Channel Occupancy Time (COT) Sharing for Sidelink

Abstract

A wireless communication system and method are provided that relate to channel occupation time (COT) sharing for sidelink communications. A first user equipment (UE) receives a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE. The first UE determines whether the second UE is one of two or more UEs intended to receive the second sidelink transmission. The first UE transmits a second sidelink transmission to the two or more UEs during a portion of the first COT based on the COT sharing. The COT sharing is in response to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of Greek Patent Application No. 20210100003, filed on January 4, 2021, entitled "CHANNEL OCCUPANCY TIME (COT) SHARING FOR SIDELINK," which is incorporated herein by reference for all applicable purposes as if fully set forth below in its entirety.

[0002] FIELD OF THE DISCLOSURE

[0002] This application relates to wireless communication systems, and more particularly, to channel occupancy time (COT) sharing for sidelink communication. [Background technology]

[0003]

[0003] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcasts, etc. These systems may be capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). A wireless multiple-access communication system may include several base stations (BSs), each simultaneously supporting communication for multiple communication devices, which may in some cases be known as user equipment (UE).

[0004] To meet the growing demand for enhanced mobile broadband connectivity, wireless communication technologies are evolving from Long Term Evolution (LTE) technology to Next Generation New Radio (NR) technology, sometimes referred to as the fifth generation (5G). For example, NR is designed to provide lower latency, higher bandwidth or throughput, and higher reliability than LTE. NR is designed to operate over a wide range of spectrum bands, for example, from low frequency bands below about 1 gigahertz (GHz) and intermediate frequency bands from about 1 GHz to about 6 GHz to high frequency bands such as millimeter wave (mmWave) bands. NR is also designed to operate across a variety of spectrum types, from licensed spectrum to unlicensed and shared spectrum. Spectrum sharing allows operators to opportunistically aggregate spectrum to dynamically support high bandwidth services. Spectrum sharing can extend the benefits of NR technology to operating entities that may not have access to licensed spectrum.

[0005] In a wireless communication network, a BS may communicate with a UE in an uplink direction and a downlink direction. Sidelink was introduced in LTE to allow a UE to send data to another UE without tunneling through the BS and / or the associated core network. LTE sidelink technology has been extended to provide device-to-device (D2D) communication, vehicle-to-everything (V2X) communication, and / or cellular vehicle-to-everything (C-V2X) communication. Similarly, NR may be extended to support sidelink communication, D2D communication, V2X communication, and / or C-V2X over licensed and / or unlicensed bands. Summary of the Invention

[0006]

[0006] The following summarizes some aspects of the present disclosure to provide a basic understanding of the described technology. This summary is not an exhaustive overview of all contemplated features of the present disclosure, nor does it identify key or critical elements of all aspects of the present disclosure, nor delineate the scope of any or all aspects of the present disclosure. Its sole purpose is to present some concepts of one or more aspects of the present disclosure in summary form as a prelude to the more detailed description presented later.

[0007]

[0007] For example, in one aspect of the present disclosure, a method of wireless communication performed by a first user equipment (UE) includes receiving a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE, determining whether the second UE is one of two or more UEs intended to receive the second sidelink transmission, and transmitting a second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, where the COT sharing is responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0008]

[0008] In an additional aspect of the present disclosure, a first user equipment (UE) includes a transceiver configured to receive a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE, and a processor coupled to the transceiver, where the processor is configured to determine whether the second UE is one of two or more UEs intended to receive the second sidelink transmission, where the transceiver is further configured to transmit a second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, where the COT sharing is responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0009]

[0009] In an additional aspect of the present disclosure, a non-transitory computer-readable medium has program code recorded thereon, the program code including: code for causing a first user equipment (UE) to receive a first sidelink transmission from a second UE during a first channel occupancy time (COT), where the first COT is associated with the second UE; code for causing the first UE to determine whether the second UE is one of two or more UEs intended to receive the second sidelink transmission; and code for causing the first UE to transmit a second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0010]

[0010] In an additional aspect of the present disclosure, a first user equipment (UE) includes means for receiving a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE, means for determining whether the second UE is one of two or more UEs intended to receive the second sidelink transmission, and means for transmitting a second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0011]

[0011] Other aspects, features, and embodiments of the present invention will become apparent to those skilled in the art upon reviewing the following description of certain exemplary embodiments of the present invention in conjunction with the accompanying figures. Although the features of the present invention may be described with respect to some embodiments and the following drawings, all embodiments of the present invention may include one or more of the advantageous features described herein. In other words, one or more embodiments may be described as having some advantageous features, but one or more of such features may also be used in accordance with various embodiments of the present invention described herein. Similarly, although exemplary embodiments may be described below as device embodiments, system embodiments, or method embodiments, it should be understood that such exemplary embodiments may be implemented in various devices, systems, and methods. [Brief description of the drawings]

[0012] [Figure 1]

[0012] FIG. 1 illustrates a wireless communication network in accordance with certain aspects of the present disclosure. [Diagram 2]

[0013] 1 is a timing diagram illustrating a radio frame structure in accordance with certain aspects of the present disclosure. [Diagram 3]

[0014] FIG. 1 illustrates a wireless communication network providing sidelink communications in accordance with certain aspects of the present disclosure. [Figure 4]

[0015] FIG. 1 illustrates a sidelink communication scheme in accordance with certain aspects of the present disclosure. [Figure 5A]

[0016] FIG. 1 is a sequence diagram illustrating a sidelink channel occupation time (COT) sharing method according to certain aspects of the present disclosure. [Figure 5B]

[0017] FIG. 1 is a timing diagram illustrating a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 6A]

[0018] FIG. 1 is a sequence diagram illustrating a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 6B]

[0019] FIG. 1 is a timing diagram illustrating a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 7]

[0020] 1 illustrates a flow diagram of a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 8A]

[0021] FIG. 1 is a sequence diagram illustrating a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 8B]

[0022] FIG. 1 is a timing diagram illustrating a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 9]

[0023] 1 illustrates a flow diagram of a sidelink COT sharing method according to certain aspects of the present disclosure. [Figure 10]

[0024] 1 is a block diagram of an example base station (BS) in accordance with certain aspects of the present disclosure. [Figure 11]

[0025] FIG. 2 is a block diagram of an example user equipment (UE) in accordance with certain aspects of the present disclosure. [Figure 12]

[0026] 1 illustrates a flow diagram of a wireless communication method according to certain aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]

[0027] The detailed description of the embodiments of the invention described below with reference to the accompanying drawings is intended as an illustration of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description of the invention includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0014]

[0028] The present disclosure generally relates to wireless communication systems, also referred to as wireless communication networks. In various aspects, the techniques and apparatuses may be used for wireless communication networks, such as Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single Carrier FDMA (SC-FDMA) networks, LTE networks, Global System for Mobile Communications (GSM) networks, Fifth Generation (5G) or New Radio (NR) networks, and other communication networks. The terms "network" and "system" described herein may be used interchangeably.

[0015]

[0029] OFDMA networks may implement radio technologies such as Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) 802.11, IEEE 802.16, IEEE 802.20, flash-OFDM, etc. UTRA, E-UTRA, and GSM are parts of the Universal Mobile Telecommunications System (UMTS). In particular, Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in documents from an organization named "3rd Generation Partnership Project" (3GPP®), and cdma2000 is described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). These various radio technologies and standards are known or being developed. For example, the 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations aimed at defining globally applicable third generation (3G) mobile phone specifications. 3GPP Long Term Evolution (LTE) is a 3GPP project aimed at improving the UMTS mobile phone standard. 3GPP may define specifications for the next generation of mobile networks, mobile systems, and mobile devices. This disclosure pertains to the evolution of wireless technologies from LTE, 4G, 5G, NR, and beyond, which involve shared access to the wireless spectrum between networks using new and different radio access technologies or collections of radio air interfaces.

[0016]

[0030] In particular, 5G networks contemplate diverse deployments, diverse spectrum, and diverse services and devices that may be implemented using an OFDM-based unified air interface. To achieve these objectives, further enhancements to LTE and LTE-A are considered, in addition to the development of new radio technologies for 5G NR networks. 5G NR is a service area that offers: (1) ultra-high density (e.g., approximately 1M nodes / km); 2(2) for the mass Internet of Things (IoT) with ultra-low complexity (e.g., on the order of 10s bits / sec), ultra-low energy (e.g., on the order of 10+ years battery life), and deep coverage with the ability to reach difficult locations; (3) for mission-critical control, including with strong security to protect sensitive personal, financial, or confidential information, ultra-high reliability (e.g., on the order of 99.9999% reliability), ultra-low latency (e.g., on the order of 1 ms), and users with or without widespread mobility; and (4) for ultra-high capacity (e.g., on the order of 10 Tbps / km 2 ), scaling to provide coverage with enhanced mobile broadband including extreme data rates (e.g., multi-Gbps rates, 100+ Mbps user experience rates), and deep awareness with advanced discovery and optimization.

[0017]

[0031] 5G NR communication systems may be implemented to use optimized OFDM-based waveforms with scalable numerology and transmission time intervals (TTIs). Additional features may also include having a common flexible framework for efficient multiplexing of services and features in dynamic and low-latency time division duplex (TDD) / frequency division duplex (FDD) designs and using advanced wireless technologies such as massive multiple-input multiple-output (MIMO), robust millimeter wave (mmWave) transmission, advanced channel coding, and device-centric mobility. The scalability of numerology in 5G NR with the scaling of subcarrier spacing may efficiently address operating diverse services across diverse spectrums and diverse deployments. For example, in various outdoor and macro coverage deployments of FDD / TDD implementations below 3 GHz, subcarrier spacing may occur at 15 kHz, for example, over bandwidths (BWs) of 5, 10, 20 MHz, etc. In various other outdoor and small cell coverage deployments with TDD greater than 3 GHz, subcarrier spacing may occur at 30 kHz over 80 / 100 MHz BW. In various other indoor wideband implementations using TDD over the unlicensed portion of the 5 GHz band, subcarrier spacing may occur at 60 kHz over 160 MHz BW. Finally, in various deployments transmitting with mmWave components at 28 GHz TDD, subcarrier spacing may occur at 120 kHz over 500 MHz BW.

[0018]

[0032] 5G NR's scalable numerology facilitates scalable TTIs for diverse latency and quality of service (QoS) requirements. For example, shorter TTIs can be used for low latency and high reliability, and longer TTIs for higher spectral efficiency. Efficient multiplexing of long and short TTIs to allow transmissions to start on symbol boundaries. 5G NR also contemplates a self-contained integrated subframe design with UL / downlink scheduling information, data, and acknowledgments in the same subframe. The self-contained integrated subframe supports communication in unlicensed or contention-based shared spectrum, adaptive UL / downlink that can be flexibly configured per cell to dynamically switch between UL and downlink to meet current traffic needs.

[0019]

[0033] Various other aspects and features of the present disclosure are further described below. It will be apparent that the teachings herein can be implemented in a wide variety of forms, and that the specific structures, functions, or both disclosed herein are merely representative and not limiting. Based on the teachings herein, those skilled in the art will appreciate that the aspects disclosed herein can be implemented independently of other aspects, and that two or more of these aspects can be combined in various ways. For example, an apparatus can be implemented or a method can be practiced using any number of the aspects described herein. Furthermore, such an apparatus can be implemented or such a method can be practiced using other structures, functions, or structures and functions in addition to or other than one or more of the aspects described herein. For example, a method can be implemented as part of a system, device, apparatus, and / or as instructions stored on a computer-readable medium for execution on a processor or computer. Furthermore, an aspect can comprise at least one element of a claim.

[0020]

[0034] Sidelink communication refers to communication between user equipment devices (UEs) without tunneling through a base station (BS) and / or a core network. Sidelink communication may be communicated via a physical sidelink control channel (PSCCH) and a physical sidelink shared channel (PSSCH). The PSCCH and PSSCH are similar to the physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) in downlink (DL) communication between a BS and a UE. For example, the PSCCH may carry sidelink control information (SCI), and the PSSCH may carry sidelink data (e.g., user data). Each PSCCH is associated with a corresponding PSSCH, where the SCI in the PSCCH may carry reservation and / or scheduling information for sidelink data transmissions in the associated PSSCH. In some implementations, the SCI in the PSCCH may be referred to as SCI part 1 (SCI-1), and an additional SCI, which may be referred to as SCI part 2 (SCI-2), may be carried in the PSSCH. The SCI-2 may include control information (e.g., transmission parameters, modulation coding scheme (MCS)) that is more specific to the data carriers in the PSSCH. Sidelink communication use cases may include V2X, enhanced mobile broadband (eMBB), industrial IoT (IIoT), and / or NR-lite.

[0021]

[0035] As used herein, the term "sidelink UE" may refer to a user equipment device that performs device-to-device communication or other types of communication with another user equipment device, independent of any tunneling through a BS (e.g., gNB) and / or associated core network. As used herein, the term "sidelink transmitting UE" may refer to a user equipment device that performs sidelink transmission operations. As used herein, the term "sidelink receiving UE" may refer to a user equipment device that performs sidelink reception operations. A sidelink UE may operate as a transmitting sidelink UE at some times and as a receiving sidelink UE at other times.

[0022]

[0036] As used herein, the terms “synchronized UE”, “sidelink synchronized UE”, “anchor UE”, or “sidelink anchor UE” refer to a sidelink UE that transmits S-SSBs to facilitate sidelink communication between multiple sidelink UEs (e.g., when operating in a standalone sidelink system), and these terms may be interchanged without departing from the scope of the present disclosure. As used herein, the terms “asynchronous UE”, “non-anchor UE”, or “client” refer to a sidelink UE that relies on an anchor UE to provide sidelink system information. A sidelink UE may act as an initiating UE at one time and as a responding UE at another time. A sidelink synchronized UE may also act as a transmitting sidelink UE and / or initiating UE at one time and as a receiving sidelink UE and / or responding UE at another time.

[0023]

[0037] The term "initiating UE" as used herein may refer to a user equipment device that initiates or acquires a channel occupancy time (COT) in a shared radio frequency band (e.g., in a shared or unlicensed spectrum) for sidelink communication. For example, the initiating UE may perform a clear channel assessment (CCA) or a Category 4 (CAT4) listen-before-talk (LBT) in the shared radio frequency band to contend for or acquire the COT. Upon passing the LBT (indicating that the channel is clear for transmission), the initiating UE may transmit a sidelink transmission during the acquired COT. The term "responding UE" as used herein may refer to a user equipment device that responds to a sidelink transmission transmitted by any initiating UE. A sidelink UE may act as an initiating UE at some times and as a responding UE at other times.

[0024]

[0038] NR supports two modes of radio resource allocation (RRA), Mode 1 RRA and Mode 2 RRA, for sidelink over licensed spectrum. Mode 1 RRA supports network-controlled RRA that may be used for in-coverage sidelink communication. For example, the serving BS (e.g., gNB) may determine radio resources on behalf of the sidelink UE and send an indication of the radio resources to the sidelink UE. In some aspects, the serving BS allows sidelink transmission along with downlink control information (DCI). However, this mode has significant base station involvement and is only operational when the sidelink UE is within the coverage area of ​​the serving BS. Mode 2 RRA supports autonomous RRA that may be used for out-of-coverage sidelink UEs or partial coverage sidelink UEs. For example, the serving BS may configure the sidelink UE (e.g., while in the coverage of the serving BS) with a sidelink resource pool that may be used for sidelink when the sidelink UE is out of the coverage of the serving BS. The serving BS may also configure the sidelink UE to act as a sidelink anchor UE to provide sidelink system information for out-of-coverage sidelink UEs to communicate sidelink communications. For example, the sidelink anchor UE may provide sidelink system information by broadcasting a sidelink-synchronization signal block (S-SSB). The S-SSB may be similar to the SSB broadcasted by the BS. For example, the S-SSB may include a synchronization signal and / or sidelink system information.Some examples of sidelink system information may include a sidelink bandwidth portion (BWP) configuration, one or more sidelink transmission resource pools, and / or one or more sidelink reception resource pools, S-SSB transmission related parameters (e.g., sidelink slots configured for S-SSB transmissions and / or S-SSB transmission periodicity), and / or any other configuration information related to sidelink communication. In some implementations, the anchor UE may also schedule other sidelink UEs for communication. Thus, the sidelink anchor UE may operate as a mini-gNB that facilitates and / or coordinates communication between sidelink UEs. The sidelink channel through which two UEs may directly communicate with each other is sometimes referred to as a PC5 interface in 5G NR.

[0025]

[0039] Sidelink communication may be in unicast, groupcast, or broadcast mode. In addition, hybrid automatic repeat request (HARQ) may be applied to unicast or groupcast sidelink communication to improve transmission reliability. For unicast communication, a sidelink transmitting UE may transmit a sidelink transmission including data to a single sidelink receiving UE and may request HARQ acknowledgement / negative-acknowledgement (ACK / NACK) feedback from the sidelink receiving UE. If the sidelink receiving UE successfully decodes data from a sidelink transmission, the sidelink receiving UE transmits an ACK. Conversely, if the sidelink receiving UE fails to decode data from a sidelink transmission, the sidelink receiving UE transmits a NACK. Upon receiving a NACK, the sidelink transmitting UE may retransmit the data. In the case of broadcast communication, a sidelink transmitting UE may transmit a sidelink transmission to a group (e.g., 2, 3, 4, 5, 6, or more) of sidelink receiving UEs in the vicinity of the sidelink transmitting UE and may not request ACK / NACK feedback for the sidelink transmission.

[0026]

[0040] Groupcast sidelink communication can be connection-based or connectionless. Connection-based groupcast sidelink communication is destined for a specific group of UEs, e.g., each belonging to a group identified by a group identifier (ID) and known to the sidelink transmitting UE. Thus, the sidelink transmitting UE may request ACK / NACK feedback from each sidelink receiving UE in the group and may also assign different feedback resources to each sidelink receiving UE in the group. In case of connectionless groupcast sidelink communication, the group of UEs that can receive the groupcast transmission may not be known to the sidelink transmitting UE. Thus, the sidelink transmitting UE may request NACK-only feedback from UEs that received the groupcast sidelink communication (successfully decoded the presence of SCI) but failed to decode information data from the groupcast sidelink communication. In some cases, the sidelink transmitting UE may also assign the same NACK-only feedback resource to all UEs that failed to decode the data.

[0027]

[0041] Providing sidelink services, such as device-to-device (D2D), vehicle-to-vehicle (V2V), vehicle-to-everything (V2X), and / or cellular vehicle-to-everything (C-V2X) communications over a dedicated or licensed spectrum is relatively straightforward since channel access in the dedicated or licensed spectrum is guaranteed. NR-Unlicensed (NR-U) can benefit sidelink services, for example, by offloading sidelink traffic to the unlicensed spectrum for free. However, channel access in a shared or unlicensed spectrum is not guaranteed. Thus, to provide sidelink services over a shared or unlicensed spectrum, sidelink user equipment devices (UEs) are required to contend for channel access in the spectrum, for example, via Clear Channel Assessment (CCA) and / or Listen-Before-Talk (LBT) procedures.

[0028]

[0042] LBT can be based on energy detection (ED) or signal detection. For energy detection-based LBT, LBT results in a pass when the signal energy measured from the channel is below a threshold. Conversely, LBT results in a fail when the signal energy measured from the channel exceeds a threshold. For signal detection-based LBT, LBT results in a pass when a channel reservation signal (e.g., a predefined preamble signal) is not detected in the channel. In addition, LBT can be various modes. The LBT mode can be, for example, Category 4 (CAT4) LBT, Category 2 (CAT2) LBT, or Category 1 (CAT1) LBT. CAT1 LBT is referred to as a non-LBT mode in which LBT is not performed before transmission. CAT2 LBT refers to LBT without a random backoff period. For example, a transmitting node may determine a channel measurement value at a certain time interval and determine whether the channel is available or not based on a comparison of the channel measurement value with an ED threshold. CAT4 LBT refers to an LBT with a random backoff and a variable contention window (CW). For example, a transmitting node may draw a random number in a certain unit of time and back off for a duration based on the drawn random number.

[0029]

[0043] In some aspects, the initiating UE may contend for the COT in the shared radio frequency band by performing a CCA or a CAT4 LBT. Upon passing the CCA or CAT4 LBT (indicating that the channel is cleared for transmission), the initiating UE may transmit a sidelink transmission to the sidelink receiving UE during the COT. In some sidelink use cases (e.g., for V2X), the sidelink data traffic may include small-sized or short data bursts (e.g., having a few bytes to tens of bytes of information data). In some aspects, the duration of the COT may depend on the regulations imposed by a regulatory authority or a certain deployment of the shared radio frequency band. Thus, in some cases, a sidelink transmission with a small-sized data burst may not occupy the entire duration of the COT. Thus, it may be desirable to share the remaining duration of the COT with the receiving UE instead of leaving the remaining COT unused.

[0030]

[0044] In NR-U, each UE is served by one serving BS, and COT sharing between the BS and served UEs is supported. For example, the BS may perform CAT4 LBT in the shared channel to compete for the COT. Upon passing the CAT4 LBT, the BS may transmit DL transmissions to the served UE during a portion of the COT. The BS may allow the served UE to utilize the remaining portion of the COT. In some cases, the BS may schedule the served UE to transmit UL transmissions during the remaining portion. The served UE may perform CAT2 LBT or no LBT when the served UE transmits during the BS-initiated COT. CAT2 LBT or non-LBT has less overhead and less uncertainty in accessing the channel. Thus, COT sharing can provide efficient operation. Similarly, the UE may perform CAT4 LBT in the shared channel to compete for the COT. Upon passing the CAT4 LBT, the UE may transmit UL transmissions (e.g., configured authorized or unauthorized transmissions) to the serving BS during a portion of the COT. The UE may share the remaining portion of the UE-initiated COT with the serving BS.

[0031]

[0045] As can be observed, BS-UE COT sharing is based on a transmitting device initiating or contending the COT and a receiving or responding device sharing the COT, but is limited to transmissions addressed to the transmitting device that initiated the COT. Since BS-UE communications are mostly unicast (e.g., transmissions from a single source to a designated receiver), BS-UE COT sharing may work well for communications between BS and served UEs. On the other hand, sidelink communications are frequently groupcast (e.g., transmissions from a single source to a group of receivers). Furthermore, a sidelink UE receiving a groupcast may in turn send another groupcast transmission to multiple sidelink UEs. Thus, COT sharing limited to sharing between an initiating device and a single responding device pair may not be suitable for sidelink use cases that primarily employ sidelink groupcast.

[0032]

[0046] The present application describes a mechanism for COT sharing in sidelink groupcast and / or broadcast communication. For example, an initiating UE (e.g., a first UE) may contend for a COT in a shared channel by performing a CAT4 LBT. Upon passing the CAT4 LBT (indicating that the channel is cleared for transmission), the initiating UE may transmit a first sidelink transmission during a portion of the COT. The first sidelink transmission may be a unicast transmission, a groupcast transmission, or a broadcast transmission. A responding UE (e.g., a second UE) of the first sidelink transmission may share the remaining portion of the COT. In some aspects, if the initiating UE is an intended recipient of the second sidelink transmission, the responding UE may be enabled to utilize the remaining portion of the COT for the second sidelink transmission in a groupcast mode (e.g., connection-based or connectionless) or a broadcast mode. In this regard, the responding UE may determine whether the initiating UE is one of two or more UEs intended to receive the second sidelink transmission. A connection-based groupcast transmission is addressed to a group of UEs known to the responding UE. For example, each UE in a group is assigned a group identifier (ID). The unconnected groupcast transmission is to be received by a group of UEs not known to the responding UE. In some cases, the unconnected groupcast transmission may be targeted to UEs in a zone. Thus, if the second sidelink transmission is in an unconnected groupcast mode, the responding UE may determine whether the initiating UE is the intended recipient based on zone information associated with the initiating UE. The zone information may relate to a geographic location of the initiating UE or a physical distance between the initiating UE and the responding UE. In some cases, the zones may be pre-configured and the initiating UE may include the zone information (e.g., a zone ID identifying a zone associated with the initiating UE) in the SCI in the first sidelink transmission.If the responding UE determines that the initiating UE is one of the two or more UEs intended to receive the second sidelink transmission, the responding UE may transmit the second sidelink transmission to the two or more UEs during the remaining part of the COT (the shared part). However, if the responding UE determines that the initiating UE is not one of the two or more UEs intended to receive the second sidelink transmission, the responding UE may refrain from transmitting the second sidelink transmission during the remaining part of the COT (the shared part).

[0033]

[0047] The first sidelink transmission may include an SCI (e.g., SCI-1 or SCI-2) and sidelink data. In some aspects, the SCI may include an indication of whether the first sidelink transmission is transmitted by a UE that initiated the COT, and the responding UE may determine whether to transmit a second sidelink transmission in the COT based on the SCI. For example, the responding UE may share the COT if the SCI indicates that the first sidelink transmission is from an initiating UE of the COT and may refrain from sharing the COT if the SCI indicates that the first sidelink transmission is not from an initiating UE of the COT. In some aspects, the SCI may include a COT-SI that includes COT sharing information (e.g., a duration of the COT for sharing) and an indication of whether the first sidelink transmission is from a UE that initiated the COT. In some aspects, the first sidelink transmission is a unicast transmission, and the responding UE may transmit ACK / NACK feedback for the first sidelink transmission to the initiating UE during the COT. In some aspects, the first sidelink transmission is a connection-based groupcast transmission, and the responding UE may send ACK / NACK feedback for the first sidelink transmission to the initiating UE during the COT. In some aspects, the first sidelink transmission is a connectionless groupcast transmission, and the responding UE may send NACK-only feedback for the first sidelink transmission to the initiating UE during the COT.

[0034]

[0048] In some aspects, the third UE may receive the second sidelink transmission during the COT. The third UE may transmit ACK / NACK feedback for the second sidelink transmission when the second sidelink transmission is a connection-based groupcast. Alternatively, the third UE may transmit NACK-only feedback for the second sidelink transmission when the second sidelink transmission is a connectionless groupcast. The third UE may determine whether to transmit ACK / NACK feedback or NACK-only feedback during the COT based on whether the third UE detects COT sharing information related to the COT (e.g., transmitted with the first sidelink transmission). In this regard, if the third UE detects the COT sharing information, the third UE may transmit ACK / NACK feedback or NACK-only feedback during the COT. However, if the third UE fails to detect the COT sharing information, the third UE may refrain from transmitting ACK / NACK feedback or NACK-only feedback during the COT.

[0035]

[0049] Aspects of the present disclosure may provide several benefits. For example, allowing responding UEs to share the COT for groupcast sidelink transmissions (which cannot perform LBT or CAT2 LBT before groupcast sidelink transmissions) may improve sidelink operation efficiency. Limiting the sharing of the COT based on whether the initiating UE of the COT is the intended recipient may avoid COT sharing propagation. COT sharing propagation may refer to the initiating UE sharing the COT with the responding UE, which may further share the COT with another UE, which may further share the COT with yet another UE, and so on. Although the present disclosure is described in the context of COT sharing for sidelink groupcast, the present disclosure may also apply to COT sharing for sidelink broadcast.

[0036]

[0050] FIG. 1 illustrates a wireless communication network 100 according to some aspects of the disclosure. The network 100 may be a 5G network. The network 100 includes several base stations (BSs) 105 (individually labeled as 105a, 105b, 105c, 105d, 105e, and 105f) and other network entities. The BSs 105 may be stations that communicate with UEs 115 (individually labeled as 115a, 115b, 115c, 115d, 115e, 115f, 115g, 115h, and 115k), and may also be referred to as evolved Node Bs (eNBs), next generation eNBs (gNBs), access points, and the like. Each BS 105 may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" may refer to this particular geographic coverage area of ​​the BS 105 and / or the BS subsystem serving that coverage area, depending on the context in which the term is used.

[0037]

[0051] The BS 105 may provide communication coverage for a macro cell, or for small cells such as pico cells or femto cells, and / or other types of cells. A macro cell may generally cover a relatively large geographic area (e.g., a few kilometers in radius) and allow unrestricted access by UEs with a service subscription with the network provider. A small cell such as a pico cell will generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with a service subscription with the network provider. Also, a small cell such as a femto cell will generally cover a relatively small geographic area (e.g., a home) and may provide unrestricted access as well as restricted access by UEs with an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in the home, etc.). A BS for a macro cell may be referred to as a macro BS. A BS for a small cell may be referred to as a small cell BS, a pico BS, a femto BS, or a home BS. In the example shown in FIG. 1, BSs 105d and 105e may be regular macro BSs, while BSs 105a-105c may be macro BSs capable of one of three-dimensional (3D) MIMO, full-dimensional (FD) MIMO, or massive MIMO. BSs 105a-105c may utilize their higher-dimensional MIMO capabilities to increase coverage and capacity by leveraging 3D beamforming in both elevation and azimuth beamforming. BS 105f may be a small cell BS, which may be a home node or a portable access point. BS 105 may support one or multiple (e.g., two, three, four, etc.) cells.

[0038]

[0052] Network 100 may support synchronous or asynchronous operation. For synchronous operation, the BSs may have similar frame timing and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing and transmissions from different BSs may not be aligned in time.

[0039]

[0053] The UEs 115 are distributed throughout the wireless network 100, and each UE 115 may be fixed or mobile. The UEs 115 may also be referred to as terminals, mobile stations, subscriber units, stations, etc. The UEs 115 may be cellular phones, personal digital assistants (PDAs), wireless modems, wireless communication devices, handheld devices, tablet computers, laptop computers, cordless phones, wireless local loop (WLL) stations, etc. In one aspect, the UEs 115 may be devices that include a universal integrated circuit card (UICC). In another aspect, the UEs may be devices that do not include a UICC. In some aspects, the UEs 115 that do not include a UICC may also be referred to as IoT devices or Internet of Everything (IoE) devices. The UEs 115a-115d are examples of mobile smartphone type devices that access the network 100. The UEs 115 may also be machines that are specially configured for connected communications, including machine type communications (MTC), enhanced MTC (eMTC), narrowband IoT (NB-IoT), etc. UEs 115e-115h are examples of various machines configured for communication accessing network 100. UEs 115i-115k are examples of vehicles equipped with wireless communication devices configured for communication accessing network 100. UE 115 may be capable of communicating with any type of BS, whether a macro BS, a small cell, etc. In FIG. 1 , the lightning bolts (e.g., communication links) indicate wireless transmissions between UE 115 and a serving BS 105, which is a BS designated to serve UE 115 on the downlink (DL) and / or uplink (UL), desired transmissions between BSs 105, backhaul transmissions between BSs, or sidelink transmissions between UEs 115.

[0040]

[0054] In operation, the BSs 105a-105c may serve the UEs 115a and 115b using 3D beamforming and coordinated spatial techniques such as coordinated multipoint (CoMP) or multi-connectivity. The macro BS 105d may perform backhaul communications with the BSs 105a-105c, as well as the small cell, BS 105f. The macro BS 105d may also transmit multicast services to which the UEs 115c and 115d are subscribed and received by the UEs 115c and 115d. Such multicast services may include mobile television or stream video, or may include other services for providing community information, such as weather emergencies, or alerts such as amber or grey alerts.

[0041]

[0055] The BSs 105 may also communicate with a core network. The core network may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the BSs 105 (which may be an example of a gNB or an access node controller (ANC) for example) may interface with the core network through backhaul links (e.g., NG-C, NG-U, etc.) and may perform radio configuration and scheduling for communications with the UEs 115. In various examples, the BSs 105 may communicate with each other directly or indirectly (e.g., through the core network) via backhaul links (e.g., X1, X2, etc.), which may be wired or wireless communication links.

[0042]

[0056] Network 100 may also support mission-critical communications with ultra-reliable and redundant links for mission-critical devices, such as UE 115e, which may be a drone. The redundant communication links with UE 115e may include links from macro BSs 105d and 105e, as well as links from small cell BS 105f. Other machine-type devices, such as UE 115f (e.g., a thermometer), UE 115g (e.g., a smart meter), and UE 115h (e.g., a wearable device), may communicate directly with BSs, such as small cell BS 105f and macro BS 105e, through network 100, or in a multi-step size configuration by communicating with another user device that relays its information to the network, such as UE 115f communicating temperature measurement information to a smart meter, UE 115g, which then reports the temperature measurement information to the network through small cell BS 105f. The network 100 may also provide additional network efficiency through dynamic low latency TDD / FDD communications, such as V2V, V2X, C-V2X communications between the UE 115i, 115j, or 115k and other UEs 115, and / or vehicle-to-infrastructure (V2I) communications between the UE 115i, 115j, or 115k and the BS 105.

[0043]

[0057] In some implementations, the network 100 utilizes an OFDM-based waveform for communication. An OFDM-based system may partition a system BW into multiple (K) orthogonal subcarriers, also commonly referred to as subcarriers, tones, bins, etc. Each subcarrier may be modulated with data. In some cases, the subcarrier spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may depend on the system BW. The system BW may also be partitioned into subbands. In other cases, the subcarrier spacing and / or the duration of the TTI may be scalable.

[0044]

[0058] In some aspects, the BS 105 can allocate or schedule transmission resources (e.g., in the form of time-frequency resource blocks (RBs)) for downlink (DL) and uplink (UL) transmissions in the network 100. DL refers to the transmission direction from the BS 105 to the UE 115, and UL refers to the transmission direction from the UE 115 to the BS 105. The communication can be in the form of a radio frame. The radio frame can be divided into multiple, e.g., about 10, subframes or slots. Each slot can be further divided into minislots. In the FDD mode, simultaneous UL and DL transmissions can occur in different frequency bands. For example, each subframe includes a UL subframe in the UL frequency band and a DL subframe in the DL frequency band. In the TDD mode, the UL and DL transmissions occur in different time periods using the same frequency band. For example, a subset of subframes (e.g., DL subframes) in a radio frame may be used for DL ​​transmission, and another subset of subframes (e.g., UL subframes) in the radio frame may be used for UL transmission.

[0045]

[0059] The DL and UL subframes may be further divided into several regions. For example, each DL or UL subframe may have predefined regions for transmission of reference signals, control information, and data. The reference signal is a predefined signal that facilitates communication between the BS 105 and the UE 115. For example, the reference signal may have a specific pilot pattern or structure, where the pilot tones may spread across an operable BW or frequency band, each located at a predefined time and a predefined frequency. For example, the BS 105 may transmit a cell-specific reference signal (CRS) and / or a channel state information reference signal (CSI-RS) to enable the UE 115 to estimate the DL channel. Similarly, the UE 115 may transmit a sounding reference signal (SRS) to enable the BS 105 to estimate the UL channel. The control information may include resource allocation and protocol control. The data may include protocol data and / or operational data. In some aspects, the BS 105 and the UE 115 may communicate using independent subframes. An independent subframe may include a portion for DL ​​communication and a portion for UL communication. An independent subframe may be DL-centric or UL-centric. A DL-centric subframe may include a duration for DL ​​communication that is longer than a duration for UL communication. A UL-centric subframe may include a duration for UL communication that is longer than a duration for UL communication.

[0046]

[0060] In some aspects, the network 100 may be an NR network deployed on a licensed spectrum. The BS 105 may transmit synchronization signals (e.g., including a primary synchronization signal (PSS) and a secondary synchronization signal (SSS)) in the network 100 to facilitate synchronization. The BS 105 may broadcast system information related to the network 100 (e.g., including a master information block (MIB), residual system information (RMSI), and other system information (OSI)) to facilitate initial network access. In some instances, the BS 105 may broadcast the PSS, SSS, and / or MIB in the form of a synchronization signal block (SSB) on a physical broadcast channel (PBCH) and may broadcast the RMSI and / or OSI on a physical downlink shared channel (PDSCH).

[0047]

[0061] In some aspects, a UE 115 attempting to access the network 100 may perform an initial cell search by detecting a PSS from the BS 105. The PSS may enable synchronization of time period timing and may indicate a physical layer identification value. The UE 115 may then receive the SSS. The SSS may enable radio frame synchronization and may provide a cell identification value that may be combined with the physical layer identification value to identify the cell. The PSS and SSS may be located in a central portion of the carrier or at any suitable frequency within the carrier.

[0048]

[0062] After receiving the PSS and SSS, the UE 115 may receive the MIB. The MIB may include system information for initial network access and scheduling information for the RMSI and / or OSI. After decoding the MIB, the UE 115 may receive the RMSI and / or OSI. The RMSI and / or OSI may include radio resource control (RRC) information related to a random access channel (RACH) procedure, paging, a control resource set (CORESET) for physical downlink control channel (PDCCH) monitoring, a physical UL control channel (PUCCH), a physical UL shared channel (PUSCH), power control, and an SRS.

[0049]

[0063] After acquiring the MIB, RMSI and / or OSI, the UE 115 may perform a random access procedure to establish a connection with the BS 105. In some examples, the random access procedure may be a four-step random access procedure. For example, the UE 115 may transmit a random access preamble, and the BS 105 may respond with a random access response. The random access response (RAR) may include a detected random access preamble identifier (ID) corresponding to the random access preamble, timing advance (TA) information, a UL grant, a temporary cell radio network temporary identifier (C-RNTI), and / or a backoff indicator. Upon receiving the random access response, the UE 115 may transmit a connection request to the BS 105, and the BS 105 may respond with a connection response. The connection response may indicate contention resolution. In some examples, the random access preamble, the RAR, the connection request, and the connection response may be referred to as message 1 (MSG1), message 2 (MSG2), message 3 (MSG3), and message 4 (MSG4), respectively. In some examples, the random access procedure may be a two-step random access procedure, where the UE 115 may transmit a random access preamble and a connection request in a single transmission, and the BS 105 may respond by transmitting a random access response and a connection response in a single transmission. The combined random access preamble and connection request in the two-step random access procedure may be referred to as Message A (MSG A). The combined random access response and connection response in the two-step random access procedure may be referred to as Message B (MSG B).

[0050]

[0064] After establishing the connection, the UE 115 and the BS 105 may enter a normal operation phase, where operation data may be exchanged. For example, the BS 105 may schedule the UE 115 for UL and / or DL ​​communication. The BS 105 may send a UL and / or DL ​​scheduling grant to the UE 115 via a PDCCH. The BS 105 may send DL communication signals to the UE 115 via a PDSCH in accordance with the DL scheduling grant. The UE 115 may send UL communication signals to the BS 105 via a PUSCH and / or PUCCH in accordance with the UL scheduling grant. The connection may be referred to as an RRC connection. When the UE 115 is actively exchanging data with the BS 105, the UE 115 is in an RRC connected state.

[0051]

[0065] In one example, after establishing a connection with the BS 105, the UE 115 may initiate an initial network attachment procedure with the network 100. The BS 105 may coordinate with various network entities or fifth generation core (5GC) entities, such as an access and mobility function (AMF), a serving gateway (SGW), and / or a packet data network gateway (PGW), to complete the network attachment procedure. For example, the BS 105 may coordinate with network entities in the 5GC to identify the UE, authenticate the UE, and / or authorize the UE to send and / or receive data in the network 100. In addition, the AMF may assign a group of tracking areas (TAs) to the UE. If the network attachment procedure is successful, a context for the UE 115 is established in the AMF. After the connection to the network is successful, the UE 115 may move around the current TA. In the case of a tracking area update (TAU), the BS 105 may request the UE 115 to periodically update the network 100 with the location of the UE 115. Alternatively, the UE 115 may only report its location to the network 100 when it enters a new TA. The TAU allows the network 100 to quickly locate the UE 115 and page the UE 115 upon receiving an incoming data packet or call for the UE 115.

[0052]

[0066] In some aspects, the BS 105 may communicate with the UE 115 using a hybrid automatic repeat request (HARQ) technique to improve communication reliability, e.g., to provide URLLC services. The BS 105 may schedule the UE 115 for PDSCH communication by sending a DL grant in the PDCCH. The BS 105 may transmit DL data packets to the UE 115 according to the schedule in the PDSCH. The DL data packets may be transmitted in the form of transport blocks (TBs). If the UE 115 successfully decodes the DL data packets, the UE 115 may transmit a HARQ positive acknowledgement (ACK) to the BS 105. Conversely, if the UE 115 fails to successfully decode the DL transmission, the UE 115 may transmit a HARQ negative acknowledgement (NACK) to the BS 105. Upon receiving a HARQ NACK from the UE 115, the BS 105 may retransmit the DL data packets to the UE 115. The retransmission may include the same coded version of the DL data as the initial transmission. Alternatively, the retransmission may include a different coded version of the DL data than the initial transmission. The UE 115 may apply soft combining to combine the coded data received from the initial transmission and the retransmission for decoding. The BS 105 and the UE 115 may also apply HARQ for UL communications using a mechanism substantially similar to DL HARQ.

[0053]

[0067] In some aspects, the network 100 may operate on a system BW or a component carrier (CC) BW. The network 100 may partition the system BW into multiple BWPs (e.g., portions). The BS 105 may dynamically assign the UE 115 to operate on a BWP (e.g., a portion of the system BW). The assigned BWP may be referred to as an active BWP. The UE 115 may monitor the active BWP for signaling information from the BS 105. The BS 105 may schedule the UE 115 for UL or DL ​​communication in the active BWP. In some aspects, the BS 105 may assign a pair of BWPs in a CC to the UE 115 for UL and DL communication. For example, the BWP pair may include one BWP for UL communication and one BWP for DL ​​communication.

[0054]

[0068] In some aspects, the network 100 may operate over a shared channel, which may include a shared frequency band or an unlicensed frequency band. For example, the network 100 may be an NR-unlicensed (NR-U) network operating over an unlicensed frequency band. In such aspects, the BS 105 and the UE 115 may be operated by multiple network operating entities. To avoid collisions, the BS 105 and the UE 115 may employ an LBT procedure to monitor transmission opportunities (TXOPs) in the shared channel. The wireless communication devices may perform an LBT in the shared channel. LBT is a channel access method that may be used in an unlicensed spectrum. When the LBT results in an LBT pass (the wireless communication device wins contention for the wireless medium), the wireless communication device may access the shared medium to transmit and / or receive data. For example, a transmitting node (e.g., the BS 105 or the UE 115) may perform an LBT prior to transmitting in the channel. When the LBT passes, the transmitting node may proceed with the transmission. When the LBT fails, the transmitting node may refrain from transmitting in the channel. In one example, LBT may be based on energy detection. For example, LBT results in a pass when the signal energy measured from the channel is below a threshold. Conversely, LBT results in a fail when the signal energy measured from the channel exceeds a threshold. In another example, LBT may be based on signal detection. For example, LBT results in a pass when a channel reservation signal (e.g., a predefined preamble signal) is not detected in the channel. Conversely, LBT results in a fail when a channel reservation signal is detected in the channel. TXOP is sometimes referred to as channel occupation time (COT).

[0055]

[0069] In some aspects, the network 100 may provide sidelink communications to enable a UE 115 to communicate with another UE 115 without tunneling through the BS 105 and / or core network, as shown in FIG. 2. As described above, sidelink communications may be communicated via a PSCCH and a PSSCH. For example, a PSCCH may carry an SCI, and a PSSCH may carry an SCI and / or sidelink data (e.g., user data). Each PSCCH is associated with a corresponding PSSCH, where an SCI in a PSCCH may carry reservation and / or scheduling information for sidelink data transmission in the associated PSSCH. In some examples, a transmitting sidelink UE 115 may indicate an SCI in two stages. In a first stage SCI (sometimes referred to as SCI-1), the UE 115 may transmit an SCI in a PSCCH that carries information for resource allocation and decodes a second stage SCI. The first tier SCI may include at least one of a priority, a PSSCH resource allocation, a resource reservation period (if enabled), a PSSCH DMRS pattern (if more than one pattern is configured), a second tier SCI format (e.g., a size of the second tier SCI), an amount of resources for the second tier SCI, a number of PSSCH demodulation reference signal (DMRS) ports, a modulation and coding scheme (MCS), etc. In the second tier SCI (which may be referred to as SCI-2), the UE 115 may transmit an SCI in the PSSCH carrying information for decoding the PSSCH. The second tier SCI may include an 8-bit L1 destination identifier (ID), an 8-bit L1 source ID, a HARQ process ID, a new data indicator (NDI), a redundancy version (RV), etc. It should be understood that these are examples and that the first tier SCI and / or the second tier SCI may include or indicate additional or different information other than those examples provided. Sidelink communications may also be communicated via a physical sidelink feedback control channel (PSFCH) that indicates an acknowledgment (ACK)-negative acknowledgment (NACK) to a previously transmitted PSSCH.

[0056]

[0070] In some aspects, the BS 105 may configure the UE 115 to operate as a sidelink synchronized or anchor UE 115 to provide sidelink system information to other sidelink UEs 115 that may be outside the coverage of the BS 105 to communicate sidelink communications. The sidelink synchronized UE 115 may transmit sidelink system information in the form of an S-SSB. The S-SSB may include synchronization signals (e.g., PSS and / or SSS) and sidelink system information such as a sidelink BWP configuration, one or more sidelink transmission resource pools, and / or one or more sidelink receiving resource pools, S-SSB transmission related parameters (e.g., sidelink slots configured for S-SSB transmissions and / or S-SSB transmission periodicity), and / or any other configuration information related to sidelink communications. In some aspects, the BS 105 may configure the sidelink synchronized UE 115 to transmit the S-SSB according to a synchronization raster defined for NR-U. In some instances, the S-SSB according to the NR-U synchronization raster may be offset from the lowest frequency of the corresponding sidelink BWP in which the S-SSB is transmitted. In some other aspects, the BS 105 may transmit the S-SSB according to a synchronization raster defined for the sidelink. The sidelink synchronization raster may be defined such that the S-SSB is aligned to the lowest frequency of the corresponding sidelink BWP in which the S-SSB is transmitted.

[0057]

[0071] In some aspects, the sidelink communication may be in a unicast mode, a groupcast mode, or a broadcast mode, where HARQ may be applied to the unicast and / or groupcast communication. For unicast communication, the sidelink sender UE 115 may transmit a sidelink transmission including data to a single sidelink receiver UE 115 and may request HARQ Acknowledgement / Negative Acknowledgement (ACK / NACK) feedback from the sidelink receiver UE 115. If the sidelink receiver UE 115 successfully decodes the data from the sidelink transmission, the sidelink receiver UE 115 transmits an ACK. Conversely, if the sidelink receiver UE 115 fails to decode the data from the sidelink transmission, the sidelink receiver UE 115 transmits a NACK. Upon receiving a NACK, the sidelink sender UE 115 may retransmit the data. In the case of broadcast communication, the sidelink sender UE 115 may send a sidelink transmission to a group (e.g., 2, 3, 4, 5, 6, or more) of sidelink receiver UEs 115 that are in the vicinity of the sidelink sender UE 115 and may not request ACK / NACK feedback for the sidelink transmission.

[0058]

[0072] In the case of groupcast communication, a sidelink sender UE 115 may send a sidelink transmission to a group (e.g., 2, 3, 4, 5, 6, or more) of sidelink receiver UEs 115. Groupcast communication may have a wide variety of use cases in the sidelink. As an example, groupcast communication may be used in a V2X use case (e.g., vehicle platooning) to command a group of vehicles near an intersection or traffic light to stop at the intersection. In some aspects, groupcast communication may be connection-based, where a group of sidelink receiver UEs 115 may be pre-configured as a group identified by a group identifier (ID). Thus, the sidelink receiver UEs 115 in a group are known to the sidelink sender UE 115, and thus the sidelink sender UE 115 may request ACK / NACK feedback from each sidelink receiver UE 115 in the group. In some cases, the sidelink sender UE 115 may provide each sidelink receiver UE with different resources (e.g., orthogonal resources) for transmitting ACK / NACK feedback. In some other aspects, the groupcast communication may be connectionless, where a group of sidelink receiver UEs 115 that can receive a groupcast transmission may not be known to the sidelink sender UE 115. In some cases, a group of sidelink receiver UEs 115 may receive the groupcast communication based on a zone or geographic location of the receiver UE 115. Since the sidelink sender UE 115 may not have knowledge of the receiving sidelink UEs 115, the sidelink sender UE 115 may request feedback of only a NACK from the sidelink receiver UE 115. For example, if the sidelink receiver UE 115 detects the presence of an SCI but fails to decode data (transport block) from the sidelink transmission, the sidelink receiver UE 115 may transmit a NACK. The sidelink receiver UE 115 may not transmit an ACK if data decoding is successful.In some cases, the sidelink receiving UEs 115 may be assigned the same resources for transmitting NACK feedback. Simultaneous NACK transmissions from multiple sidelink receiving UEs 115 on the same resources may form a Single Frequency Network (SFN) transmission (where the waveforms of multiple NACK transmissions are combined) at the sidelink transmitting UE 115. Similar to unicast communication, the sidelink transmitting UE 115 may retransmit sidelink data upon receiving a NACK for a connection-based or connectionless groupcast transmission.

[0059]

[0073] According to aspects of the disclosure, an initiating UE 115 (e.g., a first UE) may contend for the COT in a shared channel by performing a CAT4 LBT. Upon passing the CAT4 LBT (indicating that the channel is cleared for transmission), the initiating UE 115 may transmit a first sidelink transmission during a portion of the COT. The first sidelink transmission may be a unicast transmission, a groupcast transmission, or a broadcast transmission. A responding UE 115 (e.g., a second UE) of the first sidelink transmission may share the remaining portion of the COT. In some aspects, if the initiating UE 115 is an intended recipient of the second sidelink transmission, the responding UE 115 may be enabled to utilize the remaining portion of the COT for the second sidelink transmission in a groupcast mode (e.g., connection-based or connectionless) or a broadcast mode. In this regard, the responding UE 115 may determine whether the initiating UE 115 is one of two or more UEs 115 intended to receive the second sidelink transmission. If the second sidelink transmission is in unconnected groupcast mode, the responding UE 115 may determine whether the initiating UE 115 is an intended recipient based on zone information associated with the initiating UE 115. The zone information may relate to a geographic location of the initiating UE 115 or a physical distance between the initiating UE 115 and the responding UE 115. In some cases, the zones may be preconfigured and the initiating UE 115 may include the zone information (e.g., a zone ID identifying a zone associated with the initiating UE 115) in the SCI in the first sidelink transmission. In some cases, the zone information is part of the second stage SCI of the first sidelink transmission. If the responding UE 115 determines that the initiating UE 115 is one of the two or more UEs 115 intended to receive the second sidelink transmission, the responding UE 115 may transmit the second sidelink transmission to the two or more UEs during the remaining part (shared part) of the COT.However, if the responding UE 115 determines that the initiating UE 115 is not one of the two or more UEs 115 intended to receive the second sidelink transmission, the responding UE 115 may refrain from transmitting the second sidelink transmission during the remaining portion (shared portion) of the COT.

[0060]

[0074] The first sidelink transmission may include an SCI (e.g., SCI-1 or SCI-2) and sidelink data. In some aspects, the SCI may include an indication of whether the first sidelink transmission is from the UE 115 that initiated the COT, and the responding UE 115 may determine to transmit the second sidelink transmission in the COT based on the SCI indicating that the first sidelink transmission is transmitted by the initiating UE of the COT. In some aspects, the SCI may include a COT-SI including COT sharing information (e.g., a duration of the COT for sharing) and an indication of whether the first sidelink transmission is from the UE 115 that initiated the COT. In some aspects, the first sidelink transmission is a unicast transmission, and the responding UE 115 may transmit an ACK / NACK feedback to the initiating UE 115 during the COT. In some aspects, the first sidelink transmission is a connection-based groupcast transmission, and the responding UE 115 may transmit an ACK / NACK feedback to the initiating UE 115 during the COT. In some aspects, the first sidelink transmission may be a connectionless groupcast transmission, and the responding UE 115 may send a NACK-only feedback to the initiating UE 115 during the COT.

[0061]

[0075] In some aspects, the recipient UE 115 (e.g., the third UE) of the second sidelink transmission may also transmit ACK / NACK feedback for the second sidelink transmission (e.g., when the second sidelink transmission is a connection-based groupcast) or NACK-only feedback for the second sidelink transmission (e.g., when the second sidelink transmission is a connectionless groupcast). The third UE may determine whether to transmit ACK / NACK feedback or NACK-only feedback during the COT based on whether the third UE detects the COT shared information of the first sidelink transmission. In this regard, if the third UE detects the COT shared information of the first sidelink transmission, the third UE may transmit ACK / NACK feedback or NACK-only feedback during the COT. However, if the third UE fails to detect the COT shared information of the first sidelink transmission, the third UE may refrain from transmitting ACK / NACK feedback or NACK-only feedback during the COT. Mechanisms for COT sharing for sidelink communications (e.g., in groupcast or broadcast modes) are described in more detail herein.

[0062]

[0076] FIG. 2 is a timing diagram illustrating a radio frame structure 200 according to some aspects of the disclosure. The radio frame structure 200 may be employed by a BS, such as the BS 105, and a UE, such as the UE 115, in a network, such as the network 100, for communication. In particular, the BS may communicate with the UE using time-frequency resources configured as shown in the radio frame structure 200. In FIG. 2, the x-axis represents time in some arbitrary units and the y-axis represents frequency in some arbitrary units. The radio frame structure 200 includes a radio frame 201. The duration of the radio frame 201 may vary depending on the aspect. In one example, the radio frame 201 may have a duration of about 10 milliseconds. The radio frame 201 includes M slots 202, where M may be any suitable positive integer. In one example, M may be about 10.

[0063]

[0077] Each slot 202 includes a number of subcarriers 204 in frequency and a number of symbols 206 in time. The number of subcarriers 204 and / or the number of symbols 206 in a slot 202 may vary depending on the aspect, for example, based on the channel bandwidth, subcarrier spacing (SCS), and / or CP mode. One subcarrier 204 in frequency and one symbol 206 in time form one resource element (RE) 212 for transmission. A resource block (RB) 210 is formed from several consecutive subcarriers 204 in frequency and several consecutive symbols 206 in time.

[0064]

[0078] In some aspects, a BS (e.g., BS 105 of FIG. 1) may schedule a UE (e.g., UE 115 of FIG. 1) for UL and / or DL ​​communication with a time granularity of a slot 202 or minislot 208. Each slot 202 may be time partitioned into K minislots 208. Each minislot 208 may include one or more symbols 206. The minislots 208 in a slot 202 may have a variable length. For example, when a slot 202 includes N symbols 206, a minislot 208 may have a length between one symbol 206 and (N-1) symbols 206. In some aspects, a minislot 208 may have a length of about two symbols 206, about four symbols 206, or about seven symbols 206. In some examples, the BS may schedule a UE with a frequency granularity of a resource block (RB) 210 (e.g., including about 12 subcarriers 204 in 1 symbol, 2 symbols, ..., 14 symbols). In some aspects, a UE (e.g., UE 115i of FIG. 1) may communicate a sidelink with another UE (e.g., UE 115j of FIG. 1) in units of time slots similar to slot 202, as further described below with respect to FIG.

[0065]

[0079] FIG. 3 illustrates an example of a wireless communication network 300 providing sidelink communication according to aspects of the disclosure. The network 300 may correspond to a portion of the network 100 and may utilize the radio frame structure 200 for communication. Although FIG. 3 illustrates one BS 305 and five UEs 315 (shown as 315a, 315b, 315c, 315d, and 315e) for ease of explanation, it will be appreciated that aspects of the disclosure may scale to any suitable number of UEs 315 (e.g., about 2, 3, 4, 6, 7, or more) and / or BSs 305 (e.g., about 2, 3, or more). The BSs 305 and UEs 315 may be similar to the BSs 105 and UEs 115, respectively. The BSs 305 and UEs 315 may share the same radio frequency band for communication. In some instances, the radio frequency band may be a licensed band. In some instances, the radio frequency band may be an unlicensed band. In some cases, the radio frequency band may be the Frequency Range 1 (FR1) band. In some cases, the radio frequency band may be the FR2 band. In general, the radio frequency band may be any suitable frequency.

[0066]

[0080] In the network 300, some of the UEs 315 may communicate with each other in peer-to-peer communication. For example, the UE 315a may communicate with the UE 315b via the sidelink 351, the UE 315c may communicate with the UE 315d via the sidelink 352 and / or with the UE 315e via the sidelink 354, and the UE 315d may communicate with the UE 315e via the sidelink 355. The sidelinks 351, 352, 354, and 355 are unicast bidirectional links. In some aspects, the UE 315c may also communicate with the UE 315d and the UE 315e in a groupcast mode. Similarly, the UE 315d may also communicate with the UE 315c and the UE 315e in a groupcast mode. In general, the UEs 315c, 315d, 315e may communicate with each other in a unicast mode or a groupcast mode.

[0067]

[0081] Some of the UEs 315 may also communicate with the BS 305 in the UL and / or DL ​​directions via the communication links 353. For example, the UEs 315a, 315b, and 315c may be within the coverage area 310 of the BS 305 and thus in communication with the BS 305. The UEs 315d and 315e may be outside the coverage area 310 and thus not in direct communication with the BS 305. In some instances, the UE 315c may act as a relay for the UE 315d to reach the BS 305. In some aspects, some of the UEs 315 (e.g., similar to the UEs 115i-k) are associated with vehicles, and the communication via the sidelinks 351 and / or 352 may be C-V2X communication. C-V2X communication may refer to communication between a vehicle and any other wireless communication device in a cellular network.

[0068]

[0082] In some aspects, the BS 305 may configure the sidelink UE 315 to operate as a sidelink anchor UE (e.g., UE 315c). When operating as a sidelink synchronized UE, the UE 315 may broadcast an S-SSB, which may include synchronization signals (e.g., PSS and / or SSS) and sidelink system information such as a sidelink BWP configuration, one or more sidelink transmit resource pools and / or one or more sidelink receive resource pools, S-SSB transmission related parameters (e.g., sidelink slots configured for S-SSB transmissions and / or S-SSB transmission periodicity), and / or any other configuration information related to sidelink communications. Thus, other UEs (e.g., UEs 315d and 315e) that are in the vicinity of the UE 315c but may be outside the coverage of the BS 305 may listen to the S-SSB, synchronize to it, and communicate with each other based on the S-SSB. The other UEs 315d and 315e that receive sidelink system information from the UE 315c may be referred to as client UEs.

[0069]

[0083] FIG. 4 illustrates a sidelink communication scheme 400 according to some aspects of the disclosure. The scheme 400 may be employed by UEs, such as UEs 115 and 315, in a network, such as network 100 and / or 300, for sidelink communications. As shown in FIG. 4, a first UE 402a may communicate with a second UE 402b (and one or more other UEs 402) via one or more sidelink channels 410. The UEs 402 and 402b may communicate using the one or more sidelink channels 410 for P2P communications, D2D communications, V2X communications (which may include, for example, V2V communications, V2I communications, V2P communications, etc.), mesh networking, etc. In some aspects, the UEs 402 (e.g., UEs 402a and / or UEs 402b) may correspond to one or more other UEs described elsewhere herein, such as UEs 115 and / or 315. In some aspects, the sidelink channel(s) 410 may use a PC5 interface and / or may operate in a high frequency band (e.g., around 4 GHz, 5 GHz, 6 GHz, or mm-wave band). Additionally or alternatively, the UE 402 may synchronize the timing of a transmission time interval (TTI) (e.g., frame, subframe, slot, symbol, etc.) using Global Navigation Satellite System (GNSS) timing.

[0070]

[0084] As further shown in FIG. 4, the one or more sidelink channels 410 may include a PSCCH 415, a PSSCH 420, and / or a PSFCH 425. The PSCCH 415 may be used to communicate control information, similar to a PDCCH and / or a PUCCH used for cellular communications with the base station 110 over an access link or access channel. The PSSCH 420 may be used to communicate data, similar to a PDSCH and / or a PUSCH used for cellular communications with the base station 110 over an access link or access channel. In some aspects, the PSCCH 415 may carry a SCI 430, which may indicate various control information used for sidelink communications, such as one or more resources (e.g., time resources, frequency resources, spatial resources, etc.) for which a transport block (TB) 435 may be carried on the PSSCH 420. The TB 435 may include data. The PSFCH 425 may be used to communicate sidelink feedback 440, such as HARQ feedback (e.g., ACK / NACK information), transmit power control (TPC), scheduling requests (SR), etc. In some aspects, the SCI 430 in the PSCCH 415 may include the first tier SCI (e.g., resource information), and the PSSCH 420 may carry the second tier SCI (e.g., transmission parameters such as MCS used to transmit the data 435).

[0071]

[0085] In some aspects, one or more sidelink channels 410 may use resources from a sidelink resource pool. A sidelink resource pool may refer to a set of time resources (including some symbols like symbols 206 or some slots like slots 202) and frequency resources (including some subcarriers like subcarriers 204 or some RBs like RBs 210) that may be used for sidelink transmissions. In some aspects, a scheduling assignment (e.g., included in SCI 430) may be transmitted in a subchannel using a specific RB over time. In some aspects, a data transmission (e.g., on PSSCH 420) associated with a scheduling assignment may occupy adjacent RBs in the same subframe as the scheduling assignment (e.g., using frequency division multiplexing). In some aspects, a scheduling assignment and an associated data transmission are not transmitted on adjacent RBs.

[0072]

[0086] In some aspects, the UE 402 may operate using a transmission mode in which resource selection and / or scheduling is performed by the UE 402 (e.g., rather than by the base station 105 or 305). In some aspects, the UE 402 may perform resource selection and / or scheduling by sensing channel availability for transmission. In some aspects, the UE 402 may measure Received Signal Strength Indicator (RSSI) parameters (e.g., Sidelink RSSI (S-RSSI) parameters) associated with various sidelink channels, measure Reference Signal Received Power (RSRP) parameters (e.g., PSSCH-RSRP parameters) associated with various sidelink channels, measure Reference Signal Received Quality (RSRQ) parameters (e.g., PSSCH-RSRQ parameters) associated with various sidelink channels, etc., and select a channel for transmission of a sidelink communication based at least in part on the measurement(s).

[0073]

[0087] Additionally or alternatively, the UE 402 may perform resource selection and / or scheduling using the SCI 430 received in the PSCCH 415, which may indicate occupied resources, channel parameters, etc. Additionally or alternatively, the UE 402 may perform resource selection and / or scheduling by determining a Channel Busy Rate (CBR) associated with various sidelink channels, which may be used for rate control (e.g., by indicating a maximum number of resource blocks that the UE 402 may use for a particular set of subframes).

[0074]

[0088] In a transmission mode in which resource selection and / or scheduling is performed by the UE 402, the UE 402 may generate sidelink grants and transmit those grants in the SCI 430. The sidelink grant may indicate, in some aspects, one or more parameters (e.g., transmission parameters) to be used for the next sidelink transmission, such as one or more resource blocks to be used for the next sidelink transmission on the PSSCH 420 (e.g., for the TB 435), one or more subframes to be used for the next sidelink transmission, a modulation and coding scheme (MCS) to be used for the next sidelink transmission, etc. In some aspects, the UE 402 may generate a sidelink grant indicating one or more parameters for semi-persistent scheduling (SPS), such as a periodicity of the sidelink transmissions. Additionally or alternatively, the UE 402 may generate a sidelink grant for event-driven scheduling, such as for on-demand sidelink messages.

[0075]

[0089] The PSFCH resource may be from a sidelink resource pool. There may be a period for PSFCH transmission in the resource pool. In some aspects, the sidelink resource pool may include multiple slots, and the PSFCH resource may be allocated every one, two, or four slots. In some aspects, in a slot that includes the PSFCH, the PSFCH resource may be located after the PSSCH and a minimum time gap for the PSFCH (e.g., about one symbol).

[0076]

[0090] As noted above, Figure 4 is provided as one aspect. Other aspects may differ from those described with respect to Figure 4. It should be understood that while Figure 4 is illustrated for P2P or unicast sidelink communication, in other examples, a similar mechanism may be used for sidelink groupcast where data 435 may be destined for multiple sidelink UEs similar to UE 402b.

[0077]

[0091] 5A and 5B are described in conjunction with each other to illustrate COT sharing for sidelink groupcast. FIG. 5A is a sequence diagram illustrating a sidelink COT sharing method 500 according to some aspects of the present disclosure. The method 500 may be implemented among UEs 502a, 502b, 502c, and 502d operating over a shared radio frequency band (e.g., in a shared spectrum or an unlicensed spectrum). The UEs 502a-d may be similar to the UEs 115, 315, and / or 402. FIG. 5B is a timing diagram 520 illustrating the sidelink COT sharing method 500 according to some aspects of the present disclosure. In FIG. 5B, the x-axis represents time in some arbitrary units.

[0078]

[0092] At action 510, the UE 502a (e.g., an initiating UE) initiates a COT (shown as 524 in FIG. 5B) in the shared radio frequency band by performing a CAT4 LBT (shown as 522 in FIG. 5B) in the shared channel. For example, the CAT4 LBT 522 is successful (indicating the channel is clear for transmission), as indicated by the check mark.

[0079]

[0093] At action 512, upon passing the CAT4 LBT, the UE 502a transmits a sidelink transmission A (shown as 530 in FIG. 5B) during the portion 506 of the COT 524. The sidelink transmission A may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG. 4. The sidelink transmission A is a groupcast transmission with UEs 502b and 502c as intended recipients, as shown, for example, by the two arrows grouped by the dotted oval. UEs 502b and 502c (e.g., responding UEs) may receive the sidelink transmission A.

[0080]

[0094] In some aspects, sidelink transmission A may be a connection-based groupcast transmission and the SCI may include a group identifier (ID) that identifies a group to which UE 502b and UE 502c belong. Thus, UE 502b and UE 502c may receive sidelink transmission A based on the SCI indicating the group ID. In some aspects, sidelink transmission A may be a non-connection groupcast transmission and UEs may be targeted to UEs in a certain zone instead of based on the group ID. For example, UE 502b and UE 502c may be in a certain zone (geographical area or physical distance range from UE 502a) and therefore may receive sidelink transmission A. In some instances, the zones may be pre-configured and UE 502b and UE 502c may receive zone information (e.g., a zone ID that identifies a zone associated with UE 502a) in the SCI within sidelink transmission A. In some aspects, sidelink transmission A may be a broadcast transmission, and any UE, including UE 502b and UE 502c in the vicinity of UE 502a, may receive sidelink transmission A.

[0081]

[0095] Sidelink transmission A may include COT sharing information. As shown in FIG. 5B, sidelink transmission A includes an indicator 532. The indicator 532 may indicate whether sidelink transmission A 530 is transmitted by an initiating node (of COT 524) or a responding node. In some aspects, the indicator 532 may have a length of 1 bit, where a bit value of 1 may indicate an initiating node and a bit value of 0 may indicate a responding node, or vice versa. In some aspects, the indicator 532 may be a part of the first stage SCI or a part of the second stage SCI. In some aspects, the indicator 532 may be a part of the COT-SI. For example, the COT-SI may include a bitmap and the indicator 532 may correspond to a bit in the bitmap. In some instances, the COT-SI may indicate other information related to the COT 524 (e.g., the duration of the COT 524 for sharing portion 508, etc., shown in FIG. 5B).

[0082]

[0096] In some aspects, the responding UE may be enabled to transmit a groupcast transmission in the shared portion of the COT if the UE that initiated the COT is the intended recipient of the groupcast transmission. For example, after UE 502b receives sidelink transmission A, UE 502b may want to transmit sidelink transmission B in groupcast mode. Thus, UE 502b may determine whether initiating UE 502a is the intended recipient of sidelink transmission B. At action 514, UE 502b transmits sidelink transmission B (depicted as 540 in FIG. 5B ) in groupcast mode (as shown by the two arrows grouped by the dotted arrow) to UE 502a and UE 502c during the shared portion 508 of the COT 524 based on initiating UE 502a being the intended recipient of sidelink transmission B 540. Sidelink transmission B 540 may include an SCI (e.g., SCI 430) and data (e.g., data 435) as described above with respect to FIG. 4. In some aspects, the shared portion 508 may be spaced apart from the portion 506 (the unshared portion) or may begin at a certain symbol within the COT 524 .

[0083]

[0097] In some aspects, the UE 502b may perform a CAT2 LBT before transmitting a sidelink transmission B in the shared COT 524. In some aspects, the UE 502b may transmit a sidelink transmission B in the shared COT 524 without performing an LBT before the transmission. Thus, COT sharing can reduce LBT overhead and / or channel access uncertainty and thus provide efficient sidelink communications. In some aspects, the UE 502b may determine whether to not perform an LBT or to perform a CAT2 LBT before transmitting a sidelink transmission B in the shared COT 524 based on a gap duration between the sidelink transmission B and a previous transmission in the COT. For example, the UE 502b may transmit a sidelink transmission B without performing an LBT when the gap is short (e.g., shorter than a duration threshold).

[0084]

[0098] In some aspects, the UE 502b may also wish to transmit a sidelink transmission C in unicast mode to the UE 502d. The UE 502b may determine that the initiating UE 502a is not the intended recipient of the sidelink transmission C and therefore may not transmit the sidelink transmission C during the shared portion 508 of the COT 524. At action 516, the UE 502b refrains from transmitting the sidelink transmission C to the UE 502d during the COT 524, as shown by the arrow with the symbol "X" in FIG. 5A and the dotted box C with the symbol "X" in FIG. 5B. To transmit the sidelink transmission C, the UE 502b may perform a CAT4 LBT 552 in the shared channel to contend for the COT 554, as shown in FIG. 5B, and transmit the sidelink transmission C 560 upon passing the CAT4 LBT 552 (with a check mark). The sidelink transmission C560 may include an SCI (e.g., SCI430) and data (e.g., data 435), as described above with respect to FIG.

[0085]

[0099] FIG. 6A and FIG. 6B are described in conjunction with each other to illustrate COT sharing for sidelink groupcast. FIG. 6A is a sequence diagram illustrating a sidelink COT sharing method 600 according to some aspects of the present disclosure. The method 600 may be implemented among UEs 502a, 502b, 502c, and 502d operating over a shared radio frequency band (e.g., in a shared spectrum or an unlicensed spectrum). The UEs 502a-d may be similar to the UEs 115 and / or 315. FIG. 6B is a timing diagram 620 illustrating the sidelink COT sharing method 600 according to some aspects of the present disclosure. In FIG. 6B, the x-axis represents time in some arbitrary units. The method 600 is substantially similar to the method 500 described above with respect to FIG. 5A and FIG. 5B. However, in the method 600, the responding UE 502c of the sidelink transmission B may wish to transmit a sidelink transmission D in groupcast mode after receiving the sidelink transmission B.

[0086]

[0100] As described above, at action 514, the UE 502b transmits the sidelink transmission B 540 during the shared portion 508 of the COT 524 based on the initiating UE 502a of the COT 524 being the intended recipient of the sidelink transmission B 540.

[0087]

[0101] In some aspects, a UE receiving a sidelink transmission in a COT may transmit in the shared portion of the COT if the sidelink transmission is transmitted by a UE that initiated the COT. For example, after receiving sidelink transmission B from UE 502b, UE 502b may want to transmit sidelink transmission D in groupcast mode and may determine whether sidelink transmission D may be transmitted during the COT 524. UE 502b may determine whether UE 502b is the initiator UE of the COT 524.

[0088]

[0102] To assist the responding UEs of sidelink transmission B 540 in determining whether COT 524 may be shared, UE 502b may include an indicator 642 in sidelink transmission B 540, as shown in FIG. 6B. Indicator 642 may be substantially similar to indicator 532, but may indicate that sidelink transmission B 540 is transmitted by a responding UE of COT 524. Thus, UE 502c receiving sidelink transmission B may decode indicator 642 and recognize that sidelink transmission B was received from a responding UE (e.g., UE 502b) of COT 524, rather than an initiating UE of COT 524. Thus, UE 502c may determine that it may not share COT 524 to transmit sidelink transmission D.

[0089]

[0103] Upon determining at action 616 that the COT 524 is not for sharing by the UE 502c, the UE 502c refrains from transmitting a sidelink transmission D during the COT 524, as illustrated by the arrow with the symbol "X" in FIG. 6A and the dotted box D with the symbol "X" in FIG. 6B. To transmit the sidelink transmission D, the UE 502c may perform a CAT4 LBT 652 in the shared channel to contend for the COT 654, as illustrated in FIG. 6B, and upon passing the CAT4 LBT 652 (with a check mark), transmit a sidelink transmission D 660. The sidelink transmission D 660 may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG. 4.

[0090]

[0104] As can be observed, regardless of whether sidelink transmission D660 is intended to be received by UE 502b that transmitted sidelink transmission B540, UE 502c may not transmit sidelink transmission D660 during COT524 since UE 502b is not the initiating UE of COT524.

[0091]

[0105] Additionally, not allowing UE 502c to share the COT 524 based on UE 502 receiving sidelink transmission B during COT 524 from a responding node of COT 524 may avoid COT sharing from propagating from UE 502b to UE 502c (based on sidelink transmission B 540), from UE 502c to UE 502d (based on sidelink transmission D 660), etc. Preventing COT sharing to propagate may enable more fair channel access among different wireless communication devices of the same RAT or different RATs sharing the same channel, instead of starving other wireless communication devices of channel access opportunities.

[0092]

[0106] FIG. 7 is a flow diagram of a sidelink COT sharing method 700 according to some aspects of the disclosure. Aspects of the method 700 may be performed by a computing device (e.g., a processor, a processing circuit, and / or other suitable components) of a wireless communication device or other suitable means for performing the steps. For example, a wireless communication device such as a UE 115, 315, 402, or 502 may utilize one or more components, such as a processor 1102, a memory 1104, a sidelink COT sharing module 1108, a transceiver 1110, a modem 1112, and one or more antennas 1116, to perform the steps of the method 700. The method 700 may employ mechanisms similar to those described above in FIGS. 1-4, 5A-5B, and 6A-6B. As illustrated, the method 700 includes several enumerated steps, but aspects of the method 700 may include additional steps before, after, and between the enumerated steps. In some aspects, one or more of the recited steps may be omitted or performed in a different order.

[0093]

[0107] At block 710, a first UE (e.g., UE 115, 315, 502, or 1100) receives a first sidelink transmission in a shared channel during a COT (e.g., COT 524) from a second UE. The first sidelink transmission may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG.

[0094]

[0108] In block 720, the first UE may determine whether the COT is for sharing. For example, the first sidelink transmission may include COT sharing information similar to indicators 532 and / or 642. In some aspects, the COT sharing information may indicate whether COT sharing in the first COT is enabled. In some aspects, the COT sharing information may indicate whether the first sidelink transmission is transmitted by an initiating UE of the COT. If the COT sharing information indicates that the first sidelink transmission is transmitted by an initiating UE of the COT, the COT is for sharing by a responding UE of the first sidelink transmission. However, if the COT sharing information indicates that the first sidelink transmission is transmitted by a responding UE of the COT, the COT is not for sharing by a responding UE of the first sidelink transmission. Thus, the first UE may determine whether the COT is for sharing based on the COT sharing information. If the first UE determines that the COT is for sharing, the first UE proceeds to block 730.

[0095]

[0109] In block 730, the first UE determines whether the second UE is one of two or more UEs (e.g., a group of UEs) intended to receive the second sidelink transmission. In some aspects, the first UE may determine to transmit the second sidelink transmission in a connection-based groupcast mode to a particular group of receiving UEs (e.g., about 2, 3, 4, 5, 6, or more) and thus determine whether the second UE is in the particular group. In some aspects, the first UE may determine to transmit the second sidelink transmission in a connectionless groupcast mode and may determine whether the second UE is an intended recipient based on a zone associated with the second UE. The zone may be based on a geographic location of the second UE or a physical distance between the first UE and the second UE. In some instances, the zone may be pre-configured and the second UE may include the zone information (e.g., a zone ID identifying a zone associated with the second UE) in the SCI in the first sidelink transmission. If the first UE determines that the second UE is one of two or more UEs intended to receive the second sidelink transmission, the first UE proceeds to block 740.

[0096]

[0110] At block 740, the first UE transmits a second sidelink transmission to the two or more UEs during the shared portion (e.g., portion 508) of the COT based on the COT sharing. The COT sharing may be responsive to the second UE determining that it is one of the two or more UEs intended to receive the second sidelink transmission. The first UE may identify the shared portion (e.g., duration) from the COT sharing information carried in the first sidelink transmission. The second sidelink transmission may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG. 4.

[0097]

[0111] Returning to block 720, if the first UE determines that the COT is not for sharing, the first UE proceeds to block 750. In block 750, the first UE refrains from transmitting a second sidelink transmission during the shared portion of the COT. For example, the first UE may instead begin the second COT by performing a CAT4 LBT in the shared channel and transmit the second sidelink transmission during the second COT upon passing the CAT4 LBT.

[0098]

[0112] Returning to block 730, if the first UE determines that the second UE is not one of two or more UEs intended to receive the second sidelink transmission, the first UE proceeds to block 750.

[0099]

[0113] 8A and 8B are described in conjunction with each other to illustrate COT sharing for sidelink groupcast. FIG. 8A is a sequence diagram illustrating a sidelink COT sharing method 800 according to some aspects of the present disclosure. The method 800 may be implemented among UEs 502a, 502b, 502c, and 502d operating over a shared radio frequency band (e.g., in a shared spectrum or an unlicensed spectrum). The UEs 502a-d may be similar to the UEs 115 and / or 315. FIG. 8B is a timing diagram 840 illustrating the sidelink COT sharing method 800 according to some aspects of the present disclosure. In FIG. 8B, the x-axis represents time in some arbitrary units.

[0100]

[0114] Method 800 is substantially similar to methods 500, 600, and 700 and may employ mechanisms as in methods 600 and 700 described above with reference to Figures 5A-5B, 6A-6B, and 7, respectively. Method 800 further illustrates how a responding UE of a sidelink transmission may transmit ACK / NACK feedback (e.g., feedback 440 in the PSFCH 425) with COT sharing. As described above, a sidelink transmitting UE may request ACK / NACK feedback for unicast sidelink transmissions or connection-based sidelink transmissions from an intended receiving UE or a responding UE. A sidelink transmitting UE may also request NACK-only feedback for non-connection groupcast transmissions from an intended receiving UE or a responding UE. In method 800, a responding UE receiving a sidelink transmission in the COT may transmit ACK / NACK feedback in the shared portion of the COT if the responding UE can detect COT sharing information from an initiating UE of the COT, regardless of whether the sidelink transmission is transmitted by the initiating UE of the COT. In other words, the COT sharing for the PSFCH transmission is independent of the COT sharing for the PSSCH transmission. It should be understood that although method 800 is described in the context of ACK / NACK transmission with COT sharing in a groupcast transmission scenario, in other examples, a similar mechanism may be applied to ACK / NACK transmission in a unicast transmission scenario.

[0101]

[0115] As shown, at action 810, UE 502a (e.g., an initiating UE) initiates a COT (shown as 844 in FIG. 8B) by performing a CAT4 LBT (shown as 842 in FIG. 8B) in a shared channel. For example, as shown by the check mark, the CAT4 LBT 842 is successful (indicating the channel is clear for transmission).

[0102]

[0116] At action 820, upon passing the CAT4 LBT, the UE 502a transmits a sidelink transmission A (shown as 850 in FIG. 8B) during the portion 806 of the COT 844. The sidelink transmission A may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG. 4. The sidelink transmission A is a groupcast transmission with UEs 502b and 502c as intended recipients, as shown, for example, by the two arrows grouped by the dotted oval. UEs 502b and 502c (e.g., responding UEs) may receive the sidelink transmission A.

[0103]

[0117] As an example, sidelink transmission A may be a connection-based groupcast transmission, and UE 502a may request ACK / NACK feedback for sidelink transmission A from each of the intended recipients. In some aspects, UE 502a may include a PSFCH resource allocation indication (e.g., carried in an SCI) in sidelink transmission A for each of the intended recipients to send NACK / NACK feedback. In some instances, UE 502a may transmit data in a PSSCH region of a slot and indicate different PSFCH resources in the PSFCH region of the slot for different UEs. In some examples, a slot may include 14 symbols indexed from 0 to 13, the PSSCH region may include symbols 1 to 9 of the slot, and the PSFCH region may include symbols 11 and 12 of the slot. The different PSFCH resources for different intended recipients may be FDM, TDM, and / or code division multiplexed (CDM) in the PSFCH region.

[0104]

[0118] Similar to methods 500 and 600, the UE 502a may include an indicator 854 in the sidelink transmission A to provide COT sharing information related to the COT 844. The indicator 854 may indicate whether the sidelink transmission A 850 is transmitted by an initiating UE (of the COT 844) or a responding UE (of the COT 844). In some aspects, the indicator 854 may have a length of 1 bit, where a bit value of 1 may indicate an initiating node and a bit value of 0 may indicate a responding node, or vice versa. In some aspects, the indicator 854 may be a part of the first stage SCI or a part of the second stage SCI. In some aspects, the indicator 854 may be a part of the COT-SI. For example, the COT-SI may include a bitmap and the indicator 854 may correspond to a bit in the bitmap. In some instances, the COT-SI may indicate other information related to the COT 844 (e.g., the duration of the COT 844 for sharing, such as the portion 808 shown in FIG. 8B).

[0105]

[0119] Upon receiving sidelink transmission A at UE 502b, UE 502b transmits ACK / NACK feedback to UE 502a at action 822. If UE 502b successfully decodes data from sidelink transmission A 850, UE 502b may transmit an ACK. Conversely, if UE 502b detects the presence of sidelink transmission A 850 (based on successful SCI decoding) but fails to decode data from sidelink transmission A 850, UE 502b may transmit a NACK. In some aspects, UE 502b may transmit one predefined waveform sequence to indicate an ACK and may transmit a different predefined waveform sequence to indicate a NACK. Since UE 502b should transmit ACK / NACK feedback to UE 502a that initiated COT 844, UE 502b may transmit ACK / NACK feedback (shown as 852b) during the shared portion 808 of COT 844, as shown in FIG. 8B. The UE 502b may transmit ACK / NACK feedback 852b using the PSFCH resource, as indicated by sidelink transmission A 850.

[0106]

[0120] Upon receiving sidelink transmission A at UE 502c, UE 502c transmits ACK / NACK feedback to UE 502a at action 824. UE 502c may transmit an ACK or NACK depending on whether UE 502c successfully decodes data from sidelink transmission A 850. Since UE 502c should transmit ACK / NACK feedback to UE 502a that initiated COT 844, UE 502c may transmit ACK / NACK feedback (depicted as 852c) during the shared portion 808 of COT 844 as shown in FIG. 8B. UE 502c may transmit ACK / NACK feedback 852b using PSFCH resources as shown by sidelink transmission A 850.

[0107]

[0121] Similar to methods 500 and / or 600, after UE 502b receives sidelink transmission A, UE 502b may wish to transmit sidelink transmission B in groupcast mode to UE 502a, UE 502c, and UE 502d (e.g., a group of UEs identified by a group ID). UE 502b may determine that initiating UE 502a is the intended recipient of sidelink transmission B. Thus, at action 830, UE 502b transmits sidelink transmission B (shown as 860 in FIG. 8B ) in groupcast mode (as indicated by the three arrows grouped by the dotted arrows) to UE 502a, UE 502c, and UE 502d during the shared portion 508 of COT 524. Sidelink transmission B 860 may include an SCI (e.g., SCI 430) and data (e.g., data 435), as described above with respect to FIG. 4. In some aspects, the UE 502b may include a PSFCH resource allocation indication (e.g., carried in an SCI) in sidelink transmission B 860 for each of the intended recipients to send NACK / NACK feedback as described above with respect to sidelink transmission A at action 820. In some aspects, the sidelink transmission B 860 may also include an indicator 864, similar to indicator 854, for example, indicating that the sidelink transmission B 860 is transmitted by a responding UE of the COT 844.

[0108]

[0122] Upon receiving sidelink transmission B at UE 502a, UE 502a transmits ACK / NACK feedback to UE 502b at action 832. UE 502a may transmit an ACK or NACK depending on whether UE 502a successfully decodes data from sidelink transmission A 850. Since COT 844 is initiated by UE 502a, UE 502a may transmit ACK / NACK feedback (shown as 862a) during the shared portion 808 of COT 844, as shown in FIG. 8B. UE 502a may transmit ACK / NACK feedback 862a using PSFCH resources, as shown by sidelink transmission B 860.

[0109]

[0123] Upon receiving sidelink transmission B at UE 502c, UE 502c transmits ACK / NACK feedback to UE 502b at action 834. UE 502c may transmit an ACK or NACK depending on whether UE 502c successfully decodes data from sidelink transmission A 850. In some aspects, UE 502c may monitor a COT sharing indication and determine whether to transmit ACK / NACK feedback in COT 844 based on whether a COT sharing indication is detected for COT 844. As an example, UE 502c may be located at a location near UE 502a and may detect COT sharing information (indicator 854) related to COT 844 where sidelink transmission B 860 is received. Thus, UE 502c may transmit ACK / NACK feedback (shown as 862c) during the shared portion 808 of COT 844, as shown in FIG. 8B.

[0110]

[0124] Upon receiving sidelink transmission B at UE 502d, UE 502d transmits ACK / NACK feedback to UE 502b at action 836. UE 502c may transmit an ACK or NACK depending on whether UE 502d successfully decodes data from sidelink transmission A 850. In some aspects, UE 502d may monitor the COT sharing indication and may determine whether to transmit ACK / NACK feedback in COT 844 based on whether the COT sharing indication is detected for COT 844. As an example, UE 502d may be located further away from UE 502a and may not detect the COT sharing information (indicator 854) related to COT 844 where sidelink transmission B 860 is received and therefore may refrain from transmitting ACK / NACK feedback during the shared portion 806 of COT 844, as indicated by the arrow with symbol "X" in FIG. 8A and the dotted box with symbol "X" in FIG. 8B. To send ACK / NACK feedback, the UE 502d may perform a CAT4 LBT 872 in the shared channel to contend for a COT 874, as shown in FIG. 8B, and upon passing the CAT4 LBT 872 (having a checkmark), may send the ACK / NACK feedback 862d.

[0111]

[0125] As can be observed in the method 800, when a responding UE (e.g., UE 502b) shares a COT for a sidelink transmission (unicast or groupcast), the responding UE may not be aware of whether a receiving UE of the sidelink transmission may detect the COT sharing information of the COT, since each receiving UE may experience different interference. Thus, the responding UE may include a channel access type indicator of CAT4 LBT in the sidelink transmission to let the receiving UE select whether to share the COT for ACK / NACK transmission. For example, if the receiving UE cannot detect the COT sharing information for the COT, the receiving UE may perform CAT4 LBT in the shared channel to contend for another COT, and transmit the ACK / NACK during the other COT upon passing the CAT4 LBT. However, if the receiving UE detects the COT sharing information for the COT, the receiving UE may not perform LBT or may perform CAT2 LBT before transmitting the ACK / NACK in the COT. For example, the UE 502b may include a channel access type indicator 866 in the sidelink transmission B 860 as shown in FIG. 8B. The channel access type indicator 866 may indicate a CAT4 LBT for the ACK / NACK transmission. For example, based on the UE 502c detecting the indicator 854 having the COT sharing information for the COT 844, the UE 502c may switch to performing a CAT2 LBT before transmitting the ACK / NACK in action 822.

[0112]

[0126] FIG. 9 is a flow diagram of a sidelink COT sharing method 900 according to some aspects of the disclosure. Aspects of the method 900 may be performed by a computing device (e.g., a processor, a processing circuit, and / or other suitable components) of a wireless communication device or other suitable means for performing steps. For example, a wireless communication device such as a UE 115, 315, or 502 may utilize one or more components, such as a processor 1102, a memory 1104, a sidelink COT sharing module 1108, a transceiver 1110, a modem 1112, and one or more antennas 1116, to perform the steps of the method 900. The method 900 may employ mechanisms similar to those described above in FIGS. 1-4 and 8A-8B. As illustrated, the method 900 includes several enumerated steps, but aspects of the method 900 may include additional steps before, after, and between the enumerated steps. In some aspects, one or more of the enumerated steps may be omitted or performed in a different order.

[0113]

[0127] At block 910, a first UE (e.g., UE 115, 315, 402, 502, or 1100) receives a first sidelink transmission in a shared channel during a COT (e.g., COT 524) from a second UE. The first sidelink transmission may include an SCI (e.g., SCI 430) and data (e.g., data 435) as described above with respect to FIG. 4. The first UE may successfully decode the SCI and may perform decoding to decode the data from the first sidelink transmission. In some aspects, the first sidelink transmission may be a unicast transmission. In some aspects, the first sidelink transmission may be a groupcast transmission. The first sidelink transmission may also include PSFCH resource allocation information for the receiving UE to send ACK / NACK feedback for the first sidelink transmission.

[0114]

[0128] At block 920, the first UE determines ACK / NACK feedback for the first sidelink transmission. For example, the UE may perform data decoding for the first sidelink transmission. If the first UE successfully decodes data from the first sidelink transmission, the first UE may generate an ACK (e.g., a waveform sequence representing an ACK). Conversely, if the first UE fails to decode data from the first sidelink transmission, the first UE may generate a NACK (e.g., a waveform sequence representing a NACK).

[0115]

[0129] In block 930, the first UE determines whether the second UE is an initiating UE of the first COT. To assist the responding UE of the first sidelink transmission in determining whether the first COT can be shared, the first sidelink transmission may include a COT-SI indicator (e.g., indicators 532, 642, and / or 864) indicating whether the first sidelink transmission is transmitted by an initiating UE of the first COT. The COT-SI may be a portion of the SCI in the first sidelink transmission. The COT-SI indicator may also include an indication of the duration in the first COT that is for sharing. Thus, the first UE may determine whether the second UE is an initiating UE of the first COT based on the indicator. If the first UE determines that the second UE is an initiating UE of the first COT, the first UE proceeds to block 970.

[0116]

[0130] In response to determining that the second UE is an initiating UE of the first COT at block 970, the first UE performs a CAT2 LBT before transmitting an ACK / NACK in the COT. The first UE may perform a CAT2 LBT based on the ACK / NACK being transmitted within the shared portion of the first COT. In some other cases, the first UE may not perform an LBT before transmitting in the shared COT.

[0117]

[0131] In block 980, upon passing the CAT2 LBT, the first UE may transmit ACK / NACK feedback for the first sidelink transmission during the shared portion of the first COT. The first UE may obtain information related to the duration of the shared portion from the COT-SI indicator.

[0118]

[0132] Returning to block 930, if the first UE determines that the second UE is not the initiating UE of the first COT, the first UE proceeds to block 940. In block 940, the first UE determines whether COT sharing information for the first COT is detected. For example, the first UE may monitor COT-SI or COT sharing information from other UEs, for example, by performing SCI decoding on each PSCCH resource in the sidelink resource pool. Upon successfully decoding the SCI, the first UE may read information in the SCI. The first UE may determine whether COT sharing information for the first COT is detected based on the information read from the decoded SCI. If the first UE determines that COT sharing information for the first COT is detected, the first UE proceeds to block 970.

[0119]

[0133] If the first UE determines that there is no detected COT sharing information for the first COT, the first UE proceeds to block 950. In block 950, the first UE performs a CAT4 LBT in the shared channel to contend for the second COT. For example, the CAT4 LBT is passed (indicating the channel is clear for transmission).

[0120]

[0134] In block 960, upon passing the CAT4 LBT, the first UE sends ACK / NACK feedback during the second COT.

[0121]

[0135] FIG. 10 is a block diagram of an example BS 1000 according to some aspects of the disclosure. The BS 1000 may be the BS 105 in the network 100 or the BS 305 in the network 300 described above in FIG. 1. As shown, the BS 1000 may include a processor 1002, a memory 1004, a sidelink configuration module 1008, a transceiver 1010 including a modem subsystem 1012 and an RF unit 1014, and one or more antennas 1016. These elements may be coupled to each other. The term "coupled" may refer to being directly or indirectly coupled or connected to one or more intervening elements. For example, these elements may be in direct or indirect communication with each other, for example, via one or more buses.

[0122]

[0136] The processor 1002 may include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof, configured to perform the operations described herein. The processor 1002 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0123]

[0137] The memory 1004 may include cache memory (e.g., cache memory of the processor 1002), random access memory (RAM), magnetoresistive RAM (MRAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory devices, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In one aspect, the memory 1004 includes a non-transitory computer readable medium. The memory 1004 may store or have recorded thereon instructions 1006. The instructions 1006 may include instructions that, when executed by the processor 1002, cause the processor 1002 to perform the operations described herein with reference to the UE 115 with respect to aspects of the disclosure, e.g., the aspects of FIGS. 1-3. The instructions 1006 may also be referred to as program code, which may be broadly construed to include any type of computer readable statements.

[0124]

[0138] The sidelink configuration module 1008 may be implemented via hardware, software, or a combination thereof. For example, the sidelink configuration module 1008 may be implemented as a processor, circuitry, and / or instructions 1006 stored in the memory 1004 and executed by the processor 1002. In some examples, the sidelink configuration module 1008 may be incorporated within the modem subsystem 1012. For example, the sidelink configuration module 1008 may be implemented by a combination of software components (e.g., executed by a DSP or general-purpose processor) and hardware components (e.g., logic gates and circuits) within the modem subsystem 1012.

[0125]

[0139] The sidelink configuration module 1008 may communicate with various components of the BS 1000 to perform various aspects of the disclosure, such as those of Figures 1-3. For example, the sidelink configuration module 1008 may be configured to configure UEs (e.g., UEs 115, 315, 402, and 502) with a sidelink resource pool for sidelink communication, as described above, and / or configure some UEs as anchor UEs.

[0126]

[0140] As shown, the transceiver 1010 may include a modem subsystem 1012 and an RF unit 1014. The transceiver 1010 may be configured to communicate bidirectionally with other devices, such as the UE 115 and / or another core network element. The modem subsystem 1012 may be configured to modulate and / or encode data according to an MCS, e.g., an LDPC coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit 1014 may be configured to process (e.g., perform analog-to-digital or digital-to-analog conversion, etc.) the modulated / encoded data (e.g., RRC configuration, sidelink resource pool configuration) from the modem subsystem 1012 (on outbound transmissions) or of transmissions originating from another source, such as the UE 115. The RF unit 1014 may further be configured to perform analog beamforming along with digital beamforming. Although shown as being incorporated together in the transceiver 1010, the modem subsystem 1012 and / or the RF unit 1014 may be separate devices coupled to each other at the BS 105 to enable the BS 105 to communicate with other devices.

[0127]

[0141] The RF unit 1014 may provide modulated and / or processed data, e.g., data packets (or, more generally, data messages, which may include one or more data packets and other information), to the antenna 1016 for transmission to one or more other devices. This may include, for example, transmission of information to complete a connection to a network and communication with a camped UE 115 according to some aspects of the present disclosure. The antenna 1016 may further receive data messages transmitted from other devices and provide the received data messages for processing and / or demodulation in the transceiver 1010. The transceiver 1010 may provide the demodulated and decoded data to the sidelink configuration module 1008 for processing. The antenna 1016 may include multiple antennas of similar or different designs to maintain multiple transmission links.

[0128]

[0142] In one aspect, the BS 1000 may include multiple transceivers 1010 implementing different RATs (e.g., NR and LTE). In one aspect, the BS 1000 may include a single transceiver 1010 implementing multiple RATs (e.g., NR and LTE). In one aspect, the transceiver 1010 may include various components, where different combinations of components may implement different RATs.

[0129]

[0143] FIG. 11 is a block diagram of an example UE 1100 according to some aspects of the disclosure. The UE 1100 may be the UE 115 described above with respect to FIG. 1, the UE 315 described above with respect to FIG. 3, or the UE 502 described above with respect to FIG. 4, 5A-5B, 6A-6B, and 8A-8B. As shown, the UE 1100 may include a processor 1102, a memory 1104, a sidelink COT sharing module 1108, a transceiver 1110 including a modem subsystem 1112 and a radio frequency (RF) unit 1114, and one or more antennas 1116. These elements may be coupled to each other. The term "coupled" may refer to being directly or indirectly coupled or connected to one or more intervening elements. For example, these elements may be in direct or indirect communication with each other, for example, via one or more buses.

[0130]

[0144] The processors 1102 may have various characteristics as a particular type of processor. For example, they may include a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 1102 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0131]

[0145] The memory 1104 may include cache memory (e.g., cache memory of the processor 1102), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, solid-state memory devices, one or more hard disk drives, memristor-based arrays, other forms of volatile and non-volatile memory, or a combination of different types of memory. In some aspects, the memory 1104 may include a non-transitory computer-readable medium. The memory 1104 may store instructions 1106. The instructions 1106 may include instructions that, when executed by the processor 1102, cause the processor 1102 to perform operations described herein, e.g., aspects of FIGS. 1-3, 4, 5A-5B, 6A-6B, 7, 8A-8B, 9, and 12. The instructions 1106 may also be referred to as program code. The program code may be for causing the wireless communication device to perform these operations, for example, by causing one or more processors (such as processor 1102) to control or direct the wireless communication device to perform these operations. The terms "instructions" and "code" should be interpreted broadly to include any type of computer-readable statements. For example, the terms "instructions" and "code" may refer to one or more programs, routines, subroutines, functions, procedures, etc. "Instructions" and "code" may include a single computer-readable statement or many computer-readable statements, as described above with respect to FIG. 10.

[0132]

[0146] The sidelink COT sharing module 1108 may be implemented via hardware, software, or a combination thereof. For example, the sidelink COT sharing module 1108 may be implemented as a processor, circuitry, and / or instructions 1106 stored in the memory 1104 and executed by the processor 1102. In some examples, the sidelink COT sharing module 1108 may be incorporated within the modem subsystem 1112. For example, the sidelink COT sharing module 1108 may be implemented by a combination of software components (e.g., executed by a DSP or general-purpose processor) and hardware components (e.g., logic gates and circuits) within the modem subsystem 1112.

[0133]

[0147] The sidelink COT sharing module 1108 may communicate with various components of the UE 1100 to perform aspects of the disclosure, e.g., aspects of FIGS. 1-3, 4, 5A-5B, 6A-6B, 7, 8A-8B, 9, and 11. In some aspects, the sidelink COT sharing module 1108 is configured to initiate a COT (e.g., COT 524, 844) in the shared channel by performing a CAT4 LBT and transmit a first sidelink transmission (e.g., sidelink transmission 530, 850) during a portion of the COT upon passing the CAT4 LBT. The first sidelink transmission may be a unicast transmission, a groupcast transmission, or a broadcast transmission. In some aspects, the sidelink COT sharing module 1108 is configured to include an indicator (e.g., indicators 532 and 854) in the first sidelink transmission to indicate that the first sidelink transmission is an initiating UE of the COT (e.g., by indicating the shared portion of the COT) and that the COT is for sharing.

[0134]

[0148] In some aspects, the sidelink COT sharing module 1108 is configured to receive a first sidelink transmission (e.g., sidelink transmission 530, 850) from a second UE (e.g., UE 115, 315, 502, and / or 1100) during a first COT (e.g., COT 524, 844), where the first COT is initiated by the second UE. The first sidelink transmission may include an indication (e.g., indicators 642 and 864) of whether the first sidelink UE is transmitted by an initiating UE of the first COT. The sidelink COT sharing module 1108 is configured to determine whether the second UE is one of two or more UEs intended to receive the second sidelink transmission and to transmit the second sidelink transmission to the two or more UEs during a portion of the first COT based on the COT sharing. The COT sharing may be in response to the second UE determining that it is one of two or more UEs intended to receive the second sidelink transmission, e.g., as described above with respect to Figures 5A-5B, 6A-6B, and 7.

[0135]

[0149] In some aspects, the sidelink COT sharing module 1108 is configured to receive a third sidelink transmission (e.g., sidelink transmission 540, 860) from the third UE during the second COT. The third sidelink transmission may include data and may indicate that the third sidelink UE is not an initiator of the second COT. The sidelink COT sharing module 1108 is configured to determine whether data decoding from the third sidelink transmission is successful and to send ACK / NACK feedback (e.g., ACK / NACK feedback 852 and 862) to the third UE based on whether the data decoding is successful. The sidelink COT sharing module 1108 is further configured to monitor COT sharing information and monitor whether COT sharing information for the second COT is detected. The sidelink COT sharing module 1108 is further configured to determine whether to send ACK / NACK feedback during the second COT based on whether COT sharing information for the COT is detected, for example, as described above with respect to Figures 8A-8B and 9.

[0136]

[0150] As shown, the transceiver 1110 may include a modem subsystem 1112 and an RF unit 1114. The transceiver 1110 may be configured to communicate bidirectionally with other devices, such as the BS 105. The modem subsystem 1112 may be configured to modulate and / or encode data from the memory 1104 and / or the sidelink COT sharing module 1108 according to a modulation and coding scheme (MCS), e.g., a low density parity check (LDPC) coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit 1114 may be configured to process (e.g., perform analog-to-digital or digital-to-analog conversion, etc.) modulated / coded data (e.g., PSCCH, PSSCH, SCI-1, SCI-2, sidelink data, COT-SI, COT sharing information) from the modem subsystem 1112 (on outbound transmissions) or of transmissions originating from another source, such as the UE 115 or the BS 105. The RF unit 1114 may be further configured to perform analog beamforming as well as digital beamforming. Although shown as being incorporated together in the transceiver 1110, the modem subsystem 1112 and the RF unit 1114 may be separate devices coupled to each other in the UE 115 to enable the UE 115 to communicate with other devices.

[0137]

[0151] The RF unit 1114 may provide modulated and / or processed data, e.g., data packets (or, more generally, data messages, which may include one or more data packets and other information), to the antenna 1116 for transmission to one or more other devices. The antenna 1116 may further receive data messages transmitted from other devices. The antenna 1116 may provide the received data messages for processing and / or demodulation in the transceiver 1110. The transceiver 1110 may provide demodulated and decoded data (e.g., PSCCH, PSSCH, SCI-1, SCI-2, sidelink data, COT-SI, COT sharing information) to the sidelink COT sharing module 1108 for processing. The antenna 1116 may include multiple antennas of similar or different designs to maintain multiple transmission links. The RF unit 1114 may configure the antenna 1116.

[0138]

[0152] In one aspect, the transceiver 1110 is configured to receive a first sidelink transmission from a second UE (e.g., UE 115, 315, 502, and / or 1100) during a first COT, where the first COT is associated with the second UE. For example, the first COT is initiated by the second UE. A processor 1102 is coupled to the transceiver and configured to determine whether the second UE is one of two or more UEs intended to receive the second sidelink transmission. The transceiver 1110 is further configured to transmit a second sidelink transmission to the two or more UEs during a portion of the first COT based on the COT sharing. The COT sharing is in response to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0139]

[0153] In one aspect, the UE 1100 may include multiple transceivers 1110 implementing different RATs (e.g., NR and LTE). In one aspect, the UE 1100 may include a single transceiver 1110 implementing multiple RATs (e.g., NR and LTE). In one aspect, the transceiver 1110 may include various components, where different combinations of components may implement different RATs.

[0140]

[0154] FIG. 12 is a flow diagram of a wireless communication method 1200 according to some aspects of the disclosure. Aspects of the method 1200 may be performed by a computing device (e.g., a processor, a processing circuit, and / or other suitable components) of a wireless communication device or other suitable means for performing the steps. For example, a wireless communication device such as a UE 115, 315, 402, or 1100 may utilize one or more components, such as a processor 1102, a memory 1104, a sidelink COT sharing module 1108, a transceiver 1110, a modem 1112, and one or more antennas 1116, to perform the steps of the method 1200. The method 1200 may employ mechanisms similar to those described above in FIGS. 3-4, 5A-5B, 6A-6B, 7, 8A-8B, and 9. As shown, method 1200 includes several recited steps, although aspects of method 1200 may include additional steps before, after, and between the recited steps. In some aspects, one or more of the recited steps may be omitted or performed in a different order.

[0141]

[0155] At block 1210, a first UE (e.g., UE 115, 315, 502, or 1100) receives a first sidelink transmission during a first COT from a second UE, where the first COT is associated with the second UE. The first sidelink transmission may include an SCI and sidelink data. In some aspects, the SCI may indicate whether the second UE is a starting UE of the first COT. In some aspects, the SCI may include a first phase SCI and a second phase SCI. In some cases, an indication of whether the second UE is a starting UE of the first COT (e.g., indicator 532, 642, 854) may be included in the first phase SCI. In some other cases, an indication of whether the second UE is a starting UE of the first COT (e.g., indicator 532, 642, 854) may be included in the second phase SCI. In some aspects, the SCI may include a COT-SI indicating whether COT sharing in the first COT is enabled. In some instances, the first UE may utilize one or more components, such as the processor 1102, the sidelink COT sharing module 1108, the transceiver 1110, the modem 1112, and one or more antennas 1116, to perform the operations of block 1220.

[0142]

[0156] In block 1220, the first UE determines whether the second UE is one of two or more UEs intended to receive the second sidelink transmission. In some aspects, the second sidelink transmission should be transmitted in a groupcast transmission. In some aspects, a groupcast transmission is a connection-based transmission intended to be received by a particular group of UEs (associated with a group ID). Thus, the first UE may be aware of the UEs in a particular group and may determine whether the second UE is one of the UEs in the particular group. In some aspects, the groupcast transmission is connectionless. In other words, the second sidelink transmission is not intended for a particular group of UEs having a group ID. Instead, the second sidelink transmission may be intended to be received by UEs in a particular zone or area or within a particular physical distance or range from the first UE. Thus, the second UE may determine whether the first UE is one of the UEs in a particular zone based, for example, on the geographic location of the first UE or the physical distance between the first UE and the second UE. In some cases, the zones may be preconfigured and the second UE may provide zone information (e.g., a zone ID identifying a zone associated with the second UE) during the SCI in the first sidelink transmission. In some aspects, the second sidelink transmission should be transmitted in a broadcast mode for all UEs in the vicinity of the first UE, and thus the second UE is an intended receiver of the second sidelink transmission. In some cases, the first UE may utilize one or more components, such as the processor 1102, the sidelink COT sharing module 1108, the transceiver 1110, the modem 1112, and one or more antennas 1116, to perform the operations of block 1220.

[0143]

[0157] At block 1230, the first UE transmits a second sidelink transmission during a portion of the first COT (e.g., shared portion 508 or 808) to the two or more UEs based on the COT sharing. The second sidelink transmission may be a groupcast transmission or a broadcast transmission. The COT sharing may be in response to the second UE determining that it is one of the two or more UEs intended to receive the second sidelink transmission, e.g., as described above with respect to Figures 5A-5B, 6A-6B, and 7. In some instances, the first UE may utilize one or more components, such as the processor 1102, the sidelink COT sharing module 1108, the transceiver 1110, the modem 1112, and one or more antennas 1116, to perform the operations of block 1230.

[0144]

[0158] In some aspects, the first UE may transmit a second sidelink transmission during a portion of the first COT further based on an SCI (in the first sidelink transmission) indicating that the second UE is an initiating UE of the first COT.

[0145]

[0159] In some aspects, the first UE may transmit a second sidelink transmission during a portion of the first COT further based on the COT-SI (in the first sidelink transmission) indicating that COT sharing in the first COT is enabled.

[0146]

[0160] In some aspects, the first UE may transmit the second sidelink transmission in a connection-based groupcast mode. In some aspects, the first UE may transmit the second sidelink transmission in a connectionless mode. In some aspects, the first UE may transmit the second sidelink transmission in a broadcast mode.

[0147]

[0161] In some aspects, the first UE may further receive a third sidelink transmission including data from a third UE (e.g., UE 115, 315, 402, 502, or 1100) during the second COT. The first UE may determine whether the third UE is an initiating UE of the second COT, for example, based on an indication in the third sidelink transmission (e.g., indication 532, 642, 854, and / or 864). The first UE may transmit acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT in response to determining that the third UE is an initiating UE of the second COT, for example, as described above with respect to FIGS. 8A-8B and 9.

[0148]

[0162] In some aspects, the first UE may receive a third sidelink transmission including data from a third UE during the second COT. The third UE may be a responding UE of the second COT. The first UE may monitor COT shared information associated with the second COT. As described above, the COT shared information may be carried in the SCI, and thus the first UE may perform SCI decoding in the SCI resource to detect the COT shared information. The first UE may determine whether to transmit acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT based on the monitoring. In some aspects, the first UE may refrain from transmitting ACK / NACK feedback during a portion of the second COT in response to determining that there is no COT shared information associated with the second COT detected from the monitoring. In some aspects, the first UE may further perform a CAT4 LBT and transmit ACK / NACK feedback during the third COT based on the CAT4 LBT. In some aspects, the third sidelink transmission may include a channel access type indicating a CAT4 LBT mode for transmitting the ACK / NACK feedback. In some aspects, the first UE may receive COT sharing information associated with the second COT and transmit the ACK / NACK feedback during a portion of the second COT in response to receiving the COT sharing information associated with the second COT, e.g., as described above with respect to FIGs. 8A-8B and 9.

[0149]

[0163] In some aspects, the first UE may further determine whether the second UE is one of the two or more UEs intended to receive the third sidelink transmission. In response to determining that the second UE is not one of the two or more UEs intended to receive the third sidelink transmission, the first UE may refrain from transmitting the third sidelink transmission during a portion of the first COT.

[0150]

[0164] Further aspects of the present disclosure include the following.

[0151]

[0165] Aspect 1 includes a method of wireless communication performed by a first user equipment (UE), the method comprising: receiving a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE, determining whether the second UE is one of two or more UEs intended to receive the second sidelink transmission, and transmitting a second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0152]

[0166] Aspect 2 includes the method of aspect 1, wherein receiving the first sidelink transmission comprises receiving sidelink control information (SCI) from the second UE indicating whether the second UE is an initiating UE of the first COT, and transmitting the second sidelink transmission during the portion of the first COT based on the COT sharing is further based on the SCI indicating that the second UE is an initiating UE of the first COT.

[0153]

[0167] Example 3 includes the method of example 1 or 2, wherein receiving the first sidelink transmission comprises receiving, from the second UE, sidelink control information (SCI) including a COT structure indicator (COT-SI) indicating whether COT sharing in the first COT is enabled, and transmitting the second sidelink transmission during the portion of the first COT is further based on the COT-SI indicating that COT sharing in the first COT is enabled.

[0154]

[0168] Example 4 includes the method of any of examples 1 to 3, wherein transmitting the second sidelink transmission comprises transmitting the second sidelink transmission in a broadcast mode.

[0155]

[0169] Example 5 includes the method of any of examples 1 to 4, wherein transmitting the second sidelink transmission comprises transmitting the second sidelink transmission in a groupcast mode.

[0156]

[0170] Example 6 includes the method of any of Examples 1 to 5, further comprising: receiving a third sidelink transmission comprising data from a third UE during the second COT; determining whether the third UE is an initiating UE of the second COT; and in response to determining that the third UE is an initiating UE of the second COT, transmitting acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT.

[0157]

[0171] Example 7 includes the method of any of Examples 1 to 6, further comprising: receiving a third sidelink transmission comprising data from a third UE during a second COT; monitoring COT shared information associated with the second COT; and determining, based on the monitoring, whether to send acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT.

[0158]

[0172] Example 8 includes the method of any of Examples 1 to 7, further comprising: determining whether the second UE is one of the two or more UEs intended to receive the third sidelink transmission; and, in response to determining that the second UE is not one of the two or more UEs intended to receive the third sidelink transmission, refraining from transmitting the third sidelink transmission during the portion of the first COT.

[0159]

[0173] Aspect 9 includes a first user equipment (UE) comprising a memory, a transceiver, and at least one processor coupled to the memory and the transceiver, where the first UE is configured to receive a first sidelink transmission from a second UE during a first channel occupation time (COT), where the first COT is associated with the second UE, determine whether the second UE is one of two or more UEs intended to receive the second sidelink transmission, and transmit the second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

[0160]

[0174] Example 10 includes the first UE of example 9, wherein the first UE is further configured to receive sidelink control information (SCI) from the second UE indicating whether the second UE is an initiating UE of the first COT, and to transmit a second sidelink transmission during a portion of the first COT further based on the SCI indicating that the second UE is an initiating UE of the first COT.

[0161]

[0175] Example 11 includes the first UE of any of Examples 9 or 10, wherein the first UE is further configured to receive sidelink control information (SCI) from the second UE, the SCI including a COT structure indicator (COT-SI) indicating whether COT sharing in the first COT is enabled, and to transmit a second sidelink transmission during a portion of the first COT further based on the COT-SI indicating that COT sharing in the first COT is enabled.

[0162]

[0176] Example 12 includes the first UE of any of Examples 9 to 11, wherein the first UE is further configured to transmit the second sidelink transmission in a broadcast mode.

[0163]

[0177] Example 13 includes the first UE of any of Examples 9 to 12, wherein the first UE is further configured to transmit the second sidelink transmission in a groupcast mode.

[0164]

[0178] Example 14 includes the first UE of any of Examples 9 to 13, wherein the first UE is further configured to receive a third sidelink transmission comprising data from a third UE during the second COT, determine whether the third UE is an initiating UE of the second COT, and in response to determining that the third UE is an initiating UE of the second COT, transmit acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT.

[0165]

[0179] Example 15 includes the first UE of any of Examples 9 to 14, wherein the first UE is further configured to receive a third sidelink transmission comprising data from a third UE during a second COT, monitor COT shared information associated with the second COT, and determine, based on the monitoring, whether to send acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT.

[0166]

[0180] Example 16 includes the first UE of any of Examples 9 to 15, wherein the first UE is further configured to: determine to refrain from sending ACK / NACK feedback during a portion of the second COT in response to determining that there is no COT shared information associated with the second COT detected from the monitoring; perform a Category 4 (CAT4) LBT; and send ACK / NACK feedback during a third COT based on the CAT4 LBT.

[0167]

[0181] Aspect 17 includes a non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment, cause the one or more processors to perform any one of those described in aspects 1 through 8.

[0168]

[0182] Aspect 18 includes a non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising one or more instructions that, when executed by one or more processors of a first user equipment, cause the one or more processors to perform any one of the methods described in aspects 9 to 16.

[0169]

[0183]

[0041] Aspect 19 includes a first user equipment (UE) comprising one or more means for performing any one or more of the aspects recited in aspects 1-8.

[0170]

[0184]

[0041] Aspect 20 includes a first user equipment (UE) comprising one or more means for performing any one or more of aspects 9-16.

[0171]

[0185] Information and signals may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0172]

[0186] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed using a general purpose processor, a DSP, an ASIC, an 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, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0173]

[0187] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. When implemented in software executed by a processor, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or codes. Other examples and implementations fall within the scope of this disclosure and the appended claims. For example, due to the nature of the software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Features implementing the functions may also be physically located in various locations, including being distributed such that portions of the functions are implemented in different physical locations. Also, as used herein, including in the claims, "or" used in a list of items (e.g., a list of items followed by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, so for example, a list of [at least one of A, B, or C] means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0174]

[0188] As those skilled in the art will now appreciate, depending on the particular application at hand, many modifications, substitutions, and variations may be made in and to the materials, apparatus, construction, and methods of use of the devices of the present disclosure without departing from the spirit and scope thereof. In light of this, the scope of the present disclosure should not be limited to the scope of the specific embodiments illustrated and described herein, as these are merely examples of the present disclosure, but rather should be fully commensurate with the scope of the following appended claims and their functional equivalents.

Claims

1. 1. A method of wireless communication performed by a first user equipment (UE), comprising: receiving a first sidelink transmission during a first channel occupation time (COT) from a second UE, wherein the first COT is associated with the second UE; determining whether the second UE is one of two or more UEs intended to receive a second sidelink transmission, where the second sidelink transmission is a groupcast or broadcast transmission. transmitting the second sidelink transmission during the first portion of the COT to the two or more UEs based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission. A method comprising:

2. The receiving of the first sidelink transmission comprises: receiving, from the second UE, sidelink control information (SCI) indicating whether the second UE is an initiating UE of the first COT; Equipped with and transmitting the second sidelink transmission during the portion of the first COT based on the COT sharing is further based on the SCI indicating that the second UE is the initiating UE of the first COT. The method of claim 1.

3. The receiving of the first sidelink transmission comprises: receiving, from the second UE, sidelink control information (SCI) including a COT configuration indicator (COT-SI) indicating whether the COT sharing in the first COT is enabled; Equipped with and transmitting the second sidelink transmission during the portion of the first COT based on the COT-SI indicating that the COT sharing in the first COT is enabled. The method of claim 1.

4. The transmitting of the second sidelink transmission comprises: Transmitting the second sidelink transmission in a broadcast mode. The method of claim 1 , comprising:

5. The transmitting of the second sidelink transmission comprises: Transmitting the second sidelink transmission in a groupcast mode. The method of claim 1 , comprising:

6. receiving a third sidelink transmission comprising data from a third UE during the second COT; and determining whether the third UE is an initiating UE of the second COT; in response to determining that the third UE is the initiating UE of the second COT, transmitting acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT; The method of claim 1 further comprising:

7. receiving a third sidelink transmission comprising data from a third UE during the second COT; and monitoring COT share information associated with the second COT; 2. The method of claim 1, further comprising: determining whether to send acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during the second portion of COT based on the monitoring.

8. determining whether the second UE is one of two or more UEs intended to receive a third sidelink transmission; and in response to determining that the second UE is not one of the two or more UEs intended to receive the third sidelink transmission, refrain from transmitting the third sidelink transmission during the portion of the first COT. The method of claim 1 further comprising:

9. A non-transitory computer readable medium having program code recorded thereon, the program code comprising: and code for causing a first user equipment (UE) to receive a first sidelink transmission from a second UE during a first channel occupation time (COT), wherein the first COT is associated with the second UE. and code for causing the first UE to determine whether the second UE is one of two or more UEs intended to receive a second sidelink transmission, where the second sidelink transmission is a groupcast or broadcast transmission. and code for causing the first UE to transmit the second sidelink transmission to the two or more UEs during a portion of the first COT based on a COT sharing, the COT sharing responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission.

1. A non-transitory computer-readable medium comprising:

10. A first user equipment (UE), means for receiving a first sidelink transmission during a first channel occupation time (COT) from a second UE, wherein the first COT is associated with the second UE; means for determining whether the second UE is one of two or more UEs intended to receive a second sidelink transmission, where the second sidelink transmission is a groupcast or broadcast transmission. means for transmitting the second sidelink transmission during the first portion of the COT to the two or more UEs based on a COT sharing, the COT sharing being responsive to determining that the second UE is one of the two or more UEs intended to receive the second sidelink transmission. A first user equipment (UE) comprising:

11. The means for receiving the first sidelink transmission further comprises: receiving sidelink control information (SCI) from the second UE indicating whether the second UE is an initiating UE of the first COT; It is configured as follows: The means for transmitting the second sidelink transmission during the portion of the first COT further comprises:

11. The first UE of claim 10, configured to transmit the second sidelink transmission during the portion of the first COT further based on the SCI indicating that the second UE is the initiating UE of the first COT.

12. The means for receiving the first sidelink transmission further comprises: receiving, from the second UE, sidelink control information (SCI) including a COT structure indicator (COT-SI) indicating whether the COT sharing in the first COT is enabled; It is configured as follows: The means for transmitting the second sidelink transmission during the portion of the first COT further comprises: transmitting the second sidelink transmission during the portion of the first COT further based on the COT-SI indicating that the COT sharing in the first COT is enabled. The first UE according to claim 10, configured to:

13. The means for transmitting the second sidelink transmission further comprises: Broadcast mode, or Group Cast Mode 11. The first UE of claim 10, configured to transmit the second sidelink transmission on at least one of:

14. means for receiving a third sidelink transmission comprising data from a third UE during the second COT; means for determining whether the third UE is an initiating UE of the second COT; means for transmitting acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT in response to determining that the third UE is the initiating UE of the second COT; The first UE of claim 10, further comprising:

15. means for receiving a third sidelink transmission comprising data from a third UE during the second COT; means for monitoring COT share information associated with the second COT; means for determining whether to transmit acknowledgement / negative acknowledgement (ACK / NACK) feedback for the data during a portion of the second COT based on the monitoring; The first UE of claim 10, further comprising:

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