Patent Description:
In vehicle-to-everything (V2X), vehicles may be equipped with user equipment configured to wirelessly communicate with other user equipment, such as vehicle-to-vehicle (V2V) user equipment, vehicle-to-network nodes (V2N), vehicle-to-pedestrian (V2P), and/or any other type of device. The V2X messages may be used to exchange messages, such as traffic related messages, alerts, autonomous or semi-autonomous driving messages, and/or any other type of data or message. For example, a V2X message may be sent from a first vehicle via a SideLink (SL) to other nearby vehicles warning the other vehicles of a hazardous traffic condition.

Group of User Equipment (UE) may be configured to receive a SL groupcast. However, radio conditions for receiving the groupcast may vary between members of the group, whereby reception of data and/or control information transmitted over the groupcast may not be successful at some of the UE of the group. Hybrid Automatic Repeat Request (HARQ) can be used to remedy unsuccessful groupcast transmissions. However, in order for the HARQ to operate, HARQ feedback should be sent from a receiver UE back to the transmitter UE in order for the transmitter UE to learn about any unsuccessful groupcast transmissions and determine if HARQ retransmissions are needed. However, if the radio conditions between the transmitter UE and the receiver UE are poor, HARQ feedback from the receiver UE may not be received at the transmitter UE. If the HARQ uses only negative acknowledgement (NACK) feedback such as in NR SL groupcast HARQ feedback option <NUM> (NACK-only), NACKs from the group members are the only feedback. In the NACK-only operation, poor radio conditions to a receiver UE can be left hidden from the transmitter UE. R1-<NUM> discloses inter-UE coordination information of HARQ feedback.

The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

At least some embodiments facilitate delivery of feedback information for groupcast from a wireless device in case of reception problems of the groupcast at the wireless device.

Receiver wireless device may receive a groupcast from a transmitter wireless device and determine at least one trigger for requesting to modify Hybrid Automatic Repeat Request, HARQ, feedback. The receiver wireless device may transmit to one or more peer receiver wireless devices of the groupcast, based on the determined at least one trigger, at least one request to modify the HARQ feedback to the groupcast. Provided the one or more peer receiver wireless devices accept the request to modify the HARQ feedback, the transmitter wireless device may receive HARQ feedback to the groupcast even if HARQ feedback from the receiver wireless device would not be received at the transmitter wireless device. Accordingly, the request to modify HARQ feedback may cause that the peer wireless device generates modified HARQ feedback and transmits the modified HARQ feedback to the transmitter wireless devices. On the other hand, if the HARQ feedback from the receiver wireless device is received at the transmitter device, the one or more peer receiver wireless devices transmit modified HARQ feedback to the transmitter wireless device, whereby a possibility of receiving HARQ feedback from the receiver wireless devices at the transmitter wireless device may be increased which is useful particularly for situations, where one or more of the wireless devices may experience reception problems of the groupcast and for NACK-only HARQ-feedback.

In the following, modified HARQ feedback may refer to HARQ feedback to a groupcast. The groupcast may be sidelink groupcast. HARQ feedback may be transmitted from a receiver wireless device to a transmitter wireless device based on an HARQ configuration. The modified HARQ feedback may be generated, when the receiver wireless device modifies HARQ feedback generated based on the HARQ configuration or a modified HARQ configuration used by the receiver wireless device. The modified HARQ feedback may be generated based on a request from another receiver wireless device. Examples of the HARQ configurations comprise SideLink (SL) groupcast HARQ feedback option <NUM> and SL groupcast HARQ feedback option <NUM> defined by release <NUM> of the 3GPP specifications. In the HARQ feedback option <NUM>, only NACK is transmitted as HARQ feedback. In the HARQ feedback option <NUM>, the HARQ feedback may be ACK or NACK. It should be noted that although some examples are described with refence to HARQ feedback option <NUM>, also other HARQ configurations may be applied. Examples of the modified HARQ feedback may comprise (but not limited to) a receiver wireless device reversing its HARQ feedback decision from ACK into NACK based on a request from at least one peer wireless device and transmitting at least one NACK feedback, instead of not transmitting any feedback for option <NUM>, to the transmitter wireless device based on the feedback configuration provided by the request.

<FIG> shows user devices <NUM> and <NUM> configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) <NUM> providing the cell. The physical link from a user device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the user device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage. The access node provides access by way of communications of radio frequency (RF) signals and may be referred to a radio access node. It should be appreciated that the radio access network may comprise more than one access nodes, whereby a handover of a wireless connection of the user device from one cell of one access node, e.g. a source cell of a source access node, to another cell of another node, e.g. a target cell of a target access node, may be performed.

A communication system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point, access node or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network <NUM> (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of user devices (UEs) to external packet data networks, or mobile management entity (MME), etc..

The user device (also called UE, user equipment, user terminal, terminal device, wireless device, communications device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, such as a relay node.

<NUM> enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. <NUM> mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. <NUM> is expected to have multiple radio interfaces, namely below <NUM>, cmWave and mmWave, and also being capable of being integrated with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and <NUM> radio interface access comes from small cells by aggregation to the LTE. In other words, <NUM> is planned to support both inter-RAT operability (such as LTE-<NUM>) and inter-RI operability (inter-radio interface operability, such as below <NUM> - cmWave, below <NUM> - cmWave - mmWave). One of the concepts considered to be used in <NUM> networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent.

Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and railway/maritime/aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed).

The following describes in further detail suitable apparatus and possible mechanisms for implementing some embodiments. In this regard reference is first made to <FIG> which shows a schematic block diagram of an exemplary apparatus or electronic device <NUM> depicted in <FIG>, which may incorporate a transmitter according to an embodiment of the invention.

The electronic device <NUM> may for example be a communications device, wireless device, mobile terminal or user equipment of a wireless communication system. However, it would be appreciated that embodiments of the invention may be implemented within any electronic device or apparatus which may require transmission of radio frequency signals.

The apparatus <NUM> may comprise a housing <NUM> for incorporating and protecting the device. The apparatus <NUM> further may comprise a display <NUM> in the form of a liquid crystal display. In other embodiments of the invention the display may be any suitable display technology suitable to display an image or video. The apparatus <NUM> may further comprise a keypad <NUM>. In other embodiments of the invention any suitable data or user interface mechanism may be employed. For example the user interface may be implemented as a virtual keyboard or data entry system as part of a touch-sensitive display. The apparatus may comprise a microphone <NUM> or any suitable audio input which may be a digital or analogue signal input. The apparatus <NUM> may further comprise an audio output device which in embodiments of the invention may be any one of: an earpiece <NUM>, speaker, or an analogue audio or digital audio output connection. The apparatus <NUM> may also comprise a battery <NUM> (or in other embodiments of the invention the device may be powered by any suitable mobile energy device such as solar cell, fuel cell or clockwork generator). The term battery discussed in connection with the embodiments may also be one of these mobile energy devices. Further, the apparatus <NUM> may comprise a combination of different kinds of energy devices, for example a rechargeable battery and a solar cell. The apparatus may further comprise an infrared port <NUM> for short range line of sight communication to other devices. In other embodiments the apparatus <NUM> may further comprise any suitable short range communication solution such as for example a Bluetooth wireless connection or a USB/firewire wired connection.

The apparatus <NUM> may comprise a controller <NUM> or processor for controlling the apparatus <NUM>. The controller <NUM> may be connected to memory <NUM> which in embodiments of the invention may store both data and/or may also store instructions for implementation on the controller <NUM>. The controller <NUM> may further be connected to codec circuitry <NUM> suitable for carrying out coding and decoding of audio and/or video data or assisting in coding and decoding carried out by the controller <NUM>.

The apparatus <NUM> may further comprise a card reader <NUM> and a smart card <NUM>, for example a universal integrated circuit card (UICC) reader and UICC for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.

The apparatus <NUM> may comprise radio interface circuitry <NUM> connected to the controller and suitable for generating wireless communication signals for example for communication with a cellular communications network, a wireless communications system or a wireless local area network or a SL. The apparatus <NUM> may further comprise an antenna <NUM> connected to the radio interface circuitry <NUM> for transmitting radio frequency signals generated at the radio interface circuitry <NUM> to other apparatus(es) and for receiving radio frequency signals from other apparatus(es).

In some embodiments of the invention, the apparatus <NUM> comprises a camera <NUM> capable of recording or detecting imaging.

With respect to <FIG>, an example of a system within which embodiments of the present invention can be utilized is shown. The system <NUM> comprises multiple communication devices which can communicate through one or more networks. The system <NUM> may comprise any combination of wired and/or wireless networks including, but not limited to a wireless cellular telephone network (such as a GSM (<NUM>, <NUM>, <NUM>, LTE, <NUM>), UMTS, CDMA network etc.), a wireless local area network (WLAN) such as defined by any of the IEEE <NUM>. x standards, a Bluetooth personal area network, an Ethernet local area network, a token ring local area network, a wide area network, and the Internet.

For example, the system shown in <FIG> shows a mobile telephone network <NUM> and a representation of the internet <NUM>. Connectivity to the internet <NUM> may include, but is not limited to, long range wireless connections, short range wireless connections, and various wired connections including, but not limited to, telephone lines, cable lines, power lines, and similar communication pathways.

The example communication devices shown in the system <NUM> may include, but are not limited to, an electronic device or apparatus <NUM>, a combination of a personal digital assistant (PDA) and a mobile telephone <NUM>, a PDA <NUM>, an integrated messaging device (IMD) <NUM>, a desktop computer <NUM>, a notebook computer <NUM>, a tablet computer. The apparatus <NUM> may be stationary or mobile when carried by an individual who is moving. The apparatus <NUM> may also be located in a mode of transport including, but not limited to, a car, a truck, a taxi, a bus, a train, a boat, an airplane, a bicycle, a motorcycle or any similar suitable mode of transport.

Some or further apparatus may send and receive calls and messages and communicate with service providers through a wireless connection <NUM> to a base station <NUM>. The base station <NUM> may be connected to a network server <NUM> that allows communication between the mobile telephone network <NUM> and the internet <NUM>. The system may include additional communication devices and communication devices of various types.

The communication devices may communicate using various transmission technologies including, but not limited to, code division multiple access (CDMA), global systems for mobile communications (GSM), universal mobile telecommunications system (UMTS), time divisional multiple access (TDMA), frequency division multiple access (FDMA), transmission control protocol-internet protocol (TCP-IP), short messaging service (SMS), multimedia messaging service (MMS), email, instant messaging service (IMS), Bluetooth, IEEE <NUM>, Long Term Evolution wireless communication technique (LTE), <NUM> and any similar wireless communication technology. Yet some other possible transmission technologies to be mentioned here are high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSUPA), LTE Advanced (LTE-A) carrier aggregation dual-carrier, and all multi-carrier technologies. A communications device involved in implementing various embodiments of the present invention may communicate using various media including, but not limited to, radio, infrared, laser, cable connections, and any suitable connection. In the following some example implementations of apparatuses utilizing the present invention will be described in more detail.

In an example in accordance with at least some embodiments the communications of the communications devices may comprise uplink transmissions, downlink transmissions and/or SL transmissions. The uplink transmissions may be performed from a wireless device to the wireless communication system, e.g. an access node, and the downlink transmissions may be performed from the wireless communication system, e.g. an access node, to the wireless device. The uplink transmissions may be performed on an uplink shared channel, e.g. a Physical Uplink Shared Channel (PUSCH). The PUSCH may be transmitted by the wireless device based on a grant received on a downlink control channel, e.g. a Physical Downlink control Channel (PDCCH). The downlink transmissions may be performed on a downlink shared channel, e.g. a Physical Downlink Shared Channel (PDSCH). Release <NUM> specifications of the 3GPP may be referred to for examples PUSCH and PDSCH procedures. SL may refer to the interface between UEs, or wireless devices, for Device-to-Device (D2D) communication and D2D discovery. The SL enables a direct communication between proximal wireless devices. PC5 is an example of a radio interface for SL and specified in <NUM> GPP LTE, Release <NUM> and beyond. Section <NUM>. of the TS <NUM> describes SL procedures. Thus, in SL communications transmissions comprising data and/or control information do not need to go through the access network e.g. through an infrastructure node of the access network such as an eNB or a gNB. SL transmissions enable services that are often called "Proximity Services" (or ProSe) and the UEs supporting SL "ProSe'-enabled UEs. The channel defined/used by the SL may be a control channel or a data channel. A control channel that is used to broadcast basic system information for D2D communication may be the Physical SL Broadcast Channel (PSBCH). A control channel used for transmitting the D2D discovery signal may be defined as a Physical SL Discovery Channel (PSDCH). The D2D synchronization signal may be referred to as a SL Synchronization Signal (SLSS) or a D2D Synchronization Signal (D2DSS). A control channel for a SL groupcast, i.e. groupcast communications, may be a Physical SL Control Channel (PSCCH). A data channel for the SL groupcast may be a Physical SL Shared Channel (PSSCH).

SL communications may be broadcast, unicast or groupcast communications. The unicast communications may refer to transmissions from one UE to another UE, whereas the groupcast communications may refer to transmissions from one UE to a group of one or more UEs that are group members of the group, i.e. the groupcast group. In groupcast communications, a UE transmitting a groupcast transmission to the groupcast group may be referred to a transmitter UE (TX-UE) and a UE of the groupcast group receiving the groupcast transmission may be referred to a receiver UE (RX-UE). Unicast SL may refer to a SL for unicast transmission, or simply a unicast. A unicast transmission may comprise one or more unicast messages. Groupcast SL may refer to a SL for groupcast transmission, or simply a groupcast. A groupcast transmission may comprise one or more unicast messages.

Prior to performing a groupcast transmission, or a groupcast, the TX-UE transmits SL control information (SCI) on the PSCCH and PSSCH to the group members. The SCI comprises the information that enable the group members to receive and demodulate the upcoming groupcast transmission and a HARQ configuration for the groupcast transmission. The SCI comprises a <NUM>st stage on the PSCCH and a <NUM>nd stage that is multiplexed with data on the PSSCH. Therefore, the <NUM>st stage SCI is more robust against reception problems. The HARQ configuration is applied by the group members for transmitting HARQ feedback to the groupcast transmission. The HARQ configuration may comprise information indicating a HARQ option. The HARQ option may indicate resources for HARQ feedback and any conditions for transmitting HARQ feedback. In an example, a condition for the HARQ feedback may be that HARQ feedback may be an acknowledgement (ACK) or a negative acknowledgement (NACK), or the HARQ feedback may only be NACK, i.e. NACK-only. In release <NUM> of the 3GPP specifications, NR SL has developed SL groupcast transmission supporting HARQ feedback with two different options, SL groupcast HARQ feedback option <NUM> and SL groupcast HARQ feedback option <NUM>. In option <NUM>, all RX-UEs of a groupcast group use a common Physical SL Feedback Channel (PFSCH) resource to transmit NACK-only. The PSFCH resource is determined by RX-UEs in an implicit manner, by a mapping from the PSSCH resources and a source ID, i.e. the ID of TX-UE. For NR SL groupcast HARQ option <NUM> multiple receiving UEs launch PSFCH transmission on the same radio resource. In NR SL groupcast HARQ option <NUM>, each Rx UE of a pre-defined group uses a dedicated PSFCH resource to transmit UE-specific ACK/NACK. If HARQ feedback is enabled in NR SL groupcast, each UE sends its HARQ feedback individually and irrespective of their neighbors' feedback.

<FIG> illustrates an example scenario for modified HARQ feedback for a groupcast in accordance with at least some embodiments of the present invention. User equipment, UE1, transmits a groupcast <NUM> to group members of a groupcast group. The groupcast may comprise periodical transmissions of groupcast messages from the UE1 to the group members. Accordingly, the UE1 may be referred to a transmitter UE (TX-UE) of the groupcast and the group members of the groupcast group may be referred to receiver UEs (RX-UEs). The groupcast may comprise HARQ feedback from the RX-UE to the TX-UE. The groupcast, and thereby the HARQ feedback, may be configured based on control information, SL control information (SCI), transmitted by the TX-UE to the RX-UE. SCI format <NUM>-B may configure the group members to transmit NACK-only as HARQ feedback information using a common PSFCH resource. It should be noted that a groupcast group may comprise one or more group members. In this example, the group members of the group cast group comprise more than two RX-UE, i.e. UE2, UE3 and UE-n. In the example illustrated in <FIG>, UE-n may determine at least one trigger for requesting a peer UE to modify HARQ feedback information. In an example, a trigger for requesting a peer UE to modify HARQ feedback information comprises that that UE-n fails to decode a 2nd stage SCI transmitted by the UE1, which causes that the UE-n cannot send a HARQ feedback, e.g. a NACK, to a groupcast message from UE1. In case the UE1 does not receive HARQ feedback from the UE-n, UE1 is unaware of problems experienced by the UE-n in receiving the groupcast. Consequently, the UE1 cannot take any actions to alleviate the problems experienced by the UE-n. Examples of the actions to alleviate the problems comprise at least one of sending one or more retransmissions of the groupcast, increasing a transmission power of the groupcast, selecting a modulation and coding scheme (MCS) with an improved robustness for the groupcast, adapting group member association and the impacted applications etc. Due to the lack of alleviating actions, the UE-n may fail to receive the groupcast from the UE1. Based on determining the at least one trigger for requesting a peer UE to modify HARQ feedback, the UE-n may request <NUM> one or more of the peer group members to modify HARQ feedback to the groupcast. The request may be referred to a SidelinkFakeHARQRequest message. When the one or more of the group members are caused to modify the HARQ feedback, the UE1 may receive the modified HARQ feedback even if HARQ feedback from UE-n would not be received by the UE1. The SidelinkFakeHARQRequest message may be, but is not limited to, a PC5-RRC message and/or a SL Medium Access Control (MAC) protocol control element (CE).

An example ASN. <NUM> representation of the SidelinkFakeHARQRequest message may be:
<IMG>
<IMG>.

It should be noted that one or more group members, peer RX-UE(s), of the groupcast group may respond to the request <NUM>, SidelinkFakeHARQRequest message, with a SidelinkFakeHARQResponse message. The SidelinkFakeHARQResponse message may indicate the RX-UE to which extent the peer RX-UE can fulfil, or accept, the request <NUM>. In an example, a SidelinkFakeHARQResponse message may be generated by a peer RX-UE based on modifying one or more information elements (IE) of the SidelinkFakeHARQRequest message received from the RX-UE. For example in the SidelinkFakeHARQResponse message the number of consecutive modified feedbacks may be reduced or the peer RX-UE may increase a priority level for which Logical Channel Priority the HARQ is allowed to be modified or the peer RX-UE may reject the request to modify its HARQ by setting sl-FakeNACK-rxx=disabled. Accordingly, an acceptance to transmit modified HARQ feedback may be indicated by sl-FakeNACK-rxx=enabled.

In an example in accordance with at least some embodiments, the SidelinkFakeHARQRequest message, the request to modify the HARQ feedback to the groupcast, comprises one or more information elements of a group comprising: a number of consecutive modified feedbacks per transport block, sl-NrofFakeNACKs-rxx; sl-MaxTotalNrofFakeNACKs-rXX, a maximum number of accumulated modified feedbacks; a threshold for Logical Channel Priority, sl-FakeNACKpriority-rxx; flag for disabling or enabling modified HARQ feedback, sl-FakeNACK-rxx; one or more link identifiers for transmitting modified HARQ feedback, sl-FakeNACKLinkIDList; one or more identifiers of peer wireless devices for the request to modify HARQ feedback; sl-FakeNACKpeerUEIDList. In an example, the SidelinkFakeHARQRequest may be according to sidelink configuration defined in Section <NUM>. 9of <NPL> that is modified to include at least part of the following information elements:.

It should be noted that the SidelinkFakeHARQResponse message may have the same information elements, e.g. the ASN. <NUM> structure, as the SidelinkFakeHARQRequest message. In this way the peer RX UE (UE2) can generate the SidelinkFakeHARQResponse message to indicate to the requesting UE (UE-n) to which extend the peer RX UE can fulfil the request, i.e. the peer RX UE may reduce the number of consecutive modified NACKs or the peer UE may increase the priority level for which LCP the HARQ feedback is allowed to be modified or the peer UE rejects the request to modify its HARQ feedback by setting sl-FakeNACK-rxx=disabled (accordingly the acceptance to transmit modified HARQ feedback is sl-FakeNACK-rxx=enabled).

It should be noted that at least in some examples described herein, a request to at least one RX-UE to modify HARQ feedback may also be referred to a request to transmit modified HARQ feedback. For example, a request to modify HARQ feedback to a groupcast received by an RX-UE may cause the RX-UE to modify its HARQ decision for a groupcast message and the RX-UE to transmit the modified HARQ feedback as feedback to a TX-UE of the groupcast. In an example, a HARQ decision may be modified by reversing the HARQ decision. Reversing a HARQ decision may comprise reversing a positive HARQ decision into a negative HARQ decision or vice versa. In accordance with NR SL groupcast HARQ option <NUM>, only NACK may be sent as HARQ feedback, i.e. NACK-only, whereby modifying a positive HARQ decision for a successfully received groupcast message may cause the RX-UE to transmit NACK. On the other hand, a HARQ decision for an unsuccessfully received groupcast message may cause the requested RX-UE to proceed transmitting HARQ feedback, e.g. NACK, because the NR SL groupcast HARQ option <NUM> is NACK-only. Accordingly, a HARQ feedback may be modified by enforcing a NACK HARQ feedback for SL groupcast option <NUM>. In this way, the requested at least one RX-UE may be caused to transmit a NACK, regardless of whether the groupcast has been received successfully at the UE providing the HARQ feedback.

On the other hand, the request to the at least one RX-UE to modify HARQ feedback, or a request to transmit modified HARQ feedback, to a groupcast received by an RX-UE may cause the RX-UE to generate more than one HARQ feedback comprising a HARQ feedback based on HARQ configuration of the groupcast and a modified HARQ feedback a based on a modified HARQ configuration for the groupcast. For example, the generated HARQ feedback may comprise e.g. at least two HARQ feedback comprising one HARQ feedback based on NR SL groupcast HARQ option <NUM> and a further HARQ feedback based on a modified HARQ configuration. The modified HARQ configuration may be determined e.g. based on modifying the NR SL groupcast HARQ option <NUM>. In an example, the NR SL groupcast HARQ option <NUM> may be modified by reversing a positive HARQ decision into a negative HARQ decision based on the NR SL groupcast HARQ option <NUM>. In this way the at least one RX-UE may be caused to transmit NACK regardless of the HARQ decision, i.e. whether a reception of the groupcast is successful or unsuccessful. Thereby, if a HARQ decision in accordance with the NR SL groupcast HARQ option <NUM> is negative, the requested at least one RX-UE is caused to transmit NACK in accordance with the NR SL groupcast HARQ option <NUM>. On the other hand, if a HARQ decision in accordance with the NR SL groupcast HARQ option <NUM> is positive, the modified HARQ feedback may obtained by reversing the positive HARQ decision and transmitting a NACK to TX-UE. In a further example, the NR SL groupcast HARQ option <NUM> may be modified by forcing a HARQ feedback to be NACK regardless of whether the groupcast has been received successfully by the requested at least one RX-UE.

It should be note that although the above examples are described using NR SL groupcast HARQ option <NUM>, also they may be applied with other configurations as well.

<FIG>, <FIG> and <FIG> illustrate examples of methods in accordance with at least some embodiments of the present invention. Referring to <FIG>, the is provided a transmitter wireless device of a groupcast to receive HARQ feedback from a receiver wireless device in case of temporary reception problems of the groupcast at the wireless device. The HARQ feedback is provided with the help of one or more peer wireless devices that are requested by the receiver wireless device to modify HARQ feedback to the groupcast. The modification of the HARQ feedback is transparent to the transmitter wireless device, i.e. the transmitter wireless device is not aware if one or more receiver wireless devices have transmitted modified HARQ feedback.

Phase <NUM> comprises receiving, by a receiver wireless device, a groupcast, from a transmitter wireless device of the groupcast.

Phase <NUM> comprises determining, by the receiver wireless device, at least one trigger for requesting one or more peer receiver wireless devices to modify a Hybrid Automatic Repeat Request, HARQ, feedback to the groupcast.

Phase <NUM> comprises transmitting, by the receiver wireless device to the one or more peer receiver wireless devices of the groupcast, based on the determined at least one trigger, at least one request to modify the HARQ feedback to the groupcast.

In an example in accordance with at least some embodiments, the groupcast is an NR SL groupcast comprising SCI and data. SCI may comprise information indicating HARQ configuration. In an example the HARQ configuration may indicate SL groupcast HARQ feedback option <NUM> and periodic resources for the HARQ feedback.

In an example in accordance with at least some embodiments, the at least one request to modify the HARQ feedback to the groupcast is a sidelink broadcast message, a sidelink groupcast message or a sidelink unicast message.

Referring to <FIG>, the is provided a transmitter wireless device of a groupcast to receive HARQ feedback in case of reception problems of the groupcast. The HARQ feedback is provided based on a request to modify HARQ feedback to the groupcast from a receiver wireless device that is a peer to another receiver wireless device that is encountering at least one trigger for requesting to modify HARQ feedback. The modification is transparent to the transmitter wireless device.

Phase <NUM> comprises receiving, by the receiver wireless device from at least one peer wireless device of the groupcast, a request to modify a Hybrid Automatic Repeat Request, HARQ, feedback to the groupcast.

Phase <NUM> comprises determining a modified HARQ feedback based on the request.

Phase <NUM> comprises transmitting, by the receiver wireless device, the determined modified HARQ feedback to the transmitter wireless device of the groupcast.

Referring to <FIG>, the is provided a method for modified HARQ feedback for a groupcast from a transmitter wireless device.

Phase <NUM> comprises the receiver wireless device monitoring one or more triggers for requesting to modify Hybrid Automatic Repeat Request, HARQ, feedback. If a trigger is determined based on the monitoring, the method may proceed to phase <NUM>. If a trigger is not determined based on the monitoring, the monitoring may be continued in phase <NUM>.

Phase <NUM> comprises by the receiver wireless device, requesting one or more peer wireless devices to modify HARQ feedback to the groupcast based on detecting at least one trigger of the one or more triggers. In other words the one or more peer wireless devices are requested to transmit modified HARQ feedback. In an example, phase <NUM> comprises the receiver wireless device selecting one or more peer wireless devices for transmitting modified HARQ feedback and the receiver wireless device transmitting the determined one or more peer wireless devices a request to modify HARQ feedback to the groupcast.

Phase <NUM> comprises the receiver wireless device determining whether the requested peer wireless devices have accepted to transmit modified HARQ feedback and if at least a part, or at least one, of the requested peer wireless devices have accepted to transmit modified HARQ feedback, the method may proceed to phase <NUM>. In an example, in phase <NUM>, the receiver wireless may determine based on one or more responses from the one or more peer wireless devices if the requested peer wireless devices have accepted to transmit modified HARQ feedback. If at least part of the one or more peer wireless, or all of the peer wireless devices, have rejected the request, the method may proceed to phase <NUM>, where one or more further requests to modify HARQ feedback may be transmitted. The one or more further requests in phase <NUM> may be transmitted to one or more further peer wireless devices that may be (re-)selected.

Phase <NUM> comprises monitoring, by the wireless device, HARQ feedback transmitted by the one or more peer wireless devices that have accepted to transmit modified HARQ feedback. In an example, the wireless device may monitor a resource, where the one or more peer wireless devices should be transmitting the HARQ feedback. The resource may be determined based on a control information, e.g. SCI, transmitted by the transmitter wireless device, provided the control information may be at least partially received by the receiver wireless device. An example of the resource is a PFSCH that is indicated by SCI from TX-UE.

Phase <NUM> comprises, the receiver wireless device, determining based on the monitoring if the HARQ feedback is transmitted by the one or more peer wireless devices that have accepted to transmit modified HARQ feedback. The one or more peer wireless devices may comprise at least the one or more peer wireless devices that have not rejected the request, and therefore have accepted to transmit modified HARQ feedback. If the modified HARQ feedback is not determined to be transmitted, the method proceeds to phase <NUM>. In an example, phase <NUM> may comprise that the modified HARQ feedback is not determined to be transmitted based on monitoring HARQ feedback transmissions from the one or more peer wireless device that have accepted to transmit modified HARQ feedback and the method proceeds to phase <NUM>, where one or more further peer wireless devices may be reselected for transmitting modified HARQ feedback. In an example, phase <NUM> comprises that modified HARQ feedback is positively determined based on monitoring HARQ feedback transmissions from the one or more peer wireless device that have not rejected the request and the method proceeds to phase <NUM>. Phase <NUM> may comprise expecting HARQ retransmissions by the transmitter wireless device.

<FIG>, <FIG> and <FIG> illustrate examples of sequences for modified HARQ feedback in accordance with at least some embodiments of the present invention. The sequences are described using the example scenario described with <FIG>.

Referring to <FIG>, phase <NUM> comprises UE1 transmits an SCI for configuring a groupcast. The SCI may comprise information indicating SL groupcast HARQ feedback option <NUM> and periodic resources for the HARQ feedback. The SCI may be received at UE-<NUM>, UE-<NUM> and UE-n. Phase <NUM> comprises the UE-n determining to request to the UE-<NUM> for destination identifiers of at least one peer UE of the UEs of the groupcast group, i.e. in this example UE-<NUM> and UE-<NUM>. Examples of the destination identifiers comprise at least layer <NUM> identifiers (L2 IDs) of the UEs.

Phase <NUM> comprises the UE-n transmitting to the UE-<NUM> a request, UEDestIDRequest, for the destination identifiers of at least one, more than one or even all, peer UEs of the groupcast group. Phase <NUM> comprises the UE-<NUM> selecting at least one peer UE and transmitting a destination identifier of the selected at least one peer UE to the UE-n included in a response, UEDestIDResponse. In the example described with <FIG>, the UE-<NUM> is selected by UE-<NUM> and the destination identifier of UE-<NUM> is transmitted to the UE-n. In this way configuring modified HARQ feedback to the UE-<NUM> may be facilitated.

Phase <NUM> comprises the UE-n establishing a unicast link between the UE-n and the UE-<NUM>. The unicast link may be established based on the destination identifier received in the response in phase <NUM>. It should be noted that phase <NUM> may be omitted if the unicast link has already been established. Establishing the unicast link is a pre-emptive measure for sending the request to modify HARQ feedback.

Phase <NUM> comprises the UE-n transmitting a request to modify HARQ feedback, SidelinkFakeHARQRequest message, over the SL established in phase <NUM>, to the UE-<NUM>. The request in phase <NUM> may be transmitted based on the UE-n determining at least one trigger <NUM> for requesting to modify HARQ feedback. Phase <NUM> comprises the UE-<NUM> transmitting a response, SidelinkFakeHARQResponse message, to the SidelinkFakeHARQRequest message.

Examples of triggers <NUM> for transmitting a SidelinkFakeHARQRequest may be:.

Phase <NUM> comprises the UE-<NUM> transmitting a groupcast. The groupcast may comprise a groupcast transmission that is not successfully received by the UE-n. The groupcast transmission may be a SL transmission on a PSCCH. The SL transmission may comprise SCI. The SCI may comprise a <NUM>st stage that is transmitted robustly over PSCCH and a <NUM>nd stage that is transmitted less robustly by multiplexing the SCI with SL data.

In phase <NUM>, the UE-n fails to successfully receive the groupcast. It should be noted that although the UE-n may not successfully receive the whole groupcast transmission, the UE-n may successfully receive a part of the groupcast transmission. For example, the UE-n may successfully receive the <NUM>st stage of SCI, but reception of the <NUM>nd stage of the SCI may be unsuccessful.

Phase <NUM> comprises the UE-<NUM> transmitting a modified HARQ feedback, i.e. a modified HARQ, to the UE-<NUM>. Optionally, the UE-n may monitor a resource, where the HARQ feedback should be transmitted. The resource for the HARQ feedback many be determined based on the control information for the groupcast, e.g. the <NUM>st stage of SCI, provided the UE-n has received the <NUM>st stage of SCI and monitoring is enabled at the UE-n.

Phase <NUM> comprises the UE-<NUM> transmitting retransmission(s) of the groupcast based on, or triggered, by the modified HARQ feedback in phase <NUM>. In this way the UE-n may receive the retransmission(s) even if HARQ feedback from the UE-n would not be received at the UE-<NUM>.

Phase <NUM> comprises the UE-n disabling transmissions of modified HARQ feedback. In this way transmissions of modified HARQ feedback by the RX-UE, in this case UE-<NUM>, may be ended. The UE may determine to disable the transmissions of modified HARQ feedback based on determining <NUM> that a need for modified HARQ feedback has been removed, for example based on the UE-n deciding to take over its own HARQ feedback transmission, when a radio condition from UE-<NUM> is sufficient or has improved. In an example, the disabling may comprise the UE-n transmitting a SidelinkFakeHARQRequest message with sl-FakeNACK-rxx=disabled to UE that have accepted the SidelinkFakeHARQRequest message. In this way the UE-n decides to take over its own HARQ feedback transmission task by itself, when the radio condition from UE-<NUM> is getting good.

Referring to <FIG>, as a difference to the sequence in <FIG>, the UE-n requests more than one UE of the groupcast group to modify HARQ feedback and only a part of the UE accept the request to modify HARQ feedback. After phase <NUM>, in phase <NUM>, the UE-n may transmit a request, UEDestIDRequest, for the destination identifiers of at least one, more than one or even all, peer UEs of the groupcast group. Phase <NUM> comprises, UE-<NUM>, in response to the request in phase <NUM>, selecting, in phase <NUM>, more than one or even all, UEs of the groupcast group and transmitting a response, UEDestIDResponse, comprising the selected destination identifiers to the UE-n. In this example, the response to the UE-n comprises the identifiers of UE-<NUM> and UE-<NUM>. In this way configuring modified HARQ feedback to more than one UE of the groupcast group may be facilitated.

Phase <NUM> comprises the UE-n establishing a unicast SL between the UE-n and the UE-<NUM>. The unicast SL may be stablished based on the destination identifier received in the response in phase <NUM>. It should be noted that phase <NUM> may be omitted if the unicast SL has already been established.

Phase <NUM> comprises the UE-n transmitting a request to modify HARQ feedback, SidelinkFakeHARQRequest message, over the unicast SL established in phase <NUM>, to the UE-<NUM>. The request in phase <NUM> may be transmitted based on the UE-n determining at least one trigger <NUM> for transmitting a SidelinkFakeHARQRequest. Phase <NUM> comprises the UE-<NUM> transmitting a response, SidelinkFakeHARQResponse message, to the SidelinkFakeHARQRequest message.

In an example, in phase <NUM> the UE-<NUM> accepts the SidelinkFakeHARQRequest message form the UE-n, but in phase <NUM> the UE-<NUM> rejects the SidelinkFakeHARQRequest message from UE-n. It should be noted that since the UE-<NUM> rejected the SidelinkFakeHARQRequest message, the UE-n may select another UE, if available, of the groupcast group and transmit the SidelinkFakeHARQRequest message to another UE.

It should be noted that if at least one of the UE to which the SidelinkFakeHARQRequest message has been transmitted has accepted the request, further transmissions of SidelinkFakeHARQRequest message to other UE may not be necessary, since the transmissions of modified HARQ feedback are already provided by the one UE that accepted the SidelinkFakeHARQRequest message.

Referring to <FIG>, as a difference to the sequence in <FIG>, the UE-n requests all UEs of the groupcast to modify HARQ feedback over a groupcast SL. In phase <NUM>, the UE-n may transmit a request, UEDestIDRequest message, for the destination identifiers of at least one, more than one or even all, peer UEs of the groupcast group. Phase <NUM> comprises, UE-<NUM>, in response to the request in phase <NUM>, selecting, in phase <NUM>, all UEs of the groupcast group and transmitting a response, UEDestIDResponse message, comprising the selected destination identifiers to the UE-n. In this way configuring modified HARQ feedback to all of the UEs of the groupcast may be facilitated. Phase <NUM> comprises the UE-n transmitting a request to modify HARQ feedback, SidelinkFakeHARQRequest message, to all UE of the groupcast group. The request may be groupcast to the UE based on UE identifiers received in phase <NUM>. Then after phase <NUM>, in phase <NUM>, all the UEs of the groupcast group transmit modified HARQ feedback to the UE-<NUM>. In phase <NUM> the UE-n may disable transmissions of modified HARQ feedback. The UE may determine to disable the transmissions of modified HARQ feedback based on determining that a need for modified HARQ feedback has been removed, for example based on the UE-n deciding to take over its own HARQ feedback transmission, when a radio condition from UE-<NUM> is sufficient or has improved and/or overlapping/colliding communication activity has been resolved. In an example, the disabling may comprise the UE-n transmitting a SidelinkFakeHARQRequest message over groupcast with sl-FakeNACK-rxx=disabled. In this way the UE-n decides to take over its own HARQ feedback transmission task by itself, when the radio condition from UE1 is getting good.

In an example, in phases <NUM>, <NUM>, <NUM>, the UE-n may be triggered to transmit the UEDestIDRequest for establishing a unicast link, based on:.

It should be noted that irrespective of any condition described above, i.e. regardless of any actual parameters, the RX-UE, in his case the UE-n, may anyway request a destination identifier of at least one of its peer RX UE(s).

It should be noted that in phases <NUM>, <NUM>, <NUM> the request message UEDestIDRequest sent by UE-n to the TX UE is to enquire about the destination L2 ID(s) of at least one peer group member. In one embodiment the TX-UE selects (at least one of) the most appropriate peer RX-UE (in the example in <FIG>, that's UE-<NUM>) for the requesting RX-UE (UE-n) and sends the corresponding L2 ID in the UEDestIDResponse message. However, in the examples of phases <NUM> and <NUM> the UEDestIDResponse message may comprise up to all RX-UE identifiers of the groupcast group or a subset therein, so that it's up to UE-n to select the most appropriate peer RX-UE.

It should be noted that transmitting the UEDestIDRequest in phases <NUM>, <NUM>, <NUM> may be optional. For example, the UE-n may have established a PC5 connection with another group member UE, e.g. UE-<NUM> or UE-<NUM>, which means the UE-n may already know the L2 ID used by that group member. In addition, the UE-n may receive and determine the source ID of the group members groupcasting to the same group destination ID, which can be used by UE-n as the L2 destination ID of the peer UE.

In an example of phases <NUM>, <NUM>, <NUM> and <NUM>, when the UE-n has the L2 ID of at least one RX-UE, e.g. UE-<NUM> or UE-<NUM>, of the groupcast group, and the RX-UE is within a communication range from the UE-n, the UE-n may establish at least one PC5 unicast link to the RX-UE. Establishing the PC5 unicast link facilitates the UE-n to later on to transmit the SidelinkFakeHARQRequest message to (at least one of) over the established PC5 unicast link. It should be noted that the UE-n may establish PC5 unicast links to one or more further RX-UEs. In a further example, if there is already a PC5 connection between UE-n and the peer RX UE, this step can be omitted. In another embodiment, depending on how the SidelinkFakeHARQRequest message is transmitted to the peer RX UE, such a PC5 connection may also not be needed.

In an example, after at least one peer RX-UE has accepted the SidelinkFakeHARQRequest transmitted in phases <NUM>, <NUM>, <NUM> and <NUM>, if the TX-UE, in this case UE-<NUM>, transmits a next groupcast transmission, the RX-UE that has accepted the SidelinkFakeHARQRequest transmits a modified HARQ feedback. In this way, reception problems at the UE-n may be indicated to the TX-UE with the help of the modified HARQ feedback from the peer RX-UE(s).

In an example, in phase <NUM> and <NUM>, the RX-UE(s) within the same groupcast group with the UE-n transmit modified HARQ feedback on behalf of the UE-n thereby mimicking the behavior of UE-n, when the UE-n has not successfully received the groupcast. Moreover, the HARQ feedback from the RX-UE(s) may be modified even if the UE-n would have successfully received the groupcast and/or the UE-n is transmitting HARQ feedback according to groupcast control information, e.g. SCI. Therefore, the modified HARQ feedback from the RX-UE(s) may provide the RX-UE(s) to impersonate the HARQ feedback from UE-n. The TX UE receives the HARQ feedback from the RX-UE(s) of the groupcast group and the TX UE may take one or more actions to facilitate reception of the groupcast transmission or retransmissions of the groupcast transmission by the UE-n. Examples of the actions comprise HARQ retransmissions, increasing transmission power, range adaption for group members of the groupcast group, group member reselection etc..

In an alternative embodiment, phases <NUM> and <NUM>, comprises disabling, by the RX-UE, in this example the UE-n, transmissions of the modified HARQ feedback, based at least on an expiry of a timer for modified HARQ feedbacks, a number of modified HARQ feedbacks and/or improved radio conditions between the transmitter wireless device and the receiver wireless device. In an example, it may be determined that the number of modified HARQ feedbacks have been reached and/or the timer has expired, or the radio conditions have improved, whereby transmissions of the modified HARQ feedback may be disabled. If one or more of the conditions are determined by the UE-n, the UE-n may transmit a request, SidelinkFakeHARQRequest, to the peer UE-RX(s) to disable transmissions of modified HARQ feedback. It should be noted that the UE-n may monitor transmissions of modified HARQ feedback provided the UE-n has received the <NUM>st stage of SCI, where the number of modified HARQ feedbacks may be determined. On the other hand, it should be noted that if a peer RX-UE that has accepted to transmit modified HARQ feedback determines that the number of modified HARQ feedbacks have been reached and/or the timer has expired, the peer RX-UE may disable transmissions of modified HARQ feedback without a request in that regard from the UE-n. Alternatively or additionally, the peer RX-UE that has accepted to transmit modified HARQ feedback, may disable transmissions of modified HARQ feedback based on a SidelinkFakeHARQRequest indicating disabling, e.g. based on sl-FakeNACK-rxx, of the transmissions of modified HARQ feedback. After transmissions of modified HARQ feedback have been disabled, the HARQ feedback may be transmitted in accordance with control information of the groupcast, e.g. SCI, without modifying HARQ feedback.

<FIG> illustrates examples of triggers for requesting to transmit modified HARQ feedback in accordance with at least some embodiments of the present invention. The example is now described with reference to the scenario described with <FIG>. The requesting to modify HARQ feedback, or requesting to transmit modified HARQ feedback, may be triggered based on channel quality at UE-n. The channel quality at UE-n may comprise one or more regimes. The operation of the UE-n may depend on at which regime the channel quality at the UE-n is. When the channel quality at the UE-n falls within a regime, the UE-n may be triggered to transmit SidelinkFakeHARQRequest message over groupcast to one or more peer RX-UEs. In an example, three regimes may be defined based on successfully decoding of the whole SCI (regime <NUM>), decoding a part of the SCI successfully (regime <NUM>) and failing to decode the SCI from the UE-<NUM>, i.e. the TX-UE:.

<FIG> illustrates an example of an apparatus in accordance with at least some embodiments of the present invention. The apparatus may be a wireless device or UE, or a part of a wireless device or UE.

The apparatus comprises a processor <NUM> and a transceiver <NUM>. The processor is operatively connected to the transceiver for controlling the transceiver. The apparatus may comprise a memory <NUM>. The memory may be operatively connected to the processor. It should be appreciated that the memory may be a separate memory or included to the processor and/or the transceiver.

In an example, the apparatus comprises a groupcast HARQ block (HB) <NUM> connected operatively to the processor. The HB may be configured to perform one or more functionalities described in an example described herein, comprising modifying HARQ feedback, reversing HARQ feedback, determining one or more triggers for requesting to modify HARQ feedback, monitoring HARQ feedback, (re-)selecting wireless devices for modifying HARQ feedback, disabling modifying HARQ feedback and/or generating requests for modifying HARQ feedback. Based on the functionalities of the HB, the processor may control the transceiver to transmit and/or receive information, for example groupcasts, HARQ feedbacks, requests and/or responses, in accordance with one or more functionalities described in an example described herein.

According to an embodiment, the processor is configured to control the transceiver and/or to perform one or more functionalities described with a method according to an embodiment.

Embodiments may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. In the context of this document, a "memory" or "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

Reference to, where relevant, "computer-readable storage medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single/multi-processor architectures and sequencers/parallel architectures, but also specialized circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices and other devices. References to computer readable program code means, computer program, computer instructions, program instructions, instructions, computer code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device as instructions for a processor or configured or configuration settings for a fixed function device, gate array, programmable logic device, etc..

Although the above examples describe embodiments of the invention operating within a wireless device or a wireless network, it would be appreciated that the invention as described above may be implemented as a part of any apparatus comprising a circuitry in which radio frequency signals are transmitted and/or received. Thus, for example, embodiments of the invention may be implemented in a mobile phone, in a base station, in a computer such as a desktop computer or a tablet computer comprising radio frequency communication means (e.g. wireless local area network, cellular radio, etc.).

Embodiments of the inventions may be practiced in various components such as integrated circuit modules, field-programmable gate arrays (FPGA), application specific integrated circuits (ASIC), microcontrollers, microprocessors, a combination of such modules.

Claim 1:
A method comprising:
receiving, by a receiver wireless device, a groupcast, from a transmitter wireless device of the groupcast;
determining, by the receiver wireless device, at least one trigger for requesting one or more peer receiver wireless devices to modify a Hybrid Automatic Repeat Request, HARQ, feedback to the groupcast;
transmitting, by the receiver wireless device to the one or more peer receiver wireless devices of the groupcast, based on the determined at least one trigger, at least one request to modify the HARQ feedback to the groupcast; and
receiving, by the receiver wireless device, one or more responses to the at least one request, the one or more responses indicating acceptance to transmit modified HARQ feedback.