WO2022073714A1

WO2022073714A1 - Ue discovery procedures

Info

Publication number: WO2022073714A1
Application number: PCT/EP2021/074942
Authority: WO
Inventors: Min Wang; Zhang FU
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-10-08
Filing date: 2021-09-10
Publication date: 2022-04-14
Also published as: EP4226733A1

Abstract

A method (600) performed by a first UE. The method includes the first UE obtaining a first discontinuous reception (DRX) configuration associated with a UE discovery procedure for use in discovering at least a second UE. The method also includes the first UE initiating the UE discovery procedure. The method further includes the first UE applying the first DRX configuration during the period when the discovery procedure is running.

Description

UE DISCOVERY PROCEDURES

TECHNICAL FIELD

[001] Disclosed are embodiments related to user equipment (UE) discovery procedures.

BACKGROUND

[002] FIG. 1 shows the high level view of the non-roaming 5G System (5GS) architecture for vehicle-to-everything (V2X) communication over the PC5 and Uu reference points. Two user equipments (UEs) can communicate with each other either directly via a PC5 sidelink (SL) interface or they can communicate with each other through the Uu interface and via an application server (AS). A UE is any device (e.g., smartphone, computer, tablet, sensor, appliance, vehicle, etc.) capable of wireless communication with another device (e.g., another UE or an access point, such as a base station).

[003] 3GPP TR 23.752 V0.3.0 (“TR 23.752”) solution #6 describes the basic idea of the Layer-3 UE-to-Network relay (a.k.a., “relay UE”). As described in TR 23.752, the ProSe 5G relay UE entity provides the functionality to support connectivity to the network for remote UEs. The relay UE entity can be used for both public safety services and commercial services (e.g. interactive service).

[004] 1. Background of the SL interface

[005] The first standardization effort in 3 GPP for the SL interface dates back to release 12 (Rel-12), which targeted public safety use cases. The SL interface is specified to allow a UE to send data packets directly to a peer UE (i.e., without sending the data packets to the NW). Additionally, a UE-to-NW relay solution is also defined such that a first UE (the “remote UE”) can reach the NW via another UE (the “relay UE”) even when the remote UE is out of the network’s cell coverage. The remote UE communicates with the relay UE using the SL interface and the relay UE has uplink and downlink connection with the network.

[006] Since Rel-12, a number of enhancements have been introduced with the objective to enlarge the use cases that could benefit from the device-to-device technology (e.g., PC5 SL interface). In particular, in LTE Rel-14 and Rel-15, the extensions for the D2D work consist of support of vehicle-to-everything (V2X) communications, including any combination of direct communications between vehicles, pedestrians and the infrastructure. [007] While LTE V2X mainly aims at traffic safety services, 3GPP’s New Radio (NR) V2X has a much broader scope including not only basic safety services but also targeting non-safety applications, such as sensor/data sharing between vehicles with the objective to strengthen the perception of the surrounding environment. Hence a new set of applications, such as vehicle platooning, cooperative maneuver between vehicles, remote/autonomous driving may enjoy such enhanced sidelink framework.

[008] For NR sidelink (SL), unicast at access stratum is supported for services requiring high reliability. Between the a UE pair (e.g., a remote UE utilizing a relay service provided by a relay UE), there can be multiple SL unicast links and each link can support multiple SL QoS flows/radio bearers as illustrated in Figure 1 (see 3GPP TS 23.287 V16.3.0). At access stratum, each link can be identified by the source and destination Layer 2 identity (L2 ID). For instance, the PC5 unicast link 1 in FIG. 2 can be identified by the pair of L2 ID1 (i.e. corresponding to application ID1) and L2 ID2 (i.e. corresponding to application ID2).

[009] 2. Proximity Services (ProSe)

[0010] 2.1 ProSe Direct Discovery Models

[0011] 3GPP TS 23.303 V16.0.0 defines ProSe Direct Discovery Models in section 5.3.1.2. The following models for ProSe Direct Discovery exist: 1) Model A ("I am here") and 2) Model B (“who is there” or “are you there”).

[0012] 2.1.1 Model A Discovery

[0013] This model defines two roles for the ProSe-enabled UEs that are participating in ProSe Direct Discovery: 1) Announcing UE — the UE announces certain information (e.g,., an application identity (App ID)) that could be used by UEs in proximity that have permission to discover; and 2) Monitoring UE - the UE that monitors certain information of interest in proximity of announcing UEs. In this model the announcing UE broadcasts discovery requests at pre-defined discovery intervals and the monitoring UEs that are interested in these messages read them and process them. This model is equivalent to "I am here" since the announcing UE would broadcast information about itself (e.g. its ProSe Application Code in the discovery message). Both open and restricted discovery types are supported by Model A.

[0014] 2.1.1 Model B Discovery ("who is there?" / "are you there?") [0015] This model, when restricted discovery type is used, defines two roles for the ProSe-enabled UEs that are participating in ProSe Direct Discovery: i) Discoverer UE - - the UE transmits a request containing certain information about what it is interested to discover; and 2) Discoveree UE - - the UE that receives the request message can respond with some information related to the discoverer's request. This model is equivalent to "who is there/are you there" because the discoverer UE sends information about other UEs that the discoverer would like to receive responses from (e.g. the information can be about a ProSe Application Identity corresponding to a group and the members of the group can respond). The Public Safety discovery is considered restricted. The monitoring UE/discoverer UE needs to have authorization (such as through pre-provisioned parameters) to perform discovery of the appropriate service(s).

[0016] 2.2 Direct communication via ProSe UE-to-Network Relay

[0017] 3GPP TS 23.303 defines the “Direct communication via ProSe UE-to- Network Relay” in section 5.4.4. With this procedure, a ProSe UE-to-Network Relay capable UE may attach to the network (if it is not already connected) and connect to a PDN connection enabling the necessary relay traffic. FIG. 3 shows the call flow of the corresponding procedure. The Remote UE performs discovery of a ProSe UE-to-Network Relay using Model A or Model B discovery. The details of this procedure are described in section 5.3.7 of 3GPP TS 23.303.

[0018] TS 23.303 defines the Identifiers for ProSe UE-to-Network Relay discovery and selection in section 4.6.4.3.

[0019] The following parameters are used in the UE-to-Network Relay Discovery Announcement message (Model A):

[0020] The following parameters are used in the UE-to-Network Relay Discovery Solicitation message (Model B):

[0021] The following parameters are used in the UE-to-Network Relay Discovery Response message (Model B):

SUMMARY

[0022] At the last RAN2 meeting (i.e., RAN2#111-e) it was agreed that the model A and model B discovery standardized in LTE Rel-12/Rel-13 can be re-used for the Rel-17 sidelink UE-to-NW and UE-to-UE relay. For both discovery models, RAN2 has decided to not introduce a specific discovery physical channel, in other words, discovery messages will be transmitted using a same channel as for data transmission, SL communication channel, i.e., Physical Sidelink Shared Channel (PSSCH).

[0023] UE energy savings is one important performance indicator. There is no energy saving feature defined for SideLink in 3GPP Rel-16. In the 3GPP Rel-17 work item (WI) on New Radio (NR) sidelink enhancement (see RP-193231, New WID on NR sidelink enhancement), the following objective on UE Sidelink energy saving has been agreed and will be studied in 3GPP Rel-17 time frame: Sidelink Discontinuous Reception (DRX) for broadcast, groupcast, and unicast - - 1) define on- and off-durations in sidelink and specify the corresponding UE procedure; 2) specify mechanism aiming to align sidelink DRX wakeup time among the UEs communicating with each other; and specify mechanism aiming to align sidelink DRX wake-up time with Uu DRX wake-up time in an in-coverage UE.

[0024] From the above study objectives, DRX mechanisms for Sidelink will be designed and specified in 3GPP Rel-17.

[0025] Certain challenges, however, presently exist. For example, as soon as a UE has initiated a discovery procedure, the procedure will be typically repeated periodically until the procedure is concluded, i.e., either the UE has been successfully discovered by intended UEs, or the UE has successfully discovered another UE or concludes that there are no intended UEs in the proximity. Accordingly, during the discovery period (i.e., when the discovery procedure is running - - that is, the period between the time at which the discovery procedure is initiated and the time at which the discovery procedure has completed), the UE may need to be always “on” (i.e., listening for messages) in order for the UE to not miss any discovery messages transmitted by other UEs in the UE’s proximity. As a consequence of the UE listening for discovery messages during the entire discovery period, the UE will consume power during the entire period. Therefore, it is necessary to design a DRX mechanism for discovery procedures so as to reduce a UE’s power consumption, thereby increasing, for example, the UE’s battery life. [0026] Accordingly, in one aspect there is provided a method performed by a first UE, where the method includes the first UE obtaining a first discontinuous reception (DRX) configuration associated with a UE discovery procedure for use in discovering at least a second UE. The method also includes the first UE initiating the UE discovery procedure. The method further includes the first UE applying the first DRX configuration during the period when the discovery procedure is running.

[0027] In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry of a UE causes the UE to perform the above described method. In one embodiment, there is provided a carrier containing the computer program wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium. In another aspect there is provided a UE that is configured to perform the above described method. The UE may include memory and processing circuitry coupled to the memory.

[0028] An advantage of the embodiments disclosed herein is that they reduce UE power consumption, and, thereby increase UE battery life. Additionally, in certain embodiments, latency and signaling overhead are improved. This will be particular important when the requirements on public safety and V2X use cases need to be met.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0030] FIG. 1 shows the high level view of the non-roaming 5G System (5GS) architecture for vehicle-to-everything (V2X) communication.

[0031] FIG. 2 illustrates two UEs having two PC5 unicast links.

[0032] FIG. 3 illustrates a call flow.

[0033] FIG. 4. illustrates a system according to an embodiment.

[0034] FIG. 5. is a message flow diagram illustrating a message flow according to an embodiment.

[0035] FIG. 6. is a flowchart illustrating a process according to some embodiments.

[0036] FIG. 7 is a block diagram of a UE according to some embodiments.

[0037] FIG. 8 is a block diagram of a network node according to some embodiments. DETAILED DESCRIPTION

[0038] FIG. 4 illustrates a system 400 according to an embodiment. In this example, system 400 is a 5G system (5GS). System 400 includes a first UE 401 and a second UE 402, which may function as a UE-to-Network (UE-NW) relay or a UE-to-UE (UE-UE) relay (e.g., a UE-UE relay as defined in 4GPP TR 23.752). System 400 also includes a radio access network (RAN) access point AP 404 (a.k.a., “base station 404”), which in this example is a Next Generation (NG) RAN (NG-RAN) base station (denoted “gNB”), a core network 406, which in this example is a 5G core network (5GC). As shown in FIG. 4, 5GC includes an Access and Mobility Management Function (AMF) 408, a Session Management Function (SMF) 410, a User Plane Function (UPF) 412, a Policy Control Function (PCF) 414, an Application Function (AF) 416, and User Data Management (UDM) function 418.

[0039] 3GPP TR 23.752-050 describes a “ProSe direct discovery procedure.” As described in the TR, the ProSe direct discovery procedure is used for a UE (e.g., UE 401) to discover or be discovered by other UE(s) (e.g., UE 402) in proximity over the PC5 interface. The UE 401 can discover other UE(s) with interested application(s) and/or interested group(s) using the ProSe direct discovery procedure. According to 3GPP TS 22.261 V18.0.0, the 5G system shall efficiently support service discovery mechanisms where UEs can discover: the status of other UEs (e.g., sound on/off); capabilities of other UEs (e.g., the other UE is a relay UE); and/or services provided by other UEs (e.g., the UE is a color printer). Hence, UE 401 can use a discovery procedure (e.g., the Model A or Model B procedures described above) to discover UE 402.

[0040] In certain scenarios, however, it is advantageous that during the discovery procedure UE 401 is not always listening for message from other UEs. In this way, UE 401 can lower its power consumption and, thereby, increase its battery life.

[0041] Accordingly, this disclosure describes system and methods wherein one or multiple DRX configurations for discovery are provided to the UE 401 to apply for one or more discovery procedures. In case both discovery Model A and B are configured for the UE 401, there may be at least one specific DRX configuration for each model.

[0042] For each discovery model, there may be multiple different discover configurations, where each discovery configuration may have a different setting for at least one of the following discovery parameters: discovery periodicity in time, i.e., how often the UE transmits a discovery message; discovery resource allocation (pool) in time domain; discovery resource allocation (pool) in frequency domain; discovery performance requirement such as discovery probability, i.e., at what probability a discoveree can be discovered by a discover. The UE may choose a discovery configuration based on, for example, the reason for initiating the discovery procedure, and then, after choosing a discovery configuration, the UE selects a suitable DRX configurations depending on the chosen discovery configuration.

[0043] In one embodiment, UE 401 obtains the DRX configuration(s) and the discovery configuration(s) during a registration procedure as shown in FIG. 5. That is, as shown in FIG. 5, UE 401 transmits a registration request message to AMF 408, which then may send to UDM 418 a configuration request message comprising a UE ID that identifies UE 401. The configuration request message may be a Nudm SDM Get message that includes the UE ID as well as a data type indicator indicating the type of data that the AMF is requesting the UDM to provide, which in this example is set to “ProSe subscription data,” and an DRX configuration indicator set to “yes,” which indicates that the AMF is requesting the UDM to provide to the AMF DRX configuration(s) for the UE 401. Alternatively, a new type of message can be defined, for example, a “DRX Config Request” message.

[0044] After receiving the request message transmitted by the AMF, the UDM then uses the UE ID to obtain subscription information linked to the UE ID (e.g., in this case ProSe subscription data), and, based on the subscription information (and information from a PCF, if any), obtains (e.g., generates) one or more DRX configurations for UE 401 and one or more discovery configurations for UE 401, and then UDM 418 transmits to the AMF a response message comprising the DRX and discovery configurationss. After receiving the response message transmitted by UDM 418, AMF 408 transmits to UE 401 a registration response message that comprises the one or more DRX and discovery configurations.

[0045] The DRX configurations for discovery that are provided to UE 401 can be different depending on at least of the following cases: type of services (including UE-to- Network relay service and UE-to-UE relay service); applications; group IDs; discovery model (e.g., A or B). As one example, UE 401 may be provided with two DRX configurations for discovery, where the first configuration is associated with a first service type (e.g., non-emergency) and the second configuration is associated with a second service type (e.g., emergency services). Thus, when UE 401 performs a discovery procedure for an emergency service, UE 401 will apply the second DRX configuration during the discover period for the discovery procedure. That is, in the some embodiments, each discovery procedure may be initiated for a different purpose, such as for a specific service or application. In this case, the UE chooses the DRX configuration depending on what purpose the discovery procedure is being triggered.

[0046] In some embodiments, UE 401 first selects a discovery configuration based on, for example, the purpose for which UE 401 is initiating the discovery procedure, and then, after selecting a discovery configuration, UE 401 obtains at least one DRX configuration corresponding to the selected discovery configuration and applies the obtained DRX configuration(s) while the discovery procedure is running (i.e., the period between the time at which the discovery procedure is initiated and the time at which the discovery procedure has completed). A discovery configuration may comprises: i) information identifying a discovery model (e.g., Model A or Model B); ii) discovery periodicity; iii) discovery resource allocation (pool) in time domain; iv) discovery resource allocation (pool) in frequency domain; v) discovery performance requirement such as discovery probability, i.e., at what probability a discoveree can be discovered.

[0047] In another embodiment, the DRX configurations for discovery and/or the discovery configurations can also be sent from the Core network (CN) to the gNB as part of UE context information that the CN provides to the gNB. The gNB can then generate for UE 401 the DRX configurations for discovery and/or discovery configurations according to the gNB’s own policy or algorithms. In some embodiments, the discovery configurations are pre-loaded in UE 404 (e.g., installed on a SIM card of UE 401).

[0048] In some embodiments, whenever the UE has changed to a different DRX configuration for discovery, the UE may inform the selected DRX configuration to one or more of: the gNB, a the SL group with which the UE is involved, and/or to neighbouring UEs in the proximity. The signalling may be carried by at least one of the below signalling alternatives: RRC signalling (Uu or PC5); MAC CE; or layer one (LI) control signalling (PUCCH, or RACH to the gNB, while SCI to UE).

[0049] In some embodiments, prior to initiating a discovery procedure, the UE checks the information on DRX configuration of its neighbour UEs, or intended UEs, or UE groups. The information may contain one of more of: i) information identifying the discovery model applied by the UE and/or ii) information identifying DRX settings (e.g., on/off durations or the periodicity with which the UE transmits a discovery message) applied by the UE. [0050] In some embodiments, the UE 401 obtains the DRX information for UE 402 by requesting it from UE 402. In some embodiments this is accomplished by UE 401 sending a request message to the gNB 404 and gNB 404 the provides the information directly, or gNB forwards the request message to UE 402. For the latter, UE 402 can provide information to gNB, and gNB forwards the information to UE 401. Based on, for example, UE 402’ s DRX configuration, UE 401 transmits a discovery message during the time when UE 402 is active. Alternatively, if there are multiple UEs in the vicinity of UE 401 in addition to UE 402, then UE 401 selects a time slot to transmit discovery messages when there are at least X% of intended UEs are active during that slot. X can be configured by the gNB, or a controlling UE.

[0051] In embodiments in which UE 401 is a monitoring UE, the UE 401 will check information of DRX configurations of its neighbour UEs, or intended UEs, or UE groups. If there is not enough information found, the UE may ask the other UEs to provide their DRX configurations for discovery, by sending a request message to them. Based on their DRX configuration, the UE decides when the UE should be active for reception of a discovery message.

[0052] In the some embodiments, UE 401 may be configured with a first DRX configuration for both discovery and a second DRX configuration for non-discovery procedures (such as data transmission or reception). During a time period, the UE may have overlapping discovery procedure and non-discovery procedures (e.g., data transmissions or receptions). In this case, the UE may not be able to process both procedures in parallel especially when the UE has single RF chain. The UE is then configured to apply at least one of the below options to determine which DRX configuration should be chosen: 1) chose only discovery specific DRX configuration; or 2) choose the DRX configuration depending on the priority indices associated with discovery and other non-discovery procedures. That is, in some embodiments, there is a priority index associated with each discovery procedure. Other non-discovery procedures may be also associated with different priority indices. The UE can decide which procedure or specific DRX configuration should be chosen depending on priority indices. For discovery, the priority index may be configured considering at least one of: i) Type of the application/traffic/service that has triggered the discovery procedure and associated QoS requirements; ii) Category of the UE that has triggered the discovery procedure; and/or Battery life or remaining power level of the UE that has triggered the discovery procedure. As an example, the UE 401 chooses a discovery specific DRX configuration because the UE has determined that discovery has higher priority than the traffic (e.g., enhanced mobile broadband (eMBB)). As another example, the UE 401 chooses a public safety or V2X specific DRX configuration (i.e., a non-discovery DRX configuration) because the UE has determined that the current public safety or V2X service has higher priority (e.g., because it is associated with a tight latency requirement) than discovery. As yet another example, the UE chooses a discovery specific DRX configuration because the UE has determined that discovery has higher priority than the current public safety or V2X service (e.g., since it is associated with a relaxed latency requirement).

[0053] In some embodiments, in order to reduce power consumption, a specific radio channel quality threshold (e.g., RSRP, RSRQ, RSSI, SINR, SIR etc) for discovery monitoring (e.g., for discovering a relay UE) is configured to the UE 401. This threshold is mainly configured to reduce the power consumption due to UE 401 attempting to discovery a relay UE. The threshold may be set considering UE 401’s remaining battery lifetime. So, for example, when the UE has sufficient remaining battery lifetime (e.g. remaining battery life exceeds a threshold), then the quality threshold can be set to a first value, whereas when the UE has low remaining battery lifetime (e.g., remaining batter life less than the batter life threshold), the quality threshold can be set to a second value that is lower than the first value. The UE 401 only starts to monitor or initiate discovery message when UE 401’s radio signal strength is below the quality threshold.

[0054] In some embodiments, UE 401 only starts to monitor or initiate discovery in case UE has received a specific parameter from one of i) the gNB, ii) a control UE, or iii) a relay UE. That parameter may be carried in an RRC message, a MAC CE, or a LI signaling (such as PUCCH, RACH, PDCCH or SCI).

[0055] In some embodiments, as soon as the UE 401 has concluded a discovery procedure, the UE 401 will not monitor or initiate discovery for a configured time period. That period may be configured by gNB, a control UE or a relay UE. That signaling may be carried in a RRC message, a MAC CE, or a LI signaling (such as PUCCH, RACH, PDCCH or SCI).

[0056] In some embodiments, UE 401 may share a common DRX configuration for both SL communication and discovery procedure. In this common DRX configuration, at least one timer is defined for discovery monitoring or initiating. This timer may be configured according to a discovery parameter (e.g., discovery periodicity). For example, this timer is started/restarted periodically according to the discovery periodicity. After the timer is started/restarted every time, the timer runs for a configured time period, after that the timer is stopped. The UE will be only active for discovery monitoring while the timer is running. When the timer is stopped, the UE will not monitor discovery messages. A new DRX cycle may be also defined for discovery monitoring. This cycle is started when there is a need to for the UE to monitor discovery. The need is determined according to any condition described in any of the previous embodiment (e.g., UE’s radio signal strength is below a threshold, receives a signalling or new data arrival or a periodic timer is running etc).

[0057] FIG. 6 is a flowchart illustrating a process 600, according to an embodiment, that is performed by UE 401. Process 600 may begin in step s602. Step s602 comprises UE 401 obtaining a first DRX configuration associated with a UE discovery procedure for use in discovering at least a second UE (UE 402). Step s604 comprises UE 401 initiating the UE discovery procedure, thereby starting a discovery period. Step s606 comprises UE 401 applying the first DRX configuration during the discovery period.

[0058] In some embodiments, process 600 also includes UE 401 using information included in the DRX configuration to identify at least one period of time during which UE 401 should not attempt to receive any discovery messages.

[0059] In some embodiments, process 600 also includes UE 401 using information included in the first DRX configuration to identify at least one period of time during which UE 401 should listen for discovery messages.

[0060] In some embodiments, process 600 also includes UE 401 using information included in the first DRX configuration to identify at least one period of time during which the UE may transmit a discovery message.

[0061] In some embodiments, process 600 also includes, prior to initiating the discovery procedure: UE 401 selecting a discovery configuration for the discovery procedure, wherein the first DRX configuration is associated with the selected discovery configuration; and after selecting the discovery procedure, UE 401 obtaining the first DRX configuration. In some embodiments, the selected discovery configuration comprises one or more of: discovery periodicity information specifying a discovery periodicity; time domain resource information specifying a resource allocation in a time domain; frequency domain resource information specifying a resource allocation in a frequency domain; or performance information specifying a discovery performance requirement. [0062] In some embodiments, initiating the discovery procedure comprises transmitting a discovery request message.

[0063] In some embodiments, process 600 also includes UE 401 obtaining a second DRX configuration associated with the UE discovery procedure, wherein the first DRX configuration is further associated with a first service type, the second DRX configuration is further associated with a second service type.

[0064] In some embodiments, process 600 also includes, prior to initiating the discovery procedure: UE 401 determining a service type; and after determining the service type, UE 401 selecting the first DRX configuration based on the determined service type, wherein the determined service type matches the service type with which the first DRX configuration is associated.

[0065] In some embodiments, process 600 also includes UE 401 transmitting at least a portion of the first DRX configuration to the second UE.

[0066] In some embodiments, process 600 also includes UE 401 receiving at least a portion of a DRX configuration that will be applied by a neighbour UE in the proximity of UE 401. In some embodiments, the at least a portion of the DRX configuration comprises a parameter (such as a timer can be periodically started/restarted and kept running for a configured time) corresponding to a periodicity with which the neighbour UE transmits a discovery message.

[0067] FIG. 7 is a block diagram of a UE 700 (e.g., UE 401 or UE 402), according to some embodiments. As shown in FIG. 7, UE 700 may comprise: processing circuitry (PC) 702, which may include one or more processors (P) 755 (e.g., one or more general purpose microprocessors and/or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); communication circuitry 748, which is coupled to an antenna arrangement 749 comprising one or more antennas and which comprises a transmitter (Tx) 745 and a receiver (Rx) 747 for enabling UE 700 to transmit data and receive data (e.g., wirelessly transmit/receive data); and a local storage unit (a.k.a., “data storage system”) 708, which may include one or more nonvolatile storage devices and/or one or more volatile storage devices. In embodiments where PC 702 includes a programmable processor, a computer program product (CPP) 741 may be provided. CPP 741 includes a computer readable medium (CRM) 742 storing a computer program (CP) 743 comprising computer readable instructions (CRI) 744. CRM 742 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 744 of computer program 743 is configured such that when executed by PC 702, the CRI causes UE 700 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, UE 700 may be configured to perform steps described herein without the need for code. That is, for example, PC 702 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

[0068] FIG. 8 is a block diagram of an apparatus 800 (a.k.a., “network node 800”), according to some embodiments, for implementing one or more network function (e.g., for implementing AMF 408 or UDM function 418). As shown in FIG. 8, apparatus 800 may comprise: processing circuitry (PC) 802, which may include one or more processors (P) 855 (e.g., a general purpose microprocessor and/or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (i.e., apparatus 800 may be a distributed computing apparatus); at least one network interface 848 comprising a transmitter (Tx) 845 and a receiver (Rx) 847 for enabling apparatus 1300 to transmit data to and receive data from other nodes connected to a network 110 (e.g., an Internet Protocol (IP) network) to which network interface 848 is connected (directly or indirectly) (e.g., network interface 848 may be wirelessly connected to the network 110, in which case network interface 848 is connected to an antenna arrangement); and a storage unit (a.k.a., “data storage system”) 808, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In embodiments where PC 802 includes a programmable processor, a computer program product (CPP) 841 may be provided. CPP 841 includes a computer readable medium (CRM) 842 storing a computer program (CP) 843 comprising computer readable instructions (CRI) 844. CRM 842 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 844 of computer program 843 is configured such that when executed by PC 802, the CRI causes apparatus 800 to perform steps described herein (e.g., steps described herein with reference AMF 408 or UDM 418). In other embodiments, apparatus 800 may be configured to perform steps described herein without the need for code. That is, for example, PC 802 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

[0069] Summary of Various Embodiments

[0070] Al. A method (600) performed by a first user equipment, UE (401), the method comprising: obtaining (s602) a first discontinuous reception (DRX) configuration associated with a UE discovery procedure for use in discovering at least a second UE (402); initiating (s604) the UE discovery procedure; and applying (s606) the first DRX configuration during the period when the discovery procedure is running.

[0071] A2. The method of embodiment Al, further comprising the first UE using information included in the DRX configuration to identify at least one period of time during which the first UE should not attempt to receive any discovery messages.

[0072] A3. The method of embodiment Al or A2, further comprising the first UE using information included in the first DRX configuration to identify at least one period of time during which the first UE should listen for discovery messages.

[0073] A4. The method of any one of embodiments A1-A4, further comprising the first UE using information included in the first DRX configuration to identify at least one period of time during which the UE may transmit (e.g., broadcast) a discovery message (e.g., a discovery request with command=announce or discovery request with command=monitor (see 3GPP TS 23.303).

[0074] A5. The method of any one of embodiments A1-A4, further comprising, prior to initiating the discovery procedure: the first UE selecting a discovery configuration for the discovery procedure, wherein the first DRX configuration is associated with the selected discovery configuration; and after selecting the discovery procedure, the first UE obtaining the first DRX configuration.

[0075] A6. The method of embodiment A5, wherein the selected discovery configuration comprises one or more of: discovery periodicity information specifying a discovery periodicity; time domain resource information specifying a resource allocation in a time domain; frequency domain resource information specifying a resource allocation in a frequency domain; or performance information specifying a discovery performance requirement (e.g., discovery probability, i.e., at what probability a discoveree can be discovered by a discover). [0076] A7. The method of any one of embodiments A1-A6, wherein initiating the discovery procedure comprises transmitting a discovery request message (e.g., broadcasting a discover request message for announcing or transmitting a discovery request message for monitoring).

[0077] A8. The method of any one of embodiments A1-A7, further comprising: obtaining a second DRX configuration associated with the UE discovery procedure, wherein the first DRX configuration is further associated with a first service type, the second DRX configuration is further associated with a second service type.

[0078] A9. The method of embodiment A8, further comprising, prior to initiating the discovery procedure: the first UE determining a service type; and after determining the service type, the first UE selecting the first DRX configuration based on the determined service type, wherein the determined service type matches the service type with which the first DRX configuration is associated.

[0079] A10. The method of an one of embodiments A1-A9, further comprising the first UE transmitting at least a portion of the first DRX configuration to the second UE.

[0080] Al l. The method of any one of embodiments A1-A10, further comprising the first UE receiving at least a portion of a DRX configuration that will be applied by a neighbour UE in the proximity of the first UE.

[0081] A12. The method of embodiment Al l, wherein said at least a portion of the

DRX configuration comprises a parameter (such as a timer can be periodically started/restarted and kept running for a configured time) corresponding to a periodicity with which the neighbour UE transmits a discovery message.

[0082] Bl. A computer program (743) comprising instructions (744) which when executed by processing circuitry (702) of a UE (700) causes the UE (700) to perform the method of any one of embodiments A1-A12.

[0083] B2. A carrier containing the computer program of embodiment Bl, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium (742).

[0084] C 1. A UE (700), the UE (700) being adapted to perform the method of any one of embodiments Al -Al 2. [0085] C2. A UE (700), the UE (700) comprising: processing circuitry (702); and a memory (742), the memory containing instructions (744) executable by the processing circuitry, whereby the UE (700) is operative to perform the method of any one of the embodiments A1-A12.

[0086] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0087] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.

[0088] Abbreviations

[0089] CA Carrier Aggregation

[0090] CBR Channel Busy Ratio

[0091] CQI Channel Quality Indicator

[0092] CSI Channel State Information

[0093] DFN Direct Frame Number

[0094] DL Downlink

[0095] DRX Discontinuous Reception

[0096] FDD Frequency Division Duplex

[0097] GNSS Global Navigation Satellite System

[0098] HARQ Hybrid automatic repeat request

[0099] IE Information Element

[00100] MAC Medium Access Control

[00101] MIB Master Information Block

[00102] NSPS National Security and Public Safety [00103] OoC Out-of-Coverage

[00104] PDCCH Physical Downlink Control Channel

[00105] PDCP Packet Data Convergence Protocol

[00106] PDU Protocol Data Unit

[00107] PHY Physical (layer)

[00108] PL Path Loss

[00109] PMI Precoding Matrix Indicator

[00110] ProSe Proximity Services

[00111] PSCCH Physical Sidelink Control Channel

[00112] PSSCH Physical Sidelink Shared Channel

[00113] RL Relay

[00114] RLC Radio link control

[00115] RM Remote

[00116] RI Rank Indicator

[00117] RRC Radio Resource Control

[00118] RSRP Reference Signal Received Power

[00119] RSSI Received Signal Strength Indicator

[00120] RX Receive, receiver

[00121] SFN System Frame Number

[00122] SIB System Information Block

[00123] SINR Signal to interference noise ration

[00124] SL Sidelink

[00125] SLRB Sidelink Radio Bearer

[00126] SLSS Sidelink Synchronization Signals

[00127] SynchUE Synchronization UE

[00128] TDD Time Division Duplex [00129] TETRA Terrestrial Trunked Radio

[00130] TX Transmit, transmitter

[00131] UE User Equipment

[00132] UL Uplink

[00133] V2V V ehi cl e-to-vehi cl e

[00134] V2X Vehicle-to-anything

Claims

CLAIMS:

1. A method (600) performed by a first user equipment, UE (401), the method comprising: obtaining (s602) a first discontinuous reception, DRX, configuration associated with a UE discovery procedure for use in discovering at least a second UE (402); initiating (s604) the UE discovery procedure; and applying (s606) the first DRX configuration during the period when the discovery procedure is running.

2. The method of claim 1, further comprising the first UE using information included in the DRX configuration to identify at least one period of time during which the first UE should not attempt to receive any discovery messages.

3. The method of claim 1 or 2, further comprising the first UE using information included in the first DRX configuration to identify at least one period of time during which the first UE should listen for discovery messages.

4. The method of any one of claims 1-3, further comprising the first UE using information included in the first DRX configuration to identify at least one period of time during which the UE may transmit a discovery message.

5. The method of any one of claims 1-4, further comprising, prior to initiating the discovery procedure: the first UE selecting a discovery configuration for the discovery procedure, wherein the first DRX configuration is associated with the selected discovery configuration; and after selecting the discovery procedure, the first UE obtaining the first DRX configuration.

6. The method of claim 5, wherein the selected discovery configuration comprises one or more of: discovery periodicity information specifying a discovery periodicity; time domain resource information specifying a resource allocation in a time domain; frequency domain resource information specifying a resource allocation in a frequency domain; or performance information specifying a discovery performance requirement.

7. The method of any one of claims 1-6, wherein initiating the discovery procedure comprises transmitting a discovery request message.

8. The method of any one of claims 1-7, further comprising: obtaining a second DRX configuration associated with the UE discovery procedure, wherein the first DRX configuration is further associated with a first service type, the second DRX configuration is further associated with a second service type.

9. The method of claim 8, further comprising, prior to initiating the discovery procedure: the first UE determining a service type; and after determining the service type, the first UE selecting the first DRX configuration based on the determined service type, wherein the determined service type matches the service type with which the first DRX configuration is associated.

10. The method of an one of claims 1-9, further comprising the first UE transmitting at least a portion of the first DRX configuration to the second UE.

11. The method of any one of claims 1-10, further comprising the first UE receiving at least a portion of a DRX configuration that will be applied by a neighbour UE in the proximity of the first UE.

12. The method of claim 11, wherein said at least a portion of the DRX configuration comprises a parameter corresponding to a periodicity with which the neighbour UE transmits a discovery message.

13. A computer program (743) comprising instructions (744) which when executed by processing circuitry (702) of a UE (700) causes the UE (700) to perform the method of any one of claims 1-12.

14. A carrier containing the computer program of claim 13, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium (742).

15. A user equipment, UE (700), the UE (700) being configured to: obtain (s602) a first discontinuous reception, DRX, configuration associated with a UE discovery procedure for use in discovering at least a second UE (402); initiate (s604) the UE discovery procedure; and apply (s606) the first DRX configuration during the period when the discovery procedure is running.

16. A user equipment, UE (700), the UE (700) comprising: processing circuitry (702); and a memory (742), the memory containing instructions (744) executable by the processing circuitry, wherein the UE (700) is configured to. obtain (s602) a first discontinuous reception, DRX, configuration associated with a UE discovery procedure for use in discovering at least a second UE (402); initiate (s604) the UE discovery procedure; and apply (s606) the first DRX configuration during the period when the discovery procedure is running.

17. The UE of claim 15 or 16, wherein the UE is further configured to perform the method of any one of claims 2-12.