WO2024127355A1 - Methods and apparatus for providing assistance to carrier-phase-based positioning in wireless networks - Google Patents

Abstract

To assist the determination of positions of wireless devices in a wireless network using to carrier-phase-based techniques, an assisting entity in the network may receive a plurality of carrier phase error mitigation information from a plurality of position reference units (PRUs), respectively, each said information including measurements, phase error estimates, or both; construct a phase error model based on the plurality of information; and determine a plurality of phase error estimates based on the phase error model. The assisting entity may be a location management function or a designated PRU. The plurality of carrier phase error mitigation information may be received in response to respective request messages, as periodic updates, or both. The plurality of phase error estimates may then be used to mitigate phase errors when determining respective locations of one or more wireless devices using carrier phase measurements taken by the those wireless devices.

Description

METHODS AND APPARATUS FOR PROVIDING ASSISTANCE TO CARRIER- PHASE-BASED POSITIONING IN WIRELESS NETWORKS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/387,798, filed on December 16, 2022, entitled METHODS AND APPARATUS FOR PRO VDING ASSISTANCE TO CARRIER-PHASE-BASED POSITIONING IN WIRELESS NETWORKS, which is incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to wireless communications, and more specifically to devices and methods for orienting a target device in a global coordinate system using local coordinate measurements.

BACKGROUND

[0003] A wireless communications system may include one or multiple network communication devices, such as base stations, which may be otherwise known as an eNodeB (eNB), a next-generation NodeB (gNB), or other suitable terminology. Each network communication devices, such as a base station, may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE), or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers). Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., sixth generation (6G)). [0004] Device positioning is an increasingly important element of wireless communication devices. Device positioning is very useful for technologies such as automated or semi-automated vehicle piloting, in which devices may exchange position information and determine appropriate pathing based on the exchanged information. If the positioning information is not accurate, the vehicles could collide with one another.

[0005] While wireless networks employ various positioning technologies, many of those technologies are inaccurate, not always available, or require special conditions.

SUMMARY

[0006] The present disclosure relates to methods, apparatuses, and systems that support determining a location of a target device using Radio Access Technology (RAT). The location of the target device may be determined using carrier phase measurements and assistance information provided using one or more Position Reference Units (PRUs), where the assistance information is used to perform phase error estimation and mitigation.

[0007] In some implementations of the method and apparatuses described herein, a Uocation Management Function transmits a plurality of data request messages to a plurality of position reference units, respectively, each data request message requesting information for carrier phase error mitigation, the information for carrier phase error mitigation including measurements, phase error estimates, or both; receives a plurality of information for carrier phase error mitigation from the plurality of position reference units, respectively; constructs a phase error model based on the plurality of information for carrier phase error mitigation; and determines a plurality of phase error estimates based on the phase error model. The plurality of phase error estimates are configured for use in determining a location of a target wireless device by correcting carrier phase errors.

[0008] In some implementations of the method and apparatuses described herein, the Uocation Management Function receives a plurality of position reference signal (PRS) measurements from the target wireless device, each PRS measurement including a carrier phase measurement of a corresponding received PRS, and determines the location of the target wireless device by mitigating phase errors in the plurality of PRS measurements using the plurality of phase error estimates.

[0009] In some implementations of the method and apparatuses described herein, the Location Management Function receives a request for assistance data from the target wireless device and provides the plurality of phase error estimates to the target wireless device in response to receiving the request for assistance data. The target wireless device determines the location of the target wireless device by mitigating phase errors in a plurality of PRS measurements using the plurality of phase error estimates, each PRS measurement including a carrier phase measurement of a corresponding received PRS.

[0010] In some implementations of the method and apparatuses described herein, the request for assistance data from the target wireless device is communicated via Long Term Evolution (LTE) Position Protocol (LPP) signaling, and the plurality of phase error estimates are communicated via LPP signaling.

[0011] In some implementations of the method and apparatuses described herein, the plurality of data request messages are communicated via LPP signaling, and the plurality of information for carrier phase error mitigation are communicated via LPP signaling.

[0012] In some implementations of the method and apparatuses described herein, a phase error estimate of the plurality of phase error estimates includes an estimates for a phase error caused by an initial phase offset at a transmission-reception points (TRP), a carrier frequency offset, a time synchronization error, a frequency synchronization error, an antenna reference point error, or a combination thereof.

[0013] In some implementations of the method and apparatuses described herein, a Position Reference Unit of the plurality of Position Reference Units receives a plurality of downlink PRSs corresponding to a plurality of beams of a plurality of transmissionreception points (TRPs); performs a plurality of measurements on the plurality of downlink PRSs; determines a plurality of phase error estimates using the plurality of measurements; determines the information for carrier phase error mitigation using the plurality of phase error estimates; and transmits the information for carrier phase error mitigation to the Location Management Function. [0014] In some implementations of the method and apparatuses described herein, the Position Reference Unit transmits the information for carrier phase error mitigation to the Location Management Function in response to receiving a data request message of the plurality of data request messages.

[0015] In some implementations of the method and apparatuses described herein, the Position Reference Unit tracks the plurality of phase error estimates and transmits the information for carrier phase error mitigation to the Location Management Function in response to a change in one or more of the plurality of phase error estimates.

[0016] In some implementations of the method and apparatuses described herein, a first position reference unit receives a virtual- position reference unit configuration message from a Location Management Function of the wireless communication network; receives a first set of one or more phase error estimate reports from a second position reference unit; receives a second set of one or more phase error estimate reports from a third position reference unit; constructs, based on the first and second sets of phase error estimate reports, a phase error model for carrier phase error mitigation; determines a plurality of phase error estimates based on the phase error model; and provides the plurality of phase error estimates to a target wireless device. The target wireless device determines a location of the target wireless device by mitigating phase errors in a plurality of position reference signal measurements using the plurality of phase error estimates.

[0017] In some implementations of the method and apparatuses described herein, the virtual- position reference unit configuration message is received via LPP signaling.

[0018] In some implementations of the method and apparatuses described herein, the first and second phase error estimate reports are received via a sidelink PC5 interface.

[0019] In some implementations of the method and apparatuses described herein, the Location Management Function transmits the virtual-Position Reference Unit configuration message to the first Position Reference Unit and transmits a notification to a plurality of Position Reference Units indicating that the first Position Reference Unit is configured as a virtual-Position Reference Unit. The plurality of Position Reference Units includes the second and third Position Reference Units. [0020] In some implementations of the method and apparatuses described herein, the notification to plurality of Position Reference Units is included as part of a “RequestPRUData” Long Term Evolution (LTE) Position Protocol (LPP) message.

[0021] In some implementations of the method and apparatuses described herein, the target performs a plurality of position reference signal measurements of a plurality of downlink position reference signals, respectively; receives, from the first Position Reference Unit, the plurality of phase error estimates; and determines a position of the target wireless device using carrier phase-based positioning; including compensating for phase errors in the plurality of position reference signal measurements using the plurality of phase error estimates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 illustrates an example of a wireless communications system that supports carrier-phase-based position determination in accordance with aspects of the present disclosure.

[0023] FIG. 2 illustrates an example of beam positioning in an New Radio (NR) network.

[0024] FIG. 3 illustrates an example of absolute and relative positioning in wireless cellular networks.

[0025] FIG. 4 illustrates an example of a multi-cell round-trip time (RTT) procedure in a wireless network.

[0026] FIG. 5 illustrates an example of relative range estimation using RTT and a single gNB.

[0027] FIG. 6 illustrates a double-differential technique for position determination.

[0028] FIG. 7 illustrates a Radio Access Technology (RAT) configuration for position determination in accordance with aspects of the present disclosure.

[0029] FIG. 8 illustrates a procedures for position determination in an in-coverage scenario in accordance with aspects of the present disclosure. [0030] FIG. 9 illustrates a procedure for position determination in an out-of-coverage scenario in accordance with aspects of the present disclosure.

[0031] FIG. 10 illustrates a flowchart of a process for assisting the carrier-phase-based determination of a position of a wireless device in accordance with aspects of the present disclosure.

[0032] FIG. 11 is a block diagram of an example of a device that supports carrierphase-based location determination in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0033] Carrier phase measurement- based positioning is a promising RAT-dependent positioning techniques that has been widely used in Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) and the Global Navigation Satellite System (GLONASS) for centimeter-level accuracy. Stringent accuracy requirements for horizontal and vertical positioning may be readily met using carrier phase-based positioning, depending on the type of environmental scenario.

[0034] Centimeter-level accuracy for certain scenarios could be met using a carrier phase-based positioning technique; however, this is only possible under certain conditions; one of the necessary (though not sufficient) conditions is that all phase error sources (e.g., initial phase offset, time and frequency synchronization errors, carrier frequency offset CFO, Antenna reference points ARPs, Doppler velocity, and so on) are correctly mitigated. Several techniques have been proposed to mitigate these errors that impact the carrier phase measurement performance. The use of double differential method is a potential technique to mitigate part of the error sources, especially phase related errors. Double differential techniques rely on the existence of positioning reference units (PRUs) with well-known positions with centimeter-level accuracy, high PRU deployment density, and good channel conditions (such as a Line-of-Sight (LOS) link) between Transmission-Reception Points (TRPs) and PRUs and/or TRPs and target User Equipments (UEs). To this end, PRUs may be deployed and used to aid in carrier phase positioning to correct for the aforementioned impairments. PRUs may perform measurements over DownLink (DL) Positioning Reference Signals (PRSs) transmitted from different TRPs with the goal of providing assistance data allowing phase errors mitigation to a target UE. However, in order to have accurate error compensation, conventional double-differential techniques require a high deployment density of PRUs which may cause a high signaling overhead.

[0035] This disclosure presents procedures that allow for accurate error compensation and provide efficient solutions for a low density PRU deployments scenario in both incoverage and out-of-coverage cases. In this disclosure, PRU coordination is used to enable phase errors mitigation at target UEs. Error mitigation information is provided or broadcasted by a Location Management Function (LMF) as part of the assistance data upon a UE’s request. Assistance data could be provided by the LMF to the target UE in a UE- based scenario or could be directly used by the LMF in a UE-assisted/LMF-based (considering UL-based positioning) scenario.

[0036] Embodiments of the present disclosure relate to determining the position of wireless devices in a Radio Access Technology (RAT) based communication system, and in particular to high-accuracy carrier-phased based determination of the position of wireless devices. In one embodiment, an assisting entity (such as a Location Management Function or Virtual PDU) receives a plurality of information for carrier phase error mitigation from a plurality of position reference units, respectively. The plurality of information may have respectively been transmitted by the plurality of position reference units in response to a request from the assisting entity, transmitted periodically according to a configured interval, transmitted in response to a change in measured network conditions, or a combination thereof. The assisting entity constructs a phase error model based on the plurality of information, and determines a plurality of phase error estimates based on the phase error model. The plurality of phase error estimates are then used to mitigate phase errors when performing carrier-phase-based determination of a location of a target wireless device.

[0037] In some embodiments, the assisting device receives a plurality of position reference signal (PRS) measurements from the target wireless device, each PRS measurement including a carrier phase measurement of a corresponding received PRS. The assisting device then determines the location of the target wireless device by mitigating phase errors in the plurality of PRS measurements using the plurality of phase error estimates.

[0038] In some embodiments, the assisting device receives a request for assistance data from the target wireless device, and provides the plurality of phase error estimates to the target wireless device in response. The target wireless device then determines its location by mitigating phase errors in a plurality of PRS measurements using the plurality of phase error estimates, each PRS measurement including a carrier phase measurement of a corresponding received PRS.

[0039] Aspects of the present disclosure are described in the context of a wireless communications system. Aspects of the present disclosure are further illustrated and described with reference to device diagrams and flowcharts.

[0040] FIG. 1 illustrates an example of a wireless communications system 100 that supports high-precision carrier phase measurement-based positioning by mitigating phase errors using double-differential techniques in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more network entities 102, one or more UEs 104, a core network 106, and a packet data network 108. The wireless communications system 100 may further include a plurality of PRUs such as PRUs 122, and the core network 106 may include an LMF 126. The wireless communications system 100 may support various radio access technologies. In some implementations, the wireless communications system 100 may be a 4G network, such as an LTE network or an LTE- Advanced (LTE- A) network. In some other implementations, the wireless communications system 100 may be a 5G network, such as an NR network. In other implementations, the wireless communications system 100 may be a combination of a 4G network and a 5G network, or other suitable radio access technology including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20. The wireless communications system 100 may support radio access technologies beyond 5G. Additionally, the wireless communications system 100 may support technologies, such as time division multiple access (TDMA), frequency division multiple access (FDMA), or code division multiple access (CDMA), etc. [0041] The one or more network entities 102 may be dispersed throughout a geographic region to form the wireless communications system 100. One or more of the network entities 102 described herein may be included or may be referred to as a network node, a base station, a network element, a radio access network (RAN), a base transceiver station, an access point, a NodeB, an eNodeB (eNB), a next-generation NodeB (gNB), or other suitable terminology. A network entity 102 and a UE 104 or PRU 122 may communicate via a communication link 110, which may be a wireless or wired connection. For example, a network entity 102 and a UE 104 may perform wireless communication (e.g., receive signaling, transmit signaling) over a Uu interface.

[0042] A network entity 102 may provide a geographic coverage area 112 for which the network entity 102 may support services (e.g., voice, video, packet data, messaging, broadcast, etc.) for one or more UEs 104 and any PRUs 122 within the geographic coverage area 112. For example, a network entity 102 and a UE 104 may support wireless communication of signals related to services (e.g., voice, video, packet data, messaging, broadcast, etc.) according to one or multiple radio access technologies. In some implementations, a network entity 102 may be moveable, for example, a satellite associated with a non-terrestrial network. In some implementations, different geographic coverage areas 112 associated with the same or different radio access technologies may overlap, but the different geographic coverage areas 112 may be associated with different network entities 102. Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0043] The one or more UEs 104 may be dispersed throughout a geographic region of the wireless communications system 100. A UE 104 may include or may be referred to as a mobile device, a wireless device, a remote device, a remote unit, a handheld device, or a subscriber device, or some other suitable terminology. In some implementations, the UE 104 may be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally, or alternatively, the UE 104 may be referred to as an Internet-of-Things (loT) device, an Internet-of-Everything (loE) device, or machine-type communication (MTC) device, among other examples. In some implementations, a UE 104 may be stationary in the wireless communications system 100. In some other implementations, a UE 104 may be mobile in the wireless communications system 100.

[0044] The one or more UEs 104 may be devices in different forms or having different capabilities. Some examples of UEs 104 are illustrated in FIG. 1. A UE 104 may be capable of communicating with various types of devices, such as the network entities 102, other UEs 104, or network equipment (e.g., the core network 106, the packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network equipment), as shown in FIG. 1. Additionally, or alternatively, a UE 104 may support communication with other network entities 102 or UEs 104, which may act as relays in the wireless communications system 100.

[0045] A UE 104 may also be able to support wireless communication directly with other UEs 104 over a communication link 114. For example, a UE 104 may support wireless communication directly with another UE 104 over a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link 114 may be referred to as a sidelink. For example, a UE 104 may support wireless communication directly with another UE 104 over a PC5 interface.

[0046] The one or more PRUs 122 may be dispersed throughout a geographic region of the wireless communications system 100. Generally, a PRU 122 may be stationary in the wireless communications system 100, however, a PRU 122 may be in some cases be mobile in the wireless communications system 100. Whether stationary or mobile, the location of the PRU 122 is known to the PRU 122 and/or devices communicating with the PRU 122 with certainty and accuracy. For example, the location of a PRU may be known with centimeter- level accuracy.

[0047] The one or more PRUs 122 may be devices in different forms or having different capabilities. A PRU 122 may be capable of communicating with various types of devices, such as the network entities 102 or network equipment (e.g., the core network 106, the packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network equipment), as shown in FIG. 1.

[0048] A PRU 122 may also support wireless communication directly with other PRUs 122 or with UEs 104 over a communication link similar to the communication link 114 for communicating between UE 104 that is shown in FIG. 1. For example, a PRU 122 may support wireless communication directly with another PRU 122 over a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link between a PRU 122 and another PRU 122 or a UE 104 may be referred to as a sidelink. For example, a PRU 122 may support wireless communication directly with another PRU 122 or with a UE 104 over a PC5 interface.

[0049] The PRUs 122 produce information for mitigating phase errors in carrier-phasebased location determinations for devices in the wireless communication networks. For example, the PRUs 122 may produce information for carrier phase error mitigation based on measurements of signals received by a PRU 122 and the known location of that PRU 122. The measured signals may include Position Reference Signals transmitted by a TRP such as a network entity 102. The PRU 122 may in some cases provide the information for carrier phase error mitigation to a LMF 126 of the wireless communications system 100. In other case, the PRU 122 may provide the information for carrier phase error mitigation to a UE 104 of the wireless communications system 100.

[0050] A network entity 102 may support communications with the core network 106, or with another network entity 102, or both. For example, a network entity 102 may interface with the core network 106 through one or more backhaul links 116 (e.g., via an SI, N2, or another network interface). The network entities 102 may communicate with each other over the backhaul links 116 (e.g., via an X2, Xn, or another network interface). In some implementations, the network entities 102 may communicate with each other directly (e.g., between the network entities 102). In some other implementations, the network entities 102 may communicate with each other or indirectly (e.g., via the core network 106). In some implementations, one or more network entities 102 may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC). An ANC may communicate with the one or more UEs 104 through one or more other access network transmission entities, which may be referred to as a radio heads, smart radio heads, or transmission-reception points (TRPs).

[0051] In some implementations, a network entity 102 may be configured in a disaggregated architecture, which may be configured to utilize a protocol stack physically or logically distributed among two or more network entities 102, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance), or a virtualized RAN (vRAN) (e.g., a cloud RAN (C- RAN)).

[0052] The core network 106 may support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. The core network 106 may be an evolved packet core (EPC), or a 5G core (5GC), which may include a control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management functions (AMF)) and a user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (Pwireless DN) gateway (P-GW), or a user plane function (UPF)). In some implementations, the control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g., data bearers, signal bearers, etc.) for the one or more UEs 104 served by the one or more network entities 102 associated with the core network 106.

[0053] The core network 106 may communicate with the packet data network 108 over one or more backhaul links 116 (e.g., via an SI, N2, or another network interface). The packet data network 108 may include an application server 118. In some implementations, one or more UEs 104 may communicate with the application server 118. A UE 104 may establish a session (e.g., a protocol data unit (PDU) session, or the like) with the core network 106 via a network entity 102. The core network 106 may route traffic (e.g., control information, data, and the like) between the UE 104 and the application server 118 using the established session (e.g., the established PDU session). The PDU session may be an example of a logical connection between the UE 104 and the core network 106 (e.g., one or more network functions of the core network 106). [0054] The core network 106 may include a LMF 126. The LMF may comprise dedicated hardware, software running in hardware of the core network 106, or combinations thereof. The LMF 126 may provide support for determining locations of entities in the wireless communication system 100. For example, the LMF 126 may provide phase error estimates for use in carrier-phase-based determination of a location of a wireless device. The phase error estimates may be produced using information from the one or more PRUs 122 in the wireless communication system 100. The phase error estimates may be provided to a wireless device, such as a UE 104 in the wireless communication system 100, to enable the wireless device to determine its own location, or may be used by the LMF 126 to determine the location of the wireless device.

[0055] The LMF 126 may also configure other devices in the wireless communication system 100 to provide some of the capabilities of the LMF 126. For example, the LMF 126 may configure a PRU 122 as a virtual -PRU. A virtual -PRU may be configured to produce phase error estimates based on information received from one or more other PRUs 122, and to provide information for mitigating phase errors in carrier-phase-based location determination, based on the information received from the one or more other PRUs 122, to wireless devices such as the UEs 104 in the wireless communication system 100.

[0056] The LMF 126 may also notify the one or more other PRUs 122 that the PRU 122 has been configured as a virtual-PRU.

[0057] In the wireless communications system 100, the network entities 102 and the UEs 104 may use resources of the wireless communication system 100 (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers)) to perform various operations (e.g., wireless communications). In some implementations, the network entities 102 and the UEs 104 may support different resource structures. For example, the network entities 102 and the UEs 104 may support different frame structures. In some implementations, such as in 4G, the network entities 102 and the UEs 104 may support a single frame structure. In some other implementations, such as in 5G and among other suitable radio access technologies, the network entities 102 and the UEs 104 may support various frame structures (i.e., multiple frame structures). The network entities 102 and the UEs 104 may support various frame structures based on one or more numerologies.

[0058] One or more numerologies may be supported in the wireless communications system 100, and a numerology may include a subcarrier spacing and a cyclic prefix. A first numerology (e.g., /r=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. In some implementations, the first numerology (e.g., /r=0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. A second numerology (e.g., /r=l) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., /r=2) may be associated with a third subcarrier spacing (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth numerology (e.g., /r=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g., /r=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

[0059] A time interval of a resource (e.g., a communication resource) may be organized according to frames (also referred to as radio frames). Each frame may have a duration, for example, a 10 millisecond (ms) duration. In some implementations, each frame may include multiple subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, for example, a 1 ms duration. In some implementations, each frame may have the same duration. In some implementations, each subframe of a frame may have the same duration.

[0060] Additionally or alternatively, a time interval of a resource (e.g., a communication resource) may be organized according to slots. For example, a subframe may include a number (e.g., quantity) of slots. The number of slots in each subframe may also depend on the one or more numerologies supported in the wireless communications system 100. For instance, the first, second, third, fourth, and fifth numerologies (i.e., /r=0, jU=l, /r=2, jU=3, /r=4) associated with respective subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz may utilize a single slot per subframe, two slots per subframe, four slots per subframe, eight slots per subframe, and 16 slots per subframe, respectively. Each slot may include a number (e.g., quantity) of symbols (e.g., OFDM symbols). In some implementations, the number (e.g., quantity) of slots for a subframe may depend on a numerology. For a normal cyclic prefix, a slot may include 14 symbols. For an extended cyclic prefix (e.g., applicable for 60 kHz subcarrier spacing), a slot may include 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame for a normal cyclic prefix and an extended cyclic prefix may depend on a numerology. It should be understood that reference to a first numerology (e.g., /r=0) associated with a first subcarrier spacing (e.g., 15 kHz) may be used interchangeably between subframes and slots.

[0061] In the wireless communications system 100, an electromagnetic (EM) spectrum may be split, based on frequency or wavelength, into various classes, frequency bands, frequency channels, etc. By way of example, the wireless communications system 100 may support one or multiple operating frequency bands, such as frequency range designations FR1 (410 MHz - 7.125 GHz), FR2 (24.25 GHz - 52.6 GHz), FR3 (7.125 GHz - 24.25 GHz), FR4 (52.6 GHz - 114.25 GHz), FR4a or FR4-1 (52.6 GHz - 71 GHz), and FR5 (114.25 GHz - 300 GHz). In some implementations, the network entities 102 and the UEs 104 may perform wireless communications over one or more of the operating frequency bands. In some implementations, FR1 may be used by the network entities 102 and the UEs 104, among other equipment or devices for cellular communications traffic (e.g., control information, data). In some implementations, FR2 may be used by the network entities 102 and the UEs 104, among other equipment or devices for short-range, high data rate capabilities.

[0062] FR1 may be associated with one or multiple numerologies (e.g., at least three numerologies). For example, FR1 may be associated with a first numerology (e.g., /r=0), which includes 15 kHz subcarrier spacing; a second numerology (e.g., /r=l), which includes 30 kHz subcarrier spacing; and a third numerology (e.g., /r=2), which includes 60 kHz subcarrier spacing. FR2 may be associated with one or multiple numerologies (e.g., at least 2 numerologies). For example, FR2 may be associated with a third numerology (e.g., /r=2), which includes 60 kHz subcarrier spacing; and a fourth numerology (e.g., /r=3), which includes 120 kHz subcarrier spacing.

[0063] Positioning techniques supported in Rel-16 are listed in the following Table 1 :

[Table 1]

Separate positioning techniques as indicated in Table 1 can be configured and performed based on the requirements of the LMF 126 and UE 104 capabilities. The transmission of Uu (uplink and downlink) Positioning Reference Signals (PRS) enable a UE 104 to perform UE positioning-related measurements to enable the computation of a UE’s absolute location estimate and are configured per TRP, where a TRP may include a set of one or more beams. A conceptual overview is illustrated in FIG. 2.

[0064] The PRS can be transmitted by different base stations (serving and neighboring) using narrow beams over FR1 and FR2 as illustrated in FIG. 2, which is relatively different when compared to LIE where the PRS was transmitted across the whole cell. The PRS can be locally associated with a PRS Resource ID and Resource Set ID for a TRS such as a base station. Similarly, UE positioning measurements such as Reference Signal Time Difference (RSTD) and PRS RSRP measurements are made between beams (e.g., between a different pair of DL PRS resources or DL PRS resource sets) as opposed to different cells as was the case in LTE. In addition, there are additional UL positioning methods for the network to exploit in order to compute the target UE’s location.

[0065] FIG. 3 is an overview of the absolute and relative positioning scenarios using three different co-ordinate systems: an Absolute Positioning, fixed coordinate system; a Relative Positioning, variable and moving coordinate systems; and a Relative Positioning, variable coordinate system. The following RAT-dependent positioning techniques may be used in embodiments of the present disclosure to support positioning of a target device.

[0066] Downlink Time Difference of Arrival (DL-TDOA) positioning makes use of the DL RSTD (and optionally DL PRS RSRP) of downlink signals received from multiple transmission points (TP)s, at the UE. The UE 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 in relation to the neighboring TPs.

[0067] Downlink Angle of Departure (DL AoD) positioning makes use of the measured DL PRS RSRP of downlink signals received from multiple TPs, at the UE. The UE 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 other configuration information to locate the UE in relation to the neighboring TPs.

[0068] Multiple Round Trip Time (Multi-RTT) positioning uses UE reception and transmission (Rx-Tx) measurements and DL PRS RSRP of downlink signals received from multiple TRPs, measured by the UE and measured gNB Rx-Tx measurements and UL SRS- RSRP at multiple TRPs of uplink signals transmitted from UE.

[0069] The UE measures the UE Rx-Tx measurements (and optionally DL PRS RSRP of the received signals) using assistance data received from the positioning server, and the TRPs measure the gNB Rx-Tx measurements (and optionally UL SRS-RSRP of the received signals) using assistance data received from the positioning server. The measurements are used to determine the RTT at the positioning server which are used to estimate the location of the UE (See Figure 3). Multi-RTT is currently only supported for UE-assisted/NG-RAN assisted positioning techniques as noted in Table 1.

[0070] FIG. 4 illustrates computation of a RTT. A UE transmits an UpLink Sounding Reference Signal (UL-SRS) at time to. A TRS (in FIG. 4, a New Radio NodeB gNB) receives the UL-SRS at time ti, and in response transmits a DownLink SRS (DL-SRS) at time t2. The UE receives the DL-SRS at time t3. The RTT may be computes as the time A between the transmission of the UL-SRS at time to and the reception of the DL-SRS at time t3, minus the time between the reception of the UL-SRS at time ti and the transmission of the DL-SRS at time t2; that is, RTT = (t3 - to) - (t2 - ti).

[0071] FIG. 5 illustrates an implementation-based approach to compute the relative distance between two UEs. This approach is high in latency and is not efficient in terms of procedures and signaling overhead.

[0072] For Enhanced Cell ID (CID) positioning, the position of a UE is estimated with the knowledge of its serving ng-eNB, gNB and cell and is based on LIE signals. The information about the serving ng-eNB, gNB and cell may be obtained by paging, registration, or other methods. NR Enhanced Cell ID (NR E CID) positioning refers to techniques which use additional UE measurements and/or NR radio resource and other measurements to improve the UE location estimate using NR signals.

[0073] Although NR E-CID positioning may utilize some of the same measurements as the measurement control system in the RRC protocol, the UE generally is not expected to make additional measurements for the sole purpose of positioning; the positioning procedures do not supply a measurement configuration or measurement control message, and the UE reports the measurements that it has available rather than being required to take additional measurement actions.

[0074] Uplink Time Difference of Arrival (UL TDOA) positioning makes use of the UL TDOA (and optionally UL SRS-RSRP) at multiple RPs of uplink signals transmitted from UE. The RPs measure the UL TDOA (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.

[0075] Uplink Angle of Arrival (UL Ao A) positioning makes use of the measured azimuth and the zenith of arrival at multiple RPs of uplink signals transmitted from UE. The RPs measure A-AoA and 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. [0076] In addition, several RAT-Independent positioning techniques are available, examples of which are described in 3^rd Generation Partnership Program (3GPP) Technical Specification (TS) 38.305.

[0077] For example, Network-assisted GNSS techniques make use of UEs that are equipped with radio receivers capable of receiving GNSS signals. In 3GPP specifications the term GNSS encompasses both global and regional/augmentation navigation satellite systems. Examples of global navigation satellite systems include GPS, Modernized GPS, Galileo, GLONASS, and BeiDou Navigation Satellite System (BDS). Regional navigation satellite systems include Quasi Zenith Satellite System (QZSS) while the many augmentation systems, are classified under the generic term of Space Based Augmentation Systems (SBAS) and provide regional augmentation services. Different GNSSs (e.g., GPS, Galileo, etc.) can be used separately or in combination to determine the location of a UE.

[0078] Barometric pressure sensor positioning makes use of barometric sensors to determine the vertical component of the position of the UE. The UE measures barometric pressure, optionally aided by assistance data, to calculate the vertical component of its location or to send measurements to the positioning server for position calculation. Barometric positioning is combined with other positioning methods to determine the 3D position of a UE.

[0079] Wireless Local Access Network (WLAN) positioning makes use of WLAN measurements (e.g. Access Point (AP) identifiers and optionally other measurements) and databases to determine the location of the UE. The UE measures received signals from WLAN access points, optionally aided by assistance data, to send measurements to the positioning server for position calculation. Using the measurement results and a references database, the location of the UE is calculated. Alternatively, the UE may use WLAN measurements and optionally WLAN AP assistance data provided by the positioning server, to determine its location.

[0080] Bluetooth positioning makes use of Bluetooth measurements (beacon identifiers and optionally other measurements) to determine the location of the UE. The UE measures received signals from Bluetooth beacons. Using the measurement results and a references database, the location of the UE is calculated. The Bluetooth methods may be combined with other positioning methods (e.g., WLAN) to improve positioning accuracy of the UE.

[0081] A Terrestrial Beacon System (TBS) includes a network of ground-based transmitters, broadcasting signals for positioning purposes for TBS positioning. The current type of TBS positioning signals are the MBS (Metropolitan Beacon System) signals and Positioning Reference Signals (PRSs). The UE measures received TBS signals, optionally aided by assistance data, to calculate its location or to send measurements to the positioning server for position calculation.

[0082] Motion sensor positioning makes use of different sensors such as accelerometers, gyros, magnetometers, to calculate the displacement of UE. The UE estimates a relative displacement based upon a reference position and/or reference time. UE sends a report comprising the determined relative displacement which can be used to determine the absolute position. This method may be used with other positioning methods for hybrid positioning.

[0083] Table 2 and Table 3 show reference signal to measurements mapping for each of the supported RAT-dependent positioning techniques at the UE and gNB, respectively. RAT-dependent positioning techniques involve the 3 GPP RAT and core network entities to perform the position estimation of the UE, which are differentiated from RAT- independent positioning techniques which rely on GNSS, IMU sensor, WLAN and Bluetooth technologies for performing target device (UE) positioning.

[0084] Table 2: UE measurements to enable RAT-dependent positioning techniques.

[Table 2]

[0085] Table 3: gNB measurements to enable RAT-dependent positioning techniques

[Table 3]

[0086] Measurement and reporting are performed per configured RAT-dependent/ RAT- independent positioning method. The RequestLocationlnformation message body in an LTE Positioning Protocol (LPP) message is used by the location server to request positioning measurements or a position estimate from the target device, and the ProvideLocationlnformation message body in a LPP message is used by the target device to provide positioning measurements or position estimates to the location server.

[0087] According to 3GPP TS38.211, DL PRS sequence generation and mapping to physical resources can be detailed as follows:

[0088] A positioning frequency layer consists of one or more DL PRS resource sets, each of which consists of one or more DL PRS resources as described in 3GPP TS 38.214.

[0089] The UE may assume that the reference-signal sequence r(m) is defined by

where the pseudo-random sequence c(i) is defined in clause 5.2.1 of 3GPP TS 38.214. The pseudo-random sequence generator may be initialized with:

where is the slot number, the downlink PRS sequence ID

{0,1, ... ,4095} is given by the higher-layer parameter dl-PRS-SequencelD, and I is the OFDM symbol within the slot to which the sequence is mapped.

[0090] FIG. 6 illustrates double-differential techniques for location determination. In FIG. 6, the techniques are illustrated in the context of a Global Navigation Satellite System (GNSS), wherein the technique may be referred to as “differential GNSS.”

[0091] In differential GNSS, the position of a fixed GNSS receiver, referred to as a base station (Base), is known to a high degree of accuracy, such as by using conventional surveying techniques. Then, the base station determines ranges to the GNSS satellites in view using the location of the satellites determined from the precisely known orbit ephemerides and satellite time.

[0092] The base station Base compares the known position to the position calculated from the satellite ranges. Differences between the positions can be attributed to satellite ephemeris and clock errors, but mostly to errors associated with atmospheric delay. The base station sends these errors to other receivers know as rovers, such as the Mobile receiver shown, which incorporate the corrections into their position calculations.

[0093] To apply the corrections in real-time, differential GNSS requires a data link between the base station and the rovers and at least four GNSS satellites that are each in view at both the base station and the rovers. The absolute accuracy of the rover’s computed position will depend on the absolute accuracy of the base station’s known position.

[0094] Because GNSS satellites orbit high above the earth, then as long as the base station and rovers are not too far apart, the propagation paths from the satellites to the base stations and rovers pass through similar atmospheric conditions. Differential GNSS works very well with base station-to-rover separations of up to tens of kilometers. [0095] A positioning reference unit (PRU) may be used to facilitate NR carrier-phasebased positioning has been studied. For DL NR carrier-phase-based positioning, the PRU may work in a similar manner to a UE to receive the DL PRS reference signals and provide the DL carrier phase measurements to an LMF, where the double differential measurements for eliminating measurement errors can be obtained using the difference of the DL carrier phase measurements from a target UE and those from the PRU.

[0096] For UL NR carrier- phase- based positioning, the PRU works in a similar manner to a UE to transmit the UL SRS signals for positioning purposes. The TRPs provides the UL carrier phase measurements obtained from the UL SRS signals of the target UE and from the UL SRS signals of the PRU to the LMF, where the double differential measurements for eliminating measurement errors can be obtained using the difference of these UL carrier phase measurements.

[0097] The initial phases of a transmitter for different carriers may be assumed to be independent of each other. Similarly, the initial phases of a receiver for different carriers may be assumed to be independent of each other.

[0098] Using existing DL PRS and SRS signals to obtain the carrier phase measurements, determining a position of a wireless device with a horizontal accuracy of a few centimeters may be achieved at least 50% of the time under certain conditions. These conditions may include the PRU(s) being located in Line-of-Sight (LOS) with the TRP(s), and the locations of the PRU(s) and TRPs being known with centimeter-level accuracy..

[0099] The different DL measurements including DL PRS-RSRP, DL RSTD, and UE Rx-Tx Time Difference required for the supported RAT-dependent positioning techniques are shown in Table 4 below. The following measurement configurations are assumed:

• 4 Pair of DL RSTD measurements can be performed per pair of cells. Each measurement is performed between a different pair of DL PRS Resources/Resource Sets with a single reference timing, and

• 8 DL PRS RSRP measurements can be performed on different DL PRS resources from the same cell.

[Table 4]

[0100] The present disclosure describes embodiments of an apparatus and method for providing accurate phase error mitigation using double differential techniques and PRUs in low density PRU deployment scenarios. This method allows for better phase errors estimation and mitigation using DL PRS measurements from different beams associated with each PRU, and from different PRUs in LOS with TRPs and/or target UEs, to efficiently model error sources and mitigate them.

[0101] PRUs perform measurements over DL PRS transmitted by TRPs in order to enable accurate phase errors estimation and mitigation as well as help reduce integer ambiguity search space and thus resolve integer ambiguity. To reduce integer ambiguity (IA) search space, measurements from PRUs may be used to provide a target UE with an upper bound and a lower bound on IA values.

[0102] Phase error estimates produced using a PRU are provided to the target UE to assist the target UE in compensating for phase errors so that the target UE may accurately determine its position based on carrier phase measurements.

[0103] In a UE-assisted/Network-assisted positioning scenario, the information provided by one or more PRUs may be used by an LMF to compensate for phase errors in a process by which the LMF determines a location of a target UE or target wireless device.

[0104] On the other hand, in UE-based positioning scenario, the information provided by one or more PRUs may be used to provide information to a target UE via LPP signaling, which information may be used by the target UEs may determine its own position. The provided information may be position assistance data, and may include a plurality of phase error estimates.

[0105] An overview of the methods is presented as follows:

[0106] An LMF may transmit a “RequestPRUDatcT message to PRUs indicating the required phase error estimates for example measurements related to error mitigation such as initial phase offsets at TRPs, residual CFO, Antenna reference point ARP errors, time/frequency sync errors or a combination of. In this case, PRUs may perform measurements using DL PRS transmitted from different TRPs over different beams. The PRUs then report the estimated phase errors of different DL PRS signals received over different beam IDs, an associated timestamp, and a timer. The reported information may be collected by the LMF. The reported information may then be transmitted upon request to target UEs that request positioning assistance data, or may be used by the LMF to compensate for phase errors when the LMF computes a location of a target UE based on carrier phase information received from the target UE.

[0107] The phase errors estimates may be updated after the expiry of the associated timer. This enables a reduced signaling overhead since these phase errors estimates will be used in compensating for errors for many target UEs receiving DL PRS from the same TRP. This information may be provided by the LMF in response to a target UE request for a one-shot carrier phase estimation.

[0108] For low density PRU deployment scenarios and blocked and/or non-Line-of- Sight (NLOS) TRP-PRU links, different PRUs having LOS links with a TRP may coordinate to overcome the low density PRU deployment and NLOS issues. This is enabled by a PRU being pre-configured by the LMF to act like a virtual PRU that may collect phase errors estimates from different PRUs, produce a model of the error sources based on the phase error estimates, and compensate for phase errors using the model. This approach may be applied for out-of-coverage-area scenarios. In an in-coverage-area scenario, an LMF may collect the phase errors estimates from the PRUs, produce the model of the phase errors, and mitigate the phase errors using the model. [0109] For the purposes of this disclosure, a positioning-related reference signal may refer to a reference signal used for positioning purposes in order to estimate a target UE’s location, e.g., a PRS, or may refer to an existing reference signals such as CSI-RS or SRS or a new RS for carrier phase positioning. A target UE may refer to the device or entity to be localized or positioned, which may be a UE or may be another type of wireless device. In various embodiments, the term ‘PRS’ may refer to any signal such as a reference signal, which may or may not be used primarily for positioning.

[0110] In the discussions in this disclosure, PRUs and TRPs are assumed to have perfect knowledge of their positions with zero uncertainty, but embodiments are not limited thereto.

[0111] A problem addressed by this disclosure the difficulty in using a carrier phasebased positioning technique to accurately calculate a target UE position in presence of phase error sources when in a low density PRU deployment scenario.

[0112] In a first embodiment, inter-PRU coordination procedures may be used to overcome the impact of low density PRU deployments on carrier phase measurements. An LMF could request different PRUs, in LOS links with TRPs, to perform DL PRS measurements over different PRS resources in order to model the phase errors at the TRPs and mitigate them. The phase error estimation and mitigation would allow target UEs to accurately determine their positions when using a carrier- phase-measurement-based (i.e., carrier-phase-based) position determination technique. In this case, target UEs perform carrier phase measurements for DL PRS received from the same TRPs used by the PRUs to estimate the phase errors. Multiple DL-PRS measurements may be performed by multiple PRUs over multiple beams in order to collect enough measurements for phase errors modelling.

[0113] Because phase errors may arise from a combination of multiple causes, multiple independent measurements may be needed to construct a valid model of the phase errors. Accordingly, producing a phase error model based on multiple measurements from different PRUs and/or different beams enables more accurate error mitigation than phase errors estimated by one single PRU. Different DL-PRS measurements and/or phase error estimates are reported to the LMF in an in-coverage scenario and to a central unit that may be referred to herein as a virtual positioning reference unit (v-PRU) in the out-of-coverage scenario.

[0114] The v-PRU is designated and pre-configured by an LMF. The LMF may transmit an ‘ActivateY-PRld” message via LPP signaling to the designated V-PRU.

[0115] According to a first implementation, the LMF may notify other PRUs of the designation of the v-PRU. This notification may be transmitted to the other PRUs as part of the “ RequestPRUDatcT LPP message. In this case, “RequestPRUData” LPP message should indicate that phase error estimates should be reported to the designated v-PRU.

[0116] According to a second implementation, the v-PRU could transmit broadcast messages over SL PC5 interfaces to PRUs in its neighborhood in order to request that nearby PRUs report DL PRS measurements and/or phase error estimates to the v-PRU over PC 5 interfaces.

[0117] The v-PRU could be designated by the LMF based on different metrics. For example, the PRU to designate as the v-PRU may be determined based on sidelinks (SLs) with other PRUs, good SLs with the target UE, mobility and processing capabilities of the PRU (such as being able to model phase errors based on reported measurements), and the like, or a combination thereof. In one implementation, one of the PRUs that has received a “RequestPRUData ” message from the LMF could be designated as the v-PRU.

[0118] An LMF and/or a v-PRU may construct a model for phase errors based on reported measurements, and may estimate phase errors of the identified sources based on the constructed model. Phase error estimates may be used by the LMF or may be transmitted to a target UE for error compensation via LPP signaling (for example, via a “ProvideAssistanceData” LPP message).

[0119] FIG. 7 illustrates an example configuration of a wireless communication system in accordance with embodiments of the disclosure. In the example, a TRP (the NR node B gNB) has a LOS link with second PRU PRU 2 at a distance d₂ and a NLOS or Blocked link with a first PRU PRU l at a distance d , and where d₂ is greater than d₁. In the example, while the distance between the TRP gNB and the second PRU PRU 2 is greater than the distance between the TRP gNB and the first PRU PRU l, the TRP gNB and second PRU PRU 2 have a LOS link while the TRP gNB and the first PRU PRU l have a NLOS or blocked link.

[0120] Because of the NLOS/blocked link, when the first PRU PRU l performs measurements over DL PRS resources received from the TRP gNB using a carrier phasebased positioning technique, the carrier phase measurement may be inaccurate because they represent measurements on a NLOS path. This results in an inaccurate phase errors estimation at the first PRU PRU l .

[0121] On the other hand, when the second PRU PRU 2 performs measurements over DL PRS resources received from the TRP gNB using a carrier phase-based positioning technique, the larger distance d₂ between TRP gNB and second PRU PRU 2 will also impact the carrier phase measurements and may reduce phase error estimation accuracy. Generally, the smaller TRP-PRU distance, the more accurate phase error estimates will be.

[0122] As a result, in the example shown in FIG. 7, if phase error estimates from only one of the first PRU PRU l or the second PRU PRU 2 are used, they may not be sufficient for a precise carrier phase estimation and as a result the phase errors at target UE may not be correctly mitigated and the target UE position may have a higher position error. That is, in the example of FIG. 7, using phase error estimates from only one of the first and second PRUs may not be sufficient for a precise carrier phase estimation.

[0123] For LOS/NLOS detection between a TRP and a PRU, a few methods can be considered at high level. First, there exist PHY layer signal processing algorithms for LOS detections relying on hypothesis testing, Bayesian inference or machine learning techniques. For example, a UE can estimate CIR (Channel Impulse Response) and determine whether a channel link fits a LOS channel profile or a NLOS channel profile. Criteria of channel profile evaluation will be a modem implementation issue. In some examples, a LOS/NLOS detection (e.g., probability of NLOS or LOS) may be based on the relative power of the strongest ray/path to the power of at least one other paths (e.g., 2nd strongest path, sum of the power of the other paths) of the channel estimate/CIR or channel power delay profile. In some examples, a multipath detection may be based on the number of paths determined for the channel estimate/CIR or channel power delay profile.

[0124] Several DL PRS measurements, each including carrier phase measurements of the received PRS, could be performed over different beams and by different PRUs having LOS links with TRPs. Based on these measurements, each PRU might estimate phase errors and report them to an LMF in an in-coverage scenario or to a pre-configured PRU, called a virtual PRU (V-PRU), in an out-of-coverage scenario. In this case, a virtual PRU could be configured by the LMF, in order to overcome low PRU density deployment and the blocked/NLOS links between TRPs and certain PRUs. The phase error estimates reported to LMF or v-PRU enable better modelling of phase errors which allows more accurate phase error mitigation.

[0125] For example, a LMF or Virtual PRU may receive these measurements from PRU l and PRU 2 regarding two different beams/PRS resources:

wherein is a phase measurement of a first beam as received by a first PRU, i^{s a} phase measurement of a second beam as received by the first PRU, (Ppp^^ is a phase measurement of the first beam as received by a second PRU, and ^<PpppJ^{n 2}' is a phase measurement of the second beam as received by the second PRU, f is a carrier frequency, d_{TRP-PR Ui} and d_{TRP-PR U2} are distances between the TRP and the first and second RPUs, respectively,

_are integer ambiguities,

<p_{e 2} - , and p_{e 2} - are error sources impacting the carrier phase estimate, and c is the speed of light. [0126] Phase error sources may include random initial phases at TRP, time/frequency sync errors, antenna reference point (ARP) errors, carrier frequency offset CFO residuals or a combination thereof.

[0127] Because the exact location of the PRUs and the TRPs are known, the integer ambiguity value (which may be calculated using a brute-force method or any other technique) and the carrier phase could be estimated and an estimate of the range between PRU and TRP could be determined. Any difference between actual carrier phase (calculated based on real distance d between PRU and TRP) and estimated carrier phase can be attributed to errors. A model determined in accordance with these errors may be used to provide phase error estimates which can be used to more accurately determine locations for one or more target wireless devices that are in the proximity of the PRUs.

[0128] According to the first embodiment, these measurements collected from PRUs should have same timestamp and should have been performed over Tx beams quasicollocated (QCLed) with same Synchronized Signal Block (SSB) transmission (Tx) beam.

[0129] In embodiments, different Tx beams from same PRS resource set may be used to transmit DL PRSs to a same PRU, allowing that PRU to perform different phase errors measurements without having to choose another PRU candidate and thereby allowing for a greater number of measurements for use in phase error modelling at an LMF or Virtual PRU.

[0130] In embodiments, different Tx beams from different PRS resource sets may be used to transmit DL PRSs to a same PRU, allowing the PRU to perform different phase errors measurements, thereby allowing for a greater number of measurements for use in phase error modelling at an LMF or Virtual PRU.

[0131] FIG. 8 illustrates a procedures for carrier-phase-based position determination in an in-coverage scenario in a wireless communication network in accordance with aspects of the present disclosure.

[0132] At step SI, an LMF transmits a request for PRU data to a plurality of PRUs including first PRU PRU l and second PRU PRU 2. [0133] At step S2, a TRS such as a gNB transmits a DL PRS. In embodiments, the DL PRS may be transmitted using one beam. In other embodiments, the DL PRS may be transmitted using a plurality of beams.

[0134] At step S3, the plurality of PRUs perform measurements of the transmitted DL PRS. The measurements include carrier phase measurements. In embodiments wherein the DL PRS is transmitted using a plurality of beams, the measurements include carrier phase measurements for each of the plurality of beams.

[0135] In embodiments, at least one other TRS transmits at least one other DL PRS, as described in step S2, and the measurements performed at step S3 include carrier phase measurements of the at least one other DL PRS.

[0136] At step S4, each of the plurality of PRUs transmits a report to the LMF. The reports from each PRU may include, among other measurements, one or more phase error estimates based on all of the carrier phase measurements performed by that PRU at step S3. For example, each report may include a phase error estimate for each beam of each TRS that the PRU transmitting the report received a DL PRS on. Each report may also include a timestamp corresponding to the measurements and an indication regarding a timer. In embodiments, reports may be transmitted in response to requests from the LMF, periodically transmitted based on the timer, transmitted in response to a change in a phase error estimate for one of more of the beams relative to a previous phase error estimate for that beam, or a combination thereof.

[0137] At step S5, the LMF constructs a phase error model based on the reports received from the plurality of PRUs. The phase error model may be used to estimate contributions to phase error from each of a plurality of phase error sources, such as initial phase offset, time and frequency synchronization errors, carrier frequency offset CFO, Antenna reference points ARPs, Doppler velocity, and the like.

[0138] At step S6, the TRP transmits a subsequent DL PRS to a target wireless device (in FIG. 8, a target UE).

[0139] In response to receiving the subsequent DL PRS, at step S7 the target wireless device transmits a request for location-determination assistance data to the LMF. The request may include an indication of the source (for example, the TRP and beam) of the subsequent DL PRS. In some embodiments, when the location of the target wireless device is to be determined based on signals received over a plurality of beams from a plurality of TRPs, the request may also include one or more indications of sources of previous DL PRSs that were received and measured by the target wireless device and that will be used to determine the location of the target wireless device. The target wireless device also performs carrier phase measurements on the received subsequent DL PRS.

[0140] In response to receiving the request for location-determination assistance data, at step S8, the LMF produces assistance data for carrier-phase based location-determination using the phase error model constructed at step S5, and then transmits the assistance data to the target wireless device. The assistance data may include respective phase error estimates for each beam/TRP combination that will be used to determine the location of the target wireless device.

[0141] At step S9, the target wireless device determines its location using the previously-performed carrier phase measurements of DL PRSs and the assistance data.

[0142] In another embodiment, instead of transmitting a request for assistance data to the LMF at step S7, the target wireless device transmits information based on the one or measurements of DL PRSs performed at step S7 to the LMF. In such an embodiment, the LMF determines the position of the target wireless device using the assistance data produced using the phase error model and the information based on the one or measurements of DL PRSs that the LMF received from the target wireless device.

[0143] In embodiments, steps S6 through S9 may be performed a plurality of times between each performance of steps SI through S4. That is, a plurality of wireless device position determinizations may be made for each phase error model constructed in step S5, so that the wireless network overhead incurred by production of the phase error model is reduced.

[0144] FIG. 9 illustrates a procedure for carrier-phase-based position determination in an out-of-coverage scenario a wireless communication network in accordance with aspects of the present disclosure. The out-of-coverage scenario may be one in which a target wireless device may not be able to communicate with the LMF.

[0145] The operation of the procedure illustrated in FIG. 9 is similar in many respects to that shown in FIG. 8, except with the alterations described below.

[0146] At step SO in FIG. 9, the LMF indicates to a PRU that it is to operate as a Virtual PRU (v-PRU) that will perform some operations performed by the LMF in the process of FIG. 8, as shall be described below. In embodiments, the v-PRU may also perform operations described as being performed by a PRU in the procedure of FIG. 8. For example, the v-PU may also operate as, for example, PRU l .

[0147] At step ST of FIG. 9, in addition to operations indicated for step SI in the process of FIG. 8, the LMF indicates the designation of the v-PRU to the plurality of PRUs. In embodiments, an indication of the v-PRU may also be provided to the target wireless device.

[0148] At step S4’ of FIG. 9, instead of reporting the phase error estimates to the LMF as done in the process of FIG. 8, the plurality of PRUs reports the phase error estimates to the v-PRU.

[0149] At step S5’ of FIG. 9, the operations of step S5 performed by the LMF in the process of FIG. 8 are instead performed by the v-PRU.

[0150] At step S7’, instead of requesting assistance data from the LMF as in the process of FIG. 8, the target wireless device requests assistance data from the v-PRU.

[0151] At step S8’, instead of the LMF transmitting the assistance data as in the process of FIG. 8, the assistance data is transmitted by the v-PRU.

[0152] FIG. 10 illustrates a flowchart of a process 1000 for assisting the carrier-phasebased determination of a position of a wireless device in a wireless communication network in accordance with aspects of the present disclosure. The process 1000 may be performed by an LMF, by a PRU designated as a v-PRU by the LMF, or both. An entity performing the process 1000 may be referred to herein as an assisting entity. [0153] At step 1005, the assisting entity transmits requests for information based on carrier phase measurements to a plurality of PRUs.

[0154] At step 1010, the assisting entity receives a plurality of reports from the plurality of PRUs, each report including one or more information based on carrier phase measurements performed by the corresponding PRU. The carrier phase measurements may be of DL PRS(s) received over one or more beams from one or more TRPs. The reports may have been transmitted by the PRUs in response to the requests transmitted in step 1005, transmitted periodically in response the elapsing of a predetermined period of time, transmitted in response to a change in network conditions sensed by the transmitting PRU, or a combination thereof.

[0155] At step 1015, the assisting entity constructs a phase error model based on the information in the reports received from the plurality of PRUs.

[0156] At step 1020, the assisting entity determines a plurality of phase error estimates based on the phase error model. The a plurality of phase error estimates may be determined in response to a request for positioning assistance data from a target wireless device. The determination of the plurality of phase error estimates may also be based on information received from the target wireless device.

[0157] At step 1025, the plurality of phase error estimates are provided to a process for carrier-phase-based determination of the location of the target wireless device. The process for determining the location of the target wireless device may be performed by the assisting entity based on information on carrier phase measurements received by the assisting entity from the target wireless device, or may be performed by the target wireless device after the target wireless device receives the plurality of phase error estimates from the assisting entity.

[0158] Step 1025 may be performed a plurality of times (for one or more target wireless devices) for each performance of steps 1010 through 1020.

[0159] FIG. 11 is a block diagram 1100 of an example of a device 1102 that may be used to determine or assist the determination, based on carrier phases, of a position of a wireless device, in accordance with aspects of the present disclosure. The device 1102 may be an example of a UE 104 or a PRU 122 as described herein. The device 1102 may support wireless communication with one or more network entities 102, UEs 104, or any combination thereof. The device may also support wired or optical communication with network with one or more network entities 102. The device 1102 may include components for bi-directional communications including components for transmitting and receiving communications and performing calculation, such as a processor 1104, a memory 1106, a transceiver 1108, and an I/O controller 1110. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses).

[0160] The processor 1104, the memory 1106, the transceiver 1108, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. For example, the processor 1104, the memory 1106, the transceiver 1108, or various combinations or components thereof may support a method for performing one or more of the operations described herein.

[0161] In some implementations, the processor 1104, the memory 1106, the transceiver 1108, or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field- programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some implementations, the processor 1104 and the memory 1106 coupled with the processor 1104 may be configured to perform one or more of the functions described herein (e.g., executing, by the processor 1104, instructions stored in the memory 1106).

[0162] For example, the processor 1104 may support wireless communication at the device 1102 in accordance with examples as disclosed herein. Processor 1104 may be configured as or otherwise support a means for producing or using phase error estimates in accordance with the present disclosure for use in carrier-phase-based position determination of wireless devices in a wireless network.

[0163] The processor 1104 may include an intelligent hardware device (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some implementations, the processor 1104 may be configured to operate a memory array using a memory controller. In some other implementations, a memory controller may be integrated into the processor 1104. The processor 1104 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1106) to cause the device 1102 to perform various functions of the present disclosure.

[0164] The memory 1106 may include random access memory (RAM) and read-only memory (ROM). The memory 1106 may store computer- readable, computer-executable code including instructions that, when executed by the processor 1104 cause the device 1102 to perform various functions described herein. The code may be stored in a non- transitory computer-readable medium such as system memory or another type of memory. In some implementations, the code may not be directly executable by the processor 1104 but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some implementations, the memory 1106 may include, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

[0165] The I/O controller 1110 may manage input and output signals for the device 1102. The I/O controller 1110 may also manage peripherals not integrated into the device M02. In some implementations, the I/O controller 1110 may represent a physical connection or port to an external peripheral. In some implementations, the I/O controller 1110 may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS- WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In some implementations, the I/O controller 1110 may be implemented as part of a processor, such as the processor 1104. In some implementations, a user may interact with the device 1102 via the I/O controller 1110 or via hardware components controlled by the I/O controller 1110.

[0166] In some implementations, the device 1102 may include a single antenna 1112. However, in some other implementations, the device 1102 may have more than one antenna 1112 (i.e., multiple antennas), including multiple antenna panels or antenna arrays, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver 1108 may communicate bi-directionally, via the one or more antennas 1112, wired, or wireless links as described herein. For example, the transceiver 1108 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1108 may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas 1112 for transmission, and to demodulate packets received from the one or more antennas 1112.

[0167] In embodiments, different PRUs are requested to perform measurements, including carrier phase measurements, over DL PRS received from different beams and different TRPs. The PRUs then report phase error estimates to an LMF, a V-PRU, or both.

[0168] In embodiments, phase errors are modelled based on different phase measurements and phase error estimates received from different PRUs when using a RAT- dependent carrier phase-based positioning technique.

[0169] Accordingly, embodiments enable more efficient and more accurate carrierphase-based location determination in scenarios with low-density PRU deployments.

[0170] It should be noted that the methods described herein describes possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

[0171] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0172] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

[0173] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

[0174] Any connection may be properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer- readable media.

[0175] As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of’ or “one or more of’ or “one or both of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. Further, as used herein, including in the claims, a “set” may include one or more elements.

[0176] The terms “transmitting,” “receiving,” or “communicating,” when referring to a network entity, may refer to any portion of a network entity (e.g., a base station, a CU, a DU, a RU) of a RAN communicating with another device (e.g., directly or via one or more other network entities).

[0177] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described example. [0178] The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMS What is claimed is:

1. A Location Management Function, comprising: a processor; and a memory coupled with the processor, the processor configured to cause the Location Management Function to: transmit a plurality of data request messages to a plurality of position reference units, respectively, each data request message requesting information for carrier phase error mitigation, the information for carrier phase error mitigation including measurements, phase error estimates, or both; receive a plurality of information for carrier phase error mitigation from the plurality of position reference units, respectively; and determine a plurality of phase error estimates based on the plurality of information for carrier phase error mitigation, wherein the plurality of phase error estimates are configured for use in determining a location of a target wireless device by correcting carrier phase errors.

2. The Location Management Function of claim 1, wherein the processor is further configured to cause the Location Management Function to: receive a plurality of position reference signal (PRS) measurements from the target wireless device, each PRS measurement including a carrier phase measurement of a corresponding received PRS; and determine the location of the target wireless device by mitigating phase errors in the plurality of PRS measurements using the plurality of phase error estimates.

3. The Location Management Function of claim 1, wherein the processor is further configured to cause the Location Management Function to: receive a request for assistance data from the target wireless device; and provide the plurality of phase error estimates to the target wireless device in response to receiving the request for assistance data.

4. The Location Management Function of claim 3, wherein the request for assistance data from the target wireless device is communicated via Long Term Evolution (LTE) Position Protocol (LPP) signaling, and wherein the plurality of phase error estimates are communicated via LPP signaling.

5. The Location Management Function of claim 1, wherein the plurality of data request messages are communicated via Long Term Evolution (LTE) Position Protocol (LPP) signaling, and wherein the plurality of information for carrier phase error mitigation are communicated via LPP signaling.

6. The Location Management Function of claim 1, wherein a phase error estimate of the plurality of phase error estimates includes an estimates for a phase error caused by an initial phase offset at a transmission-reception points (TRP), a carrier frequency offset, a time synchronization error, a frequency synchronization error, an antenna reference point error, or a combination thereof.

7. The Location Management Function of claim 1, wherein the processor is configured to cause the Location Management to determine the plurality of phase error estimates based on the plurality of information for carrier phase error mitigation by: constructing a phase error model based on the plurality of information for carrier phase error mitigation; and determining the plurality of phase error estimates based on the phase error model.

8. A first position reference unit, comprising: a processor; and a memory coupled with the processor, the processor configured to cause the first position reference unit to: receive a virtual-position reference unit configuration message from a Location Management Function of a wireless communication network; receive a first set of one or more phase error estimate reports from a second position reference unit; receive a second set of one or more phase error estimate reports from a third position reference unit; construct, based on the first and second sets of phase error estimate reports, a phase error model for carrier phase error mitigation; determine a plurality of phase error estimates based on the phase error model; and provide the plurality of phase error estimates to a target wireless device; wherein the target wireless device determines a location of the target wireless device by mitigating phase errors in a plurality of position reference signal measurements using the plurality of phase error estimates.

9. The first position reference unit of claim 8, wherein the virtual-position reference unit configuration message is received via Long Term Evolution (LTE) Position Protocol (LPP) signaling.

10. The first position reference unit of claim 8, wherein the first and second phase error estimate reports are received via a sidelink PC5 interface.

11. An apparatus for wireless communication, comprising: a processor; and a memory coupled with the processor, the processor configured to cause the apparatus to: transmit a plurality of data request messages to a plurality of position reference units, respectively, each data request message requesting information for carrier phase error mitigation, the information for carrier phase error mitigation including measurements, phase error estimates, or both; receive a plurality of information for carrier phase error mitigation from the plurality of position reference units, respectively; construct a phase error model based on the plurality of information for carrier phase error mitigation; and determine a plurality of phase error estimates using the phase error model, wherein the plurality of phase error estimates are configured for use in determining a location of a target wireless device by correcting carrier phase errors.

12. The apparatus of claim 11, wherein the processor is further configured to cause the apparatus to: receive a plurality of position reference signal (PRS) measurements from the target wireless device, each PRS measurement including a carrier phase measurement of a corresponding received PRS; and determine the location of the target wireless device by mitigates phase errors in the plurality of PRS measurements using the plurality of phase error estimates.

13. The apparatus of claim 11, wherein the processor is further configured to cause the apparatus to: receive a request for assistance data from the target wireless device; and provide the plurality of phase error estimates to the target wireless device in response to receiving the request for assistance data, wherein the target wireless device determines the location of the target wireless device by mitigating phase errors in a plurality of position reference signal (PRS) measurements using the plurality of phase error estimates, each PRS measurement including a carrier phase measurement of a corresponding received PRS.

14. A processor for wireless communication, comprising: at least one controller coupled with at least one memory and configured to cause the processor to: transmit a plurality of data request messages to a plurality of position reference units, respectively, each data request message requesting information for carrier phase error mitigation, the information for carrier phase error mitigation including measurements, phase error estimates, or both; receive a plurality of information for carrier phase error mitigation from the plurality of position reference units, respectively; and determine a plurality of phase error estimates based on the plurality of information for carrier phase error mitigation, wherein the plurality of phase error estimates are configured for use in determining a location of a target wireless device by correcting carrier phase errors.

15. The processor for wireless communication of claim 14, wherein the controller is further configured to cause the processor to: receive a plurality of position reference signal (PRS) measurements from the target wireless device, each PRS measurement including a carrier phase measurement of a corresponding received PRS; and determine the location of the target wireless device by mitigating phase errors in the plurality of PRS measurements using the plurality of phase error estimates.

16. The processor for wireless communication of claim 14, wherein the controller is further configured to cause the processor to: receive a request for assistance data from the target wireless device; and provide the plurality of phase error estimates to the target wireless device in response to receiving the request for assistance data.

17. The processor for wireless communication of claim 16, wherein the request for assistance data from the target wireless device is communicated via Long Term Evolution (LTE) Position Protocol (LPP) signaling, and wherein the plurality of phase error estimates are communicated via LPP signaling.

18. The processor for wireless communication of claim 14, wherein the plurality of data request messages are communicated via Long Term Evolution (LTE) Position Protocol (LPP) signaling, and wherein the plurality of information for carrier phase error mitigation are communicated via LPP signaling.

19. The processor for wireless communication of claim 14, wherein a phase error estimate of the plurality of phase error estimates includes an estimates for a phase error caused by an initial phase offset at a transmission-reception points (TRP), a carrier frequency offset, a time synchronization error, a frequency synchronization error, an antenna reference point error, or a combination thereof.

20. The processor for wireless communication of claim 14, wherein the controller is further configured to cause the processor to determine the plurality of phase error estimates based on the plurality of information for carrier phase error mitigation by: constructing a phase error model based on the plurality of information for carrier phase error mitigation; and determining the plurality of phase error estimates based on the phase error model.