HARQ process for sidelink transmission

Abstract

The invention relates to a HARQ process for sidelink transmission. Apparatuses, methods, and systems for sidelink HARQ operation are disclosed. An apparatus 400 includes a transceiver 425 that receives 605 an SL grant for data transmission using an SL resource, the SL grant having a first HARQ process identifier. The apparatus 400 includes a processor 405 that selects 610 a second HARQ process identifier for data transmission using the SL resource. The processor 405 transmits 615, via the transceiver 425, the SCI including the second HARQ process identifier and transmits 620 SL data using the SL resource.

Description

[0001] This application is a divisional application of an application which entered the Chinese national phase on September 15, 2021, with PCT application number PCT / IB2020 / 000217, international application date March 23, 2020, Chinese application number 202080021586.3, and invention name “HARQ process for side link transmission”.

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 822,546, filed on March 22, 2019 by Joachim Loehr, Karthikeyan Ganesan, Prateek Basu Mallick, and Ravi Kuchibhotla, entitled “Sidelink HARQ Operation for NR Vehicular Communication,” which is incorporated herein by reference. Technical Field

[0003] The subject matter disclosed herein relates generally to wireless communications, and more particularly to sidelink HARQ operations. Background Art

[0004] The following abbreviations are defined herein, at least some of which are referenced in the following description: 3rd Generation Partnership Project ("3GPP"), 5th Generation Core Network ("5CG"), 5th Generation System ("5GS"), Authentication, Authorization and Accounting ("AAA"), Access and Mobility Management Function ("AMF"), Acknowledgement ("ACK"), Application Programming Interface ("API"), Access Stratum ("AS"), Base Station ("BS"), Control Element ("CE"), Channel State Information ("CSI"), Connected Mode ("CM", which is the NAS state in 5GS), Core Network ("CN"), Control Plane ("CP"), Data Radio Bearer ("DRB"), Downlink Control Information ("DCI"), Downlink ("DL"), Discontinuous Transmission ("DTX"), Evolved Node B ("eNB"), Evolved Packet Core ("EPC"), Evolved Packet System ("EPC"), EPS”), EPS Mobility Management (“EMM”, which is the NAS state in EPS), Evolved UMTS Terrestrial Radio Access Network (“E-UTRAN”), Frequency Division Duplex (“FDD”), Frequency Division Multiple Access (“FDMA”), General Packet Radio Service (“GPRS”), Global System for Mobile Communications (“GSM”), Hybrid Automatic Repeat Request (“HARQ”), Home Subscriber Server (“HSS”), Home Public Land Mobile Network (“HPLMN”), Information Element (“IE”), Long Term Evolution (“LTE”), Mobility Management (“MM”), Mobility Management Entity (“MME”), Negative Acknowledgement (“NACK”) or (“NAK”), New Generation (5G) Node B (“gNB”), New Generation Radio Access Network (“NG-RAN”, RAN for 5G networks), New Radio (“NR”, 5G radio access technology;Also known as “5G NR”), Non-Access Stratum (“NAS”), Network Exposure Function (“NEF”), Network Slice Selection Assistance Information (“NSSAI”), Packet Data Unit (“PDU”, used in conjunction with a “PDU Session”), Packet Switched (“PS”, e.g., Packet Switched Domain or Packet Switched Service), Physical Broadcast Channel (“PBCH”), Physical Downlink Control Channel (“PDCCH”), Physical Downlink Shared Channel (“PDSCH”), Physical Hybrid ARQ Indicator Channel (“PHICH”), Physical Random Access Channel (“PRACH”), Physical Resource Block (“PRB”), Physical Sidelink Control Channel (“PSCCH”), Physical Sidelink Shared Channel (“PSSCH”), Physical Uplink Control Channel (“PUCCH”), Physical Uplink Shared Channel (“PUSCH”), Public Land Mobile Network (“PLMN”), Quality of Service (“QoS”), Radio Access Network (“RAN”), Radio Resource Control (“RRC”), Random Access Channel ("RACH"), Reception ("RX"), Radio Link Control ("RLC"), Shared Channel ("SCH"), Session Management ("SM"), Session Management Function ("SMF"), Single Network Slice Selection Assistance Information ("S-NSSAI"), System Information Block ("SIB"), Transport Block ("TB"), Transport Block Size ("TBS"), Time Division Duplex ("TDD"), Time Division Multiplexing ("TDM"), Transmission ("TX"), Unified Data Management ("UDM"), User Data Repository ("UDR"), Uplink Control Information ("UCI"), User Entity / Equipment (Mobile Terminal) ("UE"), Uplink ("UL"), User Plane ("UP"), Universal Mobile Telecommunications System ("UMTS"), UMTS Terrestrial Radio Access ("UTRA"), UMTS Terrestrial Radio Access Network ("UTRAN"), Visited Public Land Mobile Network ("VPLMN"), and Worldwide Interoperability for Microwave Access ("WiMAX"). As used herein, "HARQ-ACK" may collectively represent positive acknowledgement ("ACK") and negative acknowledgement ("NACK") as well as discontinuous transmission ("DTX"). ACK means that the TB is correctly received, while NACK (or NAK) means that the TB is erroneously received. DTX means that the TB is not detected. ;

[0005] In certain wireless communication systems, V2X communication allows vehicles to communicate with the mobile parts of the traffic system around them. Two resource allocation modes are used in LTE V2x communication, and similar modes are introduced for NR v2x communication. Mode-1 corresponds to the V2X communication mode scheduled by the NR network. Mode-2 corresponds to the V2X communication mode scheduled by the NR UE. Mode-3 corresponds to the V2X communication mode scheduled by the LTE network. Mode-4 corresponds to the V2X communication mode scheduled by the LTE UE.

[0006] In LTE V2X, HARQ operation is limited to blind retransmission without any HARQ feedback. NR V2X communication can support HARQ feedback signaling for SL transmission. However, it is unclear how the SL HARQ process is managed for NR V2X communication, for example. Summary of the invention

[0007] A process for sidelink HARQ operation is disclosed. For example, a method for a UE for sidelink HARQ operation includes receiving a SL grant for data transmission using SL resources. Here, the SL grant indicates a first HARQ process identified by a first HARQ process identifier. The method includes selecting a second HARQ process identified by a second HARQ process identifier for data transmission using SL resources. The method includes transmitting an SCI including the selected second HARQ process identifier, and transmitting SL data using the SL resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] A more particular description of the embodiments briefly described above will be presented by reference to specific embodiments illustrated in the accompanying drawings. Understanding that these drawings depict only some embodiments and are therefore not to be considered limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0009] Figure 1 is a schematic block diagram illustrating one embodiment of a wireless communication system for sidelink HARQ operation;

[0010] Figure 2 is a diagram illustrating one embodiment of a signaling flow for transmitting a V2X UE;

[0011] Figure 3 is a diagram illustrating one embodiment of a signaling flow for sidelink data transmission;

[0012] Figure 4 is a diagram illustrating one embodiment of a user equipment apparatus that may be used for sidelink HARQ operations;

[0013] Figure 5is a diagram illustrating one embodiment of a base station apparatus that may be used for sidelink HARQ operations; and

[0014] Figure 6 is a flow chart illustrating one embodiment of a method that may be used for sidelink HARQ operations. DETAILED DESCRIPTION

[0015] As will be appreciated by those skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Thus, the embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects.

[0016] For example, the disclosed embodiments may be implemented as hardware circuits including custom very large scale integration ("VLSI") circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. The disclosed embodiments may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, etc. As another example, the disclosed embodiments may include one or more physical or logical blocks of executable code, which may be organized, for example, as an object, procedure, or function.

[0017] In addition, embodiments may take the form of a program product embodied in one or more computer-readable storage devices stored in machine-readable code, computer-readable code, and / or program code, hereinafter referred to as code. The storage device may be tangible, non-transitory, and / or non-transmitting. The storage device may not embody signals. In a certain embodiment, the storage device employs only signals for accessing the code.

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

[0019] More specific examples of storage devices (a non-exhaustive list) would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory ("RAM"), a read-only memory ("ROM"), an erasable programmable read-only memory ("EPROM" or flash memory), a portable compact disc read-only memory ("CD-ROM"), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0020] The code for performing the operations of the embodiments may be any number of lines and may be written in any combination of one or more programming languages ​​including object-oriented programming languages ​​such as Python, Ruby, Java, Smalltalk, C++, and the like, and traditional procedural programming languages ​​such as the "C" programming language, and / or machine languages ​​such as assembly languages. The code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network including a local area network ("LAN") or a wide area network ("WAN"), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0021] References to "one embodiment", "embodiment" or similar language in this specification mean that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment. Therefore, unless otherwise expressly stated, the phrases "in one embodiment", "in an embodiment" and similar language appearing throughout the specification may but do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments". Unless otherwise expressly stated, the terms "including", "comprising", "having" and their variations mean "including but not limited to". Unless otherwise expressly stated, the list of items listed does not imply that any or all items are mutually exclusive. Unless otherwise expressly stated, the terms "one", "an" and "the" also refer to "one or more".

[0022] As used herein, a list with the conjunction "and / or" includes any single item in the list or combination of items in the list. For example, a list of A, B, and / or C includes only A; only B; only C; a combination of A and B; a combination of B and C; a combination of A and C; or a combination of A, B, and C. As used herein, a list using the term "one or more" includes any single item in the list or combination of items in the list. For example, one or more of A, B, and C includes only A; only B; only C; a combination of A and B; a combination of B and C; a combination of A and C; or a combination of A, B, and C. As used herein, a list using the term "one of..." includes one and only one of any single item in the list. For example, "one of A, B, and C" includes only A, only B, or only C, and excludes the combination of A, B, and C. As used herein, "a member selected from the group consisting of A, B, and C" includes one or only one of A, B, or C, and excludes the combination of A, B, and C. As used herein, “a member selected from the group consisting of A, B and C and combinations thereof” includes only A; only B; only C; a combination of A and B; a combination of B and C; a combination of A and C; or a combination of A, B and C.

[0023] In addition, the features, structures or characteristics of the described embodiments may be combined in any suitable manner. In the following description, many specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of the embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of the specific details, or using other methods, components, materials, etc. In other cases, well-known structures, materials or operations are not shown or described in detail to avoid obscuring some aspects of the embodiments.

[0024] The various aspects of the embodiments are described below with reference to the schematic flow charts and / or schematic block diagrams of the methods, devices, systems and program products according to the embodiments. It will be understood that each frame of the schematic flow chart and / or schematic block diagram and the combination of frames in the schematic flow chart and / or schematic block diagram can be implemented by code. The code can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to generate a machine, so that instructions executed by the processor of the computer or other programmable data processing device create a device for implementing the functions / power operations specified in the flow chart and / or block diagram.

[0025] The code may also be stored in a storage device, which is capable of instructing a computer, other programmable data processing apparatus or other device to operate in a specific manner so that the instructions stored in the storage device produce an article of manufacture including instructions that implement the functions / actions specified in the flowchart and / or block diagram.

[0026] The code may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, so that the code executed on the computer or other programmable apparatus provides a process for implementing the functions / actions specified in the flowchart and / or block diagram.

[0027] The flowcharts and / or block diagrams in the accompanying drawings illustrate the possible implementation architectures, functions and operations of the devices, systems, methods and program products according to various embodiments. In this regard, each box in the flowchart and / or block diagram may represent a module, segment or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function.

[0028] It should also be noted that in some alternative implementations, the functions annotated in the blocks may not occur in the order annotated in the drawings. For example, two blocks shown in succession may actually be executed substantially simultaneously, or the blocks may sometimes be executed in the reverse order, depending on the functions involved. Other steps and methods are contemplated that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated drawings.

[0029] Although various arrow types and line types can be used in flow charts and / or block diagrams, it should be understood that they do not limit the scope of the corresponding embodiments. In fact, some arrows or other connectors can only be used to indicate the logical flow of the depicted embodiment. For example, an arrow can indicate a waiting or monitoring period of unspecified duration between the enumeration steps of the depicted embodiment. It will also be noted that each frame of the block diagram and / or flow chart and the combination of the frames in the block diagram and / or flow chart can be realized by a system based on dedicated hardware that performs a specific function or operation, or a combination of dedicated hardware and code.

[0030] The description of an element in each figure may refer to the elements of the previous figure. In all figures, the same numerals refer to the same elements, including alternative embodiments of the same elements.

[0031] In general, the present disclosure describes systems, methods, and apparatus for sidelink HARQ operations of UEs participating in V2X communications. "V2X" (Vehicle to Everything) refers to sidelink communications, which may include one or more of: "V2I" (Vehicle to Infrastructure) communications, "V2N" (Vehicle to Network) communications, "V2V" (Vehicle to Vehicle) communications, "V2P" (Vehicle to Pedestrian), "V2D" (Vehicle to Device), and "V2G" (Vehicle to Grid) communications. A V2X UE refers to a UE capable of vehicular communications using 3GPP protocols.

[0032] Mode 3 and Mode 4 support direct LTE V2X communications, but differ in how radio resources are allocated. For Mode 3, resources are allocated by the cellular network (e.g., eNB). Mode 4 does not require cellular coverage, and the vehicle (UE) autonomously selects its radio resources using a distributed scheduling scheme supported by a congestion control mechanism. Mode 4 is considered a baseline mode and represents an alternative to 802.11p or dedicated short-range communications (DSRC).

[0033] Resource allocation modes 3 and 4 have both been designed to meet latency requirements and accommodate high Doppler spread and high density vehicles for V2X communications. Here, the maximum allowed latency varies between 20ms and 100ms depending on the application. Mode 3 uses a centralized eNB scheduler as described previously. The vehicle UE and eNB communicate using the Uu interface, e.g., a BSR / SR is sent from the transmitting V2X UE to the eNB, and in response, a SL grant is received on the PDCCH (carried in the DCI).

[0034] Mode 4 uses the PC5 interface, which provides a direct LTE sidelink (SL) between two vehicle UEs. Mode 4 employs distributed UE scheduling and operates without infrastructure support, even when the UE is within eNB coverage. Note that the LTE sidelink resources are shared with the LTE uplink. Two LTE duplex modes are supported (e.g., time division and frequency division duplex). Mode 4 uses a specific resource pool configuration and semi-persistent scheduling ("SPS") to select and reserve resources for transmission.

[0035] SPS was introduced in LTE to support services that require deterministic latency, such as voice. Mode 4 adopts this concept and uses sensing to determine a set of suitable semi-persistent transmission opportunities, such as subframes and subchannels for V2X transmissions. Depending on the message size, the candidate single-subframe resources consist of one to up to L consecutive subchannels in a single subframe. The UE selects a set of candidate resources within a selection window that spans multiple subframes and contains M single-subframe resources. Parameters T1 and T2 define the selection window. T2 is determined as a function of the latency requirement. The UE continuously monitors the subframes and records the decoded SCI and SL received signal strength indicator (S-RSSI) metrics. In some embodiments, the UE considers the last 1000 subframes for selecting candidate resources.

[0036] As mentioned above, the NR V2X design uses LTE V2X operation as a baseline. NR V2X also supports both a centralized scheduling mode (e.g., network scheduling) and a distributed scheduling mode (e.g., UE scheduling). The two resource allocation modes in NR V2X are referred to as resource allocation mode-1 and mode-2.

[0037] In various embodiments, NR V2X operation supports HARQ with HARQ feedback signaling for SL transmissions (e.g., at least for unicast and potentially for groupcast SL transmissions). As described above, LTE V2X HARQ operation is limited to blind retransmissions without any HARQ feedback and therefore cannot provide a baseline for NR V2X HAR operation with HARQ feedback for SL transmissions. This raises several issues on how to manage the sidelink HARQ processes maintained for different transmission types, e.g., unicast, multicast, and broadcast, and resource allocation modes, respectively.

[0038] The present disclosure outlines several methods for efficient SL HARQ protocol operation for NR V2X. Specifically, HARQ operation for SL transmission in resource allocation mode-1 is disclosed. In addition, the UE behavior for the case when a transmitting V2X UE switches the broadcast type for different HARQ (re)transmissions of TBs transmitted on PSSCH is disclosed.

[0039] Figure 1 A wireless communication system 100 is depicted for sidelink HARQ operation in NR V2X communication of a wireless device for communicating V2X messages 125 according to an embodiment of the present disclosure. In one embodiment, the wireless communication system 100 includes at least one remote unit 105, a radio access network ("RAN") 120, and a mobile core network 140. The RAN 120 and the mobile core network 140 form a mobile communication network. The RAN 120 may be composed of a base station unit 110, with which the remote unit 105 communicates using a wireless communication link 115. Even in Figure 1 A specific number of remote units 105, base station units 110, wireless communication links 115, RAN 120, and mobile core networks 140 are depicted in the figure, and those skilled in the art will recognize that any number of remote units 105, base station units 110, wireless communication links 115, RAN 120, and mobile core networks 140 may be included in the wireless communication system 100.

[0040] In one embodiment, the RAN 120 complies with the 5G system specified in the 3GPP specification. In another embodiment, the RAN 120 complies with the LTE system specified in the 3GPP specification. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication network, such as WiMAX, among other networks. The present disclosure is not intended to be limited to any particular wireless communication system architecture or protocol implementation.

[0041] In one embodiment, the remote unit 105 may include a computing device such as a desktop computer, a laptop computer, a personal digital assistant (“PDA”), a tablet computer, a smart phone, a smart TV (e.g., a TV connected to the Internet), a smart home appliance (e.g., a home appliance connected to the Internet), a set-top box, a game console, a security system (including a security camera), a vehicle-mounted computer, a network device (e.g., a router, a switch, a modem), etc. In some embodiments, the remote unit 105 includes a wearable device such as a smart watch, a fitness band, an optical head-mounted display, etc. In addition, the remote unit 105 may be referred to as a UE, a subscriber unit, a mobile phone, a mobile station, a user, a terminal, a mobile terminal, a fixed terminal, a subscriber station, a user terminal, a wireless transmit / receive unit (“WTRU”), a device, or other terms used in the art.

[0042] The remote unit 105 may communicate directly with one or more base station units 110 in the RAN 120 via uplink ("UL") and downlink ("DL") communication signals. In addition, the UL and DL communication signals may be carried over wireless communication links 115. Here, the RAN 120 is an intermediate network that provides access to the mobile core network 140 for the remote unit 105.

[0043] In some embodiments, the remote unit 105 communicates with the application server 151 via a network connection with the mobile core network 140. For example, an application 107 (e.g., a web browser, a media client, a phone / VoIP application) in the remote unit 105 can trigger the remote unit 105 to establish a PDU session (or other data connection) with the mobile core network 140 via the RAN 120. The mobile core network 140 then relays traffic between the remote unit 105 and the application server 151 in the packet data network 150 using the PDU session. Note that the remote unit 105 can establish one or more PDU sessions (or other data connections) with the mobile core network 140. Thus, the remote unit 105 can simultaneously have at least one PDU session for communicating with the packet data network 150 and at least one PDU session for communicating with another data network (not shown).

[0044] The base station units 110 may be distributed over a geographic area. In some embodiments, the base station units 110 may also be referred to as access terminals, access points, base stations, base stations, node Bs, eNBs, gNBs, home node Bs, relay nodes, or any other term used in the art. The base station units 110 are typically part of a radio access network (“RAN”) such as RAN 120, which may include one or more controllers communicatively coupled to one or more respective base station units 110. These and other elements of a radio access network are not shown, but are well known to those of ordinary skill in the art. The base station units 110 are connected to a mobile core network 140 via the RAN 120.

[0045] The base unit 110 can serve multiple remote units 105 within a service area, such as a cell or a cell sector, via a wireless communication link 115. The base unit 110 can communicate directly with one or more remote units 105 via communication signals. Typically, the base unit 110 transmits DL communication signals to serve the remote units 105 in the time domain, frequency domain, and / or spatial domain. In addition, the DL communication signals can be carried on the wireless communication link 115. The wireless communication link 115 can be any suitable carrier in the licensed or unlicensed radio spectrum. The wireless communication link 115 facilitates communication between one or more remote units 105 and / or one or more base units 110.

[0046] In one embodiment, mobile core network 140 is a 5G core ("5GC") or an evolved packet core ("EPC"), which can be coupled to a packet data network 150, such as the Internet and private data networks and other data networks. Remote units 105 can have subscriptions or other accounts with mobile core networks 140. Each mobile core network 140 belongs to a single public land mobile network ("PLMN"). The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

[0047] The mobile core network 140 includes several network functions ("NFs"). As depicted, the mobile core network 140 includes a plurality of user plane functions ("UPFs") 145. The mobile core network 140 also includes a plurality of control plane functions, including but not limited to an access and mobility management function ("AMF") 141 serving the RAN 120, a session management function ("SMF") 143, and a policy control function ("PCF") 147. In certain embodiments, the mobile core network 140 may also include an authentication server function ("AUSF"), a unified data management function ("UDM") 149, a network repository function ("NRF") (used by various NFs to discover and communicate with each other over an API), or other NFs defined for the 5GC.

[0048] In various embodiments, the mobile core network 140 supports different types of mobile data connections and different types of network slices, where each mobile data connection utilizes a specific network slice. As used herein, a "network slice" refers to a portion of the mobile core network 140 that is optimized for certain types of traffic or communication services. A network instance may be identified by an S-NSSAI, and the set of network slices that the remote unit 105 is authorized to use is identified by an NSSAI. In some embodiments, various network slices may include instances of separate network functions, such as SMF 145 and UPF 141. In some embodiments, different network slices may share some common network functions, such as AMF 143. For ease of illustration, Figure 1 The different network slices are not shown, but their support is assumed.

[0049] Despite Figure 1 Specific numbers and types of network functions are depicted in the mobile core network 140, but those skilled in the art will recognize that any number and types of network functions may be included in the mobile core network 140. In addition, in the case where the mobile core network 140 is an EPC, the depicted network functions may be replaced with appropriate EPC entities, such as MME, S-GW, P-GW, HSS, etc. In some embodiments, the mobile core network 140 may include an AAA server.

[0050] Although Figure 1 Components of a 5G RAN and 5G core network are depicted, but the described embodiments for sidelink HARQ operations in NR V2X communications are applicable to other types of communication networks and RATs, including IEEE 802.11 variants, GSM, GPRS, UMTS, LTE variants, CDMA 2000, Bluetooth, ZigBee, Sigfoxx, etc. For example, in an LTE variant involving EPC, the AMF 143 may be mapped to the MME, the SMF to the control plane portion of the PGW and / or the MME, the UPF to the user plane portion of the SGW and PGW, the UDM / UDR to the HSS, etc.

[0051] In various embodiments, the remote units 105 may communicate directly with each other (e.g., device-to-device communication) using the V2X communication signals 125. Here, the V2X transmissions may occur on V2X resources. As described above, different V2X communication resources for different V2X modes may be provided to the remote units 105. Mode-1 corresponds to a NR network scheduled V2X communication mode. Mode-2 corresponds to a NR UE autonomous V2X communication mode. Mode-3 corresponds to a LTE network scheduled V2X communication mode. Mode-4 corresponds to a LTE UE scheduled V2X communication mode.

[0052] In addition, the remote unit 105 implements a SL HARQ process for at least some of the data communicated via the V2X communication signal 125. In some embodiments, the transmitting remote unit 105 selects a HARQ process for SL transmissions on the PSSCH. In some embodiments, the HARQ process is shared between Mode 1 SL communications and Mode 2 SL communications. In some embodiments, the HARQ process is shared between unicast, groupcast, and broadcast transmissions.

[0053] For SL HARQ operation in Mode-1, the transmitting remote unit 105 may autonomously select a HARQ process, which may be different from the HARQ process ID signaled within the SL grant. Since the purpose of the HARQ process ID in the SL grant is to identify, together with the NDI, whether SL resources are allocated for HARQ retransmissions of a previously scheduled SL TB or whether SL resources are allocated for an initial HARQ transmission, the base station unit 110 may alternatively use another identifier such as the SL grant ID to identify the retransmission or the initial grant.

[0054] In the event that a retransmission is required, the remote unit 105 may switch the transmission broadcast type used for the retransmission. For example, if the initial HARQ transmission was completed in a multicast manner, the HARQ retransmission may be completed in a unicast manner. In various embodiments, the remote unit 105 uses the same HARQ process for transmitting HARQ retransmissions to multiple receiving V2X remote units 105.

[0055] In the following description, the term RAN node is used for a base station, but it may be replaced by any other radio access node, such as BS, eNB, gNB, AP, NR, etc. In addition, the operations are mainly described in the context of 5G NR. However, the proposed solution / method is also equally applicable to other mobile communication systems that support serving cells / carriers configured for sidelink communications over the PC5 interface.

[0056] Figure 2A signaling flow diagram 200 of SL HARQ operation for a V2X transmitting UE 205 ("V2X Tx UE") according to a first solution is depicted. In the first solution, the UE 205 receiving a SL grant 225 from a RAN node 210 on a PDCCH (e.g., via a Uu interface 207) then autonomously selects a SL HARQ process for a corresponding SL transmission, e.g., a PSSCH transmission 235. The V2X Tx UE 205 sends a feedback message 245 to the RAN node 210 (e.g., a gNB) after a predefined time offset. Here, the feedback message 245 either indicates successful reception of a scheduled SL transmission or requests additional SL resources for HARQ retransmissions of the SL transmission scheduled by the SL grant, respectively. Note that the depicted V2X Tx UE 205 operates in a network scheduled V2X mode (e.g., Mode-1).

[0057] As depicted in the signaling flow diagram 200, the UE 205 first sends a SL buffer status report ("SL BSR") 220 indicating the amount of SL data available for transmission to the RAN node 210. In response, the RAN node 210 may allocate SL resources for transmission of the indicated SL data by sending a SL grant 225 on the PDCCH (i.e., in the DCI).

[0058] According to one embodiment of the first solution, the SL grant 225 contains an indication of the HARQ process ID and a new data indicator (NDI). These two fields are used only to identify whether the SL grant 225 allocates SL resources for HARQ retransmission of a previously scheduled SL TB or allocates SL resources for an initial HARQ transmission. For example, a SL grant received with an unswitched NDI value (compared to the NDI value of the last received SL grant for the same HARQ process ID) allocates SL resources for HARQ retransmission, while a SL grant received with a switched NDI value allocates SL resources for an initial HARQ transmission.

[0059] According to an alternative embodiment, instead of the HARQ process ID field, a new field may be signaled within the DCI that identifies the SL grant, for example, referred to as a "SL grant identifier (ID)". Here, the "SL grant ID" field together with the NDI field indicates to the V2XTx UE 205 whether the SL grant allocates SL resources for 1) an initial HARQ transmission or for 2) a HARQ retransmission. Thus, a SL grant received with an unswitched NDI value (compared to the NDI value of the last received SL grant for the same SL grant ID or HARQ process ID) allocates SL resources for HARQ retransmissions, while a SL grant received with a switched NDI value allocates SL resources for an initial HARQ transmission.

[0060] The SL grant 225 may further allocate resources, such as PUCCH resources and / or HARQ feedback timing related information, for example, providing information about which resource and / or when HARQ feedback should be transmitted relative to receiving the SL grant on the PDCCH. Such feedback 245 indicates to the RAN node 210 whether the PSSCH transmission 235 scheduled by the SL grant 225 was successfully received / decoded by the receiving V2X UE 215, or whether the V2X Tx UE 205 requested SL resources for HARQ retransmissions of TBs sent on the PSSCH.

[0061] The SL grant 225 may further signal the V2X Tx UE 205 the redundancy version (“RV”) to be used for the corresponding transmission of the TB on the PSSCH. According to another embodiment, the SL grant 225 may also allocate SL resources for the HARQ feedback 245 corresponding to the PSSCH transmission 235 on the PC5 interface 209.

[0062] Upon receiving the SL grant 225 on the PDCCH, the V2X Tx UE 205 generates a TB according to the allocated transmission parameters signaled in the SL grant and transmits the TB on the SL resources allocated by the SL grant 225. More specifically, the V2X Tx UE 205 selects a SL HARQ process (SL-SCH) for transmitting the TB, for example, one of the transmitting sidelink HARQ processes associated with a sidelink HARQ entity for which there is no pending HARQ retransmission. The ID of the selected HARQ process is signaled in the SCI 230 accompanying the PSSCH 235.

[0063] The SCI 230 transmitted on the PSCCH may further include SL resources for SL HARQ feedback 240, e.g., ACK / NACK, to be sent by the V2X receiving UE 215, e.g., as allocated by the SL grant 225 sent from the RAN node 210. The SCI 230 may further include a new data indicator ("NDI") that provides information to the receiving UE 215 as to whether the PSSCH transmission 235 conveys an initial HARQ transmission or a HARQ retransmission. The HARQ process ID is used together with the NDI by the receiving V2X UE 215 for HARQ soft buffer management, e.g., soft combining.

[0064] It should be noted that in addition to the HARQ process ID and NDI, the source layer 2 ID may also need to be considered for HARQ soft buffer management at the receiving UE 215, for example, only PSSCH transmissions from the same source ID are to be soft combined. Having sent the SCI 230 (PSCCH) and the SL MAC PDU (TB) 235 on the PSSCH, the V2X Tx UE 205 receives the SL HARQ feedback 240 on the allocated SL resources. In the event that the SL HARQ feedback 240 indicates a NACK (e.g., indicating that the TB was not successfully received), the V2X Tx UE 205 requests SL resources for retransmission of the TB from the RAN node 210. Such a retransmission request is transmitted on the resources allocated by the SL grant (e.g., on the PUCCH). Note that the V2X Tx UE 205 may track the SL HARQ feedback responses to ensure that each V2X receiving UE successfully receives the SL MAC PDU (TB) at least once.

[0065] Figure 3 A signaling flow diagram 300 for SL data transmission according to an embodiment of the present disclosure is depicted. The signaling flow diagram 300 involves a V2X Tx UE 205, a RAN node 210, and at least one V2X Rx UE 215. The V2X Tx UE 205 sends a SL BSR to the RAN node 210 (see messaging 305). The RAN node 210 then allocates SL resources to the V2X Tx UE 205 (see messaging 310). Note that in this case, the SL resources are used for the initial HARQ transmission of the first TB ("TB-A"). Here, the SL grant also allocates PUCCH resources for HARQ feedback (i.e., ACK / NACK) and SL resources for SL HARQ feedback.

[0066] As depicted, the RAN node 210 indicates a first HARQ process ID (e.g., HPID=X) in the SL grant. The V2X Tx UE 205 maps the first HARQ process ID to a SL HARQ process with a second HARQ process ID (e.g., HPID=Y) for SL transmission on the PC5 interface. The V2X Tx UE 205 transmits the SCI to the V2X Rx UE 215 and further transmits the TB-A on the PSSCH (see messaging 315 and 320).

[0067] The SCI (PSCCH) accompanying the SL-SCH transmission on the PSSCH signals the second HARQ process ID and NDI of the HARQ process selected by the UE (see messaging 315). Note that when SL HARQ feedback (e.g., ACK / NACK) is requested from the receiving UE 215 in response to the SL-SCH transmission, only the second HARQ process ID and NDI need to be signaled within the SCI. Therefore, for NRV2X operation, there may be two different SCI formats, one for use when HARQ feedback is requested from the receiving UE 215, and one SCI for SL-SCH transmission without HARQ feedback. According to another embodiment, the SCI for SL-SCH with HARQ feedback may also allocate SL resources for HARQ feedback from the receiving UE 215. Alternatively and / or additionally, the SCI may indicate the timing of the HARQ feedback relative to the PSSCH or PSCCH reception.

[0068] In the depicted embodiment, at least one V2X Rx UE 215 does not successfully receive TB-A and therefore sends negative feedback (i.e., HARQ NACK) corresponding to SL HARQ process ID 'Y' to the V2X Tx UE 205 (see messaging 325). Therefore, for the SL grant corresponding to HARQ process ID 'X', the V2X Tx UE 205 sends a HARQ NACK on the PUCCH to the RAN node 210 (see messaging 330). The RAN node 210 then allocates SL resources to the V2X Tx UE 205 (see messaging 335). Note that in this case, the SL resources are used for HARQ retransmissions of TB-A. Likewise, the SL grant also allocates PUCCH resources for HARQ feedback (i.e., ACK / NACK) and SL resources for SL HARQ feedback. Note that the SL grant is for the same HARQ process (i.e., HPID='X').

[0069] The V2X Tx UE 205 transmits the SCI to the V2X Rx UE 215, and further retransmits the TB-A on the PSSCH (see messaging 340 and 345). Again, the SCI indicates the same second HARQ process ID (i.e., HPID='Y') and the non-switched NDI (see messaging 340). At this time, the V2X Rx UE 215 successfully receives the TB-A, and therefore sends a positive feedback (i.e., HARQ ACK) corresponding to the SL HARQ process ID 'Y' to the V2X Tx UE 205 (see messaging 350). Therefore, for the SL grant corresponding to the HARQ process ID 'X', the V2X Tx UE 205 sends a HARQ ACK to the RAN node 210 on the PUCCH (see messaging 355). Recall that the V2X Tx UE 205 may track the SL HARQ feedback received from the V2X Rx UE 215 to ensure that each V2X Rx UE 215 successfully receives the TB-A at least once.

[0070] According to the second solution, for each carrier / serving cell, at the MAC entity for transmission on L-SCH, there is one sidelink HARQ entity that maintains multiple parallel sidelink HARQ processes. The sidelink HARQ processes are shared between all SL transmissions regardless of the type of transmission of the SL transmission, e.g., unicast, groupcast, or broadcast SL transmission, and regardless of the resource allocation mode, e.g., RAN scheduled mode (mode-1) or UE autonomous mode (mode-2).

[0071] According to an implementation of the second solution, the SL grant and its related HARQ information are associated with the sidelink HARQ process. The V2X Tx UE 205 autonomously selects the HARQ process for SL transmission according to this embodiment and delivers the HARQ information to the corresponding SL HARQ process. The HARQ information contains at least the HARQ process ID of the selected HARQ process for SL transmission, and may further contain a new data indicator (NDI), which indicates whether the corresponding SL transmission is an initial HARQ transmission or a HARQ retransmission.

[0072] According to the third solution, the transmitting V2X UE 205 may switch the broadcast type for different HARQ (re)transmissions of the TB transmitted on the PSSCH. In one embodiment of the third solution, the V2X Tx UE 205 performs the initial transmission of the TB in a groupcast mode, while the potential HARQ retransmissions are performed in a unicast mode, e.g., the HARQ retransmissions are performed to each V2X receiving UE 215. For the initial transmission of the TB, the V2X Tx UE 205 selects one of the SL HARQ processes of the SL HARQ entity, e.g., a SL HARQ process with no pending HARQ (re)transmission, as described above.

[0073] As described above, the initial transmission may be a groupcast transmission to a group of V2X receiving UEs 215. In the event that one or more UEs in the group cannot successfully decode the TB, the V2X Tx UE 205 may then perform a single unicast HARQ retransmission to those UEs. In one embodiment, each unicast HARQ transmission is performed in a separate HARQ process. However, in another embodiment of the third solution, the Tx UE 205 reuses the SL HARQ process selected for the initial transmission for (multiple) unicast HARQ retransmissions to different receiving UEs 215.

[0074] For each HARQ retransmission to one of the receiving UEs 215, the V2X Tx UE 205 may select a different redundancy version. Even if only one (and the same) SL HARQ process is used for each of multiple unicast transmissions to different Rx UEs 215, the V2X Tx UE 205 maintains an independent HARQ state / context, e.g., RV, NDI state, received HARQ feedback, for each of the receiving UEs 215. In various embodiments, the SL HARQ process may be used for a new TB transmission, e.g., an initial transmission, only when all receiving UEs 215 have successfully received the TB (e.g., no retransmissions are pending for the SL HARQ process).

[0075] For unicast retransmissions, the V2X Tx UE 205 may, while performing retransmissions, use the destination ID of each receiving UE that was unable to decode the PSSCH transmission (assuming here that 'm' Rx UEs failed to successfully receive the TB in the PSSCH), and perform 'm' SCI / PSSCH transmissions (where 'm' is an integer less than or equal to the number of members of the group of V2X receiving UEs 215). In some embodiments, beamforming may be used for these 'm' unicast transmissions, for example, if the channel state of a particular PC5 channel is known. In some embodiments, if the number of unicast transmissions (e.g., 'm') is greater than a certain (pre-)configured number, the Tx UE 205 may continue retransmitting in a groupcast manner (e.g., instead of switching to unicast retransmissions).

[0076] Figure 4 A user equipment device 400 that can be used for sidelink HARQ operations in NR V2X communications according to an embodiment of the present disclosure is depicted. In various embodiments, the user equipment device 400 is used to implement one or more of the above solutions. The user equipment device 400 is an embodiment of the remote unit 105 and / or Tx UE as described above. In addition, the user equipment device 400 may include a processor 405, a memory 410, an input device 15, an output device 420, and a transceiver 425. In some embodiments, the input device 415 and the output device 420 are combined into a single device, such as a touch screen. In some embodiments, the user equipment device 400 may not include any input device 415 and / or output device 420. In various embodiments, the user equipment device 400 may include one or more of the processor 405, the memory 410, and the transceiver 425, and may not include the input device 415 and / or the output device 420.

[0077] In one embodiment, processor 405 may include any known controller capable of executing computer-readable instructions and / or capable of performing logical operations. For example, processor 405 may be a microcontroller, a microprocessor, a central processing unit (“CPU”), a graphics processing unit (“GPU”), an auxiliary processing unit, a field programmable gate array (“FPGA”), or a similar programmable controller. In some embodiments, processor 405 executes instructions stored in memory 410 to perform the methods and routines described herein. Processor 405 is communicatively coupled to memory 410, input device 415, output device 420, and transceiver 425.

[0078] In various embodiments, the processor 405 controls the user equipment device 400 to implement the above-mentioned UE behavior. In some embodiments, the transceiver 425 receives a SL grant for data transmission using SL resources. Here, the SL grant has a first HARQ process identifier (i.e., a network HARQ process ID). The processor 405 selects a second HARQ process identifier (i.e., a SL HARQ process ID) for data transmission using SL resources. Via the transceiver 425, the processor 405 transmits an SCI including the second HARQ process identifier and transmits SL data using SL resources.

[0079] In some embodiments, the transmitter sends HARQ feedback for a first HARQ process corresponding to a SL data transmission. In such an embodiment, the SL grant indicates physical uplink control channel resources and / or HARQ feedback timing information, wherein the transmission of HARQ feedback for the data transmission for the first HARQ process is based on the SL grant. Note that in other embodiments, the SL grant for the data transmission may indicate the first HARQ process identifier without scheduling PUCCH resources.

[0080] In some embodiments, a first HARQ process identifier received in a SL grant (e.g., received in a DCI) is different from a SL HARQ process identifier signaled within an SCI. In some embodiments, the selected HARQ process is associated with a SL HARQ process for which there are no pending HARQ retransmissions. In various embodiments, the processor maps the first HARQ process to a SL HARQ process, wherein the SL HARQ process is selected independently of the first HARQ process.

[0081] In some embodiments, selecting the SL HARQ process includes autonomously selecting the SL HARQ process from a configured SL HARQ process pool. In some embodiments, the configured SL HARQ process pool is shared between network-scheduled SL data transmissions and UE-scheduled SL data transmissions. In some embodiments, the configured SL HARQ process pool is shared between unicast SL transmissions, multicast SL transmissions, and broadcast SL transmissions.

[0082] In some embodiments, transmitting SL data using SL resources includes transmitting an SCI including a SL HARQ process identifier to a SL HARQ process, and the transceiver receives SL HARQ feedback for the SL HARQ process from at least one UE. In such an embodiment, the SCI further includes a new data indicator, wherein the receiving UE performs soft combining of the transmitted SL data based at least on the SL HARQ process identifier and the new data indicator. In another embodiment, the receiving UE also performs soft combining of the transmitted SL data taking into account a source layer 2 identifier.

[0083] In some embodiments, transmitting the SL data includes performing a multicast transmission, and receiving SL HARQ feedback corresponding to the SL data transmission includes receiving a negative acknowledgement indication. In such embodiments, the processor retransmits the SL data using a unicast SL retransmission. In some embodiments, the unicast SL retransmission reuses the SL HARQ process identifier. In some embodiments, the unicast SL retransmission uses a different redundancy version than the initial SL data transmission.

[0084] In one embodiment, memory 410 is a computer-readable storage medium. In some embodiments, memory 410 includes volatile computer storage media. For example, memory 410 may include RAM including dynamic RAM ("DRAM"), synchronous dynamic RAM ("SDRAM"), and / or static RAM ("SRAM"). In some embodiments, memory 410 includes non-volatile computer storage media. For example, memory 410 may include a hard drive, flash memory, or any other suitable non-volatile computer storage device. In some embodiments, memory 410 includes volatile and non-volatile computer storage media.

[0085] In some embodiments, the memory 410 stores data related to HARQ operations. For example, the memory 410 may store V2X communication resources, HARQ processes, HARQ process ID mappings, etc. In some embodiments, the memory 410 also stores program code and related data, such as an operating system or other controller algorithms operating on the remote unit 105.

[0086] In one embodiment, input device 415 may include any known computer input device, including a touch panel, button, keyboard, stylus, microphone, etc. In some embodiments, input device 415 may be integrated with output device 420, for example, as a touch screen or similar touch-sensitive display. In some embodiments, input device 415 includes a touch screen so that text can be input using a virtual keyboard displayed on the touch screen and / or by handwriting on the touch screen. In some embodiments, input device 415 includes two or more different devices, such as a keyboard and a touch panel.

[0087] In one embodiment, the output device 420 is designed to output visual, auditory and / or tactile signals. In some embodiments, the output device 420 includes an electronically controlled display or display device capable of outputting visual data to a user. For example, the output device 420 may include, but is not limited to, an LCD display, an LED display, an OLED display, a projector, or a similar display device capable of outputting images, text, etc. to a user. As another non-limiting example, the output device 420 may include a wearable display that is separate from the rest of the user device device 400, such as a smart watch, smart glasses, a head-up display, etc., but is communicatively coupled to the rest of the user device device 400. In addition, the output device 420 may be a component of a smart phone, a personal digital assistant, a television, a desktop computer, a notebook (laptop) computer, a personal computer, a vehicle dashboard, etc.

[0088] In some embodiments, output device 420 includes one or more speakers for producing sound. For example, output device 420 can produce an auditory alarm or notification (e.g., a buzzer or beep). In some embodiments, output device 420 includes one or more tactile devices for producing vibration, motion or other tactile feedback. In some embodiments, all or part of output device 420 can be integrated with input device 415. For example, input device 415 and output device 420 can form a touch screen or similar touch-sensitive display. In other embodiments, output device 420 can be located near input device 415.

[0089] As described above, the transceiver 425 communicates with one or more network functions of the mobile communication network via one or more access networks. The transceiver 425 operates under the control of the processor 405 to transmit messages, data, and other signals, and also receives messages, data, and other signals. For example, the processor 405 can selectively activate the transceiver (or a portion thereof) at a specific time to send and receive messages.

[0090] The transceiver 425 may include one or more transmitters 430 and one or more receivers 435. Although only one transmitter 430 and one receiver 435 are shown, the user equipment device 400 may have any suitable number of transmitters 430 and receivers 435. In addition, the transmitter 430 and the receiver 435 may be any suitable type of transmitter and receiver. In addition, the transceiver 425 may support at least one network interface 440. Here, the at least one network interface 440 facilitates communication with a RAN node, such as an eNB or a gNB, using, for example, a "Uu" interface (e.g., LTE-Uu for eNB, NR-Uu for gNB). In addition, the at least one network interface 440 may include an interface for communicating with one or more network functions in the mobile core network, such as UPF 141, AMF 143, and / or SMF 145.

[0091] In one embodiment, the transceiver 425 includes a first transmitter / receiver pair for communicating with a mobile communication network on an authorized radio spectrum, and a second transmitter / receiver pair for communicating with a mobile communication network on an unauthorized radio spectrum. In some embodiments, the first transmitter / receiver pair for communicating with a mobile communication network on an authorized radio spectrum and the second transmitter / receiver pair for communicating with a mobile communication network on an unauthorized radio spectrum can be combined into a single transceiver unit, for example, a single chip that performs functions used with both authorized and unauthorized radio spectrums. In some embodiments, the first transmitter / receiver pair and the second transmitter / receiver pair can share one or more hardware components. For example, some transceivers 425, transmitters 430, and receivers 435 can be implemented as physically separated components that access shared hardware resources and / or software resources, such as a network interface 440.

[0092] In various embodiments, one or more transmitters 430 and / or one or more receivers 435 may be implemented and / or integrated into a single hardware component, such as a multi-transceiver chip, a system on chip, an application-specific integrated circuit (“ASIC”), or other types of hardware components. In some embodiments, one or more transmitters 430 and / or one or more receivers 435 may be implemented and / or integrated into a multi-chip module. In some embodiments, other components such as a network interface 440 or other hardware components / circuits may be integrated into a single chip with any number of transmitters 430 and / or receivers 435. In such embodiments, the transmitter 430 and the receiver 435 may be logically configured as a transceiver 425 using one or more common control signals, or as modular transmitters 430 and receivers 435 implemented in the same hardware chip or multi-chip module. In some embodiments, the transceiver 425 may implement a 3GPP modem (e.g., for communication via an NR or LTE access network) and a non-3GPP modem (e.g., for communication via Wi-Fi or other non-3GPP access networks).

[0093] Figure 5 A base station apparatus 500 is depicted that can be used to protect user identities and credentials according to an embodiment of the present disclosure. In various embodiments, the base station apparatus 500 is used to implement one or more of the above solutions. The base station apparatus 500 is an embodiment of the AMF as described above. In addition, the base station apparatus 500 may include a processor 505, a memory 510, an input device 515, an output device 520, and a transceiver 525. In some embodiments, the input device 515 and the output device 520 are combined into a single device, such as a touch screen. In some embodiments, the base station apparatus 500 may not include any input device 515 and / or output device 520. In various embodiments, the base station apparatus 500 may include one or more of the processor 505, the memory 510, and the transceiver 525, and may not include the input device 515 and / or the output device 520.

[0094] In one embodiment, the processor 505 may include any known controller capable of executing computer-readable instructions and / or capable of performing logical operations. For example, the processor 505 may be a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, an FPGA, or a similar programmable controller. In some embodiments, the processor 505 executes instructions stored in the memory 510 to perform the methods and routines described herein. The processor 505 is communicatively coupled to the memory 510, the input device 515, the output device 520, and the transceiver 525.

[0095] In various embodiments, the processor 505 controls the base station device 500 to implement the above-mentioned RAN node behavior. For example, the processor 505 can control the transceiver 525 to send a SL grant to the Tx UE for data transmission using SL resources, and the SL grant has a first HARQ process identifier. In the case where the SL grant for data transmission schedules a PUCCH resource for HARQ feedback corresponding to the first HARQ process identifier, the transmitter 525 receives HARQ feedback for the first HARQ process corresponding to the SL data transmission.

[0096] In one embodiment, memory 510 is a computer-readable storage medium. In some embodiments, memory 510 includes volatile computer storage media. For example, memory 510 may include RAM including dynamic RAM ("DRAM"), synchronous dynamic RAM ("SDRAM"), and / or static RAM ("SRAM"). In some embodiments, memory 510 includes non-volatile computer storage media. For example, memory 510 may include a hard drive, flash memory, or any other suitable non-volatile computer storage device. In some embodiments, memory 510 includes volatile and non-volatile computer storage media.

[0097] In some embodiments, the memory 510 stores data related to the sidelink HARQ operation. For example, the memory 510 may store V2X communication resources, HARQ process ID, HARQ configuration, etc. In some embodiments, the memory 510 also stores program code and related data, such as an operating system or other controller algorithm operating on the base station device 500.

[0098] In one embodiment, input device 515 may include any known computer input device, including a touch panel, button, keyboard, stylus, microphone, etc. In some embodiments, input device 515 may be integrated with output device 520, for example, as a touch screen or similar touch-sensitive display. In some embodiments, input device 515 includes a touch screen so that text can be input using a virtual keyboard displayed on the touch screen and / or by handwriting on the touch screen. In some embodiments, input device 515 includes two or more different devices, such as a keyboard and a touch panel.

[0099] In one embodiment, the output device 520 is designed to output visual, auditory and / or tactile signals. In some embodiments, the output device 520 includes an electronically controlled display or display device capable of outputting visual data to a user. For example, the output device 520 may include, but is not limited to, an LCD display, an LED display, an OLED display, a projector, or a similar display device capable of outputting images, text, etc. to a user. As another non-limiting example, the output device 520 may include a wearable display that is separate from the rest of the base station device 500, such as a smart watch, smart glasses, a head-up display, etc., but is communicatively coupled to the rest of the base station device 500. In addition, the output device 520 may be a component of a smart phone, a personal digital assistant, a television, a desktop computer, a notebook (laptop) computer, a personal computer, a vehicle dashboard, etc.

[0100] In some embodiments, output device 520 includes one or more speakers for producing sound. For example, output device 520 can produce an auditory alarm or notification (e.g., a buzzer or beep). In some embodiments, output device 520 includes one or more tactile devices for producing vibration, motion or other tactile feedback. In some embodiments, all or part of output device 520 can be integrated with input device 515. For example, input device 515 and output device 520 can form a touch screen or similar touch-sensitive display. In other embodiments, output device 520 can be located near input device 515.

[0101] The transceiver 525 includes at least a transmitter 530 and at least one receiver 535. One or more transmitters 530 may be used to send messages to the RAN, as described herein. Similarly, one or more receivers 535 may be used to receive messages from the RAN, as described herein. Although only one transmitter 530 and one receiver 535 are shown, the base station apparatus 500 may have any suitable number of transmitters 530 and receivers 535. In addition, the transmitter 530 and the receiver 525 may be any suitable type of transmitter and receiver.

[0102] In various embodiments, the transceiver 525 supports one or more network interfaces 540 for communicating with UE and / or network functions. For example, the transceiver 525 can support a "Uu" interface with the UE. In addition, the transceiver 525 can support various 5GC service interfaces, such as an N2 interface and / or an N3 interface.

[0103] Figure 6One embodiment of a method 600 for sidelink HARQ operation according to an embodiment of the present disclosure is depicted. In various embodiments, the method 600 is performed by a UE such as the remote unit 105, Tx UE 205, and / or user equipment device 400 described above. In some embodiments, the method 600 is performed by a processor such as a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, an FPGA, etc.

[0104] Method 600 starts and receives a SL grant for data transmission using SL resources (605). Here, the SL grant indicates a first HARQ process identified by a first HARQ process identifier. Method 600 includes selecting a second HARQ process identified by a second HARQ process identifier for data transmission using SL resources (610).

[0105] The method 600 includes transmitting an SCI including the selected second HARQ process identifier (615). The method 600 includes transmitting SL data using the SL resources. The method 600 ends.

[0106] Disclosed herein is a first device for sidelink HARQ operation according to an embodiment of the present disclosure. The first device can be implemented by a UE such as a remote unit 105, a Tx UE 205, and / or a user equipment device 400. The first device includes a transceiver that receives a SL grant for data transmission using SL resources, the SL grant having a first HARQ process identifier. The first device includes a processor that selects a second HARQ process identifier for data transmission using SL resources. Via the transceiver, the processor transmits an SCI including the second HARQ process identifier and transmits SL data using the SL resources.

[0107] In some embodiments, the transmitter sends HARQ feedback for a first HARQ process corresponding to the SL data transmission. In such embodiments, the SL grant indicates physical uplink control channel resources and / or HARQ feedback timing information, wherein the transmission of HARQ feedback for the data transmission of the first HARQ process is based on the SL grant. Note that in other embodiments, the SL grant for the data transmission may indicate the first HARQ process identifier without scheduling PUCCH resources.

[0108] In some embodiments, a first HARQ process identifier received in the SL grant (e.g., received in the DCI) is different from a second HARQ process identifier signaled in the SCI. In some embodiments, the selected HARQ process is associated with a second HARQ process for which there are no pending HARQ retransmissions. In various embodiments, the processor maps the first HARQ process to the second HARQ process, wherein the second HARQ process is selected independently of the first HARQ process.

[0109] In some embodiments, selecting the second HARQ process includes autonomously selecting the second HARQ process from a configured second HARQ process pool. In some embodiments, the configured second HARQ process pool is shared between network-scheduled SL data transmission and UE-scheduled SL data transmission. In some embodiments, the configured second HARQ process pool is shared between unicast SL transmission, multicast SL transmission, and broadcast SL transmission.

[0110] In some embodiments, transmitting SL data using SL resources includes transmitting an SCI including a second HARQ process identifier for a second HARQ process, and the transceiver receives SL HARQ feedback for the second HARQ process from at least one UE. In such an embodiment, the SCI further includes a new data indicator, wherein the receiving UE performs soft combining of the transmitted SL data based at least on the second HARQ process identifier and the new data indicator. In another embodiment, the receiving UE also takes into account the source layer 2 identifier to perform soft combining of the transmitted SL data.

[0111] In some embodiments, transmitting the SL data includes performing a multicast transmission, and receiving SL HARQ feedback corresponding to the SL data transmission includes receiving a negative acknowledgement indication. In such embodiments, the processor retransmits the SL data using a unicast SL retransmission. In some embodiments, the unicast SL retransmission reuses a second HARQ process identifier. In some embodiments, the unicast SL retransmission uses a different redundancy version than the initial SL data transmission.

[0112] Disclosed herein is a first method for sidelink HARQ operation according to an embodiment of the present disclosure. The first method may be performed by a UE such as a remote unit 105, a Tx UE 205, and / or a user equipment 400. The first method includes receiving a SL grant for data transmission using SL resources. Here, the SL grant indicates a first HARQ process identified by a first HARQ process identifier. The first method includes selecting a second HARQ process identified by a second HARQ process identifier for data transmission using SL resources. The first method includes transmitting an SCI including the selected second HARQ process identifier, and transmitting SL data using SL resources.

[0113] In some embodiments, the first method includes transmitting HARQ feedback for a first HARQ process corresponding to a SL data transmission. In such an embodiment, the SL grant indicates physical uplink control channel resources and / or HARQ feedback timing information, wherein the transmission of HARQ feedback for the data transmission of the first HARQ process is based on the SL grant. Note that in other embodiments, the SL grant for the data transmission may indicate the first HARQ process identifier without scheduling PUCCH resources.

[0114] In some embodiments, a first HARQ process identifier received in the SL grant (e.g., received in the DCI) is different from a second HARQ process identifier signaled in the SCI. In some embodiments, the selected HARQ process is associated with a second HARQ process that has no pending HARQ retransmissions. In various embodiments, the first method includes mapping the first HARQ process to the second HARQ process, wherein the second HARQ process is selected independently of the first HARQ process.

[0115] In some embodiments, selecting the second HARQ process includes autonomously selecting the second HARQ process from a configured second HARQ process pool. In some embodiments, the configured second HARQ process pool is shared between network-scheduled SL data transmission and UE-scheduled SL data transmission. In some embodiments, the configured second HARQ process pool is shared between unicast SL transmission, multicast SL transmission, and broadcast SL transmission.

[0116] In some embodiments, transmitting SL data using SL resources includes transmitting an SCI including a second HARQ process identifier for a second HARQ process, and the first method further includes receiving SL HARQ feedback for the second HARQ process from at least one UE. In such an embodiment, the SCI further includes a new data indicator, wherein the receiving UE performs soft combining of the transmitted SL data based at least on the second HARQ process identifier and the new data indicator. In another embodiment, the receiving UE also performs soft combining of the transmitted SL data taking into account a source layer 2 identifier.

[0117] In some embodiments, transmitting the SL data includes performing a multicast transmission, and receiving SL HARQ feedback corresponding to the SL data transmission includes receiving a negative acknowledgement indication. In such embodiments, the processor retransmits the SL data using a unicast SL retransmission. In some embodiments, the unicast SL retransmission reuses a second HARQ process identifier. In some embodiments, the unicast SL retransmission uses a different redundancy version than the initial SL data transmission.

[0118] Embodiments may be practiced in other specific forms. The described embodiments should be considered in all respects only as illustrative and not restrictive. Therefore, the scope of the present invention is indicated by the appended claims rather than the preceding description. All changes falling within the equivalent meaning and scope of the claims should be included within their scope.

Claims

1. A device comprising: Memory; as well as a processor, the processor being coupled to the memory and configured to cause the apparatus to: receiving a sidelink ("SL") grant for transmission of sidelink data using a sidelink resource, the SL grant indicating a first hybrid automatic repeat request ("HARQ") process identified by a first HARQ process identifier; and selecting a second HARQ process identified by a second HARQ process identifier for transmission of the sidelink data using the SL resources, wherein the second HARQ process is selected independently of the first HARQ process in response to a SL grant indicating an initial transmission of the sidelink data, and wherein, in response to a SL grant indicating a retransmission of the sidelink data, selection of the second HARQ process is based on the first HARQ process identifier; transmitting SL control information ("SCI") including the second HARQ process identifier; Using the SL resource to transmit the SL data, The SL grant indicates physical uplink control channel resources and / or HARQ feedback timing information, and the transmission of HARQ feedback for the first HARQ process is based on the SL grant.

2. The apparatus according to claim 1, wherein the processor is further configured to cause the apparatus to: transmit HARQ feedback for the first HARQ process corresponding to the transmission of the SL data using the SL resources.

3. The device according to claim 1, wherein: The first HARQ process identifier received in the SL grant is different from the second HARQ process identifier signaled within the SCI.

4. The device according to claim 1, wherein: Selecting the second HARQ process includes autonomously selecting a second HARQ process from a configured second HARQ process pool.

5. The device according to claim 4, wherein: The configured second HARQ process pool is shared between network-scheduled SL data transmission and UE-scheduled SL data transmission.

6. The device according to claim 4, wherein: The configured second HARQ process pool is shared among unicast SL transmission, multicast SL transmission and broadcast SL transmission.

7. The device according to claim 1, wherein: The selected second HARQ process is associated with a second HARQ process for which there are no pending HARQ retransmissions.

8. The apparatus of claim 1, wherein the processor is further configured to cause the apparatus to: map the first HARQ process to the second HARQ process.

9. The device according to claim 1, wherein: Transmitting the SL data using the SL resources includes transmitting an SCI including the second HARQ process identifier for the second HARQ process, wherein the processor is further configured to cause the device to: receive SL HARQ feedback for the second HARQ process from at least one user equipment device ("UE").

10. The device according to claim 9, in, Transmitting the SL data includes performing an initial multicast transmission, Wherein, receiving SL HARQ feedback includes receiving a negative acknowledgement indication, and The processor is further configured to cause the device to retransmit the SL data using unicast SL retransmission.

11. The device according to claim 10, wherein: The unicast SL retransmission reuses the second HARQ process identifier.

12. The device according to claim 10, wherein: The unicast SL retransmission uses a different redundancy version than the initial multicast transmission.

13. A method of a remote unit, comprising: receiving a sidelink ("SL") grant for transmission of sidelink data using a sidelink resource, the SL grant indicating a hybrid automatic repeat request ("HARQ") process identified by a first HARQ process identifier; and selecting a second HARQ process identified by a second HARQ process identifier for transmission of the sidelink data using the SL resources, wherein the second HARQ process is selected independently of the first HARQ process in response to a SL grant indicating an initial transmission of the sidelink data, wherein the selection of the second HARQ process is based on the first HARQ process identifier in response to a SL grant indicating a retransmission of the sidelink data; transmitting SL control information ("SCI") including the selected second HARQ process identifier; and using the SL resources to transmit the side link data, The SL grant indicates physical uplink control channel resources and / or HARQ feedback timing information, and the transmission of HARQ feedback for the first HARQ process is based on the SL grant.

14. The method according to claim 13, wherein: The first HARQ process identifier received in the SL grant is different from the second HARQ process identifier signaled within the SCI.

15. The method according to claim 13, wherein: Selecting the second HARQ process includes autonomously selecting a second HARQ process from a configured second HARQ process pool.

16. The method according to claim 15, wherein: The configured second HARQ process pool is shared between network-scheduled SL data transmission and UE-scheduled SL data transmission.

17. The method according to claim 15, wherein: The configured second HARQ process pool is shared among unicast SL transmission, multicast SL transmission and broadcast SL transmission.

18. The method according to claim 13, wherein: Transmitting the SL data using the SL resources includes transmitting an SCI including the second HARQ process identifier for the second HARQ process, the method further including receiving SL HARQ feedback for the second HARQ process from at least one user equipment device ("UE").

19. The method according to claim 18, wherein: The SCI further includes a new data indicator, wherein the receiving UE performs soft combining of the transmitted SL data based at least on the second HARQ process identifier and the new data indicator.

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