CLAIM OF PRIORITY

[0001] The present application claims the benefit of priority to Provisional Application No. 63/028,348 entitled “Groupcast Sidelink HARQ Feedback With No Location Information”, docket number TPRO 00349 US, filed May 21 , 2020, assigned to the assignee hereof and hereby expressly incorporated by reference in its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application is related to patent application entitled “HYBRID AUTOMATIC REPEAT REQUEST (HARQ) FEEDBACK MANAGEMENT BASED ON LOCATION INFORMATION AVAILABILITY FOR GROUP SIDELINK COMMUNICATION”, docket number TUTL 00349A PC and patent application entitled “DISTANCE-BASED HYBRID AUTOMATIC REPEAT REQUEST (HARQ) LOCATION UNAVAILABLE CONFIGURATION FOR GROUP SIDELINK COMMUNICATION”, docket number TUTL 00349B PC, both filed concurrently with this application and incorporated by reference in their entirety herein.

FIELD

[0003] This invention generally relates to wireless communications and more particularly to hybrid automatic repeat request (HARQ) feedback management based on location information availability and sidelink signal quality for group sidelink communication.

BACKGROUND

[0004] Many wireless communication systems that employ several base stations that provide wireless service to user equipment (UE) devices enable sidelink communication between two or more UE devices where the UE devices can communicate directly with other UE devices. Such sidelink communications sometimes include one UE device (group leader UE device) that transmits the same data to multiple UE devices in a group. Different transmission techniques often referred to as cast types can be used to transmit the same data to multiple UE devices. Cast types include at least unicast, groupcast and broadcast. A unicast transmission can only be received by the single UE device that is the intended recipient of the data. Accordingly, multiple transmissions are required to send the same data to multiple UE devices using unicast. A broadcast transmission can typically be received by all UE devices within range of the transmission. A groupcast transmission can only be received by the UE devices that are members of a group. Accordingly, for example, the group leader UE device can transmit the same data in a single transmission using groupcast to two or more UE devices in the group or can send the same data in multiple unicast transmissions to the UE devices.

SUMMARY

[0005] A receiving user equipment (UE) device transmits a distance-based hybrid automatic repeat request (HARQ) feedback message to a transmitting UE device based on sidelink signal quality when location information is unavailable. The receiving UE device is one of a group of UE devices receiving a groupcast data transmission from the transmitting UE device where the groupcast data transmission comprises a distance- based hybrid automatic repeat request (HARQ) feedback configuration. When location information is unavailable to the receiving UE device, the receiving UE device transmits the distance-based HARQ feedback if the measured signal quality of a signal received from the transmitting UE device is above a threshold and does not send the HARQ feedback if the signal quality is below the threshold. The threshold may be received from the transmitting UE device. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a block diagram of an example of a communication system including a first user equipment (UE) device, a second UE device, a third UE device, a fourth UE device, and two base stations. [0007] FIG. 2 is a block diagram of an example of a communication device suitable for use as each of the base stations.

[0008] FIG. 3 is a block diagram of an example of a UE device suitable for use as each of the UE devices.

[0009] FIG. 4 is a message flow diagram for an example where a receiving UE device determines, based on signal quality, whether to transmit distance-based FIARQ feedback when location information is unavailable to the receiving UE device.

[0010] FIG. 5 is a message flow diagram for an example where a receiving UE device determines whether to send distance-based FIARQ messages based on SL signal quality when location information is unavailable and establishes a unicast connection for group data.

[0011] FIG. 6 is a flow chart of an example of a method of managing groupcast feedback based on location information availability and signal quality.

[0012] FIG. 7 is a flow chart of an example of a method of managing groupcast feedback based on location information availability and signal quality.

DETAILED DESCRIPTION

[0013] As discussed above, different cast types can be used for communication between UE devices. Although UE device groups may be formed and used in different situations and environments, one scenario where grouping UE devices is particularly useful includes vehicle platoons where vehicles dynamically form a platoon while travelling together. All the vehicles in the platoon obtain information from the leading vehicle to manage the platoon. In some implementations, the information facilitates travel of the vehicles in the same direction in a coordinated manner and allows the vehicles to drive closer than in normal situations where there is no communication between the vehicles. Vehicles of the same platoon are involved in sharing the necessary information required to support the platoon operations where the information may include, for example, the distance between vehicles, relative speeds, and updates from roadside units (RSUs). Similar requirements also apply to the Extended Sensor use case where UE devices exchange data gathered through local sensors or live video data among vehicles, RSUs, pedestrian devices, and V2X application servers. Groupcast techniques allow efficient transmission of the information from one UE device, such as the platoon leader, to the other UE device members of the group.

[0014] In accordance with revisions of 3GPP communication specifications, sidelink communications between a transmitting UE device and receiving UE device(s) are managed with feedback messaging. In order to achieve reliable communications, for example, both unicast and groupcast communications support hybrid automatic repeat request (HARQ) feedback over sidelink in order for the transmitting UE device to determine if retransmissions are needed and if the modulation code scheme (MCS) needs to be relaxed to provide a more robust retransmission to reach the receiving peer UE device. With unicast transmissions, HARQ feedback for both acknowledgement (ACK) and negative acknowledgement (NACK) are supported and addressed to a single peer UE device. With groupcast transmissions, however, the transmitting UE device configures HARQ feedback which may include ACK/NACK feedback or only NACK feedback. The transmitting UE device of the groupcast transmission my receive HARQ feedback from multiple peer UE devices on the Physical Sidelink Feedback Channel (PSFCH). In order to save HARQ feedback resources on the PSFCH, the feedback for groupcast may be configured by the transmitting UE device for two general configurations. For a first configuration, the receiving UE device transmits HARQ-NACK on PSFCH if it fails to decode the corresponding transport block (TB) after decoding the associated PSCCH. With the first configuration, the receiving UE device transmits no signal on PSFCH otherwise. With a second configuration, the receiving UE device transmits HARQ-ACK on PSFCH if it successfully decodes the corresponding TB and it transmits HARQ-NACK on PSFCH if it does not successfully decode the corresponding TB after decoding the associated PSCCH targeting the receiving UE device. [0015] More specifically, when the transmitting UE device transmits data to group member receiving UE devices, the packet consists of both the traffic data and the header including Sidelink Control Info (SCI). The SCI is encoded with a more robust modulation coding scheme (MCS) than the data so that the receiving UE devices will more easily receive this portion of the signal. The traffic portion of the packet is encoded with a relatively less robust MCS to ensure higher data throughput. Therefore, if the receiving UE device only successfully receives the control signal portion (SCI) without successfully receiving the data portion, the receiving UE device sends a “NACK” to the transmitting UE device. For the option where both ACK and NACK are required for feedback, the receiving UE device is required to send ACK when the data portion is received successfully. When the receiving UE device cannot decode the SCI the receiving UE device does not send either ACK nor NACK. Such a situation corresponds to the HARQ DTX case where the transmitting UE device determines that the receiving UE device did not receive the packet if no feedback is received within a HARQ feedback timer.

[0016] In addition, the transmitting UE device may enable distance-based HARQ feedback. With distance-based HARQ feedback, the receiving UE device sends HARQ feedback only if the receiving UE device is within a configured communication range away from the transmitting UE device. Typically, distance-based HARQ requires NACK only feedback. For conventional systems, the transmitting UE device indicates its current Zone ID and a communication range requirement in the Sidelink Control Info (SCI). The receiving UE device calculates the distance from the current location of the receiving UE device to the center of that particular Zone ID indicated in the SCI received from the transmitting UE device. If the distance is less than the communication range requirement, the receiving UE device sends the NACK for HARQ feedback. Therefore, when distance-based HARQ is configured, the receiving UE devices that are far away from the transmitting UE device do not send HARQ feedback. Such a configuration not only reduces the use of PSFCH resources, but it prevents the transmitting UE device from making unnecessary retransmissions where a NACK is received since the retransmission will likely not be successfully received by those far away receiving UE devices. [0017] In some situations, location information is not available to a UE device. Typically, such a situation is temporary rather than an issue with the capability of the UE device. In most situations where the transmitting UE device does not have its own location information, the transmitting UE device will not configure distance-based HARQ feedback of the receiving UE devices of the group.

[0018] An issue arises when the transmitting UE device has location information and configures distance-based HARQ feedback for groupcast transmissions, but location information is unavailable to one or more of the receiving UE devices. In this case, the receiving UE device cannot determine if it is within communication range and whether HARQ feedback should be sent.

[0019] One possible mechanism to address this problem is to require any receiving UE device that does not have location information to refrain from sending HARQ feedback if distance-based HARQ feedback is configured. Such a technique has the benefit that PSFCH resources can be saved for other UE devices and useless retransmissions may be avoided. In some situations, however, the receiving UE device may be well within the communication range but HARQ feedback cannot be sent. An example of such a situation occurs when the receiving UE device passes through a coverage hole. As a result, the service performance may be unnecessarily severely degraded by restricting HARQ feedback even though the receiving UE device is within communication range of the transmitting UE device.

[0020] Another possible way to address the problem is to require that receiving UE devices to always send HARQ even when they do not have location information and distance-based HARQ feedback is configured. Such a technique is of course beneficial from the preserving the QoS, especially for high priority service. The technique, however, may result in increased use of PSFCH resources and unnecessary retransmissions, especially where the receiving UE devices are outside the communication range and the data portion of the retransmissions is not likely to be received successfully. Such situations could render the HARQ feedback system unusable. [0021] Therefore, distance-based HARQ feedback management is needed for efficient transmission of HARQ feedback when location information is unavailable to a receiving UE device. For the distance-based HARQ feedback management techniques discussed herein, the receiving UE device either transmits HARQ messages or refrains from transmitting HARQ messages when location information is unavailable based on signal strength of at least one signal received from the transmitting UE device at the receiving UE device. For the examples herein, the transmitting UE device sends a location unavailable signal strength threshold message to the receiving UE devices to configure the receiving UE devices with the threshold. In one example, the transmitting UE device determines the threshold. In another examples, the base station and/or network make the determination. In some situations, the determination is made collaboratively by the transmitting UE device and the base station and/or the network.

[0022] In some examples, the receiving UE device establishes a unicast connection with transmitting UE device when the signal strength is below the threshold but the required quality of service (QoS) of the groupcast transmissions is above a QoS threshold.

[0023] FIG. 1 is a block diagram of an example of a communication system 100 including a first user equipment (UE) device 101, a second UE device 102, a third UE device 103, a fourth UE device 104, and two base stations 106, 108. Although the techniques discussed herein may be applied to various types of systems and communication specifications, the devices of the example operate in accordance with at least one revision of a 3GPP New Radio (NR) V2X communication specification. The techniques discussed herein, therefore, may be adopted by one or more future revisions of communication specifications although the techniques may be applied to other communication specifications where sidelink or D2D is employed. More specifically the techniques may be applied to current and future releases of 3GPP NR specifications.

For example, the techniques may also be applied to 3GPP NR (Rel-17). For the example, the UE devices 101-104 may be any type of device that can receive signals from, and transmit signals to, base stations and other UE devices. The UE devices operate in the communication system that includes a plurality of base stations that each provide wireless service within a service area. For the example of FIG. 1 , the first UE device 101 is served by a first base station 106 and the other UE device 102-104 are served by either the first base station 106 or a second base station 108 and may transition between base stations in accordance with known handover techniques. Each of the UE devices 101-104, therefore, may be served by a different base station even though two or more UE devices are communicating with each other using a sidelink connection.

[0024] For the example, the first UE device 101 is a transmitting UE device and the other UE devices 102-104 are receiving UE devices and are members of a group. The group data for the group may be transmitted in groupcast transmissions from the transmitting UE device 101. In some situations, the group data may be transmitted over a unicast communication link to a member of the group. For the example, a groupcast transmission 110 including groupcast data is transmitted from the first UE device (transmitting UE device) 101 to the second UE device 102 and the third UE device 103. The group data is also sent over a unicast communication link to the fourth UE device 104. The first UE device 101 , therefore, may also be referred to as the transmitting UE device and source UE device, herein. Although the example includes three UE devices 102, 103, 104 in the group, the group may include any number of devices.

[0025] For the example of FIG. 1 , the fourth UE device 104 receives the group data in a unicast transmission 111 over unicast communication link and therefore provides FIARQ feedback in accordance with the unicast connection. The second UE device 102 and the third UE device 103 are sent the group data over a groupcast data transmission specifying a distance-based FIARQ feedback. For the example, the third UE device 103 is in a situation where distance based FIARQ is invoked. More specifically, location information is available to the third UE device 103, the third UE device determines it is within the specified communication range, and the third UE device is unable to successfully receive the data portion of the groupcast data transmission 110. As a result, the third UE device 103 transmits a distance-based FIARQ NACK message 114 in accordance with the distance-based FIARQ configuration established by the transmitting UE device 101. The HARQ messages 112, 114 are transmitted over the PSFCH in accordance with known techniques.

[0026] The second UE device 102, however, does not successfully receive the data portion of the groupcast data transmission but does not have location information for the example. With conventional systems, there is no established technique for dealing with such a situation. For the examples herein, however, the receiving UE device 102 determines whether to transmit FIARQ feedback based on the signal quality of sidelink signals 116 received from the transmitting UE device 101. For the examples herein, the signal quality is based on at least one of a Sidelink Reference Signal Received Power (SL-RSRP). Therefore, for the examples herein, the signal quality is determined by measuring one or more Demodulation reference signals (DMRS) transmitted by the transmitting UE device 101. Other techniques, however, may be used to determine the sidelink signal quality. For the discussions herein, signal quality may include only signal strength, signal power, average total received power, or signal energy. Signal quality may be based on measurement of over full bandwidth and/or narrow band. Also, the measured signal may include signals other than reference signals in some circumstances. For the example, the transmitting UE device 101 determines the location unavailable signal quality threshold and sends the threshold to the receiving UE devices in a message 118. The location unavailable signal quality threshold message 118 includes a SL-RSRP threshold for the example.

[0027] After receiving the SCI in the groupcast data transmission 110 and determining that the data portion could not be successfully received, the second UE device 102 determines whether a HARQ message should be transmitted based on the location unavailable signal quality threshold. For the examples herein, the second UE device derives NR sidelink measurement results by measuring one or multiple DMRS associated sidelink channel as configured by the first UE device. For all NR sidelink measurement results, the second UE device applies the layer 3 filtering before using the measured results for evaluation.

[0028] In one scenario, the second UE device may begin to evaluate the NR sidelink measurement continuously after it determines that location information is unavailable. In another scenario, the second UE device may begin to evaluate the NR sidelink measurement after the groupcast transmission is received.

[0029] Currently, the DMRS used for NR sidelink measurement is only available when the first UE device has data or control signal to transmit. The first UE device will not send DMRS or any other RS alone without data or control signaling which is different from the Uu case. Also, current communication specifications only specify SL- RSRP measurement for PC5-RRC unicast connections and not for groupcast transmissions. Accordingly, for the examples herein, the SL-RSRP measurements are in accordance with current communication specifications except that SL-RSRP measurements are also available for groupcast.

[0030] If the signal quality measurements are above the signal quality threshold, the second UE device 102 transmits a HARQ message 120. Otherwise, no HARQ message is transmitted. The arrow representing the HARQ message is FIG. 1 is shown a dashed line to indicate that the HARQ message 120 is transmitted in accordance with the location-unavailable configuration 116 and, therefore, is not transmitted in some circumstances.

[0031] Where the SL signal quality is below the threshold, the receive UE device may determine that the required QoS of the groupcast communication is sufficient to warrant establishment of a unicast connection to replace the groupcast link to the second UE device 102. Accordingly, in some situations, the second UE device 102 establishes a unicast link with the first UE device for the transmission of group data.

[0032] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as each of the base stations 106, 108. The base station 200 includes a controller 204, transmitter 206, and receiver 208, as well as other electronics, hardware, and code. The base station 200 is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to the base stations 102, 104 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices. The base station 200 may be a fixed device or apparatus that is installed at a particular location at the time of system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Although the base station may be referred to by different terms, the base station is typically referred to as a gNodeB or gNB when operating in accordance with one or more communication specifications of the 3GPP V2X operation. In some situations, the base station 200 may be mobile equipment that is temporarily installed at a particular location. Some examples of such equipment include mobile transceiver stations that may include power generating equipment such as electric generators, solar panels, and/or batteries. Larger and heavier versions of such equipment may be transported by trailer. In still other situations, the base station 200 may be a portable device that is not fixed to any particular location.

[0033] The controller 204 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of the base station 200. An example of a suitable controller 204 includes code running on a microprocessor or processor arrangement connected to memory.

The transmitter 206 includes electronics configured to transmit wireless signals. In some situations, the transmitter 206 may include multiple transmitters. The receiver 208 includes electronics configured to receive wireless signals. In some situations, the receiver 208 may include multiple receivers. The receiver 208 and transmitter 206 receive and transmit signals, respectively, through an antenna 210. The antenna 210 may include separate transmit and receive antennas. In some circumstances, the antenna 210 may include multiple transmit and receive antennas.

[0034] The transmitter 206 and receiver 208 in the example of FIG. 2 perform radio frequency (RF) processing including modulation and demodulation. The receiver 208, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 206 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the base station functions. The required components may depend on the particular functionality required by the base station. [0035] The transmitter 206 includes a modulator (not shown), and the receiver 208 includes a demodulator (not shown). The modulator modulates the signals to be transmitted as part of the downlink signals and can apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signals received at the base station 200 in accordance with one of a plurality of modulation orders.

[0036] The base station 200 includes a communication interface 212 for transmitting and receiving messages with other base stations. The communication interface 212 may be connected to a backhaul or network enabling communication with other base stations. In some situations, the link between base stations may include at least some wireless portions. The communication interface 212, therefore, may include wireless communication functionality and may utilize some of the components of the transmitter 206 and/or receiver 208.

[0037] FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as each of the UE devices 101-104. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, a transceiver modem, a personal digital assistant (PDA), a tablet, or a smartphone. In other examples, the UE device 300 is a machine type communication (MTC) communication device or Internet- of-Things (IOT) device. The UE device 300, therefore is any fixed, mobile, or portable equipment that performs the functions described herein. The various functions and operations of the blocks described with reference to UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated in a single device, and the functions described as performed in any single device may be implemented over several devices.

[0038] The UE device 300 includes at least a controller 302, a transmitter 304 and a receiver 306. The controller 302 includes any combination of hardware, software, and/or firmware for executing the functions described herein as well as facilitating the overall functionality of a communication device. An example of a suitable controller 302 includes code running on a microprocessor or processor arrangement connected to memory. The transmitter 304 includes electronics configured to transmit wireless signals. In some situations, the transmitter 304 may include multiple transmitters. The receiver 306 includes electronics configured to receive wireless signals. In some situations, the receiver 306 may include multiple receivers. The receiver 304 and transmitter 306 receive and transmit signals, respectively, through antenna 308. The antenna 308 may include separate transmit and receive antennas. In some circumstances, the antenna 308 may include multiple transmit and receive antennas. [0039] The transmitter 304 and receiver 306 in the example of FIG. 3 perform radio frequency (RF) processing including modulation and demodulation. The receiver 304, therefore, may include components such as low noise amplifiers (LNAs) and filters. The transmitter 306 may include filters and amplifiers. Other components may include isolators, matching circuits, and other RF components. These components in combination or cooperation with other components perform the communication device functions. The required components may depend on the particular functionality required by the communication device.

[0040] The transmitter 306 includes a modulator (not shown), and the receiver 304 includes a demodulator (not shown). The modulator can apply any one of a plurality of modulation orders to modulate the signals to be transmitted as part of the uplink signals. The demodulator demodulates the downlink signals in accordance with one of a plurality of modulation orders.

[0041] FIG. 4 is a message flow diagram 400 for an example where a receiving UE device 102 determines, based on signal quality, whether to transmit distance-based FIARQ feedback when location information is unavailable to the receiving UE device 102.

[0042] At transmission 402, the transmitting UE device 101 sends a location unavailable signal quality threshold message to the receiving UE device 102. Transmission 402, therefore, is an example of the location unavailable signal threshold transmission 118 discussed with reference to FIG. 1. The location unavailable signal threshold message provides the signal quality threshold information to the receiving UE device which is used by the receiving UE device 102 to determine whether FIARQ messages for distance-based FIARQ should transmitted when location information is unavailable to the receiving UE device 102. For the example, the location unavailable signal quality threshold message is a Medium Access Control (MAC) Control Element (CE) in the Sidelink Control Channel (SCCH) transmitted in a groupcast transmission. In some cases, the location unavailable signal quality threshold message may be a PC5-S (upper layer message) delivered in the SCCH. Furthermore, the location unavailable signal quality threshold message may be transmitted as a 1-bit indicator in the SCI. In the latter case, the signal quality threshold value may be provided by the gNB via RRC signaling or it may be preconfigured; therefore, only the 1- bit SCI indicator is needed to inform the receiving UE device whether to use the SL- RSRP measurement for this purpose. Other techniques can be used to transmit the location unavailable configuration.

[0043] At event 404, a groupcast transmission is transmitted from the transmitting UE device 101 to the receiving UE devices of the group. At transmission 406, the transmitting UE device 101 sends a distance-based HARQ configuration to the receiving UE device 102 to configure the receiving UE device for distance-based HARQ. At transmission 408, a groupcast transmission is sent by the transmitting UE device to the members of the group. The groupcast transmission includes data and the associated SCI. For the examples herein, the distance-based HARQ configuration is sent in the header of a groupcast data transmission. More specifically, the HARQ configuration is sent in the SCI of the groupcast transmission. As discussed above, the SCI is encoded with more robust modulation coding scheme (MCS) than the data so that the receiving UE devices will receive this portion of the signal with a much greater success rate. The traffic portion of the packet might be encoded with a lesser robust MCS to ensure higher data throughput. Accordingly, for the examples herein, transmission 406 and transmission 408 are part of the same transmission at event 404. The two transmissions 406, 408 are shown as separate arrows in the figures to illustrate that the SCI can be successfully received while the data may not be successfully received in some situations. For the examples, the SCI portion of transmission 406 is successfully received and the data of transmission 408 is not successfully received by the receiving UE device 102. In some situations, information related to the HARQ configuration is transmitted over multiple channels. For example, in at least one revision of the NR V2X communication specification, the SCI is sent in two stages where a first part is carried by the physical channel PSCCH and the second part is carried in PSSCH. As specified in Rel-16, one of the fields in the first stage SCI in PSCCH indicates which 2nd-stage SCI (format A or B) is used and a second stage SCI is in the PSSCH indicates either format-2A for HARQ ACK/NACK and format-2B for NACK-only. The zone ID and communication range requirement is sent in the 2B. Accordingly, the transmitting UE device could implicitly request the receiving UE device to send a distance-based HARQ by indicating the groupcast type in the SCI.

[0044] At event 410, the receiving UE device 102 determines data in the transmission 408 was not successfully received. After successfully receiving the SCI portion of the groupcast transmission, the receiving UE device 102 unsuccessfully attempts to receive the data portion.

[0045] At event 412, the receiving UE device 102 determines that location information is unavailable. For example, the receiving UE device 102 may determine that GPS service is unavailable where GPS provides the information required for the UE device to determine UE device location. In some situations, the location determination is performed at a location server at the base station with assistance from the UE device. If the UE device determines that the base station cannot provide the location information where this technique is used, the receiving UE device determines that location information is unavailable.

[0046] At event 414, the receiving UE device determines whether the measured signal quality of the SL signals transmitted from the first UE device are above the signal quality threshold previously received from the transmitting UE device 101 to determine if a HARQ message should be sent. If it is determined that the HARQ message should be sent, a HARQ message is sent at transmission 416. Otherwise, no HARQ message is sent. The arrow representing the HARQ message is shown with a dashed line in FIG. 4 to indicate that the message is not sent where the configuration does not include HARQ feedback messages for distance-based HARQ when location information is unavailable.

[0047] FIG. 5 is a message flow diagram 500 for an example where a receiving UE device 102 determines whether to send distance-based HARQ messages based on SL signal quality when location information is unavailable and establishes a unicast connection for group data. The message flow discussed with reference to FIG. 5 is an example of the message flow discussed with reference to FIG. 4. Transmissions 402, 406, 408 and events 404, 410, 412 are performed as discussed above with reference to FIG. 4.

[0048] At event 502, the receiving UE device 102 determines that the required QoS of the groupcast communication is above a QoS threshold. In order to maintain the QoS above the minimum requirement, the receiving UE device 102 determines that a unicast connection should replace the groupcast connection.

[0049] At transmission 504, the receiving UE device 102 sends a Direct Communication Request message to the transmitting UE device 101. For the example, the Direct Communication Request message is transmitted over a broadcast channel in accordance with known techniques.

[0050] At transmission 506, the transmitting UE device 101 sends a Direct Communication Accept message to the receiving UE device 102. For the example, the Direct Communication Accept message is transmitted over a broadcast channel in accordance with known techniques.

[0051] At event 508, the transmitting UE device 101 removes the receiving UE device from the groupcast list. Accordingly, the transmitting UE device 101 determines that all data associated with the group will be transmitted over the unicast link rather than in groupcast transmissions.

[0052] At event 510, a PC5-RRC connection is established between the transmitting UE device 101 and the receiving UE device 102. Therefore, a unicast connection is established between the two devices 101, 102.

[0053] At transmission 512, the transmitting UE device sends group data to the receiving UE device 102 over the PC5-RRC link. The transmission 512 includes the FIARQ feedback configuration.

[0054] At the transmission 514, the receiving UE device 102 transmits a FIARQ message in accordance with the SCI information received in the unicast transmission. If ACK is enabled for the transmission 512, the unicast FIARQ may be an ACK. Otherwise, the transmission 514 is only NACKwhen the data portion is not successfully received.

[0055] FIG. 6 is a flow chart of an example of a method 600 of managing groupcast feedback based on location information availability and signal quality. For the example, the method is performed by a UE device operating in a NR V2X system such as the system 100 described above. Accordingly, the method may be performed by the second UE device (receiving UE device) 102 when part of a group of the first UE device (transmitting UE device) 101.

[0056] At step 601 , a location unavailable signal quality threshold message is received from the transmitting UE device 101. As discussed above, location unavailable signal quality threshold message provides the signal quality threshold to the receiving UE device 102 that is to be used to determine whether FIARQ messages for distance-based FIARQ should be sent when location information is unavailable to the receiving UE device 102. For the example, the location unavailable signal quality threshold message is a Medium Access Control (MAC) Control Element (CE) in the Sidelink Control Channel (SCCFI) transmitted in a groupcast transmission. In some cases, the location unavailable signal quality threshold message may be a PC5-S (upper layer message) delivered in the SCCFI. Furthermore, the location unavailable signal quality threshold message may be transmitted as a 1-bit indicator in the SCI. In the latter case, the signal quality threshold value may be provided by the gNB via RRC signaling or it may be preconfigured; therefore, only the 1-bit SCI indicator is needed to inform the receiving UE device whether to use the SL-RSRP measurement for this purpose. Other techniques can be used to transmit the location unavailable configuration.

[0057] At step 602, a groupcast data transmission with distance-based FIARQ configuration is received. For the example, at least the SCI portion is successfully received. The data portion may not be successfully received at step 502.

[0058] At step 604, it is determined whether the data portion of the groupcast data transmission is successfully received. In accordance with known techniques, the receiving UE device 102 evaluates the information in the transmission to determine if the data has been successfully received. If the data is successfully received, the method returns to step 602 for reception of the next transmission. Otherwise, the method proceeds to step 606.

[0059] At step 606, it is determined whether location information is available. If the location of the receiving UE device 102 is known or can be determined, the method continues at step 608. Otherwise, the method proceeds to step 610.

[0060] At step 608, it is determined whether the receiving UE device 102 is within the distance range for sending HARQ feedback. The distance based on the criteria specified by the transmitting UE device is calculated and evaluated to determine if HARQ feedback is required. If the receiving UE device is not within the distance range, the method returns to step 602 to receive the next transmission without sending HARQ feedback. Otherwise, the HARQ feedback is transmitted at step 612. As discussed above, distance-based HARQ feedback includes only NACKfor the example. Accordingly, the receiving UE device 102 sends a NACK indicating that the data in the groupcast transmission was not successfully received before returning to step 602.

[0061] At step 610, the receiving UE device determines whether the measured signal quality of sidelink signals received from the transmitting UE device 101 are above the location unavailable signal quality threshold^For the examples herein, the second UE device derives NR sidelink measurement results by measuring one or multiple DMRS associated sidelink channel as configured by the first UE device. For all NR sidelink measurement results, the second UE device applies the layer 3 filtering before using the measured results for evaluation.

[0062] In one scenario, the second UE device may begin to evaluate the NR sidelink measurement continuously after it determines that location information is unavailable.

In another scenario, the second UE device may begin to evaluate the NR sidelink measurement after the groupcast transmission is received.

[0063] If the measured signal quality is above the threshold, the method proceeds to step 612 where a HARQ message is transmitted. Otherwise, the method continues at step 614 where the receiving UE device refrains from sending HARQ feedback. [0064] For the example, the method then continues to step 616 where it is determined whether the required QoS of the groupcast is above a QoS threshold. If the required QoS of the groupcast is above the QoS threshold, the method proceeds to step 618. Otherwise, the method returns to step 602 where a new groupcast message is received. In some situations, the method returns to step 601 to receive a new location unavailable signal quality threshold before receiving the next groupcast message at step 602.

[0065] At step 618, a unicast connection is established for the group data. The groupcast connection is, therefore, replaced with a unicast connection to improve quality of the connection for receiving the group data.

[0066] FIG. 7 is a flow chart of an example of a method 700 of managing groupcast feedback based on location information availability using a signal quality threshold. For the example, the method is performed by a UE device operating in a NR V2X system such as the system 100 described above. Accordingly, the method may be performed by the first UE device (transmitting UE device) 101 when transmitting groupcast transmission to a group of UE devices including the second UE device (receiving UE device) 102.

[0067] At step 702, it is determined whether distance-based FIARQ will be used for groupcast messages. The transmitting UE device evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCFI resources. If it is determined that distance-based FIARQ feedback should be used, the method continues at step 704. Otherwise, the method proceeds to step 706 where groupcast data is transmitted in a groupcast transmission with a groupcast FIARQ not based on distance configuration.

[0068] At step 704, the location unavailable signal quality threshold is determined.

For the example, the transmitting UE device 101 evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCFI resources to determine what signal threshold a receiving UE device should use in determining whether to transmit FIARQ messages when location information is unavailable. In some situations, the determination on what threshold should be used by a receiving UE device that does not have location information is at least partially performed by a base station or the network. Accordingly, the transmitting UE device 101 may provide information to the serving base station and receive instructions on determining the threshold or the actual threshold value that should be used when location information is unavailable. Also, the base station may provide criteria or information that assists the transmitting UE device in determining the location unavailable signal quality threshold.

[0069] At step 708, the location unavailable signal quality threshold is transmitted to the receiving UE devices. As discussed above, the location unavailable signal quality threshold is the threshold that is to be used by receiving UE devices. Accordingly, the threshold indicates allows the UE device to determine whether the receiving UE device transmits a HARQ message for data transmitted with a distance-based HARQ when the receiving UE device 102 does not know its location. For the example, the location unavailable signal quality threshold message is a Medium Access Control (MAC)

Control Element (CE) in the Sidelink Control Channel (SCCH) transmitted in a groupcast transmission. In some cases, the location unavailable signal quality threshold message may be a PC5-S (upper layer message) delivered in the SCCH. As discussed above, the location unavailable signal quality threshold message may be transmitted as a 1-bit indicator in the SCI. Other techniques can be used to transmit the location unavailable configuration.

[0070] At step 710, a groupcast data transmission with distance-based HARQ configuration is transmitted to a group of UE device including the second UE device (receiving UE device 102. The groupcast data transmission includes distance-based HARQ feedback configuration.

[0071] At step 712, it is determined whether the groupcast transmissions to the UE devices should continue to use distance-based HARQ or if the HARQ feedback should be switched to HARQ feedback that is not based on distance. The transmitting UE device evaluates factors such as the QoS, number of UE devices in the group, and the available PSFCH resources. If it is determined that distance-based HARQ feedback should continue to be used, the method continues at step 714. Otherwise, the method proceeds to step 706 where the next groupcast transmission uses HARQ feedback that is not based on distance.

[0072] At step 714, it is determined whether a new location unavailable signal quality threshold should be used for groupcast transmissions using distance-based HARQ. The transmitting UE device 101 evaluates factors such the QoS required for the receiving UE device, available resources and the number of UE devices in the group to determine if the threshold should be changed from the previous transmission. If no change in threshold is required, the method returns to step 710 where the transmitting UE device 101 transmits the next groupcast transmission. If a threshold change is required, the method returns to step 704 where the new threshold is determined. For the example of FIG. 7, therefore, a new location unavailable signal quality threshold is transmitted only where the threshold has changed from the previous transmission. In some situations, however, the location unavailable signal quality threshold is transmitted with each groupcast transmission. Other techniques may also be used. [0073] Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.