Method for identifying a sidelink positioning synchronization source

Abstract

The terminal device (110) includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code configured, together with the at least one processor, to cause the terminal device to at least perform the following: receive (910) from a plurality of supported terminal devices information indicating a corresponding sidelink synchronization source with which each of the plurality of supported terminal devices is synchronized; and obtain (920) a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source.

Description

[Technical Field]

[0001] Example and non-limiting embodiment relates generally to communications, and more particularly to a method for identifying sidelink positioning synchronization sources. [Background technology]

[0002] It is known for a pair of user equipment to communicate via a sidelink within a communications network. Summary of the Invention

[0003] According to an aspect, a terminal device includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code configured, together with the at least one processor, to cause the terminal device to at least: receive, from a plurality of supporting terminal devices, information indicating corresponding sidelink synchronization sources to which each of the plurality of supporting terminal devices is synchronized; and obtain a location of the terminal device based on the indicated information of the corresponding sidelink synchronization sources.

[0004] According to an aspect, a terminal device includes at least one processor and at least one memory containing computer program code configured, together with the at least one processor, to cause the terminal device to at least: indicate to a target terminal device a sidelink synchronization source to which the terminal device is synchronized; and transmit to the target terminal device a sidelink position reference signal to enable determination of the target terminal device's location based on the sidelink position reference signal and the sidelink synchronization source. In another aspect, the terminal device and the target terminal device may be different devices in a wireless network.

[0005] According to an aspect, a location management entity includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code, together with the at least one processor, configured to cause the location management entity to at least receive, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized, and use the indicated information to support positioning determination of a target terminal device.

[0006] According to an aspect, there is provided a method for determining a location of a terminal device, the method comprising, executed by a terminal device, the steps of: receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; and obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source.

[0007] According to an aspect, there is provided a method for determining a location of a target terminal device, the method comprising, executed by a terminal device, the steps of: indicating to the target terminal device a sidelink synchronization source to which the terminal device is synchronized; and transmitting to the target terminal device a sidelink position reference signal to enable determination of the location of the target terminal device based on the sidelink position reference signal and the sidelink synchronization source. In another aspect, the terminal device and the target terminal device may be different devices in a wireless network.

[0008] According to an aspect, there is provided a method for determining a location of a target terminal device, the method comprising, performed by a location management entity, the steps of: receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; and supporting a positioning determination of the target terminal device using the indicated information.

[0009] According to an aspect, a terminal device includes means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized, and means for obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source.

[0010] According to certain aspects, the terminal device comprises means for indicating to the target terminal device a sidelink synchronization source to which the terminal device is synchronized, and means for transmitting to the target terminal device a sidelink position reference signal to enable determination of the position of the target terminal device based on the sidelink position reference signal and the sidelink synchronization source.

[0011] According to an aspect, the location management entity includes means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized, and means for supporting a positioning determination of a target terminal device using the indicated information.

[0012] The foregoing aspects and other features are explained in the following description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram of one possible non-limiting system in which example embodiments may be practiced. [Figure 2] FIG. 1 illustrates an exemplary situation for SL positioning synchronization. [Figure 3] A diagram showing a signaling flow assisted by UE-based LMF. [Figure 4] A diagram showing a signaling flow not supported by UE-based LMF. [Figure 5] FIG. 1 illustrates a UE-assisted signaling flow. [Figure 6A] FIG. 10 illustrates an exemplary mapping to a synchronization offset. [Figure 6B] FIG. 1 illustrates an exemplary mapping of supporting UEs to synchronization sources. [Figure 6C] FIG. 10 illustrates an exemplary mapping of synchronization IDs to synchronization sources. [Figure 6D] FIG. 10 illustrates an exemplary mapping between S-UE SL PRS signals and synchronization offsets. [Figure 6E] FIG. 10 illustrates an exemplary mapping between SL PRS IDs and PCIs. [Figure 7] FIG. 1 is a diagram of an exemplary device configured to implement the embodiments described herein. [Figure 8] FIG. 1 illustrates a representation of an example non-volatile memory medium. [Figure 9]FIG. 10 is a diagram of an exemplary method performed using a target terminal device to implement embodiments described herein. [Figure 10] FIG. 1 is a diagram of an exemplary method performed using a support terminal device to implement embodiments described herein. [Figure 11] FIG. 1 is a diagram of an example method performed using network entities to implement embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring to FIG. 1, this figure illustrates a block diagram of one possible, non-limiting example in which embodiments may be practiced. Shown are a user equipment (UE) 110, a radio access network (RAN) node 170, and a network element 190. In the example of FIG. 1, the user equipment (UE) 110 is in wireless communication with a wireless network 100. The UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected via one or more buses 127. Each of the one or more transceivers 130 includes a receiver Rx 132 and a transmitter Tx 133. The one or more buses 127 may be an address bus, a data bus, or a control bus, and may include any interconnection mechanism, such as a series of wires on a motherboard or integrated circuit, optical fiber, or other optical communication equipment. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140 and may include one or both of portions 140-1 and / or 140-2, which may be implemented in many ways. The module 140 may be implemented in hardware as module 140-1, such as as part of one or more processors 120. The module 140-1 may also be implemented as an integrated circuit or by other hardware such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and executed by one or more processors 120. For example, the one or more memories 125 and the computer program code 123, together with the one or more processors 120, may be configured to cause the user equipment 110 to perform one or more of the operations as described herein.The UE 110 communicates with the RAN node 170 via a wireless link 111 .

[0015] In this example, the RAN node 170 is a base station that provides access to the wireless network 100 for wireless devices, such as the UE 110. The RAN node 170 may be, for example, a 5G base station, also referred to as a New Radio (NR). In 5G, the RAN node 170 may be an NG-RAN node, defined as either a gNB or an ng-eNB. A gNB is a node that provides NR user and control plane protocol terminations toward the UE and connects to the 5GC (e.g., network element 190) via an NG interface (e.g., connection 131). An ng-eNB is a node that provides NE-UTRA user and control plane protocol terminations toward the UE and connects to the 5GC via an NG interface (e.g., connection 131). An NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed units (DUs) (gNB-DUs), of which DU 195 is shown. Note that the DU 195 may include a radio unit (RU) or be coupled to and control the radio unit (RU). The gNB-CU 196 is a logical node that hosts the gNB's radio resource control (RRC), SDAP, and PDCP protocols, or the en-gNB's RRC and PDCP protocols, controlling the operation of one or more gNB-DUs. The gNB-CU 196 terminates the F1 interface connected to the gNB-DU 195. The F1 interface is shown as reference 198, which also denotes a link between a remote element of the RAN node 170 and a centralized element of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU 195 is a logical node that hosts the gNB's or en-gNB's RLC, MAC, and PHY layers, and its operation is partially controlled by the gNB-CU 196. One gNB-CU196 supports one or multiple cells.A cell may be supported using one gNB-DU 195, or a cell may be supported / shared using multiple DUs under RAN sharing. The gNB-DU 195 terminates an F1 interface 198 connected to the gNB-CU 196. Note that while the DU 195 is considered to include the transceiver 160, e.g., as part of an RU, some examples of this may include the transceiver 160 as part of a separate RU, e.g., connected to the DU 195 under control of the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station for long term evolution (LTE), or any other suitable base station or node.

[0016] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / WI / F) 161, and one or more transceivers 160, interconnected via one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor 152, the memory 155, and the network interface 161. Note that the DU 195 may also include its own one or more memories and processors and / or other hardware, although these are not shown.

[0017] The RAN node 170 includes a module 150 and may include one or both of portions 150-1 and / or 150-2, which may be implemented in many ways. The module 150 may be implemented in hardware as module 150-1, such as as part of one or more processors 152. The module 150-1 may also be implemented as an integrated circuit or by other hardware such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, which is implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and the computer program code 153, together with the one or more processors 152, are configured to cause the RAN node 170 to perform one or more of the operations as described herein. It is noted that the functionality of the module 150 may be distributed, such as distributed between the DU 195 and the CU 196, or may be implemented solely within the DU 195.

[0018] One or more network interfaces 161 communicate over a network, such as via links 176 and 131. Two or more gNBs 170 may communicate using, for example, link 176. Link 176 may be wired or wireless or both, and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0019] The one or more buses 157 may be an address bus, a data bus, or a control bus, and may include any interconnection mechanism, such as a set of wires on a motherboard or integrated circuit, optical fiber or other optical communication equipment, a wireless channel, etc. For example, one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 for a 5G gNB implementation, and other elements of the RAN node 170 may be physically located differently from the RRH / DU 195, and the one or more buses 157 may be implemented in part, for example, as optical fiber cables or other appropriate network connections to connect other elements of the RAN node 170 (e.g., a central unit (CU), gNB-CU 196) to the RRH / DU 195. Reference 198 also indicates those appropriate network links.

[0020] A RAN node / gNB may comprise one or more TRPs to which the methods described herein may be applied. Figure 1 shows that RAN node 170 comprises two TRPs: TRP51 and TRP52. RAN node 170 may host or comprise other TRPs not shown in Figure 1.

[0021] Relay nodes in NR are called integrated access backhaul nodes. The mobile termination part of the IAB node facilitates the backhaul (parent link) connection. In other words, the mobile termination part of the IAB node is responsible for the UE functionality. The distributed unit part of the IAB node facilitates the so-called access link (child link) connection (i.e., the access link UE case, or the backhaul of other IAB nodes in the case of multi-hop IAB). In other words, the distributed unit part of the IAB node is responsible for the functionality of a specific base station. The IAB situation may follow a so-called split architecture, where a central unit hosts higher layer protocols towards the UE and terminates the control plane and user plane interfaces towards the 5G core network.

[0022] Note that while the description herein indicates that a "cell" performs functions, it should be clear that the equipment forming the cell may perform those functions. A cell constitutes part of a base station; that is, there may be multiple cells per base station. For example, there may be three cells for a single carrier frequency and associated bandwidth, with each cell covering one-third of a 360-degree area, such that the coverage area of a single base station covers an approximate ellipse or circle. Furthermore, each cell may correspond to a single carrier, or a base station may use multiple carriers. Thus, if there are three 120-degree cells and two carriers per carrier, the base station contains a total of six cells.

[0023] The wireless network 100 may include one or more network elements 190, which may include core network functions, providing connectivity to further networks, such as telephone networks and / or data communication networks (e.g., the Internet), via one or more links 181. Such core network functions for 5G may include location management functions (LMF) and / or access and mobility management function(s) (AMF) and / or user plane functions (UPF) and / or session management function(s) (SMF). Such core network functions for LTE may include Mobility Management Entity (MME) / Serving Gateway (SGW) functions. Such core network functions may include self-organizing / optimizing network (SON) functions. Note that these are merely example functions that may be supported by the network element 190, and that both 5G and LTE functions may be supported. The RAN node 170 is coupled to a network element 190 via a link 131. The link 131 may be implemented, for example, as an NG interface for 5G, or an S1 interface for LTE, or other suitable interface for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / WI / F) 180, interconnected via one or more buses 185. The one or more memories 171 include computer program code 173. The computer program code 173 may include SON and / or MRO functionality 172.

[0024] Wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functions into a single software-based management entity, i.e., a virtual network. Network virtualization includes platform virtualization, which is often combined with resource virtualization. Network virtualization is categorized as either external, which combines multiple networks or portions of networks into virtual units, or internal, which provides network-like functions to software containers on a single system. It is noted that the virtualized entities resulting from network virtualization are still implemented, at some level, using hardware, such as processor 152 or 175 and memory 155 and 171, and such virtualized entities also produce technical effects.

[0025] The computer-readable memories 125, 155, and 171 may be of any type suitable for the local technology environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, non-transitory memory, transient memory, fixed memory, and removable memory. The computer-readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable for the local technology environment and may include, by way of non-limiting example, one or more of general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), and processors based on multi-core processor architectures. The processors 120, 152, and 175 may be means for performing functions such as controlling the UE 110, the RAN node 170, the network element 190, and other functions as described herein.

[0026] In general, various example embodiments of user equipment 110 may include, but are not limited to, mobile phones such as smartphones, tablets, personal digital assistants (PDAs) with wireless communication capabilities, portable computers with wireless communication capabilities, image capture devices such as digital cameras with wireless communication capabilities, gaming devices with wireless communication capabilities, music storage and playback appliances with wireless communication capabilities, Internet appliances that enable wireless Internet access and browsing, tablets with wireless communication capabilities, head-mounted displays such as head-mounted displays implementing virtual reality / augmented reality / mixed reality, and portable units or terminals incorporating combinations of these capabilities. UE 110 may also be a vehicle such as an automobile, or a UE mounted on a vehicle, a UAV such as a drone, or a UE mounted on a UAV.

[0027] The UE 110, the RAN node 170, and / or the network element 190 (and associated memory, computer program code, and modules) may be configured to implement (e.g., in part) the methods described herein, including the methods for identifying a sidelink positioning synchronization source. Accordingly, the computer program code 123, the module 140-1, the module 140-2, and other elements / features of the UE 110 shown in FIG. 1 may implement aspects related to the user equipment of the examples described herein. Similarly, the computer program code 153, the module 150-1, the module 150-2, and other elements / features of the RAN node 170 shown in FIG. 1 may implement aspects related to the gNB / TRP of the examples described herein. The computer program code 173 and other elements / features of the network element 190 shown in FIG. 1 may be configured to implement aspects related to the network element of the examples described herein.

[0028] Having thus provided a suitable, but non-limiting, technical background for the practice of the example embodiments, the example embodiments will now be more particularly described.

[0029] The Rel-18 study item RP-213588 "Revised SID: Study on expanded and improved NR positioning" for further positioning refinements has just begun. As part of the study item, support for sidelink positioning is being investigated. The relevant objective is to consider solutions for sidelink positioning taking into account the following: Targeted situations include coverage situations such as in-coverage, partial coverage, and out-of-coverage. Requirements are based on those identified in TR38.845, TS22.261, and TS22.104. Use cases include V2X (TR38.845), public safety (TR38.845), commercial (TS22.261), and IIOT (TS22.104). Spectrum includes ITS and licensed spectrum. This study includes identifying specific target performance requirements to be considered for evaluation based on input from existing 3GPP work and industry forums, and defining the evaluation methodology to be used to evaluate SL positioning for use cases and coverage situations, reusing existing methods as much as possible from sidelink communications and from positioning.

[0030] Other objectives include examining and evaluating the performance and feasibility of potential solutions for SL positioning, taking into account relative positioning, ranging, and absolute positioning. This includes assessing the bandwidth requirements needed to meet the identified accuracy requirements, examining positioning methods (e.g., TDOA, RTT, AOA / D, etc.) including the combination of SL positioning measurements with other RAT-dependent positioning measurements (e.g., Uu-based measurements), examining sidelink reference signals for positioning purposes from a physical layer perspective, including signal design, resource allocation, measurements, related procedures, etc., reusing existing reference signals, procedures, etc. from sidelink communications and from positioning as much as possible, and examining positioning architectures and signaling procedures (e.g., configuration, measurement reporting, etc.) to enable sidelink positioning covering both UE-based and network-based positioning.

[0031] Downlink time difference of arrival (DL-TDOA) and uplink time difference of arrival (UL-TDOA) were introduced in NR Rel-16 and further improved in NR Rel-17. Both of these techniques rely on measuring the time difference received from / at multiple locations to perform trilateration to estimate the UE's location. One well-known drawback of TDOA techniques is the need for tight synchronization between TRPs to have high positioning accuracy. However, round trip time (RTT) techniques are resource-expensive and more complex because they require both transmission and reception of reference signals.

[0032] In 5G NR sidelink (SL), there are multiple synchronization sources, such as gNB, GNSS, or another UE. The SL synchronization signal (SLSS) ID is used to inform other UEs about some information of a particular UE's synchronization source. For example, an out-of-coverage UE and an in-coverage UE synchronized to different sources use different SLSS IDs.

[0033] In 3GPP, the consideration of SL positioning can include considering additional methods for supported positioning methods using SL measurements, including RTT-based solutions using SL, SL-AoA, SL-TDOA, and SL-AoD. For RTT-based solutions using SL, both one-sided (also known as unidirectional) and two-sided (also known as bidirectional) RTT are considered. For SL-AoA, both the azimuth of arrival (AoA) and zenith of arrival (ZoA) are considered. SL-AoD corresponds to methods where RSRP and / or RSRPP measurements are used, similar to the DL-AoD method in Uu, and includes both the azimuth of departure (AoD) and zenith of departure (ZoD).

[0034] SL-TDOA can be an SL technique in which multiple supporting (or anchor) UEs transmit sidelink positioning reference signals (SL PRS) to a target UE, and the target UE measures the time difference between the arrival of those SL PRS signals. The measurement made by the target UE may be referred to as the sidelink reference signal time difference (SL RSTD) or SL TDOA. SL RSTD may be defined as the time between the arrival of two different SL PRS signals from different supporting UEs.

[0035] Synchronization offsets between devices cause degradation of the positioning performance of TDOA techniques. Similar to SL-TDOA, synchronization between UEs should be considered. If the synchronization offsets are known, the positioning calculation entity can correct for them before performing positioning estimation. One way to learn the offsets between nodes is to use over-the-air (OTA) measurements between devices with known locations.

[0036] Referring to FIG. 2, in some cases, such as out-of-coverage or partial coverage, a target UE (a UE to be located) does not know the exact synchronization source of another SL UE. FIG. 2 illustrates this case. In this example, UE-type RSUs (210, 212, 214, 216, and 218) are located along a highway 201 (although the RSUs may have mobile capabilities), but not all of the RSUs are under the coverage of a gNB. As shown in the figure, RSU 210 is under the coverage of gNB 170-1 in cell 202, and RSU 218 is under the coverage of gNB 170-2 in cell 204. Meanwhile, RSUs 212, 214, and 216 are neither under the coverage of the gNB 170-1 hosting cell 202 nor under the coverage of the gNB 170-2 hosting cell 204.

[0037] In this case, some of the RSUs synchronize with the gNBs via other UEs. For example, RSU 212 synchronizes with gNB 170-1 via RSU 210, and RSU 216 synchronizes with gNB 170-2 via RSU 218. However, if target UE 110 wants to correct the synchronization offset between the RSUs (212, 214) shown above the highway (synchronized with gNB1 170-1 via other RSUs / UEs) and the RSUs (e.g., 216) shown below the highway (synchronized with gNB2 170-2 via other RSUs / UEs), target UE 110 needs to know more detailed synchronization information. For ease of explanation, the embodiment shown in FIG. 2 is based on an RSU UE type, but the embodiments described herein are applicable and effective for general SL UEs. The embodiments described herein solve this and related problems. UE 110-2 is also shown in FIG. 2.

[0038] In 3GPP, an S-UE may also be described as an anchor UE or an assistant UE. For example, a supporting user equipment may include an anchor user equipment or a road side unit (RSU).

[0039] (Example 1) Example 1 illustrates the advantages and technical effects of the embodiments described herein. Example 1 is an example of a UE 110 that applies a synchronization offset during position estimation. Assume that a target UE (T_UE) 110 measures SL RSTD between two supporting UEs, S_UE_1 and S_UE_2. S_UE_1 is synchronized with source gNB_1, and S_UE_2 is synchronized with source gNB_2. The synchronization offset between gNB_1 and gNB_2 is d_12. T_UE measures SL PRS transmissions from S_UE_1 and S_UE_2 to measure SL RSTD_12=t1-t2 (t1 and t2 are the arrival times of the SL PRS from S_UE_1 and S_UE_2, respectively). After measuring SL RSTD_12, T_UE subtracts the synchronization offset d_12 to complete a corrected SL RSTD_12'=SL RSTD_12-d_12.

[0040] In the state of the art, the target UE does not determine which synchronization offset to apply for a particular S-UE SL PRS, nor does the target UE have a provision to receive this information from either the S-UE or the LMF.

[0041] Rel-17 V2X supports UEs to provide only coarse information about the synchronization source via the SLSS ID, but the current specification does not provide a way to identify which gNB a particular SL UE is synchronized to.

[0042] In Rel-16 for UE-based positioning, the LMF can provide relative time difference (RTD) information as part of the PRS assistance data. RTD helps to assist the UE in taking into account the synchronization offset between gNBs. The UE does not have the ability to request this assistance for a specific TRP.

[0043] Described herein are methods for UE 110 to determine synchronization sources for supporting UEs and mitigate the effects of synchronization offsets between supporting UEs used for SL positioning.

[0044] A target UE (T-UE) 110 and a supporting UE (S-UE) (e.g., one of 210, 212, 214, 216, 218) are involved in an SL-TDOA positioning session. The T-UE illustratively receives an SL-PRS from the S-UE.

[0045] The S-UE indicates a detailed synchronization source with which the S-UE is synchronized, possibly via another S-UE. The detailed synchronization source (e.g., gNB / eNB ID) may include the identity of the specific synchronization source (as well as the type of source). Options for how this indication may be performed include option 1 and option 2.

[0046] Option 1 is to add a new synchronization source information element to the SL-PRS configuration, for example, a synchronization ID. In this option, the S-UE may also report the mapping between the synchronization ID and the gNB / eNB ID to the LMF / T-UE.

[0047] Option 2 is to use SL PRS IDs to convey synchronization source information. Some set of SL PRS IDs may be mapped to the cell ID (e.g., PCI) of the gNB. Some SL PRS IDs may be a function of the cell ID (e.g., PCI) and the S-UE ID. The mapping / function may be hard-coded (e.g., agreed upon in advance) or signaled / transferred to the T-UE (e.g., by the LMF). In one embodiment, the UE may use different synchronization sources for different PRS resource sets (e.g., to better match with other S-UEs).

[0048] As used within this disclosure, a SL PRS ID may be configured as part of a sidelink positioning reference signal (SL PRS) configuration. The SL PRS ID may identify a sidelink synchronization source by mapping the SL PRS ID to a physical cell identifier (PCI).

[0049] If the S-UE does not provide a synchronization source and SL PRS resources are used for RSTD measurements and / or reporting, the T-UE may request the S-UE to provide a synchronization source (e.g., synchronization ID or PCI) for the SL PRS resources.

[0050] In UE-assisted positioning (where the LMF or another entity is calculating the final UE position estimate), the T-UE reports the synchronization source of the S-UE to the LMF as part of the measurement report. For example, the T-UE indicates that a set of S-UEs are associated with the same synchronization source (e.g., gNB A, synchronization ID X). For example, if the T-UE reports RSTD measurements measured from two different SL PRS resources, the T-UE also reports the two synchronization sources for this RSTD measurement. The LMF may use synchronization offset information (e.g., RTD) between the two gNBs to compensate for synchronization errors in the measurements.

[0051] In UE-based positioning (where the target UE is the entity calculating the final UE position estimate), the T-UE requests the S-UE synchronization offset from the LMF or directly from the S-UE. For many S-UEs (e.g., UE-type RSUs), the synchronization offset can be measured over-the-air. This should be reasonable for UE-type RSUs because they are static and fixed to a specific location. It may also be possible to measure the synchronization offset for other types of SL UEs (e.g., temporarily static UEs) over-the-air. The S-UE may obtain the T-UE's request directly when the LMF is not involved in the positioning (e.g., when it is completely out of coverage).

[0052] In UE-based positioning, the LMF requests synchronization source and offset information from the S-UE / gNB if it is not already available. The LMF (or the S-UE directly) signals the synchronization offset of the S-UE's source to the UE. This synchronization offset information allows the T-UE to perform mapping between the S-UE SL PRS signal and the synchronization offset. In a first option, the LMF directly signals the offset between the S-UE and the gNB. In another example related to this first option, the LMF signals the offset between different sets of SL PRS resources. In a second option, the LMF only signals the synchronization offset of the gNB. For example, if the T-UE acquires synchronization sources for different SL-PRS resources, the T-UE may use the synchronization offset of the gNB to compensate for synchronization errors in the RSTD measurements of those SL-PRS resources.

[0053] The entity that calculates the UE's position (LMF / other entity in UE-assisted positioning, UE in UE-based positioning) corrects the TDOA measurements using the synchronization offset mapping, optionally together with the S-UE's determined synchronization source.

[0054] Without the mapping between the S-UE and the synchronization offset, the T-UE cannot correct the error in the SL RSTD measurement caused by the synchronization offset, thus reducing the accuracy of the positioning measurement.

[0055] The measurements by the terminal device are corrected by the network entity using a synchronization offset between multiple supporting terminal devices, and the location of the terminal device is determined by the network entity using the corrected measurements. Although multiple supporting terminal devices may be used (in actual practice), the terminal device and method described herein are also applicable when only one supporting terminal device is used.

[0056] 3 shows a signaling flow 300 of a method for UE-based LMF-assisted positioning, in which the T-UE computes a position estimate but receives some assistance from the LMF. At 302, an SL-TDOA procedure is initiated using the LMF 390, the S_UEs (301-1, 301-2, ..., 301-N), and the T_UE 310. At 304, the T_UE 310 requests detailed synchronization sources from one or more of the S_UEs (301-1, 301-2, ..., 301-N). At 306, one or more of the S_UEs (301-1, 301-2, ..., 301-N) indicate the detailed SL synchronization sources to the T_UE 310. At 308, one or more of the S_UEs (301-1, 301-2, ..., 301-N) report the detailed synchronization sources to the LMF 390. At 310, the T_UE 310 requests synchronization offsets from the LMF 390. At 312, the LMF 390 requests one or more of the synchronization offsets from the S_UEs (301-1, 301-2, ..., 301-N).

[0057] At 313, one or more S_UEs (301-1, 301-2, ..., 301-N) transmit synchronization offsets to the LMF 390. At 314, the LMF 390 transmits a mapping of synchronization offsets to the T_UE 310. At 316, one or more S_UEs (301-1, 301-2, ..., 301-N) transmit SL PRSs to the T_UE 310. At 318, the T_UE 310 measures the SL RTD. At 320, the T_UE 310 determines a synchronization offset for each S_UE using the mapping of synchronization offsets. At 322, the T_UE 310 applies one or more synchronization offsets during position estimation.

[0058] 4 illustrates a signaling flow 400 of a method for UE-based LMF-unaided positioning, where the T-UE computes a position estimate without assistance from an LMF. This diagram can represent at least the case where the T-UE is out of coverage and the S-UE is in direct communication with the T-UE.

[0059] At 402, an SL-TDOA procedure is initiated using one or more S_UEs (401-1, 401-2, ..., 401-N) and a T_UE 410. At 404, the T_UE 410 requests a detailed synchronization source from one or more S_UEs (401-1, 401-2, ..., 401-N). At 406, one or more S_UEs (401-1, 401-2, ..., 401-N) indicate the detailed synchronization source to the T_UE 410. At 408, the T_UE 410 requests one or more synchronization offsets from one or more S_UEs (401-1, 401-2, ..., 401-N).

[0060] At 410, one or more S_UEs (401-1, 401-2, ..., 401-N) transmit a mapping of synchronization offsets to the T_UE 410. At 412, one or more S_UEs (401-1, 401-2, ..., 401-N) transmit SL PRSs to the T_UE 410. At 414, the T_UE 410 measures the SL RSTD. At 414, the T_UE 410 uses the mapping of synchronization offsets to determine an offset for each S_UE. At 416, the T_UE 410 applies the synchronization offsets during position estimation.

[0061] 5 shows a signaling flow 500 of the method for UE-assisted positioning, where the T-UE and S-UE communicate directly to exchange information.

[0062] At 502, an SL-TDOA procedure is initiated using the LMF 590, one or more S_UEs (501-1, 501-2, ..., 501-N), and the T_UE 510. At 504, the T_UE 510 requests an SL synchronization source from one or more S_UEs (501-1, 501-2, ..., 501-N). At 506, one or more S_UEs (501-1, 501-2, ..., 501-N) indicate an SL synchronization source to the T_UE 510. At 508, one or more S_UEs (501-1, 501-2, ..., 501-N) report a synchronization ID mapping to the LMF 590. At 512, one or more S_UEs (501-1, 501-2, ..., 501-N) transmit an SL PRS to the T_UE 510. At 514, the T_UE 510 measures the SL RSTD. At 516, the T_UE 510 reports the SL RSTD measurements to the LMF 590. At 518, the LMF 590 corrects the SL RSTD measurements and estimates the position of the T_UE 510.

[0063] 6A shows an example mapping 600 to synchronization offsets, where mapping 600 may include individual mappings. For example, LMF 390 of FIG. 3 may transmit 322 the entire mapping 600 or one or more of mapping 1, mapping 2, mapping 3, mapping 4, mapping 5, and mapping 6 to T_UE 310 for use by T_UE 310 in estimating its location. In FIG. 4, one of the S_UEs, such as S_UE 401-1, may transmit 416 416 one or more of mapping 1, mapping 2, mapping 3, mapping 4, mapping 5, and mapping 6 (e.g., the entire mapping 600) to T_UE 410 for T_UE 410 to estimate its location.

[0064] 6B shows a mapping 650 of supporting UEs to synchronization sources, which may be used by the target UEs (310, 410, 510) or the LMF (390, 590) to determine which supporting UEs are synchronized to which synchronization sources and further to determine SL RSTD. Within the mapping 650, there are multiple individual mappings, each indicating which synchronization source a respective supporting UE (UE_1, UE_2, UE_3) is synchronized to. The mapping 650, or any one of the individual mappings within the mapping 650, may be signaled by the supporting UEs (301-1, 301-2, 301-N, 401-1, 401-2, 401-N, 501-1, 501-2, 501-N) to the target UEs (310, 410, 510) or the LMF (390, 590).

[0065] 6C shows a mapping 675 of synchronization IDs to synchronization sources, which may include individual mappings. The S-UE may report any of the mappings between synchronization IDs and gNB / eNB IDs in 675, or the entire mapping 675, to the LMF / T-UE.

[0066] 6D shows a mapping 680 between an S-UE SL PRS signal and a synchronization offset, which may include a separate mapping. In an embodiment, the LMF (or one or more S-UEs directly) signals the synchronization offset of the S-UE's source to the UE. This synchronization offset information enables the T-UE to perform the mapping 680 between the S-UE SL PRS signal and a synchronization offset.

[0067] 6E shows a mapping 690 between SL PRS IDs and PCIs, where the mapping 690 is comprised of individual mappings. Since any set of SL PRS IDs may be mapped to a gNB's cell ID (e.g., PCI), the SL PRS IDs, along with one or more of the mappings in 690, may be used to convey synchronization source information.

[0068] Additional embodiments are directed to the case where the UE performs synchronization operations using SS / PBCH blocks transmitted from a specific gNB. Based on the examples described herein, the S-UE can inform the T-UE of the gNB it used for synchronization. It should be noted that multiple TRPs (e.g., TRP51, TRP51) may exist within a single gNB (e.g., RAN node 170). This means that TRPs may not be distinguished by physical cell IDs from the UE side. In current LPP signaling, the LMF (e.g., 190) can provide the UE (e.g., 110) with RTD (relative time difference) not only between cells but also between different TRPs within the same cell. Unless the S-UE provides the TRP ID as a synchronization source, the T-UE cannot use the RTD information to compensate measurements.

[0069] Depending on the implementation, the UE may perform synchronization using both DL PRS and SSB, and therefore the S-UE may report TRP information (e.g., TRP ID) as a synchronization source to the T-UE (or LMF) as part of the measurement report.

[0070] (Example 2) To better understand the contribution of the embodiments described herein, an example assuming an out-of-coverage situation involving a single T-UE and two different S-UEs will now be described. Based on current systems, the LMF 190 may provide the T-UE 110 with information regarding the synchronization offset between cells and / or TRPs within the same cell by broadcasting positioning assistance data. The T-UE measures the SL RSTD from two SL-PRSs transmitted by two S-UEs (e.g., 210, 212, 214, 216, 218). Although the T-UE may have synchronization offset information between cells and / or TRPs, the T-UE cannot compensate for the SL RSTD because it does not yet recognize or distinguish between the synchronization sources of the two S-UEs. Therefore, based on current state-of-the-art technology, the T-UE cannot correct the synchronization offset between the two S-UE SL PRSs. The embodiments described herein solve the above problem. For example, a T-UE may use the embodiments described herein to identify synchronization source information of an S-UE and receive the respective synchronization offset information. The T-UE can use the respective synchronization offset information to improve the accuracy of the SL positioning procedure. For example, two S-UEs (e.g., 210, 218) may each transmit synchronization information such as (PCI1, TRP#1) and (PCI#2, TRP#2) to the T-UE 110, which can then utilize the respective synchronization offset information for (PCI1, TRP#1) and (PCI#2, TRP#2) provided by the LMF 190 to compensate for SL RSTD measurements, thus improving the accuracy of the SL positioning procedure. This procedure is not contemplated in the current state of the art.

[0071] The SL-RSTD measurements may include the case of DL-PRS transmitted from the TRP and SL-PRS transmitted from the supporting UE.

[0072] Advantages and technical effects of the embodiments described herein include improved positioning accuracy, reduced impact of synchronization errors on positioning, and enabling SL-TDOA (over SL-RTT) which results in reduced resource overhead.

[0073] 7 is an example apparatus 700, which may be implemented in hardware, configured to perform embodiments described herein. The apparatus 700 comprises at least one processor 702 (e.g., FPGA and / or CPU), at least one memory 704 containing computer program code 705, where the at least one memory 704 and the computer program code 705, together with the at least one processor 702, are configured to cause the apparatus 700 to implement circuits, processes, components, modules, or functions (collectively, control 706) to perform embodiments described herein, including a method for identifying a sidelink positioning synchronization source. The memory 704 may be non-transitory memory, transient memory, volatile memory (e.g., RAM), or non-volatile memory (e.g., ROM).

[0074] The device 700 optionally includes a display and / or I / O interface 708 that can be used to display aspects or status of the methods described herein (either while one of the methods is being performed or at a later time) or to receive input from a user using a keypad, camera, touchscreen, touch area, microphone, biometric authentication, one or more sensors, etc. The device 700 includes one or more communication, e.g., network (N / W) interfaces (I / F) 710. The communication I / F 710 may be wired and / or wireless and may communicate over the Internet / other networks via any communication technology. The communication I / F 710 may comprise one or more transmitters and one or more receivers. The communication I / F 710 may comprise standard, well-known components such as amplifiers, filters, frequency converters, modulators (demodulators), and encoder / decoder circuits, as well as one or more antennas.

[0075] 2-5, including UE 110, RAN node 170 (e.g., gNB), network element 190, or any of the devices shown in Figures 2-5, including any of T_UE, S_UE, or LMF. Accordingly, processor 702 may correspond to processor 120, processor 152, and / or processor 175; memory 704 may correspond to memory 125, memory 155, and / or memory 171; computer program code 705 may correspond to computer program code 123, module 140-1, module 140-2, and / or computer program code 153, module 150-1, module 150-2, and / or computer program code 173; and communication I / F 710 may correspond to transceiver 130, antenna 128, transceiver 160, antenna 158, N / WI / F 161, and / or N / WI / F 180. Alternatively, the device 700 may be part of a self-organizing / optimizing network (SON) node, such as in the cloud, and therefore the device 700 may not correspond to a UE 110, a RAN node 170, a network element 190, or any of the devices (T_UE, S_UE, or LMF) shown in Figures 2-5.

[0076] The device 700 may also be distributed throughout the network (e.g., 100), including within and between the device 700 and any network elements (such as a network control element (NCE) 190 and / or a RAN node 170 and / or a UE 110).

[0077] 7, interface 712 allows for data communication between various items of device 700. For example, interface 712 may be one or more buses, such as an address bus, a data bus, or a control bus, and may include any interconnection mechanism, such as a series of wires on a motherboard or integrated circuit, optical fiber, or other optical communication equipment. Computer program code 705, including control 706, may include object-oriented software configured to pass data / messages between objects within computer program code 705. Device 700 need not include each of the noted features, and may include other features as well.

[0078] FIG. 8 shows a diagrammatic representation of non-volatile memory media 800a (e.g., a computer disc (CD) or digital versatile disc (DVD)) and 800b (e.g., a universal serial bus (USB) memory stick) that store instructions and / or parameters 802 that, when executed by a processor, enable the processor to perform one or more of the method steps described herein.

[0079] 9 is an exemplary method 900 for implementing example embodiments described herein. At 910, the method includes receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized. At 920, the method includes obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source. Method 900 may be performed using a target terminal device.

[0080] 10 is an exemplary method 1000 for implementing example embodiments described herein. At 1010, the method includes indicating to a target terminal device a sidelink synchronization source to which the terminal device is synchronized. At 1020, the method includes transmitting a sidelink position reference signal to the target terminal device, the position of the target terminal device being based on the sidelink position reference signal and the sidelink synchronization source. Method 1000 may be performed using supporting terminal devices.

[0081] 11 is an exemplary method 1100 for implementing example embodiments described herein. At 1110, the method includes receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized. At 1120, the method includes using the information to support positioning of the target terminal device. Method 1100 may be performed using a location management entity.

[0082] The following examples (1-63) are provided and illustrated herein for purposes of illustration only and should not be construed as limiting.

[0083] Example 1 The terminal device (T_UE) includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code, together with the at least one processor, configured to cause the terminal device to at least perform the following steps: receive, from a plurality of supporting terminal devices (S_UE), information indicating a corresponding sidelink synchronization source (e.g., a gNB) to which each of the plurality of supporting terminal devices is synchronized (steps 306, 406, 506); and obtain a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source (steps 322, 416, 518).

[0084] Example 2 The terminal device of embodiment 1, wherein the location of the terminal device is determined based on a synchronization offset (steps 320, 415) among a plurality of supporting terminal devices.

[0085] Example 3 The terminal device of any one of the first and second embodiments, wherein the reception of the information is in response to a request (steps 304, 404, 504) by the terminal device for a corresponding sidelink synchronization source to which each of the plurality of supported terminal devices is synchronized.

[0086] Example 4 The terminal device of any of embodiments 1 to 3, wherein the terminal device is caused to perform respective measurements on one or more sidelink position reference signals (steps 316, 412, 512) from a plurality of supporting terminal devices.

[0087] Example 5 5. The terminal device of embodiment 4, wherein the measurement (steps 318, 414, 514) is a sidelink reference signal time difference (SL RSTD) measurement.

[0088] Example 6 A terminal device of any of embodiments 2 to 5, wherein the terminal device (T_UE) is caused to receive (steps 314, 410) synchronization offsets between a plurality of supporting terminal devices (S_UE) from a network entity (LMF) and to determine (steps 322, 416) the location of the terminal device based on measurements (steps 318, 414) and the synchronization offsets between the plurality of supporting terminal devices (steps 314, 410).

[0089] Example 7 A terminal device of Example 6, wherein the terminal device is caused to correct (steps 322, 416) measurements using a synchronization offset (steps 314, 410) between multiple supported terminal devices, and to determine (steps 322, 416) the position of the terminal device using the corrected measurements (steps 320, 415).

[0090] Example 8 The terminal device of embodiment 4, wherein the terminal device is caused to send (step 516) a measurement report including measurements by the terminal device to a network entity (LMF).

[0091] Example 9 The terminal device of example 8, wherein the measurement report indicates (indirectly via step 510) a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized.

[0092] Example 10 9. The terminal device of embodiment 8, wherein the terminal device is caused to send (step 510) an indication to a network entity indicating a corresponding sidelink synchronization source with which each of the plurality of supported terminal devices is synchronized.

[0093] Example 11 The terminal device of example 9 or 10, wherein measurements by the terminal device are corrected by the network entity using a synchronization offset between a plurality of supporting terminal devices (step 518), and the location of the terminal device is determined by the network entity using the corrected measurements.

[0094] Example 12 The terminal device (S_UE) includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code, together with the at least one processor, configured to cause the terminal device to at least perform the following: indicate to the target terminal device (T_UE) a sidelink synchronization source (gNB) to which the terminal device is synchronized (steps 306, 406, 506), where the terminal device (S_UE) and the target terminal device (T_UE) are different devices in a wireless network; and transmit to the target terminal device (steps 316, 412) a sidelink position reference signal to enable determination of the position of the target terminal device based on the sidelink position reference signal and the sidelink synchronization source (step 414).

[0095] Example 13 13. The terminal device of embodiment 12, wherein the terminal device is caused to receive from the target terminal device a request (steps 304, 404) for a sidelink synchronization source to which the terminal device is synchronized.

[0096] Example 14 13. The terminal device of embodiment 12, wherein the terminal device is caused to send (step 508) a mapping between a sidelink synchronization source and a network device serving the terminal device to a location management entity (LMF).

[0097] Example 15 A terminal device of Example 12, wherein the terminal device is caused to provide a location management entity (LMF) with a synchronization offset between the terminal device and another terminal device (step 313), and the synchronization offset is used to determine the location of the target terminal device.

[0098] Example 16 13. The terminal device of embodiment 12, wherein the terminal device is caused to send (step 508) to a location management entity (LMF) a mapping between an identifier of the sidelink synchronization source and a network device serving the terminal device.

[0099] Example 17 17. The terminal device of embodiment 16, wherein the mapping is used by the location management entity to determine the location of the target terminal device (step 518).

[0100] Example 18 The location management entity (LMF) includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code, together with the at least one processor, configured to cause the location management entity to at least perform the following: receive information from a plurality of supporting terminal devices (S_UE) indicating a corresponding sidelink synchronization source (e.g., a gNB) to which each of the plurality of supporting terminal devices is synchronized (step 510); and use the indicated information to support position determination of a target terminal device (T_UE) (step 518).

[0101] Example 19 19. The location management entity of embodiment 18, wherein the location management entity is caused to acquire (step 313) a synchronization offset among a plurality of supporting terminal devices.

[0102] Example 20 20. The location management entity of embodiment 19, wherein the location management entity is caused to determine (step 518) a location of a target terminal device (T_UE) based on a synchronization offset among a plurality of supporting terminal devices.

[0103] Example 21 A location management entity of Example 19, wherein the location management entity is caused to provide a synchronization offset between a plurality of supporting terminal devices to a target terminal device (T_UE) (step 314), and the synchronization offset between the plurality of supporting terminal devices is used to determine the location of the target terminal device.

[0104] Example 22 A method for determining a location of a terminal device (T_UE), the method including being performed by the terminal device, and the steps may include receiving, from a plurality of supporting terminal devices (S_UE), information indicating a corresponding sidelink synchronization source (e.g., a gNB) to which each of the plurality of supporting terminal devices is synchronized (steps 306, 406, 506), and obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source (steps 322, 416, 518).

[0105] Example 23 23. The method of example 22, wherein the location of the terminal device is determined based on a synchronization offset between a plurality of supporting terminal devices.

[0106] Example 24 24. The method of embodiment 22 or 23, wherein receiving the information is in response to a request by the terminal device for a corresponding sidelink synchronization source to which each of the plurality of supported terminal devices is synchronized.

[0107] Example 25 25. The method of any of examples 22-24, further comprising performing, by the terminal device, respective measurements on one or more sidelink position reference signals from a plurality of supporting terminal devices.

[0108] Example 26 26. The method of example 25, wherein the measurement is a sidelink reference signal time difference (SL RSTD) measurement.

[0109] Example 27 The method of any of Examples 23 to 26, further comprising receiving, by the terminal device, from a network entity, a synchronization offset between a plurality of supporting terminal devices, and determining a position of the terminal device based on the measurement and the synchronization offset between the plurality of supporting terminal devices.

[0110] Example 28 28. The method of example 27, further comprising: correcting, by the terminal device, the measurements using a synchronization offset between the plurality of supporting terminal devices; and determining a position of the terminal device using the corrected measurements.

[0111] Example 29 26. The method of embodiment 25, further comprising: transmitting, by the terminal device, a measurement report to the network entity, the measurement report including the measurement value by the terminal device.

[0112] Example 30 30. The method of example 29, wherein the measurement report indicates a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized.

[0113] Example 31 30. The method of example 29, further comprising: transmitting, by the terminal device, an indication to a network entity indicating a corresponding sidelink synchronization source to which each of the plurality of supported terminal devices is synchronized.

[0114] Example 32 32. The method of embodiment 30 or 31, wherein measurements by the terminal device are corrected by a network entity using a synchronization offset between a plurality of supporting terminal devices, and the location of the terminal device is determined by the network entity using the corrected measurements.

[0115] Example 33 A method for determining a location of a target terminal device, the method comprising, executed by a terminal device (S_UE), steps including: indicating to the target terminal device (T_UE) a sidelink synchronization source (gNB) to which the terminal device is synchronized (steps 306, 406, 506); and transmitting to the target terminal device (steps 316, 412) a sidelink position reference signal to enable determination of the location of the target terminal device (step 414) based on the sidelink position reference signal and the sidelink synchronization source (steps 316, 412). In another aspect, the terminal device and the target terminal device may be different devices in a wireless network.

[0116] Example 34 34. The method of example 33, further comprising receiving a request from the target terminal device for a sidelink synchronization source to which the terminal device is synchronized.

[0117] Example 35 34. The method of embodiment 33, further comprising transmitting to a location management entity a mapping between a sidelink synchronization source and a network device serving the terminal device.

[0118] Example 36 34. The method of embodiment 33, further comprising providing a synchronization offset between the terminal device and another terminal device to a location management entity, wherein the synchronization offset is used to determine the location of the target terminal device.

[0119] Example 37 34. The method of embodiment 33, further comprising transmitting to a location management entity a mapping between an identifier of the sidelink synchronization source and a network device serving the terminal device.

[0120] Example 38 38. The method of example 37, wherein the mapping is used by a location management entity to determine the location of the target terminal device.

[0121] Example 39 A method for determining a location of a target terminal device, the method including being performed by a location management entity (LMF), and the steps may include receiving information from a plurality of supporting terminal devices (S_UE) indicating a corresponding sidelink synchronization source (gNB) to which each of the plurality of supporting terminal devices is synchronized (step 510), and using the indicated information to support positioning determination of the target terminal device (T_UE) (step 518).

[0122] Example 40 40. The method of example 39, further comprising obtaining a synchronization offset between a plurality of supporting terminal devices.

[0123] Example 41 41. The method of example 40, further comprising determining a location of the target terminal device based on a synchronization offset among a plurality of supporting terminal devices.

[0124] Example 42 41. The method of embodiment 40, further comprising providing a synchronization offset between the plurality of support terminal devices to the target terminal device, wherein the synchronization offset between the plurality of support terminal devices is used to determine the position of the target terminal device.

[0125] Example 43 1. A terminal device comprising: means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized; and means for obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source.

[0126] Example 44 44. The terminal device of example 43, wherein the location of the terminal device is determined based on a synchronization offset between a plurality of supporting terminal devices.

[0127] Example 45 45. The terminal device of embodiment 43 or 44, wherein the reception of the information is in response to a request by the terminal device for a corresponding sidelink synchronization source to which each of the plurality of supported terminal devices is synchronized.

[0128] Example 46 46. A terminal device of any of embodiments 43 to 45, further comprising means for performing respective measurements on one or more sidelink position reference signals from a plurality of supporting terminal devices.

[0129] Example 47 47. The terminal device of embodiment 46, wherein the measurement is a sidelink reference signal time difference (SL RSTD) measurement.

[0130] Example 48 The terminal device of any of Examples 44 to 47, further including means for receiving a synchronization offset between a plurality of supporting terminal devices from a network entity, and means for determining a position of the terminal device based on the measurement and the synchronization offset between the plurality of supporting terminal devices.

[0131] Example 49 49. The terminal device of example 48, further comprising means for correcting measurements using a synchronization offset between a plurality of supporting terminal devices, and means for determining a position of the terminal device using the corrected measurements.

[0132] Example 50 The terminal device of embodiment 46, further comprising means for transmitting a measurement report to a network entity, the measurement report including measurements by the terminal device.

[0133] Example 51 The terminal device of embodiment 50, wherein the measurement report indicates a corresponding sidelink synchronization source with which each of the plurality of supported terminal devices is synchronized.

[0134] Example 52 The terminal device of embodiment 50, further comprising means for transmitting an indication to a network entity indicating a corresponding sidelink synchronization source to which each of the plurality of supported terminal devices is synchronized.

[0135] Example 53 A terminal device of embodiment 51 or 52, wherein measurements by the terminal device are corrected by a network entity using a synchronization offset between a plurality of supporting terminal devices, and the location of the terminal device is determined by the network entity using the corrected measurements.

[0136] Example 54 The terminal device comprises means for indicating to the target terminal device a sidelink synchronization source to which the terminal device is synchronized, and means for transmitting to the target terminal device a sidelink position reference signal to enable determination of the position of the target terminal device based on the sidelink position reference signal and the sidelink synchronization source.

[0137] Example 55 55. The terminal device of embodiment 54, further comprising means for receiving, from the target terminal device, a request for a sidelink synchronization source to which the terminal device is synchronized.

[0138] Example 56 55. The terminal device of embodiment 54, further comprising means for transmitting to a location management entity a mapping between a sidelink synchronization source and a network device serving the terminal device.

[0139] Example 57 55. The terminal device of embodiment 54, further comprising means for providing a synchronization offset between the terminal device and another terminal device to a location management entity, the synchronization offset being used to determine the location of the target terminal device.

[0140] Example 58 55. The terminal device of embodiment 54, further comprising means for transmitting to a location management entity a mapping between an identifier of the sidelink synchronization source and a network device serving the terminal device.

[0141] Example 59 59. The terminal device of embodiment 58, wherein the mapping is used by a location management entity to determine the location of the target terminal device.

[0142] Example 60 1. A location management entity comprising: means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source with which each of the plurality of supporting terminal devices is synchronized; and means for supporting a positioning determination of a target terminal device using the indicated information.

[0143] Example 61 61. The location management entity of embodiment 60, further comprising means for obtaining a synchronization offset between a plurality of supporting terminal devices.

[0144] Example 62 62. The location management entity of embodiment 61, further comprising means for determining a location of the target terminal device based on a synchronization offset among a plurality of supporting terminal devices.

[0145] Example 63 62. The location management entity of embodiment 61, further comprising means for providing a synchronization offset between a plurality of support terminal devices to the target terminal device, wherein the synchronization offset between the plurality of support terminal devices is used to determine the location of the target terminal device.

[0146] References to "computer," "processor," and the like should be understood to encompass not only computers having a variety of architectures, such as single-processor / multiprocessor and sequential / parallel architectures, but also specialized circuitry, such as field-programmable gate arrays (FPGAs), application specific circuits (ASICs), signal processing devices, and other processing circuitry. References to computer programs, instructions, code, and the like, whether instructions for a processor or configuration settings for a fixed function device, gate array, programmable logic device, or the like, should be understood to encompass software or firmware for a programmable processor, e.g., the programmable content of a hardware device.

[0147] Memory as described herein may be of any type suitable for the local technology environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, non-transitory memory, transient memory, fixed memory and removable memory, etc. The memory may comprise a database for storing data.

[0148] As used herein, the term “circuitry” may refer to (a) hardware circuit implementations, such as implementations in analog and / or digital circuits, and (b) (where applicable) combinations of circuitry and software (and / or firmware), such as (i) a combination of a processor or (ii) a portion / software of a processor including a digital signal processor, software, and memory that function together to cause a device to perform various functions, and (c) a circuit such as a microprocessor or portion of a microprocessor that requires software or firmware for operation even when the software or firmware is not physically present. As a further example, as used herein, the term “circuitry” also covers simply the implementation of a processor (or processors) or portion of a processor and its (or their) accompanying software and / or firmware. The term “circuitry” also covers, for example, a baseband integrated circuit or application processor integrated circuit for a mobile phone, or a similar integrated circuit in a server, cellular network device, or another network device, if applicable to the particular element.

[0149] In the diagram, arrows between individual blocks represent the operational connections between the blocks and the direction of data flow at those connections.

[0150] It should be understood that the foregoing description is illustrative only. Various alternatives and modifications may be devised by those skilled in the art. For example, the features recited in the various dependent claims may be combined with each other in any suitable combination. In addition, features from the various example embodiments described above may be selectively combined into new example embodiments. Accordingly, this description is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

[0151] The following acronyms and abbreviations that may appear in the present specification and / or drawings are defined as follows (abbreviations and acronyms may be added to each other or to other characters, for example, using dashes or hyphens): 3GPP (third generation partnership project) 4G (fourth generation) 5G (fifth generation) 5GC (5G core network) 5G core network AMF (access and mobility management function) AoA (angle of arrival or azimuth of arrival) AOA / D (angle of arrival or departure or azimuth of arrival or departure) AoD (angle of departure or azimuth of departure) Angle of departure or azimuth of departure ASIC (application-specific integrated circuit) CPU (central processing unit) CU (central unit or centralized unit) DL(downlink) DL-TDOA (downlink time difference of arrival) DSP (digital signal processor) eNB (evolved Node B) Evolved Node B (e.g., LTE base station) EN-DC (E-UTRAN new radio - dual connectivity) en-gNB: A node that provides protocol termination for the NR user plane and control plane towards the UE and acts as a secondary node in the EN-DC. E-UTRA (evolved universal terrestrial radio access) Evolved Universal Terrestrial Radio Access, i.e., LTE radio access technology E-UTRAN (E-UTRA network) F1 Interface between CU and DU FPGA (field-programmable gate array) gNB: A base station for 5G / NR, i.e. a node that provides protocol termination for the NR user plane and control plane towards the UE and is connected to 5GC via the NG interface. GNSS (global navigation satellite system) IAB (integrated access and backhaul) ID (identifier) I / F(interface) IIOT (industrial internet of things) I / O (input / output) ITS (Intelligent Transport Systems) LMF (location management function) LPP (LTE positioning protocol) LTE positioning protocol LTE (long term evolution) Long Term Evolution (4G) MAC (medium access control) MME (mobility management entity) Mobility management entity MRO (mobility robustness optimization) NCE (network control element) ng or NG (new generation) ng-eNB(new generation eNB) New generation eNB NG-RAN (new generation radio access network) New generation radio access network NR (new radio) New Radio (5G) N / W(network) OTA (over the air) wireless PBCH (physical broadcast channel) PCI (physical cell ID) PDA (personal digital assistant) PDCP (Packet Data Convergence Protocol) PHY(physical layer) physical layer PRS (positioning reference signal) RAM (random access memory) RAN (radio access network) RAT (radio access technology) Rel-(release) Release RLC (radio link control) ROM (read-only memory) RRC (radio resource control) Radio resource control (protocol) RSRP (reference signal receive power) RSRPP (reference signal received path power) RSTD (reference signal time difference) RSU (road side unit) Roadside unit RTD (relative time difference) RTT (round trip time) RU (radio unit) Radio unit Rx (receiver or reception) SGW (serving gateway) SID (study item description) SL (sidelink) Sidelink SLSS (sidelink synchronization signal) SMF (session management function) SON (self-organizing / optimizing network) SS(synchronization signal) Synchronization signal SSB (synchronization signal block) S-UE or S_UE (supporting UE) Supporting UE TDOA (time difference of arrival) TR(technical report) TRP (transmission reception point) TS (technical specification) T-UE or T_UE (target UE) Target UE Tx (transmitter or transmission) UAV (unmanned aerial vehicle) UE (user equipment) User equipment (e.g., wireless, typically mobile device) UL(uplink) Uplink UPF (user plane function) Uu An interface for cellular communication between a device and a base station (e.g., a radio interface) V2X (vehicle to everything) X2 Network interface between RAN nodes and between RAN and core network Network interface between Xn NG-RAN nodes ZoA(zenith of arrival) Zenith angle of arrival ZoD (zenith of departure) Departure zenith angle

Claims

1. 1. A method for determining the location of a terminal device, comprising: receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source; and A method comprising performing steps including:

2. The method of claim 1 , wherein the location of the terminal device is determined based on a synchronization offset between the plurality of supporting terminal devices.

3. 3. The method of claim 1, wherein the receiving of the information is in response to a request by the terminal device for the corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized.

4. 4. The method of claim 1, further comprising performing, by the terminal device, respective measurements on one or more sidelink position reference signals from the plurality of supporting terminal devices.

5. 5. The method of claim 4, wherein the measurement is a Sidelink Reference Signal Time Difference (SL RSTD) measurement.

6. receiving, by the terminal device, from a network entity, the synchronization offsets among the plurality of supported terminal devices; determining the location of the terminal device based on the measurements and the synchronization offsets among the plurality of supported terminal devices; The method of any one of claims 2 to 5, further comprising:

7. correcting, by the terminal device, the measurements using the synchronization offset between the plurality of supporting terminal devices; determining the location of the terminal device using the corrected measurements; and The method of claim 6 further comprising:

8. The method of claim 4 , further comprising transmitting, by the terminal device, a measurement report to a network entity that includes the measurements by the terminal device.

9. 9. The method of claim 8, wherein the measurement report indicates the corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized.

10. 10. The method of claim 8, further comprising: transmitting, by the terminal device, an indication to the network entity indicating the corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized.

11. 11. The method of claim 9, wherein the measurements by the terminal device are corrected by the network entity using the synchronization offset between the plurality of supporting terminal devices, and the location of the terminal device is determined by the network entity using the corrected measurements.

12. 1. A method for determining the location of a target terminal device, comprising: indicating to a target terminal device a sidelink synchronization source to which the terminal device is synchronized; transmitting a sidelink position reference signal to the target terminal device to enable determination of the target terminal device's position based on the sidelink position reference signal and the sidelink synchronization source; A method comprising performing steps including:

13. 13. The method of claim 12, further comprising receiving a request from the target terminal device for the sidelink synchronization source to which the terminal device is synchronized.

14. 13. The method of claim 12, further comprising transmitting to a location management entity the mapping between the sidelink synchronization source and a network device serving the terminal device.

15. 13. The method of claim 12, further comprising providing a synchronization offset between the terminal device and another terminal device to a location management entity, the synchronization offset being used to determine the location of the target terminal device.

16. 14. The method of claim 13, further comprising transmitting to a location management entity a mapping between identifiers of the sidelink synchronization sources and network devices serving the terminal device.

17. The method of claim 16 , wherein the mapping is used by the location management entity to determine the location of the target terminal device.

18. 1. A method for determining a location of a target terminal device, comprising: receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; using the indicated information to support determining the location of the target terminal device; and A method comprising performing steps including:

19. The method of claim 18 , further comprising obtaining a synchronization offset between the plurality of supporting terminal devices.

20. The method of claim 19 , further comprising determining a location of the target terminal device based on the synchronization offset among the plurality of supporting terminal devices.

21. 20. The method of claim 19, further comprising providing the synchronization offset between the plurality of support terminal devices to the target terminal device, wherein the synchronization offset between the plurality of support terminal devices is used to determine a position of the target terminal device.

22. means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; means for obtaining a location of the terminal device based on the indicated information of the corresponding sidelink synchronization source; A terminal device comprising:

23. A terminal device according to claim 22, further comprising means for carrying out the method of any of claims 2 to 11.

24. means for indicating to a target terminal device a sidelink synchronization source to which said terminal device is synchronized; means for transmitting a sidelink position reference signal to the target terminal device, the sidelink position reference signal enabling a determination of the target terminal device's position based on the sidelink position reference signal and the sidelink synchronization source; A terminal device comprising:

25. A terminal device according to claim 24, further comprising means for carrying out the method of any of claims 13 to 17.

26. means for receiving, from a plurality of supporting terminal devices, information indicating a corresponding sidelink synchronization source to which each of the plurality of supporting terminal devices is synchronized; means for supporting a position determination of a target terminal device using said indicated information; A location management entity comprising:

27. A location management entity according to claim 26, further comprising means for performing the method of any of claims 19 to 21.

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