Long physical sidelink shared channel format for sidelink communication

Abstract

Aspects presented herein can enable a sidelink device to report or receive HARQ feedback for a sidelink channel based on a long PSFCH format. In one aspect, an apparatus transmits, to a second UE, an indication to provide HARQ feedback for at least one sidelink channel. The apparatus transmits, to the second UE, the at least one sidelink channel. The apparatus receives, from the second UE, an ACK or a NACK for the at least one sidelink channel via a PSFCH, the PSFCH comprising a long PSFCH format and being associated with a sidelink resource pool.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Patent Application No. 17 / 105,329, filed November 25, 2020, entitled “LONG PHYSICAL SIDELINK SHARED CHANNEL FORMAT FOR SIDELINK COMMUNICATION,” which is expressly incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates generally to communication systems, and more particularly, to wireless communications involving long physical sidelink shared channel (PSFCH) format. BACKGROUND

[0004] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems can employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is a set of enhancements implemented to the SUMMARY

[0006] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0007] In one aspect of the disclosure, a method, a computer readable medium, and an apparatus are provided for wireless communication at a first user equipment (UE) (e.g., a transmitter UE). The apparatus can transmit, to a second UE, an indication to provide hybrid automatic repeat request (HARQ) feedback for at least one sidelink channel. The apparatus can also transmit, to the second UE, the at least one sidelink channel. The apparatus can further receive, from the second UE via a physical sidelink feedback channel (PSFCH), an acknowledgement (ACK) or a negative ACK (NACK) for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool.

[0008] In one aspect of the disclosure, a method, a computer readable medium, and an apparatus are provided for wireless communication at a first UE (e.g., a receiver UE). The apparatus can receive, from a second UE, an indication to provide HARQ feedback for at least one sidelink channel. The apparatus can also receive, from the second UE, the at least one sidelink channel. The apparatus can further transmit, to the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool.

[0009] To the accomplishment of the foregoing and related aspects, one or more aspects comprise the features recited in the following claims, the full scope of which should be accorded to support the claims. The following description and the appended drawings describe certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects can be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

[0011] FIG. 2A is a diagram illustrating an example of a first frame, in accordance with various aspects of the disclosure.

[0012] FIG. 2B is a diagram illustrating an example of DL channels within a subframe, in accordance with various aspects of the disclosure.

[0013] FIG. 2C is a diagram illustrating an example of a second frame, in accordance with various aspects of the disclosure.

[0014] FIG. 2D is a diagram illustrating an example of UL channels within a subframe, in accordance with various aspects of the present disclosure.

[0015] Figure 3 is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

[0016] Figure 4A and Figure 4B is a diagram illustrating example aspects of a slot structure that can be used for sidelink communications.

[0017] FIG. 5A illustrates an example of wireless communications based on sidelink communications between devices.

[0018] FIG. 5B illustrates an example of wireless communications based on sidelink communications between a PLC and multiple SAs.

[0019] Figure 6 illustrates an example of periodic resources that can be reserved by a UE for sidelink communications.

[0020] Figure 7 is a diagram illustrating an example process of resource reservation.

[0021] Figure 8 is a diagram 800 illustrating an example of a two-stage PSCCH.

[0022] Figure 9 is a diagram illustrating an example PSFCH configuration.

[0023] Figure 10 is a diagram illustrating an example sidelink resource pool and structure of a sidelink slot including a PSFCH.

[0024] Figure 11A and 11B is a diagram illustrating an example sidelink resource pool providing a PSFCH with a long PSFCH format or a PSFCH with a short PSFCH format or associated therewith, in accordance with aspects of the present disclosure.

[0025] Figure 12 is a diagram illustrating an example of a long PSFCH covering a short PSFCH in a slot, in accordance with aspects of the present disclosure.

[0026] Figure 13 is a diagram illustrating an example of scheduling a long PSFCH in a slot not occupied by a short PSFCH, in accordance with aspects of the present disclosure.

[0027] Figure 14 is a diagram illustrating an example of determining whether to use a long PSFCH or a short PSFCH when a long PSFCH or a short PSFCH overlap in the same slot.

[0028] Figure 15 FIG. 1 is a diagram illustrating example HARQ reporting via short and long PSFCH formats.

[0029] Figure 16 FIG. 2 is a diagram illustrating an example of transmitting HARQ reporting using short PSFCH in a resource pool including both short PSFCH and long PSFCH.

[0030] Figure 17 FIG. 3 is a communication flow between two sidelink devices in accordance with aspects of the present disclosure.

[0031] Figure 18 FIG. 4 is a flow chart of a method of wireless communication.

[0032] Figure 19 FIG. 5 is a diagram illustrating an example of a hardware implementation for an example apparatus.

[0033] Figure 20 FIG. 6 is a flow chart of a method of wireless communication.

[0034] Figure 21 FIG. 7 is a diagram illustrating an example of a hardware implementation for an example apparatus. DETAILED DESCRIPTION

[0035] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0036] Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the particular application and design constraints imposed on the overall system.

[0037] By way of example, an element, or any portion of an element, or any combination of elements can be implemented as a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system can execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0038] Accordingly, in one or more example embodiments, the functions described can be implemented in hardware, software, or any combination thereof. If implemented in software, the functions can be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), compact disk ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable instructions or data structures accessed by a computer.

[0039] Figure 1 FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system, which can also be referred to as a wireless wide-area network (WWAN), includes base stations 102, UEs 104, an Evolved Packet Core (EPC) 160, and another core network 190 (e.g., a 5G Core (5GC)). The base stations 102 can include macro cells (high power cellular base stations) and / or small cells (low power cellular base stations). The macro cells can include base stations. The small cells can include femtocells, picocells, and microcells.

[0040] The base stations 102 configured for 4G LTE (collectively referred to as the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with the EPC 160 through the first backhaul links 132 (e.g., S I interface). The base stations 102 configured for 5G NR (collectively referred to as the Next Generation RAN (NG-RAN)) can interface with the core network 190 through the second backhaul links 184. In addition to other functions, the base stations 102 can perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 can communicate directly or indirectly (e.g., through the EPC 160 or core network 190) with each other over the third backhaul links 134 (e.g., X2 interface). The first, second, and third backhaul links 132, 184, and 134 can be wired or wireless.

[0041] The base stations 102 can wirelessly communicate with the UEs 104. Each of the base stations 102 can provide communication coverage for a respective geographic coverage area 110. There can be overlapping geographic coverage areas 110. For example, a small cell 102' can have a coverage area 110' that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells can be known as a heterogeneous network. A heterogeneous network can also include Home Evolved Node Bs (eNBs) (HeNBs), which can provide service to a restricted group known as a closed subscriber group (CSG). The communication links 120 between the base stations 102 and the UEs 104 can include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and / or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 can use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and / or transmit diversity. The communication links can be through one or more carriers, and each carrier can be a band of frequency waves having a predetermined width and can be used to transmit data between base stations 102 and UEs 104. The base stations 102 / UEs 104 can use spectrum that is fully reused, e.g., particulary for parts of the spectrum that are newly licensed by the Federal Communications Commission (FCC) to be used for mobile broadband access. The carriers can be

[0042] Certain UEs 104 can communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 can use the DL / UL WWAN spectrum. The D2D communication link 158 can use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication can be through a variety of wireless D2D communications systems, such as for example, WiMedia, Bluetooth, ZigBee, Wi-Fi based on Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards, LTE, or NR.

[0043] Some examples of sidelink communication can include vehicle-based communication devices capable of communicating according to vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) (e.g., from a vehicle-based communication device to a road infrastructure node such as a roadside unit (RSU)), vehicle-to-network (V2N) (e.g., from a vehicle-based communication device to one or more network nodes such as a base station), vehicle-to-pedestrian (V2P), cellular vehicle-to-everything (C-V2X), and / or combinations thereof and / or combinations with other devices, which can be collectively referred to as vehicle-to-everything (V2X) communications. Sidelink communications can be based on V2X or other D2D communications such as Proximity Services (ProSe), etc. In addition to UEs, sidelink communications can also be transmitted and received by other transmitting and receiving devices such as roadside units (RSUs) 107, etc. Sidelink communications can be exchanged using a PC5 interface, such as described in connection with the example slot structures of FIGs. 2A-2D. Although the following description (including the example slot structures of FIGs. 2A-2D) can provide examples of sidelink communications related to 5G NR, the concepts described herein can be applied to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless

[0044] The wireless communications system can also include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 (e.g., in a 5 GHz unlicensed frequency spectrum, etc.). When communicating in an unlicensed frequency spectrum, the STAs 152 / AP 150 can perform a clear channel assessment (CCA) prior to communicating so as to determine whether the channel is available for use.

[0045] The small cells 102' can operate in a licensed and / or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cells 102' can employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150 (e.g., 802.11 ac, 802.11 ad, etc.). The small cells 102' employing NR in an unlicensed frequency spectrum can boost coverage in the cells 102' and increase capacity for the access network.

[0046] The electromagnetic spectrum is often subdivided based on frequency / wavelength into various classes, bands, channels, etc. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz - 7. 125 GHz) and FR2 (24.25 GHz - 52.6 GHz). The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to as a “sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with respect to FR2, which is often referred to as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz - 300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

[0047] With the above in mind, unless specifically stated otherwise, it should be appreciated that the term “sub-6 GHz” or the like, if used herein, can broadly represent frequencies that can be less than 6 GHz, frequencies that can be within FR1, or frequencies that can include mid-band frequencies. Further, unless specifically stated otherwise, it should be appreciated that the term “millimeter wave” or the like, if used herein, can broadly represent frequencies that can include mid-band frequencies, frequencies that can be within FR2, or frequencies that can be within an EHF band.

[0048] A base station 102, whether a small cell 102' or a large cell (e.g., macro base station), can include and / or can be referred to as an eNB, gNodeB (gNB), or another type of base station. Some base stations, such as gNB 180 can operate in a traditional sub-6 GHz spectrum, in millimeter wave frequencies, and / or near millimeter wave frequencies in communication with the UE 104. When the gNB 180 operates in millimeter wave frequencies, the gNB 180 can be referred to as a millimeter wave base station. The millimeter wave base station 180 can utilize beamforming 182 with the UE 104 to compensate for the path loss and short range. The base station 180 and the UE 104 can each include a plurality of antennas, such as antenna elements, antenna panels, and / or antenna arrays to facilitate beamforming.

[0049] The base stations 180 can transmit to the UEs 104 in one or more transmit directions 182'. The UEs 104 can receive from the base stations 180 in one or more receive directions 182". The UEs 104 can also transmit to the base stations 180 in one or more transmit directions. The base stations 180 can receive from the UEs 104 in one or more receive directions. The base station(s) 180 / UE(s) 104 can perform beam training to determine the best receive and transmit directions for each of the base station(s) 180 / UE(s) 104. The transmit and receive directions for the base stations 180 can or can not be the same. The transmit and receive directions for the UEs 104 can or can not be the same.

[0050] The EPC 160 can include a Home Subscriber Server (HSS) 174, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 can be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 can include the Internet, an intranet, an IP Multimedia Subsystem (IMS), and a PS Streaming Service, and / or other IP services. The BM-SC 170 can provide functions for MBMS user service provisioning and

[0051] The core network 190 can include an Access and Mobility Management Function (AMF) 192, a plurality of other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 can be in communication with a Unified Data Management (UDM) 196. The AMF 192 is the control node that processes the signaling between the UEs 104 and the core network 190. Generally, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transferred

[0052] A base station can include and / or be referred to as a gNB, NodeB, eNB, access point, base transceiver station, radio base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), transmit reception point (TRP), or some other suitable terminology. The base station 102 provides an access point to a UEs 104 to an EPC 160 or core network 190. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a medical device, an implant, a sensor, an actuator, a display, or any other similar functional device. Some of the UEs 104 can be referred to as IoT devices (e.g., a parking meter, gas pump, toaster, vehicle, heart monitor, etc.). The UE 104 can also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

[0053] Referring again to Figure 1In certain aspects, the UE 104 can be configured to include a long PSFCH processing component 198. In one aspect, the long PSFCH processing component 198 can be configured to transmit, to a second UE, an indication to provide HARQ feedback for at least one sidelink channel. The long PSFCH processing component 198 can be configured to transmit the at least one sidelink channel to the second UE. The long PSFCH processing component 198 can be configured to receive, from the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool. In another aspect, the long PSFCH processing component 198 can be configured to receive, from a second UE, an indication to provide HARQ feedback for at least one sidelink channel. The long PSFCH processing component 198 can be configured to receive the at least one sidelink channel from the second UE. The long PSFCH processing component 198 can be configured to transmit, to the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool.

[0054] FIG. 2A is a diagram 200 illustrating an example of a first subframe in a 5G NR frame structure. FIG. 2B is a diagram 230 illustrating an example of DL channels in a 5G NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe in a 5G NR frame structure. FIG. 2D is a diagram 280 illustrating an example of UL channels in a 5G NR subframe. The 5G NR frame structure can be frequency division duplex (FDD) or can be time division duplex (TDD). In the case of FDD, a particular set of subcarriers (carrier system bandwidth) is dedicated for DL or UL. In the case of TDD, a particular set of subcarriers (carrier system bandwidth) is used for both DL and UL, with subframes within the set of subcarriers being dedicated for DL or UL. In the examples provided by FIGs. 2A, 2C, the 5G NR frame structure is assumed to be TDD, with subframe 4 configured with slot format 28 (mostly DL), where D is DL, U is UL, and F is flexible to use between DL / UL, and subframe 3 configured with slot format 1 (all UL). While subframes 3, 4 are shown with slot formats 1, 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. The other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with a slot format (dynamically through a DL control information (DCI), or semi- statically / statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI). It should be noted that the following description applies to a TDD 5G NR frame structure as well.

[0055] Other wireless communications technologies can have different frame structures and / or different channels. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe can include one or more time slots. A subframe can also include mini-slots, which can contain 7, 4, or 2 symbols. Depending on the slot configuration, each slot can contain 7 or 14 symbols. For slot configuration 0, each slot can contain 14 symbols, and for slot configuration 1, each slot can contain 7 symbols. A symbol on the DL can be a cyclic prefix (CP) orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbol. A symbol on the UL can be a CP-OFDM symbol (for high throughput scenarios) or a discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbol (also known as single carrier frequency division multiple access (SC-FDMA) symbol) (for power limited scenarios; limited to single stream transmission). The number of slots within a subframe is dependent on the slot configuration and the numerology. For slot configuration 0, different numerologies m0to 4allow for 1, 2, 4, 8, and 16 slots per subframe, respectively. For slot configuration 1, different numerologies 0 to 2allow for 2, 4, and 8 slots per subframe, respectively. Thus, for slot configuration 0 and numerology m, there are 14 symbols / slot and 2 μ slots / subframe. The subcarrier spacing and symbol length / duration are a function of the numerology. The subcarrier spacing can equal 2 μ * 15 kHz, where m is the numerology 0 to 4. As such, the subcarrier spacing for numerology m = 0 is 15 kHz, and the subcarrier spacing for numerology m = 4 is 240 kHz. The symbol length / duration is inversely related to the subcarrier spacing. FIGs. 2A-2D provide an example of slot configuration 0 with 14 symbols per slot and numerology m = 2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 ps. Within a frame collection, there can be one or more different bandwidth parts (BWPs) that are frequency division multiplexed (see FIG. 2B). Each BWP can have a particular numerology.

[0056] A resource grid can be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as a physical RB (PRB)) that contains 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0057] As illustrated in FIG. 2A, some of the REs carry reference (pilot) signals (RS) for the UE. The RS can include demodulation RS (DM-RS) (indicated as R for one particular configuration, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS can also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS).

[0058] FIG. 2B illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) (e.g., 1, 2, 4, 8, or 16 CCEs), each CCE including six RE groups (REGs), each REG including 12 consecutive REs in an OFDM symbol of an RB. A PDCCH within one BWP can be referred to as a control resource set (CORESET). A UE is configured to monitor PDCCH search space (e.g., common search space, UE-specific search space) for PDCCH candidates with different DCI formats and different aggregation levels during PDCCH monitoring occasions on the CORESET. Additional BWPs can be located at higher and / or lower frequencies of the channel bandwidth. A primary synchronization signal (PSS) can be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe / symbol timing and physical layer identity. A secondary synchronization signal (SSS) can be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB) that provides system bandwidth configuration and scheduling information can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block (also referred to as SS block (SSB)). The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information (such as system information blocks (SIBs)), and paging messages.

[0059] As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE can transmit DM-RS for channel estimation in the physical uplink control channel (PUCCH) and DM-RS for channel estimation in the physical uplink shared channel (PUSCH). The UE can transmit DM-RS in the first one or two symbols of a slot for the PUSCH. The UE can transmit DM-RS in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE can transmit sounding reference signals (SRS). The SRS can be transmitted in the last symbol of a slot. The SRS can have a comb structure, and the UE can transmit SRS on one of the combs. The SRS can be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0060] FIG. 2D illustrates an example of various UL channels within a subframe of a frame. The PUCCH can be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgment (ACK) (HARQ-ACK) information (ACK / negative ACK (HARQ)) feedback. The PUSCH carries data, and can additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0061] Figure 3is a block diagram of the base station 310 in communication with the UE 350 in an access network. In the DL, IP packets from the EPC 160 can be provided to a controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration associated with reporting of measurements by the UE; PDCP layer functionality associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0062] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, can include error detection on the transport channels, forward error correction (FEC) coding / decoding of the transport channels, interleaving, rate matching, mapping to physical channels, modulation / demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then split into parallel streams. Each stream can then be mapped to a OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and / or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 can be used to determine the coding and

[0063] At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the base station 310. These soft decisions can be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the base station 310 on the physical channel. The data and control signals are then provided to the controller / processor 359, which implements layer 3 and layer 2 functionality.

[0064] The controller / processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 can be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller / processor 359 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0065] Similar to the functionality described in connection with the DL transmission by the base station 310, the controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression / decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0066] Channel estimates derived by the channel estimator 358 from a reference signal or feedback transmitted by the base station 310 can be used by the TX processor 368 to select the appropriate coding and modulation schemes to be used by the UE 350, as well as to facilitate spatial processing. The spatial streams generated by the TX processor 368 can be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX can modulate an RF carrier with a respective spatial stream for transmission.

[0067] The UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

[0068] The controller / processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 can be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from the controller / processor 375 can be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0069] At least one of the TX processor 368, the RX processor 356, the controller / processor 359, the TX processor 316, the RX processor 370, or the controller / processor 375 can be configured to perform aspects related to long PSFCH processing component 198 of FIG. 1. For example, the long PSFCH processing component 198 can be configured to transmit and / or receive HARQ-ACK or HARQ-NACK in a long format PSFCH. Figure 1

[0070] Figure 4A and Figure 4B FIGs. 400 and 410 illustrate example aspects of a slot structure that can be used for sidelink communications (e.g., between UEs 104, RSUs 107, etc.), respectively. In some examples, the slot structure can be within a 5G / NR frame structure. In other examples, the slot structure can be within a LTE frame structure. Although the following description can focus on 5G NR, the concepts described herein can apply to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies. Figure 4A and Figure 4B The example slot structures in FIGs. 400-410 are merely examples and other sidelink communications can have different frame structures and / or different channels for sidelink communications. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe can include one or more slots. A subframe can also include mini-slots, which can contain 7, 4, or 2 symbols. Depending on the slot configuration, each slot can contain 7 or 14 symbols. For slot configuration 0, each slot can contain 14 symbols, and for slot configuration 1, each slot can contain 7 symbols. Figure 4A ​FIG. 400 of the Example 1 shows a single resource block of a single slot transmission, which can correspond to a 0.5 ms transmission time interval (TTI), for example. The physical sidelink control channel can be configured to occupy a number of physical resource blocks (PRBs), e.g., 10, 12, 15, 20, or 25 PRBs. The PSCCH can be limited to a single subchannel. The PSCCH duration can be configured to be 2 symbols or 3 symbols, for example. The subchannel can include 10, 15, 20, 25, 50, 75, or 100 PRBs, for example. Resources for a sidelink transmission can be selected from a resource pool including one or more subchannels. As a non-limiting example, the resource pool can include between 1-27 subchannels. The PSCCH size can be established for the resource pool, e.g., between 10-100% of one subchannel for a duration of 2 symbols or 3 symbols. In some examples, the first symbol of a subframe can be a symbol for automatic gain control (AGC) use (e.g., an AGC symbol), and the last symbol can be a symbol for transmit / receive switching time use. The AGC symbol can be used by a receiving end to adjust an operating point. Figure 4B FIG. 410 of the Example 1 shows an example where the PSCCH occupies approximately 50% of a subchannel, as one example showing a concept of the PSCCH occupying a portion of a subchannel. The physical sidelink shared channel (PSSCH) occupies at least one subchannel. In some examples, the PSCCH can include a first portion of sidelink control information (SCI), and the PSSCH can include a second portion of the SCI.

[0071] A resource grid can be used to represent the frame structure. Each time slot can include a resource block (RB) (also referred to as a physical RB (PRB)) that includes 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme. As Figure 4A and 4B As shown in FIG. 420 of the Example 1, some REs can include control information in the PSCCH, and some REs can include a demodulation RS (DMRS). At least one symbol can be used for feedback. Figure 4A and Figure 4B FIG. 430 of the Example 1 shows an example of two symbols for a physical sidelink feedback channel (PSFCH) with adjacent gap symbols. The symbols before and / or after the feedback can be used for a transition between reception of data and transmission of feedback. The gap can enable a device to switch from acting as a transmitting device to preparing to act as a receiving device, for example, in the next slot. Data can be transmitted in the remaining REs, as shown. The data can include a data message described herein. The locations of any of the data, DMRS, SCI, feedback, gap symbols, and / or LBT symbols can be different than Figure 4A and / or Figure 4BThe example shown in FIG. 4B. In some examples, multiple slots can be aggregated together.

[0072] FIG. 5A illustrates an example 500 of wireless communications between devices based on sidelink communications. The communications can be based on a slot structure as described in connection with Figure 4A-4B The slot structure of aspects described can be used for transmissions from a transmitting device to a receiving device. For example, a transmitting UE 502 can transmit a transmission 514 (e.g., including a control channel and / or a corresponding data channel), which can be received by receiving UEs 504, 506, 508. The control channel can include information for decoding the data channel and can also be used by receiving devices to avoid interference by refraining from transmitting on the occupied resources during the data transmission. The TTI to be occupied by the data transmission and the number of RBs can be indicated in a control message from the transmitting device. In addition to acting as receiving devices, UEs 502, 504, 506, 508 can each also have the capability to act as transmitting devices. Thus, UEs 506, 508 are shown transmitting transmissions 516, 520. The transmissions 514, 516, 520 can be broadcast or multicast to nearby devices. For example, UE 502 can transmit a communication (e.g., data) to be received by other UEs (e.g., 504, 506) within a range 501 of UE 502. Additionally or alternatively, an RSU 507 can receive communications from and / or transmit communications 518 to UEs 502, 506, 508.

[0073] Sidelink communications exchanged directly between devices can include discovery messages for sidelink UEs to find nearby UEs and / or can include sensing of resources reserved by other UEs in order to select resources for transmissions. Sidelink communications can be based on different types or modes of resource allocation mechanisms. In a first mode of resource allocation (which can be referred to herein as “Mode 1”), a centralized resource allocation can be provided. For example, a base station 102 or 180 can determine resources for sidelink communications and can allocate resources to different UEs 104 for sidelink transmissions. In this first mode, a sidelink UE receives an allocation of sidelink resources from the base station 102 or 180. In another example, a base station can allocate transmission (Tx) resources for sidelink communications through DCI format 3_0. Mode 1 resource allocation can support dynamic grant (DG), configured grant (CG) Type 1, and / or CG Type 2, where CG Type 1 can be activated via RRC signaling from the base station. DCI format 3_0 can be transmitted by the base station to allocate time and frequency resources and to indicate a transmission timing. The transmitting UE can determine the MCS within the limits set by the base station.

[0074] In a second resource allocation mode (which can be referred to herein as "Mode 2"), distributed resource allocation can be provided. In Mode 2, each UE (e.g., a transmitting UE) can autonomously determine resources for a sidelink transmission. To coordinate selection of sidelink resources by various UEs, each UE can use a sensing technique to monitor resource reservations by other sidelink UEs, and can select resources for a sidelink transmission from unreserved resources. For example, a transmitting UE can perform channel sensing by blindly decoding all PSCCH channels to find reserved resources of other sidelink transmissions. The transmitting UE can report available resources to an upper layer, and the upper layer can decide resource usage. These resource allocation mechanisms for sidelink can provide power saving, for example, at a physical layer or medium access control (MAC) layer. Power saving can be helpful for sidelink applications, such as public safety applications, commercial applications, wearable devices, and the like, which can include periodic and aperiodic traffic.

[0075] As described above, when operating using Mode 2 (e.g., in a distributed manner), a transmitting UE can determine resources for communication from a resource pool. A resource pool can refer to a set of time and / or frequency resources in which sidelink communication can occur. Figure 6 An example of time and frequency resources that can be used for sidelink communication is shown. A resource pool can be pre-configured (e.g., pre-loaded on a UE), configured by a base station, or otherwise determined by a UE. In some examples, a transmitting UE can randomly select resources for transmission from a resource pool. In such examples, a receiving UE can continuously monitor candidate resources to receive a communication. Additionally, in some examples, a collision or interference can occur if nearby UEs randomly select the same resources.

[0076] To receive a sidelink packet, such as in a C-V2X sidelink communication, a sidelink reception / receiving (Rx) device / UE can perform blind decoding in all sidelink subchannels. The number of subchannels can be small (such as between 1 and 27 subchannels), such that blind decoding of all subchannels can be feasible for a UE. As shown by FIGS. 400 and 410 in Figure 4A and 4B As shown by FIGS. 400 and 410 in , both PSCCH and PSSCH can be transmitted within the same slot. PSSCH can occupy up to Figure 8As described in detail, the first stage SCI containing information about the PSSCH bandwidth and resource reservation in future time slots can be sent in the PSCCH, and the second stage SCI can be found and decoded after decoding the PSCCH. The source ID and / or destination ID in the SCI can be used by the UE (e.g., the receiving UE) to distinguish whether the packet is for the UE and / or which UE it comes from. The subchannel size in V2X can have at least 10 RBs. Under C-V2X sidelink communication, the UE can be expected to decode all transmissions. Therefore, the UE can perform blind decoding on all subchannels.

[0077] Communication over a sidelink channel (e.g., D2D communication) can provide various advantages and improvements for wireless communication, such as providing ultra-low latency for communication between wireless devices. For example, in the Industrial Internet of Things (IIoT), sidelinks can enable direct programmable logic controller (PLC) and sensor / actuator (SA) communication. Figure 5B shows an example 550 of wireless communication based on sidelink communication between a PLC and multiple SAs. A wireless PLC (e.g., 552) may be required to enable flexible and simple deployment in the IIoT. For example, the PLC 552 can be configured to wirelessly control multiple (e.g., 20-50) SAs (e.g., SA 554, SA 556, and SA 558) over a sidelink (e.g., within its transmission range 551). In some instances, an IIoT device / system may have a strict latency specification of 1 to 2 ms and a 10 -6 Ultra-reliability specifications for bit error rate. However, communications through base stations may specify multiple over-the-air (OTA) transmissions, which may affect the latency and / or reliability of communications. Therefore, sidelink communications may be more suitable for IIoT devices. In some examples, IIoT services may typically be deterministic and have small packet sizes of 32-256 bytes. Therefore, the bandwidth used for this service may be lower, for example, 2 RBs may be sufficient in some cases. In addition, SA may have constraints on UE capabilities in terms of bandwidth and processing power. On the other hand, for IIoT with dedicated bands and / or unlicensed bands, the total bandwidth may be larger. In some applications, SA (e.g., SA 554, SA 556, and SA 558) can be configured not to detect / monitor all transmissions (e.g., to save power). For IIoT, the PSCCH (e.g., PLC 552) used by the transmitting device may have strict IIoT specifications, which may be challenging when the RF environment includes blocking and interference.

[0078] In some examples, a UE can use historical resource utilization of other UEs to predict future activity. For example, by identifying that a first UE periodically transmits and what resources the first UE uses when transmitting, a second UE can determine where future transmissions of the first UE are likely to occur and when they can also occur. Figure 6 An example of periodic resources 660 that can be reserved by UEs for sidelink communications is shown. Thus, by “listening” to past other UE activity (e.g., historical resource utilization), a second UE can predict future activity of other UEs and can select resources that are less likely to result in collisions and / or interference for use in transmissions. However, it can be appreciated that for the second UE to identify historical resource utilization, the second UE can operate in a “always on” mode to facilitate sensing or reception of transmissions of other UEs. Continuous monitoring by the second UE can increase power consumption or processing resources in order to identify historical resource utilization and predict future activity.

[0079] In some examples, a UE can perform partial sensing to determine historical resource utilization of other UEs. When performing partial sensing, a UE can selectively sense a subset of resources and, thus, can reduce power consumption as compared to monitoring a set of resources. However, partial sensing can not be effective when transmissions of other UEs are not periodic. For example, a UE employing partial sensing can miss information about aperiodic transmissions and, thus, can not be able to accurately predict future activity of other UEs based on determined historical resource utilization.

[0080] Radio resource allocation for sidelink communications can be based on resource reservation. For example, when a UE is ready to transmit data on a sidelink, the UE can first determine whether resources are reserved by other UEs. The UE can then reserve resources from the remaining available unreserved resources. Referring back to Figure 6 , resource allocation for each UE can be in units of one or more sub-channels (e.g., sub-channels SC 1 to SC 4) in the frequency domain and can be based on one sub-slot in the time domain. A UE can also use resources in a current slot for an initial transmission and can reserve resources in future slots for retransmissions. In this example, up to two different future slots can be reserved by UEs (e.g., UE1 and UE2) for retransmissions. Resource reservation can be limited to a window of predefined slots and sub-channels (e.g., a window of 8 slots by 4 sub-channels as shown in FIG. 600 of Figure 6 ), which collectively provides 32 available resource blocks. The window can also be referred to as a resource selection window. Each resource block in the resource selection window can be used to transmit both data and control information together.

[0081] In one aspect, a first UE (“UE1”) can reserve a subchannel (e.g., SC 4) in a current slot (e.g., slot 1) for its initial data transmission (e.g., using resources 602), and can reserve additional future slots within a window for data retransmissions (e.g., 604 and 606). For example, as shown by Figure 6 UE1 can reserve subchannel SC 2 at slot 3 and subchannel SC 3 at slot 4 for future retransmissions. UE1 can then send information to other UEs about which resources it is using and / or reserving, such as by including the reservation information in a reserved resource field of SCI (e.g., first stage SCI). A UE can be configured to reserve one, two, or three transmissions using SCI. The maximum number of reservations allowed for a UE can be preconfigured for the UE. For example, a UE can reserve up to three transmissions within a resource selection window.

[0082] As shown by Figure 6 A second UE (“UE2”) can also reserve resources in subchannels SCI and SC2 at slot 1 for its current data transmission (e.g., using resources 608), and can reserve a first data retransmission at slot 4 using subchannels SCI and SC 2 (using resources 610), and a second data retransmission at slot 7 using subchannels SC3 and SC4 (using resources 612), as shown by Figure 6 Similarly, UE2 can then send resource usage and reservation information to other UEs, such as using a reserved resource field in SCI. A UE can also be configured to make all reservations with the same number of subchannels (e.g., bandwidth). For example, resources 602, 604, and 606 reserved by UE1 can have the same number of subchannels (e.g., 1), and resources 608, 610, and 612 reserved by UE2 can have the same number of subchannels (e.g., 2). However, the starting subchannel of each reserved resource can be different. For example, resource 602 can start at SC 4, resource 604 can start at SC 2, and resource 606 can start at SC3, and so on.

[0083] Figure 7 is a diagram 700 showing an example procedure of resource reservation. When a UE (e.g., a sidelink transmitter UE) reserves resources in a periodic (e.g., every 10 slots) and aperiodic (e.g., every 100 slots) manner, the UE can reserve resources in a periodic manner (e.g., every 10 slots) and aperiodic manner (e.g., every 100 slots) for a data transmission and retransmissions. Figure 6When transmitting using the first reserved resource 702 at slot i within the period 652 shown, the UE can reserve two other resources, such as resource 704 at slot i+x and resource 706 at slot i+y, within the same period. Each of the reserved resources 702, 704, and 706 can have a number z of sub-channels. For example, if the period has 32 slots with slot indices 0 to 31, the UE can transmit the first reserved resource 702 with z sub-channels at slot 0, and can reserve a second resource with z sub-channels at slot i+x, where x is 0 < x < 31, and can further reserve a third reserved resource with z sub-channels at slot i+y, where y is x < y < 31. Table 1 below is an example reservation in slot i by a UE’s SCI. Figure 6

[0084]

[0085] Table 1

[0086] The UE can use the resources 704 and 706 for retransmission of the resource 702, such as when the transmission of the resource 702 fails. The UE can also use the reserved resources 704 and / or 706 for other purposes besides retransmission.

[0087] The sidelink resource reservation can be periodic or aperiodic. For example, a UE can periodically reserve resources, such as by indicating a reservation period in the SCI. Thus, when periodic resource reservation is enabled, the reservation in the SCI can be repeated with the signaled period. In some examples, a UE can indicate resource reservations in multiple SCI parts. For example, a UE can transmit a first part of the reservation in a physical sidelink control channel (PSCCH) region, and can transmit a second part of the reservation in a physical sidelink shared channel (PSSCH) region. For example, a first stage control (e.g., SCI-1) can be transmitted on the PSCCH and contain resource allocation and information related to decoding of a second stage control (e.g., SCI-2), while the second stage control can be transmitted on the PSSCH and contain information for decoding data (SCH). Thus, multiple resources can be indicated or reserved by a combination of a first SCI part indicated in a PSCCH region and a second SCI part in a PSSCH region. For example, the first SCI part in the PSCCH can reserve resources for the UE in the PSSCH, and the first SCI part can also indicate to a receiving UE that a second SCI part or more exists in the PSSCH (e.g., two-stage SCI). The second SCI part can reserve other resources or provide signaling and / or information to the UE that can be unrelated to the resources reserved in the first SCI part. ​

[0088] Figure 8 is a diagram 800 illustrating an example of two-stage PSCCH. To reduce control overhead and improve processing timeline, SCI for sidelink link grant can be split into two or more parts. A first SCI part 802 can be transmitted in a control region (e.g., PSCCH region 808), and a second SCI part 804 can be transmitted in a downlink traffic region (e.g., PSSCH region 810). The PSCCH region 808 and the PSSCH region 810 can together form one slot. The first SCI part 802 can include initial control information about the sidelink transmission, such as resource allocation (RA) or other resource reservation information in SCH 806, rank and modulation order of the sidelink allocation, and so on. In addition, the first SCI part 802 can also include control information about the second SCI part 804. In some examples, the control information can indicate the number (size) and code rate of resource elements of the second SCI part 804. The control information can further indicate the location (e.g., starting resource element) and code rate of the second SCI part 804. The second SCI part 804 can include remaining control information about the sidelink allocation. For example, the remaining control information can include non-time control information or other resource allocation for data transmission in SCH 806, such as source and destination IDs for the data transmission.

[0089] In one aspect, the first SCI part 802 (e.g., SCI-1) format can include one or more of the following: 1) priority (QoS value) (e.g., 3 bits); 2) PSSCH / frequency resource allocation (e.g., frequency / time resources for PSSCH), bits can depend on the number of slot reservations and / or the number of sub-channels; 3) time resource allocation, e.g., 5 or 9 bits for 2 or 3 reservations (see below); 4) resource reservation period (e.g., if enabled), where bits can depend on the number of allowed periods; 5) DMRS (e.g., PSSCH and / or PSCCH DMRS) pattern (e.g., if more than one pattern is configured), bits can depend on the number of configured patterns; 6) second SCI format (e.g., information on the size of the second SCI), which can be 2 bits; 7) beta offset for second SCI format rate matching, which can be 2 bits; 8) 2-bit beta offset for second stage control resource allocation; 9) number of PSSCH DMRS ports (e.g., 1 or 2); 10) DM-RS port, where 1 bit can be used to indicate one or two data layers; 11) 5-bit MCS; 12) other MCS table, which is 0 to 2 bits; 13) PSFCH overhead indicator, which can be 0 or 1 bit; and / or 14) one or more reserved bits (e.g., bits up to upper layers), among others. In another aspect, the first SCI part 802 can be configured to be decoded by a receiver and other sidelink UEs (e.g., such as UEs in mode 2 resource allocation) to allow / enable channel sensing and / or to avoid resource collisions. In some examples, for SCI format 1_0 in PSCCH, bits for frequency domain resource allocation (FDRA) can be determined by:

[0090] for 2 resource reservations, bits,

[0091] and for 3 resource reservations, bits.

[0092] For time domain resource allocation (TDRA), 5 bits can be used for 2 resource reservations and 9 bits can be used for 3 resource reservations.

[0093] In another aspect, the second SCI part 804 (e.g., SCI-2) format can include one or more of the following: 1) HARQ ID, where its bits can depend on the number of HARQ processes; 2) New Data Indicator (NDI), which can be 1 bit; 3) Redundancy Version (ID) - ID, which can be 2 bits; 4) Source ID (e.g., transmitter UE ID), which can be 8 bits; 5) Destination ID (e.g., receiver UE ID), which can be 16 bits; 6) HARQ enable / disable indication, which can be 1 bit; 7) SCI 2-A dedicated field: a) Broadcast type, which can be 2 bits indicating whether the transmission is broadcast, groupcast, or unicast, and / or b) CSI request, which can be 1 bit; and / or 8) SCI 2-B dedicated field (e.g., NACK dedicated groupcast): a) Zone ID, which can be 12 bits, and / or b) Communication range, which can be 4 bits, etc. SCI 2-A can refer to a 2nd stage SCI A th type, while SCI 2-B can refer to a 2nd stage SCI B th type. The second SCI part 804 can be used by a receiving device to decode an associated PSSCH.

[0094] When a transmitting device (e.g., a sidelink device, a first UE, a base station, an RSU) transmits a PSSCH over a sidelink to a receiving device (e.g., a second UE, another sidelink device), the receiving device can respond with HARQ feedback (e.g., ACK / NACK) corresponding to the received PSSCH through a physical sidelink feedback channel (PSFCH) transmission to the transmitting device. The PSFCH can share the same sidelink resource pool as the PSCCH and PSSCH, where the receiving device can determine a PSFCH resource for transmitting the HARQ feedback from a configured PSFCH resource pool. The PSFCH can be enabled for unicast and / or groupcast communications. For example, in unicast communications, the receiving device can use the PSFCH to transmit a 1-bit ACK / NACK feedback (e.g., 0 = NACK, 1 = ACK, etc.) to the transmitting device to indicate whether the transmitting device has successfully decoded the received PSSCH. For groupcast communications, the receiving device can transmit HARQ feedback via the PSFCH in one of two feedback modes. In a first feedback mode, the receiving device can transmit negative feedback (e.g., NACK) to the transmitting device when the receiving device fails to decode the received PSSCH, and the receiving device can skip transmitting positive feedback (e.g., ACK) to the transmitting device when the receiving device successfully decodes the received PSSCH. The first mode can be referred to as NACK-based feedback or NACK-only feedback. In a second mode, the receiving device can transmit positive feedback to the transmitting device when the receiving device successfully decodes the received PSSCH, and the receiving device can transmit negative feedback to the transmitting device when the receiving device fails to decode the received PSSCH.

[0095] Figure 9is a diagram 900 illustrating example PSFCH configurations. A PSFCH resource (e.g., a PSFCH resource pool) can be a system-wide feedback resource configured (e.g., loaded on a sidelink device) or configured periodically by a network (e.g., a base station). The PSFCH resource can also be configured to have a periodicity N, which can indicate a frequency of configuring resources for PSFCH in a sidelink resource pool. For example, the periodicity N can be 1, 2, or 4 slots. If N = 1 slot, it can indicate that a (e.g., available) PSFCH resource is configured in every slot within a sidelink resource pool, and if N = 2, such as shown by diagram 900, it can indicate that a PSFCH resource is configured in every two slots, and so on. In some configurations, if N = 0, it can indicate that PSFCH is disabled. A transmitting device can indicate a periodicity of a PSFCH to a receiving device in SCI (e.g., a 1-bit indication in SCI-1). In one example, as shown by diagram 900, when a PSFCH resource is configured for a slot, the PSFCH resource can occupy three OFDM symbols within the slot, where one symbol can be used for a gap 902 and two symbols can be used for a PSFCH 904. For example, the gap 902 can use a symbol before and / or after the PSFCH 904, and the gap 902 can be used by a sidelink device for a turnaround between reception of data and transmission of HARQ feedback.

[0096] The number of physical resource blocks (PRBs) for a PSFCH can be configured, such as through a bitmap. For example, in one of the PUCCH formats (e.g., format 0), there can be one resource block (RB) carrying HARQ-ACK information for a single PSSCH transmission, where a PSFCH format 0 sequence can be repeated over 2 PSFCH symbols. For example, referring back to Figure 9For a PSFCH 904 with two OFDM symbols, one symbol (e.g., symbol 908) can be used to provide HARQ feedback (e.g., ACK or NACK), and the other symbol (e.g., symbol 906) can be a replica of the HARQ feedback (e.g., a replica of symbol 908). There can also be a timing gap K configured for the PSFCH resource, where the timing gap can indicate a duration between a slot carrying a PSSCH and a corresponding slot configured with a PSFCH resource for providing HARQ feedback for the PSSCH. Thus, when a receiving device receives a PSSCH in slot n, the receiving device can transmit the corresponding HARQ feedback through the PSFCH resource in slot (n + K). For example, as shown by FIG. 900, if the timing gap K = 2, a sidelink device receiving a PSSCH at slot n can use the PSSCH resource within slot n + 2 to transmit the corresponding HARQ feedback. In some examples, there can be a minimum time gap of 2 or 3 slots between a PSFCH (e.g., HARQ feedback) and the associated PSSCH reception.

[0097] The PSFCH can be transmitted using a PUCCH format 0 waveform, which can be a sequence-based waveform without a modulation and / or coding layer. For example, the waveform of the PSFCH can be associated with one or more multiplexing cyclic shifts (CSs). In another example, the number of pairs of CSs used or supported for PSFCH transmissions that can be multiplexed in a PRB can be (pre-)configured (e.g., by upper layers) for each resource pool in {1, 2, 3, 4, 6} slots. The PSFCH resources can be (pre-)configured by rbSetPSFCH (bitmap), which will be described in detail below.

[0098] Figure 10 FIG. 1000 is a diagram 1000 illustrating an example sidelink resource pool 1002 and structure of a sidelink slot 1004 within the sidelink resource pool 1002 including a PSFCH. The sidelink resource pool 1002 can be a set of time and / or frequency resources in which sidelink communications can occur. The sidelink resource pool 1002 can be loaded on a UE or configured by a base station. In one aspect, the PSFCH can be mapped to one RB. A UE can be provided a set of PRBs for the PSFCH in the resource pool (e.g., by a PSFCH resource block setting parameter rbSetPSFCH). The UE can identify PSFCH RB candidates for subchannel j and PSSCH slot i, where 0 < i < N PSFCH , which can be determined by a periodicity of the PSFCH. The number of candidate RBs can be determined by

[0099] M subc,slot= #rbSetPSFCH / (periodPSFCH * numSubChannel),

[0100] And the candidate RBs can be determined by

[0101] (i + jN PSFCH ) * M subc,slot to (i + 1 + jN PSFCH ) * M subc,slot - 1.

[0102] For example, if N PSFCH = 2 and M subc,slot = 5, for j = 0 and i = 0, the candidate RBs can be [0, 4]; and for j = 0 and i = 1, the candidate RBs can be [5, 9]. In another aspect, a UE can be provided a set of PRBs in a resource pool for PSFCH transmission in PRBs of the resource pool. For a number of N subch subchannels of the resource pool provided by sl-NumSubchannel, and a number of PSSCH slots associated with a PSFCH slot less than or equal to , the UE can allocate from the PRBs to the slot (i + 1) among the PSSCH slots associated with the PSFCH slot and subchannel j, where And the allocation can start in ascending order of i and continue in ascending order of j. The UE can expect to be a multiple of . In another aspect, the UE can further determine the resources for multiplexing PSFCH as R = N type * M subc,slot * #CS. For example, a higher layer If equal to 1, the PRB can be associated with the starting subchannel of the corresponding PSSCH. If , the PRB can be associated with one or more subchannels of the corresponding PSSCH. The UE can select one RB from the available resources according to (P ID + M ID ) mod R, where P ID may be a transmitter ID and M ID may be a receiver ID for groupcast of SCI 2-A, and M ID = 0 otherwise. The PSFCH can be copied in previous OFDM symbols.

[0103] ​In some examples, the PSFCH can be based on a Zadoff-Chu (ZC) sequence, where the ZC sequence can be generated according to a group and a sequence number. For example, the ZC group number u = (f gh +f ss ) mod 30 can depend on the PSFCH hopping configuration (e.g., sl-PSFCH-HopID-r16). The cyclic shift hopping can be determined according to:

[0104]

[0105] where m0may depend on the PSFCH configuration on the supported CS pair, m CS may depend on the value of ACK / NACK and the HARQ mode (NACK-only or ACK / NACK), and may be a function that depends on the slot number and symbol index of the PSFCH.

[0106] In some examples, referring back to Figure 10 a sidelink slot 1004 including a PSFCH, the PSCCH can be (pre)configured to occupy {10, 12, 15, 20, 25} PRBs, and the PSCCH can also be limited to a single subchannel. The PSCCH duration can be (pre)configured to be 2 or 3 symbols. The subchannel can occupy {10, 15, 20, 25, 50, 75, 100} PRBs, and the resource pool (RP) can include 1 to 27 subchannels. For a resource pool, the PSCCH size can be fixed, such as 10% to 100% of one subchannel (e.g., the first 2 or 3 symbols), depending on the configuration. In one example, the PSSCH can occupy at least one (1) subchannel and contain a second-stage SCI, such as described in connection with Figure 8 .

[0107] As discussed in connection with FIGs. 5A and 5B, a transmitting device (e.g., PLC 552) can communicate with multiple receiving devices (e.g., SAs 554, 556, 558) over a sidelink channel. Due to the communication (e.g., PSSCH and / or PSCCH transmission / reception) between the transmitting device and the receiving devices can have a strict 1 to 2 ms latency specification and 10 -6An ultra-reliability specification for a bit error rate, a PSFCH (e.g., HARQ feedback) from a receiving device can have the same or more stringent specification, such that a transmitting device can reliably determine whether to retransmit data based on the received PSFCH (e.g., if a NACK is received or if no ACK for the data is received). Thus, when the reliability of the PSFCH is enhanced, sidelink communications can be improved. Table 1 below shows an example SNR specification for a NACK-to-ACK failure rate of 0.001 for PUCCH Format 1 (e.g., 1-RB with up to 14 symbols, 7 orthogonal cover codes (OCC)). In other words, at the SNR given in Table 1, the probability of a NACK-to-ACK can not exceed 0.1%.

[0108]

[0109]

[0110] Table 1: Minimum specification for PUCCH Format 1 with 15 kHz SCS

[0111] When receiving a PSCCH and / or PSSCH at an SNR above a threshold, a UE can reliably decode the PSCCH or PSCCH (e.g., with a failure rate below a threshold). For example, a SCI-2 decoding can specify a minimum SNR of -2 dB or 1.5 dB to achieve a bit error rate of 0.01. However, the same SNR (e.g., -2 dB or 1.5 dB) threshold can not be reliable enough for a UE to decode a PSFCH, as the SNR threshold and / or failure rate specification for the PSFCH can be relatively high. For example, a sidelink PSFCH design can use a significantly larger SNR (up to log(7)) (e.g., expanded by a factor of 7 in PUCCH Format 1), which can be approximately 5 dB to achieve a failure rate of 0.001. For certain IIoT devices, a failure rate below 0.0001 can be targeted. Thus, a PSFCH configuration using one or two symbols can not be sufficient for some IIoT devices to meet the target failure rate (e.g., 10 -6 of end-to-end (E2E) reliability), and the utilization of the PSFCH can be low (e.g., below 1%).

[0112] Aspects presented herein can improve and / or enhance the reliability of PSFCHs to enable PFSCH transmissions to achieve lower bit error rates. Aspects presented herein can also enable other messages to be multiplexed / transmitted with HARQ feedback. In one aspect of the disclosure, depending on the environment and / or configuration, a sidelink device can be configured to provide sidelink HARQ feedback (e.g., ACK or NACK) using a PSFCH with a long PSFCH format or a PSFCH with a short PSFCH format within a sidelink resource pool. In another aspect, when the payload size of a PSFCH is increased, a sidelink device can multiplex messages such as CSI reports, scheduling requests, and / or buffer status reports with HARQ feedback in a PSFCH with a long PSFCH format.

[0113] Figure 11A is a diagram 1100 illustrating an example sidelink resource pool providing a PSFCH with a long PSFCH format or a PSFCH with a short PSFCH format or associated therewith. For the purposes of the present disclosure, throughout the specification, a PSFCH with a long PSFCH format can be referred to as a “long PSFCH” or a “long format PSFCH,” and a PSFCH with a short PSFCH format can be referred to as a “short PSFCH” or a “short format PSFCH.” As illustrated by Figure 11AAs shown in the diagram 1100, a long PSFCH 1102 can occupy more than two (2) symbols within a slot, and a short PSFCH 1104 can occupy less than two symbols (e.g., one (1) or two (2) symbols) within a slot. For example, in a slot containing fourteen symbols, the long PSFCH 1102 can occupy three to fourteen symbols (i.e., the entire slot), and in a slot containing twenty symbols, the long PSFCH 1102 can occupy three to twenty symbols, and so on. Thus, the size of the long PSFCH 1102 can range from X to Y symbols, where X > 2 and Y < the number of symbols in a slot. A sidelink device can use one or more symbols within the long PSFCH 1102 or the short PSFCH 1104 to transmit HARQ feedback. For example, for a long PSFCH (e.g., 1104) with four (4) symbols, a sidelink device can use three (3) symbols or all four symbols to transmit HARQ feedback, where one symbol can be the HARQ feedback and the other symbols can be repetitions of the HARQ feedback. When more symbols are available and used to transmit HARQ feedback, the reliability of the HARQ feedback (e.g., the likelihood that the HARQ feedback is successfully transmitted to another sidelink device) can increase and improve. In some examples, the long PSFCH 1102 can occupy more than one slot, where the long PSFCH 1102 can be multi-slot long, e.g., two (2) slots, three (3) slots, and so on.

[0114] Figure 11B is a diagram 1150 illustrating an example sidelink resource pool that provides short PSFCHs 1104 or is associated with short PSFCHs 1104 without long PSFCHs. Each PSFCH 1104 within the sidelink resource pool can occupy one (1) or two (2) symbols. One or more system-wide parameters (e.g., sl-PSFCH-Period-r16) with a periodicity can apply to the resource pool and / or the short PSFCHs 1104. For example, the short PSFCHs 1104 can be configured to have a periodicity of two slots, such that a short PSFCH 1104 is available in every two slots (e.g., in slot n, slot n+2, slot n+4, slot n+6, and so on).

[0115] In one example, a long PSFCH 1102 and optionally a size of its period can be defined for a sidelink device (e.g., a UE, a transmitting UE, a receiving UE) and / or configured for a sidelink device via radio resource control (RRC) configuration (e.g., using an RRC information element (IE) for sidelink long PFSCH configuration (e.g., sl-Long-PSFCH-Config)). The long PSFCH 1102 can be configured to be available (e.g., visible) to a group of sidelink devices (e.g., sidelink devices with higher UE capabilities) and can be configured to be unavailable (e.g., invisible) to another group of sidelink devices (e.g., sidelink devices with lower UE capabilities). In another example, for example, in an IIoT-specific network with dedicated spectrum, the long PSFCH 1102 can be configured for the sidelink device via a separate resource pool with a long PSFCH format (i.e., without a short PSFCH).

[0116] Return Reference Figure 11A As shown in diagram 1100, long PSFCH 1102 and short PSFCH 1104 may coexist in the same resource pool. Thus, a sidelink device (e.g., a sidelink UE) may be configured to use long PSFCH 1102 and short PSFCH 1104 based on one or more conditions. For example, for a UE with a higher / stricter reliability specification (e.g., 10 -6 For transmissions with higher E2E reliability (e.g., higher reliability), the sidelink device may be configured to use a long PSFCH 1102 from the resource pool. For transmissions with lower reliability specifications and / or with more data to be transmitted (e.g., PSSCH), the sidelink device may be configured to use a short PSFCH 1104 from the resource pool to conserve sidelink resources.

[0117] In one aspect of the present disclosure, for a long PSFCH (e.g., 1102) that coexists with a short PSFCH (e.g., 1104) in a resource pool, the long PSFCH may override (e.g., take precedence over) the short PSFCH in the resource pool. Figure 11B As shown in the schematic diagram 1150 of FIGURE 1150, the resource pool may be configured to have a short PSFCH 1104 with a period of two (2) time slots, where a two-symbol long PSFCH may be available at time slot n, time slot n+2, time slot n+4, time slot n+6, etc. Then, as shown by Figure 12As shown in the illustration 1200, a long PSFCH 1102 can be configured for a resource pool by using extra resources 1106 (e.g., symbols) in one or more slots where a short PSFCH 1104 is configured. For example, at slot n+2, extra resources 1106 (e.g., two symbols) can be configured for the PSFCH, thereby turning the short PSFCH 1104 with two symbols into a long PSFCH 1102 with four symbols. Similarly, at slot n+6, extra resources 1106 can be configured for the PSFCH to turn the short PSFCH 1104 into a long PSFCH 1102. The extra resources 1106 can be any resources within a slot that are not occupied by the short PSFCH 1104, and the extra resources 1106 can or can not be contiguous with the short PSFCH 1104. For example, the short PSFCH 1104 can occupy the last two symbols of a slot (e.g., occupy the 13th and 14th symbols) within a 14-symbol slot. In one example, the extra resources 1106 can occupy one or more symbols before the short PSFCH 1104 (e.g., at the 11th and 12th symbols). In another example, the extra resources 1106 can occupy one or more symbols that are not contiguous with the short PSFCH 1104, such as at the 1st and 2nd symbols of a slot, at the 2nd and 5th symbols of a slot, or at the 1st, 3rd, 5th, and 7th symbols of a slot, etc. The long PSFCH 1102 can also be configured to have the same periodicity as the short PSFCH 110 (e.g., both have a periodicity of two slots, three slots, etc.)

[0118] Because the long PSFCH 1102 can use the additional resources 1106 within a slot that has a short PSFCH 1104, the periodicity of the long PSFCH 1102 can be an integer multiple of the short PSFCH 1104. For example, if the short PSFCH 1104 has a periodicity of two (2) slots in a resource pool (e.g., at slot n, slot n+2, slot n+4, slot n+6, slot n+8, and so on), the long PSFCH 1102 can be configured to have a periodicity of four (4) slots in the resource pool (e.g., slot n, slot n+4, slot n+8, slot n+12, and so on), which is an integer multiple of the short PSFCH 1104. Thus, if the long PSFCH 1102 takes priority over (e.g., overrides) the short PSFCH 1104, the resource pool can include the long PSFCH 1102 at slots n, n+4, n+8, and so on, and the resource pool can include the short PSFCH 1104 at slots n+2, n+6, n+10, and so on. In another example, the short PSFCH 1104 can have a periodicity of two slots in a resource pool (e.g., at slot n, slot n+2, slot n+4, slot n+6, slot n+8, and so on), and the long PSFCH 1102 can be configured to have a periodicity of six (6) slots in the resource pool (e.g., slot n, slot n+6, and slot n+12, and so on), which is an integer multiple of the short PSFCH 1104. Thus, if the long PSFCH 1102 takes priority over (e.g., overrides) the short PSFCH 1104, the resource pool can include the long PSFCH 1102 at slots n, n+6, n+12, and so on, and the resource pool can include the short PSFCH 1104 at slots n+2, n+4, n+8, n+10, and so on. In other words, some symbols used for data (e.g., PSSCH) can be used by a sidelink device to transmit HARQ feedback (e.g., PSFCH).

[0119] In another aspect of the disclosure, for a long PSFCH coexisting with a short PSFCH in a resource pool, the long PSFCH can be configured in slots not occupied by the short PSFCH. Figure 13 FIG. 13 is a diagram 1300 illustrating an example of configuring a long PSFCH in slots not occupied by a short PSFCH. A resource pool can be configured with a short PSFCH 1304 having a periodicity of two (2) slots (e.g., at slot n, slot n+2, slot n+4, slot n+6, slot n+8, and so on), such as by Figure 11BThe long PSFCH 1302 can be configured in slots that are not occupied by the short PSFCH 1304 (e.g., at slot n+1, slot n+3, slot n+5, slot n+7, and so on). The long PSFCH and the short PSFCH can have the same periodicity (e.g., 2 slots).

[0120] At times, the long PSFCH can be configured / scheduled in the same slot as the short PSFCH. For example, as illustrated by schematic diagram 1400, the sidelink resource pool can be configured with a short PSFCH 1404 having a periodicity of two (2) slots at slot n, slot n+2, slot n+4, slot n+6, and so on. The sidelink resource pool can also be configured with a long PSFCH 1402 having a periodicity of three (3) slots at slot n+4, slot n+7, and so on. As illustrated at 1408, the long PSFCH 1402 can overlap with the short PSFCH 140 at slot n+4 (as well as at slots n+10, n+16, and so on). Figure 14

[0121] In one example, when the long PSFCH 1402 and the short PSFCH 1404 overlap in a slot, the sidelink device can determine whether to use the long PSFCH 1402 or the short PSFCH 1404 in the slot based on the periodicity associated with the long PSFCH 1402 and the short PSFCH 1404. For example, the sidelink device can determine to use the PSFCH format having the longer periodicity. Thus, if the long PSFCH 1402 has a longer periodicity (e.g., 3 slots) than the short PSFCH 1404 (e.g., 2 slots), the sidelink device can determine to use the long PSFCH 1402 for the slot. Alternatively, the sidelink device can determine to use the PSFCH format having the shorter periodicity. Thus, the sidelink device can determine to use the short PSFCH 1404 for the slot.

[0122] In another example, when the long PSFCH 1402 and the short PSFCH 1404 overlap in a slot, the sidelink device can determine whether to use the long PSFCH 1402 or the short PSFCH 1404 in the slot based on the HARQ feedback repetition. For example, referring back to Figure 14 ​The receiving sidelink device can be configured to use eight (8) symbols and provide HARQ feedback within three consecutive slots. If the receiving sidelink device is transmitting HARQ feedback using slots n+2, n+3, and n+6, because there can be one short PSFCH 1404 in slots n+2 and n+3, the receiving sidelink device can determine to use a long PSFCH for slot n+4, such as by using a long PSFCH with six (6) symbols to meet the eight symbol HARQ transmission / retransmission specification. In other words, the sidelink device can ensure that a HARQ repetition factor K (e.g., a number of HARQ repetitions) is possible across N slots.

[0123] In another aspect of the disclosure, a long PSFCH (e.g., 1102, 1302, 1402) can be configured in a subchannel and / or slot that can be used by a group of sidelink devices (e.g., UEs with higher capabilities) and the same subchannel and / or slot can not be accessible to another group of sidelink devices (e.g., UEs with lower capabilities). This can avoid or prevent UEs of a particular group / category from using the long PSFCH for PSSCH transmissions. In other words, if a slot is configured to have a long PSFCH, the network can configure the slot to be inaccessible / visible to sidelink devices that are not capable of transmitting HARQ feedback using the long PSFCH.

[0124] After a sidelink device is configured with a short PSFCH or a long PSFCH for reporting HARQ feedback, the sidelink device can use at least one symbol within the short PSFCH or the long PSFCH to transmit HARQ feedback and can use other or remaining symbols for HARQ feedback retransmission.

[0125] Figure 15is a diagram 1500 illustrating example HARQ reporting via short and long PSFCH formats. In one aspect, when a short PSFCH 1504 is configured for a sidelink device, the sidelink can transmit HARQ feedback using a waveform similar to PUCCH format 0. For example, as shown at 1508, a transmitting device can transmit HARQ feedback using one (1) RB and two (2) symbols, where one symbol and one RB can include the HARQ feedback and the other symbol and RB can include a repetition / duplication of the HARQ feedback. In another example, as shown at 1510, a transmitting device can transmit HARQ feedback using multiple RBs and one / two symbols. For example, a transmitting device can transmit HARQ feedback using five (5) RBs and two symbols per RB, where one or more RBs of one symbol can include the HARQ feedback and one or more RBs of the other symbol can include a repetition / duplication of the HARQ feedback. By using more RBs to transmit the HARQ feedback, the reliability of the sidelink HARQ reporting can be improved.

[0126] In another aspect, when a long PSFCH 1502 is configured for a sidelink device, the sidelink can transmit HARQ feedback based at least in part on a subchannel size and / or a number of symbols X (1 < X < number of symbols of the PSFCH). For example, a transmitting device can transmit HARQ feedback and repetitions thereof using one RB and X symbols (e.g., for PUCCH format 1 and PUCCH format 4), and / or a transmitting device can transmit HARQ feedback and repetitions thereof using Y RBs (1 < Y < number of RBs in the subchannel) and X symbols (e.g., for PUCCH format 3). When transmitting HARQ feedback using Y RBs and X symbols (e.g., for PUCCH format 3) in a slot, the sidelink device can also apply modulation, error control coding, and / or cyclic redundancy check (CRC) to the transmission to improve decoding of the transmission. In one example, although PUCCH format 1 and format 4 can use one RB and X symbols, they can use different waveforms. For example, for PUCCH format 1, a sequence can be repeated across symbols, while for PUCCH format 4, error control and DMRS can be included due to the presence of more bits (e.g., PUCCH format 0 can carry 1-2 bits). As such, the sidelink device can transmit HARQ feedback using a different waveform than a sequence-based waveform. For example, referring back to Figure 15If a long PSFCH 1502 with four symbols is configured for the sidelink device, as shown at 1512, the sidelink device can transmit the HARQ feedback and its repetition using one RB and X symbols. The sidelink device can also transmit the HARQ feedback and its repetition using Y RBs and X symbols, as shown at 1514, where the sidelink device can additionally or alternatively apply modulation, error control coding, and / or CRC to the transmission. Additionally or alternatively, when a long PSFCH is configured for the transmitting device, the sidelink device can further multiplex one or more control messages with the HARQ feedback. For example, as the payload size of the PSFCH increases, the HARQ feedback can be multiplexed with channel state information (CSI) reports, scheduling requests (SRs), and / or buffer status reports, among others, which enables the UE to report / include more messages.

[0127] In another aspect of the disclosure, the transmitting sidelink device can explicitly or implicitly indicate to the receiving device whether to use a long PSFCH or a short PSFCH, and / or which PUCCH format (or Y RBs and X symbol resources) to use for transmitting the HARQ feedback.

[0128] For example, the transmitting device can explicitly indicate to the receiving device whether to use a long PSFCH or a short PSFCH via a first SCI part (SCI-1), such as using a PSFCH overhead indicator bit or a reserved bit, among other examples. The transmitting device can also explicitly indicate to the receiving device via a second SCI part (SCI-2) and / or via an upper layer (e.g., through a logical channel). In another example, the transmitting device can implicitly indicate to the receiving device whether to use a long PSFCH or a short PSFCH based at least on a priority of the traffic / data, such as using a long PSFCH when the priority of the traffic / data is greater than a threshold. The priority of the traffic / data can be included in SCI-1. In another example, the transmitting device can implicitly indicate to the receiving device whether to use a long PSFCH or a short PSFCH based at least on a modulation and coding scheme (MCS) associated with the transmission (e.g., the MCS used by the transmitting device to transmit the traffic / data). For example, the receiving device can use a long PSFCH when the MCS for the traffic / data is lower than a threshold, as a low MCS can indicate that the channel conditions are not in good conditions. Thus, more resources (e.g., a long PSFCH) can be used for the HARQ feedback to improve the reliability of the HARQ feedback. The MCS for the traffic / data can also be included in SCI-1. In another example, the transmitting device can implicitly indicate to the receiving device whether to use a long PSFCH or a short PSFCH (e.g., use a longer PSFCH format for retransmission) based at least on a quality of service (QoS) associated with the traffic / data or an event that triggers a long / short PSFCH report. For example, the receiving device can use a short PSFCH to transmit the HARQ feedback in one slot (e.g., a first slot) and use a long PSFCH to transmit a retransmission of the HARQ feedback in a different slot (e.g., a second slot, a third slot, etc.). As the HARQ feedback is a retransmission, the receiving device can use a longer PSFCH such that the likelihood of the transmitting device receiving the HARQ feedback is increased.

[0129] In another aspect, the receiving device can determine whether to use a long PSFCH or a short PSFCH based on a slot aggregation associated with the HARQ feedback. At times, the receiving device can be configured to transmit the HARQ feedback in multiple slots, such as a multi-slot PSFCH transmission with ACK / NACK repetition. For example, if the HARQ feedback is configured to be transmitted using eight (8) symbols in three slots, the receiving device can use a short PSFCH for one or two slots and a long PSFCH for the remaining slots. Thus, the eight symbols of the PSFCH can be used by the receiving device to provide the HARQ report. The RB selection for the slot aggregation can or can not include inter-slot hopping.

[0130] As discussed in connection with Figure 9As described, a timing gap K can be configured for PSFCH resources, where the timing gap can indicate a duration between a slot carrying a PSSCH and a corresponding slot configured to have a PSFCH resource for providing HARQ feedback for the PSSCH. For example, when a receiving device receives a PSSCH in slot n, the receiving device can transmit corresponding HARQ feedback through a PSFCH resource in slot (n + K). In some examples, the HARQ return time can depend on a minimum time gap (e.g., minTimeGap) and a PSFCH periodicity. The minimum time gap can be one or more slots (e.g., 2, 3, 4 slots, etc.). For example, if a PSSCH is received by a receiving device at slot n, and there is a minimum time gap of 2 slots, and a PSFCH periodicity of 4 slots, the receiving device can transmit corresponding HARQ feedback at slot n + 3 (e.g., the fourth slot that satisfies both the minimum time gap and the PSFCH periodicity).

[0131] In one aspect of the disclosure, if a receiving device is configured to transmit HARQ reports using a long PSFCH in a resource pool including both short and long PSFCHs, the receiving device can report HARQ feedback based on a minimum time gap (e.g., minTimeGap) and a periodicity / availability of the long PSFCH. For example, if a PSSCH is received by a receiving device at slot n, and there is a minimum time gap of three (3) slots, and a periodicity of the long PSFCH is two (2) slots (e.g., at slots n, n+2, n+4, n+6, etc.), the receiving device can transmit corresponding HARQ feedback at slot n + 4.

[0132] In another aspect of the disclosure, if a receiving device is configured to transmit HARQ reports using a short PSFCH in a resource pool including both short and long PSFCHs, the receiving device can report HARQ feedback based on a minimum time gap and a periodicity / availability of the short PSFCH. For example, if a PSSCH is received by a receiving device at slot n, and there is a minimum time gap of two slots and a periodicity of the short PSFCH is two slots (e.g., at slots n+1, n+3, n+5, n+7, etc.), the receiving device can transmit corresponding HARQ feedback at slot n + 3.

[0133] In another aspect of the disclosure, if a receiving device is configured to transmit HARQ reports using a short PSFCH in a resource pool including both short and long PSFCHs, the receiving device can report HARQ feedback based on a minimum time gap and a periodicity / availability of both the short and long PSFCHs. Figure 16is a diagram 1600 illustrating an example of transmitting HARQ reports using short PSFCH in a resource pool that includes both short PSFCH 1604 and long PSFCH 1602. In one example, as shown at 1606, if the receiving device determines to use long PSFCH 1602 to transmit short format HARQ (e.g., one or two symbols), the receiving device can use one or two symbols (such as the last two symbols) of the long PSFCH. In other words, the receiving device can randomly select two symbols, e.g., the transmitting device can consider symbols 1 and 2 as a first candidate, and consider symbols 3 and 4 as a second candidate, and then apply resource selection based on UE-ID. While such a configuration can enable the receiving device to maintain the same HARQ reporting behavior (e.g., using two symbols for HARQ reporting), there can be some signal power variation on the symbols in a slot since the HARQ report can be transmitted between PSSCHs.

[0134] In another example, as shown at 1608, if the receiving device determines to use long PSFCH 1602 to transmit short format HARQ (e.g., one or two symbols), the receiving device can repeat the short format HARQ on all symbols of the long PSFCH. For example, if the long PSFCH 1602 is four symbols long, and the short format HARQ occupies two symbols, the receiving device can repeat the short format HARQ twice in the long PSFCH 1602 (e.g., using all four symbols of the long PSFCH 1602). In another example, if the long PSFCH 1602 is six symbols long, and the short format HARQ occupies two symbols, the receiving device can repeat the short format HARQ three times in the long PSFCH 1602 (e.g., using all six symbols of the long PSFCH 1602), and so on. The repeated transmission of the short format HARQ using all symbols of the long PSFCH 1602 can facilitate automatic gain control (AGC) calibration, and it can also improve reception quality.

[0135] In some examples, if the transmitting device anticipates that a resource collision can occur, the transmitting device can instruct the receiving device to do RB selection. For example, the transmitting device can instruct the receiving device to apply an offset in the RB selection.

[0136] In another aspect of the disclosure, a receiving device can be configured to report HARQ feedback with slot aggregation, where the receiving device can report HARQ feedback to the transmitting device over multiple slots, and the transmitting device can combine the HARQ feedback received from multiple slots. For example, HARQ reporting with ultra-reliability can be performed using consecutive slots, such as described in connection with Figure 14 ​

[0137] Figure 17 is a communication flow 1700 for sidelink communication between a first UE 1702 (e.g., a transmitter UE) and a second UE 1704 (e.g., a receiver UE) in accordance with aspects of the present disclosure. The communication flow 1700 illustrates how the receiver UE provides HARQ feedback for a received sidelink channel using a PSFCH with a long PSFCH format.

[0138] At 1706, the first UE 1702 can transmit, to the second UE 1704, an indication to provide HARQ feedback for at least one sidelink channel. The indication can be transmitted via an SCI (e.g., SCI-1) in a PSCCH or an SCI (e.g., SCI-2) in a PSSCH. In one example, the SCI can also explicitly indicate to the second UE 1704 to use a PSFCH including a long PSFCH format to provide the HARQ feedback. In another example, the first UE 1702 can non-explicitly indicate to the second UE 1704 whether to use the long PSFCH format. For example, when the second UE 1704 transmits an ACK or a NACK in a PSFCH including the long PSFCH format or in a PSFCH including the short PSFCH format, the second UE 1704 can transmit the ACK or the NACK based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with the at least one sidelink channel.

[0139] At 1708, the first UE 1702 can transmit, to the second UE 1704, the at least one sidelink channel. The at least one sidelink channel can be a PSSCH or a PSCCH, or both.

[0140] At 1710, in response to the indication and the received sidelink channel, the second UE 1704 can transmit, via a PSFCH, an ACK or a NACK for the at least one sidelink channel, where the PSFCH can include a long PSFCH format and can be associated with a sidelink resource pool. As described in connection with Figure 11A 、 12 and 13, the long PSFCH format can include a length of at least three (3) symbols. Further, as described in Figure 11A 、 Figure 12-14 , the sidelink resource pool can support both a long PSFCH format including a length of at least three (3) symbols and a short PSFCH format including a length of less than three (3) symbols.

[0141] In one example, as described in connection with Figure 11A 、 11BAs described in connection with

[0142] In another example, as described in connection with Figure 13 PSFCHs including the long PSFCH format can be scheduled in one or more slots in the sidelink resource pool that are not occupied by PSFCHs including the short PSFCH format. PSFCHs including the long PSFCH format can also be scheduled in at least one of a designated subchannel or a designated slot that is not used by PSFCHs including the short PSFCH format.

[0143] In another example, as described in connection with Figure 14 When PSFCHs including the long PSFCH format are scheduled in the same slot as PSFCHs including the short PSFCH format in the sidelink resource pool, PSFCHs with longer periodicity can be prioritized over PSFCHs with shorter periodicity. Alternatively or additionally, PSFCHs with configured repetition resources can be prioritized over PSFCHs without configured repetition resources, where the configured repetition resources can be in consecutive slots.

[0144] As described in connection with Figure 15 and Figure 16 The second UE 1704 can transmit HARQ feedback (e.g., ACK / NACK) in one RB and at least three symbols in the PSFCH (e.g., as shown at 1512) or in multiple RBs and at least three symbols for each RB in the PSFCH (e.g., as shown at 1514), as described in connection with

[0145] In another example, the second UE 1704 can transmit an ACK or a NACK after a time gap (e.g., a minimum time gap) and based on a periodicity of the PSFCH.

[0146] When using the long PSFCH format, the transmitting UE 1704 can use two or more symbols of the PSFCH to transmit the HARQ feedback. For example, as described in connection with Figure 16As described, the second UE 1704 can transmit an ACK or a NACK in the last two symbols of the PSFCH including the long PSFCH format (e.g., as shown at 1606). In another example, when the second UE is configured to use the short PSFCH format (e.g., as shown at 1608), the second UE 1704 can transmit an ACK or a NACK in more than two symbols or all symbols of the PSFCH including the long PSFCH format. The second UE 1704 can transmit the ACK or the NACK in one (1) or two (2) symbols, where the ACK or the NACK can correspond to a HARQ repetition.

[0147] Figure 18 FIG. 18 is a flow diagram of a method of wireless communication. The method can be performed by a first UE (e.g., a transmitting UE; the UEs 104, 502, 504, 506, 508, 1702; the PLC 552; the apparatus 1902). The method can enable the first UE to receive HARQ feedback in a PSFCH having a long PSFCH format to improve reliability of the HARQ feedback.

[0148] At 1802, the first UE can transmit, to a second UE, an indication to provide HARQ feedback for at least one sidelink channel, such as described in connection with Figure 17 As described. For example, at 1706, the first UE 1702 can transmit, to the second UE 1704, a HARQ feedback indication to request the second UE 1704 to provide HARQ feedback for at least one sidelink channel. The indication can be transmitted via a SCI (e.g., SCI-1) in a PSCCH or a SCI (e.g., SCI-2) in a PSSCH. In one example, the SCI can explicitly indicate to the second UE to use a PSFCH including a long PSFCH format to provide the HARQ feedback. In another example, the first UE can non-explicitly indicate to the second UE whether to use the long PSFCH format. For example, when the second UE transmits an ACK or a NACK in a PSFCH including a long PSFCH format or in a PSFCH including a short PSFCH format, the second UE can transmit the ACK or the NACK based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with the at least one sidelink channel.

[0149] At 1804, the first UE can transmit, to the second UE, at least one sidelink channel, such as described in connection with Figure 17 As described. For example, at 1708, the first UE 1702 can transmit, to the second UE 1704, a sidelink channel (e.g., PSSCH / PSCCH). The at least one sidelink channel can be a PSSCH or a PSCCH, or both.

[0150] At 1806, the first UE can receive, from the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool, as described elsewhere. For example, at 1710, the first UE 1702 can receive, from the second UE 1704, an ACK / NACK for the transmitted sidelink channel. The long PSFCH format can include a length of at least three (3) symbols. Further, the sidelink resource pool can support both a long PSFCH format including a length of at least three (3) symbols and a short PSFCH format including a length of less than three (3) symbols. Figure 17

[0151] In one example, when a PSFCH including a long PSFCH format and a PSFCH including a short PSFCH format are scheduled in a same slot in a sidelink resource pool, the long PSFCH format can take precedence (e.g., override) the short PSFCH format. The PSFCH including the long PSFCH format can have a periodicity that is an integer multiple of the PSFCH including the short PSFCH format.

[0152] In another example, the PSFCH including the long PSFCH format can be scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH including the short PSFCH format. The PSFCH including the long PSFCH format can also be scheduled in at least one of a designated subchannel or a designated slot that is not used by the PSFCH including the short PSFCH format.

[0153] In another example, when a PSFCH including a long PSFCH format is scheduled in a same slot in a sidelink resource pool as a PSFCH including a short PSFCH format, a PSFCH with a longer periodicity can take precedence over a PSFCH with a shorter periodicity. Alternatively or additionally, a PSFCH with configured repetition resources can take precedence over a PSFCH without configured repetition resources, where the configured repetition resources can be in consecutive slots.

[0154] The first UE can receive the HARQ feedback (e.g., ACK / NACK) in one RB and at least three symbols in the PSFCH, or in multiple RBs and at least three symbols for each RB in the PSFCH. In one example, the first UE can receive at least one of a CSI report or a scheduling request in the PSFCH. The first UE can receive the ACK or the NACK after a time gap (e.g., a minimum time gap) and based on a periodicity of the PSFCH.

[0155] ​When the long PSFCH format is used, the first UE can receive HARQ feedback in two or more symbols of the PSFCH. For example, the first UE can receive an ACK or NACK in the last two symbols of the PSFCH including the long PSFCH format. In another example, when the second UE is configured to use the short PSFCH format, the first UE can receive an ACK or NACK in more than two symbols or all symbols of the PSFCH including the long PSFCH format. The first UE can receive an ACK or NACK in one (1) or two (2) symbols, where the ACK or NACK can correspond to a HARQ repetition.

[0156] Figure 19 FIG. 19 is a diagram 1900 illustrating an example of a hardware implementation for an apparatus 1902. The apparatus 1902 is a UE and includes a cellular baseband processor 1904 (also referred to as a modem) coupled with a cellular RF transceiver 1922 and one or more Subscriber Identity Modules (SIM) cards 1920, an application processor 1906 coupled with a secure digital (SD) card 1908 and a screen 1910, a Bluetooth module 1912, a wireless local area network (WLAN) module 1914, a Global Positioning System (GPS) module 1916, and a power supply 1918. The cellular baseband processor 1904 communicates with the UEs 104 and / or BSs 102 / 180 by the cellular RF transceiver 1922. The cellular baseband processor 1904 can include a computer-readable medium / memory. The computer-readable medium / memory can be non-transitory. The cellular baseband processor 1904 is responsible for the general processing, including the execution of software stored in the computer-readable medium / memory. The software, when executed by the cellular baseband processor 1904, causes the cellular baseband processor 1904 to perform the various functions described supra. The computer-readable medium / memory can also be used for storing data that is manipulated by the cellular baseband processor 1904 when executing software. The cellular baseband processor 1904 further includes a reception component 1930, a communication manager 1932, and a transmission component 1934. The communication manager 1932 includes the one or more illustrated components. The components of the communication manager 1932 can be stored in the computer-readable medium / memory and / or configured as hardware within the cellular baseband processor 1904. The cellular baseband processor 1904 can be a component of the UE 350 and can include at least one of the TX processor 368, the RX processor 356, and the controller / processor 359 and / or the memory 360. In one configuration, the apparatus 1902 can be a modem chip and include only the baseband processor 1904, and in another configuration, the apparatus 1902 can be an entire UE (e.g., see FIG. 3) and include the aforementioned other modules of the UE 350. Figure 3

[0157] ​The communication manager 1932 includes a HARQ indication component 1940 configured to send an indication to the second UE for providing HARQ feedback for at least one sidelink channel, for example, as described in conjunction with Figure 18 The communication manager 1932 also includes a sidelink channel transmission component 1942, which is configured to transmit at least one sidelink channel to the second UE, for example, as described in conjunction with Figure 18 The communication manager 1932 also includes a HARQ feedback processing component 1944, which is configured to receive an ACK or NACK for at least one sidelink channel from the second UE via a PSFCH, the PSFCH including a long PSFCH format and associated with the sidelink resource pool, for example, as described in conjunction with Figure 18 Described in 1806.

[0158] The apparatus may include a device for performing Figure 18 . Therefore, Figure 18 Each block in the aforementioned flow chart can be performed by a component, and the apparatus may include one or more of these components. The component may be one or more hardware components specifically configured to perform the stated process / algorithm, may be implemented by a processor configured to perform the stated process / algorithm, may be stored in a computer-readable medium for implementation by a processor, or some combination thereof.

[0159] In one configuration, the apparatus 1902 (and in particular the cellular baseband processor 1904) includes means for transmitting, to a second UE, an indication to provide HARQ feedback for at least one sidelink channel. The apparatus 1902 includes means for transmitting the at least one sidelink channel to the second UE. The apparatus 1902 includes means for receiving, from the second UE, an ACK or a NACK for the at least one sidelink channel via a PSFCH, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool. The indication can be transmitted via a SCI (e.g., SCI-1) in a PSCCH or a SCI (e.g., SCI-2) in a PSSCH. In one configuration, the SCI can explicitly indicate to the second UE to use a PSFCH including a long PSFCH format to provide HARQ feedback. In another configuration, the HARQ feedback (e.g., ACK or NACK) is received based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with the at least one sidelink channel. The at least one sidelink channel can be a PSSCH or a PSCCH, or both. The long PSFCH format can include a length of at least three symbols. Further, the sidelink resource pool can support both a long PSFCH format including a length of at least three symbols and a short PSFCH format including a length of less than three symbols.

[0160] In one configuration, when a PSFCH including a long PSFCH format and a PSFCH including a short PSFCH format are scheduled in a same slot in a sidelink resource pool, the long PSFCH format can be prioritized over the short PSFCH format. The PSFCH including the long PSFCH format can have a periodicity that is an integer multiple of the PSFCH including the short PSFCH format.

[0161] In another configuration, the PSFCH including the long PSFCH format can be scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH including the short PSFCH format. The PSFCH including the long PSFCH format can also be scheduled in at least one of a designated subchannel or a designated slot that is not used by the PSFCH including the short PSFCH format.

[0162] In another configuration, when the PSFCH including the long PSFCH format is scheduled in the sidelink resource pool in a same slot as the PSFCH including the short PSFCH format, a PSFCH with a longer periodicity can be prioritized over a PSFCH with a shorter periodicity. In another configuration, a PSFCH with configured repetition resources can be prioritized over a PSFCH without configured repetition resources, where the configured repetition resources can be in consecutive slots.

[0163] The apparatus 1902 can include means for receiving HARQ feedback (e.g., ACK / NACK) in one RB and at least three symbols in a PSFCH, or receiving HARQ feedback (e.g., ACK / NACK) in multiple RBs and at least three symbols for each RB in a PSFCH. In one configuration, the apparatus 1902 can include means for receiving at least one of a CSI report or a scheduling request in a PSFCH. The ACK or NACK can be received after a time gap and based on a periodicity of the PSFCH.

[0164] The apparatus 1902 can include means for receiving HARQ feedback in two or more symbols of a PSFCH when a long PSFCH format is used. In one configuration, the apparatus 1902 can receive an ACK or NACK in the last two symbols of a PSFCH including a long PSFCH format. In another configuration, the apparatus 1902 can receive an ACK or NACK in more than two symbols or all symbols of a PSFCH including a long PSFCH format when the second UE is configured to use a short PSFCH format. In another configuration, the apparatus 1902 can receive an ACK or NACK in one (1) or two (2) symbols, where the ACK or NACK can correspond to a HARQ repetition.

[0165] The aforementioned means can be one or more of the aforementioned components of the apparatus 1902 configured to perform the functions recited by the aforementioned means. As described supra, the apparatus 1902 can include the TX Processor 368, the RX Processor 356, and the controller / processor 359. In one configuration, the aforementioned means can therefore be the TX Processor 3619, the RX Processor 356, and the controller / processor 359 configured to perform the functions recited by the aforementioned means.

[0166] Figure 20 is a flow diagram 2000 of a method of wireless communication. The method can be performed by a first UE (e.g., a receiving UE; the UE 104, 502, 504, 506, 508, 1704; the SA 554, 556, 558; the apparatus 2102). The method can enable the first UE to provide HARQ feedback in a PSFCH having a long PSFCH format to improve reliability of the HARQ feedback.

[0167] At 2002, the first UE can receive, from a second UE, an indication to provide HARQ feedback for at least one sidelink channel, such as described in connection with Figure 17As described. For example, at 1706, the second UE 1704 can receive, from the first UE 1702, a HARQ feedback indication for requesting the second UE 1704 to provide HARQ feedback for the at least one sidelink channel. The indication can be received via a SCI (e.g., SCI-1) in a PSCCH or a SCI (e.g., SCI-2) in a PSSCH. In one example, the SCI can explicitly indicate to the first UE to use a PSFCH including a long PSFCH format to provide the HARQ feedback. In another example, the second UE can non-explicitly indicate to the first UE whether to use the long PSFCH format. For example, when the first UE transmits an ACK or a NACK in a PSFCH including the long PSFCH format or in a PSFCH including the short PSFCH format, the first UE can transmit the ACK or the NACK based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with the at least one sidelink channel.

[0168] At 2004, the first UE can receive, from the second UE, the at least one sidelink channel, such as described in connection with Figure 17 As described. For example, at 1708, the second UE 1704 can receive, from the first UE 1702, a sidelink channel (e.g., PSSCH / PSCCH). The at least one sidelink channel can be a PSSCH or a PSCCH, or both.

[0169] At 2006, the first UE can transmit, to the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool, such as described in connection with Figure 17 As described. For example, at 1710, the second UE 1704 can transmit, to the first UE 1702, an ACK / NACK for the received sidelink channel. The long PSFCH format can include a length of at least three (3) symbols. Further, the sidelink resource pool can support both the long PSFCH format including a length of at least three (3) symbols and the short PSFCH format including a length of less than three (3) symbols.

[0170] In one example, when a PSFCH including the long PSFCH format and a PSFCH including the short PSFCH format are scheduled in a same slot in the sidelink resource pool, the long PSFCH format can be prioritized over the short PSFCH format. The PSFCH including the long PSFCH format can have a periodicity that is an integer multiple of the PSFCH including the short PSFCH format.

[0171] In another example, a PSFCH including a long PSFCH format can be scheduled in one or more slots in the sidelink resource pool that are not occupied by a PSFCH including a short PSFCH format. The PSFCH including a long PSFCH format can also be scheduled in at least one of a designated subchannel or a designated slot that is not used by a PSFCH including a short PSFCH format.

[0172] In another example, when the PSFCH including the long PSFCH format is scheduled in the same slot in the sidelink resource pool as the PSFCH including the short PSFCH format, a PSFCH with a longer periodicity can be prioritized over a PSFCH with a shorter periodicity. Alternatively or additionally, a PSFCH with configured repetition resources can be prioritized over a PSFCH without configured repetition resources, where the configured repetition resources can be in consecutive slots.

[0173] The first UE can transmit HARQ feedback (e.g., ACK / NACK) in one RB and at least three symbols in the PSFCH, or transmit HARQ feedback (e.g., ACK / NACK) in multiple RBs and at least three symbols for each RB in the PSFCH. In one example, the first UE can transmit at least one of a CSI report or a scheduling request in the PSFCH. The first UE can transmit the ACK or NACK after a time gap (e.g., a minimum time gap) and based on a periodicity of the PSFCH.

[0174] When using a long PSFCH format, the first UE can transmit HARQ feedback in two or more symbols of the PSFCH. For example, the first UE can transmit an ACK or NACK in the last two symbols of a PSFCH including a long PSFCH format. In another example, when the first UE is configured to use a short PSFCH format, the first UE can transmit an ACK or NACK in more than two symbols or all symbols of a PSFCH including a long PSFCH format. The first UE can transmit an ACK or NACK in one (1) or two (2) symbols, where the ACK or NACK can correspond to a HARQ repetition.

[0175] Figure 21is a diagram 2100 showing an example of a hardware implementation for an apparatus 2102. The apparatus 2102 is a UE and includes a cellular baseband processor 2104 (also referred to as a modem) coupled with a cellular RF transceiver 2122 and one or more subscriber identity modules (SIM) cards 2120, an application processor 2106 coupled with a secure digital (SD) card 2108 and a screen 2110, a Bluetooth module 2112, a wireless local area network (WLAN) module 2114, a Global Positioning System (GPS) module 2116, and a power supply 2118. The cellular baseband processor 2104 communicates with the UE 104 and / or BS 102 / 180 by the cellular RF transceiver 2122. The cellular baseband processor 2104 can include a computer-readable medium / memory. The computer-readable medium / memory can be non-transitory. The cellular baseband processor 2104 is responsible for the general processing, including the execution of software stored in the computer-readable medium / memory. The software, when executed by the cellular baseband processor 2104, causes the cellular baseband processor 2104 to perform the various functions described supra. The computer-readable medium / memory can also be used for storing data that is manipulated by the cellular baseband processor 2104 when executing software. The cellular baseband processor 2104 further includes a reception component 2130, a communication manager 2132, and a transmission component 2134. The communication manager 2132 includes the one or more illustrated components. The components of the communication manager 2132 can be stored in the computer-readable medium / memory and / or configured as hardware within the cellular baseband processor 2104. The cellular baseband processor 2104 can be a component of the UE 350 and can include at least one of the TX processor 368, the RX processor 356, and the controller / processor 359 and / or the memory 360. In one configuration, the apparatus 2102 can be a modem chip and include only the baseband processor 2104, and in another configuration, the apparatus 2102 can be an entire UE (e.g., see 350) and include the aforementioned other modules of the apparatus 2102. Figure 3

[0176] The communication manager 2132 includes a HARQ process component 2140 configured to receive, from a second UE, an indication to provide HARQ feedback for at least one sidelink channel, e.g., as described in connection with 2002 of Figure 20 The communication manager 2132 further includes a sidelink channel process component 2142 configured to receive, from the second UE, the at least one sidelink channel, e.g., as described in connection with 2002 of Figure 20 ​The communication manager 2132 also includes a HARQ feedback reporting component 2144, which is configured to send an ACK or NACK for at least one sidelink channel to the second UE via a PSFCH, the PSFCH including a long PSFCH format and associated with the sidelink resource pool, for example, as described in conjunction with Figure 20 As described in 2006.

[0177] The apparatus may include a device for performing Figure 20 . Therefore, Figure 20 Each block in the aforementioned flow chart can be performed by a component, and the apparatus may include one or more of these components. The component may be one or more hardware components specifically configured to perform the stated process / algorithm, may be implemented by a processor configured to perform the stated process / algorithm, may be stored in a computer-readable medium for implementation by a processor, or some combination thereof.

[0178] In one configuration, the apparatus 2102 (and in particular the cellular baseband processor 2104) includes means for receiving an indication from a second UE to provide HARQ feedback for at least one sidelink channel. The apparatus 2102 includes means for receiving the at least one sidelink channel from the second UE. The apparatus 2102 includes means for sending an ACK or NACK for the at least one sidelink channel to the second UE via a PSFCH, the PSFCH including a long PSFCH format and associated with a sidelink resource pool. The indication may be sent via an SCI (e.g., SCI-1) in a PSCCH or an SCI (e.g., SCI-2) in a PSSCH. In one configuration, the SCI may explicitly indicate to the apparatus 2102 to use a PSFCH including a long PSFCH format to provide HARQ feedback. In another configuration, the HARQ feedback (e.g., ACK or NACK) is sent based on at least one of a priority, MCS, QoS, or timeslot aggregation associated with the at least one sidelink channel. The at least one sidelink channel may be a PSSCH or a PSCCH, or both. The long PSFCH format may include a length of at least three symbols. In addition, the sidelink resource pool may support both a long PSFCH format including a length of at least three symbols and a short PSFCH format including a length of less than three symbols.

[0179] In one configuration, when a PSFCH including a long PSFCH format and a PSFCH including a short PSFCH format are scheduled in a same slot in a sidelink resource pool, the long PSFCH format can take precedence over the short PSFCH format. The PSFCH including the long PSFCH format can have a periodicity that is an integer multiple of the PSFCH including the short PSFCH format.

[0180] In another configuration, the PSFCH including the long PSFCH format can be scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH including the short PSFCH format. The PSFCH including the long PSFCH format can also be scheduled in at least one of a designated subchannel or a designated slot that is not used by the PSFCH including the short PSFCH format.

[0181] In another configuration, when the PSFCH including the long PSFCH format is scheduled in the same slot in the sidelink resource pool as the PSFCH including the short PSFCH format, a PSFCH with a longer periodicity can take precedence over a PSFCH with a shorter periodicity. In another configuration, a PSFCH with configured repetition resources can take precedence over a PSFCH without configured repetition resources, where the configured repetition resources can be in consecutive slots.

[0182] The apparatus 2102 can include means for transmitting HARQ feedback (e.g., ACK / NACK) in one RB and at least three symbols in a PSFCH, or in multiple RBs and at least three symbols for each RB in a PSFCH. In one configuration, the apparatus 2102 can include means for transmitting at least one of a CSI report or a scheduling request in a PSFCH. The ACK or NACK can be transmitted after a time gap and based on a periodicity of the PSFCH.

[0183] The apparatus 2102 can include means for transmitting HARQ feedback in two or more symbols of a PSFCH when a long PSFCH format is used. In one configuration, the apparatus 2102 can transmit an ACK or NACK in the last two symbols of a PSFCH including a long PSFCH format. In another configuration, when the apparatus 2102 is configured to use a short PSFCH format, the apparatus 2102 can transmit an ACK or NACK in more than two symbols or all symbols of a PSFCH including a long PSFCH format. In another configuration, the apparatus 2102 can transmit an ACK or NACK in one (1) or two (2) symbols, where the ACK or NACK can correspond to a HARQ repetition.

[0184] The aforementioned units can be one or more of the aforementioned components of the apparatus 2102 configured to perform the functions recited by the aforementioned units. As described above, the apparatus 2102 can include the TX processor 368, the RX processor 356, and the controller / processor 359. As such, in one configuration, the aforementioned units can be the TX processor 368, the RX processor 356, and the controller / processor 359 configured to perform the functions recited by the aforementioned units.

[0185] It is to be understood that the specific order or hierarchy of steps in the processes / flow diagrams disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes / flow diagrams can be re-arranged. Further, some steps can be optional. The accompanying method claims present elements of the various steps in the example order, and are not meant to be limited to the specific order or hierarchy presented.

[0186] The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Terms such as "if," "as long as," and "when" should be interpreted as "in the event that... condition is met" rather than construed as "directly after" or "in response to the occurrence of" unless explicitly stated otherwise. That is, these phrases simply mean that if a condition is met, then a stated action will occur, but no temporal or causal relationship is inferred by the use of these terms unless specifically stated otherwise. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term "some" refers to one or more. Combinations such as "at least one of A, B, or C," "one or more of A, B, or C," "at least one of the group consisting of A, B, and C," "one or more of the group consisting of A, B, and C," and the like encompasses the selection of one or more of the items in the group or items from about two to about all of the items in the group. In other words, "at least one of A, B, or C" means A or B or C or any combination thereof. Logically, the term "some" can be interpreted as "one or more." All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or will be known to those of ordinary skill in the art are expressly incorporated by reference and intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words "module," "mechanism," "element," "device" and the like can not be a substitute for the word "means." As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase "means for."

[0187] The following aspects are merely illustrative and can be combined with other aspects or teachings described herein without limitation.

[0188] Aspect 1 is a method of wireless communication of a first UE, comprising: transmitting, to a second UE, an indication to provide HARQ feedback for at least one sidelink channel; transmitting, to the second UE, the at least one sidelink channel; and receiving, from the second UE via a PSFCH, an ACK or a NACK for the at least one sidelink channel, the PSFCH comprising a long PSFCH format and being associated with a sidelink resource pool.

[0189] In Aspect 2, the method of Aspect 1 further comprises that the long PSFCH format comprises a length of at least three (3) symbols.

[0190] In Aspect 3, the method of Aspect 1 or Aspect 2 further comprises that the at least one sidelink channel is a PSSCH or a PSCCH, or both.

[0191] In Aspect 4, the method of any of Aspects 1-3 further comprises that the indication is transmitted via SCI in a PSCCH or a PSSCH.

[0192] In Aspect 5, the method of any of Aspects 1-4 further comprises that the sidelink resource pool supports a long PSFCH format comprising a length of at least three (3) symbols and a short PSFCH format comprising a length of less than three (3) symbols.

[0193] In Aspect 6, the method of any of Aspects 1-5 further comprises that the long PSFCH format is prioritized over the short PSFCH format when a PSFCH comprising the long PSFCH format and a PSFCH comprising the short PSFCH format are scheduled in a same slot in the sidelink resource pool.

[0194] In Aspect 7, the method of any of Aspects 1-6 further comprises that the PSFCH comprising the long PSFCH format has a periodicity that is an integer multiple of the PSFCH comprising the short PSFCH format.

[0195] In Aspect 8, the method of any of Aspects 1-7 further comprises that the PSFCH comprising the long PSFCH format is scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH comprising the short PSFCH format.

[0196] In Aspect 9, the method of any of Aspects 1-8 further comprises that when the PSFCH comprising the long PSFCH format is scheduled in a same slot in the sidelink resource pool as the PSFCH comprising the short PSFCH format, the PSFCH with the longer periodicity is prioritized over the PSFCH with the shorter periodicity.

[0197] In aspect 10, the method of any of aspects 1-9 further includes, when a PSFCH including a long PSFCH format is scheduled in a same time slot in the sidelink resource pool as a PSFCH including a short PSFCH format, a PSFCH with configured repetition resources is prioritized over a PSFCH without configured repetition resources, wherein the configured repetition resources are in consecutive time slots.

[0198] In aspect 11, the method of any of aspects 1-10 further includes, a PSFCH including a long PSFCH format is scheduled in at least one of a designated subchannel or a designated time slot not used by a PSFCH including a short PSFCH format.

[0199] In aspect 12, the method of any of aspects 1-11 further includes, the ACK or NACK is received in one RB and at least three (3) symbols in the PSFCH.

[0200] In aspect 13, the method of any of aspects 1-12 further includes, the ACK or NACK is received in multiple RBs and at least three (3) symbols for each RB in the PSFCH.

[0201] In aspect 14, the method of any of aspects 1-13 further includes, receiving at least one of a CSI report or a scheduling request in the PSFCH.

[0202] In aspect 15, the method of any of aspects 1-14 further includes, the ACK or NACK is received in a PSFCH including a long PSFCH format or a PSFCH including a short PSFCH format, or the ACK or NACK is received based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with at least one sidelink channel.

[0203] In aspect 16, the method of any of aspects 1-15 further includes, the ACK or NACK is received after a time gap and based on a periodicity of the PSFCH.

[0204] In aspect 17, the method of any of aspects 1-16 further includes, the ACK or NACK is received in a last two symbols of a PSFCH including a long PSFCH format.

[0205] In aspect 18, the method of any of aspects 1-17 further includes, when the second UE is configured to use a short PSFCH format, the ACK or NACK is received in more than two symbols or all symbols of a PSFCH including a long PSFCH format.

[0206] In aspect 19, the method of any of aspects 1-18 further includes that the ACK or NACK is received in one (1) or two (2) symbols, the ACK or NACK corresponding to a HARQ repetition.

[0207] Aspect 20 is an apparatus for wireless communication including at least one processor coupled to a memory and configured to implement a method as in any of aspects 1-19.

[0208] Aspect 21 is an apparatus for wireless communication including means for implementing a method as in any of aspects 1-19.

[0209] Aspect 22 is a non-transitory computer-readable medium storing computer-executable code, where the code, when executed by a processor, causes the processor to implement a method as in any of aspects 1-19.

[0210] Aspect 23 is a method of wireless communication of a first UE, comprising: receiving, from a second UE, an indication to provide HARQ feedback for at least one sidelink channel; receiving, from the second UE, the at least one sidelink channel; and transmitting, to the second UE via a PSFCH, an ACK or NACK for the at least one sidelink channel, the PSFCH including a long PSFCH format and being associated with a sidelink resource pool.

[0211] In aspect 24, the method of aspect 23 further includes that the long PSFCH format includes a length of at least three (3) symbols.

[0212] In aspect 25, the method of aspect 23 or aspect 24 further includes that the at least one sidelink channel is a PSSCH or a PSCCH, or both.

[0213] In aspect 26, the method of any of aspects 23-25 further includes that the indication is received via SCI in a PSCCH or a PSSCH.

[0214] In aspect 27, the method of any of aspects 23-26 further includes that the sidelink resource pool supports a long PSFCH format including a length of at least three (3) symbols and a short PSFCH format including a length of less than three (3) symbols.

[0215] In Aspect 28, the method of any of Aspects 23-27 further includes, when a PSFCH including a long PSFCH format and a PSFCH including a short PSFCH format are scheduled in a same slot in the sidelink resource pool, the long PSFCH format is prioritized over the short PSFCH format.

[0216] In Aspect 29, the method of any of Aspects 23-28 further includes that the PSFCH including a long PSFCH format has a periodicity that is an integer multiple of the PSFCH including a short PSFCH format.

[0217] In Aspect 30, the method of any of Aspects 23-29 further includes that the PSFCH including a long PSFCH format is scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH including a short PSFCH format.

[0218] In Aspect 31, the method of any of Aspects 23-30 further includes, when the PSFCH including a long PSFCH format is scheduled in a same slot in the sidelink resource pool as the PSFCH including a short PSFCH format, the PSFCH with a longer periodicity is prioritized over the PSFCH with a shorter periodicity.

[0219] In Aspect 32, the method of any of Aspects 23-31 further includes, when the PSFCH including a long PSFCH format is scheduled in a same slot in the sidelink resource pool as the PSFCH including a short PSFCH format, the PSFCH with configured repetition resources is prioritized over the PSFCH without configured repetition resources, wherein the configured repetition resources are in consecutive slots.

[0220] In Aspect 33, the method of any of Aspects 23-32 further includes that the PSFCH including a long PSFCH format is scheduled in at least one of a designated subchannel or a designated slot that is not used by the PSFCH including a short PSFCH format.

[0221] In Aspect 34, the method of any of Aspects 23-33 further includes that the ACK or NACK is transmitted in one RB and at least three (3) symbols in the PSFCH.

[0222] In Aspect 35, the method of any of Aspects 23-34 further includes that the ACK or NACK is transmitted in multiple RBs and at least three (3) symbols for each RB in the PSFCH.

[0223] In aspect 36, the method of any of aspects 23-35, further comprising: transmitting, in the PSFCH, at least one of a CSI report or a scheduling request.

[0224] In aspect 37, the method of any of aspects 23-36, further comprising that the ACK or the NACK is transmitted in a PSFCH comprising a long PSFCH format or a PSFCH comprising a short PSFCH format, or the ACK or the NACK is transmitted based on at least one of a priority, a MCS, a QoS, or a time slot aggregation associated with the at least one sidelink channel.

[0225] In aspect 38, the method of any of aspects 23-37, further comprising that the ACK or the NACK is transmitted after a time gap and based on a periodicity of the PSFCH.

[0226] In aspect 39, the method of any of aspects 23-38, further comprising that the ACK or the NACK is transmitted in last two symbols of a PSFCH comprising a long PSFCH format.

[0227] In aspect 40, the method of any of aspects 23-39, further comprising that when the first UE is configured to use a short PSFCH format, the ACK or the NACK is transmitted in more than two symbols or all symbols of a PSFCH comprising a long PSFCH format.

[0228] In aspect 41, the method of any of aspects 23-40, further comprising that the ACK or the NACK is transmitted in one (1) or two (2) symbols, the ACK or the NACK corresponding to a HARQ repetition.

[0229] Aspect 42 is an apparatus for wireless communication including at least one processor coupled to a memory and configured to implement a method as described in any of aspects 23 to 41.

[0230] Aspect 43 is an apparatus for wireless communication including means for implementing a method as described in any of aspects 23 to 41.

[0231] Aspect 44 is a non-transitory computer-readable medium storing computer-executable code, where the code, when executed by a processor, causes the processor to implement a method as described in any of aspects 23 to 41.

Claims

1. A method of wireless communication at a first user equipment (UE), comprising: transmitting, to a second UE, an indication to provide hybrid automatic repeat request (HARQ) feedback for at least one sidelink channel; transmitting, to the second UE, at least one sidelink transmission via the at least one sidelink channel; and receiving, from the second UE via a physical sidelink feedback channel (PSFCH), an acknowledgement (ACK) or a negative ACK (NACK) for the at least one sidelink transmission, wherein the PSFCH comprises a long PSFCH format and is associated with a sidelink resource pool that also supports a short PSFCH format, wherein the long PSFCH format comprises a length of at least three symbols and the short PSFCH format comprises a length of less than three symbols, wherein the long PSFCH format is prioritized over the short PSFCH format when the PSFCH comprising the long PSFCH format and a PSFCH comprising the short PSFCH format are scheduled in a same slot in the sidelink resource pool.

2. The method of claim 1, wherein, the long PSFCH format comprises a length of four symbols.

3. The method of claim 1, wherein, the at least one sidelink channel is a physical sidelink shared channel (PSSCH) or a physical sidelink control channel (PSCCH) or both.

4. The method of claim 3, wherein, the indication is transmitted via sidelink control information (SCI) in the PSCCH or the PSSCH.

5. The method of claim 1, wherein, the PSFCH comprising the long PSFCH format has a periodicity that is an integer multiple of the PSFCH comprising the short PSFCH format.

6. The method of claim 1, wherein, the PSFCH comprising the long PSFCH format is scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH comprising the short PSFCH format.

7. The method of claim 1, wherein, when the PSFCH comprising the long PSFCH format is scheduled in the same slot as the PSFCH comprising the short PSFCH format in the sidelink resource pool, a PSFCH with a longer periodicity is prioritized over a PSFCH with a shorter periodicity.

8. The method of claim 1, wherein, when the PSFCH comprising the long PSFCH format is scheduled in the same slot as the PSFCH comprising the short PSFCH format in the sidelink resource pool, a PSFCH with configured repetition resources is prioritized over a PSFCH without configured repetition resources, wherein the configured repetition resources are in consecutive slots.

9. The method of claim 1, wherein, the PSFCH comprising the long PSFCH format is scheduled in at least one of a designated subchannel or a designated slot that is not used by the PSFCH comprising the short PSFCH format.

10. The method of claim 1, wherein, the ACK or the NACK is received in one resource block (RB) and at least three symbols in the PSFCH.

11. The method of claim 1, wherein, the ACK or the NACK is received in multiple resource blocks (RBs) and at least three symbols for each RB in the PSFCH.

12. The method of claim 1, further comprising: receiving at least one of a channel state information (CSI) report or a scheduling request (SR) in the PSFCH.

13. The method of claim 1, wherein, the ACK or the NACK is received in a PSFCH including a long PSFCH format or a PSFCH including a short PSFCH format, or the ACK or the NACK is received based on at least one of a priority, a modulation and coding scheme (MCS), a quality of service (QoS), or a time slot aggregation associated with the at least one sidelink channel.

14. The method of claim 1, wherein, the ACK or the NACK is received after a time gap and based on a periodicity of the PSFCH.

15. The method of claim 1, wherein, the ACK or the NACK is received in last two symbols of the PSFCH including the long PSFCH format.

16. The method of claim 1, wherein, when the second UE is configured to use a short PSFCH format, the ACK or the NACK is received in more than two symbols or all symbols of the PSFCH including the long PSFCH format.

17. The method of claim 1, wherein, the ACK or the NACK is received in one or two symbols, the ACK or the NACK corresponding to a HARQ repetition.

18. An apparatus for wireless communication at a first user equipment (UE), comprising: a memory; and at least one processor coupled to the memory and configured to: transmit, to a second UE, an indication to provide hybrid automatic repeat request (HARQ) feedback for at least one sidelink channel; transmit, to the second UE, at least one sidelink transmission via the at least one sidelink channel; and receive, from the second UE via a physical sidelink feedback channel (PSFCH), an acknowledgement (ACK) or a negative ACK (NACK) for the at least one sidelink transmission, wherein the PSFCH includes a long PSFCH format and is associated with a sidelink resource pool that also supports a short PSFCH format, wherein the long PSFCH format includes a length of at least three symbols and the short PSFCH format includes a length of less than three symbols, wherein the long PSFCH format is prioritized over the short PSFCH format when the PSFCH including the long PSFCH format and a PSFCH including the short PSFCH format are scheduled in a same time slot in the sidelink resource pool.

19. The apparatus of claim 18, wherein, the at least one processor configured to perform the method of any of claims 2-17.

20. A method of wireless communication at a first user equipment (UE), comprising: receiving, from a second UE, an indication to provide hybrid automatic repeat request (HARQ) feedback for at least one sidelink channel; receiving, from the second UE via the at least one sidelink channel, at least one sidelink transmission; and transmit an acknowledgement (ACK) or a negative ACK (NACK) for the at least one sidelink transmission to the second UE via a physical sidelink feedback channel (PSFCH), wherein the PSFCH comprises a long PSFCH format and is associated with a sidelink resource pool that also supports a short PSFCH format, wherein the long PSFCH format comprises a length of at least three symbols and the short PSFCH format comprises a length of less than three symbols, wherein the long PSFCH format is prioritized over the short PSFCH format when the PSFCH comprising the long PSFCH format and the PSFCH comprising the short PSFCH format are scheduled in a same slot in the sidelink resource pool.

21. The method of claim 20, wherein, the long PSFCH format comprises a length of four symbols.

22. The method of claim 20, wherein, the PSFCH comprising the long PSFCH format has a periodicity that is an integer multiple of the PSFCH comprising the short PSFCH format.

23. The method of claim 20, wherein, when the PSFCH comprising the long PSFCH format is scheduled in the same slot as the PSFCH comprising the short PSFCH format in the sidelink resource pool, a PSFCH with configured repetition resources is prioritized over a PSFCH without configured repetition resources, wherein the configured repetition resources are in consecutive slots.

24. The method of claim 20, wherein, the PSFCH comprising the long PSFCH format is scheduled in one or more slots in the sidelink resource pool that are not occupied by the PSFCH comprising the short PSFCH format.

25. The method of claim 20, wherein, when the PSFCH comprising the long PSFCH format is scheduled in the same slot as the PSFCH comprising the short PSFCH format in the sidelink resource pool, a PSFCH with a longer periodicity is prioritized over a PSFCH with a shorter periodicity.

26. The method of claim 20, wherein, the ACK or the NACK is transmitted in a PSFCH comprising a long PSFCH format or in a PSFCH comprising a short PSFCH format, or the ACK or the NACK is transmitted based on at least one of a priority, a modulation and coding scheme (MCS), a quality of service (QoS), or a time slot aggregation associated with the at least one sidelink channel.

27. The method of claim 20, wherein, the ACK or the NACK is transmitted after a time gap and based on a periodicity of the PSFCH.

28. The method of claim 20, wherein, when the first UE is configured to use a short PSFCH format, the ACK or the NACK is transmitted in more than two symbols or all symbols of the PSFCH comprising the long PSFCH format.

29. An apparatus for wireless communication at a first user equipment (UE), comprising: a memory; and at least one processor coupled to the memory and configured to: receive, from a second UE, an indication to provide hybrid automatic repeat request (HARQ) feedback for at least one sidelink channel; receive, from the second UE via the at least one sidelink channel, at least one sidelink transmission; and an acknowledgment (ACK) or a negative ACK (NACK) for the at least one sidelink transmission is sent to the second UE via a physical sidelink feedback channel (PSFCH), wherein the PSFCH includes a long PSFCH format and is associated with a sidelink resource pool, and the sidelink resource pool also supports a short PSFCH format, wherein the long PSFCH format includes a length of at least three symbols and the short PSFCH format includes a length of less than three symbols, wherein, when the PSFCH including the long PSFCH format and the PSFCH including the short PSFCH format are scheduled in the same time slot in the sidelink resource pool, the long PSFCH format takes precedence over the short PSFCH format.

30. The apparatus of claim 29, wherein, The at least one processor is configured to perform the method according to any one of claims 21 to 28.

31. A non-transitory computer readable medium storing computer executable code which, when executed by a processor, causes the processor to perform the method according to any one of claims 2 to 17.

32. A non-transitory computer readable medium storing computer executable code which, when executed by a processor, causes the processor to perform the method according to any one of claims 21 to 28.

Images