WO2025059899A1

WO2025059899A1 - Systems and methods for resuming transmission in a sidelink shared channel occupancy time

Info

Publication number: WO2025059899A1
Application number: PCT/CN2023/119973
Authority: WO
Inventors: Luanxia YANG; Shaozhen GUO; Chih-Hao Liu; Changlong Xu; Jing Sun; Xiaoxia Zhang; Siyi Chen; Hao Xu
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2023-09-20
Filing date: 2023-09-20
Publication date: 2025-03-27
Anticipated expiration: 2026-03-20

Abstract

Wireless communications systems and methods related to channel occupancy time-sharing information (COT-SI) reservation of a COT for sidelink communications in an unlicensed band are provided. In some aspects, a user equipment (UE) performs a channel access procedure to acquire one or more COTs in a sidelink channel over an unlicensed new radio (NR) band. Further, the UE transmits a COT sharing information (COT-SI) configured to reserve the one or more COTs for a future transmission via the sidelink channel.

Description

SYSTEMS AND METHODS FOR RESUMING TRANSMISSION IN A SIDELINK SHARED CHANNEL OCCUPANCY TIME

TECHNICAL FIELD

This application relates to wireless communication systems, and more particularly to systems and methods for resuming transmission in a sidelink (SL) shared channel occupancy time (COT) .

INTRODUCTION

Wireless communications 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 capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . A wireless multiple-access communications system may include a number of base stations (BSs) , each simultaneously supporting communications for multiple communication devices, which may be otherwise known as user equipment (UE) .

To meet the growing demands for expanded mobile broadband connectivity, wireless communication technologies are advancing from the long term evolution (LTE) technology to a next generation new radio (NR) technology, which may be referred to as 5^th Generation (5G) . For example, NR is designed to provide a lower latency, a higher bandwidth or a higher throughput, and a higher reliability than LTE. NR is designed to operate over a wide array of spectrum bands, for example, from low-frequency bands below about 1 gigahertz (GHz) and mid-frequency bands from about 1 GHz to about 6 GHz, to high-frequency bands such as millimeter wave (mmWave) bands. NR is also designed to operate across different spectrum types, from licensed spectrum to unlicensed and shared spectrum. Spectrum sharing enables operators to opportunistically aggregate spectrums to dynamically support high-bandwidth services. Spectrum sharing can extend the benefit of NR technologies to operating entities that may not have access to a licensed spectrum.

In a wireless communication network, a BS may communicate with a UE in an uplink direction and a downlink direction. Sidelink was introduced in LTE to allow a UE to send data to another UE without tunneling through the BS and/or an associated core network. The LTE sidelink technology had been extended to provision for 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 sidelink communications, D2D communications, V2X communications, and/or C-V2X over licensed bands and/or unlicensed bands.

BRIEF SUMMARY OF SOME EXAMPLES

The following summarizes some aspects of the present disclosure 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 neither to identify key or critical elements of all aspects of the disclosure nor to 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 summary form as a prelude to the more detailed description that is presented later.

In some aspects of the disclosure, a method of wireless communication performed by a first user equipment (UE) comprises performing a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel. The method further comprises transmitting COT sharing information (COT-SI) to one or more responding UEs. The method further comprises transmitting a first message to at least one of the one or more responding UEs during the COT. The method further comprises refraining from transmitting for a duration during the COT after transmitting the first message. The method further comprises transmitting, based on a condition, a second message to a second UE during the COT after the duration.

In some aspects, a first user equipment (UE) comprises one or more memories and one or more processors coupled to the one or more memories storing instructions that are executable by the one or more processors, individually or in any combination, configured to cause the first UE to perform a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel. The one or more processors are further configured to cause the first UE to transmit COT sharing information (COT-SI) to one or more responding UEs. The one or more processors are further configured to cause the first UE to transmit a first message to at least one of the one or more responding UEs during the COT. The one or more processors are further configured to cause the first UE to refrain from transmitting for a duration during the COT after transmitting the first message. The one or more processors are further configured to cause the first UE to transmit, based on a condition, a second message to a second UE during the COT after the duration.

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 perform a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel. The program code further comprises code for causing the first UE to transmit COT sharing information (COT-SI) to one or more responding UEs. The program code further comprises code for causing the first UE to transmit a first message to at least one of the one or more responding UEs during the COT. The program code further comprises code for causing the first UE to refrain from transmitting for a duration during the COT after transmitting the first message. The program code further comprises code for causing the first UE to transmit, based on a condition, a second message to a second UE during the COT after the duration.

In some aspects, a first user equipment (UE) comprises means for performing a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel. The first UE further comprises means for transmitting COT sharing information (COT-SI) to one or more responding UEs. The first UE further comprises means for transmitting a first message to at least one of the one or more responding UEs during the COT. The first UE further comprises means for refraining from transmitting for a duration during the COT after transmitting the first message. The first UE further comprises means for transmitting, based on a condition, a second message to a second UE during the COT after the duration.

Other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments of the present invention in conjunction with the accompanying figures. While features of the present invention may be discussed relative to certain embodiments and figures below, all embodiments of the present invention can 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 similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication network according to some aspects of the present disclosure.

FIG. 2 is a timing diagram illustrating a radio frame structure according to some aspects of the present disclosure.

FIG. 3 illustrates a wireless communication network that provisions for sidelink communications according to some aspects of the present disclosure.

FIGS. 4A-4C illustrate example diagrams illustrating radio frame resources for resuming transmission by a UE using shared channel occupancy time according to some aspects of the present disclosure.

FIGS. 5-7 illustrate example timing resource diagrams with cyclic prefix extension for resuming transmission by a UE using shared channel occupancy time according to some aspects of the present disclosure.

FIG. 8 is a block diagram of an exemplary user equipment (UE) according to some aspects of the present disclosure.

FIG. 9 is a flow diagram of a wireless communication method according to 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. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

This disclosure relates generally to wireless communications systems, also referred to as wireless communications networks. In various aspects, the techniques and apparatus 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, 5^th Generation (5G) or new radio (NR) networks, as well as other communications networks. As described herein, the terms “networks” and “systems” may be used interchangeably.

An OFDMA network may implement a radio technology 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 part of universal mobile telecommunication system (UMTS) . In particular, long term evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents provided from an organization named “3rd Generation Partnership Project” (3GPP) , and cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . These various radio technologies and standards are known or are being developed. For example, the 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations that aims to define a globally applicable third generation (3G) mobile phone specification. 3GPP long term evolution (LTE) is a 3GPP project which was aimed at improving the UMTS mobile phone standard. The 3GPP may define specifications for the next generation of mobile networks, mobile systems, and mobile devices. The present disclosure is concerned with the evolution of wireless technologies from LTE, 4G, 5G, NR, and beyond with shared access to wireless spectrum between networks using a collection of new and different radio access technologies or radio air interfaces.

In particular, 5G networks contemplate diverse deployments, diverse spectrum, and diverse services and devices that may be implemented using an OFDM-based unified, air interface. In order to achieve these goals, further enhancements to LTE and LTE-Aare considered in addition to development of the new radio technology for 5G NR networks. The 5G NR will be capable of scaling to provide coverage (1) to a massive Internet of things (IoTs) with a ultra-high density (e.g., ～1M nodes/km²) , ultra-low complexity (e.g., ～10s of bits/sec) , ultra-low energy (e.g., ～10+ years of battery life) , and deep coverage with the capability to reach challenging locations; (2) including mission-critical control with strong security to safeguard sensitive personal, financial, or classified information, ultra-high reliability (e.g., ～99.9999%reliability) , ultra-low latency (e.g., ～ 1 ms) , and users with wide ranges of mobility or lack thereof; and (3) with enhanced mobile broadband including extreme high capacity (e.g., ～ 10 Tbps/km²) , extreme data rates (e.g., multi-Gbps rate, 100+ Mbps user experienced rates) , and deep awareness with advanced discovery and optimizations.

A 5G NR communication system may be implemented to use optimized OFDM-based waveforms with scalable numerology and transmission time interval (TTI) . Additional features may also include having a common, flexible framework to efficiently multiplex services and features with a dynamic, low-latency time division duplex (TDD) /frequency division duplex (FDD) design; and with advanced wireless technologies, such as massive multiple input, multiple output (MIMO) , robust millimeter wave (mmWave) transmissions, advanced channel coding, and device-centric mobility. Scalability of the numerology in 5G NR, with scaling of subcarrier spacing, may efficiently address operating diverse services across diverse spectrum and diverse deployments. For example, in various outdoor and macro coverage deployments of less than 3GHz FDD/TDD implementations, subcarrier spacing may occur with 15 kHz, for example over 5, 10, 20 MHz, and the like bandwidth (BW) . For other various outdoor and small cell coverage deployments of TDD greater than 3 GHz, subcarrier spacing may occur with 30 kHz over 80/100 MHz BW. For other various indoor wideband implementations, using a TDD over the unlicensed portion of the 5 GHz band, the subcarrier spacing may occur with 60 kHz over a 160 MHz BW. Finally, for various deployments transmitting with mmWave components at a TDD of 28 GHz, subcarrier spacing may occur with 120 kHz over a 500 MHz BW.

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

Various other aspects and features of the disclosure are further described 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 an ordinary level of skill in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspects 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. In addition, such an apparatus may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. For example, a method may be implemented as part of a system, device, apparatus, and/or as instructions stored on a computer readable medium for execution on a processor or computer. Furthermore, an aspect may comprise at least one element of a claim.

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

In some cases, the term “sidelink UE” can refer to a user equipment device performing a device-to-device communication or other types of communications with another user equipment device independent of any tunneling through the BS (e.g., gNB) and/or an associated core network. A sidelink UE can be a “sidelink transmitting UE, ” which may refer to a user equipment device performing a sidelink transmission operation, or the sidelink UE can be a “sidelink receiving UE, ” which may refer to a user equipment device performing a sidelink reception operation (i.e., receiving transmission from a sidelink transmitting UE) . A sidelink UE may operate as a transmitting sidelink UE at one time and operate as a receiving sidelink UE at another time.

In some cases, a sidelink UE can be a “COT-initiating UE” where the sidelink may initiate or acquire a channel occupancy time (COT) in a shared radio frequency band (e.g., in a shared spectrum or an unlicensed spectrum) for sidelink communication. For instance, the initiating UE may perform a clear channel assessment (CCA) or a category 4 (CAT4) listen-before-talk (LBT) in the shared radio frequency band to contend or acquire the COT. Upon passing the LBT (indicating the channel is clear for transmission) , the initiating UE may transmit a sidelink transmission during the acquired COT, and a receiving UE may receive the sidelink transmission from the COT-initiating UE. In some cases, a sidelink UE can be a “responding UE” where the sidelink UE responds to a sidelink transmission transmitted by any COT-initiating UE using the COT. A sidelink UE may operate as a COT-initiating UE at one time and operate as a responding UE at another time.

The provisioning of sidelink services, such as device-to-device (D2D) , vehicle-to-vehicle (V2V) , vehicle-to-everything (V2X) , and/or cellular vehicle-to-everything (C-V2X) communications, over dedicated spectrum or licensed spectrum are relatively straight-forward as channel access in the dedicated spectrum or licensed spectrum is guaranteed. NR-unlicensed (NR-U) can bring benefit for sidelink services, for example, by offloading sidelink traffic to the unlicensed spectrum at no cost. However, channel access in a shared spectrum or an unlicensed spectrum is not guaranteed. Thus, to provision for sidelink services over a shared spectrum or unlicensed spectrum, sidelink user equipment devices (UEs) are required to contend for channel access in the spectrum, for example, via clear channel assessment (CCA) and/or listen-before-talk (LBT) procedures.

An LBT can be based on energy detection (ED) or signal detection. For an energy detection-based LBT, the LBT results in a pass when signal energy measured from the channel is below a threshold. Conversely, the LBT results in a failure when signal energy measured from the channel exceeds the threshold. For a signal detection-based LBT, the LBT results in a pass when a channel reservation signal (e.g., a predetermined preamble signal) is not detected in the channel. Additionally, an LBT may be in a variety of modes. An LBT mode may be, for example, a category 4 (CAT4) LBT, a category 2 (CAT2) LBT, or a category 1 (CAT1) LBT. A CAT1 LBT is referred to a no LBT mode, where no LBT is to be performed prior to a transmission. A CAT2 LBT refers to an LBT without a random backoff period. For instance, a transmitting node may determine a channel measurement in a time interval and determine whether the channel is available or not based on a comparison of the channel measurement against a ED threshold. A CAT4 LBT refers to an LBT with a random backoff and a variable contention window (CW) . For instance, a transmitting node may draw a random number and backoff for a duration based on the drawn random number in a certain time unit.

In some aspects, a COT-initiating sidelink UE may contend for a COT in a shared radio frequency band by performing CCA or a CAT4 LBT. Upon passing the CCA or CAT4 LBT (indicating the channel is cleared for transmission) , the sidelink UE may transmit a sidelink transmission to one or more sidelink receiving UEs during the COT. In some sidelink use cases (e.g., for V2X) , sidelink data traffic may include small-sized or short data bursts (e.g., with a few bytes to tens of kilobytes of information data) . In some aspects, the duration of a COT may be dependent on regulations imposed by a regulator of the shared radio frequency band or a certain deployment, which can be in the range from about 2ms to about 10 ms (e.g., which may correspond to from about 4 slots to about 20 slots in NR CV2X with 30 kHz subcarrier spacing (SCS) ) . Thus, in some instances, the sidelink transmission with the small-sized data bursts 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 or other UEs instead of leaving the remaining COT unused. In some instances, the COT-initiating UE may include COT-related information such as but not limited to the duration of the COT in its transmissions so that the receiving UEs can use the information to share/utilize the COT. For example, the initiating UE may transmit a PSCCH after initiating the COT and the SCI in the PSCCH may include the COT-related information. As another example, the initiating UE may transmit a PSCCH or a PSSCH after initiating the COT, and the SCI-1 in the PSCCH or the SCI-2 in the PSSCH, respectively, may include the COT-related information. In some cases, after receiving the SCI, SCI-1 or SCI-2, the receiving or other UEs may perform a CAT2 LBT or no LBT when the receiving or other UEs transmit during the COT initiated by the COT-initiating UE, which can be advantageous because CAT2 LBT or no LBT has less uncertainty in accessing the channel.

In some cases, it may be desirable for a COT-initiating UE to reserve at least a portion of the acquired COT for future use. For example, a COT-initiating UE may transmit a message at the start of a COT, listen for transmissions from responding UEs sharing the COT, then resume transmitting during the COT. Conflicts may arise, however, between the COT-initiating UE and responding UEs each utilizing the same shared resources associated with the COT.

Some aspects of the present disclosure disclose methods, systems and apparatus directed to resuming transmission in a sidelink shared COT. A COT-initiating UE may transmit COT sharing information (COT-SI) to a number of “responding” UEs. A responding UE is one which receives an indication of resources it may use in association with a COT, and may also be referred to as COT sharing UEs. The COT-initiating UE may transmit a message to one or more responding UE using one or more frequency channels after transmitting the COT-SI. After this initial transmission, responding UEs may use the resources they were indicated in the COT-SI to communicate with the COT-initiating UE. In some aspects, responding UEs may be allocated different frequency channels such that multiple responding UEs may communicate simultaneously with the COT-initiating UE.

The COT-initiating UE may resume transmitting at a later time during the same COT as the first transmission. In order to avoid resource conflicts, certain rules or conditions may be used to determine which UE may transmit using certain resources associated with the shared COT. A resource conflict may occur, for example, if a responding UE is only capable of communicating half-duplex, and both the responding UE and the COT-initiating UE attempt to transmit a message to each other using the same shared time and frequency resources. In some aspects, the COT-initiating UE may always resume its own COT.

In some aspects, whether the COT-initiating UE can resume its COT or not depends on the traffic target of the COT-initiating UE. For example, the COT-initiating UE may resume its COT if the target of the COT-initiating UE is not a UE that can share the COT (i.e., a responding UE) . If the COT-initiating UE indicates the whole sharable COT to all responding UEs, the target UE where the COT-initiating UE intends to transmit should not be any responding UEs who are indicated to share the COT. If the COT-initiating UE indicates the specified resource (i.e., both time and frequency) to each responding UE, then the target UE where the COT-initiating UE intends to transmit should not be the responding UE whose indicated shared resources are overlapped with the COT-initiating UE’s resumed transmission.

In some aspects, the COT-initiating UE may resume its COT if the target UE where the COT-initiating UE intends to transmit is not the responding UE whose reserved resource is overlapped with the COT-initiating UE’s resuming transmission in time i.e., a frequency division multiplexed (FDMed) responding UE. In some aspects, the ability of the COT-initiating UE to resume transmission may further depend on the transmission priority of the COT-initiating UE and the transmission priority of the FDMed responding UE. If the COT-initiating UE has higher transmission priority than the highest transmission priority among all FDMed responding UEs, then the COT-initiating UE can resume the COT.

In some aspects, a cyclic prefix extension (CPE) may be included on a resuming transmission by the COT-initiating UE. The selection of a length of the CPE may be configured, predetermined, based on a heuristic/rule etc. In some aspects, responding UEs may monitor the channel and sense when the COT-initiating UE is transmitting a CPE, and may drop a scheduled transmission if the COT-initiating UE is transmitting. In this way, the selection of a CPE length/starting position may be used to control which UEs have access to the shared COT. For example, in some aspects, the COT-initiating UE may always select the earliest starting position of the CPE i.e., 16 microseconds (us) into the symbol preceding the first message transmission symbol which may ensure that the COT-initiating UE takes priority over responding UEs (unless, for example, a responding UE has the same CPE starting position) . In some aspects, the COT-initiating UE always selects the earliest starting position for the CPE based on required channel access type among the candidate starting positions associated with the intended PSCCH/PSSCH transmission.

In some aspects, the COT-initiating UE selects the CPE starting position based on both transmission priority and CPE of FDMed responding UEs. For example, if the transmission priority of the COT-initiating UE has higher priority than the highest transmission priority among all FDMed responding UEs, the COT-initiating UE will select the CPE which is earlier than the CPE of the FDMed responding UEs. Otherwise, the COT-initiating UE may select the CPE which is later than the CPE of FDMed responding UEs. In some aspects, the CPE may start before a second CPE associated with one of the responding UEs having a lower priority than the COT-initiating UE and after a third CPE associated with a different one of the responding UEs having a higher priority than the COT-initiating UE.

In some aspects, whether the COT-initiating UE will follow a legacy rule to select the CPE or not depending on a condition. For example, the legacy rule may be that if a resource reservation is transmitted or resource reservations are detected, the UE selects the (pre) configured default CPE starting position, otherwise, a CPE starting position may be randomly selected among one or multiple CPE starting candidate positions (pre) configured per priority of the PSCCH/PSSCH transmission. In some aspects, the condition is if there is a transmission right before the slot the COT-initiating UE intends to use, then the COT-initiating UE can always select the CPE which makes the gap equal to 16us. In some aspects, the selection of CPE depends on the gaps within the COT. If any gap between any two transmissions within the COT is up to 16us, the COT-initiating UE can always select the CPE which makes the gap equal to 16us. If any gap between any two transmissions within the COT is up to 25us, the COT-initiating UE can select the CPE which make the gap equal to 25us. If these conditions are not fulfilled, the COT-initiating UE may use a legacy rule to determine the CPE starting position. A COT-initiating UE may determine the gap between two transmission by measurement, or by receiving an indication from a responding UE of a selected starting position. For example, a responding UE may indicate a CPE starting position through an SCI-1 or SCI-2.

Aspects of the present disclosure can provide several benefits. A COT-initiating UE may more fully utilize a COT which has been acquired by allowing other UEs to share that COT, and also allow the COT-initiating UE itself to use the COT at different times without causing resource conflicts. This allows for less time wasted sensing a channel in order to obtain a COT, and more efficient use of available communication resources.

FIG. 1 illustrates a wireless communication network 100 according to some aspects of the present disclosure. The network 100 may be a 5G network. The network 100 includes a number of base stations (BSs) 105 (individually labeled as 105a, 105b, 105c, 105d, 105e, and 105f) and other network entities. A BS 105 may be a station that communicates with UEs 115 (individually labeled as 115a, 115b, 115c, 115d, 115e, 115f, 115g, 115h, and 115k) 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 a BS 105 and/or a BS subsystem serving the coverage area, depending on the context in which the term is used.

A BS 105 may provide communication coverage for a macro cell or a small cell, such as a pico cell or a femto cell, and/or other types of cell. A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a pico cell, would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell, such as a femto cell, would also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG) , UEs for users in the home, and the like) . A BS for a macro cell may be referred to as a macro BS. A BS for a small cell may be referred to as a small cell BS, a pico BS, a femto BS or a home BS. In the example shown in FIG. 1, the BSs 105d and 105e may be regular macro BSs, while the BSs 105a-105c may be macro BSs enabled with one of three dimension (3D) , full dimension (FD) , or massive MIMO. The BSs 105a-105c may take advantage of their higher dimension MIMO capabilities to exploit 3D beamforming in both elevation and azimuth beamforming to increase coverage and capacity. The BS 105f may be a small cell BS which may be a home node or portable access point. A BS 105 may support one or multiple (e.g., two, three, four, and the like) cells.

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

The UEs 115 are dispersed throughout the wireless network 100, and each UE 115 may be stationary or mobile. A UE 115 may also be referred to as a terminal, a mobile station, a subscriber unit, a station, or the like. A UE 115 may be a cellular phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, or the like. In one aspect, a UE 115 may be a device that includes a Universal Integrated Circuit Card (UICC) . In another aspect, a UE may be a device that does not include a UICC. In some aspects, the UEs 115 that do not include UICCs may also be referred to as IoT devices or internet of everything (IoE) devices. The UEs 115a-115d are examples of mobile smart phone-type devices accessing network 100. A UE 115 may also be a machine specifically configured for connected communication, including machine type communication (MTC) , enhanced MTC (eMTC) , narrowband IoT (NB-IoT) and the like. The UEs 115e-115h are examples of various machines configured for communication that access the network 100. The UEs 115i-115k are examples of vehicles equipped with wireless communication devices configured for communication that access the network 100. A UE 115 may be able to communicate with any type of the BSs, whether macro BS, small cell, or the like. In FIG. 1, a lightning bolt (e.g., communication links) indicates wireless transmissions between a UE 115 and a serving BS 105, which is a BS designated to serve the UE 115 on the downlink (DL) and/or uplink (UL) , desired transmission between BSs 105, backhaul transmissions between BSs, or sidelink transmissions between UEs 115.

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

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

The network 100 may also support mission critical communications with ultra-reliable and redundant links for mission critical devices, such as the UE 115e, which may be a drone. Redundant communication links with the UE 115e may include links from the macro BSs 105d and 105e, as well as links from the small cell BS 105f. Other machine type devices, such as the UE 115f (e.g., a thermometer) , the UE 115g (e.g., smart meter) , and UE 115h (e.g., wearable device) may communicate through the network 100 either directly with BSs, such as the small cell BS 105f, and the macro BS 105e, or in multi-step-size configurations by communicating with another user device which relays its information to the network, such as the UE 115f communicating temperature measurement information to the smart meter, the UE 115g, which is then reported to the network through the small cell BS 105f. The network 100 may also provide additional network efficiency through dynamic, low-latency TDD/FDD communications, such asV2V, V2X, C-V2X communications between a UE 115i, 115j, or 115k and other UEs 115, and/or vehicle-to-infrastructure (V2I) communications between a UE 115i, 115j, or 115k and a BS 105.

In some implementations, the network 100 utilizes OFDM-based waveforms for communications. An OFDM-based system may partition the system BW into multiple (K) orthogonal subcarriers, which are also commonly referred to as subcarriers, tones, bins, or the like. Each subcarrier may be modulated with data. In some instances, the subcarrier spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system BW. The system BW may also be partitioned into subbands. In other instances, the subcarrier spacing and/or the duration of TTIs may be scalable.

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

The DL subframes and the UL subframes can be further divided into several regions. For example, each DL or UL subframe may have pre-defined regions for transmissions of reference signals, control information, and data. Reference signals are predetermined signals that facilitate the communications between the BSs 105 and the UEs 115. For example, a reference signal can have a particular pilot pattern or structure, where pilot tones may span across an operational BW or frequency band, each positioned at a pre-defined time and a pre-defined frequency. For example, a BS 105 may transmit cell specific reference signals (CRSs) and/or channel state information –reference signals (CSI-RSs) to enable a UE 115 to estimate a DL channel. Similarly, a UE 115 may transmit sounding reference signals (SRSs) to enable a BS 105 to estimate a UL channel. Control information may include resource assignments and protocol controls. Data may include protocol data and/or operational data. In some aspects, the BSs 105 and the UEs 115 may communicate using self-contained subframes. A self-contained subframe may include a portion for DL communication and a portion for UL communication. A self-contained subframe can be DL-centric or UL-centric. A DL-centric subframe may include a longer duration for DL communication than for UL communication. A UL-centric subframe may include a longer duration for UL communication than for UL communication.

In some aspects, the network 100 may be an NR network deployed over a licensed spectrum. The BSs 105 can transmit synchronization signals (e.g., including a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) ) in the network 100 to facilitate synchronization. The BSs 105 can broadcast system information associated with the network 100 (e.g., including a master information block (MIB) , remaining system information (RMSI) , and other system information (OSI) ) to facilitate initial network access. In some instances, the BSs 105 may broadcast the PSS, the SSS, and/or the MIB in the form of synchronization signal block (SSBs) over a physical broadcast channel (PBCH) and may broadcast the RMSI and/or the OSI over a physical downlink shared channel (PDSCH) .

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

After receiving the PSS and SSS, the UE 115 may receive a 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. The RMSI and/or OSI may include radio resource control (RRC) information related to random access channel (RACH) procedures, paging, control resource set (CORESET) for physical downlink control channel (PDCCH) monitoring, physical UL control channel (PUCCH) , physical UL shared channel (PUSCH) , power control, and SRS.

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

After establishing a connection, the UE 115 and the BS 105 can enter a normal operation stage, where operational data may be exchanged. For example, the BS 105 may schedule the UE 115 for UL and/or DL communications. The BS 105 may transmit UL and/or DL scheduling grants to the UE 115 via a PDCCH. The BS 105 may transmit a DL communication signal to the UE 115 via a PDSCH according to a DL scheduling grant. The UE 115 may transmit a UL communication signal to the BS 105 via a PUSCH and/or PUCCH according to a UL scheduling grant. The connection may be referred to as an RRC connection. When the UE 115 is actively exchanging data with the BS 105, the UE 115 is in an RRC connected state.

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

In some aspects, the BS 105 may communicate with a UE 115 using hybrid automatic repeat request (HARQ) techniques to improve communication reliability, for example, to provide a URLLC service. The BS 105 may schedule a UE 115 for a PDSCH communication by transmitting a DL grant in a PDCCH. The BS 105 may transmit a DL data packet to the UE 115 according to the schedule in the PDSCH. The DL data packet may be transmitted in the form of a transport block (TB) . If the UE 115 decodes the DL data packet successfully, the UE 115 may transmit a HARQ acknowledgement (ACK) to the BS 105. Conversely, if the UE 115 fails to decode the DL transmission successfully, the UE 115 may transmit a HARQ negative-acknowledgement (NACK) to the BS 105. Upon receiving a HARQ NACK from the UE 115, the BS 105 may retransmit the DL data packet to the UE 115. The retransmission may include the same coded version of DL data as the initial transmission. Alternatively, the retransmission may include a different coded version of the DL data than the initial transmission. The UE 115 may apply soft-combining to combine the encoded data received from the initial transmission and the retransmission for decoding. The BS 105 and the UE 115 may also apply HARQ for UL communications using substantially similar mechanisms as the DL HARQ.

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

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

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

In some aspects, a sidelink communication can be in a unicast mode, a groupcast mode, or a broadcast mode, where HARQ may be applied to unicast and/or groupcast communications. For unicast communication, a sidelink transmitting UE 115 may transmit a sidelink transmission including data to a single sidelink receiving UE 115 and may request a HARQ acknowledgement/negative-acknowledgement (ACK/NACK) feedback from the sidelink receiving UE 115. If the sidelink receiving UE 115 successfully decoded data from the sidelink transmission, the sidelink receiving UE 115 transmits an ACK. Conversely, if the sidelink receiving UE 115 fails to decode data from the sidelink transmission, the sidelink receiving UE 115 transmits an NACK. Upon receiving a NACK, the sidelink transmitting UE 115 may retransmit the data. For broadcast communication, a 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 a neighborhood of the sidelink transmitting UE 115 and may not request for an ACK/NACK feedback for the sidelink transmission.

For groupcast communication, a 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) . Groupcast communication may have a wide variety of use cases in sidelink. As an example, groupcast communication can be used in a V2X use case (e.g., vehicle platooning) to instruct a group of vehicles nearby an intersection or traffic light to stop at the intersection. In some aspects, a groupcast communication can be connection-based, where the group of the sidelink receiving UEs 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 UE 115, and thus the sidelink transmitting UE 115 may request an ACK/NACK feedback from each sidelink receiving UE 115 in the group. In some instances, the sidelink transmitting UE 115 may provide each sidelink receiving UE with a different resource (e.g., an orthogonal resource) for transmitting an ACK/NACK feedback. In some other aspects, a groupcast communication can be connectionless, where the group of sidelink receiving UEs 115 that can receive the groupcast transmission may be unknown to the sidelink transmitting UE 115. In some instances, the group of sidelink receiving UEs 115 may receive the groupcast communication based on a zone or geographical location of the receiving UEs 115. Since the sidelink transmitting UE 115 may not have knowledge of the receiving sidelink UEs 115, the sidelink transmitting UE 115 may request an NACK-only feedback from the sidelink receiving UEs 115, referred to as a groupcast option-1 transmission. For instance, a sidelink receiving UE 115 may transmit an NACK if the sidelink receiving UE detected the presence of SCI, but fails to decode data (transport block) from the sidelink transmission. The sidelink receiving UE 115 may not transmit an ACK if the data decoding is successful. Groupcast option-2 transmission refers to the scenario where a sidelink receiving UE transmits an ACK if the data decoding is successful and transmits an NACK if the decoding fails. In some instances, the sidelink receiving UEs 115 may be assigned with the same resource for transmitting an NACK feedback. The simultaneous NACK transmission from multiple sidelink receiving UEs 115 in the same resource may form a single frequency network (SFN) transmission (where waveforms of the multiple NACK transmissions are combined) at the sidelink transmitting UE 115. Similar to the unicast communication, the sidelink transmitting UE 115 may retransmit sidelink data upon receiving an NACK for a connection-based or connectionless groupcast transmission.

In some aspects, a COT-initiating UE may transmit COT sharing information (COT-SI) to other UEs. COT-SI may be transmitted using PSCCH or PSSCH, as a separate message or as part of an SCI-1, SCI-2, or other appropriate message structure. COT-SI may indicate time and/or frequency resources which a responding UE is allocated to use with a lesser or no LBT requirement since it is sharing the COT acquired by the COT-initiating UE. In some aspects, responding UEs are not allowed to use shared COT resources in communicating with other UEs besides the COT-initiating UE. A COT-initiating UE, however, may communicate during a COT with other UEs besides responding UEs which were indicated resources via a COT-SI.

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

Each slot 202 includes a number of subcarriers 204 in frequency and a number of symbols 206 in time. The number of subcarriers 204 and/or the number of symbols 206 in a slot 202 may vary depending on the aspects, for example, based on the channel bandwidth, the subcarrier spacing (SCS) , and/or the CP mode. One subcarrier 204 in frequency and one symbol 206 in time forms one resource element (RE) 212 for transmission. A resource block (RB) 210 is formed from a number of consecutive subcarriers 204 in frequency and a number of consecutive 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 a time-granularity of slots 202 or mini-slots 208. Each slot 202 may be time-partitioned into K number of mini-slots 208. Each mini-slot 208 may include one or more symbols 206. The mini-slots 208 in a slot 202 may have variable lengths. For example, when a slot 202 includes N number of symbols 206, a mini-slot 208 may have a length between one symbol 206 and (N-1) symbols 206. In some aspects, a 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 UE at a frequency-granularity of a resource block (RB) 210 (e.g., including about 12 subcarriers 204 in 1 symbol, 2 symbols, …, 14 symbols) . In some aspects, a UE (e.g., UE 115i of FIG. 1) may communicate sidelink with another UE (e.g., UE 115j of FIG. 1) in units of time slots similar to the slot 202.

In some aspects, an acquired COT may have a duration that is one or more mini-slots or one or more slots in length. Resources allocated to different UEs (either the COT-initiating UE or responding UEs) as indicated in a COT-SI may be indicated according to times within a mini-slot or slot structure.

FIG. 3 illustrates an example of a wireless communication network 300 that provisions for sidelink communications according to aspects of the present disclosure. The network 300 may correspond to a portion of the network 100 may utilize the radio frame structure 200 for communications. FIG. 3 illustrates one BS 305 and five UEs 315 (shown as 315a, 315b, 315c, 315d, and 315e) for purposes of simplicity of discussion, though it will be recognized that aspects of the present disclosure may scale to any suitable number of UEs 315 (e.g., the about 2, 3, 4, 6, 7 or more) and/or BSs 305 (e.g., the about 2, 3 or more) . The BS 305 and the UEs 315 may be similar to the BSs 105 and the UEs 115, respectively. The BS 305 and the UEs 315 may share the same radio frequency band for communications. In some instances, the radio frequency band may be a licensed band. In some instances, the radio frequency band may be an unlicensed band. In some instances, the radio frequency band may be a frequency range 1 (FR1) band. In some instances, the radio frequency band may be a FR2 band. In general, the radio frequency band may be at any suitable frequency.

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

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

FIGS. 4A-4C illustrate example diagrams illustrating radio frame resources for resuming transmission by a UE using shared channel occupancy time according to some aspects of the present disclosure. In each of FIGS. 4A-4C, the X-axis represents time in some units, and the Y-axis represents frequency in some units. The illustrated frame may represent a slot, mini-slot, a portion of a slot, or more than a slot in a radio frame. The arrows represent assignment/allocation/indication of frequency and/or time resources, specifically those associated with a shared COT. FIGS. 4A-4C describe the conditions under which a COT-initiating UE may resume transmission within the shared COT. Note that in some aspects, the COT-initiating UE may always resume its own COT, regardless of the status of the other UEs sharing the COT.

FIG. 4A illustrates an aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs. In some aspects, whether the COT-initiating UE can resume its COT or not depends on the traffic target of the COT-initiating UE. For example, the COT-initiating UE may resume its COT if the target of the COT-initiating UE is not a UE that can share the COT (i.e., a responding UE) . In FIG. 4A, the COT-SI indicates to each responding UE the entire COT as available for transmission, and thus the COT-sharing UE (UE 0) may only resume transmitting if to a UE which is not any of the responding UEs.

As illustrated, a COT-SI 402 is transmitted to multiple responding UEs (UE 1, UE 2, and UE 3) . UE 0 may transmit to one or more UEs at transmission 404 within the acquired COT. Subsequently, UE 1 may transmit message 406 to UE 0 using all or a part of the acquired frequency resources. UE 2 and UE 3 may transmit messages 408 and 410 respectively to UE 0.Note that messages 408 and 410 may be transmitted at overlapping time as they use different frequency resources. UE 0 may resume transmitting by transmitting message 412 to UE 4. In some aspects, UE 4 is not a responding UE in that it did not receive indicated resources of the shared COT. Since UE 4 is not a responding UE, there is not a risk that UE 4 will attempt to transmit to UE 0 during the COT, so UE 0 may freely resume transmitting to UE 4 using that resource.

FIG. 4B illustrates another aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs. In some aspects if the COT-initiating UE (UE 0) indicates a specified resource (i.e., both time and frequency) to each responding UE, then the target UE where the COT-initiating UE intends to transmit should not be the responding UE whose indicated shared resources are overlapped with the COT-initiating UE’s resumed transmission. As illustrated, the regions with hash marks are resources indicated for individual responding UEs in the COT-SI. For example, the shaded region next to message 406 indicates that the shaded region is allocated by the COT-SI for additional transmissions from UE 1. Similarly, the indicated region adjoining message 408 may be used by UE 2 to further transmit to UE 0. Since the COT-SI does not indicate the full COT to each responding UE, this allows for more flexibility in which responding UE the COT-initiating UE may communicate with during a resumed transmission. Message 414 for example may be transmitted to UE 3 since UE 3 does not have shared resources at that time. Message 416 may be transmitted to either UE 2 or UE 3 since the indicated resources for UE 2 end before the time for which message 416 is scheduled. In this way, the COT-initiating UE, in some aspects, may resume transmission to responding UEs.

FIG. 4C illustrates another aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs. In some aspects the COT-initiating UE can resume its COT if the target UE where the COT initiating UE intends to transmit is not the FDMed responding UE (i.e., the responding UE whose reserved resource is overlapped with the COT-initiating UE’s resumed transmission in time) . As illustrated, a COT-SI 402 is transmitted to multiple responding UEs (UE 1, UE 2, and UE 3) . UE 0 may transmit to one or more UEs at transmission 404 within the acquired COT. Subsequently, UE 1 may transmit message 406 to UE 0 using all or a part of the acquired frequency resources. UE 2 and UE 3 may transmit messages 408 and 410 respectively to UE 0.Note that messages 408 and 410 may be transmitted at overlapping time as they use different frequency resources. UE 1 may also transmit message 418 to UE 0. UE 0 may resume transmission via message 420 transmitted to UE 2 and/or UE 3 using different frequency resources than message 418 from UE 1. The condition illustrated here is that UE 0 may resume transmission to a responding UE that is not the FDMed responding UE, which for message 420 is UE 1 which is transmitting message 418 at the same time. Further, if UE 3 transmits message 422, then concurrent with that, UE 0 may resume transmitting by transmitting message 424 to UE 1 and/or UE 2 since they are not FDMed at that time.

In some aspects, UE 0 resuming its transmission may be further based on the transmission priority of the COT-initiating UE (UE 0) and the transmission priority of the FDMed responding UE. For example, if the COT-initiating UE (UE 0) has higher transmission priority than the highest transmission priority among all FDMed responding UEs, then the COT-initiating UE may resume the COT regardless.

FIGS. 5-7 illustrate example timing resource diagrams with cyclic prefix extension for resuming transmission by a UE using shared channel occupancy time according to some aspects of the present disclosure. In each of FIGS. 5-7, the X-axis represents time in some units, and the Y-axis represents frequency in some units. The illustrated frame may represent a slot, mini-slot, a portion of a slot, or more than a slot in a radio frame.

FIG. 5 illustrates an aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs and includes a cyclic prefix extension (CPE) on the resuming transmission. In some aspects, the selection of a length of the CPE may be configured, predetermined, based on a heuristic/rule etc. In some aspects, responding UEs may monitor the channel and sense when the COT-initiating UE is transmitting a CPE, and may drop a scheduled transmission if the COT-initiating UE is transmitting. In this way, the selection of a CPE length/starting position may be used to control which UEs have access to the shared COT. For example, in some aspects, the COT-initiating UE may always select the earliest starting position of the CPE i.e., 16 microseconds (us) into the symbol preceding the first message transmission symbol which may ensure that the COT-initiating UE takes priority over responding UEs (unless, for example, a responding UE has the same CPE starting position) . For example, the diagram in Fig. 5 illustrates a message 508 from UE 1 to UE 0 in slot 502, another slot 504, then a message 510 from the COT-initiation UE (UE 0) to UE 1 in slot 506. The expanded portion in the diagram represents one or more symbol periods immediately preceding slit 506 which includes message 510. As illustrated, the symbol period may include subdivisions 520-526 which may be 16us and/or 9us in length each. In the example above, the CPE of message 510 would be determined by UE 0 to start after subdivision 520 such that there is only a 16us gap between a transmission in slot 504 and message 510 including the CPE. In some aspects, the COT-initiating UE always selects the earliest starting position for the CPE based on required channel access type among the candidate starting positions associated with the intended PSCCH/PSSCH transmission. For example, if a channel access type requires a longer channel sensing time, a longer gap period may be used than 16us.

The diagram in FIG. 5 illustrates an example scenario, illustrating only a portion of the resources

FIG. 6 illustrates another aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs and includes a cyclic prefix extension (CPE) on the resuming transmission.

In some aspects, the COT-initiating UE selects the CPE starting position based on both transmission priority and CPE of FDMed responding UEs. For example, if the transmission priority of the COT-initiating UE has higher priority than the highest transmission priority among all FDMed responding UEs, the COT-initiating UE will select the CPE which is earlier than the CPE of the FDMed responding UEs. Otherwise, the COT-initiating UE may select the CPE which is later than the CPE of FDMed responding UEs. In some aspects, the CPE may start before a second CPE associated with one of the responding UEs having a lower priority than the COT-initiating UE and after a third CPE associated with a different one of the responding UEs having a higher priority than the COT-initiating UE. As illustrated, the symbol period may include subdivisions 620-626 which may be 16us and/or 9us in length each.

For example, FIG. 6 illustrates initial message 610 from UE 0 (the COT-initiating UE) to UE 1, responding messages 612, 614, and 618, and message 616 which resumes transmission from UE 0 to UE 1. If UE 0 has higher priority than UE 1, UE 2, and UE 3, then UE 0 may select the earliest allowable CPE start, for example allowing for a 16us gap after subdivision 620. If UE 0 has higher priority than some responding UEs but lower priority than other responding UEs, the CPE of message 616 may be selected such that it starts before only the lower priority responding UEs. For example, based on a priority determination, UE 0 may start the CPE after subdivision 622.

FIG. 7 illustrates another aspect of the present disclosure in which a COT-initiating UE (designated here as UE 0) resumes transmission during a COT shared with responding UEs and includes a cyclic prefix extension (CPE) on the resuming transmission. In some aspects, whether the COT-initiating UE will follow a legacy rule to select the CPE or not depending on a condition. In some aspects, the condition is if there is a transmission right before the slot the COT-initiating UE intends to use, then the COT-initiating UE can always select the CPE which makes the gap equal to 16us. In some aspects, the selection of CPE depends on the gaps within the COT. If any gap between any two transmissions within the COT is up to 16us, the COT-initiating UE can always select the CPE which makes the gap equal to 16us. If any gap between any two transmissions within the COT is up to 25us, the COT-initiating UE can select the CPE which make the gap equal to 25us. If these conditions are not fulfilled, the COT-initiating UE may use a legacy rule to determine the CPE starting position. A COT-initiating UE may determine the gap between two transmission by measurement, or by receiving an indication from a responding UE of a selected starting position. For example, a responding UE may indicate a CPE starting position through an SCI-1 or SCI-2.

In the example illustrated in FIG. 7, message 710 is transmitted from UE 0 (the COT-initiating UE) to a responding UE 1 in slot 702. Message 712 is a transmission from UE 2 to UE 0 in slot 704. Message 714 is a transmission from UE 3 to UE 0 in slot 706. Message 716 is a transmission from UE 0 to UE 1 in slot 708. Message 716 may include a CPE which starts at a time determined by the conditions described above. Here, there are two other gaps between messages in the shared COT, specifically gap 730 between messages 710 and 712, and gap 734 between messages 712 and 714. Depending on the duration of those gaps, UE 0 may determine a CPE start position in order to achieve a certain gap between messages 714 and 716. Similar to FIGS. 5-6, an expanded view of the symbol immediately prior to the resuming transmission of UE 0 is illustrated with subdivisions 720-726 to illustrate potential CPE start times. In some aspects, UE 0 ignores gaps 730 and 734, and selects to start the CPE after subdivision 720. In some aspects, gaps 730 and 734 are both 16us in duration, and UE 0 determines, based on at least one of gap durations 730 and 734, to start the CPE leaving a 16us gap (i.e., after subdivision 720) . In some aspects, gaps 730 and 734 are both 25us in duration, and UE 0 determines, based on at least one of gap durations 730 and 734, to start the CPE leaving a 25us gap (i.e., after subdivision 721) .

FIG. 8 is a block diagram of an exemplary UE 800 according to some aspects of the present disclosure. The UE 800 may be a UE 115 as discussed above with respect to FIG. 1. As shown, the UE 800 may include a processor 802, a memory 804, a COT sharing module 808, a transceiver 810 including a modem subsystem 812 and a radio frequency (RF) unit 814, and one or more antennas 816. These elements may be coupled with one another. The term “coupled” may refer to directly or indirectly coupled or connected to one or more intervening elements. For instance, these elements may be in direct or indirect communication with each other, for example via one or more buses.

The processor 802 may have various features as a specific-type processor. For example, these may include a CPU, a DSP, an ASIC, a controller, a FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 802 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 804 may include a cache memory (e.g., a cache memory of the processor 802) , RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, a solid state memory device, one or more hard disk drives, memristor-based arrays, other forms of volatile and non-volatile memory, or a combination of different types of memory. In some aspects, the memory 804 may include a non-transitory computer-readable medium. The memory 804 may store instructions 806. The instructions 806 may include instructions that, when executed by the processor 802, cause the processor 802 to perform operations described herein, for example, aspects of FIGS. 1-8, and 10. Instructions 806 may also be referred to as program code, which may be interpreted broadly to include any type of computer-readable statement (s) . The program code may be for causing a wireless communication device to perform these operations, for example by causing one or more processors (such as processor 802) to control or command the wireless communication device to do so. The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement (s) . For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may include a single computer-readable statement or many computer-readable statements.

The COT sharing module 808 may be implemented via hardware, software, or combinations thereof. For example, the COT sharing module 808 may be implemented as a processor, circuit, and/or instructions 806 stored in the memory 804 and executed by the processor 802. In some examples, the COT sharing module 808 can be integrated within the modem subsystem 812. For example, the COT sharing module 808 can be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the modem subsystem 812.

The COT sharing module 808 may communicate with various components of the UE 800 to perform aspects of the present disclosure, for example, aspects of FIGS. 1-7, and 9. In some aspects, the COT sharing module 808 is configured to perform a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel over an unlicensed new radio (NR) band. COT sharing module 808 is further configured to transmit using the acquired COT, stop transmitting, and resume transmitting in the same COT according to methods described herein. COT sharing module 808 is further configured to determine a cyclic prefix extension (CPE) and apply the CPE to one or more transmission according to embodiments described herein.

As shown, the transceiver 810 may include the modem subsystem 812 and the RF unit 814. The transceiver 810 can be configured to communicate bi-directionally with other devices, such as the BSs 105. The modem subsystem 812 may be configured to modulate and/or encode the data from the memory 804 and/or the COT sharing module 808 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 814 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, sidelink data, COT-SI, COT sharing information such as but not limited to duration of the COT, time/frequency locations of the reserved COTs, offsets to COT reservations, starting subchannel of reserved COTs, resource widths of reserved COTs, etc. ) from the modem subsystem 812 (on outbound transmissions) or of transmissions originating from another source such as a UE 115 or a BS 105. The RF unit 814 may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver 810, the modem subsystem 812 and the RF unit 814 may be separate devices that are coupled together at the UE 115 to enable the UE 115 to communicate with other devices. In some aspects, the transceiver 810 may be configured to transmit a COT sharing information (COT-SI) configured to reserve one or more COTs in a sidelink channel over an unlicensed new radio (NR) band, the one or more COTs acquired via a channel access procedure by the COT sharing module 808, for instance, for a future transmission via the sidelink channel.

The RF unit 814 may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may include one or more data packets and other information) , to the antennas 816 for transmission to one or more other devices. The antennas 816 may further receive data messages transmitted from other devices. The antennas 816 may provide the received data messages for processing and/or demodulation at the transceiver 810. The transceiver 810 may provide the demodulated and decoded data (e.g., PSCCH, PSSCH, SCI-1, SCI-2, sidelink data, COT-SI, COT sharing information) to the COT sharing module 808 for processing. The antennas 816 may include multiple antennas of similar or different designs in order to sustain multiple transmission links. The RF unit 814 may configure the antennas 816.

In an aspect, the UE 800 can include multiple transceivers 810 implementing different RATs (e.g., NR and LTE) . In an aspect, the UE 800 can include a single transceiver 810 implementing multiple RATs (e.g., NR and LTE) . In an aspect, the transceiver 810 can include various components, where different combinations of components can implement different RATs.

FIG. 9 is a flow diagram of a method 900 according to some aspects of the present disclosure. Aspects of the method 900 can be executed by a computing device (e.g., one or more memories and one or more processors coupled to the one or more memories storing instructions that are executable by the one or more processors, individually or in any combination, and/or other suitable components) of a wireless communication device or other suitable means for performing the steps. For example, a wireless communication device, such as the UEs 115, 315, or 800, may utilize one or more components, such as the processor 802, the memory 804, the COT sharing module 808, the transceiver 810, the modem 812, and the one or more antennas 816, to execute the steps of method 900. The method 900 may employ similar mechanisms as described above in FIGS. 1-8. As illustrated, the method 900 includes a number of enumerated steps, but aspects of the method 900 may include additional steps before, after, and in 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 901, in some aspects, a first UE (e.g., the UE 115, 315, or 800) performs a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel.

At block 902, in some aspects, the first UE transmits COT sharing information (COT-SI) to one or more responding UEs.

At block 903, in some aspects, the first UE transmits a first message to at least one of the one or more responding UEs during the COT.

At block 904, in some aspects, the first UE refrains from transmitting for a duration during the COT after transmitting the first message.

At block 905, in some aspects, the first UE transmits, based on a condition, a second message to a second UE during the COT after the duration. In some aspects the condition includes that the second message is to be transmitted using time and frequency resources that do not overlap time and frequency resources allocated to the second UE via the COT-SI. In some aspects, the second UE is not one of the responding UEs. For example, the second UE may be a different UE which does not receive COT-SI and/or does not receive an indication in COT-SI with resources to share the COT. In some aspects, the second UE is one of the one or more responding UEs. For example, under certain conditions the first UE may resume transmission and transmit a second message to a second UE which is a responding UE which is sharing the COT. In some aspects, the condition includes that the second message is to be transmitted using time resources that do not overlap time resources allocated to the second UE. In some aspects, the condition further includes that the first UE has a higher priority than all of the responding UEs that are allocated time resources overlapping the time resources to be used for transmitting the second message.

At block 906, in some aspects, the first UE transmits a cyclic prefix extension (CPE) associated with the second message. In some aspects, the CPE starts a predetermined amount of time before the second message. In some aspects, the CPE starts an amount of time before the second message based on a channel access type. In some aspects, the CPE starts an amount of time before the second message based on a first transmission priority of the second message and a second transmission priority associated with one of the one or more responding UEs. In some aspects, the CPE starts before a second CPE associated with one of the one or more responding UEs having a lower priority than the first UE and after a third CPE associated with a different one of the one or more responding UEs having a higher priority than the first UE. In some aspects, a transmission priority of the first UE has higher priority than a highest transmission priority of any of the one or more responding UEs, and the CPE starts before any CPE associated with any of the one or more responding UEs based on the transmission priority. In some aspects, the CPE starts a predetermined amount of time after a transmission from one of the one or more responding UEs. In some aspects, the CPE starts an amount of time before the second message based on a gap time between transmissions during the COT. In some aspects, the first UE measures the gap time or receives an indication of the gap time from the one or more responding UEs.

RECITATIONS OF SOME ASPECTS OF THE PRESENT DISCLOSURE

Aspect 1. A method of wireless communication performed by a first user equipment (UE) , the method comprising:

performing a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel;

transmitting COT sharing information (COT-SI) to one or more responding UEs;

transmitting a first message to at least one of the one or more responding UEs during the COT;

refraining from transmitting for a duration during the COT after transmitting the first message; and

transmitting, based on a condition, a second message to a second UE during the COT after the duration.

Aspect 2. The method of aspect 1, wherein the condition includes that the second message is to be transmitted using time and frequency resources that do not overlap time and frequency resources allocated to the second UE via the COT-SI.

Aspect 3. The method of aspect 2, wherein the second UE is not one of the one or more responding UEs.

Aspect 4. The method of aspect 2, wherein the second UE is one of the one or more responding UEs.

Aspect 5. The method of aspect 1, wherein the condition includes that the second message is to be transmitted using time resources that do not overlap time resources allocated to the second UE.

Aspect 6. The method of aspect 5, wherein the condition further includes that the first UE has a higher priority than all of the responding UEs that are allocated time resources overlapping the time resources to be used for transmitting the second message.

Aspect 7. The method of aspect 1, further comprising:

transmitting a cyclic prefix extension (CPE) associated with the second message.

Aspect 8. The method of aspect 7, wherein the CPE starts a predetermined amount of time before the second message.

Aspect 9. The method of aspect 7, wherein the CPE starts an amount of time before the second message based on a channel access type.

Aspect 10. The method of aspect 7, wherein the CPE starts an amount of time before the second message based on a first transmission priority of the second message and a second transmission priority associated with one of the one or more responding UEs.

Aspect 11. The method of aspect 10, wherein the CPE starts before a second CPE associated with one of the one or more responding UEs having a lower priority than the first UE and after a third CPE associated with a different one of the one or more responding UEs having a higher priority than the first UE.

Aspect 12. The method of aspect 7,

wherein a transmission priority of the first UE has higher priority than a highest transmission priority of any of the one or more responding UEs, and

wherein the CPE starts before any CPE associated with any of the one or more responding UEs based on the transmission priority.

Aspect 13. The method of aspect 7, wherein the CPE starts a predetermined amount of time after a transmission from one of the one or more responding UEs.

Aspect 14. The method of aspect 7, wherein the CPE starts an amount of time before the second message based on a gap time between transmissions during the COT.

Aspect 15. The method of aspect 14, wherein the first UE measures the gap time or receives an indication of the gap time from one of the one or more responding UEs.

Aspect 16. A first UE, comprising one or more memories and one or more processors coupled to the one or more memories storing instructions that are executable by the one or more processors, individually or in any combination, configured to cause the first UE to perform the methods of aspects 1-15.

Aspect 17. A non-transitory computer-readable medium (CRM) having program code recorded thereon, the program code comprises code for causing a first UE to perform the methods of aspects 1-15.

Aspect 18. A first UE comprising means for performing the methods of aspects 1-15.

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, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but 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, multiple 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 executed 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 appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of [at least one of A, B, or C] means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) .

As those of some skill in this art will by now appreciate and depending on the particular application at hand, many modifications, substitutions and variations can be made in and to the materials, apparatus, configurations and methods of use of the devices of the present disclosure without departing from the spirit and scope thereof. In light of this, the scope of the present disclosure should not be limited to that of the particular aspects illustrated and described herein, as they are merely by way of some examples thereof, but rather, should be fully commensurate with that of the claims appended hereafter and their functional equivalents.

Claims

A method of wireless communication performed by a first user equipment (UE) , the method comprising:

performing a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel;

transmitting COT sharing information (COT-SI) to one or more responding UEs;

transmitting a first message to at least one of the one or more responding UEs during the COT;

refraining from transmitting for a duration during the COT after transmitting the first message; and

transmitting, based on a condition, a second message to a second UE during the COT after the duration.
The method of claim 1, wherein the condition includes that the second message is to be transmitted using time and frequency resources that do not overlap time and frequency resources allocated to the second UE via the COT-SI.
The method of claim 2, wherein the second UE is not one of the one or more responding UEs.
The method of claim 2, wherein the second UE is one of the one or more responding UEs.
The method of claim 1, wherein the condition includes that the second message is to be transmitted using time resources that do not overlap time resources allocated to the second UE.
The method of claim 5, wherein the condition further includes that the first UE has a higher priority than all of the responding UEs that are allocated time resources overlapping the time resources to be used for transmitting the second message.
The method of claim 1, further comprising:

transmitting a cyclic prefix extension (CPE) associated with the second message.
The method of claim 7, wherein the CPE starts a predetermined amount of time before the second message.
The method of claim 7, wherein the CPE starts an amount of time before the second message based on a channel access type.
The method of claim 7, wherein the CPE starts an amount of time before the second message based on a first transmission priority of the second message and a second transmission priority associated with one of the one or more responding UEs.
The method of claim 10, wherein the CPE starts before a second CPE associated with one of the one or more responding UEs having a lower priority than the first UE and after a third CPE associated with a different one of the one or more responding UEs having a higher priority than the first UE.
The method of claim 7,

wherein a transmission priority of the first UE has higher priority than a highest transmission priority of any of the one or more responding UEs, and

wherein the CPE starts before any CPE associated with any of the one or more responding UEs based on the transmission priority.
The method of claim 7, wherein the CPE starts a predetermined amount of time after a transmission from one of the one or more responding UEs.
The method of claim 7, wherein the CPE starts an amount of time before the second message based on a gap time between transmissions during the COT.
The method of claim 14, wherein the first UE measures the gap time or receives an indication of the gap time from one of the one or more responding UEs.
A first user equipment (UE) , comprising:

one or more memories; and

one or more processors coupled to the one or more memories storing instructions that are executable by the one or more processors, individually or in any combination, configured to cause the first UE to:

perform a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel;

transmit COT sharing information (COT-SI) to one or more responding UEs;

transmit a first message to at least one of the one or more responding UEs during the COT;

refrain from transmitting for a duration during the COT after transmitting the first message; and

transmit, based on a condition, a second message to a second UE during the COT after the duration.
The UE of claim 16, wherein the condition includes that the second message is to be transmitted using time and frequency resources that do not overlap time and frequency resources allocated to the second UE via the COT-SI.
The UE of claim 17, wherein the second UE is not one of the one or more responding UEs.
The UE of claim 17, wherein the second UE is one of the one or more responding UEs.
The UE of claim 16, wherein the condition includes that the second message is to be transmitted using time resources that do not overlap time resources allocated to the second UE.
The UE of claim 20, wherein the condition further includes that the first UE has a higher priority than all of the responding UEs that are allocated time resources overlapping the time resources to be used for transmitting the second message.
The UE of claim 16, wherein the one or more processors are further configured to cause the first UE to:

transmit a cyclic prefix extension (CPE) associated with the second message.
The UE of claim 22, wherein the CPE starts a predetermined amount of time before the second message.
The UE of claim 22, wherein the CPE starts an amount of time before the second message based on a channel access type.
The UE of claim 22, wherein the CPE starts an amount of time before the second message based on a first transmission priority of the second message and a second transmission priority associated with one of the one or more responding UEs.
The UE of claim 25, wherein the CPE starts before a second CPE associated with one of the one or more responding UEs having a lower priority than the first UE and after a third CPE associated with a different one of the one or more responding UEs having a higher priority than the first UE.
The UE of claim 22,

wherein a transmission priority of the first UE has higher priority than a highest transmission priority of any of the one or more responding UEs, and

wherein the CPE starts before any CPE associated with any of the one or more responding UEs based on the transmission priority.
The UE of claim 22, wherein the CPE starts a predetermined amount of time after a transmission from one of the one or more responding UEs.
A non-transitory computer-readable medium (CRM) having program code recorded thereon, the program code comprising:

code for causing a first user equipment (UE) to perform a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel;

code for causing the first UE to transmit COT sharing information (COT-SI) to one or more responding UEs;

code for causing the first UE to transmit a first message to at least one of the one or more responding UEs during the COT;

code for causing the first UE to refrain from transmitting for a duration during the COT after transmitting the first message; and

code for causing the first UE to transmit, based on a condition, a second message to a second UE during the COT after the duration.
A first user equipment (UE) , comprising:

means for performing a channel access procedure to acquire a channel occupancy time (COT) in a sidelink channel;

means for transmitting COT sharing information (COT-SI) to one or more responding UEs;

means for transmitting a first message to at least one of the one or more responding UEs during the COT;

means for refraining from transmitting for a duration during the COT after transmitting the first message; and

means for transmitting, based on a condition, a second message to a second UE during the COT after the duration.