CN116918440A - Channel Occupancy Time (COT) sharing for side-link communications in unlicensed frequency bands - Google Patents

Abstract

Wireless communication systems and methods related to Channel Occupancy Time (COT) sharing for side-link communications in an unlicensed frequency band are provided. A method for wireless communication by a first User Equipment (UE) may include: measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and accessing a first time slot of the COT based on the first RSRP.

Description

Channel Occupancy Time (COT) sharing for side-link communications in unlicensed frequency bands

Cross Reference to Related Applications

The present application claims priority and benefit from the following applications: greek patent application No. 20210100218, entitled "ACK TRANSMISSION FOR IMPROVED COT SHARING", filed 3/31 in 2021; and greek patent application No. 20210100111, entitled "CHANNEL OCCUPANCY TIME (COT) SHARING FOR SIDELINK COMMUNICATIONS IN UNLICENSED BANDS," filed 24 at month 2021, the entire contents of each of which are hereby incorporated by reference as if fully set forth below and for all applicable purposes.

Technical Field

The present application relates to wireless communication systems, and more particularly, to Channel Occupation Time (COT) sharing for side-link communications in unlicensed frequency bands.

Background

Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be able to support communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). A wireless multiple-access communication system may include multiple Base Stations (BSs), each supporting communication for multiple communication devices, which may be referred to in other respects as User Equipment (UEs).

To meet the increasing demand for extended mobile broadband connections, wireless communication technology is evolving from Long Term Evolution (LTE) technology to next generation New Radio (NR) technology, which may be referred to as fifth generation (5G). For example, NR is designed to provide lower latency, higher bandwidth or higher throughput, and higher reliability than LTE. NR is also designed to operate across different spectrum types, from licensed spectrum to unlicensed and shared spectrum.

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

Disclosure of Invention

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

In some aspects of the disclosure, a method of performing wireless communication by a first User Equipment (UE) includes: measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and accessing a first time slot of the COT based on the first RSRP.

In some aspects, a method of performing wireless communication by a first User Equipment (UE) includes: detecting a physical side uplink shared channel (PSSCH) transmission; detecting a physical side uplink feedback channel (PSFCH) transmission transmitted in response to the PSSCH transmission within a COT having a plurality of slots; and accessing a first time slot of the plurality of time slots of the COT based on the detecting the PSFCH transmission.

In some aspects, a first User Equipment (UE) includes: a memory; and at least one processor operatively coupled to the memory and configured to: measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and accessing a first time slot of the COT based on the first RSRP.

In some aspects, a first User Equipment (UE) includes: a memory; and at least one processor operatively coupled to the memory and configured to: detecting a physical side uplink shared channel (PSSCH) transmission; detecting a physical side uplink feedback channel (PSFCH) transmission transmitted in response to the PSSCH transmission within a COT having a plurality of slots; and accessing a first time slot of the plurality of time slots of the COT based on the detecting the PSFCH transmission.

In some aspects, a non-transitory Computer Readable Medium (CRM) has program code recorded thereon, the program code comprising: code for causing a first User Equipment (UE) to measure a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission sent during a Channel Occupation Time (COT) initiated by a second UE; and code for causing the first UE to access a first time slot of the COT based on the first RSRP.

In some aspects, a non-transitory Computer Readable Medium (CRM) has program code recorded thereon, the program code comprising: code for causing a first User Equipment (UE) to detect a physical side uplink shared channel (PSSCH) transmission; code for causing a first User Equipment (UE) to detect a physical side uplink feedback channel (PSFCH) transmission sent in response to the PSSCH transmission within a COT having a plurality of slots; and code for causing a first User Equipment (UE) to access a first time slot of the plurality of time slots of the COT based on the detecting the PSFCH transmission.

In some aspects, a first User Equipment (UE) includes: means for measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and means for accessing a first time slot of the COT based on the first RSRP.

In some aspects, a first User Equipment (UE) includes: a unit for detecting physical side uplink shared channel (PSSCH) transmission; means for detecting a physical side uplink feedback channel (PSFCH) transmission sent in response to the PSSCH transmission within a COT having a plurality of slots; and means for accessing a first time slot of the plurality of time slots of the COT based on the detecting the PSFCH transmission.

Other aspects, features and embodiments of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific, exemplary embodiments of the invention in conjunction with the accompanying figures. While features of the invention may be discussed with respect to certain embodiments and figures below, all embodiments of the invention may include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the invention discussed herein. In a similar manner, while exemplary embodiments may be discussed below as a device, system, or method, it should be understood that such exemplary embodiments may be implemented in a variety of devices, systems, and methods.

Drawings

Fig. 1 illustrates a wireless communication network in accordance with some aspects of the present disclosure.

Fig. 2 is a timing diagram illustrating a radio frame structure in accordance with some aspects of the present disclosure.

Fig. 3 illustrates a wireless communication network that provides side-link communications in accordance with some aspects of the present disclosure.

Fig. 4A illustrates a schematic diagram depicting a spatial range of a COT initiated by a COT initiating UE, in accordance with some aspects of the present disclosure.

Fig. 4B illustrates a timing diagram depicting a side-uplink communication scheme in an unlicensed frequency band, in accordance with some aspects of the present disclosure.

Fig. 5 is a block diagram of an exemplary User Equipment (UE) in accordance with some aspects of the present disclosure.

Fig. 6 is a block diagram of an exemplary Base Station (BS) in accordance with some aspects of the present disclosure.

Fig. 7 is a flow chart of a wireless communication method in accordance with some aspects of the present disclosure.

Fig. 8 is a flow chart of a wireless communication method in accordance with some aspects of the present disclosure.

Fig. 9 is a block diagram conceptually illustrating an example wireless communication network.

Fig. 10 is a block diagram conceptually illustrating the design of an exemplary Base Station (BS) and User Equipment (UE) in accordance with some aspects of the present disclosure.

Fig. 11 is an example frame format for certain wireless communication systems (e.g., new Radios (NRs)) in accordance with some aspects of the present disclosure.

Fig. 12A and 12B illustrate a diagrammatic representation of an exemplary vehicle-to-everything (V2X) system in accordance with some aspects of the present disclosure.

Fig. 13 illustrates a time-frequency grid depicting an example resource pool for side-link communications in accordance with some aspects of the present disclosure.

Fig. 14 depicts an example side-link feedback channel resource pool map in accordance with aspects of the present disclosure.

Fig. 15 depicts example resource allocations in an unlicensed spectrum, in accordance with aspects of the present disclosure.

Fig. 16 depicts an example timeline for Channel Occupancy Time (COT) sharing, in accordance with some aspects of the present disclosure.

Fig. 17A and 17B provide examples of COT release due to an unused physical side uplink frequency channel (PSFCH) time slot, in accordance with some aspects of the present disclosure.

Fig. 18 is a flowchart depicting example operations for wireless communication by a first User Equipment (UE), in accordance with aspects of the present disclosure.

Fig. 19 depicts a communication device that may include various components configured to perform operations for the techniques disclosed herein, in accordance with some aspects of the present disclosure.

Detailed Description

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

The present disclosure relates generally 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, among other communication networks. As described herein, the terms "network" and "system" may be used interchangeably.

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, and the like. UTRA, E-UTRA and GSM are parts of Universal Mobile Telecommunications System (UMTS). In particular, long Term Evolution (LTE) is a release of UMTS using E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents provided from an organization named "third generation partnership project" (3 GPP), and cdma2000 is described in documents from an organization named "third generation partnership project 2" (3 GPP 2). These various radio technologies and standards are known or are being developed. For example, the third generation partnership project (3 GPP) is a collaboration between groups of telecommunications associations, which is intended to define the globally applicable third generation (3G) mobile phone specifications. 3GPP Long Term Evolution (LTE) is a 3GPP project aimed at improving the UMTS mobile telephony standard. The 3GPP may define specifications for next generation mobile networks, mobile systems, and mobile devices. The present disclosure relates to evolution of wireless technologies from LTE, 4G, 5G, NR and beyond that which share access to wireless spectrum between networks using new and different radio access technologies or sets of radio air interfaces.

In particular, 5G networks contemplate different deployments, different spectrum, and different services and devices that may be implemented using an OFDM-based unified air interface. To achieve these goals, further enhancements to LTE and LTE-a are considered in addition to developing new radio technologies for 5G NR networks. The 5G NR will be able to scale to provide the following coverage (1) to have ultra-high density (e.g., -1M node/km) ² ) Ultra-low complexity (e.g., tens of bits/second), ultra-low energy consumption (e.g., battery life of-tens of years), deep covered large-scale internet of things (IoT) capable of reaching challenging locations; (2) Including having strong security for protecting sensitive personal, financial, or confidential information, ultra-high reliability (e.g., -99.9999% reliability), ultra-low latency (e.g., -1 ms), and mission critical control of users with a wide range of mobility or lack of mobility; and (3) enhanced mobile broadband including very high capacity (e.g., -10 Tbps/km) ² ) Extremely high data rates (e.g., multiple Gbps rates, user experience rates of 100+mbps), and depth perception with advanced discovery and optimization.

The 5G NR communication system may be implemented to use an optimized OFDM-based waveform with a scalable digital scheme and Transmission Time Intervals (TTIs). Additional features may also include having a common, flexible framework to effectively multiplex services and features in a dynamic, low-latency Time Division Duplex (TDD)/Frequency Division Duplex (FDD) design; 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. Scalability of the digital scheme in 5G NR can effectively address operating various services across different spectrums and different deployments. For example, in various outdoor and macro coverage deployments with less than 3GHz FDD/TDD implementations, the subcarrier spacing may occur at 15kHz, e.g., over a Bandwidth (BW) of 5, 10, 20MHz, etc. For other various outdoor and small cell coverage deployments of TDD greater than 3GHz, the subcarrier spacing may occur at 30kHz on 80/100MHz BW. For other various indoor wideband implementations, using TDD on the unlicensed portion of the 5GHz band, the subcarrier spacing may occur at 60kHz on 160MHz BW. Finally, for various deployments where the millimeter wave component is used for transmission at 28GHz TDD, the subcarrier spacing may occur at 120kHz over 500MHz BW.

The scalable digital scheme of 5G NR facilitates scalable TTI for different latency and quality of service (QoS) requirements. For example, shorter TTIs may be used for low latency and high reliability, while longer TTIs may be used for higher spectral efficiency. Efficient multiplexing of long and short TTIs allows transmissions to start at symbol boundaries. The 5G NR also envisages a self-contained integrated subframe design in which the UL/downlink schedules information, data and acknowledgements in the same subframe. The self-contained integrated subframes support communication in an adaptive UL/downlink that is unlicensed or contention-based shared spectrum, which can be flexibly configured on a per-cell basis to dynamically switch between UL and downlink to meet current traffic demands.

Various other aspects and features of the disclosure are described further below. It should be apparent that the teachings herein may be embodied in a wide variety of forms and that any specific structure, function, or both being disclosed herein is merely representative and not limiting. Based on the teachings herein one of ordinary skill in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspect and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. Further, such an apparatus may be implemented or such a method may be practiced using other structures, functions, or structures and functions that are either different from or in addition to one or more of the aspects set forth herein. For example, the methods may be implemented as part of a system, apparatus, device, and/or as instructions stored on a computer-readable medium for execution on a processor or computer. Furthermore, an aspect may comprise at least one element of the claims.

Side-uplink communication refers to communication between user equipment devices (UEs) without tunneling through a Base Station (BS) and/or core network. The sidelink communications may be communicated over a Physical Sidelink Control Channel (PSCCH) and a Physical Sidelink Shared Channel (PSSCH). PSCCH and PSSCH are similar to a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH) in Downlink (DL) communications between a BS and a UE. For example, the PSCCH may carry side-link control information (SCI), and the PSSCH may carry side-link data (e.g., user data). Each PSCCH is associated with a corresponding PSCCH, where SCIs in the PSCCH may carry reservation and/or scheduling information for side-link data transmissions in the associated PSCCH. In some implementations, the SCIs in the PSCCH may be referred to as SCI portion 1 (SCI-1), and additional SCIs, which may be referred to as SCI portion 2 (SCI-2), may be carried in the PSSCH. SCI-2 may include control information (e.g., transmission parameters, modulation Coding Scheme (MCS)) more specific to the data carriers in the PSSCH. Examples for side-link communications may include V2X, enhanced mobile broadband (emmbb), industrial internet of things (IIoT), and/or NR-lite.

As used herein, the term "sidelink UE" may refer to a user equipment device that performs device-to-device or other types of communications with another user equipment device independently of any tunnels through a BS (e.g., a gNB) and/or an associated core network. As used herein, the term "sidelink transmitting UE" may refer to a user equipment device performing sidelink transmitting operations. As used herein, the term "sidelink receiving UE" may refer to a user equipment device performing sidelink receiving operations. The sidelink UE may operate as a transmitting sidelink UE at one time and as a receiving sidelink UE at another time.

As used herein, the term "initiating UE" may refer to a user equipment device that initiates or acquires a Channel Occupation Time (COT) for side-link communications in a shared radio frequency band (e.g., in a shared spectrum or an unlicensed spectrum). For example, the initiating UE may perform Clear Channel Assessment (CCA) or category 4 (CAT 4) Listen Before Talk (LBT) in the shared radio frequency spectrum band to contend for or acquire the COT. Once over LBT (indicating that the channel is idle for transmission), the initiating UE may send a side-uplink transmission during the acquired COT. As used herein, the term "responding UE" may refer to a user equipment device that responds to a side-uplink transmission sent by any initiating UE. The side-uplink UE may operate as an initiating UE at one time and as a responding UE at another time.

For the side-links on the licensed spectrum, the NR supports two Radio Resource Allocation (RRA) modes: mode 1RRA and mode 2RRA. The mode 1RRA supports network controlled RRAs that can be used for side-link communications in coverage. For example, a serving BS (e.g., a gNB) may determine radio resources on behalf of a sidelink UE and send an indication of the radio resources to the sidelink UE. In some aspects, the serving BS grants side-downlink transmissions with Downlink Control Information (DCI). However, for this mode there is significant base station involvement and only operation is possible when the side-link UE is located within the coverage area of the serving BS. The mode 2RRA supports autonomous RRAs that can be used for out-of-coverage or partially-coverage side-link UEs. For example, the serving BS may configure the sidelink UE (e.g., within the coverage of the serving BS) to have a sidelink resource pool that may be used for sidelink when the sidelink UE is outside the coverage of the serving BS. In 5G NR, a side uplink channel in which two UEs can directly communicate with each other may also be referred to as a PC5 interface.

The side-link communication may be in unicast mode, multicast mode or broadcast mode. Further, hybrid automatic repeat request (HARQ) may be applied to unicast or multicast side uplink communications to improve transmission reliability. For unicast communications, 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 the data from the sidelink transmission, the sidelink receiving UE sends an ACK. Conversely, if the sidelink receiving UE fails to decode the data from the sidelink transmission, the sidelink receiving UE sends a NACK. Upon receiving the NACK, the transmitting-side uplink UE may retransmit the data. For broadcast communications, a sidelink transmitting UE may transmit sidelink transmissions 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 transmissions.

Multicast side uplink communications may be connection-based or connectionless. The connection-based multicast side-link communication is destined for a particular set of UEs, e.g., each UE belongs to a group identified by a group Identifier (ID) and is known to the side-link transmitting UE. In this way, 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. For connectionless multicast side-link communications, the group of UEs that can receive the multicast transmission may be unknown to the side-link transmitting UE. In this way, the sidelink transmitting UE may request NACK feedback only for UEs that receive the multicast sidelink communication (successfully decoding the presence of SCI) but fail to decode the information data from the multicast sidelink communication. In some cases, the side-uplink transmitting UE may also assign the same NACK-only feedback resources to all UEs that fail data decoding.

Providing side-link services such as device-to-device (D2D), vehicle-to-vehicle (V2V), vehicle-to-everything (V2X) and/or cellular vehicle-to-everything (C-V2X) communication over a dedicated spectrum or licensed spectrum is relatively simple because channel access in the dedicated spectrum or licensed spectrum is guaranteed. NR unlicensed (NR-U) may bring benefits to side-link services, such as offloading side-link traffic to unlicensed spectrum for free. However, channel access in the shared spectrum or unlicensed spectrum is not guaranteed. Thus, in order to provide side-link services over a shared spectrum or unlicensed spectrum, side-link user equipment devices (UEs) are required to contend for channel access in the spectrum, e.g., via Clear Channel Assessment (CCA) and/or listen-before-talk (LBT) procedures.

LBT may be based on Energy Detection (ED) or signal detection. For energy detection based LBT, the LBT result passes when the signal energy measured from the channel is below a threshold. Conversely, when the signal energy measured from the channel exceeds a threshold, the LBT result fails. For LBT based on signal detection, when a channel reservation signal (e.g., a predetermined preamble signal) is not detected in the channel, the LBT result passes. In addition, LBT may be in multiple modes. For example, the LBT pattern may be a category 4 (CAT 4) LBT, a category 2 (CAT 2) LBT, or a category 1 (CAT 1) LBT. CAT1 LBT refers to a no LBT mode in which LBT is not performed prior to transmission. CAT2 LBT refers to LBT without a random backoff period. For example, the transmitting node may determine channel measurements in time intervals and determine whether a channel is available based on a comparison of the channel measurements to an ED threshold. CAT4 LBT refers to LBT with random back-off and variable Contention Window (CW). For example, the transmitting node may extract a random number and fall back for a duration based on the extracted random number having a particular time unit.

In some aspects, the initiating UE may contend for the COT in the shared radio frequency band by performing CCA or CAT4 LBT. Once through CCA or CAT4 LBT (indicating that the channel is cleared for transmission), the initiating UE may send a side-uplink transmission to one or more side-uplink receiving UEs during the COT. In some sidelink use cases (e.g., for V2X), the sidelink data traffic may include small size or short data bursts (e.g., having several bytes to tens of kilobytes of information data). In some aspects, the duration of the COT may depend on a provision imposed by a supervisor of the particular deployment or shared radio frequency band, which may be in a range from about 2ms to about 10ms (e.g., which may correspond to from about 4 time slots to about 20 time slots in NR CV2X with a 30kHz subcarrier spacing (SCS). Thus, in some cases, a side-link transmission with a small-sized data burst may not occupy the entire duration of the COT. Accordingly, it may be desirable to share the remaining duration of the COT with the receiving UE or other UEs, rather than leave the remaining COT unused. In some cases, the initiating UE may include COT-related information (such as, but not limited to, the duration of the COT) in its transmission so that the receiving UE may use the information to share/utilize the COT. For example, the initiating UE may send the PSCCH after initiating the COT, and the SCI in the PSCCH may include COT related information. As another example, the initiating UE may send the PSCCH or PSSCH after initiating the COT, and SCI-1 in the PSCCH or SCI-2 in the PSSCH may include COT-related information, respectively. In some cases, after receiving SCI (SCI-1 or SCI-2), when a receiving UE or other UE transmits during a COT initiated by a COT initiating UE, the receiving UE or other UE may or may not perform CAT2 LBT, which may be advantageous because CAT2 LBT or no LBT has less uncertainty in accessing the channel.

In some aspects, the provision may also specify: the COT in the shared/unlicensed band must be used in an at least substantially continuous manner so that the COT is not considered to be released until its expiration. That is, these regulations impose: after the COT is initiated by the COT-initiated UE and used for transmission, the remaining duration of the COT must be used for transmission without significant gaps (e.g., without gaps greater than 25 μs, 16 μs, 9 μs, etc.) between consecutive transmissions; otherwise, the COT may be considered to be released before its expiration, and other UEs may have to contend for a new COT in the unlicensed radio frequency spectrum band for its upcoming transmission. In NR-U, each UE is served by one serving BS, and the serving BS may manage scheduling of at least substantially back-to-back UE/BS transmissions in the COT initiated by the UE or the serving BS, so that the COT may not be considered as released until expiration of the COT. Furthermore, in some cases, such as NR-side uplink operations (such as C-V2X operations) supporting PSFCH transmission, due to the slot structure used to support PSFCH transmission, transmission gaps may occur even in the cog where there is back-to-back PSSCH transmission. For example, in C-V2X, C-V2X slots may be used for PSFCH transmissions, and even if PSSCH transmissions are sent on these slots within the COT, transmission gaps may occur in the COT (if no PSFCH transmissions are present in the slots), which may result in the COT being released due to (PSFCH) gaps in the COT.

Thus, in some aspects, in order for a first UE to share a portion of the COT initiated by a second UE (i.e., a COT-initiated UE) in a mode 2-side uplink operation supporting PSFCH transmissions, the UE may detect the PSFCH transmissions during the COT and infer that the PSFCH transmissions were sent via C-V2X slots within the COT, which allows the UE to ascertain that the COT has not been released due to unused gaps in the COT and that the COT is therefore available for sharing with the UE. For example, the COT-initiating UE may initiate the COT as discussed above and send a PSSCH transmission configured to trigger a PSFCH transmission from one or more second UEs receiving the PSSCH transmission. For example, the PSSCH transmission may include an explicit or implicit request for a PSFCH transmission from the receiving UE. In such a case, if a third UE seeking to share a portion of the COT fails to detect a PSFCH transmission during the COT, the third UE may infer that a portion of the slot for the PSFCH transmission has not been used, and thus, the COT may be considered released due to the provision of at least nearly continuous or back-to-back transmissions being enforced within the COT. On the other hand, in some cases, the third UE may detect the PSFCH transmission during the COT and may infer that the COT has not been released and is thus available for the third UE to share and utilize, as discussed above. However, this inference may be inaccurate because, although the third UE detects the PSFCH transmission during the COT, the detected PSFCH transmission may not be part of the COT and the conclusion that the third UE is still available for sharing with respect to the COT may be erroneous. Thus, there is a need for methods and systems that: the methods and systems allow a UE seeking to share or utilize a COT initiated by a COT-initiated UE in a mode 2-side uplink operation supporting PSFCH transmissions to infer whether the detected PSFCH activity corresponds to a COT of interest (e.g., a COT initiated by a COT-initiated UE), i.e., whether the detected PSFCH transmission sent during the COT is actually part of the COT or is sent using the COT.

Further, in some aspects, a first UE seeking to share/utilize a COT initiated by a second UE (i.e., a COT initiated UE) may have to be within the maximum spatial range of the COT initiated UE to be allowed to share/use the COT. This is because, for example, the interference at and experienced by the first UE when the COT-initiating UE initiates the COT may be different from the interference at and experienced by the COT-initiating UE. In other words, a successful LBT performed by the COT-initiated UE to obtain the COT may not be an indication to the first UE that the first UE may share and utilize the COT, which may be remote from the COT-initiated UE and experience different signal interference than the COT-initiated UE in some cases. In some cases, the maximum distance or spatial range from the COT-initiated UE (within which the first UE must be located to be allowed to share and use the COT) may be preconfigured, i.e., provided by the network to the UE via signaling (e.g., the COT-initiated UE, the first UE, etc.). In some cases, the UE may have a default configuration of maximum distance or spatial range (e.g., for use when the UE is outside the network). As used herein, the term "in-range UE" as used with reference to a COT-initiated UE may refer to a UE that is within the maximum spatial range of the COT-initiated UE. Furthermore, as used herein, the term "out-of-range UE" as used with reference to a COT-initiated UE may refer to a UE that is outside of the maximum spatial range of the COT-initiated UE.

In some cases, the COT-initiated UE may send a transmission within the COT after initiating the COT, and the transmission may include location data of the COT-initiated UE. For example, the COT-initiated UE may send the PSCCH after initiating the COT, and the SCI in the PSCCH may include location data of the COT-initiated UE. As another example, the COT-initiated UE may send the PSCCH or PSSCH after initiating the COT, and SCI-1 in the PSCCH or SCI-2 in the PSSCH may include location data of the COT-initiated UE, respectively. In such a case, a UE seeking to share the COT (e.g., the first UE described above) may receive the SCI (SCI-1 or SCI-2) and determine whether it is an "in-range UE" (e.g., whether the UE is located within a maximum distance or spatial range from the COT-initiating UE to be allowed to share and utilize the COT (e.g., and begin to share and utilize the COT if the UE is in fact within the maximum range)). In some aspects, a second UE that detects a PSFCH transmission within or during the COT may receive the SCI (SCI-1 or SCI-2) and use the location data of the COT-initiated UE to infer or determine whether the PSFCH is part of the COT (i.e., sent using the COT), and/or whether the UE sending the PSFCH transmission is an "in-range UE" for the COT-initiated UE.

Some aspects of the present disclosure disclose methods, systems, and apparatus for Channel Occupation Time (COT) sharing of side-link communications in unlicensed bands, particularly mode 2 side-link operation supporting PSFCH transmissions. In some aspects, a UE tracking the activity of a COT seeking to share and utilize a portion of the COT may measure a Reference Signal Received Power (RSRP) of a PSFCH transmission sent during or within the COT, and may assume or infer that the PSFCH transmission is a portion of the COT (e.g., the PSFCH transmission is sent using the COT) if the measured RSRP value of the PSFCH transmission is greater than a threshold RSRP. In some cases, the UE may make this assumption because it may be statistically expected that PSFCH transmissions from in-range UEs have larger RSRP values than those from out-of-range UEs. Thus, when the measured RSRP value exceeds the threshold RSRP value, UEs seeking to share and utilize the COT may assume that the PSFCH transmission is sent using the COT (e.g., by a UE within the range of the maximum spatial range of the COT-initiated UE), and thus, the COT has not been released due to unused gaps in the COT. In such a case, the UE tracking the activity of the COT may next continue to share and utilize a portion of the COT.

In some aspects, the COT initiating UE or another UE allowed to utilize the COT may send a transmission with a request for feedback for the transmission using the COT. For example, the COT initiating UE or another UE may use the COT to send a PSSCH transmission that includes a request for a PSFCH. In such a case, if another UE (e.g., another UE seeking to share and utilize a portion of the COT) detects a PSFCH transmitted within or during the COT in response to the PSSCH transmission, the UE may assume or infer that the PSFCH is a portion of the COT, i.e., that the PSFCH is transmitted using the COT (e.g., by a UE within a range of the maximum spatial range of the COT-initiating UE or another UE permitted to utilize the COT). In some cases, a UE seeking to share and utilize a portion of the COT may make this assumption because PSFCH transmissions sent in response to PSSCH transmissions are more likely to originate from a UE that is an in-range UE relative to the COT-initiated UE (e.g., and/or another UE allowed to utilize the COT), and thus, the PSFCH is sent using the COT that was initiated by the COT-initiated UE and used to send the PSSCH. In such a case, a UE seeking to share and utilize a portion of the COT may infer that the COT has not been released due to unused gaps in the COT, and may continue to share and utilize the portion of the COT.

In some aspects, the PSSCH transmission from the COT-initiated UE may be a multicast option-1 PSSCH transmission. In some cases, the multicast option-1 PSSCH transmission may not be part of the COT initiated by the COT-initiated UE. For example, the multicast option-1 PSSCH transmission may be transmitted using a different COT that has ended. In such a case, if a UE tracking the COT activity seeking to share and utilize a portion of the COT initiated by the COT-initiated UE detects a NACK transmission corresponding to the multicast option-1 PSSCH transmission, the UE may assume or infer that the NACK is a portion of the COT, i.e., that the NACK is sent using the COT (e.g., by a UE within a maximum spatial range of the COT-initiated UE). In some cases, the UE may make this assumption because only NACK feedback may be limited to UEs within a specific range of the COT-initiated UE. Thus, the UE may infer or assume that the NACK was sent by an in-range UE (e.g., in-range for the COT-initiated UE) using the COT, and as a result, the COT has not been released due to unused gaps in the COT. In such a case, the UE tracking the activity of the COT may then share and utilize a portion of the COT.

In some cases, if the feedback range of the UE requesting only NACK PSFCH (i.e., the UE transmitting the multicast option 1PSSCH transmission) is less than the threshold feedback range, the UE seeking to share and utilize a portion of the COT may infer that only NACK transmissions are being transmitted by nearby in-range UEs. Such a limitation may prevent UEs seeking to share and utilize a portion of the COT from erroneously: UEs outside the maximum spatial range of COT are actually within range for COT and are allowed to share and use COT (e.g., when the feedback range of UEs requesting only NACK PSFCH is much greater than the maximum spatial range of COT). In some cases, the threshold feedback range may be approximately equal to (e.g., within 10% of) the maximum spatial range of the COT.

Aspects of the present disclosure may provide several benefits. For example, some aspects allow a UE that tracks the activity of a COT seeking to share and utilize a portion of the COT to infer or determine whether a PSFCH transmission corresponds to or is part of the COT (e.g., whether the PSFCH transmission is sent using the COT), which in turn allows the UE to avoid blindly or unnecessarily assuming that the COT has been released, thereby improving the efficiency of side-link communications. Furthermore, side-link COT sharing in the unlicensed band is improved, because the UE may access portions of the COT that might otherwise be released, because provision is made to force at least near-continuous transmissions within the COT so that the COT remains active and is not considered to be released.

Fig. 1 illustrates a wireless communication network 100 in accordance with some aspects of the present disclosure. Network 100 may be a 5G network. The network 100 includes a plurality of Base Stations (BSs) 105 (labeled 105a, 105b, 105c, 105d, 105e, and 105f, respectively) and other network entities. BS 105 may be a station in communication with UEs 115 (labeled 115a, 115B, 115c, 115d, 115e, 115f, 115g, 115h, and 115k, respectively) and may also be referred to as an evolved node B (eNB), a next generation eNB (gNB), an access point, and the like. Each BS 105 may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to this particular geographic coverage area of BS 105 and/or a BS subsystem serving the coverage area, depending on the context in which the term is used.

BS 105 may provide communication coverage for a macrocell or a small cell (such as a pico cell or a femto cell) and/or other types of cells. A macro cell typically covers a relatively large geographical area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription with the network provider. A small cell (such as a pico cell) will typically cover a relatively small geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a femto cell, will also typically cover a relatively small geographic area (e.g., a residence) and may provide limited access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs of users in a home, etc.) in addition to unrestricted access. The BS of a macro cell may be referred to as a macro BS. The BS of 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 conventional macro BSs, and BSs 105a-105c may be macro BSs that enable one of three-dimensional (3D), full-dimensional (FD), or massive MIMO. BSs 105a-105c may utilize their higher dimensional MIMO capabilities to employ 3D beamforming in elevation and azimuth beamforming to increase coverage and capacity. 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 more (e.g., two, three, four, etc.) cells.

The network 100 may support synchronous or asynchronous operation. For synchronous operation, BSs may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, BSs may have different frame timing, and transmissions from different BSs may not be aligned in time.

The UEs 115 are dispersed throughout the wireless network 100, and each UE 115 may be fixed or mobile. The UE 115 may also be referred to as a terminal, mobile station, subscriber unit, station, etc. The UE 115 may be a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless telephone, a Wireless Local Loop (WLL) station, etc. In one aspect, the UE 115 may be a device that includes a Universal Integrated Circuit Card (UICC). In another aspect, the UE may be a device that does not include a UICC. In some aspects, UEs 115 that do not include UICCs may also be referred to as IoT devices or internet of everything (IoE) devices. UEs 115a-115d are examples of mobile smart phone type devices that access network 100. UE 115 may also be a machine specifically configured for connection communications including Machine Type Communications (MTC), enhanced MTC (eMTC), narrowband IoT (NB-IoT), and the like. UEs 115e-115h are examples of various machines configured for communication with access network 100. UEs 115i-115k are examples of vehicles equipped with wireless communication devices configured for communication to access network 100. The UE 115 may be capable of communicating with any type of BS, whether macro BS, small cell, or the like. In fig. 1, a lightning sphere (e.g., a communication link) indicates a wireless transmission between the UE 115 and the serving BS 105 (which is a BS designated to serve the UE 115 on the Downlink (DL) and/or Uplink (UL)), a desired transmission between BSs 105, a backhaul transmission between BSs, or a side-downlink transmission between UEs 115.

In operation, BSs 105a-105c may serve UEs 115a and 115b using 3D beamforming and a collaborative space technique, such as coordinated multipoint (CoMP) or multi-connectivity. The macro BS 105d may perform backhaul communications with BSs 105a-105c and the small cell BS 105 f. The macro BS 105d may also transmit multicast services subscribed to and received by UEs 115c and 115 d. Such multicast services may include mobile televisions or streaming video, or may include other services for providing community information, such as weather emergencies or alerts, such as amber alerts or gray alerts.

BS 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, for example, an example of a gNB or Access Node Controller (ANC)) may interface with the core network over a backhaul link (e.g., NG-C, NG-U, etc.), and may perform radio configuration and scheduling for communication with the UEs 115. In various examples, BSs 105 may communicate with each other directly or indirectly (e.g., through a core network) over a backhaul link (e.g., X1, X2, etc.), which may be a wired or wireless communication link.

The network 100 may also utilize ultra-reliable and redundant links for mission critical devices (such as the UE 115e, which may be a drone) to support mission critical communications. The redundant communication links with UE 115e may include links from macro BSs 105d and 105e, as well as links from small cell BS 105 f. 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 through network 100 directly with BSs, such as small cell BS 105f and macro BS 105e, or in a multi-step long configuration by communicating temperature measurement information to smart meter UE 115g with another user device, such as UE 115f, relaying its information to the network, and then reporting the temperature measurement information to the network through small cell BS 105 f. 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, the UE 115j, or the UE 115k and other UEs 115, and/or vehicle-to-infrastructure (V2I) communications between the UE 115I, the UE 115j, or the UE 115k and the BS 105.

In some embodiments, network 100 communicates using OFDM-based waveforms. An OFDM-based system may divide the system BW into a plurality (K) of orthogonal subcarriers, which are also commonly referred to as subcarriers, tones, bins, etc. Each subcarrier may be modulated with data. In some examples, 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 divided into sub-bands. In other examples, the subcarrier spacing and/or the duration of the TTI may be scalable.

In some aspects, BS 105 may assign or schedule transmission resources (e.g., in the form of time-frequency Resource Blocks (RBs)) for Downlink (DL) and Uplink (UL) transmissions in network 100. DL refers to a transmission direction from BS 105 to UE 115, and UL refers to a transmission direction from UE 115 to BS 105. The communication may be in the form of a radio frame. A radio frame may be divided into a plurality (e.g., about 10) subframes or slots. Each time slot may be further divided into mini-time slots. In FDD mode, simultaneous UL and DL transmissions may occur in different frequency bands. For example, each subframe includes UL subframes in the UL band and DL subframes in the DL band. In TDD mode, UL and DL transmissions occur at different time periods using the same frequency band. For example, one subset of subframes in a radio frame (e.g., DL subframes) may be used for DL transmissions, while another subset of subframes in a radio frame (e.g., UL subframes) may be used for UL transmissions.

The DL subframe and the UL subframe may be further divided into several regions. For example, each DL or UL subframe may have a predefined region for transmitting reference signals, control information, and data. The reference signal is a predetermined signal that facilitates communication between the BS 105 and the UE 115. For example, the reference signal may have a particular pilot pattern or structure in which pilot tones may span the BW or band of operation, each pilot tone being located at a predefined time and a predefined frequency. For example, BS 105 may transmit cell-specific reference signals (CRSs) and/or channel state information-reference signals (CSI-RSs) to enable UE 115 to estimate DL channels. Similarly, UE 115 may transmit Sounding Reference Signals (SRS) to enable BS 105 to estimate UL channels. The control information may include resource assignments and protocol control. The data may include protocol data and/or operational data. In some aspects, BS 105 and UE 115 may communicate using self-contained subframes. The self-contained subframe may include a portion for DL communication and a portion for UL communication. The self-contained subframes may be DL-centric or UL-centric. DL-centric sub-frames may comprise a longer duration for DL communication than for UL communication. UL-centric subframes may include a longer duration for UL communication than for DL communication.

In some aspects, network 100 may be an NR network deployed over a licensed spectrum. BS 105 may transmit synchronization signals (e.g., including a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS)) in network 100 to facilitate synchronization. BS 105 may broadcast system information associated with network 100, including, for example, a Master Information Block (MIB), remaining system information (RMSI), and Other System Information (OSI), to facilitate initial network access. In some examples, BS 105 may broadcast PSS, SSS, and/or MIB in the form of Synchronization Signal Blocks (SSBs) on a Physical Broadcast Channel (PBCH), and may broadcast RMSI and/or OSI on a Physical Downlink Shared Channel (PDSCH).

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

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 RMSI and/or OSI. After decoding the MIB, the UE 115 may receive RMSI and/or OSI. RMSI and/or OSI may include Radio Resource Control (RRC) information related to a Random Access Channel (RACH) procedure, paging, control resource set for Physical Downlink Control Channel (PDCCH) monitoring (CORESET), physical UL Control Channel (PUCCH), physical UL Shared Channel (PUSCH), power control, and SRS.

After obtaining 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), timing Advance (TA) information, UL grant, temporary cell radio network temporary identifier (C-RNTI), and/or a back-off indicator corresponding to the random access preamble. After receiving the random access response, the UE 115 may send a connection request to the BS 105, and the BS 105 may respond with the connection response. The connection response may indicate a contention resolution scheme. In some examples, the random access preamble, RAR, connection request, and connection response may be referred to as message 1 (MSG 1), message 2 (MSG 2), message 3 (MSG 3), and message 4 (MSG 4), respectively. In some examples, the random access procedure may be a two-step random access procedure in which the UE 115 may send the random access preamble and the connection request in a single transmission, and the BS 105 may respond by sending 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).

After establishing the connection, the UE 115 and BS 105 may enter a normal operating state in which operating data may be exchanged. For example, BS 105 may schedule UE 115 for UL and/or DL communications. BS 105 may send UL and/or DL scheduling grants to UE 115 via PDCCH. The BS 105 may transmit DL communication signals to the UE 115 via the PDSCH according to the DL scheduling grant. The UE 115 may transmit UL communication signals to the BS 105 via PUSCH and/or PUCCH according to UL scheduling grants. This connection may be referred to as an RRC connection. The UE 115 is in an RRC connected state when the UE 115 is actively exchanging data with the BS 105.

In one example, after establishing a connection with BS 105, UE 115 may initiate an initial network attach procedure with network 100. BS 105 may coordinate with various network entities or fifth generation core (5 GC) entities, such as Access and Mobility Functions (AMFs), serving Gateways (SGWs), and/or packet data network gateways (PGWs), to complete the network attachment process. For example, BS 105 may coordinate with network entities in 5GC to identify UEs, authenticate UEs, and/or authorize UEs to transmit and/or receive data in network 100. Further, the AMF may assign a set of Tracking Areas (TAs) to the UE. Once the network attach procedure is successful, a context is established in the AMF for the UE 115. After successful attachment to the network, the UE 115 may move around the current TA. For Tracking Area Updates (TAU), the BS 105 may request that the UE 115 periodically update the network 100 with the location of the UE 115. Alternatively, the UE 115 may report the location of the UE 115 to the network 100 only when a new TA is entered. TAU allows network 100 to quickly locate UE 115 and page UE 115 when an incoming data packet or call is received for UE 115.

In some aspects, BS 105 may communicate with UE 115 using hybrid automatic repeat request (HARQ) techniques to improve communication reliability, e.g., to provide URLLC services. BS 105 may schedule UE 115 for PDSCH communication by sending DL grants in the PDCCH. The BS 105 may transmit DL data packets to the UE 115 according to the schedule in the PDSCH. DL data packets may be transmitted in the form of Transport Blocks (TBs). If the UE 115 successfully decodes the DL data packet, the UE 115 may send a HARQ Acknowledgement (ACK) to the BS 105. In contrast, if the UE 115 fails to successfully decode the DL transmission, the UE 115 may send a HARQ Negative Acknowledgement (NACK) to the BS 105. Upon receiving the HARQ NACK from the UE 115, the BS 105 may retransmit the DL data packet to the UE 115. The retransmission may include the same encoded version of the DL data as the initial transmission. Alternatively, the retransmission may comprise a different encoded version of the DL data than the initial transmission. The UE 115 may apply soft combining to combine the encoded data received from the initial transmission and the retransmission for decoding. BS 105 and UE 115 may also apply HARQ to UL communications using a mechanism substantially similar to DL HARQ.

In some aspects, the network 100 may operate on a system BW or a Component Carrier (CC) BW. Network 100 may divide system BW into multiple BWP (e.g., portions). BS 105 may dynamically allocate UEs 115 to operate on a certain BWP (e.g., a certain portion of the system BW). The allocated BWP may be referred to as an active BWP. UE 115 may monitor active BWP to obtain signaling information from BS 105. BS 105 may schedule UE 115 for UL communication or DL communication in the active BWP. In some aspects, BS 105 may allocate a pair of BWP within a CC to UE 115 for UL and DL communications. For example, the BWP pair may include one BWP for UL communication and one BWP for DL communication.

In some aspects, network 100 may operate on a shared channel, which may include a shared frequency band or an unlicensed frequency band. For example, network 100 may be an NR unlicensed (NR-U) network operating on an unlicensed frequency band. In such aspects, BS 105 and UE 115 may be operated by multiple network operating entities. To avoid collisions, BS 105 and UE 115 may employ an LBT procedure for monitoring transmission opportunities (TXOPs) in a shared channel. The wireless communication device may perform LBT in a shared channel. LBT is a channel access scheme that may be used in unlicensed spectrum. When the LBT result is 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., BS 105 or UE 115) may perform LBT before transmitting in a channel. When LBT passes, the transmitting node may continue to transmit. When LBT fails, the transmitting node may refrain from transmitting in the channel. In one example, LBT may be based on energy detection. For example, when the signal energy measured from the channel is below a threshold, the LBT result passes. Conversely, when the signal energy measured from the channel exceeds a threshold, the LBT result is a failure. In another example, LBT may be based on signal detection. For example, when a channel reservation signal (e.g., a predetermined preamble signal) is not detected in the channel, the LBT result is passed. In contrast, when a channel reservation signal is detected in a channel, the LBT result is a failure. The TXOP may also be referred to as a Channel Occupation Time (COT).

In some aspects, the network 100 may provide side-link communications to allow a UE 115 to communicate with another UE 115 without requiring tunneling through the BS 105 and/or the core network as shown in fig. 2. As discussed above, the side-link communications may be communicated over the PSCCH and the PSSCH. For example, the PSCCH may carry SCI and the PSSCH may carry SCI and/or side-link data (e.g., user data). Each PSCCH is associated with a corresponding PSCCH, where SCIs in the PSCCH may carry reservation and/or scheduling information for side-link data transmissions in the associated PSCCH. In some examples, the transmitting side uplink UE 115 may indicate SCI in two phases. In the first stage SCI (which may be referred to as SCI-1), UE 115 may send the SCI in a PSCCH carrying information for resource allocation and decode the second stage SCI. The first stage SCI may include at least one of priority, PSSCH resource allocation, resource reservation period (if enabled), PSSCH DMRS mode (if more than one mode is configured), second stage SCI format (e.g., size of second stage SCI), amount of resources for second stage SCI, number of PSSCH demodulation reference signal (DMRS) ports, modulation and Coding Scheme (MCS), etc. In the second stage SCI (which may be referred to as SCI-2), UE 115 may send the SCI in a PSSCH that carries information for decoding the PSSCH. The second stage SCI may include a 1-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 stage SCI and/or the second stage SCI may include or indicate more or different information than those examples provided. The side-link communications may also communicate over a physical side-link feedback control channel (PSFCH) that indicates an Acknowledgement (ACK) -Negative Acknowledgement (NACK) for a previously transmitted PSSCH.

In some aspects, the side-link communication may be in a unicast mode, a multicast mode, or a broadcast mode, wherein HARQ may be applied to unicast and/or multicast communications. For unicast communications, the sidelink transmitting UE 115 may transmit a sidelink transmission including data to a single sidelink receiving UE 115 and may request HARQ acknowledgement/negative acknowledgement (ACK/NACK) feedback from the sidelink receiving UE 115. If the sidelink receiving UE 115 successfully decodes the data from the sidelink transmission, the sidelink receiving UE 115 sends an ACK. Conversely, if the sidelink receiving UE 115 fails to decode the data from the sidelink transmission, the sidelink receiving UE 115 sends a NACK. Upon receiving the NACK, the side-uplink transmitting UE 115 may retransmit the data. For broadcast communications, the sidelink transmitting UE 115 may transmit a sidelink transmission to a group of sidelink receiving UEs 115 (e.g., 2, 3, 4, 5, 6, or more) in the vicinity of the sidelink transmitting UE 115, and may not request ACK/NACK feedback for the sidelink transmission.

For multicast communications, a sidelink transmitting UE 115 may transmit sidelink transmissions to a group of sidelink receiving UEs 115 (e.g., 2, 3, 4, 5, 6, or more). Multicast communications may have a wide variety of use cases in the side-uplink. As one example, multicast communications may be used in a V2X use case (e.g., vehicle queuing) to indicate that a group of vehicles near an intersection or traffic light is parked at the intersection. In some aspects, the multicast communication may be connection-based, where the group-side uplink receiving UE 115 may be preconfigured as a group identified by a group Identifier (ID). As such, the sidelink receiving UEs 115 in the group are known to the sidelink transmitting UEs 115, and thus the sidelink transmitting UEs 115 may request ACK/NACK feedback from each of the sidelink receiving UEs 115 in the group. In some cases, the sidelink transmitting UE 115 may provide each sidelink receiving UE with different resources (e.g., orthogonal resources) for transmitting ACK/NACK feedback. In some other aspects, the multicast communication may be connectionless, wherein the set of sidelink receiving UEs 115 that may receive the multicast transmission may be unknown to the sidelink transmitting UE 115. In some cases, the set of side-uplink receiving UEs 115 may receive multicast communications based on the area or geographic location of the receiving UE 115. Since the sidelink transmitting UE 115 may not be aware of the receiving sidelink UE 115, the sidelink transmitting UE 115 may request NACK-only feedback (referred to as a multicast option 1 transmission) from the sidelink receiving UE 115. For example, if the sidelink receiving UE detects the presence of an SCI, but fails to decode data (transport blocks) from the sidelink transmission, the sidelink receiving UE 115 may send a NACK. The side-uplink receiving UE 115 may not send an ACK if the data decoding is successful. Multicast option 2 transmission refers to a scenario in which a side-uplink receiving UE sends an ACK if data decoding is successful and a NACK if decoding fails. In some cases, the same resources used to send NACK feedback may be assigned to the side-uplink receiving UE 115. Simultaneous NACK transmissions from multiple side-uplink receiving UEs 115 in the same resource may form a Single Frequency Network (SFN) transmission at the side-uplink transmitting UE 115 (where waveforms of multiple NACK transmissions are combined). Similar to unicast communications, the sidelink transmitting UE 115 may retransmit sidelink data upon receiving a NACK for a connection-based or connectionless multicast transmission.

Fig. 2 is a timing diagram illustrating a radio frame structure 200 in accordance with some aspects of the present disclosure. The radio frame structure 200 may be used for communication by BSs (such as BS 105) and UEs (such as UE 115) in a network (such as network 100). Specifically, 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 unit, and the y-axis represents frequency in some arbitrary unit. The radio frame structure 200 includes a radio frame 201. The duration of the radio frame 201 may vary according to aspects. In one example, the radio frame 201 may have a duration of approximately 10 milliseconds. The radio frame 201 includes M time slots 202, where M may be any suitable positive integer. In one example, M may be about 10.

Each slot 202 includes a plurality of subcarriers 204 in frequency and a plurality of symbols 206 in time. The number of subcarriers 204 and/or the number of symbols 206 in the time slot 202 may vary according to aspects, e.g., based on 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 a plurality of contiguous subcarriers 204 in frequency and a plurality of contiguous symbols 206 in time.

In some aspects, a BS (e.g., BS 105 in fig. 1) may schedule a UE (e.g., UE 115 in fig. 1) for UL and/or DL communications at the time granularity of slot 202 or mini-slot 208. Each time slot 202 may be time-divided into K mini-slots 208. Each mini-slot 208 may include one or more symbols 206. Mini-slots 208 in slot 202 may have a variable length. For example, when slot 202 includes N symbols 206, the length of mini-slot 208 may have a length between one symbol 206 and (N-1) symbols 206. In some aspects, mini-slot 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 the UE with a frequency granularity of Resource Blocks (RBs) 210 (e.g., including approximately 12 subcarriers 204 in 1 symbol, 2 symbols, …, 14 symbols). In some aspects, a UE (e.g., UE 115i of fig. 1) may engage in side-link communication with another UE (e.g., UE 115j of fig. 1) in units of time slots similar to time slot 202, as will be described further below with respect to fig. 4.

Fig. 3 illustrates an example of a wireless communication network 300 that provides side-link communications in accordance with aspects of the present disclosure. Network 300 may correspond to a portion of network 100 and may communicate using radio frame structure 200. While fig. 3 shows one BS 305 and five UEs 315 (shown as 315a, 315b, 315c, 315d, and 315 e) for purposes of simplifying the discussion, it should be appreciated that aspects of the present disclosure may be extended 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). BS 305 and UE 315 may be similar to BS 105 and UE 115, respectively. BS 305 and UE 315 may share the same radio frequency band for communication. In some cases, the radio frequency band may be a licensed band. In some cases, the radio frequency band may be an unlicensed band. In some cases, the radio frequency band may be a frequency range 1 (FR 1) band. In some cases, the radio frequency band may be the FR2 band. In general, the radio frequency band may be any suitable frequency.

In network 300, some of UEs 315 may communicate with each other in peer-to-peer communication. For example, UE 315a may communicate with UE 315b on side-uplink 351, UE 315c may communicate with UE 315d on side-uplink 352 and/or with UE 315e on side-link 354, and UE 315d may communicate with UE 315e on side-uplink 355. The side links 351, 352, 354, and 355 are unicast bi-directional links. In some aspects, UE 315c may also communicate with UE 315d and UE 315e in a multicast mode. Similarly, UE 315d may also communicate with UE 315c and UE 315e in multicast mode. In general, UEs 315c, 315d, 315e may communicate with each other in a unicast mode or a multicast mode.

Some of the UEs 315 may also communicate with the BS 305 in the UL direction and/or DL direction via the communication link 353. For example, UEs 315a, 315b, and 315c are located within coverage area 310 of BS 305 and may therefore communicate with BS 305. UE 315d and UE 315e are outside of coverage area 310 and, therefore, may not communicate directly with BS 305. In some cases, UE 315c may operate as a relay for UE 315d to reach BS 305. In some aspects, some of the UEs 315 are associated with a vehicle (e.g., similar to UEs 115 i-k), and the communications on the sidelines 351 and/or 352 may be C-V2X communications. C-V2X communication may refer to communication between a vehicle and any other wireless communication device in a cellular network.

Fig. 4A and 4B show schematic diagrams illustrating a spatial range of a COT initiated by a COT initiating UE and timing diagrams depicting a side-uplink communication scheme in an unlicensed frequency band, respectively, in accordance with some aspects of the present disclosure. In fig. 5B, the X-axis represents time in CV2X slots. In some aspects, the side-uplink UE 405a may acquire the COT 420 by performing Clear Channel Assessment (CCA) or category 4 (CAT 4) Listen Before Talk (LBT) in an unlicensed or shared radio frequency band. For example, as shown in example timing diagram 415a, side-link UE 405a may perform LBT procedure 445 prior to slot n to obtain COT 420 starting at slot n. In the example timing diagram 415a, the side-uplink UE 405a is shown as having acquired 4 time slots (time slots n 425a, n+1430 a, n+2435a, and n+3440 a), but it will be appreciated that the COT 420 is an illustrative example, and that the COT 420 may have any number of time slots. In example timing diagrams 415b and 415c, the COT 420 is also shown to include time slots n 425b, n+1430 b, n+2435b, and n+3440 b, and time slots n 425c, n+1430 c, n+2435c, and n+3440 c, which correspond to other side-link UEs (e.g., side-link UEs such as 405b, 405c, and 405 d) in communication with the COT originating side-link UE 405a, respectively.

In some aspects, after performing LBT procedure 445 and acquiring COT 420, side-link UE 405a may send transmission 450 using slot n 425a of example timing diagram 415 a. In some cases, the transmission 450 may be a PSCCH/PSSCH transmission and may include COT shared information. For example, the transmission may be a PSCCH transmission that includes SCI with COT shared information, such as, but not limited to, duration of COT 420, location of COT originating side uplink UE 405a, and the like. In some cases, SCI may also include a maximum spatial extent (e.g., first spatial extent 410a or second spatial extent 410 b) of COT 420. The maximum spatial range of the COT 420 may refer to a distance or spatial range from the COT originating side-uplink UE 405a beyond which other side-uplink UEs are not allowed to share or utilize the COT 420. For example, referring to fig. 4A, if the maximum spatial range of the COT 420 initiated by the COT initiation side-link UE 405a is the first spatial range 410a, the side-link UE 405b is allowed to share and use the COT 420 (e.g., starting at slot n+1430 b of the example timing diagram 415 b), while the side-link UE 405c is not allowed to share and use the COT 420 because the side-link UE 405c is outside of the first spatial range 410 a. On the other hand, if the maximum spatial range of the COT 420 initiated by the COT initiation side-link UE 405a is the second spatial range 410b, both the side-link UE 405a and the side-link UE 405b are allowed to share and use the COT 420 since both the side-link UE 405a and the side-link UE 405b are within the second spatial region 410 b. As another example, the COT-initiated transmission 450 may include a PSCCH with SCI-1 and a pscsch with SCI-2, and one or both of SCI-1 and SCI-2 may include the above-described COT sharing information (e.g., duration of the COT 420, location of the COT-initiated side uplink UE 405a, spatial extent of the COT 420, etc.). In some aspects of side-uplink operation, PSCCH transmission and PSSCH transmission may not occur independently. That is, each slot that includes a PSCCH transmission may also include a PSSCH transmission, and vice versa. Thus, in some aspects, the discussion relating to the transmission of a PSCCH or PSSCH transmission may be understood to include both PSCCH and PSSCH transmissions (e.g., and may be referred to as PSCCH transmission, PSSCH transmission, or PSCCH/PSSCH transmission).

In some aspects, the regulatory requirements imposed by regulators of unlicensed or shared radio frequency spectrum bands: in order for the COT 420 not to be considered released after the transmission 450 by the COT-initiated side-uplink UE 405a, the COT 420 may have to be used to send the transmission in a nearly continuous manner. That is, for example, the second transmission must occur almost immediately (e.g., within 25 μs, 16 μs, 9 μs, etc.) via slot n+1430 after sending the COT initiation transmission 450 via slot n 425a of the example timing diagram 415 a; otherwise, the provisioning requirements COT 420 may be considered released (e.g., and thus, a side-link UE seeking to share and use the COT 420 may have to find another COT or initiate its own COT by performing an LBT procedure). In some cases, such requirements apply to the entire COT 420, effectively requiring at least substantially back-to-back transmissions in the COT 420 (e.g., where the gap between transmissions (if any) is no greater than 25 μs, 16 μs, 9 μs, etc.) so that the COT 420 remains active and is not considered released.

Furthermore, as discussed above, any transmissions in the remaining slots of the COT 420 (slot n+1 430, slot n+2 435, and slot n+3 440) may have to come from side-link UEs that are within the maximum spatial range of the COT 420. That is, in order for transmissions occurring in the time slots of the COT 420 to be considered at least substantially back-to-back transmissions, those transmissions must originate from side-uplink UEs located within the spatial range of the COT 420. For example, if the maximum spatial range of the COT 420 is the first spatial range 410a and the side-link UE 405c is transmitting within the time slot n+1 430 (e.g., using a different COT than the COT 420), the COT 420 may be considered released (e.g., shortly after the beginning of the time slot n+1 430) because the side-link UE 405c is located outside of the first spatial range 410 a. In such a case, the side-link UE 405b may not be able to share and utilize the COT 420 for its own transmission (e.g., must use another COT or initiate its own COT by performing LBT). This may be the case where the COT 420 may be considered released and the side-link UE 405b may not be able to use the COT 420 even if the side-link UE 405b detects continuous or at least substantially back-to-back transmission activity since the start of the COT 420, since the detection includes transmission by the out-of-range uplink UE 405 c.

In some aspects, at least a portion of the time slots of the COT 420 (such as time slot n+1430 b shown in example timing diagram 415 b) may be reserved for feedback transmissions configured to be sent in response to previous transmissions, examples of such previous and feedback transmissions including PSCCH or PSSCH transmissions, and PSCFH transmissions, respectively. In some cases, if a PSFCH transmission is not sent on slot n+1430 b reserved for a PSFCH transmission, the COT 420 may be released due to unused gap 465 in the COT (e.g., because there is no PSFCH transmission in the slot reserved for a PSFCH transmission), even when a portion of the same slot n+1430 b is used by the side-link UE for transmission 455. In other words, a side-link UE seeking to share and utilize the COT 420 (e.g., seeking to transmit within time slot n+2 435c of the example timing diagram 415 c) may have to determine whether the PSFCH was actually transmitted within time slot n+1 430b prior to sharing and using time slot n+2 435 of the COT 420 in order to infer that the COT 420 was not released and remains active.

In some aspects, a side-link UE seeking to share and utilize the COT 420 may measure a Reference Signal Received Power (RSRP) of a PSFCH transmission sent during the COT 420 and infer that the PSFCH transmission is part of the COT 420, i.e., the PSFCH transmission is sent using the COT 420, if the measured RSRP exceeds a threshold RSRP value. In other words, if the measured RSRP exceeds the threshold RSRP value, the side-link UE may assume that the PSFCH transmission was sent by another side-link UE within the maximum spatial range of the COT 420 using the COT (e.g., and thus the COT remains active, and the side-link UE is allowed to share and use the COT 420). In some cases, the sidelink UE may infer that the PSFCH transmission was sent by another sidelink UE that is an in-range UE with respect to the COT 420 using the COT, because it may be statistically expected that the PSFCH transmission from the in-range UE has an RSRP value that is greater than the RSRP value of the PSFCH transmission from the out-of-range UE.

In some aspects, the threshold RSRP value may be such that the RSRP of the PSFCH transmission of the side-link UE that is within or outside of the maximum spatial range of the COT 420 is greater than or less than the threshold RSRP value, respectively. In some cases, inferences about PSFCH transmissions being sent by in-range side-link UEs using the COT 420 may allow side-link UEs seeking to share and utilize the COT 420 to ascertain that the COT 420 has not been released and remains active. In such a case, the side-link UE may then continue to access the COT 420 for its own transmission. In some cases, the measured RSRP may be less than a threshold RSRP value, and the side-link UE may then infer that the PSFCH transmitted during the COT (e.g., and whose RSRP was measured by the side-link UE seeking to use the COT 420) may not be part of the COT, i.e., the COT may not have been used to transmit the PSFCH. In such a case, the side-link UE may conclude that the COT may have been released due to unused gaps in the COT and may not continue to access the COT for its own transmission.

As an illustration, if the maximum spatial range of the COT 420 is the first spatial range 410a, the threshold RSRP value may be such that, in some cases, the RSRP value of the PSFCH transmissions from the sidelink UEs (e.g., the in-range sidelink UEs 405b, 405 d) within the first spatial range 410a is greater than the threshold RSRP value, while the RSRP value of the PSFCH transmissions from the sidelink UEs (e.g., such as the out-of-range sidelink UE 405 c) outside the first spatial range 410a is less than the threshold RSRP value. In such an example, if the side-link UE 405b seeking to share and use the COT 420 measures the RSRP of the PSFCH transmissions occurring within the COT 420, the side-link UE 405b may find that the measured RSRP is less than the threshold RSRP value and thus the PSFCH transmissions are not sent using the COT 420, i.e., the PSFCH transmissions are sent by out-of-range UEs that are not allowed to use the COT 420 (e.g., out-of-range with respect to the COT 420). In such a case, the side-link UE 405b seeking to share and use the COT 420 may assume that the COT 420 has been released and does not access the COT 420. On the other hand, if the measured RSRP is greater than the threshold RSRP value, the side-link UE 405b may infer that the PSFCH transmission is sent using the COT 420, i.e., that the PSFCH transmission is sent by an in-range UE (such as the side-link UE 405 d) that is allowed to use the COT 420, and the side-link UE 405b may then access the COT 420. For example, the side-uplink UE 405b may access the COT 420 at time slot n+2 435c for sending the transmission 460.

In some aspects, the threshold RSRP value may be predefined (e.g., in 3GPP specifications). In some aspects, the threshold RSRP value may be calculated by an NR network to which the sidelink UE performing the RSRP measurement is connected and provided to the sidelink UE via its serving BS. In some aspects, the threshold RSRP value may be calculated by a side-link UE performing RSRP measurements of PSFCH transmissions. For example, the side-uplink UE may measure or otherwise obtain an RSRP of an initial transmission (e.g., the COT-initiated transmission 450 for the COT 420) that the COT-initiated UE sent using the COT, and use the RSRP as a reference or benchmark for setting the threshold RSRP value (e.g., the threshold RSRP value may be set approximately 5dB lower than the RSRP of the COT-initiated transmission). As another example, the side-uplink UE may set the threshold RSRP value such that the RSRP values of the PSFCH transmissions from the out-of-range UE and the in-range UE are below and above the threshold RSRP value, respectively.

In some aspects, as described above, a slot of the COT 420 (such as slot n+1430 b shown in example timing diagram 415 b) may be reserved for feedback transmissions configured to be sent in response to previous transmissions, examples of such previous and feedback transmissions including PSCCH/PSSCH transmissions and PSCFH transmissions, respectively. In some cases, the PSCCH/PSCCH transmission may comprise an explicit or implicit request for a PSFCH transmission (e.g., SCI via a PSCCH). For example, the COT initiation transmission 450 sent by the COT initiation UE 405a after acquiring the COT 420 may be a PSCCH/PSSCH transmission that includes an explicit or implicit request (e.g., a PSFCH transmission) for feedback from a side-link UE receiving the PSCCH or PSSCH transmission in response to the PSCCH or PSSCH transmission. As another example, other transmissions using the COT 420 from a side-link UE that has been allowed to access the COT may be PSSCH transmissions that request PSFCH transmissions from the recipient of the PSSCH transmissions. In some cases, the PSCCH or PSSCH transmission may include COT shared information such as, but not limited to, a duration of the COT 420, a location of the COT originating side uplink UE 405a, a spatial range of the COT 420, and the like.

In such a case, if a PSCCH or PSSCH has been received and the side-link UE 405b seeking to share and use the COT 420 detects a PSFCH transmitted during the COT 420, the side-link UE 405b may infer that the PSFCH was transmitted by a nearby in-range side-link UE that is allowed to share and use the COT 420 (i.e., in range with respect to the COT 420), and thus the PSFCH is part of the COT 420 (e.g., transmitted using reserved slot n+1430 b of the COT 420). In some cases, such inference may allow the side-link UE 405b to conclude that the COT 420 has not been released due to unused gaps, and that the COT 420 remains active, in which case the side-link UE 405b may then access the COT to share and for its own transmissions. In some cases, the side-link UE 405b may infer that the PSFCH is transmitted in response to the PSCCH or PSSCH because the side-link UE 405b has also received the PSCCH or PSSCH and knows the type of corresponding PSFCH transmission that may be transmitted in response to the received PSCCH or PSSCH transmission. Further, in some cases, the sidelink UE 405b may determine that the sidelink UE 405b is in range relative to the COT 420 by using the COT shared information sent by the COT initiation transmission 450 and received by the sidelink UE 405 b. For example, the side-link UE 405b may use the location of the COT originating side-link UE 405a and the spatial range of the COT 420 to determine that the side-link UE 405b is within the maximum spatial range of the COT 420.

In some cases, the previous transmission that may trigger the PSFCH transmission may not be sent using the COT 420 (e.g., the previous transmission may be different from the COT-initiated transmission 450), and in some cases, the previous transmission may be sent using the COT 420. An example of such a prior transmission is a multicast option 1PSSCH transmission sent via a slot that is not part of the COT 420. For example, the multicast option 1PSSCH transmission may have been transmitted by the side-link UE using a COT other than COT 420 and which has ended. In some aspects, such a multicast option 1PSSCH transmission may include a request for NACK-only feedback (e.g., NACK PSFCH only) in the form of PSFCH for a side-link UE that receives the multicast option 1PSSCH transmission. In some cases, the previous transmission or another transmission by the side-link UE that initiated the COT 420 may include COT shared information, such as, but not limited to, a duration of the COT 420, a location of the COT-initiated side-link UE 405a, a spatial range of the COT 420, and the like.

In such a case, if the side-link UE 405b that has received the multicast option 1PSSCH transmission and is seeking to share and use the COT 420 detects only NACK PSFCH transmitted during the COT 420, the side-link UE 405b may infer that only NACK PSFCH was transmitted using the COT 420 by a nearby side-link UE that is within range relative to the COT 420. In some cases, the side-link UE 405b may make this inference since NACK-only feedback may be limited to UEs within the feedback range of the side-link UE requesting NACK-only feedback (i.e., within the feedback range of the side-link UE transmitting multicast option 1PSSCH transmissions). In some cases, the side-uplink UE 405b may further infer that the PSFCH is part of the COT 420 (e.g., transmitted using reserved slot n+1430 b of the COT 420) and conclude that the COT 420 has not been released due to unused gaps, and that the COT 420 remains active. In such a case, the side-uplink UE 405b may then continue to access the COT to share and for its own transmissions. In some cases, the side-link UE 405b may infer that only NACK PSFCH is sent in response to the multicast option 1PSSCH transmission because the side-link UE 405b has also received the multicast option 1PSSCH transmission and knows the type of corresponding PSFCH transmission (e.g., NACK feedback only) that may be sent in response to the received multicast option 1PSSCH transmission. In some cases, the side-link UE 405b may determine that it (i.e., the side-link UE 405 b) is in range with respect to the COT by using the COT shared information sent by the COT-initiated UE and received by the side-link UE 405 b. For example, the side-link UE 405b may use the location of the COT originating side-link UE 405a and the spatial range of the COT 420 to determine that the side-link UE 405b is located within the maximum spatial range of the COT 420.

In some cases, if the feedback range of the sidelink UE requesting only NACK PSFCH (i.e., the sidelink UE transmitting the multicast option 1PSSCH transmission) is less than the threshold feedback range, then the sidelink UE 405b may make an inference that only NACK PSFCH is transmitted by nearby in-range sidelink UEs. Such a restriction may prevent the side-link UE 405b from erroneously assuming: side-uplink UEs that are outside the maximum spatial range of the COT 420 are actually within range relative to the COT and are allowed to share and use the COT 420 (e.g., when the feedback range of side-uplink UEs requesting only NACK PSFCH is much greater than the maximum spatial range of the COT 420). In some cases, the threshold feedback range may be approximately equal to (e.g., within 10% of) the maximum spatial range of the COT 420.

Fig. 5 is a block diagram of an exemplary UE 500 in accordance with some aspects of the present disclosure. UE 500 may be UE 115 as discussed above with respect to fig. 1, UE 315 as discussed above with respect to fig. 3, or UE 405 as discussed above with respect to fig. 4. As shown, UE 500 may include a processor 502, a memory 504, a side-link COT sharing module 508, a transceiver 510 including a modem subsystem 512 and a Radio Frequency (RF) unit 514, and one or more antennas 516. These elements may be coupled to each other. The term "coupled" may mean directly or indirectly coupled or connected to one or more intermediate elements. For example, the elements may communicate with each other directly or indirectly, e.g., via one or more buses.

The processor 502 may have various features as a particular type of processor. For example, these may include CPU, DSP, 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 502 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The memory 504 may include cache memory (e.g., of the processor 502), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, solid state storage, 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, memory 504 may include a non-transitory computer-readable medium. Memory 504 may store instructions 506. The instructions 506 may include instructions that, when executed by the processor 502, cause the processor 502 to perform the operations described herein, such as the aspects of fig. 1-3, 4A-4B, 7, and 8. The instructions 506 may also be referred to as program code, which may be broadly construed to include any type of computer-readable statement. The program code may be to cause the wireless communication device to perform these operations, for example, by causing one or more processors (e.g., processor 502) to control or command the wireless communication device to do so. The terms "instructions" and "code" should be construed broadly to include any type of computer-readable statement. For example, the terms "instructions" and "code" may refer to one or more programs, routines, subroutines, functions, procedures, and the like. "instructions" and "code" may comprise a single computer-readable statement or a plurality of computer-readable statements.

The side-uplink COT sharing module 508 may be implemented via hardware, software, or a combination thereof. For example, the side-uplink COT sharing module 508 may be implemented as a processor, circuitry, and/or instructions 506 stored in the memory 504 and executed by the processor 502. In some examples, side-uplink COT sharing module 508 may be integrated within modem subsystem 512. For example, the side-uplink COT sharing module 508 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 circuitry) within the modem subsystem 512.

The side-uplink COT sharing module 508 may communicate with various components of the UE 500 to perform aspects of the disclosure, e.g., aspects of FIGS. 1-3, 4A-4B, 7, and 8. In some aspects, the side-uplink COT sharing module 508 is configured to: measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and accessing a first time slot of the COT based on the first RSRP. For example, the measured RSRP may exceed the RSRP threshold, and the side-link COT sharing module 508 may infer that the PSFCH transmission was sent using the COT, e.g., via the second time slot of the COT.

In some aspects, the side-uplink COT sharing module 508 is configured to: detecting a physical side uplink shared channel (PSSCH) transmission; detecting a physical side uplink feedback channel (PSFCH) transmission transmitted in response to the PSSCH transmission within a COT having a plurality of slots; and accessing a first time slot of the plurality of time slots of the COT based on detecting the PSFCH transmission. In some aspects, the PSSCH transmission is a multicast option 1PSSCH transmission sent via a slot that is not part of the COT. In some aspects, the PSFCH transmission includes a hybrid automatic repeat request (HARQ) Negative Acknowledgement (NACK) message. In some aspects, the COT is initiated by the second UE; and the PSFCH transmission is transmitted by one or more third UEs within feedback range of the second UE.

As shown, transceiver 510 may include a modem subsystem 512 and an RF unit 514. The transceiver 510 may be configured to bi-directionally communicate with other devices, such as the BS 105. Modem subsystem 512 may be configured to modulate and/or encode data from memory 504 and/or side-link COT sharing module 508 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 514 may be configured to process (e.g., perform analog-to-digital conversion or digital-to-analog conversion, etc.) modulated/encoded data (e.g., PSCCH, PSSCH, SCI-1, SCI-2, side-link data, COT-SI, COT shared information (such as, but not limited to, duration of COT, location data of COT-initiated UE, etc.)) (on output transmissions) or transmissions originating from another source (such as UE 115 or BS 105) from the modem subsystem 512. The RF unit 514 may also be configured to perform analog beamforming in combination with digital beamforming. Although shown as being integrated together in transceiver 510, modem subsystem 512 and RF unit 514 may be separate devices that are coupled together at UE 115 to enable UE 115 to communicate with other devices.

The RF unit 514 may provide modulated and/or processed data, such as data packets (or more generally, data messages that may include one or more data packets and other information), to the antenna 516 for transmission to one or more other devices. Antenna 516 may also receive data messages transmitted from other devices. Antenna 516 may provide received data messages for processing and/or demodulation at transceiver 510. The transceiver 510 may provide demodulated and decoded data (e.g., PSCCH, PSSCH, SCI-1, SCI-2, side-uplink data, COT-SI, COT sharing information) to the side-uplink COT sharing module 508 for processing. Antenna 516 may include multiple antennas of similar design or different designs to maintain multiple transmission links. The RF unit 514 may configure the antenna 516.

In one aspect, the UE 500 may include multiple transceivers 510 implementing different RATs (e.g., NR and LTE). In one aspect, the UE 500 may include a single transceiver 510 implementing multiple RATs (e.g., NR and LTE). In one aspect, transceiver 510 may include various components, wherein different combinations of components may implement different RATs.

Fig. 6 is a block diagram of an exemplary BS 600 in accordance with some aspects of the present disclosure. BS 600 may be BS 105 in network 100 or BS 305 in network 300 as discussed above with respect to fig. 1. As shown, BS 600 may include a processor 602, a memory 604, a side-link COT sharing module 608, a transceiver 610 including a modem subsystem 612 and a Radio Frequency (RF) unit 614, and one or more antennas 616. These elements may be coupled to each other. The term "coupled" may mean directly or indirectly coupled or connected to one or more intermediate elements. For example, the elements may communicate with each other directly or indirectly, e.g., via one or more buses.

The processor 602 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 602 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The memory 604 may include cache memory (e.g., the cache memory of the processor 602), 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, a solid state memory device, a hard disk drive, other forms of volatile and non-volatile memory, or a combination of different types of memory. In one aspect, memory 604 includes a non-transitory computer-readable medium. The memory 604 may store or have instructions 606 recorded thereon. The instructions 606 may include instructions that, when executed by the processor 602, cause the processor 602 to perform the operations described herein (e.g., aspects of the aspects of fig. 1-3, 4A-4B, 7, and 8). The instructions 1006 may also be referred to as program code, which may be broadly interpreted to include any type of computer-readable statement.

The side-uplink COT sharing module 608 may be implemented via hardware, software, or a combination thereof. For example, side-uplink COT sharing module 608 may be implemented as a processor, circuitry, and/or instructions 606 stored in memory 604 and executed by processor 602. In some examples, side-uplink COT sharing module 608 may be integrated within modem subsystem 612. For example, the side-uplink COT sharing module 608 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 circuitry) within the modem subsystem 612.

The side-uplink COT sharing module 608 may communicate with various components of the BS 600 to perform various aspects of the disclosure, such as the various aspects of FIGS. 1-3, 4A-4B, 7, and 8. For example, the side-uplink COT sharing module 608 is configured to provide the side-link UE with a threshold RSRP value as discussed above.

As shown, transceiver 610 may include a modem subsystem 612 and an RF unit 614. Transceiver 610 may be configured to bi-directionally communicate with other devices, such as UE 115 and/or another core network element. Modem subsystem 612 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.). RF unit 614 may be configured to process (e.g., perform analog-to-digital conversion or digital-to-analog conversion, etc.) modulated/encoded data (e.g., RRC configuration, side-uplink resource pool configuration) from modem subsystem 612 (on an outbound transmission) or transmitted from another source, such as UE 115. The RF unit 614 may also be configured to perform analog beamforming in conjunction with digital beamforming. Although shown as being integrated together in transceiver 610, modem subsystem 612 and/or RF unit 614 may be separate devices coupled together at BS 105 to enable BS 105 to communicate with other devices.

RF unit 614 may provide modulated and/or processed data, such as data packets (or more generally, data messages that may include one or more data packets and other information) to antenna 616 for transmission to one or more other devices. This may include, for example, transmission of information to complete attachment to the network and communication with the resident UE 115 in accordance with some aspects of the present disclosure. The antenna 616 may also receive data messages transmitted from other devices and provide the received data messages for processing and/or demodulation at the transceiver 610. The transceiver 610 may provide the demodulated and decoded data to the side-link COT sharing module 608 for processing. Antenna 616 may include multiple antennas of similar or different designs in order to maintain multiple transmission links.

In one aspect, BS 600 may include multiple transceivers 610 implementing different RATs (e.g., NR and LTE). In one aspect, BS 600 may include a single transceiver 610 that implements multiple RATs (e.g., NR and LTE). In one aspect, transceiver 610 may include various components, wherein different combinations of components may implement different RATs.

Fig. 7 is a flow chart of a side-uplink COT sharing method 700 according to some aspects of the present disclosure. Aspects of method 700 may be performed by a computing device (e.g., a processor, processing circuitry, and/or other suitable components) in a wireless communication device or other suitable unit for performing these steps. For example, a wireless communication device (such as UE 115, 315, or 405) may utilize one or more components (such as processor 502, memory 504, side-uplink COT sharing module 508, transceiver 510, modem 512, and one or more antennas 516) to perform the steps of method 700. Method 700 may employ a similar mechanism as described above in fig. 1-3, fig. 4A-4B, and fig. 5. As shown, method 700 includes a plurality of enumerated steps, although aspects of method 700 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.

At block 710, in some aspects, a first UE (e.g., UE 115, 315, or 405) measures a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission sent during a Channel Occupancy Time (COT) initiated by a second UE.

At block 720, in some aspects, the first UE accesses a first time slot of the COT based on the first RSRP.

In some aspects of method 700, the PSFCH is sent via a second time slot of the COT reserved for PSFCH transmission. In some aspects, the RSRP exceeds an RSRP threshold, which indicates transmission of the PSFCH transmission via the second slot of the COT. In some aspects, the RSRP threshold is predetermined. In some aspects, the method further comprises: the first UE receives a message indicating an RSRP threshold from a New Radio (NR) network to which the first UE is connected. In some aspects, the message is a Radio Resource Control (RRC) message or a Medium Access Control (MAC) -Control Element (CE) message. For example, the message may be received from the NR network via a BS (e.g., BS 105, BS 600, etc.).

In some aspects, the RSRP threshold is calculated by the first UE. In some aspects, the method 700 further comprises: the first UE obtaining or measuring a second RSRP of an initial transmission sent by the second UE after initiating the COT; and adjusting the RSRP threshold based on the second RSRP. In such an aspect, the RSRP threshold is adjusted to be less than the second RSRP. Further, the RSRP threshold may be adjusted to be no greater than the second RSRP.

Fig. 8 is a flow chart of a side-uplink COT sharing method 800 according to some aspects of the present disclosure. Aspects of method 800 may be performed by a computing device (e.g., a processor, processing circuitry, and/or other suitable components) in a wireless communication device or other suitable unit for performing these steps. For example, a wireless communication device (such as UE 115, 315, or 405) may utilize one or more components (such as processor 502, memory 504, side-uplink COT sharing module 508, transceiver 510, modem 512, and one or more antennas 516) to perform the steps of method 800. Method 800 may employ similar mechanisms as described above in fig. 1-3, fig. 4A-4B, and fig. 5. As shown, method 800 includes a plurality of enumerated steps, although aspects of method 800 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.

At block 810, in some aspects, a first UE (e.g., UE 115, 315, or 405) detects a physical side uplink shared channel (PSSCH) transmission.

At block 820, in some aspects, the first UE detects a physical side uplink feedback channel (PSFCH) transmission sent in response to the PSSCH transmission within a COT having a plurality of slots.

At block 830, in some aspects, the first UE accesses a first time slot of a plurality of time slots of the COT based on detecting the PSFCH transmission.

In some aspects of method 800, the PSSCH transmission is transmitted via a second slot of the plurality of slots of the COT. In some aspects, the PSSCH transmission is a multicast option 1PSSCH transmission sent via a slot that is not part of the COT. In such a case, the PSFCH transmission may include a hybrid automatic repeat request (HARQ) Negative Acknowledgement (NACK) message. In some cases, the PSFCH transmission includes only HARQ NACK messages (e.g., no ACKs). In some aspects, the COT is initiated by the second UE; and the PSFCH transmission is transmitted by one or more third UEs within feedback range of the second UE. In some aspects, the first UE is within feedback range of the second UE.

Fig. 9 illustrates an example wireless communication network 900 in which aspects of the present disclosure may be implemented. For example, the wireless communication network 900 may be an NR system (e.g., a 5G NR network). As shown in fig. 9, the wireless communication network 900 may communicate with a core network 932. The core network 932 may communicate with one or more Base Stations (BSs) 910 and/or User Equipments (UEs) 920 in the wireless communication network 900 via one or more interfaces.

As shown in fig. 9, a wireless communication network 900 may include a plurality of BSs 910a-z (each BS also referred to herein as BS 910 or collectively referred to as BS 910) and other network entities. The BS 910 may provide communication coverage for a particular geographic area (sometimes referred to as a "cell"), and depending on the location of the mobile BS 910, the BS 910 may be stationary or may move. In some examples, BS 910 may be interconnected by various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.) and/or with one or more other BSs or network nodes (not shown) in wireless communication network 900 using any suitable transport network. In the example shown in fig. 9, BSs 910a, 910b, and 910c may be macro BSs for macro cells 902a, 902b, and 902c, respectively. BS 910x may be a pico BS for pico cell 902 x. BS 910y and BS 910z may be femto BSs for femto cells 902y and 902z, respectively. The BS may support one or more cells.

BS 910 communicates with UEs 920a-y (each UE also referred to herein individually or collectively as UEs 920) in wireless communication network 900. The UEs 920 (e.g., 920x, 920y, etc.) may be dispersed throughout the wireless communication network 900, and each UE 920 may be stationary or mobile. The wireless communication network 900 may also include relay stations (e.g., relay station 910 r) (also referred to as repeaters, etc.) that receive transmissions of data and/or other information from upstream stations (e.g., BS 910a or UE 920 r) and send transmissions of data and/or other information to downstream stations (e.g., UE 920 or BS 910), or relay transmissions between UEs 920 to facilitate communications between devices.

The network controller 930 may communicate with a set of BSs 910 and provide coordination and control (e.g., via backhaul) for the BSs 910. In aspects, the network controller 930 may communicate with a core network 932 (e.g., a 5G core network (5 GC)) that the core network 932 provides various network functions such as access and mobility management, session management, user plane functions, policy control functions, authentication server functions, unified data management, application functions, network opening functions, network repository functions, network slice selection functions, and the like.

According to certain aspects as described herein, the UE 920 may be configured to transmit feedback information on a side-uplink feedback channel in the unlicensed spectrum. For example, as shown in fig. 9, UE 920a includes a Channel Occupancy Time (COT) manager 922. The COT manager 922 may be configured to perform the operations shown in fig. 18, as well as other operations described herein for improved COT sharing for side-link unlicensed operations.

Fig. 10 illustrates example components of BS 910a and UE 920a (e.g., wireless communication network 900 of fig. 9) that may be used to implement aspects of the present disclosure.

At BS 910a, transmit processor 1020 may receive data from a data source 1012 and control information from a controller/processor 1040. The control information may be used for a Physical Broadcast Channel (PBCH), a Physical Control Format Indicator Channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a Physical Downlink Control Channel (PDCCH), group common PDCCH (GC PDCCH), and the like. The data may be for a Physical Downlink Shared Channel (PDSCH) or the like. A Medium Access Control (MAC) -control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Shared Channel (PUSCH), or a physical side-downlink shared channel (PSSCH).

Processor 1020 may process (e.g., encode and symbol map) the data and control information, respectively, to obtain data symbols and control symbols. The transmit processor 1020 may also generate reference symbols such as for a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a PBCH demodulation reference signal (DMRS), and a channel state information reference symbol (CSI-RS). A Transmit (TX) multiple-input multiple-output (MIMO) processor 1030 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to Modulators (MODs) in the transceivers 1032a-1032 t. Each modulator in transceivers 1032a-1032t may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators in transceivers 1032a-1032t may be transmitted through antennas 1034a-1034t, respectively.

At UE 920a, antennas 1052a-1052r may receive the downlink signals from BS 910a and may provide received signals to demodulators (DEMODs) in transceivers 1054a-1054r, respectively. Each demodulator in transceivers 1054a-1054r may condition (e.g., filter, amplify, downconvert, and digitize) a corresponding received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 1056 may obtain the received symbols from all demodulators in transceivers 1054a-1054r, perform MIMO detection on the received symbols (if applicable), and provide detected symbols. A receive processor 1058 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 920a to a data sink 1060, and provide decoded control information to a controller/processor 1080.

On the uplink, at the UE 920a, a transmit processor 1064 may receive and process data from a data source 1062 (e.g., for a Physical Uplink Shared Channel (PUSCH)) and control information from a controller/processor 1080 (e.g., for a Physical Uplink Control Channel (PUCCH)). The transmit processor 1064 may also generate reference symbols for reference signals (e.g., for Sounding Reference Signals (SRS)). The symbols from transmit processor 1064 may be precoded by a TX MIMO processor 1066 if applicable, further processed by modulators in transceivers 1054a-1054r (e.g., for SC-FDM, etc.), and transmitted to BS 910a. At BS 910a, the uplink signals from UE 920a may be received by antennas 1034, processed by demodulators in transceivers 1032a-1032t, detected by a MIMO detector 1036 if applicable, and further processed by a receive processor 1038 to obtain decoded data and control information transmitted by UE 920 a. The receive processor 1038 may provide the decoded data to a data sink 1039 and the decoded control information to a controller/processor 1040.

Memory 1042 and memory 1082 can store data and program codes for BS 910a and UE 920a, respectively. A scheduler 1044 may schedule UEs for data transmission on the downlink and/or uplink.

The antennas 1052, processors 1066, 1058, 1064 and/or controllers/processors 1080 of UE 920a and/or the antennas 1034, processors 1020, 1030, 1038 and/or controllers/processors 1040 of BS 910a may be used to perform the various techniques and methods described herein. As shown in fig. 10, the controller/processor 1080 of the UE 920a has a COT manager 1081, which COT manager 1081 may be configured to perform the operations shown in fig. 18 as well as other operations disclosed herein for improved COT sharing for side-uplink unlicensed operations. Although shown at a controller/processor, other components of UE 920a and BS 910a may be used to perform the operations described herein.

NR may utilize Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) on uplink and downlink. NR may support half-duplex operation using Time Division Duplex (TDD). OFDM and single carrier frequency division multiplexing (SC-FDM) divide the system bandwidth into a plurality of orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. The modulation symbols may be transmitted with OFDM in the frequency domain and SC-FDM in the time domain. The interval between adjacent subcarriers may be fixed and the total number of subcarriers may depend on the system bandwidth. The minimum resource allocation called Resource Block (RB) may be 12 consecutive subcarriers. The system bandwidth may also be divided into sub-bands. For example, a subband may cover multiple RBs. The NR may support a basic subcarrier spacing (SCS) of 15kHz and may define other SCSs (e.g., 30kHz, 60kHz, 120kHz, 240kHz, etc.) with respect to the basic SCS.

Fig. 11 is a diagram showing an example of a frame format 1100 for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be divided into 10 subframes having indexes 0 to 9, each subframe being 1ms. Each subframe may include a variable number of slots (e.g., 1, 2, 4, 8, 16..times. Slots), depending on the SCS. Each slot may include a variable number of symbol periods (e.g., 7, 12, or 14 symbols), depending on the SCS. An index may be assigned to the symbol period in each slot. Mini-slots (which may be referred to as sub-slot structures) refer to transmission time intervals having a duration (e.g., 2, 3, or 4 symbols) that is less than a slot. Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission, and the link direction of each subframe may be dynamically switched. The link direction may be based on a slot format. Each slot may include DL/UL data and DL/UL control information.

In NR, a Synchronization Signal Block (SSB) is transmitted. In certain aspects, SSBs may be transmitted in bursts, where each SSB in a burst corresponds to a different beam direction for UE-side beam management (e.g., including beam selection and/or beam refinement). SSB includes PSS, SSS and two symbol PBCH. SSBs may be transmitted in fixed slot positions (e.g., symbols 0-3 shown in fig. 11). PSS and SSS may be used by the UE for cell search and acquisition. The PSS may provide half frame timing and the SS may provide CP length and frame timing. PSS and SSS may provide cell identity. The PBCH carries certain basic system information such as downlink system bandwidth, timing information within the radio frame, SS burst set period, system frame number, etc. SSBs may be organized into SS bursts to support beam scanning. Additional system information, such as Remaining Minimum System Information (RMSI), system Information Blocks (SIBs), other System Information (OSI), may be transmitted on the Physical Downlink Shared Channel (PDSCH) in certain subframes. For millimeter wave (mmWave), SSBs may be sent up to sixty-four times, for example, with up to sixty-four different beam directions. The multiple transmissions of SSBs are referred to as SS burst sets. SSBs in SS burst sets may be transmitted in the same frequency region, while SSBs in different SS burst sets may be transmitted at different frequency regions.

Example side Link communication

In some examples, two or more subordinate entities (e.g., UE 920) may communicate with each other using side-uplink signals. Real-life applications for such side-link communications may include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communications, internet of everything (IoE) communications, ioT communications, mission critical mesh, and/or various other suitable applications. In general, a sidelink signal may refer to a signal transmitted from one subordinate entity (e.g., UE 920 a) to another subordinate entity (e.g., another UE 920) without the need to relay the communication through a scheduling entity (e.g., UE 920 or BS 910), even though the scheduling entity may be used for scheduling and/or control purposes. In some examples, the licensed spectrum may be used to transmit the sidelink signal (as opposed to wireless local area networks that typically use unlicensed spectrum). One example of a side-link communication is PC5, e.g. as used in V2V, LTE and/or NR.

Various sidelink channels may be used for sidelink communications, including a Physical Sidelink Discovery Channel (PSDCH), a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), and a Physical Sidelink Feedback Channel (PSFCH). The PSDCH may carry discovery expressions that enable nearby devices to discover each other. The PSCCH may carry control signaling such as side-link resource configuration, resource reservation, and other parameters for data transmission, and the PSSCH may carry data transmission. The PSFCH may carry feedback such as Acknowledgement (ACK) and/or Negative ACK (NACK) information corresponding to the transmission on the PSSCH. In some systems (e.g., NR version 16), two-stage SCI may be supported. The two-stage SCI may include a first stage SCI (SCI-1) and a second stage SCI (e.g., SCI-2). SCI-1 may include resource reservation and allocation information, information that may be used to decode SCI-2, and so on. SCI-2 may include information that may be used to decode data and determine whether the UE is the intended recipient of the transmission. SCI-1 and/or SCI-2 may be transmitted on the PSCCH.

Fig. 12A and 12B show a diagrammatic representation of an example V2X system in accordance with some aspects of the present disclosure. For example, the vehicles shown in fig. 12A and 12B may communicate via a side-link channel, and may relay side-link transmissions, as described herein.

The V2X system provided in fig. 12A and 12B provides two complementary transmission modes. The first transmission mode (also referred to as mode 4) (shown by way of example in fig. 12A) involves direct communication (e.g., also referred to as side-link communication) between participants that are in proximity to each other in a localized area. A second transmission mode (also referred to as mode 3) (shown by way of example in fig. 12B) involves network communication through the network, which may be implemented over a Uu interface (e.g., a wireless communication interface between a Radio Access Network (RAN) and the UE).

Referring to fig. 12a, a V2x system 1200 (e.g., including vehicle-to-vehicle (V2V) communications) is shown having two vehicles 1202, 1204. The first transmission mode allows direct communication between different participants in a given geographic location. As shown, the vehicle may have a wireless communication link 1206 with a person (V2P) (e.g., via a UE) through a PC5 interface. Communication between vehicles 1202 and 1204 may also occur through PC5 interface 1208. In a similar manner, communications from the vehicle 1202 to other highway components (e.g., highway component 1210), such as traffic signals or signs (V2I), may occur through the PC5 interface 1212. With respect to each communication link shown in fig. 12A, bidirectional communication can be performed between elements, and thus each element can be a sender and a receiver of information. The V2X system 1200 may be a self-management system implemented without assistance from a network entity. Since no network service interruption occurs during a handover operation for a moving vehicle, the self-management system can achieve improved spectral efficiency, reduced cost, and improved reliability. The V2X system may be configured to operate in licensed or unlicensed spectrum, so any vehicle with equipped systems may access the common frequency and share information. Such coordinated/public spectrum operation allows for safe and reliable operation.

Fig. 12B illustrates a V2X system 1250 for communicating between a vehicle 1252 and a vehicle 1254 through a network entity 1256. These network communications may occur through discrete nodes, such as BSs (e.g., BS 910 a), that send information to the vehicles 1252, 1254 and receive information from the vehicles 1252, 1254 (e.g., relay information between the vehicles 1252, 1254). For example, network communications over vehicle-to-network (V2N) links 1258 and 1260 may be used for remote communications between vehicles, such as for communicating the presence of traffic accidents along roads or at a distance in front of highways. The wireless node may send other types of communications to the vehicle such as traffic flow conditions, road hazard warnings, environmental/weather reports, and service station availability, among other examples. Such data may be obtained from a cloud-based sharing service.

Roadside units (RSUs) may be utilized. The RSU may be used for V2I communication. In some examples, the RSU may act as a forwarding node to extend coverage for the UE. In some examples, the RSU may be co-located with the BS or may be independent. RSUs may have different classifications. For example, RSUs may be classified into UE-type RSUs and micro node B-type RSUs. The micro node B type RSU has a similar function as the macro eNB or gNB. The micro node B type RSU may utilize the Uu interface. The UE-type RSU may be used to meet stringent quality of service (QoS) requirements by minimizing collisions and improving reliability. The UE-type RSU may use a centralized resource allocation mechanism to allow efficient resource utilization. Critical information (e.g., traffic conditions, weather conditions, congestion statistics, sensor data, etc.) may be broadcast to UEs in the coverage area. The repeater may rebroadcast the critical information received from some UEs. The UE-type RSU may be a reliable synchronization source.

Example side-uplink feedback channel resource mapping in unlicensed spectrum

The UE may use resources selected from the resource pool when communicating on the side link. The resource pool may be defined as a consecutive number of Resource Blocks (RBs) in the frequency domain in units of subchannels. In other words, the resource pool may be composed of a plurality of consecutive RBs in frequency. In particular, a subchannel may be defined as one or more RBs (e.g., which are contiguous) among RBs, and a resource pool may be defined as one or more subchannels.

Fig. 13 illustrates a time-frequency grid depicting an example resource pool for side-link communications in accordance with certain aspects presented herein. As can be seen, three different resource pools (e.g., 1302, 1304, and 1306) are shown. The resource pool 1302 may be comprised of two subchannels 1308 (e.g., assigned a physical side-uplink control channel (PSCCH) and a physical side-uplink shared channel (PSSCH)) and 1310 (e.g., assigned to a PSSCH), each of the two subchannels 1308 and 1310 comprising a contiguous set of RBs across different frequencies. As shown, the resource pools 1304 and 1306 may each include four sub-channels that span different frequency bands.

In some cases, the side-uplink resource pool may be defined by a number of parameters, such as the parameters sl-StartRB-Subchannel, sl-SubchannelSize and sl-NumSubchannel, but it should be noted that they may be mentioned in any suitable way. The parameter sl-StartRB-subbhannel may define the first RB of the lowest index Subchannel of the resource pool. For example, referring to resource pool 1302, a parameter sl-StartRB-Subchannel may specify the first RB of Subchannel 1308. In addition, the parameter sl-SubchannelSize may define the number of RBs per subchannel in the resource pool, and the parameter sl-NumSubchannel may define the number of subchannels in the resource pool. Thus, for example, referring to resource pool 1302, parameter sl-numsubbhannel may define resource pool 1302 as including two subchannels (e.g., 1308 and 1310), and parameter sl-subbhannelsize may define each of subchannels 1308 and 1310 to include 10 RBs to 100 RBs.

In some cases, within each sub-channel, a side-link control channel, such as a physical side-link control channel (PSCCH), may occupy a first number of RBs (e.g., where the number is the value of the parameter sl-freqresource scch) and a first number of symbols (e.g., where the number is the value of the parameter sl-timeresource scch) that are assigned to a first sub-channel of a side-link shared data channel, such as a physical side-link shared channel (PSSCH). In some cases, the control information included in the PSCCH may allocate how many subchannels may be included within the PSCCH starting from the current subchannel in which the PSCCH was transmitted.

In some cases, the UE may need to send feedback information to indicate whether certain transmissions on the PSSCH and/or PSCCH have been successfully received. The feedback information may include Acknowledgements (ACKs) corresponding to the transmissions on the PSSCH/PSCCH that are successfully received and decoded and/or Negative ACKs (NACKs) that are unsuccessfully decoded. In some cases, the feedback information may be sent on a feedback channel known as a physical side uplink feedback channel (PSFCH). To send feedback information on the PSFCH, a set of resources may be selected from a pool of non-dedicated PSFCH resources.

An example PSFCH resource pool 1402 is shown in fig. 14. As shown, the PSFCH resource pool 1402 may be divided into a set of separate sub-resource pools 1404, each corresponding to a different side uplink sub-channel spanning a different time slot. Although certain aspects are described in terms of time slots, other suitable durations may similarly be used. For example, as shown in fig. 14, a total of eight sub-channels spanning two slots may be used to carry PSSCH/PSCCH information. Thus, the PSFCH resource pool 1402 may be divided into eight distinct sub-resource pools 1404 that are used to carry feedback information corresponding to eight distinct sub-channels spanning two time slots. Each sub-resource pool 1404 may include a plurality of resources (e.g., RBs), and the UE may select one of the plurality of resources 1406 within the sub-resource pool 1404 to transmit feedback information for each sub-channel.

The UE may determine a PSFCH resource pool and select resources for transmitting feedback information based on a plurality of parameters. Although certain names are given for such parameters, it should be noted that they may be mentioned in any suitable way. For example, in some cases, the UE may be configured with a parameter period PSFCH resource, which may indicate the period of a slot in the resource pool for PSFCH transmission. In some cases, the supported period is 0/1/2/4, where 0 means no PSFCH. In some aspects, the PSFCH transmission timing may be determined after and at the PSSCH is receivedThe following MinTimeGapPSFCH (e.g., time value) is followed by the first slot with PSFCH resources. In some cases, parametersA set of PRBs for the PSFCH in a slot may be defined. As discussed above, the PRB set may be in a slot(e.g., the number of PSSCH slots corresponding to PSFCH slots) and N _subch PSSCH (e.g., the number of PSSCH subchannels). Thus, each sub-channel/slot may have +.>And the number of PRBs. In some cases, the mapping from PSSCH resources to PSFCH PRBs may be performed time-preferentially.

The size of the PSFCH resource pool may be based onIs defined as a number of, among other things,is the number of Cyclic Shift (CS) pairs per RB configuration in the resource pool (e.g., one pair for a 1-bit ACK/NACK). In certain aspects, the->Is 1 or->Which indicates whether the PSFCH resource pool is shared for the sub-channels in the PSSCH slot. In some cases, within the pool, the PSFCH resources may be indexed by PRB, then index by CS.

In some cases, the UE may be based onCome acknowledgementPSFCH resources destined for transmitting feedback information, wherein P _ID Is the physical source ID for PSSCH from side Link control information (SCI) 0-2, and M _ID Is 0 or identifies the UE receiving the PSSCH. In some aspects, for unicast or NAK-based transmissions, M _ID =0, and the UE may send only ACKs or NAKs at the source ID related resources in the pool. For multicasting, in some aspects, the destination ID may be used to select one of the resources in the resource pool for sending feedback information.

In some cases, it may be beneficial to perform side-link communications using wideband channel operation within unlicensed spectrum in order to take advantage of the globally available "free" spectrum. However, the resource allocation in the unlicensed spectrum may be different from the resource allocation of the side-uplink communications.

For example, for operation in unlicensed spectrum, channel access in unlicensed spectrum may be divided into multiple 20MHz sub-bands, even when the system is operating in a wideband mode (e.g., multiples of 20 MHz), as there may be problems with coexistence with WiFi. To be able to access a particular 20MHz sub-band, a wireless device (e.g., UE) may first perform a Listen Before Talk (LBT) procedure to determine whether the 20MHz sub-band is available for use by the wireless device. If the wireless device senses that there are no other transmissions occurring in the 20MHz sub-band for a period of time, which indicates that the 20MHz sub-band is in an idle state, the 20MHz sub-band is available for use. In some cases, the wireless device may conclude that the 20MHz sub-band is in an idle state by sensing an energy level on the 20MHz sub-band. If the energy level of the 20MHz sub-band is below the threshold, the wireless device may conclude that the 20MHz sub-band is available for use. However, if the LBT procedure does not pass (e.g., the energy level of the 20MHz sub-band is greater than the threshold), the wireless device may attempt another 20MHz bandwidth portion. It should be noted that the 20MHz sub-channel is only an example and that the sub-bands may have different bandwidths.

To support this type of operation, such as in 5G new radio unlicensed (NR-U), an intra-cell guard band is introduced to define a guard band between each (e.g., about 20 MHz) sub-band. The passband between two adjacent intra-cell guard bands may be referred to as a "RB set" which is about 20MHz. For example, as shown in fig. 15, the unlicensed spectrum may be split into multiple RB sets including multiple RBs 1502 (e.g., each RB set spans a bandwidth of substantially 20 MHz). As shown in the example shown in fig. 15, the unlicensed spectrum may be divided into four different RB sets (including RB set 0, RB set 1, RB set 2, and RB set 3), and an intra-cell guard band 1504 may be inserted between each RB set. It should be noted that there may be a greater or lesser number of RB sets and that they may have a greater or lesser bandwidth/number of RBs. As described above, to communicate using unlicensed spectrum, a wireless device may perform an LBT procedure to sense which sets of RBs are available for communication. As shown in fig. 15, RB set 1 and RB set 2 have passed through the LBT procedure and are available/assigned for wireless devices.

In some cases, a (e.g., NR-U) system may support both contiguous uplink resource allocations and interleaved uplink resource allocations while adhering to the regulations. In interleaved uplink resource allocation, the basic unit of resource allocation for NR unlicensed channels is an interlace consisting of ten equally spaced RBs 1502 within a 20MHz frequency bandwidth (e.g., RB set) for 15KHz subcarrier spacing, for example, as shown in fig. 15. In certain aspects, for RBs belonging to the assigned interlace set but falling in the intra-cell guard band, such RBs will be assigned only when RB sets on both sides are assigned. Further, in some cases, a wireless device such as a UE may transmit in the intra-cell guard band 1504 if two sets of RBs on either side of the intra-cell guard band are allocated to the UE. Also, in some cases, if the UE is a high-capability UE, the UE may also receive transmissions within the intra-cell guard band 1504. However, if the UE is a lower capability UE, the UE may only be able to receive transmissions within the RB set and may not be able to receive transmissions in the intra-cell guard band 1504. In some cases, the UE may send information to the base station indicating the capabilities of the UE. If the capability information indicates that the UE is a low capability UE, the base station may refrain from scheduling a Physical Data Shared Channel (PDSCH) to the low capability UE on guard band RBs.

As described above, to utilize the globally available "free" spectrum, it may be beneficial to perform side-link communications using wideband channel operation within the unlicensed spectrum. However, a problem that may exist in the case of performing side-link communication in an unlicensed spectrum is due to the manner in which side-link subchannels are defined with respect to the manner in which RB sets are defined within the unlicensed spectrum. For example, as described above, the subchannels in the side-link may be continuously defined without any spacing between the different subchannels. This presents a problem when mapping these successively defined sub-channels to RB sets in an unlicensed frequency band (which includes an intra-cell guard band arranged between RB sets). For example, if the side-link subchannels are defined in a conventional manner in which the subchannels are contiguous, some of the side-link subchannels may partially overlap with the intra-cell guard bands in the unlicensed spectrum, which may result in the side-link subchannels not being usable by certain UEs (e.g., low-capability UEs) in the unlicensed spectrum. Thus, in some cases, to help alleviate these problems, the side-downlink subchannels may be localized within the RB set of the unlicensed spectrum such that no side-downlink subchannels overlap with the intra-cell guard band. Thus, by confining the side-link sub-channels to fit within the set of RBs of the unlicensed spectrum, the use of each side-link sub-channel depends only on the LBT of the set of RBs in which the side-link sub-channel is confined.

Furthermore, in some cases (e.g., NR-U), the concept of Channel Occupancy Time (COT) sharing has been introduced such that a COT acquired by a transmitter device (e.g., UE) via an LBT procedure over a particular subband (e.g., set of RBs) may be shared with another device (e.g., UE) over that subband. For example, the COT for a frequency band/sub-band may specify a time interval during which a transmitter device may continuously transmit via the frequency band before yielding a channel, e.g., stop transmitting via the frequency band for a period of time to allow another device to possibly perform LBT and begin transmitting via the frequency band.

In some cases, the COTs for the frequency bands may be specified to be limited to a particular time interval, which may depend on market, frequency band, technical considerations such as the priority of the signal and the duration of the corresponding LBT process (generally, the greater the duration of the LBT process, the greater the corresponding COTs). In some cases, the duration of the COT is typically in the range of 2 to 10ms, which may correspond to 4 to 20 slots in NR V2X with a 30KHz subcarrier spacing.

In some cases, the COT may be shared by multiple side-uplink UEs. In COT sharing, one side-link UE acquires the COT by performing LBT (e.g., category 4 (Cat 4) or type 1 LBT). Thereafter, other side-link UEs in the vicinity of the "COT-initiated" UE may be aware that the COT has been initiated and may continue to perform transmissions within the remainder of the COT by either skipping the LBT entirely or by first performing a "light" (i.e., deterministic duration) LBT (e.g., cat-2 or type 2 LBT). In some cases, a "COT-initiated" sidelink UE may notify other UEs of the initiated COT by sending to the other sidelink UEs Sidelink Control Information (SCI) indicating at least an end time associated with the COT.

COT sharing can be done in at least two variants: TDM type COT sharing, wherein the cobs are shared by time multiplexing (e.g., the UE transmits one by one until the duration of the cobs is exhausted); and FDM type COT sharing, wherein the COTs are shared by frequency multiplexing (e.g., the UE transmits simultaneously on different subchannels of the frequency band to which the COTs are applicable). In some cases, two variants of COT sharing may also be combined.

This concept of COT sharing may also be applicable to the transmission of feedback information on the side-uplink feedback channel. For example, in some cases, after performing LBT to acquire the COT on a particular set of RBs and transmitting the PSCCH/PSSCH, a transmitting node (e.g., UE) may share the COT with a responding node, allowing the responding node to transmit feedback information in the PSFCH using the same COT.

Example ACK transmission for improved COT sharing

As described above, the side-uplink UEs may share the COT to perform transmission. When COT is initiated, it is necessary to continuously utilize COT. If the transmission stops for a threshold amount of time before the end of the COT, the COT may be effectively released and subsequent transmissions may need to be performed in a new COT acquired through a new LBT procedure. For example, provision typically allows for a small duration transmission gap on the order of 16 microseconds to 25 microseconds before the COT is effectively released. Thus, for COT sharing, this means that the side-link device needs to know not only the duration of the COT (e.g., expiration time), but also whether the COT is still active when the side-link device chooses to utilize the shared COT (e.g., after the COT is first initiated, the transmission has not stopped).

FIG. 16 illustrates an example timeline for COT sharing. As shown, a first side-link UE 1602 may desire to transmit information in time slot n on a particular sub-band or channel in the unlicensed spectrum. Since there is no active COT for transmission in slot n, the first side-link UE 1602 may perform an LBT procedure 1604 to determine whether a channel is available (e.g., no transmission). In some cases, LBT procedure 1604 may include a category 4LBT procedure and may be performed by first side-link UE 1602 prior to slot n, as shown. In the example shown in fig. 16, LBT procedure 1604 may identify the channel as idle/available. In response to the channel being identified as idle/available, the first side-link UE 1602 may initiate a COT 1606 for performing the transmission. As shown, the COT 1606 may have a duration of several time slots (such as four time slots). That is, as shown, the COT 1606 may have a duration spanning time slot n, time slot n+1, time slot n+2, and time slot n+3.

After initiating the COT 1606, the first side-link UE 1602 may perform one or more side-link transmissions 1608 in time slot n. In some cases, the one or more side-link transmissions 1608 may include side-link control information (SCI) transmissions. SCI transmissions may include information indicating that the COT 1606 has been initiated by the first side-link UE 1602 and a duration of the COT 1606 (e.g., an expiration time associated with the COT 1606). One or more side-link transmissions 1608 (including SCI transmissions) may be received by other UEs, such as second side-link UE 1610 and third side-link UE 1612.

In the example shown in fig. 16, the second side-link UE has previously selected resources in slot n+1 for transmission (e.g., using a resource selection procedure) and also knows the COT 1606 initiated by the first side-link UE 1602 (e.g., based on SCI transmissions in one or more side-link transmissions 1608) (which includes slot n+1). Thus, second side uplink UE 1610 may continue to perform one or more side uplink transmissions 1614 in time slot n+1. Further, because one or more side-link transmissions 1614 are sent within time slot n+1 included within COT 1606, and because COT has been continuously utilized until time slot n+1, second side-link UE 1610 may not need to perform a category 4LBT procedure.

Similarly, third side-link UE 1612 may become aware of COT 1606 (e.g., based on SCI transmissions in one or more side-link transmissions 1608), and may have previously selected time slot n+3 to perform the transmission, as shown, with time slot n+3 also included in COT 1606. However, as shown, no transmission occurs within time slot n+2 in the COT 1606, and thus, the COT 1606 can be effectively released. Thus, the third side uplink UE 1612 may have to initiate a new COT 1616 for one or more transmissions 1618 by performing a new LBT 1620.

As shown in fig. 16, the shared COT (e.g., COT 1606) may be released due to unused time slots (e.g., time slot n+2), resulting in a relatively large transmission gap. Such unused time slots may occur due to PSFCH in the side-link. For example, certain side-link slots or portions of side-link slots may be reserved for PSFCH transmissions. In some cases, there may be a transmission gap that may result in the shared COT being released if there are no corresponding PSFCH transmissions occurring in (parts of) these slots (e.g., even if resources are reserved). In other words, PSFCH inactivity may result in a COT release since PSFCH transmissions are not guaranteed to occur in a particular time slot or within a particular portion of a time slot.

Fig. 17A and 17B provide examples of the release of COT due to an unused PSFCH slot. As shown in fig. 17A and 17B, a first side-link UE 1701 may initiate a COT 1702, the COT 1702 may have a maximum spatial region 1704, the maximum spatial region 1704 containing a second side-link UE 1706 and a third side-link UE 1708. As shown in fig. 17B, the COT 1702 may have a duration of four slots (e.g., spanning slots n, n+1, n+2, and n+3) and may be initiated by the first side-link UE 1701 via an LBT procedure 1703 performed in a slot preceding slot n.

Since both the second side-link UE 1706 and the third side-link UE1708 are within the range of the maximum space region 1704, when the second side-link UE 1706 and the third side-link UE1708 are to transmit, both the second side-link UE 1706 and the third side-link UE1708 may utilize the COT 1702 as long as the COT 1702 is active. As shown, the second side-link UE 1706 performs one or more transmissions 1710 in time slot n+1 immediately after the first side-link UE 1701. However, a portion 1712 of time slot n+1 is reserved for PSFCH transmissions, which means that one or more transmissions 1710 of the second side uplink UE 1706 terminate earlier than the end of time slot n+1. Furthermore, in the example shown in fig. 17B, no PSFCH transmission happens to occur within slot n+1, effectively freeing the COT 1702. Thus, the third side uplink UE1708 must initiate a new COT 1714 (e.g., by performing another LBT 1716) to perform one or more transmissions 1718, whereas if the PSFCH is active during time slot n+1, the third side uplink UE1708 may simply use the COT 1702.

Thus, due to PSFCH inactivity, the COT may last up to N slots (e.g., where n=1, 2, or 4 is the PSFCH period in a slot), which reduces the effectiveness of the COT sharing, since the allowable COT duration is specified to typically span several microseconds including multiple slots. This problem with PSFCH inactivity and COT sharing is particularly relevant for certain types of side-uplink transmissions, such as multicast option 1 transmissions. For example, a multicast option 1 transmission is a transmission sent by a transmitter UE on a PSSCH to a group of receiver UEs that only requires the receiver UE to send corresponding acknowledgement feedback when the receiver UE fails to decode the PSSCH transmission. That is, under multicast option 1, when the receiver UE fails to decode the corresponding PSSCH transmission, a negative acknowledgement only (NACK) is allowed to be transmitted. In other words, under multicast option 1, the receiver UE does not send an Acknowledgement (ACK) when the receiver UE correctly receives and decodes the corresponding PSSCH transmission. Thus, if the transmission has been correctly decoded by all receiver UEs, there will be no corresponding PSFCH transmission, which may lead to gaps in the transmission within the COT and thus to the COT being released. On the other hand, an ACK/NACK transmission scheme (such as multicast option 2 and unicast) will result in a feedback transmission (e.g., ACK or NACK) whenever a transmission occurs. Thus, multicast option 2 transmissions and unicast transmissions are inherently more efficient at maintaining COT than multicast option 1 transmissions.

Accordingly, aspects of the present disclosure provide techniques that help reduce the chance of inadvertently releasing shared COT when using multicast option 1 side uplink transmissions. For example, to avoid unintended release of the COT when using multicast option 1 transmissions, the receiver UE correctly decoding the multicast option 1 transmissions within the COT may continue to send ACKs. The ACK may include a dummy ACK that has no purpose other than to avoid the release of the COT and may be ignored by the transmitter UE (e.g., the UE that sent the multicast option 1 transmission).

For example, in some cases, the first UE may receive a first side-link multicast transmission that does not require an ACK to be sent when the first side-link multicast transmission is successfully decoded by the first UE. The first side uplink multicast transmission may include a side uplink multicast option 1 transmission on a PSSCH in the unlicensed spectrum. In some cases, the first side uplink multicast transmission may be received within a COT initiated by the second UE. In some cases, the COT may be shared with the first UE for transmission performed by the first UE even though the COT was initiated by the second UE. Further, in some cases, the first side-uplink multicast transmission may be received by the first UE from the second UE or some other UE transmitting with the COT.

Thus, in response to receiving the first side-link multicast transmission, the first UE may send an ACK for the first side-link multicast transmission during the COT initiated by the second UE. In some cases, a first side uplink multicast transmission may be received in a first time slot corresponding to a PSSCH and an ACK may be sent in a second time slot corresponding to a PSFCH. Further, in some cases, the first UE may send the ACK before a threshold amount of time after receiving the first side-link multicast transmission, the threshold amount of time corresponding to a maximum duration of the COT. As described above, by sending an ACK during the COT (e.g., before a threshold amount of time), the first UE may delay the release of the COT (e.g., the COT will typically be released since no feedback is sent when the first side-uplink multicast transmission is successfully received and decoded).

In some cases, the unlicensed spectrum in which the first side uplink multicast transmission is received may be shared with other radio access technologies and other devices. Thus, to ensure fairness to other technologies and devices operating in the unlicensed spectrum, an ACK for the first side uplink multicast transmission may be sent on condition of one or more criteria. By conditioning the transmission of the ACK on one or more criteria, it may be ensured that the first UE does not unnecessarily lengthen the COT and seize resources from other technologies and devices in the unlicensed spectrum that would otherwise not be substantially used. More specifically, such a condition may avoid the device from always sending ACK feedback, which may overload the PSFCH and may result in potentially prescribing that aggressive channel access not be allowed.

For example, the one or more criteria may include criteria for a device (e.g., a side-link UE) to acknowledge only actual side-link multicast option 1 transmissions. If there is no side-uplink multicast option 1 transmission on the PSSCH corresponding to the given PSFCH slot, no ACK can be sent in the PSFCH slot. In other words, if the first UE does not first receive the side-uplink multicast option 1 transmission within the COT, the first UE may not send an ACK in the PSFCH slot to delay the release of the COT.

Further, in some cases, the one or more criteria may include a COT or criteria within the COT that the transmission of the ACK must be for the first UE to be interested in using to perform the transmission. In other words, the first UE may send an ACK within the COT when the first UE is interested in using the COT for one or more other transmissions.

In some cases, the one or more criteria may include a criterion that the first UE is within a maximum spatial feedback range of the PSSCH side uplink multicast transmission to which the ACK corresponds. In other words, the first UE may send an ACK when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission. For example, referring to fig. 17A, if a first UE (e.g., a second side uplink UE 1706 or a third side uplink UE 1708) is within the maximum spatial region 1704, the first UE is allowed to transmit an ACK. However, if the first UE is outside of the maximum spatial region 1704, the first UE may refrain from sending an ACK.

In some cases, the one or more criteria may include criteria regarding that the first UE may send an ACK when the first UE intends to perform one or more transmissions (e.g., has a scheduled transmission to perform) within the COT in which it was received (e.g., sent by the second UE or some other UE). If the first UE does not intend to transmit within the COT, the first UE should not transmit an ACK in an attempt to keep the COT active (e.g., attempt to delay the release of the COT).

In some cases, the one or more criteria may include criteria that the first UE may send an ACK when the first UE already has no other feedback information to send during the COT, such as a NACK for the multicast option 1PSSCH or an ACK/NACK for the multicast option 2 or unicast transmission. If the first UE does have other feedback to send during the COT, this other feedback transmission may be sufficient to avoid release of the COT and, thus, it is not necessary to unnecessarily load the PSFCH with a dummy ACK.

In some cases, the one or more criteria may include a criterion that the first UE may send an ACK within a particular PSFCH feedback slot included in the COT. For example, in some cases, the first UE may receive an indication specifying one or more feedback slots in the COT in which an ACK may be sent. In such a case, when a feedback slot is included in the designated one or more feedback slots, the first UE may transmit an ACK in the feedback slot. For example, in some cases, the UE may receive an indication that a (pseudo) ACK may be sent in a first or second feedback slot included in the COT. Accordingly, based on the indication, the UE may transmit the ACK only in the first or second feedback slots included in the COT, and may avoid transmitting the ACK in any subsequent feedback slots. In some cases, the indication specifying the one or more feedback slots may be obtained from the serving base station, or from a second UE initiating the COT within the SCI, or from pre-configuration information in the UE.

In some cases, the first UE may receive multiple side-link multicast transmissions with its ACKs expected to be sent in the same PSFCH slot. To avoid overloading the PSFCH, there are different options for selecting which of the multiple side-link group transmissions to send the corresponding ACK for. For example, in some cases, the first UE may receive at least the second side uplink multicast transmission during the COT, where feedback is expected within the same PSFCH slot. In such a case, the first UE may decide to send only one ACK in response to receiving the first side and second side multicast transmissions. Sending only one ACK may be sufficient to delay the release of the COT.

In some cases, the first UE may select between the first side and second side uplink multicast transmissions to send an ACK for them. For example, in some cases, the UE may send the ACK according to a selection rule associated with a plurality of UEs including the first UE. In such a case, the selection rule may specify that for all of the plurality of UEs that receive both the first side and second side multicast transmissions, one of the following is to be performed: an ACK is sent for the first side-uplink multicast transmission in a feedback resource associated with the first side-uplink multicast transmission or for the second side-uplink multicast transmission in a feedback resource associated with the second side-uplink multicast transmission. In other words, the selection rule may specify which of the first side or second side multicast transmission to send the ACK, e.g., to avoid sending multiple ACKs and overloading the PSFCH. While the above example involves selecting between two side-link multicast transmissions to send an ACK for, it should be appreciated that the first UE may receive more than two side-link multicast transmissions and may select which of the more than two side-link multicast transmissions to send an ACK for.

Fig. 18 is a flow diagram illustrating example operations 1800 for wireless communication (e.g., for improved COT sharing for side-uplink unlicensed operation) in accordance with certain aspects of the present disclosure. The operations 1800 may be performed, for example, by a first UE (e.g., UE 920a in the wireless communication network 900). The operations 1800 may be implemented as software components executing and running on one or more processors (e.g., the controller/processor 1080 of fig. 10). Further, the transmission and reception of signals by the UE in operation 1800 may be implemented, for example, by one or more antennas (e.g., antenna 1052 of fig. 10). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface that obtains and/or outputs signals by one or more processors (e.g., controller/processor 1080).

At block 1802, operation 1800 may begin by: the first side-link multicast transmission is received, the first side-link multicast transmission not requiring an Acknowledgement (ACK) to be sent when the first side-link multicast transmission is successfully decoded.

At block 1804, operation 1800 may continue by: in response to receiving the first side-link multicast transmission, an ACK for the first side-link multicast transmission is sent during a Channel Occupancy Time (COT) initiated by the second UE to delay release of the COT.

In some cases, sending an ACK in block 1804 includes: the ACK is sent when a first side uplink multicast transmission corresponding to the ACK is received in the COT.

In some cases, sending an ACK in block 1804 includes: the ACK is sent when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

In some cases, sending an ACK in block 1804 includes: the ACK is sent when the first UE has scheduled transmissions to perform that fall within the COT.

In some cases, sending an ACK in block 1804 includes: the ACK is transmitted when the first UE does not have other feedback information to be transmitted during the COT.

In some cases, operation 1800 may further include: an indication of one or more feedback slots in the specified COT in which feedback information may be sent is obtained. In such a case, sending an ACK in block 1804 includes: an ACK is sent in a feedback slot when the feedback slot is included in the designated one or more feedback slots. In some cases, the indication specifying the one or more feedback slots is obtained from the serving base station, in side-uplink control information (SCI) from the second UE, or from pre-configuration information in the UE.

In some cases, operation 1800 may further include: the second side-uplink multicast transmission is received during the COT. In such a case, sending an ACK in block 1804 includes: only one ACK is sent in response to receiving the first side uplink multicast transmission and the second side uplink multicast transmission. Further, in some cases, sending an ACK in block 1804 includes: the ACK is sent according to a selection rule associated with a plurality of UEs including the first UE. In some cases, the selection rule specifies: for all of the plurality of UEs that receive both the first side-uplink multicast transmission and the second side-uplink multicast transmission, an ACK is to be sent for the first side-uplink multicast transmission in a feedback resource associated with the first side-uplink multicast transmission.

In some cases, the first side uplink multicast transmission is received in a first time slot corresponding to a physical side uplink shared channel (PSSCH), and the ACK is sent in a second time slot corresponding to a physical side uplink feedback channel (PSFCH).

Further, in some cases, sending an ACK in block 1804 includes: the ACK is sent before a threshold amount of time after receiving the first side uplink multicast transmission, the threshold amount of time corresponding to a maximum duration of the COT.

Fig. 19 illustrates a communication device 1900 that may include various components (e.g., corresponding to functional module element components) configured to perform operations of the techniques disclosed herein, such as the operations shown in fig. 18. The communications device 1900 includes a processing system 1902 coupled to a transceiver 1908 (e.g., a transmitter and/or receiver). The transceiver 1908 is configured to transmit and receive signals for the communication device 1900, such as the various signals described herein, via the antenna 1910. The processing system 1902 may be configured to perform processing functions for the communication device 1900, including processing signals received and/or to be transmitted by the communication device 1900.

The processing system 1902 includes a processor 1904 coupled to a computer-readable medium/memory 1912 via a bus 1906. In certain aspects, the computer-readable medium/memory 1912 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 1904, cause the processor 1904 to perform the operations shown in fig. 18, or other operations for performing various techniques for improved COT sharing for sidelink unlicensed operations discussed herein. In certain aspects, the computer-readable medium/memory 1912 stores code 1914 for receiving, code 1916 for transmitting, and code 1918 for obtaining.

In some cases, code for receiving 1914 may include code for receiving a first side-link multicast transmission that does not require an Acknowledgement (ACK) to be sent when the first side-link multicast transmission is successfully decoded.

In some cases, code 1916 for transmitting may include: in response to receiving the first side-link multicast transmission, sending an ACK for the first side-link multicast transmission during a Channel Occupancy Time (COT) initiated by the second UE to delay release of the COT.

In some cases, code 1916 for transmitting may include: code for sending an ACK when a first side uplink multicast transmission corresponding to the ACK is received in the COT.

In some cases, code 1916 for transmitting may include: the apparatus includes means for transmitting an ACK when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

In some cases, code 1916 for transmitting may include: code for sending an ACK when the first UE has scheduled transmissions to perform that fall within the COT.

In some cases, code 1916 for transmitting may include: the apparatus includes means for transmitting an ACK when the first UE does not have other feedback information to be transmitted during the COT.

In some cases, code 1918 for obtaining may include: code for obtaining an indication of one or more feedback slots in the specified COT in which feedback information may be transmitted.

In some cases, code 1916 for transmitting may include: the apparatus includes means for transmitting an ACK in a feedback slot when the feedback slot is included in the specified one or more feedback slots.

In some cases, code 1914 for receiving may include: code for receiving a second side-uplink multicast transmission during the COT.

In some cases, code 1916 for transmitting may include: the apparatus includes means for sending only one ACK in response to receiving the first side uplink multicast transmission and the second side uplink multicast transmission.

In some cases, code 1916 for transmitting may include: the apparatus includes means for sending an ACK according to a selection rule associated with a plurality of UEs including a first UE.

In some cases, code 1916 for transmitting may include: the method includes transmitting an ACK before a threshold amount of time after receiving the first side uplink multicast transmission, the threshold amount of time corresponding to a maximum duration of the COT.

In some aspects, the processor 1904 may include circuitry configured to implement code stored in the computer-readable medium/memory 1912, such as for performing the operations shown in fig. 18 or for performing other operations of the various techniques discussed herein for improved COT sharing for side-link unlicensed operations. For example, the processor 1904 includes circuitry 1924 for receiving, circuitry 1926 for transmitting, and circuitry 1928 for obtaining.

In some cases, the circuitry 1924 for receiving may include: circuitry for receiving a first side-link multicast transmission that does not require an Acknowledgement (ACK) to be sent when the first side-link multicast transmission is successfully decoded.

In some cases, the circuitry 1926 for transmitting may include: circuitry for transmitting an ACK for the first side-link multicast transmission during a Channel Occupancy Time (COT) initiated by the second UE to delay release of the COT in response to receiving the first side-link multicast transmission.

In some cases, the circuitry 1926 for transmitting may include: circuitry for sending an ACK when a first side uplink multicast transmission corresponding to the ACK is received in the COT.

In some cases, the circuitry 1926 for transmitting may include: circuitry for transmitting an ACK when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

In some cases, the circuitry 1926 for transmitting may include: circuitry to send an ACK when the first UE has scheduled transmissions to perform that fall within the COT.

In some cases, the circuitry 1926 for transmitting may include: circuitry to send an ACK when the first UE does not have other feedback information to send during the COT.

In some cases, the circuitry 1928 for obtaining may include: circuitry for obtaining an indication of one or more feedback slots in a given COT in which feedback information may be transmitted.

In some cases, the circuitry 1926 for transmitting may include: circuitry for transmitting an ACK in a feedback slot when the feedback slot is included in the specified one or more feedback slots.

In some cases, the circuitry 1924 for receiving may include: circuitry for receiving a second side-uplink multicast transmission during the COT.

In some cases, the circuitry 1926 for transmitting may include: circuitry for transmitting only one ACK in response to receiving the first side uplink multicast transmission and the second side uplink multicast transmission.

In some cases, the circuitry 1926 for transmitting may include: circuitry for sending an ACK according to a selection rule associated with a plurality of UEs including the first UE.

In some cases, the circuitry 1926 for transmitting may include: circuitry to send an ACK before a threshold amount of time after receiving the first side uplink multicast transmission, the threshold amount of time corresponding to a maximum duration of the COT.

Further aspects of the disclosure include the following:

aspect 1 includes a method of wireless communication performed by a first User Equipment (UE), the method comprising: measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and accessing a first time slot of the COT based on the first RSRP.

Aspect 2 includes the method of aspect 1, wherein the PSFCH is sent via a second time slot within the COT reserved for PSFCH transmission reservations.

Aspect 3 includes the method according to any one of aspects 1-2, wherein the RSRP exceeds an RSRP threshold, which indicates transmission of the PSFCH transmission via a second time slot of the COT.

Aspect 4 includes the method according to any one of aspects 1-3, wherein the RSRP threshold is predetermined.

Aspect 5 includes the method of any one of aspects 1-4, further comprising: a message indicating the RSRP threshold is received from a New Radio (NR) network to which the first UE is connected.

Aspect 6 includes the method according to any one of aspects 1-5, wherein the message is a Radio Resource Control (RRC) message or a Medium Access Control (MAC) -Control Element (CE) message.

Aspect 7 includes the method according to any one of aspects 1-6, wherein the RSRP threshold is calculated by the first UE.

Aspect 8 includes the method of any one of aspects 1-7, further comprising: measuring a second RSRP of an initial transmission sent by the second UE after initiating the COT; and adjusting the RSRP threshold based on the second RSRP.

Aspect 9 includes the method according to any one of aspects 1-8, wherein the RSRP threshold is adjusted to be less than the second RSRP.

Aspect 10 includes the method according to any one of aspects 1-9, wherein the RSRP threshold is adjusted to be no greater than the second RSRP.

Aspect 11 includes a method of wireless communication performed by a first User Equipment (UE), the method comprising: detecting a physical side uplink shared channel (PSSCH) transmission; detecting a physical side uplink feedback channel (PSFCH) transmission transmitted in response to the PSSCH transmission within a COT having a plurality of slots; and accessing a first time slot of the plurality of time slots of the COT based on the detecting the PSFCH transmission.

Aspect 12 includes the method of aspect 11, wherein the PSSCH transmission is transmitted via a second slot of the plurality of slots of the COT.

Aspect 13 includes the method of any one of aspects 11-12, wherein the PSSCH transmission is a multicast option 1PSSCH transmission sent via a slot not being part of the COT.

Aspect 14 includes the method according to any one of aspects 11-13, wherein the PSFCH transmission includes a hybrid automatic repeat request (HARQ) Negative Acknowledgement (NACK) message.

Aspect 15 includes the method according to any one of aspects 11-14, wherein the COT is initiated by a second UE; and the PSFCH transmission is sent by one or more third UEs within feedback range of the second UE.

Aspect 16 includes the method according to any one of aspects 11-15, wherein the first UE is within the feedback range of the second UE.

Aspect 17 includes a method of wireless communication performed by a first User Equipment (UE), the method comprising: receiving a first side-link multicast transmission that does not require an Acknowledgement (ACK) to be sent when the first side-link multicast transmission is successfully decoded; and in response to receiving the first side-link multicast transmission, sending the ACK for the first side-link multicast transmission during a Channel Occupancy Time (COT) initiated by a second UE.

Aspect 18 includes the method of aspect 17, wherein sending the ACK comprises: the ACK is sent when the first side uplink multicast transmission corresponding to the ACK is received in the COT.

Aspect 19 includes the method according to any one of aspects 17-18, wherein sending the ACK includes: the ACK is sent when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

Aspect 20 includes the method according to any one of aspects 17-19, wherein sending the ACK comprises: the ACK is sent when the first UE has scheduled transmissions to perform that fall within the COT.

Aspect 21 includes the method according to any one of aspects 17-20, wherein sending the ACK includes: the ACK is sent when the first UE does not have other feedback information to be sent during the COT.

Aspect 22 includes the method according to any one of aspects 17-21, further comprising: obtaining an indication specifying one or more feedback slots in the COT in which feedback information may be transmitted, wherein transmitting the ACK comprises: the ACK is transmitted within a feedback slot when the feedback slot is included within the specified one or more feedback slots.

Aspect 23 includes the method according to any of aspects 17-22, wherein the indication specifying the one or more feedback slots is obtained from a serving base station or from pre-configuration information in the UE.

Aspect 24 includes the method according to any one of aspects 17-23, further comprising: a second side-uplink multicast transmission is received during the COT.

Aspect 25 includes the method according to any one of aspects 17-24, wherein sending the ACK comprises: only one ACK is sent in response to receiving the first side uplink multicast transmission and the second side uplink multicast transmission.

Aspect 26 includes the method according to any one of aspects 17-25, wherein sending the ACK includes: transmitting the ACK according to selection rules associated with a plurality of UEs including the first UE; and the selection rule specifies: for all of the plurality of UEs that receive both the first and second side-uplink multicast transmissions, the ACK is to be sent for the first side-uplink multicast transmission in a feedback resource associated with the first side-uplink multicast transmission.

Aspect 27 includes the method of any one of aspects 17-26, wherein the first side uplink multicast transmission is received in a first time slot corresponding to a physical side uplink shared channel (PSSCH), and the ACK is sent in a second time slot corresponding to a physical side uplink feedback channel (PSFCH).

Aspect 28 includes the method according to any one of aspects 17-27, wherein sending the ACK comprises: the ACK is sent before a threshold amount of time after the first side uplink multicast transmission is received, the threshold amount of time corresponding to a maximum duration of the COT.

Aspect 29 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 device cause the one or more processors to perform the one or more instructions according to any of aspects 1-10.

Aspect 30 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 device cause the one or more processors to perform the one or more instructions according to any of aspects 11-16.

Aspect 31 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 device cause the one or more processors to perform the one or more instructions according to any of aspects 17-28.

Aspect 32 includes a first User Equipment (UE) comprising one or more units to perform any one or more of aspects 1-10.

Aspect 33 includes a first User Equipment (UE) comprising one or more units to perform any one or more of aspects 11-16.

Aspect 34 includes a first User Equipment (UE) comprising one or more units to perform any one or more of aspects 17-28.

Information and signals may be represented using any of a variety of different technologies and techniques. For example, 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.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general purpose processor, DSP, ASIC, 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 in the alternative, 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, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software for execution by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination of these. Features that perform functions may also be physically located at various locations including portions that are distributed such that the functions are performed at different physical locations. Furthermore, as used herein (including in the claims), an "or" (e.g., a list of items ending with a phrase such as "at least one of" or "one or more of") as used in the list of items indicates an inclusive list, such that, for example, a list of [ A, B, or at least one of C ] means a, or B, or C, or AB, or AC, or BC, or ABC (i.e., a and B and C).

As will be apparent to those of skill in the art so far and depending upon the particular application at hand, many modifications, substitutions, and variations may be made to the materials, apparatus, arrangement and method of use of the apparatus of the present disclosure without departing from its spirit and scope. In view of the foregoing, the scope of the present disclosure should not be limited to the particular aspects illustrated and described herein, as they are merely by way of example thereof, but rather should be fully commensurate with the scope of the appended claims and their functional equivalents.

Claims (30)

1. A method performed by a first User Equipment (UE), comprising:

measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and

a first time slot of the COT is accessed based on the first RSRP.

2. The method of claim 1, wherein the PSFCH is transmitted via a second time slot within the COT reserved for PSFCH transmission.

3. The method of claim 1, wherein the RSRP exceeds an RSRP threshold.

4. A method according to claim 3, wherein the RSRP threshold is predetermined.

5. A method according to claim 3, further comprising:

a message indicating the RSRP threshold is received from a Base Station (BS).

6. A method according to claim 3, further comprising:

determining the RSRP threshold.

7. A method according to claim 3, further comprising:

measuring a second RSRP of an initial transmission sent by the second UE after initiating the COT; and

the RSRP threshold is adjusted based on the second RSRP, wherein the RSRP threshold is adjusted to be less than the second RSRP.

8. The method of claim 1, further comprising:

detecting a physical side uplink shared channel (PSSCH) transmission;

detecting a physical side uplink feedback channel (PSFCH) transmission within the COT sent in response to the PSSCH transmission; and

the first time slot of the COT is further accessed based on the detecting the PSFCH transmission.

9. A method of wireless communication by a first User Equipment (UE), comprising:

receiving a first side-link multicast transmission that does not require an Acknowledgement (ACK) to be sent when the first side-link multicast transmission is successfully decoded; and

in response to receiving the first side-link multicast transmission, the ACK for the first side-link multicast transmission is sent during a Channel Occupancy Time (COT) initiated by a second UE.

10. The method of claim 9, wherein the sending the ACK comprises: the ACK is sent when the first side uplink multicast transmission corresponding to the ACK is received in the COT.

11. The method of claim 9, wherein the sending the ACK comprises: the ACK is sent when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

12. The method of claim 9, wherein the sending the ACK comprises: the ACK is sent when the first UE has a scheduled transmission that falls within the COT.

13. The method of claim 9, wherein the sending the ACK comprises: the ACK is sent when the first UE does not have other feedback information to be sent during the COT.

14. The method of claim 9, further comprising: obtaining an indication specifying one or more feedback slots in the COT in which feedback information can be sent, wherein the sending the ACK comprises: the ACK is transmitted in a feedback slot of the specified one or more feedback slots.

15. The method of claim 9, further comprising: a second side-uplink multicast transmission is received during the COT.

16. A first User Equipment (UE), comprising:

means for measuring a first Reference Signal Received Power (RSRP) of a physical side uplink feedback channel (PSFCH) transmission transmitted during a Channel Occupation Time (COT) initiated by a second UE; and

means for accessing a first time slot of the COT based on the first RSRP.

17. The first UE of claim 16, wherein the PSFCH is transmitted via a second time slot within the COT reserved for PSFCH transmission.

18. The first UE of claim 16, wherein the RSRP exceeds an RSRP threshold.

19. The first UE of claim 18, wherein the RSRP threshold is predetermined.

20. The first UE of claim 18, further comprising:

means for receiving a message from a Base Station (BS) indicating the RSRP threshold.

21. The first UE of claim 18, further comprising:

and means for determining the RSRP threshold.

22. The first UE of claim 18, further comprising:

means for measuring a second RSRP of an initial transmission sent by the second UE after initiating the COT; and

means for adjusting the RSRP threshold based on the second RSRP, wherein the RSRP threshold is adjusted to be less than the second RSRP.

23. The first UE of claim 16, further comprising:

a unit for detecting physical side uplink shared channel (PSSCH) transmission;

means for detecting, within the COT, a physical side uplink feedback channel (PSFCH) transmission sent in response to the PSSCH transmission; and

the apparatus further includes means for accessing the first time slot of the COT based further on the detecting the PSFCH transmission.

24. A first User Equipment (UE), comprising:

means for receiving a first side-link multicast transmission that does not require sending an Acknowledgement (ACK) when the first side-link multicast transmission is successfully decoded; and

in response to receiving the first side-link multicast transmission, transmitting the ACK for the first side-link multicast transmission during a Channel Occupancy Time (COT) initiated by a second UE.

25. The first UE of claim 24, wherein the means for sending the ACK comprises: and means for sending the ACK when the first side uplink multicast transmission corresponding to the ACK is received in the COT.

26. The first UE of claim 24, wherein the means for sending the ACK comprises: the apparatus includes means for sending the ACK when the first UE is within a maximum spatial feedback range associated with the first side uplink multicast transmission.

27. The first UE of claim 24, wherein the means for sending the ACK comprises: the apparatus includes means for sending the ACK when the first UE has a scheduled transmission that falls within the COT.

28. The first UE of claim 24, wherein the means for sending the ACK comprises: the apparatus includes means for transmitting the ACK when the first UE does not have other feedback information to be transmitted during the COT.

29. The first UE of claim 24, further comprising:

obtaining an indication of one or more feedback slots in the COT in which feedback information can be sent, wherein the means for sending the ACK comprises: and means for transmitting the ACK within a feedback slot of the specified one or more feedback slots.

30. The first UE of claim 24, further comprising:

and means for receiving a second side uplink multicast transmission during the COT.