Patent Description:
Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for managing resource reservations for sidelink communications.

Reference is made to <CIT> "Adapting transmissions in multi-transmission time interval (TTI) sidelink communication".

After considering this discussion, and particularly after reading the section entitled "Detailed Description" one will understand how the features of this disclosure provide advantages that may include desirable resource reservations for sidelink communications.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for managing resource reservations for sidelink communications. Monitoring sidelink feedback from a user equipment (UE) may be an inefficient method of determining whether resources are available for reclaiming for other transmissions. Aspects of the present disclosure provide various techniques for reclaiming one or more resource reserved for sidelink transmissions. The techniques described herein may provide an efficient method of determining whether resource reservations for sidelink transmission are available for reclaiming for other transmissions such as other sidelink transmissions (e.g., transmissions between UEs) or Uu transmissions (e.g., transmissions between UE and a base station). For instance, the techniques described herein may enable reclaiming of reserved resources without having UEs monitor all feedback transmissions (e.g., on a physical sidelink feedback channel (PSFCH)), which may lead to desirable power consumption and/or battery life of certain wireless communication devices.

The following description provides examples of sidelink resource reservation management in communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims.

As shown in <FIG>, a first UE 120a may be communicating with a second UE 120b via sidelink resource reservations as further described herein. The first UE 120a includes a resource manager 122a that determines whether any resource reservations for sidelink communications are available to be reclaimed for other transmissions, and the second UE 120b includes a resource manager 122b that determines whether any resource reservations for sidelink communications are available to be reclaimed for other transmissions, in accordance with aspects of the present disclosure.

Various sidelink channels may be used for sidelink communications, including a physical sidelink discovery channel (PSDCH), a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH). The PSDCH may carry discovery expressions that enable proximal devices to discover each other. The PSCCH may carry control signaling such as sidelink resource configurations and other parameters used for data transmissions. The PSSCH may carry data transmissions, and the PSFCH may carry feedback such as hybrid automatic repeat request (HARQ) feedback and/or channel state information related to a sidelink channel quality.

NR access (e.g., <NUM> NR) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., <NUM> or beyond), millimeter wave (mmWave) targeting high carrier frequency (e.g., <NUM> to <NUM> or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical services targeting ultra-reliable low-latency communications (URLLC). NR supports beamforming and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported, as multi-layer transmissions. Aggregation of multiple cells may be supported.

The wireless communication network <NUM> may also include relay stations (e.g., relay station 110r), also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE <NUM> or a BS <NUM>), or that relays transmissions between UEs <NUM>, to facilitate communication between devices.

<FIG> illustrates example components of BS <NUM> and UE <NUM> (e.g., in the wireless communication network <NUM> of <FIG>), which may be used to implement aspects of the present disclosure.

The control information may be for PSDCH, PSCCH, PSSCH, PSFCH, etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor <NUM> may process (e.g., encode and symbol map) the data and the control information to obtain data symbols and control symbols, respectively. The transmit processor <NUM> may also generate reference symbols, such as for a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH) demodulation reference signal (DMRS). A transmit (TX) multiple-input multiple-output (MIMO) processor <NUM> may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to modulators (MODs) 232a-232t. Each MOD <NUM> may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each MOD <NUM> may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The downlink signals from the MODs 232a-232t may be transmitted via antennas 234a-234t, respectively.

At the UE <NUM>, antennas 252a-252r may receive the downlink signals from the BS <NUM> and may provide received signals to demodulators (DEMODs) in transceivers 254a-254r, respectively. Each DEMOD in the transceiver <NUM> may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each DEMOD in the transceiver may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector <NUM> may obtain received symbols from all the DEMODs in the transceivers 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols.

On the uplink, at the UE <NUM>, a transmit processor <NUM> may receive and process data (e.g., for a physical uplink shared channel (PUSCH)) from a data source <NUM> and control information (e.g., for a physical uplink control channel (PUCCH) from the controller/processor <NUM>. The transmit processor <NUM> may also generate reference symbols for a reference signal (e.g., for a sounding reference signal (SRS)). The symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the DEMODs in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the BS <NUM>. At the BS <NUM>, the uplink signals from the UE <NUM> may be received by the antennas <NUM>, processed by the MODs <NUM>, detected by a MIMO detector <NUM> if applicable, and further processed by a receive processor <NUM> to obtain decoded data and control information sent by the UE <NUM>.

Memories <NUM> and <NUM> may store data and program codes for the BS <NUM> and the UE <NUM>, respectively. A scheduler <NUM> may schedule the UEs for <NUM> data transmission on a downlink and/or an uplink.

The controller/processor <NUM> and/or other processors and modules at the UE <NUM> may perform or direct the execution of processes for techniques described herein. For example, as shown in <FIG>, the controller/processor <NUM> of the UE <NUM> has a resource manager <NUM> that determines whether any resource reservations for sidelink communications are available to be reclaimed for other transmissions, according to aspects described herein. Although shown at the Controller/Processor, other components of the UE <NUM> and the BS <NUM> may be used to perform the operations described herein. While the examples provided herein are described with respect to a BS communicating with a UE, aspects of the present disclosure may also be applied to a UE communicating with another UE such as the UE 120a communicating with the UE 120b via sidelink transmissions as depicted in <FIG>.

<FIG> illustrate vehicle to everything (V2X) systems, in accordance with certain aspects of the present disclosure. The V2X systems, provided in <FIG> provides two complementary transmission modes. A first transmission mode involves direct communications (e.g., also referred to herein as sidelink communications between UEs) between participants in the local area. Such communications are illustrated in <FIG>. A second transmission mode involves network communications through a network as illustrated in <FIG>, which may be implemented over a Uu interface (e.g., a wireless communication interface between a radio access network (RAN) and a UE).

Referring to <FIG>, a V2X system is illustrated with two vehicles. The first transmission mode allows for direct communication between different participants in a given geographic location. As illustrated, a first vehicle <NUM> can have a wireless communication link with an individual <NUM> (V2P) (e.g., via a UE) through a PC5 interface. Communications between the first vehicle <NUM> and a second vehicle <NUM> (V2V) may also occur through a PC5 interface. In a like manner, communication may occur from the first vehicle <NUM> to other highway components, such as a traffic signal <NUM> or sign (V2I) through a PC5 interface. In each example illustrated, two-way communication may take place between elements, therefore each element may be a transmitter and a receiver of information. In the configuration provided, the first transmission mode is a self-managed system and no network assistance is provided. Such transmission modes may enable improved spectral efficiency, reduced cost, and increased reliability as network service interruptions do not occur during handover operations for moving vehicles. Resource assignments do not need coordination between operators and subscription to a network is not necessary, therefore there is reduced complexity for such self-managed systems. The V2X system may be configured to operate in a licensed or unlicensed spectrum, thus any vehicle with an equipped system may access a common frequency and share information. Such harmonized/common spectrum operations allows for safe operation. The V2X system.

Referring to <FIG>, a second of two complementary transmission modes is illustrated. In the illustrated embodiment, a vehicle <NUM> may communicate to another vehicle <NUM> through network communications. These network communications may occur through discrete nodes, such as a BS (e.g., an eNB or gNB), that send and receive information between vehicles. The network communications may be used, for example, for long range communications between the vehicles (<NUM>, <NUM>), such as noting the presence of an accident approximately <NUM> mile ahead. Other types of communication may be sent by the node to the vehicles (<NUM>, <NUM>), such as traffic flow conditions, road hazard warnings, environmental/weather reports, service station availability and other like data. Such data can be obtained from cloud-based sharing services.

In certain wireless communication systems (e.g., <NUM> NR), a UE may signal to another UE sidelink control information (SCI) that includes resource (e.g., frequency-domain resources and/or time-domain resources) reservations for sidelink communications. In certain cases, the UE may broadcast the SCI to multiple UEs to enable some of the UEs to refrain from communicating during the resource reservations. As used herein, a resource reservation for sidelink communications may refer to a selection of resources (time resources and/or frequency resources) for one or more transmissions to one or more UEs. In aspects, the resource reservation may indicate a frequency resource assignment, a time resource assignment, and/or a resource reservation period. The frequency resource assignment may include one or more frequency resources for the transmissions to one or more UEs, and the resource allocation unit in the frequency domain may be in terms of one or more resource blocks, one or more bandwidth part (BWPs) in a carrier, or one or more sub-channels in a BWP or carrier. The time resource assignment may include one or more time-domain resources for the transmission to one or more UEs, and the resource allocation unit in the time domain may be in terms of symbols, mini-slots, slots, etc. The resource reservation period may provide a periodicity with which the frequency-time resources are assigned/reserved, for example, a length of the period (e.g., in milliseconds) and a total number of periods for future transmission occasions.

The resource reservations may be for a transmission of a transport block (TB) or a retransmission of the same TB. A single SCI may include a maximum number of reservations (such as <NUM>, <NUM>, or <NUM> resource reservations), which may be a preconfigured value or configurable via control signaling (e.g., radio resource control (RRC) signaling) from a base station (e.g., BS 110a).

In sidelink communications, retransmissions may be feedback-based or non-feedback based. In aspects, retransmissions may be transmitted by a UE (a transmitting UE) based on feedback (e.g., hybrid automatic repeat request (HARQ) feedback) from another UE (a receiving UE). For example, if a transmitting UE fails to receive an acknowledgement message from a receiving UE, the transmitting UE may resend the transmission based on various HARQ operations (such as forward error correction). In other aspects, the transmitting UE may blindly resend transmissions without any feedback from the receiving UE.

In feedback-based retransmission schemes, other UEs may determine based on the feedback whether resources reserved for retransmissions may be reclaimed (e.g., used for other transmissions). In other words, other UEs may listen to the feedback channel to determine whether a resource is released or not. For instance, suppose a transmitting UE reserves resources for three transmissions to send data to a receiving UE, where the first resource reservations carries the data and the subsequent resource reservations are reserved for retransmissions in case of decoding failures encountered at the receiving UE. If the receiving UE indicates, via broadcasted feedback, that the receiving UE has successfully decoded the data via the first resource reservation, the remaining resource reservations may be reclaimed for other transmissions, for example, by the other UEs monitoring the feedback. As used herein, reclaiming a resource reservation may include communicating with a base station or UE during the reclaimed resource reservation.

It may be spectrally and time-domain inefficient to refrain from reclaiming resource reservations. For example, if the number of reservations per SCI is large (e.g., ≥ <NUM> or <NUM> resource reservations), many resources may be wasted if reserved resources are not reclaimed. Monitoring all feedback from the receiving UE may be an inefficient method (in terms of power consumption, frequency resources, and time resources) of determining whether resources are available for reclaiming for other transmissions. As a UE is already monitoring control channels, the UE would also have to monitor all the feedback channels of nearby UEs, which may increase the power consumption of the UE and/or reduce the processing capabilities of the UE.

Aspects of the present disclosure provide various techniques for reclaiming one or more resource reserved for sidelink transmissions. The techniques described herein may provide an efficient method of determining whether resource reservations for sidelink transmission are available for reclaiming for other transmissions such as other sidelink transmissions or Uu transmissions. For instance, the techniques described herein may enable reclaiming of reserved resources without having UEs monitor all feedback transmissions (e.g., on the PSFCH). In certain aspects, if the maximum number of reservations per SCI is configured (or preconfigured) above a threshold, a UE may be enabled to reclaim reservations regardless of whether the reserved resources are available for reclaiming. In other aspects, if a transmitting UE (e.g., the UE that originally reserved resources for sidelink communications) determines to release reservations, the transmitting UE may signal that the reservations are released when transmitting SCI at the next reserved transmission. In other aspects, aside from releasing resources, the transmitting UE may indicate the number of valid reservations in the SCI regardless of whether reservations are reclaimed or not.

<FIG> is a call flow diagram illustrating example operations <NUM> for reclaiming resources reserved for sidelink communications, in accordance with certain aspects of the present disclosure. As shown at <NUM> and <NUM>, a BS <NUM> may transmit control signaling (e.g., RRC signaling) to a first UE 120a and a second UE 120b, respectively. The control signaling may include a configuration that indicates a threshold value that may determine whether resource reservations are enabled for reclaiming, as further described herein. In other aspects, the UEs 120a, 120b may be preconfigured with the threshold value, such as having the threshold value stored in memory.

At <NUM>, the first UE 120a may determine resource reservations allocated for sidelink communications with the second UE 120b. At <NUM>, the first UE 120a may transmit, to the second UE 120b, control information (e.g., SCI) having an indication of the resource reservations. For example, the resource reservations may include resources for an initial transmission (associated with a first resource reservation) at slot X and subsequent feedback based retransmissions (each associated with subsequent resource reservations) at slots X + <NUM>, X + <NUM>, and X + <NUM>.

At <NUM>, the second UE 120b may determine time and frequency resource allocations for communicating with the first UE 120a based on the indication of the resource reservations. At <NUM>, the second UE 120b may communicate with the first UE 120a based on the determination of the time and frequency resource allocations with respect to the first resource reservation in the SCI.

At <NUM>, the first UE 120a may determine that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and/or other UEs. Upon making this determination, the first UE 120a may refrain from communicating with the second UE 120b during one or more resource reservations within the remaining set of the resource reservations; or the first UE 120a may communicate with one or more other UEs during one or more resource reservations within the remaining set of the resource reservations.

Alternatively, or additionally, at <NUM>, the first UE 120a may determine that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and/or other UEs. In certain aspects, other UEs may also receive the second SCI message, for example, via a sidelink control channel such as the PSCCH. The SCI that signals a reservation release may enable the UEs (including the first UE 120a, the second UE 120b, and/or other UEs) to use the resources reserved for transmissions between the first UE 120a and the second UE 120b for other transmissions.

Alternatively, or additionally, at <NUM>, the second UE 120a may determine that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and/or other UEs. Upon making this determination, the second UE 120b may refrain from communicating with the first UE 120a during one or more resource reservations within the remaining set of the resource reservations; or the second UE 120b may communicate with one or more other UEs during one or more resource reservations within the remaining set of the resource reservations.

In certain aspects, the SCI transmitted at <NUM> and/or <NUM> may have an indication of a number of valid resource reservations. For example, the SCI may have a payload size sufficient to indicate four resource reservations, but the SCI only provides two valid resource reservations and indicates that the remaining resource reservations in the SCI are invalid. As used herein, a valid resource reservation may include a resource that is scheduled for communications and may be implemented, while an invalid resource reservation may include a resource that is not scheduled for communications and may be ignored.

While the examples provided herein are described with respect to the first UE 120a communicating with the second UE 120b, aspects of the present disclosure may also be applied to the first UE 120a communicating with multiple second UEs 120b via multicast and/or broadcast sidelink communications.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a user equipment (e.g., the UE 120a in the wireless communication network <NUM>). The operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at <NUM>, where a first UE (e.g., the first UE 120a) may determine a plurality of resource reservations allocated for sidelink communications with at least one second UE (e.g., one or more second UEs 120b). At <NUM>, the first UE may transmit, to the at least one second UE, control information (e.g., SCI) having an indication of the resource reservations. At <NUM>, the first UE may communicate with the at least one second UE during at least one of the resource reservations. At <NUM>, the first UE may determine that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs. At <NUM>, the first UE may take one or more actions based on the determination that the remaining set of the resource reservations is enabled to be reclaimed by the one or more UEs.

In certain aspects, at <NUM>, the first UE may communicate with the second UE, for example, by transmitting data transmissions to the second UE in accordance with the resource reservations (e.g., at the scheduled time-domain resources and with the allocated frequency-domain resources). In other aspects, the first UE may communicate with the second UE by receiving data transmissions from the second UE in accordance with the resource reservations. In certain aspects, the resource reservations may reserve resources for feedback-based retransmissions or non-feedback based retransmissions. In other aspects, the determination of reclaiming resources may depend on the resource reservations reserving resources for feedback based retransmissions. That is, resource reservations that reserve resources for non-feedback based retransmissions may not be available for reclaiming.

In aspects, taking one or more actions at <NUM> may include the first UE refraining from communicating with the at least one second UE during one or more resource reservations within the remaining set of the resource reservations. In other aspects, taking one or more actions at <NUM> may include the first UE communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

In certain aspects, the determination of reclaiming at <NUM> may be based on various conditions, and in some cases, regardless of whether the resource reservations are actually available for reclaiming. For instance, if a maximum number of reservations per SCI is configured (or preconfigured) above a threshold (e.g., <NUM> or <NUM>), a UE may be enabled to reclaim reservations regardless of whether the reserved resources are actually available for other communications. As an example, if the SCI has a maximum of three or four reservations, the UE may enable reclaiming of reservations by other UEs. Otherwise, if the SCI has a maximum of two reservations, the UE may not enable reclaiming of reservations by other UEs.

As another example, the first UE may determine that the remaining set of the resource reservations is enabled to be reclaimed based on a threshold value associated with the resource reservations. In aspects, if a total number of the resource reservations in the control information is greater than (or equal to) the threshold value (e.g., <NUM> or <NUM>), the first UE may determine that the remaining set of the resource reservations is enabled to be reclaimed. In other aspects, if a total number of the resource reservations in the control information is less than (or equal to) the threshold value, the first UE may determine that the remaining set of the resource reservations is enabled to be reclaimed.

In other aspects, if a transmitting UE (e.g., the UE that originally reserved resources for sidelink communications) determines to release reservations, the transmitting UE may signal that the reservations are released when transmitting SCI at the next reserved transmission. As an example, suppose the transmitting UE reserves transmissions at slots X, X + <NUM>, X + <NUM>, and X + <NUM>, the transmitting UE sends an initial transmission at SlotX. After the initial transmission, the transmitting UE determines from feedback that reserved resources scheduled for the retransmissions can be reclaimed. In the reserved resources in slot X + <NUM>, the transmitting UE indicates that the remaining reservations in slots X + <NUM> and X + <NUM> are released for other transmissions. Other UEs may now determine whether the reservations are released or not based on monitoring SCI without having to continuously monitor the feedback channel.

In aspects, upon determining that the remaining set of the resource reservations is enabled to be reclaimed, the first UE may transmit another SCI message that indicates one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communications with the first UE. That is, taking one or more actions at <NUM> may include transmitting, to the at least one second UE, additional control information (e.g., a second SCI message) indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communications between the first UE and the at least one second UE.

According to certain aspects, the indication that the reserved resources are released for other communications may be explicitly or implicitly indicated in the SCI. For instance, the SCI may provide explicit signaling via a dedicated field. In aspects, the additional control information includes a field (e.g., a bit flag) indicating that the one or more resource reservations within the remaining set of the resource reservations are released.

In other aspects, the SCI may only reserve resources for the PSSCH associated with the current PSCCH on which the SCI is transmitted. In other words, the SCI may provide a resource reservation for a single PSSCH associated with the PSCCH that carried the SCI at one of the remaining resource reservation enabled for reclaiming. For instance, the first UE may transmit the additional control information within a time-domain resource (e.g., a slot, mini-slot, etc.) associated with a resource reservation following the at least one resource reservation and within the remaining set of the resource reservations with respect to operations <NUM>. The additional control information may indicate that a single resource reservation is reserved for communications between the first UE and the at least one second UE.

In aspects, the reserved resources may be indicated as being released by indicating the resource reservations as being unused or invalid. For example, the SCI may indicate that all or some of the resource reservations in the SCI are invalid. As an example, the additional control information may indicate a number of valid resource reservations in the additional control information, and the one or more resource reservations within the remaining set of the resource reservations may include invalid resource reservations in the additional control information.

Aside from releasing resources, the transmitter UE may signal the number of valid reservations in the SCI and/or indicate whether a reservation is valid or invalid. For example, the control information of operations <NUM> may indicate a number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations determined at <NUM>. In certain aspects, a certain value (e.g. all zeroes) of a reservation field may indicate that the reservation field does not correspond to a valid resource reservation (e.g., an invalid resource reservation). For example, the control information of operations <NUM> may include a plurality of reservation fields, each of the reservations fields is associated with a resource reservation, and at least one of the reservation fields has a value that indicates the resource reservation associated with the reservation field is invalid.

In other aspects, a field in the SCI may indicate the number of valid reservations in the SCI. As an example, the valid reservation fields may be sequential starting from the first reservation field in the SCI, and the field may provide the length of the valid reservations in the sequence of the reservation fields of the SCI. The reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) may be repurposed for other communications. With respect to operations <NUM>, the control information may include a sequence of reservation fields, each of the reservation fields is associated with a resource reservation, and the control information may include a field that indicates a segment of the reservations fields (a first segment or last segment) in the sequence is associated with the valid resource reservations. The field may provide the length of the segment of reservation fields. In other words, the field may be a number indicating a length of the segment of the reservation fields in the sequence. The segment of the reservation fields associated with valid resource reservations may include the first or last resource reservation in the sequence.

In certain aspects, a bitmap field in the SCI may indicate which reservation fields correspond to valid reservations. The reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) may be repurposed for other communications. With respect to operations <NUM>, the control information may include a bitmap having a plurality of bits, each of the bits of the bitmap corresponds to a resource reservation in the control information, and at least one of the bits indicates the resource reservation associated with the bit is invalid. In other aspects, a bit flag may be associated with each reservation field, and the flag may indicate whether that particular reservation is valid or invalid.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a UE (e.g., the UE 120b in the wireless communication network <NUM>). The operations <NUM> may be complimentary to the operations <NUM> performed by another UE. Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at <NUM>, where a second UE (e.g., the second UE 120b) may receive, from a first UE (e.g.. , the first UE 120a), control information (e.g., SCI) having an indication of resource reservations allocated for sidelink communications with the first UE. At <NUM>, the second UE may communicate with the first UE during at least one of the resource reservations. At <NUM>, the second UE may determine that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs. At <NUM>, the second UE may take one or more actions based on the determination that the remaining set of the resource reservations is enabled to be reclaimed by the one or more UEs.

In certain aspects, at <NUM>, the second UE may communicate with the first UE, for example, by transmitting data to the first UE in accordance with the resource reservations (e.g., at the scheduled time-domain resources and with the allocated frequency-domain resources). In other aspects, at <NUM>, the second UE may communicate with the first UE by receiving data transmissions from the second UE in accordance with the resource reservations. In aspects, the second UE may communicate with the first UE by monitoring a control channel at time-domain resources associated with the resource reservations. In some cases, the second UE may not be the target of the resource reservations for the data transmissions, but instead the second UE monitors the control channel for the control information described herein to determine when resource reservations are enabled to be reclaimed or released without having to monitor a feedback channel. In certain aspects, the resource reservations may reserve resources for feedback-based retransmissions or non-feedback based retransmissions. In other aspects, the determination of reclaiming resources may depend on the resource reservations reserving resources for feedback based retransmissions. That is, resource reservations that reserve resources for non-feedback based retransmissions may not be available for reclaiming.

In aspects, taking one or more actions at <NUM> may include the second UE refraining from communicating with the first UE during one or more resource reservations within the remaining set of the resource reservations. In other aspects, taking one or more actions at <NUM> may include the second UE communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

As another example, the second UE may determine that the remaining set of the resource reservations is enabled to be reclaimed based on a threshold value associated with the resource reservations. In aspects, if a total number of the resource reservations in the control information is greater than (or equal to) the threshold value (e.g., <NUM> or <NUM>), the second UE may determine that the remaining set of the resource reservations is enabled to be reclaimed. In other aspects, if a total number of the resource reservations in the control information is less than (or equal to) the threshold value, the second UE may determine that the remaining set of the resource reservations is enabled to be reclaimed.

In aspects, upon determining that the remaining set of the resource reservations is enabled to be reclaimed, the second UE may receive another SCI message that indicates one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communications with the first UE. With respect to operations <NUM>, the second UE may receive, from the first UE, additional control information indicating that one or more resources within the remaining set of the resource reservations are released from being reserved for communications with the first UE (e.g., including communications between the first UE and second UE or between the first UE and another UE). Based on the indication, at <NUM>, the second UE may determine that the remaining set of the resources is enabled to be reclaimed as the reservations are released. Expressed another way, the determination of reclaiming at <NUM> may be based on the reception of an indication that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communications with the first UE.

In other aspects, the SCI may only reserve resources for the PSSCH associated with the current PSCCH on which the SCI is transmitted. In other words, the SCI may provide a resource reservation for a single PSSCH associated with the PSCCH that carried the SCI at one of the remaining resource reservation enabled for reclaiming.

For instance with respect to operations <NUM>, the second UE may receive the additional control information within a time-domain resource (e.g., a slot, mini-slot, etc.) associated with a resource reservation following the at least one resource reservation and within the remaining set of the resource reservations transmit the additional control information within a time-domain resource associated with a resource reservation following the at least one resource reservation and within the remaining set of the resource reservations. The additional control information may indicate that a single resource reservation is reserved for communications with the first UE (e.g., including communications between the first UE and second UE or between the first UE and another UE).

In aspects, the reserved resources may be indicated as being released by indicating the resource reservations as being unused or invalid. For example, the SCI may indicate that all or some of the resource reservations in the SCI are invalid. As an example with respect to operations <NUM>, the additional control information may indicate a number of valid resource reservations in the additional control information, and the one or more resource reservations within the remaining set of the resource reservations may include invalid resource reservations in the additional control information.

According to certain aspects, the receiver UE may receive the number of valid reservations in the SCI and/or an indication of whether a reservation is valid or invalid. For example, the control information of operations <NUM> may indicate a number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations received at <NUM>. In certain aspects, a certain value (e.g. all zeroes) of a reservation field may indicate that the reservation field does not correspond to a valid resource reservation (e.g., an invalid resource reservation). For example, the control information of operations <NUM> may include a plurality of reservation fields, each of the reservations fields is associated with a resource reservation, and at least one of the reservation fields has a value that indicates the resource reservation associated with the reservation field is invalid.

The operations <NUM> may begin, at <NUM>, where a first UE (e.g., UE 120a) may determine a plurality of resource reservations allocated for sidelink communications with a second UE (e.g., UE 120b). At <NUM>, the first UE may transmit, to the second UE, control information (e.g., SCI) having an indication of a number of valid resource reservations including the determined resource reservations. At <NUM>, the first UE may communicate with the second UE during at least one of the resource reservations.

In certain aspects, at <NUM>, the first UE may communicate with the second UE, for example, by transmitting data transmissions to the second UE in accordance with the resource reservations (e.g., at the scheduled time-domain resources and with the allocated frequency-domain resources). In other aspects, the first UE may communicate with the second UE by receiving data transmissions from the second UE in accordance with the resource reservations.

According to certain aspects, the transmitter UE may signal the number of valid reservations in the SCI and/or indicate whether a reservation is valid or invalid. For example with respect to operations <NUM>, the control information may indicate a number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations determined at <NUM>. In certain aspects, a certain value (e.g. all zeroes) of a reservation field may indicate that the reservation field does not correspond to a valid resource reservation (e.g., an invalid resource reservation). For example, the control information may include a plurality of reservation fields, each of the reservations fields is associated with a resource reservation, and at least one of the reservation fields has a value that indicates the resource reservation associated with the reservation field is invalid.

The operations <NUM> may begin, at <NUM>, where a second UE (e.g., UE 120b) may receive, from a first UE (e.g., UE 120a), control information (e.g., SCI) having an indication of a number of valid resource reservations allocated for sidelink communications with the first UE. At <NUM>, the second UE may determine time and frequency resource allocations for communicating with the first UE based on the indication of the valid resource reservations. At <NUM>, the second UE may communicate with the first UE based on the determination of the time and frequency resource allocations.

In certain aspects, at <NUM>, the second UE may communicate with the first UE, for example, by transmitting data to the first UE in accordance with the resource reservations (e.g., at the scheduled time-domain resources and with the allocated frequency-domain resources). In other aspects, at <NUM>, the second UE may communicate with the first UE by receiving data transmissions from the second UE in accordance with the resource reservations. In aspects, the second UE may communicate with the first UE by monitoring a control channel at time-domain resources associated with the resource reservations. In some cases, the second UE may not be the target for the data transmissions associated with the resource reservations, where the second UE monitors the control channel for the control information described herein to determine when resource reservations are enabled to be reclaimed or released without having to monitor a feedback channel.

According to certain aspects, the receiver UE may receive the number of valid reservations in the SCI and/or an indication of whether a reservation is valid or invalid. For example with respect to operations <NUM>, the control information may indicate a number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations received at <NUM>. In certain aspects, a certain value (e.g. all zeroes) of a reservation field may indicate that the reservation field does not correspond to a valid resource reservation (e.g., an invalid resource reservation). For example, the control information may include a plurality of reservation fields, each of the reservations fields is associated with a resource reservation, and at least one of the reservation fields has a value that indicates the resource reservation associated with the reservation field is invalid.

While the examples provided herein are described with respect to resource reservations being set in terms of slots, aspects of the present disclosure may also be applied to other suitable time-domain units including mini-slots (sub-slots) or symbols.

<FIG> illustrates a communications device <NUM> (e.g., UE 120a or UE 120b) that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in <FIG>. The communications device <NUM> includes a processing system <NUM> coupled to a transceiver <NUM> (e.g., a transmitter and/or receiver).

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein for managing resource reservations for sidelink transmissions.

In certain aspects, computer-readable medium/memory <NUM> stores code for receiving (including code for obtaining) <NUM>, code for transmitting <NUM>, code for determining <NUM>, code for communicating <NUM>, and/or code for taking action (including code for refraining from communicating and/or code for communicating) <NUM>. In certain aspects, the processor <NUM> has circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>. The processor <NUM> includes circuitry for receiving (including circuitry for obtaining) <NUM> (an example of means for receiving), circuitry for transmitting <NUM> (an example of means for transmitting), circuitry for determining <NUM> (an example of means for determining), circuitry for communicating <NUM> (an example of means for communicating), and/or circuitry for taking action (including circuitry for refraining from communicating and/or circuitry for communicating) <NUM> (an example of means for taking action).

Means for receiving may include an antenna (e.g., the antennas 252a-252r), a transceiver (e.g., the transceivers 254a-254r), a processor (e.g., the controller/processor <NUM>), and/or circuitry for receiving (e.g., the circuitry for receiving <NUM>). Means for transmitting may include an antenna (e.g., the antennas 252a-252r), a transceiver (e.g., the transceivers 254a-254r), a processor (e.g., the controller/processor <NUM>), and/or circuitry for transmitting (e.g., the circuitry for transmitting <NUM>). Means for determining may include a processor (e.g., the controller/processor <NUM>) and/or circuitry for determining (e.g., the circuitry for determining <NUM>). Means for communicating may include a processor (e.g., the controller/processor <NUM>) and/or circuitry for communicating (e.g., the circuitry for communicating <NUM>). Means for taking action may include a processor (e.g., the controller/processor <NUM>) and/or circuitry for taking action (e.g., the circuitry for taking action <NUM>). In certain aspects, various processors and/or various circuitry may include a circuit, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

In the case of a user equipment <NUM> (see <FIG>), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus.

Claim 1:
A method of wireless communication by a first user equipment, UE, comprising:
determining (<NUM>) a plurality of resource reservations for sidelink communications with at least one second UE;
transmitting (<NUM>), to the at least one second UE, control information having an indication of the resource reservations;
communicating (<NUM>) with the at least one second UE during at least one of the resource reservations;
determining (<NUM>) that a remaining set of the resource reservations is enabled to be reclaimed by one or more UEs comprising determining that when a total number of the resource reservations in the control information is equal to or greater than a threshold value, the remaining set of the resource reservations is enabled to be reclaimed; and
taking (<NUM>) one or more actions based on the determination that the remaining set of the resource reservations is enabled to be reclaimed by the one or more UEs.