Deadlock prevention techniques for RSU synchronization chains

Abstract

Deadlock prevention techniques for roadside unit (RSU) synchronization chains are disclosed. Techniques may include, when a first synchronization reference is a synchronization reference source for a wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier, transmitting a sidelink synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, employing a second synchronization reference as a synchronization reference source for the wireless communication device, opening a wait interval, and after expiration of the wait interval, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and suppressing transmission of the SLSS on the wireless carrier when the second reference signal is not detected on the wireless carrier.

Description

Technical Field

[0001] The present disclosure generally relates to the field of wireless communications, and more particularly, to synchronizing timing of devices in a wireless communication system. Background Art

[0002] Vehicle-to-everything (V2X) communication systems may be deployed along roads to provide wireless data connectivity to vehicles traveling on the roads. The V2X communication systems may include a V2X roadside unit (RSU) that may communicate with a V2X onboard unit (OBU) of a passing vehicle. Successful communication between the V2X RSU and the V2X OBU may depend on the establishment of timing synchronization between these various devices. Summary of the invention

[0003] According to the present disclosure, an example method for wireless communication by a wireless communication device may include: when a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier, sending a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopting a second synchronization reference as a synchronization reference source for the wireless communication device, starting a waiting interval. And after the waiting interval expires, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, refraining from sending the SLSS on the wireless carrier.

[0004] An example wireless communication device according to the present disclosure may include a transceiver, a memory, and one or more processors communicatively coupled to the transceiver and the memory, wherein the one or more processors are configured to, when the first synchronization reference is a synchronization reference source for the wireless communication device, detect a first reference signal associated with the first synchronization reference on a wireless carrier, send a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopt a second synchronization reference as a synchronization reference source for the wireless communication device, start a waiting interval, and after expiration of the waiting interval, monitor a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, refrain from sending the SLSS on the wireless carrier.

[0005] An example apparatus for a wireless communication device according to the present disclosure may include: a component for detecting a first reference signal associated with a first synchronization reference on a wireless carrier when the first synchronization reference is a synchronization reference source for the wireless communication device, a component for sending a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and a component for: in response to a subsequent determination that the first synchronization reference has become unavailable, adopting a second synchronization reference as a synchronization reference source for the wireless communication device, starting a waiting interval, and after expiration of the waiting interval, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, suppressing sending the SLSS on the wireless carrier.

[0006] According to the present disclosure, an example non-transitory computer-readable medium may store instructions for wireless communication by a wireless communication device, the instructions including code, the code being used to: when a first synchronization reference is a synchronization reference source for the wireless communication device, detect a first reference signal associated with the first synchronization reference on a wireless carrier, send a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopt a second synchronization reference as the synchronization reference source for the wireless communication device, start a waiting interval, and after the waiting interval expires, monitor a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, suppress sending the SLSS on the wireless carrier.

[0007] The present summary is neither intended to identify the key or essential features of the claimed subject matter nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of the present disclosure, any or all of the drawings, and each claim. The foregoing and other features and examples will be described in more detail below in the following specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram of a positioning system according to an embodiment.

[0009] Figure 2 is a diagram of a fifth generation (5G) new radio (NR) positioning system, which shows a positioning system implemented within a 5G NR communication network (e.g., Figure 1 An embodiment of a positioning system).

[0010] Figure 3 is a diagram showing an example of a frame structure and associated terminology for NR.

[0011] Figure 4is a diagram illustrating an example of a wireless communication system.

[0012] Figure 5 is a diagram illustrating an example of an operating environment.

[0013] Figure 6 is a diagram showing an example of a first event flow.

[0014] Figure 7 is a diagram showing an example of the second event flow.

[0015] Figure 8 is a flow chart of a method for wireless communication by a wireless communication device according to an embodiment.

[0016] Fig. 9 is a block diagram of an embodiment of a UE that may be used in embodiments as described herein.

[0017] Fig.10 is a block diagram of an embodiment of a base station that may be used in embodiments as described herein.

[0018] According to some example embodiments, the same reference symbols in various drawings indicate the same elements. In addition, multiple instances of an element can be indicated by following a letter or hyphen and a second digit after the first digit of the element. For example, multiple instances of element 110 can be indicated as 110-1, 110-2, 110-3, etc., or as 110a, 110b, 110c, etc. When only the first digit is used to refer to such an element, any instance of the element will be understood (for example, the element 110 in the previous example will refer to elements 110-1, 110-2 and 110-3 or to elements 110a, 110b and 110c). DETAILED DESCRIPTION

[0019] The following description is directed to certain implementations for the purpose of describing the innovative aspects of various embodiments. However, one of ordinary skill in the art will readily recognize that the teachings herein may be applied in a variety of different ways. The described implementations may be implemented in any device, system, or network capable of sending and receiving radio frequency (RF) signals according to any communication standard, such as any of the following: the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard for ultra-wideband (UWB), the IEEE 802.11 standard (including those identified as Technical standards), Standard, Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), GSM / General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband CDMA (W-CDMA), Evolution-Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Rate Packet Data (HRPD), High Speed ​​Packet Access (HSPA), High Speed ​​Downlink Packet Access (HSDPA), High Speed ​​Uplink Packet Access (HSUPA), Evolved High Speed ​​Packet Access (HSPA+), Long Term Evolution (LTE), Advanced Mobile Phone System (AMPS), or other known signals for communicating within a wireless, cellular or Internet of Things (IoT) network (such as systems or technologies utilizing 3G, 4G, 5G, 6G or further implementations thereof).

[0020] As used herein, an "RF signal" includes electromagnetic waves that transmit information through the space between a transmitter (or transmitting device) and a receiver (or receiving device). As used herein, a transmitter may transmit a single "RF signal" or multiple "RF signals" to a receiver. However, due to the propagation characteristics of RF signals through multiple channels or paths, a receiver may receive multiple "RF signals" corresponding to each transmitted RF signal.

[0021] Additionally, unless otherwise specified, references to "reference signals," "positioning reference signals," "reference signals used for positioning," and the like may be used to refer to signals used for positioning of user equipment (UE). As described in more detail herein, such signals may include any of a variety of signal types, but may not necessarily be limited to positioning reference signals (PRS) as defined in relevant wireless standards.

[0022] Figure 1is a simplified illustration of a positioning system 100 according to an embodiment, wherein UE 105, location server 160, and / or other components of positioning system 100 can use the techniques provided herein for deadlock prevention of RSU synchronization chains. The techniques described herein can be implemented by one or more components of positioning system 100. The positioning system 100 may include: a UE 105; one or more satellites 110 (also referred to as space vehicles (SVs), which may include global navigation satellite system (GNSS) satellites (e.g., satellites of the Global Positioning System (GPS), GLONASS, Galileo, BeiDou, etc.) and / or non-terrestrial network (NTN) satellites; a base station 120; an access point (AP) 130; a location server 160; a network 170; and an external client 180. In general, the positioning system 100 may estimate the location of the UE 105 based on RF signals received by and / or transmitted from the UE 105 and the known locations of other components (e.g., GNSS satellites 110, base stations 120, APs 130) that transmit and / or receive RF signals. For additional details on specific location estimation techniques, refer to Figure 2 Discuss in more detail.

[0023] It should be noted that Figure 1 Only a generalized description of the various components is provided, any or all of which may be utilized as appropriate, and each of which may be replicated as needed. Specifically, although only one UE 105 is shown, it should be understood that many UEs (e.g., hundreds, thousands, millions, etc.) may utilize the positioning system 100. Similarly, the positioning system 100 may include more than one UE 105. Figure 1 A greater or lesser number of base stations 120 and / or APs 130 are shown. The illustrated connections connecting the various components in the positioning system 100 include data and signaling connections, which may include additional (intermediate) components, direct or indirect physical and / or wireless connections, and / or additional networks. In addition, components may be rearranged, combined, separated, replaced, and / or omitted, depending on the desired functionality. In some embodiments, for example, the external client 180 may be directly connected to the location server 160. Those of ordinary skill in the art will recognize many modifications to the illustrated components.

[0024] Depending on the desired functionality, network 170 may include any of a variety of wireless and / or wired networks. Network 170 may, for example, include any combination of public and / or private networks, local area networks and / or wide area networks, etc. In addition, network 170 may utilize one or more wired and / or wireless communication technologies. In some embodiments, network 170 may include, for example, cellular or other mobile networks, wireless local area networks (WLANs), wireless wide area networks (WWANs), and / or the Internet. Examples of network 170 include long-term evolution (LTE) wireless networks, fifth-generation (5G) wireless networks (also referred to as new radio (NR) wireless networks or 5G NR wireless networks), Wi-Fi WLANs, and the Internet. LTE, 5G, and NR are wireless technologies defined or being defined by the Third Generation Partnership Project (3GPP). Network 170 may also include more than one network and / or more than one type of network.

[0025] The base station 120 and the access point (AP) 130 may be communicatively coupled to the network 170. In some embodiments, the base station 120 may be owned, maintained and / or operated by a cellular network provider and may employ any of a variety of wireless technologies, as described below. Depending on the technology of the network 170, the base station 120 may include a Node B, an evolved Node B (eNodeB or eNB), a base transceiver station (BTS), a radio base station (RBS), an NR NodeB (gNB), a next generation eNB (ng-eNB), etc. The base station 120 as a gNB or ng-eNB may be part of a next generation radio access network (NG-RAN), which may be connected to a 5G core network (5GC) in the case where the network 170 is a 5G network. In view of the open radio access network (O-RAN) and / or virtualized radio access network (V-RAN or vRAN) in 5G or later networks, the functions performed by the base station 120 in earlier generation networks (e.g., 3G and 4G) can be divided into different functional components (e.g., radio unit (RU), distributed unit (DU), and central unit (CU)) and layers (e.g., L1 / L2 / L3), which can be performed on different devices at different locations connected, for example, via fronthaul, midhaul, and backhaul connections. As referred to herein, a "base station" (or ng-eNB, gNB, etc.) may include any or all of these functional components. For example, AP 130 may include a Wi-Fi AP or AP or an AP with cellular capabilities (e.g., 4G LTE and / or 5G NR). Thus, UE 105 can send and receive information with network-connected devices such as location server 160 by accessing network 170 via base station 120 using first communication link 133. Additionally or alternatively, because AP 130 can also be communicatively coupled with network 170, UE 105 can communicate with network-connected and Internet-connected devices (including location server 160) using second communication link 135 or via one or more other mobile devices 145.

[0026] As used herein, the term “base station” may generally refer to multiple co-located physical transmission points or a single physical transmission point that may be located at a base station 120. A transmit receive point (TRP) (also referred to as a transmit / receive point) corresponds to this type of transmission point, and the term “TRP” may be used interchangeably herein with the terms “gNB,” “ng-eNB,” and “base station.” In some cases, a base station 120 may include multiple TRPs—for example, each TRP is associated with a different antenna or a different antenna array of the base station 120. As used herein, the transmit function of a TRP may be performed with a transmit point (TP), and / or the receive function of a TRP may be performed by a receive point (RP), which may be physically separate or distinct from the TP. That is, a TRP may include both a TP and an RP. A physical transmission point may include an antenna array of a base station 120 (for example, as in a multiple-input multiple-output (MIMO) system and / or where the base station employs beamforming). The term "base station" may additionally refer to multiple non-co-located physical transmission points, which may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transmission medium) or a remote radio head (RRH) (a remote base station connected to a serving base station).

[0027] As used herein, the term "cell" may generally refer to a logical communication entity for communicating with a base station 120, and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) for distinguishing adjacent cells operating via the same or different carriers. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine type communication (MTC), narrowband Internet of Things (NB-IoT), enhanced mobile broadband (eMBB), or other protocol types) that may provide access to different types of devices. In some cases, the term "cell" may refer to a portion of a geographic coverage area (e.g., a sector) on which the logical entity operates.

[0028] Satellite 110 may be used to locate UE 105 in one or more ways. For example, satellite 110 (also referred to as space vehicle (SV)) may be part of a global navigation satellite system (GNSS) such as a global positioning system (GPS), GLONASS, Galileo, or BeiDou. Positioning using RF signals from GNSS satellites may include measuring multiple GNSS signals at a GNSS receiver of UE 105 to perform code-based and / or carrier-based positioning, which may be highly accurate. Additionally or alternatively, satellite 110 may be used for NTN-based positioning, where satellite 110 may be functionally operable as a TRP (or TP) of a network (e.g., LTE and / or NR network) and may be communicatively coupled with network 170. Specifically, reference signals (e.g., PRS) sent by satellite 110 for NTN-based positioning may be similar to reference signals sent by base station 120 and may be coordinated by location server 160. In some embodiments, satellite 110 used for NTN-based positioning may be different from satellite 110 used for GNSS-based positioning. In some embodiments, NTN nodes may include non-ground vehicles, such as aircraft, balloons, drones, etc., which may be in addition to or instead of NTN satellites.

[0029] The location server 160 may include a server and / or other computing device configured to determine an estimated location of the UE 105 and / or provide data (e.g., “assistance data”) to the UE 105 to facilitate location measurement and / or location determination of the UE 105. According to some embodiments, the location server 160 may include a Home Secure User Plane Location (SUPL) Location Platform (H-SLP), which may support a SUPL User Plane (UP) location solution defined by the Open Mobile Alliance (OMA), and may support location services for the UE 105 based on subscription information of the UE 105 stored in the location server 160. In some embodiments, the location server 160 may include a Discovery SLP (D-SLP) or an Emergency SLP (E-SLP). The location server 160 may also include an Enhanced Serving Mobile Location Center (E-SMLC), which supports the location of the UE 105 using a Control Plane (CP) location solution for LTE radio access of the UE 105. The location server 160 may further include a location management function (LMF) that supports the location of the UE 105 using a control plane (CP) location solution for NR or LTE radio access of the UE 105 .

[0030] In a CP location solution, signaling used to control and manage the location of the UE 105 may be exchanged between elements of the network 170 and with the UE 105 using existing network interfaces and protocols, and as signaling from the perspective of the network 170. In a UP location solution, signaling used to control and manage the location of the UE 105 may be exchanged between the location server 160 and the UE 105 as data from the perspective of the network 170 (e.g., data transmitted using the Internet Protocol (IP) and / or the Transmission Control Protocol (TCP)).

[0031] As previously mentioned (and discussed in more detail below), the estimated position of UE 105 may be based on measurements of RF signals transmitted from and / or received by UE 105. In particular, these measurements may provide information about the relative distances and / or angles of UE 105 from one or more components in positioning system 100 (e.g., GNSS satellites 110, APs 130, base stations 120). The estimated position of UE 105 may be geometrically estimated (e.g., using multi-angle measurements and / or multilateration) based on the distance and / or angle measurements and the known positions of the one or more components.

[0032] Although ground components such as AP 130 and base station 120 may be fixed, embodiments are not limited thereto. Mobile components may be used. For example, in some embodiments, the location of UE 105 may be estimated based at least in part on measurements of RF signals 140 transmitted between UE 105 and one or more other mobile devices 145 (which may be mobile or fixed). As shown, the other mobile devices may include, for example, mobile phone 145-1, vehicle 145-2, static communication / positioning device 145-3, or other static and / or mobile devices capable of providing wireless signals for locating UE 105, or a combination thereof. Wireless signals from mobile devices 145 for locating UE 105 may include using, for example, (including Bluetooth Low Energy (BLE)), IEEE 802.11x (e.g. ), ultra-wideband (UWB), IEEE 802.15x, or a combination thereof. The mobile device 145 may additionally or alternatively use non-RF wireless signals to locate the UE 105, such as infrared signals or other optical techniques.

[0033] The mobile device 145 may include other UEs communicatively coupled to a cellular or other mobile network (e.g., network 170). When one or more other mobile devices 145 including a UE are used for location determination of a particular UE 105, the UE 105 whose location is to be determined may be referred to as a "target UE", and each of the other mobile devices 145 used may be referred to as an "anchor UE". For location determination of the target UE, the corresponding locations of one or more anchor UEs may be known and / or determined jointly with the target UE. Direct communication between one or more other mobile devices 145 and the UE 105 may include side links and / or similar device-to-device (D2D) communication technologies. The side link defined by 3GPP is a form of D2D communication under cellular-based LTE and NR standards. UWB may be a technology by which measurements from one or more anchor devices (e.g., mobile devices 145) may be used to facilitate positioning of a target device (e.g., UE 105).

[0034] According to some embodiments, for example when the UE 105 includes a vehicle and / or merges into a vehicle, the form of D2D communication used by the mobile device 105 may include vehicle-to-everything (V2X) communication. V2X is a communication standard for vehicles and related entities to exchange information about the traffic environment. V2X may include vehicle-to-vehicle (V2V) communication between vehicles with V2X capabilities, vehicle-to-infrastructure (V2I) communication between vehicles and infrastructure-based equipment (commonly referred to as roadside units (RSUs)), vehicle-to-person (V2P) communication between vehicles and nearby personnel (pedestrians, cyclists, and other road users), etc. In addition, V2X may use any of a variety of wireless RF communication technologies. For example, cellular V2X (CV2X) is a form of V2X that uses cellular-based communications such as LTE (4G), NR (5G), and / or other cellular technologies in a direct communication mode as defined by 3GPP. Figure 1 The UE 105 shown in the figure may correspond to a component or device on a vehicle, an RSU, or other V2X entity for communicating V2X messages. In an embodiment using V2X, the static communication / positioning device 145-3 (which may correspond to an RSU) and / or the vehicle 145-2 may therefore communicate with the UE 105 and may be used to determine the location of the UE 105 using techniques similar to those used by the base station 120 and / or the AP 130 (e.g., using multi-angle measurements and / or multi-point positioning). It may be further noted that according to some embodiments, the mobile device 145 (which may include a V2X device), the base station 120, and / or the AP 130 may be used together (e.g., in a WWAN positioning solution) to determine the location of the UE 105.

[0035] The estimated position of UE 105 can be used in various applications, for example, to assist the user of UE 105 in direction finding or navigation or to assist another user (e.g., associated with external client 180) in locating UE 105. "Position" is also referred to herein as "position estimate", "estimated position", "position", "bearing", "bearing estimate", "bearing fix", "estimated bearing", "position fix" or "fix". The process of determining a position may be referred to as "positioning", "position determination", "position determination", etc. The position of UE 105 may include an absolute position of UE 105 (e.g., latitude and longitude and possibly altitude) or a relative position of UE 105 (e.g., expressed as a distance north or south, east or west and possibly above or below some other known fixed position (including, for example, the position of base station 120 or AP 130) or some other position (such as the position of UE 105 at some known previous time, or the position of mobile device 145 (e.g., another UE) at some known previous time)). The location may be specified as a geodetic location including coordinates that may be absolute (e.g., latitude, longitude, and optionally altitude), relative (e.g., relative to some known absolute location), or local (e.g., X, Y, and optionally Z coordinates according to a coordinate system defined relative to a local area, such as a factory, warehouse, university campus, shopping mall, stadium, or convention center). The location may alternatively be a city location, and may then include a street address (e.g., including a country, state, county, city, road and / or street name or label, and / or road or street number) and / or one or more of a place, a building, a portion of a building, a floor of a building, and / or a room within a building, etc. The location may also include uncertainty or error indications, such as the horizontal and likely vertical distance of the expected location error, or an indication of an area or volume (e.g., a circle or ellipse) in which the UE 105 is expected to be located with a certain confidence level (e.g., 95% confidence level).

[0036] The external client 180 may be a network server or remote application that may have some association with the UE 105 (e.g., accessible by a user of the UE 105), or may be a server, application, or computer system that provides location services to one or more other users, which may include obtaining and providing the location of the UE 105 (e.g., to enable services such as a friend or relative finder or a child or pet location). Additionally or alternatively, the external client 180 may obtain the location of the UE 105 and provide it to emergency service providers, government agencies, etc.

[0037] As previously mentioned, the example positioning system 100 may be implemented using a wireless communication network, such as an LTE-based or 5G NR-based network. Figure 2A diagram of a 5G NR positioning system 200 is shown, which illustrates an embodiment of a positioning system (e.g., positioning system 100) that implements 5G NR. The 5G NR positioning system 200 may be configured to determine the location of a UE 105 by using access nodes, which may include NR NodeBs (gNBs) 210-1 and 210-2 (collectively referred to herein as gNBs 210), ng-eNBs 214, and / or WLANs 216 to implement one or more positioning methods. The gNBs 210 and / or ng-eNBs 214 may correspond to Figure 1 The base station 120 and the WLAN 216 may correspond to Figure 1 One or more access points 130. Optionally, the 5G NR positioning system 200 can be further configured to determine the location of UE 105 by using LMF 220 (which can correspond to location server 160) to implement one or more positioning methods. Here, the 5G NR positioning system 200 includes components of UE 105 and a 5G NR network, and the 5G NR network includes a next generation (NG) radio access network (RAN) (NG-RAN) 235 and a 5G core network (5GCN) 240. A 5G network may also be referred to as an NR network; NG-RAN 235 may be referred to as a 5G RAN or NR RAN; and 5G CN240 may be referred to as an NG core network.

[0038] The 5G NR positioning system 200 may also utilize information from satellites 110. As previously described, satellites 110 may include GNSS satellites from a GNSS system, such as a Global Positioning System (GPS) or similar system (e.g., GLONASS, Galileo, BeiDou, Indian Regional Navigation Satellite System (IRNSS)). Additionally or alternatively, satellites 110 may include NTN satellites that may be communicatively coupled to LMF 220 and may be operable to serve as TRPs (or TPs) in NG-RAN 235. In this way, satellites 110 may communicate with one or more gNBs 210.

[0039] It should be noted that Figure 2Only a generalized description of the various components is provided, any or all of which may be utilized as appropriate, and each of which may be duplicated or omitted as desired. Specifically, although only one UE 105 is shown, it should be understood that many UEs (e.g., hundreds, thousands, millions, etc.) may utilize the 5G NR positioning system 200. Similarly, the 5G NR positioning system 200 may include a larger (or smaller) number of satellites 110, gNBs 210, ng-eNBs 214, wireless local area networks (WLANs) 216, access and mobility management functions (AMFs) 215, external clients 230, and / or other components. The connections shown connecting the various components in the 5G NR positioning system 200 include data and signaling connections, which may include additional (intermediate) components, direct or indirect physical and / or wireless connections, and / or additional networks. In addition, components may be rearranged, combined, separated, replaced, and / or omitted, depending on the desired functionality.

[0040] UE 105 may include and / or be referred to as a device, a mobile device, a wireless device, a mobile terminal, a terminal, a mobile station (MS), a terminal (SET) supporting secure user plane location (SUPL), or some other name. In addition, UE 105 may correspond to a cellular phone, a smart phone, a laptop computer, a tablet, a personal data assistant (PDA), a navigation device, an Internet of Things (IoT) device, or some other portable or portable device. Typically, although not necessarily, UE 105 can support wireless communications using one or more radio access technologies (RATs), such as GSM, CDMA, W-CDMA, LTE, High Rate Packet Data (HRPD), IEEE 802.11 Bluetooth, Worldwide Interoperability for Microwave Access (WiMAX TM ), 5G NR (e.g., using NG-RAN 235 and 5G CN 240), etc. The UE 105 may also support wireless communications using WLAN 216, which (like one or more RATs and as previously described with respect to Figure 1 The RATs described above can connect to other networks, such as the Internet. Using one or more of these RATs can allow UE 105 to communicate with external clients 230 (e.g., via Figure 2 Elements of the 5GCN 240 not shown in the figure, or possibly via a Gateway Mobile Location Center (GMLC) 225) and / or allowing an external client 230 to receive location information about the UE 105 (e.g., via the GMLC 225). Figure 2 The external client 230 may correspond to Figure 1 An external client 180, such as implemented in a 5G NR network or communicatively coupled with a 5G NR network.

[0041] UE 105 may include a single entity or may include multiple entities, such as in a personal area network where a user may employ audio, video and / or data I / O devices and / or body sensors and a separate wired or wireless modem. The estimate of the location of UE 105 may be referred to as a location, location estimate, location fix, fix, orientation, orientation estimate, or orientation fix, and may be geodetic, thereby providing location coordinates (e.g., latitude and longitude) of UE 105, which may or may not include an altitude component (e.g., height above sea level, height above ground level, or depth below ground level, floor level, or basement level). Alternatively, the location of UE 105 may be expressed as an urban location (e.g., expressed as a postal address or a designation of a certain point or small area in a building (such as a specific room or floor)). The location of UE 105 may also be expressed as an area or volume (defined geographically or in urban form) in which UE 105 is expected to be located with a certain probability or confidence level (e.g., 67%, 95%, etc.). The location of the UE 105 may also be a relative location, including, for example, a distance and direction or relative X, Y (and Z) coordinates defined relative to some origin at a known location, which may be defined geographically, in terms of a city, or by reference to a point, area, or volume indicated on a map, floor plan, or building plan. In the description contained herein, unless otherwise stated, the use of the term location may include any of these variations. When calculating the location of the UE, the local X, Y, and possibly Z coordinates are typically solved, and then, if necessary, the local coordinates are converted to absolute coordinates (e.g., latitude, longitude, and altitude above or below mean sea level).

[0042] Figure 2 The base stations in the NG-RAN 235 shown may correspond to Figure 1 The base stations 120 in the NG-RAN 235 may include gNBs 210. The gNBs 210 pairs in the NG-RAN 235 may be connected to each other (e.g., Figure 2 The communication interface between the base stations (gNB 210 and / or ng-eNB 214) may be referred to as an Xn interface 237. Access to the 5G network is provided to the UE 105 via wireless communication between the UE 105 and one or more of the gNBs 210, and the gNB 210 may provide wireless communication access to the 5G CN 240 on behalf of the UE 105 using 5G NR. The wireless interface between the base station (gNB 210 and / or ng-eNB 214) and the UE 105 may be referred to as an Uu interface 239. 5G NR radio access may also be referred to as NR radio access or 5G radio access. Figure 2In the figure, it is assumed that the serving gNB for UE 105 is gNB 210-1, but if UE 105 moves to another location, other gNBs (e.g., gNB 210-2) can act as the serving gNB, or can act as a secondary gNB to provide additional throughput and bandwidth to UE 105.

[0043] Figure 2 The base stations in the illustrated NG-RAN 235 may also or alternatively include a next generation evolved Node B (also referred to as ng-eNB) 214. The ng-eNB 214 may be connected to one or more gNBs 210 in the NG-RAN 235—e.g., directly or indirectly via other gNBs 210 and / or other ng-eNBs. The ng-eNB 214 may provide LTE radio access and / or evolved LTE (eLTE) radio access to the UE 105. Figure 2 Some of the gNBs 210 (e.g., gNB 210-2) and / or ng-eNBs 214 may be configured to function as positioning-only beacons that may transmit signals (e.g., positioning reference signals (PRS)) and / or may broadcast assistance data to assist in positioning of the UE 105, but may not receive signals from the UE 105 or from other UEs. Some of the gNBs 210 (e.g., gNB 210-2 and / or another gNB not shown) and / or ng-eNBs 214 may be configured to function as detection-only nodes that may scan for signals containing, for example, PRS data, assistance data, or other location data. Such detection-only nodes may not transmit signals or data to the UE, but may instead transmit signals or data (related to, for example, PRS, assistance data, or other location data) to other network entities (e.g., one or more components of the 5G CN 240, an external client 230, or a controller), which may receive and store or use the data to locate at least the UE 105. Note that while Figure 2 Only one ng-eNB 214 is shown, but some embodiments may include multiple ng-eNBs 214. Base stations (e.g., gNB 210 and / or ng-eNB 214) may communicate directly with each other via an Xn communication interface. Additionally or alternatively, the base station may communicate directly or indirectly with other components of the 5GNR positioning system 200 (such as LMF 220 and AMF 215).

[0044] The 5G NR positioning system 200 may also include one or more WLANs 216, which may be connected to a non-3GPP interworking function (N3IWF) 250 in the 5G CN 240 (e.g., in the case of an untrusted WLAN 216). For example, the WLAN 216 may support IEEE 802.11 Wi-Fi access for the UE 105 and may include one or more Wi-Fi APs (e.g., Figure 1 AP130 of 5G CN 240). Here, N3IWF 250 can be connected to other elements in 5G CN 240, such as AMF 215. In some embodiments, WLAN 216 can support another RAT, such as Bluetooth. N3IWF 250 can provide support for secure access of UE 105 to other elements in 5G CN 240 and / or can support interworking of one or more protocols used by WLAN 216 and UE 105 with one or more protocols used by other elements of 5GCN 240 (e.g., AMF 215). For example, N3IWF 250 can support IPSec tunnel establishment with UE 105, termination of IKEv2 / IPSec protocol with UE 105, termination of N2 and N3 interfaces to 5G CN 240 for control plane and user plane, respectively, and relaying uplink (UL) and downlink (DL) control plane non-access stratum (NAS) signaling between UE 105 and AMF 215 across N1 interface. In some other embodiments, WLAN 216 may be directly connected to elements in 5G CN 240 (e.g., Figure 2 215) instead of via N3IWF 250. For example, if WLAN 216 is a trusted WLAN of 5GCN 240, a direct connection of WLAN 216 to 5GCN 240 may occur and a trusted WLAN interworking function (TWIF) ( Figure 2 216). Figure 2 Only one WLAN 216 is shown in FIG. 2 , but some embodiments may include multiple WLANs 216 .

[0045] The access node may include any of a variety of network entities that enable communication between the UE 105 and the AMF 215. As described above, this may include a gNB 210, an ng-eNB 214, a WLAN 216, and / or other types of cellular base stations. However, an access node that provides the functionality described herein may additionally or alternatively include an entity that enables communication with the AMF 215. Figure 2214, or WLAN 216.

[0046] In some embodiments, access nodes such as gNB 210, ng-eNB 214, and / or WLAN 216 (alone or in combination with other components of 5G NR positioning system 200) may be configured to, in response to receiving a request for location information from LMF 220, obtain location measurements for uplink (UL) signals received from UE 105 and / or obtain downlink (DL) location measurements obtained by UE 105 for DL ​​signals received by UE 105 from one or more access nodes. As described above, although Figure 2 Access nodes (gNB 210, ng-eNB 214, and WLAN 216) configured to communicate according to 5G NR, LTE, and Wi-Fi communication protocols, respectively, are depicted, but access nodes configured to communicate according to other communication protocols may be used, such as a Node B using a Wideband Code Division Multiple Access (WCDMA) protocol for a Universal Mobile Telecommunications Service (UMTS) Terrestrial Radio Access Network (UTRAN), an eNB using an LTE protocol for an Evolved UTRAN (E-UTRAN), or an eNB using a Bluetooth protocol for a WLAN. For example, in a 4G Evolved Packet System (EPS) that provides LTE wireless access to UE 105, the RAN may include an E-UTRAN, which may include base stations including eNBs that support LTE wireless access. The core network for the EPS may include an Evolved Packet Core (EPC). The EPS may then include the E-UTRAN plus the EPC, where the E-UTRAN corresponds to Figure 2 NG-RAN 235 in, and EPC corresponds to Figure 2 5GCN 240 in. The methods and techniques described herein for obtaining the urban location of UE 105 may be applicable to such other networks.

[0047] The gNB 210 and ng-eNB 214 may communicate with the AMF 215, which in turn communicates with the LMF 220 for positioning functions. The AMF 215 may support mobility of the UE 105, including cell changes and handover of the UE 105 from an access node of a first RAT (e.g., a gNB 210, ng-eNB 214, or WLAN 216) to an access node of a second RAT. The AMF 215 may also be involved in supporting signaling connections to the UE 105 and possible data and voice bearers for the UE 105. The LMF 220 may support positioning of the UE 105 using a CP location solution when the UE 105 accesses the NG-RAN 235 or the WLAN 216, and may support positioning procedures and methods, including UE-assisted / UE-based and / or network-based procedures / methods, such as Assisted GNSS (A-GNSS), Observed Time Difference of Arrival (OTDOA) (which may be referred to as Time Difference of Arrival (TDOA) in NR), Frequency Difference of Arrival (FDOA), Real-Time Kinematics (RTK), Precise Point Positioning (PPP), Differential GNSS (DGNSS), Enhanced Cell ID (ECID), Angle of Arrival (AoA), Angle of Departure (AoD), WLAN positioning, Round Trip Signal Propagation Delay (RTT), Multi-Cell RTT, and / or other positioning procedures and methods. The LMF 220 may also process a location service request for the UE 105 received, for example, from the AMF 215 or from the GMLC 225. The LMF 220 may be connected to the AMF 215 and / or the GMLC 225. In some embodiments, a network such as 5GCN 240 may additionally or alternatively implement other types of location support modules, such as an Evolved Serving Mobile Location Center (E-SMLC) or a SUPL Location Platform (SLP). Note that in some embodiments, at least a portion of positioning functions (including determining the location of UE 105) may be performed at UE 105 (e.g., by measuring downlink PRS (DL-PRS) signals transmitted by wireless nodes such as gNB 210, ng-eNB 214, and / or WLAN 216, and / or using assistance data provided to UE 105 by, for example, LMF 220).

[0048] The Gateway Mobile Location Center (GMLC) 225 may support location requests for the UE 105 received from the external client 230, and may forward such location requests to the AMF 215 for forwarding by the AMF 215 to the LMF 220. A location response (e.g., containing a location estimate for the UE 105) from the LMF 220 may similarly be returned to the GMLC 225 directly or via the AMF 215, and the GMLC 225 may then return the location response (e.g., containing a location estimate) to the external client 230.

[0049] A network exposure function (NEF) 245 may be included in the 5GCN 240. The NEF 245 may support secure exposure of capabilities and events about the 5GCN 240 and the UE 105 to the external client 230, which may then be referred to as an access function (AF), and may enable secure provision of information from the external client 230 to the 5GCN 240. The NEF 245 may be connected to the AMF 215 and / or the GMLC 225 for the purpose of obtaining the location (e.g., city location) of the UE 105 and providing the location to the external client 230.

[0050] like Figure 2 As further shown in FIG. 1 , LMF 220 may communicate with gNB 210 and / or ng-eNB 214 using NR Positioning Protocol Annex (NRPPa) as defined in 3GPP Technical Specification (TS) 38.455. NRPPa messages may be transmitted between gNB 210 and LMF 220 and / or between ng-eNB 214 and LMF 220 via AMF 215. Figure 2 As further described in 3GPP TS 37.355, the LMF 220 and the UE 105 may communicate using the LTE Positioning Protocol (LPP) as defined in 3GPP TS 37.355. Here, LPP messages may be transmitted between the UE 105 and the LMF 220 via the AMF 215 and the serving gNB 210-1 or the serving ng-eNB 214 of the UE 105. For example, the LPP messages may be transmitted between the LMF 220 and the AMF 215 using messages for service-based operations (e.g., based on the Hypertext Transfer Protocol (HTTP)), and may be transmitted between the AMF 215 and the UE 105 using the 5G NAS protocol. The LPP protocol may be used to support positioning of the UE 105 using UE-assisted and / or UE-based positioning methods such as A-GNSS, RTK, TDOA, multi-cell RTT, AoD, and / or ECID. The NRPPa protocol can be used to support positioning of UE 105 using network-based positioning methods (such as, ECID, AoA, uplink TDOA (UL-TDOA)), and / or can be used by LMF 220 to obtain location-related information from gNB 210 and / or ng-eNB 214, such as parameters defining DL-PRS transmission from gNB 210 and / or ng-eNB 214.

[0051] In the case where the UE 105 accesses the WLAN 216, the LMF 220 may use NRPPa and / or LPP to obtain the location of the UE 105 in a manner similar to that just described for the UE 105 accessing the gNB 210 or ng-eNB 214. Thus, NRPPa messages may be transmitted between the WLAN 216 and the LMF 220 via the AMF 215 and the N3IWF 250 to support network-based positioning of the UE 105 and / or transmission of other location information from the WLAN 216 to the LMF 220. Alternatively, NRPPa messages may be transmitted between the N3IWF 250 and the LMF 220 via the AMF 215 to support network-based positioning of the UE 105 based on location-related information and / or location measurements known to or accessible to the N3IWF 250, and transmitted from the N3IWF 250 to the LMF 220 using NRPPa. Similarly, LPP and / or LPP messages may be transmitted between UE 105 and LMF 220 via AMF 215, N3IWF 250, and serving WLAN 216 for UE 105 to support UE-assisted or UE-based positioning of UE 105 by LMF 220.

[0052] In the 5G NR positioning system 200, positioning methods may be classified as "UE-assisted" or "UE-based", which may depend on where the request for determining the location of the UE 105 originates. For example, if the request originates at the UE (e.g., from an application or "app" executed by the UE), the positioning method may be classified as UE-based. On the other hand, if the request originates from an external client 230, LMF 220, or other device or service within the 5G network, the positioning method may be classified as UE-assisted (or "network-based").

[0053] In the case of UE-assisted positioning methods, the UE 105 may obtain location measurements and send the measurements to a location server (e.g., LMF 220) for use in calculating a location estimate for the UE 105. For RAT-dependent positioning methods, the location measurements may include one or more of received signal strength indicator (RSSI), round trip signal propagation time (RTT), reference signal received power (RSRP), reference signal received quality (RSRQ), reference signal time difference (RSTD), time of arrival (TOA), AoA, receive time-transmit time difference (Rx-Tx), differential AoA (DAoA), AoD, or timing advance (TA) for one or more access points of the gNB 210, ng-eNB 214, and / or WLAN 216. Additionally or alternatively, similar measurements may be made on sidelink signals sent by other UEs, which may be used as anchor points for positioning of the UE 105 if the locations of the other UEs are known. The position measurements may also or instead include measurements for a RAT-independent positioning method, such as GNSS (eg, GNSS pseudoranges of satellites 110 , GNSS code phase, and / or GNSS carrier phase), WLAN, and the like.

[0054] In the case of a UE-based positioning method, the UE 105 may obtain a position measurement (e.g., which may be the same or similar to the position measurement used for the UE-assisted positioning method) and may further calculate the position of the UE 105 (e.g., with the aid of auxiliary data received from a location server such as LMF 220, SLP or broadcast by gNB 210, ng-eNB 214, or WLAN 216).

[0055] Utilizing a network-based positioning approach, one or more base stations (e.g., gNB 210 and / or ng-eNB 214), one or more APs (e.g., in WLAN 216), or N3IWF 250 may obtain location measurements (e.g., measurements of RSSI, RTT, RSRP, RSRQ, AoA, or TOA) of signals sent by UE 105, and / or in the case of N3IWF 250 may receive measurements obtained by UE 105 or by APs in WLAN 216, and may send the measurements to a location server (e.g., LMF 220) for use in calculating a position estimate for UE 105.

[0056] Depending on the type of signal used for positioning, the positioning of UE 105 may also be classified as UL-based, DL-based, or DL-UL-based. For example, if positioning is based only on signals received at UE 105 (e.g., from a base station or other UE), positioning may be classified as DL-based. On the other hand, if positioning is based only on signals sent by UE 105 (e.g., which may be received by a base station or other UE), positioning may be classified as UL-based. DL-UL-based positioning includes positioning based on both signals sent and received by UE 105, such as RTT-based positioning. Sidelink (SL)-assisted positioning includes signals communicated between UE 105 and one or more other UEs. According to some embodiments, UL, DL, or DL-UL positioning as described herein may be able to use SL signaling as a supplement or replacement for SL, DL, or DL-UL signaling.

[0057] Depending on the type of positioning (e.g., UL, DL, or DL-UL based), the type of reference signal used may vary. For DL-based positioning, for example, these signals may include PRS (e.g., DL-PRS sent by a base station or SL-PRS sent by other UEs), which may be used for TDOA, AoD, and RTT measurements. Other reference signals (UL, DL, or DL-UL) that may be used for positioning may include a sounding reference signal (SRS), a channel state information reference signal (CSI-RS), a synchronization signal (e.g., a synchronization signal block (SSB) synchronization signal (SS)), a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a physical sidelink shared channel (PSSCH), a demodulation reference signal (DMRS), and the like. In addition, the reference signal may be sent in a Tx beam and / or received in an Rx beam (e.g., using beamforming techniques), which may affect angle measurements such as AoD and / or AoA.

[0058] Figure 3 is a diagram showing an example of a frame structure and associated terminology for NR, which can be used as the basis for physical layer communications between a UE 105 and a base station / TRP. The transmission timeline for each of the downlink and uplink can be partitioned into units of radio frames. Each radio frame can have a predetermined duration (e.g., 10 ms) and can be partitioned into 10 subframes indexed from 0 to 9, each subframe being 1 ms. Depending on the subcarrier spacing, each subframe can include a variable number of time slots. Depending on the subcarrier spacing, each time slot can include a variable number of symbol periods (e.g., 7 or 14 symbols). The symbol periods in each time slot can be assigned indices. A mini slot can include a subslot structure (e.g., 2, 3, or 4 symbols). Additionally, Figure 3The full orthogonal frequency division multiplexing (OFDM) of a subframe is shown in , which shows how a subframe is divided into multiple resource blocks (RBs) across time and frequency. A single RB may include a grid of resource elements (REs) spanning 14 symbols and 12 subcarriers.

[0059] Each symbol in a slot can indicate a link direction (e.g., downlink (DL), uplink (UL), or flexible) or data transmission, and the link direction can be switched dynamically for each subframe. The link direction can be based on the slot format. Each slot can include DL / UL data and DL / UL control information. In NR, a synchronization signal block (SSB) is transmitted. The SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a two-symbol physical broadcast channel (PBCH). The SSB can be located in a fixed slot position (such as Figure 3 PBCH is sent in symbols 0-3 shown in . PSS and SSS can be used by UE for cell search and acquisition. PSS can provide half-frame timing, and SS can provide cyclic prefix (CP) length and frame timing. PSS and SSS can provide cell identification. PBCH carries some basic system information, such as downlink system bandwidth, timing information within a radio frame, SS burst set periodicity, system frame number, etc.

[0060] Figure 4 An example wireless communication system 400 is shown. The wireless communication system 400 is composed of a plurality of roadside units (RSUs) 404-1, 404-2, 404-3, and 404-4 arranged within an enclosed space 401. A road 402 extends along the bottom surface of the enclosed space 401, allowing vehicles to pass through the enclosed space 401. According to aspects of the present disclosure, the RSUs 404-1, 404-2, 404-3, and 404-4 may be able to communicate with on-board units (OBUs) of vehicles passing through the enclosed space 401 on the road 402. In some embodiments, the RSUs 404-1, 404-2, 404-3, and 404-4 may communicate with the OBUs of passing vehicles in conjunction with providing wireless data connectivity to those vehicles.

[0061] According to aspects of the present disclosure, RSUs 404-1, 404-2, 404-3, and 404-4 may be vehicle-to-everything (V2X) RSUs configured to communicate with V2X OBUs of passing vehicles according to one or more V2X communication standards and / or protocols. For example, in some implementations, RSUs 404-1, 404-2, 404-3, and 404-4 may be configured to communicate according to V2X communication standards and / or protocols defined by one or more technical standards (TS) / or technical reports (TRs) issued by the Third Generation Partnership Project (3GPP) and / or the European Telecommunications Standards Institute (ETSI). According to aspects of the present disclosure, one or more of RSUs 404-1, 404-2, 404-3, and 404-4 may be implemented as UEs, any or all of which may communicate with Figure 1 In some implementations, one or more of the RSUs 404-1, 404-2, 404-3, and 404-4 may be implemented as base stations, any or all of which may be connected to the UE 105. Figure 1 Base station 120 or Figure 2 The gNB 210 is the same or similar to the gNB 210.

[0062] According to aspects of the present disclosure, the enclosed space 401 may be a tunnel, such as a vehicle tunnel that provides access to a road 402 underground or through an obstacle, such as, for example, a mountain or a building. Figure 4 As shown, RSUs 404-1, 404-2, 404-3, and 404-4 may be suspended from an upper surface (such as a ceiling) of the enclosure 401. RSU 404-1 is positioned closest to an open end 403 of the enclosure 401, and RSUs 404-2, 404-3, and 404-4 are positioned successively farther from the open end 403. In some embodiments, the distance between consecutive RSUs of RSUs 404-1, 404-2, 404-3, and 404-4 may be in the approximate range of 100 to 300 meters. Figure 4 As reflected by the dotted arrow in FIG. 4 , the enclosed space 401 can be Figure 4 The RSUs shown in FIG. 4 extend further, and the multiple RSUs in the wireless communication system 400 may include a plurality of RSUs along the Figure 4 Additional RSUs are positioned in a portion of the enclosed space 401 not shown.

[0063] According to aspects of the present disclosure, in order to support wireless communication with the OBU of a vehicle passing through the enclosed space 401, the RSUs 404-1, 404-2, 404-3, and 404-4 may perform synchronization operations to establish synchronization between the timing of the RSUs and between the timing of the RSUs and the timing of the OBU of the passing vehicle. In some implementations, the RSUs 404-1, 404-2, 404-3, and 404-4 may be configured to synchronize their timing with the timing indicated by the received synchronization signal and send synchronization signals indicating those timings. According to aspects of the present disclosure, each of the RSUs 404-1, 404-2, 404-3, and 404-4 may select a synchronization reference source and may synchronize its timing with the timing indicated by the received synchronization signal corresponding to the synchronization reference source. According to aspects of the present disclosure, possible synchronization references that a given RSU of RSUs 404-1, 40-4-2, 404-3, and 404-4 may be able to use as its synchronization reference source may include a Global Navigation Satellite System (GNSS) as well as other RSUs.Herein, the term SyncRef RSU is used to denote an RSU used as a synchronization reference source by another RSU.

[0064] According to aspects of the present disclosure, the RSUs 404-1, 404-2, 404-3, and 404-4 may be configured to follow a priority scheme when selecting synchronization references that they use as synchronization reference sources. In some implementations, according to the priority scheme, a GNSS reference may be given a higher priority than an RSU reference, such that if a GNSS reference is available to the RSU, the RSU will select the GNSS reference as the synchronization reference source instead of any (multiple) RSU references available to the RSU. Among the RSU references, a RSU reference corresponding to an RSU using a GNSS reference as its synchronization reference source may be given a higher priority than an RSU reference corresponding to an RSU using other RSU references as its synchronization reference source.

[0065] According to aspects of the present disclosure, RSUs 404-1, 404-2, 404-3, and 404-4 may be configured to use an alternative synchronization reference as their synchronization reference source when their currently used reference becomes unavailable. In some cases, this may involve using a reference of a lower priority than the reference that has been lost. For example, if a given one of RSUs 404-1, 404-2, 404-3, and 404-4 is using a GNSS reference as its synchronization reference source, and the GNSS reference becomes unavailable, the RSU may adopt an RSU reference corresponding to another RSU as its synchronization reference source.

[0066] Figure 5An example operating environment 500 is shown. In operating environment 500, RSUs 404-1, 404-2, 404-3, and 404-4 implement a synchronization chain. The implementation of the synchronization chain may allow Figure 4 Some RSUs of the communication system 400 synchronize their timing with the timing of a GNSS reference that is not directly available to them by propagating the GNSS reference timing from the RSUs to which the GNSS reference is available.

[0067] exist Figure 5 In the example, since Figure 4 Near the open end 403 of the enclosed space 401 in the enclosure 401, the RSU 404-1 is able to receive a reference signal 507 transmitted by a GNSS device 506 (which may be, for example, a satellite transmitter) on a wireless carrier. Therefore, the GNSS reference is available for the RSU 404-1 to use as a synchronization reference source, and the RSU 404-1 may synchronize with the GNSS reference according to the timing indicated by the reference signal 507. The RSUs 404-2, 404-3, and 404-4 located away from the open end 403 of the enclosed space 401 may not be able to receive the reference signal 507 or any other GNSS reference signal. Therefore, there is no GNSS reference available for the RSUs 404-2, 404-3, or 404-4 to use as a synchronization reference source.

[0068] To allow other RSUs to synchronize with the GNSS timing indicated by the reference signal 507, the RSU 404-1 may transmit a side link synchronization signal (SLSS) 508-1 on the wireless carrier. The RSU 404-2 (the RSU closest to the RSU 404-1) may be able to receive the SLSS 508-1, and may therefore be able to use the RSU 404-1 as a synchronization reference source. The RSU 404-2 may synchronize with the RSU 404-1 according to the timing indicated by the SLSS 508-1 - and therefore synchronize with the GNSS reference corresponding to the reference signal 507.

[0069] Similarly, RSU 404-2 may transmit SLSS 508-2 on a wireless carrier, and RSU 404-3 may receive SLSS 508-2 and use RSU 404-2 as a synchronization reference source by synchronizing with the timing indicated by SLSS 508-2. In turn, RSU 404-3 may transmit SLSS 508-3 on a wireless carrier, and RSU 404-4 may receive SLSS 508-3 and use RSU 404-3 as a synchronization reference source by synchronizing with the timing indicated by SLSS 508-3. RSU 404-4 may transmit SLSS 508-4 to enable the next RSU (not shown) in the synchronization chain to synchronize with the previous RSU and thus synchronize with the GNSS source.

[0070] According to aspects of the present disclosure, transmission of SLSSs 508-1, 508-2, 508-3, and 508-4 by respective RSUs 404-1, 404-2, 404-3, and 404-4 may involve transmission of SLSSs 508-1, 508-2, 508-3, and 508-4 as described above with reference to Figure 3 The NR frame structure discussed in the SSB section is similar to the sidelink SSB (S-SSB) transmission. Figure 3 The SSB of the SLSS 508-1, 508-2, 508-3 or 508-4 may be composed of a sidelink PSS (S-PSS), a sidelink SSS (S-SSS) and a multi-symbol physical sidelink broadcast channel (PSBCH). The S-SSB may occupy a full time slot, and the S-PSS and S-SSS may each occupy two symbols within the time slot.

[0071] It is worth noting that some RSUs in the synchronization chain in the operating environment 500 may be able to receive reference signals (such as GNSS reference signals and / or SLSS) associated with multiple synchronization references. For example, RSU 404-1 may be able to receive both reference signal 507 transmitted by GNSS device 506 and SLSS 508-2 transmitted by RSU 404-2. Similarly, RSU 404-2 may be able to receive both SLSS 508-1 transmitted by RSU 404-1 and SLSS 508-3 transmitted by RSU 4043, and RSU 404-3 may be able to receive both SLSS 508-2 transmitted by RSU 4042 and SLSS 508-4 transmitted by RSU 404-4.

[0072] According to aspects of the present disclosure, an RSU in an operating environment 500 that can receive reference signals associated with multiple synchronization references (such as GNSS reference signals and / or SLSS) can select the synchronization references according to a priority scheme (such as the above reference signals). Figure 4 404-2 as a SyncRef RSU.

[0073] According to aspects of the present disclosure, an RSU in operating environment 500 may be configured to use an alternative synchronization reference as its synchronization reference source when the reference it is currently using becomes available. If multiple alternative synchronization references are available to a given RSU, it may select from those multiple alternative sources based on factors that may include the respective priorities of the multiple alternative sources according to a priority scheme. An RSU that has only one alternative synchronization reference available to it may adopt that alternative reference when the reference it is currently using becomes unavailable.

[0074] In some embodiments, each of the RSUs 404-1, 404-2, 404-3, and 404-4 may have a corresponding synchronization reference that may be used for potential adoption in the event that it loses its synchronization reference used in conjunction with the timing of propagating a GNSS reference along a synchronization chain in the operating environment 500. For example, RSU 404-2 may be used by RSU 404-1 as a SyncRef RSU as an alternative to a GNSS reference, RSU 404-3 may be used by RSU 404-2 as a SyncRef RSU as an alternative to using RSU 404-1, and RSU 404-4 may be used by RSU 404-3 as a SyncRef RSU as an alternative to using RSU 404-2. According to aspects of the present disclosure, RSUs 404-1, 404-2, 404-3, and 404-4 may be configured to, upon losing their currently used synchronization references, adopt their alternative synchronization references as their synchronization reference sources, monitor reference signals (such as GNSS reference signals and / or SLSS) associated with their alternative synchronization references on a wireless carrier, and transmit SLSS on the wireless carrier according to the timing indicated by those reference signals.

[0075] In operating environment 500, if a GNSS reference becomes unavailable to RSU 404-1 (because, for example, GNSS device 506 stops transmitting reference signal 507, or weather conditions or other obstacle(s) prevent reference signal 507 from reaching RSU 404-1), there may be a potential for a timing deadlock to form between RSUs 404-1, 404-2, 404-3, and 404-4. Figure 6 It is shown Figure 5 6 is a block diagram of an example flow of events 600 of the manner in which loss of a GNSS reference in operating environment 500 may result in a timing deadlock.

[0076] When the event flow 600 begins, the synchronization references available to RSU 404-1 may be the GNSS reference and SyncRefRSU 404-2, the synchronization references available to RSU 404-2 may be SyncRef RSUs 404-1 and 404-3, and the synchronization references available to RSU 404-3 may be SyncRef RSUs 404-2 and 404-4. Since the priority of the GNSS reference is higher than the priority of the SyncRef RSU 404-2, RSU 404-1 may use the GNSS reference as its synchronization reference source. Since the priority of the SyncRef RSU 404-1 is higher than the priority of the SyncRef RSU 404-3, RSU 404-2 may use the SyncRef RSU 404-1 as its synchronization reference source. Since the priority of the SyncRef RSU 404-2 is higher than the priority of the SyncRef RSU 404-4, RSU 404-3 may use the SyncRef RSU 404-2 as its synchronization reference source.

[0077] According to the event flow 600, at block 605, a GNSS reference associated with a reference signal 507 transmitted by a GNSS device 506 may be lost. As mentioned above, for example, if the GNSS device 506 stops transmitting the reference signal 507, or if weather conditions or other obstacle(s) prevent the reference signal 507 from reaching the RSU 404-1, then this loss of GNSS reference may occur. At block 610, the RSU 404-1 may detect the unavailability of the GNSS reference. In response to detecting the unavailability of the GNSS reference, the RSU 404-1 may stop transmitting the SLSS 508-1 at block 615.

[0078] At block 620, RSU 404-2 may detect (based on the absence of SLSS 508-1 on the wireless carrier) the unavailability of RSU 404-1 as a SyncRef RSU. In response to detecting the unavailability of RSU 404-1 as a SyncRef RSU, RSU 404-2 may adopt RSU 404-3 as a SyncRef RSU at block 625. At block 630, RSU 404-3 has been adopted as a SyncRef RSU. RSU, RSU 404-2 may start sending SLSS 508-2 according to the timing indicated by SLSS 508-3 sent by RSU 404-3. These SLSS 508-2 may be the same as SLSS 508-4 sent by RSU 404-4, which also uses RSU 404-3 as a SyncRef RSU.

[0079] At block 635, RSU 404-3 may switch from using RSU 404-2 to using RSU 404-4 as its SyncRef RSU and may identify RSU 404-2 as an alternative, lower priority SyncRef RSU based on the SLSS 508-2 sent by RSU 404-2 beginning at block 630. The switch may not cause a change in the SLSS 508-3 sent by RSU 404-3.

[0080] At block 640, being able to receive only the SLSS 508-2 sent by RSU 404-2, RSU 404-1 may adopt RSU 404-2 as its SyncRef RSU. At block 645, RSU 404-1 may begin sending SLSS 508-1 according to the timing indicated by SLSS 508-2. The timing may correspond to the timing indicated by SLSS 508-3, which in turn may correspond to the timing indicated by SLSS 508-4. Therefore, at block 650, there may be a timing deadlock between RSUs 404-1, 404-2, 404-3, and 404-4.

[0081] Deadlock prevention techniques are disclosed herein that can be implemented to prevent RSU synchronization chains (such as Figure 5 In some embodiments, the RSU may be configured to start a waiting interval when switching from a higher priority synchronization reference to a lower priority synchronization reference. The RSU that starts the waiting interval when switching to a different synchronization reference may suspend its SLSS transmission for the duration of the waiting interval. After the waiting interval expires, the RSU may check the reference signal associated with the newly adopted synchronization reference. If the reference signal associated with the newly adopted synchronization reference is found, the RSU may resume SLSS transmission (according to the timing indicated by those reference signals). If the reference signal associated with the newly adopted synchronization reference is not found, the RSU may continue to suppress the transmission of SLSS.

[0082] Figure 7 According to various aspects of the present disclosure, the disclosed deadlock prevention technology can be represented in Figure 5700 is a block diagram of an example event flow 700 implemented in the operating environment 500 of . Before the event flow 700 begins, the RSUs 404-1, 404-2, 404-3, and 404-4 can each be configured to start a waiting interval when switching synchronization references. In some embodiments, the implementation of such a waiting interval can be limited to synchronization reference source changes involving switching from a higher priority reference to a lower priority reference. In other embodiments, such a waiting interval can also be implemented in situations involving switching between synchronization sources of similar priority. In other embodiments, such a waiting interval can be implemented in conjunction with all synchronization reference source changes, regardless of the priority of the newly adopted synchronization reference relative to the previously used synchronization reference.

[0083] When the event flow 700 begins, the synchronization references available to RSU 404-1 may be the GNSS reference and SyncRefRSU 404-2, the synchronization references available to RSU 404-2 may be SyncRef RSUs 404-1 and 404-3, and the synchronization references available to RSU 404-3 may be SyncRef RSUs 404-2 and 404-4. Since the priority of the GNSS reference is higher than the priority of the SyncRef RSU 404-2, RSU 404-1 may use the GNSS reference as its synchronization reference source. Since the priority of the SyncRef RSU 404-1 is higher than the priority of the SyncRef RSU 404-3, RSU 404-2 may use the SyncRef RSU 404-1 as its synchronization reference source. Since the priority of SyncRef RSU 404-2 is higher than that of SyncRef RSU 404-4, RSU 404-3 may use SyncRef RSU 404-2 as its synchronization reference source.

[0084] According to the event flow 700, at block 705, a GNSS reference associated with a reference signal 507 transmitted by a GNSS device 506 may be lost. As previously mentioned, for example, if the GNSS device 506 stops transmitting the reference signal 507, or if weather conditions or other obstacle(s) prevent the reference signal 507 from reaching the RSU 404-1, then this loss of GNSS reference may occur. At block 710, the RSU 404-1 may detect the unavailability of the GNSS reference. In response to detecting the unavailability of the GNSS reference, the RSU 404-1 may stop transmitting the SLSS 508-1 at block 715.

[0085] At block 720, RSU 404-2 may detect (based on the absence of SLSS 508-1 on the wireless carrier) the unavailability of RSU 404-1 as a SyncRef RSU. In response to detecting the unavailability of RSU 404-1 as a SyncRef RSU, RSU 404-2 may adopt RSU 404-3 as a SyncRef RSU at block 725. At block 730, since it has switched from using RSU 404-1 to using RSU 404-3 as a SyncRef RSU, RSU 404-2 may initiate a waiting interval during which RSU 404-2 may refrain from sending SLSS 508-2.

[0086] At block 735, RSU 404-3 may detect (based on the absence of SLSS 508-2 on the wireless carrier) the unavailability of RSU 404-2 as a SyncRef RSU. In response to detecting the unavailability of RSU 404-2 as a SyncRef RSU, RSU 404-3 may adopt RSU 404-4 as a SyncRef RSU at block 740. At block 745, since it has switched from using RSU 404-2 to using RSU 404-4 as a SyncRef RSU, RSU 404-3 may initiate a wait interval during which RSU 404-3 may refrain from sending SLSS 508-3.

[0087] At block 750, being able to receive only the SLSS 508-2 sent by RSU 404-2, RSU 404-1 may adopt RSU 404-2 as the SyncRef RSU. At block 755, since it has switched from using the GNSS reference to using RSU 404-2 as the SyncRef RSU, RSU 404-1 may start a waiting interval during which it may refrain from sending SLSS 508-1.

[0088] At block 760, RSU 404-4 may refrain from transmitting SLSS 508-4 on the wireless carrier due to the absence of SLSS 508-3 of RSU 404-3 in the wireless carrier. At block 765, RSU 404-3 may refrain from transmitting SLSS 508-3 on the wireless carrier due to the absence of SLSS 508-4 of RSU 404-4 in the wireless carrier. At block 770, RSU 404-2 may refrain from transmitting SLSS 508-2 on the wireless carrier due to the absence of SLSS 508-3 of RSU 404-3 in the wireless carrier. At block 775, RSU 404-1 may refrain from transmitting SLSS 508-1 on the wireless carrier due to the absence of SLSS 508-2 of RSU 404-2 in the wireless carrier. At block 780, the RSUs 404-1, 404-2, 404-3, and 404-4 may all be silent (suppressing SLSS transmissions), and thus timing deadlock may be avoided.

[0089] Figure 8 is a flow chart of a method 800 for wireless communication by a wireless communication device according to an embodiment. Figure 8 The components of the functions shown in one or more blocks shown in the figure may be performed by hardware and / or software components of the RSU, for example Figure 4 and Figure 5 In some embodiments, the RSU may be implemented as a UE or a base station (e.g., a gNB), and its example components are respectively shown in Fig. 9 and Fig.10 As illustrated in the figure, example components of the UE or base station are described in more detail below.

[0090] At block 810, the functionality includes detecting, by the wireless communication device, a first reference signal associated with the first synchronization reference on a wireless carrier when the first synchronization reference is a synchronization reference source for the wireless communication device. Figure 5 In the operating environment 500 of , when the RSU 404-1 is a SyncRef RSU used by the RSU 404-2 as its synchronization reference source, the RSU 404-2 can detect the SLSS 508-1 on the wireless carrier. According to some embodiments, the means for performing the functions at block 810 may include a bus 905, a processor 910, a digital signal processor (DSP) 920, a wireless communication interface 930, a memory 960 and / or other components of the UE, such as Fig. 9According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0091] At block 820, the functionality includes transmitting the SLSS on the wireless carrier according to the timing indicated by the first reference signal. Figure 5 In the operating environment 500, RSU 404-2 may send SLSS 508-2 on the wireless carrier according to the timing indicated by SLSS 508-1. According to some embodiments, the means for performing the functions at block 820 may include bus 905, processor 910, DSP 920, wireless communication interface 930, memory 960 and / or other components of the UE, such as Fig. 9 According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0092] At block 830, the functionality includes determining that a first synchronization reference has become unavailable. Figure 5 In the operating environment 500 of , RSU 404-2 may determine that RSU 404-1 is no longer available as a SyncRef RSU (e.g., based on an inability to detect and / or receive SLSS 508-1 via a wireless carrier). According to some embodiments, means for performing the functions at block 830 may include bus 905, processor 910, DSP 920, wireless communication interface 930, memory 960, and / or other components of the UE, such as Fig. 9 According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0093] At block 840, the functionality includes: in response to determining at block 830 that the first synchronization reference has become unavailable, employing a second synchronization reference as a synchronization reference source for the wireless communication device. Figure 5In the operating environment 500 of , in response to determining that RSU 404-1 is no longer available as a SyncRef RSU, RSU 404-2 may adopt RSU 404-3 as a SyncRef RSU used as a synchronization reference source for RSU 404-2. According to some embodiments, the means for performing the functions at block 840 may include a bus 905, a processor 910, a DSP 920, a wireless communication interface 930, a memory 960, and / or other components of the UE, such as Fig. 9 According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0094] At block 850, the functionality includes initiating a wait interval due to switching to a different synchronization reference at block 840. For example, at Figure 5 In the operating environment 500 of , RSU 404-2 may start a waiting interval due to switching from RSU 404-1 to RSU 404-3 as the SyncRef RSU used as the synchronization reference source for RSU 404-2. According to some embodiments, the means for performing the functions at block 850 may include a bus 905, a processor 910, a DSP 920, a wireless communication interface 930, a memory 960, and / or other components of the UE, such as Fig. 9 According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0095] At block 860, the functionality includes, after expiration of the waiting interval initiated at block 850, monitoring a second reference signal associated with a second synchronization reference on the wireless carrier, and refraining from transmitting the SLSS on the wireless carrier when the second reference signal is not detected on the wireless carrier. Figure 5In the operating environment 500 of , after the waiting interval started due to the switching from RSU 404-1 to RSU 404-3 as the SyncRef RSU used as the synchronization reference source for RSU 404-2 expires, RSU 404-2 can monitor the SLSS 508-3 associated with RSU 404-3 on the wireless carrier, and when the SLSS 508-3 is not detected on the wireless carrier, it can refrain from sending the SLSS 508-2 on the wireless carrier. According to some embodiments, the means for performing the functions at block 860 may include the bus 905, the processor 910, the DSP 920, the wireless communication interface 930, the memory 960 and / or other components of the UE, such as Fig. 9 According to some other embodiments, the means for performing the functions at block 810 may include bus 1005, processor 1010, DSP 1020, wireless communication interface 1030, memory 1060 and / or other components of the base station, such as Fig.10 As described in .

[0096] Fig. 9 is a block diagram of an embodiment of a UE 105, which may be utilized as described above (e.g., to implement Figure 4 and Figure 5 For example, UE 105 may perform Figure 8 It should be noted that Fig. 9 It is intended only to provide a general description of the various components, any or all of which may be utilized as appropriate. It may be noted that in some cases, Fig. 9 The components shown may be located in a single physical device and / or distributed among various networked devices that may be located at different physical locations. In addition, as previously mentioned, the functionality of the UE discussed in the previously described embodiments may be provided by Fig. 9 One or more of the hardware and / or software components shown in FIG.

[0097] UE 105 is shown as including hardware elements that may be electrically coupled via bus 905 (or may otherwise communicate as appropriate). The hardware elements may include processor(s) 910, which may include (but are not limited to) one or more general purpose processors (e.g., application processors), one or more special purpose processors (such as digital signal processor (DSP) chips, graphics acceleration processors, application specific integrated circuits (ASICs), etc.), and / or other processing structures or components. Processor(s) 910 may include one or more processing units, which may be housed in a single integrated circuit (IC) or multiple ICs. Fig. 9As shown, some embodiments may have a separate DSP 920, depending on the desired functionality. Position determination and / or other determinations based on wireless communication may be provided in the processor(s) 910 and / or the wireless communication interface 930 (discussed below). The UE 105 may also include one or more input devices 970, which may include but are not limited to one or more keyboards, touch screens, touch pads, microphones, buttons, dials, switches, etc.; and one or more output devices 915, which may include but are not limited to one or more displays (e.g., touch screens), light emitting diodes (LEDs), speakers, etc.

[0098] UE 105 may also include a wireless communication interface 930, which may include but is not limited to a modem, a network card, an infrared communication device, a wireless communication device and / or a chipset (such as Devices, IEEE 802.11 devices, IEEE802.15.4 devices, Wi-Fi devices, WiMAX devices, WAN devices and / or various cellular devices, etc.), etc., which can enable UE 105 to communicate with other devices as described in the above embodiments. The wireless communication interface 930 can allow, for example, eNB, gNB, ng-eNB, access point, various base stations and / or other access node types and / or other network components, computer systems and / or any other electronic devices communicatively coupled to the TRP to communicate (e.g., send and receive) data and signaling with the TRP of the network, as described herein. Communication can be performed via one or more wireless communication antennas 932 that send and / or receive wireless signals 934. According to some embodiments, (multiple) wireless communication antennas 932 may include multiple discrete antennas, antenna arrays, or any combination thereof. Antenna 932 may be able to use beams (e.g., Tx beams and Rx beams) to send and receive wireless signals. Beamforming can be performed using digital and / or analog beamforming techniques and corresponding digital and / or analog circuits. Wireless communication interface 930 may include such circuitry.

[0099] Depending on the desired functionality, the wireless communication interface 930 may include separate receivers and transmitters, or any combination of transceivers, transmitters, and / or receivers to communicate with base stations (e.g., ng-eNBs and gNBs) and other terrestrial transceivers (such as wireless devices and access points). The UE 105 may communicate with different data networks, which may include various network types. For example, the WWAN may be a CDMA network, a time division multiple access (TDMA) network, a frequency division multiple access (FDMA) network, an orthogonal frequency division multiple access (OFDMA) network, a single carrier frequency division multiple access (SC-FDMA) network, a WiMAX (IEEE 802.16) network, and the like. A CDMA network may implement one or more RATs, such as WCDMA, etc. The 5G NR standard includes IS-95, IS-2000, and / or IS-856 standards. A TDMA network may implement GSM, Digital Advanced Mobile Phone System (D-AMPS), or some other RAT. An OFDMA network may employ LTE, Advanced LTE, 5G NR, etc. 5G NR, LTE, Advanced LTE, GSM, and WCDMA are described in documents from 3GPP. 5G NR is described in documents from a consortium named "3rd Generation Partnership Project 2" (3GPP2). 3GPP and 3GPP2 documents are publicly available. A wireless local area network (WLAN) may also be an IEEE 802.11x network, and a wireless personal area network (WPAN) may be a Bluetooth network, IEEE 802.15x, or some other type of network. The techniques described herein may also be used for any combination of WWAN, WLAN, and / or WPAN.

[0100] The UE 105 may also include sensor(s) 940. The sensor(s) 940 may include, but are not limited to, one or more inertial sensors and / or other sensors (e.g., accelerometer(s), gyroscope(s), camera(s), magnetometer(s), altimeter(s), microphone(s), proximity sensor(s), light sensor(s), barometer(s), etc.), some of which may be used to obtain location-related measurements and / or other information.

[0101] Embodiments of the UE 105 may also include a global navigation satellite system (GNSS) receiver 980 capable of receiving signals 984 from one or more GNSS satellites using an antenna 982 (which may be the same as the antenna 932). Positioning based on GNSS signal measurements may be used to supplement and / or incorporate the techniques described herein. The GNSS receiver 980 may extract the location of the UE 105 from GNSS satellites of a GNSS system using conventional techniques, such as the Global Positioning System (GPS), Galileo, GLONASS, Japan's Quasi-Zenith Satellite System (QZSS), India's IRNSS, China's BeiDou Navigation Satellite System (BDS), etc. In addition, the GNSS receiver 980 may be used with various augmentation systems, such as a satellite-based augmentation system (SBAS), which may be associated with or otherwise enabled for use with one or more global and / or regional navigation satellite systems, such as the Wide Area Augmentation System (WAAS), the European Geosynchronous Navigation Overlay Service (EGNOS), the Multipurpose Satellite Augmentation System (MSAS), and / or the Geographic Augmentation Navigation System (GAGAN), among others.

[0102] It can be noted that although the GNSS receiver 980 Fig. 9910, DSP 920, and / or a processor within the wireless communication interface 930 (e.g., in a modem)). The GNSS receiver may also optionally include a positioning engine that uses the GNSS measurements from the measurement engine to determine the position of the GNSS receiver using an extended Kalman filter (EKF), a weighted least squares (WLS), a particle filter, and the like. The positioning engine may also be executed by one or more processors (e.g., (multiple) processors 910 or DSP 920).

[0103] The UE 105 may also include and / or be in communication with memory 960. The memory 960 may include, but is not limited to, local and / or network accessible storage, disk drives, drive arrays, optical storage devices, solid-state storage devices, such as random access memory (RAM) and / or read-only memory (ROM), which may be programmable, flash-updatable, etc. Such storage may be configured to implement any suitable data storage, including, but not limited to, various file systems, database structures, etc.

[0104] The memory 960 of the UE 105 may also include software elements ( Fig. 9 ), including an operating system, device drivers, executable libraries, and / or other code, such as one or more applications, which may include computer programs provided by various embodiments, and / or may be designed to implement methods provided by other embodiments and / or configure systems provided by other embodiments, as described herein. By way of example only, one or more processes described with respect to the methods discussed above may be implemented as code and / or instructions in memory 960, which may be executed by UE 105 (and / or (multiple) processors 910 or DSP 920 within UE 105). Then, in some embodiments, such code and / or instructions may be used to configure and / or adapt a general purpose computer (or other device) to perform one or more operations according to the described methods.

[0105] Fig.10 is a block diagram of an embodiment of a base station 120, which may be used as described above (e.g., to implement Figure 4 and Figure 5 For example, UE 105 may perform Figure 8 It should be noted that Fig.10 It is intended only to provide a generalized description of the various components, any or all of which may be utilized as appropriate. In some embodiments, base station 120 may correspond to a gNB, ng-eNB, and / or (more generally) a TRP.

[0106] Base station 120 is shown as including hardware elements that may be electrically coupled via bus 1005 (or may communicate in other ways as appropriate). The hardware elements may include processor 1010, which may include (but is not limited to) one or more general-purpose processors, one or more special-purpose processors (e.g., DSP chips, graphics acceleration processors, ASICs, etc.) and / or other processing structures or components. Fig.10 As shown, some embodiments may have a separate DSP 1020, depending on the desired functionality. According to some embodiments, wireless communication-based position determination and / or other determinations may be provided in the processor 1010 and / or the wireless communication interface 1030 (discussed below). The base station 120 may also include one or more input devices, which may include (but are not limited to) a keyboard, a display, a mouse, a microphone, buttons, a dial, switches, etc.; and one or more output devices, which may include (but are not limited to) a display, a light emitting diode (LED), a speaker, etc.

[0107] The base station 120 may also include a wireless communication interface 1030, which may include but is not limited to a modem, a network card, an infrared communication device, a wireless communication device and / or a chipset (eg, Devices, IEEE 802.11 devices, IEEE 802.15.4 devices, Wi-Fi devices, WiMAX devices, cellular communication facilities, etc.), etc., which can enable the base station 120 to communicate as described herein. The wireless communication interface 1030 can allow data and signaling to be transmitted (e.g., sent and received) to the UE, other base stations / TRPs (e.g., eNBs, gNBs, and ng-eNBs), and / or other network components, computer systems, and / or any other electronic devices described herein. Communication can be performed via one or more wireless communication antennas 1032 that send and / or receive wireless signals 1034.

[0108] The base station 120 may also include a network interface 1080, which may include support for wired communication technologies. The network interface 1080 may include a modem, a network card, a chipset, etc. The network interface 1080 may include one or more input and / or output communication interfaces to allow data to be exchanged with a network, a communication network server, a computer system, and / or any other electronic device described herein.

[0109] In many embodiments, the base station 120 may also include a memory 1060. The memory 1060 may include, but is not limited to, local and / or network accessible storage, disk drives, drive arrays, optical storage, solid-state storage, such as RAM and / or ROM, which may be programmable, flash-updatable, etc. Such storage may be configured to implement any suitable data storage, including, but not limited to, various file systems, database structures, etc.

[0110] The memory 1060 of the base station 120 may also include software elements ( Fig.10 ), including an operating system, device drivers, executable libraries, and / or other code, such as one or more application programs, which may include computer programs provided by various embodiments, and / or may be designed to implement methods provided by other embodiments and / or configure systems provided by other embodiments, as described herein. By way of example only, one or more processes described with respect to the method(s) discussed above may be implemented as code and / or instructions in memory 1060 that may be executed by base station 120 (and / or processor 1010 or DSP 1020 within base station 120). Then, in some embodiments, such code and / or instructions may be used to configure and / or adapt a general purpose computer (or other device) to perform one or more operations according to the described methods.

[0111] It will be apparent to those skilled in the art that substantial variations may be made depending on specific requirements. For example, custom hardware may also be used and / or specific elements may be implemented in hardware, software (including portable software, such as applets, etc.), or both. In addition, connections to other computing devices such as network input / output devices may be employed.

[0112] With reference to the accompanying drawings, the components that may include memory may include non-transitory machine-readable media. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any storage medium that participates in providing data that enables a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may involve providing instructions / codes to a processor and / or other devices for execution. Additionally or alternatively, machine-readable media may be used to store and / or carry such instructions / codes. In many embodiments, computer-readable media are physical and / or tangible storage media. Such media may take many forms, including but not limited to non-volatile media and volatile media. Common forms of computer-readable media include, for example, magnetic and / or optical media, any other physical media with hole patterns, RAM, programmable ROM (PROM), erasable PROM (EPROM), FLASH-EPROM, any other memory chip or box, or any other medium from which a computer can read instructions and / or codes.

[0113] The methods, systems and devices discussed herein are examples. Various embodiments may appropriately omit, replace or add various processes or components. For example, features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of the embodiments may be combined in a similar manner. The various components of the accompanying drawings provided herein may be embodied in hardware and / or software. In addition, technology develops, and therefore many elements are examples that do not limit the scope of the present disclosure to those specific examples.

[0114] It has proven convenient at times, primarily for reasons of common usage, to refer to such signals as bits, information, values, elements, symbols, characters, variables, terms, numbers, digits, and the like. It will be understood, however, that all of these or similar terms are associated with the appropriate physical quantities and are merely convenient labels. Unless otherwise specifically stated, as will be apparent from the above discussion, it will be understood that throughout this specification, discussions utilizing terms such as "processing," "computing," "calculating," "determining," "ascertaining," "identifying," "correlating," "measuring," "performing," and the like refer to the actions or processes of a specific apparatus, such as a special-purpose computer or similar special-purpose electronic computing device. Thus, in the context of this specification, a special-purpose computer or similar special-purpose electronic computing device is capable of manipulating or transforming signals, typically represented as physical electronic, electrical, or magnetic quantities within a memory, register, or other information storage device, transmission device, or display device of the special-purpose computer or similar special-purpose electronic computing device.

[0115] The terms "and" and "or" as used herein may include multiple meanings, which are also expected to depend at least in part on the context in which the terms are used. Generally, "or", if used in an associative list, such as A, B, or C, is intended to mean A, B, and C (used here in an inclusive sense), as well as A, B, or C (used here in an exclusive sense). In addition, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in the singular, or may be used to describe a certain combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and the subject matter claimed is not limited to this example. In addition, if used in an associative list (such as A, B, or C), the term "at least one of" may be interpreted to mean any combination of A, B, and / or C, such as A, AB, AA, AAB, AABBCCC, etc.

[0116] Several embodiments have been described, and various modifications, alternative configurations, and equivalents may be used without departing from the scope of the present disclosure. For example, the above elements may be merely components of a larger system, where other rules may take precedence over or otherwise modify the application of the various embodiments. In addition, multiple steps may be performed before, during, or after considering the above elements. Therefore, the above description does not limit the scope of the present disclosure.

[0117] In view of this description, embodiments may include different combinations of features. Implementation examples are described in the following numbered clauses:

[0118] Clause 1. A method for wireless communication by a wireless communication device, the method comprising: when a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier, sending a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopting a second synchronization reference as the synchronization reference source for the wireless communication device, starting a waiting interval, and after expiration of the waiting interval, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, suppressing sending the SLSS on the wireless carrier.

[0119] Clause 2. The method of clause 1, comprising: in response to detecting a second reference signal on a wireless carrier when the second synchronization reference is a synchronization reference source for a wireless communication device, transmitting the SLSS on the wireless carrier according to a timing indicated by the second reference signal.

[0120] Clause 3. A method according to any of clauses 1 to 2, wherein the second synchronization reference is a reference of lower priority than the first synchronization reference.

[0121] Clause 4. A method according to any one of clauses 1 to 3, wherein the wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

[0122] Clause 5. The method of clause 4, wherein the V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

[0123] Clause 6. The method of clause 5, wherein the second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

[0124] Clause 7. A method according to any of clauses 1 to 6, wherein the first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) user equipment (UE).

[0125] Clause 8. The method of any of clauses 1 to 6, wherein the first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE) and the second synchronization reference is a second SyncRef UE.

[0126] Clause 9. A wireless communication device comprising a transceiver, a memory, and one or more processors communicatively coupled to the transceiver and the memory, wherein the one or more processors are configured to: when a first synchronization reference is a synchronization reference source for the wireless communication device, detect a first reference signal associated with the first synchronization reference on a wireless carrier, send a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopt a second synchronization reference as the synchronization reference source for the wireless communication device, start a waiting interval, and after the waiting interval expires, monitor a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, refrain from sending the SLSS on the wireless carrier.

[0127] Clause 10. A wireless communication device according to clause 9, wherein the one or more processors are configured to: in response to detecting a second reference signal on the wireless carrier when the second synchronization reference is a synchronization reference source for the wireless communication device, send the SLSS on the wireless carrier according to the timing indicated by the second reference signal.

[0128] Clause 11. The wireless communication device of any of clauses 9 to 10, wherein the second synchronization reference is a lower priority reference than the first synchronization reference.

[0129] Clause 12. A wireless communication device according to any one of clauses 9 to 11, wherein the wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

[0130] Clause 13. The wireless communication device of clause 12, wherein the V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

[0131] Clause 14. The wireless communication device of clause 13, wherein the second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

[0132] Clause 15. A wireless communication device as set forth in any one of clauses 9 to 14, wherein the first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) user equipment (UE).

[0133] Clause 16. A wireless communications device as set forth in any of clauses 9 to 14, wherein the first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE) and the second synchronization reference is a second SyncRef UE.

[0134] Clause 17. An apparatus for a wireless communication device, the apparatus comprising: a component for detecting a first reference signal associated with a first synchronization reference on a wireless carrier when the first synchronization reference is a synchronization reference source for the wireless communication device, a component for sending a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and a component for: in response to a subsequent determination that the first synchronization reference has become unavailable, adopting a second synchronization reference as a synchronization reference source for the wireless communication device, starting a waiting interval, and after expiration of the waiting interval, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, suppressing sending the SLSS on the wireless carrier.

[0135] Clause 18. The apparatus of clause 17, comprising means for transmitting the SLSS on the wireless carrier according to a timing indicated by the second reference signal in response to detecting the second reference signal on the wireless carrier when the second synchronization reference is a synchronization reference source for the wireless communication device.

[0136] Clause 19. Apparatus according to any of clauses 17 to 18, wherein the second synchronization reference is a lower priority reference than the first synchronization reference.

[0137] Clause 20. An apparatus according to any of clauses 17 to 19, wherein the apparatus is one of a plurality of vehicle-to-everything (V2X) roadside units (RSUs) in a V2X RSU synchronization chain, wherein the second synchronization reference corresponds to a second one of the plurality of V2X RSUs in the V2X RSU synchronization chain.

[0138] Clause 21. The apparatus of any of clauses 17 to 20, wherein the first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) user equipment (UE).

[0139] Clause 22. An apparatus as set forth in any of clauses 17 to 20, wherein the first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE) and the second synchronization reference is a second SyncRef UE.

[0140] Clause 23. A non-transitory computer-readable medium storing instructions for wireless communication by a wireless communication device, the instructions comprising code for: when a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier, sending a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal, and in response to a subsequent determination that the first synchronization reference has become unavailable, adopting a second synchronization reference as the synchronization reference source for the wireless communication device, starting a waiting interval, and after expiration of the waiting interval, monitoring a second reference signal associated with the second synchronization reference on the wireless carrier, and when the second reference signal is not detected on the wireless carrier, refraining from sending the SLSS on the wireless carrier.

[0141] Clause 24. A non-transitory computer-readable medium according to clause 23, the instructions comprising code for: in response to detecting a second reference signal on the wireless carrier when the second synchronization reference is a synchronization reference source for the wireless communication device, sending the SLSS on the wireless carrier according to a timing indicated by the second reference signal.

[0142] Clause 25. The non-transitory computer-readable medium of any of clauses 23 to 24, wherein the second synchronization reference is a lower priority reference than the first synchronization reference.

[0143] Clause 26. The non-transitory computer-readable medium of any one of clauses 23 to 25, wherein the wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

[0144] Clause 27. The non-transitory computer-readable medium of clause 26, wherein the V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

[0145] Clause 28. The non-transitory computer-readable medium of clause 27, wherein the second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

[0146] Clause 29. The non-transitory computer-readable medium of any of clauses 23 to 28, wherein the first synchronization reference is a global navigation satellite system (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) user equipment (UE).

[0147] Clause 30. The non-transitory computer-readable medium of any of clauses 23 to 28, wherein the first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE) and the second synchronization reference is a second SyncRef UE.

Claims

1. A method for wireless communication by a wireless communication device, the method comprising: When a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier; transmitting a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal; and In response to a subsequent determination that the first synchronization reference has become unavailable: employing a second synchronization reference as the synchronization reference source for the wireless communication device; Enable the waiting interval; and After expiration of the waiting interval: monitoring, on the wireless carrier, a second reference signal associated with the second synchronization reference; as well as When the second reference signal is not detected on the wireless carrier, refraining from transmitting the SLSS on the wireless carrier.

2. The method according to claim 1, comprising: In response to detecting the second reference signal on the wireless carrier when the second synchronization reference is the synchronization reference source for the wireless communication device, transmitting a SLSS on the wireless carrier according to a timing indicated by the second reference signal.

3. The method according to claim 1, wherein: The second synchronization reference is a reference of lower priority than the first synchronization reference.

4. The method according to claim 1, wherein: The wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

5. The method according to claim 4, wherein: The V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

6. The method according to claim 5, wherein: The second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

7. The method according to claim 1, wherein: The first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) User Equipment (UE).

8. The method according to claim 1, wherein: The first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE), and the second synchronization reference is a second SyncRef UE.

9. A wireless communication device, comprising: Transceiver; Memory; as well as one or more processors communicatively coupled to the transceiver and the memory, wherein the one or more processors are configured to: When a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier; transmitting a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal; and In response to a subsequent determination that the first synchronization reference has become unavailable: employing a second synchronization reference as the synchronization reference source for the wireless communication device; Enable the waiting interval; and After expiration of the waiting interval: monitoring, on the wireless carrier, a second reference signal associated with the second synchronization reference; as well as When the second reference signal is not detected on the wireless carrier, refraining from transmitting the SLSS on the wireless carrier.

10. The wireless communication device according to claim 9, wherein: The one or more processors are configured to, in response to detecting the second reference signal on the wireless carrier when the second synchronization reference is the synchronization reference source for the wireless communication device, transmit a SLSS on the wireless carrier according to a timing indicated by the second reference signal.

11. The wireless communication device according to claim 9, wherein: The second synchronization reference is a reference of lower priority than the first synchronization reference.

12. The wireless communication device according to claim 9, wherein: The wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

13. The wireless communication device according to claim 12, wherein: The V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

14. The wireless communication device according to claim 13, wherein: The second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

15. The wireless communication device according to claim 9, wherein: The first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) User Equipment (UE).

16. The wireless communication device according to claim 9, wherein: The first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE), and the second synchronization reference is a second SyncRef UE.

17. An apparatus for a wireless communication device, the apparatus comprising: means for detecting a first reference signal associated with the first synchronization reference on a wireless carrier when the first synchronization reference is a synchronization reference source for the wireless communication device; means for transmitting a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal; as well as means for, in response to subsequently determining that the first synchronization reference has become unavailable, performing the following operations: employing a second synchronization reference as the synchronization reference source for the wireless communication device; Enable the waiting interval; and After expiration of the waiting interval: monitoring the wireless carrier for a second reference signal associated with the second synchronization reference; as well as When the second reference signal is not detected on the wireless carrier, refraining from transmitting the SLSS on the wireless carrier.

18. The apparatus according to claim 17, comprising: means for transmitting a SLSS on the wireless carrier according to a timing indicated by the second reference signal in response to detecting the second reference signal on the wireless carrier when the second synchronization reference is the synchronization reference source for the wireless communication device.

19. The device according to claim 17, wherein: The second synchronization reference is a lower priority reference than the first synchronization reference.

20. The device according to claim 17, wherein: The apparatus is one of a plurality of vehicle-to-everything (V2X) roadside units (RSUs) in a V2X RSU synchronization chain, wherein the second synchronization reference corresponds to a second one of the plurality of V2X RSUs in the V2X RSU synchronization chain.

21. The device according to claim 17, wherein: The first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) User Equipment (UE).

22. The device according to claim 17, wherein: The first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE), and the second synchronization reference is a second SyncRef UE.

23. A non-transitory computer-readable medium storing instructions for wireless communications by a wireless communications device, the instructions comprising code for: When a first synchronization reference is a synchronization reference source for the wireless communication device, detecting a first reference signal associated with the first synchronization reference on a wireless carrier; transmitting a side link synchronization signal (SLSS) on the wireless carrier according to a timing indicated by the first reference signal; and In response to a subsequent determination that the first synchronization reference has become unavailable: employing a second synchronization reference as the synchronization reference source for the wireless communication device; Enable the waiting interval; and After expiration of the waiting interval: monitoring the wireless carrier for a second reference signal associated with the second synchronization reference; and When the second reference signal is not detected on the wireless carrier, refraining from transmitting the SLSS on the wireless carrier.

24. The non-transitory computer-readable medium of claim 23, the instructions comprising code for: in response to detecting the second reference signal on the wireless carrier when the second synchronization reference is the synchronization reference source for the wireless communication device, sending the SLSS on the wireless carrier according to a timing indicated by the second reference signal.

25. The non-transitory computer readable medium of claim 23, wherein: The second synchronization reference is a reference of lower priority than the first synchronization reference.

26. The non-transitory computer readable medium of claim 23, wherein: The wireless communication device is a vehicle-to-everything (V2X) roadside unit (RSU).

27. The non-transitory computer readable medium of claim 26, wherein: The V2X RSU is one of a plurality of V2X RSUs in a V2X RSU synchronization chain.

28. The non-transitory computer readable medium of claim 27, wherein: The second synchronization reference corresponds to a second V2X RSU in the V2X RSU synchronization chain.

29. The non-transitory computer readable medium of claim 23, wherein: The first synchronization reference is a Global Navigation Satellite System (GNSS) reference and the second synchronization reference is a synchronization reference (SyncRef) User Equipment (UE).

30. The non-transitory computer readable medium of claim 23, wherein: The first synchronization reference is a first synchronization reference (SyncRef) user equipment (UE), and the second synchronization reference is a second SyncRef UE.

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