Patent Description:
The subject matter disclosed herein relates generally to wireless communications and more particularly relates to responding to a new data indicator for a hybrid automatic repeat request process.

The following abbreviations are herewith defined, at least some of which are referred to within the following description: Third Generation Partnership Project ("3GPP"), <NUM>th Generation ("<NUM>"), QoS for NR V2X Communication ("5QI/PQI"), Authentication, Authorization, and Accounting ("AAA"), Positive-Acknowledgment ("ACK"), Application Function ("AF"), Authentication and Key Agreement ("AKA"), Aggregation Level ("AL"), Access and Mobility Management Function ("AMF"), Angle of Arrival ("AoA"), Angle of Departure ("AoD"), Access Point ("AP"), Access Stratum ("AS"), Application Service Provider ("ASP"), Autonomous Uplink ("AUL"), Authentication Server Function ("AUSF"), Authentication Token ("AUTN"), Background Data ("BD"), Background Data Transfer ("BDT"), Beam Failure Detection ("BFD"), Beam Failure Recovery ("BFR"), Binary Phase Shift Keying ("BPSK"), Base Station ("BS"), Buffer Status Report ("BSR"), Bandwidth ("BW"), Bandwidth Part ("BWP"), Cell RNTI ("C-RNTI"), Carrier Aggregation ("CA"), Channel Access Priority Class ("CAPC"), Contention-Based Random Access ("CBRA"), Clear Channel Assessment ("CCA"), Common Control Channel ("CCCH"), Control Channel Element ("CCE"), Cyclic Delay Diversity ("CDD"), Code Division Multiple Access ("CDMA"), Control Element ("CE"), Contention-Free Random Access ("CFRA"), Configured Grant ("CG"), Closed-Loop ("CL"), Coordinated Multipoint ("CoMP"), Channel Occupancy Time ("COT"), Cyclic Prefix ("CP"), Cyclical Redundancy Check ("CRC"), Channel State Information ("CSI"), Channel State Information-Reference Signal ("CSI-RS"), Common Search Space ("CSS"), Control Resource Set ("CORESET"), Discrete Fourier Transform Spread ("DFTS"), Downlink Control Information ("DCI"), Downlink Feedback Information ("DFI"), Downlink ("DL"), Demodulation Reference Signal ("DMRS"), Data Network Name ("DNN"), Data Radio Bearer ("DRB"), Discontinuous Reception ("DRX"), Dedicated Short-Range Communications ("DSRC"), Discontinuous Transmission ("DTX"), Downlink Pilot Time Slot ("DwPTS"), Enhanced Clear Channel Assessment ("eCCA"), Enhanced Mobile Broadband ("eMBB"), Evolved Node B ("eNB"), Extensible Authentication Protocol ("EAP"), Effective Isotropic Radiated Power ("EIRP"), European Telecommunications Standards Institute ("ETSI"), Frame Based Equipment ("FBE"), Frequency Division Duplex ("FDD"), Frequency Division Multiplexing ("FDM"), Frequency Division Multiple Access ("FDMA"), Frequency Division Orthogonal Cover Code ("FD-OCC"), Frequency Range <NUM> - sub <NUM> frequency bands and/or <NUM> to <NUM> ("FR1"), Frequency Range <NUM> - <NUM> to <NUM> ("FR2"), Universal Geographical Area Description ("GAD"), Guaranteed Bit Rate ("GBR"), Group Leader ("GL"), <NUM> Node B or Next Generation Node B ("gNB"), Global Navigation Satellite System ("GNSS"), General Packet Radio Services ("GPRS"), Guard Period ("GP"), Global Positioning System ("GPS"), Global System for Mobile Communications ("GSM"), Globally Unique Temporary UE Identifier ("GUTI"), Home AMF ("hAMF"), Hybrid Automatic Repeat Request ("HARQ"), HARQ Process ID ("HPID"), Home Location Register ("HLR"), Handover ("HO"), Home PLMN ("HPLMN"), Home Subscriber Server ("HSS"), Hash Expected Response ("HXRES"), Identity or Identifier ("ID"), Information Element ("IE"), International Mobile Equipment Identity ("IMEI"), International Mobile Subscriber Identity ("IMSI"), International Mobile Telecommunications ("IMT"), Internet-of-Things ("IoT"), Layer <NUM> ("L1"), Layer <NUM> ("L2"), Layer <NUM> ("L3"), Licensed Assisted Access ("LAA"), Local Area Data Network ("LADN"), Local Area Network ("LAN"), Load Based Equipment ("LBE"), Listen-Before-Talk ("LBT"), Logical Channel ("LCH"), Logical Channel Group ("LCG"), Logical Channel Prioritization ("LCP"), Log-Likelihood Ratio ("LLR"), Long Term Evolution ("LTE"), Multiple Access ("MA"), Medium Access Control ("MAC"), Multimedia Broadcast Multicast Services ("MBMS"), Maximum Bit Rate ("MBR"), Minimum Communication Range ("MCR"), Modulation Coding Scheme ("MCS"), Master Information Block ("MIB"), Multiple Input Multiple Output ("MIMO"), Mobility Management ("MM"), Mobility Management Entity ("MME"), Mobile Network Operator ("MNO"), Mobile Originated ("MO"), massive MTC ("mMTC"), Maximum Power Reduction ("MPR"), Machine Type Communication ("MTC"), Multi User Shared Access ("MUSA"), Non Access Stratum ("NAS"), Narrowband ("NB"), Negative-Acknowledgment ("NACK") or ("NAK"), New Data Indicator ("NDI"), Network Entity ("NE"), Network Function ("NF"), Next Generation ("NG"), NG <NUM> S-TMSI ("NG-<NUM>-S-TMSI"), Non-Orthogonal Multiple Access ("NOMA"), New Radio ("NR"), NR Unlicensed ("NR-U"), Network Repository Function ("NRF"), Network Scheduled Mode ("NS Mode") (e.g., network scheduled mode of V2X communication resource allocation - Mode-<NUM> in NR V2X and Mode-<NUM> in LTE V2X), Network Slice Instance ("NSI"), Network Slice Selection Assistance Information ("NSSAI"), Network Slice Selection Function ("NSSF"), Network Slice Selection Policy ("NSSP"), Operation, Administration, and Maintenance System or Operation and Maintenance Center ("OAM"), Orthogonal Frequency Division Multiplexing ("OFDM"), Open-Loop ("OL"), Other System Information ("OSI"), Power Angular Spectrum ("PAS"), Physical Broadcast Channel ("PBCH"), Power Control ("PC"), UE to UE interface ("PC5"), Policy and Charging Control ("PCC"), Primary Cell ("PCell"), Policy Control Function ("PCF"), Physical Cell Identity ("PCI"), Physical Downlink Control Channel ("PDCCH"), Packet Data Convergence Protocol ("PDCP"), Packet Data Network Gateway ("PGW"), Physical Downlink Shared Channel ("PDSCH"), Pattern Division Multiple Access ("PDMA"), Packet Data Unit ("PDU"), Physical Hybrid ARQ Indicator Channel ("PHICH"), Power Headroom ("PH"), Power Headroom Report ("PHR"), Physical Layer ("PHY"), Public Land Mobile Network ("PLMN"), PC5 QoS Class Identifier ("PQI"), Physical Random Access Channel ("PRACH"), Physical Resource Block ("PRB"), Positioning Reference Signal ("PRS"), Physical Sidelink Control Channel ("PSCCH"), Primary Secondary Cell ("PSCell"), Physical Sidelink Feedback Control Channel ("PSFCH"), Physical Uplink Control Channel ("PUCCH"), Physical Uplink Shared Channel ("PUSCH"), QoS Class Identifier ("QCI"), Quasi Co-Located ("QCL"), Quality of Service ("QoS"), Quadrature Phase Shift Keying ("QPSK"), Registration Area ("RA"), RA RNTI ("RA-RNTI"), Radio Access Network ("RAN"), Random ("RAND"), Radio Access Technology ("RAT"), Serving RAT ("RAT-<NUM>") (serving with respect to Uu), Other RAT ("RAT-<NUM>") (non-serving with respect to Uu), Random Access Procedure ("RACH"), Random Access Preamble Identifier ("RAPID"), Random Access Response ("RAR"), Resource Block Assignment ("RBA"), Resource Element Group ("REG"), Radio Link Control ("RLC"), RLC Acknowledged Mode ("RLC-AM"), RLC Unacknowledged Mode/Transparent Mode ("RLC-UM/TM"), Radio Link Failure ("RLF"), Radio Link Monitoring ("RLM"), Radio Network Temporary Identifier ("RNTI"), Reference Signal ("RS"), Remaining Minimum System Information ("RMSI"), Radio Resource Control ("RRC"), Radio Resource Management ("RRM"), Resource Spread Multiple Access ("RSMA"), Reference Signal Received Power ("RSRP"), Received Signal Strength Indicator ("RSSI"), Round Trip Time ("RTT"), Receive ("RX"), Sparse Code Multiple Access ("SCMA"), Scheduling Request ("SR"), Sounding Reference Signal ("SRS"), Single Carrier Frequency Division Multiple Access ("SC-FDMA"), Secondary Cell ("SCell"), Secondary Cell Group ("SCG"), Shared Channel ("SCH"), Sidelink Control Information ("SCI"), Sub-carrier Spacing ("SCS"), Service Data Unit ("SDU"), Security Anchor Function ("SEAF"), Sidelink Feedback Content Information ("SFCI"), Serving Gateway ("SGW"), System Information Block ("SIB"), SystemInformationBlockType1 ("SIB1"), SystemInformationBlockType2 ("SIB2"), Subscriber Identity/Identification Module ("SIM"), Signal-to-Interference-Plus-Noise Ratio ("SINR"), Sidelink ("SL"), Service Level Agreement ("SLA"), Sidelink Synchronization Signals ("SLSS"), Session Management ("SM"), Session Management Function ("SMF"), Special Cell ("SpCell"), Single Network Slice Selection Assistance Information ("S-NSSAI"), Scheduling Request ("SR"), Signaling Radio Bearer ("SRB"), Shortened TMSI ("S-TMSI"), Shortened TTI ("sTTI"), Synchronization Signal ("SS"), Sidelink CSI RS ("S-CSI RS"), Sidelink PRS ("S-PRS"), Sidelink SSB ("S-SSB"), Synchronization Signal Block ("SSB"), Subscription Concealed Identifier ("SUCI"), Scheduling User Equipment ("SUE"), Supplementary Uplink ("SUL"), Subscriber Permanent Identifier ("SUPI"), Tracking Area ("TA"), TA Identifier ("TAI"), TA Update ("TAU"), Timing Alignment Timer ("TAT"), Transport Block ("TB"), Transport Block Size ("TBS"), Time-Division Duplex ("TDD"), Time Division Multiplex ("TDM"), Time Division Orthogonal Cover Code ("TD-OCC"), Temporary Mobile Subscriber Identity ("TMSI"), Time of Flight ("ToF"), Transmission Power Control ("TPC"), Transmission Reception Point ("TRP"), Transmission Time Interval ("TTI"), Transmit ("TX"), Uplink Control Information ("UCI"), Unified Data Management Function ("UDM"), Unified Data Repository ("UDR"), User Entity/Equipment (Mobile Terminal) ("UE") (e.g., a V2X UE), UE Autonomous Mode (UE autonomous selection of V2X communication resource - e.g., Mode-<NUM> in NR V2X and Mode-<NUM> in LTE V2X. UE autonomous selection may or may not be based on a resource sensing operation), Uplink ("UL"), UL SCH ("UL-SCH"), Universal Mobile Telecommunications System ("UMTS"), User Plane ("UP"), UP Function ("UPF"), Uplink Pilot Time Slot ("UpPTS"), Ultra-reliability and Low-latency Communications ("URLLC"), UE Route Selection Policy ("URSP"), Vehicle-to-Vehicle ("V2V"), Vehicle-to-Anything ("V2X"), V2X UE (e.g., a UE capable of vehicular communication using 3GPP protocols), Visiting AMF ("vAMF"), Visiting NSSF ("vNSSF"), Visiting PLMN ("VPLMN"), Wide Area Network ("WAN"), and Worldwide Interoperability for Microwave Access ("WiMAX").

In certain wireless communications networks, a new data indicator may be used.

<CIT> describes a method for identifying errors in a wireless communication system that includes transmitting data to a receiving device, receiving a receipt message and an error indicator, wherein the error indicator is associated with the data; and determining an error type based on at least one of the receipt message and the error indicator. <CIT> describes transmitting control information for an uplink transmission using multiple antennas. The described method comprises receiving a plurality of data blocks; transmitting ACK/NACK information for the received data blocks via a PHICH; transmitting, via a PDCCH, information containing an indicator which indicates whether to retransmit each of the plurality of data blocks; and receiving an uplink transmission in accordance with the combination of the ACK/NACK information and the information indicated by the indicator.

In the following, any method and/or apparatus referred to as embodiments but nevertheless do not fall within the scope of the appended claims are to be understood as examples helpful in understanding the invention.

Methods for responding to a new data indicator for a hybrid automatic repeat request process are disclosed. Apparatuses and systems also perform the functions of the methods.

<FIG> depicts an embodiment of a wireless communication system <NUM> for responding to a new data indicator for a hybrid automatic repeat request process. In one embodiment, the wireless communication system <NUM> includes remote units <NUM> and network units <NUM>. Even though a specific number of remote units <NUM> and network units <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM> and network units <NUM> may be included in the wireless communication system <NUM>.

In one embodiment, the remote units <NUM> may include computing devices, such as desktop computers, laptop computers, personal digital assistants ("PDAs"), tablet computers, smart phones, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, modems), aerial vehicles, drones, or the like. The remote units <NUM> may communicate directly with one or more of the network units <NUM> via UL communication signals. In certain embodiments, the remote units <NUM> may communicate directly with other remote units <NUM> via sidelink communication.

In various embodiments, a remote unit <NUM> may determine whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process. In some embodiments, the remote unit <NUM> may, in response to determining that the current new data indicator does not match the last received new data indicator, determine whether a negative acknowledgement has been transmitted in response to the last received sidelink grant. Accordingly, the remote unit <NUM> may be used for responding to a new data indicator for a hybrid automatic repeat request process.

In certain embodiments, a remote unit <NUM> may determine whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process. In some embodiments, the remote unit <NUM> may, in response to determining that the current new data indicator matches the last received new data indicator, determine whether a positive acknowledgement has been transmitted in response to the last received sidelink grant. Accordingly, the remote unit <NUM> may be used for responding to a new data indicator for a hybrid automatic repeat request process.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for responding to a new data indicator for a hybrid automatic repeat request process. The apparatus <NUM> includes one embodiment of the remote unit <NUM>. Furthermore, the remote unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. In some embodiments, the input device <NUM> and the display <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the remote unit <NUM> may not include any input device <NUM> and/or display <NUM>. In various embodiments, the remote unit <NUM> may include one or more of the processor <NUM>, the memory <NUM>, the transmitter <NUM>, and the receiver <NUM>, and may not include the input device <NUM> and/or the display <NUM>.

The transmitter <NUM> is used to provide UL communication signals to the network unit <NUM> and the receiver <NUM> is used to receive DL communication signals from the network unit <NUM>, as described herein.

In certain embodiments, the processor <NUM> may: determine whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator does not match the last received new data indicator, determine whether a negative acknowledgement has been transmitted in response to the last received sidelink grant.

In various embodiments, the processor <NUM> may: determine whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator matches the last received new data indicator, determine whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

<FIG> depicts one embodiment of an apparatus <NUM> that may be used for transmitting and/or receiving data. The apparatus <NUM> includes one embodiment of the network unit <NUM>. Furthermore, the network unit <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, a display <NUM>, a transmitter <NUM>, and a receiver <NUM>. As may be appreciated, the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> may be substantially similar to the processor <NUM>, the memory <NUM>, the input device <NUM>, the display <NUM>, the transmitter <NUM>, and the receiver <NUM> of the remote unit <NUM>, respectively.

In certain embodiments, the transmitter <NUM> and/or the receiver <NUM> may transmit and/or receive information described herein. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the network unit <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>.

In various embodiments, HARQ feedback error detection and handling mechanisms may be used for sidelink NR mode <NUM> operation. In such embodiments, a gNB may allocate transmission and retransmission resources for sidelink transmissions.

In various embodiments, a TX UE transmits ACK/NACK about a sidelink transmission and reception to the gNB and the gNB may not receive the ACK/NACK from the TX UE.

As used herein, the term eNB and/or gNB may be used for a base station but it may also be replaceable by any other radio access node (e.g., BS, eNB, gNB, AP, NR, and so forth). Moreover, various embodiments described herein may be in the context of <NUM> NR; however, such embodiments may be applicable to other mobile communication systems supporting serving cells and/or carriers configured for sidelink communication over a PC5 interface.

In certain embodiments, scheduling enhancements may be used for unicast and/or groupcast transmission by detecting errors (e.g., protocol errors due to NACK to ACK, DTX errors due to the erroneous physical layer decoding). In some embodiments, packet loss due to erroneous control channel decoding may be reduced.

<FIG> is a diagram illustrating one embodiment of a method <NUM> for sidelink mode <NUM> HARQ operation. The method <NUM> includes detecting <NUM> an error and performing a configuration <NUM> in response to detecting the error.

Table <NUM> shows a summary of various HARQ error handling embodiments for NR mode <NUM>.

The embodiments of Table <NUM> are described in additional detail as found in the following embodiments which are also described in relation to <FIG>.

In a first embodiment, there is a NACK to ACK error. Specifically, in the first embodiment, in NR mode <NUM>, if a transmitter UE reports a NACK to a BS upon having received a NACK from an RX UE for a groupcast or unicast transmission to request retransmission resources, and if the BS decodes the NACK as an ACK, then the TX UE may detect the error to prevent packet loss. In the first embodiment, the TX UE expects a retransmission grant from the BS, but the BS transmits DCI with a toggled NDI (e.g., indicating resources for a new initial transmission, not a retransmission). In such an embodiment, the TX UE detects the error from the toggled NDI in DCI and/or if the TB size is different. <FIG> shows one embodiment of a protocol error scenario that occurs in the first embodiment.

<FIG> is a diagram illustrating one embodiment of communications <NUM> including a NACK to ACK error. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a first communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating a first TB (e.g., TB1, a size of the first TB), a HPID = <NUM>, and an NDI = <NUM>.

In a second communication <NUM> transmitted from the TX UE <NUM> to the RX UE <NUM>, the TX UE <NUM> transmits SCI (e.g., the first TB) to the RX UE <NUM>.

In a third communication <NUM> transmitted from the RX UE <NUM> to the TX UE <NUM>, the RX UE <NUM> transmits NACK (e.g., NACK indicating that the first TB was not received correctly) to the TX UE <NUM>.

In a fourth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits a NACK indicator to the BS <NUM>. The BS <NUM> misinterprets the NACK as ACK.

In a fifth communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating a second TB (e.g., TB2, a size of the second TB), a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is toggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> the protocol error because of the toggled NDI and/or the second TB being indicated (e.g., due to the second TB having a different size than the first TB). As a result of detecting the error, the TX UE <NUM> may: <NUM>) perform an adaptive retransmission on the allocated resource with an adjusting code rate by selecting another more suitable MCS if the grant size is different from a previous grant size for the same TB; and/or <NUM>) retransmit the pending transport block (e.g., TB1) for the HARQ process (e.g., <NUM>) using an NR mode <NUM> operation; and a) perform a new transmission internally using a different SL HARQ process ID (e.g., HPID=<NUM>) based on the allocated resource in the received DCI; or b) ignore or skip the DCI grant and transmit ACK to the base station.

In various embodiments, the TX UE <NUM> determines whether a NACK has been transmitted (e.g., in the third communication <NUM>) in response to the last received sidelink grant. In some embodiments, the TX UE <NUM>, in response to determining that the NACK has been transmitted (e.g., in the third communication <NUM>) in response to the last received sidelink grant and that a current NDI does not match a last received NDI for the HARQ process, generates an autonomous HARQ retransmission for the first TB transmitted based on the last received sidelink grant. In certain embodiments, the TX UE <NUM>, in response to determining that the NACK has been transmitted (e.g., in the third communication <NUM>) in response to the last received sidelink grant and that a current NDI does not match a last received NDI for the HARQ process, selects a second HARQ process, generates a second TB , stores the second TB in a HARQ buffer corresponding to the second HARQ process, and transmits the second TB in the second HARQ process.

In a second embodiment, there is an ACK to NACK error. Specifically, in the second embodiment, in NR mode <NUM>, if a transmitter UE reports an ACK to a BS upon having received an ACK from an RX UE for a groupcast or unicast transmission to request transmission resources and, if the BS decodes ACK as NACK, then the TX UE may detect the error. In the second embodiment, the TX UE expects a new transmission grant from the BS, but the BS transmits DCI with an un-toggled NDI (e.g., indicating resources for a retransmission, not for a new transmission). In such an embodiment, the TX UE detects the error from the un-toggled NDI in DCI and the SL HARQ feedback which it received from the RX UE. <FIG> shows one embodiment of a protocol error scenario that occurs in the second embodiment.

<FIG> is a diagram illustrating another embodiment of communications <NUM> including a NACK to ACK error. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a third communication <NUM> transmitted from the RX UE <NUM> to the TX UE <NUM>, the RX UE <NUM> transmits ACK (e.g., ACK indicating that the first TB was received correctly) to the TX UE <NUM>.

In a fourth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits an ACK indicator to the BS <NUM>. The BS <NUM> misinterprets the ACK as NACK.

In a fifth communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating the first TB, a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is untoggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> the protocol error because of the untoggled NDI and the knowledge that the TX UE <NUM> transmitted an ACK to the BS <NUM>. As a result of detecting the error, the TX UE <NUM> may: <NUM>) generate a new transmission according to the resource allocated in the DCI; <NUM>) ignore or skip the DCI and transmit ACK to the BS <NUM> in the feedback corresponding to the mode <NUM> SL grant; and/or <NUM>) trigger SL BSR reporting.

In a third embodiment, a TX UE may miss DCI (e.g., having a toggled NDI compared to a previous transmission) and the TX UE may transmit a DTX to a BS, but the BS may interpret the DTX as an ACK. Specifically, in the third embodiment, in NR mode <NUM>, if the TX UE misses a DCI grant from the BS and the missed DCI contains a toggled NDI compared to its previous transmission (e.g., with the same or a different TB size), and the BS detects DTX as ACK, then, in such an embodiment, the transmission of DCI by the BS may contain a toggled NDI indicating a new transmission and the NDI is untoggled from the TX UE's perspective because the TX UE missed the previous DCI from the base station. <FIG> shows one embodiment of a protocol error scenario that occurs in the third embodiment.

<FIG> is a diagram illustrating one embodiment of communications <NUM> including a missed DCI. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a fourth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits an ACK indicator to the BS <NUM>.

The TX UE <NUM> does not detect <NUM> the DCI.

In a sixth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits a DTX indicator to the BS <NUM>. The BS <NUM> misinterprets the DTX as an ACK.

In a seventh communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating a third TB (e.g., TB3, a size of the third TB), a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is toggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> the protocol error because of the NDI being untoggled from the TX UE's <NUM> perspective and/or the third TB being indicated (e.g., due to the third TB having a different size than the first TB). As a result of detecting the error, the TX UE <NUM> may: <NUM>) generate a new transmission according to the resource allocated in the DCI; <NUM>) ignore or skip the DCI and transmit ACK to the BS <NUM> in the feedback corresponding to the mode <NUM> SL grant; and/or <NUM>) trigger SL BSR reporting. As may be appreciated, the protocol error may have resulted from the combination of the two errors (e.g., the TX UE <NUM> missing the DCI and the BS <NUM> interpreting the DTX as ACK).

In a fourth embodiment, a TX UE may miss DCI (e.g., having a toggled NDI compared to a previous transmission) and the TX UE may transmit a DTX to a BS, but the BS may interpret the DTX as a NACK. Specifically, in the fourth embodiment, in NR mode <NUM>, if TX UE misses a DCI grant from the BS and the missed DCI contains a toggled NDI compared to its previous transmission (e.g., with the same or a different TB size), and the BS detects DTX as NACK, then, in such an embodiment, the transmission of DCI by the BS may contain an untoggled NDI indicating resource for retransmission and the NDI is toggled from the TX UE's perspective because the TX UE missed the previous DCI from the BS. <FIG> shows one embodiment of a protocol error scenario that occurs in the fourth embodiment.

<FIG> is a diagram illustrating another embodiment of communications <NUM> including a missed DCI. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a second communication <NUM> transmitted from the TX UE <NUM> to the RX UE <NUM>, the TX UE <NUM> transmits SCI (e.g., the first TB) to the RX UE <NUM>. Furthermore, in the second communication <NUM>, the TX UE <NUM> may transmit the first TB in a physical layer sidelink shared channel to the RX UE <NUM> according to the received mode <NUM> SL grant in the first communication <NUM>.

In a sixth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits a DTX indicator to the BS <NUM>. As used herein, DTX may mean that a UE (e.g., TX UE) does not transmit any information (e.g., ACK and/or NACK) in a PUCCH resource. The BS <NUM> misinterprets the DTX as a NACK.

In a seventh communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating a second TB (e.g., TB2, a size of the second TB), a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is toggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> that there is no protocol error because of the NDI being toggled from the TX UE's <NUM> perspective. Accordingly, the TX UE <NUM> may operate as if no error has occurred.

In a fifth embodiment, a TX UE may miss DCI (e.g., having an untoggled NDI compared to the previous transmission) and the TX UE may transmit a DTX to a BS, but the BS may interpret the DTX as an ACK. Specifically, in the fifth embodiment, in NR mode <NUM>, if the TX UE misses a DCI grant from the BS and the missed DCI contains an untoggled NDI compared to its previous transmission (e.g., with the same or a different TB size), and the BS detects DTX as ACK, then, in such an embodiment, the transmission of DCI by the BS may contain a toggled NDI indicating a new transmission and also the NDI is toggled from the TX UE's perspective because the TX UE missed the previous DCI from the BS. <FIG> shows one embodiment of a protocol error scenario that occurs in the fifth embodiment.

<FIG> is a diagram illustrating a further embodiment of communications <NUM> including a missed DCI. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a second communication <NUM> transmitted from the TX UE <NUM> to the RX UE <NUM>, the TX UE <NUM> transmits SCI (e.g., the first TB) to the RX UE <NUM>. Furthermore, in the second communication <NUM>, the TX UE <NUM> may transmit first TB in a physical layer sidelink shared channel to the RX UE <NUM> according to the received mode <NUM> SL grant in the first communication <NUM>.

In a fourth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits a NACK indicator to the BS <NUM>.

In a fifth communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating the first TB (e.g., TB1, a size of the first TB), a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is untoggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> the protocol error because of the NDI being untoggled from the TX UE's <NUM> perspective and/or the third TB being indicated (e.g., due to the third TB having a different size than the first TB). As a result of detecting the error, the TX UE <NUM> may: <NUM>) perform an adaptive retransmission on the allocated resource with an adjusting code rate by selecting another more suitable MCS if the grant size is different from a previous grant size for the same TB; and/or <NUM>) retransmit the pending transport block (e.g., TB1) for the HARQ process (e.g., <NUM>) using an NR mode <NUM> operation; and a) perform a new transmission internally using a different SL HARQ process ID (e.g., HPID=<NUM>) based on the allocated resource in the received DCI; or b) ignore or skip the DCI grant and transmit ACK to the base station. As may be appreciated, the protocol error may have resulted from the combination of the two errors (e.g., the TX UE <NUM> missing the DCI and the BS <NUM> interpreting the DTX as ACK).

In a sixth embodiment, a TX UE may miss DCI (e.g., having an untoggled NDI compared to the previous transmission) and the TX UE may transmit a DTX to a BS, but the BS may interpret the DTX as a NACK. Specifically, in the sixth embodiment, in NR mode <NUM>, if TX UE misses a DCI grant from the BS and the missed DCI contains an untoggled NDI compared to its previous transmission (e.g., with the same or different TB size), and the BS detects DTX as NACK, then, in such an embodiment, the transmission of DCI by the BS may contain an untoggled NDI indicating a new transmission and also the NDI is untoggled from the TX UE's perspective because the TX UE missed the previous DCI from the BS. <FIG> shows one embodiment of a protocol error scenario that occurs in the sixth embodiment.

<FIG> is a diagram illustrating yet another embodiment of communications <NUM> including a missed DCI. The communications <NUM> include communications between a BS <NUM>, a TX UE <NUM>, and an RX UE <NUM>. As may be appreciated, each of the communications <NUM> described herein may include one or more messages.

In a fifth communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating the first TB (e.g., TB1, a size of the first TB), a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is toggled for the same HARQ process ID.

In a sixth communication <NUM> transmitted from the TX UE <NUM> to the BS <NUM>, the TX UE <NUM> transmits a DTX indicator to the BS <NUM>. The BS <NUM> misinterprets the DTX as a NACK.

In a seventh communication <NUM> transmitted from the BS <NUM> to the TX UE <NUM>, the BS <NUM> transmits a mode <NUM> SL grant in DCI to the TX UE <NUM>. The mode <NUM> SL grant, in this embodiment, includes information indicating the first TB (e.g., TB1, a size of the first TB) for retransmission, a HPID = <NUM>, and an NDI = <NUM>. Accordingly, the next DCI is transmitted, and the NDI is untoggled for the same HARQ process ID.

The TX UE <NUM> detects <NUM> that there is no protocol error because of the NDI being untoggled from the TX UE's <NUM> perspective. Accordingly, the TX UE <NUM> may operate as if no error has occurred.

In one embodiment, for NR mode <NUM>, if a TX UE reports NACK to a BS upon having received NACK from an RX UE for a groupcast or unicast transmission to request a retransmission resources and instead the TX UE receives DCI from the BS with an NDI toggled compared to its current NDI state for the same HARQ process ID, then the TX UE may behaves in one of the following ways: <NUM>) once the TX UE considers NDI toggled in the received DCI if it was expecting a retransmission grant, the received DCI grant may still be used for retransmission of the pending transport block stored in the HARQ buffer for that HARQ process ID (e.g., if the TX UE reported NACK for the previous SL transmission) and if the TX UE could perform adaptive retransmission (e.g., by changing a code rate by suitably selecting an MCS according to the allocated resource in the received DCI); or <NUM>) the TX UE may retransmit the pending transport block (e.g., if it is stored for retransmission in the HARQ process) rather using an NR mode <NUM> operation in which the TX UE may autonomously select suitable resource for transmission from a candidate resource set using a sensing method and the selection window is set according to the remaining packet delay budget, and, if the TX UE chooses to do retransmission using NR Mode <NUM> operation, it could further choose between one of the following sub-embodiments for treating the received DCI grant from the base station: a) the TX UE follows the DCI grant received from the base station for a new sidelink transmission if the TX UE could internally use a different HARQ process ID for transmission to receiver UEs for the sidelink transmission (e.g., by indicated within SCI a HARQ process ID that is different from the HARQ process ID indicated within the DCI from the gNB); or b) the TX UE may decide to skip or ignore the received DCI grant and as an enhancement transmit ACK to the BS.

In another embodiment, for NR mode <NUM>, if a TX UE reports ACK to the BS upon having received ACK from an RX UE for a groupcast or unicast transmission to request new transmission resources, but if the TX UE receives DCI from the BS containing NDI that it considers untoggled compared to its current state for the same HARQ process ID, then the TX UE behaves in one of the following ways: <NUM>) the TX UE follows the DCI grant received from the BS for a new sidelink transmission if the TX UE could use a different HARQ process ID for the sidelink transmission (e.g., indicated within SCI) then the HARQ process ID indicated within the DCI from the BS; <NUM>); the TX UE may decide to skip or ignore the received DCI grant and transmit ACK to the BS; and/or <NUM>) the TX UE may trigger sidelink BSR reporting to the BS.

In one example, embodiments described herein may be implemented in a MAC specification as shown in Table <NUM>.

In certain embodiments, in NR mode <NUM>, a TX UE starts a timer after transmitting NACK to a BS for a groupcast or unicast HARQ transmission (or retransmission), and before expiration of the timer, the TX UE expects a retransmission grant from the BS. In such embodiments, while the timer is running, if the TX UE does not detect a DCI with the same HARQ ID for the process in which it transmitted HARQ-NACK to gNB, the TX UE may, upon detection of the error (e.g., when the timer expires and no DCI indicating retransmission resources was received), perform a retransmission of the previous pending transport block for which a NACK was sent to the BS by switching to NR mode <NUM> operation for that HARQ process ID. In various embodiments, a TX UE may drop a packet from its buffer and signal to one or more RX UEs to clear a soft buffer for that HARQ process ID using a toggled NDI within SCI. In such embodiments, the TX UE may choose to either drop the packet or perform retransmission in NR mode <NUM> operation (e.g., based on a QoS priority of the packet to be transmitted and/or congestion metric, packet delay budget if the packet delay budget still allows performance of a retransmission), then the UE may switch to mode <NUM> and perform an autonomous retransmission. In some embodiments, a configuration of a timer may be set based on a packet delay budget. In certain embodiments, a BS doesn't schedule retransmission for a pending packet because a PDB is already exceeded.

In various embodiments, there is a misaligned counter between a gNB and a TX UE. In such embodiments, if there is an error between the gNB and the TX UE (e.g., a missed DCI and a DTX is interpreted as an ACK, a NACK is interpreted as an ACK, an ACK is interpreted as a NACK), an actual retransmission number (or redundancy version) signaled in DCI between the TX UE and the gNB may be different from that used in SCI transmitted between the TX UE and the RX UE. In one embodiment, if there is a mismatch between a retransmission number, then a TX UE may ignore the redundancy version indicated by a gNB in DCI and transmit another redundancy version (e.g., correct redundancy version) in SCI. In another embodiment, a TX UE may indicate in uplink signaling to a BS (either in L1, L2, and/or L3 signaling that corresponds to either a physical layer, a MAC layer, or RRC signaling to the BS) about a mismatch in redundancy versions via a signaled HARQ retransmission counter, one or more transmission parameters, and/or one or more HARQ parameters from the BS in DCI and/or via actual transmission between the TX UE and RX UEs in SCI.

In certain embodiments, if a gNB configures a TX UE with resources for 'k' blind repetitions, and if the TX UE receives an ACK from an RX UE before an end period of the scheduled 'k' repetition, then the TX UE may transmit an ACK to the gNB to free SL resources for other SL transmissions. In such embodiments, a time domain configuration of UL feedback resources (e.g., in terms of slots, minislots, or symbols) may be indicated either dynamically or semi statically via signaling.

In some embodiments, a gNB configures sidelink common feedback resource for every beam, spatial direction, or panel for a TX UE and the TX UE may use beam sweeping in a different spatial direction and/or time domain for repeated transmission of a same TB or to perform a multi-beam operation of a TB. In such embodiments, if RX UEs fail to decode a groupcast or broadcast transport block in a certain time slot, minislot, and/or symbol and in a certain spatial direction, RX UEs may choose to transmit NACK over a sidelink feedback resource assigned for that particular beam, spatial direction, or panel.

In various embodiments, a TX UE may associate a received NACK with a particular beam, beam spatial direction, or panel, based on the received NACK per beam, beam spatial direction, or panel. In such embodiments, the TX UE may selectively retransmit in that particular beam, spatial direction, or panel. Moreover, in such embodiments, a resource configuration of a common NACK resource set may depend on a configuration of a number of beams or panels in the TX UE. In certain embodiments, SL common feedback resources that are configured for each beam, spatial direction, or panel may be differentiated either in time, frequency, or code resource sets, and may be indicated via L1, L2, or L3 signaling.

<FIG> is a block diagram illustrating one embodiment a system <NUM> including a TX UE <NUM> that may be used in embodiments described herein. The TX UE <NUM> includes a first common NACK resource <NUM>, a second common NACK resource <NUM>, a third common NACK resource <NUM>, and a fourth common NACK resource <NUM>.

<FIG> is a flow chart diagram illustrating one embodiment of a method <NUM> for responding to a new data indicator for a hybrid automatic repeat request process. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In various embodiments, the method <NUM> includes determining <NUM> whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process. In some embodiments, the method <NUM> includes, in response to determining that the current new data indicator does not match the last received new data indicator, determining <NUM> whether a negative acknowledgement has been transmitted in response to the last received sidelink grant. It should be noted that the negative acknowledgement is based on a negative acknowledgment received from RX UEs (e.g., at least one RX UE from a groupcast transmission) in PSFCH.

In certain embodiments, the method <NUM> further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; switching from a first mode to a second mode for the first hybrid automatic repeat request process. In some embodiments, the method <NUM> further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; generating an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant.

In various embodiments, the method <NUM> further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; selecting a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; generating a second transport block corresponding to the current sidelink grant; storing the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and transmitting the second transport block in the second hybrid automatic repeat request process. In one embodiment, the method <NUM> further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; ignoring or skipping the current sidelink grant and transmitting a positive acknowledgment to a base station.

In certain embodiments, the method <NUM> further comprises, in response to determining that a positive acknowledgement has been transmitted in response to the last received sidelink grant: generating the second transport block corresponding to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process. In some embodiments, the method <NUM> further comprises, in response to the current new data indicator matching the last received new data indicator, determining whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In various embodiments, the method <NUM> further comprises, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: considering the new data indicator as toggled; generating the second transport block for the first hybrid automatic repeat request process according to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process. In one embodiment, the method <NUM> further comprises, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: performing a hybrid automatic repeat request retransmission of the first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

<FIG> is a flow chart diagram illustrating another embodiment of a method <NUM> for responding to a new data indicator for a hybrid automatic repeat request process. In some embodiments, the method <NUM> is performed by an apparatus, such as the remote unit <NUM>. In certain embodiments, the method <NUM> may be performed by a processor executing program code, for example, a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

In various embodiments, the method <NUM> includes determining <NUM> whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process. In some embodiments, the method <NUM> includes, in response to determining that the current new data indicator matches the last received new data indicator, determining <NUM> whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In certain embodiments, the method <NUM> further comprises, in response to determining: that the positive acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator matches the last received new data indicator for the first hybrid automatic repeat request process; considering the new data indicator as toggled. In some embodiments, the method <NUM> further comprises generating a second transport block for the first hybrid automatic repeat request process according to the current sidelink grant.

In various embodiments, the method <NUM> further comprises transmitting the second transport block in the first hybrid automatic repeat request process. In one embodiment, the method <NUM> further comprises, in response to determining that a negative acknowledgement has been transmitted in response to the last received sidelink grant: performing a hybrid automatic repeat request retransmission of a first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

In certain embodiments, the method <NUM> further comprises, in response to the current new data indicator not matching the last received new data indicator, determining whether a negative acknowledgement has been transmitted in response to the last received sidelink grant. In some embodiments, the method <NUM> further comprises, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: switching from a first mode to a second mode for the first hybrid automatic repeat request process; generating an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant; selecting a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; generating a second transport block corresponding to the current sidelink grant; storing the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and transmitting the second transport block in the second hybrid automatic repeat request process.

In various embodiments, the method <NUM> further comprises, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: generating a second transport block corresponding to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process.

In one embodiment, a method comprises: determining whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator does not match the last received new data indicator, determining whether a negative acknowledgement has been transmitted in response to the last received sidelink grant.

In certain embodiments, the method further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; switching from a first mode to a second mode for the first hybrid automatic repeat request process.

In some embodiments, the method further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; generating an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant.

In various embodiments, the method further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; selecting a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; generating a second transport block corresponding to the current sidelink grant; storing the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and transmitting the second transport block in the second hybrid automatic repeat request process.

In one embodiment, the method further comprises, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; ignoring or skipping the current sidelink grant and transmitting a positive acknowledgment to a base station.

In certain embodiments, the method further comprises, in response to determining that a positive acknowledgement has been transmitted in response to the last received sidelink grant: generating the second transport block corresponding to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process.

In some embodiments, the method further comprises, in response to the current new data indicator matching the last received new data indicator, determining whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In various embodiments, the method further comprises, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: considering the new data indicator as toggled; generating the second transport block for the first hybrid automatic repeat request process according to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process.

In one embodiment, the method further comprises, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: performing a hybrid automatic repeat request retransmission of the first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

In one embodiment, an apparatus comprises: a processor that: determines whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator does not match the last received new data indicator, determines whether a negative acknowledgement has been transmitted in response to the last received sidelink grant.

In certain embodiments, the processor, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; switches from a first mode to a second mode for the first hybrid automatic repeat request process.

In some embodiments, the processor, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; generates an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant.

In various embodiments, the apparatus further comprises a transmitter, wherein, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; the processor selects a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; the processor generates a second transport block corresponding to the current sidelink grant; the processor stores the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and the transmitter transmits the second transport block in the second hybrid automatic repeat request process.

In one embodiment, the processor, in response to determining: that the negative acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator does not match the last received new data indicator for the first hybrid automatic repeat request process; ignores or skips the current sidelink grant and transmitting a positive acknowledgment to a base station.

In certain embodiments, the apparatus further comprises a transmitter, wherein, in response to determining that a positive acknowledgement has been transmitted in response to the last received sidelink grant: the processor generates the second transport block corresponding to the current sidelink grant; and the transmitter transmits the second transport block in the first hybrid automatic repeat request process.

In some embodiments, in response to the current new data indicator matching the last received new data indicator, the processor determines whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In various embodiments, the apparatus further comprises a transmitter, wherein, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: the processor considers the new data indicator as toggled; the processor generates the second transport block for the first hybrid automatic repeat request process according to the current sidelink grant; and the transmitter transmits the second transport block in the first hybrid automatic repeat request process.

In one embodiment, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: the processor performs a hybrid automatic repeat request retransmission of the first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

In one embodiment, a method comprises: determining whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator matches the last received new data indicator, determining whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In certain embodiments, the method further comprises, in response to determining: that the positive acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator matches the last received new data indicator for the first hybrid automatic repeat request process; considering the new data indicator as un-toggled.

In some embodiments, the method further comprises generating a second transport block for the first hybrid automatic repeat request process according to the current sidelink grant.

In various embodiments, the method further comprises transmitting the second transport block in the first hybrid automatic repeat request process.

In one embodiment, the method further comprises, in response to determining that a negative acknowledgement has been transmitted in response to the last received sidelink grant: performing a hybrid automatic repeat request retransmission of a first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

In certain embodiments, the method further comprises, in response to the current new data indicator not matching the last received new data indicator, determining whether a negative acknowledgement has been transmitted in response to the last received sidelink grant.

In some embodiments, the method further comprises, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: switching from a first mode to a second mode for the first hybrid automatic repeat request process; generating an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant; selecting a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; generating a second transport block corresponding to the current sidelink grant; storing the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and transmitting the second transport block in the second hybrid automatic repeat request process.

In various embodiments, the method further comprises, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: generating a second transport block corresponding to the current sidelink grant; and transmitting the second transport block in the first hybrid automatic repeat request process.

In one embodiment, an apparatus comprises: a processor that: determines whether a current new data indicator in a current sidelink grant matches a last received new data indicator in a last received sidelink grant for a first hybrid automatic repeat request process; and, in response to determining that the current new data indicator matches the last received new data indicator, determines whether a positive acknowledgement has been transmitted in response to the last received sidelink grant.

In certain embodiments, the processor, in response to determining: that the positive acknowledgement has been transmitted in response to the last received sidelink grant; and that the current new data indicator matches the last received new data indicator for the first hybrid automatic repeat request process; considers the new data indicator as toggled.

In some embodiments, the processor generates a second transport block for the first hybrid automatic repeat request process according to the current sidelink grant.

In various embodiments, the apparatus further comprises a transmitter that transmits the second transport block in the first hybrid automatic repeat request process.

In one embodiment, the processor, in response to determining that a negative acknowledgement has been transmitted in response to the last received sidelink grant: performs a hybrid automatic repeat request retransmission of a first transport block stored in a hybrid automatic repeat request buffer for the first hybrid automatic repeat request process.

In certain embodiments, the processor, in response to the current new data indicator not matching the last received new data indicator, determines whether a negative acknowledgement has been transmitted in response to the last received sidelink grant.

In some embodiments, the apparatus further comprises a transmitter, wherein, in response to determining that the negative acknowledgement has been transmitted in response to the last received sidelink grant: the processor switches from a first mode to a second mode for the first hybrid automatic repeat request process; the processor generates an autonomous hybrid automatic repeat request retransmission for a first transport block transmitted based on the last received sidelink grant; the processor selects a second hybrid automatic repeat request process from a plurality of available hybrid automatic repeat request processes; the processor generates a second transport block corresponding to the current sidelink grant; the processor stores the second transport block in a hybrid automatic repeat request buffer corresponding to the second hybrid automatic repeat request process; and the transmitter transmits the second transport block in the second hybrid automatic repeat request process.

In various embodiments, the apparatus further comprises a transmitter, wherein, in response to determining that the positive acknowledgement has been transmitted in response to the last received sidelink grant: the processor generates a second transport block corresponding to the current sidelink grant; and the transmitter transmits the second transport block in the first hybrid automatic repeat request process.

Claim 1:
A method (<NUM>) performed by a user equipment, UE, (<NUM>, <NUM>), the method comprising:
determining (<NUM>) whether a current new data indicator, NDI, in a current sidelink grant matches a last received NDI in a last received sidelink grant for a first hybrid automatic repeat request, HARQ, process;
in response to the current NDI matching the last received NDI, determining whether a first positive acknowledgement, ACK, has been transmitted by the UE (<NUM>, <NUM>) in response to the last received sidelink grant; and
in response to determining that a first ACK has been transmitted, ignoring or skipping the current sidelink grant and transmitting a second ACK to a base station.