User equipment enabled sidelink ranging with adjustable bandwidth - Patents.com

Abstract

The bandwidth of a ranging signal used in a ranging session in a distributed system is dynamically adjusted based on the accuracy of ranging over multiple ranging sessions, and optionally based on the probability of a successful Listen Before Transmit (LBT) procedure over multiple ranging sessions. The accuracy of ranging may be determined, for example, based on the variance of determined distances over several ranging sessions, which may be compared to a threshold to indicate low-accuracy ranging. The bandwidth of the ranging signal may be increased based on an indication of low-accuracy ranging. If the ranging signal is broadcast on an unlicensed spectrum using an LBT procedure, the probability of a successful LBT procedure by the initiator UE, responder UE, or all participating UEs may be used to determine whether the bandwidth of the ranging signal must be reduced.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 154,607, filed February 26, 2021, entitled "USER EQUIPMENT ENABLED SIDELINK RANGING WITH ADJUSTABLE BANDWIDTH," and U.S. Non-Provisional Application No. 17 / 670,159, filed February 11, 2022, entitled "USER EQUIPMENT ENABLED SIDELINK RANGING WITH ADJUSTABLE BANDWIDTH," which are assigned to the assignee of the present application and incorporated herein by reference in their entireties. [Background technology]

[0002] Background Field The subject matter disclosed herein relates to wireless communication systems, and more particularly to methods and apparatus for ranging or positioning of user equipment in a distributed wireless communication system. Related Background

[0003] Obtaining precise location information for user equipment, such as cellular phones or other wireless communication devices, is becoming commonplace in the communications industry. For example, obtaining highly accurate locations of vehicles or pedestrians is essential for autonomous vehicle driving and pedestrian safety applications.

[0003]

[0004] A common means for determining a device's location is to use a satellite positioning system (SPS), such as the well-known Global Positioning Satellite (GPS) system or Global Navigation Satellite System (GNSS), which employ several satellites in orbit around the Earth. However, in some scenarios, location determination signals from an SPS may be unreliable or unavailable, for example, during adverse weather conditions or in areas with poor satellite signal reception, such as tunnels or parking complexes. Moreover, location information generated using an SPS is prone to inaccuracies. For example, off-the-shelf GPS positioning devices have an accuracy of a few meters, which is not optimal for ensuring safe autonomous driving and navigation.

[0004]

[0005] Cooperative or autonomous driving requires communication between vehicles, which can be direct or indirect, e.g., via infrastructure components such as roadside units (RSUs). For vehicle safety applications, both positioning and ranging are important. For example, vehicle user equipment (UE) can perform positioning and ranging using sidelink signaling, e.g., broadcasting ranging signals for other vehicle UEs or pedestrian UEs to determine the relative location of transmitters. Accurate and timely knowledge of the relative location or range to nearby vehicles enables automated vehicles to operate safely and negotiate traffic conditions. For example, round-trip time (RTT) is a commonly used technique for determining the distance between transmitters. RTT is a two-way messaging technique in which the time between sending a ranging signal from a first device and receiving an acknowledgment (e.g., in the form of a ranging return signal) from a second device (minus processing delay) corresponds to the distance (range) between the two devices.

[0005]

[0006] The accuracy of the determined distance between transmitters, and therefore the accuracy of the positioning, is also related to the bandwidth used during the transmission of the ranging signal. For example, increasing the bandwidth of the ranging signal will improve the accuracy of the determined distance. That is, a ranging session in a distributed system without infrastructure support for coordinating messaging has no centralized control of the bandwidth used during the transmission of the ranging signal. Summary of the Invention

[0006]

[0007] The bandwidth of a ranging signal used in a ranging session in a distributed system is dynamically adjusted based on the accuracy of ranging over multiple ranging sessions and, optionally, the probability of a successful listen before transmit (LBT) procedure over multiple ranging sessions. The accuracy of ranging may be determined, for example, based on the variance of determined distances over several ranging sessions, which may be compared to a threshold to indicate low accuracy ranging. The bandwidth of the ranging signal may be increased based on an indication of low accuracy ranging. If the ranging signal is broadcast over an unlicensed spectrum using the LBT procedure, the probability of a successful LBT procedure by the initiator UE, responder UE, or all participating UEs may be used to determine whether the bandwidth of the ranging signal must be reduced.

[0007]

[0008] In one implementation, a method of ranging performed by an initiating user equipment (UE) in a distributed system of UEs includes initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth, determining a distance to each responding UE during each ranging session, determining an indication of ranging accuracy to each responding UE during the multiple ranging sessions, receiving from one or more responding UEs the indications of ranging accuracy determined by the respective responding UEs during the multiple ranging sessions, and determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during a new ranging session based on the indications of ranging accuracy to each responding UE and the indications of ranging accuracy received from the one or more responding UEs.

[0008]

[0009] In one implementation, an initiating UE configured to perform ranging between user equipment (UE) in a distributed system of UEs includes a wireless transceiver configured to wirelessly communicate with an entity in a wireless network, at least one memory, and at least one processor coupled to the wireless transceiver and the at least one memory, wherein the at least one processor is configured to: initiate multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; determine a distance to each responding UE during each ranging session; determine an indication of ranging accuracy to each responding UE during the multiple ranging sessions; receive from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and determine to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0009]

[0010] In one implementation, an initiating UE configured to perform ranging between UEs in a distributed system of user equipments (UEs) includes: means for initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; means for determining a distance to each responding UE during each ranging session; means for determining an indication of ranging accuracy to each responding UE during the multiple ranging sessions; means for receiving from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and means for determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0010]

[0011] In one implementation, a non-transitory storage medium including program code stored thereon, the program code operable to configure at least one processor in an initiating UE for ranging between UEs in a distributed system of user equipments (UEs), the program code comprising instructions for initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of accuracy of ranging to each responding UE during the multiple ranging sessions; receiving from one or more responding UEs an indication of accuracy of ranging determined by a respective responding UE during the multiple ranging sessions; and determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of accuracy of ranging to each responding UE and the indication of accuracy of ranging received from the one or more responding UEs.

[0011]

[0012] In one implementation, a method of ranging performed by a responding UE in a distributed system of user equipment (UE) includes receiving initiation of multiple ranging sessions from an initiating UE using a first ranging signal bandwidth, determining a distance to the initiating UE during each ranging session, determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions, sending the indication of ranging accuracy to the initiating UE, and receiving initiation of a new ranging session from the initiating UE using a second ranging signal bandwidth different from the first ranging signal bandwidth and at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0012]

[0013] In one implementation, a responding UE configured to perform ranging between user equipment (UE) in a distributed system of UEs includes a wireless transceiver configured to wirelessly communicate with an entity in a wireless network, at least one memory, and at least one processor coupled to the wireless transceiver and the at least one memory, wherein the at least one processor is configured to: receive initiation of multiple ranging sessions from an initiating UE using a first ranging signal bandwidth; determine a distance to the initiating UE during each ranging session; determine an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; send the indication of ranging accuracy to the initiating UE; and receive initiation of a new ranging session from the initiating UE using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0013]

[0014] In one implementation, a responding UE configured to perform ranging between user equipments (UEs) in a distributed system of UEs includes: means for receiving from an initiating UE initiation of multiple ranging sessions using a first ranging signal bandwidth; means for determining a distance to the initiating UE during each ranging session; means for determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; means for sending the indication of ranging accuracy to the initiating UE; and means for receiving from the initiating UE initiation of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0014]

[0015] In one implementation, a non-transitory storage medium including program code stored thereon, the program code operable to configure at least one processor in a user equipment (UE) for ranging between UEs in a distributed system of UEs, the program code comprising instructions for receiving from an initiating UE initiation of multiple ranging sessions using a first ranging signal bandwidth; determining a distance to the initiating UE during each ranging session; determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; sending the indication of ranging accuracy to the initiating UE; and receiving from the initiating UE initiation of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0015]

[0016] Non-limiting and non-exhaustive aspects are described with reference to the following figures, in which like reference numerals refer to like parts throughout the various figures unless otherwise specified. [Brief explanation of the drawings]

[0016] [Figure 1]

[0017] FIG. 1 illustrates a wireless communication system showing distributed communication, including ranging signaling to support dynamically variable ranging signal bandwidth. [Figure 2]

[0018] FIG. 10 illustrates a signaling graph showing the timing and frequency of various messages that may be sent and received by an initiating UE and three responding UEs for a ranging or positioning session. [Figure 3]

[0019] FIG. 1 illustrates a signaling graph showing several ranging sessions over a period of time. [Figure 4A]

[0020] 10 is a graph illustrating dynamic control of the frequency range used with the PRS signal over multiple ranging sessions based on the accuracy of the determined distance. [Figure 4B]

[0021] Graph showing dynamic control of frequency ranges used with PRS signals across multiple ranging sessions based on the probability of a successful listen-before-transmit (LBT) procedure. [Figure 5]

[0022] A signaling flow in which the frequency range used with the PRS signal across multiple ranging sessions is dynamically controlled based on the determined distance accuracy or probability of LBT success. [Figure 6]

[0023] 1 is a schematic block diagram illustrating some example features of a UE configured to support dynamic adjustment of the bandwidth of a PRS during a ranging session. [Figure 7]

[0024] 10 is a flowchart illustrating a method for ranging between UEs implemented by an initiating UE. [Figure 8]

[0025] 10 is a flowchart illustrating a method for ranging between UEs implemented by a responding UE. DETAILED DESCRIPTION OF THE INVENTION

[0017]

[0026] A distributed approach may be used for ranging and positioning of vehicles, roadside units (RSUs), and pedestrians, avoiding the need for a centralized base station to coordinate and relay communications. Such communications may be used, for example, for autonomous driving and vehicle safety applications. Communications used in the distributed approach may be, for example, directly between vehicles or between vehicles and RSUs or pedestrians. These communications may include messages and information elements (IEs) that may provide vehicles with information needed for autonomous driving.

[0018]

[0027] For example, for safe operation of an autonomous vehicle, its relative location or distance to other vehicles needs to be determined. Various techniques may be used to derive the relative position between vehicles. For example, the relative position of vehicles may be derived using ranging signaling. Ranging signals may be referred to as physical ranging signals, positioning ranging signals, positioning reference signals, or physical reference signals, and may be collectively referred to as PRS signals herein. PRS signals may be broadcast, for example, by a user equipment (UE) in a vehicle, sometimes referred to as a V-UE, and received by other V-UEs and / or infrastructure, e.g., an RSU, or a UE carried by a pedestrian, using direct communication systems such as dedicated short-range communications (DSRC), cellular vehicle-to-everything (C-V2X) communications, or even 5G new radio (NR) communications. PRS signals are used to determine the distance to the broadcasting vehicle using, for example, one-way ranging, round-trip time (RTT) positioning operations, or other standard positioning operations such as time of arrival (TOA), time difference of arrival (TDOA), or observed time difference of arrival (OTDOA).

[0019]

[0028] In a distributed system, individual UEs can range with respect to other nearby UEs using messages and positioning signals transmitted directly to the other UEs. In an RTT-based ranging session, for example, multiple messages and signals are transmitted and received by each UE. For example, an initial set of pre-ranging signal messages (pre-PRS messages) to request and accept a ranging session is transmitted and received, followed by broadcasting ranging signals (PRS signals) for measurements, followed by a set of post-ranging signal messages (post-PRS messages) that exchange measurement payloads. In RTT-based ranging and positioning, for example, measurements of the time of arrival (TOA) and time of departure (TOD) of the transmitted and received PRS signals are provided in the post-PRS messages and can be used by each pair of UEs to determine the distance between them. Pre-PRS and post-PRS messages may be sent over licensed spectrum to ensure reliability, while PRS signals may be broadcast over licensed or unlicensed spectrum (e.g., to take advantage of the greater available bandwidth in the UNI-III spectrum, for example).

[0020]

[0029] The accuracy of the determined distance between transmitting UEs is related to the size of the frequency band used to transmit PRS signals. For example, increasing the PRS bandwidth can increase the accuracy of the determined distance. Unfortunately, in a distributed ranging system, centralized control of the PRS bandwidth is not feasible. For example, in a distributed ranging system in which PRS signals are transmitted over a licensed spectrum, there may be limitations on the frequency band used, for example, based on demand. In a distributed ranging system in which PRS signals are transmitted over an unlicensed spectrum, a listen-before-transmit (LBT) protocol may be employed, and the potential accuracy improvement achieved by PRS transmission over a larger frequency band may be offset by an increased LBT failure rate. Therefore, it may be desirable to dynamically enable a UE to adjust the PRS bandwidth used during a ranging session based, for example, on an indication of demand or need to increase the PRS bandwidth. Furthermore, a balancing technique may be used to minimize the increased LBT failure rate for PRS transmissions in the unlicensed spectrum.

[0021]

[0030] Thus, in one implementation, as described herein, a UE may participate in multiple ranging sessions using a ranging signal bandwidth initiated by an initiating UE. The initiating UE may determine an indication of accuracy of the determined distance to each responding UE across the multiple ranging sessions. The indication of accuracy may be based, for example, on the variance of the determined distance to each responding UE across several ranging sessions, which may be compared to a first threshold to identify low-accuracy distances. The responding UE may similarly determine an indication of accuracy of the determined distance to the initiating UE across the multiple ranging sessions and may send the indication of accuracy to the initiating UE, for example, in a message separate from the ranging session or in a post-ranging message. The initiating UE may determine, based on the indication of accuracy, whether to increase the bandwidth of the ranging signal during a subsequent ranging session, for example, if the number of low-accuracy distances for all participating UEs is greater than a second threshold. The number of ranging sessions used to determine the low-accuracy distance and the first threshold may be based on the speed of the initiating UE, while the second threshold may be based on the accuracy requirement for the ranging sessions.

[0022]

[0031] Furthermore, when ranging signals are broadcast over an unlicensed spectrum and an LBT procedure is used, the initiating UE and / or responding UE may monitor an LBT success rate over several ranging sessions, which may be compared to a third threshold to identify a low LBT success rate. The responding UE may, for example, send an indication of the LBT success rate to the initiating UE along with an indication of accuracy. The initiating UE may determine whether to reduce the bandwidth of the ranging signal during a subsequent ranging session further based on the indication of the LBT success rate determined by itself, received from the responding UE, or a combination thereof. For example, if the ranging signal for the initiating UE has a low LBT success rate, the initiating UE may reduce the bandwidth of the ranging signal during the subsequent ranging session. Similarly, if a large number of responding UEs (or all participating UEs) exhibit a low LBT success rate, e.g., a number greater than a fourth threshold, the initiating UE may reduce the bandwidth of the ranging signal during the subsequent ranging session. The number of ranging sessions used to determine a low LBT success rate may be based on the speed of the initiating UE, while the third and fourth thresholds may be based on a number of responder UEs.

[0023]

[0032] Thus, dynamically variable ranging signal bandwidth can be enabled in a distributed ranging system, e.g., a system without centralized control. Furthermore, when an LBT procedure is used, adjustment of the ranging signal bandwidth is balanced against the LBT failure rate.

[0024]

[0033] 1 illustrates a wireless communication system 100 illustrating distributed communications, including ranging signaling to support dynamically variable ranging signal bandwidths, as described herein. The wireless communication system 100 illustrates a first vehicle 102, e.g., V-UE 102, having a first wireless device in wireless communication with another V-UE 104, depicted as a second vehicle. The V-UE 102 and V-UE 104 may comprise, but are not limited to, an on-board unit (OBU), a vehicle or subsystem thereof, or various other communication devices. The V-UEs 102 and 104 function and provide communications on behalf of their associated vehicles and, therefore, may be referred to herein simply as vehicles 102 and 104 or UEs 102 and 104. The first UE 102 and second UE 104 may be, for example, two vehicles traveling on a road with other vehicles not shown.

[0025]

[0034] The wireless communication system 100 may use, for example, a vehicle-to-everything (V2X) communication standard in which information is passed between vehicles and other entities within a wireless communication network. V2X services include, for example, services for vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), vehicle-to-infrastructure (V2I), and vehicle-to-network (V2N). The V2X standard aims to develop autonomous or semi-autonomous driving systems, such as advanced driver assistance systems (ADAS), which can be used to assist drivers with critical decisions such as lane changes, speed changes, passing speeds, and, as described herein, assist with parking. Low-latency communications are used in V2X and are therefore suitable for precise relative positioning using ranging signals, such as one-way ranging, RTT, and TDOA.

[0026]

[0035] Generally, there are two modes of operation for V2X services as defined in 3rd Generation Partnership Project (3GPP®) TS 23.285. One mode of operation uses direct wireless communication between V2X entities, which is sometimes referred to as sidelink communication. The other mode of operation uses network-based wireless communication between the entities. The two modes of operation may be combined, or other modes of operation may be used, if desired.

[0027]

[0036] The wireless communication system 100 may operate using direct or indirect wireless communication between the UE 102 and the UE 104. For example, the wireless communication may be via the Proximity-Based Services (ProSe) Directional Communication (PC5) reference point, e.g., as defined in 3GPP TS 23.303, and may use wireless communication under IEEE 1609, Wireless Access in Vehicle Environments (WAVE), Intelligent Transportation Systems (ITS), and IEEE 802.11p over the 5.9 GHz ITS band, or other wireless connections directly between entities. Thus, as shown, the UE 102 and the UE 104 may communicate directly using a vehicle-to-vehicle (V2V) communication link 103. The UE 102 and the UE 104 may also communicate directly with a roadside unit (RSU) 110 via vehicle-to-infrastructure (V2I) communication links 107 and 109, respectively. The RSU 110 may include a backhaul connection to the network, as shown by the wired connection 111, but may also be via a wireless Uu interface to a base station. The RSU 110 may be, for example, a fixed infrastructure entity that may support V2X applications and exchange messages with other entities that support V2X applications. The RSU may be a logical entity that may combine V2X application logic with the functionality of a base station in a RAN, such as an eNB, ng-eNB, or eLTE (referred to as an eNB-type RSU) or gNB, or a UE (referred to as a UE-type RSU). The RSU 110 may be used for ranging with the UE 102, 104, or other UEs, and because the location of the RSU 110 may be precisely known, the RSU 110 may be used as an anchor UE, from which the location of the UE 102, 104, or other UEs may be determined. The RSU 110 may be referred to herein as a UE 110. The UEs 102, 104 and UE 110 may use direct communication links to communicate with additional entities, such as additional vehicles, RSUs, or with a UE 112 carried by a pedestrian 114.For example, UE 102 may communicate with UE 112 via V2V communication link 113, UE 104 may communicate with UE 112 via V2V communication link 115, and UE 110 may communicate with UE 112 via V2I communication link 117.

[0028]

[0037] During direct communication with one or more entities in the V2X wireless communication system 100, each entity may provide V2X information, such as an identifier for the V2X entity, as well as other information in messages such as Common Awareness Messages (CAMs) and Decentralized Notification Messages (DENMs) or Basic Safety Messages (BSMs), which may be used, for example, for ADAS or safety use cases.

[0029]

[0038] In other implementations, the UE 102 and the UE 104 may communicate with each other indirectly, e.g., through the RSU 110 via V2I communication links 107 and 109, respectively, or through other network infrastructure (not shown), e.g., using cellular vehicle-to-anything (CV2X). For example, the vehicles may communicate through base stations in a Radio Access Network (RAN), such as an evolved Node B (eNB) or next generation evolved Node B (ng-eNB) in LTE wireless access and / or evolved LTE (eLTE) wireless access, or an NR Node B (gNB) in fifth-generation (5G) wireless access.

[0030]

[0039] The UEs 102 and 104 may initiate and conduct ranging / positioning sessions, including sending pre-PRS messages, broadcasting PRS, and sending post-PRS messages over links 103, 107, 109, 113, or 115, by which the distance or relative position between the UEs 102 and 104 may be determined. The PRS broadcast by the UEs 102 and 104 may be a signal suitable for ranging, for example, as defined for DSRC or C-V2X. The PRS may be broadcast over licensed or unlicensed spectrum. For example, in some implementations, the PRS may be broadcast over one or more Unlicensed National Information Infrastructure (UNII) radio bands, including, for example, one or more of the UNII-1 radio band, the UNII-2A radio band, the UNII-2B radio band, or the UNII-3 radio band. When broadcasting over unlicensed spectrum, a listen-before-transmit (LBT) protocol may be employed.

[0031]

[0040] If UEs 102 and 104 broadcast a PRS in V2V link 103, the distance or relative position between UE 102 and UE 104 can be determined directly. If UEs 102 and 104 broadcast a PRS in V2I links 107 and 109 or via links 113 and 115, the distance or relative position between UE 102 and UE 110 or UE 112, and between UE 104 and UE 110 or UE 112, can be determined directly.

[0032]

[0041] Direct wireless communication between the UEs 102, 104, 110, and 112 does not require any network infrastructure and allows for low-latency communication, which is advantageous for precise ranging or positioning. Thus, such direct wireless communication may be desirable for ranging over short distances, for example, with nearby vehicles or infrastructure.

[0033]

[0042] A UE, for example, any of the V-UE 102, V-UE 104, RSU 110, and UE 112 shown in FIG. 1, may be configured to perform ranging and / or positioning operations, such as RTT-based ranging.

[0034]

[0043] 2 illustrates, by way of example, a signaling graph 200 showing the timing and frequency of various messages that may be transmitted and received by an initiating UE (UEX) and three responding UEs (UEA, UEB, and UEC) for a ranging or positioning session. For example, FIG. 2 illustrates a capability message 201 and an RTT-based ranging session 202 during which several messages are sent between the initiating and responding UEs, including a pre-PRS message 204 for requesting and accepting the ranging session, a PRS signal 206 for measurements, and a post-PRS message 208 for exchanging measurement payloads. Each set of pre-PRS 204, PRS 206, and post-PRS 208 may be considered a single unit or PRS cycle. Each PRS cycle includes a pre-PRS message 204, a PRS signal 206, and a post-PRS message 208 and may therefore be referred to herein as a ranging session 202. The ranging session (PRS cycle) may be periodic with a period T_r, and the capability messages may be periodic with a period T_c, where T_r>T_c. In Figure 2, signaling from the initiator UEX is labeled with an "X," signaling from the first responder UEA is labeled with an "A," signaling from the second responder UEB is labeled with a "B," and signaling from the third responder UEC is labeled with a "C." The signaling from the initiator UEX is the first box in each of the pre-PRS message 204, PRS signal 206, and post-PRS message 208, followed by the responding UEs (UEA, UEB, and UEC).

[0035]

[0044] As shown, UEs, including the initiating UE and the responding UE, may broadcast capability messages 201. The capability messages may include information that is not part of the ranging session but can be used by the initiating UE to initiate a ranging session with selected UEs. For example, the capability messages may be on the ITS spectrum and may include the UE ID, the ranging capabilities of the UE, the channels the UE is configured to use, MIMO (multiple-input multiple-output) capabilities, etc. The capability messages may further indicate whether the UE needs to determine its location or whether its location is known, and it may act as an anchor UE for positioning other UEs. While FIG. 2 shows capability messages 201 as having the same order as messages in ranging session 202, it should be understood that the order may actually be different.

[0036]

[0045] A pre-PRS message 204 (e.g., a pre-ranging message) is used by a UE to request and acknowledge a ranging session. As shown, the pre-PRS message 204 may be transmitted over a licensed spectrum to ensure reliability. The pre-PRS message 204 may be broadcast or unicast, for example, using a radio resource control (RRC) connection. The initiating UE broadcasts an initial pre-PRS message 204 (gray box marked with an X), sometimes referred to as a pre-PRS request message, to indicate a ranging session between the initiating UE and the responding UE, which may provide information about the ranging session. For example, the pre-PRS message 204 from the initiating UE may include IDs for participating UEs (i.e., initiator and responder IDs). The pre-PRS request message may include a ranging session ID, a channel for the PRS broadcast by the initiating UE and the responding UE, a PRS broadcast time, a maximum listen-before-transmit (LBT) time, etc. The pre-PRS request message from the initiating UE EX may include, for example, a PRS ID to be used by the initiating UE and, in some implementations, a PRS ID to be used by the responding UE. If the PRS ID is to be fixed across multiple PRS exchanges (e.g., for multiple units during the ranging session 202), the initiating UE may include an ID associated with the current PRS exchange, e.g., a session ID. The initiating UE may determine when the PRS signal 206 will be transmitted, which may be configured at a higher layer in the initiating UE, for example. The initiating UE may indicate the timing of the PRS by sending a time slot number to approximate the desired PRS transmission time. In some implementations, the time slot may be subject to local clock error. The initiating UE may further provide the timing of the PRS to be sent by the responding UE, as well as a maximum LBT time or other timing information. The initiating UE may further indicate the frequency band to be used to broadcast the PRS signal 206 by the initiating and responding UEs.For example, the frequency of the PRS may be selected from an available set of total bandwidth, or the frequency of the PRS may be selected by sensing interference and choosing one or more channels whose average interference reference signal received power (RSRP) is less than a threshold. As described herein, the initiating UE may dynamically change the frequency bands used by the initiating UE and responding UE to broadcast the PRS based on, for example, an accuracy determination and, in some implementations, the success of the LBT. The initiating UE may indicate the number of PRS cycles it will perform during the ranging session 202. The number of PRS cycles may be configured at higher layers. The pre-PRS message for each PRS cycle may indicate, for example, the current PRS cycle relative to the total PRS cycles requested, where the number of current cycles increments after the completion of each cycle.

[0037]

[0046] The initial pre-PRS request message from the initiating UE is received and decoded by the responding UE identified in the initial pre-PRS message. The responding UE may send a pre-PRS message 204 (gray boxes labeled A, B, and C) acknowledging the initial pre-PRS request message, which may further provide information about the ranging session. Each responding UE may indicate the PRS ID it will use or may indicate that it will use the PRS ID indicated in the initial pre-PRS message. If the PRS ID will be fixed across multiple PRS exchanges (e.g., multiple PRS cycles during the ranging session 202), the responding UE may include an ID, e.g., a session ID, associated with the current PRS exchange received in the initial pre-PRS message from the initiating UE. The responding UE may broadcast the pre-PRS message 204, which can be received by the initiating UE (and other responding UEs). In some implementations, each responding UE may send the pre-PRS message 204 using unicast over an RRC connection to the initiating UE.

[0038]

[0047] PRS signals 206 are exchanged by participating UEs. The initiating UE and responding UE know the expected timing and frequency of the PRS signals and know the PRS ID (and any session ID used with the exchanged one) used to broadcast the PRS signals 206. The PRS signals 206 may be, for example, a quadrature phase shift keying (QPSK) modulated pseudo-noise (PN) sequence and may include a ranging session ID. The PRS signals 206 may be broadcast on a licensed spectrum or on an unlicensed spectrum that may be subject to LBT restrictions. In some implementations, when using an unlicensed spectrum, the initiating UE X may reserve transmissions for the responding UEs U E A, U E B, and U E C , so the responding UE may not need to perform LBT for PRS transmissions. For example, the initiating UE X broadcasts its PRS signal 206 (white box marked with an X) at the determined time indicated in the initial pre-PRS message 204. In some implementations, when a PRS signal is deployed in an unlicensed spectrum, an initiating UE broadcasts its PRS signal at a time determined by the LBT constraints plus a random waiting time. In some implementations, the LBT can be Category 2 LBT with fixed-window clear channel assessment (CCA) or Category 4 LBT with variable-window CCA. The initiating UE uses the PRS signal corresponding to the PRS ID and uses the frequency resources indicated in its initial pre-PRS message 204. The initiating UE stores the time instance when the PRS signal was broadcast, and the responding UE stores the time instance when the PRS signal was received. In some implementations, the time instance can be subject to local clock error.

[0039]

[0048] Similar to the initiating UE, each responding UE broadcasts its PRS signal 206 (white boxes labeled A, B, and C) at the time and frequency assigned by the initiating UE in the initial pre-PRS message 204. In some implementations, when PRS signals are deployed in an unlicensed spectrum, each responding UE may broadcast its PRS signal at a time determined by the LBT constraints plus a random waiting time. The LBT may be Category 2 LBT using fixed-window CCA or Category 4 LBT using variable-window CCA. In some examples, the LBT procedure may fail, and after the waiting time, the responding UE will not be able to broadcast its PRS signal. If the LBT procedure is successful (or is not used, for example, because the PRS signal is broadcast on a licensed spectrum or the initiating UE reserved transmission time for the responding UE), each responding UE uses the PRS signal corresponding to the PRS ID and uses the frequency resources indicated in the initial pre-PRS request message 204. Each responding UE stores the time instance when its PRS signal was broadcast, and the initiating UE (and, optionally, other responding UEs) stores the time instance when the PRS signal was received. In some implementations, the time instances may be subject to local clock error.

[0040]

[0049] Thus, each UE records the time of departure (ToD) of its broadcasted PRS signal and measures the time of arrival (ToA) of received PRS signals from other UEs. The PRS signals may be signals suitable for ranging, for example, as defined for DSRC or C-V2X. The ToA and ToD resolution of the PRS signal increases with increasing frequency bandwidth. In some implementations, the angle of departure (AoD) and angle of arrival (AoA) of the broadcasted and received PRS signals may also be measured. Broadcasting over unlicensed spectrum is advantageous because wider frequency bands are available. For example, in some implementations, the PRS may be broadcast over one or more UNII radio bands, including, for example, one or more of the UNII-1 radio band, the UNII-2A radio band, the UNII-2B radio band, or the UNII-3 radio band.

[0041]

[0050] A post-PRS message 208 is sent by each UE to exchange measurement payloads. As shown, the post-PRS message 208 may be transmitted over a licensed spectrum to ensure reliability. In some implementations, the post-PRS message 208 may be broadcast or unicast using an RRC connection. An initiator UE X sends its post-PRS message 208 (the shaded box marked with an X) to indicate when it broadcasts the PRS signal 206 (ToD) and when the PRS signal from the responding UE was received (ToA). In some implementations, the ToA may be calculated as a relative time to the ToD of its broadcasted PRS signal, and a relative time may be given. In some implementations, the relative time may be approximated to the nearest multiple of the time scale shared by the initiator and responding UEs. In some implementations, the initiator UE may provide an indication of its location in the post-PRS message 208, if known. For example, the location of the initiating UE may be its location at a particular time, such as the broadcast time of its PRS signal or the arrival time of the PRS signal from the responding UE. The post-PRS message 208 may further include the AoD of its PRS signal 206 and the AoA of the PRS signal 206 received from the responding UE, the orientation of the initiating UE, a broadcast indicator of the PRS signal 206, a reception indicator of the PRS from the responding UE, and other relevant measurements including, for example, map information, the location of reflectors relative to the UE, etc.

[0042]

[0051] Similar to the initiating UE, each responding UE sends its post-PRS signal 208 (shaded boxes labeled A, B, C) to provide a measurement payload. Each responding UE may indicate whether it received a PRS signal from the initiating UE and may indicate when it broadcasts the PRS signal 206 (ToD) and when the PRS signal from the first UE (and, optionally, from other responding UEs) was received (ToA). In some implementations, the ToD may be calculated as a relative time to the ToA of the PRS signal from the initiating UE (and, optionally, to the ToA of the PRS from the other responding UEs). In some implementations, the relative time may be approximated to the nearest multiple of the time scale shared by the initiating UE and the responding UE. In some implementations, the responding UE may provide an indication of its location in the post-PRS message 208, if known. For example, the location of a given responding UE may be a location at a particular time, such as the time of arrival of a PRS signal from the initiating UE or the time of departure of its broadcasted PRS signal. The post-PRS message 208 may further include the AoD of its PRS signal 206 and the AoA of the PRS signal 206 received from the initiating UE (and optionally received from other responding UEs), the orientation of the initiating UE, a broadcast indicator of the PRS signal 206, a reception indicator of the PRS from the responding UE, and other related measurements including, for example, map information, locations of reflectors relative to the UE, etc. As described herein, the post-PRS message 208 sent by the responding UE may further include information related to the determined accuracy of the ranging session and, optionally, the success rate of the LBT process.

[0043]

[0052] After receiving the post-PRS message, the initiating UE (and responding UE) may calculate its distance (and, in some implementations, its location) using, for example, a Kalman filter. The initiating UE may send the next cycle of pre-PRS messages at a time indicated by higher layers or determined autonomously by the initiating UE.

[0044]

[0053] The time between the first pre-PRS message 204 and the last post-PRS message 208 may be the duration of the ranging session, e.g., 100 milliseconds. The duration of each broadcasted PRS signal 206 may be, e.g., 47 microseconds. In some implementations, multiple PRS cycles, e.g., multiple instances of pre-PRS messages 204, PRS 206, and post-PRS messages 208, may be used together to provide greater accuracy.

[0045]

[0054] Both the initiating UE and the responding UE may determine the distance between them based on the ToD and ToA of the broadcasted PRS signal. For example, the RTT between any pair of UEs (which may be any pair of initiating and responding UEs) may be calculated as the PRS distance as the difference between ToD1 and ToA2 minus the difference between ToA1 and ToD2, e.g., i ToD for signals i and ToA i (where i=1 for the PRS broadcast from the first UE and i=2 for the PRS broadcast by the second UE).

[0046]

number

[0047]

[0055] The RTT value is the round trip time of a signal, so the range (distance) between UE1 and UE2 can be determined as RTT / 2c, where c is the speed of light.

[0048]

[0056] If the locations of one or more responding UEs are known, the distance between the initiating UE and the responding UE may be used together with the known location of the responding UE to determine the location of the other UE, and thus the ranging session may be a positioning session. A responding UE with a known location that may be used for positioning may be referred to herein as an anchor UE. The location of the anchor UE may be provided to other UEs through messaging, for example, in a pre-PRS message or a post-PRS message. If the distances to multiple anchor UEs are determined, the locations of the multiple anchor UEs may be used in multilateral positioning to determine the location of the initiating UE (or other responding UEs).

[0049]

[0057] Angle measurements, e.g., AoD and AoA, can be used, for example, to assist in positioning. As an example, the relative positions of two UEs can be determined based on the distance between them and the measured AoA. Once the relative positions of the UEs are determined, if the actual position of one of the UEs is known (this can be provided, for example, in the pre-PRS message 204 or post-PRS message 208), the actual position of the other UE can be determined. If the positions of the two UEs are known by a third UE, the distance between the third UE and each of the other two UEs will result in two possible positions for the third UE, which can be resolved based on AoD / AoA information. AoD can be useful, for example, when the resolution of the AoA is insufficient or incorrect. AoD can be measured, for example, based on the known orientation of the UE (e.g., determined by a magnetometer) and the direction of the transmitted signal relative to the UE (e.g., relative to the UE's antenna array used for beamforming). The AoA may be measured based on the phase difference of received signals at different antenna elements of the antenna array and the known orientation of the UE, for example, as determined by a magnetometer. Additionally, geographic constraints may be used to assist positioning by constraining the vehicle's possible locations based on locations that are accessible to the vehicle, such as roads.

[0050]

[0058] 3 shows, by way of example, a signaling graph 300 illustrating several ranging sessions involving initiator UEX and responders UEA, UEB, and UEC over a period of time. As shown, capability messages 301 are exchanged, followed by a series of ranging sessions 3101, 3102, ... 310, which may be collectively referred to as ranging session 310. N As shown, each ranging session 3101, 3102, ... 310 N are the pre-PRS messages 3121, 3122, ... 312 N and PRS signals 3141, 3142, ... 314 N and Post PRS messages 3161, 3162, ... 316 N and are sent by the initiator UE X (labeled X) or the responder UE A (labeled A), UE B (labeled B), and UE C (labeled C). Additional UEs may participate in the ranging session. It should be understood that equivalently, the ranging session 310 may be considered as a separate PRS cycle within a single ranging session. The ranging session 310 (PRS cycle) may be periodic with a period T_r, and the capability messages may be periodic with a period T_c, where T_r>T_c.

[0051]

[0059] As described above, the determined distance between transmitting UEs, and therefore the accuracy of distance-based location estimates, is related to the size of the frequency band used to transmit the PRS signals. For example, PRS signals transmitted using a larger frequency band will generally produce more accurate distance estimates than PRS signals transmitted using a smaller frequency band. However, in a distributed ranging system, there is no centralized control of the PRS bandwidth to be used in a ranging session. For example, there may be multiple concurrent ranging sessions competing for PRS resources, e.g., timing and frequency. Therefore, there may be limited frequency resources available, particularly on licensed spectrum. Furthermore, although unlicensed spectrum may have larger available frequency resources, the failure rate of the LBT procedure may increase when a larger frequency band is used for PRS transmission. In the absence of centralized control of PRS bandwidth, it is desirable for UEs involved in a ranging session to dynamically control the size of the bandwidth used for PRS signals to improve accuracy performance without interfering with other ranging sessions and increasing the LBT failure rate, which may offset any gains in accuracy performance.

[0052]

[0060] 4A is a graph 400 illustrating dynamic control of frequency ranges used with PRS signals over multiple ranging sessions based on the accuracy of the determined distance. FIG. 4A illustrates, for example, PRS signals 4141, 4142, ..., 414, which may be collectively referred to as PRS signals 414, transmitted by an initiator UEX (labeled X) or a responder UEA (labeled A), UEB (labeled B), and UEC (labeled C) during several (K+1) ranging sessions. K and 414 K+1 , and the pre-PRS and post-PRS messages during the ranging session are not shown in FIG. 4A.

[0053]

[0061] The initiating UEX may initiate ranging sessions using a first frequency bandwidth for PRS signals during some ranging sessions. For example, as shown in FIG. 4A, PRS signals 4141, 4142, ..., 414 K may use a first frequency bandwidth 422. As indicated by the dotted lines, additional or alternative frequency bandwidths 424, 426, and 428 may be available for use in the licensed or unlicensed spectrum used with the PRS signal 414. UEs participating in the ranging sessions, e.g., UEX, UEA, UEB, and UEC, may continuously or periodically monitor the accuracy of the distance determined using the PRS signal over several (K) ranging sessions, for example, to generate an indication of the accuracy of the ranging over the several (K) ranging sessions. The number (K) of ranging sessions for which the accuracy of the ranging may be determined may be determined depending on the speed of the initiating UEX. For example, if the speed of the initiating UEX is high, the number (K) of ranging sessions may be relatively small to minimize the distance traveled by the initiating UEX using low-accuracy ranging before adjustments are made; conversely, if the speed of the initiating UEX is low, the number (K) of ranging sessions may be relatively large to improve the results of the accuracy determination. The initiating UE may provide an indication of the number of ranging sessions (K) in a pre-PRS message, a post-PRS message, or in some implementations to the responding UE. The indication of the number of ranging sessions (K) may be the speed of the initiating UE or the value of K. In some implementations, the responding UE may independently determine the speed and / or the number of ranging sessions (K) of the initiating UE based on, for example, the speed of the responding UE (which may be 0 if the UE is stationary) and the change over time in the distance between the initiating UE and the responding UE or the reported location of the initiating UE (e.g., as reported in the post-PRS message), as well as known geographic constraints, such as constraining the possible relative locations of the initiating UE to the responding UE based on locations that are accessible to vehicles, such as roads.

[0054]

[0062] As an example, the accuracy of a ranging measurement over several (K) ranging sessions may be determined by the UE based on the variance of its derived ranging values ​​over several (K) ranging sessions. The variance may be determined, for example, as the mean square deviation of each number (distance) from the mean of the data set over several (K) ranging sessions. The initiating UE may, for example, determine the variance of the determined distance to each responding UE over several (K) ranging sessions. The responding UE may determine the variance of the determined distance to the initiating UE over several (K) ranging sessions. In some implementations, the responding UE may further determine the variance of the determined distances to other responding UEs over several (K) ranging sessions. Each determined variance may be compared to a predetermined threshold, for example, an accuracy threshold α. For example, a variance greater than the accuracy threshold α may indicate that the distances determined over several (K) ranging sessions have low accuracy. The accuracy of ranging by a UE participating in a ranging session may be flagged if it is determined to be low, for example, based on a variance greater than the accuracy threshold α, or equivalently, if it is determined to be high, for example, based on a variance less than the accuracy threshold α. If desired, other techniques may be used to determine the precision of ranging. For example, instead of variance, other statistical analyses, such as the use of standard deviation, may be used to determine the precision of ranging.

[0055]

[0063] The accuracy threshold α may be correlated with the speed of the initiating UEX. For example, if the speed of the initiating UEX is high, i.e., while the initiating UEX is moving quickly, high accuracy may be desired and the accuracy threshold α may be set relatively low, and conversely, if the speed of the initiating UEX is low, high accuracy may not be needed when the initiating UEX is moving slowly or is stationary and the accuracy threshold α may be set relatively high. Similar to the indication of several (K) ranging sessions given to the responding UE, the initiating UEX may provide an indication of the accuracy threshold α, for example, as the speed or value of the accuracy threshold α of the initiating UEX, or the responding UE may independently determine the speed and / or the accuracy threshold α of the initiating UEX.

[0056]

[0064] The responding UE may send to the initiating UE X an indication of the accuracy of the ranging over several (K) ranging sessions. For example, the responding UE may send a message including a flag indicating low accuracy ranging (or equivalently, a flag indicating high accuracy of ranging). In some implementations, the responding UE may send the determined variance (or other metric of the accuracy of the ranging), and the initiating UE X may compare the variance from each responding UE with an accuracy threshold α to flag the accuracy of the ranging from each responding UE as low accuracy (or equivalently as high accuracy).

[0057]

[0065] In one implementation, the responding UE may send an indication of the ranging accuracy over several (K) ranging sessions to the initiating UE in a message that is separate and independent from the ranging sessions, i.e., that is not part of a pre-PRS message, a PRS signal, or a post-PRS message. For example, the ranging accuracy reporting message may be transmitted over the ITS spectrum. In some implementations, to reduce overhead, the ranging accuracy reporting message may be sent with a period T_a that is greater than the period T_r of the ranging sessions, i.e., T_a > T_r. As an example, the ranging accuracy reporting message may be sent every K ranging sessions or more frequently than K ranging sessions.

[0058]

[0066] In another implementation, the responding UE may send an indication of the ranging accuracy over several (K) ranging sessions to the initiating UE in a post-PRS message during each ranging session. For example, the indication of the ranging accuracy over the previous K ranging sessions may be included in a message field in each post-PRS message. Thus, the ranging accuracy reporting message may have a period T_a that is the same as the period T_r of the ranging session, i.e., T_a=T_r.

[0059]

[0067] The initiating UEX may use ranging accuracy indications determined by itself (e.g., for each responding UE) and from responding UEs (e.g., for the initiating UE and, in some implementations, for other responding UEs) to determine whether to increase the frequency range of the PRS signal. For example, the initiating UEX may determine the number of low-accuracy indications from all participating UEs and decide to increase the PRS bandwidth during a subsequent ranging session that uses the number of low-accuracy indications, e.g., by determining whether the number of low-accuracy indications is above or below a threshold. For example, in one implementation, the initiating UEX may determine the average number of low-accuracy indications (e.g., the total number of low-accuracy indications flagged as low-accuracy divided by the total number of distances determined by participating UEs), compare the average number of low-accuracy indications with a threshold, e.g., an increase threshold β, and increase the frequency range of the PRS signal if the average number of low-accuracy indications is greater than the increase threshold β. The increase threshold β may be determined according to the accuracy requirements for the ranging or positioning application. For example, if a ranging or positioning application requires high accuracy ranging / positioning, the increase threshold β may be set relatively low (e.g., closer to 0), and conversely, if a ranging or positioning application does not require high accuracy ranging / positioning, the increase threshold β may be set relatively high (e.g., closer to 1).

[0060]

[0068] Therefore, if the average number of low accuracy indications is greater than the increase threshold β, the initiating UE may increase the frequency range of the PRS signals during subsequent ranging sessions. For example, referring to FIG. 4A, after K ranging sessions, the initiating UE may determine that the frequency range of the PRS signals should be increased based on the ranging accuracy indications from participating UEs during ranging sessions 1-K. Thus, during the pre-PRS request message for the K+1 ranging session, the initiating UE may determine that the initiating UE and responding UE have increased the frequency range of the PRS signals. K A second frequency bandwidth 432 that is larger than the first frequency bandwidth 422 used in PRS414 K+1 The frequency bandwidth is increased in discrete steps, for example by a discrete number of bandwidths 424 (PRS414 K+1 During subsequent ranging sessions, if the ranging accuracy continues to be determined to be low, additional bandwidth, for example, bandwidths 426 and 428, may be added incrementally.

[0061]

[0069] 4B is a graph 450 illustrating dynamic control of frequency ranges used with PRS signals across multiple ranging sessions based on the likelihood of LBT success. Dynamic control of frequency ranges used with PRS signals based on LBT success may be in addition to or an alternative to dynamic control of frequency ranges used with PRS signals based on ranging accuracy shown in FIG. 4A. FIG. 4B illustrates, for example, PRS signals 4641, 4642, ..., 464, which may be collectively referred to as PRS signals 464, transmitted by initiator U E (labeled X) or responder U E (labeled A), U E (labeled B), and U E (labeled C) during several (K+1) ranging sessions. K and 464 K+14B, the pre-PRS messages and post-PRS messages during the ranging session are not shown in FIG. 4B. In FIG. 4B, a PRS signal 464 is broadcast over unlicensed spectrum using the LBT procedure. Successful broadcasts of the PRS signal 464 are shown in FIG. 4B by white boxes, while unsuccessful broadcasts of the PRS signal 464 due to LBT failures are shown by dark gray boxes.

[0062]

[0070] As shown in FIG. 4B, the initiator UEX transmits PRS signals 4641, 4642, ..., 464 K 4. As shown in FIG. 4, a ranging session may commence using a first frequency bandwidth 472 for a signal measurement. As shown by the dotted lines, additional or alternative frequency bandwidths 474, 476, and 478 may be available in the unlicensed spectrum, for example, to decrease frequency bandwidth 472, as shown by bandwidth 474, or to increase frequency bandwidth 474, as shown by bandwidths 476 and 478.

[0063]

[0071] One or more of the UEs participating in the ranging session, e.g., the initiator UE, the responding UEs, e.g., UEs 1, 2, and 3, or a combination thereof, may monitor and record the number of successful (or equivalently unsuccessful) LBTs resulting in PRS transmissions over several (K) ranging sessions to generate an indication of successful LBT procedures over several (K) ranging sessions. As described above, the number (K) of ranging sessions may be determined according to the speed of the initiator UE. For example, the average number of successful LBT procedures may be determined based on the number of successful LBT procedures recorded by the UE (e.g., resulting in PRS transmissions by the UE shown in FIG. 4B by the white boxes) divided by the number of ranging sessions (e.g., K ranging sessions). The average number of successful LBT procedures may be compared to a predetermined threshold, e.g., a success threshold γ. For example, if the determined number of LBT successes for a UE (e.g., the average number of successful LBT procedures) is less than a success threshold γ, the UE may flag its LBT procedures over several (K) ranging sessions as low probability. The success threshold γ may be set based on the number of responding UEs (or equivalently, the number of participating UEs, which is simply the number of responding UEs plus the initiating UE). The number of responding UEs may be determined by each participating UE based on the responding UE ID provided in the pre-PRS request message from the initiating UE, if broadcast, or may be included in the pre-PRS request message from the initiating UE, if unicast. For example, the success threshold γ may be set relatively high if there is a large number of responding UEs and relatively low if there are fewer responding UEs.

[0064]

[0072] The responding UE may send an indication of successful LBT procedures over several (K) ranging sessions to the initiating UE X. The message including the indication of successful LBT procedures may include, for example, a flag indicating a low probability of success (or equivalently, a flag indicating a high probability of success). In some implementations, the responding UE may send the average number of successful LBT procedures (or another metric of LBT success), and the initiating UE X may compare the average number of successful LBT procedures with a success threshold γ to flag any responding UE as having a low probability of LBT success (or equivalently, as a high probability).

[0065]

[0073] The responding UE may include an indication of a successful LBT procedure in the same message as the ranging accuracy indication described in Figure 4 A. Thus, for example, the message with the indication of a successful LBT procedure may be in a message that is separate and independent from the ranging session, which may have a period greater than the period of the ranging session, or may be included in a post-PRS message with the same period as the ranging session.

[0066]

[0074] The initiating UEX may use the indication of successful LBT procedures determined by itself, the indication of successful LBT procedures received from each responding UE, or a combination thereof to determine whether to reduce the frequency range of the PRS signal. For example, in one implementation, the initiating UEX may determine whether to reduce the bandwidth of the PRS during a subsequent ranging session based on the indication of successful LBT procedures determined by itself. For example, if the initiating UEX flags its LBT procedures over several (K) ranging sessions as low probability based on the number of LBT successes (e.g., the average number of successful LBT procedures) for the initiating UEX that is less than a success threshold γ, the initiating UEX may decide to reduce the bandwidth of the PRS during a subsequent ranging session.

[0067]

[0075] In another implementation, the initiating UEX may receive an indication of a successful LBT procedure from one or more responding UEs (e.g., the responding UE may send an indication only if its LBT procedure is flagged as low probability). The initiating UEX may determine the number of responding UEs with a low probability of LBT success and may decide to reduce the PRS bandwidth during a subsequent ranging session using some responding UEs with a low probability of LBT success, e.g., by determining whether the number of responding UEs with a low probability of LBT success is above or below a threshold. For example, in one implementation, the initiating UEX may determine the average number of low probabilities of LBT success (e.g., the total number of responding UEs with a low probability of LBT success divided by the total number of responding UEs), compare the average number of low probabilities of LBT success with a threshold, e.g., a UE threshold δ, and reduce the frequency range of the PRS signal if the average number of responding UEs with a low probability of LBT success is greater than the UE threshold δ. The UE threshold δ may be determined according to the number of responding UEs (or equivalently, the number of participating UEs, which is simply the number of responding UEs plus the initiating UE). The number of responding UEs may be determined by each participating UE based on the responding UE ID provided in the pre-PRS request message from the initiating UE, if broadcast, or may be included in the pre-PRS request message from the initiating UE, if unicast. For example, the UE threshold δ may be set relatively high if there is a large number of responding UEs and relatively low if there are fewer responding UEs.

[0068]

[0076] In another implementation, the initiating UE may further include itself with the responding UE in determining the number of UEs with a low probability of LBT success. For example, the initiating UE may compare the total number of UEs (including the initiating UE and the responding UE) with a low probability of LBT success, and may decide to reduce the bandwidth of the PRS during a subsequent ranging session using some UEs with a low probability of LBT success by, for example, determining whether the number of UEs with a low probability of LBT success is above or below a threshold based on the total number of participating UEs.

[0069]

[0077] Therefore, the initiating UEX may determine to reduce the frequency range of the PRS signal during a subsequent ranging session based on the success of the LBT of itself, the responding UE, or a combination thereof. For example, referring to FIG. 4B, after K ranging sessions, the initiating UEX may determine that the frequency range of the PRS signal should be reduced based on the success of the LBT during ranging sessions 1-K. Thus, during the pre-PRS request message for ranging session K+1, the initiating UEX may determine that the initiating UEX and the responding UE are using PRS4641-PRS4642. K A second frequency bandwidth 482 smaller than the first frequency bandwidth 472 used in PRS464 K+1 The frequency bandwidth is reduced in discrete steps, for example by a discrete number of bandwidths 474 (PRS464 K+1 4A ) in a first increment. If the LBT success continues to be determined to be low during subsequent ranging sessions, the additional bandwidth may be gradually decreased. Furthermore, it should be understood that a decrease in the PRS bandwidth due to a low probability of LBT success may be offset by an increase in the PRS bandwidth due to a low ranging accuracy, as described in FIG. 4A .

[0070]

[0078] FIG. 5 illustrates an example of a signaling flow 500 in which the frequency ranges used with PRS signals across multiple ranging sessions are dynamically controlled based on the accuracy of the determined distance and / or the probability of LBT success, as described herein. The initiator UE X 502 and responders UE A 504A, UE B 504B, and UE C 504C (sometimes collectively referred to as responder UEs 504) may be one or more of the vehicle-based UEs (V-UEs) 102 and 104, the RSU 110, or the UE 112, as described in FIG. 1. While FIG. 5 illustrates signaling for a ranging procedure involving three responder UEs 504, it should be understood that there may be additional responder UEs that would involve additional communications and stages similar to those shown in FIG. 5. The communications between the UEs 502 and 504 in FIG. 5 may be direct communications between the entities and may not involve infrastructure devices, such as base stations, for forwarding messages between the entities.

[0071]

[0079] At stage 510, a first ranging session is conducted between the UE 502 and the UE 504 using a first PRS bandwidth (BW1). For example, the ranging session may include pre-PRS messages, PRS signals, and post-PRS messages between the initiating UE 502 and the responding UE 504, for example, as described in FIG. 2. The initiating UE 502 may, for example, send a pre-PRS message to the responding UE 504 that identifies the first PRS bandwidth (BW1) to be used in the ranging session. Each of the UEs 502 and 504 may determine a distance between the transmitting UEs, for example, the initiating UE 502 determines a distance to each responding UE 504, and each responding UE 504 determines a distance to the initiating UE 502 and, in some implementations, a distance to each other responding UE 504. Further, in some implementations, the known location of the anchor UE may be given, for example, in a post-PRS message, and the location of the initiating UE 502 (and any responding UE 504 with an unknown location) may be determined using multilateral positioning and some additional information such as AoA or AoD or position and distance of the PRS signal, or geographic information such as street location.

[0072]

[0080] Multiple ranging sessions may be conducted between UE 502 and UE 504 using the first PRS bandwidth (BW1), similar to stage 510. For example, in stage 520, a Kth ranging session is conducted between UE 502 and UE 504 using the first PRS bandwidth (BW1).

[0073]

[0081] In stage 530X, the initiating UEX 502 may determine the accuracy of the ranging and / or the success of the LBT (e.g., whether the PRS is transmitted over an unlicensed spectrum), for example, as described with respect to FIG. 4A and FIG. 4B. For example, as described in FIG. 4A, the accuracy of the ranging may be determined based on the variance of the determined distance to each responding UE 504 over several (K) ranging sessions. The variance of the distance to each responding UE 504 may be compared to an accuracy threshold α to determine whether each variance should be flagged as indicating a low-accuracy distance for the K ranging sessions. As described above, the value of K and the accuracy threshold α may be based on the speed of the initiating UEX 502.

[0074]

[0082] As described in FIG. 4B , when the PRS is broadcast over an unlicensed spectrum and an LBT procedure is used, the initiating UEX 502 may further determine an indication of LBT success during the PRS transmission. For example, the initiating UEX 502 may determine the number of successful LBT procedures (e.g., the number of successful transmissions of the PRS) during several (K) ranging sessions. The average number of successful LBT procedures may be determined, for example, by dividing the number of successful LBT procedures by the number of PRS transmissions by the initiating UEX 502 during the K ranging sessions. The average number of successful LBT procedures may be compared to a success threshold γ to determine whether the initiating UE has a low probability of a successful LBT procedure, for example, whether the average number of LBT successes for the initiating UEX 502 is less than the success threshold γ. The success threshold γ may be set based on the number of responding UEs 504.

[0075]

[0083] In each of stages 530A, 530B, and 530C, the responding UEs 504, 506, and 508, respectively, may determine the accuracy of the ranging and / or the success of the LBT (e.g., whether the PRS is transmitted over the unlicensed spectrum), e.g., as described with reference to FIGS. 4A and 4B and similar to the description in stage 530X. For example, as described in FIG. 4A, the accuracy of the ranging may be determined based on the variance of the determined distances from the responding UE 504 to the initiating UE 502 over several (K) ranging sessions. In some implementations, the variance of the determined distances among the responding UEs 504 may also be determined. The variances of the distances to the initiating UE 502 (and optionally other responding UEs 504) may be compared to an accuracy threshold α to determine whether each variance should be flagged as indicating a low-accuracy distance for the K ranging sessions. As described above, the value of K and the accuracy threshold α may be based on the velocity of the initiating UE 502 and may be provided by the UE 502 in the pre-PRS message or may be determined independently by the responding UE 504. If the dispersion among the responding UEs 504 is determined, the accuracy threshold used to flag low-accuracy ranging may be based on the velocity of the responding UE 504.

[0076]

[0084] Further, as described in FIG. 4B , when a PRS is broadcast over an unlicensed spectrum and a responding UE 504 performs an LBT procedure, the responding UE 504 may further determine an indication of LBT success during PRS transmission. For example, each responding UE may determine the number of successful LBT procedures (e.g., the number of successful transmissions of the PRS) during several (K) ranging sessions. The average number of successful LBT procedures may be determined, for example, by dividing the number of successful LBT procedures by the number of PRS transmissions by the responding UE 504 during the K ranging sessions. The average number of successful LBT procedures may be compared to a success threshold γ to determine whether the responding UE 504 has a low probability of a successful LBT procedure, for example, whether the average number of LBT successes for the responding UE 504 is less than the success threshold γ. The success threshold gamma γ may be set based on the number of responding UEs 504.

[0077]

[0085] One or more of the responding UEs 504 provide an indication of the determined accuracy of ranging to the initiating UEX 502 (and, optionally, an indication of the probability of LBT success, if determined). The responding UE 504 may, for example, provide an indication to the initiating UEX 502 only if the ranging is determined to be of low accuracy (or, equivalently, if the ranging is determined to be of high accuracy), or each responding UE 504 may provide an indication to the initiating UEX 502 indicating whether the ranging accuracy is low or high. Similarly, if the probability of LBT success is determined, the responding UE 504 may send a message to the initiating UEX 502 only if a low probability of LBT success is determined (or, equivalently, if a high probability of LBT success is determined), or each responding UE 504 may provide an indication to the initiating UEX 502 indicating whether the probability of LBT success is low or high.

[0078]

[0086] In stage 540, for example, the responding UE 504 may provide an indication of the ranging accuracy (and optionally, an indication of the probability of LBT success, if determined) in a message that is separate from the ranging session. For example, if determined, the indication of the ranging accuracy and / or the probability of LBT success may be sent to the initiating UE 502 in an ITS message or other direct message. In some implementations, the indication of the ranging accuracy and / or the probability of LBT success may be a determined metric such as the variance of distance or the number (or average number) of successful LBT procedures, and upon receipt, the initiating UE 502 may apply an appropriate threshold to flag UEs with low-accuracy ranging or a low probability of LBT success. If a separate message such as the message shown in stage 540 is used, the message may be sent at a period greater than the period of the ranging session to reduce overhead.

[0079]

[0087] In another example, at stage 545, the responding UE 504 may provide an indication of ranging accuracy (and optionally, an indication of the probability of LBT success, if determined) in a post-PRS message during a ranging session using the first PRS bandwidth (BW1). In some implementations, the indication of ranging accuracy and / or the probability of LBT success may be a determined metric such as the variance of distance or the number (or average number) of successful LBT procedures, and upon receipt, the initiating UE 502 may apply an appropriate threshold to flag UEs with low-accuracy ranging or a low probability of LBT success. When a post-PRS message such as the message shown in stage 545 is used, the indication of ranging accuracy and / or the probability of LBT success may be sent with the same periodicity as the ranging session, i.e., an indication of ranging accuracy and / or the probability of LBT success over the previous K ranging sessions may be reported during each ranging session.

[0080]

[0088] At stage 550, the initiating UEX 502 determines whether to adjust the bandwidth of the PRS used in a subsequent ranging session between the UE 502 and the UE 504 based on the ranging accuracy (and, optionally, the probability of LBT success) determined during stage 530X and received during stage 540 or 545, as described in FIG. 4A and FIG. 4B. For example, as described in FIG. 4A, if the number (e.g., average) of low accuracy indications is greater than an increase threshold β, the initiating UEX 502 may determine to increase the frequency range of the PRS signal during the subsequent ranging session. The increase threshold β may be based on the accuracy requirement of the ranging application for the initiating UEX 502. Additionally or alternatively, if the probability of LBT success is low for the initiating UEX 502, the responding UE 504, or a combination thereof, the bandwidth of the PRS used in the subsequent ranging session may be decreased, as described in FIG. 4B. For example, as determined in stage 530X, if the probability of LBT success for the initiating UEX502 is low (e.g., the number (e.g., average) of successful LBT procedures over K ranging sessions is less than a success threshold γ), the initiating UEX502 may determine to reduce the bandwidth of the PRS used in the subsequent ranging session. Furthermore, if the number (e.g., average) of responding UEs 504 with a low probability of successful LBT procedures (e.g., received in stage 540 or 545) is greater than a UE threshold δ, the initiating UEX502 may determine to reduce the bandwidth of the PRS used in the subsequent ranging session. Similarly, if the number (e.g., average) of combined initiating UEX502 and responding UEs 504 with a low probability of successful LBT procedures (e.g., received in stage 540 or 545) is greater than a UE threshold δ, the initiating UEX502 may determine to reduce the bandwidth of the PRS used in the subsequent ranging session.A decision to decrease the bandwidth of the PRS used in a subsequent ranging session due to a low probability of LBT success may offset a decision to increase the bandwidth of the PRS used in a subsequent ranging session due to low-accuracy ranging.

[0081]

[0089] In step 560, a new ranging session is conducted between the UE 502 and the UE 504 using a second PRS bandwidth (BW2), which may be different from the first PRS bandwidth BW1, and may be adjusted by the initiating UE 502 based on the determination of step 550. For example, the initiating UE 502 may decide to increase the bandwidth for the PRS (based on low-accuracy ranging without an offsetting decrease in bandwidth due to a low probability of LBT success) and may send a pre-PRS message to the responding UE 504 identifying the increased second PRS bandwidth (BW2) to be used in the new ranging session. In another example, the initiating UE 502 may decide to decrease the bandwidth for the PRS (based on a low probability of LBT success without an offsetting increase in bandwidth due to low-accuracy ranging) and may send a pre-PRS message to the responding UE 504 identifying the reduced second PRS bandwidth (BW2) to be used in the new ranging session. The UE performs ranging using a PRS with the second PRS bandwidth. Each of the UEs 502 and 504 may determine the distance between the transmitting UEs, e.g., the initiating UE 502 determines the distance to each responding UE 504, and each responding UE 504 determines the distance to the initiating UE 502 and, in some implementations, the distance to each other responding UE 504. Further, in some implementations, the known location of the anchor UE may be given, for example, in the post-PRS message, and the location of the initiating UE 502 (and any responding UEs 504 with unknown locations) may be determined using multilateral positioning and some additional information, such as the AoA or AoD or position and distance of the PRS signal, or geographic information such as street location.

[0082]

[0090] The initiating UE 502 and the responding UE 504 may continuously or periodically perform steps 530X, 530A, 530B, 530C, 540 or 545 and 550 during the previous K ranging sessions, for example, the responding UE 504 periodically providing an indication of accuracy and, optionally, success of the LBT in a separate message (as in step 540) or in each post-PRS message (as in step 545).

[0083]

[0091] 6 shows a schematic block diagram illustrating some example features of a user equipment (UE) 600, which may be a UE in a vehicle 102 or 104 shown in FIG. 1 , an RSU 110, or a UE 112 carried by a pedestrian 114. The UE 600 may be configured to act as an initiating UE, e.g., UEX, or a responding UE, e.g., UEA, in which the bandwidth of the PRS may be dynamically adjusted during a ranging session, as described herein. If the UE 600 is a V-UE, it may be configured to control autonomous driving of a vehicle, e.g., the vehicle 102. For example, the UE 600 may include a vehicle interface 605, by means of which commands for autonomous driving may be provided to the vehicle and sensory inputs including speed and acceleration may be provided from the vehicle to the UE 600. The UE 600 may include, for example, one or more processors 602, a memory 604, an inertial measurement unit (IMU) 607, which may include, for example, an accelerometer, a gyroscope, a magnetometer, etc., that may be used to detect the vehicle's orientation relative to a global or local reference frame, and movement or one or more movement characteristics, a satellite positioning system (SPS) receiver 613, for example, for determining a GPS position, and external interfaces, including, for example, a wireless wide area network (WWAN) transceiver 610 and a wireless local area network (WLAN) transceiver 614, that may be operably coupled to one or more connections 606 (e.g., buses, lines, fibers, links, etc.) to the non-transitory computer-readable medium 620 and the memory 604. The UE 600 may further include additional items not shown, such as, for example, a user interface, which may include a display, a keypad such as a virtual keypad on the display, or other input device through which a user may interface with the user device. In some example implementations, all or a portion of the UE 600 may take the form of a chipset or the like.

[0084]

[0092] The transceiver 610 may be, for example, a cellular transceiver configured to transmit and receive direct communications in a wireless network, as shown in FIG. 1. The transceiver 610 may include a transmitter 611 enabled to transmit one or more signals over one or more types of wireless communication networks and a receiver 612 for receiving one or more signals transmitted over one or more types of wireless communication networks. The transceiver 614 may be, for example, a short-range transceiver and may be configured to transmit and receive direct communications in a wireless network, as shown in FIG. 1. The transceiver 614 may include a transmitter 615 enabled to transmit one or more signals, including ranging signals (PRS signals), pre-ranging (pre-PRS) messages, and post-ranging (post-PRS) messages, over one or more types of wireless communication networks, and combine and separate messages, and a receiver 616 for receiving one or more signals, including, for example, PRS, pre-PRS messages, and post-PRS messages, transmitted over one or more types of wireless communication networks. The transceivers 610 and 614 enable the UE 600 to communicate with traffic entities using a D2D communication link, such as DSRC, C-V2X, or 5G NR.

[0085]

[0093] In some embodiments, the UE 600 may include an antenna 609, which may be internal or external. The antenna 609 may be used to transmit and / or receive signals processed by the transceiver 610 and / or transceiver 614. In some embodiments, the antenna 609 may be coupled to the transceiver 610 and / or transceiver 614. In some embodiments, measurements of signals received (transmitted) by the UE 600 may be performed at the connection point between the antenna 609 and the transceiver 610 and / or transceiver 614. For example, measurement points of reference for measurements of received (transmitted) RF signals may be the input (output) terminal of the receivers 612, 616 (transmitters 611, 615) and the output (input) terminal of the antenna 609. In a UE 600 with multiple antennas 609 or an antenna array, the antenna connector may be considered a virtual point representing the aggregate output (input) of the multiple antennas. The phase difference of the received signal at multiple antennas or antenna arrays may be used to determine the AoA of the signal relative to the antenna array, which may be converted to a local or global reference frame based on the known orientation of the UE 600, for example, based on the orientation of the UE 600 measured by the IMU 607.

[0086]

[0094] The one or more processors 602 may be implemented using a combination of hardware, firmware, and software. For example, the one or more processors 602 may be configured to perform the functions described herein by implementing one or more instructions or program code 608 on a non-transitory computer-readable medium, such as the medium 620 and / or the memory 604. In some embodiments, the one or more processors 602 may represent one or more circuits configurable to perform at least a portion of a data signal computing procedure or process related to the operation of the UE 600.

[0087]

[0095] The medium 620 and / or memory 604 may store instructions or program code 608, which, when executed by one or more processors 602, include executable code or software instructions that cause the one or more processors 602 to operate as a special-purpose computer programmed to perform the techniques disclosed herein. As shown in the UE 600, the medium 620 and / or memory 604 may include one or more components or modules that can be implemented by the one or more processors 602 to perform the methods described herein. While the components or modules are shown as software in the medium 620 executable by the one or more processors 602, it should be understood that the components or modules may be stored in the memory 604 or may be dedicated hardware either within or external to the one or more processors 602.

[0088]

[0096] A number of software modules and data tables may reside in the medium 620 and / or memory 604 and be utilized by the one or more processors 602 to manage both the communications and functionality described herein. It should be appreciated that the organization of the contents of the medium 620 and / or memory 604 shown in the UE 600 is only an example, and thus the functionality of the modules and / or data structures may be combined, separated, and / or structured in different ways depending on the implementation of the UE 600.

[0089]

[0097] The medium 620 and / or the memory 604 may include a ranging module 621 that, when implemented by one or more processors 602 as described herein, configures the one or more processors 602 to participate in a ranging session as an initiating UE or a responding UE. The ranging module 621 may include, for example, a pre-ranging module (pre-PRS message module 622), a ranging signal module (PRS module 624), a post-ranging module (post-PRS message module 626), and a ranging module 628.

[0090]

[0098] The medium 620 and / or the memory 604 may include a pre-PRS message module 622 that, when implemented by the one or more processors 602, configures the one or more processors 602 to generate and transmit or receive pre-ranging messages, such as pre-PRS messages, via the transceiver 614 to initiate or accept a ranging session. The pre-PRS messages may be broadcast, multicast, or unicast (using an RRC connection). In some implementations, the PRS messages may be transmitted and received over a licensed spectrum. The pre-PRS messages may be pre-PRS start messages for initiating a ranging session or pre-PRS response messages for acknowledging the pre-PRS start messages. The pre-PRS start message (e.g., a pre-PRS request message from an initiating UE) includes identifiers for the initiating UE and one or more responding UEs for the ranging session and indicates ranging signal resources for participating UEs, including the time and bandwidth of the ranging (PRS) signals to be broadcast during the ranging session. The participating UEs may be determined, for example, from a capability message received by the UE 600. The pre-PRS request message may further include a PRS ID, a session ID, etc. The pre-PRS request message may further provide an indication of the velocity of the initiating UE or other indication for determining the number of ranging sessions (K) over which the accuracy of the ranging (and, optionally, the success of the LBT) is determined, as well as an accuracy threshold α.

[0091]

[0099] The medium 620 and / or memory 604 may include a PRS module 624 that, when implemented by the one or more processors 602 as described herein, configures the one or more processors 602 to broadcast and receive ranging signals to and from other UEs during a ranging session via the transceiver 614 using PRS resources indicated in a pre-PRS request message from the initiating UE. The ranging signals may be PRS signals, such as, for example, quadrature phase shift keying (QPSK) modulated pseudo-noise (PN) sequences, as described herein. The ranging signals may be broadcast in an assigned bandwidth, at an assigned time, and using a PRS identifier assigned in the pre-PRS request message. The ranging signals may be broadcast and received over licensed or unlicensed spectrum in accordance with Category 2 or Category 4 LBT constraints. The success or failure of the LBT procedure over multiple ranging sessions may be monitored and stored. The one or more processors 602 may be configured, for example, to measure the ToD of the broadcasted ranging signal and the ToA of the received ranging signal, and may be configured to measure the AoD of the broadcasted ranging signal and the AoA of the received ranging signal.

[0092]

[0100] The medium 620 and / or memory 604 may include a post-PRS message module 626 that, when implemented by one or more processors 602 as described herein, configures the one or more processors 602 to send and receive post-ranging messages to and from other UEs during a ranging session via the transceiver 614. The post-PRS message may include, for example, an indication of the ToD, and in some implementations, the AoD, of the broadcasted ranging signal and an indication of the ToA, and in some implementations, the AoA, of the received ranging signal. In some implementations, the ToD and ToA indications may be the difference between the ToD and the ToA. In some implementations, the post-PRS message may include an indication of the location of the UE, e.g., whether the UE is an anchor UE used to position another UE. In some implementations, the post-PRS message sent to the initiator UE may include an indication of the accuracy of ranging over several (K) ranging sessions and / or an indication of the probability of success of the LBT over several (K) ranging sessions.

[0093]

[0101] The medium 620 and / or memory 604 may include a ranging module 628 that, when implemented by the one or more processors 602, configures the one or more processors 602 to determine distances to other UEs based on the ToDs and ToAs of broadcast and received ranging signals measured by the UE 600 and received in post-PRS messages from the other UEs.

[0094]

[0102] The medium 620 and / or the memory 604 may include a location module 630 that, when implemented by the one or more processors 602, configures the one or more processors 602 to determine a location for the UE 600 based on, for example, one or more distances to the broadcasting UEs and their location information using multilateral positioning or other suitable techniques as described herein. For example, the one or more processors 602 may implement a Kalman filter or an extended Kalman filter to determine the location of the UE 600.

[0095]

[0103] The medium 620 and / or memory 604 may include an accuracy module 632 that, when implemented by the one or more processors 602, configures the one or more processors 602 to determine an indication of the accuracy of ranging performed by the UE 600 over several (K) ranging sessions. The accuracy of the ranging may be determined based on the variance (or other statistical metric, such as standard deviation) of determined distances to other UEs over several (K) ranging sessions, e.g., to each responding UE if the UE 600 is the initiating UE, or to the initiating UE (and, optionally, other responding UEs) if the UE 600 is the responding UE. The variance of distances over the several (K) ranging sessions to each responder may be compared to an accuracy threshold α to determine whether each variance should be flagged as indicating a low-accuracy distance. The one or more processors 602 may be configured to determine the value of K and the accuracy threshold α based on the velocity of the initiating UE. The one or more processors 602 may be configured to send an indication of the accuracy of ranging over the previous K ranging sessions, e.g., in each post-PRS message, to the initiating UE or receive an indication of the accuracy of ranging over the previous K ranging sessions, via the transceiver 614. In another implementation, the one or more processors 602 may be configured to send a message to the initiating UE or receive an indication of the accuracy of ranging over the previous K ranging sessions, e.g., in an ITS message or other direct message to the initiating UE, via the transceiver 614.

[0096]

[0104] The medium 620 and / or memory 604 may include an LBT success module 634 that, when implemented by the one or more processors 602, configures the one or more processors 602 to determine an indication of a probability of LBT success during PRS transmission over the previous K ranging sessions when the PRS is broadcast over an unlicensed spectrum and an LBT procedure is used. The indication of LBT success may be determined based on the number (e.g., average) of successful LBT procedures over the previous K ranging sessions. The average number of successful LBT procedures may be compared to a success threshold γ to determine whether the UE should be flagged as having a low probability of LBT success, e.g., whether the average number of LBT successes is less than the success threshold γ. The one or more processors 602 may be configured to determine the value of K based on the velocity of the initiating UE and the success threshold γ, which is based on the number of participating or responding UEs during the ranging session. The one or more processors 602 may be configured to send an indication of the probability of success of the LBT over the previous K ranging sessions to the initiating UE or receive an indication of the probability of success of the LBT over the previous K ranging sessions, for example, in each post-PRS message, via the transceiver 614, from the responding UE. In another implementation, the one or more processors 602 may be configured to send a message to the initiating UE or receive an indication of the probability of success of the LBT over the previous K ranging sessions, for example, separate from the ranging session in an ITS message or other direct message to the initiating UE, via the transceiver 614. The probability of success of the LBT may be sent to the initiating UE in the same message as the indication of the ranging accuracy.

[0097]

[0105] The medium 620 and / or memory 604 may include a PRS BW adjustment module 636 that, when implemented by the one or more processors 602, configures the one or more processors 602 to determine whether the PRS bandwidth during a subsequent ranging session, for example, when the UE 600 is an initiating UE, may be increased due to, for example, low ranging accuracy, or decreased due to, for example, a low probability of LBT success, or a combination thereof. The one or more processors 602 may be configured to determine whether the number (e.g., average number) of indications of low accuracy ranging from participating UEs is greater than an increase threshold β, and if so, the frequency range used for PRS signals during the subsequent ranging session is gradually increased. The one or more processors 602 may be configured to determine the increase threshold β based on the accuracy requirement of the ranging application for the initiating UE 502. Additionally or alternatively, the one or more processors 602 may be configured to determine whether the probability of LBT success for the initiating UE, the responding UE, or a combination thereof is low, and if so, gradually reduce the frequency range used for PRS signals during subsequent ranging sessions. For example, the one or more processors 602 may be configured to determine whether the probability of LBT success for the initiating UE is low based on whether the number (e.g., average) of successful LBT procedures performed by the initiating UE over K ranging sessions is less than a success threshold γ. In another example, the one or more processors 602 may be configured to determine whether the probability of LBT success for the responding UE is low based on whether the number (e.g., average) of responding UEs indicating a low probability of LBT success is greater than a UE threshold δ. In another example, the one or more processors 602 may be configured to determine whether the probability of LBT success for all participating UEs (including the initiating UE and the responding UE) is low based on whether the number (e.g., average) of all UEs indicating a low probability of LBT success is greater than a UE threshold δ.The one or more processors 602 can be configured to determine the UE threshold δ based on the number of responding or participating UEs in a ranging session. The one or more processors 602 can be configured to adjust the PRS bandwidth during a subsequent ranging session based on a determination that the PRS bandwidth during the subsequent ranging session should be adjusted.

[0098]

[0106] The methods described herein may be implemented by various means depending on the application. For example, these methods may be implemented in hardware, firmware, software, or any combination thereof. In a hardware implementation, the one or more processors 602 may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, or combinations thereof.

[0099]

[0107] For a firmware and / or software implementation, the methods may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. Any machine-readable medium tangibly embodying instructions may be used in implementing the methodologies described herein. For example, software code may be stored in non-transitory computer-readable medium 620 or memory 604 coupled to and executed by one or more processors 602. The memory may be implemented within the one or more processors or external to the one or more processors. The term "memory," as used herein, may refer to long-term, short-term, volatile, non-volatile, or any other type of memory, and should not be limited to a specific type or number of memories or the type of medium on which the memory is stored.

[0100]

[0108] If implemented in firmware and / or software, the functions may be stored as one or more instructions or program code 608 on a non-transitory computer-readable medium, such as medium 620 and / or memory 604. Examples include computer-readable media encoded with data structures and computer-readable media encoded with computer program code 608. For example, a non-transitory computer-readable medium having program code 608 stored thereon may include program code 608 for supporting adjustment of the bandwidth of PRS signals during a ranging session in a manner consistent with disclosed embodiments. The non-transitory computer-readable medium 620 includes a physical computer storage medium. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such non-transitory 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 store desired program code 608 in the form of instructions or data structures and that can be accessed by a computer; as used herein, disk and disc include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs; disks typically reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0101]

[0109] In addition to being stored on the computer-readable medium 620, the instructions and / or data may be provided as signals on a transmission medium contained within a communications device. For example, a communications device may include a transceiver 610 having signals indicative of instructions and data. The instructions and data are configured to cause one or more processors to implement the functions outlined in the claims. That is, the communications device includes a transmission medium with signals indicative of information to perform the disclosed functions.

[0102]

[0110] Memory 604 may represent any data storage mechanism. Memory 604 may include, for example, primary memory and / or secondary memory. Primary memory may include, for example, random access memory, read-only memory, etc. While shown in this example as being separate from one or more processors 602, it should be understood that all or a portion of the primary memory may be provided within one or more processors 602 or, in some cases, co-located / coupled with one or more processors 602. Secondary memory may include, for example, the same or similar type of memory as the primary memory and / or one or more data storage devices or systems, such as, for example, disk drives, optical disk drives, tape drives, solid-state memory drives, etc.

[0103]

[0111] In some implementations, the secondary memory may be operatively capable of receiving, or possibly configurable to couple to, a non-transitory computer-readable medium 620. Thus, in some example implementations, the methods and / or apparatuses presented herein may take the form, in whole or in part, of a computer-readable medium 620, which may include computer-implementable code 608 stored thereon, which, when executed by one or more processors 602, may be operatively enabled to perform all or a portion of the example operations described herein. The computer-readable medium 620 may be part of the memory 604.

[0104]

[0112] 7 is a flowchart 700 illustrating a method of ranging performed by an initiating UE in a distributed system of UEs. The initiating UE may be, for example, UEX in FIGS. 2, 3, 4A, 4B, 5 or UE 600 in FIG. 6.

[0105]

[0113] In block 702, the initiating UE may initiate multiple ranging sessions using the first ranging signal bandwidth with multiple responding UEs, for example, as described in steps 510 and 520 of Figures 2 and 3 and Figure 5. The means for initiating multiple ranging sessions using the first ranging signal bandwidth with multiple responding UEs may be, for example, the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a ranging module 621 and a pre-PRS message module 622.

[0106]

[0114] At block 704, the initiating UE may determine a distance to each responding UE during each ranging session, e.g., as described in steps 510 and 520 of Figures 2 and 3 and 5. The means for determining a distance to each responding UE during each ranging session may be, e.g., the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as ranging module 621 and ranging module 628.

[0107]

[0115] At block 706, the initiating UE determines an indication of the accuracy of ranging to each responding UE during the multiple ranging sessions, e.g., as described in Figures 4A and 5 at stage 530X. The means for determining an indication of the accuracy of ranging to each responding UE during the multiple ranging sessions may be one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632.

[0108]

[0116] At block 708, the initiating UE receives from one or more responding UEs an indication of the accuracy of the ranging measurements determined by each responding UE during the multiple ranging sessions, e.g., as described in Figure 4A and steps 540 and 545 of Figure 5. For example, the indication of the accuracy of the ranging measurements received from each of the one or more responding UEs may be received in a message that is separate from the ranging session, e.g., the message shown in step 540 of Figure 5. In another example, the indication of the accuracy of the ranging measurements received from each of the one or more responding UEs may be received in a post-ranging message during each ranging session, such as the message shown in step 545 of Figure 5. The means for receiving from one or more responding UEs an indication of the accuracy of the ranging determined by each responding UE during multiple ranging sessions may be, for example, a transceiver 614 and one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as a ranging module 621, a post-PRS message module 626, and an accuracy module 632.

[0109]

[0117] In block 710, the initiating UE determines to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs, for example, as described in step 550 of Figures 4A and 5. The means for determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs can be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the PRS BW adjustment module 636.

[0110]

[0118] In one implementation, the indication of accuracy of ranging to each responding UE may be determined over a predetermined number of ranging sessions, for example, as described in stage 530X of FIG. 4A and FIG. 5, where the predetermined number of ranging sessions is based on the velocity of the initiating UE. The initiating UE may determine the indication of accuracy of ranging to each responding UE during the multiple ranging sessions by determining a variance of the determined distance to each responding UE over the predetermined number of ranging sessions and comparing the variance of the determined distance to each responding UE to a predetermined threshold, for example, as described in stage 530X of FIG. 4A and FIG. 5. The indication of accuracy of ranging to each responding UE during the multiple ranging sessions may be based on a comparison of the variance of the determined distance to each responding UE to a predetermined threshold, for example, as described in stage 530X of FIG. 4A and FIG. 5. The predetermined threshold may be based on the velocity of the initiating UE, for example. The means for determining the variance of the determined distance to each responding UE over a predetermined number of ranging sessions may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632. The means for comparing the variance of the determined distance to each responding UE with a predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632.

[0111]

[0119] In some implementations, the initiating UE may determine to adjust the first ranging signal bandwidth to the second ranging signal bandwidth by determining a number of indications of accuracy of ranging based on the ranging accuracy indication to each responding UE and the ranging accuracy indications received from one or more responding UEs, for example, as described in stage 550 of Figures 4A and 5. The initiating UE may compare the number of ranging accuracy indications with a predetermined threshold, for example, as described in stage 550 of Figures 4A and 5. The initiating UE may determine to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold, for example, as described in stage 550 of Figures 4A and 5. The means for determining the number of ranging accuracy indications based on the ranging accuracy indication to each responding UE and the ranging accuracy indications received from one or more responding UEs may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the accuracy module 632 and the PRS BW adjustment module 636. The means for comparing the number of ranging accuracy indications with a predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the PRS BW adjustment module 636. The means for determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the PRS BW adjustment module 636.

[0112]

[0120] For example, the initiating UE may determine the number of ranging accuracy indications by determining an average number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, where the average number of ranging accuracy indications is compared to a predetermined threshold, e.g., as described in step 550 of Figures 4A and 5. The initiating UE may further initiate new ranging sessions with the multiple responding UEs using the second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold, e.g., as described in steps 550 and 560 of Figures 4A and 5. The predetermined threshold may be based on an accuracy requirement for the ranging session, for example. Determining an average number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, wherein the average number of ranging accuracy indications is compared to a predetermined threshold, can be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a PRS BW adjustment module 636. Means for initiating new ranging sessions with the multiple responding UEs using the second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold can be, for example, the transceiver 614 and one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a ranging module 621, a pre-PRS message module 622, and a PRS BW adjustment module 636.

[0113]

[0121] In one implementation, ranging signals during the multiple ranging sessions may be broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure. The initiating UE may determine to adjust the first ranging signal bandwidth to the second ranging signal bandwidth further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from one or more responding UEs regarding a probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof, as described in step 550 of FIG. 4B and FIG. 5 .

[0114]

[0122] For example, in one implementation, the initiating UE may record the number of successful LBT procedures performed by the initiating UE during several ranging sessions, e.g., as described in stage 530X of Figures 4B and 5. The means for recording the number of successful LBT procedures performed by the initiating UE during several ranging sessions may be, e.g., the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the ranging module 621, the PRS module 624, and the LBT success module 634. The initiating UE may determine an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during several ranging sessions, e.g., as described in stage 530X of Figures 4B and 5. The means for determining the average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during several ranging sessions may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as LBT success module 634. The initiating UE may compare the average number of successful LBT procedures with a predetermined threshold, for example, as described in stage 550 of FIG. 4B and FIG. 5. The means for comparing the average number of successful LBT procedures with a predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as LBT success module 634. The initiating UE may determine to reduce the first ranging signal bandwidth during the new ranging session based on the comparison of the average number of successful LBT procedures with the predetermined threshold, for example, as described in stage 550 of FIG. 4B and FIG. 5.The means for determining to reduce the first ranging signal bandwidth during a new ranging session based on a comparison of the average number of successful LBT procedures and a predetermined threshold may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as PRS BW adjustment module 636. For example, as described in steps 530X and 550 of FIG. 4B and FIG. 5, for example, the number of ranging sessions among the multiple ranging sessions may be a predetermined number based on the speed of the initiating UE, and the predetermined threshold may be based on the number of responding UEs.

[0115]

[0123] In another example, in one implementation, the initiating UE may receive from one or more responding UEs an indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions, e.g., as described in FIG. 4B and stages 540 and 545 of FIG. 5. The means for receiving from one or more responding UEs an indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions may be, for example, the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a ranging module 621, a post-PRS message module 626, and an LBT success module 634. The initiating UE may determine the number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions, as described, for example, in FIG. 4B and in stage 550 of FIG. 5. The means for determining the number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as LBT success module 634. The initiating UE may compare the number of UEs with a probability of a successful LBT procedure with a predetermined threshold, as described, for example, in FIG. 4B and in stage 550 of FIG. 5. The means for comparing the number of UEs with a probability of a successful LBT procedure with a predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as an LBT success module 634.The initiating UE may determine to reduce the first ranging signal bandwidth during the new ranging session based on a comparison between the number of UEs with a probability of a successful LBT procedure and a predetermined threshold, for example, as described in FIG. 4B and step 550 of FIG. 5. The means for determining to reduce the first ranging signal bandwidth during the new ranging session based on a comparison between the number of UEs with a probability of a successful LBT procedure and a predetermined threshold may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the PRS BW adjustment module 636. For example, the number of UEs with a probability of a successful LBT procedure may be further based on the probability of a successful LBT procedure determined by the initiating UE, for example, as described in FIG. 4B and step 530X and step 550 of FIG. 5. For example, the number of ranging sessions may be a predetermined number based on the speed of the initiating UE, and the predetermined threshold may be based on the number of responding UEs, as described in FIG. 4B and step 530X and step 550 of FIG. 5.

[0116]

[0124] In one implementation, the initiating UE may adjust the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to the decision to adjust the first ranging signal bandwidth to the second ranging signal bandwidth, for example, as described in stage 560 of Figures 4A and 5. The means for adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to the decision to adjust the first ranging signal bandwidth to the second ranging signal bandwidth may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the PRS BW adjustment module 636.

[0117]

[0125] 8 is a flowchart 800 illustrating a method of ranging performed by a responding UE in a distributed system of UEs. The responding UE may be, for example, UE A in FIGS. 2, 3, 4A, 4B, 5 or UE 600 in FIG. 6.

[0118]

[0126] In block 802, the responding UE may receive from the initiating UE the initiation of multiple ranging sessions using the first ranging signal bandwidth, e.g., as described in steps 510 and 520 of Figures 2 and 3 and Figure 5. The means for receiving from the initiating UE the initiation of multiple ranging sessions using the first ranging signal bandwidth may be, e.g., the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a ranging module 621 and a pre-PRS message module 622.

[0119]

[0127] At block 804, the responding UE may determine a distance to the initiating UE during each ranging session, e.g., as described in steps 510 and 520 of Figures 2 and 3 and 5. The means for determining a distance to the initiating UE during each ranging session may be, e.g., the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as ranging module 621 and ranging module 628.

[0120]

[0128] In block 806, the responding UE determines an indication of accuracy of ranging to the initiating UE during the multiple ranging sessions, e.g., as described in Figures 4A and stage 530A of Figure 5. The means for determining an indication of accuracy of ranging to the initiating UE during the multiple ranging sessions may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632.

[0121]

[0129] At block 808, the responding UE sends an indication of the ranging accuracy to the initiating UE, e.g., as described in FIG. 4A and steps 540 and 545 of FIG. 5. For example, the indication of the ranging accuracy may be sent in a message that is separate from the ranging session, e.g., the message shown in step 540 of FIG. 5. In another example, the indication of the ranging accuracy may be sent in a post-ranging message during each ranging session, such as the message shown in step 545 of FIG. 5. The means for sending the indication of the ranging accuracy to the initiating UE may be, for example, the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the ranging module 621, the post-PRS message module 626, and the accuracy module 632.

[0122]

[0130] In block 810, the responding UE receives from the initiating UE initiation of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and at least partially responsive to the ranging accuracy indication sent to the initiating UE, e.g., as described in Figure 4A and step 560 of Figure 5. The means for receiving from the initiating UE initiation of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and at least partially responsive to the ranging accuracy indication sent to the initiating UE can be, e.g., the transceiver 614 and one or more processors 602 having dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as a ranging module 621 and a pre-PRS message module 622.

[0123]

[0131] In one implementation, the indication of the accuracy of the ranging is determined over a predetermined number of ranging sessions, for example, as described in stage 530A of Figures 4A and 5, where the predetermined number of ranging sessions is based on the velocity of the initiating UE. The responding UE may determine the indication of the accuracy of the ranging to the initiating UE during multiple ranging sessions by, for example, determining a variance of the distance to the initiating UE over the predetermined number of ranging sessions and comparing the variance of the distance to a predetermined threshold, for example, as described in stage 530A of Figures 4A and 5. The indication of the accuracy of the ranging may be based on, for example, a comparison of the variance of the distance to a predetermined threshold, for example, as described in stage 530A of Figures 4A and 5. The predetermined threshold may be based on, for example, the velocity of the initiating UE. The means for determining the variance of distance to the initiating UE over a predetermined number of ranging sessions may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632. The means for comparing the variance of distance to a predetermined threshold may be, for example, one or more processors 602 with dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as accuracy module 632.

[0124]

[0132] In one implementation, ranging signals during the multiple ranging sessions may be broadcast over the unlicensed spectrum using a listen-before-transmit (LBT) procedure. The responding UE may determine an indication of the probability of successful LBT procedures performed during the multiple ranging sessions, for example, as described in step 530A of FIG. 4B and FIG. 5. The means for determining the indication of the probability of successful LBT procedures performed during the multiple ranging sessions may be, for example, the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the ranging module 621, the PRS module 624, and the LBT success module 634. The responding UE may send an indication of the probability of successful LBT procedures to the initiating UE, for example, as described in steps 540 and 545 of FIG. 4B and FIG. 5. The means for sending the indication of the probability of a successful LBT procedure to the initiating UE may be, for example, the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the ranging module 621, the post-PRS message module 626, and the LBT success module 634. The initiation of a new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure, for example, as described in steps 550 and 560 of FIG.

[0125]

[0133] For example, in one implementation, the responding UE may record the number of successful LBT procedures performed during several ranging sessions, e.g., as described in stage 530A of Figures 4B and 5. The means for recording the number of successful LBT procedures performed during several ranging sessions may be, e.g., the transceiver 614 and one or more processors 602 with dedicated hardware or implementing executable code or software instructions in the memory 604 and / or medium 620, such as the ranging module 621, the PRS module 624, and the LBT success module 634. The responding UE may determine an average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during several ranging sessions, e.g., as described in stage 530A of Figures 4B and 5. The means for determining the average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during a number of ranging sessions may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as LBT success module 634. The responding UE may compare the average number of successful LBT procedures with a predetermined threshold, for example, as described in stage 530A of FIG. 4B and FIG. 5. The means for comparing the average number of successful LBT procedures with a predetermined threshold may be, for example, one or more processors 602 having dedicated hardware or implementing executable code or software instructions in memory 604 and / or medium 620, such as LBT success module 634. The indication of the probability of successful LBT procedures may be based on a comparison of the average number of successful LBT procedures with a predetermined threshold, for example, as described in stage 530A of FIG. 4B and FIG. 5.For example, as described in step 530A of Figures 4B and 5, the number of ranging sessions may be a predetermined number based, for example, on the speed of the initiating UE, and the predetermined threshold may be based on the number of responding UEs.

[0126]

[0134] References throughout this specification to "one example," "an example," "certain examples," or "exemplary implementation" mean that a particular feature, structure, or characteristic described with respect to a feature and / or example may be included in at least one feature and / or example of the claimed subject matter. Thus, appearances of the phrases "in one example," "an example," "in certain examples," or "in certain implementations," or other similar phrases, in various places throughout this specification do not necessarily all refer to the same features, examples, and / or limitations. Furthermore, particular features, structures, or characteristics may be combined in one or more examples and / or characteristics.

[0127]

[0135] Some portions of the detailed descriptions contained herein have been presented in terms of algorithms or symbolic representations of operations on binary digital signals stored within the memory of a particular apparatus or special-purpose computing device or platform. In the context of this particular specification, the term particular apparatus or the like includes a general-purpose computer that has been programmed to perform particular operations pursuant to instructions from program software. Algorithmic descriptions or symbolic representations are examples of techniques used by those skilled in the signal processing or related arts to convey the substance of their work to others skilled in the art. An algorithm, as used herein, and generally, is considered to be a self-consistent sequence of operations or similar signal processing leading to a desired result. In this context, operations or processing involve physical manipulations of physical quantities. Typically, though not necessarily, such quantities may take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, primarily for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, numbers, numerals, or the like. It should be understood, however, that all of these or similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless otherwise expressly stated, as will be apparent from the description herein, it should be appreciated that throughout this specification, descriptions utilizing terms such as "processing," "computing," "calculating," "determining," and the like refer to the operations or processes of a particular apparatus, such as a special purpose computer, a special purpose computing apparatus, or a similar special purpose electronic computing device. Thus, in the context of this specification, a special purpose computer or a similar special purpose electronic computing device is capable of manipulating or transforming signals, generally represented as electronic or magnetic physical quantities, within the memory, registers, or other information storage, transmission, or display devices of the special purpose computer or similar special purpose electronic computing device.

[0128]

[0136] In the above detailed description, numerous specific details have been set forth to provide a thorough understanding of the claimed subject matter. However, it will be understood by those skilled in the art that the claimed subject matter may be practiced without these specific details. In other instances, methods and apparatuses that would be known to those skilled in the art have not been described in detail so as not to obscure the claimed subject matter.

[0129]

[0137] As used herein, the terms "and," "or," and "and / or" can have a variety of meanings that are expected to depend, at least in part, on the context in which such terms are used. In general, when "or" is used to link a list such as A, B, or C, it shall mean A, B, and C, which is used herein in an inclusive sense, as well as A, B, or C, which is used herein in an exclusive sense. Furthermore, as used herein, the term "one or more" may be used to describe any feature, structure, or characteristic in the singular, or it may be used to describe multiple features, structures, or characteristics, or some other combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example, and that claimed subject matter is not limited to this example.

[0130]

[0138] While what are presently considered to be exemplary features have been illustrated and described, those skilled in the art will recognize that various other modifications may be made and equivalents may be substituted without departing from the claimed subject matter. Additionally, many modifications may be made to adapt a particular situation to the teachings of claimed subject matter without departing from the central concept described herein.

[0131]

[0139] Example implementations are described in the following numbered clauses.

[0132]

[0140] Clause 1. A method of ranging performed by an initiating UE in a distributed system of user equipment (UE), comprising: initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of ranging accuracy to each responding UE during the multiple ranging sessions; receiving from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0133]

[0141] Clause 2. The method of clause 1, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session.

[0134]

[0142] Clause 3. The method of any of clauses 1 or 2, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session.

[0135]

[0143] Clause 4. The method of any of clauses 1 to 3, wherein the indication of ranging accuracy to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the velocity of the initiating UE.

[0136]

[0144] Clause 5. The method of clause 4, wherein determining an indication of accuracy of ranging to each responding UE during the multiple ranging sessions comprises determining a variance of determined distances to each responding UE over a predetermined number of ranging sessions, and comparing the variance of determined distances to each responding UE with a predetermined threshold, wherein the indication of accuracy of ranging to each responding UE during the multiple ranging sessions is based on a comparison of the variance of determined distances to each responding UE with the predetermined threshold.

[0137]

[0145] Clause 6. The method of clause 5, wherein the predetermined threshold is based on a speed of the initiating UE.

[0138]

[0146] Clause 7. The method of any of clauses 1 to 6, wherein determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth comprises: determining a number of ranging accuracy indications based on the ranging accuracy indications to each responding UE and the ranging accuracy indications received from the one or more responding UEs; comparing the number of ranging accuracy indications with a predetermined threshold; and determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold.

[0139]

[0147] Clause 8. The method of clause 7, wherein determining the number of ranging accuracy indications comprises determining an average of the number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, wherein the average number of ranging accuracy indications is compared to a predetermined threshold, and the method further comprises initiating new ranging sessions with the multiple responding UEs using a second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold.

[0140]

[0148] Clause 9. The method of clause 8, wherein the predetermined threshold is based on an accuracy requirement for the ranging session.

[0141]

[0149] Clause 10. The method of any of clauses 1 to 9, wherein the ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and wherein determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth is further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from one or more responding UEs regarding a probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof.

[0142]

[0150] Clause 11. The method of clause 10, further comprising: recording a number of successful LBT procedures performed by the initiating UE during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; and determining to reduce a first ranging signal bandwidth during a new ranging session based on a comparison between the average number of successful LBT procedures and the predetermined threshold.

[0143]

[0151] Clause 12. The method of clause 11, wherein the number of ranging sessions among the multiple ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0144]

[0152] Clause 13. The method of clause 10, further comprising: receiving, from one or more responding UEs, an indication of a probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; comparing the number of UEs with the probability of a successful LBT procedure with a predetermined threshold; and determining to reduce a first ranging signal bandwidth during the new ranging session based on a comparison of the number of UEs with the probability of a successful LBT procedure with the predetermined threshold.

[0145]

[0153] Clause 14. The method of clause 13, wherein the number of UEs with a probability of successful LBT procedure is further based on a probability of successful LBT procedure determined by the initiating UE.

[0146]

[0154] Clause 15. The method of clause 13, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0147]

[0155] Clause 16. The method of any of clauses 1-15, further comprising adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during a new ranging session in response to a decision to adjust the first ranging signal bandwidth to the second ranging signal bandwidth.

[0148]

[0156] Clause 17. An initiating UE configured to perform ranging between UEs in a distributed system of user equipment (UE), the initiating UE including: a wireless transceiver configured to wirelessly communicate with an entity in a wireless network; at least one memory; and at least one processor coupled to the wireless transceiver and the at least one memory, wherein the at least one processor is configured to: initiate multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; determine a distance to each responding UE during each ranging session; determine an indication of ranging accuracy to each responding UE during the multiple ranging sessions; receive from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and determine to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0149]

[0157] Clause 18. The initiating UE of clause 17, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session.

[0150]

[0158] Clause 19. An initiating UE according to either clause 17 or 18, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session.

[0151]

[0159] Clause 20. An initiating UE according to any of clauses 17 to 19, wherein the indication of ranging accuracy to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the speed of the initiating UE.

[0152]

[0160] Clause 21. The initiating UE of Clause 20, configured to determine an indication of the accuracy of ranging to each responding UE during multiple ranging sessions by configuring at least one processor to: determine a variance of the determined distance to each responding UE over a predetermined number of ranging sessions; and compare the variance of the determined distance to each responding UE with a predetermined threshold, wherein the indication of the accuracy of ranging to each responding UE during the multiple ranging sessions is based on a comparison of the variance of the determined distance to each responding UE with the predetermined threshold.

[0153]

[0161] Clause 22. The initiating UE of clause 21, wherein the predetermined threshold is based on a speed of the initiating UE.

[0154]

[0162] Clause 23. An initiating UE as described in any of Clauses 17 to 22, wherein at least one processor is configured to determine a number of ranging accuracy indications based on the ranging accuracy indications to each responding UE and the ranging accuracy indications received from one or more responding UEs, compare the number of ranging accuracy indications with a predetermined threshold, and decide to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold.

[0155]

[0163] Clause 24. The initiating UE of Clause 23, wherein the at least one processor is configured to determine the number of ranging accuracy indications by determining an average number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, wherein the average number of ranging accuracy indications is compared to a predetermined threshold, and the at least one processor is further configured to initiate new ranging sessions with the multiple responding UEs using a second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold.

[0156]

[0164] Clause 25. The initiating UE of clause 24, wherein the predetermined threshold is based on an accuracy requirement for the ranging session.

[0157]

[0165] Clause 26. The initiating UE of any of Clauses 17 to 25, wherein the ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and wherein the at least one processor is configured to determine to adjust the first ranging signal bandwidth to the second ranging signal bandwidth further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from one or more responding UEs regarding the probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof.

[0158]

[0166] Clause 27. The initiating UE of Clause 26, wherein the at least one processor is further configured to: record a number of successful LBT procedures performed by the initiating UE during a number of ranging sessions; determine an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during the number of ranging sessions; compare the average number of successful LBT procedures with a predetermined threshold; and determine to reduce the first ranging signal bandwidth during the new ranging session based on the comparison of the average number of successful LBT procedures with the predetermined threshold.

[0159]

[0167] Clause 28. The initiating UE of clause 27, wherein the number of ranging sessions among the plurality of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0160]

[0168] Clause 29. The initiating UE of Clause 26, wherein the at least one processor is further configured to: receive from one or more responding UEs an indication of a probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determine a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; compare the number of UEs with the probability of a successful LBT procedure with a predetermined threshold; and determine to reduce the first ranging signal bandwidth during the new ranging session based on a comparison of the number of UEs with the probability of a successful LBT procedure with the predetermined threshold.

[0161]

[0169] Clause 30. The initiating UE of clause 29, wherein the number of UEs with a probability of successful LBT procedure is further based on a probability of successful LBT procedure determined by the initiating UE.

[0162]

[0170] Clause 31. The initiating UE of clause 29, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0163]

[0171] Clause 32. The initiating UE of any of Clauses 17 to 31, wherein the at least one processor is further configured to adjust the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to a decision to adjust the first ranging signal bandwidth to the second ranging signal bandwidth.

[0164]

[0172] Clause 33. An initiating UE configured to perform ranging between UEs in a distributed system of user equipment (UE), the initiating UE comprising: means for initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; means for determining a distance to each responding UE during each ranging session; means for determining an indication of ranging accuracy to each responding UE during the multiple ranging sessions; means for receiving from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and means for determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0165]

[0173] Clause 34. The initiating UE of clause 33, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session.

[0166]

[0174] Clause 35. An initiating UE according to either clause 33 or 34, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session.

[0167]

[0175] Clause 36. An initiating UE according to any of clauses 33 to 35, wherein the indication of ranging accuracy to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the speed of the initiating UE.

[0168]

[0176] Clause 37. The initiating UE of clause 36, wherein the means for determining an indication of accuracy of ranging to each responding UE during the multiple ranging sessions comprises: means for determining a variance of determined distances to each responding UE over a predetermined number of ranging sessions; and means for comparing the variance of determined distances to each responding UE with a predetermined threshold, wherein the indication of accuracy of ranging to each responding UE during the multiple ranging sessions is based on a comparison of the variance of determined distances to each responding UE with the predetermined threshold.

[0169]

[0177] Clause 38. The initiating UE of clause 37, wherein the predetermined threshold is based on a speed of the initiating UE.

[0170]

[0178] Clause 39. An initiator UE as described in any of Clauses 33 to 38, wherein the means for determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth comprises: means for determining a number of ranging accuracy indications based on the ranging accuracy indications to each responding UE and the ranging accuracy indications received from one or more responding UEs; means for comparing the number of ranging accuracy indications with a predetermined threshold; and means for determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold.

[0171]

[0179] Clause 40. The initiating UE of Clause 39, wherein the means for determining the number of ranging accuracy indications comprises means for determining an average number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, wherein the average number of ranging accuracy indications is compared to a predetermined threshold, and the initiating UE further comprises means for initiating new ranging sessions with the multiple responding UEs using a second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold.

[0172]

[0180] Clause 41. The initiating UE according to clause 40, wherein the predetermined threshold is based on an accuracy requirement for the ranging session.

[0173]

[0181] Clause 42. An initiating UE as described in any of Clauses 33 to 41, wherein the ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and wherein the means for determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth further uses at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from one or more responding UEs regarding the probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof.

[0174]

[0182] Clause 43. The initiating UE of Clause 42, further comprising: means for recording a number of successful LBT procedures performed by the initiating UE during a number of ranging sessions; means for determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during the number of ranging sessions; means for comparing the average number of successful LBT procedures with a predetermined threshold; and means for determining to reduce the first ranging signal bandwidth during the new ranging session based on a comparison between the average number of successful LBT procedures and the predetermined threshold.

[0175]

[0183] Clause 44. The initiating UE of clause 43, wherein the number of ranging sessions among the plurality of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0176]

[0184] Clause 45. The initiating UE of clause 42, further comprising: means for receiving from one or more responding UEs an indication of a probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; means for determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; means for comparing the number of UEs with the probability of a successful LBT procedure with a predetermined threshold; and means for determining to reduce the first ranging signal bandwidth during the new ranging session based on a comparison of the number of UEs with the probability of a successful LBT procedure with the predetermined threshold.

[0177]

[0185] Clause 46. The initiating UE of clause 45, wherein the number of UEs with a probability of successful LBT procedure is further based on a probability of successful LBT procedure determined by the initiating UE.

[0178]

[0186] Clause 47. The initiating UE of clause 45, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0179]

[0187] Clause 48. The initiating UE of any of clauses 33 to 47, further comprising means for adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to a decision to adjust the first ranging signal bandwidth to the second ranging signal bandwidth.

[0180]

[0188] Clause 49. A non-transitory storage medium having program code stored thereon, the program code operable to configure at least one processor in an initiating UE for ranging between UEs in a distributed system of user equipments (UEs), the program code comprising instructions for initiating multiple ranging sessions with multiple responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of ranging accuracy to each responding UE during the multiple ranging sessions; receiving from one or more responding UEs an indication of ranging accuracy determined by each responding UE during the multiple ranging sessions; and determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during the new ranging session based on the indication of ranging accuracy to each responding UE and the indication of ranging accuracy received from the one or more responding UEs.

[0181]

[0189] Clause 50. The non-transitory storage medium of clause 49, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session.

[0182]

[0190] Clause 51. A non-transitory storage medium according to either clause 49 or 50, wherein the indication of the accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session.

[0183]

[0191] Clause 52. A non-transitory storage medium according to any of clauses 49 to 51, wherein the indication of ranging accuracy to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the velocity of the initiating UE.

[0184]

[0192] Clause 53. The non-transitory storage medium of Clause 52, wherein the program code for determining an indication of accuracy of ranging to each responding UE during a plurality of ranging sessions comprises: determining a variance of determined distances to each responding UE over a predetermined number of ranging sessions; and comparing the variance of determined distances to each responding UE to a predetermined threshold; wherein the indication of accuracy of ranging to each responding UE during the plurality of ranging sessions is based on a comparison of the variance of determined distances to each responding UE to the predetermined threshold.

[0185]

[0193] Clause 54. The non-transitory storage medium of clause 53, wherein the predetermined threshold is based on a speed of the initiating UE.

[0186]

[0194] Clause 55. A non-transitory storage medium according to any of Clauses 49 to 54, wherein the program code for determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth comprises program code for: determining a number of ranging accuracy indications based on the ranging accuracy indications to each responding UE and the ranging accuracy indications received from one or more responding UEs; comparing the number of ranging accuracy indications with a predetermined threshold; and determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications with the predetermined threshold.

[0187]

[0195] Clause 56. The non-transitory storage medium of Clause 55, wherein the program code for determining the number of ranging accuracy indications comprises program code for determining an average of the number of ranging accuracy indications for all UEs participating in the multiple ranging sessions, wherein the average number of ranging accuracy indications is compared to a predetermined threshold, and the non-transitory storage medium further comprises program code for initiating new ranging sessions with the multiple responding UEs using a second ranging signal bandwidth in response to comparing the average number of ranging accuracy indications to the predetermined threshold.

[0188]

[0196] Clause 57. The non-transitory storage medium of clause 56, wherein the predetermined threshold is based on an accuracy requirement for the ranging session.

[0189]

[0197] Clause 58. The non-transitory storage medium of any of clauses 49 to 57, wherein the ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and wherein the program code for determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth further uses at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from one or more responding UEs regarding the probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof.

[0190]

[0198] Clause 59. The non-transitory storage medium of Clause 58, further comprising program code for: recording a number of successful LBT procedures performed by the initiating UE during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiating UE and the number of LBT procedures performed by the initiating UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; and determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison of the average number of successful LBT procedures with the predetermined threshold.

[0191]

[0199] Clause 60. The non-transitory storage medium of clause 59, wherein the number of ranging sessions among the plurality of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0192]

[0200] Clause 61. The non-transitory storage medium of clause 58, further comprising program code for: receiving, from one or more responding UEs, an indication of a probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; comparing the number of UEs with the probability of a successful LBT procedure with a predetermined threshold; and determining to reduce a first ranging signal bandwidth during the new ranging session based on a comparison of the number of UEs with the probability of a successful LBT procedure with the predetermined threshold.

[0193]

[0201] Clause 62. The non-transitory storage medium of clause 61, wherein the number of UEs with a probability of a successful LBT procedure is further based on a probability of a successful LBT procedure determined by the initiating UE.

[0194]

[0202] Clause 63. The non-transitory storage medium of clause 61, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0195]

[0203] Clause 64. The non-transitory storage medium of Clause 63, further comprising program code for adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during a new ranging session in response to a determination to adjust the first ranging signal bandwidth to the second ranging signal bandwidth.

[0196]

[0204] Clause 65. A method of ranging performed by a responding UE in a distributed system of user equipment (UE), comprising: receiving initiation of multiple ranging sessions from an initiating UE using a first ranging signal bandwidth; determining a distance to the initiating UE during each ranging session; determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; sending the indication of ranging accuracy to the initiating UE; and receiving initiation of a new ranging session from the initiating UE using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0197]

[0205] Clause 66. The method of clause 65, wherein the indication of the accuracy of the ranging is sent in a message that is separate from the ranging session.

[0198]

[0206] Clause 67. The method of either clause 65 or 66, wherein the indication of the accuracy of the ranging is sent in a post ranging message during each ranging session.

[0199]

[0207] Clause 68. The method of any of clauses 65 to 67, wherein the indication of the ranging accuracy is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE.

[0200]

[0208] Clause 69. The method of clause 68, wherein determining an indication of accuracy of ranging to the initiating UE during multiple ranging sessions comprises determining a variance of distances to the initiating UE over a predetermined number of ranging sessions and comparing the variance of distances to a predetermined threshold, wherein the indication of accuracy of ranging is based on a comparison of the variance of distances to the predetermined threshold.

[0201]

[0209] Clause 70. The method of clause 69, wherein the predetermined threshold is based on a speed of the initiating UE.

[0202]

[0210] Clause 71. The method of any of clauses 65-70, wherein the ranging signals during the multiple ranging sessions are broadcast over the unlicensed spectrum using a listen-before-transmit (LBT) procedure, the method further comprising: determining an indication of a probability of a successful LBT procedure performed during the multiple ranging sessions; and sending the indication of the probability of a successful LBT procedure to the initiating UE; and wherein initiating a new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure.

[0203]

[0211] Clause 72. The method of clause 71, wherein determining an indication of the probability of successful LBT procedures comprises: recording a number of successful LBT procedures performed during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during the number of ranging sessions; and comparing the average number of successful LBT procedures with a predetermined threshold, wherein the indication of the probability of successful LBT procedures is based on comparing the average number of successful LBT procedures with the predetermined threshold.

[0204]

[0212] Clause 73. The method of clause 72, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0205]

[0213] Clause 74. A responding UE configured to perform ranging between UEs in a distributed system of user equipment (UE), the responding UE comprising: a wireless transceiver configured to wirelessly communicate with an entity in a wireless network; at least one memory; and at least one processor coupled to the wireless transceiver and the at least one memory, wherein the at least one processor is configured to: receive initiation of multiple ranging sessions from an initiating UE using a first ranging signal bandwidth; determine a distance to the initiating UE during each ranging session; determine an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; send the indication of ranging accuracy to the initiating UE; and receive initiation of a new ranging session from the initiating UE using a second ranging signal bandwidth different from the first ranging signal bandwidth, the responding UE being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0206]

[0214] Clause 75. The responding UE of clause 74, wherein the indication of the ranging accuracy is sent in a message that is separate from the ranging session.

[0207]

[0215] Clause 76. The responding UE of either clause 74 or 75, wherein the indication of the ranging accuracy is sent in a post ranging message during each ranging session.

[0208]

[0216] Clause 77. A responding UE according to any of clauses 74 to 76, wherein the indication of the accuracy of the ranging is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE.

[0209]

[0217] Clause 78. The responding UE of Clause 77, configured to determine an indication of accuracy of ranging to the initiating UE during multiple ranging sessions by configuring at least one processor to: determine a variance of distances to the initiating UE over a predetermined number of ranging sessions; and compare the variance of distances to a predetermined threshold; wherein the indication of accuracy of ranging is based on the comparison of the variance of distances to the predetermined threshold.

[0210]

[0218] Clause 79. The responding UE of clause 78, wherein the predetermined threshold is based on a speed of the initiating UE.

[0211]

[0219] Clause 80. A responding UE as described in any of clauses 74 to 79, wherein ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and wherein the at least one processor is further configured to: determine an indication of a probability of a successful LBT procedure performed during the multiple ranging sessions; and send the indication of the probability of a successful LBT procedure to the initiating UE; and wherein initiation of a new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure.

[0212]

[0220] Clause 81. The responding UE of clause 80, configured to determine an indication of the probability of successful LBT procedures by configuring at least one processor to: record a number of successful LBT procedures performed during a number of ranging sessions; determine an average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during the number of ranging sessions; and compare the average number of successful LBT procedures with a predetermined threshold, wherein the indication of the probability of successful LBT procedures is based on the comparison of the average number of successful LBT procedures with the predetermined threshold.

[0213]

[0221] Clause 82. The responding UE of clause 81, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on the number of responding UEs.

[0214]

[0222] Clause 83. A responding UE configured for ranging between UEs in a distributed system of user equipment (UE), the responding UE comprising: means for receiving initiation of multiple ranging sessions from an initiating UE using a first ranging signal bandwidth; means for determining a distance to the initiating UE during each ranging session; means for determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; means for sending the indication of ranging accuracy to the initiating UE; and means for receiving initiation of a new ranging session from the initiating UE using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0215]

[0223] Clause 84. The responding UE of clause 83, wherein the indication of the ranging accuracy is sent in a message that is separate from the ranging session.

[0216]

[0224] Clause 85. The responding UE of either clause 83 or 84, wherein the indication of the ranging accuracy is sent in a post ranging message during each ranging session.

[0217]

[0225] Clause 86. A responding UE according to any of clauses 83 to 85, wherein the indication of the accuracy of the ranging is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the velocity of the initiating UE.

[0218]

[0226] Clause 87. The responding UE of clause 86, wherein the means for determining an indication of accuracy of ranging to the initiating UE during a plurality of ranging sessions comprises: means for determining a variance of distances to the initiating UE over a predetermined number of ranging sessions; and means for comparing the variance of distances to a predetermined threshold, wherein the indication of accuracy of ranging is based on a comparison of the variance of distances to the predetermined threshold.

[0219]

[0227] Clause 88. The responding UE of clause 87, wherein the predetermined threshold is based on a speed of the initiating UE.

[0220]

[0228] Clause 89. The responding UE of any of clauses 83-88, further comprising: means for determining an indication of a probability of a successful LBT procedure performed during the multiple ranging sessions, wherein the ranging signals during the multiple ranging sessions are broadcast over the unlicensed spectrum using a listen-before-transmit (LBT) procedure; and means for sending the indication of the probability of a successful LBT procedure to the initiating UE, wherein initiating a new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure.

[0221]

[0229] Clause 90. The responding UE of clause 89, wherein the means for determining an indication of the probability of successful LBT procedures comprises: means for recording a number of successful LBT procedures performed during a number of ranging sessions; means for determining an average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during the number of ranging sessions; and means for comparing the average number of successful LBT procedures with a predetermined threshold, wherein the indication of the probability of successful LBT procedures is based on comparing the average number of successful LBT procedures with the predetermined threshold.

[0222]

[0230] Clause 91. The responding UE of clause 91, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0223]

[0231] Clause 92. A non-transitory storage medium having program code stored thereon, the program code operable to configure at least one processor in a responding UE for ranging between UEs in a distributed system of user equipment (UE), the program code comprising instructions for receiving from an initiating UE initiation of multiple ranging sessions using a first ranging signal bandwidth; determining a distance to the initiating UE during each ranging session; determining an indication of ranging accuracy to the initiating UE during the multiple ranging sessions; sending the indication of ranging accuracy to the initiating UE; and receiving from the initiating UE initiation of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth, the new ranging session being at least partially responsive to the indication of ranging accuracy sent to the initiating UE.

[0224]

[0232] Clause 93. The non-transitory storage medium of clause 92, wherein the indication of the accuracy of the ranging is sent in a message that is separate from the ranging session.

[0225]

[0233] Clause 94. The non-transitory storage medium of either clause 92 or 93, wherein the indication of the accuracy of the ranging is sent in a post ranging message during each ranging session.

[0226]

[0234] Clause 95. A non-transitory storage medium according to any of clauses 92 to 94, wherein the indication of the ranging accuracy is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on the velocity of the initiating UE.

[0227]

[0235] Clause 96. The non-transitory storage medium of clause 85, wherein the program code for determining an indication of accuracy of ranging to the initiating UE during multiple ranging sessions comprises program code for: determining a variance of distances to the initiating UE over a predetermined number of ranging sessions; and comparing the variance of distances to a predetermined threshold; and wherein the indication of accuracy of ranging is based on the comparison of the variance of distances to the predetermined threshold.

[0228]

[0236] Clause 97. The non-transitory storage medium of clause 96, wherein the predetermined threshold is based on a speed of the initiating UE.

[0229]

[0237] Clause 98. The non-transitory storage medium of any of clauses 92-97, further comprising program code for: determining an indication of a probability of a successful LBT procedure performed during the multiple ranging sessions, wherein the ranging signals during the multiple ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure; and sending the indication of the probability of a successful LBT procedure to an initiating UE, wherein initiating a new ranging session including a second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure.

[0230]

[0238] Clause 99. The non-transitory storage medium of clause 98, comprising: program code for determining an indication of the probability of a successful LBT procedure; recording a number of successful LBT procedures performed during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures and the number of LBT procedures performed by the responding UE during the number of ranging sessions; and comparing the average number of successful LBT procedures with a predetermined threshold, wherein the indication of the probability of a successful LBT procedure is based on comparing the average number of successful LBT procedures with the predetermined threshold.

[0231]

[0239] Clause 100. The non-transitory storage medium of clause 99, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

[0232]

[0240] Accordingly, it is intended that claimed subject matter not be limited to the particular examples disclosed, but that such claimed subject matter also include all embodiments falling within the scope of the appended claims and their equivalents. The inventions described in the claims of the present application as originally filed are set forth below. [C1] 1. A method of ranging performed by an initiating user equipment (UE) in a distributed system of UEs, comprising: initiating a plurality of ranging sessions with a plurality of responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of accuracy of ranging to each responding UE during the plurality of ranging sessions; receiving from one or more responding UEs an indication of an accuracy of ranging determined by each responding UE during the plurality of ranging sessions; determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during a new ranging session based on the indication of accuracy of the ranging to each responding UE and the indication of accuracy of the ranging received from the one or more responding UEs; A method comprising: [C2] The method of C1, wherein the indication of accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session. [C3] The method of C1, wherein the indication of accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session. [C4] The method of C1, wherein the indication of the accuracy of the ranging to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE. [C5] Determining the indication of the accuracy of the ranging to each responding UE during the plurality of ranging sessions comprises: determining a variance of the determined distances to each responding UE over the predetermined number of ranging sessions; comparing the variance of the determined distances to each responding UE with a predetermined threshold; wherein the indication of the accuracy of the ranging to each responding UE during the plurality of ranging sessions is based on the comparison of the variance of the determined distance to each responding UE to the predetermined threshold. The method of claim C4, comprising: [C6] The method of C5, wherein the predetermined threshold is based on the velocity of the initiating UE. [C7] determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth; determining a number of ranging accuracy indications based on the indication of the ranging accuracy to each responding UE and the indications of the ranging accuracy received from the one or more responding UEs; comparing the number of indications of accuracy of the ranging to a predetermined threshold; determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications to the predetermined threshold; and The method of C1, comprising: [C8] determining the number of ranging accuracy indications comprises determining an average of the number of ranging accuracy indications for all UEs participating in the plurality of ranging sessions, wherein the average number of ranging accuracy indications is compared to the predetermined threshold; The method includes initiating the new ranging session with the plurality of responding UEs using the second ranging signal bandwidth in response to the comparison of the average of the number of ranging accuracy indications to the predetermined threshold. The method of C7, further comprising: [C9] The method of C8, wherein the predetermined threshold is based on an accuracy requirement for the ranging session. [C10] ranging signals during the plurality of ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, The method of claim 1, wherein determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth is further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from the one or more responding UEs regarding a probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof. [C11] recording a number of successful LBT procedures performed by the initiator UE during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiator UE and a number of LBT procedures performed by the initiator UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the average number of successful LBT procedures and the predetermined threshold; and The method of C10, further comprising: [C12] The method of C11, wherein the number of ranging sessions among the plurality of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs. [C13] receiving from the one or more responding UEs the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during the some of the ranging sessions among the plurality of ranging sessions; comparing the number of UEs with the probability of a successful LBT procedure to a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the number of UEs having the probability of a successful LBT procedure and the predetermined threshold; and The method of C10, further comprising: [C14] The method of C13, wherein the number of UEs with the probability of a successful LBT procedure is further based on the probability of a successful LBT procedure determined by the initiating UE. [C15] The method of C13, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs. [C16] responsive to a determination to adjust the first ranging signal bandwidth to the second ranging signal bandwidth, adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session. [C17] 1. An initiating user equipment (UE) configured for ranging between UEs in a distributed system of UEs, comprising: a wireless transceiver configured to wirelessly communicate with entities in a wireless network; at least one memory; at least one processor coupled to the wireless transceiver and the at least one memory; wherein the at least one processor comprises: initiating a plurality of ranging sessions with a plurality of responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of accuracy of ranging to each responding UE during the plurality of ranging sessions; receiving from one or more responding UEs an indication of an accuracy of ranging determined by each responding UE during the plurality of ranging sessions; determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during a new ranging session based on the indication of accuracy of the ranging to each responding UE and the indication of accuracy of the ranging received from the one or more responding UEs; an initiating UE configured to: [C18] The initiating UE of C17, wherein the indication of accuracy of the ranging received from each of the one or more responding UEs is received in a message that is separate from the ranging session. [C19] The initiating UE of C17, wherein the indication of accuracy of the ranging received from each of the one or more responding UEs is received in a post ranging message during each ranging session. [C20] The initiating UE of C17, wherein the indication of the accuracy of the ranging to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE. [C21] The at least one processor: determining a variance of the determined distances to each responding UE over the predetermined number of ranging sessions; comparing the variance of the determined distances to each responding UE with a predetermined threshold; wherein the indication of the accuracy of the ranging to each responding UE during the plurality of ranging sessions is based on the comparison of the variance of the determined distance to each responding UE to the predetermined threshold. 20. The initiator UE of claim 19, wherein the initiator UE is configured to determine the indication of accuracy of the ranging to each responder UE during the multiple ranging sessions by being configured to perform the following: [C22] The initiating UE of C21, wherein the predetermined threshold is based on the velocity of the initiating UE. [C23] The at least one processor: determining a number of ranging accuracy indications based on the indication of the ranging accuracy to each responding UE and the indications of the ranging accuracy received from the one or more responding UEs; comparing the number of indications of accuracy of the ranging to a predetermined threshold; determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications to the predetermined threshold; and 18. The initiator UE of claim 17, configured to determine to adjust the first ranging signal bandwidth to the second ranging signal bandwidth by being configured to perform: [C24] the at least one processor is configured to determine the number of ranging accuracy indications by determining an average of the number of ranging accuracy indications for all UEs participating in the plurality of ranging sessions, wherein the average of the number of ranging accuracy indications is compared to the predetermined threshold; the at least one processor is further configured to initiate the new ranging session with the plurality of responding UEs using the second ranging signal bandwidth in response to the comparison of the average of the number of ranging accuracy indications to the predetermined threshold. The initiator UE according to C23. [C25] The initiating UE of C24, wherein the predetermined threshold is based on an accuracy requirement for the ranging session. [C26] ranging signals during the plurality of ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, 18. The initiating UE of claim 17, wherein the at least one processor is configured to determine to adjust the first ranging signal bandwidth to the second ranging signal bandwidth further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from the one or more responding UEs regarding a probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof. [C27] The at least one processor: recording a number of successful LBT procedures performed by the initiator UE during a number of ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiator UE and a number of LBT procedures performed by the initiator UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the average number of successful LBT procedures and the predetermined threshold; and 27. The initiating UE of claim 26, further configured to: [C28] The initiating UE of C27, wherein the number of ranging sessions among the plurality of ranging sessions is a predetermined number based on a velocity of the initiating UE, and the predetermined threshold is based on a number of responding UEs. [C29] The at least one processor: receiving from the one or more responding UEs the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during the some of the ranging sessions among the plurality of ranging sessions; comparing the number of UEs with the probability of a successful LBT procedure to a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the number of UEs having the probability of a successful LBT procedure and the predetermined threshold; and 27. The initiating UE of claim 26, further configured to: [C30] The initiating UE of C29, wherein the number of UEs with the probability of a successful LBT procedure is further based on the probability of a successful LBT procedure determined by the initiating UE. [C31] The initiating UE of C29, wherein the number of ranging sessions is a predetermined number based on a velocity of the initiating UE, and the predetermined threshold is based on a number of responding UEs. [C32] 18. The initiator UE of claim 17, wherein the at least one processor is further configured to adjust the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to a determination to adjust the first ranging signal bandwidth to the second ranging signal bandwidth. [C33] 1. A method of ranging performed by a responding user equipment (UE) in a distributed system of UEs, comprising: receiving from an initiating UE an initiation of a plurality of ranging sessions using a first ranging signal bandwidth; determining a distance to the initiator UE during each ranging session; determining an indication of accuracy of ranging to the initiating UE during the plurality of ranging sessions; sending the indication of the accuracy of the ranging to the initiator UE; receiving from the initiating UE a start of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and responsive at least in part to the indication of accuracy of the ranging sent to the initiating UE; A method comprising: [C34] The method of C33, wherein the indication of the accuracy of the ranging is sent in a message that is separate from the ranging session. [C35] The method of C33, wherein the indication of the accuracy of the ranging is sent in a post ranging message during each ranging session. [C36] The method of C33, wherein the indication of the accuracy of the ranging is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE. [C37] Determining the indication of the accuracy of the ranging to the initiating UE during the plurality of ranging sessions includes: determining a variance of the distances to the initiator UE over the predetermined number of ranging sessions; comparing the variance of the distances to a predetermined threshold; wherein the indication of the accuracy of the ranging is based on the comparison of the variance of the distances to the predetermined threshold. The method of C36, comprising: [C38] The method of C37, wherein the predetermined threshold is based on the velocity of the initiating UE. [C39] The ranging signals during the plurality of ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, and the method includes: determining an indication of a probability of a successful LBT procedure being performed during said plurality of ranging sessions; sending the indication of the probability of a successful LBT procedure to the initiating UE, wherein the initiation of the new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure. The method of C33, further comprising: [C40] Determining the indication of the probability of a successful LBT procedure comprises: Recording the number of successful LBT procedures performed during several ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures and a number of LBT procedures performed by the responding UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; wherein the indication of the probability of successful LBT procedures is based on the comparison of the average number of successful LBT procedures to the predetermined threshold. The method of C39, comprising: [C41] The method of C40, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs. [C42] 1. A responding user equipment (UE) configured for ranging between UEs in a distributed system of UEs, comprising: a wireless transceiver configured to wirelessly communicate with entities in a wireless network; at least one memory; at least one processor coupled to the wireless transceiver and the at least one memory; wherein the at least one processor comprises: receiving from an initiating UE an initiation of a plurality of ranging sessions using a first ranging signal bandwidth; determining a distance to the initiator UE during each ranging session; determining an indication of accuracy of ranging to the initiating UE during the plurality of ranging sessions; sending the indication of the accuracy of the ranging to the initiator UE; receiving from the initiating UE a start of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and responsive at least in part to the indication of accuracy of the ranging sent to the initiating UE; a responding UE configured to: [C43] The responding UE of C42, wherein the indication of the accuracy of the ranging is sent in a message that is separate from the ranging session. [C44] The responding UE of C42, wherein the indication of the accuracy of the ranging is sent in a post ranging message during each ranging session. [C45] The responding UE of C42, wherein the indication of the accuracy of the ranging is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE. [C46] The at least one processor: determining a variance of the distances to the initiator UE over the predetermined number of ranging sessions; comparing the variance of the distances to a predetermined threshold; wherein the indication of the accuracy of the ranging is based on the comparison of the variance of the distances to the predetermined threshold. 46. ​​The responding UE of claim 45, wherein the responding UE is configured to determine the indication of accuracy of the ranging to the initiating UE during the multiple ranging sessions by being configured to perform the following: [C47] The responding UE of C46, ​​wherein the predetermined threshold is based on the velocity of the initiating UE. [C48] ranging signals during the plurality of ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, wherein the at least one processor: determining an indication of a probability of a successful LBT procedure being performed during said plurality of ranging sessions; sending the indication of the probability of a successful LBT procedure to the initiating UE, wherein the initiation of the new ranging session including the second ranging signal bandwidth is further at least partially responsive to the indication of the probability of a successful LBT procedure. The responding UE of C42, further configured to: [C49] The at least one processor: Recording the number of successful LBT procedures performed during several ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures and a number of LBT procedures performed by the responding UE during the number of ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; wherein the indication of the probability of successful LBT procedures is based on the comparison of the average number of successful LBT procedures to the predetermined threshold. 49. The responding UE of claim 48, wherein the responding UE is configured to determine the indication of the probability of a successful LBT procedure by being configured to: [C50] The responding UE of C49, wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

Claims

1. 1. A method of ranging performed by an initiating user equipment (UE) in a distributed system of UEs, comprising: initiating a plurality of ranging sessions with a plurality of responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of accuracy of ranging to each responding UE during the plurality of ranging sessions; receiving from one or more responding UEs an indication of an accuracy of ranging determined by each responding UE during the plurality of ranging sessions; determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during a new ranging session based on the indication of accuracy of the ranging to each responding UE and the indication of accuracy of the ranging received from the one or more responding UEs; A method comprising:

2. The indication of accuracy of the ranging received from each of the one or more responding UEs comprises: received in a message that is separate from the ranging session; or The method of claim 1 , wherein the ranging time is received in a post-ranging message during each ranging session.

3. 2. The method of claim 1, wherein the indication of the accuracy of the ranging to each responding UE is determined over a predetermined number of ranging sessions, wherein the predetermined number of ranging sessions is based on a velocity of the initiating UE.

4. Determining the indication of the accuracy of the ranging to each responding UE during the plurality of ranging sessions comprises: determining a variance of the determined distances to each responding UE over the predetermined number of ranging sessions; comparing the variance of the determined distances to each responding UE with a predetermined threshold; wherein the indication of the accuracy of the ranging to each responding UE during the plurality of ranging sessions is based on the comparison of the variance of the determined distances to each responding UE to the predetermined threshold, wherein the predetermined threshold is based on the velocity of the initiating UE. The method of claim 3 comprising:

5. determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth comprises: determining a number of ranging accuracy indications based on the indication of the ranging accuracy to each responding UE and the indications of ranging accuracy received from the one or more responding UEs; comparing the number of indications of accuracy of the ranging to a predetermined threshold; determining to increase the first ranging signal bandwidth to the second ranging signal bandwidth based on the comparison of the number of ranging accuracy indications to the predetermined threshold; and The method of claim 1 , comprising:

6. determining the number of ranging accuracy indications comprises determining an average of the number of ranging accuracy indications for all UEs participating in the plurality of ranging sessions, wherein the average number of ranging accuracy indications is compared to the predetermined threshold; The method includes initiating the new ranging session with the plurality of responding UEs using the second ranging signal bandwidth in response to the comparison of the average of the number of ranging accuracy indications to the predetermined threshold.

6. The method of claim 5, further comprising: wherein the predetermined threshold is based on an accuracy requirement for the ranging session.

7. ranging signals during the plurality of ranging sessions are broadcast over an unlicensed spectrum using a listen-before-transmit (LBT) procedure, wherein:

2. The method of claim 1, wherein determining to adjust the first ranging signal bandwidth to the second ranging signal bandwidth is further based on at least one of a probability of a successful LBT procedure determined by the initiating UE during the multiple ranging sessions, an indication received from the one or more responding UEs regarding a probability of a successful LBT procedure performed by each responding UE during the multiple ranging sessions, or a combination thereof.

8. Recording the number of successful LBT procedures performed by the initiator UE during several ranging sessions; determining an average number of successful LBT procedures based on the number of successful LBT procedures performed by the initiator UE and the number of LBT procedures performed by the initiator UE during the several ranging sessions; comparing the average number of successful LBT procedures with a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the average number of successful LBT procedures and the predetermined threshold; and 8. The method of claim 7, further comprising:

9. receiving from the one or more responding UEs the indication of the probability of a successful LBT procedure performed by each responding UE during some ranging sessions among the plurality of ranging sessions; determining a number of UEs with a probability of a successful LBT procedure based at least on the indication of the probability of a successful LBT procedure performed by each responding UE during the some ranging sessions among the plurality of ranging sessions; comparing the number of UEs with the probability of a successful LBT procedure with a predetermined threshold; determining to reduce the first ranging signal bandwidth during the new ranging session based on the comparison between the number of UEs with the probability of a successful LBT procedure and the predetermined threshold; and The method of claim 7 further comprising:

10. 10. The method of claim 9, wherein the number of UEs with the probability of a successful LBT procedure is further based on the probability of a successful LBT procedure determined by the initiating UE.

11. The method of claim 9 , wherein the number of ranging sessions is a predetermined number based on a speed of the initiating UE, and the predetermined threshold is based on a number of responding UEs.

12. 10. The method of claim 1, further comprising: adjusting the first ranging signal bandwidth to the second ranging signal bandwidth during the new ranging session in response to a determination to adjust the first ranging signal bandwidth to the second ranging signal bandwidth.

13. 1. An initiating user equipment (UE) configured for ranging between UEs in a distributed system of UEs, comprising: a wireless transceiver configured to wirelessly communicate with entities in a wireless network; at least one memory; at least one processor coupled to the wireless transceiver and the at least one memory; wherein the at least one processor comprises: initiating a plurality of ranging sessions with a plurality of responding UEs using a first ranging signal bandwidth; determining a distance to each responding UE during each ranging session; determining an indication of accuracy of ranging to each responding UE during the plurality of ranging sessions; receiving from one or more responding UEs an indication of an accuracy of ranging determined by each responding UE during the plurality of ranging sessions; determining to adjust the first ranging signal bandwidth to a second ranging signal bandwidth different from the first ranging signal bandwidth during a new ranging session based on the indication of accuracy of the ranging to each responding UE and the indication of accuracy of the ranging received from the one or more responding UEs; an initiating UE configured to:

14. 1. A method of ranging performed by a responding User Equipment (UE) in a distributed system of UEs, comprising: receiving from an initiating UE an initiation of a plurality of ranging sessions using a first ranging signal bandwidth; determining a distance to the initiator UE during each ranging session; determining an indication of accuracy of ranging to the initiating UE during the plurality of ranging sessions; sending the indication of the accuracy of the ranging to the initiating UE; receiving from the initiating UE a start of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and at least partially responsive to the indication of accuracy of the ranging sent to the initiating UE; A method comprising:

15. 1. A responding user equipment (UE) configured for ranging between UEs in a distributed system of UEs, comprising: a wireless transceiver configured to wirelessly communicate with entities in a wireless network; at least one memory; at least one processor coupled to the wireless transceiver and the at least one memory; wherein the at least one processor comprises: receiving from an initiating UE an initiation of a plurality of ranging sessions using a first ranging signal bandwidth; determining a distance to the initiator UE during each ranging session; determining an indication of accuracy of ranging to the initiating UE during the plurality of ranging sessions; sending the indication of the accuracy of the ranging to the initiating UE; receiving from the initiating UE a start of a new ranging session using a second ranging signal bandwidth different from the first ranging signal bandwidth and at least partially responsive to the indication of accuracy of the ranging sent to the initiating UE; a responding UE configured to:

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