Device access in unlicensed bands

Abstract

Certain aspects of the present disclosure provide techniques for sidelink communications in an unlicensed spectrum. A method, performable by a user equipment (UE), includes measuring a frequency band, at least at a start time of a time interval, to determine whether the frequency band is idle, the time interval comprising a plurality of time periods. While measuring the frequency band, the UE decodes any signals received on the frequency band to determine whether a Clear to Send (CTS) signal has been received on the frequency band.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to Greek Patent Application No. 20200100371, filed on June 24, 2020, which is hereby assigned to the assignee of the present application and is hereby expressly incorporated herein by reference in its entirety as if fully set forth below and for all applicable purposes.

[0003] introduction

[0004] Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for reserving time intervals for wireless communications between certain devices.

[0005] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, to name a few.

[0006] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is an enhancement to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by using OFDMA with a cyclic prefix (CP) on the downlink (DL) and uplink (UL) to improve spectrum efficiency, reduce costs, improve services, utilize new spectrum, and better integrate with other open standards. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0007] However, as demand for mobile broadband access continues to grow, there is a need for further improvements to NR and LTE technologies. These improvements may also apply to other multiple access technologies and the telecommunication standards that employ them.

[0008] Overview

[0009] The systems, methods, and devices of the present disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. After considering this discussion, and particularly after reading the section entitled "Detailed Description," one will understand how the features of the present disclosure provide advantages.

[0010] Certain aspects relate to a method for wireless communication by a first user equipment. In some examples, the method includes: measuring a frequency band by the first UE at least at the start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods. In some examples, the method includes: decoding any signal received on the frequency band by the first UE while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band. In some examples, the method includes: when a CTS signal is received from one or more of the multiple UEs at a first time within the time interval, suppressing further measurement of the frequency band in the remaining portion of the time interval after the first time to determine whether the frequency band is idle, the first time being within a first time period of the multiple time periods. In some examples, the method includes: when no CTS signal is received from one or more of the multiple UEs within the time interval, transmitting a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0011] Certain aspects relate to a first user equipment (UE). In some examples, the apparatus includes a memory and a processor coupled to the memory. In some examples, the processor and the memory are configured to: start measuring a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods. In some examples, the processor and the memory are configured to: decode any signal received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band. In some examples, the processor and the memory are configured to: when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, suppress further measuring the frequency band to determine whether the frequency band is idle within a remaining portion of the time interval after the first time, the first time being within a first time period of the multiple time periods. In some examples, the processor and the memory are configured to: when no CTS signal is received from one or more of the multiple UEs within the time interval, transmit a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval, wherein the first CTS signal indicates to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0012] Certain aspects relate to a first user equipment (UE) for wireless communication. In some examples, the device includes: means for measuring a frequency band starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods. In some examples, the device includes: means for decoding any signal received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band. In some examples, the device includes: when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, means for refraining from further measuring the frequency band to determine whether the frequency band is idle for a remainder of the time interval after the first time, the first time being within a first time period of the multiple time periods. In some examples, the device includes: when no CTS signal is received from one or more of the multiple UEs during the time interval, a device for transmitting a first CTS signal to the multiple UEs and one or more other wireless devices during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0013] Certain aspects relate to a non-transitory computer-readable storage medium for wireless communication implemented by a first UE. In some examples, the non-transitory computer-readable storage medium includes: code for measuring a frequency band by the first UE starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods. In some examples, the non-transitory computer-readable storage medium includes: code for decoding any signal received on the frequency band by the first UE while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band. In some examples, the non-transitory computer-readable storage medium includes: code for suppressing further measuring the frequency band to determine whether the frequency band is idle within a remaining portion of the time interval after the first time in the time interval when a CTS signal is received from one or more of the multiple UEs at the first time in the time interval, the first time being within a first time period of the multiple time periods. In some examples, the non-transitory computer-readable storage medium includes: code for transmitting a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval when no CTS signal is received from one or more of the multiple UEs within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0014] To accomplish the foregoing and related ends, one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and accompanying drawings set forth in detail certain illustrative features of the one or more aspects. However, these features are indicative of but a few of the various ways in which the principles of the various aspects may be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order that the manner in which the above-recited features of the present disclosure may be understood in detail, a more particular description of what has been briefly summarized above may be given with reference to various aspects, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only certain aspects of the disclosure and are not to be considered limiting of its scope, as the description may admit to other equally effective aspects.

[0017] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0018] Figure 2 is a block diagram conceptually illustrating designs of two example user equipment (UEs) in accordance with certain aspects of the present disclosure.

[0019] Figure 3is a diagram conceptually illustrating an example of a first UE communicating with one or more other UEs according to aspects of the present disclosure.

[0020] Figure 4 is a diagram illustrating an example frame format in accordance with certain aspects of the present disclosure.

[0021] Figure 5 is a diagram illustrating an example model of multiple wireless devices operating in an unlicensed spectrum in accordance with certain aspects of the present disclosure.

[0022] Figure 6 is an illustration of certain aspects of the present disclosure in which Figure 5 Signal diagram for a series of example scenarios of randomness induced by the listen-before-talk (LBT) function performed by one of the CV2X devices.

[0023] Figure 7 is an explanation of certain aspects of the present disclosure. Figure 5 Signal diagram of an example timeline of CV2X device communications.

[0024] Figure 8 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0025] Figure 9 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0026] Figure 10 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0027] Figure 11 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0028] Figure 12 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0029] Figure 13 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0030] Figure 14 is a signal diagram illustrating an example timeline of CV2X window preservation by a CV2X device in accordance with certain aspects of the present disclosure.

[0031] Figure 15is a signal diagram illustrating an example timeline of time division multiple access (TDMA) window configurations in accordance with certain aspects of the present disclosure.

[0032] Figure 16 is a flow diagram illustrating example operations for wireless communications in accordance with certain aspects of the present disclosure.

[0033] Figure 17 Illustrated are communications devices that may include various components configured to perform operations for the techniques disclosed herein, in accordance with aspects of the present disclosure.

[0034] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized in other aspects without specific recitation.

[0035] Detailed description

[0036] Various aspects of the present disclosure provide apparatuses, methods, processing systems, and computer-readable media for facilitating communication between wireless devices. For example, the techniques described herein may involve using time division multiple access (TDMA) techniques on a frequency band to divide time into a first window and a second window for communication. In some examples, a first group of wireless devices is configured to communicate during the first window, and a second group of wireless devices is configured to communicate during the second window. According to one or more examples, using separate windows provides fair use of the frequency band for the two different groups of devices.

[0037] In some examples, a first group of wireless devices may be configured to perform a listen-before-talk (LBT) sensing procedure prior to a first window to determine whether the frequency band is idle or if there is too much interference caused by other wireless devices. These wireless devices may be preconfigured for LBT or may be configured by one or more of the base stations (BSs) of the core network (CN) or radio access network (RAN). If the frequency band is determined to be idle, the first group of wireless devices may transmit a clear-to-send (CTS) signal to alert other devices in the first group of devices of the start of the first window. In some examples, the CTS signal may be configured to notify the second group of devices of the duration of the first window. Accordingly, the second group of wireless communication devices refrains from communicating during the first time window. Once the first time window ends, a second time window begins, and the first group of wireless devices ceases communicating. This allows the second group of devices to communicate during the second time window. In one example, the first group of wireless devices may implement TDMA-based time partitioning, which allows for fair use of the frequency band between the first group of wireless devices and the second group of wireless devices.

[0038] Such techniques may be used, for example, in sidelink communications between wireless communication devices. In other examples, the wireless communication devices may include cellular vehicle-to-everything (CV2X) devices. It should be noted that while certain aspects are described with respect to CV2X devices and communications in unlicensed bands, it can be appreciated that various aspects may be similarly applicable to other scenarios, such as any communications in unlicensed bands (e.g., sidelink communications), communications in licensed bands (e.g., sidelink communications), and the like.

[0039] The following description provides examples of techniques for reserving time windows for TDMA-based transmissions in unlicensed spectrum. Various examples may omit, substitute, or add various procedures or components as appropriate. For example, the methods described may be performed in an order different from the order described, and various steps may be added, omitted, or combined. Moreover, the features described with reference to some examples may be combined in some other examples. For example, a device or method may be implemented using any number of aspects described herein. In addition, the scope of the present disclosure is intended to cover such devices or methods that are practiced using other structures, functionalities, or structures and functionalities that are supplementary to or in addition to the various aspects of the present disclosure described herein. It should be understood that any aspect of the present disclosure disclosed herein may be implemented by one or more elements of the claims. The word "exemplary" is used herein to mean "used as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as superior to or superior to other aspects.

[0040] In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a specific radio access technology (RAT) and may operate on one or more frequencies. RAT may also be referred to as a radio technology, air interface, etc. Frequency may also be referred to as a carrier, subcarrier, subchannel (e.g., a subcarrier group), frequency band, frequency tone, subband, etc. Each frequency may support a single RAT in a given geographic area to avoid interference between wireless networks of different RATs. The techniques described herein may be used for various wireless networks and radio technologies. Although various aspects may be described herein using terms typically associated with 3G, 4G, and / or new radio (e.g., 5G NR) wireless technologies, various aspects of the present disclosure may be applied in communication systems based on other generations.

[0041] NR access can support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or above), millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or above), massive machine type communication (MTC) targeting non-backward compatible MTC technology, and / or mission-critical services targeting ultra-reliable low latency communication (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTIs) to meet corresponding quality of service (QoS) requirements. In addition, these services can coexist in the same subframe.

[0042] NR supports beamforming and dynamically configurable beam directions. MIMO transmission with precoding can also be supported. In some examples, the MIMO configuration in the DL can support up to 8 transmit antennas (with multi-layer DL transmission of up to 8 streams) and up to 2 streams per UE. In some examples, multi-layer transmission of up to 2 streams per UE can be supported. In some examples, up to 8 serving cells can be used to support aggregation of multiple cells. It should be noted that the above is an example range, and any suitable MIMO configuration is supported in the present disclosure.

[0043] Figure 1 An example wireless communication network 100 is illustrated in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be a NR system (e.g., a 5G NR network). Figure 1 As shown in FIG, wireless communication network 100 may be in communication with a core network (CN) 132. CN 132 may be in communication with one or more base stations (BSs) 110 and / or user equipments (UEs) 120 in wireless communication network 100 via one or more interfaces.

[0044] like Figure 1 , the wireless communication network 100 may include several BSs 110a-z (each also individually referred to herein as BS 110, or collectively referred to as BS 110) and other network entities. BS 110 may provide communication coverage for a particular geographic area (sometimes referred to as a "cell"), which may be stationary or mobile depending on the location of mobile BS 110. In some examples, BSs 110 may interconnect with each other and / or to one or more other BSs or network nodes (not shown) in the wireless communication network 100 using any suitable transport network via various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.). Figure 1In the example shown in FIG, BSs 110a, 110b, and 110c may be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x may be a pico BS for pico cell 102x. BSs 110y and 110z may be femto BSs for femto cells 102y and 102z, respectively. A BS may support one or more cells. A network controller 130 may communicate with a group of BSs 110 and provide coordination and control for these BSs 110 (e.g., via a backhaul).

[0045] BS 110 communicates with UEs 120a-y (each also individually referred to herein as UE 120 or collectively referred to herein as UE 120) in the wireless communication network 100. UEs 120 (e.g., 120c, 120x, 120y, etc.) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. In one example, a quadcopter, drone, or any other unmanned aerial vehicle (UAV) or remotely piloted aerial system (RPAS) 120c may be configured to function as a UE. The wireless communication network 100 may also include a relay station (e.g., relay station 110r) (also referred to as a relay, etc.) that receives transmissions of data and / or other information from an upstream station (e.g., BS 110a or UE 120r) and sends transmissions of data and / or other information to a downstream station (e.g., UE 120 or BS 110), or that relays transmissions between UEs 120 to facilitate communication between the devices.

[0046] In some examples of the wireless communication network 100, sidelink communications can be established between UEs and / or BSs without relying on UE IDs or control information from a base station. For example, such as when UE 120b is out of range of cell 102a, UE 120a can initiate sidelink communications with UE 120b without relying on a direct connection with a base station (e.g., base station 110a). Figure 1 Any UE illustrated in the present disclosure may serve as a scheduling entity or primary sidelink device, while another UE may serve as a subordinate entity or non-primary (e.g., secondary) sidelink device. Furthermore, the UE may be configured to transmit synchronization signaling for the sidelink, as described throughout this disclosure. Accordingly, one or more UEs may serve as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and / or mesh network, to initiate and / or schedule synchronization signaling.

[0047] According to certain aspects, UE 120 may be configured to transmit and receive clear-to-send (CTS) signals over a wireless interface, such as in one or more unlicensed frequency bands. Figure 1As shown in FIG, a first UE 120a and a second UE 120b include a reservation manager 140. The reservation manager 140 is configured to start measuring a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including a plurality of time periods. The reservation manager 140 may also be configured to decode any signal received on the frequency band while measuring the frequency band to determine whether a Clear to Send (CTS) signal has been received over the frequency band. When a CTS signal is received from one or more of the plurality of UEs at a first time within the time interval, the reservation manager 140 may cause the first UE 120a and / or the second UE 120b to refrain from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period of the plurality of time periods. When no CTS signal is received from one or more of the multiple UEs within the time interval, the reservation manager 140 may cause the first UE 120a and / or the second UE 120b to transmit a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval, wherein the first CTS signal indicates to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE 120a wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0048] As used herein, the term “idle” is intended to describe noise or interfering signals on a frequency band as either undetectable by the UE 120 or detectable but below a threshold power level (e.g., relatively low reference signal received power (RSRP), received signal strength indicator (RSSI), or any other suitable metric) as received by the UE 120. As used herein, the term “busy” is intended to describe noise or interfering signals on a frequency band as detectable by the UE 120 or detectable and above a threshold power level (e.g., relatively high RSSI) as received by the UE 120.

[0049] Figure 2 Illustrated are a first UE 120a and a second UE 120b (e.g., in Figure 1 Example component 200 of the wireless communication network 100).

[0050] At the first UE 120a, the transmit processor 220 may receive data from the data source 212 and control information from the processor / processors 240. The control information may be for the physical broadcast channel (PBCH), the physical sidelink broadcast channel (PSBCH), the physical control format indicator channel (PCFICH), the physical hybrid ARQ indicator channel (PHICH), the physical downlink control channel (PDCCH), the group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), the physical sidelink shared channel (PSSCH), etc. The medium access control (MAC)-control element (MAC-CE) is a MAC layer communication structure that can be used to exchange control commands between wireless nodes. The MAC-CE may be carried in a shared channel, such as the physical downlink shared channel (PDSCH), the physical uplink shared channel (PUSCH), or the physical sidelink shared channel (PSSCH).

[0051] Processor 220 may process (e.g., encode and symbol map) data and control information to obtain data symbols and control symbols, respectively. Transmit processor 220 may also generate reference symbols (such as for a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a channel state information reference signal (CSI-RS)). A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on data symbols, control symbols, and / or reference symbols, as applicable, and may provide output symbol streams to modulators (MODs) 232a-232t. Each modulator 232 may process its respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a signal. The signals from modulators 232a-232t may be transmitted via antennas 234a-234t, respectively.

[0052] At the second UE 120b, antennas 252a-252r may receive signals from the first UE 120a and may provide received signals to demodulators (DEMODs) 254a-254r, respectively, within the transceiver. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) its respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 256 may receive received symbols from all demodulators 254a-254r, perform MIMO detection on the received symbols where applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data to a data sink 260, and provide decoded control information to a controller / processor 280.

[0053] At the second UE 120b, a transmit processor 264 may receive and process data from a data source 262 and control information from a controller / processor 280. The transmit processor 264 may also generate reference symbols for a reference signal, such as a sounding reference signal (SRS). The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266, if applicable, further processed by demodulators 254a-254r in the transceiver (e.g., for SC-FDM, etc.), and transmitted to the first UE 120a. At the first UE 120a, the signal from the second UE 120b may be received by an antenna 234, processed by a modulator 232, detected by a MIMO detector 236, if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the second UE 120b. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to a controller / processor 240.

[0054] Memories 242 and 282 may store data and program codes for first UE 120a and second UE 120b, respectively. Scheduler 244 / 284 may schedule UEs for data transmission / reception.

[0055] The antennas 252, processors 266, 258, 264, and / or controller / processor 280 of the second UE 120b and / or the antennas 234, processors 220, 230, 238, and / or controller / processor 240 of the first UE 120a may be used to perform the various techniques and methods described herein. Figure 2As shown in FIG, the controller / processor of the two UEs includes a reservation manager 140. The reservation manager 140 is configured to start measuring a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including a plurality of time periods. The reservation manager 140 may also be configured to decode any signal received on the frequency band while measuring the frequency band to determine whether a clear-to-send (CTS) signal has been received over the frequency band. When a CTS signal is received from one or more of the plurality of UEs at a first time within the time interval, the reservation manager 140 may cause the first UE 120a and / or the second UE 120b to refrain from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period of the plurality of time periods. When no CTS signal is received from one or more of the multiple UEs within the time interval, the reservation manager 140 may cause the first UE 120a and / or the second UE 120b to transmit a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval, wherein the first CTS signal indicates to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE 120a and / or the second UE 120b wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0056] NR can utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP). NR can support half-duplex operation using time division duplexing (TDD). OFDM and single-carrier frequency division multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are also often referred to as tones, bins, etc. Each subcarrier can be modulated with data. Modulation symbols can be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The minimum resource allocation (so-called resource block (RB)) can be 12 consecutive subcarriers. The system bandwidth can also be divided into subbands. For example, a subband can cover multiple RBs. NR can support a base subcarrier spacing (SCS) of 15 kHz, and other SCSs (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.) can be defined relative to the base SCS.

[0057] Figure 3 302a and one or more second UEs 302b (collectively referred to as "UE 302"). In various examples, any one of the first UE 302a and the second UE 302b may correspond to a UE in the wireless communication network 100 (e.g., Figure 1 and 2UE 120a or UE 120b) or other suitable node.

[0058] In some examples, the first UE 302a and the second UE 302b can use sidelink signals to conduct direct D2D communication. D2D communication can use downlink / uplink WWAN spectrum and / or unlicensed spectrum. D2D communication can use one or more sidelink channels (e.g., frequency bands) on these spectrums, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication can be carried out through various wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0059] The sidelink signals may include sidelink data 306 (i.e., sidelink traffic) and sidelink control information 308. Broadly speaking, the first UE 302a and the one or more second UEs 302b may use one or more data channels and control channels to communicate the sidelink data 306 and the sidelink control information 308. In some aspects, the data channel comprises a PSSCH, and the control channel comprises a PSCCH and / or a physical sidelink feedback channel (PSFCH).

[0060] The sidelink control information 308 may include a source transmit signal (STS), a direction select signal (DSS), and a destination receive signal (DRS). The DSS / STS may allow a UE 302 (e.g., 302a, 302b) to request a time duration for which a sidelink channel is to be available for sidelink signals; and the DRS may allow a UE 302 to indicate, for example, the availability of the sidelink channel for the requested time duration. Accordingly, the first UE 302a and the second UE 302b may negotiate the availability and use of sidelink channel resources before communicating sidelink data 306 information.

[0061] In some configurations, any one or more of the first UE 302a or the second UE 302b may periodically / aperiodically transmit or broadcast sidelink synchronization signaling to increase the probability of being detected by another UE or BS. For example, one or more of the first UE 302a and the second UE 302b may periodically / aperiodically transmit a sidelink synchronization signal in one or more time slots of a specific time window. In some examples, the UE is configured or preconfigured with information indicating the position and duration of the time window within the frame (e.g., which time slots within the frame, and how many time slots there are) (e.g., by CN 132 or BS 110). In some aspects, the UE may be configured or preconfigured with the position and duration of the time window via messaging between the UEs or messaging received from the BS (e.g., radio resource control (RRC) signaling) (e.g., by CN 132 or BS 110).

[0062] Figure 3 The channels or carriers illustrated in FIG. 1 for transmitting the sidelink data 306 and the sidelink control information 308 are not necessarily all channels or carriers that may be utilized in sidelink communications between the first UE 302 a and the second UE 302 b, and one of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other data, control, and feedback channels.

[0063] Figure 4 4 is a diagram showing an example of a frame format 400. The transmission timeline for each data transmission and reception may be divided into units of radio frames 402. In NR, a basic transmission time interval (TTI) may be referred to as a time slot. In NR, a subframe may contain a variable number of time slots (e.g., 1, 2, 4, 8, 16, ... N time slots), depending on the subcarrier spacing (SCS). NR may support a base SCS of 15 kHz, and other SCSs (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.) may be defined relative to the base SCS. Figure 4 In the example shown in , the SCS is 120kHz. Figure 4 As shown in FIG, subframe 404 (subframe 0) contains 8 time slots (slots 0, 1, ... 7) with a duration of 0.125 ms. The symbol and slot lengths scale with the subcarrier spacing. Each time slot may include a variable number of symbol (e.g., OFDM symbol) periods (e.g., 7 or 14 symbols), depending on the SCS. Figure 4 For the 120 kHz SCS shown in , each of slots 406 (Slot 0) and 408 (Slot 1) includes 14 symbol periods (slots with indices 0, 1, ... 13) having a duration of 0.25 ms.

[0064] In the sidelink, a sidelink synchronization signal block (S-SSB), referred to as an SS block or SSB, is transmitted. The SSB may include a primary SS (PSS), a secondary SS (SSS), and / or a two-symbol physical sidelink broadcast channel (PSBCH). In some examples, the SSB may be transmitted up to sixty-four times in up to sixty-four different beam directions. Up to 64 transmissions of the SSB are referred to as an SS burst set. The SSBs in an SS burst set may be transmitted in the same frequency region, while the SSBs in different SS burst sets may be transmitted in different frequency regions.

[0065] exist Figure 4 In the example shown in , in subframe 404, SSB is transmitted in every time slot (time slot 0, 1...7). Figure 4 In the example shown in , in time slot 406 (time slot 0), SSB 410 is transmitted in codewords 4, 5, 6, and 7, and SSB 412 is transmitted in codewords 8, 9, 10, and 11, while in time slot 408 (time slot 1), SSB 414 is transmitted in codewords 2, 3, 4, and 5, and SSB 416 is transmitted in codewords 6, 7, 8, and 9, and so on. The SSB may include a primary SS (PSS), a secondary SS (SSS), and a two-codeword physical sidelink broadcast channel (PSBCH). The PSS and SSS may be used by the UE to establish sidelink communications (e.g., transmission and / or reception of data and / or control channels). The PSS may provide half-frame timing, and the SS may provide cyclic prefix (CP) length and frame timing. The PSBCH carries some basic system information, such as system bandwidth, timing information within a radio frame, SS burst set periodicity, system frame number, etc. The SSB may be organized into SS bursts to support beam sweeping. Further system information, such as Remaining Minimum System Information (RMSI), System Information Blocks (SIBs), and Other System Information (OSI), may be transmitted on the Physical Sidelink Shared Channel (PSSCH) in certain subframes.

[0066] The allocation of frames, subframes, time slots, etc. may be provided by network protocols and rules applicable to wireless communications in a licensed spectrum. For example, establishing time synchronization when operating in a licensed spectrum may include: (i) using a global navigation satellite system (GNSS) as a common time reference (e.g., current coordinate Coordinated Universal Time (UTC)) from which the UE derives frame and time slot boundaries; and (ii) using an in-band signaling method by which transmissions from two UEs and the BS are scheduled to avoid collisions.

[0067] However, due to the scarcity of licensed spectrum (e.g., overcrowding), certain aspects of wireless communications (e.g., CV2X communications) cannot operate exclusively in the licensed spectrum. As a result, it is possible that CV2X communications can operate in frequency bands of the unlicensed spectrum. Thus, in some examples, GNSS-based synchronization between CV2X devices (e.g., UE and / or BS) can be applied in the unlicensed spectrum. In some aspects, GNSS-based synchronization between CV2X devices can be achieved without signaling overhead (e.g., without synchronization signaling). However, if GNSS-based synchronization is unavailable or undesirable due to, for example, reliability issues, synchronization between CV2X devices can be established via periodic, in-band broadcast signaling of synchronization signals (e.g., signaling of internal clock information between CV2X devices to support synchronization).

[0068] As discussed, the dedicated spectrum used for licensed wireless communications can be significantly congested. In fact, there may be scenarios where the licensed spectrum would be unavailable to users due to overcrowding. Currently, CV2X (e.g., sidelink) communication over unlicensed spectrum is a developing technology. As mentioned, procedures designed for licensed spectrum operation (such as channel access and synchronization) may not be applicable under unlicensed spectrum conditions due to interference from other devices and regulatory restrictions. Therefore, procedures for deploying CV2X operations in unlicensed spectrum that are applicable to both LTE and NR are desired as this will reduce congestion in the licensed spectrum, thereby improving cellular network capacity.

[0069] Example Techniques for Time Division Multiple Access (TDMA)-Based Communications in Unlicensed Bands

[0070] Various aspects of the present disclosure provide for implementing TDMA-based techniques and frame formats to support CV2X communications in unlicensed spectrum. In one example, a CV2X device is configured for periodic communication intervals (e.g., TDMA aspects), where time is divided into a "CV2X window" and a "non-CV2X window." In this example, a CV2X device may communicate during a periodic CV2X window in an unlicensed spectrum, while suppressing communication during a non-CV2X window to allow other wireless devices an opportunity to transmit and receive data. Within a CV2X window, a CV2X device may communicate using aspects of the same frame format used in a licensed spectrum. In one example, a CV2X device may divide a CV2X window into time slots, such as Figure 4 As explained in .

[0071] In certain aspects, the duration of the CV2X window and the non-CV2X window may depend, for example, on fairness, implementation, and / or performance considerations. For example, if a particular area has a relatively high volume of wireless communication traffic on unlicensed spectrum, the duration of the CV2X window may be reduced and the duration of the non-CV2X window may be increased. Such an implementation prevents overcrowding of the frequency band and interference with other non-CV2X devices. In another example, if a particular area has a relatively high number of CV2X devices and / or a relatively high volume of wireless communication between CV2X devices, the duration of the CV2X window may be increased and the duration of the non-CV2X window may be reduced, if fairness permits.

[0072] Generally speaking, non-CV2X devices are not designed for (or expected to operate with) such TDMA. Thus, CV2X devices may be configured or pre-configured (e.g., by CN 132 or BS 110) to implement TDMA time partitioning (e.g., CV2X windows and non-CV2X windows) on non-CV2X devices. However, regulatory enforcement rules for unlicensed spectrum operation restrict access to a frequency band when the band is detected to be busy. Thus, in certain aspects, implementation of TDMA operation by CV2X devices may include a listen-before-talk (LBT) procedure.

[0073] Figure 5 is a schematic diagram illustrating an example network 500 of multiple CV2X devices operating in an unlicensed spectrum. In the illustrated example, five CV2X devices (e.g., a first CV2X device 502a, a second CV2X device 502b, a third CV2X device 502c, a fourth CV2X device 502d, and a fifth CV2X device 502e—collectively, CV2X devices 502) may operate in an unlicensed spectrum with other non-CV2X devices (e.g., non-CV2X devices 504a-c—collectively, non-CV2X devices 504). While the provided example illustrates four automotive CV2X devices and a drone CV2X device in a traffic context, it can be appreciated that the CV2X devices and environments may extend beyond these and include other wireless communication devices and environments. For example, the CV2X devices 502 may include a UE operated by a highway authority (e.g., Figure 1 The LBT function may be implemented on a CV2X device (e.g., a UE 120) and / or a roadside unit (RSU), and may be implemented on a motorcycle or carried by a user (e.g., a pedestrian, a cyclist, etc.), or may be implemented on an air vehicle (e.g., a drone). As will be described in more detail below, a subset of CV2X devices may perform LBT functionality for a given CV2X window.

[0074] In certain aspects, a characteristic of licensed CV2X communications is that all transmissions are timed to a rigid and regular time grid (e.g., Figure 4This timing structure naturally carries over to wireless communication procedures such as resource allocation (scheduling), retransmission, feedback signaling, etc., many of which are controlled by operators / controllers with spectrum usage rights (e.g., Figure 1 Although the unlicensed band does not have such a timing structure, the CV2X device in the unlicensed band can implement the timing structure on the non-CV2X device (e.g., WiFi device, etc.).

[0075] For example, if multiple CV2X devices are all time synchronized, those devices can implement a common time-frequency communication structure in an unlicensed band. In one example, time synchronization can be established based on global navigation satellite system (GNSS) signals (i.e., all CV2X devices use the same GNSS time reference for mapping to facilitate a time slot structure for communication). Alternatively, if GNSS is not available, time synchronization can be achieved via signaling between two or more CV2X devices. For example, a CV2X device can signal information from its internal clock(s) to one or more other CV2X devices. In some examples, two or more CV2X devices can achieve time synchronization by following the same concepts and principles as the channel access procedure.

[0076] One challenge for establishing time-synchronized communications in unlicensed spectrum is overcoming timing inconsistencies introduced by the listen-before-talk (LBT) procedure between CV2X devices 502, which can prevent communications from being aligned with the time grid. For example, interference detected by a first CV2X device 502a may not be detected by a second CV2X device 502b, which can cause the first device 502a to begin transmitting before the LBT function of the second CV2X device 502b is complete.

[0077] Figure 6 is a signal diagram illustrating an example timeline 600 of signaling for each of a plurality of CV2X devices (e.g., a first CV2X device 606a, a second CV2X device 606b, a third CV2X device 606c, a fourth CV2X device 606d, and a fifth CV2X device 606e—collectively referred to herein as the CV2X devices 606), wherein each of the plurality of CV2X devices 606 attempts to communicate (e.g., transmit and / or receive) CV2X data beginning at a start time 602a of a CV2X window 604. Specifically, Figure 6The randomness of the timing at which each CV2X device 606 can transmit CV2X data is illustrated, where the randomness is caused by interference local to each CV2X device 606 and the backoff period configuration of each CV2X device 606. That is, each CV2X device 606 may experience different local interference levels relative to other CV2X devices 606 due to its different location relative to the other CV2X devices. Furthermore, each CV2X device 606 may be configured to use a backoff period that is different from the backoff period of one or more other devices. Thus, each of the five CV2X devices 606 is illustrated as an example timeline showing interference conditions and possible LBT functional outcomes for each of their attempts to begin transmission at the start time 602a of the CV2X window 604.

[0078] Each CV2X device 606 is configured or preconfigured (e.g., by the CN 132 or the BS 110) to perform an LBT function before the start of the CV2X window 604. For example, each CV2X device 606 may "listen" or receive ambient energy transmitted over the frequency band before the start 602a of the CV2X window 604. If one or more of the CV2X devices 606 detect ambient energy on the frequency band (e.g., signaling transmitted by a non-CV2X device), those CV2X devices 606 may continue listening until they determine that the frequency band is idle. Once the CV2X devices 606 determine that the frequency band is idle, they may continue listening during a Distributed Coordination Function (DCF) Intra-Frame Spacing (DIFS) period 610, which may begin upon determining that the frequency band is idle. By continuing to listen during the DIFS period 610 rather than immediately initiating transmission of CV2X data over the frequency band, the CV2X devices 606 take a less aggressive approach to reserving the CV2X window 604 in the frequency band. Less aggressive approaches may support compliance with fair use regulations for unlicensed spectrum. If a CV2X device 606 determines that the band has become busy during the DIFS period (e.g., a non-CV2X device begins signaling during the DIFS period), the CV2X device may defer its transmission. In some examples, the duration of the DIFS period 610 may be determined by the respective CV2X device 606 according to the IEEE 802.11 standard.

[0079] In timeline 600, each CV2X device 606 initiates the LBT function at the same time before the start of the CV2X window 604. For example, the CV2X device 606 can start the LBT function at any suitable time (e.g., 9 us to 200 us) before the start of the CV2X window 604, where the LBT function lasts for any suitable time duration (e.g., 25 us). In some aspects, the LBT function is performed during a (DIFS) period.

[0080] In timeline 600, if a DIFS period 610 begins immediately after a frequency band initially sensed as busy becomes idle (e.g., when local interference 608 is no longer detected on the frequency band or the power of local interference 608 is below a threshold, e.g., the time between local interference 608a and CV2X data 614a is idle time 611), each CV2X device 606 implements a backoff period. For example, the frequency band may be idle during the backoff period or when no other devices (e.g., CV2X devices and / or non-CV2X devices) are transmitting (e.g., when no local interference is detected). The backoff period may include a random number of time windows (e.g., time slots) during which the CV2X device performs the LBT function during each time window. That is, if the CV2X device detects that the frequency band is busy immediately before and / or during the DIFS period 610 , the CV2X device may defer transmission of CV2X data until after the DIFS period 610 and after a backoff period starting after the DIFS period 610 .

[0081] Figure 6 Each CV2X device 606 illustrated in FIG. 6 shares a common start time 602a and a common end time 602b of a CV2X window 604, during which the CV2X devices 606 are configured to communicate over an unlicensed frequency band. In a first timeline 600a, the first CV2X device 606a performs an LBT function during a DIFS period 610a, which occurs some time later than local interference 608a (e.g., signaling from a non-CV2X device) on the frequency band. Thus, because the local interference 608a does not occur immediately before or during the DIFS period, the first CV2X device 606a does not implement a backoff period before transmitting CV2X data 614a. That is, the first CV2X device 606a can begin transmitting CV2X data 614a immediately upon the start of the CV2X window 604.

[0082] In the second timeline 600b, the second CV2X device 606b detects local interference 608b on the frequency band and performs LBT functionality during a DIFS period 610b that begins once the frequency band becomes idle (e.g., the local interference 608b ends). Here, because the DIFS period 610b begins immediately after the frequency band becomes idle, the second CV2X device 606b implements a backoff period 612b before transmitting CV2X data 614b. In this example, the backoff period 612b includes four time periods. Because no interference was detected throughout the backoff period 612b, the second CV2X device 606b can begin transmitting CV2X data 614b at the end of the backoff period 612b.

[0083] In a third timeline 600c, a third CV2X device 606c detects local interference 608c on the frequency band and performs an LBT function during a DIFS period 610c that begins once the third CV2X device 606c determines that the local interference 608c has ended. Because the DIFS period 610c occurs immediately after the frequency band becomes idle, the third CV2X device 606c implements a backoff period 612c before transmitting CV2X data 614c. In this example, the backoff period 612c includes seven time periods, further delaying the transmission of CV2X data relative to the delay experienced by the second CV2X device 606b. Because no interference was detected throughout the duration of the backoff period 612c, the third CV2X device 606c is able to begin transmitting CV2X data 614c at the end of the backoff period 612c.

[0084] In the fourth timeline 600d, a fourth CV2X device 606d may detect local interference 608d on the frequency band that extends into the CV2X window 604. Here, because the DIFS period 610d begins immediately after the frequency band becomes idle, the fourth CV2X device 606d implements a backoff period 612d before transmitting CV2X data 614d. In this example, the backoff period 612d includes two time periods. Because no interference was detected during the backoff period 612d, the fourth CV2X device 606d can begin transmitting CV2X data 614d at the end of the backoff period 612d.

[0085] In the fifth timeline 600e, the fifth CV2X device 606e detects local interference 608e on the frequency band and performs LBT functionality during a DIFS period 610e that begins immediately after the frequency band becomes idle (e.g., the local interference 608e ends). Thus, the fifth CV2X device 606e implements a backoff period 612e (having five time periods). As illustrated, the fifth CV2X device 606e detects intermittent interference during the backoff period 612e, further delaying the transmission of CV2X data 614e. In some examples, the CV2X device 606e can restart at any time period within the backoff period 612 if local interference is detected during that time period. In this example, the fifth CV2X device 614e detects additional local interference 616 during the second time period 618 of the backoff period 612e. Accordingly, the additional local interference 616 subsequently ends, and the fifth CV2X device 614e can restart the backoff period at the second time period rather than restarting the entire backoff period.

[0086] Note that the first CV2X device 606a is the only example where the CV2X data transmission begins at the expected time, e.g., at the start 602a of the CV2X window 604. Accordingly, as described below, the CV2X devices 606 may perform additional communications to improve their ability to retain and effectively communicate over the CV2X window 604.

[0087] Example Techniques for Preserving a CV2X Window Using Grant-to-Talk (CTS) Signaling

[0088] Certain aspects relate to implicitly implementing CV2X and non-CV2X TDMA modes on an unlicensed band. Here, the TDMA mode is known to the CV2X device 606, but may not be known to the non-CV2X devices, so that the CV2X device 606 can implement access to the unlicensed band for both the CV2X device 606 and the non-CV2X device during separate time periods (e.g., CV2X window 604 and non-CV2X window), thereby allowing a first time window for non-CV2X devices to communicate and a second time window for CV2X devices 606 to communicate. In some examples, the CV2X device 606 is (pre)configured with the TDMA mode (e.g., timing and duration). Alternatively, the CV2X device 606 can access the unlicensed band via a licensed band network (e.g., Figure 1 The TDMA mode configuration is received via signaling from the BS 110 or CN 132 of the CV2X device 606 or via signaling in the unlicensed band network (e.g., signaling between CV2X devices 606). Implementing such a TDMA mode in the unlicensed band allows the CV2X devices 606 to operate using the same slot timing structure as used in licensed operation (e.g., no changes in procedures such as resource allocation, retransmission, etc.).

[0089] Because non-CV2X devices are unaware of any TDMA pattern, the CV2X devices 606 may attempt to make the non-CV2X devices aware of the TDMA pattern through implicit means. In one example, before the start of each CV2X window 604, the CV2X devices 606 may dedicate a short period of time to perform LBT functions, preserve the CV2X window 604, and perform signaling between the CV2X devices 606 to align the communication timing of the CV2X devices 606.

[0090] Figure 7 is a signal diagram illustrating an example timeline 700 of communications over a CV2X window 704 reserved by a first CV2X device 702a and a second CV2X device 702b (collectively, CV2X devices 702). The first CV2X device 702a and the second CV2X device 702b may correspond to Figure 5 and 6As illustrated, the CV2X window 704 falls between the first non-CV2X time duration 706a and the second non-CV2X time duration 706b. The non-CV2X device 714 (e.g., Figure 5 The non-CV2X device 504 (e.g., a local interference 708) generates non-CV2X signaling (e.g., local interference 708) during the first non-CV2X time duration 706a and the second non-CV2X time duration 706b, but does not generate non-CV2X signaling during the CV2X window 704 because the CV2X device 702 is communicating during the time window. During the CV2X window 704, the CV2X device 702 may transmit and receive data using a transmission time interval (TTI) 718. The TTI 718 may have a duration equal to a frame, a subframe, a time slot, or any suitable number of symbols.

[0091] In the example timeline 700, CV2X devices 702 attempt to reserve a CV2X window 704 so that they can communicate on an unlicensed band. Initially, sometime before the start of the CV2X window 704, a first CV2X device 702a performs an LBT function during a first DIFS period 710a, and a second CV2X device 702b performs an LBT function during a second DIFS period 710b. Because interference caused by non-CV2X devices 714 is relatively low, the CV2X devices 702 will find the band idle immediately before the start of the CV2X window 704. Consequently, each CV2X device 702 then transmits a clear-to-talk (CTS) signal 716 at the start of the CV2X window 704. In this example, the first CV2X device 702a transmits a first CTS signal 716a, and simultaneously, the second CV2X device 702b transmits a second CTS signal 716b. The CTS signal 716 may also be the same signal, or at least have the same content (e.g., an indication of a channel occupancy time (COT) equal to the duration of the CV2X window 704 minus some or all of the duration of the CTS signal 716). That is, because the CTS signal(s) 716 occupy time within the CV2X window 704 and one or more other CV2X devices 702 may need to process the CTS signal(s) 716, the COT is equal to the remaining portion of the time interval (e.g., the CV2X window 704) over which the CV2X device 702 may communicate CV2X data.

[0092] This CTS signal 716 may be understood by the non-CV2X devices 714 and may prevent them from accessing the frequency band during the CV2X window 704. Thus, each CV2X device 702 may attempt to reserve the CV2X window 704, regardless of whether one or more of the CV2X devices 702 have any intention to communicate during the CV2X window 704. With all devices transmitting the CTS signal 716, a larger number of non-CV2X devices may be informed of the reservation, thereby improving protection of the CV2X window 702 from interference.

[0093] However, it should be noted that other scenarios may have frequency bands that are more heavily saturated with local interference and may delay the start of the CV2X window. For example, interference from non-CV2X devices may delay the transmission of the CTS signal to a time that occurs after the start of the CV2X window. It may even happen that a CV2X device is unable to complete the LBT function within the CV2X window due to severe local interference. In such a scenario, waiting for each CV2X device to complete its LBT function before commencing CV2X communication may be inefficient (e.g., the CV2X devices may be unable to communicate for an extended period of time).

[0094] However, in some cases, not all CV2X devices will experience equally severe congestion on a frequency band. Thus, some approaches may include initiating access to the frequency band via CV2X device(s) that experience relatively less interference on the same frequency band than other CV2X devices.

[0095] Example Technique for Preserving a CV2X Window Using CTS Signaling by the Time-First CV2X Device

[0096] In some examples, CV2X devices may be configured to not only measure the ambient energy on the frequency band during the LBT function, but also attempt to decode CTS signals transmitted by other CV2X devices within that energy. For example, a first CV2X device may receive and decode a CTS signal while performing the LBT function. The CTS signal may be transmitted by a second CV2X device that senses the frequency band as idle. The CTS signal is configured to retain a COT corresponding to the remaining CV2X window period. Receipt of the CTS signal transmitted by the second CV2X device may trigger the first CV2X device to terminate the LBT function and deem the frequency band available for CV2X communication until the end of the CV2X window. In some examples, the first CV2X device determines that the received CTS signal was transmitted by the second CV2X device because the COT duration indicated in the CTS signal matches the end of the CV2X window configured or preconfigured by the first CV2X device (e.g., by CN 132 or BS 110).

[0097] In this example, after the first CV2X device receives and decodes the CTS signal transmitted by the second CV2X device, the first CV2X device will suspend the LBT function but will not transmit an additional CTS signal because this would interfere with other CV2X communications during the CV2X window. In practice, the CV2X device that completes the LBT function first and determines that the frequency band is free (in this example, the first CV2X device) reserves the frequency band for all other CV2X devices within range.

[0098] Figure 8 Is to explain CV2X equipment (e.g. Figure 7 FIG20 is a signal diagram of an example timeline 800 in which a plurality of CV2X devices (e.g., a first CV2X device 702a, a second CV2X device 702b, a third CV2X device 702c, and a fourth CV2X device 702d) are operating on an unlicensed frequency band. The CV2X devices 702 may attempt to reserve the CV2X window 704 on the unlicensed frequency band by collectively performing an initial LBT procedure.

[0099] As illustrated in the example timeline 800, a first CV2X device 702a detects a first instance 708a of local interference on a frequency band and, once the local interference ends (e.g., the frequency band becomes idle), performs a first DIFS period 710a. Because the first DIFS period 710a begins immediately after the local interference ends, the first CV2X device 702a initiates a first backoff procedure 712a after the first DIFS period 710a. Similarly, a second CV2X device 702b detects a second instance 708b of local interference on a frequency band and, once the local interference ends, performs a second DIFS period 710b. Because the second DIFS period 710b begins immediately after the local interference ends, the second CV2X device 702b initiates a second backoff procedure 712b after the second DIFS period 710b. Like the first and second CV2X devices, the third CV2X device 702c detects a third instance 708c of local interference on the frequency band and executes a third DIFS period 710c once the local interference ends. Because the third DIFS period 710c begins immediately after the local interference ends, the third CV2X device 702c initiates a third backoff procedure 712c after the third DIFS period 710c.

[0100] In example timeline 800, the fourth CV2X device 702d may detect a fourth instance 708d of local interference on the frequency band, but the fourth instance 708d of local interference ends before the fourth CV2X device 702d performs a fourth DIFS period 710d. Accordingly, the fourth CV2X device 702d does not perform a backoff procedure after the fourth DIFS period 710d. Instead, because the fourth CV2X device 702d did not detect any interference on the frequency band during the DIFS period 710d, the fourth CV2X device 702d transmits a CTS signal 716d to preserve the CV2X window 704 in a manner similar to TDMA. In this example, each of the first CV2X device 702a, the second CV2X device 702b, and the third CV2X device 702c receives and decodes the CTS signal 716d during their respective DIFS periods and / or backoff periods and terminates their respective backoff periods. Thus, all CV2X devices 702 stop their respective LBT functions after detecting the CTS signal that reserves the CV2X window. Thereafter, all four CV2X devices 702 may begin CV2X communication within the remaining COT 802 of the CV2X window 704 (starting 705 after the completion of the CTS signal 716d or during the transmission of the CTS signal 716d).

[0101] Accordingly, the transmission of the CTS signal 716d can be used to overcome the aforementioned challenges for establishing time-synchronized communications in unlicensed spectrum. In this example, because the CV2X devices 702 listen for the CTS signal during their respective DIFS periods 710, any one or more of the CV2X devices 702 can notify the other CV2X devices of the start of the remaining COT 802, thereby aligning the timing of communications between the CV2X devices 702. As a result, timing inconsistencies between the CV2X devices 702 caused by the listen-before-talk (LBT) protocol can be reduced or eliminated, and communications between the CV2X devices 702 can be aligned with the time grid via the transmission of the CTS signal 716d.

[0102] Figure 9is a signal diagram illustrating an example timeline 900 in which CV2X devices 702 retain a CV2X window 704. In the example timeline 900, each CV2X device 702 detects local interference before the CV2X window 704. Accordingly, each CV2X device initiates a backoff period. For example, the second CV2X device 702b detects a second instance 708b of local interference on the frequency band. Upon detecting that the frequency band is idle (e.g., determining that the frequency band no longer has any local interference), the second CV2X device 702b waits for a second DIFS period 710b. Because the second DIFS period 710b begins immediately after the second instance 708b of local interference, the second CV2X device 702b waits for a second backoff period 712b while continuing to monitor the frequency band for local interference and a CTS signal. Similarly, the third CV2X device 702c detects a third instance 708c of local interference on the frequency band. Upon detecting that the frequency band is idle, the third CV2X device 702c waits for a third DIFS period 710c followed by a third backoff period 712c while continuing to monitor the frequency band for local interference and a CTS signal. The fourth CV2X device 702d detects a fourth instance 708d of local interference on the frequency band. Upon detecting that the frequency band is idle, the fourth CV2X device 702d waits for a fourth DIFS period 710d followed by a fourth backoff period 712d while continuing to monitor the frequency band for local interference and a CTS signal.

[0103] The first CV2X device 702a also performs an LBT function and detects a first instance of local interference 708a on the frequency band. Once the first CV2X device 702a no longer detects the local interference 708a, the first CV2X device 702a executes a first DIFS period 710a. Because the first DIFS period 710a begins immediately after the first instance of local interference 708a, the first CV2X device 702a executes a first backoff period 712a. Upon completion of the first backoff period 712a, the first CV2X device 702a determines that the frequency band is still clear (e.g., no local interference was detected during the first backoff period 712a), and thus, the first CV2X device 702a transmits a CTS signal 716a. Here, the CTS signal 716a prompts the remaining CV2X devices to terminate their respective backoff periods and begin communicating on the frequency band within the remaining COT 902 of the CV2X window 704 (which begins 705 after the completion of the CTS signal 716a or during the transmission of the CTS signal 716a). Thus, the CV2X devices 702 are configured to stop their respective LBT processes after having transmitted the CTS that reserves the CV2X window 704.

[0104] Note that in Figure 8 and 9In the example of FIG, , the CV2X devices 702 may not all share the same backoff period, as each device may randomly select its own backoff period duration. Such an approach may result in the CV2X devices 702 taking a more aggressive approach to reserving time intervals in the frequency band. For example, with varying backoff period durations, there is a greater likelihood that one or more of the CV2X devices 702 will have a relatively short backoff period duration, thereby providing the CV2X devices with more opportunities to transmit CTS signals. Such an approach may improve communication between the CV2X devices 702 by providing the CV2X devices 702 with more opportunities to preserve the CV2X window in environments with relatively high local interference levels.

[0105] Figure 10 is a signal diagram illustrating an example timeline 1000 in which the CV2X devices 702 reserve the CV2X window 704. In the example timeline 1000, each CV2X device 702 is configured with the same backoff period 712 duration (eg, each CV2X device 702 is configured with four backoff intervals).

[0106] Each CV2X device 702 can use a common random generator algorithm, but separately generate its own backoff period 712 using the GPS signal as a common seed. Thus, the random generator at each CV2X device 702 can produce the same backoff period duration for each CV2X device 702 because each device's generator uses a common signal (e.g., the GPS clock time in the GPS signal) to generate the duration. Using such an approach can result in less aggressive reservation of time intervals in the frequency band, which can enhance compliance with regulations regarding fair use of unlicensed spectrum. Note that in this example, a CV2X device 702 that initiates its backoff procedure later than the other devices will still be able to terminate its backoff procedure upon detecting a CTS transmitted by another device. For example, as illustrated, the second CV2X device 702b and the fourth CV2X device 702d complete their LBT functions (e.g., pre-DIFS, DIFS 710, and / or backoff period 712) simultaneously. As a result, the second CV2X device 702b and the fourth CV2X device 702d both transmit CTS signals (716b and 716d—collectively, 716). Accordingly, the first CV2X device 702a and the third CV2X device 702c terminate their LBT functionality upon receiving the CTS signal 716. Here, the transmission of the CTS signal 716 prompts the remaining CV2X devices to terminate their respective backoff periods and begin communicating on the frequency band within the remaining COT 1002 of the CV2X window 704 (which begins 705 after the completion of one or more CTS signals 716 or during the transmission of one or more CTS signals 716).

[0107] Figure 11 is a signal diagram illustrating an example timeline 1100 of a CV2X device 702 reserving a CV2X window. In this example timeline 1100, the CV2X device 702 may Figure 4 CV2X data is transmitted within the CV2X window 704 (the time slot structure explained in ).

[0108] Each CV2X device 702 performs an initial LBT procedure. Because the level of local interference 708 detected by each CV2X device 702 may vary, the LBT procedure for one device begins at a different time relative to the other devices. Here, the CV2X window 704 begins at a first time 1102. However, because the CV2X devices 702 either detect local interference 708 or perform LBT procedures, no device can transmit CV2X data at the start of the CV2X window 704. Therefore, the devices monitor the frequency band to detect a CTS signal.

[0109] However, if the CV2X devices 702 do not have coordinated timing for CV2X communications, then CV2X data transmissions may be initiated at any time within the CV2X window 704 (assuming the CTS signal has been detected). This may complicate procedures such as resource reservation and may require each CV2X device 702 to perform blind decoding of all signals received during the CV2X window 704. Thus, in some aspects, the CV2X devices 702 are configured to transmit data according to a predefined slot pattern (e.g., Figure 4 and 7 ) communicates CV2X data within a CV2X window 704. For example, the size of the CV2X window 704 may be set such that it has a duration of a finite number of time slots. Note that although the example of "time slots" is used, any suitable TTI duration may be used.

[0110] like Figure 11As illustrated in FIG, the first CV2X device 702a is the first to complete the LBT function and transmit a CTS signal 716a. However, because the CV2X device 702 is limited to communicating CV2X data on a predefined time slot pattern, and because the CTS signal 716a does not fall within or end with a full time slot, the CV2X device 702 may wait until the next full time slot after the CTS signal 716a to begin communicating. Here, the next full time slot begins at the second time 1104. Thus, at the beginning of the second time 1104, the CV2X device 702 may anticipate that CV2X data communication is about to occur. Here, the second CV2X device 702b transmits CV2X data 1108b during the first full time slot, and the fourth CV2X device receives CV2X data 1108d. At a third time 1106 , the first CV2X device 702 a transmits CV2X data 1108 a on the frequency band at a second full time slot having a predefined time slot pattern starting at the third time 1106 .

[0111] Figure 12 is a signal diagram illustrating an example timeline 1200 of the CV2X device 702 retaining a CV2X window. Figure 11 Transmissions within the CV2X window 704 may occur according to a predefined time slot pattern. Here, the first CV2X device 702a transmits a first CTS signal 716a during a first time slot (e.g., a time duration starting at the second time 1104 and ending at the third time 1106) in the CV2X window 704 having a predefined time slot pattern. Because the CTS signal 716a occupies only a portion of the first time slot, CV2X communication may not begin until the start of the second time slot in the CV2X window (assuming the CV2X window 704 is long enough to include more than one CV2X time slot). Thus, the CV2X device 702 may begin CV2X communication at the start of the second time slot (e.g., after the third time 1106 at which the first time slot ends and the second time slot begins). Here, the first CV2X device 702a performs CV2X communication 1108a during the second time slot.

[0112] It should be noted that in some scenarios, the first CV2X device 702a may not detect / receive a CTS signal transmitted by one or more other CV2X devices, even if the first CV2X device 702a is performing LBT functionality and listening for CTS signals. In some cases, the first CV2X device 702a may be out of range of one or more other CV2X devices, and / or local interference may be strong enough to prevent decoding of the CTS signal. Furthermore, using a CTS signal transmitted from only one of the other CV2X devices to preserve the CV2X window may cause fewer than all surrounding non-CV2X devices to defer communications during the CV2X window. For example, non-CV2X devices local only to the CV2X device that transmitted the CTS signal may decode the CTS signal and defer communications during the CV2X window, while other non-CV2X devices in the field that did not receive the CTS signal may continue to transmit or attempt to transmit within the CV2X window. Solutions to these issues are described in the following examples.

[0113] As mentioned in the previous example, a CV2X device may terminate the LBT function if it detects a CTS signal transmitted by another CV2X device. However, in some aspects, the termination of the LBT function may be triggered not only by the detection of a CTS signal, but also by the detection of a control channel (e.g., a physical sidelink control channel (PSCCH)) transmission.

[0114] Accordingly, as in Figure 11 and 12 As explained in

[15] , communication between CV2X devices 702 can be improved by reducing or eliminating the CV2X devices' reliance on hardware resources for blind decoding and by communicating only during predefined time slot patterns. Such an approach also improves communication timing because all CV2X devices 702 use a common timing approach.

[0115] Figure 13 13 is a signal diagram illustrating an example timeline 1300 in which a CV2X device 702 maintains a CV2X window. Here, the CV2X device 702 is configured to detect both CTS signals and physical control channel signals (e.g., PSCCH signals) from other CV2X devices 702 on a frequency band while performing LBT functionality. Here, each CV2X device 702 detects local interference 708 during a non-CV2X window 706a. Accordingly, when the local interference 708 ceases or the frequency band is determined to be idle, each CV2X device 702 waits during a respective DIFS period 710 before communicating CV2X data 1314.

[0116] In the example timeline 1300, the fourth CV2X device 702d does not detect the fourth instance 708d of local interference immediately before the fourth DIFS 710d. Thus, the fourth CV2X device 702d does not implement a backoff period after the fourth DIFS 710d. Instead, because the fourth CV2X device 702d does not detect local interference during the fourth DIFS 710d, the fourth CV2X device 702d transmits a fourth CTS signal 716d at the beginning 1302 of the CV2X window 704. The first CV2X device 702a and the second CV2X device 702b, while performing LBT functionality, hear the fourth CTS signal 716d and both devices terminate their respective backoff periods (712a and 712b) and wait until the first time slot 1310 in the CV2X window 704 before commencing CV2X communication. Here, the second CV2X device initiates CV2X communication 1314b.

[0117] However, the third CV2X device 702c does not hear the fourth CTS signal 716d transmitted by the fourth CV2X device 702d. It is possible that the third instance of local interference 708c sensed by the third CV2X device 702c overpowers the fourth CTS signal 716d. Consequently, the third CV2X device 702c performs a third DIFS 710c followed by a third backoff period 712c. However, during the third backoff period 712c, the third CV2X device 702c detects a control channel signal transmitted by the second CV2X device 702b during its CV2X communication 1314. Upon detecting the control channel, the third CV2X device 702c terminates the third backoff period 712c of the LBT function and waits until at least the subsequent second time slot 1312 before commencing CV2X communication.

[0118] In some aspects, the third CV2X device 702c may transmit a third CTS signal 716c to ensure that any non-CV2X devices and CV2X devices local to the third CV2X device 702c are aware of the reservation of the remaining portion of the CV2X window 704. For example, because the third CV2X device 702c did not hear the CTS signal previously transmitted by the fourth CV2X device 702d, any non-CV2X devices and / or CV2X devices local to the third CV2X device 702c may also have missed the previously transmitted CTS. In some examples, after sensing the control channel signaling, the third CV2X device 702c may transmit the third CTS signal 716c via the last OFDM symbol (e.g., a gap symbol) of the CV2X time slot (in this case, the first time slot 1310) in which the control channel was sensed.

[0119] Accordingly, if one or more CV2X devices 702 do not receive a CTS signal, the termination of the LBT procedure at the one or more CV2X devices 702 may also be triggered by detecting a CV2X PSCCH. In this example, although one or more CV2X devices 702 do not detect a CTS signal, the one or more CV2X devices 702 may still be aware of the CV2X window reservation by receiving a PSCCH signal, thereby improving coordinated communication between the CV2X devices 702 in an environment with high interference.

[0120] Figure 14 is a signal diagram illustrating an example timeline 1400 of the CV2X device 702 reserving a CV2X window. In some aspects, the CV2X device 702 may be configured to transmit additional CTS signals within the CV2X window until the start of the next CV2X slot.

[0121] In example timeline 1400, the fourth CV2X device 702d determines that the frequency band is clear and transmits a time-first CTS signal 716d before the first CV2X time slot 1404. Both the first CV2X device 702a and the second CV2X device 702b detect and receive the CTS signal 716d and terminate their respective LBT functions (712a and 712b). During the next CTS time slot 1408, all three devices transmit one or more CTS signals until the start of the first CV2X time slot 1404. The CV2X devices 702 may also be configured to transmit additional CTS signals (1402a, 1402b, and 1402d) aligned with a timing grid configured or preconfigured at each CV2X device (e.g., by the CN 132 or the BS 110). This provides the benefit of having CTS signals transmitted by different devices aligned in time to form a single frequency network (SFN) type transmission. It should be noted that only CTS transmissions occurring after the first CTS signal 716d can be transmitted so that their transmissions are aligned with the CTS time slot of the timing grid, while the first CTS transmission can be transmitted at any time. SFN-type transmissions can boost the power of CTS signals to improve their effective range. In this example, the timing grid provides a switching gap 1410 immediately before the start of the next CV2X time slot 1406 to provide the CV2X device 702 with sufficient time to switch to receive mode (if necessary) (e.g., the CV2X device transmitting the CTS signal is already in transmit mode).

[0122] In the example timeline 1400, local interference caused by non-CV2X devices prevents the third CV2X device 702c from receiving and / or decoding CTS signals transmitted by other devices until the last CTS signal (the temporally last CTS signal transmitted by the first CV2X device 702a, the second CV2X device 702b, and the fourth CV2X device 702d) is transmitted immediately before the first CV2X time slot 1404. Because there are no remaining CTS time slots in the timing grid before the first CV2X time slot 1404, the third CV2X device 702c can send a CTS signal 1412 during the last symbol and / or gap period of the first CV2X time slot 1404. As a result, the CTS signal 1412 transmitted by the third CV2X device 702c can improve the range of CV2X and non-CV2X devices that will receive CTS signaling during the CV2X window 704. This will also trigger early termination of LBT for other CV2X devices that missed the CTS signal transmitted before the first CV2X time slot 1404.

[0123] Accordingly, if one or more CV2X devices 702 are informed of the CV2X window reservation by receiving a PSCCH signal, then those one or more CV2X devices 702 may ensure that additional CV2X devices 702 are aware of the CV2X window 704 by transmitting a CTS signal (e.g., CTS signal 716c). This improves coordinated communication between CV2X devices 702 in environments with high interference, because the additional CTS signal may notify other CV2X devices that did not receive the initial CTS signal or PSCCH signal.

[0124] Example Techniques for Device Access in Unlicensed Bands Using Time Division Multiple Access (TDMA)

[0125] In certain aspects, each of the plurality of CV2X devices may be configured to operate as part of a global system that utilizes a common CV2X TDMA window communication scheme. For example, each of the plurality of CV2X devices may utilize a known duration and periodicity of a CV2X window to communicate with other CV2X devices in the plurality of CV2X devices. Here, the plurality of CV2X devices may be configured (e.g., by a network, according to a network standard) to communicate using a CV2X window having a common duration and a common periodicity known to each of the plurality of CV2X devices.

[0126] In certain aspects, multiple CV2X devices may be configured to determine an ad hoc CV2X TDMA window communication scheme for a local CV2X device group. In this example, a set of CV2X devices located near each other may form a group with its own TDMA window communication scheme. For example, the ad hoc CV2X TDMA window communication scheme may differ from the network standard and may be based on local communication parameters, including how busy the local frequency band is, how many CV2X devices are in the local CV2X device group, how frequently the CV2X devices in the group need to communicate, and any other suitable local communication parameters. Accordingly, the local CV2X device group may be able to flexibly determine a CV2X TDMA window communication scheme that can be optimized for the group's communication needs.

[0127] In certain aspects, CV2X devices may be configured to operate using a common CV2X TDMA window communication scheme as a system-level baseline configuration. As discussed, the common CV2X TDMA window communication scheme is network-configurable and may provide a common window duration and common periodicity corresponding to the maximum desired or network-allowed channel utilization for multiple CV2X devices. That is, the common CV2X TDMA window communication scheme may be configured to provide multiple CV2X devices with maximum utilization of the frequency band based on large-scale coexistence considerations and other RAT considerations. However, one or more CV2X devices in a group of CV2X devices that are local to one another may determine that the common CV2X TDMA window communication scheme should be adjusted to meet the needs and communication requirements of the local group of CV2X devices. For example, one or more CV2X devices in the local group of devices may determine that the frequency band utilization corresponding to the common CV2X TDMA window communication scheme is unnecessary or even overly aggressive for other RATs in the area and may instead determine to use a smaller TDMA window duration and / or skip certain TDMA windows.

[0128] Figure 15 1 is a signal diagram illustrating an example timeline 1500 of a time division multiple access (TDMA) window configuration according to certain aspects of the present disclosure. As shown, a baseline configuration 1502 (e.g., a common CV2X TDMA window communication scheme) may provide a relatively aggressive TDMA window periodicity, where each TDMA window has a relatively long duration. However, a local group of CV2X devices may not require such frequent TDMA windows and / or such long TDMA window durations. Accordingly, a local group configuration 1504 may reduce the CV2X duration and / or periodicity to accommodate the communication requirements of the local group.

[0129] In some aspects, a CV2X device group may be formed by local devices, and a group CV2X TDMA window communication scheme may be generated for communications within the device group. In some examples, each CV2X device in the group may attempt to secure a TDMA window for a frequency channel at the start of each TDMA window (according to the group configuration) by sending a CTS indicating the TDMA window duration. In some examples, any CTS transmitted within the group may be configured to distinguish the group CTS from another CTS transmitted by another CV2X device from the same group or another group. If a CTS with a group TDMA window duration is detected, the CV2X devices in the group may, as described above, Figure 7-14 If a CTS from another group is detected (e.g., a CTS with a different TDMA window duration), the CV2X devices that are not part of the other group may ignore the CTS signal and wait until a CTS signal from the CV2X device group is detected.

[0130] Figure 16 1 is a flow diagram illustrating example operations 1600 for wireless communication in accordance with certain aspects of the present disclosure. Operations 1600 may be performed, for example, by a first wireless device (e.g., such as UE 120a on a sidelink) acting as an originating wireless device. Operations 1600 may be implemented as a process on one or more processors (e.g., Figure 2 The software components of the reservation manager 140 are executed and run on the controller / processor 240 / 280 of the wireless device. In addition, the signal transmission and reception by the first wireless device in operation 1600 may be performed by one or more antennas (e.g., Figure 2 In some aspects, the transmission and / or reception of signals by the first wireless device may be achieved by obtaining and / or outputting signals via a bus interface of one or more processors (e.g., controller / processor 240 / 280).

[0131] Operations 1600 may begin by, at block 1605 , the first UE beginning to measure a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including a plurality of time periods.

[0132] Operations 1600 may continue by decoding, by the first UE while measuring the frequency band, any signals received on the frequency band at block 1610 to determine whether a Clear to Send (CTS) signal is received over the frequency band.

[0133] Operation 1600 may continue by, in box 1615, suppressing further measurements of the frequency band to determine whether the frequency band is idle within the remaining portion of the time interval after the first time in the time interval when a CTS signal is received from one or more of the multiple UEs at the first time in the time interval, the first time being within the first time period of the multiple time periods.

[0134] Operation 1600 may continue by transmitting a first CTS signal to the multiple UEs and one or more other wireless devices within the time interval in box 1620 when no CTS signal is received from one or more of the multiple UEs within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the multiple UEs via the frequency band during the time interval.

[0135] In certain aspects, communication timing between the first UE and one or more of the plurality of UEs is aligned with the plurality of time periods.

[0136] In certain aspects, operations 1600 further include, when the physical sidelink control channel signal is received at a second time in the time interval, refraining from further measuring the frequency band to determine whether the frequency band is idle for a remainder of the time interval after the second time.

[0137] In certain aspects, transmitting the first CTS signal when no CTS signal is received during the time interval includes transmitting the first CTS signal after receiving a physical sidelink control channel signal at the second time.

[0138] In certain aspects, the operations 1600 further include, when the CTS signal is received at the first time of the time interval, transmitting a second CTS signal via a last symbol in a second time period immediately following the first time period.

[0139] In certain aspects, the operations 1600 further include, when a CTS signal is received at a first time in the time interval, transmitting an additional CTS signal with each symbol occurring after the first time and during the first time period.

[0140] In certain aspects, the frequency band includes sidelinks in an unlicensed spectrum.

[0141] In certain aspects, operation 1600 further includes synchronizing timing between the first UE and at least a second UE of the plurality of UEs using one or more of: a global navigation satellite system (GNSS) time reference shared by each of the plurality of UEs and the first UE; or signaling internal clock information between the first UE and one or more of the plurality of UEs.

[0142] In certain aspects, measuring the frequency band includes determining that the frequency band is idle; and transmitting the first CTS signal to the plurality of UEs includes refraining from transmitting the first CTS signal to the plurality of UEs until after a backoff period, the backoff period being a duration of time between determining that the frequency band is idle and transmitting the first CTS signal.

[0143] In certain aspects, operations 1600 further include randomly generating, by the first UE, a duration of the backoff period.

[0144] In certain aspects, the operations 1600 further include randomly generating a duration of the backoff period based on a global positioning system (GPS) signal.

[0145] Figure 17 Illustrated are operations that may include being configured to perform the techniques disclosed herein (such as Figure 17 17. The communication device 1700 includes various components (e.g., corresponding to means-plus-function components) for performing the operations illustrated in FIG. 17. The communication device 1700 includes a processing system 1702 coupled to a transceiver 1708 (e.g., a transmitter and / or a receiver). The transceiver 1708 is configured to transmit and receive signals for the communication device 1700 (such as the various signals described herein) via an antenna 1710. The processing system 1702 can be configured to perform processing functions for the communication device 1700, including processing signals received and / or to be transmitted by the communication device 1700.

[0146] The processing system 1702 includes a processor 1704 coupled to a computer readable medium / memory 1712 via a bus 1706. In some aspects, the computer readable medium / memory 1712 is configured to store data that, when executed by the processor 1704, causes the processor 1704 to perform Figure 17 The instructions (e.g., computer-executable code) for performing the operations illustrated in or other operations for the various techniques discussed herein for performing sidelink communications in an unlicensed band.

[0147] In certain aspects, the computer-readable medium / memory 1712 stores code 1732 (e.g., an example of an apparatus for performing the above operations) for measuring a frequency band by a first UE starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods.

[0148] In certain aspects, the computer-readable medium / memory 1712 stores code 1734 (e.g., an example of a means for performing the foregoing operations) for decoding, by a first UE, any signals received on a frequency band while measuring the frequency band to determine whether a Clear to Send (CTS) signal is received over the frequency band.

[0149] In certain aspects, the computer-readable medium / memory 1712 stores code 1736 (e.g., an example of an apparatus for performing the foregoing operations) for refraining from further measuring the frequency band to determine whether the frequency band is idle for a remainder of the time interval after the first time in the time interval when a CTS signal is received from one or more of the plurality of UEs at the first time in the time interval, the first time being within a first time period of the plurality of time periods.

[0150] In certain aspects, computer-readable medium / memory 1712 stores code 1738 (e.g., an example of an apparatus for performing the operations described above) for transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval when no CTS signal is received from one or more of the plurality of UEs during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval. One or more of codes 1732-1738 may be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device. In certain aspects, processor 1704 executes code stored in computer-readable medium / memory 1712. In certain aspects, computer-readable medium / memory 1712 is an example of reservation manager 140.

[0151] In certain aspects, additionally or alternatively, the processor 1704 includes circuitry configured to implement code stored in the computer-readable medium / memory 1712. The processor 1704 includes circuitry 1718 (e.g., an example of a means for performing the above operations) for measuring a frequency band by the first UE starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including a plurality of time periods.

[0152] Processor 1704 includes circuitry 1720 (eg, an example of a means for performing the above operations) for decoding, by the first UE, any signals received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band.

[0153] Processor 1704 includes a circuit system 1722 (e.g., an example of an apparatus for performing the above operations) for suppressing further measurements of the frequency band to determine whether the frequency band is idle within a remaining portion of the time interval after the first time within the time interval when a CTS signal is received from one or more of the multiple UEs at the first time within the time interval, the first time being within a first time period of the multiple time periods.

[0154] Processor 1704 includes circuitry 1724 (e.g., an example of a means for performing the above operations) for transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval when no CTS signal is received from one or more of the plurality of UEs during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval. One or more of circuitry 1718-1724 may be implemented by one or more of a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device. In some aspects, processor 1704 is an example of reservation manager 140.

[0155] The transceiver 1708 may provide a means for receiving information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to power saving of smart repeaters based on trigger signals, etc.). The information may be communicated to other components of the device 1700. The transceiver 1708 may be a reference to Figure 2 Examples of various aspects of the described transceiver 232 / 254. Antenna 1710 may correspond to a single antenna or a set of antennas and may be referenced Figure 2 Examples of various aspects of the described antennas 234 / 252 . The transceiver 1708 may provide a means for transmitting signals generated by the other components of the device 1700 .

[0156] Example aspects

[0157] Aspect 1: A method for wireless communication by a first user equipment (UE), the method comprising: measuring a frequency band by the first UE starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods; decoding by the first UE any signal received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band; when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, refraining from further measuring the frequency band for a remaining portion of the time interval after the first time to determine whether the frequency band is idle, the first time being within a first time period of the multiple time periods; and when a CTS signal is not received from one or more of the plurality of UEs within the time interval, transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval.

[0158] Aspect 2: The method of aspect 1, wherein communication timing between the first UE and one or more of the plurality of UEs is aligned with the plurality of time periods.

[0159] Aspect 3: The method of Aspect 1 or 2 further includes, when a physical side link control channel signal is received at a second time in the time interval, suppressing further measurement of the frequency band in the remaining part of the time interval after the second time to determine whether the frequency band is idle.

[0160] Aspect 4: The method of any one of aspects 1-3, wherein when no CTS signal is received during the time interval, transmitting the first CTS signal includes transmitting the first CTS signal after receiving the physical sidelink control channel signal at the second time.

[0161] Aspect 5: The method according to any one of aspects 1-4, further comprising, when a CTS signal is received at a first time in the time interval, transmitting a second CTS signal through a last symbol in a second time period immediately following the first time period.

[0162] Aspect 6: The method of any of aspects 1-5, further comprising, when a CTS signal is received at a first time in the time interval, transmitting an additional CTS signal with each symbol occurring after the first time and during the first time period.

[0163] Aspect 7: The method of any of aspects 1-6, wherein the frequency band comprises a sidelink in an unlicensed spectrum.

[0164] Aspect 8: The method of any one of Aspects 1-7 further includes synchronizing timing between the first UE and at least a second UE among the multiple UEs using one or more of the following: a global navigation satellite system (GNSS) time reference shared by each of the multiple UEs and the first UE; or signaling internal clock information between the first UE and one or more of the multiple UEs.

[0165] Aspect 9: A method as in any of Aspects 1-8, wherein: measuring the frequency band includes determining that the frequency band is idle; and transmitting the first CTS signal to the multiple UEs includes suppressing transmitting the first CTS signal to the multiple UEs until after a backoff period, the backoff period being the time duration between determining that the frequency band is idle and transmitting the first CTS signal.

[0166] Aspect 10: The method according to any one of aspects 1-9, further comprising randomly generating, by the first UE, a duration of the backoff period.

[0167] Aspect 11: The method of aspect 10, further comprising randomly generating the duration of the backoff period based on a global positioning system (GPS) signal.

[0168] Aspect 12: A first user equipment (UE), comprising: a memory; and a processor coupled to the memory, wherein the memory and the processor are configured to: start measuring a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods; decode any signal received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band; when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, refrain from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period of the multiple time periods; and when a CTS signal is not received from one or more of the plurality of UEs within the time interval, transmit a first CTS signal to the plurality of UEs and one or more other wireless devices within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval.

[0169] Aspect 13: The UE of Aspect 12, wherein communication timing between the first UE and one or more of the plurality of UEs is aligned with the plurality of time periods.

[0170] Aspect 14: A UE as in either Aspect 12 or 13, wherein the memory and the processor are further configured to, when a physical sidelink control channel signal is received at a second time in the time interval, suppress further measurement of the frequency band in the remaining part of the time interval after the second time to determine whether the frequency band is idle.

[0171] Aspect 15: A UE as in any one of Aspects 12-14, wherein the memory and the processor configured to transmit a first CTS signal are further configured to, when no CTS signal is received during the time interval, transmit the first CTS signal after receiving a physical sidelink control channel signal at a second time.

[0172] Aspect 16: The UE of any one of Aspects 12-15 further includes a transceiver coupled to the memory and the processor, wherein the memory and the processor are further configured to: when a CTS signal is received at a first time in the time interval, use the transceiver to transmit a second CTS signal through the last codeword in a second time period immediately following the first time period.

[0173] Aspect 17: The UE of any one of Aspects 12-16 further includes a transceiver coupled to the memory and the processor, wherein the memory and the processor are further configured to: when a CTS signal is received at a first time in the time interval, use the transceiver to transmit an additional CTS signal through each codeword occurring after the first time and during the first time period.

[0174] Aspect 18: The UE of any one of aspects 12-17, wherein the frequency band comprises a sidelink in an unlicensed spectrum.

[0175] Aspect 19: A UE as in any of Aspects 12-18, wherein the memory and the processor are further configured to: synchronize timing between the first UE and at least a second UE of the multiple UEs using one or more of: a global navigation satellite system (GNSS) time reference shared by each of the multiple UEs and the first UE; or signaling internal clock information between the first UE and one or more of the multiple UEs.

[0176] Aspect 20: A UE as in any of Aspects 12-19, wherein: the memory and the processor configured to measure the frequency band are further configured to determine that the frequency band is idle; and the memory and the processor configured to transmit a first CTS signal to the multiple UEs are further configured to refrain from transmitting the first CTS signal to the multiple UEs until after a backoff period, the backoff period being the time duration between determining that the frequency band is idle and transmitting the first CTS signal.

[0177] Aspect 21: The UE of any one of aspects 12-20, wherein the memory and the processor are further configured to randomly generate a duration of the backoff period.

[0178] Aspect 22: The UE of any one of aspects 12-21, wherein the memory and the processor are further configured to randomly generate the duration of the backoff period based on a Global Positioning System (GPS) signal.

[0179] Aspect 23: A first user equipment (UE) for wireless communication, comprising: a device for measuring a frequency band starting at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods; a device for decoding any signal received on the frequency band while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band; when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, a device for suppressing further measuring the frequency band to determine whether the frequency band is idle during the remaining portion of the time interval after the first time, the first time being within a first time period among the multiple time periods; and when a CTS signal is not received from one or more of the plurality of UEs within the time interval, a device for transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval.

[0180] Aspect 24: The UE of Aspect 23, wherein communication timing between the first UE and one or more of the plurality of UEs is aligned with the plurality of time periods.

[0181] Aspect 25: A UE as in either Aspect 23 or 24, further comprising, when a physical sidelink control channel signal is received at a second time in the time interval, a device for suppressing further measurement of the frequency band in the remaining part of the time interval after the second time to determine whether the frequency band is idle.

[0182] Aspect 26: The UE of any one of Aspects 23-25, further comprising means for transmitting the first CTS signal after receiving the physical sidelink control channel signal at the second time when no CTS signal is received during the time interval.

[0183] Aspect 27: The UE according to any one of aspects 23-26, further comprising: means for transmitting a second CTS signal through a last symbol in a second time period immediately following the first time period when a CTS signal is received at a first time in the time interval.

[0184] Aspect 28: The UE of any one of aspects 23-27, further comprising: means for, when a CTS signal is received at a first time in the time interval, transmitting an additional CTS signal with each symbol occurring after the first time and during the first time period.

[0185] Aspect 29: The UE of any one of Aspects 23-28, wherein the frequency band comprises a sidelink in an unlicensed spectrum.

[0186] Aspect 30: A non-transitory computer-readable storage medium for wireless communication implemented by a first UE, comprising code for the following operations: measuring a frequency band by the first UE at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including multiple time periods; decoding any signal received on the frequency band by the first UE while measuring the frequency band to determine whether a clear to send (CTS) signal is received over the frequency band; when a CTS signal is received from one or more of a plurality of UEs at a first time within the time interval, refraining from further measuring the frequency band to determine whether the frequency band is idle during a remaining portion of the time interval after the first time, the first time being within a first time period of the multiple time periods; and when a CTS signal is not received from one or more of the plurality of UEs within the time interval, transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices within the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval.

[0187] Aspect 31: A first user equipment (UE), comprising: a memory and one or more processors configured to perform the method of one or more of aspects 1-11.

[0188] Aspect 32: A first user equipment (UE), comprising: one or more devices for performing the method of one or more of aspects 1-11.

[0189] Aspect 33: A non-transitory computer-readable storage medium for enabling wireless communication by a first UE, comprising code for executing the method of one or more of aspects 1-11.

[0190] Additional considerations

[0191] The techniques described herein may be used for various wireless communication technologies such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), Advanced LTE (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. A CDMA network may implement radio technologies such as Universal Terrestrial Radio Access (UTRA) and cdma2000. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95, and IS-856 standards. A TDMA network may implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and others. UTRA and E-UTRA are parts of the Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization called the 3rd Generation Partnership Project (3GPP). cdma2000 and UMB are described in documents from an organization called the 3rd Generation Partnership Project 2 (3GPP2). NR is an emerging wireless communication technology under development.

[0192] In 3GPP, the term "cell" can refer to the coverage area of a Node B (NB) and / or the NB subsystem serving that coverage area, depending on the context in which the term is used. In NR systems, the terms "cell" and base station (BS), next-generation Node B (gNB or g-Node B), access point (AP), distributed unit (DU), carrier, or transmit reception point (TRP) can be used interchangeably. A BS can provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell can cover a relatively large geographic area (e.g., several kilometers in radius) and can allow unrestricted access by UEs with service subscriptions. A pico cell can cover a relatively small geographic area and can allow unrestricted access by UEs with service subscriptions. A femto cell can cover a relatively small geographic area (e.g., a residence) and can allow restricted access by UEs associated with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in a residence, etc.). A BS for a macro cell can be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS.

[0193] Within this document, the term "user equipment (UE)" or "CV2X device" refers broadly to a wide variety of devices and technologies. UE and CV2X devices may include several hardware structural components sized, shaped, and arranged to facilitate communication; such components may include antennas, antenna arrays, RF chains, amplifiers, one or more processors, and the like electrically coupled to one another. For example, some non-limiting examples of UE or CV2X devices include mobile devices, cellular (cell) phones, smartphones, Session Initiation Protocol (SIP) phones, laptops, personal computers (PCs), notebooks, netbooks, smartbooks, tablets, personal digital assistants (PDAs), and a wide variety of embedded systems, e.g., corresponding to the "Internet of Things" (IoT). UE or CV2X devices may also be automobiles or other transportation vehicles, remote sensors or actuators, robots or robotic devices, satellite radios, Global Positioning System (GPS) devices, object tracking devices, drones, multicopters, quadcopters, remote control devices, consumer and / or wearable devices (such as glasses), wearable cameras, virtual reality devices, smart watches, health or fitness trackers, digital audio players (e.g., MP3 players), cameras, game consoles, etc. UE or CV2X devices may also be digital home or smart home devices, such as home audio, video, and / or multimedia devices, appliances, vending machines, smart lighting devices, home security systems, smart meters, etc. UE or CV2X devices may also be smart energy devices, security devices, solar panels or solar arrays, municipal infrastructure equipment (e.g., smart grids, public WiFi, etc.), industrial automation and enterprise equipment, logistics controllers, agricultural equipment, military defense equipment (such as vehicles, aircraft, ships, and weapons), etc. Furthermore, UE or CV2X devices may provide connected health or telemedicine support, such as remote healthcare. Telehealth devices may include telehealth monitoring devices and telehealth supervisory devices, whose communications may be given priority treatment or prioritized access over other types of information, for example, in the form of prioritized access for critical service data transmission and / or associated QoS for critical service data transmission.

[0194] Within this document, the term "non-CV2X device" broadly refers to devices and technologies that use different wireless communication technologies than those used by CV2X devices. For example, non-CV2X devices may communicate using the IEEE 802.11 protocol to form a wireless local area network (WLAN), while CV2X devices may communicate according to a cellular radio protocol (e.g., GSM, LTE, 5G, etc.). Examples of non-CV2X devices include WiFi routers, WiFi bridges, WiFi cards, and any other suitable devices that communicate using the IEEE 802.11 protocol.

[0195] In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication between some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communications, the subordinate entities utilize the resources allocated by the scheduling entity. The base station is not the only entity that can be used as a scheduling entity. In some examples, a UE may act as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may act as a scheduling entity in a peer-to-peer (P2P) network and / or in a mesh network. In the mesh network example, UEs may communicate directly with each other in addition to communicating with the scheduling entity.

[0196] Each method disclosed herein includes one or more operations or actions for implementing the method. Operations and / or actions can be interchangeable with each other. In other words, unless a specific order of operations or actions is specified, the order and / or use of specific operations and / or actions can be modified.

[0197] As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single members. As an example, "at least one of a, b, or c" is intended to encompass: a, b, c, ab, ac, bc, and abc, as well as any combination with multiples of the same elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c).

[0198] As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or another data structure), ascertaining, and the like. Furthermore, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Furthermore, "determining" may include resolving, selecting, choosing, establishing, and the like.

[0199] The preceding description is provided to enable anyone skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the universal principles defined herein may be applied to other aspects. Accordingly, the claims are not intended to be limited to the aspects shown herein, but rather should be granted the full scope consistent with the claim language, wherein singular references to elements are not intended to mean "one and only one" (unless specifically stated otherwise) but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. All structural and functional equivalents of the various aspects described throughout this disclosure that are currently or hereafter known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly stated in the claims. No element of a claim should be interpreted under 35 U.S.C. §112(f) unless the element is explicitly recited using the phrase "means for..." or, in the case of a method claim, the element is recited using the phrase "step for..."

[0200] The various operations of the methods described above may be performed by any suitable device capable of performing the corresponding functions. These devices may include various hardware and / or software components and / or modules, including but not limited to circuits, application specific integrated circuits (ASICs), or processors. Generally, where there are operations illustrated in the figures, these operations may have corresponding counterpart means-plus-function components with similar numbering.

[0201] The various illustrative logical blocks, modules, and circuits described in conjunction with the present disclosure may be implemented or executed with a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device (PLD), 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 commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0202] If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. Depending on the specific application and overall design constraints of the processing system, the bus may include any number of interconnecting buses and bridges. The bus may link together various circuits including a processor, a machine-readable medium, and a bus interface. The bus interface may be used to connect a network adapter, etc., to the processing system via the bus. The network adapter may be used to implement signal processing functions at the physical (PHY) layer. In a user terminal (see Figure 1 ), a user interface (e.g., a keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits, such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art and will not be described further. The processor may be implemented using one or more general and / or special purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry capable of executing software. Those skilled in the art will recognize how to best implement the functionality described with respect to the processing system, depending on the specific application and the overall design constraints imposed on the overall network or system.

[0203] If implemented in software, each function may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Software should be broadly interpreted to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media includes both computer storage media and communication media, including any media that facilitates the transfer of a computer program from one location to another. The processor may be responsible for managing the bus and general processing, including executing software modules stored on a machine-readable storage medium. A computer-readable storage medium may be coupled to the processor so that the processor can read and write information from / to the storage medium. In an alternative embodiment, the storage medium may be integrated into the processor. As an example, the machine-readable medium may include a transmission line, a carrier modulated by data, and / or a computer-readable storage medium having instructions stored thereon that is separate from the wireless node, all of which may be accessed by the processor via a bus interface. Alternatively or additionally, the machine-readable medium or any portion thereof may be integrated into the processor, such as a cache and / or general register file. As examples, examples of machine-readable storage media may include RAM (random access memory), flash memory, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage media, or any combination thereof. Machine-readable media may be embodied in a computer program product.

[0204] A software module may include a single instruction or many instructions and may be distributed across several different code segments, between different programs, and across multiple storage media. A computer-readable medium may include multiple software modules. These software modules include instructions that, when executed by a device (such as a processor), cause a processing system to perform various functions. These software modules may include a transmitting module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. As an example, when a triggering event occurs, a software module may be loaded from a hard drive into RAM. During the execution of a software module, the processor may load some instructions into a cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When describing the functionality of a software module below, it will be understood that such functionality is implemented by the processor when the processor executes instructions from the software module.

[0205] Likewise, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies (such as infrared (IR), radio, and microwave), then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies (such as infrared, radio, and microwave) are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Disks typically reproduce data magnetically, while discs reproduce data optically using lasers. Thus, in some aspects, computer-readable media may include non-transitory computer-readable media (e.g., tangible media). Additionally, for other aspects, computer-readable media may include transient computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0206] Thus, certain aspects may include a computer program product for performing the operations presented herein. For example, such a computer program product may include a computer-readable medium having instructions stored (and / or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, such as for performing the operations described herein and in Figure 16 Instructions for the operations explained in .

[0207] In addition, it should be appreciated that the modules and / or other appropriate means for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by the user terminal and / or base station where applicable. For example, such a device can be coupled to a server to facilitate the transfer of the means for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage device (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.) so that once the storage device is coupled to or provided to the user terminal and / or base station, the device can obtain the various methods. In addition, any other suitable technology suitable for providing the methods and techniques described herein to a device can be utilized.

Claims

1. A method for wireless communication by a first user equipment (UE), the method comprising: Measuring a frequency band by the first UE at least at a start time of a time interval to determine whether the frequency band is idle, where the time interval includes a plurality of time periods; decoding, by the first UE while measuring the frequency band, any signal received on the frequency band to determine whether a Clear to Send (CTS) signal is received over the frequency band; When a CTS signal is received from one or more of the plurality of UEs at a first time within the time interval, refraining from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period among the plurality of time periods; as well as When no CTS signal is received from one or more of the plurality of UEs during the time interval, transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with the one or more of the plurality of UEs over the frequency band during the time interval, and The communication timing between the first UE and the one or more of the multiple UEs is aligned with the multiple time periods.

2. The method of claim 1, further comprising: When a physical sidelink control channel signal is received at a second time in the time interval, further measuring the frequency band is suppressed for a remaining portion of the time interval after the second time to determine whether the frequency band is idle.

3. The method of claim 2, wherein when no CTS signal is received during the time interval, transmitting the first CTS signal comprises transmitting the first CTS signal after receiving the physical sidelink control channel signal at the second time.

4. The method of claim 1, further comprising: When the CTS signal is received at the first time of the time interval, a second CTS signal is transmitted through a last symbol in a second time period immediately following the first time period.

5. The method of claim 1, further comprising: When the CTS signal is received at the first time of the time interval, an additional CTS signal is transmitted with each symbol occurring after the first time and during the first time period. The method of claim 1 , wherein the frequency band comprises a sidelink in an unlicensed spectrum.

7. The method of claim 1, further comprising: Synchronizing timing between the first UE and at least a second UE of the plurality of UEs using one or more of: a Global Navigation Satellite System (GNSS) time reference shared by each of the plurality of UEs and the first UE; or Internal clock information is signaled between the first UE and one or more of the plurality of UEs.

8. The method of claim 1, wherein: Measuring the frequency band includes determining that the frequency band is idle; and Transmitting the first CTS signal to the plurality of UEs includes refraining from transmitting the first CTS signal to the plurality of UEs until after a backoff period, the backoff period being a duration of time between determining that the frequency band is idle and transmitting the first CTS signal.

9. The method of claim 8, further comprising: The duration of the backoff period is randomly generated by the first UE.

10. The method of claim 9, further comprising: The duration of the backoff period is randomly generated based on a global positioning system (GPS) signal.

11. An apparatus for wireless communication at a first user equipment (UE), comprising: one or more memories; as well as one or more processors coupled to the one or more memories, wherein the one or more processors are configured to cause the first UE to: measuring a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval including a plurality of time periods; decoding any signals received on the frequency band while measuring the frequency band to determine whether a clear-to-send (CTS) signal is received over the frequency band; When a CTS signal is received from one or more of the plurality of UEs at a first time within the time interval, refraining from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period among the plurality of time periods; as well as When no CTS signal is received from one or more of the plurality of UEs during the time interval, transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with the one or more of the plurality of UEs over the frequency band during the time interval, and Wherein communication timing between the first UE and the one or more of the plurality of UEs is aligned with the plurality of time periods.

12. An apparatus as claimed in claim 11, wherein the one or more processors are further configured to enable the first UE: when receiving a physical sidelink control channel signal at a second time in the time interval, to suppress further measurement of the frequency band within the remaining part of the time interval after the second time to determine whether the frequency band is idle.

13. An apparatus as claimed in claim 12, wherein the one or more processors configured to cause the first UE to transmit the first CTS signal are further configured to cause the first UE to: when no CTS signal is received during the time interval, transmit the first CTS signal after receiving the physical side link control channel signal at the second time.

14. The apparatus as claimed in claim 11 further comprises a transceiver coupled to the one or more memories and the one or more processors, wherein the one or more processors are further configured to enable the first UE: when receiving the CTS signal at the first time in the time interval, to use the transceiver to transmit a second CTS signal through the last codeword in a second time period immediately following the first time period.

15. The apparatus of claim 11, further comprising a transceiver coupled to the one or more memories and the one or more processors, wherein the one or more processors are further configured to enable the first UE: when receiving the CTS signal at the first time in the time interval, to use the transceiver to transmit an additional CTS signal by each codeword occurring after the first time and during the first time period.

16. The apparatus of claim 11, wherein the frequency band comprises a sidelink in an unlicensed spectrum.

17. The apparatus of claim 11, wherein the one or more processors are further configured to cause the first UE to: synchronize timing between the first UE and at least a second UE of the plurality of UEs using one or more of: a Global Navigation Satellite System (GNSS) time reference shared by each of the plurality of UEs and the first UE, or Internal clock information is signaled between the first UE and one or more of the plurality of UEs.

18. The apparatus of claim 11, wherein: The one or more processors configured to cause the first UE to measure the frequency band are further configured to cause the first UE to determine that the frequency band is idle; and The one or more processors configured to cause the first UE to transmit the first CTS signal to the multiple UEs are further configured to cause the first UE to: refrain from transmitting the first CTS signal to the multiple UEs until after a backoff period, the backoff period being the time duration between determining that the frequency band is idle and transmitting the first CTS signal.

19. The apparatus of claim 18, wherein the one or more processors are further configured to cause the first UE to randomly generate a duration of the backoff period.

20. The apparatus of claim 19, wherein the one or more processors are further configured to cause the first UE to randomly generate the duration of the backoff period based on a Global Positioning System (GPS) signal.

21. A first user equipment (UE) for wireless communication, comprising: means for starting to measure a frequency band at least at a start time of a time interval to determine whether the frequency band is idle, the time interval comprising a plurality of time periods; means for decoding any signals received on the frequency band while measuring the frequency band to determine whether a clear-to-send (CTS) signal is received over the frequency band; means for refraining from further measuring the frequency band to determine whether the frequency band is idle during a remainder of the time interval after the first time, upon receiving a CTS signal from one or more of the plurality of UEs at a first time within the time interval, the first time being within a first time period of the plurality of time periods; as well as means for transmitting, when no CTS signal is received from one or more of the plurality of UEs during the time interval, a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with one or more of the plurality of UEs over the frequency band during the time interval, and Wherein communication timing between the first UE and the one or more of the plurality of UEs is aligned with the plurality of time periods.

22. The first UE according to claim 21, further comprising: When a physical sidelink control channel signal is received at a second time in the time interval, means for refraining from further measuring the frequency band to determine whether the frequency band is idle for a remainder of the time interval after the second time.

23. The first UE according to claim 22, further comprising: Means for transmitting the first CTS signal after receiving the physical sidelink control channel signal at the second time when no CTS signal is received during the time interval.

24. The first UE according to claim 21, further comprising: means for transmitting a second CTS signal through a last symbol in a second time period immediately following the first time period when a CTS signal is received at the first time of the time interval.

25. The first UE according to claim 21, further comprising: Means for transmitting an additional CTS signal when a CTS signal is received at the first time of the time interval with each symbol occurring after the first time and during the first time period.

26. The first UE of claim 21, wherein the frequency band comprises a sidelink in an unlicensed spectrum.

27. A non-transitory computer-readable storage medium for wireless communication implemented by a first UE, comprising code for: Measuring a frequency band by the first UE at least at a start time of a time interval to determine whether the frequency band is idle, where the time interval includes a plurality of time periods; decoding, by the first UE while measuring the frequency band, any signal received on the frequency band to determine whether a Clear to Send (CTS) signal is received over the frequency band; When a CTS signal is received from one or more of the plurality of UEs at a first time within the time interval, refraining from further measuring the frequency band to determine whether the frequency band is idle for a remaining portion of the time interval after the first time, the first time being within a first time period among the plurality of time periods; and When no CTS signal is received from one or more of the plurality of UEs during the time interval, transmitting a first CTS signal to the plurality of UEs and one or more other wireless devices during the time interval, the first CTS signal indicating to the one or more other wireless devices that the frequency band is busy during the time interval, wherein the first UE wirelessly communicates with the one or more of the plurality of UEs over the frequency band during the time interval, and Wherein communication timing between the first UE and the one or more of the plurality of UEs is aligned with the plurality of time periods.

28. The non-transitory computer-readable storage medium of claim 27, further comprising code for executing the method of any one of claims 2-10.

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