Timing information exchange for enhanced sidelink positioning

Abstract

Timing information exchange for enhanced sidelink positioning is described. An apparatus is configured to identify a synchronization reference type of a synchronization reference source based on a synchronization of a UE to the synchronization reference source. The apparatus is configured to provide, to at least one of an LMF or another UE as a basis of communications thereby, a first indication of the synchronization reference type, a quality metric, or a variation time. Another apparatus is configured to receive at least one of a first indication of a synchronization reference type of a synchronization reference source associated with synchronization of a UE, a quality metric, or a variation time from at least one of an LMF or another UE. The apparatus is configured to communicate based on the first indication of the synchronization reference type, the quality metric, or the variation time.

Description

TIMING INFORMATION EXCHANGE FOR ENHANCED SIDELINK POSITIONINGCROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of and priority to Greek Patent Application No. 20230100671 , entitled “TIMING INFORMATION EXCHANGE FOR ENHANCED SIDELINK POSITIONING” and filed on August 10, 2023, which is expressly incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates generally to communication systems, and more particularly, to wireless communications utilizing positioning.INTRODUCTION

[0003] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0004] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3 GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT)), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latencycommunications (URLLC). Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.BRIEF SUMMARY

[0005] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects. This summary neither identifies key or critical elements of all aspects nor delineates the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0006] In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may comprise a user equipment (UE), and the method may be performed at a UE. The apparatus is configured to identify a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE. The apparatus is also configured to detect a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The apparatus is also configured to provide, to at least one of a location management function (LMF) or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time.

[0007] In the aspect, the method includes identifying a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or a synchronization reference UE. The method also includes detecting a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount thatwas corrected in a last one or more synchronization updates. The method also includes providing, to at least one of a LMF or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time.

[0008] In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may comprise a UE, and the method may be performed at a UE. The apparatus is configured to receive, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The apparatus is also configured to communicate based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time.

[0009] In the aspect, the method includes receiving, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The method also includes communicating based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time.

[0010] To the accomplishment of the foregoing and related ends, the one or more aspects may include the features hereinafter fully described and particularly pointed out in the claims. The following description and the drawings set forth in detail certainillustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. l is a diagram illustrating an example of a wireless communications system and an access network.

[0012] FIG. 2A is a diagram illustrating an example of a first frame, in accordance with various aspects of the present disclosure.

[0013] FIG. 2B is a diagram illustrating an example of downlink (DL) channels within a subframe, in accordance with various aspects of the present disclosure.

[0014] FIG. 2C is a diagram illustrating an example of a second frame, in accordance with various aspects of the present disclosure.

[0015] FIG. 2D is a diagram illustrating an example of uplink (UL) channels within a subframe, in accordance with various aspects of the present disclosure.

[0016] FIG. 3 is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

[0017] FIG. 4 is a diagram illustrating an example of a UE positioning based on reference signal measurements.

[0018] FIG. 5 is a diagram illustrating examples of a UE positioning based on reference signal measurements and quality metrics.

[0019] FIG. 6 is a call flow diagram for wireless communications, in accordance with various aspects of the present disclosure.

[0020] FIG. 7 is a diagram illustrating examples of timing information exchange for enhanced sidelink positioning, in accordance with various aspects of the present disclosure.

[0021] FIG. 8 is a call flow diagram for wireless communications, in accordance with various aspects of the present disclosure.

[0022] FIG. 9 is a flowchart of a method of wireless communication, in accordance with various aspects of the present disclosure.

[0023] FIG. 10 is a flowchart of a method of wireless communication, in accordance with various aspects of the present disclosure.

[0024] FIG. 11 is a flowchart of a method of wireless communication, in accordance with various aspects of the present disclosure.

[0025] FIG. 12 is a flowchart of a method of wireless communication, in accordance with various aspects of the present disclosure.

[0026] FIG. 13 is a diagram illustrating an example of a hardware implementation for an example apparatus and / or network entity.

[0027] FIG. 14 is a diagram illustrating an example of a hardware implementation for an example network entity.

[0028] FIG. 15 is a diagram illustrating an example of a hardware implementation for an example network entity.DETAILED DESCRIPTION

[0029] Wireless communication networks, such as an LTE network and / or a 5G NR network, among other examples of wireless communication networks, may be designed to support positioning of wireless devices. For instance, based on reference signal communications between anchor entities such as network nodes (e.g., base stations, eNBs, gNBs, transmission reception points (TRPs), etc.) and a wireless device, a UE may determine a location / position of the wireless device using a time difference of arrival (TDoA) associated with the reference signal communications. As one example for TDoA, a wireless device may position itself or another wireless device based on the difference of arrival times of the positioning reference signals. In uplink-like TDoA, a wireless device may transmit a positioning reference signal (PRS) and anchor entities may report the time at which they received this PRS back to the wireless device, and based on the differences between arrival times and anchor entity locations, the wireless device location may be calculated. In downlink-like TDoA, multiple anchor entities may transmit PRSs, a wireless device may receive those PRS transmissions, and based on the difference in arrival times and the anchor entity locations, the wireless device location may be calculated. In a UE-to-universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN) (Uu) interface positioning, an anchor entity may report a quality metric for the relative time difference between itself and a synchronization reference source. The quality metric may be associated with a relative time difference (RTD), e.g., the rtd-Quality field in RTD-InfoElement, which may be used in anchor entity selection.

[0030] However, if the anchor entities are not fully synchronized with their synchronization reference source(s) (e.g., a global navigation satellite system (GNSS), a network node, an independent synchronization reference UE, and / or the like), uncertainty may be introduced to the arrival times and the time difference measurements, which in turn may introduce uncertainty to the calculated location. For example, an anchor entity may be synchronized to a synchronization reference source(s), and over some time, the synchronization may drift by an amount of time for which correction should be applied to avoid synchronization errors. Yet, examples for synchronization error management do not provide for mitigation of impacts due to synchronization errors between anchor UEs for sidelink (SL) TDoA measurements.

[0031] Various aspects relate generally to wireless network positioning. Some aspects more specifically relate to timing information exchange for enhanced sidelink positioning. In some examples, synchronization information is exchanged according to aspects for mitigating impacts of synchronization errors among anchor UEs, e.g., for SL-based TDoA measurements. In some examples, methods and apparatuses are provided to exchange synchronization information of anchor UEs between a UE and an LMF or another UE, and the synchronization information may be associated with a synchronization reference source, a RTD, synchronization quality information, a synchronization reference type, a variation time, and / or the like. In one example, a first UE may be configured to identify a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or an independent synchronization reference UE. The first UE may also be configured to detect a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The first UE may also be configured to provide, to at least one of an LMF or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source or the variation time. In another example, a first UE may be configured to receive, from at least one of an LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source or a variation time, where the synchronization reference source isassociated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or an independent synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The first UE may also be configured to communicate based on the first indication of the synchronization reference type of the synchronization reference source and the variation time.

[0032] Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In one example, by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs, the described techniques can be used to correct synchronization errors between anchor UEs for SL positioning measurements. In another example, by correcting such synchronization errors, the described techniques can be used to improve wireless device positioning accuracy for wireless communication networks.

[0033] The detailed description set forth below in connection with the drawings describes various configurations and does not represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0034] Several aspects of telecommunication systems are presented with reference to various apparatus and methods. These apparatus and methods are described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0035] By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or moreprocessors. When multiple processors are implemented, the multiple processors may perform the functions individually or in combination. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise, shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, or any combination thereof.

[0036] Accordingly, in one or more example aspects, implementations, and / or use cases, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, such computer-readable media can include a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the types of computer- readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

[0037] While aspects, implementations, and / or use cases are described in this application by illustration to some examples, additional or different aspects, implementations and / or use cases may come about in many different arrangements and scenarios. Aspects, implementations, and / or use cases described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, aspects, implementations, and / or use cases may come about via integrated chip implementations and other non-module-component based devices(e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail / purchasing devices, medical devices, artificial intelligence (Al)-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described examples may occur. Aspects, implementations, and / or use cases may range a spectrum from chip-level or modular components to non-modular, non-chip- level implementations and further to aggregate, distributed, or original equipment manufacturer (OEM) devices or systems incorporating one or more techniques herein. In some practical settings, devices incorporating described aspects and features may also include additional components and features for implementation and practice of claimed and described aspect. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders / summers, etc.). Techniques described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, aggregated or disaggregated components, end-user devices, etc. of varying sizes, shapes, and constitution.

[0038] Deployment of communication systems, such as 5G NR systems, may be arranged in multiple manners with various components or constituent parts. In a 5G NR system, or network, a network node, a network entity, a mobility element of a network, a radio access network (RAN) node, a core network node, a network element, or a network equipment, such as a base station (BS), or one or more units (or one or more components) performing base station functionality, may be implemented in an aggregated or disaggregated architecture. For example, a BS (such as a Node B (NB), evolved NB (eNB), NRBS, 5GNB, access point (AP), a transmission reception point (TRP), or a cell, etc.) may be implemented as an aggregated base station (also known as a standalone BS or a monolithic BS) or a disaggregated base station.

[0039] An aggregated base station may be configured to utilize a radio protocol stack that is physically or logically integrated within a single RAN node. A disaggregated base station may be configured to utilize a protocol stack that is physically or logically distributed among two or more units (such as one or more central or centralized units (CUs), one or more distributed units (DUs), or one or more radio units (RUs)). In some aspects, a CU may be implemented within a RAN node, and one or more DUsmay be co-located with the CU, or alternatively, may be geographically or virtually distributed throughout one or multiple other RAN nodes. The DUs may be implemented to communicate with one or more RUs. Each of the CU, DU and RU can be implemented as virtual units, i.e., a virtual central unit (VCU), a virtual distributed unit (VDU), or a virtual radio unit (VRU).

[0040] Base station operation or network design may consider aggregation characteristics of base station functionality. For example, disaggregated base stations may be utilized in an integrated access backhaul (IAB) network, an open radio access network (O- RAN (such as the network configuration sponsored by the 0-RAN Alliance)), or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN)). Disaggregation may include distributing functionality across two or more units at various physical locations, as well as distributing functionality for at least one unit virtually, which can enable flexibility in network design. The various units of the disaggregated base station, or disaggregated RAN architecture, can be configured for wired or wireless communication with at least one other unit.

[0041] FIG. 1 is a diagram 100 illustrating an example of a wireless communications system and an access network. The illustrated wireless communications system includes a disaggregated base station architecture. The disaggregated base station architecture may include one or more CUs 110 that can communicate directly with a core network 120 via a backhaul link, or indirectly with the core network 120 through one or more disaggregated base station units (such as a Near-Real Time (Near-RT) RAN Intelligent Controller (RIC) 125 via an E2 link, or a Non-Real Time (Non-RT) RIC 115 associated with a Service Management and Orchestration (SMO) Framework 105, or both). A CU 110 may communicate with one or more DUs 130 via respective midhaul links, such as an Fl interface. The DUs 130 may communicate with one or more RUs 140 via respective fronthaul links. The RUs 140 may communicate with respective UEs 104 via one or more radio frequency (RF) access links. In some implementations, the UE 104 may be simultaneously served by multiple RUs 140.

[0042] Each of the units, i.e., the CUs 110, the DUs 130, the RUs 140, as well as the Near- RT RICs 125, the Non-RT RICs 115, and the SMO Framework 105, may include one or more interfaces or be coupled to one or more interfaces configured to receive or to transmit signals, data, or information (collectively, signals) via a wired or wireless transmission medium. Each of the units, or an associated processor or controllerproviding instructions to the communication interfaces of the units, can be configured to communicate with one or more of the other units via the transmission medium. For example, the units can include a wired interface configured to receive or to transmit signals over a wired transmission medium to one or more of the other units. Additionally, the units can include a wireless interface, which may include a receiver, a transmitter, or a transceiver (such as an RF transceiver), configured to receive or to transmit signals, or both, over a wireless transmission medium to one or more of the other units.

[0043] In some aspects, the CU 110 may host one or more higher layer control functions. Such control functions can include radio resource control (RRC), packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), or the like. Each control function can be implemented with an interface configured to communicate signals with other control functions hosted by the CU 110. The CU 110 may be configured to handle user plane functionality (i.e., Central Unit - User Plane (CU-UP)), control plane functionality (i.e., Central Unit - Control Plane (CU-CP)), or a combination thereof. In some implementations, the CU 110 can be logically split into one or more CU-UP units and one or more CU-CP units. The CU-UP unit can communicate bidirectionally with the CU-CP unit via an interface, such as an El interface when implemented in an 0-RAN configuration. The CU 110 can be implemented to communicate with the DU 130, as necessary, for network control and signaling.

[0044] The DU 130 may correspond to a logical unit that includes one or more base station functions to control the operation of one or more RUs 140. In some aspects, the DU 130 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers (such as modules for forward error correction (FEC) encoding and decoding, scrambling, modulation, demodulation, or the like) depending, at least in part, on a functional split, such as those defined by 3 GPP. In some aspects, the DU 130 may further host one or more low PHY layers. Each layer (or module) can be implemented with an interface configured to communicate signals with other layers (and modules) hosted by the DU 130, or with the control functions hosted by the CU 110.

[0045] Lower-layer functionality can be implemented by one or more RUs 140. In some deployments, an RU 140, controlled by a DU 130, may correspond to a logical nodethat hosts RF processing functions, or low-PHY layer functions (such as performing fast Fourier transform (FFT), inverse FFT (iFFT), digital beamforming, physical random access channel (PRACH) extraction and filtering, or the like), or both, based at least in part on the functional split, such as a lower layer functional split. In such an architecture, the RU(s) 140 can be implemented to handle over the air (OTA) communication with one or more UEs 104. In some implementations, real-time and non-real-time aspects of control and user plane communication with the RU(s) 140 can be controlled by the corresponding DU 130. In some scenarios, this configuration can enable the DU(s) 130 and the CU 110 to be implemented in a cloud-based RAN architecture, such as a vRAN architecture.

[0046] The SMO Framework 105 may be configured to support RAN deployment and provisioning of non-virtualized and virtualized network elements. For non-virtualized network elements, the SMO Framework 105 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements that may be managed via an operations and maintenance interface (such as an 01 interface). For virtualized network elements, the SMO Framework 105 may be configured to interact with a cloud computing platform (such as an open cloud (O-Cloud) 190) to perform network element life cycle management (such as to instantiate virtualized network elements) via a cloud computing platform interface (such as an 02 interface). Such virtualized network elements can include, but are not limited to, CUs 110, DUs 130, RUs 140 andNear-RTRICs 125. In some implementations, the SMO Framework 105 can communicate with a hardware aspect of a 4G RAN, such as an open eNB (O- eNB) 111, via an 01 interface. Additionally, in some implementations, the SMO Framework 105 can communicate directly with one or more RUs 140 via an 01 interface. The SMO Framework 105 also may include a Non-RT RIC 115 configured to support functionality of the SMO Framework 105.

[0047] The Non-RT RIC 115 may be configured to include a logical function that enables non-real-time control and optimization of RAN elements and resources, artificial intelligence (Al) / machine learning (ML) (AI / ML) workflows including model training and updates, or policy-based guidance of applications / features in the Near- RT RIC 125. The Non-RT RIC 115 may be coupled to or communicate with (such as via an Al interface) the Near-RT RIC 125. The Near-RT RIC 125 may be configured to include a logical function that enables near-real-time control and optimization ofRAN elements and resources via data collection and actions over an interface (such as via an E2 interface) connecting one or more CUs 110, one or more DUs 130, or both, as well as an O-eNB, with the Near-RT RIC 125.

[0048] In some implementations, to generate AI / ML models to be deployed in the Near-RT RIC 125, the Non-RT RIC 115 may receive parameters or external enrichment information from external servers. Such information may be utilized by the Near-RT RIC 125 and may be received at the SMO Framework 105 or the Non-RT RIC 115 from non-network data sources or from network functions. In some examples, the Non-RT RIC 115 or the Near-RT RIC 125 may be configured to tune RAN behavior or performance. For example, the Non-RT RIC 115 may monitor long-term trends and patterns for performance and employ AI / ML models to perform corrective actions through the SMO Framework 105 (such as reconfiguration via 01) or via creation of RAN management policies (such as Al policies).

[0049] At least one of the CU 110, the DU 130, and the RU 140 may be referred to as a base station 102. Accordingly, a base station 102 may include one or more of the CU 110, the DU 130, and the RU 140 (each component indicated with dotted lines to signify that each component may or may not be included in the base station 102). The base station 102 provides an access point to the core network 120 for a UE 104. The base station 102 may include macrocells (high power cellular base station) and / or small cells (low power cellular base station). The small cells include femtocells, picocells, and microcells. A network that includes both small cell and macrocells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). The communication links between the RUs 140 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to an RU 140 and / or downlink (DL) (also referred to as forward link) transmissions from an RU 140 to a UE 104. The communication links may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and / or transmit diversity. The communication links may be through one or more carriers. The base station 102 / UEs 104 may use spectrum up to fMHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Ex MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent toeach other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell).

[0050] Certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL / UL wireless wide area network (WWAN) spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communications systems, such as for example, Bluetooth™ (Bluetooth is a trademark of the Bluetooth Special Interest Group (SIG)), Wi-Fi™ (Wi-Fi is a trademark of the Wi-Fi Alliance) based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

[0051] The wireless communications system may further include a Wi-Fi AP 150 in communication with UEs 104 (also referred to as Wi-Fi stations (STAs)) via communication link 154, e.g., in a 5 GHz unlicensed frequency spectrum or the like. When communicating in an unlicensed frequency spectrum, the UEs 104 / AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

[0052] The electromagnetic spectrum is often subdivided, based on frequency / wavelength, into various classes, bands, channels, etc. In 5GNR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz - 7.125 GHz) and FR2 (24.25 GHz - 52.6 GHz). Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz - 300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

[0053] The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Recent 5G NR studies have identified an operating band for these mid-band frequencies as frequency range designation FR3 (7.125 GHz - 24.25 GHz). Frequency bands falling within FR3 may inherit FR1 characteristics and / or FR2 characteristics, and thus may effectively extend features of FR1 and / or FR2 into midband frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operation beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR2-2 (52.6 GHz - 71 GHz), FR4 (71 GHz - 114.25 GHz), and FR5 (114.25 GHz - 300 GHz). Each of these higher frequency bands falls within the EHF band.

[0054] With the above aspects in mind, unless specifically stated otherwise, the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, FR4, FR2-2, and / or FR5, or may be within the EHF band.

[0055] The base station 102 and the UE 104 may each include a plurality of antennas, such as antenna elements, antenna panels, and / or antenna arrays to facilitate beamforming. The base station 102 may transmit a beamformed signal 182 to the UE 104 in one or more transmit directions. The UE 104 may receive the beamformed signal from the base station 102 in one or more receive directions. The UE 104 may also transmit a beamformed signal 184 to the base station 102 in one or more transmit directions. The base station 102 may receive the beamformed signal from the UE 104 in one or more receive directions. The base station 102 / UE 104 may perform beam training to determine the best receive and transmit directions for each of the base station 102 / UE 104. The transmit and receive directions for the base station 102 may or may not be the same. The transmit and receive directions for the UE 104 may or may not be the same.

[0056] The base station 102 may include and / or be referred to as a gNB, Node B, eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a TRP, network node, network entity, network equipment, or some other suitable terminology. The base station 102 can be implemented as an integrated access andbackhaul (IAB) node, a relay node, a sidelink node, an aggregated (monolithic) base station with a baseband unit (BBU) (including a CU and a DU) and an RU, or as a disaggregated base station including one or more of a CU, a DU, and / or an RU. The set of base stations, which may include disaggregated base stations and / or aggregated base stations, may be referred to as next generation (NG) RAN (NG-RAN).

[0057] The core network 120 may include an Access and Mobility Management Function (AMF) 161, a Session Management Function (SMF) 162, a User Plane Function (UPF) 163, a Unified Data Management (UDM) 164, one or more location servers 168, and other functional entities. The AMF 161 is the control node that processes the signaling between the UEs 104 and the core network 120. The AMF 161 supports registration management, connection management, mobility management, and other functions. The SMF 162 supports session management and other functions. The UPF 163 supports packet routing, packet forwarding, and other functions. The UDM 164 supports the generation of authentication and key agreement (AKA) credentials, user identification handling, access authorization, and subscription management. The one or more location servers 168 are illustrated as including a Gateway Mobile Location Center (GMLC) 165 and a Location Management Function (LMF) 166. However, generally, the one or more location servers 168 may include one or more location / positioning servers, which may include one or more of the GMLC 165, the LMF 166, a position determination entity (PDE), a serving mobile location center (SMLC), a mobile positioning center (MPC), or the like. The GMLC 165 and the LMF 166 support UE location services. The GMLC 165 provides an interface for clients / applications (e.g., emergency services) for accessing UE positioning information. The LMF 166 receives measurements and assistance information from the NG-RAN and the UE 104 via the AMF 161 to compute the position of the UE 104. The NG-RAN may utilize one or more positioning methods in order to determine the position of the UE 104. Positioning the UE 104 may involve signal measurements, a position estimate, and an optional velocity computation based on the measurements. The signal measurements may be made by the UE 104 and / or the base station 102 serving the UE 104. The signals measured may be based on one or more of a satellite positioning system (SPS) 170 (e.g., one or more of a Global Navigation Satellite System (GNSS), global position system (GPS), non-terrestrial network (NTN), or other satellite position / location system), LTE signals, wireless local area network(WLAN) signals, Bluetooth signals, a terrestrial beacon system (TBS), sensor-based information (e.g., barometric pressure sensor, motion sensor), NR enhanced cell ID (NRE-CID) methods, NR signals (e.g., multi -round trip time (Multi -RTT), DL angle- of-departure (DL-AoD), DL time difference of arrival (DL-TDOA), UL time difference of arrival (UL-TDOA), and UL angle-of-arrival (UL-AoA) positioning), and / or other systems / signals / sensors.

[0058] Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor / actuator, a display, or any other similar functioning device. Some of the UEs 104 may be referred to as loT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc.). The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. In some scenarios, the term UE may also apply to one or more companion devices such as in a device constellation arrangement. One or more of these devices may collectively access the network and / or individually access the network.

[0059] Referring again to FIG. 1, in certain aspects, the UE 104 may have a SL timing information exchange component 198 (“component 198”) that may be configured to identify a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or a synchronization reference UE. The component 198 may also be configured to detect a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The component 198 may also be configured to provide, to at least one of a LMF or a second UE, at least one of a first indication ofthe synchronization reference type of the synchronization reference source, a quality metric, or the variation time. The component 198 may also be configured to identify a satellite constellation associated with the GNSS. The component 198 may also be configured to report, to the LMF or the second UE, a second indication of the satellite constellation. The component 198 may also be configured to identify cell information associated with the network node. The component 198 may also be configured to report, to the LMF or the second UE in the first indication, indicia of the cell information. The component 198 may also be configured to identify a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. The component 198 may also be configured to report, to the LMF or the second UE, the reception time and the frequency location. The component 198 may also be configured to identify cell information associated with the quality metric. The component 198 may also be configured to report, to the LMF or the second UE, a second indication of the cell information in at least one of the first indication or signaling separate from the first indication. In some aspects, the component 198 may be configured to receive, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, and a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The component 198 may also be configured to communicate based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time. The component 198 may also be configured to receive, from the LMF or the second UE, a second indication of a satellite constellation, where the satellite constellation is associated with the GNSS. The component 198 may also be configured to receive, from the LMF or the second UE, indicia of cell information in the first indication, where the cell information is associated with the network node. The component 198 may also be configured to receive, from the LMF or the second UE, a reception time of a S-SSB and a frequency location associated with thesynchronization to the synchronization reference UE. The component 198 may also be configured to generate an adjusted timing parameter for the communication based on at least one of the synchronization reference type or the variation time. The component 198 may also be configured to receive, from the LMF or the second UE, indicia of cell information in at least one of the first indication or signaling separate from the first indication. The component 198 may also be configured to perform a positioning calculation based on at least one of the communication or the adjusted timing parameter. In certain aspects, the base station 102 may have a SL timing information exchange component 199 (“component 199”) that may be configured to operate in a commensurate manner with the component 198. The component 199 may be configured to provide synchronization information to a UE. The component 199 may also be configured to communicate with at least one of the UE or another UE based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time. Accordingly, aspects provide for synchronization information exchange for mitigating impacts of synchronization errors among anchor UEs, e.g., for SL-based TDoA measurements. In aspects, methods and apparatuses are provided to exchange synchronization information of anchor UEs between a UE and an LMF or another UE, and the synchronization information may be associated with a synchronization reference source, a RTD, synchronization quality information, a synchronization reference type, a variation time, and / or the like.

[0060] FIG. 2A is a diagram 200 illustrating an example of a first subframe within a 5G NR frame structure. FIG. 2B is a diagram 230 illustrating an example of DL channels within a 5G NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe within a 5G NR frame structure. FIG. 2D is a diagram 280 illustrating an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency division duplexed (FDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for either DL or UL, or may be time division duplexed (TDD) in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by FIGs. 2A, 2C, the 5G NR frame structure is assumed to be TDD, with subframe 4 being configured with slot format 28 (with mostly DL), where D is DL, U is UL, and F isflexible for use between DL / UL, and subframe 3 being configured with slot format 1 (with all UL). While subframes 3, 4 are shown with slot formats 1, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI), or semi- statically / statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI). Note that the description infra applies also to a 5G NR frame structure that is TDD.

[0061] FIGs. 2A-2D illustrate a frame structure, and the aspects of the present disclosure may be applicable to other wireless communication technologies, which may have a different frame structure and / or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 14 or 12 symbols, depending on whether the cyclic prefix (CP) is normal or extended. For normal CP, each slot may include 14 symbols, and for extended CP, each slot may include 12 symbols. The symbols on DL may be CP orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (for power limited scenarios; limited to a single stream transmission). The number of slots within a subframe is based on the CP and the numerology. The numerology defines the subcarrier spacing (SCS) (see Table 1). The symbol length / duration may scale with 1 / SCS.Table 1: Numerology, SCS, and CP

[0062] For normal CP (14 symbols / slot), different numerologies p 0 to 4 allow for 1, 2, 4, 8, and 16 slots, respectively, per subframe. For extended CP, the numerology 2 allows for 4 slots per subframe. Accordingly, for normal CP and numerology p, there are 14 symbols / slot and 2^ slots / subframe. The subcarrier spacing may be equal to 2 * 15 kHz, where g is the numerology 0 to 4. As such, the numerology p=0 has a subcarrier spacing of 15 kHz and the numerology p=4 has a subcarrier spacing of 240 kHz. The symbol length / duration is inversely related to the subcarrier spacing. FIGs. 2A-2D provide an example of normal CP with 14 symbols per slot and numerology p=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 ps. Within a set of frames, there may be one or more different bandwidth parts (BWPs) (see FIG. 2B) that are frequency division multiplexed. Each BWP may have a particular numerology and CP (normal or extended).

[0063] A resource grid may be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as physical RBs (PRBs)) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0064] As illustrated in FIG. 2A, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include demodulation RS (DM-RS) (indicated as R for one particular configuration, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS mayalso include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS).

[0065] FIG. 2B illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE including six RE groups (REGs), each REG including 12 consecutive REs in an OFDM symbol of an RB. A PDCCH within one BWP may be referred to as a control resource set (CORESET). A UE is configured to monitor PDCCH candidates in a PDCCH search space (e.g., common search space, UE-specific search space) during PDCCH monitoring occasions on the CORESET, where the PDCCH candidates have different DCI formats and different aggregation levels. Additional BWPs may be located at greater and / or lower frequencies across the channel bandwidth. A primary synchronization signal (PSS) may be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe / symbol timing and a physical layer identity. A secondary synchronization signal (SSS) may be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB), may be logically grouped with the PSS and SSS to form a synchronization signal (SS)ZPBCH block (also referred to as SS block (SSB)). The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs), and paging messages.

[0066] As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on theparticular PUCCH format used. The UE may transmit sounding reference signals (SRS). The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequencydependent scheduling on the UL.

[0067] FIG. 2D illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgment (ACK) (HARQ-ACK) feedback (i.e., one or more HARQ ACK bits indicating one or more ACK and / or negative ACK (NACK)). The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0068] FIG. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. In the DL, Internet protocol (IP) packets may be provided to a controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs),demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0069] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding / decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation / demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and / or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and / or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318Tx. Each transmitter 318Tx may modulate a radio frequency (RF) carrier with a respective spatial stream for transmission.

[0070] At the UE 350, each receiver 354Rx receives a signal through its respective antenna 352. Each receiver 354Rx recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal includes aseparate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to the controller / processor 359, which implements layer 3 and layer 2 functionality.

[0071] The controller / processor 359 can be associated with at least one memory 360 that stores program codes and data. The at least one memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets. The controller / processor 359 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0072] Similar to the functionality described in connection with the DL transmission by the base station 310, the controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression / decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re- segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0073] Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by the base station 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354Tx. Each transmitter 354Tx may modulate an RF carrier with a respective spatial stream for transmission.

[0074] The UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318Rx receives a signal through its respective antenna 320. Each receiver 318Rx recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

[0075] The controller / processor 375 can be associated with at least one memory 376 that stores program codes and data. The at least one memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets. The controller / processor 375 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0076] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to perform aspects in connection with the component 198 of FIG. 1. At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 may be configured to perform aspects in connection with the component 199 of FIG. 1.

[0077] FIG. 4 is a diagram 400 illustrating an example of a UE positioning based on reference signal measurements. The UE 404 may transmit UL-SRS 412 at time TSRS TX and receive DL positioning reference signals (PRS) (DL-PRS) 410 at time TPRS_RX. The TRP 406 may receive the UL-SRS 412 at time TSRS RX and transmit the DL-PRS 410 at time TPRS TX. The UE 404 may receive the DL-PRS 410 before transmitting the UL-SRS 412, or may transmit the UL-SRS 412 before receiving the DL-PRS 410. In both cases, a positioning server (e.g., location server(s)168) or the UE 404 may determine the RTT 414 based on ||TSRS_RX - TPRS_TX| - |TSRS_TX - TPRS_RX||. Accordingly, multi-RTT positioning may make use of the UE Rx-Tx time difference measurements (i.e., |TSRS_TX - TPRS _RX|) and DL-PRS reference signal received power (RSRP) (DL-PRS-RSRP) of downlink signals received from multiple TRPs 402, 406 and measured by the UE 404, and the measured TRP Rx-Tx time difference measurements (i.e., |TSRS_RX - TPRS _TX|) and UL-SRS-RSRP at multiple TRPs 402, 406 of uplink signals transmitted from UE 404. The UE 404 measures the UE Rx-Tx time difference measurements (and optionally DL-PRS-RSRP of the received signals) using assistance data received from the positioning server, and the TRPs 402, 406measure the gNB Rx-Tx time difference measurements (and optionally UL-SRS- RSRP of the received signals) using assistance data received from the positioning server. The measurements may be used at the positioning server or the UE 404 to determine the RTT, which is used to estimate the location of the UE 404. Other methods are possible for determining the RTT, such as for example using DL-TDOA and / or UL-TDOA measurements.

[0078] DL-AoD positioning may make use of the measured DL-PRS-RSRP of downlink signals received from multiple TRPs 402, 406 at the UE 404. The UE 404 measures the DL-PRS-RSRP of the received signals using assistance data received from the positioning server, and the resulting measurements are used along with the azimuth angle of departure (A-AoD), the zenith angle of departure (Z-AoD), and other configuration information to locate the UE 404 in relation to the neighboring TRPs 402, 406.

[0079] DL-TDOA positioning may make use of the DL reference signal time difference (RSTD) (and optionally DL-PRS-RSRP) of downlink signals received from multiple TRPs 402, 406 at the UE 404. The UE 404 measures the DL RSTD (and optionally DL-PRS-RSRP) of the received signals using assistance data received from the positioning server, and the resulting measurements are used along with other configuration information to locate the UE 404 in relation to the neighboring TRPs 402, 406.

[0080] UL-TDOA positioning may make use of the UL relative time of arrival (RTOA) (and optionally UL-SRS-RSRP) at multiple TRPs 402, 406 of uplink signals transmitted from UE 404. The TRPs 402, 406 measure the UL-RTOA (and optionally UL-SRS- RSRP) of the received signals using assistance data received from the positioning server, and the resulting measurements are used along with other configuration information to estimate the location of the UE 404.

[0081] UL-AoA positioning may make use of the measured azimuth angle of arrival (A-AoA) and zenith angle of arrival (Z-AoA) at multiple TRPs 402, 406 of uplink signals transmitted from the UE 404. The TRPs 402, 406 measure the A-AoA and the Z-AoA of the received signals using assistance data received from the positioning server, and the resulting measurements are used along with other configuration information to estimate the location of the UE 404.

[0082] Additional positioning methods may be used for estimating the location of the UE 404, such as for example, UE-side UL-AoD and / or DL-AoA. Note that data / measurements from various technologies may be combined in various ways to increase accuracy, to determine and / or to enhance certainty, to supplement / complement measurements, and / or to substitute / provide for missing information.

[0083] Wireless communication networks may support positioning of wireless devices. For instance, based on reference signal communications between anchor entities such as network nodes (e.g., base stations, eNBs, gNBs, transmission reception points TRPs, etc.) and a wireless device, a UE may determine a location / position of the wireless device using a TDoA associated with the reference signal communications. As one example for TDoA, a wireless device may position itself or another wireless device based on the difference of arrival times of the positioning reference signals. In uplinklike TDoA, a wireless device may transmit a PRS and anchor entities may report the time at which they received this PRS back to the wireless device, and based on the differences between arrival times and anchor entity locations, the wireless device location may be calculated. In downlink-like TDoA, multiple anchor entities may transmit PRSs, a wireless device may receive those PRS transmissions, and based on the difference in arrival times and the anchor entity locations, the wireless device location may be calculated. In a Uu interface positioning, an anchor entity may report a quality metric for the relative time difference between itself and a synchronization reference source. The quality metric may be the rtd-Quality field in RTD- InfoElement, which may be used in anchor entity selection. However, if the anchor entities are not fully synchronized with their synchronization reference source(s) (e.g., a GNSS, a network node, an independent synchronization reference UE, and / or the like), uncertainty may be introduced to the arrival times and the time difference measurements, which in turn may introduce uncertainty to the calculated location. For example, an anchor entity may be synchronized to a synchronization reference source(s), and over some time, the synchronization may drift by an amount of time for which correction should be applied to avoid synchronization errors. Yet, examples for synchronization error management do not provide for mitigation of impacts due to synchronization errors between anchor UEs for sidelink SL TDoA measurements.

[0084] FIG. 5 is a diagram 500 illustrating examples of a UE positioning based on reference signal measurements and quality metrics. Diagram 500 shows a configuration 550, a configuration 560, and a configuration 570, respectively illustrating examples for TDoA positioning in which a wireless device (e.g., a UE 502) may position itself or another device based on the difference of arrival times of a positioning signal(s) associated with anchor entities 504.

[0085] In the configuration 550, the UE 502 is associated with uplink-like TDoA. The UE 502 may transmit a PRS 506 to the anchor entities 504, which may in turn provide reports 508 (e.g., indicating the time(s) at which they received the PRS 506) back to the UE 502. Based on the differences between arrival times in the reports 508 and the locations of the anchor entities 504, the UE 502 location may be calculated.

[0086] In the configuration 560, the UE 502 is associated with downlink-like TDoA. The UE 502 may receive PRSs 510 transmitted from the anchor entities 504. Based on the differences between arrival times of the PRSs 510 and the locations of the anchor entities 504, the UE 502 location may be calculated.

[0087] In the configuration 570, the UE 502 may be associated with Uu interface positioning. An anchor entity 504’ (e.g., of the anchor entities 504) may report a quality metric 512, e.g., to the UE 502 and / or to an LMF, for the relative time difference (RTD) between the anchor entity 504’ and a synchronization reference source. The quality metric 512 may be the rtd-Quality field in RTD-InfoElement, e.g., as shown in a reporting configuration 514, which may be used in anchor entity selection. In one example, a timing quality value may indicate a numerical value of the quality metric 512 and a timing quality resolution may indicate the units, e.g., the resolution, for the timing quality value, such as 0.1 m, 1 m, 10 m, 30 m, etc.

[0088] Various aspects herein for timing information exchange for enhanced sidelink positioning enable synchronization information exchanges to mitigate impacts of synchronization errors among anchor UEs, such as for SL-based TDoA measurements. Exchanging synchronization information (e.g., associated with a synchronization reference source, an RTD, synchronization quality information, a synchronization reference type, a variation time, and / or the like) of anchor UEs between a UE and an LMF or another UE improves positioning. Correcting synchronization errors between anchor UEs for SL positioning measurements is enabled by providing synchronization reference types of synchronization referencesources and variation times for LMFs and SL UEs. Additionally, improvements to wireless device positioning accuracy for wireless communication networks is provided by correcting such synchronization errors.

[0089] FIG. 6 is a call flow diagram 600 for wireless communications, in various aspects. Call flow diagram 600 illustrates timing information exchange for enhanced sidelink positioning associated with a wireless device (a UE 602, by way of example) that may be configured to communicate with a synchronization reference source 604 and / or a LMF / UE 606. The synchronization reference source 604 type may be a GNSS, a network node (e.g., a base station, such as a gNB or other type of base station, by way of example, as shown), an independent synchronization reference UE, an independent synchronization reference, and / or the like. The LMF / UE 606 may be an LMF or a UE, or may represent both an LMF and a UE, in aspects. Aspects described for the synchronization reference source 604 as a base station may be performed by the base station in aggregated form and / or by one or more components of the base station in disaggregated form. Additionally, or alternatively, the aspects may be performed by the UE 602 autonomously, in addition to, and / or in lieu of, operations of the synchronization reference source 604 and / or the LMF / UE 606.

[0090] In the illustrated aspect, the UE 602 may be configured to receive synchronization information 608, which the synchronization reference source 604 and / or the LMF / UE 606 may be configured to provide / transmit. The synchronization information 608 may include one or more of a synchronization reference type, a UE identifier, cell information, a time associated with the synchronization reference source 604, and / or the like. A synchronization reference source may be a device, system, and / or the like, which is configured to provide a synchronizing reference, such as a time, frame number, counter, etc., by which a wireless device may synchronize itself with respect thereto. A synchronization reference source may also be a device, system, and / or the like, which is configured to transmit a synchronization reference signal (e.g., a S- SSB). A synchronization reference type may be GNSS, network (e.g., gNB / eNB), an independent synchronization reference UE, or another device as described herein, and in aspects a synchronization reference type may be associated with a configuration or implementation through which a wireless device communicates with a synchronization reference source. In aspects, the time may be a time since a last synchronization update (e.g., indicated / represented as subframes, microseconds,milliseconds, seconds, etc.), may be a qualitative time period measured with respect to a threshold value (e.g., a threshold that may be configured to identify updates for relative times such as very recent, recent, not recent, long ago, etc.). In other aspects, the time may be a time since a last synchronization update (e.g., an absolute time (such as, but without limitation, coordinated universal time (UTC)), a time period associated with a system frame number (SFN), a time period associated with a direct frame number (DFN), and / or the like.

[0091] In some aspects, the synchronization reference source 604 may be associated with at least one of an implementation of the anchor entity, a communication layer message of the LMF of the LMF / UE 606, or another UE, a configuration at the UE 602, a request from the UE 602, and / or the like.

[0092] The UE 602 may be configured to identify (at 610) a synchronization reference type of a synchronization reference source (e.g., the synchronization reference source 604) based on a synchronization of the UE 602 to the synchronization reference source 604 and / or the synchronization information 608. In aspects, the synchronization reference source may be one or more of a GNSS, a network node, an independent synchronization reference UE (e.g., that is synchronized to itself), an independent synchronization reference (e.g., that is unsynchronized), and / or the like. The synchronization reference type may be a GNSS, a UE synchronized directly to a GNSS, a UE synchronized indirectly to a GNSS, a base station (e.g., a gNB, an eNB, etc.), a UE synchronized directly to a gNB / eNB, a UE synchronized indirectly to a gNB / eNB, a UE synchronized to a synchronization reference UE (e.g., an independent synchronization reference UE, where the anchor entity itself is an independent synchronization reference), and / or the like.

[0093] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS, the UE 602 may be configured to identify (at 610) a satellite constellation associated with the GNSS (e.g., which satellite constellation was utilized for the synchronization reference source 604). In some aspects, where the synchronization reference type is based on the synchronization to the network node, the UE 602 may be configured to identify (at 610) cell information associated with the network node (e.g., cell identifying information for the synchronization reference source 604). In some aspects, where the synchronization reference type is based on the synchronization to the synchronization reference UE, the UE 602 maybe configured to identify (e.g., as a portion of 610) a reception time of a SL SSB (S- SSB) (e.g., absolute time, SFN, DFN, etc.) and a frequency location associated with the synchronization to the synchronization reference UE (e.g., an absolute radio frequency channel number (ARFCN)).

[0094] The UE 602 may be configured to detect (at 612) a variation time associated with an anchor entity, where the variation time includes at least one of a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE 606 may be configured to detect (at 612) the variation time associated with the anchor entity based on a PRS signal received from the anchor entity and / or based on a report, received from the anchor entity, of a reception time for a PRS signal that was provided / transmitted to the anchor entity by the UE 602, as described herein. In some aspects, the UE 602 may not detect the variation time or may skip one or more detections of the variation time.

[0095] The UE 602 may be configured to provide, to at least one of a LMF or a second UE (e.g., the LMF / UE 606), a first indication 614 of the synchronization reference type of the synchronization reference source 604, a quality metric, and / or the variation time. In aspects, the second UE, or the UE of the LMF / UE 606 may be a SL UE associated with the UE 602. In some aspects, the variation time may be a RTD between a first ToA associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE (e.g., the UE of the LMF / UE 606, etc.), where the second UE may be configured as a SL UE associated with the UE 602. The first indication 614 may be provided to the LMF / UE 606 as a basis of communications thereby, e.g., for a communication basis of the LMF / UE 606.

[0096] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS, the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606), a second indication of the satellite constellation. In some aspects, where the synchronization reference type is based on the synchronization to the network node, the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606), a second indication of the cellinformation. In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference, the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606), the reception time of a received S-SSB and the frequency location associated with the synchronization to the independent synchronization UE / reference. In some aspects, the satellite constellation, the cell information, and / or the reception time and the frequency location may be reported by the UE 602 with or in the first indication 614, the quality metric, and / or the variation time.

[0097] Accordingly, aspects herein enable the correction of synchronization errors between anchor UEs for SL positioning measurements by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs, which allows improvements to wireless device positioning accuracy for wireless communication networks, e.g., by correcting such synchronization errors.

[0098] FIG. 7 is a diagram 700 illustrating examples of timing information exchange for enhanced sidelink positioning, in various aspects. Diagram 700 may be an aspect of call flow diagram 600 in FIG. 6. Diagram 700 shows a UE 702 that may be synchronized with one or more of synchronization reference sources 706, and that may be configured to perform SL communication(s) 718 with a SL UE 704, according to aspects herein.

[0099] As illustrated, the UE 702 may be configured to receive, and one or more of the synchronization reference sources 706 may be configured to provide / transmit, synchronization information 716. The synchronization information 716 may be an aspect of the synchronization information 608 in FIG. 6. That is, the synchronization information 716 may include one or more of a synchronization reference type, a UE identifier, cell information, a time associated with the synchronization reference sources 706, and / or the like, as described herein. The synchronization reference sources 706 may include a GNSS 708, a network node 710 (e.g., TRP, base station (eNB, gNB, etc.), and / or the like), a UE 712 (e.g., a synchronization reference UE, an independent synchronization reference UE that may be synchronized to itself, etc.), a UE 714 (e.g., an independent synchronization reference that may be unsynchronized), and / or the like.

[0100] In aspects, the UE 702 may be configured to receive PRS information 724 may include a PRS(s) from anchor entities and / or may be based on reports, received fromanchor entities, of reception times for a PRS signal that was provided / transmitted to the anchor entities by the UE 702, as described herein. The UE 702 may be configured to identify (e.g., as described above for 610 in FIG. 6) a synchronization reference type of a synchronization reference source (e.g., of the synchronization reference sources 706) based on a synchronization of the UE 702 to one or more of the synchronization reference sources 706 and / or the synchronization information 716. The UE 702 may also be configured to detect (e.g., as described above for 612 in FIG. 6) a variation time associated with an anchor entity, where the variation time includes at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates, e.g., based at least in part on the synchronization information 716 and / or the PRS information 724.

[0101] The UE 702 may be configured to provide / transmit, to an LMF 722 (e.g., using a core network (CN) communication 720, e.g., viaNG-RAN) and / or a second UE (e.g., the SL UE 704 using the SL communication(s) 718), a first indication of the synchronization reference type of a utilized one of the synchronization reference sources 706 and / or the variation time (e.g., as similarly described for FIG. 6 (the first indication 614)). In aspects, when the UE 702 provides / transmits the first indication of the synchronization reference type and the variation time to the LMF 722 (e.g., using a core network (CN) communication 720), the LMF 722 may then provide the first indication of the synchronization reference type and the variation time to the second UE (e.g., the SL UE 704 using the CN communication 726, e.g., via NG- RAN). Accordingly, the SL UE 704 may receive an indication of the synchronization reference type and the variation time, which may enable the SL UE 704 to perform communications and / or corrections for synchronization errors.

[0102] FIG. 8 is a call flow diagram 800 for wireless communications, in various aspects. Call flow diagram 800 may be an aspect of call flow diagram 600 in FIG. 6 and / or diagram 700 in FIG. 7. Call flow diagram 800 illustrates timing information exchange for enhanced sidelink positioning associated with a wireless device (a UE 802, by way of example) that may be configured to communicate with an anchor entity(ies) 804 and / or a LMF / UE 806. The anchor entity(ies) 804 may be one or more TRPs, network nodes, base stations, gNBs, eNBs, UEs, and / or the like, by way of example. The LMF / UE 806 may be an LMF or a UE, or may represent both an LMF and aUE, in aspects. Aspects described for the anchor entity(ies) 804 as a base station(s) may be performed by the base station(s) in aggregated form and / or by one or more components of the base station in disaggregated form. Additionally, or alternatively, the aspects may be performed by the UE 802 autonomously, in addition to, and / or in lieu of, operations of the anchor entity(ies) 804 and / or the LMF / UE 806. Call flow diagram 800 may be an aspect of call flow diagram 600 in FIG. 6 and / or diagram 700 in FIG. 7. In aspects, the UE 802 may be a representation of the SL UE 704 in FIG. 7.

[0103] In the illustrated aspect, the UE 802 may be configured to receive, from at least one of a LMF or a second UE (e.g., the LMF / UE 806), at least one of a first indication 808 of a synchronization reference type of a synchronization reference source, a quality metric, and / or a variation time. The synchronization reference type may be associated with a synchronization of the UE 802 to the synchronization reference source and may be one or more of: a GNSS, a network node, a synchronization reference UE (e.g., that is synchronized to itself), an independent synchronization reference (e.g., that is unsynchronized), and / or the like. The synchronization reference type may be a GNSS, a UE synchronized directly to a GNSS, a UE synchronized indirectly to a GNSS, a base station (e.g., a gNB, an eNB, etc.), a UE synchronized directly to a gNB / eNB, a UE synchronized indirectly to a gNB / eNB, a UE synchronized to an independent synchronization reference UE, where the anchor entity 804 itself is an independent synchronization reference, and / or the like. The variation time may be associated with the anchor entity 804 and may include at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

[0104] In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE of the LMF / UE 806 may be configured to identify the synchronization reference type and / or to detect the variation time associated with the anchor entity 804 based on a PRS signal received from the anchor entity 804 and / or based on a report, received from the anchor entity 804, of a reception time for a PRS signal that was provided / transmitted to the anchor entity 804 by such UE 802, as described herein. In some aspects, the variation time may bea RTD between a first ToA associated with a first reference signal from the anchor entity 804 and a second ToA associated with a second reference signal from the UE 802.

[0105] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS, the UE 802 may be configured to receive, from the LMF or the second UE (e.g., the LMF / UE 806), a second indication of the satellite constellation. In some aspects, where the synchronization reference type is based on the synchronization to the network node, the UE 802 may be configured to receive, from the LMF or the second UE (e.g., the LMF / UE 806), a second indication of the cell information. In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference, the UE 802 may be configured to receive, from the LMF or the second UE (e.g., the LMF / UE 806), the reception time of a received S-SSB and the frequency location associated with the synchronization to the independent synchronization UE / reference. In some aspects, the satellite constellation, the cell information, and / or the reception time and the frequency location may be received by the UE 802with or in the first indication 808.

[0106] The UE 802 may be configured to provide / transmit and / or receive a communication(s) 810 based on at least one of the first indication 808 of the synchronization reference type of the synchronization reference source, the quality metric, and / or the variation time. In aspects, the UE 802 may provide / transmit the communication(s) 810 for positioning of the UE 802 and / or of another wireless device. As one example, the UE 802 may be configured to receive and / or transmit PRS information using the communication(s) 810. That is, the communication(s) 810 may include a PRS(s) from the anchor entity(ies) 804 and / or may be based on reports, received from the anchor entity(ies) 804, using the communication(s) 810, of reception times for a PRS signal that was provided / transmitted, using the communication(s) 810, to the anchor entity(ies) 804 by the UE 802, as described herein.

[0107] The UE 802 may be configured to generate (at 812) an adjusted timing parameter for the communication(s) 810 based on at least one of the synchronization reference type or the variation time indicated by the first indication 808. For example, the variation time may include at least one of a first time since a last synchronization update, asecond time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. Based on the variation time, the UE 802 may generate the adjusted timing parameter to compensate for the variation time and to correct the synchronization error represented by the variation time.

[0108] The UE 802 may be configured to perform (at 814) a positioning calculation based on at least one of the communication(s) 810 or the adjusted timing parameter. For example, the UE 802 may be configured to perform (at 814) a positioning calculation for itself. In aspects where the communi cation(s) 810 include PRS information that may be utilized for positioning, the UE 802 may apply the adjusted timing parameter generated (at 812) to account for synchronization error and calculate its position.

[0109] FIG. 9 is a flowchart 900 of a method of wireless communication, in various aspects. The method may be performed by a UE (e.g., the UE 104, 502, 602, 702, 704; the apparatus 1304). In some aspects, the method may include aspects described in connection with the communication flow in FIG. 6 and / or aspects described in FIGs. 7, 8. The method may be for timing information exchange for enhanced sidelink positioning and may enable correction of synchronization errors between anchor UEs for SL positioning measurements, as well as improvements for wireless device positioning accuracy for wireless communication networks, by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs.

[0110] At 902, the UE identifies a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or a synchronization reference UE. As an example, the identification may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 identifying such a synchronization reference type for a synchronization reference source (e.g., the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)).[OHl] The UE 602 may be configured to receive synchronization information 608 (e.g., 716 in FIG. 7), which the synchronization reference source 604 (e.g., 706, 708, 710, 712,714 in FIG. 7) and / or the LMF / UE 606 (e.g., 726, 704 in FIG. 7) may be configured to provide / transmit. The synchronization information 608 (e.g., 716 in FIG. 7) may include one or more of a synchronization reference type, a UE identifier, cell information, a time associated with the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7), and / or the like. In aspects, the time may be a time since a last synchronization update (e.g., indicated / represented as subframes, microseconds, milliseconds, seconds, etc.), may be a qualitative time period measured with respect to a threshold value (e.g., a threshold that may be configured to identify updates for relative times such as very recent, recent, not recent, long ago, etc.). In other aspects, the time may be a time since a last synchronization update (e.g., an absolute time (such as, but without limitation, coordinated universal time (UTC)), a time period associated with a system frame number (SFN), a time period associated with a direct frame number (DFN), and / or the like.

[0112] In some aspects, the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7) may be associated with at least one of an implementation of the anchor entity, a communication layer message of the LMF of the LMF / UE 606 (e.g., 726, 704 in FIG. 7), or another UE, a configuration at the UE 602, a request from the UE 602, and / or the like.

[0113] The UE 602 may be configured to identify (at 610) a synchronization reference type of a synchronization reference source (e.g., the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)) based on a synchronization of the UE 602 to the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7) and / or the synchronization information 608 (e.g., 716 in FIG. 7). In aspects, the synchronization reference source may be one or more of a GNSS (e.g., 706, 708 in FIG. 7), a network node (e.g., 706, 710 in FIG. 7), a synchronization reference UE (e.g., that is synchronized to itself) (e.g., 706, 712 in FIG. 7), an independent synchronization reference (e.g., that is unsynchronized) (e.g., 706, 714 in FIG. 7), and / or the like. The synchronization reference type may be a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized directly to a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized indirectly to a GNSS (e.g., 706, 708 in FIG. 7), a base station (e.g., a gNB, an eNB, etc.) (e.g., 706, 710 in FIG. 7), a UE synchronized directly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized indirectly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized to a synchronization reference UE (e.g., anindependent synchronization reference UE (e.g., 706, 712 in FIG. 7), where the anchor entity itself is an independent synchronization reference (e.g., 706, 714 in FIG. 7)), and / or the like.

[0114] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS (e.g., 706, 708 in FIG. 7), the UE 602 may be configured to identify (at 610) a satellite constellation associated with the GNSS (e.g., 706, 708 in FIG. 7) (e.g., which satellite constellation was utilized for the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)). In some aspects, where the synchronization reference type is based on the synchronization to the network node (e.g., 706, 710 in FIG. 7), the UE 602 may be configured to identify (at 610) cell information associated with the network node (e.g., 706, 710 in FIG. 7) (e.g., cell identifying information for the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)). In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7), the UE 602 may be configured to identify (e.g., as a portion of 610) a reception time of a SL SSB (S-SSB) (e.g., absolute time, SFN, DFN, etc.) and a frequency location associated with the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7) (e.g., an absolute radio frequency channel number (ARFCN)).

[0115] In some aspects, the UE detects a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. As an example, the detection may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 detecting such a time variation.

[0116] The UE 602 may be configured to detect (at 612) a variation time associated with an anchor entity, where the variation time includes at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE 602 may be configured to detect(at 612) the variation time associated with the anchor entity based on a PRS signal received from the anchor entity and / or based on a report, received from the anchor entity, of a reception time for a PRS signal that was provided / transmitted to the anchor entity by the UE 602 (e.g., 724 in FIG 7), as described herein.

[0117] At 904, the UE provides, to at least one of a LMF or a second UE as a basis of communications thereby, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time, wherein the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. As an example, the provision may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 providing such an indication / quality metric / variation time for an LMF and / or a UE (e.g., the LMF / UE 606).

[0118] The UE 602 may be configured to provide, to at least one of a LMF or a second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a first indication 614 (e.g., 718, 720 in FIG. 7) of the synchronization reference type of the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7), the quality metric, and / or the variation time. In aspects, the second UE, or the UE of the LMF / UE 606 (e.g., 726, 704 in FIG. 7) may be a SL UE associated with the UE 602. In some aspects, the variation time may be a RTD between a first ToA associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE (e.g., the UE of the LMF / UE 606 (e.g., 726, 704 in FIG. 7), etc.), where the second UE may be configured as a SL UE associated with the UE 602.

[0119] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS (e.g., 706, 708 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a second indication of the satellite constellation. In some aspects, where the synchronization reference type is based on the synchronization to the network node (e.g., 706, 710 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a second indication of the cell information. In some aspects, where the synchronization reference type isbased on the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), the reception time of a received S-SSB and the frequency location associated with the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7). In some aspects, the satellite constellation, the cell information, and / or the reception time and the frequency location may be reported by the UE 602 with or in the first indication 614 (e.g., 718, 720 in FIG. 7), the quality metric, and / or the variation time.

[0120] Accordingly, aspects herein enable the correction of synchronization errors between anchor UEs for SL positioning measurements by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs, which allows improvements to wireless device positioning accuracy for wireless communication networks, e.g., by correcting such synchronization errors.

[0121] FIG. 10 is a flowchart 1000 of a method of wireless communication, in various aspects. The method may be performed by a UE (e.g., the UE 104, 502, 602, 702, 704; the apparatus 1304). In some aspects, the method may include aspects described in connection with the communication flow in FIG. 6 and / or aspects described in FIGs. 7, 8. The method may be for timing information exchange for enhanced sidelink positioning and may enable correction of synchronization errors between anchor UEs for SL positioning measurements, as well as improvements for wireless device positioning accuracy for wireless communication networks, by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs.

[0122] At 1002, the UE identifies a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or a synchronization reference UE. As an example, the identification may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 identifying such a synchronization reference type for a synchronization reference source (e.g., the synchronization reference source 604).

[0123] The UE 602 may be configured to receive synchronization information 608 (e.g., 716 in FIG. 7), which the synchronization reference source 604 (e.g., 706, 708, 710, 712,714 in FIG. 7) and / or the LMF / UE 606 (e.g., 726, 704 in FIG. 7) may be configured to provide / transmit. The synchronization information 608 (e.g., 716 in FIG. 7) may include one or more of a synchronization reference type, a UE identifier, cell information, a time associated with the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7), and / or the like. In aspects, the time may be a time since a last synchronization update (e.g., indicated / represented as subframes, microseconds, milliseconds, seconds, etc.), may be a qualitative time period measured with respect to a threshold value (e.g., a threshold that may be configured to identify updates for relative times such as very recent, recent, not recent, long ago, etc.). In other aspects, the time may be a time since a last synchronization update (e.g., an absolute time (such as, but without limitation, coordinated universal time (UTC)), a time period associated with a system frame number (SFN), a time period associated with a direct frame number (DFN), and / or the like.

[0124] In some aspects, the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7) may be associated with at least one of an implementation of the anchor entity, a communication layer message of the LMF of the LMF / UE 606 (e.g., 726, 704 in FIG. 7), or another UE, a configuration at the UE 602, a request from the UE 602, and / or the like.

[0125] The UE 602 may be configured to identify (at 610) a synchronization reference type of a synchronization reference source (e.g., the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)) based on a synchronization of the UE 602 to the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7) and / or the synchronization information 608 (e.g., 716 in FIG. 7). In aspects, the synchronization reference source may be one or more of a GNSS (e.g., 706, 708 in FIG. 7), a network node (e.g., 706, 710 in FIG. 7), a synchronization reference UE (e.g., that is synchronized to itself) (e.g., 706, 712 in FIG. 7), an independent synchronization reference (e.g., that is unsynchronized) (e.g., 706, 714 in FIG. 7), and / or the like. The synchronization reference type may be a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized directly to a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized indirectly to a GNSS (e.g., 706, 708 in FIG. 7), a base station (e.g., a gNB, an eNB, etc.) (e.g., 706, 710 in FIG. 7), a UE synchronized directly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized indirectly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized to a synchronization reference UE (e.g., anindependent synchronization reference UE (e.g., 706, 712 in FIG. 7), where the anchor entity itself is an independent synchronization reference (e.g., 706, 714 in FIG. 7)), and / or the like.

[0126] At 1004, the UE determines if the synchronization reference source is GNSS. If so, the flowchart 1000 continues to 1006; if not, the flowchart 1000 continues to 1016. As an example, the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0127] At 1006, the UE identifies a satellite constellation associated with the GNSS. As an example, the identification may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 identifying such a satellite constellation.

[0128] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS (e.g., 706, 708 in FIG. 7), the UE 602 may be configured to identify (at 610) a satellite constellation associated with the GNSS (e.g., 706, 708 in FIG. 7) (e.g., which satellite constellation was utilized for the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)).

[0129] At 1008, the UE determines if the synchronization reference source is a network node.If so, the flowchart 1000 continues to 1010; if not, the flowchart 1000 continues to 1016. As an example, the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0130] At 1010, the UE identifies cell information associated with the network node. As an example, the identification may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 identifying such a cell information.

[0131] In some aspects, where the synchronization reference type is based on the synchronization to the network node (e.g., 706, 710 in FIG. 7), the UE 602 may be configured to identify (at 610) cell information associated with the network node (e.g., 706, 710 in FIG. 7) (e.g., cell identifying information for the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7)).

[0132] At 1012, the UE determines if the synchronization reference source is an independent synchronization UE or an independent synchronization reference. If so, the flowchart 1000 continues to 1014; if not, the flowchart 1000 continues to 1016. As an example,the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0133] At 1014, the UE identifies a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. As an example, the identification may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 identifying such a reception time and frequency location.

[0134] In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7), the UE 602 may be configured to identify (e.g., as a portion of 610) a reception time of a SL SSB (S-SSB) (e.g., absolute time, SFN, DFN, etc.) and a frequency location associated with the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7) (e.g., an absolute radio frequency channel number (ARFCN)).

[0135] At 1016, the UE detects a variation time associated with an anchor entity, where the variation time comprises at least one of a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. As an example, the detection may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 detecting such a time variation.

[0136] The UE 602 may be configured to detect (at 612) a variation time associated with an anchor entity, where the variation time includes at least one of a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE 602 may be configured to detect (at 612) the variation time associated with the anchor entity based on a PRS signal received from the anchor entity and / or based on a report, received from the anchor entity, of a reception time for a PRS signal that was provided / transmitted to the anchor entity by the UE 602 (e.g., 724 in FIG 7), as described herein.

[0137] At 1018, the UE provides, to at least one of a LMF or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time. As an example, the provision may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 providing such an indication / quality metric / variation time for an LMF and / or a UE (e.g., the LMF / UE 606).

[0138] The UE 602 may be configured to provide, to at least one of a LMF or a second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a first indication 614 (e.g., 718, 720 in FIG. 7) of the synchronization reference type of the synchronization reference source 604 (e.g., 706, 708, 710, 712, 714 in FIG. 7), the quality metric, and / or the variation time. In aspects, the second UE, or the UE of the LMF / UE 606 (e.g., 726, 704 in FIG. 7) may be a SL UE associated with the UE 602. In some aspects, the variation time may be a RTD between a first ToA associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE (e.g., the UE of the LMF / UE 606 (e.g., 726, 704 in FIG. 7), etc.), where the second UE may be configured as a SL UE associated with the UE 602.

[0139] At 1020, the UE determines if the synchronization reference source is GNSS. If so, the flowchart 1000 continues to 1008; if not, t the flowchart 1000 may return to 1002 and further perform a next synchronization error monitoring iteration and / or correction. As an example, the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0140] At 1022, the UE reports, to the LMF or the second UE, a second indication of the satellite constellation. As an example, the reporting may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 reporting such an indication.

[0141] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS (e.g., 706, 708 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a second indication of the satellite constellation.

[0142] At 1024, the UE determines if the synchronization reference source is a network node. If so, the flowchart 1000 continues to 1012; if not, the flowchart 1000 may return to1002 and further perform a next synchronization error monitoring iteration and / or correction. As an example, the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0143] At 1026, the UE reports, to the LMF or the second UE, a second indication of the cell information. As an example, the reporting may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 reporting such an indication.

[0144] In some aspects, where the synchronization reference type is based on the synchronization to the network node (e.g., 706, 710 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), a second indication of the cell information.

[0145] At 1028, the UE determines if the synchronization reference source is an independent synchronization UE or an independent synchronization reference. If so, the flowchart 1000 continues to 1016; if not, the flowchart 1000 may return to 1002 and further perform a next synchronization error monitoring iteration and / or correction. As an example, the determination may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13.

[0146] At 1030, the UE reports, to the LMF or the second UE, the reception time and the frequency location. As an example, the reporting may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7 illustrate an example of the UE 602 reporting such a reception time and frequency location.

[0147] In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7), the UE 602 may be configured to report, to the LMF or the second UE (e.g., the LMF / UE 606 (e.g., 726, 704 in FIG. 7)), the reception time of a received S-SSB and the frequency location associated with the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7).

[0148] In some aspects, the satellite constellation, the cell information, and / or the reception time and the frequency location may be reported by the UE 602 with or in the first indication 614 (e.g., 718, 720 in FIG. 7), the quality metric, and / or the variation time at 1018.

[0149] From 1030, the flowchart 1000 may return to 1002 and further perform a next synchronization error monitoring iteration and / or correction.

[0150] FIG. 11 is a flowchart 1100 of a method of wireless communication, in various aspects. The method may be performed by a UE (e.g., the UE 104, 502, 602, 702, 704; the apparatus 1304). In some aspects, the method may include aspects described in connection with the communication flow in FIG. 8 and / or aspects described in FIGs. 6, 7. The method may be for timing information exchange for enhanced sidelink positioning and may enable correction of synchronization errors between anchor UEs for SL positioning measurements, as well as improvements for wireless device positioning accuracy for wireless communication networks, by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs.

[0151] At 1102, the UE receives, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. As an example, the reception may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 receiving such a first indication of a synchronization reference type, quality metric, and / or a variation time from an LMF or a UE (e.g., the LMF / UE 806).

[0152] The UE 802 may be configured to receive, from at least one of a LMF or a second UE (e.g., the LMF / UE 806) (e.g., 722, 704 in FIG. 7), a first indication 808 (e.g., 614 in FIG. 6; 718, 726 in FIG. 7) of a synchronization reference type of a synchronization reference source and a variation time. The synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7) may be associated with a synchronization of the UE 802 to the synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7) and may be one or more of: a GNSS (e.g., 706, 708 in FIG. 7), a network node (e.g., 706, 710 in FIG. 7), an independent synchronizationreference UE (e.g., that is synchronized to itself) (e.g., 706, 712 in FIG. 7), an independent synchronization reference (e.g., that is unsynchronized) (e.g., 706, 714 in FIG. 7), and / or the like. The synchronization reference type may be a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized directly to a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized indirectly to a GNSS (e.g., 706, 708 in FIG. 7), a base station (e.g., a gNB, an eNB, etc.) (e.g., 706, 710 in FIG. 7), a UE synchronized directly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized indirectly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized to an independent synchronization reference UE (e.g., 706, 712 in FIG. 7), where the anchor entity 804 itself is an independent synchronization reference (e.g., 706, 714 in FIG. 7), and / or the like. The variation time may be associated with the anchor entity 804 and may include at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

[0153] In aspects, the variation time (e.g., detected (at 610) in FIG. 6) may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE of the LMF / UE 806 (e.g., 722, 704 in FIG. 7) may be configured to identify the synchronization reference type and / or to detect the variation time associated with the anchor entity 804 based on a PRS signal (e.g., 724 in FIG. 7) received from the anchor entity 804 and / or based on a report, received from the anchor entity 804, of a reception time for a PRS signal (e.g., 724 in FIG. 7) that was provided / transmitted to the anchor entity 804 by such UE 802, as described herein. In some aspects, the variation time may be a RTD between a first ToA associated with a first reference signal from the anchor entity 804 and a second ToA associated with a second reference signal from the UE 802.

[0154] At 1104, the UE communicates based on the first indication of the synchronization reference type of the synchronization reference source and the variation time. As an example, the communication may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 communicating based on the first indication of the synchronization reference type and the variation time with an LMF or a UE and / or with an anchor entity (e.g., the LMF / UE 806 and / or the anchor entity(ies) 804).

[0155] The UE 802 may be configured to provide / transmit and / or receive a communication(s) 810 based on at least one of the first indication 808 (e.g., 718, 726 in FIG. 7) of the synchronization reference type of the synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7), the quality metric, and / or the variation time. In aspects, the UE 802 may provide / transmit the communication(s) 810 for positioning of the UE 802 and / or of another wireless device. As one example, the UE 802 may be configured to receive and / or transmit PRS information (e.g., 724 in FIG. 7) using the communication(s) 810. That is, the communication(s) 810 may include a PRS(s) (e.g., 724 in FIG. 7) from the anchor entity(ies) 804 and / or may be based on reports, received from the anchor entity(ies) 804, using the communication(s) 810, of reception times for a PRS signal (e.g., 724 in FIG. 7) that was provided / transmitted, using the communication(s) 810, to the anchor entity(ies) 804 by the UE 802, as described herein.

[0156] The UE 802 may be configured to generate (at 812) an adjusted timing parameter for the communication(s) 810 based on at least one of the synchronization reference type or the variation time indicated by the first indication 808 (e.g., 718, 726 in FIG. 7). For example, the variation time may include at least one of a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In aspects, the variation time may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. Based on the variation time, the UE 802 may generate (at 812) the adjusted timing parameter to compensate for the variation time and to correct the synchronization error represented by the variation time. The UE 802 may be configured to perform (at 814) a positioning calculation based on at least one of the communication(s) 810 or the adjusted timing parameter. For example, the UE 802 may be configured to perform (at 814) a positioning calculation for itself. In aspects where the communication(s) 810 include PRS information (e.g., 724 in FIG. 7) that may be utilized for positioning, the UE 802 may apply the adjusted timing parameter generated (at 812) to account for synchronization error and calculate its position.

[0157] FIG. 12 is a flowchart 1200 of a method of wireless communication, in various aspects. The method may be performed by a UE (e.g., the UE 104, 502, 602, 702, 704;the apparatus 1304). In some aspects, the method may include aspects described in connection with the communication flow in FIG. 8 and / or aspects described in FIGs. 6, 7. The method may be for timing information exchange for enhanced sidelink positioning and may enable correction of synchronization errors between anchor UEs for SL positioning measurements, as well as improvements for wireless device positioning accuracy for wireless communication networks, by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs.

[0158] At 1202, the UE receives, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source or a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. As an example, the reception may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 receiving such a first indication of a synchronization reference type, a quality metric, and / or a variation time from an LMF or a UE (e.g., the LMF / UE 806).

[0159] The UE 802 may be configured to receive, from at least one of a LMF or a second UE (e.g., the LMF / UE 806) (e.g., 722, 704 in FIG. 7), at least one of a first indication 808 (e.g., 614 in FIG. 6, 718, 726 in FIG. 7) of a synchronization reference type of a synchronization reference source, a quality metric, and / or a variation time. The synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7) may be associated with a synchronization of the UE 802 to the synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7) and may be one or more of: a GNSS (e.g., 706, 708 in FIG. 7), a network node (e.g., 706, 710 in FIG. 7), a synchronization reference UE (e.g., that is synchronized to itself) (e.g., 706, 712 in FIG. 7), an independent synchronization reference (e.g., that is unsynchronized) (e.g., 706, 714 in FIG. 7), and / or the like. The synchronization reference type may be a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized directlyto a GNSS (e.g., 706, 708 in FIG. 7), a UE synchronized indirectly to a GNSS (e.g., 706, 708 in FIG. 7), a base station (e.g., a gNB, an eNB, etc.) (e.g., 706, 710 in FIG. 7), a UE synchronized directly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized indirectly to a gNB / eNB (e.g., 706, 710 in FIG. 7), a UE synchronized to an independent synchronization reference UE (e.g., 706, 712 in FIG. 7), where the anchor entity 804 itself is an independent synchronization reference (e.g., 706, 714 in FIG. 7), and / or the like. The variation time may be associated with the anchor entity 804 and may include at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

[0160] In aspects, the variation time (e.g., detected (at 610) in FIG. 6) may be based on an average of at least two more of the last one or more synchronization updates, and in some aspects, the variation time may be representative of a drift in time. In aspects, the UE of the LMF / UE 806 (e.g., 722, 704 in FIG. 7) may be configured to identify the synchronization reference type and / or to detect the variation time associated with the anchor entity 804 based on a PRS signal (e.g., 724 in FIG. 7) received from the anchor entity 804 and / or based on a report, received from the anchor entity 804, of a reception time for a PRS signal (e.g., 724 in FIG. 7) that was provided / transmitted to the anchor entity 804 by such UE 802, as described herein. In some aspects, the variation time may be a RTD between a first ToA associated with a first reference signal from the anchor entity 804 and a second ToA associated with a second reference signal from the UE 802.

[0161] At 1202, the UE may perform one or more additional receiving operations.

[0162] As one example, at 1204, the UE receives, from the LMF or the second UE, a second indication of a satellite constellation, where the satellite constellation is associated with the GNSS, where the synchronization reference type is based on the synchronization to the GNSS. As an example, the reception may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 receiving such a second indication from an LMF or a UE (e.g., the LMF / UE 806).

[0163] In some aspects, where the synchronization reference type is based on the synchronization to the GNSS (e.g., 706, 708 in FIG. 7), the UE 802 may be configuredto receive, from the LMF or the second UE (e.g., the LMF / UE 806) (e.g., 606 in FIG. 6; 726, 704 in FIG. 7), a second indication of the satellite constellation.

[0164] As one example, at 1206, the UE receives, from the LMF or the second UE, a second indication of cell information, where the cell information is associated with the network node, where the synchronization reference type is based on the synchronization to the network node. As an example, the reception may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 receiving such a second indication from an LMF or a UE (e.g., the LMF / UE 806).

[0165] In some aspects, where the synchronization reference type is based on the synchronization to the network node (e.g., 706, 710 in FIG. 7), the UE 802 may be configured to receive, from the LMF or the second UE (e.g., the LMF / UE 806) (e.g., 606 in FIG. 6; 726, 704 in FIG. 7)), a second indication of the cell information.

[0166] As one example, at 1208, the UE receives, from the LMF or the second UE, a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE, where the synchronization reference type is based on the synchronization to the synchronization reference UE. As an example, the reception may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 receiving such a reception time and frequency location from an LMF or a UE (e.g., the LMF / UE 806).

[0167] In some aspects, where the synchronization reference type is based on the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7), the UE 802 may be configured to receive, from the LMF or the second UE (e.g., the LMF / UE 806 (e.g., 606 in FIG. 6; 726, 704 in FIG. 7)), the reception time of a received S-SSB and the frequency location associated with the synchronization to the independent synchronization UE / reference (e.g., 706, 712, 714 in FIG. 7).

[0168] In some aspects, the satellite constellation, the cell information, and / or the reception time and the frequency location may be received by the UE 802 separately from the first indication 808 (e.g., 614 in FIG. 6; 718, 720 in FIG. 7) at 1202.

[0169] At 1210, the UE communicates based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the qualitymetric, or the variation time. As an example, the communication may be performed by one or more of the component 198, the transceiver 1322, and / or the antenna 1380 in FIG. 13. FIGs. 6, 7, 8 illustrate an example of the UE 802 communicating based on the first indication of the synchronization reference type and the variation time with an LMF or a UE and / or with an anchor entity (e.g., the LMF / UE 806 and / or the anchor entity(ies) 804).

[0170] The UE 802 may be configured to provide / transmit and / or receive a communication(s) 810 based on at least one of the first indication 808 (e.g., 718, 726 in FIG. 7) of the synchronization reference type of the synchronization reference source (e.g., 604 in FIG. 6; 706, 708, 710, 712, 714 in FIG. 7), the quality metric, and / or the variation time. In aspects, the UE 802 may provide / transmit the communication(s) 810 for positioning of the UE 802 and / or of another wireless device. As one example, the UE 802 may be configured to receive and / or transmit PRS information (e.g., 724 in FIG. 7) using the communication(s) 810. That is, the communication(s) 810 may include a PRS(s) (e.g., 724 in FIG. 7) from the anchor entity(ies) 804 and / or may be based on reports, received from the anchor entity(ies) 804, using the communication(s) 810, of reception times for a PRS signal (e.g., 724 in FIG. 7) that was provided / transmitted, using the communication(s) 810, to the anchor entity(ies) 804 by the UE 802, as described herein.

[0171] Based on the variation time, the UE 802 may generate (at 812) the adjusted timing parameter to compensate for the variation time and to correct the synchronization error represented by the variation time. The UE 802 may be configured to perform (at 814) a positioning calculation based on at least one of the communication(s) 810 or the adjusted timing parameter. For example, the UE 802 may be configured to perform (at 814) a positioning calculation for itself. In aspects where the communication(s) 810 include PRS information (e.g., 724 in FIG. 7) that may be utilized for positioning, the UE 802 may apply the adjusted timing parameter generated (at 812) to account for synchronization error and calculate its position.

[0172] FIG. 13 is a diagram 1300 illustrating an example of a hardware implementation for an apparatus 1304. The apparatus 1304 may be a UE, a component of a UE, or may implement UE functionality. In some aspects, the apparatus 1304 may include at least one cellular baseband processor 1324 (also referred to as a modem) coupled to one or more transceivers 1322 (e.g., cellular RF transceiver). The cellular basebandprocessor(s) 1324 may include at least one on-chip memory 1324'. In some aspects, the apparatus 1304 may further include one or more subscriber identity modules (SIM) cards 1320 and at least one application processor 1306 coupled to a secure digital (SD) card 1308 and a screen 1310. The application processor(s) 1306 may include on-chip memory 1306'. In some aspects, the apparatus 1304 may further include a Bluetooth module 1312, a WLAN module 1314, an SPS module 1316 (e.g., GNSS module), one or more sensor modules 1318 (e.g., barometric pressure sensor / altimeter; motion sensor such as inertial measurement unit (IMU), gyroscope, and / or accelerometer(s); magnetometer, audio and / or other technologies used for positioning), additional memory modules 1326, a power supply 1330, and / or a camera 1332. The Bluetooth module 1312, the WLAN module 1314, and the SPS module 1316 may include an on-chip transceiver (TRX) (or in some cases, just a receiver (RX)). The Bluetooth module 1312, the WLAN module 1314, and the SPS module 1316 may include their own dedicated antennas and / or utilize the antennas 1380 for communication. The cellular baseband processor(s) 1324 communicates through the transceiver(s) 1322 via one or more antennas 1380 with the UE 104 and / or with an RU associated with a network entity 1302. The cellular baseband processor(s) 1324 and the application processor(s) 1306 may each include a computer-readable medium / memory 1324', 1306', respectively. The additional memory modules 1326 may also be considered a computer-readable medium / memory. Each computer-readable medium / memory 1324', 1306', 1326 may be non-transitory. The cellular baseband processor(s) 1324 and the application processor(s) 1306 are each responsible for general processing, including the execution of software stored on the computer- readable medium / memory. The software, when executed by the cellular baseband processor(s) 1324 / application processor(s) 1306, causes the cellular baseband processor(s) 1324 / application processor(s) 1306 to perform the various functions described supra. The cellular baseband processor(s) 1324 and the application processor(s) 1306 are configured to perform the various functions described supra based at least in part of the information stored in the memory. That is, the cellular baseband processor(s) 1324 and the application processor(s) 1306 may be configured to perform a first subset of the various functions described supra without information stored in the memory and may be configured to perform a second subset of the various functions described supra based on the information stored in the memory. Thecomputer-readable medium / memory may also be used for storing data that is manipulated by the cellular baseband processor(s) 1324 / application processor(s) 1306 when executing software. The cellular baseband processor(s) 1324 / application processor(s) 1306 may be a component of the UE 350 and may include the at least one memory 360 and / or at least one of the TX processor 368, the RX processor 356, and the controller / processor 359. In one configuration, the apparatus 1304 may be at least one processor chip (modem and / or application) and include just the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, and in another configuration, the apparatus 1304 may be the entire UE (e.g., see UE 350 of FIG. 3) and include the additional modules of the apparatus 1304.

[0173] As discussed supra, the component 198 may be configured to identify a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of: a GNSS, a network node, or a synchronization reference UE. The component 198 may also be configured to detect a variation time associated with an anchor entity, where the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The component 198 may also be configured to provide, to at least one of a LMF or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time. The component 198 may also be configured to identify a satellite constellation associated with the GNSS. The component 198 may also be configured to report, to the LMF or the second UE, a second indication of the satellite constellation. The component 198 may also be configured to identify cell information associated with the network node. The component 198 may also be configured to report, to the LMF or the second UE in the first indication, indicia of the cell information. The component 198 may also be configured to identify a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. The component 198 may also be configured to report, to the LMF or the second UE, the reception time and the frequency location. The component 198 may also be configured to identify cell information associated with the quality metric. The component 198 may also be configured to report, to the LMFor the second UE, a second indication of the cell information in at least one of the first indication or signaling separate from the first indication. In some aspects, the component 198 may be configured to receive, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, and a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. The component 198 may also be configured to communicate based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time. The component 198 may also be configured to receive, from the LMF or the second UE, a second indication of a satellite constellation, where the satellite constellation is associated with the GNSS. The component 198 may also be configured to receive, from the LMF or the second UE, indicia of cell information in the first indication, where the cell information is associated with the network node. The component 198 may also be configured to receive, from the LMF or the second UE, a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. The component 198 may also be configured to generate an adjusted timing parameter for the communication based on at least one of the synchronization reference type or the variation time. The component 198 may also be configured to receive, from the LMF or the second UE, indicia of cell information in at least one of the first indication or signaling separate from the first indication. The component 198 may also be configured to perform a positioning calculation based on at least one of the communication or the adjusted timing parameter. The component 198 may be further configured to perform any of the aspects described in connection with the flowcharts in any of FIGs. 9, 10, 11, 12, and / or any of the aspects performed by a UE for any of FIGs. 5, 6, 7, 8. The component 198 may be within the cellular baseband processor(s) 1324, the application processor(s) 1306, or both the cellular baseband processor(s) 1324 and the application processor(s) 1306. The component 198 may be one or more hardware componentsspecifically configured to carry out the stated processes / algorithm, implemented by one or more processors configured to perform the stated processes / algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. When multiple processors are implemented, the multiple processors may perform the stated processes / algorithm individually or in combination. As shown, the apparatus 1304 may include a variety of components configured for various functions. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for identifying a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, where the synchronization reference type is one or more of a GNSS, a network node, or a synchronization reference UE. In the configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for detecting a variation time associated with an anchor entity, where the variation time comprises at least one of a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In the configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for providing, to at least one of a LMF or a second UE, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or the variation time. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for identifying a satellite constellation associated with the GNSS. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for reporting, to the LMF or the second UE, a second indication of the satellite constellation. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for identifying cell information associated with the network node. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for reporting, to the LMF or the second UE in the first indication,indicia of the cell information. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for identifying a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for reporting, to the LMF or the second UE, the reception time and the frequency location. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for identifying cell information associated with the quality metric. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for reporting, to the LMF or the second UE, a second indication of the cell information in at least one of the first indication or signaling separate from the first indication. In another configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for receiving, from at least one of a LMF or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, where the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a GNSS, a network node, or a synchronization reference UE, where the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates. In the configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for communicating based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for receiving, from the LMF or the second UE, a second indication of a satellite constellation, where the satellite constellation is associated with the GNSS. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the applicationprocessor(s) 1306, may include means for receiving, from the LMF or the second UE, indicia of cell information in the first notification, where the cell information is associated with the network node. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for receiving, from the LMF or the second UE, a reception time of a S-SSB and a frequency location associated with the synchronization to the synchronization reference UE. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for receiving, from the LMF or the second UE, indicia of cell information in at least one of the first indication or signaling separate from the first indication. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for generating an adjusted timing parameter for the communication based on at least one of the synchronization reference type or the variation time. In one configuration, the apparatus 1304, and in particular the cellular baseband processor(s) 1324 and / or the application processor(s) 1306, may include means for performing a positioning calculation based on at least one of the communication or the adjusted timing parameter. The means may be the component 198 of the apparatus 1304 configured to perform the functions recited by the means. As described supra, the apparatus 1304 may include the TX processor 368, the RX processor 356, and the controller / processor 359. As such, in one configuration, the means may be the TX processor 368, the RX processor 356, and / or the controller / processor 359 configured to perform the functions recited by the means.

[0174] FIG. 14 is a diagram 1400 illustrating an example of a hardware implementation for a network entity 1402. The network entity 1402 may be a BS, a component of a BS, or may implement BS functionality. The network entity 1402 may include at least one of a CU 1410, a DU 1430, or an RU 1440. For example, depending on the layer functionality handled by the component 199, the network entity 1402 may include the CU 1410; both the CU 1410 and the DU 1430; each of the CU 1410, the DU 1430, and the RU 1440; the DU 1430; both the DU 1430 and the RU 1440; or the RU 1440. The CU 1410 may include at least one CU processor 1412. The CU processor(s) 1412 may include on-chip memory 1412'. In some aspects, the CU 1410 may further include additional memory modules 1414 and a communications interface 1418. TheCU 1410 communicates with the DU 1430 through a midhaul link, such as an Fl interface. The DU 1430 may include at least one DU processor 1432. The DU processor(s) 1432 may include on-chip memory 1432'. In some aspects, the DU 1430 may further include additional memory modules 1434 and a communications interface 1438. The DU 1430 communicates with the RU 1440 through a fronthaul link. The RU 1440 may include at least one RU processor 1442. The RU processor(s) 1442 may include on-chip memory 1442'. In some aspects, the RU 1440 may further include additional memory modules 1444, one or more transceivers 1446, antennas 1480, and a communications interface 1448. The RU 1440 communicates with the UE 104. The on-chip memory 1412', 1432', 1442' and the additional memory modules 1414, 1434, 1444 may each be considered a computer-readable medium / memory. Each computer-readable medium / memory may be non-transitory. Each of the processors 1412, 1432, 1442 is responsible for general processing, including the execution of software stored on the computer-readable medium / memory. The software, when executed by the corresponding processor(s) causes the processor(s) to perform the various functions described supra. The computer-readable medium / memory may also be used for storing data that is manipulated by the processor(s) when executing software.

[0175] As discussed supra, the component 199 may be configured to operate in a commensurate manner with the component 198. The component 199 may be configured to provide synchronization information to a UE. The component 199 may also be configured to communicate with at least one of the UE or another UE based on the first indication of the synchronization reference type of the synchronization reference source, the quality metric, and / or the variation time. The component 199 may be further configured to perform any of the aspects described in connection with the flowcharts in any of FIGs. 9, 10, 11, 12, and / or any of the aspects performed by a network node / entity for any of FIGs. 5, 6, 7, 8. The component 199 may be within one or more processors of one or more of the CU 1410, DU 1430, and the RU 1440. The component 199 may be one or more hardware components specifically configured to carry out the stated processes / algorithm, implemented by one or more processors configured to perform the stated processes / algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. When multiple processors are implemented, the multipleprocessors may perform the stated processes / algorithm individually or in combination. The network entity 1402 may include a variety of components configured for various functions. In one configuration, the network entity 1402 may include means for operating in a commensurate manner with the component 198. In one configuration, the network entity 1402 may include means for providing synchronization information to a UE. In one configuration, the network entity 1402 may include means for communicating with at least one of the UE or another UE based on the first indication of the synchronization reference type of the synchronization reference source, the quality metric, and / or the variation time. The means may be the component 199 of the network entity 1402 configured to perform the functions recited by the means. As described supra, the network entity 1402 may include the TX processor 316, the RX processor 370, and the controller / processor 375. As such, in one configuration, the means may be the TX processor 316, the RX processor 370, and / or the controller / processor 375 configured to perform the functions recited by the means.

[0176] FIG. 15 is a diagram 1500 illustrating an example of a hardware implementation for a network entity 1560. In one example, the network entity 1560 may be within the core network 120. The network entity 1560 may include at least one network processor 1512. The network processor(s) 1512 may include on-chip memory 1512'. In some aspects, the network entity 1560 may further include additional memory modules 1514. The network entity 1560 communicates via the network interface 1580 directly (e.g., backhaul link) or indirectly (e.g., through a RIC) with the CU 1502 and / or the UE 104. The on-chip memory 1512' and the additional memory modules 1514 may each be considered a computer-readable medium / memory. Each computer-readable medium / memory may be non-transitory. The network processor(s) 1512 is responsible for general processing, including the execution of software stored on the computer-readable medium / memory. The software, when executed by the corresponding processor(s) causes the processor(s) to perform the various functions described supra. The computer-readable medium / memory may also be used for storing data that is manipulated by the processor(s) when executing software.

[0177] As discussed supra, the component 199 may be configured to operate in a commensurate manner with the component 198. The component 199 may beconfigured to provide synchronization information to a UE. The component 199 may also be configured to communicate with at least one of the UE or another UE based on the first indication of the synchronization reference type of the synchronization reference source, the quality metric, and / or the variation time. The component 199 may be further configured to perform any of the aspects described in connection with the flowcharts in any of FIGs. 9, 10, 11, 12, and / or any of the aspects performed by a network node / entity for any of FIGs. 5, 6, 7, 8. The component 199 may be within the network processor(s) 1512. The component 199 may be one or more hardware components specifically configured to carry out the stated processes / algorithm, implemented by one or more processors configured to perform the stated processes / algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. When multiple processors are implemented, the multiple processors may perform the stated processes / algorithm individually or in combination. The network entity 1560 may include a variety of components configured for various functions. In one configuration, the network entity 1560 may include means for operating in a commensurate manner with the component 198. In one configuration, the network entity 1560 may include means for providing synchronization information to a UE. In one configuration, the network entity 1560 may include means for communicating with at least one of the UE or another UE based on the first indication of the synchronization reference type of the synchronization reference source, the quality metric, and / or the variation time. The means may be the component 199 of the network entity 1560 configured to perform the functions recited by the means.

[0178] Wireless communication networks may support positioning of wireless devices. For instance, based on reference signal communications between anchor entities such as network nodes (e.g., base stations, eNBs, gNBs, TRPs, etc.) and a wireless device, a UE may determine a location / position of the wireless device using a TDoA associated with the reference signal communications. As one example for TDoA, a wireless device may position itself or another wireless device based on the difference of arrival times of the positioning reference signals. In uplink-like TDoA, a wireless device may transmit a PRS and anchor entities may report the time at which they received this PRS back to the wireless device, and based on the differences between arrival times and anchor entity locations, the wireless device location may becalculated. In downlink-like TDoA, multiple anchor entities may transmit PRSs, a wireless device may receive those PRS transmissions, and based on the difference in arrival times and the anchor entity locations, the wireless device location may be calculated. In a Uu interface positioning, an anchor entity may report a quality metric for the relative time difference between itself and a synchronization reference source. The quality metric may be the rtd-Quality field in RTD-InfoElement, which may be used in anchor entity selection. However, if the anchor entities are not fully synchronized with their synchronization reference source(s) (e.g., a GNSS, a network node, an independent synchronization reference UE, and / or the like), uncertainty may be introduced to the arrival times and the time difference measurements, which in turn may introduce uncertainty to the calculated location. For example, an anchor entity may be synchronized to a synchronization reference source(s), and over some time, the synchronization may drift by an amount of time for which correction should be applied to avoid synchronization errors. Yet, examples for synchronization error management do not provide for mitigation of impacts due to synchronization errors between anchor UEs for SL TDoA measurements.

[0179] Various aspects herein for timing information exchange for enhanced sidelink positioning enable synchronization information exchanges to mitigate impacts of synchronization errors among anchor UEs, such as for SL-based TDoA measurements. Exchanging synchronization information (e.g., associated with a synchronization reference source, an RTD, synchronization quality information, a synchronization reference type, a variation time, and / or the like) of anchor UEs between a UE and an LMF or another UE improves positioning. Correcting synchronization errors between anchor UEs for SL positioning measurements is enabled by providing synchronization reference types of synchronization reference sources and variation times for LMFs and SL UEs. Additionally, improvements to wireless device positioning accuracy for wireless communication networks is provided by correcting such synchronization errors.

[0180] It is understood that the specific order or hierarchy of blocks in the processes / flowcharts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes / flowcharts may be rearranged. Further, some blocks may be combined oromitted. The accompanying method claims present elements of the various blocks in a sample order, and are not limited to the specific order or hierarchy presented.

[0181] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not limited to the aspects described herein, but are to be accorded the full scope consistent with the language claims. Reference to an element in the singular does not mean “one and only one” unless specifically so stated, but rather “one or more.” Terms such as “if,” “when,” and “while” do not imply an immediate temporal relationship or reaction. That is, these phrases, e.g., “when,” do not imply an immediate action in response to or during the occurrence of an action, but simply imply that if a condition is met then an action will occur, but without requiring a specific or immediate time constraint for the action to occur. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof’ include any combination of A, B, and / or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof’ may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. Sets should be interpreted as a set of elements where the elements number one or more. Accordingly, for a set of X, X would include one or more elements. When at least one processor is configured to perform a set of functions, the at least one processor, individually or in any combination, is configured to perform the set of functions. Accordingly, each processor of the at least one processor may be configured to perform a particular subset of the set of functions, where the subset is the full set, a proper subset of the set, or an empty subset of the set. If a first apparatus receives data from or transmits data to a second apparatus, the data may be received / transmitted directly between thefirst and second apparatuses, or indirectly between the first and second apparatuses through a set of apparatuses. A device configured to “output” data, such as a transmission, signal, or message, may transmit the data, for example with a transceiver, or may send the data to a device that transmits the data. A device configured to “obtain” data, such as a transmission, signal, or message, may receive, for example with a transceiver, or may obtain the data from a device that receives the data. Information stored in a memory includes instructions and / or data. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are encompassed by the claims. Moreover, nothing disclosed herein is dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”

[0182] As used herein, the phrase “based on” shall not be construed as a reference to a closed set of information, one or more conditions, one or more factors, or the like. In other words, the phrase “based on A” (where “A” may be information, a condition, a factor, or the like) shall be construed as “based at least on A” unless specifically recited differently.

[0183] The following aspects are illustrative only and may be combined with other aspects or teachings described herein, without limitation.

[0184] Aspect 1 is a method of wireless communication at a first user equipment (UE), comprising: identifying a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, wherein the synchronization reference type is one or more of a global navigation satellite system (GNSS), a network node, or a synchronization reference UE; and providing, to at least one of a location management function (LMF) or a second UE as a basis of communications thereby, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or a variation time, wherein the variation time comprises at least one of a first time since a last synchronization update, a second time for the lastsynchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

[0185] Aspect 2 is the method of aspect 1, wherein the variation time includes the first time since the last synchronization update, wherein the first time is based on at least one of a number of symbols, an absolute time, or a relative time associated with a time duration threshold.

[0186] Aspect 3 is the method of any of aspects 1 and 2, wherein the variation time includes the second time for the last synchronization update, wherein the second time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

[0187] Aspect 4 is the method of any of aspects 1 to 3, wherein the variation time includes the correction amount that was corrected in the last one or more synchronization updates.

[0188] Aspect 5 is the method of aspect 4, wherein the variation time is based on an average of at least two more of the last one or more synchronization updates.

[0189] Aspect 6 is the method of any of aspects 1 to 5, wherein the synchronization reference type is based on the synchronization to the GNSS, wherein the method further comprises: identifying a satellite constellation associated with the GNSS; and reporting, to the LMF or the second UE, a second indication of the satellite constellation.

[0190] Aspect 7 is the method of aspect 6, wherein reporting the second indication of the satellite constellation includes reporting the second indication in the first indication.

[0191] Aspect 8 is the method of any of aspects 1 to 5, wherein the synchronization reference type is based on the synchronization to the network node, wherein the method further comprises: identifying cell information associated with the network node; and reporting, to the LMF or the second UE in the first indication, indicia of the cell information.

[0192] Aspect 9 is the method of any of aspects 1 to 5, wherein the synchronization reference type is based on the synchronization to the synchronization reference UE, wherein the method further comprises: identifying a reception time of a sidelink (SL) synchronization signal block (S-SSB) and a frequency location associated with the synchronization to the synchronization reference UE; and reporting, to the LMF or the second UE, the reception time and the frequency location.

[0193] Aspect 10 is the method of aspect 9, wherein the reception time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

[0194] Aspect 11 is the method of any of aspects 1 to 10, wherein the quality metric is associated with at least one of: an implementation of the anchor entity; a communication layer message of the LMF or another UE; a configuration at the first UE; or a request from the first UE; or cell information associated with the quality metric.

[0195] Aspect 12 is the method of any of aspects 1 to 11, further comprising: identifying cell information associated with the quality metric; and reporting, to the LMF or the second UE, a second indication of the cell information in at least one of the first indication or signaling separate from the first indication.

[0196] Aspect 13 is the method of any of aspects 1 to 12, wherein the quality metric is a relative time difference (RTD) between a first time of arrival (ToA) associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE, wherein the second UE is configured as a sidelink (SL) UE with the first UE.

[0197] Aspect 14 is a method of wireless communication at a first user equipment (UE), comprising: receiving, from at least one of a location management function (LMF) or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, wherein the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE, wherein the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates; and communicating based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time.

[0198] Aspect 15 is the method of aspect 14, wherein the variation time includes the first time since the last synchronization update, wherein the first time is based on at leastone of a number of symbols, an absolute time, or a relative time associated with a time duration threshold.

[0199] Aspect 16 is the method of any of aspects 14 and 15, wherein the variation time includes the second time for the last synchronization update, wherein the second time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

[0200] Aspect 17 is the method of any of aspects 14 to 16, wherein the variation time includes the correction amount that was corrected in the last one or more synchronization updates.

[0201] Aspect 18 is the method of aspect 17, wherein the variation time is based on an average of at least two more of the last one or more synchronization updates.

[0202] Aspect 19 is the method of any of aspects 14 to 18, wherein the synchronization reference type is based on the synchronization to the GNSS, wherein the method further comprises: receiving, from the LMF or the second UE, a second indication of a satellite constellation, wherein the satellite constellation is associated with the GNSS.

[0203] Aspect 20 is the method of aspect 19, wherein receiving the second indication of the satellite constellation includes receiving the second indication in the first indication.

[0204] Aspect 21 is the method of any of aspects 14 to 18, wherein the synchronization reference type is based on the synchronization to the network node, wherein the method further comprises: receiving, from the LMF or the second UE, indicia of cell information in the first indication, wherein the cell information is associated with the network node.

[0205] Aspect 22 is the method of any of aspects 14 to 18, wherein the synchronization reference type is based on the synchronization to the synchronization reference UE, wherein the method further comprises: receiving, from the LMF or the second UE, a reception time of a sidelink (SL) synchronization signal block (S-SSB) and a frequency location associated with the synchronization to the synchronization reference UE.

[0206] Aspect 23 is the method of aspect 22, wherein the reception time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

[0207] Aspect 24 is the method of any of aspects 14 to 23, wherein the quality metric is associated with at least one of: an implementation of the anchor entity; a communication layer message of the LMF or another UE; a configuration at the first UE; a request from the first UE; or cell information associated with the quality metric.

[0208] Aspect 25 is the method of aspect 24, further comprising: receiving, from the LMF or the second UE, indicia of cell information in at least one of the first indication or signaling separate from the first indication.

[0209] Aspect 26 is the method of any of aspects 14 to 25, wherein the quality metric is a relative time difference (RTD) between a first time of arrival (ToA) associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE, wherein the second UE is configured as a sidelink (SL) UE with the first UE.

[0210] Aspect 27 is an apparatus for wireless communication including means for implementing any of aspects 1 to 13.

[0211] Aspect 28 is a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer executable code, the code when executed by at least one processor causes the at least one processor to implement any of aspects 1 to 13.

[0212] Aspect 29 is an apparatus for wireless communication at a network node. The apparatus includes a memory; and at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to implement any of aspects 1 to 13.

[0213] Aspect 30 is the apparatus of aspect 29, further including at least one of a transceiver or an antenna coupled to the at least one processor.

[0214] Aspect 31 is an apparatus for wireless communication including means for implementing any of aspects 14 to 26.

[0215] Aspect 32 is a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer executable code, the code when executed by at least one processor causes the at least one processor to implement any of aspects 14 to 26.

[0216] Aspect 33 is an apparatus for wireless communication at a network node. The apparatus includes a memory; and at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to implement any of aspects 14 to 26.

[0217] Aspect 34 is the apparatus of aspect 33, further including at least one of a transceiver or an antenna coupled to the at least one processor.

[0218] Aspect 35 is an apparatus for wireless communication at a user equipment (UE), comprising: at least one memory; and at least one processor coupled to the at least one memory and, based at least in part on information stored in the at least one memory, the at least one processor, individually or in any combination, is configured to perform the method of any of aspects 1 to 13.

[0219] Aspect 36 is an apparatus for wireless communication at a user equipment (UE), comprising means for performing each step in the method of any of aspects 1 to 13.

[0220] Aspect 37 is the apparatus of any of aspects 35 to 36, further comprising a transceiver configured to receive or to transmit in association with the method of any of aspects 1 to 13.

[0221] Aspect 38 is a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer executable code at a user equipment (UE), the code when executed by at least one processor causes the at least one processor to perform the method of any of aspects 1 to 13.

[0222] Aspect 39 is an apparatus for wireless communication at a user equipment (UE), comprising: at least one memory; and at least one processor coupled to the at least one memory and, based at least in part on information stored in the at least one memory, the at least one processor, individually or in any combination, is configured to perform the method of any of aspects 14 to 26.

[0223] Aspect 40 is an apparatus for wireless communication at a user equipment (UE), comprising means for performing each step in the method of any of aspects 14 to 26.

[0224] Aspect 41 is the apparatus of any of aspects 39 to 40, further comprising a transceiver configured to receive or to transmit in association with the method of any of aspects 14 to 26.

[0225] Aspect 42 is a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer executable code at a user equipment (UE), the code when executed by at least one processor causes the at least one processor to perform the method of any of aspects 14 to 26.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. An apparatus for wireless communication at a first user equipment (UE), comprising: at least one memory; and at least one processor coupled to the at least one memory and, based at least in part on information stored in the at least one memory, the at least one processor, individually or in any combination, is configured to: receive, from at least one of a location management function (LMF) or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, wherein the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE, wherein the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates; and communicate based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time.

2. The apparatus of claim 1, wherein the variation time includes the first time since the last synchronization update, wherein the first time is based on at least one of a number of symbols, an absolute time, or a relative time associated with a time duration threshold.

3. The apparatus of claim 1, wherein the variation time includes the second time for the last synchronization update, wherein the second time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

4. The apparatus of claim 1, wherein the variation time includes the correction amount that was corrected in the last one or more synchronization updates.

5. The apparatus of claim 4, wherein the variation time is based on an average of at least two more of the last one or more synchronization updates.

6. The apparatus of claim 1, wherein the synchronization reference type is based on the synchronization to the GNSS, wherein the at least one processor, individually or in any combination, is further configured to: receive, from the LMF or the second UE, a second indication of a satellite constellation, wherein the satellite constellation is associated with the GNSS.

7. The apparatus of claim 6, wherein to receive the second indication of the satellite constellation, the at least one processor, individually or in any combination, is configured to receive the second indication in the first indication.

8. The apparatus of claim 1, wherein the synchronization reference type is based on the synchronization to the network node, wherein the at least one processor, individually or in any combination, is further configured to: receive, from the LMF or the second UE, indicia of cell information in the first indication, wherein the cell information is associated with the network node.

9. The apparatus of claim 1, wherein the synchronization reference type is based on the synchronization to the synchronization reference UE, wherein the at least one processor, individually or in any combination, is further configured to: receive, from the LMF or the second UE, a reception time of a sidelink (SL) synchronization signal block (S-SSB) and a frequency location associated with the synchronization to the synchronization reference UE.

10. The apparatus of claim 9, wherein the reception time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

11. The apparatus of claim 1, wherein the quality metric is associated with at least one of: an implementation of the anchor entity; a communication layer message of the LMF or another UE; a configuration at the first UE; a request from the first UE; or cell information associated with the quality metric.

12. The apparatus of claim 1, wherein the at least one processor, individually or in any combination, is further configured to: receive, from the LMF or the second UE, indicia of cell information in at least one of the first indication or signaling separate from the first indication.

13. The apparatus of claim 1, wherein the quality metric is a relative time difference (RTD) between a first time of arrival (ToA) associated with a first reference signal from the anchor entity and a second ToA associated with a second reference signal from the second UE, wherein the second UE is configured as a sidelink (SL) UE with the first UE.

14. The apparatus of claim 1, further comprising a transceiver coupled to the at least one processor, wherein to communicate based on the first indication of the synchronization reference type of the synchronization reference source and the variation time, the at least one processor, individually or in any combination, is configured to: communicate, via the transceiver, based on the first indication of the synchronization reference type of the synchronization reference source and the variation time.

15. An apparatus for wireless communication at a first user equipment (UE), comprising: at least one memory; and at least one processor coupled to the at least one memory and, based at least in part on information stored in the at least one memory, the at least one processor, individually or in any combination, is configured to:identify a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, wherein the synchronization reference type is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE; and provide, to at least one of a location management function (LMF) or a second UE as a basis of communications thereby, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or a variation time, wherein the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

16. The apparatus of claim 15, wherein the variation time includes the first time since the last synchronization update, wherein the first time is based on at least one of a number of symbols, an absolute time, or a relative time associated with a time duration threshold.

17. The apparatus of claim 15, wherein the variation time includes the second time for the last synchronization update, wherein the second time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

18. The apparatus of claim 15, wherein the variation time includes the correction amount that was corrected in the last one or more synchronization updates.

19. The apparatus of claim 18, wherein the variation time is based on an average of at least two more of the last one or more synchronization updates.

20. The apparatus of claim 15, wherein the synchronization reference type is based on the synchronization to the GNSS, wherein the at least one processor, individually or in any combination, is further configured to: identify a satellite constellation associated with the GNSS; and report, to the LMF or the second UE, a second indication of the satellite constellation.

21. The apparatus of claim 20, wherein to report the second indication of the satellite constellation, the at least one processor, individually or in any combination, is configured to report the second indication in the first indication.

22. The apparatus of claim 15, wherein the synchronization reference type is based on the synchronization to the network node, wherein the at least one processor, individually or in any combination, is further configured to: identify cell information associated with the network node; and report, to the LMF or the second UE in the first indication, indicia of the cell information.

23. The apparatus of claim 15, wherein the synchronization reference type is based on the synchronization to the synchronization reference UE, wherein the at least one processor, individually or in any combination, is further configured to: identify a reception time of a sidelink (SL) synchronization signal block (S-SSB) and a frequency location associated with the synchronization to the synchronization reference UE; and report, to the LMF or the second UE, the reception time and the frequency location.

24. The apparatus of claim 23, wherein the reception time is at least one of an absolute time, a time period associated with a system frame number (SFN), or a time period associated with a direct frame number (DFN).

25. The apparatus of claim 15, wherein the quality metric is associated with at least one of: an implementation of an anchor entity; a communication layer message of the LMF or another UE; a configuration at the first UE; or a request from the first UE; or cell information associated with the quality metric.

26. The apparatus of claim 25, wherein the at least one processor, individually or in any combination, is further configured to: identify cell information associated with the quality metric; and report, to the LMF or the second UE, a second indication of the cell information in at least one of the first indication or signaling separate from the first indication.

27. The apparatus of claim 15, wherein the quality metric is a relative time difference (RTD) between a first time of arrival (ToA) associated with a first reference signal from an anchor entity and a second ToA associated with a second reference signal from the second UE, wherein the second UE is configured as a sidelink (SL) UE with the first UE.

28. The apparatus of claim 15, further comprising a transceiver coupled to the at least one processor, wherein to provide the first indication of the synchronization reference type of the synchronization reference source and the variation time, the at least one processor, individually or in any combination, is configured to: provide, via the transceiver to at least one of the LMF or the second UE, the first indication of the synchronization reference type of the synchronization reference source and the variation time.

29. A method of wireless communication for a first user equipment (UE), comprising: receiving, from at least one of a location management function (LMF) or a second UE, at least one of a first indication of a synchronization reference type of a synchronization reference source, a quality metric, or a variation time, wherein the synchronization reference type is associated with a synchronization of the first UE to the synchronization reference source and is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE, wherein the variation time is associated with an anchor entity and comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates; andcommunicating based on at least one of the first indication of the synchronization reference type of the synchronization reference source, the quality metric, or the variation time.

30. A method of wireless communication for a first user equipment (UE), comprising: identifying a synchronization reference type of a synchronization reference source based on a synchronization of the first UE to the synchronization reference source, wherein the synchronization reference type is one or more of: a global navigation satellite system (GNSS), a network node, or a synchronization reference UE; providing, to at least one of a location management function (LMF) or a second UE as a basis of communications thereby, at least one of a first indication of the synchronization reference type of the synchronization reference source, a quality metric, or a variation time, wherein the variation time comprises at least one of: a first time since a last synchronization update, a second time for the last synchronization update, or a correction amount that was corrected in a last one or more synchronization updates.

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