Wireless communication device synchronization

Abstract

Certain aspects of the present disclosure provide techniques for sidelink communications in an unlicensed spectrum. A method that can be performed by a device includes: sensing interference in a channel in each time interval of a plurality of time intervals in a time sequence until the interference is sensed to be below a threshold for one of the plurality of time intervals, or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals being a time window. The method may also include: sensing interference above a threshold in a first portion of a time interval of the plurality of time intervals. The method may also include: sensing interference below a threshold in a second portion of a time interval of the plurality of time intervals, the second portion occurring later in time than the first portion.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to Greek Patent Application No. 20200100213, filed on April 27, 2020, which is hereby assigned to the present assignee and is hereby expressly incorporated by reference in its entirety, as if set forth below and for all applicable purposes. Technical Field

[0003] Aspects of the present disclosure relate to wireless communications and, more particularly, to techniques for synchronization of wireless communication devices. Background Art

[0004] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, 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, Advanced LTE (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, Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, and the like.

[0005] 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., 5GNR) is an example of an emerging telecommunication standard. NR is a collection of enhancements to the LTE mobile standard released by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, improving services, utilizing new spectrum, and using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) to better integrate with other open standards. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0006] However, as the demand for mobile broadband access continues to grow, there is a need for further improvements to NR and LTE technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies. Summary of the invention

[0007] The systems, methods, and devices of the present disclosure each have multiple aspects, no single aspect being solely responsible for its desired attributes. Without limiting the scope of the present disclosure as expressed in the appended claims, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled "Detailed Description," one will understand how the features of the present disclosure provide improved techniques for synchronization of wireless communication devices (e.g., those communicating in one or more unlicensed frequency bands).

[0008] Certain aspects of the subject matter described in the present disclosure may be implemented in a device for wireless communication. The device generally includes a memory and a processor coupled to the memory. The processor and the memory are configured to: sense interference in a channel in each of a plurality of time intervals in chronological order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window. The processor and the memory are also configured to: sense interference above a threshold in a first portion of a time interval in the plurality of time intervals. The processor and the memory are also configured to: sense interference below a threshold in a second portion of a time interval in the plurality of time intervals, the second portion occurring later in time than the first portion. The processor and the memory are also configured to: send one of a portion of a reservation signal or a synchronization signal (SS) corresponding to the second portion in the second portion of the plurality of time intervals.

[0009] Certain aspects of the subject matter described in the present disclosure may be implemented in a device for wireless communication. The device generally includes a memory and a processor coupled to the memory. The processor and the memory are configured to transmit the size of a time window, wherein the time window includes a plurality of time intervals, and the size of the time window is based at least in part on the number of previous time intervals in which interference is sensed to be higher than a threshold. The processor and the memory are also configured to sense interference in the channel in each of the plurality of time intervals in chronological order until the interference is sensed to be lower than the threshold in one of the plurality of time intervals, or the interference is sensed to be higher than the threshold in all the plurality of time intervals. The processor and the memory are also configured to send a synchronization signal (SS) in one of the plurality of time intervals when the interference is sensed to be lower than the threshold for one of the plurality of time intervals. The processor and the memory are also configured to avoid sending the SS in the time window when the interference is sensed to be higher than the threshold for all the plurality of time intervals.

[0010] Certain aspects of the subject matter described in the present disclosure may be implemented in a method for wireless communication by a device. The method generally includes: sensing interference in a channel for each of a plurality of time intervals in a time sequence until the interference is sensed to be below a threshold for one of the plurality of time intervals, or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window. The method also includes: sensing interference above a threshold in a first portion of a time interval in the plurality of time intervals. The method also includes: sensing interference below a threshold in a second portion of a time interval in the plurality of time intervals, the second portion occurring later in time than the first portion. The method also includes: sending one of a reservation signal or a portion of a synchronization signal (SS) corresponding to the second portion in the second portion of a time interval in the plurality of time intervals.

[0011] Certain aspects of the subject matter described in the present disclosure may be implemented in a method for wireless communication by a device. The method generally includes: transmitting a size of a time window, wherein the time window includes a plurality of time intervals, and the size of the time window is based at least in part on the number of previous time intervals in which interference is sensed to be above a threshold. The method also includes: sensing interference in a channel in each of the plurality of time intervals in a chronological order until the interference is sensed to be below the threshold for one of the plurality of time intervals, or the interference is sensed to be above the threshold for all of the plurality of time intervals. The method also includes: sending a synchronization signal (SS) in one of the plurality of time intervals when the interference is sensed to be below the threshold for one of the plurality of time intervals. The method also includes: avoiding sending the SS in the time window when the interference is sensed to be above the threshold for all of the plurality of time intervals.

[0012] Certain aspects of the subject matter described in the present disclosure may be implemented by a device for wireless communication. The device generally includes: a unit for sensing interference in a channel in each of a plurality of time intervals in chronological order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window. The device also includes: a unit for sensing interference above a threshold in a first portion of a time interval in the plurality of time intervals. The device also includes: a unit for sensing interference below a threshold in a second portion of the plurality of time intervals, the second portion occurring later in time than the first portion. The device also includes: a unit for sending one of a reservation signal or a portion of a synchronization signal (SS) corresponding to the second portion in a second portion of a time interval in the plurality of time intervals.

[0013] Certain aspects of the subject matter described in the present disclosure may be implemented by a device for wireless communication. The device generally includes: a unit for transmitting a size of a time window, wherein the time window includes a plurality of time intervals, and the size of the time window is based at least in part on the number of previous time intervals in which interference is sensed to be above a threshold. The device also includes: a unit for sensing interference in a channel in each of the plurality of time intervals in a chronological order until interference is sensed to be below a threshold for one of the plurality of time intervals or interference is sensed to be above a threshold for all of the plurality of time intervals. The device also includes: a unit for sending a synchronization signal (SS) in one of the plurality of time intervals when interference is sensed to be below a threshold for one of the plurality of time intervals. The device also includes: a unit for avoiding sending the SS in the time window when interference is sensed to be above a threshold for all of the plurality of time intervals.

[0014] Certain aspects of the subject matter described in the present disclosure may be implemented in a non-transitory computer-readable medium having instructions stored thereon, which, when executed by a device, cause the device to perform operations for wireless communication, including: sensing interference in a channel for each time interval in a plurality of time intervals in a time sequence until the interference is sensed to be below a threshold for one of the plurality of time intervals, or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window. The method also includes: sensing interference above the threshold in a first portion of a time interval in the plurality of time intervals. The method also includes: sensing interference below the threshold in a second portion of a time interval in the plurality of time intervals, the second portion occurring later in time than the first portion. The operations also include: sending one of a reservation signal or a portion of a synchronization signal (SS) corresponding to the second portion in the second portion of a time interval in the plurality of time intervals.

[0015] Certain aspects of the subject matter described in the present disclosure may be implemented by a non-transitory computer-readable medium having instructions stored thereon that, when executed by a device, cause the device to perform operations for wireless communication, including transmitting a size of a time window, wherein the time window includes a plurality of time intervals, the size of the time window being based at least in part on the number of previous time intervals in which interference was sensed to be above a threshold. The operations also include sensing interference in a channel in each of the plurality of time intervals in a chronological order until interference is sensed to be below the threshold for one of the plurality of time intervals or interference is sensed to be above the threshold for all of the plurality of time intervals. The operations also include sending a synchronization signal (SS) in one of the plurality of time intervals when interference is sensed to be below the threshold for one of the plurality of time intervals. The operations also include avoiding sending the SS in the time window when interference is sensed to be above the threshold for all of the plurality of time intervals.

[0016] Certain aspects of the subject matter described in the present disclosure may be implemented in a method for wireless communication by a user equipment (UE). The method generally includes: sensing interference in a channel for multiple time intervals in a time sequence until no interference is found in one of the multiple time intervals, or no interference is found for all multiple time intervals, and the multiple time intervals form a time window. In some aspects, the method includes: when no interference is found for one of the multiple time intervals, sending a synchronization signal (SS) in one of the multiple time intervals. In some aspects, the method includes: when interference is found for all multiple time intervals, avoiding sending the SS in the time window.

[0017] Certain aspects of the subject matter described in the present disclosure may be implemented in a user equipment (UE) configured for wireless communication. The apparatus generally includes a processor and a memory coupled to the processor. In some examples, the processor and the memory may be configured to sense interference in a channel for multiple time intervals in chronological order until no interference is found for one of the multiple time intervals or no interference is found for all multiple time intervals. In some examples, when no interference is found for one of the multiple time intervals, the processor and the memory may be configured to send a synchronization signal (SS) in one of the multiple time intervals. In some examples, when interference is found for all multiple time intervals, the processor and the memory may be configured to avoid sending the SS in a time window.

[0018] Certain aspects of the subject matter described in the present disclosure may be implemented in an apparatus configured for wireless communication. In some examples, the apparatus may include: a unit for sensing interference in a channel for multiple time intervals in a time sequence until no interference is found for one of the multiple time intervals or no interference is found for all multiple time intervals, and the multiple time periods form a time window. In some examples, the apparatus may include: a unit for sending a synchronization signal (SS) in one of the multiple time intervals when no interference is found for one of the multiple time intervals. In some examples, the apparatus may include: a unit for avoiding sending the SS in the time window when interference is found for all multiple time intervals.

[0019] Certain aspects of the subject matter described in the present disclosure may be implemented in a non-transitory computer-readable storage medium having instructions stored thereon for performing a method for wireless communication. In some examples, the method includes sensing interference in a channel for a plurality of time intervals in chronological order until no interference is found for one of the plurality of time intervals or interference is found for all of the plurality of time intervals, the plurality of time intervals forming a time window. In some examples, when no interference is found for one of the plurality of time intervals, the method includes sending a synchronization signal (SS) in one of the plurality of time intervals. In some examples, when interference is found for all of the plurality of time intervals, the method includes avoiding sending the SS in the time window.

[0020] To achieve the aforementioned and related purposes, one or more aspects include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of one or more aspects. However, these features are only indicative of some of the various ways in which the principles of the various aspects can be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A more specific description briefly outlined above may be provided by reference to some of the various aspects shown in the accompanying drawings so that the manner in which the above-mentioned features of the present disclosure are understood in detail. It should be noted, however, that the accompanying drawings illustrate only certain typical aspects of the present disclosure and are therefore not to be considered limiting of its scope, as the specification may recognize other equally effective aspects.

[0022] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0023] Figure 2is a block diagram conceptually illustrating designs of an exemplary base station (BS) and user equipment (UE) in accordance with certain aspects of the present disclosure.

[0024] Figure 3 is a diagram conceptually illustrating an example of a first UE communicating with one or more other UEs according to various aspects of the present disclosure.

[0025] Figure 4 is a diagram illustrating an example frame format in accordance with certain aspects of the present disclosure.

[0026] Figure 5 is a diagram conceptually illustrating an exemplary cellular vehicle-to-everything (CV2X) network in accordance with various aspects of the present disclosure.

[0027] Figure 6 is a block diagram illustrating example time slots in a frequency channel in accordance with certain aspects of the present disclosure.

[0028] Figure 7 is a block diagram illustrating example time slots in a frequency channel in accordance with certain aspects of the present disclosure.

[0029] Figure 8 is a block diagram illustrating example time slots in a frequency channel in accordance with certain aspects of the present disclosure.

[0030] Fig. 9 is a flow chart illustrating example operations for wireless communications in accordance with certain aspects of the present disclosure.

[0031] Fig.10 According to aspects of the present disclosure, a communication device is shown that may include various components configured to perform operations for the techniques disclosed herein.

[0032] Fig.11 is a flow chart illustrating example operations for wireless communications in accordance with certain aspects of the present disclosure.

[0033] Fig.12 A communications device is shown that may include various components configured to perform operations for the techniques disclosed herein in accordance with various aspects of the present disclosure.

[0034] Fig.13 is a flow chart illustrating example operations for wireless communications in accordance with certain aspects of the present disclosure.

[0035] Fig.14 A communications device is shown that may include various components configured to perform operations for the techniques disclosed herein in accordance with various aspects of the present disclosure.

[0036] 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 utilized on other aspects without specific recitation. DETAILED DESCRIPTION

[0037] Various aspects of the present disclosure provide apparatus, methods, processing systems, and computer-readable media for synchronization between wireless communication devices (e.g., user equipment, base stations, etc.). In some aspects, the techniques are applicable to synchronization between wireless communication devices operating in an unlicensed spectrum. In some aspects, the techniques are applicable to synchronization between wireless communication devices communicating via a sidelink (e.g., in a vehicle-to-everything (V2X) network). It should be noted that although certain aspects are described for sidelink communications in an unlicensed spectrum, these aspects may be applicable to other suitable wireless communication networks and / or scenarios.

[0038] In certain aspects, the following disclosure relates to techniques for communicating synchronization signaling between wireless communication devices. Wireless communication between devices may require synchronization of signaling between devices. For example, a device may periodically broadcast synchronization signaling, which other devices may use to find, synchronize to, and identify other devices. However, broadcast synchronization signaling may cause interference with other signals transmitted over the same frequency channel.

[0039] Thus, in some examples, a wireless communication device may be configured to perform a listen-before-talk (LBT) channel sensing process prior to broadcasting a synchronization signal in order to first determine whether a frequency channel is subject to excessive interference from other signaling. In certain aspects, a wireless communication device may receive information (e.g., from another wireless communication device, such as a base station (BS), a core network (CN) node, or a user equipment (UE)) about the location and duration (e.g., the duration within a frame including multiple time slots) of a time window for sending a synchronization signal. The information may indicate a starting point of the window (e.g., an offset from the starting point of the frame, e.g., in units of one or more of a frame index and a time slot index, or other suitable identifiers / metrics), a periodic interval of the window, a transmission time interval (TTI) of the window, etc.). The wireless communication device may then perform LBT channel sensing immediately prior to the starting point of the window, and in some cases, once or more within the window, to sense the amount of interference on the frequency channel before and / or during the window, such as Figure 6-8 This provides the wireless communication device with the ability to opportunistically broadcast a synchronization signal during portions of a window where little or no interference is detected.

[0040] In certain aspects, LBT channel sensing is performed to determine whether there is an interference signal on the frequency channel on which the wireless communication device is to send a synchronization signal. In one example, the wireless communication device performs LBT channel sensing immediately before the first time slot of the window to determine whether there is an interference signal on the frequency channel. If the frequency channel is idle, the wireless communication device can send a synchronization signal on the first time slot in the window. If interference is detected on the frequency channel, the wireless communication device can perform LBT channel sensing again just before the second time slot of the window. The wireless communication device can continue to perform LBT channel sensing in the time order of the time slots in the window until no interference is detected.

[0041] If the frequency channel is determined to be idle before the transmission of the synchronization signal, the risk of collision or path loss is reduced because the idle channel indicates that no other signals on the frequency channel interfere with the synchronization signal. In addition, by establishing a window with multiple time slots for transmitting synchronization signals, the possibility of encountering idle periods on the frequency channel is increased. In an example in which a wireless communication device sends a synchronization signal through a frequency channel in an unlicensed spectrum, the technology described herein provides a method of communication consistent with regulations for the reasonable use of unlicensed spectrum (e.g., by not overcrowding frequency channels with signaling that may interfere with other devices). By making communication practices consistent with fair use regulations, these communications can be operated on unlicensed spectrum. Therefore, due to the scarcity of licensed spectrum, the transmission of synchronization signaling, etc. can be migrated to unlicensed spectrum.

[0042] The techniques discussed herein allow synchronization of devices communicating in an unlicensed band without causing interference to other devices operating in the unlicensed band, thereby enhancing device coexistence. In addition, the techniques herein allow such synchronization between devices when satellite-based synchronization techniques are not available, thereby enhancing access to the unlicensed band / medium. The techniques also take into account the potential unavailability of the unlicensed band due to the communication of other devices (e.g., by using LBT and the time windows for sending synchronization signals discussed herein).

[0043] Thus, the techniques herein improve the reliability of the synchronization process in unlicensed spectrum, making it more likely that a synchronization signal will be sent when expected and correctly decoded. Thus, these techniques can help improve latency by reducing the time a device must wait to achieve synchronization. These techniques further improve data decoding reliability by allowing devices to synchronize more quickly and therefore be able to decode transmissions.

[0044] For example, these techniques may be used in sidelink communications between wireless communication devices. In other examples, the wireless communication devices may include cellular vehicle-to-everything (CV2X) devices.

[0045] The following description provides examples of techniques for synchronization between wireless communication devices and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made in the functions and arrangements of the elements discussed without departing from the scope of the present disclosure. Individual examples may omit, replace, or add individual processes or components as appropriate. For example, the described method may be performed in an order different from the order described, and individual steps may be added, omitted, or combined. In addition, the features described with respect to some examples may be combined in some other examples. For example, using any number of aspects set forth herein, a device may be implemented or a method may be practiced. In addition, the scope of the present disclosure is intended to cover such devices or methods practiced using other structures, functions, or structures and functions other than or different from the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of the claims. The word "exemplary" used herein means "used as an example, instance, or illustration". Any aspect described as "exemplary" herein is not necessarily to be interpreted as superior to other aspects.

[0046] Generally, 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, frequency channel, tone, subband, etc. Each frequency may support a single RAT in a given geographic area to avoid interference between wireless networks with different RATs.

[0047] The techniques described herein can 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 to other communication systems based on generations.

[0048] NR access can support various wireless communication services, such as enhanced mobile broadband (eMBB) for broadband (e.g., 80 megahertz (MHz) or higher), millimeter wave (mmW) for high carrier frequencies (e.g., 25 gigahertz (GHz) or higher), massive machine type communication MTC (mMTC) for non-backward compatible MTC technology, and / or mission critical 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. NR supports beamforming and can dynamically configure beam directions. MIMO transmission with precoding can also be supported. The MIMO configuration in DL can support up to 8 transmit antennas, and multi-layer DL transmission up to 8 streams and up to 2 streams per UE. Multi-layer transmission of up to 2 streams per UE can be supported. Aggregation of multiple cells can be supported with up to 8 serving cells.

[0049] Figure 1 An exemplary wireless communication network 100 is shown 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 , the wireless communication network 100 may communicate with a core network 132. The core network 132 may communicate with one or more base stations (BSs) 110 and / or user equipments (UEs) 120 in the wireless communication network 100 via one or more interfaces.

[0050] like Figure 1 As shown in , the wireless communication network 100 may include several BSs 110a-z (each BS is also referred to herein individually as BS 110 or collectively as BSs 110) and other network entities. BS 110 may provide communication coverage for a specific geographic area (sometimes referred to as a "cell"), which may be stationary or may move depending on the location of the mobile BS 110. In some examples, BS 110 may be interconnected to each other and / or to one or more other BSs or network nodes (not shown) in the wireless communication network 100 through various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.) using any suitable transport network. Figure 1In the example shown, 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 be coupled to a set of BSs 110 and provide coordination and control (e.g., via a backhaul) for these BSs 110.

[0051] The BS 110 communicates with UEs 120a-y (each UE is also referred to herein individually as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120d, 120x, 120y, etc.) may be dispersed throughout the wireless communication network 100, and each UE 120 may be fixed or mobile. In one example, a quadcopter, a drone, or any other unmanned aerial vehicle (UAV) or a remotely piloted aerial system (RPAS) 120d may be configured to function as a UE. The wireless communication network 100 may also include a relay station (e.g., a relay station 110r), also referred to as a relay station, etc., which 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 relays transmissions between UEs 120 to facilitate communication between devices.

[0052] 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 base stations. For example, UE 120a can initiate sidelink communications with UE 120b without relying on a direct connection with a base station (e.g., base station 110a) (e.g., if UE 120b is located outside of the range of cell 102a). Figure 1 Any UE shown in can be used as a scheduling entity or a master sidelink device, while other UEs can be used as slave entities or non-master (e.g., auxiliary) sidelink devices. In addition, the UE can be configured to send synchronization signaling for the sidelink, as described throughout the present disclosure. Thus, one or more UEs can be used as a scheduling entity in a device-to-device (D2D), point-to-point (P2P), or vehicle-to-vehicle (V2V) network, and / or a mesh network to initiate and / or schedule synchronization signaling.

[0053] According to certain aspects, base station 110 and UE 120 may be configured to transmit synchronization signals over a wireless interface, for example, in one or more unlicensed frequency bands. Figure 1As shown in , BS 110a includes a listen-before-talk (LBT) module 140. LBT module 140 can be configured to sense interference in a channel for multiple time intervals in a time sequence until no interference is found for one of the multiple time intervals or no interference is found for all of the multiple time intervals, the multiple time intervals forming a time window. In some examples, the time window can provide a timing resource for sending a synchronization signal (SS).

[0054] According to aspects of the present disclosure, the LBT module 140 may also be configured to send SS in one of the multiple time intervals when no interference is found for one of the multiple time intervals, and avoid sending SS in the time window when interference is found for all of the multiple time intervals.

[0055] like Figure 1 As shown in , UE 120a includes LBT module 140. Similar to BS 110a, LBT module 140 of UE 120 can be configured to sense interference in a channel for multiple time intervals in a time sequence until no interference is found for one of the multiple time intervals or interference is found for all of the multiple time intervals, and the multiple time intervals form a time window. In some examples, the time window can provide a timing resource for sending a synchronization signal (SS).

[0056] According to aspects of the present disclosure, the LBT module 140 may also be configured to send SS in one of the multiple time intervals when no interference is found for one of the multiple time intervals, and avoid sending SS in the time window when interference is found for all of the multiple time intervals.

[0057] In certain aspects, the LBT module 140 may be configured to sense interference in a frequency channel in each of a plurality of time intervals (e.g., a plurality of time slots) in a temporal order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window for sending a synchronization signal (SS). The LBT module 140 may also be configured to sense interference above a threshold in a first portion (e.g., less than all symbols in the time slot) of a time interval in the plurality of time intervals. The LBT module may also be configured to sense interference below a threshold in a second portion of a time interval in the plurality of time intervals, the second portion occurring later in time than the first portion. The LBT module 140 may also be configured to send one of a reserved signal corresponding to the second portion or a portion of the SS in the second portion of a time interval in the plurality of time intervals.

[0058] In certain aspects, the LBT module 140 may be configured to transmit a size of a time window, wherein the time window includes a plurality of time intervals, the size of the time window being based at least in part on the number of previous time intervals in which interference was sensed to be above a threshold. The LBT module 140 may also be configured to sense interference in the channel in each of the plurality of time intervals in a chronological order until interference is sensed to be below a threshold for one of the plurality of time intervals, or interference is sensed to be above a threshold for all of the plurality of time intervals. The LBT module 140 may also be configured to send a synchronization signal (SS) in one of the plurality of time intervals when interference is sensed to be below a threshold for one of the plurality of time intervals. The LBT module 140 may also be configured to avoid sending the SS in the time window when interference is sensed to be above a threshold for all of the plurality of time intervals.

[0059] Figure 2 BS 110a and UE 120a (eg, Figure 1 1 , an exemplary component 200 of a wireless communication network 100 of the present invention may be used to implement various aspects of the present disclosure.

[0060] At BS 110a, transmit processor 220 may receive data from data source 212 and control information from controller / processor 240. Control information may be for a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH), a physical downlink control channel (PDCCH), a group common (GC) PDCCH, etc. Data may be for a physical downlink shared channel (PDSCH), etc. A medium access control (MAC)-control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. A MAC-CE may be carried in a shared channel, such as a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel (PSSCH).

[0061] The processor 220 may process (e.g., encode and symbol map) data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols, for example, for a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a channel state information reference signal (CSI-RS). The 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 (if applicable), and may provide an output symbol stream to modulators (MODs) 232a-232t. Each modulator 232 may process a corresponding 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 up-convert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 232a-232t may be sent via antennas 234a-234t, respectively.

[0062] At UE 120a, antennas 252a-252r can receive downlink signals from BS 110a and can provide received signals to demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator 254 can condition (e.g., filter, amplify, downconvert, and digitize) a corresponding received signal to obtain input samples. Each demodulator can further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 256 can obtain received symbols from all demodulators 254a-254r, perform MIMO detection on the received symbols (if applicable), and provide detected symbols. Receive processor 258 can process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 120a to data sink 260, and provide decoded control information to controller / processor 280.

[0063] On the uplink, at the UE 120a, a transmit processor 264 may receive and process data from a data source 262 (e.g., for a physical uplink shared channel (PUSCH)) and control information from a controller / processor 280 (e.g., for a physical uplink control channel (PUCCH)). The transmit processor 264 may also generate reference symbols for reference signals (e.g., for 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 a modulator in a transceiver 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the BS 110a. At the BS 110a, the uplink signal from the UE 120a may be received by the antenna 234, processed by the modulator 232, detected by the MIMO detector 236 (if applicable), and further processed by the receive processor to obtain decoded data and control information transmitted by the UE 120a. The receive processor 238 may provide decoded data to a data sink 239 and decoded control information to a controller / processor 240 .

[0064] Memories 242 and 282 may store data and program codes for BS 110a and UE 120a, respectively.A scheduler 244 may schedule UEs for data transmission on the downlink and / or uplink.

[0065] The antenna 252, processors 266, 258, 264, and / or controller / processor 280 of the UE 120a, and / or the antenna 234, processors 220, 230, 238, and / or controller / processor 240 of the BS 110a may be used to perform the various techniques and methods described herein. Figure 2 As shown in the figure, the controller / processor 240 of BS 110a has an LBT module 140, which can be configured to sense interference in the channel for multiple time intervals in a time sequence until no interference is found for one time interval among the multiple time intervals or no interference is found for all the multiple time intervals, and the multiple time intervals form a time window for sending a synchronization signal (SS).

[0066] According to aspects of the present disclosure, the LBT module 140 may also be configured to send SS in one of the multiple time intervals when no interference is found for one of the multiple time intervals, and avoid sending SS in the time window when interference is found for all of the multiple time intervals.

[0067] In some aspects, the LBT module 140 may be configured to sense interference in a frequency channel in each of a plurality of time intervals (e.g., a plurality of time slots) in a time order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window. In some examples, the time window may provide a timing resource for sending a synchronization signal (SS). The LBT module 140 may also be configured to sense interference above a threshold in a first portion of a time interval in the plurality of time intervals (e.g., less than all symbols in the time slot). The LBT module may also be configured to sense interference below a threshold in a second portion of a time interval in the plurality of time intervals, the second portion occurring later in time than the first portion. The LBT module 140 may also be configured to send one of a reserved signal or a portion of the SS corresponding to the second portion in the second portion of a time interval in the plurality of time intervals.

[0068] In certain aspects, the LBT module 140 may be configured to transmit a size of a time window, wherein the time window includes a plurality of time intervals, the size of the time window being based at least in part on the number of previous time intervals during which interference was sensed to be above a threshold. The LBT module 140 may also be configured to sense interference in the channel in each of the plurality of time intervals in a chronological order until interference is sensed to be below a threshold for one of the plurality of time intervals or interference is sensed to be above a threshold for all of the plurality of time intervals. The LBT module 140 may also be configured to send a synchronization signal (SS) in one of the plurality of time intervals when interference is sensed to be below a threshold for one of the plurality of time intervals. The LBT module 140 may also be configured to avoid sending the SS in the time window when interference is sensed to be above a threshold for all of the plurality of time intervals.

[0069] like Figure 2 As shown in , the controller / processor 280 of UE 120a also has an LBT module 140, which can be configured to: sense interference in the channel for multiple time intervals in time sequence until no interference is found for one of the multiple time intervals or interference is found for all multiple time intervals, and the multiple time intervals form a time window. In some examples, the time window can provide a timing resource for sending a synchronization signal (SS).

[0070] According to aspects of the present disclosure, the LBT module 140 may also be configured to send the SS in one of the multiple time intervals when no interference is found for one of the multiple time intervals, and avoid sending the SS in the time window when interference is found for all of the multiple time intervals. Although shown on the controller / processor, other components of the UE 120a and the BS 110a may be used to perform the operations described herein.

[0071] NR can utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. NR can support half-duplex operation using time division duplex (TDD). OFDM and single carrier frequency division multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones, binary, etc. Each subcarrier can be modulated with data. Modulation symbols can be sent using OFDM in the frequency domain and using SC-FDM in the time domain. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The minimum resource allocation, called a 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 basic subcarrier spacing (SCS) of 15 kilohertz (kHz), and other SCSs (e.g., 30kHz, 60kHz, 120kHz, 240kHz, etc.) can be defined for the basic SCS.

[0072] Figure 3 302a and one or more second UEs 302b (collectively referred to as "second UEs 302b") are conceptually illustrated as sidelink communications between a first UE 302a and one or more second UEs 302b. In various examples, any one of the first UE 302a and the second UE 302b may correspond to a UE (e.g., Figure 1 120a, UE 120b or UE 120c in the wireless communication network 100) or other suitable nodes in the wireless communication network 100. Although not shown in the figure, it is contemplated that one or more second UEs 302b may alternatively be one or more base stations (e.g., Figure 1 BS 110a).

[0073] In some examples, the first UE 302a and the second UE 302b can use the sidelink signal for direct D2D communication. D2D communication can use downlink / uplink wireless wide area network (WWAN) spectrum and / or unlicensed spectrum. D2D communication can use one or more sidelink channels on these spectrums, such as physical sidelink broadcast channel (PSBCH), physical sidelink discovery channel (PSDCH), physical sidelink shared channel (PSSCH) and physical sidelink control channel (PSCCH). D2D communication can be through a variety of wireless D2D communication systems, such as FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

[0074] The sidelink signals may include sidelink data 306 (i.e., sidelink traffic) and sidelink control information 308. In general, 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 certain aspects, the data channel includes the PSSCH, and the control channel includes the PSCCH and / or a physical sidelink feedback channel (PSFCH).

[0075] 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 or STS may provide a UE 302 (e.g., 302a, 302b) with a request duration to keep the sidelink channel available for sidelink signals; and the DRS may be provided to the UE 302 to indicate (e.g., for a requested duration) the availability of the sidelink channel. Thus, the first UE 302a and the second UE 302b may negotiate the availability and use of the sidelink channel resources prior to communication of the sidelink data 306 information.

[0076] In some configurations, any one or more of the first UE 302a or the second UE 302b may periodically / aperiodically send or broadcast sidelink synchronization signaling to increase the chance 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 send a sidelink synchronization signal in one or more time slots in a specific time window. In some examples, the UE is pre-configured with information indicating the position and duration of the time window in the frame (e.g., the time slot and quantity in the frame). In certain aspects, the UE may be configured with the position and duration of the time window via messaging between UEs or messaging received from a BS (e.g., RRC signaling).

[0077] Figure 3 The channels or carriers shown are not necessarily all channels or carriers that may be used between the first UE 302a and the second UE 302b in sidelink communications, and one of ordinary skill in the art will recognize that other channels or carriers (e.g., other data, control, and feedback channels) may be used in addition to those shown.

[0078] Figure 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 a subcarrier spacing (SCS). NR may support a basic SCS of 15 kHz, and other SCSs may be defined for the basic SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.). Figure 4 In the example shown, the SCS is 120kHz. Figure 4 As shown, subframe 404 (subframe 0) includes 8 time slots (time slots 0, 1, ..., 7) with a duration of 0.125 ms. Symbol and time slot lengths vary as the subcarrier spacing varies. Depending on the SCS, each time slot may include a different number of symbol (e.g., OFDM symbol) periods (e.g., 7 or 14 symbols). Figure 4 For the illustrated 120 kHz SCS, each of slots 406 (slot 0) and slot 408 (slot 1) includes 14 symbol periods (with slots indexed 0, 1, ..., 13) having a duration of 0.25 ms.

[0079] In the sidelink, a sidelink synchronization signal block (S-SSB) is transmitted, referred to as an SS block or SSB. The SSB may include a primary SS (PSS), a secondary SS (SSS), and / or a dual-symbol physical sidelink broadcast channel (PSBCH). In some examples, the SSB may be transmitted up to 64 times with up to 64 different beam directions. Up to 64 transmissions of the SSB are referred to as an SS burst set. The SSBs in one 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.

[0080] exist Figure 4 In the example shown, in subframe 404, SSB is transmitted in each of a plurality of time slots (time slots 0, 1, ..., 7). Figure 4In the example shown, in time slot 406 (time slot 0), SSB 410 is sent in symbols 4, 5, 6, 7, and SSB 412 is sent in symbols 8, 9, 10, 11, while in time slot 408 (time slot 1), SSB 414 is sent in symbols 2, 3, 4, 5, and SSB 416 is sent in symbols 6, 7, 8, 9, and so on. SSBs may include a primary SS (PSS), a secondary SS (SSS), and a two-symbol physical sidelink broadcast channel (PSBCH). The UE may use the PSS and SSS 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 PBSCH carries some basic system information, such as system bandwidth, timing information within a radio frame, SS burst set period, system frame number, etc. The SSBs may be organized into SS bursts to support beam scanning. Other system information, such as remaining minimum system information (RMSI), system information blocks (SIBs) and other system information (OSI), may be sent on a physical sidelink shared channel (PSSCH) in certain subframes.

[0081] Cellular vehicle-to-everything (CV2X) communications (e.g., in NR or LTE) are typically synchronous systems, as transmissions are usually based on Figure 4 The time and frequency resources shown are aligned. The allocation of frames, subframes, time slots, etc. is provided by the network protocols and rules applied to wireless communications in the licensed spectrum. For example, LTE-CV2X and NR-CV2X follow similar principles to establish time synchronization when operating in the licensed spectrum, including: (i) using the Global Navigation Satellite System (GNSS) as a common time reference (e.g., the current 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 the UE and the BS are scheduled to avoid conflicts.

[0082] However, due to the scarcity of licensed spectrum (e.g., overcrowding), certain aspects of wireless communications (e.g., CV2X communications) may not operate only in the licensed spectrum. Therefore, CV2X communications may operate in frequency bands of unlicensed spectrum. Therefore, in some examples, GNSS-based synchronization between CV2X devices (e.g., UE and / or BS) can be applied to the unlicensed spectrum. In some aspects, GNSS-based synchronization between CV2X devices can be achieved without signaling overhead (e.g., no synchronization signaling). However, if GNSS-based synchronization is not available or desired due to reliability issues, synchronization between CV2X devices is preferably established via periodic in-band broadcast signaling of synchronization signals.

[0083] However, currently there is no in-band signaling procedure for CV2X operation in unlicensed spectrum. Therefore, a procedure for establishing synchronization between CV2X devices operating in unlicensed spectrum that is applicable to both LTE and NR is desired.

[0084] Example Techniques for Device Synchronization in Unlicensed Bands

[0085] Various aspects of the present disclosure provide synchronization between wireless communication devices (e.g., CV2X devices in unlicensed spectrum), and such as without GNSS assistance. In some aspects, these techniques allow one or more devices to send synchronization signals while reducing or eliminating signal loss caused by interference from other signals originating from non-CV2X devices using the same spectrum. In some aspects, these techniques use, for example, a listen-before-talk (LBT) channel sensing mechanism that provides a method that complies with regulations for the reasonable use of unlicensed spectrum and does not negatively affect transmissions from other devices. As described below, LBT channel sensing is configured to first identify whether a channel is idle before sending a synchronization signal. This reduces or eliminates signal loss caused by signal interference or conflict on the same frequency band. In some aspects, multiple synchronization signals and partial synchronization signals can be sent during a time window for communication of synchronization signals, which increases the chance of the signal being detected by a receiver, and when two or more CV2X devices send the same synchronization signal at the same time, more effective transmission diversity is generated.

[0086] Figure 5 is a schematic diagram of an example network 500 illustrating multiple CV2X devices operating in an unlicensed spectrum. In the example shown, seven CV2X devices (e.g., a first CV2X device 502a, a second CV2X device 502b, a third CV2X device 502c, a fourth CV2X device 502d, a fifth CV2X device 502e, a sixth CV2X device 502f, and a seventh CV2X device 502g) may operate in an unlicensed spectrum with other non-CV2X devices (e.g., non-CV2X devices 504a-c - collectively referred to as non-CV2X devices 504). In some examples, the first CV2X device 502a, the sixth CV2X device 502f, and the third CV2X device 502c may be part of a fleet. Although the examples provided illustrate six automotive CV2X devices and drone or other aerial vehicle CV2X devices in a traffic environment, it will be appreciated that the CV2X devices and environments may be extended beyond these and include other wireless communication devices and environments. For example, the CV2X devices 502 may include a UE (e.g., Figure 1The UE 120 in the vehicle and / or a roadside unit (RSU) operated by a highway agency, and may be a device implemented on a motorcycle or a device carried by a user (e.g., a pedestrian, a cyclist, etc.), or may be implemented on another aircraft (e.g., a helicopter).

[0087] The CV2X device 502 may include a UE (eg, Figure 1 The UE 120 of the present invention may be a device implemented on a motorcycle or a device carried by a user (e.g., a pedestrian, a cyclist, etc.), or a device implemented as a roadside unit. Here, as will be described in further detail below, a subset of CV2X devices (e.g., the first CV2X device 502a) may perform an LBT process for a given CV2X window.

[0088] In certain aspects, if multiple CV2X devices 502 are 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 a global navigation satellite system (GNSS) signal (i.e., all CV2X devices 502 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 using an internal clock of the CV2X device 502 and / or possibly following the same concepts and principles as the channel access process.

[0089] Figure 6 is a block diagram illustrating an example of transmission of a sidelink synchronization signal (e.g., a sidelink synchronization information block (S-SSB)) in a frequency channel (e.g., an unlicensed band). In this example, a CV2X device (e.g., Figure 5 The CV2X device 502a in FIG. 5 may be configured to transmit a synchronization signal (e.g., synchronization signals 606a-606c, collectively referred to as synchronization signals 606) during a time interval 604 (e.g., time slots) of a plurality of time intervals within a window of time (e.g., windows 602a-602c, collectively referred to as window 602). The synchronization signal 606 may be used by other CV2X devices 502 to synchronize with the timing of the CV2X device 502a transmitting the synchronization signal 606. The CV2X device 502a transmitting the synchronization signal may use GNSS as a common time reference to determine synchronization timing, generate its own time reference, and the like.

[0090] As shown, each time window 602 includes four time slots numbered 1 to 4. However, it is to be understood that the number of time slots recorded throughout the specification is an example and may be modified to include fewer or more time slots depending on the size of the window 602, the digital scheme, the frequency channel, or any other suitable metric. Each window 602 may occur periodically, as defined by an indication (e.g., a syncOffsetIndicator or any other suitable indication). The syncOffsetIndicator may define an offset from the start of the frame at which the window 602 begins, a periodic interval of the window 602 (e.g., every 160ms or less), a transmission time interval (TTI) of the window 602, and the like. In some examples, the CV2X device 502a is configured with one or more syncOffsetIndicators. In some examples, the CV2X device 502a is configured with one or more syncOffsetIndicators by another device (e.g., another CV2X device or BS 110a and / or CN 132) via radio resource control (RRC) signaling.

[0091] In certain aspects, the CV2X device 502a may be configured with multiple syncOffsetIndicators, wherein each syncOffset Indicator corresponds to a different offset, periodic interval, and / or TTI relative to another of the multiple synchOffsetIndicators. Thus, the starting point, time period, and / or duration of each window 602 associated with a syncOffsetIndicator may be different relative to other syncOffset Indicators. However, in some examples, each window 602 is separated from another window (e.g., each window associated with a syncOffsetIndicator may not overlap in time). For example, a window 602 associated with a first syncOffsetIndicator may not overlap in time with another window of a second syncOffsetIndicator. Thus, a synchronization signal sent by a first CV2X device within a first window associated with the first syncOffsetIndicator will not conflict with another synchronization signal sent by a second CV2X device within a second window associated with the second syncOffsetIndicator. As Figure 6As shown in FIG. 6 , syncOffsetIndicator-1 608a defines the starting point of the first window 602a, and each window 602 that occurs periodically thereafter. In addition, syncOffsetIndicator-2 608b defines the starting point of another window of another set of periodic windows (not shown). Therefore, the other window starts after the first window 602a, and the two windows do not overlap.

[0092] In certain aspects, the CV2X device 502a selects or is configured to use a syncOffsetIndicator associated with a window 602 that has a duration long enough to provide the CV2X device 502a with a high probability of having an idle time interval 604 for transmitting a synchronization signal 606, and / or is small enough so that the time interval 604 is available for non-CV2X devices 504 to communicate. That is, the CV2X device 502a may select or be configured to use the window 602 based on traffic load conditions (e.g., for CV2X and / or non-CV2X networks) measured by a device (e.g., the CV2X device 502a, a roadside unit, or the BS 110a). The measured traffic load conditions may include a channel busy ratio (CBR), a data traffic overhead (DTO), and any other suitable metric for measuring and indicating traffic load conditions. In some examples, the window 602 may only be used to transmit synchronization signals for synchronizing the CV2X devices 502. Thus, the CV2X device 502a may also be configured to use a syncOffsetIndicator associated with a window 602 that is small enough to prevent the CV2X device 502a and any other CV2X device 502 from transmitting data through the window 602, but long enough to transmit synchronization signals. This provides the CV2X device 502a with the opportunity to determine an appropriate time window length, period, digital scheme, etc. based on environmental conditions to allow other non-CV2X devices 504 an appropriate amount of time for non-CV2X communications on the same frequency channel.

[0093] Prior to each window 602, the CV2X device 502a may perform a listen-before-talk (LBT) 610 channel sensing function to "listen" or sense other signals that may interfere with the transmission of the synchronization signal of the CV2X device 502a. The LBT 610 may last for any suitable time, such as 25us. As shown, the CV2X device 502a performs a first LBT 610a just before the first time slot of the first window 602a. Here, the CV2X device 502a senses interference on the frequency channel for the entire duration of the first LBT 610a. Due to the interference, the CV2X device 502a avoids transmitting the synchronization signal in the first time slot. Due to the interference detected in the first time slot, the CV2X device 502a performs a second LBT 610b during the first time slot and just before the second time slot of the first window 602a. If interference is detected again during the entire duration of the second LBT 610b, the CV2X device 502a performs a third LBT 610c during the second time slot just before the third time slot of the first window 602a. The CV2X device 502a may perform LBT for each time slot in the first window 602a in a time sequence until no interference is sensed. Thus, a fourth LBT 610d is performed during the third time slot of the first window 602a, and no interference is detected on the frequency channel. If no interference is sensed just before the fourth time slot of the first window 602a, the CV2X device 502a transmits a first synchronization signal 606a in the fourth time slot.

[0094] Thus, for each window 602, the CV2X device 502a may perform an LBT 610 to sense channel interference just before one or more time slots within the window 602. In certain aspects, after the CV2X device 502a transmits a synchronization signal in a time slot, the CV2X device 502a may not perform any additional LBT 610 for the window 602 that includes the time slot, even if there are additional time slots in the window and there is no interference on the frequency channel. Thus, once the CV2X device 502a has transmitted a synchronization signal during a window 602, the CV2X device 502a may avoid transmitting additional synchronization signals in the remaining time slots of the same window 602. If interference is sensed during each LBT 610 performed in the window 602, the CV2X device 502a may avoid transmitting a synchronization signal during the window 602.

[0095] For example, during the second window 602b, the CV2X device 502a may perform the fifth LBT 610e just before the first time slot of the second window 602b. In this example, since the CV2X device 502a does not sense interference on the frequency band, the CV2X device 502a may send the second synchronization signal 606b during the first time slot of the second window 602b. During the third window 602c, the CV2X device 502a may perform the sixth LBT 610f just before the first time slot of the third window 602c. In this example, since the CV2X device 502a senses interference on the frequency band, the CV2X device 502a may avoid sending the synchronization signal 606. Then, the CV2X device 502b may perform the seventh LBT 610g just before the second time slot of the third window. If the CV2X device 502a does not detect any interference on the frequency band during the seventh LBT, the CV2X device 502a may then transmit a third synchronization signal 606c during the second time slot of the third window 602c.

[0096] In some examples, whether the frequency channel contains interference is determined based on an amount of power associated with one or more interfering signals measured on the frequency channel during the LBT 610. For example, if the measured amount of power is greater than a threshold, the CV2X device 502a may determine that interference exists on the frequency channel and may avoid sending the synchronization signal 606. On the other hand, if the measured amount of power is less than the threshold, the CV2X device 502a may determine that there is no interference on the frequency channel and may continue to send the synchronization signal 606 on the next time slot.

[0097] In some examples, the channel is a sidelink channel in an unlicensed spectrum, and the sidelink channel is used for vehicle-to-everything communication. In some examples, the CV2X device 502a is configured to send a synchronization signal 606, wherein the synchronization signal 606 includes an indication of one or more time slot numbers and a frame number corresponding to the time slot and frame in which the synchronization signal 606 is sent. In this way, another CV2X device 502a receiving the synchronization signal 606 can determine frame-level and time slot-level synchronization with the sending CV2X device 502a.

[0098] Although Figure 6 The example of FIG. 602 shows the transmission of the synchronization signal 606 during one time slot (e.g., the first available time slot) in each window, but it is understood that multiple time slots in a single window can be used to send synchronization signals, as described below. In particular, in some aspects, once no interference is found before the time slot of the window 602, the synchronization signal 606 can be sent in time sequence in the time slot and in one or more (e.g., all or a fixed number, etc.) remaining time slots (if any).

[0099] Figure 7 is a block diagram illustrating an example of transmission of a sidelink synchronization signal (e.g., a sidelink synchronization information block (S-SSB)) in a frequency channel (e.g., an unlicensed band). In this example, a CV2X device (e.g., Figure 5 The CV2X device 502a in FIG. 5 may be configured to transmit a plurality of synchronization signals (e.g., synchronization signals 706a-706e, collectively referred to as synchronization signals 706) during a plurality of time intervals 704 (e.g., time slots) within a window of time (e.g., windows 702a-702c, collectively referred to as window 702). For example, when no interference is found during the LBT 710 performed prior to the time slot, the CV2X device 502a may transmit the synchronization signals through the time slot and one or more subsequent time slots in the window. Figure 7 As shown, syncOffsetIndicator-1 708a defines the starting point of the first window 702a, and each window 702 that appears periodically thereafter. In addition, syncOffsetIndicator-2 708b defines the starting point of another window of another set of periodic windows (not shown). Therefore, the other window starts after the first window 702a, and the first window 702a is separated from the other windows (e.g., the two windows do not overlap).

[0100] Figure 7 Three windows 702 are included, each with four time slots 704. Before the start of the first window 702a, the CV2X device 502a performs a first LBT 710a and senses interference. Similarly, when the CV2X device 502a performs a second LBT 710b before the second time slot, and performs a third LBT 710c before the third time slot, the CV2X device 502a senses interference. However, when the CV2X device 502a performs an LBT 710d before the fourth time slot, no interference is detected. Therefore, the CV2X device 502a sends a synchronization signal 706a during the fourth time slot.

[0101] In the example shown, the CV2X device 502a also performs a fifth LBT 710e before the first time slot in the second window 702b. If no interference is sensed before the first time slot, the CV2X device 502a sends a second synchronization signal 706b in the first time slot. In addition, in this example, when no interference is sensed in a given time slot, when there are remaining time slots in the window, the CV2X device 502a sends the synchronization signal 706 in time sequence in one or more additional time slots (in this example, one additional time slot) after the given time slot. Therefore, the CV2X device 502a sends a third synchronization signal 706c in the second time slot of the second window 702b.

[0102] In this example, the CV2X device 502a performs the sixth LBT 710f before the first time slot of the third window 702c, but avoids sending the synchronization signal 706 due to interference on the frequency band. The CV2X device 502a then performs the seventh LBT 730g before the second time slot, and because no interference is sensed, the CV2X device 502a sends the fourth synchronization signal 706d during the second time slot, and sends the fifth synchronization signal 706e on the third time slot of the third window 702c.

[0103] In certain aspects, all CV2X devices 502 that are synchronized with each other but are not within network coverage and do not have GNSS available can simultaneously transmit the same synchronization signal 706 when all other CV2X devices transmit the synchronization signal 706 (e.g., in the same subframe or time slot corresponding to the same offset indicator value). If each of the CV2X devices 502 transmits the same synchronization signal 706 at the same time, this results in an effective increase in the received power of the synchronization signal 706 for a particular time interval, which increases the geographic area in which the synchronization signal 706 can be detected relative to the synchronization signal 706 being transmitted from only a single CV2X device. However, it should be noted that the CV2X device 502 can synchronize with other CV2X devices using the same techniques when the CV2X device 502 is within network coverage and / or has GNSS availability. For example, a CV2X device can synchronize with one or more other CV2X devices using a common synchronization source based on a synchronization signal transmitted by a synchronization reference device (e.g., CV2X device 502a).

[0104] Back to Figure 1 , the first UE 120a and the second UE 120c may simultaneously transmit the same synchronization signal 706. Due to the superposition of their signaling, the third UE 120b with increased power receives the synchronization signal 706 relative to the synchronization signal 706 transmitted from only one of the first UE 120a or the second UE 120c. Of course, in this example, it is assumed that the first UE 120a and the second UE 120c have established synchronization of communication, possibly by receiving synchronization signaling from another device (e.g., BS 110a) outside the range of the third UE 120b.

[0105] It should be noted that this power gain is very important in unlicensed spectrum because it will help reduce the signal loss of the synchronization signal 706 due to local interference. That is, the power gain may increase the probability that another CV2X device 502 detects the synchronization signal 706 even if the other CV2X device 502 encounters interference at its location. Therefore, in some examples, the CV2X device 502a that intends to send a synchronization signal can perform LBT channel sensing over multiple consecutive time slots 704 of the window 702.

[0106] As mentioned above Figure 6 and Figure 7 As described above, if the CV2X device 502 senses that the frequency channel is idle for the LBT duration that occurs just before the start of the time slot, the CV2X device 502 may send a synchronization signal on the time slot. However, in certain aspects, if the CV2X device 502 senses that the frequency channel is idle for the LBT duration that occurs within the time slot, the CV2X device 502 may send a partial synchronization signal on the remaining portion of the time slot. For example, the partial synchronization signal may be sent in any remaining complete OFDM symbol of the time slot or in the next symbol of the subsequent time slot.

[0107] In certain aspects, when performing LBT within a time slot, the CV2X device 502 may sense that the frequency channel becomes idle during the time slot, but when the determination is made, there may not be any complete OFDM symbols within the time slot. Therefore, the CV2X device 502 may determine that the next opportunity to begin transmitting a signal is during a portion of the OFDM symbol. In this case, the CV2X device 502 may transmit a "dummy" signal (e.g., a randomly generated sequence) during the remainder of the partial OFDM symbol to prevent the frequency channel from being captured by another device (e.g., a non-CV2X device 504).

[0108] For example, the CV2X device 502 may fill the remainder of a partial OFDM symbol by sending a dummy sequence and then immediately send a synchronization signal in a subsequent full time slot and / or OFDM symbol. That is, after sending the dummy sequence, the CV2X device 502 may send a partial synchronization signal on the next full OFDM symbol of the current time slot and an entire synchronization signal on the next full time slot. In one example, a CV2X device 502 with a 30kHz subcarrier spacing (SCS) has a time slot duration of 0.5ms, and if the CV2X device 502 uses a 25us LBT channel sensing measurement, the synchronization signal may be transmitted over two full time slots. This allows up to 1ms of channel occupancy time (COT) (e.g., the amount of time provided by the size of the window 702, or the amount of time remaining in the window 702).

[0109] In some aspects, the CV2X device 502 may increase the LBT duration by the duration of a portion of the OFDM symbol instead of sending a dummy signal to fill a portion of the OFDM symbol. In some aspects, when the CV2X device 502 sending the synchronization signal is out of the network and GNSS, the CV2X device 502 may send the synchronization signal in a partial time slot instead of a dummy signal. In some aspects, when the duration of 2 consecutive (full) time slots is within the COT allowed by the LBT duration requirement (e.g., when the channel is sensed to be idle for 25us, where 25us is the duration of the required idle time), the transmission of the synchronization signal is configured in the partial time slot.

[0110] Figure 8 is a block diagram illustrating an exemplary time slot, such as for transmitting synchronization signals (e.g., S-SSB) by multiple CV2X devices 502 in a frequency channel (e.g., an unlicensed band). Figure 8 A first synchronization signal 806a is shown being sent by a first CV2X device 502a, and a second synchronization signal 806b is shown being sent by a second CV2X device 502b on the same frequency channel and during the same time window 802. In some examples, the first synchronization signal 806a is the same signal as the second synchronization signal 806b. Also shown is an indication of synchronization signal power received on the frequency channel by a third device 502c when receiving the synchronization signals 806a and 806b sent by the first CV2X device 502a and the second CV2X device 502b.

[0111] In this example, the first CV2X device 502a and the second CV2X device 502b may perform LBT channel sensing before sending a synchronization signal. If the first CV2X device 502a is geographically separated from the second CV2X device 502b, the amount of interference activity on the frequency band sensed at each device may be different. As shown, local interference 812 to the first CV2X device 502a begins before the window 802 and continues to the end of the second time slot of the window 802. The first CV2X device 502b also begins performing LBT 810 before the start of the window 802 and immediately detects the local interference 812. Here, the first CV2X device 502a continuously performs LBT 810 through the first two time slots and into the third time slot of the window 802. Here, the LBT duration requirement 808 (e.g., 25us) can control how early before the start of the window 802, the first CV2X device 502b starts LBT 810. If the local interference 812 ends at the end of the second time slot of the window 802 , the first CV2X device 502a may continue to perform the LBT 810 once the local interference 812 ends to meet the LBT duration requirement 808 .

[0112] In this example, each time slot includes 14 OFDM symbols, wherein the third time slot symbol 814 is shown in an exploded view. Here, the LBT 810 ends within the third time slot of the window 802, leaving only a portion of the time slot. More specifically, the LBT 810 ends midway through the third OFDM symbol of the third time slot symbol 814. Although the first CV2X device 502a may transmit a portion of the synchronization signal corresponding to the remaining portion of the symbol, in this example, the first CV2X device 502a transmits a dummy signal over the remaining portion of the third OFDM symbol to avoid any other nearby devices from transmitting. At the beginning of the fourth OFDM signal, the first CV2X device 502a may begin transmitting a portion of the synchronization signal corresponding to the remaining portion of the third time slot of the window 802, and then transmit the synchronization signal over the entire fourth time slot. Therefore, the synchronization signaling 806a of the first CV2X device 502a includes signaling over a portion of the third time slot of the window 802 and the entire fourth time slot.

[0113] As previously described, the second CV2X device 502b may be geographically separated from the first CV2X device 502a and may therefore encounter different local interference (not shown). In this example, the second CV2X device 502b that is synchronized with the first CV2X device 502a (e.g., transmitting synchronization signals on the same window 802) may begin transmitting synchronization signals 806b in a portion of the second time slot and throughout the third time slot. As a result, the third CV2X device 502c receives synchronization signaling with relatively high power during the latter portion of the third time slot while the first CV2X device 502a and the second CV2X device 502b are transmitting simultaneously. As a result, the third CV2X device 502c may better detect / decode the synchronization signal because it is more robust to any local interference that the third CV2X device 502c may encounter.

[0114] Fig. 9 9 is a flow chart illustrating example operations 900 for wireless communication according to certain aspects of the present disclosure. For example, a BS (e.g., Figure 1 110a) in the wireless communication network 100 or by a UE or a CV2X device (e.g., Figure 1 Operation 900 is performed by a UE / CV2X device 120a) in the wireless communication network 100.

[0115] Operation 900 may be implemented as a processor on one or more processors (e.g., Figure 2 In addition, the sending and receiving of signals in operation 900 can be performed, for example, via one or more antennas (e.g., Figure 2In some aspects, the sending and / or receiving of signals may be achieved by obtaining and / or outputting signals via a bus interface of one or more processors (eg, controller / processor 240 / 280).

[0116] Operations 900 may begin at a first block 905 by sensing interference in a channel for a plurality of time intervals in time sequence until no interference is found for one of the plurality of time intervals or no interference is found for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0117] In certain aspects, when no interference is found for one of the plurality of time intervals, the operations 900 may continue at a second block 910 by sending a synchronization signal (SS) in one of the plurality of time intervals.

[0118] In certain aspects, when interference is found for all of the plurality of time intervals, operations 900 may continue at a third block 915 by refraining from transmitting the SS in the time window.

[0119] In some aspects, the channel comprises a sidelink in an unlicensed spectrum.

[0120] In certain aspects, the sidelink is used for vehicle-to-everything communications.

[0121] In certain aspects, the SS includes a slot number corresponding to a time interval among a plurality of time intervals and a frame number corresponding to the time window.

[0122] In some aspects, each time interval corresponds to a time slot.

[0123] In some aspects, the time windows occur periodically.

[0124] In certain aspects, operations 900 further include receiving signaling indicating a size of the time window.

[0125] In certain aspects, the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different sized time window.

[0126] In certain aspects, the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different time window, wherein the time window is separated from the different time windows.

[0127] In certain aspects, the operations 900 further include transmitting the SS in one or more time intervals in the plurality of time intervals later in time than the one time interval in the plurality of time intervals when no interference is found for the one time interval in the plurality of time intervals.

[0128] In some aspects, sensing interference in the channel for the time interval includes sensing interference in the channel for a time duration prior to a start of the time interval.

[0129] In some aspects, sensing interference in a channel includes: continuously sensing the channel within a time window, wherein interference is found in a first part of a time interval among multiple time intervals, wherein no interference is found in a second part of a time interval among the multiple time intervals that is later in time than the first part, and wherein sending SS in a time interval among the multiple time intervals includes: sending SS in a second part of a time interval among the multiple time intervals.

[0130] In certain aspects, the operations 900 further include transmitting the SS in one or more time intervals of the plurality of time intervals that are later in time than a time interval of the plurality of time intervals.

[0131] In some aspects, the channel is used for communication between multiple devices outside the range of network coverage.

[0132] In some aspects, the plurality of devices lack synchronization with the global navigation satellite system.

[0133] Fig.10 1. A communication device 1000 is shown, which may include various components (eg, corresponding to functional module components) configured to perform operations of the techniques disclosed herein, such as Fig. 9 The communication device 1000 includes a processing system 1002 coupled to a transceiver 1008 (e.g., a transmitter and / or a receiver). The transceiver 1008 is configured to send and receive signals for the communication device 1000, such as the various signals described herein, via an antenna 1010. The processing system 1002 may be configured to perform processing functions for the communication device 1000, including processing signals received and / or to be transmitted by the communication device 1000.

[0134] The processing system 1002 includes a processor 1004 coupled to a computer readable medium / memory 1012 via a bus 1006. In some aspects, the computer readable medium / memory 1012 is configured to store instructions (e.g., computer executable code) that, when executed by the processor 1004, cause the processor 1004 to perform Fig. 9The operations shown in , or other operations for performing the various techniques discussed herein for performing sidelink communications in an unlicensed band.

[0135] In certain aspects, the computer-readable medium / memory 1012 stores code 1034 for sensing interference in a channel for a plurality of time intervals in a time sequence until no interference is found for one of the plurality of time intervals or no interference is found for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0136] In certain aspects, the computer readable medium / memory 1012 stores code 1036 for sending a synchronization signal (SS) in one of the plurality of time intervals when no interference is found for the one of the plurality of time intervals.

[0137] In certain aspects, the computer-readable medium / memory 1012 stores code 1038 for avoiding transmitting the SS in a time window when interference is found for all of the plurality of time intervals.

[0138] In certain aspects, the processor 1004 has circuitry configured to implement code stored in the computer readable medium / memory 1012. The processor 1004 includes circuitry 1018 for sensing interference in the channel for a plurality of time intervals in time sequence until no interference is found for one of the plurality of time intervals or interference is found for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0139] In certain aspects, processor 1004 includes circuitry 1020 for sending a synchronization signal (SS) in one of the plurality of time intervals when no interference is found for the one of the plurality of time intervals.

[0140] In certain aspects, processor 1004 includes circuitry 1022 for avoiding sending the SS in the time window when interference is found for all of the plurality of time intervals.

[0141] Fig.11 1 is a flow diagram of example operations 1100 for wireless communications in accordance with certain aspects of the present disclosure. For example, operations 1100 may be performed by a BS (e.g., Figure 1 110a) in the wireless communication network 100 or by a UE or a CV2X device (e.g., Figure 1 The method is performed by a UE / CV2X device 120a) in the radio communication network 100.

[0142] Operation 1100 may be performed as an operation on one or more processors (e.g., Figure 2In addition, the sending and receiving of signals in operation 1100 can be achieved, for example, by one or more antennas (e.g., Figure 2 In some aspects, the sending and / or receiving of signals can be implemented via a bus interface of one or more processors (eg, controller / processor 240 / 280) to obtain and / or output signals.

[0143] Operation 1100 may begin at a first block 1105 by sensing interference in a channel for each of a plurality of time intervals in chronological order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0144] Operations 1100 may continue with performing a second block 1110 by sensing interference above a threshold value during a first portion of one of the plurality of time intervals.

[0145] Operations 1100 may continue with performing a third block 1115 by sensing that interference is below a threshold during a second portion of the plurality of time intervals, the second portion occurring later in time than the first portion.

[0146] Operations 1100 may continue with fourth block 1120 by transmitting, in the second portion of one of the plurality of time intervals, one of a reservation signal or a portion of a synchronization signal (SS) corresponding to the second portion.

[0147] In certain aspects, each of the plurality of time intervals includes a plurality of symbols, wherein a second portion of one of the plurality of time intervals is a portion of a first symbol of the corresponding plurality of symbols, wherein operation 1100 further includes sending a reservation signal on a remaining portion of the first symbol.

[0148] In certain aspects, sending the SS in a second portion of the plurality of time intervals includes sending the SS in a second symbol of the respective plurality of symbols, the second symbol occurring immediately in time after the first symbol.

[0149] In certain aspects, the size of the time window is a function of a previous time interval in which interference above a threshold was sensed.

[0150] In certain aspects, the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a time window of a different size.

[0151] Fig.121. A communication device 1200 is shown, which may include various components (eg, corresponding to functional module components) configured to perform operations of the techniques disclosed herein, such as Fig.11 The communication device 1200 includes a processing system 1202 coupled to a transceiver 1208 (e.g., a transmitter and / or a receiver). The transceiver 1208 is configured to send and receive signals for the communication device 1200 via an antenna 1210, such as the various signals described herein. The processing system 1202 can be configured to perform processing functions for the communication device 1200, including processing signals received and / or to be transmitted by the communication device 1200.

[0152] The processing system 1202 includes a processor 1204 coupled to a computer-readable medium / memory 1212 via a bus 1206. In some aspects, the computer-readable medium / memory 1212 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 1204, cause the processor 1204 to perform Fig.11 The operations shown in , or other operations for performing the various techniques discussed herein for performing sidelink communications in an unlicensed band.

[0153] In some aspects, the computer-readable medium / memory 1212 stores: code 1234 for sensing interference in a channel in each of a plurality of time intervals in a time sequence until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0154] In certain aspects, the computer readable medium / memory 1212 stores code 1236 for sensing interference above a threshold value during a first portion of one of a plurality of time intervals.

[0155] In some aspects, the computer readable medium / memory 1212 stores code 1238 for sensing interference below a threshold during a second portion of one of a plurality of time intervals, the second portion occurring later in time than the first portion.

[0156] In certain aspects, the computer readable medium / memory 1212 stores code 1240 for transmitting, in a second portion of the plurality of time intervals, one of the reservation signals or a portion of a synchronization signal (SS) corresponding to the second portion.

[0157] In certain aspects, the processor 1204 has circuitry configured to implement code stored in the computer readable medium / memory 1212. The processor 1204 includes circuitry 1218 for sensing interference in the channel in each of a plurality of time intervals in a temporal order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window.

[0158] In certain aspects, processor 1204 includes circuitry 1220 for sensing interference above a threshold value during a first portion of one of the plurality of time intervals.

[0159] In some aspects, the processor 1204 includes circuitry 1222 for sensing that interference is below a threshold during a second portion of one of the plurality of time intervals, the second portion occurring later in time than the first portion.

[0160] In some aspects, processor 1004 includes circuitry 1224 for transmitting, in the second portion of one of the plurality of time intervals, one of a reservation signal or a portion of a synchronization signal (SS) corresponding to the second portion.

[0161] Fig.13 13 is a flow chart illustrating example operations 1300 for wireless communication in accordance with certain aspects of the present disclosure. Figure 1 110a) in the wireless communication network 100 or by a UE or a CV2X device (e.g., Figure 1 Operation 1300 is performed by a UE / CV2X device 120a) in the wireless communication network 100.

[0162] can be used as a processor in one or more processors (e.g., Figure 2 Operation 1300 may be implemented by software components executed and running on the controller / processor 240 / 280 of the device. In addition, the operation 1300 may be implemented by, for example, one or more antennas (e.g., Figure 2 The antenna 234 / 252 of the controller 234 / 252 implements the transmission and reception of the signal in operation 1300. In some aspects, the transmission and / or reception of the signal can be implemented via a bus interface of one or more processors (e.g., controller / processor 240 / 280) to obtain and / or output the signal.

[0163] Operations 1300 may begin at a first block 1305 by communicating a size of a time window, wherein the time window includes a plurality of time intervals, the size of the time window being based at least in part on a number of previous time intervals in which interference above a threshold was sensed.

[0164] Operation 1300 may continue with second block 1310 by sensing interference in the channel in each of the plurality of time intervals in chronological order until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals.

[0165] Operations 1300 may continue with a third block 1315 by sending a synchronization signal (SS) in one of the plurality of time intervals when interference is sensed to be below a threshold for the one of the plurality of time intervals.

[0166] Operations 1300 may continue with fourth block 1320 by refraining from transmitting the SS in the time window when interference above the threshold is sensed for all of the plurality of time intervals.

[0167] Fig.14 A communication device 1400 is shown that may include various components (eg, corresponding to functional module unit components) configured to perform operations of the techniques disclosed herein, such as Fig.13 . The communication device 140 includes a processing system 1402 coupled to a transceiver 1408 (e.g., a transmitter and / or a receiver). The transceiver 1408 is configured to transmit and receive signals for the communication device 1400 via an antenna 1410, such as various signals as described herein. The processing system 1402 can be configured to perform processing functions for the communication device 1400, including processing signals received and / or transmitted by the communication device 1400.

[0168] The processing system 1402 includes a processor 1404 coupled to a computer readable medium / memory 1412 via a bus 1406. In some aspects, the computer readable medium / memory 1412 is configured to store instructions (e.g., computer executable code) that, when executed by the processor 1404, cause the processor 1404 to perform Fig.13 The operations shown in , or other operations for performing the various techniques discussed herein for performing sidelink communications in an unlicensed band.

[0169] In certain aspects, the computer-readable medium / memory 1412 stores code 1434 for communicating a size of a time window comprising a plurality of time intervals, the size of the time window being based at least in part on a number of previous time intervals in which interference above a threshold was sensed.

[0170] In certain aspects, the computer readable medium / memory 1412 stores code 1436 for sensing interference in a channel in each of a plurality of time intervals in a time sequence until the interference is sensed to be below a threshold for one of the plurality of time intervals or the interference is sensed to be above a threshold for all of the plurality of time intervals.

[0171] In certain aspects, the computer readable medium / memory 1412 stores code 1438 for sending a synchronization signal (SS) in one of the plurality of time intervals when interference below a threshold is sensed for one of the plurality of time intervals.

[0172] In certain aspects, the computer-readable medium / memory 1412 stores code 1440 for avoiding transmitting the SS in a time window when interference above a threshold is sensed for all of the plurality of time intervals.

[0173] In certain aspects, the processor 1404 has circuitry configured to implement code stored in the computer readable medium / memory 1412. The processor 1404 includes circuitry 1418 for communicating a size of a time window, wherein the time window includes a plurality of time intervals, the size of the time window being based at least in part on a number of previous time intervals in which interference above a threshold was sensed.

[0174] In some aspects, processor 1404 includes circuitry 1420 for sensing interference in a channel in each of a plurality of time intervals sequentially in time until interference is sensed to be below a threshold for one of the plurality of time intervals or is sensed to be above a threshold for all of the plurality of time intervals.

[0175] In certain aspects, the processor 1404 includes circuitry 1422 for sending a synchronization signal (SS) in one of the plurality of time intervals when interference below a threshold is sensed for one of the plurality of time intervals.

[0176] In certain aspects, processor 1404 includes circuitry 1424 for refraining from transmitting the SS in the time window when interference above a threshold is sensed for all of the plurality of time intervals.

[0177] Example aspects

[0178] Aspect 1: A device for wireless communication, comprising: a memory; and a processor coupled to the memory, wherein the processor and the memory are configured to: sense interference in a channel in each time interval of a plurality of time intervals in chronological order until the interference is sensed to be lower than a threshold for one time interval of the plurality of time intervals, or until the interference is sensed to be higher than a threshold for all of the plurality of time intervals, the plurality of time intervals forming a time window; sense that the interference will be higher than the threshold in a first part of the one time interval of the plurality of time intervals; sense that the interference will be lower than the threshold in a second part of the one time interval of the plurality of time intervals, the second part occurring later in time than the first part; and, in the second part of the one time interval of the plurality of time intervals, send one of a reservation signal or a part of a synchronization signal (SS) corresponding to the second part.

[0179] Aspect 2: An apparatus according to Aspect 1, wherein each of the multiple time intervals includes multiple symbols, wherein the second part of the one of the multiple time intervals is a part of the first symbol of the corresponding multiple symbols, and wherein the processor and the memory are also configured to send the reserved signal through the remaining part of the first symbol.

[0180] Aspect 3: A device according to any one of Aspect 1 and Aspect 2, wherein the processor and the memory are configured to: send the SS in the second part of the multiple time intervals, and are also configured to: send the SS in the second symbol of the corresponding multiple symbols, and the second symbol appears immediately after the first symbol in time.

[0181] Aspect 4: The apparatus according to any one of aspects 1-3, wherein the size of the time window is a function of the number of previous time intervals in which interference above a threshold was detected.

[0182] Aspect 5: The apparatus according to any one of aspects 1-4, wherein the processor and the memory are further configured to: receive signaling indicating a size of the time window.

[0183] Aspect 6: An apparatus according to any one of Aspects 1-5, wherein the start time of the time window is based on an offset indicator among a plurality of offset indicators, wherein each offset indicator among the plurality of offset indicators is associated with a time window of a different size.

[0184] Aspect 7: The apparatus according to any one of aspects 1-6, wherein a first time window associated with the first offset indicator is separate from a second time window associated with the second offset indicator.

[0185] Aspect 8: A device according to any one of Aspects 1-7, wherein the processor and the memory are configured to: send the SS in the second part of the one of the multiple time intervals when interference is sensed to be lower than the threshold for the one of the multiple time intervals, and are also configured to: send the SS in one or more time intervals in the multiple time intervals that are later in time than the one of the multiple time intervals.

[0186] Aspect 9: The device according to any one of Aspects 1-8, wherein the processor and the memory are configured to: sense interference in the channel for a time interval, and are also configured to: sense interference in the channel for a duration before the start of the time interval.

[0187] Aspect 10: The apparatus of any one of Aspects 1-9, wherein the channel comprises: a sidelink in an unlicensed spectrum, and wherein the sidelink is used for vehicle-to-everything communication.

[0188] Aspect 11: The apparatus according to any one of aspects 1-10, wherein the SS includes: a time slot number corresponding to the one time interval among the plurality of time intervals, and a frame number corresponding to the time window.

[0189] Aspect 12: The apparatus according to any one of aspects 1-11, wherein each time interval corresponds to a time slot.

[0190] Aspect 13: The apparatus according to any one of aspects 1-12, wherein the time window occurs periodically.

[0191] Aspect 14: The device according to any one of aspects 1-13, wherein the channel is used for communication between multiple devices outside the coverage of the network.

[0192] Aspect 15: The apparatus according to any one of aspects 1-14, wherein the plurality of devices lack synchronization with a global navigation satellite system.

[0193] Aspect 16: A device for wireless communication, comprising: a memory; and a processor coupled to the memory, the processor and the memory being configured to: transmit a size of a time window, wherein the time window includes multiple time intervals, and the size of the time window is based at least in part on the number of previous time intervals during which interference is sensed to be higher than a threshold; sense interference in a channel in each of the multiple time intervals in chronological order until the interference is sensed to be lower than the threshold for one of the multiple time intervals, or the interference is sensed to be higher than the threshold for all of the multiple time intervals; when interference is detected to be lower than the threshold for the one of the multiple time intervals, send a synchronization signal (SS) in the one of the multiple time intervals; and when interference is sensed to be higher than the threshold for all of the multiple time intervals, avoid sending the SS in the time window.

[0194] Aspect 17: The apparatus according to aspect 16, wherein the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a time window of a different size.

[0195] Aspect 18: An apparatus according to any one of Aspects 16 and 17, wherein the processor and the memory are configured to: sense interference in the channel, and are also configured to: continuously sense the channel in the time window, wherein interference higher than the threshold is sensed in a first part of the one of the multiple time intervals, wherein interference lower than the threshold is sensed in a second part of the one of the multiple time intervals, and the second part occurs later in time than the first part; and wherein the processor and the memory are configured to: send the SS in the one of the multiple time intervals, and are also configured to: send the SS in the second part of the one of the multiple time intervals.

[0196] Aspect 19: The apparatus according to any one of aspects 16-18, wherein the processor and the memory are further configured to: send the SS in one or more time intervals in the multiple time intervals that are later in time than the one time interval in the multiple time intervals.

[0197] Aspect 20: The apparatus according to any one of aspects 16-19, wherein the SS includes a time slot number corresponding to the one time interval among the plurality of time intervals, and a frame number corresponding to the time window.

[0198] Aspect 21: The device according to any one of aspects 16-20, wherein the channel is used for communication between multiple devices located outside the coverage of the network.

[0199] Aspect 22: The apparatus according to any one of aspects 16-21, wherein the plurality of devices lack synchronization with a global navigation satellite system.

[0200] Aspect 23: The apparatus of any one of Aspects 16-22, wherein the channel comprises a sidelink in an unlicensed spectrum, and wherein the sidelink is used for vehicle-to-everything communication.

[0201] Aspect 24: A method for wireless communication by a device, comprising: sensing interference in a channel in each time interval of a plurality of time intervals in chronological order until the interference is sensed to be lower than a threshold for one time interval of the plurality of time intervals, or the interference is sensed to be higher than the threshold for all of the plurality of time intervals, the plurality of time intervals being a time window; in a first part of the one of the plurality of time intervals, the sensed interference is higher than the threshold; in a second part of the one of the plurality of time intervals which is later in time than the first part, the sensed interference is lower than the threshold; and, in the second part of the one of the plurality of time intervals, sending one of the parts of a reservation signal or a synchronization signal (SS) corresponding to the second part.

[0202] Aspect 25: A method according to Aspect 24, wherein each of the multiple time intervals includes multiple symbols, wherein the second part of the one of the multiple time intervals is a part of the first symbol of the corresponding multiple symbols, and wherein the method further includes: sending the reserved signal on the remaining part of the first symbol.

[0203] Aspect 26: A method according to any one of Aspects 24 and 25, wherein sending the SS in the second part of the multiple time intervals includes: sending the SS in a second symbol of the corresponding multiple symbols, and the second symbol appears immediately after the first symbol in time.

[0204] Aspect 27: The apparatus according to any one of aspects 24-26, wherein the size of the time window is a function of the number of previous time intervals in which interference above a threshold was sensed.

[0205] Aspect 28: An apparatus according to any one of aspects 24-27, wherein the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a time window of a different size.

[0206] Aspect 29: A method for wireless communication by a device, comprising: transmitting the size of a time window, wherein the time window includes multiple time intervals, and the size of the time window is at least partially based on the number of previous time intervals during which interference greater than a threshold is sensed; sensing interference in a channel in each of the multiple time intervals in chronological order until the interference is sensed to be lower than the threshold for one of the multiple time intervals, or the interference is sensed to be higher than the threshold for all of the multiple time intervals; when the interference is sensed to be lower than the threshold for the one of the multiple time intervals, sending SS in the one of the multiple time intervals; and when the interference is sensed to be higher than the threshold for all of the multiple time intervals, avoiding sending a synchronization signal (SS) in the time window.

[0207] Aspect 30: The method according to aspect 29, wherein the start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a time window of a different size.

[0208] Aspect 31: A method for wireless communication by a device, comprising: sensing interference in a channel for multiple time intervals in a time sequence until no interference is found for one of the multiple time intervals, or interference is found for all of the multiple time intervals, and the multiple time intervals form a time window; when no interference is found for one of the multiple time intervals, sending a synchronization signal (SS) in one of the multiple time intervals; and when interference is found for all of the multiple time intervals, avoiding sending the SS in the time window.

[0209] Aspect 32: The method according to Aspect 31, wherein the channel includes a side link in an unlicensed spectrum.

[0210] Aspect 33: The method according to Aspect 32, wherein the sidelink is used for vehicle-to-everything communication.

[0211] Aspect 34: The method according to any one of aspects 31-33, wherein the SS includes a time slot number corresponding to one of the plurality of time intervals, and a frame number corresponding to the time window.

[0212] Aspect 35: A method according to any one of aspects 31-34, wherein each time interval corresponds to a time slot.

[0213] Aspect 36: The method according to any one of Aspects 31-35, wherein the time window occurs periodically.

[0214] Aspect 37: The method according to any one of aspects 31-36 further includes: receiving signaling indicating the size of the time window.

[0215] Aspect 38: A method according to any one of Aspects 31-37, wherein the start time of the time window is based on an offset indicator among a plurality of offset indicators, wherein each offset indicator among the plurality of offset indicators is associated with a time window of a different size.

[0216] Aspect 39: A method according to any one of Aspects 31-38, wherein the start time of the time window is based on an offset indicator among multiple offset indicators, wherein each offset indicator among the multiple offset indicators is associated with a different time window, and wherein the time window is separated from the different time windows.

[0217] Aspect 40: The method according to any one of Aspects 31-39 further includes: when no interference is found for one of the multiple time intervals, sending the SS in one or more time intervals in the multiple time intervals that are later in time than one of the multiple time intervals.

[0218] Aspect 41: The method according to any one of aspects 31-40, wherein, for a time interval, sensing interference in the channel comprises: sensing interference in the channel before a start point of the time interval.

[0219] Aspect 42: A method according to any one of Aspects 31-41, wherein sensing interference in the channel includes: continuously sensing the channel within the time window, wherein interference is found in a first part of a time interval among the multiple time intervals, wherein no interference is found in a second part of a time interval among the multiple time intervals, and the second part occurs later in time than the first part, wherein sending an SS in a time interval among the multiple time intervals includes: sending the SS in the second part of the one of the multiple time intervals.

[0220] Aspect 43: The method according to aspect 42 further comprises: sending the SS in one or more time intervals in the plurality of time intervals that are later in time than the one time interval in the plurality of time intervals.

[0221] Aspect 44: The method according to aspect 42 or 43, wherein the channel is used for communication between multiple devices located outside the network coverage.

[0222] Aspect 45: The method according to Aspect 44, wherein the plurality of devices lack synchronization with a global navigation satellite system.

[0223] Aspect 46: A user equipment (UE) for wireless communication, comprising: a memory and one or more processors for executing the method according to any one of aspects 31-45.

[0224] Aspect 47: A user equipment (UE), comprising: one or more units for performing the method according to any one of aspects 1-45.

[0225] Aspect 48: A non-transitory computer-readable storage medium having stored thereon instructions for executing the method for wireless communication by a user equipment (UE) according to any one of aspects 1-45.

[0226] Other considerations

[0227] The techniques described herein can 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 can implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, and the like. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. CDMA2000 covers interim standards (e.g., IS-2000, IS-95, and IS-856). A TDMA network can 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, etc. UTRA and E-UTRA are part 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 named "3rd Generation Partnership Project" (3GPP). CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). NR is an emerging wireless communication technology under development.

[0228] In 3GPP, the term "cell" may refer to the coverage area of ​​a Node B (NB) and / or a NB subsystem serving the coverage area, depending on the context in which the term is used. In NR systems, the term "cell" and BS, next-generation Node B (gNB or gNodeB), access point (AP), distributed unit (DU), carrier, or transmit receive point (TRP) may be used interchangeably. The BS may provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell may cover a relatively large geographic area (e.g., a radius of several kilometers) and may allow unrestricted access to UEs with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access to UEs with service subscriptions. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow limited access by UEs associated with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs of users in a home, etc.). A BS for a macro cell may 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.

[0229] UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a customer premises equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical apparatus, a biometric sensor / device, a wearable device (such as a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (e.g., a smart ring, a smart bracelet, etc.)), an entertainment device (e.g., a music device, a video device, a satellite wireless unit, etc.), a vehicle-mounted component or sensor, a smart meter / sensor, an industrial manufacturing device, a global positioning system device, or any other suitable device configured to communicate via a wireless or wired medium. Some UEs may be considered machine type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which can communicate with a BS, another device (e.g., a remote device), or some other entity. A wireless node can provide, for example, connectivity to a network (e.g., a wide area network such as the Internet or a cellular network) or to a network via a wired or wireless communication link. Some UEs may be considered Internet of Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

[0230] In some examples, access to the air interface can be scheduled. The scheduling entity (e.g., BS) allocates resources for communication between some or all devices and apparatuses in its service area or cell. The scheduling entity may be responsible for scheduling, allocating, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communications, the subordinate entity utilizes the resources allocated by the scheduling entity. The base station is not the only entity that can act as a scheduling entity. In some examples, the UE may act as a scheduling entity, and resources for one or more subordinate entities (e.g., one or more other UEs) may be scheduled, and other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, the 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, in addition to communicating with the scheduling entity, the UEs may also communicate directly with each other.

[0231] The method disclosed herein includes one or more steps or actions for implementing the method. These method steps and / or actions may be interchangeable without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0232] 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. For example, "at least one of a, b, or c" is intended to cover a, b, c, ab, ac, bc, and abc, as well as any combination with multiples of the same element (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc or any other ordering of a, b, and c).

[0233] As used herein, the term "determining" includes a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, a database, or another data structure), inferring, 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.

[0234] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but to conform to the full scope consistent with the expression of the claims, wherein, unless otherwise specifically stated, reference to an element in the singular form is not intended to mean "one and only one", but "one or more". Unless otherwise explicitly stated, the term "some" refers to one or more. All structural and functional equivalents of the elements of the various aspects described in this disclosure, which are known or will be known to a person of ordinary skill in the art, are expressly incorporated herein by reference, and are intended to be included by the claims. In addition, there is no disclosure herein that is intended to be dedicated to the public, regardless of whether such disclosure is explicitly recorded in the claims. No claim element is to be interpreted according to the provisions of 35 U.S.C. § 112 (f), unless the element is explicitly recorded using the phrase "unit for...", or in the case of a method claim, the element is recorded using the phrase "step for...".

[0235] The various operations of the method described above can be performed by any suitable unit capable of performing the corresponding functions. The unit may include various hardware and / or software components and / or modules, including but not limited to: circuits, application specific integrated circuits (ASICs) or processors. Typically, where there are operations shown in the figure, those operations may have corresponding counterpart functional module components with similar numbers.

[0236] The various illustrative logic blocks, modules, and circuits described in conjunction with the present disclosure may be implemented or performed using 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. The 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, a combination of one or more microprocessors and a DSP core, or any other such configuration.

[0237] 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 also 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, etc., which are well known in the art and therefore will not be described any further. The processor may be implemented using one or more general and / or special purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits that can execute software. Those skilled in the art will recognize that how to best implement the functionality described for the processing system depends on the specific application and the overall design constraints imposed on the entire system.

[0238] If implemented in software, the functions may be stored on or sent through a computer-readable medium as one or more instructions or codes. Whether referred to as software, firmware, middleware, microcode, hardware description language or other terms, software should be broadly interpreted as meaning instructions, data or any combination thereof. Computer-readable media include both computer storage media and communication media, and communication media include any media that facilitates the transfer of computer programs from one place to another. The processor may be responsible for managing the bus and general processing, which includes executing software modules stored on a machine-readable storage medium. A computer-readable storage medium may be coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. In an alternative, a storage medium may be integrated into a processor. For example, a 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 separated from a wireless node, all of which may be accessed by a processor through a bus interface. Alternatively or in addition, a machine-readable medium or any part thereof may be integrated into a processor, such as a cache and / or a general register file in this case. For example, 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.

[0239] A software module may include a single instruction or many instructions, and may be distributed over several different code segments, distributed among different programs, and distributed across multiple storage media. A computer-readable medium may include multiple software modules. A software module includes instructions that, when executed by a device such as a processor, cause a processing system to perform various functions. A software module may include a sending module and a receiving module. Each software module may be located in a single storage device or distributed across multiple storage devices. For example, when a triggering event occurs, a software module may be loaded from a hard drive into a RAM. During the execution of a software module, a processor may load some of the 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 a processor. It will be understood that when the functions of a software module are mentioned below, such functions are implemented by the processor when executing instructions from the software module.

[0240] Additionally, 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. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Optical disks, where magnetic disks typically reproduce data magnetically, and optical disks reproduce data optically with 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 transitory computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0241] 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. For example, a computer program product for performing the operations described herein and in Fig. 9 , Fig.11 and Fig.13 The operations shown in the instructions.

[0242] In addition, it should be appreciated that the modules and / or other appropriate units 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 transmission of units for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage unit (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or a floppy disk, etc.) so that the user terminal and / or base station can obtain the various methods when the storage unit is coupled to or provided to the device. In addition, any other suitable technology for providing the methods and techniques described herein to a device can be utilized.

[0243] It is to be understood that the claims are not limited to the precise configuration and components shown above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A device for wireless communication, comprising: Memory; as well as a processor coupled to the memory, the processor and the memory being configured to: sensing interference in a channel in each of a plurality of time intervals sequentially in time, the plurality of time intervals forming a time window, wherein sensing interference in the channel comprises continuously performing listen before talk (LBT) throughout a subset of the plurality of time intervals; During a first portion of a time interval in the plurality of time intervals, it is sensed that interference will be above a threshold; During a second portion of the one of the plurality of time intervals, the interference is sensed to be below the threshold, the second portion occurring later in time than the first portion; and In the second portion of the one of the plurality of time intervals, one of a reservation signal or a portion of a synchronization signal SS is transmitted, wherein the portion of the SS has the same length as the second portion of the one of the plurality of time intervals.

2. The device according to claim 1, wherein Each of the multiple time intervals includes multiple symbols, wherein the second part of the one of the multiple time intervals is a part of a first symbol of the corresponding multiple symbols, and wherein the processor and the memory are further configured to send the reservation signal through a remaining part of the first symbol.

3. The device according to claim 2, wherein: The processor and the memory are configured to transmit the SS in the second portion of the plurality of time intervals and to transmit the SS in a second symbol of the corresponding plurality of symbols, the second symbol occurring immediately after the first symbol in time.

4. The device according to claim 1, wherein: The size of the time window is a function of the number of previous time intervals in which interference above a threshold was sensed.

5. The device according to claim 1, wherein: The processor and memory are further configured to receive signaling indicating a size of the time window.

6. The device according to claim 1, wherein: The start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different size time window.

7. The device according to claim 6, wherein: A first time window associated with the first offset indicator is separate from a second time window associated with the second offset indicator.

8. The device according to claim 1, wherein: The processor and the memory are further configured to transmit the SS in one or more time intervals of the plurality of time intervals that are later in time than the one time interval of the plurality of time intervals.

9. The device according to claim 1, wherein: The processor and the memory are configured to sense interference in the channel for a time interval and to sense interference in the channel for a duration prior to a start of the time interval.

10. The device according to claim 1, wherein: The channel includes a sidelink in an unlicensed spectrum, and wherein the sidelink is used for vehicle-to-everything communication.

11. The device according to claim 1, wherein: The SS includes: a time slot number corresponding to the one time interval among the plurality of time intervals, and a frame number corresponding to the time window.

12. The device according to claim 1, wherein: Each time interval corresponds to a time slot.

13. The apparatus according to claim 1, wherein: The time windows occur periodically.

14. The apparatus according to claim 1, wherein: The channel is used for communication between multiple devices outside the network coverage.

15. The device according to claim 14, wherein: The plurality of devices lack synchronization with the global navigation satellite system.

16. A device for wireless communication, comprising: Memory; as well as a processor coupled to the memory, the processor and the memory being configured to: transmitting a size of a time window, wherein the time window comprises a plurality of time intervals, the size of the time window being based at least in part on a number of previous time intervals during which interference above a threshold was sensed; sensing interference in the channel in each of the plurality of time intervals in time order until interference is sensed to be below the threshold for one of the plurality of time intervals or is sensed to be above the threshold for all of the plurality of time intervals, wherein sensing interference in the channel in each of the plurality of time intervals is based on an amount of power associated with one or more interfering signals measured on the channel during a listen-before-talk (LBT) during each of the plurality of time intervals; When interference lower than the threshold is sensed for the one of the plurality of time intervals, transmitting a synchronization signal SS in a next time interval of the plurality of time intervals after the one of the plurality of time intervals; and When interference above the threshold is sensed for all of the plurality of time intervals, the SS is avoided from being transmitted in the time window.

17. The device according to claim 16, wherein: The start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different size time window.

18. The apparatus according to claim 16, wherein: The processor and the memory are configured to sense interference in the channel, and further configured to continuously sense the channel in the time window, wherein the interference is sensed to be above the threshold in a first portion of the one of the plurality of time intervals, wherein the interference is sensed to be below the threshold in a second portion of the one of the plurality of time intervals, the second portion occurring later in time than the first portion; and The processor and the memory are configured to: send the SS in the one time interval among the multiple time intervals, and are further configured to: send the SS in the second part of the one time interval among the multiple time intervals.

19. The apparatus according to claim 18, wherein: The processor and the memory are further configured to transmit the SS in one or more time intervals of the plurality of time intervals that are later in time than the one time interval of the plurality of time intervals.

20. The apparatus of claim 16, wherein: The SS includes a slot number corresponding to the one of the plurality of time intervals, and a frame number corresponding to the time window.

21. The apparatus of claim 16, wherein: The channel is used for communication between multiple devices located outside the network coverage.

22. The apparatus according to claim 21, wherein The plurality of devices lack synchronization with the global navigation satellite system.

23. The apparatus of claim 16, wherein: The channel includes a sidelink in an unlicensed spectrum, and wherein the sidelink is used for vehicle-to-everything communication.

24. A method for wireless communication by a device, comprising: sensing interference in the channel in each of a plurality of time intervals in time order, the plurality of time intervals being a time window, wherein sensing interference in the channel comprises continuously performing listen before talk (LBT) throughout a subset of the plurality of time intervals; During a first portion of a time interval in the plurality of time intervals, it is sensed that interference will be above a threshold; During a second portion of the one of the plurality of time intervals, the interference is sensed to be below the threshold, the second portion occurring later in time than the first portion; and In the second portion of the one of the plurality of time intervals, one of a reservation signal or a corresponding portion of a synchronization signal SS is transmitted, wherein the portion of the SS has the same length as the second portion of the one of the plurality of time intervals.

25. The method according to claim 24, wherein: Each of the multiple time intervals includes multiple symbols, wherein the second part of the one of the multiple time intervals is a part of a first symbol of the corresponding multiple symbols, and wherein the method further includes: sending the reservation signal on a remaining part of the first symbol.

26. The method according to claim 25, wherein: Transmitting the SS in the second portion of the plurality of time intervals includes transmitting the SS in a second symbol of the corresponding plurality of symbols, the second symbol occurring immediately in time after the first symbol.

27. The method according to claim 24, wherein: The size of the time window is a function of the number of previous time intervals during which interference above a threshold was sensed.

28. The method of claim 24, wherein: The start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different size time window.

29. A method for wireless communication by a device, comprising: transmitting a size of a time window, wherein the time window comprises a plurality of time intervals, the size of the time window being based at least in part on a number of previous time intervals during which interference greater than a threshold was sensed; sensing interference in the channel in each of the plurality of time intervals in time order until interference is sensed to be below the threshold for one of the plurality of time intervals or is sensed to be above the threshold for all of the plurality of time intervals, wherein sensing interference in the channel in each of the plurality of time intervals is based on an amount of power associated with one or more interfering signals measured on the channel during a listen-before-talk (LBT) during each of the plurality of time intervals; When interference lower than the threshold is sensed for the one of the plurality of time intervals, transmitting a synchronization signal SS in a next time interval of the plurality of time intervals after the one of the plurality of time intervals; and When interference above the threshold is sensed for all of the plurality of time intervals, the SS is avoided from being transmitted in the time window.

30. The method of claim 29, wherein: The start time of the time window is based on an offset indicator of a plurality of offset indicators, wherein each offset indicator of the plurality of offset indicators is associated with a different size time window.

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