WO2021191761A1 - Second stage sidelink control information feedback - Google Patents

Abstract

Apparatuses, methods, and systems are disclosed for second stage sidelink control information feedback. One method (700) includes receiving (702) first stage sidelink control information. The method (700) includes not receiving (704) second stage sidelink control information. The method (700) includes transmitting (706) feedback indicating that the second stage sidelink control information was not received.

Description

SECOND STAGE SIDELINK CONTROL INFORMATION FEEDBACK

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Patent Application Serial Number 62/993,840 entitled “APPARATUSES, METHODS, AND SYSTEMS FOR ROBUST AND EFFICIENT TRANSMISSIONS ON SIDELINK” and fried on March 24, 2020 for Prateek Basu Mallick, which is incorporated herein by reference in its entirety.

FIELD

[0002] The subject matter disclosed herein relates generally to wireless communications and more particularly relates to second stage sidelink control information feedback.

BACKGROUND

[0003] In certain wireless communications networks, a transmitting device may not know whether second stage sidelink control information was properly received.

BRIEF SUMMARY

[0004] Methods for second stage sidelink control information feedback are disclosed. Apparatuses and systems also perform the functions of the methods. One embodiment of a method includes receiving first stage sidelink control information. In some embodiments, the method includes not receiving second stage sidelink control information. In various embodiments, the method includes transmitting feedback indicating that the second stage sidelink control information was not received.

[0005] One apparatus for second stage sidelink control information feedback includes a receiver that: receives first stage sidelink control information; and does not receive second stage sidelink control information. In various embodiments, the apparatus includes a transmitter that transmits feedback indicating that the second stage sidelink control information was not received.

[0006] Another embodiment of a method for second stage sidelink control information feedback includes transmitting first stage sidelink control information. In some embodiments, the method includes transmitting second stage sidelink control information. In various embodiments, the method includes monitoring for feedback indicating that the second stage sidelink control information was not received.

[0007] Another apparatus for second stage sidelink control information feedback includes a transmitter that: transmits first stage sidelink control information; and transmits second stage sidelink control information. In various embodiments, the apparatus includes a processor that monitors for feedback indicating that the second stage sidelink control information was not received.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] 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:

[0009] Figure 1 is a schematic block diagram illustrating one embodiment of a wireless communication system for second stage sidelink control information feedback;

[0010] Figure 2 is a schematic block diagram illustrating one embodiment of an apparatus that may be used for second stage sidelink control information feedback;

[0011] Figure 3 is a schematic block diagram illustrating one embodiment of an apparatus that may be used for second stage sidelink control information feedback;

[0012] Figure 4 is a flow chart diagram illustrating one embodiment of a method for control signaling;

[0013] Figure 5 is a diagram illustrating one embodiment of a table indicating results if Stage-2 is not received successfully;

[0014] Figure 6 is a diagram illustrating one embodiment of a table indicating results if Stage-2 is received successfully;

[0015] Figure 7 is a flow chart diagram illustrating one embodiment of a method for second stage sidelink control information feedback; and

[0016] Figure 8 is a flow chart diagram illustrating another embodiment of a method for second stage sidelink control information feedback.

DETAIFED DESCRIPTION

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 read only 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.

[0023] 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).

[0024] 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.

[0025] 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. [0026] 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.

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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. [0031] 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.

[0032] 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.

[0033] Figure 1 depicts an embodiment of a wireless communication system 100 for second stage sidelink control information feedback. 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.

[0034] 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, user equipment (“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 UL communication signals. In certain embodiments, the remote units 102 may communicate directly with other remote units 102 via sidelink communication.

[0035] 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 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 (“OAM”), a session management function (“SMF”), a user plane function (“UPF”), an application function, an authentication server function (“AUSF”), security anchor functionality (“SEAF”), trusted non-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.

[0036] In one implementation, the wireless communication system 100 is compliant with NR protocols standardized in third generation partnership project (“3GPP”), wherein the network unit 104 transmits using an OFDM modulation scheme on the downlink (“DL”) and the remote units 102 transmit on the uplink (“UL”) using a single-carrier frequency division multiple access (“SC-FDMA”) scheme or an orthogonal frequency division multiplexing (“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, Sigfoxx, among other protocols. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

[0037] 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.

[0038] In various embodiments, a remote unit 102 may receive first stage sidelink control information. In some embodiments, the remote unit 102 may not receive second stage sidelink control information. In various embodiments, the remote unit 102 may transmit feedback indicating that the second stage sidelink control information was not received. Accordingly, the remote unit 102 may be used for second stage sidelink control information feedback.

[0039] In certain embodiments, a network unit 104 may transmit first stage sidelink control information. In some embodiments, the network unit 104 may transmit second stage sidelink control information. In various embodiments, the network unit 104 may monitor for feedback indicating that the second stage sidelink control information was not received. Accordingly, the network unit 104 may be used for second stage sidelink control information feedback.

[0040] Figure 2 depicts one embodiment of an apparatus 200 that may be used for second stage sidelink control information feedback. 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.

[0041] 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.

[0042] 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. [0043] 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.

[0044] 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.

[0045] 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.

[0046] In certain embodiment, the receiver 212: receives first stage sidelink control information; and does not receive second stage sidelink control information. In various embodiments, the transmitter 210 transmits feedback indicating that the second stage sidelink control information was not received.

[0047] 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. [0048] Figure 3 depicts one embodiment of an apparatus 300 that may be used for second stage sidelink control information feedback. 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, a transmitter 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.

[0049] In certain embodiment, the transmitter 310: transmits first stage sidelink control information; and transmits second stage sidelink control information. In various embodiments, the processor 302 monitors for feedback indicating that the second stage sidelink control information was not received.

[0050] In certain embodiments, there may not be a way for a vehicle to everything (“V2X”) transmitter UE to tell if expected but not received HARQ feedback is because a receiver did not receive Stage- 1 sidelink control information (“SCI”), Stage-2 SCI, or due to the receiver not providing a feedback (e.g., if it is situated outside a minimum communication range (“MCR”) or does not have its location). One embodiment of a transmission and/or reception sequence is shown in Figure 4Error! Reference source not found.. In various embodiments, a transmitter may make a transmission more robust in response to receiving feedback about Stage-2 SCI (e.g., by increasing transmit power, changing modulation and coding scheme (“MCS”), etc.).

[0051] Figure 4 is a flow chart diagram illustrating one embodiment of a method 400 for control signaling (e.g., sequence of control signaling to receive data (physical sidelink shared channel (“PSSCH”))). The method 400 includes transmitting 402 SCI Stage-1, transmitting 404 SCI Stage-2, and transmitting 406 data (PSSCH).

[0052] In some embodiments, if hybrid automatic repeat request (“HARQ”) feedback is to be provided by a receiver, this may be indicated by a transmitter using a flag in 1st stage SCI. An additional feedback (“FB”) option (e.g., Option 1 or Option 2) may be indicated by the 1st stage SCI. The additional FB may be based on a signaled format for the 2nd stage SCI indicated in the 1st stage.

[0053] In certain embodiments, if Stage-1 (e.g., 1st stage) SCI is received but not Stage-2 SCI is not received, then a receiver may send feedback indicating “Stage-2-not-received” to a transmitter. The “Stage -2-not-received” feedback indicates that the Stage-2 (e.g., 2nd stage) reception failed and, upon receiving this feedback, the transmitter may decide to make the 2nd stage transmission more robust. Transmission of the second stage (or any transmission) can be made more robust using at least one means available to the transmitter (e.g., making the 2nd stage SCI transmission with higher power, conservative MCS, making repetitions, using different diversity schemes, etc.).

[0054] In various embodiments, Option 1 based HARQ feedback may be used. In such embodiments, “Stage-2 -not-received” may be indicated using part of a normal physical sidelink feedback channel (“PSFCH”) resource. Further, there may be more than one common feedback resource available to all potential receiver UEs (e.g., one bit or resource for conventional negative acknowledgment or non-acknowledgement (“NACK”) feedback transmitted by receivers that fail to decode PSSCH and another common feedback bit or resource used by receivers that fail to receive the 2nd stage successfully). Certain receivers may not be able to determine if they are intended recipients since both source and destination IDs for a transmission are included in a 2nd Stage SCI that these receivers fail to receive.

[0055] In some embodiments, “Stage-2 -not-received” may be indicated if Option 2 based HARQ feedback needs to be provided, as deduced from Stage- 1 SCI. “Stage-2-not-received” may be indicated using reserved time-frequency resources (e.g., physical resource blocks (“PRBs”)), CDM cyclic shifts, and/or one or more reserved specific M_IDs. The reserved specific M_IDs may be used by UEs that can’t determine if they are intended recipients.

[0056] In certain embodiments, “Stage-2 -not-received” may be indicated if Option 2 based HARQ feedback needs to be provided by including an Option 1 (e.g., NACK only) feedback resource inside Option 2 PSFCH feedback resources. Potential receivers may randomly pick a reserved CDM cyclic shift and/or an M_ID to provide the “Stage-2 -not-received” feedback to a transmitter.

[0057] In various embodiments, a receiver may try to decode PSSCH blindly for a different new data indicator (“NDI”), redundancy version (“RV”), and so forth based on control information received in Stage-1 SCI and then decide (e.g., in upper layer) to provide any feedback after determining if it is part of an intended destination based on the presence of source and destination L2 ID bits in MAC or in upper layers. In such embodiments, if a UE determines that it is an intended recipient (e.g., source and destination L2 IDs are known), the UE uses its own intended PSFCH resource. Its own intended PSFCH resource may contain two bits or resources for feedback: one for regular HARQ feedback and another for the “Stage-2 -not-received” information. In some embodiments, a receiver UE may try to decode PSSCH blindly for a different NDI, RV, and so forth based on control information received in Stage- 1 SCI, if Stage-2 is not successfully received. [0058] In certain embodiments, a transmitter, upon neither receiving “Stage-2-not- received” feedback nor HARQ feedback corresponding to a PSSCH decode failure may conclude that first stage SCI itself was not received and may make a 1st Stage SCI transmission more robust. However, in such embodiments, if only “Stage-2-not-received” feedback is received then the transmitter may make a 2nd Stage SCI transmission more robust. If both cases occur simultaneously (e.g., complete discontinuous transmission (“DTX”) from one or more receiver UEs) and upon receiving one or more “Stage-2 -not-received” feedback, the transmitter may make both 1st and 2nd stage SCI transmissions more robust.

[0059] Specifically, Figure 5 is a diagram illustrating one embodiment of a table 500 indicating results if Stage-2 is not received successfully. Moreover, Figure 6 is a diagram illustrating one embodiment of a table 600 indicating results if Stage-2 is received successfully.

[0060] Figure 7 is a flow chart diagram illustrating one embodiment of a method 700 for second stage sidelink control information feedback. In some embodiments, the method 700 is performed by an apparatus, such as the remote unit 102. In certain embodiments, the method 700 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.

[0061] In various embodiments, the method 700 includes receiving 702 first stage sidelink control information. In some embodiments, the method 700 includes not receiving 704 second stage sidelink control information. In various embodiments, the method 700 includes transmitting 706 feedback indicating that the second stage sidelink control information was not received.

[0062] In certain embodiments, the feedback comprises a common feedback bit. In some embodiments, the common feedback bit is transmitted together with a data feedback bit indicating whether physical sidelink shared channel data is successfully decoded. In various embodiments, the feedback is transmitted using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

[0063] Figure 8 is a flow chart diagram illustrating another embodiment of a method 800 for second stage sidelink control information feedback. In some embodiments, the method 800 is performed by an apparatus, such as the network unit 104. In certain embodiments, the method 800 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.

[0064] In various embodiments, the method 800 includes transmitting 802 first stage sidelink control information. In some embodiments, the method 800 includes transmitting 804 second stage sidelink control information. In various embodiments, the method 800 includes monitoring 806 for feedback indicating that the second stage sidelink control information was not received.

[0065] In certain embodiments, the feedback comprises a common feedback bit. In some embodiments, the common feedback bit is received together with a data feedback bit indicating whether physical sidelink control channel data is successfully decoded. In various embodiments, the feedback is received using at least one reserved time -frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

[0066] In one embodiment, the method 800 further comprises, in response to receiving the feedback indicating that the second stage sidelink control information was not received, retransmitting the second stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or a combination thereof. In certain embodiments, the method 800 further comprises, in response to not receiving the feedback and not receiving data feedback indicating whether physical sidelink shared channel data is successfully decoded, retransmitting the first stage sidelink control information and the second stage sidelink control information using enhanced transmission, transmitting new first stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or some combination thereof.

[0067] In one embodiment, a method comprises: receiving first stage sidelink control information; not receiving second stage sidelink control information; and transmitting feedback indicating that the second stage sidelink control information was not received.

[0068] In certain embodiments, the feedback comprises a common feedback bit.

[0069] In some embodiments, the common feedback bit is transmitted together with a data feedback bit indicating whether physical sidelink shared channel data is successfully decoded. [0070] In various embodiments, the feedback is transmitted using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

[0071] In one embodiment, an apparatus comprises: a receiver that: receives first stage sidelink control information; and does not receive second stage sidelink control information; and a transmitter that transmits feedback indicating that the second stage sidelink control information was not received.

[0072] In certain embodiments, the feedback comprises a common feedback bit.

[0073] In some embodiments, the common feedback bit is transmitted together with a data feedback bit indicating whether physical sidelink shared channel data is successfully decoded. [0074] In various embodiments, the feedback is transmitted using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

[0075] In one embodiment, a method comprises: transmitting first stage sidelink control information; transmitting second stage sidelink control information; and monitoring for feedback indicating that the second stage sidelink control information was not received.

[0076] In certain embodiments, the feedback comprises a common feedback bit.

[0077] In some embodiments, the common feedback bit is received together with a data feedback bit indicating whether physical sidelink control channel data is successfully decoded. [0078] In various embodiments, the feedback is received using at least one reserved time- frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

[0079] In one embodiment, the method further comprises, in response to receiving the feedback indicating that the second stage sidelink control information was not received, retransmitting the second stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or a combination thereof.

[0080] In certain embodiments, the method further comprises, in response to not receiving the feedback and not receiving data feedback indicating whether physical sidelink shared channel data is successfully decoded, retransmitting the first stage sidelink control information and the second stage sidelink control information using enhanced transmission, transmitting new first stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or some combination thereof.

[0081] In one embodiment, an apparatus comprises: a transmitter that: transmits first stage sidelink control information; and transmits second stage sidelink control information; and a processor that monitors for feedback indicating that the second stage sidelink control information was not received.

[0082] In certain embodiments, the feedback comprises a common feedback bit.

[0083] In some embodiments, the common feedback bit is received together with a data feedback bit indicating whether physical sidelink control channel data is successfully decoded.

[0084] In various embodiments, the feedback is received using at least one reserved time- frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof. [0085] In one embodiment, the transmitter, in response to receiving the feedback indicating that the second stage sidelink control information was not received, retransmits the second stage sidelink control information using enhanced transmission, transmits new second stage sidelink control information using enhanced transmission, or a combination thereof. [0086] In certain embodiments, the transmitter, in response to not receiving the feedback and not receiving data feedback indicating whether physical sidelink shared channel data is successfully decoded, retransmits the first stage sidelink control information and the second stage sidelink control information using enhanced transmission, transmits new first stage sidelink control information using enhanced transmission, transmits new second stage sidelink control information using enhanced transmission, or some combination thereof.

[0087] 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 A method comprising: receiving first stage sidelink control information; not receiving second stage sidelink control information; and transmitting feedback indicating that the second stage sidelink control information was not received.

2 The method of claim 1, wherein the feedback comprises a common feedback bit.

3. The method of claim 2, wherein the common feedback bit is transmitted together with a data feedback bit indicating whether physical sidelink shared channel data is successfully decoded.

4. The method of claim 1, wherein the feedback is transmitted using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

5. An apparatus comprising: a receiver that: receives first stage sidelink control information; and does not receive second stage sidelink control information; and a transmitter that transmits feedback indicating that the second stage sidelink control information was not received.

6 The apparatus of claim 5, wherein the feedback comprises a common feedback bit.

7. The apparatus of claim 6, wherein the common feedback bit is transmitted together with a data feedback bit indicating whether physical sidelink shared channel data is successfully decoded.

8 The apparatus of claim 5, wherein the feedback is transmitted using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

9 A method comprising: transmitting first stage sidelink control information; transmitting second stage sidelink control information; and monitoring for feedback indicating that the second stage sidelink control information was not received.

10. The method of claim 9, wherein the feedback comprises a common feedback bit.

11. The method of claim 10, wherein the common feedback bit is received together with a data feedback bit indicating whether physical sidelink control channel data is successfully decoded.

12. The method of claim 9, wherein the feedback is received using at least one reserved time- frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

13. The method of claim 9, further comprising, in response to receiving the feedback indicating that the second stage sidelink control information was not received, retransmitting the second stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or a combination thereof.

14. The method of claim 9, further comprising, in response to not receiving the feedback and not receiving data feedback indicating whether physical sidelink shared channel data is successfully decoded, retransmitting the first stage sidelink control information and the second stage sidelink control information using enhanced transmission, transmitting new first stage sidelink control information using enhanced transmission, transmitting new second stage sidelink control information using enhanced transmission, or some combination thereof.

15. An apparatus comprising: a transmitter that: transmits first stage sidelink control information; and transmits second stage sidelink control information; and a processor that monitors for feedback indicating that the second stage sidelink control information was not received.

16. The apparatus of claim 15, wherein the feedback comprises a common feedback bit.

17. The apparatus of claim 16, wherein the common feedback bit is received together with a data feedback bit indicating whether physical sidelink control channel data is successfully decoded.

18. The apparatus of claim 15, wherein the feedback is received using at least one reserved time-frequency resource, a code division multiplexing cyclic shift, a reserved identifier, or some combination thereof.

19. The apparatus of claim 15, wherein the transmitter, in response to receiving the feedback indicating that the second stage sidelink control information was not received, retransmits the second stage sidelink control information using enhanced transmission, transmits new second stage sidelink control information using enhanced transmission, or a combination thereof.

20. The apparatus of claim 15, wherein the transmitter, in response to not receiving the feedback and not receiving data feedback indicating whether physical sidelink shared channel data is successfully decoded, retransmits the first stage sidelink control information and the second stage sidelink control information using enhanced transmission, transmits new first stage sidelink control information using enhanced transmission, transmits new second stage sidelink control information using enhanced transmission, or some combination thereof.