Select retransmission mode based on minimum duration

Abstract

This invention discloses devices, methods, and systems for supporting hybrid BR and HFBT. One device (600) includes: a processor (605) providing a physical (“PHY”) layer (255) and a media access control (“MAC”) layer (260); and a transceiver (625) communicating on a sidelink channel. The processor (605) determines (805) a minimum duration between a first resource for HARQ transmission of a transport block (“TB”) and a second resource for HARQ transmission of the TB. Here, the minimum duration includes the sum of: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of the TB, and a third time for retransmitting the TB. The processor (605) selects (810) a retransmission mode based on the minimum duration and selects (815) sidelink resources for retransmission of the TB based on the selected retransmission mode.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 024,425, filed May 13, 2020, entitled “Mixed Blind Retransmission and HARQ Feedback-Based Transmission” by Karthikeyan Ganesan, Prateek Basu Mallick, Joachim Loehr, and Ravi Kuchibhotla, which is incorporated herein by reference. This application claims priority to International Patent Application No. PCT / IB2021 / 053175, filed April 16, 2021, entitled “Combined Blind and Feedback Based Repeatation” by Prateek Basu Mallick, Karthikeyan Ganesan, Joachim Loehr, and Ravi Kuchibhotla, which is incorporated herein by reference. Technical Field

[0003] The subject matter disclosed herein generally relates to wireless communication, and more specifically, to a hybrid of blind retransmission and HARQ-based feedback-supported transmission. Background Technology

[0004] In some wireless communication systems that support sidelink (“SL”) communication, the transmitting user equipment (“UE”) may seek Hybrid Automatic Repeat Request (“HARQ”) feedback to determine whether further retransmission is required. Summary of the Invention

[0005] A process for supporting a hybrid approach of blind retransmission (“BR”) and HARQ-based feedback transmission (“HFBT”) is disclosed. The process may be implemented by an apparatus, system, method, or computer program product.

[0006] A method for a user equipment (“UE”) includes determining a minimum duration between a first resource for a Hybrid Automatic Repeat Request (“HARQ”) transmission of a transport block (“TB”) and a second resource for a HARQ transmission of the TB. Here, the minimum duration includes the sum of: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of the TB, and a third time for retransmitting the TB. The method includes: selecting a retransmission mode based on the minimum duration, wherein the retransmission mode includes one of a blind retransmission (“BR”) mode and a HARQ feedback-based transmission (“HFBT”) mode; and selecting sidelink resources for the retransmission of the TB based on the selected retransmission mode. Attached Figure Description

[0007] A more specific description of the embodiments briefly described above will be presented by referring to specific embodiments illustrated in the accompanying drawings. It should be understood that these drawings depict only some embodiments and should therefore not be considered limiting; the embodiments will be described and explained in additional particular detail using the accompanying drawings, in which:

[0008] Figure 1 This is a schematic block diagram illustrating one embodiment of a wireless communication system that supports a hybrid BR and HFBT.

[0009] Figure 2A This is a block diagram illustrating one embodiment of the 5G New Radio (“NR”) protocol stack;

[0010] Figure 2B This is a block diagram illustrating one embodiment of the PC5 protocol stack;

[0011] Figure 3 This is a diagram illustrating one embodiment of a process for sensing and resource selection (reselection);

[0012] Figure 4A This is a diagram illustrating one embodiment of the timeline of the sensing and resource selection (reselection) process;

[0013] Figure 4B This is a diagram illustrating an embodiment of a timeline for a sensing and resource selection (reselection) process with reassessment;

[0014] Figure 5 This is a diagram illustrating one embodiment of transmission based on hybrid feedback;

[0015] Figure 6 This is a diagram illustrating one embodiment of a user equipment device that can be used to support a hybrid BR and HFBT setup;

[0016] Figure 7This is a diagram illustrating one embodiment of a network device that can be used to support a hybrid BR and HFBT setup;

[0017] Figure 8 This is a flowchart illustrating an embodiment of a first method for supporting the mixing of BR and HFBT. Detailed Implementation

[0018] Those skilled in the art will understand that aspects of the embodiments may be embodied as systems, devices, methods, or program products. Therefore, embodiments may take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, microcode, etc.), or embodiments combining software and hardware aspects.

[0019] For example, the disclosed embodiments may be implemented as hardware circuitry (including custom very large-scale integration (“VLSI”) circuitry or gate arrays), off-the-shelf semiconductors (e.g., 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, or the like. 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 objects, procedures, or functions.

[0020] Furthermore, embodiments may take the form of a program product embodied in one or more computer-readable storage devices storing machine-readable code, computer-readable code, and / or program code (hereinafter referred to as code). The storage device may be tangible, non-transitory, and / or non-transferable. The storage device may not embody signals. In certain embodiments, the storage device uses only signals to access the code.

[0021] Any combination of one or more computer-readable media may be used. The computer-readable media may be a computer-readable storage medium. The computer-readable storage medium may be a storage device for storing code. The storage device may be, for example (but not limited to), an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, device, or apparatus, or any suitable combination of the foregoing.

[0022] Further specific examples of storage devices (a non-exhaustive list) will include the following: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (“RAM”), read-only memory (“ROM”), erasable programmable read-only memory (“EPROM” or flash memory), portable optical disc read-only memory (“CD-ROM”), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium that may contain or store programs for use by or in conjunction with an instruction execution system, device, or apparatus.

[0023] The code used to implement the operations of the embodiments may be written in any number of lines and may include one or more of the following programming languages: object-oriented programming languages ​​(e.g., Python, Ruby, Java, Smalltalk, C++, or similar), conventional procedural programming languages ​​(e.g., the "C" programming language or similar), and / or machine languages ​​(e.g., assembly language). The code may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including local area networks ("LANs"), wireless LANs ("WLANs"), or wide area networks ("WANs"), or may be connected to an external computer (e.g., via the Internet through an Internet service provider ("ISP").

[0024] Furthermore, the features, structures, or characteristics described in the embodiments can be combined in any suitable manner. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments, including examples of programming, software modules, user selection, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc. However, those skilled in the art will recognize that the embodiments can be practiced without one or more of these specific details or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail so as not to obscure aspects of the embodiments.

[0025] Throughout this specification, references to "an embodiment," "embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Therefore, unless expressly specified otherwise, the phrases "in an embodiment," "in an embodiment," and similar language appearing throughout this specification may (but not necessarily) refer to the same embodiment, but rather mean "one or more, but not all, embodiments." Unless expressly specified otherwise, the terms "comprising," "including," "having," and variations thereof mean "comprising (but not limited to)." Unless expressly specified otherwise, the list of items does not imply that any or all items are mutually exclusive. Unless expressly specified otherwise, the terms "a" and "described" also refer to "one or more."

[0026] As used herein, a list containing the conjunction “and / or” includes any single item in the list or a 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 of…” includes any single item in the list or a 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, excluding combinations of A, B, and C. As used herein, “a member selected from the group consisting of A, B, and C” includes one and only one of A, B, or C, excluding combinations of A, B, and C. As used in this article, “selecting members of a group consisting of A, B, and C and their combinations” includes only A, only B, only C, combinations of A and B, combinations of B and C, combinations of A and C, or combinations of A, B, and C.

[0027] Aspects of the embodiments are described below with reference to schematic flowcharts and / or schematic block diagrams of methods, apparatus, systems, and program products according to the embodiments. It should be understood that each block of the schematic flowcharts and / or schematic block diagrams, and combinations of blocks in the schematic flowcharts and / or schematic block diagrams, can be implemented by code. This code can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine, such that instructions executable by the processor of the computer or other programmable data processing apparatus create components for implementing the functions / actions specified in the flowcharts and / or block diagrams.

[0028] The code may also be stored in a storage device, which may instruct a computer, other programmable data processing equipment or other device to operate in a particular manner, such that the instructions stored in the storage device produce an article of writing containing instructions that implement the functions / actions specified in the flowchart and / or block diagram.

[0029] The code may also be loaded onto a computer, other programmable data processing equipment or other device to cause a series of operational steps to be performed on the computer, other programmable equipment or other device to produce a computer-implemented process, such that the code executing on the computer or other programmable device provides a process for implementing the functions / actions specified in the flowchart and / or block diagram.

[0030] The flowcharts and / or block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of the device, system, method, and program products according to various embodiments. In this regard, each block in the flowcharts and / or block diagrams may represent a code module, segment, or portion containing one or more executable instructions for implementing a specified logical function.

[0031] It should also be noted that in some alternative implementations, the functions described in the boxes may not occur in the order shown in the figures. For example, two boxes shown consecutively may actually be executed substantially concurrently, or the boxes may sometimes be executed in reverse order, depending on the functionality involved. Other steps and methods that are functionally, logically, or effectically equivalent to one or more boxes or portions thereof in the illustration figures are conceivable.

[0032] While various arrow and line types may be used in flowcharts and / or block diagrams, they should not be construed as limiting the scope of the corresponding embodiments. In fact, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For example, an arrow may indicate a wait or monitoring period of unspecified duration between enumeration steps in a depicted embodiment. It should also be noted that each block in the block diagram and / or flowchart description, and combinations of blocks in the block diagram and / or flowchart, may be implemented by a system based on dedicated hardware or a combination of dedicated hardware and code that performs the specified function or action.

[0033] The description of the elements in each figure can be referenced to the elements in the previous figures. The same numbers refer to the same elements in all figures, including alternative embodiments of the same elements.

[0034] Generally, this disclosure describes systems, methods, and apparatus for supporting a hybrid BR and HFBT architecture. In NR V2X, the transmitting UE can choose to seek HARQ feedback to determine whether further retransmission is needed, or it can perform a specific number of blind retransmissions, i.e., without seeking HARQ feedback for a particular transmission.

[0035] In R16 sidelink (“SL”) V2X, another transmission (retransmission) mode may exist that combines blind retransmission with feedback-based retransmission for the same TB to achieve certain sidelink performance benefits. While it is possible to dynamically enable / disable (seek / not seek) SL HARQ feedback in the SL PHY using sidelink control information, this introduces several problems. For example, the MAC may be unsure why it did not receive feedback when it was expected and may make incorrect decisions (e.g., inferring a retransmission); or the MAC may receive feedback that is not expected because feedback was not sought. Furthermore, the RRC configuration for enabling / disabling HARQ feedback per logical channel is not intended for this hybrid of HARQ feedback-based retransmissions.

[0036] This disclosure provides solutions to support a hybrid approach of blind retransmission and HARQ-based transmission for TBs from resource allocation mode 2, and vice versa, for example, by taking into account the following factors:

[0037] • The minimum time gap between consecutive resources that meets the HARQ round-trip time (“RTT”) requirement of TB.

[0038] • A resource pool with Physical Side Link Feedback Channel (“PSFCH”) resources, and

[0039] • Resource pools without PSFCH resources

[0040] In some embodiments, the Side Link Control Information (“SCI”) may carry a HARQ Feedback Request flag, thereby allowing a mix of BR and HFBT for a TB. In some embodiments, the UE may initiate blind retransmission to obtain a minimum level of link budget and conflict resolution and continue feedback-based retransmissions for fine-tuning resource usage.

[0041] Regarding HARQ feedback, when PSFCH resources are (pre)configured in the resource pool, a hybrid of blind retransmission and feedback-based retransmission is supported, depending on the UE implementation scheme, and is subject to the total count of the maximum number of transmissions (retransmissions) and ordered HARQ operations.

[0042] In that case, it is important to clarify the following: Physical Side Link Shared Channel (“PSSCH”) resources are acknowledged. The PSFCH will be sent in response to the PSFCH scheduled by the SCI carrying a feedback request, not a future reserved PSFCH. Ordered or out-of-order operation: In Uu, due to the complexity of the UE implementation and the complexity of the HARQ process, retransmission for the same TB is not allowed before feedback to the TB. The same principle should apply to SL.

[0043] Careful consideration must be given to the significant differences that arise with the on / off state of dynamic HARQ feedback when deciding whether or not to apply out-of-order (OO) HARQ constraints. Consider the following scenarios: 1) B2B (Blind to Blind). In this case, no OO HARQ constraint is required. 2) B2F (Blind to Feedback). In this case, no OO HARQ constraint is required either. 3) F2F (Feedback to Feedback). In this case, typical UE implementation assumptions and reasonable specification complexity necessitate OO HARQ constraints. 4) F2B (Feedback to Blind). In this case, typical UE implementation assumptions and reasonable specification complexity necessitate OO HARQ constraints.

[0044] In various embodiments, the new higher-layer parameter notifies the Tx UE of the minimum time interval between consecutive resources based on HARQ RTT, the RP with PSFCH and the RP without PSFCH resources during the initial resource selection triggering of Mode 2.

[0045] In some embodiments, new resource selection (reselection) triggers a notification to the UE to reselect resources before m-T3 or during the resource reassessment step at m-T3, based on the minimum HARQ RTT time interval, the RP with PSFCH, and the RP without PSFCH resources. The Tx UE can be configured with one or more conditions to switch from blind retransmission to HARQ feedback-based retransmission or vice versa—based on CSI reports, CBR measurements, remaining PDB, etc.

[0046] In some embodiments, the MAC layer will further instruct the PHY when to signal in the SCI whether HARQ feedback is enabled for the transmission and the HARQ feedback option. Deciding whether and when to switch from BR to HARQ feedback-enabled mode in the MAC layer allows for some simple implementations because the HARQ protocol is running at the MAC layer; for example, the MAC layer expects feedback from the PHY when HARQ feedback is enabled. Furthermore, HARQ protocol aspects (e.g., decisions on whether to transmit a new TB or perform further retransmissions of the TB) are also made in the MAC layer based on PSFCH feedback.

[0047] Based on packet transmission priority, TB retransmission count, remaining PDB, MCR, and CSI reports, the number of reserved resources not completed when the initial resource selection (reselection) is triggered is limited. Transmission on reserved resources is conditional on the priority value of the current packet and the priority value of the reserved resource; otherwise, it is based on the CBR value, CSI reports, etc.

[0048] Figure 1 A wireless communication system 100 for supporting a hybrid BR and HFBT according to embodiments of the present disclosure is depicted. 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 basic unit 121, and the remote unit 105 communicates with the basic unit 121 using a wireless communication link 123. Even Figure 1 The system depicts a specific number of remote units 105, basic units 121, wireless communication links 123, RAN 120, and mobile core network 140, but those skilled in the art will recognize that the wireless communication system 100 may include any number of remote units 105, basic units 121, wireless communication links 123, RAN 120, and mobile core network 140.

[0049] In one implementation, RAN 120 conforms to the 5G system specified in the 3rd Generation Partnership Project (“3GPP”) specifications. For example, RAN 120 may be a next-generation RAN (“NG-RAN”) implementing, for example, NR RAT and / or Long Term Evolution (“LTE”) RAT. In another instance, RAN 120 may contain non-3GPP RATs (e.g., Alternatively, it may conform to the Institute of Electrical and Electronics Engineers (“IEEE”) 802.11 series of WLANs. In another embodiment, RAN 120 conforms to the LTE system specified in the 3GPP specification. However, more generally, the wireless communication system 100 may implement other open or proprietary communication networks, such as WiMAX or the IEEE 802.16 series of standards and other networks. This disclosure is not intended to limit implementation to any particular wireless communication system architecture or protocol.

[0050] In one embodiment, remote unit 105 may include a computing device, such as a desktop computer, laptop computer, personal digital assistant (“PDA”), tablet computer, smartphone, smart TV (e.g., a TV connected to the Internet), smart appliance (e.g., an appliance connected to the Internet), set-top box, game console, security system (including surveillance cameras), in-vehicle computer, network device (e.g., router, switch, modem), or the like. In some embodiments, remote unit 105 includes a wearable device, such as a smartwatch, fitness tracker, optical head-mounted display, or the like. Furthermore, remote unit 105 may be referred to as UE, user unit, mobile device, mobile station, user, terminal, mobile terminal, fixed terminal, user station, user terminal, wireless transmit / receive unit (“WTRU”), apparatus, or other terms used in the art. In various embodiments, remote unit 105 includes a user identity and / or identification module (“SIM”) and mobile equipment (“ME”) that provide mobile terminal functions (e.g., radio transmission, handover, voice encoding and decoding, error detection and correction, signaling, and access to a SIM). In some embodiments, the remote unit 105 may include terminal equipment (“TE”) and / or be embedded in an appliance or device (e.g., a computing device, as described above).

[0051] Remote unit 105 can communicate directly with one or more of the base units 121 in RAN 120 via uplink (“UL”) and downlink (“DL”) communication signals. Additionally, the UL and DL communication signals can be carried via wireless communication link 123. Here, RAN 120 is an intermediate network providing remote unit 105 with access to the mobile core network 140. Furthermore, one remote unit 105 can communicate directly with another remote unit 105 using sidelink (“SL”) communication signal 113 (i.e., without relaying through base unit 121). In some embodiments, SL communication uses a PC5 interface.

[0052] In some embodiments, remote unit 105 communicates with application server 151 via a network connection to mobile core network 140. For example, application 107 in remote unit 105 (e.g., a web browser, media client, telephone, and / or Internet Protocol Voice Telephony (“VoIP”) application) can trigger remote unit 105 to establish a Protocol Data Unit (“PDU”) session (or other data connection) with mobile core network 140 via RAN 120. Mobile core network 140 then uses the PDU session to relay services between remote unit 105 and application server 151 in packet data network 150. The PDU session represents a logical connection between remote unit 105 and user plane function (“UPF”) 141.

[0053] To establish a PDU session (or PDN connection), remote unit 105 must register with mobile core network 140 (also referred to as "attached to mobile core network" in the context of fourth-generation ("4G") systems). Note that remote unit 105 may establish one or more PDU sessions (or other data connections) with mobile core network 140. Therefore, remote unit 105 may have at least one PDU session for communicating with packet data network 150. Remote unit 105 may establish additional PDU sessions to communicate with other data networks and / or other communication peers.

[0054] In the context of a 5G system (“5GS”), the term “PDU session” refers to a data connection that provides end-to-end (“E2E”) user plane (“UP”) connectivity between a remote unit 105 and a specific data network (“DN”) via UPF 141. A PDU session supports one or more Quality of Service (“QoS”) streams. In some embodiments, a one-to-one mapping may exist between QoS streams and QoS profiles, such that all packets belonging to a particular QoS stream have the same 5G QoS identifier (“5QI”).

[0055] In the context of a 4G / LTE system, such as an Evolved Packet System (“EPS”), a Packet Data Network (“PDN”) connection (also known as an EPS session) provides end-to-end connectivity between the remote unit and the PDN. The PDN connectivity process establishes an EPS bearer, i.e., a tunnel between the remote unit 105 and the packet gateway (“PGW”, not shown) in the mobile core network 140. In some embodiments, a one-to-one mapping may exist between the EPS bearer and a QoS profile, such that all packets belonging to a particular EPS bearer have the same QoS Class Identifier (“QCI”).

[0056] Basic unit 121 may be distributed across a geographical area. In some embodiments, basic unit 121 may also be referred to as an access terminal, access point, base station, base station, node-B (“NB”), evolved node B (abbreviated as eNodeB or “eNB”, also referred to as an evolved universal terrestrial radio access network (“E-UTRAN”) node B), 5G / NR node B (“gNB”), home node-B, relay node, RAN node, or referred to by any other terminology used in the art. Basic unit 121 typically comprises a portion of a RAN (e.g., RAN 120) communicatively coupled to one or more controllers corresponding to basic unit 121. These and other elements of the radio access network are not described but are generally well known to those skilled in the art. Basic unit 121 is connected to mobile core network 140 via RAN 120.

[0057] Basic unit 121 can serve several remote units 105 within a service area (e.g., a cell or cell sector) via wireless communication link 123. Basic unit 121 can communicate directly with one or more of the remote units 105 via communication signals. Typically, basic unit 121 transmits DL communication signals to serve the remote units 105 in the time, frequency, and / or spatial domains. Furthermore, DL communication signals can be carried via wireless communication link 123. Wireless communication link 123 can be any suitable carrier in licensed or unlicensed radio spectrum. Wireless communication link 123 facilitates communication between one or more of the remote units 105 and one or more of the basic unit 121. Note that during NR operation (also known as "NR-U") on shared spectrum, basic unit 121 communicates with remote units 105 via unlicensed radio spectrum.

[0058] In one embodiment, the mobile core network 140 is a 5GC or evolved packet core (“EPC”) that may be coupled to a packet data network 150, such as the Internet, private data networks, and other data networks. The remote unit 105 may have a subscription or other account to the mobile core network 140. Each mobile core network 140 belongs to a single Public Land Mobile Network (“PLMN”). This disclosure is not intended to limit implementation to any particular wireless communication system architecture or protocol.

[0059] Mobile core network 140 includes several network functions (“NFs”). As depicted, mobile core network 140 includes at least one UPF 141. Mobile core network 140 also includes multiple control plane (“CP”) functions, including (but not limited to) Access and Mobility Management Functions (“AMF”) 143, Session Management Functions (“SMF”) 145, Policy Control Functions (“PCF”) 147, and Unified Data Management Functions (“UDM”) serving RAN 120. In some embodiments, the UDM is co-located with the User Data Repository (“UDR”) and is depicted as a combined entity “UDM / UDR” 149. In various embodiments, mobile core network 140 may also include an Authentication Server Function (“AUSF”), a Network Repository Function (“NRF”) (used by various NFs to discover and communicate with each other via an Application Programming Interface (“API”), or other NFs defined for 5GC. In some embodiments, mobile core network 140 may include an Authentication, Authorization, and Accounting (“AAA”) server.

[0060] In various embodiments, the mobile core network 140 supports different types of mobile data connections and different types of network slices, wherein each mobile data connection utilizes a specific network slice. Here, a "network slice" refers to a portion of the mobile core network 140 optimized for a specific type of service or communication service. Network examples may be identified by Single Network Slice Selection Assistance Information ("S-NSSAI"), while a set of network slices authorized for use by the remote unit 105 is identified by Network Slice Selection Assistance Information ("NSSAI"). Here, "NSSAI" refers to a vector value containing one or more S-NSSAI values. In some embodiments, various network slices may contain individual examples of 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 Different network slices are not shown, but their support is assumed.

[0061] although Figure 1While a specific number and type of network functions are described, those skilled in the art will recognize that the mobile core network 140 may contain any number and type of network functions. Furthermore, in the LTE variant of the mobile core network 140 where the EPC is an EPC, the described network functions can be replaced by appropriate EPC entities (e.g., Mobility Management Entity (“MME”), Serving Gateway (“SGW”), PGW, Home Subscriber Server (“HSS”), and the like). For example, AMF 143 may be mapped to the MME, SMF 145 may be mapped to the control plane portion of the PGW and / or to the MME, UPF 141 may be mapped to the SGW and the user plane portion of the PGW, UDM / UDR 149 may be mapped to the HSS, etc.

[0062] In various embodiments, remote units 105 can communicate directly with each other using SL communication signals 113 (e.g., device-to-device communication). In one embodiment, the SL communication signals support V2X (vehicle-to-everything) communication. Remote units 105 may have different V2X communication resources for different V2X modes. V2X resource allocation mode 1 refers to NR-based SL communication over network scheduling resources. In this mode, SL resources are allocated by basic unit 121, for example, for remote units 105 within range.

[0063] In contrast, V2X resource allocation mode 2 corresponds to NR-based SL communication using UE-scheduled resources. This mode is characterized by remote unit 105 autonomously selecting resources based on a sensing process. In various embodiments, sensing occurs within a specific (e.g., pre-configured) resource pool. The remote unit 105, with the SL data and / or control signaling to be transmitted, then selects resources for transmission and retransmission, provided the resources are not being used by other remote units 105 with higher priority services.

[0064] In some embodiments, remote unit 105 may hold resources for an appropriate amount of time until a reselection event is triggered. Resources may be reserved by remote unit 105 for various purposes, such as blind retransmission and HARQ-based retransmission, wherein information regarding resource reservation is indicated in sidelink control information (“SCI”).

[0065] In some embodiments, when UL transmissions conflict with SL transmissions (e.g., SL synchronization signal block (“SSB”) transmissions) (i.e., they overlap in the time domain), remote unit 105 prioritizes UL transmissions over SL transmissions.

[0066] Although Figure 1The components of the 5G RAN and 5G core network are described, but the described embodiments for supporting BR and HFBT hybridization are applicable to other types of communication networks and RATs, including IEEE 802.11 variants, Global System for Mobile Communications (“GSM”, i.e., 2G digital cellular network), General Packet Radio Service (“GPRS”), General Mobile Telecommunications System (“UMTS”), LTE variants, CDMA 2000, Bluetooth, ZigBee, Sigfox and the like.

[0067] In the following description, the term "RAN node" is used for a base station, but it can be replaced by any other radio access node (e.g., gNB, eNB, base station ("BS"), access point ("AP"), etc.). Furthermore, the operation is primarily described in the context of 5G NR. However, the proposed solution / method is also applicable to other mobile communication systems that support a hybrid BR and HFBT architecture.

[0068] Figure 2A An NR protocol stack 200 according to an embodiment of this disclosure is depicted. Although Figure 2A The illustration shows UE 205, RAN node 207, and AMF 209 in a 5G core network (“5GC”), but these represent a group of remote units 105 interacting with basic unit 121 and mobile core network 140. As depicted, protocol stack 200 includes user plane protocol stack 201 and control plane protocol stack 203. User plane protocol stack 201 includes physical (“PHY”) layer 210, media access control (“MAC”) layer 215, radio link control (“RLC”) layer 220, packet data convergence protocol (“PDCP”) layer 225, and service data adaptation protocol (“SDAP”) layer 230. Control plane protocol stack 203 includes physical layer 210, MAC layer 215, RLC layer 220, and PDCP layer 225. Control plane protocol stack 203 also includes radio resource control (“RRC”) layer 235 and non-access layer (“NAS”) layer 240.

[0069] The AS protocol stack of control plane protocol stack 203 consists of at least RRC, PDCP, RLC, and MAC layers, and a physical layer. The AS protocol stack of user plane protocol stack 201 consists of at least SDAP, PDCP, RLC, and MAC layers, and a physical layer. Layer 2 (“L2”) is divided into SDAP, PDCP, RLC, and MAC layers. Layer 3 (“L3”) includes the RRC layer 235 and NAS layer 240 of the control plane and includes, for example, the Internet Protocol (“IP”) layer or PDU layer (note the depiction) of the user plane. L1 and L2 are referred to as “lower layers”, such as PUCCH / PUSCH or MAC control elements (“CE”), while L3 and above (such as IP layers, transport layers (e.g., TCP, UDP, DCCP, SCTP), application layers (e.g., HTTP, SIP, SMTP, POP, etc.)) are referred to as “higher layers” or “upper layers”. As an example, “upper-layer signaling” may refer to signaling exchange at RRC layer 235.

[0070] Physical layer 210 provides the transport channel to MAC layer 215. MAC layer 215 provides the logical channel to RLC layer 220. RLC layer 220 provides the RLC channel to PDCP layer 225. PDCP layer 225 provides radio bearers to SDAP layer 230 and / or RRC layer 235. SDAP layer 230 provides QoS flows to 5GC. RRC layer 235 provides the addition, modification, and release of carrier aggregation and / or dual connectivity. RRC layer 235 also manages the establishment, configuration, maintenance, and release of signaling radio bearers (“SRB”) and data radio bearers (“DRB”). In some embodiments, the RRC entity is used for the detection and recovery from radio link failures.

[0071] In 5GC, NAS layer 240 is located between UE 205 and AMF 209. NAS messages are transparently transmitted through the RAN. NAS layer 240 is used to manage the establishment of communication sessions and to maintain continuous communication with UE 205 as UE 205 moves between different cells in the RAN. In contrast, AS layer is located between UE 205 and the RAN and carries information via the radio portion of the network. Although Figure 2A It is not described in the text, but the IP layer exists above the NAS layer 240, the transport layer exists above the IP layer, and the application layer exists above the transport layer.

[0072] Figure 2B A PC5 protocol stack 250 according to an embodiment of this disclosure is depicted. Although Figure 2BThe transmitter (“Tx”) UE251 and receiver (“Rx”) UE253 are shown, but these represent a group of UEs communicating peer-to-peer via PC5, and other embodiments may involve different UEs. As depicted, the PC5 protocol stack includes a PHY layer 255, a MAC layer 260, an RLC layer 265, a PDCP layer 270, and an RRC and SDAP layer (depicted as a combined element “RRC / SDAP” 275) for the control plane and user plane, respectively.

[0073] The AS protocol stack of the control plane in the PC5 interface consists of at least RRC, PDCP, RLC, MAC, and PHY layers. The AS protocol stack of the user plane in the PC5 interface consists of at least SDAP, PDCP, RLC, MAC, and PHY layers. L2 is divided into SDAP, PDCP, RLC, and MAC layers. L3 includes the RRC layer of the control plane and, for example, the IP layer of the user plane. Similar to the NR protocol stack, in the PC5 protocol stack, L1 and L2 are called "lower layers," while L3 and above (e.g., transport layer, V2X layer, application layer) are called "higher layers" or "upper layers."

[0074] In some embodiments, a new RRC configuration exists that enables some logical channels (“LCH”) to operate in a hybrid feedback mode (e.g., a mode with a combination of blind retransmission and feedback-based retransmission) or to use a feedbackless mode by using new code points in the RRC LCHSL HARQ configuration. Feedbackless mode transmissions (e.g., blind retransmissions) can be performed for a predetermined number or a variable number of transmissions.

[0075] In some embodiments, the transmitter may switch to and remain in a specific mode with HARQ feedback. In one embodiment, the switching occurs after several (x') transmissions, where x' may be pre-configured or determined using various methods (e.g., those described herein). The variability of the number of blind retransmissions may be based on changing channel conditions, etc.

[0076] In various embodiments, an LCH operating in hybrid feedback mode may be considered for resource allocation along with other logical channels that have HARQ feedback enabled or disabled. In some embodiments, an LCH operating in hybrid feedback mode may be considered for resource allocation only with other logical channels having the same HARQ feedback mode (e.g., with logical channels in hybrid feedback mode).

[0077] In some embodiments, there may not be a new RRC configuration that allows some LCHs to operate in a hybrid feedback mode (or equivalent no-feedback mode). In such embodiments, only two cases occur: 1) The TB contains only LCHs with feedback enabled, wherein a certain number (e.g., x') of BRs are performed, followed by one or more HARQ-based feedback-based transmissions (retransmissions); 2) The TB contains only LCHs with feedback disabled: in one embodiment, only BRs may be performed; in another embodiment, a certain number of blind retransmissions may be performed, followed by one or more HARQ-based feedback-based transmissions (retransmissions).

[0078] In various embodiments, if the requested feedback option is HARQ feedback option 2, then the Tx UE counts the number of NACK and / or discontinuous transmission (“DTX”) feedbacks (e.g., total_failures). If the number total_failures exceeds a threshold (e.g., threshold_total_failures), then the Tx UE performs 'x' blind retransmissions.

[0079] In some embodiments, the hybrid HARQ operation mode is implemented as HARQ-enabled transmission, where the UE autonomously triggers retransmissions without receiving HARQ feedback from the Rx UE.

[0080] In some embodiments, if the MAC layer determines that the TB contains only a LCH with HARQ feedback enabled due to Logical Channel Prioritization (“LCP”), then the MAC layer delivers the TB to the PHY layer, and the PHY layer may further determine whether to transmit the TB in “hybrid mode” based on current channel conditions (e.g., the priority of the TB). In one instance, in hybrid mode, the first x HARQ transmissions of the TB do not request HARQ feedback in the Side Link Control Information (“SCI”), and for the X+1 transmission, the UE may request HARQ feedback from the receiver UE in the SCI. For the first 'X' retransmissions, the PHY layer may trigger some autonomous retransmissions from the MAC layer by indicating “NACK” for a determined number of BRs (e.g., x' transmissions) within the MAC layer—without receiving HARQ feedback from any receiver or receiving (“RX”) UE on the Physical Side Link Feedback Channel (“PSFCH”).

[0081] In such embodiments, from the MAC layer's perspective, "hybrid mode" operation is treated as a standard HARQ enabled transmission. Therefore, the MAC layer is unaware whether the HARQ feedback delivered from the PHY layer is internally and / or autonomously triggered, or whether it is derived from the HARQ feedback received from the receiving UE on the PSFCH.

[0082] In some embodiments, if the MAC layer determines, due to LCP, that the TB contains only an LCH with HARQ feedback disabled, then the MAC layer delivers the TB to the PHY layer, and the PHY layer can further determine whether to transmit the TB in "hybrid mode" based on current channel conditions, the priority of the TB, etc. In one instance, in hybrid feedback mode, the first x HARQ transmissions of the TB do not request HARQ feedback in the SCI, and for the X+1 transmissions (and subsequent retransmissions), HARQ feedback is requested from the receiver UE in the SCI. For the first X+1 retransmissions (and subsequent retransmissions), the PHY layer can initiate retransmissions based on HARQ feedback. Retransmissions are only performed when "NACK" feedback or DTX is received from one or more receivers; otherwise (e.g., all received HARQ feedbacks are acknowledgment ("ACK") feedback), no further retransmissions are performed. From the MAC layer's perspective, "hybrid mode" is considered a normal HARQ-enabled transmission.

[0083] In various embodiments, a minimum duration can be defined to indicate the minimum time interval between two HARQ transmissions of a transport block, and the minimum time interval can be considered by the Tx UE during SL resource selection.

[0084] In some embodiments, the SL resources for all HARQ transmissions (or retransmissions) of the TB can be selected by the Tx UE such that, in the time domain, the Tx UE has sufficient time to receive HARQ feedback on the HARQ transmissions of the TB from the Rx UE on the PSFCH and to decide whether to perform further HARQ transmissions (or retransmissions) for the TB and to perform HARQ retransmissions. It will be understood that the new minimum duration parameter may be beneficial in scenarios where: the MAC layer of the Tx UE selects SL resources for x' blind HARQ transmissions of the TB and the PHY layer of the Tx UE decides to request HARQ feedback from the receiving UE after the y-th transmission (y < x) to determine whether further HARQ transmissions are necessary.

[0085] In some embodiments, the PHY layer of the Tx UE indicates to the MAC layer that, for SL resource selection, there should be sufficient time between TB transmissions to allow for the collection of HARQ feedback. The minimum time distance between HARQ transmissions of the TB can be signaled from the PHY layer to the MAC layer as a new input parameter for the resource selection process. In one instance, the minimum processing time may indicate the minimum time between two HARQ transmissions, similar to a HARQ round-trip time (“RTT”) value or a K3 value for the Uu interface. In various embodiments, the new parameter minimum time distance between HARQ transmissions of the TB may be a fixed predefined value or may be defined based on UE capabilities.

[0086] In some embodiments, if LCP results in TB having LCHs configured for hybrid mode, then only the PHY layer is allowed to use hybrid operating mode. In such embodiments, RRC may configure some LCHs to have a "hybrid feedback mode".

[0087] Figure 3 A process 300 for sidelink sensing and resource selection (reselection) according to embodiments of the present disclosure is depicted. Process 300 can be performed by a Tx UE, such as UE 205 and / or Tx UE 251. Process 300 begins at block 305, where the Tx UE decodes Physical Sidelink Control Channel (“PSCCH”) transmissions from other UEs and measures the corresponding Physical Sidelink Shared Channel (“PSSCH”) energy. At block 310, the Tx UE collects sensing information, including reserved resources and sidelink reference signal received power (“SL-RSRP”) measurements. The SL-RSRP measurement allows the Tx UE to select appropriate resources and avoid interfering with any existing communications.

[0088] In box 315, the Tx UE forms a candidate resource set by excluding itself and high-power resources. The Tx UE excludes resources whose measured reference signal received power (“RSRP”) exceeds a threshold, and if the service priority in the measured resource is higher than the Tx UE's service priority, then the resource is considered occupied. Note that if the Tx UE has a higher-priority service, then the Tx UE can choose to occupy the resource. In this way, even if the resource has already been reserved by other UEs, a higher-priority service can still occupy the resource.

[0089] In box 320, the Tx UE selects a transmission resource with a start time of "m". Note that the selected resource can be semi-persistent or alternatively reserved for a maximum number of times. In resource allocation mode 2, the Tx UE performs continuous sensing, and when a resource selection event is triggered in the Tx UE (e.g., a transport block arrives), the Tx UE considers its most recent sensing results before the resource selection trigger time.

[0090] As described in more detail below, higher-level parameters can indicate the minimum time gap (also known as minimum duration) requirement between consecutive resources, where the selection of transmission resources takes the minimum time gap into account. If HARQ feedback is enabled, then the timing gap between two adjacent resources should be greater than the PSFCH period. This will result in additional latency. For some SL data with high reliability and low latency requirements, it is necessary to support HARQ feedback to improve reliability. Furthermore, blind transmissions can be applied to reduce latency, and more retransmissions can also improve reliability.

[0091] In box 325, the Tx UE re-evaluates the resource selection, for example, shortly before initiating transmission on the selected resource. The re-evaluation may consider late SCI reception, i.e., reception after the sensing window, to ensure the selected resource is still suitable for transmission. In decision box 330, the Tx UE determines whether the reselection was triggered by the re-evaluation step. If yes, the Tx UE returns to box 310 to collect sensing information, etc. If no, the Tx UE initiates transmission at box 335.

[0092] In decision box 340, the Tx UE again determines whether resource reselection is needed. If yes, the Tx UE restarts the process by returning to box 310 to collect sensing information, etc. If no, the Tx UE continues to use the resource reservation and starts transmission again at box 335.

[0093] Figure 4A and 4B A timeline depicting a sidelink sensing and resource selection (reselection) procedure triggered at time n according to embodiments of this disclosure is provided. These timelines illustrate the behavior of Tx UE 251.

[0094] Figure 4A The first timeline 400 depicts the sensing and resource selection (reselection) process triggered at time n, which has not been re-evaluated before (m-T3). Its first reserved resource is at time m. Figure 4A The sensing window 401 and selection window 403 are shown, where n is the trigger time for resource allocation. In one embodiment, the sensing window 401 includes sensing results between 1100ms and 100ms before the trigger time n. As discussed above, the Tx UE 251 performing the sensing measures the SL-RSRP of the PSCCH or PSSCH.

[0095] Between the end of sensing window 401 and trigger time n, there is a processing time T. proc,0 This corresponds to the time required to process tasks and / or exchange information in the lower layers (i.e., PHY layer 255 and MAC layer 260). Between the trigger time n and the selection window 403, there is another processing time T1, which corresponds to the time required to process tasks and / or exchange information in the lower layers (i.e., PHY layer 255 and MAC layer 260).

[0096] Tx UE 251 selects transmission resources for its transmission (retransmission) based on the sensing results and the resource selection window. The selection window 403 begins shortly after the resource selection in the Tx UE is triggered (i.e., the transmission block arrives), and the maximum window size is limited to the remaining delay budget of the transmission block.

[0097] After excluding reserved resources from the selection window, Tx UE 251 randomly selects resources from a set of the best remaining resources. In one embodiment, a threshold amount (e.g., 20%) of the best resources with a measured RSRP less than a threshold power based on service priority is selected. Note that the threshold resource amount may be based on service priority. If the remaining resources after the exclusion procedure are less than the threshold amount of all resources in selection window 403, then Tx UE 251 may relax the RSRP threshold (e.g., up to 3 dB) until it has at least the threshold amount (20%, 30%, or 50% based on service priority) for all resources in the selection window for resource allocation.

[0098] In some embodiments, the final selection of resources is completed in the MAC layer 260 upon receiving a set of unoccupied resources from the PHY layer 255. Resource selection in the MAC layer 260 is based on a random process. The selected resources are not periodic.

[0099] In some embodiments, the Tx UE 251 may reserve additional resources indicated in the SCI. Reserved resources may be independent in time and frequency. As described in more detail below, the number of unused reserved resources may be limited, for example, based on packet transmission priority, the number of retransmissions for the TB, the remaining packet delay budget (“PDB”), the minimum communication range (“MCR”), and / or channel state information (“CSI”) reports.

[0100] Figure 4B A second timeline 410 is depicted for the sensing and resource selection (reselection) process initially triggered at time n. When a reassessment occurring at m-T3 determines that a resource is no longer available, the process has a first reserved resource at time m within a reselection window 411. The new reassessment cutoff becomes (m'-T3). After a resource is selected by Tx UE 251 in resource allocation mode 2, there are several reasons why resource reselection is necessary. One reason could be that a service with a higher priority than the service that Tx UE 251 wishes to transmit is reserved for reception from another nearby UE.

[0101] In resource allocation mode 2, a higher layer (i.e., MAC layer 260) may request a lower layer (i.e., PHY layer 255) to determine a subset of resources from which the higher layer will select resources for PSSCH / PSCCH transmissions. To trigger this process, in slot n, the higher layer provides the following parameters for this PSSCH / PSCCH transmission:

[0102] • The resource pool from which it reports resources;

[0103] • L1 priority, prio TX ;

[0104] • Remaining group delay budget;

[0105] • The number of sub-channels used for PSSCH / PSCCH transmission in a time slot, L subCH ;

[0106] •Optionally, the resource reservation interval P in milliseconds rsvp_TX .

[0107] The following higher-level parameters affect this process:

[0108] ·t2min_SelectionWindow: For prio TX Given a value, the internal parameter T 2min The corresponding value is set from the higher-level parameter t2min_SelectionWindow.

[0109] ·SL-ThresRSRP_pi_pj: This higher-level parameter is for each combination (p i , p j Provides the RSRP threshold, where p i It is the value of the priority field from 0 to 1 in the received SCI format, and p j This is the priority of resource transmission selected by Tx UE 251; for a given call to this procedure, p j =prio TX .

[0110] • RSforSensing selects whether to use PSSCH-RSRP or PSCCH-RSRP for Tx UE 251 measurements.

[0111] • reservationPeriodAllowed

[0112] ·t0_SensingWindow: The internal parameter T0 is defined as the number of time slots corresponding to t0_SensingWindow ms.

[0113] ·k, the minimum time interval between resources used for HARQ-based retransmissions.

[0114] Resource retention interval P rsvp_TX (If provided) the conversion from milliseconds to logical time slots results in P′ rsvp_TX .symbol: This indicates a set of time slots that may belong to the sidelink resource pool.

[0115] The following steps can be used for resource selection:

[0116] In step 1), R is used for transmission. x,y Candidate single-slot resources are defined as slots. A set of L with sub-channels x+j subCH Continuous sub-channels, where j = 0,...,L subCH -1. Tx UE 251 Assumption: Any set of L in the corresponding resource pool within the time interval [n+T1, n+T2] subCH A continuous subchannel corresponds to a candidate single-slot resource, where

[0117] • In the case of 0≤T1≤T proc,1 In this case, the choice of T1 depends on the UE implementation scheme, where T proc,1 Defined in 3GPP TS38.214;

[0118] If T 2min If the delay is shorter than the remaining packet delay budget (in the time slot), then T2 depends on the UE implementation scheme, which is subject to T. 2min ≤T2≤Remaining packet budget (in the time slot); otherwise, T2 is set to the remaining packet delay budget (in the time slot).

[0119] The total number of candidate single-slot resources is determined by M. total Marking.

[0120] In step 2), the sensing window is defined by the time slot range [n–T0, n–T] proc,0 Define T0 and T proc,1 As defined above, TxUE 251 will monitor time slots belonging to the sidelink resource pool within the sensing window, excluding the time slots in which its own transmission occurs. TxUE 251 will perform the following actions based on the PSCCH decoded in these time slots and the measured RSRP.

[0121] In step 3), the internal parameter Th(p) i From equal to prio TX The given value of p j and each priority value p i The higher-level parameter SL-ThresRSRP_pi_pj is set to the corresponding value.

[0122] In step 4) set S A It is initialized to a set of all candidate single-slot resources.

[0123] In step 5), if any candidate single-slot resource R x,y If all of the following conditions are met, then Tx UE 251 is from set S. A Exclude it:

[0124] • The UE has not yet monitored the time slot in step 2.

[0125] • Any periodic value allowed by the higher-level parameter reservationPeriodAllowed, and within time slots. The received SCI format is assumed to be 0 to 1, where the “resource retention period” field is set to that periodic value and indicates that all sub-channels of the resource pool in this time slot will satisfy condition c in step 6.

[0126] In step 6), if any candidate single-slot resource R x,y If all of the following conditions are met, then Tx UE 251 is from set S. A Exclude it:

[0127] a.UE in time slot The received SCI format is 0 to 1, and the "Resource Retention Period" field (if present) and "Priority" field in the received SCI format 0 to 1 respectively indicate the value P. rsvp_RX and prio RX ;

[0128] b. The RSRP measurement performed according to clause 8.4.2.1 of the received SCI format 0 to 1 is higher than Th(prio RX );

[0129] c. In time slots The SCI format received in the middle is assumed to be in the time slot. The same SCI format received (if and only if the received SCI format 0 to 1 contains a "resource retention period" field) is used to determine the relationship between the received SCI format and the SCI format for q = 1, 2, ..., Q and j = 0, 1, ..., C. resel -1 An overlapping set of resource blocks and time slots. Here, P′ rsvp_RX It is converted into P in units of logical time slots. rsvp_RX If P rsvp_RX <T scal And n′-m≤P′ rsvp_RX ,So Where time slot n belongs to set So Otherwise time slot It belongs to the set The first time slot after time slot n; otherwise Q = 1.

[0130] In step 7) if set S A The number of remaining candidate single-slot resources is less than 0.2 M. total Then each priority value Th(p) i ) of Th(p i (Increase by 3dB and the process continues in step 4.) Tx UE 251 reports to higher layer set SA .

[0131] Figure 5 A process 500 for a hybrid feedback-based transmission is described. Process 500 includes receiving a sidelink grant 505 and selecting a destination 510. Process 500 also includes selecting a retransmission mode 515 (e.g., blind retransmission mode, HARQ-based transmission mode, or a combination of blind retransmission and HARQ-based transmission mode) based on the minimum time gap between consecutive HARQ transmissions of the TB. Process 500 includes selecting a resource 520 for the sidelink TB based on the minimum time gap. Then, process 500 includes performing a retransmission 525.

[0132] According to an embodiment of the first solution, MAC layer 260 determines whether to switch the retransmission mode (i.e., from blind retransmission (“BR”) to HARQ-based transmission (“HFBT”) or vice versa). In the first solution, the LCH configured for resource selection in resource allocation mode 2 can be (pre-)configured by RAN node 207 for enabling and disabling SL HARQ feedback using separate RRC code points as explained above, where 'SL HARQ feedback disabled' also means configuring blind retransmission.

[0133] In one embodiment of the first solution, MAC layer 260 determines a hybrid mode switching decision between blind retransmission and HARQ-based retransmission (and vice versa), and correspondingly notifies timing constraints, such as the minimum time interval between resources for corresponding HARQ retransmissions of TB. A resource pool with PSFCH resources is provided to PHY layer 225 as part of the initial resource selection (reselection) triggering of resource allocation mode 2. Based on these input parameters, Tx UE 251 can perform candidate resource selection (i.e., at PHY layer 255) and report the candidate resource set to MAC layer 260.

[0134] In this embodiment, the MAC layer 260 selects the corresponding resource pool with PSFCH resources based on the LCH hybrid mode configuration.

[0135] In another implementation of the first solution, if MAC layer 260 dynamically enables / disables SL HARQ feedback (regardless of LCH configuration), the selection between a resource pool containing PSFCH resources and a resource pool without PSFCH resources can also be dynamically changed, and therefore MAC layer 260 triggers a resource selection (reselection) procedure for this HARQ procedure ID to switch between a resource pool without PSFCH resources and a resource pool with PSFCH resources.

[0136] An example implementation of the first solution, namely the 3GPP specification TS 38.214, can be shown below:

[0137] • In resource allocation mode 2, the higher layer may request the UE to determine a subset of resources from which the higher layer will select resources for PSSCH / PSCCH transmissions. To trigger this process, in slot n, the higher layer provides the following parameters for this PSSCH / PSCCH transmission:

[0138] ο will be the resource pool from which it reports resources;

[0139] οL1 priority, prio TX ;

[0140] ο Remaining group delay budget;

[0141] The number of sub-channels used for PSSCH / PSCCH transmission in a time slot, L subCH ;

[0142] οOptional, resource reservation interval in milliseconds, P rsvp_TX .

[0143] The following higher-level parameters affect this process:

[0144] οt2min_SelectionWindow: For prio TX Given a value, the internal parameter T 2min The corresponding value is set from the higher-level parameter t2min_SelectionWindow.

[0145] οSL-ThresRSRP_pi_pj: This higher-level parameter is for each combination (p i ,p j Provides the RSRP threshold, where p i It is the value of the priority field from 0 to 1 in the received SCI format, and p j This refers to the priority of resource transmission selected by the UE; for a given call in this procedure, p j =prio TX .

[0146] οRSforSensing selects whether the UE uses PSSCH-RSRP or PSCCH-RSRP for measurement, as defined in Clause 8.4.2.1.

[0147] οreservationPeriodAllowed

[0148] οt0_SensingWindow: The internal parameter T0 is defined as the number of time slots corresponding to t0_SensingWindow ms.

[0149] οk, the minimum time interval between resources used for HARQ-based retransmissions.

[0150] In an alternative embodiment of the first solution, the PHY layer 255 makes a decision regarding switching retransmission modes. In some implementations, the PHY layer 255 may additionally notify the MAC layer 260 of a report on candidate time slots and candidate resource sets in which SL HARQ feedback is enabled for each retransmission attempt (or alternatively, where SL HARQ feedback is disabled for each retransmission attempt), and the MAC layer 260 may thus select resources for each HARQ-based retransmission based on the minimum time slot of the HARQ RTT.

[0151] In another embodiment of the first solution, MAC layer 260 determines, based on a predefined criterion, whether to switch from HARQ-based retransmission to blind retransmission within the TB transmission, or vice versa. For example, the decision may also be left to the UE implementation. According to one embodiment of this approach, PHY layer 255 provides a set of candidate resources, and MAC layer 260 selects SL resources based on SL HARQ enable / disable. When selecting resources, MAC layer 260 considers the minimum time interval between resources used for corresponding HARQ retransmissions of the TB.

[0152] Here, MAC layer 260 can further instruct PHY layer 255 when to signal in SCI whether SL HARQ feedback is enabled for retransmission and SL HARQ feedback option 1 or SL HARQ feedback option 2. According to SL HARQ feedback option 1, if the receiver UE (i.e., the target UE) fails to decode the corresponding TB after decoding the associated PSCCH and otherwise does not transmit a signal on the PSFCH, then it transmits HARQ-NACK on the PSFCH (i.e., if the Rx UE successfully decodes the corresponding TB, then it will not transmit HARQ-ACK on the PSFCH). According to SL HARQ feedback option 2, if the receiver UE (“Rx UE”) successfully decodes the corresponding TB, then it transmits HARQ-ACK on the PSFCH. Additionally, if the Rx UE fails to decode the corresponding TB after decoding the associated PSCCH targeted by the receiver UE, then it transmits HARQ-NACK on the PSFCH. As used in this document, "HARQ-ACK" indicates a positive acknowledgment ("ACK"), while "HARQ-NACK" indicates a negative acknowledgment ("NACK"). ACK means that the TB was received correctly, while NACK (or NAK) means that the TB was received incorrectly, and discontinuous transmission ("DTX") means that the TB was not detected.

[0153] Note that deciding whether and when to switch from blind retransmission to HARQ feedback-enabled retransmission in MAC layer 260 allows for some simple implementations because the HARQ protocol is running on MAC layer 260. For example, MAC layer 260 expects feedback from PHY layer 255 when HARQ feedback is enabled. Furthermore, HARQ protocol aspects (e.g., decisions on whether to transmit a new TB or perform further retransmissions of the TB) are also made in MAC layer 260 based on PSFCH feedback.

[0154] In another implementation of the first solution, MAC layer 260 notifies PHY layer 255 that a first number of retransmissions (e.g., 1, 2, etc.) are blind retransmissions and that subsequent retransmissions (e.g., the third and thereafter) are HARQ-based retransmissions. In various embodiments, the first number of blind retransmissions may be determined as follows: 1) the total number of transmissions may depend on one or more of the following: link budget requirements that can be determined and / or mapped from the minimum communication range (“MCR”), SL path loss (e.g., unicast), allowed MCS (e.g., code rate), and the transmission power of the Tx UE (e.g., the total number of transmissions may differ for MCR'a' and MCR'b', and for multicast communication, the worst-case path loss is used if available); 2) the total number of BR and HARQ-based retransmissions (“HFBT”) may depend on the overall reliability to be achieved taking into account delay boundaries (e.g., packet delay budget (“PDB”)).

[0155] In one instance, Tx UE 251 determines the number of BRs to be performed for a given PDB, and then the UE decides to enable retransmission based on HARQ feedback. In another instance, the PDB or remaining PDB can be used to determine the number of feedback-based transmissions available, given the RTT between transmission and reception for the corresponding HARQ feedback. If this would be less than what is required to achieve a given reliability for a given MCR, then Tx UE 251 can save time by making some blind transmissions (or retransmissions). As you may understand, the terms transmission and retransmission are used interchangeably herein. A transmission can be a first transmission or a retransmission, and a retransmission can refer to the first transmission.

[0156] In some embodiments, the first number of blind retransmissions can be determined as the base value of the HARQ operating point. The base value may mean a maximum integer value less than (or equal to) the HARQ operating point. The HARQ operating point itself can be determined using statistical observations of PC5 links used for the same destination or for other destinations of the same or different cast-types.

[0157] In another implementation of the first solution, MAC layer 260 provides a bitmap of the time slots in which blind retransmission and HARQ-based retransmission are enabled.

[0158] In another implementation of the first solution, the MAC layer 260 notifies the PHY layer 255 in advance of the switch between the two implementation schemes described above, or the MAC layer 260 dynamically switches between blind retransmission and HARQ-based retransmission to the PHY layer 255, and vice versa.

[0159] According to the second solution, reliability and / or congestion parameters are considered when making hybrid mode switching decisions between blind retransmissions and HARQ-based retransmissions (or vice versa). In one embodiment of the second solution, the minimum communication range (“MCR”) is used as input to determine the number of blind retransmissions and HARQ-based retransmissions required to satisfy the reliability of the selected MCS. The MCR is the distance (range) from the Tx UE 251 to which QoS implementation is practically applicable, for example, in meters. In some embodiments, the MCR is assigned by the V2X layer / application layer and is signaled to the access layer along with the Quality of Service (“QoS”) (indicated using the quality indicator (i.e., “PQI”) of the PC5 interface). The QoS applicable to V2X messages must be implemented within this range. The MCR is therefore important when seeking HARQ feedback from the Rx UE.

[0160] In another embodiment of the second solution, the hybrid mode switching decision is based on the availability of MCR and / or Channel Busy Rate (“CBR”) measurements. During congestion, the number of blind retransmissions and HARQ-based retransmissions (and vice versa) can be dynamically changed after initial determination. As used herein, CBR is a measurement used in the Tx UE to control congestion when Resource Allocation Mode 2 is applied. In some embodiments, CBR can be calculated in each subframe as a portion of the resource pool that is busy (e.g., in the most recent 100ms). If the received energy level in a resource is above a given threshold, then the resource is considered busy. The CBR measurement reflects congestion in the media.

[0161] In one instance of the dynamic number of BR and HFBT, a higher required reliability, priority, and / or MCR will mean that the Tx UE performs one or more blind retransmissions, followed by HARQ-based retransmissions. In another instance, this determination is based on CBR; for example, for a higher CBR, unnecessary blind retransmissions are avoided, and therefore, at least for a lower MCR value, HARQ-based retransmissions are performed.

[0162] As described above, in resource allocation mode 2, there is a resource re-evaluation step after the initial candidate resource selection and before the actual transmission time slot. In some embodiments of the second solution, the Tx UE 251 can monitor any additional triggers from the MAC layer 260 that switch from blind retransmission to HARQ feedback-based retransmission (or vice versa), i.e., mixed-mode handover triggers. When a trigger for a mixed-mode handover (i.e., a switch from HARQ feedback-based retransmission to blind retransmission / from blind retransmission to HARQ feedback-based retransmission) arrives before or at 'm-T3', and then, if either the pre-selected or reserved resources does not meet the minimum time slot required for the handover target transmission (blind retransmission or HARQ feedback-based retransmission), then resource reselection is triggered to find a new set of resources that meets the minimum HARQ RTT gap. In another approach, the triggering of a switch from blind retransmission to HARQ-based retransmission (or vice versa) from MAC layer 260 contains the slot offset from the nth retransmission as a parameter to implement the switch accordingly at PHY layer 255.

[0163] In another implementation of the second solution, MAC layer 260 may switch from blind retransmission to HARQ-feedback-based retransmission based on timing constraints for uncompleted reserved resources meeting the minimum HARQ RTT time gap. In another approach, MAC layer 260 may notify PHY layer 255 to further reserve future resources based on the minimum HARQ RTT time gap. In yet another approach, the switch from blind retransmission to HARQ-feedback-based retransmission may dynamically change the number of future resource reservations performed by MAC layer 260 and ultimately signaled in the SCI.

[0164] In another embodiment of the second solution, the number of uncompleted reserved resources determined by MAC layer 260 may be based on one or more combinations of: QoS of packet transmission, MCR value, total number of blind retransmissions and / or retransmissions based on HARQ feedback, CBR measurement and / or CSI report.

[0165] In another embodiment of the second solution, the handover from blind retransmission to HARQ-based retransmission can be based on a CSI report received from the corresponding destination ID or on a CBR measurement. The time slot between the CBR measurement received at Tx UE 251 and the resource selection (reselection) or triggering for the handover between blind transmission and HARQ-based retransmission can be configured on the Tx UE side based on the UE's packet transmission processing capacity or priority, or the remaining PDB.

[0166] In another embodiment, Tx UE 251 may use reserved resources that do not meet the minimum HARQ RTT gap for transmission of another TB, where the TB priority is equal to or less than the priority of the reserved resource, with a lower priority implying a higher PPPP / QCI value. If the priority value of the TB is higher than the priority of the reserved resource, then Tx UE 251 will not transmit in the reserved resource.

[0167] In another implementation, Tx UE 251 may transmit in reserved resources based on one or more of the following (regardless of the TB priority): the time when the CBR measurement is below a certain configured threshold, the MCR value, the total number of retransmissions, CSI reports, etc., as explained in the examples above.

[0168] The third solution addresses SL / UL prioritization in NR. For NR UL / SL prioritization between sidelink SSB and UL transmissions, the sidelink-SSB (“SL-SSB”) has a pre-configured priority and is lower than the UL-TX. For Tx UEs that use the SL-SSB as an SL synchronization reference UE (“SyncRef UE”) via transmission, when the SL-SSB is given lower priority than the UL transmission, other neighboring UEs depending on the SL-SSB from the Tx UE may be affected (i.e., may lose synchronization).

[0169] In one embodiment, when one of the configured SyncRef UEs (i.e., the Tx UE) has a UL transmission with a higher priority than the SL-SSB transmission, the RAN node 207 reselects another SyncRef UE from the candidate SyncRef UE list, thereby reducing the priority of the SL-SSB transmission. In another embodiment, SyncRef UE reselection occurs only when consecutive SL-SSB transmissions have a lower priority than UL transmissions. As used herein, reducing priority means allocating sufficient UE resources for the transmission of the prioritized transmission.

[0170] In some embodiments, the Tx UE can transmit simultaneously on both the uplink channel and the sidelink channel. However, due to transmission power constraints, when sidelink transmissions overlap with uplink transmissions in the time domain, the Tx UE must reduce the priority of either the sidelink or uplink transmission (i.e., by reducing the transmission power of the transmission with reduced priority). In other embodiments, the Tx UE cannot transmit simultaneously on both the uplink channel and the sidelink channel. Here, when sidelink transmissions overlap with uplink transmissions in the time domain, the Tx UE must reduce the priority of either the sidelink or uplink transmission (i.e., by discarding the transmission with reduced priority).

[0171] In some embodiments, the Tx UE notifies the RAN node 207 of the actual SL-SSB transmission configuration in an SL slot among the candidate SL slots reserved for SL-SSB transmissions, as part of UE auxiliary information or any RRC configuration message or MAC control element (“CE”), enabling the RAN node 207 to reschedule the UL without overlapping with the SL-SSB transmission.

[0172] In some embodiments, the Tx UE notifies the RAN node 207 that its SL-SSB transmissions have a lower priority than UL transmissions, and therefore the Tx UE transmits a reselection trigger for its own SyncRef UE state to the RAN node 207 as part of UE auxiliary information or any RRC configuration message or MAC CE. The RAN node 207 immediately performs a reselection of another SyncRef UE from the candidate list after receiving the trigger from the Tx UE.

[0173] Figure 6 User equipment device 600, which can be used to support hybrid BR and HFBT according to embodiments of the present disclosure, is depicted. In various embodiments, user equipment device 600 is used to implement one or more of the solutions described above. User equipment device 600 may be an embodiment of remote unit 105 and / or UE 205 described above. Furthermore, user equipment device 600 may include processor 605, memory 610, input device 615, output device 620, and transceiver 625.

[0174] In some embodiments, input device 615 and output device 620 are combined into a single device, such as a touchscreen. In some embodiments, user equipment device 600 may not include any input device 615 and / or output device 620. In various embodiments, user equipment device 600 may include one or more of processor 605, memory 610, and transceiver 625, and may not include input device 615 and / or output device 620.

[0175] As depicted, transceiver 625 includes at least one transmitter 630 and at least one receiver 635. In some embodiments, transceiver 625 communicates with one or more cells (or radio coverage areas) supported by one or more basic units 121. In various embodiments, transceiver 625 may operate on unlicensed spectrum. Furthermore, transceiver 625 may include multiple UE boards supporting one or more beams. Additionally, transceiver 625 may support at least one network interface 640 and / or application programming interface 645. Application programming interface 645 may support one or more APIs. Network interface 640 may support 3GPP reference points, such as Uu, N1, PC5, etc. Other network interfaces 640 may be supported, as will be understood by those skilled in the art.

[0176] In one embodiment, processor 605 may include any known controller capable of executing computer-readable instructions and / or performing logical operations. For example, processor 605 may be a microcontroller, microprocessor, central processing unit (“CPU”), graphics processing unit (“GPU”), auxiliary processing unit, field-programmable gate array (“FPGA”), or similar programmable controller. In some embodiments, processor 605 executes instructions stored in memory 610 to perform the methods and routines described herein. Processor 605 is communicatively coupled to memory 610, input device 615, output device 620, and transceiver 625. In some embodiments, processor 605 may include an application processor (also referred to as a “main processor”) that manages application domains and operating system (“OS”) functions, and a baseband processor (also referred to as a “baseband radio processor”) that manages radio functions.

[0177] In various embodiments, the processor 605 controls the user equipment device 600 to perform the aforementioned UE behavior. For example, the processor 605 provides the PHY layer 255 and the MAC layer 260 with a minimum duration between a first resource for HARQ transmission of the TB and a second resource for HARQ transmission of the TB. Here, the minimum duration includes the sum of the following: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of the TB, and a third time for retransmitting the TB.

[0178] Processor 605 selects a retransmission mode based on the minimum duration (i.e., determines whether to switch retransmission modes). Here, the retransmission mode includes one of the following: blind retransmission and HFBT mode. Processor 605 selects the retransmission-side link resources based on the selected retransmission mode as TB.

[0179] In some embodiments, PHY layer 255 determines a minimum duration, provides a set of candidate resources, and notifies MAC layer 260 of candidate time slots in which sidelink HARQ feedback is enabled for each retransmission attempt. In such embodiments, MAC layer 260 selects a sidelink resource based on the minimum time slot. In some embodiments, MAC layer 260 selects a retransmission mode and chooses a sidelink resource from the set of candidate resources provided by PHY layer 255. In such embodiments, MAC layer 260 selects a sidelink resource based on the minimum time slot.

[0180] In some embodiments, MAC layer 260 selects a first resource and a second resource for HARQ transmissions with a minimum duration of TB. In some embodiments, MAC layer 260 dynamically enables HARQ feedback for TB and triggers resource selection in response to enabling HARQ feedback. In such embodiments, resource selection triggered in response to enabling HARQ feedback includes switching to a resource pool containing PSFCH resources.

[0181] In some embodiments, the retransmission mode is selected based on blind retransmission and HARQ feedback-based transmission. In some embodiments, the first number of retransmissions are blind retransmissions, and subsequent retransmissions are based on HARQ feedback transmission. In some embodiments, the MAC layer 260 sends a bitmap of time slots to the PHY layer 255, the bitmap indicating where blind retransmission is enabled and where HARQ feedback-based transmission is enabled.

[0182] In some embodiments, the processor 605 further determines the number of blind retransmissions and HARQ-based transmissions required to meet reliability requirements, and reduces the number of blind retransmissions in response to increased channel congestion. In some embodiments, selecting a retransmission mode includes switching from blind retransmission mode to HFBT mode based on CSI (e.g., CSI reports received from the corresponding destination ID) and / or CBR of the sidelink channel.

[0183] In one embodiment, memory 610 is a computer-readable storage medium. In some embodiments, memory 610 includes volatile computer storage media. For example, memory 610 may include RAM, including dynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and / or static RAM (“SRAM”). In some embodiments, memory 610 includes non-volatile computer storage media. For example, memory 610 may include a hard disk drive, flash memory, or any other suitable non-volatile computer storage device. In some embodiments, memory 610 includes both volatile and non-volatile computer storage media.

[0184] In some embodiments, memory 610 stores data related to supporting BR and HFBT hybrid operation. For example, memory 610 may store various parameters, board / beam configurations, resource assignments, strategies, and the like as described above. In some embodiments, memory 610 also stores program code and related data, such as operating systems or other controller algorithms operating on user equipment device 600.

[0185] In one embodiment, input device 615 may include any known computer input device, including a touchpad, button, keyboard, light pen, microphone, or the like. In some embodiments, input device 615 may be integrated with output device 620 as, for example, a touchscreen or similar touch-sensitive display. In some embodiments, input device 615 includes a touchscreen that allows text to be entered using a virtual keyboard displayed on the touchscreen and / or by handwriting on the touchscreen. In some embodiments, input device 615 includes two or more different devices, such as a keyboard and a touchpad.

[0186] In one embodiment, output device 620 may be designed to output visual, auditory, and / or tactile signals. In some embodiments, output device 620 includes an electronically controllable display or display device capable of outputting visual data to a user. For example, output device 620 may include (but is not limited to) an LCD display, LED display, OLED display, projector, or similar display device capable of outputting images, text, or the like to a user. As another non-limiting example, output device 620 may include a wearable display, such as a smartwatch, smart glasses, head-mounted display, or the like, that is separate from but communicatively coupled to the remainder of user equipment device 600. Furthermore, output device 620 may be a component of a smartphone, personal digital assistant, television, desktop computer, laptop computer, personal computer, vehicle dashboard, or the like.

[0187] In some embodiments, the output device 620 includes one or more speakers for generating sound. For example, the output device 620 may generate an auditory alarm or notification (e.g., a beep or ring). In some embodiments, the output device 620 includes one or more haptic devices for generating vibration, motion, or other haptic feedback. In some embodiments, the output device 620 may be wholly or partially integrated with the input device 615. For example, the input device 615 and the output device 620 may form a touchscreen or similar touch-sensitive display. In other embodiments, the output device 620 may be located near the input device 615.

[0188] Transceiver 625 communicates with one or more network functions of a mobile communication network via one or more access networks. Transceiver 625 operates under the control of processor 605 to transmit and receive messages, data, and other signals. For example, processor 605 may selectively activate transceiver 625 (or a portion thereof) at specific times to send and receive messages.

[0189] Transceiver 625 includes at least one transmitter 630 and at least one receiver 635. One or more transmitters 630 may be used to provide UL communication signals to base unit 121, such as the UL transmission described herein. Similarly, one or more receivers 635 may be used to receive DL communication signals from base unit 121, as described herein. Although only one transmitter 630 and one receiver 635 are described, user equipment device 600 may have any suitable number of transmitters 630 and receivers 635. Furthermore, transmitters 630 and receivers 635 may be of any suitable type. In one embodiment, transceiver 625 includes a first transmitter / receiver pair for communicating with a mobile communication network via licensed radio spectrum and a second transmitter / receiver pair for communicating with a mobile optical communication network via unlicensed radio spectrum.

[0190] In some embodiments, a first transmitter / receiver pair for communicating with a mobile communication network via licensed radio spectrum and a second transmitter / receiver pair for communicating with a mobile communication network via unlicensed radio spectrum may be combined into a single transceiver unit, such as a single chip that performs functions for use with both licensed and unlicensed radio spectrum. In some embodiments, the first transmitter / receiver pair and the second transmitter / receiver pair may share one or more hardware components. For example, some transceivers 625, transmitters 630, and receivers 635 may be implemented as physically separate components that access shared hardware and / or software resources, such as (for example) a network interface 640.

[0191] In various embodiments, transceiver 625 can operate on both an uplink channel and a sidelink channel. In some embodiments, transceiver 625 can transmit on both the uplink channel and the sidelink channel simultaneously. However, due to transmission power constraints, when a sidelink transmission overlaps with an uplink transmission in the time domain, processor 605 must reduce the priority of either the sidelink or uplink transmission (i.e., by reducing the transmission power of the reduced-priority transmission). In other embodiments, transceiver 625 cannot transmit on both the uplink channel and the sidelink channel simultaneously. Here, when a sidelink transmission overlaps with an uplink transmission in the time domain, the processor must reduce the priority of either the sidelink or uplink transmission (i.e., by discarding the reduced-priority transmission).

[0192] Examples of sidelink (“SL”) transmissions include (but are not limited to) sidelink synchronization signal blocks (“SL-SSB”), control channel transmissions (e.g., PSFCH, SL CSI reports in SL MAC CE, SL MAC CE, etc.), combined SL feedback and SL data transmissions, and SL data / PSSCH transmissions. Examples of uplink (“UL”) transmissions include (but are not limited to) random access channel (“RACH”) transmissions, sounding reference signal (“SRS”) transmissions, scheduling request (“SR”) transmissions, physical uplink control channel (“PUCCH”) transmissions (e.g., PUCCH UL HARQ feedback (i.e., ACK / NACK), PUCCH SL HARQ feedback (i.e., ACK / NACK), PUCCH CSI, irregular PUCCH, etc.) and PUSCH transmissions (e.g., UL data, MAC CE, PUSCH UL HARQ feedback (i.e., ACK / NACK), PUSCH CSI, PUSCH SL HARQ feedback (i.e., ACK / NACK)).

[0193] In various embodiments, one or more transmitters 630 and / or one or more receivers 635 may be implemented and / or integrated into a single hardware component, such as a multi-transceiver chip, a single-chip system, an application-specific integrated circuit (“ASIC”), or other types of hardware components. In some embodiments, one or more transmitters 630 and / or one or more receivers 635 may be implemented and / or integrated into a multi-chip module. In some embodiments, other components, such as network interface 640 or other hardware components / circuits, may be integrated with any number of transmitters 630 and / or receivers 635 into a single chip. In this embodiment, transmitters 630 and receivers 635 may be logically configured as transceivers 625 using one or more common control signals or as modular transmitters 630 and receivers 635 configured to be implemented in the same hardware chip or multi-chip module.

[0194] Figure 7 A network device 700, which can be used to support a hybrid BR and HFBT configuration according to embodiments of the present disclosure, is depicted. In one embodiment, the network device 700 may be an implementation of a RAN node, such as the basic unit 121, RAN node 207, or gNB as described above. Furthermore, the network device 700 may include a processor 705, a memory 710, an input device 715, an output device 720, and a transceiver 725.

[0195] In some embodiments, the input device 715 and the output device 720 are combined into a single device, such as a touchscreen. In some embodiments, the network device 700 may not include any input device 715 and / or output device 720. In various embodiments, the network device 700 may include one or more of a processor 705, a memory 710, and a transceiver 725, and may not include input device 715 and / or output device 720.

[0196] As depicted, transceiver 725 includes at least one transmitter 730 and at least one receiver 735. Here, transceiver 725 communicates with one or more remote units 105. Additionally, transceiver 725 may support at least one network interface 740 and / or application programming interface 745. Application programming interface 745 may support one or more APIs. Network interface 740 may support 3GPP reference points, such as Uu, N1, N2, and N3. Other network interfaces 740 may be supported, as will be understood by those skilled in the art.

[0197] In one embodiment, processor 705 may include any known controller capable of executing computer-readable instructions and / or performing logical operations. For example, processor 705 may be a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, or similar programmable controller. In some embodiments, processor 705 executes instructions stored in memory 710 to perform the methods and routines described herein. Processor 705 is communicatively coupled to memory 710, input device 715, output device 720, and transceiver 725.

[0198] In various embodiments, network device 700 is a RAN node (e.g., gNB) communicating with one or more UEs, as described herein. In such embodiments, processor 705 controls network device 700 to perform the RAN behaviors described above. When operating as a RAN node, processor 705 may include an application processor (also referred to as a "main processor") that manages application domains and operating system ("OS") functions, and a baseband processor (also referred to as a "baseband radio processor") that manages radio functions.

[0199] In one embodiment, memory 710 is a computer-readable storage medium. In some embodiments, memory 710 includes volatile computer storage media. For example, memory 710 may include RAM, including dynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and / or static RAM (“SRAM”). In some embodiments, memory 710 includes non-volatile computer storage media. For example, memory 710 may include a hard disk drive, flash memory, or any other suitable non-volatile computer storage device. In some embodiments, memory 710 includes both volatile and non-volatile computer storage media.

[0200] In some embodiments, memory 710 stores data related to supporting BR and HFBT hybridization. For example, memory 710 may store parameters, configurations, resource assignments, policies, and the like as described above. In some embodiments, memory 710 also stores program code and related data, such as operating systems or other controller algorithms operating on network device 700.

[0201] In one embodiment, input device 715 may include any known computer input device, including a touchpad, button, keyboard, light pen, microphone, or the like. In some embodiments, input device 715 may be integrated with output device 720, for example, as a touchscreen or similar touch-sensitive display. In some embodiments, input device 715 includes a touchscreen that allows text to be entered using a virtual keyboard displayed on the touchscreen and / or by handwriting on the touchscreen. In some embodiments, input device 715 includes two or more different devices, such as a keyboard and a touchpad.

[0202] In one embodiment, output device 720 may be designed to output visual, auditory, and / or tactile signals. In some embodiments, output device 720 includes an electronically controllable display or display device capable of outputting visual data to a user. For example, output device 720 may include (but is not limited to) an LCD display, LED display, OLED display, projector, or similar display device capable of outputting images, text, or the like to a user. As another non-limiting example, output device 720 may include a wearable display, such as a smartwatch, smart glasses, head-mounted display, or the like, which is separate from but communicatively coupled to the remainder of network device 700. Furthermore, output device 720 may be a component of a smartphone, personal digital assistant, television, desktop computer, laptop computer, personal computer, vehicle dashboard, or the like.

[0203] In some embodiments, the output device 720 includes one or more speakers for generating sound. For example, the output device 720 may generate an auditory alarm or notification (e.g., a beep or ring). In some embodiments, the output device 720 includes one or more haptic devices for generating vibration, motion, or other haptic feedback. In some embodiments, the output device 720 may be wholly or partially integrated with the input device 715. For example, the input device 715 and the output device 720 may form a touchscreen or similar touch-sensitive display. In other embodiments, the output device 720 may be located near the input device 715.

[0204] Transceiver 725 includes at least one transmitter 730 and at least one receiver 735. Similarly, one or more transmitters 730 can be used to communicate with a UE, as described herein. Similarly, one or more receivers 735 can be used to communicate with network functions in a PLMN and / or RAN, as described herein. Although only one transmitter 730 and one receiver 735 are described, network device 700 may have any suitable number of transmitters 730 and receivers 735. Furthermore, transmitters 730 and receivers 735 may be of any suitable type.

[0205] Figure 8 One embodiment of a method 800 for supporting BR and HFBT hybridization is depicted according to embodiments of the present disclosure. In various embodiments, method 800 is performed by a user equipment device in a mobile communication network, such as the remote unit 105, UE 205, and / or user equipment device 600 described above. In some embodiments, method 800 is performed by a processor, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, or the like.

[0206] Method 800 begins by determining a minimum duration between a first resource for HARQ transmission of the TB and a second resource for HARQ transmission of the TB. Here, the minimum duration includes the sum of the following: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of the TB, and a third time for retransmitting the TB. The first method includes: selecting a retransmission mode based on the minimum duration (i.e., determining whether to switch retransmission modes), wherein the retransmission mode includes one of a blind retransmission mode and an HFBT mode; and selecting sidelink resources for retransmission of the TB based on the selected retransmission mode. Method 800 ends.

[0207] This document discloses a first device for supporting hybrid BR and HFBT transmissions according to embodiments of the present disclosure. The first device may be implemented by a user equipment device in a mobile communication network, such as the remote unit 105, UE 205, and / or user equipment device 600 described above. The first device includes: a processor providing a physical (“PHY”) layer and a media access control (“MAC”) layer; and a transceiver communicating on a sidelink channel. The processor determines a minimum duration between a first resource for hybrid automatic repeat request (“HARQ”) transmission of a transport block (“TB”) and a second resource for HARQ transmission of the TB. Here, the minimum duration includes the sum of: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of the TB, and a third time for retransmitting the TB. The processor selects a retransmission mode based on the minimum duration (i.e., determines whether to switch retransmission modes), wherein the retransmission mode includes one of a blind retransmission mode and a HARQ feedback-based transmission (“HFBT”) mode; and selects sidelink resources for TB retransmission based on the selected retransmission mode.

[0208] In some embodiments, the PHY layer determines a minimum duration, provides a set of candidate resources, and notifies the MAC layer of candidate time slots in which sidelink HARQ feedback is enabled for each retransmission attempt. In such embodiments, the MAC layer selects a sidelink resource based on the minimum time slot. In some embodiments, the MAC layer selects a retransmission mode and chooses a sidelink resource from the set of candidate resources provided by the PHY layer. In such embodiments, the MAC layer selects a sidelink resource based on the minimum time slot.

[0209] In some embodiments, the MAC layer selects a first resource and a second resource for a HARQ transmission with a minimum duration of TB. In some embodiments, the MAC layer dynamically enables HARQ feedback for TB and triggers resource selection in response to enabling HARQ feedback. In such embodiments, resource selection triggered in response to enabling HARQ feedback includes switching to a resource pool containing Physical Side Link Feedback Channel (“PSFCH”) resources.

[0210] In some embodiments, the retransmission mode is selected based on blind retransmission and HARQ feedback-based transmission. In some embodiments, the first number of retransmissions are blind retransmissions, and subsequent retransmissions are based on HARQ feedback transmission. In some embodiments, the MAC layer sends a bitmap of time slots to the PHY layer, the bitmap indicating where blind retransmission is enabled and where HARQ feedback-based transmission is enabled.

[0211] In some embodiments, the processor further determines the number of blind retransmissions and HARQ-based transmissions required to meet reliability requirements and reduces the number of blind retransmissions in response to increased channel congestion. In some embodiments, selecting a retransmission mode includes switching from blind retransmission mode to HFBT mode based on channel state information (“CSI”) (e.g., a report received from the corresponding destination ID) and / or the channel busy rate (“CBR”) of the sidelink channel.

[0212] This document discloses a first method for supporting BR and HFBT hybrid operations according to embodiments of the present disclosure. The first method can be performed by a user equipment device in a mobile communication network, such as the remote unit 105, UE 205, and / or user equipment device 600 described above. The first method includes determining a minimum duration between a first resource for HARQ transmission of TB and a second resource for HARQ transmission of TB. Here, the minimum duration includes the sum of: a first time for receiving HARQ feedback, a second time for determining whether to perform a retransmission of TB, and a third time for retransmitting TB. The first method includes: selecting a retransmission mode based on the minimum duration (i.e., determining whether to switch retransmission modes), wherein the retransmission mode includes one of a blind retransmission mode and an HFBT mode; and selecting sidelink resources for TB retransmission based on the selected retransmission mode.

[0213] In some embodiments, the PHY layer determines a minimum duration, the method further including the PHY layer providing a set of candidate resources and notifying the MAC layer of candidate time slots in which sidelink HARQ feedback is enabled for each retransmission attempt. In such embodiments, the MAC layer selects a sidelink resource based on the minimum time slot. In some embodiments, the MAC layer selects a retransmission mode and wherein the MAC layer selects a sidelink resource from the set of candidate resources provided by the PHY layer. In such embodiments, the MAC layer selects a sidelink resource based on the minimum time slot.

[0214] In some embodiments, the first method includes selecting a first resource for a HARQ transport with a minimum duration of TB and selecting a second resource for the HARQ transport of TB. In some embodiments, the MAC layer selects the first and second resources. In some embodiments, the first method includes dynamically enabling HARQ feedback for TB and triggering resource selection in response to enabling HARQ feedback. In some embodiments, resource selection in response to enabling HARQ feedback includes selecting a resource pool containing PSFCH resources.

[0215] In some embodiments, the retransmission mode selection is based on a combination of blind retransmission and HARQ feedback-based transmission. In some embodiments, a first number of retransmissions are blind retransmissions, and subsequent retransmissions are based on HARQ feedback transmission. In some embodiments, the first method includes sending a bitmap of time slots from the MAC layer to the PHY layer, the bitmap indicating where blind retransmission is enabled and where HARQ feedback-based transmission is enabled.

[0216] In some embodiments, the first method includes determining the number of blind retransmissions and HARQ-based transmissions required to meet reliability requirements, and reducing the number of blind retransmissions in response to increased channel congestion. In some embodiments, selecting a retransmission mode includes switching from blind retransmission mode to HFBT mode based on CSI (e.g., CSI reports received from the corresponding destination ID) and / or CBR of the sidelink channel.

[0217] The embodiments may be practiced in other specific forms. The described embodiments should be considered illustrative rather than limiting in all respects. The scope of the invention is therefore indicated by the appended claims rather than by the foregoing description. All variations within the equivalent meaning and scope of the claims are included within their scope.

Claims

1. A user equipment (UE) for wireless communication, the UE comprising: At least one memory; as well as At least one processor, coupled to the at least one memory and configured such that the UE: Determine the minimum time gap between a first resource for a first Hybrid Automatic Repeat Request (HARQ) transmission of a block TB and a second resource for a second HARQ transmission of the TB, wherein the minimum time gap comprises the sum of the following: Used to receive HARQ feedback immediately; The second time used to determine whether to perform a retransmission of the TB; as well as The third time used to perform the retransmission of the TB; as well as A set of sidelink SL resources for the retransmission of the TB is selected, at least in part, based on the minimum time interval.

2. The UE of claim 1, wherein the at least one processor is further configured such that the UE provides a physical PHY layer and a media access control (MAC) layer, wherein the at least one processor is further configured such that the PHY layer indicates a set of candidate resources to the MAC layer, and wherein, in order to select the set of SL resources, the at least one processor is further configured such that the MAC layer selects the SL resources at least in part based on the minimum time interval.

3. The UE of claim 2, wherein, in order to determine the minimum time slot, the at least one processor is configured such that the PHY layer determines the minimum time slot, and wherein the at least one processor is configured such that the PHY layer instructs the MAC layer to enable SL HARQ feedback for retransmission attempts in one or more candidate time slots.

4. The UE of claim 1, wherein the at least one processor is configured such that the UE selects the first resource for the first HARQ transmission of the TB and selects the second resource for the second HARQ transmission of the TB based on the minimum time interval.

5. The UE of claim 4, wherein the at least one processor is configured to cause the UE to provide a Media Access Control (MAC) layer configured to select the first resource and the second resource.

6. The UE of claim 1, wherein the at least one processor is configured such that the UE enables HARQ feedback for the TB and performs resource selection in response to enabling the HARQ feedback.

7. The UE of claim 6, wherein, in order to perform the resource selection, the at least one processor is configured to cause the UE to switch to a resource pool containing Physical Side Link Feedback Channel (PSFCH) resources.

8. The UE of claim 1, wherein the at least one processor is configured such that the UE selects a retransmission mode at least in part based on the minimum time gap, wherein the retransmission mode includes a blind retransmission mode or a transmission HFBT mode based on HARQ feedback.

9. The UE of claim 8, wherein the at least one processor is configured such that the UE further selects the retransmission mode based on a pattern of blind retransmission and HARQ feedback-based transmission, wherein a first number of retransmissions are blind retransmissions and a second number of subsequent retransmissions are HARQ feedback-based transmissions.

10. The UE of claim 8, wherein, in order to select the retransmission mode, the at least one processor is configured such that the UE switches from the blind retransmission mode to the HFBT mode based on channel state information (CSI), or based on the channel busy rate (CBR) of the SL channel, or based on both of the above.

11. The UE of claim 1, wherein the at least one processor is configured such that the UE transmits a bitmap of time slots from the Media Access Control (MAC) layer to the Physical PHY layer, and wherein the bitmap of time slots identifies enabled blind retransmissions and enabled HARQ-based feedback transmissions.

12. The UE of claim 1, wherein the at least one processor is configured such that the UE: Determine the number of blind retransmissions that meet reliability requirements and the number of transmissions based on HARQ feedback; and The number of blind retransmissions is reduced in response to changes in channel congestion.

13. A processor for wireless communication, the processor comprising: At least one controller, coupled to at least one memory and configured such that the processor: Determine the minimum time gap between a first resource for a first Hybrid Automatic Repeat Request (HARQ) transmission of a block TB and a second resource for a second HARQ transmission of the TB, wherein the minimum time gap comprises the sum of the following: Used to receive HARQ feedback immediately; The second time used to determine whether to perform a retransmission of the TB; as well as The third time used to perform the retransmission of the TB; as well as A set of sidelink SL resources for the retransmission of the TB is selected, at least in part, based on the minimum time interval.

14. The processor of claim 13, further comprising: The physical PHY layer and the media access control (MAC) layer, wherein the at least one controller is further configured such that the PHY layer indicates a set of candidate resources to the MAC layer, and wherein, in order to select the set of SL resources, the at least one controller is further configured such that the MAC layer selects the SL resources at least in part based on the minimum time interval.

15. The processor of claim 14, wherein, in order to determine the minimum time slot, the at least one controller is configured such that the PHY layer determines the minimum time slot, and wherein the at least one controller is configured such that the PHY layer indicates to the MAC layer that one or more candidate time slots in which SL HARQ feedback is enabled for retransmission attempts are performed.

16. The processor of claim 13, wherein the at least one controller is configured such that the processor selects the first resource for the first HARQ transmission of the TB and selects the second resource for the second HARQ transmission of the TB based on the minimum time interval.

17. The processor of claim 16, wherein the at least one controller is configured such that the processor provides a Media Access Control (MAC) layer configured to select the first resource and the second resource.

18. The processor of claim 13, wherein the at least one controller is configured to enable HARQ feedback for the TB and perform resource selection in response to enabling HARQ feedback, wherein, in order to perform the resource selection, the at least one controller is configured to switch the processor to a resource pool containing physical sidelink feedback channel (PSFCH) resources.

19. The processor of claim 13, wherein the at least one controller is configured such that the processor transmits a bitmap of time slots from the Media Access Control (MAC) layer to the Physical PHY layer, and wherein the bitmap of time slots identifies enabled blind retransmissions and enabled HARQ-based feedback transmissions.

20. A method for execution at a user equipment (UE), the method comprising: Determine the minimum time interval between a first resource for a first hybrid automatic repeat request (HARQ) transmission of a block TB and a second resource for a second HARQ transmission of the TB. as well as A set of sidelink SL resources for retransmission of the TB is selected, at least in part, based on the minimum time interval. The minimum time interval mentioned above includes the sum of the following: Used to receive HARQ feedback immediately; The second time used to determine whether to perform the retransmission of the TB; as well as The third time used to perform the retransmission of the TB.

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