WO2024164305A1

WO2024164305A1 - Sl-u ssb enhancement in wideband operation

Info

Publication number: WO2024164305A1
Application number: PCT/CN2023/075401
Authority: WO
Inventors: Siyi Chen; Jing Sun; Xiaoxia Zhang; Chih-Hao Liu; Changlong Xu; Shaozhen GUO; Luanxia YANG
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2023-02-10
Filing date: 2023-02-10
Publication date: 2024-08-15
Anticipated expiration: 2025-08-10
Also published as: CN120642481A; EP4662940A1

Abstract

An apparatus for wireless communication at a user equipment (UE) includes a transceiver; a memory storing computer-executable instructions; and a processor coupled with the transceiver and the memory and configured to manage transmission and reception of a sidelink synchronization signal block (SL-SSB). The apparatus receives, via the transceiver, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band. The apparatus transmits or receives, via the transceiver, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

Description

SL-U SSB ENHANCEMENT IN WIDEBAND OPERATION

BACKGROUND Technical Field

The present disclosure relates to wireless communications including a sidelink synchronization signal block (SSB) in wideband operation on unlicensed or shared spectrum.

Introduction

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR) . 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT) ) , and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB) , massive machine type communications (mMTC) , and ultra-reliable low latency communications (URLLC) . Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

In some aspects, the techniques described herein relate to an apparatus for wireless communication at a user equipment (UE) , including: a transceiver; a memory storing computer-executable instructions; and a processor coupled with the transceiver and the memory and configured to execute the computer-executable instructions to: receive, via the transceiver, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmit or receive, via the transceiver, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.

In some aspects, the techniques described herein relate to an apparatus, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.

In some aspects, the techniques described herein relate to an apparatus, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations. In some implementations, the minimum resource block set excludes resource blocks in the guard band between the first 20-MHz channel and the other channel in the bandwidth part and excludes resource blocks in one or more other guard bands for at least one other wireless device.

In some aspects, the techniques described herein relate to an apparatus, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein to transmit or receive the SL-SSB on the SL-SSB occasion based on the reference resource block set, the processor is configured to execute the instructions to transmit or receive the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.

In some aspects, the techniques described herein relate to an apparatus, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.

In some aspects, the techniques described herein relate to an apparatus, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.

In some aspects, the techniques described herein relate to an apparatus, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.

In some aspects, the techniques described herein relate to an apparatus, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on consecutive resource block sets.

In some aspects, the techniques described herein relate to an apparatus, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to select one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.

In some aspects, the techniques described herein relate to a method of wireless communication, including: receiving, at a wireless device, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmitting or receiving, at the wireless device, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

In some aspects, the techniques described herein relate to a method, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.

In some aspects, the techniques described herein relate to a method, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.

In some aspects, the techniques described herein relate to a method, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.

In some aspects, the techniques described herein relate to a method, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.

In some aspects, the techniques described herein relate to a method, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations. In some aspects, the techniques described herein relate to a method, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein transmitting or receiving the SL-SSB on the SL-SSB occasion based on the reference resource block set includes transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.

In some aspects, the techniques described herein relate to a method, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.

In some aspects, the techniques described herein relate to a method, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.

In some aspects, the techniques described herein relate to a method, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.

In some aspects, the techniques described herein relate to a method, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.

In some aspects, the techniques described herein relate to a method, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions includes transmitting the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.

In some aspects, the techniques described herein relate to a method, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions includes transmitting the SL-SSB on consecutive resource block sets.

In some aspects, the techniques described herein relate to a method, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions includes selecting one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.

In some aspects, the techniques described herein relate to an apparatus for wireless communication at a user equipment (UE) , including: means for receiving an indication of a frequency location of a first sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and means for transmitting the first SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band; and means for receiving a second SL-SSB on the SL-SSB occasion.

In some aspects, the techniques described herein relate to a non-transitory computer-readable medium storing computer-executable instructions that when executed by a processor of a wireless device, cause the wireless device to: receive an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmit or receive the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

In some aspects, the techniques described herein relate to a method of wireless communication for a base station, including: transmitting an indication of a frequency location of a reference sidelink synchronization signal block (SL-SSB) occasion within a bandwidth part of a shared frequency band.

The disclosure also provides an apparatus (e.g., a base station (BS) ) including a memory storing computer-executable instructions and at least one processor configured to execute the computer-executable instructions to perform the above methods for the BS, an apparatus including means for performing the above methods for the BS, and a computer-readable medium storing computer-executable instructions for performing the above methods for the BS.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIG. 2A is a diagram illustrating an example of a first 5G NR frame.

FIG. 2B is a diagram illustrating an example of downlink channels within a 5G NR subframe.

FIG. 2C is a diagram illustrating an example of a second 5G NR frame.

FIG. 2D is a diagram illustrating an example of uplink channels within a 5G NR subframe.

FIG. 3 is a diagram of an example of a first wireless communication device in communication with a second wireless communication device.

FIG. 4 is a diagram of an example of resource block (RB) sets for communications between wireless communication devices.

FIG. 5 is a diagram illustrating an example of sidelink synchronization signal block (SL-SSB) occasions within RB sets for communications between wireless communication devices such as UEs.

FIG. 6 is a message diagram illustrating example messages between a base station and one or more UEs.

FIG. 7 is a resource diagram illustrating a bitmap for indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.

FIG. 8 is a resource diagram illustrating a bitmap for indicating whether the non-reference RB sets within the bandwidth part include a SL-SSB occasion.

FIG. 9 is a conceptual data flow diagram illustrating the data flow between different means/components in an example UE including a SL-SSB component.

FIG. 10 is a flowchart of an example method for operating a UE for transmitting or receiving a SL-SSB.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

The described features generally relate to synchronization signal blocks (SSBs) for sidelink communications, which may also be referred to as direct link communications. As used herein, a direct link refers to a direct wireless communications path from a first wireless device to a second wireless device. For example, in fifth generation (5G) new radio (NR) communication technologies a direct link between two user equipment (UEs) may be referred to as a sidelink (SL) , as opposed to communications over the Uu interface (e.g., from gNB to user equipment (UE) . Direct links may be utilized in D2D communication technologies that can include vehicle-to-vehicle (V2V) communications, vehicle-to-infrastructure (V2I) communications (e.g., from a vehicle-based communication device to road infrastructure nodes) , vehicle-to-network (V2N) communications (e.g., from a vehicle-based communication device to one or more network nodes, such as a base station) , a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. In V2X communications, vehicle-based communication devices can communicate with one another and/or with infrastructure devices over a direct link channel.

In an aspect, the described features relate to a sidelink SSB in an unlicensed band or shared spectrum. Shared spectrum may refer to a portion of spectrum that devices belonging to different networks are allowed to access. In some implementations, the shared spectrum may be referred to as unlicensed spectrum or an unlicensed band. Sidelink communications on such shared spectrum may be referred to as SL-U. In some cases, a general license may apply to shared spectrum. A listen before talk (LBT) or channel assessment (CA) procedure may be applicable to communications in shared spectrum.

A SSB may carry information for identifying a device and allowing other devices to synchronize with the device. For example, in 5G NR, a base station may transmit a SSB on one or more beams. User equipment (UEs) may determine a cell identifier (ID) based on the SSB. The SSB may also include a broadcast channel (BCH) that allows the UEs to locate system information. Similarly, in sidelink communications, a UE may transmit an SSB to identify the UE and provide information about services offered by the UE.

Shared spectrum offers the potential to expand available resources for sidelink communications. For example, large portions of spectrum may be designated as shared spectrum between frequency range 1 (FR1) and frequency range 2 (FR2) (e.g., 5.9 GHz –7.1 GHz) , within FR2, or at higher frequencies. Shared spectrum, however, presents several technical difficulties in transmitting sidelink SSBs. First, shared spectrum may utilize basic channel units of 20 MHz. The basic channel units may include a resource block (RB) set separated from another basic channel unit by an intra-cell guard band, which may vary in size depending on capabilities of different UEs. For multiple UEs to receive a SL-SSB, the SL-SSB may need to be transmitted on a subset of the RB set that is common to all of the UEs and does not overlap the guard band for any UE. The available RBs may be referred to as a common minimum RB-set. Second, the size of the shared spectrum may result in inefficiencies in signaling specific frequency locations. Conventionally, an absolute radio frequency channel number (ARFCN) has been used to indicate a specific frequency, for example, a carrier center frequency. An ARFCN may correspond to a width of 5 kHz for frequencies less than 3000 MHz, and may correspond to 15 kHz for frequencies from 3000 MHz to 24,260 MHz. Accordingly, ARFCN values of 600,000 to 2,016,666 may indicate frequencies in the frequency range 3000 MHz to 24,260 MHz. As noted above, however, only some frequency locations may be used for SL-SSBs, so dedicating a large number of bits for signaling large ARFCN values to indicate an SL-SSB location may be inefficient. Third, the LBT or CA mechanisms for shared spectrum may delay or prevent transmission of an SL-SSB on a specific RB set.

In an aspect, the present disclosure provides signaling mechanisms for SL-SSB. In particular, a UE may receive an indication of a frequency location of the SL-SSB within a bandwidth part of a shared frequency band. For instance, the indication may be received in a radio resource control (RRC) message transmitted by a base station or another UE. The indication may specify the frequency location of a reference resource block set. The reference resource block set may be separated from another channel in the bandwidth part by a guard band. The UE may transmit or receive the SL-SSB on a SL-SSB occasion based on the reference resource block set. In some implementations, the SL-SSB occasion may be within a common minimum resource block set. In some implementations, the UE may attempt to transmit or receive the SL-SSB on multiple SL-SSB occasions to improve likelihood of LBT success.

The disclosed SL-SSB related signaling may resolve ambiguity regarding the frequency location of SL-SSBs. Further, the signaling may be more efficient than conventional ARFCN based signaling. For example, the number of bits to indicate the frequency location may be based on a number of RB sets in a bandwidth part rather than a number of ARFCNs in a frequency range. The ability to attempt transmission on more than one SL-SSB occasion may improve likelihood of LBT success and successful transmission and reception of the SL-SSB.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs) , central processing units (CPUs) , application processors, digital signal processors (DSPs) , reduced instruction set computing (RISC) processors, systems on a chip (SoC) , baseband processors, field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more example implementations, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media, which may be referred to as non-transitory computer-readable media. Non-transitory computer-readable media may exclude transitory signals. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN) ) includes base stations 102, UEs 104, an Evolved Packet Core (EPC) 160, and another core network 190 (e.g., a 5G Core (5GC) ) . The base stations 102 may include macrocells (high power cellular base station) and/or small cells (low power cellular base station) . The macrocells include base stations. The small cells include femtocells, picocells, and microcells.

In an aspect, one or more of the UEs 104 may include a SL-SSB component 140 configured to control transmission and/or reception of SL-SSBs with other UEs 104. The SL-SSB component 140 may include an indication receiving component 142 configured to receive an indication of a frequency location of a SL-SSB within a bandwidth part of a shared frequency band. The SL-SSB component 140 may include a SL-SSB receiving component 144 configured to receive the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location. The SL-SSB component 140 may include a SL-SSB transmitting component 146 configured to transmit the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location. The reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

In an aspect, one or more of the UEs 104 (e.g., a second UE) may also include a SL-SSB component 140. The SL-SSB component 140 of the second UE 104 may be configured to transmit a first SL-SSB to the first UE 104 and receive a second SL-SSB transmitted by the first UE 104.

In an aspect, one or more of the base stations 102 may include a sidelink configuration component 120 that is configured to transmit the indication of the frequency location of the SL-SSB within a bandwidth part of a shared frequency band. For example, the sidelink configuration component 120 may be configured to transmit a radio resource control (RRC) message with the indication. For example, the indication may be associated with an RRC configuration of the bandwidth part.

The base stations 102 configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) ) may interface with the EPC 160 through first backhaul links 132 (e.g., S1 interface) , which may be wired or wireless. The base stations 102 configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN) ) may interface with core network 190 through second backhaul links 184, which may be wired or wireless. In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160 or core network 190) with each other over third backhaul links 134 (e.g., X2 interface) . The third backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102'may have a coverage area 110'that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macrocells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) . The communication links 112 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 112 may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 /UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than for UL) . The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell) .

Certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL/UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH) , a physical sidelink discovery channel (PSDCH) , a physical sidelink shared channel (PSSCH) , and a physical sidelink control channel (PSCCH) . D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR. In an aspect, the D2D communication link 158 may be configured with direct link carrier aggregation for a plurality of component carriers.

The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 /AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

The small cell 102'may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102'may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cell 102', employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network.

The electromagnetic spectrum is often subdivided, based on frequency/wavelength, into various classes, bands, channels, etc. In 5G NR two initial operating bands have been identified as frequency range designations FR1 (410 MHz –7.125 GHz) and FR2 (24.25 GHz –52.6 GHz) . The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “Sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” (mmW) band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz –300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

With the above aspects in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, or may be within the EHF band. Communications using the mmW radio frequency band have extremely high path loss and a short range. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the path loss and short range.

The base station 180 may transmit a beamformed signal to the UE 104 in one or more transmit directions 182'. The UE 104 may receive the beamformed signal from the base station 180 in one or more receive directions 182” . The UE 104 may also transmit a beamformed signal to the base station 180 in one or more transmit directions. The base station 180 may receive the beamformed signal from the UE 104 in one or more receive directions. The base station 180 /UE 104 may perform beam training to determine the best receive and transmit directions for each of the base station 180 /UE 104. The transmit and receive directions for the base station 180 may or may not be the same. The transmit and receive directions for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service, and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN) , and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The core network 190 may include an Access and Mobility Management Function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 may be in communication with a Unified Data Management (UDM) 196. The AMF 192 is the control node that processes the signaling between the UEs 104 and the core network 190. Generally, the AMF 192 provides QoS flow and session management. All user Internet protocol (IP) packets are transferred through the UPF 195. The UPF 195 provides UE IP address allocation as well as other functions. The UPF 195 is connected to the IP Services 197. The IP Services 197 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service, and/or other IP services.

The base station may include and/or be referred to as a gNB, Node B, eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , a transmit reception point (TRP) , or some other suitable terminology. The base station 102 provides an access point to the EPC 160 or core network 190 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or any other similar functioning device. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc. ) . The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

FIG. 2A is a diagram 200 illustrating an example of a first subframe within a 5G NR frame structure. FIG. 2B is a diagram 230 illustrating an example of DL channels within a 5G NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe within a 5G NR frame structure. FIG. 2D is a diagram 280 illustrating an example of UL channels within a 5G NR subframe. The 5G NR frame structure may be frequency domain duplex (FDD) in which for a particular set of subcarriers (carrier system bandwidth) , subframes within the set of subcarriers are dedicated for either DL or UL, or may be time domain duplex (TDD) in which for a particular set of subcarriers (carrier system bandwidth) , subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by FIGs. 2A, 2C, the 5G NR frame structure is assumed to be TDD, with subframe 4 being configured with slot format 28 (with mostly DL) , where D is DL, U is UL, and X is flexible for use between DL/UL, and subframe 3 being configured with slot format 34 (with mostly UL) . While subframes 3, 4 are shown with slot formats 34, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI) , or semi-statically/statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI) . Note that the description infra applies also to a 5G NR frame structure that is TDD.

Other wireless communication technologies may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms) . Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 7 or 14 symbols, depending on the slot configuration. For slot configuration 0, each slot may include 14 symbols, and for slot configuration 1, each slot may include 7 symbols. The symbols on DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also referred to as single carrier frequency-division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to a single stream transmission) . The number of slots within a subframe is based on the slot configuration and the numerology. For slot configuration 0, different numerologies μ 0 to 5 allow for 1, 2, 4, 8, 16, and 32 slots, respectively, per subframe. For slot configuration 1, different numerologies 0 to 2 allow for 2, 4, and 8 slots, respectively, per subframe. Accordingly, for slot configuration 0 and numerology μ, there are 14 symbols/slot and 2^μslots/subframe. The subcarrier spacing and symbol length/duration are a function of the numerology. The subcarrier spacing may be equal to 2^μ*15 kHz, where μ is the numerology 0 to 5. As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and the numerology μ=5 has a subcarrier spacing of 480 kHz. The symbol length/duration is inversely related to the subcarrier spacing. FIGs. 2A-2D provide an example of slot configuration 0 with 14 symbols per slot and numerology μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs.

A resource grid may be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as physical RBs (PRBs) ) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs) . The number of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include demodulation RS (DM-RS) (indicated as R_x for one particular configuration, where 100x is the port number, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS may also include beam measurement RS (BRS) , beam refinement RS (BRRS) , and phase tracking RS (PT-RS) .

FIG. 2B illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) , each CCE including nine RE groups (REGs) , each REG including four consecutive REs in an OFDM symbol. A primary synchronization signal (PSS) may be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe/symbol timing and a physical layer identity. A secondary synchronization signal (SSS) may be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI) . Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH) , which carries a master information block (MIB) , may be logically grouped with the PSS and SSS to form a synchronization signal (SS) /PBCH block. The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs) , and paging messages.

As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH) . The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE may transmit sounding reference signals (SRS) . The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

FIG. 2D illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI) , such as scheduling requests, a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a rank indicator (RI) , and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR) , a power headroom report (PHR) , and/or UCI.

FIG. 3 is a block diagram 300 of a first wireless communication device 310 in communication with a second wireless communication device 350, e.g., via V2V/V2X/D2D communication. The device 310 may comprise a transmitting device communicating with a receiving device, e.g., device 350, via V2V/V2X/D2D communication. The communication may be based, e.g., on sidelink. The transmitting device 310 may comprise a UE, an RSU, etc. The receiving device may comprise a UE, an RSU, etc. Packets may be provided to a controller/processor 375 that implements layer 3 and layer 2 functionality. Layer 3 includes a RRC layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the device 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the device 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the device 350. If multiple spatial streams are destined for the device 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by device 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by device 310 on the physical channel. The data and control signals are then provided to the controller/processor 359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be coupled with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. The controller/processor 359 may provide demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the transmission by device 310, the controller/processor 359 may provide RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression /decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ; RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by device 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

The transmission is processed at the device 310 in a manner similar to that described in connection with the receiver function at the device 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be coupled with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. The controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

At least one of the TX processor 368, the RX processor 356, and the controller/processor 359 may be configured to perform aspects in connection with the SL-SSB component 140 of FIG. 1. Similarly, at least one of the TX processor 316, the RX processor 370, and the controller/processor 375 may be configured to perform aspects in connection with the SL-SSB component 140 of FIG. 1.

FIG. 4 is a diagram 400 illustrating an example of RB sets for communications between wireless communication devices such as UEs. For example, there may be five UEs 104 within a cell that are configured for sidelink communications within a bandwidth part (BWP) 402. Each pair of UEs may be configured with different RB sets, for example, based on capabilities of each UE. For example, a base station may configure each UE with an inter-cell guard band for both transmitting on an uplink (UL) and receiving on a downlink (DL) . Similarly, an inter-cell guard band may apply when transmitting on a sidelink or receiving on a sidelink.

For example, as illustrated in FIG. 4, a first UE (UE0) may be configured with a guardband (GB) 414 for communications 410 with a second UE (UE1) . The GB 414 may separate each RB set 412 within the BWP 402. Similarly, the first UE may be configured with a GB 424 for communications 420 with a third UE (UE2) . The GB 424 may be smaller than the GB 414, for example, due to greater receive capabilities of the third UE than the second UE. The RB sets 422 may be larger (i.e., include more RBs) than the RB sets 412. The fourth UE (UE3) may be configured with a GB 434 for communications 430 with the fifth UE (UE4) . The GB 434 may be greater than the GB 414 and the GB 424. Accordingly, the RB set 432 may be smaller than the RB set 412 or RB set 422. In some implementations, the smallest RB set among the configured UEs may be referred to as a common minimum RB set or a minimum overlapping RB set. In some implementations, the common minimum RB set may be the intersection of all the supported RB set configuration. For example, the supported RB set configurations may be defined in a standards document or regulation.

A SL-SSB 440 may be transmitted over a number of RBs. For example, as illustrated in FIG. 2B, an SSB on a Uu link is conventionally transmitted over 20 RBs. With a 15 kHz sub-carrier spacing (SCS) , 20 RBs may be equal to 3.6 MHz. In some 3GPP release 16 and 17 systems, a SL-SSB may span 11 common RBs within a SL bandwidth part. Larger SCS may result in a larger portion of bandwidth for transmission of the SSB. For communications in unlicensed spectrum, where the 20 MHz basic channel unit and the GB limit the size of the RB set, the selection of a frequency location for the SL-SSB 440 may be limited. For example, there may be an occupied channel bandwidth (OCB) requirement that a transmission occupy between 80%and 100%of the 20 MHz channel. In unlicensed spectrum, the SL-SSB may be enhanced to meet the OCB requirement, for example via repetition over more RBs. For example, a UE 104 may transmit a SL-SSB on the minimum RB set 432 such that the SL-SSB transmission satisfies the OCB requirement and the other UEs can receive the SL-SSB. The SL-SSB 440 may use a large portion of an RB set 432 (e.g., at least 80%) . Because the SL-SSB 440 should not overlap a GB, only some locations within the RB set 432 may be appropriate for the SL-SSB 440.

Conventionally, an absolute radio frequency channel number (ARFCN) 450 is used to indicate a center frequency of an SSB. Although not to scale, the number of ARFCNs 450 may be much greater than the number of RBs in a RB set. For example, there may be 1333 ARFCNs within a 20 MHz basic channel unit over 3000 MHz. In an aspect, signaling an ARFCN may be inefficient for indicating a location of a SL-SSB, for example, because a large number of ARFCNs may correspond to inappropriate locations for the SL-SSB and, in some cases, multiple ARFCNs may indicate the same RBs.

FIG. 5 is a diagram 500 illustrating an example of SL-SSB occasions within RB sets for communications between wireless communication devices such as UEs. A bandwidth part 504 may be configured on a shared frequency band 502. The bandwidth part 504 may include multiple channels 506 (e.g., channels 506a, 506b, and 506c) . Each UE may be configured with an RB set in each channel 506. For example, RB sets for three UEs (UE0 510, UE1 520, and UE2 530) are illustrated. Each UE may be configured with a corresponding GB 514, 524, 534, (e. g., based on a receive capability of the UE) . In some implementations, a minimum RB set may be a size of the smallest RB set configured for a UE. For example, as illustrated, the RB set 522 for the UE 520 may be the smallest because the GB 534 is the largest. Accordingly a minimum RB set 540 may be the same size as the RB set 522. In some implementations, the minimum RB set 540 may be a smallest configurable size for a UE (e.g., based on a maximum GB size) even if no UE is actually configured with the minimum RB set 540. The minimum RB set 540 within each channel may be common to each of the UEs 510, 520, 530. Accordingly, if an SL-SSB is transmitted in the minimum RB set 540, each UE configured with an RB set on that channel 506 may receive the SL-SSB.

In an aspect, instead of indicating an ARFCN for the center frequency of the SL-SSB, an indication may identify a location of a reference SL-SSB occasion 550. An SL-SSB occasion may refer to a frequency location on which an SL-SSB may be transmitted. In some implementations, because the SL-SSB occasion is within a 20 MHz basic channel unit, within a RB set, or within a minimum RB set, the indication may efficiently indicate the location of the SL-SSB occasion. Further, the SL-SSB occasion may be a reference SL-SSB occasion or the RB set may be a reference RB set in one channel that corresponds to SL-SSB occasions in other channels. The SL-SSB occasion in each channel may have a same relative position such that a UE may determine the SL-SSB occasion in each channel based on a reference SL-SSB occasion or reference RB set.

In a first example, the indication may be a value similar to an ARFCN, but with a different formula to indicate the center frequency of the SL-SSB. For instance, a defined RRC parameter such as sl-AbsoluteFrequencySSB may be used to signal an index indicating the location of the SL-SSB. In an implementation, the following formula may indicate the center frequency (F_S-SSB) of the SL-SSB:
F_S-SSB=F_BWP+ ΔF ×index

where F_BWP is the starting frequency of the bandwidth part 504, ΔF is a pre-configured or configured step size, and the index is the signaled value. ΔF may be, for example, pre-configured in a standards document or regulation or configured via broadcast or RRC signaling. For instance, ΔF may be 15 kHz, 20 MHz, or another configured size. In the illustrated example, the ΔF 550 may be configured as 10 MHz. The index (e.g., 3) may be selected to confine the SL-SSB within one RB set (e.g., a minimum RB set) . In some implementations, the formula may further include an offset (e.g., to adjust the position of the SL-SSB occasion within the RB set. The offset may be pre-configured or configured. For instance, a ΔF 570 of 20 MHz and offset 572 of 10 MHz may be used to indicate the reference SL-SSB occasion in the illustrated example.
F_S-SSB=F_BWP+ ΔF ×index + offset

In a second example, the frequency location of the SL-SSB occasion may be a center frequency location of an RB set. The indication may indicate which RB set includes the reference SL-SSB location. The size of the indication may be based on a number of configured RB sets within the BWP, which may be much smaller than the number of ARFCNs. For example, in the illustrated example, two bits (e.g., 01) may be used to indicate the three possible RB sets. In some implementations, a defined RRC parameter such as sl-AbsoluteFrequencySSB may be used with a different interpretation of the value to indicate the RB set including the reference SL-SSB occasion. In some implementations, a new parameter may be defined to indicate the RB set including the reference SL-SSB occasion.

In a third example, the frequency location of the SL-SSB occasion 550 may be indicated as an RB offset 580 of a first resource block of the SL-SSB occasion 550 from a first RB of the bandwidth part 504. The offset 580 may be selected such that the SL-SSB occasion 550 is within an RB set (e.g., a minimum RB set) . The RB offset 580 may be signaled as an RRC parameter.

In an aspect, the RB-set configuration could be different for different links. For example due different intra-cell guard band sizes. However, synchronization of nodes to transmit the SL-SSB in the same frequency may allow single frequency network (SFN) transmission. The use of the minimum RB-set 540 among all the possible RB-set configurations to carry the SL-SSB may allow the communication of different links with different RB-set configurations. Hence, in some implementations, the RB-set offset may be chosen such that the SL-SSB falls within the minimum RB-set 540 and does not overlap any GB (e.g., GB 514, 524, or 534) .

In another aspect, support for multiple candidate SL-SSB occasions when a resource pool for a UE includes multiple RB sets may mitigate LBT uncertainty. For example, if a UE is configured with a single SL-SSB occasion 550, the UE may be unable to transmit SL-SSB on the single SL-SSB occasion 550 if there is another device using the channel such that the UE detects energy during the LBT procedure. If the UE is configured with multiple SL-SSB occasions 550 (e.g., based on the reference SL-SSB occasion 550) , the UE may perform the LBT procedure on each channel, and select one or more channels that pass the LBT procedure for transmitting the SL-SSB.

As illustrated in FIG. 5, the other SL-SSB occasions 552 may correspond to the reference SL-SSB occasion 550. For instance, the other SL-SSB occasions 552 may have the same relative frequency position with respect to a center of the channel 506 as the reference SL-SSB occasion. The position of the other SL-SSB occasions 552 may similarly be defined relative to the RB set 512 or minimum RB set 540. The number of candidate SL-SSB occasions may be pre-defined or configured via RRC signaling.

In a first example, the candidate SL-SSB occasions may be in every RB set. That is, the number of SL-SSB occasions may depend on the number of RB sets within the bandwidth part 504. In a second example, the RRC signaling may include an absolute bitmap that indicates whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion. That is, each bit of the bitmap may indicate whether a corresponding RB set includes an SL-SSB occasion. In a third example, the RRC signaling may indicate a resource indication value indicating a number of consecutive resource block sets within the bandwidth part 504, starting from the reference resource block set, that include SL-SSB occasions. In a fourth example, the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part 504, starting from the resource block set in a frequency channel (e.g., channel 506c) above the reference resource block set and wrapping around to lower frequency channels (e.g. RB set 512a in channel 506a) , includes a SL-SSB occasion 552.

When a UE has an SL-SSB to transmit and passes the LBT procedure for one or more SL-SSB occasions, the UE may determine one or more SL-SSB occasions on which to transmit the SL-SSB. In some implementations, the UE may transmit the SL-SSB on all of the channels or RB sets that pass the LBT procedure. Transmission on multiple sets may increase frequency diversity and/or allow soft combining of the SL-SSB from different RB sets. In some implementations, the UE may transmit the SL-SSB on consecutive resource block sets that pass the LBT procedure. In some implementations, the UE may select one of the SL-SSB occasions that satisfies the condition for transmitting the SL-SSB. Transmission on a single RB set may avoid splitting transmit power among multiple channels, which may increase the range of the transmission compared to transmitting the SL-SSB on multiple channels.

FIG. 6 is a message diagram 600 illustrating example messages between a base station 602 and one or more UEs 510, 520. The base station 602 may configure UEs within its coverage area with parameters. In some implementations, the UEs 510, 520 may be connected to the base station 602, for example, via a Uu link with an RRC connection. The base station 602 may transmit RRC configuration messages to the UEs 510, 520. In some implementations, a UE 520 may not be connected to the base station 602 or may not receive an RRC configuration message. Another UE 510 may forward the content of an RRC message to the UE 520.

In an aspect, the base station 602 may transmit an indication 610 of a frequency location of a SL-SSB within a bandwidth part of a shared frequency band. For example, the indication 610 may indicate a frequency location of a SL-SSB occasion 550 within the bandwidth part 504 of the shared frequency band 502. In some implementations, the indication 610 is an RRC configuration message. The indication 610 may also configure the bandwidth part 504 and/or the RB sets 512, 522, 532. As discussed above, the indication 610 may have a format that is specific to shared spectrum that may be more efficient than signaling an ARFCN of the center frequency of the SL-SSB. In some implementations, a first UE 510 that receives the indication 610 may forward the content of the indication to one or more other UEs 520. For example, the first UE 510 may transmit an indication 612, which may be, for example, a sidelink RRC message.

In an aspect, the first UE 510 may determine one or more SL-SSB occasions 550, 552 based on the indication 610. The UE 510 may transmit a SL-SSB 620 on the one or more SL-SSB occasions 550, 552. For instance, the SL-SSB may include a sidelink primary synchronization signal (S-PSS) , a sidelink secondary synchronization signal (S-SSS) and a physical sidelink broadcast channel (PSBCH) . In some implementations, transmitting the SL-SSB 620 may include an interlaced RB transmission for all of S-PSS/S-SSS/PSBCH. In another example, transmitting the SL-SSB 620 may use interlaced RB transmission for PSBCH only, and apply an occupied channel bandwidth (OCB) exemption to S-PSS and S-SSS. In some implementations, transmitting the SL-SSB 620 may include repeating the S-PSS/S-SSS/PSBCH N times in frequency domain, and there may be a gap between the repetitions to meet an OCB requirement. In some implementations, transmitting the SL-SSB 620 may repeat only S-PSS/S-SSS K times in frequency domain, and the PSBCH may be rate matched. There may be a gap between the repetitions to meet OCB requirement. In some implementations, transmitting the SL-SSB 620 may keep the legacy S-PSS/S-SSS/PSBCH (e.g., in licensed spectrum) while repeating PSBCH N times in frequency domain and rate-matching PSBCH to S-PSS/S-SSS symbols, and there may be a gap between the PSBCH repetition (s) to meet OCB requirements. Transmitting the SL-SSB 620 may optionally apply an OCB exemption to all of S-PSS/S-SSS/PSBCH.

The second UE 520 may also determine the one or more SL-SSB occasions 550, 552 based on the indication 610 or the indication 612. The second UE 520 may receive the SL-SSB 620 on the one or more SL-SSB occasions 550, 552. For example, the UE 520 may be configured to receive the SL-SSB 620 using any of the transmission formats discussed above. The second UE 520 may also transmit an SL-SSB 630 on the one or more SL-SSB occasions 550, 552. The first UE 510 and the second UE 520 may select different time-domain resources for transmitting the SL-SSB 620 and the SL-SSB 630. For example, the LBT procedure may ensure that only one of the first UE 510 or the second UE 520 transmits on the channel. The second UE 520 may transmit the SL-SSB in the same manner that the first UE 510 transmits the SL-SSB, except the S-PSS, S-SSS, and PBSCH may be different.

The SL-SSB 620 may allow the receiving second UE 520 to receive other sidelink channels such as a physical sidelink control channel (PSCCH) and physical sidelink shared channel (PSSCH) from the UE 510. Similarly, the SL-SSB 630 may allow the receiving first UE 510 to receive PSCCH and/or PSSCH from the UE 520. Accordingly, after exchange of at least one of the SL-SSB 620 or SL-SSB 630, the first UE 510 and the second UE 520 may engage in sidelink communication 640.

FIG. 7 is a resource diagram 700 illustrating a bitmap 710 for indicating whether each of the resource block sets 512 within the bandwidth part 504 includes a SL-SSB occasion 550, 552. The bitmap 710 may be a field in the indicator 610. The bitmap 710 may have a length equal to a number of RB sets configured in the bandwidth part 504. For example, as illustrated, the bandwidth part 504 may include four RB sets 512 (e.g., 512a, 512b, 512c, and 512d) . The bitmap 710 may have a value of 0101, which indicates that RB sets 512b and 512d include a SL-SSB occasion 550 or 552.

FIG. 8 is a resource diagram 800 illustrating a bitmap 810 for indicating whether the non-reference RB sets 512 within the bandwidth part 504 include a SL-SSB occasion 552. The bitmap 810 may be a field in the indicator 610. The indicator 610 may indicate the reference RB set (e.g., RB set 512b) . The bitmap 810 may have a length equal to one less than the number of RB sets configured in the bandwidth part 504. For example, as illustrated, the bandwidth part 504 may include four RB sets 512 (e.g., 512a, 512b, 512c, and 512d) and the bitmap 810 may have a length of three. The bitmap 810 may have a value of 010. The bitmap 810 indicates whether each of the other resource block sets 512 within the bandwidth part 504, starting from a RB set 512c in a frequency channel 506c above the reference RB set 512b and wrapping around a highest frequency channel in the bandwidth part 504 (e.g., channel 506d) to lower frequency channels (e.g., channel 506a) , includes a SL-SSB occasion. Accordingly, as illustrated, the bitmap 810 indicates that RB sets 512b and 512d include a SL-SSB occasion 550 or 552.

FIG. 9 is a conceptual data flow diagram 900 illustrating the data flow between different means/components in an example UE 904, which may be an example of the UE 104 including SL-SSB component 140.

The UE 904 also may include a receiver component 910 and a transmitter component 912. The receiver component 910 may include, for example, a RF receiver for receiving the signals described herein. The transmitter component 912 may include for example, an RF transmitter for transmitting the signals described herein. In some implementations, the receiver component 910 and the transmitter component 912 may be co-located in a transceiver such as the Tx/Rx 354 in FIG. 3.

The receiver component 910 may receive downlink signals or sidelink signals such as the indication 610 or 612, the SL-SSBs 620 or 630, and the communications 640. The receiver component 910 may pass the indication 610 or 612 to the indication receiving component 142. The receiver component 910 may pass the SL-SSB 620 or 630 to the SL-SSB receiving component 144.

The indication receiving component 142 may receive the indication 610 or 612. The indication receiving component 142 may decode a received indication to determine the SL-SSB occasions. The indication receiving component 142 may determine one or more values signaled in the indication 610 such as the ΔF 560, the offset 572, the RB offset 580, an index 920, an RB index 930, the bitmap 710, the bitmap 810, or a resource indication value (RIV) 940. The indication receiving component 142 may then determine a reference RB set and/or reference SL-SSB occasion 550 based on the signaled values. In some implementations, the indication receiving component 142 may determine whether one or more of the other RB sets configured for the UE 904 includes a corresponding SL-SSB occasion 552. The indication receiving component 142 may output the reference SL-SSB occasion 550 and any corresponding SL-SSB occasions 552 to both the SL-SSB receiving component 144 and the SL-SSB transmitting component 146.

The SL-SSB receiving component 144 may be configured to receive the SL-SSB 620, 630 on an SL-SSB occasion 550, 552 based on a reference resource block set at the frequency location. For example, the SL-SSB receiving component 144 may monitor signals received on the indicated SL-SSB occasions 550, 552 via the receiver component 910 for the SL-SSB 620, 630.

The SL-SSB transmitting component 146 may be configured to transmit the SL-SSB 620, 630 on an SL-SSB occasion 550, 552 based on a reference resource block set at the frequency location. For example, the SL-SSB receiving component 144 may generate an SL-SSB signal for transmission on the indicated SL-SSB occasions 550, 552 via the transmitter component 912.

FIG. 10 is a flowchart of an example method 1000 for operating a UE 104 (e.g., the first UE 104) for transmitting or receiving a SL-SSB in shared spectrum. The method 1000 may be performed by a UE (such as the UE 104, which may include the memory 360 and which may be the entire UE 104 or a component of the UE 104 such as the SL-SSB component 140, the TX processor 368, the RX processor 356, or the controller/processor 359) . The method 1000 may be performed by the SL-SSB component 140 in communication with a sidelink configuration component 120 of a base station 102 and/or a SL-SSB component 140 of a second UE 104.

At block 1010, the method 1000 includes receiving, at a wireless device, an indication of a frequency location of a SL-SSB within a bandwidth part of a shared frequency band. In an aspect, for example, the UE 104, the RX processor 356 and/or the controller/processor 359 may execute the SL-SSB component 140, the transmitter component 912, and/or the indication receiving component 142 to receive, at the wireless device (e.g., UE 104, 510, 520, or 904) an indication 610 of a frequency location of a SL-SSB 620, 630 within a bandwidth part 504 of a shared frequency band 502. In some implementations, the indication 610 includes an index 920 of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion 550 based on a starting frequency of the bandwidth part 504, a step size (e.g., ΔF 560) , and the index 920. In some implementations, the center frequency of the SL-SSB occasion 550 is further based on an offset 572 from a start of a step. In some implementations, the indication 610 identifies a center frequency of the reference resource block set (e.g., RB set 512b) as an index of resource block sets (e.g., RB index 930) within the bandwidth part 504. In some implementations, the indication 610 includes an offset (e.g., RB offset 580) of a first resource block of the SL-SSB occasion 550 from a first resource block of the bandwidth part 504. In some implementations, the reference resource block set (e.g., RB set 512b) is within a minimum resource block set 540 that is an intersection of a set of supported resource block set configurations. In some implementations, the minimum resource block set 540 excludes resource blocks in the guard band (e.g., GB 514) between the first 20-MHz channel (e.g., channel 506a) and the other channel (e.g., 506b) in the bandwidth part 504 and excludes resource blocks in one or more other guard bands (e.g., GB 524 or 534) for at least one other wireless device. Accordingly, the UE 104, the RX processor 356 and/or the controller/processor 359 executing the SL-SSB component 140, the receiver component 910, and/or the indication receiving component 142 may provide means for receiving, at a wireless device, an indication of a frequency location of a SL-SSB within a bandwidth part of a shared frequency band.

At block 1020, the method 1000 includes transmitting or receiving the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location. In an aspect, for example, the UE 104, the TX processor 368, the RX processor 356 and/or the controller/processor 359 may execute the SL-SSB component 140, the SL-SSB transmitting component 146 and/or the SL-SSB receiving component 144 to transmit or receive the SL-SSB 620, 630 on an SL-SSB occasion 550, 552 based on a reference resource block set (e.g., . RB set 512b) at the frequency location. The reference resource block set of the SL-SSB is within a first 20-MHz channel 506a separated from another channel 506b in the bandwidth part 504 by a GB 514.

In some implementations, a plurality of SL-SSB occasions 552 are supported in other resource block sets 512 within the bandwidth part 504 corresponding to the frequency location of the SL-SSB within the reference resource block set (e.g., RB set 512b) . In such implementations, at sub-block 1022, the block 1020 may optionally include transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a LBT condition. For example, in some implementations, at sub-block 1024, the block 1020 may optionally include transmitting the SL-SSB on each SL-SSB occasion that satisfies the LBT condition. In some implementations, at sub-block 1026, the block 1020 may optionally include transmitting the SL-SSB on consecutive resource block sets. In some implementations, at sub-block 1028, the block 1020 may optionally include selecting one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB. For example, the SL-SSB transmitting component 146 may randomly or pseudo-randomly select the one SL-SSB occasion.

Accordingly, the UE 104, the RX processor 356, and/or the controller/processor 359 executing the SL-SSB component 140, the SL-SSB transmitting component 146 and/or the SL-SSB receiving component 144 may provide means for transmitting or receiving the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location.

SOME FURTHER EXAMPLE CLAUSES

Implementation examples are described in the following numbered clauses:

Clause 1. An apparatus for wireless communication at a user equipment (UE) , comprising: a transceiver; a memory storing computer-executable instructions; and a processor coupled with the transceiver and the memory and configured to execute the computer-executable instructions to: receive, via the transceiver, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmit or receive, via the transceiver, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

Clause 2. The apparatus of clause 1, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.

Clause 3. The apparatus of clause 2, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.

Clause 4. The apparatus of clause 1, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.

Clause 5. The apparatus of clause 1, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.

Clause 6. The apparatus of any of clauses 1-5, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations.

Clause 7. The apparatus of any of clauses 1-6, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein to transmit or receive the SL-SSB on the SL-SSB occasion based on the reference resource block set, the processor is configured to execute the instructions to transmit or receive the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.

Clause 8. The apparatus of clause 7, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.

Clause 9. The apparatus of clause 7, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.

Clause 10. The apparatus of clause 7, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.

Clause 11. The apparatus of clause 7, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.

Clause 12. The apparatus of any of clauses 7-11, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.

Clause 13. The apparatus of any of clauses 7-11, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on consecutive resource block sets.

Clause 14. The apparatus of any of clauses 7-11, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to select one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.

Clause 15. A method of wireless communication, comprising: receiving, at a wireless device, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmitting or receiving, at the wireless device, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

Clause 16. The method of clause 15, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.

Clause 17. The method of clause 16, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.

Clause 18. The method of clause 15, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.

Clause 19. The method of clause 15, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.

Clause 20. The method of any of clauses 15-20, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations.

Clause 21. The method of any of clauses 15-20, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein transmitting or receiving the SL-SSB on the SL-SSB occasion based on the reference resource block set comprises transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.

Clause 22. The method of clause 21, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.

Clause 23. The method of clause 21, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.

Clause 24. The method of clause 21, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.

Clause 25. The method of clause 21, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.

Clause 26. The method of any of clauses 21-24, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises transmitting the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.

Clause 27. The method of any of clauses 21-24, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises transmitting the SL-SSB on consecutive resource block sets.

Clause 28. The method of any of clauses 21-24, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises selecting one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.

Clause 29. An apparatus for wireless communication at a user equipment (UE) , comprising: means for receiving an indication of a frequency location of a first sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and means for transmitting the first SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band; and means for receiving a second SL-SSB on the SL-SSB occasion.

Clause 30. The apparatus of clause 29, wherein the means for transmitting the first SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location is configured to transmit the SL-SSB according to the method of any of clauses 15-28.

Clause 31. A non-transitory computer-readable medium storing computer-executable instructions that when executed by a processor of a wireless device, cause the wireless device to: receive an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and transmit or receive the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.

Clause 32. The non-transitory computer-readable medium of clause 31, wherein the computer-executable instructions comprise instructions to perform the method of any of clauses 15-28.

It is understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

Claims

An apparatus for wireless communication at a user equipment (UE) , comprising:

a transceiver;

a memory storing computer-executable instructions; and

a processor coupled with the transceiver and the memory and configured to execute the computer-executable instructions to:

receive, via the transceiver, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and

transmit or receive, via the transceiver, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.
The apparatus of claim 1, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.
The apparatus of claim 2, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.
The apparatus of claim 1, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.
The apparatus of claim 1, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.
The apparatus of claim 1, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations.
The apparatus of claim 1, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein to transmit or receive the SL-SSB on the SL-SSB occasion based on the reference resource block set, the processor is configured to execute the instructions to transmit or receive the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.
The apparatus of claim 7, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.
The apparatus of claim 7, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.
The apparatus of claim 7, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.
The apparatus of claim 7, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.
The apparatus of claim 7, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.
The apparatus of claim 7, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to transmit the SL-SSB on consecutive resource block sets.
The apparatus of claim 7, wherein to transmit the SL-SSB on one or more of the plurality of SL-SSB occasions, the processor is configured to execute the instructions to select one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.
A method of wireless communication, comprising:

receiving, at a wireless device, an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and

transmitting or receiving, at the wireless device, the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.
The method of claim 15, wherein the indication includes an index of a sidelink absolute frequency indicating a center frequency of the SL-SSB occasion based on a starting frequency of the bandwidth part, a step size, and the index.
The method of claim 16, wherein the center frequency of the SL-SSB occasion is further based on an offset from a start of a step.
The method of claim 15, wherein the indication identifies a center frequency of the reference resource block set as an index of resource block sets within the bandwidth part.
The method of claim 15, wherein the indication includes an offset of a first resource block of the SL-SSB occasion from a first resource block of the bandwidth part.
The method of claim 15, wherein the reference resource block set is within a minimum resource block set that is an intersection of a set of supported resource block set configurations.
The method of claim 15, wherein a plurality of SL-SSB occasions are supported in other resource block sets within the bandwidth part corresponding to the frequency location of the SL-SSB within the reference resource block set, wherein transmitting or receiving the SL-SSB on the SL-SSB occasion based on the reference resource block set comprises transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions that satisfy a listen before talk (LBT) condition.
The method of claim 21, wherein the plurality of SL-SSB occasions includes one SL-SSB occasion in each of the other resource block sets within the bandwidth part.
The method of claim 21, wherein the indication includes a bitmap indicating whether each of the resource block sets within the bandwidth part includes a SL-SSB occasion.
The method of claim 21, wherein the indication includes a resource indication value indicating a number of consecutive resource block sets within the bandwidth part, starting from the reference resource block set, that include SL-SSB occasions.
The method of claim 21, wherein the indication includes a bitmap indicating whether each of the other resource block sets within the bandwidth part, starting from a resource block set in a frequency channel above the reference resource block set and wrapping around to lower frequency channels, includes a SL-SSB occasion.
The method of claim 21, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises transmitting the SL-SSB on each SL-SSB occasion that satisfies the LBT condition.
The method of claim 21, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises transmitting the SL-SSB on consecutive resource block sets.
The method of claim 21, wherein transmitting or receiving the SL-SSB on one or more of the plurality of SL-SSB occasions comprises selecting one of the SL-SSB occasions that satisfies the LBT condition for transmitting the SL-SSB.
An apparatus for wireless communication at a user equipment (UE) , comprising:

means for receiving an indication of a frequency location of a first sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band;

means for transmitting the first SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band; and

means for receiving a second SL-SSB on the SL-SSB occasion.
A non-transitory computer-readable medium storing computer-executable instructions that when executed by a processor of a wireless device, cause the wireless device to:

receive an indication of a frequency location of a sidelink synchronization signal block (SL-SSB) within a bandwidth part of a shared frequency band; and

transmit or receive the SL-SSB on an SL-SSB occasion based on a reference resource block set at the frequency location, wherein the reference resource block set of the SL-SSB is within a first 20-MHz channel separated from another channel in the bandwidth part by a guard band.