • system control logic 508 may include one or more memory controllers to provide an interface to system memory 504.
  • System memory 504 may be used to load and store data and/or instructions.
  • memory 504 of device 500 may include any suitable volatile memory, such as suitable dynamic random access memory (DRAM).
  • DRAM dynamic random access memory
  • NVM/memory 506 may include one or more tangible, non-transitory computer-readable media for storing data and/or instructions.
  • NVM/memory 506 may include any suitable non-volatile memory such as flash memory and/or any suitable non-volatile storage device, such as HDD (Hard Disk Drive, hard disk drive), CD (Compact Disc) , CD-ROM) drive, at least one of DVD (Digital Versatile Disc, Digital Versatile Disc) drive.
  • NVM/memory 506 may include a portion of the storage resources installed on the device of device 500, or it may be accessed by the device, but not necessarily part of the device. For example, NVM/storage 506 may be accessed over the network via network interface 510 .
  • system memory 504 and NVM/memory 506 may include temporary and permanent copies of instructions 520, respectively.
  • the instructions 520 may include instructions that, when executed by at least one of the processors 502, cause the device 500 to implement the methods shown in FIGS. 3-14.
  • instructions 520 , hardware, firmware, and/or software components thereof may additionally/alternately reside in system control logic 508 , network interface 510 , and/or processor 502 .
  • At least one of the processors 502 may be packaged with logic for one or more controllers of the system control logic 508 to form a system-in-package (SiP). In one embodiment, at least one of the processors 502 may be integrated on the same die with logic for one or more controllers of the system control logic 508 to form a system on a chip (SoC).
  • SiP system-in-package
  • SoC system on a chip
  • Program code may be applied to input instructions to perform the functions described herein and to generate output information.
  • the output information can be applied to one or more output devices in a known manner.
  • a processing system includes any system having a processor such as, for example, a digital signal processor (DSP), microcontroller, application specific integrated circuit (ASIC), or microprocessor.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • the program code may be implemented in a high-level procedural language or an object-oriented programming language to communicate with the processing system.
  • the program code may also be implemented in assembly or machine language, if desired.
  • the mechanisms described herein are not limited to the scope of any particular programming language. In either case, the language may be a compiled language or an interpreted language.
  • IP cores may be stored on tangible computer-readable storage media and provided to multiple customers or production facilities for loading into the manufacturing machines that actually manufacture the logic or processors.
  • module or “unit” may refer to, be or include: an application specific integrated circuit (ASIC), an electronic circuit, a (shared, dedicated or group) process executing one or more software or firmware programs and/or memory, combinational logic circuits, and/or other suitable components that provide the described functionality.
  • ASIC application specific integrated circuit
  • electronic circuit a (shared, dedicated or group) process executing one or more software or firmware programs and/or memory, combinational logic circuits, and/or other suitable components that provide the described functionality.
  • ASIC application specific integrated circuit
  • process executing one or more software or firmware programs and/or memory, combinational logic circuits, and/or other suitable components that provide the described functionality.
  • Embodiments of the mechanisms disclosed herein may be implemented in hardware, software, firmware, or a combination of these implementation methods.
  • Embodiments of the present application may be implemented as a computer program or program code executing on a programmable system including multiple processors, a memory system (including volatile and non-volatile memory and/or storage elements) , multiple input devices, and multiple output devices.
  • Program code may be applied to input instructions to perform the functions described herein and to generate output information.
  • the output information can be applied to one or more output devices in a known manner.
  • a processing system includes any system having a processor such as, for example, a digital signal processor (DSP), microcontroller, application specific integrated circuit (ASIC), or microprocessor.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • the program code may be implemented in a high-level procedural language or an object-oriented programming language to communicate with the processing system.
  • the program code may also be implemented in assembly or machine language, if desired.
  • the mechanisms described in this application are not limited in scope to any particular programming language. In either case, the language may be a compiled language or an interpreted language.
  • the disclosed embodiments may be implemented in hardware, firmware, software, or any combination thereof.
  • one or more aspects of at least some embodiments may be implemented by representative instructions stored on a computer-readable storage medium, the instructions representing various logic in a processor, which when read by a machine cause The machine fabricates logic for performing the techniques described in this application.
  • IP cores may be stored on tangible computer-readable storage media and provided to multiple customers or production facilities for loading into the manufacturing machines that actually manufacture the logic or processors.
  • Such computer readable storage media may include, but are not limited to, non-transitory tangible arrangements of items manufactured or formed by machines or equipment, including storage media such as: hard disks Any other type of disk including floppy disks, optical disks, compact disks Disk Read Only Memory (CD-ROM), Compact Disk Rewritable (CD-RW), and Magneto-Optical Optical Disks; Semiconductor Devices such as Read Only Memory (ROM), such as Dynamic Random Access Memory (DRAM) and Static Random Access Random Access Memory (RAM) such as memory (SRAM), Erasable Programmable Read Only Memory (EPROM), Flash Memory, Electrically Erasable Programmable Read Only Memory (EEPROM); Phase Change Memory (PCM); Magnetic Cards or optical card; or any other type of medium suitable for storing electronic instructions.
  • ROM Read Only Memory
  • DRAM Dynamic Random Access Memory
  • RAM Static Random Access Random Access Memory
  • SRAM Static Random Access Random Access Memory
  • EPROM Erasable Programmable Read Only Memory
  • Flash Memory Electrically Er
  • embodiments of the present application also include non-transitory computer-readable storage media containing instructions or containing design data, such as a hardware description language (HDL), which defines the structures, circuits, devices, Processor and/or System Characteristics.
  • HDL hardware description language

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Abstract

本申请的实施例涉及一种中继UE重选方法，包括：发现第一中继UE并且选择与第一中继UE建立第一直接链路，第一直接链路用于远程UE与第一中继UE进行直接通信；和测量通过第一直接链路接收到的来自第一中继UE的信号，并获得信号的测量结果；在测量结果小于第一阈值的情况下，进行中继UE重选。本申请的实施例还涉及一种机器可读存储介质以及用户设备。

Description

一种中继UE重选方法、介质及设备
本申请要求于2020年8月19日提交中国专利局，申请号为202010839827.7，发明名称“一种中继下Relay重选测量方法”，以及2020年9月30日提交中国专利局，申请号为202011061600.0，发明名称“一种中继UE重选方法、介质及设备”的中国专利申请优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请的一个或多个实施例通常涉及通信领域，具体涉及一种中继UE重选的方法、介质及设备。
背景技术
设备到设备通信(Device-to-Device，D2D)，在3GPP(3rd Generation Partnership Project，第三代合作伙伴计划)中也称为邻近服务(Proximity Service，ProSe)，能够实现物理上邻近的设备之间的直接通信，而无需经由网络传送。ProSe可以节省网络资源，在网络覆盖不可用时允许公共安全通信、社交网络、文件传输和设备之间的其他服务。例如位于网络覆盖范围之外的用户设备(User Equipment，UE)，也称为远程UE(Remote UE)，可以通过另一个UE连接到网络以实现与网络的通信。为远程UE提供与网络连接功能的UE也被称为中继UE(UE-to-Network Relay，Relay UE)。
当为远程UE服务的中继UE不再合适时(例如，远程UE与该中继UE之间的通信质量不佳，和/或其他情况)，远程UE可以进行中继UE的重选，从而选择与其他中继UE建立直接通信并通过所选的其他中继UE保持与网络的连接。通常，在与中继UE建立连接后，远程UE会周期性的测量中继UE发送的发现消息的信号强度，以便进行中继重选。
发明内容
以下从多个方面介绍本申请，以下多个方面的实施方式和有益效果可互相参考。
第一方面，本申请的实施方式提供了一种中继UE(relay UE)重选方法，所述方法用于远程UE(remote UE)，包括：发现第一中继UE并且选择与所述第一中继UE建立第一直接链路，所述第一直接链路用于所述远程UE与所述第一中继UE进行直接通信；和测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，并获得所述信号的测量结果；在所述测量结果小于第一阈值的情况下，进行中继UE重选。
在一些实施方式中，在完成与所述第一中继UE建立所述第一直接链路之后，停止发送和/或停止接收发现消息(discovery message)，或
向所述第一中继UE发送用于建立所述第一直接链路的请求消息，以及停止发送 和/或停止接收所述发现消息。
在一些实施方式中，所述信号包括：与物理侧链路共享信道(PSSCH)和/或物理侧链路控制信道(PSCCH)关联的参考信号。
在一些实施方式中，所述测量结果包括以下参数中的至少一种：与物理侧链路共享信道(PSSCH)或物理侧链路控制信道(PSCCH)关联的参考信号的接收功率、接收质量、强度。
在一些实施方式中，在所述测量结果小于第一阈值的情况下，进行中继UE重选，包括，在所述测量结果小于所述第一阈值的情况下，发送和/或接收所述发现消息。
在一些实施方式中，在所述测量结果小于第一阈值的情况下，进行中继UE重选，包括，在所述测量结果小于第二阈值的情况下，发送和/或接收所述发现消息，并且在所述测量结果小于所述第一阈值的情况下，进行中继UE重选，其中，所述第二阈值大于所述第一阈值。
在一些实施方式中，在接收到来自所述第一中继UE的拒绝消息(Direct Communication Reject)的情况下，发送和/或接收所述发现消息，其中所述拒绝消息用于拒绝所述远程UE向所述第一中继UE发送的用于建立所述第一直接链路的请求。
在一些实施方式中，测量来自所述第一中继UE的侧链路发现参考信号(Sidelink Discovery Reference Signal)，在所述侧链路发现参考信号的测量结果大于等于第三阈值的情况下，停止发送和/或停止接收发现消息。
在一些实施方式中，所述侧链路发现参考信号的测量结果包括：侧链路发现参考信号的接收功率(SD-RSRP)，接收质量、强度中的至少一个。
在一些实施方式中，在所述测量结果大于等于第四阈值的情况下，以第一周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号；以及在所述测量结果小于第四阈值的情况下，以第二周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，其中，所述第二周期小于所述第一周期。
在一些实施方式中，在所述远程UE处于RRC-CONNECTED状态的情况下，以第三周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号；以及在所述远程UE处于RRC-IDLE或RRC-INACTIVE状态的情况下，以第四周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，其中，所述第四周期大于所述第三周期。
在一些实施方式中，所述发现消息包括以下消息中的至少一个：用于所述中继UE发现所述远程UE的广播消息(Announcement)、用于所述远程UE发现所述中继UE的请求消息(Solicitation)以及所述中继UE对于所述请求的响应消息(Response)。
第二方面，本申请的实施方式提供了一种机器可读介质，在所述介质上存储有指令，当所述指令在所述机器上运行时，使得所述机器执行第一方面所述的方法。
第三方面，本申请的实施方式提供了一种设备，包括：处理器；存储器，在所述存储器上存储有指令，当所述指令被所述处理器运行时，使得所述用户设备执行第一方面所述的方法。
根据本申请的一些方面，通过停止远程UE与中继UE之间的直接发现流程，并 且当远程UE测量通过第一直接链路接收到的来自第一中继UE的信号的测量结果小于第一阈值的情况下，重新开始直接发现流程并进行中继UE重选，能够减少UE功耗的浪费。
附图说明
图1是根据本申请实施例的一种应用场景的示意图；
图2是根据本申请实施例的远程UE和中继UE交互的流程示意图；
图3是根据本申请一个实施例的中继UE重选方法的流程图；
图4是根据本申请另一个实施例的中继UE重选方法的流程图；
图5是本申请一个实施例的用户设备的框图。
具体实施方式
下面结合具体实施例和附图对本申请做进一步说明。
应当理解的是，虽然在这里可能使用了术语“第一”、“第二”等等来描述各个单元或是数据，但是这些单元或数据不应当受这些术语限制。使用这些术语仅仅是为了将一个特征与另一个特征进行区分。举例来说，在不背离示例性实施例的范围的情况下，第一特征可以被称为第二特征，并且类似地第二特征可以被称为第一特征。
应注意的是，在本说明书中，相似的标号和字母在下面的附图中表示类似项，因此，一旦某一项在一个附图中被定义，则在随后的附图中不需要对其进行进一步定义和解释。另外，说明书中出现的“A和/或B”表示只有A、只有B，以及A和B的三种可能性。
为使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请的实施方式作进一步地详细描述。
图1是根据本申请实施例的一种应用场景的示意图，该场景中包括用户设备11，12和13以及网络设备2。
为了下述各实施例的描述清楚简洁，首先给出一些技术术语的简要介绍：
1)用户设备，又称为终端、终端设备，是一种向用户提供语音和/或数据连通性的设备，常见的终端设备例如包括：车载设备、手机、平板电脑、笔记本电脑、掌上电脑、移动互联网设备(mobile internet device，MID)、可穿戴设备(例如包括：智能手表、智能手环、计步器等)、个人数字助理、便携式媒体播放器、导航设备、视频游戏设备、机顶盒、虚拟现实和/或增强现实设备、物联网设备、工业控制设备、流媒体客户端设备、电子书、阅读设备、POS机、V2X(Vehicle to Everything，车对外界的信息交换)终端设备、SL(Sidelink，侧链路)/ProSe终端设备、路侧单元(Road Site Unit，RSU)以及其他设备等。
2)网络设备，又称为无线接入网(Radio Access Network，RAN)设备，是一种将用户设备接入到无线网络的设备，其包括各种通信制式中的网络设备，例如包括但不限于：基站、演进型节点B(evolved Node B，eNB)、无线网络控制器(radio network controller，RNC)、节点B(Node B，NB)、网络设备控制器(Base Station Controller， BSC)、网络设备收发台(Base Transceiver Station,BTS)、家庭网络设备(例如，Home evolved NodeB，或Home Node B，HNB)、基带单元(BaseBand Unit，BBU)等。网络设备包括了各类频率制式的网络设备，例如包括但不限于：低频网络设备、高频网络设备。
如图1所示，UE12以及UE13通过Uu接口实现与网络设备2的通信连接。他们之间的通信可以基于，但不限于，第三代(3rd-Generation，3G)移动通信系统、第四代(4th-Generation，4G)移动通信系统、第五代(5th generation，5G)系统、新空口(new radio，NR)系统或者与5G系统具有相同架构的通信系统以及后续的其他移动通信系统。
在图1所示的场景中，UE11可以通过与UE12或UE13建立直接链路以便通过网络设备2接入网络。这里，UE11被称为远程UE(Remote UE)，为远程UE11提供支持其到网络的连接功能的UE12和UE13被称为中继UE(UE-to-Network Relay，Relay UE)。
本领域技术人员能够理解，这里是以远程UE经由中继UE通过网络设备接入网络，本申请的技术方案同样适用于远程UE经由中继UE与另一远程UE进行通信的情况，此时，中继UE也被称为UE到UE中继(UE-to-UE Relay)。
另外，图1中所示的UE12和UE13都接入网络设备2，但是本领域技术人员能够理解，UE12和UE13也可以接入不同的网络设备。
为了在UE11和UE12或UE13之间建立直接链路，要求远程UE(例如，UE11)或中继UE(例如，UE12或UE13)能够检测和发现另一个UE(例如，UE11能够发现UE12或者UE13，或者UE12或者UE13能够发现UE11)。
在3GPP标准TS 23.303中定义了使用E-UTRA(Evolved-UMTS Terrestrial Radio Access，进化的UMTS陆地无线接入)或WLAN(Wireless Local Area Network，无线局域网)直接无线电信号检测和识别附近的另一个UE的过程的邻近服务直接发现(ProSe Direct Discovery)流程。下面将邻近服务直接发现流程简称为直接发现流程。根据3GPP标准TS23.303 5.3.1.2的规定，直接发现流程包括两种模式，即，模式A和模式B。
其中，在模式A中，中继UE发送用于直接发现的广播消息(UE-to-Network Relay Discovery Announcement message)，远程UE监听该广播消息。
在模式B中，远程UE发送用于直接发现的请求消息(UE-to-Network Relay Discovery Solicitation message)。匹配了请求消息中包含的中继服务代码(Relay Service Code)的中继UE向远程UE发出响应消息(UE-to-Network Relay Discovery Response message)。
当远程UE通过上述直接发现流程检测和发现到一个或多个候选中继UE(candidate relay UE)后，选择一个满足条件的中继UE以建立直接链路。例如，在图1所示的场景中，UE11通过直接发现检测和发现了中继UE12和中继UE13，并且从中选择了满足条件的UE12以建立直接链路。这里的条件可以包括，但不限定于：满足ProSe层准则，满足接入层准则等。
如果存在多个候选中继UE的情况下，即，在发现了多个满足上述条件的候选中继UE的情况下，那么选择具有接入层准则最高排名的(the highest ranking)的候选中继UE。
远程UE11与中继UE12之间的通信可以是一对一邻近服务直接通信(One-to-one ProSe Direct Communication)，或者V2X(Vehicle To Everything)通信(定义于3GPP TS 23.285)以及直接在两个或更多个邻近用户设备之间进行的其他类型的无线通信。远程UE11与中继UE12之间的通信链路可以被称为直接链路(Direct Link)、层2链路(Layer-2 link)、PC5单播链路(unicast link)或侧链路(Sidelink)，通信接口为PC5接口。
如上所述，当远程UE11通过直接发现并且选择和中继UE12成功建立了直接链路之后，远程UE11可以通过中继UE12与网络进行通信。
同样，本领域技术人员能够理解，远程UE经由中继UE与另一远程UE进行通信的情况下，上述的发现、选择并与中继UE建立直接链路的过程是相同的。
当远程UE选择的中继UE不再合适的时候，例如，当前的中继UE的信号质量较差，或者远程UE远离当前所选择的中继UE的情况下，为了获得到网络的连接服务，远程UE发起中继UE重选(UE-to-network relay reselection)流程，以便重新选择中继UE。
以图1中所示的场景为例，当满足了中继UE重选的条件时，远程UE11会发起中继UE重选流程，经过中继UE重选，最终远程UE11可能会选择中继UE13并与之建立直接链路，进而接入网络。
在3GPP标准TS 24.334中定义的其中一种中继UE重选的条件是，中继UE不再满足标准中相关条款规定的低协议层的标准(lower layers criteria)的情况。上述标准中规定的低协议层的标准可以包括中继UE的侧链路参考信号的接收功率(Sidelink Discovery Reference Signal Received Power，SD-RSRP)的要低于阈值q-RxLevMin。这里，SD-RSRP是与物理侧链路发现信道(PSDCH)相关联的解调参考信号的接收功率。这就要求远程UE和中继UE在建立直接链路之后，仍然需要进行直接发现，并且周期性的测量发现信号的接收功率，即上述SD-RSRP。
如上所述，现有技术的方案在远程UE和中继UE建立了直接链路之后，为了之后的中继UE的重选，仍然需要通过上述的模式A或模式B的形式进行直接发现流程，因此会造成远程UE功耗的浪费。
下面以具体的实施例对本申请的技术方案以及本申请的技术方案进行详细说明。下面这几个具体的实施例可以相互结合，对于相同或相似的概念或过程在某些实施例中不再赘述。
图2是根据本申请实施例的远程UE和中继UE的交互的示意图。如图2所示，在步骤201，远程UE和中继UE之间进行如上所述的模式A或模式B的直接发现流程。本领域技术人员能够理解，直接发现流程也不局限于上述的模式A或模式B，也可以是其他的发现流程。
当远程UE通过直接发现流程发现并选择了中继UE之后，在步骤202，向中继UE发送用于建立直接链路的请求消息，例如，直接通信请求消息(Direct Communication Request)。
在步骤203，中继UE会向远程UE发送用于指示接受直接链路建立的消息，例如，直接通信接受消息(Direct Communication Accept)。中继UE向远程UE发送了所述消息后，可以认为远程UE与中继UE之间的直接链路成功建立。远程UE接收到所述消息后， 可以认为远程UE与中继UE之间的直接链路成功建立。中继UE可以检查包含在上述用于建立直接链路的请求消息中的用户信息(User Info)以及IP地址配置(IP Address Config)，在完成了认证并成功建立安全关联之后，向远程UE发送用于指示接受直接链路建立的消息。
为了解决现有技术中存在的远程UE的功耗浪费，根据本申请实施例的中继UE重选的方法，可以停止远程UE和中继UE之间的直接发现流程和/或停止测量其他中继UE，以减少功耗浪费。
如图2所示，根据本申请一个实施例的中继UE重选的方法，停止直接发现流程和/或停止测量其他中继UE可以在步骤203之后，即远程UE和中继UE建立了直接链路之后(选项1)。
或者，根据本申请的另一个实施例，也可以在步骤202，即远程UE向中继UE发送用于建立直接链路的请求消息之后停止直接发现流程和/或停止测量其他中继UE(选项2)。相比于在步骤203之后停止直接发现流程和/或停止测量其他中继UE的情况，更早的停止直接发现流程和/或停止测量其他中继UE，能够更多的节省UE的功耗。
上述停止直接发现流程包括，但不限于，远程UE停止发送和/或停止接收发现消息。其中，发现消息包括，但不限于，在根据3GPP标准TS23.303规定的两种直接发现模式中发送/接收的消息，例如，上述直接发现的广播消息(UE-to-Network Relay Discovery Announcement message)、上述直接发现的请求消息(UE-to-Network Relay Discovery Solicitation message)、上述响应消息(UE-to-Network Relay Discovery Response message)，和/或直接发现流程中发送/接收的其他信息。另外，这里所说的停止接收发现消息也可以是停止监听发现消息。
上述停止直接发现流程可以是指停止该远程UE与该中继UE之间的发现流程，包括远程UE停止向该中继UE发送发现消息、或中继UE停止接收该远程UE发送的发现消息、或中继UE停止向该远程UE发送的发现消息。若中继UE还要发现其他UE或被其他UE发现，中继UE可仍然进行发现过程，包括接收发现消息和/或发送发现消息。
以下将结合附图3和附图4分别对图2中所述的根据本申请的中继UE重选方法的两种实施方式进行具体的说明。
附图3是根据本申请一个实施例的中继UE重选方法的流程图。如图3所示，在步骤301，远程UE发现并选择第一中继UE(例如，UE12)。
在一个实例中，远程UE可以通过上述的直接发现流程的模式A或者模式B发现一个或多个中继UE的候选。
如3GPP标准TS24.334中所规定的，如果只有一个中继UE候选满足条件，则远程UE选择该中继UE；如果有多个中继UE候选都满足条件的情况下，可以从多个中继UE候选中选择排名最高的一个中继UE。
本领域技术人员能够理解，这里说的排名可以基于例如远程UE所测量到的来自中继UE的信号的测量结果。例如，可以是与物理侧链路发现信道(PSDCH)相关联的参考信号，也可以是与物理侧链路共享信道(PSSCH)，或物理侧链路控制信道(PSCCH)关联的参考信号。在发现消息通过PSSCH传输时，可以使用与PSSCH或 PSCCH关联的参考信号。因此，测量来自中继UE的信号可以是测量来自中继UE的承载发现消息的PSSCH的参考信号，和/或调度该PSSCH的PSSCH的参考信号。一个信道关联的参考信号可以理解为该参考信号用于解调该信道，也可以理解为该信道上传输的参考信号。参考信号可以是解调参考信号。
在一个实例中，信号的测量结果可以是信号的接收功率，也可以是信号的接收质量，或者是信号的强度中的至少一个。
在一个实例中，可以预先配置或者是网络设备配置用于衡量信号的测量结果的阈值，并利用该阈值来选择中继UE。例如，选择测量结果高于或等于上述阈值的一个UE作为中继UE；或者，如果多个中继UE候选的信号测量结果都高于上述阈值的情况下，选择测量结果最大的UE作为中继UE等等。
本领域技术人员能够理解，上述阈值可以是3GPP标准中规定的中继UE重选所需的接收功率的最小值(q-RxLevMin)，或者是该最小值与minHyst的和，其中minHyst表示迟滞参数，等等。
当步骤301中远程UE发现并选择了第一中继UE之后，在步骤302，远程UE会与所选择的第一中继UE建立第一直接链路，使得远程UE通过该第一直接链路与第一中继UE进行直接通信，从而通过第一中继UE与网络连接(UE-To-Network Relay)或者与另一个远程UE连接(UE-To-UE Relay)。
如上所述，当远程UE通过直接发现流程发现并选择了第一中继UE之后，会向第一中继UE发送用于建立直接链路的请求消息，例如，直接通信请求消息。
接下来，第一中继UE会检查包含在上述直接通信请求消息(Direct Communication Request)中的用户信息(User Info)以及IP地址配置(IP Address Config)，在完成了相互的认证程序并成功建立安全关联之后，第一中继UE会向远程UE发送用于指示接受直接链路建立的消息，例如，直接通信接受消息(Direct Communication Accept)，至此，远程UE与第一中继UE完成了直接链路的建立。
根据本申请实施例的中继UE重选方法，在接下来的步骤303，为了减少UE的功耗浪费，远程UE会停止直接发现流程和/或停止测量其他中继UE。
远程UE停止直接发现流程可以是停止发送发现消息(discovery message)、停止接收发现消息或者是同时停止发送和停止接收发现消息。
具体的，对于模式A的直接发现流程，发现消息是指来自中继UE的广播消息(UE-to-Network Relay Discovery Announcement message)。
对于模式B的直接发现流程，发现消息是指用于直接发现的请求消息(UE-to-Network Relay Discovery Solicitation message)，以及来自中继UE的对于请求消息的响应(UE-to-Network Relay Discovery Response message)。
根据本申请实施例的方法，远程UE可以是仅仅停止接收发现消息，即不接收来自中继UE的广播或者响应；也可以是仅仅停止发送发现消息，即不发送请求消息；还可以是同时停止接收和停止发送发现消息。本领域技术人员能够理解，相比于现有技术，由于远程UE停止了直接发现流程和/或停止测量其他中继UE，不进行相关信息的接收或发送，因此可以减少UE的功耗。
另外，在一个可选的实例中，停止直接发现流程也可以通过发送相关的指示消息来表示，例如指示关闭所述邻近服务直连发现的请求消息(ProSe Direct Discovery Close Request)等。
在步骤304，通过第一直接链路，远程UE接收来自第一中继UE的信号，并且测量这些信号以获得测量结果，以便触发远程UE进行中继UE重选。
根据本申请实施例的中继UE重选方法，由于远程UE停止了直接发现流程，不能接收并测量来自中继UE的发现消息关联的参考信号，因此需要通过其他方式触发中继UE重选。
在第一直接链路上远程UE和第一中继UE可以传输PC5信令和PC5用户面数据。在接入层中，第一直接链路上的PC5信令和PC5用户面数据可以通过侧链通信传输。具体的，PSSCH可以承载PC5信令和PC5用户面数据。当第一中继UE向远程UE发送PC5用户面数据或PC5信令时，第一中继UE需要向远程UE发送承载数据或信令的PSSCH，第一中继UE还可以向远程UE发送PSCCH。该PSCCH与PSSCH相关联，PSCCH是用于调度PSSCH的，或者PSCCH是用于指示传输PSSCH的资源的。第一直接链路建立之后，可以认为PC5RRC连接也建立了。PSSCH还可以承载PC5RRC信令。
在远程UE和第一中继UE建立了第一直接链路之后，远程UE可以经由第一直接链路接收到来自第一中继UE的信号，并且测量这些信号以获得测量结果。或者远程UE可以经由侧链通信接收到来自第一中继UE的信号，并且测量这些信号以获得测量结果。
如果第一中继UE没有向远程UE发送PC5用户面数据或PC5信令，远程UE可以发起keep-alive过程，即远程UE向第一中继UE发送keep-alive消息。第一中继UE接收到keep-alive消息后，向远程UE发送keep-alive Ack消息。Keep-alive消息和keep-alive Ack消息可以通过PSSCH发送。因此，远程UE可以测量承载keep-alive Ack消息的PSSCH的关联的参考信号的接收功率，用于中继UE重选或触发远程UE进行发现过程。或者，如果第一中继UE没有向远程UE发送PC5用户面数据或PC5信令，第一中继UE发起keep-alive过程，即第一中继UE向远程UE发送keep-alive消息。因此，远程UE可以测量承载keep-alive Ack消息的PSSCH的关联的参考信号的接收功率，用于中继UE重选或触发远程UE进行发现过程。远程UE接收到keep-alive消息后，向第一中继UE发送keep-alive Ack消息。
在一个实例中，远程UE测量的来自第一中继UE的信号可以包括侧链路信号，其中侧链路信号可以包括侧链通信信号、侧链路参考信号，例如与PSSCH相关联的侧链路参考信号以及与PSCCH相关联的侧链路参考信号中的至少一个。
在一个实例中，上述的测量结果可以包括，但不限于，信号的接收功率、接收质量、信号强度，和/或指示远程UE与中继UE之间的通信质量的其他信息。例如，与PSSCH相关联的参考信号的接收功率，或者与PSCCH相关联的参考信号强度，或者是不同参考信号的不同测量结果的任意组合，诸如与PSSCH相关联的参考信号的接收质量以及与PSCCH相关联的参考信号的接收功率。
要说明的是，图3所示的实施例虽然描述的是远程UE在停止直接发现流程之后测 量来自中继UE的信号并获得测量结果，但本领域技术人员能够理解，因为在步骤302中，一旦远程UE与第一中继UE建立了第一直接链路，就能够通过第一直接链路测量来自第一中继UE的信号并获得测量结果，因此步骤303和步骤304也可以是同时发生的，本申请对此不作具体限定。
根据本申请的其他实施例，可以在其他时间点停止直接发现流程，例如，图2所示的在远程UE向第一中继UE发送用于建立直接链路的直接通信请求消息(Direct Communication Request)之后且远程UE与第一中继UE建立第一直接链路之前停止。
接下来，在步骤305，确定上述步骤304中的信号的测量结果是否小于第一阈值。如果信号的测量结果大于等于第一阈值，则表示当前的第一中继UE仍然是合适的，则远程UE继续执行对第一中继UE的信号的测量。
如果信号的测量结果小于第一阈值，则执行步骤306，根据本申请实施例的中继UE重选方法，远程UE进行直接发现流程以便进行中继UE重选，和/或测量其他中继UE。测量其他中继UE可以与步骤301中的测量中继UE的信号的方法相同。
在一个实例中，第一阈值可以是预先配置或者是网络设备配置的。第一阈值可以设定成满足3GPP标准中规定的中继UE重选所需的接收功率的最小值(q-RxLevMin)，也可以等于上述步骤301中远程UE通过直接发现流程发现并选择第一中继UE所使用的阈值。
在步骤305中，利用信号的测量结果与第一阈值进行比较，但是本领域技术人员能够理解，也可以使用基于信号的测量结果所确定的值与第一阈值进行比较。例如，信号的测量结果加上一个功率值与第一阈值比较。该功率值可以是第一中继UE向远程UE指示的。
比如，可以基于由参考信号的接收功率所确定的值，例如，经由相关的数学计算得到的结果与第一阈值比较。
另外，本领域技术人员也能够理解，在满足了一些其他条件时，即使上述步骤305中确定的信号的测量结果大于等于第一阈值的情况下，也会触发远程UE进行直接发现流程以便进行中继UE重选，和/或测量其他中继UE。
这些其他条件可以是例如，远程UE接收到来自中继UE的用于拒绝建立第一直接链路的消息，例如，直接通信拒绝消息(Direct Communication Reject)，或者远程UE接收到来自中继UE的用于释放第一直接链路的消息，例如，释放直接通信的释放消息(Direct Communication Release)，或者在用于建立直接链路的请求消息，或直接通信设置(Direct Communication Setup)或直接通信保活消息(Direct Communication Keeplive)连续M次重发之后，远程UE未从中继UE收到任何响应，或者在M次连续重传PC5发现消息(PC5 Discovery)以触发远程UE和中继UE之间的信号强度测量之后，远程UE未从中继UE收到任何响应，或者远程UE检测到侧链无线链路失败(sidelink radio link failure)等。其中，直接通信拒绝消息用于指示中继UE拒绝远程UE提出的建立直接通信的请求，直接通信的释放消息用于指示中继UE要求释放与远程UE之间的直接通信的消息。
接下来，在步骤306，远程UE进行直接发现流程，具体的，远程UE接收和/或发 送发现消息，例如，可以重新开始接收来自中继UE的用于直接发现的广播消息(UE-to-Network Relay Discovery Announcement message)，或者远程UE重新开始发送用于直接发现的请求消息(UE-to-Network Relay Discovery Solicitation message)，也可以是远程UE重新开始接收来自中继UE的对于请求消息的响应(UE-to-Network Relay Discovery Response message)。
然后在步骤307，远程UE发现并选择第二中继UE，例如UE13。
同样，本领域技术人员能够理解，远程UE发现的第二中继UE也可以是一个或多个的情况。这里，远程UE通过直接发现流程发现并选择第二中继UE的过程与上述步骤301中发现并选择第一中继UE的过程相同，例如可以基于来自第二中继UE的信号的测量结果进行选择，同样也可以设定信号测量结果的阈值等等，在此不再赘述。该测量结果的阈值可以是第一阈值，或者为第一阈值加上一个偏移值。或者，第二中继UE的测量结果与第一中继UE的测量结果之间满足一定条件。例如，第二中继UE的测量结果大于第一中继UE的测量结果。或者，第二中继UE的测量结果大于第一中继UE的测量结果加上一个偏移值。
接下来，在步骤308，在判断第二中继UE满足条件的情况下，远程UE会选择第二中继UE并与之建立直接链路。
具体的，在步骤308，远程UE会与所选择的第二中继UE建立第二直接链路。与上述步骤302相同，当远程UE通过直接发现流程发现并选择了第二中继UE之后，会向第二中继UE发送用于建立直接链路的直接通信请求消息(Direct Communication Request)，以触发相互的认证，在完成了相互的认证程序并成功建立安全关联之后，第二中继UE会向远程UE发送用于指示直接链路成功建立的直接通信接受消息(Direct Communication Accept)，远程UE与第二中继UE完成了直接链路的建立，至此，远程UE完成了中继UE重选。
根据上述图3所示的本申请的一个实施例的中继UE重选方法，远程UE在与中继UE建立了直接链路之后，停止了直接发现流程，并且当远程UE测量通过第一直接链路接收到的来自第一中继UE的信号的测量结果小于第一阈值的情况下，重新开始直接发现流程并进行中继UE重选，因此能够减少UE功耗的浪费。
虽然图3中在确定通过第一直接链路接收到的信号的测量结果小于第一阈值的情况下，进行直接发现流程，本领域的技术人员应该可以理解，还可以在满足其他条件的情况下，进行直接发现流程。
例如，在通过第一直接链路接收的信号的测量结果小于第二阈值的情况下，进行直接发现流程，和/或测量其他中继UE，其中第二阈值大于第一阈值。换句话说，如果远程UE和中继UE之间的通信质量在持续恶化的情况下，可以通过这样的方式更早地重启直接发现流程，和/或测量其他中继UE，以便更快地完成中继UE重选。
同样，虽然上述步骤中将通过第一直接链路接收到的信号的测量结果与第二阈值进行比较，本领域技术人员能够理解，这样的比较也可以在基于信号的测量结果所确定的值与第二阈值进行比较。例如，信号的测量结果加上一个功率值与第二阈值比较。该功率值可以是第一中继UE向远程UE指示的。
比如，可以是将测量的与PSSCH相关联的参考信号的接收功率与第二阈值比较，也可以是将由参考信号的接收功率所确定的值，例如，经由相关的数学计算得到的结果与第二阈值比较。
在通过第一直接链路接收到的来自第一中继UE的信号的测量结果小于第二阈值并因此重启直接发现流程和/或测量其他中继UE的情况下，远程UE继续测量通过第一直接链路接收到的来自第一中继UE的信号，当测量结果小于第一阈值的情况下，再进行中继UE重选。
在该实例中，第二阈值同样可以是预配置或者网络设备配置的。在一个实例中，第二阈值可以是第一阈值与minHyst的和值，其中minHyst表示迟滞参数。
另外，本领域技术人员能够理解，在这个实例中，用于远程UE选择第二中继UE的阈值可以是步骤301中的阈值，或者等于第一阈值或第二阈值。
相比于图3所示的实施例，根据本申请的该实例的中继UE重选方法，可以更早的开启远程UE对中继UE的直接发现流程，并且进行中继UE信号质量的测量，从而在满足了中继UE重选条件的情况下，能够更快的完成中继UE重选。
附图4是根据本申请另一实施例的中继UE重选方法的流程图。与上述图3所示的实施例不同，在图4所示的实施例中，远程UE会更早的停止直接发现流程，从而能够更多的节省UE的功耗。
如图4所示，在步骤401，远程UE通过直接发现流程发现并选择第一中继UE，并且在步骤402，远程UE向第一中继UE发送直接通信请求消息(Direct Communication Request)用于请求与第一中继UE建立直接链路。步骤401和步骤402的过程可参考前述图3中的步骤301，在此不再赘述。
在远程UE发送直接通信请求消息(Direct Communication Request)之后，在步骤403，远程UE停止直接发现流程。本领域技术人员同样可以理解，远程UE停止直接发现流程也可以和发送直接通信请求消息的同时进行，本申请的实施例对此不作具体的限定。
同样，远程UE可以停止接收来自中继UE的用于直接发现的广播消息(UE-to-Network Relay Discovery Announcement message)，或者停止发送用于直接发现的请求消息(UE-to-Network Relay Discovery Solicitation message)，也可以是远程UE停止接收来自中继UE的对于请求消息的响应(UE-to-Network Relay Discovery Response message)，或者也可以通过发送相关的指示消息来表示，例如指示关闭所述邻近服务直连发现的请求消息(ProSe Direct Discovery Close Request)，具体的可参考前述的步骤303，在此不再赘述。
如果远程UE与第一中继UE成功建立了第一直接链路，第一中继UE会向远程UE发送直接通信接受消息(Direct Communication Accept)，此时，步骤404的判断为是。根据本申请实施例的方法，接下来进行步骤405。
在步骤405，通过第一直接链路，远程UE接收来自中继UE的信号，并且测量这些信号以获得测量结果，以便触发远程UE进行中继UE重选。
在步骤406，确定上述步骤405中的信号的测量结果是否小于第一阈值。如果信号 的测量结果大于等于第一阈值，则表示当前的中继UE仍然是合适的，则远程UE继续执行对第一中继UE的信号的测量。
如果步骤406中确定信号的测量结果小于第一阈值，则执行步骤407，根据本申请实施例的中继UE重选方法，远程UE重启直接发现流程以便进行中继UE重选。
在步骤407，远程UE重启直接发现。
在步骤408，远程UE通过直接发现流程重新发现并选择第二中继UE。
在步骤409，在判断第二中继UE满足条件的情况下，远程UE会选择第二中继UE并与之建立直接链路。
以上的步骤405-409与前述图3的实施例中的步骤304-308相同，具体可以参考前述步骤304-308的描述，在此不再赘述。
在如图4所示的实施例中，如果在步骤404中的判断为否，表示第一中继UE向远程UE发送了直接通信拒绝消息(Direct Communication Reject)，远程UE没有与第一中继UE成功建立第一直接链路，此时，方法流程转到步骤407，也就是远程UE重启直接发现，以便发现其他合适的中继UE。
同样，在发现并选择其他中继UE的过程中，仍然执行上述步骤401-409的方法，在此不再赘述。
根据上述图4所示的本申请的一个实施例的中继UE重选方法，远程UE在与中继UE建立了直接链路之前，就停止了直接发现流程，相比于图3所示的实施例，进而能够进一步的减少UE功耗的浪费。
进一步的，根据本申请的另一个实例，在图4所示的中继UE重选方法的实施例的基础上，还可以更早的停止直接发现流程，以进一步节省远程UE的功耗。
根据本申请的另一个实例，与上述图4所示的实施例的区别在于，当远程UE通过直接发现流程发现了满足条件的中继UE后就停止直接发现流程。这里所说的条件可以是来自中继UE的信号质量较好的情况，例如远程UE通过直接发现流程发现中继UE，并通过测量来自中继UE的承载发现消息的信道的参考信号的测量结果大于第三阈值的情况下，停止直接发现流程。
本领域技术人员能够理解，这里说的测量结果可以是信号的接收功率，或者是信号的接收质量、信号的强度中的至少一个。
第三阈值可以是预配置或者通过网络设备配置的，可以大于等于上述的第一阈值或者第二阈值，本申请的实施例对此不作具体的限定。
相比于图4所示的实施例，这种情况下能够进一步的节省远程UE的功耗。
同样，根据本申请的另一个实例，远程UE与中继UE建立直接链路之后并不立刻停止直接发现流程。而是当来自中继UE的信号质量较好的情况下，例如远程UE通过测量来自中继UE的信号的测量结果大于第三阈值的情况下，再停止直接发现流程。
本领域技术人员能够理解，这里说的信号可以是上述与物理侧链路发现信道(PSDCH)相关联的参考信号，也可以是与物理侧链路共享信道(PSSCH)，或物理侧链路控制信道(PSCCH)关联的参考信号。信号的测量结果可以是信号的接收功率，或者是信号的接收质量、信号的强度中的至少一个。
第三阈值可以是预配置或者通过网络设备配置的，可以大于等于上述的第一阈值或者第二阈值，本申请的实施例对此不作具体的限定。
另外需要说明的是，在图3的步骤307和308以及图4的步骤408和409中，仅显示了远程UE发现并选择第二中继UE以建立第二直接链路的过程，但是本领域技术人员能够理解，在远程UE发现并选择第二中继UE以建立第二直接链路的过程中同样可以执行前述如图3或图4所示的根据本申请的中继UE重选方法。
以上通过图3和图4对根据本申请的中继UE重选方法进行了详细的说明，远程UE可以通过在不同的时刻停止直接发现流程从而达到节省UE功耗的目的。
更进一步的，根据本申请的实施例的中继UE重选方法，还可以通过其他的方式进一步的节省UE的功耗。
在一个实例中，远程UE可以根据自身的状态选择是否进行直接发现流程或者是对中继UE的信号质量进行测量。
例如，当远程UE处于RRC-CONNECTED状态的情况下，远程UE与中继UE之间需要在直接链路上进行数据传输，远程UE可以进行直接发现流程或者是对中继UE的信号进行测量以便当中继UE不再合适时，进行中继UE重选。
而当远程UE处于RRC-IDLE或者是RRC-INACTIVE的状态时，远程UE与中继UE之间不需要进行数据传输，此时，远程UE可以选择不进行直接发现流程或者对中继UE的信号进行测量。
为了维持远程UE和中继UE的直接链路，当接收到检查直接链路的可用性(viability)的请求或者是保活定时器T4102过期的情况下，远程UE和中继UE之间会进行直接链路保活(keepalive)流程。当没有接收到来自中继UE的保活消息(Direct Communication Keepalive)或者保活响应消息(Direct Communication Keepalive ACK)的情况下，远程UE再重新开启直接发现流程并进行中继UE重选。
根据本申请上述实例的中继UE重选方法，当远程UE处于RRC-IDLE或者是RRC-INACTIVE的状态的情况下，能够进一步的节省UE的功耗。
根据本申请的又一个实例，远程UE可以测量来自中继UE(例如，第一中继UE，或者第二中继UE)的信号，并且根据信号的测量结果来调整测量周期。具体而言，来自中继UE的信号的测量结果显示远程UE与中继UE之间的通信质量越好(例如，信号强度越大、接收功率越高、接收质量越好，等等)，上述测量周期越长。这样，可以进一步减少UE的功耗。
例如，当远程UE测量的来自中继UE的信号的测量结果大于等于第四阈值的情况下，以第一周期进行信号的测量。当测量结果小于第四阈值的情况下，以第二周期进行信号的测量。其中，第二周期小于第一周期。
在一个实例中，第四阈值可以是预配置或者通过网络设备配置的，也可以等于上述实施例中的第一阈值或者第二阈值，或者任意值等等。
本领域技术人员能够理解，当远程UE和中继UE之间的信号质量较好的情况下，以较长的周期进行信号的测量，可以进一步的节省远程UE的功耗。
同样，对于远程UE处于不同状态下的情况，也可以通过信号测量周期的变化来 达到节省功耗的目的。
例如，当远程UE处于RRC-CONNECTED状态的情况下，以第三周期测量来自中继UE的信号；在远程UE处于RRC-IDLE或RRC-INACTIVE状态的情况下，以第四周期测量来自中继UE的信号，其中，第四周期大于第三周期。
本领域技术人员能够理解，上述的第一周期、第二周期、第三周期、第四周期可以是预配置或者通过网络设备配置的，周期的长短可以根据实际需要进行调整，本申请的实施例不对此做具体限定。
进一步的，本领域技术人员能够理解，根据本申请的上述调整信号测量周期的两个实例也可以单独应用在远程UE中，以达到节省远程UE功耗的技术效果。
在图3和图4的实施例的基础上，结合上述例如基于远程UE的状态进行直接发现流程或者基于信号测量的结果进行测量周期的调整等实例，可以衍生出多种组合，但是本领域技术人员可以理解的是，在不冲突的情况下，不同组合下的各个实施例都构成本申请的中继UE重选的方法。
在侧链通信中，单播通信的两个UE之间，UE发送PSSCH/PSCCH的功率可以侧链路的信道情况来确定，例如，根据两个UE之间的路损确定。例如，路损越大，发送功率越大，路损越小，发送功率越小。由于信号的发送功率随着侧链路的信道情况来确定，因此，信号的接收功率并不一定能反映出两个UE之间的信道情况。对于中继场景，远程UE与第一中继UE建立第一直接链路后，远程UE与第一中继UE的PC5RRC连接也认为是建立了。第一中继UE向远程UE发送的PSSCH/PSCCH(包括PSSCH参考信号/PSCCH参考信号)的功率可以根据侧链路的信道情况来确定。例如，信道情况可以包括第一中继UE与远程UE之间的路损。这种情况下，远程UE根据PSSCH/PSCCH的参考信号的接收功率并不一定能确定出与第一中继UE之间的信道情况。从而远程UE根据该接收功率判断是否触发中继UE重选和/或测量其他中继UE和/或进行发现流程不够准确。
为了使得远程UE根据更准确反映信道情况的测量结果进行中继UE重选和/或测量其他中继UE和/或进行发现流程，可以采用以下方法。
远程UE确定第一中继UE发送的信号的第一接收功率。其中，第一中继UE发送的信号可以包括PSSCH和/或PSCCH的参考信号。第一中继UE发送所述信号的功率为第一发送功率，第一发送功率是第一中继UE考虑了远程UE与第一中继UE之间的侧链信道情况时确定的信号的发送功率。第一发送功率根据远程UE与第一中继UE之间的侧链信道情况确定的。侧链信道情况包括路损。其中，远程UE与第一中继UE建立了侧链单播链路，或PC5单播链路，或PC5RRC连接，或直接链路，或层2链路。
第一中继UE向远程UE发送第一功率指示信息，用于指示第一功率。第一功率可以是第一中继UE的信号的发送功率余量。第一中继UE可以根据远程UE与第一中继UE之间的侧链信道情况确定第一功率。第一功率等于第二发送功率减去第一发送功率。其中，第二发送功率为第一中继UE不考虑远程UE与第一中继UE之间的侧链信道情况时的信号的发送功率。也就是说，第二发送功率与远程UE与第一中继 UE之间的侧链信道情况无关。例如，第二发送功率是根据第一中继UE的下行路损和/或最大发送功率确定的。或者，第二发送功率为第一中继UE发送发现消息的功率。发送发现消息的功率可以理解为发送承载发现消息的信道的参考信号的功率。承载发现消息的信道可以为PSSCH或PSDCH。
远程UE根据第一接收功率和第一功率确定是否触发中继UE重选和/或测量其他中继UE和/或进行发现流程。远程UE可以根据第一接收功率和第一功率进行中继UE重选。例如，如果第一接收功率加上第一功率小于或等于预设的阈值，则触发中继UE重选和/或测量其他中继UE和/或进行发现流程。
另一种方法是远程UE与第一中继UE建立侧链单播链路，或PC5单播链路，或PC5RRC连接，或直接链路，或层2链路后，第一中继UE向远程UE发送的用于远程UE测量的信号不考虑远程UE与第一中继UE之间的侧链信道情况。用于远程UE测量的信号可以是承载发现消息的信道的参考信号。承载发现消息的信道可以为PSSCH或PSDCH。
可以理解的是，UE为了实现上述功能，其包含了执行各个功能相应的硬件结构和/或软件模块。本领域技术人员应该很容易意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，本申请能够以硬件或硬件和计算机软件的结合形式来实现。某个功能究竟以硬件还是计算机软件驱动硬件的方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
本申请实施例可以根据上述方法示例对UE进行功能模块的划分，例如，可以对应各个功能划分各个功能模块，也可以将两个或两个以上的功能集成在一个处理模块中。上述集成的模块既可以采用硬件的形式实现，也可以采用软件功能模块的形式实现。需要说明的是，本申请实施例中对模块的划分是示意性的，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式。
在本申请实施例中，上述各实施例之间可以相互参考和借鉴，相同或相似的步骤以及名词均不再一一赘述。
现在参考图5，为根据本申请的一个实施例的用户设备500的框图。用户设备500可以包括一个或多个处理器502，与处理器502中的至少一个连接的系统控制逻辑508，与系统控制逻辑508连接的系统内存504，与系统控制逻辑508连接的非易失性存储器(NVM)506，以及与系统控制逻辑508连接的网络接口510。
处理器502可以包括一个或多个单核或多核处理器。处理器502可以包括通用处理器和专用处理器(例如，图形处理器，应用处理器，基带处理器等)的任何组合。在本文的实施例中，处理器502可以被配置为执行根据如图2-4所示的各种实施例的一个或多个实施例。
在一些实施例中，系统控制逻辑508可以包括任意合适的接口控制器，以向处理器502中的至少一个和/或与系统控制逻辑508通信的任意合适的设备或组件提供任意合适的接口。
在一些实施例中，系统控制逻辑508可以包括一个或多个存储器控制器，以提供 连接到系统内存504的接口。系统内存504可以用于加载以及存储数据和/或指令。在一些实施例中设备500的内存504可以包括任意合适的易失性存储器，例如合适的动态随机存取存储器(DRAM)。
NVM/存储器506可以包括用于存储数据和/或指令的一个或多个有形的、非暂时性的计算机可读介质。在一些实施例中，NVM/存储器506可以包括闪存等任意合适的非易失性存储器和/或任意合适的非易失性存储设备，例如HDD(Hard Disk Drive，硬盘驱动器)，CD(Compact Disc，光盘)驱动器，DVD(Digital Versatile Disc，数字通用光盘)驱动器中的至少一个。
NVM/存储器506可以包括安装在设备500的装置上的一部分存储资源，或者它可以由设备访问，但不一定是设备的一部分。例如，可以经由网络接口510通过网络访问NVM/存储506。
特别地，系统内存504和NVM/存储器506可以分别包括：指令520的暂时副本和永久副本。指令520可以包括：由处理器502中的至少一个执行时导致设备500实施如图3-14所示的方法的指令。在一些实施例中，指令520、硬件、固件和/或其软件组件可另外地/替代地置于系统控制逻辑508，网络接口510和/或处理器502中。
在一个实施例中，处理器502中的至少一个可以与用于系统控制逻辑508的一个或多个控制器的逻辑封装在一起，以形成系统封装(SiP)。在一个实施例中，处理器502中的至少一个可以与用于系统控制逻辑508的一个或多个控制器的逻辑集成在同一管芯上，以形成片上系统(SoC)。
本申请的各方法实施方式均可以以软件、磁件、固件等方式实现。
可将程序代码应用于输入指令，以执行本文描述的各功能并生成输出信息。可以按已知方式将输出信息应用于一个或多个输出设备。为了本申请的目的，处理系统包括具有诸如例如数字信号处理器(DSP)、微控制器、专用集成电路(ASIC)或微处理器之类的处理器的任何系统。
程序代码可以用高级程序化语言或面向对象的编程语言来实现，以便与处理系统通信。在需要时，也可用汇编语言或机器语言来实现程序代码。事实上，本文中描述的机制不限于任何特定编程语言的范围。在任一情形下，该语言可以是编译语言或解释语言。
至少一个实施例的一个或多个方面可以由存储在计算机可读存储介质上的表示性指令来实现，指令表示处理器中的各种逻辑，指令在被机器读取时使得该机器制作用于执行本文所述的技术的逻辑。被称为“IP核”的这些表示可以被存储在有形的计算机可读存储介质上，并被提供给多个客户或生产设施以加载到实际制造该逻辑或处理器的制造机器中。
虽然本申请的描述将结合较佳实施例一起介绍，但这并不代表此申请的特征仅限于该实施方式。恰恰相反，结合实施方式作发明介绍的目的是为了覆盖基于本申请的权利要求而有可能延伸出的其它选择或改造。为了提供对本申请的深度了解，以下描述中将包含许多具体的细节。本申请也可以不使用这些细节实施。此外，为了避免混乱或模糊本申请的重点，有些具体细节将在描述中被省略。需要说明的是，在不冲突 的情况下，本申请中的实施例及实施例中的特征可以相互组合。
此外，各种操作将以最有助于理解说明性实施例的方式被描述为多个离散操作；然而，描述的顺序不应被解释为暗示这些操作必须依赖于顺序。特别是，这些操作不需要按呈现顺序执行。
如这里所使用的，术语“模块”或“单元”可以指代、是或者包括：专用集成电路(ASIC)、电子电路、执行一个或多个软件或固件程序的(共享、专用或组)处理器和/或存储器、组合逻辑电路和/或提供所描述的功能的其他合适的组件。
在附图中，以特定布置和/或顺序示出一些结构或方法特征。然而，应该理解，可以不需要这样的特定布置和/或排序。在一些实施例中，这些特征可以以不同于说明性附图中所示的方式和/或顺序来布置。另外，在特定图中包含结构或方法特征并不意味着暗示在所有实施例中都需要这样的特征，并且在一些实施例中，可以不包括这些特征或者可以与其他特征组合。
本申请公开的机制的各实施例可以被实现在硬件、软件、固件或这些实现方法的组合中。本申请的实施例可实现为在可编程系统上执行的计算机程序或程序代码，该可编程系统包括多个处理器、存储系统(包括易失性和非易失性存储器和/或存储元件)、多个输入设备以及多个输出设备。
可将程序代码应用于输入指令，以执行本申请描述的各功能并生成输出信息。可以按已知方式将输出信息应用于一个或多个输出设备。为了本申请的目的，处理系统包括具有诸如例如数字信号处理器(DSP)、微控制器、专用集成电路(ASIC)或微处理器之类的处理器的任何系统。
程序代码可以用高级程序化语言或面向对象的编程语言来实现，以便与处理系统通信。在需要时，也可用汇编语言或机器语言来实现程序代码。事实上，本申请中描述的机制不限于任何特定编程语言的范围。在任一情形下，该语言可以是编译语言或解释语言。
在一些情况下，所公开的实施例可以以硬件、固件、软件或其任何组合来实现。在一些情况下，至少一些实施例的一个或多个方面可以由存储在计算机可读存储介质上的表示性指令来实现，指令表示处理器中的各种逻辑，指令在被机器读取时使得该机器制作用于执行本申请所述的技术的逻辑。被称为“IP核”的这些表示可以被存储在有形的计算机可读存储介质上，并被提供给多个客户或生产设施以加载到实际制造该逻辑或处理器的制造机器中。
这样的计算机可读存储介质可以包括但不限于通过机器或设备制造或形成的物品的非瞬态的有形安排，其包括存储介质，诸如：硬盘任何其它类型的盘，包括软盘、光盘、紧致盘只读存储器(CD-ROM)、紧致盘可重写(CD-RW)以及磁光盘；半导体器件，例如只读存储器(ROM)、诸如动态随机存取存储器(DRAM)和静态随机存取存储器(SRAM)之类的随机存取存储器(RAM)、可擦除可编程只读存储器(EPROM)、闪存、电可擦除可编程只读存储器(EEPROM)；相变存储器(PCM)；磁卡或光卡；或适于存储电子指令的任何其它类型的介质。
因此，本申请的各实施例还包括非瞬态的计算机可读存储介质，该介质包含指令 或包含设计数据，诸如硬件描述语言(HDL)，它定义本申请中描述的结构、电路、装置、处理器和/或系统特征。

Claims (14)

  1. 一种中继UE(relay UE)重选方法，所述方法用于远程UE(remote UE)，其特征在于，包括：
    发现第一中继UE并且选择与所述第一中继UE建立第一直接链路，所述第一直接链路用于所述远程UE与所述第一中继UE进行直接通信；和
    测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，并获得所述信号的测量结果；
    在所述测量结果小于第一阈值的情况下，进行中继UE重选。
  2. 如权利要求1所述的方法，其特征在于，还包括：
    在完成与所述第一中继UE建立所述第一直接链路之后，停止发送和/或停止接收发现消息，或
    向所述第一中继UE发送用于建立所述第一直接链路的请求消息，以及停止发送和/或停止接收所述发现消息。
  3. 如权利要求1或2所述的方法，其特征在于，所述信号包括：与物理侧链路共享信道(PSSCH)和/或物理侧链路控制信道(PSCCH)关联的参考信号。
  4. 如权利要求3所述的方法，其特征在于，所述测量结果包括以下参数中的至少一种：信号的接收功率、接收质量、强度。
  5. 如权利要求2所述的方法，其特征在于，在所述测量结果小于第一阈值的情况下，进行中继UE重选，包括，
    在所述测量结果小于所述第一阈值的情况下，发送和/或接收所述发现消息。
  6. 如权利要求2所述的方法，其特征在于，在所述测量结果小于第一阈值的情况下，进行中继UE重选，包括，
    在所述测量结果小于第二阈值的情况下，发送和/或接收所述发现消息，并且在所述测量结果小于所述第一阈值的情况下，进行中继UE重选，其中，所述第二阈值大于所述第一阈值。
  7. 如权利要求2所述的方法，其特征在于，还包括：
    在接收到来自所述第一中继UE的拒绝消息的情况下，发送和/或接收所述发现消息，其中所述拒绝消息用于拒绝所述远程UE向所述第一中继UE发送的用于建立所述第一直接链路的请求。
  8. 如权利要求2所述的方法，其特征在于，还包括
    测量来自所述第一中继UE的发现消息关联的参考信号，在所述发现消息关联的参考信号的测量结果大于等于第三阈值的情况下，停止发送和/或停止接收发现消息。
  9. 如权利要求8所述的方法，其特征在于，所述发现消息关联的参考信号的测量结果包括：发现消息关联的参考信号的接收功率，接收质量、强度中的至少一个。
  10. 如权利要求1-9所述的方法，其特征在于，还包括
    在所述测量结果大于等于第四阈值的情况下，以第一周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号；以及
    在所述测量结果小于第四阈值的情况下，以第二周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，
    其中，所述第二周期小于所述第一周期。
  11. 如权利要求1-9所述的方法，其特征在于，还包括
    在所述远程UE处于RRC-CONNECTED状态的情况下，以第三周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号；以及
    在所述远程UE处于RRC-IDLE或RRC-INACTIVE状态的情况下，以第四周期测量通过所述第一直接链路接收到的来自所述第一中继UE的信号，
    其中，所述第四周期大于所述第三周期。
  12. 如权利要求2-11所述的方法，其特征在于，所述发现消息包括以下消息中的至少一个：
    用于所述中继UE发现所述远程UE的广播消息(Announcement)、用于所述远程UE发现所述中继UE的请求消息(Solicitation)以及所述中继UE对于所述请求的响应消息(Response)。
  13. 一种机器可读介质，其特征在于，在所述介质上存储有指令，当所述指令在所述机器上运行时，使得所述机器执行权利要求1至12中任意一项所述的方法。
  14. 一种设备，其特征在于，包括：
    处理器；
    存储器，在所述存储器上存储有指令，当所述指令被所述处理器运行时，使得所述用户设备执行权利要求1至12中任意一项所述的方法。
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