CN114080062A

CN114080062A - Method, medium and equipment for reselecting relay UE

Info

Publication number: CN114080062A
Application number: CN202011061600.0A
Authority: CN
Inventors: 才宇; 徐海博; 姚楚婷
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-08-19
Filing date: 2020-09-30
Publication date: 2022-02-22
Anticipated expiration: 2040-09-30
Also published as: CN114080062B; WO2022037456A1

Abstract

The embodiment of the application relates to a method for reselecting relay UE, which comprises the following steps: discovering a first relay UE and selecting to establish a first direct link with the first relay UE, the first direct link being used for direct communication between a remote UE and the first relay UE; and measuring a signal from the first relay UE received through the first direct link and obtaining a measurement result of the signal; and when the measurement result is smaller than the first threshold value, performing the relay UE reselection. Embodiments of the present application also relate to a machine-readable storage medium and a user equipment.

Description

Method, medium and equipment for reselecting relay UE

Technical Field

One or more embodiments of the present application relate generally to the field of communications, and in particular, to a method, medium, and apparatus for relay UE reselection.

Background

Device-to-Device communication (D2D), also known as Proximity Service (ProSe) in 3GPP (3rd Generation Partnership Project), enables direct communication between physically proximate devices without transport over a network. ProSe may save network resources, allow public safety communications, social networking, file transfer, and other services between devices when network coverage is not available. For example, a User Equipment (UE) located outside the coverage of the network, also referred to as a remote UE (remote UE), may connect to the network through another UE to enable communication with the network. A UE that provides a function of connecting with a Network for a remote UE is also called a Relay UE (UE-to-Network Relay UE).

When the relay UE serving the remote UE is no longer suitable (e.g., the quality of communication between the remote UE and the relay UE is poor, and/or other circumstances), the remote UE may perform a reselection of the relay UE to select to establish direct communication with other relay UEs and to maintain a connection with the network through the selected other relay UEs. In general, after establishing a connection with a relay UE, a remote UE periodically measures the signal strength of a discovery message sent by the relay UE for relay reselection.

Disclosure of Invention

The present application is described below in terms of several aspects, embodiments and advantages of which are mutually referenced.

In a first aspect, an embodiment of the present application provides a relay ue (relay ue) reselection method, where the method is used for a remote ue (remote ue), and includes: discovering a first relay UE and selecting to establish a first direct link with the first relay UE, the first direct link for the remote UE to communicate directly with the first relay UE; and measuring a signal from the first relay UE received through the first direct link and obtaining a measurement result of the signal; and when the measurement result is smaller than a first threshold value, performing the relay UE reselection.

In some embodiments, after completing establishing the first direct link with the first relay UE, ceasing to send and/or cease to receive discovery messages (discovery messages), or

Transmitting a request message for establishing the first direct link to the first relay UE, and stopping transmitting and/or stopping receiving the discovery message.

In some embodiments, the signal comprises: reference signals associated with a Physical Sidelink Shared Channel (PSSCH) and/or a Physical Sidelink Control Channel (PSCCH).

In some embodiments, the measurement comprises at least one of the following parameters: received power, received quality, strength of a reference signal associated with a physical side link shared channel (PSSCH) or a physical side link control channel (PSCCH).

In some embodiments, performing relay UE reselection if the measurement result is less than a first threshold comprises sending and/or receiving the discovery message if the measurement result is less than the first threshold.

In some embodiments, performing the relay UE reselection if the measurement result is less than a first threshold value comprises transmitting and/or receiving the discovery message if the measurement result is less than a second threshold value, and performing the relay UE reselection if the measurement result is less than the first threshold value, wherein the second threshold value is greater than the first threshold value.

In some embodiments, the discovery message is sent and/or received upon receiving a Reject message (Direct Communication Reject) from the first relay UE, wherein the Reject message is for rejecting a request sent by the remote UE to the first relay UE to establish the first Direct link.

In some embodiments, a Sidelink Discovery Reference Signal (Sidelink Discovery Reference Signal) from the first relay UE is measured, and in the case that a measurement result of the Sidelink Discovery Reference Signal is greater than or equal to a third threshold, transmission and/or reception of a Discovery message is stopped.

In some embodiments, the measurement of the side link discovery reference signal comprises: a received power of a side link discovery reference signal (SD-RSRP), a received quality, and a strength.

In some embodiments, in the case that the measurement result is greater than or equal to a fourth threshold, measuring a signal from the first relay UE received through the first direct link at a first cycle; and measuring a signal from the first relay UE received through the first direct link at a second period when the measurement result is less than a fourth threshold, wherein the second period is less than the first period.

In some embodiments, signals from the first relay UE received over the first direct link are measured for a third period with the remote UE in an RRC-CONNECTED state; and measuring a signal from the first relay UE received over the first direct link with a fourth period if the remote UE is in an RRC-IDLE or RRC-INACTIVE state, wherein the fourth period is greater than the third period.

In some embodiments, the discovery message comprises at least one of the following messages: a broadcast message (notification) for the relay UE to discover the remote UE, a request message (Solicitation) for the remote UE to discover the relay UE, and a Response message (Response) for the relay UE to the request.

In a second aspect, embodiments of the present application provide a machine-readable medium having stored thereon instructions which, when executed on the machine, cause the machine to perform the method of the first aspect.

In a third aspect, an embodiment of the present application provides an apparatus, including: a processor; a memory having instructions stored thereon that, when executed by the processor, cause the user equipment to perform the method of the first aspect.

According to some aspects of the present disclosure, waste of UE power consumption can be reduced by stopping a direct discovery procedure between a remote UE and a relay UE, and restarting the direct discovery procedure and performing a relay UE reselection when a measurement result of the remote UE measuring a signal from a first relay UE received through a first direct link is less than a first threshold.

Drawings

FIG. 1 is a schematic diagram of an application scenario according to an embodiment of the present application;

fig. 2 is a schematic flow chart of remote UE and relay UE interaction according to an embodiment of the present application;

fig. 3 is a flowchart of a method for reselecting a relay UE according to an embodiment of the present application;

fig. 4 is a flow chart of a method of relay UE reselection according to another embodiment of the present application;

fig. 5 is a block diagram of a user equipment of an embodiment of the present application.

Detailed Description

The present application is further described with reference to the following detailed description and the accompanying drawings.

It is to be understood that, although the terms 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 merely to distinguish one feature from another. For example, a first feature may be termed a second feature, and, similarly, a second feature may be termed a first feature, without departing from the scope of example embodiments.

It should be noted that in this specification, like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings. In addition, "a and/or B" appearing in the specification means three possibilities of only a, only B, and a and B.

To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of an application scenario according to an embodiment of the present application, where the scenario includes

user devices

11, 12, and 13 and a network device 2.

For the sake of clarity and conciseness of the following description of the various embodiments, a brief introduction of some technical terms is first given:

1) a user equipment, also called a terminal, a terminal device, is a device providing voice and/or data connectivity to a user, and common terminal devices include, for example: in-Vehicle devices, mobile phones, tablet computers, notebook computers, palmtop computers, Mobile Internet Devices (MID), wearable devices (including smart watches, smart bands, pedometers, etc.), personal digital assistants, portable media players, navigation devices, video game devices, set-top boxes, virtual reality and/or augmented reality devices, internet of things devices, industrial control devices, streaming media client devices, electronic books, reading devices, POS machines, V2X (Vehicle to outside information exchange) terminal devices, SL (Sidelink)/ProSe terminal devices, Road side units (Road Site units, RSUs), and other devices, etc.

2) A Network device, also called a Radio Access Network (RAN) device, is a device for accessing a user equipment to a wireless Network, and includes Network devices in various communication systems, for example, including but not limited to: a Base Station, an evolved Node B (eNB), a Radio Network Controller (RNC), a Node B (NB), a network equipment Controller (BSC), a network equipment Transceiver Station (BTS), a Home network equipment (e.g., Home evolved Node B or Home Node B, HNB), a BaseBand Unit (BBU), and the like. The network device includes network devices of various frequency systems, for example, but not limited to: low-frequency network equipment and high-frequency network equipment.

As shown in fig. 1, UE12 and UE13 implement communication connections with network device 2 through a Uu interface. The communication between them can be based on, but not limited to, a third Generation (3rd-Generation, 3G) mobile communication system, a fourth Generation (4th-Generation, 4G) mobile communication system, a fifth Generation (5 th-Generation, 5G) system, a New Radio (NR) system or a communication system having the same architecture as the 5G system and other subsequent mobile communication systems.

In the scenario shown in fig. 1, UE11 may access the network through network device 2 by establishing a direct link with UE12 or UE 13. Here, the UE11 is referred to as a remote UE (remote UE), and the UE12 and the 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 UEs).

Those skilled in the art will understand that, here, the remote UE accesses the network through the network device via the Relay UE, and the technical solution of the present application is also applicable to the case where the remote UE communicates with another remote UE via the Relay UE, in this case, the Relay UE is also referred to as UE-to-UE Relay (UE-to-UE Relay).

In addition, both UE12 and UE13 shown in fig. 1 access network device 2, but those skilled in the art will appreciate that UE12 and UE13 may also access different network devices.

To establish a direct link between the UE11 and the UE12 or UE13, it is required that the remote UE (e.g., UE11) or relay UE (e.g., UE12 or UE13) be able to detect and discover another UE (e.g., UE11 is able to discover UE12 or UE13, or UE12 or UE13 is able to discover UE 11).

A proximity services Direct Discovery (ProSe Direct Discovery) procedure for a procedure of detecting and identifying another UE nearby using an E-UTRA (Evolved-UMTS Terrestrial Radio Access) or WLAN (Wireless Local Area Network) Direct Radio signal is defined in the 3GPP standard TS 23.303. The proximity service direct discovery procedure is hereinafter simply referred to as a direct discovery procedure. According to the specifications of 3GPP standard TS23.3035.3.1.2, the direct discovery procedure includes two modes, mode a and mode B.

In the mode a, the Relay UE transmits a broadcast message (UE-to-Network Relay Discovery notification message) for direct Discovery, and the remote UE listens to the broadcast message.

In mode B, the remote UE sends a request message for direct Discovery (UE-to-Network Relay Discovery request message). The Relay UE that matches the Relay Service Code (Relay Service Code) included in the request message issues a Response message (UE-to-Network Relay Discovery Response message) to the remote UE.

After the remote UE detects and discovers one or more candidate relay UEs (candidate relay UEs) through the direct discovery procedure, a relay UE satisfying the condition is selected to establish a direct link. For example, in the scenario shown in fig. 1, the UE11 detected and discovered the relay UE12 and the relay UE13 through direct discovery, and selected therefrom the UE12 that satisfies the condition to establish the direct link. The conditions herein may include, but are not limited to: meeting ProSe layer criteria, meeting access layer criteria, etc.

If there are multiple candidate relay UEs, i.e., if multiple candidate relay UEs satisfying the above conditions are found, then the candidate relay UE with the highest ranking of access stratum criteria is selected.

The Communication between the remote UE11 and the relay UE12 may be One-To-One ProSe Direct Communication (One-To-One ProSe Direct Communication), or V2X (Vehicle To event) Communication (defined in 3GPP TS 23.285) and other types of wireless Communication conducted directly between two or more neighboring 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 Sidelink (Sidelink), and the communication interface is a PC5 interface.

As described above, after the remote UE11 successfully establishes a direct link through direct discovery and selection and relay UE12, the remote UE11 may communicate with the network through relay UE 12.

Also, those skilled in the art will appreciate that the above procedures for discovering, selecting, and establishing a direct link with a relay UE are the same in the case where the remote UE communicates with another remote UE via the relay UE.

When the relay UE selected by the remote UE is no longer suitable, for example, the signal quality of the current relay UE is poor, or the remote UE is far away from the current selected relay UE, in order to obtain a connection service to the network, the remote UE initiates a relay UE reselection (UE-to-network relay reselection) procedure so as to reselect the relay UE.

Taking the scenario shown in fig. 1 as an example, when the condition for relay UE reselection is satisfied, the remote UE11 may initiate a relay UE reselection procedure, and through the relay UE reselection, the remote UE11 may finally select the relay UE13 and establish a direct link therewith to access the network.

One of the conditions for a reselection of a relay UE defined in the 3GPP standard TS24.334 is that the relay UE no longer meets the lower protocol layer standard (lower layer criteria) specified in the relevant clause of the standard. The standard of the lower protocol layer specified in the above standard may include that the Received Power (SD-RSRP) of the Sidelink Discovery Reference Signal Received Power (SD-RSRP) of the relay UE is lower than the threshold q-RxLevMin. Here, 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, i.e., the SD-RSRP mentioned above.

As described above, after the remote UE and the relay UE establish the direct link, the prior art scheme still needs to perform the direct discovery procedure in the form of mode a or mode B for the subsequent reselection of the relay UE, thereby causing a waste of power consumption of the remote UE.

The technical means of the present application and the technical means of the present application will be described in detail below with specific examples. The following specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.

Fig. 2 is a schematic diagram of interaction of a remote UE and a relay UE according to an embodiment of the present application. As shown in fig. 2, in step 201, a direct discovery procedure of mode a or mode B as described above is performed between the remote UE and the relay UE. Those skilled in the art will understand that the direct discovery process is not limited to the above-mentioned mode a or mode B, and may be other discovery processes.

After the remote UE discovers and selects the relay UE through the Direct discovery procedure, a Request message for establishing a Direct link, for example, a Direct Communication Request message (Direct Communication Request) is transmitted to the relay UE in step 202.

In step 203, the relay UE may send a message, e.g., a Direct Communication Accept message (Direct Communication Accept), to the remote UE indicating acceptance of the Direct link setup. After the relay UE sends the message to the remote UE, it may be considered that the direct link between the remote UE and the relay UE is successfully established. After receiving the message, the remote UE may consider that the direct link between the remote UE and the relay UE is successfully established. The relay UE may check User information (User Info) and IP Address configuration (IP Address Config) included in the request message for establishing the direct link, and after the authentication is completed and the security association is successfully established, transmit a message indicating acceptance of direct link establishment to the remote UE.

In order to solve the power consumption waste of the remote UE in the prior art, according to the method for reselecting the relay UE in the embodiment of the present application, the direct discovery process between the remote UE and the relay UE and/or the measurement of other relay UEs may be stopped, so as to reduce the power consumption waste.

As shown in fig. 2, according to the method for reselecting a relay UE in one embodiment of the present application, stopping the direct discovery procedure and/or stopping measuring other relay UEs may be after step 203, that is, after the remote UE and the relay UE establish a direct link (option 1).

Alternatively, according to another embodiment of the present application, the direct discovery procedure and/or the measurement of other relay UEs may also be stopped after the remote UE sends the request message for establishing the direct link to the relay UE in step 202 (option 2). Stopping the direct discovery procedure and/or stopping measuring other relay UEs earlier than in the case of stopping the direct discovery procedure and/or stopping measuring other relay UEs after step 203 can save more power consumption of the UE.

The stop direct discovery procedure includes, but is not limited to, the remote UE stopping sending and/or receiving discovery messages. The Discovery message includes, but is not limited to, messages transmitted/received in two direct Discovery modes defined according to the 3GPP standard TS23.303, such as the above-mentioned broadcast message for direct Discovery (UE-to-Network Discovery notification message), the above-mentioned request message for direct Discovery (UE-to-Network Discovery notification message), the above-mentioned Response message (UE-to-Network Discovery Response message), and/or other information transmitted/received in the direct Discovery procedure. In addition, the stop receiving discovery message may be a stop listening discovery message.

The stopping of the direct discovery procedure may refer to stopping the discovery procedure between the remote UE and the relay UE, including the remote UE stopping sending the discovery message to the relay UE, or the relay UE stopping receiving the discovery message sent by the remote UE, or the relay UE stopping sending the discovery message to the remote UE. If the relay UE also discovers or is discovered by other UEs, the relay UE may still perform a discovery process, including receiving a discovery message and/or transmitting a discovery message.

Two embodiments of the method for reselecting a relay UE according to the present application illustrated in fig. 2 will be described in detail below with reference to fig. 3 and 4, respectively.

Fig. 3 is a flow chart of a relay UE reselection method according to one embodiment of the present application. As shown in fig. 3, at step 301, the remote UE discovers and selects a first relay UE (e.g., UE 12).

In one example, the remote UE may discover candidates for one or more relay UEs via mode a or mode B of the direct discovery procedure described above.

If only one relay UE candidate satisfies the condition, the remote UE selects the relay UE, as specified in 3GPP standard TS 24.334; if a plurality of relay UE candidates all satisfy the condition, a highest ranked one of the relay UE candidates may be selected from the plurality of relay UE candidates.

Those skilled in the art will appreciate that the ranking referred to herein may be based on, for example, measurements of signals from relay UEs as measured by the remote UE. For example, the reference signal may be associated with a Physical Sidelink Discovery Channel (PSDCH), or may be associated with a physical sidelink shared channel (PSCCH), or a Physical Sidelink Control Channel (PSCCH). When the discovery message is transmitted over the psch, a reference signal associated with the psch or PSCCH may be used. Thus, measuring the signal from the relay UE may be measuring a reference signal of a psch carrying a discovery message from the relay UE and/or a reference signal of a psch scheduling the psch. 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.

In one example, the measurement of the signal may be at least one of a received power of the signal, a received quality of the signal, or a strength of the signal.

In one example, a threshold for measuring the signal measurement may be pre-configured or configured by the network device, and the relay UE may be selected using the threshold. For example, one UE whose measurement result is higher than or equal to the above threshold is selected as the relay UE; or, if the signal measurement results of a plurality of relay UE candidates are all higher than the above threshold, selecting the UE with the largest measurement result as the relay UE, and so on.

Those skilled in the art will appreciate that the threshold may be the minimum value of the received power required for the relay UE reselection (q-RxLevMin) specified in the 3GPP standard, or the sum of this minimum value and minHyst, where minHyst represents a hysteresis parameter, and so on.

After the remote UE discovers and selects the first Relay UE in step 301, the remote UE establishes a first direct link with the selected first Relay UE in step 302, so that the remote UE directly communicates with the first Relay UE through the first direct link, and thus connects with a Network (UE-To-Network Relay) or another remote UE (UE-To-UE Relay) through the first Relay UE.

As described above, after the remote UE discovers and selects the first relay UE through the direct discovery procedure, a request message for establishing a direct link, for example, a direct communication request message, is transmitted to the first relay UE.

Next, the first relay UE checks the User information (User Info) and the IP Address configuration (IP Address Config) included in the Direct Communication Request message (Direct Communication Request), and after completing the mutual authentication procedure and successfully establishing the security association, the first relay UE sends a message indicating acceptance of Direct link establishment, for example, a Direct Communication acceptance message (Direct Communication Accept), to the remote UE, so that the remote UE and the first relay UE complete establishment of the Direct link.

According to the method for reselecting a relay UE in the embodiment of the present application, in the following step 303, in order to reduce the power consumption waste of the UE, the remote UE may stop the direct discovery procedure and/or stop measuring other relay UEs.

The remote UE stopping the direct discovery procedure may be stopping sending discovery messages (discovery messages), stopping receiving discovery messages, or stopping sending and stopping receiving discovery messages at the same time.

Specifically, for the direct Discovery procedure of mode a, the Discovery message refers to a broadcast message (UE-to-Network Relay Discovery notification message) from the Relay UE.

For the direct Discovery procedure of mode B, the Discovery message refers to a request message (UE-to-Network Relay Discovery request message) for direct Discovery and a Response (UE-to-Network Relay Discovery Response message) to the request message from the Relay UE.

According to the method of the embodiment of the present application, the remote UE may simply stop receiving the discovery message, i.e., does not receive the broadcast or response from the relay UE; or just stop sending the discovery message, i.e. not send the request message; it is also possible to stop receiving and stop sending discovery messages simultaneously. Those skilled in the art will appreciate that compared to the prior art, the power consumption of the UE may be reduced because the remote UE stops the direct discovery procedure and/or stops measuring other relay UEs without receiving or transmitting related information.

In addition, in an optional example, stopping the Direct Discovery procedure may also be indicated by sending a related indication message, such as a Request message (ProSe Direct Discovery Close Request) indicating to turn off the proximity service Direct Discovery.

At step 304, the remote UE receives signals from the first relay UE over the first direct link and measures the signals to obtain measurements to trigger relay UE reselection by the remote UE.

According to the method for reselecting the relay UE in the embodiment of the present application, 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, the relay UE needs to be triggered to reselect 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. In the access stratum, PC5 signaling and PC5 user plane data on the first direct link may be transmitted through sidelink communications. In particular, the PSSCH may carry PC5 signaling and PC5 user plane data. When the first relay UE sends PC5 user plane data or PC5 signaling to the remote UE, the first relay UE needs to send a PSCCH carrying data or signaling to the remote UE, which may also send a PSCCH to the remote UE. The PSCCH is associated with a PSCCH that is used to schedule the PSCCH or that indicates the resources on which the PSCCH is transmitted. After the first direct link is established, the PC5 RRC connection may be considered established as well. The PSSCH may also carry PC5 RRC signaling.

After the remote UE and the first relay UE establish the first direct link, the remote UE may receive signals from the first relay UE via the first direct link and measure the signals to obtain measurement results. Or the remote UE may receive signals from the first relay UE via sidelink communication and measure these signals to obtain measurement results.

If the first relay UE does not send PC5 user plane data or PC5 signaling to the remote UE, the remote UE may initiate a keep-alive procedure, i.e., the remote UE sends a keep-alive message to the first relay UE. And after receiving the keep-alive message, the first relay UE sends a keep-alive Ack message to the remote UE. The Keep-alive message and the Keep-alive Ack message may be transmitted through the PSSCH. Therefore, the remote UE may measure the received power of the associated reference signal of the PSSCH carrying the keep-alive Ack message for relaying UE reselection or triggering the remote UE to perform the discovery procedure. Or, 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 procedure, i.e., the first relay UE sends a keep-alive message to the remote UE. Therefore, the remote UE may measure the received power of the associated reference signal of the PSSCH carrying the keep-alive Ack message for relaying UE reselection or triggering the remote UE to perform the discovery procedure. And after receiving the keep-alive message, the remote UE sends a keep-alive Ack message to the first relay UE.

In one example, the signals from the first relay UE measured by the remote UE may include sidelink signals, wherein the sidelink signals may include at least one of sidelink communication signals, sidelink reference signals, such as a sidelink reference signal associated with a PSCCH, and a sidelink reference signal associated with a PSCCH.

In one example, the measurement results may include, but are not limited to, received power of signals, received quality, signal strength, and/or other information indicative of communication quality between the remote UE and the relay UE. For example, the received power of the reference signal associated with the PSCCH, 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 PSCCH and the received power of the reference signal associated with the PSCCH.

It is noted that, although the embodiment shown in fig. 3 describes that the remote UE measures the signal from the relay UE and obtains the measurement result after stopping the direct discovery procedure, those skilled in the art can understand that, since, in step 302, once the remote UE establishes the first direct link with the first relay UE, the remote UE can measure the signal from the first relay UE through the first direct link and obtain the measurement result, step 303 and step 304 may also occur simultaneously, which is not specifically limited in this application.

According to other embodiments of the present application, the Direct discovery procedure may be stopped at other points in time, for example, after 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 as shown in fig. 2.

Next, in step 305, it is determined whether the measurement of the signal in step 304 above is less than a first threshold. If the measurement result of the signal is greater than or equal to the first threshold, indicating that the current first relay UE is still suitable, the remote UE continues to perform measurement of the signal of the first relay UE.

If the measurement result of the signal is smaller than the first threshold, step 306 is executed, according to the method for reselecting a relay UE of the embodiment of the present application, the remote UE performs a direct discovery procedure for reselecting the relay UE, and/or measures other relay UEs. The method of measuring the other relay UEs may be the same as the method of measuring the signals of the relay UEs in step 301.

In one example, the first threshold may be pre-configured or network device configured. The first threshold may be set to satisfy the minimum value of the received power (q-RxLevMin) required for the reselection of the relay UE specified in the 3GPP standard, or may be equal to the threshold used by the remote UE to discover and select the first relay UE through the direct discovery procedure in step 301.

In step 305, the measurement of the signal is compared to a first threshold, but one skilled in the art will appreciate that a value determined based on the measurement of the signal may also be used to compare to the first threshold. For example, the measurement of the signal plus a power value is compared to a first threshold. The power value may be indicated to the remote UE by the first relay UE.

For instance, the result, e.g. via a mathematical calculation of the correlation, may be compared with the first threshold value based on a value determined by the received power of the reference signal.

In addition, those skilled in the art will also understand that when some other conditions are satisfied, even if the measurement result of the signal determined in step 305 is greater than or equal to the first threshold, the remote UE is triggered to perform a direct discovery procedure for performing relay UE reselection, and/or to measure other relay UEs.

These other conditions may be, for example, the remote UE receiving a message from the relay UE to Reject the establishment of the first Direct link, e.g., a Direct Communication Reject message (Direct Communication Reject), or the remote UE receives a message from the relay UE to Release the first Direct link, e.g., a Release message to Release Direct Communication (Direct Communication Release), or after M successive retransmissions of a request message for establishing a Direct link, or a Direct Communication Setup (Direct Communication Setup) or a Direct Communication keep-alive message (Direct Communication keep), the remote UE does not receive any response from the relay UE, or after M consecutive retransmissions of the PC5 Discovery message (PC5 Discovery) to trigger signal strength measurements between the remote UE and the relay UE, the remote UE does not receive any response from the relay UE, or the remote UE detects a sidelink radio link failure (sidelink radio link failure), etc. The direct communication reject message is used for indicating the relay UE to reject the request for establishing direct communication proposed by the remote UE, and the release message of direct communication is used for indicating the relay UE to require the release of the message of direct communication with the remote UE.

Next, in step 306, the remote UE performs a direct Discovery procedure, and specifically, the remote UE receives and/or transmits a Discovery message, for example, may restart to receive a broadcast message for direct Discovery from the Relay UE (UE-to-Network Relay Discovery notification message), or restart to transmit a request message for direct Discovery (UE-to-Network Relay Discovery notification message), or restart to receive a Response to the request message from the Relay UE (UE-to-Network Relay Discovery Response message).

The remote UE then discovers and selects a second relay UE, e.g., UE13, in step 307.

Likewise, those skilled in the art will appreciate that the second relay UE discovered by the remote UE may be one or more instances. Here, the process of discovering and selecting the second relay UE by the remote UE through the direct discovery procedure is the same as the process of discovering and selecting the first relay UE in step 301, for example, the remote UE may select based on the measurement result of the signal from the second relay UE, and may also set the threshold of the signal measurement result, and so on, which is not described herein again. The threshold value of the measurement result may be the first threshold value or the first threshold value plus an offset value. Or, 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. Or the measurement result of the second relay UE is greater than the measurement result of the first relay UE plus an offset value.

Next, in step 308, the remote UE selects the second relay UE and establishes a direct link with the second relay UE if it is determined that the second relay UE satisfies the condition.

Specifically, in step 308, the remote UE establishes a second direct link with the selected second relay UE. As in step 302, after the remote UE discovers and selects the second relay UE through the Direct discovery procedure, it sends a Direct Communication Request message (Direct Communication Request) for establishing a Direct link to the second relay UE to trigger mutual authentication, and after completing a mutual authentication procedure and successfully establishing a security association, the second relay UE sends a Direct Communication Accept message (Direct Communication Accept) for indicating that the Direct link is successfully established to the remote UE, and the remote UE and the second relay UE complete the establishment of the Direct link, so that the remote UE completes the reselection of the relay UE.

According to the method for reselecting a relay UE in one embodiment of the present application shown in fig. 3, after the remote UE establishes the direct link with the relay UE, the direct discovery procedure is stopped, and when the remote UE measures that the measurement result of the signal from the first relay UE received through the first direct link is smaller than the first threshold, the direct discovery procedure is restarted and the relay UE is reselected, so that the waste of the power consumption of the UE can be reduced.

Although the direct discovery procedure is performed in fig. 3 in the case where it is determined that the measurement result of the signal received through the first direct link is less than the first threshold, it will be understood by those skilled in the art that the direct discovery procedure may also be performed in the case where other conditions are satisfied.

For example, in case the measurement result of the signal received through the first direct link is smaller than a second threshold, where the second threshold is larger than the first threshold, a direct discovery procedure is performed, and/or other relay UEs are measured. In other words, if the communication quality between the remote UE and the relay UE is continuously deteriorating, the direct discovery procedure may be restarted earlier and/or other relay UEs may be measured in such a way as to complete the relay UE reselection more quickly.

Also, although the measurement of the signal received via the first direct link is compared to the second threshold in the above steps, those skilled in the art will appreciate that such a comparison may also be made between a value determined based on the measurement of the signal and the second threshold. For example, the measurement of the signal plus a power value is compared to a second threshold. The power value may be indicated to the remote UE by the first relay UE.

For example, the measured received power of the reference signal associated with the psch may be compared with a second threshold, or a value determined by the received power of the reference signal, for example, a result obtained through a mathematical calculation of correlation may be compared with the second threshold.

In case the measurement result of the signal from the first relay UE received through the first direct link is smaller than the second threshold and thus the direct discovery procedure is restarted and/or other relay UEs are measured, the remote UE continues to measure the signal from the first relay UE received through the first direct link, and in case the measurement result is smaller than the first threshold, the relay UE reselects.

In this example, the second threshold may also be preconfigured or network device configured. In one example, the second threshold may be a sum of the first threshold and minHyst, where minHyst represents a hysteresis parameter.

In addition, those skilled in the art will appreciate that in this example, 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.

Compared with the embodiment shown in fig. 3, according to the method for reselecting the relay UE in the example of the present application, the direct discovery process of the remote UE to the relay UE can be started earlier, and the signal quality of the relay UE is measured, so that the relay UE can be reselected more quickly when the condition for reselecting the relay UE is satisfied.

Fig. 4 is a flowchart of a method for reselecting a relay UE according to another embodiment of the present application. Unlike the embodiment shown in fig. 3, in the embodiment shown in fig. 4, the remote UE stops the direct discovery process earlier, so that the power consumption of the UE can be saved more.

As shown in fig. 4, the remote UE discovers and selects the first relay UE through the Direct discovery procedure in step 401, and the remote UE transmits a Direct Communication Request message (Direct Communication Request) to the first relay UE for requesting establishment of a Direct link with the first relay UE in step 402. The process of step 401 and step 402 can refer to step 301 in fig. 3, which is not described herein again.

After the remote UE sends the Direct Communication Request message (Direct Communication Request), the remote UE stops the Direct discovery procedure in step 403. It will also be understood by those skilled in the art that the remote UE may stop the direct discovery procedure at the same time as sending the direct communication request message, and the embodiment of the present application is not limited thereto.

Likewise, the remote UE may stop receiving the broadcast message for Direct Discovery from the Relay UE (UE-to-Network Relay Discovery notification message), or stop sending the Request message for Direct Discovery (UE-to-Network Relay Discovery message), or stop receiving the Response to the Request message from the Relay UE (UE-to-Network Relay Discovery message), or may be represented by sending a related indication message, for example, a Request message indicating to Close the proximity service Direct Discovery (ProSe Direct Discovery Close Request), which may refer to the foregoing step 303 for details, and is not described herein again.

If the remote UE and the first relay UE successfully establish the first Direct link, the first relay UE sends a Direct Communication Accept message (Direct Communication Accept) to the remote UE, and at this time, the determination in step 404 is yes. According to the method of an embodiment of the application, step 405 follows.

In step 405, the remote UE receives signals from the relay UE over the first direct link and measures the signals to obtain measurement results in order to trigger the remote UE to perform relay UE reselection.

In step 406, it is determined whether the measurement of the signal in step 405 above is less than a first threshold. If the measurement result of the signal is greater than or equal to the first threshold, indicating that the current relay UE is still suitable, the remote UE continues to perform measurement of the signal of the first relay UE.

If it is determined in step 406 that the measurement result of the signal is smaller than the first threshold, step 407 is executed, and according to the method for reselecting a relay UE in the embodiment of the present application, the remote UE restarts the direct discovery procedure so as to perform the reselection of the relay UE.

In step 407, the remote UE restarts direct discovery.

In step 408, the remote UE rediscover and selects a second relay UE through a direct discovery procedure.

In step 409, the remote UE selects the second relay UE and establishes a direct link with the second relay UE if it is determined that the second relay UE satisfies the condition.

The steps 405 and 409 are the same as the steps 304 and 308 in the embodiment of fig. 3, and reference may be made to the description of the steps 304 and 308, which is not repeated herein.

In the embodiment shown in fig. 4, if the determination in step 404 is no, which indicates that the first relay UE has sent a Direct Communication Reject message (Direct Communication Reject) to the remote UE, and the remote UE has not successfully established the first Direct link with the first relay UE, the method flow goes to step 407, where the remote UE restarts Direct discovery to discover other suitable relay UEs.

Likewise, in the process of discovering and selecting other relay UEs, the method of steps 401 and 409 are still performed, and will not be described herein again.

According to the method for reselecting the relay UE in the embodiment of the present application shown in fig. 4, before the remote UE establishes the direct link with the relay UE, the direct discovery procedure is stopped, and compared with the embodiment shown in fig. 3, the waste of the UE power consumption can be further reduced.

Further, according to another example of the present application, on the basis of the embodiment of the method for reselecting a relay UE shown in fig. 4, the direct discovery procedure may be stopped earlier, so as to further save power consumption of the remote UE.

According to another example of the present application, the difference from the embodiment shown in fig. 4 is that the direct discovery procedure is stopped when the remote UE discovers a relay UE satisfying the condition through the direct discovery procedure. The condition may be that the signal quality from the relay UE is good, for example, when the remote UE discovers the relay UE through the direct discovery procedure and measures that a measurement result of a reference signal of a channel carrying the discovery message from the relay UE is greater than a third threshold, the direct discovery procedure is stopped.

It will be understood by those skilled in the art that the measurement result 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 preconfigured or configured by a network device, and may be greater than or equal to the first threshold or the second threshold, which is not specifically limited in the embodiment of the present application.

In this case, power consumption of the remote UE can be further saved compared to the embodiment shown in fig. 4.

Also, according to another example of the present application, the direct discovery procedure is not stopped immediately after the remote UE establishes the direct link with the relay UE. However, when the signal quality 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 procedure is stopped.

Those skilled in the art will appreciate that the signal referred to herein may be the reference signal associated with the Physical Sidelink Discovery Channel (PSDCH) described above, or may be the reference signal associated with the physical sidelink shared channel (psch), or the Physical Sidelink Control Channel (PSCCH). The measurement result of the signal may be a received power of the signal, or at least one of a received quality of the signal, a strength of the signal.

It should be noted that, in steps 307 and 308 of fig. 3 and steps 408 and 409 of fig. 4, only the process of discovering and selecting a second relay UE by the remote UE to establish the second direct link is shown, but those skilled in the art can understand that the foregoing relay UE reselection method according to the present application as shown in fig. 3 or fig. 4 can also be performed in the process of discovering and selecting a second relay UE by the remote UE to establish the second direct link.

As described in detail with reference to fig. 3 and 4, the relay UE reselection method according to the present application may be implemented by stopping the direct discovery process at different times, so as to achieve the purpose of saving power consumption of the UE.

Furthermore, according to the method for reselecting the relay UE in the embodiment of the present application, the power consumption of the UE may be further saved in other manners.

In one example, the remote UE may select whether to perform a direct discovery procedure or measure the signal quality of the relay UE according to its own status.

For example, in the case that 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, the remote UE may perform a direct discovery procedure or perform measurement on a signal of the relay UE so as to perform reselection of the relay UE when the relay UE is no longer appropriate.

And when the remote UE is in the RRC-IDLE state or the RRC-INACTIVE state, data transmission between the remote UE and the relay UE is not required, and at this time, the remote UE may choose not to perform the direct discovery procedure or measure the signal of the relay UE.

In order to maintain the direct link between the remote UE and the relay UE, a direct link keep alive (keepalive) procedure is performed between the remote UE and the relay UE when a request for checking availability (availability) of the direct link is received or when the keep alive timer T4102 expires. When the keep-alive message (Direct Communication keep alive) or the keep-alive response message (Direct Communication keep alive ACK) from the relay UE is not received, the remote UE restarts the Direct discovery procedure and performs the relay UE reselection.

According to the method for reselecting the relay UE in the above example of the application, when the remote UE is in the state of RRC-IDLE or RRC-INACTIVE, the power consumption of the UE can be further saved.

According to yet another example of the present application, the remote UE may measure a signal from a relay UE (e.g., a first relay UE, or a second relay UE) and adjust a measurement period according to the measurement result of the signal. Specifically, the measurement result of the signal from the relay UE shows that the better the communication quality between the remote UE and the relay UE (e.g., the higher the signal strength, the higher the reception power, the better the reception quality, etc.), the longer the above-described measurement period. In this way, the power consumption of the UE can be further reduced.

For example, when the measurement result of the signal from the relay UE measured by the remote UE is equal to or greater than the fourth threshold value, the measurement of the signal is performed at the first cycle. And under the condition that the measurement result is smaller than the fourth threshold value, measuring the signal at the second period. Wherein the second period is less than the first period.

In one example, the fourth threshold may be preconfigured or configured by the network device, and may be equal to the first threshold or the second threshold in the above embodiments, or any value, and so on.

Those skilled in the art will appreciate that when the signal quality between the remote UE and the relay UE is good, the measurement of the signal is performed at a longer period, which can further save the power consumption of the remote UE.

Similarly, for the remote UE in different states, the purpose of saving power consumption can be achieved by the change of the signal measurement period.

For example, in the case where the remote UE is in the RRC-CONNECTED state, the signal from the relay UE is measured in the third period; the signal from the relay UE is measured with a fourth period with the remote UE in an RRC-IDLE or RRC-INACTIVE state, wherein the fourth period is greater than the third period.

Those skilled in the art can understand that the first period, the second period, the third period, and the fourth period may be preconfigured or configured through a network device, and the length of the period may be adjusted according to actual needs, which is not specifically limited in the embodiments of the present application.

Further, those skilled in the art can understand that the two examples of adjusting the signal measurement period according to the present application can also be applied in the remote UE separately, so as to achieve the technical effect of saving the power consumption of the remote UE.

On the basis of the embodiments of fig. 3 and fig. 4, in combination with the above examples, such as performing a direct discovery procedure based on the state of the remote UE or adjusting the measurement period based on the result of the signal measurement, various combinations may be derived, but those skilled in the art will understand that, in a case of no conflict, each embodiment in different combinations constitutes the method for reselecting the relay UE of the present application.

In sidelink communications, the power at which a UE transmits psch/PSCCH between two UEs in unicast communication may be determined by the channel condition of the sidelink, e.g., based on the path loss between the two UEs. For example, the larger the path loss, the larger the transmission power, and the smaller the path loss, the smaller the transmission power. Since the transmission power of the signal is determined according to the channel condition of the sidelink, the reception power of the signal does 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 PC5 RRC connection between the remote UE and the first relay UE is also considered to be established. The power of the PSCCH/PSCCH (including the PSCCH reference signal/PSCCH reference signal) transmitted by the first relay UE to the remote UE may be determined based on the channel conditions of the sidelink. For example, the channel condition may include a path loss between the first relay UE and the remote UE. In this case, the remote UE may not necessarily determine the channel condition with the first relay UE according to the received power of the reference signal of the psch/PSCCH. Therefore, the remote UE judges whether to trigger the relay UE to reselect and/or measure other relay UEs and/or perform a discovery process according to the received power, and the process is not accurate enough.

In order to enable the remote UE to perform the relay UE reselection and/or measure other relay UEs and/or perform the discovery procedure according to the measurement result which more accurately reflects the channel condition, the following method may be adopted.

The remote UE determines a first received power of a signal transmitted by the first relay UE. The signal transmitted by the first relay UE may include a reference signal of the PSCCH and/or PSCCH. The power of the first relay UE for transmitting the signal is a first transmission power, and the first transmission power is the transmission power of the signal determined by the first relay UE in consideration of a side-chain channel condition between the remote UE and the first relay UE. The first transmit power is determined based on a sidelink channel condition between the remote UE and the first relay UE. The side-chain channel condition includes path loss. Wherein the remote UE establishes a sidelink 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 transmits first power indication information to the remote UE for indicating the first power. The first power may be a transmission power headroom of a signal of the first relay UE. The first relay UE may determine the first power based on a sidelink channel condition between the remote UE and the first relay UE. The first power is equal to the second transmit power minus the first transmit power. Wherein the second transmission power is a transmission power of the signal when the first relay UE does not consider a side-chain channel condition between the remote UE and the first relay UE. That is, the second transmit power is independent of a sidelink channel condition between the remote UE and the first relay UE. For example, the second transmission power is determined according to the downlink path loss and/or the maximum transmission power of the first relay UE. Or, the second transmission power is the power at which the first relay UE transmits the discovery message. The power at which the discovery message is transmitted may be understood as the power at which the reference signal of the channel carrying the discovery message is transmitted. The channel carrying the discovery message may be the psch or the PSDCH.

And the remote UE determines whether to trigger the reselection of the relay UE and/or measure other relay UEs and/or perform a discovery process according to the first receiving power and the first power. The remote UE may perform a relay UE reselection based on 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 reselect and/or measure other relay UEs and/or perform a discovery procedure.

Another method is that after the remote UE establishes a sidelink 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 signal sent by the first relay UE to the remote UE for remote UE measurement does not consider the sidelink channel condition between the remote UE and the first relay UE. The signal for remote UE measurement may be a reference signal of a channel carrying the discovery message. The channel carrying the discovery message may be the psch or the PSDCH.

It is understood that the UE includes corresponding hardware structures and/or software modules for performing the respective functions in order to implement the above-mentioned functions. Those of skill in the art would readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

In the embodiment of the present application, the UE may be divided into functional modules according to the above method example, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.

In the embodiments of the present application, the above embodiments may be referred to and referred to by each other, and the same or similar steps and terms are not repeated.

Referring now to fig. 5, shown is a block diagram of a user equipment 500 in accordance with one embodiment of the present application. User device 500 may include one or more processors 502, system control logic 508 coupled to at least one of processors 502, system memory 504 coupled to system control logic 508, non-volatile memory (NVM)506 coupled to system control logic 508, and network interface 510 coupled to system control logic 508.

Processor 502 may include one or more single-core or multi-core processors. The processor 502 may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, baseband processors, etc.). In embodiments herein, the processor 502 may be configured to perform one or more embodiments in accordance with the various embodiments shown in fig. 2-4.

In some embodiments, system control logic 508 may include any suitable interface controllers 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.

In some embodiments, 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 in some embodiments, such as suitable Dynamic Random Access Memory (DRAM).

NVM/memory 506 may include one or more tangible, non-transitory computer-readable media for storing data and/or instructions. In some embodiments, NVM/memory 506 may include any suitable non-volatile memory such as flash memory and/or any suitable non-volatile storage device, such as at least one of an HDD (Hard Disk Drive), CD (Compact Disc) Drive, DVD (Digital Versatile Disc) Drive.

NVM/memory 506 may comprise a portion of a storage resource installed on a device of device 500 or it may be accessible by, but not necessarily a part of, the device. For example, NVM/storage 506 may be accessed over a network via network interface 510.

In particular, system memory 504 and NVM/storage 506 may each include: a temporary copy and a permanent copy of instructions 520. The instructions 520 may include: instructions that when executed by at least one of the processors 502 cause the apparatus 500 to perform the method as shown in fig. 3-4. In some embodiments, the instructions 520, hardware, firmware, and/or software components thereof may additionally/alternatively be located in the system control logic 508, the network interface 510, and/or the processor 502.

In one embodiment, at least one of the processors 502 may be packaged together with logic for one or more controllers of 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 system control logic 508 to form a system on a chip (SoC).

The method embodiments of the present application may be implemented in software, magnetic, firmware, etc.

Program code may be applied to input instructions to perform the functions described herein and generate output information. The output information may be applied to one or more output devices in a known manner. For purposes of this application, a processing system includes any system having a processor such as, for example, a Digital Signal Processor (DSP), a microcontroller, an Application Specific Integrated Circuit (ASIC), or a microprocessor.

The program code may be implemented in a high level procedural or object oriented programming language to communicate with a processing system. The program code can also be implemented in assembly or machine language, if desired. Indeed, the mechanisms described herein are not limited in scope to any particular programming language. In any case, the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented by representative instructions stored on a computer-readable storage medium, which represent various logic in a processor, which when read by a machine causes the machine to fabricate logic to perform the techniques described herein. These representations, known as "IP cores" may be stored on a tangible computer-readable storage medium and provided to a number of customers or manufacturing facilities to load into the manufacturing machines that actually make the logic or processor.

While the description of the present application will be described in conjunction with the preferred embodiments, it is not intended that the features of the present application be limited to this embodiment. Rather, the invention has been described in connection with embodiments for the purpose of covering alternatives and modifications as may be extended based on the claims of the present application. In the following description, numerous specific details are included to provide a thorough understanding of the present application. The present application may be practiced without these particulars. Moreover, some of the specific details have been omitted from the description in order to avoid obscuring or obscuring the focus of the present application. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Further, various operations will be described as multiple discrete operations, in a manner that is most helpful in understanding the illustrative embodiments; however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.

As used herein, the term "module" or "unit" may refer to, be, or include: an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and/or memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

In the drawings, some features of the structures or methods are shown in a particular arrangement and/or order. However, it is to be understood that such specific arrangement and/or ordering may not be required. In some embodiments, these features may be arranged in a manner and/or order different from that shown in the illustrative figures. Additionally, the inclusion of structural or methodical features in a particular figure is not meant to imply that such features are required in all embodiments, and in some embodiments, these features may not be included or may be combined with other features.

Embodiments of the mechanisms disclosed herein may be implemented in hardware, software, firmware, or a combination of these implementations. Embodiments of the application may be implemented as computer programs or program code executing on programmable systems comprising multiple processors, a storage system (including volatile and non-volatile memory and/or storage elements), multiple input devices, and multiple output devices.

The program code may be implemented in a high level procedural or object oriented programming language to communicate with a processing system. The program code can also be implemented in assembly or machine language, if desired. Indeed, the mechanisms described in this application are not limited in scope to any particular programming language. In any case, the language may be a compiled or interpreted language.

In some cases, the disclosed embodiments may be implemented in hardware, firmware, software, or any combination thereof. In some cases, one or more aspects of at least some embodiments may be implemented by representative instructions stored on a computer-readable storage medium, which represent various logic in a processor, which when read by a machine causes the machine to fabricate logic to perform the techniques described herein. These representations, known as "IP cores" may be stored on a tangible computer-readable storage medium and provided to a number of customers or manufacturing facilities to load into the manufacturing machines that actually make the logic or processor.

Such computer-readable storage media may include, but are not limited to, non-transitory tangible arrangements of articles of manufacture or formation by machines or devices that include storage media such as: hard disk any other type of disk including floppy disks, optical disks, compact disk read-only memories (CD-ROMs), compact disk rewritables (CD-RWs), and magneto-optical disks; semiconductor devices such as Read Only Memory (ROM), Random Access Memory (RAM) such as Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM), Erasable Programmable Read Only Memory (EPROM), flash memory, Electrically Erasable Programmable Read Only Memory (EEPROM); phase Change Memory (PCM); magnetic or optical cards; or any other type of media suitable for storing electronic instructions.

Thus, embodiments of the present application also include non-transitory computer-readable storage media that contain instructions or that contain design data, such as Hardware Description Language (HDL), that define the structures, circuits, devices, processors, and/or system features described herein.

Claims

1. A method for reselection of a relay UE (relay UE), the method being used for a remote UE (remote UE), and comprising:

discovering a first relay UE and selecting to establish a first direct link with the first relay UE, the first direct link for the remote UE to communicate directly with the first relay UE; and

measuring a signal from the first relay UE received through the first direct link, and obtaining a measurement result of the signal;

and when the measurement result is smaller than a first threshold value, performing the relay UE reselection.

2. The method of claim 1, further comprising:

stopping sending and/or stopping receiving discovery messages after completing establishing the first direct link with the first relay UE, or

3. The method of claim 1 or 2, wherein the signal comprises: reference signals associated with a Physical Sidelink Shared Channel (PSSCH) and/or a Physical Sidelink Control Channel (PSCCH).

4. The method of claim 3, wherein the measurement results include at least one of the following parameters: received power, received quality, strength of the signal.

5. The method of claim 2, wherein in the case that the measurement result is less than a first threshold, performing a relay UE reselection comprises,

transmitting and/or receiving the discovery message if the measurement result is less than the first threshold.

6. The method of claim 2, wherein in the case that the measurement result is less than a first threshold, performing a relay UE reselection comprises,

and if the measurement result is smaller than a second threshold value, the discovery message is sent and/or received, and if the measurement result is smaller than the first threshold value, the relay UE reselection is carried out, wherein the second threshold value is larger than the first threshold value.

7. The method of claim 2, further comprising:

transmitting and/or receiving the discovery message upon receiving a reject message from the first relay UE, wherein the reject message is for rejecting a request sent by the remote UE to the first relay UE for establishing the first direct link.

8. The method of claim 2, further comprising

And measuring a discovery message associated reference signal from the first relay UE, and stopping transmitting and/or stopping receiving the discovery message when the measurement result of the discovery message associated reference signal is greater than or equal to a third threshold value.

9. The method of claim 8, wherein the measurement of the reference signal associated with the discovery message comprises: at least one of a received power, a received quality, and a strength of a reference signal associated with the discovery message.

10. The method of claims 1-9, further comprising

Measuring a signal from the first relay UE received through the first direct link at a first cycle if the measurement result is greater than or equal to a fourth threshold; and

measuring a signal from the first relay UE received through the first direct link at a second period if the measurement result is less than a fourth threshold,

wherein the second period is less than the first period.

11. The method of claims 1-9, further comprising

Measuring signals from the first relay UE received over the first direct link with a third period with the remote UE in an RRC-CONNECTED state; and

measuring signals from the first relay UE received over the first direct link for a fourth period with the remote UE in an RRC-IDLE or RRC-INACTIVE state,

wherein the fourth period is greater than the third period.

12. The method of claims 2-11, wherein the discovery message comprises at least one of:

a broadcast message (notification) for the relay UE to discover the remote UE, a request message (Solicitation) for the remote UE to discover the relay UE, and a Response message (Response) for the relay UE to the request.

13. A machine-readable medium having stored thereon instructions which, when executed on the machine, cause the machine to perform the method of any one of claims 1 to 12.

14. An apparatus, comprising:

a processor;

a memory having instructions stored thereon that, when executed by the processor, cause the user equipment to perform the method of any of claims 1-12.