Indicating availability for sidelink communication

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; identify future available information (FAI) that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and transmit the FAI based at least in part on determining that the availability condition is satisfied. Numerous other aspects are provided.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for indicating availability for sidelink communication.

BACKGROUND

SUMMARY

In some aspects, a method of wireless communication, performed by a user equipment (UE), may include determining that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; identifying future available information (FAI) that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and transmitting the FAI based at least in part on determining that the availability condition is satisfied.

In some aspects, a method of wireless communication, performed by a UE, may include receiving a plurality of FAI messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; and transmitting, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

In some aspects, a UE for wireless communication may include a memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to determine that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; identify FAI that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and transmit the FAI based at least in part on determining that the availability condition is satisfied.

In some aspects, a UE for wireless communication may include a memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to receive a plurality of FAI messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; and transmit, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to determine that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; identify FAI that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and transmit the FAI based at least in part on determining that the availability condition is satisfied.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to receive a plurality of FAI messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; and transmit, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

In some aspects, an apparatus for wireless communication may include means for determining that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; means for identifying FAI that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and means for transmitting the FAI based at least in part on determining that the availability condition is satisfied.

In some aspects, an apparatus for wireless communication may include means for receiving a plurality of FAI messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; and means for transmitting, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

DETAILED DESCRIPTION

As indicated above,FIG.1is provided as an example. Other examples may differ from what is described with respect toFIG.1.

Controller/processor240of base station110, controller/processor280of UE120, and/or any other component(s) ofFIG.2may perform one or more techniques associated with indicating availability and/or recommended instances for sidelink communication, as described in more detail elsewhere herein. For example, controller/processor240of base station110, controller/processor280of UE120, and/or any other component(s) ofFIG.2may perform or direct operations of, for example, process1100ofFIG.11, process1200ofFIG.12, and/or other processes as described herein. Memories242and282may store data and program codes for base station110and UE120, respectively. In some aspects, memory242and/or memory282may comprise a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed by one or more processors of the base station110and/or the UE120, may perform or direct operations of, for example, process1100ofFIG.11, process1200ofFIG.12, and/or other processes as described herein. A scheduler246may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE120may include means for determining that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; means for identifying future available information (FAI) that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; means for transmitting the FAI based at least in part on determining that the availability condition is satisfied; and/or the like. In some aspects, UE120may include means for receiving a plurality of future available information (FAI) messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; means for transmitting, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof; and/or the like. In some aspects, such means may include one or more components of UE120described in connection withFIG.2, such as controller/processor280, transmit processor264, TX MIMO processor266, MOD254, antenna252, DEMOD254, MIMO detector256, receive processor258, and/or the like.

As indicated above,FIG.2is provided as an example. Other examples may differ from what is described with respect toFIG.2.

FIG.3is a diagram illustrating an example300of sidelink communications, in accordance with various aspects of the present disclosure.

As shown inFIG.3, a first UE305-1may communicate with a second UE305-2(and one or more other UEs305) via one or more sidelink channels310. The UEs305-1and305-2may communicate using the one or more sidelink channels310for P2P communications, D2D communications, V2X communications (e.g., which may include V2V communications, V2I communications, V2P communications, and/or the like), mesh networking, and/or the like. In some aspects, the UEs305(e.g., UE305-1and/or UE305-2) may correspond to one or more other UEs described elsewhere herein, such as UE120. In some aspects, the one or more sidelink channels310may use a PC5 interface and/or may operate in a high frequency band (e.g., the 5.9 GHz band). Additionally, or alternatively, the UEs305may synchronize timing of transmission time intervals (TTIs) (e.g., frames, subframes, slots, symbols, and/or the like) using global navigation satellite system (GNSS) timing.

As further shown inFIG.3, the one or more sidelink channels310may include a physical sidelink control channel (PSCCH)315, a physical sidelink shared channel (PSSCH)320, and/or a physical sidelink feedback channel (PSFCH)325. The PSCCH315may be used to communicate control information, similar to a physical downlink control channel (PDCCH) and/or a physical uplink control channel (PUCCH) used for cellular communications with a base station110via an access link or an access channel. The PSSCH320may be used to communicate data, similar to a physical downlink shared channel (PDSCH) and/or a physical uplink shared channel (PUSCH) used for cellular communications with a base station110via an access link or an access channel. For example, the PSCCH315may carry sidelink control information (SCI)330, which may indicate various control information used for sidelink communications, such as one or more resources (e.g., time resources, frequency resources, spatial resources, and/or the like) where a transport block (TB)335may be carried on the PSSCH320. The TB335may include data. The PSFCH325may be used to communicate sidelink feedback340, such as hybrid automatic repeat request (HARQ) feedback (e.g., acknowledgement or negative acknowledgement (ACK/NACK) information), transmit power control (TPC), a scheduling request (SR), and/or the like.

In some aspects, a UE305may operate using a transmission mode where resource selection and/or scheduling is performed by the UE305(e.g., rather than a base station110). In some aspects, the UE305may perform resource selection and/or scheduling by sensing channel availability for transmissions. For example, the UE305may measure a received signal strength indicator (RSSI) parameter (e.g., a sidelink-RSSI (S-RSSI) parameter) associated with various sidelink channels, may measure a reference signal received power (RSRP) parameter (e.g., a PSSCH-RSRP parameter) associated with various sidelink channels, may measure a reference signal received quality (RSRQ) parameter (e.g., a PSSCH-RSRQ parameter) associated with various sidelink channels, and/or the like, and may select a channel for transmission of a sidelink communication based at least in part on the measurement(s).

Additionally, or alternatively, the UE305may perform resource selection and/or scheduling using SCI330received in the PSCCH315, which may indicate occupied resources, channel parameters, and/or the like. Additionally, or alternatively, the UE305may perform resource selection and/or scheduling by determining a channel busy rate (CBR) associated with various sidelink channels, which may be used for rate control (e.g., by indicating a maximum number of resource blocks that the UE305can use for a particular set of subframes).

In the transmission mode where resource selection and/or scheduling is performed by a UE305, the UE305may generate sidelink grants, and may transmit the grants in SCI330. A sidelink grant may indicate, for example, one or more parameters (e.g., transmission parameters) to be used for an upcoming sidelink transmission, such as one or more resource blocks to be used for the upcoming sidelink transmission on the PSSCH320(e.g., for TBs335), one or more subframes to be used for the upcoming sidelink transmission, a modulation and coding scheme (MCS) to be used for the upcoming sidelink transmission, and/or the like. In some aspects, a UE305may generate a sidelink grant that indicates one or more parameters for semi-persistent scheduling (SPS), such as a periodicity of a sidelink transmission. Additionally, or alternatively, the UE305may generate a sidelink grant for event-driven scheduling, such as for an on-demand sidelink message.

FIG.4is a diagram illustrating an example400of sidelink communications and access link communications, in accordance with various aspects of the present disclosure.

As shown inFIG.4, a transmitter (Tx) UE405and a receiver (Rx) UE410may communicate with one another via a sidelink, as described above in connection withFIG.3. As further shown, in some sidelink modes, a base station110may communicate with the Tx UE405via a first access link. Additionally, or alternatively, in some sidelink modes, the base station110may communicate with the Rx UE410via a second access link. The Tx UE405and/or the Rx UE410may correspond to one or more UEs described elsewhere herein, such as the UE120ofFIG.1. Thus, a sidelink may refer to a direct link between UEs120, and an access link may refer to a direct link between a base station110and a UE120. Sidelink communications may be transmitted via the sidelink, and access link communications may be transmitted via the access link. An access link communication may be either a downlink communication (from a base station110to a UE120) or an uplink communication (from a UE120to a base station110).

FIG.5is a diagram illustrating an example500of resource scheduling for sidelink communications, in accordance with various aspects of the present disclosure.

As shown inFIG.5, a resource pool505for sidelink communications may include a number of resource blocks (RBs)510. Each RB may have a frequency domain component (sometimes referred to as a sub-channel, a sub-band, a sub-carrier, and/or the like) and a time domain component (sometimes referred to as a subframe, a slot, and/or the like). The frequency domain component may be characterized by a specified sub-band (which may include one or more sub-carriers). The time domain component may be a specified time allocation (e.g., a specified number of frames, subframes, slots, symbols, and/or the like). An RB510may carry sidelink control information (SCI)515, which may indicate various control information used for sidelink communications, as described above in connection withFIG.3. The SCI515may be transmitted via a PSCCH of the RB510. An RB510may include a PSSCH520for transmitting data.

In some aspects, a UE305may perform resource selection and/or scheduling of resources in the resource pool505by reserving one or more RBs510. The UE305may be configured to autonomously reserve the one or more RBs510by transmitting the RB selection(s) in SCI515. The RB510to be reserved may be selected based at least in part on a specified sensing parameter, sensing procedure, SCI515received from another UE305, and/or the like. Different UEs may reserve different RBs510. InFIG.5, the shading of an RB510corresponds to the UE (e.g., UE A, UE B, or UE C) that has reserved the RB510.

As shown inFIG.5, for example, the UE A may reserve a first RB525, corresponding to a first sub-band530(e.g., in a frequency domain) and a first time period535. The UE A may transmit SCI540in the first RB525. The SCI540may include a scheduling assignment reserving a second RB545, corresponding to a second sub-band550and a second time period555. As shown, in some aspects, the first and second sub-bands530and550may be different sub-bands. In some aspects, the first and second sub-bands530and550may be the same sub-band.

The SCI540transmitted in the second RB545may include a scheduling assignment reserving a third RB560, corresponding to the second sub-band550and a third time period565. In some aspects, the third RB560may correspond to a sub-band that is different than the second sub-band550, although they are shown as the same sub-band. The SCI540transmitted in the third RB560may include a scheduling assignment reserving a fourth RB570, corresponding to a third sub-band575and a fourth time period580. As shown, in some aspects, the first, second, and third sub-bands530,550, and575may be different sub-bands. In some aspects, any two or more of the first, second, and third sub-bands530,550, and575may be the same sub-band.

The RBs525,545,560, and570reserved by the UE A for sidelink communication via the SCI540may be selected from a set of available RBs510. An available RB510may include an RB510having frequency and time resources that are available for sidelink communications. The resource pool505also may include unavailable RBs585. An unavailable RB585may be an RB510having frequency resources that are unavailable for sidelink communications, time resources that are unavailable for sidelink communications, or a combination thereof.

Sidelink communications have been developed for new radio (NR), in the V2X context, for licensed spectrum with two modes of radio resource allocations (RRAs). In Mode 1, a base station (e.g., BS110described in connection withFIG.1) schedules sidelink resources to be used by UEs120for sidelink communications. Mode 2 supports autonomous RRA (RRA by one or more UEs120instead of a BS110) but has been developed based at least in part on assumptions that may not hold true for contexts other than V2X (e.g., more generic sidelink use cases, such as pedestrian UEs in V2X, industrial and/or factory automation, and/or the like). For example, sidelink in the V2X context is developed primarily for broadcasting and multicasting, with less emphasis on unicasting. V2X sidelink is also developed under the assumption that the UE120has a dedicated sidelink radio (which UEs120that are not configured specifically for V2X may not have), and that this dedicated sidelink radio does not consume power as rapidly as other UE radios. To reduce transmission collisions in V2X sidelink, UEs120monitor SCIs from other UEs120within a sensing window. V2X sidelink radios are not configured to monitor the availability of other UEs for sidelink communication, but, rather, are configured to use repetitive transmissions to increase the likelihood of receipt.

In use cases other than V2X, UEs may be used for unicast communications and may not include a dedicated sidelink radio. Additionally, or alternatively, in use cases other than V2X, UE radios may be more frequently unavailable for sidelink communications for any number of reasons. For example, a UE radio may be involved in concurrent communications (e.g., other sidelink communications, access link communications, wide band communications, and/or the like); a UE radio may be configured to be periodically deactivated to save power; a UE may have more limited scanning/sensing capability than a typical V2X sidelink radio (e.g., a UE may be limited in the number of SCIs it can decode per subframe); a UE may be forced to deactivate its transmitter to meet a duty-cycle ratio limit (e.g., in some unlicensed bands); and/or the like.

Some techniques and apparatuses described herein enable a UE to transmit an indication of future available information (FAI) that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication, or a combination thereof, thereby providing efficient use of resources in sidelink communications as well as enabling inter-UE communications that might otherwise be difficult or impossible. Some techniques and apparatuses described herein enable a UE to request, from another UE, recommended instances for sidelink communications, and/or enable another UE to indicate recommended instances for sidelink communications (whether or not in response to a request). In this way, aspects of the techniques and apparatuses described herein may enable autonomous NR sidelink communications between UEs in use cases other than (and in addition to) V2X. Aspects of the techniques for providing availability information described herein may reduce the likelihood of collisions between communications, increasing the likelihood of successful communications, which may reduce latency, improve performance, reduce network congestion (e.g., due to retransmissions), and/or the like.

FIG.6is a diagram illustrating an example600of indicating availability for sidelink communications, in accordance with various aspects of the present disclosure. As shown inFIG.6, a UE120may communicate with one or more other UEs120(shown as “sidelink UEs” inFIG.6) via sidelink communications.

As shown by reference number605, the UE120may determine that an availability condition is satisfied. The availability condition may relate to an availability of the UE120for sidelink communication. Determining that the availability condition is satisfied may include determining that the UE120will be unavailable for an amount of time that is greater than or equal to a threshold amount of time in an upcoming time period (e.g., one or more slots, subframes, frames, or another time period). The availability of the UE120for sidelink communication may include availability of the UE120for sidelink reception and/or availability of the UE120for sidelink transmission.

In some aspects, the availability condition may be expressed in terms of a threshold percentage of available time and/or frequency. For example, the availability condition may be satisfied if the UE120will be unavailable for greater than or equal to A % of time for an upcoming B time periods. The B time periods may include B seconds, B milliseconds, B symbols, B slots, B subframes, B frames, and/or the like. As an example, an availability condition may be satisfied if the UE120will be unavailable for sidelink communications for greater than or equal to 50% of an upcoming 10 time periods.

In some aspects, the UE120may be configured with the availability condition. In some aspects, the UE120may receive an indication of the availability condition from a base station110, another UE120, and/or the like. For example, if there is a cluster or group of sidelink UEs120, then the UE120may receive the indication of the availability condition from a cluster head UE120or group head UE120. In some aspects, the indication of the availability condition may include an indication of the availability parameters A and B.

As shown by reference number610, the UE120may identify future available information (FAI). The FAI may indicate at least one of a time domain availability of the UE120for sidelink communication or a frequency domain availability of the UE120for sidelink communication, or a combination thereof. Time domain availability of the UE120may be indicated, by the FAI, in terms of seconds, milliseconds, symbols, slots, subframes, frames, and/or the like. Frequency domain availability of the UE120may be indicated, by the FAI, in terms of sub-carriers, carriers, sub-bands (e.g., sub-bandwidths, bandwidth parts, and/or the like), bands (e.g., having a bandwidth), sub-channels, frequency ranges, and/or the like. Combinations of time and frequency domain availability may be indicated, by the FAI, in terms of combinations of any of the above time and frequency units. For example, combinations of time and frequency domain availability may be indicated, by the FAI, in terms of resource elements (REs), resource blocks (RBs), sub-channels, channels, and/or the like.

The FAI may include committed FAI (CFAI)615, potential FAI (PFAI)620, alternative FAI (AFAI)625, or a combination thereof. As shown, the FAI may indicate a resource configuration630corresponding to an upcoming set of time periods, where each box in the illustrated resource configuration630represents a time period. The resource configuration630may include time periods during which the UE120will be communicating via an access link, in which case the UE120will be unavailable for sidelink communication, as shown. The remaining time periods may include time periods during which the UE120will be available for sidelink communication.

The CFAI615may indicate one or more time periods during which the UE120will be available for sidelink communication, as indicated by the boxes containing a “C,” one or more time periods during which the UE120will be unavailable for sidelink communication, as indicated by the boxes containing an “X,” or a combination thereof. As discussed below in connection withFIG.7, the CFAI615may additionally, or alternatively, indicate one or more sub-carriers on which the UE120will be available for sidelink communication, one or more sub-carriers on which the UE120will be unavailable for sidelink communication, or a combination thereof.

The PFAI620may indicate one or more time periods during which the UE120potentially will be available for sidelink communication—for example, one or more time periods during which the UE120will be available for sidelink communication if requested to be available during the one or more time periods by another UE120, as indicated by boxes containing a “P.” As discussed below in connection withFIG.7, the PFAI620may additionally, or alternatively, indicate one or more sub-carriers on which the UE120will be available for sidelink communication if requested to be available by another UE120. In some aspects, the PFAI620may indicate one or more time periods during which the UE120will be available for sidelink communications if the UE120receives the request from the other UE120within a specified amount of time before the first time period of the one or more time periods begins.

The AFAI625may indicate one or more alternative time periods during which the UE120will be available for sidelink communication as an alternative to the CFAI615and/or one or more alternative time periods during which the UE120will be unavailable for sidelink communication as an alternative to the CFAI615. Additionally, or alternatively, the AFAI625may indicate one or more alternative sub-carriers on which the UE120will be available for sidelink communication as an alternative to the CFAI615and/or one or more alternative sub-carriers on which the UE120will be unavailable for sidelink communication as an alternative to the CFAI615.

In some aspects, the FAI may include a bitmap, where a value of a bit in the bitmap indicates whether the UE120is available for sidelink communication during a time period corresponding to the bit. The value of the bit (alone or in combination with one or more values of one or more additional bits) may indicate the type of availability corresponding to a time period such as, for example, committed availability, potential availability, and/or the like. As discussed below in connection withFIG.7, the bitmap may indicate whether the UE120is available and/or unavailable for sidelink communication on one or more sub-carriers. In some aspects, the bitmap may indicate whether the UE120is available and/or unavailable for sidelink communication in a combination of a time period and one or more sub-carriers. In some aspects, the FAI may include separate bitmaps for different sub-carriers, sub-channels, and/or the like.

For example, a bitmap may include a bit string (e.g., a set of bits) associated with CFAI615and a bit string associated with PFAI620, where a “0” corresponding to a particular time period in both bit strings indicates that the UE120will be unavailable for sidelink communication during the corresponding time period. A “1” in the CFAI615bit string may indicate that the UE120will be available during the corresponding time period (e.g., regardless of whether another UE120requests the UE120to be available in the time period). A “1” in the PFAI bit string may indicate that the UE120potentially will be available during the corresponding time period (e.g., will be available if requested to be available in the time period by another UE120). The AFAI625may indicate an alternative resource configuration635, in which, for example, a “0” in the AFAI bit string may indicate unavailability of the UE120during the corresponding time period and a “1” in the AFAI bit string may indicate availability (e.g., only potential availability, only committed availability, or either potential availability or committed availability) of the UE120during the corresponding time period. In AFAI625, a “1” may correspond to committed availability (e.g., as described in connection with CFAI615), potential availability (e.g., as described in connection with PFAI620), or either. As shown, the UE120may use the AFAI625, for example, to indicate an alternative resource configuration635that specifies a different set of time periods during which the UE120may communicate via an access link.

As shown by reference number640, the UE120may transmit the FAI to the one or more sidelink UEs120. In some aspects, the UE120may transmit the FAI based at least in part on determining that the availability condition is satisfied. The UE120may transmit the FAI via sidelink control information (SCI), in a medium access control (MAC) control element (CE) (MAC-CE) (e.g., a MAC-CE scheduled by the SCI), and/or the like. In some aspects, the UE120may transmit an FAI indicator in SCI, where the FAI indicator indicates whether the MAC-CE includes the FAI for the UE120.

The UE120may repeat the transmission of the FAI. In some aspects, the FAI may be transmitted using a single bitmap to indicate availability of the UE120for a set of time periods. The same bitmap may be used to indicate availability of the UE120for additional sets of time periods by repeating the resource configuration for additional time periods. For example, the bitmap corresponding to the 10 time periods illustrated inFIG.6may indicate availability for 50 time periods by repeating the resource configuration, indicated in a single bitmap, 5 times. In aspects, the FAI may be transmitted periodically. The periodicity of the transmission of the FAI may be specified with respect to any number of different parameters. For example, the FAI may be transmitted and/or the resource configuration indicated by the FAI may be interpreted as repeating with a periodicity of C seconds, where C is less than or equal to B and where the modulus of B and C is 0.

Aspects of the FAI indicating techniques described above may be used to broadcast the availability of a UE120for sidelink communications, such that other UEs120may be able to determine the availability of the UE120and configure their sidelink communications with the UE120accordingly. This may facilitate a reduction in transmission overhead by reducing or eliminating a need for redundant communications, which may result in power savings, more efficient use of radio resources, and/or enhancement of link reliability. Aspects of the FAI techniques described above may be used to enable negotiation between UEs120for scheduling sidelink communications that work for all UEs120participating in the sidelink communications. Aspects of the FAI techniques described above also may enable more efficient and reliable communications between a UE and multiple other devices, such as by facilitating negotiation of sidelink communications between the UE and the other devices.

FIG.7is a diagram illustrating another example700of indicating availability for sidelink communications, in accordance with various aspects of the present disclosure.

As shown by reference number705, FAI may indicate a combination of time domain availability and frequency domain availability of the UE120for sidelink communication. For example, each of the blocks may represent an RB. As shown, the FAI may include a combination of time and frequency availability, and may include a bitmap710, where a value of a bit in the bitmap710indicates whether the UE120will be available (or potentially will be available) for sidelink communication during a time period corresponding to the bit and on one or more sub-carriers corresponding to the bit. In some aspects, FAI may indicate availability only in terms of a frequency domain, in which case, each value of a bit in the bitmap may indicate whether the UE120will be available (or potentially will be available) for sidelink communication on one or more sub-carriers corresponding to the bit.

As shown inFIG.7, the bitmap710may include a bit string715associated with CFAI (a “CFAI bit string”715) and a bit string720associated with PFAI (a “PFAI bit string”720). A “0” corresponding to a particular time period and frequency combination in both bit strings715and720indicates that the UE120will be unavailable for sidelink communication during the corresponding time period and on the corresponding carrier or carriers. A “1” in the CFAI bit string715may indicate that the UE120will be available during the corresponding time period and on the corresponding carrier or carriers. A “1” in the PFAI bit string720may indicate that the UE120potentially will be available during the corresponding time period and on the corresponding carrier or carriers (e.g., will be available if requested to be available by another UE, as described elsewhere herein). In some aspects, a bitmap710may include any number of different combinations of CFAI bit strings715, PFAI bit strings720, and/or AFAI bit strings.

FIG.8is a diagram illustrating another example800of indicating availability for sidelink communications, in accordance with various aspects of the present disclosure.

As shown by reference number805, FAI may include future scanning frequency information (FSFI) that indicates one or more sets of frequency resources (e.g., sub-carriers) that will be scanned by the UE120and/or one or more sets of frequency resources (e.g., sub-carriers) that will not be scanned by the UE120. InFIG.8, each block represents a set of frequency resources, such as a set of sub-carriers, a set of sub-bands, a set of sub-channels, and/or the like. As shown, the FAI may be indicated by a bitmap810having a bit string associated with FSFI, where a “0” corresponding to a particular set of frequency resources may indicate that the UE120does not scan the corresponding set of frequency resources. A “1” corresponding to a particular set of frequency resources may indicate that the UE120scans the corresponding set of frequency resources.

In some aspects, the UE120may be configured to transmit the FSFI in response to determining that an availability condition is satisfied, where the availability condition includes a bandwidth scanning condition. For example, the UE120may determine that the availability condition is satisfied by determining that the UE120is capable of scanning an amount of a bandwidth resource pool that is less than or equal to a threshold amount of the bandwidth resource pool. In some aspects, the bandwidth scanning condition may be expressed in terms of a threshold percentage of the bandwidth resource pool. For example, the availability condition may be satisfied if the UE120is capable of scanning less than or equal to D % of the bandwidth resource pool. In some aspects, the threshold percentage (or other threshold value), such as the value of D may be configured for the UE120by a base station110or another UE120.

FIG.9is a diagram illustrating an example900of indicating recommended instances for sidelink communications, in accordance with various aspects of the present disclosure. As shown inFIG.9, a UE120(shown as “helper UE” inFIG.9) and one or more other UEs120(shown as “sidelink UEs” inFIG.9) may communicate with each other.

As shown by reference number905, the helper UE120may receive a plurality of future available information (FAI) messages from a plurality of UEs (shown as UE A, UE B, . . . , UE X). UE A, UE B, . . . , UE X may be sidelink UEs120. Each FAI message may indicate a time domain availability of a respective UE A, UE B, . . . , or UE X, for sidelink communication and/or a frequency domain availability of the respective UE A, UE B, . . . , or UE X, for sidelink communication. Each FAI message may include CFAI, PFAI, AFAI, and/or FSFI, as described above. The plurality of FAI messages may be included in at least one of a plurality of sidelink control information messages, a plurality of medium access control (MAC) control elements, or a combination thereof.

As shown by reference number910, the helper UE120may transmit, via a sidelink channel to one or more sidelink UEs120, an indication of a set of recommended instances for sidelink communication. The set of recommended instances may be based at least in part on the plurality of FAI messages. The set of recommended instances may indicate one or more recommended time periods for sidelink communication and/or one or more recommended sub-carriers for sidelink communication. In some aspects, the set of recommended instances may be transmitted based at least in part on determining that a threshold number of the plurality of UEs (UE A, UE B, . . . , UE X) have overlapping time and/or frequency availability (e.g., associated with each recommended instance of the set of recommended instances).

As shown, the set of recommended instances may be expressed as an aggregated FAI, based on CFAI A associated with UE A (shown by reference number915), CFAI B associated with UE B (shown by reference number920), CFAI X associated with UE X (shown by reference number925), and/or the like. The set of recommended instances may be indicated using a bitmap930in the same way that FAI may be indicated, as described above. For example, the recommended instances may indicate time and/or frequency resources in which all of the UEs (UE A, UE B, . . . , UE X) are available (e.g., by using a bit value of “1”). The recommended instances may indicate time and/or frequency resources in which none of the UEs (UE A, UE B, . . . , UE X) are available (e.g., by using a bit value of “0”). The recommended instances may indicate time and/or frequency resources in which a threshold number of UEs (UE A, UE B, . . . , UE X) are available (e.g., illustrated by an optional bit value of “(1)”). The recommended instances may indicate time and/or frequency resources in which a threshold number of UEs (UE A, UE B, . . . , UE X) are unavailable (e.g., illustrated by an optional bit value of “(0)”).

In some aspects, the indication of the set of recommended instances may be transmitted in accordance with a recommended instance of the set of recommended instances (e.g., during a recommended time period and/or on a recommended set of frequency resources). The indication of the set of recommended instances may be transmitted in SCI. In some aspects, the indication of the set of recommended instances may be transmitted in a MAC-CE. The helper UE120may transmit an FAI indicator in SCI, where the FAI indicator indicates whether the MAC-CE (e.g., scheduled by the SCI) includes an indication of a set of recommended instances. The indication of the set of recommended instances may be transmitted based at least in part on the helper UE120being configured to transmit a physical sidelink broadcast channel (PSBCH). The indication of the set of recommended instances or information that identifies a resource for obtaining the indication of the set of recommended instances may be transmitted in the PSBCH. Thus, the helper UE120may be designated and/or configured to monitor SCI and transmit the set of recommendation instances based at least in part on the helper UE120also being configured to transmit the PSBCH.

As explained further below in connection withFIG.10, the indication of the set of recommended instances may be transmitted to another UE120based at least in part on receiving a request from the other UE120for the set of recommended instances. In some aspects, a set of recommended instances transmitted to a UE120in response to receiving a request from the UE120may include recommended instances that are specific to the requesting UE120. For example, a recommended instance may include one or more recommended time periods for the requesting UE120to communicate using sidelink communication and/or one or more recommended sub-carriers for the requesting UE120to communicate using sidelink communication. A recommended instance transmitted in response to receiving a request from a requesting UE120may be based at least in part on FAI associated with the requesting UE120, FAI associated with another UE120identified in the request, FAI associated with other sidelink UEs120, and/or the like.

As indicated above,FIG.9is provided as an example. Other examples may differ from what is described with respect toFIG.9.

FIG.10is a diagram illustrating another example1000of indicating recommended instances for sidelink communications, in accordance with various aspects of the present disclosure. As shown inFIG.10, a requestor UE1005, a UE A1010, and a helper UE1015may communicate with one another via sidelink communication. The UE1005, UE A1010, and/or the helper UE1015may be, or be similar to, the UE120described in connection withFIG.1.

As shown by reference number1020, the requestor UE1005may transmit a request for one or more recommended instances for sidelink communication. The requestor UE1005may transmit the request to a specific helper UE1015and/or the requestor UE1005may broadcast the request. As shown by reference number1025, the helper UE1015may transmit an indication of a set of recommended instances. The set of recommended instances may indicate one or more recommended time periods for sidelink communication and/or one or more recommended sub-carriers for sidelink communication. The helper UE1015may transmit the set of recommended instances to the requestor UE1005and/or may broadcast the set of recommended instances. The request and/or the indication of the set of recommended instances may be transmitted via a sidelink channel.

In some aspects, the requestor UE1005may transmit the request for one or more recommended instances based at least in part on a determination that information identifying one or more recommended instances has not been received for a threshold amount of time. For example, the helper UE1015may have previously transmitted an indication of a set of recommended instances, and the requestor UE1005may have received that indication (or may have missed that indication). Upon determining that the requestor UE1005has not received any subsequent indications (e.g., after receipt of a prior indication) of recommended instances for greater than or equal to a threshold amount of time, the requestor UE1005may transmit the request.

In some aspects, the requestor UE1005may transmit the request via SCI and/or a MAC-CE. For example, the requestor UE1005may be configured to use one or more bits in SCI to transmit the request. The requestor UE1005may transmit FAI (e.g., CFAI) associated with the requestor UE1005in the request. When a MAC-CE is used to transmit FAI associated with the UE1005, the UE1005may transmit the request in the MAC-CE, and the request may include the FAI associated with the requestor UE1005.

The helper UE1015may transmit the indication of the set of recommended instances based at least in part on receiving the request. The helper UE1015may transmit the indication of the set of recommended instances via a sidelink communication in accordance with a recommended instance of the set of recommended instances (e.g., in a recommended time period and/or on a recommended set of frequency resources). In some aspects, the helper UE1015may transmit the indication of the set of recommended instances via a sidelink communication in accordance with CFAI associated with the requestor UE1005. As explained above, the helper UE1015may receive a plurality of future available information (FAI) messages from a plurality of UEs (e.g., requestor UE1005, UE A1010, etc.), and may determine the set of recommended instances based at least in part on the plurality of FAI messages.

In some aspects, the requestor UE1005may transmit the request to facilitate communication with one or more specific UEs (e.g., UE A1010). For example, as shown by reference number1030, the requestor UE1005may determine a failure to communicate with the UE A1010. The requestor UE1005may determine a failure to communicate when the requestor UE1005fails to establish a data path with the UE A1010, when the requestor UE1005fails to receive a response from the UE A1010, and/or the like. For example, the requestor UE1005may determine a failure to communicate with the UE A1010in response to determining that the requestor UE1005has failed to establish a data path with the UE A1010within a threshold amount of time after an initial transmission to the UE A1010.

The request may include an identifier (“UE ID”) that identifies the UE A1010. The requestor UE1005may use one or more bits in SCI to transmit the request, and the one or more bits may indicate the UE ID. In some aspects, the requestor UE1005may transmit FAI (e.g., CFAI) associated with the requestor UE1005in the request. In some aspects, the requestor UE1005may include the UE ID in a MAC-CE, and may set a bit in SCI to indicate whether the MAC-CE includes the UE ID and/or other information related to the request.

As shown by reference number1035, the helper UE1015may receive FAI associated with the UE A1010. The set of recommended instances may be based at least in part on the FAI associated with the UE A1010. In some aspects, the request may include one or more additional identifiers that identify one or more additional specific UEs for which the set of recommended instances is requested. The indication of the set of recommended instances may include, or may be based at least in part on, one or more FAI messages received from the one or more specific UEs.

In some aspects, the request for the set of recommended instances may include a request for a recommended FAI for the requestor UE1005. The request may include at least one of an amount of time that the requestor UE1005is available for an upcoming time period or one or more identifiers corresponding to one or more UEs with which the other UE is to communicate, or a combination thereof. The set of recommended instances may be determined based at least in part on the amount of time, the one or more identifiers, or a combination thereof.

Aspects of the FAI techniques described above may be used to enable negotiation between UEs for scheduling sidelink communications that work for all UEs participating. Aspects of the FAI techniques described above also may enable more efficient and reliable communications between a UE and one or more other specific UEs, such as by facilitating negotiation of sidelink communications between the UE and the other devices. Aspects of the techniques described above also may enable a UE to preserve power and utilize radio resources more efficiently by enabling the UE to request help, from a helper UE, with establishing sidelink communication with one or more other UEs, thereby reducing or eliminating the need for redundant transmissions in an attempt to establish the communications.

As indicated above,FIG.10is provided as an example. Other examples may differ from what is described with respect toFIG.10.

Aspects of the FAI indication techniques described above in connection withFIGS.6-10may facilitate enabling autonomous sidelink communications between UEs in V2X as well as in more general use case contexts. Aspects of the techniques described above may also facilitate reducing transmission collisions in sidelink communications and reducing power consumption by UEs due to a reduction in transmission overhead due to retransmissions.

FIG.11is a diagram illustrating an example process1100performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process1100is an example where the UE (e.g., UE120and/or the like) performs operations associated with indicating availability for sidelink communications.

As shown inFIG.11, in some aspects, process1100may include determining that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication (block1110). For example, the UE120(e.g., using receive processor258, transmit processor264, controller/processor280, memory282, and/or the like) may determine that an availability condition is satisfied, as described above. In some aspects, the availability condition relates to an availability of the UE for sidelink communication.

As further shown inFIG.11, in some aspects, process1100may include identifying FAI that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication (block1120). For example, the UE (e.g., using receive processor258, transmit processor264, controller/processor280, memory282, and/or the like) may identify FAI that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication, as described above.

As further shown inFIG.11, in some aspects, process1100may include transmitting the FAI based at least in part on determining that the availability condition is satisfied (block1130). For example, the UE (e.g., using transmit processor264, controller/processor280, memory282, and/or the like) may transmit the FAI based at least in part on determining that the availability condition is satisfied, as described above.

In a first aspect, the FAI comprises CFAI that indicates at least one of: one or more time periods during which the UE will be available for sidelink communication, one or more time periods during which the UE will be unavailable for sidelink communication, one or more sub-carriers on which the UE will be available for sidelink communication, one or more sub-carriers on which the UE will be unavailable for sidelink communication, or a combination thereof.

In a second aspect, alone or in combination with the first aspect, the FAI further comprises AFAI that indicates at least one of: one or more alternative time periods during which the UE will be available for sidelink communication as an alternative to the CFAI, one or more alternative time periods during which the UE will be unavailable for sidelink communication as an alternative to the CFAI, one or more alternative sub-carriers on which the UE will be available for sidelink communication as an alternative to the CFAI, one or more alternative sub-carriers on which the UE will be unavailable for sidelink communication as an alternative to the CFAI, or a combination thereof.

In a third aspect, alone or in combination with one or more of the first and second aspects, determining that the availability condition is satisfied comprises determining that the UE will be unavailable for an amount of time that is greater than or equal to a threshold amount of time in an upcoming time period.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the FAI comprises a bitmap, wherein a value of a bit in the bitmap indicates whether the UE is available for sidelink communication during a time period corresponding to the bit, whether the UE is available for sidelink communication on one or more sub-carriers corresponding to the bit, or whether the UE is available for sidelink communication in a combination of a time period and one or more sub-carriers corresponding to the bit.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the availability of the UE for sidelink communication comprises at least one of: availability of the UE for sidelink reception, availability of the UE for sidelink transmission, or a combination thereof.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process1100includes receiving an indication of the availability condition.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, transmitting the FAI comprises transmitting the FAI via SCI.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, transmitting the FAI comprises transmitting the FAI in a MAC-CE.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process1100includes transmitting an FAI indicator in the SCI, wherein the FAI indicator indicates whether the MAC-CE includes the FAI for the UE.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the FAI comprises PFAI that indicates at least one of: one or more time periods during which the UE will be available for sidelink communication if requested to be available by another UE, one or more sub-carriers on which the UE will be available for sidelink communication if requested to be available by another UE, or a combination thereof.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the FAI includes at least one of committed FAI, potential FAI, alternative FAI, or a combination thereof.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the FAI is transmitted periodically.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, the availability condition comprises a bandwidth scanning condition, and the FAI comprises FSFI that indicates one or more sub-carriers that will be scanned by the UE.

In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, determining that the availability condition is satisfied comprises determining that the UE is capable of scanning an amount of a bandwidth resource pool that is less than or equal to a threshold amount of the bandwidth resource pool.

In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, process1100includes transmitting a request for a recommended instance for sidelink communication, the recommended instance comprising at least one of one or more recommended time periods for the UE to communicate using sidelink communication, one or more recommended sub-carriers for the UE to communicate using sidelink communication, or a combination thereof.

In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the request for the recommended instance is transmitted based at least in part on a determination that information identifying one or more recommended instances has not been received for a threshold amount of time.

In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, transmitting the request for the recommended instance comprises transmitting the request via at least one of SCI, a MAC-CE, or a combination thereof.

In an eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, process1100includes receiving an indication of the recommended instance from another UE.

In a nineteenth aspect, alone or in combination with one or more of the first through eighteenth aspects, the indication of the recommended instance is received in at least one of a time period or a sub-carrier in which the UE is available according to the FAI.

In a twentieth aspect, alone or in combination with one or more of the first through nineteenth aspects, the request for the recommended instance comprises a request for a recommended instance for sidelink communication with one or more specific UEs, and the request includes one or more identifiers corresponding to the one or more specific UEs.

In a twenty first aspect, alone or in combination with one or more of the first through twentieth aspects, the recommended instance includes one or more FAIs corresponding to the one or more specific UEs.

In a twenty second aspect, alone or in combination with one or more of the first through twenty first aspects, the recommended instance includes a recommended FAI for the UE based at least in part on the FAI transmitted by the UE.

In a twenty third aspect, alone or in combination with one or more of the first through twenty second aspects, the request for the recommended instance includes a request for a recommended FAI for the UE, the request includes at least one of an amount of time that the UE is available for an upcoming time period, one or more identifiers corresponding to one or more UEs with which the UE is to communicate, or a combination thereof.

In a twenty fourth aspect, alone or in combination with one or more of the first through twenty third aspects, process1100includes communicating based at least in part on the recommended instance.

FIG.12is a diagram illustrating an example process1200performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process1200is an example where the UE (e.g., UE120and/or the like) performs operations associated with indicating availability for sidelink communications.

As shown inFIG.12, in some aspects, process1200may include receiving a plurality of FAI messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication (block1210). For example, the UE (e.g., using receive processor258, controller/processor280, memory282, and/or the like) may receive a plurality of FAI messages from a plurality of UEs, as described above. In some aspects, each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication.

As further shown inFIG.12, in some aspects, process1200may include transmitting, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof (block1220). For example, the UE (e.g., using transmit processor264, controller/processor280, memory282, and/or the like) may transmit, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, as described above. In some aspects, the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

In a first aspect, the plurality of FAI messages are included in at least one of a plurality of sidelink control information messages, a plurality of MAC-CEs, or a combination thereof.

In a second aspect, alone or in combination with the first aspect, the indication of the set of recommended instances is transmitted in a recommended instance of the set of recommended instances.

In a third aspect, alone or in combination with one or more of the first and second aspects, the indication of the set of recommended instances is transmitted in sidelink control information.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the indication of the set of recommended instances is transmitted in a MAC-CE.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, process1200includes transmitting an FAI indicator in sidelink control information, wherein the FAI indicator indicates whether the MAC-CE includes the indication of the set of recommended instances.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the indication of the set of recommended instances is transmitted based at least in part on the UE being configured to transmit a PSBCH.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the indication of the set of recommended instances or information that identifies a resource for obtaining the indication of the set of recommended instances is transmitted in the PSBCH.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the indication of the set of recommended instances is transmitted to another UE based at least in part on receiving a request from the other UE for the set of recommended instances.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the request includes FAI for the other UE, and the indication of the set of recommended instances is transmitted to the other UE in at least one of an available time period or an available sub-carrier indicated in the FAI for the other UE.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the request includes one or more identifiers that identify one or more specific UEs for which the set of recommended instances is requested.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the indication of the set of recommended instances includes or is based at least in part on one or more FAI messages received from the one or more specific UEs.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the indication of the set of recommended instances includes a recommended FAI for the other UE based at least in part on an FAI received from the other UE.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, the request for the set of recommended instances includes a request for a recommended FAI for the other UE and at least one of an amount of time that the other UE is available for an upcoming time period or one or more identifiers corresponding to one or more UEs with which the other UE is to communicate, and the set of recommended instances is determined based at least in part on the amount of time, the one or more identifiers, or a combination thereof.

Aspect 1: A method of wireless communication performed by a user equipment (UE), comprising: determining that an availability condition is satisfied, wherein the availability condition relates to an availability of the UE for sidelink communication; identifying future available information (FAI) that indicates at least one of a time domain availability of the UE for sidelink communication or a frequency domain availability of the UE for sidelink communication; and transmitting the FAI based at least in part on determining that the availability condition is satisfied.

Aspect 2: The method of aspect 1, wherein the FAI comprises committed FAI (CFAI) that indicates at least one of: one or more time periods during which the UE will be available for sidelink communication, one or more time periods during which the UE will be unavailable for sidelink communication, one or more sub-carriers on which the UE will be available for sidelink communication, one or more sub-carriers on which the UE will be unavailable for sidelink communication, or a combination thereof.

Aspect 3: The method of aspect 2, wherein the FAI further comprises alternative FAI (AFAI) that indicates at least one of: one or more alternative time periods during which the UE will be available for sidelink communication as an alternative to the CFAI, one or more alternative time periods during which the UE will be unavailable for sidelink communication as an alternative to the CFAI, one or more alternative sub-carriers on which the UE will be available for sidelink communication as an alternative to the CFAI, one or more alternative sub-carriers on which the UE will be unavailable for sidelink communication as an alternative to the CFAI, or a combination thereof.

Aspect 4: The method of any of the preceding aspects, wherein determining that the availability condition is satisfied comprises determining that the UE will be unavailable for an amount of time that is greater than or equal to a threshold amount of time in an upcoming time period.

Aspect 5: The method of any of the preceding aspects, wherein the FAI comprises a bitmap, wherein a value of a bit in the bitmap indicates whether the UE is available for sidelink communication during a time period corresponding to the bit, whether the UE is available for sidelink communication on one or more sub-carriers corresponding to the bit, or whether the UE is available for sidelink communication in a combination of a time period and one or more sub-carriers corresponding to the bit.

Aspect 6: The method of any of the preceding aspects, wherein the availability of the UE for sidelink communication comprises at least one of: availability of the UE for sidelink reception, availability of the UE for sidelink transmission, or a combination thereof.

Aspect 7: The method of any of the preceding aspects, further comprising receiving an indication of the availability condition.

Aspect 8: The method of any of the preceding aspects, wherein transmitting the FAI comprises transmitting the FAI via sidelink control information (SCI).

Aspect 9: The method of any of the preceding aspects, wherein transmitting the FAI comprises transmitting the FAI in a medium access control (MAC) control element (CE) (MAC-CE).

Aspect 10: The method of aspect 9, further comprising transmitting an FAI indicator in sidelink control information (SCI), wherein the FAI indicator indicates whether the MAC-CE includes the FAI for the UE.

Aspect 11: The method of any of the preceding aspects, wherein the FAI comprises potential FAI (PFAI) that indicates at least one of: one or more time periods during which the UE will be available for sidelink communication if requested to be available by another UE, one or more sub-carriers on which the UE will be available for sidelink communication if requested to be available by another UE, or a combination thereof.

Aspect 12: The method of any of the preceding aspects, wherein the FAI includes at least one of committed FAI, potential FAI, alternative FAI, or a combination thereof.

Aspect 13: The method of any of the preceding aspects, wherein the FAI is transmitted periodically.

Aspect 14: The method of any of the preceding aspects, wherein the availability condition comprises a bandwidth scanning condition, and wherein the FAI comprises future scanning frequency information (FSFI) that indicates one or more sub-carriers that will be scanned by the UE.

Aspect 15: The method of aspect 14, wherein determining that the availability condition is satisfied comprises determining that the UE is capable of scanning an amount of a bandwidth resource pool that is less than or equal to a threshold amount of the bandwidth resource pool.

Aspect 16: The method of any of the preceding aspects, further comprising transmitting a request for a recommended instance for sidelink communication, the recommended instance comprising at least one of: one or more recommended time periods for the UE to communicate using sidelink communication, one or more recommended sub-carriers for the UE to communicate using sidelink communication, or a combination thereof.

Aspect 17: The method of aspect 16, wherein the request for the recommended instance is transmitted based at least in part on a determination that information identifying one or more recommended instances has not been received for a threshold amount of time.

Aspect 18: The method of any of aspects 16-17, wherein transmitting the request for the recommended instance comprises transmitting the request via at least one of sidelink control information (SCI), a medium access control (MAC) control element (CE), or a combination thereof.

Aspect 19: The method any of aspects 16-18, further comprising receiving an indication of the recommended instance from another UE.

Aspect 20: The method of aspect 19, wherein the indication of the recommended instance is received in at least one of a time period or a sub-carrier in which the UE is available according to the FAI.

Aspect 21: The method of any of aspects 16-20, wherein the request for the recommended instance comprises a request for a recommended instance for sidelink communication with one or more specific UEs, and wherein the request includes one or more identifiers corresponding to the one or more specific UEs.

Aspect 22: The method of aspect 21, wherein the recommended instance includes one or more FAIs corresponding to the one or more specific UEs.

Aspect 23: The method of any of aspects 21-22, wherein the recommended instance includes a recommended FAI for the UE based at least in part on the FAI transmitted by the UE.

Aspect 24: The method of any of aspects 16-23, wherein the request for the recommended instance includes a request for a recommended FAI for the UE, wherein the request includes at least one of: an amount of time that the UE is available for an upcoming time period, one or more identifiers corresponding to one or more UEs with which the UE is to communicate, or a combination thereof.

Aspect 25: The method of any of aspects 16-24, further comprising communicating based at least in part on the recommended instance.

Aspect 26: A method of wireless communication performed by a user equipment (UE), comprising: receiving a plurality of future available information (FAI) messages from a plurality of UEs, wherein each FAI message indicates at least one of a time domain availability of a respective UE, of the plurality of UEs, for sidelink communication or a frequency domain availability of the respective UE for sidelink communication; and transmitting, via a sidelink channel, an indication of a set of recommended instances based at least in part on the plurality of FAI messages, wherein the set of recommended instances indicates one or more recommended time periods for sidelink communication, one or more recommended sub-carriers for sidelink communication, or a combination thereof.

Aspect 27: The method of aspect 26, wherein the plurality of FAI messages are included in at least one of a plurality of sidelink control information messages, a plurality of medium access control (MAC) control elements, or a combination thereof.

Aspect 28: The method of any of aspects 26-27, wherein the indication of the set of recommended instances is transmitted in a recommended instance of the set of recommended instances.

Aspect 29: The method of any of aspects 26-28, wherein the indication of the set of recommended instances is transmitted in sidelink control information.

Aspect 30: The method of any of aspects 26-29, wherein the indication of the set of recommended instances is transmitted in a medium access control (MAC) control element (CE) (MAC-CE).

Aspect 31: The method of aspect 30, further comprising transmitting an FAI indicator in sidelink control information, wherein the FAI indicator indicates whether the MAC-CE includes the indication of the set of recommended instances.

Aspect 32: The method of any of aspects 26-31, wherein the indication of the set of recommended instances is transmitted based at least in part on the UE being configured to transmit a physical sidelink broadcast channel (PSBCH).

Aspect 33: The method of aspect 32, wherein the indication of the set of recommended instances or information that identifies a resource for obtaining the indication of the set of recommended instances is transmitted in the PSBCH.

Aspect 34: The method of any of aspects 26-33, wherein the indication of the set of recommended instances is transmitted to another UE based at least in part on receiving a request from the other UE for the set of recommended instances.

Aspect 35: The method of aspect 34, wherein the request includes FAI for the other UE, and wherein the indication of the set of recommended instances is transmitted to the other UE in at least one of an available time period or an available sub-carrier indicated in the FAI for the other UE.

Aspect 36: The method of any of aspects 34-35, wherein the request includes one or more identifiers that identify one or more specific UEs for which the set of recommended instances is requested.

Aspect 37: The method of aspect 36, wherein the indication of the set of recommended instances includes or is based at least in part on one or more FAI messages received from the one or more specific UEs.

Aspect 38: The method of any of aspects 34-37, wherein the indication of the set of recommended instances includes a recommended FAI for the other UE based at least in part on an FAI received from the other UE.

Aspect 39: The method of any of aspects 34-38, wherein the request for the set of recommended instances includes a request for a recommended FAI for the other UE and at least one of an amount of time that the other UE is available for an upcoming time period or one or more identifiers corresponding to one or more UEs with which the other UE is to communicate; and wherein the set of recommended instances is determined based at least in part on the amount of time, the one or more identifiers, or a combination thereof.