Patent Description:
"Downlink" or "forward link" refers to the communication link from the BS to the UE, and "uplink" or "reverse link" refers to the communication link from the UE to the BS.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE, NR, and other radio access technologies.

<NPL>) discusses the HARQ mechanism for NR V2X and makes some corresponding proposals.

Advantageous, optional features of the invention are then set out in the appended dependent claims. In the following description, any embodiment referred to and not falling within the scope of the claims is merely an example useful to the understanding of the invention.

In some aspects, a method of wireless communication, performed by a wireless communication device, may include receiving a sidelink communication on a sidelink. The sidelink communication may include at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication. The method may include transmitting, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication.

In some aspects, a wireless communication device 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 sidelink communication on a sidelink, where the sidelink communication includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication. The memory and the one or more processors may be configured to transmit, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication.

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 wireless communication device, may cause the one or more processors to receive a sidelink communication on a sidelink, where the sidelink communication includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication, and transmit, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication.

In some aspects, an apparatus for wireless communication may include means for receiving a sidelink communication on a sidelink, where the sidelink communication includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication, and means for transmitting, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication.

<FIG> is a diagram illustrating an example of a wireless network <NUM> in accordance with the present disclosure. A base station (BS) is an entity that communicates with user equipment (UEs) and may also be referred to as an NR BS, a Node B, a gNB, a <NUM> node B (NB), an access point, or a transmit receive point (TRP).

In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network <NUM> through various types of backhaul interfaces such as a direct physical connection, or a virtual network using any suitable transport network.

A relay BS may also be referred to as a relay station, a relay base station, or a relay.

Wireless network <NUM> may be a heterogeneous network that includes BSs of different types, such as macro BSs, pico BSs, femto BSs, and/or relay BSs.

MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, and/or location tags that may communicate with a base station, another device (e.g., remote device), or some other entity.

A RAT may also be referred to as a radio technology, and/or an air interface. A frequency may also be referred to as a carrier, and/or a frequency channel.

For example, the UEs <NUM> may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, or a vehicle-to-infrastructure (V2I) protocol), and/or a mesh network.

Transmit processor <NUM> may also process system information (e.g., for semi-static resource partitioning information (SRPI)) and control information (e.g., CQI requests, grants, upper layer signaling) and provide overhead symbols and control symbols. Transmit processor <NUM> may also generate reference symbols for reference signals (e.g., a cell-specific reference signal (CRS), a demodulation reference signal (DMRS)) and synchronization signals (e.g., the primary synchronization signal (PSS) or a secondary synchronization signal (SSS)).

A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), and/or CQI, among other examples.

The symbols from transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM), and transmitted to base station <NUM>. The transceiver may be used by a processor (e.g., controller/processor <NUM>) and memory <NUM> to perform aspects of any of the methods described herein (for example, as described with reference to <FIG>).

The transceiver may be used by a processor (e.g., controller/processor <NUM>) and memory <NUM> to perform aspects of any of the methods described herein (for example, as described with reference to <FIG>).

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with sidelink feedback messaging, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. In some aspects, memory <NUM> and/or memory <NUM> may include a non-transitory computer-readable medium storing one or more instructions (e.g., code and/or program code) for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, and/or interpreting) by one or more processors of the base station <NUM> and/or the UE <NUM>, may cause the one or more processors, the UE <NUM>, and/or the base station <NUM> to perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. In some aspects, executing instructions may include running the instructions, converting the instructions, compiling the instructions, and/or interpreting the instructions, among other examples.

In some aspects, a wireless communication device, such as BS <NUM> or UE <NUM>, may include means for receiving a sidelink communication on a sidelink, where the sidelink communication includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication, means for transmitting, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication, and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>, such as controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, and/or receive processor <NUM>. In some aspects, such means may include one or more components of base station <NUM> described in connection with <FIG>, such as antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, and/or antenna <NUM>.

While blocks in <NUM> are illustrated as distinct components, the functions described above with respect to the blocks may be implemented in a single hardware, software, or combination component or in various combinations of components.

<FIG> is a diagram illustrating an example <NUM> of sidelink communications, in accordance with various aspects of the present disclosure.

As shown in <FIG>, a first wireless communication device <NUM>-<NUM> may communicate with a second wireless communication device <NUM>-<NUM> (and one or more other wireless communication devices <NUM>) via one or more sidelink channels <NUM>. The wireless communication devices <NUM>-<NUM> and <NUM>-<NUM> may communicate using the one or more sidelink channels <NUM> for P2P communications, D2D communications, V2X communications (e.g., which may include V2V communications, V2I communications, V2P communications), and/or mesh networking. In some aspects, wireless communication devices <NUM> (e.g., wireless communication device <NUM>-<NUM> and/or wireless communication device <NUM>-<NUM>) may correspond to one or more UEs <NUM>, BSs <NUM>, IAB nodes, and/or the like. In some aspects, one or more sidelink channels <NUM> may use a PC5 interface and/or may operate in a high frequency band (e.g., the <NUM> band). Additionally, or alternatively, wireless communication devices <NUM> may 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 in <FIG>, one or more sidelink channels <NUM> may include a physical sidelink control channel (PSCCH) <NUM>, a physical sidelink shared channel (PSSCH) <NUM>, and/or a physical sidelink feedback channel (PSFCH) <NUM>. The PSCCH <NUM> may 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 BS <NUM> via an access link or an access channel. PSSCH <NUM> may 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 BS <NUM> via an access link or an access channel. For example, PSCCH <NUM> may carry sidelink control information (SCI) <NUM>, which may indicate various control information used for sidelink communications, such as one or more resources (e.g., time resources, frequency resources, spatial resources) where a transport block (TB) <NUM> may be carried on the PSSCH <NUM>. TB <NUM> may include data. PSFCH <NUM> may be used to communicate sidelink feedback <NUM>, 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. An ACK may include, for example, two identical OFDM symbols, a resource block, a sequence (like Uu PUCCH-format0), and/or a bit. A first symbol may be used for automatic gain control training.

PSCCH, PSSCH, and PSFCH may allow time division multiplexing (TDM) between the channels at transmission, but may not allow frequency division multiplexing (FDM). A PSFCH resource may be implicitly derived, and resources may be frequency division multiplexed if corresponding to PSSCHs in different subchannels and/or different slots. For groupcast feedback, code division multiplexing and FDM may be allowed between PSFCH resources used by different receive UEs for HARQ feedback of the same PSSCH transmission. Feedback may include only NACK, or ACK or NACK. Feedback may be limited to a threshold distance between UEs, and the threshold may be indicated in SCI.

In some aspects, HARQ feedback (ACK/NACK) for downlink Uu may be carried on an uplink channel, such as in a physical uplink control channel or piggybacked on a physical uplink shared channel. The HARQ feedback may acknowledge downlink data on a PDSCH or a downlink grant on PDSCH (SPS release). HARQ feedback may use a codebook that is semi-static (ACK/NACK bit sent if no grant is received) or dynamic (ACK/NACK bit sent if grant is received). A downlink assignment index (DAI) counter may help to track missing grants, which may cause a mismatch in a number of feedback bits between the BS <NUM> and UE <NUM>. Code block group (CBG) ACK may also be supported for the downlink. As for the uplink, an ACK may be implicitly indicated via a new data indicator toggle in an uplink grant. Beam management may help to close a link overcoming high path loss, such as for mmWave beams. However, sidelink has some extra considerations for grants. For example, stages of multi-stage grants may be transmitted by different nodes (grant may be split between Uu downlink control information (DCI) and SCI). Also, a single UE may communicate with multiple UEs on multiple sidelinks (unicast or groupcast). UEs may relay grants from other UEs.

In some aspects, the one or more sidelink channels <NUM> may use resource pools. For example, a scheduling assignment (e.g., included in SCI <NUM>) may be transmitted in subchannels using specific resource blocks (RBs) across time. In some aspects, data transmissions (e.g., on PSSCH <NUM>) associated with a scheduling assignment may occupy adjacent RBs in the same subframe as the scheduling assignment (e.g., using frequency division multiplexing). In some aspects, a scheduling assignment and associated data transmissions are not transmitted on adjacent RBs.

In some aspects, a wireless communication device <NUM> may operate using a transmission mode where resource selection and/or scheduling is performed by wireless communication device <NUM> (e.g., rather than a BS <NUM>). In some aspects, wireless communication device <NUM> may perform resource selection and/or scheduling by sensing channel availability for transmissions. For example, wireless communication device <NUM> may measure an RSSI parameter (e.g., a sidelink-RSSI (S-RSSI) parameter) associated with various sidelink channels, may measure an RSRP parameter (e.g., a PSSCH-RSRP parameter) associated with various sidelink channels, may measure an RSRQ parameter (e.g., a PSSCH-RSRQ parameter) associated with various sidelink channels, and may select a channel for transmission of a sidelink communication based at least in part on the measurement(s).

Additionally, or alternatively, wireless communication device <NUM> may perform resource selection and/or scheduling using SCI <NUM> received in the PSCCH <NUM>, which may indicate occupied resources and/or channel parameters. Additionally, or alternatively, wireless communication device <NUM> may 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 wireless communication device <NUM> can use for a particular set of subframes).

In the transmission mode where resource selection and/or scheduling is performed by a wireless communication device <NUM>, wireless communication device <NUM> may generate sidelink grants, and may transmit the grants in SCI <NUM>. 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 PSSCH <NUM> (e.g., for TBs <NUM>), one or more subframes to be used for the upcoming sidelink transmission, and/or an MCS to be used for the upcoming sidelink transmission. In some aspects, a wireless communication device <NUM> may 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, wireless communication device <NUM> may generate a sidelink grant for event-driven scheduling, such as for an on-demand sidelink message.

<FIG> is a diagram illustrating an example <NUM> of sidelink communications and access link communications, in accordance with the present disclosure.

As shown in <FIG>, wireless communication device <NUM> and a wireless communication device <NUM> may communicate with one another via a sidelink, as described above in connection with <FIG>. As further shown, in some sidelink modes, a BS <NUM> may communicate with wireless communication device <NUM> via a first access link. Additionally, or alternatively, in some sidelink modes, BS <NUM> may communicate with wireless communication device <NUM> via a second access link. Wireless communication device <NUM> and/or wireless communication device <NUM> may correspond to one or more UEs <NUM>, BSs <NUM>, and/or integrated access and backhaul (IAB) nodes. As an example, "sidelink" may refer to a direct link between UEs <NUM>, and "access link" may refer to a direct link between a BS <NUM> and a UE <NUM>. Sidelink communications may be transmitted on a PC5 interface 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 BS <NUM> to a UE <NUM>) or an uplink communication (from a UE <NUM> to a BS <NUM>) on a Uu interface.

As described above, a wireless communication device may communicate with a BS on a Uu interface associated with an access link. For example, a wireless communication device may transmit a PUCCH communication on an uplink to convey an acknowledgement message to acknowledge downlink data. Additionally, or alternatively, the wireless communication device may include an acknowledgment message with a PUSCH communication.

Similarly, a first wireless communication device may communicate with a second wireless communication device on a PC5 interface associated with a sidelink. In this case, the first wireless communication device may transmit a feedback message, such as an ACK message or a NACK message on PSFCH. In this case, the first wireless communication device may TDM a PSCCH, PSSCH, and a PSFCH for transmission, but may not FDM the aforementioned channels. A PSFCH for conveying feedback information may be used for single-stage grants, grants for a single sidelink, and/or other scenarios. However, other types of grants and links, such as multi-stage grants and multi-link connections may be used.

Some aspects described herein enable sidelink feedback messaging that is based at least in part on a particular timing. For example, when a wireless communication device receives information, such as a grant, data on a resource identified by a grant, a multi-stage grant, a multi-packet grant, a relaying communication, the wireless communication device may transmit one or more feedback messages to acknowledge the information. In this case, the wireless communication may transmit the one or more feedback messages after a time period since receiving the information. The wireless communication device may determine the time period based at least in part on one or more factors such as a type of sidelink communication, a type of feedback message, a quantity of stages for a multi-stage grant, and/or which channel is used for the feedback message. In some aspects, the wireless communication device may determine a minimum time period that is to occur before transmitting the feedback message. In this way, the wireless communication device enables relaying grant acknowledgements and/or multi-stage grant acknowledgements. As a result, the wireless communication device reduces latency and enables other devices to conserve processing resources and signaling resources with improved communication of grants.

In some aspects, the time period may include a time duration between when a sidelink communication is received and when a feedback message is transmitted. In some aspects, the time period may be based at least in part on one or more timestamps, and/or one or more processes. For example, a time period may be a result of a comparison of a first time stamp associated with the sidelink communication and a second timestamp associated with initiation of transmission of the feedback message or completion of the feedback message. In another example, the time period may be defined by the start or completion of one or more processes. In some aspects, the time period may account for other time durations or processes that may occur between receiving a sidelink communication and transmitting the feedback message. In some aspects, the time period may apply to one stage of a multi-stage grant or to all stages of the multi-stage grant.

Feedback may be provided for multi-stage grants. Each stage of a multi-stage grant with m stages may be polar-encoded or independently encoded. The number of packets at a stage may be fixed/configured or dynamically indicated in one or more previous stages. For example, a granted resource may carry data to a relay UE, which must then relayed by a separate unicast to m UEs, and each of the m packets may carry special instructions (e.g., part of sidelink grant) for the coressponding UE. The multiple stages may be received from multiple sources. For example, a sidelink Mode <NUM> receive grant may be sent by a base station on a Uu to a UE, asking the UE to receive on a sepcific sidelink resource. That resource may still carry SCI (on the PSCCH) that now acts as the second stage of the grant (e.g., <NUM>st stage from Uu, <NUM>nd stage from sidelink). ACKs for the stages may also be transmitted to one or more nodes, such as to the base station, to the sidelink UE on a PSFCH, or to both.

<FIG> is a diagram illustrating an example <NUM> of sidelink feedback messaging, in accordance with the present disclosure. As shown in <FIG>, example <NUM> includes a first wireless communication device <NUM>, a second wireless communication device <NUM>, and a BS <NUM>.

As further shown in <FIG>, and by reference number <NUM>, wireless communication device <NUM> may receive information for acknowledgement. For example, wireless communication device <NUM> may receive information for acknowledgement from wireless communication device <NUM>, from BS <NUM>, and/or from BS <NUM> via wireless communication device <NUM>. In some aspects, wireless communication device <NUM> may receive a grant that wireless communication device <NUM> is to acknowledge. For example, wireless communication device <NUM> may receive the grant from BS <NUM> (e.g., via wireless communication device <NUM>, in some aspects). Additionally, or alternatively, wireless communication device <NUM> may receive data on a resource granted by a grant and may be triggered to acknowledge the received data (or to negatively acknowledge a failure to receive data on the resource granted by the grant).

As further shown in <FIG>, and by reference number <NUM>, wireless communication device <NUM> may transmit a feedback message, such as an ACK on a PSCCH or a PUSCH. For example, wireless communication device <NUM> may transmit the feedback message to wireless communication device <NUM>. Additionally, or alternatively, wireless communication device <NUM> may transmit a feedback message to a plurality of wireless communication devices <NUM> and/or to BS <NUM>.

In some aspects, wireless communication device <NUM> may transmit the feedback message after a time period since receiving the information for acknowledgment. The information for acknowledgement may be referred to as a sidelink communication, and may involve a dynamic or configured grant. The time period may be a minimum time period or may extend an existing time gap between a sidelink communication and the feedback message. The time period may be based at least in part on one or more factors that are described below.

In some aspects, wireless communication device <NUM> may determine a time period based at least in part on a type of feedback message. For example, the feedback message may be an acknowledgment on a PSFCH or PSCCH. The feedback message may be a MAC-CE on a PSSCH or a PUCCH. Some types of feedback may involve a longer time period than other types.

In some aspects, wireless communication device <NUM> may determine the time period based at least in part on a type of the sidelink communication. For example, the sidelink communication may be a packet or a multi-stage packet. The sidelink communication may be a grant or a multi-stage grant. The time period may be based at least in part on how many packets are in a multi-stage packet or how many packets are in a multi-stage grant. In some aspects, wireless communication device <NUM> may receive a two-stage grant or a higher-stage (e.g., n stage) grant. In the case of a two-stage grant, wireless communication device <NUM> may receive a stage-<NUM> grant in an SCI of a PSCCH, and the SCI may direct wireless communication device <NUM> to receive a stage-<NUM> grant in an SCI mapped to a set of contiguous resource blocks in a PSSCH. Additionally, or alternatively, for an n-stage grant, wireless communication device <NUM> may receive an n-<NUM>-stage grant that includes information for decoding an n-<NUM>-stage grant (e.g., frequency or time resource information for the n-<NUM>-stage grant), which may include information for decoding an n-stage grant (e.g., frequency or time resource information for the n-stage grant). In some aspects, the sidelink communication may be one stage of a multi-stage grant, and wireless communication device <NUM> may determine the time period based at least in part on a timing of another stage of the multi-stage grant.

Similarly, for a multi-packet grant, wireless communication device <NUM> may receive a plurality of independently encoded packets conveying a grant (e.g., or a stage of a multi-stage grant). For example, for a multi-stage, multi-packet grant, a first stage grant may include information identifying a quantity of packets for a second stage grant. Additionally, or alternatively, the quantity of packets may be fixed in a standard. In some aspects, wireless communication device <NUM> may receive a multi-packet grant for relaying to a plurality of wireless communication devices <NUM>. For example, each packet, of the multi-packet grant, may identify a different wireless communication device <NUM> to which wireless communication device <NUM> is to relay the packet. In some aspects, the sidelink communication is one packet of a multi-packet sidelink transmission, and wireless communication device <NUM> may determine the time period based at least in part on a timing of another packet of the multi-packet sidelink transmission.

In some aspects, wireless communication device <NUM> may receive a multi-packet grant or a multi-stage grant from a plurality of granting sources. For example, wireless communication device <NUM> may receive a first stage of a grant from BS <NUM>, which may cause wireless communication device <NUM> to receive a second stage of the grant from wireless communication device <NUM>. In this case, wireless communication device <NUM> may be triggered to transmit acknowledgement messages to a plurality of different devices (e.g., the plurality of granting sources).

In some aspects, wireless communication device <NUM> may determine the time period based at least in part on a time or frequency resource allocation of one or more stages or packets. For example, wireless communication device <NUM> may determine a timing for a first stage and/or packet based at least in part on a timing of second stage and/or packet. One of these stages may be a last stage that has to be decoded for identifying the time or frequency resource allocation of another stage.

In some aspects, the sidelink communication may correspond to the multi-stage grant, and wireless communication device <NUM> may determine the time period based at least in part on a quantity of stages in the multi-stage grant.

In some aspects, wireless communication device <NUM> may determine a minimum value for the time period that may be necessary. The minimum value may be due to a capability of the wireless communication device <NUM> or another wireless communication device (e.g., wireless communication device <NUM>). Wireless communication device <NUM> may determine that a time period, as described for various aspects herein, may be a minimum time period. A minimum time period may be a smallest time duration for wireless communication device <NUM> to wait until transmitting the feedback message.

Wireless communication device <NUM> may transmit a feedback message (ACK) separately or bundled with other ACKs (e.g., subsets of ACKs). An ACK may be transmitted if all elements of a bundle are decoded, and a NACK may be transmitted otherwise. All packets of a stage may be bundled, or a packet may be bundled with all or a subset of previous packets that may be needed for decoding in order to determine the resource for the packet. ACKs for bundles of control packets may similar to CBG-based feedback, but applied to control messages instead of data messages. An ACK codebook may be semi-static, with a fixed number of bits regardless of a number of bundles to transmit. An ACK codebook may be more dynamic, and ACKs may be sent only for packets known to be present. A packet may be known to be present based at least in part on indications from previous packets (if decoded). A DAI-like mechanism may help to avoid mismatches between a transmitter and a receiver as to how many ACKs to expect. For example, ACKs may be indicated in the first stage and/or ordered based on the stage or a packet within the stage. ACK bits may be jointly encoded/transmitted (like Uu HARQ codebook) or separately encoded/transmitted (e.g., each ACK has its own PSFCH resource).

In some aspects, wireless communication device <NUM> may determine a time period based at least in part on a type of sidelink communication, where the sidelink communication is a particular feedback message payload or a bundling configuration. In some aspects, wireless communication device <NUM> may bundle a plurality of acknowledgement feedback messages for transmission. For example, with regard to a multi-stage grant or multi-packet grant, rather than transmitting a separate feedback message for each received packet, wireless communication device <NUM> may bundle two or more received packets into a single feedback message. In this case, based at least in part on successfully decoding each received packet of a group of received packets, wireless communication device <NUM> may transmit a single acknowledgement message for the group of received packets. Alternatively, based at least in part on a failure to successfully decode one or more of the group of received packets, wireless communication device <NUM> may transmit a negative acknowledgement message. In some aspects, wireless communication device <NUM> may bundle feedback messages related to a common stage. Additionally, or alternatively, wireless communication device <NUM> may bundle feedback messages related to linked stages. For example, when a first stage of a grant includes information for decoding a second stage of the grant, wireless communication device <NUM> may bundle feedback messages for the first stage of the grant and the second stage of the grant.

In some aspects, wireless communication device <NUM> may order acknowledgement messages in a bundled feedback message based at least in part on a stage and/or a packet order within a stage. In some aspects, wireless communication device <NUM> may jointly encode or separately encode acknowledgement bits in a bundled feedback message. In some aspects, wireless communication device <NUM> may configure bundling based at least in part on a characteristic of a network. For example, for relaying information, wireless communication device <NUM> may configure which feedback messages to bundle based at least in part on a quantity of hops and/or a quantity of alternative routes available. In some aspects, wireless communication device <NUM> may determine the time period based at least in part on which feedback messages to bundle based at least in part on a quantity of hops and/or a quantity of alternative routes available.

As mentioned above, feedback messages, such as grant ACKs, may be relayed. For example, UE <NUM> may sent a packet to UE <NUM>, with instructions to transmit the packet to UE <NUM> and UE <NUM>. UE <NUM> may transmit an ACK/NACK for the packet back to UE <NUM>. UE <NUM> may also transmit an ACK/NACK indicating a successful delivery of the packet to UE <NUM>, UE <NUM>, or both. Alternatively, UE <NUM> may not need to transmit an ACK/NACK for successful delivery to UE <NUM>, because eventually a higher layer ACK/NACK (e.g., radio link control (RLC) ACK) may be transmitted back from UE <NUM>. However, a specific higher layer ACK/NACK may be absent (RLC unacknowledged mode), or may incur higher latency or network overhead. For example, an RLC NACK may be relayed back from UE <NUM> to UE <NUM> to UE <NUM>. Then, UE <NUM> may re-transmit the whole upper-layer packet. Whereas if UE <NUM> immediately determines that the specific packet had a HARQ NACK from UE <NUM> to UE <NUM>, UE <NUM> may indicate specific resources for UE <NUM> on which UE <NUM> may re-send the next HARQ attempt. In another example, if the packet was sent with CBG-based ACK/NACK, UE <NUM> may reduce the resource grant to match the number of CBGs to be retransmitted. Even if there is a HARQ failure (e.g., NACK until max attempts reached), UE <NUM> may instruct UE <NUM> to retransmit the packet as a new packet. Various combinations of relaying grants, multi-stage grants, and ACK bundling may be used.

In some aspects, wireless communication device <NUM> may determine the time period based at least in part on a timing of a feedback message relayed from another wireless communication device. Wireless communication device <NUM> may receive, from wireless communication device <NUM>, a packet for relaying to BS <NUM> and may acknowledge receipt of the packet for relaying. Additionally, or alternatively, based at least in part on relaying the packet, wireless communication device <NUM> may receive an acknowledgement of a success of relaying the packet and may relay the acknowledgement to wireless communication device <NUM>, as described in more detail herein. In some aspects, wireless communication device <NUM> may transmit a feedback message based at least in part on relaying information. For example, wireless communication device <NUM> may bundle an acknowledgement of a received packet from wireless communication device <NUM> with an acknowledgement from BS <NUM> that wireless communication device <NUM> successfully relayed the received packet to BS <NUM>.

In some aspects, distance-based NACK rules may be used for relaying. For example, for V2X, wireless communication device <NUM> may not transmit a feedback message if wireless communication device <NUM> is too far away. With relaying, if multiple routes to a final destination are present, and a source is always expected to be close to one of the routes, wireless communication device <NUM> may determine the time period based at least in part on a location of the final destination and any hops in between. A threshold distance for the final destination or for a hop may be adjusted based at least in part on a function of a quantity of relay node locations, or a quantity of known relay node locations. In some aspects, wireless communication device <NUM> may determine the time period based at least in part on at least one of a quantity of hops in a multi-hop communication, a quantity of alternative routes for the multi-hop communication, a quantity of sources for a plurality of received packets, one or more locations of hops for the multi-hop communication, or some combination thereof.

In some aspects, wireless communication device <NUM> may determine the time period based at least in part on how sidelink resources are mapped to sidelink resource blocks. Sidelink resources may be divided into blocks, and a last few resources within each block may carry feedback channels to all sidelink resources in the block. A mapping of sidelink resources to the blocks may be pre-defined. Mapping may be based at least in part on sidelink resource locations, a link identifier, or an identifier for wireless communication device <NUM>. Mapping may be used for both time and frequency allocation of feedback resources. In some aspects, wireless communication device <NUM> may determine the time period to be based at least in part on an end of a sidelink resource block mapped for feedback messages. This may be needed to meet minimum processing delay requirements.

In some aspects, wireless communication device <NUM> may transmit feedback messages considered unsuitable for sidelink (e.g., sidelink channel quality indicator). Such feedback messages may be transmitted via a medium access control control element (MAC CE) instead of on a PUCCH, and some feedback messages may be relayed over Uu. Wireless communication device <NUM> may determine the time period based at least in part on whether a feedback message is considered unsuitable.

Wireless communication devices benefit from more reliable feedback messages. If a feedback message is transmitted too soon, the feedback message may not be processed efficiently. If a wireless communication device is able to account for various factors, and even determine a minimum time period, as described herein, feedback messages may be received more successfully and sidelink communications will improve. Improved sidelink communications may cause the wireless communication device to conserve processing resources and signaling resources.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a wireless communication device, in accordance with the present disclosure. Example process <NUM> is an example where the wireless communication device (e.g., BS <NUM>, UE <NUM>, wireless communication devices <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>) performs operations associated with sidelink feedback timing.

As shown in <FIG>, in some aspects, process <NUM> may include receiving a sidelink communication on a sidelink (block <NUM>). For example, the wireless communication device (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>) may receive a sidelink communication on a sidelink, as described above. In some aspects, the sidelink communication includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication (block <NUM>). For example, the wireless communication device (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>) may transmit, on the sidelink after a time period since receiving the sidelink communication, a feedback message acknowledging receiving the sidelink communication, as described above.

In a first aspect, process <NUM> includes determining the time period based at least in part on one or more of a type of the sidelink communication or a type of the feedback message.

In a second aspect, alone or in combination with the first aspect, the sidelink communication corresponds to the multi-stage grant, and process <NUM> further includes determining the time period based at least in part on a quantity of stages in the multi-stage grant.

In a third aspect, alone or in combination with one or more of the first and second aspects, process <NUM> includes determining the time period based at least in part on whether the feedback message is carried on one of a physical sidelink feedback channel, a physical sidelink control channel, a physical sidelink shared channel, or a physical uplink control channel.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process <NUM> includes determining the time period based at least in part on one or more of a payload or bundling configuration of the feedback message.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, process <NUM> includes determining the time period based at least in part on an end of a sidelink resource block mapped for feedback messages.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process <NUM> includes determining the time period based at least in part on a time or frequency resource allocation of one or more stages or packets.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the sidelink communication is one stage of a multi-stage grant, and process <NUM> includes determining the time period based at least in part on a timing of another stage of the multi-stage grant.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the sidelink communication is one packet of a multi-packet sidelink transmission, and process <NUM> includes determining the time period based at least in part on a timing of another packet of the multi-packet sidelink transmission.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process <NUM> includes determining the time period based at least in part on a timing of a feedback message relayed from another wireless communication device.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, process <NUM> includes determining the time period based at least in part on at least one of a quantity of hops in a multi-hop communication, a quantity of alternative routes for the multi-hop communication, a quantity of sources for a plurality of received packets, one or more locations of hops for the multi-hop communication, or some combination thereof.

It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, and/or a combination of hardware and software.

A used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single members.

Claim 1:
A wireless communication device for wireless communication, comprising:
a memory; and
one or more processors, coupled to the memory, configured to:
receive (<NUM>) a sidelink communication on a sidelink, wherein the sidelink communication is of a type that includes at least one of a grant, data received on a resource identified by the grant, a multi-stage grant, a multi-packet grant, or a relaying communication; and
transmit (<NUM>), on the sidelink and after a time period since receiving the sidelink communication, a feedback message, wherein the feedback message is configured to acknowledge the received sidelink communication, and wherein the time period is a minimum time period to wait before transmitting the feedback message and is based at least in part on a capability of the wireless communication device and either one of: the type of the sidelink communication or a type of the feedback message,
wherein the type of the feedback message includes an acknowledgment message on a physical sidelink feedback channel, PSFCH, or physical sidelink control channel, PSCCH, or a MAC control element, MAC-CE, on a physical sidelink shared channel, PSSCH, or physical uplink control channel, PUCCH.