Patent Description:
The following abbreviations are herewith defined, at least some of which are referred to within the following description: Third Generation Partnership Project ("3GPP"), Fifth Generation Core Network ("5CG"), Fifth Generation System ("5GS"), Authentication, Authorization and Accounting ("AAA"), Access and Mobility Management Function ("AMF"), Positive-Acknowledgment ('ACK'), Application Programming Interface ("API"), Access Stratum ("AS"), Base Station ("BS"), Control Element ("CE"), Channel State Information ("CSI"), Connection Mode ("CM", this is a NAS state in 5GS), Core Network ("CN"), Control Plane ("CP"), Data Radio Bearer ("DRB"), Dedicated Short Range Communication ("DSRC"), Downlink Control Information ("DCI"), Downlink ("DL"), Discontinuous Transmission ('DTX'), Evolved Node-B ("eNB"), Evolved Packet Core ("EPC"), Evolved Packet System ("EPS"), EPS Mobility Management ("EMM", this is a NAS state in EPS), Evolved UMTS Terrestrial Radio Access ("E-UTRA"), Frequency Division Duplex ("FDD"), Frequency Division Multiple Access ("FDMA"), General Packet Radio Service ("GPRS"), Global System for Mobile Communications ("GSM"), Hybrid Automatic Repeat Request ("HARQ"), Home Subscriber Server ("HSS"), Home Public Land Mobile Network ("HPLMN"), Information Element ("IE"), Long Term Evolution ("LTE"), Mobility Management ("MM"), Mobility Management Entity ("MME"), Negative-Acknowledgment ('NACK') or ("NAK"), New Generation (<NUM>) Node-B ("gNB"), New Generation Radio Access Network ("NG-RAN", a RAN used for 5GS networks), New Radio ("NR", a <NUM> radio access technology; also referred to as "<NUM> NR"), Non-Access Stratum ("NAS"), Network Exposure Function ("NEF"), Network Slice Selection Assistance Information ("NSSAI"), Orthogonal Frequency Division Multiplexing ("OFDM"), Packet Data Unit ("PDU", used in connection with `PDU Session'), Packet Switched ("PS", e.g., Packet Switched domain or Packet Switched service), Physical Broadcast Channel ("PBCH"), Physical Cell Identity ("PCI"), Physical Downlink Control Channel ("PDCCH"), Physical Downlink Shared Channel ("PDSCH"), Pattern Division Multiple Access ("PDMA"), Physical Hybrid ARQ Indicator Channel ("PHICH"), Physical Random Access Channel ("PRACH"), Physical Resource Block ("PRB"), Physical Sidelink Control Channel ("PSCCH"), Physical Sidelink Shared Channel ("PSSCH"), Physical Sidelink Feedback Channel ("PSFCH"), Physical Uplink Control Channel ("PUCCH"), Physical Uplink Shared Channel ("PUSCH"), Public Land Mobile Network ("PLMN"), Quality of Service ("QoS"), Radio Access Network ("RAN"), Radio Resource Control ("RRC"), Random-Access Channel ("RACH"), Reference Signal ("RS"), Registration Area ("RA", similar to tacking area list used in LTE/EPC), Registration Management ("RM", refers to NAS layer procedures and states), Receive ("RX"), Radio Link Control ("RLC"), Scheduling Request ("SR"), Shared Channel ("SCH"), Session Management ("SM"), Session Management Function ("SMF"), Service Provider ("SP"), Sidelink Control Information ("SCI"), Signal-to-Interference-Plus-Noise Ratio ("SINR"), Single Network Slice Selection Assistance Information ("S-NSSAI"), Sounding Reference Signal ("SRS"), System Information Block ("SIB"), Supplementary Uplink ("SUL"), Tracking Area ("TA"), Transport Block ("TB"), Transport Block Size ("TBS"), Time-Division Duplex ("TDD"), Time Division Multiplex ("TDM"), Transmission/Reception Point ("TRP", can be a UE or BS), Transmission Time Interval ("TTI"), Transmit ("TX"), Unified Data Management ("UDM"), User Data Repository ("UDR"), Uplink Control Information ("UCI"), User Entity/Equipment (Mobile Terminal) ("UE"), Uplink ("UL"), User Plane ("UP"), Universal Mobile Telecommunications System ("UMTS"), Visited Public Land Mobile Network ("VPLMN"), and Worldwide Interoperability for Microwave Access ("WiMAX"). As used herein, "HARQ-ACK" may represent collectively the Positive Acknowledge ('ACK') and the Negative Acknowledge ('NACK') and Discontinuous Transmission ('DTX'). ACK means that a TB is correctly received while NACK (or NAK) means a TB is erroneously received. DTX means that no TB was detected.

In certain wireless communication systems, V2X communication allows vehicles to communicate with moving parts of the traffic system around them. Two resource allocation modes are used in LTE V2X communication and similar modes are defined for NR V2X communication. These modes support direct V2X communications but differ on how they allocate the radio resources. Mode-<NUM> corresponds to a NR network-scheduled V2X communication mode. Mode-<NUM> corresponds to a NR UE-scheduled V2X communication mode. Mode-<NUM> corresponds to an LTE network-scheduled V2X communication mode. Mode-<NUM> corresponds to an LTE UE-scheduled V2X communication mode.

In case of Mode-<NUM> and Mode-<NUM>, resources are allocated by the cellular network, e.g., gNB for Mode-<NUM> and eNB, for the Mode-<NUM>. In case of Mode-<NUM> and Mode-<NUM>, these do not require cellular coverage, and vehicles autonomously select their radio resources using a distributed scheduling scheme supported by congestion control mechanisms from pre-configured resource Pool(s). Mode-<NUM> and Mode-<NUM> resources can also be allocated by the RAN for in-coverage UEs.

In LTE V2X, HARQ operation is limited to blind retransmission without any HARQ feedback. NR V2X communication may support HARQ feedback signaling for SL transmission. However, it is unclear how the transmitting V2X UE is to report the necessity of retransmission to gNB and receive suitable re-transmission resources.

R1-<NUM> is a discussion document for 3GPP TSGRAN WG1 #<NUM> by Samsung, titled "Considerations on Sidelink HARQ Procedure" which discusses sidelink HARQ procedures.

Claims <NUM> and <NUM> each define an apparatus. Claim <NUM> defines a method. 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.

The storage devices may be tangible, nontransitory, and/or non-transmission.

Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an objectoriented 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.

As used herein, a list using the terminology "one of' includes one and only one of any single item in the list. " As used herein, "a member selected from the group consisting of A, B, and C and combinations thereof' includes only A, only B, only C, a combination of A and B, a combination of B and C, a combination of A and C or a combination of A, B and C.

The code may 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 flowchart diagrams and/or block diagrams.

Generally, the present disclosure describes systems, methods, and apparatus for aggregating HARQ feedback and sidelink retransmission procedure for UEs engaged in V2X communication. "V2X" (vehicle-to-everything) refers sidelink communications may include one or more of: "V2I "(vehicle-to-infrastructure) communications, "V2N" (vehicle-to-network), "V2V" (vehicle-to-vehicle) communications, "V2P" (vehicle-to-pedestrian), "V2D" (vehicle-to-device) and "V2G" (vehicle-to-grid) communications. A V2X UE refers to a UE capable of vehicular communication using 3GPP protocol(s).

Mode-<NUM> and Mode-<NUM> support direct NR V2X communications but differ on how they allocate the radio resources. Likewise, Mode-<NUM> and Mode-<NUM> support direct LTE V2X communications but differ on how they allocate the radio resources. For Mode-<NUM> and Mode-<NUM>, sidelink resources are allocated by the cellular network, e.g., gNB for Mode-<NUM> (NR V2X) and eNB for Mode-<NUM> (LTE V2X). As such, at least the transmitter V2X UE must be in-coverage of the NR/LTE RAN. In contrast, Mode-<NUM> and Mode-<NUM> do not require cellular network coverage, and vehicles (i.e., UEs) autonomously select their radio resources using a distributed scheduling scheme supported by congestion control mechanisms. Mode-<NUM> is considered the baseline mode and represents an alternative to <NUM>. 11p or dedicated short range communications (DSRC).

All the resource allocation modes have been designed to satisfy the latency requirements and accommodate high Doppler spreads and high density of vehicles for V2X communications. For example, the maximum allowed latency may vary between <NUM> and <NUM>, depending on the application. Note that SL Resources are shared with the Uu uplink.

As noted above, Mode-<NUM> and Mode-<NUM> use the centralized RAN (gNB/eNB) scheduler. The vehicular UE and RAN use the Uu interface to communicate, e.g., sending of BSR/SR from the transmitting V2X UE to the RAN and receiving in response a SL grant on the PDCCH (DCI). Mode-<NUM> and Mode-<NUM> employ distributed UE scheduling, thus operating without infrastructure support, although the UEs could be in RAN coverage. The various modes use the PC5 interface, which offers direct sidelink (SL) communication between two or more UEs.

In LTE-based V2X only broadcast type transmission is supported, whereas in NR-based V2X, supports broadcast ("BC"), unicast ("UC") and groupcast ("GC") transmission types (also referred to as "cast types"). It is assumed that higher layers of the transmitter V2X UE indicate whether a packet is to be sent via unicast, groupcast, or broadcast. As used herein, "unicast" refers to the transmitter V2X UE having a single receiver V2X UE associated with the V2X transmission. As used herein, "groupcast" refers to the transceiver V2X UE communicating with a specific subset of V2X UEs in its vicinity (more than one UE, e.g., using a group address). In contrast, a broadcast transmission enables the transmitter V2X UE to communicate with all UEs that are in its range. Note that for unicast and groupcast transmissions, a receiver V2X UE will discard a packet not addressed to the V2X UE, e.g., individually or to a group of which the receiver V2X is a member.

In various embodiments, NR V2X operation supports HARQ with HARQ feedback signaling for SL transmissions, e.g., at least for unicast and groupcast SL transmission. In Mode-<NUM> for unicast and groupcast, HARQ feedback signaling is supported for the transmitter UE via Uu link to report an indication to gNB to indicate the need for retransmission of a TB transmitted by the transmitter UE.

While the PC5 link efficiency may be improved using HARQ feedback, details of how the transmitter UE reports the necessity of re-transmission to gNB and receives suitable resources are not yet clear. Specifically, it is unclear how HARQ ACK/NACK can be indicated to the gNB if there are no resources available in UL. As not all SL transmissions require HARQ feedback, it may not be practical to allocate PUCCH ACK/ NACK feedback resources for every possible transmission on sidelink.

The present disclosure outlines several methods for supporting efficient retransmission for V2X communication. In particular, the HARQ operation for a SL transmission in the resource allocation Mode-<NUM> is disclosed. Furthermore, a new MAC CE is described for requesting re-transmission resources to the gNB.

<FIG> depicts a wireless communication system <NUM> for aggregating HARQ feedback and sidelink retransmission procedure for V2X wireless devices communicating messages via V2X communication signals <NUM>, according to embodiments of the disclosure. In one embodiment, the wireless communication system <NUM> includes at least one remote unit <NUM>, a radio access network ("RAN") <NUM>, and a mobile core network <NUM>. The RAN <NUM> and the mobile core network <NUM> form a mobile communication network. The RAN <NUM> may be composed of a base unit <NUM> with which the remote unit <NUM> communicates using wireless communication links <NUM>. Even though a specific number of remote units <NUM>, base units <NUM>, wireless communication links <NUM>, RANs <NUM>, and mobile core networks <NUM> are depicted in <FIG>, one of skill in the art will recognize that any number of remote units <NUM>, base units <NUM>, wireless communication links <NUM>, RANs <NUM>, and mobile core networks <NUM> may be included in the wireless communication system <NUM>.

In one implementation, the RAN <NUM> is compliant with the <NUM> system specified in the 3GPP specifications. In another implementation, the RAN <NUM> is compliant with the LTE system specified in the 3GPP specifications. More generally, however, the wireless communication system <NUM> may implement some other open or proprietary communication network, for example WiMAX, among other networks.

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), smart appliances (e.g., appliances 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), or the like. Moreover, the remote units <NUM> may be referred to as the UEs, subscriber units, mobiles, mobile stations, users, terminals, mobile terminals, fixed terminals, subscriber stations, user terminals, wireless transmit/receive unit ("WTRU"), a device, or by other terminology used in the art.

The remote units <NUM> may communicate directly with one or more of the base units <NUM> in the RAN <NUM> via uplink ("UL") and downlink ("DL") communication signals. Furthermore, the UL and DL communication signals may be carried over the wireless communication links <NUM>. Here, the RAN <NUM> is an intermediate network that provides the remote units <NUM> with access to the mobile core network <NUM>.

In some embodiments, the remote units <NUM> communicate with an application server <NUM> via a network connection with the mobile core network <NUM>. For example, an application <NUM> (e.g., web browser, media client, telephone/VoIP application) in a remote unit <NUM> may trigger the remote unit <NUM> to establish a PDU session (or other data connection) with the mobile core network <NUM> via the RAN <NUM>. The mobile core network <NUM> then relays traffic between the remote unit <NUM> and the application server <NUM> in the packet data network <NUM> using the PDU session. Note that the remote unit <NUM> may establish one or more PDU sessions (or other data connections) with the mobile core network <NUM>. As such, the remote unit <NUM> may concurrently have at least one PDU session for communicating with the packet data network <NUM> and at least one PDU session for communicating with another data network (not shown).

The base units <NUM> may be distributed over a geographic region. In certain embodiments, a base unit <NUM> may also be referred to as an access terminal, an access point, a base, a base station, a Node-B, an eNB, a gNB, a Home Node-B, a relay node, or by any other terminology used in the art. The base units <NUM> are generally part of a radio access network ("RAN"), such as the RAN <NUM>, that may include one or more controllers communicably coupled to one or more corresponding base units <NUM>. These and other elements of radio access network are not illustrated but are well known generally by those having ordinary skill in the art. The base units <NUM> connect to the mobile core network <NUM> via the RAN <NUM>.

The base units <NUM> may serve a number of remote units <NUM> within a serving area, for example, a cell or a cell sector, via a wireless communication link <NUM>. The base units <NUM> may communicate directly with one or more of the remote units <NUM> via communication signals. Generally, the base units <NUM> transmit DL communication signals to serve the remote units <NUM> in the time, frequency, and/or spatial domain. Furthermore, the DL communication signals may be carried over the wireless communication links <NUM>. The wireless communication links <NUM> may be any suitable carrier in licensed or unlicensed radio spectrum. The wireless communication links <NUM> facilitate communication between one or more of the remote units <NUM> and/or one or more of the base units <NUM>.

In one embodiment, the mobile core network <NUM> is a <NUM> core ("5GC") or the evolved packet core ("EPC"), which may be coupled to a packet data network <NUM>, like the Internet and private data networks, among other data networks. A remote unit <NUM> may have a subscription or other account with the mobile core network <NUM>. Each mobile core network <NUM> belongs to a single public land mobile network ("PLMN").

The mobile core network <NUM> includes several network functions ("NFs"). As depicted, the mobile core network <NUM> includes multiple user plane functions ("UPFs") <NUM>. The mobile core network <NUM> also includes multiple control plane functions including, but not limited to, an Access and Mobility Management Function ("AMF") <NUM> that serves the RAN <NUM>, a Session Management Function ("SMF") <NUM>, a Policy Control Function ("PCF") <NUM>, and a Unified Data Management function ("UDM") <NUM>. In certain embodiments, the mobile core network <NUM> may also include an Authentication Server Function ("AUSF"), a Network Repository Function ("NRF") (used by the various NFs to discover and communicate with each other over APIs), or other NFs defined for the 5GC.

In various embodiments, the mobile core network <NUM> supports different types of mobile data connections and different types of network slices, wherein each mobile data connection utilizes a specific network slice. Here, a "network slice" refers to a portion of the mobile core network <NUM> optimized for a certain traffic type or communication service. A network instance may be identified by a S-NSSAI, while a set of network slices for which the remote unit <NUM> is authorized to use is identified by NSSAI. In certain embodiments, the various network slices may include separate instances of network functions, such as the SMF <NUM> and UPF <NUM>. In some embodiments, the different network slices may share some common network functions, such as the AMF <NUM>. The different network slices are not shown in <FIG> for ease of illustration, but their support is assumed.

Although specific numbers and types of network functions are depicted in <FIG>, one of skill in the art will recognize that any number and type of network functions may be included in the mobile core network <NUM>. Moreover, where the mobile core network <NUM> is an EPC, the depicted network functions may be replaced with appropriate EPC entities, such as an MME, S-GW, P-GW, HSS, and the like. In certain embodiments, the mobile core network <NUM> may include a AAA server.

While <FIG> depicts components of a <NUM> RAN and a <NUM> core network, the described embodiments for sidelink HARQ operation in NR V2X communication apply to other types of communication networks and RATs, including IEEE <NUM> variants, GSM, GPRS, UMTS, LTE variants, CDMA <NUM>, Bluetooth, ZigBee, Sigfoxx, and the like. For example, in an LTE variant involving an EPC, the AMF <NUM> may be mapped to an MME, the SMF mapped to a control plane portion of a PGW and/or to an MME, the UPF map to an SGW and a user plane portion of the PGW, the UDM/UDR maps to an HSS, etc..

In various embodiments, the remote units <NUM> may communicate directly with each other (e.g., device-to-device communication) using V2X communication signals <NUM>. Here, V2X transmissions may occur on V2X resources. As discussed above, a remote unit <NUM> may be provided with different V2X communication resources for different V2X modes. Mode-<NUM> corresponds to a NR network-scheduled V2X communication mode. Mode-<NUM> corresponds to a NR UE-scheduled V2X communication mode. Mode-<NUM> corresponds to an LTE network-scheduled V2X communication mode. Mode-<NUM> corresponds to an LTE UE-scheduled V2X communication mode.

Moreover, the remote units <NUM> implement SL HARQ processes for at least some data transferred over V2X communication signals <NUM>. According to the invention, a transmitting remote unit <NUM> aggregates SL HARQ feedback and decides between groupcast-based retransmission or M-unicast-based retransmission. Here, 'M-unicast' refers to an integer number of unicast retransmissions required for V2X retransmission.

According to the invention, the transmitting remote unit <NUM> transmits aggregated feedback to RAN <NUM> (e.g., gNB). Here, the aggregated feedback may include one or more of the following: a) aggregated PSFCH ACK/NAK feedback, b) request for either groupcast or M-unicast re-transmission, c) the number of V2X remote units <NUM> requiring retransmission (e.g., the integer 'M'), and d) the total number of group members (e.g., receiving V2X remote units <NUM>). In certain embodiments, the RAN <NUM> (e.g., the base unit <NUM>) makes a decision for either groupcast or M-unicast re-transmission using the aggregated feedback. The base unit <NUM> signals the decision to the transmitting V2X remote unit <NUM>, along with required resources. The transmitting V2X remote unit <NUM> then performs retransmission accordingly.

In various embodiments, the use of SL grant ID in DCI allows the transmitting V2X remote unit <NUM> to send the aggregated feedback in any UL transmission opportunity. In various embodiments, the transmitting V2X remote unit <NUM> uses a special MAC CE for requesting retransmission resources to the base unit <NUM>.

In the following descriptions, the term "RAN node" is used for the base station but it is replaceable by any other radio access node, e.g., BS, eNB, gNB, AP, NR, TRP, etc. Further the operations are described mainly in the context of <NUM> NR. However, the proposed solutions/methods are also equally applicable to other mobile communication systems supporting serving cells/carriers being configured for Sidelink Communication over PC5 interface.

<FIG> a signaling flow diagram for a procedure <NUM> for aggregating HARQ feedback in a V2X transmitting UE ("V2X Tx UE") <NUM>, according embodiments of the disclosure. The procedure <NUM> shows one implementation of the first step in the procedure <NUM>, discussed below with reference to <FIG>. The procedure <NUM> involved the V2X Tx UE <NUM>, a RAN node <NUM>, and a plurality of V2X receiving UEs ("V2X Rx UEs") <NUM> - shown are a first V2X receiving UE ("V2X Rx UE-<NUM>") 215A and a second V2X receiving UE ("V2X Rx UE-<NUM>") 215B.

The procedure <NUM> begins and the V2X Tx UE <NUM> sends an interest indicator (e.g., SL BSR/SR) to the RAN node <NUM> (see messaging <NUM>) and receives in response a SL grant (e.g., Dynamic Grant or Configured Grant) in DCI on the PDCCH (see messaging <NUM>). An example DCI format for SL grant is discussed below with reference to <FIG>.

Upon receiving the grant for sidelink transmission in a NR DCI format, the V2X Tx UE <NUM> transmits SCI (PSCCH), e.g., after Ka time units (e.g., milliseconds, OFDM symbols or similar) (see messaging <NUM>). The V2X Rx UEs <NUM> will receive SCI and - after successfully decoding the same (see blocks <NUM>, <NUM>) - will attempt to receive and decode PSSCH (see messaging <NUM>, blocks <NUM>, <NUM>). If any V2X Rx UE <NUM> is unable to successfully decode the PSSCH, it will feedback 'NACK' to the V2X Tx UE <NUM> (e.g., on PSFCH), as described in <CIT>, titled "Feedback Request Determination". In certain embodiments, if the V2X Rx UE(s) <NUM> able to decode the PSSCH successfully will feedback 'ACK' to the V2X Tx UE <NUM> (e.g., on PSFCH), as described in <CIT>. Note that the Sidelink Control Information ("SCI") may indicate to the V2X Rx UEs <NUM> the SL HARQ resources to use for sending SL feedback (e.g., ACK/NACK), as described in <CIT>.

The V2X Tx UE <NUM> attempts to receive (i.e., "listens" for) SL feedback from the V2X Rx UE(s) over a specific window of time. The window of time may be UE implementation, pre-specified, and/or may be (pre)configurable. Note that if a V2X Rx UE <NUM> does not successfully receive and decode the SCI, then it will not attempt to receive/decode PSSCH and thus will not send feedback to the V2X Tx UE <NUM>. In the depicted embodiment, the first V2X Rx UE 215A successfully decodes the PSSCH transmission (see block <NUM>), but the second V2X Rx UE 215B is unsuccessful in decoding the PSSCH transmission (see block <NUM>). As such, the first V2X Rx UE 215A sends ACK feedback to the V2X Tx UE <NUM> (see messaging <NUM>), while the second V2X Rx UE 215B sends NACK feedback to the V2X Tx UE <NUM> (see messaging <NUM>).

Upon receiving all feedback(s) until certain time (corresponding to the end of the feedback window), the V2X Tx UE <NUM> needs to aggregate the individual SL feedbacks. Feedback aggregation is discussed in further detail below, with reference to <FIG>. Because at least the second V2X Rx UE 215B did not successfully receive the SL data (PSSCH), the Aggregated HARQ feedback message indicates that SL retransmission is needed (see messaging <NUM>). As depicted, the RAN node <NUM> sends a SL grant for retransmission (see messaging <NUM>), wherein the V2X Tx UE <NUM> then performs retransmission accordingly.

<FIG> depicts a procedure <NUM> for sidelink retransmission procedure, according embodiments of the disclosure. The procedure <NUM> involves the V2X transmitting UE ("V2X Tx UE") <NUM>, the RAN node <NUM>, and at least one V2X Rx UE <NUM>.

The procedure <NUM> begins as the V2X Tx UE <NUM> sends a SL BSR (or other indication) to the RAN node <NUM> (see messaging <NUM>) and receives (via Uu interface <NUM>) a SL grant (e.g., Dynamic Grant or Configured Grant) in DCI on the PDCCH (see messaging <NUM>). As depicted, the SL grant indicates a HARQ process ID ("HPID") and also allocates a PUCCH resource for aggregated HARQ feedback.

The V2X Tx UE <NUM> transmits (via PC5 interface <NUM>) SCI to the V2X Rx UE(s) <NUM> and further transmits the SL TB on PSSCH (see messaging <NUM> and <NUM>). Here, the SCI may indicate a HARQ process ID and may indicate resources (e.g., PSFCH) for sending SL feedback. While only one V2X Rx UE <NUM> is depicted in <FIG> for ease of illustration, in other embodiments the V2X Tx UE <NUM> transmits to multiple V2X Rx UEs <NUM>.

As discussed above, each V2X Rx UE <NUM> receiving the SCI attempts to receive and decode the PSSCH <NUM>. In certain embodiments, a V2X Rx UE <NUM> that successfully decodes the PSSCH transmits a SL HARQ ACK (see messaging <NUM>). In certain embodiments, a V2X Rx UE <NUM> that fails to decode the PSSCH transmits a SL HARQ NACK (see messaging <NUM>). In certain embodiments, a V2X Rx UE <NUM> that does not detect the PSSCH transmits a SL HARQ DTX (see messaging <NUM>).

According to a first solution, the V2X Tx UE <NUM> sends aggregated HARQ feedback and optionally triggers SL retransmission as described in the following four steps:.

In step <NUM>, the V2X Tx UE <NUM> aggregates the SL HARQ feedback (see block <NUM>). The aggregation can be done in one of the following ways:.

According to the first option, if there is at least one NACK feedback received by the V2X Tx UE <NUM>, it concludes that a re-transmission needs to be made for the said PSSCH transmission. Accordingly, the aggregated HARQ feedback is "NACK.

According to a second option, if a V2X Rx UE <NUM> is able to decode the PSSCH successfully, then it will feedback 'ACK' to the V2X Tx UE <NUM>. In this case, the V2X Tx UE <NUM> determines whether all the intended recipients have been able to decode the said PSSCH transmission. This can be done by checking if the number of Acks received is same as the total number of receiving V2X UEs in the group. The value "total number of receiving V2X UEs in the group" can be determined based on application layer discovery and/ or using the methods described in <CIT>. If the expected number of Ack feedback is not received by the V2X Tx UE <NUM>, then the V2X Tx UE <NUM> concludes that a re-transmission needs to be made for the said PSSCH transmission (SL data). Accordingly, the aggregated HARQ feedback is `NACK.

According to a third option, if at least one ACK feedback is received from all expected V2X Rx UEs <NUM>, then the aggregated HARQ feedback is 'ACK'. Note that the V2X Tx UE <NUM> may perform book-keeping to track from which V2X Rx UE <NUM> a feedback was received and if ACK or NACK was received, and from which V2X Rx UE <NUM> it has not yet received any feedback. Accordingly, an ACK should have been received from each V2X Rx UE <NUM> at least once (for any of the transmission or retransmissions) in order for the aggregated HARQ feedback to be 'ACK'.

According to a fourth option, if the V2X Tx UE <NUM> is not monitoring the "total number of receiving V2X UEs in the group" and only ACK feedback(s) is received until "certain time" (i.e., no NACK/DTX received during the feedback window), then the aggregated HARQ feedback is 'ACK'. Otherwise (i.e., if a NACK or DTX is received), the aggregated HARQ feedback is 'NACK' (see first option, above).

In Step <NUM>, the V2X Tx UE <NUM> determines a number 'M' of V2X Rx UE(s) <NUM> that failed to decode the SL Data (see block <NUM>, refer also <FIG> step 5a-5b). If 'M' is greater than a threshold number, then the V2X Tx UE <NUM> selects groupcast as the cast-type for re-transmission. Otherwise, the V2X Tx UE <NUM> selects iterative unicast (i.e., 'M' unicast re-transmissions) as the cast-type for re-transmission.

In Step <NUM>, the V2X Tx UE <NUM> indicates the aggregated feedback to the RAN node <NUM> (see block <NUM> and messaging <NUM>). To this end, one of more of the following information can be included in the Aggregated HARQ Feedback message shown in step 5c of <FIG>: A) Aggregated Feedback (ACK or NACK), as described previously, B) Request/ Suggestion for groupcast or 'M' unicast re-transmissions (i.e., according, to the cast-type selected in Step <NUM>), C) The integer 'M', and D) the total number of group members and/or total number of group members providing HARQ feedback. Recall, 'M' represents the number of V2X Rx UE(s) <NUM> that failed to decode the SL Data.

If all the intended recipients have successfully received and decoded the PSSCH packet, the V2X Tx UE <NUM> signals an ACK to the RAN node <NUM> at a specific transmission opportunity. Alternatively, the V2X Tx UE <NUM> may perform DTX at the said specific transmission opportunity. Upon receiving the ACK (or DTX), the RAN node <NUM> may concludes that the transmitter does not need any re-transmission resources for the said PSSCH transmission.

To transmit the HARQ feedback (aggregated), the transmitter needs resources for transmission to RAN node <NUM>. As an example, if the transmitter concludes that a re-transmission needs to be made for the said PSSCH transmission, it needs resources for transmission of NACK to RAN node <NUM>. These resources carry one or more of the information described by Aggregated HARQ Feedback Message items A-D, above. Further details on transmitting the Aggregated HARQ Feedback Message are discussed below with reference to <FIG>.

In Step <NUM>, the RAN node <NUM> may decide if the V2X Tx UE <NUM> is to be given resources for groupcast or rather for 'M' Unicast re-transmissions based on its implementation and signal the result (i.e., SL grant for re-transmission and optionally indicate the cast-type) along with as many/ much required resources for re-transmission(s) to the V2X Tx UE <NUM> (see optional messaging <NUM>). The V2X Tx UE <NUM> receives and implements the SL grant for retransmission (see block <NUM>).

<FIG> depicts a timeline <NUM> of transmission and re-transmission, according to embodiments of the disclosure. The timeline <NUM> is form the perspective of the V2X Tx UE <NUM>, which communicates with a RAN node <NUM> (not shown in <FIG>) and at least three V2X Rx UEs <NUM> (i.e., UE-<NUM>, UE-<NUM>, and UE-<NUM>).

At time 't<NUM>', the V2X Tx UE <NUM> receives a DCI grant <NUM> for initial transmission ("In-Tx") of PSSCH packet on PC5. Here, the DCI grant <NUM> also allocates resources for transmission of SL feedback to RAN node <NUM>.

At time 't<NUM>', the V2X Tx UE <NUM> sends SCI <NUM> in PSCCH on PC5. The interval <NUM> between receiving the DCI and sending the SCI is Ka time units (e.g., milliseconds, OFDM symbols or similar) after the reception of the said DCI.

At time 't<NUM>', the V2X Tx UE <NUM> sends a packet (TB) <NUM> in PSSCH on PC5. The interval <NUM> between sending the SCI and sending the PSSCH is Kb time units after the reception of the said SCI.

During the window 'tF,' the V2X Tx UE <NUM> listens for SL feedback <NUM> (e.g., on PSFCH) from the group of V2X Rx UE <NUM>. In the depicted embodiment, HARQ feedback is received from the UE-<NUM>, UE-<NUM>, and UE-<NUM>. As discussed above, each Rx UE <NUM> may send ACK, NACK or DTX. The V2X Tx UE <NUM> prepares aggregated feedback according to the principles described herein.

At time 't<NUM>', the V2X Tx UE <NUM> sends aggregated HARQ feedback <NUM> in PUCCH on Uu. The interval <NUM> between receiving the DCI and sending the aggregated HARQ feedback <NUM> is Kc time units after the reception of the said DCI. The interval <NUM> between the end of the window tF (i.e., last PSFCH opportunity) and the sending of the aggregated HARQ feedback is Kd time units after the end of the window.

The resources for transmission of the aggregated HARQ feedback to RAN node <NUM> are available after Kc time units from the reception of the said DCI (alternatively, after Kd time units from the end of the window tF). The parameter 'Kc' (alternatively, the parameter Kd) may be signaled in the DCI <NUM>. In addition, the actual PRB resources for feedback transmission can be done, for example using the 'pucch-ResourceCommon' information element.

In some embodiments, an integer (<NUM>. <NUM>) signaled in the DCI <NUM> points to an entry into a <NUM>-row table where each row configures a set of cell-specific PUCCH resources/parameters. Alternatively, in other embodiments the network provides a dedicated PUCCH-Config corresponding to a (active) bandwidth part, for example using the 'n1PUCCH-An' information element, HARQ resource used otherwise for PUCCH for DL SPS. The actual PUCCH-Resource is configured in PUCCH-Config, e.g., as described in 3GPP TS <NUM>-f40. The feedback resource on PUCCH may be also implicitly allocated, e.g., depends on the first CCE index of PDCCH (SL grant). Alternatively, the PUCCH resources for ACK/NACK transmission ("A/N PUCCH resources") could be linked to PSSCH resources included in the DCI format (e.g., DCI format 5A).

At time 't<NUM>', the RAN node <NUM> optionally sends a DCI grant <NUM> for retransmission of the PSSCH packet on PC5 (e.g., for the case where the Aggregated HARQ feedback indicates 'NACK' for at least on V2X Rx UE <NUM>). Here, the V2X Tx UE <NUM> again sends SCI and PSSCH and receives SL HARQ feedback for the retransmission as described above.

<FIG> depicts an example DCI <NUM>, according to embodiments of the disclosure. Where the A/N PUCCH resources are linked to PSSCH resources included in the DCI format (e.g., the depicted DCI format 5A), the ACK/NACK resource feedback from the V2X Tx UE <NUM> to the RAN node <NUM> may be transmitted at an Offset from the parameter 'FirstSubchannelIdx' or from the last PRB of the PSSCH (e.g., FirstSubchannelIdx + RIV + Offset). Here, the Offset may be predefined or may be signaled in the said DCI, together with Kc.

Therefore, using the resources indicated implicitly or explicitly in the DCI, the Aggregated HARQ Feedback message is transmitted to RAN node <NUM> after Kc time units.

Referring again to <FIG>, in Step <NUM> the RAN node <NUM> decides whether the V2X Tx UE <NUM> is to be given resources for groupcast or rather for 'M' Unicast re-transmissions based on its implementation and signal the result (re-transmission grant and optionally the cast-type) along with as many/ much required resources for re-transmission(s) to the V2X Tx UE <NUM>. The V2X Tx UE makes re-transmission(s) accordingly.

In an alternative implementation of <FIG>, the DCI allocating the PC5 transmission grant to the V2X Tx UE may be identified using a grant-ID (e.g., `SL grant ID'). The aggregated feedback will be signaled back to the RAN node <NUM> by the V2X Tx UE <NUM> indicating this grant-ID. This allows the V2X Tx UE to send the aggregated feedback in any UL transmission opportunity without having to wait until Kc time units. In various embodiments, the `grant-Id' can also be a HARQ process ID.

According to a second solution, a new MAC control element ("MAC CE") is used to request re-transmission resources to the RAN node <NUM>. This new MAC CE is designed with a corresponding reserved logical channel ID. The V2X Tx UE <NUM> is to trigger a scheduling request ("SR") if there are no resources available to transmit the MAC CE and in that sense this MAC CE is allowed to trigger SR. The scheduling request ("SR") configuration can be specific for this purpose.

In the MAC CE, the V2X Tx UE <NUM> indicates a grant-ID which is same as the one that network signals in the DCI used for communicating the transmission grant for the said PSSCH transmission. Based on this grant-ID, the network can know exactly the resource size for retransmission of the said packet on PC5. Alternatively, the V2X Tx UE <NUM> may include a Buffer Occupancy ("BO") with the same size as for the initial TB transmission of the said PSSCH packet in the said MAC CE. As a further alternative, one or more of the following information is included in the MAC CE: a) Aggregated Feedback (ACK or NACK) as described previously, b) Request/ Suggestion for groupcast or 'M' unicast re-transmissions; c) The integer 'M'; and d) Total number of group members and/or Total number of group members providing HARQ feedback.

Next, a RAN node <NUM> decision follows on groupcast or M-unicast, signaling the same to the V2X Tx UE <NUM> along with as many/ much required resources and V2X Tx UE <NUM> making then required re-transmission(s) accordingly.

In various embodiments, the RAN node <NUM> in DCI for scheduling transmission from the V2X Tx UE <NUM> (message <NUM> in <FIG>) includes 'n' UL ACK/ NACK Feedback resources which the transmitter will use to transmit/ forward the individual feedback(s) from the V2X Rx UE(s) <NUM>. The V2X Tx UE <NUM> does not perform any feedback aggregation in this case.

In various embodiments, the RAN node <NUM> in DCI for scheduling transmission from the V2X Tx UE <NUM> (message <NUM> in <FIG>) includes resources for 'n' CSI Reports which includes CQI, RI, PMI or non-codebook which the transmitter will use to transmit/ forward the individual CSI report(s) from the V2X Rx UE(s) <NUM>. The V2X Tx UE <NUM> may or may not perform any CSI aggregation using an indicated compression in this case. In another embodiment, the V2X Rx UE(s) <NUM> indicates the CSI report directly to the RAN node <NUM> using the resources provided by RAN node <NUM> in the DCI (forwarded by the V2X Tx UE <NUM> to the V2X Rx UE(s) <NUM>).

In case a Mode switch happens after the transmission of the SL Data and the V2X Tx UE <NUM> needs to switch to Mode-<NUM> based resource allocation, the V2X Tx UE <NUM> is to revert to the RAN node <NUM> indicating that the allocated ACK/ NACK resources in the DCI message are no more required. In another embodiment, the V2X Tx UE <NUM> does not switch mode if the ACK/ NACK resources in the DCI message are provided by the RAN node <NUM> already.

<FIG> depicts a user equipment apparatus <NUM> that may be used for aggregating HARQ feedback and sidelink retransmission procedure, according to embodiments of the disclosure. In various embodiments, the user equipment apparatus <NUM> is used to implement one or more of the solutions described above. The user equipment apparatus <NUM> may be one embodiment of the AMF, described above. Furthermore, the user equipment apparatus <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, an output device <NUM>, and a transceiver <NUM>. In some embodiments, the input device <NUM> and the output device <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the user equipment apparatus <NUM> may not include any input device <NUM> and/or output device <NUM>. In various embodiments, the user equipment apparatus <NUM> may include one or more of: the processor <NUM>, the memory <NUM>, and the transceiver <NUM>, and may not include the input device <NUM> and/or the output device <NUM>.

In various embodiments, the processor <NUM> controls the user equipment apparatus <NUM> to implement the above described UE behaviors. In some embodiments, the processor <NUM> transmits SL data (via transceiver <NUM>) the to a set of receiver V2X UEs and listens for SL feedback from the set of the receiver V2X UEs, the SL feedback indicating whether a receiver V2X UE successfully decoded the SL data transmission. The processor <NUM> aggregates HARQ feedback and sends an Aggregated Feedback message to a RAN node (via transceiver <NUM>), the Aggregated Feedback message containing the aggregated HARQ feedback.

In certain embodiments, the processor further determines a transmission mode for retransmission of the SL data, wherein the transmission mode is selected from: groupcast transmission and M-unicast transmissions. Here, M is an integer less than the number of receiver V2X UEs. In such embodiments, the Aggregated Feedback message requests the determined transmission mode. In some embodiments, the transceiver receives a re-transmission grant from the RAN node, where the re-transmission grant indicates a cast type for the retransmission. In such embodiments, the processor performs retransmission of the SL data according to a cast type indicated in the re-transmission grant.

In various embodiments, the SL feedback is received over a sidelink channel, such as PSCCH, PSSCH, or a sidelink feedback channel. In certain embodiments, the SL feedback includes an ACK indicating successful reception and decoding of the SL data. In certain embodiments, the SL feedback includes a NACK indicating unsuccessful decoding of the SL data. In certain embodiments, the SL feedback includes a DTX indication that no PSSCH (carrying the SL data) was detected. In certain embodiments, the receiver V2X UE does not receive the control signaling (i.e., PSCCH) scheduling the PSSCH, therefore the receiver V2X UE does not send any SL feedback.

In some embodiments, aggregating HARQ feedback includes generating an ACK if all UEs in the set of receiver V2X UEs transmit ACK and otherwise generating a NACK. In such embodiments, the processor may track from which receiver V2X UE a SL feedback (ACK or NACK) was received and from which receiver V2X UE no SL feedback has been received.

In some embodiments, aggregating HARQ feedback includes determining whether a number of positive acknowledgements received is same as a total number of UEs in the set of receiver V2X UEs and generating a negative acknowledgement if the number of positive acknowledgements received is not the same as the total number of UEs in the set of receiver V2X UEs.

In some embodiments, aggregating HARQ feedback includes tracking which ones of the set of receive V2X UEs transmit positive acknowledgement. In such embodiments, transmitting the Aggregated Feedback message to the RAN node includes sending a positive acknowledgement to the RAN node in response to each V2X UE transmitting at least one positive acknowledgement message to the user equipment apparatus <NUM> (i.e., the transmitter V2X UE).

In some embodiments, the Aggregated Feedback message indicates a number of receiver V2X UEs that provided SL feedback and/or a total number of UEs in the set of receiver V2X UEs. In some embodiments, transmitting the Aggregated Feedback message to a RAN node includes the processor identifying a grant of feedback resources on a Uu interface to the RAN node, said grant identified using DCI received from the RAN node. In certain embodiments, the feedback resources are available an indicated amount of time after reception of the DCI (i.e., indicated by the parameter 'Kc' or 'Kd' signaled in the DCI, as discussed above).

In some embodiments, the SL feedback from the receiver V2X UEs is to be received within a window of time after transmission of the SL data. In such embodiments, the feedback resources are available an indicated amount of time after the window of time for receiving SL feedback. In certain embodiments, the feedback resources include a set of physical resource blocks, wherein the processor further identifies the set of physical resource blocks using the DCI. In some embodiments, the memory <NUM> stores data related to sidelink HARQ operation. For example, the memory <NUM> may store V2X communication resources, HARQ processes, and the like. In certain embodiments, the memory <NUM> also stores program code and related data, such as an operating system or other controller algorithms operating on the remote unit <NUM>.

As discussed above, the transceiver <NUM> communicates with one or more network functions of a mobile communication network via one or more access networks. The transceiver <NUM> operates under the control of the processor <NUM> to transmit messages, data, and other signals and also to receive messages, data, and other signals. For example, the processor <NUM> may selectively activate the transceiver <NUM> (or portions thereof) at particular times in order to send and receive messages.

The transceiver <NUM> may include one or more transmitters <NUM> and one or more receivers <NUM>. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the user equipment apparatus <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>. Further, the transmitter(s) <NUM> and the receiver(s) <NUM> may be any suitable type of transmitters and receivers. Additionally, the transceiver <NUM> may support at least one network interface <NUM>. Here, the at least one network interface <NUM> facilitates communication with a RAN node, such as an eNB or gNB, for example using the "Uu" interface (e.g., LTE-Uu for eNB, NR-Uu for gNB). Additionally, the at least one network interface <NUM> may include an interface used for communications with one or more network functions in the mobile core network, such as a UPF <NUM>, an AMF <NUM>, and/or a SMF <NUM>.

In one embodiment, the transceiver <NUM> includes a first transmitter/receiver pair used to communicate with a mobile communication network over licensed radio spectrum and a second transmitter/receiver pair used to communicate with a mobile communication network over unlicensed radio spectrum.

In various embodiments, one or more transmitters <NUM> and/or one or more receivers <NUM> may be implemented and/or integrated into a single hardware component, such as a multitransceiver chip, a system-on-a-chip, an application-specific integrated circuit ("ASIC"), or other type of hardware component. In certain embodiments, one or more transmitters <NUM> and/or one or more receivers <NUM> may be implemented and/or integrated into a multi-chip module. In some embodiments, other components such as the network interface <NUM> or other hardware components/circuits may be integrated with any number of transmitters <NUM> and/or receivers <NUM> into a single chip. In such embodiment, the transmitters <NUM> and receivers <NUM> may be logically configured as a transceiver <NUM> that uses one more common control signals or as modular transmitters <NUM> and receivers <NUM> implemented in the same hardware chip or in a multi-chip module. In certain embodiments, the transceiver <NUM> may implement a 3GPP modem (e.g., for communicating via NR or LTE access networks) and a non-3GPP modem (e. , for communicating via Wi-Fi or other non-3GPP access networks).

<FIG> depicts a base station apparatus <NUM> that may be used for protecting the user identity and credentials, according to embodiments of the disclosure. In various embodiments, the base station apparatus <NUM> is used to implement one or more of the solutions described above. The base station apparatus <NUM> may be one embodiment of the AMF, described above. Furthermore, the base station apparatus <NUM> may include a processor <NUM>, a memory <NUM>, an input device <NUM>, an output device <NUM>, and a transceiver <NUM>. In some embodiments, the input device <NUM> and the output device <NUM> are combined into a single device, such as a touchscreen. In certain embodiments, the base station apparatus <NUM> may not include any input device <NUM> and/or output device <NUM>. In various embodiments, the base station apparatus <NUM> may include one or more of: the processor <NUM>, the memory <NUM>, and the transceiver <NUM>, and may not include the input device <NUM> and/or the output device <NUM>.

For example, the processor <NUM> may be a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or similar programmable controller.

In various embodiments, the processor <NUM> controls the base station apparatus <NUM> to implement the above described RAN node behaviors. For example, the processor <NUM> may receive (via transceiver <NUM>) a SL BSR from a V2X UE. In response, the processor <NUM> may allocate to the V2X UE PSCCH, PSSCH, and/or PUCCH resources. If PUCCH resources are allocated with the SL grant, the processor <NUM> receives (via transceiver <NUM>) aggregated HARQ feedback.

In some embodiments, the memory <NUM> stores data related to sidelink HARQ operation. For example, the memory <NUM> may store V2X communication resources, HARQ process IDs, UE configurations, and the like. In certain embodiments, the memory <NUM> also stores program code and related data, such as an operating system or other controller algorithms operating on the base station apparatus <NUM>.

As another, non-limiting, example, the output device <NUM> may include a wearable display separate from, but communicatively coupled to, the rest of the base station apparatus <NUM>, such as a smart watch, smart glasses, a heads-up display, or the like.

The transceiver <NUM> includes at least transmitter <NUM> and at least one receiver <NUM>. One or more transmitters <NUM> may be used to send messages to the RAN, as described herein. Similarly, one or more receivers <NUM> may be used to receive messages from the RAN, as described herein. Although only one transmitter <NUM> and one receiver <NUM> are illustrated, the base station apparatus <NUM> may have any suitable number of transmitters <NUM> and receivers <NUM>. Further, the transmitter(s) <NUM> and the receiver(s) <NUM> may be any suitable type of transmitters and receivers.

In various embodiments, the transceiver <NUM> supports one or more network interfaces <NUM> for communicating with a UE and/or network function. For example, the transceiver <NUM> may support an "Uu" interface with the UE. Additionally, the transceiver <NUM> may support various 7GC service interfaces, such as the N2 interface and/or N3 interface.

<FIG> depicts one embodiment of a method <NUM> for aggregating HARQ feedback and sidelink retransmission procedure, according to embodiments of the disclosure. In various embodiments, the method <NUM> is performed by a transmitter V2X UE, such as the remote unit <NUM>, the UE <NUM>, and/or the user equipment apparatus <NUM>, described above. In some embodiments, the method <NUM> is performed by a processor, such as a microcontroller, a microprocessor, a CPU, a GPU, an auxiliary processing unit, a FPGA, or the like.

The method <NUM> begins and transmits <NUM> SL data to a set of receiver V2X UEs. The method <NUM> includes listening <NUM> for SL feedback from the set of receiver V2X UEs, the SL feedback indicating whether a receiver V2X UE successfully decoded the SL data transmission. The method <NUM> includes aggregating <NUM> HARQ feedback in the transmitter V2X UE. The method <NUM> includes transmitting <NUM> an Aggregated Feedback message to a RAN node. The method <NUM> ends.

Disclosed herein is a first apparatus for managing uplink preemption, according to embodiments of the disclosure. The first apparatus may be implemented by a transmitter V2X UE, such as the remote unit <NUM>, the UE <NUM>, and/or the user equipment apparatus <NUM>. The first apparatus includes a transceiver that transmits SL data to a set of receiver V2X UEs and listens for SL feedback from the set of the receiver V2X UEs, the SL feedback indicating whether a receiver V2X UE successfully decoded the SL data transmission. The first apparatus also includes a processor that aggregates HARQ feedback and sends an Aggregated Feedback message to a RAN node, the Aggregated Feedback message containing the aggregated HARQ feedback.

In some embodiments, aggregating HARQ feedback includes tracking which ones of the set of receive V2X UEs transmit positive acknowledgement. In such embodiments, transmitting the Aggregated Feedback message to the RAN node includes sending a positive acknowledgement to the RAN node in response to each V2X UE transmitting at least one positive acknowledgement message to the first apparatus.

In some embodiments, the Aggregated Feedback message indicates a number of receiver V2X UEs that provided SL feedback and/or a total number of UEs in the set of receiver V2X UEs. In some embodiments, transmitting the Aggregated Feedback message to a RAN node includes the processor identifying a grant of feedback resources on a Uu interface to the RAN node, said grant identified using DCI received from the RAN node. In certain embodiments, the feedback resources are available an indicated amount of time after reception of the DCI.

In some embodiments, listening for SL feedback from the set of receiver V2X UEs includes waiting to receive the SL feedback during a window of time after transmission of the SL data. In such embodiments, the feedback resources are available an indicated amount of time after the window of time for receiving SL feedback. In certain embodiments, the feedback resources include a set of physical resource blocks, wherein the processor further identifies the set of physical resource blocks using the DCI.

Disclosed herein is a first method for aggregating HARQ feedback and sidelink retransmission procedure, according to embodiments of the disclosure. The first method may be performed by a transmitter V2X UE, such as the remote unit <NUM>, the UE <NUM>, and/or the user equipment apparatus <NUM>. The first method includes transmitting SL data to a set of receiver V2X UEs and listening for SL feedback from the set of receiver V2X UEs, the SL feedback indicating whether a receiver V2X UE successfully decoded the SL data transmission. The first method includes aggregating HARQ feedback in the transmitter V2X UE and transmitting an Aggregated Feedback message to a RAN node, the Aggregated Feedback message containing the aggregated HARQ feedback.

In various embodiments, the SL feedback is received over a sidelink channel, such as PSCCH or a sidelink feedback channel. In certain embodiments, the SL feedback includes an ACK indicating successful reception and decoding of the SL data. In certain embodiments, the SL feedback includes a NACK indicating unsuccessful decoding of the SL data. In certain embodiments, the SL feedback includes a DTX indication that no SL data was detected. In some embodiments, aggregating HARQ feedback in the transmitter V2X UE includes generating an ACK if all UEs in the set of receiver V2X UEs transmit ACK and otherwise generating a NACK. In such embodiments, the processor may track from which receiver V2X UE a SL feedback (ACK or NACK) was received and from which receiver V2X UE no SL feedback has been received.

In some embodiments, aggregating HARQ feedback in the transmitter V2X UE includes determining whether a number of positive acknowledgements received is same as a total number of UEs in the set of receiver V2X UEs and generating a negative acknowledgement if the number of positive acknowledgements received is not the same as the total number of UEs in the set of receiver V2X UEs.

In some embodiments, aggregating HARQ feedback in the transmitter V2X UE includes tracking which ones of the set of receive V2X UEs transmit positive acknowledgement. In such embodiments, transmitting the Aggregated Feedback message to the RAN node includes sending a positive acknowledgement to the RAN node in response to each V2X UE transmitting at least one positive acknowledgement message to the transmitter V2X UE.

Claim 1:
A processor (<NUM>) for wireless communication, comprising:
at least one controller coupled with at least one memory (<NUM>) and configured to cause the processor (<NUM>) to:
output (<NUM>) sidelink, "SL", data to a set of receiver vehicle-to-everything, V2X, UEs (<NUM>, <NUM>, <NUM>);
listen (<NUM>) for SL feedback from the set of receiver V2X UEs, the SL feedback indicating whether a receiver V2X UE successfully decoded the SL data;
aggregate (<NUM>) hybrid automatic repeat request, "HARQ", feedback received as SL feedback from the receiver V2X UEs, wherein aggregating HARQ feedback comprises generating a positive acknowledgement if all UEs in the set of receiver V2X UEs transmit positive acknowledgement and otherwise generating a negative acknowledgement;
output (<NUM>) an aggregated feedback message to a radio access network, "RAN", node, the aggregated feedback message containing the aggregated HARQ feedback; and
characterised by determining
a transmission mode for retransmission of the SL data, wherein the transmission mode is selected from: groupcast transmission and M-unicast transmissions, wherein M is an integer less than the number of receiver V2X UEs, wherein the aggregated feedback message requests the determined transmission mode.