Distributed joint access for unlicensed sidelink

Aspects of the disclosure relate to distributed joint access of an unlicensed sidelink channel Each sidelink device may perform independent and asynchronous listen before talk (LBT) of the unlicensed sidelink channel with a respective back-off timer value. The first sidelink device to complete back-off may transmit a joint access synchronization (JAS) signal indicating a duration of time that the unlicensed sidelink channel may be accessed by sidelink devices. Synchronized access sharing of the unlicensed sidelink channel across different active sidelinks may then be achieved through distributed handshake signaling.

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication systems, and more particularly, to wireless communication using a sidelink channel Embodiments can provide and enable techniques for utilizing unlicensed spectrum in sidelink communications.

INTRODUCTION

In many existing wireless communication systems, a cellular network is implemented by enabling wireless user equipment to communicate with another by signaling with a nearby base station or cell. As a user equipment moves across the service area, handovers take place such that each user equipment maintains communication with one another via its respective best cell.

Another scheme for a wireless communication system is frequently referred to as a mesh or peer-to-peer (P2P) network, whereby wireless user equipment may signal one another directly, rather than via an intermediary base station or cell.

Somewhat in between these schemes is a system configured for sidelink signaling. With sidelink signaling, a wireless user equipment communicates in a cellular system, generally under the control of a base station. However, the wireless user equipment is further configured for sidelink signaling directly between user equipment without passing through the base station.

As the demand for mobile broadband access continues to increase, research and development continue to advance wireless communication technologies not only to meet the growing demand for mobile broadband access, but also to advance and enhance the user experience with mobile communications.

BRIEF SUMMARY OF SOME EXAMPLES

Various aspects of the present disclosure relate to distributed joint access of an unlicensed sidelink channel. Each sidelink device may perform independent and asynchronous listen before talk (LBT) of the unlicensed sidelink channel with a respective back-off timer value. The first sidelink device to complete back-off may transmit a joint access synchronization (JAS) signal indicating a duration of time that the unlicensed sidelink channel may be accessed by sidelink devices. Synchronized access sharing of the unlicensed sidelink channel across different active sidelinks may then be achieved through distributed handshake signaling.

In one aspect of the disclosure, a method of sidelink wireless communication is disclosed. The method includes listening to a sidelink channel comprising unlicensed spectrum, initializing a back-off timer when the sidelink channel is idle, and upon expiration of the back-off timer, if the sidelink channel remains idle, transmitting an initial joint access synchronization signal comprising an initial duration of time that the sidelink channel is accessible to sidelink devices.

Another aspect of the disclosure provides an apparatus for sidelink wireless communication. The apparatus includes a processor, a transceiver communicatively coupled to the process, and a memory communicatively coupled to the processor. The processor is configured to listen to a sidelink channel comprising unlicensed spectrum, initialize a back-off timer when the sidelink channel is idle, and upon expiration of the back-off timer, if the sidelink channel remains idle, transmit an initial joint access synchronization signal comprising an initial duration of time that the sidelink channel is accessible to sidelink devices.

Another aspect of the disclosure provides an apparatus for sidelink wireless communication. The apparatus includes means for listening to a sidelink channel comprising unlicensed spectrum, means for initializing a back-off timer when the sidelink channel is idle, and upon expiration of the back-off timer, if the sidelink channel remains idle, means for transmitting an initial joint access synchronization signal comprising an initial duration of time that the sidelink channel is accessible to sidelink devices.

Another aspect of the disclosure provides a non-transitory computer-readable medium storing computer executable code. The non-transitory computer-readable medium includes code for listening to a sidelink channel comprising unlicensed spectrum, initializing a back-off timer when the sidelink channel is idle, and upon expiration of the back-off timer, if the sidelink channel remains idle, transmitting an initial joint access synchronization signal comprising an initial duration of time that the sidelink channel is accessible to sidelink devices.

Examples of additional aspects of the disclosure follow. In some aspects of the disclosure, the method further includes transmitting one or more additional joint access synchronization signals at periodic intervals after the initial joint access synchronization signal, in which the one or more additional joint access synchronization signals each include a respective remaining duration of time that the sidelink channel is accessible to the sidelink devices. In some examples, the remaining duration of time is calculated based on the initial duration of time of the initial joint access synchronization signal and an amount of lapsed time since transmitting the initial joint access synchronization signal. In some examples, the one or more additional joint access synchronization signals are transmitted at periodic intervals corresponding to a number of slots. In some examples, an additional joint access synchronization signal is transmitted each slot.

In some aspects of the disclosure, the initial joint access synchronization signal is transmitted from a first transmitting device to synchronize access to the sidelink channel by the first transmitting device and one or more additional transmitting devices through distributed handshake signaling. In some examples, the distributed handshake signaling includes transmitting a request signal from the first transmitting device, in which the request signal indicates a first requested duration of time for the first transmitting device to utilize the sidelink channel to transmit a sidelink signal. The distributed handshake signaling may further include receiving a confirmation signal at the first transmitting device, in which the confirmation signal indicates availability of the sidelink channel for the first requested duration of time. Upon completion of the handshake signaling, the sidelink signal may then be transmitted from the transmitting device over the sidelink channel In some aspects of the disclosure, the first transmitting device may receive an additional request signal that indicates an additional requested duration of time overlapping the first requested duration of time for an additional transmitting device of the one or more additional transmitting devices to utilize the sidelink channel to transmit an additional sidelink signal.

In some aspects of the disclosure, the method further includes freezing the back-off timer when the sidelink channel becomes busy. In some aspects of the disclosure, the method further includes canceling the back-off timer upon receiving another joint access synchronization signal during a back-off time set by the back-off timer.

DETAILED DESCRIPTION

The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now toFIG. 1, as an illustrative example without limitation, a simplified schematic illustration of an access network100is provided.

In general, a base station (BS) serves each cell. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. A BS may also be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a GNodeB or some other suitable terminology.

InFIG. 1, two high-power base stations110and112are shown in cells102and104; and a third high-power base station114is shown controlling a remote radio head (RRH)116in cell106. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the cells102,104, and106may be referred to as macrocells, as the high-power base stations110,112, and114support cells having a large size. Further, a low-power base station118is shown in the small cell108(e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc.) which may overlap with one or more macrocells. In this example, the cell108may be referred to as a small cell, as the low-power base station118supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints. It is to be understood that the access network100may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The base stations110,112,114,118provide wireless access points to a core network for any number of mobile apparatuses.

FIG. 1further includes a quadcopter or drone120, which may be configured to function as a base station. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station such as the quadcopter120.

In general, base stations may include a backhaul interface for communication with a backhaul portion of the network. The backhaul may provide a link between a base station and a core network, and in some examples, the backhaul may provide interconnection between the respective base stations. The core network is a part of a wireless communication system that is generally independent of the radio access technology used in the radio access network. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network. Some base stations may be configured as integrated access and backhaul (IAB) nodes, where the wireless spectrum may be used both for access links (i.e., wireless links with UEs), and for backhaul links. This scheme is sometimes referred to as wireless self-backhauling. By using wireless self-backhauling, rather than requiring each new base station deployment to be outfitted with its own hard-wired backhaul connection, the wireless spectrum utilized for communication between the base station and UE may be leveraged for backhaul communication, enabling fast and easy deployment of highly dense small cell networks.

The access network100is illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the 3rd Generation Partnership Project (3GPP), but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus that provides a user with access to network services.

Within the access network100, the cells may include UEs that may be in communication with one or more sectors of each cell. For example, UEs122and124may be in communication with base station110; UEs126and128may be in communication with base station112; UEs130and132may be in communication with base station114by way of RRH116; UE134may be in communication with low-power base station118; and UE136may be in communication with mobile base station120. Here, each base station110,112,114,118, and120may be configured to provide an access point to a core network (not shown) for all the UEs in the respective cells.

In another example, a mobile network node (e.g., quadcopter120) may be configured to function as a UE. For example, the quadcopter120may operate within cell102by communicating with base station110. In some aspects of the disclosure, two or more UE (e.g., UEs126and128) may communicate with each other using peer to peer (P2P) or sidelink signals127without relaying that communication through a base station (e.g., base station112).

Unicast or broadcast transmissions of control information and/or traffic information from a base station (e.g., base station110) to one or more UEs (e.g., UEs122and124) may be referred to as downlink (DL) transmission, while transmissions of control information and/or traffic information originating at a UE (e.g., UE122) may be referred to as uplink (UL) transmissions. In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an OFDM waveform, carries one resource element (RE) per subcarrier. A slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1 ms. Multiple subframes may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

The air interface in the access network100may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, multiple access for uplink (UL) or reverse link transmissions from UEs122and124to base station110may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), sparse code multiple access (SCMA), single-carrier frequency division multiple access (SC-FDMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing downlink (DL) or forward link transmissions from the base station110to UEs122and124may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), single-carrier frequency division multiplexing (SC-FDM) or other suitable multiplexing schemes.

In the radio access network100, the ability for a UE to communicate while moving, independent of their location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of a mobility management entity (MME). In various aspects of the disclosure, an access network100may utilize DL-based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE's connection from one radio channel to another). In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE124may move from the geographic area corresponding to its serving cell102to the geographic area corresponding to a neighbor cell106. When the signal strength or quality from the neighbor cell106exceeds that of its serving cell102for a given amount of time, the UE124may transmit a reporting message to its serving base station110indicating this condition. In response, the UE124may receive a handover command, and the UE may undergo a handover to the cell106.

In a network configured for UL-based mobility, UL reference signals from each UE may be utilized by the network to select a serving cell for each UE. In some examples, the base stations110,112, and114/116may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs), unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs122,124,126,128,130, and132may receive the unified synchronization signals, derive the carrier frequency and slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE124) may be concurrently received by two or more cells (e.g., base stations110and114/116) within the access network100. Each of the cells may measure a strength of the pilot signal, and the access network (e.g., one or more of the base stations110and114/116and/or a central node within the core network) may determine a serving cell for the UE124. As the UE124moves through the access network100, the network may continue to monitor the uplink pilot signal transmitted by the UE124. When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network100may handover the UE124from the serving cell to the neighboring cell, with or without informing the UE124.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources (e.g., time-frequency resources) for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs or scheduled entities utilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as a scheduling entity.

That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs). In other examples, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, UE138is illustrated communicating with UEs140and142. In some examples, the UE138is functioning as a scheduling entity or a primary sidelink device, and UEs140and142may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE may function as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example, UEs140and142may optionally communicate directly with one another in addition to communicating with the scheduling entity138.

Thus, in a wireless communication network with scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, or a mesh configuration, a scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources. Referring now toFIG. 2, a block diagram illustrates a scheduling entity202and a plurality of scheduled entities204(e.g.,204aand204b). Here, the scheduling entity202may correspond to a base station110,112,114, and/or118. In additional examples, the scheduling entity202may correspond to a UE138, the quadcopter120, or any other suitable node in the radio access network100. Similarly, in various examples, the scheduled entity204may correspond to the UE122,124,126,128,130,132,134,136,138,140, and142, or any other suitable node in the radio access network100.

As illustrated inFIG. 2, the scheduling entity202may broadcast user data traffic206to one or more scheduled entities204(the user data traffic may be referred to as downlink user data traffic). In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at the scheduling entity202. Broadly, the scheduling entity202is a node or device responsible for scheduling user data traffic in a wireless communication network, including the downlink transmissions and, in some examples, uplink user data traffic210from one or more scheduled entities to the scheduling entity202. Another way to describe the system may be to use the term broadcast channel multiplexing. In accordance with aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity204. Broadly, the scheduled entity204is a node or device that receives scheduling control information, including but not limited to scheduling grants, synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity202.

The scheduling entity202may broadcast control information208including one or more control channels, such as a PBCH; a PSS; a SSS; a physical control format indicator channel (PCFICH); a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH); and/or a physical downlink control channel (PDCCH), etc., to one or more scheduled entities204. The PHICH carries HARQ feedback transmissions such as an acknowledgment (ACK) or negative acknowledgment (NACK). HARQ is a technique well known to those of ordinary skill in the art, wherein packet transmissions may be checked at the receiving side for accuracy, and if confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc.

Uplink user data traffic210and/or downlink user data traffic206including one or more traffic channels, such as a physical downlink shared channel (PDSCH) or a physical uplink shared channel (PUSCH) (and, in some examples, system information blocks (SIBs)), may additionally be transmitted between the scheduling entity202and the scheduled entity204. Transmissions of the control and user data traffic information may be organized by subdividing a carrier, in time, into suitable slots.

Furthermore, the scheduled entities204may transmit uplink control information212including one or more uplink control channels (e.g., the physical uplink control channel (PUCCH)) to the scheduling entity202. Uplink control information (UCI) transmitted within the PUCCH may include a variety of packet types and categories, including pilots, reference signals, and information configured to enable or assist in decoding uplink traffic transmissions. In some examples, the control information212may include a scheduling request (SR), i.e., request for the scheduling entity202to schedule uplink transmissions. Here, in response to the SR transmitted on the control channel212, the scheduling entity202may transmit downlink control information208that may schedule the slot for uplink packet transmissions.

Uplink and downlink transmissions may generally utilize a suitable error correcting block code. In a typical block code, an information message or sequence is split up into information blocks, and an encoder at the transmitting device then mathematically adds redundancy to the information message. Exploitation of this redundancy in the encoded information message can improve the reliability of the message, enabling correction for any bit errors that may occur due to the noise. Some examples of error correcting codes include Hamming codes, Bose-Chaudhuri-Hocquenghem (BCH) codes, turbo codes, low-density parity check (LDPC) codes, Walsh codes, and polar codes. Various implementations of scheduling entities202and scheduled entities204may include suitable hardware and capabilities (e.g., an encoder and/or decoder) to utilize any one or more of these error correcting codes for wireless communication.

In some examples, scheduled entities such as a first scheduled entity204aand a second scheduled entity204bmay utilize sidelink signals for direct D2D communication. Sidelink signals may include sidelink user data traffic214and sidelink control216. Sidelink control information216may include a source transmit signal (STS), a direction selection signal (DSS), a destination receive signal (DRS), and a physical sidelink HARQ indicator channel (PSHICH). The DSS/STS may provide for a scheduled entity204to request a duration of time to keep a sidelink channel available for a sidelink signal; and the DRS may provide for the scheduled entity204to indicate availability of the sidelink channel, e.g., for a requested duration of time. An exchange of DSS/STS and DRS (e.g., handshake) may enable different scheduled entities performing sidelink communications to negotiate the availability of the sidelink channel prior to communication of the sidelink user data traffic214. The PSHICH may include HARQ acknowledgment information and/or a HARQ indicator from a destination device, so that the destination may acknowledge traffic received from a source device.

The channels or carriers illustrated inFIG. 2are not necessarily all of the channels or carriers that may be utilized between a scheduling entity202and scheduled entities204, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels.

FIG. 3is a diagram300illustrating an example of a hardware implementation for scheduling entity202according to aspects of the present disclosure. Scheduling entity202may employ a processing system314. Scheduling entity202may be implemented with a processing system314that includes one or more processors304. Examples of processors304include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, scheduling entity202may be configured to perform any one or more of the functions described herein. That is, the processor304, as utilized in scheduling entity202, may be used or configured to implement any one or more of the processes described herein.

In this example, the processing system314may be implemented with a bus architecture, represented generally by the bus302. The bus302may include any number of interconnecting buses and bridges depending on the specific application of the processing system314and the overall design constraints. The bus302communicatively couples together various circuits including one or more processors (represented generally by the processor304), a memory305, and computer-readable media (represented generally by the computer-readable medium306). The bus302may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits. A bus interface308provides an interface between the bus302and a transceiver310. The transceiver310provides a communication interface or a means for communicating with various other apparatuses over a transmission medium. Depending upon the nature of the apparatus, a user interface312(e.g., keypad, display, speaker, microphone, joystick) may also be provided.

At least one processor304is responsible for managing the bus302and general processing, including the execution of software stored on the computer-readable medium306. The software, when executed by the processor304, causes the processing system314to perform the various functions described below for any particular apparatus. The computer-readable medium306and the memory305may also be used for storing data that is manipulated by the processor304when executing software.

In some aspects of the disclosure, the computer-readable medium306may include communication instructions352. The communication instructions352may include instructions for performing various operations related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. For example, the communication instructions352may include code for configuring the processing system314and communication interface310to communicate and control a plurality of scheduled entities using sidelink communication. In some aspects of the disclosure, the computer-readable medium306may include processing instructions354. The processing instructions354may include instructions for performing various operations related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein. In one example, the processing instructions354include code that may be executed by the processor304to control and schedule sidelink communication as described inFIGS. 7-19.

In some aspects of the disclosure, at least one processor304may include a communication circuit342. The communication circuit342may include one or more hardware components that provide the physical structure that performs various processes related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. For example, the communication circuit342may be configured to control and schedule sidelink communication among a plurality of scheduled entities. The communication circuit342may transmit or broadcast sidelink grants or control information to the scheduled entities using a downlink control channel (e.g., PDCCH) via the communication interface310. In some aspects of the disclosure, the processor304may also include a processing circuit343. The processing circuit343may include one or more hardware components that provide the physical structure that performs various processes related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein.

The circuitry included in the processor304is provided as non-limiting examples. Other means for carrying out the described functions exists and is included within various aspects of the present disclosure. In some aspects of the disclosure, the computer-readable medium306may store computer-executable code comprising instructions configured to perform various processes described herein. The instructions included in the computer-readable medium306are provided as non-limiting examples. Other instructions configured to carry out the described functions exist and are included within various aspects of the present disclosure.

FIG. 4is a diagram400illustrating an example of a hardware implementation for a scheduled entity204according to aspects of the present disclosure. The scheduled entity204may employ a processing system414. The scheduled entity204may be implemented with a processing system414that includes one or more processors404. For example, the scheduled entity204may be a user equipment (UE) as illustrated in any one or more ofFIGS. 1 and/or 2.

Examples of processors404include microprocessors, microcontrollers, DSPs, FPGAs, PLDs, state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, scheduled entity204may be configured to perform any one or more of the functions described herein. That is, the processor404, as utilized in scheduled entity204, may be used or configured to implement any one or more of the processes described herein, for example, inFIGS. 7-19.

In this example, the processing system414may be implemented with a bus architecture, represented generally by the bus402. The bus402may include any number of interconnecting buses and bridges depending on the specific application of the processing system414and the overall design constraints. The bus402communicatively couples together various circuits including one or more processors (represented generally by the processor404), a memory405, and computer-readable media (represented generally by the computer-readable medium406). The bus402may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits. A bus interface408provides an interface between the bus402and a transceiver410. The transceiver410provides a communication interface or a means for communicating with various other apparatuses over a transmission medium. Depending upon the nature of the apparatus, a user interface412(e.g., keypad, display, speaker, microphone, joystick) may also be provided.

At least one processor404is responsible for managing the bus402and general processing, including the execution of software stored on the computer-readable medium406. The software, when executed by the processor404, causes the processing system414to perform the various functions described below for any particular apparatus. The computer-readable medium406and the memory405may also be used for storing data that is manipulated by the processor404when executing software.

In some aspects of the disclosure, the computer-readable medium406may include communication instructions452. The communication instructions452may include instructions for performing various operations related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. In some aspects of the disclosure, the instructions452may include code for configuring the scheduled entity to perform sidelink communication as described in relation to FIGS.7-19. In some aspects of the disclosure, the computer-readable medium406may include processing instructions454. The processing instructions454may include instructions for performing various operations related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein. In some aspects of the disclosure, the processing instructions454may include code for configuring the scheduled entity to perform sidelink communication as described in relation toFIGS. 7-19. In some aspects of the disclosure, the computer-readable medium406may include back-off timer instructions456. The back-off timer instructions456may include instructions for controlling a back-off timer415, which may be maintained, for example, in memory405. For example, the back-off timer instructions456may include instructions for calculating a back-off value for the back-off timer415and/or for initializing, freezing, and/or canceling the back-off timer415, as described in relation toFIGS. 12-19. In addition, the back-off timer instructions456may further include other suitable instructions for using and controlling the back-off timer415.

In some aspects of the disclosure, at least one processor404may include a communication circuit440. The communication circuit440may include one or more hardware components that provide the physical structure that performs various processes related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. For example, the communication circuit440may be configured to perform sidelink communication as described in relation toFIGS. 7-19. In some aspects of the disclosure, the processor404may also include a processing circuit442. The processing circuit442may include one or more hardware components that provide the physical structure that performs various processes related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein. For example, the processing circuit442may be configured to perform sidelink communication as described in relation toFIGS. 7-19. In some aspects of the disclosure, the processor404may also include a back-off timer control circuit446. The back-off timer control circuit446may include one or more hardware components that provide the physical structure to perform various processes related to controlling the back-off timer415. For example, the back-off timer control circuit446may be configured to calculate a back-off value for the back-off timer415and/or to initialize, freeze, cancel, and/or otherwise use the back-off timer415as described in relation toFIGS. 12-19.

The circuitry included in the processor404is provided as non-limiting examples. Other means for carrying out the described functions exists and is included within various aspects of the present disclosure. In some aspects of the disclosure, the computer-readable medium406may store computer-executable code comprising instructions configured to perform various processes described herein. The instructions included in the computer-readable medium406are provided as non-limiting examples. Other instructions configured to carry out the described functions exist and are included within various aspects of the present disclosure.

According to various aspects of the disclosure, wireless communication may be implemented by dividing transmissions, in time, into frames, wherein each frame may be further divided into subframes or slots. These subframes or slots may be DL-centric, UL-centric, or sidelink-centric, as described below. For example,FIG. 5is a diagram illustrating an example of a downlink (DL)-centric slot500according to some aspects of the disclosure. The DL-centric slot is referred to as a DL-centric slot because a majority (or, in some examples, a substantial portion) of the slot includes DL data. In the example shown inFIG. 5, time is illustrated along a horizontal axis, while frequency is illustrated along a vertical axis. The time-frequency resources of the DL-centric slot500may be divided into a DL burst502, a DL traffic portion504and an UL burst506.

The DL burst502may exist in the initial or beginning portion of the DL-centric slot. The DL burst502may include any suitable DL information in one or more channels. In some examples, the DL burst502may include various scheduling information and/or control information corresponding to various portions of the DL-centric slot. In some configurations, the DL burst502may be a physical DL control channel (PDCCH), as indicated inFIG. 5. The DL-centric slot may also include a DL traffic portion504. The DL traffic portion504may sometimes be referred to as the payload of the DL-centric slot. The DL traffic portion504may include the communication resources utilized to communicate DL user data traffic from the scheduling entity202(e.g., eNB) to the scheduled entity204(e.g., UE). In some configurations, the DL traffic portion504may be a physical DL shared channel (PDSCH).

The UL burst506may include any suitable UL information in one or more channels. In some examples, the UL burst506may include feedback information corresponding to various other portions of the DL-centric slot. For example, the UL burst506may include feedback information corresponding to the control portion502and/or DL traffic portion504. Non-limiting examples of feedback information may include an ACK signal, a NACK signal, a HARQ indicator, and/or various other suitable types of information. The UL burst506may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests (SRs), and various other suitable types of information.

As illustrated inFIG. 5, the end of the DL traffic portion504may be separated in time from the beginning of the UL burst506. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduled entity204(e.g., UE)) to UL communication (e.g., transmission by the scheduled entity204(e.g., UE)). One of ordinary skill in the art will understand that the foregoing is merely one example of a DL-centric slot and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

FIG. 6is a diagram showing an example of an uplink (UL)-centric slot600according to some aspects of the disclosure. The UL-centric slot is referred to as a UL-centric slot because a majority (or, in some examples, a substantial portion) of the slot includes UL data. In the example shown inFIG. 6, time is illustrated along a horizontal axis, while frequency is illustrated along a vertical axis. The time-frequency resources of the UL-centric slot600may be divided into a DL burst602, an UL traffic portion604and an UL burst606.

The DL burst602may exist in the initial or beginning portion of the UL-centric slot. The DL burst602inFIG. 6may be similar to the DL burst502described above with reference toFIG. 5. The UL-centric slot may also include an UL traffic portion604. The UL traffic portion604may sometimes be referred to as the payload of the UL-centric slot. The UL traffic portion604may include the communication resources utilized to communicate UL user data traffic from the scheduled entity204(e.g., UE) to the scheduling entity202(e.g., eNB). In some configurations, the UL traffic portion604may be a physical UL shared channel (PUSCH). As illustrated inFIG. 6, the end of the DL burst602may be separated in time from the beginning of the UL traffic portion604. This time, separation may sometimes be referred to as a gap, guard period, guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduling entity202(e.g., UE)) to UL communication (e.g., transmission by the scheduling entity202(e.g., UE)).

The UL burst606inFIG. 6may be similar to the UL burst506described above with reference toFIG. 5. The UL burst606may additionally or alternatively include information pertaining to channel quality indicator (CQI), sounding reference signals (SRSs), and various other suitable types of information. One of ordinary skill in the art will understand that the foregoing is merely one example of an UL-centric slot, and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

In some circumstances, two or more scheduled entities204(e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one scheduled entity204(e.g., UE1) to another scheduled entity204(e.g., UE2) without relaying that communication through the scheduling entity202(e.g., eNB), even though the scheduling entity202(e.g., eNB) may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum).

However, communication using sidelink signals may increase the relative likelihood of signal interference in certain circumstances. For example, without the aspects described in the present disclosure, interference may occur between the sidelink signals and the DL/UL control/scheduling information of nominal traffic. That is, the DL/UL control/scheduling information of nominal traffic may not be as well protected. As another example, without the aspects described in the present disclosure, interference may occur between sidelink signals originating from different scheduled entities204(e.g., UEs). That is, concurrently transmitted sidelink signals may collide and/or interfere with each other. Aspects of the present disclosure provide for an interference management scheme for concurrent sidelink signals and sidelink-centric subframes or slots that enable sidelink interference management.

FIG. 7is a diagram illustrating an example of a sidelink-centric slot700according to some aspects of the present disclosure. In some configurations, this sidelink-centric slot may be utilized for broadcast communication. A broadcast communication may refer to a point-to-multipoint transmission by one scheduled entity204(e.g., UE1) to a set of one or more scheduled entities204(e.g., UE2-UEN). In this example, the sidelink-centric slot includes a DL burst702, which may include a PDCCH. In some aspects, the DL burst702may be similar to the DL burst502described in greater detail above with reference toFIG. 5. Additionally or alternatively, the DL burst702may include grant information related to the sidelink signal or sidelink communication. Non-limiting examples of grant information may include generic grant information and link-specific grant information. Link-specific grant information may refer to information that enables a specific sidelink communication to occur between two particular scheduled entities204(e.g., UEs). In comparison, generic grant information may refer to information that generally enables sidelink communications to occur within a particular cell, without specifying a particular sidelink communication.

Notably, as illustrated inFIG. 7, the DL burst702may be included in the beginning or initial portion of the sidelink-centric slot. By including the DL burst702in the beginning or initial portion of the sidelink-centric slot, the likelihood of interfering with the DL bursts502,602of DL-centric and UL-centric slots of nominal traffic can be reduced or minimized. In other words, because the DL-centric slot, the UL-centric slot, and the sidelink-centric slot have their DL control information communicated during a common portion of their respective slots, the likelihood of interference between the DL control information and the sidelink signals can be reduced or minimized That is, the DL bursts502,602of DL-centric and UL-centric slots (of nominal traffic) are relatively better protected.

The sidelink-centric slot700may also include a source transmit signal (STS)704portion (formerly referred to as, or similar to a, request-to-send (RTS) portion). The STS704portion may refer to a portion of the slot during which one scheduled entity204(e.g., a UE utilizing a sidelink signal) communicates a request signal (i.e., an STS) indicating a requested duration of time to keep a sidelink channel available for a sidelink signal. One of ordinary skill in the art will understand that the STS may include various additional or alternative information without necessarily deviating from the scope of the present disclosure. In some configurations, the STS may include a group destination identifier (ID). The group destination ID may correspond to a group of devices that are intended to receive the STS. In some configurations, the STS may indicate a duration of the sidelink transmission, and/or may include a reference signal (RS) to enable channel estimation and RX-yielding, a modulation and coding scheme (MCS) indicator, and/or various other information. In some examples, the STS RS may be transmitted at a higher (e.g., boosted) power level to provide additional protection of the broadcast. Further, the STS MCS indicator may be utilized to inform the receiving device of the MCS utilized for transmissions in the sidelink data portion706. Here, the reference signal (RS) may take any suitable form or structure on the channel that may be useful for interference management (e.g., by creating a predictable amount of interference) and channel management at the receiver. In some configurations, the STS (or, in other examples, the DRS) may include a release flag, configured to explicitly signal that the transmitting device is releasing sidelink resources that may have previously been requested by the transmitting device, or in other words, sending an explicit release signal to indicate that a sidelink device is releasing a sidelink resource. Therefore, the release flag may be set in explicit sidelink signaling (e.g., STS/DRS) to indicate that a sidelink device is releasing a sidelink resource so that other users, which may have been backing off, can get back into trying to access or use the sidelink resources that were previously unavailable.

A first scheduled entity204(e.g., UE1) may transmit an STS to one or more other scheduled entities204(e.g., UE2, UE3) to request that the other scheduled entities204(e.g., UE2, UE3) refrain from using the sidelink channel for the requested duration of time, thereby leaving the sidelink channel available for first scheduled entity204(e.g., UE1). By transmitting the STS, the first scheduled entity204(e.g., UE1) can effectively reserve the sidelink channel for a sidelink signal. This enables distributed scheduling and management of interference that might otherwise occur from another sidelink communication from other scheduled entities204(e.g., UE2, UE3). Put another way, because the other scheduled entities204(e.g., UE2, UE3) are informed that the first scheduled entity204(e.g., UE1) will be transmitting for the requested period of time, the likelihood of interference between sidelink signals is reduced.

The sidelink-centric slot700may also include a sidelink traffic portion706. The sidelink traffic portion706may sometimes be referred to as the payload or sidelink-burst of the sidelink-centric slot. In an example where the sidelink-centric slot is utilized for broadcast communications, the sidelink traffic portion706may carry a physical sidelink broadcast channel (PSBCH) (formerly a physical sidelink shared channel (PSSCH)), as indicated inFIG. 7. The sidelink traffic portion706may include the communication resources utilized to communicate sidelink user data traffic from one scheduled entity204(e.g., UE1) to one or more other scheduled entities204(e.g., UE2, UE3).

According to a further aspect of the disclosure, a broadcast sidelink-centric slot may take on certain characteristics based on whether or not the broadcast is separated from other sidelink devices that utilize unicast sidelink-centric slots as described above. Here, a broadcast sidelink-centric slot utilized in the absence of unicast sidelink-centric slot transmissions may be referred to as an orthogonalized broadcast, while a broadcast sidelink-centric slot utilized in the presence of unicast sidelink-centric slot transmissions may be referred to as an in-band broadcast.

The sidelink traffic portion706may be configured utilizing a suitable MCS selected according to channel conditions. In one example, the receiving device may select an MCS based on a measurement of a receive power of a reference signal in the STS704portion, and a measurement of interference. For example, in low receive power and/or high interference scenarios, the receiving device may select a more robust MCS, e.g., utilizing a lower modulation order and/or a lower coding rate.

The sidelink-centric slot700may also include an UL burst708. In some aspects, the UL burst708may be similar to the UL burst506,606described above with reference toFIGS. 5-6. Notably, as illustrated inFIG. 7, the UL burst708may be included in the end portion of the sidelink-centric slot700. By including the UL burst708in the end portion of the sidelink-centric slot, the likelihood of interfering with the UL bursts506,606of DL-centric and UL-centric slots of nominal traffic is minimized or reduced. In other words, because the DL-centric slot, the UL-centric slot, and the sidelink-centric slot have their UL bursts506,606,708communicated during a similar portion of their respective slot, the likelihood of interference between those UL bursts506,606,708is minimized or reduced. That is, the UL bursts506,606of DL-centric and UL-centric slots (of nominal traffic) are relatively better protected.

FIG. 8is a diagram illustrating an example of multiple concurrent sidelink-centric slots800according to some aspects of the present disclosure. In some configurations, the sidelink-centric slots may be utilized for broadcast communication. Although the example illustrated inFIG. 8shows three slots (e.g., SLOTN, SLOTN+1, SLOTN+2), one of ordinary skill in the art will understand that any plural number of slots may be included without deviating from the scope of the present disclosure. The first slot (e.g., SLOTN) may include a DL burst802(e.g., PDCCH, as described in greater detail above) and an STS portion804(as also described in greater detail above). The STS portion804may indicate a duration that extends across more than one slot (e.g., SLOTN, SLOTN+1, SLOTN+2). In other words, the STS may indicate a requested duration of time to keep the sidelink channel available for sidelink signals, and that requested duration may extend until the end of the last slot (e.g., SLOTN+2) of a plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2). Therefore, although the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2) each include a sidelink traffic portion806,812,818, not every slot requires the STS portion804. By not including the STS portion804in every slot of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2), the overall amount of overhead is relatively lower than it would otherwise be (e.g., if the STS portion804was included in every slot). By reducing overhead, relatively more of the slots (e.g., SLOTN+1, SLOTN+2) lacking the STS portion804can be utilized for communication of the sidelink traffic portion812,818, which thereby increases relative throughput.

Within the first slot (e.g., SLOTN), the STS portion804may be followed by a sidelink traffic portion806(which is described in greater detail above with reference to the sidelink traffic portion706inFIG. 7). The sidelink traffic portion806may be followed by the UL burst808(which is described in greater detail above with reference to the UL burst708inFIG. 7). In the example illustrated in FIG.8, every slot (e.g., SLOTN+1, SLOTN+2) following the first slot (e.g., SLOTN) includes a DL burst810,816at an initial/beginning portion of each slot and an UL burst814,820at the end portion of each slot. By providing the DL burst810,816at the initial/beginning of each slot and providing the UL burst814,820at the end portion of each slot, the sidelink-centric slots have a structure that minimizes the likelihood of interference with DL/UL control/scheduling information of nominal traffic (as described in greater detail above).

FIG. 9is a diagram illustrating another example of a sidelink-centric slot900according to some aspects of the present disclosure. In some configurations, this sidelink-centric slot, or a slot having similar structure, may be utilized for a unicast communication. A unicast communication may refer to a point-to-point transmission by a scheduled entity204(e.g., UE1) to a particular scheduled entity204(e.g., UE2).

In each of the sidelink-centric slots that follow, as described below, for a given device, certain fields or portions of the slot may correspond to transmissions from that device or reception at that device, depending on whether that given device is transmitting sidelink traffic or receiving sidelink traffic. As illustrated in each ofFIGS. 9-13, a time gap (e.g., guard interval, guard period, etc.) between adjacent data portions, if any, may enable a device to transition from a listening/receiving state (e.g., during DSS904for a non-primary device) to a transmitting state (e.g., during STS906for a non-primary device); and/or to transition from a transmitting state (e.g., during STS906for a non-primary device) to a listening/receiving state (e.g., during DRS908for either a primary or non-primary transmitting device). The duration of such a time gap or guard interval may take any suitable value, and it should be understood that the illustrations inFIGS. 9-13are not to scale with respect to time. Many such time gaps are shown in the various illustrations to represent some aspects of particular embodiments, but it should be understood that the illustrated time gaps may be wider or narrower than they appear, and in some examples, an illustrated time gap may not be utilized, while in other examples, the lack of a time gap might be replaced with a suitable time gap between regions of a slot. In some aspects of the disclosure, a particular slot may be structured with time gaps corresponding to TX-RX transitions as well as RX-TX transitions, in order that the same slot structure may accommodate the operation of a given device both when that device is transmitting sidelink traffic, and when that device is receiving sidelink traffic.

In the example illustrated inFIG. 9, the sidelink-centric slot includes a DL burst902, which may include a physical downlink control channel (PDCCH). In some aspects, the DL burst902may be configured the same as or similar to the DL burst502(e.g., PDCCH) described in greater detail above with reference toFIG. 5. Additionally or alternatively, the DL burst902may include grant information related to the sidelink signal or sidelink communication. Non-limiting examples of grant information may include generic grant information and link-specific grant information. Link-specific grant information may refer to information that enables a specific sidelink communication to occur between two particular scheduled entities204(e.g., UEs). In comparison, generic grant information may refer to information that generally enables sidelink communications to occur within a particular cell, without specifying a particular sidelink communication.

Notably, as illustrated inFIG. 9, the DL burst902may be included in the beginning or initial portion of the sidelink-centric slot900. By including the DL burst902in the beginning or initial portion of the sidelink-centric slot900, the likelihood of interfering with the DL bursts502,602of DL-centric and UL-centric slots of nominal traffic is minimized In other words, because the DL-centric slot500, the UL-centric slot600, and the sidelink-centric slot900have their DL control information communicated during a common portion of their respective slots, the likelihood of interference between the DL control information and the sidelink signals is minimized That is, the DL bursts502,602of DL-centric and UL-centric slots (of nominal traffic) are relatively better protected.

The sidelink-centric slot900may further include a primary request signal such as a direction selection signal (DSS)904, and a secondary request signal such as a source transmit signal (STS)906. In various examples, the content of the DSS and the STS may take different formats. As one example, the DSS904may be utilized for direction selection and the STS906may be utilized as a request signal. Here, direction selection refers to the selection whether a primary sidelink device transmits a request signal in the STS, or whether a primary sidelink device receives a request signal (i.e., a non-primary or secondary sidelink device transmits a request signal in the STS). In this example, the DSS may include a destination ID (e.g., corresponding to a non-primary or secondary sidelink device) and a direction indication. In this manner, a listening sidelink device that receives the DSS transmission and is not the device corresponding to the destination ID need not necessarily be active and monitoring for the STS transmission. In this example, the STS may include an indication of a requested duration of time to reserve a sidelink channel for sidelink data. Accordingly, with the STS/DSS portions of the sidelink-centric slot900, a request for reservation of the sidelink channel in a desired direction between a primary and a non-primary sidelink device may be established.

In another example, content of the DSS904and the STS906may be substantially similar to one another, although the DSS904may be utilized by a primary sidelink device and the STS906may be utilized by a secondary sidelink device. The DSS and/or STS may be utilized by a scheduled entity204(e.g., UE) as a request signal to indicate a requested duration of time to keep a sidelink channel available for a sidelink signal. One of ordinary skill in the art will understand that the DSS and/or STS may include various additional or alternative information without necessarily deviating from the scope of the present disclosure. In some configurations, the DSS and/or STS may include a destination identifier (ID). The destination ID may correspond to a specific apparatus intended to receive the STS/DSS (e.g., UE2). In some configurations, the DSS and/or STS may indicate a duration of the sidelink transmission, and/or may include a reference signal to enable channel estimation and RX-yielding, a modulation and coding scheme (MCS) indicator, and/or various other information. Here, the MCS indicator may be utilized to inform the receiving device of the MCS utilized for transmissions in the sidelink traffic portion.

A primary device may transmit a primary request signal (e.g., a DSS) during a primary request portion of a slot (e.g., DSS904), and a non-primary device (e.g., a secondary device) may transmit a secondary request signal (e.g., an STS) during a secondary request portion of the slot (e.g., STS906portion). A primary device may refer to a device (e.g., a UE or scheduled entity204) that has priority access to the sidelink channel During an association phase, one device may be selected as the primary device and another device may be selected as the non-primary (e.g., secondary) device. In some configurations, the primary device may be a relay device that relays a signal from a non-relay device to another device, such as a scheduling entity202(e.g., base station). The relay device may experience relatively less path loss (when communicating with the scheduling entity202(e.g., base station)) relative to the path loss experienced by the non-relay device.

During the DSS904portion, the primary device transmits a DSS, and the non-primary device listens for the DSS from a primary device. On the one hand, if the non-primary device detects a DSS during the DSS904portion, then the non-primary device will not transmit an STS during the STS906portion. On the other hand, if the non-primary device does not detect a DSS during the DSS904portion, then the non-primary device may transmit an STS during the STS906portion.

If the sidelink channel is available for the requested duration of time, an apparatus identified or addressed by the destination ID in the STS/DSS, which receives the STS/DSS, may communicate a confirmation signal, such as a destination receive signal (DRS), during the DRS908portion. The DRS may indicate availability of the sidelink channel for the requested duration of time. The DRS may additionally or alternatively include other information, such as a source ID, a duration of the transmission, a signal to interference plus noise ratio (SINR) (e.g., of the received RS from the source device), an RS to enable TX-yielding, CQI information, and/or various other suitable types of information. The exchange of STS/DSS and DRS enable the scheduled entities204(e.g., UEs) performing the sidelink communications to negotiate the availability of the sidelink channel prior to the communication of the sidelink signal, thereby minimizing the likelihood of interfering sidelink signals. In other words, without the STS/DSS and DRS, two or more scheduled entities204(e.g., UEs) might concurrently transmit sidelink signals using the same resources of the sidelink traffic portion910, thereby causing a collision and resulting in avoidable retransmissions.

The sidelink-centric slot may also include a sidelink traffic portion910. The sidelink traffic portion910may sometimes be referred to as the payload or sidelink-burst of the sidelink-centric slot. In an example where the sidelink-centric slot is utilized for unicast transmissions, the sidelink traffic portion910may carry a physical sidelink shared channel (PSSCH). The sidelink traffic portion910may include the communication resources utilized to communicate sidelink user data traffic from one scheduled entity204(e.g., UE1) to a second scheduled entity204(e.g., UE2). In some configurations, the MCS of the sidelink signal communicated in the sidelink traffic portion910may be selected based on the CQI feedback included in the DRS908.

The sidelink-centric slot may also include a sidelink acknowledgment portion912. In some aspects, the sidelink acknowledgment portion912may carry a physical sidelink HARQ indicator channel (PSHICH). After communicating the sidelink signal in the sidelink traffic portion910, acknowledgment information may be communicated between the scheduled entities204(e.g., UEs) utilizing the sidelink acknowledgment portion912. Non-limiting examples of such acknowledgment information may include an ACK signal, a NACK signal, a HARQ indicator, and/or various other suitable types of acknowledgment information. For example, after receiving and successfully decoding a sidelink signal from UE1in the sidelink traffic portion910, UE2may transmit an ACK signal to the UE1in the sidelink acknowledgment portion912of the sidelink-centric slot.

The sidelink-centric slot may also include an UL burst914. In some aspects, the UL burst914may be configured the same as or similar to the UL burst506,606described above with reference toFIGS. 5-6. Notably, as illustrated in the example ofFIG. 9, the UL burst914may be included in the end portion of the sidelink-centric slot. By including the UL burst914in the end portion of the sidelink-centric slot, the likelihood of interfering with the UL burst506,606of DL-centric and UL-centric slots of nominal traffic is minimized In other words, because the DL-centric slot, the UL-centric slot, and the sidelink-centric slot have their UL burst506,606,914communicated during the same or similar portion of their respective slot, the likelihood of interference between those UL bursts506,606,914is reduced. That is, the UL bursts506,606of DL-centric and UL-centric slots (of nominal traffic) are relatively better protected.

FIGS. 10-11, described below, illustrate multiple concurrent sidelink-centric slots according to some aspects of the disclosure. As with the example described above in relation toFIG. 9, in some configurations, the concurrent sidelink-centric slots inFIGS. 10 and 11may be utilized for unicast communication. Although the examples illustrated inFIGS. 10 and 11show three slots (e.g., SLOTN, SLOTN+1, SLOTN+2), one of ordinary skill in the art will understand that any plural number of concurrent sidelink-centric slots may be included as described herein without deviating from the scope of the present disclosure.

Referring now specifically toFIG. 10, a diagram illustrates an example of multiple concurrent sidelink-centric slots1000according to an aspect of the present disclosure. The first slot (e.g., SLOTN) may include the DL burst1002(e.g., PDCCH, as described in greater detail above), DSS1004, STS1006, and DRS1008(as also described in greater detail above). In this example, the request signal communicated during DSS1004and/or STS1006may indicate a duration that extends across the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2). In other words, the request signal may indicate a requested duration of time to keep the sidelink channel available for sidelink signals, and that requested duration may extend until the end of the last slot (e.g., SLOTN+2) of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2). If the sidelink channel is available for that requested duration of time, then the confirmation signal (e.g., DRS) may be communicated in the DRS1008portion (as described in greater detail above).

Although the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2) each include a sidelink traffic portion1010,1016,1022, not every slot necessarily requires DSS1004and/or STS1006. By not including DSS1004and/or STS1006in every slot of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2), the overall amount of overhead is relatively lower than it would otherwise be (e.g., if DSS1004and/or STS1006were included in every slot). By reducing overhead, relatively more of the slots (e.g., SLOTN+1, SLOTN+2) lacking DSS1004and/or STS1006can be utilized for communication of the sidelink traffic1016,1022, which thereby increases relative throughput.

Within the first slot (e.g., SLOTN), DSS1004, STS1006, and DRS1008may be followed by a first sidelink traffic portion1010(which is described in greater detail above with reference to the sidelink traffic portion910inFIG. 9). The sidelink traffic portions1010,1016, and1022may each be followed by respective UL bursts1012,1018, and1026(which are described in greater detail above with reference to the UL burst914inFIG. 9). In the example illustrated inFIG. 10, every slot (e.g., SLOTN+1, SLOTN+2) following the first slot (e.g., SLOTN) includes a DL burst1014,1020at an initial/beginning portion of each slot and an UL burst1018,1026at the end portion of each slot. By providing the DL burst1014,1020at the initial/beginning of each slot and providing the UL burst1018,1026at the end portion of each slot, the sidelink-centric slots have a structure that minimizes the likelihood of interference with DL/UL control/scheduling information of nominal traffic (as described in greater detail above).

In the example illustrated inFIG. 10, the sidelink-centric slots1000include a single sidelink acknowledgment portion1024in a last/final slot (e.g., SLOTN+2) of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2). The acknowledgment information communicated in the sidelink acknowledgment portion1024in the last/final slot (e.g., SLOTN+2) may correspond to the sidelink signals included in one or more (e.g., all) preceding sidelink traffic portions1010,1016,1022. For example, the sidelink acknowledgment portion1024may include a HARQ identifier corresponding to sidelink signals communicated throughout the sidelink traffic portions1010,1016,1022of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2). Because the sidelink acknowledgment portion1024is not included in every slot (e.g., SLOTN, SLOTN+1), the overall amount of overhead is relatively lower than it would otherwise be (e.g., if a sidelink acknowledgment portion were included in every slot). By reducing overhead, relatively more of the slots (e.g., SLOTN, SLOTN+1) lacking the sidelink acknowledgment portion1024can be utilized for communication of sidelink user data traffic, which thereby increases relative throughput. However, one of ordinary skill in the art will readily understand that the example illustrated inFIG. 10is non-limiting and alternative configurations may exist without necessarily deviating from the scope of the present disclosure.

FIG. 11is a diagram illustrating one example of such an alternative configuration of multiple concurrent sidelink-centric slots1100. Various aspects illustrated inFIG. 11(e.g., DL bursts1102,1116,1124; DSS1104; STS1106; DRS1108; and UL bursts1114,1122,1130) are described above with reference toFIG. 7and therefore will not be repeated here to avoid redundancy. An aspect in which the example illustrated inFIG. 11may differ from the example illustrated inFIG. 10is that the example inFIG. 11includes a sidelink acknowledgment portion1112,1120,1128in every slot of the plurality of slots (e.g., SLOTN, SLOT1+, SLOTN+2). For example, each sidelink acknowledgment portion1112,1120, and1128may respectively communicate acknowledgment information corresponding to a sidelink signal included in the sidelink traffic portion1110,1118, and1126in its slot. By receiving acknowledgment information corresponding to the sidelink signal in that particular slot, the scheduled entity204(e.g., UE) may obtain relatively better specificity regarding the communication success of each sidelink signal. For example, if only one sidelink signal in a single sidelink traffic portion (e.g., sidelink traffic portion1110) is not successfully communicated, retransmission can be limited to only the affected sidelink traffic portion (e.g., sidelink traffic portion1110) without the burden of retransmitting unaffected sidelink traffic portions (e.g., other sidelink traffic portions1118,1126).

The above examples of sidelink-centric subframes or slots utilize licensed spectrum for wireless communication. However, in various aspects of the present disclosure, sidelink signals may also be transmitted over unlicensed spectrum. In some examples, access to unlicensed spectrum may involve sharing the unlicensed spectrum with traditional types of unlicensed wireless communication, such as Wi-Fi, Bluetooth, LTE-U (Long Term Evolution (LTE) in unlicensed spectrum), LAA (Licensed-Assisted Access), or MuLTEfire. To provide fair sharing of the unlicensed spectrum between unlicensed devices (e.g., both sidelink devices and other types of unlicensed devices), sidelink wireless communication over unlicensed spectrum may utilize “Listen Before Talk” (LBT). LBT is a contention-based protocol used in wireless communication that allows several wireless devices to utilize the same spectrum or channel. For example, before a device can transmit a signal over the shared channel, the device may first check (listen) to determine that the channel is not currently in use. If the channel is not being used (e.g., the channel is idle or silent), the device can transmit the signal over the shared channel.

LBT may also utilize a back-off procedure in which a device having traffic to send generates a random back-off time after detecting the unlicensed channel is idle, and then decrements a back-off timer initialized with the random back-off time until the unlicensed channel becomes busy or the timer reaches zero. If the unlicensed channel becomes busy prior to expiration of the back-off timer, the device may freeze the timer. When the back-off timer expires (or decrements to zero), the device may transmit the traffic.

In addition, to enable joint access of the unlicensed spectrum for multiple sidelinks, where each sidelink corresponds to a unicast link (or wireless connection) between two sidelink devices, sidelink transmissions may further be synchronized among the different concurrently active sidelinks. In other unlicensed networks, such as LTE-U, LAA and MuLTEfire, synchronization is typically achieved via control signaling either over a licensed spectrum or over a backhaul connection. However, since each unicast sidelink is between two wireless sidelink devices, back-haul signaling is not available. Moreover, control signaling over licensed spectrum may not be available or practical in many situations.

Therefore, in accordance with various aspects of the present disclosure, each sidelink device with traffic to send may perform independent and asynchronous LBT using a random or calculated back-off timer value selected to promote fair access to the unlicensed channel. The first sidelink device to complete the back-off procedure may then transmit a joint access synchronization (JAS) signal to synchronize access to the unlicensed channel among the various sidelink devices.

FIG. 12is a diagram illustrating synchronized access in unlicensed sidelink wireless communication according to some embodiments. In the example shown inFIG. 12, two sidelinks (A->B and C->D) share an unlicensed channel (spectrum). Sidelink A->B corresponds to a sidelink between UEAand UEB, while sidelink C->D corresponds to a sidelink between UECand UED. If both UEAand UEChave traffic to transmit, each may perform independent and asynchronous LBT. For example, UEAmay have traffic to transmit before UEC, and therefore, UEAmay initiate the LBT procedure prior to UEC. UEAand UECmay each listen to the unlicensed channel (e.g., turn on their respective receivers to monitor the carrier for any over-the-air transmissions by other devices), and if the channel is idle, generate a respective back-off time (value) and initialize a respective back-off timer with the generated back-off value. In the example shown inFIG. 12, the back-off value generated by UECis less than the back-off value generated by UEA. Thus, the back-off timer of UECexpires before the back-off timer of UEA.

Upon expiration of the back-off timer, UECgenerates and transmits the JAS signal1202over the unlicensed channel to synchronize access to the unlicensed channel among sidelink devices (e.g., UEAand UEC). The JAS signal1202may include, for example, network allocation vector (NAV) information that indicates a duration of time that the sidelink channel may be accessed by sidelink devices. The NAV information effectively reserves the unlicensed channel for sidelink communication for the indicated duration of time. In some examples, the duration of time may correspond to an amount of traffic that UEChas to send. For example, UECmay calculate the duration of time based on a transmit buffer status (e.g., fullness of the transmit buffer). In some examples, the JAS signal may be compatible with other unlicensed wireless technology, such as Wi-Fi, Bluetooth, LTE-U, LAA, and/or MuLTEfire, to enable other unlicensed devices to determine the duration of time that the unlicensed channel may be busy. In other examples, UECmay transmit one or more separate compatible signals including the NAV information.

After transmission of the JAS signal1202, synchronized access to the unlicensed channel across various active sidelinks may be achieved through distributed handshake signaling. In various aspects of the present disclosure, the distributed handshake signaling may be implemented using an unlicensed sidelink-centric slot structure including a DSS, STS and DRS exchange.

FIG. 13is a diagram1300illustrating an example of an unlicensed sidelink-centric slot according to some embodiments. The example of the unlicensed sidelink-centric slot illustrated inFIG. 13includes an LBT portion1302, a JAS portion1304, a DSS portion1306, an STS portion1308, a DRS portion1310, a sidelink traffic portion1312and a sidelink acknowledgment portion1314. Thus, the unlicensed sidelink-centric slot is similar to the licensed sidelink-centric slot shown inFIG. 9with the exception that the unlicensed sidelink-centric slot includes the LBT1302and JAS1304portions and does not include an UL burst or control portion.

Within the LBT portion1302, as described above, one or more unlicensed sidelink devices perform LBT with back-off timers initialized to respective back-off values. If the unlicensed channel remains idle, at the expiration of a back-off timer of one of the unlicensed sidelink devices (e.g., UECshown inFIG. 12), the unlicensed sidelink device generates and transmits the JAS signal within the JAS portion1304. The JAS portion1304may include, for example, NAV information indicating a duration of time that unlicensed sidelink devices may access the unlicensed channel.

A time gap (e.g., a guard interval, etc.) between the JAS portion1304and the DSS portion1306allows a primary device to transition from a listening/receiving state to a transmitting state (during DSS). If one or more non-primary devices do not detect a DSS signal during the DSS portion1306, then the non-primary devices may transmit respective STS signals during the STS portion1308. As long as the interference between different sidelinks remains within acceptable levels (e.g., the SINR experienced at a sidelink receiving device is greater than a threshold when two or more transmitting sidelink devices concurrently transmit STS signals during the STS portion1308), each sidelink receiving device may transmit a respective DRS signal during DRS portion1310to enable concurrent transmissions of multiple sidelink signals over the unlicensed channel. Additional description regarding the DSS1306, STS1308and DRS1310portions are provided above (e.g., with reference toFIG. 9) and therefore will not be repeated to avoid redundancy.

As also described in greater detail above, the sidelink signal(s) may be communicated in the sidelink traffic portion1312of the unlicensed sidelink-centric slot. After communicating the sidelink signal in the sidelink traffic portion1312, acknowledgment information may be communicated (e.g., from UEBand UEDto UEAand UES, respectively, shown inFIG. 12) in the sidelink acknowledgment portion1314. In some configurations, the sidelink acknowledgment portion1314may be a physical sidelink HARQ indicator channel (PSHICH).

FIG. 14is a diagram illustrating an example of multiple, concurrent, unlicensed sidelink-centric slots according to some embodiments. The example shown inFIG. 14includes the LBT portion1402and JAS portion1404, as discussed above in connection withFIG. 13. However, instead of the JAS signal indicating that the unlicensed channel is reserved for sidelink communications for a single slot, the JAS signal indicates that the unlicensed channel is reserved for sidelink communications for two or more slots. In the example shown inFIG. 14, the unlicensed channel is reserved for two slots (e.g., SLOTNand SLOTN+1). Each slot (e.g., SLOTNand SLOTN+1) includes a respective DSS portion1406, STS portion1408, DRS portion1410, sidelink traffic portion1412and sidelink acknowledgment portion1414.

In addition, each slot (e.g., SLOTNand SLOTN+1) includes a respective JAS portion1404. The first JAS signal in SLOTNincludes the initial (or entire) duration of time that the unlicensed channel is reserved for sidelink communications. Subsequent JAS signals (e.g., the JAS signal in SLOTN+1) include a remaining duration of time that the unlicensed channel is reserved for sidelink communications. In some examples, the remaining duration of time may be calculated based on the initial duration of time and an amount of lapsed time that has occurred since transmission of the first JAS signal in the first slot (e.g., SLOTN). For example, if the initial duration of time is 1 ms and the amount of time that has lapsed since transmission of the initial duration of time is 0.2 ms, the remaining duration of time may be calculated as a difference between the initial duration of time and the amount of lapsed time (e.g., 1 ms−0.2 ms=0.8 ms). However, it should be understood that any suitable function utilizing the initial duration of time and amount of lapsed time may be used to calculate the remaining duration of time.

Each of the JAS signals may be transmitted by the original sidelink device that transmitted the initial JAS signal in the first slot (e.g., SLOTN). The inclusion of JAS signals in subsequent slots may enable new sidelink devices to transmit STS/DRS/sidelink signals each slot. For example, a sidelink device that did not receive the first JAS signal may still be able to transmit within the reserved period of time by receiving a subsequent JAS signal.

FIG. 15is a diagram illustrating an example of multiple, concurrent, unlicensed sidelink-centric slots according to some embodiments. The example shown inFIG. 15includes the LBT portion1502and JAS portion1504indicating the unlicensed channel is reserved for two or more slots, as discussed above in connection withFIG. 14. In addition, the DSS1506and/or STS1508may also indicate a transmission duration that extends across more than one slot (e.g., SLOTN, SLOTN+1, SLOTN+2). If the sidelink channel is available for that requested duration of time, then the DRS may be communicated in the DRS portion1510(as described in greater detail above). Although the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2) each include a sidelink traffic portion1512,1518,1524, not every slot requires DSS1506and/or STS1508. By not including DSS1506and/or STS1508in every slot of the plurality of slots (e.g., SLOTN, SLOTN+1, SLOTN+2), the overhead may be reduced, as described above in connection withFIG. 10.

Each of the sidelink traffic portions1512,1518, and1524may be followed by a respective sidelink acknowledgment portion1514,1520, and1526. In addition, one or more of the sidelink acknowledgment portions1514,1520, and1526may be followed by a subsequent JAS portion1516and1522. As indicated above, each subsequent JAS portion1516and1522may include a remaining duration of time that the sidelink channel is reserved for sidelink communications to enable new sidelink devices to access the unlicensed channel In some examples, as shown inFIG. 15, each slot (e.g., SLOTN, SLOTN+1, SLOTN+2) may include a JAS portion1504,1516, and1522. In other examples, the subsequent JAS signals may be transmitted at periodic intervals after the initial joint access synchronization signal (e.g., corresponding to a number of slots). For example, a subsequent JAS signal may be transmitted every x-SLOT's, where x is an integer number greater than or equal to1.

In some examples, if a subsequent JAS signal is sent every x-SLOT's, each access (e.g., continuous sidelink signal transmission duration) may be up to x-SLOT's without requiring a break in between slots. For example, as described above in connection withFIG. 10, acknowledgment information may be transmitted after the last slot or immediately prior to a JAS signal instead of in between each slot to enable continuous transmission of sidelink user data traffic over two or more slots.

FIG. 16is a flow chart illustrating a process1600for unlicensed sidelink communication in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In the following description, a sidelink signal transmission is discussed with reference to a transmitting device and a receiving device. It will be understood that either device may the user equipment126and/or128illustrated inFIG. 1; and/or the scheduled entity204illustrated inFIGS. 2 and 4. In some examples, the process1600may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1602, a transmitting device with traffic to send may listen to a sidelink channel including unlicensed spectrum (e.g., an unlicensed sidelink channel). At block1604, the transmitting device may determine whether the unlicensed sidelink channel is idle. For example, the transmitting device may determine whether traffic is currently being transmitted over the unlicensed sidelink channel. If the unlicensed sidelink channel is busy (N branch of1604), at block1606, the transmitting device waits until the channel is idle.

If the unlicensed sidelink channel is idle (Y branch of1604), at block1608, the transmitting device generates a back-off value and initializes a back-off timer with the back-off value. In some examples, the back-off value may be randomly selected from a set of possible back-off values (e.g., values within a contention window). In other examples, the back-off value may be generated based on the type of traffic (e.g., priority associated with traffic) to be sent. In still other examples, the back-off value may be generated to provide fair access to the unlicensed sidelink channel by different types of unlicensed devices (e.g., unlicensed sidelink devices and other unlicensed devices, such as Wi-Fi, Bluetooth, etc.).

AlthoughFIG. 16illustrates block1608occurring after block1604and when the unlicensed sidelink channel is idle, in another example, block1608may be performed before block1604. In this example, if the unlicensed sidelink channel is busy, the transmitting device may freeze the back-off timer until the channel becomes idle.

At block1610, the transmitting device may determine whether the back-off timer has expired. If the back-off timer has not expired (N branch of1610), at block1612, the transmitting device may determine whether a JAS signal has been received from another sidelink device. If a JAS signal has been received from another sidelink device (Y branch of1612), at block1614, the transmitting device cancels the back-off timer. If a JAS signal is not received prior to expiration of the back-off timer (N branch of1614and Y branch of1610), at block1614, the transmitting device generates and transmits a JAS signal to synchronize access to the unlicensed sidelink channel by the transmitting device and any other sidelink devices that may have traffic to transmit.

FIG. 17is a flow chart illustrating a process1700for unlicensed sidelink communication in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In the following description, a sidelink signal transmission is discussed with reference to a transmitting device and a receiving device. It will be understood that either device may the user equipment126and/or128illustrated inFIG. 1; and/or the scheduled entity204illustrated inFIGS. 2 and 4. In some examples, the process1700may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1702, a transmitting device with traffic to send may listen to a sidelink channel including unlicensed spectrum (e.g., an unlicensed sidelink channel). At block1704, the transmitting device may determine whether the unlicensed sidelink channel is idle. For example, the transmitting device may determine whether traffic is currently being transmitted over the unlicensed sidelink channel. If the unlicensed sidelink channel is busy (N branch of1704), the process returns to block1702, where the transmitting device listens to the sidelink channel.

If the unlicensed sidelink channel is idle (Y branch of1704), at block1706, the transmitting device generates a back-off value and initializes a back-off timer with the back-off value. In some examples, the back-off value may be randomly selected from a set of possible back-off values (e.g., values within a contention window). In other examples, the back-off value may be generated based on the type of traffic (e.g., priority associated with traffic) to be sent. In still other examples, the back-off value may be generated to provide fair access to the unlicensed sidelink channel by different types of unlicensed devices (e.g., unlicensed sidelink devices and other unlicensed devices, such as Wi-Fi, Bluetooth, etc.).

At block1708, the transmitting device may determine whether the back-off timer has expired. If the back-off timer has not expired (N branch of1708), at block1710, the transmitting device may determine whether a JAS signal has been received from another sidelink device. If a JAS signal has not been received (N branch of1710), at block1712, the transmitting device may determine whether the unlicensed sidelink channel is idle. If the unlicensed sidelink channel is not idle (N branch of block1712), at block1714, the transmitting device may freeze the back-off timer at a current value thereof. For example, the unlicensed sidelink channel may become busy when traffic other than sidelink traffic (e.g., traffic generated by another unlicensed device, such as a Wi-Fi, Bluetooth, LTE-U, LAA, or MuLTEfire device) is present on the unlicensed channel. The process then returns to block1702, where the transmitting device listens to the unlicensed sidelink channel Once the unlicensed sidelink channel becomes idle again (Y branch of1704), the transmitting device may re-initialize the back-off timer at the current value (e.g., the value when the back-off timer was frozen).

Returning to decision block1710, if a JAS signal has been received from another sidelink device before expiration of the back-off timer (Y branch of1710), at block1716, the transmitting device cancels the back-off timer. However, if a JAS signal is not received prior to expiration of the back-off timer (N branch of1710and Y branch of1708), and the channel remain idle (Y branch of1712), at block1718, the transmitting device generates and transmits a JAS signal to synchronize access to the unlicensed sidelink channel by the transmitting device and any other sidelink devices that may have traffic to transmit.

FIG. 18is a flow chart illustrating a process1800for unlicensed sidelink communication in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In the following description, a sidelink signal transmission is discussed with reference to a transmitting device and a receiving device. It will be understood that either device may the user equipment126and/or128illustrated inFIG. 1; and/or the scheduled entity204illustrated inFIGS. 2 and 4. In some examples, the process1800may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1802, a transmitting device preparing to send a JAS signal may calculate an initial (or total) duration of time that the sidelink channel should be accessible to sidelink devices. In some examples, the total duration of time may correspond to an amount of traffic that the transmitting device has to send. For example, the transmitting device may calculate the total duration of time based on a transmit buffer status (e.g., fullness of the transmit buffer).

At block1804, the transmitting device may transmit a first JAS signal with the total duration of time. In some examples, the JAS signal may include NAV information indicating the total duration of time. The NAV information effectively reserves the unlicensed channel for sidelink communication for the indicated total duration of time. In some examples, the JAS signal may be compatible with other unlicensed wireless technology, such as Wi-Fi, Bluetooth, LTE-U, LAA, and/or MuLTEfire, to enable other unlicensed devices to determine the total duration of time that the unlicensed channel may be busy. In other examples, the transmitting device may also transmit one or more separate compatible signals including the NAV information.

At block1806, the transmitting device may determine whether to send an additional JAS signal within the total reserved duration of time. In some examples, an additional JAS signal may enable new sidelink devices to transmit sidelink signals within the reserved duration of time. For example, a sidelink device that did not receive the first JAS signal may still be able to transmit within the reserved period of time by receiving a subsequent JAS signal. If the transmitting device determines that an additional JAS signal should be sent (Y branch of block1806), at block1808, the transmitting device calculates a remaining duration of time that the unlicensed channel is reserved for sidelink communications. In some examples, the remaining duration of time may be calculated as a difference between the initial duration of time and an amount of lapsed time that has occurred since transmission of the first JAS signal. At block1810, the transmitting device may then send the additional JAS signal with the remaining duration of time. If there are no additional JAS signals to be sent (N branch of block1806), the process ends.

FIG. 19is a flow chart illustrating a process1900for unlicensed sidelink communication in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In the following description, a sidelink signal transmission is discussed with reference to a transmitting device and a receiving device. It will be understood that either device may the user equipment126and/or128illustrated inFIG. 1; and/or the scheduled entity204illustrated inFIGS. 2 and 4. In some examples, the process1900may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block1902, a transmitting device may transmit a JAS signal including a total duration of time to reserve an unlicensed sidelink channel for sidelink communication. For example, the JAS signal may include NAV information indicating the total duration of time. At block1904, the transmitting device may transmit a request signal indicating a requested first duration of time within the total duration of time for the transmitting device to utilize the unlicensed sidelink channel to transmit a sidelink signal. In some examples, the transmitting device is a primary device, and the request signal may include both a primary request signal (e.g., a DSS) and a secondary request signal (e.g., STS). If the transmitting device is not a primary device, the request signal may include only the secondary request signal (e.g., STS). In addition, if the transmitting device is not a primary device, the transmitting device may further receive an additional request signal from an additional device indicating an additional requested duration of time overlapping the first duration of time for the additional device to utilize the unlicensed sidelink channel to transmit an additional sidelink signal.

At block1906, the transmitting device may then receive a confirmation signal (e.g., a DRS) from a receiving device. The confirmation signal may indicate the availability of the unlicensed sidelink channel for the first requested duration of time. At block1908, the transmitting device may then transmit the sidelink signal over the unlicensed sidelink channel.