Intermittent reception enhancement using multiple sidelink feedback channel opportunities

Abstract

A method, system, and device for wireless communications are described. A user equipment (UE) can receive, while operating in a discontinuous reception mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The UE can transmit at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity of the set of feedback channel opportunities. The UE can start a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel opportunity, during which the UE refrains from monitoring for retransmissions of the sidelink data message.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application No. 18 / 053,473 by Liu et al., entitled "DISCONTINUOUS RECEPTION ENHANCEMENT WITH MULTIPLE SIDELINK FEEDBACK CHANNEL OPPORTUNITIES," filed November 8, 2022, which is assigned to the assignee of the present application and expressly incorporated herein by reference.

[0002] The following relates to wireless communications, including discontinuous reception enhancement using multiple sidelink feedback channel opportunities. [Background technology]

[0003] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcasts, and so on. These systems may be capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth-generation (4G) systems, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), or LTE-A Pro systems, and fifth-generation (5G) systems, sometimes referred to as New Radio (NR) systems. These systems may employ technologies such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA), or Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM). A wireless multiple-access communication system may include one or more base stations, each supporting wireless communication for communication devices, which may be known as user equipment (UE). Summary of the Invention

[0004] The described techniques relate to improved methods, systems, devices, and apparatuses that support discontinuous reception (DRX) enhancement using multiple sidelink feedback channel opportunities. For example, the described techniques provide for a user equipment (UE) to select a physical sidelink feedback channel (PSFCH) opportunity (e.g., a feedback opportunity) from a set of allocated PSFCH opportunities, after which a round-trip-time (RTT) timer is started. For example, the UE may receive a grant scheduling a transmission to the UE (e.g., that a sidelink data message is scheduled for transmission to the UE). The grant may further identify feedback resources allocated to the UE for the sidelink data message. For example, the grant may identify a set of feedback channel opportunities (e.g., configuring multiple PSFCH opportunities for a hybrid automatic repeat / request (HARQ) process for the sidelink data message). The UE may receive a sidelink data message and determine a feedback status for the sidelink data message (e.g., HARQ-acknowledgement (HARQ-ACK) acknowledgement / negative acknowledgment (ACK / NACK) information, such as whether the UE was able to successfully receive and decode the sidelink data message). The UE may send a feedback message indicating the feedback status during at least one of the PSFCH opportunities and start an RTT timer after the PSFCH opportunity based on the at least one PSFCH opportunity.That is, the RTT timer may be started after the same PSFCH opportunity at which the HARQ-ACK feedback is transmitted, or after a different PSFCH opportunity in the set of PSFCH opportunities. For example, the RTT timer may be started after the first PSFCH opportunity in the set, after the last PSFCH opportunity in the set, after an intermediate PSFCH opportunity in the set, or based on the result of an LBT procedure performed before each PSFCH opportunity (e.g., when operating on a shared channel). In some embodiments, the duration of the RTT timer may be adjusted based on the PSFCH opportunity after which the RTT timer is started. Thus, the UE may start the RTT timer after a PSFCH opportunity in the set, and upon expiration, may start a retransmission timer to monitor for retransmission of the sidelink data message.

[0005] A method for wireless communication in a UE is described that may include, while operating in a DRX mode, receiving, on a shared radio frequency spectrum band, a grant for scheduling a sidelink data message for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; and starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, wherein the UE refrains from monitoring for retransmissions of the sidelink data message during the starting.

[0006] An apparatus for wireless communication in a UE is described, which 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, while operating in a DRX mode, to receive, on a shared radio frequency spectrum band, a grant for scheduling sidelink data messages for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages; transmit, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; start, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message; and, during the start-up, inhibit the UE from monitoring for retransmissions of the sidelink data message.

[0007] Another apparatus for wireless communication in a UE is described that may include: means for receiving, while operating in a DRX mode, on a shared radio frequency spectrum band, a grant for scheduling a sidelink data message for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; and means for starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, wherein during the starting, the UE refrains from monitoring for retransmissions of the sidelink data message.

[0008] A non-transitory computer-readable medium is described that stores code for wireless communication in a UE, the code may include instructions executable by a processor, the instructions including: receiving, while operating in a DRX mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message; and inhibiting, during the starting, the UE from monitoring for retransmissions of the sidelink data message.

[0009] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction that identifies a first feedback channel opportunity in a set of feedback channel opportunities, and a round-trip timer may have been started after the first feedback channel opportunity.

[0010] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction for determining that a listen-before-talk (LBT) procedure performed before the first feedback channel opportunity was unsuccessful, and transmitting at least one feedback message at a subsequent feedback channel opportunity from a set of feedback channel opportunities associated with the successful LBT procedure while starting a round-trip timer after the first feedback channel opportunity.

[0011] Some embodiments of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for extending a duration of a retransmission timer while the UE monitors the sidelink channel for a second grant for scheduling a retransmission of the sidelink data message based on the round-trip timer being started after the first feedback channel opportunity.

[0012] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction for performing an LBT procedure before each feedback channel opportunity in the set of feedback channel opportunities to determine whether a feedback channel opportunity may be available for transmitting at least one feedback message, and identifying a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, wherein a round-trip timer may have been started after the first feedback channel opportunity.

[0013] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction for determining that each feedback channel opportunity in the set of feedback channel opportunities may be associated with an unsuccessful LBT procedure, and identifying a last feedback channel opportunity in the set of feedback channel opportunities based on each feedback channel opportunity being associated with an unsuccessful LBT procedure, wherein a round-trip timer may have been started after the last feedback channel opportunity.

[0014] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction that identifies a last feedback channel opportunity in a set of feedback channel opportunities, and a round-trip timer may have been started after the last feedback channel opportunity.

[0015] Some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for identifying a feedback channel opportunity within the set of feedback channel opportunities after which the round-trip timer may be started, and selecting a duration for the round-trip timer based on the feedback channel opportunity within the set of feedback channel opportunities after which the round-trip timer may be started.

[0016] Some embodiments of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for determining an expected scheduling time for a retransmission of the sidelink data message, wherein the duration for the round-trip timer may be further based on the expected scheduling time.

[0017] Some embodiments of the methods, apparatuses, and non-transitory computer-readable media described herein may further comprise an operation, feature, means, or instruction to refrain from monitoring the sidelink channel to detect a second grant scheduling a retransmission of the sidelink data message for the duration of the round-trip timer.

[0018] In some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein, the round-trip timer may be started after at least one feedback channel opportunity, during which at least one feedback message may have been transmitted, or after a different feedback channel opportunity within a set of feedback channel opportunities.

[0019] In some embodiments of the methods, apparatus, and non-transitory computer-readable media described herein, the set of feedback channel opportunities includes in-band feedback channel opportunities or a mix of in-band and out-of-band feedback channel opportunities. [Brief explanation of the drawings]

[0020] [Figure 1] 1 illustrates an example of a wireless communication system that supports discontinuous reception (DRX) enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 2] 1 illustrates an example of a wireless communication system that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 3A] 1 illustrates an example of a feedback configuration that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 3B] 1 illustrates an example of a feedback configuration that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 3C] 1 illustrates an example of a feedback configuration that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 4]1 illustrates an example of a feedback configuration that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 5] 1 illustrates a block diagram of a device that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 6] 1 illustrates a block diagram of a device that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 7] FIG. 1 illustrates a block diagram of a communications manager supporting DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 8] FIG. 1 illustrates a diagram of a system including a device that supports DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 9] 10 shows a flowchart illustrating a method for supporting DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 10] 10 shows a flowchart illustrating a method for supporting DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. [Figure 11] 10 shows a flowchart illustrating a method for supporting DRX enhancement using multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] Some user equipment (UE) may use a round-trip time (RTT) timer during a hybrid automatic repeat / request acknowledgment (HARQ-ACK) procedure while in discontinuous reception (DRX) mode. For example, a sidelink UE (e.g., a UE performing sidelink communication) may receive a grant on a shared radio frequency spectrum band to schedule a sidelink message for the UE. This grant may also identify resources (e.g., HARQ-ACK feedback resources) to be used for transmitting a feedback message related to the sidelink message. The UE receives the sidelink message via the assigned resources and transmits HARQ-ACK feedback (e.g., positive / negative acknowledgement (ACK / NACK) information) on those resources. If a NACK is transmitted, the UE anticipates a retransmission of the sidelink message associated with the NACK. The UE traditionally starts the RTT timer after the PSFCH opportunity where the HARQ-ACK feedback is transmitted (e.g., on the HARQ-ACK resource) if the UE does not anticipate a retransmission being scheduled. Alternatively, the UE may enter a sleep state in DRX mode, in which the UE does not monitor the sidelink control channel for retransmissions. When the RTT timer expires, the UE starts a retransmission timer, during which the UE monitors for grants to schedule retransmissions and for scheduled retransmissions. However, advanced networks may schedule multiple physical sidelink feedback channel (PSFCH) opportunities (e.g., feedback channel opportunities) for the UE. This can result in inconsistencies and confusion regarding when the UE starts the RTT timer (e.g., after which PSFCH opportunity, such as after the PSFCH opportunity where the HARQ-ACK feedback is transmitted or after a different PSFCH opportunity) and the corresponding retransmission.

[0022] Thus, the described techniques provide for a UE to select a PSFCH opportunity (e.g., a feedback opportunity) from a set of assigned PSFCH opportunities, after which an RTT timer is started. For example, the UE may receive a grant scheduling a transmission to the UE (e.g., that a sidelink data message is scheduled for transmission to the UE). The grant may further identify feedback resources assigned to the UE for the sidelink data message. For example, the grant may identify a set of feedback channel opportunities (e.g., configuring multiple PSFCH opportunities for a HARQ process for the sidelink data message). The UE may receive a sidelink data message and determine a feedback status for the sidelink data message (e.g., HARQ-ACK acknowledgment / negative acknowledgment (ACK / NACK) information, such as whether the UE was able to successfully receive and decode the sidelink data message). The UE may transmit a feedback message indicating the feedback status during at least one of the PSFCH opportunities and start an RTT timer after the PSFCH opportunity based on the at least one PSFCH opportunity. That is, the RTT timer may be started after the same PSFCH opportunity at which the HARQ-ACK feedback is being transmitted, or after a different PSFCH opportunity within the set of PSFCH opportunities. For example, the RTT timer may be started after the first PSFCH opportunity in the set, after the last PSFCH opportunity in the set, after an intermediate PSFCH opportunity in the set, or based on the results of an LBT procedure performed before each PSFCH opportunity (e.g., when operating on a shared channel). In some embodiments, the duration of the RTT timer may be adjusted based on the PSFCH opportunity after which the RTT timer is started.Accordingly, the UE may start an RTT timer after a PSFCH opportunity in the set, and upon expiration may start a retransmission timer to monitor for retransmission of the sidelink data message.

[0023] Aspects of the present disclosure are first described in the context of a wireless communication system and are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts relating to DRX enhancement using multiple sidelink feedback channel opportunities.

[0024] 1 illustrates an example of a wireless communication system 100 that supports DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The wireless communication system 100 may include one or more network entities 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be a network that operates in accordance with a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or other systems and radio technologies, including future systems and radio technologies not explicitly mentioned herein.

[0025] The network entities 105 may be dispersed throughout a geographic area and may include devices of different types or with different capabilities to form the wireless communication system 100. In various embodiments, the network entities 105 may be referred to as network elements, mobility elements, radio access network (RAN) nodes, or network equipment, among other terms. In some embodiments, the network entities 105 and the UEs 115 may communicate wirelessly via one or more communication links 125 (e.g., radio frequency (RF) access links). For example, the network entities 105 may support a coverage area 110 (e.g., a geographic coverage area) within which the UEs 115 and the network entities 105 may establish one or more communication links 125. The coverage area 110 may be one example of a geographic area within which the network entities 105 and the UEs 115 may support communication of signals according to one or more radio access technologies (RATs).

[0026] The UEs 115 may be dispersed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be stationary or mobile, or may be both at different times. The UEs 115 may be devices of different types or with different capabilities. Some example UEs 115 are shown in FIG. 1. The UEs 115 described herein may be capable of supporting communication with various types of devices, such as other UEs 115 or network entities 105, as shown in FIG. 1.

[0027] As described herein, a node of the wireless communication system 100, which may be referred to as a network node or a wireless node, may be a network entity 105 (e.g., any network entity described herein), a UE 115 (e.g., any UE described herein), a network controller, an apparatus, a device, a computing system, one or more components, or another suitable processing entity configured to perform any of the techniques described herein. For example, a node may be a UE 115. As another example, a node may be a network entity 105. As another example, a first node may be configured to communicate with a second node or a third node. In one aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a UE 115. In another aspect of this example, the first node may be a UE 115, the second node may be a network entity 105, and the third node may be a network entity 105. In yet other aspects of this embodiment, the first node, the second node, and the third node may be different for these embodiments. Similarly, references to a UE 115, a network entity 105, an apparatus, a device, a computing system, etc. may include disclosure that the UE 115, the network entity 105, the apparatus, the device, the computing system, etc. are nodes. For example, a disclosure that the UE 115 is configured to receive information from the network entity 105 also discloses that the first node is configured to receive information from the second node.

[0028] In some embodiments, the network entities 105 may communicate with the core network 130, with each other, or with both. For example, the network entities 105 may communicate with the core network 130 via one or more backhaul communication links 120 (e.g., according to an S1, N2, N3, or other interface protocol). In some embodiments, the network entities 105 may communicate with each other via the backhaul communication links 120 (e.g., according to an X2, Xn, or other interface protocol), either directly (e.g., directly between the network entities 105) or indirectly (e.g., via the core network 130). In some embodiments, the network entities 105 may communicate with each other via the midhaul communication links 162 (e.g., according to a midhaul interface protocol), or via the fronthaul communication links 168 (e.g., according to a fronthaul interface protocol), or via any combination thereof. The backhaul communication link 120, the midhaul communication link 162, or the fronthaul communication link 168 may be or may include one or more wired links (e.g., electrical links, optical fiber links), one or more wireless links (e.g., radio links, wireless optical links), among other examples or various combinations thereof. The UE 115 may communicate with the core network 130 via the communication link 155.

[0029] One or more of the network entities 105 described herein may include or may be referred to as a base station 140 (e.g., base transceiver station, radio base station, NR base station, access point, radio transceiver, Node B, eNode B (eNodeB, eNB), next generation Node B or gigaNode B (all of which may be referred to as gNB), 5G NB, next-generation eNB (ng-eNB), Home Node B, Home eNode B, or other suitable terminology). In some embodiments, the network entities 105 (e.g., base stations 140) may be implemented in a converged (e.g., monolithic, standalone) base station architecture that may be configured to utilize protocol stacks that are physically or logically integrated within a single network entity 105 (e.g., a single RAN node such as the base station 140).

[0030] In some embodiments, the network entities 105 may be implemented in a split architecture (e.g., split base station architecture, split RAN architecture) that may be configured to utilize a protocol stack that is physically or logically distributed between two or more network entities 105, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration supported by the O-RAN Alliance), or a virtualized RAN (vRAN) (e.g., cloud RAN (C-RAN)). For example, the network entity 105 may include one or more of a central unit (CU) 160, a distributed unit (DU) 165, a radio unit (RU) 170, a RAN Intelligent Controller (RIC) 175 (e.g., a Near-Real Time RIC (RT-RIC), a Non-Real Time RIC (non-RT-RIC)), a Service Management and Orchestration (SMO) 180 system, or any combination thereof. The RU 170 may also be referred to as a radio head, a smart radio head, a remote radio head (RRH), a remote radio unit (RRU), or a transmission reception point (TRP). In a disaggregated RAN architecture, one or more components of the network entity 105 may be co-located, or one or more components of the network entity 105 may be located in distributed locations (e.g., separate physical locations).In some embodiments, one or more network entities 105 of the split RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0031] The division of functionality among the CU 160, the DU 165, and the RU 170 is flexible and can support different functionality depending on which functions (e.g., network layer functions, protocol layer functions, baseband functions, RF functions, and any combination thereof) are performed in the CU 160, the DU 165, or the RU 170. For example, a functional division of a protocol stack may be adopted between the CU 160 and the DU 165, such that the CU 160 can support one or more layers of the protocol stack and the DU 165 can support one or more different layers of the protocol stack. In some embodiments, the CU 160 can host upper protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functionality and signaling (e.g., Radio Resource Control (RRC), service data adaptation protocol (SDAP), Packet Data Convergence Protocol (PDCP)). The CU 160 can be connected to one or more DUs 165 or RUs 170, which can host lower protocol layers, such as layer 1 (L1) (e.g., physical (PHY) layer) or L2 (e.g., radio link control (RLC) layer, medium access control (MAC) layer) functionality and signaling, each of which can be at least partially controlled by the CU 160. Additionally or alternatively, a functional division of the protocol stack may be employed between the DU 165 and the RU 170, such that the DU 165 can support one or more layers of the protocol stack and the RU 170 can support one or more different layers of the protocol stack. The DU 165 can support one or more different cells (e.g., via one or more RUs 170).In some cases, the functional division between the CU 160 and the DU 165 or between the DU 165 and the RU 170 may be within a protocol layer (e.g., some functions related to a protocol layer may be performed by one of the CU 160, the DU 165, or the RU 170, while other functions of the protocol layer may be performed by a different one of the CU 160, the DU 165, or the RU 170). The CU 160 may be further functionally divided into a CU control plane (CU-CP) function and a CU user plane (CU-UP) function. The CU 160 may be connected to one or more DUs 165 via midhaul communication links 162 (e.g., F1, F1-c, F1-u), and the DU 165 may be connected to one or more RUs 170 via fronthaul communication links 168 (e.g., an open fronthaul (FH) interface). In some embodiments, the midhaul communication link 162 or the fronthaul communication link 168 may be implemented according to an interface (e.g., a channel) between layers of a protocol stack supported by the corresponding network entities 105 communicating over such communication link.

[0032] In a wireless communication system (e.g., wireless communication system 100), radio access infrastructure and spectrum resources can support wireless backhaul link capabilities to supplement wired backhaul connections, thereby providing an IAB network architecture (e.g., to the core network 130). In some cases, in an IAB network, one or more network entities 105 (e.g., IAB nodes 104) can be partially controlled by each other. One or more IAB nodes 104 may be referred to as donor entities or IAB donors. One or more DUs 165 or one or more RUs 170 can be partially controlled by one or more CUs 160 associated with the donor network entity 105 (e.g., donor base station 140). One or more donor network entities 105 (e.g., IAB donors) can communicate with one or more additional network entities 105 (e.g., IAB nodes 104) via supported access links and backhaul links (e.g., backhaul communication links 120). An IAB node 104 may include an IAB mobile termination (IAB-MT) that is controlled (e.g., scheduled) by the associated IAB donor's DU 165. The IAB-MT may include a separate set of antennas for relaying communications with the UE 115, or may share the same antenna (e.g., of the RU 170) of the IAB node 104 that is used for access via the IAB node's DU 165 (e.g., referred to as a virtual IAB-MT, vIAB-MT). In some embodiments, the IAB node 104 may include a DU 165 that supports communication links with additional entities (e.g., the IAB node 104, the UE 115) in the access network's (e.g., downstream) relay chain or relay configuration.In such cases, one or more components of the split RAN architecture (e.g., one or more IAB nodes 104, or components of an IAB node 104) may be configured to operate in accordance with the techniques described herein.

[0033] For example, an access network (AN) or RAN may include communications between an access node (e.g., an IAB donor), an IAB node 104, and one or more UEs 115. The IAB donor may facilitate connectivity between the core network 130 and the AN (e.g., via a wired or wireless connection to the core network 130). That is, an IAB donor may refer to a RAN node that has a wired or wireless connection to the core network 130. The IAB donor may include a CU 160 and at least one DU 165 (e.g., with an RU 170), where the CU 160 can communicate with the core network 130 over an interface (e.g., a backhaul link). The IAB donor and IAB node 104 can communicate over an F1 interface according to a protocol (e.g., an F1 AP protocol) that defines signaling messages. Additionally or alternatively, CU160 may communicate with the core network via an interface that may be an example of a portion of a backhaul link, and may communicate with other CU160 (e.g., CU160 associated with an alternative IAB donor) via an Xn-C interface that may be an example of a portion of a backhaul link.

[0034] An IAB node 104 may refer to a RAN node that provides IAB functionality (e.g., access to the UE 115, wireless self-backhaul capability). The DU 165 may function as a distributed scheduling node toward a child node associated with the IAB node 104, and the IAB-MT may function as a scheduled node toward a parent node associated with the IAB node 104. That is, an IAB donor may be referred to as a parent node that communicates with one or more child nodes (e.g., an IAB donor may relay a transmission for a UE through one or more other IAB nodes 104). Additionally or alternatively, an IAB node 104 may also be referred to as a parent node or child node to other IAB nodes 104, depending on the relay chain or relay configuration of the AN. Therefore, the IAB-MT entity of the IAB node 104 can provide a Uu interface for the child IAB node 104 to receive signaling from the parent IAB node 104, and the DU interface (e.g., DU 165) can provide a Uu interface for the parent IAB node 104 to signal to the child IAB node 104 or UE 115.

[0035] For example, the IAB node 104 may be referred to as a parent node that supports communication for a child IAB node, or as a child IAB node that is associated with an IAB donor, or both. The IAB donor may include a CU 160 that has a wired or wireless connection (e.g., backhaul communication link 120) to the core network 130 and may function as a parent node for the IAB node 104. For example, the DU 165 of the IAB donor may relay transmissions to the UE 115 via the IAB node 104, or may directly signal transmissions to the UE 115, or both. The CU 160 of the IAB donor may signal establishment of a communication link to the IAB node 104 via the F1 interface, and the IAB node 104 may schedule transmissions (e.g., transmissions relayed from the IAB donor to the UE 115) via the DU 165. That is, data can be relayed to and from the IAB node 104 via signaling over the NR Uu interface to the MT of the IAB node 104. Communications with the IAB node 104 can be scheduled by the DU 165 of the IAB donor, and communications with the IAB node 104 can also be scheduled by the DU 165 of the IAB node 104.

[0036] When the techniques described herein are applied in the context of a split-RAN architecture, one or more components of the split-RAN architecture may be configured to support DRX enhancement using multiple sidelink feedback channel opportunities as described herein. For example, some operations described as being performed by the UE 115 or a network entity 105 (e.g., a base station 140) may also or alternatively be performed by one or more components of the split-RAN architecture (e.g., the IAB node 104, the DU 165, the CU 160, the RU 170, the RIC 175, the SMO 180).

[0037] The UE 115 may include or be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, and a "device" may also be referred to as a unit, a station, a terminal, or a client, among other examples. The UE 115 may also include or be referred to as a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some embodiments, the UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various items such as a home appliance, a vehicle, a meter, among other examples.

[0038] The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115, which may act as relays, as shown in FIG. 1, and network entities 105 and network equipment, including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples.

[0039] The UE 115 and the network entity 105 can communicate wirelessly with each other over one or more communication links 125 (e.g., access links) using resources associated with one or more carriers. The term “carrier” may refer to a set of RF spectrum resources having a defined physical layer structure for supporting the communication link 125. For example, a carrier used for the communication link 125 may include a portion of an RF spectrum band (e.g., a bandwidth part (BWP)) operating 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 coordinating operation on the carrier, user data, or other signaling. The wireless communication system 100 can support communication with the UE 115 using carrier aggregation or multi-carrier operation. The UE 115 can be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation can be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. Communications between the network entity 105 and other devices may refer to communications between those devices and any portion (e.g., entity, sub-entity) of the network entity 105. For example, when referring to the network entity 105, the terms "transmitting," "receiving," or "communicating" may refer to any portion of the network entity 105 (e.g., base station 140, CU 160, DU 165, RU 170) of the RAN communicating with another device (e.g., directly or through one or more other network entities 105).

[0040] In some embodiments, such as in a carrier aggregation configuration, a carrier may also have acquisition signaling or control signaling that coordinates operation with respect to other carriers. A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute RF channel number (EARFCN)) and may be identified according to a channel raster for detection by the UE 115. A carrier may operate in a standalone mode, in which initial acquisition and connection by the UE 115 may be accomplished via that carrier, or the carrier may operate in a non-standalone mode, in which connection is anchored using a different carrier (e.g., of the same or different radio access technology).

[0041] The communication links 125 shown in the wireless communication system 100 may include, among other transmission configurations, downlink transmissions (e.g., forward link transmissions) from the network entity 105 to the UE 115, uplink transmissions (e.g., reverse link transmissions) from the UE 115 to the network entity 105, or both. A carrier may carry downlink or uplink communications (e.g., in FDD mode) or may be configured to carry downlink and uplink communications (e.g., in TDD mode).

[0042] A carrier may be associated with a particular bandwidth of the RF spectrum, and in some embodiments, the carrier bandwidth may be referred to as the “system bandwidth” of that carrier or wireless communications system 100. For example, the carrier bandwidth may be one of a set of bandwidths (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)) for a particular radio access technology carrier. Devices (e.g., network entities 105, UEs 115, or both) of the wireless communications system 100 may have a hardware configuration that supports communication using a particular carrier bandwidth or may be configurable to support communication using one of a set of carrier bandwidths. In some embodiments, the wireless communications system 100 may include network entities 105 or UEs 115 that support simultaneous communication using carriers associated with multiple carrier bandwidths. In some embodiments, each served UE 115 may be configured to operate using a portion (e.g., a sub-band, BWP) or all of the carrier bandwidth.

[0043] A signal waveform transmitted over 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 MCM techniques, a resource element may refer to a resource of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, where the symbol period and the subcarrier spacing may be inversely proportional. The amount 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), such that a relatively large amount of resource elements (e.g., within a transmission duration) and a relatively higher-order modulation scheme can accommodate a relatively higher communication rate. Wireless communication resources may refer to a combination of RF spectrum resources, time resources, and spatial resources (e.g., spatial layers, beams), where the use of multiple spatial resources can improve the data rate or data integrity for communication with the UE 115.

[0044] One or more numerologies for a carrier may be supported, and a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs with the same or different numerologies. In some embodiments, a UE 115 may be configured with multiple BWPs. In some embodiments, a single BWP for a carrier may be active at a given time, and communication for the UE 115 may be limited to one or more active BWPs.

[0045] The time interval for the network entity 105 or the UE 115 may be, for example, T s =1 / (Δf max N f) seconds, in which case Δf max may represent the supported subcarrier spacing, and N f may represent the supported Discrete Fourier Transform (DFT) sizes. The communication resource time intervals may be organized according to radio frames, each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., in the range 0 to 1023).

[0046] Each frame may include multiple subframes or slots, which are numbered consecutively, and each subframe or slot may have the same duration. In some embodiments, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a certain amount of slots. Alternatively, each frame may include a variable amount of slots, and the amount of slots may depend on the subcarrier spacing. Each slot may include a certain amount of symbol periods (e.g., depending on the length of a cyclic prefix prepended to each symbol period). In some wireless communication systems 100, a slot may be further divided into multiple minislots, which are associated with one or more symbols. Excluding the cyclic prefix, each symbol period may be divided into one or more (e.g., N f The duration of a symbol period may depend on the subcarrier spacing or the frequency band of operation.

[0047] A subframe, slot, minislot, or symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI). In some embodiments, the TTI duration (e.g., the amount of symbol periods within a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

[0048] For communication using the carriers, physical channels may be multiplexed according to various techniques. For example, physical control channels and physical data channels may be multiplexed for signaling over downlink carriers using one or more of time division multiplexing (TDM), frequency division multiplexing (FDM), or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for the physical control channels may be defined by a set of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of that carrier. One or more control regions (e.g., CORESET) may be configured for a set of UEs 115. For example, one or more of the UEs 115 may monitor or search the control region for control information according to one or more search space sets, where each search space set may include one or more control channel candidates at one or more aggregation levels arranged in a cascaded manner. The aggregation level for control channel candidates may refer to the amount of control channel resources (e.g., control channel elements (CCEs)) associated with coded information for a control information format having a given payload size. The search space sets may include a common search space set configured to transmit control information to multiple UEs 115 and a UE-specific search space set for transmitting control information to a specific UE 115.

[0049] The network entity 105 may provide communication coverage via one or more cells, e.g., macro cells, small cells, hot spots, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used in connection with communication with the network entity 105 (e.g., using a carrier) and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), etc.) for distinguishing adjacent cells. In some embodiments, a cell may also refer to the coverage area 110 in which the logical communication entity operates, or a portion (e.g., a sector) of the coverage area 110. Such a cell may 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 network entity 105. For example, a cell may be or include, among other examples, a building, a subset of a building, or an outside space between or overlapping with a coverage area 110.

[0050] A macro cell generally covers a relatively large geographic area (e.g., a few kilometers in radius) and may allow unrestricted access by UEs 115 that subscribe to service with the network provider that supports the macro cell. A small cell may be associated with a lower-power network entity 105 (e.g., a lower-power base station 140) compared to a macro cell, and the small cell may operate using the same or a different (e.g., licensed, unlicensed) frequency band as the macro cell. A small cell may provide unrestricted access to UEs 115 that subscribe to service with the network provider, or it may provide restricted access to UEs 115 that have an association with the small cell (e.g., UEs 115 in a closed subscriber group (CSG), UEs 115 associated with users in their homes or offices). The network entity 105 may support one or more cells and may also support communication via those one or more cells using one or more component carriers.

[0051] In some embodiments, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that can provide access to different types of devices.

[0052] In some embodiments, the network entities 105 (e.g., base stations 140, RUs 170) may be mobile and therefore may provide communication coverage for moving coverage areas 110. In some embodiments, different coverage areas 110 associated with different technologies may overlap, but may be supported by the same network entity 105. In some other embodiments, overlapping coverage areas 110 associated with different technologies may be supported by different network entities 105. The wireless communication system 100 may include, for example, a heterogeneous network in which different types of network entities 105 provide coverage for various coverage areas 110 using the same or different radio access technologies.

[0053] The wireless communication system 100 may support synchronous or asynchronous operation. For synchronous operation, the network entities 105 (e.g., base stations 140) may have similar frame timing, and transmissions from different network entities 105 may be approximately aligned in time. For asynchronous operation, the network entities 105 may have different frame timing, and transmissions from different network entities 105 may, in some embodiments, not be aligned in time. The techniques described herein may be used in connection with either synchronous or asynchronous operation.

[0054] Some UEs 115, such as MTC 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 may refer to data communication technologies that enable devices to communicate with each other or with a network entity 105 (e.g., a base station 140) without human intervention. In some examples, M2M communication or MTC may include communication from devices that incorporate sensors or meters to measure or capture information and relay such information to a central server or application program that uses the information, or present the information to a human who interacts with an application program. Some UEs 115 can be designed to collect information or enable automated behavior of machines or other devices. Example applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business billing.

[0055] Some UEs 115 may be configured to employ a power-reducing operating mode, such as half-duplex communication (e.g., a mode that supports one-way communication via transmission or reception, but not simultaneous transmission and reception). In some embodiments, half-duplex communication may be performed at a reduced peak rate. Other power-saving techniques for the UEs 115 include entering a power-saving deep sleep mode when not engaged in active communication, operating using a limited bandwidth (e.g., in accordance with narrowband communication), or a combination of these techniques. For example, some UEs 115 may be configured to operate using a narrowband protocol type associated with a defined portion or range (e.g., a set of subcarriers or resource blocks (RBs)) within a carrier, within a carrier's guard band, or outside the carrier.

[0056] The wireless communication system 100 may be configured to support ultra-reliable or low-latency communications, or various combinations thereof. For example, the wireless communication system 100 may be configured to support ultra-reliable low-latency communications (URLLC). The UE 115 may be designed to support ultra-reliable, low-latency, or critical functions. Ultra-reliable communications may include private or group communications and may be supported by one or more services, such as push-to-talk, video, or data. Support for ultra-reliable, low-latency functions may include service prioritization, and such services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, and ultra-reliable low-latency may be used interchangeably herein.

[0057] In some embodiments, the UEs 115 may be configured to support direct communication with other UEs 115 via a device-to-device (D2D) communication link 135 (e.g., according to a peer-to-peer (P2P) protocol, a D2D protocol, or a sidelink protocol). In some embodiments, one or more UEs 115 of a group performing D2D communication may be within a coverage area 110 of a network entity 105 (e.g., a base station 140, an RU 170) and may support aspects of such D2D communication being configured (e.g., scheduled) by the network entity 105. In some embodiments, one or more UEs 115 of such a group may be outside the coverage area 110 of the network entity 105 or may be unable or not configured to receive transmissions from the network entity 105. In some embodiments, a group of UEs 115 communicating via D2D communication may support a one-to-many (1:M) system, with each UE 115 transmitting to each of the other UEs 115 in the group. In some embodiments, the network entity 105 may facilitate scheduling of resources for D2D communication. In some other embodiments, D2D communication may occur between the UEs 115 without the involvement of the network entity 105.

[0058] In some systems, the D2D communication link 135 may be an example of a communication channel between vehicles (e.g., UEs 115), such as a sidelink communication channel. In some embodiments, the vehicles may communicate using vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination thereof. The vehicles may signal information related to traffic conditions, signal scheduling, weather, safety, emergency situations, or any other information relevant to the V2X system. In some embodiments, the vehicles in the V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., network entity 105, base station 140, RU 170) using vehicle-to-network (V2N) communication, or both.

[0059] 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 5G core (5G core, 5GC), which may include at least one control plane entity (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) that manages access and mobility, and at least one user plane entity (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)) that routes packets or interconnects to external networks. The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for UEs 115 served by network entities 105 (e.g., base stations 140) associated with the core network 130. User IP packets may be forwarded through a user plane entity, which may provide IP address allocation and other functions. The user plane entity may connect to IP services 150 associated with one or more network operators. The IP services 150 may include access to the Internet, intranet(s), IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0060] The wireless communication system 100 can operate using one or more frequency bands, which may range from 300 megahertz (MHz) to 300 gigahertz (GHz). The 300 MHz to 3 GHz region is commonly known as the ultra-high frequency (UHF) region or decimeter band because wavelengths range in length from approximately 1 decimeter to 1 meter. Although UHF waves may be blocked or redirected by buildings and environmental features, sometimes referred to as clusters, these waves can penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Communications using UHF waves can be associated with smaller antennas and shorter distances (e.g., less than 100 kilometers) compared to communications using lower frequency and longer waves in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz.

[0061] The wireless communications system 100 may also operate using the super high frequency (SHF) region, also known as the centimeter band, which may range from 3 GHz to 30 GHz, or the extremely high frequency (EHF) region of the spectrum, also known as the millimeter band (e.g., 30 GHz to 300 GHz). In some embodiments, the wireless communications system 100 may support millimeter wave (mmW) communications between the UE 115 and the network entity 105 (e.g., base station 140, RU 170), and EHF antennas on capable devices may be smaller and more closely spaced than UHF antennas. In some embodiments, such technology may facilitate the use of antenna arrays within the device. However, propagation of EHF transmissions may experience greater attenuation and shorter distances than SFH or UHF transmissions. The technologies disclosed herein may be employed across transmissions using one or more different frequency ranges, and the designated uses of bands across these frequency ranges may vary by country or regulatory body.

[0062] The wireless communication system 100 may utilize both licensed and unlicensed RF spectrum bands. For example, the wireless communication system 100 may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology using unlicensed bands, such as the 5 GHz industrial, scientific, and medical (ISM) band. While operating using unlicensed RF spectrum bands, devices such as the network entity 105 and the UE 115 may employ carrier sensing for collision detection and avoidance. In some embodiments, operation using the unlicensed band may be based on a carrier aggregation configuration (e.g., LAA) in conjunction with component carriers operating using licensed bands. Operation using the unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

[0063] A network entity 105 (e.g., base station 140, RU 170) or a UE 115 may be equipped with multiple antennas that can be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of the network entity 105 or UE 115 may be arranged in one or more antenna arrays or antenna panels that support MIMO operations or are capable of transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be collocated in an antenna assembly, such as an antenna tower. In some embodiments, antennas or antenna arrays associated with the network entity 105 may be located in various geographic locations. The network entity 105 may include an antenna array having a set of rows and columns of antenna ports that the network entity 105 can use to support beamforming of communications with the UE 115. Similarly, the UE 115 may include one or more antenna arrays that are capable of supporting various MIMO or beamforming operations. Additionally or alternatively, the antenna panel may support RF beamforming for signals transmitted through the antenna ports.

[0064] The network entity 105 or the UE 115 may use MIMO communications to exploit multipath signal propagation and increase spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. Multiple signals may be transmitted by a transmitting device, for example, via different antennas or different combinations of antennas. Similarly, multiple signals may be received by a receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry information associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

[0065] Beamforming, sometimes referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that can be used at a transmitting or receiving device (e.g., network entity 105, UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting and receiving devices. Beamforming can be achieved by combining signals communicated through antenna elements of an antenna array such that some signals propagating along a particular orientation relative to the antenna array experience constructive interference, while other signals experience destructive interference. Adjusting signals communicated through antenna elements may include the transmitting or receiving device applying an amplitude offset, a phase offset, or both to signals carried through its associated antenna element. The adjustment associated with each of the antenna elements can be defined by a beamforming weight set associated with a particular orientation (e.g., relative to the transmitting or receiving device's antenna array or some other orientation).

[0066] The network entity 105 or the UE 115 may use beam sweeping techniques as part of a beamforming operation. For example, the network entity 105 (e.g., base station 140, RU 170) may use multiple antennas or antenna arrays (e.g., antenna panels) to perform a beamforming operation for directional communication with the UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted multiple times along different directions by the network entity 105. For example, the network entity 105 may transmit signals according to different beamforming weight sets associated with different directions of transmission. The transmissions along different beam directions may be used to identify beam directions (e.g., by a transmitting device such as the network entity 105 or by a receiving device such as the UE 115) for subsequent transmission or reception by the network entity 105.

[0067] Some signals, such as data signals associated with a particular receiving device, may be transmitted by a transmitting device (e.g., transmitting network entity 105, transmitting UE 115) along a single beam direction (e.g., a direction associated with the receiving device, such as the receiving network entity 105 or the receiving UE 115). In some embodiments, the beam direction associated with a transmission along a single beam direction may be determined based on signals transmitted along one or more beam directions. For example, the UE 115 may receive one or more of the signals transmitted by the network entity 105 along different directions and may report to the network entity 105 an indication of the signal received by the UE 115 that has the highest signal quality or an acceptable signal quality.

[0068] In some embodiments, transmission by a device (e.g., by the network entity 105 or the UE 115) can be performed using multiple beam directions, and the device can use a combination of digital precoding or beamforming to generate a combined beam for transmission (e.g., from the network entity 105 to the UE 115). The UE 115 can report feedback indicating precoding weights for one or more beam directions, which may correspond to a set of configured beams across the system bandwidth or one or more subbands. The network entity 105 can transmit reference signals (e.g., cell-specific reference signals (CRS), channel state information reference signals (CSI-RS)), which may be precoded or non-precoded. The UE 115 can provide feedback regarding beam selection, which can be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, or a port selection type codebook). Although these techniques are described with reference to signals transmitted along one or more directions by the network entity 105 (e.g., base station 140, RU 170), the UE 115 may employ similar techniques to transmit a signal multiple times along different directions (e.g., to identify a beam direction for subsequent transmission or reception by the UE 115) or to transmit a signal along a single direction (e.g., to transmit data to a receiving device).

[0069] A receiving device (e.g., UE 115) may perform receive operations according to multiple receive configurations (e.g., directional listening) when receiving various signals from the receiving device (e.g., network entity 105), such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, the receiving device may perform receive according to multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of the antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of the antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some embodiments, the receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). A single receiving configuration may be aligned along a beam direction determined based on listening along different receiving configuration directions (e.g., a beam direction determined to have the highest signal strength, highest signal-to-noise ratio (SNR), or acceptable signal quality based on listening along multiple beam directions).

[0070] The wireless communication system 100 may be a packet-based network operating according to a layered protocol stack. In the user plane, communication at the bearer or PDCP layer may be IP-based. The RLC layer may perform packet segmentation and reassembly to communicate over logical channels. The MAC layer may perform priority handling and multiplexing of logical channels onto transport channels. The MAC layer may also implement error detection, error correction, or both to support retransmissions to improve link efficiency. In the control plane, the RRC layer may provide establishment, configuration, and maintenance of an RRC connection between the UE 115 and the network entity 105 or core network 130 supporting radio bearers for user plane data. The PHY layer may map transport channels to physical channels.

[0071] The UE 115 and the network entity 105 can support retransmission of data to increase the likelihood of successful reception. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood of correct reception of data over a communication link (e.g., communication link 125, D2D communication link 135). HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions). In some embodiments, a device can support same-slot HARQ feedback, in which case the device can provide HARQ feedback within a particular slot regarding data received via a previous symbol in that slot. In some other embodiments, the device can provide HARQ feedback in a subsequent slot or according to some other time interval.

[0072] While operating in the DRX mode, the UE 115 can receive a grant for scheduling a sidelink data message for the UE 115 on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The UE 115 can transmit at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity of the set of feedback channel opportunities. The UE 115 can start a round-trip timer (e.g., an RTT timer) associated with the at least one feedback message based at least in part on the at least one feedback channel opportunity, during which the UE 115 refrains from monitoring for retransmissions of the sidelink data message.

[0073] 2 illustrates an example of a wireless communication system 200 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The wireless communication system 200 may implement aspects of the wireless communication system 100. The wireless communication system 200 may include a UE 205 and a UE 210, which may be examples of corresponding devices described herein.

[0074] A wireless communication system may support HARQ-ACK operations for cellular (e.g., Uu interface-based) and / or sidelink (e.g., PC5 interface-based) communications. The HARQ-ACK operation confirms that a receiving device was able to successfully receive and decode a data message (and / or a grant scheduling the transmission of the data message) or that a receiving device was unable to successfully receive and decode a data message (and / or a grant scheduling the data message). In some aspects, resources (e.g., time resources, frequency resources, spatial resources, and / or code resources) used to convey HARQ-ACK feedback may be indicated in the grant scheduling the data message and / or may be known (e.g., configured (pre) in the network or employed). A transmitting device that receives an ACK indication in the HARQ-ACK feedback considers its data message transmission successful. A transmitting device that receives a NACK indication in the HARQ-ACK feedback or receives no feedback considers its data message transmission unsuccessful. Accordingly, the transmitting device can send another grant to the receiving device scheduling a retransmission to the receiving device of the data message associated with the NACK. In some aspects, the data message can be associated with a HARQ process identifier used for the initial data message transmission, the HARQ-ACK feedback transmission for the data message, and / or any associated retransmissions of the data message. The HARQ process identifier associated with the data message can be indicated in the grant scheduling the data message, in RRC signaling (pre-)configuring aspects of the data message, or in separate signaling.

[0075] For sidelink communications, multiple feedback channel opportunities (e.g., PSFCH opportunities or PSFCH candidates) can be allocated for sidelink data messages. Each feedback channel opportunity generally defines an opportunity for a receiving device to transmit HARQ-ACK feedback for a sidelink data message. For example, in some networks, a PSFCH HARQ timeline provides one opportunity (e.g., one feedback channel opportunity) for a PSFCH transmission. If the HARQ-ACK feedback occurs in a shared radio frequency spectrum band, a listen-before-talk (LBT) procedure can be performed on that channel immediately before or initially during the feedback channel opportunity. If the LBT procedure fails (e.g., if the channel is busy and therefore unavailable for communicating HARQ-ACK feedback), the transmitting device can interpret the absence of a feedback message as a NACK for the corresponding sidelink data message and schedule a retransmission.

[0076] The wireless communication system 200 may support multiple PSFCH opportunities or candidates (e.g., feedback channel opportunity(s)) for HARQ-ACK feedback (e.g., feedback message transmission). That is, to accommodate one physical sidelink shared channel (PSSCH) transmission (e.g., a sidelink data message), multiple PSFCH candidates (e.g., a set of feedback channel opportunities) may be allocated across different slots, with or without multiple frequency-domain multiplexing opportunities in different LBT subbands. A receiving device typically transmits HARQ-ACK feedback on the earliest / closest PSFCH candidate that clears the LBT procedure. For example, a UE (such as UE 205 and / or UE 210) may determine the slot(s) and / or resource block (RB) set(s) for HARQ-ACK feedback transmission based on the HARQ timeline and (pre-)configured resources for multiple PSFCH candidates. Thus, one PSFCH slot (e.g., a slot in which a sidelink data message is transmitted) may be mapped to different PSFCH instances in the time domain and / or different PSFCH resources in different RB set(s).

[0077] A UE (e.g., UE 205 and / or UE 210) may also operate in a DRX mode in which, when there is no expected uplink or downlink data (or sidelink data), the UE enters a sleep mode (e.g., turns off one or more modules, components, functions, etc.) and refrains from monitoring the channel. In some aspects, the DRX operation may be for a particular HARQ process identifier, such that while in the DRX sleep mode for that HARQ identifier associated with a given sidelink communication, the UE can switch to other operations or communications (e.g., perform other communications or functions during the DRX sleep period for that HARQ process identifier). This allows the UE to conserve power (at least for that HARQ process identifier) ​​by turning off such modules or functions.

[0078] For cellular networks (e.g., Uu-based networks), a DRX procedure can be defined for the UE. In the downlink, the UE can start an RTT timer (e.g., drx-HARQ-RTT-TimerDL) for the corresponding HARQ process after HARQ feedback. If the drx-HARQ-RTT-TimerDL timer expires and data was not successfully decoded, the UE starts a retransmission timer (e.g., drx-RetransmissionTimerDL) for the corresponding HARQ process after the expiration of the drx-HARQ-RTT-TimerDL timer. In the uplink, the UE starts the drx-HARQ-RTT-TimerUL for the corresponding HARQ process at the first symbol after the end of the first transmission (in a bundle) of the corresponding PUSCH transmission. If the drx-HARQ-RTT-TimerUL timer expires, the UE starts the drx-RetransmissionTimerUL timer for the corresponding HARQ process at the first symbol after the expiration of drx-HARQ-RTT-TimerUL.For NR-U communication, if the PDSCH-to-HARQ_feedback timing value indicates a non-numeric k1 value, the UE starts the drx-RetransmissionTimerDL timer at the first symbol after the PDSCH transmission for the corresponding HARQ process.

[0079] However, such techniques may be insufficient in some embodiments to support HARQ for sidelink communications. In the case of unicast or groupcast option 2 transmissions, the RTT timer used for sidelink communications (e.g., sl-drx-HARQ-RTT-Timer) is started at the first slot after the corresponding PSFCH instance carrying HARQ-ACK feedback or if the HARQ-ACK feedback is dropped due to priority rules. In the case of groupcast option 1 sidelink communications (e.g., NACK-only HARQ-ACK feedback), the sl-drx-HARQ-RTT-Timer is started at the first slot after the corresponding PSFCH instance carrying NACK feedback or if the NACK feedback is dropped due to priority rules or if the NACK feedback is not sent due to an acknowledgment (e.g., ACK). However, if multiple PSFCH candidates are introduced, this may result in confusion regarding when the UE starts the RTT timer (e.g., ambiguity regarding which PSFCH opportunity is associated with the UE starting the sl-drx-HARQ-RTT-Timer).

[0080] Thus, aspects of the techniques described herein provide various techniques for a UE (e.g., the UE 205 in this example) to determine when to activate or start an RTT timer for a sidelink data message when a set of feedback channel opportunities (e.g., PSFCH opportunities or PSFCH candidates) is indicated for that sidelink data message. For example, at 215, the UE 210 (e.g., the transmitting device, or the transmitting sidelink UE in this example) may transmit or provide a grant to the UE 205 to schedule the sidelink data message. The sidelink data message may be scheduled on a shared radio frequency spectrum band (e.g., in an unlicensed band where the LBT procedure is performed prior to transmission on the channel). The grant may include a sidelink control information-1 (SCI-1) message transmitted on a physical sidelink control channel (PSCCH) and / or an SCI-2 message transmitted on the PSSCH. In some examples, the grant may include both an SCI-1 message and an SCI-2 message. The UE 210 may transmit or provide a sidelink data message to the UE 205 in accordance with the grant. The grant may indicate or identify a set of feedback channel opportunities (e.g., PSFCH opportunities or PSFCH candidates) associated with the sidelink data message. The set of feedback channel opportunities may be within the same LBT band(s) and / or RB set(s) for the sidelink data message and / or grant, or within different LBT band(s) and / or RB set(s). The set of feedback channel opportunities may be within the same slot(s) or different slot(s) for the sidelink data message and / or grant.

[0081] The UE 205 may receive or obtain a grant and may monitor allocated resources for receiving or obtaining a sidelink data message. The UE 205 may identify or determine a feedback status for the sidelink data message. The feedback status may include an ACK status if the UE 205 is able to successfully receive and decode (e.g., recover sidelink data from) the sidelink data message and / or the grant scheduling the sidelink data message, or may include a NACK status if the UE 205 is unable to successfully receive and decode the sidelink data message and / or the grant scheduling the sidelink data message. Accordingly, the UE 205 may transmit or provide 220 a feedback message indicating the feedback status of the sidelink data message during at least one feedback channel opportunity from the set of feedback channel opportunities.

[0082] The UE 205 may initiate or start a round-trip timer (e.g., an RTT timer, Sl-drx-HARQ-RTT-Timer) based at least on the feedback channel opportunity in which the feedback message was transmitted. For example, the UE 205 may start the RTT timer at the first symbol or slot after the feedback channel opportunity in which the feedback message was transmitted, after the first feedback channel opportunity in the set, after an intermediate feedback channel opportunity in the set, or after the last feedback channel opportunity in the set of feedback channel opportunities. In some embodiments, the RTT timer may be started after a feedback channel opportunity associated with a successful LBT procedure (e.g., based on the result of an LBT procedure performed immediately before or first performed during each feedback channel opportunity).

[0083] In some embodiments, the duration of the RTT timer may be selected, modified, or set to a value based on the feedback channel opportunity in the set after which the RTT timer is started. For example, if the UE 205 starts the RTT timer after the first or early PSFCH opportunity in the set, the duration of the RTT timer may be extended (e.g., to extend beyond the remaining PSFCH opportunities in the set). As another example, if the UE 205 starts the RTT timer after the last or later PSFCH opportunity in the set, the duration of the RTT timer may be shortened in anticipation of a retransmission of a sidelink data message. In some embodiments, the duration of the RTT timer may be based on when a retransmission is expected to be scheduled. For example, the duration of the RTT timer may be based on when the UE 205 anticipates that a retransmission of a sidelink data message will be scheduled by the UE 210.

[0084] While the RTT timer is running, the UE 205 may generally refrain from monitoring for retransmissions of sidelink data messages. After expiration of the RTT timer, the UE 205 may start or activate a retransmission timer (e.g., sl-drx-RetransmissionTimer) during which the UE 205 monitors for a grant scheduling a retransmission of the sidelink data message and / or for a retransmission of the sidelink data message. That is, the UE 205 may configure the retransmission timer with a duration that covers the expected reception of a grant and a retransmission of the sidelink data message. In some embodiments, the duration of the retransmission timer may be selected, modified, or set to a value based on a feedback channel opportunity in the set after which the RTT timer is started. For example, if the UE 205 starts the RTT timer after the first or initial PSFCH opportunity in the set, the duration of the retransmission timer may be extended (e.g., to reduce the retransmission time). While the retransmission timer is running (e.g., not expired), the UE 205 may generally monitor for retransmissions of the sidelink data message (e.g., for grants to schedule retransmissions and / or for retransmissions of the sidelink data message).

[0085] 3A-3C illustrate an example feedback configuration 300 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The feedback configuration 300 may implement aspects of the wireless communication systems 100 and / or 200. Aspects of the feedback configuration 300 may be implemented in or by a UE, which may be an example of a corresponding device described herein.

[0086] As mentioned above, aspects of the techniques described herein provide for a UE to initiate or start an RTT timer after a feedback channel opportunity (e.g., a PSFCH candidate) in a set of feedback channel opportunities based at least in part on which PSFCH candidate is selected. The UE may receive a sidelink data message, determine a feedback status for the message, and send a feedback message indicating the feedback message to a transmitting device (e.g., a sidelink UE that schedules transmission of the sidelink data message to the UE). The UE may start an RTT timer after one of the PSFCH candidates based at least in part on which PSFCH candidate is selected for transmitting the feedback message.

[0087] For example, referring first to the feedback configuration 300-a of FIG. 3A, a UE may receive or obtain a grant to schedule a sidelink data message for that UE on a shared (e.g., unlicensed) spectrum. This may include the UE receiving a grant 305 in an SCI message(s) scheduling a sidelink data message 310, the sidelink data message 310 being received on the PSSCH. The grant 305 may indicate or identify resources (e.g., time resources, frequency resources, spatial resources, or code resources) for the sidelink data message 310 on the PSSCH. The grant 305 may also indicate or identify a set of feedback channel opportunities. In the non-limiting example shown in the feedback configuration 300-a, three feedback channel opportunities are shown by way of example only. Thus, in this example, the set of feedback channel opportunities includes feedback channel opportunity 315 (e.g., for PSFCH candidate #0), feedback channel opportunity 320 (e.g., for PSFCH candidate #1), and feedback channel opportunity 325 (e.g., for PSFCH candidate #2).

[0088] Each PSFCH candidate in the set of PSFCH candidates (e.g., a set of feedback channel opportunities) may generally identify resources (e.g., time, frequency, spatial, or code resources) and / or other parameters to be used by the UE to transmit a feedback message indicating the feedback status of the sidelink data message 310 (e.g., whether the UE was able to successfully receive and decode the grant 305 and / or the sidelink data message 310). As described, the sidelink data message may be communicated in a shared or unlicensed spectrum, such that an LBT procedure is performed immediately before or at the beginning of each PSFCH candidate in the set to determine whether the feedback message may be transmitted (e.g., to verify that the channel is free or available for use).

[0089] Feedback configuration 300-a illustrates an example embodiment in which the UE starts the RTT timer after the first feedback channel opportunity in the set of feedback channel opportunities (e.g., at the first symbol or slot after feedback channel opportunity 315). That is, the UE can identify or determine which PSFCH candidate in the set is the first PSFCH candidate (e.g., PSFCH candidate #0) and start the RTT timer at the first symbol or slot after the first PSFCH candidate in the set. The UE can identify the first PSFCH candidate in the set based on grant 305 or other signaling that (pre-)configures the set of PSFCH candidates for the HARQ process associated with the sidelink data message. That is, in this example embodiment, the UE can default to the first PSFCH candidate, after which the RTT timer is started.

[0090] In some aspects, the UE may or may not be able to transmit a feedback message after the first PSFCH candidate, but can still initiate or start the RTT timer after the first PSFCH candidate. That is, the UE may fail the LBT in the first slot (e.g., the slot in which the first PSFCH candidate is), but the UE can still start the RTT timer after the feedback channel opportunity 315. Instead, the UE can continue to perform an LBT procedure before each PSFCH candidate and transmit a feedback message in the PSFCH candidate associated with the successful LBT procedure.

[0091] In some aspects, the duration of a retransmission (ReTx) timer (e.g., sl-drx-RetransmissionTimer) is based on starting the RTT timer after the first PSFCH candidate (e.g., extending the duration of the ReTx timer). As mentioned above, the UE may be operating in DRX mode, in which the UE sleeps for the HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE may monitor for grants scheduling retransmissions of the sidelink data message and / or for retransmissions of the sidelink data message. In the feedback configuration 300-a, this may include the UE monitoring for grants 330 scheduling retransmissions of the sidelink data message 335. In some embodiments, a longer ReTx timer may help adapt to the uncertainty of the HARQ-ACK LBT for that channel.

[0092] Referring now to feedback configuration 300-b of FIG. 3B , a UE may receive or obtain a grant to schedule a sidelink data message for the UE on a shared (e.g., unlicensed) spectrum. This may include the UE receiving a grant 305 in an SCI message(s) scheduling a sidelink data message 310, which is received on the PSSCH. The grant 305 may indicate or identify resources in the PSSCH for the sidelink data message 310. The grant 305 may also indicate or identify a set of feedback channel opportunities. In the non-limiting example shown in feedback configuration 300-b, three feedback channel opportunities are shown by way of example only. Thus, in this example, the set of feedback channel opportunities includes feedback channel opportunity 315 (e.g., for PSFCH candidate #0), feedback channel opportunity 320 (e.g., for PSFCH candidate #1), and feedback channel opportunity 325 (e.g., for PSFCH candidate #2).

[0093] Each PSFCH candidate in the set of PSFCH candidates (e.g., a set of feedback channel opportunities) may generally identify resources and / or other parameters to be used by the UE to transmit a feedback message indicating the feedback status of the sidelink data message 310. As described, the sidelink data message may be communicated in a shared spectrum or an unlicensed spectrum, such that an LBT procedure is performed immediately before or at the beginning of each PSFCH candidate in the set to determine whether a feedback message may be transmitted.

[0094] Feedback configuration 300-b illustrates an example embodiment in which the UE starts the RTT timer after the first feedback channel opportunity in a set of feedback channel opportunities that is associated with a successful LBT procedure (e.g., at the first symbol or slot after that feedback channel opportunity). That is, the UE may perform an LBT procedure immediately before or at the beginning of each PSFCH candidate and start the RTT timer at the first symbol or slot after the first PSFCH candidate in the set that has a successful LBT procedure. That is, in this example embodiment, the UE may base the PSFCH candidate after which the RTT timer is started on the PSFCH candidate based on the results of the LBT procedure performed for each PSFCH candidate.

[0095] In feedback configuration 300-b, the UE may perform an LBT procedure associated with a feedback channel opportunity 315 and determine that the LBT procedure was unsuccessful (e.g., the UE was unable to capture the channel). The UE may perform another LBT procedure associated with a feedback channel opportunity 320 and determine that the LBT procedure was successful (e.g., the UE was able to capture the channel for transmitting a feedback message). Thus, in this example, the UE may start or activate an RTT timer after the feedback channel opportunity 320, in which case the UE refrains from monitoring for a grant 330 scheduling a retransmission of the sidelink data message 335 and, optionally, transmits the feedback message during the feedback channel opportunity 320.

[0096] If the UE determines that each PSFCH candidate in the set is associated with an unsuccessful LBT procedure (e.g., the LBT procedure fails for all PSFCH candidates), the UE may start the RTT timer after the last PSFCH candidate in the set (e.g., after feedback channel opportunity 325). For example, the UE may identify or determine the last PSFCH candidate in the set and, based on each PSFCH candidate having an unsuccessful LBT procedure, start the RTT timer after the last feedback channel opportunity (e.g., after feedback channel opportunity 320).

[0097] Thus, the feedback configuration 300-b illustrates an embodiment in which a sidelink receiving device (e.g., UE) starts the RTT timer immediately after the first PSFCH transmission or, if all LBT procedures have failed, immediately after the last PSFCH candidate slot. Starting the RTT timer after a feedback message transmission allows the UE to start the retransmission timer with more precise timing (e.g., when ACK / NACK feedback is detected at the sidelink transmitting device). If the LBT procedure fails for each PSFCH candidate, the sidelink transmitting device can assume a NACK after the last PSFCH candidate and retransmit the transport block (TB) (e.g., the sidelink data message 335). Thus, the RTT timer can be started after the last PSFCH candidate if a shared or unlicensed channel is unavailable for transmitting the feedback message.

[0098] In some embodiments, the UE may transmit or provide multiple feedback message transmissions to ensure that the transmitting device can receive the feedback status indication. If the transmitting device determines that the HARQ-ACK feedback has been missed or dropped (e.g., not received), it may also consider starting the RTT timer after the transmission of the first transmitted feedback message if the feedback message transmission is repeated for the remaining PSFCH candidates. If a feedback message has been transmitted only once (e.g., after the first PSFCH candidate associated with a successful LBT procedure) but not received by the transmitting device, the transmitting device may wait until the last PSFCH candidate, assume a NACK, and retransmit the sidelink data message 335. In that situation, the ReTx timer may have been started too early. Therefore, the duration of the ReTx timer may also be extended based on the PSFCH candidate after which the RTT timer is started.

[0099] As mentioned above, the UE may be operating in DRX mode, in which the UE sleeps for a HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE may monitor for grants scheduling retransmissions of the sidelink data message and / or for retransmissions of the sidelink data message. In feedback configuration 300-b, this may include the UE monitoring for grants scheduling retransmissions of the sidelink data message 335.

[0100] Referring to the feedback configuration 300-c of FIG. 3C , a UE may receive or obtain a grant to schedule a sidelink data message for the UE on a shared (e.g., unlicensed) spectrum. This may include the UE receiving a grant 305 in an SCI message(s) scheduling a sidelink data message 310, which is received on the PSSCH. The grant 305 may indicate or identify resources on the PSSCH for the sidelink data message 310. The grant 305 may also indicate or identify a set of feedback channel opportunities. In the non-limiting example shown in the feedback configuration 300-c, three feedback channel opportunities are shown by way of example only. Thus, in this example, the set of feedback channel opportunities includes a feedback channel opportunity 315 (e.g., for PSFCH candidate #0), a feedback channel opportunity 320 (e.g., for PSFCH candidate #1), and a feedback channel opportunity 325 (e.g., for PSFCH candidate #2).

[0101] Each PSFCH candidate in the set of PSFCH candidates (e.g., a set of feedback channel opportunities) may generally identify resources and / or other parameters to be used by the UE to transmit a feedback message indicating the feedback status of the sidelink data message 310. As described, the sidelink data message 310 may be communicated in a shared spectrum or an unlicensed spectrum, such that an LBT procedure is performed immediately before or at the beginning of each PSFCH candidate in the set to determine whether a feedback message may be transmitted.

[0102] Feedback configuration 300-c illustrates an example embodiment in which the UE starts the RTT timer after the last feedback channel opportunity in the set of feedback channel opportunities. That is, the UE may or may not perform an LBT procedure immediately before or at the beginning of each PSFCH candidate, and may start the RTT timer at the first symbol or slot after the last PSFCH candidate, regardless of the outcome of the LBT procedure(s). That is, in this example, the UE may base the PSFCH candidate after which the RTT timer is started on PSFCH candidate #2 being the last PSFCH candidate in the set of PSFCH candidates.

[0103] Thus, in this embodiment, the UE may initiate or start the RTT timer after the feedback channel opportunity 320, in which case the UE refrains from monitoring for grants 330 scheduling retransmissions of the sidelink data message 335.

[0104] Thus, feedback configuration 300-c illustrates an example embodiment in which a sidelink receiving device (e.g., a UE) starts the RTT timer immediately after the last PSFCH candidate slot. Starting the RTT timer after the last PSFCH candidate can reduce delays, such as when a feedback message is transmitted at or near the last PSFCH candidate in a set (or when HARQ-ACK feedback is missed by the transmitting device, such as in a groupcast option 1 scenario). For groupcast option 1, the UE (e.g., a sidelink transmitting device) can wait until the last PSFCH candidate to determine the feedback status (e.g., to save power, prioritize processing / communication, etc.). To ensure that a retransmission occurs after the retransmission timer has started, the transmitting device can select a ReTx resource after the last PSFCH candidate and / or can also shorten the duration of the RTT timer to allow monitoring of the ReTx resource.

[0105] As mentioned above, the UE may be operating in DRX mode, in which the UE sleeps for a HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE may monitor for grants scheduling retransmissions of the sidelink data message and / or for retransmissions of the sidelink data message. In the feedback configuration 300-c, this may include the UE monitoring for grants scheduling retransmissions of the sidelink data message 335.

[0106] 4 illustrates an example feedback configuration 400 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The feedback configuration 400 may implement aspects of the wireless communication systems 100 and / or 200 and / or the feedback configuration 300. Aspects of the feedback configuration 400 may be implemented in or by a UE, which may be an example of a corresponding device described herein.

[0107] As mentioned above, aspects of the techniques described herein provide for a UE to initiate or start an RTT timer after a feedback channel opportunity (e.g., a PSFCH candidate) in a set of feedback channel opportunities based at least in part on which PSFCH candidate is selected. The UE may receive a sidelink data message, determine a feedback status for the message, and send a feedback message indicating the feedback message to a transmitting device (e.g., a sidelink UE that schedules transmission of the sidelink data message to the UE). The UE may start an RTT timer after one of the PSFCH candidates based at least in part on which PSFCH candidate is selected for transmitting the feedback message.

[0108] For example, a UE may receive or obtain a grant to schedule a sidelink data message for the UE on a shared (e.g., unlicensed) spectrum. This may include the UE receiving a grant in SCI message(s) scheduling the sidelink data message, which is received on the PSSCH. The grant may indicate or identify resources (e.g., time resources, frequency resources, spatial resources, or code resources) for the sidelink data message on the PSSCH. The grant may also indicate or identify a set of feedback channel opportunities. In the non-limiting example shown in FIG. 4, three feedback channel opportunities are shown by way of example only. Thus, in this example, the set of feedback channel opportunities includes feedback channel opportunity 405 (e.g., for PSFCH candidate #0), feedback channel opportunity 410 (e.g., for PSFCH candidate #1), and feedback channel opportunity 415 (e.g., for PSFCH candidate #2).

[0109] However, in the embodiment shown in FIG. 4, the duration of the RTT timer can be selected based on the first feedback channel opportunity in the set associated with starting the RTT timer. That is, in some embodiments, the grant initially scheduling a sidelink data message transmission to the UE can also identify the retransmission resources to be used. Thus, the UE can know when it needs to start the retransmission timer to monitor for retransmission of the sidelink data message. If the UE knows the retransmission resources (e.g., the expected scheduling time for the retransmission) of the sidelink data message, the UE can more accurately select the RTT duration. In some aspects, this may include setting the RTT timer based on when the RTT timer starts (e.g., after which PSFCH candidate) within the set of PSFCH candidate locations and the start of the retransmission resources. This may include setting the RTT timer duration to expire a (pre)defined time before the start of the retransmission resources.

[0110] 4, the RTT timer may be started after feedback channel opportunity 405, after feedback channel opportunity 410, or after feedback channel opportunity 415, and the duration of the RTT timer may be set based on the PSFCH candidate after which the RTT timer is selected. For example, if the RTT timer is started after feedback channel opportunity 405, the UE may extend the duration of the RTT timer. If the RTT timer is started after feedback channel opportunity 410, the UE may shorten the duration of the RTT timer or use a (pre-)configured duration. If the RTT timer is started after feedback channel opportunity 415, the UE may shorten the duration of the RTT timer. This may support an RTT timer duration that is different (e.g., modified) from the (pre-)configured or determined RTT timer duration.

[0111] Accordingly, the UE may send a feedback message to the transmitting device and may refrain from monitoring for retransmissions for the duration of the RTT timer. Upon expiration of the RTT timer, the UE may switch to an awake or active state in DRX mode and monitor the channel for grants scheduling retransmissions of sidelink messages and / or retransmissions of sidelink messages.

[0112] 5 shows a block diagram 500 of a device 505 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The device 505 may be one example of aspects of a UE 115 as described herein. The device 505 may include a receiver 510, a transmitter 515, and a communications manager 520. The device 505 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0113] The receiver 510 may provide a means for receiving information, such as packets, user data, control information, or any combination thereof, associated with various traffic channels (e.g., control channels, data channels, traffic channels associated with DRX enhancement using multiple sidelink feedback channel opportunities). The information may be passed to other components of the device 505. The receiver 510 may utilize a single antenna or a set of multiple antennas.

[0114] The transmitter 515 may provide a means for transmitting signals generated by other components of the device 505. For example, the transmitter 515 may transmit information such as packets, user data, control information, or any combination thereof associated with various traffic channels (e.g., control channels, data channels, traffic channels associated with DRX enhancement using multiple sidelink feedback channel opportunities). In some embodiments, the transmitter 515 may be collocated with the receiver 510 within a transceiver module. The transmitter 515 may utilize a single antenna or a set of multiple antennas.

[0115] The communications manager 520, the receiver 510, the transmitter 515, or various combinations thereof or various components thereof may be examples of means for performing various aspects of DRX enhancement using multiple sidelink feedback channel opportunities as described herein. For example, the communications manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof may support a method for performing one or more of the functions described herein.

[0116] In some embodiments, the communications manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof, may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a digital signal processor (DSP), a central processing unit (CPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a microcontroller, discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or supporting means for performing the functions described in this disclosure. In some embodiments, the processor and a memory coupled to the processor may be configured to perform one or more of the functions described herein (e.g., by the processor executing instructions stored in the memory).

[0117] Additionally or alternatively, in some embodiments, the communications manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof, may be implemented in code executed by a processor (e.g., as communications management software or firmware). When implemented in code executed by a processor, the functionality of the communications manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, a microcontroller, or any combination of these or other programmable logic devices (e.g., configured as or supporting means for performing the functions described in this disclosure).

[0118] In some embodiments, communications manager 520 can be configured to perform various operations (e.g., receiving, acquiring, monitoring, outputting, transmitting) using or in cooperation with receiver 510, transmitter 515, or both. For example, communications manager 520 can receive information from receiver 510 and transmit information to transmitter 515, or can be integrated in combination with receiver 510, transmitter 515, or both to acquire information, output information, or perform various other operations as described herein.

[0119] The communications manager 520 may support wireless communications in the UE according to embodiments as disclosed herein. For example, the communications manager 520 may be configured or support means for receiving, while operating in DRX mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The communications manager 520 may be configured or support means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message. The communications manager 520 may be configured or support means for starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of the sidelink data message.

[0120] By including or configuring the communications manager 520 according to embodiments as described herein, the device 505 (e.g., a processor controlling or coupled to the receiver 510, the transmitter 515, the communications manager 520, or a combination thereof) can support techniques for improved RTT timer startup when multiple PSFCH candidates are indicated for a sidelink data message. The RTT timer can be started after the first PSFCH candidate, after an intermediate candidate, after the last PSFCH candidate, or based on the results of the LBT procedure performed for each PSFCH candidate.

[0121] 6 shows a block diagram 600 of a device 605 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The device 605 may be one example of aspects of the device 505 or the UE 115 as described herein. The device 605 may include a receiver 610, a transmitter 615, and a communications manager 620. The device 605 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0122] The receiver 610 may provide a means for receiving information, such as packets, user data, control information, or any combination thereof, associated with various traffic channels (e.g., control channels, data channels, traffic channels associated with DRX enhancement using multiple sidelink feedback channel opportunities). The information may be passed to other components of the device 605. The receiver 610 may utilize a single antenna or a set of multiple antennas.

[0123] The transmitter 615 may provide a means for transmitting signals generated by other components of the device 605. For example, the transmitter 615 may transmit information such as packets, user data, control information, or any combination thereof associated with various traffic channels (e.g., control channels, data channels, traffic channels associated with DRX enhancement using multiple sidelink feedback channel opportunities). In some embodiments, the transmitter 615 may be collocated with the receiver 610 within a transceiver module. The transmitter 615 may utilize a single antenna or a set of multiple antennas.

[0124] The device 605, or various components thereof, may be an example of a means for performing various aspects of DRX enhancement using multiple sidelink feedback channel opportunities, as described herein. For example, the communications manager 620 may include a grant manager 625, a feedback manager 630, an RTT manager 635, or any combination thereof. The communications manager 620 may be an example of aspects of the communications manager 520, as described herein. In some embodiments, the communications manager 620, or various components thereof, may be configured to perform various operations (e.g., receiving, acquiring, monitoring, outputting, transmitting) using or in cooperation with the receiver 610, the transmitter 615, or both. For example, the communications manager 620 may receive information from the receiver 610 and transmit information to the transmitter 615, or may be integrated in combination with the receiver 610, the transmitter 615, or both to acquire information, output information, or perform various other operations as described herein.

[0125] The communications manager 620 may support wireless communications in the UE according to embodiments as disclosed herein. The grant manager 625 may be configured or support means for receiving, while operating in DRX mode, grants for scheduling sidelink data messages for the UE on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages. The feedback manager 630 may be configured or support means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message. The RTT manager 635 may be configured or support means for starting, based on the at least one feedback channel opportunity, a round trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of the sidelink data message.

[0126] FIG. 7 shows a block diagram 700 of a communications manager 720 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The communications manager 720 may be an example of aspects of the communications manager 520, the communications manager 620, or both, as described herein. The communications manager 720, or various components thereof, may be an example of a means for performing various aspects of the DRX enhancement using multiple sidelink feedback channel opportunities, as described herein. For example, the communications manager 720 may include a grant manager 725, a feedback manager 730, an RTT manager 735, a PSFCH opportunity manager 740, an LBT manager 745, an RTT duration manager 750, or any combination thereof. Each of these components may communicate with each other directly or indirectly (e.g., via one or more buses).

[0127] The communications manager 720 may support wireless communications in the UE according to embodiments as disclosed herein. The grant manager 725 may be configured or support means for receiving, while operating in DRX mode, grants for scheduling sidelink data messages for the UE on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages. The feedback manager 730 may be configured or support means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message. The RTT manager 735 may be configured or support means for starting, based on the at least one feedback channel opportunity, a round trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of the sidelink data message.

[0128] In some embodiments, the PSFCH opportunity manager 740 may be configured or support a means for identifying a first feedback channel opportunity in a set of feedback channel opportunities, and a round-trip timer is started after the first feedback channel opportunity.

[0129] In some embodiments, the PSFCH opportunity manager 740 may be configured or support a means for determining that an LBT procedure performed before a first feedback channel opportunity was unsuccessful. In some embodiments, the PSFCH opportunity manager 740 may be configured or support a means for transmitting at least one feedback message at a subsequent feedback channel opportunity in a set of feedback channel opportunities associated with a successful LBT procedure while starting a round-trip timer after the first feedback channel opportunity.

[0130] In some embodiments, the PSFCH opportunity manager 740 may be configured with or may support a means for extending the duration of the retransmission timer while the UE monitors the sidelink channel for a second grant for scheduling a retransmission of the sidelink data message based on the round-trip timer being started after the first feedback channel opportunity.

[0131] In some embodiments, LBT manager 745 may be configured or support a means for performing an LBT procedure before each feedback channel opportunity in a set of feedback channel opportunities to determine whether a feedback channel opportunity is available for transmitting at least one feedback message. In some embodiments, LBT manager 745 may be configured or support a means for identifying a first feedback channel opportunity in a set of feedback channel opportunities that is associated with a successful LBT procedure, and a round-trip timer is started after the first feedback channel opportunity.

[0132] In some embodiments, LBT manager 745 may be configured with or support a means for determining that each feedback channel opportunity in the set of feedback channel opportunities is associated with an unsuccessful LBT procedure. In some embodiments, LBT manager 745 may be configured with or support a means for identifying the last feedback channel opportunity in the set of feedback channel opportunities based on each feedback channel opportunity being associated with an unsuccessful LBT procedure, and a round-trip timer is started after the last feedback channel opportunity.

[0133] In some embodiments, the PSFCH opportunity manager 740 may be configured with or support a means for identifying the last feedback channel opportunity in a set of feedback channel opportunities, and a round-trip timer is started after the last feedback channel opportunity.

[0134] In some embodiments, RTT duration manager 750 may be configured or support a means for identifying a feedback channel opportunity within a set of feedback channel opportunities after which a round trip timer will be started. In some embodiments, RTT duration manager 750 may be configured or support a means for selecting a duration for the round trip timer based on a feedback channel opportunity within a set of feedback channel opportunities after which a round trip timer will be started.

[0135] In some embodiments, the RTT duration manager 750 may be configured or support means for determining an expected scheduling time for a retransmission of a sidelink data message, wherein the duration for the round trip timer is further based on the expected scheduling time.

[0136] In some embodiments, the RTT manager 735 may be configured or support a means to refrain from monitoring the sidelink channel to detect a second grant for scheduling a retransmission of a sidelink data message for the duration of the round-trip timer. In some embodiments, the round-trip timer is started after at least one feedback channel opportunity during which at least one feedback message is transmitted, or after a different feedback channel opportunity within a set of feedback channel opportunities. In some embodiments, the set of feedback channel opportunities includes in-band feedback channel opportunities or a mix of in-band and out-of-band feedback channel opportunities.

[0137] 8 shows a diagram of a system 800 including a device 805 supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The device 805 may be an example of or may include components of a device 505, a device 605, or a UE 115, as described herein. The device 805 may communicate (e.g., wirelessly) with one or more network entities 105, one or more UEs 115, or any combination thereof. The device 805 may include components for two-way voice and data communication, including components for transmitting and receiving communications, such as a communications manager 820, an input / output (I / O) controller 810, a transceiver 815, an antenna 825, memory 830, code 835, and a processor 840. These components may be in electronic communication or may be coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., bus 845).

[0138] The I / O controller 810 can manage input and output signals for the device 805. The I / O controller 810 can also manage peripheral devices not built into the device 805. In some cases, the I / O controller 810 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 810 can utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS / 2®, UNIX®, LINUX®, or another known operating system. Additionally or alternatively, the I / O controller 810 can represent or interact with a modem, keyboard, mouse, touchscreen, or similar device. In some cases, the I / O controller 810 can be implemented as part of a processor, such as the processor 840. In some cases, a user can interact with the device 805 through the I / O controller 810 or through hardware components controlled by the I / O controller 810.

[0139] In some cases, the device 805 may include a single antenna 825. However, in some other cases, the device 805 may have two or more antennas 825, which may be capable of simultaneously transmitting or receiving multiple wireless transmissions. The transceiver 815 may communicate bidirectionally via one or more antennas 825, a wired link, or a wireless link, as described herein. For example, the transceiver 815 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 815 may also include a modem for modulating packets, providing the modulated packets to one or more antennas 825 for transmission, and demodulating packets received from the one or more antennas 825. The transceiver 815, or the transceiver 815 and one or more antennas 825, may be one example of the transmitter 515, the transmitter 615, the receiver 510, the receiver 610, or any combination thereof or components thereof, as described herein.

[0140] The memory 830 may include random access memory (RAM) and read-only memory (ROM). The memory 830 may store computer-readable computer-executable code 835, which includes instructions that, when executed by the processor 840, cause the device 805 to perform various functions described herein. The code 835 may be stored in a non-transitory computer-readable medium, such as system memory or another type of memory. In some cases, the code 835 may not be directly executable by the processor 840, but rather (e.g., when compiled and executed) may cause a computer to perform functions described herein. In some cases, the memory 830 may include a basic I / O system (BIOS), which may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0141] The processor 840 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, 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 other cases, the memory controller may be incorporated within the processor 840. The processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks supporting DRX enhancement using multiple sidelink feedback channel opportunities). For example, the device 805, or a component of the device 805, may include the processor 840 and the memory 830 coupled to or to the processor 840, where the processor 840 and the memory 830 are configured to perform various functions described herein.

[0142] The communications manager 820 may support wireless communications in the UE according to embodiments as disclosed herein. For example, the communications manager 820 may be configured or support means for receiving, while operating in DRX mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The communications manager 820 may be configured or support means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message. The communications manager 820 may be configured or support means for starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of the sidelink data message.

[0143] By including or configuring the communications manager 820 according to embodiments as described herein, the device 805 can support techniques for improved RTT timer startup when multiple PSFCH candidates are indicated for a sidelink data message. The RTT timer can be started after the first PSFCH candidate, after an intermediate candidate, after the last PSFCH candidate, or based on the results of the LBT procedure performed for each PSFCH candidate.

[0144] In some embodiments, the communications manager 820 may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or in cooperation with the transceiver 815, the one or more antennas 825, or any combination thereof. Although the communications manager 820 is shown as a separate component, in some embodiments, one or more functions described with reference to the communications manager 820 may also be supported or performed by the processor 840, the memory 830, the code 835, or any combination thereof. For example, the code 835 may include instructions executable by the processor 840 to cause the device 805 to perform various aspects of DRX enhancement using multiple sidelink feedback channel opportunities as described herein, or the processor 840 and the memory 830 may be configured to perform or support such operations.

[0145] FIG. 9 shows a flowchart illustrating a method 900 for supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The operations of method 900 may be implemented by a UE or components thereof, as described herein. For example, the operations of method 900 may be performed by a UE 115, as described with reference to FIGS. 1-8. In some embodiments, the UE may execute a set of instructions to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using dedicated hardware.

[0146] At 905, the method may include receiving, while operating in a DRX mode, a grant for scheduling sidelink data messages for the UE on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages. The operations of 905 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 905 may be performed by a grant manager 725, such as described with reference to FIG. 7.

[0147] At 910, the method may include transmitting at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity of the set of feedback channel opportunities. The operations of 910 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 910 may be performed by a feedback manager 730, such as described with reference to FIG. 7.

[0148] At 915, the method may include starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of sidelink data messages. The operations of 915 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 915 may be performed by an RTT manager 735, as described with reference to FIG. 7.

[0149] FIG. 10 shows a flowchart illustrating a method 1000 for supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The operations of method 1000 may be implemented by a UE or components thereof, as described herein. For example, the operations of method 1000 may be performed by a UE 115, as described with reference to FIGS. 1-8. In some embodiments, the UE may execute a set of instructions to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using dedicated hardware.

[0150] At 1005, the method may include receiving, while operating in a DRX mode, a grant for scheduling sidelink data messages for the UE on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages. The operations of 1005 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1005 may be performed by a grant manager 725, as described with reference to FIG. 7.

[0151] At 1010, the method may include transmitting at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity of the set of feedback channel opportunities. The operations of 1010 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1010 may be performed by a feedback manager 730, such as described with reference to FIG. 7.

[0152] At 1015, the method may include identifying a first feedback channel opportunity in a set of feedback channel opportunities, wherein the round-trip timer is started after the first feedback channel opportunity. The operations of 1015 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1015 may be performed by a PSFCH opportunity manager 740, such as described with reference to FIG. 7.

[0153] At 1020, the method may include starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of sidelink data messages. The operations of 1020 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1020 may be performed by an RTT manager 735, such as described with reference to FIG. 7.

[0154] FIG. 11 shows a flowchart illustrating a method 1100 for supporting DRX enhancement using multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The operations of method 1100 may be implemented by a UE or components thereof, as described herein. For example, the operations of method 1100 may be performed by a UE 115, as described with reference to FIGS. 1-8. In some embodiments, the UE may execute a set of instructions to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using dedicated hardware.

[0155] At 1105, the method may include receiving, while operating in a DRX mode, a grant for scheduling sidelink data messages for the UE on the shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data messages. The operations of 1105 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1105 may be performed by a grant manager 725, as described with reference to FIG. 7.

[0156] At 1110, the method may include transmitting at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity of the set of feedback channel opportunities. The operations of 1110 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1110 may be performed by a feedback manager 730, such as described with reference to FIG. 7.

[0157] At 1115, the method may include performing an LBT procedure before each feedback channel opportunity in the set of feedback channel opportunities to determine whether the feedback channel opportunity is available for transmitting at least one feedback message. The operations of 1115 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1115 may be performed by an LBT manager 745, such as described with reference to FIG. 7.

[0158] At 1120, the method may include identifying a first feedback channel opportunity in a set of feedback channel opportunities associated with a successful LBT procedure, wherein the round-trip timer is started after the first feedback channel opportunity. The operations of 1120 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1120 may be performed by an LBT manager 745, such as described with reference to FIG. 7.

[0159] At 1125, the method may include starting, based on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, during which the UE refrains from monitoring for retransmissions of sidelink data messages. The operations of 1125 may be performed in accordance with embodiments as disclosed herein. In some embodiments, aspects of the operations of 1125 may be performed by an RTT manager 735, as described with reference to FIG. 7.

[0160] The following provides a summary of aspects of the disclosure.

[0161] Aspect 1: A method for wireless communication in a UE, while operating in a DRX mode, comprising: receiving, on a shared radio frequency spectrum band, a grant for scheduling a sidelink data message for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; and starting, based at least in part on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, wherein during the start-up, the UE suppresses monitoring for retransmissions of the sidelink data message.

[0162] Aspect 2: The method of aspect 1, further comprising identifying a first feedback channel opportunity in a set of feedback channel opportunities, wherein the round-trip timer is started after the first feedback channel opportunity.

[0163] Aspect 3: The method of aspect 2, further including: determining that an LBT procedure performed before a first feedback channel opportunity was unsuccessful; and, while starting a round-trip timer after the first feedback channel opportunity, transmitting at least one feedback message at a subsequent feedback channel opportunity from a set of feedback channel opportunities associated with the successful LBT procedure.

[0164] Aspect 4: The method of any of aspects 2 or 3, further comprising extending a duration of a retransmission timer while the UE monitors the sidelink channel for a second grant scheduling a retransmission of the sidelink data message based at least in part on the round-trip timer being started after the first feedback channel opportunity.

[0165] Aspect 5: The method of any of aspects 1 to 4, further comprising: performing an LBT procedure before each feedback channel opportunity in a set of feedback channel opportunities to determine whether a feedback channel opportunity is available for transmitting at least one feedback message; and identifying a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, wherein a round-trip timer is started after the first feedback channel opportunity.

[0166] Aspect 6: The method of aspect 5, further including: determining that each feedback channel opportunity in the set of feedback channel opportunities is associated with an unsuccessful LBT procedure; and identifying a last feedback channel opportunity in the set of feedback channel opportunities based at least in part on each feedback channel opportunity being associated with an unsuccessful LBT procedure, wherein the round-trip timer is started after the last feedback channel opportunity.

[0167] Aspect 7: The method of any of aspects 1 to 6, further comprising identifying a last feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is started after the last feedback channel opportunity.

[0168] Aspect 8: The method of any of aspects 1-7, further including: identifying a feedback channel opportunity within a set of feedback channel opportunities, after which a round-trip timer is to be started; and selecting a duration for the round-trip timer based at least in part on the feedback channel opportunity within the set of feedback channel opportunities, after which a round-trip timer is to be started.

[0169] Aspect 9: The method of aspect 8, further comprising determining an expected scheduling time for a retransmission of the sidelink data message, wherein a duration for the round-trip timer is further based on the expected scheduling time.

[0170] Aspect 10: The method of any of aspects 1-9, further comprising: refraining from monitoring a sidelink channel for a duration of the round-trip timer to detect a second grant scheduling a retransmission of the sidelink data message.

[0171] Aspect 11: The method of any of aspects 1 to 10, wherein the round-trip timer is started after at least one feedback channel opportunity, during which at least one feedback message is transmitted, or after a different feedback channel opportunity within a set of feedback channel opportunities.

[0172] Aspect 12: The method of any of aspects 1-11, wherein the set of feedback channel opportunities includes in-band feedback channel opportunities or a mix of in-band and out-of-band feedback channel opportunities.

[0173] Aspect 13: An apparatus for wireless communication in a 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 any of the methods of aspects 1 to 12.

[0174] Aspect 14: An apparatus for wireless communication in a UE, the apparatus comprising at least one means for performing the method of any of aspects 1-12.

[0175] Aspect 15: A non-transitory computer-readable medium storing code for wireless communication in a UE, the code including instructions executable by a processor, the instructions performing the method of any of aspects 1-12.

[0176] It should be noted that the methods described herein illustrate possible implementations, and that the operations and steps can be rearranged or modified, other implementations are possible, and further, aspects from two or more of these methods can be combined.

[0177] Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for illustrative purposes, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used throughout much of the description, the techniques described herein may be applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the techniques described may also 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.

[0178] The information and signals described herein may be represented using any of a wide variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout this description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0179] The various example blocks and components described in connection with the disclosure herein may be implemented or performed using a general purpose processor, a DSP, an ASIC, a CPU, an 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. A general purpose processor may be a microprocessor, but alternatively, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0180] The functions described herein may be implemented using hardware, software executed by a processor, firmware, or any combination thereof. If implemented using software executed by a processor, the functions may be stored on or transmitted using one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. The features implementing those functions may also be physically located in various locations, including being distributed such that portions of the functions are implemented in different physical locations.

[0181] Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media can be any available medium that can be accessed by a general-purpose 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 (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or processor. Also, any connection can be properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of computer-readable media. As used herein, disk and disc include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs. Disks can reproduce data magnetically, and discs can reproduce data optically using a laser. Combinations of the above are also included within the scope of computer-readable media.

[0182] As used herein, including in the claims, "or" as used in a list of items (e.g., a list of items followed by a phrase such as "at least one of" or "one or more of") is intended to indicate an inclusive list, such as, for example, a list of at least one of A, B, or C means 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 referring to a closed set of conditions. For example, an example step described as "based on condition A" may 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" is intended to be interpreted the same as the phrase "based at least in part on."

[0183] The terms "determine" or "determining" encompass various actions, and thus "determining" can include calculating, computing, processing, deriving, investigating, looking up (such as via looking up in a table, database, or another data structure), resolving, and the like. "Determining" can also include receiving (e.g., receiving information), accessing (e.g., accessing data stored in a memory), and the like. "Determining" can also include resolving, obtaining, selecting, choosing, establishing, and other such similar actions.

[0184] In the accompanying figures, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes among the similar components. If only a first reference label is used herein, the description is applicable to any of the similar components having the same first reference label, regardless of a second reference label or other subsequent reference labels.

[0185] The description set forth herein with reference to the accompanying drawings illustrates exemplary configurations and does not represent every embodiment that may be implemented or that is within the scope of the claims. As used herein, the term "exemplary" means "serving as an example, instance, or illustration" and does not mean "preferred" or "advantageous over other embodiments." The Detailed Description includes specific details for the purpose of providing an understanding of the described technology. However, these technologies may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

[0186] The description herein is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. An apparatus for wireless communication in a user equipment (UE), comprising: a processor; a memory coupled to the processor; instructions stored in the memory and executable by the processor, the instructions causing the device to: receiving, while operating in a discontinuous reception mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; Activating a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel opportunity, wherein during the activation, the UE refrains from monitoring for retransmissions of the sidelink data message.

2. The instructions to the device further include:

2. The apparatus of claim 1, executable by the processor to identify a first feedback channel opportunity in the set of feedback channel opportunities, the round-trip timer being started after the first feedback channel opportunity.

3. The instructions to the device further include: determining that a listen-before-talk (LBT) procedure performed prior to the first feedback channel opportunity was unsuccessful; 3. The apparatus of claim 2, wherein the apparatus is executable by the processor to cause the at least one feedback message to be transmitted at a subsequent feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure while starting the round trip timer after the first feedback channel opportunity.

4. The instructions to the device further include:

3. The apparatus of claim 2, wherein the apparatus is executable by the processor to extend a duration of a retransmission timer while the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message based at least in part on the round-trip timer being started after the first feedback channel opportunity.

5. The instructions to the device further include: performing a listen-before-talk (LBT) procedure before each feedback channel opportunity in the set of feedback channel opportunities to determine whether the feedback channel opportunity is available for transmitting the at least one feedback message; 2. The apparatus of claim 1, wherein the apparatus is executable by the processor to identify a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, and wherein the round-trip timer is started after the first feedback channel opportunity.

6. The instructions to the device further include: determining that each feedback channel opportunity in the set of feedback channel opportunities is associated with an unsuccessful LBT procedure; 6. The apparatus of claim 5, wherein the apparatus is executable by the processor to identify a last feedback channel opportunity in the set of feedback channel opportunities based at least in part on each feedback channel opportunity being associated with an unsuccessful LBT procedure, and wherein the round-trip timer is started after the last feedback channel opportunity.

7. The instructions to the device further include:

2. The apparatus of claim 1, executable by the processor to identify a last feedback channel opportunity in the set of feedback channel opportunities, the round-trip timer being started after the last feedback channel opportunity.

8. The instructions to the device further include: identifying a feedback channel opportunity within the set of feedback channel opportunities after which the round-trip timer will be started; 2. The apparatus of claim 1, wherein the apparatus is executable by the processor to select a duration for the round-trip timer based at least in part on a feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer is to be started.

9. The instructions to the device further include:

10. The apparatus of claim 8, wherein the apparatus is executable by the processor to determine an expected scheduling time for the retransmission of the sidelink data message, and wherein the duration for the round-trip timer is further based on the expected scheduling time.

10. The instructions to the device further include:

2. The apparatus of claim 1, wherein the apparatus is executable by the processor to refrain from monitoring a sidelink channel to detect a second grant scheduling the retransmission of the sidelink data message for a duration of the round-trip timer.

11. 2. The apparatus of claim 1, wherein the round-trip timer is started after the at least one feedback channel opportunity during which the at least one feedback message is transmitted, or after a different feedback channel opportunity within the set of feedback channel opportunities.

12. The apparatus of claim 1 , wherein the set of feedback channel opportunities includes in-band feedback channel opportunities or a mix of in-band and out-of-band feedback channel opportunities.

13. 1. A method for wireless communication in a user equipment (UE), comprising: receiving, while operating in a discontinuous reception mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; and transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; and and starting a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel opportunity, wherein during the starting, the UE refrains from monitoring for retransmissions of the sidelink data message.

14. and identifying a first feedback channel opportunity in the set of feedback channel opportunities, the round-trip timer being started after the first feedback channel opportunity. The method of claim 13.

15. determining that a listen-before-talk (LBT) procedure performed prior to the first feedback channel opportunity was unsuccessful; and transmitting the at least one feedback message at a subsequent feedback channel opportunity of the set of feedback channel opportunities associated with a successful LBT procedure while starting the round trip timer after the first feedback channel opportunity; The method of claim 14 further comprising:

16. and extending a duration of a retransmission timer while the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message based at least in part on the round trip timer being started after the first feedback channel opportunity.

15. The method of claim 14.

17. performing a listen-before-talk (LBT) procedure before each feedback channel opportunity in the set of feedback channel opportunities to determine whether the feedback channel opportunity is available for transmitting the at least one feedback message; and identifying a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, wherein the round-trip timer is started after the first feedback channel opportunity. The method of claim 13.

18. determining that each feedback channel opportunity in the set of feedback channel opportunities is associated with an unsuccessful LBT procedure; and identifying a last feedback channel opportunity in the set of feedback channel opportunities based at least in part on each feedback channel opportunity being associated with an unsuccessful LBT procedure, wherein the round-trip timer is started after the last feedback channel opportunity.

18. The method of claim 17.

19. and identifying a last feedback channel opportunity in the set of feedback channel opportunities, the round-trip timer being started after the last feedback channel opportunity. The method of claim 13.

20. identifying a feedback channel opportunity within the set of feedback channel opportunities after which the round-trip timer is to be started; selecting a duration for the round-trip timer based at least in part on a feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer will be started; The method of claim 13 further comprising:

21. determining an expected scheduling time for the retransmission of the sidelink data message, wherein the duration for the round trip timer is further based on the expected scheduling time.

21. The method of claim 20.

22. and refraining from monitoring a sidelink channel for a duration of the round-trip timer to detect a second grant scheduling the retransmission of the sidelink data message. The method of claim 13.

23. 14. The method of claim 13, wherein the round-trip timer is started after the at least one feedback channel opportunity during which the at least one feedback message is transmitted, or after a different feedback channel opportunity within the set of feedback channel opportunities.

24. 14. The method of claim 13, wherein the set of feedback channel opportunities includes in-band feedback channel opportunities or a mix of in-band and out-of-band feedback channel opportunities.

25. 1. An apparatus for wireless communication in a user equipment (UE), comprising: means for receiving, while operating in a discontinuous reception mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; and means for transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; and means for starting a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel opportunity, wherein during the starting, the UE refrains from monitoring for retransmissions of the sidelink data message.

26. means for identifying a first feedback channel opportunity in the set of feedback channel opportunities, the round-trip timer being started after the first feedback channel opportunity.

26. The apparatus of claim 25.

27. means for determining that a listen-before-talk (LBT) procedure performed prior to the first feedback channel opportunity was unsuccessful; means for transmitting the at least one feedback message at a subsequent feedback channel opportunity of the set of feedback channel opportunities associated with a successful LBT procedure while starting the round trip timer after the first feedback channel opportunity; 27. The apparatus of claim 26, further comprising:

28. and means for extending a duration of a retransmission timer while the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message based at least in part on the round trip timer being started after the first feedback channel opportunity.

27. The apparatus of claim 26.

29. means for performing a listen-before-talk (LBT) procedure before each feedback channel opportunity in the set of feedback channel opportunities to determine whether the feedback channel opportunity is available for transmitting the at least one feedback message; means for identifying a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, wherein the round trip timer is started after the first feedback channel opportunity.

26. The apparatus of claim 25.

30. 1. A non-transitory computer-readable medium storing code for wireless communication in a user equipment (UE), comprising: The code includes instructions executable by a processor, the instructions receiving, while operating in a discontinuous reception mode, a grant for scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmitting, during at least one feedback channel opportunity of the set of feedback channel opportunities, at least one feedback message indicating a feedback status of the sidelink data message; activating, based at least in part on the at least one feedback channel opportunity, a round-trip timer associated with the at least one feedback message, wherein during the activation, the UE refrains from monitoring for retransmissions of the sidelink data message.

Images