WO2024065380A1

WO2024065380A1 - Feedback for multi-channel sidelink communication

Info

Publication number: WO2024065380A1
Application number: PCT/CN2022/122519
Authority: WO
Inventors: Yong Liu; Laura Luque SANCHEZ; Naizheng ZHENG; Timo Erkki Lunttila; Jianguo Liu; Renato Barbosa ABREU; Nuno Manuel KIILERICH PRATAS; Thomas Haaning Jacobsen; Torsten WILDSCHEK; Ling Yu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2024-04-04

Abstract

Embodiments of the present disclosure relate to devices, methods, apparatuses and computer readable storage media of feedback for multi-channel sidelink communication. A first device performs a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel. If at least two listen-before-talks (LBTs) of the plurality of LBTs pass before at least two resources of the plurality of resources, the first device transmits, to a second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel. The first device also transmits, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.

Description

FEEDBACK FOR MULTI-CHANNEL SIDELINK COMMUNICATION

FIELDS

Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium of feedback for multi-channel sidelink communication.

BACKGROUND

Hybrid automatic repeat request (HARQ) feedback is allowed for sidelink communication in licensed spectrum. A physical sidelink feedback channel (PSFCH) for sidelink communication is defined to carry HARQ feedback to a physical sidelink shared channel (PSSCH) over sidelink between user equipment (UEs) . To handle listen-before-talk (LBT) uncertainty in unlicensed spectrum, repeated PSFCH resources may be configured in multi-channels. In some scenarios, repetition of PSFCH transmissions may not be necessary.

SUMMARY

In a first aspect of the present disclosure, there is provided a first device. The first device comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first device at least to perform: performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources, transmitting, to the second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.

In a second aspect of the present disclosure, there is provided a second device. The second device comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second device at least to perform: receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel, wherein at least two listen-before-talks of the first device pass before at least the first and second resources.

In a third aspect of the present disclosure, there is provided a method. The method comprises: at a first device, performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources, transmitting, to the second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.

In a fourth aspect of the present disclosure, there is provided a method. The method comprises: at a second device, receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel, wherein at least two listen-before-talks of the first device pass before at least the first and second resources.

In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources, means for transmitting, to the second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and means for transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.

In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and means for receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel, wherein at least two listen-before-talks of the first device pass before at least the first and second resources.

In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the third or fourth aspect.

It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 2A illustrates an example frame structure of a sidelink slot with a physical sidelink control channel (PSCCH) , a PSSCH and a PSFCH according to some example embodiments of the present disclosure;

FIG. 2B illustrates example mapping between PSSCHs and PSFCHs according to some example embodiments of the present disclosure;

FIG. 2C illustrates an example configuration of repeated PSFCH resources according to some example embodiments of the present disclosure;

FIG. 3 illustrates an example signaling diagram of a feedback process according to some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of a method according to some example embodiments of the present disclosure;

FIG. 5A illustrates a diagram of example mapping in the case of the frequency-domain repeated feedback resources according to some example embodiments of the present disclosure;

FIG. 5B illustrates a diagram of example mapping in the case of the time-domain repeated feedback resources according to some example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of a method according to some example embodiments of the present disclosure;

FIG. 7 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 8 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first, ” “second” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” , “comprising” , “have” , “having” , “include” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR) , Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , an NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

As used herein, the term “resource” , “transmission resource” , “resource block” (RB) , or “physical resource block” (PRB) may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in a time domain, a resource in a frequency domain, a resource in a space domain, a resource in a code domain, or any other resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

As used herein, the term “sidelink” (SL) refers to a communication link between terminal devices. Resources in sidelink may be configured by the network. Sidelink communication in unlicensed band may be a use case in industrial automation of a private network.

As described above, HARQ feedback is allowed for sidelink communication in licensed spectrum. In Release 16 (Rel-16) , for the fifth generation (5G) Vehicle to Everything (V2X) with New Radio (NR) sidelink, a PSFCH for sidelink communication is defined to carry HARQ feedback over the sidelink (at physical layer) from user equipment (UE) which is an intended recipient of a transmission over a physical sidelink shared channel (PSSCH) (henceforth also referred to an Rx UE) to a UE which performs the transmission (henceforth also referred to a Tx UE) .

For PSFCH, a sequence is transmitted in one physical resource block (PRB) repeated over two Orthogonal Frequency Division Multiplexing (OFDM) symbols, the first of which can be used for Automatic Generation Control (AGC) , near the end of a sidelink resource in a slot. The sequence as base sequence may be (pre-) configured per sidelink resource pool. For PSSCH-to-HARQ timing, an NR NB (for example, gNB) may configure a parameter K with the unit of slots. The time occasion for PSFCH is determined from K. For a PSSCH transmission with its last symbol in slot n, HARQ feedback is in slot n+a where a is the smallest integer larger than or equal to K with the condition that slot n+a contains PSFCH resources.

To handle listen-before-talk (LBT) uncertainty in unlicensed spectrum, repeated PSFCH resources may be configured in multi-channels (e.g., two RB sets in two channels) . If LBTs pass for more than one RB set, repetition of PSFCH transmissions may not be necessary and thus cause resource waste.

Example embodiments of the present disclosure propose an enhanced scheme of PSFCH transmissions for multi-channel sidelink communication in unlicensed spectrum. This scheme may be applied in the scenario with repeated resources of a sidelink feedback channel (for example, PSFCH) configured at multiple channels to handle LBT uncertainty. The key idea is that when LBTs pass for more than one resource of the sidelink feedback channel associated with the latest sidelink data channel (for example, PSSCH) from a device, then the resources are used to transmit feedbacks to the latest sidelink data channel and a previous unacknowledged sidelink data channel from the same device.

The proposed scheme may improve resource efficiency of PSFCH transmissions and in the meantime reduce PSFCH transmission latency in unlicensed spectrum.

FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the communication environment 100, a plurality of communication devices, including a first device 110 and a second device 120, can communicate with each other.

In the following, for the purpose of illustration, some example embodiments are described with the first and

second devices

110 and 120 operating as terminal devices and communicating in sidelink (SL) . In SL communications, one of the first and

second devices

110 and 120 is a transmitting (TX) device (or a transmitter) , and the other of the first and

second devices

110 and 120 is a receiving (RX) device (or a receiver) . It is to be understood that, in some example embodiments, either or both of the first and

second devices

110 and 120 may operate as network devices or other devices.

Communications in the communication environment 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) , the fifth generation (5G) , the sixth generation (6G) , and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA) , Frequency Division Multiple Access (FDMA) , Time Division Multiple Access (TDMA) , Frequency Division Duplex (FDD) , Time Division Duplex (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiple (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

The first and

second devices

110 and 120 can communicate over a sidelink control channel such as a physical sidelink control channel (PSCCH) , a sidelink data channel such as PSSCH, and a sidelink feedback channel such as PSFCH. An example of a slot format of PSCCH, PSSCH, and PSFCH is shown in FIG. 2A.

The time resources for PSFCH may be (pre-) configured to occur once in every 1, 2, or 4 slots. The HARQ feedback resource (on PSFCH) may be derived from the resource location of PSCCH and/or PSSCH. For example, for a PSSCH transmission with its last symbol in slot n, HARQ feedback for PSSCH with the last symbol in slot n may be in slot n+a where a is the smallest integer larger than or equal to K which is configured by the network. Example mapping between PSSCHs and PSFCHs is shown in FIG. 2B where the period of PSFCH resources is configured as 2, and K is configured as 2.

To handle LBT uncertainty in unlicensed spectrum, repeated PSFCH resources may be configured in multiple radio channels. For the purpose of discussion, a radio channel may be simplify called as a channel. A radio channel may usually occupy 20 MHz or 10 MHz. As shown in FIG. 2C, two groups of

RBs

205 and 210 may be configured for PSFCH in two

channels

215 and 220. An RB set may be positioned in a radio channel.

By using the repeated resources, the robust of the HARQ feedback may be improved. To improve resource efficiency, if LBTs pass for more than one RB set, PSFCH resources in some RB set (s) may be used for feedback for the previous PSSCH transmission (s) .

FIG. 3 shows an example signaling diagram of a feedback process 300 according to some example embodiments of the present disclosure. For the purposes of discussion, the process 300 will be discussed in the example scenario that the second device 120 acts as a transmitting device and the first device 110 acts as a receiving device.

In the process 300, the second device 120 may transmit (305) to the first device 110 data via a sidelink data channel (referred to as a first sidelink data channel) . The first device 110 may be required to transmit feedback upon receiving (310) the transmission from the second device 120. As shown in FIG. 3, the first device 110 may perform (315) a plurality of LBTs before a plurality of resources for a sidelink feedback channel associated with the first sidelink data channel. If at least two of the LBTs pass before at least two of the resources, the first device 110 may transmit (320) , to the second device 120, on a first resource of the at least two resources, feedback (referred to as first feedback) for a transmission via the first sidelink data channel. In addition, the first device 110 may transmit (325) , to the second device 120, on a different second resource of the at least two resources, feedback (referred to as second feedback) for a transmission from the second device 120 via a previous sidelink data channel (referred to as a second sidelink data channel) .

The second device 120 may receive (330) , from the first device 110, on the first resource, the first feedback for the transmission via the first sidelink data channel and receive (335) on the second resource the second feedback for the transmission via the previous second sidelink data channel.

In this way, the repeated resources for sidelink feedback may be well utilized, thereby improving resource efficiency and avoiding resource waste. Moreover, sidelink feedback latency in unlicensed spectrum may be reduced, and sidelink (re) transmission may be more efficient.

FIG. 4 shows a flowchart of an example method 400 implemented at the first device 110 in accordance with some example embodiments of the present disclosure.

At block 405, the first device 110 performs a plurality of LBTs before a plurality of resources for a sidelink feedback channel (such as PSFCH) associated with a first sidelink data channel (such as PSSCH) . The resource may have any suitable granularity, for example, including some RBs, some OFDM symbols, and/or the like.

In some example embodiments, repeated PSFCH resources may be (pre-) configured in multiple RB sets in multiple channels for reliability of HARQ feedback. For each of the repeated PSFCH resources, an independent LBT may be performed for channel access.

The resources may be repeated in a time domain and/or a frequency domain. For example, a plurality of radio channels (or channels) in one time occasion may be configured for the feedback. As an alternative example, a plurality of time occasions may be configured for the feedback.

In response to at least two LBTs passing before at least two resources, at block 410, the first device 110 transmits, to the second device 120, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel. Moreover, at block 415, the first device 110 transmits, to the second device 120, on a different second resource of the at least two resources, second feedback for a transmission from the second device 120 via a previous second sidelink data channel.

In some example embodiments, if the resources are repeated in different radio channels in an occasion of the sidelink feedback channel, the first resource may comprise a set of resource blocks in a radio channel in the occasion of the sidelink feedback channel, and the second resource may comprise a set of resource blocks in a different radio channel in the occasion.

In some example embodiments, if the resources are repeated in different occasions of the sidelink feedback channel, the first resource may comprise a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource may comprise a set of resource blocks in a different occasion of the sidelink feedback channel.

Example mapping of the sidelink feedback channels and the sidelink data channels will be discussed below with reference to FIGS. 5A and 5B.

Reference is first made to FIG. 5A which shows a diagram 500 of example mapping in the case of the frequency-domain repeated feedback resources according to some example embodiments of the present disclosure.

In this example, two repeated

resources

505 and 510 of a sidelink feedback channel (for example, PSFCH) are configured in two RB sets 515 and 520, labeled as RB set 1 and RB set 2, in two radio channels for feedback (for example, HARQ feedback) of a sidelink data channel (for example, PSSCH) . In a slot 525, labeled as slot 4, LBTs pass for both RB set 1 and RB set 2. In this case, the resource 505 in RB set 1 are used for feedback to the latest sidelink data channel, and the resource 510 in RB set 2 may be used for feedbacks to previous unacknowledged PSSCHs.

For example, when the LBTs associated with the different PSFCH symbols within a slot are successfully completed in more than one of the configured RB sets, at a repeated PSFCH resource originally configured for HARQ feedback corresponding to a PSSCH (latest PSSCH) transmitted from a Tx UE to an Rx UE, a PSFCH conveying the HARQ feedback to a previous unacknowledged PSSCH from the same Tx UE may be transmitted by the Rx UE. Thus, the resource efficiency may be improved while the feedback latency may be reduced.

The concept may be applied similarly to the case with a plurality of occasions (e.g., N occasions, where N represent any positive integer) is configured for the sidelink feedback channel which may be PSFCH. If LBT passes before an occasion (e.g., occasion i with 1<=i<N) , the resources at the following occasions (e.g., occasion i+1, …, N) can be used for feedback to previous unacknowledged sidelink data channels (such as PSSCHs) from the same device.

FIG. 5B shows a diagram 540 of example mapping in the case of the time-domain repeated feedback resources according to some example embodiments of the present disclosure.

In this example, two

occasions

545 and 550 are configured for the sidelink feedback channel which may be PSFCH. If LBT passes before the occasion 545, the resource at the following occasion 550 may be used for feedback to a previous unacknowledged sidelink data channel from the same transmitter.

It is to be understood that two repeated resources are shown in FIGS. 5A and 5B only for the purpose of illustration, without suggesting any limitation. Multiple repeated resources may be configured and more than one previous sidelink data channels may be acknowledged using the remaining resources of the repeated resources.

Still with reference to FIG. 4, in some example embodiments, the first feedback may be transmitted using a first sequence, and the second feedback may be transmitted using a different second sequence. The different sequences may be generated from the same base sequence or different base sequences which may be configured by the network. By employing different sequences for feedback to different sidelink data channels, the Tx device may differentiate the feedback to a previous unacknowledged sidelink data channel from the feedback to the latest sidelink data channel.

In some example embodiments, if the first feedback is a positive acknowledgement (ACK) , the first feedback may be transmitted using a cyclic shift of the first sequence. If the first feedback is a negative acknowledgment (NACK or NAK) , the first feedback may be transmitted using a different cyclic shift of the first sequence. If the second feedback is ACK, the second feedback may be transmitted using a cyclic shift of the second sequence. If the second feedback is NACK, the second feedback may be transmitted using a different cyclic shift of the second sequence.

In some example embodiments, the second sequence may be associated with the second sidelink data channel. In some example embodiments, the first device 110 may determine, based on the association of the second sequence and the second sidelink data channel, the second sequence from a plurality of sequences available for acknowledgement to a previous sidelink data channel.

For example, a set of M sequences (where M represents any suitable positive integer) may be (pre-) configured for and available to (HARQ) feedbacks to previous sidelink data channels (for example, PSSCHs) . Each sequence corresponds to a previous sidelink data channel, for example, sequence i (1<=i<=M) corresponds to PSSCH _j-i where the latest PSSCH may be denoted as PSSCH _j.

In some example embodiments, a sequence of the plurality of sequences may be associated with at least one of: a slot index of a previous sidelink data channel, or an identification (ID) of an HARQ process (for example, an HARQ ID or an HARQ process ID) associated with a previous sidelink data channel.

For example, in the slot index based approach, each sequence may correspond to a slot prior to the slot (slot q) with the latest PSSCH transmitted, e.g., sequence i (1<=i<=M) corresponds to slot q-i. Sequence i is used for PSFCH conveying HARQ feedback to a previous unacknowledged PSSCH transmitted in slot q-i.

As an alternative example, in the HARQ ID based approach, each sequence may be mapped to a HARQ ID by implying predetermined ordering. For example, sequence 0 may correspond to the lowest unacknowledged HARQ ID, and sequence 1 may correspond to the next lowest unacknowledged HARQ ID. Alternatively, the reverse ordering may be applied.

The association of the sequences and the previous sidelink data channels may be predefined or (pre) configured by the network. Based on the predefined or (pre) configured association, both the first device 110 (as a RX device) and the second device 120 (as a TX device) may know which previous sidelink data channel (s) may be acknowledged.

In some example embodiments, the second sidelink data channel is pre-configured to be acknowledged by the first device. For example, it may be (pre-) configured which previous unacknowledged sidelink data channel the (HARQ) feedback should acknowledge at the repeated resource (s) . Accordingly, the first device 110 as well as the second device 120 may be aware of the second sidelink data channel to be acknowledged.

In some example embodiments, the first device 110 may receive, from the second device 120, an indication of at least one previous sidelink data channel in sidelink control information (SCI) via the first sidelink data channel. The at least one previous sidelink data channel comprises the second sidelink data channel. Thus, the first device 110 may determine the second sidelink data channel from the indicated at least one previous sidelink data channel.

In some example embodiments, the indication of the at least one previous sidelink data channel may comprise an indication for a slot index of the at least one previous sidelink data channel. In some example embodiments, the indication for the slot index of the at least one previous sidelink data channel may comprise an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.

For example, in the slot index approach, the slot (for example, a slot index) with previous unacknowledged sidelink data channel (such as PSSCH) transmitted can be indicated in the SCI. The slot index may be an offset relative to the slot with the latest PSSCH transmitted.

In some example embodiments, the indication of the at least one previous sidelink data channel may comprises an identification of an HARQ process (also referred to as an HARQ process ID) associated with the at least one previous sidelink data channel.

As such, the second device 120 may dynamically indicate to the first device 110 which unacknowledged sidelink data channel (such as PSSCH) the feedback should acknowledge at the repeated resource (s) . Which previous unacknowledged PSSCH may be indicated in the SCI of the latest PSSCH or a PSCCH associated with the latest PSSCH, for example, by indicating which HARQ process ID (s) is currently unacknowledged or the associated slot (s) where the unacknowledged PSSCH (s) was originally transmitted. Thereby, the feedback and retransmission efficiency may be further improved while improving the resource efficiency.

In some example embodiments, if a plurality of previous sidelink data channels need to be acknowledged by the first device 110, the first device 110 may determine the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or HARQ process IDs associated with the plurality of previous sidelink data channels.

For example, in the HARQ process ID based approach, if there is a single (PSFCH) resource available for providing feedback, then the first device 110 (as a Rx device) and the second device 120 (as a Tx) may implicitly assume that the sidelink data channel (such as PSSCH) (or HARQ process IDs) being acknowledged follows a specific ordering rule such as lower (or higher) HARQ process IDs first. If there are multiple resources (for example, RBs or RBs in multiple RB sets) available for providing feedback, then the same ordering principles may be for example that the lowest RB (or the RB in the lowest RB set) of the sidelink feedback channel (for example, PSFCH) may be used for the lowest HARQ process ID. The similar principles can be applied in the slot index based approach.

In some example embodiments, if the latest sidelink data channel (such as PSSCH) occupies multiple channels, multiple repeated PRBs of the sidelink feedback channel (for example, PSFCH) may be used for (HARQ) feedbacks to multiple previous unacknowledged PSSCHs from the Tx UE (for example, the second device 120) . The following association rule between the repeated PSFCH PRBs and previous unacknowledged PSSCHs can be followed. If the multiple previous unacknowledged PSSCHs are in different slots, the latest previous unacknowledged PSSCH associates with the lowest PSFCH PRB index. If the multiple previous unacknowledged PSSCHs are in the same slot, the previous unacknowledged PSSCH with the lowest channel index associates with the lowest PSFCH PRB index.

In some example embodiments, if the first device 110, which may be a Rx UE, does not receive an indication of which unacknowledged sidelink data channel, which may be PSSCH, the HARQ feedback should acknowledge at the repeated resource (s) of the sidelink feedback channel, which may be PSFCH, at the repeated PSFCH resource, the second device 120 may choose not to transmit to reduce mutual interference of transmissions of sidelink feedback channels or transmit the sidelink feedback channel conveying feedback corresponding to the latest sidelink data channel transmitted from the second device 120, which may be a Tx UE, to improve link level transmission reliability of the sidelink feedback channel.

FIG. 6 shows a flowchart of an example method 600 implemented at the second device 120 in accordance with some example embodiments of the present disclosure.

At block 610, the second device 120 receives, from the first device 110, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel.

At block 620, the second device 120 receives, from the first device 110, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel. At least two LBTs of the first device 110 pass before at least the first and second resources.

In some example embodiments, the first feedback may be received using a first sequence, and the second feedback may be received using a different second sequence. As such, the second device 120 may differentiate the feedback to a previous unacknowledged sidelink data channel from the feedback to the latest sidelink data channel.

In some example embodiments, the second device 120 may further identify the second sidelink data channel based on association of the second sequence and the second sidelink data channel.

In some example embodiments, the second sequence may be associated with at least one of: a slot index of the second sidelink data channel, or an identification of a hybrid automatic repeat request process associated with the second sidelink data channel.

In some example embodiments, the first feedback is received using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is received using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or the second feedback is received using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is received using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.

In some example embodiments, the second device 120 may further transmit, to the first device 110, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel. The at least one previous sidelink data channel comprises the second sidelink data channel. In this way, the second device 120 may dynamically indicate to the first device 110 unacknowledged sidelink data channel (s) to be acknowledged.

In some example embodiments, the indication of the at least one previous sidelink data channel may comprise an indication for a slot index of the at least one previous sidelink data channel.

In some example embodiments, the indication for the slot index of the at least one previous sidelink data channel may comprise an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.

In some example embodiments, the indication of the at least one previous sidelink data channel may comprise an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.

In some example embodiments, the second device 120 may further identify the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.

In some example embodiments, the second sidelink data channel may be pre-configured to be acknowledged by the first device.

In some example embodiments, the first resource may comprise a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource may comprise a set of resource blocks in a different radio channel in the occasion.

In some example embodiments, the first resource may comprise a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource may comprise a set of resource blocks in a different occasion of the sidelink feedback channel.

All operations and features of the second device 120 or the TX device or UE or the transmitter as described above with reference to FIGS. 1 to 5B are likewise applicable to the method 600 and have similar effects. For the purposes of simplification, the details will be omitted.

In some example embodiments, a first apparatus capable of performing any of the method 400 (for example, the first device 110 in FIG. 1 may comprise means for performing the respective operations of the method 400) . The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first device 110 in FIG. 1.

In some example embodiments, the first apparatus comprises means for performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and means for in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources, transmitting, to the second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.

In some example embodiments, the first feedback is transmitted using a first sequence, and the second feedback is transmitted using a different second sequence.

In some example embodiments, the second sequence is associated with the second sidelink data channel.

In some example embodiments, the first apparatus further comprises: means for determining, based on the association of the second sequence and the second sidelink data channel, the second sequence from a plurality of sequences available for acknowledgement to a previous sidelink data channel.

In some example embodiments, a sequence of the plurality of sequences is associated with at least one of: a slot index of a previous sidelink data channel, or an identification of a hybrid automatic repeat request process associated with a previous sidelink data channel.

In some example embodiments, the first feedback is transmitted using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is transmitted using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or the second feedback is transmitted using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is transmitted using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.

In some example embodiments, the indication of the at least one previous sidelink data channel comprises an indication for a slot index of the at least one previous sidelink data channel.

In some example embodiments, the indication for the slot index of the at least one previous sidelink data channel comprises an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.

In some example embodiments, the indication of the at least one previous sidelink data channel comprises an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.

In some example embodiments, the first apparatus further comprises: means for determining the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.

In some example embodiments, the second sidelink data channel is pre-configured to be acknowledged by the first device.

In some example embodiments, the first resource comprises a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different radio channel in the occasion.

In some example embodiments, the first resource comprises a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different occasion of the sidelink feedback channel.

In some example embodiments, the first apparatus further comprises means for performing other operations in some example embodiments of the method 400 or the first device 110. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the first apparatus.

In some example embodiments, a second apparatus capable of performing any of the method 600 (for example, the second device 120 in FIG. 1 may comprise means for performing the respective operations of the method 600) . The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second device 120 in FIG. 1.

In some example embodiments, the second apparatus comprises means for receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and means for receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel, wherein at least two listen-before-talks of the first device pass before at least the first and second resources.

In some example embodiments, the first feedback is received using a first sequence, and the second feedback is received using a different second sequence.

In some example embodiments, the second apparatus further comprises: means for identifying the second sidelink data channel based on association of the second sequence and the second sidelink data channel.

In some example embodiments, the second sequence is associated with at least one of: a slot index of the second sidelink data channel, or an identification of a hybrid automatic repeat request process associated with the second sidelink data channel.

In some example embodiments, the second apparatus further comprises: means for transmitting, to the first device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.

In some example embodiments, the second apparatus further comprises: means for identifying the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.

In some example embodiments, the second apparatus further comprises means for performing other operations in some example embodiments of the method 600 or the second device 120. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the second apparatus.

FIG. 7 is a simplified block diagram of a device 700 that is suitable for implementing example embodiments of the present disclosure. The device 700 may be provided to implement a communication device, for example, the first device 110 or the second device 120 as shown in FIG. 1. As shown, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more communication modules 740 coupled to the processor 710.

The communication module 740 is for bidirectional communications. The communication module 740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 740 may include at least one antenna.

The processor 710 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 724, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , an optical disk, a laser disk, and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 722 and other volatile memories that will not last in the power-down duration.

A computer program 730 includes computer executable instructions that are executed by the associated processor 710. The instructions of the program 730 may include instructions for performing operations/acts of some example embodiments of the present disclosure. The program 730 may be stored in the memory, e.g., the ROM 724. The processor 710 may perform any suitable actions and processing by loading the program 730 into the RAM 722.

The example embodiments of the present disclosure may be implemented by means of the program 730 so that the device 700 may perform any process of the disclosure as discussed with reference to FIG. 1 to FIG. 6. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some example embodiments, the program 730 may be tangibly contained in a computer readable medium which may be included in the device 700 (such as in the memory 720) or other storage devices that are accessible by the device 700. The device 700 may load the program 730 from the computer readable medium to the RAM 722 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

FIG. 8 shows an example of the computer readable medium 800 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 800 has the program 730 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non-transitory computer readable medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first device, comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the first device at least to perform:

performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and

in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources,

transmitting, to a second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and

transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.
The first device of claim 1, wherein the first feedback is transmitted using a first sequence, and the second feedback is transmitted using a different second sequence.
The first device of claim 2, wherein the second sequence is associated with the second sidelink data channel.
The first device of claim 3, wherein the first device is further caused to perform:

determining, based on the association of the second sequence and the second sidelink data channel, the second sequence from a plurality of sequences available for acknowledgement to a previous sidelink data channel.
The first device of claim 4, wherein a sequence of the plurality of sequences is associated with at least one of:

a slot index of a previous sidelink data channel, or

an identification of a hybrid automatic repeat request process associated with a previous sidelink data channel.
The first device of any of claims 2-4, wherein

the first feedback is transmitted using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is transmitted using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or

the second feedback is transmitted using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is transmitted using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.
The first device of any of claims 1-6, wherein the first device is further caused to perform:

receiving, from the second device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.
The first device of claim 7, wherein the indication of the at least one previous sidelink data channel comprises an indication for a slot index of the at least one previous sidelink data channel.
The first device of claim 8, wherein the indication for the slot index of the at least one previous sidelink data channel comprises an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.
The first device of claim 7, wherein the indication of the at least one previous sidelink data channel comprises an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.
The first device of any of claims 7-10, wherein the at least one previous sidelink data channel comprises a plurality of previous sidelink data channels, and the first device is further caused to perform:

determining the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.
The first device of any of claims 1-6, wherein the second sidelink data channel is pre-configured to be acknowledged by the first device.
The first device of any of claims 1-12, wherein the first resource comprises a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different radio channel in the occasion.
The first device of any of claims 1-12, wherein the first resource comprises a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different occasion of the sidelink feedback channel.
A second device, comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the second device at least to perform:

receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and

receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel,

wherein at least two listen-before-talks of the first device pass before at least the first and second resources.
The second device of claim 15, wherein the first feedback is received using a first sequence, and the second feedback is received using a different second sequence.
The second device of claim 16, wherein the second device is further caused to perform:

identifying the second sidelink data channel based on association of the second sequence and the second sidelink data channel.
The second device of claim 17, wherein the second sequence is associated with at least one of:

a slot index of the second sidelink data channel, or

an identification of a hybrid automatic repeat request process associated with the second sidelink data channel.
The second device of any of claims 16-18, wherein

the first feedback is received using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is received using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or

the second feedback is received using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is received using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.
The second device of any of claims 15-19, wherein the second device is further caused to perform:

transmitting, to the first device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.
The second device of claim 20, wherein the indication of the at least one previous sidelink data channel comprises an indication for a slot index of the at least one previous sidelink data channel.
The second device of claim 21, wherein the indication for the slot index of the at least one previous sidelink data channel comprises an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.
The second device of claim 20, wherein the indication of the at least one previous sidelink data channel comprises an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.
The second device of any of claims 20-23, wherein the at least one previous sidelink data channel comprises a plurality of previous sidelink data channels, and the second device is further caused to perform:

identifying the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.
The second device of any of claims 15-19, wherein the second sidelink data channel is pre-configured to be acknowledged by the first device.
The second device of any of claims 15-25, wherein the first resource comprises a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different radio channel in the occasion.
The second device of any of claims 15-25, wherein the first resource comprises a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different occasion of the sidelink feedback channel.
A method, comprising:

at a first device,

performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and

in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources,

transmitting, to a second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and

transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.
The method of claim 28, wherein the first feedback is transmitted using a first sequence, and the second feedback is transmitted using a different second sequence.
The method of claim 29, wherein the second sequence is associated with the second sidelink data channel.
The method of claim 30, further comprising:

determining, based on the association of the second sequence and the second sidelink data channel, the second sequence from a plurality of sequences available for acknowledgement to a previous sidelink data channel.
The method of claim 31, wherein a sequence of the plurality of sequences is associated with at least one of:

a slot index of a previous sidelink data channel, or

an identification of a hybrid automatic repeat request process associated with a previous sidelink data channel.
The method of any of claims 29-32, wherein

the first feedback is transmitted using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is transmitted using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or

the second feedback is transmitted using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is transmitted using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.
The method of any of claims 28-33, further comprising:

receiving, from the second device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.
The method of claim 34, wherein the indication of the at least one previous sidelink data channel comprises an indication for a slot index of the at least one previous sidelink data channel.
The method of claim 35, wherein the indication for the slot index of the at least one previous sidelink data channel comprises an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.
The method of claim 34, wherein the indication of the at least one previous sidelink data channel comprises an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.
The method of any of claims 34-37, further comprising:

determining the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.
The method of any of claims 28-33, wherein the second sidelink data channel is pre-configured to be acknowledged by the first device.
The method of any of claims 28-39, wherein the first resource comprises a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different radio channel in the occasion.
The method of any of claims 28-39, wherein the first resource comprises a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different occasion of the sidelink feedback channel.
A method, comprising:

at a second device,

receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and

receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel,

wherein at least two listen-before-talks of the first device pass before at least the first and second resources.
The method of claim 42, wherein the first feedback is received using a first sequence, and the second feedback is received using a different second sequence.
The method of claim 43, further comprising:

identifying the second sidelink data channel based on association of the second sequence and the second sidelink data channel.
The method of claim 44, wherein the second sequence is associated with at least one of:

a slot index of the second sidelink data channel, or

an identification of a hybrid automatic repeat request process associated with the second sidelink data channel.
The method of any of claims 43-45, wherein

the first feedback is received using a cyclic shift of the first sequence if the first feedback is a positive acknowledgement, and the first feedback is received using a different cyclic shift of the first sequence if the first feedback is a negative acknowledgment, and/or

the second feedback is received using a cyclic shift of the second sequence if the second feedback is a positive acknowledgement, and the second feedback is received using a different cyclic shift of the second sequence if the second feedback is a negative acknowledgment.
The method of any of claims 42-46, further comprising:

transmitting, to the first device, an indication of at least one previous sidelink data channel in sidelink control information via the first sidelink data channel or via a sidelink control channel associated with the first sidelink data channel, the at least one previous sidelink data channel comprising the second sidelink data channel.
The method of claim 47, wherein the indication of the at least one previous sidelink data channel comprises an indication for a slot index of the at least one previous sidelink data channel.
The method of claim 48, wherein the indication for the slot index of the at least one previous sidelink data channel comprises an offset of the slot index of the at least one previous sidelink data channel relative to a slot index of the first sidelink data channel.
The method of claim 47, wherein the indication of the at least one previous sidelink data channel comprises an identification of a hybrid automatic repeat request process associated with the at least one previous sidelink data channel.
The method of any of claims 47-50, further comprising:

identifying the second sidelink data channel from the plurality of previous sidelink data channels according to ordering of the plurality of previous sidelink data channels based on slot indexes of the plurality of previous sidelink data channels, and/or identifications of hybrid automatic repeat request processes associated with the plurality of previous sidelink data channels.
The method of any of claims 42-46, wherein the second sidelink data channel is pre-configured to be acknowledged by the first device.
The method of any of claims 42-52, wherein the first resource comprises a set of resource blocks in a radio channel in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different radio channel in the occasion.
The method of any of claims 42-52, wherein the first resource comprises a set of resource blocks in an occasion of the sidelink feedback channel, and the second resource comprises a set of resource blocks in a different occasion of the sidelink feedback channel.
A first apparatus, comprising:

means for performing a plurality of listen-before-talks before a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel; and

in response to at least two listen-before-talks of the plurality of listen-before-talks passing before at least two resources of the plurality of resources,

means for transmitting, to the second device, on a first resource of the at least two resources, first feedback for a transmission from the second device via the first sidelink data channel, and

means for transmitting, to the second device, on a different second resource of the at least two resources, second feedback for a transmission from the second device via a previous second sidelink data channel.
A second apparatus, comprising:

means for receiving, from a first device, on a first resource of a plurality of resources for a sidelink feedback channel associated with a first sidelink data channel, first feedback for a transmission from the second device to the first device via the first sidelink data channel; and

means for receiving, from the first device, on a different second resource of the plurality of resources, second feedback for a transmission from the second device to the first device via a previous second sidelink data channel,

wherein at least two listen-before-talks of the first device pass before at least the first and second resources.
A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of any of claims 28-41 or the method of any of claims 42-54.