Sl-u channel acquisition with a multi-priority window

Abstract

Devices and techniques for SL-U acquisition with a multi-priority window are provided. An example device (e.g., an anchor wireless transmit / receive unit (WTRU)) may receive configuration information that indicates a time, after reception of a first sidelink positioning reference signal (SL-PRS), within which to send a second SL-PRS. The device may receive the first SL-PRS. The device may perform a first listen before talk (LBT) procedure associated with a first priority within a first window of time. On a condition that the device does not acquire a channel occupancy time (COT) based on the first LBT procedure, the device may perform a second LBT procedure associated with a second priority in a second window of time. The device may send a transmission. Content of the transmission may depend on whether the device was able to acquire the COT during the time within which to send the second SL-PRS.

Description

SL-U CHANNEL ACQUISITION WITH A MULTI-PRIORITY WINDOWCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 531,065, filed August ?, 2023, the contents of which is incorporated by reference herein.BACKGROUND

[0001] Mobile communications using wireless communication continue to evolve. A fifth generation may be referred to as 5G. A previous (legacy) generation of mobile communication may be, for example, fourth generation (4G) long term evolution (LTE).SUMMARY

[0002] Devices and techniques for SL-U channel acquisition with a multi-priority window are provided herein.

[0003] An example device (e.g., a wireless transmit / receive unit (WTRU)) may receive configuration information that indicates a time, after reception of a first sidelink positioning reference signal (SL-PRS), within which to send a second SL-PRS. The device may receive the first SL-PRS. The device may perform a first listen before talk (LBT) procedure associated with a first priority within a first window of time. On a condition that the WTRU does not acquire a channel occupancy time (COT) based on the first LBT procedure, the device may perform a second LBT procedure associated with a second priority in a second window of time. The device may send a transmission. Content of the transmission may depend on whether the WTRU was able to acquire the COT during the time within which to send the second SL-PRS.

[0004] The device may determine a duration of the first window of time based on a third priority associated with the first SL-PRS. The duration of the first window of time may be inversely proportional to the third priority.

[0005] The device may determine, based on local sidelink channel measurements, at least one of: a duration of the first window of time, a duration of the second window of time, the first priority, or the second priority.

[0006] On a condition that the WTRU was able to acquire the COT during the time within which to send the second SL-PRS, the transmission may include the second SL-PRS and control information that indicates a resource associated with the second SL-PRS. The device may select a sidelink resource in which to send the second SL-PRS. The transmission may include the second SL-PRS. The transmission may be sent to a target WTRU or a server WTRU via the sidelink resource.

[0007] On a condition that the WTRU was unable to acquire the COT during the time within which to send the second SL-PRS, the transmission may include an indication that a current session has been aborted and an indication that the current session was aborted because the WTRU was unable to acquire the COT.

[0008] At least a portion of the first window of time and a portion of the second window of time may overlap. The configuration information may indicate an offset between a start of the first window of time and a start of the second window of time.

[0009] The time within which to send the second SL-PRS may begin at a start of the first window of time, and end at an end of the second window of time. The WTRU acquire the COT during the time within which to send the second SL-PRS by acquiring a resource in which to send the second SL-PRS before the end of the second window of time.

[0010] An example device (e.g., an anchor WTRU) may receive a first sidelink positioning reference signal (SL-PRS). The device may perform a type 1 listen before talk (LBT) with a first priority level within a first window to acquire a channel occupancy time (COT). The device may, on a condition that the anchor WTRU does not acquire the COT in the first window, perform a type 1 LBT with a second priority level in a second window. The device may send a transmission.

[0011] The device may select a sidelink resource within a duration from the first SL-PRS. The transmission may include a second SL-PRS. The transmission may be sent to a target or server WTRU using the sidelink resource.

[0012] The device may, on a condition that the second SL-PRS fails to be transmitted to the target / server WTRU: abort a current RTT session; and transmit an abort indication to the target / server WTRU.

[0013] The device may receive configuration information. The configuration information may indicate the first window, the second window, and the duration. The first window may start when the anchor WTRU receives the first SL-PRS.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Furthermore, like reference numerals in the figures indicate like elements.

[0015] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0016] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0017] FIG. 1 C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment.

[0018] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment.

[0019] FIG. 2 illustrates an example of a WTRU sensing with two non-overlapping windows (e.g., multipriority window).

[0020] FIG. 3 illustrates an example of a WTRU sensing with overlapping sensing windows.

[0021] FIG. 4 illustrates an example of overlapping start-aligned multi-priority sensing windows (e.g., where the two windows start at the same time).

[0022] FIG. 5 illustrates an example of multi-priority channel acquisition for SL-PRS transmission.

[0023] FIG. 6 illustrates an example shared COT with a SL-PRS based COT busy signal and anchorWTRU ACK / NACK feedback.

[0024] FIG. 7 illustrates an example shared COT with SL-PRS based COT busy signal.

[0025] FIG. 8 illustrates an example shared COT with SL-PRS based COT busy signal (e.g., with anchorWTRU ACK / NACK).

[0026] FIG. 9 illustrates an example shared COT with SL-PRS based COT busy signal.

[0027] FIG. 10 illustrates an example server WTRU RTT selection procedure (e.g., with target and anchor WTRU channel measurements).

[0028] FIG. 11 illustrates an example server WTRU RTT selection procedure.

[0029] FIG. 12 illustrates an example of multi-RTT shared COT SL-U positioning.DETAILED DESCRIPTION

[0030] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communicationssystems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0031] As shown in FIG. 1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a ON 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a “station” and / or a “ST A”, may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0032] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0033] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to asa cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in desired spatial directions.

[0034] 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).

[0035] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0036] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0037] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR Radio Access, which may establish the air interface 116 using New Radio (NR).

[0038] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., an eNB and a gNB).

[0039] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0040] The base station 114b in FIG. 1 A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG. 1 A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106 / 115.

[0041] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may be utilizing a NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0042] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use commoncommunication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0043] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0044] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0045] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0046] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It willbe appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0047] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0048] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.

[0049] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0050] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0051] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It willbe appreciated that the WTRU 102 may acquire location information by way of any suitable locationdetermination method while remaining consistent with an embodiment.

[0052] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0053] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0054] FIG. 1 C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology 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.

[0055] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0056] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling ofusers in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0057] The CN 106 shown in FIG. 1 C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0058] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0059] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0060] 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.

[0061] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0062] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0063] In representative embodiments, the other network 112 may be a WLAN.

[0064] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad- hoc” mode of communication.

[0065] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in in 802.11 systems. For CSMA / CA, the STAs (e.g., every 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.

[0066] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0067] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHzchannels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0068] Sub 1 GHz modes of operation are supported by 802.11af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 n, and802.11 ac. 802.11 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11 ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non- TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter type Control / Machine-type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0069] WLAN systems, which may support multiple channels, and channel bandwidths, such as802.11 n, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0070] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0071] FIG. 1 D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the

[0072] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0073] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0074] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0075] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E- UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0076] The CN 115 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0077] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0078] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernetbased, and the like.

[0079] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b,102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0080] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0081] In view of Figures 1A-1 D, and the corresponding description of Figures 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0082] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or may performing testing using over-the-air wireless communications.

[0083] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0084] Feature(s) associated with new radio (NR) positioning are provided herein.

[0085] Feature(s) associated with NR Uu positioning specified downlink (DL)-based, uplink (UL)-based, and / or DL and UL-based positioning are provided herein.

[0086] Feature(s) associated with DL-based positioning are provided herein.

[0087] In DL-based positioning, DL-PRS may be sent from multiple TRPs to a WTRU. The WTRU may observe and / or measure downlink signals from the TRPs. For WTRU-B positioning, the WTRU may calculate its position. For WTRU-A positioning, the WTRU may transmit the downlink measurement to the network. For angle-based positioning, the WTRU may report the Angle of Arrival (AoA) and / or RSRP of the downlink signals from the TRPs. For timing-based positioning, the WTRU may report RSTD. These techniques may use transmission timing synchronization among the TRPs. Positioning calculation errors may come from synchronization error and / or multipath.

[0088] Feature(s) associated with UL-based positioning are provided herein.

[0089] In uplink positioning, the WTRU may send UL-PRS for positioning, configured by RRC, to the TRP. The network may calculate the position of the WTRU (e.g., based on the coordination of all the TRPs receiving UL-PRS from the WTRU).

[0090] Feature(s) associated with UL and DL-based positioning are provided herein.

[0091] In UL and DL-based positioning, the WTRU may measure a receive-transmit (Rx-Tx) time difference between received DL-PRS and UL-PRS transmitted. The Rx-Tx time difference and / or RSRP may be reported to the network. The network may coordinate the TRPs to calculate the position of the WTRU.

[0092] Feature(s) associated with sidelink (SL) positioning are provided herein.

[0093] SL positioning may be used (e.g., in RAN1) for SL-only-based positioning and / or a combination of SL- and Uu-based positioning. SL positioning may include SL-RTT (Round Trip Time), SL-AoA, and / or SL-TDoA (Time Difference of Arrival) (e.g., which may be supported for R18 SL positioning). For SL-TDoA, techniques based on DL-TDoA and UL-TDoA may be considered.

[0094] A “timi ng / angle positioning method” may refer to a positioning technique that uses reference signals such as SL-PRS. The WTRU may receive multiple reference signals from WTRU(s). The WTRU may measure the RSTD, RSRP, and / or AoA. Examples of angle / timing positioning techniques include SL- AoD or SL-TDOA positioning. The WTRU may transmit SL-PRS to WTRU(s). The WTRU may receive measurements (e.g., RSTD, AoA, RSRP) for determination of the locations of the WTRU that transmitted SL-PRS.

[0095] A “RTT positioning method” may refer to any positioning techniques that uses multiple (e.g., two) WTRUs to transmit SL-PRS to each other. An anchor WTRU may transmit SL-PRS to the target WTRU. If the target WTRU receives SL-PRS from the anchor WTRU, the target WTRU may transmit SL-PRS to the anchor WTRU. The target WTRU may measure a WTRU Tx-Rx time difference (e.g., the difference between transmission time of SL PRS from the target WTRU and reception time of SL-PRS transmitted from the anchor WTRU). The target WTRU may report the WTRU Tx-Rx time difference to the anchor WTRU / network (e.g., gNB, LMF). In an example, a “target WTRU” may refer to a WTRU whose location is to be determined by a peer WTRU (e.g., server WTRU) and / or the network (e.g., LMF, gNB). An “anchor WTRU” may refer to the WTRU that transmits and / or receives SL-PRS to assist a peer WTRU (e.g., target WTRU, server WTRU) to determine the target WTRU’s location. The target WTRU may determine its location based on the measurements made on SL-PRS. The target WTRU may send measurements to the network or peer WTRU so that the network or peer WTRU can determine the target WTRU’s location.

[0096] “Network” may include AMF, LMF, gNB or NG-RAN. “Pre-configuration” and “configuration” may be used interchangeably herein. A “non-serving gNB” and “neighboring gNB” may be used interchangeably herein. A “gNB” and “TRP” may be used interchangeably herein. “PRS” or “PRS resource” may be used interchangeably herein. “PRS(s)” or “PRS resource(s)” may be used interchangeably herein. The aforementioned “PRS(s)” or “PRS resource(s)” may belong to different PRS resource sets. “PRS” or “DL- PRS” or “DL PRS” may be used interchangeably herein. “Measurement gap” or “Measurement gap pattern” may be used interchangeably herein. “Measurement gap pattern” may include parameters (e.g., measurement gap duration, measurement gap repetition period, and / or measurement gap periodicity, etc.).

[0097] A PRU may be a WTRU or TRP whose location (e.g., altitude, latitude, geographic coordinate, or local coordinate) is known by the network (e.g., gNB, LMF). Capabilities of PRU may be the same as a WTRU or TRP (e.g., capable of receiving PRS or transmit SRS or SRS for positioning, report measurements, and / or transmit PRS). The WTRUs acting as PRUs may be used by the network for calibration purposes (e.g., correct unknown timing offset, correct unknown angle offset).

[0098] An LMF is a non-limiting example of a node or entity (e.g., network node or entity) that may be used for or to support positioning. Another node or entity may be substituted for LMF while still being consistent with the features described herein.

[0099] An SL reference signal (e.g., a new SL reference signal), SL-PRS, may be introduced (e.g., in R18 to SL positioning measurements specific to SL positioning). A SL-PRS transmission may use a comb pattern and / or a pseudorandom-based sequence. The SL-PRS transmission may be based on one or more (e.g., two) resource allocation schemes (e.g., Scheme 1 and Scheme 2). In Scheme 1 , SL-PRS resource allocation may be performed by the NW. In Scheme 2, a WTRU may perform autonomous SL-PRSresource allocation based on legacy SL Mode 2 resource selection (e.g., SL sensing). The WTRU may obtain time and / or frequency resource(s) for SL-PRS transmission from the network by sending a buffer status request. The WTRU may be configured to receive a resource allocation from the network without sending the buffer status request. The WTRU may receive SL-PRS configuration from the network (e.g., LMF, gNB). The WTRU may receive an indication from the network of the time and / or frequency resource(s) to use for transmission of SL-PRS.

[0100] A SL-PRS configuration may include at least one of the following parameters: a number of symbols, transmission power, a number of SL-PRS resources included in SL-PRS resource set, a muting pattern for SL-PRS (for example, the muting pattern may be expressed via a bitmap), a periodicity, a type of SL-PRS (e.g., periodic, semi-persistent, or aperiodic), a slot offset for periodic transmission for SL-PRS, vertical shift of SL-PRS pattern in the frequency domain, a time gap during repetition, a repetition factor, an RE (resource element) offset, a comb pattern, a comb size, a spatial relation, QCL information (e.g., QCL target, QCL source) for SL-PRS, a number of PRUs, a number of TRPs, Absolute Radio-Frequency Channel Number (ARFCN), a subcarrier spacing, an expected RSTD, uncertainty in expected RSTD, a start Physical Resource Block (PRB), bandwidth, BWP ID, number of frequency layers, start / end time for PRS transmission, on / off indicator for SL-PRS, TRP ID, SL-PRS ID, cell ID, global cell ID, PRU ID, and / or applicable time window. The WTRU may apply an SL-PRS configuration under a condition that the current time is within the applicable time window.

[0101] Feature(s) associated with SL-U channel access are provided herein.

[0102] SL operation in unlicensed spectrum may be used (e.g., in 3GPP R18). A WTRU may perform a listen before talk (LBT)-based channel access to acquire a channel for SL transmissions. The channel access may be a type 1 or type 2 channel access (e.g., similar to those applied NR U framework). The LBT-based channel access may ensure SL-U operation is compliant with regulatory requirements in unlicensed spectrum. For example, a SL-U transmission may meet standards (e.g., requirements) regarding maximum Channel Occupancy Time (mCOT), Occupied Channel Bandwidth (OCB), and / or Power Spectral Density (PSD).

[0103] A first type of channel access (e.g., type 1 channel access) may be based on LBT sensing with random back-off and / or a variable extended CCA period. The parameters (e.g., a contention window size to determine the CCA period) may be included in a Channel Access Priority Class (CAPC) configuration. A WTRU may perform type 1 channel access using a CAPC configuration (e.g., based on a data QoS requirement).

[0104] A second type of channel access (e.g., type 2 channel access) may be based on LBT sensing in a (pre)configured fixed period (e.g., 25 microseconds (type 2A) or 16 microseconds (type 2B). For a SLtransmission with duration below 482 microseconds, a type 2C channel access may be applied to acquire a channel access (e.g., without performing sensing). A WTRU may perform type 2 channel access to share a COT initiated by another WTRU.

[0105] A WTRU may perform one or more actions prior to performing a sidelink transmission (e.g., a SL- PRS transmission) over an unlicensed carrier in out-of-coverage scenarios. For example, a Tx WTRU may acquire channel access for transmission over the unlicensed carrier (e.g., according to the local regulations for the use of the shared spectrum, for example, listen before talk (LBT)). type 1 LBT may refer to random duration LBT. type 2 LBT may refer to deterministic duration LBT. type 2 LBT may be allowed (e.g., only allowed) for short signal transmissions or to share the channel occupancy initiated by a companion device.

[0106] A Tx WTRU may perform SL resource allocation (e.g., following the SL-U process).

[0107] Due to channel access uncertainty over an unlicensed carrier, Tx and / or Rx transmission(s) of RTT procedure may not be guaranteed within a short time. This may cause a performance issue for RTT based positioning (e.g., because it may make the measurements unsuitable for position determination due to WTRU motion, clock drift at Tx / Rx, etc.).

[0108] RTT transmissions may be kept within an acceptable and / or (pre)configured time window T for positioning in SL-U.

[0109] Feature(s) associated with SL-U channel acquisition with a multi-priority window.

[0110] A WTRU may be configured with one or more (e.g., two) priority levels. The priority levels may be associated with the positioning configuration over the unlicensed carrier. The WTRU may be configured with one or more (e.g., two) windows of time. The WTRU may perform a first LBT procedure (e.g., a type 1 LBT) associated with the first priority level (e.g., within the first window of time). If the WTRU can acquire a COT, the WTRU may transmit PRS (e.g., during the first window). Otherwise (e.g., if the WTRU does not acquire a COT), the WTRU may perform a second LBT procedure (e.g., type 1 LBT) associated with the second priority level (e.g., during the second window of time). The WTRU may determine one or more type 1 LBT channel access parameters according to a (pre)configured priority levels. In some examples, a priority level (e.g., one priority level) may be associated with a set of type 1 LBT channel access parameters. The set pf parameters may include one or more of the following: a number of LBT sensing slots in a contention window, a number of LBT sensing slots in a deferred duration, a number of deferred durations in a contention window, an energy detection threshold, and / or a maximum channel occupancy duration (mCOT).

[0111] A higher priority level may be associated with a set of type 1 LBT channel access parameters with fewer number of sensing slots and / or defer durations and / or higher ED threshold so that a WTRU may acquire a channel more quickly. The WTRU may apply a shorter mCOT so that the WTRU may release thechannel more quickly. In some examples, the WTRU may receive a priority level associated with the window (e.g., explicitly) from the network (e.g., LMF, gNB) or a peer WTRU (e.g., server WTRU, anchor WTRU) via a semi-static message (e.g., RRC, LPP, SLPP). For example, the priority level may be indicated as “high” or “low”, or with numerical values (e.g., 2 corresponds to high priority level, 1 corresponds to medium priority level, 0 corresponds to low priority). The WTRU may select the SL resource within a duration T from the received SL-PRS (e.g., during the second window). The duration T may be a time, after reception of a first SL-PRS, within which to send a second SL-PRS. The WTRU may transmit SL-PRS and / or SCI using the selected SL resource.

[0112] In some examples, a WTRU may be configured with a priority (e.g., a single priority). The WTRU may derive (e.g., may be configured to derive) a first priority and a second priority based on the configured priority. For example, a first priority may be the configured priority and the second priority may be a priority one step higher than the first priority.

[0113] An anchor WTRU may receive a configuration for an RTT procedure. The configuration may include configuration parameters such as, for example, T (e.g., a time, after reception of a first SL-PRS, within which to send a second SL-PRS), the first window, and the second window.

[0114] The anchor WTRU may receive an SL-PRS transmission (e.g., a first SL-PRS from a target / server WTRU). The anchor WTRU may take measurements over the SL-PRS (e.g., according to the determined resource and SL-PRS configuration).

[0115] The anchor WTRU may perform a first LBT procedure (e.g., a type 1 LBT) associated with the first priority level and associated LBT parameters (e.g., within the first window of time). The first window of time may start at PRS reception (e.g., reception of the first SL-PRS) from the target WTRU.

[0116] On a condition that the WTRU does not acquire a channel occupancy time (COT) based on the first LBT procedure (e.g., if the anchor WTRU is not able to acquire the channel / COT within the first window), the anchor WTRU may perform a second LBT procedure associated with a second priority in a second window of time (e.g., type 1 LBT with the second priority level in the second window). The anchor WTRU may select the SL resource within a duration T from the received SL-PRS.

[0117] The anchor WTRU may send a transmission. For example, the anchor WTRU may transmit SL- PRS and / or SCI to the target / server WTRU (e.g., over the selected resource). The content of the transmission may depend on whether the WTRU was able to acquire the COT during the time within which to send the second SL-PRS. For example, if the anchor WTRU is not able to transmit SL-PRS to the target / server WTRU, the anchor WTRU may abort the current RTT session. The anchor WTRU may transmit an abort indication to the target / server WTRU. The anchor WTRU may be configured with a time duration within which WTRU will transmit abort indication upon failure to acquire the COT for PRStransmission. The anchor WTRU may further be configured with LBT parameters (e.g., priority, etc.) to acquire the channel for the transmission of abort indication. The priority may be the configured / indicated priority for PRS transmission, the first priority or the second priority.

[0118] Feature(s) associated with target WTRU coordination (e.g., to enable RTT SL-PRS transmissions sharing a COT with SL-PRS based COT busy signal transmission) are provided herein.

[0119] A target WTRU and an anchor WTRU may share a COT. If the target WTRU determines to use SL-PRS for COT busy signal, the target WTRU may transmit a first COT busy signal to the anchor WTRU. The target WTRU may receive (e.g., from the anchor WTRU) SL-PRS in a second COT busy signal. The content of the received COT busy signal may be indicated in SCI. The target WTRU may take measurements (e.g., for positioning) on the COT busy signal.

[0120] The target WTRU may transmit a (pre)configuration to the anchor WTRU. The (pre)configuration may include one or more of the following: a first SL-PRS resource configuration for transmission to the anchor WTRU; and / or a second SL-PRS resource configuration for reception from the anchor WTRU

[0121] The target WTRU may transmit a first SL-PRS transmission (e.g., with associated SCI). The SL- PRS may include COT sharing information to the anchor WTRU. For example, the COT sharing information may include a first COT busy signal configuration. The first COT busy signal configuration may include one or more of: a transmission duration (e.g., number of symbols / slots); a type of the signal used in the transmission (e.g., a SL-PRS configuration, PSSCH or a pre-configured signal); and / or a resource allocation of the transmission.

[0122] If the type of indicated first COT busy signal follows the first SL-PRS configuration, the target WTRU may perform one or more of the following operations. For example, the target WTRU may transmit a first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI). The target WTRU may receive a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration). The associated SCI may provide the second COT busy signal configuration. The second COT busy signal configuration may include one or more of the following: a SL-PRS configuration; and / or a transmission duration.

[0123] The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second SL- PRS transmission (e.g., according to the second SL-PRS resource configuration).

[0124] The target WTRU may receive a second COT busy signal (e.g., according to the received second COT busy signal indication). The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second COT busy signal transmission.

[0125] The target WTRU may receive a measurement report from the anchor WTRU. The measurement report may include the measurement (e.g., RTT) results on the first SL-PRS transmission and first COT busy signal transmission.

[0126] If the type of indicated first COT busy signal does not follow the first SL-PRS configuration, the target WTRU may perform one or more of the following operations. For example, the target WTRU may transmit a first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI).

[0127] The target WTRU may receive a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration).

[0128] The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second SL- PRS transmission (e.g., according to the second SL-PRS resource configuration).

[0129] The WTRU may receive a measurement reporting from the anchor WTRU (e.g., including RTT results on the first SL-PRS transmission).

[0130] Feature(s) associated with anchor WTRU coordination (e.g., to enable RTT SL-PRS transmissions sharing a COT with SL-PRS based COT busy signal transmission) are provided herein.

[0131] A target WTRU and an anchor WTRU may share a COT. The anchor WTRU may determine the configuration for SL-PRS for a second COT busy signal for transmission (e.g., based on the configuration of the received first COT busy signal from the target WTRU).

[0132] The anchor WTRU may receive a (pre)configuration from the target WTRU. The (pre)configuration may include a first SL-PRS resource configuration for reception from the target WTRU; and / or a second SL-PRS resource configuration for transmission to the target WTRU.

[0133] The anchor WTRU may receive a first SL-PRS transmission (e.g., with associated SCI). The SCI may include COT sharing information (e.g., from the target WTRU). The COT sharing information my include a first COT busy signal configuration. The first COT busy signal configuration may include one or more of the following: transmission duration (e.g., number of symbols / slots); a type of the signal used in the transmission (e.g., a SL-PRS config , PSSCH or a pre-configured signal); and / or a resource allocation of the transmission.

[0134] The anchor WTRU may perform a SL positioning measurement (e.g., RTT) on the SL-PRS transmission (e.g., according to the (pre)configured first SL-PRS resource configuration.

[0135] If the type of indicated first COT busy signal follows (e.g., matches) the first SL-PRS configuration, the anchor WTRU may perform one or more of the following operations. For example, the anchor WTRU may receive a first COT busy signal transmission (e.g., according to the COT sharinginformation indicated in the received SCI). The anchor WTRU may buffer the received first COT busy signal.

[0136] The anchor WTRU may receive a second COT busy signal configuration (e.g., based on the received first COT busy signal). For example, the second COT busy signal configuration may include an identical SL-PRS pattern; and / or a transmission duration (e.g., based on the SL-PRS pattern used for the first COT busy signal).

[0137] The anchor WTRU may perform a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration with the associated SCI). The second SL-PRS resource configuration may include at least the determined second COT busy signal configuration.

[0138] The anchor WTRU may transmit a second COT busy signal (e.g., according to the determined second COT busy signal configuration). The anchor WTRU may perform an SL positioning measurement (e.g., RTT) on the buffered first COT busy signal transmission. The anchor WTRU may send a measurement reporting. The measurement report may include the measurement (e.g., RTT) results on the first SL-PRS transmission and first COT busy signal transmission

[0139] If the type of indicated first COT busy signal does not follow (e.g., does not match) the first SL- PRS configuration, the anchor WTRU may perform one or more of the following operations. For example, the anchor WTRU may determine a second COT busy signal configuration (e.g., based on a (pre)configured signal and / or PSSCH, if there is SL data in the buffer).

[0140] The anchor WTRU may perform a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration). The anchor WTRU may transmit a second COT busy signal (e.g., according to the determined second COT busy signal configuration). The anchor WTRU may send a measurement reporting (e.g., RTT measurements results) on the first SL-PRS transmission.

[0141] A server WTRU may select an RTT procedure based on channel sensing and anchor WTRU feedback.

[0142] The server WTRU may determine success probabilities for an individual or shared COT. For example, the WTRU may determine success probabilities based on channel measurements reported by a peer WTRU (e.g., an anchor WTRU and / or target WTRU) and measurements performed by the server WTRU. WTRU capabilities (e.g., SL-PRS measurement / processing) of the anchor WTRU and / or target WTRU may be reported to the server WTRU. The server WTRU may consider the WTRU capabilities in the determination of the success probabilities. The WTRU may determine whether to use a shared COT or individual COT for positioning (e.g., based on one or more of the success probabilities).

[0143] The server WTRU may transmit a request to an anchor WTRU (or target WTRU). The request may be a request for the channel measurements and WTRU processing capabilities (e.g., preparation time to transmit SL-PRS, measurements processing time, etc.).

[0144] The server WTRU may receive an anchor WTRU response about the channel measurements (e.g., CBR, RSSI, hypothetical LBT success). The anchor WTRU capabilities may include a PRS measurement time, a PRS TX preparation time, RTT report processing, etc.

[0145] The server WTRU may determine parameter(s) relevant to the RTT positioning procedure. For example, the parameter(s) may include one or more of: a maximum COT duration, a priority class for COT initiation, and / or a COT-busy signal nature / duration. The server WTRU may determine the parameter(s) based on the anchor WTRU processing capabilities.

[0146] The server WTRU may derive one or more of the following metrics (e.g., based on local channel measurements performed by the server WTRU, the determined RTT / COT parameters, and / or the received anchor WTRU feedback, for example, channel measurements): a first success probability associated with initiating a shared COT to share among the target and the anchor WTRUs; and / or a second success probability associated with initiating an individual COT for the target WTRU transmission.

[0147] The server WTRU may determine a first RTT procedure (e.g., associated with using a shared COT) if the first success probability is higher than a first (e.g., configured) threshold. Otherwise (e.g., if the first success probability is lower than the first threshold), if the second success probability is higher than a second (e.g., configured) threshold, the server WTRU may choose a second RTT procedure (e.g., associated with using an individual COT).

[0148] Otherwise (e.g., if the first success probability is lower than the first threshold and the second success probability is lower than the second threshold), the server WTRU may select an RTT fail ure / abort procedure (e.g., indicating that the unlicensed channel is not suitable for positioning).

[0149] The server WTRU may indicate the determined RTT procedure to the anchor WTRU.

[0150] Feature(s) associated with a shared COT multi-RTT procedure from a target WTRU are provided herein.

[0151] The target WTRU may be configured with a plurality of anchor WTRUs (e.g., M anchor WTRUs) to perform RTT-based positioning. The target WTRU may determine the order of transmission for the M anchor WTRUs. The WTRU transmits SL-PRS to the M anchor WTRUs (e.g., using an SCI indication). The SCI indication may indicate the transmission order for the anchor WTRUs. If the WTRU receives SL-PRS from at least N anchor WTRUs, the target WTRU may report measurements to a server WTRU (e.g., according to the determined order of transmission). Otherwise (e.g., if the WTRU receives SL-PRS from fewer than N anchor WTRUs), the target WTRU may report an error to the network.

[0152] The target WTRU may transmit target assistance information to M anchor WTRUs. The target assistance information may indicate for the anchor WTRUs to perform resource selection prior to COT start, a potential start time indication (e.g., tO and a window length), and a set of transmission orders.

[0153] The target WTRU may determine one or more of: LBT parameter(s), a COT busy type / duration (e.g., COT_Busy_l & II type / duration), a transmission order for M anchors for PRS and RTT reports to perform the RTT procedure in a shared COT using at least the number of anchors M, anchor WTRUs capabilities to transmit SL-PRS after having received SL-PRS from the target WTRU, and / or anchor WTRUs capabilities to process measurements to prepare RTT measurement report.

[0154] The target WTRU may perform LBT (e.g., a type 1 LBT). The target WTRU may perform LBT to acquire channel access for RTT procedure (e.g., based on determined LBT parameters).

[0155] The target WTRU may determine one or more SCI parameter(s). The SCI parameters may include at least one of the following: a remaining COT duration; a channel access priority class (e.g., used for COT acquisition); COT_Busy_l and II (e.g., the duration and type for COT_Busy_l, the duration and type for COT_Busy_ll, I prior to PRS, and II prior to RTT reports); a transmission order for the anchor WTRUs’ PRS transmissions (e.g., a transmission order may be a dynamic indication selecting one of the pre-configured transmission orders, for example, an index selecting a pre-configured transmission order); a transmission resource for the anchor WTRUs’ PRS transmissions; a transmission resource for the anchor WTRUs’ RTT reporting.

[0156] The target WTRU may transmit a positioning transmission to the anchor WTRUs. The positioning transmission may include SL-PRS and / or the determined SCI parameters.

[0157] The target WTRU may transmit a COT_Busy_l signal (e.g., to the anchor WTRUs). The COT_Busy_l signal may include extended SL-PRS.

[0158] If the target WTRU detects SL-PRS transmissions from N anchors (e.g., where N is larger than a (pre)configured threshold), the target WTRU may transmit a COT Busy II signal (e.g., where the COT Busy II signal is a pre-configured type).

[0159] Otherwise (e.g., If the target WTRU detects SL-PRS transmissions from fewer than N anchors), the target WTRU may transmit an abort indication to the anchor WTRUs. The abort indication may abort the current RTT procedure. The target WTRU may indicate the abort indication to a server WTRU (e.g., with a reason indication).

[0160] The target WTRU may receive RTT measurement reports (e.g., in the transmission order indicated in the SCI for anchors PRS transmissions). The target WTRU may transmit local and / or anchor WTRU RTT reports to the server WTRU. The target WTRU may receive location information from the server WTRU.

[0161] Feature(s) associated with positioning and ranging are provided herein. Feature(s) described herein related to positioning may be used for ranging as well (e.g., without any limitation). Positioning may refer to a technique or scheme to estimate a geographical location of a WTRU. Ranging may refer to a method / scheme to estimate a distance between WTRUs. “Positioning of a WTRU” or “location information of a WTRU” may be used interchangeably with “a distance between WTRUs” (e.g., in the case where the feature being described is used for ranging).

[0162] Positioning of the WTRU may include an absolute position (e.g., the coordinates, the zone ID) or a relative position (e.g., which may include the range, distance, and / or propagation time, and / or RTT to another node, for example, another WTRU, RSU, PRU, or gNB).

[0163] A WTRU may determine the signals for SL-PRS. The WTRU may use one or more of the following reference signals as an SL-PRS: DMRS of PSSCH and / or PSCCH; SLSS (S-PSS, S-SSS); PTRS; PSFCH; SL-CSI-RS; and / or a new RS for positioning purposes.A WTRU may receive SL-PRS configuration(s). A WTRU may determine an SL-PRS configuration. The WTRU may receive the SL-PRS configuration from another node (e.g., another WTRU or gNB). The SL- PRS configuration may include one or more of the following: a resource pool (e.g., for SL-PRS transmission, reception, and / or sidelink measurement reporting); an SL-PRS resource ID; an SL-PRS sequence ID, or other IDs used to generate SL-PRS sequence; a time-frequency of SL-PRS resource; an SL-PRS resource element offset; an SL-PRS resource slot offset; an SL-PRS symbol offset; SL-PRS QCL information; an SL-PRS resource set ID; a list of SL-PRS resources in the resource set; a number of SL- PRS symbols; a muting pattern for SL-PRS; muting parameters (e.g., repetition factor, muting options); SL- PRS resource power; a periodicity of SL-PRS transmission; spatial direction information of SL-PRS transmission (e.g., beam information, angles of transmission); spatial direction information of SL-RS reception (e.g., beam ID used to receive SL-RS, angle of arrival); a frequency layer ID; a WTRU ID; and / or an SL-PRS ID.

[0164] Feature(s) associated with WTRU behavior are provided herein.

[0165] The WTRU may send a request to the network for configuration (e.g., PRS configurations, SRS for positioning (SRSp) configurations, etc.) in a PUSCH, PUCCH, UCI, MAC-CE, RRC or LPP message. The request from the WTRU may include configurations of a measurement gap, a PRS processing window, or a window for transmission of SRSp. The WTRU may send an acknowledgement message (e.g., in PUSCH or PUCCH) for the grant received from the network.

[0166] A plurality of conditions / criteria may be used in combination. The WTRU may be configured with more than one condition (e.g., and associated WTRU behavior). The WTRU may determine which behavior to use based on the applicable condition(s).

[0167] The WTRU may measure DL-PRS (e.g., inside or outside of an active BWP). The WTRU may transmit SRSp (e.g., inside or outside of active BWP).

[0168] The WTRU may be (pre)configured with parameters (e.g., measurement gaps, PRS processing windows, PRS configurations, SRSp configurations). For example, the WTRU may be (pre)configured with parameters via a semi-static message (e.g., LPP, RRC).

[0169] Action(s) that the WTRU determines to take may be configured by the network. For example, the WTRU may be configured with a rule. The WTRU may determine to take an associated action (e.g., according to the rule).

[0170] The WTRU may include (e.g., in addition to the measurements made on PRS) at least one of the following cell-related measurements: SSB RSRP from the serving cell with corresponding cell ID; SSB RSRP from the neighboring cell(s) with corresponding cell I D(s); RSRP of CSI-RS with CSI-RS resource ID; and / or RSRS of DM-RS.

[0171] A WTRU may perform LBT-based channel sensing (e.g., to acquire the channel occupancy for transmission over an unlicensed carrier). The LBT may follow a type 1 channel access procedure (e.g., with random back-off and a variable extended CCA period based on a contention window of which the size is selected based on Channel Access Priority Class (CAPC) configuration). A WTRU may perform a type 2 channel access procedure to share a COT. type 2A and 2B channel access may be performed when a transmission gap is 25 microseconds and 16 microseconds, respectively. If a transmission gap is smaller than 16 microseconds, type 2C channel access may be applied (e.g., with an immediate transmission after the gap without performing sensing).

[0172] A WTRU may perform resource allocation for a sidelink transmission (e.g., PSSCH transmission or SL-PRS transmission). A WTRU may perform resource allocation based on channel sensing windows and detected SCIs.

[0173] A WTRU may receive a resource indication for a transmission of PSSCH or SL-PRS. The resource indication may be provided by a WTRU (e.g., another SL-WTRU or by gNB).

[0174] As used herein, “network” may include AMF, LMF, gNB or NG-RAN. “Pre-configuration”, “(pre)configuration” and “configuration” may be used interchangeably herein. The terms “non-serving gNB” and “neighboring gNB” may be used interchangeably herein. The terms “gNB” and “TRP” may be used interchangeably herein. “PRS,” “SRS,” “SRS for positioning,” and / or “SRS for positioning purpose” may be used interchangeably herein. “PRS” or “PRS resource” may be used interchangeably herein. “PRS(s)” or “PRS resource(s)” may be used interchangeably herein. The aforementioned “PRS(s)” or “PRS resource(s)” may belong to different PRS resource sets. “PRS,” “DL-PRS,” and / or “DL PRS” may be used interchangeably herein. “Measurement gap” or “Measurement gap pattern” may be used interchangeablyherein. “Measurement gap pattern” may include parameters such as measurement gap duration, measurement gap repetition period, and / or measurement gap periodicity.

[0175] A PRU may be a WTRU or TRP whose location (e.g., altitude, latitude, geographic coordinate, or local coordinate) is known by the network (e.g., gNB, LMF). Capabilities of a PRU may be the same as a WTRU or TRP (e.g., capable of receiving PRS or transmit SRS or SRS for positioning, report measurements, or transmit PRS). The WTRUs acting as PRUs may be used by the network for calibration purposes (e.g., correct unknown timing offset, correct unknown angle offset).

[0176] An LMF is a non-limiting example of a node or entity (e.g., network node or entity) that may be used for (or to support) positioning. Any other node or entity may be substituted for LMF and still be consistent with feature(s) described herein.

[0177] The WTRU may receive one or more preconfigured threshold(s) from the network (e.g., LMF, gNB).

[0178] The LOS indicator may be hard (e.g., 1 or O) or soft indicator (e.g., 0, 0.1 , 0.2. ..,1). The LOS indicator may indicate a likelihood of the presence of an LOS path between TRP and WTRU or along PRS. The LOS indicator may be associated with a TRP or PRS resource ID (e.g., index). The WTRU may receive the LOS indicator from the network (e.g., per TRP or resource ID). The WTRU may determine the LOS indicator (e.g., per TRP or resource ID based on measurements).

[0179] A WTRU location may be expressed in terms of altitude, latitude, geographic coordinate, local coordinate, and / or the like.

[0180] Example configurations for RS for positioning are provided herein. Example configurations for PRS are provided herein. The configurations described herein for PRS may be applicable for PRS, SL- PRS, or any other signal used in the positioning techniques.

[0181] A PRS configuration may include at least one of the following parameters: number of symbols, transmission power, number of PRS resources included in PRS resource set, muting pattern for PRS (e.g., the muting pattern may be expressed via a bitmap), periodicity, type of PRS (e.g., periodic, semi-persistent, or aperiodic), slot offset for periodic transmission for PRS, vertical shift of PRS pattern in the frequency domain, time gap during repetition, repetition factor, resource element (RE) offset, comb pattern, comb size, spatial relation, QCL information (e.g., QCL target, QCL source) for PRS, number of PRUs, number of TRPs, Absolute Radio-Frequency Channel Number (ARFCN), subcarrier spacing, expected RSTD, uncertainty in expected RSTD, start Physical Resource Block (PRB), bandwidth, BWP ID, number of frequency layers, start / end time for PRS transmission, on / off indicator for PRS, TRP ID, PRS ID, cell ID, global cell ID, PRU ID, applicable time window, and / or the like. The WTRU may apply a PRS configurationunder a condition that the current time is within the applicable time window. “ID” may be used interchangeably with “index” herein.

[0182] Example configurations for SRS for positioning are provided herein.

[0183] SRS for positioning (SRSp) or an SRS configuration may include at least one of: a resource ID; comb offset values, cyclic shift values; a start position in the frequency domain; a number of SRSp symbols; a shift in the frequency domain for SRSp; a frequency hopping pattern; a type of SRSp (e.g., aperiodic, semi-persistent or periodic); a sequence ID (e.g., used to generate SRSp), or other IDs used to generate SRSp sequence; spatial relation information, indicating which reference signal (e.g., DL RS, UL RS, CSI-RS, SRS, DM-RS) or SSB (e.g., SSB ID, cell ID of the SSB) the SRSp is related to spatially where the SRSp and DL RS may be aligned spatially; QCL information (e.g., a QCL relationship between SRSp and other reference signals or SSB); a QCL type (e.g., QCL type A, QCL type B, QCL type C, QCL type D); resource set ID; a list of SRSp resources in the resource set; transmission power related information; pathloss reference information which may contain index for SSB, CSI-RS or PRS; periodicity of SRSp transmission; and / or spatial information such as spatial direction information of SRSp transmission (e.g., beam information, angles of transmission), spatial direction information of DL RS reception (e.g., beam ID used to receive DL RS, angle of arrival). “ID” may be used interchangeably with “index”.

[0184] Example SL PRS configurations are provided herein.

[0185] An SL-PRS configuration may include at least one of the following parameters: a number of symbols, a transmission power, a number of SL-PRS resources included in SL-PRS resource set, a muting pattern for SL-PRS (e.g., the muting pattern may be expressed via a bitmap), a periodicity, a type of SL- PRS (e.g., periodic, semi-persistent, or aperiodic), a slot offset for periodic transmission for SL-PRS, a vertical shift of SL-PRS pattern in the frequency domain, a time gap during repetition, a repetition factor, RE offset, comb pattern, comb size, spatial relation, QCL information (e.g., QCL target, QCL source) for SL-PRS, number of PRUs, number of TRPs, ARFCN, subcarrier spacing, expected RSTD, uncertainty in expected RSTD, start PRB, bandwidth, BWP ID, a number of frequency layers, a start / end time for PRS transmission, an on / off indicator for SL-PRS, TRP ID, SL-PRS ID, cell ID, global cell ID, PRU ID, and / or an applicable time window. The WTRU may apply an SL-PRS configuration under a condition that the current time is within the applicable time window.

[0186] Example measurements are provided herein.

[0187] A “WTRU Rx-Tx time difference” may refer to the difference between the arrival time of a reference signal received by a first WTRU from the transmission of a second WTRU and the transmission time of the reference signal transmitted from the first WTRU. The WTRU Rx-Tx time difference may beassociated with a PRS resource ID and / or an SRSp resource ID. The received reference signal and the transmitted reference signals may be SL-PRS.

[0188] RSTD may refer to the difference in time of arrival between PRSs transmitted from a reference TRP and target TRP. The WTRU may be configured with the reference TRP index and target TRP index. The WTRU may be configured with the PRS resource indices to make measurements. The WTRU may determine the time of arrival from TRP (e.g., based on one or more PRS resources associated with the TRP). The RSTD may refer to the difference in time of arrival between the reference PRS transmitted from a TRP and the target PRS transmitted from a TRP.

[0189] “WTRU Rx-Tx time difference” may refer to the difference between arrival time of the reference signal transmitted by the TRP and transmission time of the reference signal transmitted from the WTRU. The WTRU Rx-Tx time difference may be associated with a PRS resource ID and / or an SRSp resource ID.

[0190] An example server WTRU role is provided herein.

[0191] The role of a server WTRU may be implemented at the target device. The role of the server WTRU may be implemented at a WTRU different from the target WTRU. If the server WTRU role is implemented at the target WTRU, the anchor WTRU may transmit an SL RTT report to the target / server WTRU.

[0192] If the server WTRU role is implemented at a WTRU different from the target WTRU, the anchor WTRU may send the RTT report to the server WTRU. If the server WTRU role is implemented at a WTRU different from the target WTRU, the anchor WTRU may send the RTT report to the target WTRU. The target WTRU may (e.g., subsequently) provide the anchor RTT measurement report to the server WTRU (e.g., for position calculations).

[0193] If measurements are taken at the target WTRU and anchor WTRU, the server WTRU may perform positioning measurements to determine the position of the target WTRU. The server WTRU may provide the determined location of the target WTRU to the target WTRU and / or anchor WTRU.

[0194] A server WTRU may have LMF capabilities. A server WTRU may provide the PRS configurations (e.g., SL-PRS configurations) to a first set of WTRUs (e.g., anchor WTRUs), and to a second set of WTRUs (e.g., target WTRUs).

[0195] A server WTRU may not have LMF capabilities.

[0196] LMF capabilities may include at least one or more of the following: a capability to provide RS configuration (e.g., SL PRS configurations) to another WTRU; a capability to configure a positioning method (e.g., RTT, TDOA-based positioning method, AoA, AoD); a capability to schedule time and / or frequency resources for RS transmission or reception for another WTRU; a capability to receive a reportfrom another WTRU where the report consists of measurements (e.g., RSTD, RSRP, WTRU Rx-Tx RTT) and associated SL-PRS information; a capability to process the measurements and determine the location of another WTRU based on the measurements; a capability to receive the location information (e.g., an estimate of the WTRU location) from the WTRU and forward it to the Location Client Server (LCS)

[0197] A server WTRU (e.g., with or without the LMF capabilities) may receive a set of SL-PRS configurations from an LMF (e.g., LMF in the network, WTRU with LMF capability) or peer WTRU (e.g., server WTRU). A set of PRS configurations may include a plurality of subsets of SL-PRS configurations. A server WTRU may provide received PRS configurations (e.g., subset of SL-PRS configurations, set of SL- PRS configurations) to a first set of WTRUs (e.g., anchor WTRUs), and to a second set of WTRUs (e.g., target WTRUs).

[0198] An example of SL RTT in unlicensed spectrum is provided herein.

[0199] The target WTRU(s), server WTRU, and / or anchor WTRU(s) may be configured with a positioning technique (e.g., RTT-based positioning method, SL RTT) by the network (e.g., LMF, gNB) and / or peer WTRU (e.g., WTRU with LMF capability). The WTRU may receive a configuration message from the network (e.g., via LPP or RRC message).

[0200] An SL RTT procedure in unlicensed spectrum may be performed by a target WTRU, one or more anchor WTRUs, and / or a server WTRU. An SL multi-RTT procedure in unlicensed spectrum may be performed by a target WTRU, a set of anchor WTRUs, and / or a server WTRU.

[0201] A server WTRU may determine to trigger a SL position session (e.g., to determine a target WTRU’s location information based on a SL RTT procedure). In unlicensed spectrum, a target WTRU and / or anchor WTRU may perform a SL RTT procedure, as described herein.

[0202] The SL RTT procedure in individual COTs may involve one or more actions by a WTRU. For example, a target WTRU may initiate a first COT. The target WTRU may perform a forward SL-PRS transmission to an anchor WTRU in the first COT. The anchor WTRU may perform a measurement of the received forward SL-PRS transmission in the first COT. The anchor WTRU may (e.g., subsequently) initiate a second COT. The anchor WTRU may perform a backward SL-PRS transmission to the target WTRU (e.g., in the second COT). The anchor WTRU may perform a transmission including a reporting of measurement result of the forward SL-PRS transmission in the second COT.

[0203] An SL multi-RTT procedure in different COTs may involve one or more actions by a WTRU. For example, a target WTRU may initiate a first COT. The target WTRU may perform a forward SL-PRS transmission to anchor WTRUs in the first COT. The anchor WTRUs (e.g., each anchor WTRU) may perform the measurement of the forward SL-PRS transmission. The anchor WTRUs (e.g., each anchorWTRU) may initiate an individual COT for a backward SL-PRS transmission and the measurement reporting transmission.

[0204] An SL RTT procedure in a shared COT may involve one or more actions by a WTRU. For example, a target WTRU may initiate a first COT. The target WTRU may perform a forward SL-PRS transmission to an anchor WTRU in the first COT. The anchor WTRU may perform a measurement of the received forward SL-PRS transmission in the first COT. The anchor WTRU may (e.g., subsequently) perform a backward SL-PRS transmission to the target WTRU in the same COT (e.g., by sharing the first COT). The anchor WTRU may perform a transmission including a reporting of measurement result of the forward SL-PRS transmission in the first COT.

[0205] An SL multi-RTT procedure in a shared COTs may involve one or more actions by a WTRU. For example, a target WTRU may initiate a first COT. The target WTRU may perform a forward SL-PRS transmission to one or more anchor WTRUs in the first COT. The anchor WTRUs (e.g., each anchor WTRU) may perform the measurement of the forward SL-PRS transmission. The anchor WTRUs (e.g., each anchor WTRU) may perform a backward SL-PRS transmission and the measurement reporting transmission in the first COT.

[0206] An anchor WTRU may perform the backward SL-PRS transmission by sharing the first COT (e.g., the COT initiated by a target WTRU). The anchor WTRU may (e.g., subsequently) initiate a different COT for the transmission of measurement reporting for the forward SL-PRS transmission received in the first COT.

[0207] Feature(s) associated with SL-U channel acquisition with a multi-priority window are provided herein.

[0208] Example SL-U multi-priority channel access configuration(s) are provided herein.

[0209] A WTRU (e.g., an anchor WTRU) may receive a channel access configuration to initiate a COT. The COT initiation may be related to the backward PRS transmission of the RTT procedure. The channel access configuration may include one or more of the following parameters.

[0210] The channel access configuration may include an Rx-Tx time threshold T (e.g., a time, after reception of a first sidelink positioning reference signal (SL-PRS), within which to send a second SL-PRS). The Rx-Tx time threshold may refer to the time by which the WTRU receiving the first PRS transmission (e.g., forward SL-RPS transmission) transmits a second PRS transmission (e.g., backward SL-PRS transmission) for the RTT procedure to be valid. T may be specified in milliseconds. T may be specified in the units of sub-frame, slot, or symbols. The Rx-Tx time threshold parameter T may be provided to a WTRU (e.g., in the field of packet delay budget for SL communication). The WTRU may interpret this as T if the configuration is for SL-PRS transmission in a positioning session.

[0211] The channel access configuration may include a first window ‘w1.’ The first window may specify a window of time. For example, the window’s duration may be expressed in terms of the number of slots, subframes, frames, symbols, or seconds. In an example configuration, the first window may be configured using a start time and an end time. The first window may be configured using a start time and a duration. The time within which to send the second SL-PRS may begin at the start of the first window of time (e.g., the start time for the first window may be defined relative to the WTRU receiving a first SL-PRS transmission). The first window start time may be defined relative to the slot or symbol(s) where the WTRU receives an SL-PRS transmission (e.g., a forward SL-PRS transmission of the SL RTT based positioning). The start of the first window may be an offset (e.g., a configured offset) from the received SL-PRS transmission. The offset may be configured to the WTRU as part of the configuration. The offset may be known through pre-configuration. The offset may be related to the WTRU processing time.

[0212] The channel access configuration may include a first priority for COT initiation. A WTRU may be configured with a first priority (e.g., that the WTRU will use to initiate a COT in the first window, w1). The first priority may be the normal priority of the SL-PRS transmission (e.g., backward SL-PRS transmission) that WTRU is configured to transmit. The first priority may be linked to the priority of the received SL-PRS transmission (e.g., forward SL-PRS transmission) that the WTRU receives (e.g., prior to COT initiation).

[0213] A WTRU may receive more than one configuration for a first window and for a first priority.

[0214] The channel access configuration may include a second window ‘w2.’ The second widow may specify a window in time. In an example configuration, the second window may be configured using a start time and end time. The second window may be configured using a start time and a duration. The start time for the second window may be defined relative to the WTRU receiving a first SL-PRS transmission. The second window start time may be defined relative to the slot or symbol(s) where the WTRU receives SL- PRS transmission (e.g., forward SL-PRS transmission of the SL RTT based positioning). The start time for the second window may be defined relative to the first window (e.g., the end time of the first window). The time within which to send the second SL-PRS may end at the end of the second window of time.

[0215] The channel access configuration may include a second priority for COT initiation. A WTRU may be configured with a second priority (e.g., that the WTRU may use to initiate a COT in the second window, w2). The second priority may be linked to the priority of the received SL-PRS transmission (e.g., forward SL-PRS transmission) that the WTRU receives (e.g., prior to COT initiation). The WTRU may determine the second priority based on the first priority. For example, the second priority may be a level (e.g., one level) higher than the first priority. If the lower values are attributed to higher priorities for indication purpose, the second priority may be the first priority minus one.

[0216] The channel access configuration may include an energy detection (ED) threshold. A WTRU may be (pre)configured with different ED thresholds for LBT sensing in the first and second window. A target WTRU may indicate the ED threshold(s) to an anchor WTRU (e.g., in an SL U RTT procedure). The indication may be carried in SCI, MAC and / or RRC signaling.

[0217] A WTRU may receive more than one configuration for a second window and for a second priority.

[0218] The WTRU (e.g., an anchor WTRU) may be configured with a window (e.g., one window) for LBT. The WTRU may perform a type 1 LBT with a first priority and associated LBT parameters within the first window. If the anchor WTRU is not able to acquire the channel / COT within the window, the anchor WTRU may perform type 1 LBT with a second priority within the window. The WTRU may determine to perform the type 1 LBT with the second priority if the remaining time during the window is greater than a threshold (e.g., a configured threshold). The WTRU may determine to perform the type 1 LBT with the second priority if the elapsed time during the window is smaller than a threshold (e.g., a configured threshold). The WTRU may select the SL resource within a duration T from the received SL-PRS within the window. The configured window may be used in a combination with SL-PRS transmission and / or reception procedure described herein.

[0219] The WTRU may receive a forward SL-PRS transmission (e.g., a first SL-PRS).

[0220] The WTRU (e.g., an anchor WTRU) may receive the forward SL-PRS transmission. The WTRU may receive SL-PRS (e.g., along with associated control information, for example, SCI. The SCI may indicate one or more of the following: a priority of the SL-PRS transmission; a time frequency resource used for the SL-PRS transmission; an RTT method indication; and / or a multi-priority window selection.

[0221] The SCI may provide the indication of the individual COT based RTT positioning. The RTT method indication may be implicit (e.g., WTRU does not receive any COT sharing information in the control information).

[0222] The WTRU may receive an indication to use a multi-priority window (e.g., based channel sensing according to the prior configuration for the transmission of backward SL-PRS transmission).

[0223] The WTRU may receive an indication of a first priority window and a first priority (e.g., from a set of configured first priority windows). The WTRU may determine the second priority window and a second priority (e.g., based on the indication of the first priority window).

[0224] The WTRU may receive an indication of a first priority window and a second priority window (e.g., from a set of configured first and second priority windows).

[0225] The WTRU may receive an indication selecting a configuration (e.g., from a set of pre-configured configurations). A configuration (e.g., each configuration) may identify a first priority window with a first priority and a second priority window with a second priority.

[0226] The WTRU may determine a first priority for the first window and a second priority for the second window (e.g., based on the priority of the SL-PRS transmission).

[0227] A WTRU may determine one or more SL multi-priority parameter(s).

[0228] A WTRU (e.g., an anchor WTRU) may determine the parameter(s) for a channel access procedure for SL-PRS transmission (e.g., forward or backward SL-PRS transmission for SL based RTT procedure over the shared spectrum). The channel access parameter(s) may include a start / duration for a first priority window (e.g., first window of time), a start / duration for a second priority window (e.g., second window of time), and / or the priorities to be used for the first window and for a second window (e.g., the first priority and the second priority).

[0229] The WTRU may determine the multi-window channel access parameter(s) based on the priority of (e.g., associated with) the received forward (e.g., first) SL-PRS transmission. For example, an anchor WTRU may determine a duration of a first window based a (pre)configured association between the duration of the first window and a SL-PRS priority indicated for the forward and / or backward SL-PRS transmission from a target WTRU. The duration of the first window of time may be inversely proportional to the third priority. For example, a higher priority may be associated with a shorter duration. If channel is busy in the first window, a WTRU may apply LBT in the second window earlier for higher priority SL-PRS transmission.

[0230] The WTRU may determine the multi-window channel access parameter(s) based on local channel measurements. The local channel measurements may be related to the energy measurements over unlicensed carrier. The local channel measurements may include sidelink sensing based measurements (e.g., a channel busy ratio).

[0231] The WTRU may determine the multi-window channel access parameter(s) based on an indication received as part of first SL-PRS transmission. The indication may be an (e.g., explicit) indication for multiwindow channel access parameters. The received indication may select a multi-window configuration from a set of pre-configured configurations.

[0232] The WTRU may determine the multi-window channel access parameter(s) based on the local channel measurements and an indication received as part of first SL-PRS transmission.

[0233] The WTRU may determine the multi-window channel access parameter(s) based on the priority (e.g., the priority configured with the positioning procedure or positioning session). In an example, theWTRU may choose the parameters associated with the first priority (and first window) and the second priority (and the second window) based on the configured priority value.

[0234] The WTRU may determine the first window channel access parameter(s) based on any of the examples described herein. The WTRU may derive the second window parameter(s) based on the determined parameters for the first window.

[0235] An example SL multi-priority channel access procedure is provided herein.

[0236] A WTRU (e.g., an anchor WTRU) may begin a channel access procedure for SL-PRS transmission (e.g., forward or backward SL-PRS transmission for SL based RTT procedure over the shared spectrum).

[0237] A WTRU may perform a first LBT procedure associated with a first priority within a first window of time (e.g., start the LBT channel access procedure for SL-U according to a determined first window and a first priority). The type of the LBT may be type 1 random duration LBT. The WTRU may use a first priority to derive the type 1 LBT parameter(s). The WTRU may perform the channel sensing / LBT over the unlicensed carrier. The unlicensed carrier may be a carrier in which the WTRU receives a SL-PRS transmission (e.g., a forward SL-PRS transmission of RTT based positioning procedure).

[0238] The WTRU may acquire the COT during the time within which to send the second SL-PRS (e.g., by acquiring a resource in which to send the second SL-PRS before the end of the second window of time). If the WTRU is able to acquire the channel (e.g., prior to the end time of the first window), the WTRU may transmit the SL-PRS transmission (e.g., transmission on the suitable resource of the acquired COT). In this case, WTRU may not perform channel sensing in the second window. On a condition that the WTRU does not acquire a COT based on the first LBT procedure (e.g., if the WTRU is not able to acquire COT in the first window), the WTRU may perform a second LBT procedure associated with a second priority in a second window of time (e.g., channel sensing in the second window). The LBT parameter(s) to use for channel sensing in the second window may be derived from the second priority. The WTRU may apply a second ED threshold for LBT sensing in the second window. The WTRU may send a transmission. For example, if the WTRU is able to acquire COT in the second window (e.g., at the successful completion of the type 1 LBT procedure with LBT parameters derived from the second window), the WTRU may transmit the (e.g., a second) SL-PRS transmission (e.g., backward SL-PRS transmission of the RTT based SL positioning procedure). FIG. 2 illustrates an example of a WTRU sensing with two non-overlapping windows (e.g., multi-priority window).

[0239] FIG. 3 illustrates an example of a WTRU sensing with overlapping sensing windows. As shown in FIG. 3, at least a portion of the first window of time and a portion of the second window of time overlap. As shown in FIGs. 2 and 3, the time within which to send the second SL-PRS may begin at the start of the firstwindow of time, and end at the end of the second window of time. In Fig. 3, the WTRU may process the first LBT and the second LBT procedure in parallel, e.g., during the overlapping part of the first window and the second window.

[0240] The WTRU may start a first window. The WTRU may perform channel sensing. The WTRU may be configured with a second window start time. The second window start time may be prior to the end time of the first window (e.g., to avoid the initial delay of COT acquisition at the start of the second window). The WTRU may receive configuration information that indicates an offset between a start of the first window of time and a start of the second window of time (e.g., the offset may be provided to the WTRU as part of the configuration). The WTRU may generate type 1 LBT parameter(s) for the second priority linked to the second window. The WTRU may start performing channel sensing for the second window in overlap with the first window. The overlapping sensing windows-based channel sensing is illustrated in FIG. 3.

[0241] FIG. 4 illustrates an example of overlapping start-aligned multi-priority sensing windows (e.g., where the two windows start at the same time). In this example, the WTRU may generate the type 1 LBT channel sensing parameter(s) for the windows according to the first and second priorities. The WTRU may perform channel sensing for the two windows at the same time. The WTRU may handle the LBT handling for the second window and the second priority such that the WTRU does not let the second window finish prior to the end time of the first window. For example, the WTRU may not to decrement the sensing counter in the second window.

[0242] Feature(s) associated with a backward SL-PRS transmission are provided herein.

[0243] The WTRU (e.g., an anchor WTRU) may send a transmission. The content of the transmission may depend on whether the WTRU was able to acquire the COT during the time within which to send the second SL-PRS. For example, the WTRU may perform the backward SL-PRS transmission upon successful channel sensing in the first window or in the second window. For example, on a condition that the WTRU was able to acquire the COT during the time within which to send the second SL-PRS, the transmission may include the second SL-PRS and control information that indicates a resource associated with the second SL-PRS. The WTRU may transmit SL-PRS along with SCI. The SCI may indicate the resource used for backward SL-PRS transmission.

[0244] The WTRU may select a sidelink resource in which to send the transmission (e.g., which includes the second / backward SL-PRS). For example, the WTRU may reserve a resource for its RTT report transmission (e.g., subsequent to the backward SL-PRS transmission). The reserved resource for SL RTT report transmission may be indicated in the SCI with the backward SL-PRS transmission. The reservation of SL-U resource for RTT report transmission may be based on channel conditions. The transmission may be sent to a target WTRU or a server WTRU via the sidelink resource.

[0245] The COT sharing for the transmission of RTT report with the backward SL-PRS transmission may be based on the time that the WTRU is able to access the channel for the backward SL-PRS transmission. The WTRU may reserve and indicate the RTT reporting resource (e.g., if the WTRU is able to select the SL-PRS resource within the second window). The selection of an SL-PRS transmission resource in second window may imply that WTRU has had more time to process the SL-PRS received in the forward PRS transmission of the RTT procedure. The WTRU may share the backward SL-PRS transmission COT with the SL RTT reporting resource (e.g., based on the WTRU’s processing time). The WTRU may determine COT sharing between backward the SL-PRS transmission and the RTT report (e.g., based on the time instant when the WTRU acquires the channel for its backward SL-PRS transmission and the WTRU’s processing capabilities).

[0246] Feature(s) associated with LBT failure and abortion of the RTT session are provided herein.

[0247] On a condition that the WTRU (e.g., an anchor WTRU) was unable to acquire the COT during the time within which to send the second SL-PRS (e.g., if the WTRU is not able to acquire the channel within the configured duration T after the reception of forward SL-PRS transmission of the RTT procedure), the WTRU may abort the current RTT session. The WTRU may send a transmission that includes an indication that a current session has been aborted (e.g., an abort indication) to the target WTRU (e.g., through which the WTRU received PRS transmission, for example, a forward SL-PRS transmission). The WTRU may send the abort indication to the server WTRU. The abort indication may identify the RTT session and the abort cause. The abort cause may indicate that the abort was initiated because the WTRU was unable to acquire the COT (e.g., because of the channel access failure). The abort indication may be transmitted as a MAC CE or an RRC message.

[0248] The WTRU may perform channel sensing to be able to transmit the abort indication over the SL- U. A SL-WTRU may perform the channel access with the first priority to acquire the COT for the abort indication transmission. The WTRU may wait a configured duration prior to starting the channel sensing for abort indication transmission.

[0249] FIG. 5 illustrates an example of multi-priority channel acquisition for SL-PRS transmission.

[0250] A WTRU may be configured with one or more (e.g., two) priority levels. The WTRU may be configured with configurations for one or more (e.g., two) windows. The WTRU may perform a type 1 LBT with the first priority level (e.g., within the first window). If the WTRU can acquire a COT, the WTRU may receive PRS (e.g., during the first window). Otherwise (e.g., if the WTRU does not acquire a COT), the WTRU may perform a type 1 LBT with the second priority level (e.g., during the second window). The WTRU may select the SL resource within a duration T from the received SL-PRS (e.g., during the second window). The WTRU may transmit SL-PRS and / or SCI using the selected SL resource.

[0251] An anchor WTRU may receive a configuration for an RTT procedure. The configuration may include configuration parameters such as, for example, T, the first window, and the second window.

[0252] The anchor WTRU may receive an SL-PRS transmission (e.g., from a target / server WTRU). The anchor WTRU may take measurements over the SL-PRS (e.g., according to the determined resource and SL-PRS configuration).

[0253] The anchor WTRU may perform a type 1 LBT with the first priority level and associated LBT parameters (e.g., within the first window). The first window may start at PRS reception from the target WTRU.

[0254] If the anchor WTRU is not able to acquire the channel / COT within the first window, the anchor WTRU may perform type 1 LBT with the second priority level (e.g., in the second window). The anchor WTRU may select the SL resource within a duration T from the received SL-PRS.

[0255] The anchor WTRU may transmit SL-PRS and / or SCI to the target / server WTRU (e.g., over the selected resource). If the anchor WTRU is not able to transmit SL-PRS to the target / server WTRU, the anchor WTRU may abort the current RTT session. The anchor WTRU may transmit an abort indication to the target / server WTRU.

[0256] Target WTRU coordination may be used to enable RTT SL-PRS transmissions sharing a COT with SL-PRS based COT busy signal transmission

[0257] An example SL-U shared COT PRS transmission configuration is provided herein.

[0258] A WTRU (e.g., a first WTRU) may transmit one or more of the following configuration elements to another WTRU (e.g., a second WTRU).

[0259] The configuration elements may include a first SL PRS resource configuration. The first SL-PRS resource configuration may include the SL-PRS resource configuration for the forward transmission (e.g., first WTRU to second WTRU) of the RTT procedure.

[0260] The configuration elements may include a second SL PRS resource configuration. The second SL-PRS resource configuration may include the SL-PRS resource configuration for the backward transmission (e.g., second to first WTRU) of the RTT procedure.

[0261] The configuration elements may include a start time indication. The start time indication may be an indication for the forward SL-PRS transmission timing. The first WTRU (e.g., a target WTRU) may transmit according to the indicated timing (e.g., subject to channel access success). Timing may be indicated in terms of absolute time, relative time with respect to a reference, frame index, subframe index, slot index, and / or slot index.

[0262] The configuration elements may include a shared COT indication. The WTRU may provide an indication that the SL RTT session will be based on a shared COT. More than one WTRU may use the COT (e.g., shared COT) for transmission or reception of data and / or signals.

[0263] The configuration elements may include an ACK / NACK configuration for the shared COT RTT procedure.

[0264] The configuration elements may include a COT busy I configuration. The COT busy I configuration may provide a set of types that a WTRU may use to keep the COT busy between a SL-PRS transmission (e.g., forward SL-PRS transmission) and a subsequent SL-PRS transmission (e.g., a backward SL-PRS transmission). The configuration may indicate one or more of the following types: a SL PRS resource configuration; a known or configured sequence or a set of known or configured sequences; a random sequence (e.g., a sequence of complex numbers generated by a pseudo number generator); and / or shared channel data.

[0265] The COT busy I configuration may include a first part of COT busy I and a second part of COT busy I. In this case, the COT busy I configuration may include the types and durations for the first and the second part.

[0266] An example SL-U channel access procedure for a shared COT is provided herein.

[0267] A WTRU may select parameters (e.g., suitable parameters) for channel sensing (e.g., to acquire the COT over the SL-U). The LBT parameters to perform channel sensing may be based on one or more of the following.

[0268] The LBT parameters to perform channel sensing may be based on priority of the SL-PRS transmission (e.g., the WTRU obtains the priority of the SL-PRS from higher layer).

[0269] The LBT parameters to perform channel sensing may be based on the length of the COT in order to finish the RTT session in the same COT. The length of the COT (e.g., expressed in terms of seconds, the number of slots, frames, subframes or symbols) may be selected to perform forward SL-PRS transmission and backward SL-PRS transmission in the same COT (e.g., accommodating the measurement time and preparation time for SL-PRS transmission). The length of the COT may be selected to perform forward SL-PRS transmission, backward SL-PRS transmission, and / or RTT reporting in the same COT (e.g., including the WTRU processing times required for each intermediate step).

[0270] Feature(s) associated with forward SL-PRS transmission are provided herein.

[0271] A WTRU (e.g., a target WTRU) may perform the forward SL-PRS transmission (e.g., upon successful COT acquisition over SL-U). The WTRU may transmit SL-PRS (e.g., along with SCI). The SCI may indicate any of the following: a priority of the SL-PRS transmission; a time frequency resource used forthe SL-PRS transmission; and / or COT sharing information. SCI may provide the COT sharing information to the receiving WTRU. The COT sharing information may include one or more of the following elements: a priority value used to determine COT acquisition LBT parameters; a remaining COT duration; a resource allocation for the backward SL-PRS transmission (e.g., the WTRU may perform resource allocation for the backward SL-PRS transmission and indicate the resource allocation to the Rx WTRU to be used for the backward SL-PRS transmission, for example, the resource allocation may be a time frequency resource, only time resource, or only frequency resource indication for the backward SL-PRS transmission); an RTT report inclusion indicator (e.g., COT sharing information may include the indication for the SL Rx WTRU whether the same COT can be used for RTT reporting, for example, the Rx WTRU may keep the COT occupied with a second COT busy signal between the backward SL-PRS transmission and the RTT report transmission); and / or a first COT busy signal indication.

[0272] The first COT busy signal indication may include a transmission duration. The transmission duration for the first COT busy signal may be provided in absolute time with suitable units (e.g., milliseconds, microseconds, number of symbols, slots, frames, or subframes). The duration of the first COT busy signal may be indicated in terms of slots and symbol duration. The reference slots and symbols may be for a given sub-carrier spacing or for the active sub-carrier spacing.

[0273] The first COT busy signal indication may include a type of the first COT busy signal used in the transmission. For example, the type of the first COT busy signal may be an SL PRS; a (pre)configured sequence or a set of (pre)configured sequences; a random sequence; shared channel data (e.g., the shared channel data may be sent to the same WTRU as the forward PRS transmission or the WTRU may send shared channel data to a Rx WTRU different from the recipient of the forward SL-PRS transmission); and / or a resource allocation for the transmission (e.g., a time frequency resource, only a time resource, or only a frequency resource indication for the first COT busy signal transmission).

[0274] The first COT busy signal indication may include a first part of COT busy I and a second part of COT busy I. In this case, the COT busy I indication may provide the types and durations (e.g., for each of the first and the second part).

[0275] Feature(s) associated with a first COT busy signal transmission are provided herein.

[0276] A WTRU (e.g., a target WTRU) may perform the transmission of the first COT busy signal. The first COT busy signal transmission may start a delay (e.g., fixed or configured delay) after the forward SL- PRS transmission. The WTRU will transmit the first COT busy signal for the type (e.g., SL PRS, random sequence, shared channel data). The duration may be indicated in the COT sharing information transmitted with the forward SL-PRS transmission.

[0277] The WTRU may transmit the first part of the first COT busy signal (e.g., if the configuration has been provided for a first part and for a second part of the first COT busy signal).

[0278] A WTRU may receive an ACK / NACK.

[0279] A WTRU (e.g., a target WTRU) may receive feedback from a second WTRU (e.g., in response to the forward SL-PRS transmission after the first part of first COT busy signal). The feedback may be positive feedback (e.g., an ACK), or negative feedback (e.g., a NACK).

[0280] The WTRU may determine to continue a shared COT RTT procedure (e.g., based on the received feedback). If an ACK is determined, the WTRU may continue the shared COT procedure. If a NACK is determined, the WTRU may stop the shared COT RTT procedure. The WTRU may fall back to individual COT RTT procedure (e.g., if a NACK is determined). The WTRU may wait to receive the backward SL-PRS transmission within the RTT time threshold.

[0281] Feature(s) associated with a second part of the first COT busy signal transmission are provided herein.

[0282] A WTRU (e.g., a target WTRU) may perform the transmission of a second part of first COT busy signal. The second part of the first COT busy signal transmission may start after a delay (e.g., a fixed delay after the first part of first COT busy signal). The second part of first COT busy signal transmission may start after reception of feedback from a second WTRU (e.g., in response to forward SL-PRS transmission). The WTRU may transmit the second part of first COT busy signal (e.g., based on the received feedback). The WTRU may transmit the second part if (e.g., only if) the received feedback is a positive acknowledgment.

[0283] Feature(s) associated with a backward SL-PRS transmission are provided herein.

[0284] A WTRU (e.g., a target WTRU) may receive a backward SL-PRS transmission from a different WTRU (e.g., the WTRU that received the SL-PRS from the target WTRU and / or anchor WTRU). For example, the WTRU may receive the backward SL-PRS transmission after the forward SL-PRS transmission and / or first COT busy signal transmission. The WTRU may receive the backward SL-PRS transmission from a different WTRU (e.g., on a time frequency resource indicated in the SCI of the forward SL-PRS transmission). The SCI of the forward SL-PRS transmission may indicate (e.g., only indicate) the time. The time may be the absolute time or a time with a window within which a WTRU may receive the backward SL-PRS transmission. The WTRU may receive the backward SL-PRS transmission in response to its forward SL-PRS transmission. The other WTRU may perform the resource allocation for the backward SL-PRS transmission.

[0285] The SL-PRS transmission (e.g., the backward SL-PRS transmission) may indicate the transmission of a second COT busy signal (e.g., following the SL-PRS transmission). The indication for the second COT busy signal may be received in the SCI accompanying the SL-PRS transmission. Theindication for the second COT busy signal may include one or more of the following: the transmission duration for the second COT busy signal; the type of the second COT busy signal (e.g., a SL PRS; a known sequence or a set of known sequences; a random sequence; and / or shared channel data; and / or resource allocation for the transmission. The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the second COT busy signal transmission.

[0286] A second COT busy signal may be received.

[0287] A WTRU may receive an indication for a second COT busy signal in a received SL-PRS transmission (e.g., a backward SL-PRS transmission). The WTRU may receive the second COT busy signal parameters in the SCI accompanying a SL-PRS transmission (e.g., a backward SL-PRS transmission of an RTT procedure).

[0288] If the second COT busy signal is determined to be carrying SL-PRS, the WTRU may make measurements over these signals. The measurements may be used to compute RTT measurement results. The measurements may be reported as part of RTT measurements report.

[0289] An implicit indication of the content of the second COT busy signal may be sent / received.

[0290] The target WTRU may determine that the second COT busy signal includes the same signal as the first COT busy signal (e.g., without receiving an explicit indication, for example, via SCI) about the second COT busy signal (e.g., from the anchor WTRU). For example, the target WTRU may determine to use SL PRS for the first COT busy signal. The target WTRU may determine that the anchor WTRU transmits the SL PRS using the same sequence (e.g., generated by the same random number generator, same seed for the random number generator, same linear feedback shift register for the random number generator) in the second COT busy signal. The WTRU may receive an indication or configuration from the network or peer WTRU (e.g., WTRU with LMF capability, server WTRU) to determine the content of the second COT busy signal (e.g., implicitly).

[0291] A measurement report may be received.

[0292] A WTRU may receive a measurement report (e.g., after the reception of the second COT busy signal). The WTRU may send the measurement report to the LMF and / or peer WTRU (e.g., server WTRU). The WTRU may send the measurement report via Sidelink Positioning Protocol (SLPP), LPP, RRC, MAC- CE, SCI, or UCI.

[0293] The WTRU may receive the measurement report on the resource for which the reservation indication is received in the SCI (e.g., accompanying second SL-PRS transmission). The WTRU may receive the measurement report with no prior reservation indication.The WTRU may receive measurement reports based on one or more of the following signal measurements (e.g., made at a second WTRU, for example, an anchor WTRU): a first (e.g., forward) SL-PRS transmission; a first COT busy signal; a first part of first COT busy signal; a second part of first COT busy signal; a second (e.g., backward) SL-PRS transmission; and / or a second COT busy signal.

[0294] The received measurement report may include Rx-Tx time difference measurements from a received signal and / or a transmitted signal from a second WTRU (e.g., an anchor WTRU).

[0295] Example Rx-Tx time difference(s) are provided herein.

[0296] An example of an Rx-Tx time difference is the difference between the time of arrival of SL-PRS and time of transmission of SL-PRS. The time of arrival or time of transmission may be expressed in terms one or more of: absolute time, reference time with respect to a reference, subframe index, frame index, slot index, and / or symbol index. The time of arrival or time of transmission may be expressed in terms timing of a subframe, frame, slot(s) or symbol(s) which contain received or transmitted SL-PRS, respectively.

[0297] An RTT measurements report may be prepared.

[0298] A WTRU (e.g., a target WTRU) may prepare or generate an Rx-Tx time difference measurements report (e.g., based on the first SL-PRS transmission and the second SL-PRS transmission). The first-SL PRS transmission may be the forward SL-PRS transmission that the WTRU transmits. The second SL-PRS transmission may be backward transmission that the SL-WTRU receives.

[0299] The WTRU may prepare Rx-Tx time difference measurements based on the first SL-PRS transmission, first COT busy signal, and / or the second SL-PRS transmission. The WTRU may compute two time difference measurements. A first measurement may be between the first SL-PRS transmission and the second SL-PRS transmission. A second measurement may be between the first COT busy signal and the second SL-PRS transmission.

[0300] The WTRU may prepare Rx-Tx time difference measurements based on the first SL-PRS transmission, first COT busy signal, the second SL-PRS transmission, and / or the second COT busy signal. The WTRU may compute two time-difference measurements. A first measurement may be between the first SL-PRS transmission and the second SL-PRS transmission. A second measurement may be between the first COT busy signal and the second COT busy signal (e.g., Rx-Tx time based on transmission time of the first COT busy signal and reception time of the second COT busy signal).

[0301] The WTRU may use a reference time (e.g., a suitable reference time) for the first and second COT busy signals (e.g., to determine the time difference measurements). The start of the slot for the first / second COT busy signal may be used as the reference transmit / receive time. The start of the symbol time used for transmission of first / second COT busy signals may be used as the referencetransmit / recei ved time. The precise transmit / receive time may be used as a time reference for the first / second COT busy signals (e.g., to determine RTT time difference).

[0302] The WTRU may include an indication in the measurement report of which signal is used for determination of Rx-Tx time difference (e.g., whether the time of arrival or transmitted time of the first or second COT busy signal) .

[0303] The WTRU may receive a configuration or indication from the network or peer WTRU (e.g., server WTRU) about which signal(s) (e.g., first SL PRS transmission, second SL PRS transmission, COT busy I signal, and / or COT busy II signal, as illustrated in FIG. 6) to use for determination of the Rx-Tx time difference.

[0304] The WTRU may prepare measurement reports based on one or more of the following: a transmit for first (forward) SL-PRS transmission; a transmit time for first COT busy signal; a transmit time for first part of first COT busy signal; a transmit time for second part of first COT busy signal; a receive time for a second (backward) SL-PRS transmission; and / or a receive time for a second COT busy signal.

[0305] The measurement report may include Rx-Tx time difference measurements from a received signal and / or a transmitted signal from a WTRU (e.g., a target WTRU).

[0306] The WTRU may determine to use first SL-PRS, second SL-PRS, a first COT busy signal, and / or a second COT busy signal to determine the Rx-Tx time difference (e.g., based on a channel condition). The channel condition may include a LOS or NLOS indicator associated with SL-PRS. For example, the WTRU may determine to use COT busy signal (e.g., in addition to SL-PRS) to determine the Rx-Tx time difference (e.g., if the LOS indicator associated with the received or transmitted SL-PRS is below the configured threshold).

[0307] The channel condition may include RSRP or RSRPP of a reference signal (e.g., SL-PRS, SL- SSB, SL-CSI-RS). For example, the WTRU may determine to use COT busy signal (e.g., in addition to SL- PRS) to determine the RSRP measurement (e.g., if the received SL-PRS is below the configured threshold).

[0308] Target WTRU coordination of SL RTT procedure may be performed (e.g., with ACK / NACK transmission from an anchor WTRU).

[0309] A target WTRU may perform a SL RTT procedure (e.g., including a feedback, for example, an ACK / NACK transmission from one or more anchor WTRUs, as illustrated in FIG. 6)

[0310] FIG. 6 illustrates an example shared COT with a SL-PRS based COT busy signal and anchor WTRU ACK / NACK feedback.

[0311] A WTRU (e.g., a target WTRU), may transmit a (pre)configuration to an anchor WTRU. The (pre)configuration may include one or more of the following: a first SL-PRS resource configuration for transmission to an anchor WTRU, a second SL-PRS resource configuration for reception from an anchor WTRU, and / or an ACK / NACK configuration for the shared COT RTT procedure.

[0312] The WTRU may transmit a first SL-PRS transmission (e.g., with associated SCI) to an anchor WTRU. The SCI may include COT sharing information. The COT sharing information may include one or more of: a first COT busy signal configuration (e.g., including the first part and the second part), and, for each part, a transmission duration (e.g., number of symbols / slots), a type of the signal used in the transmission (e.g., a SL-PRS configuration, PSSCH, or a pre-configured signal), and / or a resource allocation of the transmission.

[0313] If the type of indicated first COT busy signal follows the first SL-PRS configuration, the WTRU may transmit the first part of first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI).

[0314] If the type of indicated first COT busy signal does not follow the first SL-PRS configuration, the WTRU may transmit the first part of first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI).

[0315] The WTRU (e.g., a target WTRU) may receive an ACK from the anchor WTRU. The WTRU may (e.g., upon receiving an ACK) transmit the second part of first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI).

[0316] The WTRU (e.g., a target WTRU) may receive a NACK from the anchor WTRU. The target WTRU may not transmit second part of first COT busy signal (e.g., if the WTRU receives a NACK from the anchor WTRU.

[0317] In case of NACK reception, the WTRU (e.g., a target WTRU) may receive a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration with the associated SCI). The SCI may provide the second COT busy signal configuration. The second COT busy signal configuration may include one or more of the following: a SL-PRS configuration, and / or a transmission duration.

[0318] The WTRU (e.g., a target WTRU) may perform a SL positioning measurement (e.g., RTT) on the second SL-PRS transmission (e.g., according to the second SL-PRS resource configuration).

[0319] The WTRU (e.g., a target WTRU) may receive a second COT busy signal (e.g., according to the received second COT busy signal indication). The WTRU (e.g., a target WTRU) may perform a SL positioning measurement (e.g., RTT) on the second COT busy signal transmission.

[0320] The WTRU (e.g., a target WTRU) may receive a measurement report from the anchor WTRU. The measurement report may include the measurement (e.g., RTT results) on the first SL-PRS transmission and first COT busy signal transmission (e.g., the first part and the second part).

[0321] The WTRU (e.g., a target WTRU) may receive a measurement reporting from the anchor WTRU (e.g., RTT results on the first SL-PRS transmission).

[0322] FIG. 7 illustrates an example shared COT with SL-PRS based COT busy signal.

[0323] A target WTRU and an anchor WTRU may share a COT. If the target WTRU determines to use SL-PRS for COT busy signal, the target WTRU may transmit a first COT busy signal to the anchor WTRU. The target WTRU may receive (e.g., from the anchor WTRU) SL-PRS in a second COT busy signal. The content of the received COT busy signal may be indicated in SCI. The target WTRU may take measurements (e.g., for positioning) on the COT busy signal.

[0324] The target WTRU may transmit a (pre)configuration to the anchor WTRU. The (pre)configuration may include one or more of the following: a first SL-PRS resource configuration for transmission to the anchor WTRU; and / or a second SL-PRS resource configuration for reception from the anchor WTRU

[0325] The target WTRU may transmit a first SL-PRS transmission (e.g., with associated SCI). The SL- PRS may include COT sharing information to the anchor WTRU. For example, the COT sharing information may include a first COT busy signal configuration. The first COT busy signal configuration may include one or more of: a transmission duration (e.g., number of symbols / slots); a type of the signal used in the transmission (e.g., a SL-PRS config , PSSCH or a pre-configured signal); and / or a resource allocation of the transmission.

[0326] If the type of indicated first COT busy signal follows the first SL-PRS configuration, the target WTRU may perform one or more of the following operations. For example, the target WTRU may transmit a first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI). The target WTRU may receive a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration). The associated SCI may provide the second COT busy signal configuration. The second COT busy signal configuration may include one or more of the following: a SL-PRS configuration; and / or a transmission duration.

[0327] The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second SL- PRS transmission (e.g., according to the second SL-PRS resource configuration).

[0328] The target WTRU may receive a second COT busy signal (e.g., according to the received second COT busy signal indication). The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second COT busy signal transmission.

[0329] The target WTRU may receive a measurement report from the anchor WTRU. The measurement report may include the measurement (e.g., RTT) results on the first SL-PRS transmission and first COT busy signal transmission.

[0330] If the type of indicated first COT busy signal does not follow the first SL-PRS configuration, the target WTRU may perform one or more of the following operations. For example, the target WTRU may transmit a first COT busy signal transmission (e.g., according to the COT sharing information indicated in the transmitted SCI).

[0331] The target WTRU may receive a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration).

[0332] The target WTRU may perform an SL positioning measurement (e.g., RTT) on the second SL- PRS transmission (e.g., according to the second SL-PRS resource configuration).

[0333] The WTRU may receive a measurement reporting from the anchor WTRU (e.g., including RTT results on the first SL-PRS transmission).

[0334] Anchor WTRU coordination may be used to enable RTT SL-PRS transmissions sharing a COT with SL-PRS based COT busy signal transmission.

[0335] An SL-U shared COT SL-PRS configuration may be received.

[0336] A WTRU (e.g., an anchor WTRU) may receive one or more of the following configuration elements from another device.

[0337] The WTRU may receive a first SL PRS resource configuration. The first SL-PRS resource configuration may include the SL-PRS resource configuration for the forward transmission of the RTT procedure.

[0338] The WTRU may receive a second SL PRS resource configuration. The second SL-PRS resource configuration may include the SL-PRS resource configuration for the backward transmission of the RTT procedure.

[0339] The WTRU may receive a start time indication. The configuration may include an indication for the forward SL-PRS transmission timing.

[0340] The WTRU may receive a shared COT indication. The WTRU may receive an indication that the SL RTT session will be based on shared COT.

[0341] The WTRU may receive an ACK / NACK configuration for the shared COT RTT procedure.The WTRU may receive a COT busy I configuration. The configuration may include a set of types of signals that a WTRU may receive (e.g., transmitted to keep the COT busy between a SL-PRS transmission, for example, forward SL-PRS transmission, and a subsequent SL-PRS transmission, for example, a backwardSL-PRS transmission). The configuration may indicate one or more of the following types for COT busy I signal: an SL PRS resource configuration; a known sequence or a set of known sequences; a random sequence; and / or shared channel data.

[0342] The COT busy I signal may include a first part of COT busy I and a second part of COT busy I. In this case, the COT busy I configuration may include the types and durations for the first and the second part (e.g., each of the first and the second part).

[0343] A forward SL-PRS transmission may be received.

[0344] A WTRU (e.g., an anchor WTRU) may receive the forward SL-PRS transmission. The WTRU may receive SL-PRS (e.g., along with SCI). The SCI may indicate one or more of the following: a priority of the SL-PRS transmission; a time frequency resource used for the SL-PRS transmission; and / or COT sharing information.

[0345] The SCI may provide the COT sharing information to the WTRU. The COT sharing information may include one or more of the following elements: a priority value used to determine COT acquisition LBT parameters; a remaining COT duration; a resource allocation for the backward SL-PRS transmission (e.g., the resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the backward SL-PRS transmission); an RTT report inclusion indicator (e.g., an indication of whether the same COT can be used for RTT reporting, for example, if the same COT is to be used for RTT reporting, the WTRU may keep the COT occupied with a second COT busy signal between the backward SL-PRS transmission and the RTT report transmission); and / or a first COT busy signal configuration.

[0346] The first COT busy signal configuration may include a transmission duration. The transmission duration for the first COT busy signal may be provided in absolute time with suitable units (e.g., milliseconds or microseconds). The duration of first COT busy signal may be indicated in terms of slots and / or symbol duration. The reference slots and / or symbols can be for a reference sub-carrier spacing or for the active sub-carrier spacing.

[0347] The first COT busy signal configuration may include a type of the first COT busy signal used in the transmission. The type of the first COT busy signal may be a SL PRS configuration; a known sequence or a set of known sequences; a random sequence; shared channel data (e.g., that may be destined to the WTRU receiving the forward PRS transmission, or that may be destined to a different WTRU); and / or a resource allocation for the transmission. The resource allocation may be time frequency resource, only a time resource, or only a frequency resource indication for the first COT busy signal transmission.

[0348] The WTRU may determine the type of the first COT busy signal based on one or more of: the priority of the positioning procedure / session, reliability specifications, accuracy specifications, QoSspecifications related to the positioning procedure, received assistance information, channel sensing, etc. For example, the WTRU may determine to use the SL-PRS as the type of first COT busy signal if the priority of the positioning procedure / session is higher than a (e.g., configured) threshold. If the priority is below the threshold, the WTRU may determine a random or known sequence as the type of the first COT busy signal.

[0349] The first COT busy signal indication may include a first part of COT busy I and a second part of COT busy I. In this case, the COT busy I indication may include the types and durations for the first and the second part (e.g., each of the first and the second part).

[0350] A first COT busy signal may be received.

[0351] A WTRU (e.g., an anchor WTRU) may receive the transmission of the first COT busy signal. The first COT busy signal transmission may start after a delay (e.g., a fixed delay after the forward SL-PRS transmission). The WTRU may receive the first COT busy signal for the type and the duration indicated in the COT sharing information received with the forward SL-PRS transmission.

[0352] The WTRU may receive the first part of the first COT busy signal if the configuration has been provided for a first part and for a second part of the first COT busy signal.

[0353] If the first COT busy signal or first part of the first COT busy signal is determined to be carrying SL-PRS, the WTRU may buffer these signals. The WTRU may take measurements over these signals. The measurements may be used to compute RTT measurement results. The measurements may be reported as part of RTT measurements report.

[0354] An ACK / NACK to the RTT procedure may be transmitted.

[0355] A WTRU (e.g., an anchor WTRU) may transmit ACK / NACK feedback (e.g., in response to a received first SL-PRS transmission). The ACK / NACK feedback may be for the RTT procedure. The WTRU will transmit ACK if the WTRU agrees to continue the shared COT RTT procedure (e.g., according to the received configuration). The WTRU may transmit NACK to indicate that the WTRU will not share the COT of the first (e.g., forward) SL-PRS transmission.

[0356] The feedback may have one or more (e.g., more than two) outcomes. For example, an ACK may continue the shared COT RTT procedure. A NACK may indicate a fallback to individual COT RTT procedure. The feedback may be an abort indication for the RTT procedure. The WTRU may transmit no feedback to indicate abort (e.g., if no feedback will be considered abort at a second WTRU, for example, a target WTRU).

[0357] The WTRU may determine a suitable resource for the ACK / NACK transmission. The ACK / NACK resource may be determined based on the resource of the first (e.g., forward) SL-PRS transmission. TheACK / NACK resource may be based on one or more of the following: a resource of the first SL-PRS transmission; a resource of the first part of first COT busy signal; a WTRU ID of a WTRU (e.g., an anchor WTRU); a WTRU ID of a second WTRU (e.g., a target WTRU); and / or an indication (e.g., an explicit indication) in the control information received with first SL-PRS transmission.

[0358] A second part of the first COT busy signal may be received.

[0359] A WTRU (e.g., an anchor WTRU) may receive a second part of the first COT busy signal. The second part of the first COT busy signal may start after a delay (e.g., a fixed delay after the first part of first COT busy signal). The second part of the first COT busy signal transmission may start after the ACK / NACK transmission. The WTRU may receive the second part of the first COT busy signal based on the transmitted feedback. The WTRU may receive the second part if (e.g., only if) the transmitted feedback is a positive acknowledgment for RTT procedure (e.g., an ACK).

[0360] If the second part of the first COT busy signal is determined to be carrying SL-PRS, the WTRU may buffer the signals. The WTRU may take measurements over the signals. The measurements may be used to compute RTT measurement results. The measurements may be reported as part of RTT measurements report.

[0361] A backward SL-PRS transmission may be transmitted.

[0362] A WTRU (e.g., an anchor WTRU) may transmit a backward SL-PRS transmission (e.g., after the first COT busy signal). The WTRU may transmit the backward SL-PRS transmission on a time frequency resource (e.g., that the WTRU received in the SCI of the forward SL-PRS transmission). The SCI of the forward SL-PRS transmission may indicate (e.g., only indicate) the time. The time may be the absolute time or a time with a window within which a WTRU may receive the backward SL-PRS transmission. The WTRU may perform autonomous resource allocation over the SL resources (e.g., Mode 2 based resource allocation) to transmit the backward SL-PRS transmission (e.g., in response to received forward SL-PRS transmission).

[0363] The SL-PRS transmission (e.g., backward SL-PRS transmission) may indicate the transmission of RTT report and / or the resource for the RTT report transmission. The RTT report indication may be determined based on the received indication (e.g., in the SCI of the forward SL-PRS transmission).

[0364] The WTRU may reserve a resource for RTT report transmission. The WTRU may indicate the reserved resource (e.g., in the SCI of the backward SL-PRS transmission).

[0365] The SL-PRS transmission (e.g., backward SL-PRS transmission) may indicate the transmission of a second COT busy signal (e.g., subsequent to the SL-PRS transmission). The WTRU (e.g., an anchor WTRU) may transmit the indication for the second COT busy signal (e.g., in the SCI accompanying the SL- PRS transmission). The indication for the second COT busy signal may include one or more of thefollowi ng: a transmission duration for the second COT busy signal; a type of the second COT busy signal; a SL PRS configuration; a (pre)configured sequence or a set of (pre)configured sequences; a random sequence; shared channel data; and / or a resource allocation for the transmission. The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the second COT busy signal transmission.

[0366] The WTRU (e.g., an anchor WTRU) may determine the transmission type of the second COT busy signal (e.g., based on the received first COT busy signal from a target WTRU). The WTRU may determine to use the same type of COT busy signal as the received first COT busy signal.

[0367] The WTRU may determine a transmission duration of the second COT busy signal (e.g., based on WTRU processing capability of the target WTRU). The target WTRU and the anchor WTRU may exchange WTRU capability information (e.g., the processing and measurement time required for a SL-PRS transmission). The WTRU (e.g., an anchor WTRU) may determine a processing time (e.g., based on the target WTRU’s capability and / or the configuration of backward SL-PRS transmission, for example, the SL- PRS pattern). The WTRU may determine the duration of second COT busy signal (e.g., based on the processing time).

[0368] The WTRU (e.g., an anchor WTRU) may determine the frequency resource of the second COT busy signal (e.g., based on a (pre)configured implicit association with the frequency resource of the received first COT busy signal, for example, if the two signals are of the same type, for example, a SL-PRS sequence using the same pattern). The implicit association may be a frequency offset. For example, if the offset is zero, an identical frequency resource may be applied for the second COT busy signal. If the offset is a number of RB(s) and / or sub-carrier, the WTRU may determine the frequency resource of the second COT signal based on the offset.

[0369] A second COT busy signal may be transmitted.

[0370] The WTRU (e.g., an anchor WTRU) may transmit a second COT busy signal (e.g., following transmission of SL-PRS transmissions, for example, a backward SL-PRS transmission). The WTRU may transmit second COT busy signal according to the parameters transmitted in the SCI (e.g., the SCI accompanying a SL-PRS transmission, for example, a backward SL-PRS transmission of an RTT procedure).

[0371] A type of the second COT busy signal may be determined.

[0372] The WTRU (e.g., an anchor WTRU) may determine the type of the second COT busy signal (e.g., based on the first COT busy signal). The WTRU may select the type of second COT busy signal SL- PRS (e.g., if the type of the received first COT busy signal is SL-PRS).

[0373] The WTRU may select the type of second COT busy signal without consideration of (e.g., independent of) the type of first COT busy signal. The WTRU may select the type to be a known sequence, a sequence from a known or configured set of sequences, or a random sequence.

[0374] The WTRU may perform shared channel data transmission as a second COT busy signal. The WTRU may (e.g., may only) perform data transmission to another WTRU from which the WTRU received a COT sharing indication.

[0375] The WTRU may perform data transmission to a WTRU different from the WTRU providing COT sharing indication. The data transmission to a different WTRU may be subject to conditions (e.g., a priority condition, and a duration condition). The WTRU may transmit to a different WTRU if the priority of the data is higher than (e.g., by a known / configured / defined offset from) the priority used for COT acquisition.

[0376] Example RTT measurements reports are provided herein.

[0377] A WTRU (e.g., an anchor WTRU) may prepare an Rx-Tx time difference measurements report (e.g., based on the first SL-PRS transmission and / or the second SL-PRS transmission). The first-SL PRS transmission may be the forward SL-PRS transmission that WTRU receives. The second SL-PRS transmission may be backward transmission that the WTRU (e.g., SL-WTRU) transmits.

[0378] The WTRU may prepare Rx-Tx time difference measurements (e.g., based on the first SL-PRS transmission, first COT busy signal, and / or the second SL-PRS transmission). A WTRU may compute one or more (e.g., two) time-difference measurements. A first measurement may be between the first SL-PRS transmission and the second SL-PRS transmission. A second measurement may be between the first COT busy signal and the second SL-PRS transmission.

[0379] The WTRU may prepare Rx-Tx time difference measurements based on the first SL-PRS transmission, first COT busy signal, the second SL-PRS transmission, and / or the second COT busy signal. The WTRU may compute one or more (e.g., two) time-difference measurements. A first measurement may be between the first SL-PRS transmission and the second SL-PRS transmission. A second measurement may be between the first COT busy signal and the second COT busy signal.

[0380] The WTRU may use a reference time (e.g., a suitable reference time) for the first and second COT busy signal (e.g., to determine the time difference measurements). For example, the start of the slot for the first / second COT busy signal may be used as the reference received / transmit time. The start of the symbol time used for transmission of first / second COT busy signals may be used as the reference received / transmit time. The precise received / transmit time may be used as time reference for first / second COT busy signals (e.g., to determine the RTT time difference).

[0381] The WTRU may prepare RTT measurement reports based on one or more of the following signals: a first (e.g., forward) SL-PRS transmission; a first COT busy signal; a first part of the first COTbusy signal; a second part of the first COT busy signal; a second (e.g., backward) SL-PRS transmission; and / or a second COT busy signal.

[0382] An RTT measurement report may include Rx-Tx time difference measurements (e.g., from one or more of a received signal and a transmitted signal at the WTRU, for example, an anchor WTRU).

[0383] A measurement report may be transmitted.

[0384] The WTRU may transmit the measurement report (e.g., after the transmission of the second COT busy signal).

[0385] The WTRU may select the resource for RTT reporting (e.g., prior to the backward SL-PRS transmission). In this case, the WTRU may indicate the reporting resource (e.g., in the SCI of the backward transmission). The WTRU may use the resource to transmit RTT measurements report (e.g., after the transmission of second COT busy signal).

[0386] The WTRU may perform resource allocation for RTT reporting (e.g., after the backward SL-PRS transmission, or after the second COT busy signal transmission).

[0387] The transmission of the measurement report may be performed in the same COT used to perform the second SL-PRS transmission. This may be the case, for example, if the second COT busy signal is transmitted to maintain the COT ownership.

[0388] The WTRU may perform a channel access procedure (e.g., on the unlicensed SL carrier) to transmit measurement report. The LBT parameter(s) for channel sensing may be determined (e.g., based on the priority of the SL-PRS transmission).

[0389] An anchor WTRU may perform an SL RTT procedure (e.g., with an ACK / NACK transmission).

[0390] The anchor WTRU may perform the SL RTT procedure including feedback (e.g., an ACK / NACK transmission) to the target WTRU, as illustrated in FIG. 8.

[0391] The WTRU (e.g., an anchor WTRU) may receive a (pre)configuration from a target WTRU. The (pre)configuration may include one or more of the following: a first SL-PRS resource configuration (e.g., for reception from a target WTRU), a second SL-PRS resource configuration (e.g., for transmission to a Target WTRU), and / or an ACK / NACK configuration for the shared COT RTT procedure.

[0392] The WTRU (e.g., an anchor WTRU) may receive a first SL-PRS transmission (e.g., with associated SCI). The SCI may include COT sharing information from a target WTRU. The COT sharing information may include a first COT busy signal configuration. The first COT busy signal configuration may include one or more of the following (e.g., for the first part and for the second part): a transmission duration (e.g., number of symbols / slots), a type of the signal used in the transmission (e.g., a SL-PRS configuration, PSSCH, or a pre-configured signal), and / or a resource allocation of the transmission.

[0393] The WTRU (e.g., an anchor WTRU) may perform an SL positioning measurement (e.g., RTT) on the SL-PRS transmission (e.g., according to the (pre)configured first SL-PRS resource configuration).

[0394] If the type of indicated first COT busy signal follows the first SL-PRS configuration, the WTRU (e.g., an anchor WTRU) may receive a first part of the first COT busy signal transmission (e.g., according to the COT sharing information indicated in the received SCI). The WTRU may buffer the received first part of the first COT busy signal.

[0395] The WTRU (e.g., an anchor WTRU) may transmit an ACK to the target WTRU (e.g., according to the (pre)configuration).

[0396] The WTRU (e.g., an anchor WTRU) may receive a second part of the first COT busy signal transmission (e.g., according to the COT sharing information). The WTRU may buffer the second part of the first COT busy signal.

[0397] The WTRU (e.g., an anchor WTRU) may determine a second COT busy signal configuration (e.g., based on the received first COT busy signal, for example, an identical SL-PRS pattern, a transmission duration based on the SL-PRS pattern used for the first COT busy signal).

[0398] The WTRU (e.g., an anchor WTRU) may determine a second COT busy signal configuration (e.g., based on a (pre)configured signal and / or PSSCH if there is SL data in the buffer).

[0399] The WTRU (e.g., an anchor WTRU) may perform a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration with the associated SCI). The SCI may include the determined second COT busy signal configuration.

[0400] The WTRU (e.g., an anchor WTRU) may transmit a second COT busy signal (e.g., according to the determined second COT busy signal configuration).

[0401] The WTRU (e.g., an anchor WTRU) may perform a SL positioning measurement (e.g., RTT) on the buffered first COT busy signal transmission. The WTRU (e.g., an anchor WTRU) may send a measurement reporting. The measurement reporting may include the measurement (e.g., RTT) results on the first SL-PRS transmission, second SL-PRS transmission, and / or first COT busy signal transmission. The WTRU (e.g., an anchor WTRU) may send the measurement reporting. The measurement reporting may include the measurement (e.g., RTT) results on the first SL-PRS transmission and / or the second SL- PRS transmission.

[0402] FIG. 8 illustrates an example shared COT with SL-PRS based COT busy signal (e.g., with anchor WTRU ACK / NACK). FIG. 9 illustrates an example shared COT with SL-PRS based COT busy signal.

[0403] A target WTRU and an anchor WTRU may share a COT. The anchor WTRU may determine the configuration for SL-PRS for a second COT busy signal for transmission (e.g., based on the configuration of the received first COT busy signal from the target WTRU).

[0404] The anchor WTRU may receive a (pre)configuration from the target WTRU. The (pre)configuration may include a first SL-PRS resource configuration for reception from the target WTRU; and / or a second SL-PRS resource configuration for transmission to the target WTRU.

[0405] The anchor WTRU may receive a first SL-PRS transmission (e.g., with associated SCI). The SCI may include COT sharing information (e.g., from the target WTRU). The COT sharing information my include a first COT busy signal configuration. The first COT busy signal configuration may include one or more of the following: transmission duration (e.g., number of symbols / slots); a type of the signal used in the transmission (e.g., a SL-PRS config , PSSCH or a pre-configured signal); and / or a resource allocation of the transmission.

[0406] The anchor WTRU may perform a SL positioning measurement (e.g., RTT) on the SL-PRS transmission (e.g., according to the (pre)configured first SL-PRS resource configuration.

[0407] If the type of indicated first COT busy signal follows (e.g., matches) the first SL-PRS configuration, the anchor WTRU may perform one or more of the following operations. For example, the anchor WTRU may receive a first COT busy signal transmission (e.g., according to the COT sharing information indicated in the received SCI). The anchor WTRU may buffer the received first COT busy signal.

[0408] The anchor WTRU may receive a second COT busy signal configuration (e.g., based on the received first COT busy signal). For example, the second COT busy signal configuration may include an identical SL-PRS pattern; and / or a transmission duration (e.g., based on the SL-PRS pattern used for the first COT busy signal).

[0409] The anchor WTRU may perform a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration with the associated SCI). The second SL-PRS resource configuration may include at least the determined second COT busy signal configuration.

[0410] The anchor WTRU may transmit a second COT busy signal (e.g., according to the determined second COT busy signal configuration). The anchor WTRU may perform an SL positioning measurement (e.g., RTT) on the buffered first COT busy signal transmission. The anchor WTRU may send a measurement reporting. The measurement report may include the measurement (e.g., RTT) results on the first SL-PRS transmission and first COT busy signal transmission

[0411] If the type of indicated first COT busy signal does not follow (e.g., does not match) the first SL-PRS configuration, the anchor WTRU may perform one or more of the following operations. For example,the anchor WTRU may determine a second COT busy signal configuration (e.g., based on a (pre)configured signal and / or PSSCH, if there is SL data in the buffer).

[0412] The anchor WTRU may perform a second SL-PRS transmission (e.g., according to the (pre)configured second SL-PRS resource configuration). The anchor WTRU may transmit a second COT busy signal (e.g., according to the determined second COT busy signal configuration). The anchor WTRU may send a measurement reporting (e.g., RTT measurements results) on the first SL-PRS transmission.

[0413] A server WTRU may select an RTT procedure (e.g., based on channel measurements and / or anchor WTRU feedback.

[0414] Feature(s) associated with channel measurement and a WTRU capability request are provided herein.

[0415] A WTRU (e.g., a server WTRU) may transmit a request to a second WTRU. The request may request feedback on the channel measurements and / or other WTRU capabilities. The second WTRU may be an anchor WTRU. The second WTRU may be a target WTRU. The WTRU may transmit the request to the second WTRU (e.g., an anchor WTRU). The WTRU may transmit a request to a second WTRU (e.g., an anchor WTRU) and a third WTRU (e.g., a target WTRU). The second WTRU and / or the third WTRU may represent a second group of WTRUs and a third group of WTRUs, respectively.

[0416] A WTRU may transmit the channel measurements request to the second and / or third WTRU (e.g., each WTRU), for example, individually as unicast transmission. The WTRU may transmit the request in the form of groupcast transmission (e.g., to a group of WTRUs). For example, the WTRU may transmit a groupcast channel measurement request to a second group. The request may include a destination WTRU ID assigned to the second group. The WTRU may transmit a groupcast channel measurement request to a third group. The request may include a destination WTRU ID assigned to the third group.

[0417] The channel measurements may include the channel sensing for the unlicensed carrier operation. The channel measurements may include the channel sensing for sidelink resource allocation (e.g., Mode 2 based resource allocation).

[0418] The measurement request may indicate measurement configuration parameter(s). The WTRU may request different types of channel measurement for the second and / or third group. The measurement configuration parameter(s) may include measurement type, the measurement start time (e.g., absolute or relative), measurement duration, minimum measurement duration, antenna configuration to be used, etc.

[0419] The requested parameter(s) for channel measurements may include one or more of the following: a Channel Busy Ratio (CBR) of a set of SL resource pool(s); a CO (channel occupancy) ratio; a set of RSSI values (e.g., for a set of SL resource pools with suitable time frequency granularity used for computation of these values); future resources (e.g., for which the other WTRU has detected SL resource reservations); asuccess rate for a hypothetical LBT at a second WTRU, an anchor WTRU, and / or a third WTRU (e.g., a target WTRU); and / or a preferred RTT procedure and / or COT type. The second WTRU and / or third WTRU may be (pre)configured to determine the preferred RTT procedure and / or COT type (e.g., based on local channel measurements. The WTRU may indicate a preferred RTT procedure in a shared COT (e.g., if the channel is busy).

[0420] The requested parameters for WTRU capabilities may include one or more of the following: a PRS measurement time (e.g., SL-PRS measurement time); a preparation time for SL-PRS transmission; and / or an RTT report processing time.

[0421] Feedback of channel measurements and / or WTRU capabilities may be received.

[0422] The WTRU (e.g., a server WTRU) may receive the feedback on the channel measurements and / or the WTRU capabilities. The feedback may be in response to the WTRU’s request.

[0423] The WTRU may receive the feedback from a second WTRU (e.g., an anchor WTRU). The WTRU may receive a feedback from the second WTRU (e.g., an anchor WTRU), and / or a third WTRU (e.g., a target WTRU). The second WTRU and the third WTRU may represent a second group of WTRUs and a third group of WTRUs, respectively.

[0424] Example local channel measurements are provided herein.

[0425] The WTRU (e.g., a server WTRU) may perform local channel measurements.

[0426] The WTRU may perform the local channel measurement (e.g., prior to transmitting feedback request to other WTRUs). The WTRU may perform the local channel measurement after transmitting the feedback request. The WTRU may perform the local channel measurement after receiving the feedback of channel measurements from the other WTRU(s).

[0427] The configuration parameters for performing local channel measurements may be the same as provided in the WTRU request for feedback to the other WTRU(s). The configuration parameters for performing local channel measurements may be selected (e.g., independently of the feedback request parameters).

[0428] The local channel measurements may include the channel sensing for the unlicensed carrier operation. The local channel measurements may include the channel sensing for sidelink resource allocation (e.g., Mode 2 based resource allocation).

[0429] The estimated parameters for channel measurements may include one or more of the following: a CBR of a set of SL resource pool(s); a set of RSSI values (e.g., for a set of SL resource pools with suitable time frequency granularity used for computation of these values); future resources (e.g., for whichthe other WTRU has detected SL resource reservations); and / or a success rate for a hypothetical LBT at a second WTRU.

[0430] RTT procedures parameter(s) may be determined.

[0431] The WTRU (e.g., a server WTRU) may determine the parameter(s) relevant for an RTT positioning method (e.g., over SL-U carrier). The WTRU may determine the parameters for RTT based positioning using COT-based (e.g., individual COT-based) SL-PRS forward / backward transmissions. The WTRU may determine the parameters for RTT-based positioning using shared COT-based SL-PRS forward / backward transmissions. The WTRU may determine the RTT-based positioning parameters for individual and for shared COT based positioning procedures.

[0432] The determination may be for one or more of the following parameters for RTT procedures: a maximum COT duration, a priority class for COT initiation, a first COT-busy signal type / duration (e.g., the first COT busy signal may include a first part and a second part), and / or a second COT busy signal type / duration.

[0433] The determination of the parameter(s) for RTT procedure may be based on one or more of the following: WTRU processing capabilities (e.g., as received in the feedback); a number of a first set of WTRUs in the procedure (e.g., anchor WTRUs); a number of a second set of WTRUs in the procedure (e.g., target WTRUs); backward SL-PRS transmission(s) sharing the COT with forward SL-PRS transmission; RTT reports sharing the COT with one or more SL-PRS transmissions; and / or an ACK / NAK transmission from the first set of WTRUs (e.g., anchor WTRUs).

[0434] RTT procedure selection metric(s) may be derived.

[0435] The WTRU (e.g., a server WTRU) may derive metrics (e.g., the relevant metrics) to select suitable RTT procedure. For example, the WTRU may derive the metrics using a SL RTT procedure in different COTs or a SL RTT procedure in a shared COT.

[0436] The WTRU may derive one or more of the following metrics from the local channel measurements, the determined RTT / COT parameters, and / or the received feedback (e.g., channel measurements) from anchor and / or target WTRU(s).

[0437] The metric(s) may include one or more of: a first success probability to initiate a shared COT based RTT procedure (e.g., with forward, backward SL-PRS transmissions and RTT reports sharing the same COT); a second success probability to initiate a shared COT based RTT procedure (e.g., with forward and backward SL-PRS transmissions sharing the same COT); and / or a third success probability to initiate an individual COT for a SL-PRS transmission (e.g., forward SL-PRS transmission).

[0438] The WTRU may determine the success probabilities based on a combination of one or more of the following: local measurement(s); a measurement received in a target WTRU’s feedback (e.g., in accordance with the requested parameters); a measurement received in an anchor WTRU’s feedback (e.g., in accordance with the requested parameters); received target WTRU’s WTRU capabilities (e.g., in accordance with the requested parameters; and / or received anchor WTRU’s WTRU capabilities (e.g., in accordance with the requested parameters).

[0439] The success probability computation may be defined as the hypothesis test to initiate a COT with a given set of parameters (e.g., such as duration and / or priority, etc.). The success probability computation may be defined as the hypothesis test to initiate a COT with a given set of parameters based on the channel measurements / sensing results, received feedback, and / or channel measurements performed locally. The WTRU may perform a hypothesis test for COT initiation N number of times (e.g., to compute the success probability). N may be a configured parameter.

[0440] An RTT procedure may be determined.

[0441] The WTRU (e.g., a server WTRU) may determine an SL RTT positioning procedure (e.g., based on the derived success probabilities). The RTT positioning method determination may include the RTT method and / or the COT type to be used for the RTT method. For example, a WTRU may determine whether to use different COTs or a shared COT for a SL RTT positioning procedure (e.g., and corresponding SL RTT parameters).

[0442] The WTRU may determine the RTT positioning method (e.g., the suitable RTT positioning method) based on the success probabilities (e.g., the success probabilities determined using the channel measurements / sensing). The WTRU may determine a first RTT procedure (e.g., SHARED COT for forward / backward SL-PRS transmission and RTT reports) if the first success probability is higher than a first (e.g., configured) threshold. Otherwise (e.g., if the first success probability is not higher than the first threshold), if the second success probability is higher than a second (e.g., configured) threshold, the WTRU may choose a second RTT procedure (e.g., SHARED COT for forward / backward SL-PRS transmission). Otherwise (e.g., if the first success probability is not higher than the first threshold and the second success probability is not higher than the second threshold), if the third success probability is higher than a third (e.g., configured) threshold, the WTRU may choose a second RTT procedure (e.g., individual COT). Otherwise (e.g., if none of the success probabilities are higher than their respective thresholds), the WTRU may select an RTT failure / abort (e.g., implying that the unlicensed channel is currently not suitable for positioning procedure).

[0443] The WTRU may determine the RTT positioning method (e.g., the suitable RTT positioning method) based on (e.g., directly based on) the channel sensing measurements. The WTRU may use oneor more of the following measurements for RTT procedure determination: the channel measurements made at a second set of WTRUs (e.g., anchor WTRUs); the channel measurements made at a third set of WTRUs (e.g., Target WTRUs); and / or the local channel measurements made at the WTRU (e.g., a server WTRU).

[0444] The WTRU (e.g., a server WTRU) may determine the RTT procedure based on the indication of the (e.g., preferred) RTT method from a second set of WTRUs (e.g., anchor WTRUs). The WTRU may determine the RTT procedure based on the indication of the (e.g., preferred) RTT method from a second set of WTRUs and from a third set of WTRUs.

[0445] An example indication of the determined RTT procedure is provided herein.

[0446] The WTRU (e.g., a server WTRU) may provide an indication of the determined RTT procedure. The indication may include the determined procedure and / or the parameters relevant for the determined procedure. The parameters may be related to the SL-PRS configurations, channel acquisition for the unlicensed carrier (e.g., such as priority class, COT sharing information, COT busy signals I and II with types / durations), etc.

[0447] The WTRU (e.g., a server WTRU) may determine the SL-PRS configurations for a second set of WTRUs (e.g., anchor WTRUs), and for a third set of WTRUs (e.g., target WTRUs), for example, based on the COT type and determined RTT procedure. The WTRU may determine a first SL-PRS configuration for a first COT type (e.g., shared COT), and a second SL-PRS configuration for a second COT type (e.g., individual COT).

[0448] The WTRU (e.g., a server WTRU) may receive a set of SL-PRS configurations (e.g., from LMF). The WTRU may distribute the received configurations (e.g., from the LMF) to a second set of WTRUs (e.g., anchor WTRUs), and / or a third set of WTRUs (e.g., target WTRUs). The received configurations (e.g., from the LMF) may be configurations (e.g., independent configurations) for different COT types and / or for different RTT procedures. In this case, the WTRU (e.g., a server WTRU) may select SL-PRS configurations (e.g., suitable SL-PRS configurations) for a second set of WTRUs and / or for a third set of WTRUs based on the determined RTT procedure and / or COT type.

[0449] The WTRU may provide the indication of the selected RTT procedure to a second set of WTRUs (e.g., anchor WTRUs). The WTRU may provide the indication of the selected RTT procedure to a third set of WTRUs (e.g., target WTRUs).

[0450] The WTRU may transmit the determined procedure indication (e.g., as PHY, MAC or RRC based signaling).

[0451] An SL RTT procedure may be based on channel measurements (e.g., from a target WTRU and / or an anchor WTRU).

[0452] The WTRU may determine an SL RTT procedure based on channel measurements of the target WTRU and / or anchor WTRU(s) (e.g., as illustrated in FIG. 10).

[0453] The WTRU (e.g., a server WTRU) may transmit a request to the target and / or anchor WTRUs for the channel measurements and / or WTRU processing capabilities.

[0454] The WTRU (e.g., a server WTRU) may receive target / anchor WTRUs’ feedback about the channel measurements (e.g., CBR, RSSI, hypothetical LBT success) and / or the target / anchor WTRUs’ processing capabilities (e.g., PRS measurement time, PRS TX time, RTT report processing etc.).

[0455] The WTRU (e.g., a server WTRU) may determine RTT positioning parameter(s) (e.g., RTT positioning method relevant parameters). The RTT positioning parameter(s) may include a maximum COT duration, priority class for COT initiation, and / or COT-busy signal nature / duration (e.g., based on anchor WTRU processing capabilities).

[0456] The WTRU (e.g., a server WTRU) may derive one or more of the following metrics (e.g., based on the local channel sensing, determined RTT / COT parameters, and / or received target / anchor feedback: a first success probability to initiate a shared COT (e.g., to share among the target and / or the anchor WTRUs), and / or a second success probability to initiate an individual COT (e.g., for the target WTRU transmission).

[0457] The WTRU (e.g., a server WTRU) may determine a first RTT procedure (e.g., SHARED COT) if first success probability is higher than a first (e.g., configured) threshold. Otherwise (e.g., if the first success probability is not higher than the first threshold), if the second success probability is higher than a second configured threshold, the server WTRU may choose a second RTT procedure (e.g., individual COT). Otherwise (e.g., if neither the first nor the second success probabilities are higher than their respective thresholds), the server WTRU may select RTT failure / abort (e.g., unlicensed channel not suitable for positioning).

[0458] The WTRU (e.g., a server WTRU) may indicate the determined RTT procedure to the target and / or anchor WTRUs.

[0459] FIG. 10 illustrates an example server WTRU RTT selection procedure (e.g., with target and anchor WTRU channel measurements). FIG. 11 illustrates an example server WTRU RTT selection procedure.

[0460] A server WTRU may select an RTT procedure based on channel sensing and anchor WTRU feedback.

[0461] The server WTRU may determine success probabilities for an individual or shared COT. For example, the WTRU may determine success probabilities based on channel measurements reported by apeer WTRU (e.g., an anchor WTRU and / or target WTRU) and measurements performed by the server WTRU. WTRU capabilities (e.g., SL-PRS measurement / processing) of the anchor WTRU and / or target WTRU may be reported to the server WTRU. The server WTRU may consider the WTRU capabilities in the determination of the success probabilities. The WTRU may determine whether to use a shared COT or individual COT for positioning (e.g., based on one or more of the success probabilities).

[0462] The server WTRU may transmit a request to an anchor WTRU (or target WTRU). The request may be a request for the channel measurements and WTRU processing capabilities (e.g., preparation time to transmit SL-PRS, measurements processing time, etc.).

[0463] The server WTRU may receive an anchor WTRU response about the channel measurements (e.g., CBR, RSSI, hypothetical LBT success). The anchor WTRU capabilities may include a PRS measurement time, a PRS TX preparation time, RTT report processing, etc.

[0464] The server WTRU may determine parameter(s) relevant to the RTT positioning procedure. For example, the parameter(s) may include one or more of: a maximum COT duration, a priority class for COT initiation, and / or a COT-busy signal nature / duration. The server WTRU may determine the parameter(s) based on the anchor WTRU processing capabilities.

[0465] The server WTRU may derive one or more of the following metrics (e.g., based on local channel measurements performed by the server WTRU, the determined RTT / COT parameters, and / or the received anchor WTRU feedback, for example, channel measurements): a first success probability associated with initiating a shared COT to share among the target and the anchor WTRUs; and / or a second success probability associated with initiating an individual COT for the target WTRU transmission.

[0466] The server WTRU may determine a first RTT procedure (e.g., associated with using a shared COT) if the first success probability is higher than a first (e.g., configured) threshold. Otherwise (e.g., if the first success probability is lower than the first threshold), if the second success probability is higher than a second (e.g., configured) threshold, the server WTRU may choose a second RTT procedure (e.g., associated with using an individual COT).

[0467] Otherwise (e.g., if the first success probability is lower than the first threshold and the second success probability is lower than the second threshold), the server WTRU may select an RTT fail ure / abort procedure (e.g., indicating that the unlicensed channel is not suitable for positioning).

[0468] The server WTRU may indicate the determined RTT procedure to the anchor WTRU.

[0469] Feature(s) associated with a shared COT multi-RTT procedure from a target WTRU are provided herein.

[0470] An example SL-U shared COT PRS transmission configuration is provided herein.

[0471] A WTRU (e.g., a target WTRU) may transmit one or more of the following configuration elements.

[0472] The configuration elements may include assistance information to a first set of WTRUs (e.g., anchor WTRUs). The assistance information may indicate for the first set of WTRUs to perform resource selection (e.g., prior to COT initiation where SL-PRS transmissions will be performed). The WTRU may indicate a potential start time indication for a first SL-PRS transmission (e.g., a forward SL-PRS transmission). The WTRU may provide an estimate start time for the forward SL-PRS transmission, or a start time with a window / duration within which the first set of WTRUs may receive the forward SL-PRS transmission.

[0473] The configuration elements may include a set of transmission orders for the first set of WTRUs (e.g., anchor WTRUs) to use for their transmission in the shared COT-based RTT procedure.

[0474] The configuration elements may include a mapping of the first set of (e.g., anchor) WTRU identities to a second set of identities (e.g., which the WTRU may use to indicate the transmission order for the first set of anchor WTRUs).

[0475] The configuration elements may include a first SL PRS resource configuration. The first SL-PRS resource configuration may include the SL-PRS resource configuration for the forward transmission of the RTT procedure.

[0476] The configuration elements may include a second SL PRS resource configuration. The second SL-PRS resource configuration may include the SL-PRS resource configurations for the backward transmission of the RTT procedure (e.g., from one or more WTRU recipients of the first / forward SL-PRS transmission).

[0477] The configuration elements may include a shared COT indication. The WTRU may provide an indication that the SL RTT session will be based on a shared COT. The indication may include the information of the transmissions that will share the COT (e.g., forward SL-PRS transmissions, backward SL-PRS transmission, and / or RTT measurement reports).

[0478] The configuration elements may include a COT busy I configuration. The configuration may provide a set of types that a WTRU may use (e.g., to keep the COT busy between a SL-PRS transmission, for example, forward SL-PRS transmission and / or a subsequent SL-PRS transmission, for example, a backward SL-PRS transmission). The configuration may indicate one or more of the following types: an SL PRS resource configuration; a known sequence or a set of known sequences; a random sequence; and / or shared channel data.

[0479] The COT busy I signal may include a first part of the COT busy I signal and a second part of the COT busy I signal. In this case, the COT busy I configuration may include the types and durations for the first and second parts (e.g., each of the first and the second parts).

[0480] The configuration elements may include a COT busy II configuration. The configuration may include a set of types that a WTRU may use (e.g., to keep the COT busy between a set of SL-PRS transmissions, for example, backward SL-PRS transmissions and / or subsequent RTT reports). The configuration may indicate one or more of the following types: an SL PRS resource configuration; a known sequence or a set of known sequences; a random sequence; and / or shared channel data.

[0481] RTT procedure parameter(s) may be determined.

[0482] The WTRU (e.g., target WTRU) may determine the RTT procedure parameter(s). For example, the RTT procedure parameter(s) may include one or more of the following: LBT parameters for COT acquisition (e.g., priority, COT duration); a first COT busy signal (e.g., type / duration); a second COT busy signal (e.g., type / duration); a transmission order for a first set of WTRUs (e.g., anchor WTRUs) for PRS transmission; and / or a transmission order for the first set of WTRUs (e.g., anchor WTRUs) for RTT reports transmissions

[0483] The parameter(s) may indicate for a WTRU to perform the RTT procedure in a shared COT (e.g., using at least a number of anchors, M, and the anchor WTRUs’ capabilities, for example, preparation time to transmit SL-PRS, measurements processing time, etc.).

[0484] The RTT procedure parameters may be determined based on one or more of the following: a number of a first set of WTRUs (e.g., anchor WTRUs); the capabilities of the first set of WTRUs (e.g., anchor WTRUs, for example, preparation time to transmit SL-PRS, measurements processing time, etc.); the capabilities of a WTRU (e.g., target WTRU, for example, preparation time to transmit SL-PRS, measurements processing time, etc.); priority of the SL-PRS transmission; a length of the COT (e.g., required to finish the RTT session in the same COT, for example, the length of the COT may be selected to perform forward SL-PRS transmission and / or backward SL-PRS transmission in the same COT accommodating the measurement time and preparation time for SL-PRS transmission, or the length of the COT may be selected to perform forward SL-PRS transmission, backward SL-PRS transmission, and / or RTT reporting in the same COT including the WTRU processing times required for each intermediate step); the channel conditions at a first WTRU (e.g., a target WTRU); and / or the channel conditions at a second WTRU (e.g., an anchor WTRU).

[0485] An example SL-U channel access procedure for a shared COT is provided herein.

[0486] A WTRU (e.g., a target WTRU) may perform LBT-based channel sensing (e.g., to acquire the COT for RTT procedure). The WTRU may perform LBT-based channel sensing according to the determined LBT parameter(s).

[0487] An example forward SL-PRS transmission is provided herein.

[0488] The WTRU (e.g., a target WTRU) may perform the forward SL-PRS transmission (e.g., based on successful COT acquisition over SL-U). The WTRU may transmit SL-PRS (e.g., along with accompanying control information). The control information may be transmitted in SCI. The control information may indicate one or more of the following: a priority of the SL-PRS transmission; a time frequency resource used for the SL-PRS transmission; a priority value used to determine COT acquisition LBT parameters; and / or a remaining COT duration.

[0489] The control information may include a transmission order for anchor WTRUs’ PRS transmissions. The transmission order may be an indication (e.g., a dynamic indication). The transmission order may select (indicate) one of the (pre)configured transmission orders (e.g., an index selecting a (pre)configured transmission order). The transmission order may be a static or semi-static transmission order. In this case, an indication (e.g., a dynamic indication) for the transmission order may not be transmitted. The transmission order may be a static or semi-static order. The WTRU (e.g., a target WTRU) may override the semi-static order (e.g., by providing a dynamic indication in the SCI).

[0490] The WTRU may determine a dynamic indication (e.g., an indication in SCI).

[0491] The dynamic indication may be an explicit indication. The WTRU may indicate a sequential order (e.g., in a SCI indication) of WTRU IDs. For example, the SCI indication may include N bit positions, a bit position (e.g., each bit position) may be indicated with a WTRU ID. The length of the bit position may be determined by the number of anchor WTRUs in the multi-RTT procedure. The WTRU ID may be based on an anchor WTRU group ID (e.g., (pre)configured by a server WTRU and / or LMF). The WTRU ID may be based on a network-assigned WTRU ID.

[0492] The dynamic indication may be an implicit indication. A set of transmission orders in an anchor WTRU group may be (pre)configured. The transmission orders (e.g., each transmission order) may be denoted by a respective index. A WTRU may indicate the index (e.g., in SCI) to indicate a transmission order.

[0493] The control information may include a resource allocation for the backward SL-PRS transmissions. The WTRU may perform resource allocation for the backward SL-PRS transmissions. The WTRU may indicate the resource allocation to the recipient WTRU(s) (e.g., anchor WTRU(s)) to be used for their backward SL-PRS transmission(s). The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication (e.g., for the backward SL-PRS transmission).

[0494] The control information may include an RTT report inclusion indicator. COT sharing information may include an indication (e.g., for the SL Rx WTRU) of whether the same COT can be used for RTT reporting. If RTT reports may be transmitted in a different COT, the WTRU (e.g., a target WTRU) mayinitiate a second COT for RTT reporting. The WTRU may indicate that a second COT for RTT reporting will be initiated by a second WTRU (e.g., an anchor WTRU).

[0495] The control information may include a transmission order for anchor WTRUs’ RTT report transmissions. The transmission order may be a dynamic indication (e.g., selecting one of the (pre)configured transmission orders, for example, an index selecting a (pre)configured transmission order). The transmission order may be a static or semi-static transmission order. In this case, a dynamic indication for transmission order may not be transmitted. The transmission order may be a static or semi-static order. The WTRU (e.g., a target WTRU) may override the semi-static order (e.g., by providing a dynamic indication in the SCI).

[0496] The control information may include a resource allocation for the RTT measurement reports. The WTRU may perform resource allocation for the RTT report transmissions. The WTRU may indicate the resource allocation to the recipient WTRUs (e.g., anchor WTRUs). The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication (e.g., for the RTT report transmissions).

[0497] The control information may include a first COT busy signal indication. The first COT busy signal indication may include one or more of the following.

[0498] The first COT busy signal indication may include transmission duration. The transmission duration for the first COT busy signal may be provided in absolute time with suitable units (e.g., milliseconds or microseconds). The duration of first COT busy signal may be indicated in terms of slots and / or symbol duration. The reference slots and / or symbols may be for a given sub-carrier spacing or for the active sub-carrier spacing.

[0499] The first COT busy signal indication may include a type of the first COT busy signal used in the transmission. The type of the first COT busy signal may be a SL PRS configuration, a known sequence or a set of known sequences, a random sequence, shared channel data (e.g., the shared channel data may be destined to one or more of the first set of WTRUs, for example, anchor WTRUs, recipient of forward PRS transmission, or the WTRU may send shared channel data to a WTRU different from the recipients of the forward SL-PRS transmission), and / or a resource allocation for the transmission. The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the first COT busy signal transmission.

[0500] The control information may include a second COT busy signal indication. The second COT busy signal indication may include one or more of the following.

[0501] The second COT busy signal indication may include a transmission duration. The transmission duration for the second COT busy signal may be provided in absolute time with suitable units (e.g.,milliseconds or microseconds). The duration of first COT busy signal may be indicated in terms of slots and / or symbol duration. The reference slots and / or symbols may be for a given sub-carrier spacing or for the active sub-carrier spacing.

[0502] The second COT busy signal indication may include a type of the second COT busy signal used in the transmission. The type of the second COT busy signal may include one or more of: a SL PRS configuration; a known sequence or a set of known sequences; a random sequence; shared channel data (e.g., the shared channel data may be destined to one or more of the first set of WTRUs, for example, anchor WTRUs, recipient of forward PRS transmission, or the WTRU may send shared channel data to a WTRU different from the recipients of the forward SL-PRS transmission); and / or a resource allocation for the transmission. The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the second COT busy signal transmission.

[0503] Feature(s) associated with a first COT busy signal transmission are provided herein.

[0504] A WTRU (e.g., a target WTRU) may perform the transmission of the first COT busy signal. The first COT busy signal transmission may start after a delay (e.g., a fixed delay after the forward SL-PRS transmission). A WTRU may transmit the first COT busy signal for the type and / or the duration indicated in the control information (e.g., SCI, transmitted with the forward SL-PRS transmission).

[0505] Feature(s) associated with reception of backward SL-PRS transmissions are provided herein.

[0506] The WTRU (e.g., a target WTRU) may receive a backward SL-PRS transmission from a first set of WTRUs (e.g., anchor WTRUs), for example, after the forward SL-PRS transmission and / or first COT busy signal transmission. The WTRU may receive the backward SL-PRS transmissions on a time frequency resource (e.g., that was transmitted in the SCI of the forward SL-PRS transmission). The SCI of the forward SL-PRS transmission may indicate (e.g., only indicate) the time. The time may be the absolute time or a time with a window within which a WTRU may the backward SL-PRS transmission. The WTRU may receive the backward SL-PRS transmissions in response to the forward SL-PRS transmission (e.g., where the other WTRU performs the resource allocation for the backward SL-PRS transmission).

[0507] The WTRU (e.g., a target WTRU) may receive the backward SL-PRS transmission from a first set of WTRUs (e.g., anchor WTRUs) in the known transmission order. The transmission order for backward SL-PRS transmissions may be semi-static. The WTRU may have indicated the dynamic transmission order in the SCI of the forward SL-PRS transmission.

[0508] Feature(s) associated with determining sufficient PRS transmissions received for multi-RTT validity are provided herein.

[0509] The WTRU (e.g., a target WTRU) may determine whether the WTRU has received sufficient SL- PRS transmissions for a valid multi-RTT procedure.

[0510] If the WTRU (e.g., a target WTRU) successfully receives SL-PRS transmissions from N anchors (e.g., where N is larger than a (pre)configured threshold), the WTRU may determine that the current RTT session has sufficient measurements received. The WTRU may consider reception of a SL-PRS transmission successful if the WTRU is able to successfully decode the SCI of the SL-PRS transmission. The WTRU may consider reception of a SL-PRS transmission successful if the measured RSRP of the received SL-PRS transmission is larger than a (e.g., configured) threshold.

[0511] If the WTRU determines to have received sufficient SL-PRS transmissions, the WTRU may determine to transmit a second COT busy signal. Otherwise (e.g., if the WTRU has not received sufficient SL-PRS transmissions), the WTRU (e.g., a target WTRU) may abort the ongoing RTT session. In this case, the WTRU may transmit an abort indication to a first set of WTRUs (e.g., anchor WTRUs). The first set of WTRUs may not transmit the measurement reports (e.g., based on receiving the abort indication) for the session for which the first set of WTRUs received the abort indication.

[0512] The WTRU may indicate the abort of the current RTT session to a server WTRU (e.g., with a reason indication).

[0513] A second COT busy signal may be transmitted.

[0514] If the WTRU determines to transmit a second COT busy signal (e.g., upon validation of a multi- RTT procedure) the WTRU may transmit the second COT busy signal. The transmission of the second COT busy signal may follow the parameter(s) indicated in the SCI of the forward SL-PRS transmission.

[0515] The WTRU may not transmit a second COT busy signal. This may be the case if the RTT measurement reports are transmitted in a COT separate from the COT used for SL-PRS transmissions.

[0516] An example SL-U channel access procedure for RTT reports is provided herein.

[0517] The WTRU (e.g., a target WTRU) may determine LBT parameter(s) to initiate a COT for the RTT reports from a second set of WTRUs (e.g., anchor WTRUs).

[0518] The WTRU (e.g., a target WTRU) may perform the LBT-based channel sensing (e.g., to acquire the COT for RTT reports). The WTRU may perform the LBT-based channel sensing according to the determined LBT parameter(s).

[0519] An example request for RTT reports is provided herein.

[0520] The WTRU (e.g., a target WTRU) may transmit a request to a second set of WTRUs (e.g., anchor WTRUs) to receive RTT measurement reports. The request may be transmitted as PHY, MAC, or RRC signaling. The associated control information may indicate one or more of the following: a priority of the transmission; a time frequency resource used for the request transmission; a priority value used todetermine COT acquisition LBT parameters; a remaining COT duration; a transmission order for the anchor WTRUs’ RTT report transmissions; and / or a resource allocation for the RTT measurement reports.

[0521] The transmission order may be a dynamic indication selecting one of the (pre)configured transmission orders (e.g., an index selecting a pre-configured transmission order). The transmission order may be a static or semi-static transmission order. In this case, a dynamic indication for transmission order may not be transmitted. The transmission order may be a static or semi-static order. The WTRU (e.g., a target WTRU) may override the semi-static order (e.g., by providing a dynamic indication in the SCI).

[0522] The WTRU may perform resource allocation for the RTT reports transmissions. The WTRU may indicate the resource allocation to the recipient WTRUs (e.g., anchor WTRUs). The resource allocation may be a time frequency resource, only a time resource, or only a frequency resource indication for the RTT measurement reports.

[0523] A WTRU (e.g., an anchor WTRU) may determine a transmission timing for a measurement report of a received forward SL-PRS transmission (e.g., based on an explicit indication of transmission order). The WTRU may receive the indication (e.g., in the request transmission by a target WTRU and / or in the SCI associated with a forward SL-PRS transmission from a target WTRU).

[0524] The WTRU (e.g., an anchor WTRU) may determine a transmission timing for a measurement report of a received forward SL-PRS transmission (e.g., based on the received transmission order for the backward SL-PRS transmissions in the COT initiated by the target WTRU). The WTRU may apply the same backward SL-PRS transmission order to the measurement reporting transmission.

[0525] Measurement reports may be received.

[0526] The WTRU may receive measurement reports from a set of WTRUs (e.g., anchor WTRUs, for example, after the transmission of the second COT busy signal).

[0527] The WTRU may receive the measurement report on the resource for which a reservation indication was transmitted (e.g., in the SCI accompanying forward SL-PRS transmission).

[0528] The WTRU may receive the measurement reports with no prior reservation indication.

[0529] A WTRU (e.g., a target WTRU) may receive the RTT reports from a set of WTRUs (e.g., anchor WTRUs) in the (e.g., known) transmission order. The transmission order for RTT report transmissions may be semi-static order. The WTRU may have indicated the transmission order as a dynamic transmission order (e.g., in the SCI of the forward SL-PRS transmission).

[0530] Example RTT measurements reports are provided herein.

[0531] A WTRU (e.g., a target WTRU) may prepare an Rx-Tx time difference measurements report (e.g., based on the first SL-PRS transmission and / or the backward SL-PRS transmission(s)). The first-SLPRS transmission may be the forward SL-PRS transmission that the WTRU transmits. The second SL-PRS transmission(s) may be transmission(s) that the WTRU (e.g., SL-WTRU) receives.

[0532] The WTRU may prepare Rx-Tx time difference measurements (e.g., based on the forward SL- PRS transmission, first COT busy signal, and / or the backward SL-PRS transmission(s)). A WTRU may compute one or more (e.g., two) sets of time-difference measurements. A first set of measurement may be between the forward SL-PRS transmission and the backward SL-PRS transmissions. A second set of measurement may be between the first COT busy signal and the backward SL-PRS transmissions.

[0533] The WTRU may use a reference time (e.g., a suitable reference time) for the first COT busy signal (e.g., to determine the time difference measurements). The start of the slot for the first COT busy signal may be used as the reference transmit / receive time. The start of the symbol time used for transmission of first COT busy signals may be used as the reference transmit / received time. The precise transmit / receive time may be used as time reference for first COT busy signals (e.g., to determine RTT time difference).

[0534] FIG. 12 illustrates an example of multi-RTT shared COT SL-U positioning.

[0535] The target WTRU may be configured with a plurality of anchor WTRUs (e.g., M anchor WTRUs) to perform RTT-based positioning. The target WTRU may determine the order of transmission for the M anchor WTRUs. The WTRU transmits SL-PRS to the M anchor WTRUs (e.g., using an SCI indication). The SCI indication may indicate the transmission order for the anchor WTRUs. If the WTRU receives SL-PRS from at least N anchor WTRUs, the target WTRU may report measurements to a server WTRU (e.g., according to the determined order of transmission). Otherwise (e.g., if the WTRU receives SL-PRS from fewer than N anchor WTRUs), the target WTRU may report an error to the network.

[0536] The target WTRU may transmit target assistance information to M anchor WTRUs. The target assistance information may indicate for the anchor WTRUs to perform resource selection prior to COT start, a potential start time indication (e.g., tO and a window length), and a set of transmission orders.

[0537] The target WTRU may determine one or more of: LBT parameter(s), a COT busy type / duration (e.g., COT_Busy_l & II type / duration), a transmission order for M anchors for PRS and RTT reports to perform the RTT procedure in a shared COT using at least the number of anchors M, anchor WTRUs capabilities to transmit SL-PRS after having received SL-PRS from the target WTRU, and / or anchor WTRUs capabilities to process measurements to prepare RTT measurement report.

[0538] The target WTRU may perform LBT (e.g., a type 1 LBT). The target WTRU may perform LBT to acquire channel access for RTT procedure (e.g., based on determined LBT parameters).

[0539] The target WTRU may determine one or more SCI parameter(s). The SCI parameters may include at least one of the following: a remaining COT duration; a channel access priority class (e.g., usedfor COT acquisition); COT_Busy_l and II (e.g., the duration and type for I, duration for II, I prior to PRS, and II prior to RTT reports); a transmission order for the anchor WTRUs’ PRS transmissions (e.g., a transmission order may be a dynamic indication selecting one of the pre-configured transmission orders, for example, an index selecting a pre-configured transmission order); a transmission resource for the anchor WTRUs’ PRS transmissions; a transmission resource for the anchor WTRUs’ RTT reporting.

[0540] The target WTRU may transmit a positioning transmission to the anchor WTRUs. The positioning transmission may include SL-PRS and / or the determined SCI parameters.

[0541] The target WTRU may transmit a COT_Busy_l signal (e.g., to the anchor WTRUs). The COT_Busy_l signal may include extended SL-PRS.

[0542] If the target WTRU detects SL-PRS transmissions from N anchors (e.g., where N is larger than a (pre)configured threshold), the target WTRU may transmit a COT Busy II signal (e.g., where the COT Busy II signal is a pre-configured type).

[0543] Otherwise (e.g., If the target WTRU detects SL-PRS transmissions from fewer than N anchors), the target WTRU may transmit an abort indication to the anchor WTRUs. The abort indication may abort the current RTT procedure. The target WTRU may indicate the abort indication to a server WTRU (e.g., with a reason indication).

[0544] The target WTRU may receive RTT measurement reports (e.g., in the transmission order indicated in the SCI for anchors PRS transmissions). The target WTRU may transmit local and / or anchor WTRU RTT reports to the server WTRU. The target WTRU may receive location information from the server WTRU.

[0545] Although features and elements described above are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments, or in various combinations with or without other features and elements.

[0546] Although the implementations described herein may consider 3GPP specific protocols, it is understood that the implementations described herein are not restricted to this scenario and may be applicable to other wireless systems. For example, although the solutions described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it is understood that the solutions described herein are not restricted to this scenario and are applicable to other wireless systems as well.

[0547] The processes described above may be implemented in a computer program, software, and / or firmware incorporated in a computer-readable medium for execution by a computer and / or processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted over wired and / or wireless connections) and / or computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random accessmemory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and / or optical media such as compact disc (CD)-ROM disks, and / or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, terminal, base station, RNC, and / or any host computer.

[0548] It is understood that the entities performing the processes described herein may be logical entities that may be implemented in the form of software (e.g., computer-executable instructions) stored in a memory of, and executing on a processor of, a mobile device, network node or computer system. That is, the processes may be implemented in the form of software (e.g., computer-executable instructions) stored in a memory of a mobile device and / or network node, such as the node or computer system, which computer executable instructions, when executed by a processor of the node, perform the processes discussed. It is also understood that any transmitting and receiving processes illustrated in figures may be performed by communication circuitry of the node under control of the processor of the node and the computer-executable instructions (e.g., software) that it executes.

[0549] The various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination of both. Thus, the implementations and apparatus of the subject matter described herein, or certain aspects or portions thereof, may take the form of program code (e.g., instructions) embodied in tangible media including any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the subject matter described herein. In the case where program code is stored on media, it may be the case that the program code in question is stored on one or more media that collectively perform the actions in question, which is to say that the one or more media taken together contain code to perform the actions, but that - in the case where there is more than one single medium - there is no requirement that any particular part of the code be stored on any particular medium. In the case of program code execution on programmable devices, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and / or storage elements), at least one input device, and at least one output device. One or more programs that may implement or utilize the processes described in connection with the subject matter described herein, e.g., through the use of an API, reusable controls, or the like. Such programs are preferably implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.

[0550] Although example embodiments may refer to utilizing aspects of the subject matter described herein in the context of one or more stand-alone computing systems, the subject matter described herein is not so limited, but rather may be implemented in connection with any computing environment, such as a network or distributed computing environment. Still further, aspects of the subject matter described herein may be implemented in or across a plurality of processing chips or devices, and storage may similarly be affected across a plurality of devices. Such devices might include personal computers, network servers, handheld devices, supercomputers, or computers integrated into other systems such as automobiles and airplanes.

[0551] In describing preferred embodiments of the subject matter of the present disclosure, as illustrated in the Figures, specific terminology is employed for the sake of clarity. The claimed subject matter, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

Claims

CLAIMSWhat is Claimed:1 . A wireless transmit / receive unit (WTRU) comprising: a processor configured to: receive configuration information that indicates a time, after reception of a first sidelink positioning reference signal (SL-PRS), within which to send a second SL-PRS; receive the first SL-PRS; perform a first listen before talk (LBT) procedure associated with a first priority within a first window of time; on a condition that the WTRU does not acquire a channel occupancy time (COT) based on the first LBT procedure, perform a second LBT procedure associated with a second priority in a second window of time; and send a transmission, wherein a content of the transmission depends on whether the WTRU was able to acquire the COT during the time within which to send the second SL-PRS.

2. The WTRU of claim 1, wherein the processor is further configured to determine a duration of the first window of time based on a third priority associated with the first SL-PRS, wherein the duration of the first window of time is inversely proportional to the third priority.

3. The WTRU of claim 1, wherein the processor is further configured to determine, based on local sidelink channel measurements, at least one of: a duration of the first window of time, a duration of the second window of time, the first priority, or the second priority.

4. The WTRU of claim 1, wherein on a condition that the WTRU was able to acquire the COT during the time within which to send the second SL-PRS, the transmission comprises the second SL-PRS and control information that indicates a resource associated with the second SL-PRS.

5. The WTRU of claim 4, wherein the processor is further configured to select a sidelink resource in which to send the second SL-PRS, and wherein: the transmission comprises the second SL-PRS, and the transmission is sent to a target WTRU or a server WTRU via the sidelink resource.

6. The WTRU of claim 1, wherein on a condition that the WTRU was unable to acquire the COT during the time within which to send the second SL-PRS, the transmission comprises an indication that a current session has been aborted and an indication that the current session was aborted because the WTRU was unable to acquire the COT.

7. The WTRU of claim 1 , wherein at least a portion of the first window of time and a portion of the second window of time overlap, and the configuration information further indicates an offset between a start of the first window of time and a start of the second window of time.

8. The WTRU of claim 1 , wherein the time within which to send the second SL-PRS begins at a start of the first window of time, and ends at an end of the second window of time, and the WTRU being able to acquire the COT during the time within which to send the second SL-PRS comprises the WTRU acquiring a resource in which to send the second SL-PRS before the end of the second window of time.

9. A method, performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information that indicates a time, after reception of a first sidelink positioning reference signal (SL-PRS), within which to send a second SL-PRS; receiving the first SL-PRS; performing a first listen before talk (LBT) procedure associated with a first priority within a first window of time; on a condition that the WTRU does not acquire a channel occupancy time (COT) based on the first LBT procedure, performing a second LBT procedure associated with a second priority in a second window of time; and sending a transmission, wherein a content of the transmission depends on whether the WTRU was able to acquire the COT during the time within which to send the second SL-PRS.

10. The method of claim 9, wherein the method further comprises determining a duration of the first window of time based on a third priority associated with the first SL-PRS, wherein the duration of the first window of time is inversely proportional to the third priority.11 . The method of claim 9, wherein the method further comprises determining, based on local sidelink channel measurements, at least one of: a duration of the first window of time, a duration of the second window of time, the first priority, or the second priority.

12. The method of claim 9, wherein on a condition that the WTRU was able to acquire the COT during the time within which to send the second SL-PRS, the transmission comprises the second SL-PRS and control information that indicates a resource associated with the second SL-PRS.

13. The WTRU of claim 12, wherein the method further comprises selecting a sidelink resource in which to send the second SL-PRS, and wherein: the transmission comprises the second SL-PRS, and the transmission is sent to a target WTRU or a server WTRU via the sidelink resource.

14. The method of claim 9, wherein on a condition that the WTRU was unable to acquire the COT during the time within which to send the second SL-PRS, the transmission comprises an indication that a current session has been aborted and an indication that the current session was aborted because the WTRU was unable to acquire the COT.

15. The method of claim 9, wherein at least a portion of the first window of time and a portion of the second window of time overlap, and the configuration information further indicates an offset between a start of the first window of time and a start of the second window of time.

16. The method of claim 9, wherein the time within which to send the second SL-PRS begins at a start of the first window of time, and ends at an end of the second window of time, and the WTRU being able to acquire the COT during the time within which to send the second SL-PRS comprises the WTRU acquiring a resource in which to send the second SL-PRS before the end of the second window of time.

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