Reclamation Reservation in Sidelink Communication

Abstract

Certain aspects of the present disclosure provide techniques for managing resource reservation in sidelink communication. A method that may be performed by a first user equipment (UE) includes: determining a plurality of resource reservations allocated for sidelink communication with at least one second UE; and sending control information with an indication of the resource reservation to the at least one second UE. The method further includes: communicating with the at least one second UE during at least one of the resource reservations; and determining that a remaining set of the resource reservations can be reclaimed by one or more UEs. The method further includes: taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. application Ser. No. 17 / 031,371, filed Sep. 24, 2020, which claims the benefit and priority of U.S. Provisional Patent Application Ser. No. 62,907,018, filed Sep. 27, 2019, the entire contents of both of which are hereby incorporated by reference. Technical Field

[0003] Aspects of the present disclosure relate to wireless communication, and more particularly, aspects of the present disclosure relate to techniques for managing resource reservation for sidelink communication. Background Art

[0004] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasting, etc. These wireless communication systems may employ multiple access technologies that are capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). By way of example, examples of such multiple access systems include Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, Advanced LTE (LTE - A) systems, Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single - Carrier Frequency Division Multiple Access (SC - FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD - SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at the city, national, regional, and even global levels. New Radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is an enhanced set of the LTE mobile standard released by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing cost, enhancing services, leveraging new spectrums, and better integrating with other open standards using OFDMA with cyclic prefix (CP) on the downlink (DL) and on the uplink (UL). To this end, NR supports beamforming, multiple - input multiple - output (MIMO) antenna technology, and carrier aggregation.

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

[0007] The systems, methods, and devices of the present disclosure each have several aspects, none of which alone is responsible for its desirable attributes. Without limiting the scope of the present disclosure as expressed by the following claims, some features will now be briefly discussed. After considering this discussion and particularly after reading the section entitled "Detailed Description," one will understand how the features of the present disclosure provide advantages that can include desirable resource reservation for sidelink communication.

[0008] Certain aspects provide a method for wireless communication by a first user equipment (UE). Generally speaking, the method includes: determining a plurality of resource reservations allocated for sidelink communication with at least one second UE; and sending control information having an indication of the resource reservation to the at least one second UE. The method further includes: communicating with the at least one second UE during at least one of the resource reservations; and determining that a remaining set of the resource reservations can be reclaimed by one or more UEs. The method further includes: taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

[0009] Certain aspects provide a method for wireless communication by a second UE. Generally speaking, the method includes: receiving control information having an indication of a resource reservation allocated for sidelink communication with a first UE from the first UE; and communicating with the first UE during at least one of the resource reservations. The method further includes: determining that a remaining set of the resource reservations can be reclaimed by one or more UEs; and taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

[0010] Certain aspects provide a method for wireless communication by a first UE. Generally speaking, the method includes: determining a plurality of resource reservations allocated for sidelink communication with a second UE; and sending control information having an indication of the number of valid resource reservations including the determined resource reservations to the second UE. The method further includes: communicating with the second UE during at least one of the resource reservations.

[0011] Certain aspects provide a method for wireless communication by a second UE. Generally speaking, the method includes: receiving control information having an indication of the number of valid resource reservations allocated for sidelink communication with a first UE from the first UE. The method further includes: determining a time and frequency resource allocation for communicating with the first UE based on the indication of the valid resource reservation; and communicating with the first UE based on the determination of the time and frequency resource allocation.

[0012] Certain aspects provide an apparatus for wireless communication. Generally, the apparatus includes a memory, a processor, and a transceiver. The processor is coupled to the memory, wherein the processor and the memory are configured to: determine a plurality of resource reservations allocated for sidelink communication with at least one UE. The transceiver is configured to: send control information having an indication of the resource reservation to at least one UE; and communicate with at least one UE during at least one of the resource reservations. The processor and the memory are further configured to: determine that a remaining set of the resource reservations can be reclaimed by one or more UEs; and take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

[0013] Certain aspects provide an apparatus for wireless communication. Generally, the apparatus includes a transceiver, a memory, and a processor. The transceiver is configured to: receive control information having an indication of a resource reservation allocated for sidelink communication with a UE from the UE; and communicate with the UE during at least one of the resource reservations. The processor is coupled to the memory, wherein the processor and the memory are configured to: determine that a remaining set of the resource reservations can be reclaimed by one or more UEs; and take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

[0014] Certain aspects provide an apparatus for wireless communication. Generally, the apparatus includes a memory, a processor, and a transceiver. The processor is coupled to the memory, wherein the processor and the memory are configured to: determine a plurality of resource reservations allocated for sidelink communication with a UE. The transceiver is configured to: send control information having an indication of a number of valid resource reservations including the determined resource reservations to the UE; and communicate with the UE during at least one of the resource reservations.

[0015] Certain aspects provide an apparatus for wireless communication. Generally, the apparatus includes a memory, a processor, and a transceiver. The transceiver is configured to: receive control information having an indication of a number of valid resource reservations allocated for sidelink communication with a UE from the UE. The processor is coupled to the memory, wherein the processor and the memory are configured to: determine a time and frequency resource allocation for communicating with the UE based on the indication of the valid resource reservation. The transceiver is further configured to: communicate with the UE based on the determination of the time and frequency resource allocation.

[0016] Certain aspects provide an apparatus for wireless communication. Generally speaking, the apparatus includes: a unit for determining a plurality of resource reservations allocated for sidelink communication with at least one UE; a unit for sending control information with an indication of the resource reservation to at least one UE; a unit for communicating with at least one UE during at least one of the resource reservations; a unit for determining that a remaining set of resource reservations can be reclaimed by one or more UEs; and a unit for taking one or more actions based on the determination that the remaining set of resource reservations can be reclaimed by one or more UEs.

[0017] Certain aspects provide an apparatus for wireless communication. Generally speaking, the apparatus includes: a unit for receiving, from a UE, control information with an indication of a resource reservation allocated for sidelink communication with the UE; a unit for communicating with the UE during at least one of the resource reservations; a unit for determining that a remaining set of resource reservations can be reclaimed by one or more UEs; and a unit for taking one or more actions based on the determination that the remaining set of resource reservations can be reclaimed by one or more UEs.

[0018] Certain aspects provide an apparatus for wireless communication. Generally speaking, the apparatus includes: a unit for determining a plurality of resource reservations allocated for sidelink communication with a UE; a unit for sending control information with an indication of the number of valid resource reservations including the determined resource reservations to the UE; and a unit for communicating with the UE during at least one of the resource reservations.

[0019] Certain aspects provide an apparatus for wireless communication. Generally speaking, the apparatus includes: a unit for receiving, from a UE, control information with an indication of the number of valid resource reservations allocated for sidelink communication with the UE; a unit for determining a time and frequency resource allocation for communicating with the UE based on the indication of the valid resource reservation; and a unit for communicating with the UE based on the determination of the time and frequency resource allocation.

[0020] Certain aspects provide a computer-readable medium having instructions stored thereon for performing the following operations: determining a plurality of resource reservations allocated for sidelink communication with at least one UE; sending control information with an indication of the resource reservation to at least one UE; communicating with at least one UE during at least one of the resource reservations; determining that a remaining set of resource reservations can be reclaimed by one or more UEs; and taking one or more actions based on the determination that the remaining set of resource reservations can be reclaimed by one or more UEs.

[0021] Certain aspects provide a computer-readable medium having instructions stored thereon for performing the following operations: receiving control information from a UE indicating a reservation of resources allocated for sidelink communication with the UE; communicating with the UE during at least one of the resource reservations; determining that a remaining set of the resource reservations can be reclaimed by one or more UEs; and taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by one or more UEs.

[0022] Certain aspects provide a computer-readable medium having instructions stored thereon for performing the following operations: determining a plurality of resource reservations allocated for sidelink communication with a UE; sending control information to the UE indicating a number of valid resource reservations including the determined resource reservations; and communicating with the UE during at least one of the resource reservations.

[0023] Certain aspects provide a computer-readable medium having instructions stored thereon for performing the following operations: receiving control information from a user equipment (UE) indicating a number of valid resource reservations allocated for sidelink communication with the UE; determining a time and frequency resource allocation for communicating with the UE based on the indication of the valid resource reservations; and communicating with the UE based on the determination of the time and frequency resource allocation.

[0024] To achieve the foregoing and related purposes, one or more aspects include the features described in detail hereinafter and particularly pointed out in the claims. The following description and the drawings set forth in detail certain illustrative features of one or more aspects. However, these features are indicative of only some of the various ways in which the principles of the various aspects may be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To enable a more particular understanding of the above-described features of the present disclosure, a more specific description may be had by reference to the aspects, some of which are illustrated in the drawings. It is to be noted, however, that the drawings illustrate only certain typical aspects of the present disclosure and are therefore not to be considered limiting of its scope, for the description may admit of other equally effective aspects.

[0026] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0027] Figure 2 is a block diagram conceptually illustrating an example design of a base station (BS) and a user equipment (UE) in accordance with certain aspects of the present disclosure.

[0028] Figure 3A and Figure 3B illustrates a vehicle - to - everything (V2X) system in accordance with certain aspects of the present disclosure.

[0029] Figure 4 is a call flow diagram illustrating example operations for managing resource reservation for sidelink communication in accordance with certain aspects of the present disclosure.

[0030] Figure 5 is a flowchart illustrating example operations for wireless communication by a first UE in accordance with certain aspects of the present disclosure.

[0031] Figure 6 is a flowchart illustrating example operations for wireless communication by a second UE in accordance with certain aspects of the present disclosure.

[0032] Figure 7 is a flowchart illustrating other example operations for wireless communication by a first UE in accordance with certain aspects of the present disclosure.

[0033] Figure 8 is a flowchart illustrating other example operations for wireless communication by a second UE in accordance with certain aspects of the present disclosure.

[0034] Figure 9 illustrates a communication device in accordance with aspects of the present disclosure, which may include various components configured to perform operations for the techniques disclosed herein.

[0035] For ease of understanding, where possible, the same reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized in other aspects without specific recitation. Detailed Description

[0036] Aspects of the present disclosure provide apparatus, methods, processing systems, and computer-readable media for managing resource reservation for sidelink communication. Monitoring sidelink feedback from a user equipment (UE) can be an inefficient way to determine whether resources are available for reclamation for other transmissions. Aspects of the present disclosure provide various techniques for reclaiming one or more resources reserved for sidelink transmissions. The techniques described herein can provide an efficient way to determine whether a resource reservation for a sidelink transmission is available for reclamation for other transmissions, such as other sidelink transmissions (e.g., transmissions between UEs) or Uu transmissions (e.g., transmissions between a UE and a base station). For example, the techniques described herein can enable reclamation of reserved resources without having the UE monitor all feedback transmissions (e.g., on a physical sidelink feedback channel (PSFCH)), which can result in desirable power consumption and / or battery life for some wireless communication devices.

[0037] The following description provides examples of sidelink resource reservation management in a communication system without limiting the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of the elements discussed without departing from the scope of the present disclosure. Various processes or components may be omitted, replaced, or added as appropriate for each example. For example, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with respect to some examples may be combined with those of other examples. For instance, an apparatus may be implemented or a method may be practiced using any number of aspects set forth herein. Further, the scope of the present disclosure is intended to cover such apparatus or methods implemented using other structures, functions, or a combination of structures and functions in addition to or different from the aspects of the present disclosure set forth herein. It should be understood that any aspect of the present disclosure disclosed herein may be embodied by one or more elements of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects.

[0038] In general, any number of wireless networks can be deployed in a given geographical area. Each wireless network can support a specific radio access technology (RAT) and can operate on one or more frequencies. The RAT may also be referred to as a radio technology, air interface, etc. The frequency may also be referred to as a carrier, subcarrier, frequency channel, tone, subband, etc. Each frequency can support a single RAT in a given geographical area to avoid interference between wireless networks with different RATs. In some cases, a 5G NR RAT network may be deployed.

[0039] Figure 1 FIG. 1 shows an example wireless communication network 100 in which aspects of the present disclosure may be implemented. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network).

[0040] As Figure 1 shown, a first UE 120a may communicate with a second UE 120b via sidelink resource reservation, as further described herein. In accordance with various aspects of the present disclosure, the first UE 120a includes a resource manager 122a that determines whether any resource reservation for sidelink communication is available for being reclaimed for other transmissions, and the second UE 120b includes a resource manager 122b that determines whether any resource reservation for sidelink communication is available for being reclaimed for other transmissions.

[0041] Various sidelink channels may be used for sidelink communication, 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 nearby devices to discover each other. The PSCCH may carry control signaling, such as sidelink resource configuration for data transmission and other parameters. 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 sidelink channel quality.

[0042] NR access (e.g., 5G technology) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeted at wide bandwidths (e.g., 80 MHz or above), millimeter wave (mmWave) targeted at high carrier frequencies (e.g., 24 GHz to 53 GHz or above), massive machine type communication MTC (mMTC) targeted at backward-incompatible MTC technology, and / or mission-critical services targeted at ultra-reliable low latency communication (URLLC). These services may include latency and reliability requirements. These services may also have different Transmission Time Intervals (TTIs) to meet corresponding Quality of Service (QoS) requirements. Additionally, these services may coexist in the same subframe. NR supports beamforming and may dynamically configure beam directions. MIMO transmission with precoding may also be supported as multi-layer transmission. Aggregation of multiple cells may be supported.

[0043] As Figure 1As shown, the wireless communication network 100 may include several base stations (BSs) 110a - z (each BS is also referred to individually as BS 110 or collectively as BS 110 herein) and other network entities. The BS 110 may provide communication coverage for a specific geographical area (sometimes referred to as a "cell"), which may be fixed or may move according to the location of the mobile BS 110. In some examples, the BSs 110 may be interconnected with each other and / or with one or more other BSs or network nodes (not shown) in the wireless communication network 100 through various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.) using any suitable transmission network. In Figure 1 the example shown, BSs 110a, 110b, and 110c may be macro BSs for macro cells 102a, 102b, and 102c respectively. BS 110x may be a pico BS for pico cell 102x. BSs 110y and 110z may be femto BSs for femto cells 102y and 102z respectively. A BS may support one or more cells. The BS 110 communicates with user equipment (UE) 120a - y (each UE is also referred to individually as UE 120 or collectively as UE 120 herein) in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc.) may be dispersed throughout the wireless communication network 100, and each UE 120 may be fixed or mobile.

[0044] The wireless communication network 100 may also include relay stations (e.g., relay station 110r) (which are also referred to as repeaters, etc.), which receive transmissions of data and / or other information from an upstream station (e.g., BS 110a or UE 120r) and send transmissions of data and / or other information to a downstream station (e.g., UE 120 or BS 110), or relay transmissions between UEs 120 to facilitate communication between devices.

[0045] The network controller 130 may be coupled to a group of BSs 110 and provide coordination and control for these BSs 110. The network controller 130 may communicate with the BSs 110 via the backhaul. The BSs 110 may also communicate with each other via wireless backhaul or wired backhaul (e.g., directly or indirectly).

[0046] Figure 2 Examples of components of BS 110a and UE 120a (e.g., in Figure 1 the wireless communication network 100) are shown, which may be used to implement aspects of the present disclosure.

[0047] At BS 110, the transmit processor 220 may receive data from the data source 212 and control information from the controller / processor 240. The control information may be used for PSDCH, PSCCH, PSSCH, PSFCH, etc. The data may be used for the physical downlink shared channel (PDSCH), etc. The processor 220 may process (e.g., encode and symbol map) the data and control information respectively to obtain data symbols and control symbols. The processor 220 may also generate reference symbols such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and physical broadcast channel (PBCH) demodulation reference signal (DMRS). The transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, control symbols, and / or reference symbols (if applicable), and may provide an output symbol stream to the modulators (MOD) 232a - 232t. Each MOD 232 may process the corresponding output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each MOD 232 may further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The downlink signals from the MOD 232a - 232t may be transmitted via the antennas 234a - 234t respectively.

[0048] At UE 120, the antennas 252a - 252r may receive the downlink signals from BS 110 and may provide the received signals to the demodulators (DEMOD) 254a - 254r in the transceiver respectively. Each demodulator 254 in the transceiver may condition (e.g., filter, amplify, down-convert, and digitize) the corresponding 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. The MIMO detector 256 may obtain the received symbols from all the DEMODs 254a - 254r in the transceiver, perform MIMO detection on the received symbols (if applicable), and provide the detected symbols. The receive processor 258 may process (e.g., demodulate, de-interleave, and decode) the detected symbols, provide the decoded data for UE 120a to the data sink 260, and provide the decoded control information to the controller / processor 280.

[0049] On the uplink, at the UE 120, the transmit processor 264 may receive and process data from the data source 262 (e.g., for the physical uplink shared channel (PUSCH)) and control information from the controller / processor 280 (e.g., for the physical uplink control channel (PUCCH)). The transmit processor 264 may also generate reference symbols for reference signals (e.g., for sounding reference signals (SRS)). Symbols from the transmit processor 264 may be precoded by the TX MIMO processor 266 (if applicable), further processed by the DEMOD 254a - 254r in the transceiver (e.g., for SC - FDM, etc.), and sent to the BS 110. At the BS 110, the uplink signal from the UE 120 may be received by the antenna 234, processed by the MOD 232, detected by the MIMO detector 236 (if applicable), and further processed by the receive processor 238 to obtain the decoded data and control information sent by the UE 120. The receive processor 238 may provide the decoded data to the data sink 239 and the decoded control information to the controller / processor 240.

[0050] The memories 242 and 282 may store data and program codes for the BS 110 and the UE 120, respectively. The scheduler 244 may schedule the UE 120 for data transmission on the downlink and / or uplink.

[0051] The controller / processor 280 and / or other processors and modules at the UE 120 may execute or direct the execution of processes for the techniques described herein. For example, as Figure 2 shown, according to aspects described herein, the controller / processor 280 of the UE 120 has a resource manager 281 that determines whether any resource reservation for sidelink communication is available for being reclaimed for other transmissions. Although shown at the controller / processor, other components of the UE 120 and the BS 110 may be used to perform the operations described herein. Although the examples provided herein are described with the BS communicating with the UE, aspects of the present disclosure may also be applied to the UE communicating with another UE, such as the UE 120a communicating with the UE 120b via a sidelink transmission as depicted in Figure 1 depicted.

[0052] Figure 3A and Figure 3B illustrates a vehicle - to - everything (V2X) system according to certain aspects of the present disclosure. Figure 3A and Figure 3BThe V2X system provided in [document] provides two complementary transmission modes. The first transmission mode involves direct communication between participants in a local area (e.g., also referred to herein as sidelink communication between UEs). Such communication is shown in Figure 3A [document]. The second transmission mode involves network communication through a network as shown in Figure 3B [document], which can be implemented through the Uu interface (e.g., a wireless communication interface between a radio access network (RAN) and a UE).

[0053] Referring to Figure 3A [document], the V2X system is shown using two vehicles. The first transmission mode allows direct communication between different participants at a given geographical location. As shown, the first vehicle 302 can have a wireless communication link (V2P) with the individual 304 through the PC5 interface (e.g., via a UE). Communication between the first vehicle 302 and the second vehicle 306 (V2V) can also occur through the PC5 interface. In a similar manner, communication from the first vehicle 302 to other highway components (such as traffic signal 308 or sign) (V2I) can occur through the PC5 interface. In each of the examples shown, two-way communication can occur between the elements, so each element can be both a sender and a receiver of information. In the provided configuration, the first transmission mode is a self-managed system and does not provide network assistance. Such a transmission mode can achieve improved spectral efficiency, reduced cost, and increased reliability because there is no network service interruption during handover operations for mobile vehicles. Resource allocation does not require coordination between operators, and subscription to the network is not necessary, thus reducing the complexity for such a self-managed system. The V2X system can be configured to operate in licensed or unlicensed spectrum, so any vehicle equipped with the system can access the common frequency and share information. Such coordinated / common spectrum operation allows for safe operation. The V2X system

[0054] Referring to Figure 3B [document], the second of the two complementary transmission modes is shown. In the illustrated embodiment, the vehicle 310 can communicate with another vehicle 312 through network communication. These network communications can occur through discrete nodes (such as a BS (e.g., eNB or gNB)) that send and receive information between the vehicles. Network communication can be used, for example, for remote communication between vehicles (310, 312), such as notifying that there is an accident approximately 1 mile ahead. The node can send other types of communication to the vehicles (310, 312), such as traffic flow conditions, road hazard warnings, environmental / weather reports, service station availability, and other similar data. Such data can be obtained from cloud-based shared services.

[0055] Example of reclaim reservation in sidelink communication

[0056] In some wireless communication systems (e.g., 5G NR), a UE may signal sidelink control information (SCI) to another UE, which includes resource reservation (e.g., frequency-domain resource and / or time-domain resource) for sidelink communication. In some cases, a UE may broadcast SCI to multiple UEs so that some of the UEs can avoid communication during resource reservation. As used herein, resource reservation for sidelink communication may refer to the selection of resources (time resources and / or frequency resources) for one or more transmissions to one or more UEs. In various aspects, the resource reservation may indicate frequency resource assignment, time resource assignment, and / or resource reservation period. The frequency resource assignment may include one or more frequency resources for transmissions to one or more UEs, and the resource allocation unit in the frequency domain may be based on one or more resource blocks, one or more bandwidth parts (BWPs) in a carrier, or one or more subchannels in a BWP or carrier. The time resource assignment may include one or more time-domain resources for transmissions to one or more UEs, and the resource allocation unit in the time domain may be based on symbols, mini-slots, time slots, etc. The resource reservation period may provide the periodicity of assigned / reserved frequency-time resources, e.g., the length of the period (e.g., in milliseconds) and the total number of periods for future transmission opportunities.

[0057] Resource reservation may be used for the transmission of a transport block (TB) or the retransmission of the same TB. A single SCI may include a maximum number of reservations (such as 2, 3, or 4 resource reservations), which may be pre-configured values or configured via control signaling (e.g., radio resource control (RRC) signaling) from a base station (e.g., BS110a).

[0058] In sidelink communication, retransmission may be feedback-based or non-feedback-based. In various aspects, the retransmission may be sent by a UE (the transmitting UE) based on feedback (e.g., hybrid automatic repeat request (HARQ) feedback) from another UE (the receiving UE). For example, if the transmitting UE fails to receive an acknowledgment message from the receiving UE, the transmitting UE may retransmit the transmission based on various HARQ operations (such as forward error correction). In other aspects, the transmitting UE may blindly retransmit the transmission without any feedback from the receiving UE.

[0059] In a feedback-based retransmission scheme, other UEs can determine based on the feedback whether the resources reserved for retransmission can be reclaimed (e.g., for other transmissions). In other words, other UEs can listen to the feedback channel to determine whether the resources are released. For example, assume that the transmitting UE reserves resources for three transmissions of data to the receiving UE, where the first resource reservation carries the data and the subsequent resource reservations are reserved for retransmission in case of a decoding failure at the receiving UE. If the receiving UE indicates via the broadcast feedback that the receiving UE has successfully decoded the data via the first resource reservation, the remaining resource reservations can be reclaimed for other transmissions, such as by other UEs monitoring the feedback. As used herein, reclaiming a resource reservation can include communicating with the base station or the UE during the reclaimed resource reservation.

[0060] Avoiding reclaiming resource reservations can be inefficient in the frequency and time domains. For example, if the number of reservations per SCI is large (e.g., ≥ 3 or 4 resource reservations), many resources may be wasted if the reserved resources are not reclaimed. Monitoring all feedback from the receiving UE can be an inefficient way to determine whether the resources are available for reclamation for other transmissions (in terms of power consumption, frequency resources, and time resources). Since the UE is already monitoring the control channel, the UE would also have to monitor all feedback channels of nearby UEs, which may increase the power consumption of the UE and / or reduce the processing capacity of the UE.

[0061] Aspects of the present disclosure provide various techniques for reclaiming one or more resources reserved for sidelink transmissions. The techniques described herein can provide an efficient method for determining whether a resource reservation for a sidelink transmission is available for reclamation for other transmissions, such as other sidelink transmissions or Uu transmissions. For example, the techniques described herein can enable the reclamation of reserved resources without having the UE monitor all feedback transmissions (e.g., on the PSFCH). In some aspects, if the maximum number of reservations per SCI is configured (or preconfigured) to be above a threshold, the UE can be enabled to reclaim the reservation regardless of whether the reserved resources are available for reclamation. In other aspects, if the transmitting UE (e.g., the UE that initially reserved the resources for sidelink communication) determines to release the reservation, the transmitting UE can signal the release of the reservation at the transmission of the next reserved SCI. In other aspects, in addition to releasing the resources, the transmitting UE can indicate the number of valid reservations in the SCI regardless of whether the reservation is reclaimed.

[0062] Figure 4is a call flow diagram illustrating an example operation 400 for reclaiming resources reserved for sidelink communication in accordance with certain aspects of the present disclosure. As shown at 402 and 404, the BS 110 may send control signaling (e.g., RRC signaling) to the first UE 120a and the second UE 120b, respectively. The control signaling may include a configuration indicating a threshold value that may determine whether a resource reservation can be reclaimed, as further described herein. In other aspects, the UEs 120a, 120b may be pre-configured with a threshold value, such as storing the threshold value in a memory.

[0063] At 406, the first UE 120a may determine a resource reservation allocated for sidelink communication with the second UE 120b. At 408, the first UE 120a may send control information (e.g., SCI) with an indication of the resource reservation to the second UE 120b. For example, the resource reservation may include resources for an initial transmission (associated with a first resource reservation) at time slot X and subsequent feedback-based retransmissions at time slots X+5, X+10, and X+16 (each retransmission associated with a subsequent resource reservation).

[0064] At 410, the second UE 120b may determine a time and frequency resource allocation for communicating with the first UE 120a based on the indication of the resource reservation. At 412, the second UE 120b may communicate with the first UE 120a based on the determination of the time and frequency resource allocation for the first resource reservation in the SCI.

[0065] At 414, the first UE 120a may determine that the remaining set of resource reservations can be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and / or other UEs. When making this determination, the first UE 120a may avoid communicating with the second UE 120b during one or more resource reservations within the remaining set of resource reservations; alternatively, the first UE 120a may communicate with one or more other UEs during one or more resource reservations within the remaining set of resource reservations.

[0066] Alternatively or additionally, at 416, the first UE 120a may determine that the remaining set of resource reservations can be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and / or other UEs. In certain aspects, the other UEs may also receive a second SCI message, for example, via a sidelink control channel such as PSCCH. The SCI signaling the 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 transmission between the first UE 120a and the second UE 120b for other transmissions.

[0067] Alternatively or additionally, at 418, the second UE 120a may determine that the remaining set of resource reservations can be reclaimed by one or more UEs including the first UE 120a, the second UE 120b, and / or other UEs. When making this determination, the second UE 120b may avoid communicating with the first UE 120a during one or more resource reservations within the remaining set of 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 resource reservations.

[0068] In some aspects, the SCI sent at 408 and / or 416 may have an indication of the 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 resources that are scheduled for communication and can be implemented, while an invalid resource reservation may include resources that are not scheduled for communication and can be ignored.

[0069] Although 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 apply to the first UE 120a communicating with multiple second UEs 120b via multicast and / or broadcast sidelink communication.

[0070] Figure 5 is a flow chart showing an example operation 500 for wireless communication in accordance with certain aspects of the present disclosure. Operation 500 may be performed, for example, by a user equipment (e.g., UE 120a in the wireless communication network 100). Operation 500 may be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Additionally, the sending and receiving of signals by the UE in operation 500 may be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In some aspects, the sending or receiving of signals by the UE may be implemented via a bus interface of one or more processors (e.g., the controller / processor 280) for acquiring and / or outputting signals.

[0071] Operation 500 may start at 502, where a first UE (e.g., first UE 120a) may determine a plurality of resource reservations allocated for sidelink communication with at least one second UE (e.g., one or more second UEs 120b). At 504, the first UE may send control information (e.g., SCI) with an indication of the resource reservation to at least one second UE. At 506, the first UE may communicate with at least one second UE during at least one of the resource reservations. At 508, the first UE may determine that the remaining set of resource reservations can be reclaimed by one or more UEs. At 510, the first UE may take one or more actions based on the determination that the remaining set of resource reservations can be reclaimed by one or more UEs.

[0072] In some aspects, at 506, the first UE may communicate with the second UE, for example, by sending a data transmission to the second UE according to the resource reservation (e.g., at a scheduled time-domain resource and with an allocated frequency-domain resource). In other aspects, the first UE may communicate with the second UE by receiving a data transmission from the second UE according to the resource reservation. In some aspects, the resource reservation may reserve resources for feedback-based retransmission or non-feedback-based retransmission. In other aspects, the determination of reclaiming resources may depend on the resource reservation that reserves resources for feedback-based retransmission. That is, the resource reservation that reserves resources for non-feedback-based retransmission may not be available for reclamation.

[0073] In various aspects, taking one or more actions at 510 may include: the first UE avoiding communicating with at least one second UE during one or more of the resource reservations within the remaining set of resource reservations. In other aspects, taking one or more actions at 510 may include: the first UE communicating with another UE during one or more of the resource reservations within the remaining set of resource reservations.

[0074] In some aspects, the determination of reclamation at 508 may be based on various conditions and, in some cases, is independent of whether the resource reservation is actually available for reclamation. For example, if the maximum number reserved per SCI is configured (or pre-configured) to be higher than a threshold (e.g., 3 or 4), the UE may be enabled to reclaim the reservation regardless of whether the reserved resources are actually available for other communications. As an example, if an SCI has at most three or four reservations, the UE may allow other UEs to reclaim the reservation. Otherwise, if an SCI has at most two reservations, the UE may not allow other UEs to reclaim the reservation.

[0075] As another example, the first UE may determine that the remaining set of resource reservations can be reclaimed based on a threshold associated with the resource reservation. In various aspects, if the total number of resource reservations in the control information is greater than (or equal to) a threshold value (e.g., 3 or 4), the first UE may determine that the remaining set of resource reservations can be reclaimed. In other aspects, if the total number of 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 resource reservations can be reclaimed.

[0076] In other aspects, if the sending UE (e.g., the UE that initially reserved resources for sidelink communication) determines to release the reservation, the sending UE may signal the release of the reservation when sending the SCI at the next reserved transmission. As an example, assume the sending UE reserves transmissions at time slots X, X + 5, X + 10, and X + 16. The sending UE sends an initial transmission at time slot X. After the initial transmission, the sending UE determines from the feedback that the reserved resources scheduled for retransmission can be reclaimed. Among the reserved resources in time slot X + 5, the sending UE indicates that the remaining reservations in time slots X + 10 and X + 16 are released for other transmissions. Other UEs can now determine whether to release the reservation based on monitoring the SCI without having to continuously monitor the feedback channel.

[0077] In various aspects, when determining that the remaining set of resource reservations can be reclaimed, the first UE may send a message to another SCI indicating that one or more resource reservations within the remaining set of resource reservations are released from being reserved for communication with the first UE. That is, taking one or more actions at 510 may include sending additional control information (e.g., a second SCI message) to at least one second UE indicating that one or more resource reservations within the remaining set of resource reservations are released from being reserved for communication between the first UE and at least one second UE.

[0078] According to certain aspects, an indication that reserved resources are released for other communication may be indicated explicitly or implicitly in the SCI. For example, the SCI may provide explicit signaling via a dedicated field. In some aspects, the additional control information includes a field (e.g., a bit flag) that indicates that one or more resource reservations within the remaining set of resource reservations are released.

[0079] In other aspects, the SCI may reserve resources only for a PSSCH associated with the current PSCCH on which the SCI is sent. In other words, the SCI may provide resource reservation for a single PSSCH associated with the PSCCH that carries the SCI at one of the remaining resource reservations in the remaining resource reservations available for reclamation. For example, a first UE may send additional control information in a time domain resource (e.g., a time slot, a mini-slot, etc.) associated with a resource reservation that follows at least one resource reservation and is within the remaining set of resource reservations for operation 500. The additional control information may indicate that a single resource reservation is reserved for communication between the first UE and at least one second UE.

[0080] In various aspects, reserved resources may be indicated as released by indicating the resource reservation as 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 the number of valid resource reservations in the additional control information, and one or more resource reservations within the remaining set of resource reservations may include invalid resource reservations in the additional control information.

[0081] In addition to releasing resources, the transmitting UE may also signal the number of valid reservations in the SCI and / or indicate whether a reservation is valid or invalid. For example, the control information for operation 500 may indicate the number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations determined at 502. In some aspects, a particular value (e.g., all zeros) 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 for operation 500 may include multiple reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and at least one reservation field in the reservation fields having a value indicating that the resource reservation associated with the reservation field is invalid.

[0082] In other aspects, a field in the SCI can indicate the number of valid reservations in the SCI. As an example, the valid reservation fields can be arranged sequentially starting from the first reservation field in the SCI, and this field can provide the length of the valid reservation in the sequence of reservation fields in the SCI. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 500, the control information can include a sequence of reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and the control information can include a field indicating that a segment (the first segment or the last segment) of the reservation fields in the sequence is associated with a valid resource reservation. This field can provide the length of the segment of the reservation fields. In other words, this field can be a number indicating the length of the segment of the reservation fields in the sequence. The segment of the reservation fields associated with the valid resource reservation can include the first resource reservation or the last resource reservation in the sequence.

[0083] In some aspects, a bitmap field in the SCI can indicate which reservation fields correspond to valid reservations. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 500, the control information can include a bitmap having a plurality of bits, each bit in the bits of the bitmap corresponding to a resource reservation in the control information, and at least one bit in the bits indicating that the resource reservation associated with that bit is invalid. In other aspects, a bit flag can be associated with each reservation field, and this flag can indicate whether the particular reservation is valid or invalid.

[0084] Figure 6 is a flowchart showing an example operation 600 for wireless communication according to certain aspects of the present disclosure. Operation 600 can be performed, for example, by a UE (e.g., UE 120b in the wireless communication network 100). Operation 600 can be complementary to operation 500 performed by another UE. Operation 600 can be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Further, the transmission and reception of signals by the UE in operation 600 can be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In some aspects, the transmission or reception of signals by the UE can be implemented via the bus interface for obtaining and / or outputting signals of one or more processors (e.g., the controller / processor 280).

[0085] Operation 600 may begin at 602, where a second UE (e.g., second UE 120b) may receive control information (e.g., SCI) from a first UE (e.g., first UE 120a) having an indication of a resource reservation allocated for sidelink communication with the first UE. At 604, the second UE may communicate with the first UE during at least one of the resource reservations in the resource reservation. At 606, the second UE may determine that a remaining set of the resource reservation can be reclaimed by one or more UEs. At 608, the second UE may take one or more actions based on the determination that the remaining set of the resource reservation can be reclaimed by one or more UEs.

[0086] In some aspects, at 606, the second UE may communicate with the first UE, for example, by sending data to the first UE according to the resource reservation (e.g., at a scheduled time-domain resource and with an allocated frequency-domain resource). In other aspects, at 606, the second UE may communicate with the first UE by receiving a data transmission from the second UE according to the resource reservation. In various aspects, the second UE may communicate with the first UE by monitoring a control channel at a time-domain resource associated with the resource reservation. In some cases, the second UE may not be the target of the resource reservation for data transmission, but instead, the second UE monitors the control channel for the control information described herein to determine when the resource reservation can be reclaimed or released without having to monitor a feedback channel. In some aspects, the resource reservation may reserve resources for feedback-based retransmission or non-feedback-based retransmission. In other aspects, the determination of reclaiming resources may depend on the resource reservation that reserves resources for feedback-based retransmission. That is, the resource reservation that reserves resources for non-feedback-based retransmission may not be available for reclaiming.

[0087] In various aspects, taking one or more actions at 608 may include: the second UE avoiding communicating with the first UE during one or more of the resource reservations within the remaining set of the resource reservation. In other aspects, taking one or more actions at 608 may include: the second UE communicating with another UE during one or more of the resource reservations within the remaining set of the resource reservation.

[0088] In some aspects, the determination of reclaimability at 606 can be based on various conditions and, in some cases, is independent of whether the resource reservation is actually available for reclaiming. For example, if the maximum number reserved per SCI is configured (or pre-configured) to be higher than a threshold (e.g., 3 or 4), the UE can be enabled to reclaim the reservation regardless of whether the reserved resources are actually available for other communications. As an example, if an SCI has at most three or four reservations, the UE can allow other UEs to reclaim the reservation. Otherwise, if an SCI has at most two reservations, the UE may not allow other UEs to reclaim the reservation.

[0089] As another example, a second UE can determine that the remaining set of resource reservations can be reclaimed based on a threshold associated with the resource reservation. In aspects, if the total number of resource reservations in the control information is greater than (or equal to) a threshold value (e.g., 3 or 4), the second UE can determine that the remaining set of resource reservations can be reclaimed. In other aspects, if the total number of resource reservations in the control information is less than (or equal to) the threshold value, the second UE can determine that the remaining set of resource reservations can be reclaimed.

[0090] In aspects, when determining that the remaining set of resource reservations can be reclaimed, the second UE can receive another SCI message that indicates that one or more resource reservations within the remaining set of resource reservations are released from being reserved for communication with a first UE. Regarding operation 600, the second UE can receive additional control information from the first UE that indicates that one or more resources within the remaining set of resource reservations are released from being reserved for communication with the first UE (e.g., including communication between the first UE and the second UE or between the first UE and another UE). Based on this indication, at 606, the second UE can determine that the remaining set of resources can be reclaimed due to the reservation being released. In other words, the determination of reclaimability at 606 can be based on receiving an indication that one or more resource reservations within the remaining set of resource reservations are released from being reserved for communication with the first UE.

[0091] According to some aspects, an indication that reserved resources are released for other communications can be indicated explicitly or implicitly in the SCI. For example, the SCI can provide explicit signaling via a dedicated field. In some aspects, the additional control information includes a field (e.g., a bit flag) that indicates that one or more resource reservations within the remaining set of resource reservations are released.

[0092] In other aspects, the SCI may only reserve resources for a PSSCH associated with the current PSCCH on which the SCI is sent. In other words, the SCI may provide resource reservation for a single PSSCH associated with the PSCCH that carries the SCI at one of the remaining resource reservations in the remaining resource reservations available for reclamation.

[0093] For example, with respect to operation 600, the second UE may receive additional control information within a time domain resource (e.g., a time slot, a mini-slot, etc.) associated with a resource reservation that follows at least one resource reservation and is within the remaining set of resource reservations, and may send additional control information within a time domain resource associated with a resource reservation that follows at least one resource reservation and is within the remaining set of resource reservations. The additional control information may indicate that a single resource is reserved for communication with the first UE (e.g., including communication between the first UE and the second UE or between the first UE and another UE).

[0094] In various aspects, reserved resources may be indicated as released by indicating the resource reservation as 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 operation 600, the additional control information may indicate the number of valid resource reservations in the additional control information, and one or more resource reservations within the remaining set of resource reservations may include invalid resource reservations in the additional control information.

[0095] 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 for operation 600 may indicate the number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservation received at 602. In certain aspects, a particular value (e.g., all zeros) 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 for operation 600 may include multiple reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and at least one of the reservation fields in the reservation fields having a value indicating that the resource reservation associated with the reservation field is invalid.

[0096] In other aspects, a field in the SCI can indicate the number of valid reservations in the SCI. As an example, the valid reservation fields can be sequentially arranged starting from the first reservation field in the SCI, and this field can provide the length of the valid reservation in the sequence of reservation fields of the SCI. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 600, the control information can include a sequence of reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and the control information can include a field indicating that a segment (the first segment or the last segment) of the reservation fields in the sequence is associated with a valid resource reservation. This field can provide the length of the segment of the reservation fields. In other words, this field can be a number indicating the length of the segment of the reservation fields in the sequence. The segment of the reservation fields associated with the valid resource reservation can include the first resource reservation or the last resource reservation in the sequence.

[0097] In some aspects, a bitmap field in the SCI can indicate which reservation fields correspond to valid reservations. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 600, the control information can include a bitmap having a plurality of bits, each bit in the bits of the bitmap corresponding to a resource reservation in the control information, and at least one bit in the bits indicating that the resource reservation associated with that bit is invalid. In other aspects, a bit flag can be associated with each reservation field, and this flag can indicate whether the particular reservation is valid or invalid.

[0098] Figure 7 is a flowchart showing an example operation 700 for wireless communication according to certain aspects of the present disclosure. Operation 700 can be performed, for example, by a user equipment (e.g., UE 120a in the wireless communication network 100). Operation 700 can be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Additionally, the transmission and reception of signals by the UE in operation 700 can be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In some aspects, the transmission or reception of signals by the UE can be implemented via the bus interface of one or more processors (e.g., the controller / processor 280) for acquiring and / or outputting signals.

[0099] Operation 700 may begin at 702, where a first UE (e.g., UE 120a) may determine a plurality of resource reservations allocated for sidelink communication with a second UE (e.g., UE 120b). At 704, the first UE may send control information to the second UE indicating the number of valid resource reservations including the determined resource reservations. At 706, the first UE may communicate with the second UE during at least one of the resource reservations.

[0100] In some aspects, at 506, the first UE may communicate with the second UE, for example, by sending a data transmission to the second UE according to the resource reservation (e.g., at scheduled time-domain resources and with allocated frequency-domain resources). In other aspects, the first UE may communicate with the second UE by receiving a data transmission from the second UE according to the resource reservation.

[0101] According to some aspects, the transmitter UE may also signal the number of valid reservations in the SCI and / or indicate whether the reservation is valid or invalid. For example, with respect to operation 700, the control information may indicate the number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservations determined at 702. In some aspects, a particular value (e.g., all zeros) 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 reservation field in the reservation fields being associated with a resource reservation, and at least one of the reservation fields in the reservation fields having a value indicating that the resource reservation associated with the reservation field is invalid.

[0102] 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 arranged sequentially starting from the first reservation field in the SCI, and this field may provide the length of the valid reservations in the sequence of reservation fields in the SCI. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) may be reused for other communications. With respect to operation 700, the control information may include a sequence of reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and the control information may include a field indicating which segment (the first segment or the last segment) of the reservation fields in the sequence is associated with the valid resource reservations. This field may provide the length of the segment of the reservation fields. In other words, this field may be a number indicating the length of the segment of the reservation fields in the sequence. The segment of the reservation fields associated with the valid resource reservations may include the first resource reservation or the last resource reservation in the sequence.

[0103] In some aspects, the bitmap field in the SCI can indicate which of the reserved fields correspond to valid reservations. Reserved fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 700, the control information can include a bitmap having a plurality of bits, each of the bits in the bitmap corresponding to a resource reservation in the control information, and at least one of the bits indicating that the resource reservation associated with that bit is invalid. In other aspects, a bit flag can be associated with each reserved field, and the flag can indicate whether the particular reservation is valid or invalid.

[0104] Figure 8 is a flowchart showing an example operation 800 for wireless communication according to some aspects of the present disclosure. Operation 800 can be performed, for example, by a UE (e.g., UE 120b in wireless communication network 100). Operation 800 can be complementary to operation 700 performed by another UE. Operation 800 can be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Additionally, the transmission and reception of signals by the UE in operation 800 can be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In some aspects, the transmission or reception of signals by the UE can be implemented via a bus interface of one or more processors (e.g., the controller / processor 280) for acquiring and / or outputting signals.

[0105] Operation 800 can begin at 802, where a second UE (e.g., UE 120b) can receive control information (e.g., SCI) from a first UE (e.g., UE120a) having an indication of the number of valid resource reservations allocated for sidelink communication with the first UE. At 804, the second UE can determine a time and frequency resource allocation for communicating with the first UE based on the indication of the valid resource reservations. At 806, the second UE can communicate with the first UE based on the determination of the time and frequency resource allocation.

[0106] In some aspects, at 806, a second UE may communicate with a first UE, for example, by sending data to the first UE according to a resource reservation (e.g., at scheduled time-domain resources and with allocated frequency-domain resources). In other aspects, at 806, a second UE may communicate with a first UE by receiving a data transmission from the second UE according to a resource reservation. In various aspects, a second UE may communicate with a first UE by monitoring a control channel at time-domain resources associated with a resource reservation. In some cases, the second UE may not be the target for data transmission associated with a resource reservation, where the second UE monitors the control channel for the control information described herein to determine when it can reclaim or release the resource reservation without having to monitor a feedback channel.

[0107] According to some aspects, a 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 operation 800, the control information may indicate the number of valid resource reservations in the control information, and the valid resource reservations may include the resource reservation received at 802. In some aspects, a particular value (e.g., all zeros) 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 multiple reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and at least one reservation field in the reservation fields having a value indicating that the resource reservation associated with the reservation field is invalid.

[0108] 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 arranged sequentially starting from the first reservation field in the SCI, and this field may provide the length of the valid reservation in the sequence of reservation fields in the SCI. Reservation fields that do not correspond to valid reservations (e.g., invalid resource reservations) may be reused for other communications. With respect to operation 800, the control information may include a sequence of reservation fields, each reservation field in the reservation fields being associated with a resource reservation, and the control information may include a field indicating which segment (first segment or last segment) of the reservation fields in the sequence is associated with a valid resource reservation. This field may provide the length of the segment of the reservation fields. In other words, this field may be a number indicating the length of the segment of the reservation fields in the sequence. The segment of the reservation fields associated with a valid resource reservation may include the first resource reservation or the last resource reservation in the sequence.

[0109] In some aspects, the bitmap fields in the SCI can indicate which reserved fields correspond to valid reservations. Reserved fields that do not correspond to valid reservations (e.g., invalid resource reservations) can be reused for other communications. Regarding operation 800, the control information can include a bitmap having multiple bits, each of the bits of the bitmap corresponding to a resource reservation in the control information, and at least one of the bits indicating that the resource reservation associated with that bit is invalid. In other aspects, a bit flag can be associated with each reserved field, and the flag can indicate whether the particular reservation is valid or invalid.

[0110] Although the examples provided herein are described with respect to resource reservations based on time slots, aspects of the present disclosure can also be applied to other suitable time domain units including micro - time slots (sub - time slots) or symbols.

[0111] Figure 9 A communication device 900 (e.g., UE 120a or UE 120b) is shown, which can include various components (e.g., corresponding to unit - plus - function components) configured to perform operations for the techniques disclosed herein, such as Figures 5 - 8 the operations shown. The communication device 900 includes a processing system 902 coupled to a transceiver 908 (e.g., a transmitter and / or a receiver). The transceiver 908 is configured to transmit and receive signals for the communication device 900 via an antenna 910, such as the various signals described herein. The processing system 902 can be configured to perform processing functions for the communication device 900, including processing signals received by or to be transmitted by the communication device 900.

[0112] The processing system 902 includes a processor 904 coupled to a computer - readable medium / memory 912 via a bus 906. In some aspects, the computer - readable medium / memory 912 is configured to store instructions (e.g., computer - executable code) that, when executed by the processor 904, cause the processor 904 to perform Figures 5 - 8 the operations shown or other operations for performing the various techniques discussed herein for managing resource reservations for sidelink transmissions.

[0113] In some aspects, computer-readable medium / memory 912 stores code for receiving (including code for obtaining) 914, code for transmitting 916, code for determining 918, code for communicating 920, and / or code for taking an action (including code for avoiding communication and / or code for communicating) 922. In some aspects, processor 904 has circuitry configured to implement the code stored in computer-readable medium / memory 912. Processor 904 includes circuitry for receiving (including circuitry for obtaining) 924 (an example of a unit for receiving), circuitry for transmitting 926 (an example of a unit for transmitting), circuitry for determining 928 (an example of a unit for determining), circuitry for communicating 930 (an example of a unit for communicating), and / or circuitry for taking an action (including circuitry for avoiding communication and / or circuitry for communicating) 932 (an example of a unit for taking an action).

[0114] The unit for receiving may include an antenna (e.g., antennas 252a - 252r), a transceiver (e.g., transceivers 254a - 254r), a processor (e.g., controller / processor 280), and / or circuitry for receiving (e.g., circuitry for receiving 924). The unit for transmitting may include an antenna (e.g., antennas 252a - 252r), a transceiver (e.g., transceivers 254a - 254r), a processor (e.g., controller / processor 280), and / or circuitry for transmitting (e.g., circuitry for transmitting 926). The unit for determining may include a processor (e.g., controller / processor 280) and / or circuitry for determining (e.g., circuitry for determining 928). The unit for communicating may include a processor (e.g., controller / processor 280) and / or circuitry for communicating (e.g., circuitry for communicating 930). The unit for taking an action may include a processor (e.g., controller / processor 280) and / or circuitry for taking an action (e.g., circuitry for taking an action 932). In some aspects, the various processors and / or the various circuits may include circuitry designed to perform the functions described herein, 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.

[0115] In addition to the above examples, many examples of specific combinations are within the scope of the present disclosure, some of which are detailed below:

[0116] Example 1: A method for wireless communication by a first user equipment (UE), comprising: determining a plurality of resource reservations allocated for sidelink communication with at least one second UE; sending control information with an indication of the resource reservations to the at least one second UE; communicating with the at least one second UE during at least one of the resource reservations; determining that a remaining set of the resource reservations can be reclaimed by one or more UEs; and taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

[0117] Example 2: The method according to Example 1, wherein determining that the remaining set of the resource reservations can be reclaimed comprises: determining that the remaining set of the resource reservations can be reclaimed based on a threshold value associated with the resource reservations.

[0118] Example 3: The method according to Example 2, wherein determining that the remaining set of the resource reservations can be reclaimed comprises: determining that if a total number of the resource reservations in the control information is equal to or greater than the threshold value, the remaining set of the resource reservations can be reclaimed.

[0119] Example 4: The method according to Examples 1-3, wherein taking one or more actions comprises: sending additional control information to the at least one second UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communication between the first UE and the at least one second UE.

[0120] Example 5: The method according to Example 4, wherein the additional control information comprises a field indicating that the one or more resource reservations within the remaining set of the resource reservations are released.

[0121] Example 6: The method according to Example 4, wherein sending the additional control information comprises: sending 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; and the additional control information indicates that a single resource reservation is reserved for communication between the first UE and the at least one second UE.

[0122] Example 7: The method according to Example 4, wherein the additional control information indicates 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 comprise invalid resource reservations in the additional control information.

[0123] Example 8: The method according to any one of Examples 1-7, wherein the control information indicates a quantity of valid resource reservations in the control information; and the valid resource reservations include the determined resource reservations.

[0124] Example 9: The method according to Example 8, wherein the control information includes a plurality of reservation fields; each of the reservation fields in the reservation fields is associated with a resource reservation; and at least one of the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

[0125] Example 10: The method according to Example 8, wherein the control information includes a sequence of reservation fields; each of the reservation fields in the reservation fields is associated with a resource reservation; the control information includes a field indicating that a segment of the reservation fields in the sequence is associated with the valid resource reservation; the field is a number indicating a length of the segment of the reservation fields in the sequence; and the segment of the reservation fields includes a first resource reservation in the sequence.

[0126] Example 11: The method according to Example 8, wherein the control information includes a bitmap having a plurality of bits; each of the bits in the bitmap corresponds to a resource reservation in the control information; and at least one of the bits indicates that the resource reservation associated with the bit is invalid.

[0127] Example 12: The method according to any one of Examples 1-11, wherein taking one or more actions includes: avoiding communicating with the at least one second UE during one or more resource reservations within the remaining set of the resource reservations.

[0128] Example 13: The method according to any one of Examples 1-11, wherein taking one or more actions includes: communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

[0129] Example 14: A method for wireless communication by a second user equipment (UE), comprising: receiving, from a first UE, control information having an indication of a resource reservation allocated for sidelink communication with the first UE; communicating with the first UE during at least one of the resource reservations; determining that a remaining set of the resource reservations can be reclaimed by one or more UEs; and taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

[0130] Example 15: The method according to Example 14, wherein determining that the remaining set of the resource reservation can be recycled includes: determining that the remaining set of the resource reservation can be recycled based on a threshold value.

[0131] Example 16: The method according to Example 15, wherein determining that the remaining set of the resource reservation can be recycled includes: determining that if the quantity of the resource reservation in the control information is equal to or greater than the threshold value, then the remaining set of the resource reservation can be recycled.

[0132] Example 17: The method according to Examples 14-16, further comprising: receiving additional control information from the first UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservation are released from being reserved for communication with the first UE.

[0133] Example 18: The method according to Example 14, wherein the additional control information includes a field indicating that the one or more resource reservations within the remaining set of the resource reservation are released.

[0134] Example 19: The method according to Example 17, wherein receiving the additional control information includes: receiving the additional control information within a time domain resource associated with a resource reservation that follows the at least one resource reservation and is within the remaining set of the resource reservation; and the additional control information indicates that a single resource reservation is reserved for communication with the first UE.

[0135] Example 20: The method according to Example 17, wherein the additional control information indicates the quantity of valid resource reservations in the additional control information; and the one or more resource reservations within the remaining set of the resource reservation include invalid resource reservations in the additional control information.

[0136] Example 21: The method according to Examples 14-20, wherein the control information indicates the quantity of valid resource reservations in the control information; and the valid resource reservations include the determined resource reservations.

[0137] Example 22: The method according to Example 21, wherein the control information includes a plurality of reservation fields; each reservation field in the reservation fields is associated with a resource reservation; and at least one reservation field in the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

[0138] Example 23: The method according to Example 21, wherein the control information includes a sequence of reserved fields; each of the reserved fields in the reserved fields is associated with a resource reservation; the control information includes a field indicating that a segment of the reserved fields in the sequence is associated with a valid resource reservation; the field is a number indicating the length of the segment of the reserved fields in the sequence; and the segment of the reserved fields includes a first resource reservation in the sequence.

[0139] Example 24: The method according to Example 21, wherein the control information includes a bitmap having a plurality of bits; each of the bits in the bitmap corresponds to a resource reservation in the control information; and at least one of the bits indicates that the resource reservation associated with the bit is not valid.

[0140] Example 25: The method according to Examples 14-24, wherein taking one or more actions includes: avoiding communicating with the first UE during one or more resource reservations within the remaining set of the resource reservations.

[0141] Example 26: The method according to Examples 14-24, wherein taking one or more actions includes: communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

[0142] Example 27: An apparatus for wireless communication, comprising: a processing system configured to: determine a plurality of resource reservations allocated for sidelink communication with at least one user equipment (UE); and a transceiver configured to: send control information having an indication of the resource reservations to the at least one UE, and communicate with the at least one UE during at least one of the resource reservations; wherein the processing system is further configured to: determine that a remaining set of the resource reservations can be reclaimed by one or more UEs; and take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

[0143] Example 28: The apparatus according to Example 27, wherein the control information indicates a number of valid resource reservations in the control information; and the valid resource reservations include the determined resource reservations.

[0144] Example 29: A device for wireless communication, comprising: a transceiver configured to: receive control information from a user equipment (UE) having an indication of a resource reservation for sidelink communication with the UE, and communicate with the UE during at least one of the resource reservations; and a processing system configured to: determine that a remaining set of the resource reservations can be reclaimed by one or more UEs, and take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

[0145] Example 30: The device according to Example 29, wherein the control information indicates a number of valid resource reservations in the control information; and the valid resource reservations include the determined resource reservations.

[0146] The techniques described herein can be used in various wireless communication technologies such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. CDMA networks may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers the IS-2000, IS-95, and IS-856 standards. TDMA networks may implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks may implement radio technologies such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). Cdma2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). NR is an emerging wireless communication technology being developed.

[0147] The techniques described herein can be used for the wireless networks and radio technologies mentioned above and other wireless networks and radio technologies. For clarity, although aspects herein may be described using terms commonly associated with 3G, 4G, and / or 5G wireless technologies, aspects of the present disclosure can be applied to communication systems based on other generations.

[0148] In 3GPP, the term "cell" can refer to the coverage area of a Node B (NB) and / or the NB subsystem serving that coverage area, depending on the context in which the term is used. In an NR system, the terms "cell" and BS, Next Generation Node B (gNB or gNodeB), Access Point (AP), Distributed Unit (DU), carrier, or Transmission and Reception Point (TRP) can be used interchangeably. A BS can provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell can cover a relatively large geographic area (e.g., with a radius of several kilometers) and can allow unrestricted access by UEs with a service subscription. A pico cell can cover a relatively small geographic area and can allow unrestricted access by UEs with a service subscription. A femto cell can cover a relatively small geographic area (e.g., a residence) and can allow restricted access by UEs associated with that femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in a residence, etc.). The BS for a macro cell can be referred to as a macro BS. The BS for a pico cell can be referred to as a pico BS. The BS for a femto cell can be referred to as a femto BS or a home BS.

[0149] A UE may also be referred to as a mobile station, terminal, access terminal, user unit, station, customer premise equipment (CPE), cellular phone, smart phone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, appliance, medical device or apparatus, biometric sensor / device, wearable device (such as a smart watch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet, etc.)), entertainment device (e.g., music device, video device, satellite radio unit, etc.), vehicle component or sensor, smart meter / sensor, industrial manufacturing device, global positioning system device, or any other suitable device configured to communicate via wireless or wired media. Some UEs may be considered machine type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which may communicate with a BS, another device (e.g., a remote device), or other entities. A wireless node may provide a connection to or from a network (e.g., a wide area network such as the Internet or a cellular network) via a wired communication link or a wireless communication link. Some UEs may be considered Internet of Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

[0150] Some wireless networks (e.g., LTE) utilize Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and Single Carrier Frequency Division Multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, frequency bands, etc. Each subcarrier can be modulated with data. Generally, OFDM is utilized in the frequency domain and SC-FDM is utilized in the time domain to transmit modulated symbols. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can depend on the system bandwidth. For example, the subcarrier spacing can be 15 kHz and the minimum resource allocation (referred to as a "resource block" (RB)) can be 12 subcarriers (or 180 kHz). Thus, for system bandwidths of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), the nominal Fast Fourier Transform (FFT) size can be equal to 128, 256, 512, 1024, or 2048, respectively. The system bandwidth can also be divided into subbands. For example, a subband can cover 1.08 MHz (e.g., 6 RBs), and for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, there can be 1, 2, 4, 8, or 16 subbands, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is a 1 ms subframe.

[0151] NR can utilize OFDM with CP on both the uplink and downlink and can include support for half-duplex operation using TDD. In NR, the subframe is still 1 ms, but the basic TTI is referred to as a slot. The subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16,... slots), which depends on the subcarrier spacing. An NR RB is 12 consecutive frequency subcarriers. NR can support a basic subcarrier spacing of 15 kHz, and other subcarrier spacings can be defined relative to the basic subcarrier spacing, e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing. Beamforming can be supported and the beam direction can be configured dynamically. MIMO transmission with precoding can also be supported. In some examples, the MIMO configuration in the DL can support up to 8 transmit antennas, with multi-layer DL transmission up to 8 streams and up to 2 streams per UE. In some examples, multi-layer transmission with up to 2 streams per UE can be supported. Aggregation of multiple cells with up to 8 serving cells can be supported.

[0152] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all of the devices and apparatuses within its serving area or cell. The scheduling entity can be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for a scheduled communication, the subordinate entity utilizes the resources allocated by the scheduling entity. The base station is not the only entity that can be used as a scheduling entity. In some examples, a UE can be used as a scheduling entity and can schedule resources for one or more subordinate entities (e.g., one or more other UEs), and other UEs can utilize the resources scheduled by the UE for wireless communication. In some examples, a UE can be used as a scheduling entity in a peer-to-peer (P2P) network and / or a mesh network. In a mesh network example, in addition to communicating with the scheduling entity, UEs can also communicate directly with each other.

[0153] In some examples, two or more subordinate entities (e.g., UEs) can communicate with each other using sidelink signals. Real-life applications of such sidelink communication can include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communication, Internet of Everything (IoE) communication, IoT communication, mission-critical mesh, and / or various other suitable applications. Generally, a sidelink signal can refer to a signal transmitted from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without the need to relay the communication through a scheduling entity (e.g., a UE or a BS), even though a scheduling entity can be used for scheduling and / or control purposes. In some examples, licensed spectrum can be used to transmit sidelink signals (as opposed to wireless local area networks which typically use unlicensed spectrum).

[0154] The methods disclosed herein include one or more steps or acts for implementing the method. These method steps and / or acts can be interchanged with each other without departing from the scope of the claims. In other words, unless a specific order of the steps or acts is specified, the order and / or use of specific steps and / or acts can be modified without departing from the scope of the claims.

[0155] As used herein, the phrase referring to “at least one” of a list of items refers to any combination of those items, including a single member. By way of example, “at least one of a, b, or c” is intended to cover a, b, c, a - b, a - c, b - c, and a - b - c, as well as any combination of multiples of the same elements (e.g., a - a, a - a - a, a - a - b, a - a - c, a - b - b, a - c - c, b - b, b - b - b, b - b - c, c - c, and c - c - c or any other ordering of a, b, and c).

[0156] As used herein, the term "determine" encompasses a variety of actions. For example, "determine" can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, database, or another data structure), ascertaining, etc. Additionally, "determine" can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), etc. Further, "determine" can include parsing, selecting, choosing, establishing, etc.

[0157] The foregoing description is provided to enable any person skilled in the art to make and use the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein the reference to an element in the singular is not intended to mean "one and only one" but "one or more" unless specifically so stated. The term "some" refers to one or more unless specifically stated otherwise. All structural and functional equivalents of the elements of the various aspects described throughout this disclosure are expressly incorporated herein by reference and are intended to be encompassed by the claims, which are known or will be known to those skilled in the art. Further, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the phrase "step for".

[0158] The various operations of the methods described above can be performed by any suitable unit capable of performing the corresponding functions. These units can include a variety of hardware and / or software components and / or modules, including but not limited to: circuits, application specific integrated circuits (ASICs), or processors. Generally, where there are operations shown in the figures, those operations can have corresponding paired units plus functional components with similar numbers.

[0159] The various illustrative logical blocks, modules, and circuits described in connection with the present disclosure may be implemented or performed using a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0160] If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. Depending on the particular application and overall design constraints of the processing system, the bus may include any number of interconnecting buses and bridges. The bus may connect various circuits including a processor, machine-readable media, and a bus interface. In addition, the bus interface may be used to connect a network adapter to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of the user equipment 120 (see Figure 1 ), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also connect various other circuits such as a timing source, peripherals, voltage regulators, power management circuits, etc., which are well known in the art and will not be described further herein. The processor may be implemented using one or more general purpose processors and / or dedicated processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits that can execute software. Those skilled in the art will recognize how best to implement the functions described for the processing system in light of the particular application and overall design constraints imposed on the overall system.

[0161] If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code. Whether referred to as software, firmware, middleware, microcode, hardware description language, or other terms, software shall be construed broadly to mean instructions, data, or any combination thereof. A computer-readable medium includes both a computer storage medium and a communication medium, where the communication medium includes any medium that facilitates transfer of a computer program from one place to another. A processor may be responsible for managing the bus and general processing, which includes executing software modules stored on a machine-readable storage medium. The computer-readable storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In an alternative, the storage medium may be part of the processor. By way of example, a machine-readable medium may include a transmission line, a carrier modulated with data, and / or a computer-readable storage medium with instructions stored thereon separate from a wireless node, all of which may be accessed by the processor via a bus interface. Alternatively or in addition, a machine-readable medium or any part thereof may be integrated into the processor, such as may be the case with a cache and / or a general register file. By way of example, examples of a machine-readable medium may include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. A machine-readable medium may be embodied in a computer program product.

[0162] Software modules may include a single instruction or many instructions and may be distributed over several different code segments, in different programs, or across multiple storage media. A computer-readable medium may include several software modules. Software modules include instructions that, when executed by a device such as a processor, cause a processing system to perform various functions. Software modules may include a sending module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, when a triggering event occurs, a software module may be loaded from a hard drive into RAM. During the execution of a software module, the processor may load some of the instructions into a cache to increase access speed. Subsequently, one or more cache lines may be loaded into the general register file for execution by the processor. When the functions of a software module are referred to hereinafter, it will be understood that such functions are implemented by the processor when executing instructions from the software module.

[0163] In addition, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and optical disc, where disks typically reproduce data magnetically, while discs use lasers to optically reproduce data. Thus, in some aspects, a computer-readable medium may include a non-transitory computer-readable medium (e.g., a tangible medium). Additionally, for other aspects, a computer-readable medium may include a transitory computer-readable medium (e.g., a signal). The above combinations should also be included within the scope of computer-readable media.

[0164] Accordingly, some aspects may include a computer program product for performing the operations presented herein. For example, such a computer program product may include a computer-readable medium having instructions stored (and / or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, e.g., instructions for performing the operations described and shown in Figures 5 - 8 the drawings.

[0165] Furthermore, it should be appreciated that modules and / or other suitable units for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by a user terminal and / or a base station, where applicable. For example, such a device can be coupled to a server to facilitate the transfer of units for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage unit (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk), such that the user terminal and / or the base station can acquire the various methods when the storage unit is coupled to or provided to the device. Additionally, any other suitable techniques for providing the methods and techniques described herein to a device can be used.

[0166] It should be understood that the claims are not limited to the exact configurations and components shown above. Various modifications, changes, and variations can be made in the arrangement, operation, and details of the methods and apparatuses described above without departing from the scope of the claims.

Claims

1. A method of wireless communication by a first user equipment (UE), comprising: Determining a plurality of resource reservations for sidelink communication with at least one second UE; Sending control information having an indication of the resource reservations to the at least one second UE; Communicating with the at least one second UE during at least one of the resource reservations; Determining that a remaining set of the resource reservations can be reclaimed by one or more UEs, including: determining that if 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 can be reclaimed; And Taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

2. The method according to claim 1, wherein, Taking one or more actions includes: Sending additional control information to the at least one second UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communication between the first UE and the at least one second UE.

3. The method according to claim 2, wherein The additional control information includes a field indicating that the one or more resource reservations within the remaining set of the resource reservations are released.

4. The method according to claim 2, wherein: Sending the additional control information includes: sending the additional control information within a time domain resource associated with a resource reservation that follows the at least one resource reservation and is within the remaining set of the resource reservations; and The additional control information indicates that a single resource reservation is reserved for communication between the first UE and the at least one second UE.

5. The method according to claim 2, wherein: The additional control information indicates 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 include invalid resource reservations in the additional control information.

6. The method according to claim 1, wherein: The control information indicates a number of valid resource reservations in the control information; and The valid resource reservations include the determined resource reservations.

7. The method according to claim 6, wherein: The control information includes a plurality of reservation fields; Each of the reservation fields is associated with a resource reservation; and At least one of the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

8. The method according to claim 6, wherein: The control information includes a sequence of reservation fields; Each of the reservation fields is associated with a resource reservation; The control information includes a field indicating that a segment of the reservation fields in the sequence is associated with the valid resource reservations; The field is a number indicating a length of the segment of the reservation fields in the sequence; and The segment of the reservation fields includes a first resource reservation in the sequence.

9. The method according to claim 6, wherein: The control information includes a bitmap having a plurality of bits; Each bit in the bitmap corresponds to a resource reservation in the control information; and At least one of the bits indicates that the resource reservation associated with the bit is invalid.

10. The method according to claim 1, wherein Taking one or more actions includes: avoiding communicating with the at least one second UE during one or more resource reservations within the remaining set of the resource reservations.

11. The method according to claim 1, wherein Taking one or more actions includes: communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

12. A method for wireless communication by a second user equipment (UE), comprising: Receiving control information from a first UE indicating a resource reservation for sidelink communication with the first UE; Communicating with the first UE during at least one of the resource reservations; Determining that a remaining set of the resource reservations can be reclaimed by one or more UEs, including: determining that if the number of the resource reservations in the control information is equal to or greater than a threshold, the remaining set of the resource reservations can be reclaimed; And Taking one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

13. The method according to claim 12, further comprising: Receiving additional control information from the first UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communication with the first UE.

14. The method according to claim 13, wherein, The additional control information includes a field indicating that the one or more resource reservations within the remaining set of the resource reservations are released.

15. The method according to claim 13, wherein: Receiving the additional control information includes: receiving the additional control information within a time domain resource associated with a resource reservation that follows the at least one resource reservation and is within the remaining set of the resource reservations; and The additional control information indicates that a single resource reservation is reserved for communication with the first UE.

16. The method according to claim 13, wherein: The additional control information indicates the 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 include invalid resource reservations in the additional control information.

17. The method according to claim 12, wherein: The control information indicates the number of valid resource reservations in the control information; and The valid resource reservations include the determined resource reservations.

18. The method according to claim 17, wherein: The control information includes a plurality of reservation fields; Each of the reservation fields is associated with a resource reservation; and At least one of the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

19. The method according to claim 17, wherein: The control information includes a sequence of reservation fields; Each of the reservation fields is associated with a resource reservation; The control information includes a field indicating that a segment of the reserved field in the sequence is associated with the valid resource reservation; The field is a number indicating the length of the segment of the reserved field in the sequence; and The segment of the reserved field includes a first resource reservation in the sequence.

20. The method according to claim 17, wherein: The control information includes a bitmap having a plurality of bits; Each of the bits in the bitmap corresponds to a resource reservation in the control information; and At least one of the bits indicates that the resource reservation associated with the bit is not valid.

21. The method according to claim 12, wherein, Taking one or more actions includes: avoiding communicating with the first UE during one or more resource reservations within the remaining set of the resource reservations.

22. The method according to claim 12, wherein, Taking one or more actions includes: communicating with another UE during one or more resource reservations within the remaining set of the resource reservations.

23. An apparatus for wireless communication, comprising: A memory; A processor coupled to the memory, the processor and the memory being configured to: determine a plurality of resource reservations for sidelink communication with at least one user equipment (UE); And A transceiver configured to: Send control information having an indication of the resource reservation to the at least one UE; And Communicate with the at least one UE during at least one of the resource reservations; Wherein, the processor and the memory are further configured to: Determine that the remaining set of the resource reservations can be reclaimed by one or more UEs by determining that if the total number of the resource reservations in the control information is equal to or greater than a threshold value, then the remaining set of the resource reservations can be reclaimed; and Take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

24. The device according to claim 23, wherein, The transceiver is further configured to: Send additional control information to the at least one UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communication between the apparatus and the at least one UE.

25. The device according to claim 24, wherein, The additional control information includes a field indicating that one or more resource reservations within the remaining set of the resource reservations are released.

26. The apparatus according to claim 24, wherein: The transceiver is further configured to: send the additional control information within a time domain resource associated with a resource reservation that follows the at least one resource reservation and is within the remaining set of the resource reservations; and The additional control information indicates that a single resource reservation is reserved for communication between the apparatus and the at least one UE.

27. The apparatus according to claim 24, wherein: The additional control information indicates the number of valid resource reservations in the additional control information; and One or more resource reservations within the remaining set of the resource reservations include invalid resource reservations in the additional control information.

28. The apparatus according to claim 23, wherein: the control information indicates the number of valid resource reservations in the control information; and the valid resource reservations include the determined resource reservations.

29. The apparatus according to claim 28, wherein: the control information includes a plurality of reservation fields; each of the reservation fields in the reservation fields is associated with a resource reservation; and at least one of the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

30. The apparatus according to claim 28, wherein: the control information includes a sequence of reservation fields; each of the reservation fields in the reservation fields is associated with a resource reservation; the control information includes a field indicating that a segment of the reservation fields in the sequence is associated with the valid resource reservations; the field is a number indicating the length of the segment of the reservation fields in the sequence; and the segment of the reservation fields includes the first resource reservation in the sequence.

31. The apparatus according to claim 28, wherein: the control information includes a bitmap having a plurality of bits; each of the bits in the bitmap corresponds to a resource reservation in the control information; and at least one of the bits indicates that the resource reservation associated with the bit is invalid.

32. The device according to claim 23, wherein The transceiver is further configured to: avoid communicating with the at least one UE during one or more resource reservations within the remaining set of the resource reservations.

33. The device according to claim 23, wherein, The transceiver is further configured to: communicate with another UE during one or more resource reservations within the remaining set of the resource reservations.

34. An apparatus for wireless communication, comprising: a transceiver configured to: receive control information from a user equipment (UE) indicating a resource reservation for sidelink communication with the UE; and communicate with the UE during at least one of the resource reservations; a memory; and a processor coupled to the memory, the processor and the memory being configured to: determine that the remaining set of the resource reservations can be reclaimed by one or more UEs by determining that if the number of the resource reservations in the control information is equal to or greater than a threshold value, then the remaining set of the resource reservations can be reclaimed; and take one or more actions based on the determination that the remaining set of the resource reservations can be reclaimed by the one or more UEs.

35. The apparatus according to claim 34, wherein the transceiver is further configured to: receive additional control information from the UE, the additional control information indicating that one or more resource reservations within the remaining set of the resource reservations are released from being reserved for communication with the UE.

36. The device according to claim 35, wherein, The additional control information includes a field indicating that the one or more resource reservations within the remaining set of the resource reservations are released.

37. The apparatus according to claim 35, wherein: The transceiver is further configured to: receive the additional control information within a time-domain resource associated with a resource reservation that follows the at least one resource reservation and is within the remaining set of the resource reservation; and The additional control information indicates that a single resource reservation is reserved for communication with the UE.

38. The apparatus according to claim 35, wherein: The additional control information indicates the number of valid resource reservations in the additional control information; and One or more of the resource reservations within the remaining set of the resource reservation include invalid resource reservations in the additional control information.

39. The apparatus according to claim 34, wherein: The control information indicates the number of valid resource reservations in the control information; and The valid resource reservations include the determined resource reservations.

40. The apparatus according to claim 39, wherein: The control information includes a plurality of reservation fields; Each of the reservation fields is associated with a resource reservation; and At least one of the reservation fields has a value indicating that the resource reservation associated with the reservation field is invalid.

41. The apparatus according to claim 39, wherein: The control information includes a sequence of reservation fields; Each of the reservation fields is associated with a resource reservation; The control information includes a field indicating that a segment of the reservation fields in the sequence is associated with the valid resource reservation; The field is a number indicating the length of the segment of the reservation fields in the sequence; and The segment of the reservation fields includes a first resource reservation in the sequence.

42. The apparatus according to claim 39, wherein: The control information includes a bitmap having a plurality of bits; Each of the bits in the bitmap corresponds to a resource reservation in the control information; and At least one of the bits indicates that the resource reservation associated with the bit is not valid.

43. The apparatus according to claim 34, wherein, The transceiver is further configured to: Avoid communicating with the UE during one or more of the resource reservations within the remaining set of the resource reservation.

44. The apparatus according to claim 34, wherein, The transceiver is further configured to: Communicate with another UE during one or more of the resource reservations within the remaining set of the resource reservation.

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