Method and apparatus for resource selection and congestion control for SL-prs

Abstract

A wireless transmit / receive unit (WTRU) may receive information indicating a sidelink positioning reference signal (SL-PRS) priority threshold, and may receive information triggering an SL-PRS transmission, the SL-PRS transmission having an associated priority. The WTRU may determine a first type of SL-PRS resource and a second type of SL-PRS resource based on the sensing during the sensing window. The SL-PRS resource of the first type may be a resource that is not multiplexed with other WTRUs. The SL-PRS resource of the second type may be a resource multiplexed with other WTRUs. The WTRU may select available resources to include in an SL-PRS candidate resource set based on the priority associated with the SL-PRS transmission and the SL-PRS priority threshold. The WTRU may select one or more SL-PRS resources from the set of SL-PRS candidate resources. The WTRU may transmit the SL-PRS in the selected one or more SL-PRS resources.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 445,549 filed on February 14, 2023, U.S. Provisional Application No. 63 / 421,810 filed on November 2, 2022, and U.S. Provisional Application No. 63 / 395,551 filed on August 5, 2022, the contents of which are incorporated herein by reference. Background Art

[0003] NR vehicle communication (V2X) is designed to support sidelink communication between different vehicles. In NR V2X, the resources used for sidelink transmission / reception are constructed as resource pools. The resource pool includes a collection of continuous frequency resources that repeat in time following a bitmap pattern. A wireless transmit / receive unit (WTRU) may be configured with one or more resource pools. For a WTRU within coverage, the resource pool may be configured via a system information block (SIB) or radio resource control (RRC) signaling. For a WTRU outside coverage, the resource pool may be (pre) configured. Summary of the invention

[0004] A wireless transmit / receive unit (WTRU) may receive information indicating a sidelink positioning reference signal (SL-PRS) priority threshold. The WTRU may receive information triggering a SL-PRS transmission, the SL-PRS transmission having an associated priority. The WTRU may determine a first type of SL-PRS resource and a second type of SL-PRS resource based on sensing during a sensing window. The first type of SL-PRS resource may be a resource that is not multiplexed with other WTRUs. The second type of SL-PRS resource may be a resource that is multiplexed with other WTRUs. The WTRU may select available resources to include in a SL-PRS candidate resource set based on the priority associated with the SL-PRS transmission and the SL-PRS priority threshold. The SL-PRS candidate resource set may include at least the first type of SL-PRS resource or the second type of SL-PRS resource. The WTRU may select one or more SL-PRS resources from the SL-PRS candidate resource set. The WTRU may send a SL-PRS in the selected one or more SL-PRS resources. The WTRU may determine SL-PRS resources reserved by other WTRUs. Under the condition that the priority associated with the SL-PRS transmission is lower than the SL-PRS priority threshold, the WTRU may select available resources from both the first type of SL-PRS resources and the second type of SL-PRS resources. Under the condition that the priority associated with the SL-PRS transmission is higher than or equal to the SL-PRS priority threshold, the WTRU may select available resources from only the first type of SL-PRS resources. The first type of SL-PRS resources may be resources that are not multiplexed at the resource element (RE) level with other WTRUs. The second type of SL-PRS resources may be resources that are multiplexed at the resource element (RE) level with other WTRUs. The information triggering the SL-PRS transmission may be received from a higher layer in the WTRU. The information triggering the SL-PRS transmission may be received from a non-access stratum (NAS) layer. The WTRU may select available resources to include in the SL-PRS candidate resource set during a resource selection window (RSW). The WTRU may send sidelink control information (SCI) indicating SL-PRS information. The SL-PRS information may indicate a SL-PRS mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate like elements, and in which:

[0006] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0007] Figure 1B is an example of an embodiment in which Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within an illustrated communication system;

[0008] Figure 1C is an example of an embodiment in which Figure 1A A system diagram of an example Radio Access Network (RAN) and an example Core Network (CN) used within the illustrated communication system;

[0009] Figure 1D is an example of an embodiment in which Figure 1A A system diagram of another example RAN and another example CN used within the illustrated communication system;

[0010] Figure 2 An example of multiple consecutive PSSCH symbols for potential SL-PRS transmission is shown;

[0011] Figure 3 An example is shown of how a WTRU determines different types of available resources for SL-PRS transmission;

[0012] Figure 4 An example is shown where a WTRU prioritizes the selection of resources without multiplexing and without overlapping with other transmissions;

[0013] Figure 5 An example is shown in which a WTRU determines the availability of each SL-PRS pattern based on detection of a reservation pattern;

[0014] Figure 6 An example of a SL-PRS structure in a dedicated resource pool for SL-PRS is shown;

[0015] Figure 7 An example is shown where a WTRU fills the remaining symbols of a mini-slot used for SL-PRS;

[0016] Figure 8 An example of a WTRU (UE) triggering resource reselection upon detecting a change in an associated periodic SL-PRS procedure from a peer WTRU (UE) is shown;

[0017] Fig. 9 An example method for resource allocation in a dedicated resource pool for SL-PRS is shown;

[0018] Fig.10 An example method for resource allocation in a shared resource pool between SL-PRS and sidelink data is shown;

[0019] Fig.11 An example method for congestion control in a dedicated resource pool for SL-PRS is shown;

[0020] Fig.12 An example method for congestion control in a shared resource pool between SL-PRS and sidelink data communications is shown;

[0021] Fig.13 An example method for determining an SCI to indicate SL-PRS information is shown;

[0022] Fig.14 An example of sensing for determining a first type of SL-PRS resource and a second type of SL-PRS resource is shown; and

[0023] Fig.15 An example method for determining SL-PRS candidate resource sets based on priority is shown. DETAILED DESCRIPTION

[0024] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 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 discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0025] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood 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. For example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (STA)) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), consumer electronic devices, and devices operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0026] The communication system 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, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an evolved Node B (eNB), a Home Node B, a Home evolved Node B, a Next Generation Node B (such as a gNode B (gNB)), a New Radio (NR) Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0027] Base station 114a may be part of RAN 104, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), and relay nodes. Base station 114a and / or base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of a licensed spectrum and an unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, 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 send and / or receive signals in a desired spatial direction.

[0028] 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).

[0029] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology, such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), that may use Wideband CDMA (WCDMA) to establish the air interface 116. 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 ​​Uplink (UL) Packet Access (HSUPA).

[0030] 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) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology (such as NR radio access) that may establish the air interface 116 using NR.

[0032] 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 together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0033] 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), and GSM EDGE (GERAN).

[0034] Figure 1AThe base station 114b in may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in local areas such as commercial venues, homes, vehicles, campuses, industrial facilities, sky corridors (e.g., for use by drones), and roads. 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 cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, the base station 114 b may have a direct connection to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0035] The RAN 104 may be in communication with the CN 106, 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 different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the specification, the CN 106 may be 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. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0036] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides 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), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication 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 or a different RAT.

[0037] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication 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 via different wireless links). Figure 1A The illustrated WTRU 102c 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.

[0038] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, 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. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0039] 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 associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), state machine, etc. The processor 118 may perform signal decoding, 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. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0040] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from a base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV, or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0041] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, 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.

[0042] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0043] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an 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 a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a 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, and a secure digital (SD) memory card, among others. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0044] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control 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, etc.

[0045] 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 from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0046] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules 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 electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, frequency modulation (FM) radio units, digital music players, media players, video game player modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices and activity trackers, etc. The peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geographic location sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and a humidity sensor, etc.

[0047] 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 specific subframes for both UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via signal processing performed by hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via the processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0048] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0049] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-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 evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0050] Each of the evolved Node 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, and scheduling of users in the UL and / or DL, among other things. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0051] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0052] The MME 162 may be connected to each of the evolved Node-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, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. 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.

[0053] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an 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 the user plane during an inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0054] 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.

[0055] 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 be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts 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 other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0056] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0057] In a representative embodiment, the other network 112 may be a WLAN.

[0058] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and destined for the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and destined for a target outside the BSS may be transmitted to the AP to be delivered to the corresponding target. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the target STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the target STA (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0059] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may send beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense 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.

[0060] High throughput (HT) STAs may communicate using a 40 MHz wide channel (eg, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels) to form a 40 MHz wide channel.

[0061] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and the data can be sent by sending STA. At the receiver of the receiving STA, the above-mentioned operation for 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0062] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0063] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum 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 (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) a 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (which only supports a 1MHz operating mode) is transmitting to the AP, all available bands may be considered busy even if most of the available bands remain idle.

[0064] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0065] Figure 1D1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0066] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 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, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send 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, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or the gNB 180c).

[0067] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, 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 the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0068] 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 a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeB 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0069] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b and routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0070] Figure 1DThe illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although the aforementioned elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0071] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, and mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 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, and services for MTC access. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 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.

[0072] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy implementation and QoS, and providing DL data notifications. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0073] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the 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 DL packets, and providing mobility anchoring, etc.

[0074] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts 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 other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b via the UPFs 184a, 184b via the N3 interfaces to the UPFs 184a, 184b and the N6 interfaces between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0075] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following items may be performed by one or more simulation devices (not shown): WTRU102a to 102d, base station 114a to 114b, evolved Node B 160a to 160c, MME 162, SGW 164, PGW 166, gNB180a to 180c, AMF 182a to 182b, UPF 184a to 184b, SMF 183a to 183b, DN 185a to 185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device can be used to test other devices and / or simulate network and / or WTRU functions.

[0076] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions 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. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. A simulation device may be directly coupled to another device for the purpose of testing and / or performing tests using over-the-air wireless communications.

[0077] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0078] Each sidelink transmission spans one time slot, which includes a physical sidelink shared channel (PSSCH) and a physical sidelink control channel (PSCCH). PSSCH and PSCCH are frequency division multiplexed (FDM) and time division multiplexed (TDM). Sidelink control information (SCI) is divided into two parts, which are the first stage SCI and the second stage SCI. The first stage SCI indicates the resources used for sidelink transmission, the QoS of the transmission (e.g., priority), the demodulation reference signal (DMRS), the phase tracking reference signal (PTRS) for sidelink transmission, and the second SCI format. The second stage SCI indicates the remaining control information. SCI can be used to reserve resources for future transmissions within a resource pool.

[0079] From the perspective of sidelink scheduling, sidelink resources may be scheduled by the network (i.e., Mode 1) or selected autonomously by the WTRU (i.e., Mode 2). If the WTRU performs Mode 2, it may perform sensing by decoding the SCI from other WTRUs before selecting sidelink resources to avoid selecting resources reserved by other WTRUs. For WTRU autonomous resource allocation (i.e., Mode 2), it is specified how the WTRU performs sensing and performs resource selection for sidelink data communication. For example, the WTRU is (pre) configured with a resource pool for sensing and resource allocation. The WTRU performs sensing during the sensing window to detect transmissions and resource reservations from other WTRUs (e.g., via SCI decoding). Then, when data arrives, the WTRU triggers resource selection to select resources for its transmission. The WTRU selects a resource selection window (RSW) based on a packet delay budget (PDB). In the RSW, the WTRU first determines which resources are reserved by another WTRU and excludes them from a set of optional resources. The WTRU may select resources from a set of optional resources for transmission in the RSW. The WTRU may select resources for periodic transmissions and aperiodic transmissions.

[0080] Sidelink Channel State Information Reference Signal (SL-CSI-RS) is supported for unicast communications to support the transmitting WTRU in determining transmission parameters (e.g., power and rank). The transmitting WTRU may indicate the presence of SL-CSI-RS by using SCI. CSI-RS transmission may trigger CSI reporting. CSI reporting latency may be configurable via, for example, PC5 RRC. Each report is associated with one SL-CSI-RS transmission.

[0081] Congestion control is designed to help the network manage the use of resource pools to ensure appropriate resource usage by different WTRUs. Two parameters are defined for congestion control: Channel Busy Rate (CBR) and Channel Occupancy Rate (CR). CBR indicates the ratio between the number of busy subchannels and the total number of subchannels over a period of time. CR indicates the amount of resources used by the WTRU over a period of time.

[0082] For congestion control, the following parameters are controlled based on the congestion level of the resource pool: transmit power, bandwidth, modulation and coding scheme (MCS); the number of transmissions for one transport block (TB), and CR.

[0083] NR Uu positioning specifies a downlink (DL)-based positioning method, an uplink (UL)-based positioning method, and a DL+UL-based positioning method.

[0084] In the DL-based positioning method, a DL-positioning reference signal (PRS) may be transmitted to the WTRU from multiple transmit and receive points (TRPs). The WTRU may observe the measured downlink signals from the TRPs. The WTRU may be (pre)configured to perform a WTRU-based positioning method (WTRU-B) and / or a WTRU-assisted positioning method (WTRU-A). For the WTRU-B method, the WTRU may calculate or determine its positioning, and for the WTRU-A method, the WTRU may return downlink measurement results to the network. For the angle-based method, the WTRU may report the angle of arrival (AoA) and reference signal received power (RSRP) of the downlink signal from the TRP. For the timing-based method, the WTRU may report the reference signal time difference (RSTD). The above methods require transmission timing synchronization between the TRPs. Positioning calculation errors mainly come from synchronization errors and multipath.

[0085] In the UL-based positioning method, the WTRU may transmit the UL-PRS configured by RRC to the TRP for positioning. The network may then calculate the positioning of the WTRU based on the coordination of all TRPs that receive the UL-PRS from the WTRU.

[0086] In the UL and DL based methods, the WTRU may measure the Rx-Tx time difference between the received DL-PRS and the transmitted UL-PRS. The Rx-Tx time difference and RSRP are reported to the network. The network may then coordinate the TRP to calculate the WTRU's positioning.

[0087] Examples of sidelink SL positioning methods include timing / angle positioning methods and round-trip time (RTT) positioning methods.

[0088] A timing / angle positioning method may refer to any positioning method that uses a reference signal such as a SL-PRS. The WTRU may receive multiple reference signals from the WTRU and measure, for example, RSTD, RSRP, and / or AoA. Examples of timing / angle positioning methods are SL Angle of Departure (AoD) positioning or SL Time Distance of Arrival (TDOA) positioning. In an example, the WTRU may send a SL-PRS to the WTRU, and the receiver performs measurements (e.g., RSTD, AoA, RSRP) to determine the location of the WTRU that has sent the SL-PRS.

[0089] The RTT positioning method may refer to any positioning method that requires two WTRUs to send SL-PRS to each other. In an example, the anchor WTRU may send the SL-PRS to the target WTRU. Once the target WTRU receives the SL-PRS from the anchor WTRU, the target WTRU may send the SL-PRS to the anchor WTRU. The target WTRU may measure the WTRU Tx-Rx time difference, which is the difference between the transmission time of the SL-PRS from the target WTRU and the reception time of the SL-PRS sent from the anchor WTRU. The target WTRU may report the WTRU Tx-Rx time difference to the anchor WTRU.

[0090] The absolute positioning of the WTRU may be expressed in terms of a geographic coordinate system (GCS) or a local coordinate system (LCS).

[0091] The relative positioning of the target WTRU may be expressed in terms of distance and / or angle to another WTRU (eg, an anchor WTRU) and / or a reference point with a known location.

[0092] The SL-PRS configuration may include at least one of the following: SL-PRS resource identification (ID); SL-PRS sequence ID, or other ID used to generate SL-PRS sequence; SL-PRS resource element offset; SL-PRS resource slot offset; SL-PRS symbol offset; SL-PRS quasi-colocation (QCL) information; SL-PRS resource set ID; a list of SL-PRS resources in a resource set; the number of SL-PRS symbols; a muting mode, muting parameters (such as repetition factor), and muting options for SL-PRS; SL-PRS resource power; the periodicity of SL-PRS transmission; spatial direction information of SL-PRS transmission (e.g., beam information, transmission angle); spatial direction information of SL-RS reception (e.g., beam ID, arrival angle for receiving SL-RS); frequency layer ID; WTRU ID; or SL-PRS ID.

[0093] For sidelink positioning, the Sidelink Positioning Reference Signal (SL-PRS) intended for determining the position of the WTRU in the sidelink may use a shared resource pool with normal sidelink data or a dedicated resource pool used only for reference signal transmission.

[0094] In positioning, the QoS (e.g., priority, accuracy, latency, availability, and reliability) of the positioning service for positioning depends on the quality of SL-PRS transmission / reception, which may be very different from the QoS of normal data transmission. It is expected that different QoS parameters may require different SL-PRS transmission / reception characteristics. For resource allocation, in a shared resource pool, it is necessary to design a resource allocation scheme taking into account the tolerance of different collision levels between SL-PRS and data to reduce the collision between different SL-PRS and between SL-PRS and normal data. In a dedicated resource pool, a resource allocation scheme for mitigating the collision between SL-PRS transmissions needs to be considered. Finally, if many WTRUs are using SL-PRS, congestion may occur, so a method for controlling congestion in a resource pool needs to be considered. It is necessary to determine how the WTRU performs resource allocation and congestion control for SL-PRS in a shared resource pool and a dedicated resource pool.

[0095] In an embodiment, consider resource allocation (RA) in a dedicated resource pool. A WTRU (e.g., a target WTRU) may determine which set of available resources to select for SL-PRS transmission based on the number of available resources in each set. A WTRU (e.g., a target WTRU) may perform the following process for resource allocation in a dedicated resource pool for SL-PRS. The WTRU may be (pre)configured with a dedicated resource pool for SL-PRS transmission. The WTRU may be (pre)configured with a threshold X% of resources of a first type and a threshold Y% of resources of a second type to perform SL-PRS selection, respectively, where X% and Y% are functions of the QoS (e.g., priority, accuracy, latency, availability, and / or reliability) of the positioning service. For example, a first set of resources may include a set of time slots for SL-PRS transmission, and a second set of resources may include a set of SL-PRS patterns for SL-PRS transmission. The WTRU may receive QoS information for the positioning service and the SL-PRS pattern to be selected from another node (e.g., an anchor WTRU). The WTRU may determine the values ​​of X and Y based on the QoS received from the other node. The WTRU may perform sensing by decoding the SCI to determine a first set and a second set of available resources. The WTRU may perform the following operations to select SL-PRS resources for transmission: if the first set of resources is greater than X%, the WTRU may select SL-PRS resources from the first set, otherwise, if the second set of resources is greater than Y%, the WTRU may select SL-PRS resources from the second set. If the SL-PRS resources are selected, the WTRU may send the SL-PRS in the selected set of resources. Otherwise, the WTRU may request other nodes (e.g., an anchor WTRU) to change the SL-PRS pattern.

[0096] In an embodiment, consider RA in a shared resource pool. The WTRU may determine which RSRP threshold to apply to determine the availability of each reserved resource based on whether the resource is reserved for normal data communication or SL-PRS. In the case where the number of available resources is less than the threshold, the WTRU may request another WTRU to change the SL-PRS mode. The WTRU (e.g., the target WTRU) may perform the following process for resource allocation in a shared resource pool between SL-PRS and sidelink communication. The WTRU may be (pre) configured with a shared resource pool for SL-PRS and data communication and a threshold X% of available resources for SL-PRS selection. The WTRU may be (pre) configured with two sets of SD-RSRP thresholds. One set of RSRP thresholds may be applied to SL-PRS resources, and another set of RSRP thresholds may be applied to data transmission. The WTRU may receive QoS information for positioning services and the SL-PRS mode to be selected from another node (e.g., an anchor WTRU). The WTRU may perform sensing by decoding the SCI for reserved transmission resources from other WTRUs. For each reserved resource, the WTRU may determine whether the reserved resource is for SL-PRS or for normal data communication. The WTRU may determine a set of available resources for SL-PRS transmission using a first set of RSRP thresholds and a second set of RSRP thresholds, wherein the WTRU may apply the first set of thresholds to resources associated with SL-PRS and the WTRU may apply the second set of thresholds to resources associated with data communication. The WTRU may perform the following operations for SL-PRS selection: if the number of available resources is greater than X%, the WTRU may select resources for SL-PRS using a subset of the available resources and indicate in the SCI that the resources are reserved for SL-PRS transmission, otherwise, the WTRU may request other nodes (e.g., an anchor WTRU) to change the SL-PRS mode or switch to another resource pool for SL-PRS selection.

[0097] In an embodiment, congestion control in a dedicated resource pool is considered. The WTRU may determine a first set of transmission (Tx) parameters for the SL-PRS based on a first QoS parameter for a positioning service, and determine a second set of Tx parameters for the SL-PRS based on a second QoS parameter. The WTRU may perform the following process for congestion control in a dedicated resource pool for the SL-PRS. The WTRU may be (pre)configured with a dedicated resource pool for the SL-PRS. The WTRU may be (pre)configured with two sets of Tx parameter thresholds based on CBR, wherein the first set is associated with a first positioning QoS parameter and the second set is associated with a second positioning QoS parameter. For example, the maximum bandwidth may be a function of the accuracy / priority requirement, and the number of SL-PRS transmissions within a period may be a function of the latency requirement. The WTRU may determine the Tx parameters based on the QoS value, the CBR, and the associated Tx parameter thresholds. The WTRU may perform SL-PRS transmission based on the determined transmission parameters.

[0098] In an embodiment, congestion control in a shared resource pool is considered. The WTRU may determine which set of Tx parameters to use based on whether the SL-PRS is multiplexed with data. The WRU may use both a first set of Tx parameters for an independent SL-PRS and a first set of parameters and a second set of parameters for multiplexing the SL-PRS with data. The WTRU may perform the following process for congestion control in a shared resource pool between the SL-PRS and the sidelink communication. The WTRU may be (pre) configured with a shared resource pool for SL-PRS and data communication. The WTRU may be (pre) configured with two sets of Tx parameters according to CBR, wherein the first set may be used for SL-PRS transmission (e.g., Tx power, bandwidth, CR limit for SL-PRS, comb N, number of symbols, etc.), and the second set may be used for data transmission. The WTRU may determine the Tx parameters for the SL-PRS based on whether the SL-PRS is an independent SL-PRS or a SL-PRS multiplexed with sidelink data. For an independent SL-PRS, the WTRU may apply a first set of Tx parameters. For SL-PRS multiplexed with sidelink data, the WTRU may determine Tx parameters based on both the first set of Tx parameter thresholds and the second set of Tx parameter thresholds (e.g., each Tx parameter needs to meet a threshold in the first set or the second set). The WTRU may perform SL-PRS transmission based on the determined transmission parameters.

[0099] The WTRU may determine the signal to use for the SL-PRS. The WTRU may use one or any of the following reference signals as the SL-PRS: DMRS of PSSCH and / or PSCCH; Sidelink Synchronization Signal (SLSS) (e.g., Sidelink Primary Synchronization Signal (S-PSS), Sidelink Secondary Synchronization Signal (S-SSS)), Phase Tracking Reference Signal (PTRS); SL-CSI-RS; Physical Sidelink Feedback Channel (PSFCH); or a new reference signal (RS) designed for positioning purposes.

[0100] In an embodiment, the WTRU may determine the QoS of the positioning service. The QoS of the positioning service may be used to determine one or more of the following: priority, accuracy, latency, reliability, minimum communication range (MCR), and / or positioning availability requirements of the positioning service. The QoS of the positioning service may be determined based on one or any combination of the following:

[0101] The QoS of the positioning service may be determined based on a (pre)configuration in the resource pool and / or the WTRU. For example, in a shared resource pool between the SL-PRS and the sidelink data communication, the WTRU may be (pre)configured with a priority associated with the SL-PRS transmission. The WTRU may indicate the (pre)configured priority of the sidelink positioning service in one or more transmissions associated with the SL-PRS transmission.

[0102] The QoS of the positioning service may be determined based on one or more parameters of the SL-PRS transmission and / or reception. For example, the WTRU may determine the QoS (e.g., accuracy / priority) of the positioning service based on the bandwidth of the SL-PRS. For example, the WTRU may be (pre)configured with one or more QoS levels of the positioning service. Each QoS level may be associated with a bandwidth of the SL-PRS. The WTRU may determine the QoS of the positioning service based on the bandwidth of the SL-PRS transmission / reception.

[0103] The QoS of the positioning service may be determined based on the SL-PRS reception requirements (e.g., minimum received SL-RSRP or maximum received timing error). For example, the WTRU may determine one or more QoS (e.g., accuracy / priority) of the positioning service based on the SL-RSRP reception requirements of the SL-PRS. For example, the WTRU may be (pre)configured with one or more QoS levels of the positioning service, where each QoS level may be associated with a SL-RSRP reception level of the SL-PRS. The WTRU may determine the QoS of the positioning service based on the required SL-PRSP level of the SL-PRS.

[0104] The QoS of the positioning service may be determined based on an implicit / explicit indication from another node (e.g., another WTRU or a gNB). For example, the WTRU may implicitly / explicitly receive one or more QoS parameters for the positioning service from another WTRU or a gNB. The WTRU may receive one or more QoS parameters based on receiving the SL-PRS configuration (e.g., priority, bandwidth, comb size, number of repetitions, periodicity) and the SL-PRS measurement report configuration (e.g., priority, periodicity, latency).

[0105] The QoS of the positioning service may be determined based on one or more parameters of the DL-PRS reception and / or UL-PRS transmission that are (pre)configured or communicated to the WTRU. For example, for hybrid sidelink and Uu positioning, the WTRU may determine the QoS (e.g., accuracy / priority) of the positioning service based on the bandwidth of the UL-PRS and / or DL-PRS. For example, the WTRU may be (pre)configured with one or more QoS levels of the positioning service. Each QoS level may be associated with a bandwidth of the UL-PRS and / or DL-PRS. The WTRU may determine the QoS of the positioning service based on the bandwidth of the SL-PRS transmission / reception.

[0106] The QoS of the positioning service may be determined based on one or more parameters (eg, priority, latency, periodicity) of the SL-PRS measurement report.

[0107] The QoS of the positioning service may be determined based on one or more parameters (eg, priority, latency, periodicity) for DL-PRS measurement reporting.

[0108] The QoS of the positioning service may be determined based on the positioning method. For example, the WTRU may be (pre)configured with one or more QoS parameters associated with the positioning method. For example, the WTRU may be (pre)configured with a priority associated with each positioning method.

[0109] The WTRU may determine the priority of the SL-PRS based on the broadcast type of the SL-PRS. In an embodiment, the WTRU may determine the priority of the SL-PRS based on the broadcast type (e.g., unicast, groupcast, or broadcast) associated with the SL-PRS. In an example, the WTRU may be (pre)configured with three priorities, each of which may be associated with a broadcast type. The WTRU may determine the priority of the SL-PRS based on the broadcast type of the SL-PRS. In an example, the WTRU may be (pre)configured with different priority offsets, and each priority offset may be associated with a broadcast type of the SL-PRS. The WTRU may determine the priority of the SL-PRS based on other factors (e.g., accuracy, latency, etc.) and the broadcast type of the SL-PRS.

[0110] The WTRU may prioritize SL-PRS of different broadcast types. In an embodiment, the WTRU may need to prioritize the transmission and / or reception of SL-PRS of different broadcast types. The WTRU may determine which SL-PRS to prioritize based on the (pre)configured priority broadcast type of the SL-PRS. For example, the WTRU may prioritize the broadcast SL-PRS first. The WTRU may then prioritize the multicast SL-PRS, and finally the unicast SL-PRS may not be prioritized.

[0111] The WTRU may indicate in its transmissions QoS parameters for the sidelink positioning service. The WTRU may indicate in one or more of its transmissions one or any combination of QoS parameters for the sidelink positioning service. For example, the WTRU may indicate one or more parameters of the QoS for the positioning service in the SCI sent in association with the SL-PRS.

[0112] The WTRU may determine a resource pool for SL-PRS transmission. In an embodiment, the WTRU may be (pre)configured with one or any combination of the following resource pools for SL-PRS transmission: a dedicated resource pool for SL-PRS transmission; a dedicated resource pool for transmission and / or reception of SL-PRS configuration; a shared resource pool for SL-PRS and sidelink communication; and a dedicated resource pool for sidelink positioning transmission, which dedicated resource pool may include one or more of the following: SL-PRS transmission, HARQ feedback for SL-PRS transmission, sidelink positioning assistance information, and sidelink positioning measurement reports.

[0113] The WTRU may determine which resource pool to use for SL-PRS transmission based on one or any combination of the following.

[0114] The WTRU may determine which resource pool to use for SL-PRS transmission based on whether a dedicated resource pool for SL-PRS or sidelink positioning is (pre)configured. For example, if a dedicated resource pool is (pre)configured, the WTRU may prioritize the dedicated resource pool for SL-PRS or sidelink positioning. Otherwise, if no dedicated resource pool is configured, the WTRU may select a shared resource pool for SL-PRS transmission.

[0115] The WTRU may determine which resource pool to use for SL-PRS transmission based on the QoS of the positioning service (e.g., priority, accuracy, latency and / or positioning availability). For example, the WTRU may determine which resource pool to use based on the QoS of the resource pool. For example, if the accuracy / priority requirement of the positioning service is greater than a threshold, the WTRU may determine to use a dedicated resource pool for SL-PRS or sidelink positioning. Otherwise, if the accuracy / priority requirement of the positioning service is less than the threshold, the WTRU may use a shared resource pool with sidelink data communication. In an example, the WTRU may be (pre)configured with a certain QoS (e.g., a certain accuracy / priority requirement) to use one resource pool for SL-PRS (e.g., a dedicated resource pool for SL-PRS). Then, if the QoS required by the WTRU meets the (pre)configured QoS threshold, the WTRU may use the resource pool for SL-PRS transmission (e.g., a dedicated resource pool). Otherwise, the WTRU may use another resource pool for SL-PRS transmission (e.g., a shared resource pool).

[0116] The WTRU may determine which resource pool to use for SL-PRS transmission based on the SL-PRS transmission mode. For example, the WTRU may determine the SL-PRS transmission mode. The WTRU may determine which type of resource pool to use for the selected SL-PRS transmission mode based on whether the SL-PRS mode is supported in the resource pool. The WTRU may determine to use a first type of resource pool (e.g., a dedicated resource pool) for a first SL-PRS mode. The WTRU may determine to use a second type of resource pool for a second SL-PRS mode.

[0117] The WTRU may determine which resource pool to use for SL-PRS transmission based on the type of SL-PRS transmission. For example, the WTRU may use a first type of resource pool (e.g., a dedicated resource pool) for periodic SL-PRS transmission. The WTRU may use a second type of resource pool (e.g., a shared resource pool) for aperiodic SL-PRS transmission.

[0118] The WTRU may determine which resource pool to use for SL-PRS transmission based on the sidelink conditions between the WTRU and one or more receiver WTRUs. The sidelink conditions between the transmitter WTRU and the receiver WTRU may be determined based on one or any combination of the distance between the two WTRUs and the channel conditions (e.g., SL-RSRP measured in the SL-PRS and / or data communication between the two WTRUs, the path loss of the channel between the two WTRUs). For example, if the distance between the two WTRUs (e.g., which may be determined based on the area ID of the Tx WTRU and / or the Rx WTRU) is greater than a threshold, the WTRU may use one resource pool (e.g., a dedicated resource pool for SL-PRS or sidelink positioning). Otherwise, if, for example, the distance between the two WTRUs is less than the threshold, the WTRU may use another resource pool (e.g., a shared resource pool). The distance threshold may be (pre)configured in the resource pool and / or indicated to the WTRU from another node (e.g., a gNB or another WTRU). The distance threshold may be (pre)configured based on the QoS of the positioning service (e.g., the accuracy / priority requirements of the positioning service). For example, if the SL-RSRP for data communication between two WTRUs is less than a threshold, the WTRU may use one resource pool (e.g., a dedicated resource pool). Otherwise, the WTRU may use another resource pool (e.g., a shared resource pool). The SL-RSRP threshold may be (pre)configured in the resource pool and / or indicated to the WTRU from another node (e.g., a gNB or another WTRU). The SL-RSRP threshold may be (pre)configured based on the QoS of the positioning service (e.g., the accuracy / priority requirements of the positioning service).

[0119] The WTRU may determine which resource pool to use for SL-PRS transmission based on one or more parameters (pre)configured in the resource pool. The parameters (pre)configured in the resource pool may be one or more of the following: maximum and / or minimum bandwidth for SL-PRS, parameters for open loop power control (OLPC), closed loop power control (CLPC) transmission power (e.g., maximum power, whether SL or DL ​​path loss compensation is (pre)configured and associated values ​​of α and P0), a set of allowable SL-PRS patterns, channel occupancy for SL-PRS transmission, sidelink positioning and / or sidelink data communication, priority of SL-PRS in a shared resource pool, maximum number of WTRUs in a group for sidelink positioning (e.g., which may be explicitly (pre)configured or may be implicitly determined based on the amount of resources or feedback resources (pre)configured in the resource pool), and / or CBR thresholds in the resource pool. In an example, the WTRU may prioritize resource pools with higher bandwidth for SL-PRS transmission. In an example, the WTRU may prioritize resource pools that allow higher channel occupancy for SL-PRS transmission or sidelink positioning. In an example, the WTRU may prioritize resource pools without OLPC. In an example, the WTRU may prioritize resource pools that allow denser comb patterns for SL-PRS. In an example, the WTRU may prioritize resource pools that support a higher number of WTRUs in a group. In an example, the WTRU may prioritize resource pools that allow denser SL-PRS patterns. In an example, the WTRU may prioritize resource pools that allow comb 1 SL-PRS, where the SL-PRS is in all resource elements (REs) of a symbol.

[0120] The WTRU may determine which resource pool to use for SL-PRS transmission based on the sidelink positioning method. For example, the WTRU may determine to select a shared resource pool for a group of positioning methods (e.g., positioning methods that do not require transmission coordination between multiple WTRUs, such as RTT, AoA, AoD). The WTRU may determine to select a dedicated resource pool for another group of positioning methods (e.g., positioning methods that require coordination between multiple Tx WTRUs, such as TDOA, sidelink carrier phase positioning).

[0121] The WTRU may determine which resource pool to use for SL-PRS transmission based on the amount of required side link resources in the period. For example, if the amount of required resources is less than a (pre-)configured threshold, the WTRU may select a resource pool of a first type, and if the amount of required resources is greater than the threshold, the WTRU may select a resource pool of a second type. The threshold for the amount of resources may be (pre-)configured per resource pool.

[0122] The WTRU may determine which resource pool to use for SL-PRS transmission based on the number of WTRUs in the positioning group. For example, if the number of WTRUs in the sidelink positioning group is greater than a threshold, the WTRU may select a resource pool or a type of resource pool (e.g., a dedicated resource pool). Otherwise, the WTRU may select another resource pool or another type of resource pool (e.g., a shared resource pool). The threshold for the number of WTRUs in the group may be (pre)configured per resource pool.

[0123] The WTRU may determine which resource pool to use for SL-PRS transmission based on the CBR of the resource pools. For example, the WTRU may prioritize resource pools with lower CBR.

[0124] The WTRU may determine which resource pool to use for SL-PRS transmission based on an indication from another node. For example, the WTRU may receive an indication from another node (e.g., an anchor WTRU or a gNB) of which resource pool will perform SL-PRS transmission. The WTRU may select the indicated resource pool from the other node.

[0125] The WTRU may switch resource pools used for transmission of SL-PRS. In an embodiment, the WTRU may use one resource pool for SL-PRS transmission. For one resource selection for SL-PRS, the WTRU may determine whether to keep the same resource pool or select another resource pool. The decision may be based on one or any combination of the following: the CBR of the resource pool, the channel occupancy (CR) of the WTRU's SL-PRS transmission in the resource pool, an implicit / explicit indication from another WTRU, and the sidelink positioning measurement report status from another WTRU.

[0126] The decision on whether to keep the same resource pool or select another resource pool may be based on the CBR of the resource pool. For example, if the CBR of the resource pool is greater than a threshold, the WTRU may switch to another resource pool. If the CBR of the resource pool is less than the threshold, the WTRU may use the same resource pool for SL-PRS transmission.

[0127] The decision on whether to keep the same resource pool or select another resource pool may be based on the channel occupancy (CR) of the SL-PRS transmission of the WTRU in the resource pool. For example, if the CR of the SL-PRS of the WTRU in the resource pool is greater than a threshold, the WTRU may switch to another resource pool. For example, the WTRU may be (pre-)configured with a maximum CR for the SL-PRS. If the WTRU reaches the maximum allowed CR for the SL-PRS, the WTRU may switch to another resource pool.

[0128] The decision on whether to keep the same resource pool or select another resource pool may be based on an implicit / explicit indication from another WTRU. For example, the WTRU may receive an indication from another WTRU (e.g., an anchor WTRU or a target WTRU) to switch to a different resource pool. The WTRU may switch to another resource upon receiving the indication.

[0129] The decision on whether to keep the same resource pool or select another resource pool may be based on the sidelink positioning measurement report status from another WTRU.For example, the WTRU may determine to switch to another resource pool based on the sidelink positioning measurement report status from another WTRU.

[0130] For example, if the measured report does not meet the condition (e.g., SL-RSRP is less than a threshold or the error of the timing measurement is greater than a threshold), the WTRU may switch to another resource pool. The SL-RSRP threshold and / or the timing measurement threshold may be based on the QoS of the positioning service. If the WTRU does not receive a measurement report from another WTRU (e.g., an anchor WTRU or a target WTRU) within a period, the WTRU may switch to another resource pool.

[0131] The WTRU may determine the granularity of the selected resources for SL-PRS transmission. In an example, the WTRU may perform resource allocation for one or more SL-PRS transmissions. The WTRU may determine the availability of each resource in the resource selection window. The WTRU may determine the granularity of each resource to determine its availability. The granularity of each resource in the time domain may be one or any combination of RE level, SL-PRS duration level, or timeslot level.

[0132] The granularity of each resource in the time domain may be at the RE level. For example, the WTRU may select a SL-PRS pattern to transmit and may determine the availability of each RE in the SL-PRS pattern. For example, the WTRU may determine whether there are any WTRUs that have reserved resources (e.g., SL-PRS resources) that conflict with one or more REs of its selected SL-PRS pattern.

[0133] The granularity of each resource in the time domain may be at the SL-PRS duration level. For example, the WTRU may be (pre)configured with multiple time domain SL-PRS resources in a time slot. The WTRU may determine the availability of each SL-PRS resource in the time domain.

[0134] The granularity of each resource in the time domain may be at the time slot level. For example, in the time domain, the WTRU may determine the availability of each time slot. The WTRU may determine whether there are any WTRUs that have reserved resources (e.g., for SL-PRS transmission) in the time slot. If there are no WTRUs that have reserved conflicting resources in the time slot (e.g., there are no WTRUs that have reserved resources in the time slot and the measured SL-RSRP is greater than a threshold), the WTRU may determine the time slot as available.

[0135] The WTRU may determine the availability of resources in the frequency domain. The WTRU may determine the granularity of each resource to determine its availability in the frequency domain. The granularity of each resource in the frequency domain may be one or any combination of the following: RE level, subchannel level, and resource pool bandwidth level.

[0136] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on one or any combination of the following.

[0137] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the (pre)configuration in the resource pool.

[0138] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on implicit / explicit indications from another node (e.g., another WTRU, a gNB, or an LMF).

[0139] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the QoS requirement of the positioning service. For example, if the QoS (e.g., accuracy requirement) of the positioning service is greater than a threshold, the WTRU may determine the slot level resource availability granularity, otherwise, if the QoS (e.g., accuracy requirement) of the positioning service is less than the threshold, the WTRU may determine the RE level granularity.

[0140] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the CBR of the resource pool. For example, if the CBR of the resource pool is less than a threshold, the WTRU may determine the slot level resource availability granularity, otherwise, if the CBR of the resource pool is greater than a threshold, the WTRU may use the SL-PRS duration level granularity. Alternatively, if the CBR of the resource pool is greater than another threshold, the WTRU may use the RE level resource granularity.

[0141] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the WTRU's CR sidelink transmission and / or SL-PRS transmission.

[0142] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the bandwidth determined to be used for SL-PRS transmission. For example, if the determined bandwidth of the SL-PRS is greater than a threshold, the WTRU may use RE level resource granularity, otherwise, if the determined bandwidth is less than the threshold, the WTRU may use slot level resource granularity.

[0143] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the number of symbols used for associated control signaling, AGC, and / or TX / RX switching symbols. For example, if the number of symbols used for associated control signaling, AGC (automatic gain control), SL-PRS, and / or Tx / Rx switching is greater than a threshold, the WTRU may use slot level resource granularity. Otherwise, if the number of associated control signaling, AGC, SL-PRS, and / or Tx / Rx switching is less than the threshold, the WTRU may use mini-slot level (e.g., SL-PRS resource level) resource granularity.

[0144] The WTRU may determine the granularity of the selected resources for SL-PRS transmission based on the ratio of available candidate resources within the RSW. For example, when the ratio is below a (pre)configured threshold, the WTRU may use different types of resources to perform resource selection. For example, the WTRU may switch from using type 1 resources to using type 2 resources in resource selection.

[0145] The WTRU may determine SL-PRS transmission parameters. In an example, the WTRU may perform SL-PRS transmission. The WTRU may determine one or more SL-PRS transmission parameters, which may include one or any combination of the following parameters.

[0146] The one or more SL-PRS transmission parameters may include parameters of the SL-PRS resource, which may include one or any combination of the following parameters: QoS associated with the SL-PRS resource, transmit power, the number of subchannels used for each SL-PRS resource, the number of symbols and / or time slots used for each SL-PRS transmission resource, a reference resource pattern (e.g., comb tooth size, RE offset and / or comb pattern), sequence ID, cyclic shift and / or time / frequency resource for SL-PRS transmission.

[0147] The one or more SL-PRS transmission parameters may include the number of SL-PRS resource repetitions / retransmissions in a period.

[0148] The one or more SL-PRS transmission parameters may include the type of SL-PRS transmission. For example, the WTRU may determine whether the SL-PRS transmission is periodic, aperiodic, or semi-persistent.

[0149] The one or more SL-PRS transmission parameters may include the periodicity of the SL-PRS process. For example, the WTRU may determine to perform periodic or semi-persistent SL-PRS transmission. The WTRU may then determine the periodicity of the SL-PRS transmission.

[0150] The one or more SL-PRS transmission parameters may include the number of periods used for a SL-PRS process, sidelink positioning session, and / or window. For example, the WTRU may determine the number of periods used to send the SL-PRS. The number of periods used for SL-PRS transmission and / or the number of remaining periods may be indicated in the associated transmission of the SL-PRS (e.g., in the SCI associated with the SL-PRS).

[0151] The WTRU may determine the selectivity of a resource. In an embodiment, the WTRU may perform resource selection in a resource pool, thereby allowing resources to be shared between multiple types of transmissions (e.g., sharing between SL-PRS and sidelink data). The WTRU may perform sensing in a sensing window to detect resource reservations for resources in a resource selection window. The WTRU may determine whether a reserved resource in a resource selection window is selectable. If the WTRU determines that a reserved resource is selectable, the WTRU may include the reserved resource from a set of selectable resources, and the WTRU may select the resource for its transmission. Otherwise, if the WTRU determines that the reserved resource is not selectable, the WTRU may exclude the reserved resource from the set of selectable resources, and the WTRU may not select the reserved resource for its transmission. The selectivity of the reserved resource may be determined based on whether the reserved resource is for a first type of transmission (e.g., SL-PRS) or a second type of transmission (e.g., normal sidelink data) and / or the SL-RSRP measured in the reserved transmission. The type of transmission in the reserved resource may be indicated in the SCI of the reserved transmission.

[0152] In an embodiment, the WTRU may be (pre)configured with two SL-RSRP thresholds to determine the selectability / availability of reserved resources, where a first SL-RSRP threshold may be used for a first type of reserved resources (e.g., for SL-PRS transmissions) and a second SL-RSRP threshold may be used for a second type of reserved resources (e.g., for sidelink data transmissions). If the resource is reserved for the first type of transmission, the WTRU may determine the reserved resource as selectable if the SL-RSRP is less than the first SL-RSRP threshold. If the resource is reserved for the second type of transmission, the WTRU may determine the resource as selectable if the SL-RSRP is less than the second SL-RSRP threshold. In another example, the WTRU may consider resources reserved by one type of resource (e.g., resources reserved for SL-PRS) as non-selectable without considering the SL-RSRP of the transmission for which the resource is reserved.

[0153] The WTRU may reserve resources for one type of sidelink transmission. In an embodiment, the WTRU may perform a sidelink transmission. The WTRU may reserve resources for a potential transmission. The WTRU may indicate (e.g., in a transmitted SCI) whether the reserved resources are for a first type of transmission (e.g., SL-PRS) or a second type of transmission (e.g., normal sidelink data).

[0154] The WTRU may indicate a priority of reserved resources for SL-PRS. In an embodiment, the WTRU may reserve resources for SL-PRS transmission. The WTRU may indicate (e.g., in an SCI of a reserved transmission) a QoS (e.g., priority) associated with the reserved resources for SL-PRS transmission. In a first example, the WTRU may be (pre)configured with a priority of SL-PRS. The WTRU may indicate the (pre)configured priority in a reserved transmission (e.g., in an SCI). In another example, the WTRU may indicate (e.g., a one-bit indicator in an SCI associated with a reserved transmission) that the reserved resources are available for one type of transmission (e.g., SL-PRS transmission).

[0155] The WTRU may indicate information about the SL-PRS resource. The WTRU may indicate information about the SL-PRS, which may be indicated in the associated transmitted SCI, MAC CE, PC5 and / or NAS (e.g., LPP, i.e., LTE positioning protocol). For example, the WTRU may indicate the time and frequency of the SL-PRS in the first SCI. The WTRU may indicate one or any combination of the following information in the associated transmitted first SCI, second SCI, MAC CE and / or PC5 RRC: SL-PRS mode (which may include SL-PRS mode index, time and frequency offset, comb size and / or number of SL-PRS symbols used for one SL-PRS resource) and the receiver of the SL-PRS (e.g., destination ID associated with the SL-PRS).

[0156] When the amount of available resources for SL-PRS transmission is small, the WTRU may take action. In an embodiment, if the amount of available resources for SL-PRS transmission in a resource pool (e.g., a shared resource pool or a dedicated resource pool) is less than a threshold that can be (pre)configured in the resource pool, the WTRU may perform one or any combination of the following.

[0157] The WTRU may perform the selection and transmission based on the current set of available resources. For example, if the number of available resources for SL-PRS is less than a threshold, the WTRU may select one or more resources for SL-PRS from the current set of available resources. The WTRU may determine whether to perform such a process based on the QoS of the sidelink positioning service. For example, if the QoS of the sidelink positioning service meets the condition (e.g., the latency of the positioning service is less than a threshold), the WTRU may perform such a process, otherwise, the WTRU may perform another process, such as indicating to another node, switching to another resource pool, and / or increasing the SL-RSRP threshold.

[0158] The WTRU may increase the SL-RSRP threshold. For example, the WTRU may determine whether to increase the SL-RSRP threshold based on one or more QoS of the sidelink positioning service in order to have more available resources for SL-PRS transmission. For example, if the latency of the positioning service is less than the threshold, the WTRU may increase the SL-RSRP threshold, otherwise, the WTRU may perform another process (e.g., transmit an indication to another node). In the case of low-latency positioning services, this method may be triggered to help the WTRU find sufficient available resources for SL-PRS transmission.

[0159] For example, if the accuracy / priority of the positioning service is less than a threshold, the WTRU may increase the SL-RSRP threshold, otherwise, the WTRU may not increase the SL-RSRP threshold. The WTRU may perform another process, such as switching resource pools, indicating to another node, and / or changing the SL-PRS pattern.

[0160] The WTRU may transmit an indication to another node (e.g., a gNB or another WTRU such as an anchor WTRU or a target WTRU). For example, the WTRU may transmit an indication to another node to implicitly / explicitly indicate that the amount of resources used for SL-PRS transmission is less than the threshold. The WTRU may transmit a request to change the SL-PRS mode.

[0161] The WTRU may change the SL-PRS pattern. For example, if the number of available resources for SL-PRS transmission is less than a threshold, the WTRU may change the SL-PRS pattern. For example, the WTRU may reduce the transmission bandwidth or increase the comb size (i.e., reduce the density of SL-PRS REs).

[0162] The WTRU may trigger a resource pool (re)selection. For example, if the amount of available resources for SL-PRS transmission is less than a threshold, the WTRU may reselect another resource pool (eg, switch to a dedicated resource pool).

[0163] The WTRU may determine whether to prioritize SL-PRS or data transmission in the side link resources.

[0164] In an example, the WTRU may have a sidelink resource for potential sidelink transmissions. The WTRU may determine whether to prioritize the SL-PRS, the sidelink data transmission, or both based on one or any combination of the following. The WTRU may determine whether to prioritize the SL-PRS, the sidelink data transmission, or both based on a priority associated with the SL-PRS and a priority associated with the data transmission. For example, the WTRU may prioritize transmissions with higher priorities. The WTRU may determine whether to prioritize the SL-PRS, the sidelink data transmission, or both based on the QoS requirements of the SL-PRS and the bandwidth of the sidelink data. For example, the WTRU may be (pre)configured with a minimum bandwidth for SL-PRS transmission, and if the bandwidth of the sidelink resource is less than the (pre)configured minimum bandwidth for the SL-PRS, the WTRU may determine not to transmit the SL-PRS in the sidelink resource, otherwise, the WTRU may consider transmitting the SL-PRS in the sidelink resource.

[0165] The WTRU may determine whether to embed the SL-PRS in the sidelink transmission.

[0166] In an example, in the sidelink resources, the WTRU may determine to prioritize the transmission of the sidelink data. The WTRU may determine whether to embed the SL-PRS in the sidelink resources based on one or any combination of the following. The WTRU may determine whether to embed the SL-PRS in the sidelink resources based on the destination associated with the SL-PRS and the sidelink data. For example, if the SL-PRS and the sidelink data are associated with the same destination (e.g., the same L2 destination ID), the WTRU may embed the SL-PRS with the sidelink data. For example, if the WTRU receiving the SL-PRS belongs to a receiver set for sidelink data, the WTRU may embed the SL-PRS with the sidelink data. The WTRU may determine whether to embed the SL-PRS in the sidelink resources based on the broadcast type associated with the SL-PRS and the sidelink data. For example, if the SL-PRS and the sidelink data are associated with a broadcast service, the WTRU may embed the SL-PRS with the sidelink data.

[0167] The WTRU may determine which SL-PRS to prioritize. In an example, in a sidelink resource, the WTRU may determine to send a sidelink data transmission. The WTRU may determine to prioritize SL-PRS transmissions associated with the same destination ID (e.g., L2 destination ID) of the sidelink data. In another example, in a sidelink resource, the WTRU may determine to prioritize SL-PRS transmissions. The WTRU may determine to construct a TB for sidelink data having the same destination ID associated with the prioritized SL-PRS.

[0168] The WTRU may determine a priority for sending a SL-PRS associated with sidelink data. In an embodiment, the WTRU may send the SL-PRS together with the sidelink data. The WTRU may determine a priority for sending based on the priorities of both the SL-PRS and the sidelink data. For example, the priority of sending (e.g., the priority indicated in the SCI) may be the highest priority of the SL-PRS and the sidelink data.

[0169] The WTRU may determine how to indicate in the SCI of the SL-PRS transmission. The WTRU may determine how to indicate the priority of the SL-PRS transmission in the SCI (e.g., the first SCI). In an example, the WTRU may indicate the (pre)configured priority (e.g., the highest priority) for each SL-PRS transmission in the SCI. If the priority of the SL-PRS transmission is greater than the (pre)configured priority to be indicated in the SCI, the WTRU may indicate the actual priority of the SL-PRS transmission. In an example, the WTRU may be (pre)configured with an offset of the priority to be indicated in the SCI. The WTRU may then calculate or determine the priority to be indicated in the SCI (e.g., the first SCI) based on the priority provided by the higher layer (e.g., the MAC layer) and the (pre)configured offset value. For example, the priority indicated in the SCI may be the priority provided by the higher layer minus the (pre)configured offset. The WTRU may indicate the priority indicated by the higher layer of the SL-PRS in another field of the first SCI, in the second SCI, and / or in the MAC CE.

[0170] The WTRU may be (pre)configured with a PSFCH opportunity to send a second SL-PRS in the RTT method. In an embodiment, the WTRU may use the PSFCH as a second SL-PRS transmission for the RTT positioning method. For example, the WTRU may be (pre)configured with a PSFCH resource (e.g., in the same timeslot as the PSFCH resource for sidelink data). The WTRU may also be (pre)configured with a mapping between PSCCH / PSSCH resources to send a first SL-PRS and an associated PSFCH for the SL-PRS. When a SL-PRS transmission is detected in a PSCCH / PSSCH resource, the WTRU may send the SL-PRS in the associated PSFCH.

[0171] The WTRU may indicate its first SL-PRS transmission and request the receiving WTRU to send a second SL-PRS in the PSFCH. The WTRU may indicate its first SL-PRS transmission in the PSCCH / PSSCH resources. The WTRU may implicitly and / or explicitly request the receiving WTRU to send a second SL-PRS in the associated PSFCH resources for the RTT positioning method. Such request / indication may be conveyed in the SCI and / or MAC CE of the associated SL-PRS transmission. In the PSCCH / PSSCH resources, the WTRU may send a standalone SL-PRS or send the SL-PRS with the sidelink data.

[0172] The WTRU may determine whether to send a PSSCH-DMRS for an independent SL-PRS. In an embodiment, the WTRU may determine whether to send an independent SL-PRS in a shared resource pool. The WTRU may send a PSSCH-DMRS in a time slot with a SL-PRS. The WTRU may determine whether to send a PSSCH-DMRS in a transmission based on one or any combination of the following (e.g., to support backward compatibility of R16 / 17 WTRUs in resource allocation). The WTRU may determine whether to send a PSSCH-DMRS in a transmission based on a (pre) configuration in a resource pool. For example, the WTRU may be (pre) configured in a resource pool whether to send a PSSCH-DMRS. The WTRU may determine whether to send a PSSCH-DMRS based on a resource pool configuration. The WTRU may determine whether to send a PSSCH-DMRS in a transmission based on a resource allocation pattern. For example, for mode 1, the WTRU may not send a PSSCH-DMRS, and for mode 2, the WTRU may send a PSSCH-DMRS. The WTRU may determine whether to send PSSCH-DMRS in the transmission based on whether PSSCH-DMRS or PSCCH-DMRS is (pre)configured for resource allocation in the resource pool. For example, if PSSCH-DMRS is (pre)configured for resource allocation, the WTRU may send PSSCH-DMRS. Alternatively, if PSCCH-DMRS is (pre)configured for resource allocation, the WTRU may not send PSSCH-DMRS in a standalone SL-PRS.

[0173] The WTRU may determine the maximum SL-PRS duration based on the (pre)configured PSSCH-DMRS patterns in the resource pool. The WTRU may determine the maximum SL-PRS duration based on the set of (pre)configured PSSCH-DMRS patterns in the resource pool. For example, for each (pre)configured PSSCH-DMRS pattern, the WTRU may determine the maximum number of consecutive symbols used for PSSCH. The maximum SL-PRS duration may be determined based on the maximum number of consecutive symbols used for PSSCH. The WTRU may determine the maximum SL-PRS duration based on the PSSCH-DMRS pattern with the maximum number of consecutive symbols used for PSSCH. For example, Figure 2 As shown, the WTRU may be (pre)configured with two PSSCH-DMRS patterns, wherein the first PSSCH-DMRS pattern has a maximum of six consecutive PSSCH symbols, which may allow the WTRU to send SL-PRS with a maximum duration of six symbols. The second PSSCH-DMRS pattern has a maximum of three consecutive PSSCH symbols, which may allow the WTRU to send SL-PRS with a maximum duration of three symbols.

[0174] The WTRU may determine which PSSCH-DMRS pattern to send based on the selected SL-PRS duration. In an embodiment, the WTRU may be (pre)configured with multiple PSSCH-DMRS patterns, each of which may have a maximum potential SL-PRS duration. The WTRU may determine which PSSCH-DMRS pattern to send based on the selected SL-PRS pattern (e.g., the expected SL-PRS duration).

[0175] The WTRU may indicate the SL-PRS parameters for its associated SL-PRS pattern. In an embodiment, the WTRU may indicate one or any combination of the following parameters regarding the SL-PRS pattern to be sent in the time slot: the number of SL-PRS patterns in the time slot (e.g., the WTRU may determine whether to send a SL-PRS pattern for each set of consecutive time slots for PSSCH, and may further indicate which set of consecutive time slots the WTRU is sending); comb size; RE offset; SL-PRS duration; time-frequency resources used for each SL-PRS pattern; SL-PRS resource ID; SL-PRS sequence ID, or other ID used to generate the SL-PRS sequence; SL-PRS resource element offset; SL-PRS resource time slot offset; SL-PRS QCL information; SL-PRS resource set ID; SL-PRS resource power; periodicity of SL-PRS transmission; number of periods for SL-PRS transmission; spatial direction information for SL-PRS transmission (e.g., beam information, transmission angle); spatial direction information for SL-RS reception (e.g., beam ID, arrival angle for receiving SL-RS); frequency layer ID; WTRU ID; and SL-PRS ID.

[0176] The WTRU may determine where the SL-PRS information will be indicated. The WTRU may determine where the SL-PRS information will be indicated (e.g., in a first SCI, a second SCI, and / or a MAC CE) based on whether it is sending a standalone SL-PRS or sending the SL-PRS with sidelink data. For example, if the WTRU sends a standalone SL-PRS, the WTRU may use a first SCI to indicate the SL-PRS information. Alternatively, if the WTRU sends the SL-PRS with sidelink data, the WTRU may use a second SCI and / or a MAC CE to indicate the SL-PRS information. For example, for a standalone SL-PRS, the WTRU may use one or any combination of more than one (pre)configured fields in the SCI (e.g., second stage SCI format, beta offset, MCS, MCS table, etc.) to send the SL-PRS information. For SL-PRS transmission with data, the WTRU may use a second SCI to indicate the SL-PRS information. For example, the WTRU may be (pre)configured with a new second SCI format (e.g., SCI format 2-C). In an example, the WTRU may use one code point in the second stage SCI format to indicate the new second SCI. In another example, the WTRU may use one reserved bit to indicate the new second SCI format.

[0177] The WTRU may indicate information about the independent SL-PRS. In an example, the WTRU may use the SCI to indicate information about the independent SL-PRS. In another example, the WTRU may use a second SCI (e.g., a new SCI format) and / or a MAC CE to indicate information about the independent SL-PRS.

[0178] The WTRU may indicate information for sending the SL-PRS with the data. In an example, the WTRU may use a second SCI (eg, a new SCI format) and / or a MAC CE to indicate information about the independent SL-PRS.

[0179] In an embodiment, the WTRU may determine to send the SL-PRS with the sidelink data. In an example, the WTRU may use TDM to send the SL-PRS and the sidelink data (e.g., the sidelink data and the SL-PRS occupy two different sets of symbols). In an example, the WTRU may multiplex the SL-PRS and the sidelink data at the resource element (RE) level. For example, the SL-PRS and the sidelink data may be multiplexed in the same symbol, but they may occupy different sets of REs. The WTRU may indicate the multiplexing scheme between the SL-PRS and the sidelink data in the associated SCI transmission. For example, the WTRU may indicate the multiplexing scheme between the SL-PRS and the sidelink data in the second SCI. The WTRU may determine which multiplexing scheme (e.g., TDM or RE level) to use between the SL-PRS and the sidelink data based on one or any combination of (re) configuration, QoS of the data and / or QoS of the SL-PRS, broadcast type associated with the data and / or SL-PRS, and destination associated with the data and / or SL-PRS.

[0180] The WTRU may determine which multiplexing scheme (e.g., TDM or RE level) to use between the SL-PRS and the sidelink data based on the (pre) configuration in the resource pool. For example, in one resource pool, the WTRU may be (pre) configured to perform TDM multiplexing between the SL-PRS and the sidelink data. In another resource pool, the WTRU may be (pre) configured to multiplex between the SL-PRS and the sidelink data at the RE level.

[0181] The WTRU may determine which multiplexing scheme (e.g., TDM or RE level) to use between the SL-PRS and the sidelink data based on the QoS of the data and / or the QoS of the SL-PRS. For example, for a low QoS SL-PRS, the WTRU may use RE level multiplexing to multiplex between the SL-PRS and the sidelink data. Alternatively, for high QoS requirements (e.g., high accuracy or high priority), the WTRU may use TDM multiplexing to multiplex the SL-PRS with the sidelink data.

[0182] The WTRU may determine which multiplexing scheme (e.g., TDM or RE level) to use between the SL-PRS and the sidelink data based on the type of transmission associated with the data and / or the SL-PRS. For example, the WTRU may allow multiplexing between the SL-PRS and the data using RE level for unicast transmission of the SL-PRS and the sidelink data. However, for broadcast transmission of the SL-PRS, the WTRU may use TDM multiplexing to multiplex the SL-PRS and the sidelink data.

[0183] The WTRU may determine which multiplexing scheme (e.g., TDM or RE level) to use between the SL-PRS and the sidelink data based on the destination associated with the data and / or the SL-PRS. For example, if the SL-PRS and the sidelink data are targeted to the same destination, the WTRU may use RE level multiplexing between the SL-PRS and the sidelink data. Otherwise, the WTRU may use TDM multiplexing between the SL-PRS and the sidelink data.

[0184] The WTRU may determine the type of available resources for SL-PRS transmission. In an embodiment, the WTRU may determine a set of available resources for SL-PRS transmission in a resource selection window. The WTRU may determine the type of each available resource for SL-PRS transmission in the resource selection window based on potential multiplexing schemes with other reserved resources in the resource selection window. The WTRU may determine whether an available resource for SL-PRS transmission belongs to one or any combination of the following types. In a first type of resource, the SL-PRS resource may not be multiplexed with other reserved resources in frequency, and it may not be time multiplexed with other reserved resources in the same time slot. For example, for this type of resource, there is no other WTRU that reserves the resource in the entire time slot. In a second type of resource, the SL-PRS resource may be multiplexed with other reserved resources in frequency. For example, for this type of resource, there may be one or more reservations in the same time slot but in different subchannels. In a third type of resource, the SL-PRS resource may be multiplexed with other reserved resources in both time and frequency. For example, for this type of resource, there may be another WTRU reserved with a different SL-PRS pattern that overlaps in a time-frequency resource that may be orthogonal to the SL-PRS pattern of this WTRU. In a fourth type of resource, a SL-PRS resource may be multiplexed with another reserved SL-PRS resource in the same slot but in a different symbol set.

[0185] exist Figure 3In the example shown, the WTRU may select one or more SL-PRS patterns that span one slot in one subchannel. After the sensing window, the WTRU may be indicated or receive information about the set of reserved patterns / REs (shown in the reservation pattern). The WTRU may select one SL-PRS pattern that spans the bandwidth of one subchannel in one slot or half a slot as shown in the selected pattern. The WTRU may select a first type of resource, which is shown in the "first type of resource" circle. In this type of resource, the SL-PRS pattern is not time or frequency multiplexed with any reserved resource. The WTRU may select a second type of resource, which is shown in the "second type of resource" circle. In this type of resource, the SL-PRS pattern may be frequency multiplexed within another reserved pattern in another subchannel. The WTRU may select a third type of resource, which is shown in the "third type of resource" circle. In this type of resource, the SL-PRS pattern may be both time multiplexed and frequency multiplexed with another reserved pattern. The WTRU may select a fourth type of resource, which is shown in the circle "Fourth type of resource." In this type of resource, the SL-PRS pattern may be in the same timeslot as the reserved SL-PRSR pattern but in a different symbol set.

[0186] The WTRU may determine which type of resources to select for SL-PRS transmission. In an embodiment, the WTRU may select one or more SL-PRS patterns in a resource selection window for SL-PRS transmission. The WTRU may prioritize resources of one type (e.g., a first type) over resources of other types (e.g., a second type) based on potential multiplexing schemes with other reserved resources. In an example, the WTRU may select one or more SL-PRS resources by selecting resources of one type with a higher probability than selecting resources of another type. In another example, if the number / percentage of resources of one type (e.g., resources of the first type) is greater than a threshold, the WTRU may first select (e.g., randomly select) one or more resources for SL-PRS from resources of that type. Otherwise, if the number / percentage of resources of that type is less than a threshold, the WTRU may select (e.g., randomly select) one or more resources for SL-PRS from resources of both types (e.g., the first type and the second type). The WTRU may continue to perform this process until it can select enough resources for SL-PRS transmission, or all types of resources are considered. A threshold for the number / percentage of selectable resources may be (pre)configured in the resource pool, which threshold may be fixed or configurable according to the QoS of the sidelink positioning service.

[0187] exist Figure 4In the example shown, the WTRU may select resources for transmission of a SL-PRS pattern. For an available resource (e.g., an available SL-PRS pattern), the WTRU may determine whether the available resource belongs to a first type of resource or a second type of resource, wherein the first type of resource includes resources without any reservation in a time slot (e.g., when the WTRU transmits an SL-PRS in the resource, such SL-PRS may not overlap with any other transmission in time or frequency) and the second type of resource, wherein the second type of resource may have a SL-PRS pattern reserved in a time slot (e.g., when the WTRU transmits an SL-PRS in the resource, such SL-PRS may overlap with another transmission in time and frequency). The WTRU may first determine a set of resources that belong to the first type of resources. If the number / percentage of available resources of the first type is greater than a (pre)configured threshold (e.g., X%), the WTRU may select (e.g., randomly select) one or more SL-PRS resources from the first type of resources. Otherwise, if the number / percentage of available resources of the first type is less than the threshold (e.g., less than X%) and the number / percentage of resources of the first type and resources of the second type is greater than a second threshold (e.g., Y%), the WTRU may select one or more of the first type of resources and the second type of resources. If the number of available resources of the first type of resources and the second type of resources is less than Y%, the WTRU may perform one or any combination of the following: switch resource pools, indicate to another node, increase the SL-RSRP threshold, change the SL-PRS pattern. The values ​​of X and Y may be (pre-)configured, which may be a function of the QoS of the sidelink positioning service.

[0188] The WTRU may determine the selectivity / availability of a SL-PRS pattern. In an embodiment, the WTRU may determine the selectivity of a SL-PRS pattern based on a gap between the SL-PRS pattern and a reserved SL-PRS pattern. For example, if a gap (e.g., a frequency gap) between a SL-PRS pattern and another reserved SL-PRS pattern is greater than a threshold, the WTRU may consider the SL-PRS pattern to be available. The threshold may be based on the QoS of the WTRU's sidelink positioning service and / or the QoS of the service (e.g., the sidelink positioning service) for which the reserved resources are provided.

[0189] The WTRU may determine the selectivity / availability of a SL-PRS pattern based on potential multiplexing between the SL-PRS pattern and the reserved SL-PRS pattern. For example, the WTRU may prioritize one type of SL-PRS (e.g., a first type of SL-PRS, where the SL-PRS resource may not be multiplexed with other resources in the same time slot) over another type of SL-PRS (e.g., a third type of SL-PRS, where the SL-PRS resource may be multiplexed in time and frequency with other reserved SL-PRS patterns based on using two different SL-RSRP thresholds for each type of SL-PRS resource. For example, the WTRU may detect a WTRU that has reserved a SL-PRS pattern. The WTRU may determine the availability of the reserved pattern (e.g., whether the reserved SL-PRS pattern is selectable) based on the type of the reserved pattern (e.g., whether it is a type one or other type of reserved pattern) and the associated SL-RSRP. For example, to determine the availability of a reserved SL-PRS, the WTRU may apply a first SL-RSRP threshold for a first type of SL-PRS, and it may apply a second SL-RSRP threshold for a second type of SL-PRS.

[0190] exist Figure 5 In the example shown, the WTRU may consider one SL-PRS pattern as available if the frequency gap between the SL-PRS pattern and the reserved SL-PRS pattern is greater than one RE. The WTRU may detect the reserved first pattern as indicated in the Type 1 box. The WTRU may determine that the second pattern as indicated in the Type 2 box is not available, and may determine that the third pattern as indicated in the Type 3 box is not available because the gap between the second pattern / third pattern and the first pattern is one RE. However, the WTRU may consider the fourth pattern as indicated in the Type 4 box as available because the gap between the fourth pattern and the first pattern is two REs.

[0191] The WTRU may determine which type of resources to select for SL-PRS transmission. The WTRU may determine which type of resources to select for SL-PRS transmission based on one or any combination of the following.

[0192] The WTRU may determine which type of resources to select for SL-PRS transmission based on the (pre-)configured types of resources in the resource pool. For example, the WTRU may be (pre-)configured with a certain type of SL-PRS resources in the resource pool. The WTRU may select one of the (pre-)configured types for SL-PRS transmission. For example, the WTRU may be (pre-)configured with only resources of the first type (i.e., resources that are not multiplexed in frequency and are in the same time slot as other SL-PRS resources). The WTRU may select resources of the first type for SL-PRS transmission.

[0193] The WTRU may determine which type of resource to select for SL-PRS transmission based on the QoS of the positioning service. For example, the WTRU may select the first type of resource for high accuracy requirements. Alternatively, for low accuracy requirements, the WTRU may select the second type of resource. For low latency requirements, the WTRU may select the third type of resource. Otherwise, for relaxed latency requirements, the WTRU may select the first type of resource or the second type of resource.

[0194] The WTRU may determine which type of resource to select for SL-PRS transmission based on the CBR of the resource pool. For example, if the CBR of the resource pool is less than a threshold, the WTRU may select a first type of resource. Otherwise, if the CBR of the resource pool is greater than a threshold, the WTRU may select a third type of resource.

[0195] The WTRU may determine which type of resources to select for SL-PRS transmission based on: an indication from another node (e.g., another WTRU), the positioning method, the broadcast type of the SL-PRS transmission, the distance to the receiving WTRU and / or the requesting WTRU, the sidelink channel to the receiving WTRU and / or the requesting WTRU, the positioning accuracy of the WTRU or the positioning accuracy of an associated WTRU, the measurement parameters to be measured, the output of the positioning process (which may be an absolute positioning or a relative positioning), and the amount of SL-PRS transmissions within a period.

[0196] The WTRU may determine the maximum time gap between transmissions of the SL-PRS. The WTRU (e.g., a target WTRU) may select a plurality of SL-PRS resources to perform transmission and repetition of the SL-PRS. The WTRU may determine the maximum time gap between transmissions of the SL-PRS (e.g., the maximum time gap between the initial transmission and the last repetition of the SL-PRS in one SL-PRS cycle) based on one or any combination of the following. The WTRU may determine the maximum time gap based on a (pre) configuration. For example, the WTRU may be (pre) configured with the maximum time gap between transmissions of the SL-PRS in a cycle. The WTRU may select a SL-PRS resource to satisfy the (pre) configured value. The WTRU may determine the maximum time gap based on an indication from a peer WTRU. For example, a WTRU (e.g., an anchor WTRU) may indicate to a WTRU (e.g., a target WTRU) the maximum time gap between its initial transmission and repetition of the SL-PRS in a cycle. The receiver WTRU may determine the maximum time gap between the initial transmission and repetition of the SL-PRS based on its processing capabilities. In an example, a WTRU may indicate a maximum time gap to a network (e.g., a gNB) to support the network in SL-PRS scheduling. In an example, the WTRU may take the indicated maximum time gap into account during resource allocation. For example, the WTRU may select SL-PRS resources such that the maximum gap between SL-PRS resources is guaranteed. The WTRU may determine the maximum time gap based on a (pre)configured measurement gap / positioning processing window (MG / PPW) duration for a receiver WTRU. For example, the WTRU may receive an MG / PPW configuration for the receiver WTRU, which may include an MG / PPW length. A transmitter WTRU (e.g., a target WTRU) may determine that the maximum time gap between an initial transmission and a retransmission of a SL-PRS in a period is less than the indicated MG / PPW length. The method may be triggered to help the transmitter WTRU select resources within the MG / PPW of the receiver WTRU. The WTRU may determine the maximum time gap based on the QoS (e.g., latency) of the positioning service. For example, the WTRU may be (pre)configured with multiple maximum time gaps between the transmission of the SL-PRS in a period, where each maximum time gap may be associated with a QoS requirement for the positioning service. The WTRU may determine which time gap will be used for resource selection based on the required QoS for the positioning service. For example, for low latency requirements, the WTRU may use a small gap between the transmission of the SL-PRS in a period. Alternatively, for less stringent latency requirements, the WTRU may select a larger maximum time gap between the transmission of the SL-PRS in a period. The WTRU may determine the maximum time gap based on the SL-PRS reception capability of the receiver WTRU. The WTRU may determine the maximum time gap based on the positioning method.For example, the WTRU may use a first maximum time gap for a first positioning method (e.g., SL-TDOA). Alternatively, the WTRU may use a second maximum time gap for a second positioning method (e.g., RTT). The WTRU may determine the maximum time gap based on the channel conditions between the transmitter and the receiver (e.g., the coherence time of the channel, the synchronization drift rate, the phase drift rate, etc.). For example, if the channel between the transmitter and the receiver satisfies the first condition (e.g., the coherence time is less than a (pre-)configured threshold), the WTRU may use a first maximum time gap between the transmissions of the SL-PRS in the period. If the channel between the two WTRUs satisfies the second condition (e.g., the coherence time is greater than the threshold), the WTRU may use a second maximum time gap between the transmissions of the SL-PRS in the period.

[0197] The WTRU may trigger SL-PRS resource (re)selection for a periodic SL-PRS process. In an embodiment, the WTRU may select a periodic SL-PRS process (e.g., each SL-PRS process may be associated with a HARQ process that may be similar to a periodic SL process) to periodically send the SL-PRS. Prior to transmission in each SL-PRS period, the WTRU may determine whether to keep using the current SL-PRS process or reselect another SL-PRS process. Such a decision may be determined based on one or any combination of the following. The decision may be based on the SL-PRS measurement report status from a peer WTRU. For example, if the WTRU does not receive one or more expected SL-PRS measurement reports from a peer WTRU, the WTRU may trigger resource reselection for the SL-PRS. For example, if a SL-PRS measurement report received from a peer WTRU indicates a bad result (e.g., SL-RSRP is less than a (pre)configured threshold, or the peer WTRU implicitly indicates that it may not correctly receive SL-PRS in one or more SL-PRS opportunities), the WTRU may trigger resource reselection for the SL-PRS. The decision may be based on one or more WTRUs being added / removed from the group. The decision may be based on whether the CBR of the resource pool is greater than a threshold and / or whether the CR of the WTRU is greater than a threshold. The decision may be based on whether the peer WTRU indicates its MG / PPW configuration. In an example, when the peer WTRU indicates its MG / PPW configuration, if the WTRU does not have any periodic SL-PRS process selected for the peer WTRU, the WTRU may trigger resource selection. In an example, when an indication of MG / PPW configuration is received from a peer WTRU, if an existing periodic SL-PRS process is not aligned with the configured MG / PPW of the peer WTRU, the WTRU may trigger resource reselection.

[0198] The WTRU may be (pre)configured with multiple types of dedicated resource pools for SL-PRS. In an embodiment, the WTRU may be (pre)configured with one or more resource pools for SL-PRS, wherein one resource pool may have one or any combination of the following parameters. The parameter may be the number of TDM mini-slots for SL-PRS in a timeslot (e.g., X mini-slots for SL-PRS). A resource pool may have one mini-slot for SL-PRS, which may span the entire timeslot. Another resource pool may have two TDM mini-slots for SL-PRS. Another resource pool may have three TDM mini-slots for SL-PRS. The parameter may be whether the resource pool allows Tx-Rx switching between mini-slot SL-PRS. For example, a resource pool may allow Tx-Rx switching between mini-slot SL-PRS by having GAP symbols between mini-slot SL-PRS. Another resource pool may not allow Tx-Rx switching between mini-slot SL-PRSs, where the WTRU may not have a GAP symbol between two mini-slots for SL-PRSs. The parameter may be whether to enable / disable RE level multiplexing between two SL-PRS patterns. The parameter may be the location of the PSCCH / PSSCH and / or SCI to indicate its associated SL-PRS (e.g., whether the PSCCH / PSSCH and / or SCI for indicating its associated SL-PRS is at the beginning of the slot or at the beginning of each mini-slot for each SL-PRS).

[0199] The WTRU may determine the structure of each mini-slot for SL-PRS with an associated PSCCH. The WTRU may determine the structure of each mini-slot for SL-PRS. In an embodiment, the mini-slot may include a PSCCH resource to indicate the SL-PRS at the beginning of the mini-slot. For example, a mini-slot for SL-PRS may include, in sequence, one symbol for AGC (e.g., to converge the AGC for PSCCH reception), one or more symbols for PSCCH after the AGC symbol, another symbol for AGC after the PSCCH symbol (e.g., to converge the AGC for SL-PRS reception), one or more symbols for SL-PRS after the second AGC symbol, and a GAP symbol at the end of the mini-slot for SL-PRS may be optionally (pre)configured. The WTRU may be (pre)configured with one GAP symbol at the end of each mini-slot for SL-PRS. Alternatively, the WTRU may be (pre)configured with only one GAP symbol at the end of the slot.

[0200] The WTRU may determine the structure of the entire time slot with a PSCCH at the beginning of the time slot. In an embodiment, the WTRU may be (pre)configured with a PSCCH symbol at the beginning of the time slot, which may be used to indicate the associated SL-PRS in different mini-time slots. For example, the WTRU may be (pre)configured with multiple PSCCH resources, each of which may be used to indicate a SL-PRS pattern in a mini-time slot for SL-PRS. The WTRU may determine which PSCCH resource will indicate its SL-PRS pattern based on its selected SL-PRS pattern (e.g., which mini-time slot the SL-PRS pattern is in and the comb size and RE offset of the selected SL-PRS pattern). After one or more symbols for PSCCH, the WTRU may be (pre)configured with one or more mini-time slots for SL-PRS. In each mini-time slot for SL-PRS, the WTRU may be (pre)configured with an AGC symbol followed by one or more symbols for SL-PRS. In an example, the WTRU may be (pre)configured with a GAP symbol after each mini-slot for SL-PRS. In an example, the WTRU may be (pre)configured with a GAP symbol only at the end of a slot.

[0201] In such Figure 6 In the example shown, the WTRU may be (pre)configured with one or more resource pools as in Option 1 (Options 1-1 and 1-2) and / or Option 2. In Option 1 and Option 2, there are two mini-slots for SL-PRS in one slot. For Option 1, there is no GAP symbol between the two mini-slots for SL-PRS in Option 1-1, while there is a GAP symbol between the two mini-slots for SL-PRS in Option 1-2. In Option 1, the PSCCH region is located at the beginning of the slot. In Option 2, the PSCCH region is located at the beginning of each mini-slot for SL-PRS. The WTRU may be (pre)configured with a mapping between PSCCH and SL-PRS, where the WTRU may select which position of the PSCCH to indicate the associated SL-PRS based on the selected SL-PRS mode and the time / frequency position of the SL-PRS.

[0202] The WTRU may determine which resource pool to request / select for SL-PRS transmission. In an embodiment, the WTRU may request a dedicated resource pool for SL-PRS transmission from another node (e.g., another WTRU, gNB, LMF). In an embodiment, the WTRU may be (pre)configured with multiple resource pools for SL-PRS. The WTRU may select one of the resource pools for SL-PRS transmission. The WTRU may determine which resource pool to request / select based on one or any combination of the following. The WTRU may determine which resource pool to request / select based on the QoS of the positioning service (e.g., latency, accuracy, reliability, range). For example, for a high-range positioning service, the WTRU may request / select a resource pool with a higher SL-PRS duration in the resource pool. For example, the WTRU may request a resource pool in which the SL-PRS resources span the entire time slot. For example, for low latency requirements, the WTRU may request / select a resource pool with multiple mini-slots for SL-PRS that is TDMed in a time slot. This method can help the WTRU have more resources for SL-PRS transmission in a short period. The WTRU may determine which resource pool to request / select based on the positioning method. For example, for the SL-TDOA positioning method, the WTRU may request a resource pool with no GAP between two mini-time slots used for SL-PRS. Alternatively, for the RTT positioning method, the WTRU may request a resource pool with a GAP between two consecutive mini-time slots used for SL-PRS. This method may be triggered to support the WTRU to send and receive within the time slot. The WTRU may determine which resource pool to request / select based on the availability of resources in the pool. For example, the WTRU may determine which resource pool to request / select based on the availability of resources in each pool. The WTRU may determine the resource pool with the maximum availability (e.g., 90% availability) among the pre-configured resource pools. The WTRU may determine which resource pool to request / select based on the priority associated with the resource pool. For example, the WTRU may be configured with a priority level for each resource pool by the network or a peer WTRU. The WTRU may determine to select a resource pool associated with a priority level above a preconfigured threshold.In an example, the WTRU may receive an indication from a peer WTRU or the network that a subset of the preconfigured resource pools is used.

[0203] The WTRU may select a second SL-PRS in response to a first SL-PRS resource of an RTT method. In an embodiment, the WTRU (e.g., an anchor WTRU) may be involved in a positioning process of the RTT method. The WTRU may receive information about a first SL-PRS resource. The WTRU may determine to select a second SL-PRS in response to a first SL-PRS resource. The WTRU may determine which SL-PRS resource to prioritize based on one or any combination of the following items (including resource pool configuration). For example, if a GAP symbol between two mini-slots for SL-PRS is (pre) configured, the WTRU may prioritize selecting a second SL-PRS resource (e.g., a response SL-PRS resource) that is in the same slot as the first SL-PRS resource. Alternatively, if a GAP symbol between two mini-slots for SL-PRS is not (pre) configured, the WTRU may reduce the priority of selecting a second SL-PRS resource that is in the same slot as the first SL-PRS resource. The WTRU may prioritize selecting a second SL-PRS resource in a different slot.

[0204] The WTRU may prioritize SL-PRS resources that are in the same timeslot as SL-PRS resources of WTRUs in the group. In an embodiment, the WTRU may perform resource selection for a positioning method (e.g., SL-TDOA). One WTRU (e.g., an anchor WTRU) may first select SL-PRS resources and indicate the resources to other WTRUs in the positioning group. The WTRU may select SL-PRS resources based on indicated / reserved SL-PRS resources from other WTRUs. For example, the WTRU may prioritize the selection of SL-PRS resources that are in the same timeslot or in adjacent timeslots as indicated / reserved SL-PRS resources from other WTRUs. The method may be triggered to help a group of WTRUs select adjacent SL-PRS resources.

[0205] The WTRU may determine the maximum SL-PRS transmission duration in the resource pool. The WTRU may determine the maximum SL-PRS transmission duration in the resource pool based on the (pre)configured maximum number of SL-PRS symbols for a mini-slot for SL-PRS. For example, the WTRU may be (pre)configured with a resource pool, wherein in each slot, the WTRU may be (pre)configured with a plurality of TDMed mini-slots for SL-PRS transmission. The WTRU may select a SL-PRS mode wherein the maximum duration is limited by the maximum (pre)configured number of SL-PRS symbols in a mini-slot.

[0206] The WTRU may determine the comb size N and the SL-PRS duration M for SL-PRS transmission. In an example, the WTRU may select the SL-PRS duration of M symbols to be equal to the duration of the (pre)configured SL-PRS in the mini-slot. In an example, the WTRU may select M symbols to be less than the duration of the (pre)configured SL-PRS in the mini-slot. If M is less than the (pre)configured SL-PRS duration in the mini-slot, the WTRU may perform one or any combination of the following. The WTRU may send only M symbols and keep the remaining symbols of the mini-slot empty. The WTRU may repeat the selected SL-PRS pattern in the remaining symbols of the mini-slot. If after a certain number of repetitions, if the WTRU still has remaining symbols to fill, the WTRU may repeat each symbol in the SL-PRS pattern sequentially (e.g., from the first symbol of the SL-PRS pattern or from the last symbol of the SL-PRS pattern) until all symbols of the mini-slot for SL-PRS are filled.

[0207] The WTRU may be (pre)configured with one or more procedures / rules to fill the SL-PRS symbols in the mini-slot, including leaving the remaining symbols unused. The WTRU may implicitly / explicitly indicate the procedures / rules it uses to fill the SL-PRS. The WTRU may indicate the procedures / rules in the associated SCI. The method may be triggered to help the receiver WTRU to properly decode the SL-PRS.

[0208] exist Figure 7 In the example shown, the WTRU may determine to fill the remaining symbols of the mini-slot including four symbols for SL-PRS. In the first mini-slot for SL-PRS, the WTRU selects an SL-PRS pattern with M=3, and the WTRU may repeat the first symbol of the selected SL-PRS pattern to fill the last symbol of the mini-slot for SL-PRS. In the second mini-slot, the WTRU selects an SL-PRS pattern with M=2.

[0209] In an embodiment, the WTRU may determine to send a SL-PRS pattern having a duration of M symbols, the duration of the M symbols being greater than the number of SL-PRS symbols in a mini-slot. The WTRU may send the SL-PRS in multiple mini-slots in a slot, which may be consecutive. In an example, the WTRU may select a SL-PRS pattern in a mini-slot, and the WTRU may repeat the selected SL-PRS pattern in a subsequent mini-slot. In an example, the WTRU may use a mini-slot to send a first portion of the SL-PRS. The WTRU may use a subsequent mini-slot to send the remainder of the SL-PRS pattern. In an example, the WTRU may send the SL-PRS across mini-slots. The WTRU may send the SL-PRS in a symbol (e.g., an AGC symbol or a GAP symbol) between two mini-slots. The WTRU may use an associated SCI to indicate such transmission behavior. For example, the WTRU may indicate the selected SL-PRS mode, the number of mini-slots used to send the SL-PRS pattern, whether cross-mini-slot transmission is applied, and / or whether the WTRU uses SL-PRS repetition in multiple mini-slots or the WTRU sends different parts in different mini-slots.

[0210] The WTRU may determine to send the SL-PRS for a shorter duration than the (pre-)configured SL-PRS duration in the mini-slot for the SL-PRS. The WTRU may determine whether it may send the SL-PRS for a shorter duration than the (pre-)configured SL-PRS duration in the mini-slot based on one or any combination of the following: the bandwidth of the SL-PRS; the comb size of the SL-PRS; and whether RE level multiplexing between two SL-PRS patterns is allowed.

[0211] In an example, if the SL-PRS spans the entire bandwidth of the resource pool and RE level multiplexing between two SL-PRS patterns is not allowed in the resource pool, the WTRU may determine to send the SL-PRS in a shorter duration than the (pre-)configured SL-PRS duration in the mini-slot. In an example, if the SL-PRS spans the entire bandwidth of the resource pool and FDM between two SL-PRS patterns may not be expected (e.g., the WTRU may use comb 1), the WTRU may determine to send the SL-PRS in a shorter duration than the (pre-)configured SL-PRS duration in the mini-slot.

[0212] In an embodiment, a WTRU may determine to select resources for itself and another peer WTRU. The WTRU may select one resource for itself and another resource for transmission by the peer WTRU. The WTRU may select two resources such that a time gap between the two resources may need to satisfy one or more conditions. The minimum time gap between the two resources may be determined based on the WTRU processing capability. The maximum time gap between the two resources may be determined based on the QoS of the positioning service. For example, for an accuracy requirement, the time gap between two SL-PRS resources may be less than a threshold. The threshold may be (pre)configured based on the QoS of the positioning service (e.g., accuracy and / or latency requirements).

[0213] The WTRU may use the SCI to indicate / reserve resources for transmissions of other WTRUs. In an embodiment, the WTRU may use the SCI (e.g., the first SCI) to reserve resources for transmissions of itself and other WTRUs. In an example, the WTRU may use two bit fields (e.g., in the first SCI) to indicate / reserve resources for sidelink transmissions (e.g., SL-PRS transmissions), one of which may be used to reserve resources for itself and another bit field may be used to reserve resources for transmissions of another WTRU. In an example, the WTRU may use one bit field to reserve / indicate sidelink resources (e.g., for SL-PRS transmissions). The WTRU may use one bit to indicate whether the reserved resources are for itself or for other WTRUs. In an example, the WTRU may use one bit field to indicate / reserve multiple sidelink resources (e.g., for SL-PRS transmissions). The WTRU may reserve / indicate a first set of resources for its transmission (e.g., the first resources in time). The WTRU may indicate a second set of resources for transmissions of other WTRUs (e.g., the second resources in time).

[0214] In an embodiment, a WTRU may use one or more transmissions in one resource pool to indicate / reserve transmit resources (e.g., SL-PRS) in another resource pool. The indicated / reserved transmit resources may be used by the WTRU to perform a sidelink transmission. The indicated / reserved transmit resources may be used by another WTRU to perform a transmission. In an example, for inter-WTRU coordination, a WTRU may use one or more transmissions in a sidelink data resource pool to indicate / reserve SL-PRS resources for its peer WTRU in a dedicated resource pool for SL-PRS transmission. In an example, for an RTT method, a WTRU may use one or more transmissions in one resource pool (e.g., a sidelink data resource pool) to indicate / reserve SL-PRS resources in another resource pool (e.g., a dedicated resource pool for SL-PRS) for transmissions for itself and other WTRUs. The WTRU may (e.g., implicitly or explicitly) indicate which resource is used for its SL-PRS transmission and which resource is used for transmissions of other WTRUs. In both examples, the WTRU may indicate resource information for SL-PRS transmission and reception to support a peer WTRU in performing SL-PRS transmission and / or reception. Such information may include one or more of the following: resource pool ID, SL-PRS time / frequency resources, repetition, SL-PRS pattern, and periodicity of SL-PRS. The WTRU may use SCI, MAC CE, RRC, and / or NAS (e.g., LPP for sidelink) to indicate / reserve resources for SL-PRS in another resource pool (e.g., a dedicated resource pool).

[0215] The WTRU may determine the availability of indicated resources for SL-PRS transmission. In an embodiment, the WTRU may receive an indication of one or more resources for SL-PRS transmission (e.g., from a peer WTRU). The WTRU may perform a resource evaluation to determine whether the indicated resources are available. If the resources are available, the WTRU may perform a transmission (e.g., SL-PRS transmission) in the indicated resources. Otherwise, if the resources are not available, the WTRU may perform one or any combination of the following: transmit an indication to the peer WTRU, and select another resource for SL-PRS transmission.

[0216] The WTRU may reselect one or more reserved / selected resources. In an embodiment, the WTRU may determine to reselect a periodic SL-PRS process. The WTRU may reselect a periodic SL-PRS process due to preemption (e.g., another WTRU has reserved conflicting resources). For an RTT-based sidelink positioning method, the WTRU may determine a resource selection window for new SL-PRS resources based on the timing of the associated periodic SL-PRS resources from the peer WTRU. The WTRU may be expected to send a SL-PRS before the peer WTRU performs a SL-PRS transmission. The WTRU may select a resource selection window for the new SL-PRS, wherein the latest time slot in the resource selection window may be located before the reserved SL-PRS resources of the peer WTRU in a cycle. The duration between the latest time slot in the resource selection window and the reserved resources for the SL-PRS transmission of the peer WTRU may be based on the processing capability of the WTRU. The WTRU may select a resource selection window.

[0217] A WTRU may trigger a resource reselection due to preemption by itself and a peer WTRU. In an embodiment, the WTRU may perform a preemption check on two resources, one of which is available for transmission by the WTRU and the other is available for transmission by the peer WTRU. In an example, the WTRU may determine to reselect both SL-PRS resources if the time gap between the two resources is less than a threshold. If the WTRU maintains one of the selected resources, the method may be triggered to help the WTRU find a suitable resource for both WTRUs to reduce constraints in resource selection.

[0218] The WTRU may trigger resource selection for a periodic SL-PRS process. In an embodiment, the WTRU may reserve a periodic SL-PRS process that is associated with another periodic SL-PRS process of a peer WTRU. The WTRU may trigger resource reselection for a periodic SL-PRS process based on detection of a change of an associated periodic SL-PRS process of a peer WTRU. If the WTRU detects a change of a periodic SL-PRS process of a peer WTRU (e.g., the peer WTRU performs resource reselection and changes to another periodic SL-PRS process), the WTRU may trigger resource selection and change to another periodic SL-PRS to accommodate the RTT sidelink positioning process.

[0219] Figure 8 An example is shown where a WTRU triggers resource reselection upon detecting a change in the associated periodic SL-PRS procedure from a peer WTRU.

[0220] like Figure 8As shown, WTRU1 and WTRU2 first select two associated periodic SL-PRS procedures, where WTRU1 selects a Type 2 SL-PRS procedure and WTRU2 selects a Type 1 SL-PRS procedure. WTRU1 performs resource reselection and changes to a Type 4 SL-PRS procedure. WTRU2 detects the change in periodic SL-PRS procedure from WTRU1 and triggers resource selection to change to a Type 3 SL-PRS procedure to align with the Type 4 SL-PRS procedure from WTRU1.

[0221] The WTRU may determine whether to send SL-PRS in reserved resources. In an embodiment, the WTRU may reserve periodic resources for SL-PRS transmission. The WTRU may receive an indication of periodic resources for SL-PRS transmission by another node (e.g., another WTRU). The WTRU may determine whether to perform SL-PRS transmission in one or more reserved / indicated resources based on one or any combination of the following.

[0222] The WTRU may determine whether to perform SL-PRS transmission in one or more reserved / indicated resources based on the reception status of one or more previous SL-PRS resources. For example, for the RTT-based method, in one SL-PRS transmission / reception cycle, the WTRU may determine whether to send the SL-PRS based on whether it correctly received the SL-PRS from the peer WTRU in one or more previous SL-PRS resources. If the WTRU did not correctly receive one or more SL-PRS from the peer WTRU, the WTRU may not send the SL-PRS. Otherwise, if the WTRU correctly received the SL-PRS from the peer WTRU, the WTRU may send in the reserved SL-PRS resources.

[0223] The WTRU may determine whether to perform SL-PRS transmission in one or more reserved / indicated resources based on the measurement reporting status of one or more previous SL-PRS measurement reporting occasions. In an example, the WTRU may expect to receive one SL-PRS measurement report for one or more SL-PRS transmissions of periodic SL-PRS resources. If the WTRU has not received a SL-PRS measurement report from one or more (e.g., N) previous SL-PRS measurement reporting occasions, the WTRU may determine not to send SL-PRS in the reserved resources. The value of N may be (pre)configured.

[0224] The WTRU may determine to release a periodic SL-PRS process. In an embodiment, the WTRU may reserve a periodic SL-PRS process. The WTRU may determine whether to release the SL-PRS process. The WTRU may not perform SL-PRS transmission in the set of reserved resources for SL-PRS transmission. The decision on whether to release the SL-PRS process may be based on one or any combination of the following.

[0225] The decision on whether to release the SL-PRS process may be based on whether the number of transmission cycles is greater than a threshold. For example, the WTRU may determine to perform SL-PRS transmission in N cycles. The value of N may be indicated from another node (e.g., another WTRU or a gNB). If the number of SL-PRS cycles is greater than N, the WTRU may release the periodic resources used for SL-PRS transmission.

[0226] The decision on whether to release the SL-PRS process may be based on the reception status of one or more previous SL-PRS resources. For example, for the RTT-based method, if the WTRU has not correctly received N (e.g., consecutive N) expected SL-PRS transmissions from a peer WTRU, the WTRU may determine to release the periodic SL-PRS process. The value of N may be (pre)configured.

[0227] The decision on whether to release the SL-PRS process may be based on the SL-PRS measurement report status of one or more previous periods. In an example, for the RTT-based method, in each period, the WTRU (e.g., the target WTRU) may perform SL-PRS transmission. The WTRU may receive SL-PRS and SL-PRS measurement reports from a peer WTRU (e.g., the anchor WTRU). If the WTRU has not received a SL-PRS measurement report from another WTRU (e.g., the peer WTRU) in the past one or more SL-PRS measurement report periods, the WTRU may determine whether to release the periodic SL-PRS process. Otherwise, the WTRU may perform SL-PRS transmission in reserved resources. In an example, for the SL-PRS transmission-based method, the WTRU (e.g., the target WTRU) may perform SL-PRS transmission and it may expect to receive SL-PRS measurement reports from a peer WTRU. The WTRU may determine whether to send SL-PRS in a reserved resource based on whether it has received a SL-PRS measurement report from another WTRU (e.g., the peer WTRU) in the past one or more SL-PRS measurement report periods. If the WTRU has not received a SL-PRS measurement report from a peer WTRU in the past one or more SL-PRS measurement reporting periods, the WTRU may not perform SL-PRS transmission in the reserved resources. Otherwise, the WTRU may perform SL-PRS transmission in the reserved resources.

[0228] When releasing the periodic SL-PRS process, the WTRU may perform one or any combination of the following: transmitting an indication to another node (e.g., another WTRU or a gNB), reselecting another SL-PRS resource (which may be periodic or non-periodic), and terminating the positioning session.

[0229] The WTRU may use the SL-PRS reception timing as a reference for the SL-PRS transmission timing. In the RTT-based approach, the WTRU may perform SL-PRS reception and SL-PRS transmission. The WTRU may use the SL-PRS reception timing as a reference for the SL-PRS transmission timing. The WTRU may indicate (e.g., in an SCI, MAC CE, PC5 RRC, and / or NAS) to a peer WTRU that the SL-PRS reception timing of the peer WTRU is used for SL-PRS transmission. The WTRU may then not perform SL-PRS measurement reporting (e.g., Tx-Rx timing measurement). For example, the WTRU may indicate such an indication in an SCI (e.g., a first SCI or a second SCI).

[0230] The WTRU may determine which WTRU (including itself) will initiate the SL-PRS resource selection process. The WTRU may determine which WTRU (including itself) will initiate the SL-PRS resource selection process based on one or any combination of the following. The WTRU may determine which WTRU (including itself) will initiate the SL-PRS resource selection process based on the initiator of the positioning session. In an example, a target WTRU may initiate a positioning session to locate its position. The target WTRU may first initiate the SL-PRS resource process. The WTRU may indicate its resource selection results to the remaining WTRUs in the group. The remaining WTRUs in the group may perform resource allocation based on the selected SL-PRS resources from the resource allocation initiator. In an example, an anchor WTRU may initiate a positioning session to locate the position of one or more target WTRUs. The anchor WTRU may initiate its resource allocation process and select a SL-PRS resource. Other WTRUs in the group (e.g., target WTRUs) may perform resource selection based on the selected SL-PRS resources from the anchor WTRU. The WTRU may determine which WTRU (including itself) shall initiate the SL-PRS resource selection procedure based on an indicator from another node (e.g., LMF). For example, the network (e.g., LMF) may request one WTRU in the positioning group to perform resource allocation. Other WTRUs may perform resource selection for SL-PRS based on the initiator of the SL-PRS procedure.

[0231] The WTRU may perform resource selection for the SL-PRS based on the reserved SL-PRS of another WTRU. The WTRU may coordinate the resource allocation process between the WTRUs in the positioning group. For example, the WTRU may determine one or any combination of the following resource allocation parameters. The WTRU may determine the bandwidth, the SL-PRS pattern (comb size, offset), and the number of repetitions. The WTRU may determine the SL-PRS periodicity. For example, the WTRU may select the same SL-PRS periodicity as the SL-PRS periodicity selected by the initiator WTRU. The WTRU may determine a resource selection window for a first SL-PRS and / or a first set of SL-PRS resources, which may include the first SL-PRS and its repetitions in one SL-PRS period. For example, the resource selection window of the follower WTRU may be selected based on one or any combination of the following. The resource selection window of the follower WTRU may be selected based on the number of WTRUs in the group. For example, the WTRU may select a larger resource selection window for a group with a higher number of group members. The resource selection window of the follower WTRU may be selected based on the mobility of the WTRUs in the group. For example, the WTRU may be (pre)configured with two resource allocation window ranges, where a first range may be used if the speed of the WTRU is greater than a (pre)configured threshold, and a second resource allocation window range may be used if the speed of the WTRU is less than the threshold. The resource selection window of the follower WTRU may be selected based on the QoS of the positioning service. For example, the WTRU may be configured with multiple ranges of resource selection windows, where each range may be associated with a QoS requirement (e.g., accuracy requirement) of the positioning service. The WTRU may determine which resource allocation window to use based on the QoS requirement of the positioning service. Such parameters may be determined based on the selected SL-PRS resources from the initiator of the resource allocation process in the group.

[0232] A WTRU may request another WTRU to stop transmitting in a reserved resource. A WTRU (e.g., the initiator of a SL-PRS resource allocation procedure) may request another WTRU to stop transmitting in one or more reserved SL-PRS resources. A WTRU may request the WTRU to change the SL-PRS configuration or to continue using a periodic SL-PRS procedure. Such a decision may be determined based on whether the reserved resources conflict semi-persistently with another periodic SL-PRS resource from another WTRU. For example, if two periodic SL-PRS procedures conflict semi-persistently, the WTRU may request one of the two WTRUs to change the SL-PRS configuration (e.g., change the offset). Otherwise, the WTRU may request one of the two WTRUs to stop transmitting in the current period.

[0233] The WTRU may determine which SL-PRS resource will perform preemption. In an embodiment, a WTRU (e.g., a target WTRU) may reserve a periodic SL-PRS process. For each SL-PRS period, the WTRU may determine whether a preemption check will be performed and reselect the reserved resources if a conflict is detected. The WTRU may determine the frequency of the preemption check and which SL-PRS resource will perform preemption (e.g., check for conflicts and reselect resources if conflicts are detected) based on one or any combination of the following. The WTRU may determine the frequency of the preemption check and which SL-PRS resource will perform preemption based on whether the SL-PRS resource is within the MG / PPW of the peer WTRU. In an example, if the reserved SL-PRS resource is within the MG / PPW of the peer WTRU, the WTRU may perform a preemption check, otherwise, if the reserved SL-PRS resource is outside the MG / PPW of the peer WTRU, the WTRU may not perform preemption. The method may be triggered to help the peer WTRU have the best resources to perform measurements. In an example, if the reserved SL-PRS resources are within the MG / PPW of the peer WTRU, the WTRU may not perform a preemption check, otherwise, if the reserved SL-PRS resources are outside the MG / PPW of the peer WTRU, the WTRU may perform preemption. The method may be triggered to help the peer WTRU have SL-PRS resources for measurement. The WTRU may determine the frequency of the preemption check and which SL-PRS resource to perform preemption based on the periodic preemption check. For example, the WTRU may be required to perform a preemption check at least before a (pre)configured number of SL-PRS periods, a (pre)configured number of MG / PPWs, and / or a (pre)configured number of SL-PRS measurement reporting periods. The WTRU may determine the frequency of the preemption check and which SL-PRS resource to perform preemption based on the CBR of the resource pool. For example, if the CBR of the resource pool is greater than a threshold, the WTRU may determine to perform preemption, otherwise, if the CBR of the resource pool is less than the threshold, the WTRU may skip performing preemption. The WTRU may determine the frequency of preemption checks and which SL-PRS resources to perform preemption on based on the QoS of the positioning service. For example, if the accuracy requirement of the positioning service is greater than a threshold, the WTRU may perform preemption, otherwise, the WTRU may skip performing preemption.

[0234] The WTRU may determine a resource (re)selection window for SL-PRS resources. In an embodiment, the WTRU may determine the resource selection window for SL-PRS based on the (pre)configured MG / PPW of the peer WTRU. For example, the WTRU may (re)select SL-PRS resources to be within the MG / PPW window per WTRU. In an embodiment, the WTRU may determine the resource selection window for SL-PRS based on the QoS (e.g., latency) of the location service. The WTRU may indicate the selected resources to the peer WTRU, and the WTRU may request the peer WTRU to change its MG / PPW configuration according to the newly selected SL-PRS resources.

[0235] The WTRU may perform an action after conflict detection. The WTRU may perform a preemption check on one or more SL-PRS resources. The WTRU may detect a conflict of reserved SL-PRS resources. The WTRU may determine to perform one or any combination of the following on the conflicting resources: perform resource (re)selection and stop using the reserved resources. The WTRU may continue to use the periodic SL-PRS procedure after stopping using one or more conflicting resources. For example, if the WTRU's reserved resources are within the MG / PPW of another WTRU, the WTRU may stop using the reserved resources.

[0236] The WTRU may determine which procedure to follow (e.g., perform resource (re)selection or stop using reserved resources) based on one or any combination of the following. The WTRU may determine which procedure to follow based on the number of reserved resources within a period (e.g., measurement reporting window, MG / PPW window). For example, if the number of reserved resources within the window is less than a threshold, the WTRU may (re)select the reserved resources, otherwise, if the number of reserved resources is greater than the threshold, the WTRU may stop using the reserved resources. The WTRU may determine which procedure to follow based on the MG / PPW length. For example, if the MG / PPW is less than a threshold, the WTRU may discard the reserved resources, otherwise, if the MG / PPW is greater than the threshold, the WTRU may reselect another resource. The WTRU may determine which procedure to follow based on the QoS (e.g., accuracy) requirements of the positioning service. For example, if the accuracy of the positioning service is greater than a threshold, the WTRU may reselect another resource due to conflict detection, otherwise, if the accuracy requirement of the positioning service is less than the threshold, the WTRU may stop using the reserved resources without reselecting another resource.

[0237] The WTRU may determine a channel busy rate (CBR) measurement in a dedicated resource pool. In an embodiment, the WTRU may determine the CBR of a resource pool that may be dedicated to SL-PRS transmission. The CBR may be determined based on the CBR in each time slot and / or SL-PRS duration within the measurement window. For example, the CBR in the resource pool may be the average CBR of all time slots / SL-PRS durations in the measurement window. The WTRU may determine the CBR in each time slot and / or SL-PRS duration based on one or any combination of the following. The WTRU may determine the CBR in each time slot and / or SL-PRS duration based on the ratio of the number of occupied SL-PRS patterns in each subchannel and / or bandwidth of the resource pool to the number of (pre) configured SL-PRS patterns. For example, the WTRU may determine the number of available SL-PRS patterns based on SCI decoding. The WTRU may determine the CBR in each time slot based on the ratio of the number of occupied SL-PRS patterns to the number of (pre) configured patterns. The WTRU may determine the CBR in each time slot and / or SL-PRS duration based on the received signal strength indicator (RSSI) measured in the bandwidth of the subchannel or resource pool per SL-PRS duration and / or time slot. For example, the WTRU may be (pre)configured with multiple SL-PRS resources in the time domain of each side link time slot. The WTRU may determine the availability of a resource in the time domain of the subchannel or resource pool based on the measured RSSI. If the RSSI of the SL-PRS resource measured in the time domain of a subchannel or resource pool bandwidth is greater than a threshold, the WTRU may consider the resource to be occupied, otherwise, the WTRU may consider the resource to be unoccupied. The WTRU may determine the CBR in each time slot and / or SL-PRS duration based on the ratio of the number of occupied PSCCH resources to the number of (pre)configured PSCCH resources in the CBR measurement window. In an example, the WTRU may determine whether the PSCCH resource is occupied based on the RSRP / RSSI measurement of the resources (pre)configured for the PSCCH. If the RSRP / RSSI in the (pre)configured resources for the PSCCH is greater than a threshold, the WTRU may consider the resources as occupied, otherwise, the WTRU may determine that the resources are not occupied. In an example, the WTRU may determine whether the PSCCH resources are occupied based on the detection of the SCI in the (pre)configured resources. If the WTRU detects the SCI in the (pre)configured PSCCH, the WTRU may consider the resources as occupied, otherwise, the WTRU may consider the resources as not occupied.

[0238] The CBR calculation in a period may be determined based on one or any combination of the following. The CBR calculation in a period may be determined based on the WTRU's selected SL-PRS pattern, which may include the comb size (e.g., in a time slot), bandwidth, and / or number of repetitions. The CBR calculation in a period may be determined based on a multiplexing scheme for SL-PRS transmission. For example, if the WTRU determines to perform a SL-PRS transmission without multiplexing with another transmission at the same time-frequency resource, the CBR in a SL-PRS duration and / or time slot may be determined as a binary value, where if there is a SL-PRS pattern transmitted in the time slot / SL-PRS duration, the time slot / SL-PRS duration may be considered occupied. Otherwise, the time slot may be considered unoccupied. For example, if the WTRU determines to select one SL-PRS pattern from a set of SL-PRS patterns in the SL-PRS duration, the WTRU may allow multiplexing with another SL-PRS pattern. The CBR in one SL-PRS pattern and / or timeslot may be determined based on the ratio of the number of occupied patterns to the (pre)configured patterns for simultaneous transmission at the same time-frequency resource. The CBR calculation in a period may be determined based on the SL-PRS pattern configuration in the resource pool. The CBR calculation in a period may be determined based on the bandwidth of the SL-PRS transmission. For example, the granularity of the CBR calculation in the frequency domain may be determined based on the bandwidth of the SL-PRS transmission. If the WTRU uses the entire bandwidth of the resource pool for SL-PRS transmission, the WTRU may use the entire resource pool bandwidth as the granularity of the CBR calculation in the frequency domain. Otherwise, if the WTRU uses subchannel-based transmission for SL-PRS, the WTRU may use the bandwidth of the subchannel as the granularity of the CBR calculation in the frequency domain.

[0239] The WTRU may determine a channel occupancy ratio (CR) for SL-PRS transmission. The WTRU may determine the CR for SL-PRS based on a ratio of the number of occupied resources to the number of resources configured in the CR calculation window.

[0240] The WTRU may use one or any combination of the following as the granularity of resources for CR calculation in the frequency domain. The WTRU may use resource elements (REs). For example, the WTRU may calculate the CR as the ratio between the number of occupied REs and the number of (pre)configured REs in the CR calculation window. The WTRU may use SL-PRS patterns. For example, the WTRU may calculate the CR as the ratio between the number of occupied SL-PRS patterns and the number of (pre)configured SL-PRS patterns in the CR calculation window. The WTRU may use subchannels. For example, the WTRU may calculate the CR as the ratio between the number of occupied subchannels and the number of (pre)configured subchannels in the CR calculation window.

[0241] The WTRU may use one or any combination of the following as the granularity of resources for CR calculation in the time domain. The WTRU may use symbols. For example, the WTRU may calculate the CR as the ratio between the number of occupied symbols and the number of (pre)configured symbols for SL-PRS transmission in the CR calculation window. The WTRU may use SL-PRS resource duration in the time domain. For example, the WTRU may calculate the CR as the ratio between the number of occupied SL-PRS resource periods and the number of (pre)configured SL-PRS resource periods in the CR calculation window. The WTRU may use time slots. For example, the WTRU may calculate the CR as the ratio between the number of occupied time slots and the number of (pre)configured time slots in the CR calculation window.

[0242] The WTRU may determine the channel occupancy in the shared resource pool. In an embodiment, the WTRU may maintain one or any combination of the following channel occupancies in the shared resource pool between the sidelink communication and the SL-PRS: a channel occupancy ratio (CR) for SL-PRS transmission, a CR for sidelink data transmission, or a CR for both SL-PRS and sidelink data transmission.

[0243] The WTRU may determine transmission parameters for the SL-PRS. In an embodiment, the WTRU may determine one or any combination of the following transmission parameters for the SL-PRS: SL-PRS pattern, which may include transmission bandwidth, comb size, number of symbols, and number of repetitions; periodicity; transmit power; number of retransmissions of each SL-PRS in a period; and multiplexing type with other transmissions.

[0244] One or any combination of the transmission parameters of the SL-PRS may be determined based on one or any combination of: the CBR of the resource pool; the CR of the WTRU, which may include a CR for SL-PRS transmission, a CR for sidelink data transmission, and / or a CR for both SL-PRS and sidelink data transmission; or one or more QoS parameters of the sidelink positioning service. For example, the WTRU may be (pre)configured with a set of transmission parameters for each QoS parameter of the sidelink positioning service. For example, the WTRU may be (pre)configured with the accuracy / priority of the positioning service using a set of transmission parameters (e.g., comb size, transmission bandwidth, and transmission power of the SL-PRS). The WTRU may be (pre)configured with the latency of the positioning service using another set of transmission parameters (e.g., number of retransmissions, periodicity). The WTRU may be (pre)configured with the reliability / availability of the sidelink positioning service using another set of transmission parameters. The WTRU may determine the transmission parameters of the SL-PRS based on the QoS parameters of the WTRU.

[0245] The WTRU may determine transmit parameters for transmission in a resource. In an embodiment, the WTRU may determine one or more transmit parameters in a transmission resource. Such determination may be based on whether the resource is for a standalone SL-PRS, a SL-PRS multiplexed with sidelink data, or for sidelink data only. In an example, the WTRU may be (pre)configured with two sets of transmit (Tx) parameters, wherein a first set of Tx parameters (e.g., Tx power, transmit bandwidth, MCS, number of retransmissions for one TB, etc.) may be associated with sidelink data transmission, and a second set of Tx parameters (e.g., Tx power, SL-PRS mode, bandwidth, comb size, number of symbols used for SL-PRS, number of repetitions) may be associated with SL-PRS transmission. Each set of parameters may be further (pre)configured based on the CBR of the resource pool, the CR of the WTRU (e.g., CR for SL-PRS transmission, CR for sidelink data transmission, and / or CR for both SL-PRS and sidelink data transmission), QoS for data transmission, and / or QoS associated with a sidelink positioning service. The WTRU may determine Tx parameters for each transmission in the resource pool based on whether the resources are for standalone SL-PRS, SL-PRS multiplexed with sidelink data, or sidelink data only. For example, if the WTRU uses resources for standalone SL-PRS, the WTRU may use a second set of Tx parameters based on the CBR of the resource pool, the CR of the WTRU, and the QoS of the sidelink positioning service. If the WTRU uses resources for SL-PRS and sidelink data, the WTRU may determine the transmission parameters based on both the first set of transmission parameters and the second set of transmission parameters.

[0246] The WTRU may determine whether to discard the SL-PRS resource. In an embodiment, the WTRU may be instructed or selected for a resource for SL-PRS transmission. The WTRU may determine whether to perform SL-PRS transmission in the resource based on one or any combination of the following: the CR for the SL-PRS and / or the CR for the SL-PRS and sidelink data, or whether the resource belongs to the WTRU's silent mode. For example, the WTRU may determine the silent mode for periodic SL-PRS transmission. The WTRU may implicitly / explicitly indicate its silent mode in one or more transmissions associated with the SL-PRS. If the resource is not within the WTRU's silent mode, the WTRU may determine to send the SL-PRS in the resource.

[0247] The WTRU may determine the availability of a subchannel slot based on the type of transmission in the subchannel slot. In an embodiment, the WTRU may determine the availability of a subchannel slot based on the type of transmission detected in the subchannel slot. For example, the WTRU may be (pre)configured with multiple RSSI thresholds. Each RSSI threshold may be associated with a type of subchannel slot. For example, the WTRU may be (pre)configured with three RSSI thresholds, wherein a first RSSI threshold may be used for sidelink data transmission, a second threshold may be used for sidelink data transmission with SL-PRS, and a third RSSI threshold may be used for independent SL-PRS. The WTRU may also use one of the three RSSI thresholds (e.g., the third RSSI threshold) for sidelink transmissions not detected in the subchannel slot. The WTRU may determine each type of transmission in the subchannel slot by an indication of the transmission associated with the transmission in the subchannel slot (e.g., in the SCI). The WTRU may determine the availability of each subchannel slot using the associated RSSI threshold to calculate the CBR in the CBR measurement window.

[0248] The WTRU may calculate multiple CBRs for each type of transmission. The WTRU may determine to calculate multiple CBRs, where each CBR may be associated with the CBR occupied by one type of transmission. For example, the WTRU may calculate the CBR due to the transmission of a standalone SL-PRS, the CBR due to the transmission of sidelink data, the CBR due to the transmission of sidelink data with SL-PRS, the CBR due to undetected transmissions, and / or the CBR due to all types of sidelink transmissions.

[0249] The WTRU may calculate multiple channel occupancy rates (CRs). The WTRU may determine to calculate multiple CRs, where each CR may be associated with a channel busy rate occupied by one type of transmission. For example, the WTRU may calculate a CR for transmission of a standalone SL-PRS, a CR for transmission of sidelink data, a CR for transmission of sidelink data with SL-PRS, and / or a CR for all types of sidelink transmissions.

[0250] The WTRU may use multiple RSSI thresholds to calculate multiple CBRs. The WTRU may be (pre)configured with multiple RSSI thresholds to determine the availability of a subchannel timeslot in a CBR measurement (e.g., the availability of a subchannel in a timeslot). The WTRU may calculate multiple CBRs, where each CBR may be associated with an RSSI threshold. For example, for each RSSI threshold, the WTRU may determine the ratio between the number of busy subchannel timeslots in the CBR measurement window and the total number of subchannel timeslots, where if the RSSI measured in the subchannel timeslot is greater than the RSSI threshold, the channel timeslot may be considered busy. For example, the WTRU may be (pre)configured with two RSSI thresholds, where one RSSI threshold (e.g., a low RSSI threshold) may be used to consider SL-PRS transmissions. The WTRU may be (pre)configured with another RSSI threshold (e.g., a high RSSI threshold) that may be used to capture normality to calculate sidelink data transmissions.

[0251] The WTRU may use two CBRs to adjust its sidelink transmissions. In an embodiment, the WTRU may use a CBR associated with a first RSSI threshold (e.g., a first CBR) to adjust one or more transmission parameters associated with a SL-PRS (e.g., a standalone SL-PRS and / or a SL-PRS with data). The WTRU may use a CBR associated with a second RSSI threshold (e.g., a second CBR) to adjust one or more transmission parameters associated with a sidelink data transmission (e.g., only sidelink data and / or a SL-PRS with sidelink data). For example, the WTRU may be (pre) configured with a range of SL-PRS transmission parameters (e.g., Tx power, SL-PRS mode, bandwidth, comb size, number of symbols used for SL-PRS, number of repetitions) for each range of the first CBR. The WTRU may determine which transmission parameters to use based on whether the first CBR belongs to which range. For example, the WTRU may be (pre) configured with a range of data transmission parameters (e.g., Tx power, transmission bandwidth, MCS, number of retransmissions for one TB, etc.) for each range of the second CBR. The WTRU may determine which sidelink data transmission parameters to use based on whether the second CBR falls within which range.

[0252] If the CR is greater than a threshold, the WTRU may adjust the transmission parameters of the SL-PRS. If the CR is greater than a (pre)configured threshold, the WTRU may determine to adjust the transmission parameters of the SL-PRS. For example, if the CR is greater than a (pre)configured threshold, the WTRU may increase the comb size, reduce the SL-PRS duration and / or reduce the SL-PRS transmission bandwidth. In an example, the WTRU may be (pre)configured with a CR limit for independent SL-PRS transmission. If the CR for an independent SL-PRS is greater than a threshold, the WTRU may additionally multiplex the SL-PRS with data.

[0253] The WTRU may determine which measurement parameters to request. In an embodiment, a WTRU (e.g., a target WTRU) may request another WTRU (e.g., an anchor WTRU) to report one or more SL-PRS measurement parameters. The requested WTRU may perform SL-PRS measurements and report the set of measurement parameters based on the indicated / requested SL-PRS measurement parameters from the requesting WTRU. In an embodiment, a WTRU (e.g., an anchor WTRU) may autonomously determine one or more SL-PRS measurement parameters to perform measurements and report to another node (e.g., a gNB, an LMF, another WTRU such as a target WTRU, an anchor WTRU). The SL-PRS measurement parameters may include, for example, SL reference signal received power (RSRP), reference signal received path power (SL-RSRPP), transmit and receive time difference (Tx-Rx difference), reference signal time difference (RSTD), departure time (ToD), departure angle (AoD), arrival time (ToA), timing error group (TEG), arrival phase (PoA), departure phase (PoD), arrival phase difference (DPoA) and departure phase difference (DPoD).

[0254] The WTRU may determine which measurement parameter or parameters to request. The WTRU (e.g., target WTRU) may determine which SL-PRS measurement parameters to report / request based on one or any combination of the following. The WTRU may determine which SL-PRS measurement parameters to report / request based on the positioning method. For example, for the RTT method, the WTRU may report / request the Tx-Rx difference and SL-RSRP of the SL-PRS. For the SL-TDOA method, the WTRU may request / report RSTD, ToA and / or SL-RSRP. The WTRU may determine which SL-PRS measurement parameter to report / request based on the capabilities of the RxWTRU. For example, the Tx WTRU may request the Rx WTRU to report SL-RSRPP and LOS / NLOS (line-of-sight / non-line-of-sight) conditions based on the capabilities of the Rx WTRU. For example, the Rx WTRU may indicate its SL-PRS measurement capabilities. The Tx WTRU may request the Rx WTRU to report a certain SL-PRS measurement parameter based on the capabilities of the Rx WTRU. The WTRU may determine which SL-PRS measurement parameters to report / request based on the QoS of the positioning service (e.g., priority, accuracy, latency, positioning availability). For example, if the QoS of the positioning service (e.g., accuracy) is greater than a threshold, the WTRU may request / report a certain parameter. For example, if the accuracy requirement of the positioning service is greater than a threshold, the WTRU may request / report an indication of a LOS / NLOS condition, otherwise, the WTRU may not be allowed to request the Rx WTRU to measure and report the LOS / NLOS condition. The WTRU may determine which SL-PRS measurement parameters to report / request based on the quality of a reported SL-PRS measurement. For example, the anchor WTRU may report SL-RSRP and RSTD, where the reported SL-RSRP is less than a (pre)configured threshold. The target WTRU may request the anchor WTRU to additionally report the LOS / NLOS condition to help the anchor WTRU determine whether the calculated distance between the two WTRUs is based on the LOS condition or the NLOS condition.

[0255] The WTRU may report a quality indicator of a measurement. A WTRU (e.g., an anchor WTRU) may determine and report a quality indicator of one or more SL-PRS measurement parameters. For example, the WTRU may (e.g., implicitly) report / indicate the quality of its measurements. The quality indicator may indicate whether the WTRU has experienced large fluctuations in power measurements and time measurements. It may also indicate a variable in the measurement, where the WTRU may indicate an error bound for a certain SL-PRS measurement parameter. For example, the WTRU may indicate a measured value of the SL-RSRP. The WTRU may indicate an error bound for the measured SL-RSRP. The WTRU may trigger reporting of a quality indicator of one or more SL-PRS measurement parameters based on one or any combination of the following: an indication from another node, and whether the quality indicator is less than / greater than a threshold or whether the error bound is greater than / less than a threshold. For example, if the error bound is greater than a (pre)configured threshold, the WTRU (e.g., an anchor WTRU) may report a quality indicator. For example, if the quality indicator is greater than a (pre)configured threshold, the WTRU may report the quality indicator, which may implicitly indicate that the measurement is good, and the target WTRU may use such report to derive its distance. The method may be motivated to support the target WTRU in determining which report to use when calculating its distance.

[0256] The WTRU may perform an action upon receiving a quality indicator of a measurement. In an embodiment, a WTRU (e.g., a target WTRU) may be (pre)configured with one or more thresholds for a quality indicator of a SL-PRS measurement parameter. If the quality indicator is greater than a first threshold, the WTRU may perform a first action, and if the quality indicator is less than a second threshold, the WTRU may perform a second action. A high value of the quality indicator may correspond to a good measurement. The first threshold and the second threshold may be the same or different. The first action may be to select the reported measurement to be forwarded to the network (e.g., LMF). The second action may be one or more of: removing the report from a set of measurement reports to the network (e.g., LMF); triggering resource selection for the SL-PRS to send more SL-PRS to the reporting WTRU; sending more SL-PRS to the WTRU; changing the SL-PRS configuration (e.g., adding more SL-PRS resources, increasing transmit power, increasing SL-PRS bandwidth, reducing the SL-PRS comb size, and / or increasing the SL-PRS duration); and removing the WTRU (e.g., anchor WTRU) from the positioning group.

[0257] The WTRU may determine the measurement reporting granularity of the measurement parameters. The WTRU (e.g., anchor WTRU) may determine the granularity of one or more (e.g., each) measurement parameters to report to another node (e.g., target WTRU, LMF, gNB). In the report, the WTRU may indicate which granularity is used to report the SL-PRS measurement parameters. The WTRU may determine the granularity of each measurement parameter based on one or any combination of the following. The WTRU may determine the granularity of each measurement parameter based on an indication from another node (e.g., target WTRU, gNB, LMF). For example, the target WTRU may indicate the granularity of one or more SL-PRS measurement parameters (e.g., ToA, RSTD, Tx-Rx) to the anchor WTRU. The anchor WTRU may perform SL-PRS measurements and reports using the granularity indicated by the target WTRU. The WTRU may determine the granularity of each measurement parameter based on the positioning method. For example, for one SL-PRS measurement parameter, the WTRU may be (pre)configured with one granularity for each positioning method. The WTRU may determine which granularity to use to perform measurements and reports based on the positioning method that the WTRU is using. For example, for SL-RSRP measurement and reporting, the WTRU may be (pre)configured with one granularity for angle-based methods (e.g., AoA, AoD) and another granularity for timing-based methods (SL-TDOA, RTT). The WTRU may determine which granularity to use based on the positioning method used. The WTRU may determine the granularity of each measurement parameter based on the QoS of the positioning service (e.g., priority, accuracy, latency, positioning availability). For example, the WTRU may be (pre)configured with multiple granularities of SL-PRS measurement parameters. Each granularity may be associated with a positioning accuracy requirement. The WTRU may determine which granularity to use based on the positioning accuracy requirement of the positioning service. The WTRU may determine the granularity of each measurement parameter based on the distance between the SL-PRS transmitter (e.g., target WTRU) and the SL-PRS receiver (e.g., anchor WTRU). For example, the WTRU may be (pre)configured with multiple granularities, each of which may be associated with a range of distances between the transmitter and the receiver. The WTRU may determine which granularity to use for the SL-PRS measurement parameters based on which (pre)configured range the distance between the SL-PRS transmitter and the receiver belongs to. The WTRU may determine the granularity of each measurement parameter based on the propagation time between the transmitter and the receiver. For example, the WTRU may be (pre)configured with multiple granularities. Each granularity may be associated with a range of propagation time between the transmitter and the receiver. The WTRU may determine which granularity to use for the SL-PRS measurement parameters based on which (pre)configured range the propagation time between the SL-PRS transmitter and the receiver belongs to.The WTRU may determine the granularity of each measurement parameter based on the value of the SL-PRS measurement parameter (e.g., RSTD, AoA, AoD, distance, ToA, ToD). For example, the WTRU may be (pre-)configured with multiple SL-PRS granularities for the SL-PRS measurement parameter. Each granularity may be used for a range of SL-PRS measurement parameters. The WTRU may determine which granularity to use based on which (pre-)configured range the value of the SL-PRS measurement parameter belongs to.

[0258] The WTRU may determine the MG / PPW configuration. In an embodiment, the WTRU (e.g., a target WTRU) may determine its MG / PPW configuration (e.g., offset, periodicity, and MG / PPW length) to perform SL-PRS measurements and SL-PRS measurement processing. The WTRU may determine the MG / PPW configuration based on one or any combination of the following. The WTRU may determine the MG / PPW configuration based on the SL-PRS configuration (e.g., offset, periodicity of the SL-PRS). For example, the WTRU may determine that the MG / PPW is configured per a (pre)configured number of SL-PRS periods. The WTRU may configure the MG / PPW to be the same as the offset of the SL-PRS. The WTRU may determine the MG / PPW configuration based on the SL-PRS measurement report configuration. For example, the WTRU (e.g., an anchor WTRU) may determine that the MG / PPW is configured so that the WTRU may be able to measure the SL-PRS within the MG / PPW for at least a (pre)configured number of times. The (pre)configured number of MG / PPWs between two reports may be indicated by another node (e.g., LMF, target WTRU), and the (pre)configured number of MG / PPWs may be determined based on the QoS of the positioning service. The WTRU may configure the MG / PPW to be the same as the offset of the SL-PRS measurement report. The WTRU may determine the MG / PPW configuration based on the QoS of the positioning service. For example, if the positioning service has high accuracy and / or low latency requirements, the WTRU may determine to configure a longer MG / PPW with a shorter periodicity. If the positioning service requires low accuracy and / or high latency, the WTRU may determine to configure a shorter MG / PPW with a longer periodicity.

[0259] The WTRU may trigger resource (re)selection based on the MG / PPW indicated from the Rx WTRU. In an embodiment, if the SL-PRS resources reserved by the WTRU (e.g., the target WTRU) for the peer WTRU are within the MG / PPW of the peer WTRU, the WTRU (e.g., the target WTRU) may trigger resource (re)selection for the SL-PRS upon receiving the MG / PPW of the peer WTRU. In an example, if the reserved SL-PRS resources of the WTRU (e.g., the target WTRU) are within the configured MG / PPW, the WTRU (e.g., the target WTRU) may trigger resource (re)selection for the SL-PRS upon receiving (e.g., from another WTRU or from the LMF) a MG / PPW configuration for itself.

[0260] In an embodiment, the WTRU may perform resource allocation in a dedicated resource pool for SL-PRS.The WTRU may determine which set of available resources to select for SL-PRS transmission based on the number of available resources in each set. Fig. 9An example method 900 for resource allocation in a dedicated resource pool for SL-PRS is shown. A WTRU may be (pre)configured with a dedicated resource pool for SL-PRS transmission 910. The WTRU may receive information indicating the dedicated resource pool for SL-PRS transmission. The WTRU may be (pre)configured with a threshold for a first type of resource and a threshold for a second type of resource to perform SL-PRS selection / transmission 920. For example, the WTRU may receive information indicating a first threshold (e.g., X%) for a first type of resource and a second threshold (e.g., Y%) for a second type of resource. X% and Y% may be a function of the QoS (e.g., priority, accuracy, latency, availability and / or reliability) of the positioning service. The first type of resource may be a first set of resources, and the second type of resource may be a second set of resources. For example, the first set of resources may include a set of time slots for SL-PRS transmission (e.g., TDM), and the second set of resources may include a set of REs in a time slot according to a (pre)configured SL PRS pattern. In a time slot, there may be multiple resources of the second type. The first type of resource may be a resource that is not RE-level multiplexed with other WTRUs. The second type of resource may be a resource that is RE-level multiplexed with other WTRUs. X% may represent a ratio between the number of resources of the first type available for resource selection and the total number of resources of the first type. Y% may represent a ratio between the number of resources of the second type available for resource selection and the total number of resources of the second type. In an example, the WTRU may determine X% and Y% based on resource allocation for non-positioning services (e.g., data communications). For example, the WTRU may receive a priority level for data communications and determine X% and Y% based on the priority level associated with the data communications. The WTRU may receive QoS information for positioning services and a SL-PRS pattern to be selected from another node (e.g., an anchor WTRU) 930. The WTRU may determine the values ​​of X and Y based on the QoS information received from the other node 940. The WTRU may perform sensing to determine a first set and a second set of available resources 950. The WTRU may perform sensing by decoding an SCI. The WTRU may obtain resource reservation information indicated in the decoded SCI and perform RSRP measurement on the PSCCH carrying the decoded SCI. In another example, the WTRU may measure the RSRP of the PSSCH associated with the PSCCH. The WTRU may determine that a timeslot may be a resource of the first type available for resource selection when any of the following may occur: the WTRU does not decode any SCI including resource reservation for the timeslot when sensing, or the WTRU decodes an SCI including resource reservation for the timeslot when sensing and the associated RSRP is below a (pre)configured threshold.The WTRU may determine that a set of REs in a slot according to a (pre)configured SL PRS pattern available for resource selection may be a second type of resource when any of the following may occur: the WTRU does not decode any SCI including resource reservation for the set of REs in the slot, or the WTRU decodes an SCI including resource reservation for the set of REs in the slot upon sensing and the associated RSRP is below a (pre)configured threshold. The WTRU may select SL-PRS resources for transmission 960. If the first set of resources (e.g., the number of resources in the first set) is greater than X%, the WTRU may select SL-PRS resources from the first set. If the first set of resources (e.g., the number of resources in the first set) is equal to or less than X% and the first and second sets of resources (e.g., the number of resources in the first and second sets) are greater than Y%, the WTRU may select SL-PRS resources from the first set and the second set. The WTRU may send SL-PRS in the selected resources 970. If the WTRU does not select SL-PRS resources, the WTRU may request other nodes (eg, an anchor WTRU) to change the SL-PRS mode.

[0261] In an embodiment, the WTRU may perform resource allocation in a shared resource pool between SL-PRS and sidelink data. The WTRU may determine which threshold (e.g., RSRP threshold) to apply to determine the availability of each reserved resource based on whether the resource is reserved for normal data communication or SL-PRS. If the amount of available resources is less than the threshold, the WTRU may request another WTRU to change the SL-PRS mode. Fig.10An example method 1000 for resource allocation in a shared resource pool between SL-PRS and sidelink data is shown. A WTRU may be (pre)configured with a shared resource pool for SL-PRS and data communication 1010. The WTRU may receive information indicating the shared resource pool. The WTRU may be (pre)configured with a threshold (e.g., X%) of available resources for SL-PRS selection 1020. The WTRU may receive information indicating a threshold X% of available resources for SL-PRS selection. The WTRU may be (pre)configured with two sets of RSRP thresholds 1030. The WTRU may receive information indicating a set of RSRP thresholds. One set of RSRP thresholds may be applied to SL-PRS resources and another set of RSRP thresholds may be applied to data transmission. The WTRU may receive QoS information for positioning services and a SL-PRS mode to be selected from another node (e.g., an anchor WTRU) 1040. The WTRU may perform sensing 1050. The WTRU may perform sensing by decoding SCIs from other WTRUs that may be used to reserve transmission resources. For each reserved resource, the WTRU may determine whether the reserved resource is for SL-PRS or for normal data communication. The WTRU may determine a set of available resources for SL-PRS transmission 1060. The WTRU may determine a set of available resources for SL-PRS transmission using a first set of RSRP thresholds and a second set of RSRP thresholds. The WTRU may apply the first set of RSRP thresholds to resources associated with SL-PRS. The WTRU may apply the second set of RSRP thresholds to resources associated with data communication. The WTRU may select SL-PRS resources 1070. If the number of available resources is greater than X%, the WTRU may select resources for SL-PRS using the available resources and indicating in the SCI that the resources are reserved for SL-PRS transmission. If the number of available resources is not greater than X%, the WTRU may request other nodes (e.g., an anchor WTRU) to change the SL-PRS mode or switch to another resource pool for SL-PRS selection. The WTRU may send the SL-PRS in the selected SL-PRS resources 1080.

[0262] In an embodiment, for congestion control in a dedicated resource pool for SL-PRS, the WTRU may determine a first set of transmit (Tx) parameters for the SL-PRS based on a first QoS parameter of a positioning service, and determine a second set of Tx parameters for the SL-PRS based on a second QoS parameter. Fig.11An example method 1100 for congestion control in a dedicated resource pool for SL-PRS is shown. A WTRU may be (pre)configured with a dedicated resource pool for SL-PRS 1110. The WTRU may receive information indicating the dedicated resource pool for SL-PRS. The WTRU may be (pre)configured with two sets of Tx parameter thresholds 1120. The Tx parameter thresholds may be a function of the CBR. The WTRU may receive information indicating the two sets of Tx parameter thresholds. A first set of Tx parameter thresholds may be associated with a first positioning QoS parameter. A second set of Tx parameter thresholds may be associated with a second positioning QoS parameter. For example, the maximum bandwidth may be a function of the accuracy / priority requirement, and the number of SL-PRS transmissions within a period may be a function of the latency requirement. The WTRU may determine Tx parameters 1130 based on, for example, the QoS parameters, the CBR, and the associated Tx parameter thresholds. The WTRU may transmit the SL-PRS 1140 based on or using the determined transmission parameters.

[0263] In an embodiment, the WTRU may perform congestion control in a shared resource pool. The WTRU may determine which set of Tx parameters to use based on whether the SL-PRS is multiplexed with data. The WTRU may use both a first set of Tx parameters for a standalone SL-PRS and a first set of parameters and a second set of parameters for multiplexing the SL-PRS with data. Fig.12An example method 1200 for congestion control in a shared resource pool between SL-PRS and sidelink data communications is shown. A WTRU may be (pre)configured with a shared resource pool for SL-PRS and SL data communications 1210. The WTRU may receive information indicating a shared resource pool for SL-PRS and SL data communications. The WTRU may be (pre)configured with two sets of transmit (Tx) parameters 1220. The WTRU may receive information indicating two sets of Tx parameters. The two sets of Tx parameters may be a function of the CBR. A first set of Tx parameters may be used for SL-PRS transmission (e.g., Tx power, bandwidth, CR limit for SL-PRS, comb N, number of symbols, etc.). A second set of TX parameters may be used for data transmission. The WTRU may receive information about two RSSI thresholds 1230. In an example, the RSSI thresholds may be (pre)configured in the resource pool. A first RSSI threshold may be used for a standalone SL-PRS and a second RSSI threshold may be used for other transmissions (e.g., PSSCH / PSCCH transmissions). The WTRU may determine the CBR of the resource pool 1240. If the sub-channel slot is transmitted by an independent SL-PRS, the WTRU may use a first RSSI threshold to determine the availability of the sub-channel slot. If the sub-channel slot is not transmitted by an independent SL-PRS, the WTRU may use a second RSSI threshold to determine the availability of the sub-channel slot. The WTRU may determine Tx parameters for the SL-PRS based on whether the SL-PRS is an independent SL-PRS or an SL-PRS multiplexed with sidelink data 1250. For example, for an independent SL-PRS, the WTRU may apply a first set of Tx parameters, and for an SL-PRS multiplexed with sidelink data, the WTRU may determine the Tx parameters based on both the first set of Tx parameter thresholds and the second set of Tx parameter thresholds (e.g., each Tx parameter needs to meet a threshold in the first set or the second set). The WTRU may send the SL-PRS based on or using the determined transmit parameters 1260.

[0264] In an embodiment, the WTRU may determine the SCI to indicate the SL-PRS information. The WTRU may perform SL-PRS transmission. The WTRU may determine which SCI will indicate information about its SL-PRS transmission based on whether the WTRU is transmitting a standalone SL-PRS or a SL-PRS with data. Fig.13An example method 1300 for determining an SCI to indicate SL-PRS information is shown. A WTRU may be (pre)configured with SL-PRS information to indicate in the SCI 1310. The WTRU may receive information indicating SL-PRS information to indicate in the SCI. For example, the SL-PRS information may be a SL-PRS pattern (e.g., comb size, RE offset, SL-PRS duration). The WTRU may determine which SCI will indicate the SL-PRS information (e.g., SL-PRS pattern) 1320. For example, if the WTRU sends a standalone SL-PRS, the WTRU may use a first SCI (e.g., an SCI sent in a PSCCH) to indicate the SL-PRS information, and if the WTRU sends a SL-PRS with data, the WTRU may use a second SCI (e.g., an SCI sent in a PSSCH) to indicate the SL-PRS information. The WTRU may send the SCI 1330.

[0265] Fig.14 An example of sensing for determining a first type of SL-PRS resource and a second type of SL-PRS resource is shown. The WTRU may perform sensing during a sensing window to determine a first type of resource and a second type of resource. The first type of resource may be a resource that is not RE-level multiplexed with other WTRUs. The second type of resource may be a resource that is RE-level multiplexed with other WTRUs. A resource selection trigger may occur, for example, at time n. A resource may be selected during a resource selection window (RSW), for example, between time n+1 and n+2.

[0266] Fig.15An example method 1500 for determining a set of SL-PRS candidate resources based on priority is shown. A WTRU may receive configuration information 1510 indicating a SL-PRS priority threshold. The priority threshold information may be (pre)configured in a resource pool. The priority threshold information may be indicated in higher layer signaling (e.g., WTRU-specific signaling). The WTRU may receive information 1520 triggering SL-PRS transmission. The information triggering SL-PRS transmission may be received from a higher layer in the WTRU. The information triggering SL-PRS transmission may be received from a non-access stratum (NAS) layer. The triggered SL-PRS transmission may have an associated priority. The priority may be indicated from a higher layer. The WTRU may determine a first type of SL-PRS resource and a second type of SL-PRS resource 1530. The determination may be based on sensing during a sensing window. The sensing may be performed per time slot or per sub-time slot. The sensing may determine or provide information about SL-PRS resources reserved by other WTRUs. The first type of SL-PRS resources may be resources that are not multiplexed with other WTRUs. The first type of SL-PRS resource may be a resource that is not multiplexed at the resource element (RE) level with other WTRUs. The second type of SL-PRS resource may be a resource that is multiplexed at the resource element (RE) level with other WTRUs. The second type of SL-PRS resource may be a resource that is multiplexed at the resource element (RE) level with other WTRUs. The WTRU may select available resources to include in the SL-PRS candidate resource set 1540. Selecting available resources to include in the SL-PRS candidate resource set may be performed during a resource selection window (RSW). The WTRU may select available resources based on a priority associated with the SL-PRS transmission and a SL-PRS priority threshold. The SL-PRS candidate resource set may include at least the first type of SL-PRS resource or the second type of SL-PRS resource. Under the condition that the priority associated with the SL-PRS transmission is lower than the SL-PRS priority threshold, the WTRU may select available resources from both the first type of SL-PRS resource and the second type of SL-PRS resource. The WTRU may select available resources from only the first type of SL-PRS resources, provided that the priority associated with the SL-PRS transmission is greater than or equal to the SL-PRS priority threshold. The WTRU may select one or more SL-PRS resources from the set of SL-PRS candidate resources 1550. The WTRU may transmit the SL-PRS in the selected one or more SL-PRS resources 1560.

[0267] A (pre)configured WTRU may also mean that the WTRU receives information about the configuration.

[0268] Although features and elements are described above in specific combinations, it will be understood by those of ordinary skill in the art that each feature or element may be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (sent via a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method for use by a wireless transmit / receive unit (WTRU), the method comprising: receiving information indicating a sidelink positioning reference signal (SL-PRS) priority threshold; receiving information triggering a SL-PRS transmission, the SL-PRS transmission having an associated priority; determining a first type of SL-PRS resource and a second type of SL-PRS resource based on sensing during a sensing window, wherein the first type of SL-PRS resource is a resource that is not multiplexed with other WTRUs, and wherein the second type of SL-PRS resource is a resource that is multiplexed with other WTRUs; selecting, based on the priority associated with the SL-PRS transmission and the SL-PRS priority threshold, available resources to include in a SL-PRS candidate resource set, wherein the SL-PRS candidate resource set includes at least the first type of SL-PRS resources or the second type of SL-PRS resources; Select one or more SL-PRS resources from the SL-PRS candidate resource set; and The SL-PRS is sent using the selected one or more SL-PRS resources.

2. The method according to claim 1, wherein the sensing further comprises: Determine the SL-PRS resources reserved by other WTRUs.

3. The method according to any one of claims 1 or 2, wherein selecting available resources to include in the SL-PRS candidate resource set further comprises: On the condition that the priority associated with the SL-PRS transmission is lower than the SL-PRS priority threshold, available resources are selected from both the first type of SL-PRS resources and the second type of SL-PRS resources.

4. The method according to any one of claims 1 to 3, wherein selecting available resources to include in the candidate resource set further comprises: Selecting available resources from among only the first type of SL-PRS resources on the condition that the priority associated with the SL-PRS transmission is higher than or equal to the SL-PRS priority threshold.

5. The method according to any one of claims 1 to 4, wherein the first type of SL-PRS resources are resources that are not multiplexed at the resource element (RE) level with other WTRUs, and wherein the second type of SL-PRS resources are resources that are multiplexed at the resource element (RE) level with other WTRUs.

6. The method according to any one of claims 1 to 5, wherein the information triggering SL-PRS transmission is received from a higher layer in the WTRU.

7. The method according to any one of claims 1 to 6, wherein the information triggering SL-PRS transmission is received from a non-access stratum (NAS) layer.

8. The method according to any one of claims 1 to 7, wherein selecting available resources to include in the SL-PRS candidate resource set is performed during a resource selection window (RSW).

9. The method according to any one of claims 1 to 8, further comprising: Sidelink control information (SCI) indicating SL-PRS information is transmitted.

10. The method according to any one of claims 1 to 9, wherein the SL-PRS information indicates a SL-PRS pattern.

11. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising: Receiver; Transmitter; and A processor, wherein: The receiver is configured to receive information indicating a sidelink positioning reference signal (SL-PRS) priority threshold; The receiver is further configured to receive information triggering a SL-PRS transmission, the SL-PRS transmission having an associated priority; The processor is configured to determine a first type of SL-PRS resource and a second type of SL-PRS resource based on sensing during a sensing window, wherein the first type of SL-PRS resource is a resource that is not multiplexed with other WTRUs, and wherein the second type of SL-PRS resource is a resource that is multiplexed with other WTRUs; The processor is further configured to select available resources to include in a SL-PRS candidate resource set based on the priority associated with the SL-PRS transmission and the SL-PRS priority threshold, wherein the SL-PRS candidate resource set includes at least the first type of SL-PRS resources or the second type of SL-PRS resources; The processor is further configured to select one or more SL-PRS resources from the SL-PRS candidate resource set; and The transmitter is configured to transmit the SL-PRS using the selected one or more SL-PRS resources.

12. The WTRU of claim 11, wherein the processor is further configured to determine SL-PRS resources reserved by other WTRUs.

13. A WTRU according to any one of claims 11 or 12, wherein the processor is further configured to: select available resources from both the first type of SL-PRS resources and the second type of SL-PRS resources under the condition that the priority associated with the SL-PRS transmission is lower than the SL-PRS priority threshold.

14. A WTRU according to any one of claims 11 to 13, wherein the processor is further configured to: select available resources from only the first type of SL-PRS resources under the condition that the priority associated with the SL-PRS transmission is higher than or equal to the SL-PRS priority threshold.

15. A WTRU according to any one of claims 11 to 14, wherein the first type of SL-PRS resources are resources that are not multiplexed at the resource element (RE) level with other WTRUs, and wherein the second type of SL-PRS resources are resources that are multiplexed at the resource element (RE) level with other WTRUs.

16. The WTRU of any one of claims 11 to 15, wherein the information triggering SL-PRS transmission is received from a higher layer in the WTRU.

17. The WTRU of any one of claims 11 to 16, wherein the information triggering the SL-PRS transmission is received from a non-access stratum (NAS) layer.

18. The WTRU of any one of claims 11 to 17, wherein the processor is further configured to select available resources to include in the SL-PRS candidate resource set during a resource selection window (RSW).

19. The WTRU of any one of claims 11 to 18, wherein the transmitter is further configured to transmit sidelink control information (SCI) indicating SL-PRS information.

20. The WTRU of any one of claims 11 to 19, wherein the SL-PRS information indicates a SL-PRS pattern.

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