Patent Description:
Aspects of the disclosure relate generally to wireless communications.

Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (<NUM>), a second-generation (<NUM>) digital wireless phone service (including interim <NUM> and <NUM> networks), a third-generation (<NUM>) high speed data, Intemet-capable wireless service and a fourth-generation (<NUM>) service (e.g., Long Term Evolution (LTE) or WiMax). There are presently many different types of wireless communication systems in use, including cellular and personal communications service (PCS) systems. Examples of known cellular systems include the cellular analog advanced mobile phone system (AMPS), and digital cellular systems based on code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), the Global System for Mobile communications (GSM), etc..

A fifth generation (<NUM>) wireless standard, referred to as New Radio (NR), calls for higher data transfer speeds, greater numbers of connections, and better coverage, among other improvements. The <NUM> standard, according to the Next Generation Mobile Networks Alliance, is designed to provide data rates of several tens of megabits per second to each of tens of thousands of users, with <NUM> gigabit per second to tens of workers on an office floor. Several hundreds of thousands of simultaneous connections should be supported in order to support large sensor deployments. Consequently, the spectral efficiency of <NUM> mobile communications should be significantly enhanced compared to the current <NUM> standard. Furthermore, signaling efficiencies should be enhanced and latency should be substantially reduced compared to current standards.

Leveraging the increased data rates and decreased latency of <NUM>, among other things, vehicle-to-everything (V2X) communication technologies are being implemented to support autonomous driving applications, such as wireless communications between vehicles, between vehicles and the roadside infrastructure, between vehicles and pedestrians, etc. The document <CIT> describes method and apparatus for multi-antenna transmission in vehicle to vehicle communication.

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

A V-UE is a type of UE and may be any in-vehicle wireless communication device, such as a navigation system, a warning system, a heads-up display (HUD), an on-board computer, an in-vehicle infotainment system, an automated driving system (ADS), an advanced driver assistance system (ADAS), etc. Alternatively, a V-UE may be a portable wireless communication device (e.g., a cell phone, tablet computer, etc.) that is carried by the driver of the vehicle or a passenger in the vehicle. The term "V-UE" may refer to the in-vehicle wireless communication device or the vehicle itself, depending on the context. A P-UE is a type of UE and may be a portable wireless communication device that is carried by a pedestrian (i.e., a user that is not driving or riding in a vehicle). Generally, UEs can communicate with a core network via a RAN, and through the core network the UEs can be connected with external networks such as the Internet and with other UEs. Of course, other mechanisms of connecting to the core network and/or the Internet are also possible for the UEs, such as over wired access networks, wireless local area network (WLAN) networks (e.g., based on Institute of Electrical and Electronics Engineers (IEEE) <NUM>, etc.) and so on.

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

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

In some implementations that support positioning of UEs, a base station may not support wireless access by UEs (e.g., may not support data, voice, and/or signaling connections for UEs), but may instead transmit reference RF signals to UEs to be measured by the UEs and/or may receive and measure signals transmitted by the UEs. Such base stations may be referred to as positioning beacons (e.g., when transmitting RF signals to UEs) and/or as location measurement units (e.g., when receiving and measuring RF signals from UEs).

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

<FIG> illustrates an example wireless communications system <NUM>, according to aspects of the disclosure. The wireless communications system <NUM> (which may also be referred to as a wireless wide area network (WWAN)) may include various base stations <NUM> (labelled "BS") and various UEs <NUM>. The base stations <NUM> may include macro cell base stations (high power cellular base stations) and/or small cell base stations (low power cellular base stations). In an aspect, the macro cell base stations <NUM> may include eNBs and/or ng-eNBs where the wireless communications system <NUM> corresponds to an LTE network, or gNBs where the wireless communications system <NUM> corresponds to a NR network, or a combination of both, and the small cell base stations may include femtocells, picocells, microcells, etc..

The base stations <NUM> may collectively form a RAN and interface with a core network <NUM> (e.g., an evolved packet core (EPC) or <NUM> core (5GC)) through backhaul links <NUM>, and through the core network <NUM> to one or more location servers <NUM> (e.g., a location management function (LMF) or a secure user plane location (SUPL) location platform (SLP)). The location server(s) <NUM> may be part of core network <NUM> or may be external to core network <NUM>. In addition to other functions, the base stations <NUM> may perform functions that relate to one or more of transferring user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations <NUM> may communicate with each other directly or indirectly (e.g., through the EPC / 5GC) over backhaul links <NUM>, which may be wired or wireless.

In an aspect, one or more cells may be supported by a base station <NUM> in each geographic coverage area <NUM>. A "cell" is a logical communication entity used for communication with a base station (e.g., over some frequency resource, referred to as a carrier frequency, component carrier, carrier, band, or the like), and may be associated with an identifier (e.g., a physical cell identifier (PCI), an enhanced cell identifier (ECI), a virtual cell identifier (VCI), a cell global identifier (CGI), etc.) for distinguishing cells operating via the same or a different carrier frequency. In some cases, different cells may be configured according to different protocol types (e.g., machine-type communication (MTC), narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access for different types of UEs. Because a cell is supported by a specific base station, the term "cell" may refer to either or both the logical communication entity and the base station that supports it, depending on the context. In some cases, the term "cell" may also refer to a geographic coverage area of a base station (e.g., a sector), insofar as a carrier frequency can be detected and used for communication within some portion of geographic coverage areas <NUM>.

While neighboring macro cell base station <NUM> geographic coverage areas <NUM> may partially overlap (e.g., in a handover region), some of the geographic coverage areas <NUM> may be substantially overlapped by a larger geographic coverage area <NUM>. For example, a small cell base station <NUM>' (labelled "SC" for "small cell") may have a geographic coverage area <NUM>' that substantially overlaps with the geographic coverage area <NUM> of one or more macro cell base stations <NUM>. A network that includes both small cell and macro cell base stations may be known as a heterogeneous network. A heterogeneous network may also include home eNBs (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG).

The communication links <NUM> between the base stations <NUM> and the UEs <NUM> may include uplink (also referred to as reverse link) transmissions from a UE <NUM> to a base station <NUM> and/or downlink (DL) (also referred to as forward link) transmissions from a base station <NUM> to a UE <NUM>. The communication links <NUM> may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links <NUM> may be through one or more carrier frequencies. Allocation of carriers may be asymmetric with respect to downlink and uplink (e.g., more or less carriers may be allocated for downlink than for uplink).

The wireless communications system <NUM> may further include a mmW base station <NUM> that may operate in millimeter wave (mmW) frequencies and/or near mmW frequencies in communication with a UE <NUM>.

Transmit beams may be quasi-co-located, meaning that they appear to the receiver (e.g., a UE) as having the same parameters, regardless of whether or not the transmitting antennas of the network node themselves are physically co-located. In NR, there are four types of quasi-co-location (QCL) relations.

Transmit and receive beams may be spatially related. A spatial relation means that parameters for a second beam (e.g., a transmit or receive beam) for a second reference signal can be derived from information about a first beam (e.g., a receive beam or a transmit beam) for a first reference signal. For example, a UE may use a particular receive beam to receive a reference downlink reference signal (e.g., synchronization signal block (SSB)) from a base station. The UE can then form a transmit beam for sending an uplink reference signal (e.g., sounding reference signal (SRS)) to that base station based on the parameters of the receive beam.

In <NUM>, the frequency spectrum in which wireless nodes (e.g., base stations <NUM>/<NUM>, UEs <NUM>/<NUM>) operate is divided into multiple frequency ranges, FR1 (from <NUM> to <NUM>), FR2 (from <NUM> to <NUM>), FR3 (above <NUM>), and FR4 (between FR1 and FR2). mmW frequency bands generally include the FR2, FR3, and FR4 frequency ranges. As such, the terms "mmW" and "FR2" or "FR3" or "FR4" may generally be used interchangeably.

In a multi-carrier system, such as <NUM>, one of the carrier frequencies is referred to as the "primary carrier" or "anchor carrier" or "primary serving cell" or "PCell," and the remaining carrier frequencies are referred to as "secondary carriers" or "secondary serving cells" or "SCells. " In carrier aggregation, the anchor carrier is the carrier operating on the primary frequency (e.g., FR1) utilized by a UE <NUM>/<NUM> and the cell in which the UE <NUM>/<NUM> either performs the initial radio resource control (RRC) connection establishment procedure or initiates the RRC connection re-establishment procedure. The primary carrier carries all common and UE-specific control channels, and may be a carrier in a licensed frequency (however, this is not always the case). A secondary carrier is a carrier operating on a second frequency (e.g., FR2) that may be configured once the RRC connection is established between the UE <NUM> and the anchor carrier and that may be used to provide additional radio resources. In some cases, the secondary carrier may be a carrier in an unlicensed frequency. The secondary carrier may contain only necessary signaling information and signals, for example, those that are UE-specific may not be present in the secondary carrier, since both primary uplink and downlink carriers are typically UE-specific. This means that different UEs <NUM>/<NUM> in a cell may have different downlink primary carriers. The same is true for the uplink primary carriers. The network is able to change the primary carrier of any UE <NUM>/<NUM> at any time. This is done, for example, to balance the load on different carriers. Because a "serving cell" (whether a PCell or an SCell) corresponds to a carrier frequency / component carrier over which some base station is communicating, the term "cell," "serving cell," "component carrier," "carrier frequency," and the like can be used interchangeably.

In the example of <FIG>, one or more Earth orbiting satellite positioning system (SPS) space vehicles (SVs) <NUM> (e.g., satellites) may be used as an independent source of location information for any of the illustrated UEs (shown in <FIG> as a single UE <NUM> for simplicity). A UE <NUM> may include one or more dedicated SPS receivers specifically designed to receive SPS signals <NUM> for deriving geo location information from the SVs <NUM>. An SPS typically includes a system of transmitters (e.g., SVs <NUM>) positioned to enable receivers (e.g., UEs <NUM>) to determine their location on or above the Earth based, at least in part, on signals (e.g., SPS signals <NUM>) received from the transmitters. Such a transmitter typically transmits a signal marked with a repeating pseudo-random noise (PN) code of a set number of chips. While typically located in SVs <NUM>, transmitters may sometimes be located on ground-based control stations, base stations <NUM>, and/or other UEs <NUM>.

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

Leveraging the increased data rates and decreased latency of NR, among other things, vehicle-to-everything (V2X) communication technologies are being implemented to support intelligent transportation systems (ITS) applications, such as wireless communications between vehicles (vehicle-to-vehicle (V2V)), between vehicles and the roadside infrastructure (vehicle-to-infrastructure (V2I)), and between vehicles and pedestrians (vehicle-to-pedestrian (V2P)). The goal is for vehicles to be able to sense the environment around them and communicate that information to other vehicles, infrastructure, and personal mobile devices. Such vehicle communication will enable safety, mobility, and environmental advancements that current technologies are unable to provide. Once fully implemented, the technology is expected to reduce unimpaired vehicle crashes by <NUM>%.

Still referring to <FIG>, the wireless communications system <NUM> may include multiple V-UEs <NUM> that may communicate with base stations <NUM> over communication links <NUM> (e.g., using the Uu interface). V-UEs <NUM> may also communicate directly with each other over a wireless sidelink <NUM>, with a roadside access point <NUM> (also referred to as a "roadside unit") over a wireless sidelink <NUM>, or with UEs <NUM> over a wireless sidelink <NUM>. A wireless sidelink (or just "sidelink") is an adaptation of the core cellular (e.g., LTE, NR) standard that allows direct communication between two or more UEs without the communication needing to go through a base station. Sidelink communication may be unicast or multicast, and may be used for device-to-device (D2D) media-sharing, V2V communication, V2X communication (e.g., cellular V2X (cV2X) communication, enhanced V2X (eV2X) communication, etc.), emergency rescue applications, etc. One or more of a group of V-UEs <NUM> utilizing sidelink communications may be within the geographic coverage area <NUM> of a base station <NUM>. Other V-UEs <NUM> in such a group may be outside the geographic coverage area <NUM> of a base station <NUM> or be otherwise unable to receive transmissions from a base station <NUM>. In some cases, groups of V-UEs <NUM> communicating via sidelink communications may utilize a one-to-many (<NUM>:M) system in which each V-UE <NUM> transmits to every other V-UE <NUM> in the group. In some cases, a base station <NUM> facilitates the scheduling of resources for sidelink communications. In other cases, sidelink communications are carried out between V-UEs <NUM> without the involvement of a base station <NUM>.

In an aspect, the sidelinks <NUM>, <NUM>, <NUM> may operate over a wireless communication medium of interest, which may be shared with other wireless communications between other vehicles and/or infrastructure access points, as well as other RATs. A "medium" may be composed of one or more time, frequency, and/or space communication resources (e.g., encompassing one or more channels across one or more carriers) associated with wireless communication between one or more transmitter / receiver pairs.

In an aspect, the sidelinks <NUM>, <NUM>, <NUM> may be cV2X links. A first generation of cV2X has been standardized in LTE, and the next generation is expected to be defined in NR. cV2X is a cellular technology that also enables device-to-device communications. and Europe, cV2X is expected to operate in the licensed ITS band in sub-<NUM>. Other bands may be allocated in other countries. Thus, as a particular example, the medium of interest utilized by sidelinks <NUM>, <NUM>, <NUM> may correspond to at least a portion of the licensed ITS frequency band of sub-<NUM>. However, the present disclosure is not limited to this frequency band or cellular technology.

In an aspect, the sidelinks <NUM>, <NUM>, <NUM> may be dedicated short-range communications (DSRC) links. DSRC is a one-way or two-way short-range to medium-range wireless communication protocol that uses the wireless access for vehicular environments (WAVE) protocol, also known as IEEE <NUM>. 11p, for V2V, V2I, and V2P communications. IEEE <NUM>. 11p is an approved amendment to the IEEE <NUM> standard and operates in the licensed ITS band of <NUM> (<NUM>-<NUM>) in the U. In Europe, IEEE <NUM>. 11p operates in the ITS G5A band (<NUM> - <NUM>). Other bands may be allocated in other countries. The V2V communications briefly described above occur on the Safety Channel, which in the U. is typically a <NUM> channel that is dedicated to the purpose of safety. The remainder of the DSRC band (the total bandwidth is <NUM>) is intended for other services of interest to drivers, such as road rules, tolling, parking automation, etc. Thus, as a particular example, the mediums of interest utilized by sidelinks <NUM>, <NUM>, <NUM> may correspond to at least a portion of the licensed ITS frequency band of <NUM>.

Alternatively, the medium of interest may correspond to at least a portion of an unlicensed frequency band shared among various RATs. Although different licensed frequency bands have been reserved for certain communication systems (e.g., by a government entity such as the Federal Communications Commission (FCC) in the United States), these systems, in particular those employing small cell access points, have recently extended operation into unlicensed frequency bands such as the Unlicensed National Information Infrastructure (U-NII) band used by wireless local area network (WLAN) technologies, most notably IEEE <NUM>. 11x WLAN technologies generally referred to as "Wi-Fi. " Example systems of this type include different variants of CDMA systems, TDMA systems, FDMA systems, orthogonal FDMA (OFDMA) systems, single-carrier FDMA (SC-FDMA) systems, and so on.

Communications between the V-UEs <NUM> are referred to as V2V communications, communications between the V-UEs <NUM> and the one or more roadside access points <NUM> are referred to as V2I communications, and communications between the V-UEs <NUM> and one or more UEs <NUM> (where the UEs <NUM> are P-UEs) are referred to as V2P communications. The V2V communications between V-UEs <NUM> may include, for example, information about the position, speed, acceleration, heading, and other vehicle data of the V-UEs <NUM>. The V2I information received at a V-UE <NUM> from the one or more roadside access points <NUM> may include, for example, road rules, parking automation information, etc. The V2P communications between a V-UE <NUM> and a UE <NUM> may include information about, for example, the position, speed, acceleration, and heading of the V-UE <NUM> and the position, speed (e.g., where the UE <NUM> is carried by a user on a bicycle), and heading of the UE <NUM>.

Note that although <FIG> only illustrates two of the UEs as V-UEs (V-UEs <NUM>), any of the illustrated UEs (e.g., UEs <NUM>, <NUM>, <NUM>, <NUM>) may be V-UEs. In addition, while only the V-UEs <NUM> and a single UE <NUM> have been illustrated as being connected over a sidelink, any of the UEs illustrated in <FIG>, whether V-UEs, P-UEs, etc., may be capable of sidelink communicaiton. Further, although only UE <NUM> was described as being capable of beam forming, any of the illustrated UEs, including V-UEs <NUM>, may be capable of beam forming. Where V-UEs <NUM> are capable of beam forming, they may beam form towards each other (i.e., towards other V-UEs <NUM>), towards roadside access points <NUM>, towards other UEs (e.g., UEs <NUM>, <NUM>, <NUM>, <NUM>), etc. Thus, in some cases, V-UEs <NUM> may utilize beamforming over sidelinks <NUM>, <NUM>, and <NUM>.

The wireless communications system <NUM> may further include one or more UEs, such as UE <NUM>, that connects indirectly to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links. In the example of <FIG>, UE <NUM> has a D2D P2P link <NUM> with one of the UEs <NUM> connected to one of the base stations <NUM> (e.g., through which UE <NUM> may indirectly obtain cellular connectivity) and a D2D P2P link <NUM> with WLAN STA <NUM> connected to the WLAN AP <NUM> (through which UE <NUM> may indirectly obtain WLAN-based Internet connectivity). In an example, the D2D P2P links <NUM> and <NUM> may be supported with any well-known D2D RAT, such as LTE Direct (LTE-D), WiFi Direct (WiFi-D), Bluetooth®, and so on. As another example, the D2D P2P links <NUM> and <NUM> may be sidelinks, as described above with reference to sidelinks <NUM>, <NUM>, and <NUM>.

<FIG> illustrates an example wireless network structure <NUM>. For example, a 5GC <NUM> (also referred to as a Next Generation Core (NGC)) can be viewed functionally as control plane (C-plane) functions <NUM> (e.g., UE registration, authentication, network access, gateway selection, etc.) and user plane (U-plane) functions <NUM>, (e.g., UE gateway function, access to data networks, IP routing, etc.) which operate cooperatively to form the core network. User plane interface (NG-U) <NUM> and control plane interface (NG-C) <NUM> connect the gNB <NUM> to the 5GC <NUM> and specifically to the user plane functions <NUM> and control plane functions <NUM>, respectively. In an additional configuration, an ng-eNB <NUM> may also be connected to the 5GC <NUM> via NG-C <NUM> to the control plane functions <NUM> and NG-U <NUM> to user plane functions <NUM>. Further, ng-eNB <NUM> may directly communicate with gNB <NUM> via a backhaul connection <NUM>. In some configurations, a Next Generation RAN (NG-RAN) <NUM> may have one or more gNBs <NUM>, while other configurations include one or more of both ng-eNBs <NUM> and gNBs <NUM>. Either (or both) gNB <NUM> or ng-eNB <NUM> may communicate with one or more UEs <NUM> (e.g., any of the UEs described herein).

Another optional aspect may include a location server <NUM>, which may be in communication with the 5GC <NUM> to provide location assistance for UE(s) <NUM>. The location server <NUM> can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.), or alternately may each correspond to a single server. The location server <NUM> can be configured to support one or more location services for UEs <NUM> that can connect to the location server <NUM> via the core network, 5GC <NUM>, and/or via the Internet (not illustrated). Further, the location server <NUM> may be integrated into a component of the core network, or alternatively may be external to the core network (e.g., a third party server, such as an original equipment manufacturer (OEM) server or service server).

<FIG> illustrates another example wireless network structure <NUM>. A 5GC <NUM> (which may correspond to 5GC <NUM> in <FIG>) can be viewed functionally as control plane functions, provided by an access and mobility management function (AMF) <NUM>, and user plane functions, provided by a user plane function (UPF) <NUM>, which operate cooperatively to form the core network (i.e., 5GC <NUM>). The functions of the AMF <NUM> include registration management, connection management, reachability management, mobility management, lawful interception, transport for session management (SM) messages between one or more UEs <NUM> (e.g., any of the UEs described herein) and a session management function (SMF) <NUM>, transparent proxy services for routing SM messages, access authentication and access authorization, transport for short message service (SMS) messages between the UE <NUM> and the short message service function (SMSF) (not shown), and security anchor functionality (SEAF). The AMF <NUM> also interacts with an authentication server function (AUSF) (not shown) and the UE <NUM>, and receives the intermediate key that was established as a result of the UE <NUM> authentication process. In the case of authentication based on a UMTS (universal mobile telecommunications system) subscriber identity module (USIM), the AMF <NUM> retrieves the security material from the AUSF. The functions of the AMF <NUM> also include security context management (SCM). The SCM receives a key from the SEAF that it uses to derive access-network specific keys. The functionality of the AMF <NUM> also includes location services management for regulatory services, transport for location services messages between the UE <NUM> and a location management function (LMF) <NUM> (which acts as a location server <NUM>), transport for location services messages between the NG-RAN <NUM> and the LMF <NUM>, evolved packet system (EPS) bearer identifier allocation for interworking with the EPS, and UE <NUM> mobility event notification. In addition, the AMF <NUM> also supports functionalities for non-3GPP (Third Generation Partnership Project) access networks.

Functions of the UPF <NUM> include acting as an anchor point for intra-/inter-RAT mobility (when applicable), acting as an external protocol data unit (PDU) session point of interconnect to a data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, quality of service (QoS) handling for the user plane (e.g., uplink/ downlink rate enforcement, reflective QoS marking in the downlink), uplink traffic verification (service data flow (SDF) to QoS flow mapping), transport level packet marking in the uplink and downlink, downlink packet buffering and downlink data notification triggering, and sending and forwarding of one or more "end markers" to the source RAN node. The UPF <NUM> may also support transfer of location services messages over a user plane between the UE <NUM> and a location server, such as an SLP <NUM>.

The functions of the SMF <NUM> include session management, UE Internet protocol (IP) address allocation and management, selection and control of user plane functions, configuration of traffic steering at the UPF <NUM> to route traffic to the proper destination, control of part of policy enforcement and QoS, and downlink data notification. The interface over which the SMF <NUM> communicates with the AMF <NUM> is referred to as the N11 interface.

Another optional aspect may include an LMF <NUM>, which may be in communication with the 5GC <NUM> to provide location assistance for UEs <NUM>. The LMF <NUM> can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.), or alternately may each correspond to a single server. The LMF <NUM> can be configured to support one or more location services for UEs <NUM> that can connect to the LMF <NUM> via the core network, 5GC <NUM>, and/or via the Internet (not illustrated). The SLP <NUM> may support similar functions to the LMF <NUM>, but whereas the LMF <NUM> may communicate with the AMF <NUM>, NG-RAN <NUM>, and UEs <NUM> over a control plane (e.g., using interfaces and protocols intended to convey signaling messages and not voice or data), the SLP <NUM> may communicate with UEs <NUM> and external clients (not shown in <FIG>) over a user plane (e.g., using protocols intended to carry voice and/or data like the transmission control protocol (TCP) and/or IP).

User plane interface <NUM> and control plane interface <NUM> connect the 5GC <NUM>, and specifically the UPF <NUM> and AMF <NUM>, respectively, to one or more gNBs <NUM> and/or ng-eNBs <NUM> in the NG-RAN <NUM>. The interface between gNB(s) <NUM> and/or ng-eNB(s) <NUM> and the AMF <NUM> is referred to as the "N2" interface, and the interface between gNB(s) <NUM> and/or ng-eNB(s) <NUM> and the UPF <NUM> is referred to as the "N3" interface. The gNB(s) <NUM> and/or ng-eNB(s) <NUM> of the NG-RAN <NUM> may communicate directly with each other via backhaul connections <NUM>, referred to as the "Xn-C" interface. One or more of gNBs <NUM> and/or ng-eNBs <NUM> may communicate with one or more UEs <NUM> over a wireless interface, referred to as the "Uu" interface.

The functionality of a gNB <NUM> is divided between a gNB central unit (gNB-CU) <NUM> and one or more gNB distributed units (gNB-DUs) <NUM>. The interface <NUM> between the gNB-CU <NUM> and the one or more gNB-DUs <NUM> is referred to as the "F1" interface. A gNB-CU <NUM> is a logical node that includes the base station functions of transferring user data, mobility control, radio access network sharing, positioning, session management, and the like, except for those functions allocated exclusively to the gNB-DU(s) <NUM>. More specifically, the gNB-CU <NUM> hosts the radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols of the gNB <NUM>. A gNB-DU <NUM> is a logical node that hosts the radio link control (RLC), medium access control (MAC), and physical (PHY) layers of the gNB <NUM>. Its operation is controlled by the gNB-CU <NUM>. One gNB-DU <NUM> can support one or more cells, and one cell is supported by only one gNB-DU <NUM>. Thus, a UE <NUM> communicates with the gNB-CU <NUM> via the RRC, SDAP, and PDCP layers and with a gNB-DU <NUM> via the RLC, MAC, and PHY layers.

<FIG> illustrates an example of a wireless communications system <NUM> that supports wireless unicast sidelink establishment, according to aspects of the disclosure. In some examples, wireless communications system <NUM> may implement aspects of wireless communications systems <NUM>, <NUM>, and <NUM>. Wireless communications system <NUM> may include a first UE <NUM> and a second UE <NUM>, which may be examples of any of the UEs described herein. As specific examples, UEs <NUM> and <NUM> may correspond to V-UEs <NUM> in <FIG>, UE <NUM> and UE <NUM> in <FIG> connected over D2D P2P link <NUM>, or UEs <NUM> in <FIG> and <FIG>.

In the example of <FIG>, the UE <NUM> may attempt to establish a unicast connection over a sidelink with the UE <NUM>, which may be a V2X sidelink between the UE <NUM> and UE <NUM>. As specific examples, the established sidelink connection may correspond to sidelinks <NUM> and/or <NUM> in <FIG>. The sidelink connection may be established in an omni-directional frequency range (e.g., FR1) and/or a mmW frequency range (e.g., FR2). In some cases, the UE <NUM> may be referred to as an initiating UE that initiates the sidelink connection procedure, and the UE <NUM> may be referred to as a target UE that is targeted for the sidelink connection procedure by the initiating UE.

For establishing the unicast connection, access stratum (AS) (a functional layer in the UMTS and LTE protocol stacks between the RAN and the UE that is responsible for transporting data over wireless links and managing radio resources, and which is part of Layer <NUM>) parameters may be configured and negotiated between the UE <NUM> and UE <NUM>. For example, a transmission and reception capability matching may be negotiated between the UE <NUM> and UE <NUM>. Each UE may have different capabilities (e.g., transmission and reception, <NUM> quadrature amplitude modulation (QAM), transmission diversity, carrier aggregation (CA), supported communications frequency band(s), etc.). In some cases, different services may be supported at the upper layers of corresponding protocol stacks for UE <NUM> and UE <NUM>. Additionally, a security association may be established between UE <NUM> and UE <NUM> for the unicast connection. Unicast traffic may benefit from security protection at a link level (e.g., integrity protection). Security requirements may differ for different wireless communications systems. For example, V2X and Uu systems may have different security requirements (e.g., Uu security does not include confidentiality protection). Additionally, IP configurations (e.g., IP versions, addresses, etc.) may be negotiated for the unicast connection between UE <NUM> and UE <NUM>.

In some cases, UE <NUM> may create a service announcement (e.g., a service capability message) to transmit over a cellular network (e.g., cV2X) to assist the sidelink connection establishment. Conventionally, UE <NUM> may identify and locate candidates for sidelink communications based on a basic service message (BSM) broadcasted unencrypted by nearby UEs (e.g., UE <NUM>). The BSM may include location information, security and identity information, and vehicle information (e.g., speed, maneuver, size, etc.) for the corresponding UE. However, for different wireless communications systems (e.g., D2D or V2X communications), a discovery channel may not be configured so that UE <NUM> is able to detect the BSM(s). Accordingly, the service announcement transmitted by UE <NUM> and other nearby UEs (e.g., a discovery signal) may be an upper layer signal and broadcasted (e.g., in an NR sidelink broadcast). In some cases, the UE <NUM> may include one or more parameters for itself in the service announcement, including connection parameters and/or capabilities it possesses. The UE <NUM> may then monitor for and receive the broadcasted service announcement to identify potential UEs for corresponding sidelink connections. In some cases, the UE <NUM> may identify the potential UEs based on the capabilities each UE indicates in their respective service announcements.

The service announcement may include information to assist the UE <NUM> (e.g., or any initiating UE) to identify the UE transmitting the service announcement (UE <NUM> in the example of <FIG>). For example, the service announcement may include channel information where direct communication requests may be sent. In some cases, the channel information may be RAT-specific (e.g., specific to LTE or NR) and may include a resource pool within which UE <NUM> transmits the communication request. Additionally, the service announcement may include a specific destination address for the UE (e.g., a Layer <NUM> destination address) if the destination address is different from the current address (e.g., the address of the streaming provider or UE transmitting the service announcement). The service announcement may also include a network or transport layer for the UE <NUM> to transmit a communication request on. For example, the network layer (also referred to as "Layer <NUM>" or "L3") or the transport layer (also referred to as "Layer <NUM>" or "L4") may indicate a port number of an application for the UE transmitting the service announcement. In some cases, no IP addressing may be needed if the signaling (e.g., PC5 signaling) carries a protocol (e.g., a real-time transport protocol (RTP)) directly or gives a locally-generated random protocol. Additionally, the service announcement may include a type of protocol for credential establishment and QoS-related parameters.

After identifying a potential sidelink connection target (UE <NUM> in the example of <FIG>), the initiating UE (UE <NUM> in the example of <FIG>) may transmit a connection request <NUM> to the identified target UE <NUM>. In some cases, the connection request <NUM> may be a first RRC message transmitted by the UE <NUM> to request a unicast connection with the UE <NUM> (e.g., an "RRCDirectConnectionSetupRequest" message). For example, the unicast connection may utilize the PC5 interface for the sidelink, and the connection request <NUM> may be an RRC connection setup request message. Additionally, the UE <NUM> may use a sidelink signaling radio bearer <NUM> to transport the connection request <NUM>.

After receiving the connection request <NUM>, the UE <NUM> may determine whether to accept or reject the connection request <NUM>. The UE <NUM> may base this determination on a transmission/reception capability, an ability to accommodate the unicast connection over the sidelink, a particular service indicated for the unicast connection, the contents to be transmitted over the unicast connection, or a combination thereof. For example, if the UE <NUM> wants to use a first RAT to transmit or receive data, but the UE <NUM> does not support the first RAT, then the UE <NUM> may reject the connection request <NUM>. Additionally or alternatively, the UE <NUM> may reject the connection request <NUM> based on being unable to accommodate the unicast connection over the sidelink due to limited radio resources, a scheduling issue, etc. Accordingly, the UE <NUM> may transmit an indication of whether the request is accepted or rejected in a connection response <NUM>. Similar to the UE <NUM> and the connection request <NUM>, the UE <NUM> may use a sidelink signaling radio bearer <NUM> to transport the connection response <NUM>. Additionally, the connection response <NUM> may be a second RRC message transmitted by the UE <NUM> in response to the connection request <NUM> (e.g., an "RRCDirectConnectionResponse" message).

In some cases, sidelink signaling radio bearers <NUM> and <NUM> may be the same sidelink signaling radio bearer or may be separate sidelink signaling radio bearers. Accordingly, a radio link control (RLC) layer acknowledged mode (AM) may be used for sidelink signaling radio bearers <NUM> and <NUM>. A UE that supports the unicast connection may listen on a logical channel associated with the sidelink signaling radio bearers. In some cases, the AS layer (i.e., Layer <NUM>) may pass information directly through RRC signaling (e.g., control plane) instead of a V2X layer (e.g., data plane).

If the connection response <NUM> indicates that the UE <NUM> accepted the connection request <NUM>, the UE <NUM> may then transmit a connection establishment <NUM> message on the sidelink signaling radio bearer <NUM> to indicate that the unicast connection setup is complete. In some cases, the connection establishment <NUM> may be a third RRC message (e.g., an "RRCDirectConnectionSetupComplete" message). Each of the connection request <NUM>, the connection response <NUM>, and the connection establishment <NUM> may use a basic capability when being transported from one UE to the other UE to enable each UE to be able to receive and decode the corresponding transmission (e.g., the RRC messages).

Additionally, identifiers may be used for each of the connection request <NUM>, the connection response <NUM>, and the connection establishment <NUM>. For example, the identifiers may indicate which UE <NUM>/<NUM> is transmitting which message and/or for which UE <NUM>/<NUM> the message is intended. For physical (PHY) layer channels, the RRC signaling and any subsequent data transmissions may use the same identifier (e.g., Layer <NUM> IDs). However, for logical channels, the identifiers may be separate for the RRC signaling and for the data transmissions. For example, on the logical channels, the RRC signaling and the data transmissions may be treated differently and have different acknowledgement (ACK) feedback messaging. In some cases, for the RRC messaging, a physical layer ACK may be used for ensuring the corresponding messages are transmitted and received properly.

One or more information elements may be included in the connection request <NUM> and/or the connection response <NUM> for UE <NUM> and/or UE <NUM>, respectively, to enable negotiation of corresponding AS layer parameters for the unicast connection. For example, the UE <NUM> and/or UE <NUM> may include packet data convergence protocol (PDCP) parameters in a corresponding unicast connection setup message to set a PDCP context for the unicast connection. In some cases, the PDCP context may indicate whether or not PDCP duplication is utilized for the unicast connection. Additionally, the UE <NUM> and/or UE <NUM> may include RLC parameters when establishing the unicast connection to set an RLC context for the unicast connection. For example, the RLC context may indicate whether an AM (e.g., a reordering timer (t-reordering) is used) or an unacknowledged mode (UM) is used for the RLC layer of the unicast communications.

Additionally, the UE <NUM> and/or UE <NUM> may include medium access control (MAC) parameters to set a MAC context for the unicast connection. In some cases, the MAC context may enable resource selection algorithms, a hybrid automatic repeat request (HARQ) feedback scheme (e.g., ACK or negative ACK (NACK) feedback), parameters for the HARQ feedback scheme, carrier aggregation, or a combination thereof for the unicast connection. Additionally, the UE <NUM> and/or UE <NUM> may include PHY layer parameters when establishing the unicast connection to set a PHY layer context for the unicast connection. For example, the PHY layer context may indicate a transmission format (unless transmission profiles are included for each UE <NUM>/<NUM>) and a radio resource configuration (e.g., bandwidth part (BWP), numerology, etc.) for the unicast connection. These information elements may be supported for different frequency range configurations (e.g., FR1 and FR2).

In some cases, a security context may also be set for the unicast connection (e.g., after the connection establishment <NUM> message is transmitted). Before a security association (e.g., security context) is established between the UE <NUM> and UE <NUM>, the sidelink signaling radio bearers <NUM> and <NUM> may not be protected. After a security association is established, the sidelink signaling radio bearers <NUM> and <NUM> may be protected. Accordingly, the security context may enable secure data transmissions over the unicast connection and the sidelink signaling radio bearers <NUM> and <NUM>. Additionally, IP layer parameters (e.g., link-local IPv4 or IPv6 addresses) may also be negotiated. In some cases, the IP layer parameters may be negotiated by an upper layer control protocol running after RRC signaling is established (e.g., the unicast connection is established). As noted above, the UE <NUM> may base its decision on whether to accept or reject the connection request <NUM> on a particular service indicated for the unicast connection and/or the contents to be transmitted over the unicast connection (e.g., upper layer information). The particular service and/or contents may be also indicated by an upper layer control protocol running after RRC signaling is established.

After the unicast connection is established, the UE <NUM> and UE <NUM> may communicate using the unicast connection over a sidelink <NUM>, where sidelink data <NUM> is transmitted between the two UEs <NUM> and <NUM>. The sidelink <NUM> may correspond to sidelinks <NUM> and/or <NUM> in <FIG>. In some cases, the sidelink data <NUM> may include RRC messages transmitted between the two UEs <NUM> and <NUM>. To maintain this unicast connection on sidelink <NUM>, UE <NUM> and/or UE <NUM> may transmit a keep alive message (e.g., "RRCDirectLinkAlive" message, a fourth RRC message, etc.). In some cases, the keep alive message may be triggered periodically or on-demand (e.g., event-triggered). Accordingly, the triggering and transmission of the keep alive message may be invoked by UE <NUM> or by both UE <NUM> and UE <NUM>. Additionally or alternatively, a MAC control element (CE) (e.g., defined over sidelink <NUM>) may be used to monitor the status of the unicast connection on sidelink <NUM> and maintain the connection. When the unicast connection is no longer needed (e.g., UE <NUM> travels far enough away from UE <NUM>), either UE <NUM> and/or UE <NUM> may start a release procedure to drop the unicast connection over sidelink <NUM>. Accordingly, subsequent RRC messages may not be transmitted between UE <NUM> and UE <NUM> on the unicast connection.

<FIG> is a block diagram illustrating various components of an example UE <NUM>, according to aspects of the disclosure. In an aspect, the UE <NUM> may correspond to any of the UEs described herein. As a specific example, the UE <NUM> may be a V-UE, such as V-UE <NUM> in <FIG>. For the sake of simplicity, the various features and functions illustrated in the block diagram of <FIG> are connected together using a common data bus that is meant to represent that these various features and functions are operatively coupled together. Those skilled in the art will recognize that other connections, mechanisms, features, functions, or the like, may be provided and adapted as necessary to operatively couple and configure an actual UE. Further, it is also recognized that one or more of the features or functions illustrated in the example of <FIG> may be further subdivided, or two or more of the features or functions illustrated in <FIG> may be combined.

The UE <NUM> may include at least one transceiver <NUM> connected to one or more antennas <NUM> and providing means for communicating (e.g., means for transmitting, means for receiving, means for measuring, means for tuning, means for refraining from transmitting, etc.) with other network nodes, such as V-UEs (e.g., V-UEs <NUM>), infrastructure access points (e.g., roadside access point <NUM>), P-UEs (e.g., UEs <NUM>), base stations (e.g., base stations <NUM>), etc., via at least one designated RAT (e.g., cV2X or IEEE <NUM>. 11p) over one or more communication links (e.g., communication links <NUM>, sidelinks <NUM>, <NUM>, <NUM>, mmW communication link <NUM>). The at least one transceiver <NUM> may be variously configured for transmitting and encoding signals (e.g., messages, indications, information, and so on), and, conversely, for receiving and decoding signals (e.g., messages, indications, information, pilots, and so on) in accordance with the designated RAT. In an aspect, the at least one transceiver <NUM> and the antenna(s) <NUM> may form a (wireless) communication interface of the UE <NUM>.

As used herein, a "transceiver" may include at least one transmitter and at least one receiver in an integrated device (e.g., embodied as a transmitter circuit and a receiver circuit of a single communication device) in some implementations, may comprise a separate transmitter device and a separate receiver device in some implementations, or may be embodied in other ways in other implementations. In an aspect, a transmitter may include or be coupled to a plurality of antennas (e.g., antenna(s) <NUM>), such as an antenna array, that permits the UE <NUM> to perform transmit "beamforming," as described herein. Similarly, a receiver may include or be coupled to a plurality of antennas (e.g., antenna(s) <NUM>), such as an antenna array, that permits the UE <NUM> to perform receive beamforming, as described herein. In an aspect, the transmitter(s) and receiver(s) may share the same plurality of antennas (e.g., antenna(s) <NUM>), such that the UE <NUM> can only receive or transmit at a given time, not both at the same time. In some cases, a transceiver may not provide both transmit and receive functionalities. For example, a low functionality receiver circuit may be employed in some designs to reduce costs when providing full communication is not necessary (e.g., a receiver chip or similar circuitry simply providing low-level sniffing).

The UE <NUM> may also include a satellite positioning service (SPS) receiver <NUM>. The SPS receiver <NUM> may be connected to the one or more antennas <NUM> and may provide means for receiving and/or measuring satellite signals. The SPS receiver <NUM> may comprise any suitable hardware and/or software for receiving and processing SPS signals, such as global positioning system (GPS) signals. The SPS receiver <NUM> requests information and operations as appropriate from the other systems, and performs the calculations necessary to determine the UE's <NUM> position using measurements obtained by any suitable SPS algorithm.

One or more sensors <NUM> may be coupled to at least one processor <NUM> and may provide means for sensing or detecting information related to the state and/or environment of the UE <NUM>, such as speed, heading (e.g., compass heading), headlight status, gas mileage, etc. By way of example, the one or more sensors <NUM> may include a speedometer, a tachometer, an accelerometer (e.g., a microelectromechanical systems (MEMS) device), a gyroscope, a geomagnetic sensor (e.g., a compass), an altimeter (e.g., a barometric pressure altimeter), etc..

The at least one processor <NUM> may include one or more central processing units (CPUs), microprocessors, microcontrollers, ASICs, processing cores, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), or the like that provide processing functions, as well as other calculation and control functionality. The at least one processor <NUM> may therefore provide means for processing, such as means for determining, means for calculating, means for receiving, means for transmitting, means for indicating, etc. The at least one processor <NUM> may include any form of logic suitable for performing, or causing the components of the UE <NUM> to perform, at least the techniques described herein.

The at least one processor <NUM> may also be coupled to a memory <NUM> providing means for storing (including means for retrieving, means for maintaining, etc.) data and software instructions for executing programmed functionality within the UE <NUM>. The memory <NUM> may be on-board the at least one processor <NUM> (e.g., within the same integrated circuit (IC) package), and/or the memory <NUM> may be external to the at least one processor <NUM> and functionally coupled over a data bus.

The UE <NUM> may include a user interface <NUM> that provides any suitable interface systems, such as a microphone/speaker <NUM>, keypad <NUM>, and display <NUM> that allow user interaction with the UE <NUM>. The microphone/speaker <NUM> may provide for voice communication services with the UE <NUM>. The keypad <NUM> may comprise any suitable buttons for user input to the UE <NUM>. The display <NUM> may comprise any suitable display, such as, for example, a backlit liquid crystal display (LCD), and may further include a touch screen display for additional user input modes. The user interface <NUM> ay therefore be a means for providing indications (e.g., audible and/or visual indications) to a user and/or for receiving user input (e.g., via user actuation of a sensing device such a keypad, a touch screen, a microphone, and so on).

In an aspect, the UE <NUM> may include a sidelink manager <NUM> coupled to the at least one processor <NUM>. The sidelink manager <NUM> may be a hardware, software, or firmware component that, when executed, causes the UE <NUM> to perform the operations described herein. For example, the sidelink manager <NUM> may be a software module stored in memory <NUM> and executable by the at least one processor <NUM>. As another example, the sidelink manager <NUM> may be a hardware circuit (e.g., an ASIC, a field-programmable gate array (FPGA), etc.) within the UE <NUM>.

For sidelink communications among two or more UEs, it is sometimes necessary for a transmitting UE to either increase or decrease its transmit power to improve hearability of the transmitted signal(s) at the receiving UE(s). This is known as transmit power control (TPC). Transmit power may be increased to meet a threshold signal strength at the receiver, or decreased to minimize interference with other transmitters using the frequency spectrum. There are two types of transmit power control, open loop and closed loop. In open loop transmit power control, the transmitting UE determines its transmission power using its own power setting algorithm. There is no feedback input from the receiver. In closed loop transmit power control, the transmitting UE uses feedback from the receiving UE(s) to determine its transmission power. In some cases, the receiving UE may specifically request a certain transmit power. Open loop transmit power control may be used during connection establishment, before the receiving UE(s) can provide feedback to the transmitting UE. Once a sidelink has been established (e.g., as illustrated in <FIG>), closed loop power control can be used.

As noted above, groups of UEs (e.g., V-UEs <NUM> in <FIG>, UEs <NUM> in <FIG>, UEs <NUM> and <NUM> in <FIG>) may communicate over a sidelink. If closed/open loop transmit power control is employed for sidelink group communications, the UEs in the group settle (and track) on a transmit power that enables them to communicate with the other UEs in the group. In general, the active (transmitting and/or receiving) group members may or may not be known to all UEs in the group. Specifically, the active group members may be known to all UEs in the group, as may be the case in a closed group. Alternatively, in the case of an open group, the active group members may not be known to all UEs in the group. As another alternative, the active group members may only be known to the group leader, which may be the case in open and closed groups.

An issue related to transmit power control procedures for sidelink group communications is how to admit new UEs into the group. For example, there needs to be a mechanism for a non-member UE to discover the presence of the group. If a group announcement discovery procedure is used, then it needs to be determined which member UE(s) send the group announcement and with what transmit power. When a new UE joins the group, it will trigger a re-evaluation of the transmit power selection at the existing member UEs to reach this new member UE.

Accordingly, the present disclosure provides techniques for sidelink group management for transmit power-controlled group communications. The techniques of the present disclosure assume that a sidelink group communication session exists among a group of UEs. A group leader may or may not exist. Further, the transmit power control procedures are assumed to have settled for the existing group members, and the member UEs have determined a transmit power to use for their sidelink transmissions that will reach all the other UEs (or a given subset of those UEs) in the group.

The group of UEs determines one or more UEs in the group to periodically transmit group presence announcement messages, as well as a transmit power that the one or more UEs should use for those group presence announcements. A group presence announcement message should include at least an identifier specific to the group. In an aspect, the group identifier may be a Layer <NUM> (i.e., access stratum layer) group identifier. Alternatively, in another aspect, the group identifier may be an application layer group identifier. A group presence announcement message may be an application layer message, an NAS layer (e.g., a V2X layer) message, or an RRC layer message. More specifically, the type of message depends on which layer is controlling the group announcements and/or group management. For example, a group presence announcement message may be an RRC layer message if the sidelink communications group is an open group, as RRC will likely be more efficient in that case. As another example, a group presence announcement message may be an application layer message if the sidelink communications group is a closed group, as group management may be controlled at the application layer level in that case. A group presence announcement message may be sent over a physical sidelink discovery channel (PSDCH) or one or more sidelink communications physical channels (e.g., physical sidelink control channel (PSCCH) and/or physical sidelink shared channel (PSSCH)).

In an aspect, all of the UEs in the sidelink communications group may transmit the group presence announcement messages. For example, if there is no group leader, then every UE can transmit group presence announcement messages. In an aspect, group presence announcement messages may be synchronized transmissions among all of the UEs. For example, the group presence announcement messages may be aligned on a system frame number (SFN). This is helpful to reduce the resource overhead associated with the transmission of group presence announcement messages, and when there is no specific requirements on the spatial directivity of the transmissions (e.g., in FR1).

In an aspect, instead of some or all of the group members transmitting group presence announcement messages, only the group leader transmits group presence announcement messages.

In an aspect, the group leader may select a subset of the UEs in the sidelink communications group to transmit group presence announcement messages. The group leader may also provide a configuration for group presence announcement message transmissions, including at least a periodicity and a time offset among the selected UE(s). The group leader may stagger the time offset configuration(s) for the selected UE(s) such that the equivalent periodicity of the group presence announcement message transmissions from the perspective of the group are reduced by a factor of the number of UEs selected. For example, if the group leader determines that group presence announcement messages should be transmitted every one second and selects two UEs to transmit group presence announcement messages, each selected UE would transmit a group presence announcement message every two seconds.

In an aspect, the subset of the UEs selected to transmit group presence announcement messages may be based, at least in part, on signal strength measurements (e.g., RSRP, RSRQ) between the UEs in the sidelink communications group. In an aspect, the group leader can select a UE if the signal strength of a transmission from that UE to one or more of the other UEs in the group is below a configured threshold. Specifically, if a UE is well-connected to all or most other UEs in the group, as indicated by a high RSRP associated with that UE, then it may not be at the edge of the group, but rather, more centrally located. However, if the signal strength associated with a UE or a subset of UEs is low (i.e., below some threshold), then it is possible that that UE or subset of UEs is located on the edge of the group. In that case, it would be beneficial for that UE/subset of UEs to broadcast group presence announcement messages, as they are more likely to be heard by non-group UEs outside of, or further from, the geographic location of the sidelink communications group.

In an aspect, similar to the above, the group leader can select a UE or a subset of UEs to broadcast group presence announcement messages if the signal strength of transmissions from that UE on one or more transmit beams to one or more of the other UEs in the group is below a configured threshold. The signal strength of transmissions from a UE may be determined by a receiving UE using either any receive beam or the best receive beam to receive such transmissions. If the sidelink communications group is operating in mmW (e.g., FR2), the selected UE(s) may transmit the group presence announcement messages in a beamformed manner using multiple transmit beams. In this case, the selected UEs should be selected not based only on the signal strength of a given transmit beam, but the signal strength of multiple transmit beams.

In an aspect, a UE transmitting group presence announcement messages may determine the transmit power for a group presence announcement message transmission based, at least in part, on (<NUM>) a transmit power configuration that the UE is using to transmit other sidelink physical channels to the group members, (<NUM>) a downlink pathloss measurement to a serving base station, (<NUM>) a sidelink pathloss to a group leader (if there is one), (<NUM>) a transmit power configuration received from the group leader (if there is one), and/or (<NUM>) a maximum transmit power configuration for the UE that does not exceed the UE's maximum transmit power capability.

The transmit power configuration received from the group leader (option (<NUM>) above) may include a maximum transmit power to use for group presence announcement message transmissions and/or an upper bound on the incremental transmit power increase that the UE may use beyond the transmit power it is using for sidelink transmissions to other group members. This option may be used in the following example scenario. In the example scenario, sidelink transmit power control is used within the sidelink communications group. Further, the group leader determines the maximum transmit power the members of the group can use based on pathloss measurements to a serving base station (which may be serving all, or at least most, of the member UEs). That is, interference from uplink UE transmissions at the base station are being managed only by the group leader, instead of each member individually. As a sidelink communications group is local (i.e., the member UEs are within wireless communication range of each other, and therefore likely a relatively small geographic area), using only measurements from the group leader should be sufficient, as they would likely be nearly the same for all other member UEs. In such an example scenario, the group leader can determine how much of an incremental increase in the transmit power the selected UE(s) can use beyond the transmit power used for normal sidelink communications within the group.

In an aspect, the UE transmitting the group presence announcement messages may determine one or more transmit spatial configurations (i.e., transmit beams) to use for the group presence messages. The chosen transmit spatial configurations may include at least the transmit beams that have been determined to be "not good" transmit beams for communicating with other group members. In particular, the UE may determine the set of transmit beams (transmit spatial configurations) for which the signal strength measured by one or more of the other member UEs is below a configured threshold, meaning that the set of transmit beams includes beams that are likely not directed at the member UEs. The UE may transmit the group presence announcement messages using one or more of the transmit beams in the determined set. The assumption is that by selecting one or more transmit beams that are not directed at the other UEs in the sidelink communications group, the transmit beams are more likely to be detected by UEs that are not members of the group.

<FIG> illustrates an example wireless communications system <NUM>, according to aspects of the disclosure. In the example of <FIG>, a group of UEs (illustrated as UEs <NUM>, <NUM>, and <NUM>) have formed a sidelink communications group. The member UEs may communicate among each other over various sidelinks, illustrated by dashed arrows, which may correspond to sidelinks <NUM> and/or <NUM> in <FIG> or sidelink <NUM> in <FIG>. In the example of <FIG>, the UE <NUM> is the group leader, and the UE <NUM> has been selected, or otherwise determined, to be the UE that transmits group presence announcement messages. The remaining UEs <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> (collectively, UEs <NUM>) are member UEs that are not the group leader and do not transmit group presence announcement messages. Note, however, that there may not be a group leader, or the group leader may transmit group presence announcement messages rather than any of the other UEs.

To differentiate among the UEs illustrated in <FIG>, the UE <NUM> may be referred to herein as the group leader UE <NUM>, the UEs <NUM> may be referred to as regular member UEs <NUM>, and the UE <NUM> may be referred to as the transmitting UE <NUM>. As will be appreciated, there may be more or fewer regular member UEs <NUM> than the three illustrated in <FIG>, and there may be more transmitting UEs <NUM> that the one illustrated in <FIG>.

In an aspect, the transmitting UE <NUM> may have been selected/determined based on having a signal strength to one or more other UEs <NUM>/<NUM> that is less than a threshold (which may be configured by the group leader UE <NUM>, the serving base station, a network entity, the applicable standard, etc.). For example, given its distance from regular member UE <NUM>-<NUM>, the signal strength of sidelink transmissions received at the regular member UE <NUM>-<NUM> may be less than the threshold, and based on that determination, the transmitting UE <NUM> is selected to transmit group presence announcement messages. As can be seen in the example of <FIG>, the lower signal strength of transmissions from the transmitting UE <NUM> to the regular member UE <NUM>-<NUM> indicates that the transmitting UE <NUM> is on the edge of the sidelink communications group.

In an aspect, the UEs <NUM>, <NUM>, and <NUM> in <FIG> may operate in a mmW frequency range (e.g., FR2), and may therefore use beamforming (transmit and receive) to communicate over the illustrated sidelinks. In this case, the transmitting UE <NUM> may be selected/determined based on the signal strength of beamformed transmissions from the transmitting UE <NUM> to one or more of the other UEs <NUM>/<NUM> being below a threshold. As above, the threshold may be configured by the group leader UE <NUM>, the serving base station, a network entity, the applicable standard, etc. For example, given its distance from regular member UE <NUM>-<NUM>, the signal strength of beamformed sidelink transmissions received at the regular member UE <NUM>-<NUM> may be less than the threshold. The signal strength may be determined by the regular member UE <NUM>-<NUM> using any receive beam or the best receive beam to receive sidelink transmissions from the transmitting UE <NUM>.

Once selected/determined, the transmitting UE <NUM> periodically transmits group presence announcement messages <NUM>. If operating in FR1, the transmitting UE <NUM> may transmit group presence announcement messages <NUM> omni-directionally. Alternatively, if operating in a mmW frequency range, the transmitting UE <NUM> may transmit the group presence announcement messages in a beamformed manner using one or more transmit beams. The one or more transmit beams may include at least one transmit beam that has a received signal strength at one or more of the other UEs <NUM>/<NUM> in the group that is lower than a threshold determined to be acceptable for communicating with the other group members. For example, the transmitting UE <NUM> may select transmit beam <NUM> to transmit group presence announcement messages <NUM>. As shown in <FIG>, the transmit beam <NUM> would be a poor choice for communicating with the other UEs in the sidelink communications group, which is why it was selected, but may provide sufficient received signal strength at a non-member UE <NUM> to be detectable by the non-member UE <NUM>.

<FIG> illustrates an example method <NUM> for wireless communication, according to aspects of the disclosure. In an aspect, the method <NUM> may be performed by a UE participating in a sidelink communications group (e.g., any of the UEs described herein). In a specific example, the UE may correspond to transmitting UE <NUM> in <FIG>.

At <NUM>, the UE communicates with one or more member UEs (e.g., UEs <NUM> and <NUM> in <FIG>) of the sidelink communications group. In an aspect, operation <NUM> may be performed by the at least one transceiver <NUM>, the at least one processor <NUM>, memory <NUM>, and/or sidelink manager <NUM>, any or all of which may be considered means for performing this operation.

At <NUM>, the UE transmits group presence announcement messages for the sidelink communications group based on a determination, based on communicating with the one or more member UEs, of at least a transmit power for the group presence announcement messages and that the UE is expected to transmit the group presence announcement messages for the sidelink communications group. In an aspect, operation <NUM> may be performed by the at least one transceiver <NUM>, the at least one processor <NUM>, memory <NUM>, and/or sidelink manager <NUM>, any or all of which may be considered means for performing this operation.

As will be appreciated, a technical advantage of the method <NUM> is increased efficiency for determining the transmit power control within a group of UEs connected over a sidelink.

The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an ASIC, a field-programable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

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

In one or more example aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

Claim 1:
A method for wireless communication performed by a user equipment, UE (<NUM>, <NUM>, <NUM>), participating in a sidelink communications group, comprising:
communicating (<NUM>) with one or more member UEs (<NUM>, <NUM>) of the sidelink communications group; and
transmitting (<NUM>) group presence announcement messages (<NUM>) for the sidelink communications group based on a determination, based on communicating (<NUM>) with the one or more member UEs (<NUM>, <NUM>), of at least a transmit power for the group presence announcement messages and that the UE (<NUM>, <NUM>, <NUM>) is expected to transmit the group presence announcement messages for the sidelink communications group, wherein the UE (<NUM>, <NUM>, <NUM>) is one of a subset of member UEs of the sidelink communications group that transmits the group presence announcement messages (<NUM>) for the sidelink communications group.