Method and apparatus for transmitting sidelink control information indicating no sidelink data

Abstract

Devices, methods, and systems for transmitting sidelink control information indicating no sidelink data are disclosed. One method (400) includes determining (402), at a user equipment, that no sidelink data is available for a destination. The method (400) includes transmitting (404) sidelink control information indicating that no sidelink data is available for the destination to the destination and triggering a channel state information feedback response from the destination. The method (400) includes monitoring (406) for receipt of the channel state information feedback response from the destination.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Patent Application No. 63 / 022,994, entitled “APPARATUSES, METHODS, AND SYSTEMS FOR HARQ-BASED RLF MECHANISM NR V2X COMMUNICATION” and filed on May 11, 2020 for Joachim Application No. 63 / 022,994, which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The subject matter disclosed herein relates generally to wireless communication and more particularly to transmitting sidelink control information indicating no sidelink data. BACKGROUND

[0004] In certain wireless communication networks, sidelink control information can be transmitted. Typically, the sidelink control information is transmitted with data. SUMMARY

[0005] Methods for transmitting sidelink control information indicating no sidelink data are disclosed. Devices and systems also perform the functions of the methods. One embodiment of a method includes determining, at a user equipment, that no sidelink data is available for a destination. In some embodiments, the method includes transmitting sidelink control information indicating that no sidelink data is available for the destination to the destination and triggering a channel state information feedback response from the destination. In certain embodiments, the method includes monitoring for receipt of the channel state information feedback response from the destination.

[0006] A device for transmitting sidelink control information indicating no sidelink data includes a processor that determines that no sidelink data is available for a destination. In various embodiments, the device includes a transmitter that transmits sidelink control information indicating that no sidelink data is available for the destination to the destination and triggers a channel state information feedback response from the destination, where the processor monitors for receipt of the channel state information feedback response from the destination.

[0007] Another embodiment of a method for a radio link failure procedure includes receiving, at a user equipment, information indicating a discontinuous transmission. In some embodiments, the method includes incrementing a discontinuous transmission counter of a radio link failure procedure. In certain embodiments, the method includes initiating a discontinuous transmission timer.

[0008] Another apparatus for a radio link failure procedure includes a receiver that receives information indicating a discontinuous transmission. In various embodiments, the apparatus includes a processor that increments a discontinuous transmission counter of a radio link failure procedure and initiates a discontinuous transmission timer.

[0009] Yet another embodiment of a method for a logical channel prioritization procedure includes performing a logical channel prioritization procedure at a user equipment. In some embodiments, the method includes determining, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled. In certain embodiments, the method includes transmitting sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmitting the transport block.

[0010] Yet another apparatus for a logical channel prioritization procedure includes a processor that performs a logical channel prioritization procedure and determines, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled. In various embodiments, the apparatus includes a transmitter that transmits sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmitting the transport block. BRIEF DESCRIPTION OF DRAWINGS

[0011] More specific descriptions of the embodiments briefly described above will be rendered by reference to specific embodiments illustrated in the drawings which are presented for the sole purpose of illustration of the embodiments and are not intended to limit the scope thereof. The embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0012] Figure 1 is a schematic block diagram illustrating one embodiment of a wireless communication system for transmitting sidelink control information indicating no sidelink data;

[0013] Figure 2 is a schematic block diagram illustrating one embodiment of an apparatus that can be used for transmitting sidelink control information indicating no sidelink data;

[0014] Figure 3 is a schematic block diagram illustrating one embodiment of an apparatus that can be used for transmitting sidelink control information indicating no sidelink data;

[0015] Figure 4 is a flow diagram illustrating one embodiment of a method for transmitting sidelink control information indicating no sidelink data;

[0016] Figure 5 is a flow diagram illustrating one embodiment of a method for a radio link failure procedure; and

[0017] is a flow diagram illustrating one embodiment of a method for a radio link failure procedure; andFigure 6 is a flowchart illustrating one embodiment of a method for a logical channel prioritization procedure. DETAILED DESCRIPTION

[0018] As will be appreciated by those skilled in the art, aspects of the embodiments can be embodied as a system, device, method or program product. Accordingly, the embodiments can take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that can all generally be referred to herein as a "circuit," "module" or "system." Furthermore, the embodiments can take the form of a program product embodied in one or more computer readable storage devices having computer readable code stored (and / or encoded) therein. The storage devices can be tangible, non-transitory, and / or non-transmission. The storage devices can not embody signals. In particular embodiments, the storage devices only employ signals for accessing the code.

[0019] Certain of the functional units described in this specification can be labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module can be implemented as a hardware circuit comprising custom very-large-scale integration ("VLSI") circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module can also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

[0020] Modules can also be implemented in code and / or software for execution by various types of processors. An identified module of code may, for instance, include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure or function. Nevertheless, the executables of an identified module need not be physically located together, but can include disparate instructions stored in different locations which, when joined logically together, include the module and achieve the stated purpose for the module.

[0021] Indeed, a module of code can be a single instruction, or many instructions, and can even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data can be identified within the modules and can be embodied in any suitable form and organized within any suitable type of data structure. The operational data can be collected as a single data set, or can be distributed over different locations including over different computer readable storage devices. Where a module or portions of a module are implemented in software, the software portions are stored in one or more computer readable storage devices.

[0022] Any combination of one or more computer readable medium can be utilized. The computer readable medium can be a computer readable storage medium. The computer readable storage medium can be a storage device storing the code. The storage device can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0023] More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory ("RAM"), a read-only memory ("ROM"), an erasable programmable read-only memory ("EPROM" or Flash memory), a portable compact disc read-only memory ("CD-ROM"), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium can be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0024] Code for carrying out operations for embodiments can be any number of lines and can be written in any combination of one or more programming languages, including an object oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the "C" programming language, or the like, and / or machine languages such as assembly languages. The code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network ("LAN") or a wide area network ("WAN"), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0025] Reference throughout this specification to "one embodiment", "an embodiment", or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment", "in an embodiment", and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise be

[0026] Furthermore, the described features, structures, or characteristics of the embodiments can be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

[0027] Aspects of the embodiments are described below with reference to exemplary flowcharts and / or exemplary block diagrams of methods, apparatuses, systems, and program products according to the embodiments. It will be understood that each block of the exemplary flowcharts and / or exemplary block diagrams, and combinations of blocks in the exemplary flowcharts and / or exemplary block diagrams, can be implemented by code. The 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 the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowcharts and / or block diagrams block or blocks.

[0028] The code can also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function / act specified in the flowcharts and / or block diagrams block or blocks.

[0029] The code can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowcharts and / or block diagrams block or blocks.

[0030] The flowcharts and / or block diagrams in the figures illustrate the architecture, functionality, and operations of possible implementations of apparatuses, systems, methods and program products according to various embodiments. In this regard, each block in the flowcharts and / or block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the flowcharts and / or block diagrams can include a number of functions or acts that can be rearranged in other

[0031] It is also noted that the functions related to the blocks in the diagrams can not occur in the order shown in the diagrams. For example, two blocks shown in succession can in fact be executed substantially concurrently or can sometimes be executed in the reverse order depending on the functionality involved. These and other steps and methods that are equivalent in function, logic or effect to those illustrated can be substituted for the ones shown.

[0032] Although various arrow types and line types can be employed in the flowchart and / or block diagrams, these are understood to be taken in a generic sense, merely indicating various embodiments of the corresponding steps. For example, an arrow can indicate a waiting or monitoring period of time, as well as being merely a chronological progression of the steps. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations thereof, can be implemented by special purpose hardware-based systems that perform the specified functions or steps, or combinations of special purpose hardware and code.

[0033] In the drawings, description of elements can refer to elements in previous figures. Like numbers refer to like elements throughout the several figures of the drawings.

[0034] Figure 1 Embodiments of a wireless communication system 100 for transmitting sidelink control information indicating no sidelink data are depicted. In one embodiment, the wireless communication system 100 includes remote units 102 and network units 104. Even though a specific number of remote units 102 and network units 104 are depicted in the wireless communication system 100, one of skill in the art will recognize that any number of remote units 102 and network units 104 can be included in the wireless communication system 100. Figure 1 Although a specific number of remote units 102 and network units 104 are depicted in the wireless communication system 100, one of skill in the art will recognize that any number of remote units 102 and network units 104 can be included in the wireless communication system 100.

[0035] In one embodiment, a remote unit 102 can include a computing device, such as a desktop computer, laptop computer, personal digital assistant (“PDA”), tablet computer, smart phone, smart television (e.g., a television connected to the Internet), set-top box, game console, security system (including security cameras), vehicle

[0036] The network units 104 can be distributed throughout a geographic region. In certain embodiments, the network units 104 can also be referred to as and / or include an access point, an access terminal, a base, a base station, a location server, a core network (“CN”), a radio network entity, a NodeB, an Evolved Node B (“eNB”), a 5G NodeB (“gNB”), a home NodeB, a relay node, a device, a core network, an aerial server, a radio access node, an access point (“AP”), New Radio (“NR”), a network entity, an access and mobility management function (“AMF”), a unified data management (“UDM”), a unified data repository (“UDR”), UDM / UDR, a policy control function (“PCF”), a radio access network (“RAN”), a network slice selection function (“NSSF”), operations, administration, and management (“OAM”), a session management function (“SMF”), a user plane function (“UPF”), an application function, an authentication server function (“AUSF”), security anchor functionality (“SEAF”), trusted non-3GPP gateway function (“TNGF”), or by any other terminology used in the art. The network units 104 are generally part of a radio access network that includes one or more controllers communicably coupled to one or more corresponding network units 104. The radio access network is typically communicably coupled to one or more core networks, which can be coupled to other networks, like the Internet and public switched telephone networks, among other networks. These and other elements of radio access and core networks are not illustrated but are well known by those having ordinary skill in the art.

[0037] In one implementation, the wireless communication system 100 is compliant with the NR protocols standardized in the Third Generation Partnership Project (“3GPP”), wherein the network units 104 transmit using an OFDM modulation scheme on the downlink (“DL”) and the remote units 102 transmit on the uplink (“UL”) using a Single-Carrier Frequency Division Multiple Access (“SC-FDMA”) scheme or an Orthogonal Frequency Division Multiplexing (“OFDM”) scheme. More generally, however, the wireless communication system 100 can implement some other open or proprietary communication protocol, such as WiMAX, Institute of Electrical and Electronics Engineers (“IEEE”) 802.11 variants, Global System for Mobile Communications (“GSM”), General Packet Radio Service (“GPRS”), Universal Mobile ZigBee, Sigfoxx, and other protocols. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

[0038] The network units 104 can serve a number of remote units 102 within a serving area, for example, a cell or a cell sector, via wireless communication links. The network units 104 transmit DL communication signals to serve the remote units 102 in the time, frequency, and / or spatial domain.

[0039] In various embodiments, a remote unit 102 can determine, at a user equipment, that no sidelink data is available for a destination. In some embodiments, the remote unit 102 can transmit, to the destination, sidelink control information indicating that no sidelink data is available for the destination and trigger a channel state information feedback response from the destination. In certain embodiments, the remote unit 102 can monitor for receipt of the channel state information feedback response from the destination. Thus, the remote unit 102 can be used to transmit sidelink control information indicating no sidelink data.

[0040] In certain embodiments, a remote unit 102 can receive, at a user equipment, information indicating a discontinuous transmission. In some embodiments, the remote unit 102 can increment a discontinuous transmission counter of a radio link failure procedure. In various embodiments, the remote unit 102 can start a discontinuous transmission timer. Thus, the remote unit 102 can be used in a radio link failure procedure.

[0041] In certain embodiments, a remote unit 102 can perform, at a user equipment, a logical channel prioritization procedure. In some embodiments, the remote unit 102 can determine, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled. In various embodiments, the remote unit 102 can transmit sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmitting the transport block. Thus, the remote unit 102 can be used in a logical channel prioritization procedure.

[0042] Figure 2 One embodiment of an apparatus 200 that can be used to transmit sidelink control information indicating no sidelink data is depicted. The apparatus 200 includes one embodiment of the remote unit 102. Furthermore, the remote unit 102 can include a processor 202, a memory 204, an input device 206, a display 208, a transmitter 210, and a receiver 212. In some embodiments, the input device 206 and the display 208 are combined into a single device, such as a touch screen. In certain embodiments, the remote unit 102 can not include any input device 206 and / or display 208. In various embodiments, the remote unit 102 can include one or more of the processor 202, the memory 204, the transmitter 210, and the receiver 212, and can not include the input device 206 and / or the display 208.

[0043] In one embodiment, the processor 202 can include any known controller capable of executing computer-readable instructions and / or capable of performing logical operations. For example, the processor 202 can be a microcontroller, a microprocessor, a central processing unit ("CPU"), a graphics processing unit ("GPU"), an auxiliary processing unit, a field programmable gate array ("FPGA"), or similar programmable controller. In some embodiments, the processor 202 executes instructions stored in the memory 204 to perform methods and routines described herein. The processor 202 is communicatively coupled to the memory 204, the input device 206, the display 208, the transmitter 210, and the receiver 212.

[0044] In one embodiment, the memory 204 is a computer-readable storage medium. In some embodiments, the memory 204 includes volatile computer storage media. For example, the memory 204 can include RAM, including dynamic RAM ("DRAM"), synchronous dynamic RAM ("SDRAM"), and / or static RAM ("SRAM"). In some embodiments, the memory 204 includes non-volatile computer storage media. For example, the memory 204 can include a hard disk drive, a flash memory, or any other suitable non-volatile computer storage device. In some embodiments, the memory 204 includes both volatile and non-volatile computer storage media. In some embodiments, the memory 204 also stores program code and related data, such as an operating system or other controller algorithms operating on the remote unit 102.

[0045] In one embodiment, the input device 206 can include any known computer input device, including a touch panel, buttons, a keyboard, a stylus, a microphone, etc. In some embodiments, the input device 206 can be integrated with the display 208 as, for example, a touch screen or similar touch-sensitive display. In some embodiments, the input device 206 includes a touch screen such that text can be input using a virtual keyboard displayed on the touch screen and / or by handwriting on the touch screen. In some embodiments, the input device 206 includes two or more different devices, such as a keyboard and a touch panel.

[0046] In one embodiment, display 208 can include any known electronically controllable display or display device. Display 208 can be designed to output visual, audible, and / or tactile signals. In some embodiments, display 208 includes an electronic display capable of outputting visual data to a user. For example, the display 208 can include, but is not limited to, a liquid crystal display (“LCD”), a light emitting diode (“LED”) display, an organic light emitting diode (“OLED”) display, a projector, or similar display device capable of outputting images, text, etc. to a user. As another non-limiting example, the display 208 can include a wearable display, such as a smart watch, smart glasses, a heads-up display, etc. Further, the display 208 can be a component of a smart phone, a personal digital assistant, a television, a table computer, a notebook (laptop) computer, a personal computer, a vehicle dashboard, etc.

[0047] In certain embodiments, display 208 includes one or more speakers for producing sound. For example, display 208 can produce an audible alert or notification (e.g., a beep or chime). In some embodiments, display 208 includes one or more haptic devices for producing vibrations, motion, or other haptic feedback. In some embodiments, all or portions of display 208 can be integrated with input device 206. For example, input device 206 and display 208 can form a touchscreen or similar touch-sensitive display. In other embodiments, display 208 can be located near input device 206.

[0048] In some embodiments, processor 202 can determine that no sidelink data is available for a destination. In various embodiments, transmitter 210 can transmit, to the destination, sidelink control information indicating that no sidelink data is available for the destination and trigger a channel state information feedback response from the destination, where the processor monitors for receipt of the channel state information feedback response from the destination.

[0049] In certain embodiments, receiver 212 can receive information indicating a discontinuous transmission. In various embodiments, processor 202 can: increment a discontinuous transmission counter of a radio link failure procedure; and initiate a discontinuous transmission timer.

[0050] In some embodiments, processor 202 can: perform a logical channel prioritization procedure; and determine, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled. In various embodiments, transmitter 210 can transmit sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

[0051] Although only one transmitter 210 and one receiver 212 are illustrated, the remote unit 102 can have any suitable number of transmitters 210 and receivers 212. The transmitter 210 and receiver 212 can be any suitable type of transmitters and receivers. In one embodiment, the transmitter 210 and receiver 212 can be part of a transceiver.

[0052] Figure 3 One embodiment of an apparatus 300 that can be used to transmit sidelink control information indicating no sidelink data is depicted. The apparatus 300 includes one embodiment of the network unit 104. Furthermore, the network unit 104 can include a processor 302, a memory 304, an input device 306, a display 308, a transmitter 310, and a receiver 312. As can be appreciated, the processor 302, the memory 304, the input device 306, the display 308, the transmitter 310, and the receiver 312 can be substantially similar to the processor 202, the memory 204, the input device 206, the display 208, the transmitter 210, and the receiver 212, respectively, of the remote unit 102.

[0053] In some embodiments, radio link monitoring (“RLM”) can be performed, e.g., using a user equipment (“UE”) to network (“Uu”) interface (e.g., NR, LTE). If the RLM procedure indicates that the UE is out of sync with respect to the DL (e.g., a hypothetical block error rate (“BLER”) target for a physical downlink control channel (“PDCCH”) exceeds a threshold, e.g., 10%) for a duration, the UE can declare a radio link failure (“RLF”) and can initiate a recovery procedure. Recovery over Uu can include attempting to reestablish a radio resource control (“RRC”) connection on a different cell. In direct communication between UEs (“PC5”), it can be meaningful to perform radio link monitoring to determine whether the radio link between two UEs is good enough, and if not, the UE can not have to attempt to transmit to the other UE. In certain embodiments, upon declaring RLF, the UE can immediately or later clear the context of the other UE and release memory space.

[0054] In various embodiments, a RLF mechanism at a transmitting (“TX”) UE can be based on hybrid automatic repeat request (“HARQ”) feedback. In certain embodiments, the TX UE counts a number of consecutive discontinuous transmissions (“DTX”) received from a receiving (“RX”) UE in response to a physical sidelink shared channel (“PSSCH”) transmission. In some embodiments, if the counter exceeds a predefined threshold (e.g., x number of consecutive DTX for a particular link and / or connection received from the RX UE), RLF can be declared and subsequent actions can be taken.

[0055] In certain embodiments, channel state information (“CSI”) reporting can be used. A sidelink channel state information (“SL-CSI”) reporting procedure can be used to provide sidelink channel state information to a peer UE. In various embodiments, for each pair of source Layer-2 identifier (“ID”) and destination Layer-2 ID, the MAC entity can: if a SL-CSI report has been triggered by SCI and not cancelled: then 1) if the MAC entity has allocated SL resources for a new transmission: then a) instruct the multiplexing and assembly procedure to generate a Sidelink CSI report MAC CE; b) cancel the triggered SL-CSI report; 2) else, if the MAC entity has been configured by RRC to transmit using SL-RNTI or SLCS-RNTI: then trigger a scheduling request.

[0056] In some embodiments, SCI format 0-1 can be used to schedule PSSCH and 2nd stage SCI on PSSCH. The following information can be transmitted using SCI format 0-1: 1) priority - 3 bits; 2) frequency resource assignment - if the value of the higher layer parameter sl-MaxNumPerReserve is configured to 2, then 8 bits; else if the value of the higher layer parameter sl-MaxNumPerReserve is configured to 3, then 12 bits; 3) time resource assignment - if the value of the higher layer parameter sl-MaxNumPerReserve is configured to 2, then 5 bits; else if the value of the higher layer parameter sl-MaxNumPerReserve is configured to 3, then 9 bits; 4) resource reservation period - if the higher parameter sl-MultiReserveResource is configured, then 2 bits; else 0 bits; 5) demodulation reference signal (“DMRS”) pattern - if more than one DMRS pattern is configured by the higher layer parameter sl-PSSCH-DMRS-TimePattern, then [x] bits; else 0 bits; 6) 2nd stage SCI format - [x] bits; 6) beta_offset indicator - [2] bits, as provided by the higher layer parameter sl-BetaOffsets2ndSCI; 7) number of DMRS ports - 1 bit; 8) modulation and coding scheme - 5 bits; and 9) reserved - [2-4] bits, as determined by the higher layer parameter sl-NumReservedBits, with value set to zero.

[0057] ​​​In various embodiments, SCI format 0-2 is used for decoding of PSSCH transmission. The following information can be transmitted by SCI format 0-2: HARQ process ID - [x] bits; new data indicator - 1 bit; redundancy version - 2 bits; source ID - 8 bits; destination ID - 16 bits; CSI request - 1 bit; if the type 1 groupcast is indicated by the 2nd stage SCI format field in the corresponding SCI format 0-1, the following fields exist: zone ID - 12 bits; and communication range requirement - 4 bits.

[0058] In various embodiments, if a TX UE transmits sidelink (“SL”) data in a blind retransmission mode and hybrid automatic repeat request (“HARQ”) feedback is disabled, there can be an effective radio link failure (“RLF”) mechanism at the transmitter (“TX”) user equipment (“UE”). In some embodiments, the determination of whether to use a HARQ feedback mode for transmission of a transport block (“TB”) depends on the configuration of the highest priority logical channel within the TB for a particular destination (e.g., it can happen that the UE uses blind retransmission for a certain period of time). In such embodiments, HARQ feedback can be enabled for each TB transmission for a particular destination.

[0059] In a first embodiment, in addition to HARQ feedback for a HARQ-based RLF mechanism running on the TX UE, channel state information (“CSI”) feedback can also be considered. In the case of a lack of SL data for a destination for which a HARQ-based RLF procedure is running, the TX UE can convey sidelink control information (“SCI”) to a destination for which the CSI request bit is set to “1” (e.g., requesting CSI information). If the TX UE does not receive a CSI report from a receiver (“RX”) UE even if requested, the TX UE can consider the lack of CSI medium access control (“MAC”) control element (“CE”) to be the same as a discontinuous reception (“DTX”) for the HARQ-based RLF procedure. Furthermore, if a MAC protocol data unit (“PDU”) is transmitted to the RX UE without HARQ feedback support (e.g., using a blind retransmission mode), the CSI report can be used for the RLF procedure (e.g., the lack of requested CSI report is considered and / or handled as a DTX).

[0060] In a second embodiment, only SCI can be transmitted without a corresponding physical sidelink shared channel (“PSSCH”) transmission. To save sidelink (“SL”) resources, only SCI can be sent without any PSSCH transmission. In this embodiment, only SCI can be used in a case where no SL data is available for the destination and the TX UE wants to trigger the HARQ feedback transmission of the RX UE for RLF measurement and / or procedure (e.g., HARQ-based RLF procedure). In one embodiment of the second embodiment, to reduce the transmission power and reduce interference, the TX UE can convey only SCI without a physical sidelink shared channel (“PS-SCH”) transmission. Upon reception of only SCI, the RX UE can acknowledge the reception of the SCI by sending a hybrid automatic repeat request (“HARQ”) acknowledgement (“ACK”). In some embodiments of the second embodiment, the SCI indicates no associated PSSCH transmission (e.g., one reserved bit in the first stage SCI can be used to indicate lack of PSSCH transmission). In certain embodiments of the second embodiment, a SCI field or a combination of SCI fields is set to a predefined value, indicating lack of PSSCH transmission.

[0061] In a third embodiment, the UE starts a timer after it has received a DTX from the RX UE and has incremented the DTX counter of the RLF procedure. Upon reception of a HARQ feedback (e.g., ACK and / or negative acknowledgement (“NACK”)) or a DTX, the timer stops in case an ACK and / or NACK is received or restarts in case a next DTX is received. When the timer expires, the UE resets the DTX counter for RLF detection to zero. The timer can be used to account for scenarios where certain TBs are transmitted in a blind retransmission mode, where no HARQ feedback is received from the RX UE.

[0062] In a fourth embodiment, a UE can indicate within SCI that HARQ feedback is enabled even if a TB only contains data for logical channels (“LCHs”) whose HARQ feedback is disabled due to logical channel prioritization (“LCP”) procedures. As can be appreciated, LCH configuration by the network can be useful if the RLF mechanism requires HARQ feedback to work properly. In one embodiment of the fourth embodiment, a TX UE can use a hybrid mode of operation for transmitting a TB, where the TX UE requires HARQ feedback from the RX UE after a certain number of blind retransmissions. The number of (re)transmissions after which the TX UE requests HARQ feedback (e.g., to enable HARQ feedback for any further retransmissions) can be preconfigured or determined by the TX UE. In another embodiment of the fourth embodiment, a TX UE can enable SL HARQ feedback based on the distance between multiple resources indicated in DCI (e.g., SL HARQ feedback is enabled by the TX UE if the distance between multiple resources enables it to implement HARQ round-trip reception timing).

[0063] As can be appreciated, any of the embodiments described herein can be configured for a given destination identifier (“ID”), source and destination Layer-2 ID pairs corresponding to a UE-to-UE interface (“PC5”) radio resource control (“RRC”) connection and / or SL LCH. For a particular destination and / or LCH, a UE can rely on an upper layer keep-alive message.

[0064] Figure 4 FIG. 4 is a flow diagram illustrating one embodiment of a method 400 for transmitting sidelink control information indicating no sidelink data. In some embodiments, the method 400 is performed by an apparatus, such as the remote unit 102. In certain embodiments, the method 400 can be performed by a processor executing program code, such as a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

[0065] In various embodiments, the method 400 includes determining 402, at a user equipment, that no sidelink data is available for a destination. In some embodiments, the method 400 includes transmitting 404, to the destination, sidelink control information indicating that no sidelink data is available for the destination and triggering a channel state information feedback response from the destination. In certain embodiments, the method 400 includes monitoring 406 for receipt of the channel state information feedback response from the destination.

[0066] In certain embodiments, the sidelink control information includes a channel state information request bit indicating a request for the channel state information feedback response. In some embodiments, the method further includes indicating a discontinuous transmission in response to monitoring for receipt of the channel state information feedback response resulting in no receipt of the channel state information feedback response.

[0067] Figure 5 FIG. 15 is a flow diagram illustrating one embodiment of a method 1500 for a radio link failure procedure. In some embodiments, the method 1500 can be performed by a device, such as the remote unit 102. In certain embodiments, the method 1500 can be performed by a processor executing program code, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, etc.

[0068] In various embodiments, the method 1500 includes receiving 1502, at a user equipment, information indicating a discontinuous transmission. In some embodiments, the method 1500 includes incrementing 1504 a discontinuous transmission counter for a radio link failure procedure. In certain embodiments, the method 1500 includes starting 1506 a discontinuous transmission timer.

[0069] In certain embodiments, the method further includes stopping the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback. In some embodiments, the method further includes restarting the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission. In various embodiments, the method further includes resetting the discontinuous transmission timer to zero in response to the discontinuous transmission timer expiring.

[0070] Figure 6 FIG. 16 is a flow diagram illustrating one embodiment of a method 1600 for a logical channel prioritization procedure. In some embodiments, the method 1600 can be performed by a device, such as the remote unit 102. In certain embodiments, the method 1600 can be performed by a processor executing program code, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, etc.

[0071] In various embodiments, the method 1600 includes performing 1602, at a user equipment, a logical channel prioritization procedure. In some embodiments, the method 1600 includes determining 1604, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels that disable hybrid automatic repeat request feedback. In certain embodiments, the method 1600 includes transmitting 1606 sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmitting the transport block.

[0072] In certain embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled includes transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after a predetermined number of blind retransmissions of the transmission. In some embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled includes transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

[0073] In one embodiment, a method comprises determining, at a user equipment, that no sidelink data is available for a destination; transmitting, to the destination, sidelink control information indicating that no sidelink data is available for the destination and triggering a channel state information feedback response from the destination; and monitoring for receipt of the channel state information feedback response from the destination.

[0074] In certain embodiments, the sidelink control information comprises a channel state information request bit indicating a request for a channel state information feedback response.

[0075] In some embodiments, the method further comprises indicating a discontinuous transmission in response to monitoring for receipt of the channel state information feedback response resulting in no receipt of the channel state information feedback response.

[0076] In one embodiment, an apparatus comprises a user equipment, the apparatus further comprising: a processor that determines that no sidelink data is available for a destination; and a transmitter that transmits, to the destination, sidelink control information indicating that no sidelink data is available for the destination and triggering a channel state information feedback response from the destination; wherein the processor monitors for receipt of the channel state information feedback response from the destination.

[0077] In certain embodiments, the sidelink control information comprises a channel state information request bit indicating a request for a channel state information feedback response.

[0078] In some embodiments, the processor indicates a discontinuous transmission in response to monitoring for receipt of the channel state information feedback response resulting in no receipt of the channel state information feedback response.

[0079] In one embodiment, a method comprises receiving, at a user equipment, information indicating a discontinuous transmission; incrementing a discontinuous transmission counter of a radio link failure procedure; and initiating a discontinuous transmission timer.

[0080] In certain embodiments, the method further comprises stopping the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback.

[0081] In some embodiments, the method further comprises re-initiating the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission.

[0082] In various embodiments, the method further comprises resetting the discontinuous transmission timer to zero in response to the discontinuous transmission timer expiring.

[0083] In one embodiment, an apparatus comprising a user equipment, the apparatus further comprising: a receiver that receives information indicating a discontinuous transmission; and a processor that: increments a discontinuous transmission counter of a radio link failure procedure; and initiates a discontinuous transmission timer.

[0084] In certain embodiments, the processor stops the discontinuous transmission timer in response to receiving hybrid automatic repeat request feedback.

[0085] In some embodiments, the processor re-initiates the discontinuous transmission timer in response to receiving information indicating a second discontinuous transmission.

[0086] In various embodiments, the processor resets the discontinuous transmission timer to zero in response to the discontinuous transmission timer expiring.

[0087] In one embodiment, a method comprising: performing a logical channel prioritization procedure at a user equipment; determining, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled; and transmitting sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

[0088] In certain embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after a predetermined number of blind retransmissions.

[0089] In some embodiments, transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

[0090] In one embodiment, an apparatus comprising a user equipment, the apparatus further comprising: a processor that: performs a logical channel prioritization procedure; and determines, based on the logical channel prioritization procedure, that a transport block contains only data for logical channels for which hybrid automatic repeat request feedback is disabled; and a transmitter that transmits sidelink control information indicating that hybrid automatic repeat request feedback is enabled for transmission of the transport block.

[0091] In certain embodiments, the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled comprises the transmitter transmitting the sidelink control information indicating that hybrid automatic repeat request feedback is enabled after a predetermined number of blind retransmissions.

[0092] In some embodiments, the transmitter transmitting the sidelink control information indicating hybrid automatic repeat request feedback enabled comprises the transmitter transmitting the sidelink control information indicating hybrid automatic repeat request feedback is enabled in response to a distance between resources being less than a threshold distance.

[0093] Embodiments can be practiced in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the application is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning of and equivalency of the claims are to be embraced within their scope.

Claims

1. A method performed by a first user equipment (UE), the method comprising: determining that no sidelink data is available for a second UE; transmitting, to the second UE, sidelink control information (SCI), wherein the SCI indicates that no sidelink data is available for the second UE, and wherein the SCI triggers a channel state information (CSI) feedback response from the second UE; monitoring for receipt of the CSI feedback response from the second UE; and in response to monitoring for receipt of the CSI feedback response resulting in no receipt of the CSI feedback response, indicating a discontinuous transmission.

2. The method of claim 1, wherein the SCI includes a CSI request bit indicating a request for the CSI feedback response.

3. A first user equipment (UE) comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the first UE to: determine that no sidelink data is available for a second UE; and transmit, to the second UE, sidelink control information (SCI), wherein the SCI indicates that no sidelink data is available for the second UE, and wherein the SCI triggers a channel state information (CSI) feedback response from the second UE; monitor for receipt of the CSI feedback response from the second UE; and in response to monitoring for receipt of the CSI feedback response resulting in no receipt of the CSI feedback response, indicate a discontinuous transmission.

4. The first UE of claim 3, wherein the SCI includes a CSI request bit indicating a request for a CSI feedback response.

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