WO2025183601A1

WO2025183601A1 - User equipment positioning method and apparatus

Info

Publication number: WO2025183601A1
Application number: PCT/SE2024/050194
Authority: WO
Inventors: Min Wang; Stefan WÄNSTEDT; Peter ÖKVIST
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2024-02-29
Filing date: 2024-02-29
Publication date: 2025-09-04
Anticipated expiration: 2026-08-29

Abstract

A method performed by a network node is described, alongside corresponding methods for a first user equipment and a second user equipment. The method for a network node comprises triggering a device-to-device (D2D) location verification procedure for a first user equipment (UE), transmitting a D2D location verification procedure request to the first UE, receiving D2D positioning measurement information based on the D2D location verification procedure request, and performing the D2D location verification procedure using the D2D positioning measurement information.

Description

USER EQUIPMENT POSITIONING METHOD AND APPARATUS

Technical Field

Embodiments of the present disclosure relate to methods and apparatus in communication networks, and particularly methods and apparatus for location verification in non-terrestrial communication networks.

Background

Fifth Generation (5G) and Fourth Generation (4G) New Radio (NR) cellular networks (for example 3rd Generation Partnership Project (3GPP) networks) may be implemented in a nonterrestrial network (NTN). A NTN system is a wireless communications system that operates above the surface of the Earth, often through the use of satellites. That is, a terrestrial network may comprise a radio network node (e.g. a base station (gNB), centralized unit base station (gNB-CU), distributed unit base station (gNB-DU), relay node, Integrated Access and Backhaul (IAB) node, Transmission and Reception Point (TRP), and/or radio network controller) and/or a core network node (e.g. Mobile Switching Centre (MSC), Mobility Management Entity (MME), Operations and Maintenance (O&M) Centre, Operational Support System (OSS), SelfOrganizing Networks (SON), and/or positioning nodes). NTNs are networks, or segments of networks, which use an airborne or space-borne vehicle such as a satellite to embark a transmission equipment relay node or base station.

There are several different types of satellite that may be employed in a NTN, some of which are outlined in Table 1 below:

Table 1 : A table detailing different types of satellite that may be present in a NTN.

A NTN network may comprise one or more of the platforms recited in Table 1. Alternatively or additionally, a NTN network may comprise any other platform type not recited in Table 1. A NTN network may further comprise one or more user equipments (UEs) which are serviced by the satellites or platforms within a targeted service area.

Known NTNs may comprise one or more satellite gateways that connect the NTN to a public data network. In an example, a GEO satellite may be fed by one or more satellite gateways that are deployed across the satellite targeted coverage. The satellite targeted coverage may be regional or continental coverage, for example, with each UE in a cell being served by one satellite gateway. In a further example, a non-GEO satellite may be served successively by one or more satellite gateways at a time. The wider network or system may then ensure service and feeder link continuity between each successive serving satellite gateway with a sufficient time duration to proceed with mobility anchoring and handover procedures. The NTN may further comprise a feeder link or radio link between each satellite gateway and the satellite or UAS platform. Additionally or alternatively, the NTN may further comprise a service link or radio link between each UE in the network and the satellite or UAS platform.

Furthermore, in a NTN a satellite or UAS platform may implement either a transparent or a regenerative payload. That is, a satellite may implement a transparent payload wherein a waveform signal is repeated by the payload with the waveform substantially unchanged. T ransparent payloads may include for example radio frequency filtering, frequency conversion, and frequency amplification. A satellite may also implement a regenerative payload wherein the satellite processes the waveform signal, wherein the satellite effectively has all of the functions of a base station (gNB) onboard the satellite. Regenerative payloads may include for example radio frequency filtering, frequency conversion, frequency amplification, frequency demodulation, frequency decoding, frequency switching and/or routing, frequency coding, and frequency modulation. Accordingly, a satellite in a NTN system may comprise processing circuitry and a memory configured to perform onboard processing of a payload. The satellite or UAS platform may generate several beams over a given service area bound by its field of view. The footprints of each beam may for example be elliptical in shape. The field of view of the satellite/UAS platform may depend on the on-board antenna diagram and/or the minimum elevation angle of the satellite.

For NTNs comprising two or more satellites (for example, forming a constellation of satellites), the NTN may further comprise inter-satellite links (ISL). ISLs may require regenerative payloads on the satellites which form the ISLs. Further, ISLs may operate in radio frequency (RF) bands or in optical frequency bands.

Figure 1 depicts various examples of NTN reference architectures. The architecture in Figure 1A includes a transparent satellite. The architecture in Figure 1 B includes a regenerative satellite without an ISL. The architecture in Figure 1C includes two regenerative satellites with an ISL. The architecture in Figure 1 D includes a regenerative satellite with a separate centralized unit base station (gNB-CU) and distributed unit base station (gNB-DU) .

As shown in each of Figure 1A, Figure 1 B, Figure 1C, and Figure 1 D, the NTN architecture includes a UE 102 and a public data network 122, with the architecture of Figure 1C comprising a plurality of UEs 102 and public data networks 122. Each NTN further includes a core network node (CN) 118, connected to the data network 122 via an N6 interface 120. Each architecture also includes a base station 108, connected to the CN node 118 via the NG interface 116. The gNB 108 may form a part of a satellite 106 in the NTN as shown in Figure 1 B and Figure 1 C, or may be formed as part of a separate node as shown in Figure 1A. Alternatively, the NTN may have a separate gNB-CU 108 and gNB-DU 108 as shown in Figure 1 D. Each UE 102 and gNB 108 (or more specifically the gNB-DU as in the case of Figure 1 D) may be connected by a service link 114 or radio link 114, which more specifically may be a NR Uu connection (wherein a Uu connection is a connection between a UE and the network, for example a gNB). The CN 118 and the gNB 108 (or more specifically the gNB-CU as in the case of Figure 1 D) may be connected by a NG interface 116. The NG interface 116 may be implemented over a Satellite-Radio Interface (SRI).

As shown in Figure 1 , the NTN may comprise a Next-Generation Radio Access Network 104 (NG-RAN) comprising the gNB 108 and satellite 106 (either integrated or separate) alongside a NTN gateway 112. As shown in Figure 1 C, a NTN gateway 112 may be provided for each satellite 106. The satellite 106 and NTN gateway 112 may together be considered to be a Remote Radio Unit 110. Furthermore, as depicted in Figure 1C, a ISL 124 may be present between the satellites 106 of the NTN. In addition to the architectures presented in Figure 1 , some NTNs may include multiconnectivity capabilities, where transparent or regenerative NTN-based NG-RAN systems are combined with terrestrial-based NG-RAN systems or further NTN-based NG-RAN systems. In such systems, a UE may be connected and served simultaneously by a NTN-based NG-RAN and a terrestrial based access, which may be either NR or Evolved Universal Terrestrial Radio Access (EUTRA). Alternatively, a UE may be connected and served simultaneously by a NTN- based NG-RAN and a further NTN-based NG-RAN.

NTN may operate using beam-based coverage, using the typical beam footprint sizes outlined in Table 1 . Figure 2 depicts examples of reference NTN architectures based on a regenerative payload with beam-based coverage. The reference NTN architectures as shown in Figure 2A and Figure 2B comprise one or more user equipments 202, one or more satellites or UAS platforms 206, and a gateway 212. The gateway 212 is connected to a data network 222. The satellites 206 are connected to one another by an ISL 224, and the satellites 206 are further connected to the gateway 212 by feeder links 228. The gateway 212 may further be connected to or integrated with a base station 208. A satellite 206 is connected to the user equipments 202 via a service link or access link 214. The service link 214 may be implemented using one or more beams that each form a beam footprint or spotbeam 226.

Figure 2A depicts an example NTN scenario based on a regenerative payload, with beambased coverage. Figure 2B depicts a specific example NTN scenario of a bent pipe transponder architecture, which is a form of transparent payload architecture. In a bent pipe transponder architecture as shown in Figure 2B, the gNB or base station may be integrated in the gateway or connected to the gateway via a terrestrial connection (for example, one or more of: wire, optic fibre, and/or wireless link).

As shown in Figure 1 and Figure 2, NTN systems rely on communication between satellites and user equipments, with the satellites often being located at significant orbit heights as detailed in Table 1. Accordingly, NTN systems may be characterised by a path loss that is higher than the expected path loss of terrestrial networks. To overcome this pathloss, example architectures may require that the access and feeder links are operated in line-of-sight conditions and/or that the UE is equipped with an antenna offering high beam directivity.

As shown in Figure 2A, a communication satellite may generate a plurality of beams over a given area. Each beam may be considered as having a corresponding footprint, and each footprint may be elliptical. In example systems, the footprint of each beam may be considered as corresponding with a cell or a cell may be considered to consist of a plurality of beam footprints. The footprint of a beam may also be referred to as a spotbeam. The spotbeam may move over the surface of the Earth with the satellite’s movement and/or the Earth’s rotation, or may be fixed relative to a position on the surface of the Earth (for example, by use of a beam pointing mechanism used by the satellite to compensate for its motion). The size of the spotbeam may be dependent on the design of the NTN network, ranging from tens to thousands of kilometres as detailed in Table 1.

NTN systems may support one or more of the following types of beam footprints or cells:

• Earth-Fixed footprints/cells, which are provisioned by one or more beams continuously covering the same geographical areas (for example, in the case of a GEO satellite);

• Quasi-Earth-Fixed footprints/cells, which are provisioned by one or more beams covering one geographic area for a first time period and a different geographic area for a further time period (for example, in the case of Non-Geostationary (NGSO) Satellite Systems that generate steerable beams); and

• Earth-Moving footprints/cells, which are provisioned by one or more beams whose coverage area slides over the Earth’s surface (for example, in the case of NGSO Satellite Systems that generate fixed or non-steerable beams).

Of the three cell types outlined above, Quasi-Earth-Fixed cells and Earth-Moving cells may be more commonly deployed.

It should be noted that the terms “cell” and “beam” or “footprint” may be used interchangeably in this context.

In comparison to the cells of a terrestrial network, an NTN beam may provide a wider footprint and therefore may cover an area outside the area defined by the serving cell of the network. Beam footprints covering adjacent cells may overlap and cause intercell interference. This intercell interference may cause a notable impact to the signal strength of each spotbeam, for example because of the decrease in signal strength of the spotbeam in the outwards radial direction from the centre of the spotbeam. This decrease in signal strength may be caused by the high elevation angle and long distance to the network-side (or satellite-borne) transceiver which may result in a difference between the distance from the cell centre to the satellite and the distance from a point on the spotbeam edge to the satellite. To mitigate this interference, known NTN architectures may configure different cells with different carrier frequencies and polarization modes. In the case of moving cells, each cell (or beam footprint) moves across the surface of the Earth as its serving satellite moves along its orbit. In contrast, in the case of quasi-Earth-fixed cells the cell area remains fixed to the same geographical area regardless of satellite movement for a particular time period. In order to enable this, a serving satellite may have means for dynamically directing the beam(s) it generates such that the same area of the Earth is covered despite the movement of the satellite. However, as the satellite orbits around the Earth, the same satellite may only be able to cover the same area on Earth for a limited time (unless for example the satellite is in a geostationary orbit). Accordingly, for quasi-Earth-fixed cells different satellites may be tasked with covering a certain geographical cell area at different time periods. When this task is switched from one satellite to another, this results in one cell being replaced by another with both cells covering the same geographical area. A similar cell replacement process may occur when a satellite covering a certain geographical area switches its feeder link (for example, because it has moved away from its old gateway and/or gNB and becomes closer to another gateway and/or gNB). As a consequence of the cell replacement process, UEs connected in the old cell (that is, UEs in RRC_CONNECTED state located in the old cell) may have to be handed over or otherwise moved from the old cell to the new cell (for example, using RRC connection reestablishment), and UEs camping on the old cell (that is, UEs in one of RRCJDLE or RRCJNACTIVE state located in the old cell) may have to perform cell reselection to the new cell.

Cell switches may be implemented using a hard switch and/or a soft switch. In a hard switch system, there may be an instantaneous switch from the old cell to the new cell. That is, the new cell may appear in the same instance that the old cell disappears. However, such switching may result in interruptions to the handover process for UEs in the old cell and reduce the likelihood of seamless/interruption free handover. Further, hard switching may result in an overload of the access resources in the new cell, due to a peak in potential access attempts resulting from UEs in the old cell attempting to access the new cell immediately after the cell switch. In contrast, in a soft switch configuration there may be a time period during which the new cell and the old cell coexist and overlap, covering the same geographical area. This coexistence/overlap may allow time for connected UEs to be handed over from the old cell to the new cell, and/or for camping UEs to reselect to the new cell. This in turn may facilitate redistribution of the access load in the new cell and thereby provide better conditions for handovers with shorter interruption time. Accordingly, soft switch configurations may be preferred in quasi-Earth-fixed cell deployments.

In NR deployments, positioning is used to determine the location of a UE in a network. For example, an objective of positioning in Long Term Evolution (LTE) and/or NR networks is to fulfil regulatory requirements for emergency call localization with a target of achieving horizontal accuracy of under 50m. An example architecture for supporting positioning in NR is shown in Figure 3. As shown in Figure 3, the network comprises a UE 302, an NG-RAN 304 which may comprise a base station including a eNB/ng-eNB and/or a gNB 308, an Access and Mobility Management Function (AMF) 330, a Location Management Function or Location Node (LMF) 332, an Enhanced Serving Mobile Location Centre (E-SMLC) 334, and a Secure User Plane Location (SUPL) Location Platform (SLP) 336. The eNB 308 may comprise one or more Transmission Points (TP) and the gNB may comprise one or more TRPs.

In the architecture of Figure 3, the interactions between the gNB 308 and UE 302 are supported by the Radio Resource Control (RRC) protocol and so are NR-Uu interactions 314. In contrast, the eNB acts as a location node and interfaces with the UE via the LTE Positioning Protocol (LPP) using LTE-Uu interactions 314. LPP is a common protocol between both NR and LTE architectures. There are also interactions between the location note and the gNB via the NR Positioning Protocol-Annex (NRPPa) protocol. This may be via AMF 330 using Control Plane Interfaces (NG-C) or CN Gateways 320. The gNB and eNB may also interact through a connection Xn 324, for example an ISL.

Figure 4 depicts a signal diagram for a positioning procedure for a location service. The system of Figure 4 comprises a UE 402, base station 408, AMF 430, LMF 432, and various 5G Core Network (5GC) Location Services (LCS) and associated entities. When the AMF 430 receives a Location Service Request (for example, in the case of a UE 402 being in CM-IDLE state) the AMD performs a network triggered service request in order to establish a signalling connection with the UE and assign a specific serving gNB or NG-eNB. Accordingly, at the start of the flow shown in Figure 4 it is assumed that the UE 402 is in connected mode. That is, any signalling that might be required to bring UE 402 into connected mode prior to step 1a is not depicted in Figure 4. The signalling connection may however be later released (e.g. by the NG-RAN node as a result of signalling and data inactivity) including while positioning is ongoing.

As shown Step 1a of Figure 4, an entity in the 5GC (for example, a Gateway Mobile Location Center (GMLC)) may request a location service (for example, positioning services) for a target UE 402 to a serving AMF 430. Alternatively or additionally, as shown in Step 1b of Figure 4 the serving AMF 430 for the target UE may determine a need for a location service (for example, to locate the UE 402 for an emergency call). Further alternatively or additionally, as shown in Step 1c of Figure 4 the UE 402 may request a location service (for example, positioning or delivery of assistance data) to the serving AMF 430 at the Non-Access Stratum (NAS) level. That is, in each of the options for Step 1 , the serving AMF 430 for the UE 402 obtains a Location Service Request. As shown in Step 2 of Figure 4, the AMF 430 transmits the received Location Service Request to an LMF 432.

The LMF 432 may then instigate location procedures with the serving eNB/gNB (and optionally with further neighbouring eNB/gNB) in the NG-RAN, for example to obtain positioning measurements or assistance data as shown in Step 3a of Figure 4. Alternatively or additionally to Step 3a, the LMF 432 may instigate location procedures with the UE 402 (for example, to obtain a location estimate or positioning measurements or to transfer location assistance data to the UE) as shown in Step 3b of Figure 4. That is, in each of the options for Step 3, the LMF 432 may instigate location procedures to obtain positioning measurements and assistance data.

As shown in Step 4 of Figure 4, the LMF 432 may then provide a location service response to the AMD 430 and may include any necessary results (e.g. success or failure indication and, if requested and obtained, a location estimate for the UE 402).

If Step 1a is performed, the AMF 430 may return a location service response to the 5GC entity that transmitted the Location Service Request and include any needed results (for example, a location estimate for the UE 402). Alternatively or additionally, if Step 1 b is performed the AMF 430 may use the location service response received in Step 4 to assist the service that triggered the Location Service Request in Step 1 b (for example, the AMF 430 may provide a location estimate associated with an emergency call to a GMLC). Further alternatively or additionally, if Step 1c is performed then the AMF 430 may return a location service response to the UE 402 and may include any needed results (for example, a location estimate for the UE 402). In specific examples, Step 3a and Step 3b may involve different position methods to obtain location related measurements for a target UE and from these methods compute a further location estimate. Optionally, the methods may further compute additional UE information such as UE velocity.

3GPP NR Rel-18 Work Item “Revised WID: NR NTN (Non-Terrestrial Networks) enhancements” (RP-223534) defines network verified UE location methods as follows:

• “Based on RAN 1 conclusions of the study phase, RAN to prioritize the specification of necessary enhancements to multi-RTT to support the network verified UE location in NTN assuming a single satellite in view [RAN 1, 2, 3, 4],

• DL-TDoA methods for verification may be considered as lower priority and if time permits and condition in Note is satisfied." From the study objective of RP-223534, it is observed that the study will focus on enhancement of multi-RTT in NTN assuming a single satellite in view and that the solution will reuse the NR llu positioning framework as the baseline. Accordingly, in arrangements in which the above methods of positioning are performed in a NTN system, the satellite (acting as a TRP) may transmit positioning reference signals at multiple time instants (where the satellite location at each time instant may be considered as a virtual TRP). At each time instant, the UE may perform a downlink (DL) positioning measurement and provide the measurement results to the LMF. Similarly, the UE may transmit an uplink (UL) positioning reference signal (e.g. a Sounding Reference Signal (SRS)) at multiple time instances. Further, the satellite may perform UL positioning measurements at each time instant and provide the measurement results to the LMF. Based on the received positioning measurement results, the LMF may then compute the location of the UE. Further, in such a positioning procedure, the LMF may need to exchange corresponding positioning configurations and assisting information with each gNB/TRP and/or the UE.

Accordingly, positioning procedures may suffer from large signalling overheads and long latencies. A UE may not be allowed to run any service before its location is verified successfully, and a UE with critical latency requirements would fail to satisfy the QoS requirements due to the long latency introduced by the positioning procedure. This leads to an overall reduction in the efficiency and performance of the network. It may therefore be necessary to further develop solutions to reduce signalling overhead and latency in the positioning procedure in NTN networks.

Summary

It is an object of the present disclosure to provide positioning methods with improved efficiency, for example in NTN systems.

Embodiments of the disclosure aim to provide apparatuses and methods that alleviate some or all of the problems identified.

A first embodiment of the present disclosure provides method performed by a network node. The method comprises triggering a device-to-device (D2D) location verification procedure for a first UE, transmitting a D2D location verification procedure request to the first UE, receiving D2D positioning measurement information based on the D2D location verification procedure request, and performing the D2D location verification procedure using the D2D positioning measurement information.

A second embodiment of the present disclosure provides a method performed by a first UE. The method comprises receiving a D2D location verification procedure request from a network node, establishing a D2D positioning procedure with a second UE, and providing D2D positioning measurement information to the network node based on the established D2D positioning procedure.

A third embodiment of the present disclosure provides a method performed by a second UE. The method comprises establishing a D2D positioning procedure with a first UE based on a D2D location verification procedure request from a network node, and providing D2D positioning measurement information to the network node based on the established D2D positioning procedure.

A fourth embodiment of the present disclosure provides a method performed in a network. The network comprises a network node, a first UE, and a second UE. The method comprises triggering a D2D positioning procedure between the first UE and the second UE, and triggering a D2D location verification procedure between the first UE and the network node. The method further comprises providing D2D positioning measurement information to the network node based on the D2D positioning procedure, and performing the D2D location verification procedure at the network node using the D2D positioning measurement information.

A fifth embodiment of the present disclosure provides network node comprising processing circuitry and a memory containing instructions executable by the processing circuitry. The network node is configured to: trigger a D2D location verification procedure for a first UE, transmit a D2D location verification procedure request to the first UE, receive D2D positioning measurement information based on the D2D location verification procedure request, and perform the D2D location verification procedure using the D2D positioning measurement information.

A sixth embodiment of the present disclosure provides a first UE comprising processing circuitry and a memory containing instructions executable by the processing circuitry. The first user equipment is configured to receive a D2D location verification procedure request from a network node, establish a D2D positioning procedure with a second UE, and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

A seventh embodiment of the present disclosure provides a second UE comprising processing circuitry and a memory containing instructions executable by the processing circuitry. The second UE is configured to establish a D2D positioning procedure with a first UE based on a D2D location verification procedure request from a network node, and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

Further embodiments provide methods, network nodes and systems as discussed herein.

Brief Description of Drawings

For a better understanding of the present disclosure, and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1A, Figure 1 B, Figure 1C, and Figure 1 D (collectively referred to as Figure 1) are diagrams of various NTN reference architectures;

Figure 2A and Figure 2B (collectively referred to as Figure 2) are diagrams of further NTN reference architectures;

Figure 3 is a diagram of a positioning reference architecture;

Figure 4 is a signal diagram for a positioning procedure for a location service;

Figure 5 is a flowchart of a method for a network node, in accordance with embodiments;

Figure 6 is a flowchart of a method for a first UE, in accordance with embodiments;

Figure 7 is a flowchart of a method for a second UE, in accordance with embodiments;

Figure 8 is a flowchart of a method for a network, in accordance with embodiments;

Figure 9 is a schematic diagram of a network, in accordance with embodiments;

Figure 10A and Figure 10B (collectively referred to as Figure 10) are schematic diagrams of a user equipment, in accordance with embodiments;

Figure 11A and Figure 11 B (collectively referred to as Figure 11) are schematic diagrams of a user equipment, in accordance with embodiments; Figure 12A, Figure 12B, Figure 12C, and Figure 12D (collectively referred to as

Figure 12) are diagrams presenting an overview of multi-Round Trip Time methods, in accordance with embodiments;

Figure 13 is a flowchart of a sensing and resource selection procedure in accordance with embodiments;

Figure 14A and Figure 14B (collectively referred to as Figure 14) are timelines of a sensing and resource selection procedure in accordance with embodiments;

Figure 15A and Figure 15B (collectively referred to as Figure 15) are diagrams presenting sidelink positioning procedures in accordance with embodiments;

Figure 16 is a signal diagram of a positioning method, in accordance with embodiments;

Figure 17A and Figure 17B (collectively referred to as Figure 17) are further signal diagrams of a positioning method, in accordance with embodiments; and

Detailed Description

For the purpose of explanation, details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed. It will be apparent, however, to those skilled in the art that the embodiments may be implemented without these specific details or with an equivalent arrangement.

The following sets forth specific details, such as particular embodiments for purposes of explanation and not limitation. It will be appreciated by one skilled in the art that other embodiments may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as to not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers that are specially adapted to carry out the processing disclosed herein, based on the execution of such programs. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, the technology may additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understood to comprise one or more processors, one or more processing modules or one or more controllers, and the terms computer, processor, processing module and controller may be employed interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, the term “processor” or “controller” also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

The term “NTN node” is herein used to denote one or more radio network nodes or other equipments present at an airborne or space-borne vehicle such as a satellite or UAS platform, configured to receive radio signals from a UE operating on the surface of the Earth. NTN node receivers may have specific RF characteristics (e.g. sensitivity) and/or may operate in specific RF bands dedicated for NTN operation. NTN nodes may additionally comprise a gNB of a specific type, for example a gNB configured for NTN operation.

The terms “location server”, “LMF”, “E-SMLC”, and “positioning server” may be considered to be interchangeable and refer to other hardware capable of performing such functions and/or executing software. Similarly, the terms “gNB”, “eNB”, “base station”, “satellite” and “TRP” may be considered to be interchangeable and refer to other hardware capable of performing such functions and/or executing software. The terms “serving cell”, “serving satellite”, “neighbour cell”, and “neighbour satellite” may also be considered to be interchangeable and refer to other hardware capable of performing such functions and/or any associated executing software.

The term “time resource” as used herein may correspond to any type of physical resource or radio resource that may be expressed in terms of length of time. Examples of appropriate time resources may include: symbol, time slot, subframe, radio frame, time transmission interval (TTI), interleaving time, slot, sub-slot, and/or mini-slot.

Figure 5 is a flowchart of a method (S500) for a network node, in accordance with embodiments. As shown in Step S502 of Figure 5, the method may comprise the network node triggering a device-to-device (D2D) location verification procedure. The location verification procedure may be with reference to a first UE, wherein the first UE is a UE that is to have its location verified. The network node may Accordingly, the first UE may be a target UE for the positioning method.

As shown in Step S504 of Figure 5, the method may comprise the network node transmitting the D2D location verification procedure request to the first UE in order for the first UE to process the request. The network node may then receive D2D positioning measurement information as shown in Step S506 of Figure 5. The network node may receive the D2D positioning measurement information from the first UE and/or from another entity involved in the D2D procedure such as a second UE or anchor UE. Finally, the method may comprise the network node performing the D2D location verification procedure using the D2D positioning measurement information, as shown in S508 of Figure 5.

Figure 6 is a flowchart of a method (S600) for a first user equipment, in accordance with embodiments. This method may be implemented in an NTN concurrently with the method depicted in Figure 5, and is thus compatible with this method. As shown in Step S602 of Figure 6, the method may comprise the first UE receiving a D2D location verification procedure request from a network node. In response to receipt of this request, the first UE may establish a D2D positioning procedure with a second UE, as shown in step S604 of Figure 6. Following this, the first UE may provide or report D2D positioning measurement information to the network node as shown in Step S606 of Figure 6.

Figure 7 is a flowchart of a method (S700) for a second user equipment, in accordance with embodiments. This method may be implemented in an NTN concurrently with the methods depicted in Figure 5 and Figure 6, and is thus compatible with these methods. As shown in Step S702 of Figure 7, the method may comprise the second UE establishing a D2D positioning procedure with a first UE. Following this, the second UE may provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

Figure 8 is a flowchart of a method (S800) for a network, in accordance with embodiments. In particular, this method is analogous to a network in which the methods of Figure 5, Figure 6, and Figure 7 are implemented simultaneously. Accordingly, the network in which the method of Figure 8 is implemented may include a network node, a first UE, and a second UE. This method may comprise triggering a D2D positioning procedure between a first UE and a second UE (Step S802 of Figure 8) and triggering a D2D location verification procedure between a first UE and a network node (Step S804 of Figure 8). As shown in Figure 8, the method may further comprise providing D2D positioning measurement information to the network node based on the D2D positioning procedure. Following this, the method may comprise performing the D2D location verification procedure at the network node using the D2D positioning measurement information, as shown in Step S808 of Figure 8.

The method of Figure 8 may be performed by any suitable apparatus, for example a communication network. An example of a suitable network node is depicted in Figure 9. As depicted in Figure 9, the communication network 900 performing the method may comprise a first user equipment 902, a second user equipment 904, and a network node 906. An example of a user equipment suitable for use in the communication network 900 as a first user equipment 902 and/or a second user equipment 904 is depicted in Figure 10.

As depicted in Figure 10A, the UE 1000 (which may be a first UE or a second UE) may comprise a processor 1002, interfaces 1004, and a memory 1006 storing a computer program 1008. The steps of the method, for example as depicted in Figure 6 or Figure 7, may be performed in accordance with the computer program 1008 stored on the memory 1006, and may be executed by the processor 1002 in conjunction with one or more interfaces 1004.

Accordingly, the first UE may comprise processing circuitry and a memory containing instructions executable by the processing circuitry, whereby the first UE is configured to receive a D2D location verification procedure request from a network node, establish a D2D positioning procedure with a second UE, and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

Alternatively or additionally, the second UE may comprise processing circuitry and a memory containing instructions executable by the processing circuitry, whereby the second UE is configured to establish a D2D positioning procedure with a first UE based on a D2D location verification procedure request from a network node, and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

As depicted in Figure 10B, the method step of receiving a D2D location verification procedure request from a network node (Step S602) may be performed by a receiver 1014 of the UE 1000. The method step of establishing a D2D positioning procedure with a second UE (Step S604) may be performed by an establisher 1010 of the UE 1000. The step of providing D2D positioning measurement information to a network node based on the established D2D positioning procedure (Step S606) may be performed by a provider 1012 of the UE 1000.

Alternatively, the method step of establishing a D2D positioning procedure with a first UE based on a D2D location verification procedure request from a network node (Step S702) may be performed by an establisher 1010 of the UE 1000. The method step of providing D2D positioning measurement information to the network node based on the established D2D positioning procedure (Step S704) may be performed by a provider 1012 of the UE 1000.

An example of a network node 906 suitable for use in the communication network 900 is depicted in Figure 11. As depicted in Figure 11 A, the network node 1100 may comprise a processor 1102, interfaces 1104, and a memory 1106 storing a computer program 1108. The steps of the method, for example as depicted in Figure 5, may be performed in accordance with the computer program 1108 stored on the memory 1106, and may be executed by the processor 1102 in conjunction with one or more interfaces 1104.

Accordingly, the network node may comprise processing circuitry and a memory containing instructions executable by the processing circuitry, whereby the network node is configured to: trigger a D2D location verification procedure for a first UE, transmit a D2D location verification procedure request to the first UE, receive D2D positioning measurement information based on the D2D location verification procedure request, and perform the D2D location verification procedure using the D2D positioning measurement information.

As depicted in Figure 11 B, the method step of triggering a D2D location verification procedure for a first user equipment (Step S502) may be performed by a trigger 1114 of the network node 1100. The method step of transmitting a D2D location verification procedure request to the first UE (Step S504) may be performed by a transmitter 1110 of the network node 1100. The method step of receiving D2D positioning measurement information based on the D2D location verification procedure request (Step S506) may be performed by a receiver 1112 of the network node 1100. The method step of performing the D2D location verification procedure using the D2D positioning measurement information (Step S508) may be performed by a performer 1116 of the network node 1100.

In a specific example of the above methods, a UE in RRCJDLE mode may attempt to access an NTN network. In response, a network entity or network node in the network (for example, an LMF) may attempt to position the UE. In accordance with the present disclosure, the network node may use D2D positioning to assist and/or bolster the positioning procedure.

In specific embodiments, the first UE may be configured to determine whether the network node supports a D2D location verification procedure. For example, the first UE may read the System Information Blocks (SIBs) in the NTN cell and performing a check of whether the satellite/network node of the NTN supports network verified UE location processes. The first UE may more specifically check if the SIB carries information that the network node supports D2D positioning procedures. If supported, the NTN network node may correspondingly provide D2D positioning resources (for example, the D2D location verification procedure request) in the SIB. The NTN network node may indicate whether it supports the feature of network verified UE location by configuring or providing UE location network verification settings in the SIBs. For example, the NTN cell may be determined to support for the feature of UE location network verification if the feature related settings are present in the SIBs of the NTN cell. Alternatively or additionally, the NTN cell may be determined to not support the feature of UE location network verification if the feature related settings are not present in the SIBs of the NTN cell. The feature related settings may comprise one or more of the following: settings relating to configuration of a positioning reference point (e.g. onboard the satellite/network node, on the gNB, and/or the uplink time synchronization reference point), settings relating to specifying cell supported positioning methods, settings relating to configuration of positioning reference signal resources, Ephemeris data, Koffset data, Kmac data, and/or settings defining assistance information of a TRP positioning procedure.

Alternatively or additionally, the NTN network node may indicate whether it supports the feature of network verified UE location by transmitting an explicit indicator indicating whether the NTN cell supports the feature of network verified UE location. This explicit indicator may be signalled in the SIBs. For example, the indicator may be a binary indicator with two values, wherein a first value indicates that the NTN cell supports the feature of network verified UE location and a second value indicates that the NTN cell does not support the feature of network verified UE location. Alternatively, the indicator may be a single-value indicator wherein the presence of the indicator indicates that the NTN cell supports the feature of network verified UE location and the absence of the indicator indicates that the NTN cell does not support the feature of network verified UE location. Further alternatively, the indicator may be a singlevalue indicator wherein the absence of the indicator indicates that the NTN cell supports the feature of network verified UE location, and the presence of the indicator indicates that the NTN cell does not support the feature of network verified UE location.

Once the first UE has determined that the NTN cell supports network verified UE location processes, the first UE may initiate D2D procedures to enable or apply a D2D positioning procedures with a selected second UEs. Each second UE may be a neighbouring UE, and in more specific embodiments a plurality of neighbouring UEs may be employed as second UEs. In addition to the D2D positioning procedure, the first UE may also initiate an access procedure towards the NTN cell to set up an RRC connection. That is, the first UE may be configured to establish a RRC Connection between a base station and the first UE. Alternatively or additionally, the network node may be configured to establish a RRC Connection between a base station and the first UE. The first UE may establish the D2D positioning procedure with the second UE in parallel with establishing the RRC connection between the base station and the first UE. Alternatively, the first UE may establish the D2D positioning procedure with the second UE sequentially with establishing the RRC connection between the base station and the first UE. That is, the first UE performs a first procedure (either establishing the RRC connection between the base station and the first UE or establish the D2D positioning procedure with the second UE) and after completion of the first procedure the first UE initiates the remaining of the two procedures.

During the D2D positioning procedure, the first UE may operate as a target UE. That is, the first UE may operate as the UE to be positioned. The second UE may accordingly be an anchor UE. That is, the second UE may operate as a reference UE which provides positioning assistance to the first UE.

In order to undertake a D2D positioning procedure, the first UE may determine or select a second UE. This determination may be based on the received D2D location verification procedure request. Alternatively, the selection of a second UE may be performed by another UE, such as a positioning server UE. Accordingly, the network node and/or the first UE may be configured to receive an indication of an identity of the second UE from a positioning server UE. Alternatively or additionally, the network node may be configured determine a second UE for the D2D location verification procedure. For example, the network node may be configured to perform a selection process for the second UE. Alternatively, the network node may be configured to receive an indication of an identity of the second UE from the first UE. However, having the first UE or positioning server UE perform the selection process may improve the speed of the positioning procedure. The second UE may be configured to establish the D2D positioning procedure with the first UE via a positioning server UE. Alternatively or additionally, the second UE may be configured to establish the D2D positioning procedure with the first UE via the network node.

The determination of one or more second UEs may be based on one or more of the following criteria:

• if the second UE supports a D2D positioning procedure;

• if the location of the second UE has previously been verified by the network node (that is, if the location of the second UE is known);

• if the radio channel quality between the first UE and the second UE is above a certain and/or pre-configured threshold (and in a more specific example, wherein the threshold is measured in days or hours); and/or

• if the first UE and second UE hold a trust relation. Where one or more second UEs have been selected, the network may determine that D2D procedures are enabled in order to undertake D2D procedures. Accordingly, specific examples may comprise determining, by the first UE, to enable D2D procedures and transmitting an indication, by the first UE to the network node, indicating that D2D procedures are enabled. Alternatively, specific examples may comprise determining, by the network node, to enable D2D procedures.

Any of the first UE and/or the one or more second UEs may be configured to transmit D2D positioning measurement information to the network node. That is, the first UE and/or any second UEs may be configured to collect D2D positioning measurement information, and then may forward the D2D positioning measurement information to the network node and/or to a further positioning server UE. Accordingly, the network node may receive the D2D positioning measurement information from the first UE and/or the second UE. Specific methods may comprise transmitting the D2D positioning measurement information from the or each second UE to the first UE, and transmitting the D2D positioning measurement information from the first UE to the network node. Alternatively, specific methods may comprise transmitting the D2D position measurement information from the or each second UE to the network node. Alternatively or additionally, the gNB/eNB present in the network may assist in the collection and transmission of D2D positioning measurement information to the network node. Accordingly, the gNB may signal D2D positioning measurement information to the network node.

In general, after the RRC connection is established, the network node may trigger a further location verification procedure for the first UE. Accordingly, the network node may be configured to transmit a D2D location verification procedure request comprising an indication that a further positioning method is to be undertaken. The location verification procedure may require the first UE and the satellites/TRPs to perform a Uu positioning method in order for the network node to verify the location of the first UE. In specific examples, the further positioning procedure is one or more of: a multiple Round Trip Time (multi-RTT) positioning method, a Time Difference of Arrival (TDOA) positioning method, a Angle of Departure (AoD) positioning method, an Angle of Arrival (AoA) positioning method, a New Radio Enhanced Cell Identification (NR E-CID) positioning method, and Assisted Global Navigation Satellite System (GNSS) positioning.

Enhanced Cell ID positioning methods associate a device (such as a first UE) to the serving area of a serving cell, and then may further determine a finer granularity of UE position using further information. NR E-CID positioning techniques specifically use additional UE measurements and/or NR radio resource measurements to improve the UE location estimate.

Assisted GNSS positioning involves retrieving GNSS information by a device (e.g. first UE or network node) which is used to determine the location of the first UE in combination with assistance information provided to the device by the E-SMLC of the network.

TDOA positioning methods include Uplink TDOA (UL-TDOA) methods and Downlink TDOA (DL-TDOA) methods. DL-TDOA methods use positioning measurements performed by a UE (for example, the first UE, second UE, or positioning server UE) on a Positioning Reference Signal (PRS) transmitted by multiple TRPs. For example, the positioning measurements for DL-TDOA methods may include downlink reference signal time difference (DL RSTD) measurements. In contrast, UL-TDOA position methods use positioning measurements performed by the network node on uplink signals transmitted by the first UE at multiple TRPs. The reference points may measure the UL-TDOA (and may optionally further measure UL SRS Reference Signal Received Power (RSRP)) of the received signals using assistance data received from a further positioning server, and the resulting measurements may be used alongside other configuration information to estimate the location of the UE.

Multi-RTT positioning methods use multiple RTT measurements for first UE position estimation. For each RTT measurement, the first UE time difference and the network node time difference are measured. That is, a round trip time from measurements in downlink and uplink is determined for positioning purposes. An example of an embodiment implementing Multi-RTT positioning methods is depicted in Figure 12.

As detailed above, NR provides DL-PRS and UL-SRS signals. The DL-PRS signal may be a permuted and staggered comb Quadrature Phase Shift Keying (comb-QPSK) signal carrying a pseudonoise (PN) sequence, while the UL-SRS signal may be a regular comb signal carrying a Zadoff-Chu sequence. Both types of signals may be correlated at the respective end point with a corresponding replica signal. The time instance where the correlation peak occurs may allow for a determination of a delay between the transmitter and receiver.

As shown in Figure 12A, for each pair of UE and gNB, RTT may be calculated using Equation 1 :

RTT = gNB_Rx — gNB_Tx — (UE_Rx — UE_Tx)

Equation 1 where gNB_Tx is the time that a first signal is transmitted by the gNB 1202, UE_Rx is the time that the first signal is received by the UE 1204, UE_Tx is the time that a second signal is transmitted by the UE 1204, and gNB_Rx is the time that the second signal is received by the gNB 1202.

As shown in Figure 12B, an RTT may be determined between a UE 1204 (for example, the first UE) and multiple gNBs 1202. The gNBs 1202 therefore provide static locations which may be used as reference points when determining the location of the UE. In the specific example of Figure 12B, RTT 1 may be determined between the UE 1204 and a first gNB acting as static location 1. RTT2 may be determined between the UE 1204 and a second gNB acting as static location 2. RTT3 may be determined between the UE 1204 and a third gNB acting as static location 3. RTT4 may be determined between the UE 1204 and a fourth gNB acting as static location 4. Each of RTT1 , RTT2, RTT3, and RTT4 may be calculated using Equation 1. After RTTS for all pairs of gNB and UE are determined, an LMF or positioning server may estimate the distance between the UE and each gNB, and in turn the UE position relative to each gNB may be determined.

A more specific example depicting multi-RTT based UE location verification in NTN is depicted in Figure 12C. In this case, the network may configure positioning resources. The network may also configure the period of RTT measurement. After triggering measurements, the first UE 1204 and/or the network node 1202 may periodically measure DL-PRS and transmit UL-SRS resources according to the configured positioning resources. From this, the network node 1202 and/or first UE 1204 may report a time difference measurement to a positioning server. The reporting may occur for example after each measurement, or in bulk once all measurements are completed. After the measurements are reported, the positioning server may determine the RTTs (for example using Equation 1) and calculate the position of the first UE.

As shown in Figure 12C, in each RTT measurement the gNB 1202 may transmit a DL-PRS at time tdO in downlink towards a first UE 1204. The satellite 1206 of the NTN may receive and transmit the PRS to the first UE 1204 at time td 1 , and the first UE 1204 may receive and start to measure the PRS at time td2. In a corresponding manner, the first UE 1204 may transmit SRS towards the gNB 1202 at time tuO. The satellite node 1206 may receive and transmit the SRS to the gNB 1202 at time tu1 , and the gNB 1202 may receive and start to measure SRS at time tu2.

In this way, an RTT from the view of the gNB 1202 (RTT_gNEt) may be determined at or after tu2 using Equation 2: RTTg _{N B} — (tu₂ tdo) (tu₀ td₂~)

Equation 2

Further, a practical RTT from the view of the satellite (RTT_sat) may be determined using Equation 3:

Equation 3

It should be understood that the specific timing sequences depicted above are one definition of RTT, and that further definitions may be available and suitable for implementation in a NTN system. Accordingly, other suitable definitions of RTT may be applied to the present examples interchangeably where appropriate.

The time sequence depicted in Figures 12A and 12C may be repeated, as shown in Figure 12D. That is, the time sequence between gNB 1202, satellite 1206, and first UE 1204 may be repeated at least at times T1 , T2, and T3. In Figure 12D, T1 indicates a time in which a first RTT measurement may be started, need, triggered, or initiated. Similarly, T2 indicates a time in which a second RTT measurement may be started, need, triggered, or initiated. T3 indicates a time in which a third RTT measurement may be started, need, triggered, or initiated. Accordingly, T1 , T2, and T3 all fall within one multi-RTT measurement. In a specific example, T1 may be equal to tdO, td1 , td2, tuO, tu1 , and/or tu2 depending on the node being analysed. The time sequence definitions provided in Figure 12D (that is, with respect to T1 , T2, and T3) may be referred to or considered as positioning measurement sequences, set of positioning measurements, positioning measurement sets, and/or repeating positioning measurements.

In specific examples, when estimating the location of the first UE using RTT measurements it is important to know the location of the TRP/satellite transmitting PRS resource(s) which the first UE may use to perform time difference measurements (for example, tu2 and tdO in Equation 2). In order to achieve this in NR multi-RTT positioning, TRPs may be deployed at fixed locations (as shown in Figure 12B) and each TRP may provide a DL-PRS ID that is unique to that TRP in the assistance data. In NTN networks where a satellite is to be used for UE position estimation, due to the mobile nature of the satellite the positioning server or LMF may provide time instances to the gNB and/or the first UE in which the gNB/first UE is to perform time difference measurement. Alternatively or additionally, the positioning server may provide assistance data to the satellite node for performing time difference measurements for position estimation of the first UE. Accordingly, the mobile satellites transmitting PRS resources, calculation of a distance or range for position estimation Range_sat-UE may be calculated using Equation 4:

Equation 4 where P_UE and P_sat are position estimates for the first UE and satellite respectively at the associated time estimated using multi-RTT measurements, and c is the speed of light.

In specific examples, the assistance data provided to the UE by the positioning server may include a time instance (for example td1) at which the first UE should perform positioning measurements on the DL PRS resource(s) transmitted by the satellite node. The assistance data may also include a time instance (for example tuO) when the first UE should configure to start transmission of SRS resource(s) for positioning measurement(s).

In NTN systems, there may be one or more satellites involved in a positioning procedure for a first UE. In a system where a single satellite is involved in the positioning procedure, the first UE may perform RTT measurements with the same satellite at different locations. Accordingly, these multiple measurements may be used to estimate the first UE position with reference to the Earth. NTN assistance data may consider mobile TRPs where multiple RTT measurements are performed on the PRS transmitted by the same satellite from different locations at different time instants. In order to locate a first UE or target UE, the multiple measurement instances may be taken together to mimic different TRPs. Therefore, at each measurement instance, both the first UE and satellite/gNB may need to provide position and/or time difference reports.

In addition, if there are multiple satellites available for target UE positioning, the above methods may be repeated using a plurality of satellites to further improve the accuracy of position estimation.

AoD positioning methods, and more specifically downlink AoD (DL-AoD) methods, measure DL PRS RSRP of downlink signals received from multiple TRPs at the UE. That is, the first UE measures the DL PRS RSRP of the received signals using assistance data received from a positioning server of the network, and a network device then uses the resulting measurements alongside other configuration information to estimate the first UE position.

AoA positioning methods, and more specifically uplink AoA (UL-AoA) methods, measure azimuth (A-AoA) and zenith (Z-AoA) angles of arrival at multiple TRPs of uplink signals transmitted by the UE. That is, the TRPs measure A-AoA and Z-AoA of signals received from the first UE using assistance data received from the positioning server of the network, and a network device then uses the resulting measurements alongside other configuration information to estimate the first UE position.

Accordingly, the further location verification procedures may fall into one of the following categories:

• UE-Assisted, wherein the UE performs measurements with or without assistance from the network and may further send these measurements to a network E-SMLC where the position calculation may take place;

• UE-Based, wherein the UE performs measurements and calculates its own position with assistance from the network; and

• Standalone, wherein the UE performs measurements and calculates its own position without network assistance.

In comparison to LTE, NR positioning may benefit from larger bandwidth and finer beamforming and may therefore localize a user equipment (UE) with higher accuracy. Accordingly, NR networks including NTN may support any of the above positioning methods, and it will be appreciated that in examples where one of the methods above is specified any of the remaining methods may be substituted as appropriate.

In some examples, the first UE may have already completed its D2D positioning procedure (between the first UE and the second UE) when it receives the D2D location verification procedure request from the network node. If the D2D positioning procedure has not been completed when the request is received, the UE may wait until the D2D positioning procedure is completed before joining the location verification procedure initiated by the network node and/or reporting positioning measurement results to the positioning server. In such a case, the first UE may transmit an indication to the network node, indicating that the first UE is undertaking a D2D positioning procedure. The network node may accordingly be configured to receive an indication from the first UE indicating that the first UE is undertaking a D2D positioning procedure.

Upon receiving the D2D location verification procedure request from the network node, indicating that the first UE needs to join the location verification procedure, the first UE may report the estimated first UE location computed using the D2D positioning procedure to the network node. Alternatively or additionally, the first UE may report the D2D positioning measurement information directly to the network node, such that the network node may estimate the first UE location. Accordingly, in some examples the network node may comprise a positioning server/LMF.

In other embodiments, one or more second UEs or anchor UEs which formed a part of the D2D positioning procedure may report D2D positioning measurement information to the network node, for example by transmitting D2D positioning measurement information directly to the network node and/or reporting the estimated first UE location computed using the D2D positioning procedure to the network node. The second UEs may provide D2D positioning measurement information to the network node as well as or instead of the first UE.

Furthermore, a positioning server UE which formed a part of the D2D positioning procedure may report D2D positioning measurement information to the network node, for example by transmitting D2D positioning measurement information directly to the network node and/or reporting the estimated first UE location computed using the D2D positioning procedure to the network node.

Where the system allows a second UE or positioning server UE to report D2D positioning measurement information to the network node, this D2D positioning measurement information to the network node may be compared to the D2D positioning measurement information to the network node provided by the first UE for verification. This may allow for detection of untrustworthy or malicious UEs (e.g. a second UE or positioning server UE that is providing false information to the network), particularly in situations where the position of the first UE has already been verified or estimated using a further positioning method.

If the location of the first UE is successfully verified by the network with the assistance of D2D positioning methods, an ongoing verification procedure being performed by the UE and/or network node (for example, any of the Uu methods detailed above) may be terminated early without waiting for the ongoing verification procedure to complete. Accordingly, the network node may be configured to terminate an ongoing Uu positioning method performed by the network node, based on the received indication. Alternatively or additionally, the first UE may be configured to receive an indication from the network node indicating that the D2D location verification procedure has successfully verified the location of the first UE and may further be configured to terminate an ongoing further location verification procedure performed by the first UE, based on the received indication.

In further examples, further verification procedure being performed by the network node and/or the first UE may be omitted or skipped if the network node has determined that the location of the first UE is being verified or has already been successfully verified using a D2D positioning procedure. In order to facilitate this, the network node may be configured to receive an indication from the first UE indicating that the first UE has previously undertaken a device-to- device positioning procedure at a time that is below a certain threshold. In a specific example, the threshold may be measured in seconds. In a further specific example, the threshold may be equal to a verification threshold divided by the UE's mobility speed. The verification threshold may be 10km.

The network node may be further configured to terminate or omit an ongoing Uu positioning method performed by the network node, based on the received indication. The first UE may be configured to transmit transmitting an indication to the network node indicating that the first UE is undertaking a device-to-device positioning procedure for this purpose.

Where the D2D positioning procedure between the first UE and second UE was initiated earlier than the location verification procedure between the network node and the first UE, by providing D2D positioning measurement information to the network node the location of the first UE may be verified faster than if the D2D positioning measurement information had not been made available.

In order to determine that a first UE location has been verified, the network node may be configured to determine a difference between the D2D positioning measurement information and expected positioning measurement information, and determine that the D2D positioning measurement information is verified if the difference is less than a predetermined threshold. Furthermore, the network node may be configured to determine that the first UE is a trusted UE (wherein a trusted UE is a UE with a known location) if the D2D location verification procedure successfully verifies a location of the first UE. If the D2D location verification procedure successfully verifies a location of the first UE, the network node may transmit an indication from the network node to the first UE indicating that the D2D location verification procedure has successfully verified the location of the first UE.

Where the location of the first UE has been verified successfully, the UE may begin or continue its RRC connection setup procedure, in order to set up a Packet Data Unit (PDU) session and Data Radio Bearers (DRBs) for subsequent data transmission and/or reception. That is, the network node may be configured to establish a RRC connection between a base station and the first UE. Alternatively or additionally, the network node may be configured to terminate the RRC connection between the base station and the first UE if the D2D location verification procedure fails to verify a location of the first UE. Further, the first UE may be configured to establish a RRC Connection between a base station and the first UE. Alternatively or additionally, the first UE may be configured to terminate the RRC connection between the base station and the first UE if the D2D location verification procedure fails to verify a location of the first UE.

The D2D positioning measurement information may be one or more of: Sidelink (SL) positioning measurement information, Bluetooth positioning measurement information, Zigbee positioning measurement information, and Wi-Fi positioning measurement information. Accordingly, in specific examples the D2D positioning procedure may be one or more of: a SL positioning procedure, a Bluetooth positioning procedure, a Zigbee positioning procedure, and a Wi-Fi positioning procedure. As detailed above, any one of the above specific positioning methods which are supported by the NTN cell may be indicated in the SIBs of the cell.

In specific arrangements, SL positioning measurement information is used to verify the location of a first UE. Sidelink transmissions over NR are enhancements of Proximity Based Services (ProSe) specified for LTE. In particular, enhancements include:

• Added support for unicast and groupcast transmissions, wherein the Physical Sidelink Feedback Channel (PSFCH) is introduced for a receiver UE to reply a decoding status to a transmitter UE;

• Grant-free transmissions are provided in NR sidelink transmissions to improve latency performance;

• Enhanced channel sensing and resource selection procedures are supported in order to reduce collisions among SL transmissions launched from different UEs, which in turn may result in new designs of PSCCH; and

• Congestion control and QoS management may be supported in NR SL transmissions to improve connection density.

In order to enable the above enhancements, the following physical channels and reference signals are introduced in NR:

• Physical Sidelink Shared Channel (PSSCH): PSSCH may be transmitted by a SL transmitter UE to convey SL transmission data, SIBs for RRC configuration, and part of the SL control information (SCI);

• Physical Sidelink Feedback Channel (PSFCH): PSFCH may be transmitted by a SL receiver UE for unicast and groupcast to convey 1 bit of information over 1 resource block for Hybrid Automatic Repeat Request (HARQ) acknowledgement (ACK) and negative ACK (NACK). In some systems, channel state information (CSI) may be carried in the medium access control (MAC) control element (CE) over PSSCH rather than PSFCH;

• Physical Sidelink Common Control Channel (PSCCH): PSCCH may be transmitted by a transmitter UE when the traffic to be sent to a receiver UE arrives at the transmitter UE, to convey a part of the SCI to be decoded by any UE for channel sensing purposes. The SCI may include for example the reserved time-frequency resources for transmissions, and demodulation reference signal (DM RS) patterns and antenna ports.

• Sidelink Primary/Secondary Synchronization Signal (S-PSS/S-SSS): through detecting S-PSS/S-SSS, a UE may determine the characteristics of the UE transmitting the S- PSS/S-SSS. A UE may for example perform an initial cell search involving a series of processes to acquire timing and frequency synchronization measurements together with the Synchronization Signal IDs (SSIDs) of the other UEs. It should be noted that the UE sending the S-PSS/S-SSS may not necessarily be involved in SL transmissions. Further, a node (e.g. UE, gNB, eNB, etc) sending the S-PSS/S-SSS may be referred to as a synchronization source. In specific embodiments, there may be 2 S-PSS sequences and 336 S-SSS sequences forming a total of 672 SSIDs in a cell.

• Physical Sidelink Broadcast Channel (PSBCH): PSBCH may be transmitted as a synchronization signal or PSBCH block (SSB), for example alongside S-PSS/S-SSS signals. The SSB may have the same numerology as the PSSCH and/or PSCCH on that carrier. The SBB may be transmitted within the bandwidth of the configured Bandwidth Part (BWP). The PSBCH may convey information related to synchronization, for example one or more of: a direct frame number (DFN), an indication of a slot and/or symbol level time resources for sidelink transmissions, and/or in-coverage indicator. In specific examples, the SSB may be transmitted periodically, for example at every 160 ms.

• Demodulation Reference Signals (DMRS), Phase Tracking Reference Signals (PT- RS), and Channel State Information Reference Signals (CSIRS): These physical reference signals may be supported by NR downlink/uplink transmissions may further be adopted by sidelink transmissions. In some examples, the PT-RS may only be applicable for Frequency Range 2 (FR2) transmissions.

In addition, two-stage sidelink control information (SCI) may be used to support SL positioning measurement information. That is, the Downlink Control Information (DCI) forthe SL procedure may comprise two-stage SCI. In some embodiments, only part of the SCI is sent on the PSCCH. For example, only a first stage of the SCI may be sent on the PSCCH. The first stage may be used for channel sensing purposes, for example sensing time-frequency resources for transmissions, DMRS patterns, and/or antenna ports. The first stage SCI may also be readable by all UEs in a network. In contrast, the second stage SCI may comprise scheduling and control information, for example 8-bit source identity (ID) information, 16-bit destination ID, Network Device Interface (NDI) information, Remote Video (RV) information, and/or HARQ process ID. The second stage SCI may be sent on the PSSCH to be decoded by the receiver UE, for example a first UE or a second UE.

NR SL transmissions may have two modes of resources allocation. For example, in a first mode (Mode 1) the SL resources may be scheduled by a gNB. In a second mode (Mode 2) the UE may autonomously select SL resources from one or more configured or pre-configured SL resource pools based on the channel sensing mechanism. For an in-coverage UE, either Mode 1 or Mode 2 may be used for SL transmissions. For an out-of-coverage UE, Mode 2 may be used for SL transmissions.

Mode 1 supports both a dynamic grant of resources and a configured grant of resources. In dynamic grant, when the traffic to be sent over SL arrives at a transmitter UE, the transmitter UE may launch a four-message exchange procedure to request SL resources from a gNB (for example, status report (SR) on UL grant, and/or buffer status report (BSR) on UL grant for data on SL sent to the UE). During a resource request procedure, a gNB may allocate a SL radio network temporary identifier (SL-RNTI) to the transmitter UE. If the SL resource request is granted by a gNB, then the gNB may indicate the resource allocation for the PSCCH and the PSSCH in the DCI conveyed by PDCCH with a cyclic redundancy check (CRC) scrambled with the SL-RNTI. When a transmitter UJE receives the DCI, the transmitter UE may obtain the grant only if the scrambled CRC of the DCI may be successfully solved by the assigned SL-RNTI. The transmitter UE may then indicate the time-frequency resources and the transmission scheme of the allocated PSSCH in the PSCCH. The transmitter UE may further launch the PSCCH and the PSSCH on the allocated resources for SL transmissions. When a grant is obtained from a gNB, a transmitter UE may transmit a single transport block (TB). This makes dynamic grant particularly suitable for traffic with loose latency requirements.

For traffic with a strict latency requirement, performing the four-message exchange procedure to request SL resources may result in unacceptable latency. In such cases, a transmitter UE may perform the four-message exchange procedure prior to traffic arrival in order to request a set of resources. Accordingly, the requested resources may be reserved in a periodic manner by obtaining one or more grants from a gNB. When traffic to be sent over the SL arrives at the transmitter UE, the transmitter UE may launch the PSCCH and the PSSCH on the upcoming resource allocation. This may be referred to as grant-free transmissions. In both dynamic grant and configured grant, a SL receiver UE may not receive the DCI, as the DCI is addressed to the transmitter UE. Accordingly, the receiver UE may perform blind decoding to identify the presence of PSCCH and find resources for the PSSCH through the SCI. Furthermore, when the transmitter UE launches the PSCCH, CRC may be inserted in the SCI without scrambling. In present examples, the transmitter UE may be a first UE or a second UE. Alternatively, the receiver UE may be a first UE or a second UE.

In Mode 2 resource allocation, when traffic arrives at a transmitter UE, the transmitter UE may autonomously select resources from the PSCCH and the PSSCH. To further minimize the latency of the feedback HARQ ACK/NACK transmissions and subsequent retransmissions, the transmitter UE may additionally reserve resources for PSCCH/PSSCH for retransmissions. A transmitter UE may repeat a TB transmission along with the initial TB transmission, which may enhance the probability of successful TB decoding and thus reduce the likelihood of needed further retransmissions. This mechanism may also be referred to as blind retransmission. As a result, when traffic arrives at a transmitter UE, the transmitter UE may select resources for one or more of the following transmissions: the PSSCH associated with the PSCCH for initial transmission and optionally blind retransmissions, and/or the PSSCH associated with the PSCCH for retransmissions.

Since each transmitter UE in SL Mode 2 may automatically select resources for the aforementioned transmissions, it may be difficult to prevent different transmitter UEs from selecting the same resources. A resource selection procedure may therefore be imposed in Mode 2 operation based on channel sensing. The resource selection procedure may require measuring RSRP on different subchannels. The resource selection procedure may further require knowledge of UE power level of DMRS on the PSSCH or DMRS on the PSCCH for one or more of the UEs in the network, based on the network configuration. This information may become available after a receiver SCI is launched by the one or more UEs in the network.

In accordance with the above, Mode 2 operation may be a form of UE autonomous resource selection. Mode 2 operation uses UE sensing within a configured or pre-configured resource pool, within which the resources are not in use by other UEs with higher-priority traffic, and allows for a UE to select an appropriate amount of resources for its own transmissions. Once the resources are selected, the UE may transmit and re-transmit using the resources a number of times, or until a cause of resource reselection is triggered.

Mode 2 sensing procedure may select and reserve resources for a variety of purposes, reflecting that NR Vehicle-to-Everything (V2X) introduces SL HARQ in support of unicast and groupcast in the physical layer. In an example, NR V2X may reserve resources to be used for a number of blind transmissions/re-transmissions and/or HARQ-feedback-based transmissions/re-transmissions of a TB, in which case the resources may be indicated in the SCI(s) scheduling the TB. Alternatively or additionally, mode 2 sensing procedure may be used to select resources for the initial transmission of a later transmission block. In this case, the resources may be indicated in the SCI scheduling of a current transport block, for example in a manner similar to LTW-V2X schemes. Finally, an initial transmission of a transport block may be performed after sensing and/or resource selection. The initial transmission may not include a reservation.

Figure 13 depicts an example of Mode 2 resource allocation performed by a transmitter UE. In this specific example, the resource allocation method begins with decoding the PSCCH of other UEs and measuring corresponding PSSCH energy (Step S1302). After this, the UE may collect sensing information (Step S1304). The sensing information may include reserved resources and SL-RSRP measurements. The transmitter UE may then form a candidate set of resources by excluding it’s own resources and further high-energy resources from the measured resources (Step S1306). Following this, the UE may select a number of timefrequency resources (Tx) either semi-persistently or up to a maximum reservation from a known start time (m) (Step S1308) and then re-evaluate the resource selection (Step S1310). If re-selection is triggered (Step S1312) the transmitting UE may repeat Steps S1304, S1306, S1308, and S1310. If re-selection is not triggered, the transmitter UE may begin transmitting (Step S1314) until resource re-selection is triggered (Step S1316). If resource re-selection is not triggered or determined to not be necessary, the transmitter UE may continue using the reservation. If resource re-selection is triggered, the method may be restarted from Step S1304.

The first-stage SCIs transmitted by UEs on PSCCH may indicate the time-frequency resources in which the UE will transmit a PSSCH. These SCI transmissions may be used by sensing UEs to maintain a record of which resources have been reserved by other UEs in the recent past. When a resource selection is triggered (for example, by traffic arrival or by a reselection trigger), the UE may consider a sensing window associated with the resource selection. The sensing window may start at a configured or pre-configured time in the past and may finish shortly before the trigger time. In a specific example, the window may be 1100ms wide. In an alternative example, the window may be 100 ms wide. The 100ms option may be particularly suited for aperiodic traffic, whereas the 100ms may be particularly suited for periodic traffic. A sensing UE may further measure the SL-RSRP in the slots of the sensing window. This SL- RSRP may indicate the level of interference associated with the sensing UE transmitting in the associated slots. In NR-V2X, SL-RSRP may be a configurable and/or pre-configurable measurement of either PSSCH-RSRP or PSCCH-RSRP.

The sensing UE may select resources for its transmission(s)/re-transmission(s) from within the resource selection window. In accordance with the above examples, the resource selection window may start shortly after the trigger for selection/reselection of resources. Further, the resource selection window may not be longer than the remaining latency budget for the associated packet to be transmitted. Reserved resources in the selection window with SL- RSRP above a certain threshold may be excluded from being candidates by the sensing UE (Step S1306). In specific examples, the threshold may be set according to the priorities of the traffic of the sensing and transmitting UEs. This may ensure that a higher priority transmission from a sensing UE may occupy resources which are reserved by a transmitting UE with low SL-RSRP and/or lower-priority traffic in order to improve the operational efficiency of the SL procedure.

If the set of resources in the selection window which have not been excluded is less than a certain proportion of available resources within the window, the SP-RSRP exclusion threshold may be relaxed. For example, the SP-RSRP exclusion threshold may be related in 3 dB steps. In specific examples, the proportion may be set by a configuration (or pre-configuration) of 20%, 35%, or 50% for one or more traffic priorities. More specifically, in some examples each traffic priority may have an associated configuration or pre-configuration. The UE may then select an appropriate amount of resources randomly from the non-excluded set of resources. The resources selected may not be periodic. In a specific example, up to three resources may be indicated in each SCI transmission, which may each be independently located in time and frequency. When the indicated resources are for semi-persistent transmission of another transport block, the range of supported periodicities may be expanded compared to LTE-V2X, in order to cover the envisioned use cases in NR-V2X.

Figure 14 depicts a timeline of the sensing and resource (re-)selection windows with respect to the time of trigger n. As shown in Figure 14A, the sensing window ends at time n, and has a duration TO. The selection window begins at time n, and has a duration of T2. T1 is a delay between the trigger time n and the beginning of the selection process. Time T_proc is the processing time associated with the sensing window, that is, the time between the sensing process ending and the trigger of the selection process. During the selection window, a number of resources m may be reserved. Duration T2 may be less than or equal to a packet delay budget (PDB) and may be greater than or equal to a minimum value T_min. Figure 14B depicts a second timeline of sensing and resource selection and re-selection, the second timeline including a resource re-evaluation step. Before transmitting in a reserved resource, a sensing UE may re-evaluate the set of resources from which it can select (Step S1310). For example, a sensing UE may re-evaluate to determine whether its intended transmission is still suitable. This re-evaluation may take into account late-arriving SCIs (e.g. due to an aperiodic higher-priority service starting to transmit after the end of the original sensing window). If the reserved resources would not form a part of the set for selection at the time of re-evaluation (T3) then new resources may be selected from the updated resource reselection window. The cut-off time T3 may occur before transmission, and may occur sufficiently before transmission to allow the UE to perform calculations for resource reselection. During the re-selection window, a number of resources m’ may be reserved.

As discussed above, resource re-selection may be triggered. Any suitable trigger for reselection may be used. In addition, it may be possible to configure a resource pool with a preemptive function designed to help accommodate sidelink traffic. For example, a resource pool may be pre-configured such that a UE reselects all of the resources it had already reserved in a particular slot if another nearby UE with higher priority indicates it will transmit in any of the selected resources (implying a high-priority aperiodic traffic arrival at the other UE) and/or the SL-RSRP is above the exclusion threshold. The application of pre-emption may apply between all priorities of data traffic. Alternatively or additionally, the application of pre-emption may apply when the priority of the pre-empting traffic is higher than a threshold and/or higher than that of the pre-empted traffic. A UE may not need to consider the possibility of pre-emption later than time T3, even if before the slot containing the reserved resources.

A UE implementing SL procedures (including a first UE, a second UE, a transmitting UE, and/or a sensing UE) may derive its own synchronization from one or more of the following sources: GNSS, a gNB or eNB, a further UE transmitting Signalling Link Selection Signals (SLSS) (herein referred to as a SyncRef UE), and/or the internal clock of the UE. Having a UE derive its own synchronization from GNSS information or information received from a eNB/gNB may be preferred due to improved synchronization quality. SynchRef UEs may be distinguished between those which are directly synchronized to GNSS or a gNB/eNB, those which are one step removed from GNSS or a gNB/eNB, and those which are 2 or more steps removed from GNSS or a gNB/eNB. A UE unable to find another synchronization reference may accordingly use its own internal clock to transmit S-SSB.

The V2X synchronization procedure may define a hierarchy or set of priorities amongst synchronization references and may further require each UE to continuously search the hierarchy to in order to obtain the highest quality synchronization reference available. The hierarchy may be as follows, with Level 1 being the most preferred synchronization reference:

Level 1. Either GNSS or eNB/gNB, according to a configuration or preconfiguration;

Level 2. A SyncRef UE directly synchronized to a Level 1 source;

Level 3. A SyncRef UE synchronized to a Level 2 source (that is, indirectly synchronized to a Level 1 source);

Level 4. Whichever of GNSS or eNB/gNB was not configured/pre- configured as the Level 1 source;

Level 5. A SyncRef UE directly synchronized to a Level 4 source;

Level 6. A SyncRef UE synchronized to a Level 5 source (that is, indirectly synchronized to a Level 4 source);

Level 7. Any other SyncRef UE;

Level 8. UE's internal clock.

The NR V2X scheme may allow for merging of hierarchies derived from GNSS and gNB/eNB, such that a UE is able to move between hierarchies without loss of SL service. In a further example, use of Levels 4-6 may be disabled when GNSS is used as Level 1, since the gNb/eNB may not be synchronized to GNSS, such that it can be guaranteed that there is no deviation from the hierarchy being derived from GNSS.

The SL Synchronization Identity Signal (SLSSID) may convey information about the synchronization source of the transmitting UE. For example, if a UE is further away from a high-quality source of GNSS/eNB/gNB, the UE may have a lower synchronization quality and thus may transmit a lower quality SLSS. There may be a series of association rules among SLSS IDs that facilitate the identification and propagation of high-quality synchronization sources through a network. In specific examples of NR-V2X, there may be 672 SLSS IDs divided into 0, 1 , ... , 335 for in-coverage indication and 336, ... , 671 for out-of-coverage indication. The special SLSS IDs of 0, 336, and 337 in NR-V2X may be used equivalently to 0, 168, and 169 respectively in LTE-V2X.

Figure 15 depicts SL positioning for a UE in different coverage scenarios. In Figure 15A, the second UE (1506) provides SL measurement assistance to a first UE (1504). The second UE may be referred to as an assisting UE or reference UE. The first UE may be referred to as a target UE. Accordingly, fora first UE (1504) out of coverage, there may be a plurality of options available for positioning the first UE. As shown in Figure 15A, for a first UE (1504) out of coverage, the first UE may connect to the gNB 1502 via a U2N relay UE, for example an SL relay UE. In this case, the network may be involved in the positioning procedure for the first UE. Alternatively, the first UE may apply UE- based positioning by involving an assisting UE. If an assisting UE is not available in proximity to the first UE, the first UE may reach an assisting UE via a relay UE.

As shown in Figure 15B, a first UE or target UE (1504) may require assistance from multiple second UEs or reference UEs (1506). For example, a first UE using a positioning method including DL-TDOA, UL-TDOA, and/or Multi-RTT may require multiple assisting/reference UEs. For these SL based positioning methods, a tight synchronization between the multiple second UEs may be needed such that the transmissions of positioning measurement information from each second UE arrive in a synchronized fashion. This may improve positioning accuracy and reduce interference amongst second UEs. Accordingly, the network according to specific examples may comprise a plurality of second UEs and the associated method may comprise triggering a D2D positioning procedure between the first UE and each second UE.

The one or more second UEs in the network may be configured to transmit D2D positioning measurement information to the first UE, for example such that the first UE can collate the D2D positioning measurement information and forward it to the network node. Accordingly, the first UE may be configured to obtain D2D positioning measurement information from a second UE based on the D2D location verification procedure request and transmit the D2D positioning measurement information to the network node.

In cases where the network node successfully verifies the location of the first UE, for example using the D2D positioning measurement information provided by the first UE, the first UE may be configured to terminate an ongoing further location verification procedure that is being performed. For example, the network node may be configured to transmit an indication to the first UE indicating that the D2D location verification procedure has successfully verified the location of the first UE if the D2D location verification procedure successfully verifies a location of the first UE. Accordingly, the first UE may be configured to receive an indication from the network node indicating that the D2D location verification procedure has successfully verified the location of the first UE. The first UE may then be further configured to terminate an ongoing further location verification procedure performed by the first UE, based on the received indication. Figure 16 is a signal diagram for a method in accordance with embodiments, in particular where no second UEs are available to support D2D positioning. As shown in Figure 16, the network comprises a UE 1604 acting as a first UE or target UE, a gNB 1602 hosted on a satellite, an AMF 1610 and an LMF 1612. After a RRC connection is established between the UE 1604 and the satellite 1602, the AMF 1610 may be selected and trigger a verification of the UE 1604 location. This location is then verified using a Uu positioning procedure. As a D2D positioning procedure is not available, additional signalling latency and overhead may be introduced by the Uu positioning procedure in comparison to a system where D2D positioning procedures are available.

Alternatively, in accordance with the signal diagram of Figure 16, the UE may trigger a SL positioning procedure before initializing the initial access procedure. After the RACH procedure is completed, the UE may enter into RRC_CONNECTED mode. When the network triggers a location verification procedure, the UE may have already completed the SL positioning procedure. In this case, the UE may inform the LMF that the UE’s location has been recently determined by the SL positioning procedure. The LMF may then determine not to trigger a Uu positioning procedure as shown in Figure 16. Instead, the UE may be asked to provide the SL positioning measurement results to the LMF, based on which the LMF may determine if the UE’s location is verified. If the UE’s location is verified successfully, the UE may continue its RRC connection setup procedure to setup a PDU session and DRBs for subsequent data transmission and/or reception. Otherwise, the UE may be rejected by the network for further access.

Figure 17 is a further signal diagram for a method in accordance with embodiments. As shown in Figure 17, the network comprises a UE 1704 acting as a first UE or target UE, a gNB 1702 hosted on a satellite, and a network node formed of an AMF 1710 and an LMF 1712. The network of Figure 17 additionally comprises two second UEs 1706 (anchor UE1 and UE2) however it will be appreciated that any number of anchor UEs may be used. The network node may be a core network node. As shown in Figure 17, the core network node may comprise the AMF 1710 and/or the LMF 1712. The network node and/or AMF 1710 and/or LMF 1712 may additionally be connected to the network via a satellite. In an alternative arrangement, the gNB 1702 may be hosted by a terrestrial network node.

As shown in Figure 17A, the location of the first UE 1704 may be successfully by the LMF according to the received SL positioning measurement results. In this case, the UE may continue its RRC connection setup procedure to setup a PDU session and DRBs for subsequent data transmission and/or reception. Alternatively, and as shown in Figure 17B, the LMF 1712 may fail to verify the location of the first UE 1704 according to the received SL positioning measurement results. In this case, the RRC connection between the first UE 1704 and gNB 1702 may be terminated.

The first UE may be in any of RRC IDLE, RRC INACTIVE, and/or RRC CONNECTED mode. Accordingly, and as depicted in Figure 17, present examples may include establishing a RRC connection between the base station and the first UE. In an alternative example to that depicted in Figure 17, when accessing an NTN network, a first UE in RRC IDLE may be positioned by a network node (e.g., the LMF) based on both the positioning measurement results obtained in a SL positioning procedure and the positioning measurement results obtained in a Uu positioning procedure.

In a further example, in an NTN network, a first UE in RRC INACTIVE or RRC CONNECTED may be positioned by a network node (e.g., the LMF) based on the positioning measurement results obtained in a SL positioning procedure. Alternatively, in an NTN network, a first UE in RRC INACTIVE or RRC CONNECTED may be positioned by a network node (e.g., the LMF) based on both the positioning measurement results obtained in a SL positioning procedure and the positioning measurement results obtained in an Uu positioning procedure.

In case where the first UE is in RRC_IN ACTIVE or RRC_CONNECTED, whenever the network node initiates a positioning procedure/network verification procedure for the first UE, the network node may query whether the first UE has already obtained its location and/or its positioning measurement via any SL positioning procedure. If the answer is yes, the network node may instruct the first UE to provide those results to the network node. The network node may further decide to not initiate the Uu positioning procedure, or early terminate the Uu positioning procedure if the SL positioning measurement results are deemed to be enough to verify the first UE’s location.

Where the first UE is in RRC NACTIVE, the first UE may rely on small data transmission (SDT) to transmit SL positioning measurement results and/or its location to the LMF.

Any signalling exchanged between a first UE/second UE and the network node may carried via a LPP message or a NAS signalling. Any signalling exchanged between a gNB and the network node may be carried via a NRPPa message or a NGAP signalling.

Aspects of the present disclosure may enable a first UE or target UE to report D2D positioning measurement information to an LMF in order to verify the location of the first UE. That is, aspects of the present disclosure may provide methods for reducing latency and signalling overhead when positioning a UE in a NTN system, by using information from D2D processes such as sidelink positioning in addition to llu positioning when determining the UE position entering an NTN network. Aspects may therefore make use of D2D positioning frameworks such as SL positioning frameworks where the cell supports this feature. Support of D2D positioning may be indicated in System Information Block (SIB) signalling using a new indication.

A network initiated verification procedure may use only D2D positioning measurement information or a combination of D2D positioning measurement information and Uu positioning measurement information. Before Uu positioning and/or network verification procedure is initiated, the UE location information may already have been obtained from a D2D procedure (such as a SL procedure) by involving one or more neighbouring UEs in the positioning procedure. Accordingly, the intended Uu positioning and/or network verification procedure may be terminated or completed early (for example, an ongoing network verification procedure may be terminated early without waiting for the verification procedure to complete based on a Uu positioning method). Uu positioning message exchange between the UE and LMF and/or between the gNB and LMF may be avoided, thus further reducing signalling overhead and latency.

In accordance with the above, new criteria may be defined for the selection of one or more second UEs or anchor UEs to be involved in the D2D positioning procedure, in order to assist a first UE in the verification of its location in a network initiated verification procedure. Alternatively or additionally, allowing another UE (e.g. an anchor UE or positioning server UE) to report information that is output from a D2D positioning procedure to the LMF may allow for said UE to provide fake information when reporting to the LMF. In cases where the first UE has already had its location verified by the network and is thus considered a trusted UE, a rogue UE acting as an anchor UE or positioning server UE may be detected (for example, when it is detected that there is a large deviance between the reported D2D positioning measurement information and expected positioning measurement information).

The methods of the present disclosure may be implemented in hardware, or as software modules running on one or more processors. The methods may also be carried out according to the instructions of a computer program, and the present disclosure also provides a computer readable medium having stored thereon a program for carrying out any of the methods described herein. A computer program embodying the disclosure may be stored on a computer readable medium, or it could, for example, be in the form of a signal such as a downloadable data signal provided from an Internet website, or it could be in any other form.

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure.

It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, RAM, etc. As will be appreciated by one of skill in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like.

References in the present disclosure to “one embodiment”, “an embodiment” and so on, indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It should be understood that, although the terms “first”, “second” and so on may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including”, when used herein, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components and/ or combinations thereof. The terms “connect”, “connects”, “connecting” and/or “connected” used herein cover the direct and/or indirect connection between two elements.

The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. For the avoidance of doubt, the scope of the disclosure is defined by the claims.

Claims

1 . A method (S500) performed by a network node, the method comprising: triggering (S502) a device-to-device, D2D, location verification procedure for a first user equipment, UE; transmitting (S504) a D2D location verification procedure request to the first UE; receiving (S506) D2D positioning measurement information based on the D2D location verification procedure request; and performing (S508) the D2D location verification procedure using the D2D positioning measurement information.

2. A method (S500) as claimed in Claim 1 , wherein the method further comprises: establishing a Radio Resource Control, RRC, connection between a base station and the first UE.

3. A method (S500) as claimed in any of Claims 1 and 2, wherein the method further comprises: determining a difference between the D2D positioning measurement information and expected positioning measurement information; and determining that the D2D positioning measurement information is verified if the difference is less than a predetermined threshold.

4. A method (S500) as claimed in any of Claims 1 to 3, wherein the method further comprises: if the D2D location verification procedure successfully verifies a location of the first UE, determining that the first UE is a trusted UE.

5. A method (S500) as claimed in any of Claims 1 to 4, wherein the method further comprises: if the D2D location verification procedure successfully verifies a location of the first UE, transmitting an indication to the first UE indicating that the D2D location verification procedure has successfully verified the location of the first UE.

6. A method (S500) as claimed in any of Claims 1 to 5, wherein the method further comprises: if the D2D location verification procedure fails to verify a location of the first UE, terminating the RRC connection between the base station and the first UE.

7. A method (S500) as claimed in any preceding claim, wherein the method further comprises: undertaking a further positioning method.

8. A method (S500) as claimed in Claim 7, wherein the further positioning procedure is one or more of: a multiple Round Trip Time (multi-RTT) positioning method, a Time Difference of Arrival (TDOA) positioning method, a Angle of Departure (AoD) positioning method, an Angle of Arrival (AoA) positioning method, and a New Radio Enhanced Cell Identification (NR E- CID) positioning method.

9. A method (S500) as claimed in any of Claims 7 and 8, wherein the D2D location verification procedure request comprises an indication that the further positioning method is to be undertaken.

10. A method (S500) as claimed in any of Claims 1 to 9, wherein the method further comprises: receiving an indication from the first UE indicating that the first UE is undertaking a device-to-device positioning procedure.

11. A method (S500) as claimed in any of Claims 1 to 10, wherein the method further comprises: receiving an indication from the first UE indicating that the first UE has previously undertaken a device-to-device positioning procedure at a time that is below a certain threshold.

12. A method (S500) as claimed in any of Claims 10 and 11 , wherein the method further comprises: terminating an ongoing Uu positioning method performed by the network node, based on the received indication.

13. A method (S500) as claimed in any preceding claim, wherein the network node is a core network node.

14. A method (S500) as claimed in Claim 13, wherein the core network node comprises an Access and Mobility Management Function, AMF, and/or a Location Management Function, LMF.

15. A method (S500) as claimed in any of Claims 13 and 14, wherein the core network node is connected by a satellite or a terrestrial network node.

16. A method (S500) as claimed in any preceding claim, wherein the method further comprises: determining a second UE for the D2D location verification procedure.

17. A method (S500) as claimed in Claim 16, wherein the method further comprises: receiving an indication of an identity of the second UE from the first UE.

18. A method (S500) as claimed in any of Claims 16 and 17, wherein the method further comprises: receiving an indication of an identity of the second UE from a positioning server UE.

19. A method (S500) as claimed in any of Claims 16 to 18, wherein the method further comprises: performing a selection process for the second UE.

20. A method (S500) as claimed in any of Claims 16 to 19, wherein the determination of the second UE is based on one or more of the following criteria: if the second UE supports a D2D positioning procedure; if the location of the second UE has previously been verified by the network node; if the radio channel quality between the first UE and the second UE is above a certain threshold; and/or if the first UE and second UE hold a trust relation.

21. A method (S500) as claimed in any preceding claim, the method further comprises: receiving the D2D positioning measurement information from the first UE and/or the second UE.

22. A method (S500) as claimed in any preceding claim, wherein the D2D positioning measurement information is one or more of: Sidelink, SL, positioning measurement information, Bluetooth positioning measurement information, Zigbee positioning measurement information, and Wi-Fi positioning measurement information.

23. A method (S600) performed by a first user equipment, UE, the method comprising:

Receiving (S602) a device-to-device, D2D, location verification procedure request from a network node; establishing (S604) a D2D positioning procedure with a second UE; and providing (S606) D2D positioning measurement information to the network node based on the established D2D positioning procedure.

24. A method (S600) as claimed in Claim 23, wherein the method further comprises: establishing a Radio Resource Control, RRC, Connection between a base station and the first UE.

25. A method (S600) as claimed in any of Claims 23 and 24, wherein the method further comprises: receiving an indication from the network node indicating that the D2D location verification procedure has successfully verified the location of the first UE.

26. A method (S600) as claimed in Claim 25, wherein the method further comprises: terminating an ongoing further location verification procedure performed by the first UE, based on the received indication.

27. A method (S600) as claimed in any of Claims 23 and 24, wherein the method further comprises: if the D2D location verification procedure fails to verify a location of the first UE, terminating the RRC connection between the base station and the first UE.

28. A method (S600) as claimed in any of Claims 23 to 27, wherein the method further comprises: transmitting an indication to the network node indicating that the first UE is undertaking a device-to-device positioning procedure.

29. A method (S600) as claimed in any of Claims 23 to 28, wherein the first UE is a target UE.

30. A method (S600) as claimed in any of Claims 23 to 29, wherein the method further comprises: determining the second UE for a D2D positioning procedure.

31. A method (S600) as claimed in Claim 30, wherein the method further comprises: determining the second UE for a D2D positioning procedure based on the received D2D location verification procedure request.

32. A method (S600) as claimed in any of Claims 23 to 31, wherein the method further comprises: obtaining the D2D positioning measurement information from the second UE based on the D2D location verification procedure request; and transmitting the D2D positioning measurement information to the network node.

33. A method (S600) as claimed in any of Claims 23 to 32, wherein the method further comprises: establishing the D2D positioning procedure with the second UE in parallel with establishing the RRC connection between the base station and the first UE.

34. A method (S600) as claimed in Claim 23 to 32, wherein the method further comprises: establishing the D2D positioning procedure with the second UE sequentially with establishing the RRC connection between the base station and the first UE.

35. A method (S600) as claimed in any of Claims 23 to 34, wherein the method further comprises: determining whether the network node supports a D2D location verification procedure.

36. A method (S600) as claimed in any of Claims 23 to 35, wherein the first UE is in RRC IDLE, RRC INACTIVE, and/or RRC CONNECTED mode.

37. A method (S700) performed by a second user equipment, UE, the method comprising: establishing (S702) a device-to-device, D2D, positioning procedure with a first UE based on a D2D location verification procedure request from a network node; and providing (S704) D2D positioning measurement information to the network node based on the established D2D positioning procedure.

38. A method (S700) as claimed in Claim 37, wherein the second UE is an anchor UE.

39. A method (S700) as claimed in any of Claims 37 and 38, wherein the second UE fulfils one or more of the following criteria: the second UE supports a D2D positioning procedure; the location of the second UE has previously been verified by the network node; the radio channel quality between the first UE and the second UE is above a certain threshold; and/or if the first UE and second UE hold a trust relation.

40. A method (S700) as claimed in any of Claims 37 to 39, wherein the method further comprises: establishing the D2D positioning procedure with the first UE via a positioning server UE.

41. A method (S700) as claimed in any of Claims 37 to 40, wherein the method further comprises: establishing the D2D positioning procedure with the first UE via the network node.

42. A method (S800) performed by a network, the network comprising a network node, a first user equipment, UE, and a second UE, the method comprising: triggering (S802) a device-to-device, D2D, positioning procedure between the first UE and the second UE; triggering (S804) a D2D location verification procedure between the first UE and the network node; providing (S806) D2D positioning measurement information to the network node based on the D2D positioning procedure; and performing (S808) the D2D location verification procedure at the network node using the D2D positioning measurement information.

43. A method (S800) as claimed in Claim 42, wherein the method further comprises: determining, by the first UE, to enable D2D procedures; and transmitting an indication, by the first UE to the network node, indicating that D2D procedures are enabled.

44. A method (S800) as claimed in Claim 42, wherein the method further comprises: determining, by the network node, to enable D2D procedures.

45. A method (S800) as claimed in any of Claims 42 to 44, wherein the method further comprises: transmitting the D2D positioning measurement information from the second UE to the first UE; and transmitting the D2D positioning measurement information from the first UE to the network node.

46. A method (S800) as claimed in any of Claims 42 to 44, wherein the method further comprises: transmitting the D2D position measurement information from the second UE to the network node.

47. A method (S800) as claimed in any of Claims 42 to 46, wherein the network comprises a plurality of second UEs and wherein the method comprises: triggering a D2D positioning procedure between the first UE and each second UE.

48. A method (S800) as claimed in any of Claims 42 to 47, wherein the network further comprises a base station and wherein the method further comprises: establishing a Radio Resource Control, RRC, connection between the base station and the first UE.

49. A method (S800) as claimed in Claim 48, wherein the base station is hosted by a satellite or a terrestrial network node.

50. A method (S800) as claimed in any of Claims 42 to 49, wherein the method further comprises: if the D2D location verification procedure successfully verifies a location of the first UE, determining by the network node that the first UE is a trusted UE.

51. A method (S800) as claimed in any of Claims 42 to 50, wherein the method further comprises: if the D2D location verification procedure successfully verifies a location of the first UE, transmitting an indication from the network node to the first UE indicating that the D2D location verification procedure has successfully verified the location of the first UE.

52. A method (S800) as claimed in any of Claims 42 to 51, wherein the method further comprises: if the D2D location verification procedure fails to verify a location of the first UE, terminating the RRC connection between the network node and the first UE.

53. A network node (1100) comprising processing circuitry (1102) and a memory (1106) containing instructions executable by the processing circuitry (1102), whereby the network node (1100) is configured to: trigger a device-to-device, D2D, location verification procedure for a first UE; transmit a D2D location verification procedure request to the first UE; receive D2D positioning measurement information based on the D2D location verification procedure request; and perform the D2D location verification procedure using the D2D positioning measurement information.

54. A network node (1100) as claimed in Claim 53, wherein the network node is further configured to perform any of the methods as claimed in Claims 2 to 22.

55. A first user equipment, UE, (1000) comprising processing circuitry (1002) and a memory (1006) containing instructions executable by the processing circuitry (1002), whereby the first UE (1000) is configured to: receive a device-to-device, D2D, location verification procedure request from a network node; establish a D2D positioning procedure with a second UE; and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

56. A first user equipment (1000) as claimed in Claim 55, wherein the first user equipment is further configured to perform any of the methods as claimed in Claims 24 to 36.

57. A second user equipment, UE, (1000) comprising processing circuitry (1002) and a memory (1006) containing instructions executable by the processing circuitry (1002), whereby the second UE (1000) is configured to: establish a device-to-device, D2D, positioning procedure with a first UE based on a D2D location verification procedure request from a network node; and provide D2D positioning measurement information to the network node based on the established D2D positioning procedure.

58. A second user equipment as claimed in Claim 57. Wherein the second user equipment is further configured to perform any of the methods as claimed in Claims 38 to 41.