System AMD methods for rediscovery in location management function assisted sidelink positioning

Abstract

A first wireless transmit / receive unit (WTRU) comprises a processor configured to determine to reject a SL positioning service request from a second WTRU. The processor may send a service accept message to the second WTRU based on the determination to reject the SL positioning service request. The service accept message may include a pending indication that the first WTRU will determine whether a server WTRU can assist with the SL position service request. The processor may send a SL positioning service information to the server WTRU, receive a rediscovery request from the server WTRU in response to the SL positioning service information, determine that the rediscovery request is unsuccessful, and / or send a first reject message to the second WTRU. The first reject message may include one or more of a first cause code that indicates a cause associated with the first reject message, a periodic timer, or a back-off time.

Description

SYSTEM AMD METHODS FOR REDISCOVERY IN LOCATION MANAGEMENT FUNCTION ASSISTED SIDELINK POSITIONINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 586,594, filed September 29, 2023, the entire contents of which are incorporated herein by reference as if fully set forth.BACKGROUND

[0002] A 5G location service may provide the functionality to provide the positioning information of a WTRU. The positioning of a WTRU may be supported by a Radio Access Technology (RAT) dependent position method, which relies on, for example, 3GPP RAT measurements obtained by a target WTRU and / or on measurements obtained by an Access Network of 3GPP RAT signals transmitted by a target WTRU. The positioning of a WTRU may also be supported by RAT independent position methods, which may rely on non-RAT measurements obtained by a WTRU and / or on other information. Location information for one or multiple target WTRUs may be requested by and reported to a Location Services (LCS) client, an Application Function (AF) within or external to a 3GPP operator network, or a control plane Network Function (NF) within the 3GPP system. For location requests from an LCS client or an AF, privacy (e.g., settings) verification of the target WTRU may be enabled to check whether it is allowed to acquire the WTRU location information.SUMMARY

[0003] A first wireless transmit / receive unit (WTRU) may comprise a processor. The processor may be configured to determine to reject a sidelink (SL) positioning service request from a second WTRU. The processor may be configured to send a service accept message to the second WTRU based on the determination to reject the SL positioning service request. The service accept message may include, for example, a pending indication that the first WTRU will determine whether a server WTRU can assist with the SL position service request. The processor may be configured to send a SL positioning service information to the server WTRU. The processor may be configured to receive a rediscovery request from the server WTRU in response to the SL positioning service information. The processor may be configured to determine that the rediscovery request is unsuccessful. The processor may be configured tosend a first reject message to the second WTRU. The first reject message may include, for example, one or more of a first cause code that indicates a cause associated with the first reject message, a periodic timer, or a back-off time.

[0004] In some examples, the processor may be configured to determine to reject the SL positioning service request from the second WTRU based on one or more of the following. For example, the processor may determine to reject the SL positioning service request from the second WTRU based on a determination that a SL reference WTRU in not within proximity of the first WTRU. The processor may determine to reject the SL positioning service request from the second WTRU based on a determination that a previously discovered SL reference WTRU is no longer within proximity of the first WTRU. The processor may determine to reject the SL positioning service request from the second WTRU based on congestion (e.g., WTRU experiencing a reduced quality of service (QoS) due to network capacity overload) experienced by the first WTRU on SL resources. The processor may determine to reject the SL positioning service request from the second WTRU based on a determination that connection failure has occurred with a SL reference WTRU.

[0005] The first cause code may include, for example, an indication that no SL reference WTRUs are within proximity of the first WTRU. The first cause code may include an indication that not enough SL reference WTRUs are within proximity of the first WTRU. The first cause code may include an indication that the first WTRU is experiencing congestion on SL resources. The first cause code may include an indication that the first WTRU cannot establish a connection with a SL reference WTRU.

[0006] In some examples, the processor may be configured to send a second reject message to the server WTRU in response to the determination that the rediscovery request is unsuccessful. The second reject message may include, for example, a second cause code associated with the rediscovery request.

[0007] The second cause code may include, for example, an indication that a SL reference WTRU has deployed a power saving technique and / or an indication that there are not enough SL reference WTRUs that are discovered within proximity of the first WTRU.

[0008] In some examples, the processor may be configured to determine that the rediscovery request is unsuccessful based on a latency requirement. The processor may be configured to determine that the rediscovery request is unsuccessful based on a power saving mode of the first WTRU. The processor may be configured to determine that the rediscovery request is unsuccessful based on a number of rediscovery attempts to identify one or more SL reference WTRUs, where the number of rediscovery attempts may be based on a timer value.

[0009] In some examples, the processor may be configured to receive a SL positioning service request from the second WTRU.

[0010] In some examples, the processor may be configured to discover one or more reference WTRUs based on the SL positioning service request.

[0011] In some examples, the processor may be configured to discover a subset of SL reference WTRUs based on the determination to reject the SL positioning service request. The processor may be configured to determine that the rediscovery request is unsuccessful based on a timer value.

[0012] In some examples, the processor may be configured to send SL positioning service information to the server WTRU for a result calculation based on the determination that the rediscovery request was unsuccessful based on a timer value. The result calculation may include, for example, a list of identifiers associated with the subset of SL reference WTRUs and / or a list of capabilities associated with the subset of SL reference WTRUs.

[0013] The WTRU may be configured to perform a method that includes one or more of the following steps. The method may include determining to reject a sidelink (SL) positioning service request from a second WTRU. The method may include sending a service accept message to the second WTRU based on the determination to reject the SL positioning service request. The service accept message may include, for example, a pending indication that the first WTRU will determine whether a server WTRU can assist with the SL position service request. The method may include sending a SL positioning service information to the server WTRU. The method may include receiving a rediscovery request from the server WTRU in response to the SL positioning service information. The method may include determining that the rediscovery request is unsuccessful. The method may include sending a first reject message to the second WTRU. The first reject message may include, for example, one or more of a first cause code that indicates a cause associated with the first reject message, a periodic timer, or a back-off time.

[0014] In some examples, the method may include determining to reject the SL positioning service request from the second WTRU based on one or more of the following. For example, the method may include determining to reject the SL positioning service request from the second WTRU based on a determination that a SL reference WTRU in not within proximity of the first WTRU. The method may include determining to reject the SL positioning service request from the second WTRU based on a determination that a previously discovered SL reference WTRU is no longer within proximity of the first WTRU. The method may include determining to reject the SL positioning service request from the second WTRU based on congestion (e.g., WTRU experiencing a reduced quality of service (QoS) due to networkcapacity overload) experienced by the first WTRU on SL resources. The method may include determining to reject the SL positioning service request from the second WTRU based on a determination that connection failure has occurred with a SL reference WTRU.

[0015] The first cause code may include, for example, an indication that no SL reference WTRUs are within proximity of the first WTRU. The first cause code may include an indication that not enough SL reference WTRUs are within proximity of the first WTRU. The first cause code may include an indication that the first WTRU is experiencing congestion on SL resources. The first cause code may include an indication that the first WTRU cannot establish a connection with a SL reference WTRU.

[0016] In some examples, the method may include sending a second reject message to the server WTRU in response to the determination that the rediscovery request is unsuccessful. The second reject message may include, for example, a second cause code associated with the rediscovery request.

[0017] The second cause code may include, for example, an indication that a SL reference WTRU has deployed a power saving technique and / or an indication that there are not enough SL reference WTRUs that are discovered within proximity of the first WTRU.

[0018] In some examples, the method may include determining that the rediscovery request is unsuccessful based on a latency requirement. The method may include determining that the rediscovery request is unsuccessful based on a power saving mode of the first WTRU. The method may include determining that the rediscovery request is unsuccessful based on a number of rediscovery attempts to identify one or more SL reference WTRUs, where the number of rediscovery attempts may be based on a timer value.

[0019] In some examples, the method may include receiving a SL positioning service request from the second WTRU.

[0020] In some examples, the method may include discovering one or more reference WTRUs based on the SL positioning service request.

[0021] In some examples, the method may include discovering a subset of SL reference WTRUs based on the determination to reject the SL positioning service request. The method may include determining that the rediscovery request is unsuccessful based on a timer value.

[0022] In some examples, the method may include sending SL positioning service information to the server WTRU for a result calculation based on the determination that the rediscovery request was unsuccessful based on a timer value. The result calculation may include, for example, a list of identifiers associated with the subset of SL reference WTRUs and / or a list of capabilities associated with the subset of SL reference WTRUs.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0024] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0025] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0026] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0027] FIG. 2 is a block diagram illustrating an example reference model of a Next Generation Radio Access Network for location services.

[0028] FIG. 3 is a procedural diagram illustrating example sidelink positioning operations assisted by LMF and discovery failure at the target WTRU.

[0029] FIG. 4 is a procedural diagram illustrating an example SL positioning operation assisted by the SL positioning server WTRU with a discovery failure at the SL target WTRU.

[0030] FIG. 5 is a procedural diagram illustrating an example SL positioning operation assisted by the SL positioning server WTRU with a discovery failure at the SL server WTRU.DETAILED DESCRIPTION

[0031] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content by sharing system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0032] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a CN 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a "station" and / or a "STA," may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as a WTRU.

[0033] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0034] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may berelatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e. , one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0035] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0036] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0037] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE- Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0038] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access, which may establish the air interface 116 using New Radio (NR).

[0039] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance, using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., a eNB and a gNB).

[0040] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e. , Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0041] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellularbased RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106 / 115.

[0042] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may be utilizing a NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0043] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0044] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0045] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0046] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0047] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive I , UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0048] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0049] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11 , for example.

[0050] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0051] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0052] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0053] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0054] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0055] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology tocommunicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0056] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0057] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0058] The CN 106 shown in FIG. 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0059] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attachment of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0060] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0061] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0062] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit- switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0063] Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0064] In representative embodiments, the other network 112 may be a WLAN.

[0065] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an "ad-hoc" mode of communication.

[0066] When using the 802.11 ac infrastructure mode of operation or a similar mode of operation, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in 802.11 systems. For CSMA / CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0067] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0068] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped onto the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0069] Sub 1 GHz modes of operation are supported by 802.11 af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11af and 802.11 ah relative to those used in 802.11n, and 802.11ac. 802.11af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non- TVWS spectrum. According to a representative embodiment, 802.11ah may support Meter Type Control / Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities, including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0070] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHzmode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remain idle and may be available.

[0071] In the United States, the available frequency bands, which may be used by 802.11 are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz, depending on the country code.

[0072] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0073] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0074] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs)of various or scalable lengths (e.g., containing varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0075] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c, and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0076] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0077] The CN 115 shown in FIG. 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements is depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0078] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NASsignaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized by WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non- 3GPP access technologies such as WiFi.

[0079] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a U PF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating WTRU IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0080] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0081] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0082] In view of Figures 1A-1 D, and the corresponding description of Figures 1A-1D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0083] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or may perform testing using over-the-air wireless communications.

[0084] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0085] When a SL target WTRU performs a discovery procedure to discover SL reference WTRUs, it may not find any SL reference WTRU. In that case, depending upon the request, e.g., if SL-MT-LR, the WTRU may send an error code to location management function (LMF) indicating “no reference WTRU found,” and / or if it is requested by SL client WTRU, then the WTRU may send a reject message to client WTRU with and error code “no reference WTRU found”.

[0086] When a SL target WTRU performs a discovery procedure to discover a SL reference WTRU, it may not find enough SL reference WTRUs as needed per positioning requirement. In that case the WTRU notifies the LMF and / or SideLink (SL) positioning server WTRU by including the list of SL reference WTRUs that may be discovered and / or list of WTRUs which may not be discovered. Based on the received list, the LMF and / or SL positioning server WTRU requests the SL target WTRU to perform rediscovery by providing rediscovery indication, and / oradditional parameters such retry timer, and minimum number of required SL reference WTRUs. The WTRU may also provide indication to abort the procedure.

[0087] SL positioning server may fail to assist with the SL positioning request when the SL target WTRU sends a request for positioning service because the SL positioning server may be overloaded, (e.g., congestion), may be far-away such that the required positioning accuracy and latency may not be met and / or may become unavailable due to mobility. In that case, the SL positioning server may send a reject message to the SL target WTRU stating the appropriate cause code as a reason for rejection (e.g., “SL positioning server WTRU unavailable”, “SL positioning server unable to fulfil positioning requirements”, “congestion”, and / or “can not establish connection”).

[0088] There are several different types of location requests supported.

[0089] A first location request may be a Mobile Terminated Location Request (MT-LR) in which an LCS client or AF may send a location request to the 5G Network for the location of a target WTRU.

[0090] A second location request may be a Mobile Originated Location Request (MO-LR) in which a WTRU may send a request to the 5G Network for location related information for the WTRU.

[0091] A third location request may be an Immediate Location Request in which an LCS client or AF may send or instigate a location request for a target WTRU(s) and may expect to receive a response containing location information for the target WTRU(s) within a short time period. The Immediate Location Request may be used for an MT-LR or MO-LR.

[0092] A fourth location request may be a Deferred Location Request in which an LCS client or AF may send a location request to the 5G network for a target WTRU(s) and may expect to receive a response when an indicated event occurs for the target WTRU at some future time. The Deferred Location Request may be used for an MT-LR.

[0093] FIG. 2 is a block diagram illustrating an example reference model 200 of a Next Generation Radio Access Network for location services. In FIG. 2, the (R)AN may represent a Next Generation Radio Access Network (NG-RAN), a trusted non-3GPP access network, or an untrusted non-3GPP access network. The access network may be involved in the handling of various positioning procedures, including positioning of a target WTRU, provisioning of location related information not associated with a particular target WTRU, and / or transfer of positioning messages between an AMF or LMF and a target WTRU.

[0094] AFs and NFs may access LCS services from a Gateway Mobile Location Centre (GMLC) in the same 3GPP operator network.

[0095] LCS clients may access LCS services from the GMLC and an External AF may access LCS services from a Network Exposure Function (NEF).

[0096] The GMLC may handle the request from the external LCS client and AF, via NEF if the AF is external, and may forward the location request to the proper NF.

[0097] The Location Retrieval Function (LRF) may be responsible for retrieving or validating location information and may be collocated with a GMLC or standalone.

[0098] The Location Management Function (LMF) may manage the overall coordination and scheduling of resources required for the location of a WTRU that is registered with or accessing a 5G core network (5GCN). The LMF may calculate or verify final location related information and its achieved accuracy.

[0099] A sidelink (SL) based positioning service may be implemented.

[0100] SL positioning may be defined as positioning WTRU using PC5 to obtain an absolute position, a relative position, or ranging information. Ranging refers to determining the distance between two or more WTRUs and / or the direction of one WTRU (e.g., a Target WTRU) from another WTRU (e.g., a Reference WTRU) via the PC5 interface.

[0101] For SL positioning purposes, one or more of the following definitions may apply.

[0102] A SL target WTRU and / or target WTRU may refer to a WTRU whose distance, direction, and / or position is measured with the support of one or multiple SL Reference WTRUs using SL in the ranging based service and SL positioning.

[0103] A located WTRU may refer to a SL Reference WTRU, SL positioning reference WTRU and / or reference WTRU, of which the location is known or can be known using Uu based positioning. A Located WTRU may be used to determine the location of a Target WTRU using SL positioning.

[0104] A SL reference WTRU may refer to a WTRU supporting the positioning of a target WTRU, for example, by transmitting and / or receiving reference signals for positioning, providing positioning-related information, etc., using SL.

[0105] A SL positioning client WTRU, SL client WTRU and / or client WTRU may refer to a third- party WTRU, other than a SL reference WTRU or target WTRU, which initiates a ranging and / or SL positioning service request on behalf of the application residing on the third-party WTRU.

[0106]

[0107] The ranging and / or SL positioning operations may be performed either as a network- assisted operation or a WTRU-only operation. In the network-assisted operation, the 5G core (5GC) NF(s) may be involved in the service request handling and result calculation. In theWTRU-only operation, the service request handling and result calculation operations may be performed by the WTRU.

[0108] When a network-assisted operation is used, the location management function (LMF) defined in the 5G Location Service may support the triggering of SL positioning, coordination of SL positioning operation, and delivery of the result to the client. The ranging and / or SL positioning service request may be initiated by a WTRU (e.g., SL positioning client WTRU, target WTRU, SL reference WTRU), a 5GC NF, an LCS client, or an AF.

[0109] When WTRU-only operation is used, WTRUs may interact with each other over PC5 as necessary to perform SL positioning operations. The SL positioning server WTRU may be defined to coordinate the SL positioning operation and the calculation of the positioning result. The SL positioning server WTRU (e.g., SL server WTRU, positioning server WTRU, server WTRU) may provide method determination, assistant data distribution, and / or location calculation functionalities for SL positioning and ranging based service.

[0110] Network (NW) assisted SL positioning may be implemented.

[0111] NW assisted SL positioning may be used to estimate the location of a WTRU with the assistance of the network by using the location of one or more located WTRUs and the distance and / or direction between the WTRU and the Located WTRU(s).

[0112] The NW assisted SL positioning feature may be implemented when the WTRU can establish a NAS (non access stratum) signaling connection and / or when the WTRU cannot establish a NAS signaling connection.

[0113] When a WTRU can establish a NAS connection, the WTRU may enter a CM-Connected state by performing a WTRU triggered Service Request for 5GC-MO-LR or performing a Network triggered Service Request for 5GC-NI-LR or 5GC-MT-LR. As the target WTRU can establish a NAS signaling connection with the AMF, the functionality specified in 5G Location Service may be reused, including, for example, 5GC-MO-LR, 5GC-MT-LR, and / or 5GC-NI-LR.

[0114] When a network connection can be established, one or more of the following principles may apply. The target WTRU or LMF may determine whether network assisted SL positioning will be applied. The target WTRU may discover located WTRU(s) for network assisted SL positioning. The target WTRU and located WTRU(s) may perform ranging and / or SL positioning. The target WTRU may include the WTRU identity of the located WTRU(s) to the LMF and the ranging measurement data or estimation result. The LMF may interact with GMLC to get the location of the located WTRU. The LMF may use the location of the located WTRU(s) together with the ranging and / or SL positioning measurement data and / or estimation results reported by the target WTRU and / or by the located WTRUs to estimate the location of the target WTRU.

[0115] When the target WTRU cannot establish the NAS connection with AMF due to the target WTRU being out of coverage or any other reason (e.g., invalid subscription, rejection by NW), the following principles may apply. The target WTRU may perform the located WTRU's discovery and / or selection. The target WTRU may transmit its ranging measurements / results to the located WTRU(s). The located WTRU(s) may report the ranging and / or SL positioning measurement result to the LMF. This report may include ranging measurements / results received from the target WTRU. The endpoints for LPP messages are the LMF and the located WTRU(s). The LMF may use the received information to calculate the location of the Target WTRU and / or provide the resulting location via the located WTRU to the target WTRU or via 5G NF to the LCS client or the application server.

[0116] SL positioning services may be exposed to one or more WTRUs.

[0117] A WTRU (e.g., SL positioning client WTRU) may request SL positioning through PC5 or via the NW. When the SL positioning client WTRU requests SL positioning service through the PC5 connection, the SL positioning client WTRU may discover one of the reference WTRUs and target WTRUs. The SL positioning client WTRU may invoke the ranging and / or SL positioning service request to the discovered reference WTRU and target WTRU for obtaining the ranging and / or SL positioning result between the reference WTRU and target WTRU. This request may include the user info of SL Positioning Client UE, Reference UE, and / or Target UE. After receiving the SL positioning service request, SL positioning service operation with LMF and / or SL positioning server WTRU may be performed.

[0118] Discovery error handling for SL positioning procedures may be implemented.

[0119] The reference WTRU and the target WTRU may perform SL positioning by coordinating with the SL positioning server UE or LMF, which may assist with calculating and disseminating positioning results. The SL positioning server WTRU may be used when (e.g., only when) the target WTRU and reference WTRUs are out of coverage (no NAS connection) unless an LMF advises the SL positioning server to take over. When either the reference WTRU or target WTRU is in coverage (having NAS connection), the LMF may be involved. If the target WTRU is in coverage, the target WTRU may contact the LMF for coordination. And, if the reference WTRU is in coverage and the target WTRU is out of coverage, the SL reference WTRU may contact LMF for coordination.

[0120] When a target WTRU receives a positioning request from a LMF (MT-LR) or a SL client WTRU (MO-LR), the target WTRU may discover and / or select one or more located WTRUs and / or SL reference WTRUs used in the ranging and / or SL positioning procedure. There maybe situations where a target WTRU or a client WTRU may be unable to discover any target WTRUs, SL positioning server WTRUs, or SL reference WTRUs. This situation may be due to several reasons, including that the distance between the WTRUs is too large, causing the SNR to be below the required threshold, the WTRU is experiencing congestion (e.g., reduced quality of service (QoS) due to network capacity overload), high mobility, etc. Similarly, there may also be a situation where the target WTRU may discover some SL reference WTRUs but could not discover sufficient SL reference WTRUs to execute the desired positioning accuracy.

[0121] Additionally or alternatively, the SL target WTRU or SL client WTRU may be in a power saving mode, preventing the performance of a continuous or more frequent search for a SL target WTRU, a SL positioning server WTRU, or a SL reference WTRU.

[0122] Given the above, the following problems may need to be addressed.

[0123] A first problem may be how the target WTRU handles a SL reference WTRU discovery failure. A second problem may be how the target WTRU handles a SL positioning server WTRU discovery failure. A third problem may be how the LMF / SL positioning server WTRU handles when the SL reference WTRU discovery fails at the target WTRU.

[0124] The present disclosure may assume that the WTRU supports PC5 signaling (5G ProSe enabled WTRU). The ProSe (proximity based service) layer in the WTRUs may support this PC5 signaling.

[0125] The WTRU may have the capability of ranging and / or SL positioning and / or the capability of SL positioning server WTRU. Here, SL positioning may refer to the positioning via a PC5 interface, and ranging may refer to determining the distance between two or more WTRUs and / or the direction and / or relative positioning of one WTRU to another WTRU.

[0126] A rediscovery of SL reference WTRUs for a LMF assisted SL positioning procedure may be implemented.

[0127] A SL target WTRU (WTRU1) may be triggered for location requests, for example, by an AF or LCS in the SL-MT-LR procedure. The SL target WTRU may attempt to discover SL reference WTRUs and / or SL located WTRUs for the positioning operation as requested by the LMF. However, the SL target WTRU may fail to locate any or enough SL reference WTRUs. In this case, the SL target WTRU may either send an error message to the LMF or send the list of discovered and undiscovered SL reference WTRUs together with the capabilities of the SL reference WTRUs. Based on the received WTRU IDs, capabilities, and / or positioning requirements, the LMF may instruct the SL target WTRU to perform rediscovery for a certain time window until the desired number of SL reference WTRUs is discovered.

[0128] A SL target WTRU (WTRU1) may be triggered for location requests in the SL-MO-LR procedure. The SL target WTRU may then receive a set of parameters as part of the configuration from the LMF, which is utilized by the SL target WTRU to handle the failure.

[0129] FIG. 3 is a procedural diagram illustrating an example sidelink positioning operation 300 assisted by LMF and discovery failure at the target WTRU.

[0130] As shown in FIG. 3, the SL target WTRU (WTRU1) may be triggered for a location request. At 0a, the location request may be triggered by AF or LCS. At 0b, the WTRU1 may receive a message from the LMF via the serving AMF. This SL-MT-LR request may include the application layer IDs of the other WTRUs (WTRU2 to WTRUn), the types of required location results (e.g., relative locations or distances and / or directions), SL reference WTRU(s) for relative locations, timer value (to re-attempt or back-off), latency requirements, min. # of reference WTRUs, and / or min # of located WTRUs determined based on the positioning requirements.

[0131] At 1 , the SL target WTRU (WTRU1) may attempt to discover the other WTRUs (WTRU2 to WTRUn) using their Application Layer IDs if provided by the LMF. If no WTRU IDs are provided by the LMF, the SL target WTRU may perform open discovery, for example, to discover SL reference WTRUs.

[0132] The SL target WTRU may discover (1) all reference WTRUs as provided by the LMF (WTRU2-WTRUn) in step 0b, (2) a subset x # of WTRUs, (3) one or more other reference WTRUs that were not in the list provided by the LMF, and (4) none of the WTRUs as requested by the LMF in step 0b.

[0133] At 2, the WTRU1 may obtain one or more capabilities for the discovered WTRUs.

[0134] At 3, the WTRU1 may return a supplementary services SL-MT-LR response to the serving AMF in an UL NAS TRANSPORT message. The response may include a list of the discovered WTRUs (using application layer ID and / or GPSI), a list of newly discovered WTRUs (that are not in the list of WTRU IDs received from the LMF), and / or one or more error codes with a cause value (e.g., no reference WTRU discovered, too few reference WTRUs discovered, a particular WTRU is unavailable, WTRU unauthorized for discovery). The target WTRU may share the capabilities of the discovered WTRUs.

[0135] At 4, the serving AMF may forward the SL-MT-LR response to the LMF. The SL-MT-LR response may include a list of the discovered WTRUs (using application layer ID and / or GPSI), their capabilities, a list of newly discovered WTRUs (that are not in the list of WTRU IDs received from the LMF), and / or one or more error codes with a cause value (e.g., no referenceWTRU discovered, too few reference WTRUs discovered, a particular WTRU is unavailable, WTRU unauthorized for discovery).

[0136] At 5, the LMF may receive a list of discovered SL reference WTRUs and, based on the positioning requirements, the LMF may determine whether or not the SL target WTRU has discovered enough SL reference WTRUs / located WTRUs. If not, the LMF may request the SL target WTRU to perform a rediscovery of the SL reference WTRUs (e.g., to find more WTRUs, if possible).

[0137] The LMF may provide one or more of a timer value, latency requirement(s), and / or a minimum number of SL reference WTRUs to the SL target WTRU.

[0138] The timer value may be provided by the LMF so SL reference WTRUs may be discovered by the SL target WTRU within a certain window until a desired number is reached (e g., a periodic timer to make periodic attempts, an explicit max time value for the case of stringent latency requirements, and / or a back-off timer to back off if the desired result is not achieved automatically).

[0139] The latency requirements may be associated with the positioning for the desired positioning service (e.g., max tolerable delay, implying that the positioning response doesn't take too long for any mission critical services).

[0140] The minimum number of SL reference WTRUs may be associated with the desired positioning service.

[0141] At 6, the LMF may send an SL-MT-LR request to the serving AMF as a supplementary services message. The SL-MT-LR request may include a rediscovery indication, a timer value, a new list of SL reference WTRUs / located WTRUs, a minimum number of SL reference WTRUs, and / or the capability required for the SL reference WTRUs.

[0142] At 7, the serving AMF may forward the SL-MT-LR request to WTRU1 , for example, using a DL NAS TRANSPORT message. The forwarded SL-MT-LR request may include the rediscovery indication, the timer value, the new list of SL reference WTRUs / located WTRUs, the minimum number of SL reference WTRUs, and / or the capability required for the SL reference WTRUs.

[0143] At 8, the SL target WTRU may receive the rediscovery request from the LMF. Based on the received parameters, the SL target WTRU may perform rediscovery, starts the respective timer, and may continue performing re-attempts until requirements are met before the timer expires, as indicated in 7. The requirements may imply a minimum number of SL references WTRUs with the required capability for the desired SL positioning service. The SL target WTRUmay send a new list of SL reference WTRUs to the LMF, for example, when the desired number is reached.

[0144] At 5-8, as an alternative, the LMF may look up another target WTRU, if available in the proximity, and may initiate the sidelink positioning operations 300 with the newly selected target WTRU.

[0145] In the SL-MT-LR request, the LMF may send a new set of parameters as part of the configuration message. The new set of parameters may include the timer value, the list of SL reference WTRUs / located WTRUs, the minimum number of SL reference WTRUs, the capability required for the SL reference WTRUs for each positioning service, and / or the number of required SL reference WTRUs which may be different per QoS or per positioning method.

[0146] If there is no NAS connection or the LMF has instructed the SL positioning server WTRU to assist with the positioning, the sidelink positioning operation 300 may be coordinated by the SL positioning server WTRU.

[0147] As an example, within a rediscovery of SL reference WTRUs for LMF assisted SL positioning procedure, the LMF may receive the list of undiscovered WTRUs (based on the received WTRU IDs from the LMF) and / or one or more error codes with a cause value (e.g., no reference WTRU discovered, too few reference WTRUs discovered).

[0148] The LMF may, based on the positioning requirements and information from the SL target WTRU, determine whether or not the SL target WTRU has discovered enough SL reference WTRUs / located WTRUs.

[0149] The LMF may send a request to the SL target WTRU to perform a rediscovery of the SL reference WTRUs (to find more WTRUs if possible). The LMF may provide one or more additional parameters to the SL target WTRU, such as a rediscovery indication, a timer value, latency requirements, a new list of SL reference WTRUs / located WTRUs, a minimum number of SL reference WTRUs, and / or the capability required for the SL reference WTRUs.

[0150] The LMF may, as an alternative, send a new set of parameters as part of the configuration message. The new set of parameters may include the timer value, the list of SL reference WTRUs / located WTRUs, the minimum number of SL reference WTRUs, and / or the capability required for the SL reference WTRUs for each positioning service.

[0151] As an example, within a rediscovery of SL reference WTRUs for LMF assisted SL positioning procedure, the SL target WTRU may send to the LMF in a NAS message via AMF the list of undiscovered WTRUs (based on the received UE IDs from LMF) and / or one or more error codes with a cause value (e.g., no reference WTRU discovered, too few reference WTRUs discovered).

[0152] The SL target WTRU may receive from the LMF via the AMF in a DL NAS TRANSPORT message a request to perform rediscovery with a rediscovery indication and additionally the timer value, the new list of SL reference WTRUs / located WTRUs, the minimum number of SL reference WTRUs, and / or the capability required for the SL reference WTRUs.

[0153] The SL target WTRU may, based on the received parameters, perform rediscovery, start the respective timer, and / or continue performing re-attempts until the requirements are met. The SL target WTRU may send a new list of SL reference WTRUs to the LMF, for example, when the desired number is reached.

[0154] A procedure for SL positioning service operation based on the interaction between a client WTRU (e.g., a SL client WTRU) and a SL positioning server WTRU may be implemented.

[0155] The SL client WTRU may trigger a SL positioning request to the SL target WTRU which initiates the discovery procedure for SL reference WTRU / SL located WTRU discovery based on the positioning request. The discovery procedure may or may not be successful because the SL target WTRU is under congestion, didn't find any SL reference WTRUs, and / or didn't find enough SL reference WTRUs as required by the positioning service.

[0156] If the discovery procedure is unsuccessful, the target WTRU may reject the positioning request from the client WTRU by sending a rejection message with an error code and a cause value. Additionally or alternatively, if the discovery procedure is unsuccessful, the SL target WTRU may not send (e.g., immediately send) a rejection message but, instead, may coordinate with the SL reference WTRU and initiate a rediscovery of SL reference WTRUs.

[0157] FIG. 4 is a procedural diagram illustrating an example SL positioning operation 400 assisted by the SL positioning server WTRU with a discovery failure at the SL target WTRU.

[0158] As shown in FIG. 4, at 1 , the SL target WTRU may be triggered for a location request, for example, by a SL client WTRU.

[0159] At 2, the SL target WTRU may perform the SL reference WTRU discovery and connection setup with the discovered reference WTRUs.

[0160] Prior to proceeding with the location request, the SL target WTRU may determine if one or more of the following have occurred: (a) have not found any SL reference WTRUs in proximity; (b) previously discovered SL reference WTRU(s) have moved away due to mobility;(c) experience congestion as it is already serving enough client WTRUs; (d) unable to make a connection with the indicated SL reference WTRU(s); and / or (e) have discovered some / subset of SL reference WTRUs based on the positioning request received from SL client WTRU.

[0161] At 3a, if it is determined that any of occurrences (a)-(d) (at 2) have occurred, the SL target WTRU may send a reject message to the SL client WTRU with a cause code (e.g., "No SL reference WTRU," "Not enough SL reference WTRU," "Cannot establish a connection with SL reference WTRU," "Congestion," a periodic timer in case of re-attempts, and / or a back-off time in case of congestion).

[0162] The WTRU1 may send a service accept message with pending indication. The pending indication may indicate to the SL positioning client WTRU that WTRU1 is querying with the SL positioning Server WTRU if position service is possible. The WTRU1 may perform 3b with the SL positioning server WTRU.

[0163] At 3b, if it is determined that occurrence (e) (at 2) has occurred, the SL target WTRU may not directly send the reject message. Instead, the SL target WTRU may perform X number of attempts at intervals based on the default timer value. The number of attempts may be, for example, the number of rediscovery attempts until the target WTRU may have discovered a sufficient amount of SL reference WTRUs. The number attempts and / or rediscovery attempts may be capped and / or limited, for example, by the timer value (e.g., attempt until timer expires). The SL target WTRU may send SL positioning service information to the SL positioning server WTRU or the SL positioning server for result calculation, including the list of discovered reference WTRU IDs and their capabilities.

[0164] At 4, based on the positioning requirements, the SL positioning server WTRU may determine whether or not the SL target WTRU has discovered enough SL reference WTRUs. If not, the SL positioning server WTRU may request a rediscovery.

[0165] At 5, the SL positioning server may request the SL target WTRU to perform a rediscovery of the SL reference WTRUs (to find more if possible) and / or may include a general timer value.

[0166] The request to the SL target WTRU to perform a rediscovery may include one or more of a timer, latency requirement(s), and / or a minimum number of SL reference WTRUs.

[0167] The timer may be a periodic timer to make periodic attempts and an explicit max time in case of stringent latency requirements to discover SL reference WTRUs until the desired number is reached.

[0168] The latency requirement(s) on the positioning may include a maximum tolerable delay that ensures the positioning response doesn't take too long for mission critical services.

[0169] The minimum number of SL reference WTRUs may be associated with the desired service.

[0170] At 6, the SL target WTRU may receive a rediscovery request from an SL positioning server.

[0171] The SL target WTRU may determine if the request can be met (e.g., if there is an explicit timer that requires more frequent rediscovery attempts or if the latency requirements are too tight) and may consider one or more power saving requirements deployed by the SL target WTRU.

[0172] Additionally or alternatively, the target WTRU may initially meet the requirements but cannot find more SL reference WTRUs and has reached max attempts / time.

[0173] At 7a, if any of the requirements of the rediscovery request (at 6) cannot be met, the SL target WTRU may send a reject message to the SL client WTRU, for example, in response to the positioning request. The SL target WTRU may release the link with the SL client WTRU and the SL client WTRU, upon reception of the reject message, may proceed to discover another SL target WTRU for positioning service request.

[0174] At 7b, if any of the requirements of the rediscovery request (at 6) cannot be met, the SL target WTRU may respond to the SL positioning server with a reject message and / or an error stating the cause (e.g., "Power saving deployed," "Not enough SL reference WTRU," etc ).

[0175] In the SL positioning operation 400, the SL positioning server WTRU may be replaced with the LMF. The functionality remains the same whether the LMF or the SL positioning server WTRU assists with the positioning service, for example, because the SL target WTRU (if there is NAS connection - default scenario) sends the location request to the LMF. If there is no NAS connection, the SL target WTRU sends the location request to the SL location server WTRU or if the LMF explicitly instructs that the SL positioning server WTRU is used instead of the LMF.

[0176] A procedure for rediscovery of SL reference WTRUs for SL server WTRU assisted SL positioning due to a failure at the target WTRU may be implemented.

[0177] The SL positioning server WTRU (or LMF) may determine whether or not the SL target WTRU has discovered enough SL reference WTRUs based on the positioning requirements.

[0178] The SL positioning server WTRU (or LMF) may request the SL target WTRU for rediscovery to find more SL reference WTRUs. The request may include a timer, latency requirements on the positioning, and / or a minimum number of SL reference WTRUs for the desired service.

[0179] The SL positioning server WTRU (or LMF) may receive a reject message stating the cause (e.g., "Power saving deployed," "Not enough SL reference UE," etc.). In this case, the SLpositioning server WTRU may release the link with the SL target WTRU and may send a configuration update to the SL client WTRU with another available SL target WTRU ID.

[0180] The SL target WTRU (WTRU1) may determine a potential reject cause when the SL target WTRU cannot find any SL reference WTRUs, cannot establish a connection with the SL reference WTRU, and / or cannot discover one or more (e.g., all) the SL reference WTRUs as required by the SL positioning server and / or the client WTRU.

[0181] The SL target WTRU (WTRU1) may send a reject message to the SL client WTRU with a cause code (e.g., "No SL reference UE," Not enough SL reference WTRU," "Cannot establish a connection with SL reference WTRU," "Congestion," and / or a periodic timer in case of reattempts or a back-off time in case of congestion).

[0182] The SL target WTRU (WTRU1) may send a service accept message with a pending indication. The pending indication may indicate to the SL positioning client WTRU that WTRU1 is querying with the SL positioning Server WTRU if position service is possible.

[0183] The SL target WTRU (WTRU1) may not directly send a rejection message to the client WTRU. Instead, the SL target WTRU (WTRU1) may make a certain (e.g., predetermined) number of discovery attempts at intervals based on the default timer value and / or the configurations received from the LMF as to the minimum number of reference WTRUs required per service.

[0184] The SL target WTRU (WTRU1) may receive a rediscovery request from the SL positioning server and may determine if the rediscovery request can be met (e.g., SL target WTRU is in power saving and cannot make frequent rediscovery attempts to meet latency requirements or has already made max attempts / time).

[0185] The SL target WTRU (WTRU1) may respond with a reject message to the SL positioning server, stating the cause (e.g., "Power saving deployed," "Not enough SL reference WTRU," etc.).

[0186] The SL positioning server may fail to assist with the SL positioning request because it is overloaded (e.g., congestion, may be far away so the required positioning accuracy and latency cannot be met, and / or has become unavailable due to mobility).

[0187] FIG. 5 is a procedural diagram illustrating an example SL positioning operation 500 assisted by the SL positioning server WTRU with a discovery failure at the SL server WTRU.

[0188] As shown in FIG. 5, at 1 , the SL target WTRU may be triggered for a location request (e.g., by a SL client WTRU).

[0189] At 2, the SL target WTRU may determine to use the SL positioning server for SL positioning service or the LMF based on the NAS status (e.g., no NAS or with NAS).

[0190] At 3, if the SL target WTRU has a NAS connection (in-coverage), the LMF may instruct the target WTRU to send the positioning request to the SL positioning server WTRU, for example, instead of the LMF.

[0191] At 4, the SL target WTRU may discover a SL positioning server WTRU and may send a positioning request to the SL positioning server WTRU.

[0192] At 5, the SL positioning server WTRU may determine its availability based on the received request.

[0193] The SL positioning server WTRU may determine that the SL positioning server WTRU is unavailable if the SL positioning server WTRU cannot meet the positioning requirements (e.g., latency and accuracy) while having enough bandwidth to accommodate requests for any mission critical services.

[0194] The SL positioning server WTRU may determine it is unavailable if, while being discoverable, the SL positioning server WTRU cannot establish a connection due to congestion at the SL positioning server WTRU.

[0195] The SL positioning server WTRU may determine the SL positioning server WTRU will be unavailable while already providing service to the SL target WTRU.

[0196] At 6a, if unavailable, the SL positioning server WTRU may send a reject message to the SL target WTRU stating the appropriate cause value as a reason for rejection (e.g., "SL positioning server UE unavailable," "SL positioning server unable to fulfill positioning requirements," "Congestion," "Can not establish connection" etc.).

[0197] At 6b, the SL positioning server WTRU may provide an unavailability indication to the LMF and a target WTRU ID, for example, so the LMF can lookup alternative SL server WTRUs in the proximity. The SL positioning server WTRU may notify the LMF in advance and / or as soon as an error condition is triggered so the LMF doesn't instruct other SL target WTRUs to select that server WTRU.

[0198] At 6c, if the target WTRU ID was included with the unavailability indicator to the LMF (at 6b), the LMF may provide one or more alternate positioning server WRTU IDs to the SL target WTRU and / or to the SL positioning server WTRU, which are available in the proximity of the target WTRU.

[0199] The LMF may provide any back-off or retry timer to the SL target WTRU, for example, so the SL target WTRU may perform re-attempts before the SL target WTRU notifies the SL clientWTRU that the SL target WTRU cannot be discovered or the SL target WTRU cannot establish a connection with the SL positioning server WTRU. If the SL server WTRU has received any updates from the LMF, the SL server WTRU may include one or more alternate SL positioning server WTRU IDs, for example, so the target WTRU (WTRU1) may use the SL server WTRU for positioning service.

[0200] At 7, after receiving the rejection message, the SL target WTRU may determines to (a) wait for the given timer and continue performing re-attempts until the timer expires, (b) lookup another SL server WTRU (e.g., as provided by the LMF or perform discovery again without knowing the ID of available server WTRU), and / or (c) send a positioning request to the LMF instead of the SL positioning server WTRU.

[0201] At 8, based on the prior determination (at 7a, 7b, or 7c), the SL target WTRU may reattempt, find a new SL positioning server, and / or send a new positioning request to the LMF.

[0202] At 9, if the select SL server WTRU is unavailable after the re-attempts and the select SL server cannot find any other SL positioning server WTRUs, the select SL server WTRU may notify the SL client WTRU that the SL positioning server WTRU is unavailable.

[0203] Additionally or alternatively, if there is a NAS connection and the LMF initially instructed the SL target WTRU to switch to the SL positioning server WTRU for positioning services, the SL target WTRU may send a notification to the LMF stating that "SL positioning server WTRU unavailable" if the SL positioning server WTRU becomes unavailable.

[0204] A procedure for rediscovery of SL reference WTRUs for SL server WTRU assisted SL positioning due to a failure at the SL positioning WTRU may be implemented.

[0205] The SL positioning WTRU may receive a positioning request from the SL target WTRU.

[0206] The SL positioning WTRU may determine if the SL positioning WTRU cannot meet the positioning requirements (e.g., latency and accuracy), if to the SL positioning WTRU can establish a connection (e.g., if experiencing congestion), and / or if the SL positioning WTRU will be unavailable soon.

[0207] The SL positioning WTRU may send a reject message to the SL target WTRU indicating the appropriate cause value as a reason for rejection (e.g., "SL positioning server UE unavailable," "SL positioning server unable to fulfill positioning requirements," "Congestion," "Can not establish a connection," etc.).

[0208] The SL positioning WTRU may provide an unavailability indication and / or a target WTRU ID to the LMF, for example, so the LMF can lookup one or more alternative SL server WTRUs in the proximity.

[0209] The SL positioning WTRU may receive one or more alternate positioning server WTRU IDs for the SL target WTRU from the LMF, which may be included in the rejection message.

[0210] The SL positioning WTRU may provide a back-off and / or a retry timer to the SL target WTRU, for example, so the SL target WTRU can perform re-attempts before the SL target WTRU notifies the SL client WTRU that the SL target WTRU cannot establish a connection with a positioning server.

[0211] The SL target WTRU may receive a reject message from the SL positioning server WTRU indicating the appropriate cause value as a reason for rejection (e.g., "SL positioning server UE unavailable," "SL positioning server unable to fulfill positioning requirements," "Congestion," "Can not establish connection" etc.).

[0212] The SL target WTRU may receive one or more alternate positioning server WTRU IDs from the LMF or the SL positioning server along with the reject cause code.

[0213] The SL target WTRU may determine whether to wait for the given timer to expire and / or continue performing re-attempts or to lookup another SL server WTRU (e.g., using the ID provided by the LMF or by performing discovery again without knowing the ID of available server WTRUs), after receiving the rejection message.

[0214] The SL target WTRU may send a reject message to the SL client WTRU with a cause code (e.g., "SL positioning server unavailable").

[0215] The SL target WTRU may send a positioning request message to the LMF indicating with cause that "SL positioning server unavailable," for example, so the LMF can take over the positioning service.

[0216] The LMF may provide one or more alternate positioning server WTRU IDs to the SL target WTRU and / or the SL positioning server WTRU.

Claims

CLAIMS:

1. A first wireless transmit / receive unit (WTRU) comprising: a processor configured to: determine to reject a sidelink (SL) positioning service request from a second WTRU; send a service accept message to the second WTRU based on the determination to reject the SL positioning service request, wherein the service accept message comprises a pending indication that the first WTRU will determine whether a server WTRU can assist with the SL position service request; send a SL positioning service information to the server WTRU; receive a rediscovery request from the server WTRU in response to the SL positioning service information; determine that the rediscovery request is unsuccessful; and send a first reject message to the second WTRU, the first reject message comprising one or more of a first cause code that indicates a cause associated with the first reject message, a periodic timer, or a back-off time.

2. The first WTRU of claim 1 , wherein the processor is configured to determine to reject the SL positioning service request from the second WTRU based on one or more of: a determination that a SL reference WTRU in not within proximity of the first WTRU; a determination that a previously discovered SL reference WTRU is no longer within proximity of the first WTRU; congestion experienced by the first WTRU on SL resources; or a determination that connection failure has occurred with a SL reference WTRU.

3. The first WTRU of claim 1 or 2, wherein the first cause code comprises one or more of: an indication that no SL reference WTRUs are within proximity of the first WTRU; an indication that not enough SL reference WTRUs are within proximity of the first WTRU; an indication that the first WTRU is experiencing congestion on SL resources; or an indication that the first WTRU cannot establish a connection with a SL reference WTRU.

4. The first WTRU of any of claims 1 to 3, wherein the processor is configured to:send a second reject message to the server WTRU in response to the determination that the rediscovery request is unsuccessful, the second reject message comprising a second cause code associated with the rediscovery request.

5. The first WTRU of claim 4, wherein the second cause code comprises an indication that a SL reference WTRU has deployed a power saving technique or an indication that there are not enough SL reference WTRUs that are discovered within proximity of the first WTRU.

6. The first WTRU of any of claims 1 to 5, wherein the processor is configured to determine that the rediscovery request is unsuccessful based on a latency requirement, a power saving mode of the first WTRU, or a number of rediscovery attempts to identify one or more SL reference WTRUs, wherein the number of rediscovery attempts is based on a timer value.

7. The first WTRU of any of claims 1 to 6, wherein the processor is configured to: receive a SL positioning service request from the second WTRU.

8. The first WTRU of any of claims 1 to 7, wherein the processor is configured to: discover one or more reference WTRUs based on the SL positioning service request.

9. The first WTRU of any of claims 1 to 8, wherein the processor is configured to: discover a subset of SL reference WTRUs based on the determination to reject the SL positioning service request; and determine that the rediscovery request is unsuccessful based on a timer value.

10. The first WTRU of claim 8, wherein the processor is configured to: send SL positioning service information to the server WTRU for a result calculation based on the determination that the rediscovery request was unsuccessful based on a timer value, wherein the result calculation comprises a list of identifiers associated with the subset of SL reference WTRUs or a list of capabilities associated with the subset of SL reference WTRUs.

11. A method performed by a first wireless transmit / receive unit (WTRU), the method comprising: determining to reject a sidelink (SL) positioning service request from a second WTRU;sending a service accept message to the second WTRU based on the determination to reject the SL positioning service request, wherein the service accept message comprises a pending indication that the first WTRU will determine whether a server WTRU can assist with the SL position service request; sending a SL positioning service information to the server WTRU; receiving a rediscovery request from the server WTRU in response to the SL positioning service information; determining that the rediscovery request is unsuccessful; and sending a first reject message to the second WTRU, the first reject message comprising one or more of a first cause code that indicates a cause associated with the first reject message, a periodic timer, or a back-off time.

12. The method of claim 11 , wherein the method comprises determining to reject the SL positioning service request from the second WTRU based on one or more of: a determination that a SL reference WTRU in not within proximity of the first WTRU; a determination that a previously discovered SL reference WTRU is no longer within proximity of the first WTRU; congestion experienced by the first WTRU on SL resources; or a determination that connection failure has occurred with a SL reference WTRU.

13. The method of claim 11 or 12, wherein the first cause code comprises one or more of: an indication that no SL reference WTRUs are within proximity of the first WTRU; an indication that not enough SL reference WTRUs are within proximity of the first WTRU; an indication that the first WTRU is experiencing congestion on SL resources; or an indication that the first WTRU cannot establish a connection with a SL reference WTRU.

14. The method of any of claims 11 to 13, wherein the method comprises: sending a second reject message to the server WTRU in response to the determination that the rediscovery request is unsuccessful, the second reject message comprising a second cause code associated with the rediscovery request.

15. The method of claim 14, wherein the second cause code comprises an indication that a SL reference WTRU has deployed a power saving technique or an indication that there are not enough SL reference WTRUs that are discovered within proximity of the first WTRU.

16. The method of any of claims 11-15, wherein the method comprises determining that the rediscovery request is unsuccessful based on a latency requirement, a power saving mode of the first WTRU, or a number of rediscovery attempts to identify one or more SL reference WTRU, wherein the number of rediscovery attempts is based on a timer value.

17. The method of any of claims 11-16, wherein the method comprises: receiving a SL positioning service request from the second WTRU.

18. The method of any of claims 11-17, wherein the method comprises: discovering one or more reference WTRUs based on the SL positioning service request.

19. The method of any of claims 11-18, wherein the method comprises: discovering a subset of SL reference WTRUs based on the determination to reject the SL positioning service request; and determining that the rediscovery request is unsuccessful based on a timer value.

20. A first wireless transmit / receive unit (WTRU) comprising: a processor configured to: receive a discovery request from a second WTRU, wherein the second WTRU is a sidelink client WTRU; initiate a discovery procedure for one or more sidelink reference WTRUs based on the discovery request; determine that the discovery request is unsuccessful based on the discovery procedure; and send a reject message to the second WTRU, the reject message comprising a cause code that indicates a cause associated with the reject message, a periodic timer, or a back-off time.

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