Sidelink synchronization signals for connected user equipment

Abstract

Methods, systems, and apparatus for wireless communication are described. A sidelink UE can be configured to have a synchronization reference signal that can be used by the UE to synchronize time and frequency resources. First and second UEs can perform beam sweep procedures to identify transmit and receive beams to be used for communication between the UEs. A synchronization reference signal procedure can be initiated, and the first UE can receive a sidelink synchronization reference signal from the second UE using the established receive beam. UEs can align time and frequency resources for communication between the UEs, and UEs can communicate via a sidelink channel based on time synchronization, frequency synchronization, or both determined using the sidelink synchronization signal. In some cases, a sidelink UE can simultaneously receive multiple synchronization reference signals from multiple sidelink UEs, where each synchronization reference signal may include a UE identifier.

Description

[0001] Cross-references

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 008,579, filed April 10, 2020, entitled “Sidelink Synchronization Signal for Connected User Equipment”, and U.S. Patent Application No. 17 / 203,105, filed March 16, 2021, entitled “Sidelink Synchronization Signal for Connected User Equipment”, each of which is assigned to the assignee of this application. Technical Field

[0003] The following generally refers to wireless communication, and in particular to sidelink synchronization signals for connected user equipment (UE).

[0004] background

[0005] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, message sending and receiving, broadcasting, and so on. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth-generation (4G) systems (such as Long Term Evolution (LTE) systems, LTE-A Advanced (LTE-A) systems, or LTE-A Pro systems) and fifth-generation (5G) systems, which may be referred to as New Radio (NR) systems. These systems can employ various technologies, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or Discrete Fourier Transform Extended Orthogonal Frequency Division Multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include one or more base stations or one or more network access nodes, each of which simultaneously supports communication with multiple communication devices, which may also be referred to as User Equipment (UE).

[0006] Some wireless communication systems support the establishment of sidelink channels for communication between two devices (such as two UEs). The two UEs can perform synchronization procedures to establish transmit and receive beams for communication between them, and the UEs can synchronize resources. Conventional synchronization procedures may inefficiently utilize resources and may result in unreliable synchronization.

[0007] Overview

[0008] The described technology relates to methods, systems, devices, and apparatuses supporting improved sidelink synchronization signals for connected user equipment (UEs). Generally, the described technology provides improved synchronization of time and frequency resources for sidelink communication between one or more UEs. In some cases, the sidelink UE may be configured to have a synchronization reference signal that can be used by the UE to synchronize time and frequency resources. Thus, a first UE may perform a beam sweep procedure with a second UE to identify the transmit beam, receive beam, or both to be used for communication on the sidelink channel between the first and second UEs. The first and second UEs may also establish initial time and frequency synchronization via the beam sweep procedure. In some cases, one or more UEs may move relative to another UE, or the network environment may change, and a transmitting UE (e.g., the second UE) may initiate the transmission of a synchronization reference signal to a receiving UE (e.g., the first UE). Thus, the first UE can receive a first sidelink synchronization reference signal from the second UE via the established receive beam through the sidelink channel.

[0009] For example, a first UE may use one or more beams identified in the beam sweep procedure to establish a sidelink connection with a second UE. For example, each of the first and second UEs may identify a transmit beam, a receive beam, or both. The first UE may use the transmit beam of the established sidelink connection identified in the beam sweep procedure to transmit a sidelink synchronization reference signal, while the second UE may use the receive beam of the established sidelink connection identified in the beam sweep procedure to receive the sidelink synchronization reference signal. The first and second UEs may align time and frequency resources for communication between the first and second UEs. The first and second UEs may transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal. In some cases, a sidelink UE may simultaneously receive multiple synchronization reference signals from multiple sidelink UEs, wherein each synchronization reference signal may include UE identifier information to distinguish the reference signals.

[0010] A method for wireless communication by a first UE is described. The method may include: performing a beam sweep procedure with a second UE to identify a receive beam to be used for communication with the second UE on a sidelink channel; receiving a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmitting a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0011] An apparatus for wireless communication by a first UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to: perform a beam sweep procedure with a second UE to identify a receive beam to be used for communication with the second UE on a sidelink channel; receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel based on a time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0012] Another device for wireless communication by a first UE is described. The device may include: means for performing a beam sweep procedure with a second UE to identify a receive beam to be used for communication with the second UE on a sidelink channel; means for receiving a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and means for transmitting a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0013] A non-transient computer-readable medium is described, storing code for wireless communication by a first UE. The code may include instructions executable by a processor to: perform a beam sweep procedure with a second UE to identify a receive beam to be used for communication with the second UE on a sidelink channel; receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0014] Examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for: receiving periodic control signaling indicating that a first sidelink synchronization reference signal is transmitted by a second UE, and using a receive beam to monitor the sidelink channel based on the periodicity to locate the transmission of the first sidelink synchronization reference signal.

[0015] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for receiving control signaling that schedules the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be received according to the control signaling.

[0016] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for transmitting control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be received according to the control signaling.

[0017] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, transmitting control signaling may include operations, features, means, or instructions for transmitting control signaling based on detected movement of a first UE, a second UE, or both.

[0018] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for: receiving control signaling instructing a semi-persistent transmission schedule for transmitting a first sidelink synchronization reference signal by a second UE, and using a receive beam to monitor the sidelink channel based on the semi-persistent transmission schedule to locate the transmission of the first sidelink synchronization reference signal.

[0019] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for receiving a second synchronization reference signal from a third UE via a sidelink channel using a receive beam, and for transmitting a second transmission via the sidelink channel based on time synchronization, frequency synchronization or both determined using the second synchronization reference signal.

[0020] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, receiving a second synchronization reference signal may include operations, features, means, or instructions for receiving a second synchronization reference signal indicating an identifier of a third UE, the identifier of which is different from the identifier of the second UE indicated in a first side-link synchronization reference signal.

[0021] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, transmitting a first transmission via a sidelink channel may include operations, features, means, or instructions for transmitting the first transmission via a sidelink channel using a beam having a beamwidth that is narrower than the receiving beam.

[0022] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, first and second side link synchronization reference signals can be received concurrently or simultaneously.

[0023] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for receiving a side link synchronization signal block (SSB) from a second UE.

[0024] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, the periodicity of the transmission of the first sidelink synchronization reference signal may be shorter than the periodicity of the transmission of the sidelink SSB.

[0025] A method for wireless communication by a first UE is described. The method may include: performing a beam sweep procedure with a second UE to identify a transmit beam to be used for communication with the second UE on a sidelink channel; transmitting a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and conveying a first transmission via the sidelink channel using the transmit beam based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0026] An apparatus for wireless communication by a first UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are executable by the processor to cause the apparatus to: perform a beam sweep procedure with a second UE to identify a transmit beam to be used for communication with the second UE on a sidelink channel; transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel using the transmit beam based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0027] Another device for wireless communication by a first UE is described. The device may include: means for performing a beam sweep procedure with a second UE to identify a transmit beam to be used for communication with the second UE on a sidelink channel; means for transmitting a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and means for using the transmit beam to transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0028] A non-transient computer-readable medium is described, storing code for wireless communication by a first UE. The code may include instructions executable by a processor to perform: performing a beam sweep procedure with a second UE to identify a transmit beam to be used for communication with the second UE on a sidelink channel; transmitting a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and conveying a first transmission via the sidelink channel using the transmit beam based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0029] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for transmitting periodic control signaling indicative of the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be transmitted according to the periodicity.

[0030] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for transmitting control signaling that schedules the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be transmitted according to the control signaling.

[0031] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for receiving control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be transmitted according to the control signaling.

[0032] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for transmitting control signaling instructing a semi-persistent transmission schedule for the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be transmitted according to the control signaling.

[0033] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, transmitting a first sidelink synchronization reference signal may include operations, features, means or instructions for transmitting a first sidelink synchronization reference signal that indicates an identifier of a first UE.

[0034] Some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein may further include operations, features, means or instructions for transmitting side-link SSB transmissions.

[0035] In some examples of the methods, apparatus (devices) and non-transient computer-readable media described herein, the periodicity of the transmission of the first sidelink synchronization reference signal may be shorter than the periodicity of the transmission of the sidelink SSB. Brief description of the attached diagram

[0037] Figures 1 to 3 Examples of wireless communication systems supporting sidelink synchronization signals for connected user equipment (UE) are described in accordance with various aspects of this disclosure.

[0038] Figure 4 An example of the process flow for sidelink synchronization signals for a connected UE, supported by various aspects of this disclosure, is explained.

[0039] Figure 5 and 6 A block diagram of a device supporting sidelink synchronization signals for a connected UE is shown, according to various aspects of this disclosure.

[0040] Figure 7 A block diagram of a communication manager supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, is shown.

[0041] Figure 8 A diagram of a system including a device supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, is shown.

[0042] Figures 9 to 12 A flowchart illustrating a method for supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown.

[0043] Detailed description

[0044] Wireless communication systems can support both access links and sidelinks for communication between wireless devices. An access link can refer to a communication link between a user equipment (UE) and a base station. For example, an access link can support uplink signaling, downlink signaling, and connection procedures between devices (such as a UE and a base station). A sidelink can refer to any communication link between similar wireless devices (e.g., a communication link between UEs, a backhaul communication link between base stations, etc.). It should be noted that while the various examples provided herein are discussed with respect to UE sidelink devices, such sidelink technologies can be used for any type of wireless device using sidelink communication. For example, a sidelink can support device-to-device (D2D) communication, vehicle-to-everything (V2X) or vehicle-to-vehicle (V2V) communication, message relay, discovery signaling, beacon signaling, or any combination of these or other signals transmitted over the air from one wireless device to one or more other wireless devices.

[0045] Some wireless communication systems support the establishment of a sidelink channel for communication between two devices (such as two UEs). Before communication occurs on the sidelink channel, the two UEs perform a synchronization procedure (e.g., beam sweep procedure) by using a synchronization signal block (SSB) to establish the transmit and receive beams to be used for communication between the two UEs. In some cases, the UEs may synchronize time and frequency resources during the synchronization procedure. In other cases, the sidelink UE may move or the network environment may change, causing time and frequency resources to become out of sync between the two UEs. To periodically resynchronize time and frequency resources, the UEs may again perform a synchronization procedure by using a beam sweep with an SSB, which involves determining the transmit beam, receive beam, time resources, and frequency resources between the two UEs. In some cases, performing a beam sweep procedure to resynchronize time and frequency resources may be inefficient in utilizing resources because the transmit and receive beam pairs initially determined by the sidelink UE may not need to be updated. Furthermore, since the amount of resources required to transmit SSBs across multiple beams may be large, the periodicity of beam sweep synchronization procedures may be infrequent, and this could lead to unreliable transmission between two UEs, as the UEs may operate with outdated time and frequency synchronization.

[0046] In some wireless communication systems, a sidelink UE can be configured to transmit sidelink reference signals (such as sidelink synchronization reference signals) to other sidelink UEs on pre-determined beam pairs to update time synchronization, frequency synchronization, or both. Thus, each sidelink UE can transmit a SSB on one or more beams via a beam sweep procedure to initially establish transmit and receive beam pairs and time and frequency synchronization (e.g., initial time and frequency synchronization) between the sidelink UEs. Upon initial establishment, the UE can use the synchronization reference signal to update time and frequency resource synchronization on the established beam pairs. In some implementations, the synchronization reference signal can be dynamically transmitted as network conditions change or as one or two sidelink UEs move relative to each other, or the synchronization signal can be transmitted periodically or semi-persistently. In some cases, the synchronization reference signal is transmitted more frequently than an SSB transmitted on multiple beams because the synchronization reference signal uses fewer resources. In some implementations, a sidelink UE can receive multiple synchronization reference signals from multiple UEs, where each synchronization reference signal includes UE identifier information (e.g., UE ID) to distinguish each synchronization reference signal. In some implementations, a sidelink UE can simultaneously transmit one or more synchronization reference signals to one or more other sidelink UEs.

[0047] Specific aspects of the subject matter described herein can be implemented to achieve one or more advantages. The described techniques can support improved resource synchronization between sidelink UEs, as well as other advantages, by improving reliability, reducing signaling overhead, and increasing resource utilization efficiency. Thus, the supported techniques can include improved network operation, and in some examples, enhanced network efficiency and other benefits.

[0048] The aspects of this disclosure are initially described in the context of a wireless communication system. Subsequently, aspects concerning process flow are described. The aspects of this disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts relating to sidelink synchronization signals for connected UEs.

[0049] Figure 1 Examples of a wireless communication system 100 supporting sidelink synchronization signals for connected UEs according to various aspects of this disclosure are described. The wireless communication system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be a Long Term Evolution (LTE) network, an Advanced LTE (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communication system 100 may support enhanced broadband communication, ultra-reliable (e.g., mission-critical) communication, low latency communication, communication with low-cost and low-complexity devices, or any combination thereof.

[0050] Base station 105 can be distributed across a geographical area to form wireless communication system 100, and can be different types of devices or devices with different capabilities. Base station 105 and UE 115 can communicate wirelessly via one or more communication links 125. Each base station 105 can provide a coverage area 110, and UE 115 and base station 105 can establish one or more communication links 125 on the coverage area 110. Coverage area 110 can be an example of a geographical area over which base station 105 and UE 115 can support signal communication according to one or more radio access technologies.

[0051] Each UE 115 can be distributed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 can be stationary or mobile, or stationary and mobile at different times. Each UE 115 can be a different type of device or a device with different capabilities. Figure 1 The document describes some example UE 115s. The UE 115 described herein can communicate with various types of devices, such as other UE 115s, base station 105, or network equipment (e.g., core network nodes, relay equipment, integrated access and backhaul (IAB) nodes, or other network equipment). Figure 1 As shown in the image.

[0052] Each base station 105 may communicate with the core network 130, or with each other, or both. For example, base station 105 may interface with the core network 130 via one or more backhaul links 120 (e.g., via S1, N2, N3, or other interfaces). Base stations 105 may communicate with each other directly (e.g., directly between base stations 105), indirectly (e.g., via the core network 130), or directly and indirectly on backhaul links 120 (e.g., via X2, Xn, or other interfaces). In some examples, backhaul link 120 may be or include one or more radio links.

[0053] One or more of the base stations 105 described herein may include, or may be referred to by those skilled in the art as, base transceiver station, radio base station, access point, radio transceiver, B node, evolved B node (eNB), next-generation B node or gigabit B node (any of which may be referred to as gNB), home B node, home evolved B node, or other suitable terms.

[0054] UE 115 may include or be referred to as a mobile device, wireless device, remote device, handheld device, or subscriber device, or any other suitable term, wherein "device" may also be referred to as a unit, station, terminal, or client, etc. UE 115 may also include or be referred to as a personal electronic device, such as a cellular phone, personal digital assistant (PDA), tablet computer, laptop computer, or personal computer. In some examples, UE 115 may include or be referred to as a wireless local loop (WLL) station, Internet of Things (IoT) device, Internet of Everything (IoE) device, or machine-type communication (MTC) device, which may be implemented in various objects such as appliances or vehicles, meters, etc.

[0055] The UE 115 described herein can communicate with various types of devices, such as other UEs 115 that sometimes act as relays, as well as base station 105 and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, relay base stations, etc. Figure 1 As shown in the image.

[0056] UE 115 and base station 105 can wirelessly communicate with each other via one or more communication links 125 on one or more carriers. The term "carrier" can refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communication link 125. For example, a carrier for communication link 125 may include a portion of the radio spectrum band (e.g., a bandwidth portion (BWP)) operating according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling coordinating carrier operation, user data, or other signaling. Wireless communication system 100 may support communication with UE 115 using carrier aggregation or multi-carrier operation. UE 115 may be configured to have multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used in conjunction with both frequency division duplex (FDD) and time division duplex (TDD) component carriers.

[0057] The signal waveform transmitted on the carrier may include multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques, such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform extended OFDM (DFT-S-OFDM)). In a system employing MCM, a resource element may include a symbol period (e.g., the duration of a modulation symbol) and a subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the code rate of the modulation scheme, or both). Thus, the more resource elements the UE 115 receives and the higher the order of the modulation scheme, the higher the data rate the UE 115 can achieve. Wireless communication resources can refer to a combination of radio frequency spectrum resources, temporal resources, and spatial resources (e.g., spatial layers or beams), and using multiple spatial layers can further improve the data rate or data integrity of communication with the UE 115.

[0058] The time interval of base station 105 or UE 115 can be expressed as a multiple of a basic time unit, such as the sampling period T. s =1 / (Δf) max ·N f ) seconds, where Δf max This can represent the maximum supported subcarrier spacing, while N f This can represent the maximum supported Discrete Fourier Transform (DFT) size. The time interval of the communication resources can be organized according to radio frames, each with a specified duration (e.g., 10 milliseconds (ms)). Each radio frame can be identified by a System Frame Number (SFN) (e.g., ranging from 0 to 1023).

[0059] Each frame may include multiple consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some examples, a frame may (e.g., in the time domain) be divided into subframes, and each subframe may be further divided into several time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include several symbol periods (e.g., depending on the length of the cyclic prefix added before each symbol period). In some wireless communication systems 100, time slots may be further divided into multiple mini-time slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N) symbols. f (Number) sampling periods. The duration of a symbol period can depend on the subcarrier interval or the operating frequency band.

[0060] A subframe, time slot, mini-slot, or symbol can be the smallest scheduling unit of the wireless communication system 100 (e.g., in the time domain) and can be referred to as a transmission time interval (TTI). In some examples, the duration of the TTI (e.g., the number of symbol periods in the TTI) can be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communication system 100 can be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

[0061] Physical channels can be multiplexed on a carrier using various techniques. Physical control channels and physical data channels can be multiplexed on a downlink carrier, for example, using one or more of Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for physical control channels can be defined by the number of symbol periods and can extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESET) can be configured for a set of UEs 115. For example, one or more UEs 115 can monitor or search control regions for control information based on one or more search space sets, and each search space set can include one or more control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for control channel candidates can refer to the number of control channel resources (e.g., control channel elements (CCEs)) associated with coded information in a control information format having a given payload size. The search space set may include a common search space set configured to send control information to multiple UEs 115 and a UE-specific search space set configured to send control information to a particular UE 115.

[0062] In some examples, base station 105 may be mobile, and thus provide communication coverage to mobile geographic coverage areas 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. Wireless communication system 100 may include, for example, a heterogeneous network, in which different types of base stations 105 use the same or different radio access technologies to provide coverage to various geographic coverage areas 110.

[0063] Wireless communication system 100 may be configured to support ultra-reliable communication or low latency communication, or various combinations thereof. For example, wireless communication system 100 may be configured to support ultra-reliable low latency communication (URLLC) or mission-critical communication. UE 115 may be designed to support ultra-reliable, low latency, or mission-critical functions (e.g., mission-critical functions). Ultra-reliable communication may include private or group communication and may be supported by one or more mission-critical services, such as Mission-Critical Talk-to-Talk (MCPTT), Mission-Critical Video (MCVideo), or Mission-Critical Data (MCData)). Support for mission-critical functions may include prioritization of services, and mission-critical services may be used for public safety or general business applications. The terms ultra-reliable, low latency, mission-critical, and ultra-reliable low latency are used interchangeably herein.

[0064] In some examples, UE 115 may also be able to communicate directly with other UE 115 on a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UE 115s utilizing D2D communication may be within the geographic coverage area 110 of base station 105. Other UE 115s in such a group may be outside the geographic coverage area 110 of base station 105 or may be unable to receive transmissions from base station 105 for other reasons. In some examples, groups of UE 115s communicating via D2D communication may utilize a one-to-many (1:M) system, where each UE 115 transmits to every other UE 115 in the group. In some examples, base station 105 facilitates the scheduling of resources for D2D communication. In other cases, D2D communication is performed between the individual UE 115s without involving base station 105.

[0065] In some systems, the D2D communication link 135 may be an example of a communication channel (such as a sidelink communication channel) between vehicles (e.g., UE 115). In some examples, vehicles may communicate using vehicle-to-vehicle (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination of these communications. Vehicles may signal information relating to traffic conditions, signaling, weather, safety, emergencies, or any other information related to the V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure (such as roadside units), or with the network, or with both, via vehicle-to-network (V2N) communication through one or more network nodes (e.g., base station 105).

[0066] Core network 130 provides user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. Core network 130 can be an evolved packet core (EPC) or a 5G core (5GC). The EPC or 5GC may include at least one control plane entity (e.g., a Mobility Management Entity (MME), Access and Mobility Management Function (AMF)) for managing access and mobility, and at least one user plane entity (e.g., a Serving Gateway (S-GW), Packet Data Network (PDN) Gateway (P-GW), or User Plane Function (UPF)) for routing packets or interconnecting to external networks. The control plane entity manages non-access stratum (NAS) functions, such as mobility, authentication, and bearer management of UE 115 served by base station 105 associated with core network 130. User IP packets can be delivered through the user plane entity, which provides IP address allocation and other functions. The user plane entity can connect to network operator IP service 150. Carrier IP services 150 may include access to the Internet, intranets, IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0067] Some network devices (such as base station 105) may include sub-components, such as access network entity 140, which may be an example of an access node controller (ANC). Each access network entity 140 may communicate with each UE 115 through one or more other access network transport entities 145, which may be referred to as a radio headend, smart radio headend, or transmit / receive point (TRP). Each access network transport entity 145 may include one or more antenna panels. In some configurations, the various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio headends and ANCs) or combined into a single network device (e.g., base station 105).

[0068] Wireless communication system 100 can operate using one or more frequency bands, typically in the range of 300 MHz to 300 GHz. Generally, the 300 MHz to 3 GHz band is referred to as a UHF band or decimeter band because the wavelengths range from approximately 1 decimeter to 1 meter. UHF waves can be blocked or redirected by buildings and environmental features, but these waves can penetrate various structures sufficiently for macrocells to provide service to UE 115 located indoors. Compared to transmissions using smaller frequencies and longer waves in the lower HF or VHF portions of the spectrum below 300 MHz, UHF wave transmission can be associated with smaller antennas and shorter ranges (e.g., less than 100 km).

[0069] Wireless communication system 100 may utilize both licensed and unlicensed radio spectrum bands. For example, wireless communication system 100 may employ licensed assisted access (LAA), LTE unlicensed (LTE-U) radio access technology, or NR technology in unlicensed frequency bands (such as the 5 GHz Industrial, Scientific, and Medical (ISM) band). When operating in unlicensed radio spectrum bands, devices (such as base station 105 and UE 115) may employ carrier sensing for collision detection and avoidance. In some examples, operation in unlicensed frequency bands may be based on carrier aggregation configuration (e.g., LAA) in coordination with component carriers operating in licensed frequency bands. Operation in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, etc.

[0070] Base station 105 or UE 115 may be equipped with multiple antennas that can be used to employ technologies such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of base station 105 or UE 115 may be located within one or more antenna arrays or antenna panels that can support MIMO operation or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may coexist at an antenna assembly (such as an antenna tower). In some examples, the antennas or antenna arrays associated with base station 105 may be located in different geographical locations. Base station 105 may have an antenna array with several rows and columns of antenna ports that base station 105 can use to support beamforming for communication with UE 115. Similarly, UE 115 may have one or more antenna arrays that can support various MIMO or beamforming operations. Additionally or alternatively, the antenna panel may support radio frequency beamforming for signals transmitted via the antenna ports.

[0071] Beamforming (also known as spatial filtering, directional transmission, or directional reception) is a signal processing technique that can be used at a transmitting or receiving device (e.g., base station 105, UE 115) to shape or guide an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting and receiving devices. Beamforming can be achieved by combining signals transmitted via antenna elements of an antenna array, such that some signals propagating relative to a particular orientation of the antenna array experience constructive interference, while others experience destructive interference. Adjustments to the signals transmitted via the antenna elements may include the transmitting or receiving device applying amplitude offset, phase offset, or both to the signals carried via the antenna elements associated with that device. The adjustments associated with each antenna element may be defined by a beamforming weight set associated with a particular orientation (e.g., the antenna array relative to the transmitting or receiving device, or relative to some other orientation).

[0072] Base station 105 or UE 115 may use beamsweeping techniques as part of beamforming operations. For example, base station 105 may use multiple antennas or antenna arrays (e.g., antenna panels) for beamforming operations to facilitate directional communication with UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted multiple times by base station 105 in different directions. For example, base station 105 may transmit signals based on different beamforming weight sets associated with different transmission directions. Transmissions in different beam directions may be used (e.g., by the transmitting device (such as base station 105) or the receiving device (such as UE 115)) to identify the beam direction that base station 105 uses for later transmission or reception.

[0073] Some signals (such as data signals associated with a specific receiving device) may be transmitted by base station 105 in a single beam direction (e.g., the direction associated with the receiving device (such as UE 115)). In some examples, the beam direction associated with transmission along a single beam direction may be determined based on the signals transmitted in one or more beam directions. For example, UE 115 may receive one or more signals transmitted by base station 105 in different directions and may report to base station 105 an indication of the signals received by UE 115 with the highest signal quality or other acceptable signal quality.

[0074] In some examples, transmissions performed by a device (e.g., by base station 105 or UE 115) may be executed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate combined beams for transmission (e.g., from base station 105 to UE 115). UE 115 may report feedback indicating precoding weights for one or more beam directions, and this feedback may correspond to a configured number of beams across the system bandwidth or one or more subbands. Base station 105 may transmit reference signals that may be precoded or unprecoded (e.g., cell-specific reference signals (CRS), channel state information reference signals (CSI-RS)). UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., multi-panel type codebook, linear combination type codebook, port selection type codebook). Although these techniques are described with reference to signals transmitted by base station 105 in one or more directions, UE 115 may use similar techniques to transmit signals multiple times in different directions (e.g., to identify the beam direction used by UE 115 for subsequent transmission or reception) or to transmit signals in a single direction (e.g., to transmit data to a receiving device).

[0075] A receiver device (e.g., UE 115) may attempt multiple receive configurations (e.g., directional listening) when receiving various signals (such as synchronization signals, reference signals, beam selection signals, or other control signals) from base station 105. For example, the receiver device may attempt multiple receive directions by: receiving via different antenna subarrays; processing received signals according to different antenna subarrays; receiving according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of the antenna array (e.g., different directional listening weight sets); or processing received signals according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of the antenna array, any of which may be referred to as "listening" according to different receive configurations or receive directions. In some examples, the receiver device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned on a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have the highest signal strength, highest signal-to-noise ratio (SNR), or other acceptable signal quality based on listening according to multiple beam directions).

[0076] In some wireless communication systems, a sidelink UE 115 can be configured to have a synchronization reference signal that can be used by the UE 115 to synchronize time and frequency resources. Thus, the first UE 115 can perform a beam sweep procedure with the second UE 115 to identify the receive and transmit beams to be used for communication on the sidelink channel between the first UE 115 and the second UE 115. The first UE 115 and the second UE 115 can also establish initial time and frequency synchronization via the beam sweep procedure. In some cases, the UE 115 may move relative to the receiver, or the network environment may change, which may initiate (e.g., trigger) the transmitting UE 115 (e.g., the second UE 115) to transmit a synchronization reference signal (e.g., the first UE 115) to the receiving UE 115. In some cases, the UE 115 can be configured to transmit the synchronization reference signal periodically, and triggering the transmission of the synchronization reference signal may not be necessary. The first UE 115 may use the established receive beam to receive a first sidelink synchronization reference signal (e.g., a dynamically triggered synchronization reference signal, a periodically or semi-persistently transmitted synchronization reference signal) from the second UE 115 via a sidelink channel. The first UE 115 and the second UE 115 may align time and frequency resources for communication between the first UE 115 and the second UE 115. The first UE 115 and the second UE 115 may transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal. In some cases, the sidelink UE 115 may simultaneously receive multiple synchronization reference signals from multiple sidelink UEs 115, wherein each synchronization reference signal may include UE identifier information.

[0077] Figure 2 An example of a wireless communication system 200 supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, is described. The wireless communication system 200 may include a base station 105-a and UEs 115-a and 115-b, which may be as described in reference... Figure 1 Examples of base station 105 and UE 115 are described. Base station 105-a serves a geographic coverage area 110-a. In some cases, base station 105-a may provide a resource pool to UEs 115-a and 115-b. In some cases, UEs 115-a and 115-b may communicate via a sidelink channel and may perform resource synchronization using a synchronization reference signal. Additionally or alternatively, other radio devices (such as base station 105, or a combination of UE 115 and base station 105) may implement sidelink resource synchronization procedures.

[0078] UE 115-a and UE 115-b can be connected to base station 105-a respectively (e.g., in connected mode) and can communicate on communication channels 205-a and 205-b respectively. In some cases, base station 105-a can allocate resource pools (including time resources, frequency resources, or both) to UE 115-a and UE 115-b respectively on communication channels 205-a and 205-b. In some cases, the resource pools can be used by UE 115 for sidelink communication between UE 115-a and 115-b. In some cases, base station 105-a can instruct scheduling for sidelink communication between UE 115-a and 115-b. In some cases, UE 115-a and UE 115-b can autonomously determine sidelink communication.

[0079] To establish a sidelink connection between UE 115-a and 115-b, UE 115-a and 115-b may perform a beam sweep procedure to determine the beam pair used for communication between the two UE 115s. In some examples, UE 115-a may participate in a beam sweep operation to establish an active transmit beam and an active receive beam with UE 115-b. UE 115 may establish a wide transmit and receive beam 210 and a narrow transmit and receive beam 215. To establish transmit and receive beams (e.g., wide beam 210 and / or narrow beam 215), UE 115 (such as UE 115-a) may broadcast S-SSB 240 on multiple beams. S-SSB 240 may include one or more Physical Sidelink Broadcast Channels (PSBCH) 220, one or more Sidelink Primary Synchronization Signals (S-PSS) 225, one or more Sidelink Secondary Synchronization Signals (S-SSS) 230, and one or more gaps 235. One or more S-PSS 225s, or one or more S-SSS 230s, or combinations thereof, may be used for time tracking, or frequency tracking, or combinations thereof. In some cases, one or more S-SSS 225s, one or more S-SSS 230s, or combinations thereof may include an identifier of the UE 115 transmitting S-SSB 240 (e.g., an identifier of UE 115-a). One or more PSBCH 220s may include information about the system. For example, one or more PSBCH 220s may indicate the frame number, duplex configuration (e.g., TDD configuration), bandwidth configuration (e.g., SL-BWP), coverage (e.g., in-coverage, out-of-coverage), synchronization source, etc., of PSBCH 200. In some cases, PSBCH 220s may include DMRS that can be used for time tracking, frequency tracking, or both. Another UE 115 (such as UE 115-b) may receive S-SSB 240 from UE 115-a on one or more beams. UE 115-b can use the received S-SSB 240 to track the time or frequency, or both, between UE 115-a and UE 115-b, and determine the transmit and receive beams 215 between UE 115.

[0080] For example, UE 115-a may transmit relatively wide shaped beams (e.g., wide beams 210), which may be transmitted to different sectors or geographic directions within a time duration. In some cases, each wide beam 210 may be associated with an S-SSB 240, in which synchronization signals (e.g., S-PSS 225 and S-SSS 230) and PSBCH transmission 220 may be transmitted in the corresponding beam direction. In some cases, UE 115-b may also transmit relatively wide shaped beams (e.g., wide beams 210) within the same or different durations. UE 115-b may measure the synchronization signals received on one or more wide beams 210 from UE 115-a and select wide beam pairs based on this measurement, and may indicate the wide beam pairs to UE 115-a or base station 105-a or both. In some scenarios, UE 115-a may measure the synchronization signal received on the wide beam 210 from UE 115-b, select a wide beam pair based on this measurement, and indicate the wide beam pair to UE 115-b or base station 105-a, or both. In some scenarios, the wide beam pair may be selected based on a measurement performed by UE 115-a or UE 115-b, or both. In some implementations, base station 105-a may indicate the selected wide beam pair to UEs 115-a and 115-b. The beam sweep procedure may result in a beam pair including wide beams 210-a and 210-b.

[0081] In some situations, the wide beam 210 may not be narrow enough, or may not have sufficient beamforming gain to provide reliable communication between UE 115-a and UE 115-b. Therefore, it may be beneficial for UE 115-a and UE 115-b to use beam thinning to generate a narrower beamformed signal suitable for communication, which can have a narrower coverage area but higher gain. During beam thinning, one or both of UE 115-a and 115-b may sweep the narrow-shaped beam 215 within the range covered by the selected wide beam 210. For example, UE 115-a may beam sweep the narrow beam 215 within the range of the wide beam 210-a. UE 115-b may beam sweep the narrow beam 215 within the range of the wide beam 210-b. Similar to wide beampair selection, one or both of UEs 115 can receive synchronization signals on one or more narrow beams 215, measure the received synchronization signals, and determine the beamp pair to be used for sidelink communication between UEs 115-a and UE 115-b. For example, UE 115-a, UE 115-b, or both, or base station 105-a can select narrow beams 215-a and 215-b as a narrow beampair.

[0082] In some scenarios, the SSB can be used by UEs 115-a and 115-b to synchronize time and frequency resources used for communication between the two UEs 115. For example, UE 115-a may transmit a signal to UE 115-b. UE 115-b may expect to receive the signal at a certain time (e.g., zero time). However, UEs 115-a and 115-b are separated by distance, which may cause a propagation delay due to the finite speed of the signal. Thus, UE 115-a may transmit the signal at a time before the time when UE 115-b expects the signal. For example, UE 115-b may expect to receive the signal at zero time, so UE 115-a may transmit the signal at a time before zero time based on the separation distance between UE 115-a and UE 115-b. To determine when to transmit and receive signals, UE 115 can perform synchronization procedures, such as the SSB beam sweep procedure.

[0083] In some cases, the synchronization protocol may also take into account the varying carrier frequencies at different UEs 115. For example, the carrier frequency generator (such as an oscillator) may be different between the various UEs 115. The oscillator in UE 115-a may tick (e.g., oscillate) faster than the oscillator in UE 115b, or vice versa. Thus, UEs 115-a and 115-b may have different perceptions of the same frequency. For example, UE 115-a may identify 30 GHz as a lower frequency than it actually is (e.g., 29.9999 GHz), while UE 115-b may identify 30 GHz as a higher frequency than it actually is (e.g., 30.9999 GHz). Frequency differences between two UEs 115 using OFDM may result in the inability to maintain the orthogonality of the OFDM subcarriers, which may lead to a lower signal-to-noise ratio of the signal received at the receiving UE 115. In some situations, even if two UEs 115 are transmitting and receiving at 30 GHz, relative movement between them can cause a Doppler shift effect, resulting in the frequency received by a UE 115 differing from the original transmitted frequency. For example, UE 115-a may transmit a signal to UE 115-b at 30 GHz while simultaneously moving towards UE 115-b. Due to the Doppler shift, UE 115-b may receive the signal at a slightly higher carrier frequency, and this frequency difference can lead to orthogonality problems in OFDM subcarriers.

[0084] In some wireless communication systems, UE 115 may rely on SSB beam sweeping for time and frequency resource synchronization. However, SSB beam sweeping procedures can require significant resources and may be performed infrequently (e.g., periodically every 160 ms). For example, SSBs may also be transmitted on multiple beams, even though transmit and receive beams 210 (e.g., beams 210-a and 210-b) have been determined by the connected UE 115. In some cases, UE 115-a may not receive each SSB transmitted by UE 115-b on multiple beams 210 for time and frequency tracking, or vice versa, which may lead to inefficient use of resources. Network conditions or UE 115 movement may also change drastically within 160 ms, and infrequent synchronization may result in unreliable transmissions. Furthermore, some UE 115s may not be configured to transmit SSBs. Thus, improved time and frequency synchronization procedures can improve reliability in the network. In some wireless communication systems, for two UE 115s (such as UE 115-a and 115-b) connected to a selected beam pair, UE 115 may avoid beam sweeping for resource synchronization.

[0085] In some scenarios, the connected UE 115 can perform resource synchronization using a reference signal (such as a synchronization reference signal), which is transmitted and received by the UE 115 in established transmit and receive beams (e.g., beams 215-a and 215-b). The synchronization reference signal can be a side-link UE-to-UE reference signal configured for time tracking, frequency tracking, or a combination thereof. In some scenarios, information included in PSBCH 220 for time and frequency tracking can be received from base station 105-a. Thus, the UE 115 may not need to transmit PSBCH 220 for time and frequency tracking, and therefore the UE 115 can use the synchronization reference signal for time and frequency synchronization.

[0086] The synchronization reference signal can be transmitted periodically, dynamically (e.g., on demand), or semi-persistently. If the synchronization reference signal is transmitted periodically, the periodicity of transmitting the synchronization reference signal can be less than the periodicity of transmitting S-SSB 240 (e.g., less than 160 ms), allowing the synchronization reference signal to be transmitted more frequently than S-SSB 140. If the synchronization reference signal is transmitted semi-persistently, the reference signal can be turned on and off. When the reference signal is on, it can be transmitted periodically. The reference signal can be automatically turned on and off by the UE 115 transmitting the reference signal, or it can be turned on or off by the base station 105-a. In some cases, the synchronization reference signal can be turned on or off based on network conditions or based on the relative movement (e.g., speed, direction) between UEs 115-a and 115-b. For example, if UE 115-a and 115-b do not move relative to each other, or do not meet the threshold or move relative to each other, the reference signal can be turned off, while if UE 115 moves relative to each other, or moves relative to each other at a speed that meets a pre-configured threshold, the reference signal can be turned on.

[0087] Similarly, reference signals can be turned on and off on demand based on similar conditions. In some cases, if the reference signal is configured to be turned on and off on demand, a pre-configured number of reference signals can be transmitted each time the reference signal is turned on, instead of periodically. In some cases, base station 105 or transmitting UE 115 can turn on the reference signal. In some cases, receiving UE 115 can transmit a request to base station 105 or transmitting UE 115 to turn on the reference signal on demand or semi-persistently. For example, base station 105-a or UE 115-a can turn on the reference signal on demand, and UE 115-a can transmit the reference signal to UE 115-b a pre-configured number of times (such as once) on narrow beam 215-a, and then base station 105-a or UE 115-a can turn off the reference signal, or the reference signal can be configured to turn off after a pre-configured number of transmissions (such as one in this example).

[0088] The reference signal may include time and frequency information that the receiving UE 115 may use to align time resources, frequency resources, or a combination thereof with the transmitting UE 115. The UE 115 may then communicate on the sidelink channel based on time synchronization, frequency synchronization, or both determined by the synchronization reference signal.

[0089] Figure 3 Examples of a wireless communication system 300 supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, are described. The wireless communication system 300 may include UEs 115-c, 115-d, and 115-e, which may be as described in reference... Figure 1 and 2Examples of UE 115 described. In some cases, UEs 115-c, 115-d, and 115-e can communicate with a base station, as shown in the reference. Figure 1 and 2 As described. In some cases, UEs 115-c, 115-d, and 115-e can communicate via a sidelink channel and can perform resource synchronization using a synchronization reference signal. Additionally or alternatively, other radio devices (such as a base station, or a combination of UE 115 and base station 105) can implement the sidelink resource synchronization procedure.

[0090] In some implementations, multiple UEs 115 can communicate with each other via sidelink channels. UEs 115-c, 115-d, and 115-e may have performed sidelink beam sweep procedures to establish sidelink connections with one or more other UEs 115. (See reference...) Figure 2 As described, the beam sweep procedure may have established a wide transmit / receive beam 310 at one or more UEs 115, or a narrow transmit / receive beam 315 at one or more UEs 115, or a combination thereof, and may have established initial resource (e.g., time, frequency) synchronization. In some cases, a beam can be used to transmit or receive signals from multiple UEs 115. For example, UE 115-c may transmit signals to or receive signals from UEs 115-d or 115-e on the wide beam 310, or both. Each UE 115 may be configured to have a narrow beam 315 that may vary from UE 115 to UE 115. For example, UE 115-c and UE 115-d may communicate using beams 315-a and 315-c. UE 115-c and UE 115-e may communicate using beams 315-b and 315-f. UE 115-d and UE 115-e can communicate using beams 315-d and 315-e. In some cases, beams 315-a through 315-e can each be used by the UE 115 from which the beam originates to transmit signals to or receive signals from another UE 115.

[0091] After connections are established between UEs 115, transmit / receive beams are determined, and initial resource synchronization is performed, network conditions may change, or UEs 115 may move relative to each other while remaining connected. In some cases, due to changes in network conditions or relative movement between UEs 115, time or frequency resources between one or more UEs 115 may become out of sync (e.g., asynchronous). To resynchronize time and frequency resources, the transmitting UE 115 may periodically, on demand, semi-persistently, or a combination thereof transmit one or more sidelink synchronization reference signals to the receiving UE 115. The synchronization reference signals may include time information or frequency information of the transmitting UE 115, or both. In some cases, the synchronization reference signals may also include an identifier of the transmitting UE 115, such as a unique identifier for UE 115.

[0092] In some scenarios, UE 115 may transmit multiple reference signals to one or more UE 115s simultaneously. For example, UE 115-e may simultaneously transmit a sidechain synchronization reference signal to UE 115-d on beam 315-a and to UE 115-c on beam 315-f. In some scenarios, UE 115 may simultaneously receive multiple reference signals from one or more UE 115s. In some scenarios, the receiving UE 115 may receive multiple simultaneous reference signals via a wide beam 310 (e.g., an omnidirectional beam) or a narrow beam 315. For example, UE 115-c may simultaneously receive synchronization reference signals from UE 115-d and UE 115-e on a wide beam 310, because the wide beam 310 can be configured for communication with both UE 115-d and 115-e. UE 115-c may identify which received synchronization reference signal is associated with which UE 115 based on the UE identifier included in the synchronization reference signal. Subsequently, UE 115-c can be aligned with time resources, frequency resources, or both for communication with UE 115-d and UE 115-e.

[0093] Figure 4 An example of a process flow 400 supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, is explained. Process flow 400 may illustrate an example sidelink resource synchronization procedure. For example, UEs 115-f, 115-g, and 115-h can synchronize time and frequency resources with each other. UEs 115-f, 115-g, and 115-h can be referenced... Figures 1 to 4Examples of corresponding wireless devices described. In some cases, instead of UE 115 implementing the resource synchronization procedure, different types of wireless devices (e.g., base stations) may perform the resource synchronization procedure. The following alternative examples can be implemented, some of which may be performed in a different order than described or not at all. In some cases, the steps may include additional features not mentioned below, or further steps may be added.

[0094] At position 405, UEs 115-f, 115-g, and 115-h can execute sidelink beam sweep procedures, as shown in reference... Figure 2 As described. In some scenarios, each UE 115 may participate in a beam-sweeping procedure with one or more other UE 115s. For example, UEs 115-f, 115-k, and 115-h may communicate with each other in some combination on a sidelink channel. UE 115-f may establish a connection with UE 115-g or UE 115-h, or both. UE 115-g may establish a connection with UE 115-f or UE 115-h, or both. UE 115-h may establish a connection with UE 115-f or UE 115-g, or both. In the beam-sweeping procedure, each UE 115 may determine one or more transmit / receive wide beams, or one or more transmit / receive narrow beams, or combinations thereof, for communicating with one or more UEs 115.

[0095] At 410, UEs 115-f, 115-g, and 115-h can execute control signaling procedures. In some cases, control signaling can be transmitted via the Physical Sidelink Control Channel (PSCCH), which may include Sidelink Control Information (SCI) messages. The control signaling may include information regarding resource allocation on the Physical Sidelink Shared Channel (PSSCH). In some cases, UE 115 (such as UE 115-f) may transmit periodic control signaling to one or more sidelink UEs 115 indicating that UE 115-f transmits a first sidelink synchronization reference signal. In some cases, UE 115 (such as UE 115-g) may receive periodic control signaling from one or more sidelink UEs 115 indicating that UE 115-f, 115-h, or both may transmit a first sidelink synchronization reference signal. In some cases, UE 115 (e.g., UE 115-f) may transmit control signaling to one or more sidelink UE 115s to schedule the transmission of a first sidelink synchronization reference signal by UE 115-f, wherein the first sidelink synchronization reference signal may be received according to the control signaling. In some cases, UE 115 (e.g., UE 115-g) may receive control signaling from one or more sidelink UE 115s to schedule the transmission of a first sidelink synchronization reference signal by UE 115-f, 115-h, or both, wherein the first sidelink synchronization reference signal may be received according to the control signaling.

[0096] In some scenarios, UE 115 (such as UE 115-g) may transmit control signaling requesting UE 115-f, 115-h, or both to transmit a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal may be received according to the control signaling. In some scenarios, UE 115 (such as UE 115-g) may transmit control signaling based on detected movement of UE 115-f, detected movement of UE 115 connected to UE 115-f, or both. In some scenarios, UE 115 (such as UE 115-g) may receive control signaling from one or more UE 115-f or 115-h indicating a semi-persistent transport schedule for transmitting the first sidelink synchronization reference signal by UE 115-h, or 115-h, or both.

[0097] At positions 415 and 420, UE 115-f and UE 115-h may simultaneously transmit a sidelink synchronization reference signal to UE 115-g. In some cases, UE 115-g may simultaneously receive the sidelink synchronization reference signal via a wide receive beam previously defined in the beam sweep procedure with UE 115-f and 115-h. UE 115-f and 115-h may be configured to simultaneously receive the synchronization reference signal via the previously configured wide beam. In some cases, UE 115-g may receive the synchronization reference signal from UE 115-f and 115-h at different times. In such cases, UE 115-g may receive each synchronization reference signal on a narrow beam selected for communication with UE 115 that transmitted the synchronization reference signal. In some cases, each synchronization reference signal may indicate an identifier of the UE 115 that transmitted the reference signal, wherein this identifier may be different from the identifier of another UE 115. The identifier included in the synchronization reference signal can be used by the receiving UE 115 to determine which UE 115 the reference signal is associated with. In some cases, UE 115 may transmit multiple synchronization reference signals to multiple UE 115s simultaneously. For example, UE 115-f may transmit synchronization reference signals to UE 115-g at different times or at the same time, at 420 and to UE 115-h at 425.

[0098] At 430, UEs 115-f, 115-g, and 115-g can communicate with each other. In some cases, one or more UEs 115 can transmit a first transmission to one or more other UEs 115 via a sidelink channel based on time synchronization, frequency synchronization, or both determined using a first sidelink synchronization reference signal.

[0099] Figure 5 A block diagram 500 of a device 505 supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Device 505 may be an example of various aspects of a UE 115 as described herein. Device 505 may include a receiver 510, a communication manager 515, and a transmitter 520. Device 505 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0100] Receiver 510 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to sidelink synchronization signals for connected UEs). This information can be transmitted to other components of device 505. Receiver 510 can be a reference... Figure 8 Examples of various aspects of the transceiver 820 described. The receiver 510 may utilize a single antenna or an array of antennas.

[0101] Communication manager 515 may perform a beam sweep procedure with the second UE to identify a receive beam for communication with the second UE on a sidelink channel; receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel based on a time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal. Communication manager 515 may also perform a beam sweep procedure with the second UE to identify a transmit beam for communication with the second UE on a sidelink channel; transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel using the transmit beam based on a time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal. Communication manager 515 may be an example of various aspects of communication manager 810 described herein.

[0102] The communication manager 515 or its sub-components may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functionality of the communication manager 515 or its sub-components may be performed by a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable 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 in this disclosure.

[0103] The communication manager 515 or its subcomponents may be physically located at various locations, including being distributed such that portions of the functionality are implemented by one or more physical components at different physical locations. In some examples, according to various aspects of this disclosure, the communication manager 515 or its subcomponents may be separate and distinct components. In some examples, according to various aspects of this disclosure, the communication manager 515 or its subcomponents may be combined with one or more other hardware components, including but not limited to input / output (I / O) components, transceivers, network servers, another computing device, one or more other components described in this disclosure, or combinations thereof.

[0104] Transmitter 520 can transmit signals generated by other components of device 505. In some examples, transmitter 520 may coexist with receiver 510 in a transceiver module. For example, transmitter 520 may be a reference... Figure 8 Examples of various aspects of the transceiver 820 described. The transmitter 520 may utilize a single antenna or an array of antennas.

[0105] The communication manager 515 described herein can be implemented to achieve one or more potential advantages. One implementation may allow device 505 to synchronize resources more efficiently among multiple devices 505. For example, device 505 may transmit or receive synchronization reference signals destined for one or more other devices 505 to synchronize time and frequency resources.

[0106] By including or configuring a communication manager 515 according to an example as described herein, device 505 (e.g., a processor that controls or otherwise couples to receiver 515, transmitter 520, communication manager 915, or a combination thereof) can support techniques for more efficient use of communication resources and reduced power consumption based on reducing the number of beams transmitting SSBs thereon during the synchronization process.

[0107] Figure 6 A block diagram 600 of a device 605 supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Device 605 may be an example of device 505 as described herein or of various aspects of UE 115. Device 605 may include a receiver 610, a communication manager 615, and a transmitter 650. Device 605 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0108] Receiver 610 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to sidelink synchronization signals for connected UEs). This information can be transmitted to other components of device 605. Receiver 610 can be a reference... Figure 8 Examples of various aspects of the transceiver 820 described. The receiver 610 may utilize a single antenna or an array of antennas.

[0109] Communication manager 615 may be an example of aspects of communication manager 515 as described herein. Communication manager 615 may include beam sweep procedure module 620, synchronization reference signal module 625, side link transmission module 630, beam sweep procedure manager 635, synchronization reference signal manager 640, and side link transmission manager 645. Communication manager 615 may be an example of aspects of communication manager 810 as described herein.

[0110] The beam sweeping protocol module 620 can perform a beam sweeping protocol with the second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel. The synchronization reference signal module 625 can receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweeping protocol. The sidelink transmission module 630 can transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0111] The beam sweep procedure manager 635 can perform a beam sweep procedure with the second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel. The synchronization reference signal manager 640 can use the transmit beam identified in the beam sweep procedure to transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel. The sidelink transmission manager 645 can use the transmit beam to transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0112] Transmitter 650 can transmit signals generated by other components of device 605. In some examples, transmitter 650 may coexist with receiver 610 in a transceiver module. For example, transmitter 650 may be a reference... Figure 8 Examples of various aspects of the transceiver 820 described. The transmitter 650 may utilize a single antenna or an array of antennas.

[0113] Figure 7 A block diagram 700 is shown illustrating a communication manager 705 supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure. The communication manager 705 may be an example of aspects of the communication manager 515, communication manager 615, or communication manager 810 described herein. The communication manager 705 may include a beam sweep procedure module 710, a synchronization reference signal module 715, a sidelink transmission module 720, a control signaling module 725, a sidelink monitoring module 730, an S-SSB module 735, a beam sweep procedure manager 740, a synchronization reference signal manager 745, a sidelink transmission manager 750, a control signaling manager 755, and an S-SSB manager 760. Each of these modules may communicate directly or indirectly with each other (e.g., via one or more buses).

[0114] The beam sweeping protocol module 710 can perform a beam sweeping protocol with the second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel. The synchronization reference signal module 715 can receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweeping protocol. The sidelink transmission module 720 can transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0115] The control signaling module 725 may receive periodic control signaling indicating the transmission of a first sidelink synchronization reference signal. The sidelink monitoring module 730 may use a receive beam to monitor the sidelink channel based on periodicity to locate the transmission of the first sidelink synchronization reference signal. In some examples, the control signaling module 725 may receive control signaling scheduling the transmission of the first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling. In some examples, the control signaling module 725 may transmit control signaling requesting the transmission of the first sidelink synchronization reference signal by a second UE, wherein the first sidelink synchronization reference signal is received according to the control signaling. In some examples, the control signaling module 725 may transmit control signaling based on detected movement of a first UE, a second UE, or both. In some examples, the control signaling module 725 may receive control signaling indicating a semi-persistent transmission schedule for the transmission of the first sidelink synchronization reference signal by a second UE. In some instances, the sidelink monitoring module 730 may use a receive beam to monitor the sidelink channel based on a semi-persistent transmission schedule to locate the transmission of the first sidelink synchronization reference signal.

[0116] In some examples, the synchronization reference signal module 715 may receive a second synchronization reference signal from a third UE via a sidelink channel using a receive beam. In some examples, the sidelink transmission module 720 may transmit a second transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the second sidelink synchronization reference signal. In some examples, the synchronization reference signal module 715 may receive a second synchronization reference signal indicating an identifier of a third UE, which is different from the identifier of the second UE indicated in the first sidelink synchronization reference signal.

[0117] In some cases, the periodicity of the transmission of the first sidelink synchronization reference signal is shorter than the periodicity of the transmission of the sidelink SSB. In some examples, the sidelink transmission module 720 may use a beam with a narrower beamwidth than the received beam to transmit the first transmission via the sidelink channel. In some cases, the first and second sidelink synchronization reference signals are received concurrently or simultaneously. The S-SSB module 735 may receive the sidelink SSB transmission from the second UE.

[0118] The beam sweep procedure manager 740 can perform a beam sweep procedure with the second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel. The synchronization reference signal manager 745 can use the transmit beam identified in the beam sweep procedure to transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel. The sidelink transmission manager 750 can use the transmit beam to transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0119] In some examples, the synchronization reference signal manager 745 may transmit a first sidelink synchronization reference signal indicating an identifier of a first UE. The control signaling manager 755 may transmit periodic control signaling indicating the transmission of the first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the periodicity. In some examples, the control signaling manager 755 may transmit control signaling scheduling the transmission of the first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

[0120] In some examples, the control signaling manager 755 may receive control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling. In some examples, the control signaling manager 755 may transmit control signaling instructing a semi-persistent transmission schedule for the transmission of the first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

[0121] The S-SSB manager 760 can transmit sidelink SSB transmissions. In some cases, the periodicity of the transmission of the first sidelink synchronization reference signal is shorter than the periodicity of the sidelink SSB transmission.

[0122] Figure 8 A diagram of a system 800 including device 805 supporting sidelink synchronization signals for a connected UE, according to various aspects of this disclosure, is shown. Device 805 may be an example of device 505, device 605, or UE 115 as described herein, or a component including such devices. Device 805 may include components for bidirectional voice and data communication, including components for transmitting and receiving communications, including a communication manager 810, an I / O controller 815, a transceiver 820, an antenna 825, a memory 830, and a processor 840. These components may be in electronic communication via one or more buses (e.g., bus 845).

[0123] The communication manager 810 can perform a beam sweep procedure with the second UE to identify a receive beam for communication with the second UE on a sidelink channel; receive a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmit a first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal. The communication manager 810 can also perform a beam sweep procedure with the second UE to identify a transmit beam for communication with the second UE on a sidelink channel; transmit the first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and transmit the first transmission via the sidelink channel using the transmit beam based on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0124] The I / O controller 815 manages the input and output signals of the device 805. The I / O controller 815 can also manage peripheral devices not integrated into the device 805. In some cases, the I / O controller 815 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 815 may utilize an operating system, such as... Or another known operating system. In other cases, the I / O controller 815 may represent or interact with a modem, keyboard, mouse, touchscreen, or similar device. In some cases, the I / O controller 815 may be implemented as part of a processor. In some cases, a user may interact with the device 805 via the I / O controller 815 or via hardware components controlled by the I / O controller 815.

[0125] Transceiver 820 can communicate bidirectionally via one or more antennas, wired or wireless links, as described above. For example, transceiver 820 can represent a wireless transceiver and can communicate bidirectionally with another wireless transceiver. Transceiver 820 may also include a modem to modulate packets and provide the modulated packets to the antenna for transmission, and to demodulate packets received from the antenna.

[0126] In some cases, a wireless device may include a single antenna 825. However, in other cases, the device may have more than one antenna 825, which may be able to transmit or receive multiple wireless transmissions concurrently.

[0127] Memory 830 may include random access memory (RAM) and read-only memory (ROM). Memory 830 may store computer-readable, computer-executable code 835, including instructions that, when executed, cause the processor to perform the various functions described herein. In some cases, memory 830 may particularly include a basic I / O system (BIOS) that controls basic hardware or software operations, such as interaction with peripheral components or devices.

[0128] Processor 840 may include intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, processor 840 may be configured to use a memory controller to operate a memory array. In other cases, the memory controller may be integrated into processor 840. Processor 840 may be configured to execute computer-readable instructions stored in memory (e.g., memory 830) to cause device 805 to perform various functions (e.g., supporting various functions or tasks for sidelink synchronization signals of connected UEs).

[0129] Code 835 may include instructions for implementing various aspects of this disclosure, including instructions for supporting wireless communication. Code 835 may be stored in a non-transitory computer-readable medium, such as system memory or other types of memory. In some cases, code 835 may not be directly executed by processor 840, but may cause a computer (e.g., when compiled and executed) to perform the functions described herein.

[0130] By including or configuring a communication manager 810 according to an example as described herein, device 805 can support techniques for increased reliability and efficiency in resource synchronization, since SSB does not have to be transmitted on multiple beams each time device 805 performs a resource synchronization procedure.

[0131] Figure 9 A flowchart illustrating a method 900 for supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Operation of method 900 can be implemented by a UE 115 or its components as described herein. For example, operation of method 900 can be implemented by referring to... Figures 5 to 8 The described communication manager is used to perform this function. In some examples, the UE can execute a set of instructions to control the functional elements of the UE to perform the following functions. Alternatively or alternatively, the UE can use dedicated hardware to perform aspects of the following functions.

[0132] At 905, the UE may perform a beam sweep procedure with the second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel. The operation of 905 may be performed according to the method described herein. In some examples, aspects of the operation of 905 may be as described in reference... Figures 5 to 8 The described beam sweep procedure module is used to execute it.

[0133] At 910, the UE can receive the first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure. Operation of 910 can be performed according to the method described herein. In some examples, aspects of the operation of 910 can be determined by reference to... Figures 5 to 8 The described synchronization reference signal module is used for execution.

[0134] At 915, the UE may transmit the first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using a first sidelink synchronization reference signal. Operation of 915 may be performed according to the methods described herein. In some examples, aspects of operation of 915 may be determined by reference to... Figures 5 to 8 The described sidelink transmission module is used to perform this.

[0135] Figure 10 A flowchart illustrating a method 1000 for supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Operation of method 1000 can be implemented by a UE 115 or its components as described herein. For example, operation of method 1000 can be implemented by, as referred to... Figures 5 to 8 The described communication manager is used to perform this function. In some examples, the UE can execute a set of instructions to control the functional elements of the UE to perform the following functions. Alternatively or alternatively, the UE can use dedicated hardware to perform aspects of the following functions.

[0136] At point 1005, the UE may perform a beam sweep procedure with the second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel. The operation of point 1005 may be performed according to the method described herein. In some examples, aspects of the operation of point 1005 may be as described in reference... Figures 5 to 8 The described beam sweep procedure module is used to execute it.

[0137] At 1010, the UE may receive control signaling to schedule the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling. The operation of 1010 may be performed according to the method described herein. In some examples, aspects of the operation of 1010 may be determined by reference to... Figures 5 to 8 The control signaling module described is used to execute this.

[0138] At point 1015, the UE can receive the first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure. The operation of point 1015 can be performed according to the method described herein. In some examples, aspects of the operation of point 1015 can be determined by referring to... Figures 5 to 8 The described synchronization reference signal module is used for execution.

[0139] At 1020, the UE may transmit the first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both determined using a first sidelink synchronization reference signal. The operation of 1020 may be performed according to the methods described herein. In some examples, aspects of the operation of 1020 may be determined by reference to... Figures 5 to 8 The described sidelink transmission module is used to perform this.

[0140] Figure 11 A flowchart illustrating a method 1100 for supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Operation of method 1100 can be implemented by a UE 115 or its components as described herein. For example, operation of method 1100 can be implemented by, as referred to... Figures 5 to 8 The described communication manager is used to perform this function. In some examples, the UE can execute a set of instructions to control the functional elements of the UE to perform the following functions. Alternatively or alternatively, the UE can use dedicated hardware to perform aspects of the following functions.

[0141] At 1105, the UE may perform a beam sweep procedure with the second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel. The operation of 1105 may be performed according to the method described herein. In some examples, aspects of the operation of 1105 may be as described in reference... Figures 5 to 8 The described beam sweep procedure manager is used to execute it.

[0142] At 1110, the UE can transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure. The operation of 1110 can be performed according to the method described herein. In some examples, aspects of the operation of 1110 can be determined by reference to... Figures 5 to 8 The described synchronization reference signal manager is used to perform this.

[0143] At 1115, the UE may use a transmit beam to deliver the first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both corresponding to a first sidelink synchronization reference signal. The operation of 1115 may be performed according to the methods described herein. In some examples, aspects of the operation of 1115 may be determined by reference to... Figures 5 to 8 The described sidelink transport manager is used to perform this.

[0144] Figure 12 A flowchart illustrating a method 1200 for supporting sidelink synchronization signals for a connected UE according to various aspects of this disclosure is shown. Operation of method 1200 can be implemented by a UE 115 or its components as described herein. For example, operation of method 1200 can be implemented by, as referred to... Figures 5 to 8 The described communication manager is used to perform this function. In some examples, the UE can execute a set of instructions to control the functional elements of the UE to perform the following functions. Alternatively or alternatively, the UE can use dedicated hardware to perform aspects of the following functions.

[0145] At 1205, the UE may perform a beam sweep procedure with the second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel. The operation of 1205 may be performed according to the method described herein. In some examples, aspects of the operation of 1205 may be as described in reference... Figures 5 to 8 The described beam sweep procedure manager is used to execute it.

[0146] At 1210, the UE may receive control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling. The operation of 1210 may be performed according to the method described herein. In some examples, aspects of the operation of 1210 may be determined by reference to... Figures 5 to 8 The control signaling manager described is used to execute this.

[0147] At point 1215, the UE can transmit a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure. The operation of point 1215 can be performed according to the method described herein. In some examples, aspects of the operation of point 1215 can be determined by reference to... Figures 5 to 8 The described synchronization reference signal manager is used to perform this.

[0148] At 1220, the UE may use a transmit beam to deliver the first transmission via the sidelink channel based on time synchronization, frequency synchronization, or both corresponding to a first sidelink synchronization reference signal. The operation of 1220 may be performed according to the methods described herein. In some examples, aspects of the operation of 1220 may be determined by reference to... Figures 5 to 8 The described sidelink transport manager is used to perform this.

[0149] The following provides an overview of the various aspects of this disclosure:

[0150] Aspect 1: A method for wireless communication by a first UE, comprising: performing a beam sweep procedure with a second UE to identify a receive beam to be used for communication with the second UE on a sidelink channel; receiving a first sidelink synchronization reference signal from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure; and transmitting a first transmission via the sidelink channel based at least in part on a time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

[0151] Aspect 2: The method of aspect 1 further includes: receiving periodic control signaling indicating that a first sidelink synchronization reference signal is transmitted by a second UE; and using a receive beam to monitor the sidelink channel at least in part based on the periodicity to locate the transmission of the first sidelink synchronization reference signal.

[0152] Aspect 3: The method of any one of Aspects 1 to 2 further includes: receiving control signaling to schedule the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling.

[0153] Aspect 4: The method of any one of Aspects 1 to 2 further includes: transmitting control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling.

[0154] Aspect 5: The method of aspect 4, wherein transmitting the control signaling includes transmitting the control signaling at least in part based on the detected movement of the first UE, the second UE, or both.

[0155] Aspect 6: The method of any one of Aspects 1 to 5 further includes: receiving control signaling indicating a semi-persistent transmission schedule for the transmission of a first sidelink synchronization reference signal by a second UE; and using a receive beam to monitor the sidelink channel to locate the transmission of the first sidelink synchronization reference signal, at least in part based on the semi-persistent transmission schedule.

[0156] Aspect 7: The method of any one of Aspects 1 to 6 further includes: receiving a second synchronization reference signal from a third UE via a side link channel using a receive beam; and transmitting a second transmission via the side link channel based at least in part on time synchronization, frequency synchronization, or both determined using the second synchronization reference signal.

[0157] Aspect 8: The method of aspect 7, wherein receiving the second synchronization reference signal includes: receiving a second synchronization reference signal indicating an identifier of a third UE, the identifier of the third UE being different from the identifier of the second UE indicated in the first side link synchronization reference signal.

[0158] Aspect 9: The method of any one of Aspects 7 and 8, wherein transmitting the first transmission via a sidelink channel comprises: transmitting the first transmission via a sidelink channel using a beam having a narrower beamwidth than the received beam.

[0159] Aspect 10: The method of any one of Aspects 7 to 9, wherein the first and second side link synchronization reference signals are received concurrently or simultaneously.

[0160] Aspect 11: The method of any one of Aspects 1 to 10 further includes: receiving a side link synchronization signal block from the second UE.

[0161] Aspect 12: The method of aspect 11, wherein the periodicity of the transmission of the first side link synchronization reference signal is shorter than the periodicity of the transmission of the side link synchronization signal block.

[0162] Aspect 13: A method for wireless communication by a first UE, comprising: performing a beam sweep procedure with a second UE to identify a transmit beam to be used for communication with the second UE on a sidelink channel; transmitting a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure; and conveying a first transmission via the sidelink channel using the transmit beam based at least in part on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

[0163] Aspect 14: The method of aspect 13 further includes: transmitting periodic control signaling indicating the transmission of a first side link synchronization reference signal, wherein the first side link synchronization reference signal is transmitted according to the periodicity.

[0164] Aspect 15: The method of any one of Aspects 13 to 14 further includes: transmitting control signaling for scheduling the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

[0165] Aspect 16: The method of any one of Aspects 13 to 14 further includes: receiving control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

[0166] Aspect 17: The method of any one of Aspects 13 to 16 further includes: transmitting control signaling indicating a semi-persistent transmission schedule for the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

[0167] Aspect 18: The method of any one of Aspects 13 to 17, wherein transmitting the first sidelink synchronization reference signal comprises: transmitting a first sidelink synchronization reference signal indicating an identifier of the first UE.

[0168] Aspect 19: The method of any one of Aspects 13 to 18 further includes: transmitting a transmission-side link synchronization signal block.

[0169] Aspect 20: The method of aspect 19, wherein the periodicity of the transmission of the first side link synchronization reference signal is shorter than the periodicity of the transmission of the side link synchronization signal block.

[0170] Aspect 21: An apparatus for wireless communication by a first UE, comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method as described in any one of Aspects 1 to 12.

[0171] Aspect 22: An apparatus for wireless communication by a first UE, comprising at least one means for performing a method as described in any one of Aspects 1 to 12.

[0172] Aspect 23: A non-transient computer-readable medium storing code for wireless communication by a first UE, the code including instructions executable by a processor to perform methods as described in any one of Aspects 1 to 12.

[0173] Aspect 24: An apparatus for wireless communication by a first UE, comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method as described in any one of Aspects 13 to 20.

[0174] Aspect 25: An apparatus for wireless communication by a first UE, comprising at least one means for performing a method as described in any one of aspects 13 to 20.

[0175] Aspect 26: A non-transient computer-readable medium storing code for wireless communication by a first UE, the code including instructions executable by a processor to perform methods as described in any one of Aspects 13 to 20.

[0176] It should be noted that the methods described in this paper describe possible implementations, and the operations and steps can be rearranged or otherwise modified, and other implementations are also possible. Furthermore, aspects from two or more methods can be combined.

[0177] While aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for illustrative purposes, and the terms LTE, LTE-A, LTE-A Pro, or NR may be used in most of the description, the techniques described herein can also be applied to networks other than LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques can be applied to a variety of other wireless communication systems, such as Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, and other systems and radio technologies not explicitly mentioned herein.

[0178] The information and signals described herein can be represented using any of a wide variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout this description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0179] The various illustrative boxes and components described herein can be implemented or executed using a general-purpose processor, DSP, ASIC, CPU, 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. The general-purpose processor may be a microprocessor, but in alternatives, the processor may be any processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors working in conjunction with a DSP core, or any other such configuration).

[0180] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored or transmitted as one or more instructions or code on a computer-readable medium. Other examples and implementations fall within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Features implementing the functions can also be physically located in various locations, including being distributed such that different parts of the function are implemented at different physical locations.

[0181] Computer-readable media includes both non-transient computer storage media and communication media, encompassing any medium that facilitates the transfer of a computer program from one location to another. Non-transient storage media can be any available medium accessible to a general-purpose or special-purpose computer. By way of example and not limitation, non-transient computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc (CD) ROM or other optical disc storage, magnetic disk storage or other magnetic storage devices, or any other non-transient medium that can be used to carry or store desired program code in the form of instructions or data structures and is accessible to a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Similarly, any connection is also legitimately referred to as computer-readable media. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then that coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable media. As used in this article, disk and disc include CDs, laser discs, optical discs, DVDs, floppy disks, and Blu-ray discs, where disks often magnetically reproduce data while discs optically reproduce data using lasers. Combinations of these media are also included within the scope of computer-readable media.

[0182] As used herein (including in the claims), the word "or" in an enumeration of items (e.g., an enumeration of items accompanied by phrases such as "at least one of" or "one or more of") indicates an inclusive enumeration, such that an enumeration of at least one of, for example, A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Similarly, as used herein, the phrase "based on" should not be interpreted as referring to a closed set of conditions. For example, an example step described as "based on condition A" may be based on both condition A and condition B without departing from the scope of this disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on".

[0183] In the accompanying drawings, similar components or features may have the same reference numerals. Furthermore, components of the same type may be distinguished by a dash following the reference numeral and a second reference numeral used to differentiate between similar components. If only the first reference numeral is used in the description, the description may apply to any of the similar components having the same first reference numeral, regardless of the second reference numeral or other subsequent reference numerals.

[0184] This document, illustrated with reference to the accompanying drawings, describes exemplary configurations but does not represent all examples that can be implemented or fall within the scope of the claims. The term "example" as used herein means "serving as an example, instance, or illustration" and does not imply "superior" or "outperforming" other examples. This detailed description includes specific details to provide an understanding of the described techniques. However, these techniques may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0185] The description provided herein is intended to enable those skilled in the art to make or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the universal principles defined herein can be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for wireless communication by a first user equipment (UE), comprising: A means for using a sidelink synchronization signal block to perform a beam sweep procedure with a second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel; A means for receiving a first sidelink synchronization reference signal from a second UE via the sidelink channel using the receive beam identified in the beam sweep procedure, wherein the first sidelink synchronization reference signal is different from the sidelink synchronization signal block, and wherein the transmission of the first sidelink synchronization reference signal uses fewer resources than the transmission of the sidelink synchronization signal block. as well as A means for transmitting a first transmission via the sidelink channel based at least in part on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

2. The device as claimed in claim 1, further comprising: A means for receiving periodic control signaling indicating that the second UE transmits the first side link synchronization reference signal; as well as A means for using the received beam to monitor the sidelink channel, at least in part, based on the periodicity, to locate the transmission of the first sidelink synchronization reference signal.

3. The device as claimed in claim 1, further comprising: A means for receiving control signaling to schedule the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling.

4. The device of claim 1, further comprising: A means for transmitting control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling.

5. The apparatus of claim 4, wherein the means for transmitting the control signaling comprises: A means for transmitting the control signaling based at least in part on the detected motion of the first UE, the second UE, or both.

6. The device of claim 1, further comprising: A means for receiving control signaling indicating a semi-persistent transport scheduling for the transmission of the first side link synchronization reference signal by the second UE; as well as A means for using the receive beam to monitor the sidelink channel, at least in part, based on the semi-persistent transport schedule, to locate the transmission of the first sidelink synchronization reference signal.

7. The device of claim 1, further comprising: A means for receiving a second sidelink synchronization reference signal from a third UE via the sidelink channel using the receiving beam; as well as A means for transmitting a second transmission via the sidelink channel based at least in part on time synchronization, frequency synchronization, or both determined using the second sidelink synchronization reference signal.

8. The apparatus of claim 7, wherein the means for receiving the second side link synchronization reference signal comprises: A means for receiving a second sidelink synchronization reference signal indicating the identifier of the third UE, wherein the identifier of the third UE is different from the identifier of the second UE indicated in the first sidelink synchronization reference signal.

9. The apparatus of claim 7, wherein the means for transmitting the first transmission via the sidelink channel comprises: A means for transmitting the first transmission via the side link channel using a beam having a narrower beamwidth than the received beam.

10. The device of claim 7, wherein the first side link synchronization reference signal and the second side link synchronization reference signal are received concurrently or simultaneously.

11. The device of claim 1, further comprising: A means for receiving side link synchronization signal block transmission from the second UE.

12. The device of claim 11, wherein the periodicity of the transmission of the first side link synchronization reference signal is shorter than the periodicity of the transmission of the side link synchronization signal block.

13. An apparatus for wireless communication by a first user equipment (UE), comprising: A means for using a sidelink synchronization signal block to perform a beam sweep procedure with a second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel; A means for transmitting a first sidelink synchronization reference signal to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure, wherein the first sidelink synchronization reference signal is different from the sidelink synchronization signal block, and wherein the transmission of the first sidelink synchronization reference signal uses fewer resources than the transmission of the sidelink synchronization signal block. as well as A means for using the transmit beam to transmit a first transmission via the sidelink channel based at least in part on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

14. The apparatus of claim 13, further comprising: A means for transmitting periodic control signaling indicating the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the periodicity.

15. The apparatus of claim 13, further comprising: A means for transmitting control signaling to schedule the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

16. The apparatus of claim 13, further comprising: A means for receiving control signaling requesting the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

17. The apparatus of claim 13, further comprising: A means for transmitting control signaling instructing a semi-persistent transmission schedule for the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

18. The apparatus of claim 13, wherein the means for transmitting the first side link synchronization reference signal comprises: A means for transmitting a first sidelink synchronization reference signal indicating the identifier of the first UE.

19. The apparatus of claim 13, further comprising: A device for transmitting side-link synchronization signal blocks.

20. The device of claim 19, wherein the periodicity of the transmission of the first side link synchronization reference signal is shorter than the periodicity of the transmission of the side link synchronization signal block.

21. A method for wireless communication by a first user equipment (UE), comprising: The sidelink synchronization signal block is used to perform a beam sweep procedure with the second UE to identify the receive beam to be used for communication with the second UE on the sidelink channel; The first sidelink synchronization reference signal is received from the second UE via the sidelink channel using the receive beam identified in the beam sweep procedure, wherein the first sidelink synchronization reference signal is different from the sidelink synchronization signal block, and wherein the transmission of the first sidelink synchronization reference signal uses fewer resources than the transmission of the sidelink synchronization signal block. as well as The first transmission is conveyed via the sidelink channel based at least in part on time synchronization, frequency synchronization, or both determined using the first sidelink synchronization reference signal.

22. The method of claim 21, further comprising: Receive periodic control signaling indicating that the second UE shall transmit the first side link synchronization reference signal; as well as The receiving beam is used to monitor the sidelink channel at least in part based on the periodicity in order to locate the transmission of the first sidelink synchronization reference signal.

23. The method of claim 21, further comprising: The system receives control signaling to schedule the transmission of the first side link synchronization reference signal, wherein the first side link synchronization reference signal is received according to the control signaling.

24. The method of claim 21, further comprising: Control signaling is transmitted to request the transmission of the first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is received according to the control signaling.

25. The method of claim 21, further comprising: Receive control signaling indicating semi-persistent transport scheduling for the second UE to transmit the first side link synchronization reference signal; as well as The receive beam is used to monitor the sidelink channel at least in part based on the semi-persistent transport scheduling in order to locate the transmission of the first sidelink synchronization reference signal.

26. The method of claim 21, further comprising: The second synchronization reference signal is received from the third UE via the side link channel using the received beam; as well as The second transmission is conveyed via the side link channel based at least in part on time synchronization, frequency synchronization, or both determined using the second synchronization reference signal.

27. A method for wireless communication by a first user equipment (UE), comprising: The sidelink synchronization signal block is used to perform a beam sweep procedure with the second UE to identify the transmit beam to be used for communication with the second UE on the sidelink channel; The first sidelink synchronization reference signal is transmitted to the second UE via the sidelink channel using the transmit beam identified in the beam sweep procedure, wherein the first sidelink synchronization reference signal is different from the sidelink synchronization signal block, and the transmission of the first sidelink synchronization reference signal uses fewer resources than the transmission of the sidelink synchronization signal block. as well as The first transmission is carried out via the sidelink channel using the transmit beam, based at least in part on time synchronization, frequency synchronization, or both corresponding to the first sidelink synchronization reference signal.

28. The method of claim 27, further comprising: The system transmits periodic control signaling indicating the transmission of a first sidelink synchronization reference signal, wherein the first sidelink synchronization reference signal is transmitted according to the periodicity.

29. The method of claim 27, further comprising: Control signaling is transmitted to schedule the transmission of the first side link synchronization reference signal, wherein the first side link synchronization reference signal is transmitted according to the control signaling.

30. The method of claim 27, further comprising: A control signaling requesting the transmission of a first sidelink synchronization reference signal is received, wherein the first sidelink synchronization reference signal is transmitted according to the control signaling.

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