CN116803152A - Method and apparatus for side-link positioning - Google Patents

Abstract

A method performed by a first wireless transmit/receive unit (WTRU) is provided, the method may include: requesting support from one or more potential assistant WTRUs (a-WTRUs); receiving a response message from one or more potential a-WTRUs, wherein the response message includes information indicating a coverage status within a network of the one or more potential a-WTRUs; determining a group of a-WTRUs from the one or more potential a-WTRUs based on the received response message; determining a synchronization source based on the coverage status of each a-WTRU of the determined group of a-WTRUs; and reporting the determined synchronization source to the determined group of A-WTRUs.

Description

Method and apparatus for side-link positioning

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional application 63/136,558 filed on 1 month 12 of 2021 and U.S. provisional application 63/228,955 filed on 8 month 3 of 2021, the contents of which are incorporated herein by reference.

Background

Third generation partnership project (3 GPP) specifications for new air interface vehicle-to-everything (V2X) may support side-link communications between different vehicles. The resources for side-link transmission/reception may be constructed as a resource pool. The resource pool may be composed of a set of consecutive frequency resources that repeat in time following a bitmap pattern.

A wireless transmit/receive unit (WTRU) may be configured with or configured to use one or more resource pools. For WTRUs within coverage, the resource pool may be configured via a System Information Block (SIB) and/or via Radio Resource Control (RRC) signaling. For out-of-coverage WTRUs, the resource pool may be preconfigured.

Each side-uplink transmission may span one slot on the PSSCH and/or PSCCH. The PSSCH and PSCCH can use FDM and TDM multiplexing. The side-uplink control information (SCI) may be divided into two parts, which may be a first-stage SCI and a second-stage SCI. The first stage SCI may indicate resources for side-link transmission, quality of service (QoS) of the transmission (e.g., priority), demodulation reference signals (DMRS), or Phase Tracking Reference Signals (PTRS) for side-link transmission and/or second SCI format. The second level SCI may indicate the remaining control information. SCI may be used to reserve one or more resources for future transmissions within a resource pool.

From the perspective of the side-uplink scheduling, the side-uplink resources may be scheduled by the network (i.e., mode 1) and autonomously selected by the WTRU (i.e., mode 2). If the WTRU uses mode 2, it may perform sensing by decoding SCI from other WTRUs before selecting side-link resources to avoid selecting resources reserved by other WTRUs.

The SL-CSI-RS may be supported for unicast to support a transmit (Tx) WTRU when determining Tx parameters (e.g., power and rank). The Tx WTRU may indicate the presence of one or more side-uplink channel state information reference signals (SL-CSI-RS) by using the SCI. The CSI-RS transmission may trigger CSI reporting. And the CSI reporting delay may be configured via a PC5 RRC message. Each reporting instance may be associated with one or more SL-CSI-RS transmissions.

The 3GPP may provide a DL-based positioning method, an UL-based positioning method, and a dl+ul-based positioning method of positioning specification. In a DL-based positioning method, DL-PRSs may be sent from multiple transmit-receive points (TRPs) to WTRUs. The WTRU may observe and/or measure downlink signals from the TRP. For the WTRU-B method, the WTRU may calculate its location and for the WTRU-a method, the WTRU may return downlink measurements to the network. For angle-based methods, the WTRU may report an angle of arrival (AoA) of a downlink signal from the TRP and a Reference Signal Received Power (RSRP). For timing-based methods, the WTRU may report a Reference Signal Time Difference (RSTD). The above method may require transmission timing synchronization between TRPs. The positioning calculation errors mainly come from synchronization errors and multipath.

In an uplink positioning method, a WTRU may send an uplink positioning reference signal (UL-PRS) configured by RRC to a TRP for positioning. The network may then calculate the location of the WTRU based on coordination of all TRPs receiving UL-PRSs from the WTRU.

In both UL and DL based approaches, the WTRU may measure the Rx-Tx time difference between the received DL-PRS and the transmitted UL-PRS. The Rx-Tx time difference and RSRP may be reported to the network. The network may then coordinate the TRP to calculate the location of the WTRU.

Disclosure of Invention

Methods and apparatus for side-link positioning are described herein. A method performed by a first wireless transmit/receive unit (WTRU) is provided, the method may include: requesting support from one or more potential assistant WTRUs (a-WTRUs); receiving a response message from one or more potential a-WTRUs, wherein the response message includes information indicating a coverage status within a network of the one or more potential a-WTRUs; determining a group of a-WTRUs from the one or more potential a-WTRUs based on the received response message; determining a synchronization source based on the coverage status of each a-WTRU of the determined group of a-WTRUs; and reporting the determined synchronization source to the determined group of A-WTRUs.

The method may also compromise determining from the one or more potential a-WTRUs that the group of a-WTRUs is based on a quality of service (QoS) requirement of a location service of the first WTRU. The method may also compromise where the determined synchronization source is a base station under the condition that each of the a-WTRUs in the determined group is within the coverage area of the network. The method may also compromise where the determined synchronization source is any WTRU if at least one of the a-WTRUs in the determined group is not within the coverage area of the network. The method may also compromise that the any WTRU is the first WTRU.

The method may also compromise that the first WTRU sends information to the determined group of a-WTRUs for receiving a side-uplink (SL) positioning synchronization signal (slbss) transmission. The method may also compromise that the first WTRU sends the slps transmission to the determined set of a-WTRUs to synchronize a SL positioning reference signal (SL-PRS) for the determined set of a-WTRUs. The method may also compromise that the slps transmission is one of a SL-PRS, a side-link synchronization signal (SLSS), a demodulation reference signal (DMRS), a Phase Tracking Reference Signal (PTRS), or a channel state information reference signal (CSI-RS). The method may also compromise that the first WTRU determines the periodicity of the slps transmissions based on a quality of service (QoS) requirement of a location service associated with the determined group of a-WTRUs. The method may also compromise that the first WTRU sends the slps transmission using the determined periodicity.

Drawings

A more detailed understanding of the description may be derived from the following description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, and in which:

FIG. 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

fig. 1B is a system diagram illustrating an exemplary wireless transmit/receive unit (WTRU) that may be used within the communication system shown in fig. 1A according to one embodiment;

fig. 1C is a system diagram illustrating an exemplary Radio Access Network (RAN) and an exemplary Core Network (CN) that may be used within the communication system shown in fig. 1A according to one embodiment;

fig. 1D is a system diagram illustrating another exemplary RAN and another exemplary CN that may be used in the communication system shown in fig. 1A according to one embodiment;

fig. 2 is an example in which a WTRU uses SCI to indicate SL-PRS mode;

FIG. 3 is a flowchart of steps for performing an exemplary side-uplink positioning procedure;

FIG. 4 is an exemplary signaling flow in which a P-WTRU transmits SL-PRS and all A-WTRUs receive the SL-PRS (e.g., a method based on SL-PRS transmission);

fig. 5 is an exemplary signaling flow in which all a-WTRUs transmit SL-PRS and P-WTRUs receive the SL-PRS (e.g., a method based on SL-PRS transmissions);

Fig. 6 is an exemplary signaling flow in which all WTRUs transmit/receive SL-PRS (e.g., methods based on SL-PRS transmission and reception);

fig. 7 depicts an example in which a WTRU determines which resources to use for transmitting a synchronization signal;

fig. 8 depicts an example in which a WTRU dynamically selects synchronized transmission resources;

fig. 9 is a diagram illustrating a scenario in which all a-WTRUs are in coverage and a scenario in which one or more a-WTRUs are out of coverage;

fig. 10 is a diagram illustrating an exemplary synchronization offset between two WTRUs; and is also provided with

Fig. 11 is a diagram illustrating an exemplary procedure for determining an offset time between two WTRUs.

Detailed Description

Fig. 1A is a diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messages, broadcasts, etc., to a plurality of wireless users. Communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, communication system 100 may employ one or more channel access methods, such as Code Division Multiple Access (CDMA), time Division Multiple Access (TDMA), frequency Division Multiple Access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero-tail unique word discrete fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filter OFDM, filter Bank Multicarrier (FBMC), and the like.

As shown in fig. 1A, the communication system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a Radio Access Network (RAN) 104, a Core Network (CN) 106, a Public Switched Telephone Network (PSTN) 108, the internet 110, and other networks 112, although it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. For example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a Station (STA), may be configured to transmit and/or receive wireless signals, and may include User Equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular telephones, personal Digital Assistants (PDAs), smartphones, laptop computers, netbooks, personal computers, wireless sensors, hot spot or Mi-Fi devices, internet of things (IoT) devices, watches or other wearable devices, head Mounted Displays (HMDs), vehicles, drones, medical devices and applications (e.g., tele-surgery), industrial devices and applications (e.g., robots and/or other wireless devices operating in an industrial and/or automated processing chain environment), consumer electronic devices, devices operating on a commercial and/or industrial wireless network, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

Communication system 100 may also include base station 114a and/or base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the internet 110, and/or the other networks 112. As an example, the base stations 114a, 114B may be Base Transceiver Stations (BTSs), node bs, evolved node bs (enbs), home node bs, home evolved node bs, next generation node bs, such as a gnnode B (gNB), new air interface (NR) node bs, site controllers, access Points (APs), wireless routers, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

Base station 114a may be part of RAN 104 that may also include other base stations and/or network elements (not shown), such as Base Station Controllers (BSCs), radio Network Controllers (RNCs), relay nodes, and the like. Base station 114a and/or base station 114b may be configured to transmit and/or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a particular geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in an embodiment, the base station 114a may include three transceivers, i.e., one for each sector of a 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 a cell. For example, beamforming may be used to transmit and/or receive signals in a desired spatial direction.

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, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable Radio Access Technology (RAT).

More specifically, as noted above, communication 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, or the like. For example, the base station 114a and WTRUs 102a, 102b, 102c in the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) terrestrial radio access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 116.WCDMA may include communication protocols such as High Speed Packet Access (HSPA) and/or evolved HSPA (hspa+). HSPA may include high speed Downlink (DL) packet access (HSDPA) and/or high speed Uplink (UL) packet access (HSUPA).

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 use Long Term Evolution (LTE) and/or LTE-advanced (LTE-a) and/or LTE-advanced Pro (LTE-a Pro) to establish the air interface 116.

In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may use NR to establish the air interface 116.

In embodiments, 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, e.g., using a Dual Connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e.g., enbs and gnbs).

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 1X, CDMA EV-DO, tentative standard 2000 (IS-2000), tentative standard 95 (IS-95), tentative standard 856 (IS-856), global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM EDGE (GERAN), and the like.

The base station 114B in fig. 1A may be, for example, a wireless router, home node B, home evolved node B, or access point, and may utilize any suitable RAT to facilitate wireless connections in local areas such as business, home, vehicle, campus, industrial facility, air corridor (e.g., for use by drones), road, etc. In an 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 pico cell or femto cell. As shown in fig. 1A, the base station 114b may be directly connected to the internet 110. Thus, the base station 114b may not need to access the internet 110 via the CN 106.

The RAN 104 may communicate with a CN 106, which may be any type of network configured to provide voice, data, application, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102 d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location based services, prepaid calls, internet connections, video distribution, etc., and/or perform advanced security functions such as user authentication. Although not shown in fig. 1A, it should be appreciated that RAN 104 and/or CN 106 may communicate directly or indirectly with other RANs that employ the same RAT as RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104 that may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, wiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the internet 110, and/or other networks 112.PSTN 108 may include circuit-switched telephone networks that provide Plain Old Telephone Services (POTS). The internet 110 may include a global system for interconnecting computer networks and devices using common communication protocols, such as Transmission Control Protocol (TCP), user Datagram Protocol (UDP), and/or Internet Protocol (IP) in the TCP/IP internet protocol suite. Network 112 may include wired and/or wireless communication networks owned and/or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

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

Fig. 1B is a system diagram illustrating an exemplary WTRU 102. As shown in fig. 1B, 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 peripheral devices 138, etc. It should be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

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), any other type of Integrated Circuit (IC), a state machine, or the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, which may be coupled to a transmit/receive element 122. Although fig. 1B depicts the processor 118 and the transceiver 120 as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signals to and receive signals from a base station (e.g., base station 114 a) 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 one embodiment, the transmit/receive element 122 may be an emitter/detector configured to emit and/or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and/or receive RF and optical signals. It should be appreciated that the transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted as a single element in fig. 1B, 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.

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

The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker/microphone 124, a keypad 126, and/or a display/touchpad 128, such as a Liquid Crystal Display (LCD) display unit or an Organic Light Emitting Diode (OLED) display unit. The processor 118 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. Further, 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. 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 never physically locate memory access information on the WTRU 102, such as on a server or home computer (not shown), and store the data in that memory.

The processor 118 may receive power from the power source 134 and may be configured to distribute and/or control power to 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 battery packs (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to a 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 information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114 b) over the air interface 116 and/or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with an embodiment.

The processor 118 may also be coupled to other peripheral devices 138, which may beThe peripheral devices may include one or more software modules and/or hardware modules that provide additional features, functionality, and/or wired or wireless connections. For example, the number of the cells to be processed, peripheral devices 138 may include accelerometers, electronic compasses, satellite transceivers, digital cameras (for photographs and/or video), universal Serial Bus (USB) ports, vibrating devices, television transceivers, hands-free headsets, wireless communications devices, and the like,Modules, frequency Modulation (FM) radio units, digital music players, media players, video game player modules, internet browsers, virtual reality and/or augmented reality (VR/AR) devices, activity trackers, and the like. The peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: gyroscopes, accelerometers, hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors; geographic position sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, humidity sensors, and the like.

WTRU 102 may include a full duplex radio for which transmission and reception of some or all signals (e.g., associated with a particular subframe for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and/or simultaneous. The full duplex radio station may include an interference management unit for reducing and/or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing by a processor (e.g., a separate processor (not shown) or via processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which some or all signals are transmitted and received (e.g., associated with a particular subframe for UL (e.g., for transmission) or DL (e.g., for reception).

Fig. 1C is a system diagram illustrating a RAN 104 and a CN 106 according to one embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using an E-UTRA radio technology. RAN 104 may also communicate with CN 106.

RAN 104 may include enode bs 160a, 160B, 160c, but it should be understood that 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 to communicate with the WTRUs 102a, 102B, 102c over the air interface 116. In an embodiment, the evolved node bs 160a, 160B, 160c may implement MIMO technology. Thus, the enode B160 a may use multiple antennas to transmit wireless signals to the WTRU 102a and/or to receive wireless signals from the WTRU 102a, for example.

Each of the evolved node bs 160a, 160B, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and/or DL, and the like. As shown in fig. 1C, the enode bs 160a, 160B, 160C may communicate with each other over an X2 interface.

The CN 106 shown in fig. 1C may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be appreciated that any of these elements may be owned and/or operated by entities other than the CN operator.

The MME 162 may be connected to each of the evolved node bs 162a, 162B, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating the user of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, and the like. MME 162 may provide control plane functionality for switching between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and/or WCDMA.

SGW 164 may be connected to each of the evolved node bs 160a, 160B, 160c in RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102 c. The SGW 164 may perform other functions such as anchoring user planes during inter-enode B handover, triggering paging when DL data is available to the WTRUs 102a, 102B, 102c, managing and storing the contexts of the WTRUs 102a, 102B, 102c, etc.

The SGW 164 may be connected to a PGW 166 that may provide the WTRUs 102a, 102b, 102c with access to a packet switched network, such as the internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to a circuit-switched network (such as the PSTN 108) to facilitate communications between the WTRUs 102a, 102b, 102c and legacy landline communication 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 other networks 112, which may include other wired and/or wireless networks owned and/or operated by other service providers.

Although the WTRU is depicted in fig. 1A-1D as a wireless terminal, it is contemplated that in some representative embodiments such a terminal may use a wired communication interface with a communication network (e.g., temporarily or permanently).

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

A WLAN in an 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 access or interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic to and/or from the BSS. Traffic originating outside the BSS and directed to the STA may arrive through the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. 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 pass the traffic to the destination STA. Traffic between STAs within a BSS may be considered and/or referred to as point-to-point traffic. Point-to-point traffic may be sent between (e.g., directly between) the source and destination STAs using Direct Link Setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z Tunnel DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

When using the 802.11ac infrastructure mode of operation or similar modes of operation, the AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access/collision avoidance (CSMA/CA) may be implemented, for example, in an 802.11 system. For CSMA/CA, STAs (e.g., each STA), including the AP, may listen to the primary channel. If the primary channel is listened to/detected by a particular STA and/or determined to be busy, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time in a given BSS.

High Throughput (HT) STAs may communicate using 40MHz wide channels, for example, by combining a primary 20MHz channel with an adjacent or non-adjacent 20MHz channel to form a 40MHz wide channel.

Very High Throughput (VHT) STAs may support channels that are 20MHz, 40MHz, 80MHz, and/or 160MHz wide. 40MHz and/or 80MHz channels may be formed by combining consecutive 20MHz channels. The 160MHz channel may be formed by combining 8 consecutive 20MHz channels, or by combining two non-consecutive 80MHz channels (this may be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data may pass through a segment parser that may split the data into two streams. An Inverse Fast Fourier Transform (IFFT) process and a time domain process may be performed on each stream separately. These streams may be mapped to two 80MHz channels and data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed and the combined data may be sent to a Medium Access Control (MAC).

The 802.11af and 802.11ah support modes of operation below 1 GHz. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11 ac. The 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the television white space (TVWS) spectrum, and the 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter type control/Machine Type Communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including supporting (e.g., supporting only) certain bandwidths and/or limited bandwidths. MTC devices may include batteries with battery lives above a threshold (e.g., to maintain very long battery lives).

WLAN systems that can support multiple channels, and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and/or limited by STAs from all STAs operating in the BSS (which support a minimum bandwidth mode of operation). In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only) 1MHz mode, the primary channel may be 1MHz wide, even though the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and/or other channel bandwidth modes of operation. The carrier sense and/or Network Allocation Vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because the STA is transmitting to the AP (only supporting 1MHz mode of operation), all available frequency bands may be considered busy even if most available frequency bands remain idle.

The available frequency band for 802.11ah in the united states is 902MHz to 928MHz. In korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

Fig. 1D is a system diagram illustrating a RAN 104 and a CN 106 according to one embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. RAN 104 may also communicate with CN 106.

RAN 104 may include gnbs 180a, 180b, 180c, but it should be understood that RAN 104 may include any number of gnbs while remaining consistent with an embodiment. Each of the gnbs 180a, 180b, 180c may include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the gnbs 180a, 180b, 180c may implement MIMO technology. For example, gnbs 180a, 108b may utilize beamforming to transmit signals to gnbs 180a, 180b, 180c and/or to receive signals from gnbs 180a, 180b, 180 c. Thus, the gNB 180a may use multiple antennas to transmit wireless signals to the WTRU 102a and/or receive wireless signals from the WTRU 102a, for example. In an embodiment, the gnbs 180a, 180b, 180c may implement carrier aggregation techniques. 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 the unlicensed spectrum while the remaining component carriers may be on the licensed spectrum. In embodiments, the gnbs 180a, 180b, 180c may implement coordinated multipoint (CoMP) techniques. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180 c).

The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using transmissions associated with the scalable parameter sets. For example, the OFDM symbol interval and/or OFDM subcarrier interval may vary from one transmission to another, from one cell to another, and/or from one portion of the wireless transmission spectrum to another. The WTRUs 102a, 102b, 102c may communicate with the gnbs 180a, 180b, 180c using various or scalable length subframes or Transmission Time Intervals (TTIs) (e.g., including different numbers of OFDM symbols and/or continuously varying absolute time lengths).

The gnbs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in an independent configuration and/or in a non-independent configuration. In a standalone configuration, the WTRUs 102a, 102B, 102c may communicate with the gnbs 180a, 180B, 180c while also not accessing other RANs (e.g., such as the enode bs 160a, 160B, 160 c). In an independent configuration, the WTRUs 102a, 102b, 102c may use one or more of the gnbs 180a, 180b, 180c as mobility anchor points. In an independent configuration, the WTRUs 102a, 102b, 102c may use signals in unlicensed frequency bands to communicate with the gnbs 180a, 180b, 180 c. In a non-standalone configuration, the WTRUs 102a, 102B, 102c may communicate or connect with the gnbs 180a, 180B, 180c, while also communicating or connecting with other RANs (such as the enode bs 160a, 160B, 160 c). For example, the WTRUs 102a, 102B, 102c may implement DC principles to communicate with one or more gnbs 180a, 180B, 180c and one or more enodebs 160a, 160B, 160c substantially simultaneously. In a non-standalone configuration, the enode bs 160a, 160B, 160c may serve as mobility anchors for the WTRUs 102a, 102B, 102c, and the gnbs 180a, 180B, 180c may provide additional coverage and/or throughput for serving the WTRUs 102a, 102B, 102 c.

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 UL and/or DL, support of network slices, interworking between DC, NR, and E-UTRA, routing of user plane data towards User Plane Functions (UPFs) 184a, 184b, routing of control plane information towards access and mobility management functions (AMFs) 182a, 182b, and so on. As shown in fig. 1D, gnbs 180a, 180b, 180c may communicate with each other through an Xn interface.

The CN 106 shown in fig. 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. Although the foregoing elements are depicted as part of the CN 106, it should be appreciated that any of these elements may be owned and/or operated by entities other than the CN operator.

The AMFs 182a, 182b may be connected to one or more of the gnbs 180a, 180b, 180c in the RAN 104 via an N2 interface and may function as control nodes. For example, the AMFs 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slices (e.g., handling of different Protocol Data Unit (PDU) sessions with different requirements), selection of a particular SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMFs 182a, 182b may use network slices to customize CN support for the WTRUs 102a, 102b, 102c based on the type of service used by the WTRUs 102a, 102b, 102 c. For example, different network slices may be established for different use cases, such as services relying on ultra high reliability low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, and so on. The AMFs 182a, 182b may provide control plane functionality for switching between the RAN 104 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-a Pro, and/or non-3 GPP access technologies, such as WiFi.

The SMFs 183a, 183b may be connected to AMFs 182a, 182b in the CN 106 via an N11 interface. The SMFs 183a, 183b may also be connected to UPFs 184a, 184b in the CN 106 via an N4 interface. SMFs 183a, 183b may select and control UPFs 184a, 184b and configure traffic routing through UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions such as managing and assigning WTRU IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, ethernet-based, etc.

UPFs 184a, 184b may be connected to one or more of the gnbs 180a, 180b, 180c in the RAN 104 via an N3 interface that may provide the WTRUs 102a, 102b, 102c with access to a packet-switched network, such as the internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-host PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, and the like.

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

In view of fig. 1A-1D and the corresponding descriptions of fig. 1A-1D, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more emulation devices (not shown): the WTRUs 102a-d, base stations 114a-B, evolved node bs 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMFs 182a-B, UPFs 184a-B, SMFs 183a-B, DN 185a-B, and/or any other devices described herein. The emulated device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device may be used to test other devices and/or analog network and/or WTRU functions.

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

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

Abbreviations and acronyms as used herein are provided below:

ACK acknowledgement

AoA angle of arrival

AoD departure angle

A-WTRU assistant-WTRU

BLER block error Rate

CB is contention-based (e.g., access, channel, resource)

CBR channel busy rate

CP cyclic prefix

CP-OFDM conventional OFDM (depending on cyclic prefix)

CQI channel quality indicator

CR channel occupancy

CRC cyclic redundancy check

CSI channel state information

D2D device-to-device transmission (e.g., LTE side uplink)

DCI downlink control information

DFT-s-OFDM digital Fourier transform spread OFDM

DL downlink

DMRS demodulation reference signal

FB feedback

FDD frequency division duplexing

FDM frequency division multiplexing

The InC is in the coverage area of the cell

LBT listen before talk

LLC low latency communication

LTE LTE Long term evolution, e.g. from 3GPP LTE R8 and beyond

MAC medium access control

NACK negative ACK

MBB mass broadband communication

MC multi-carrier

MCS modulation and coding scheme

OFDM orthogonal frequency division multiplexing

OOB out-of-band (emission)

OoC out of coverage of cell

OTDOA observe time difference of arrival

P _cmax Total available UE power in a given TI

PC5-S PC5 signaling

PDB packet delay budget

PHY physical layer

PSCCH physical SL control channel

PSFCH physical SL feedback channel

PSS primary synchronization signal

PSSCH physical SL shared channel

PSSCH-RSRP PSSCH reference Signal received Power

P-WTRU positioning WTRU

QoS quality of service (from the physical layer point of view)

RNTI radio network identifier

RRC radio resource control

RRM radio resource management

RS reference signal

RSRP reference signal received power

RSRQ reference signal reception quality

RSTD reference signal time difference

Round trip time of RTT

Signal strength indicator received by S-RSSI SL

SL side-links

SL-PRS side-link positioning reference signal

SS synchronization signal

SSS secondary synchronization signal

SLSS side uplink synchronization signal

SL-PRS side-link positioning reference signal

SL-RSRP side-uplink reference signal received power

SL-RSRQ side uplink reference signal receiving quality

Signal strength indicator received by SL-RSSI side-link

S-PSS side uplink primary synchronization signal

S-PSS side uplink secondary synchronization signal

TB transport block

TDD time division duplexing

TDM time division multiplexing

ToA arrival time

ToD departure time

TTI transmission time interval

TRP transmitting/receiving point

TRX transceiver

UL uplink

Ultra-reliable low-latency communication of URLLC

V2X vehicle communication

Current methods for Uu positioning may have several drawbacks. One disadvantage may be coverage. For example, in some cases, uu positioning may not be able to help locate an out-of-coverage WTRU. Another disadvantage may be accuracy. For example, multipath propagation may severely degrade the performance of DL/UL/DL & UL based methods. Another disadvantage may be delay. For example, high precision positioning may introduce delays due to the higher layer configuration required in Uu positioning. Another disadvantage may be power efficiency. For Uu positioning, for example, power consumption may be a problem for the WTRU because the WTRU may need to boost its Tx power to reach the neighboring cell.

Side-link positioning may be beneficial. For example, coverage may be enhanced. The side-uplink positioning may provide positioning for both the in-coverage WTRU and the out-of-coverage WTRU. The accuracy may be enhanced. With the auxiliary WTRU covering the blind spot, the side-link positioning may provide additional dimensions to improve positioning accuracy. The delay may be enhanced. The side-link positioning can be quickly supplemented to achieve high accuracy by autonomously formulating positioning groups, reducing delay. The power efficiency may be enhanced. For side-uplink positioning, power consumption for the P-WTRU may be increased because the transmit power and allocated positioning workload may be reduced by using the auxiliary WTRU.

Side-uplink positioning for a P-WTRU may require synchronization of a group of assistant WTRUs (a-WTRUs) and reference signal transmission/reception between the WTRUs. Thus, a method of determining a group of A-WTRUs to support P-WTRU location is desirable. After the group of a-WTRUs are formulated, a method of synchronizing SL-PRS transmissions/receptions to facilitate measurements and reporting may be necessary.

Embodiments are provided herein that may provide a solution to some or all of the above problems. The embodiments described herein for positioning may be used for ranging without any limitation. Positioning may be referred to as a method or scheme of estimating the geographic location of a WTRU. Ranging may be referred to as a method or scheme of estimating the distance between WTRUs. When the method is used for ranging, "location of WTRU" or "location information of WTRU" may be used interchangeably with "distance between WTRUs".

An overview is provided herein that includes at least some of the described embodiments. The exemplary embodiments described below may focus on the behavior of the P-WTRU. In some embodiments, a WTRU (i.e., a P-WTRU) may perform the following procedure upon a location request from a higher layer or any logically equivalent layer.

The WTRU may broadcast a location assistant message that may include its location status (e.g., its estimated location and error information, its area ID, speed, direction, etc.), qoS requirements of the location service (e.g., location accuracy, delay), and/or a location method supported by the side-link (e.g., OTDOA, RTT, aoA, aoD, etc.). The WTRU may receive a response message from the potential assistant WTRU.

The WTRU may determine a group of a-WTRUs and synchronization source-WTRUs (serving as synchronization sources for the group) based on QoS requirements for location services, a location status of each a-WTRU (e.g., a coarse distance to the P-WTRU), and/or a side-uplink measurement of each WTRU (e.g., RSRP, LOS/NLOS status of response messages). The WTRU may determine when/whether to synchronize. In some examples, a P-WTRU may require more A-WTRUs for high positioning accuracy and fewer A-WTRUs for low positioning accuracy. The P-WTRU may select the N a-WTRUs with the highest RSRP or with the shortest area distance, etc. In some examples, the P-WTRU may select a synchronization source WTRU in the middle of the group or a WTRU with the highest position accuracy, synchronize to the highest synchronization source, etc.

The WTRU may determine a positioning method (e.g., RTT, OTDOA, aoA, aoD) based on the positioning state of the a-WTRU and the QoS requirements of the positioning. The WTRU may select a SL-PRS transmission mode (SL-PRS resource pool, number of subchannels per transmission, number of repetitions, periodicity, time/frequency offset, comb value, etc.) and a measurement report configuration based on a set of A-WTRUs, qoS for location services, CBR of the resource pool, CR of the WTRU, etc. The WTRU may send a SL-PRS transmission pattern and a reporting configuration to the group A-WTRU in a positioning assistant acknowledgement message.

For some methods, such as the OTDOA-based side-uplink positioning method, if the WTRU determines to receive SL-PRS, the WTRU may receive synchronization signals from the synchronization source WTRU and receive SL-PRS from the normal A-WTRU. The WTRU may calculate its location based on the timing of receipt of the synchronization signal of the synchronization source WTRU, the SL-PRS of the normal A-WTRU, and the relative location between each pair of A-WTRUs. If the WTRU determines to transmit the SL-PRS, the WTRU may receive one or more synchronization signals from a synchronization source WTRU. The WTRU may transmit the SL-PRS using a timing of a received synchronization signal from a synchronization source WTRU. The WTRU may receive measurement reports from each a-WTRU and calculate its location.

The following examples may focus on the behavior of the a-WTRU. In the following embodiments, a WTRU (i.e., an a-WTRU) may perform the following operations upon a location request from a higher layer such as the RRC layer or any logical equivalent.

The WTRU may receive a location assistant message from another WTRU (i.e., a P-WTRU). The WTRU may determine whether to transmit a response message (i.e., whether to become an a-WTRU) based on its location status, side-uplink measurements, the number of supported P-WTRUs, and/or the side-uplink positioning methods it supports. The response message may include the WTRU location status and supported side-uplink positioning methods. The WTRU may resolve how to coordinate the modes of multiple P-WTRUs. For example, the WTRU may only respond if it detects LOS and/or RSRP greater than a threshold. The WTRU may be allowed to support up to N P-WTRUs.

The WTRU may receive a location assistant acknowledgement message. If the WTRU is selected as the synchronization source WTRU, the WTRU may send a synchronization signal in the configured resources. Otherwise (i.e., if the WTRU is selected as a normal a-WTRU), the WTRU may receive a synchronization signal from the synchronization source-WTRU.

For some methods, such as the OTDOA-based side-uplink positioning method, if the WTRU is configured to transmit SL-PRS, the WTRU may transmit SL-PRS using a reference timing of the synchronization signal. If the WTRU is configured to receive SL-PRS, the WTRU may receive SL-PRS from another WTRU (P-WTRU). The WTRU may report side uplink measurements (e.g., RSTD between two SL-PRSs or between one SL-PRS and a synchronization signal).

The following examples may focus on the behavior of the P-WTRU. In some embodiments, a WTRU (i.e., a P-WTRU) may perform the following operations upon a location request from a higher layer (e.g., RRC or any logical equivalent) or network.

The WTRU may broadcast a location assistant message that may include its location status (e.g., its estimated location and error information, its area ID, speed, direction, etc.), qoS requirements for location services (e.g., location accuracy, delay), supported location methods (OTDOA, RTT, aoA, aoD, etc.), and/or cell ID.

The WTRU may receive a response message from the potential assistant WTRU. The WTRU may determine a set of potential a-WTRUs based on QoS requirements for location services, a location status of each a-WTRU (e.g., relative distance from the P-WTRU), side-uplink measurements of each WTRU (e.g., RSRP, LOS/NLOS status of response messages), coverage status of potential a-WTRUs, connection status, and cell ID. The WTRU may report the set of potential a-WTRUs to the network.

The WTRU may receive a set of a-WTRUs (from a set of potential a-WTRUs), a reference WTRU (within the coverage area of the WTRU), a SL-PRS transmission/reception mode, and reporting configurations for itself and/or the set of a-WTRUs from the network. The WTRU may forward the group of A-WTRUs, the reference WTRU, the SL-PRS transmission/reception pattern, and the reporting configuration to the A-WTRU.

For the OTDOA method, if the WTRU is configured to receive SL-PRS, the WTRU may receive a synchronization signal from the reference WTRU and SL-PRS from the normal A-WTRU. The WTRU may perform side-uplink measurements (SL-PRS and RSTD between synchronization signals from a reference WTRU). The WTRU may report one or more side uplink measurements to the gNB. The WTRU may receive a synchronization signal from a reference WTRU if the WTRU is configured to transmit SL-PRS. The WTRU may transmit the SL-PRS using the timing of the received synchronization signal. The WTRU may receive measurement reports from each a-WTRU. The WTRU may report the combined side-uplink measurements from the a-WTRU to the gNB.

The following examples may focus on the behavior of the a-WTRU. In some embodiments, a WTRU (i.e., an a-WTRU) may perform the following steps upon request from an upper layer.

The WTRU may receive a location assistant message from another WTRU (i.e., a P-WTRU). The WTRU may determine whether to transmit a response message based on the QoS requirements of the location service, its location status, side-uplink measurements, the number of supported P-WTRUs, its supported location methods, coverage status, connection status, and cell ID (i.e., the WTRU may become an a-WTRU). The response message may include the WTRU location status and supported positioning methods.

The WTRU may receive a location assistant acknowledgement message. If the WTRU is selected as the reference WTRU, the WTRU may use the downlink timing reference to transmit a synchronization signal in the configured resources. Otherwise (i.e., if the WTRU is selected as a normal a-WTRU), the WTRU may receive a synchronization signal from the reference WTRU.

For the OTDOA method, if the WTRU is configured to transmit SL-PRS, the WTRU may transmit SL-PRS using a reference timing of the synchronization signal. If the WTRU is configured to receive SL-PRSs, the WTRU may receive SL-PRSs from another one or more WTRUs (e.g., a P-WTRU). The WTRU may report side-uplink measurements (e.g., RSTD between two SL-PRSs or between one SL-PRS and a synchronization signal) to the P-WTRU.

Embodiments related to the design of SL-PRS are described herein. In some embodiments, the WTRU may determine a signal of the SL-PRS. For example, the WTRU may use one or any of the following reference signals as the SL-PRS: DMRS of PSSCH and/or PSCCH; SLSS (e.g., S-PSS, S-SSS); PTRS; SL-CSI-RS; or a new RS designed for positioning purposes.

In some embodiments, the WTRU may be configured with multiple SL-PRS types. The WTRU may be configured or pre-configured to use one or more SL-PRS types. Each type may be associated with reference signals, resources, etc. for SL-PRS transmission. For example, the WTRU may be configured or pre-configured with two SL-PRS types. The first SL-PRS type may use the PSSCH and/or the DMRS of the PSCCH. The SL-PRS type may be transmitted with side-link data. The second SL-PRS type may use a new RS designed for positioning purposes. The SL-PRS type may or may not be transmitted with side-uplink data.

The SL-PRS type may be determined based on one or more of the following parameters/configurations: (1) Aperiodic, semi-persistent, or periodic transmissions; (2) Bandwidth (e.g., number of subchannels used for SL-PRS transmission); (3) Frequency density (e.g., number of REs for SL-PRS per RB in the same OFDM symbol); (4) Time density (e.g., the number of OFDM symbols containing SL-PRS in a slot); (5) Transmission power (e.g., whether power boost is used); (6) An associated control channel (e.g., whether the SL-PRS transmission is indicated by the SCI); or (7) a priority level (e.g., each SL-PRS type may have different Tx and Rx priority levels). Due to the half duplex capability of the WTRU, when SL-PRS Tx/Rx overlaps with other higher priority channels/signals Rx/Tx, the priority level may be used to determine whether the SL-PRS Tx/Rx should be discarded.

In some embodiments, the WTRU may determine the SL-PRS type. The WTRU may determine which SL-PRS type to use based on one or any combination of factors. For example, the WTRU may determine which type to use based on a pool of resources used or determined for SL-PRS transmission. For example, a WTRU may be configured or pre-configured with multiple resource pools, and each resource pool may be associated with one or more SL-PRS types. The WTRU may determine which SL-PRS type to transmit based on a pool of resources used or determined for SL-PRS transmission/reception. The term "resource pool" is used interchangeably herein with Tx resource pool and Rx resource pool.

The WTRU may determine a SL-PRS type to use based on QoS requirements of a positioning service. For example, if the positioning service requires low positioning accuracy, the WTRU may use the first SL-PRS type (i.e., SL-PRS using the PSSCH and/or DMRS of the PSCCH). Alternatively or in addition, if the positioning service requires high positioning accuracy, the WTRU may use a second SL-PRS type (i.e., SL-PRS using a new RS designed for positioning). In another example, the SL-PRS type may be determined based on QoS (e.g., priority, delay, etc.) of associated traffic, services, and/or packets. For example, the SL-PRS may be transmitted within PSSCH resources, and its associated PSCCH may indicate the presence of the SL-PRS in the scheduled PSSCH. In a PSCCH (e.g., a first stage SCI or a second stage SCI), a corresponding QoS for PRS transmissions may be indicated. Based on the QoS indication, the SL-PRS type may be determined.

The WTRU may determine a SL-PRS type to use based on CBR of the resource pool. For example, the WTRU may use a first SL-PRS type if the CBR of the resource pool is greater than a threshold, and may use a second SL-PRS type if the CBR of the resource pool is less than the threshold.

The WTRU may determine a SL-PRS type to use based on location information and/or movement information of the WTRU. For example, a WTRU may use one SL-PRS type for low speed and/or relative speed with another WTRU, and another SL-PRS type may be used for high speed and/or relative speed with another WTRU.

The WTRU may determine the type of SL-PRS to use based on a distance between one WTRU (e.g., P-WTRU) and another WTRU (e.g., a-WTRU) and/or at least one side-uplink channel measurement between the two WTRUs. For example, if the distance between two WTRUs is greater than a threshold, the WTRU may use a first SL-PRS type, and if the distance between two WTRUs is less than the threshold, it may use a second SL-PRS type. For example, if a side-uplink channel measurement (e.g., SL-RSRP, SL-RSSI, SL-RSRQ) between two WTRUs is less than a threshold, the WTRU may use a first SL-PRS type (e.g., a first SL-PRS type) and if the side-uplink channel measurement between the two WTRUs is greater than the threshold, it may use a second SL-PRS type (e.g., a second SL-PRS type).

The WTRU may determine the type of SL-PRS to use based on the coverage information and/or WTRU status information. For example, if both WTRUs are in coverage, the WTRU may use one SL-PRS type (e.g., a first SL-PRS type) and if one of the WTRUs is out of network coverage, it may use the other SL-PRS type (e.g., a second SL-PRS type).

The WTRU may determine the SL-PRS type to use based on attributes or measurements of the received SL-PRS. For example, a first SL-PRS type may be used if the WTRU receives a first SL-PRS of a first type with a measurement above a threshold, and a second SL-PRS type may be used if it receives a second SL-PRS of a second type with a measurement above the threshold. The measurement may consist of at least one of signal strength, signal quality, doppler, coherence time, delay spread, or coherence bandwidth estimation.

The WTRU may determine a SL-PRS type to use based on the RRC configuration. For example, a group of WTRUs coordinating SL positioning may negotiate to determine the SL-PRS type and configure via PC 5-RRC.

The WTRU may determine the SL-PRS type to use based on a configured or used minimum communication range.

In some embodiments, the WTRU may determine a resource pool for SL-PRS. For example, in some approaches, a WTRU may be configured or preconfigured with multiple resource pools to transmit SL-PRS. The WTRU may determine which resource pool to transmit the SL-PRS based on one or any combination of the following. For example, the WTRU may determine a resource pool for transmitting SL-PRS based on QoS requirements of a positioning service. For example, the WTRU may be configured for one or more SL-PRS patterns in each resource pool. Each SL-PRS pattern may be associated with one or more sets of QoS requirements. The WTRU may then determine which resource pool to select based on the QoS requirements of the location services.

The WTRU may determine a resource pool for transmitting SL-PRS based on the positioning method used. For example, each resource pool may configure or pre-configure the WTRU with one or more positioning methods (e.g., OTDOA, aoA, aoD, RTT and/or any combination of these methods). The WTRU may then determine the resource pool to use based on the positioning method it uses.

The WTRU may determine a resource pool for transmitting SL-PRSs based on positioning information and/or movement information of the WTRU.

The WTRU may determine the resource pool for transmitting the SL-PRS based on a distance between one WTRU (e.g., a-WTRU) and another WTRU (e.g., a-WTRU) and/or a side-uplink channel between the two WTRUs. For example, the WTRU may be configured or preconfigured with multiple resource pools. Each resource pool may be associated with a maximum and/or maximum distance of two WTRUs in the group. The WTRU may then determine which resource pool to use based on the distance of the WTRUs in the group accordingly.

The WTRU may determine a resource pool for transmitting SL-PRSs based on the coverage information and/or the WTRU status information.

The WTRU may determine a resource pool for transmitting SL-PRSs based on the WTRU's mobility information. For example, the WTRU may be configured or preconfigured with multiple resource pools. Each resource pool may be associated with a maximum and/or minimum speed/relative speed of the WTRU. The WTRU may then determine which resource pool to use based on the speed of the WTRUs in the group.

In some embodiments, the WTRU may use the SCI to indicate information regarding SL-PRS transmissions. For example, in some approaches, the WTRU may transmit SL-PRS according to a pattern. The SL-PRS pattern may include one or any combination of the following: (1) a number of subchannels for each SL-PRS transmission; (2) number of repetitions; (3) a sequence ID; (4) cyclic shift; (5) silence mode; (6) periodicity of SL-PRS; (7) time/frequency offset; or (8) comb values.

In some approaches, the WTRU may use the SCI to indicate SL-PRS transmissions. The method may be used to help one WTRU avoid SL-PRS transmissions by performing sensing (e.g., decoding SCI) for another WTRU. The WTRU may indicate the SL-PRS pattern using one or any combination of the following procedures SCI. For example, the WTRU may use a SCI associated with SL-PRS transmission. In some cases, the system may configure a set of SL-PRS patterns. The WTRU may then indicate the mode index in the SCI. In some cases, the WTRU may indicate the SL-PRS pattern in the first and/or second SCIs. The mode may be indicated implicitly by the second SCI format or explicitly using one or more bit fields in the SCI. Each bit field may represent one or a combination of parameters defined for the SL-PRS mode.

In some examples, the WTRU may use SCI associated with other transmissions. For example, in some cases, a WTRU may be configured or pre-configured with two resource pools, one of which may be used to transmit normal side-uplink data and the other of which may be used to transmit SL-PRS. The WTRU may use SCI associated with data transmission in one resource pool to indicate/reserve the SL-PRS transmission mode in another resource pool.

Fig. 2 is an exemplary diagram 200 in which a WTRU uses SCI to indicate SL-PRS mode. As shown in fig. 2, in option 1, the WTRU may use the SCI associated with the SL-PRS transmission to indicate the SL-PRS mode. In option 2, the WTRU may use the SCI (possibly in another resource pool) associated with the data transmission to indicate the SL-PRS mode.

In some embodiments, a WTRU (e.g., a P-WTRU) may use higher layer messages (e.g., PC5 RRC, NAS, MAC CE, or any logical equivalent) to indicate SL-PRS transmissions. In some embodiments, the WTRU may be configured or preconfigured with two resource pools, one of which may be used to indicate the SL-PRS pattern transmitted in the other resource pool. In some approaches, the WTRU may be configured or pre-configured with one resource pool for both SL-PRS transmissions and data transmissions. The WTRU may indicate the SL-PRS pattern using data transmissions in the same resource pool. The method can be used for avoiding blind detection of SL-PRS.

Fig. 3 is a flow chart illustrating an exemplary side-link positioning procedure 300. The sidelink positioning procedure may comprise any combination of the steps shown in fig. 3. At 302, the WTRU receives a side uplink location request from another WTRU (e.g., a P-WTRU) or an upper layer of the WTRU (e.g., RRC, NAS, MAC or other logical equivalent). At 304, one of the WTRUs (e.g., a P-WTRU or an a-WTRU) may initiate an a-WTRU formation procedure to support one or more P-WTRUs to locate its position. At 306, after determining a group of A-WTRUs, one or more WTRUs may perform SL-PRS resource allocation. At 308, one or more WTRUs may perform SL-PRS transmission and reception. At 310, one or more WTRUs may perform side-uplink measurements. At 312, a side-uplink positioning measurement report is created. At 314, an entity (e.g., a network or a P-WTRU) may calculate a location of the WTRU based on the obtained side-uplink measurements and reports.

Methods of determining an A-WTRU are described herein. In some approaches, the WTRU may trigger transmission of the location request message based on the location trigger. For example, a WTRU (e.g., a P-WTRU or a-WTRU) may trigger transmission of a message (e.g., a location assistant request or discovery message) based on one or any combination of the following triggers: when the WTRU initiates a location service requiring support for side-uplink communications; or when the WTRU receives a location request message from another node (e.g., a gNB or another WTRU).

The P-WTRU or a-WTRU may initiate location services using a location assistant request message. In one approach, the message may be initiated by the P-WTRU to initiate service by requesting that the A-WTRU support locating the position of the P-WTRU. In some methods, the message may be initiated by the A-WTRU to provide location services to the P-WTRU. For example, the message may include an identity of the WTRU (e.g., WTRU ID). The message may contain an identification of the location service (e.g., location service ID, destination ID). In particular, the WTRU may configure one or more IDs, each of which may be associated with one location service. The WTRU may then include the location service ID in the message based on its registered location services.

The message may include location information of the WTRU. The WTRU's location information may include its location (e.g., absolute coordinates, relative locations to other entities, area information, error limits, etc.). In particular, the WTRU may include its estimated location and potential error bound in the message. Alternatively or in addition, the WTRU may include its area ID in the message. The positioning information may be obtained from the last positioning session and/or from another positioning method (e.g., a RAT independent method such as GNSS). The WTRU may also indicate "unknown" location information in the message if it does not know its location.

The message may include movement information of the WTRU. The movement information of the WTRU may include speed, heading, lane information, etc. For example, the WTRU may include its absolute speed and/or a relative speed with another entity (e.g., another WTRU) in the message.

The message may contain QoS requirements of the location services. The QoS requirements of the location services may include priority of the location services, location accuracy, delay, and/or measurement reporting periodicity. For example, the WTRU may be configured or preconfigured with one or more location QoS profiles. Each location may be associated with one or more of the above-described parameters. The WTRU may indicate a location QoS profile ID in the message to support QoS required by other WTRUs to determine location services.

The message may contain serving cell information. The serving cell information may include a cell ID, a neighbor cell ID, a set of cells involved in positioning services, a PLMN ID, etc. For example, the WTRU may indicate a cell ID, PLMN, etc. in a message to facilitate other WTRUs to determine to be either an A-WTRU or a P-WTRU.

The message may contain overlay information. The coverage information may include an InC or OoC indication. For example, the WTRU may indicate whether it is in coverage or out of coverage. The WTRU may also instruct other WTRUs to become the coverage status required by the a-WTRU. For example, a WTRU may require other WTRUs within coverage to become an a-WTRU.

The message may include RRC state information of the WTRU. The RRC state information may include one or any combination of states (i.e., connected, idle, inactive).

The message may include the positioning methods supported by the WTRU. In particular, the WTRU may indicate which side-link positioning methods (e.g., OTDOA, RTT, aoA, aoD, etc.) may be used.

The message may contain synchronization information. The WTRU may indicate the synchronization source it is using for message transmission, the time gap between synchronization reception and message transmission, and/or the synchronization source it may use to reference a subsequent side-link transmission (e.g., SL-PRS). For example, the WTRU may indicate the transmission timing (e.g., UTC timing) of its message. For example, a WTRU (e.g., a P-WTRU) may indicate additional information about the synchronization source. The information may be one or more of the following: a synchronization source WTRU ID for the group; the SSID of the synchronization source synchronizes the location of the source WTRU (e.g., coordinates, zone ID, etc.); priority of the synchronization source; or link quality between the WTRU and the synchronization source. For example, if the WTRU is synchronized with a network node (e.g., a gNB), the WTRU may include Uu RSRP. In some cases, if the WTRU is synchronized with another WTRU (e.g., a synchronization source WTRU), the WTRU may include a SL-SSB-RSRP measured from a SL-SSB from the synchronization source WTRU.

The message may contain the transmission power of the message.

The message may include a condition for the a-WTRU. In particular, the WTRU may indicate a condition for becoming an A-WTRU. The criteria may include one or any combination of the following requirements. Such requirements may include minimum and/or maximum distance to the P-WTRU. For example, the WTRU may implicitly/explicitly indicate a maximum allowed distance to be an A-WTRU. The WTRU may include its location information in the message and then the potential a-WTRU may calculate the distance between the two WTRUs. If the distance is less than the maximum distance indicated in the message, it may be responsive to the message.

These requirements may include side-link measurements. For example, the WTRU may indicate a minimum side-link channel (e.g., SL-RSRP, SL-RSSI, SL-RSRQ) between two WTRUs that become the A-WTRU.

These requirements may include NLOS/LOS status. For example, the WTRU may indicate whether the WTRU with a certain NLOS state may be an A-WTRU.

These requirements may include coverage information, WTRU status information, and/or cell ID. In some examples, the WTRU may need to be potentially an A-WTRU in coverage. The WTRU may indicate the PLMN in the message and it may require that the WTRU be within coverage of the same LMN. In another example, the WTRU may allow a potential A-WTRU to be in-coverage or out-of-coverage.

These requirements may include WTRU status. For example, the WTRU may indicate which RRC state in the WTRU may become an A-WTRU. For example, the WTRU may require the A-WTRU to be in an inactive or connected state. If the potential WTRU determines to be an A-WTRU for the WTRU, it may switch its RRC state.

These requirements may include synchronization information. In some examples, the WTRU may require the A-WTRU to use the same synchronization source and/or the same SSID. In some examples, the WTRU may require synchronization of the a-WTRU with a network node (e.g., a gNB or GNSS). In another example, the WTRU may require the A-WTRU to have its synchronization source priority greater than a threshold.

These requirements may include supported positioning methods. For example, the P-WTRU may indicate the positioning method to use. The WTRU may then determine whether to respond to the message based on whether it is able to support the indicated positioning method.

These requirements may include positioning metrics. For example, the P-WTRU may indicate whether it needs to determine its absolute position or its relative position.

In some embodiments, a WTRU (e.g., an A-WTRU) may determine that one WTRU (including itself) is an A-WTRU. In one such method, the a-WTRU may perform one or any combination of the following: sending a message in response to the location assistant message (e.g., a location assistant response); transmitting a message (e.g., a location assistant message) to provide location services to the P-WTRU; transmitting and/or receiving SL-PRSs from other WTRUs; or report location measurements to other WTRUs (e.g., P-WTRUs) and/or network nodes (e.g., gnbs).

In some examples, the WTRU may determine whether to be an a-WTRU based on one or any combination of the following factors. In one example, the WTRU may determine whether to be an a-WTRU based on a location service ID (e.g., a destination ID or a group ID) indicated in the location assistant request message.

The WTRU may determine whether to be an a-WTRU based on location information of the WTRU. For example, if the WTRU has its location information (e.g., area ID and/or location coordinates) and the location error is less than a threshold, it may be determined to be an a-WTRU. Otherwise, the WTRU may not become a WTRU. The location error may be determined based on the time the WTRU last acquired its location and the movement characteristics of the WTRU.

The WTRU may determine whether to be an a-WTRU based on distances to other WTRUs (e.g., P-WTRUs). In particular, if the distance to other WTRUs (e.g., P-WTRUs) is less than a threshold, the WTRU may become an a-WTRU. The distance threshold may be configured or preconfigured according to a positioning service or according to a positioning method. Alternatively or in addition, the threshold distance may be indicated to the WTRU from another WTRU (e.g., a P-WTRU) via a message (e.g., a location assistant message).

The WTRU may determine whether to be an a-WTRU based on the WTRU's mobility information. The WTRU may determine an A-WTRU to be a P-WTRU based on mobility information of the P-WTRU and/or the A-WTRU. In one example, if the relative speed between the WTRU itself and the P-WTRU is less than a threshold, it may be determined to be an a-WTRU. In some examples, if the relative speed of the WTRUs is less than a threshold and the speed of each WTRU is less than another threshold, it may be determined to be an a-WTRU.

The WTRU may determine whether to be an a-WTRU based on QoS requirements of the location services. For example, the WTRU may be configured or preconfigured to support a certain QoS requirement level. If the WTRU may meet the QoS requirements (e.g., qoS profile) indicated in the location assistant request message, it may determine to be an A-WTRU.

The WTRU may determine whether to be an a-WTRU based on a side-link requirement to aid in locating the WTRU's location. In particular, the WTRU may determine to be an A-WTRU based on side-uplink measurements between the WTRU and the P-WTRU. For example, if a side-uplink measurement (e.g., SL-RSRP, SL-RSSI, SL-RSRQ) between the WTRU itself and other WTRUs (e.g., P-WTRUs) is greater than a threshold, it may become an A-WTRU. The side uplink measurements may be measured on transmission of a location assistant request message from the P-WTRU. The side-uplink measurement threshold may be configured according to a resource pool, location services, or it may be indicated by another WTRU (e.g., a P-WTRU). The side-uplink measurement threshold may be a function of the distance between two WTRUs.

The WTRU may determine whether to be an a-WTRU based on LOS/NLOS detection. The WTRU may determine to be an a-WTRU based on LOS/NLOS status between itself and other WTRUs (e.g., other a-WTRUs or P-WTRUs). For example, if the side-link between the WTRU itself and the WTRU is LOS, it may become an A-WTRU. Otherwise, it may not become a WTRU. The WTRU may detect LOS/NLOS based on a side-uplink measurement (e.g., SL-RSRP, SL-RSRQ, RSSI) and/or a combination of distances between the two WTRUs. In particular, if the SL-RSRP of a link between two WTRUs is less than a threshold, the link may be considered as LOS; otherwise, it may treat the link as NLOS. The SL-RSRP threshold may be a function of the distance between two WTRUs. The WTRU may also detect LOS/NLOS based on statistics (e.g., variance, average) of received power or amplitude in the frequency domain of signals received from other WTRUs over a particular bandwidth.

The WTRU may determine to be an a-WTRU based on its own and the P-WTRU's serving cell information. In one example, the WTRU may determine to be an a-WTRU if its serving cell is the same as the serving cell of the P-WTRU. In some examples, if the WTRU has the same PLMN as the P-WTRU, it may be determined to be an A-WTRU. The PLMN of the P-WTRU may be indicated to the WTRU by a location assistant request message. In some examples, if its current serving cell belongs to a group of cells, the WTRU may determine to be an a-WTRU, which may be indicated by the P-WTRU in the location assistant request message. If the current serving cell of the WTRU does not belong to the group of cells, the WTRU may request the current serving cell to handover to one of the group of cells. If the WTRU does not have a serving cell, the WTRU may perform initial access to one of the cells in a set of cell IDs to become an A-WTRU for the P-WTRU.

The WTRU may determine whether to be an a-WTRU based on the positioning methods supported by the WTRU. An a-WTRU may determine to be an a-WTRU if at least one of its supported positioning methods belongs to a set of methods requested by other WTRUs (e.g., P-WTRUs). For example, the P-WTRU may request an AoA or AoD method. If the WTRU supports one of the methods (AoA or AoD), it may be determined to be an A-WTRU. Otherwise, it may not become a WTRU.

The WTRU may determine whether to be an a-WTRU based on synchronization information of the WTRU and/or another WTRU (e.g., a P-WTRU). For example, if the WTRU is synchronized with a high priority synchronization source (e.g., a GNSS and/or a gNB or another network node), it may determine to be an a-WTRU. For example, if the WTRU uses the same synchronization source as the P-WTRU, it may be determined to be an A-WTRU. For example, if its original synchronization source is the same as the synchronization source from the P-WTRU, the WTRU may determine to be an A-WTRU. For example, if the P-WTRU is synchronized with the gNB, the WTRU may determine to be an A-WTRU. Alternatively, if the P-WTRU is synchronized with the GNSS, the A-WTRU may determine to be an A-WTRU if it is synchronized with the GNSS. In some cases, if the WTRU synchronizes to a synchronization source that has a higher or equal priority than the synchronization source of the P-WTRU, it may be determined to be an a-WTRU.

The WTRU may determine whether to be an A-WTRU based on a maximum number of supported P-WTRUs. The WTRU may determine an A-WTRU to be a P-WTRU based on a maximum number of supported P-WTRUs. In particular, the WTRU may be configured or pre-configured to support a maximum number of P-WTRUs. The WTRU may then determine whether to support another P-WTRU based on the number of WTRUs it supports.

The WTRU may determine whether to be an a-WTRU based on CBR of the resource pool, load of the WTRU, and/or CR of the WTRU. For example, if the CBR of the resource pool is less than a threshold and/or the load of the WTRU is less than another threshold and/or the CR of the WTRU is less than a threshold, the WTRU may determine to be an a-WTRU.

The WTRU may determine whether to be an a-WTRU based on location metrics (e.g., absolute location and relative location). For example, the WTRU may determine whether it may be an A-WTRU based on the required positioning metrics. Specifically, if the P-WTRU wants to obtain absolute positioning, the WTRU may determine not to be an A-WTRU; however, if the P-WTRU wants to obtain a relative position, the WTRU may determine to be an A-WTRU.

The WTRU may determine whether to be an a-WTRU based on the coverage status. The WTRU may determine an a-WTRU to be a P-WTRU based on its coverage status. For example, for absolute positioning, if the WTRU is within network coverage, it may be determined to be an a-WTRU. In some cases, the WTRU may determine not to be an A-WTRU. For relative positioning, the WTRU may determine to be an A-WTRU regardless of coverage status.

The WTRU may determine whether to be an a-WTRU based on Uu RSRP. In some examples, the WTRU may determine to be an a-WTRU if Uu RSRP is greater than a threshold. In some cases, the WTRU may determine not to be an A-WTRU. In some examples, the WTRU may determine to be an a-WTRU if Uu RSRP is less than a threshold. Otherwise, the WTRU may determine not to be an A-WTRU.

The WTRU may determine to be an a-WTRU based on a distance to the P-WTRU and a side-uplink measurement. In particular, if the distance between two WTRUs is less than a threshold and the SL-RSRP is greater than the threshold, the WTRU may become an a-WTRU. In another example, the WTRU may determine to be an A-WTRU based on the LOS/NLOS indication and a distance to the P-WTRU. In particular, if the link between the WTRU itself and other WTRUs (e.g., P-WTRUs) is NLOS, it may not be an a-WTRU.

In some embodiments, the WTRU may indicate location related information in a location assistant response message. For example, a WTRU (e.g., an A-WTRU) may send a response message to another node (e.g., a P-WTRU or gNB) to support the node to determine a group of A-WTRUs. The response message may include one or any combination of the following: location information of the WTRU (e.g., area id, GPS); distance to another WTRU (e.g., P-WTRU); movement information of the WTRU; qoS requirements for location services; or side-uplink measurements to other WTRUs (e.g., P-WTRUs). For example, the WTRU may indicate SL-RSRP, SL-RSSI, or SL-RSRQ for the side-link with the P-WTRU in the response message.

The response message may include LOS/NLOS detection. For example, the WTRU may indicate whether the link between itself is LOS or NLOS.

The response message may include one or any combination of the following: serving cell information by which, for example, the WTRU may indicate a cell ID and a PLMN ID; positioning methods supported by the WTRU; synchronization information by which, for example, the WTRU may indicate which synchronization source the WTRU is using (e.g., the gNB or another network node, GNSS, reference WTRU, etc.); uu RSRP of the current cell (e.g., the WTRU may indicate measured Uu RSRP of the current cell when the WTRU is within network coverage); a cell coverage status of the WTRU (e.g., the WTRU may indicate whether the WTRU is in coverage or out of coverage); SL-SSB-RSRP (e.g., if the WTRU is synchronized with another WTRU, the WTRU may include the RSRP measured in the SL-SSB (i.e., SL-SSB-RSRP), or the maximum number of supported P-WTRUs, the CBR of the resource pool, the load of the WTRU, and/or the CR of the WTRU.

The WTRU may determine whether the WTRU may be a WTRU. In some embodiments, a WTRU (e.g., a P-WTRU) may collect messages from one or more WTRUs and then determine whether each of the WTRUs may be an a-WTRU based on one or any combination of factors. The factor may include a relative distance between the WTRU and the WTRU. For example, if a WTRU is within range of a P-WTRU, the WTRU may determine it as an a-WTRU.

The factor may include a change in a relative distance from the P-WTRU. For example, if the change in the relative distance between the P-WTRU and the candidate A-WTRU is less than a threshold, the P-WTRU may determine that the WTRU is an A-WTRU. For example, the WTRUs may be configured or pre-configured with a period to determine whether a WTRU may be an a-WTRU. The WTRU may measure a change in the relative distance between the two devices to determine whether the candidate device may be an a-WTRU. If the change in the relative distance between the two devices is less than a threshold, the candidate WTRU may be selected as an A-WTRU. In some cases, the candidate WTRU may not be an A-WTRU. The threshold for relative distance change may be configured or preconfigured by the LMF, which may further depend on the QoS requirements of the location services.

The factors may include QoS requirements of the location services. For example, the P-WTRU may determine whether a candidate WTRU may be an A-WTRU based on QoS requirements for location services. Specifically, for a QoS requirement, the WTRU may determine that a candidate WTRU is an a-WTRU; however, for more stringent QoS requirements (e.g., for more accurate requirements or faster location updates), the P-WTRU may determine that the WTRU is not an a-WTRU.

The factors may include side-link measurements to other WTRUs (e.g., P-WTRUs). For example, a WTRU may be configured or preconfigured with a SL-RSRP range, where a candidate WTRU may be an a-WTRU if a side-uplink channel between two WTRUs is within the range. In some cases, the P-WTRU may determine that the candidate WTRU will not become an A-WTRU. The SL-RSRP threshold may be configured or preconfigured according to location services and possibly according to location QoS requirements.

The factors may include LOS/NLOS detection. For example, the P-WTRU may determine that one candidate WTRU may be an A-WTRU if it has an LOS channel with the P-WTRU. In some cases, the P-WTRU may determine that the candidate WTRU cannot be an A-WTRU.

The factor may include serving cell information. For example, the candidate WTRU may indicate its cell ID and possibly its PLMN ID. In some methods, if the candidate WTRU and the a-WTRU are camped on the same cell, the WTRU may determine that the candidate WTRU is the a-WTRU. In some methods, if the candidate WTRU and the a-WTRU belong to the same PLMN ID, the WTRU may determine that the candidate WTRU is the a-WTRU.

The factors may include positioning methods supported by the WTRU. For example, the candidate WTRU may indicate the positioning methods it supports. The P-WTRU may determine whether a supported positioning method of the candidate WTRU is available for determining the location of the P-WTRU. If the P-WTRU determines to use one of the supported positioning methods to determine the location of the WTRU, it may treat the candidate WTRU as an A-WTRU; otherwise, it may not treat the candidate WTRU as an a-WTRU.

The factor may include synchronization information. For example, the candidate WTRU may indicate which synchronization source (e.g., gNB or another network node, GNSS, reference WTRU, etc.) the WTRU is using. The P-WTRU may determine whether the candidate WTRU may be an A-WTRU based on the P-WTRU and a synchronization source of the candidate WTRU. For example, if they use the same synchronization source, the P-WTRU may determine that the candidate WTRU is an A-WTRU. In some cases, if it uses a different type of synchronization source (e.g., the P-WTRU uses a network node such as a gNB as the synchronization source, and the candidate WTRU is using GNSS as the synchronization source), the WTRU may determine that the candidate WTRU is not an a-WTRU.

The factor may include Uu RSRP of the current cell. For example, if the WTRU is within network coverage, the WTRU may indicate the measured Uu RSRP of the current cell. The P-WTRU may determine whether the candidate WTRU may be an A-WTRU based on the indicated Uu RSRP. In particular, the P-WTRU may select a number of candidate WTRUs as its A-WTRU based on its Uu RSRP determination. In some cases, the P-WTRU may be configured or pre-configured with a Uu RSRP range to determine whether the WTRU may be an A-WTRU. For example, the P-WTRU may select a number of WTRUs with the highest Uu RSRP. The WTRU may be an a-WTRU if Uu RSRP of the candidate WTRU is within a configured or preconfigured range; in some cases, the WTRU may not be a WTRU.

The factors may include a cell coverage status of the WTRU. For example, if the P-WTRU is in coverage, the WTRU may select a candidate WTRU to be in coverage of the same cell or the same PLMN. In some cases, if the P-WTRU is out of coverage, the WTRU may select a candidate WTRU as the A-WTRU regardless of coverage status.

The factor may include a priority of the synchronization source. For example, the P-WTRU may be configured or pre-configured to select candidate WTRUs as A-WTRUs based on priority of the synchronization source. The WTRU may then select a number of candidate WTRUs to be the a-WTRU based on the priority of the synchronization source indicated in the message sent to the P-WTRU.

The factors may include SL-SSB-RSRP. For example, if the candidate WTRU is synchronized with another WTRU, the WTRU may include the RSRP measured in the SL-SSB (i.e., SL-SSB-RSRP). The P-WTRU may determine which candidate WTRU is to be the A-WTRU based on the SL-SSB-RSRP provided in the message sent to the P-WTRU.

In some methods, a WTRU may determine a group of A-WTRUs. In one such method, a WTRU (e.g., a P-WTRU) may determine the group of a-WTRUs based on one or any combination of: positioning information of the WTRU; movement information of the WTRU; qoS requirements for location services; a side-uplink requirement to aid in locating WTRU positioning; serving cell information; covering information; WTRU status information; positioning methods supported by the WTRU; synchronization information; CBR of the resource pool, load of the WTRU, and/or CR of the WTRU; or a connection status with the WTRU. For example, the WTRU may prioritize WTRUs that have an existing connection with itself. For example, the WTRU may prioritize WTRUs that have an existing unicast/multicast session with itself to become an a-WTRU.

In some methods, a WTRU (e.g., a P-WTRU) may determine a number of A-WTRUs to locate a position of the P-WTRU. The number of WTRUs may be determined based on QoS requirements of the location services. For high positioning accuracy requirements, the WTRU may require a large number of A-WTRUs, and for low positioning accuracy requirements, it may require a smaller number of A-WTRUs. The number of a-WTRUs may be based on the number of TRPs involved in the WTRU's positioning procedure. In particular, when the number of TRPs is smaller, the WTRU may require more A-WTRUs, and when the number of TRPs is larger, it may require fewer A-WTRUs.

In some approaches, the WTRU may be configured or preconfigured to know which WTRU to prioritize as an a-WTRU. In particular, the WTRU may select the WTRU as an a-WTRU if the WTRU satisfies one or more conditions of one or more parameters. For example, a WTRU may consider it as a possible a-WTRU if it meets one or any combination of the following conditions: the WTRU's positioning error bound is less than an error threshold; the distance to the P-WTRU is less than a threshold and/or greater than another threshold; the speed of the WTRU is less than a threshold and/or the relative speed between the WTRU and the P-WTRU is less than a threshold; SL-RSRP is greater than the threshold; the WTRU has LOS links to the P-WTRU and/or other A-WTRUs; a synchronization source of the a-WTRU (e.g., the synchronization source of the WTRU is greater than a threshold, the number of hops to the original synchronization source is less than a threshold, or the synchronization source of the WTRU is a network node such as a gNB or GNSS); or coverage status of the a-WTRU (e.g., whether the WTRU is in coverage or Uu RSRP is in range).

If the number of potential A-WTRUs is greater than the number of required A-WTRUs, the WTRU (e.g., P-WTRU) may further select the WTRU downward based on predefined rules. For example, among all WTRUs that satisfy one or more conditions of one or more parameters, the WTRU may select a group of WTRUs with the highest SL-RSRP. In another example, the WTRU may prioritize WTRUs that have existing connections with themselves (e.g., existing unicast/multicast sessions). In another example, the WTRU may select the group of WTRUs having the lowest margin of error. The WTRU may also select a group of WTRUs having the lowest distance.

In one embodiment, a WTRU (e.g., a P-WTRU) may broadcast a message to the P-WTRU to indicate a group of A-WTRUs supporting a positioning procedure. The WTRU may first include the ID of each WTRU in the message. The WTRU may then generate an L2 ID to indicate group location. The ID may then be transmitted to WTRUs in the group.

In another embodiment, the WTRU may use the L2 ID to perform a group-side uplink positioning procedure. In particular, the WTRU may include an L2 ID in a message to request other WTRUs to perform SL-PRS transmission/reception and/or side-uplink positioning measurement reporting. The WTRU may include the L2 ID in a transmission associated with its SL-PRS transmission. The method may be used for other WTRUs in the group to determine whether the message is for group location.

In another embodiment, a WTRU (e.g., an A-WTRU) may monitor a side-link resource pool to decode the SCI. The WTRU may then decode the SCI with the L2-ID of the previously transmitted indication. The WTRU may then perform SL-PRS transmission/reception and/or side-uplink positioning measurement reporting to support positioning of the P-WTRU.

In some embodiments, the WTRU may report the side-uplink positioning measurements to the network. For example, in some approaches, the WTRU may report group response WTRUs and associated information (e.g., SL-RSRP, location information, synchronization information, etc.) to a network (e.g., a gNB or LMF) to support the network in determining a group of a-WTRUs. The WTRU may be configured or preconfigured with a set of conditions to report a response a-WTRU. In particular, if the responding WTRU satisfies one or any combination of several conditions, the WTRU may report the responding WTRU to a network node (e.g., a gNB). For example, if the link between the WTRU and the responding WTRU is LOS, the WTRU may report the responding WTRU to a network node (e.g., a gNB). The LOS/NLOS indication may be detected by the reporting WTRU and/or may be indicated by the responding WTRU in a location assistant response message. If the side-uplink measurements (e.g., SL-RSRP, SL-RSSI, SL-RSRQ) between the WTRU and the responding WTRU are greater than a threshold, the WTRU may report the responding WTRU to a network node (e.g., gNB). If the distance between the two WTRUs is less than a threshold and/or greater than another threshold, the WTRU may report a responding WTRU to a network node (e.g., a gNB).

In some examples, the WTRU may be further configured with a maximum number of potential A-WTRUs to report. It may be configured with thresholds (e.g., SL-RSRP threshold, distance threshold) to report the group of responding WTRUs. The method may be used to reduce the number of potential WTRUs to report to the network.

In some methods, the WTRU may update a group of A-WTRUs. A WTRU (e.g., a P-WTRU) may update a group of WTRUs in a group for positioning. The WTRU may perform one or any of the following procedures to add/remove one or more a-WTRUs and/or P-WTRUs. For example, the WTRU may report side-link positioning measurements to the network to support the network to determine a group of A-WTRUs. The WTRU may send the set of updated A-WTRU and/or SL-PRS configurations and reports. The WTRU may reconfigure SL-PRS resource allocation and reporting.

Based on one or any combination of parameters or conditions, the WTRU may remove one WTRU (including itself) from the group a-WTRUs or add one WTRU to the group a-WTRUs. For example, the WTRU may remove or add the WTRU to the group A-WTRU based on the WTRU's location information. For example, if the positioning accuracy of the WTRU becomes worse than a threshold. The WTRU may report to another entity (e.g., the gNB, P-WTRU, or other WTRU) and/or exclude itself from the list of a-WTRUs.

The WTRU may remove or add WTRUs to the group a-WTRUs based on the WTRU's location information. The WTRU may remove or add WTRUs to the group of a-WTRUs based on the distance between the a-WTRU and other WTRUs (e.g., P-WTRUs). For example, if the distance between the WTRU (e.g., P-WTRU) itself and the a-WTRU becomes less than a threshold, it may add one WTRU to the group of a-WTRUs. Alternatively or in addition, if the distance between the WTRU itself and the a-WTRU becomes greater than another threshold, it may remove one a-WTRU in the group of a-WTRUs. The distance threshold may be configured by a network node such as a gNB or LFM. Alternatively or in addition, the threshold may be configured or preconfigured according to the location services.

The WTRU may remove or add WTRUs to the group a-WTRUs based on the WTRU's mobility information. The WTRU may remove or add WTRUs to the group a-WTRUs based on the side-uplink measurements. For example, if a WTRU (e.g., a P-WTRU) detects that the RLF of the link between two WTRUs and/or the SL-RSRP of the link between two WTRUs becomes greater than a threshold, it may remove another WTRU from the group a-WTRUs. For example, if a WTRU (e.g., a P-WTRU) detects a certain SL-RSRP, it may add a WTRU to the group a-WTRUs.

The WTRU may remove or add to the group a-WTRUs based on the LOS/NLOS of the link between the WTRU and the other WTRU (e.g., P-WTRU). For example, if a WTRU (e.g., a P-WTRU) detects that the channel between the P-WTRU and the a-WTRU has NLOS, it may determine to remove the WTRU from a group of a-WTRUs. Alternatively or in addition, if the WTRU detects that the channel between the WTRU and the P-WTRU is LOS, it may add a WTRU to the group a-WTRU.

The WTRU may remove or add WTRUs to the group a-WTRUs based on the synchronization information. The WTRU may remove or add the WTRU to the group a-WTRUs based on the CBR of the resource pool, the load of the WTRU, and/or the CR of the WTRU. The WTRU may remove or add the WTRU to the group a-WTRU based on the connection status with the WTRU. For example, if a node (e.g., a P-WTRU or gNB) establishes a unicast/multicast link with a WTRU, it may include WTRUs to a group of A-WTRUs.

The WTRU may remove or add WTRUs to the group a-WTRUs based on the accuracy of the side-uplink positioning measurement report. For example, a node (e.g., a P-WTRU or a gNB) may exclude a WTRU from the group a-WTRUs if the side-uplink positioning measurement report of one or more parameters is not within an expected range and/or the WTRU has not reported side-uplink positioning measurements in one or more reporting occasions.

In some approaches, the WTRU may determine a positioning method and a reporting configuration. For example, a WTRU may determine a positioning method and associated reporting parameters for one or more WTRUs. In particular, the WTRU may determine one or any combination of the following: positioning methods (e.g., carrier phase based positioning methods, OTDOA, aoA, aoD, RTT, and any combination of these methods); side-uplink positioning measurement reports (RSTD, T_ (Rx-Tx) (time gap between PRS transmission and reception), aoA, aoD, toA, toD, SL-RSRP, SL-RSRQ, SL-RSSI, etc.); a group of WTRUs transmitting SL-PRS and/or a group of WTRUs receiving SL-PRS; or a group of WTRUs transmitting and receiving SL-PRSs.

Regarding carrier phase based positioning methods, the WTRU may measure the arrival phase (PoA) of the SL-PRS transmissions, the difference between poas (DPoA), to help determine the location of the WTRU.

Such a determination may be determined based on one or any combination of parameters or conditions. The determination may be based on configuration or pre-configuration. The determination may be based on synchronization information of the WTRUs in the group. For example, a WTRU may require a high priority synchronization source (e.g., GNSS or gNB) WTRU to perform SL-PRS transmission or reception and a low priority synchronization source WTRU to perform SL-PRS transmission and reception. For example, if the synchronization accuracy between WTRUs in a group is low, the WTRUs may use an angle-based method (e.g., aoA, aoD), and if the synchronization accuracy between WTRUs in a group is high, the WTRUs may use a time-based method (e.g., OTDOA). The synchronization accuracy may be determined based on the synchronization source (e.g., priority of the synchronization source and/or side-uplink measurements of the synchronization signal).

The determination may be based on QoS requirements of the location services. For example, the WTRU may use SL-PRS transmission or SL-PRS reception based methods for low latency positioning services, and the WTRU may use SL-PRS transmission and reception based methods for latency tolerant positioning services.

The determination may be based on a distance between two WTRUs. For example, the WTRU may determine which positioning method to use based on a distance between itself and the A-WTRU (e.g., the furthest WTRU). For example, if the distance between the P-WTRU and the farthest WTRU is greater than a threshold, the WTRU may select an angle method (e.g., aoA or AoD); otherwise, the WTRU may use a timing-based approach.

The determination may be based on coverage information and/or WTRU status information. For example, if all WTRUs are within cell coverage, the WTRU may use a method based on SL-PRS transmission (i.e., the P-WTRU performs SL-PRS transmission) or on SL-PRS reception (the P-WTRU performs SL-PRS reception). The method can be used to reduce the SL-PRS transmission. For example, a WTRU (e.g., a P-WTRU) may require an out-of-coverage WTRU to perform SL-PRS transmission or reception and may require an out-of-coverage WTRU to perform SL-PRS transmission and reception.

The determination may be based on CBR of the resource pool, load of the WTRU, and/or CR of the WTRU.

The determination may be based on the availability of synchronization offsets between WTRUs in the group. For example, if the WTRU does not have a synchronization offset to another a-WTRU for a period of time, the WTRU may perform RTT, aoA, or AoD methods. Otherwise, if the WTRU has all synchronization offsets for other A-WTRUs in the group, the WTRU may use OTDOA or TDOA methods.

The determination may be based on whether the output is a relative or absolute position.

The determination may be based on a current location error of the P-WTRU. In particular, the WTRU may determine which positioning method to use based on the current location error of the WTRU. In particular, if the current location error of the WTRU is less than a threshold, the WTRU may use a carrier phase based approach. Otherwise, the WTRU may use other positioning methods.

In one example, the WTRU may combine multiple positioning methods in one positioning procedure. For example, for a group of A-WTRUs, the WTRU may perform a TOA method and an RTT method, wherein if the WTRU does not have synchronization offset information for the WTRU, the WTRU may need one WTRU to transmit and receive SL-PRS. However, the WTRU may perform a time of arrival (ToA) method, wherein the WTRU may need the WTRU to transmit or receive SL-PRS if the WTRU has synchronization offset information for the WTRU.

In another example, the WTRU may perform different synchronization methods in different phases to obtain the highest position accuracy. For example, in a first interval, the WTRU may first perform a positioning method, such as an angle method, to obtain a first level of positioning accuracy. Then, in a second interval, the WTRU may perform another positioning method, such as a carrier phase based method, to obtain a second level of positioning accuracy.

In another example, the WTRU may perform multiple positioning methods simultaneously. In particular, the WTRU may perform a timing-based method and a carrier phase-based method to help determine the location of the WTRU. In particular, the WTRU may perform SL-PRS transmission/reception. The WTRU may then need the a-WTRU to perform both phase and time measurements and report the location measurement results to the WTRU or the network. The WTRU may determine whether to use multiple positioning methods simultaneously based on the positioning accuracy requirements and/or the delay requirements of the positioning service.

Fig. 4 illustrates an exemplary signaling flow 400 in which a P-WTRU 402 transmits SL-PRS to all a-WTRUs 404a and 404b receiving the SL-PRS transmission (e.g., a method based on the SL-PRS transmission). As shown in fig. 4, the WTRU may select a P-WTRU to transmit SL-PRS and one or more a-WTRUs to receive SL-PRS and perform side-uplink positioning measurements.

Figure 5 illustrates an exemplary signaling flow 500 in which all a-WTRUs 504a and 504b transmit SL-PRS (a method based on SL-PRS transmissions) to a P-WTRU. As shown in fig. 5, the WTRU may select all a-WTRUs to transmit SL-PRS and select P-WTRUs to receive SL-PRS and perform side-uplink positioning measurements.

Fig. 6 illustrates an exemplary signaling flow 600 in which all WTRUs transmit/receive SL-PRS (methods based on SL-PRS transmission and reception). As shown, the WTRU may select all WTRUs (both P-WTRUs and a-WTRUs) to transmit and receive SL-PRSs. In some methods, a WTRU may select a WTRU that performs one group of SL-PRS transmissions, another group of WTRUs that performs SL-PRS reception, and another group of WTRUs that performs both SL-PRS transmissions and reception.

Methods for synchronization are described herein. In some methods, a WTRU may transmit a side uplink positioning synchronization signal for a group of WTRUs. In one such example, a WTRU may transmit a synchronization signal for a group of WTRUs to synchronize the transmission timing of the WTRUs in the group. The WTRU may use one or any of the following as a side-downlink synchronization signal: SL-PRS; SLSS (S-PSS, S-SSS); DMRS; PTRS; CSI-RS; or a new signal designed for positioning synchronization.

A WTRU (e.g., a P-WTRU or a-WTRU in a group) may use the timing of the side-uplink positioning synchronization signal to perform one or any combination of the following procedures. For example, the WTRU may perform the side-uplink positioning measurements using the timing of the positioning synchronization signal. In particular, the WTRU may still derive its transmit and receive timing using the timing of the normal side-uplink synchronization procedure. However, the WTRU may use the timing of the positioning synchronization signal to derive the measurement (e.g., RSTD, toA). The WTRU may report an offset between its normal side-link synchronization timing and positioning synchronization timing to support other WTRUs to perform side-link measurements (e.g., RSTD).

The WTRU may use the timing of the positioning synchronization signal to perform other transmissions, such as SL-PRS and data transmissions, using the reference time. In particular, the WTRU may use the side-uplink positioning synchronization signal to derive positioning Direct Frame Number (DFN) timing. In some approaches, the WTRU may use the positioning DFN to transmit and receive all side-link transmissions. In some approaches, the WTRU may use the positioning DFN to transmit SL-PRS and other positioning synchronization signals. It may transmit and receive side-link data using a normal side-link DFN, which may be derived from normal side-link transmissions.

In some approaches, the WTRU may be configured with multiple positioning synchronization types. In one such method, the WTRU may be configured or preconfigured to transmit and/or receive one or more positioning synchronization types. Each type may be associated with one or any combination of the following. For example, each type may be associated with a reference signal for synchronous transmission. For example, the first positioning synchronization type may use the DMRS of the PSCCH and/or PSCCH. The second positioning synchronization type may use SL-CSI-RS and the third positioning synchronization type may use a new signal designed for positioning synchronization.

Each type may be associated with resources for positioning synchronous transmissions. In particular, one synchronization type may use a set of resources that may include the number of subchannels per transmission, RS pattern, number of repetitions, resource area, etc.

For example, a first positioning synchronization type may use configured or pre-configured resources for normal side-uplink transmissions, and a second positioning synchronization type may use configured or pre-configured resources for positioning synchronization purposes only.

In some examples, the WTRU may be configured or preconfigured with two positioning synchronization types. The first positioning synchronization type may use the DMRS of the PSCCH and/or PSCCH. The resources for the first positioning synchronization type may be dynamically selected by the WTRU or scheduled by the network. The second positioning synchronization type may use a new signal designed for positioning synchronization. The resources for the second positioning synchronization type may be configured or preconfigured according to the resource pool and/or according to the carrier.

In some approaches, the WTRU may determine a location synchronization type. The WTRU may determine which positioning synchronization type to use for transmission and/or reception based on one or any combination of the following parameters or conditions. For example, when the WTRU receives a location synchronization request from another node (e.g., WTRU or gNB), the WTRU may determine which location synchronization type to use. For example, a WTRU may receive a positioning synchronization transmission request from a peer WTRU, which may have an existing unicast session and PC5 RRC connection with the WTRU. The message may indicate which positioning synchronization type is requested. The WTRU may transmit a positioning synchronization type upon request.

The WTRU may determine which positioning synchronization type to use based on the QoS requirements of the positioning service. For example, if the positioning service requires low positioning accuracy, the WTRU may use a first positioning synchronization type (e.g., synchronization of DMRS using PSSCH and/or PSCCH). Alternatively or in addition, if the positioning service requires high positioning accuracy, the WTRU may use a third type of positioning synchronization (e.g., positioning synchronization using new signals designed for positioning).

The WTRU may determine which positioning synchronization type to use based on the CBR of the resource pool and/or the CR of the WTRU. For example, if the CBR of the resource pool and/or the CR of the WTRU is greater than a threshold, the WTRU may use the first positioning synchronization type. The method can be used to reduce the number of side-uplink transmissions and reduce the congestion of the resource pool.

The WTRU may determine which positioning synchronization type to use based on the WTRU's positioning information and/or movement information. For example, if the positioning error of the WTRU is less than a threshold, the WTRU may use a first positioning synchronization type, and if the positioning error of the WTRU is greater than the threshold, it may use a second positioning synchronization type.

The WTRU may determine which positioning synchronization type to use based on a distance from one WTRU (e.g., P-WTRU) to another WTRU (e.g., a-WTRU). For example, if the distance between two WTRUs in a group is within one range, the WTRU may use a positioning synchronization type, and if the distance between two WTRUs in the group is within another range, it may use a second positioning synchronization type.

Alternatively or in addition, the WTRU may determine which positioning synchronization type to use based on: side uplink measurements between two WTRUs in a group; or coverage information and/or WTRU status information. For example, if all WTRUs are within the coverage of the same network node (e.g., a gNB) or the same PLMN, a group of WTRUs may use a first synchronization type (e.g., a SL-PRS DMRS). If the group of WTRUs is out of coverage or partially out of coverage, the P-WTRU may determine to use a second synchronization type (e.g., a new signal designed for positioning synchronization).

The WTRU may determine which positioning synchronization type to use based on the positioning methods used in the group. For example, the WTRU may use a first positioning synchronization type for angle-based methods (e.g., aoA, aoD) and a second positioning synchronization type for timing-based methods (e.g., OTDOA).

The WTRU may determine which positioning synchronization type to use based on the synchronization source used for the reference synchronization signal.

In some methods, a WTRU may determine whether a group of WTRUs need the WTRU to transmit a positioning synchronization signal. In some such solutions, a group of WTRUs may need the WTRUs to transmit positioning synchronization signals to synchronize the transmission timing of the WTRUs in the group and/or to support the WTRUs to perform side-uplink measurements. In some solutions, the group of WTRUs may use synchronization sources from other entities (e.g., other WTRUs, gnbs, and/or GNSS) that may not belong to the group. A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a positioning synchronization source for a group of WTRUs by transmitting a synchronization signal based on one or any combination of parameters or conditions.

For example, a WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a location synchronization source for a group of WTRUs based on the coverage status and/or RRC status of the WTRUs in the group. For example, if all WTRUs are within network coverage (InC), the group may not need the WTRUs to transmit positioning synchronization signals. The WTRUs in the group may use the downlink timing of the network node (e.g., the gNB) to synchronize the side downlink transmission timing. A WTRU (e.g., an a-WTRU) may report Timing Advance (TA) information to other WTRUs (e.g., P-WTRUs) to support the WTRU in a side-uplink measurement report. For example, if multiple WTRUs are outside of network coverage (OoC), the group may require one WTRU to transmit a positioning synchronization signal. The method may be initiated to synchronize the transmission timing of the InC and OoC WTRUs. For example, if one WTRU is OoC and all other WTRUs are InC, the network may or may not need one WTRU to transmit a positioning synchronization signal.

A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a location synchronization source for each WTRU in the group based on synchronization information for the group. For example, if all WTRUs in the group are synchronized to one synchronization source (e.g., GNSS, one gNB, or one SSID), the group may not need one WTRU to transmit synchronization signals. For example, a WTRU (e.g., a P-WTRU) may be required to transmit a synchronization signal to a group. One WTRU (e.g., an a-WTRU or a P-WTRU) in the group is synchronized directly/indirectly to the GNSS.

For example, if the WTRUs in a group use different synchronization sources, the group may require one WTRU to transmit a synchronization signal. In particular, if one group of WTRUs uses one synchronization source and the other group of WTRUs uses another synchronization source, the group may require one WTRU to transmit a positioning synchronization signal to synchronize the WTRUs in the group.

A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a location synchronization source for a group of WTRUs based on QoS requirements of a location service. For example, if the positioning accuracy requirement is less than a threshold, the group may not need one WTRU to transmit the positioning synchronization signal. If the accuracy requirement of the location service is greater than a threshold, the group may require one WTRU to transmit a location synchronization signal.

A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a source of positioning synchronization for the group of WTRUs based on whether the WTRU has synchronization offset information between itself and other WTRUs in the group. For example, if a WTRU (e.g., a P-WTRU) does not have synchronization offset information between itself and one or more WTRUs, the group may require one WTRU to transmit positioning synchronization to the group. For example, if a WTRU (e.g., a P-WTRU) does not obtain synchronization offset information from one or more WTRUs in the group for a period of time, the group may require one WTRU to transmit positioning synchronization to the group.

A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a source of positioning synchronization for a group of WTRUs based on a positioning method for the group. For example, for synchronous fault-tolerant positioning methods such as RTT and angle-based methods, the WTRU may not need any WTRUs in the group to transmit positioning synchronization signals to the group. However, for synchronization error sensitive positioning methods such as OTDOA methods, TDOA methods, the WTRU may require one WTRU to transmit positioning synchronization to the group.

A WTRU (e.g., a P-WTRU) may determine whether to assign the WTRU as a positioning synchronization source for a group of WTRUs based on a highest synchronization priority as a configuration of the gNB/eNB or GNSS. For example, if the WTRU configures GNSS (pre) to the highest synchronization priority, the WTRU may need one WTRU in the group to transmit a positioning synchronization signal to the group. Otherwise, if the gNB/eNB is (pre) configured to the highest synchronization priority, the WTRU may not need any WTRU in the group to transmit a positioning synchronization signal to the group.

In one embodiment, the WTRU may trigger the transmission of the positioning synchronization signal to the group of WTRUs based on one or any combination of the following.

Based on the WTRU changing synchronization source, the WTRU may trigger a positioning synchronization signal to be sent to the group of WTRUs. Superficially, if the WTRU changes synchronization source, it may trigger a sending side uplink positioning synchronization signal to the group. For example, if the WTRU changes synchronization from one SyncRef WTRU (i.e., a synchronization reference WTRU) to another SyncRef WTRU, the WTRU may trigger sensing of a synchronization positioning synchronization signal to the group. For example, if the WTRU changes synchronization from the gNB/eNB to the syncRef WTRU or vice versa, it may trigger sending a side-uplink positioning synchronization signal to the group.

Based on the WTRU changing coverage status, the WTRU may trigger a positioning synchronization signal to be sent to the group of WTRUs. For example, if the WTRU changes from out-of-coverage to in-coverage of a cell, or if it changes from in-coverage to out-of-coverage of a cell, it may trigger sending a side-uplink positioning signal to the group.

The WTRU may trigger the sending of the positioning synchronization signal to the group based on the WTRU receiving an indication from another WTRU that implicitly triggers the sending of the positioning synchronization to the group.

The WTRU may send a positioning synchronization signal to the group of WTRUs based on the SL-PRS transmission trigger. For example, the WTRU may trigger transmission of a side-uplink positioning synchronization signal based on its SL-PRS transmission. In particular, the WTRU may transmit a side uplink positioning synchronization signal prior to each SL-PRS transmission.

The WTRU may send a positioning synchronization signal to the group of WTRUs based on the SL-PRS reception trigger. For example, the WTRU may trigger transmission of a side-uplink positioning synchronization signal based on its SL-PRS reception. In particular, the WTRU may transmit a side uplink positioning synchronization signal before each SL-PRS reception resource.

The WTRU may send a positioning synchronization period signal to the group of WTRUs based on the SL-PRS reception period trigger. For example, the WTRU may perform periodic SL-PRS reception. The WTRU may determine to transmit a side uplink positioning synchronization signal according to a SL-PRS reception period. The WTRU may transmit a side uplink positioning synchronization signal prior to each SL-PRS reception period.

The WTRU may trigger a transmission of a positioning synchronization signal to the group of WTRUs based on the reception of the side-uplink positioning measurement report. For example, the WTRU may perform reception of a side-uplink positioning measurement report. The WTRU may determine to receive a transmit side uplink positioning synchronization signal based on the side uplink positioning measurement report.

The WTRU may trigger sending a positioning synchronization signal to the group of WTRUs based on the transmission of the side-uplink position measurement reporting period. For example, the WTRU may perform transmission of a side-uplink positioning measurement report. The WTRU may determine to transmit a side-uplink positioning synchronization signal based on the side-uplink positioning measurement report.

In some methods, the WTRU may determine a WTRU that transmits a synchronization signal. In some approaches, the P-WTRU may determine to be the synchronization source. In some approaches, a WTRU (e.g., a P-WTRU) may determine which WTRU transmits a positioning synchronization signal to synchronize the side-link timing of WTRUs in a group. The synchronization source WTRU (i.e., the WTRU transmitting the synchronization signal) may be selected based on one or any combination of parameters or conditions.

For example, a synchronization source WTRU (i.e., a WTRU transmitting a synchronization signal) may be selected based on the location of the WTRU in the group. For example, one WTRU (e.g., a P-WTRU) may select a synchronization source WTRU. The coordinates of the synchronization source WTRU may be the closest to the weighted average coordinates of all or a group of WTRUs in the group. The method may be initiated to select a synchronization source WTRU in the middle of the group.

A synchronization source WTRU (i.e., a WTRU transmitting synchronization signals) may be selected based on the location information of the WTRU. For example, if one WTRU has a positioning error bound less than a threshold, it may be selected as the synchronization source WTRU.

A synchronization source WTRU (i.e., a WTRU transmitting synchronization signals) may be selected based on the WTRU's mobility information. For example, if the speed of a WTRU is less than a threshold, it may be selected as the synchronization source. For example, a fixed WTRU may be selected as the synchronization source. For example, a WTRU having a low relative velocity with a P-WTRU may be selected as the synchronization source WTRU.

The synchronization source WTRU (i.e., the WTRU transmitting the synchronization signal) may be selected based on a side-uplink channel between the synchronization source WTRU and another WTRU (e.g., a P-WTRU). For example, if the side-link (e.g., SL-RSRP, SL-RSSI, SL-RSRQ) between one WTRU itself and the P-WTRU is greater than a threshold, it may be selected as the synchronization source. In some examples, a WTRU may be selected as the synchronization source if it has the strongest link (e.g., highest SL-RSRP, SL-RSSI, or SL-RSRQ) between itself and the P-WTRU.

The synchronization source WTRU (i.e., the WTRU transmitting the synchronization signal) may be selected based on LOS/NLOS detection. For example, if the side-link between the WTRU itself and the P-WTRU is considered to be LOS, it may be selected as the synchronization source.

A synchronization source WTRU (i.e., a WTRU transmitting synchronization signals) may be selected based on the coverage information and/or WTRU status information. For example, in a group with InC and OoC WTRUs, inC may be selected as the synchronization source. For example, one rrc_connected WTRU may be selected as the synchronization source WTRU in a group of WTRUs having different RRC states.

A synchronization source WTRU (i.e., a WTRU transmitting a synchronization signal) may be selected based on the synchronization information. For example, if the WTRU synchronizes to the highest priority synchronization source, it may be selected as the synchronization source WTRU.

In some approaches, the WTRU may trigger a positioning synchronization signal transmission. For example, the WTRU may trigger a location synchronization transmission, or trigger a request for another WTRU to transmit a location synchronization signal. The trigger may be based on one or any combination of parameters or conditions.

Triggering may be performed when one or more parameters of the side-uplink positioning measurement report are outside of an expected range. The expected range of a parameter (e.g., RSTD) may be determined by the WTRU based on an estimated distance between two WTRUs, or may be indicated by other WTRUs. The triggering may be performed when the WTRU has not received one or more expected side-uplink measurement reports. Triggering may be performed when the speed of the WTRU and/or the relative speed with other WTRUs (e.g., P-WTRUs) becomes greater than and/or less than a threshold. Triggering may be performed when the WTRU synchronizes to a higher/lower synchronization priority. Triggering may be performed when a side-link measurement between two WTRUs becomes greater/less than a threshold. Triggering may be performed when a WTRU detects an NLOS link with another WTRU. Triggering may be performed when the WTRU moves out of coverage or into network coverage.

In some methods, the WTRU may determine resources to transmit the synchronization signal. For example, in some solutions, resources for synchronous transmission may be configured or preconfigured according to carrier and/or according to a resource pool. The synchronization resources may be configured or preconfigured for positioning synchronization. Alternatively or in addition, the synchronization resources may be configured or preconfigured for positioning synchronization and normal data transmission. The WTRU may be configured or preconfigured with periodic synchronization transmission resources. The WTRU may configure or pre-configure one or more transmission occasions during each cycle. In some solutions, the WTRU may autonomously select resources for synchronous transmission. The WTRU may perform semi-persistent synchronization resource selection and/or dynamic synchronization resource selection.

The WTRU may determine one or any combination of the following: the periodicity of the synchronous transmissions; according to the synchronous transmission times of the synchronous period; and/or whether the synchronization signal is transmitted in one synchronization resource, which may be configured or pre-configured or selected by the WTRU.

Such determination may be based on one or any combination of conditions or parameters, such as attributes of the synchronization source, such as priority, ID, coverage status, and the like. For example, the WTRU may be configured or preconfigured with a set of synchronization resources based on synchronization priority. The WTRU may select the synchronization resource accordingly based on the priority of the synchronization source.

Such determination may be based on the periodicity of the SL-PRS and/or positioning measurement reports. For example, the WTRU may determine a synchronization period to align with the SL-PRS transmission period. The synchronous transmission resources may be transmitted before each SL-PRS period. For example, the WTRU may determine to transmit in one synchronization period every N SL-PRS periods. Alternatively, the WTRU may determine to transmit in N synchronization periods according to one SL-PRS period. The information for N (e.g., exact value of N, minimum value of N, maximum value of N) may be configured or preconfigured according to the resource pool and/or location services.

Such determination may be based on QoS requirements of the location services. In particular, the WTRU may determine the periodicity and/or the number of synchronized transmissions per period based on QoS requirements of the location services. For example, for high precision required location services, the WTRU may select a low synchronization period and a large number of synchronization transmissions per period. Alternatively, the WTRU may select a high synchronization period and a low number of synchronization transmissions per period for low precision required location services. Such determination may also be based on CBR of the resource pool and/or CR of the WTRUs.

Fig. 7 illustrates an example in which a WTRU may determine which resources to use for transmitting a synchronization signal. As shown in fig. 7, the WTRU may be configured or preconfigured with one synchronization resource per synchronization period. The WTRU may be indicated (e.g., by a P-WTRU) a SL-PRS pattern for transmission by one or a group of WTRUs, which may include a SL-PRS periodicity. The WTRU may then determine to transmit a synchronization signal prior to each SL-PRS period.

Fig. 8 illustrates an example in which a WTRU dynamically selects synchronized transmission resources. As shown in fig. 8, a WTRU may be indicated with the SL-PRS periodicity of a group of WTRUs. The WTRU may then perform dynamic synchronization resource selection and transmit synchronization signals in the selected resources every 2 SL-PRS periods.

In some approaches, a network node (e.g., a gNB) may indicate which WTRUs are to transmit a positioning synchronization signal to synchronize the group of WTRUs. The network node (e.g., gNB) may also schedule resources for positioning synchronization signal transmissions.

The WTRU may indicate further information related to the synchronous transmission. These parameters may be included in a channel associated with the positioning synchronization signal (e.g., PSBCH, PSDCH, PSCCH and/or PSCCH). The information may be one or any combination of the following: the location of the WTRU; an identity of the WTRU; identification of a positioning group; synchronization information; or coverage status of the WTRU.

In some approaches, the WTRU may determine with which synchronization source to synchronize. In some such methods, the WTRU may detect multiple synchronization sources, one of which may be associated with positioning synchronization and another of which may be associated with normal side-uplink data transmission. The WTRU and/or a group of WTRUs (e.g., P-WTRU and a-WTRU thereof) may determine their synchronization sources based on one or any combination of parameters or conditions. For example, the WTRU may determine its synchronization source based on a configuration or a pre-configuration. For example, the WTRU may be configured or preconfigured to always synchronize to a positioning synchronization source for positioning related transmissions/receptions such as SL-PRS, positioning measurement reports, and the like. Alternatively or in addition, the WTRU may be configured or preconfigured to always synchronize with normal side-uplink data transmissions for both normal data transmissions and location related transmissions/receptions.

The WTRU may determine its synchronization source based on the priority of the synchronization source. In particular, the WTRU may synchronize to a source with a higher synchronization priority. The synchronization source WTRU may be configured or preconfigured with rules to determine the priority of its synchronous transmissions. The isochronous transmission priority may be indicated in the isochronous transmission. Alternatively or in addition, the priority of the synchronization source may be configured or preconfigured according to the location services.

The WTRU may determine its synchronization source based on the SL-RSRP associated with the synchronization source. For example, if the SL-RSRP of the synchronization source is greater than a threshold, the WTRU may synchronize to the synchronization source and/or the WTRU may synchronize to the synchronization source with the highest SL-RSRP.

The WTRU may determine its synchronization source based on the coverage status of one or more WTRUs in the group. In particular, a WTRU (e.g., a P-WTRU) may determine which synchronization source to synchronize for the group (e.g., the P-WTRU and the A-WTRU) based on a coverage status of the WTRU. For example, for an out-of-coverage scenario (i.e., all WTRUs in the group are out of coverage), the group of WTRUs may be synchronized to a GNSS or synchronization source WTRU. Alternatively or in addition, if all WTRUs in the group are in coverage, the synchronization source of the group may be a gNB or another network node, synchronization source WTRU, or GNSS. Finally, if the group of WTRUs is in partial coverage, the synchronization source of the group of WTRUs may be a GNSS or synchronization source WTRU.

In some examples, if all WTRUs in the group are within the coverage of one gNB or another network node or one PLMN, the group of WTRUs may determine to synchronize to the gNB or another network node.

In some examples, if one or more WTRUs within the group (e.g., a P-WTRU and a-WTRU supporting a P-WTRU) are within network coverage, the group of WTRUs may synchronize to one of the WTRUs within network coverage. The selected WTRU may then transmit a synchronization signal for other WTRUs to synchronize their transmission/reception of the positioning signal. Alternatively or in addition, all WTRUs may select GNSS as their synchronization source for this scenario.

In some examples, if all WTRUs in the group are out of coverage, the group of WTRUs may select one of the WTRUs to transmit the synchronization signal. The WTRU transmitting the synchronization signal may be determined by other conditions. Alternatively or in addition, if all WTRUs are out of coverage, all WTRUs may use GNSS as a synchronization source.

The WTRU may determine its synchronization source based on Uu RSRP. In some examples, the group of WTRUs may select the WTRU as the synchronization source based on the Uu RSRP of the WTRU. In particular, if the WTRU has the highest Uu RSRP, the P-WTRU may select it as the synchronization source.

The WTRU may determine its synchronization source based on SL-SSB-RSRP. In some examples, the group of WTRUs may select the WTRU as the synchronization source based on the SL-SSB-RSRP of the synchronization source. In particular, if the WTRU has the highest SL-SSB-RSRP, the P-WTRU may select it as the synchronization source. The SL-SSB-RSRP may be included in a response message sent to the P-WTRU.

The WTRU may determine its synchronization source based on the QoS of the location services.

The WTRU may determine its synchronization source based on a positioning method used to determine the location of the WTRU.

In some approaches, the WTRU may pre-compensate for the over-the-air (OTA) time of the positioning synchronization signal from the source. In one such method, the WTRU may determine its side-uplink transmission timing by performing pre-compensation of the synchronous transmission time. In particular, first, the WTRU may determine a transmission duration of the positioning synchronization signal, and then the WTRU may shift its side uplink transmission timing based on the transmission duration of the synchronization signal (e.g., the WTRU may shift its side uplink transmission timing by a period equal to the OTA time of the synchronization signal). The transmit OTA time of the synchronization signal may be determined based on the distance between the synchronization source WTRU and the WTRU itself. Alternatively, it may be indicated by the synchronization source (e.g., similar to TA).

In some embodiments, the WTRU may determine a SL-SSB-RSRP threshold for transmitting the SL-SSB. For example, in some solutions, a WTRU may be configured or preconfigured with two SL-SSB-RSRP thresholds to determine whether it should transmit a SL-SSB, where one threshold may be associated with normal side-uplink communications and the other threshold may be associated with location services. When configured with location services, the WTRU may use a threshold associated with the location services. In some cases, a threshold associated with normal side-link communications may be used when it is not configured with location services.

Figure 9 shows a scenario in which all a-WTRUs 902a, 902b, and 902c are in coverage and a scenario in which one or more a-WTRUs 902a, 902b, and/or 902c are out of coverage. As shown in fig. 9, in an "out-of-coverage" scenario, the a-WTRU 902c is out-of-coverage.

At 910, the P-WTRU 904 determines the synchronization source of the group of A-WTRUs 902a, 902b, and 902 c. If all of the a-WTRUs 902a, 902b, and 902c are within the coverage of the network, the gNB may act as a synchronization source. Conversely, if one or more of the a-WTRUs 902a, 902b, or 902c are outside of network coverage (e.g., a-WTRU 902c shown in fig. 9), the P-WTRU 904 will act as a synchronization source.

Further, at 912, the P-WTRU determines a periodicity of SLSS transmissions. As shown in fig. 9, the location services may have small delay requirements or large delay may be required. If there is a small delay requirement, there may be a short SLSS period. If there is a large delay requirement, there may be a long SLSS period.

In another embodiment, the WTRU may determine a synchronization offset between itself and another node (e.g., another WTRU, RSU, gNB, etc.). The synchronization offset may be determined as a slot boundary difference between two WTRUs.

Fig. 10 illustrates an exemplary synchronization offset between two WTRUs. As shown in fig. 10, WTRU1 1002a and WTRU2 1002b have a time offset (i.e., T) between the slot boundary 1006a of WTRU1 1002a and the slot boundary 1006b of WTRU 1006b _off )1004。

In another embodiment, the WTRU may perform a procedure to determine a synchronization offset between the WTRU and another WTRU. For example, the WTRU may perform RTT and measurement reporting to determine a synchronization offset between the WTRU and another WTRU.

Fig. 11 illustrates determining two WTRUs, 1102a and1102b T between _off 1104. As indicated in fig. 11, WTRU1 a may perform transmission/reception of SL-PRS and receive measurement reports from WTRU 2b (e.g., t2, t3, and/or t3-t 2) to determine a synchronization offset between WTRU11102a and WTRU2 1102 b. The synchronization offset between WTRU 1102a and WTRU2 1102b may be determined based on t1, t2, t3, and t 4. Specifically T _off 1104 may be calculated as follows:

the WTRU may further calculate RTT, which may indicate twice the propagation time between two WTRUs, as follows:

in another embodiment, the WTRU may trigger a synchronization offset determination procedure (e.g., RTT transmission/reception and measurement reporting procedure) to determine a synchronization offset between the WTRU (e.g., P-WTRU) and another WTRU (e.g., a-WTRU). The WTRU trigger may be based on one or any combination of the following: (1) periodicity; (2) the WTRU changing synchronization sources; (3) the WTRU changing coverage status; and/or (4) the WTRU receiving an indication from another WTRU that implicitly/explicitly indicates a likelihood of a synchronization offset change between the two WTRUs.

In another embodiment, the WTRU may transmit information about the synchronization offset between the two WTRUs to another node. In particular, the P-WTRU may send information to the network regarding synchronization offsets between itself and other WTRUs (e.g., A-WTRUs). In one approach, the synchronization offset between a WTRU (e.g., a P-WTRU) and other WTRUs (e.g., a-WTRUs) may be calculated by the WTRU itself. Alternatively, a synchronization offset between a WTRU (e.g., a P-WTRU) and another WTRU (e.g., an A-WTRU) may be transmitted by the A-WTRU to the WTRU. In another approach, the A-WTRU may transmit information regarding synchronization offsets between different A-WTRUs to the P-WTRU or the network. These procedures may be initiated to help the P-WTRU or the network calculate the P-WTRU's location accurately.

In another embodiment, the WTRU may send Timing Advance (TA) information to another node to support the node in calculating the location of the P-WTRU. In one example, the A-WTRU may send TA information to the P-WTRU to calculate its location. The WTRU may send its TA information in a side-uplink positioning measurement message. The WTRU (e.g., P-WTRU) may also send TA information for all a-WTRUs in the group to the network to assist the network in determining its location information. In another example, the A-WTRU may send its TA information directly to the network.

In another embodiment, a WTRU (e.g., a P-WTRU) may receive location information from an A-WTRU in the group. The WTRU may then receive location information for the gNB of each corresponding a-WTRU. The WTRU may then determine TA information for each a-WTRU to determine the synchronization offset between itself and each WTRU. For the WTRU assisted positioning method, the WTRU may then forward the location information of the a-WTRUs in the group to the network. The method may be initiated to assist the network in determining the location of the WTRU based on the side-links.

Although the features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with other features and elements. Additionally, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer readable medium for execution by a computer or processor. Examples of computer readable media include electronic signals (transmitted over a wired or wireless connection) and computer readable storage media. Examples of computer readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as internal hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and Digital Versatile Disks (DVDs)). A processor associated with the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims (20)

1. A method performed by a first wireless transmit/receive unit (WTRU), the method comprising:

requesting support from one or more potential assistant WTRUs (a-WTRUs);

receiving a response message from one or more potential a-WTRUs, wherein the response message includes information indicating a coverage status within a network of the one or more potential a-WTRUs;

determining a group of a-WTRUs from the one or more potential a-WTRUs based on the received response message;

determining a synchronization source based on the coverage status of each a-WTRU of the determined group of a-WTRUs; and

reporting the determined synchronization source to the determined group of a-WTRUs.

2. The method of claim 1, wherein determining the group of a-WTRUs from the one or more potential a-WTRUs is based on a quality of service (QoS) requirement of a location service of a first WTRU.

3. The method of claim 1 wherein the determined synchronization source is a base station on the condition that each of the a-WTRUs in the determined group is within the coverage area of the network.

4. The method of claim 1 wherein the determined synchronization source is any WTRU on the condition that at least one of the a-WTRUs in the determined group is not within the coverage area of the network.

5. The method of claim 4 wherein the any WTRU is the first WTRU.

6. The method of claim 4 wherein the first WTRU sends information to the determined group of a-WTRUs for receiving a side-uplink (SL) positioning synchronization signal (slbss) transmission.

7. The method of claim 6 wherein the first WTRU sends the slps transmission to the determined set of a-WTRUs to synchronize SL positioning reference signals (SL-PRS) for the determined set of a-WTRUs.

8. The method of claim 7, wherein the slps transmission is one of a SL-PRS, a side-link synchronization signal (SLSS), a demodulation reference signal (DMRS), a Phase Tracking Reference Signal (PTRS), or a channel state information reference signal (CSI-RS).

9. The method of claim 4 wherein the first WTRU determines the periodicity of the slps transmissions based on quality of service (QoS) requirements of location services associated with the determined group of a-WTRUs.

10. The method of claim 9, wherein the first WTRU sends the slps transmission using the determined periodicity.

11. A first wireless transmit/receive unit (WTRU), the first WTRU comprising:

A transmitter;

a receiver; and

a processor;

wherein the transmitter is configured to request support from one or more potential assistant WTRUs (a-WTRUs);

wherein the receiver is configured to receive a response message from one or more potential a-WTRUs, wherein the response message includes information indicating a coverage status within a network of the one or more potential a-WTRUs;

wherein the processor is configured to determine a group of a-WTRUs from the one or more potential a-WTRUs based on the received response message;

wherein the processor is further configured to determine a synchronization source based on the coverage status of each a-WTRU of the determined group of a-WTRUs; and

wherein the receiver is further configured to report the determined synchronization source to the determined group of a-WTRUs.

12. The first WTRU of claim 10, wherein the processor is further configured to determine the group of a-WTRUs from the one or more potential a-WTRUs based on quality of service (QoS) requirements of location services of the WTRUs.

13. The first WTRU of claim 11, wherein the determined synchronization source is a base station on a condition that each of the a-WTRUs in the determined group is within a coverage area of the network.

14. The first WTRU of claim 11, wherein the determined synchronization source is any WTRU on the condition that at least one of the a-WTRUs in the determined group is not within the coverage area of the network.

15. The first WTRU of claim 14, wherein the any WTRU is the first WTRU.

16. The first WTRU of claim 14, wherein the first WTRU sends information to the determined group of a-WTRUs for receiving a side uplink (SL) positioning synchronization signal (slbss) transmission.

17. The first WTRU of claim 16, wherein the first WTRU sends the slps transmission to the determined set of a-WTRUs to synchronize a SL positioning reference signal (SL-PRS) for the determined set of a-WTRUs.

18. The first WTRU of claim 17, wherein the slps transmission is one of a SL-PRS, a side-uplink synchronization signal (SLSS), a demodulation reference signal (DMRS), a Phase Tracking Reference Signal (PTRS), or a channel state information reference signal (CSI-RS).

19. The first WTRU of claim 14, wherein the first WTRU determines the periodicity of the slps transmissions based on quality of service (QoS) requirements of location services associated with the determined group of a-WTRUs.

20. The first WTRU of claim 19, wherein the transmitter is further configured to send the slps transmission using the determined periodicity.