Patent Publication Number: US-2021176669-A1

Title: Resource reservation for multiple sidelinks

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/945,037, filed Dec. 6, 2019, which is hereby incorporated by reference in its entirety as if fully set forth below and for all applicable purposes. 
    
    
     TECHNICAL FIELD 
     This application relates to wireless communication systems, and more particularly to a sidelink user equipment (UE) reserving resources for multiple sidelinks. 
     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 for D2D, V2X, and/or C-V2X over a dedicated spectrum, a licensed spectrum, and/or an unlicensed spectrum. 
     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. 
     For example, in an aspect of the disclosure, a method of wireless communication includes communicating, by a first wireless communication device with a second wireless communication device, a reservation indicating a plurality of reserved resources for a plurality of sidelink communications; and communicating, by the first wireless communication device with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of reserved resources. 
     In an additional aspect of the disclosure, an apparatus includes a transceiver configured to communicate, with a second wireless communication device, a reservation indicating a plurality of reserved resources for a plurality of sidelink communications; and communicate, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of reserved resources. 
     In an additional aspect of the disclosure, a non-transitory computer-readable medium having program code recorded thereon, the program code includes code for causing a first wireless communication device to communicate, with a second wireless communication device, a reservation indicating a plurality of reserved resources for a plurality of sidelink communications; and code for causing the first wireless communication device to communicate, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of reserved resources. 
     In an additional aspect of the disclosure, an apparatus includes means for communicating, with a second wireless communication device, a reservation indicating a plurality of reserved resources for a plurality of sidelink communications; and means for communicating, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of reserved resources. 
     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  illustrates 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. 
         FIG. 4A  illustrates a physical sidelink control channel (PSCCH)/physical sidelink shared channel (PSSCH) multiplexing configuration according to some aspects of the present disclosure. 
         FIG. 4B  illustrates a PSCCH/PSSCH multiplexing configuration according to some aspects of the present disclosure. 
         FIG. 4C  illustrates a PSCCH/PSSCH multiplexing configuration according to some aspects of the present disclosure. 
         FIG. 4D  illustrates a PSCCH/PSSCH multiplexing configuration according to some aspects of the present disclosure. 
         FIG. 5  is a block diagram of a user equipment (UE) according to some aspects of the present disclosure. 
         FIG. 6  is a block diagram of an exemplary base station (BS) according to some aspects of the present disclosure. 
         FIG. 7A  illustrates a sidelink resource reservation for multiple sidelinks according to some aspects of the present disclosure. 
         FIG. 7B  is a signaling diagram illustrating a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 8A  illustrates a sidelink resource reservation for multiple sidelinks according to some aspects of the present disclosure. 
         FIG. 8B  is a signaling diagram illustrating a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 9A  illustrates a sidelink resource reservation for multiple sidelinks according to some aspects of the present disclosure. 
         FIG. 9B  is a signaling diagram illustrating a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 10A  illustrates a sidelink resource reservation for multiple sidelinks according to some aspects of the present disclosure. 
         FIG. 10B  is a signaling diagram illustrating a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 11A  illustrates a sidelink resource reservation for multiple sidelinks according to some aspects of the present disclosure. 
         FIG. 11B  is a signaling diagram illustrating a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 12A  illustrates a sidelink communication scenario according to some aspects of the present disclosure. 
         FIG. 12B  is a flow diagram of a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 13A  illustrates a sidelink communication scenario according to some aspects of the present disclosure. 
         FIG. 13B  is a flow diagram of a sidelink communication method according to some aspects of the present disclosure. 
         FIG. 14  is a flow diagram of a sidelink 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 embodiments, 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, 5th 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-A are 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., ˜1 M nodes/km 2 ), ultra-low complexity (e.g., ˜10 s 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/km 2 ), extreme data rates (e.g., multi-Gbps rate, 100+ Mbps user experienced rates), and deep awareness with advanced discovery and optimizations. 
     The 5G NR may be implemented to use optimized OFDM-based waveforms with scalable numerology and transmission time interval (TTI); 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 3 GHz 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 NR vehicle-to-everything (V2X), a transmitting UE may initiate SCI and sidelink data transmission to a peer or receiving UE. The transmitting UE is responsible for selecting resources for the sidelink transmission, for example, by performing channel sensing. 
     The present application describes mechanisms for a sidelink UE to reserve multiple sidelink resources for multiple sidelinks. A sidelink resource is a time-frequency resource including one or more resource elements. For instance, a sidelink resource may include a number of subcarriers in frequency and a number of symbols, a number of mini-slots  208 , or a number of slots  202  in time. In some aspects, a first UE may reserve multiple sidelink resources and may transmit first SCI indicating a reservation for the multiple reserved sidelink resources. In some aspects, the first SCI may indicate an assignment of each reserved resource (e.g., one or more resource elements). For instance, the first SCI may indicate a first reserved resource of the multiple reserved resources assigned for transmission by the first UE to a second UE and may indicate a second reserved resource of the multiple reserved resources assigned for transmission by the second UE to the first UE or to a third UE different from the first UE. Accordingly, the first UE may transmit sidelink data to the second UE using the first reserved resource and the second UE may subsequently transmit sidelink data to the first UE or the third UE using the second reserved resource. In some aspects, the second UE may transmit second SCI (in the PSCCH of the second resource) before transmitting sidelink data in the second resource. In this regard, the second SCI may repeat the reservation for the second resource. In some aspects, the second UE may duplicate the first SCI in the PSCCH of the second resource. 
     In some aspects, SCI may also carry sidelink acknowledgement/negative-acknowledgement (ACK/NACK) feedback, scheduling request (SR), buffer status report (BSR), and/or a resource release indication. In some aspects, if a sidelink UE detects a reserved resource is released, the sidelink UE may use the released resource for transmission. In some aspects, if a sidelink UE detects a reservation indicating multiple reserved resources, but does not detect a sidelink UE assigned to a reserved resource indicating a transmission in the reserved resource, the sidelink UE may reclaim the resource for transmission, for example, based on a spatial reuse. In some other aspects, a sidelink UE may transmit in a resource of a multi-resource reservation when there is no reservation detected from a UE reserving the multi-resource reservation and there is no transmission indication detected from the UE assigned to the resource. 
     Aspects of the present disclosure can provide several benefits. For example, the reservation of multiple sidelink resources for multiple sidelinks instead of each transmitting UE performing channel sensing and reserving a resource for its own transmission can potentially reduce latency, and thus may be beneficial for ultra-reliable low-latency communication (URLLC). Additionally, the inclusion of a resource release indication in SCI allows a sidelink UE to release an unused reserved sidelink resource and allows another sidelink UE to transmit in the resource that may otherwise by wasted. Thus, the disclosed embodiments can improve resource utilization efficiency. Further, the reclaiming of a reserved resource based on a spatial reuse can further improve resource utilization efficiency. 
       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  105   a ,  105   b ,  105   c ,  105   d ,  105   e , and  105   f ) and other network entities. A BS  105  may be a station that communicates with UEs  115  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). ABS for a macro cell may be referred to as a macro BS. ABS 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  105   d  and  105   e  may be regular macro BSs, while the BSs  105   a - 105   c  may be macro BSs enabled with one of three dimension (3D), full dimension (FD), or massive MIMO. The BSs  105   a - 105   c  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  105   f  may be a small cell BS which may be a home node or portable access point. ABS  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  115   a - 115   d  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  115   e - 115   h  are examples of various machines configured for communication that access the network  100 . The UEs  115   i - 115   k  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  105   a - 105   c  may serve the UEs  115   a  and  115   b  using 3D beamforming and coordinated spatial techniques, such as coordinated multipoint (CoMP) or multi-connectivity. The macro BS  105   d  may perform backhaul communications with the BSs  105   a - 105   c , as well as small cell, the BS  105   f . The macro BS  105   d  may also transmits multicast services which are subscribed to and received by the UEs  115   c  and  115   d . 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  115   e , which may be a drone. Redundant communication links with the UE  115   e  may include links from the macro BSs  105   d  and  105   e , as well as links from the small cell BS  105   f . Other machine type devices, such as the UE  115   f  (e.g., a thermometer), the UE  115   g  (e.g., smart meter), and UE  115   h  (e.g., wearable device) may communicate through the network  100  either directly with BSs, such as the small cell BS  105   f , and the macro BS  105   e , or in multi-step-size configurations by communicating with another user device which relays its information to the network, such as the UE  115   f  communicating temperature measurement information to the smart meter, the UE  115   g , which is then reported to the network through the small cell BS  105   f . The network  100  may also provide additional network efficiency through dynamic, low-latency TDD/FDD communications, such as V2V, V2X C-V2X communications between a UE  115   i ,  115   j , or  115   k  and other UEs  115 , and/or vehicle-to-infrastructure (V2I) communications between a UE  115   i ,  115   j , or  115   k  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  (MSG 1 ), message  2  (MSG 2 ), message  3  (MSG 3 ), and message  4  (MSG 4 ), respectively. In some examples, the random access procedure may be a two-step random access procedure, 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. 
     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 scheduling grants may be transmitted in the form of DL control information (DCI). The BS  105  may transmit a DL communication signal (e.g., carrying data) 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. 
     In some aspects, the BS  105  may communicate with a UE  115  using 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  receives the DL data packet successfully, the UE  115  may transmit a HARQ ACK to the BS  105 . Conversely, if the UE  115  fails to receive the DL transmission successfully, the UE  115  may transmit a HARQ 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 and/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 a listen-before-talk (LBT) procedure to monitor for transmission opportunities (TXOPs) in the shared channel. A TXOP may also be referred to as channel occupancy time (COT). 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. 
     An LBT can be based on energy detection 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 or a category 2 (CAT2) LBT. A CAT2 LBT refers to an LBT without a random backoff period. A CAT4 LBT refers to an LBT with a random backoff and a variable contention window (CW). 
     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. A transmitting UE  115  may select a resource from a resource pool for sidelink transmission, for example, based on channel sensing. For instance, the UE  115  may monitor the resource pool for SCI from other sidelink UEs  115  and may determine that a resource is available when no SCI is detected. After selecting the resource, the transmitting UE  115  may transmit SCI (e.g., in a PSCCH of the selected resource) indicating a reservation for the selected resource and/or scheduling information for the sidelink transmission. The transmitting UE  115  may subsequently transmit sidelink data (e.g., in a PSSCH of the selected resource) to a peer or receiving UE  115  according to the scheduling information. In this regard, a receiving UE is understood to be a UE that receives data (e.g., over a PSSCH) from another UE in a sidelink communication, while a transmitting UE is understood to be a UE that transmits data (e.g., over a PSSCH) to another UE in a sidelink communication. Over time, a single UE may be both a receiving UE and a transmitting UE. For example, in an initial sidelink communication a UE may be a receiving UE and in a later sidelink communication the same UE may be a transmitting UE, or vice versa. 
     In some aspects, a sidelink transmitting UE  115  may reserve multiple resources for communications over multiple sidelinks (e.g., the sidelinks  351 ,  352 , and  354 ) by one or more other UEs  115  in addition to sidelink transmissions by the UE  115  itself. Additionally, a UE  115  may release an unused reserved resource to allow another sidelink UE  115  to reclaim the unused resources for sidelink transmissions. Further, a UE  115  may opportunistically reclaim a resource reserved for another UE  115  based on a spatial reuse. Mechanisms for reserving resources for multiple sidelink communications and reclaiming reserved resources for sidelink communication are described in greater detail herein. 
       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 an example, 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 ). 
       FIG. 3  illustrates an example of a wireless communication network  300  that provisions for sidelink communications according to embodiments of the present disclosure. The network  300  may be similar to the network  100 . The network  300  may use a radio frame structure similar to radio frame structure  200  for communication.  FIG. 3  illustrates one BSs  305  and five UEs  315  (shown as  315   a ,  315   b ,  315   c ,  315   d , and  315   e ) for purposes of simplicity of discussion, though it will be recognized that embodiments of the present disclosure may scale to any suitable number of UEs  315  and/or BSs  305  (e.g., the about 3, 3, 6, 7, 8, or more). The BS  305  and the UEs  315  may be similar to the BSs  105  and the UEs  115 , respectively. The BSs  305  and the UEs  315  may communicate over the same spectrum. 
     In the network  300 , some of the UEs  315  may communicate with each other in peer-to-peer communications. For example, the UE  315   a  may communicate with the UE  315   b  over a sidelink  351 , the UE  315   c  may communicate with the UE  315   d  over another sidelink  352 , and the UE  315   d  may communicate with the UE  315   e  over yet another sidelink  354 . The sidelinks  351 ,  352 , and  354  are unicast bidirectional links. 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  315   a ,  315   b , and  315   c  are within a coverage area  310  of the BS  305 , and thus may be in communication with the BS  305 . The UE  315   d  and UE  315   e  are outside the coverage area  310 , and thus may not be in direct communication with the BS  305 . In some instances, the UE  315   c  may operate as a relay for the UE  315   d  and/or UE  315   e  to reach the BS  305 . In some aspects, some of the UEs  315  are associated with vehicles (e.g., similar to the UEs  115   i - 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-4D  illustrates various PSCCH/PSSCH multiplexing configurations for sidelink communication. In  FIGS. 4A-4D , the PSCCH/PSSCH multiplexing configurations  430 ,  440 ,  450 , and  460  may be employed by BSs such as the BSs  105  and  305  and/or UEs such as the UEs  115  and/or  315  in a network such as the networks  100  and/or  300 . In particular, the UEs may communicate with each other over sidelinks (e.g., the sidelinks  351  and  352 ) using resources configured as shown in the configuration  430 ,  440 ,  450 , or  460 . Additionally, the x-axes represent time in some arbitrary units, and the y-axes represent frequency in some arbitrary units. 
       FIG. 4A  illustrates a PSCCH/PSSCH multiplexing configuration  430  according to some aspects of the present disclosure. In the configuration  430 , a PSSCH  410  and a PSCCH  420  are time-multiplexed in a sidelink resource  406 . The sidelink resource may span a frequency band  402  and a time duration  404 . The sidelink resource  406  may have a transmission structure similar to the structure shown in  FIG. 2  discussed above. For instance, the sidelink resource  406  may include a number of subcarriers  204  in frequency and a number of symbols  206 , a number of mini-slots  208 , or a number of slots  202  in time. In some instances, the frequency band  402  may be within a licensed band. In some other instances, the frequency band  402  may be within a shared radio frequency band in a shared spectrum or an unlicensed spectrum. In some instances, the frequency band  402  may be within a 5 gigahertz (GHz) band or a 6 GHz band and may be shared among multiple network operating entities and/or multiple radio access technologies (RATs). 
       FIG. 4B  illustrates a PSCCH/PSSCH multiplexing configuration  440  according to some aspects of the present disclosure. The configuration  440  is substantially similar to the configuration  430 , where the PSSCH  410  is time-multiplexed with the PSCCH  420 . However, the PSCCH  420  may occupy a narrower bandwidth than the PSSCH  410 . 
       FIG. 4C  illustrates a PSCCH/PSSCH multiplexing configuration  450  according to some aspects of the present disclosure. In the configuration  450 , the PSSCH  410  and the PSCCH  420  are frequency-multiplexed in the sidelink resource  406 . 
       FIG. 4D  illustrates a PSCCH/PSSCH multiplexing configuration  460  according to some aspects of the present disclosure. In the configuration  460 , the PSSCH  410  and the PSCCH  420  are multiplexed in time and frequency in the sidelink resource  406 . In some aspects, the configuration  460  may be suitable for sidelink transmissions that use cyclic-prefix-OFDM (CP-OFDM) waveforms. 
     A network (e.g., the networks  100  and/or  300 ) may utilize any of the PSCCH/PSSCH multiplexing configurations  430 ,  440 ,  450 , or  460  for sidelink communication. Prior to a sidelink communication, the PSCCH/PSSCH multiplexing configuration, the starting symbol (e.g., the symbols  206 ), the number of symbols, and/or the number of subcarriers (e.g., the subcarriers  204 ) for a PSSCH  410  and/or the number of symbols and the number of subcarriers for a PSCCH  420  are known to all UEs (e.g., in the UEs  115  and  315 ) in the network, for example, based on a pre-configuration by the BS. In each resource  406 , the PSCCH  420  is associated with the PSSCH  410 . For instance, the PSCCH  420  may carry SCI indicating scheduling information for sidelink data carried in the corresponding PSSCH  410 . In some instances, a resource  406  may also include a physical sidelink feedback channel (PSFCH), for example, time-multiplexed with the PSCCH  420  and PSCCH  420 . The PSFCH may be used to carry HARQ ACK/NACKs when a sidelink communication utilizes HARQ. 
     During a sidelink communication, a transmitting UE (e.g., the UEs  115  and/or  315 ) may initiate the sidelink transmission by transmitting SCI in a PSCCH  420  (of a resource  406 ) indicating scheduling information for sidelink data in the corresponding PSSCH  410 . The scheduling information may indicate time and/or frequency resources in the PSSCH  410  where sidelink data is to be transmitted. The scheduling information may indicate transmission parameters, such as a MCS level and/or a DMRS pattern, to be used for transmitting the sidelink data. A receiving UE may monitor for SCI in the PSCCH  420  and receive sidelink data based on detected SCI. The receiving UE may determine whether the receiving UE is the intended destination based on a destination ID included in the sidelink data. 
     There are two modes of sidelink resource allocations. In mode-1, a BS (e.g., the BSs  105  and/or  305 ) may determine sidelink resources (e.g., for PSCCH  420 , PSSCH  410 , and PSFCH) for a transmitting UE. In other words, the BS determines a sidelink resource on behalf of the transmitting UE. The BS may transmit a dynamic grant (e.g., via PDCCH DCI) to the transmitting UE. The dynamic sidelink grant may indicate the sidelink resource. The transmitting UE may transmit SCI in the PSCCH  420  to indicate a sidelink data resources (in the PSSCH  410 ) to a receiving UE. 
     In mode-2, a transmitting UE may determine sidelink resources instead of a BS. In this regard, sidelink UEs may be preconfigured with a resource pool for sidelink operations. A resource pool is a set of resources that are allocated for sidelink communications. The resource pool includes a plurality of resource elements (e.g., time-frequency resources). The set of resources of the resource pool may include contiguous resource blocks, non-contiguous resource blocks, or a combination thereof. In some examples, resources may be indicated as particular RBs (e.g., RBs  210 ), time resources may be indicated as one or more slots (e.g., slots  202 , mini-slots  208 , etc.), frequency resources may be indicated as a subband or subchannel, or the resources can be indicated differently. For instance, the resource pool may include a number of sidelink resources similar to the resources  406  arranged as shown in the configuration  430 ,  440 ,  450 , or  460  of  FIG. 4A, 4B, 4C , or  4 D, respectively. The time and frequency resource locations of the PSCCH  420  are known based on a selected PSCCH/PSSCH multiplexing configuration (e.g., the configurations  430 ,  440 ,  450 , and  460 ). A transmitting UE may perform channel sensing in the PSCCH  420  regions of the resource pool, for example, by monitoring and decoding SCIs transmitted by other sidelink UEs. Based on the SCI monitoring and decoding, the transmitting UE may determine whether a sidelink resource  406  is being used by another sidelink UE and how long and/or in which subband a sidelink UE may occupy a sidelink resource  406 . The transmitting UE may also perform sidelink channel measurements to determine interference in the sidelink resources  406  within the resource pool. The transmitting UE may select a resource  406  from the resource pool for a sidelink communication based on the monitoring and/or channel measurements. For example, the selected resource  406  may be a resource with a minimal amount of interference among resources in the resource pool as seen by the transmitting UE. The sidelink communication may be an initial transmission or a retransmission, for example, when using HARQ as discussed above. In general, a sidelink transmitting UE is responsible for reserving or selecting sidelink resources for its own transmissions to a peer or receiving UE. 
     The present disclosure provides techniques to extend sidelink resource reservation to multiple sidelinks, where a first sidelink UE (e.g., the UE  315   c  of  FIG. 3 ) may reserve multiple resources for transmission to a second sidelink UE (e.g., the UE  315   d  of  FIG. 3 ) and for transmission from the second sidelink UE back to the first sidelink UE or to a third sidelink UE (e.g., the UE  315   e  of  FIG. 3 ). The multiple sidelink resource reservation can reduce communication latency, for example, to facilitate URLLC. 
       FIG. 5  is a block diagram of an exemplary UE  500  according to some aspects of the present disclosure. The UE  500  may be a UE  115  discussed above in  FIG. 1  or a UE  315  of  FIG. 3 . As shown, the UE  500  may include a processor  502 , a memory  504 , a sidelink communication module  508 , a transceiver  510  including a modem subsystem  512  and a radio frequency (RF) unit  514 , and one or more antennas  516 . These elements may be in direct or indirect communication with each other, for example via one or more buses. 
     The processor  502  may include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor  502  may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The memory  504  may include a cache memory (e.g., a cache memory of the processor  502 ), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an aspect, the memory  504  includes a non-transitory computer-readable medium. The memory  504  may store, or have recorded thereon, instructions  506 . The instructions  506  may include instructions that, when executed by the processor  502 , cause the processor  502  to perform the operations described herein with reference to the UEs  115  in connection with aspects of the present disclosure, for example, aspects of  FIGS. 1-3, 4A-4D, 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, and 14 . Instructions  506  may also be referred to as program code. 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  502 ) 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 sidelink communication module  508  may be implemented via hardware, software, or combinations thereof. For example, the sidelink communication module  508  may be implemented as a processor, circuit, and/or instructions  506  stored in the memory  504  and executed by the processor  502 . In some instances, the sidelink communication module  508  can be integrated within the modem subsystem  512 . For example, the sidelink communication module  508  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  512 . 
     The sidelink communication module  508  may be used for various aspects of the present disclosure, for example, aspects of  FIGS. 1-3, 4A-4D, 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B, 13A-13B, and 14 . In some aspects, the UE  500  may function as a transmitting UE reserving multiple resources for multiple sidelinks. In this regard, the sidelink communication module  508  is configured to reserve multiple sidelink resources, transmit first SCI indicating a reservation for the multiple reserved sidelink resources. In some aspects, the first SCI may indicate an assignment of each reserved resource. As explained above, a sidelink resource can include one or more resource elements that span a certain frequency and a certain time. Accordingly, each reserved resource can include one or more resource elements. For instance, the first SCI may indicate a first reserved resource (e.g., one or more resource elements) of the multiple reserved resources assigned for transmission by the UE  500  to a second UE and may indicate a second reserved resource (e.g., one or more resource elements) of the multiple reserved resources assigned for transmission by the second UE to the UE  500  or to another UE. Thus, the sidelink communication module  508  is configured to transmit sidelink data to the second UE using the first reserved resource. In some aspects, the sidelink communication module  508  is configured to receive, from a BS (e.g., the BSs  105  and/or  305 ), a configuration (e.g., time and frequency locations for resources usable for sidelinks) for a resource pool for sidelink communication, store the configuration information in the memory  504 , perform channel sensing according to the resource pool configuration information, and select the multiple sidelink resources from the resource pool based on the channel sensing. 
     In some aspects, the UE  500  may be a UE assigned with a resource from a multi-resource reservation. In this regard, the sidelink communication module  508  is configured to monitor for SCI, detect a multi-resource reservation from another UE reserving a resource for the UE  500 , transmit sidelink data using the reserved resource. In some aspects, the sidelink communication module  508  is configured to transmit SCI repeating an indication of the resource reserved for the UE  500  prior to the sidelink data transmission. In some aspects, the sidelink communication module  508  is configured to transmit SCI repeating the entire multi-resource reservation (e.g., indicating all resources reserved by the multi-resource reservation. 
     In some aspects, the sidelink communication module  508  is configured to include an HARQ ACK/NACK, an SR, and/or a BSR in SCI. The HARQ ACK/NACK may be a feedback for previous sidelink data received by the UE  500 . The SR and/or BSR may be a resource request for transmission over a sidelink. In some instances, the SR and/or BSR may be a request for transmitting over a sidelink to the UE that reserved the multi-resource reservation. In some other instances, the SR and/or BSR may indicate that the request is for transmitting a UE different from the UE that reserved the multi-resource reservation. 
     In some aspects, the sidelink communication module  508  is configured to monitor for SCI indicating a release indication for a reserved resource and transmit in the resource upon detecting a release of the resource. In some aspects, the sidelink communication module  508  is configured to monitor for SCI indicating a multi-resource reservation (reserving multiple resources for multiple sidelinks) and for SCI indicating a transmission in a reserved resource, and reclaim the resource for transmission if no SCI indicating a transmission in the reserved resource is detected. In some aspects, the sidelink communication module  508  is configured to refrain from transmitting in a resource if SCI including a multi-resource reservation indicating the resource is detected (from the reserving UE) or SCI indicating a transmission in the resource is detected (from the UE assigned to the resource by the multi-resource reservation). Mechanisms for reserving multiple sidelink resources for multiple sidelinks are described in greater detail herein. 
     As shown, the transceiver  510  may include the modem subsystem  512  and the RF unit  514 . The transceiver  510  can be configured to communicate bi-directionally with other devices, such as the BSs  105 . The modem subsystem  512  may be configured to modulate and/or encode the data from the memory  504  and/or the sidelink communication module  508  according to a modulation and coding scheme (MCS), e.g., a low-density parity check (LDPC) coding scheme, a turbo coding scheme, a convolutional coding scheme, a polar coding scheme, a digital beamforming scheme, etc. The RF unit  514  may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data (e.g., PSCCH, PSSCH, PSFCH, SCI, HARQ ACK/NACK, BSR, SR, resource release indication) from the modem subsystem  512  (on outbound transmissions) or of transmissions originating from another source such as a UE  115  or a BS  105 . The RF unit  514  may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver  510 , the modem subsystem  512  and the RF unit  514  may be separate devices that are coupled together at the UE  115  to enable the UE  115  to communicate with other devices. 
     The RF unit  514  may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas  516  for transmission to one or more other devices. The antennas  516  may further receive data messages transmitted from other devices. The antennas  516  may provide the received data messages for processing and/or demodulation at the transceiver  510 . The transceiver  510  may provide the demodulated and decoded data (e.g., resource pool configuration, RRC configuration) to the sidelink communication module  508  for processing. The antennas  516  may include multiple antennas of similar or different designs in order to sustain multiple transmission links. The RF unit  514  may configure the antennas  516 . 
     In an example, the transceiver  510  is configured to communicate, with a second wireless communication device, a reservation indicating a plurality of reserved resources for a plurality of sidelink communication and communicate, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of reserved resources, for example, by coordinating with the sidelink communication module  508 . The first resource may include a subset of the plurality of reserved resources (e.g., one or more resource elements from the plurality of reserved resources). 
     In an aspect, the UE  500  can include multiple transceivers  510  implementing different RATs (e.g., NR and LTE). In an aspect, the UE  500  can include a single transceiver  510  implementing multiple RATs (e.g., NR and LTE). In an aspect, the transceiver  510  can include various components, where different combinations of components can implement different RATs. 
       FIG. 6  is a block diagram of an exemplary BS  600  according to some aspects of the present disclosure. The BS  600  may be a BS  105  in the network  100  as discussed above in  FIG. 1 . As shown, the BS  600  may include a processor  602 , a memory  604 , a sidelink configuration module  608 , a transceiver  610  including a modem subsystem  612  and a RF unit  614 , and one or more antennas  616 . These elements may be in direct or indirect communication with each other, for example via one or more buses. 
     The processor  602  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  602  may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The memory  604  may include a cache memory (e.g., a cache memory of the processor  602 ), 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  604  may include a non-transitory computer-readable medium. The memory  604  may store instructions  606 . The instructions  606  may include instructions that, when executed by the processor  602 , cause the processor  602  to perform operations described herein, for example, aspects of  FIGS. 1-3, 4A-4D, 7A-7B, 8A-8B, 9A-9B, 10A-10B, and 11A-11B . Instructions  606  may also be referred to as code, which may be interpreted broadly to include any type of computer-readable statement(s) as discussed above with respect to  FIG. 5 . 
     The sidelink configuration module  608  may be implemented via hardware, software, or combinations thereof. For example, the sidelink configuration module  608  may be implemented as a processor, circuit, and/or instructions  606  stored in the memory  604  and executed by the processor  602 . In some instances, the sidelink configuration module  608  can be integrated within the modem subsystem  612 . For example, the sidelink configuration module  608  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  612 . 
     The sidelink configuration module  608  may be used for various aspects of the present disclosure, for example, aspects of  FIGS. 1-3, 4A-4D, 7A-7B, 8A-8B, 9A-9B, 10A-10B, and 11A-11B . The sidelink configuration module  608  is configured to allocate a resource pool for sidelink communications, transmits a configuration to a UE (e.g., by the UEs  115 ,  315 , and/or  500 ) to indicate the resource pool configuration (e.g., time and/or frequency locations of resources in the pool). Mechanisms for facilitating reservation of multiple resources for multiple sidelinks are described in greater detail herein. 
     As shown, the transceiver  610  may include the modem subsystem  612  and the RF unit  614 . The transceiver  610  can be configured to communicate bi-directionally with other devices, such as the UEs  115  and/or  500  and/or another core network element. The modem subsystem  612  may be configured to modulate and/or encode data according to a MCS, e.g., a LDPC coding scheme, a turbo coding scheme, a convolutional coding scheme, a polar coding scheme, a digital beamforming scheme, etc. The RF unit  614  may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data (e.g., sidelink resource pool configuration, sidelink grants) from the modem subsystem  612  (on outbound transmissions) or of transmissions originating from another source such as a UE  115  and/or UE  500 . The RF unit  614  may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver  610 , the modem subsystem  612  and/or the RF unit  614  may be separate devices that are coupled together at the BS  105  to enable the BS  105  to communicate with other devices. 
     The RF unit  614  may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas  616  for transmission to one or more other devices. This may include, for example, transmission of information to complete attachment to a network and communication with a camped UE  115  or  500  according to some aspects of the present disclosure. The antennas  616  may further receive data messages transmitted from other devices and provide the received data messages for processing and/or demodulation at the transceiver  610 . The transceiver  610  may provide the demodulated and decoded data (e.g., sidelink CQI, sidelink channel sensing information, HARQ ACK/NACK, BSR) to the sidelink configuration module  608  for processing. The antennas  616  may include multiple antennas of similar or different designs in order to sustain multiple transmission links. 
     In an example, the transceiver  610  is configured to, transmit sidelink grant to a sidelink receiving UE, receive sidelink channel information, sidelink BSRs, and/or sidelink ACK/NACK from the sidelink receiving UE, for example, by coordinating with the sidelink configuration module  608 . 
     In an aspect, the BS  600  can include multiple transceivers  610  implementing different RATs (e.g., NR and LTE). In an aspect, the BS  600  can include a single transceiver  610  implementing multiple RATs (e.g., NR and LTE). In an aspect, the transceiver  610  can include various components, where different combinations of components can implement different RATs. 
       FIG. 7A  will be discussed in relation to  FIG. 7B  to illustrate a sidelink communication scheme  700 . The scheme  700  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink transmitting UE may reserve multiple sidelink resources for its own transmission and for transmissions by one or more other UEs over one or more other sidelinks (e.g., the sidelinks  351 ,  352 , and/or  354 ) as shown in the scheme  700 . In the illustrated example of  FIGS. 7A and 7B , a UE  715   a  corresponds to a sidelink transmitting UE that selects or reserves multiple sidelink resources, which may be used by the UE  715   a  to transmit to a peer or receiving UE  715   b  and for the UE  715   b  to transmit to the UE  715   a  and/or another UE  715   c . The UEs  715   a ,  715   b , and  715   c  are substantially similar to the UEs  115 ,  315 , and/or  500 . In some aspects, the UEs  715   a ,  715   b , and  715   c  may correspond to the UEs  315   c ,  315   d , and  315   e , respectively. 
     While the scheme  700  is illustrated with three sidelink UEs, the scheme  700  may be applied by a sidelink transmitting UE to sequentially reserve resources for any suitable number of UEs (e.g., about 3, 4, 5 or more) over multiple sidelinks, for example, in a chained manner. In general, a transmitting UE i  may reserve resources sequentially for K number of UEs, denoted as UE i+1  to UE i+K , where K may be 1, 2, 3 or more. For instance, the UE i  reserves one or more resources for the UE i  to transmit to a UE i+1 , one or more resources for a UE i+1  to transmit to a UE i+2 , one or more resources for a UE i+2  to transmit to a UE i+3 , and so on. 
       FIG. 7A  illustrates a resource reservation  702  for multiple sidelinks according to some aspects of the present disclosure. In  FIG. 7A , the x-axis represents time in some arbitrary units, and the y-axis represents frequency in some arbitrary units. In general, time resources include one or more symbols (which can be grouped in slots or mini-slots), and frequency resources include one or more subcarriers (which can be grouped in subbands or subchannels) as discussed in relation to  FIG. 2 . For purposes of simplicity of discussion, the resource reservation  702  is illustrated using the PSCCH/PSSCH multiplexing configuration  460  of  FIG. 4D  and uses the same reference numerals as in  FIG. 4D . However, the scheme  700  may utilize any other suitable PSCCH/PSSCH multiplexing configuration (e.g., the configurations  430 ,  440 , or  450 ).  FIG. 7B  is a signaling diagram illustrating a sidelink communication method  704  according to some aspects of the present disclosure. The method  704  may be implemented among the sidelink UEs  715   a ,  715   b , and  715   c . As illustrated, the method  704  includes a number of enumerated steps, but embodiments of the method  704  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 step  720 , the UE  715   a  determines multiple sidelink resources for transmission to the UE  715   b  and for the UE  715   b  to transmit to the UE  715   a  and/or the UE  715   c . In this regard, the UE  715   a  may select multiple resource  706   a ,  706   b , and  706   c  (shown in  FIG. 7A ) similar to the resources  406  from a resource pool  708 . The resource pool  708  may include a number of resources similar to the resource  706 . In some aspects, the resource pool  708  may be preconfigured, for example, by a BS (e.g., the BSs  105 ,  305 , and/or  600 ) while the UE  715   a  is within a coverage of the BS. The UE  715   a  may store configuration information related to the resource pool  708  in a memory, such as the memory  504 . While  FIG. 7A  illustrates the resource pool  708  in a continuous time-frequency region, the resource pool  708  may include resources distributed in time and/or frequency. Additionally, while  FIG. 7A  illustrates the resources  706   a ,  706   b , and  706   c  as resources over different subchannels or subbands  402  in different time intervals, the reserved resources  706   a ,  706   b , and  706   c  may be located at any suitable time-frequency locations within the resource pool  708 . 
     In some aspects, the UE  715   a  may select the resources  706   a ,  706   b , and  706   c  by performing channel sensing and/or measurements on the resource pool, for example, on a per subchannel or subband  402  basis. In this regard, the UE  715   a  may perform the sensing in each subband  402   a ,  402   c , and  402   c  based on monitoring and/or decoding of SCIs transmitted by other UEs in the PSCCH region of the resource pool as discussed above. For instance, the UE  715   a  may receive a signal from each frequency band  402   a ,  402   b , and  402   c , perform blind decoding in the PSCCH region to determine whether an SCI is detected from the signal. As an example, the UE  715   a  may reserve the resource  706   a  for transmission to the UE  715   b  and may reserve the resources  706   b  and  706   c  for transmissions by the UE  715   b . In some instances, the UE  715   a  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to perform channel sensing, channel measurements, and/or reserve the sidelink resource  706 . In some aspects, some sidelink communications may have a higher service priority than other sidelink communications. When the UE  715   a  is reserving resources for high priority services, the UE  715   a  may disregard reservations for lower priority services. In other words, when a resource is reserved for a low-priority service, the UE  715   a  may override the low-priority reservation and reserve the resource. 
     At step  730 , the UE  715   a  transmits SCI A indicating the reservations for the resources  706   a ,  706   b , and  706   c . The UE  715   a  may transmit SCI A as shown in  FIG. 7A , where the SCI A is shown as SCI A  712  carried in a PSCCH  420  of the resource  706   a  and indicating the reserved resources  706   a ,  706   b , and  706   c  as shown by the dotted arrows. In some aspects, the SCI A  712  may indicate whether a reserved resource  706   a ,  706   b ,  706   c  is reserved for transmission by the UE  715   a  or for transmission by the UE  715   b  or whether all reserved resources  706   a ,  706   b ,  706   c  are reserved for the UE  715   a . In some aspects, the SCI A  712  may indicate a total M number of reservations. In the illustrated example of  FIG. 7A , the SCI A  712  may indicate a total of 3 reservations. In some other aspects, the SCI A  712  may indicate a total number of subchannels reserved for the multiple reservations. In some aspects, the UE  715   a  may assign each resource  706   a ,  706   b ,  706   c  to a particular sidelink (e.g., the sidelinks  351 ,  352 , and/or  354 ) and the SCI A  712  may indicate the link assignment for each resource  706   a ,  706   b ,  706   c . In other words, the SCI A  712  may indicate reserved resources per sidelink. For instance, the SCI A may indicate that the resource  706   a  is reserved for transmission by the UE  715   a  to the UE  715   b , the resource  706   b  is reserved for transmission by the UE  715   b  to the UE  715   a , and the resource  706   c  is reserved for transmission by the UE  715   b  to the UE  715   c . In some instances, the UE  715   a  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to transmit the SCI A  712 . 
     In some aspects, the SCI A  712  be part of a two-staged SCI, where the SCI A  712  is a first stage SCI. In this regard, a first stage SCI may be carried in a PSCCH  420  and may include information related to channel sensing. For instance, the first stage SCI may indicate resource reservations, for instance, time slots or time intervals and/or frequency subchannels where the reserved resources are located and/or a periodicity of the reserved resource. As such, other UEs may decode the first stage SCI and determine whether a resource is reserved or available based on the first stage SCI. A second stage SCI may be transmitted in a PSSCH  410  to indicate transmission parameters that are related to the transmission in the PSSCH  410 . In some instances, the second stage SCI may be encoded using a polar code. In some instances, the second stage SCI may be demodulated and/or decoded based on a PSSCH DMRS carried in the PSSCH. 
     At step  740 , the UE  715   a  transmits sidelink data A to the UE  715   b  in the PSSCH  410  of the resource  706   a  based on the SCI A  712 . In some aspects, when the SCI A  712  is a first stage SCI, the UE  715   a  may transmit a second stage SCI in the PSSCH of the resource  706   a . The second stage SCI may indicate transmission parameters, such as a MCS, used for transmitting the sidelink data. In some instances, the UE  715   a  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to transmit the sidelink data to the UE  715   b.    
     At step  750 , the UE  715   b  transmits sidelink data B 1  to the UE  715   a  in the PSSCH  410  of the resource  706   b . In this regard, the UE  715   b  may monitor for SCI and detect the SCI A  712 . The UE  715   b  may decode the SCI A  712 . The UE  715   b  may receive sidelink data A from the UE  715   a  based on the decoded SCI A  712 . The UE  715   b  may transmit sidelink data B 1  to the UE  715   a  using the resource  706   b  based on the SCI A  712  indicating the resource  706   b  reserved for the UE  715   b  to transmit to the UE  715   a . In some instances, the UE  715   b  may determine transmission parameters (e.g., MCS) for the sidelink data B 1  and may indicate the transmission parameters to the UE  715   a , for example, via a stage two SCI in the PSSCH  410  of the resource  706   b . In some instances, the UE  715   b  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to receive the SCI A  712 , perform blind decoding to recover sidelink resource reservation information carried by SCI A  712 , receive the sidelink data A in the resource  706   a  based on the resource reservation information, and transmit the sidelink data B 1  using the resource  706  resource reservation information. 
     At step  760 , the UE  715   b  transmits sidelink data B 2  to the UE  715   c  in the PSSCH  410  of the resource  706   c . In this regard, the UE  715   b  may determine that the SCI A  712  includes a reservation for the resource  706   c  for the UE  715   b  transmit to the UE  715   c . The UE  715   b  may transmit the sidelink data B 2  using substantially similar mechanisms as in the step  750 . 
     In some aspects, a BS (e.g., the BSs  105 ,  305 , and/or  600 ) may configure a resource usage pattern for using the resources  706  reserved by the UE  715   a . For instance, the BS may indicate that the resource  706   a  is for is for transmission from the UE  715   a  to the UE  715   b , the resource  706   b  is for is for transmission from the UE  715   b  to the UE  715   c , and the resource  706   c  is for is for transmission from the UE  715   b  to the UE  715   c . Alternatively, the BS may indicate that every other reserved resource is for transmission from the UE  715   a  to the UE  715   b . In some aspects, the BS may determine the resource usage pattern based on traffic pattern or traffic needs at the UEs  715   a ,  715   b , and/or  715   c  known by the BS or predicted by the BS. In some aspects, the BS may indicate the reserved resources and/or the resource usage pattern to the UE  715   a ,  715   b , and/or  715   c  via RRC configurations. 
     The scheme  700  assumes that the UE  715   c  may detect and decode the SCI A  712  transmitted by the UE  715   a  and thus may be aware of the reservation of the resource  706   c  for the sidelink data B 2  from the UE  715   b . However, in some instances, the UE  715   c  may be able to detect and decode transmission from the UE  715   b , but may not be able to detect and/or decode transmission from the UE  715   c . Accordingly, in some aspects, the UE  715   b  may repeat at least some of the reservation information received from the SCI A  712  to facilitate channel sensing and/or detection at the UE  715   c  as discussed below. 
       FIG. 8A  will be discussed in relation to  FIG. 8B  to illustrate a sidelink communication scheme  800 . The scheme  800  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink transmitting UE may reserve multiple sidelink resources for its own transmission and for transmissions by one or more other UEs over a sequence of one or more other sidelinks (e.g., the sidelinks  351 ,  352 , and/or  354 ) and a peer UE may repeat the indication of at least some of the reservations as shown in the scheme  800 . The scheme  800  is discussed using a similar sidelink communication scenario among sidelink UEs  715   a ,  715   b , and  715   c  as in  FIG. 7B . 
       FIG. 8A  illustrates a resource reservation  802  for multiple sidelinks according to some aspects of the present disclosure. In  FIG. 8A , the x-axis represents time in some arbitrary units, and the y-axis represents frequency in some arbitrary units. In general, time resources include one or more symbols (which can be grouped in slots or mini-slots), and frequency resources include one or more subcarriers (which can be grouped in subbands or subchannels). The resource reservation  802  is described using the same resource pool structure as in  FIG. 7A , and may use the same reference numerals as in  FIG. 7A  for simplicity&#39;s sake.  FIG. 8B  is a signaling diagram illustrating a sidelink communication method  804  according to some aspects of the present disclosure. The method  804  may be implemented among the sidelink UEs  715   a ,  715   b , and  715   c . As illustrated, the method  804  includes a number of enumerated steps, but embodiments of the method  804  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. 
     In the illustrated example of  FIG. 8B , the UE  715   a  and the UE  715   b  can detect each other&#39;s transmissions as shown by the checkmark. The UE  715   b  and the UE  715   c  can detect each other&#39;s transmissions as shown by the checkmark. However, the UE  715   c  and the UE  715   a  may not detect each other&#39;s transmissions as shown by the cross symbol. Accordingly, in the method  804 , the UE  715   b  may transmit SCI repeating a resource reservation to be used for sidelink transmission to the UE  715   c.    
     Generally speaking, the method  804  includes features similar to the method  704  in many respects. For example, steps  720 ,  730 ,  740 , and  760  are similar to steps  820 ,  830 ,  840 , and  860 , respectively. Accordingly, for sake of brevity, details of those steps will not be repeated here. 
     At step  820 , the UE  715   a  determines multiple sidelink resources for transmission to the UE  715   b  and for the UE  715   b  to transmit to the UE  715   c . For instance, the UE  715   a  reserves the resource  706   a  for transmission from the UE  715   a  to the UE  715   b  and the resource  706   b  for transmission from the UE  715   b  to the UE  715   c  as shown in  FIG. 8A . 
     At step  830 , the UE  715   a  transmits SCI A (shown as SCI A  812  in  FIG. 8A ) indicating the reservations for the resources  706   a  and  706   b  (e.g., M=2). 
     At step  840 , the UE  715   a  transmits sidelink data A to the UE  715   b  in the PSSCH  410  of resource  706   a.    
     At step  850 , the UE  715   b  transmits SCI B repeating the reservation for the resource  706   b , which may be subsequently used for transmission to the UE  715   c . The UE  715   a  may transmit SCI B as shown in  FIG. 8A , where the SCI B is shown as SCI B  814  carried in a PSCCH  420  of the resource  706   b  and indicating the reserved resource  706   b  as shown by the dotted arrow. In some aspects, the UE  715   b  may echo or duplicate all the reservations indicated by the SCI A  812  received from the UE  715   a . In other words, the SCI B  814  may indicate the reservations for the resources  706   a  and the resource  706   b . The repeated transmission or indication of the reservation for the resource  706   b  by the UE  715   b  enables the UE  715   c  to detect the reservation, that may otherwise be missed by the UE  715   c . In some instances, the UE  715   b  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to generate SCI B  814  by including the reservation for the resource  706   b  indicated by the SCI A  812  and transmit the SCI B  812  to the UE  715   c.    
     In some aspects, the SCI B  814  may be a first stage SCI of a two-staged SCI. The UE  715   b  may transmit a second stage SCI in the PSSCH  410  of the resource  706   b  to indicate scheduling information (e.g., MCS) to be used for sidelink data transmission in the resource  706   b.    
     At step  860 , the UE  715   b  transmits sidelink data B to the UE  715   c  in the PSSCH  410  of resource  706   b  according to the scheduling information. For instance, the UE  715   c  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to receive the SCI B  814 , perform blind decoding to recover sidelink resource reservation information carried by SCI B  814 , receive the sidelink data B in the resource  706   b  based on the resource reservation information. 
       FIG. 9A  will be discussed in relation to  FIG. 9B  to illustrate a sidelink communication scheme  900 . The scheme  900  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink transmitting UE may reserve multiple sidelink resources for its own transmission and for transmissions by one or more other UEs over one or more other sidelinks (e.g., the sidelinks  351 ,  352 , and/or  354 ) and may additionally reserve resources for sidelink feedbacks (e.g., HARQ AKC/NACK) as shown in the scheme  900 . The scheme  900  is discussed using a similar sidelink communication scenario among sidelink UEs  715   a ,  715   b , and  715   c  as in  FIG. 7B . 
       FIG. 9A  illustrates a resource reservation  902  for multiple sidelinks according to some aspects of the present disclosure. In  FIG. 9A , the x-axis represents time in some arbitrary units, and the y-axis represents frequency in some arbitrary units. In general, time resources include one or more symbols (which can be grouped in slots or mini-slots), and frequency resources include one or more subcarriers (which can be grouped in subbands or subchannels). The resource reservation  902  is similar to the resource reservation  802  in  FIG. 8A .  FIG. 9B  is a signaling diagram illustrating a sidelink communication method  904  according to some aspects of the present disclosure. The method  904  may be implemented among the sidelink UEs  715   a ,  715   b , and  715   c . As illustrated, the method  904  includes a number of enumerated steps, but embodiments of the method  904  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. 
     Generally speaking, the method  904  includes features similar to the method  804  in many respects. For example, steps  920 ,  930 ,  940 , and  960  are similar to steps  820 ,  830 ,  840 , and  860 , respectively. Accordingly, for sake of brevity, details of those steps will not be repeated here. Please refer to the corresponding descriptions above. However, the method  904  allows an HARQ ACK/NACK to be included in an SCI transmission. 
     In this regard, at step  930 , the UE  715   a  transmits SCI A (shown as SCI A  912  in  FIG. 9A ). The SCI A  912  may indicate the reservations for the resources  706   a  and  706   b  and may additionally indicate a PSFCH reservation for the UE  715   b  to feedback a HARQ ACK/NACK for a subsequent sidelink data A transmission from the UE  715  at step  940 . In this regard, the SCI A  912  may indicate that the HARQ ACK/NACK may be carried by SCI in the resource  706   b.    
     At step  950 , upon receiving the SCI A  912  and the sidelink data A from the UE  715   a , the UE  715   b  transmits SCI B (shown as SCI B  914  in  FIG. 9A ) in the PSCCH  420  of the resource  706   b . In some aspects, the SCI B  914  may be a first stage SCI of a two-staged SCI. The SCI B  914  may be received by the UE  715   a  and the UE  715   c  as shown by the arrows to the UE  715   a  and UE  715   c , respectively. The SCI B  914  may indicate a HARQ ACK/NACK for the sidelink data A in addition to repeating the reservation for the resource  706   b  for a subsequent sidelink transmission to the UE  715   c . In this regard, the UE  715   b  may generate a HARQ ACK if the sidelink data A is received and decoded successfully. Alternatively, the UE  715   b  may generate a HARQ NACK if the UE  715   b  fails to decode the sidelink data A. In some instances, the HARQ ACK/NACK may be a single bit indicating a 1 for ACK or a 0 for NACK. In some other instances, the HARQ ACK/NACK may be a sequence selected from a HARQ ACK/NACK codebook. In some instances, the UE  715   b  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to generate a HARQ ACK/NACK for the sidelink data A and generate the SCI B  914  based on the HARQ ACK/NACK and the reservation for the resource  706   b.    
     At step  960 , the UE  715   b  transmits sidelink data B to the UE  715   c  in the PSSCH  410  of resource  706   b.    
     In some aspects, if the SCI B  914  indicates an NACK, the UE  715   a  may subsequently reserve another resource for a retransmission of the sidelink data A. Conversely, if the SCI B  914  indicates an ACK, the UE  715   a  may subsequently reserve a resource for a new transmission (e.g., a new TB). 
       FIG. 10A  will be discussed in relation to  FIG. 10B  to illustrate a sidelink communication scheme  1000 . The scheme  1000  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink transmitting UE may reserve multiple sidelink resources for its own transmission and for transmissions by one or more other UEs over one or more other sidelinks (e.g., the sidelinks  351 ,  352 , and/or  354 ) and may additionally reserve resources for sidelink SRs as shown in the scheme  1000 . The scheme  1000  is discussed using a similar sidelink communication scenario among sidelink UEs  715   a ,  715   b , and  715   c  as in  FIG. 7B . 
       FIG. 10A  illustrates a resource reservation  1002  for multiple sidelinks according to some aspects of the present disclosure. In  FIG. 10A , the x-axis represents time in some arbitrary units, and the y-axis represents frequency in some arbitrary units. In general, time resources include one or more symbols (which can be grouped in slots or mini-slots), and frequency resources include one or more subcarriers (which can be grouped in subbands or subchannels). The resource reservation  1002  is similar to the resource reservation  802  and  902 .  FIG. 10B  is a signaling diagram illustrating a sidelink communication method  1004  according to some aspects of the present disclosure. The method  1004  may be implemented among the sidelink UEs  715   a ,  715   b , and  715   c . As illustrated, the method  1004  includes a number of enumerated steps, but embodiments of the method  1004  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. 
     Generally speaking, the method  1004  includes features similar to the method  804  in many respects. For example, steps  1020 ,  1030 ,  1040 , and  1060  are similar to steps  820 ,  830 ,  840 , and  830 , respectively. Accordingly, for sake of brevity, details of those steps will not be repeated here. Please refer to the corresponding descriptions above. However, the method  1004  allows an SR to be included in an SCI transmission. 
     In this regard, at step  1030 , the UE  715   a  transmits SCI A (shown as SCI A  1012  in  FIG. 10A ). The SCI A  1012  may indicate the reservations for the resources  706   a  and  706   b  and may additionally indicate a reservation for the UE  715   b  to transmit an SR or BSR. In this regard, the SCI A  912  may indicate that the SR or BSR may be carried by SCI in the resource  706   b.    
     At step  1050 , upon receiving the SCI A  1012 , the UE  715   b  transmits SCI B (shown as SCI B  1014  in  FIG. 10A ) in the PSCCH  420  of the resource  706   b . In some aspects, the SCI B  1014  may be a first stage SCI of a two-staged SCI. The SCI B  1014  may be received by the UE  715   a  and the UE  715   c  as shown by the arrows to the UE  715   a  and UE  715   c , respectively. The SCI B  1014  may indicate an SR or a BSR in addition to repeating the reservation for the resource  706   b  for a subsequent sidelink transmission to the UE  715   c . In this regard, the UE  715   b  may determine that the resource  706   b  may not be sufficient for carrying all sidelink data to the UE  715   c , and thus the UE  715   b  may indicate an SR in the SCI B  1014 . Additionally or alternatively, the UE  715   b  may determine that there is data ready for transmission to the UE  715   a , and thus may indicate an SR or a BSR in the SCI B  1014 . In some instances, the SCI B  1014  may indicate an SR for each sidelink using a single bit, where a bit value of 1 may indicate an SR is enabled (e.g., requesting for resource) and a bit value of 0 may indicate an SR is disabled (e.g., no request for resource). In some instances, the SCI B  1014  may indicate a BSR for each sidelink, where the BSR may indicate an amount of data ready for transmission. In some instances, the UE  715   b  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to generate one or more SRs or BSRs based on whether there is additional data ready for transmission to the UE  715   a  and/or the UE  715   c  and generate the SCI B  1014  based on the SRs or BSRs and the reservation for the resource  706   b.    
     At step  1060 , the UE  715   b  transmits sidelink data B to the UE  715   c  in the PSSCH  410  of resource  706   b.    
     In some aspects, the SCI B  1014  may include an SR or a BSR indicating there is no data for transmission in the resource  706   b , and thus the resource  706   b  may return to the UE  715   a.    
       FIG. 11A  will be discussed in relation to  FIG. 11B  to illustrate a sidelink communication scheme  1100 . The scheme  1100  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink transmitting UE may reserve multiple sidelink resources for its own transmission and for transmissions by one or more other UEs over one or more other sidelinks (e.g., the sidelinks  351 ,  352 , and/or  354 ) and may additionally indicate a release of a reserved resource as shown in the scheme  1100 . The scheme  1100  is discussed using a similar sidelink communication scenario among sidelink UEs  715   a ,  715   b , and  715   c  as in  FIG. 7B . 
       FIG. 11A  illustrates a resource reservation  1102  for multiple sidelinks according to some aspects of the present disclosure. In  FIG. 11A , the x-axis represents time in some arbitrary units, and the y-axis represents frequency in some arbitrary units. In general, time resources include one or more symbols (which can be grouped in slots or mini-slots), and frequency resources include one or more subcarriers (which can be grouped in subbands or subchannels). The resource reservation  1102  is similar to the resource reservation  802  in  FIG. 8A .  FIG. 11B  is a signaling diagram illustrating a sidelink communication method  1004  according to some aspects of the present disclosure. The method  1104  may be implemented among the sidelink UEs  715   a ,  715   b , and  715   c . As illustrated, the method  1104  includes a number of enumerated steps, but embodiments of the method  1104  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. 
     Generally speaking, the method  1104  includes features similar to the method  804  in many respects. For example, steps  1120 ,  1130 , and  1140  are similar to steps  820 ,  830 , and  840 , respectively. Accordingly, for sake of brevity, details of those steps will not be repeated here. Please refer to the corresponding descriptions above. However, the method  1104  additionally illustrate techniques for releasing a reserved sidelink resource and/or reclaiming a released sidelink resource. 
     In this regard, at step  1130 , the UE  715   a  transmits SCI A (shown as SCI A  1112  in  FIG. 11A ). Similar to the SCI A  812 , the SCI A  1112  may indicate that the resource  706   a  is reserved for transmission from the UE  715   a  to the UE  715   b  and the resource  706   b  is reserved for transmission from the UE  715   b  to the UE  715   c . In some aspects, the SCI A  1112  may also indicate whether the UE  715   b  may release the resource  706   b  if the UE  715   b  has no data for transmission. 
     At step  1150 , upon receiving the SCI A, the UE  715   b  transmits SCI B (shown as SCI B  1114  in  FIG. 10A ) in the PSCCH  420  of the resource  706   b  to indicate a release of the resource  706   b  reserved for the UE  715   b . In this regard, the UE  715   b  may determine that there is no data ready for transmission to the UE  715   c , and thus may release the reserved resource  706   b . In some instances, the SCI B  1114  may indicate the release of the reserved resource  706   b  by using a single bit, where a bit value of 0 may indicate that the resource  706   b  is released and a bit value of 1 may indicate that the resource  706   b  is not released. In some instances, the UE  715   b  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to transmit SCI B  1114  including a bit indicating that the reserved resource  706  is released. In some aspects, the SCI B  1114  may be a first stage SCI of a two-staged SCI. 
     At step  1160 , upon detecting that the reserved resource  706   b  is released, the UE  715   c  transmit sidelink data C to the UE  715   b  or any other sidelink UE using the released resource  706   b . For instance, the UE  715   c  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to monitor for SCI in the PSCCH  420  of the resource  706   b , detect the SCI B  1114  from the monitoring, determine that the SCI B  1114  indicating the released resource  706   b , and transmit the sidelink data C using the released resource  706   b.    
     In some other instances, at step  1150 , the SCI B  1114  may indicate all released resources. For instance, the UE  715   a  may have reserved two resources  706  for transmission to the UE  715   b , but may use only one of the reserved resources  706  and release the other resource  706 . Thus, the UE  715   b  may indicate the resource  706  released by the UE  715   a  and the UE  715   b . In general, a transmitting UE 1  may reserve resources sequentially for K number of UEs, denoted as UE 1+1  to UE i+K , where K may be 2, 3 or more. For instance, the UE 1  reserves a resource for a UE i+1  to transmit to a UE i+2 , a resource for a UE i+2  to transmit to a UE i+3 , and so on. A UE j , where j is between 1 and K, may indicate resource(s) released by the UE j  or resource(s) released by all UEs from UE i    1  to UE j−1 . The released resource(s) may be reclaimed by any UE detecting an indication of the released resource. 
       FIG. 12A  will be discussed in relation to  FIG. 12B  to illustrate a sidelink communication scheme  1200 . The scheme  1200  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink UE may reclaim a reserved resource for sidelink communication as shown in the scheme  1200 . 
       FIG. 12A  illustrates a sidelink communication scenario  1202  according to some aspects of the present disclosure. As shown, the scenario  1202  includes sidelink UEs  1215   a ,  1215   b , and  1215   c . The sidelink UEs  1215  may be similar to the UEs  115 ,  315 ,  500 , and/or  715 . The sidelink UE  1215   a  may be correspond to the transmitting UE  715   a  that reserves multiple resources (e.g., the resources  406  and/or  706 ) for multiple sidelinks as shown in the schemes  700 ,  800 ,  900 ,  1000 , and/or  1100  discussed above with respect to  FIGS. 7, 8, 9, 10 , and/or  11 , respectively. For instance, the UE  1215   a  may reserve two resources, a resource A (e.g., the resource  706   a ) for transmission by the UE  1215   a  and a resource B (e.g., the resource  706   b ) for transmission by the UE  1215   b . In the illustrated example of  FIG. 12A , the UE  1215   c  may detect a transmission from the UE  1215   a  as shown by the checkmark, but may not detect a transmission from the UE  1215   b  as shown by the cross symbol. 
       FIG. 12B  is a flow diagram of a sidelink communication method  1204  according to some aspects of the present disclosure. Aspects of the method  1204  can be implemented by the UE  1215   c . For example, the UE  1215   c  may utilize one or more components, such as the processor  502 , the memory  504 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to execute the steps of method  1204 . As illustrated, the method  1204  includes a number of enumerated steps, but aspects of the method  1204  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  1220 , the UE  1215   c  determines whether SCI (e.g., the SCIs  712 ,  812 ,  814 .  912 ,  914 ,  1012 ,  1014 ,  1112 , and/or  1114 ) indicating a transmission in the reserved resource B is detected from the UE  1215   a  and/or the UE  1215   b . For instance, the UE  1215   a  may transmit SCI in the PSCCH (e.g., the PSCCH  420 ) of the resource A to indicate a reservation for the resource A and the resource B and the UE  1215   b  may transmit SCI in the PSCCH of the resource B to indicate the reservation for the resource B as discussed above in the schemes  800 ,  900 , and  1000 . Thus, the UE  1215   c  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to monitor for SCI in the PSCCH of the resource A and the resource B, determine whether SCI indicating a transmission in the resource B is detected in the PSCCH of the resource A or the resource B. 
     If the UE  1215   c  detects SCI indicating a transmission in the reserved resource B is detected from the UE  1215   a  or the UE  1215   b , the UE  1215   c  proceeds to block  1240 . At block  1240 , the UE  1215   c  refrains from transmitting in the resource in response to detecting SCI indicating a transmission in the reserved resource B. Thus, the UE  1215   c  may not transmit in the resource B as long as the UE  1215   c  detects SCI indicating a transmission in the resource B irrespective of whether the detected SCI is from UE  1215   a  (reserving the resource B) or UE  1215   b  (assigned with the reserved resource B). Accordingly, in the scenario  1202 , the UE  1215   c  may not reclaim the resource B for transmission. 
     If the UE  1215   c  does not detect any SCI from the UE  1215   a  and/or the UE  1215   b  indicating a transmission in the reserved resource B, the UE  1215   c  proceeds to block  1230 . At block  1230 , the UE  1215   c  reclaims the released resource B for transmission. Thus, the UE  1215   c  may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to transmit sidelink data using the resource B. 
       FIG. 13A  will be discussed in relation to  FIG. 13B  to illustrate a sidelink communication scheme  1300 . The scheme  1300  may be employed by UEs such as the UEs  115 ,  315 , and/or  500  in a network such as the networks  100  and  300 . In particular, a sidelink UE may reclaim a reserved resource for sidelink communication as shown in the scheme  1300 . 
       FIG. 13A  illustrates a sidelink communication scenario  1302  according to some aspects of the present disclosure. The scenario  1302  is similar to the scenario  1202  shown in  FIG. 12 . For instance, the UE  1215   a  may reserve two resources, a resource A (e.g., the resource  706   a ) for transmission by the UE  1215   a  and a resource B (e.g., the resource  706   b ) for transmission by the UE  1215   b.    
       FIG. 13B  is a flow diagram of a sidelink communication method  1304  according to some aspects of the present disclosure. Aspects of the method  1304  can be implemented by the UE  1215   c . For example, the UE  1215   c  may utilize one or more components, such as the processor  502 , the memory  504 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to execute the steps of method  1204 . As illustrated, the method  1304  includes a number of enumerated steps, but aspects of the method  1304  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  1320 , the UE  1215   c  detects SCI (e.g., the SCIs  712 ,  812 ,  814 .  912 ,  914 ,  1012 ,  1014 ,  1112 , and/or  1114 ) from UE  1215   a  reserving the resource B, for example, using similar mechanisms as described in block  1220 . 
     At block  1330 , the UE  1215  determines whether SCI indicating a transmission in the reserved resource B is detected from the UE  1215   b , for example, using similar mechanisms as described in block  1220 . 
     If the UE  1215   c  detects SCI indicating a transmission in the reserved resource B is detected from the UE  1215   b , the UE  1215   c  proceeds to block  1340 . At block  1240 , the UE  1215   c  refrains from transmitting in the resource in response to detecting SCI indicating a transmission in the reserved resource B. 
     If the UE  1215   c  does not detect any SCI from the UE  1215   b  a transmission in the reserved resource B, the UE  1215   c  proceeds to block  1330 . At block  1330 , the UE  1215   c  reclaims the released resource B for transmission. For instance, the UE  1215   c  transmits sidelink data in the reclaimed resource B. 
     As can be observed, the method  1300  differs from the method  1200  by allowing the UE  1215   c  to reclaim the reserved resource B for transmission if the UE  1215   c  does not detect SCI from the UE  1215   b  assigned to the reserved resource. In other words, if the UE  1215   c  cannot detect a transmission from the assigned UE  1215   b , the UE  1215   c &#39;s transmission may not interfere with the UE  1215   b &#39;s transmission. Thus, the UE  1215   c  may reclaim the reserved resource B based on a spatial reuse of the reserved resource B. 
       FIG. 14  is a flow diagram of a sidelink communication method  1400  according to some aspects of the present disclosure. Aspects of the method  1400  can be executed by a computing device (e.g., a processor, processing circuit, and/or other suitable component) of a wireless communication device or other suitable means for performing the steps. For example, a wireless communication device, such as the UE  115 ,  315 ,  500 ,  715 , and/or  1215  may utilize one or more components, such as the processor  502 , the memory  504 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to execute the steps of method  1400 . The method  1400  may employ similar mechanisms as in the schemes  700 ,  800 ,  900 ,  1000 ,  1100 ,  1200 , and/or  1300  discussed above with respect to  FIGS. 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B , and/or  13 A- 13 B, respectively. As illustrated, the method  1400  includes a number of enumerated steps, but aspects of the method  1400  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  1410 , a first wireless communication device communicates, with a second wireless communication device, a reservation indicating a plurality of resources (e.g., the sidelink resources  406  and/or  706 ) for a plurality of sidelink communications (e.g., sidelink data). The plurality of resources reserved for the plurality of sidelink communications are sidelink resources (each including one or more resource elements) as discussed above with reference to  FIGS. 4A-4D, 7A-7B, 8A-8B, 9A-9B, 10A-10B, 11A-11B, 12A-12B , and/or  13 A- 13 B. In some instances, the first wireless communication device may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to communicate the reservation indicating the plurality of resource for the plurality of sidelink communications. 
     In some aspects, the reservation indicates the plurality of resources in a plurality of subchannels (e.g., the subbands  402   a ,  402   b ,  402   c ). In some aspects, the reservation indicates an assignment of a first resource (e.g., one or more resource elements) to the first sidelink communication and an assignment of a second resource (e.g., one or more resource elements) of the plurality of resources to a second sidelink communication of the plurality of sidelink communications. 
     At block  1420 , the first wireless communication device communicates, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using the first resource of the plurality of resources. In some instances, the first wireless communication device may utilize one or more components, such as the processor  502 , the sidelink communication module  508 , the transceiver  510 , the modem  512 , and the one or more antennas  516 , to communicating the first sidelink communication. 
     In some aspects, the first wireless communication device may correspond to the transmitting UE  715   a  or the UE  1215   a  reserving the plurality of resources and the second wireless communication device may correspond to the UE  715   b ,  715   c ,  1215   b , or  1215   c . Accordingly, the first wireless communication may select the plurality resources, for example, from a resource pool as discussed above in scheme  700 , and transmit the reservation to the second wireless communication device. In some aspects, the first wireless communication may transmit SCI (e.g., the SCI  712 ,  812 ,  912 ,  1012 , and/or  1112 ) indicating the reservation. 
     In some aspects, the second wireless communication device may correspond to the transmitting UE  715   a  or the UE  1215   a  reserving the plurality of resources and the first wireless communication device may correspond to the UE  715   b ,  715   c ,  1215   b , or  1215   c . Accordingly, the first wireless communication may receive the reservation from the second wireless communication device. In some aspects, the block  1420  may include transmitting, by the first wireless communication device to the third wireless communication device, the first sidelink communication in the first resource. In some aspects, the third wireless communication device corresponds to the second wireless communication device. In some aspects, the third wireless communication device is different than the second wireless communication device. In some aspects, the first wireless communication device may further transmit, second SCI indicating at least the first resource indicated by the first SCI, for example, as discussed in the schemes  800  with reference to  FIGS. 8A-8B . In some aspects, the second SCI may indicate an HARQ ACK/NACK as discussed in the scheme  900  with reference to  FIGS. 9A-9B . In some aspects, the second SCI may indicate an SR or a BSR as discussed in the scheme  1000  with reference to  FIGS. 10A-10B . 
     In some aspects, the first wireless communication device may transmit, an indication indicating that there is no sidelink transmission in a second resource of the plurality of resources reserved for the first wireless communication device, for example, as discussed in the scheme  1100  with reference to  FIGS. 11A-11B . 
     Further aspects of the present disclosure include a method of wireless communication. The method of wireless communication includes communicating, by a first wireless communication device with a second wireless communication device, a reservation indicating a plurality of resources for a plurality of sidelink communications. The method of wireless communication also includes communicating, by the first wireless communication device with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of resources. 
     The method may also include one or more of the following features. For instance, the method may include where the reservation indicates the plurality of resources in a plurality of subchannels. The reservation indicates an assignment of the first resource to the first sidelink communication and an assignment of a second resource of the plurality of resources to a second sidelink communication of the plurality of sidelink communications. The communicating the reservation includes transmitting, by the first wireless communication device to the second wireless communication device, sidelink control information (SCI) indicating the reservation. The communicating the reservation includes receiving, by the first wireless communication device from the second wireless communication device, first sidelink control information (SCI) indicating the reservation. The communicating the first sidelink communication includes transmitting, by the first wireless communication device to the third wireless communication device, the first sidelink communication in the first resource. The third wireless communication device corresponds to the second wireless communication device. The third wireless communication device is different than the second wireless communication device. The method may include transmitting, by the first wireless communication device, second SCI indicating at least the first resource indicated by the first SCI. The method may include transmitting, by the first wireless communication device, second SCI repeating the reservation indicated by the first SCI. The communicating the first sidelink communication includes receiving, by the first wireless communication device from the third wireless communication device, the first sidelink communication; and the method further includes transmitting, by the first wireless communication device, second SCI indicating an acknowledgement/negative-acknowledgement ACK/NACK) for the first sidelink communication. The method may include transmitting, by the first wireless communication device, second SCI indicating at least one of a scheduling request (SR) or a buffer status report (BSR) based on the reservation. The method may include transmitting, by the first wireless communication device, an indication indicating that there is no sidelink transmission in a second resource of the plurality of resources reserved for the first wireless communication device. The method may include receiving, by the first wireless communication device, an indication indicating that there is no sidelink transmission in at least a second resource of the plurality of resources; and transmitting, by the first wireless communication device, a repeat of the indication. The method may include detecting, by the first wireless communication device, an indication indicating that there is no sidelink transmission in a reserved resource; and transmitting, by the first wireless communication device, a sidelink communication using the reserved resource in response to the detecting. The method may include detecting, by the first wireless communication device, an indication of a fourth wireless communication device reserving a second resource; and refraining, by the first wireless communication device, from transmitting in the second resource in response to the detecting. The method may include detecting, by the first wireless communication device, an indication of a fourth wireless communication device reserving a second resource; monitoring, by the first wireless communication device, for a transmission in the second resource in response to the detecting; and transmitting, by the first wireless communication device, a sidelink communication using the second resource in response to a determination that no transmission is detected in the second resource from the monitoring. 
     Further aspects of the present disclosure include an apparatus including a transceiver configured to communicate, with a second wireless communication device, a reservation indicating a plurality of resources for a plurality of sidelink communications; and communicate, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of resources. 
     The apparatus may also include one or more of the following features. For instance, the apparatus may include where the reservation indicates the plurality of resources in a plurality of subchannels. The reservation indicates an assignment of the first resource to the first sidelink communication and an assignment of a second resource of the plurality of resources to a second sidelink communication of the plurality of sidelink communications. The transceiver configured to communicate the reservation is configured to transmit, to the second wireless communication device, sidelink control information (SCI) indicating the reservation. The transceiver configured to communicate the reservation is configured to receive, from the second wireless communication device, first sidelink control information (SCI) indicating the reservation. The transceiver configured to communicate the first sidelink communication is configured to transmit, to the third wireless communication device, the first sidelink communication in the first resource. The third wireless communication device corresponds to the second wireless communication device. The third wireless communication device is different than the second wireless communication device. The transceiver is further configured to transmit second SCI indicating at least the first resource indicated by the first SCI. The transceiver is further configured to transmit second SCI repeating the reservation indicated by the first SCI. The transceiver configured to communicate the first sidelink communication is configured to receive, from the third wireless communication device, the first sidelink communication; and the transceiver is further configured to transmit second SCI indicating an acknowledgement/negative-acknowledgement ACK/NACK) for the first sidelink communication. The transceiver is further configured to transmit second SCI indicating at least one of a scheduling request (SR) or a buffer status report (BSR) based on the reservation. The transceiver is further configured to transmit an indication indicating that there is no sidelink transmission in a second resource of the plurality of resources reserved for the apparatus. The transceiver is further configured to receive an indication indicating that there is no sidelink transmission in at least a second resource of the plurality of resources; and transmit a repeat of the indication. The transceiver is further configured to transmit a sidelink communication using the reserved resource in response to the detection. The apparatus may include a processor configured to detect an indication of a fourth wireless communication device reserving a second resource; and refrain from transmitting in the second resource in response to the detection. The transceiver is further configured to transmit a sidelink communication using the second resource in response to a determination that no transmission is detected in the second resource from the monitoring. 
     Further aspects of the present disclosure include a non-transitory computer-readable medium having program code recorded thereon. The non-transitory computer-readable medium includes code for causing a first wireless communication device to communicate, with a second wireless communication device, a reservation indicating a plurality of resources for a plurality of sidelink communications. The non-transitory computer-readable medium also includes code for causing the first wireless communication device to communicate, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of resources. 
     The non-transitory computer-readable medium may also include one or more of the following features. For instance, the non-transitory computer-readable medium may include where the reservation indicates the plurality of resources in a plurality of subchannels. The reservation indicates an assignment of the first resource to the first sidelink communication and an assignment of a second resource of the plurality of resources to a second sidelink communication of the plurality of sidelink communications. The code for causing the first wireless communication device to communicate the reservation is configured to transmit, to the second wireless communication device, sidelink control information (SCI) indicating the reservation. The code for causing the first wireless communication device to communicate the reservation is configured to receive, from the second wireless communication device, first sidelink control information (SCI) indicating the reservation. The code for causing the first wireless communication device to communicate the first sidelink communication is configured to transmit, to the third wireless communication device, the first sidelink communication in the first resource. The third wireless communication device corresponds to the second wireless communication device. The third wireless communication device is different than the second wireless communication device. The non-transitory computer-readable medium may include code for causing the first wireless communication device to transmit second SCI indicating at least the first resource indicated by the first SCI. The non-transitory computer-readable medium may include code for causing the first wireless communication device to transmit second SCI repeating the reservation indicated by the first SCI. The code for causing the first wireless communication device to communicate the first sidelink communication is configured to receive, from the third wireless communication device, the first sidelink communication; and the program code may include code for causing the first wireless communication device to transmit second SCI indicating an acknowledgement/negative-acknowledgement ACK/NACK) for the first sidelink communication. The non-transitory computer-readable medium may include code for causing the first wireless communication device to transmit second SCI indicating at least one of a scheduling request (SR) or a buffer status report (BSR) based on the reservation. The non-transitory computer-readable medium may include code for causing the first wireless communication device to transmit an indication indicating that there is no sidelink transmission in a second resource of the plurality of resources reserved for the first wireless communication device. The non-transitory computer-readable medium may include code for causing the first wireless communication device to receive an indication indicating that there is no sidelink transmission in at least a second resource of the plurality of resources; and code for causing the first wireless communication device to transmit a repeat of the indication. The non-transitory computer-readable medium may include code for causing the first wireless communication device to detect an indication indicating that there is no sidelink transmission in a reserved resource, code for causing the first wireless communication device to transmit a sidelink communication using the reserved resource in response to the detection. The non-transitory computer-readable medium may include code for causing the first wireless communication device to detect an indication of a fourth wireless communication device reserving a second resource; and code for causing the first wireless communication device to refrain from transmitting in the second resource in response to the detection. The non-transitory computer-readable medium may include code for causing the first wireless communication device to detect an indication of a fourth wireless communication device reserving a second resource; code for causing the first wireless communication device to monitor for a transmission in the second resource in response to the detection; and code for causing the first wireless communication device to transmit a sidelink communication using the second resource in response to a determination that no transmission is detected in the second resource from the monitoring. 
     Further aspects of the present disclosure include an apparatus including means for communicating, with a second wireless communication device, a reservation indicating a plurality of resources for a plurality of sidelink communications. The apparatus also includes means for communicating, with a third wireless communication device, a first sidelink communication of the plurality of sidelink communications using a first resource of the plurality of resources. 
     The apparatus may also include one or more of the following features. For instance, the apparatus may include where the reservation indicates the plurality of resources in a plurality of subchannels. The reservation indicates an assignment of the first resource to the first sidelink communication and an assignment of a second resource of the plurality of resources to a second sidelink communication of the plurality of sidelink communications. The means for communicating the reservation is configured to transmit, to the second wireless communication device, sidelink control information (SCI) indicating the reservation. The means for communicating the reservation is configured to receive, from the second wireless communication device, first sidelink control information (SCI) indicating the reservation. The means for communicating the first sidelink communication is configured to transmit, to the third wireless communication device, the first sidelink communication in the first resource. The third wireless communication device corresponds to the second wireless communication device. The third wireless communication device is different than the second wireless communication device. The apparatus may include means for transmitting second SCI indicating at least the first resource indicated by the first SCI. The apparatus may include means for transmitting second SCI repeating the reservation indicated by the first SCI. The means for communicating the first sidelink communication is configured to receive, from the third wireless communication device, the first sidelink communication; and the apparatus may include means for transmitting second SCI indicating an acknowledgement/negative-acknowledgement ACK/NACK) for the first sidelink communication. The apparatus may include means for transmitting second SCI indicating at least one of a scheduling request (SR) or a buffer status report (BSR) based on the reservation. The apparatus may include means for transmitting an indication indicating that there is no sidelink transmission in a second resource of the plurality of resources reserved for the apparatus. The apparatus may include means for receiving an indication indicating that there is no sidelink transmission in at least a second resource of the plurality of resources; and means for transmitting a repeat of the indication. The apparatus may include means for detecting an indication indicating that there is no sidelink transmission in a reserved resource, means for transmitting a sidelink communication using the reserved resource in response to the detection. The apparatus may include means for detecting an indication of a fourth wireless communication device reserving a second resource; and means for refraining from transmitting in the second resource in response to the detection. The apparatus may include means for detecting an indication of a fourth wireless communication device reserving a second resource; means for monitoring for a transmission in the second resource in response to the detection; and means for transmitting a sidelink communication using the second resource in response to a determination that no transmission is detected in the second resource from the monitoring. 
     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 embodiments 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.