WO2023209576A1

WO2023209576A1 - Transmitting sidelink feedback with a reduced number of feedback bits

Info

Publication number: WO2023209576A1
Application number: PCT/IB2023/054261
Authority: WO
Inventors: Alexander Golitschek Edler Von Elbwart; Karthikeyan Ganesan; Joachim Löhr; Prateek Basu Mallick; Vijay Nangia; Ravi Kuchibhotla
Original assignee: Lenovo (Singapore) Pte. Ltd.
Priority date: 2022-04-26
Filing date: 2023-04-25
Publication date: 2023-11-02

Abstract

Apparatuses, methods, and systems are disclosed for transmitting sidelink ("SL") feedback with a reduced number of feedback bits. One method (500) includes determining (502) feedback and transmitting (504) the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

Description

TRANSMITTING SIDELINK FEEDBACK WITH A REDUCED NUMBER OF FEEDBACK

BITS

FIELD

[0001] The subject matter disclosed herein relates generally to wireless communications and more particularly relates to transmitting sidelink (“SL”) feedback with a reduced number of feedback bits.

BACKGROUND

[0002] In certain wireless communications networks, SL feedback may be transmitted. In such networks, there may be more SL feedback to be transmitted than there are available resources for transmitting the SL feedback.

BRIEF SUMMARY

[0003] Methods for transmitting SL feedback with a reduced number of feedback bits are disclosed. Apparatuses and systems also perform the functions of the methods. One embodiment of a method includes determining, in a communication device, feedback. In some embodiments, the method includes transmitting the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0004] One apparatus for transmitting SL feedback with a reduced number of feedback bits includes a communication device. In some embodiments, the apparatus includes a processor to determine feedback. In various embodiments, the apparatus includes a transmitter to transmit the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits. [0005] Another embodiment of a method for transmitting SL feedback with a reduced number of feedback bits includes receiving, at a communication device, information triggering feedback on a feedback channel. The information indicates a resource for the feedback channel. In some embodiments, the method includes determining the feedback. The feedback includes a plurality of bits combined into a single feedback bit. In certain embodiments, the method includes transmitting the feedback on the feedback channel.

[0006] Another apparatus for transmitting SL feedback with a reduced number of feedback bits includes a communication device. In some embodiments, the apparatus includes a receiver to receive information triggering feedback on a feedback channel. The information indicates a resource for the feedback channel. In various embodiments, the apparatus includes a processor to determine the feedback. The feedback includes a plurality of bits combined into a single feedback bit. In certain embodiments, the apparatus includes a transmitter to transmit the feedback on the feedback channel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only some embodiments and are not therefore to be considered to be limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0008] Figure 1 is a schematic block diagram illustrating one embodiment of a wireless communication system for transmitting SL feedback with a reduced number of feedback bits;

[0009] Figure 2 is a schematic block diagram illustrating one embodiment of an apparatus that may be used for transmitting SL feedback with a reduced number of feedback bits;

[0010] Figure 3 is a schematic block diagram illustrating one embodiment of an apparatus that may be used for transmitting SL feedback with a reduced number of feedback bits;

[0011] Figure 4 is a schematic block diagram illustrating one embodiment of a system for transmitting SL feedback with a reduced number of feedback bits;

[0012] Figure 5 is a flow chart diagram illustrating one embodiment of a method for transmitting SL feedback with a reduced number of feedback bits; and

[0013] Figure 6 is a flow chart diagram illustrating another embodiment of a method for transmitting SL feedback with a reduced number of feedback bits.

DETAILED DESCRIPTION

[0014] As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine readable code, computer readable code, and/or program code, referred hereafter as code. The storage devices may be tangible, non-transitory, and/or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

[0015] Certain of the functional units described in this specification may be labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very-large-scale integration (“VLSI”) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

[0016] Modules may also be implemented in code and/or software for execution by various types of processors. An identified module of code may, for instance, include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may include disparate instructions stored in different locations which, when joined logically together, include the module and achieve the stated purpose for the module.

[0017] Indeed, a module of code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different computer readable storage devices. Where a module or portions of a module are implemented in software, the software portions are stored on one or more computer readable storage devices.

[0018] Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing the code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0019] More specific examples (a non-exhaustive list) of the storage device would include the following: 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), a portable compact disc readonly memory (“CD-ROM”), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0020] Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an object oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the "C" programming language, or the like, and/or machine languages such as assembly languages. The code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (“LAN”) or a wide area network (“WAN”), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0021] Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.

[0022] Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment.

[0023] Aspects of the embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by code. The code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

[0024] The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

[0025] The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

[0026] The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods and program products according to various embodiments. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function(s). [0027] It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated Figures.

[0028] Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and code.

[0029] The description of elements in each figure may refer to elements of proceeding figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements.

[0030] Figure 1 depicts an embodiment of a wireless communication system 100 for transmitting SL feedback with a reduced number of feedback bits. In one embodiment, the wireless communication system 100 includes remote units 102 and network units 104. Even though a specific number of remote units 102 and network units 104 are depicted in Figure 1, one of skill in the art will recognize that any number of remote units 102 and network units 104 may be included in the wireless communication system 100.

[0031] In one embodiment, the remote units 102 may include computing devices, such as desktop computers, laptop computers, personal digital assistants (“PDAs”), tablet computers, smart phones, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, modems), aerial vehicles, drones, or the like. In some embodiments, the remote units 102 include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, the remote units 102 may be referred to as subscriber units, mobiles, mobile stations, users, terminals, mobile terminals, fixed terminals, subscriber stations, UE, user terminals, a device, or by other terminology used in the art. The remote units 102 may communicate directly with one or more of the network units 104 via uplink (“UL”) communication signals. In certain embodiments, the remote units 102 may communicate directly with other remote units 102 via SL communication.

[0032] The network units 104 may be distributed over a geographic region. In certain embodiments, a network unit 104 may also be referred to and/or may include one or more of an access point, an access terminal, a base, a base station, a location server, a core network (“CN”), a radio network entity, a Node-B, an evolved node-B (“eNB”), a 5G node-B (“gNB”), a Home Node-B, a relay node, a device, a core network, an aerial server, a radio access node, an access point (“AP”), new radio (“NR”), a network entity, an access and mobility management function (“AMF”), a unified data management (“UDM”), a unified data repository (“UDR”), a UDM/UDR, a policy control function (“PCF”), a radio access network (“RAN”), a network slice selection function (“NSSF”), an operations, administration, and management (“0AM”), a session management function (“SMF”), a user plane function (“UPF”), an application function, an authentication server function (“AUSF”), security anchor functionality (“SEAF”), trusted non- third generation partnership project (“3GPP”) gateway function (“TNGF”), or by any other terminology used in the art. The network units 104 are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding network units 104. The radio access network is generally communicably coupled to one or more core networks, which may be coupled to other networks, like the Internet and public switched telephone networks, among other networks. These and other elements of radio access and core networks are not illustrated but are well known generally by those having ordinary skill in the art.

[0033] In one implementation, the wireless communication system 100 is compliant with NR protocols standardized in 3GPP, wherein the network unit 104 transmits using an orthogonal frequency division multiplexing (“OFDM”) modulation scheme on the downlink (“DL”) and the remote units 102 transmit on the UL using a single-carrier frequency division multiple access (“SC-FDMA”) scheme or an OFDM scheme. More generally, however, the wireless communication system 100 may implement some other open or proprietary communication protocol, for example, WiMAX, institute of electrical and electronics engineers (“IEEE”) 802. 11 variants, global system for mobile communications (“GSM”), general packet radio service (“GPRS”), universal mobile telecommunications system (“UMTS”), long term evolution (“LTE”) variants, code division multiple access 2000 (“CDMA2000”), Bluetooth®, ZigBee, Sigfox, among other protocols. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

[0034] The network units 104 may serve a number of remote units 102 within a serving area, for example, a cell or a cell sector via a wireless communication link. The network units 104 transmit DL communication signals to serve the remote units 102 in the time, frequency, and/or spatial domain.

[0035] In various embodiments, a remote unit 102 may determine, in a communication device, feedback. In some embodiments, the remote unit 102 may transmit the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits. Accordingly, the remote unit 102 may be used for transmitting SL feedback with a reduced number of feedback bits.

[0036] In certain embodiments, a remote unit 102 may receive, at a communication device, information triggering feedback on a feedback channel. The information indicates a resource for the feedback channel. In some embodiments, the remote unit 102 may determine the feedback. The feedback includes a plurality of bits combined into a single feedback bit. In certain embodiments, the method includes transmitting the feedback on the feedback channel. Accordingly, the remote unit 102 may be used for transmitting SL feedback with a reduced number of feedback bits.

[0037] Figure 2 depicts one embodiment of an apparatus 200 that may be used for transmitting SL feedback with a reduced number of feedback bits. The apparatus 200 includes one embodiment of the remote unit 102. Furthermore, the remote unit 102 may include a processor 202, a memory 204, an input device 206, a display 208, a transmitter 210, and a receiver 212. In some embodiments, the input device 206 and the display 208 are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit 102 may not include any input device 206 and/or display 208. In various embodiments, the remote unit 102 may include one or more of the processor 202, the memory 204, the transmitter 210, and the receiver 212, and may not include the input device 206 and/or the display 208.

[0038] The processor 202, in one embodiment, may include any known controller capable of executing computer-readable instructions and/or capable of performing logical operations. For example, the processor 202 may be a microcontroller, a microprocessor, a central processing unit (“CPU”), a graphics processing unit (“GPU”), an auxiliary processing unit, a field programmable gate array (“FPGA”), or similar programmable controller. In some embodiments, the processor 202 executes instructions stored in the memory 204 to perform the methods and routines described herein. The processor 202 is communicatively coupled to the memory 204, the input device 206, the display 208, the transmitter 210, and the receiver 212.

[0039] The memory 204, in one embodiment, is a computer readable storage medium. In some embodiments, the memory 204 includes volatile computer storage media. For example, the memory 204 may include a RAM, including dynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and/or static RAM (“SRAM”). In some embodiments, the memory 204 includes non-volatile computer storage media. For example, the memory 204 may include a hard disk drive, a flash memory, or any other suitable non-volatile computer storage device. In some embodiments, the memory 204 includes both volatile and non-volatile computer storage media. In some embodiments, the memory 204 also stores program code and related data, such as an operating system or other controller algorithms operating on the remote unit 102.

[0040] The input device 206, in one embodiment, may include any known computer input device including a touch panel, a button, a keyboard, a stylus, a microphone, or the like. In some embodiments, the input device 206 may be integrated with the display 208, for example, as a touchscreen or similar touch-sensitive display. In some embodiments, the input device 206 includes a touchscreen such that text may be input using a virtual keyboard displayed on the touchscreen and/or by handwriting on the touchscreen. In some embodiments, the input device 206 includes two or more different devices, such as a keyboard and a touch panel.

[0041] The display 208, in one embodiment, may include any known electronically controllable display or display device. The display 208 may be designed to output visual, audible, and/or haptic signals. In some embodiments, the display 208 includes an electronic display capable of outputting visual data to a user. For example, the display 208 may include, but is not limited to, a liquid crystal display (“LCD”), a light emitting diode (“LED”) display, an organic light emitting diode (“OLED”) display, a projector, or similar display device capable of outputting images, text, or the like to a user. As another, non-limiting, example, the display 208 may include a wearable display such as a smart watch, smart glasses, a heads-up display, or the like. Further, the display 208 may be a component of a smart phone, a personal digital assistant, a television, a table computer, a notebook (laptop) computer, a personal computer, a vehicle dashboard, or the like.

[0042] In certain embodiments, the display 208 includes one or more speakers for producing sound. For example, the display 208 may produce an audible alert or notification (e.g., a beep or chime). In some embodiments, the display 208 includes one or more haptic devices for producing vibrations, motion, or other haptic feedback. In some embodiments, all or portions of the display 208 may be integrated with the input device 206. For example, the input device 206 and display 208 may form a touchscreen or similar touch-sensitive display. In other embodiments, the display 208 may be located near the input device 206.

[0043] In certain embodiments, the processor 202 to determine feedback. In various embodiments, the transmitter 210 to transmit the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0044] In some embodiments, the receiver 212 to receive information triggering feedback on a feedback channel. The information indicates a resource for the feedback channel. In various embodiments, the processor 202 to determine the feedback. The feedback includes a plurality of bits combined into a single feedback bit. In certain embodiments, the transmitter 210 to transmit the feedback on the feedback channel.

[0045] Although only one transmitter 210 and one receiver 212 are illustrated, the remote unit 102 may have any suitable number of transmitters 210 and receivers 212. The transmitter 210 and the receiver 212 may be any suitable type of transmitters and receivers. In one embodiment, the transmitter 210 and the receiver 212 may be part of a transceiver.

[0046] Figure 3 depicts one embodiment of an apparatus 300 that may be used for transmitting SL feedback with a reduced number of feedback bits. The apparatus 300 includes one embodiment of the network unit 104. Furthermore, the network unit 104 may include a processor 302, a memory 304, an input device 306, a display 308, atransmitter 310, and a receiver 312. As may be appreciated, the processor 302, the memory 304, the input device 306, the display 308, the transmitter 310, and the receiver 312 may be substantially similar to the processor 202, the memory 204, the input device 206, the display 208, the transmitter 210, and the receiver 212 of the remote unit 102, respectively.

[0047] It should be noted that one or more embodiments described herein may be combined into a single embodiment.

[0048] In certain embodiments, especially for SL transmissions on an unlicensed channel (e.g., shared spectrum), it is possible that physical SL shared channel (“PSSCH”) transmissions are not directly associated with a feedback timing for acknowledgment (“ACK”) and/or nonacknowledgement (“NACK”) transmission. These feedback bits may be transmitted at a later time (e.g., due to a pre-determined procedure or due to an explicit triggering mechanism). In these cases, it is possible that the number of accumulated feedback bits, potentially including feedback bits for transmissions that are associated with a feedback timing, exceed the capacity of the physical SL feedback channel (“PSFCH”).

[0049] In some embodiments, ACK and/or NACK (“ACK/NACK”) feedback bits may be combined to reduce a number of transmitted ACK/NACK bits, and/or a PSFCH resource may be determined for such ACK/NACK bits.

[0050] In various embodiments, for SL unicast transmission, a receive (“RX”) UE sends ACK if it has successfully decoded a transport block (“TB”) carried in a PSSCH or it sends NACK if it has not decoded the TB after decoding the Ist-stage SL configuration information (“SCI”). For SL groupcast transmissions, two options (e.g., option 1 and option 2) are supported for the SL hybrid automatic repeat request (“HARQ”) feedback in new radio (“NR”) vehicle to everything (“V2X”). For option 1, an RX UE transmits NACK if it has not successfully decoded the TB (e.g., after decoding the Ist-stage SCI -stage SCI) and if its relative distance to a transmit (“TX”) UE (e.g., referred as TX-RX distance) is less than or equal to a required communication range (e.g., indicated in the 2nd-stage SCI -stage SCI). Otherwise, the RX UE does not transmit any HARQ feedback. As the HARQ feedback for this option would only include NACK, option 1 is referred to as NACK-only feedback.

[0051] In certain embodiments, a PSFCH symbol that can be used for HARQ feedback for a given PSSCH transmission corresponds to the PSFCH symbol in a first slot with PSFCH after a configured or preconfigured number of K slots after the PSSCH. K represents the minimum number of slots within the resource pool between a slot with a PSSCH transmission and the slot containing PSFCH for the HARQ feedback of this transmission. Consider that the last symbol of a PSSCH transmission is on slot n. The HARQ feedback for this transmission is expected in slot n + a, where a is the smallest integer equal or higher than K such that slot n + a contains PSFCH. For example, if the earliest possible slot for the HARQ feedback (e.g., slot n+a does not contain PSFCH, then the HARQ feedback is sent at the next slot containing PSFCH (e.g., after slot n+a). The time gap of at least K slots allows considering the RX UE’s processing delay in decoding the physical SL control channel (“PSCCH”) and generating the HARQ feedback. K can be equal to 2 or 3, and a single value of K can be configured or preconfigured per resource pool. This allows several RX UEs using the same resource pool to use the same mapping of PSFCH resources for the HARQ feedback. With the parameter K, the ' PSSCH slots associated with a slot with PSFCH can be determined. In an example with K=3, the N=4 PSSCH slots associated with the PSFCHs at slot n+6 correspond to PSSCH slots n, n+1, n+2, and n+3. [0052] In some embodiments, with L sub-channels in a resource pool and N PSSCH slots associated with a slot containing PSFCH, there are then N times L sub-channels associated with a PSFCH symbol. With M physical resource blocks (“PRBs”) available for PSFCH in a PSFCH symbol, there are M PRBs available for the HARQ feedback of transmissions over N times L subchannels. With M configured to be a multiple of N times L, then a distinct set of M_set = M/(N ■ L) PRBs can be associated with the HARQ feedback for each sub-channel within a PSFCH period. The first set of M_set PRBs among the M PRBs available for PSFCH are associated with the HARQ feedback of a transmission in the first sub-channel in the first slot. The second set of M_set PRBs are associated with the HARQ feedback of a transmission in the first sub-channel in the second slot and so on. For example, if N = 4, L = 3 and with all PRBs in a PSFCH symbol available for PSFCH, the HARQ feedback for a transmission at PSSCH x is sent on the set x of M_set PRBs in the corresponding PSFCH symbol, with x=l, . . . , 12. For a transmission in a PSSCH with LPSSCH>1 sub-channels, LPSSCH times M_set PRBs could be available for the HARQ feedback of this transmission.

[0053] In various embodiments, a set of M_set PRBs associated with a sub-channel are shared among multiple RX UEs in case of ACK/NACK feedback for groupcast communications (e.g., option 2) or in the case of different PSSCH transmissions in the same sub-channel. For each PRB available for PSFCH, there are Q cyclic shift pairs available to support the ACK or NACK feedback of Q RX UEs within the PRB. For a resource pool, the number of cyclic shift pairs Q is configured or preconfigured and can be equal to 1, 2, 3 or 6. With each PSFCH used by one RX UE, F available PSFCHs can be used for the ACK/NACK feedback of up to F RX UEs. The F PSFCHs can be determined based on two options: either based on the LPSSCH sub-channels used by a PSSCH or based only on the starting sub-channel used by a PSSCH (e.g., based only on one subchannel for the case when LPSSCH >1). Thus, F can be computed based on: (i) LPSSCH sub-channels of a PSSCH; (ii) M_set PRBs for PSFCH associated with each sub-channel; and (iii) Q cyclic shift pairs available in each PRB. Depending on which of two supported HARQ feedback options is configured or preconfigured, there are either then F= LPSSCH ■ M_set ■(? PSFCHs (e.g., associated with the LPSSCH sub-channels of a PSSCH) or F= M_set -Q PSFCHs (e.g., associated with the starting sub-channel of a PSSCH) available for multiplexing the HARQ feedback for the PSSCH.

[0054] In certain embodiments, similarly to a physical uplink control channel (“PUCCH”) in NR on a UE to network (“Uu”) interface, the available F PSFCHs are indexed based on a PRB index (e.g., frequency domain) and a cyclic shift pair index (e.g., code domain). Depending on a configured or preconfigured option, there are either LPSSCH ■ M_set or M_set PRBs available for PSFCH. The mapping of the PSFCH index i (i=0,l,2,...,F-l) to the LPSSCH ■ M_set or M_set PRBs and to the Q cyclic shift pairs is such that the PSFCH index i first increases with the PRB index until reaching the number of available PRBs for PSFCH (i.e., LPSSCH ■ Mset or Mset). Then, it increases with the cyclic shift pair index, again with the PRB index, and so forth.

[0055] In some embodiments, among the F PSFCHs available for the HARQ feedback of a given transmission, an RX UE selects for its HARQ feedback the PSFCH with index i given by: i=(TiD+RiD)mod(F), where TID is the layer 1 identifier (“ID”) of the TX UE (e.g., indicated in the 2nd-stage SCI). RID= for unicast ACK/NACK feedback and groupcast NACK-only feedback (e.g., option 1). For groupcast ACK/NACK feedback (e.g., option 2), RID is equal to the RX UE identifier within the group, which is indicated by higher layers. For a number X of RX UEs within a group, the RX UE identifier is an integer between 0 and X— 1. An RX UE determines which PRB and cyclic shift pair should be used for sending its HARQ feedback based on the PSFCH index i. The RX UE uses the first or second cyclic shift from the cyclic shift pair associated with the selected PSFCH index i to send NACK or ACK, respectively.

[0056] In various embodiments, if more HARQ feedback bits should be transmitted in PSFCH resources available to a UE in a PSFCH occasion, one or more of the HARQ feedback bits are combined to a single feedback bit that are to be transmitted in a PSFCH resource.

[0057] In certain embodiments, a number N of PSSCH resources associated with PSFCHs in a certain slot is limited. Consequently, the number of ACK/NACK bits that can be transmitted in a PSFCH symbol in a given slot by a UE is limited as well. This limit may be exceeded particularly if the feedback needs not only to include the ACK/NACK for N PSSCHs, but additionally for feedback that has been postponed or triggered (e.g., resulting from a PDSCH-to- HARQ feedback timing indicator field of an SCI format providing an inapplicable or non- numerical value). Such an inapplicable value may be represented by a value of -1. By this value, the control information indicates that no explicit ACK/NACK feedback timing is given. Rather an extra control information (e.g., transmitted at a later time) may then be used to trigger the transmission of such ACK/NACK feedback.

[0058] In a first embodiment, one or more ACK/NACK bits associated with a PSSCH for which no explicit ACK/NACK feedback timing is given are transmitted on a PSFCH resource that is indicated by a control information triggering the transmission of ACK/NACK feedback (e.g., HARQ feedback).

[0059] According to a first implementation of the first embodiment, one or more ACK/NACK bits associated with a PSSCH for which no explicit ACK/NACK feedback timing is given are combined to a single bit. The combination may be determined as described herein in a second embodiment or any of its implementations.

[0060] According to a second implementation of the first embodiment, the one or more ACK/NACK bits, possibly combined according to the first implementation, are transmitted using specific cyclic shift pairs of a Zadoff-Chu sequence, where a cyclic shift pair includes one cyclic shift for ACK and another cyclic shift for NACK. In one example, the cyclic shift pairs are preconfigured (e.g., by radio resource control (“RRC”) signaling).

[0061] According to a third implementation of the first embodiment, the one or more ACK/NACK bits, possibly combined according to the first implementation, are transmitted using a Zadoff-Chu sequence which may be different from the Zadoff-Chu sequence or sequences used for the transmission of other ACK/NACK feedback bits (e.g., for transmission of ACK/NACK bits associated with a PSSCH for which an explicit ACK/NACK feedback timing other than an inapplicable value is indicated, or for transmission of ACK/NACK bits associated with a PSSCH for which an ACK/NACK feedback timing is implicitly determined by a rule such as according to specifications for PSFCH resource determination). In one example, the Zadoff-Chu sequence is pre-configured (e.g., by RRC signaling).

[0062] According to a second embodiment, a UE uses at least a partial combination of ACK/NACK bits so that a resulting number of ACK/NACK bits is aligned with a number of ACK/NACK bits that are available to the UE in a PSFCH symbol. Consider al as the number of bits that are available to the UE in a PSFCH symbol for ACK/NACK transmission (e.g., a capacity of how many bits can be transmitted), and a2 as the number of bits that the UE has in store to transmit in that PSFCH symbol (e.g., the number of PSSCHs for which the UE is requested to transmit ACK/NACK feedback). In certain implementations of the second embodiment, the UE combines a2- al+\ bits to a single ACK/NACK bit.

[0063] The ACK/NACK bits to be transmitted in a PSFCH symbol within a sub-channel can be ordered by the time slot in which the corresponding PSSCH was transmitted and/or received. This temporal order may be used to differentiate the ACK/NACK bits that are to be combined, and further may be useful to determine the PSFCH resource on which a corresponding ACK/NACK bit is transmitted. From the perspective of a slot npsFCH in which the PSFCH is transmitted, the ACK/NACK bits corresponding to the PSSCH transmissions can then be indexed as bo, bi, . . . , ba2-i. As a matter of simplicity, but without loss of generality, consider an ascending order of bits with respect to time e.g., bo as the ACK/NACK bit corresponding to the PSSCH transmission out of the plurality of PSSCH transmissions for which ACK/NACK feedback is to be transmitted that was transmitted and/or received earliest prior to slot npsFCH (e.g., the most antecedent or prior one), and b_a2-i as the ACK/NACK bit corresponding to the PSSCH transmission, out of the plurality of PSSCH transmissions for which ACK/NACK feedback is to be transmitted, that was transmitted and/or received closest in time to slot npsFCH (e.g., the most recent one). However, it should be noted that the PSSCHs do not need to be transmitted and/or received in consecutive slots. For example, for a2=5 bits, the PSSCH transmission associated with ACK/NACK bit bo may have been transmitted and/or received in slot npsFCH- 10, the PSSCH transmission associated with ACK/NACK bit bi may have been transmitted/received in slot npsFCH-7, and so forth.

[0064] According to a first implementation of the second embodiment, the UE combines bits bo to bits b_a2-ai to a single bit (e.g., with the resulting bit value replacing bit b_a2-ai). Subsequently, the remaining al bits b_a2-ai to b_a2-i can be transmitted on the available PSFCH resources.

[0065] According to a second implementation of the second embodiment, the UE combines bits ba?-i to bits b_a2-j to a single bit (e.g., with the resulting bit value replacing bit b«7-i). Subsequently, the remaining al bits after the combination step bo to bai-i can be transmitted on the available PSFCH resources.

[0066] According to a third implementation of the second embodiment, the bits that are to be combined are configurable (e.g., by means of RRC signaling). For example, one option is the combination of the most antecedent bits (e.g., which is according to the behavior of the first implementation of the first embodiment), another option is the combination of the most recent bits (e.g., which is according to the behavior of the second implementation of the first embodiment).

[0067] In a specific implementation, if ACK is represented by logical true and NACK is represented by logical false, the combination of a plurality of bits to a single bit can be efficiently accomplished by a logical AND operation on the plurality of bits. As a consequence, the resulting bit will represent ACK (e.g., logical true) if and only if all of the plurality of bits represent logical true, and will represent NACK (e.g., logical false) otherwise.

[0068] In another specific implementation, if ACK is represented by logical false and NACK is represented by logical true, the combination of a plurality of bits to a single bit can be efficiently accomplished by a logical OR operation on the plurality of bits. As a consequence, the resulting bit will represent ACK (e.g., logical false) if and only if all of the plurality of bits represent logical false, and will represent NACK (e.g., logical true) otherwise.

[0069] Figure 4 is a schematic block diagram illustrating one embodiment of a system 400 for transmitting SL feedback with a reduced number of feedback bits. The system 400 includes a first UE 402 and a second UE 404. Each of the communications in the system 400 may include one or more messages. The first UE 402 determines 406 feedback. In a first communication 408, the first UE 402 transmits the feedback on a feedback channel to the second UE 404. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0070] Figure 5 is a flow chart diagram illustrating one embodiment of a method 500 for transmitting SL feedback with a reduced number of feedback bits. In some embodiments, the method 500 is performed by an apparatus, such as the remote unit 102. In certain embodiments, the method 500 may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

[0071] In various embodiments, the method 500 includes determining 502, in a communication device, feedback. In some embodiments, the method 500 includes transmitting 504 the feedback on a feedback channel. A capacity of the feedback channel includes a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback includes the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0072] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback. In some embodiments: a third set of feedback bits comprises a third number of bits combined to the single feedback bit, wherein bits in the third set of feedback bits are a subset of bits in the second set of feedback bits; and the third number of bits is less than or equal to the second number of bits minus the first number of bits plus one.

[0073] In various embodiments, the third set of feedback bits corresponds to oldest feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. In one embodiment, the third set of feedback bits corresponds to most recent feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. [0074] Figure 6 is a flow chart diagram illustrating another embodiment of a method 600 for transmitting SL feedback with a reduced number of feedback bits. In some embodiments, the method 600 is performed by an apparatus, such as the remote unit 102. In certain embodiments, the method 600 may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

[0075] In various embodiments, the method 600 includes receiving 602, at a communication device, information triggering the determination of feedback for transmission on a feedback channel. The information may indicate a resource for the feedback channel. In some embodiments, the method 600 includes determining 604 the feedback. The feedback includes a plurality of bits combined into a single feedback bit. In certain embodiments, the method 600 includes 606 transmitting the feedback on the feedback channel so that the information triggering the generation of feedback for transmission on a feedback channel also triggers the transmission of the determined feedback on a feedback channel.

[0076] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback. In some embodiments, transmitting the feedback on the feedback channel comprises transmitting the feedback using a cyclic shift of a Zadoff-Chu sequence.

[0077] In various embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback, and transmitting the feedback comprises transmitting a first cyclic shift for an acknowledgment (ACK) and a second cyclic shift for a non -acknowledgement (NACK). In one embodiment, the cyclic shift is configured by radio resource control (RRC) signaling.

[0078] In one embodiment, an apparatus comprises: a processor to determine feedback; and a transmitter to transmit the feedback on a feedback channel, wherein: a capacity of the feedback channel comprises a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SU shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback comprises the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0079] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback.

[0080] In some embodiments: a third set of feedback bits comprises a third number of bits combined to the single feedback bit, wherein bits in the third set of feedback bits are a subset of bits in the second set of feedback bits; and the third number of bits is less than or equal to the second number of bits minus the first number of bits plus one.

[0081] In various embodiments, the third set of feedback bits corresponds to oldest feedback bits of the second set of feedback bits with respect to transmission on the feedback channel.

[0082] In one embodiment, the third set of feedback bits corresponds to most recent feedback bits of the second set of feedback bits with respect to transmission on the feedback channel.

[0083] In one embodiment, a method in a communication device comprises: determining feedback; and transmitting the feedback on a feedback channel, wherein: a capacity of the feedback channel comprises a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a SL shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback comprises the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

[0084] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback.

[0085] In some embodiments: a third set of feedback bits comprises a third number of bits combined to the single feedback bit, wherein bits in the third set of feedback bits are a subset of bits in the second set of feedback bits; and the third number of bits is less than or equal to the second number of bits minus the first number of bits plus one.

[0086] In various embodiments, the third set of feedback bits corresponds to oldest feedback bits of the second set of feedback bits with respect to transmission on the feedback channel.

[0087] In one embodiment, the third set of feedback bits corresponds to most recent feedback bits of the second set of feedback bits with respect to transmission on the feedback channel.

[0088] In one embodiment, an apparatus comprises: a receiver to receive information triggering feedback on a feedback channel, wherein the information indicates a resource for the feedback channel; a processor to determine the feedback, wherein the feedback comprises a plurality of bits combined into a single feedback bit; and a transmitter to transmit the feedback on the feedback channel. [0089] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback.

[0090] In some embodiments, the transmitter further to transmit the feedback using a cyclic shift of a Zadoff-Chu sequence.

[0091] In various embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback, and transmitting the feedback comprises transmitting a first cyclic shift for an acknowledgment (ACK) and a second cyclic shift for a non-acknowledgement (NACK).

[0092] In one embodiment, the cyclic shift is configured by radio resource control (RRC) signaling.

[0093] In one embodiment, a method in a communication device comprises: receiving information triggering feedback on a feedback channel, wherein the information indicates a resource for the feedback channel; determining the feedback, wherein the feedback comprises a plurality of bits combined into a single feedback bit; and transmitting the feedback on the feedback channel.

[0094] In certain embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback.

[0095] In some embodiments, transmitting the feedback on the feedback channel comprises transmitting the feedback using a cyclic shift of a Zadoff-Chu sequence.

[0096] In various embodiments, the feedback comprises hybrid automatic repeat request (HARQ) feedback, and transmitting the feedback comprises transmitting a first cyclic shift for an acknowledgment (ACK) and a second cyclic shift for a non-acknowledgement (NACK).

[0097] In one embodiment, the cyclic shift is configured by radio resource control (RRC) signaling.

[0098] Embodiments may be practiced in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1 . An apparatus for wireless communication, the apparatus comprising: a processor; and a memory coupled to the processor, the memory comprising instructions executable by the processor to cause the apparatus to: determine feedback; and transmit the feedback on a feedback channel, wherein: a capacity of the feedback channel comprises a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a sidelink (SL) shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback comprises the single feedback bit and the second set of feedback bits that are not part of the plurality of bits.

2. The apparatus of claim 1, wherein the feedback comprises hybrid automatic repeat request (HARQ) feedback.

3. The apparatus of claim 1, wherein: a third set of feedback bits comprises a third number of bits combined to the single feedback bit, wherein bits in the third set of feedback bits are a subset of bits in the second set of feedback bits; and the third number of bits is less than or equal to the second number of bits minus the first number of bits plus one.

4. The apparatus of claim 3, wherein the third set of feedback bits corresponds to oldest feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. The apparatus of claim 3, wherein the third set of feedback bits corresponds to most recent feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. A method at a communication device, the method comprising: determining feedback; and transmitting the feedback on a feedback channel, wherein: a capacity of the feedback channel comprises a first number of bits corresponding to a first set of feedback bits, wherein each feedback bit of the first set of feedback bits corresponds to a transmission on a sidelink (SL) shared channel; a second set of feedback bits having a second number of bits is available for transmission on the feedback channel; the second number of bits is greater than the first number of bits; a plurality of bits from the second set of feedback bits are combined to a single feedback bit; and the feedback comprises the single feedback bit and the second set of feedback bits that are not part of the plurality of bits. The method of claim 6, wherein the feedback comprises hybrid automatic repeat request (HARQ) feedback. The method of claim 6, wherein: a third set of feedback bits comprises a third number of bits combined to the single feedback bit, wherein bits in the third set of feedback bits are a subset of bits in the second set of feedback bits; and the third number of bits is less than or equal to the second number of bits minus the first number of bits plus one. The method of claim 8, wherein the third set of feedback bits corresponds to oldest feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. The method of claim 8, wherein the third set of feedback bits corresponds to most recent feedback bits of the second set of feedback bits with respect to transmission on the feedback channel. An apparatus for wireless communication, the apparatus comprising: a processor; and a memory coupled to the processor, the memory comprising instructions executable by the processor to cause the apparatus to: receive information triggering feedback on a feedback channel, wherein the information indicates a resource for the feedback channel; determine the feedback, wherein the feedback comprises a plurality of bits combined into a single feedback bit; and transmit the feedback on the feedback channel. The apparatus of claim 11, wherein the feedback comprises hybrid automatic repeat request (HARQ) feedback. The apparatus of claim 11, wherein the instructions are further executable by the processor to cause the apparatus to transmit the feedback using a cyclic shift of a Zadoff- Chu sequence. The apparatus of claim 12, wherein the feedback comprises hybrid automatic repeat request (HARQ) feedback, and transmitting the feedback comprises transmitting a first cyclic shift for an acknowledgment (ACK) and a second cyclic shift for a nonacknowledgement (NACK). The apparatus of claim 14, wherein the first cyclic shift is configured by radio resource control (RRC) signaling.