Recycling resources based on side-chain feedback

Abstract

Methods, systems, and devices for wireless communication are described. The techniques described relate to classifying resources in a system such that a user equipment (UE) can determine whether a resource can be reclaimed. At least two classes can be defined for resources, and the UE can use various criteria for classifying resources in the system. For example, the UE can include a first set of resources in an "available" class and a second set of resources in an "occupied" class. Resources in the "occupied" class can be indicated as occupied by sidelink channel information of another UE. In the case where resources are indicated as being reserved for retransmission by another UE but no feedback is detected, the UE can use additional parameters to determine whether these resources can be reclaimed for its own transmission and can classify the resources accordingly.

Description

[0001] Cross-reference

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 932,874, filed Nov. 8, 2019, by Baghel et al., entitled "RECLAIMING RESOURCES BASED ON SIDELINK FEEDBACK"; and U.S. Patent Application No. 17 / 090,449, filed Nov. 5, 2020, by Baghel et al., entitled "RECLAIMING RESOURCES BASED ON SIDELINK FEEDBACK"; each of which is assigned to the assignee of the present application. Technical Field

[0003] The following generally relates to wireless communication and, more specifically, to reclaiming resources based on sidelink feedback. Background Art

[0004] Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcasting, etc. These systems are capable of supporting communication with multiple users by sharing the available system resources, such as time, frequency, and power. Examples of such multi-access systems include fourth-generation (4G) systems such as Long-Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth-generation (5G) systems that may be referred to as New Radio (NR) systems. These systems may employ techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or Discrete Fourier Transform Spread OFDM (DFT-S-OFDM). A wireless multi-access communication system may include one or more base stations or one or more network access nodes, each of which simultaneously supports communication for multiple communication devices, where the communication devices may also be referred to as user equipment (UE).

[0005] Some wireless systems may support sidelink communication (e.g., vehicle-to-vehicle (V2V), vehicle-to-everything (V2X) systems, etc.), where UEs may communicate with other UEs on allocated sidelink resources. However, in order to ensure efficient radio frequency spectrum usage within the system, techniques for reclaiming unused resources may be needed. Summary of the Invention

[0006] The described techniques relate to improved methods, systems, devices, and apparatuses for supporting resource recycling based on sidelink feedback. Generally, the described techniques provide for classifying resources in a system such that a user equipment (UE) can determine whether a resource can be recycled for the UE's own transmission. These resources may be sidelink resources used by devices in a vehicle-to-everything (V2X) system. At least two classes can be defined for these resources, and the UE can use various criteria to classify these resources. For example, the UE can define an "available" class for a first set of available resources that have not been previously indicated as occupied (e.g., based on previously received sidelink channel information (SCI) from another UE). Resources in the "available" class can have a reference signal received power (RSRP) that meets a predefined threshold or can meet other criteria. The UE can also define an "occupied" class for a second set of resources, where the second set of resources can be indicated as occupied by the SCI of another UE. The "occupied" class can include resources that are designated as retransmission resources allocated for another UE (e.g., resources designated for retransmission for another UE). Additionally, the UE can determine that a negative acknowledgment (NACK) feedback has been detected for a corresponding transmission of a packet associated with the SCI of another UE. The NACK can indicate that the resource is not available for allocation (and is being used by the other UE for retransmission), and thus the retransmission resources can be included in the "occupied" class.

[0007] If a set of resources is indicated by the SCI of another UE as reserved for retransmission but no NACK feedback is detected, the UE can use additional parameters to determine whether these resources can be recycled for the UE's own transmission, and the UE can classify these resources accordingly (e.g., available or occupied). For example, if no NACK feedback is detected, the UE can determine whether the priority of the packet of the other UE is equal to or less than the priority of the UE's own packet. If so, the UE can consider these resources as "available", and these resources can be used to transmit the UE's packet. However, if the priority of the packet of the other UE is higher than the priority of the UE's own packet, these resources can be considered as "occupied", and the UE can allocate other resources for transmitting its packet. The use of packet priority can mitigate the problem in this case when the UE does not detect feedback information for the packet of the other UE (or when no feedback is sent from an additional UE communicating with the other UE). Additionally, in the case where the UE detects an acknowledgment (ACK), the resources allocated for retransmission by the other UE can be available (e.g., because the initial packet may not undergo retransmission), and the UE can classify such resources as "available".

[0008] Describes a method for wireless communication in a first UE. The method may include: receiving, by the first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE; monitoring for sidelink feedback information in response to an initial transmission of the first packet by the second UE; identifying a category of the one or more resources based on whether the sidelink feedback information is detected during the monitoring; and allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0009] Describes an apparatus for wireless communication in a first UE. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to perform the following operations: receiving, by the first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE; monitoring for sidelink feedback information in response to an initial transmission of the first packet by the second UE; identifying a category of the one or more resources based on whether the sidelink feedback information is detected during the monitoring; and allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0010] Describes another apparatus for wireless communication in a first UE. The apparatus may include units for: receiving, by the first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE; monitoring for sidelink feedback information in response to an initial transmission of the first packet by the second UE; identifying a category of the one or more resources based on whether the sidelink feedback information is detected during the monitoring; and allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0011] Describes a non - transitory computer - readable medium storing code for wireless communication at a first UE. The code may include instructions executable by a processor to perform the following operations: receive, at the first UE, a SCI that indicates one or more resources reserved for a re - transmission of a first packet by a second UE; monitor for side - chain feedback information in response to an initial transmission of the first packet by the second UE; identify a category of the one or more resources based on whether the side - chain feedback information is detected during the monitoring; and allocate, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0012] Some examples of the methods, apparatuses, and non - transitory computer - readable media described herein may further include operations, features, units, or instructions for determining an absence of the side - chain feedback information based on the monitoring, wherein identifying the category may be based on the absence of the side - chain feedback information.

[0013] Some examples of the methods, apparatuses, and non - transitory computer - readable media described herein may further include operations, features, units, or instructions for identifying a first priority of the first packet and identifying a second priority of the second packet, wherein the category of the one or more resources may be identified based on a comparison of the first priority and the second priority.

[0014] Some examples of the methods, apparatuses, and non - transitory computer - readable media described herein may further include operations, features, units, or instructions for identifying that the first priority may be equal to the second priority based on the comparison, and based on the first priority being equal to the second priority, and allocating the set of resources to include the one or more resources and using the one or more resources to transmit the second packet.

[0015] Some examples of the methods, apparatuses, and non - transitory computer - readable media described herein may further include operations, features, units, or instructions for identifying that the first priority may be less than the second priority based on the comparison, and based on the first priority being less than the second priority, and allocating the set of resources to include the one or more resources and using the one or more resources to transmit the second packet.

[0016] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, units, or instructions for determining that a first priority may be higher than a second priority, and for using the set of resources to transmit the second packet, wherein, based on the first priority being higher than the second priority, the set of resources may be allocated to exclude the one or more resources.

[0017] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the side-chain feedback information includes a negative acknowledgment.

[0018] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, units, or instructions for detecting the side-chain feedback information based on the monitoring, wherein identifying the category may be based on the detected side-chain feedback information.

[0019] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, units, or instructions for using the set of resources to transmit the second packet, wherein, based on the detected side-chain feedback information, the set of resources may be allocated to exclude the one or more resources.

[0020] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the side-chain feedback information includes a negative acknowledgment.

[0021] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, units, or instructions for using the one or more resources to transmit the second packet based on the detected side-chain feedback information, and for allocating the set of resources to include the one or more resources.

[0022] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the side-chain feedback information includes a positive acknowledgment.

[0023] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, units, or instructions for detecting that a reference signal received power (RSRP) associated with the one or more resources may be lower than a configured threshold, and for using the one or more resources to transmit the second packet based on the detected reference signal received power and for allocating the set of resources to include the one or more resources.

[0024] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the monitoring to obtain the sidelink feedback information may include operations, features, elements, or instructions for monitoring a physical sidelink feedback channel to obtain the sidelink feedback information sent to the second UE.

[0025] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the category of the one or more resources includes an available category or an occupied category.

[0026] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the first UE and the second UE operate in a vehicle-to-everything system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 and 2 shows an example of a wireless communication system in accordance with aspects of the present disclosure.

[0028] Figure 3 shows an example of sidelink resource configuration in accordance with aspects of the present disclosure.

[0029] Figure 4 shows an example of a processing flow in a system in accordance with aspects of the present disclosure.

[0030] Figure 5 and 6 shows a block diagram of a device in accordance with aspects of the present disclosure.

[0031] Figure 7 shows a block diagram of a communication manager in accordance with aspects of the present disclosure.

[0032] Figure 8 shows a diagram of a system including a device in accordance with aspects of the present disclosure.

[0033] Figures 9 to 13 shows a flowchart illustrating a method in accordance with aspects of the present disclosure. DETAILED DESCRIPTION

[0034] A user equipment (UE) may communicate directly with other UEs via sidelink communication. For example, the UE may communicate with a second UE via a sidelink in a vehicle-to-everything (V2X) system. In some cases, the UE may implement a feedback process (e.g., a hybrid automatic repeat request (HARQ) process) to improve the reliability of communication between the UE and another sidelink device. For example, when a device sends data to the UE, the UE may send information about the reception status of the data to the sending device, such as an indication of whether the data was successfully decoded. This type of information may be referred to as feedback or HARQ feedback. In some cases, the UE may reserve future sidelink resources for retransmissions in case of an unsuccessful reception or decoding of a transmission (e.g., by another device or UE). In the case of sidelink communication, a physical sidelink feedback channel (PSFCH) may be used to send feedback for transmissions on the sidelink.

[0035] According to the techniques described herein, the UE may attempt to reclaim unused sidelink resources that were previously indicated to be reserved for possible retransmissions by other UEs. In some cases, the UE may classify sidelink resources to determine whether these resources may be used for resource selection. For example, a resource may be unused or available if there is no sidelink channel information (SCI) indicating that the resource will be occupied, or if the UE measures a reference signal received power (RSRP) below a configured threshold. When the SCI indicates a reservation and a negative acknowledgment (NACK) is detected for the corresponding initial transmission, the UE may classify the resource as occupied for retransmission.

[0036] In addition, when no feedback is detected for a previously reserved resource indicated by the SCI, the UE may configure parameters to determine the classification of the sidelink resource. In some examples, the UE may receive the SCI and determine, based on the SCI, that a set of resources is reserved for retransmission of an initial transmission by another UE. The UE may then monitor for, but not detect, a NACK on the PSFCH. Based on the non-detection of a NACK for the resource, the UE may compare the priority of the initial packet of the other UE (to be retransmitted) with the packet that the UE wants to send on the reclaimed resource. If the packet of the reclaiming UE has a priority that is equal to or higher than the priority of the packet used by the other UE for retransmission, the resource may be reclaimed for transmission. Otherwise, when the packet of the reclaiming UE has a priority lower than the priority of the packet used by the other UE for retransmission, the resource may not be reclaimed. Accordingly, the UE may improve resource utilization in sidelink communication by appropriately reclaiming resources that would otherwise be wasted system resources for additional transmissions.

[0037] Aspects of the present disclosure are initially described in the context of a wireless communication system. Aspects of the present disclosure are further illustrated and described with reference to apparatus diagrams, system diagrams, and flowcharts related to reclaiming resources based on sidelink feedback.

[0038] Figure 1 An example of a wireless communication system 100 in accordance with aspects of the present disclosure is shown. The wireless communication system 100 includes one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 can be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, the wireless communication system 100 can support enhanced broadband communication, ultra-reliable (e.g., mission-critical) communication, low latency communication, communication with low-cost and low-complexity devices, or combinations thereof. The wireless communication system 100 can support reclaiming resources based on sidelink feedback to enhance resource utilization and efficiency in the system.

[0039] The base stations 105 can be dispersed throughout a geographic area to form the wireless communication system 100, and can be devices of different forms or with different capabilities. The base stations 105 and the UEs 115 can communicate wirelessly via one or more communication links 125. Each base station 105 can provide a coverage area 110, and the UEs 115 and the base stations 105 can establish one or more communication links 125 over the coverage area 110. The coverage area 110 can be an example of a geographic area over which the base stations 105 and the UEs 115 support communication of signals according to one or more radio access technologies.

[0040] The UEs 115 can be dispersed in the coverage area 110 of the wireless communication system 100, and each UE 115 can be stationary, mobile, or both at different times. The UEs 115 can be devices of different forms or with different capabilities. Figure 1 Some example UEs 115 are shown. As Figure 1 shown, the UEs 115 described herein can communicate with various types of devices, such as other UEs 115, base stations 105, or network devices (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network devices).

[0041] Base station 105 can communicate with the core network 130, communicate with each other, or perform both types of communication. For example, base station 105 can interface with the core network 130 via one or more backhaul links 120 (e.g., via S1, N2, N3, or other interfaces). Base station 105 can communicate directly with each other (e.g., directly between base stations 105), indirectly (e.g., via the core network 130), or both, via backhaul link 120 (e.g., via X2, Xn, or other interfaces). In some examples, backhaul link 120 can be or include one or more wireless links.

[0042] One or more of the base stations 105 described herein can include or can be referred to by those skilled in the art as a base station transceiver, radio base station, access point, radio transceiver, Node B, evolved Node B (eNB), next-generation Node B, or giga Node B (any of which can be referred to as a gNB), home Node B, home eNB, or other suitable terms.

[0043] UE 115 can include or can be referred to as a mobile device, wireless device, remote device, handheld device, or user equipment, or some other suitable term, where "device" can also be referred to as a unit, station, terminal, or client, etc. UE 115 can also include or can be referred to as a personal electronic device, such as a cellular phone, personal digital assistant (PDA), tablet computer, laptop computer, or personal computer. In some examples, UE 115 can also include or be referred to as a wireless local loop (WLL) station, Internet of Things (IoT) device, Internet of Everything (IoE) device, or machine type communication (MTC) device, etc., which can be implemented in various objects such as devices, or vehicles, meters, etc.

[0044] UE 115 described herein can communicate with various types of devices, such as Figure 1 as shown, various types of devices such as other UEs 115 that can sometimes act as repeaters, as well as base stations 105 and network devices including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations.

[0045] UE 115 and base station 105 can communicate wirelessly with each other via one or more carriers over one or more communication links 125. The term "carrier" may refer to a set of radio spectrum resources having a defined physical layer structure for supporting communication link 125. For example, a carrier for communication link 125 may include a portion of a radio spectrum band (e.g., a bandwidth part (BWP)) that operates according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling for coordinating operation for the carrier, user data, or other signaling. The wireless communication system 100 may support communication with UE 115 using carrier aggregation or multi-carrier operation. According to a carrier aggregation configuration, UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation may be used with frequency division duplex (FDD) and time division duplex (TDD) component carriers.

[0046] The signal waveform transmitted on a carrier may be composed of multiple subcarriers (e.g., using a multi-carrier modulation (MCM) technique such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing an MCM technique, a resource element may consist of a symbol period (e.g., the duration of a modulation symbol) and a subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements received by UE 115 and the higher the order of the modulation scheme, the higher the data rate of UE 115 may be. Wireless communication resources may refer to a combination of radio spectrum resources, time resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communication with UE 115.

[0047] One or more numerology schemes may be supported for a carrier, where the numerology scheme may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerology schemes. In some examples, UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time, and the communication of UE 115 may be limited to one or more active BWPs.

[0048] The time interval of base station 105 or UE 115 may be expressed as a multiple of a basic time unit, which may refer to T s =1 / (Δf max ·Nf ) sampling period in seconds, where Δf max can represent the maximum supported subcarrier spacing, N f can represent the maximum supported Discrete Fourier Transform (DFT) size. The time interval of the communication resources can be organized according to each radio frame having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame can be identified by a System Frame Number (SFN) (e.g., ranging from 0 to 1023).

[0049] Each frame can include a plurality of consecutively numbered subframes or time slots, and each subframe or time slot can have the same duration. In some examples, a frame (e.g., in the time domain) can be divided into subframes, and each subframe can be further divided into a plurality of time slots. Alternatively, each frame can include a variable number of time slots, and the number of time slots can depend on the subcarrier spacing. Each time slot can include a plurality of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communication systems 100, a time slot can be further divided into a plurality of mini - slots containing one or more symbols. Except for the cyclic prefix, each symbol period can contain one or more (e.g., N f ones) sampling periods. The duration of the symbol period can depend on the subcarrier spacing or the operating frequency band.

[0050] A subframe, time slot, mini - slot, or symbol can be the smallest scheduling unit of the wireless communication system 100 (e.g., in the time domain), and can be referred to as a Transmission Time Interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in the TTI) can be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communication system 100 can be dynamically selected (e.g., in units of short - time TTI (sTTI) bursts).

[0051] Physical channels can be multiplexed on a carrier according to various techniques. The physical control channel and the physical data channel can be multiplexed on a downlink carrier using, for example, one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region for the physical control channel (e.g., a control resource set (CORESET)) can be defined by a plurality of symbol periods and can span the system bandwidth of the carrier or a subset of the system bandwidth. One or more control regions (e.g., CORESETs) can be configured for a group of UEs 115. For example, one or more of the UEs 115 can monitor or search a control region for control information according to one or more search space sets, and each search space set can include one or more control channel candidates arranged in a cascaded manner with one or more aggregation levels. The aggregation level of a control channel candidate can refer to the number of control channel resources (e.g., control channel elements (CCEs)) associated with the coded information for a control information format having a given payload size. The search space set can include a common search space set configured to send control information to a plurality of UEs 115 and a UE-specific search space set for sending control information to a specific UE 115.

[0052] Each base station 105 can provide communication coverage via one or more cells (e.g., macro cells, small cells, hotspots, or other types of cells or various combinations of the foregoing). The term "cell" can refer to a logical communication entity used for communication with a base station 105 (e.g., via a carrier) and can be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), etc.) for distinguishing adjacent cells. In some examples, a cell can also refer to a geographic coverage area 110 or a portion of the geographic coverage area 110 (e.g., a sector) on which the logical communication entity operates. Such a cell can range from a smaller area (e.g., a structure, a subset of a structure) to a larger area depending on various factors such as the capabilities of the base station 105. For example, a cell can be or include a building, a subset of a building, or an external space between or overlapping with the geographic coverage area 110, etc.

[0053] Macro cells typically cover a relatively large geographical area (e.g., with a radius of several kilometers) and can allow UEs 115 with a service subscription to the network provider supporting the macro cell to have unrestricted access. Compared with macro cells, small cells can be associated with a lower-power base station 105, and small cells can operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands compared with macro cells. Small cells can provide unrestricted access to UEs 115 with a service subscription to the network provider, or can provide restricted access to UEs associated with the small cell (e.g., UEs 115 in a closed subscriber group (CSG), UEs 115 of a home user, etc.). The base station 105 can support one or more cells and can also support communication using one or more component carriers.

[0054] In some examples, a carrier can support multiple cells and can be configured with different cell types according to different protocol types that can provide access for different types of devices (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)).

[0055] In some examples, the base station 105 can be movable, thus providing communication coverage for a mobile geographical coverage area 110. In some examples, different geographical coverage areas 110 associated with different technologies can overlap, but different geographical coverage areas 110 can be supported by the same base station 105. In other examples, overlapping geographical coverage areas 110 associated with different technologies can be supported by different base stations 105. The wireless communication system 100 can include, for example, a heterogeneous network, where different types of base stations 105 use the same or different radio access technologies to provide coverage for various geographical coverage areas 110.

[0056] The wireless communication system 100 can support synchronous or asynchronous operation. For synchronous operation, the base stations 105 can have similar frame timings, and transmissions from different base stations 105 can be approximately aligned in time. For asynchronous operation, the base stations 105 can have different frame timings, and transmissions from different base stations can be misaligned in time. The techniques described herein can be used for synchronous or asynchronous operation.

[0057] Some UEs 115, such as MTC devices or IoT devices, can be low-cost or low-complexity devices and can provide automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC can refer to data communication technologies that allow devices to communicate with each other or with a base station 105 without human intervention. In some examples, M2M communication or MTC can include communication from devices integrated with sensors or meters that are used to measure or capture information and relay that information to a central server or application, which can utilize the information or present the information to a person interacting with the application. Some UEs 115 can be designed to collect information or implement automated behavior of machines or other devices. Example applications of MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, medical monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based commercial billing.

[0058] Some UEs 115 can be configured to employ operating modes for reducing power consumption, such as half-duplex communication (e.g., a mode that supports one-way communication via transmission or reception but does not support transmission and reception simultaneously). In some examples, half-duplex communication can be performed at a reduced peak rate. Other power saving techniques for UEs 115 include entering a power saving "deep sleep" mode when not participating in active communication, operating on a limited bandwidth (e.g., according to narrowband communication), or a combination of these techniques. For example, some UEs 115 can be configured for operation using a narrowband protocol type associated with a defined portion or range within a carrier, within a guard band of the carrier, or outside the carrier (e.g., a set of subcarriers or resource blocks (RBs)).

[0059] The wireless communication system 100 can be configured to support ultra-reliable communication or low-latency communication, or various combinations thereof. For example, the wireless communication system 100 can be configured to support ultra-reliable low-latency communication (URLLC) or mission-critical communication. UEs 115 can be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission-critical functions). Ultra-reliable communication can include private communication or group communication and can be supported by one or more mission-critical services such as mission-critical push-to-talk (MCPTT), mission-critical video (MCVideo), or mission-critical data (MCData). Support for mission-critical functions can include prioritization of services, and mission-critical services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission-critical, and ultra-reliable low-latency can be used interchangeably herein.

[0060] In some examples, UE 115 is also capable of directly communicating with other UEs 115 via a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) protocol or a D2D protocol). Using D2D communication, one or more UEs 115 may be within the geographic coverage area 110 of the base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of the base station 105 or may not be able to receive transmissions from the base station 105. In some examples, a group of UEs 115 communicating via D2D communication may utilize a one-to-many (1:M) system, where each UE 115 transmits to each other UE 115 in the group. In some examples, the base station 105 assists in scheduling resources for D2D communication. In other cases, D2D communication is performed between UEs 115 without involving the base station 105.

[0061] In some systems, the D2D communication link 135 may be an example of a communication channel, such as a sidelink communication channel between vehicles (e.g., UE 115). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination of these communications. Vehicles may send information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information related to the V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure (such as a roadside unit) or communicate with the network using vehicle-to-network (V2N) communication via one or more network nodes (e.g., base station 105), or both.

[0062] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or a 5G core (5GC), which may include: at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)); and at least one user plane entity that routes packets or interconnects to an external network (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions for UEs 115 served by the base station 105 associated with the core network 130, such as mobility, authentication, and bearer management. User IP packets may be transmitted through the user plane entity, which may provide IP address allocation and other functions. The user plane entity may be connected to the network operator IP service 150. The operator IP service 150 may include access to the Internet, an intranet, an IP multimedia subsystem (IMS), or packet-switched (PS) streaming services.

[0063] At least some network devices, such as base station 105, may include subcomponents such as access network entity 140, which may be an example of an access node controller (ANC). Each access network entity 140 may communicate with UE 115 via a number of other access network transmission entities 145, which may be referred to as radio heads, intelligent radio heads, or transmit / receive points. Each access network transmission entity 145 may include one or more antenna panels. In some configurations, the various functions of each access network entity or base station 105 may be distributed among various network devices (e.g., radio heads and ANCs) or combined into a single network device (e.g., base station 105).

[0064] Wireless communication system 100 may operate using one or more frequency bands, e.g., in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or the decimeter band because the wavelength range is from approximately one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features, however, the waves may penetrate structures sufficiently for a macro cell to serve a UE 115 located indoors. Compared to transmissions using lower frequencies and longer waves in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz, UHF wave transmissions may be associated with smaller antennas and shorter distances (e.g., less than 100 km).

[0065] Wireless communication system 100 may also operate in the super-high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz (also known as the centimeter band), or in the extremely high frequency (EHF) region (also known as the millimeter wave band) of the spectrum (e.g., from 30 GHz to 300 GHz). In some examples, wireless communication system 100 may support millimeter wave (mmW) communication between UE 115 and base station 105, and the EHF antennas of the corresponding devices may be even smaller and more closely spaced than UHF antennas. In some examples, this may facilitate the use of antenna arrays within the device. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter distances than SHF or UHF transmissions. The techniques disclosed herein may be used across transmissions using one or more different frequency regions, and the designation of frequency bands across these frequency regions may vary by country or regulatory authority.

[0066] Wireless communication system 100 may utilize both licensed radio spectrum bands and unlicensed radio spectrum bands. For example, wireless communication system 100 may employ Licensed-Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band (e.g., 5 GHz Industrial, Scientific, and Medical (ISM) band). When operating in an unlicensed radio spectrum band, devices such as base station 105 and UE 115 may employ carrier sensing for collision detection and avoidance. In some examples, operation in an unlicensed band may be based on a carrier aggregation configuration in combination with a component carrier operating in a licensed band (e.g., LAA). Operations in the unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, etc.

[0067] Base station 105 or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of base station 105 or UE 115 may be located within one or more antenna arrays or antenna panels, where the antenna array or antenna panel may support MIMO operation, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly such as an antenna tower. In some examples, the antennas or antenna arrays associated with base station 105 may be located at different geographical locations. Base station 105 may have an antenna array that has a number of rows and columns of antenna ports that base station 105 may use to support beamforming for communication with UE 115. Similarly, UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for signals transmitted via an antenna port.

[0068] Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., base station 105, UE 115) to shape or manipulate an antenna beam (e.g., transmit beam, receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining signals transmitted via the antenna elements of an antenna array such that some signals propagating in a particular orientation relative to the antenna array experience constructive interference while other signals experience destructive interference. The adjustment of the signals transmitted via the antenna elements may include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to the signals carried via the antenna elements associated with the device. The adjustment associated with each antenna element may be defined by a set of beamforming weights associated with an orientation (e.g., relative to the antenna array of the transmitting device or receiving device or relative to some other orientation).

[0069] The wireless communication system 100 can be a packet-based network operating according to a hierarchical protocol stack. In the user plane, the communication at the bearer or Packet Data Convergence Protocol (PDCP) layer can be IP-based. The Radio Link Control (RLC) layer can perform packet segmentation and reassembly for communication over logical channels. The Medium Access Control (MAC) layer can perform prioritization and multiplexing of logical channels to transport channels. The MAC layer can also use error detection techniques, error correction techniques, or both to support retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer can provide support between the UE 115 and the base station 105 or the core network 130 for the establishment, configuration, and maintenance of the RRC connection for the radio bearers of the user plane data. At the physical layer, the transport channels can be mapped to physical channels.

[0070] The UE 115 and the base station 105 can support retransmission of data to increase the likelihood of successful data reception. HARQ feedback is a technique for increasing the likelihood of correctly receiving data over the communication link 125. HARQ can include a combination of error detection (e.g., using Cyclic Redundancy Check (CRC)), Forward Error Correction (FEC), and retransmission (e.g., Automatic Repeat Request (ARQ)). HARQ can improve throughput at the MAC layer under poor radio conditions (e.g., low signal-to-noise ratio conditions). In some examples, the device can support simultaneous-slot HARQ feedback, where the device can provide HARQ feedback for data received in the previous symbols in a particular slot in that slot. In other cases, the device can provide HARQ feedback in a subsequent slot or according to some other time interval. During sidelink operation, the HARQ feedback can be sent via the PSFCH.

[0071] The wireless communication system 100 can be a distributed system, where the UE 115 monitors and receives packets from one or more other UEs 115. For example, when two UEs 115 communicate with each other, a third UE 115 can monitor the transmission between the two UEs 115. Additionally, such a system can support the use of feedback information (e.g., ACK / NACK) sent via the PSFCH to indicate whether a packet has been successfully received and decoded. Thus, the transmitting UE 115 can reserve (e.g., using the SCI) one or more additional resources for retransmission in case the initially transmitted packet is not received or not correctly decoded.

[0072] However, the resources reserved for retransmission may not be utilized, especially when the initial transmission of the packet is successfully received and decoded at the receiving UE 115. In this case, it may be difficult for other UEs 115 to efficiently reclaim these unused resources. Specifically, a UE 115 that monitors the transmission of the PSFCH including feedback information may not detect the PSFCH, or the PSFCH may not be transmitted. Therefore, the absence of feedback may not clearly indicate whether the resources previously reserved for retransmission are available. Thus, a technique to further assist the UE 115 in determining whether the retransmission resources can be reclaimed may be desirable.

[0073] The UE 115 can determine whether resources can be reclaimed for transmissions made by the UE 115, classify the resources, and optionally evaluate the priority of the transmission relative to the priority of retransmission scheduled for the resources. In some examples, the resources are sidelink resources used by the UE 115 in a V2X system, for example, on the communication link 135. At least two categories can be defined for the resources, and the UE 115 can use various conditions to classify the resources. For example, the UE 115 can define an "available" category for a first set of resources that have not been previously indicated as occupied (e.g., according to an SCI received previously from another UE 115). The resources in this set can also have an RSRP below a predefined threshold, or can meet other criteria. The UE 115 can define an "occupied" category for a second set of resources, where the second set of resources can be indicated as occupied by an SCI of another UE 115, and the "occupied" category can include, for example, resources designated as retransmission resources allocated by another UE 115.

[0074] Additionally or alternatively, the UE 115 can determine that feedback (e.g., ACK or NACK) is detected for a corresponding transmission of a packet associated with an SCI of another UE 115. For example, if the UE 115 detects a NACK, the feedback can indicate that the resources cannot be reclaimed by the UE 115 (and can be used by another UE 115 for retransmission) and are thus included in the "occupied" category.

[0075] If a set of resources is indicated by the SCI of another UE 115 to be reserved for retransmission, but the UE 115 attempting to reclaim the resources does not detect a NACK feedback, then the reclaiming UE 115 can use additional parameters to determine whether the resources can be reclaimed for its own transmission and can classify the resources accordingly (e.g., as available or occupied). For example, if no NACK feedback is detected, the reclaiming UE 115 can determine whether the priority of the retransmission of another UE 115 is equal to or less than the priority of the transmission or retransmission of the UE 115 itself. If so, the UE 115 can consider the resources as "available", and the resources can be used to transmit packets of the UE 115. However, if the priority of the retransmission of another UE 115 is higher than the priority of the transmission or retransmission of the UE 115 itself, the resources can be considered "occupied", and the UE 115 can allocate other resources for transmitting its packets. In cases where the UE 115 is unable to detect feedback information on the PSFCH for the packets of another UE 115 (or if no feedback has been sent from the receiving UE 115), the use of packet priorities can help mitigate the problems in such cases. Additionally, in cases where the UE 115 detects an ACK, the resources allocated by another UE 115 for retransmission can be available (e.g., because the initial packet may not undergo retransmission), and the UE 115 can classify such resources as "available".

[0076] Figure 2 FIG. shows an example of a wireless communication system 200 in accordance with aspects of the present disclosure. In some examples, the wireless communication system 200 may implement aspects of the wireless communication system 100. The wireless communication system 200 may be a New Radio V2X system and may include UEs 115-a, 115-b, and 115-c, which may be examples of the UE 115 as referenced Figure 1 as described. The UEs 115-a, 115-b, and 115-c are capable of reclaiming sidelink resources based on whether feedback for the sidelink resources on the Physical Sidelink Feedback Channel (PSFCH) 210 is detected for the Physical Sidelink Shared Channel (PSSCH) 205.

[0077] Similar to the Uu communication (from base station 105 to UE 115), the sidelink communication may involve a HARQ feedback process for reliability purposes. For example, UE 115-a may receive HARQ feedback for a sidelink transmission that is conveyed to UE 115-b in PSSCH 205-a. The sidelink transmission may be a unicast transmission to a single UE 115 (e.g., UE 115-b), or a multicast or broadcast transmission to multiple receiving UEs 115. In some cases, the physical sidelink control channel (PSCCH) may be used to indicate the PSSCH resources that are used to carry the sidelink transmission. The HARQ feedback for PSSCH 205-a may be conveyed in PSFCH 210.

[0078] The UEs 115 in the wireless communication system 200 may be distributed throughout the system and communicate via the sidelink such that each UE 115 may attempt to monitor and receive packets from many other UEs 115 via the sidelink. For example, when UE 115-b successfully receives a packet from UE 115-a via PSSCH 205-a, UE 115-b may send an ACK to UE 115-a on PSFCH 210. Additionally, when UE 115-b incorrectly receives a packet or is unable to decode a packet received from UE 115-a via PSSCH 205-a, UE 115-b may send a NACK to UE 115-a on PSFCH 210.

[0079] In a New Radio V2X system, a transmitting UE 115 (e.g., UE 115-a) may reserve extra resources (about 2 to 4 extra resources) for its possible retransmissions, and the extra resources are indicated to one or more sidelink UEs 115 via an SCI. This reservation mechanism can improve system performance; however, it may also cause resource overbooking problems, where, in some cases, such as when the reserved resources are not used for retransmissions and not released for other UEs 115, the resource overbooking problems may lead to performance degradation. For example, in an example where UE 115-b may not successfully receive PSSCH 205-a, UE 115-a may reserve resources (e.g., time / frequency resources) on PSSCH 205-b for retransmitting packets on PSSCH 205-a. When UE 115-a receives a NACK on PSFCH 210, the resources on PSSCH 205-b can be used for retransmission. In some cases, assuming the original reserving UE 115-a does not use the reserved resource PSSCH 205-b (e.g., in the case of sidelink mode 2), UE 115-c can benefit from using the reserved resource PSSCH 205-b for its PSSCH 205-c transmission. For example, in mode 2, UE 115 can determine the sidelink resources (e.g., from a pool or resources) to be used independently of the scheduling from the base station 105. For example, UE 115-c can be configured with sidelink resources configured (e.g., pre-configured) by the base station 105 or the network so that UE 115-c can autonomously select a set of configured resources for transmission.

[0080] UE 115-c can continuously monitor PSFCH 210 to obtain feedback related to all detected reservations (e.g., by one or more UEs 115-a or 115-b) to determine whether the resources can be reclaimed by UE 115-c (e.g., whether PSFCH 210 indicates an ACK). However, UE 115-c may be limited in its ability to monitor several PSFCH 210s based on its capabilities and may not receive some PSFCH 210s. Additionally or alternatively, the UE 115-b transmitting PSFCH 210 is capable of transmitting several PSFCH 210s simultaneously to meet the maximum power reduction (MPR) or additional MPR (AMPR) configuration. These limitations may pose problems for UE 115-a to efficiently reclaim the reserved PSSCH 205-b, and UE 115-c may make additional considerations.

[0081] For example, the UE 115-c may divide the sidelink resources into different categories (e.g., at least two categories), such as available or occupied. The available resources for resource selection categories may include resources that are unused or available for the UE 115-c, e.g., because no SCI indicating the resources as occupied, or because the UE 115-c can measure the RSRP of the resources to be below the configured threshold. The occupied resources for resource selection categories may include resources indicated by the SCI as occupied by another UE 115-a, and the UE 115-a receives a NACK via the PSFCH 210, and the NACK indicates the intention for retransmission on the reserved resources.

[0082] When the UE 115-c may not be able to detect a NACK on the PSFCH 210 for the resources indicated by the SCI as occupied (e.g., PSSCH 205-b), special classification rules may be defined. In some cases, the UE 115-a may not detect the PSFCH 210 for the PSSCH 205-a from the UE 115-b, so the UE 115-a may perform retransmission of the packets in the PSSCH 205-a in the PSSCH 205-b. Therefore, the UE 115-c that may attempt to reclaim the resources reserved for the PSSCH 205-c may reclaim the following resources: for which the UE 115-c detects the absence of a NACK (in the PSFCH 210), and the priority of the packet originally reserving the PSSCH 205-b is equal to or lower than the priority of the UE 115-c's own packet for transmission on the PSSCH 205-c. These resources previously reserved by the UE 115-a for the PSSCH 205-5 may be regarded as available categories for the resource selection algorithm by the UE 115-c.

[0083] If the priority of the reserved resources for which the UE 115-c (which is planning to reclaim the reserved resources of the PSSCH 205-b) does not detect a NACK (in the PSFCH 210) is higher than the priority of the UE 115-c's own packet for transmission on the PSSCH 205-c, then the resources for the PSSCH 205-b are still used for the retransmission of the UE 115-a and may be regarded as occupied for the resource selection algorithm by the UE 115-c.

[0084] Figure 3An example of a sidelink resource configuration 300 in accordance with aspects of the present disclosure is shown. In some examples, the sidelink resource configuration 300 may implement aspects of the wireless communication system 100 and the wireless communication system 200. The sidelink resource configuration 300 may be used for the PSSCH and may include a number of time slots 305, each time slot 305 including sidelink resources in a subchannel 335.

[0085] As shown, sidelink resources in the subchannel 335 that are not scheduled by the SCI may be solid-colored (e.g., no shading or pattern), while reserved resources may be shaded. A system-wide gap in the resources of the PSSCH may allow feedback to be transmitted on the PSFCH 340. Additionally, corresponding shading may indicate information related to a common packet. For example, the subchannel 310-a may be used for an initial packet transmission, the HARQ resource 345-a may be used for HARQ feedback from the receiver of the initial packet transmission, and the subchannel 310-b may be reserved for a retransmission of the packet based on the HARQ feedback. Similarly, the subchannels 315-a to 330-a may be used for different initial packet transmissions, the HARQ resources 345-b to 345-e may be used for HARQ feedback from each receiver of the initial packet transmissions, respectively, and the subchannels 315-b to 330-b may be reserved for retransmissions of each packet based on the corresponding HARQ feedback for each packet.

[0086] In some examples, retransmission resources may not be reserved, as shown for the initial packet transmission in the subchannel 320-a and the available resources in the corresponding subchannel 335 in the time slot 305-c. In some cases, the HARQ resources 345 may be grouped by UE 115 numbering such that feedback for odd-numbered UEs 115 is grouped into resources in two adjacent subchannels, while feedback for even-numbered UEs 115 is grouped into resources in another two consecutive subchannels.

[0087] UE 115 attempting to reclaim resources in time slots 305-c and 305-d can monitor the PSFCH 340-b to obtain feedback on the HARQ resources 345. UE 115 may have received an SCI that reserves sub-channels 310-b, 315-b, 325-b, and 330-b. If UE 115 detects a NACK in the HARQ resource 345-a, UE 115 can determine that sub-channel 310-b can be used for retransmitting the packet in sub-channel 310-a, and UE 115 may not be reclaimed for its own use. In another case, if UE 115 detects an ACK in the HARQ resource 345-b, UE 115 can determine that sub-channel 315b may not be used for retransmitting the packet in sub-channel 315a, and UE 115 may be reclaimed for its own PSSCH transmission.

[0088] In the case where no NACK feedback is detected in the HARQ resources 345-d or 345-e, UE 115 can use additional parameters to determine whether the sub-channels 325-b and 330-b can be reclaimed for its own transmission respectively, and can classify the sub-channels 325-b and 330-b accordingly. For example, if no NACK feedback is detected in the HARQ resource 345-d, then UE 115 determines that the priority of the packet in sub-channel 325-a is equal to or less than the priority of the packet transmitted by UE 115, and UE 115 can consider the sub-channel 325-b resource as "available", and the resource can be used to transmit the packet of UE 115.

[0089] In another example, if no NACK feedback is detected in the HARQ resource 345-e, UE 115 determines that the priority of the packet in sub-channel 330-a is higher than the priority of its own packet used for transmission by UE 115. Therefore, sub-channel 330-b can be regarded as "occupied", and UE 115 can not reclaim these resources, and can allocate other resources for transmitting its packet. In the case where UE 115 does not detect feedback information in the PSFCH 340-b for a packet from another UE 115 (or in the case where no feedback is sent), the use of packet priority can help alleviate the problem in this case.

[0090] Figure 4An example of a processing flow 400 in a system according to aspects of the present disclosure is shown. In some examples, the processing flow 400 may implement aspects of the wireless communication system 100 and the wireless communication system 200. The processing flow 400 is shown to be implemented by UEs 115-d, 115-e, and 115-f, which may be part of a V2X system and may be examples of UEs as described with respect to Figure 1 and 2 . For example, UE 115-d may be an example of UE 115-c of Figure 2 , UE 115-e may be an example of UE 115-b of Figure 2 , and UE 115-f may be an example of UE 115-a of Figure 2 .

[0091] In the following description of the processing flow 400, the operations of UEs 115-d, 115-e, and 115-f may occur in an order different from the exemplary order shown. Some of the operations shown may also be excluded from the processing flow 400, or other operations may be added to the processing flow 400. It should be understood that although UEs 115-d, 115-e, and 115-f are shown performing multiple operations of the processing flow 400, any wireless device may perform the operations shown.

[0092] At 405, UE 115-f may send and UE 115-e may receive an SCI that indicates one or more resources reserved for a retransmission of a first packet by UE 115-f (e.g., a retransmission after an original data transmission such as at 410). In some examples, UE 115-d may also receive the SCI sent by UE 115-f.

[0093] At 410, UE 115-f may send and UE 115-e may attempt to receive and decode the first packet (e.g., a data transmission).

[0094] At 415, UE 115-e may selectively send and UE 115-f may receive feedback for the reception of the first packet at 410, such as an ACK or NACK.

[0095] At 420, UE 115-d may monitor one or more channels (e.g., PSFCH) to obtain sidelink feedback information sent from UE 115-e to UE 115-f, where the sidelink feedback information is in response to an initial transmission of a first packet at 410. In some cases, the monitoring may include: UE 115-d determines the absence of sidelink feedback information based on the monitoring, such as the absence of a NACK, where the classification of resources at 430 may be based on the absence of sidelink feedback information. Alternatively, UE 115-d may detect sidelink feedback information (e.g., ACK or NACK) during the monitoring, where the classification of resources at 430 may be based on the detected sidelink feedback information. In some cases, at 420, UE 115-d may monitor the RSRP and detect that the RSRP associated with the one or more resources is below a configured threshold.

[0096] At 425, UE 115-d may selectively identify the packet priorities of the first packet and a second packet to be sent by UE 115-d at 435.

[0097] At 430, UE 115-d may classify resources into several categories, which may include an available category, or an occupied category, or both. For example, UE 115-d may identify the category of one or more retransmission resources based on whether sidelink feedback information is detected during the monitoring at 420. Identifying the category of the one or more resources may be based on a comparison of the first priority and the second priority determined at 425. For example, if UE 115-d identifies that the first priority is equal to or less than the second priority at least in part based on the comparison, the one or more resources may be classified as available. Otherwise, if UE 115-d identifies that the first priority is greater than the second priority at least in part based on the comparison, the one or more resources may be classified as occupied.

[0098] At 435, UE 115-d may allocate a set of resources for sending the second packet at 440, where one or more retransmission resources may be included in the set of resources based on the identified category of the one or more resources.

[0099] At 440, UE 115-d may send and UE 115-f may receive a second packet. UE 115-d may send the second packet to additional or alternative UEs 115 not shown. In some cases, UE 115-d may use the one or more resources to send the second packet based on the first priority being equal to or less than the second priority and the group of resources being allocated to include the one or more resources. In other cases, UE 115-d may send the second packet excluding the one or more resources based on the first priority being higher than the second priority. In some examples, UE 115-d may use the group of resources to send the second packet, where the group of resources may be allocated to exclude the one or more resources based on sidelink feedback information such as NACK detected at 420. In other examples, UE 115-d may use the group of resources to send the second packet, where the group of resources may be allocated to include the one or more resources based on sidelink feedback information such as ACK detected at 420. In some examples, UE 115-d may use the one or more resources to send the second packet based on the reference signal received power detected at 420 and the group of resources being allocated to include the one or more resources.

[0100] Figure 5 FIG. 500 is a block diagram of a device 505 in accordance with aspects of the present disclosure. Device 505 may be an example of aspects of UE 115 as described herein. Device 505 may include a receiver 510, a communication manager 515, and a transmitter 520. Device 505 may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0101] The receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channel information, data channel information, and information related to reclaiming resources based on sidelink feedback, etc.). The information may be passed to other components of device 505. The receiver 510 may be an example of aspects of the transceiver 820 described with reference to Figure 8 The receiver 510 may utilize a single antenna or a group of antennas.

[0102] The communication manager 515 may receive, from a first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. The communication manager 515 may monitor for sidechain feedback information responsive to an initial transmission of the first packet by the second UE. The communication manager 515 may identify a category of the one or more resources based on whether sidechain feedback information is detected during the monitoring. The communication manager 515 may allocate, for a first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources. The communication manager 515 may be an example of aspects of the communication manager 810 described herein.

[0103] The communication manager 515 or its subcomponents may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functions of the communication manager 515 or its subcomponents may be performed by 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, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this disclosure.

[0104] The communication manager 515 or its subcomponents may physically be located in various positions, including being distributed such that portions of the functionality are implemented by one or more physical devices in different physical locations. In some examples, aspects of the communication manager 515 or its subcomponents may be separate and distinct components in accordance with various aspects of this disclosure. In some examples, aspects of the communication manager 515 or its subcomponents may be combined with one or more other hardware components, including but not limited to input / output (I / O) components, transceivers, network servers, another computing device, one or more other components described in this disclosure, or combinations thereof.

[0105] The transmitter 520 may transmit signals generated by other components of the device 505. In some examples, the transmitter 520 may be collocated with the receiver 510 in a transceiver module. For example, the transmitter 520 may be an example of aspects of the transceiver 820 described with reference to Figure 8 The transmitter 520 may utilize a single antenna or a set of antennas.

[0106] In some examples, the communication manager 515 may be implemented as an integrated circuit or chipset of a mobile device modem, and the receiver 510 and the transmitter 520 may be implemented as analog components (e.g., amplifiers, filters, antennas) coupled to the mobile device modem to enable wireless transmission and reception over one or more frequency bands.

[0107] As described herein, the communication manager 515 can be implemented to realize one or more potential advantages. One implementation can allow the device 505 to determine whether a set of resources allocated to another device can be reclaimed for communication between the device 505 and the base station. Based on the technique for determining whether a set of resources can be reclaimed, the device 505 can use the reclaimed resources to communicate with the base station.

[0108] Accordingly, the device 505 can communicate using resources that may not have been otherwise utilized, and correspondingly, the device can improve the spectral efficiency of the wireless communication system. Additionally, the device 505 can communicate using resources that may not have been otherwise available for the device 505 to communicate. In some examples, based on reclaiming resources allocated to other devices, the device 505 can communicate with a lower latency and a higher speed, which can provide a better user experience, save power, and extend battery life.

[0109] Figure 6 FIG. 600 is a block diagram of a device 605 in accordance with aspects of the present disclosure. The device 605 can be an example of aspects of the device 505 or the UE 115 as described herein. The device 605 can include a receiver 610, a communication manager 615, and a transmitter 640. The device 605 can also include a processor. Each of these components can communicate with one another (e.g., via one or more buses).

[0110] The receiver 610 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channel information, data channel information, and information related to reclaiming resources based on sidelink feedback, etc.). The information can be passed to other components of the device 605. The receiver 610 can be an example of aspects of the transceiver 820 described with reference to Figure 8 The receiver 610 can utilize a single antenna or a set of antennas.

[0111] The communication manager 615 can be an example of aspects of the communication manager 515 as described herein. The communication manager 615 can include an SCI manager 620, a sidelink feedback monitor 625, a resource organizer 630, and a transmit controller 635. The communication manager 615 can be an example of aspects of the communication manager 810 described herein.

[0112] The SCI manager 620 can receive, from a first UE, an SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE.

[0113] The sidelink feedback monitor 625 can monitor for sidelink feedback information responsive to an initial transmission of a first packet by a second UE.

[0114] The resource organizer 630 can identify a category of one or more resources based on whether sidelink feedback information is detected during the monitoring.

[0115] The transmission controller 635 can allocate, for the first UE, a set of resources for transmitting a second packet, where one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0116] The transmitter 640 can transmit signals generated by other components of the device 605. In some examples, the transmitter 640 can be collocated with the receiver 610 in a transceiver module. For example, the transmitter 640 can be an example of aspects of the transceiver 820 described with reference to Figure 8 The transmitter 640 can use a single antenna or a set of antennas.

[0117] Figure 7 FIG. 700 is a block diagram of a communication manager 705 in accordance with aspects of the present disclosure. The communication manager 705 can be an example of aspects of the communication manager 515, the communication manager 615, or the communication manager 810 described herein. The communication manager 705 can include an SCI manager 710, a sidelink feedback monitor 715, a resource organizer 720, a transmission controller 725, a priority identifier 730, and an RSRP monitor 735. Each of these modules can communicate directly or indirectly with each other (e.g., via one or more buses).

[0118] The SCI manager 710 can receive, for the first UE, an SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. In some cases, the first UE and the second UE operate in a vehicle-to-everything system.

[0119] The sidelink feedback monitor 715 can monitor for sidelink feedback information responsive to an initial transmission of a first packet by a second UE. In some examples, the sidelink feedback monitor 715 can determine, based on the monitoring, an absence of sidelink feedback information, where the identified category is based on the absence of sidelink feedback information. In some examples, the sidelink feedback monitor 715 can detect, based on the monitoring, sidelink feedback information, where the identified category is based on the detected sidelink feedback information. In some examples, the sidelink feedback monitor 715 can monitor a physical sidelink feedback channel for sidelink feedback information to be sent to the second UE. In some cases, the sidelink feedback information includes a negative acknowledgment. In some cases, the sidelink feedback information includes a positive acknowledgment.

[0120] The resource organizer 720 may identify the category of one or more resources based on whether sidelink feedback information is detected during monitoring. In some cases, the category of one or more resources includes an available category or an occupied category.

[0121] The transmission controller 725 may be allocated a set of resources for transmitting a second packet by a first UE, wherein one or more resources are included in the set of resources based on the identified category of one or more resources. In some examples, the transmission controller 725 may use one or more resources to transmit the second packet based on the first priority being equal to the second priority and allocating a set of resources to include one or more resources. In some examples, the transmission controller 725 may use one or more resources to transmit the second packet based on the first priority being less than the second priority and allocating a set of resources to include one or more resources.

[0122] In some examples, the transmission controller 725 may use a set of resources to transmit the second packet, wherein a set of resources is allocated to exclude one or more resources based on the first priority being higher than the second priority. In some examples, the transmission controller 725 may use a set of resources to transmit the second packet, wherein a set of resources is allocated to exclude one or more resources based on the detected sidelink feedback information. In some examples, the transmission controller 725 may use one or more resources to transmit the second packet based on the detected sidelink feedback information and allocating a set of resources to include one or more resources. In some examples, the transmission controller 725 may use one or more resources to transmit the second packet based on the detected reference signal received power and allocating a set of resources to include one or more resources.

[0123] The priority identifier 730 may identify the first priority of the first packet. In some examples, the priority identifier 730 may identify the second priority of the second packet, wherein identifying the category of one or more resources is based on a comparison of the first priority and the second priority. In some examples, the priority identifier 730 may identify the first priority being equal to the second priority based on the comparison. In some examples, the priority identifier 730 may identify the first priority being less than the second priority based on the comparison. In some examples, the priority identifier 730 may determine that the first priority is higher than the second priority.

[0124] The RSRP monitor 735 may detect that the reference signal received power associated with one or more resources is lower than a configured threshold.

[0125] Figure 8FIG. shows a system 800 including a device 805 in accordance with aspects of the present disclosure. The device 805 may be an example of or include components of the device 505, the device 605, or the UE 115 as described herein. The device 805 may include components for two-way voice and data communication, including components for sending and receiving communications, including a communication manager 810, an I / O controller 815, a transceiver 820, an antenna 825, a memory 830, and a processor 840. These components may communicate electronically via one or more buses (e.g., bus 845).

[0126] The communication manager 810 may: receive, from a first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE; monitor for sidechain feedback information responsive to an initial transmission of the first packet by the second UE; identify a category of the one or more resources based on whether sidechain feedback information is detected during the monitoring; and allocate, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based on the identified category of the one or more resources.

[0127] The I / O controller 815 may manage input and output signals of the device 805. The I / O controller 815 may also manage peripheral devices not integrated into the device 805. In some cases, the I / O controller 815 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 815 may utilize an operating system such as or other known operating systems. In other cases, the I / O controller 815 may represent or interact with a modem, a keyboard, a mouse, a touch screen, or similar devices. In some cases, the I / O controller 815 may be implemented as part of a processor. In some cases, a user may interact with the device 805 via the I / O controller 815 or via hardware components controlled by the I / O controller 815.

[0128] As described above, the transceiver 820 may communicate bi-directionally via one or more antennas, wired or wireless links. For example, the transceiver 820 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 820 may also include: a modem for modulating packets and providing the modulated packets to the antenna for transmission, and for demodulating packets received from the antenna.

[0129] In some cases, a wireless device may include a single antenna 825. However, in some cases, the device may have more than one antenna 825, which may be capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0130] The memory 830 may include a random access memory (RAM) and a read-only memory (ROM). The memory 830 may store computer-readable computer-executable code 835, which includes instructions that, when executed, cause the processor to perform the various functions described herein. In some cases, the memory 830 may also contain a basic input / output system (BIOS), which may control basic hardware or software operations, such as interactions with peripheral components or devices.

[0131] The processor 840 may include intelligent hardware devices (e.g., a general-purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an ASIC, an FPGA, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 840 may be configured to operate a memory array using a memory controller. In some cases, the memory controller may be integrated into the processor 840. The processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks that support resource recovery based on side-chain feedback).

[0132] The code 835 may include instructions for implementing aspects of the present disclosure, including instructions for supporting wireless communication. The code 835 may be stored in a non-transitory computer-readable medium such as system memory or other types of memory. In some cases, the code 835 may not be directly executable by the processor 840, but may cause a computer (e.g., when compiled and executed) to perform the functions described herein.

[0133] Figure 9 A flowchart illustrating a method 900 in accordance with aspects of the present disclosure is shown. The operations of the method 900 may be implemented by a UE 115 (e.g., a first UE) or its components as described herein. For example, the operations of the method 900 may be performed by a communication manager as described with reference to Figures 5 to 8 In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0134] At 905, the first UE may receive an SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. The operation of 905 may be performed in accordance with the methods described herein. In some examples, aspects of the operation of 905 may be performed by an SCI manager as described with reference to Figures 5 to 8 described.

[0135] At 910, a first UE may monitor for sidelink feedback information in response to an initial transmission of a first packet by a second UE. Operations at 910 may be performed according to the methods described herein. In some examples, aspects of the operations at 910 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0136] At 915, the first UE may identify a category of one or more resources based on whether sidelink feedback information is detected during the monitoring. Operations at 915 may be performed according to the methods described herein. In some examples, aspects of the operations at 915 may be performed by a resource organizer as described with reference to Figures 5 to 8 described.

[0137] At 920, the first UE may allocate a set of resources for transmitting a second packet, where one or more resources are included in the set of resources based on the identified category of one or more resources. Operations at 920 may be performed according to the methods described herein. In some examples, aspects of the operations at 920 may be performed by a transmission controller as described with reference to Figures 5 to 8 described.

[0138] Figure 10 FIG. 1000 is a flow diagram illustrating a method 1000 in accordance with aspects of the present disclosure. Operations of method 1000 may be implemented by a UE 115 (e.g., a first UE) or components thereof as described herein. For example, operations of method 1000 may be performed by a communication manager as described with reference to Figures 5 to 8 described. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0139] At 1005, the first UE may receive an SCI that indicates one or more resources reserved for a retransmission of the first packet by the second UE. Operations at 1005 may be performed according to the methods described herein. In some examples, aspects of the operations at 1005 may be performed by an SCI manager as described with reference to Figures 5 to 8 described.

[0140] At 1010, the first UE may monitor for sidelink feedback information in response to an initial transmission of a first packet by a second UE. Operations at 1010 may be performed according to the methods described herein. In some examples, aspects of the operations at 1010 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0141] At 1015, a first UE may determine the absence of sidelink feedback information based on monitoring, where the identification category is based on the absence of sidelink feedback information. The operations at 1015 may be performed according to the methods described herein. In some examples, aspects of the operations at 1015 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0142] At 1020, a first UE may identify the category of one or more resources based on whether sidelink feedback information is detected during monitoring. The operations at 1020 may be performed according to the methods described herein. In some examples, aspects of the operations at 1020 may be performed by a resource organizer as described with reference to Figures 5 to 8 described.

[0143] At 1025, a first UE may allocate a set of resources for transmitting a second packet, where one or more resources are included in the set of resources based on the identified category of the one or more resources. The operations at 1025 may be performed according to the methods described herein. In some examples, aspects of the operations at 1025 may be performed by a transmission controller as described with reference to Figures 5 to 8 described.

[0144] Figure 11 FIG. shows a flowchart of a method 1100 according to aspects of the present disclosure. The operations of method 1100 may be implemented by a UE 115 (e.g., a first UE) or its components as described herein. For example, the operations of method 1100 may be performed by a communication manager as described with reference to Figures 5 to 8 described. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0145] At 1105, a first UE may receive an SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. The operations at 1105 may be performed according to the methods described herein. In some examples, aspects of the operations at 1105 may be performed by an SCI manager as described with reference to Figures 5 to 8 described.

[0146] At 1110, a first UE may identify a first priority of a first packet. The operations at 1110 may be performed according to the methods described herein. In some examples, aspects of the operations at 1110 may be performed by a priority identifier as described with reference to Figures 5 to 8 described.

[0147] At 1115, a first UE may monitor to obtain sidelink feedback information in response to an initial transmission of a first packet by a second UE. The operations at 1115 may be performed according to the methods described herein. In some examples, aspects of the operations at 1115 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0148] At 1120, the first UE may determine the absence of sidelink feedback information based on the monitoring, wherein the identification category is based on the absence of sidelink feedback information. The operations at 1120 may be performed according to the methods described herein. In some examples, aspects of the operations at 1120 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0149] At 1125, the first UE may identify a second priority of a second packet, wherein the identification of one or more resource categories is based on a comparison of the first priority and the second priority. The operations at 1125 may be performed according to the methods described herein. In some examples, aspects of the operations at 1125 may be performed by a priority identifier as described with reference to Figures 5 to 8 described.

[0150] At 1130, the first UE may identify one or more resource categories based on whether sidelink feedback information is detected during the monitoring. The operations at 1130 may be performed according to the methods described herein. In some examples, aspects of the operations at 1130 may be performed by a resource organizer as described with reference to Figures 5 to 8 described.

[0151] At 1135, the first UE may allocate a set of resources for transmitting the second packet, wherein one or more resources are included in the set of resources based on the identified one or more resource categories. The operations at 1135 may be performed according to the methods described herein. In some examples, aspects of the operations at 1135 may be performed by a transmission controller as described with reference to Figures 5 to 8 described.

[0152] Figure 12 FIG. shows a flowchart of a method 1200 according to aspects of the present disclosure. The operations of method 1200 may be implemented by a UE 115 (e.g., a first UE) or its components as described herein. For example, the operations of method 1200 may be performed by a communication manager as described with reference to Figures 5 to 8 described. In some examples, the UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0153] At 1205, a first UE may receive a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. The operations at 1205 may be performed according to the methods described herein. In some examples, aspects of the operations at 1205 may be performed by an SCI manager as described with reference to Figures 5 to 8 described.

[0154] At 1210, the first UE may monitor for sidelink feedback information in response to an initial transmission of the first packet by the second UE. The operations at 1210 may be performed according to the methods described herein. In some examples, aspects of the operations at 1210 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0155] At 1215, the first UE may detect sidelink feedback information based on the monitoring, wherein an identification category is based on the detected sidelink feedback information. The operations at 1215 may be performed according to the methods described herein. In some examples, aspects of the operations at 1215 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 described.

[0156] At 1220, the first UE may identify a category of one or more resources based on whether sidelink feedback information is detected during the monitoring. The operations at 1220 may be performed according to the methods described herein. In some examples, aspects of the operations at 1220 may be performed by a resource organizer as described with reference to Figures 5 to 8 described.

[0157] At 1225, the first UE may allocate a set of resources for transmitting a second packet, wherein one or more resources are included in the set of resources based on the identified category of the one or more resources. The operations at 1225 may be performed according to the methods described herein. In some examples, aspects of the operations at 1225 may be performed by a transmission controller as described with reference to Figures 5 to 8 described.

[0158] Figure 13 FIG. shows a flowchart of a method 1300 according to aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 (e.g., a first UE) or its components as described herein. For example, the operations of method 1300 may be performed by a communication manager as described with reference to Figures 5 to 8 described. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform the functions described herein. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described herein.

[0159] At 1305, a first UE may receive a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE. The operation at 1305 may be performed according to the methods described herein. In some examples, aspects of the operation at 1305 may be performed by an SCI manager as described with reference to Figures 5 to 8 the SCI manager described.

[0160] At 1310, a first UE may monitor for sidelink feedback information in response to an initial transmission of a first packet by a second UE. The operation at 1310 may be performed according to the methods described herein. In some examples, aspects of the operation at 1310 may be performed by a sidelink feedback monitor as described with reference to Figures 5 to 8 the sidelink feedback monitor described.

[0161] At 1315, a first UE may detect that a reference signal received power associated with one or more resources is below a configured threshold. The operation at 1315 may be performed according to the methods described herein. In some examples, aspects of the operation at 1315 may be performed by an RSRP monitor as described with reference to Figures 5 to 8 the RSRP monitor described.

[0162] At 1320, a first UE may identify a category of one or more resources based on whether sidelink feedback information is detected during monitoring. The operation at 1320 may be performed according to the methods described herein. In some examples, aspects of the operation at 1320 may be performed by a resource organizer as described with reference to Figures 5 to 8 the resource organizer described.

[0163] At 1325, a first UE may allocate a set of resources for transmitting a second packet, where one or more resources are included in the set of resources based on the identified category of one or more resources. The operation at 1325 may be performed according to the methods described herein. In some examples, aspects of the operation at 1325 may be performed by a transmission controller as described with reference to Figures 5 to 8 the transmission controller described.

[0164] At 1330, a first UE may use one or more resources to transmit a second packet based on the detected reference signal received power and the allocation of a set of resources to include one or more resources. The operation at 1330 may be performed according to the methods described herein. In some examples, aspects of the operation at 1330 may be performed by a transmission controller as described with reference to Figures 5 to 8 the transmission controller described.

[0165] Example 1: A method for wireless communication in a first UE, comprising: receiving, by the first UE, a SCI that indicates one or more resources reserved for a retransmission of a first packet by a second UE; monitoring for obtaining sidelink feedback information in response to an initial transmission of the first packet by the second UE; identifying a category of the one or more resources at least partially based on whether the sidelink feedback information is detected during the monitoring; and allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources at least partially based on the identified category of the one or more resources.

[0166] Example 2: The method according to Example 1, further comprising: determining at least partially based on the monitoring a lack of sidelink feedback information, wherein identifying the category is at least partially based on the lack of the sidelink feedback information.

[0167] Example 3: The method according to Example 2, further comprising: identifying a first priority of the first packet; and identifying a second priority of the second packet, wherein identifying the category of the one or more resources is at least partially based on a comparison between the first priority and the second priority.

[0168] Example 4: The method according to Examples 1 to 3, further comprising: determining at least partially based on the comparison that the first priority is equal to the second priority; and at least partially based on the first priority being equal to the second priority, and allocating the set of resources to include the one or more resources, using the one or more resources to transmit the second packet.

[0169] Example 5: The method according to Examples 1 to 3, further comprising: determining at least partially based on the comparison that the first priority is less than the second priority; and at least partially based on the first priority being less than the second priority, and allocating the set of resources to include the one or more resources, using the one or more resources to transmit the second packet.

[0170] Example 6: The method according to Examples 1 to 3, further comprising: determining that the first priority is higher than the second priority; and using the set of resources to transmit the second packet, wherein at least partially based on the first priority being higher than the second priority, the set of resources is allocated to exclude the one or more resources.

[0171] Example 7: The method according to Examples 2 to 6, wherein the sidelink feedback information includes a negative acknowledgment.

[0172] Example 8: The method according to any one of Examples 1 to 7 further includes: detecting the sidelink feedback information at least in part based on the monitoring, wherein identifying the category is at least in part based on the detected sidelink feedback information.

[0173] Example 9: The method according to Example 8 further includes: using the set of resources to transmit the second packet, wherein the set of resources is allocated to exclude the one or more resources at least in part based on the detected sidelink feedback information.

[0174] Example 10: The method according to Example 9, wherein the sidelink feedback information includes a negative acknowledgment.

[0175] Example 11: The method according to any one of Examples 8 to 10 further includes: using the one or more resources to transmit the second packet at least in part based on the detected sidelink feedback information and allocating the set of resources to include the one or more resources.

[0176] Example 12: The method according to Example 11, wherein the sidelink feedback information includes a positive acknowledgment.

[0177] Example 13: The method according to any one of Examples 1 to 12 further includes: detecting that the RSRP associated with the one or more resources is below a configured threshold; and using the one or more resources to transmit the second packet at least in part based on the detected RSRP and allocating the set of resources to include the one or more resources.

[0178] Example 14: The method according to any one of Examples 1 to 13, wherein the monitoring for obtaining the sidelink feedback information includes: monitoring a physical sidelink feedback channel for obtaining the sidelink feedback information sent to the second UE.

[0179] Example 15: The method according to any one of Examples 1 to 14, wherein the category of the one or more resources includes an available category or an occupied category.

[0180] Example 16: The method according to any one of Examples 1 to 15, wherein the first UE and the second UE operate in a vehicle-to-everything system.

[0181] Example 17: An apparatus for wireless communication includes at least one unit for performing the method according to any one of Examples 1 to 16.

[0182] Example 18: An apparatus for wireless communication includes a processor and a memory coupled to the processor, the processor and the memory being configured to cause the apparatus to perform the method according to any one of Examples 1 to 16.

[0183] Example 19: A non-transitory computer-readable medium storing code for wireless communication, including a processor, a memory in electronic communication with the processor, and instructions stored in the memory and executable by the processor to cause the device to perform the method according to any one of Examples 1 to 16.

[0184] It should be noted that the above method describes possible implementations, and the operations and steps can be rearranged or otherwise modified, and other implementations are also possible. In addition, aspects of two or more methods can be combined.

[0185] Although aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for purposes of example, and the LTE, LTE-A, LTE-A Pro, or NR terms may be used in most of the description, the techniques described herein can be applied outside of LTE, LTE-A, LTE-A Pro, or NR applications. For example, the described techniques can be applicable to various other wireless communication systems, such as: Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, and other systems and radio technologies not explicitly mentioned herein.

[0186] The information and signals described herein can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0187] The various illustrative blocks and modules described in connection with the disclosure herein can be implemented or performed with a general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor can be a microprocessor, but alternatively, the processor can be any conventional processor, controller, microcontroller, or state machine. The processor can 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).

[0188] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted via a computer-readable medium as one or more instructions or code. Other examples and implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the above functions can be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination of these items. The features for implementing the functions can also be physically located in various positions, including being distributed such that parts of the functions are implemented at different physical locations.

[0189] Computer-readable media includes both non-transitory computer storage media and communication media, where the communication media includes any medium that facilitates transfer of a computer program from one place to another. The non-transitory storage media can be any available media that can be accessed by a general or special purpose computer. By way of example and not limitation, non-transitory computer-readable media can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc read-only memory (CD-ROM) or other optical disc storage, magnetic disk storage or other magnetic disk storage devices, or any other non-transitory medium that can be used to carry or store desired program code units in the form of instructions or data structures and that can be accessed by a general or special purpose computer or a general or special purpose processor computer. Also, 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 technology such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology such as infrared, radio, and microwave is included in the definition of computer-readable medium. As used herein, disks and discs include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically, while discs reproduce data optically with a laser. Combinations of the above are also included within the scope of computer-readable media.

[0190] As used herein, including in the claims, the "or" as used in a list of items (e.g., a list of items beginning with a phrase such as "at least one" or "one or more") indicates an inclusive list, such that a list of at least one of A, B, or C, for example, represents A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" should not be construed as a reference to a closed set of conditions. For example, an exemplary step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on".

[0191] In the drawings, similar components or features may have the same reference numerals. Additionally, various components of the same type may be distinguished by following the reference numeral with a dash and a second label that differentiates between similar components. If only the first reference numeral is used in the specification, the description applies to any one of the similar components having the same first reference numeral, regardless of the second reference numeral or any other subsequent reference numerals.

[0192] The description provided herein describes example configurations and does not represent all examples that can be implemented or that are within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration" and not "preferred" or "advantageous over other examples". The detailed description includes specific details for providing an understanding of the described techniques. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0193] The description provided herein is to enable a person of ordinary skill in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to a person of ordinary skill in the art, and the general principles defined herein can be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for wireless communication in a first user equipment (UE), comprising: receiving, by the first UE, sidelink channel information indicating one or more resources reserved for a retransmission of a first packet by a second UE; monitoring for sidelink feedback information in response to an initial transmission of the first packet by the second UE; identifying a category of the one or more resources at least in part based on whether the sidelink feedback information is detected during the monitoring; allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources at least in part based on the identified category of the one or more resources; identifying a category of the one or more resources at least in part based on whether the sidelink feedback information is detected during the monitoring includes: determining a lack of the sidelink feedback information at least in part based on the monitoring; and when determining the lack of the sidelink feedback information: identifying a first priority of the first packet; identifying a second priority of the second packet; and comparing the first priority and the second priority, wherein identifying the category of the one or more resources is at least in part based on the comparison of the first priority and the second priority.

2. The method according to claim 1, wherein, the first packet is transmitted by the second UE to a third UE.

3. The method according to claim 1, further comprising: identifying that the first priority is equal to the second priority at least in part based on the comparison; and and allocating the set of resources to include the one or more resources at least in part based on the first priority being equal to the second priority, and using the one or more resources to transmit the second packet.

4. The method according to claim 1, further comprising: identifying that the first priority is less than the second priority at least in part based on the comparison; and and allocating the set of resources to include the one or more resources at least in part based on the first priority being less than the second priority, and using the one or more resources to transmit the second packet.

5. The method according to claim 1, further comprising: determining that the first priority is higher than the second priority; and and using the set of resources to transmit the second packet, wherein the set of resources is allocated to exclude the one or more resources at least in part based on the first priority being higher than the second priority.

6. The method according to claim 2, wherein, the sidelink feedback information includes a negative acknowledgment.

7. The method according to claim 1, further comprising: detecting the sidelink feedback information at least in part based on the monitoring, wherein identifying the category is at least in part based on the detected sidelink feedback information.

8. The method according to claim 7, further comprising: using the set of resources to transmit the second packet, wherein the set of resources is allocated to exclude the one or more resources at least in part based on the detected sidelink feedback information.

9. The method according to claim 8, wherein, the sidelink feedback information includes a negative acknowledgment.

10. The method according to claim 7, further comprising: using the one or more resources to transmit the second packet, at least in part based on the detected sidelink feedback information and allocating the set of resources to include the one or more resources.

11. The method according to claim 10, wherein, the sidelink feedback information includes a positive acknowledgment.

12. The method according to claim 1, further comprising: detecting that a reference signal received power associated with the one or more resources is lower than a configured threshold; and using the one or more resources to transmit the second packet, at least in part based on the reference signal received power and allocating the set of resources to include the one or more resources.

13. The method according to claim 1, wherein, monitoring for obtaining the sidelink feedback information includes: monitoring a physical sidelink feedback channel for obtaining the sidelink feedback information sent to the second UE.

14. The method according to claim 1, wherein, the category of the one or more resources includes an available category or an occupied category.

15. The method according to claim 1, wherein, the first UE and the second UE operate in a vehicle-to-everything system.

16. An apparatus for wireless communication at a first user equipment (UE), comprising: a unit for receiving, by the first UE, sidelink channel information indicating one or more resources reserved for a retransmission of a first packet by a second UE; a unit for monitoring for obtaining sidelink feedback information in response to an initial transmission of the first packet by the second UE; a unit for identifying a category of the one or more resources, at least in part based on whether the sidelink feedback information is detected during the monitoring; a unit for allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources, at least in part based on the identified category of the one or more resources, wherein the unit for identifying a category of the one or more resources, at least in part based on whether the sidelink feedback information is detected during the monitoring, includes: a unit for determining, at least in part based on the monitoring, a lack of the sidelink feedback information; and a unit for operating as follows when determining the lack of the sidelink feedback information: identifying a first priority of the first packet; identifying a second priority of the second packet; and comparing the first priority and the second priority, wherein identifying the category of the one or more resources is at least in part based on the comparison of the first priority and the second priority.

17. The apparatus according to claim 16, wherein, the first packet is sent by the second UE to a third UE.

18. The apparatus according to claim 16, further comprising: a unit configured to identify that the first priority is equal to the second priority, at least in part based on the comparison; and a unit configured to allocate the set of resources to include the one or more resources and use the one or more resources to transmit the second packet, at least in part based on the first priority being equal to the second priority.

19. The apparatus according to claim 16, further comprising: a unit configured to identify that the first priority is less than the second priority, at least in part based on the comparison; and a unit configured to allocate the set of resources to include the one or more resources and use the one or more resources to transmit the second packet, at least in part based on the first priority being less than the second priority.

20. The apparatus according to claim 16, further comprising: a unit configured to determine that the first priority is higher than the second priority; and a unit configured to use the set of resources to transmit the second packet, wherein the set of resources is allocated to exclude the one or more resources, at least in part based on the first priority being higher than the second priority.

21. The apparatus according to claim 16, further comprising: a unit configured to detect the side-chain feedback information, at least in part based on the monitoring, wherein the identifying of the category is at least in part based on the detected side-chain feedback information.

22. The apparatus according to claim 21, further comprising: a unit configured to use the set of resources to transmit the second packet, wherein the set of resources is allocated to exclude the one or more resources, at least in part based on the detected side-chain feedback information.

23. The apparatus according to claim 21, further comprising: a unit configured to allocate the set of resources to include the one or more resources and use the one or more resources to transmit the second packet, at least in part based on the detected side-chain feedback information.

24. The apparatus according to claim 16, further comprising: a unit configured to detect that the reference signal received power associated with the one or more resources is lower than a configured threshold; and a unit configured to allocate the set of resources to include the one or more resources and use the one or more resources to transmit the second packet, at least in part based on the reference signal received power.

25. The apparatus according to claim 16, wherein the unit configured to perform the monitoring for obtaining the side-chain feedback information further comprises: a unit configured to monitor a physical side-chain feedback channel for obtaining the side-chain feedback information sent to the second UE.

26. The apparatus according to claim 16, wherein the category of the one or more resources includes an available category or an occupied category.

27. An apparatus for wireless communication at a first user equipment (UE), comprising: a processor, a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the following operations: Receiving, by the first UE, sidelink channel information indicating one or more resources reserved for a retransmission of a first packet by a second UE; Monitoring to obtain sidelink feedback information responsive to an initial transmission of the first packet by the second UE; Identifying a category of the one or more resources based at least in part on whether the sidelink feedback information is detected during the monitoring; Allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based at least in part on the identified category of the one or more resources; wherein, to identify the category of the one or more resources based at least in part on whether the sidelink feedback information is detected during the monitoring, the instructions further cause the apparatus to: Determining at least in part based on the monitoring a lack of the sidelink feedback information; and When determining the lack of the sidelink feedback information: Identifying a first priority of the first packet; Identifying a second priority of the second packet; and Comparing the first priority and the second priority, wherein identifying the category of the one or more resources is based at least in part on the comparison of the first priority and the second priority.

28. A non-transitory computer-readable medium storing code for wireless communication by a first user equipment (UE), the code including instructions executable by a processor to: Receiving, by the first UE, sidelink channel information indicating one or more resources reserved for a retransmission of a first packet by a second UE; Monitoring to obtain sidelink feedback information responsive to an initial transmission of the first packet by the second UE; Identifying a category of the one or more resources based at least in part on whether the sidelink feedback information is detected during the monitoring; Allocating, by the first UE, a set of resources for transmitting a second packet, wherein the one or more resources are included in the set of resources based at least in part on the identified category of the one or more resources, wherein, to identify the category of the one or more resources based at least in part on whether the sidelink feedback information is detected during the monitoring, the instructions are further executable by the processor to: Determining at least in part based on the monitoring a lack of the sidelink feedback information; and When determining the lack of the sidelink feedback information: Identifying a first priority of the first packet; Identifying a second priority of the second packet; and Comparing the first priority and the second priority, wherein identifying the category of the one or more resources is based at least in part on the comparison of the first priority and the second priority.

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