Sidelink control signaling using unlicensed spectrum

Abstract

This disclosure provides systems, methods, and apparatus, including computer programs encoded on a computer storage medium, for sidelink control signaling using unlicensed spectrum. A wireless device may perform a listen-before-talk (LET) procedure prior to accessing a channel of the unlicensed spectrum, and may be unable to access the unlicensed spectrum in some cases. In some implementations, a wireless device may additionally transmit control signaling with resources that may be used to transmit sidelink synchronization signal blocks (S-SSBs). For example, a wireless device may multiplex a control signal with an S-SSB, such as frequency domain multiplexing, so that the control signal may be transmitted according to a relaxed LET threshold. In some implementations, the control signal may include information such as an indication of LBT failure or LBT status, or may be used to detect radio link failure (RTF), or may be used for short control signals to synchronize sidelink clusters, among other examples.

Description

[0001] Cross-references

[0002] This patent application claims priority to U.S. patent application No. 17 / 889,344, filed by Xue et al. on August 16, 2022, entitled “SIDELINK CONTROLSIGNALING USING UNLICENSED SPECTRUM,” which is assigned to the assignee of this application and is expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates to wireless communications, including sidelink control signaling using unlicensed spectrum. Background Art

[0004] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcasting, etc. These systems may be able to support communication with multiple users by sharing available system resources (such as time, frequency and power). Examples of such multiple access systems include fourth generation (4G) systems (such as long term evolution (LTE) systems, advanced LTE (LTE-A) systems or LTE-A Pro systems) and fifth generation (5G) systems (which may be referred to as new radio (NR) systems). These systems may use techniques such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA) or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include one or more base stations (BS) or one or more network access nodes, each base station or network access node simultaneously supporting communication for multiple communication devices, which may be further referred to as user equipment (UE). Summary of the invention

[0005] The systems, methods, and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0006] One innovative aspect of the subject matter described in the present disclosure can be implemented in a method for wireless communication at a user equipment (UE). The method can include sending a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band, and sending control signaling using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

[0007] Another innovative aspect of the subject matter described in the present disclosure can be implemented in an apparatus for wireless communication at a UE. The apparatus may include one or more interfaces configured to output a sidelink SSB using a first resource of a channel of an unlicensed radio spectrum band, and to output control signaling using a second resource of a channel of an unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

[0008] Another innovative aspect of the subject matter described in the present disclosure can be implemented in another apparatus for wireless communication at a UE. The apparatus may include a component for sending a sidelink SSB using a first resource of a channel of an unlicensed radio spectrum band and a component for sending control signaling using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

[0009] Another innovative aspect of the subject matter described in the present disclosure can be implemented in a non-transitory computer-readable medium storing code for wireless communication at a UE. The code may include instructions executable by a processor to use a first resource of a channel of an unlicensed radio spectrum band to send a sidelink SSB and use a second resource of the channel of the unlicensed radio spectrum band to send control signaling, wherein the control signaling is frequency division multiplexed with the SSB.

[0010] Some implementations of the methods, apparatus, and non-transitory computer-readable media described herein may include operations, features, modules, or instructions for receiving an indication of a resource allocation for an unlicensed radio spectrum band and sending control signaling using a second resource according to the resource allocation. In some implementations, the control signaling may be sent according to a transmit time interval (TTI) associated with the resource allocation.

[0011] Some implementations of the methods, apparatus, and non-transitory computer-readable media described herein may include operations, features, components, or instructions for selecting a second resource of the channel based on a device identifier, an index of a TTI associated with sending control signaling, or a combination thereof.

[0012] In some implementations of the methods, apparatus, and non-transitory computer-readable media described herein, the control signaling may include an indication of a listen-before-talk (LBT) failure, an indication of a number of LBT attempts, or a combination thereof.

[0013] In some implementations of the methods, apparatus, and non-transitory computer-readable media described herein, sending control signaling associated with SSB frequency division multiplexing is associated with LBT exemption.

[0014] Some implementations of the methods, apparatus, and non-transitory computer-readable media described herein may also include operations, features, modules, or instructions for detecting a radio link failure (RLF) with another side link device, and sending control signaling may be associated with the RLF.

[0015] Details of one or more specific implementations of the subject matter described in the present disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. Note that the relative dimensions in the drawings may not be drawn to scale.

[0016] Details of one or more specific implementations of the subject matter described in the present disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. Note that the relative dimensions in the drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 An example of a wireless communication system that supports sidelink control signaling using unlicensed spectrum is shown.

[0018] Figure 2 An example of a signaling diagram to support sidelink control signaling using unlicensed spectrum is shown.

[0019] Figure 3 and Figure 4 An example of resource configuration to support sidelink control signaling using unlicensed spectrum is shown.

[0020] Figure 5 and Figure 6 An example of a process flow to support sidelink control signaling using unlicensed spectrum is shown.

[0021] Figure 7 and Figure 8 Examples of signaling diagrams and resource configurations to support sidelink control signaling using unlicensed spectrum are shown.

[0022] Fig. 9 An example of a process flow to support sidelink control signaling using unlicensed spectrum is shown.

[0023] Fig.10 A diagram of a system including a device that supports sidelink control signaling using unlicensed spectrum is shown.

[0024] Fig.11 A flow chart illustrating a method of supporting sidelink control signaling using unlicensed spectrum is shown.

[0025] The same reference numbers and designations in different drawings indicate the same elements. DETAILED DESCRIPTION

[0026] For the purpose of describing the innovative aspects of the present disclosure, the following description refers to some specific implementations. However, one of ordinary skill in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The described specific implementations can be implemented in any device, system, or network capable of sending and receiving radio frequency (RF) signals in accordance with any one of the Institute of Electrical and Electronics Engineers (IEEE) 16.11 standards or any one of the following: IEEE 802.11 standards, Standard, Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), GSM / General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution-Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed ​​Packet Access (HSPA), High Speed ​​Downlink Packet Access (HSDPA), High Speed ​​Uplink Packet Access (HSUPA), Evolved High Speed ​​Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals for communicating within a wireless, cellular or Internet of Things (IOT) network, such as a system utilizing third generation (3G) technology, fourth generation (4G) technology, or fifth generation (5G) technology, or another specific implementation thereof.

[0027] In some wireless communication systems, wireless devices may operate using an unlicensed radio spectrum band that may be shared for access between one or more types of wireless devices. In order to mitigate communication conflicts between wireless devices, such as interference between transmissions using unlicensed spectrum, the wireless device may be configured to perform a listen-before-talk (LBT) procedure before accessing a channel on the unlicensed spectrum (such as before performing a transmission on the unlicensed spectrum). In some implementations (such as implementations according to one or more communication standards), some wireless devices may perform the LBT procedure asynchronously, while some other wireless devices may perform the LBT procedure synchronously, such as according to a timeslot boundary or some other interval. In some such implementations, a wireless device that performs the LBT procedure synchronously may be at a relative disadvantage when competing for access to the unlicensed spectrum with a wireless device that performs the LBT procedure asynchronously because the wireless device that performs the LBT procedure synchronously may have fewer opportunities to compete for access. For example, a Wi-Fi access point (AP) may perform an LBT procedure asynchronously, while a user equipment (UE) (such as a sidelink UE configured to support communications with one or more other UEs based on a sidelink communication link or a device-to-device (D2D) communication link) may perform an LBT procedure synchronously, which may limit the UE's opportunity to obtain channel access for sidelink communications compared to the Wi-Fi AP.

[0028] To increase resource availability for sidelink communications, a UE may be configured to use resources available for certain transmissions, such as sidelink synchronization signal block (S-SSB) transmissions, to additionally transmit control signaling, such as one or more short control signals, which may be multiplexed with the S-SSB transmissions in the frequency domain. In some implementations, such techniques may utilize relaxed LBT sensing thresholds associated with S-SSB transmissions, or utilize LBT exemptions or clear channel exemption states associated with S-SSB transmissions, among other features. In some implementations, control signaling for multiplexing with S-SSB transmissions may be configured to support certain types of signaling, such as using short control signals to convey indications of LBT failures or LBT states, or to support detection of radio link failures (RLFs), such as at a receiving UE, and other information. Such techniques may increase the availability of unlicensed spectrum to UEs performing sidelink communications, which may support control signaling that increases the reliability of sidelink communications between UEs communicating using unlicensed spectrum.

[0029] Specific implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages. For example, as a result of multiplexing control signaling with S-SSB transmissions, the UE may increase sidelink communication continuity or reliability because the UE may have a higher likelihood of being able to access unlicensed spectrum. Additionally or alternatively, the UE may be able to utilize control signaling multiplexed with S-SSB transmissions to increase the likelihood of detecting LBT failures and initiating sidelink recovery mechanisms. Furthermore, in some implementations, one or more UEs may belong to a sidelink cluster, and such techniques for multiplexing control signaling with S-SSB transmissions may increase the likelihood of being able to send a sidelink remaining minimum system information (S-RMSI) signal.

[0030] Figure 1 An example of a wireless communication system 100 that supports sidelink control signaling using unlicensed spectrum is shown. The wireless communication system 100 may include one or more network entities 105, one or more UEs 115, and a core network 130. In some implementations, the wireless communication system 100 may be a Long Term Evolution (LTE) network, an Advanced LTE (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or a network operating according to other systems and radio technologies (including future systems and radio technologies not explicitly mentioned herein).

[0031] The network entities 105 may be dispersed throughout a geographic area to form the wireless communication system 100, and may include devices in different forms or with different capabilities. In various examples, the network entities 105 may be referred to as network elements, mobility elements, radio access network (RAN) nodes, or network equipment, among other names. In some implementations, the network entities 105 and the UEs 115 may communicate wirelessly via one or more communication links 125, such as radio frequency (RF) access links. For example, the network entities 105 may support a coverage area 110, such as a geographic coverage area, over which the UEs 115 and the network entities 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area within which the network entities 105 and the UEs 115 may support signal communications according to one or more radio access technologies (RATs).

[0032] The UEs 115 may be dispersed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be stationary or mobile, or stationary and mobile at different times. The UEs 115 may be devices in different forms or with different capabilities. Figure 1 Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein are capable of supporting communication with various types of devices, such as Figure 1Communicate with other UEs 115 or network entities 105) as shown.

[0033] As described herein, a node of the wireless communication system 100 (which may be referred to as a network node or a wireless node) may be a network entity 105 (such as any network entity described herein), a UE 115 (such as any UE described herein), a network controller, an apparatus, a device, a computing system, one or more components, or another suitable processing entity configured to perform any of the techniques described herein. For example, the node may be a UE 115. As another example, the node may be a network entity 105. As another example, a first node may be configured to communicate with a second node or a third node. In one aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a UE 115. In another aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a network entity 105. In yet other aspects of this example, the first node, the second node, and the third node may be different relative to these examples. Similarly, references to UE 115, network entity 105, apparatus, device, computing system, etc. may include disclosure of UE 115, network entity 105, apparatus, device, computing system, etc. as a network node. For example, a disclosure that UE 115 is configured to receive information from network entity 105 also discloses that the first node is configured to receive information from the second node.

[0034] In some implementations, the network entities 105 may communicate with the core network 130, or with each other, or both. For example, the network entities 105 may communicate with the core network 130 via one or more backhaul communication links 120 (such as according to S1, N2, N3, or other interface protocols). In some implementations, the network entities 105 may communicate with each other via the backhaul communication links 120 (such as according to X2, Xn, or another interface protocol) directly (such as directly between the network entities 105) or indirectly (such as via the core network 130). In some implementations, the network entities 105 may communicate with each other via the midhaul communication links 162 (such as according to the midhaul interface protocol) or the fronthaul communication links 168 (such as according to the fronthaul interface protocol), or any combination thereof. The backhaul communication links 120, the midhaul communication links 162, or the fronthaul communication links 168 may be or include one or more wired links (such as electrical links, optical fiber links), one or more wireless links (such as radio links, wireless optical links), and other examples or various combinations thereof. UE 115 may communicate with core network 130 via communication link 155 .

[0035] One or more of the network entities 105 described herein may include or may be referred to as a base station (BS) 140 (such as a transceiver base station, a radio BS, an NR BS, an access point, a radio transceiver, a Node B, an evolved Node B (eNB), a next-generation Node B, or a giga-Node B (any of which may be referred to as a gNB), a 5G NB, a next-generation eNB (ng-eNB), a home Node B, a home evolved Node B, or other suitable terms). In some specific implementations, the network entity 105 (such as BS 140) may be implemented in an aggregated (such as a monolithic, stand-alone) BS architecture, which may be configured to utilize a protocol stack physically or logically integrated within a single network entity 105 (such as a single RAN node, such as BS 140).

[0036] In some implementations, the network entity 105 may be implemented in a disaggregated architecture, such as a disaggregated BS architecture, a disaggregated RAN architecture, which may be configured to utilize a protocol stack physically or logically distributed between two or more network entities 105, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) such as a network configuration sponsored by the O-RAN Alliance, or a virtualized RAN (vRAN) such as a cloud RAN (C-RAN). For example, the network entity 105 may include one or more of the following: a central unit (CU) 160, a distributed unit (DU) 165, a radio unit (RU) 170, a RAN intelligent controller (RIC) 175 such as a near real-time RIC (near RT RIC), a non-real-time RIC (non-RT RIC), a service management and orchestration (SMO) 180 system, or any combination thereof. RU 170 may also be referred to as a radio head, a smart radio head, a remote radio head (RRH), a remote radio unit (RRU), or a transmit receive point (TRP). One or more components of the network entity 105 in the decomposed RAN architecture may be co-located, or one or more components of the network entity 105 may be located in distributed locations (such as separate physical locations). In some implementations, one or more network entities 105 of the decomposed RAN architecture may be implemented as virtual units (such as virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0037] The functional split between CU 160, DU 165, and RU 170 is flexible and may support different functionalities, depending on which functions (such as network layer functions, protocol layer functions, baseband functions, RF functions, and any combination thereof) are performed at CU 160, DU 165, and RU 170. For example, a functional split of a protocol stack may be employed between CU 160 and DU 165, such that CU 160 may support one or more layers of a protocol stack, and DU 165 may support one or more different layers of a protocol stack. In some implementations, CU 160 may host higher protocol layer (such as layer 3 (L3), layer 2 (L2)) functionality and signaling (such as radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP)). The CU 160 may be connected to one or more DUs 165 or RUs 170, and the one or more DUs 165 or RUs 170 may host lower protocol layers, such as layer 1 (L1) (such as a physical (PHY) layer) or L2 (such as a radio link control (RLC) layer, a medium access control (MAC) layer) functionality and signaling, and each may be at least partially controlled by the CU 160. Additionally or alternatively, a functional split of the protocol stack may be employed between the DU 165 and the RU 170, such that the DU 165 may support one or more layers of the protocol stack, and the RU 170 may support one or more different layers of the protocol stack. The DU 165 may support one or more different cells (such as via one or more RUs 170). In some implementations, the functional split between the CU 160 and the DU 165 or between the DU 165 and the RU 170 may be within the protocol layer (such as some functions of the protocol layer may be performed by one of the CU 160, DU 165, or RU 170, while other functions of the protocol layer are performed by a different one of the CU 160, DU 165, or RU 170). The CU 160 may be further functionally split into CU control plane (CU-CP) functions and CU user plane (CU-UP) functions. The CU 160 may be connected to one or more DUs 165 via midhaul communication links 162 (such as F1, F1-c, F1-u), and the DU 165 may be connected to one or more RUs 170 via fronthaul communication links 168 (such as an open fronthaul (FH) interface). In some implementations, the midhaul communication link 162 or the fronthaul communication link 168 may be implemented based on interfaces (such as channels) between layers of a protocol stack supported by respective network entities 105 that communicate via these communication links.

[0038] In some wireless communication systems (such as wireless communication system 100), the infrastructure and spectrum resources for radio access may support wireless backhaul link capabilities to supplement the wired backhaul connection, thereby providing an IAB network architecture (such as to the core network 130). In some specific implementations, in the IAB network, one or more network entities 105 (such as IAB nodes 104) may be partially controlled by each other. One or more IAB nodes 104 may be referred to as donor entities or IAB donors. One or more DUs 165 or one or more RUs 170 may be partially controlled by one or more CUs 160 associated with a donor network entity 105 (such as a donor BS 140). One or more donor network entities 105 (such as an IAB donor) may communicate with one or more additional network entities 105 (such as IAB nodes 104) via supported access and backhaul links (such as backhaul communication links 120). The IAB node 104 may include an IAB mobile termination (IAB-MT) controlled (such as scheduled) by a DU 165 of a coupled IAB donor. The IAB-MT may include an independent set of antennas for relaying communications with the UE 115, or may share the same antennas (such as RU 170) of the IAB node 104 accessed via the DU 165 of the IAB node 104 (such as referred to as a virtual IAB-MT (vIAB-MT)). In some implementations, the IAB node 104 may include a DU 165 that supports communication links with additional entities (such as IAB nodes 104, UE 115) within a relay chain or configuration (such as downstream) of the access network. In such implementations, one or more components of the decomposed RAN architecture (such as one or more IAB nodes 104 or components of the IAB node 104) may be configured to operate according to the techniques described herein.

[0039] In a specific implementation in which the techniques described herein are applied in the context of a disaggregated RAN architecture, one or more components of the disaggregated RAN architecture may be configured to support sidelink control signaling using unlicensed spectrum as described herein. For example, some operations described as being performed by UE 115 or network entity 105 (such as BS 140) may additionally or alternatively be performed by one or more components of the disaggregated RAN architecture (such as IAB node 104, DU 165, CU 160, RU 170, RIC 175, SMO 180).

[0040] UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a user device, or some other appropriate terminology, where a "device" may also be referred to as a unit, a station, a terminal, or a client, among other examples. UE 115 may also include or may be referred to as a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some specific implementations, UE 115 may include or may be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communication (MTC) device, etc., which may be implemented in various objects such as appliances or vehicles, meters, and the like.

[0041] The UE 115 described herein may be capable of communicating with various types of devices, such as other UEs 115, which may sometimes act as relays, as well as network entities 105 and network equipment (including macro eNBs or gNBs, small cell eNBs or gNBs, or relay BSs, etc.), such as Figure 1 shown.

[0042] The UE 115 and the network entity 105 may use resources associated with one or more carriers to wirelessly communicate with each other via one or more communication links 125 (such as access links). The term "carrier" may refer to a set of RF spectrum resources having a physical layer structure defined for supporting the communication link 125. For example, a carrier for the communication link 125 may include a portion of an RF spectrum band (such as a bandwidth portion (BWP)) that operates according to one or more physical layer channels for a given radio access technology (such as LTE, LTE-A, LTE-APro, NR). Each physical layer channel may carry acquisition signaling (such as synchronization signals, system information), control signaling for coordinating carrier operations, user data, or other signaling. The wireless communication system 100 may support communications with the UE 115 using carrier aggregation or multi-carrier operation. According to the carrier aggregation configuration, the UE 115 may be configured to have multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation may be used for both frequency division duplex (FDD) component carriers and time division duplex (TDD) component carriers. Communication between the network entity 105 and other devices may refer to communication between these devices and any part (such as an entity, a sub-entity) of the network entity 105. For example, the terms "send", "receive" or "communicate" when referring to the network entity 105 may refer to any part of the network entity 105 (such as BS 140, CU 160, DU 165, RU 170) of the RAN communicating with another device (such as directly or via one or more other network entities 105).

[0043] The signal waveform transmitted via the carrier may be composed of multiple subcarriers (such as using multi-carrier modulation (MCM) techniques, such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system using MCM technology, a resource element may refer to a symbol period (such as the duration of a modulation symbol) and a resource of a subcarrier, where the symbol period and the subcarrier spacing may be inversely related. The number of bits carried by each resource element may depend on the modulation scheme (such as the order of the modulation scheme, the coding rate of the modulation scheme, or both), so that a relatively high number of resource elements (such as in the transmission duration) and a relatively high order modulation scheme may correspond to a relatively high communication rate. Wireless communication resources may refer to a combination of RF spectrum resources, time resources, and spatial resources (such as spatial layers or beams), and the use of multiple spatial resources may increase the data rate or data integrity used for communication with UE 115.

[0044] One or more parameter sets for a carrier may be supported, and the parameter set may include subcarrier spacing (Δf) and cyclic prefix. A carrier may be divided into one or more BWPs with the same or different parameter sets. In some implementations, a UE 115 may be configured with multiple BWPs. In some implementations, a single BWP for a carrier may be active at a given time, and communications for a UE 115 may be limited to one or more active BWPs.

[0045] The time interval for the network entity 105 or the UE 115 may be expressed as a multiple of a basic time unit. In some implementations, the basic time unit may refer to a sampling period T s =1 / (Δf max ·N f ) seconds, where Δf max It can represent the supported subcarrier spacing, and N f The supported discrete Fourier transform (DFT) size may be indicated. The time intervals of the communication resources may be organized according to radio frames each having a specific duration, such as 10 milliseconds (ms). Each radio frame may be identified by a system frame number (SFN), such as in the range of 0 to 1023.

[0046] Each frame may include a plurality of consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some implementations, a frame may be divided into subframes (such as in the time domain), and each subframe may be further divided into a certain number of time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include a certain number of symbol periods (such as this depends on the length of the cyclic prefix added in front of each symbol period). In some wireless communication systems 100, the time slot may be further divided into a plurality of micro-time slots associated with one or more symbols. Excluding the cyclic prefix, each symbol period may be associated with one or more (such as N) time slots. f The duration of a symbol period may depend on the subcarrier spacing or the operating band.

[0047] A subframe, slot, mini-slot, or symbol may be the smallest scheduling unit of the wireless communication system 100 (such as in the time domain), and may be referred to as a transmit time interval (TTI). In some implementations, the TTI duration (such as the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communication system 100 may be dynamically selected (such as in bursts of shortened TTIs (sTTIs)).

[0048] Physical channels may be multiplexed according to various techniques for communicating using carriers. Physical control channels and physical data channels may be multiplexed, for example, using one or more of a time division multiplexing (TDM) technique, a frequency division multiplexing (FDM) technique, or a hybrid TDM-FDM technique for signaling via a downlink carrier. A control region for a physical control channel, such as a control resource set (CORESET), may be defined by a set of symbol periods and may extend across a system bandwidth or a subset of a system bandwidth of a carrier. One or more control regions, such as CORESETs, may be configured for a set of UEs 115. For example, one or more of the UEs 115 may monitor or search the control region for control information according to one or more search space sets, and each search space set may include one or more control channel candidates in one or more aggregation levels arranged in a cascaded manner. The aggregation level of the control channel candidates may refer to the number of control channel resources, such as control channel elements (CCEs), associated with the coding information for a control information format having a given payload size. The search space sets may include a common search space set configured for transmitting control information to multiple UEs 115 , and a UE-specific search space set for transmitting control information to a specific UE 115 .

[0049] In some implementations, the network entities 105 (such as BS 140, RU 170) can be mobile and thus provide communication coverage for mobile coverage areas 110. In some implementations, different coverage areas 110 associated with different technologies can overlap, but different coverage areas 110 can be supported by the same network entity 105. In some other examples, overlapping coverage areas 110 associated with different technologies can be supported by different network entities 105. The wireless communication system 100 can include, for example, a heterogeneous network in which different types of network entities 105 use the same or different radio access technologies to provide coverage for various coverage areas 110.

[0050] The wireless communication system 100 may support synchronous or asynchronous operation. For synchronous operation, the network entities 105 (such as BS 140) may have similar frame timing, and transmissions from different network entities 105 may be approximately aligned in time. For asynchronous operation, the network entities 105 may have different frame timing, and in some implementations, transmissions from different network entities 105 may not be aligned in time. The techniques described herein may be used for either synchronous operation or asynchronous operation.

[0051] Some UEs 115, such as MTC or IoT devices, may be low-cost or low-complexity devices and may provide automated communication between machines, such as via machine-to-machine (M2M) communication. M2M communication or MTC may refer to data communication technology that allows devices to communicate with each other or with a network entity 105, such as BS 140, without human intervention. In some implementations, M2M communication or MTC may include communication from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application that uses the information or presents the information to a person interacting with the application. Some UEs 115 may be designed to collect information or implement automated behavior of machines or other devices. Examples of applications for MTC devices include: smart metering, inventory monitoring, water level monitoring, equipment monitoring, health care monitoring, field survival monitoring, weather and geographic event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based commercial charging.

[0052] The wireless communication system 100 may be configured to support ultra-reliable communication or low-latency communication or various combinations thereof. For example, the wireless communication system 100 may be configured to support ultra-reliable low-latency communication (URLLC). The UE 115 may be designed to support ultra-reliable, low-latency or critical functions. Ultra-reliable communication may include private communication or group communication, and may be supported by one or more services (such as push-to-talk, video or data). Support for ultra-reliable, low-latency functions may include prioritization of services, and such services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency and ultra-reliable low-latency may be used interchangeably herein.

[0053] In some implementations, a UE 115 may be configured to support communication directly with other UEs 115 via a device-to-device (D2D) communication link 135 (such as according to a peer-to-peer (P2P), D2D, or sidelink protocol). In some implementations, one or more UEs 115 in a group that are performing D2D communication may be within a coverage area 110 of a network entity 105 (such as a BS 140, RU 170), which may support various aspects of such D2D communication configured (such as scheduling) by the network entity 105. In some implementations, one or more UEs 115 of such a group may be outside of the coverage area 110 of the network entity 105, or may otherwise be unable or not configured to receive transmissions from the network entity 105. In some implementations, a group of UEs 115 communicating via D2D communication may support a one-to-many (1:M) system, in which each UE 115 transmits to each other UE 115 in the group. In some implementations, the network entity 105 may facilitate scheduling of resources for D2D communications. In some other examples, D2D communications may be performed between UEs 115 without involving the network entity 105.

[0054] In some systems, the D2D communication link 135 can be an example of a communication channel (such as a sidelink communication channel) between vehicles (such as UE 115). In some specific implementations, the vehicles can communicate using vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination of these items. The vehicles can signal information related to traffic conditions, signal scheduling, weather, safety, emergency situations, or any other information related to the V2X system. In some specific implementations, vehicles in the V2X system can communicate with roadside infrastructure (such as roadside units) using vehicle-to-network (V2N) communication, or communicate with the network via one or more network nodes (such as network entity 105, BS140, RU170), or both.

[0055] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or a 5G core (5GC), and the EPC or 5GC may include at least one control plane entity (such as a mobility management entity (MME), an access and mobility management function (AMF)) for managing access and mobility, and at least one user plane entity (such as a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)) for routing packets or interconnecting to an external network. The control plane entity may manage non-access layer (NAS) functions, such as mobility, authentication, and bearer management of UE115 served by a network entity 105 (such as BS140) associated with the core network 130. User IP packets may be delivered through the user plane entity, which may provide IP address allocation and other functions. The user plane entity may be connected to an IP service 150 for one or more network operators. IP services 150 may include access to the Internet, an intranet, an IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0056] The wireless communication system 100 may operate using one or more frequency bands that may be in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally speaking, the region from 300 MHz to 3 GHz is referred to as the ultra-high frequency (UHF) region or decimeter band because the wavelength ranges from about one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features (which may be referred to as clusters), but these waves may be sufficient to penetrate structures so that macro cells provide services to UEs 115 located indoors. Communications using UHF waves may be associated with smaller antennas and shorter ranges (such as less than 100 kilometers) compared to communications using lower frequencies and longer waves in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz.

[0057] The wireless communication system 100 may utilize both licensed RF spectrum bands and unlicensed RF spectrum bands. For example, the wireless communication system 100 may employ license assisted access (LAA), LTE unlicensed (LTE-U) radio access technology, or NR technology using unlicensed bands (such as the 5 GHz Industrial, Scientific, and Medical (ISM) band). When operating using unlicensed RF spectrum bands, devices such as network entities 105 and UE 115 may employ carrier sensing for conflict detection and avoidance. In some specific implementations, operations using unlicensed bands may be associated with a carrier aggregation configuration in coordination with component carriers operating using licensed bands (such as LAA). Operations performed using unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, and the like.

[0058] The network entity 105 (such as BS 140, RU 170) or UE 115 may be equipped with multiple antennas, which can be used to employ technologies such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of the network entity 105 or UE 115 may be located in one or more antenna arrays or antenna panels, which may support MIMO operation or transmit or receive beamforming. For example, one or more BS antennas or antenna arrays may be co-located at an antenna assembly (such as an antenna tower). In some specific implementations, the antennas or antenna arrays associated with the network entity 105 may be located at different geographical locations. The network entity 105 may include an antenna array having a collection of multiple rows and columns of antenna ports that the network entity 105 can use to support beamforming for communication with the UE 115. Similarly, the UE 115 may include one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, the antenna panel may support RF beamforming for signals sent via the antenna ports.

[0059] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that can be used at a transmitting device or a receiving device (such as a network entity 105, a UE 115) to form or direct an antenna beam (such as a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming can be achieved by combining signals conveyed via antenna elements of an antenna array so that some signals propagating along a particular orientation relative to the antenna array experience constructive interference, while other signals experience destructive interference. Adjustments to signals conveyed via antenna elements may include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to signals carried via antenna elements associated with the device. Adjustments associated with each antenna element may be defined by a set of beamforming weights associated with a particular orientation (such as relative to the antenna array of the transmitting device or the receiving device, or relative to some other orientation).

[0060] Some implementations such as V2X or other D2D implementations may use sidelink communications to exchange messages between UEs 115 configured to support sidelink communications, wherein UEs 115 in such configurations may be referred to as sidelink UEs. In various implementations, UEs 115 may use licensed bands, unlicensed bands, or both to send sidelink messages. In some implementations, such as deployments without direct control or management via a network entity, UEs 115 may operate in sidelink resource allocation (RA) mode 2, for which the network entity 105 may indicate a resource pool and related configurations (such as using preconfiguration). In RA mode 2, UEs 115 may use sensing and reservations for random channel access to use a resource pool (such as a resource pool allocated to RA mode 2) to send sidelink communications. For example, UEs 115 may perform an LBT procedure to assess whether a sidelink channel has no transmissions from other devices, which may mitigate channel conflicts and interference. In some implementations, UEs 115 performing sidelink communications may establish a unicast connection via the PC5-RRC protocol. The unicast connection may support hybrid automatic repeat request (HARQ) feedback, which the UE 115 may utilize for transmit-side detection of radio link failure (RLF). For example, a transmitting UE 115 may detect a configured number of consecutive discontinuous transmission (DTX) communications from another UE 115, instead of a valid HARQ response, upon which the UE 115 may report the RLF to upper layers (such as via the MAC layer). In some implementations, the UE 115 may utilize additional methods for performing sidelink communications, such as discontinuous reception (DRX), partial sensing, and inter-UE coordination.

[0061] In some implementations, the UE 115 may perform sidelink communications on an unlicensed band, such as an FR1 unlicensed band, which may involve the UE 115 competing with other devices for channel access. To support such techniques, regulations or communication standards may be associated with coexistence mechanisms, such as a listen-before-talk (LBT) procedure, to mitigate interference or communication conflicts. For example, an initiating node may perform a Type 1 LBT to send data, which may be performed in accordance with operation in a dominant load-based equipment (LBE) mode.

[0062] In some implementations, the UE 115 may perform synchronous channel access for sidelink communications using configured intervals, such as configured TTIs or slot boundaries. For example, the receiving UE 115 may monitor a physical sidelink control channel (PSCCH), such as having a fixed time-frequency position in a subchannel, to identify valid sidelink transmissions. Thus, the transmitting UE 115 may transmit the PSCCH according to periodic timing in order to successfully receive the transmission. However, some techniques for synchronization may limit the opportunity for the UE 115 to obtain channel access for sidelink transmissions. In some environments, when the UE 115 cannot obtain channel access after repeated LBT attempts, the UE 115 may experience an LBT failure. The UE 115 may report the LBT failure to another wireless device, which may declare an RLF. In contrast, a Wi-Fi access point (AP) may perform asynchronous channel access, which may include occupying a channel immediately after a successful type 1 LBT operation. However, UE 115 may perform channel access at TTI boundaries (e.g., slot boundaries), and the duration between TTI boundaries or the duration between ending a transmission and initiating a subsequent LBT operation may be sufficient for the Wi-Fi AP to obtain floating LBT, such that UE 115 may lose channel access for sidelink communications. Thus, according to these and other examples, the Wi-Fi AP may have more opportunities to obtain channel access, which may cause UE 115 to lack channel access for sidelink communications.

[0063] In some implementations, the UE 115 may use filler signals to occupy the channel of the unlicensed spectrum before the TTI boundary. Such techniques may be combined with the UE 115 using mini-slots to provide more channel access opportunities for sidelink communications, which may improve coexistence with Wi-Fi APs. Additionally or alternatively, the UE 115 may attempt to overcome channel resource shortages by sharing channel occupancy time or using floating sidelink synchronization signal blocks (S-SSBs). However, such techniques may consume processing and overhead resources.

[0064] To increase resource availability for sidelink communications, UE 115 may be configured to use resources available for certain transmissions (such as S-SSB transmissions) to additionally transmit control signaling (such as one or more short control signals), which may be multiplexed with the S-SSB transmissions in the frequency domain. In some implementations, such techniques may utilize relaxed LBT sensing thresholds associated with S-SSB transmissions, or utilize LBT exemptions or idle channel exemption states associated with S-SSB transmissions, among other features. In some implementations, control signaling for multiplexing with S-SSB transmissions may be configured to support certain types of signaling, such as using short control signals to convey indications of LBT failures or LBT status, or to support detection of RLF (such as at a receiving UE 115) and other information. Such techniques may increase the availability of unlicensed spectrum for UEs performing sidelink communications, which may support control signaling that increases the reliability of sidelink communications between UEs using unlicensed spectrum.

[0065] Figure 2 An example of a signaling diagram 200 for supporting sidelink control signaling using unlicensed spectrum is shown. In some implementations, the signaling diagram 200 can illustrate an example of one or more aspects of the wireless communication system 100. For example, each of the UE 115-a and the UE 115-b can be as described in reference Figure 1 Examples of UE 115 are described. UE 115-a and UE 115-b can be examples of UEs configured for sidelink communications using unlicensed spectrum on a communication link 215 (such as a unidirectional or bidirectional communication link, which can be an example of a PC5 interface). UE 115-a and UE 115-b can be located between APs 210, which can also operate using unlicensed spectrum. AP 210 can be an example of a Wi-Fi access point, which can perform asynchronous channel access operations, such as asynchronous LBT operations. AP 210 and UE 115 of the signaling diagram can operate within region 205, which can be associated with an energy detection (ED) threshold for LBT operations.

[0066] In order to facilitate spectrum access between UE 115 and AP 210, the device attempting to perform a transmission may be configured to detect the energy of a frequency resource before performing the transmission, which may support the device to evaluate the frequency resource for other nodes to transmit. Using such an evaluation, the device may determine whether to use the frequency resource to perform the transmission. For example, UE 115 or AP 210 may access a channel on an unlicensed spectrum after performing an LBT procedure. In some specific implementations, UE 115 may perform an LBT procedure according to TTI timing (such as time slot timing), while AP 210 may perform an LBT procedure without timing restrictions (such as asynchronously performing the LBT procedure), and UE 115 and AP 210 may refrain from accessing the channel unless the detected interference level is below an ED threshold (such as approximately negative seventy-two (-72) decibel-milliwatts (dBm)). In some specific implementations, LBT failure may occur due to the UE 115 being unable to obtain access to the channel, which may be associated with a channel occupied by other devices (such as other UEs 115 or other APs 210). The UE 115 may use a timer or counter to detect or initiate an LBT failure and may report the failure to other devices of the network, such as another UE 115 or a network entity 105 (not shown), which may include declaring an RLF.

[0067] For some communications, the UE 115 or AP 210 may perform relaxed LBT sensing, which may be associated with a lower ED threshold or exemption from performing LBT operations, such as when sending short control signaling. As used herein, short control signaling transmissions may refer to transmissions used by a device to convey management or control signaling (such as frames or other messages) without sensing the channel for the presence of other signals. For example, the AP 210 may be configured to send a beacon signal after a Type 2 LBT instead of a Type 1 LBT that may be used for other Wi-Fi communications. In addition, the network entity 105 may be configured to send a demodulation reference signal DRS after a Type 2 LBT, such as in LAA or NR-U implementations. In some implementations, the use of short control signaling transmissions may be associated with a communication standard that may specify the number of short control signaling transmissions during an observation period, or the duration of short control signaling transmissions during an observation period, or both. In some implementations, S-SSB transmissions by UE 115 can be characterized as or otherwise meet criteria for short control signaling and can be specified based on the SFN used for timing propagation.

[0068] To reduce channel resource shortages, UE 115 may be configured to support multiplexing of short control signaling with S-SSB transmissions, which may include techniques for sending S-SSB signals in a non-SFN manner, such as having a transmission timing that is not limited to SFN timing or an indication of sending SFN. For example, UE 115 may be configured to support using a first resource of a channel of an unlicensed radio spectrum band to send S-SSBs, and using a second resource of a channel of an unlicensed radio spectrum band to send control signaling (such as a short control signal). In some specific implementations, control signaling may be frequency division multiplexed with S-SSBs. For example, UE 115 may receive an indication of a resource pool for S-SSB transmission, which may also be used to send short control signaling that is frequency division multiplexed with S-SSB transmissions. UE 115-a may use a relaxed LBT threshold to send S-SSBs, or may not perform LBT operations. Thus, UE 115-a may also send short control signaling with a relaxed LBT threshold, or send short control signaling without performing LBT operation, such as when short control signaling is multiplexed with S-SSB.

[0069] In some implementations, signaling diagram 200 may illustrate a system in which resources, such as resources for short control signaling, are divided into multiple subchannels, and UE 115-a may access these resources according to various procedures. For example, UE 115-a may interleave short control signaling using frequency resources of a channel that is discontinuous with another frequency resource of a channel used to send S-SSBs. In some other implementations, UE 115-a may randomly configure subchannels during one or more S-SSB opportunities. In some implementations, UE 115-a may occupy a subchannel pattern according to a predefined pattern. Additionally or alternatively, UE 115-a may implement a sensing or reservation mechanism to access one or more subchannels.

[0070] In some implementations, UE 115-a and UE 115-b may use short control signaling to support recovery operations following a communication failure, such as an LBT failure, RLF, or other loss or degradation of communication. For example, UE 115-a and UE 115-b may be configured to use short control signaling to maintain a communication link 215, which may involve responding to an LBT failure by activating a recovery mechanism, such as attempting to communicate using different communication resources. Additionally or alternatively, UE 115 may implement short control signaling multiplexed with S-SSB transmission to convey to another UE 115 the status of an LBT attempt, such as indicating the number of LBT attempts, which may support early warning of a risk of LBT failure. In some implementations, UE 115-a and UE 115-b may perform receiver-side RLF detection associated with short control signaling that may be sent periodically. Additionally or alternatively, UE 115 may use short control signaling multiplexed with S-SSB transmissions to support parallel sidelink clusters, or relay S-RMSI, among other examples.

[0071] Figure 3 An example of a resource configuration 300 for supporting sidelink control signaling using unlicensed spectrum is shown. Resource configuration 300 illustrates a configuration that can be referenced by Figure 1 and Figure 2 The described wireless communication system 100 or signaling diagram 200 supports various aspects of wireless communication.

[0072] Resource configuration 300 illustrates an example of resources 340, which may refer to communication resources in the time domain, communication resources in the frequency domain, or both. For example, resource configuration 300 may be implemented for one or more channels 320 in the frequency domain and for one or more configuration intervals 330 in the time domain. In the time domain, each resource 340 may be associated with a corresponding transmission interval 335 (such as a time slot, a mini-time slot, or other transmission interval or transmission interval index). According to the communication configuration, each of the transmission intervals 335 may be associated with one or more TTIs. In some specific implementations, various aspects of the resources 340 for the transmission intervals 335 may be specified according to a resource set 350, which may involve specifying one or more transmission intervals 335 through the indication of the parameter SSBTimeAllocationX, X∈{1,2,3}. In the frequency domain, each resource 340 may be associated with a corresponding subchannel 325, where each subchannel may be a part of a channel 320, such as a control subchannel. Channel 320 may refer to a channel of an unlicensed spectrum, and configuration interval 330 may refer to a resource configuration interval, such as an applicability duration or a repetition duration, which may be a duration configured by a communication standard or a duration configured by a network entity 105, such as an interval of 160 ms or another integer multiple of a TTI. Resource configuration 300, or one or more resource sets 350, or a set of one or more resources 340 may be examples of a resource pool that may be available to a UE 115, such as a sidelink UE 115.

[0073] In some implementations, such as when operating using an unlicensed band associated with LBT operation, the UE 115 may receive a configuration of such a resource pool, which may indicate opportunities available for sending control signaling frequency-division multiplexed with S-SSB transmissions, such as resources 340 or transmission intervals 335. For example, the UE 115 may receive an indication of one or more aspects of a resource configuration 300 from the network entity 105, which may refer to resources 340 of an unlicensed radio spectrum band. Using the resources 340, the UE 115 may send one or more short control signals 360 concurrently with the S-SSB 345 in accordance with relaxed LBT sensing, including such transmissions following a Type 2 LBT or LBT exemption.

[0074] In some implementations, the UE 115 may receive an indication of how to access the configuration of the subchannels 325, or an indication of what may be transmitted using a given subchannel 325 or resource 340, or any combination thereof, which may include an indication that such transmission may be performed in a non-SFN manner. For example, some of the resources 340 may be used to transmit an S-SSB 345, and some of the resources 340 may be used to transmit one or more short control signals 360. In the illustrative example, the UE 115 may transmit an S-SSB 345-a using subchannels 325-c and 325-d during a transmission interval 335-a, and may transmit a short control signal 360-a and a short control signal 360-b using subchannels 325-b and 325-a, respectively, during the same transmission interval 335-a. Thus, the UE 115 may transmit the short control signals 360-a and 360-b and the S-SSB 345-a according to the transmission interval 335-a or its TTI of the resource configuration 300, or otherwise according to the resource set 350-a. The resources 340 may be configured according to various patterns that may support interleaving the short control signals 360 using resources 340 that are not contiguous with the resources 340 used to transmit the S-SSB 345.

[0075] According to various techniques, the UE 115 may access one or more resources 340 for sidelink communication. In some implementations, the UE 115 may select the resource 340 using a device identifier (such as a UE identifier, a group identifier, a pseudo-identifier), an index of the transmit interval 335, an index of the TTI, or a combination thereof. Additionally or alternatively, the UE 115 may be configured to access a randomly selected subchannel 325 or resource 340, including such selection during at least one S-SSB opportunity or each S-SSB opportunity that the UE 115 is attempting to access, which may refer to one or more of the transmit intervals 335 of the configuration interval 330. In some implementations, the UE 115 may perform a hash function that uses an identifier associated with the UE 115 and an index of the transmit interval 335 (such as a slot index) as input to determine the index of the subchannel 325.

[0076] In some implementations, the UE 115 may occupy a pattern of subchannels 325, such as a pattern in the frequency domain, a pattern in the time domain, or both, which may include a predefined set specified in an L3 configuration or other configuration. In some implementations, the pattern of accessing subchannels 325 may be utilized by performing a sensing and reservation procedure, which may be simplified relative to other sensing and reservation procedures. For example, the short control signal 360 may carry an indication, such as a low bit indication, of whether the transmission using one or more resources 340 is periodic or otherwise repeated, or is associated with a single channel use. In some implementations, including environments where the transmission of the short control signal 360 is periodic or otherwise repeated, the UE 115 may sense (such as via a received signal strength indicator (RSSI) measurement, which may be an alternative to decoding the sidelink control information (SCI)) the associated pool of subchannels 325 within a duration prior to occupying the pattern of subchannels 325. Additionally or alternatively, the UE 115 may perform a sensing or reservation mechanism based on a resource pool based on Mode 2.

[0077] Figure 4 An example of a resource configuration 400 for supporting sidelink control signaling using unlicensed spectrum is shown. The resource configuration 400 may be a reference Figure 3 Examples of various aspects of the described resource configuration 300 and may be illustrated by reference to Figure 1 and Figure 2 Aspects of wireless communications supported by the described wireless communication system 100 or signaling diagram 200. In some implementations, resource sets 350 of the resource configuration 400 may be allocated (such as by the network entity 105) for use by the UE 115 in transmitting short control signals 360 multiplexed in the frequency domain with transmissions of the S-SSB 345. For example, the resource set 350-c may correspond to the parameter sl-SSBTimeAllocation1, and the resource set 350-d may correspond to the parameter sl-SSBTimeAllocation2.

[0078] Resource configuration 400 may be configured by UE 115 (such as reference Figure 2The described sidelink UE 115-A and UE 115-b) can maintain a communication link on a subchannel 325 or other resource in the frequency domain, such as a bidirectional signaling link or a sidelink. In some specific implementations, the resource configuration 400 can be implemented to handle LBT failures according to sidelink RA mode 2, such as when one or both of UE 115-a or 115-b cannot access a channel of an unlicensed spectrum. For example, the resource pool associated with the resource configuration 400 can support sending one or more S-SSBs 345 by relaxing a reference signal received power (RSRP) threshold on a current synchronization source (such as in the event of a risk of LBT failure, even if UE 115-A and UE 115-b are close to each other), or by exempting the LBT procedure from being performed.

[0079] If the conditions for LBT failure are met, a UE 115 supporting sidelink communication, such as UE 115-a or UE 115-b, may send an indication of LBT failure using a short control signal 360 multiplexed with the S-SSB 345, which may include an indication of a recovery mechanism. For example, if the sidelink UE 115-a identifies an LBT failure, the UE 115-a may send an indication of LBT failure in a short control signal 360-e multiplexed with the S-SSB 345-c. Additionally or alternatively, if the UE 115-b identifies an LBT failure, the UE 115-b may send an indication of LBT failure in a short control signal 360-f multiplexed with the S-SSB 345-d. In some other examples, if UE 115-b receives a short control signal 360-e that may indicate an LBT failure as identified by UE 115-a, the sidelink UE 115-b may send a response, such as a recovery signal, using a short control signal 360-f multiplexed with the S-SSB 345-d.

[0080] In various implementations, the indication of LBT failure may trigger the receiving UE 115 to initiate a recovery mechanism, such as a recovery mechanism understood between UEs 115 performing sidelink communications. In some implementations, the recovery mechanism may include a frequency domain response, such as hopping to another frequency resource of an unlicensed spectrum to reestablish a connection. Additionally or alternatively, the recovery mechanism may include a space domain response, which may include the UE 115 attempting to recover the connection in a different beam space that may have less interference from other RATs. Additionally or alternatively, the recovery mechanism may include a time domain response, which may include the UE 115 attempting to recover the connection supporting a more robust channel access as a floating channel occupancy time transmission.

[0081] Figure 5 An example of a process flow 500 for supporting sidelink control signaling using unlicensed spectrum is shown. The process flow 500 may be implemented as described in detail with reference to Figure 1 and Figure 2 Various aspects of the described wireless communication system 100 and signaling diagram 200 may be implemented by these aspects. For example, the process flow 500 may be implemented by UE 115-c and UE 115-d, which may be reference UEs 115-c and 115-d. Figure 1 and Figure 2 In the following description of process flow 500, operations between UE 115-c and UE 115-d may be sent in an order different from the example order shown, or the operations may be performed in a different order or at a different time. Some operations may also be omitted from process flow 500, and other operations may be added to process flow 500.

[0082] In the example of process flow 500, UE 115-c may use one or more short control signals (such as reference Figure 3 and Figure 4 360) to indicate the LBT status to the UE 115-d, which may support early warning of the risk of LBT failure. Specifically, as part of the periodic transmission, the UE 115-c may signal the LBT status to the UE 115-d at 505, at 510, or at both 505 and 510. The short control signal of 505 or 510 may be frequency division multiplexed with the S-SSB, which may support the implementation of a relaxed LBT procedure or LBT exemption.

[0083] The LBT status indication of process flow 500 may include various indications. In some implementations, the LBT status indication at 505 or 510 may include statistics regarding LBT attempts (such as an indication of the total number of attempts, or an indication of the number of failed attempts), including statistics for sending S-SSB, for sending broadcast or multicast, or for sending unicast transmissions (such as for a third UE 115, not shown), or any combination thereof, as well as other examples. Additionally or alternatively, the LBT status indication of UE 115-c may include statistics regarding LBT attempts made specifically to support transmissions to UE 115-d. Additionally or alternatively, the LBT status indication of UE 115-c may include statistics regarding LBT failures due to other RATs, such as LBT failures due to detected Wi-Fi transmissions. In various implementations, the LBT status indication at 505 or 515 may support preemptive recovery to improve resource availability for sidelink communications between UE 115-c and UE 115-d, such as an indication of alternative or candidate communication resources (such as an indication of candidate frequency domain resources, or candidate time domain resources, or candidate spatial resources, or candidate RATs, or any combination thereof). In some implementations, UE 115-c may send an indication of LBT failure at 515, which may trigger a request as described in reference to FIG. Figure 4 The recovery mechanism described may include an indication of continuing one or more aspects of the recovery mechanism indicated in the LBT status indication of 505 or 510.

[0084] Figure 6 An example of a process flow 600 for supporting sidelink control signaling using unlicensed spectrum is shown. The process flow 600 may illustrate an example of performing RLF detection on the receiver side using short control signaling of unlicensed spectrum. In some implementations, the process flow 600 may be implemented as respectively referring to Figure 1 and Figure 2 Aspects of the described wireless communication system 100 and signaling diagram 200 may be implemented by or may be implemented by these aspects. For example, the process flow 600 may be implemented by UE 115-e, UE 115-f, and UE 115-g, which may be as described in reference Figure 1 and Figure 2 An example of UE 115 described. In the following description of process flow 600, operations between UE 115-e, UE 115-f, UE 115-g may be sent in an order different from the example order shown, or these operations may be performed in a different order or at a different time. Some operations may also be omitted from process flow 600, and other operations may be added to process flow 600.

[0085] In some implementations, UE 115-e and UE 115-g may be synchronized, which may include both UE 115-e and UE 115-g transmitting S-SSBs (such as the S-SSB transmissions illustrated at 605, 615, 620, and 625). The S-SSB transmissions of UE 115-e and UE 115-g may each include a SFN, which may be common between the transmissions of UE 115-e and UE 115-g. Thus, in some examples, UE 115-f may not be able to distinguish between the S-SSB transmissions of UE 115-e and the S-SSB transmissions of UE 115-g, which may be associated with such S-SSB transmissions being inappropriate for UE 115-f to assess the RLF conditions of UE 115-e and UE 115-g.

[0086] In the example of process flow 600, a UE 115 may be configured to perform receiver-side RLF detection using measurements of periodically transmitted short control signaling from other UEs 115, which may be multiplexed with S-SSB transmissions according to examples as disclosed herein. For example, UE 115-f may monitor periodic short control signaling from at least UE 115-e, such as at 610 and 630. If the link quality assessed by measuring such short control signaling drops below a threshold, such as RSRP or reference signal received quality (RSRQ), UE 115-f may detect RLF. In some embodiments, UE 115-f may also be capable of performing receiver-side RLF detection for UE 115-g, which may utilize a short control signal from UE 115-g having an indication unique to UE 115-g (such as a UE identifier), or may utilize a short control signal from UE 115-g that is not sent concurrently with the short control signaling of 610 and 630, among other examples.

[0087] Figure 7 An example of a signaling diagram 700 and a resource configuration 750 for supporting sidelink control signaling using unlicensed spectrum is shown. The signaling diagram 700 may be an example of one or more aspects of the wireless communication system 100 and the signaling diagram 200. For example, UE 115-h, UE 115-i, UE 115-j, UE 115-k, UE 115-m, UE 115-n, and UE 115-p may each be as described in reference Figure 1 and Figure 2 An example of a UE 115 is described.

[0088] UE 115-j may operate as a central node of a sidelink cluster 705-a including leaf nodes UE 115-h, UE 115-i, UE 115-j, and UE 115-k. In some implementations, UE 115-j may broadcast control information 715 (such as S-SSB or S-RMSI) that may be received by leaf nodes UE 115-h, UE 115-i, and UE 115-k to support various aspects of managing the sidelink cluster 705-a. UE 115-n may operate as a central node of a sidelink cluster 705-b including leaf nodes UE 115-m, UE 115-n, and UE 115-p. In some implementations, UE 115-n may broadcast control information 720 (such as S-SSB or S-RMSI) that may be received by leaf node UE 115-m and UE 115-p to support various aspects of managing the sidelink cluster 705-b.

[0089] In some implementations, a resource pool that supports multiplexing of short control signals with S-SSB transmissions may be utilized to support sidelink cluster 705-a and sidelink cluster 705-b operating as parallel sidelink clusters with the same sidelink timing or otherwise related sidelink timing. For example, transmission of S-SSBs may be performed with relaxed LBT sensing or LBT exemption, and it may be beneficial for sidelink clusters 705-a and 705-b to support transmission of S-RMSI in a similar manner.

[0090] In an illustrative example, UE 115-j may be a timing parent node for UE 115-k, and UE 115-k may be a timing parent node for UE 115-n. As part of concurrent operation of sidelink clusters 705-a and 705-b, UE 115-j and UE 115-n may transmit during the same transmit interval 335, such as using the same resource set 350-e, which may be defined at least in part by parameter sl-SSBTimeAllocation1. In such an example, UE 115-j and UE 115-n may each transmit an S-SSB 345-e using a symbol frame number, and may transmit respective S-RMSI signals on different subchannels 325. For example, UE 115-j may transmit S-RMSI 760-a, and UE 115-n may transmit S-RMSI 760-b. In some implementations, UE 115-k may transmit S-SSB 345-f during a different transmission interval 335, such as using resource set 350-f, which may be multiplexed with other short control signaling or other short control signaling may be omitted (such as omitting S-RMSI). In this way, both UE 115-j and UE 115-n may be less sensitive to LBT blocking when transmitting S-RMSI.

[0091] Figure 8 An example of a signaling diagram 800 and a resource configuration 850 for supporting sidelink control signaling using unlicensed spectrum is shown. The signaling diagram 800 may be an example of one or more aspects of the wireless communication system 100 and the signaling diagram 200. For example, each of the UE 115-q, UE 115-r, UE 115-s, and UE 115-t may be as described in reference Figure 1 and Figure 2 Described are examples of UE 115. UE 115-r may be a central node of a sidelink cluster 805 for which UE 115-q, UE 115-s, and UE 115-t may operate as leaf node UEs.

[0092] In some implementations, UE 115-r may broadcast control information 815 (such as S-SSB or S-RMSI) that may be received by UE 115-q, UE 115-s, and UE 115-t to support various aspects of managing the sidelink cluster 805. To support operation in a star topology, the central node UE 115-r may implement relaying of the control information 815 using selected leaf node UEs 115, thereby supporting a relatively large coverage area of ​​the sidelink cluster 805. For example, UE 115-r may operate as a synchronization UE using UE 115-s and UE 115-t, which may involve relaying SLSS or S-RMSI or both and other control signaling. To support such techniques, UE 115-r may schedule transmission of control signaling (such as S-RMSI) by UE 115-s and UE 115-t using short control signal 360, which may include SFN-based transmissions that may be scheduled using a network layer (such as a layer 3 (L3) protocol). In some specific implementations, such as when per-opportunity random subchannel selection is used, UE 115-r may indicate (such as request, via indication 820) in a hash function that UE 115-s and UE 115-t use the same identifier (such as a common identifier, an identifier of UE 115-r, a pseudo-identifier, a group identifier) ​​to select resources 340 or subchannels 325, thereby supporting one or more transmissions by UE 115-s and UE 115-t using common resources 340. In the illustrative example, UE 115-r may transmit S-RMSI 760-c multiplexed with S-SSB 345-g using resource set 350-g, and UE 115-s and UE 115-t may each support relaying of at least a portion of S-RMSI 760-c by transmitting S-RMSI 760-d multiplexed with S-SSB 345-h using resource set 350-h. In some implementations, UE 115-r may assign the same resource pattern to relay UE 115-s and UE 115-t (such as an implementation in which a predefined pattern is used).

[0093] Fig. 9 An example of a process flow 900 for supporting sidelink control signaling using unlicensed spectrum is shown. In some implementations, the process flow 900 may implement Figures 1 to 8 The various aspects described may be implemented by these aspects. For example, various aspects of process flow 900 may be implemented by UE 115-v and UE 115-u, which may be as described in reference Figure 1 and Figure 2 In some implementations, aspects of process flow 900 may be implemented by a network entity 105-a, which may be a network entity such as described in reference Figure 1An example of a network entity 105 is described. In the following description of process flow 900, operations between UE 115-v, UE 115-u, and network entity 105-a may be sent in an order different from the example order shown, or these operations may be performed in a different order or at a different time. Some operations may also be omitted from process flow 900, and other operations may be added to process flow 900.

[0094] At 930, UE 115-v may use resources of a channel of an unlicensed radio spectrum band to send an S-SSB. UE 115-v may also use a second resource of a channel of an unlicensed radio spectrum band to send control signaling. In some implementations, the control signaling may be frequency division multiplexed with the S-SSB. In some implementations, UE 115-v may interleave the control signaling using frequency resources that are discontinuous with the frequency resources of the channel used to send the S-SSB. In some implementations, the control signaling may be associated with a broadcast transmission. Additionally or alternatively, the control signaling may include an indication of a device identifier for performing resource selection.

[0095] S-SSB transmission may exempt the LBT procedure (such that UE 115-v may send S-SSB without performing the LBT procedure, or UE 115-v may send S-SSB after performing a relaxed LBT procedure). Therefore, when sending control signaling multiplexed with S-SSB, UE 115-v may also be exempted from performing the LBT procedure. In some specific implementations, UE 115-v may send multiplexed control signaling due to LBT failure. For example, if UE 115-v experiences LBT failure, control signaling may be sent to UE 115-u, which may trigger a recovery mode. Therefore, UE 115-v and UE 115-u may restore the connection by switching to different subbands, switching to different beam spaces, or using more robust channels and other recovery methods.

[0096] In some implementations, the UE 115-v may perform signaling at 930 based on the RLF with the other side link device detected at 910. Additionally or alternatively, the UE 115-v may perform signaling at 930 based on control signaling received from the UE 115-u at 915. For example, the UE 115-v may measure the control signaling at 915 and may perform signaling at 930 if the signal quality signaling at 915 is below a threshold.

[0097] In some embodiments, the UE 115-v may perform signaling at 930 based on a resource allocation, which may include a resource selection, including a selection associated with the RLF failure detected at 910 or the signaling at 915, among other examples. For example, at 905, the UE 115-u and the UE 115-v may receive an indication of a resource allocation for an unlicensed radio spectrum band from the network entity 105-a. The resource allocation may indicate a resource or a TTI or both for performing the signaling at 930. Additionally or alternatively, at 920, the UE 115-v may select one or more resources of a channel based on a device identifier at an index of the TTI, and may also reserve the selected resources at 925 by sending a signal (such as a broadcast signal) to the network entity 105-a, to the UE 115-u, or to both.

[0098] Fig.10 A diagram of a system 1000 including a device 1005 that supports sidelink control signaling using unlicensed spectrum is shown. The device 1005 may communicate (such as wirelessly) with one or more network entities (such as one or more components of one or more network entities 105), one or more UEs 115, or any combination thereof. The device 1005 may include components for two-way voice and data communications, including components for sending and receiving communications, such as a communication manager 1020, an input / output (I / O) controller 1010, a transceiver 1015, an antenna 1025, a memory 1030, code 1035, and a processor 1040. These components may be in electronic communication or otherwise coupled (such as operatively, communicatively, functionally, electronically, electrically) via one or more buses (such as a bus 1045).

[0099] I / O controller 1010 can manage input and output signals of device 1005. I / O controller 1010 can also manage peripheral devices that are not integrated into device 1005. In some implementations, I / O controller 1010 can represent a physical connection or port to an external peripheral device. In some implementations, I / O controller 1010 can utilize an operating system, such as or another known operating system. Additionally or alternatively, the I / O controller 1010 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some implementations, the I / O controller 1010 may be implemented as part of a processor or processing system (such as the processor 1040). In some implementations, a user may interact with the device 1005 via the I / O controller 1010 or via hardware components controlled by the I / O controller 1010.

[0100] In some implementations, the device 1005 may include a single antenna 1025. However, in some other implementations, the device 1005 may have more than one antenna 1025, which can concurrently send or receive multiple wireless transmissions. The transceiver 1015 can communicate bidirectionally via one or more antennas 1025, wired or wireless links, as described herein. For example, the transceiver 1015 may represent a wireless transceiver and can communicate bidirectionally with another wireless transceiver. The transceiver 1015 may also include a modem for modulating packets, providing the modulated packets to one or more antennas 1025 for transmission, and demodulating packets received from one or more antennas 1025. In some implementations, the transceiver 1015 may include one or more interfaces, such as one or more interfaces coupled to one or more antennas 1025 configured to support various receiving or obtaining operations or one or more interfaces coupled to one or more antennas 1025 configured to support various sending or output operations, or a combination thereof. In some implementations, the transceiver 1015 may include or be configured to be coupled to one or more processors or memory components that are operable to perform the following operations: use received or obtained information or signals to perform or support operations, or generate information or other signals for transmission or other output, or any combination of these operations. In some implementations, the transceiver 1015, or the transceiver 1015 and one or more antennas 1025, or the transceiver 1015 and one or more antennas 1025 and one or more processors or memory components (such as processor 1040, or memory 1030, or both) may be included in a chip or chip component installed in the device 1005.

[0101] The memory 1030 may include random access memory (RAM) and read-only memory (ROM). The memory 1030 may store computer-readable, computer-executable code 1035 including instructions that, when executed by the processor 1040, cause the device 1005 to perform various functions described herein. The code 1035 may be stored in a non-transitory computer-readable medium such as a system memory or another type of memory. In some implementations, the code 1035 may not be directly executable by the processor 1040, but may cause a computer (such as when compiled and executed) to perform the functions described herein. In some implementations, among other things, the memory 1030 may include a basic I / O system (BIOS) that may control basic hardware or software operations, such as interaction with peripheral components or devices.

[0102] Processor 1040 may be any one or more suitable processors capable of executing scripts or instructions of one or more software programs stored in device 1005 (such as in memory 1030). In some specific implementations, processor 1040 may be a component of a processing system. A processing system may generally refer to a system or a series of machines or components that receive inputs and process these inputs to produce an output set (which may be delivered to other systems or components of device 1005, for example). For example, a processing system of device 1005 may refer to a system including various other components or subcomponents of device 1005, such as processor 1040, or transceiver 1015, or communication manager 1020, or other components or combinations of components of device 1005. A processing system of device 1005 may interface with other components of device 1005, and may process information (such as input or signals) received from other components, or output information to other components. For example, a chip or modem of device 1005 may include a processing system and one or more interfaces for outputting information or for obtaining information or both. One or more interfaces may be implemented as or otherwise include a first interface configured to output information and a second interface configured to obtain information, or the same interface configured to output information and obtain information, as well as other specific implementations. In some specific implementations, one or more interfaces may refer to an interface between a processing system of a chip or modem and a transmitter, so that the device 1005 can send information output from the chip or modem. Additionally or alternatively, in some specific implementations, one or more interfaces may refer to an interface between a processing system of a chip or modem and a receiver, so that the device 1005 can obtain information or signal input, and the information can be passed to the processing system. Those of ordinary skill in the art will readily recognize that the first interface may also obtain information or signal input, and the second interface may also output information or signal output.

[0103] According to examples disclosed herein, the communication manager 1020 can support wireless communications. For example, the communication manager 1020 can be configured to or otherwise support components for sending a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band and sending control signaling using a second resource of the channel of the unlicensed radio spectrum band. In some implementations, the control signaling can be frequency division multiplexed with the SSB.

[0104] In some implementations, the communications manager 1020 can be configured or otherwise support components for receiving an indication of a resource allocation for an unlicensed radio spectrum band, and sending control signaling using the second resource can be based on the resource allocation.

[0105] In some implementations, control signaling can be sent based on a TTI associated with a resource allocation.

[0106] In some implementations, the communications manager 1020 can be configured or otherwise support components for selecting a second resource of the channel based on a device identifier, an index of a TTI associated with sending control signaling, or a combination thereof.

[0107] In some implementations, the communications manager 1020 can be configured or otherwise support components for sending a signal to reserve a second resource for the channel.

[0108] In some implementations, the control signaling can include an indication of an LBT failure, an indication of the number of LBT attempts, or a combination thereof.

[0109] In some implementations, the communications manager 1020 can be configured or otherwise support components for detecting a RLF with the other side link device, and sending the control signaling can be associated with the RLF.

[0110] In some implementations, the control signaling can include an instruction to restore the sidelink communication link using a second channel of the unlicensed radio spectrum band.

[0111] In some implementations, the communications manager 1020 can be configured or otherwise support components for receiving second control signaling from the other side link device, and sending the control signaling can be associated with a signal quality measurement of the second control signaling satisfying a threshold.

[0112] In some implementations, sending control signaling with SSB frequency division multiplexing can be associated with LBT exemption.

[0113] In some implementations, sending control signaling with SSB frequency division multiplexing can be associated with LBT failure.

[0114] In some implementations, to support sending control signaling, the communications manager 1020 may be configured or otherwise support components for interleaving control signaling using a second frequency resource of a channel that is discontinuous with a first frequency resource of a channel associated with sending an SSB.

[0115] In some implementations, control signaling can be associated with a broadcast transmission.

[0116] In some implementations, the control signaling can include an indication of a device identifier for performing resource selection.

[0117] In some implementations, the communication manager 1020 may be configured to use or otherwise cooperate with the transceiver 1015, one or more antennas 1025, or any combination thereof to perform various operations (such as receiving, monitoring, transmitting). Although the communication manager 1020 is illustrated as a component of the transceiver 1015, in some implementations, one or more functions described with reference to the communication manager 1020 may be supported or performed by the transceiver 1015, the processor 1040, the memory 1030, the code 1035, or any combination thereof. For example, the code 1035 may include instructions that are executable by the processor 1040 to cause the device 1005 to perform various aspects of sidelink control signaling using unlicensed spectrum as described herein, or the processor 1040 and the memory 1030 may be otherwise configured to perform or support such operations.

[0118] Fig.11 A flow chart illustrating a method 1100 for supporting sidelink control signaling using unlicensed spectrum is shown. The operations of the method 1100 may be implemented by a UE or a component thereof as described herein. For example, the operations of the method 1100 may be implemented by a UE or a component thereof as described herein. Figures 1 to 10 The described UE 115 may be performed. In some specific implementations, the UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0119] At 1105, the method may include transmitting a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band. The operations of 1105 may be performed according to examples as disclosed herein.

[0120] At 1110, the method may include sending control signaling using a second resource of a channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB. The operations of 1110 may be performed according to examples as disclosed herein.

[0121] The following provides an overview of some aspects of the disclosure:

[0122] Aspect 1: A method for wireless communication, the method comprising: using a first resource of a channel of an unlicensed radio spectrum band to send a side link SSB; and using a second resource of the channel of the unlicensed radio spectrum band to send control signaling, wherein the control signaling is frequency division multiplexed with the SSB.

[0123] Aspect 2: The method according to aspect 1 further comprises: receiving an indication of resource allocation of the unlicensed radio spectrum band, wherein sending the control signaling using the second resource is performed according to the resource allocation.

[0124] Aspect 3: The method according to aspect 2, wherein sending the control signaling is performed according to a TTI associated with the resource allocation.

[0125] Aspect 4: The method according to any one of aspects 1 to 3 further includes: selecting the second resource of the channel according to a device identifier, an index of a TTI associated with sending the control signaling, or a combination thereof.

[0126] Aspect 5: The method according to any one of Aspects 1 to 4 further includes: sending a signal to reserve the second resource of the channel.

[0127] Aspect 6: The method according to any one of aspects 1 to 5, wherein the control signaling includes an indication of LBT failure, an indication of the number of LBT attempts, or a combination thereof.

[0128] Aspect 7: The method according to any one of aspects 1 to 6 further includes: detecting a RLF with the other side link device, wherein sending the control signaling is associated with the RLF.

[0129] Aspect 8: The method according to aspect 7, wherein the control signaling includes an instruction to restore a sidelink communication link using a second channel of the unlicensed radio spectrum band.

[0130] Aspect 9: The method according to any one of aspects 1 to 8 further includes: receiving a second control signaling from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

[0131] Aspect 10: The method according to any one of Aspects 1 to 9, wherein sending the control signaling with the SSB frequency division multiplexing is associated with LBT exemption.

[0132] Aspect 11: The method according to any one of Aspects 1 to 10, wherein sending the control signaling with the SSB frequency division multiplexing is associated with LBT failure.

[0133] Aspect 12: The method according to any one of Aspects 1 to 11, wherein sending the control signaling comprises: interleaving the control signaling using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with sending the SSB.

[0134] Aspect 13: The method according to any one of aspects 1 to 12, wherein the control signaling is associated with a broadcast transmission.

[0135] Aspect 14: The method according to any one of aspects 1 to 13, wherein the control signaling includes an indication of a device identifier for performing resource selection.

[0136] Aspect 15: A device for wireless communication, the device comprising one or more interfaces, the one or more interfaces being configured to: use a first resource of a channel of an unlicensed radio spectrum band to output a side link SSB; and use a second resource of the channel of the unlicensed radio spectrum band to output control signaling, wherein the control signaling is frequency division multiplexed with the SSB.

[0137] Aspect 16: An apparatus according to Aspect 15, wherein the one or more interfaces are configured to: obtain an indication of a resource allocation of the unlicensed radio spectrum band, wherein outputting the control signaling is performed using the second resource according to the resource allocation.

[0138] Aspect 17: The apparatus according to Aspect 16, wherein outputting the control signaling is performed according to a TTI associated with the resource allocation.

[0139] Aspect 18: An apparatus according to any one of Aspects 15 to 17, wherein the one or more interfaces are configured to: select the second resource of the channel based on a device identifier, an index of a TTI associated with outputting the control signaling, or a combination thereof.

[0140] Aspect 19: The apparatus according to any one of aspects 15 to 18, wherein the one or more interfaces are configured to: output a signal to reserve the second resource of the channel.

[0141] Aspect 20: An apparatus according to any one of aspects 15 to 19, wherein the control signaling includes an indication of LBT failure, an indication of the number of LBT attempts, or a combination thereof.

[0142] Aspect 21: An apparatus according to any one of aspects 15 to 20, wherein the one or more interfaces are configured to: detect a RLF with another side link device, wherein outputting the control signaling is associated with the RLF.

[0143] Aspect 22: An apparatus according to Aspect 21, wherein the control signaling includes an indication to resume a sidelink communication link using a second channel of the unlicensed radio spectrum band.

[0144] Aspect 23: An apparatus according to any one of Aspects 15 to 22, wherein the one or more interfaces are configured to: obtain second control signaling from the other side link device, wherein outputting the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

[0145] Aspect 24: An apparatus according to any one of Aspects 15 to 23, wherein the control signaling output with the SSB frequency division multiplexing is associated with LBT exemption.

[0146] Aspect 25: An apparatus according to any one of Aspects 15 to 24, wherein the control signaling outputted with the SSB frequency division multiplexing is associated with LBT failure.

[0147] Aspect 26: An apparatus according to any one of Aspects 15 to 25, wherein the one or more interfaces are configured to: interleave the control signaling using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with outputting the SSB.

[0148] Aspect 27: An apparatus according to any one of aspects 15 to 26, wherein the control signaling is associated with a broadcast transmission.

[0149] Aspect 28: An apparatus according to any one of aspects 15 to 27, wherein the control signaling includes an indication of a device identifier for performing resource selection.

[0150] Aspect 29: An apparatus according to any one of aspects 15 to 28, the apparatus being included in a UE.

[0151] Aspect 30: An apparatus for wireless communication, the apparatus comprising: a component for sending a side link SSB using a first resource of a channel of an unlicensed radio spectrum band; and a component for sending control signaling using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

[0152] Aspect 31: The apparatus according to aspect 30 further comprises: means for receiving an indication of a resource allocation of the unlicensed radio spectrum band, wherein sending the control signaling is performed using the second resource in accordance with the resource allocation.

[0153] Aspect 32: The apparatus according to Aspect 31, wherein sending the control signaling is performed according to a TTI associated with the resource allocation.

[0154] Aspect 33: The apparatus according to any one of aspects 30 to 32 further comprises: a component for selecting the second resource of the channel according to a device identifier, an index of a TTI associated with sending the control signaling, or a combination thereof.

[0155] Aspect 34: The apparatus according to any one of Aspects 30 to 33 further includes: a component for sending a signal to reserve the second resource of the channel.

[0156] Aspect 35: An apparatus according to any one of aspects 30 to 34, wherein the control signaling includes an indication of LBT failure, an indication of the number of LBT attempts, or a combination thereof.

[0157] Aspect 36: The apparatus according to any one of aspects 30 to 35 further includes: a component for detecting a RLF with the other side link device, wherein sending the control signaling is associated with the RLF.

[0158] Aspect 37: An apparatus according to Aspect 36, wherein the control signaling includes an indication to restore a sidelink communication link using a second channel of the unlicensed radio spectrum band.

[0159] Aspect 38: The apparatus according to any one of Aspects 30 to 37 further comprises: a component for receiving a second control signaling from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

[0160] Aspect 39: An apparatus according to any one of Aspects 30 to 38, wherein sending the control signaling with the SSB frequency division multiplexing is associated with LBT exemption.

[0161] Aspect 40: An apparatus according to any one of Aspects 30 to 39, wherein sending the control signaling with the SSB frequency division multiplexing is associated with LBT failure.

[0162] Aspect 41: An apparatus according to any one of Aspects 30 to 40, wherein the component for sending the control signaling includes: a component for interleaving the control signaling using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with sending the SSB.

[0163] Aspect 42: An apparatus according to any one of aspects 30 to 41, wherein the control signaling is associated with a broadcast transmission.

[0164] Aspect 43: An apparatus according to any one of aspects 30 to 42, wherein the control signaling includes an indication of a device identifier for performing resource selection.

[0165] Aspect 44: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the following operations: using a first resource of a channel of an unlicensed radio spectrum band to send a sidelink synchronization signal block (SSB); and using a second resource of the channel of the unlicensed radio spectrum band to send control signaling, wherein the control signaling is frequency division multiplexed with the SSB.

[0166] Aspect 45: A non-transitory computer-readable medium according to Aspect 44, wherein the instructions are capable of being further executed by the processor to: receive an indication of a resource allocation for the unlicensed radio spectrum band, wherein sending the control signaling is performed using the second resource based on the resource allocation.

[0167] Aspect 46: The non-transitory computer-readable medium of aspect 45, wherein sending the control signaling is performed according to a TTI associated with the resource allocation.

[0168] Aspect 47: A non-transitory computer-readable medium according to any one of Aspects 44 to 46, wherein the instructions are capable of being further executed by the processor to: select the second resource of the channel based on a device identifier, an index of a TTI associated with sending the control signaling, or a combination thereof.

[0169] Aspect 48: The non-transitory computer readable medium of any one of aspects 44 to 47, wherein the instructions are further executable by the processor to: send a signal to reserve the second resource of the channel.

[0170] Aspect 49: The non-transitory computer-readable medium of any one of aspects 44 to 48, wherein the control signaling comprises an indication of an LBT failure, an indication of a number of LBT attempts, or a combination thereof.

[0171] Aspect 50: The non-transitory computer-readable medium according to any one of aspects 44 to 49, wherein the instructions are further executable by the processor to: detect a RLF with another side link device, wherein sending the control signaling is associated with the RLF.

[0172] Aspect 51: The non-transitory computer-readable medium of aspect 50, wherein the control signaling comprises an indication to resume a sidelink communication link using a second channel of the unlicensed radio spectrum band.

[0173] Aspect 52: A non-transitory computer-readable medium according to any one of Aspects 44 to 51, wherein the instructions are capable of being further executed by the processor to: receive a second control signaling from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

[0174] Aspect 53: A non-transitory computer-readable medium according to any one of aspects 44 to 52, wherein sending the control signaling with the SSB frequency division multiplexing is associated with LBT exemption.

[0175] Aspect 54: The non-transitory computer-readable medium of any one of aspects 44 to 53, wherein sending the control signaling with the SSB frequency division multiplexing is associated with an LBT failure.

[0176] Aspect 55: A non-transitory computer-readable medium according to any one of Aspects 44 to 54, wherein the instructions for sending the control signaling are executable by the processor to: interleave the control signaling using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with sending the SSB.

[0177] Aspect 56: The non-transitory computer-readable medium of any one of aspects 44 to 55, wherein the control signaling is associated with a broadcast transmission.

[0178] Aspect 57: The non-transitory computer-readable medium of any one of aspects 44 to 56, wherein the control signaling includes an indication of a device identifier for performing resource selection.

[0179] As used herein, the term "determine" or "determine" encompasses a wide variety of actions, and thus, "determine" may include calculating, computing, processing, deriving, investigating, searching (such as via searching in a table, database, or other data structure), reasoning, ascertaining, and similar actions. Additionally, "determine" may include receiving (such as receiving information), accessing (such as accessing data stored in a memory), and similar actions. Additionally, "determine" may include parsing, selecting, choosing, establishing, and other such similar actions.

[0180] As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items (including single members). As an example, "at least one of a, b, or c" is intended to cover: a, b, c, ab, ac, bc, and abc.

[0181] The various illustrative logical components, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the specific implementations disclosed herein may be implemented as electronic hardware, computer software, or a combination of the two. The interchangeability of hardware and software has been generally described in terms of functionality and is illustrated in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented using hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0182] Hardware and data processing devices for implementing the various illustrative logics, logic blocks, modules, and circuits described in conjunction with the various aspects disclosed herein may be implemented or executed using a general purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. In some implementations, specific processes and methods may be performed by circuits specific to a given function.

[0183] In one or more aspects, the functions described may be implemented using hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents, or in any combination thereof. Specific implementations of the subject matter described in this specification may also be implemented as one or more computer programs, such as one or more modules of computer program instructions encoded on computer storage media for execution by a data processing device or for controlling the operation of a data processing device.

[0184] If implemented in software, the function can be stored or sent on a computer-readable medium using one or more instructions or codes. The process of the method or algorithm disclosed herein can be implemented in a processor executable software module that can reside on a computer-readable medium. Computer-readable media include both computer storage media and communication media, and communication media include any medium that can realize the transfer of a computer program from one location to another. The storage medium can be any available medium that a computer can access. By way of example and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, disk storage devices or other magnetic storage devices, or any other medium that can be used to store the desired program code in the form of an instruction or data structure and can be accessed by a computer. In addition, any connection can be appropriately referred to as a computer-readable medium. Disks and optical disks as used herein include compact discs (CDs), laser optical disks, optical optical disks, digital versatile discs (DVDs), floppy disks, and blue-ray discs. Disks can reproduce data magnetically, and optical disks can reproduce data optically using lasers. The above combination should also be included in the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as a code and instruction set, or any combination of code and instruction sets, on a machine-readable medium or computer-readable medium, which may be incorporated into a computer program product.

[0185] Various modifications to the specific implementations described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other specific implementations without departing from the spirit or scope of the disclosure. Thus, the claims are not intended to be limited to the specific implementations shown herein, but should be granted the widest scope consistent with the disclosure, the principles and features disclosed herein.

[0186] Additionally, one of ordinary skill in the art will readily recognize that the terms "upper" and "lower" are sometimes used for ease of describing the drawings and indicate relative positions corresponding to the orientation of the drawings on a correctly oriented page, and may not reflect the correct orientation of any device as implemented.

[0187] Certain features described in this specification in the context of a single implementation may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable subcombination. Furthermore, while features may be described above as functioning in some combination and even initially claimed as such, one or more features from a claimed combination may be removed from the combination, and a claimed combination may involve subcombinations or variations of subcombinations.

[0188] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be understood as requiring such operations to be performed in the specific order shown or in a sequential order, or to perform all illustrated operations to achieve the desired result. In addition, the accompanying drawings can schematically depict one or more example processes in the form of a flow chart. However, other operations not depicted can be incorporated into the example processes schematically illustrated. For example, one or more additional operations can be performed before, after, at the same time, or between any operations in the illustrated operations. In some environments, multitasking and parallel processing may be advantageous. In addition, the separation of various system components in the specific implementation described above should not be understood as requiring such separation in all specific implementations, but it should be understood that the described program components and systems can usually be integrated together in a single software product, or be packaged in multiple software products. In addition, other specific implementations are within the scope of the following claims. In some specific implementations, the actions narrated in the claims can be performed in different orders and still achieve the desired result.

Claims

1. A device for wireless communication, the device comprising: One or more interfaces, the one or more interfaces being configured to: outputting a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band; and Control signaling is output using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

2. The apparatus of claim 1, wherein the one or more interfaces are configured to: An indication of a resource allocation of the unlicensed radio spectrum band is obtained, wherein outputting the control signaling using the second resource is performed in accordance with the resource allocation.

3. The apparatus of claim 2, wherein outputting the control signaling is performed according to a transmission time interval (TTI) associated with the resource allocation.

4. The apparatus according to claim 1, further comprising a processing system, wherein the processing system is configured to: The second resource of the channel is selected according to a device identifier, an index of a transmission time interval (TTI) associated with outputting the control signaling, or a combination thereof.

5. The apparatus of claim 1 , wherein the one or more interfaces are configured to: Output a signal to reserve the second resource of the channel.

6. The apparatus of claim 1, wherein the control signaling comprises an indication of a listen-before-talk (LBT) failure, an indication of a number of LBT attempts, or a combination thereof.

7. The apparatus according to claim 1, further comprising a processing system, wherein the processing system is configured to: A radio link failure (RLF) with another side link device is detected, wherein outputting the control signaling is associated with the RLF.

8. The apparatus of claim 7, wherein the control signaling includes an instruction to resume a sidelink communication link using a second channel of the unlicensed radio spectrum band.

9. The apparatus of claim 1, wherein the one or more interfaces are configured to: A second control signaling is obtained from the other side link device, wherein outputting the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

10. The apparatus of claim 1, wherein the control signaling outputted with the SSB frequency division multiplexing is associated with a listen before talk (LBT) exemption.

11. The apparatus of claim 1, wherein the control signaling outputted with the SSB frequency division multiplexing is associated with a listen-before-talk (LBT) failure.

12. The apparatus according to claim 1, further comprising a processing system, wherein the processing system is configured to: The control signaling is interleaved using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with outputting the SSB.

13. The apparatus of claim 1, wherein the control signaling is associated with a broadcast transmission.

14. The apparatus of claim 1, wherein the control signaling includes an indication of a device identifier for performing resource selection.

15. The apparatus of claim 1, the apparatus being included in a user equipment (UE).

16. A method for wireless communication, the method comprising: transmitting a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band; as well as Control signaling is sent using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

17. The method according to claim 16, further comprising: An indication of a resource allocation of the unlicensed radio spectrum band is received, wherein sending the control signaling using the second resource is performed in accordance with the resource allocation.

18. The method of claim 17, wherein sending the control signaling is performed according to a transmission time interval (TTI) associated with the resource allocation.

19. The method according to claim 16, further comprising: The second resource of the channel is selected based on a device identifier, an index of a transmission time interval (TTI) associated with sending the control signaling, or a combination thereof.

20. The method according to claim 16, further comprising: Send a signal to reserve the second resource of the channel.

21. The method of claim 16, wherein the control signaling comprises an indication of a listen-before-talk (LBT) failure, an indication of a number of LBT attempts, or a combination thereof.

22. The method according to claim 16, further comprising: A radio link failure (RLF) is detected with another side link device, wherein sending the control signaling is associated with the RLF.

23. The method of claim 22, wherein the control signaling includes an indication to resume a sidelink communication link using a second channel of the unlicensed radio spectrum band.

24. The method according to claim 16, further comprising: A second control signaling is received from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

25. The method of claim 16, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen before talk (LBT) exemption.

26. The method of claim 16, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen before talk (LBT) failure.

27. The method of claim 16, wherein sending the control signaling comprises: The control signaling is interleaved using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with outputting the SSB.

28. The method of claim 16, wherein the control signaling is associated with a broadcast transmission.

29. The method of claim 16, wherein the control signaling includes an indication of a device identifier for performing resource selection.

30. An apparatus for wireless communication, the apparatus comprising: means for transmitting a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band; and Means for sending control signaling using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

31. The apparatus according to claim 30, further comprising: Means for receiving an indication of a resource allocation for the unlicensed radio spectrum band, wherein sending the control signaling using the second resource is in accordance with the resource allocation.

32. The apparatus of claim 31, wherein sending the control signaling is performed according to a transmission time interval (TTI) associated with the resource allocation.

33. The apparatus according to claim 30, further comprising: means for selecting the second resource of the channel based on a device identifier, an index of a transmission time interval (TTI) associated with outputting the control signaling, or a combination thereof.

34. The apparatus of claim 30, further comprising: Means for sending a signal to reserve the second resource of the channel.

35. The apparatus of claim 30, wherein the control signaling comprises an indication of a listen-before-talk (LBT) failure, an indication of a number of LBT attempts, or a combination thereof.

36. The apparatus of claim 30, further comprising: Means for detecting a radio link failure (RLF) with another side link device, wherein sending said control signaling is associated with said RLF.

37. An apparatus according to claim 36, wherein the control signaling includes an instruction to resume a sidelink communication link using a second channel of the unlicensed radio spectrum band.

38. The apparatus of claim 30, further comprising: Means for receiving second control signaling from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

39. The apparatus of claim 30, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen before talk (LBT) exemption.

40. The apparatus of claim 30, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen-before-talk (LBT) failure.

41. The apparatus of claim 30, wherein the means for sending the control signaling comprises: Means for interleaving the control signaling using a second frequency resource of the channel that is non-contiguous with a first frequency resource of the channel associated with outputting the SSB.

42. The apparatus of claim 30, wherein the control signaling is associated with a broadcast transmission.

43. The apparatus of claim 30, wherein the control signaling includes an indication of a device identifier for performing resource selection.

44. A non-transitory computer readable medium storing code for wireless communication, the code comprising instructions executable by a processor to: transmitting a sidelink synchronization signal block (SSB) using a first resource of a channel of an unlicensed radio spectrum band; and Control signaling is sent using a second resource of the channel of the unlicensed radio spectrum band, wherein the control signaling is frequency division multiplexed with the SSB.

45. The non-transitory computer readable medium of claim 44, wherein the instructions are further executable by the processor to: An indication of a resource allocation of the unlicensed radio spectrum band is received, wherein sending the control signaling using the second resource is performed in accordance with the resource allocation.

46. ​​The non-transitory computer-readable medium of claim 45, wherein sending the control signaling is performed according to a transmission time interval (TTI) associated with the resource allocation.

47. The non-transitory computer readable medium of claim 44, wherein the instructions are further executable by the processor to: The second resource of the channel is selected according to a device identifier, an index of a transmission time interval (TTI) associated with outputting the control signaling, or a combination thereof.

48. The non-transitory computer readable medium of claim 44, wherein the instructions are further executable by the processor to: Send a signal to reserve the second resource of the channel.

49. The non-transitory computer-readable medium of claim 44, wherein the control signaling comprises an indication of a listen-before-talk (LBT) failure, an indication of a number of LBT attempts, or a combination thereof.

50. The non-transitory computer readable medium of claim 44, wherein the instructions are further executable by the processor to: A radio link failure (RLF) with another side link device is detected, wherein outputting the control signaling is associated with the RLF.

51. The non-transitory computer-readable medium of claim 50, wherein the control signaling comprises an instruction to restore a sidelink communication link using a second channel of the unlicensed radio spectrum band.

52. The non-transitory computer readable medium of claim 44, wherein the instructions are further executable by the processor to: A second control signaling is received from the other side link device, wherein sending the control signaling is associated with a signal quality measurement of the second control signaling satisfying a threshold.

53. The non-transitory computer readable medium of claim 44, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen before talk (LBT) exemption.

54. The non-transitory computer readable medium of claim 44, wherein sending the control signaling with the SSB frequency division multiplexing is associated with a listen before talk (LBT) failure.

55. The non-transitory computer readable medium of claim 44, wherein the instructions for outputting the control signaling are executable by the processor to: The control signaling is interleaved using a second frequency resource of the channel that is discontinuous with a first frequency resource of the channel associated with outputting the SSB.

56. The non-transitory computer readable medium of claim 44, wherein the control signaling is associated with a broadcast transmission.

57. The non-transitory computer-readable medium of claim 44, wherein the control signaling includes an indication of a device identifier for performing resource selection.

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