Time-Reversal Precoding for Sidelink-Based Positioning

Abstract

Techniques for wireless communications are disclosed. In one aspect, a user equipment (UE) derives a time-reversal (TR) precoder based at least in part on an estimated channel between a first UE and a second UE, and sends a TR-precoded sidelink (SL) positioning reference signal (PRS) to the second UE. The estimated channel can be based on channel state information (CSI) associated with a wideband (WB) reference signal (RS). The TR precoder can be based on transmission or reception on a SL communication channel between the first UE and the second UE.

Description

Claiming priority

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Greek Patent Application No. 20210100170, entitled "TIME REVERSAL PRECODING FOR SIDELINK BASED POSITIONING," filed on March 18, 2021, which is assigned to the assignee of the present application and is expressly incorporated by reference in its entirety into this specification. [Technical field]

[0002] Aspects of the present disclosure generally relate to wireless communications. [Background technology]

[0003]

[0003] Wireless communication systems have evolved through various generations, including first generation analog wireless telephone service (1G), second generation (2G) digital wireless telephone service (including intermediate 2.5G and 2.75G networks), third generation (3G) high speed data, Internet-enabled wireless service, and fourth generation (4G) service (e.g., Long Term Evolution (LTE) or WiMax). Currently, there are many different types of wireless communication systems in use, including cellular and personal communication service (PCS) systems. Examples of known cellular systems include Cellular Analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), and the like.

[0004]

[0004] The fifth generation (5G) wireless standard, called New Radio (NR), requires, among other improvements, higher data rates, a larger number of connections, and better coverage. The 5G standard by the Next Generation Mobile Network Alliance is designed to provide data rates of tens of megabits per second to each of tens of thousands of users, and 1 gigabit per second to a few dozen workers on an office floor. To support large sensor deployments, hundreds of thousands of simultaneous connections should be supported. Thus, the spectral efficiency of 5G mobile communications should be significantly enhanced compared to the current 4G standard. Furthermore, signaling efficiency should be enhanced and latency should be significantly reduced compared to the current standard.

[0005]

[0005] In particular, leveraging the increased data rates and reduced latency of 5G, vehicle-to-everything (V2X) communication technologies are being implemented to support autonomous driving applications, such as wireless communications between vehicles, between vehicles and roadside infrastructure, between vehicles and pedestrians, etc. Summary of the Invention

[0006]

[0006] The following presents a simplified summary related to one or more aspects disclosed herein. As such, the following summary is not intended to be an extensive overview related to all contemplated aspects, nor is it intended to identify key or critical elements related to all contemplated aspects or to delineate the scope related to any particular aspect. As such, the following summary has the sole purpose of presenting some concepts related to one or more aspects related to the mechanisms disclosed herein in a simplified form prior to the detailed description presented below.

[0007]

[0007] In one aspect, a method of wireless communication performed by a first UE includes deriving a time reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE, and sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0008]

[0008] In one aspect, a method of wireless communication performed by a first UE includes receiving a wideband reference signal (WB RS) from a second UE, determining channel state information (CSI) based at least in part on the WB RS, and sending the CSI to the second UE.

[0009]

[0009] In one aspect, a method of wireless communication performed by a first UE includes receiving a WB RS from a second UE, estimating a channel between the second UE and the first UE based at least in part on the WB RS, deriving a TR precoder based on the estimated channel, and sending the TR precoder to the second UE.

[0010]

[0010] In one aspect, a method of wireless communication performed by a first UE includes sending a WB RS to a second UE and receiving a TR precoded SL-PRS from the second UE.

[0011]

[0011] In one aspect, the first UE includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, wherein the at least one processor is configured to derive a TR precoder based at least in part on an estimated channel between the first UE and the second UE, and to send a TR precoded SL-PRS to the second UE.

[0012]

[0012] In one aspect, the first UE includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, wherein the at least one processor is configured to receive a WB RS from the second UE, determine a CSI based at least in part on the WB RS, and send the CSI to the second UE.

[0013]

[0013] In one aspect, the first UE includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, where the at least one processor is configured to receive a WB RS from the second UE, estimate a channel between the second UE and the first UE based at least in part on the WB RS, derive a TR precoder based on the estimated channel, and send the TR precoder to the second UE.

[0014]

[0014] In one aspect, the first UE includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, wherein the at least one processor is configured to send a WB RS to the second UE and receive a TR precoded SL-PRS from the second UE.

[0015]

[0015] In one aspect, the first UE includes means for deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE, and means for sending a TR precoded SL-PRS to the second UE.

[0016]

[0016] In one aspect, the first UE includes means for receiving a WB RS from the second UE, means for determining a CSI based at least in part on the WB RS, and means for sending the CSI to the second UE.

[0017]

[0017] In one aspect, the first UE includes means for receiving a WB RS from the second UE, means for estimating a channel between the second UE and the first UE based at least in part on the WB RS, means for deriving a TR precoder based on the estimated channel, and means for sending the TR precoder to the second UE.

[0018] In one aspect, the first UE includes means for sending a WB RS to the second UE and means for receiving a TR precoded SL-PRS from the second UE.

[0019]

[0019] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to derive a TR precoder based at least in part on an estimated channel between the first UE and a second UE, and to send a TR precoded SL-PRS to the second UE.

[0020]

[0020] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to receive a WB RS from a second UE, determine a CSI based at least in part on the WB RS, and send the CSI to the second UE.

[0021]

[0021] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to receive a WB RS from a second UE, estimate a channel between the second UE and the first UE based at least in part on the WB RS, derive a TR precoder based on the estimated channel, and send the TR precoder to the second UE.

[0022]

[0022] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to send a WB RS to a second UE and receive a TR precoded SL-PRS from the second UE.

[0023] Other objects and advantages associated with the embodiments disclosed herein will become apparent to those skilled in the art based on the accompanying drawings and detailed description.

[0024]

[0024] The accompanying drawings are presented to aid in the explanation of various aspects of the present disclosure and are provided merely to illustrate, not to limit, the aspects. [Brief description of the drawings]

[0025] [Figure 1]

[0025] FIG. 1 illustrates an example wireless communication system according to an aspect of the present disclosure. [Figure 2A]

[0026] FIG. 1 illustrates an example wireless network structure, according to aspects of the present disclosure. [Figure 2B] FIG. 1 illustrates an example wireless network structure, according to aspects of the present disclosure. [Diagram 3]

[0027] FIG. 1 illustrates an example of a wireless communication system supporting unicast sidelink establishment, according to aspects of the present disclosure. [Figure 4]

[0028] 1 is a block diagram illustrating various components of an example user equipment (UE) in accordance with aspects of the present disclosure. [Figure 5A]

[0029] FIG. 1 illustrates two methods for single cell UE positioning that can be implemented when the cell contains multiple UEs engaged in SL communications. [Figure 5B] FIG. 1 illustrates two methods for single cell UE positioning that can be implemented when the cell contains multiple UEs engaged in SL communications. [Figure 6]

[0030] 4 illustrates a flowchart of an example process related to TR precoding for SL-based positioning, in accordance with an aspect of the disclosure. [Figure 7]

[0031] 4 is a messaging and event diagram illustrating a process associated with TR precoding for SL-based positioning, in accordance with an embodiment of the present disclosure. [Figure 8]

[0032] 4 is a messaging and event diagram illustrating a process associated with TR precoding for SL-based positioning, in accordance with an embodiment of the present disclosure. [Figure 9]

[0033] 4 is a messaging and event diagram illustrating a process associated with TR precoding for SL-based positioning, in accordance with an embodiment of the present disclosure. [Figure 10]

[0034] 4 illustrates a flowchart of an example process related to TR precoding for SL-based positioning, in accordance with an aspect of the disclosure. [Figure 11]

[0035] 4 illustrates a flowchart of an example process related to TR precoding for SL-based positioning, in accordance with an aspect of the disclosure. [Figure 12]

[0036] 4 illustrates a flowchart of an example process related to TR precoding for SL-based positioning, in accordance with an aspect of the disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026]

[0037] Aspects of the present disclosure are provided in the following description and associated drawings, directed to various examples provided for illustration purposes. Alternative aspects may be devised without departing from the scope of the present disclosure. Additionally, well-known elements of the present disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the present disclosure.

[0027]

[0038] The words "exemplary" and / or "example" are used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" and / or "example" is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term "aspects of the present disclosure" does not require that all aspects of the present disclosure include the described feature, advantage or mode of operation.

[0028]

[0039] Those skilled in the art will appreciate that the information and signals described below 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 referred to throughout the following description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, depending in part on the particular application, in part on the desired design, in part on the corresponding technology, etc.

[0029]

[0040] Further, many aspects are described in terms of a sequence of actions to be performed, for example, by elements of a computing device. It will be appreciated that the various actions described herein may be performed by specific circuitry (e.g., an application specific integrated circuit (ASIC)), by program instructions executed by one or more processors, or by a combination of both. Furthermore, a sequence of actions described herein may be considered to be embodied as a whole in any form of non-transitory computer-readable storage medium storing a corresponding set of computer instructions that, when executed, cause or instruct an associated processor of a device to perform the functions described herein. Thus, various aspects of the present disclosure may be embodied in a number of different forms, all of which are contemplated to fall within the scope of the claimed subject matter. Moreover, for each of the aspects described herein, the corresponding form of any such aspect may be described herein, for example, as "logic configured to" perform the described actions.

[0030]

[0041] As used herein, the terms "user equipment" (UE), "vehicle UE" (V-UE), "pedestrian UE" (P-UE), and "base station" are not intended to be specific or, as the case may be, limited to any particular radio access technology (RAT) unless otherwise stated. In general, a UE may be any wireless communication device (e.g., a vehicle on-board computer, a vehicle navigation device, a mobile phone, a router, a tablet computer, a laptop computer, a tracking device, a wearable (e.g., a smart watch, glasses, an augmented reality (AR) / virtual reality (VR) headset, etc.), a vehicle (e.g., a car, a motorcycle, a bicycle, etc.), an Internet of Things (IoT) device, etc.) used by a user to communicate over a wireless communication network. A UE may be mobile or (e.g., at some times) stationary and may communicate with a radio access network (RAN). As used herein, the term "UE" may be referred to interchangeably as a "mobile device", "access terminal" or "AT", "client device", "wireless device", "subscriber device", "subscriber terminal", "subscriber station", "user terminal" or UT, "mobile terminal", "mobile station", or variations thereof.

[0031]

[0042] A V-UE is a type of UE and may be any in-vehicle wireless communication device, such as a navigation system, a warning system, a head-up display (HUD), an on-board computer, etc. Alternatively, a V-UE may be a portable wireless communication device (e.g., a cell phone, a tablet computer, etc.) carried by a driver of the vehicle or a passenger in the vehicle. The term "V-UE" may refer to an in-vehicle wireless communication device or the vehicle itself, depending on the context. A P-UE is a type of UE and may be a portable wireless communication device carried by a pedestrian (i.e., a user not driving or riding in the vehicle). In general, a UE may communicate with a core network via a RAN, through which the UE may be connected with an external network, such as the Internet, and with other UEs. Of course, other mechanisms for connecting to a core network and / or the Internet are also possible for a UE, such as via a wired access network, a wireless local area network (WLAN) network (e.g., based on IEEE 802.11, etc.), etc.

[0032]

[0043] A base station may operate according to one of several RATs in communication with UEs depending on the network in which it is deployed, and may alternatively be referred to as an access point (AP), network node, Node B, evolved Node B (eNB), next generation eNB (ng-eNB), new radio (NR) Node B (also referred to as gNB or gNode B), etc. A base station may be used primarily to support wireless access by UEs, including supporting data, voice and / or signaling connections for supported UEs. In some systems, a base station may provide purely edge node signaling functions, while in other systems it may provide additional control and / or network management functions. A communication link through which a UE may send signals to a base station is referred to as an uplink (UL) channel (e.g., reverse traffic channel, reverse control channel, access channel, etc.). A communication link through which a base station may send signals to a UE is referred to as a downlink (DL) or forward link channel (e.g., paging channel, control channel, broadcast channel, forward traffic channel, etc.). The term Traffic Channel (TCH) as used herein can refer to either a UL / reverse traffic channel or a DL / forward traffic channel.

[0033]

[0044] The term "base station" may refer to a single physical transmit reception point (TRP) or multiple physical TRPs that may or may not be collocated. For example, if the term "base station" refers to a single physical TRP, the physical TRP may be an antenna of the base station corresponding to a cell (or several cell sectors) of the base station. If the term "base station" refers to multiple collocated physical TRPs, the physical TRP may be an array of antennas of the base station (e.g., as in a multiple-input multiple-output (MIMO) system or in cases where the base station employs beamforming). If the term "base station" refers to multiple non-collocated physical TRPs, the physical TRP may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transport medium) or a remote radio head (RRH) (a remote base station connected to a serving base station). Alternatively, the non-collocated physical TRP may be a serving base station that receives measurement reports from a UE and a neighbor base station whose reference RF signal the UE is measuring. A TRP is a point from which a base station transmits and receives wireless signals, and therefore, as used herein, references to transmission from or reception at a base station should be understood as referring to the particular TRP of the base station.

[0034]

[0045] In some implementations that support positioning of UEs, a base station may not support wireless access by the UE (e.g., may not support data, voice, and / or signaling connections for the UE), but instead may transmit reference RF signals to the UE to be measured by the UE and / or may receive and measure signals transmitted by the UE. Such a base station may be referred to as a positioning beacon (e.g., when it transmits RF signals to the UE) and / or a location measurement unit (e.g., when it receives and measures RF signals from the UE).

[0035]

[0046] An "RF signal" comprises electromagnetic waves of a given frequency that transport information through space between a transmitter and a receiver. As used herein, a transmitter may transmit a single "RF signal" or multiple "RF signals" to a receiver. However, a receiver may receive multiple "RF signals" corresponding to each transmitted RF signal due to the propagation characteristics of RF signals through a multipath channel. The same transmitted RF signal on different paths between a transmitter and a receiver may be referred to as a "multipath" RF signal. As used herein, an RF signal may be referred to as a "wireless signal" or simply as a "signal" when it is clear from the context that the term "signal" refers to a wireless signal or an RF signal.

[0036]

[0047] 1 illustrates an exemplary wireless communication system 100 according to an aspect of the disclosure. The wireless communication system 100 (sometimes referred to as a wireless wide area network (WWAN)) may include various base stations 102 (labeled as "BS") and various UEs 104. The base stations 102 may include macrocell base stations (high-power cellular base stations) and / or small cell base stations (low-power cellular base stations). In an aspect, the macrocell base stations 102 may include eNBs and / or ng-eNBs where the wireless communication system 100 corresponds to an LTE network, or gNBs where the wireless communication system 100 corresponds to an NR network, or a combination of both, and the small cell base stations may include femtocells, picocells, microcells, etc.

[0037]

[0048] The base stations 102 collectively form a RAN and may interface with a core network 174 (e.g., Evolved Packet Core (EPC) or 5G Core (5GC)) through backhaul links 122 and to one or more location servers 172 (e.g., a Location Management Function (LMF) or a Secure User Plane Location (SUPL) Location Platform (SLP)) through the core network 174. The location servers 172 may be part of the core network 174 or may be external to the core network 174. In addition to other functions, the base stations 102 may perform functions related to one or more of the following: forwarding user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, Multimedia Broadcast Multicast Service (MBMS), subscriber and equipment tracing, RAN Information Management (RIM), paging, positioning, and delivery of alert messages. The base stations 102 may communicate with each other directly or indirectly (e.g., through EPC / 5GC) via backhaul links 134, which may be wired or wireless.

[0038]

[0049] The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage to a respective geographic coverage area 110. In an aspect, one or more cells may be supported by the base stations 102 in each geographic coverage area 110. A "cell" is a logical communication entity used for communication with a base station (e.g., over some frequency resource, referred to as a carrier frequency, component carrier, carrier, band, etc.) and may be associated with an identifier (e.g., physical cell identifier (PCI), enhanced cell identifier (ECI), virtual cell identifier (VCI), cell global identifier (CGI), etc.) to distinguish cells operating over the same or different carrier frequencies. In some cases, different cells may be configured according to different protocol types (e.g., machine type communication (MTC), narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access to different types of UEs. Because a cell is supported by a particular base station, the term "cell" may refer to either or both of the logical communication entity and the base station that supports it, depending on the context. In some cases, the term “cell” may also refer to a geographic coverage area (e.g., a sector) of a base station, so long as the carrier frequency can be detected and used for communication within any portion of the geographic coverage area 110.

[0039]

[0050] The geographic coverage areas 110 of neighboring macrocell base stations 102 may overlap partially (e.g., in handover regions), but some of the geographic coverage areas 110 may be significantly overlapped by larger geographic coverage areas 110. For example, a small cell base station 102' (labeled "SC" for "small cell") may have a geographic coverage area 110' that significantly overlaps with the geographic coverage area 110 of one or more macrocell base stations 102. A network that includes both small cell base stations and macrocell base stations may be known as a heterogeneous network. A heterogeneous network may also include Home eNBs (HeNBs) that may serve restricted groups known as Closed Subscriber Groups (CSGs).

[0040]

[0051] The communication link 120 between the base station 102 and the UE 104 may include uplink transmissions (also referred to as reverse link) from the UE 104 to the base station 102, and / or downlink (DL) transmissions (also referred to as forward link) from the base station 102 to the UE 104. The communication link 120 may use MIMO antenna techniques, including spatial multiplexing, beamforming, and / or transmit diversity. The communication link 120 may be through one or more carrier frequencies. The allocation of carriers may be asymmetric with respect to the downlink and uplink (e.g., more or fewer carriers may be allocated for the downlink than for the uplink).

[0041]

[0052] The wireless communication system 100 may further include a wireless local area network (WLAN) access point (AP) 150 communicating with a WLAN station (STA) 152 via a communication link 154 in an unlicensed frequency spectrum (e.g., 5 GHz). When communicating in the unlicensed frequency spectrum, the WLAN STA 152 and / or the WLAN AP 150 may perform a clear channel assessment (CCA) procedure or a listen-before-talk (LBT) procedure before communicating to determine if a channel is available.

[0042]

[0053] The small cell base station 102' may operate in licensed and / or unlicensed frequency spectrums. When operating in an unlicensed frequency spectrum, the small cell base station 102' may employ LTE or NR technology and use the same 5 GHz unlicensed frequency spectrum used by the WLAN AP 150. A small cell base station 102' employing LTE / 5G in an unlicensed frequency spectrum may boost coverage to and / or increase capacity of an access network. NR in an unlicensed spectrum may be referred to as NR-U. LTE in an unlicensed spectrum may be referred to as LTE-U, Licensed Assisted Access (LAA), or MulteFire.

[0043]

[0054] The wireless communication system 100 may further include a mmW base station 180 that may operate in mmW and / or near-mmW frequencies in communication with the UE 182. Extremely high frequency (EHF) is a portion of RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this band may be called millimeter waves. Near-mmW may extend down to frequencies of 3 GHz, with a wavelength of 100 millimeters. The very high frequency (SHF) band extends between 3 GHz and 30 GHz, also called centimeter waves. Communications using the mmW / near-mmW radio frequency bands have high path loss and relatively short range. The mmW base station 180 and the UE 182 may utilize beamforming (transmit and / or receive) over the mmW communication link 184 to compensate for the extremely high path loss and short range. Moreover, it will be appreciated that in alternative configurations, one or more base stations 102 may also transmit using mmW or near mmW and beamforming. Thus, it will be appreciated that the above description is by way of example only and should not be construed as limiting various aspects disclosed herein.

[0044]

[0055] Transmit beamforming is a technique for focusing an RF signal in a particular direction. Traditionally, when a network node (e.g., a base station) broadcasts an RF signal, it broadcasts the signal in all directions (omnidirectionally). In transmit beamforming, the network node determines where a given target device (e.g., UE) is located (relative to the transmitting network node) and projects a stronger downlink RF signal in that particular direction, thereby providing a faster (in terms of data rate) and stronger RF signal to the receiving device(s). To change the directionality of the RF signal when transmitting, the network node can control the phase and relative amplitude of the RF signal at each of the one or more transmitters broadcasting the RF signal. For example, the network node may use an array of antennas (called a "phased array" or "antenna array") that creates beams of RF waves that can be "steered" to point in different directions without actually moving the antennas. In particular, RF current from the transmitter is fed to the individual antennas with the proper phase relationship so that the waves from the separate antennas add together to increase radiation in the desired direction while canceling and suppressing radiation in undesired directions.

[0045]

[0056] A transmit beam may be quasi-colocated, meaning that the transmit beam appears to a receiver (e.g., a UE) to have the same parameters, regardless of whether the network node's transmit antennas themselves are physically colocated. In NR, there are four types of quasi-colocated (QCL) relationships. In particular, a QCL relationship of a given type means that some parameters for a second reference RF signal on a second beam may be derived from information about a source reference RF signal on a source beam. Thus, if the source reference RF signal is QCL type A, the receiver can use the source reference RF signal to estimate the Doppler shift, Doppler spread, average delay, and delay spread of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL type B, the receiver can use the source reference RF signal to estimate the Doppler shift and Doppler spread of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL type C, the receiver can use the source reference RF signal to estimate the Doppler shift and Doppler spread of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL Type D, the receiver may use the source reference RF signal to estimate spatial receive parameters of a second reference RF signal transmitted on the same channel.

[0046]

[0057] In receive beamforming, a receiver uses receive beams to amplify RF signals detected on a given channel. For example, the receiver can increase the gain setting and / or adjust the phase setting of an array of antennas in a particular direction to amplify (e.g., increase its gain level) an RF signal received from that direction. Thus, when a receiver is said to beamform in a direction, it means that the beam gain in that direction is high relative to the beam gains along other directions, or that the beam gain in that direction is highest compared to the beam gains in that direction of all other receive beams available to the receiver. This results in a stronger received signal strength (e.g., Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Interference-Plus-Noise Ratio (SINR), etc.) of the RF signal received from that direction.

[0047]

[0058] The transmit beam and the receive beam may be spatially related. The spatial relationship means that the parameters for the second beam (e.g., transmit or receive beam) of the second reference signal may be derived from information about the first beam (e.g., receive or transmit beam) of the first reference signal. For example, the UE may use a particular receive beam to receive a reference downlink reference signal (e.g., Synchronization Signal Block (SSB)) from a base station. The UE may then form a transmit beam for sending an uplink reference signal (e.g., Sounding Reference Signal (SRS)) to that base station based on the parameters of the receive beam.

[0048]

[0059] Note that a "downlink" beam can be either a transmit beam or a receive beam, depending on the entity forming it. For example, if the base station forms a downlink beam to transmit a reference signal to the UE, the downlink beam is a transmit beam. However, if the UE forms a downlink beam, it is a receive beam to receive the downlink reference signal. Similarly, an "uplink" beam can be either a transmit beam or a receive beam, depending on the entity forming it. For example, if the base station forms an uplink beam, it is an uplink receive beam, and if the UE forms an uplink beam, it is an uplink transmit beam.

[0049]

[0060] In 5G, the frequency spectrum in which wireless nodes (e.g., base stations 102 / 180, UEs 104 / 182) operate is divided into multiple frequency ranges: FR1 (450 to 6000 MHz), FR2 (24250 to 52600 MHz), FR3 (above 52600 MHz), and FR4 (between FR1 and FR2). The mmW frequency band generally includes the FR2, FR3, and FR4 frequency ranges. Thus, the terms "mmW" and "FR2" or "FR3" or "FR4" may generally be used interchangeably.

[0050]

[0061] In a multi-carrier system, such as 5G, one of the carrier frequencies is referred to as the "primary carrier" or "anchor carrier" or "primary serving cell" or "PCell," and the remaining carrier frequencies are referred to as the "secondary carrier" or "secondary serving cell" or "SCell." In carrier aggregation, the anchor carrier is a carrier operating on a primary frequency (e.g., FR1) utilized by the UE 104 / 182 and the cell in which the UE 104 / 182 either performs an initial radio resource control (RRC) connection establishment procedure or initiates an RRC connection re-establishment procedure. The primary carrier carries all common and UE-specific control channels and may be a carrier in licensed frequencies (although this is not always the case). The secondary carrier is a carrier operating on a second frequency (e.g., FR2) that may be configured once an RRC connection is established between the UE 104 and the anchor carrier and may be used to provide additional radio resources. In some cases, the secondary carrier may be a carrier in unlicensed frequencies. The secondary carrier may contain only the necessary signaling information and signals, e.g., nothing UE-specific may be present in the secondary carrier, since both the primary uplink carrier and the primary downlink carrier are typically UE-specific. This means that different UEs 104 / 182 in a cell may have different downlink primary carriers. The same is true for the uplink primary carrier. The network may change the primary carrier of any UE 104 / 182 at any time. This is done, for example, to balance the load on different carriers. Since a "serving cell" (whether a PCell or a SCell) corresponds to a carrier frequency / component carrier over which some base station is communicating, terms such as "cell", "serving cell", "component carrier", "carrier frequency", etc. may be used interchangeably.

[0051]

[0062] For example, still referring to FIG. 1, one of the frequencies utilized by the macrocell base station 102 may be an anchor carrier (or “PCell”), and the other frequencies utilized by the macrocell base station 102 and / or the mmW base station 180 may be secondary carriers (“SCells”). Simultaneous transmission and / or reception of multiple carriers allows the UE 104 / 182 to significantly increase its data transmission and / or reception rates. For example, two 20 MHz aggregated carriers in a multi-carrier system would theoretically lead to a doubling of the data rate (i.e., 40 MHz) compared to that achieved by a single 20 MHz carrier.

[0052]

[0063] In the example of FIG. 1, one or more Earth-orbiting Satellite Positioning System (SPS) Space Vehicles (SVs) 112 (e.g., satellites) may be used as independent sources of location information for any of the illustrated UEs (shown in FIG. 1 as a single UE 104 for simplicity). The UE 104 may include one or more dedicated SPS receivers specially designed to receive SPS signals 124 to derive geolocation information from the SVs 112. An SPS typically includes a system of transmitters positioned to enable a receiver (e.g., UE 104) to determine the location of the receiver on or above the Earth based at least in part on signals (e.g., SPS signals 124) received from a transmitter (e.g., SVs 112). Such transmitters typically transmit signals marked with a repetitive pseudorandom noise (PN) code of a set number of chips. Although typically located in the SVs 112, transmitters may sometimes be located on ground-based control stations, base stations 102, and / or other UEs 104.

[0053]

[0064] Use of the SPS signals 124 may be augmented by various satellite-based augmentation systems (SBAS), which may be associated with or otherwise enabled for use with one or more global and / or regional navigation satellite systems. For example, the SBAS may include augmentation system(s) that provide integrity information, differential corrections, and the like, such as the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), the Multi-functional Satellite Augmentation System (MSAS), the Global Positioning System (GPS) Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAN), and the like. Thus, an SPS as used herein may include any combination of one or more global and / or regional navigation satellite systems and / or augmentation systems, and SPS signals 124 may include SPS signals, SPS-like signals, and / or other signals related to such one or more SPSs.

[0054]

[0065] In particular, leveraging the increased data rates and reduced latency of NR, vehicle-to-everything (V2X) communication technology is being implemented to support Intelligent Transport Systems (ITS) applications, such as wireless communications between vehicles (vehicle-to-vehicle (V2V)), between vehicles and roadside infrastructure (vehicle-to-infrastructure (V2I)), and between vehicles and pedestrians (vehicle-to-pedestrian (V2P)). The goal is for vehicles to be able to sense the environment around them and communicate that information to other vehicles, infrastructure, and personal mobile devices. Such vehicular communications would enable safety, mobility, and environmental improvements that current technologies cannot provide. When fully implemented, the technology is expected to reduce unimpaired vehicle crashes by 80%.

[0055]

[0066] Still referring to FIG. 1 , the wireless communication system 100 may include multiple V-UEs 160 that may communicate with the base station 102 over the communication link 120 (e.g., using the Uu interface). The V-UEs 160 may also communicate directly with each other over wireless sidelink 162, with a roadside access point 164 (also referred to as a “roadside unit”) over wireless sidelink 166, or with the UE 104 over wireless sidelink 168. The wireless sidelink (or simply “sidelink”) is an adaptation of the core cellular (e.g., LTE, NR) standard that enables direct communication between two or more UEs without that communication having to go through a base station. Sidelink communications may be unicast or multicast and may be used for D2D media sharing, V2V communications, V2X communications (e.g., cellular V2X (cV2X) communications, enhanced V2X (eV2X) communications, etc.), emergency rescue applications, etc. One or more of the groups of V-UEs 160 utilizing sidelink communications may be within the geographic coverage area 110 of the base station 102. Other V-UEs 160 in such groups may be outside the geographic coverage area 110 of the base station 102 or may not otherwise be able to receive transmissions from the base station 102. In some cases, a group of V-UEs 160 communicating via sidelink communications may utilize a one-to-many (1:M) system in which each V-UE 160 transmits to every other V-UE 160 in the group. In some cases, the base station 102 facilitates scheduling of resources for sidelink communications. In other cases, sidelink communications occur between the V-UEs 160 without the involvement of the base station 102.

[0056]

[0067] In one aspect, the sidelinks 162, 166, 168 may operate over a wireless communications medium of interest that may be shared with other vehicular and / or infrastructure access points, as well as other wireless communications between other RATs. The "medium" may be comprised of one or more time, frequency, and / or spatial communications resources (e.g., encompassing one or more channels across one or more carriers) associated with wireless communications between one or more transmitter / receiver pairs.

[0057]

[0068] In one aspect, the sidelinks 162, 166, 168 may be cV2X links. The first generation of cV2X has been standardized in LTE, and the next generation is expected to be defined in NR. cV2X is a cellular technology that also enables device-to-device communication. In the United States and Europe, cV2X is expected to operate in licensed ITS bands in the sub-6 GHz. In other countries, other bands may be allocated. Thus, as a specific example, the medium of interest utilized by the sidelinks 162, 166, 168 may correspond to at least a portion of the sub-6 GHz licensed ITS frequency band. However, the present disclosure is not limited to this frequency band or cellular technology.

[0058]

[0069] In one aspect, the sidelinks 162, 166, 168 may be dedicated short-range communication (DSRC) links. DSRC is a unidirectional or bidirectional short- to medium-range wireless communication protocol that uses the wireless access for vehicular environments (WAVE) protocol, also known as IEEE 802.11p, for V2V, V2I, and V2P communications. IEEE 802.11p is an approved amendment to the IEEE 802.11 standard and operates in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz) in the United States. In Europe, IEEE 802.11p operates in the ITS G5A band (5.875-5.905 MHz). Other bands may be allocated in other countries. The V2V communications briefly described above occur on a safety channel, which in the United States is typically a 10 MHz channel dedicated to safety purposes. The remainder of the DSRC band (total bandwidth of 75 MHz) is intended for other services of interest to drivers, such as road regulations, toll collection, parking automation, etc. Thus, as a specific example, the medium of interest utilized by the sidelinks 162, 166, 168 may correspond to at least a portion of the 5.9 GHz licensed ITS frequency band.

[0059]

[0070] Alternatively, the medium of interest may correspond to at least a portion of an unlicensed frequency band shared among various RATs. Although different licensed frequency bands are reserved for some communication systems (e.g., by government agencies such as the Federal Communications Commission (FCC) in the United States), these systems, particularly those employing small cell access points, have recently extended their operation to unlicensed frequency bands, such as the Unlicensed National Information Infrastructure (U-NII) bands used by Wireless Local Area Network (WLAN) technologies, most notably the IEEE 802.11x WLAN technology commonly referred to as "Wi-Fi". Exemplary systems of this type include different variants of CDMA systems, TDMA systems, FDMA systems, Orthogonal FDMA (OFDMA) systems, Single Carrier FDMA (SC-FDMA) systems, and the like.

[0060]

[0071] Communications between V-UEs 160 are referred to as V2V communications, communications between V-UEs 160 and one or more roadside access points 164 are referred to as V2I communications, and communications between V-UEs 160 and one or more UEs 104 (where UEs 104 are P-UEs) are referred to as V2P communications. V2V communications between V-UEs 160 may include, for example, information regarding the position, speed, acceleration, orientation, and other vehicle data of V-UEs 160. V2I information received at V-UEs 160 from one or more roadside access points 164 may include, for example, road rules, parking automation information, etc. V2P communications between V-UEs 160 and UEs 104 may include, for example, information regarding the position, speed, acceleration, and orientation of V-UEs 160, and the position, speed (e.g., if UEs 104 are carried by a user on a bicycle), and orientation of UEs 104.

[0061]

[0072] It should be noted that while FIG. 1 illustrates only two of the UEs as V-UEs (V-UE 160), any of the illustrated UEs (e.g., UEs 104, 152, 182, 190) may be V-UEs. Additionally, while only V-UE 160 and a single UE 104 are illustrated as being connected via sidelink, any of the UEs illustrated in FIG. 1 may be capable of sidelink communication, whether V-UE or P-UE, etc. Additionally, while only UE 182 has been described as being capable of beamforming, any of the illustrated UEs, including V-UE 160, may be capable of beamforming. If V-UE 160 is capable of beamforming, they may beamform toward each other (i.e., toward other V-UEs 160), toward roadside access point 164, toward other UEs (e.g., UEs 104, 152, 182, 190), etc. Thus, in some cases, V-UE 160 may utilize beamforming over sidelinks 162, 166, and 168.

[0062]

[0073] The wireless communication system 100 may further include one or more UEs, such as UE 190, that indirectly connect to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links. In the example of FIG. 1, the UE 190 has a D2D P2P link 192 with one of the UEs 104 connected to one of the base stations 102 (e.g., through which the UE 190 may indirectly obtain cellular connectivity) and a D2D P2P link 194 with a WLAN STA 152 connected to a WLAN AP 150 (through which the UE 190 may indirectly obtain WLAN-based Internet connectivity). In an example, the D2D P2P links 192 and 194 may be supported with any well-known D2D RAT, such as LTE Direct (LTE-D), WiFi Direct® (WiFi®-D), Bluetooth®, etc. As another example, the D2D P2P links 192 and 194 may be sidelinks, such as those described above with respect to the sidelinks 162, 166, and 168.

[0063]

[0074] 2A illustrates an exemplary wireless network structure 200. For example, a 5GC 210 (also referred to as Next Generation Core (NGC)) may be considered functionally as a control plane function (C-plane) 214 (e.g., UE registration, authentication, network access, gateway selection, etc.) and a user plane function (U-plane) 212 (e.g., UE gateway function, access to data network, IP routing, etc.) that operate cooperatively to form a core network. A user plane interface (NG-U) 213 and a control plane interface (NG-C) 215 connect a gNB 222 to the 5GC 210, specifically to the user plane function 212 and the control plane function 214, respectively. In an additional configuration, a ng-eNB 224 may also be connected to the 5GC 210 via the NG-C 215 to the control plane function 214 and the NG-U 213 to the user plane function 212. Additionally, the ng-eNB 224 may communicate directly with the gNB 222 via a backhaul connection 223. In some configurations, the next generation RAN (NG-RAN) 220 may have only one or more gNBs 222, while other configurations include one or more of both the ng-eNB 224 and the gNB 222. Either the gNB 222 or the ng-eNB 224 (or both) may communicate with the UE 204 (e.g., any of the UEs described herein). In one aspect, two or more UEs 204 may communicate with each other via a wireless sidelink 242, which may correspond to the wireless sidelink 162 in FIG. 1.

[0064]

[0075] Another optional aspect may include a location server 230, which may be in communication with the 5GC 210 to provide location assistance to the UE 204. The location servers 230 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.) or, alternatively, each may correspond to a single server. The location servers 230 may be configured to support one or more location services for the UE 204 that may connect to the location server 230 via the core network, the 5GC 210, and / or via the Internet (not shown). Additionally, the location server 230 may be incorporated into a component of the core network or, alternatively, may be external to the core network.

[0065]

[0076] 2B illustrates another exemplary wireless network structure 250. The 5GC 260 (which may correspond to the 5GC 210 in FIG. 2A) may be considered functionally as a control plane function provided by an access and mobility management function (AMF) 264 and a user plane function provided by a user plane function (UPF) 262, which operate cooperatively to form a core network (i.e., the 5GC 260). A user plane interface 263 and a control plane interface 265 connect the ng-eNB 224 to the 5GC 260, specifically to the UPF 262 and the AMF 264, respectively. In an additional configuration, the gNB 222 may also be connected to the 5GC 260 via a control plane interface 265 to the AMF 264 and a user plane interface 263 to the UPF 262. Additionally, the ng-eNB 224 may communicate directly with the gNB 222 via a backhaul connection 223, with or without gNB direct connectivity to the 5GC 260. In some configurations, the NG-RAN 220 may have only one or more gNBs 222, while other configurations include one or more of both the ng-eNB 224 and the gNB 222. The base stations of the NG-RAN 220 communicate with the AMF 264 via an N2 interface and with the UPF 262 via an N3 interface. Either (or both) of the gNBs 222 or the ng-eNB 224 may communicate with a UE 204 (e.g., any of the UEs described herein). In one aspect, two or more UEs 204 may communicate with each other via a sidelink 242, which may correspond to the sidelink 162 in FIG. 1.

[0066]

[0077] The functions of the AMF 264 include registration management, connection management, reachability management, mobility management, lawful interception, transport for session management (SM) messages between the UE 204 and a session management function (SMF) 266, a transparent proxy service for routing SM messages, access authentication and access authorization, transport for short message service (SMS) messages between the UE 204 and a short message service function (SMSF) (not shown), and a security anchor function (SEAF). The AMF 264 also interacts with an authentication server function (AUSF) (not shown) and the UE 204 to receive intermediate keys established as a result of the UE 204 authentication process. In case of UMTS (Universal Mobile Telecommunications System) Subscriber Identity Module (USIM) based authentication, the AMF 264 retrieves security material from the AUSF. The functions of the AMF 264 also include security context management (SCM). The SCM receives keys from the SEAF that it uses to derive access network specific keys. The AMF 264 functions also include location service management for barred services, transport for location service messages between the UE 204 and the LMF 270 acting as the location server 230, transport for location service messages between the NG-RAN 220 and the LMF 270, Evolved Packet System (EPS) bearer identifier allocation for interworking with EPS, and UE 204 mobility event notification. Additionally, the AMF 264 also supports functions for non-3GPP access networks.

[0067]

[0078] The functions of the UPF 262 include serving as an anchor point for intra / inter-RAT mobility (when applicable), serving as an external protocol data unit (PDU) session point for interconnection to a data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, Quality of Service (QoS) handling for the user plane (e.g., uplink / downlink rate enforcement, reflective QoS marking in the downlink), uplink traffic validation (Service Data Flow (SDF) to QoS flow mapping), transport level packet marking in the uplink and downlink, downlink packet buffering and downlink data notification triggering, and sending and forwarding one or more "termination markers" to the source RAN node. The UPF 262 may also support the transfer of location service messages over the user plane between the UE 204 and a location server, such as the SLP 272.

[0068]

[0079] The functions of the SMF 266 include session management, UE Internet Protocol (IP) address allocation and management, selection and control of user plane functions, configuration of traffic steering in the UPF 262 to route traffic to the appropriate destination, control of policy enforcement and parts of QoS, and downlink data notification. The interface through which the SMF 266 communicates with the AMF 264 is called the N11 interface.

[0069]

[0080] Another optional aspect may include an LMF 270, which may be in communication with the 5GC 260 to provide location assistance to the UE 204. The LMF 270 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.) or, alternatively, each may correspond to a single server. The LMF 270 may be configured to support one or more location services for the UE 204 that may be connected to the LMF 270 via a core network, the 5GC 260, and / or via the Internet (not shown). The SLP 272 may support similar functions as the LMF 270, except that the LMF 270 may communicate with the AMF 264, the NG-RAN 220, and the UE 204 via a control plane (e.g., using interfaces and protocols intended to carry signaling messages rather than voice or data), and the SLP 272 may communicate with the UE 204 and external clients (not shown in FIG. 2B) via a user plane (e.g., using protocols intended to carry voice and / or data, such as Transmission Control Protocol (TCP) and / or IP).

[0070]

[0081] 3 illustrates an example of a wireless communication system 300 supporting wireless unicast sidelink establishment according to aspects of the present disclosure. In some examples, the wireless communication system 300 may implement aspects of the wireless communication systems 100, 200, and 250. The wireless communication system 300 may include a first UE 302 and a second UE 304, which may be examples of any of the UEs described herein. As specific examples, the UEs 302 and 304 may correspond to the V-UE 160 in FIG. 1, the UE 190 and UE 104 in FIG. 1 connected via the sidelink 192, or the UE 204 in FIG. 2A and FIG. 2B.

[0071]

[0082] In the example of FIG. 3, the UE 302 may attempt to establish a unicast connection over a sidelink with the UE 304, which may be a V2X sidelink between the UE 302 and the UE 304. As a particular example, the established sidelink connection may correspond to the sidelink 162 and / or 168 in FIG. 1 or the sidelink 242 in FIG. 2A and FIG. 2B. The sidelink connection may be established in an omnidirectional frequency range (e.g., FR1) and / or an mmW frequency range (e.g., FR2). In some cases, the UE 302 may be referred to as an initiating UE that initiates the sidelink connection procedure, and the UE 304 may be referred to as a target UE that is targeted for the sidelink connection procedure by the initiating UE.

[0072]

[0083] To establish a unicast connection, Access Stratum (AS) (a functional layer in the UMTS and LTE protocol stack between the RAN and the UE, responsible for transporting data over wireless links and managing radio resources, and is part of Layer 2) parameters may be configured and negotiated between the UE 302 and the UE 304. For example, transmit and receive capability matching may be negotiated between the UE 302 and the UE 304. Each UE may have different capabilities (e.g., transmit and receive, 64 quadrature amplitude modulation (QAM), transmit diversity, carrier aggregation (CA), supported communication frequency band(s), etc.). In some cases, different services may be supported at higher layers of the corresponding protocol stacks for the UE 302 and the UE 304. Furthermore, a security association may be established between the UE 302 and the UE 304 for the unicast connection. Unicast traffic may benefit from security protection (e.g., integrity protection) at the link level. Security requirements may differ for different wireless communication systems. For example, the V2X system and the Uu system may have different security requirements (e.g., Uu security does not include confidentiality protection). Additionally, IP configurations (e.g., IP version, addresses, etc.) may be negotiated for unicast connections between UE302 and UE304.

[0073]

[0084] In some cases, the UE 304 may create a service announcement (e.g., a service capability message) to be transmitted over a cellular network (e.g., cV2X) to assist in sidelink connection establishment. Conventionally, the UE 302 may identify and locate candidates for sidelink communication based on a broadcasted basic service message (BSM) decrypted by a nearby UE (e.g., the UE 304). The BSM may include location information, security and identification information, and vehicle information (e.g., speed, operation, size, etc.) for the corresponding UE. However, for a different wireless communication system (e.g., D2D or V2X communication), a discovery channel may not be configured such that the UE 302 can detect the BSM(s). Thus, the service announcement (e.g., discovery signal) transmitted by the UE 304 and other nearby UEs is a higher layer signal and may be broadcast (e.g., in an NR sidelink broadcast). In some cases, the UE 304 may include one or more parameters about itself in the service announcement, including connection parameters and / or capabilities it possesses. The UE 302 may then monitor and receive the broadcasted service announcements to identify potential UEs for a corresponding sidelink connection. In some cases, the UE 302 may identify potential UEs based on the capabilities that each UE indicates in their respective service announcements.

[0074]

[0085] The service announcement may include information to assist the UE 302 (e.g., or any initiating UE) to identify the UE (UE 304 in the example of FIG. 3) that sends the service announcement. For example, the service announcement may include channel information if a direct communication request may be sent. In some cases, the channel information may be RAT-specific (e.g., specific to LTE or NR) and may include a resource pool in which the UE 302 sends the communication request. Furthermore, the service announcement may include a specific destination address (e.g., Layer 2 destination address) for the UE if the destination address is different from the current address (e.g., the address of the streaming provider or the UE sending the service announcement). The service announcement may also include a network or transport layer for the UE 302 to send the communication request. For example, the network layer (also referred to as "Layer 3" or "L3") or the transport layer (also referred to as "Layer 4" or "L4") may indicate a port number of the application for the UE sending the service announcement. In some cases, IP addressing may not be required if the signaling (e.g., PC5 signaling) directly carries a protocol (e.g., Real-time Transport Protocol (RTP)) or provides a locally generated random protocol. Additionally, the service announcement may include some type of protocol for credential establishment and QoS related parameters.

[0075]

[0086] After identifying a potential sidelink connection target (UE 304 in the example of FIG. 3), the initiating UE (UE 302 in the example of FIG. 3) may send a connection request 315 to the identified target UE 304. In some cases, the connection request 315 may be a first RRC message (e.g., an "RRC Direct Connection Setup Request" message) sent by the UE 302 to request a unicast connection with the UE 304. For example, the unicast connection may utilize a PC5 interface for the sidelink and the connection request 315 may be an RRC Connection Setup Request message. Furthermore, the UE 302 may use the sidelink signaling radio bearer 305 to transport the connection request 315.

[0076]

[0087] After receiving the connection request 315, the UE 304 may determine whether to accept or reject the connection request 315. The UE 304 may base this decision on transmit / receive capabilities, an ability to accommodate a unicast connection over the sidelink, a particular service indicated for the unicast connection, content to be transmitted over the unicast connection, or a combination thereof. For example, if the UE 302 wishes to use a first RAT to transmit or receive data, but the UE 304 does not support the first RAT, the UE 304 may reject the connection request 315. Additionally or alternatively, the UE 304 may reject the connection request 315 based on an inability to accommodate a unicast connection over the sidelink due to limited radio resources, scheduling issues, etc. Thus, the UE 304 may send an indication of whether the request is accepted or rejected in the connection response 320. Similar to the UE 302 and the connection request 315, the UE 304 may use the sidelink signaling radio bearer 310 to transport the connection response 320. Further, the connection response 320 may be a second RRC message (eg, an “RRCDirectConnectionResponse” message) sent by the UE 304 in response to the connection request 315.

[0077]

[0088] In some cases, the sidelink signaling radio bearer 305 and the sidelink signaling radio bearer 310 may be the same sidelink signaling radio bearer or may be separate sidelink signaling radio bearers. Thus, a radio link control (RLC) layer acknowledged mode (AM) may be used for the sidelink signaling radio bearers 305 and 310. UEs that support unicast connections may listen on a logical channel associated with the sidelink signaling radio bearer. In some cases, the AS layer (i.e., Layer 2) may pass information directly through RRC signaling (e.g., control plane) instead of the V2X layer (e.g., data plane).

[0078]

[0089] If the connection response 320 indicates that the UE 304 accepted the connection request 315, the UE 302 may send a connection establishment 325 message on the sidelink signaling radio bearer 305 to indicate that the unicast connection setup is complete. In some cases, the connection establishment 325 may be a third RRC message (e.g., an "RRCDirectConnectionSetupComplete" message). Each of the connection request 315, the connection response 320, and the connection establishment 325 may use basic capabilities to enable each UE to be able to receive and decode the corresponding transmission (e.g., an RRC message) when being transported from one UE to the other UE.

[0079]

[0090] Additionally, an identifier may be used for each of the connection request 315, the connection response 320, and the connection establishment 325. For example, the identifier may indicate which UE 302 / 304 is sending which message and / or which UE 302 / 304 the message is intended for. In a physical (PHY) layer channel, the RRC signaling and subsequent data transmission may use the same identifier (e.g., Layer 2 ID). However, in a logical channel, the identifier may be separate for the RRC signaling and for the data transmission. For example, on a logical channel, the RRC signaling and the data transmission may be treated differently and have different acknowledgement (ACK) feedback messaging. In some cases, for the RRC messaging, a physical layer ACK may be used to ensure that the corresponding message is properly transmitted and received.

[0080]

[0091] For a unicast connection, one or more information elements may be included in the connection request 315 and / or connection response 320 for the UE 302 and / or UE 304, respectively, to enable negotiation of corresponding AS layer parameters. For example, the UE 302 and / or UE 304 may include Packet Data Convergence Protocol (PDCP) parameters in the corresponding unicast connection setup message to set up a PDCP context for the unicast connection. In some cases, the PDCP context may indicate whether PDCP duplication is utilized for the unicast connection. Furthermore, the UE 302 and / or UE 304 may include RLC parameters when establishing the unicast connection to set up an RLC context for the unicast connection. For example, the RLC context may indicate whether AM is used (e.g., t-reordering is used) or unacknowledged mode (UM) is used for the RLC layer of the unicast communication.

[0081]

[0092] Further, the UE302 and / or UE304 may include MAC parameters to set a medium access control (MAC) context for the unicast connection. In some cases, the MAC context may enable a resource selection algorithm, a hybrid automatic repeat request (HARQ) feedback scheme (e.g., ACK or negative ACK (NACK) feedback), parameters for a HARQ feedback scheme, carrier aggregation, or a combination thereof for the unicast connection. Further, the UE302 and / or UE304 may include PHY layer parameters when establishing a unicast connection to set a PHY layer context for the unicast connection. For example, the PHY layer context may indicate a transmission format (unless a transmission profile is included for each UE302 / 304) and a radio resource configuration (e.g., bandwidth portion (BWP), numerology, etc.) for the unicast connection. These information elements may be supported for different frequency range configurations (e.g., FR1 and FR2).

[0082]

[0093] In some cases, security context may also be set for the unicast connection (e.g., after the connection establishment 325 message is sent). Before a security association (e.g., security context) is established between the UE 302 and the UE 304, the sidelink signaling radio bearers 305 and 310 may not be protected. After a security association is established, the sidelink signaling radio bearers 305 and 310 may be protected. Thus, the security context may enable unicast connections as well as secure data transmission over the sidelink signaling radio bearers 305 and 310. Furthermore, IP layer parameters (e.g., link-local IPv4 or IPv6 addresses) may also be negotiated. In some cases, the IP layer parameters may be negotiated by a higher layer control protocol operating after the RRC signaling is established (e.g., the unicast connection is established). As mentioned above, the UE 304 may base its decision on whether to accept or reject the connection request 315 on the particular service(s) indicated for the unicast connection and / or content to be transmitted over the unicast connection (e.g., higher layer information). The particular service(s) and / or content may also be indicated by a higher layer control protocol operating after the RRC signaling is established.

[0083]

[0094] After the unicast connection is established, the UE 302 and the UE 304 may communicate using a unicast connection over the sidelink 330, where sidelink data 335 is transmitted between the two UEs 302 and 304. The sidelink 330 may correspond to the sidelink 162 and / or 168 in FIG. 1 and / or the sidelink 242 in FIG. 2A and FIG. 2B. In some cases, the sidelink data 335 may include RRC messages transmitted between the two UEs 302 and 304. To maintain this unicast connection over the sidelink 330, the UE 302 and / or the UE 304 may transmit keep-alive messages (e.g., “RRC Direct Link Alive” message, fourth RRC message, etc.). In some cases, the keep-alive messages may be triggered periodically or on-demand (e.g., event-triggered). Thus, the triggering and transmission of the keep-alive messages may be invoked by the UE 302 or by both the UE 302 and the UE 304. Additionally or alternatively, a MAC Control Element (CE) (e.g., defined over the sidelink 330) may be used to monitor the status of the unicast connection on the sidelink 330 and maintain that connection. When the unicast connection is no longer needed (e.g., the UE 302 travels far enough away from the UE 304), either the UE 302 and / or the UE 304 may initiate a release procedure to drop the unicast connection over the sidelink 330. Thus, subsequent RRC messages may not be transmitted between the UE 302 and the UE 304 on the unicast connection.

[0084]

[0095] FIG. 4 is a block diagram illustrating various components of an exemplary UE 400 according to aspects of the disclosure. In an aspect, the UE 400 may correspond to any of the UEs described herein. As a specific example, the UE 400 may be a V-UE, such as the V-UE 160 in FIG. 1. For simplicity, the various features and functions illustrated in the block diagram of FIG. 4 are connected to each other using a common data bus, which is meant to represent that these various features and functions are operatively coupled to each other. Those skilled in the art will recognize that other connections, mechanisms, features, functions, etc. may be provided and adapted as necessary to operatively couple and configure an actual UE. Furthermore, it should also be recognized that one or more of the features or functions illustrated in the example of FIG. 4 may be further subdivided, or two or more of the features or functions illustrated in FIG. 4 may be combined.

[0085]

[0096] The UE 400 may include at least one transceiver 404 connected to one or more antennas 402, which provides means for communicating (e.g., means for transmitting, means for receiving, means for measuring, means for tuning, means for refraining from transmitting, etc.) with other network nodes, such as a V-UE (e.g., V-UE 160), an infrastructure access point (e.g., roadside access point 164), a P-UE (e.g., UE 104), a base station (e.g., base station 102), etc., via at least one designated RAT (e.g., cV2X or IEEE 802.11p) over one or more communication links (e.g., communication link 120, sidelinks 162, 166, 168, mmW communication link 184). The transceiver 404 may be variously configured for transmitting and encoding signals (e.g., messages, instructions, information, etc.) and conversely for receiving and decoding signals (e.g., messages, instructions, information, pilots, etc.) in accordance with the designated RAT.

[0086]

[0097] A "transceiver" as used herein may in some implementations include at least one transmitter and at least one receiver in an integrated device (e.g., implemented as transmitter and receiver circuits in a single communications device), in some implementations may comprise separate transmitter and receiver devices, or in other implementations may be implemented in other ways. In one aspect, a transmitter may include or be coupled to multiple antennas, such as an antenna array (e.g., antenna(s) 402), that enable the UE 400 to perform transmit "beamforming" as described herein. Similarly, a receiver may include or be coupled to multiple antennas, such as an antenna array (e.g., antenna(s) 402), that enable the UE 400 to perform receive beamforming as described herein. In one aspect, a transmitter(s) and a receiver(s) may share the same multiple antennas (e.g., antenna(s) 402) such that the UE 400 can only receive or transmit at a given time, rather than both receive and transmit at the same time. In some cases, a transceiver may not provide both transmit and receive functionality: for example, in order to reduce cost when it is not necessary to provide full communication, some designs may employ reduced functionality receiver circuitry (e.g., a receiver chip or similar circuitry that merely provides low-level sniffing).

[0087]

[0098] The UE 400 may also include a Satellite Positioning Service (SPS) receiver 406. The SPS receiver 406 may be connected to the one or more antennas 402 and may provide a means for receiving and / or measuring satellite signals. The SPS receiver 406 may comprise any suitable hardware and / or software for receiving and processing SPS signals, such as Global Positioning System (GPS) signals. The SPS receiver 406 requests information and actions from other systems as appropriate, and performs the calculations necessary to determine the position of the UE 400 using measurements obtained by any suitable SPS algorithms.

[0088]

[0099] The one or more sensors 408 may be coupled to the processing system 410 and may provide a means for sensing or detecting information related to the state and / or environment of the UE 400, such as speed, orientation (e.g., compass heading), headlight status, gas mileage, etc. By way of example, the one or more sensors 408 may include a speedometer, a tachometer, an accelerometer (e.g., a micro-electromechanical system (MEMS) device), a gyroscope, a geomagnetic sensor (e.g., a compass), an altimeter (e.g., a barometric altimeter), etc.

[0089]

[0100] The processing system 410 may include one or more microprocessors, microcontrollers, ASICs, processing cores, digital signal processors, etc. that provide processing functions as well as other computational and control functions. Accordingly, the processing system 410 may alternatively be referred to as a processor, one or more processors, or at least one processor. The processing system 410 may thus provide means for processing, such as means for determining, means for calculating, means for receiving, means for transmitting, means for instructing, etc. The processing system 410 may include any form of logic suitable to implement or cause components of the UE 400 to implement at least the techniques described herein.

[0090]

[0101] The processing system 410 may also be coupled to a memory 414 that provides a means for storing (including a means for retrieving, a means for maintaining, etc.) data and software instructions for executing programmed functions within the UE 400. The memory 414 may be on-board the processing system 410 (e.g., in the same integrated circuit (IC) package) and / or the memory 414 may be external to the processing system 410 and operatively coupled via a data bus.

[0091]

[0102] The UE 400 may include a user interface 450 providing any suitable interface system, such as a microphone / speaker 452, a keypad 454, and a display 456, to enable user interaction with the UE 400. The microphone / speaker 452 may provide voice communication services with the UE 400. The keypad 454 may comprise any suitable buttons for user input to the UE 400. The display 456 may comprise any suitable display, such as, for example, a backlit liquid crystal display (LCD), and may further include a touchscreen display for additional user input modes. The user interface 450 may thus be a means for providing instructions (e.g., audible and / or visual instructions) to a user and / or for receiving user input (e.g., via user actuation of a sensing device, such as a keypad, touchscreen, microphone, etc.).

[0092]

[0103] In one aspect, the UE 400 may include a sidelink manager 470 coupled to the processing system 410. The sidelink manager 470 may be a hardware, software, or firmware component that, when executed, causes the UE 400 to perform the operations described herein. For example, the sidelink manager 470 may be a software module stored in the memory 414 and executable by the processing system 410. As another example, the sidelink manager 470 may be a hardware circuit (e.g., an ASIC, a field programmable gate array (FPGA), etc.) within the UE 400.

[0093]

[0104] Figures 5A and 5B show two methods for single-cell UE positioning that can be implemented when a cell includes multiple UEs engaged in SL communication. In Figures 5A and 5B, a UE transmitting an SL-PRS may be referred to as a "TxUE" and a UE receiving an SL-PRS may be referred to as an "RxUE." The methods shown in Figures 5A and 5B have the technical advantage of not requiring any uplink transmission, which can save power.

[0094]

[0105] In Figure 5A, a relay UE 500 (with a known location) participates in positioning estimation of a remote UE 502 without needing to perform any UL PRS transmission to a base station 504 (e.g., a gNB). As shown in Figure 5A, the remote UE 502 receives a DL-PRS from a BS 504 and transmits a SL-PRS to the relay UE 500. This SL-PRS transmission from the remote UE 502 can be low power because it does not need to reach the BS 504, but only the nearby relay UE 500.

[0095]

[0106] In Figure 5B, multiple relay UEs including relay UE 500 acting as a first relay UE and relay UE 506 acting as a second relay UE transmit SL-PRS signals (SL-PRS1 and SL-PRS2, respectively) to remote UE 502. In contrast to the method shown in Figure 5A, where remote UE 502 was a TxUE and relay UE 500 was a RxUE, in Figure 5B, their roles are reversed, relay UE 500 and relay UE 506 are TxUEs, and remote UE 502 is a RxUE. In this scenario, too, the SL-PRS signals transmitted by TxUEs can be low power and no UL communication is required.

[0096]

[0107] However, there are some technical challenges. For example, the accuracy of radio-based positioning can be significantly affected by non-line-of-sight (NLOS) multipath propagation, which is inevitable in some scenarios such as urban areas and typical indoor environments. Distance / range estimation (e.g., by ToA measurements) has difficulty in first path detection in NLOS multipath propagation channels. In the low SNR range, low-power first paths may not be successfully detected by the receiver. Therefore, the technical challenge is how to enhance the ability to detect the first arriving path in NLOS multipath channels under low SNR.

[0097]

[0108] 5A and 5B, communication between the TxUE and the RxUE may occur in NLOS multipath channel conditions with low SNR, and therefore, the SL-PRS transmission from the TxUE to the RxUE may benefit from techniques that improve the SNR.

[0098]

[0109] To address the above technical challenges, a number of techniques are presented herein to improve the SNR of sidelink transmissions, including SL transmissions for positioning. More specifically, a technique of time reversal (TR) precoding for sidelink-based positioning is presented herein. In TR precoding, the transmitted reference signal is pre-filtered with a time-reversal channel impulse response (CIR) between the UE and the BS. This is represented by the following equation:

[0099]

number

[0100] S is the unfiltered reference signal, S t is the prefiltered reference signal, h(-t) * is the time-reversed filter and is the time-reversed CIR between the UE and the BS. The resulting received signal is written as

[0101]

number

[0102] At the receiver, the equivalent CIR is the convolution of the time-reversed channel and the real channel, i.e.

[0103]

number

[0104] This is the autocorrelation of the channel. The calculation of the equivalent channel has the effect of compressing the channel. Thus, TR precoding compresses the multipath channel, thereby improving the SNR and in particular the accuracy of the time of arrival (ToA) estimation.

[0105]

[0110] Precoding a transmitted signal based on channel conditions assumes that the channel is reciprocal, i.e., a transmission in one direction (e.g., from BS to UE) has the same channel conditions as a transmission in the reverse direction (e.g., from UE to BS). Due to channel reciprocity, h(t) and h(-t) * It can be estimated that there is a high degree of correlation between the 1000 and 10000 MHz bands. TR precoding must reflect the channel between the transmitter and the receiver, and is therefore typically based on channel state information (CSI). However, the current specification does not consider the use of TR precoding for SL communications, much less the scenario shown in Figures 5A and 5B.

[0106]

[0111] FIG. 6 is a flowchart of an example process 600 related to TR precoding for SL-based positioning according to an aspect of the disclosure. In some aspects, one or more process blocks of FIG. 6 may be performed by a first user equipment (UE) (e.g., UE 104 of FIG. 1). In some aspects, one or more process blocks of FIG. 6 may be performed by another device or group of devices separate from or including the first user equipment (UE). Additionally or alternatively, one or more process blocks of FIG. 6 may be performed by one or more components of the device 400, such as the processing system 410, the transceiver 404, the memory 414, the user interface 450, and / or the sidelink manager 470, any or all of which may be considered as a means for performing the operations.

[0107]

[0112] As shown in FIG. 6, the process 600 may include deriving a time-reversed (TR) precoder based at least in part on an estimated channel between the first UE and the second UE (block 610). The means for performing the operations in block 610 may include the processing system 410 of the UE 400. For example, the processing system 410 of the UE 400 may estimate a channel based on a signal sent by another UE and received by the UE 400 and compute a filter that precodes the signal using a time-reversed version of the impulse response of the channel before transmitting the signal on the same channel. The estimated channel may be a SL communication channel, e.g., a channel where the spectrum is designated for DL ​​transmission and reception, and will undergo some resource allocation process, different from the unlicensed spectrum for WIFI or other technologies.

[0108]

[0113] 6, the process 600 may include sending a TR precoded sidelink (SL) positioning reference signal (PRS) to the second UE (block 620). The means for performing the operations in block 610 may include the transceiver 404 of the UE 400 and the processing system 410. For example, the processing system 410 of the UE 400 may TR precode the SL-PRS signal to be transmitted, and the transceiver 404 of the UE 400 may send the TR precoded SL-PRS to the second UE.

[0109]

[0114] Process 600 may include additional aspects, such as any single aspect or any combination of aspects described below and / or in conjunction with one or more other processes described elsewhere herein. Although Figure 6 illustrates example blocks of process 600, in some aspects process 600 may include additional, fewer, different, or differently arranged blocks than those shown in Figure 6. Additionally or alternatively, two or more of the blocks of process 600 may be performed in parallel.

[0110]

[0115] As will be explained in more detail below in FIGS. 7-9, there are many ways in which the TR precoder may be derived.

[0111]

[0116] FIG. 7 is a messaging and event diagram illustrating a process 700 related to TR precoding for SL-based positioning according to an aspect of the disclosure. FIG. 7 illustrates block 610 of FIG. 6 in more detail. As shown in FIG. 7, in some aspects, deriving a TR precoder based at least in part on an estimated channel between a first UE (TxUE 702) and a second UE (RxUE 704) (block 610) comprises the following steps: The TxUE 702 sends a wideband (WB) RS to the RxUE 704 (block 706). The RxUE 704 measures the WB RS and determines a CSI based at least in part on the WB RS (block 708). Optionally, the TxUE 702 sends a trigger message, such as an SCI message, to the RxUE 704 to request CSI information (block 709). The TxUE 702 receives CSI associated with the WB RS from the RxUE 704 (block 710). In some aspects, the CSI was sent by the RxUE 704 in response to any trigger message of block 709. Alternatively, the CSI is sent in response to receiving the WB RS in block 706. The TxUE 702 estimates a channel between the TxUE 702 and the RxUE 704 based at least in part on the CSI (block 712). The TxUE 702 derives a TR precoder based at least in part on the estimated channel between the TxUE 702 and the RxUE 704. In the example shown in FIG. 7, the TxUE 702 then transmits the TR precoded SL-PRS to the RxUE 704 (block 620). In the example shown in FIG. 7, the RxUE 704 can then perform a positioning operation, such as, for example, determining a ToA for the TR precoded SL-PRS (block 714).

[0112]

[0117] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS (e.g., a wideband reference signal transmitted by the UE rather than the BS or gNB). In some aspects, the WB RS is associated with at least one SL-PRS. Since the WB RS characterizes the sidelink channel and is used to determine the TR precoder from the channel estimates, and is aware that the channel may be time- or frequency-varying, it is useful if the WB RS and the SL-PRS are close to each other in terms of time, frequency, or both. For example, the WB RS and the SL-PRS may be considered to be close to each other in time if they are no more than a threshold duration apart. The threshold duration may be set based on channel conditions, e.g., how quickly channel characteristics change over time, UE mobility, e.g., how fast or slow the UE is moving, and other considerations. Thus, in some aspects, the WB RS and the SL-PRS may be considered to be close to each other if they are within the same slot, adjacent slots, or other predefined interval in the time domain. Similarly, the WB RS and the SL-PRS may be considered to be adjacent in frequency if they are within the same subcarrier or a threshold number of subcarriers apart. The threshold number of subcarriers may be set based on channel characteristics, UE capabilities, and other considerations. Thus, in some aspects, the WB RS and the SL-PRS may be considered to be adjacent to each other if they are within the same resource block, adjacent resource blocks, or other predefined separation in the frequency domain.

[0113]

[0118] In some aspects, the CSI comprises positioning CSI used for positioning rather than data transmission. In some aspects, the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof. In some aspects, the CSI is received from the second UE via a physical sidelink shared channel (PSSCH). In some aspects, the CSI is associated with a specific SL-PRS resource. In some aspects, the CSI is associated with a channel sounding RS for CSI-RS feedback. In some aspects, the CSI is received aperiodically. In some aspects, the CSI is received in response to a trigger message sent from the first UE to the second UE. In some aspects, the trigger message comprises a sidelink control information (SCI) message.

[0114]

[0119] FIG. 8 is a messaging and event diagram illustrating a process 800 related to TR precoding for SL-based positioning according to an aspect of the disclosure. FIG. 8 illustrates block 610 of FIG. 6 in more detail. As shown in FIG. 8, in some aspects, deriving a TR precoder based at least in part on an estimated channel between a first UE (TxUE 702) and a second UE (RxUE 704) (block 610) comprises the following steps: The TxUE 702 sends a wideband (WB) RS to the RxUE 704 (block 802). The RxUE 704 measures the WB RS and determines a CSI based at least in part on the WB RS (block 804). The RxUE 704 derives a TR precoder, for example, at least in part on the CSI (block 806). The TxUE 702 receives a TR precoder from the RxUE 704 (block 808). In the example shown in Figure 8, the TxUE 702 transmits the TR-precoded SL-PRS to the RxUE 704 (block 620). Although not shown in Figure 8, the RxUE 704 may then perform a positioning operation, such as determining the ToA of the TR-precoded SL-PRS.

[0115]

[0120] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS. In some aspects, the WB RS is associated with at least one SL-PRS. In some aspects, the WB RS is within a threshold distance of the TR-precoded SL-PRS in the time domain, the frequency domain, or both.

[0116]

[0121] FIG. 9 is a messaging and event diagram illustrating a process 900 related to TR precoding for SL-based positioning according to an aspect of the disclosure. FIG. 9 illustrates block 610 of FIG. 6 in more detail. As shown in FIG. 9, in some aspects, deriving a TR precoder based at least in part on an estimated channel between a first UE (TxUE 702) and a second UE (RxUE 704) (block 610) comprises the following steps: The TxUE 702 can optionally send a trigger message to the RxUE 704 that triggers the RxUE 704 to generate a WB RS toward the TxUE 702 (block 902). In some aspects, the trigger may be a sidelink control information (SCI) message. As shown in FIG. 9, the RxUE 704 sends a WB RS to the TxUE 702 (block 904). The TxUE 702 may then estimate a channel from the RxUE 704 to the TxUE 702, e.g., by measuring the WB RS and determining the CSI (block 906). In some aspects, the TxUE 702 may then derive a TR precoder, e.g., based on the estimated channel between the RxUE 704 and the TxUE 702 (block 908). In the example shown in FIG. 9, the TxUE 702 transmits the TR precoded SL-PRS to the RxUE 704 (block 620). Although not shown in FIG. 9, the RxUE 704 may then perform a positioning operation, e.g., determining the ToA of the TR precoded SL-PRS.

[0117]

[0122] In some aspects, the WB RS is received in response to a trigger message sent from the first UE to the second UE. In some aspects, the trigger message comprises a Sidelink Control Information (SCI) message. In some aspects, the WB RS comprises a Sidelink Positioning Reference Signal (SL-PRS), a Channel Sounding RS, or a WB Beacon RS. In some aspects, the WB RS is associated with at least one SL-PRS.

[0118]

[0123] FIG. 10 is a flowchart of an example process 1000 related to TR precoding for SL-based positioning according to an aspect of the disclosure. In some aspects, one or more process blocks of FIG. 6 may be performed by a first user equipment (UE) (e.g., UE 104 of FIG. 1). In some aspects, one or more process blocks of FIG. 6 may be performed by another device or group of devices separate from or including the first user equipment (UE). Additionally or alternatively, one or more process blocks of FIG. 6 may be performed by one or more components of device 400, such as processing system 410, transceiver 404, memory 414, user interface 450, and / or sidelink manager 470, any or all of which may be considered as a means for performing the operations.

[0119]

[0124] As shown in FIG. 10, the process 1000 may include receiving a wideband reference signal (WB RS) from a second UE (block 1010). Means for performing the operations in block 1010 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the UE 400 may receive the WB RS via the transceiver 404 as described above. In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS. In some aspects, the WB RS is proximate in time, frequency, or both to the TR precoded SL-PRS. In some aspects, the WB RS is associated with at least one other SL-PRS.

[0120]

[0125] 10, the process 1000 may include determining channel state information (CSI) based at least in part on the WB RS (block 1020). Means for performing operations at block 1020 may include the processing system 410 of the UE 400 and the sidelink manager 470. For example, the processing system 410 of the UE 400 may determine the channel state information (CSI) based at least in part on the WB RS, as described above.

[0121]

[0126] As further shown in FIG. 10, the process 1000 may include sending the CSI to the second UE (block 1030). Means for performing operations at block 1030 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the processing system 410 of the UE 400 may instruct the transceiver 404 to send the CSI to the second UE as described above. In some aspects, the CSI comprises a positioning CSI used for positioning rather than data transmission. In some aspects, the CSI comprises a full or partial channel impulse response (CIR), a full or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof. In some aspects, the CSI is sent to the second UE via a physical sidelink shared channel (PSSCH). In some aspects, the CSI is associated with a particular SL-PRS resource. In some aspects, the CSI is associated with a channel sounding RS for CSI-RS feedback. In some aspects, the CSI is sent aperiodically. In some aspects, the CSI is sent in response to receiving a trigger message from the second UE. In some aspects, receiving the trigger message comprises receiving a sidelink control information (SCI) message.

[0122]

[0127] 10, the process 1000 may optionally include receiving a TR-precoded SL-PRS from the second UE (block 1040). Means for performing operations at block 1040 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the UE 400 may receive the TR-precoded SL-PRS via the transceiver 404.

[0123]

[0128] 10, the process 1000 may optionally include performing a positioning operation using the TR-precoded SL-PRS (block 1050). Means for performing an operation at block 1050 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the UE 400 may calculate its location using information collected from the TR-precoded SL-PRS.

[0124]

[0129] Process 1000 may include additional aspects, such as any single aspect or any combination of aspects described below and / or in conjunction with one or more other processes described elsewhere herein. Although Figure 10 illustrates example blocks of process 1000, in some aspects process 1000 may include additional, fewer, different, or differently arranged blocks than those illustrated in Figure 10. Additionally or alternatively, two or more of the blocks of process 1000 may be performed in parallel.

[0125]

[0130] FIG. 11 is a flowchart of an example process 1100 related to TR precoding for SL-based positioning according to an aspect of the disclosure. In some aspects, one or more process blocks of FIG. 6 may be performed by a first user equipment (UE) (e.g., UE 104 of FIG. 1). In some aspects, one or more process blocks of FIG. 6 may be performed by another device or group of devices separate from or including the first user equipment (UE). Additionally or alternatively, one or more process blocks of FIG. 6 may be performed by one or more components of the device 400, such as the processing system 410, the transceiver 404, the memory 414, the user interface 450, and / or the sidelink manager 470, any or all of which may be considered as a means for performing the operations.

[0126]

[0131] 11, the process 1100 may include receiving a wideband (WB) reference signal (RS) from the second UE (block 1110). The means for performing the operations in block 1110 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the UE 400 may receive the WB RS via the transceiver 404 as described above. In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0127]

[0132] 11, the process 1100 may include estimating a channel between the second UE and the first UE based at least in part on the WB RS (block 1120). The means for performing the operations at block 1120 may include the processing system 410 of the UE 400. For example, the UE 400 may estimate a channel between itself and the second UE based at least in part on the WB RS using the processing system 410, as described above.

[0128]

[0133] 11, the process 1100 may include deriving a time-reversal (TR) precoder based on the estimated channel (block 1130). Means for performing operations at block 1130 may include the processing system 410 of the UE 400. For example, the UE 400 may use the processing system 410 to derive the time-reversal (TR) precoder based on the estimated channel, as described above.

[0129]

[0134] 11, the process 1100 may include sending the TR precoder to the second UE (block 1140). The means for performing the operations at block 1140 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the processing system 410 of the UE 400 may instruct the transceiver 404 to send the TR precoder to the second UE, as described above.

[0130]

[0135] As further shown in FIG. 11, the process 1100 may optionally include receiving a TR-precoded SL-PRS from the second UE (block 1150). Means for performing the operations in block 1140 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the UE 400 may receive the TR-precoded SL-PRS via the transceiver 404 as described above. In some aspects, the WB RS is proximate to the TR-precoded SL-PRS in time, frequency, or both. In some aspects, the WB RS is associated with at least one other SL-PRS.

[0131]

[0136] 11, the process 1100 may optionally include performing a positioning system using the TR-precoded SL-PRS (block 1160). The means for performing the operations in block 1140 may include the processing system 410 of the UE 400. For example, the UE 400 may calculate its location using information collected from the TR-precoded SL-PRS.

[0132]

[0137] Process 1100 may include additional aspects, such as any single aspect or any combination of aspects described below and / or in conjunction with one or more other processes described elsewhere herein. Although Figure 11 shows example blocks of process 1100, in some aspects process 1100 may include additional, fewer, different, or differently arranged blocks than those shown in Figure 11. Additionally or alternatively, two or more of the blocks of process 1100 may be performed in parallel.

[0133]

[0138] FIG. 12 is a flow chart of an example process 1200 related to TR precoding for SL-based positioning according to an aspect of the disclosure. In some aspects, one or more process blocks of FIG. 6 may be performed by a first user equipment (UE) (e.g., UE 104 of FIG. 1). In some aspects, one or more process blocks of FIG. 6 may be performed by another device or group of devices separate from or including the first user equipment (UE). Additionally or alternatively, one or more process blocks of FIG. 6 may be performed by one or more components of the device 400, such as the processing system 410, the transceiver 404, the memory 414, the user interface 450, and / or the sidelink manager 470, any or all of which may be considered as a means for performing the operations.

[0134]

[0139] As shown in FIG. 12, the process 1200 may include sending a wideband reference signal (WB RS) to the second UE (block 1210) and receiving a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE (block 1220). Means for performing the operations in blocks 1210 and 1220 may include the transceiver 404 and the processing system 410 of the UE 400. For example, the processing system 410 may instruct the transceiver 404 to send the WB RS to the second UE, and the transceiver 404 may receive the TR precoded SL-PRS as described above. In some aspects, the WB RS is sent in response to receiving a trigger message from the second UE. In some aspects, receiving the trigger message comprises receiving a sidelink control information (SCI) message. In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS. In some aspects, the WB RS is adjacent in time, frequency, or both to a TR-precoded SL-PRS. In some aspects, the WB RS is associated with at least one other SL-PRS.

[0135]

[0140] 12, the process 1200 may optionally include performing a positioning operation using the TR-precoded SL-PRS (block 1230). Means for performing the operation at block 1230 may include the processing system 410 of the UE 400. For example, the UE 400 may calculate its location using information collected from the TR-precoded SL-PRS.

[0136]

[0141] Process 1200 may include additional aspects, such as any single aspect or any combination of aspects described below and / or in conjunction with one or more other processes described elsewhere herein. Although Figure 12 shows example blocks of process 1200, in some aspects process 1200 may include additional, fewer, different, or differently arranged blocks than those shown in Figure 12. Additionally or alternatively, two or more of the blocks of process 1200 may be performed in parallel.

[0137]

[0142] Additional aspects include, but are not limited to, the following.

[0138]

[0143] In one aspect, the first UE comprises means for deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE, and means for sending a TR precoded SL-PRS to the second UE.

[0139]

[0144] In another aspect, the first UE comprises means for receiving a WB RS from the second UE, means for determining a CSI based at least in part on the WB RS, and means for sending the CSI to the second UE.

[0140]

[0145] In another aspect, the first UE comprises means for receiving a WB RS from the second UE, means for estimating a channel between the second UE and the first UE based at least in part on the WB RS, means for deriving a TR precoder based on the estimated channel, and means for sending the TR precoder to the second UE.

[0141]

[0146] In another aspect, the first UE comprises means for sending a WB RS to the second UE and means for receiving a TR precoded SL-PRS from the second UE.

[0142]

[0147] In another aspect, a non-transitory computer-readable medium stores a set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to derive a TR precoder based at least in part on an estimated channel between the first UE and a second UE and to send a TR precoded SL-PRS to the second UE.

[0143]

[0148] In another aspect, a non-transitory computer-readable medium stores a set of instructions comprising one or more instructions that, when executed by one or more processors of a first user UE, cause the first UE to receive a WB RS from a second UE, determine a CSI based at least in part on the WB RS, and send the CSI to the second UE.

[0144]

[0149] In another aspect, a non-transitory computer-readable medium stores a set of instructions comprising one or more instructions that, when executed by one or more processors of a first user UE, cause the first UE to receive a WB RS from a second UE, estimate a channel between the second UE and the first UE based at least in part on the WB RS, derive a TR precoder based on the estimated channel, and send the TR precoder to the second UE.

[0145]

[0150] In another aspect, a non-transitory computer-readable medium stores a set of instructions comprising one or more instructions that, when executed by one or more processors of a first UE, cause the first UE to send a WB RS to a second UE and receive a TR precoded SL-PRS from the second UE.

[0146]

[0151] In the above detailed description, it can be seen that different features are grouped together in examples. This mode of disclosure should not be understood as an intention that the exemplary clauses have more features than those explicitly stated in each clause. Rather, various aspects of the present disclosure may include fewer than all features of each exemplary clause disclosed. Thus, the following clauses should be considered to be incorporated herein, and each clause can exist as a separate example by itself. Although each dependent clause may refer to a specific combination with one of the other clauses in the clause, the aspect(s) of that dependent clause are not limited to a specific combination. It will be appreciated that other exemplary clauses may also include combinations of the dependent clause aspect(s) with any other dependent clause or independent clause subject matter, or combinations of any features with other dependent and independent clauses. Various aspects disclosed herein expressly include certain combinations (e.g., inconsistent aspects, such as defining an element as both an insulator and a conductor) unless these combinations are expressly expressed or can be easily inferred to be not intended. Moreover, it is also contemplated that aspects of a clause may be included in any other independent clause, even if that clause is not directly dependent on that independent clause.

[0147]

[0152] Example aspects are described in the following numbered clauses:

[0148]

[0153] Clause 1. A method of wireless communication performed by a first user equipment (UE), comprising: deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE; and sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0149]

[0154] Clause 2. The method of clause 1, wherein deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and the second UE comprises deriving the TR precoder based at least in part on transmissions or receptions on a sidelink (SL) communication channel between the first UE and the second UE.

[0150]

[0155] Clause 3. The method of any one of clauses 1 to 2, wherein deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises sending a wideband reference signal (WB RS) to the second UE, receiving channel state information (CSI) associated with the WB RS from the second UE, estimating a channel between the first UE and the second UE based at least in part on the CSI, and deriving a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0151]

[0156] Clause 4. The method of clause 3, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0152]

[0157] Clause 5. The method of any one of clauses 3 to 4, wherein the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0153]

[0158] Clause 6. The method of any of clauses 3 to 5, wherein the WB RS is associated with at least one other SL-PRS.

[0154]

[0159] Clause 7. The method of any of clauses 3 to 6, wherein the CSI comprises positioning CSI that is used for positioning rather than data transmission.

[0155]

[0160] Clause 8. Any of the methods of clauses 3 to 7, wherein the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0156]

[0161] Clause 9. The method of any of clauses 3 to 8, wherein the CSI is received from the second UE via a physical sidelink shared channel (PSSCH).

[0157]

[0162] Clause 10. The method of any of clauses 3 to 9, wherein the CSI is associated with a particular SL-PRS resource.

[0158]

[0163] Clause 11. The method of any of clauses 3 to 10, wherein the CSI is associated with a channel sounding RS for CSI-RS feedback.

[0159]

[0164] Clause 12. The method of any one of clauses 3 to 11, wherein the CSI is received aperiodically.

[0160]

[0165] Clause 13. The method of clause 12, wherein the CSI is received in response to sending a trigger message to the second UE.

[0161]

[0166] Clause 14. The method of clause 13, wherein sending the trigger message comprises sending a sidelink control information (SCI) message.

[0162]

[0167] Clause 15. The method of any of clauses 1 to 14, wherein deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises sending a wideband reference signal (WB RS) to the second UE and receiving the TR precoder from the second UE.

[0163]

[0168] Clause 16. The method of clause 15, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0164]

[0169] Clause 17. The method of any of clauses 15 to 16, wherein the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0165]

[0170] Clause 18. The method of any of clauses 15 to 17, wherein the WB RS is associated with at least one other SL-PRS.

[0166]

[0171] Clause 19. The method of any of clauses 1 to 18, wherein deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises receiving a wideband reference signal (WB RS) from the second UE, estimating a channel between the first UE and the second UE based at least in part on the WB RS, and deriving a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0167]

[0172] Clause 20. The method of clause 19, wherein the WB RS is received in response to sending a trigger message from the first UE to the second UE.

[0168]

[0173] Clause 21. The method of clause 20, wherein sending the trigger message comprises sending a sidelink control information (SCI) message.

[0169]

[0174] Clause 22. The method of any of clauses 19 to 21, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0170]

[0175] Clause 23. The method of any one of clauses 19 to 22, wherein the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0171]

[0176] Clause 24. The method of any of clauses 19 to 23, wherein the WB RS is associated with at least one other SL-PRS.

[0172]

[0177] Clause 25. A method of wireless communication performed by a first user equipment (UE), the method comprising: receiving a wideband reference signal (WB RS) from a second UE; determining channel state information (CSI) based at least in part on the WB RS; and sending the CSI to the second UE.

[0173]

[0178] Clause 26. The method of clause 25, further comprising receiving a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0174]

[0179] Clause 27. The method of clause 26, further comprising performing a positioning operation using the TR precoded SL-PRS.

[0175]

[0180] Clause 28. The method of any of clauses 25 to 27, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0176]

[0181] Clause 29. The method of any one of clauses 25 to 28, wherein the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0177]

[0182] Clause 30. The method of any of clauses 25 to 29, wherein the WB RS is associated with at least one other SL-PRS.

[0178]

[0183] Clause 31. The method of any of clauses 25 to 30, wherein the CSI comprises positioning CSI that is used for positioning rather than data transmission.

[0179]

[0184] Clause 32. The method of any of clauses 25 to 31, wherein the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0180]

[0185] Clause 33. The method of any of clauses 25 to 32, wherein the CSI is sent to the second UE via a physical sidelink shared channel (PSSCH).

[0181]

[0186] Clause 34. The method of any of clauses 25 to 33, wherein the CSI is associated with a particular SL-PRS resource.

[0182]

[0187] Clause 35. The method of any of clauses 25 to 34, wherein the CSI is associated with a channel sounding RS for CSI-RS feedback.

[0183]

[0188] Clause 36. The method of any one of clauses 25 to 35, wherein the CSI is sent aperiodically.

[0184]

[0189] Clause 37. The method of clause 36, wherein the CSI is sent in response to receiving a trigger message from the second UE.

[0185]

[0190] Clause 38. The method of clause 37, wherein receiving the trigger message comprises receiving a sidelink control information (SCI) message.

[0186]

[0191] Clause 39. A method of wireless communication performed by a first user equipment (UE), the method comprising: receiving a wideband (WB) reference signal (RS) from a second UE; estimating a channel between the second UE and the first UE based at least in part on the WB RS; deriving a time-reversal (TR) precoder based on the estimated channel; and sending the TR precoder to the second UE.

[0187]

[0192] Clause 40. The method of clause 39, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0188]

[0193] Clause 41. The method of any of clauses 39 to 40, further comprising receiving a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0189]

[0194] Clause 42. The method of clause 41, further comprising performing a positioning operation using the TR precoded SL-PRS.

[0190]

[0195] Clause 43. The method of any of clauses 41 to 42, wherein the WB RS is adjacent to the TR precoded SL-PRS in terms of time, frequency, or both.

[0191]

[0196] Clause 44. The method of any of clauses 41 to 43, wherein the WB RS is associated with at least one other SL-PRS.

[0192]

[0197] Clause 45. A method of wireless communication performed by a first user equipment (UE), the method comprising: sending a wideband reference signal (WB RS) to a second UE; and receiving a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0193]

[0198] Clause 46. The method of clause 45, further comprising performing a positioning operation using the TR precoded SL-PRS.

[0194]

[0199] Clause 47. The method of any of clauses 45 to 46, wherein the WB RS is sent in response to receiving a trigger message from the second UE.

[0195]

[0200] Clause 48. The method of clause 47, wherein receiving the trigger message comprises receiving a sidelink control information (SCI) message.

[0196]

[0201] Clause 49. The method of any of clauses 45 to 48, wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0197]

[0202] Clause 50. The method of any of clauses 45 to 49, wherein the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0198]

[0203] Clause 51. The method of any of clauses 45 to 50, wherein the WB RS is associated with at least one other SL-PRS.

[0199]

[0204] Clause 52. An apparatus comprising a memory and at least one processor communicatively coupled to the memory, wherein the memory and the at least one processor are adapted to perform any of the functions of clauses 1 to 51. 2. An apparatus configured to carry out any of the methods described above.

[0200]

[0205] Clause 53. Apparatus comprising means for carrying out the method according to any of clauses 1 to 51.

[0201]

[0206] Clause 54. A non-transitory computer readable medium storing computer executable instructions, the computer executable comprising at least one instruction for causing a computer or processor to perform a method according to any one of clauses 1 to 51.

[0202]

[0207] Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0203]

[0208] Moreover, those skilled in the art will appreciate that the various exemplary logic blocks, modules, circuits, and algorithm steps described with respect to the aspects disclosed herein may be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, the various exemplary components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in various ways for each particular application, but such aspect decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0204]

[0209] The various example logic blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed using a general purpose processor, a DSP, an ASIC, 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 alternatively, the processor may be any conventional 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.

[0205]

[0210] The methods, sequences and / or algorithms described in connection with the aspects disclosed herein may be implemented directly in hardware, in software modules executed by a processor, or in a combination of the two. The software modules may reside in a random access memory (RAM), a flash memory, a read only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal (e.g., UE). Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

[0206]

[0211] In one or more exemplary aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and computer communication media, including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0207]

[0212] In one aspect, a method of wireless communication performed by a first user equipment (UE) includes deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE, and sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0208]

[0213] In some aspects, deriving the TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises deriving the TR precoder based at least in part on transmissions or receptions on a sidelink (SL) communications channel between the first UE and the second UE.

[0209]

[0214] In some aspects, deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises sending a wideband reference signal (WB RS) to the second UE; receiving channel state information (CSI) associated with the WB RS from the second UE; estimating a channel between the first UE and the second UE based at least in part on the CSI; and deriving a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0210]

[0215] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

[0211]

[0216] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0212]

[0217] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0213]

[0218] In some aspects, the CSI comprises positioning CSI, which is used for positioning rather than data transmission.

[0214]

[0219] In some aspects, the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0215]

[0220] In some aspects, the CSI is received from the second UE via a physical sidelink shared channel (PSSCH).

[0216]

[0221] In some aspects, the CSI is associated with a particular SL-PRS resource.

[0217]

[0222] In some aspects, the CSI is associated with a channel sounding reference signal (RS) for CSI-RS feedback.

[0218]

[0223] In some aspects, the CSI is received aperiodically.

[0219]

[0224] In some aspects, the CSI is received in response to sending a trigger message to the second UE.

[0220]

[0225] In some aspects, sending the trigger message comprises sending a sidelink control information (SCI) message.

[0221]

[0226] In some aspects, deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE comprises sending a wideband reference signal (WB RS) to the second UE and receiving the TR precoder from the second UE.

[0222]

[0227] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

[0223]

[0228] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0224]

[0229] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0225]

[0230] In some aspects, deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE comprises receiving a wideband reference signal (WB RS) from the second UE, estimating a channel between the first UE and the second UE based at least in part on the WB RS, and deriving a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0226]

[0231] In some aspects, the WB RS is received in response to sending a trigger message from the first UE to the second UE.

[0227]

[0232] In some aspects, sending the trigger message comprises sending a sidelink control information (SCI) message.

[0228]

[0233] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

[0229]

[0234] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0230]

[0235] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0231]

[0236] In one aspect, a method of wireless communication performed by a first user equipment (UE) includes receiving a wideband reference signal (WB RS) from a second UE, determining channel state information (CSI) based at least in part on the WB RS, and sending the CSI to the second UE.

[0232]

[0237] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0233]

[0238] In some aspects, the method includes receiving a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0234]

[0239] In some aspects, the method includes performing a positioning operation using a TR precoded SL-PRS.

[0235]

[0240] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0236]

[0241] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0237]

[0242] In some aspects, the CSI comprises positioning CSI, which is used for positioning rather than data transmission.

[0238]

[0243] In some aspects, the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0239]

[0244] In some aspects, the CSI is sent to the second UE via a physical sidelink shared channel (PSSCH).

[0240]

[0245] In some aspects, the CSI is associated with a particular SL-PRS resource.

[0241]

[0246] In some aspects, the CSI is associated with a channel sounding reference signal (RS) for CSI-RS feedback.

[0242]

[0247] In some aspects, the CSI is sent aperiodically.

[0243]

[0248] In some aspects, the CSI is sent in response to receiving a trigger message from the second UE.

[0244]

[0249] In some aspects, receiving the trigger message comprises receiving a sidelink control information (SCI) message.

[0245]

[0250] In one aspect, a method of wireless communication performed by a first user equipment (UE) includes receiving a wideband (WB) reference signal (RS) from a second UE, estimating a channel between the second UE and a first UE based at least in part on the WB RS, deriving a time-reversal (TR) precoder based on the estimated channel, and sending the TR precoder to the second UE.

[0246]

[0251] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

[0247]

[0252] In some aspects, the method includes receiving a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0248]

[0253] In some aspects, the method includes performing a positioning operation using a TR precoded SL-PRS.

[0249]

[0254] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0250]

[0255] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0251]

[0256] In one aspect, a method of wireless communication performed by a first user equipment (UE) includes sending a wideband reference signal (WB RS) to a second UE and receiving a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0252]

[0257] In some aspects, the WB RS is sent in response to receiving a trigger message from the second UE.

[0253]

[0258] In some aspects, receiving the trigger message comprises receiving a sidelink control information (SCI) message.

[0254]

[0259] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0255]

[0260] In some aspects, the method includes performing a positioning operation using a TR precoded SL-PRS.

[0256]

[0261] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0257]

[0262] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0258]

[0263] In one aspect, a first user equipment (UE) includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, where the at least one processor is configured to derive a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE, and send a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0259]

[0264] In some aspects, the at least one processor is configured to derive the TR precoder based at least in part on an estimated channel between the first UE and the second UE to derive the TR precoder based at least in part on transmission or reception over a sidelink (SL) communication channel between the first UE and the second UE.

[0260]

[0265] In some aspects, the at least one processor is configured, when deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE, to send a wideband reference signal (WB RS) to the second UE, receive channel state information (CSI) associated with the WB RS from the second UE, estimate a channel between the first UE and the second UE based at least in part on the CSI, and derive a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0261]

[0266] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0262]

[0267] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0263]

[0268] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0264]

[0269] In some aspects, the CSI comprises positioning CSI, which is used for positioning rather than data transmission.

[0265]

[0270] In some aspects, the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0266]

[0271] In some aspects, the CSI is received from the second UE via a physical sidelink shared channel (PSSCH).

[0267]

[0272] In some aspects, the CSI is associated with a particular SL-PRS resource.

[0268]

[0273] In some aspects, the CSI is associated with a channel sounding RS for CSI-RS feedback.

[0269]

[0274] In some aspects, the CSI is received aperiodically.

[0270]

[0275] In some aspects, the CSI is received in response to sending a trigger message to the second UE.

[0271]

[0276] In some aspects, the at least one processor is configured to send a sidelink control information (SCI) message when sending the trigger message.

[0272]

[0277] In some aspects, the at least one processor is configured to send a wideband reference signal (WB RS) to the second UE and receive the TR precoder from the second UE when deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0273]

[0278] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0274]

[0279] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0275]

[0280] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0276]

[0281] In some aspects, the at least one processor, when deriving a TR precoder based at least in part on an estimated channel between the first UE and the second UE, is configured to receive a wideband reference signal (WB RS) from the second UE, estimate a channel between the first UE and the second UE based at least in part on the WB RS, and derive a TR precoder based at least in part on the estimated channel between the first UE and the second UE.

[0277]

[0282] In some aspects, the WB RS is received in response to sending a trigger message from the first UE to the second UE.

[0278]

[0283] In some aspects, the at least one processor is configured to send a sidelink control information (SCI) message when sending the trigger message.

[0279]

[0284] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0280]

[0285] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0281]

[0286] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0282]

[0287] In one aspect, a first user equipment (UE) includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, where the at least one processor is configured to receive a wideband reference signal (WB RS) from a second UE, determine channel state information (CSI) based at least in part on the WB RS, and send the CSI to the second UE.

[0283]

[0288] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0284]

[0289] In some aspects, the at least one processor is further configured to receive a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0285]

[0290] In some aspects, the at least one processor is further configured to perform a positioning operation using the TR precoded SL-PRS.

[0286]

[0291] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0287]

[0292] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0288]

[0293] In some aspects, the CSI comprises positioning CSI, which is used for positioning rather than data transmission.

[0289]

[0294] In some aspects, the CSI comprises a complete or partial channel impulse response (CIR), a complete or partial channel frequency response (CFR), a power delay profile, Doppler information, or a combination thereof.

[0290]

[0295] In some aspects, the CSI is sent to the second UE via a physical sidelink shared channel (PSSCH).

[0291]

[0296] In some aspects, the CSI is associated with a particular SL-PRS resource.

[0292]

[0297] In some aspects, the CSI is associated with a channel sounding RS for CSI-RS feedback.

[0293]

[0298] In some aspects, the CSI is sent aperiodically.

[0294]

[0299] In some aspects, the CSI is sent in response to receiving a trigger message from the second UE.

[0295]

[0300] In some aspects, the at least one processor is configured to receive a sidelink control information (SCI) message upon receiving the trigger message.

[0296]

[0301] In one aspect, a first user equipment (UE) includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, where the at least one processor is configured to receive a wideband (WB) reference signal (RS) from a second UE, estimate a channel between the second UE and the first UE based at least in part on the WB RS, derive a time-reversal (TR) precoder based on the estimated channel, and send the TR precoder to the second UE.

[0297]

[0302] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0298]

[0303] In some aspects, the at least one processor is further configured to receive a TR precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0299]

[0304] In some aspects, the at least one processor is further configured to perform a positioning operation using the TR precoded SL-PRS.

[0300]

[0305] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0301]

[0306] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0302]

[0307] In one aspect, a first user equipment (UE) includes a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, where the at least one processor is configured to send a wideband reference signal (WB RS) to a second UE and receive a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0303]

[0308] In some aspects, the WB RS is sent in response to receiving a trigger message from the second UE.

[0304]

[0309] In some aspects, the trigger message comprises a sidelink control information (SCI) message.

[0305]

[0310] In some aspects, the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding RS, or a WB beacon RS.

[0306]

[0311] In some aspects, the at least one processor is further configured to perform a positioning operation using the TR precoded SL-PRS.

[0307]

[0312] In some aspects, the WB RS is adjacent in time, frequency, or both to the TR precoded SL-PRS.

[0308]

[0313] In some aspects, the WB RS is associated with at least one other SL-PRS.

[0309]

[0314] In one aspect, a first user equipment (UE) includes means for deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE, and means for sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0310]

[0315] In one aspect, a first user equipment (UE) includes means for receiving a wideband reference signal (WB RS) from a second UE, means for determining channel state information (CSI) based at least in part on the WB RS, and means for sending the CSI to the second UE.

[0311]

[0316] In one aspect, a first user equipment (UE) includes means for receiving a wideband (WB) reference signal (RS) from a second UE, means for estimating a channel between the second UE and the first UE based at least in part on the WB RS, means for deriving a time-reversal (TR) precoder based on the estimated channel, and means for sending the TR precoder to the second UE.

[0312]

[0317] In one aspect, a first user equipment (UE) includes means for sending a wideband reference signal (WB RS) to a second UE and means for receiving a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0313]

[0318] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment (UE), cause the UE to derive a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE, and send a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE.

[0314]

[0319] In one aspect, a non-transitory computer-readable medium storing a set of instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment (UE), cause the UE to receive a wideband reference signal (WB RS) from a second UE, determine channel state information (CSI) based at least in part on the WB RS, and send the CSI to the second UE.

[0315]

[0320] In one aspect, a non-transitory computer-readable medium storing a set of instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment (UE), cause the UE to receive a wideband (WB) reference signal (RS) from a second UE, estimate a channel between the second UE and the first UE based at least in part on the WB RS, derive a time-reversal (TR) precoder based on the estimated channel, and send the TR precoder to the second UE.

[0316]

[0321] In one aspect, a non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment (UE), cause the UE to send a wideband reference signal (WB RS) to a second UE and receive a time-reversed (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE.

[0317]

[0322] Although the above disclosure illustrates exemplary aspects of the present disclosure, it should be noted that various changes and modifications may be made herein without departing from the scope of the present disclosure as defined by the appended claims. The functions, steps and / or actions of the method claims according to the aspects of the present disclosure described herein need not be performed in any particular order. Furthermore, although elements of the present disclosure may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

Claims

1. 1. A method of wireless communication performed by a first user equipment (UE), comprising: deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE; sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE; A method comprising:

2. 2. The method of claim 1, wherein deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE comprises deriving the TR precoder based at least in part on transmission or reception on a sidelink (SL) communication channel between the first UE and the second UE.

3. Deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE includes sending a wideband reference signal (WB RS) to the second UE; receiving the TR precoder from the second UE; or receiving, from the second UE, channel state information (CSI) associated with the WB RS; estimating a channel between the first UE and the second UE based at least in part on the CSI; and deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE; The method of claim 1 , comprising:

4. The method of claim 3 , wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

5. 1. A method of wireless communication performed by a first user equipment (UE), the method comprising: receiving a wideband reference signal (WB RS) from a second UE; determining channel state information (CSI) based at least in part on the WB RS; sending the CSI to the second UE; A method comprising:

6. 1. A method of wireless communication performed by a first user equipment (UE), comprising: receiving a wideband (WB) reference signal (RS) from a second UE; estimating a channel between the second UE and the first UE based at least in part on the WB RS; deriving a time-reversal (TR) precoder based on the estimated channel; and sending the TR precoder to the second UE; A method comprising:

7. 1. A method of wireless communication performed by a first user equipment (UE), the method comprising: sending a wideband reference signal (WB RS) to the second UE; receiving a time-reversal (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE; A method comprising:

8. A first user equipment (UE), Memory, At least one transceiver; at least one processor communicatively coupled to the memory and to the at least one transceiver, the at least one processor comprising: deriving a time-reversal (TR) precoder based at least in part on an estimated channel between the first UE and a second UE; sending a TR-precoded sidelink positioning reference signal (SL-PRS) to the second UE via the at least one transceiver; A first user equipment (UE) configured to:

9. 9. The first UE of claim 8, wherein to derive the TR precoder based at least in part on the estimated channel between the first UE and the second UE, the at least one processor is configured to derive the TR precoder based at least in part on transmission or reception on a side link (SL) communication channel between the first UE and the second UE.

10. The at least one processor sends a wideband reference signal (WB RS) to the second UE to derive the TR precoder based at least in part on the estimated channel between the first UE and the second UE; receiving the TR precoder from the second UE via the at least one transceiver; or receiving, via the at least one transceiver, channel state information (CSI) associated with the WB RS from the second UE, estimating the channel between the first UE and the second UE based at least in part on the CSI, and deriving the TR precoder based at least in part on the estimated channel between the first UE and the second UE; The first UE of claim 8 , configured to:

11. The first UE of claim 8 , wherein the WB RS comprises a sidelink positioning reference signal (SL-PRS), a channel sounding reference signal (RS), or a WB beacon RS.

12. The first UE of claim 8 , wherein the WB RS is within a threshold distance from the TR-precoded SL-PRS in a time domain, a frequency domain, or both.

13. A user equipment (UE), Memory, At least one transceiver; at least one processor communicatively coupled to the memory and to the at least one transceiver, the at least one processor comprising: receiving a wideband reference signal (WB RS) from a second UE via the at least one transceiver; determining channel state information (CSI) based at least in part on the WB RS; sending the CSI to the second UE via the at least one transceiver; A user equipment (UE) configured to:

14. A user equipment (UE), Memory, At least one transceiver; at least one processor communicatively coupled to the memory and to the at least one transceiver, the at least one processor comprising: receiving a wideband (WB) reference signal (RS) from a second UE via the at least one transceiver; estimating a channel between the first UE and the second UE based at least in part on the WB RS; deriving a time-reversal (TR) precoder based on the estimated channel; and sending the TR precoder to the second UE via the at least one transceiver; A user equipment (UE) configured to:

15. A user equipment (UE), Memory, At least one transceiver; at least one processor communicatively coupled to the memory and to the at least one transceiver, the at least one processor comprising: sending a wideband reference signal (WB RS) to a second UE via the at least one transceiver; receiving a time-reversal (TR) precoded sidelink positioning reference signal (SL-PRS) from the second UE via the at least one transceiver; A user equipment (UE) configured to:

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