Discontinuous reception enhancements with multiple sidelink feedback channel opportunities

Abstract

Methods, systems, and devices for wireless communication are described. When operating in a discontinuous reception mode, a user equipment (UE) may receive a grant to schedule a sidelink data message for the UE over a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The UE may transmit at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel occasion of the set of feedback channel occasions. The UE may initiate a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel occasion, during which the UE suppresses monitoring of retransmission of the sidelink data message.

Description

[0001] Cross-reference

[0002] This patent application claims priority to U.S. Patent Application No. 18 / 053,473, entitled "DISCONTINUOUS RECEPTION ENHANCEMENT WITH MULTIPLE SIDELINK FEEDBACK CHANNEL OPPORTUNITIES", filed on Nov. 8, 2022 by Liu et al., which is assigned to the assignee of the present application and is hereby incorporated by reference in its entirety. Field of the Invention

[0003] The following relates to wireless communication, including discontinuous reception enhancement with multiple sidelink feedback channel opportunities. Background Art

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

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support discontinuous reception (DRX) enhancements with multiple sidelink feedback channel opportunities. For example, the described techniques enable a user equipment (UE) to select a physical sidelink feedback channel (PSFCH) timing (e.g., a feedback timing) from a set of allocated PSFCH timings and then start a round-trip time (RTT) timer. For example, the UE may receive a grant for a transmission scheduled for the UE (e.g., a sidelink data message scheduled for transmission to the UE). The grant may further identify the feedback resources allocated to the UE for the sidelink data message. For example, the grant may identify a set of feedback channel timings (e.g., multiple PSFCH timings may be configured for a hybrid automatic repeat / request (HARQ) process for the sidelink data message). The UE may receive the sidelink data message and determine the feedback status of the sidelink data message (e.g., hybrid automatic repeat / request acknowledgment (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 send a feedback message indicating the feedback status during at least one PSFCH timing and initiate the RTT timer after the PSFCH timing based on the at least one PSFCH timing. That is, the RTT timer may be initiated after the same PSFCH timing at which the HARQ-ACK feedback is sent or after a different PSFCH timing in the set of PSFCH timings. For example, the RTT timer may be initiated after the first PSFCH timing in the set, after the last PSFCH timing in the set, after an intermediate PSFCH timing in the set, or based on the result of a listen-before-talk (LBT) process performed before each PSFCH timing (e.g., when operating in a shared channel). In some examples, the duration of the RTT timer may be adjusted based on after which PSFCH timing the RTT timer is initiated. Thus, the UE may initiate the RTT timer after a PSFCH timing in the set and, upon expiration, initiate a retransmission timer to monitor for a retransmission of the sidelink data message.

[0006] A method for wireless communication at a UE is described. The method may include: when operating in DRX mode, receiving, on a shared radio frequency spectrum band, a grant for a sidelink data message scheduled for the UE, the grant indicating a set of feedback channel timings associated with the sidelink data message; sending at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel timing in the set of feedback channel timings; and initiating, based on the at least one feedback channel timing, a round-trip timer associated with the at least one feedback message, during which the UE suppresses monitoring for a retransmission of the sidelink data message.

[0007] Describes an apparatus for wireless communication at a UE. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to: when operating in DRX mode, receive, on a shared radio frequency spectrum band, a grant scheduling a sidelink data message for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmit at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and initiate, 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 suppresses monitoring for retransmissions of the sidelink data message.

[0008] Describes another apparatus for wireless communication at a UE. The apparatus may include: means for receiving, when operating in DRX mode, on a shared radio frequency spectrum band, a grant 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 at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and means for initiating, 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 suppresses monitoring for retransmissions of the sidelink data message.

[0009] Describes a non-transitory computer-readable medium storing code for wireless communication at a UE. The code may include instructions executable by a processor to: when operating in DRX mode, receive, on a shared radio frequency spectrum band, a grant scheduling a sidelink data message for the UE, the grant indicating a set of feedback channel opportunities associated with the sidelink data message; transmit at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and initiate, 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 suppresses monitoring for retransmissions of the sidelink data message.

[0010] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for: identifying a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer may be initiated after the first feedback channel opportunity.

[0011] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: determining that a listen-before-talk (LBT) process performed before the first feedback channel opportunity was unsuccessful; and transmitting the at least one feedback message in a subsequent feedback channel opportunity in the set of feedback channel opportunities that is associated with a successful LBT process while initiating the round-trip timer after the first feedback channel opportunity.

[0012] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: extending a duration of a retransmission timer based on the round-trip timer being initiated after the first feedback channel opportunity, during which duration the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message.

[0013] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: performing an LBT process 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 that is associated with a successful LBT process, wherein the round-trip timer may be initiated after the first feedback channel opportunity.

[0014] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: determining that each feedback channel opportunity in the set of feedback channel opportunities may be associated with an unsuccessful LBT process; 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 process, wherein the round-trip timer may be initiated after the last feedback channel opportunity.

[0015] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: identifying a last feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer may be initiated after the last feedback channel opportunity.

[0016] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: identifying which feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer may be initiated; and selecting a duration of the round-trip timer based on which feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer may be initiated.

[0017] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: determining an expected scheduling time for the retransmission of the sidelink data message, wherein the duration of the round-trip timer is further based on the expected scheduling time.

[0018] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for: refraining from monitoring a sidelink channel during the duration of the round-trip timer to detect a second grant scheduling the retransmission of the sidelink data message.

[0019] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the round-trip timer may be initiated after the at least one feedback channel occasion during which the at least one feedback message is transmitted or after different feedback channel occasions in the set of feedback channel occasions.

[0020] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the set of feedback channel occasions includes in-band feedback channel occasions or a mixture of in-band feedback channel occasions and out-of-band feedback channel occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Examples that illustrate a wireless communication system supporting discontinuous reception (DRX) enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0022] Figure 2 Examples that illustrate a DRX-enhanced wireless communication system supporting multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0023] Figures 3A to 3C Examples that illustrate a DRX-enhanced feedback configuration supporting multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0024] Figure 4 Examples that illustrate a DRX-enhanced feedback configuration supporting multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0025] Figure 5 AND Figure 6 Examples that illustrate a block diagram of a DRX-enhanced device supporting multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0026] Figure 7 Examples that illustrate a block diagram of a DRX-enhanced communication manager supporting multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure.

[0027] Figure 8 A diagram illustrating a system including a device supporting DRX enhancements with multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure.

[0028] Figures 9 to 11 A flowchart illustrating a method for supporting DRX enhancements with multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. Detailed Description

[0029] Some user equipment (UE) may use a round-trip time (RTT) timer during a hybrid automatic repeat / request acknowledgement (HARQ-ACK) procedure during discontinuous reception (DRX) mode. For example, a sidelink UE (e.g., a UE performing sidelink communication) may receive a grant scheduling a sidelink message on a shared radio frequency spectrum band. The grant may also identify a resource (e.g., a HARQ-ACK feedback resource) to be used for transmitting a feedback message for the sidelink message. The UE receives the sidelink message on the allocated resource and transmits HARQ-ACK feedback (e.g., acknowledgement / negative acknowledgement (ACK / NACK) information) in the resource. When transmitting a NACK, the UE expects a retransmission of the sidelink message associated with the NACK. In cases where the UE does not expect a retransmission to be scheduled, the UE traditionally initiates the RTT timer after the PSFCH occasion for transmitting the HARQ-ACK feedback (e.g., in the HARQ-ACK resource). Instead, the UE may enter a sleep state of the DRX mode, where the UE does not monitor the sidelink control channel for retransmissions. When the RTT timer expires, the UE initiates a retransmission timer, during which the UE monitors for a grant scheduling a retransmission and the scheduled retransmission. However, an advanced network may schedule multiple physical sidelink feedback channel (PSFCH) occasions (e.g., feedback channel occasions) for the UE. This results in inconsistencies and confusion regarding when the UE initiates (e.g., after which PSFCH occasion, such as after the PSFCH occasion for transmitting the HARQ-ACK feedback or after a different PSFCH occasion) the RTT timer and the corresponding retransmission.

[0030] Thus, the described techniques provide for a UE to select a PSFCH occasion (e.g., a feedback occasion) from the set of allocated PSFCH occasions, after which an RTT timer is started. For example, the UE may receive a grant for a transmission scheduled for the UE (e.g., a sidelink data message scheduled for transmission to the UE). The grant may further identify the feedback resources allocated to the UE for the sidelink data message. For example, the grant may identify a set of feedback channel occasions (e.g., multiple PSFCH occasions may be configured for a HARQ process for the sidelink data message). The UE may receive the sidelink data message and determine a feedback status for the sidelink data message (e.g., (HARQ-ACK) acknowledgement / negative acknowledgement (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 PSFCH occasion and initiate the RTT timer after the PSFCH occasion based on the at least one PSFCH occasion. That is, the RTT timer may be initiated after the same PSFCH occasion on which the HARQ-ACK feedback is sent or after a different PSFCH occasion in the set of PSFCH occasions. For example, the RTT timer may be initiated after the first PSFCH occasion in the set, after the last PSFCH occasion in the set, after an intermediate PSFCH occasion in the set, or based on the result of a LBT process performed before each PSFCH occasion (e.g., when operating in a shared channel). In some examples, the duration of the RTT timer may be adjusted based on after which PSFCH occasion the RTT timer is initiated. Thus, the UE may initiate the RTT timer after a PSFCH occasion in the set and, upon expiration, initiate a retransmission timer to monitor for a retransmission of the sidelink data message.

[0031] Aspects of the present disclosure are first described in the context of a wireless communication system. Aspects of the present disclosure are further illustrated by device diagrams, system diagrams, and flowcharts relating to DRX enhancements with multiple sidelink feedback channel opportunities and are described with reference to these diagrams.

[0032] Figure 1 An example of a wireless communication system 100 supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure is illustrated. 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 Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or a network operating in accordance with other systems and radio technologies, including future systems and radio technologies not explicitly mentioned herein.

[0033] Network entity 105 can be dispersed throughout a geographical area to form a wireless communication system 100 and can include devices in different forms or with different capabilities. In various examples, network entity 105 can be referred to as a network element, a mobility element, a radio access network (RAN) node, or network equipment, among other designations. In some examples, network entity 105 and UE 115 can communicate wirelessly via one or more communication links 125 (e.g., radio frequency (RF) access links). For example, network entity 105 can support a coverage area 110 (e.g., a geographical coverage area) within which UE 115 and network entity 105 can establish one or more communication links 125. Coverage area 110 can be an example of a geographical area within which network entity 105 and UE 115 can support signal communication according to one or more radio access technologies (RATs).

[0034] UE 115 can be dispersed throughout coverage area 110 of wireless communication system 100, and each UE 115 can be stationary or mobile, or stationary and mobile at different times. UE 115 can be devices in different forms or with different capabilities. Figure 1 Some example UEs 115 are illustrated herein. UEs 115 described herein may be capable of supporting communication with various types of devices (such as other UEs 115 or network entity 105 as shown). Figure 1 as shown).

[0035] 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, a device, an equipment, a computing system, one or more components, or another suitable processing entity configured to perform any of the techniques described herein. For example, the node may be a UE 115. As another example, the node may be a network entity 105. As yet 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 other aspects of this example, the first node, the second node, and the third node may be different from these examples. Similarly, references to UE 115, network entity 105, device, equipment, computing system, etc. may include the disclosure of UE 115, network entity 105, device, equipment, computing system, etc. as nodes. For example, the disclosure that UE 115 is configured to receive information from network entity 105 also discloses that a first node is configured to receive information from a second node.

[0036] In some examples, network entity 105 may communicate with core network 130, or with each other, or both. For example, network entity 105 may communicate with core network 130 via one or more backhaul communication links 120 (e.g., according to S1, N2, N3, or other interface protocols). In some examples, network entity 105 may communicate with each other directly (e.g., directly between network entities 105) or indirectly (e.g., via core network 130) via backhaul communication links 120 (e.g., according to X2, Xn, or other interface protocols). In some examples, network entity 105 may communicate with each other via midhaul communication link 162 (e.g., according to midhaul interface protocol) or fronthaul communication link 168 (e.g., according to fronthaul interface protocol) or any combination thereof. Backhaul communication link 120, midhaul communication link 162, or fronthaul communication link 168 may be or include one or more wired links (e.g., electrical link, optical fiber link), one or more wireless links (e.g., radio link, wireless optical link), and other examples or various combinations thereof. UE 115 may communicate with core network 130 via communication link 155.

[0037] One or more of the network entities 105 described herein may include or may be referred to as a base station 140 (e.g., transceiver base station, radio base station, NR base station, access point, radio transceiver, Node B, evolved Node B (eNB), next-generation Node B or giga Node B (either of which may be referred to as gNB), 5G NB, next-generation eNB (ng-eNB), home Node B, home evolved Node B, or other suitable terms). In some examples, the network entity 105 (e.g., base station 140) may be implemented in an integrated (e.g., monolithic, stand-alone) base station architecture that may be configured to utilize a protocol stack physically or logically integrated within a single network entity 105 (e.g., a single RAN node, such as base station 140).

[0038] In some examples, the network entity 105 may be implemented in a disaggregated architecture (e.g., disaggregated base station architecture, disaggregated RAN architecture) that may be configured to utilize a protocol stack 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 sponsored 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 the following: a central unit (CU) 160, a distributed unit (DU) 165, a radio unit (RU) 170, a RAN intelligent controller (RIC) 175 (e.g., near-real-time RIC (near RT RIC), 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, intelligent radio head, remote radio head (RRH), remote radio unit (RRU), or transmit receive point (TRP). One or more components of the network entity 105 in a disaggregated RAN architecture 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 examples, one or more network entities 105 of a disaggregated RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0039] The functional split between the CU 160, DU 165, and RU 170 is flexible and can support different functions, depending on which functions are performed at the CU 160, DU 165, or RU 170 (e.g., network layer functions, protocol layer functions, baseband functions, RF functions, and any combination thereof). For example, a functional split of the protocol stack can be adopted between the CU 160 and 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 examples, the CU 160 can host higher protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functions 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 DU 165s or RU 170s, and one or more DU 165s or RU 170s 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) functions and signaling, and can each be at least partially controlled by the CU 160. Additionally or alternatively, a functional split of the protocol stack can be adopted between the DU 165 and 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 RU 170s). In some cases, the functional split between the CU 160 and DU 165 or between the DU 165 and RU 170 can be within a protocol layer (e.g., some functions of a protocol layer can be performed by one of the CU 160, DU 165, or RU 170, while other functions of that protocol layer are performed by a different one of the CU 160, DU 165, or RU 170). The CU 160 can be further functionally split into a CU control plane (CU-CP) and a CU user plane (CU-UP) function. The CU 160 can be connected to one or more DU 165s via an intermediate transport communication link 162 (e.g., F1, F1-c, F1-u), and the DU 165 can be connected to one or more RU 170s via a fronthaul communication link 168 (e.g., open fronthaul (FH) interface). In some examples, the intermediate transport communication link 162 or the fronthaul communication link 168 can be implemented according to the interfaces (e.g., channels) between the layers of the protocol stack, which are supported by the respective network entities 105 communicating via these communication links.

[0040] In some wireless communication systems (e.g., wireless communication system 100), the infrastructure and spectrum resources for radio access may support wireless backhaul link capabilities to supplement wired backhaul connections, thereby providing an IAB network architecture (e.g., to core network 130). In some cases, in an IAB network, one or more network entities 105 (e.g., IAB node 104) may 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 may be partially controlled by one or more CUs 160 associated with a donor network entity 105 (e.g., donor base station 140). One or more donor network entities 105 (e.g., IAB donors) may communicate with one or more additional network entities 105 (e.g., IAB nodes 104) via the supported access and backhaul links (e.g., backhaul communication link 120). The IAB node 104 may include an IAB mobile terminal (IAB-MT) controlled (e.g., scheduled) by the DU 165 of the coupled IAB donor. The IAB-MT may include a separate antenna set for relaying communication with the UE 115 or may share the same antenna (e.g., of the RU 170) of the IAB node 104 for access via the DU 165 of the IAB node 104 (e.g., referred to as a virtual IAB-MT (vIAB-MT)). In some examples, the IAB node 104 may include a DU 165 that supports communication links with additional entities (e.g., IAB node 104, UE 115) within a relay chain or configuration (e.g., downstream) of the access network. In such cases, one or more components of the split RAN architecture (e.g., one or more IAB nodes 104 or components of the IAB node 104) may be configured to operate according to the techniques described herein.

[0041] For example, the access network (AN) or RAN may include communication between an access node (e.g., an IAB donor), an IAB node 104, and one or more UEs 115. The IAB donor may facilitate a connection between the core network 130 and the AN (e.g., via a wired or wireless connection to the core network 130). That is, the IAB donor may refer to a RAN node having 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., and an RU 170), in which case the CU 160 may communicate with the core network 130 via an interface (e.g., a backhaul link). The IAB donor and the IAB node 104 may communicate via an F1 interface according to a protocol that defines signaling messages (e.g., the F1 AP protocol). Additionally or alternatively, the CU 160 may communicate with the core network via an interface (which may be an example of a part of the backhaul link), and may communicate with other CUs 160 (e.g., CUs 160 associated with alternative IAB donors) via an Xn-C interface (which may be an example of a part of the backhaul link).

[0042] The IAB node 104 may refer to a RAN node that provides IAB functions (e.g., access for UEs 115, wireless self-backhaul capabilities, etc.). The DU 165 may act as a distributed scheduling node towards the child nodes associated with the IAB node 104, and the IAB-MT may act as a scheduled node towards the parent node associated with the IAB node 104. That is, the IAB donor may be referred to as a parent node that communicates with one or more child nodes (e.g., the IAB donor may relay transmissions of UEs through one or more other IAB nodes 104). Additionally or alternatively, depending on the relay chain or configuration of the AN, the IAB node 104 may also be referred to as a parent node or a child node of other IAB nodes 104. Thus, the IAB-MT entity of the IAB node 104 may provide a Uu interface for a child IAB node 104 to receive signaling from a parent IAB node 104, and a DU interface (e.g., the DU 165) may provide a Uu interface for a parent IAB node 104 to signal to a child IAB node 104 or a UE 115.

[0043] For example, the IAB node 104 can be referred to as a parent node supporting communication for a sub-IAB node or as a sub-IAB node associated with an IAB donor or both. The IAB donor can include a CU 160 having a wired or wireless connection (e.g., a fronthaul communication link 120) to the core network 130 and can act as the parent node of the IAB node 104. For example, the DU 165 of the IAB donor can relay transmissions to the UE 115 via the IAB node 104, or can signal transmissions directly to the UE 115, or both. The CU 160 of the IAB donor can signal the communication link establishment to the IAB node 104 via the F1 interface, and the IAB node 104 can 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. Communication with the IAB node 104 can be scheduled by the DU 165 of the IAB donor, and communication with the IAB node 104 can be scheduled by the DU 165 of the IAB node 104.

[0044] In the case where the techniques described herein are applied in the context of a split RAN architecture, one or more components of the split RAN architecture can be configured to support DRX enhancements with multiple sidelink feedback channel opportunities as described herein. For example, some operations described as being performed by the UE 115 or the network entity 105 (e.g., the base station 140) can additionally 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).

[0045] The UE 115 can include or can be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable term, where "device" can also be referred to as a unit, a station, a terminal, or a client, etc. The UE 115 can also include or can 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 examples, the UE 115 can include or can 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 communication (MTC) device, etc., which can be implemented in various objects such as appliances or vehicles, meters, etc.

[0046] The UE 115 described herein may be capable of communicating with various types of devices, such as other UEs 115 that may sometimes act as relays, and network entities 105 and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, etc., as Figure 1 shown.

[0047] The UE 115 and the network entity 105 may wirelessly communicate with each other via 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 physical layer structure defined to support the communication link 125. For example, a carrier for the communication link 125 may include a portion (e.g., bandwidth part (BWP)) of an RF spectrum band 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 for coordinating carrier operation, user data, or other signaling. The wireless communication system 100 may support communication with the UE 115 using carrier aggregation or multi-carrier operation. According to a carrier aggregation configuration, the UE 115 may be configured to have multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation may be used for both frequency division duplex (FDD) and time division duplex (TDD) component carriers. Communication between the network entity 105 and other devices may refer to communication between these devices and any part (e.g., entity, sub-entity) of the network entity 105. For example, the terms "transmit", "receive", or "communicate" when referring to the network entity 105 may refer to any part of the network entity 105 of the RAN (e.g., base station 140, CU 160, DU 165, RU 170) communicating with another device (e.g., directly or via one or more other network entities 105).

[0048] In some examples, such as in a carrier aggregation configuration, a carrier may also have acquisition signaling or control signaling for coordinating the operation of other carriers. A carrier may be associated with a frequency channel (e.g., evolved universal mobile telecommunications system terrestrial radio access (E-UTRA) absolute RF channel number (EARFCN)) and may be identified according to a channel raster for discovery by the UE 115. A carrier may operate in an independent mode, in which case initial acquisition and connection may be performed by the UE 115 via the carrier, or a carrier may operate in a non-independent mode, in which case a different carrier (e.g., of the same or different radio access technology) is used to anchor the connection.

[0049] The communication link 125 shown in the wireless communication system 100 may include a downlink transmission (e.g., forward link transmission) from the network entity 105 to the UE 115, an uplink transmission (e.g., reverse link transmission) from the UE 115 to the network entity 105, or both, as well as other transmission configurations. A carrier may carry downlink communication or uplink communication (e.g., in FDD mode), or may be configured to carry both downlink communication and uplink communication (e.g., in TDD mode).

[0050] A carrier may be associated with a particular bandwidth of the RF spectrum, and in some examples, the carrier bandwidth may be referred to as the "system bandwidth" of the carrier or the wireless communication system 100. For example, the carrier bandwidth may be one of a set of bandwidths of carriers of a particular radio access technology (e.g., 1.4 megahertz (MHz), 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, 40 MHz, or 80 MHz). Devices of the wireless communication system 100 (e.g., the network entity 105, the UE 115, or both) may have a hardware configuration that supports communication using a particular carrier bandwidth, or may be capable of being configured to support communication using one of a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a network entity 105 or a UE 115 that supports concurrent communication using carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured to operate using a portion (e.g., subband, BWP) or all of the carrier bandwidth.

[0051] The signal waveform transmitted via a carrier may include a plurality of subcarriers (e.g., using a multicarrier modulation (MCM) technique such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing an MCM technique, a resource element may refer to the resource of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, in which case the symbol period and the subcarrier spacing may be inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the decoding rate of the modulation scheme, or both), such that a relatively high number of resource elements (e.g., during the transmission duration) and a relatively high order of the modulation scheme may correspond to a relatively high communication rate. Wireless communication resources may refer to a combination of RF spectrum resources, time resources, and spatial resources (e.g., spatial layer or beam), and the use of multiple spatial resources may increase the data rate or data integrity for communication with the UE 115.

[0052] One or more parameter sets for a carrier are supported, and the parameter sets may include subcarrier spacing (Δf) and cyclic prefix. The carrier may be divided into one or more BWPs with the same or different parameter sets. In some examples, UE 115 may be configured with multiple BWPs. In some examples, a single BWP of a carrier may be active at a given time, and the communication of UE 115 may be restricted to one or more active BWPs.

[0053] The time intervals for network entity 105 or UE 115 can be expressed as multiples of a basic time unit, which may refer to the sampling period T, for example. s = 1 / (Δf max ·N f ) seconds, where Δf max may represent the supported subcarrier spacing, and N f may represent the supported discrete Fourier transform (DFT) size. The time intervals of communication resources can be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame can be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0054] Each frame may include a plurality of consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may also be divided into a certain number of time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include a certain number of symbol periods (e.g., depending on the length of the cyclic prefix appended to each symbol period). In some wireless communication systems 100, a time slot may be further divided into a plurality of mini-slots associated with one or more symbols. Excluding the cyclic prefix, each symbol period may be associated with one or more (e.g., N f ones) sampling periods. The duration of the symbol period may depend on the subcarrier spacing or the operating frequency band.

[0055] A subframe, time slot, mini-slot, or symbol may be the smallest scheduling unit (e.g., in the time domain) of wireless communication system 100 and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of wireless communication system 100 may be dynamically selected (e.g., in a burst of shortened TTIs (sTTIs)).

[0056] Physical channels can be multiplexed according to various techniques for communication using a carrier. For example, one or more of time-division multiplexing (TDM) techniques, frequency-division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques can be used to multiplex physical control channels and physical data channels for signaling via a downlink carrier. The control region of a physical control channel (e.g., a control resource set (CORESET)) can be defined by a set of symbol periods and can extend across the system bandwidth of a carrier or a subset of the system bandwidth. One or more control regions (e.g., CORESETs) can be configured for a set of UEs 115. For example, one or more of the UEs 115 can monitor or search a control region for control information according to one or more search space sets, and each search space set can include one or more control channel candidates in one or more aggregation levels arranged in a cascaded manner. The aggregation level of a control channel candidate can refer to the amount of control channel resources (e.g., control channel elements (CCEs)) associated with the coded information for a control information format with a given payload size. The search space sets can 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.

[0057] The network entity 105 can provide communication coverage via one or more cells (e.g., macro cells, small cells, hotspots, or other types of cells or any combination thereof). The term "cell" can refer to a logical communication entity for communicating with the network entity 105 (e.g., using a carrier) and can be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or other identifier) for distinguishing adjacent cells. In some examples, a cell can also refer to a coverage area 110 or a portion of the coverage area 110 (e.g., a sector) on which the logical communication entity operates. Depending on various factors such as the capabilities of the network entity 105, the range of such cells can be from a smaller area (e.g., a structure, a subset of a structure) to a larger area. For example, a cell can be or can include a building, a subset of a building, or an external space between or overlapping the coverage areas 110, etc.

[0058] Macro cells generally cover a relatively large geographical area (e.g., with a radius of several kilometers) and can allow unrestricted access for UEs 115 having a service subscription with the network provider supporting the macro cell. Small cells can be associated with a lower power network entity 105 (e.g., a lower power base station 140) (as compared to macro cells), and small cells can operate using the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells can provide unconstrained access to UEs 115 having a service subscription with the network provider, or can provide constrained access to UEs 115 associated with the small cell (e.g., UEs 115 in a closed subscriber group (CSG), UEs 115 associated with users in a home or office). The network entity 105 can support one or more cells and can also use one or more component carriers to support communication via one or more cells.

[0059] In some examples, a carrier can support multiple cells and can be configured with different cells according to different protocol types that can provide access for different types of devices (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)).

[0060] In some examples, the network entity 105 (e.g., base station 140, RU 170) can be movable and thus provide communication coverage for a mobile coverage area 110. In some examples, although different coverage areas 110 associated with different technologies can overlap, different coverage areas 110 can be supported by the same network entity 105. In some other examples, overlapping coverage areas 110 associated with different technologies can be supported by different network entities 105. The wireless communication system 100 can include, for example, a heterogeneous network in which different types of network entities 105 use the same or different radio access technologies to provide coverage for various coverage areas 110.

[0061] The wireless communication system 100 can support synchronous or asynchronous operation. For synchronous operation, the network entities 105 (e.g., base stations 140) can have similar frame timings, and transmissions from different network entities 105 can be approximately aligned in time. For asynchronous operation, the network entities 105 can have different frame timings, and in some examples, transmissions from different network entities 105 can be misaligned in time. The techniques described herein can be used for synchronous or asynchronous operation.

[0062] Some UEs 115 (such as MTC or IoT devices) can be low-cost or low-complexity devices and can allow automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC can refer to data communication technologies that allow devices to communicate with each other or a device to communicate with a network entity 105 (e.g., base station 140) without human intervention. In some examples, M2M communication or MTC can include communication from devices with integrated sensors or meters to measure or capture information and relay such information to a central server or application that uses the information or presents the information to a person interacting with the application. Some UEs 115 can be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include: smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wilderness survival monitoring, weather and geographical event monitoring, formation management and tracking, remote security sensing, physical access control, and transaction-based commercial charging.

[0063] Some UEs 115 can be configured to operate in power consumption-reducing modes, such as half-duplex communication (e.g., a mode that supports one-way communication via transmission or reception but not concurrent transmission and reception). In some examples, half-duplex communication can be performed at a reduced peak rate. Other energy-saving techniques for UEs 115 include: entering a power-saving deep sleep mode when not participating in active communication, operating with limited bandwidth (e.g., according to narrowband communication), or a combination of these techniques. For example, some UEs 115 can 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 guard band of the carrier, or outside the carrier.

[0064] The wireless communication system 100 can be configured to support ultra-reliable communication or low-latency communication or various combinations thereof. For example, the wireless communication system 100 can be configured to support ultra-reliable low-latency communication (URLLC). The UEs 115 can be designed to support ultra-reliable, low-latency, or critical functions. Ultra-reliable communication can include private communication or group communication and can be supported by one or more services (such as push-to-talk, video, or data). Support for ultra-reliable, low-latency functions can include prioritization of services, and such services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, and ultra-reliable low-latency can be used interchangeably herein.

[0065] In some examples, UE 115 may be configured to communicate directly with other UEs 115 via a device-to-device (D2D) communication link 135 (e.g., according to a peer-to-peer (P2P), D2D, or sidelink protocol). In some examples, one or more UEs 115 performing D2D communication in a group may be within the coverage area 110 of a network entity 105 (e.g., base station 140, RU 170), and this network entity may support aspects of such D2D communication configured (e.g., scheduled) by the network entity 105. In some examples, one or more UEs 115 of such a group may be outside the coverage area 110 of the network entity 105, or may otherwise not be or be configured not to receive transmissions from the network entity 105. In some examples, a group of UEs 115 communicating via D2D communication may support a one-to-many (1:M) system, where each UE 115 transmits to each of the other UEs 115 in the group. In some examples, the network entity 105 may facilitate the scheduling of resources for D2D communication. In some other examples, D2D communication may be performed between UEs 115 without involving the network entity 105.

[0066] In some systems, the D2D communication link 135 may be an example of a communication channel (such as a sidelink communication channel) between vehicles (e.g., UE 115). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination of these. Vehicles may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information related to the V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure (such as roadside units), or communicate with the network via vehicle-to-network (V2N) communication via one or more network nodes (e.g., network entity 105, base station 140, RU 170), or both.

[0067] The core network 130 can provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 can be an evolved packet core (EPC) or a 5G core (5GC), which can include at least one control plane entity for managing access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity for routing packets or interconnecting to an external network (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity can manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management of the UE 115 served by a network entity 105 (e.g., a base station 140) associated with the core network 130. User IP packets can be transferred through the user plane entity, which can provide IP address allocation and other functions. The user plane entity can be connected to the IP services 150 of one or more network operators. The IP services 150 can include access to the Internet, an intranet, an IP multimedia subsystem (IMS), or packet switched streaming services.

[0068] The wireless communication system 100 can operate using one or more frequency bands that can be in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or the decimeter band, because in terms of length, the wavelength range is from about one decimeter to one meter. UHF waves can be blocked or redirected by buildings and environmental features (which can be referred to as clusters), but these waves can be sufficient to penetrate structures so that macro cells can serve UEs 115 located indoors. Compared with communications using smaller frequencies and longer wavelengths in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz, communications using UHF waves can be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers).

[0069] The wireless communication system 100 may also operate using the super high frequency (SHF) band, which may be in the range of 3 GHz to 30 GHz (also known as the centimeter band), or using the extremely high frequency (EHF) band of the spectrum (e.g., from 30 GHz to 300 GHz) (also known as the millimeter band). In some examples, the wireless communication system 100 may support millimeter wave (mmW) communication between the UE 115 and network entities 105 (e.g., base station 140, RU 170), and the EHF antennas of the corresponding devices may be smaller and closer spaced than UHF antennas. In some examples, such techniques may facilitate the use of antenna arrays within a device. However, the propagation of EHF transmissions may be affected by even greater attenuation and shorter ranges than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions using one or more different frequency regions, and the use of frequency bands designated across these frequency regions may vary by country or regulatory body.

[0070] The wireless communication system 100 may utilize licensed and unlicensed RF spectrum bands. For example, the wireless communication system 100 may use an unlicensed band (such as the 5 GHz industrial, scientific, and medical (ISM) band) to employ licensed-assisted access (LAA), long term evolution unlicensed (LTE-U) radio access technology, or NR technology. When operating using an unlicensed RF spectrum band, devices such as network entities 105 and UE 115 may employ carrier sensing for collision detection and avoidance. In some examples, the operation using an unlicensed band may be based on a carrier aggregation configuration in combination with the operation of a component carrier using a licensed band (e.g., LAA). Operations using unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer (P2P) transmissions, or device-to-device (D2D) transmissions, etc.

[0071] The network entity 105 (e.g., base station 140, RU 170) or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of the network entity 105 or UE 115 may be located within one or more antenna arrays or antenna panels, which may support MIMO operation or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as at an antenna tower. In some examples, the antennas or antenna arrays associated with the network entity 105 may be located at different geographical locations. The network entity 105 may include an antenna array having a set of antenna ports arranged in multiple rows and columns that the network entity 105 may use for beamforming to support communication with the UE 115. Similarly, the UE 115 may include one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support RF beamforming for signals transmitted via the antenna ports.

[0072] The network entity 105 or UE 115 may use MIMO communication to exploit multipath signal propagation and improve spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may be transmitted, for example, by a transmitting device via different antennas or different combinations of antennas. Similarly, the 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 for channel measurement and reporting. MIMO techniques include: single-user MIMO (SU-MIMO), for which multiple spatial layers are transmitted to the same receiving device; and multi-user MIMO (MU-MIMO), for which multiple spatial layers are transmitted to multiple devices.

[0073] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that can be used at a transmitting device or a 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 device and the receiving device. Beamforming can be achieved by combining signals communicated via the antenna elements of an antenna array such that some signals propagating in a particular direction relative to the antenna array experience constructive interference while other signals experience destructive interference. The adjustment of the signals communicated via the antenna elements can include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to the signals carried via the antenna elements associated with the device. The adjustment associated with each of these antenna elements can be defined by a set of beamforming weights associated with a particular direction (e.g., relative to the antenna array of the transmitting device or the receiving device or relative to some other direction).

[0074] Network entity 105 or UE 115 can use beam scanning techniques as part of beamforming operations. For example, network entity 105 (e.g., base station 140, RU 170) can use multiple antennas or antenna arrays (e.g., antenna panels) to perform beamforming operations for directional communication with UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) can be transmitted multiple times by network entity 105 in different directions. For example, network entity 105 can transmit signals according to different sets of beamforming weights associated with different transmission directions. Transmission along different beam directions can be used to identify (e.g., by the transmitting device such as network entity 105, or by the receiving device such as UE115) the beam directions for later transmission or reception by network entity 105.

[0075] Some signals (such as data signals associated with a particular receiving device) can 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 receiving network entity 105 or receiving UE 115). In some examples, the beam direction associated with transmission along a single beam direction can be determined based on signals transmitted along one or more beam directions. For example, UE 115 can receive one or more of the signals transmitted by network entity 105 in different directions and can report to network entity 105 an indication of the signal that UE 115 receives with the highest signal quality or other acceptable signal quality.

[0076] In some examples, transmissions performed by a device (e.g., by network entity 105 or UE 115) may be carried out using multiple beam directions, and the device may use a combination of digital precoding or beamforming to generate a combined beam for transmission (e.g., from network entity 105 to UE 115). UE 115 may report feedback indicating precoding weights for one or more beam directions, and the feedback may correspond to a configured set of beams across the system bandwidth or one or more sub-bands. Network entity 105 may transmit reference signals (e.g., cell-specific reference signal (CRS), channel state information reference signal (CSI-RS)), which may or may not be precoded. UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., multi-panel codebook, linear combination codebook, port selection codebook). Although these techniques are described with reference to signals transmitted by network entity 105 (e.g., base station 140, RU 170) in one or more directions, UE 115 may use similar techniques for transmitting signals multiple times in different directions (e.g., for identifying beam directions used by UE 115 for subsequent transmission or reception), or for transmitting signals in a single direction (e.g., for transmitting data to a receiving device).

[0077] A receiving device (e.g., UE 115) may perform receiving operations according to multiple receiving configurations (e.g., directional listening) when receiving various signals (such as synchronization signals, reference signals, beam selection signals, or other control signals) from a receiving device (e.g., network entity 105). For example, the receiving device may perform receiving according to multiple receiving directions by: receiving via different antenna sub-arrays, processing the received signals according to different antenna sub-arrays, receiving according to different sets of receive beamforming weights (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or processing the received signals according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array, where any of these may refer to "listening" according to different receiving configurations or receiving directions. In some examples, the receiving device may use a single receiving configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receiving configuration may be aligned along a beam direction determined based on listening according to different receiving configuration directions (e.g., a beam direction determined to have the highest signal strength, highest signal-to-noise ratio (SNR), or other acceptable signal quality based on listening according to multiple beam directions).

[0078] The wireless communication system 100 can be a packet-based network operating according to a layered protocol stack. In the user plane, the communication at the bearer or PDCP layer can be IP-based. The RLC layer can perform packet segmentation and reassembly for conveyance via logical channels. The MAC layer can perform priority handling and multiplexing from logical channels into transport channels. The MAC layer can also implement error detection techniques, error correction techniques, or both to support retransmission to improve link efficiency. In the control plane, the RRC layer can provide the establishment, configuration, and maintenance of an RRC connection that supports radio bearers for user plane data between the UE 115 and the network entity 105 or the core network 130. The PHY layer can map the transport channels to physical channels.

[0079] The UE 115 and the network entity 105 can support the retransmission of data to increase the likelihood that the data is successfully received. Hybrid Automatic Repeat Request (HARQ) feedback is a technique for increasing the likelihood of correctly receiving data via a communication link (e.g., communication link 125, D2D communication link 135). HARQ can include a combination of error detection (e.g., using Cyclic Redundancy Check (CRC)), Forward Error Correction (FEC), and retransmission (e.g., Automatic Repeat Request (ARQ)). HARQ can improve the throughput at the MAC layer under poor radio conditions (e.g., low signal-to-noise ratio conditions). In some examples, the device can support same-slot HARQ feedback, in which case the device can provide HARQ feedback for data received via previous symbols in a particular slot during that slot. In some other examples, the device can provide HARQ feedback in a subsequent slot or according to some other time interval.

[0080] When operating in DRX mode, the UE 115 can receive a grant scheduling a sidelink data message for the UE 115 on a shared radio frequency spectrum band, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The UE 115 can send at least one feedback message indicating a feedback state of the sidelink data message during at least one of the feedback channel opportunities in the set of feedback channel opportunities. The UE 115 can initiate a round-trip timer (e.g., 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 suppresses monitoring for retransmission of the sidelink data message.

[0081] Figure 2 An example of a wireless communication system 200 supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure is illustrated. The wireless communication system 200 can implement aspects of the wireless communication system 100. The wireless communication system 200 can include a UE 205 and a UE 210, which can be examples of the corresponding devices described herein.

[0082] A wireless communication system may support HARQ-ACK operations for cellular (e.g., based on the Uu interface) and / or sidelink (e.g., based on the PC5 interface) communications. The HARQ-ACK operation confirms that the receiving device is able to successfully receive and decode a data message (and / or a grant for scheduling the transmission of the data message), or confirms that the receiving device is unable to successfully receive and decode the data message (and / or the grant for the data message). In some aspects, the resources (e.g., time, frequency, space, and / or code resources) used to convey HARQ-ACK feedback may be indicated in the grant for scheduling the data message and / or may be otherwise known (e.g., (pre)-configured or otherwise adopted within the network). A transmitting device that receives an ACK indication in the HARQ-ACK feedback considers the data message transmission to be successful. A transmitting device that receives a NACK indication in the HARQ-ACK feedback or a transmitting device that has no feedback considers the data message transmission to be unsuccessful. Accordingly, the transmitting device may send another grant to the receiving device that schedules a retransmission of the data message associated with the NACK to the receiving device. In some aspects, a data message may be associated with a HARQ process identifier for the initial data message transmission, the transmission of the HARQ-ACK feedback regarding the data message, and / or any associated retransmission of the data message. The HARQ process identifier associated with the data message may be indicated in the grant for scheduling the data message, in the RRC signaling (pre)-configuration aspect of the data message, or in a separate signaling.

[0083] For sidelink communications, multiple feedback channel opportunities (e.g., PSFCH opportunities or candidates) may be allocated for sidelink data messages. Each feedback channel opportunity generally defines an opportunity for the receiving device to send HARQ-ACK feedback for a sidelink data message. For example, in some networks, the PSFCH HARQ timeline provides one opportunity (e.g., one feedback channel opportunity) for PSFCH transmission. If the HARQ-ACK feedback occurs in a shared radio frequency spectrum band, a listen-before-talk (LBT) process may be performed on the channel just before the feedback channel opportunity or initially during the feedback channel opportunity. If the LBT process fails (e.g., the channel is busy and thus unavailable for conveying HARQ-ACK feedback), then the transmitting device may interpret the lack of a feedback message as a NACK for the corresponding sidelink data message and schedule a retransmission.

[0084] The wireless communication system 200 may support multiple PSFCH opportunities or candidates (e.g., feedback channel opportunities) for HARQ-ACK feedback (e.g., feedback message transmission). That is, in response to a physical sidelink shared channel (PSSCH) transmission (e.g., sidelink data message), multiple PSFCH candidates (e.g., a set of feedback channel opportunities) may be allocated on different time slots with or without multiple frequency-domain multiplexing opportunities in different LBT subbands. The receiving device typically sends HARQ-ACK feedback at the earliest / latest PSFCH candidate that clears the LBT procedure. For example, a UE (such as UE 205 and / or UE 210) may determine a time slot and / or a set of resource blocks (RBs) for HARQ-ACK feedback transmission based on the HARQ timeline and the (pre)-configured resources for the multiple PSFCH candidates. Thus, a PSSCH time slot (e.g., the time slot during which the sidelink data message is transmitted) may be mapped to different PSFCH instances in the time domain and / or different PSFCH resources in different RB sets.

[0085] The UE (e.g., such as UE 205 and / or UE 210) may also operate in a DRX mode, where 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 avoids monitoring the channel. In some aspects, the DRX operation may be specific to a particular HARQ process identifier, such that when in the DRX sleep mode for the HARQ identifier associated with a given sidelink communication, the UE may switch to other operations or communications (e.g., perform other communications or functions during the DRX sleep cycle for that HARQ process identifier). This enables the UE to save power (at least with respect to the HARQ process identifier) by turning off such modules or functions.

[0086] For a cellular network (e.g., a Uu-based network), a DRX process can be defined for a UE. In the downlink, the UE may 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 the data is not successfully decoded, the UE starts a retransmission timer (e.g., drx-RetransmissionTimerDL) for the corresponding HARQ process after the drx-HARQ-RTT-TimerDL timer expires. In the uplink, the UE starts the drx-HARQ-RTT-TimerUL for the corresponding HARQ process in the first symbol after the end of the first transmission (within a bundle) of the corresponding PUSCH. If the drx-HARQ-RTT-TimerUL timer expires, the UE starts the drx-RetransmissionTimerUL timer for the corresponding HARQ process in the first symbol after the drx-HARQ-RTT-TimerUL timer expires. For NR-U communication, if the PDSCH-to-HARQ_feedback timing value indicates a non-numerical k1 value, the UE starts the drx-RetransmissionTimerDL in the first symbol after the PDSCH transmission for the corresponding HARQ process.

[0087] However, in some examples, such techniques may not be sufficient to support HARQ for sidelink communication. For unicast or multicast option 2 transmission, an RTT timer (e.g., sl-drx-HARQ-RTT-Timer) for sidelink communication is started in the first slot after the corresponding PSFCH instance carrying the HARQ-ACK feedback, or if the HARQ-ACK feedback is discarded due to priority rules. For multicast option 1 sidelink communication (e.g., only NACK HARQ-ACK feedback), the sl-drx-HARQ-RTT-Timer is started in the first slot after the corresponding PSFCH instance carrying the NACK feedback, or the NACK feedback is discarded due to priority rules, or no NACK feedback is sent due to a positive acknowledgement (e.g., ACK). However, when multiple PSFCH candidates are introduced, this results in confusion regarding when the UE starts the RTT timer (e.g., ambiguity regarding which PSFCH occasion is associated with the UE starting the sl-drx-HARQ-RTT-Timer).

[0088] Accordingly, aspects of the techniques described herein provide various techniques for determining when a UE (e.g., UE 205 in this example) starts or otherwise initiates an RTT timer for a sidelink data message when indicating a set of feedback channel opportunities (e.g., PSFCH opportunities or candidates) for the sidelink data message. For example, at 215, UE 210 (e.g., a transmitting device, or in this example, a transmitting sidelink UE) may send or otherwise provide a grant scheduling a sidelink data message. The sidelink data message may be scheduled on a shared radio frequency spectrum band (e.g., in an unlicensed band where an LBT procedure is performed before 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 a PSSCH. In some examples, the grant may include both an SCI-1 message and an SCI-2 message. UE 210 may send or otherwise provide the sidelink data message to UE 205 according to the grant. The grant may indicate or otherwise identify a set of feedback channel opportunities (e.g., PSFCH opportunities or candidates) associated with the sidelink data message. The set of feedback channel opportunities may be in the same or different LBT bands and / or RB sets relative to the sidelink data message and / or the grant. The set of feedback channel opportunities may be in the same or different time slots relative to the sidelink data message and / or the grant.

[0089] UE 205 may receive or otherwise obtain the grant and monitor the allocated resources to receive or otherwise obtain the sidelink data message. UE 205 may identify or otherwise determine the feedback status of the sidelink data message. The feedback status may include an ACK status when UE 205 is able to successfully receive and decode the sidelink data message (e.g., recover the sidelink data from it) and / or the grant scheduling the sidelink data message, or the feedback status may include a NACK status when UE 205 is unable to successfully receive and decode the sidelink data message and / or the grant scheduling the sidelink data message. Accordingly, UE205 may send or otherwise provide a feedback message at 220 that indicates the feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities.

[0090] The UE 205 may initiate or otherwise start a round-trip timer (e.g., RTT timer, Sl-drx-HARQ-RTT-Timer) at least based on the feedback channel opportunity during which a feedback message is sent. For example, the UE 205 may initiate the RTT timer in the first symbol or time slot after the feedback channel opportunity for sending the feedback message, after the first feedback channel opportunity in the set, after the intermediate feedback channel opportunity in the set, or after the last feedback channel opportunity in the feedback channel opportunity set. In some examples, the RTT timer may be started after a feedback channel opportunity associated with a successful LBT procedure (e.g., based on the result of the LBT procedure performed just before or initially during each feedback channel opportunity).

[0091] In some examples, the duration of the RTT timer may be selected, modified, or otherwise set to a value based on which feedback channel opportunity in the set the RTT timer is started after. For example, when the UE 205 initiates the RTT timer after the first or early PSFCH opportunity in the set, the duration of the RTT timer may be extended (e.g., extended beyond the remaining PSFCH opportunities in the set). As another example, when the UE 205 initiates the RTT timer after the last or late PSFCH opportunity in the set, the duration of the RTT timer may be shortened to anticipate a retransmission of the sidelink data message. In some examples, 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 expects a retransmission of the sidelink data message scheduled by the UE 210.

[0092] When the RTT timer is initiated, the UE 205 can generally avoid monitoring for retransmissions of sidelink data messages. After the RTT timer expires, the UE 205 can start or otherwise initiate a retransmission timer (e.g., sl-drx-RetransmissionTimer), during which the UE 205 monitors for retransmissions of scheduled sidelink data messages and / or grants for retransmissions of sidelink data messages. That is, the UE 205 can set the retransmission timer to have a duration that covers the expected reception of the grant and the duration of the retransmission of the sidelink data message. In some examples, the duration of the retransmission timer can be selected, modified, or otherwise set based on the value at which the RTT timer is started after which feedback channel opportunity in the set. For example, when the UE 205 initiates the RTT timer after the first or early PSFCH opportunity in the set, the duration of the retransmission timer can be extended (e.g., to reduce the retransmission time). When the retransmission timer is running (e.g., has not expired), the UE 205 can generally monitor for retransmissions of sidelink data messages (e.g., grants for scheduled retransmissions and / or retransmissions of sidelink data messages).

[0093] Figures 3A to 3C An example of a feedback configuration 300 that supports DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure is illustrated. The feedback configuration 300 can implement aspects of the wireless communication system 100 and / or 200. Aspects of the feedback configuration 300 can be implemented at or by a UE, which can be an example of the corresponding device described herein.

[0094] As discussed above, aspects of the techniques described herein provide that the UE initiates or otherwise starts the RTT timer at least in part based on which PSFCH candidate is selected after a feedback channel opportunity (e.g., a PSFCH candidate) in a set of feedback channel opportunities. The UE can receive a sidelink data message, determine the feedback status of the message, and send a feedback message indicating the feedback message to the transmitting device (e.g., sidelink UE scheduling to send the sidelink data message to the UE). The UE can initiate the RTT timer at least in part based on which PSFCH candidate is selected for sending the feedback message after one of the PSFCH candidates.

[0095] For example and turning first to Figure 3AIn the feedback configuration 300-a, the UE may receive or otherwise obtain a grant for scheduling a sidelink data message for the UE on a shared (e.g., unlicensed) frequency band. This may include the UE receiving the grant 305 in an SCI message that schedules the sidelink data message 310, where the sidelink data message 310 is received on the PSSCH. The grant 305 may indicate or otherwise identify the resources (e.g., time resources, frequency resources, spatial resources, or code resources) for the sidelink data message 310 in the PSSCH. The grant 305 may also indicate or otherwise identify a set of feedback channel opportunities. In the non-limiting example illustrated in the feedback configuration 300-a, only three feedback channel opportunities are shown by way of example. 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).

[0096] Each PSFCH candidate in the set of PSFCH candidates (e.g., the set of feedback channel opportunities) may generally identify the resources (e.g., time resources, frequency resources, spatial resources, or code resources) and / or other parameters to be used by the UE for transmitting 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 discussed, the sidelink data message may be communicated in a shared or unlicensed frequency band such that an LBT procedure is performed just before or at the start of each PSFCH candidate in the set to determine whether the feedback message may be transmitted (e.g., to ensure that the channel is idle or otherwise available).

[0097] The feedback configuration 300-a illustrates an example in which the UE initiates an RTT timer after the first feedback channel opportunity in the set of feedback channel opportunities (e.g., in the first symbol or time slot after the feedback channel opportunity 315). That is, the UE may identify or otherwise determine which PSFCH candidate in the set is the first PSFCH candidate (e.g., PSFCH candidate #0) and initiate the RTT timer in the first symbol or time slot after the first PSFCH candidate in the set. The UE may identify the first PSFCH candidate in the set based on the grant 305 or the set of PSFCH candidates for the HARQ procedure associated with the sidelink data message may be (pre)-configured in other signaling. That is, in this example, the UE may default to the first PSFCH candidate after which the RTT timer is started.

[0098] In some aspects, the UE may or may not be able to send a feedback message after the first PSFCH candidate, but may still start or otherwise initiate the RTT timer after the first PSFCH candidate. That is, the UE may fail LBT at the first time slot (e.g., the time slot where the first PSFCH candidate is located), but the UE may still initiate the RTT timer after the feedback channel opportunity 315. Conversely, the UE may continue to perform the LBT process before each PSFCH candidate and send a feedback message in the PSFCH candidate associated with the successful LBT process.

[0099] In some aspects, the duration of the retransmission (ReTx) timer (e.g., sl-drx-RetransmissionTimer) is based on the RTT timer initiated after the first PSFCH candidate (e.g., extending the duration of the ReTx timer). As discussed above, the UE may operate in the DRX mode, where the UE sleeps with respect to the HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE may monitor the grant for retransmission of the scheduled sidelink data message and / or the retransmission of the sidelink data message. In the feedback configuration 300-a, this may include the UE monitoring the grant 330 for retransmission of the scheduled sidelink data message 335. In some examples, a longer ReTx timer may help accommodate the HARQ-ACK LBT uncertainty of the channel.

[0100] Next, turning to Figure 3B the feedback configuration 300-b, the UE may receive or otherwise obtain a grant for scheduling a sidelink data message for the UE on a shared (e.g., unlicensed) frequency band. This may include the UE receiving the grant 305 in the SCI message scheduling the sidelink data message 310, where the sidelink data message 310 is received on the PSSCH. The grant 305 may indicate or otherwise identify the resources in the PSSCH for the sidelink data message 310. The grant 305 may also indicate or otherwise identify the set of feedback channel opportunities. In the non-limiting example illustrated in the feedback configuration 300-b, only three feedback channel opportunities are shown as an example. Thus, in this example, the set of feedback channel opportunities includes the feedback channel opportunity 315 (e.g., for PSFCH candidate #0), the feedback channel opportunity 320 (e.g., for PSFCH candidate #1), and the feedback channel opportunity 325 (e.g., for PSFCH candidate #2).

[0101] Each PSFCH candidate in the PSFCH candidate set (e.g., the set of feedback channel opportunities) can generally identify the resources and / or other parameters of the feedback message to be used by the UE to send the feedback status indicating the sidelink data message 310. As discussed, the sidelink data message can be conveyed in a shared or unlicensed band, such that the LBT process is performed just before or at the start of each PSFCH candidate in the set to determine whether the feedback message can be sent.

[0102] Feedback configuration 300-b illustrates an example in which the UE initiates the RTT timer after the first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT process (e.g., in the first symbol or time slot after the feedback channel opportunity). That is, the UE can perform the LBT process just before or at the start of each PSFCH candidate, and initiate the RTT timer in the first symbol or time slot after the first PSFCH candidate in the set with a successful LBT process. That is, in this example, the UE can base on which PSFCH candidate to initiate the RTT timer after based on the result of the LBT process performed for each PSFCH candidate.

[0103] In feedback configuration 300-b, the UE can perform the LBT process associated with feedback channel opportunity 315 and determine that the LBT process is unsuccessful (e.g., the UE cannot capture the channel). The UE can perform another LBT process associated with feedback channel opportunity 320 and determine that the LBT process is successful (e.g., the UE can capture the channel for sending the feedback message). Thus, and in this example, the UE can start or otherwise initiate the RTT timer after feedback channel opportunity 320, where the UE avoids monitoring the grant 330 for resending the scheduled sidelink data message 335 and optionally sends the feedback message during feedback channel opportunity 320.

[0104] In the case where the UE determines that each PSFCH candidate in the set is associated with an unsuccessful LBT process (e.g., the LBT process fails for all PSFCH candidates), the UE can initiate the RTT timer after the last PSFCH candidate in the set (e.g., after feedback channel opportunity 325). For example, the UE can identify or otherwise determine the last PSFCH candidate in the set and initiate the RTT timer after the last feedback channel opportunity (e.g., after feedback channel opportunity 320) based on each PSFCH candidate with an unsuccessful LBT process.

[0105] Accordingly, feedback configuration 300-b illustrates an example in which a sidelink receiving device (e.g., a UE) starts the RTT timer after all LBT procedures fail or after the first PSFCH transmission or the last PSFCH candidate time slot. Starting the RTT timer after the feedback message is sent allows the UE to start the retransmission timer with more accurate timing (e.g., if an ACK / NACK feedback is detected at the sidelink transmitting device). If the LBT procedure fails at each PSFCH candidate, the sidelink transmitting device may assume NACK after the last PSFCH candidate and retransmit the transport block (TB) (e.g., sidelink data message 335). Thus, the RTT timer can be started after the last PSFCH candidate when the shared or unlicensed channel is not available for sending the feedback message.

[0106] In some examples, the UE may send or otherwise provide multiple feedback message transmissions to ensure that the transmitting device can receive a feedback status indication. If the transmitting device determines that the HARQ-ACK feedback is lost or discarded (e.g., not received), if the feedback message transmission is repeated among the remaining PSFCH candidates, the RTT timer may also be considered to be started after the first transmitted feedback message transmission. If the feedback message is only sent 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 to assume NACK and retransmit the sidelink data message 335. In this case, the ReTx timer may start too early. Thus, the ReTx timer duration can be extended based on after which PSFCH candidate the RTT timer is started.

[0107] As discussed above, the UE may operate in a DRX mode, in which the UE sleeps with respect to the HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE may monitor the grant for retransmission of the scheduled sidelink data message and / or the retransmission of the sidelink data message. In feedback configuration 300-b, this may include the UE monitoring the grant 330 for retransmission of the sidelink data message 335.

[0108] Moving on to Figure 3CFor feedback configuration 300-c, the UE may receive or otherwise obtain a grant for scheduling a sidelink data message for the UE on a shared (e.g., unlicensed) frequency band. This may include the UE receiving grant 305 in an SCI message that schedules sidelink data message 310, where sidelink data message 310 is received on the PSSCH. Grant 305 may indicate or otherwise identify the resources in the PSSCH for sidelink data message 310. Grant 305 may also indicate or otherwise identify a set of feedback channel opportunities. In the non-limiting example illustrated in 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 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).

[0109] Each PSFCH candidate in the set of PSFCH candidates (e.g., the set of feedback channel opportunities) may generally identify the resources and / or other parameters to be used by the UE for transmitting a feedback message indicating the feedback status of sidelink data message 310. As discussed, sidelink data message 310 may be communicated in a shared or unlicensed frequency band such that an LBT procedure is performed just before or at the start of each PSFCH candidate in the set to determine whether the feedback message may be transmitted.

[0110] Feedback configuration 300-c illustrates an example in which the UE initiates an RTT timer after the last feedback channel opportunity in the set of feedback channel opportunities. That is, regardless of the result of the LBT procedure, the UE may or may not perform the LBT procedure immediately before or at the start of each PSFCH candidate and initiate the RTT timer in the first symbol or time slot after the last PSFCH candidate. That is, in this example, the UE may base on which PSFCH candidate to initiate the RTT timer on the basis that PSFCH candidate #2 is the last PSFCH candidate in the set of PSFCH candidates.

[0111] Thus, and in this example, the UE may start or otherwise initiate the RTT timer after feedback channel opportunity 320, where the UE avoids monitoring for grant 330 that schedules a retransmission of sidelink data message 335.

[0112] Accordingly, feedback configuration 300-c illustrates an example where a sidelink receiving device (e.g., a UE) starts the RTT timer right after the last PSFCH candidate slot. Starting the RTT timer after the last PSFCH candidate can reduce latency, such as when the feedback message is sent in the last or near last PSFCH candidate in the set (or when the transmitting device loses the HARQ-ACK feedback, such as in the multicast option 1 scenario). For multicast option 1, the UE (e.g., the sidelink transmitting device) can wait until the last PSFCH candidate determines the feedback status (e.g., to save power, prioritize processing / communication, etc.). To ensure that retransmission occurs after the retransmission timer has started, the transmitting device can select the ReTx resource after the last PSFCH candidate and / or the duration of the RTT timer can be shorter to allow monitoring of the ReTx resource.

[0113] As discussed above, the UE can operate in DRX mode, where the UE sleeps with respect to the HARQ process identifier associated with the sidelink data message 310. During the ReTx timer, the UE can monitor the grant for retransmission of the scheduled sidelink data message and / or the retransmission of the sidelink data message. In feedback configuration 300-c, this can include the UE monitoring the grant 330 for retransmission of the sidelink data message 335.

[0114] Figure 4 An example of a feedback configuration 400 that supports DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure is illustrated. Aspects of feedback configuration 400 can implement aspects of wireless communication system 100 and / or 200 and / or aspects of feedback configuration 300. Aspects of feedback configuration 400 can be implemented at or by a UE, which can be an example of the corresponding device described herein.

[0115] As discussed above, aspects of the techniques described herein provide for the UE to start or otherwise initiate the RTT timer at least somewhat based on which PSFCH candidate is selected after a feedback channel opportunity (e.g., a PSFCH candidate) in a set of feedback channel opportunities. The UE can receive a sidelink data message, determine the feedback status of the message, and send a feedback message indicating the feedback message to the transmitting device (e.g., the sidelink UE schedules the sidelink data message to be sent to the UE). The UE can initiate the RTT timer at least somewhat based on which PSFCH candidate is selected for sending the feedback message after one of the PSFCH candidates.

[0116] For example, a UE may receive or otherwise obtain a grant for scheduling a sidelink data message for the UE on a shared (e.g., unlicensed) frequency band. This may include the UE receiving the grant in an SCI message that schedules the sidelink data message, where the sidelink data message is received on the PSSCH. The grant may indicate or otherwise identify resources (e.g., time resources, frequency resources, spatial resources, or code resources) for the sidelink data message in the PSSCH. The grant may also indicate or otherwise identify a set of feedback channel opportunities. In Figure 4 In the illustrated non-limiting example, only three feedback channel opportunities are shown by way of example. 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).

[0117] However, in Figure 4 In the example illustrated in, the duration of the RTT timer may be selected based on the first feedback channel opportunity in the set associated with the initiation of the RTT timer. That is, in some examples, the grant for the transmission of the sidelink data message initially scheduled for the UE may also identify the retransmission resources to be used. Thus, the UE may know when to start the retransmission timer in order to monitor for retransmissions of the sidelink data message. When the UE knows the retransmission resources for the sidelink data message (e.g., the expected scheduling time for retransmission), the UE may more accurately select the duration of the RTT. In some aspects, this may include setting the RTT timer based on when the RTT timer is started in the set of PSFCH candidate positions (e.g., after which PSFCH candidate) and the initiation of the retransmission resources. This may include setting the duration of the RTT timer to expire at a predefined time before the retransmission resources begin.

[0118] Thus, and as Figure 4 shown in, 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 which PSFCH candidate the RTT timer is selected after. 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 a duration of the RTT timer that is different from (e.g., modified from) the (pre)-configured or otherwise determined duration of the RTT timer.

[0119] Accordingly, the UE may send a feedback message to the transmitting device and avoid monitoring for retransmissions during the duration of the RTT timer. When the RTT timer expires, the UE may switch to the wake or active state of the DRX mode and monitor the channel for a grant for retransmission of the scheduled sidelink message and / or retransmission of the sidelink message.

[0120] Figure 5 Block diagram 500 illustrates a device 505 supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. Device 505 may be an example of aspects of UE 115 as described herein. Device 505 may include a receiver 510, a transmitter 515, and a communication manager 520. Device 505 may also include a processor. Each of these components may communicate with each other (e.g., via one or more buses).

[0121] The receiver 510 may provide components for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to DRX enhancements with multiple sidelink feedback channel opportunities). The information may be passed to other components of device 505. The receiver 510 may utilize a single antenna or an array of multiple antennas.

[0122] The transmitter 515 may provide components for transmitting signals generated by other components of device 505. For example, the transmitter 515 may transmit information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to DRX enhancements with multiple sidelink feedback channel opportunities). In some examples, the transmitter 515 may be co-located with the receiver 510 in a transceiver module. The transmitter 515 may utilize a single antenna or an array of multiple antennas.

[0123] The communication manager 520, the receiver 510, the transmitter 515, or various combinations thereof or their various components may be examples of components for performing aspects of DRX enhancements with multiple sidelink feedback channel opportunities as described herein. For example, the communication manager 520, the receiver 510, the transmitter 515, or various combinations thereof or their components may support methods for performing one or more of the functions described herein.

[0124] In some examples, the communication manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof may be implemented in hardware (e.g., in a communication management circuit). 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 components, discrete hardware components, or any combination thereof that are configured to or otherwise support components for performing the functions described in this disclosure. In some examples, the processor and the 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).

[0125] Additionally or alternatively, in some examples, the communication 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., implemented as communication management software or firmware). If implemented in code executed by a processor, the functions of the communication manager 520, the receiver 510, the transmitter 515, or various combinations or components thereof may be performed by a general purpose processor, DSP, CPU, ASIC, FPGA, microcontroller, or any combination of these or other programmable logic devices that are configured to or otherwise support components for performing the functions described in this disclosure.

[0126] In some examples, the communication manager 520 may be configured to use or otherwise cooperate with the receiver 510, the transmitter 515, or both to perform various operations (e.g., receive, obtain, monitor, output, transmit). For example, the communication manager 520 may receive information from the receiver 510, convey information to the transmitter 515, or integrate in combination with the receiver 510, the transmitter 515, or both to obtain information, output information, or perform various other operations as described herein.

[0127] The communication manager 520 may support wireless communication at a UE in accordance with examples disclosed herein. For example, the communication manager 520 may be configured to or otherwise support components for receiving a grant for a sidelink data message scheduled for the UE on a shared radio frequency spectrum band when operating in DRX mode, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The communication manager 520 may be configured to or otherwise support components for transmitting at least one feedback message indicating a feedback status of the sidelink data message during at least one of the feedback channel opportunities in the set of feedback channel opportunities. The communication manager 520 may be configured to or otherwise support components for initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for a retransmission of the sidelink data message.

[0128] By including or configuring the communication manager 520 in accordance with examples described herein, a device 505 (e.g., a processor that controls or otherwise couples to a receiver 510, a transmitter 515, the communication manager 520, or a combination thereof) may support techniques for improving RTT timer initiation when multiple PSFCH candidates are indicated for a sidelink data message. The RTT timer may be initiated after a first PSFCH candidate, after an intermediate candidate, after a last PSFCH candidate, or based on results of a LBT procedure performed for each PSFCH candidate.

[0129] Figure 6 Block diagram 600 illustrates a device 605 supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The device 605 may be an example of aspects of the device 505 or UE 115 described herein. The device 605 may include a receiver 610, a transmitter 615, and a communication 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).

[0130] The receiver 610 may provide components for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to DRX enhancements with 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 collection of multiple antennas.

[0131] The transmitter 615 may provide components for transmitting signals generated by other components of the device 605. For example, the transmitter 615 may transmit information associated with various information channels (e.g., control channels, data channels, information channels related to DRX enhancements with multiple sidelink feedback channel opportunities), such as packets, user data, control information, or any combination thereof. In some examples, the transmitter 615 may be co-located with the receiver 610 in a transceiver module. The transmitter 615 may utilize a single antenna or an array of multiple antennas.

[0132] The device 605 or its various components may be examples of components for performing various aspects of DRX enhancements with multiple sidelink feedback channel opportunities as described herein. For example, the communication manager 620 may include a grant manager 625, a feedback manager 630, an RTT manager 635, or any combination thereof. The communication manager 620 may be an example of aspects of the communication manager 520 as described herein. In some examples, the communication manager 620 or its various components may be configured to use or otherwise cooperate with the receiver 610, the transmitter 615, or both to perform various operations (e.g., receive, obtain, monitor, output, transmit). For example, the communication manager 620 may receive information from the receiver 610, convey information to the transmitter 615, or integrate with the receiver 610, the transmitter 615, or both to obtain information, output information, or perform various other operations as described herein.

[0133] The communication manager 620 may support wireless communication at the UE according to the examples disclosed herein. The grant manager 625 may be configured to or otherwise support components for receiving a grant for a sidelink data message scheduled for the UE on a shared radio frequency spectrum band when operating in DRX mode, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The feedback manager 630 may be configured to or otherwise support components for transmitting at least one feedback message indicating a feedback state of the sidelink data message during at least one of the feedback channel opportunities in the set of feedback channel opportunities. The RTT manager 635 may be configured to or otherwise support components for initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for retransmission of the sidelink data message.

[0134] Figure 7Block diagram 700 illustrates a communication manager 720 that supports DRX enhancements with multiple sidelink feedback channel opportunities, in accordance with one or more aspects of the present disclosure. The communication manager 720 may be an example of the communication manager 520, the communication manager 620, or aspects of both as described herein. The communication manager 720 or its various components may be examples of components for performing various aspects of DRX enhancements with multiple sidelink feedback channel opportunities as described herein. For example, the communication manager 720 may include a grant manager 725, a feedback manager 730, an RTT manager 735, a PSFCH timing manager 740, an LBT manager 745, an RTT duration manager 750, or any combination thereof. Each of these components may communicate directly or indirectly with each other (e.g., via one or more buses).

[0135] The communication manager 720 may support wireless communication at a UE in accordance with examples as disclosed herein. The grant manager 725 may be configured to or otherwise support components for receiving a grant for a sidelink data message scheduled for the UE on a shared radio frequency spectrum band while operating in DRX mode, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The feedback manager 730 may be configured to or otherwise support components for sending at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities. The RTT manager 735 may be configured to or otherwise support components for initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for retransmission of the sidelink data message.

[0136] In some examples, the PSFCH timing manager 740 may be configured to or otherwise support components for identifying a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the first feedback channel opportunity.

[0137] In some examples, the PSFCH timing manager 740 may be configured to or otherwise support components for determining that a LBT procedure performed prior to the first feedback channel opportunity was unsuccessful. In some examples, the PSFCH timing manager 740 may be configured to or otherwise support components for sending the at least one feedback message in subsequent feedback channel opportunities in the set of feedback channel opportunities associated with a successful LBT procedure while initiating the round-trip timer after the first feedback channel opportunity.

[0138] In some examples, the PSFCH timing manager 740 may be configured to or otherwise support components for extending the duration of a retransmission timer based on the round-trip timer being initiated after the first feedback channel timing, during which duration the UE monitors the sidelink channel for a second grant for retransmission of the scheduled sidelink data message.

[0139] In some examples, the LBT manager 745 may be configured to or otherwise support components for performing a LBT procedure before each feedback channel timing in a set of feedback channel timings to determine whether the feedback channel timing is available for transmitting the at least one feedback message. In some examples, the LBT manager 745 may be configured to or otherwise support components for identifying a first feedback channel timing in the set of feedback channel timings associated with a successful LBT procedure, wherein the round-trip timer is initiated after the first feedback channel timing.

[0140] In some examples, the LBT manager 745 may be configured to or otherwise support components for determining that each feedback channel timing in the set of feedback channel timings is associated with an unsuccessful LBT procedure. In some examples, the LBT manager 745 may be configured to or otherwise support components for identifying a last feedback channel timing in the set of feedback channel timings based on each feedback channel timing being associated with an unsuccessful LBT procedure, wherein the round-trip timer is initiated after the last feedback channel timing.

[0141] In some examples, the PSFCH timing manager 740 may be configured to or otherwise support components for identifying a last feedback channel timing in a set of feedback channel timings, wherein the round-trip timer is initiated after the last feedback channel timing.

[0142] In some examples, the RTT duration manager 750 may be configured to or otherwise support components for identifying which feedback channel timing in the set of feedback channel timings the round-trip timer will be initiated after. In some examples, the RTT duration manager 750 may be configured to or otherwise support components for selecting the duration of the round-trip timer based on which feedback channel timing in the set of feedback channel timings the round-trip timer will be initiated after.

[0143] In some examples, the RTT duration manager 750 may be configured to or otherwise support components for determining the expected scheduling time of the retransmission of the sidelink data message, wherein the duration of the round-trip timer is further based on the expected scheduling time.

[0144] In some examples, the RTT manager 735 may be configured to or otherwise support components for avoiding monitoring the sidelink channel during the duration of the round-trip timer to detect a second grant scheduling a retransmission of the sidelink data message. In some examples, the round-trip timer is initiated after the at least one feedback channel occasion during which the at least one feedback message is sent or after different feedback channel occasions in the set of feedback channel occasions. In some examples, the set of feedback channel occasions includes in-band feedback channel occasions or a mix of in-band and out-of-band feedback channel occasions.

[0145] Figure 8 FIG. illustrates a diagram of a system 800 including a device 805 supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure. The device 805 may be an example of the device 505, the device 605, or the UE 115 as described herein, or include components thereof. The device 805 may communicate with one or more network entities 105, one or more UEs 115, or any combination thereof (e.g., wirelessly). The device 805 may include components for two-way voice and data communication, including components for sending and receiving communications, such as a communication manager 820, an input / output (I / O) controller 810, a transceiver 815, an antenna 825, a memory 830, code 835, and a processor 840. These components may communicate electronically or otherwise be coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., bus 845).

[0146] The I / O controller 810 may manage input and output signals of the device 805. The I / O controller 810 may also manage peripheral devices not integrated 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 may utilize an operating system, such as or another known operating system. Additionally or alternatively, the I / O controller 810 may represent or interact with a modem, a keyboard, a mouse, a touch screen, or similar devices. In some cases, the I / O controller 810 may be implemented as part of a processor (such as the processor 840). In some cases, a user may interact with the device 805 via the I / O controller 810 or via hardware components controlled by the I / O controller 810.

[0147] In some cases, device 805 may include a single antenna 825. However, in some other cases, device 805 may have more than one antenna 825, and the more than one antenna may be capable of concurrently transmitting or receiving multiple wireless transmissions. Transceiver 815 may communicate bidirectionally via one or more antennas 825, wired or wireless links, as described herein. For example, transceiver 815 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. Transceiver 815 may also include a modem that is configured to: modulate a packet; provide the modulated packet to one or more antennas 825 for transmission; and demodulate a packet received from one or more antennas 825. Transceiver 815 or transceiver 815 and one or more antennas 825 may be examples of transmitter 515, transmitter 615, receiver 510, receiver 610, or any combination thereof or their components, as described herein.

[0148] Memory 830 may include random access memory (RAM) and read-only memory (ROM). Memory 830 may store computer-readable, computer-executable code 835 that includes instructions that, when executed by processor 840, cause device 805 to perform the various functions described herein. Code 835 may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, code 835 may not be directly executable by processor 840 but may (e.g., when compiled and executed) cause a computer to perform the functions described herein. In some cases, among other things, memory 830 may also contain a basic input / output system (BIOS) that may control basic hardware or software operations, such as interactions with peripheral components or devices.

[0149] Processor 840 may include intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, processor 840 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated into processor 840. Processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 830) to cause device 805 to perform various functions (e.g., support functions or tasks for DRX enhancement with multiple sidelink feedback channel opportunities). For example, device 805 or components of device 805 may include processor 840 and memory 830 coupled to or coupled with processor 840, and processor 840 and memory 830 are configured to perform the various functions described herein.

[0150] The communication manager 820 may support wireless communication at a UE in accordance with the examples disclosed herein. For example, the communication manager 820 may be configured to or otherwise support components for receiving a grant for a sidelink data message scheduled for the UE on a shared radio frequency spectrum band when operating in DRX mode, the grant indicating a set of feedback channel opportunities associated with the sidelink data message. The communication manager 820 may be configured to or otherwise support components for sending at least one feedback message indicating a feedback state of the sidelink data message during at least one of the feedback channel opportunities in the set of feedback channel opportunities. The communication manager 820 may be configured to or otherwise support components for initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for a retransmission of the sidelink data message.

[0151] By including or configuring the communication manager 820 in accordance with the examples described herein, the device 805 may support techniques for improving the RTT timer when multiple PSFCH candidates are indicated for a sidelink data message. The RTT timer may be initiated after the first PSFCH candidate, after an intermediate candidate, after the last PSFCH candidate, or based on the result of a LBT procedure performed for each PSFCH candidate.

[0152] In some examples, the communication manager 820 may be configured to use or otherwise cooperate with the transceiver 815, one or more antennas 825, or any combination thereof to perform various operations (e.g., receive, monitor, transmit). Although the communication manager 820 is illustrated as a separate component, in some examples, one or more of the functions described with reference to the communication manager 820 may 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 that, when executed by the processor 840, cause the device 805 to perform various aspects of DRX enhancements with multiple sidelink feedback channel opportunities as described herein, or the processor 840 and the memory 830 may otherwise be configured to perform or support such operations.

[0153] Figure 9 A flowchart illustrating a method 900 for supporting DRX enhancements with multiple sidelink feedback channel opportunities in accordance with one or more aspects of the present disclosure is shown. 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 Figures 1 to 8 above. In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0154] At 905, the method may include: receiving, while operating in DRX mode, a grant 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 operation at 905 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operation at 905 may be performed by a grant manager 725 as described with reference to Figure 7 the grant manager 725 described above.

[0155] 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 in the set of feedback channel opportunities. The operation at 910 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operation at 910 may be performed by a feedback manager 730 as described with reference to Figure 7 the feedback manager 730 described above.

[0156] At 915, the method may include: initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for retransmission of the sidelink data message. The operation at 915 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operation at 915 may be performed by an RTT manager 735 as described with reference to Figure 7 the RTT manager 735 described above.

[0157] Figure 10 FIG. illustrates a flow diagram of a method 1000 supporting DRX enhancements with 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 Figures 1 to 8 the UE 115 described above. In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0158] At 1005, the method may include: receiving, while operating in DRX mode, a grant 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 operation at 1005 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operation at 1005 may be performed by a grant manager 725 as described with reference to Figure 7 the grant manager 725 described above.

[0159] At 1010, the method may include: sending at least one feedback message indicating a feedback status of a sidelink data message during at least one feedback channel occasion in a set of feedback channel occasions. The operation at 1010 may be performed according to the examples disclosed herein. In some examples, aspects of the operation at 1010 may be performed by a feedback manager 730 as described with reference to Figure 7 as described.

[0160] At 1015, the method may include: identifying a first feedback channel occasion in a set of feedback channel occasions, wherein a round-trip timer is initiated after the first feedback channel occasion. The operation at 1015 may be performed according to the examples disclosed herein. In some examples, aspects of the operation at 1015 may be performed by a PSFCH occasion manager 740 as described with reference to Figure 7 described.

[0161] At 1020, the method may include: initiating a round-trip timer associated with at least one feedback message based on at least one feedback channel occasion, during which the UE suppresses monitoring for retransmission of the sidelink data message. The operation at 1020 may be performed according to the examples disclosed herein. In some examples, aspects of the operation at 1020 may be performed by an RTT manager 735 as described with reference to Figure 7 described.

[0162] Figure 11 Illustrates a flowchart of a method 1100 for supporting DRX enhancements with 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 its components as described herein. For example, the operations of method 1100 may be performed by a UE 115 as described with reference to Figures 1 to 8 described. In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0163] At 1105, the method may include: receiving, while operating in DRX mode, a grant scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel occasions associated with the sidelink data message. The operation at 1105 may be performed according to the examples disclosed herein. In some examples, aspects of the operation at 1105 may be performed by a grant manager 725 as described with reference to Figure 7 described.

[0164] At 1110, the method may include: sending at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel occasion in a set of feedback channel occasions. The operation at 1110 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation at 1110 may be performed by a feedback manager 730 as described with reference to Figure 7 described.

[0165] At 1115, the method may include: performing a LBT procedure before each feedback channel occasion in the set of feedback channel occasions to determine whether the feedback channel occasion is available for sending the at least one feedback message. The operation at 1115 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation at 1115 may be performed by a LBT manager 745 as described with reference to Figure 7 described.

[0166] At 1120, the method may include: identifying a first feedback channel occasion in the set of feedback channel occasions associated with a successful LBT procedure, wherein a round-trip timer is initiated after the first feedback channel occasion. The operation at 1120 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation at 1120 may be performed by a LBT manager 745 as described with reference to Figure 7 described.

[0167] At 1125, the method may include: initiating a round-trip timer associated with the at least one feedback message based on the at least one feedback channel occasion, during which the UE suppresses monitoring for retransmission of the sidelink data message. The operation at 1125 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation at 1125 may be performed by a RTT manager 735 as described with reference to Figure 7 described.

[0168] An overview of aspects of the present disclosure is provided below:

[0169] Aspect 1: A method for wireless communication at a UE, the method comprising: receiving, when operating in DRX mode, a grant scheduling a sidelink data message for the UE on a shared radio frequency spectrum band, the grant indicating a set of feedback channel occasions associated with the sidelink data message; sending at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel occasion in the set of feedback channel occasions; and initiating a round-trip timer associated with the at least one feedback message based at least in part on the at least one feedback channel occasion, during which the UE suppresses monitoring for retransmission of the sidelink data message.

[0170] Aspect 2: The method according to aspect 1, the method further comprising: identifying a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the first feedback channel opportunity.

[0171] Aspect 3: The method according to aspect 2, the method further comprising: determining that the LBT procedure performed before the first feedback channel opportunity is unsuccessful; and transmitting the at least one feedback message in subsequent feedback channel opportunities in the set of feedback channel opportunities associated with a successful LBT procedure while initiating the round-trip timer after the first feedback channel opportunity.

[0172] Aspect 4: The method according to any one of aspects 2 to 3, the method further comprising: at least partially extending the duration of the retransmission timer based on the round-trip timer being initiated after the first feedback channel opportunity, during which duration the UE monitors the sidelink channel for a second grant for retransmission of the scheduled sidelink data message.

[0173] Aspect 5: The method according to any one of aspects 1 to 4, the method further comprising: 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 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 initiated after the first feedback channel opportunity.

[0174] Aspect 6: The method according to aspect 5, the method further comprising: 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 at least partially based on each feedback channel opportunity being associated with an unsuccessful LBT procedure, wherein the round-trip timer is initiated after the last feedback channel opportunity.

[0175] Aspect 7: The method according to any one of aspects 1 to 6, the method further comprising: identifying a last feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the last feedback channel opportunity.

[0176] Aspect 8: The method according to any one of aspects 1 to 7, the method further comprising: identifying which feedback channel opportunity in the set of feedback channel opportunities the round-trip timer will be initiated after; and selecting the duration of the round-trip timer at least partially based on which feedback channel opportunity in the set of feedback channel opportunities the round-trip timer will be initiated after.

[0177] Aspect 9: The method according to aspect 8, the method further comprising: determining an expected scheduling time for the retransmission of the sidelink data message, wherein the duration of the round-trip timer is further based on the expected scheduling time.

[0178] Aspect 10: The method according to any one of aspects 1 to 9, the method further comprising: avoiding monitoring the sidelink channel during the duration of the round-trip timer to detect a second grant scheduling the retransmission of the sidelink data message.

[0179] Aspect 11: The method according to any one of aspects 1 to 10, wherein the round-trip timer is initiated after the at least one feedback channel occasion during which the at least one feedback message is transmitted or after different feedback channel occasions in the set of feedback channel occasions.

[0180] Aspect 12: The method according to any one of aspects 1 to 11, wherein the set of feedback channel occasions includes in-band feedback channel occasions or a mixture of in-band feedback channel occasions and out-of-band feedback channel occasions.

[0181] Aspect 13: An apparatus for wireless communication at a UE, the apparatus comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method according to any one of aspects 1 to 12.

[0182] Aspect 14: An apparatus for wireless communication at a UE, the apparatus comprising: at least one component for performing the method according to any one of aspects 1 to 12.

[0183] Aspect 15: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code including instructions executable by a processor to perform the method according to any one of aspects 1 to 12.

[0184] It should be noted that the methods described herein describe possible specific implementations, and the operations and steps may be rearranged or otherwise modified and other specific implementations are also possible. In addition, aspects from two or more methods may be combined.

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

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

[0187] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed using a general purpose processor, DSP, ASIC, CPU, 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 in the alternative, the processor may be any processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0188] 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 as one or more instructions or code on a computer-readable medium or transmitted using one or more instructions or code on a computer-readable medium. Other examples and specific implementations are within the scope of the present 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 of these items. The features implementing the functions may also be physically located at different positions, including being distributed such that portions of the functions are implemented at different physical locations.

[0189] A computer-readable medium includes both a non-transitory computer storage medium and a communication medium, where the communication medium includes any medium that facilitates transfer of a computer program from one location to another. The non-transitory storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, the non-transitory computer-readable medium can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc read-only memory (CD-ROM) or other optical disc storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code components in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if software is transmitted 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 in the definition of computer-readable medium. As used herein, disk and disc include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc. The disk can magnetically reproduce data, and the disc can optically reproduce data using lasers. Combinations of the above are also included within the scope of computer-readable medium.

[0190] As used herein (including in the claims), the "or" used in a list of items (e.g., a list of items accompanied by language such as "at least one of" or "one or more of") indicates an inclusive listing such that, for example, the listing 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). Additionally, as used herein, the phrase "based on" should not be construed as a reference to a closed set of conditions. For example, an example step described as "based on condition A" can be based on condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on".

[0191] The term "determine" encompasses a variety of actions, and thus, "determine" can include operations such as calculating, computing, processing, deriving, investigating, looking up (such as looking up in a table, database, or other data structure), ascertaining, and similar actions. Additionally, "determine" can include receiving (e.g., receiving information), accessing (e.g., accessing data stored in a memory), etc. Further, "determine" can include parsing, obtaining, selecting, choosing, establishing, and other such similar actions.

[0192] In the drawings, like components or features may have the same reference numerals. Additionally, various components of the same type may be distinguished by adding a dash and a second numeral used to differentiate between like components after the reference numeral. If only the first reference numeral is used in the specification, the description may apply to any one of the like components having the same first reference numeral, regardless of the second or other subsequent reference numerals.

[0193] The description set forth herein in connection with the drawings describes example configurations and does not represent all examples that may be implemented or that are within the scope of the claims. The term "example" as used herein means "serving as an example, instance, or illustration" and not "preferred" or "advantageous over other examples." The detailed description includes specific details for providing an understanding of the described techniques. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0194] The present description is provided to enable a person of ordinary skill in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for wireless communication at a user equipment (UE), the apparatus 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: receive, when operating in a discontinuous reception mode, a grant 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; send at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and initiate a round-trip timer associated with the at least one feedback message at least in part based on the at least one feedback channel opportunity, during which the UE suppresses monitoring for a retransmission of the sidelink data message.

2. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: identify a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the first feedback channel opportunity.

3. The apparatus according to claim 2, wherein the instructions are further executable by the processor to cause the apparatus to: determine that a listen-before-talk (LBT) procedure performed before the first feedback channel opportunity is unsuccessful; and send the at least one feedback message in subsequent feedback channel opportunities in the set of feedback channel opportunities associated with a successful LBT procedure while initiating the round-trip timer after the first feedback channel opportunity.

4. The apparatus according to claim 2, wherein the instructions are further executable by the processor to cause the apparatus to: extend a duration of a retransmission timer at least in part based on the round-trip timer being initiated after the first feedback channel opportunity, during which the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message.

5. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: perform 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 sending the at least one feedback message; and identify a first feedback channel opportunity in the set of feedback channel opportunities associated with a successful LBT procedure, wherein the round-trip timer is initiated after the first feedback channel opportunity.

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

7. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Identify a last feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the last feedback channel opportunity.

8. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Identify which feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer will be initiated; and Select a duration of the round-trip timer based at least in part on which feedback channel opportunity in the set of feedback channel opportunities after which the round-trip timer will be initiated.

9. The apparatus according to claim 8, wherein the instructions are further executable by the processor to cause the apparatus to: Determine an expected scheduling time for the retransmission of the sidelink data message, wherein the duration of the round-trip timer is further based on the expected scheduling time.

10. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Avoid monitoring the sidelink channel during the duration of the round-trip timer to detect a second grant scheduling the retransmission of the sidelink data message.

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

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

13. A method for wireless communication at a user equipment (UE), the method comprises: Receiving, when operating in a discontinuous reception mode, a grant 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 at least one feedback message indicating a feedback status of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and Initiating 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 suppresses monitoring for a retransmission of the sidelink data message.

14. The method according to claim 13, the method further comprises: Identifying a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the first feedback channel opportunity.

15. The method according to claim 14, the method further comprises: Determining that a listen-before-talk (LBT) procedure performed before the first feedback channel opportunity was unsuccessful; and While initiating the round-trip timer after the first feedback channel opportunity, the at least one feedback message is sent in subsequent feedback channel opportunities in the set of feedback channel opportunities that are associated with a successful LBT procedure.

16. The method according to claim 14, the method further comprises: At least partially based on the round-trip timer being initiated after the first feedback channel opportunity, extending the duration of a retransmission timer, during which duration the UE monitors the sidelink channel for a second grant for retransmission of the scheduled sidelink data message.

17. The method according to claim 13, the method further comprises: 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 sending the at least one feedback message; and Identifying a first feedback channel opportunity in the set of feedback channel opportunities that is associated with a successful LBT procedure, wherein the round-trip timer is initiated after the first feedback channel opportunity.

18. The method according to claim 17, the method further comprises: 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 at least partially based on each feedback channel opportunity being associated with an unsuccessful LBT procedure, wherein the round-trip timer is initiated after the last feedback channel opportunity.

19. The method according to claim 13, the method further comprises: Identifying a last feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the last feedback channel opportunity.

20. The method according to claim 13, the method further comprises: Identifying which feedback channel opportunity in the set of feedback channel opportunities the round-trip timer will be initiated after; and Selecting the duration of the round-trip timer at least partially based on which feedback channel opportunity in the set of feedback channel opportunities the round-trip timer will be initiated after.

21. The method according to claim 20, the method further comprises: Determining the expected scheduling time for the retransmission of the sidelink data message, wherein the duration of the round-trip timer is further based on the expected scheduling time.

22. The method according to claim 13, the method further comprises: Avoiding monitoring the sidelink channel during the duration of the round-trip timer to detect a second grant for retransmission of the scheduled sidelink data message.

23. The method according to claim 13, wherein the round-trip timer is initiated after the at least one feedback channel opportunity during which the at least one feedback message is sent or after a different feedback channel opportunity in the set of feedback channel opportunities.

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

25. An apparatus for wireless communication at a user equipment (UE), the apparatus comprising: means for receiving, when operating in a discontinuous reception mode, a grant for a sidelink data message scheduled 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; means for transmitting at least one feedback message indicating a feedback state of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and means for initiating 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 suppresses monitoring for a retransmission of the sidelink data message.

26. The apparatus according to claim 25, the apparatus further comprising: means for identifying a first feedback channel opportunity in the set of feedback channel opportunities, wherein the round-trip timer is initiated after the first feedback channel opportunity.

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

28. The apparatus according to claim 26, the apparatus further comprising: means for extending a duration of a retransmission timer based at least in part on the round-trip timer being initiated after the first feedback channel opportunity, during which the UE monitors a sidelink channel for a second grant scheduling a retransmission of the sidelink data message.

29. The apparatus according to claim 25, the apparatus further comprising: 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; and 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 initiated after the first feedback channel opportunity.

30. A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE), the code comprising instructions executable by a processor to: receive, when operating in a discontinuous reception mode, a grant for a sidelink data message scheduled 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; transmit at least one feedback message indicating a feedback state of the sidelink data message during at least one feedback channel opportunity in the set of feedback channel opportunities; and Initiate a round-trip timer associated with the at least one feedback message, at least in part based on the at least one feedback channel occasion, during which the UE suppresses monitoring for retransmission of the sidelink data message.

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