Patent Description:
The present disclosure relates generally to communication systems, and more particularly, to vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V), or other device-to-device (D2D) communication.

Some communication may be performed directly between User Equipment (UEs). Examples of such communication include D2D communication, V2X communication, V2V communication, etc. There exists a need for further improvements in wireless communication between UEs. These improvements may also be applicable to other wireless communication technologies and the telecommunication standards that employ these technologies. Patent application <CIT> relates to a method for receiving a data packet from a first communication device by a second communication device in a wireless network comprising the following steps: - awaiting the data packet at the second communication device; determining a context information related to the data packet by the second communication device; if the data packet is not received successfully, controlling transmission of a negative acknowledgement indicator, NACK, and/or transmission of a channel quality indicator, CQI, by the second communication device to the first communication device based on the context information.

In an aspect of the disclosure, a method is provided for wireless communication at a receiving device. The method includes receiving, from a transmitting device, at least a portion of a message for a service group, wherein the message comprises a D2D message and measuring a signal strength for the message received from the transmitting device. The method includes determining whether the receiving device is within a range of the transmitting device based on the measured signal strength for the message and determining to send Hybrid Automatic Repeat Request (HARQ) feedback to the transmitting device when the receiving device is within the range of the transmitting device.

In another aspect of the disclosure, an apparatus is provided for wireless communication at a receiving device. The apparatus includes means for receiving, from a transmitting device, at least a portion of a message for a service group, wherein the message comprises a D2D message and means for measuring a signal strength for the received message received from the transmitting device. The apparatus includes means for determining whether the receiving device is within a range of the transmitting device based on the measured signal strength for the received message and means for determining to send Hybrid Automatic Repeat Request (HARQ) feedback to the transmitting device when the receiving device is within the range of the transmitting device.

In another aspect of the disclosure, a computer-readable medium is provided for wireless communication at a receiving device. The computer-readable medium stores computer executable code for wireless communication at a receiving device, the code when executed by a processor cause the processor to receive, from a transmitting device, at least a portion of a message for a service group, wherein the message comprises a D2D message, measure a signal strength for the received message received from the transmitting device, determine whether the receiving device is within a range of the transmitting device based on the measured signal strength for the received message, and determine to Hybrid Automatic Repeat Request (HARQ) feedback to the transmitting device when the receiving device is within the range of the transmitting device.

In another aspect of the disclosure, a method is provided for wireless communication at a transmitting device. The method includes transmitting a message to a service group for an intended range, wherein the message comprises a D2D message and receiving Hybrid Automatic Repeat Request (HARQ) feedback from at least one receiving device. The method includes measuring a signal strength for the HARQ feedback and determining whether the HARQ feedback is from a receiving device within the intended range based on the signal strength measured for the HARQ feedback. The method includes determining to resend the message when the HARQ feedback is from the receiving device within the intended range.

In another aspect of the disclosure, an apparatus is provided for wireless communication at a transmitting device. The apparatus includes means for transmitting a message to a service group for an intended range, wherein the message comprises a D2D message. The apparatus includes means for receiving HARQ feedback from at least one receiving device and means for measuring a signal strength for the HARQ feedback. The apparatus includes means for determining whether the HARQ feedback is from a receiving device within the intended range based on the signal strength measured for the HARQ feedback and means for determining to resend the message when the HARQ feedback is from the receiving device within the intended range.

In another aspect of the disclosure, a computer-readable medium is provided for wireless communication at a transmitting device. The computer-readable medium stores computer executable code that, when executed by a processor, cause the processor to transmit a message to a service group for an intended range, wherein the message comprises a D2D message, receive HARQ feedback from at least one receiving device, measure a signal strength for the HARQ feedback, determine whether the HARQ feedback is from a receiving device within the intended range based on the signal strength measured for the HARQ feedback, and determine to resend the message when the HARQ feedback is from the receiving device within the intended range.

Wireless communication may involve transmissions from a transmitting device for receipt by at least one receiving device. For example, a transmitting device may transmit a message via V2V/V2X/D2D to a receiving vehicle. The message may be multicast from the transmitting device and may be intended to be reliably delivered to certain receiving devices, e.g., devices for a corresponding service group, within a certain area including the transmitting device. In order to ensure that the message is reliably received by the receiving device(s), the transmitting device may listen for feedback from receiving devices(s) to determine whether the message was received correctly. Receiving device(s) that do not successfully receive the message may respond to the transmitting device with a Negative Acknowledgement (NACK). The NACK may prompt the transmitting device to retransmit the message. However, a receiving device that is too distant from the transmitting device to correctly receive the message may respond with a NACK causing the transmitting device to retransmit the message in vain. Such feedback and wasted retransmissions for receiving devices that may be distant from the transmitting device degrade system performance. This problem may be especially challenging in a V2X/V2V/D2D environment due to the highly mobile nature of transmitters and/or receivers.

Aspects presented herein provide solutions in which feedback can be limited from receivers that are distant from the transmitting device. For example, aspects may include the receiving device determining whether it is an intended receiver of the message and/or whether it should provide feedback for the message based on a measured signal strength of the received message. Additional aspects enable the transmitting device to limit undesirable retransmissions when feedback is received from a receiving device at an undesirable distance from the transmitting device. For example, a transmitting device may determine whether to retransmit a message based on a measured signal strength of received negative feedback. Aspects may help to reduce system degradation due to retransmissions to distant receiving devices, and therefore, may improve the efficient use of wireless resources. Aspects may also help to avoid reception of feedback from unintended receiving devices that are a part of a service group yet are not proximate to a transmitting device.

Accordingly, in one or more examples, the functions described may be implemented in hardware, software, or any combination thereof.

The wireless communications system (also referred to as a wireless wide area network (WWAN)) includes base stations <NUM>, UEs <NUM>, an Evolved Packet Core (EPC) <NUM> and another core network <NUM> (such as a <NUM> Core (5GC)).

The base stations <NUM> configured for <NUM> LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC <NUM> through backhaul links <NUM> (e.g., S1 interface). The base stations <NUM> configured for <NUM> NR (that may be referred to as gNodeBs (gNBs) and collectively referred to as Next Generation RAN (NG-RAN)) may interface with 5GC <NUM> through backhaul links <NUM>. The base stations <NUM> may communicate directly with each other over backhaul links <NUM> (e.g., X2 interface), or indirectly with each other through the EPC <NUM> or 5GC <NUM>.

For example, the small cell <NUM>' may have a coverage area <NUM>' that overlaps the coverage area <NUM> of one or more base stations <NUM>, e.g., macro base stations. A network that includes both small cell and macro cells may be known as a heterogeneous network. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

A base station <NUM>, whether a small cell <NUM>' or a large cell (e.g., macro base station), may include an eNB, gNB, or other type of base station. Some base stations <NUM>, such as a gNB, may operate in a traditional sub <NUM> spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies in communication with the UE <NUM>. When the base station <NUM> operates in mmW or near mmW frequencies, the base station <NUM> may be referred to as an mmW base station. The mmW base station, e.g., base station <NUM>, may utilize beamforming <NUM> with the UE <NUM> to compensate for the extremely high path loss and short range.

Devices may use beamforming to transmit and receive communication. For example, <FIG> illustrates that a base station <NUM> may transmit a beamformed signal to the UE <NUM> in one or more transmit directions <NUM>'. Although beamformed signals are illustrated between UE <NUM> and base station <NUM>/<NUM>, aspects of beamforming may similarly be applied by UE <NUM> or RSU <NUM> to communicate with another UE <NUM> or road side unit (RSU) <NUM>, such as based on V2X, V2V, or other D2D communication.

The Core Network <NUM> may include an Access and Mobility Management Function (AMF) <NUM>, other AMFs <NUM>, a Session Management Function (SMF) <NUM>, and a User Plane Function (UPF) <NUM>. The AMF <NUM> is the control node that processes the signaling between the UEs <NUM> and the Core Network <NUM>.

The base station may comprise or be referred to as a gNB, Node B, evolved Node B (eNB), an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit reception point (TRP), or some other suitable terminology. The base station <NUM> provides an access point to the EPC <NUM> or Core Network <NUM> for a UE <NUM>.

Some wireless communication networks may include vehicle-based communication devices that can communicate from vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) (e.g., from the vehicle-based communication device to road infrastructure nodes such as a RSU), vehicle-to-network (V2N) (e.g., from the vehicle-based communication device to one or more network nodes, such as a base station), and/or a combination thereof and/or with other devices, which can be collectively referred to as vehicle-to-anything (V2X) communications. Referring again to <FIG>, in certain aspects, a UE <NUM>, e.g., a transmitting Vehicle User Equipment (VUE) or other UE, may be configured to transmit messages directly to another UE <NUM>. The communication may be based on V2V/V2X/V2I or other D2D communication, such as Proximity Services (ProSe), etc. Communication based on V2V, V2X, V2I, and/or other D2D may also be transmitted and received by other transmitting and receiving devices, such as RSU <NUM>, etc. Aspects of the communication may be based on communication across the PC5 interface or sidelink communication e.g., as described in connection with the example in <FIG>. Although the following description may provide examples for V2X/D2D communication in connection with <NUM> NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

Referring again to <FIG>, in certain aspects, a UE <NUM>, such as a transmitting Vehicle User Equipment (VUE) or other UE, may be configured to transmit messages directly to another UE <NUM>'. The communication may be based on V2V/V2X or other D2D communication, such as Proximity Services (ProSe). Aspects presented herein provide a way for communication between the devices, e.g., engaged in PC5 based communication or other D2D communication, to have improved reliability while avoiding inefficient use of resources to retransmit to receivers at an undesirable distance. For example, the transmitting device, whether a UE, RSU, or base station, may comprise a message component <NUM> that is configured to generate a message for a service group. The UE <NUM> may be configured to determine an intended range for a service group, and transmit the message for the service group based, at least in part, on the intended range. A receiving UE (e.g., UE <NUM>') may be configured to receive, from the transmitting UE (e.g., UE <NUM>), at least a portion of the message for the service group, and measure a signal strength for the message received from UE <NUM>. The UE <NUM>' may include a determination component <NUM> configured to determine whether to send HARQ feedback to UE <NUM> based on the signal strength measured for the message,. In some aspects, the message component <NUM> of UE <NUM> may be configured to receive HARQ feedback from at least the UE <NUM>', measure a signal strength for the HARQ feedback, and determine whether to resend the message based on the signal strength measured for the HARQ feedback.

<FIG> illustrates example diagrams <NUM> and <NUM> illustrating examples slot structures that may be used for wireless communication between UE <NUM> and UE <NUM>, e.g., for sidelink communication. The slot structure may be within a <NUM>/NR frame structure. This is merely one example, and other wireless communication technologies may have a different frame structure and/or different channels. Diagram <NUM> illustrates a single slot transmission, e.g., which may correspond to a <NUM> transmission time interval (TTI). Diagram <NUM> illustrates an example two-slot aggregation, e.g., an aggregation of two <NUM> TTIs. Diagram <NUM> illustrates a single RB, whereas diagram <NUM> illustrates N RBs. In diagram <NUM>, <NUM> RBs being used for control is merely one example. The number of RBs may differ.

Each time slot may include a resource block (RB) (also referred to as physical RBs (PRBs)) that extends <NUM> consecutive subcarriers. As illustrated in <FIG>, some of the REs may comprise control information, e.g., along with demodulation RS (DMRS). In some aspects, the control information may indicate an intended range for corresponding data. The intended range may help devices receiving the data to determine whether to provide feedback to the device that transmitted the data. <FIG> also illustrates that symbol(s) may comprise CSI-RS. The symbols in <FIG> that are indicated for DMRS or CSI-RS indicate that the symbol comprises DMRS or CSI-RS REs. Such symbols may also comprise REs that include data. For example, if a number of ports for DMRS or CSI-RS is <NUM> and a comb-<NUM> pattern is used for DMRS/CSI-RS, then half of the REs may comprise the RS and the other half of the REs may comprise data. A CSI-RS resource may start at any symbol of a slot, and may occupy <NUM>, <NUM>, or <NUM> symbols depending on a configured number of ports. CSI-RS can be periodic, semi-persistent, or aperiodic (e.g., based on DCI triggering). For time/frequency tracking, CSI-RS may be either periodic or aperiodic. CSI-RS may be transmitted in bursts of two or four symbols that are spread across one or two slots. The control information may comprise Sidelink Control Information (SCI). At least one symbol may be used for feedback, as described herein. A symbol prior to and/or after the feedback may be used for turnaround between reception of data and transmission of the feedback. Although symbol <NUM> is illustrated for data, it may instead be a gap symbol to enable turnaround for feedback in symbol <NUM>. Another symbol, e.g., at the end of the slot may be used as a gap. The gap enables a device to switch from operating as a transmitting device to prepare to operate as a receiving device, e.g., in the following slot. Data may be transmitted in the remaining REs, as illustrated. The data may comprise the data message described herein. The position of any of the SCI, feedback, and LBT symbols may be different than the example illustrated in <FIG>. Multiple slots may be aggregated together. <FIG> also illustrates an example aggregation of two slots. The aggregated number of slots may also be larger than two. When slots are aggregated, the symbols used for feedback and/or a gap symbol may be different that for a single slot. While feedback is not illustrated for the aggregated example, symbol(s) in a multiple slot aggregation may also be allocated for feedback, as illustrated in the one slot example.

<FIG> is a block diagram <NUM> of a first wireless communication device <NUM> in communication with a second wireless communication device <NUM>, e.g., via V2V/V2X/D2D communication. The device <NUM> may comprise a transmitting device communicating with a receiving device, e.g., device <NUM>, via V2V/V2X/D2D communication. The communication may be based, e.g., on sidelink. The first wireless communication device <NUM> may comprise a UE, an RSU, etc. The receiving device may comprise a UE, an RSU, etc. In addition to the other components illustrated in <FIG>, the wireless communication devices <NUM>, <NUM> may each comprise a message component <NUM>, <NUM> and/or a determination component <NUM>, <NUM>. The message component <NUM>, <NUM> may be configured to generate and transmit a message for the service group based, at least in part, on the intended range. The message component <NUM>, <NUM> may also be configured to determine whether to retransmit a message based on a signal strength of feedback received from receiving device(s). The determination component <NUM>, <NUM> may be configured to determine whether to send a feedback for the message based on a signal strength of at least a portion of the message. As an example, least one of the TX processor <NUM>, the RX processor <NUM>, or the controller/processor <NUM> of device <NUM> or the TX processor <NUM>, the RX processor <NUM>, or the controller/processor <NUM> may be configured to perform aspects described in connection with <NUM> and/or <NUM> of <FIG>.

Packets may be provided to a controller/processor <NUM> that implements layer <NUM> and layer <NUM> functionality.

Wireless communication may include multicast or broadcast communication directly between UEs. As an example, multicast sidelink communication may be performed via a PC5 interface. UEs may communicate using sidelink multicast or broadcast based on V2X communication, V2V communication, or other D2D communication, for example. A multicast may involve a transmission from one UE that is intended to be decoded by UEs that are part of a service group. A service group may comprise one or more UEs. A group ID identifying the service group may be comprised in the message, e.g., in Sidelink Control Information (SCI) of the multicast message, and/or as part of the MAC layer destination address.

<FIG> illustrates an example of communication <NUM> between multiple UEs, e.g., based on V2X/V2V/other D2D communication. In some examples, a transmitting UE <NUM> may be a vehicle or a device installed in a vehicle as part a V2V/V2X network, e.g., based on <NUM>/NR communication or LTE communication. In some examples, the transmitting UE <NUM> may be a UE that is not associated with a vehicle. Such V2V/V2X/other D2D communication may involve the transmission of information from the transmitting UE <NUM> to another receiving UE, e.g., any of <NUM>, <NUM>, <NUM>, <NUM>. For example, the communication from the transmitting UE <NUM> may be directed to a service group of RX UEs, e.g., a subset from among receiving UEs <NUM>, <NUM>, <NUM>, <NUM>. While the example illustrates communication between vehicles, the aspects presented herein may also be applicable to any transmitting and/or receiving device engaged in V2X/V2V/other D2D communication, e.g., based on PC5. The transmitting and/or receiving devices may comprise a UE, such as a vehicle. Aspects may also be applicable to an RSU <NUM> or a base station <NUM>, <NUM> communicating as a transmitting device or receiving device based on V2V/V2X or direct D2D communication. Thus, although the aspects of the present application are described using the example of a receiving UE and a transmitting UE, the aspects are applicable to other devices that may be engaged in PC5 communication.

In a PC5 multicast, for example, a transmitting UE <NUM> may ensure that all intended receivers in the service group and in proximity of the transmitting UE accurately receive the message. If the intended receivers, e.g., in the service group and/or in the proximity of the transmitting UE, do not receive the message accurately, the transmitting UE may retransmit the message in order to ensure accurate receipt of the message.

In order to improve reliability, feedback may be sent back from the receiving UEs in the service group. For example, if a particular UE does not correctly receive the message, the UE may transmit feedback, such as a NACK indicating to the transmitting UE that there was an error in receiving the message. In response to the NACK, the transmitting UE may retransmit the message.

However, negative feedback from distant UEs may cause the transmitting UE <NUM> to retransmit the message and may degrade the overall system performance. For example, the receiving UE may be at a distance from the transmitting UE <NUM> such that the receiving UE will not be expected to correctly receive the message. Such retransmissions would degrade overall system performance through an inefficient use of wireless resources and through unnecessary potential interference to other wireless communication.

As an example, UEs <NUM>, <NUM>, and <NUM> may be associated with the service group. UE <NUM> may have correctly received the message <NUM> from UE <NUM> and may not transmit a NACK. UE <NUM> may have experienced an error in receiving the message. Thus, UE <NUM> may transmit a NACK <NUM> indicating to UE <NUM> that the message was not accurately received. In response to the NACK <NUM>, the transmitting UE <NUM> may determine to retransmit the message <NUM> as retransmission <NUM>'. However, negative feedback, e.g., NACK(s), may be received from far away receivers that are outside the desired proximity of the transmitting UE <NUM>. As illustrated in <FIG>, the UE may intend for UEs within an intended area/range <NUM> to receive the message reliably. UE <NUM> that is outside the intended area/range <NUM> may receive at least a part of the message <NUM> and send a NACK <NUM> to UE <NUM>. However, UE <NUM> may be at such a distance that UE <NUM> is unlikely to receive the message <NUM> correctly even with a retransmission from UE <NUM>. Additionally, based on the service requirement, there may be no need for the UE at the distance of UE <NUM> to receive the message. Therefore, the message may be irrelevant for UE <NUM>.

While a group ID, e.g., a common destination ID, may be used to identify a multicast service group, in an ad hoc V2X/V2V/D2D environment, it may be difficult to manage or establish a common group identifier that is known to vehicles in the service group that are also in the proximity of the transmitting UE because of the mobile nature of the transmitters and/or receivers. Receiving UEs that are distant from the transmitting UE <NUM> may be a part of the service group and know the group ID. The distant UEs may attempt to receive the message, regardless of their distance from the message sender.

Aspects are presented that help to limit undesirable feedback from distant UEs and to avoid retransmissions based on such feedback. Aspects enable a receiver to determine whether it is an intended receiver of the message. The receiver can then determine whether to send feedback based on whether or not the receiver is an intended receiver of the message. For example, the receiving UE may avoid sending feedback if the UE is not in the intended area/range <NUM> for the message. A transmitting UE <NUM> may be configured to control retransmissions based on a parameter of the received NACK(s). The aspects presented herein may be used independently or may be employed together. The aspects presented herein help to ensure that messages are reliably received within an intended area and in a way that limits feedback and/or retransmissions for UEs at an undesirable distance.

The receiving UE <NUM><NUM>, <NUM>, or <NUM> may filter feedback for a received message (e.g., message <NUM>) based on a measured signal strength for the received message. For example, a determination component <NUM>, as illustrated for UE <NUM>, may determine whether to send feedback for a message based on a measured signal strength for the message. The receiving UE <NUM>, <NUM>, <NUM>, or <NUM> may receive, from the transmitting UE <NUM>, at least a portion of the message <NUM> for the service group, measure a signal strength for the portion of the received message, and determine whether to send feedback (e.g., NACK <NUM>) to the transmitting UE <NUM> based on the measured signal strength for the message. In some aspects, the measured signal strength may include a Received Signal Strength Indicator (RSSI) and/or a Reference Signal Received Power (RSRP). In this way, feedback from distant UEs can be reduced so that the UEs within an intended range of the transmitting UE <NUM> may send the feedback, thereby increasing the performance and reliability of the overall system.

The signal strength may be measured based on a control portion of the message. The signal strength may be measured based on a data portion of the message. The signal strength may be measured based on both a data portion of the message and a control portion of the message.

The receiving UE <NUM><NUM>, <NUM>, or <NUM> may compare the measured signal strength (e.g., RSSI/RSRP) with a threshold, to determine if the receiving UE is an intended receiver or not, e.g., a receiver within an intended range. The receiving UE may use more than one threshold, e.g., a lower bound and an upper bound, to determine whether the signal strength is within a window of signal strengths. The receiving UE may use a range, e.g., based on the lower bound and the upper bound to determine whether the receiving UE is an intended receiver. In some aspects, the threshold may be based on an intended range for the message. For example, the achieved range/distance by the transmitting UE <NUM> (e.g., sender) may be linked to a quality of service (QoS) parameter. The QoS parameter may be defined for the type of communication. In an example, the QoS parameter may be for V2X communication. The RSSI/RSRP threshold may be mapped from any of a QoS parameter, a <NUM> QoS Indicator (5QI), a range for the message, etc. In some aspects, a RSSI/RSRP threshold may be based, at least in part, on a QoS parameter for the service group. For example, the QoS parameter may be a stand-alone range parameter, or may be comprised in a 5QI that includes a range requirement.

The threshold may be configured by the transmitting UE <NUM>. The threshold may be based on a predefined or preconfigured threshold. The receiving UE <NUM>, <NUM>, <NUM>, or <NUM> may receive an indication <NUM> of a parameter from the transmitting UE <NUM>, wherein the threshold may be based at least in part on the parameter. In some aspects, the indication <NUM> of the parameter may be comprised in the message <NUM>. In other aspects, the parameter may be provided to the receiving UE separately from the message <NUM>. As an example, the measured signal strength (e.g., RSSI/RSRP) threshold may be preconfigured based on the QoS parameter associated with a particular group service. For example, in connection with a configuration of the receiving UE to listen to the group ID of the V2X multicast service, the corresponding signal strength threshold for providing feedback for messages of the service group may be also configured. As another example, the measured signal strength threshold may be included in the control information of the V2X message <NUM> itself. For example, the measured signal strength threshold may be dynamically adjustable. The transmitting UE <NUM> may adjust the intended range by dynamically adjusting the threshold per transmission.

In some aspects, the message may comprise an Information Element (IE) associated with a group ID information for the service group. In some aspects, the message may comprise an IE that is generated as a hash of group ID information for the service group and the indication of the signal strength threshold parameter. In some aspects, the message may comprise both an IE that is generated as a hash of group ID information for the service group and an IE that contains the indication of the signal strength threshold parameter.

For example, if the transmitting UE <NUM> is to send a group ID plus a limited set of extra information, the transmitting UE <NUM> may hash the group ID + extra information into the IE which provides a shorter identifier that can be embedded in the control portion of the message <NUM>. The use of the IE may reduce the overhead burden of the message while providing the group ID information and the additional information for the signal strength parameter used to determine whether to send feedback. For example, the extra information may indicate the RSSI/RSRP threshold. In another example, the extra information may indicate information, e.g., at least one parameter, that can be used by the UE to determine the RSSI/RSSP threshold. In another example, the transmitting UE <NUM> may hash the group ID into the IE which provides a shorter identifier, and may include both this IE and the extra information in the message <NUM>.

In some aspects, the receiving UE <NUM>, <NUM>, <NUM>, or <NUM> may determine to send the feedback (e.g., a ACK or a NACK <NUM>) if the signal strength that is measured for the message meets a threshold or is within a range. For example, the receiving UE may transmit negative HARQ feedback (e.g., a NACK) to the transmitting UE <NUM> if the message <NUM> is not correctly received and the signal strength of a measured portion of the message meets the threshold signal strength or is within a range of signal strengths. In another example, the receiving UE may transmit positive HARQ feedback (e.g., an ACK) to the transmitting UE <NUM> if the message is correctly received and the signal strength of a measured portion of the message meets the threshold signal strength or is within a range of signal strengths.

On the other hand, if the receiving UE measures a signal strength for the message that is below the threshold or outside the range, the receiving UE may determine to refrain from sending the feedback to the transmitting UE <NUM>, regardless of whether the packet is received correctly or not. Thus, the UE might not send a NACK even if the message is incorrectly received and might not send an ACK even if the message is correctly received.

The transmitting UE may transmit the message at a transmission power. The receiving UE may use a delta in connection with the transmission power at which the message was transmitted to determine whether the receiving UE is an intended receiver and whether to send feedback. The receiving UE may also use other parameters to determine whether to send feedback. For example, the receiving UE may use parameters received in a control message (e.g., sidelink control information SCI). The receiving UE may use a current interference level of the receiving UE, a channel busy ratio (CBR) of the receiving UE, etc. to determine whether to send feedback.

The transmitting UE <NUM> may be configured to determine the intended range for the service group and to transmit the message <NUM> for the service group based, at least in part, on the determined range. For example, the transmitting UE <NUM> may provide the indication <NUM> of the parameter for the signal strength threshold associated with the service group. The signal strength threshold may be used by receiving UEs <NUM>, <NUM>, <NUM>, or <NUM> to determine whether to send the feedback to the message. For example, the indication <NUM> of the parameter may be comprised in the message <NUM>. By providing the indication, UEs within proximity of the transmitting UE <NUM> (e.g., with intended area/range <NUM>) may send the feedback, and distant UEs (e.g., outside the intended area/range <NUM>) may avoid sending feedback, thereby increasing the performance and reliability of the overall system.

Alternately or additionally, the transmitting UE <NUM> may control retransmission attempts based on a signal strength of NACK received from one or more receiving UEs. For example, a retransmission component <NUM> of the transmitting UE <NUM> may determine whether to retransmit a message based on a signal strength of the received feedback. In the example in <FIG>, the transmitting UE <NUM> may multicast the message <NUM> to the service group and receive HARQ feedback from at least one receiving UE. The transmitting UE <NUM> may measure a signal strength for the HARQ feedback, and determine whether to resend the message (e.g., as retransmission <NUM>') based on the measured signal strength for the HARQ feedback. HARQ feedback may be received in a common resource in time and frequency. If more than one receiving UE fails to receive the message <NUM>, more than one UE may send negative HARQ feedback to the transmitting UE <NUM>. In some aspects, the HARQ feedback from multiple UEs may be transmitted at the same time or in an overlapping manner. The feedback from multiple UEs may have a single frequency network (SFN) effect. The SFN effect may happen when multiple transmitters simultaneously send the same signal over the same frequency resource so that the signals can be combined by a receiver. Thus, the HARQ feedback may comprise combined NACK feedback from any receiving UE that did not receive the message correctly. The transmitting UE <NUM> may assess the signal strength of the combined NACK feedback in the common resource in order to determine whether to retransmit the message. In some aspects, the transmitting UE <NUM> may determine to resend the message if the signal strength measured for the negative HARQ feedback meets a second threshold, then the transmitting UE <NUM> may resend the message for the service group. When the signal strength of the combined NACK is above the second threshold, it may indicate that multiple receiving UEs did not receive the message correctly or may indicate that at least one UE within the intended range of the message did not receive the message correctly. On the other hand, the transmitting UE <NUM> may determine to refrain from resending the message if the signal strength measured for the negative HARQ feedback is below the second threshold. When the combined NACK has a signal strength below the second threshold, it may indicate that a small number or a single receiving UE did not receive the message correctly, that the receiving UEs are not proximate to the transmitting UE <NUM>, and/or that no receiving UEs within the intended range of the message were unsuccessful in receiving the message. By measuring the signal strength, the transmitting UE <NUM> may avoid wasting wireless resources by limiting retransmissions of the message, thereby increasing the efficiency and reliability of the overall system.

For example, the transmitting UE <NUM> may determine the received strength of the NACK from receiving UEs. If the RSSI / RSRP of the NACK exceeds a second threshold, then the transmitting UE <NUM> may decide to retransmit. In some aspects, the second threshold may be based on at least one of an intended range for the message and/or a QoS requirement for the message. When multiple receiving UEs in a desired range do not receive the message, the combined signal strength of the NACKs may be higher than when one or two UEs do not receive the message. If the signal strength measured for the HARQ feedback exceeds the second threshold, which may indicate multiple receiving UEs in desired range do not receive the message, rather than one or two receiving UEs not receiving the message. In this way, the transmitting UE <NUM> may retransmit the message when multiple receiving UEs in desired range do not receive the message, and may avoid unnecessary retransmitting.

<FIG> illustrates an example communication flow <NUM> between a transmitting device <NUM> and a receiving device <NUM>. The communication may be based on V2X/V2V/D2D communication, e.g., PC5 multicast communication. In some aspects, the communication may be based on other D2D direct communication, such as ProSe. Although <FIG> illustrates an example of communication between a transmitting device <NUM> and a receiving device <NUM> that are illustrated as UEs, the concepts are equally applicable to a base station, an RSU, a mobile UE, a vehicle UE, etc. that are engaged in PC5 based communication, V2X/V2V communication or other direct D2D communication. The method may help to avoid retransmissions to a receiving device that may be too distant to correctly receive a message. The method may help reduce system degradation due to such retransmissions, and therefore, may improve the efficient use of wireless resources. The method may also help to avoid reception of feedback from unintended receiving devices that are a part of a service group yet are not proximate to a transmitting device.

At <NUM>, the transmitting device <NUM> may determine an intended range for a service group. Because negative feedback from distant receiving devices may cause the transmitting device to retransmit the message to receiving devices outside of the intended range and degrade the overall system performance, feedback may be limited to receiving devices within the intended range (e.g., in the proximity of the transmitting device <NUM>).

At <NUM>, the transmitting device <NUM> may transmit a message for the service group. For example, the transmitting device may multicast the message to the service group. The transmitting device <NUM> may provide an indication of a parameter for a first signal strength threshold associated with the service group, where the first signal strength threshold may be used by the receiving device <NUM> to determine whether to send feedback to the message. At <NUM>, the receiving device <NUM> may determine a first signal strength threshold based on the indication of the parameter, where the parameter may be an explicit indication of the first signal strength threshold or a QoS parameter associated with the service group from which the first signal strength threshold may be determined. In an alternate example, the message may not contain an indication of the parameter. In some examples, the receiving device <NUM> may determine the signal strength threshold, e.g., based on a QoS associated with the service group or based on other information. For example, the receiving device <NUM> may determine the signal strength threshold based on previously received or preconfigured information. The signal strength threshold may be preconfigured at the receiving device. The receiving device <NUM> may receive, from the transmitting device <NUM>, at least a portion of the message for the service group.

At <NUM>, the receiving device <NUM> may measure a signal strength for the message received from the transmitting device <NUM>. The signal strength measured for the HARQ feedback may comprise at least one of an RSSI and/or RSRP.

At <NUM>, the receiving device <NUM> may determine whether to send feedback to the transmitting device <NUM> based on the signal strength measured for the message. If the measured signal strength is below the threshold, the receiving device <NUM> may determine that it does not need to send feedback regardless of whether the message is correctly received.

At <NUM>, the receiving device <NUM> may send feedback to the transmitting device <NUM>. For example, the receiving device <NUM> may determine to send the feedback if the signal strength measured for the message meets a first threshold. For example, the receiving device <NUM> may transmit negative HARQ feedback to the transmitting device <NUM> if the message is not correctly received. In another example, the receiving device <NUM> may transmit positive feedback if the message is received correctly. The transmitting device <NUM> may receive the HARQ feedback from the receiving device <NUM>.

At <NUM>, the transmitting device <NUM> may measure a signal strength for the HARQ feedback.

At <NUM>, the transmitting device <NUM> may determine whether to resend the message based on the signal strength measured for the HARQ feedback. For example, when the HARQ feedback comprises negative HARQ feedback, the transmitting device <NUM> may determine to resend the message, e.g., in retransmission <NUM>, if the signal strength measured for the negative HARQ feedback meets a second threshold, then the transmitting device <NUM> may resend the message for the service group. For example, the transmitting device <NUM> may determine to refrain from resending the message if the signal strength measured for the negative HARQ feedback is below the second threshold.

<FIG> is a flowchart <NUM> of a method of wireless communication at a receiving device. The method may be performed, for example, by a receiving UE or a component of a UE (e.g., UE <NUM>, <NUM>, <NUM>; receiving device <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>, which may include memory and which may be an entire UE or a component of a UE). The apparatus may communicate with a transmitting device (e.g., transmitting UE <NUM>, transmitting device <NUM>). The apparatus may comprise an RSU <NUM>, or a component of an RSU <NUM>, a base station <NUM>, <NUM> or component of a base station engaged in PC5 communication. The wireless communication may comprise D2D communication, such as V2X communication, V2V communication, or other D2D communication, as described herein. To facilitate an understanding of the techniques and concepts described herein, the method of flowchart <NUM> may be discussed with reference to the examples illustrated in <FIG> and <FIG>. Optional aspects may be illustrated in dashed lines. Aspects presented herein may help to limit feedback to intended receiving devices, e.g., to devices that are part of a service group and that are within an intended range of the transmitting device. The method may help to avoid triggering transmissions at a transmitting device to a receiving device that may be too distant to correctly receive a message. The method may help reduce system degradation due to such retransmissions, and therefore, may improve the efficient use of wireless resources. The method may also help to avoid feedback from unintended receiving devices that are a part of a service group yet are not proximate to a transmitting device.

At <NUM>, the receiving device may receive, from the transmitting device, at least a portion of a message for a service group. The reception of the message may be performed, e.g., by reception component <NUM> of apparatus <NUM>. In some aspects, the message may comprise an information element associated with a group ID for the service group. The message may comprise a V2X/V2V/D2D message. The message may be received via multicast in one example. An example of a multicast is a groupcast for a group of UEs.

At <NUM>, the receiving device may receive a parameter (e.g., a QoS parameter) from the transmitting device, where the threshold may be based at least in part on the parameter. The parameter may be received, e.g., by reception component <NUM> of apparatus <NUM> and provided to determination component <NUM>. In some aspects, the threshold may be configured at the transmitting device. In some aspects, the indication of the parameter may be included in the received message. As an example, the measured signal strength (e.g., RSSI/RSRP) threshold may be configured based on the QoS parameter associated with the multicast service. In an example, the parameter may be the threshold for the measured signal strength.

For example, when the receiving device is configured to listen to the group ID of the message, e.g., a group ID of a V2X multicast service, the corresponding threshold may be also configured. As an example, a configured threshold may be preconfigured or provisioned via a protocol, e.g., open mobile alliance device management (OMA-DM) protocol via a user plane for the receiving device, or a UE policy provisioning protocol via a control plane. As another example, the measured signal strength (e.g., RSSI/RSRP) threshold may be included in the control information of the message, e.g., in SCI of the V2X multicast message. For example, the measured signal strength (e.g., RSSI/RSRP) threshold may be dynamically adjustable. The transmitting device (e.g., multicast sender) may adjust the transmission range by dynamically adjusting the threshold per transmission.

In some aspects, the message may include an information element based on a hash of a group ID for the service group and the parameter for the signal strength threshold. For example, if the transmitting device (e.g., the multicast sender) is to send a group ID plus a limited set of extra information, the transmitting device may hash the group ID + extra information into an information element (e.g., a shorter identifier) that is embedded in the control portion of the message. For example, the extra information may include the RSSI/RSRP threshold or a parameter that enables the receiving device to determine the RSSI/RSRP threshold.

At <NUM>, the receiving device may measure a signal strength for the received message. The measurement may be performed, e.g., by measurement component <NUM> of apparatus <NUM>. In some aspects, the signal strength measured for the message comprises at least one of an RSSI, an RSRP, or a combination of RSSI and RSRP. For example, the receiving device may measure the signal strength (e.g., RSSI/RSRP) for the received message. In some aspects, the signal strength may be measured based on a control portion of the message, a data portion of the message, or both a data portion of the message and a control portion of the message.

As illustrated at <NUM>, the receiving device may determine whether the receiving device is within a range of the transmitting device based on the measured signal strength for the received message. The range may be based on a distance from the transmitting device in which receiving devices are intended to correctly receive the message. The determination may be performed, e.g., by range component <NUM> of apparatus <NUM>. The receiving device may compare the measured signal strength (e.g., RSSI/RSRP) with a threshold, to determine if the receiving device is the "intended" receiver or not. In some aspects, the threshold may be based on an intended range for the received message. For example, the achieved range/distance by the transmitting device (e.g., sender) may be linked to a QOS parameter defined for the received message. The RSSI/RSRP threshold may be mapped from the QoS parameter, 5QI, range, etc. for the received message. In some aspects, the RSSI/RSRP threshold may be based at least in part on the QoS parameter. For example, the QoS parameter may be a "stand-alone" range parameter, or 5QI which incorporates range requirement. The receiving device may use more than one threshold, e.g., an upper threshold and a lower threshold to determine whether the UE is within an intended range. For example, the receiving device may determine whether the measured signal strength is within a signal strength range having an upper bound and a lower bound.

At <NUM>, the receiving device may determine whether to send a feedback to the transmitting device based on the signal strength measured for the received message. For example, the receiving device may determine to send feedback to the transmitting device when the receiving device is within the range of the transmitting device, e.g., an intended range for accurate reception of the message. The feedback may include HARQ feedback. The determination may be performed, e.g., by determination component <NUM> of apparatus <NUM>. In some aspects, the receiving device may determine to send the feedback if the signal strength measured for the received message meets the threshold. When the measured signal strength meets a threshold signal strength, it may be an indication that the receiving device is within an intended range of the transmitting device. Therefore, the receiving device may determine that it should send feedback to the transmitting device.

For example, if the measured signal strength meets the threshold, the receiving device may determine whether the message is received correctly, as illustrated at <NUM>. In other examples, the determination about whether the message is received correctly may be made prior to determining the measured signal strength. The determination may be performed, e.g., by determination component <NUM> of apparatus <NUM>. The receiving UE may use a delta in connection with the transmission power at which the message was transmitted to determine whether the receiving UE is an intended receiver and/or whether to send feedback. The receiving UE may also use other parameters to determine whether to send feedback. For example, the receiving UE may use parameters received in a control message (e.g., sidelink control information SCI). The receiving UE may use a current interference level of the receiving UE, a channel busy ratio (CBR) of the receiving UE, etc. to determine whether to send feedback.

For example, the receiving device may transmit negative HARQ feedback (e.g., a NACK) to the transmitting device if the message is not correctly received, as illustrated at <NUM>. The receiving device may transmit positive HARQ feedback (e.g., an ACK) to the transmitting device if the message is correctly received, as illustrated at <NUM>. The feedback may be transmitted, e.g., by feedback component <NUM> of apparatus <NUM>.

If the signal strength measured for the message is below the threshold, the receiving device may determine that it is not within the intended range of the transmitting device. Thus, the receiving device may determine to refrain from sending the feedback to the transmitting device, regardless of whether the packet is received correctly or not, as illustrated at <NUM>. In this way, the method disclosed herein may help to avoid feedback from distant UEs, and may help to avoid retransmissions. Aspects of the method may improve performance and reliability of the overall communication system.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a receiving device or a component of a receiving device that receives wireless communication from a transmitting device. The apparatus may comprise a UE <NUM> or a component of a UE, an RSU <NUM> or a component of an RSU, or a base station <NUM>, <NUM> or component of a base station engaged in PC5 communication. The wireless communication may comprise a V2X, V2V, or other D2D communication, as described herein.

The apparatus includes a reception component <NUM> configured to receive, from a transmitting device, at least a portion of a message for a service group, e.g., as described in connection with <NUM> in <FIG>. The reception component may be further configured to receive an indication of a parameter (e.g., the QoS parameter) from the transmitting device, as described in connection with <NUM>. The reception component may use a group ID for a service group to receive the message. The apparatus includes a measurement component <NUM> configured to measure a signal strength for the received message, e.g., as described in connection with <NUM> in <FIG>. The apparatus includes a determination component <NUM> configured to determine whether to send feedback to the transmitting device based on the signal strength measured for the received message, e.g., as described in connection with <NUM> and/or <NUM> of <FIG>. The apparatus includes a feedback component <NUM> configured to transmit a HARQ feedback, via a transmission component <NUM>, to the transmitting device, e.g., as described in connection with <NUM> and/or <NUM> of <FIG>.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the computer-readable medium/memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium/memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium/memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. In one configuration, the processing system <NUM> may be a component of a UE, e.g., device <NUM>, and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>. Alternatively, the processing system <NUM> may comprise the entire device <NUM>, e.g., an entire UE.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for receiving, from a transmitting UE, at least a portion of a message for a service group. The apparatus may include means for measuring a signal strength for the received message received and for determining whether the receiving device is within a range of the transmitting device based on the measured signal strength for the received message. The apparatus may include means for determining to send the feedback when the first receiving device is within the range. The apparatus may include means for sending the feedback, e.g., including sending negative HARQ feedback if the message is not received correctly and sending positive HARQ feedback if the message is received correctly. The apparatus may include means for receiving a parameter from the transmitting device, wherein the threshold is based on the parameter.

<FIG> is a flowchart <NUM> of a method of wireless communication at a transmitting device. The transmitting device may comprise a UE <NUM> or a component of a UE, an RSU <NUM> or a component of an RSU, or a base station <NUM>, <NUM> or component of a base station, e.g., engaged in PC5 communication. The method may be performed, for example, by a transmitting UE <NUM>; transmitting device <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>, which may include memory and which may be an entire UE or a component of a UE. The wireless communication may comprise D2D communication, such as V2X communication, V2V communication, or other D2D communication. To facilitate an understanding of the techniques and concepts described herein, the method of flowchart <NUM> may be discussed with reference to the examples illustrated in <FIG> and <FIG>. Optional aspects may be illustrated in dashed lines. Aspects presented herein may help to limit feedback to avoid retransmissions to a receiving device that may be too distant to correctly receive a message. The method may help reduce system degradation due to such retransmissions, and therefore, may improve the efficient use of wireless resources. The method may also help to avoid reception of feedback from unintended receiving devices that are a part of a service group yet are not proximate to a transmitting device.

At <NUM>, the transmitting device determines an intended range for the service group. The intended range may correspond to a distance from the transmitting device in which receiving device are intended to correctly receive a message. The intended range may be determined, e.g., based on a QoS profile associated with the service group, e.g., a 5QI. The determination may be performed, e.g., by determination component <NUM> of apparatus <NUM>.

At <NUM>, the transmitting device may transmit a message for the service group based, at least in part, on the determined range. The message may comprise a V2X message or a D2D message, for example. The message may be transmitted, e.g., by transmission component <NUM> of apparatus <NUM>. The message may include a control portion and a data portion.

The transmitting device may provide a parameter for the signal strength threshold associated with the service group, as illustrated at <NUM>. The transmitting device may provide the signal strength threshold itself as the parameter or may provide a parameter that enables the receiving device to determine the signal strength threshold. The parameter may be provided, e.g., by IE component <NUM> and/or indication component <NUM>, via transmission component <NUM> of apparatus <NUM>. For example, the parameter may assist receiving devices in determining a signal strength threshold in order to determine whether to send the feedback to the message. Thus, the parameter may help the transmitting device to receive limited feedback from receivers within an intended area. In some aspects, the parameter may include a QoS parameter associated with a service group. The parameter provides information that enables receiving devices to determine whether they are an intended receiver, e.g., based on proximity through the signal strength threshold. For example, the parameter may be comprised in the message.

The message may further comprise an information element associated with a group ID for the service group. The group ID may be provided, e.g., by group ID component <NUM> of apparatus <NUM>. In some aspects, the transmitting device may hash the group ID with the parameter to generate the information element, as illustrated at <NUM>.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a transmitting device or a component of a transmitting device that transmits wireless communication to a receiving device. The apparatus may comprise a UE <NUM> or a component of a UE, an RSU <NUM> or a component of an RSU, or a base station <NUM>, <NUM> or component of a base station engaged in PC5 communication. The wireless communication may comprise a V2X, V2V, or other D2D communication, as described herein.

The apparatus includes a reception component <NUM> that receives feedback from receiving UE(s). The apparatus includes a determination component <NUM> for determining an intended range for a service group. The apparatus may include a transmission component <NUM> for transmitting a message for the service group based, at least in part, on the determined range.

The apparatus may also include an IE component <NUM> for hashing a group ID with an indication of the parameter to generate information element. For example, the apparatus may include an indication component <NUM> for providing a parameter for the signal strength threshold associated with the service group. For example, the signal strength threshold may be used by RX devices to determine whether to send the feedback to the message. For example, the parameter may be comprised in the message. For example, the apparatus may include a group ID component <NUM> for providing a group ID. For example, the message may further comprise the information element associated with the group ID for the service group and the indication.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of <FIG>, <FIG> and <FIG>. As such, each block in the aforementioned flowcharts of <FIG>, <FIG> and <FIG> may be performed by a component and the apparatus may include one or more of those components.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium/memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium/memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. In one configuration, the processing system <NUM> may be a component of device <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>. Alternatively, the processing system <NUM> may comprise the entire device <NUM>, e.g., an entire UE.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for determining an intended range for a service group. The apparatus may include means for transmitting a message for the service group based, at least in part, on the determined range. The apparatus may include means for providing a parameter for a signal strength threshold associated with the service group. The apparatus may include means for hashing a group ID and/or parameter in order to generate an IE.

<FIG> is a flowchart <NUM> of a method of wireless communication at a transmitting device. The transmitting device may comprise a UE <NUM>, a component of a UE <NUM>, an RSU <NUM>, a component of an RSU <NUM>, a base station <NUM>, <NUM>, or component of a base station, e.g., engaged in PC5 communication. The method may be performed, for example, by transmitting UE <NUM>; transmitting device <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>, which may include memory and which may be an entire UE or a component of a UE. The wireless communication may comprise D2D communication, such as V2X communication, V2V communication, or other D2D communication. To facilitate an understanding of the techniques and concepts described herein, the method of flowchart <NUM> may be discussed with reference to the examples illustrated in <FIG> and <FIG>. Optional aspects may be illustrated in dashed lines. Aspects presented herein may help to limit retransmissions to avoid retransmissions to a receiving device that may be too distant to correctly receive a message. The method may help reduce system degradation due to such retransmissions, and therefore, may improve the efficient use of wireless resources. The method may also help to avoid reception of feedback from unintended receiving devices that are a part of a service group yet are not proximate to a transmitting device.

At <NUM>, the transmitting device may transmit a message to a service group for an intended range. The message may be transmitted, e.g., via multicast. An example of a multicast is a groupcast to a group of UEs. The transmission may be performed, e.g., by transmission component <NUM> of apparatus <NUM>. The message may comprise a V2X message or a D2D message.

As illustrated at <NUM>, the transmitting device may provide a parameter for a signal strength threshold. The signal strength threshold may help receiving devices to determine whether they are an intended receiver, e.g., within the intended range. The receiving devices may use the signal strength threshold to determine whether to provide feedback for the message. The parameter may be provided, e.g., by parameter component <NUM> of apparatus <NUM>.

At <NUM>, the transmitting device may receive HARQ feedback from at least one receiving device. The feedback may be received, e.g., by reception component <NUM> of apparatus <NUM>. The feedback may include combined feedback from multiple UEs that is received in a common resource.

At <NUM>, the transmitting device may measure a signal strength for the HARQ feedback. The measurement may be performed, e.g., by measurement component <NUM> of apparatus <NUM>. The measurement may be based on RSSI and/or RSRP, for example. In the example in which the feedback includes combined feedback, the transmitting device may measure the combined signal strength of the combined feedback in the common resource.

At <NUM>, the transmitting device may determine whether the HARQ feedback is from receiving device(s) within the intended range and/or whether the combined signal strength meets a threshold. The determination may be based on the signal strength measured for the HARQ feedback. For example, a signal strength that meets the threshold may indicate that at least one receiving device is within the intended range of the transmitting device. The determination may be performed, e.g., by range component <NUM> of apparatus <NUM>.

At <NUM>, the transmitting device may use the measurement to determine whether to resend the message based on the signal strength measured for the HARQ feedback. For example, the transmitting device may determine to resend the message when the HARQ feedback is from receiving device(s) within the intended range or when the measured signal strength meets a threshold signal strength level. The determination may be performed, e.g., by determination component <NUM> of apparatus <NUM>. The HARQ feedback may be received in a common resource in time and frequency. Thus, the HARQ feedback may comprise combined feedback from one or more receiving devices.

In some aspects, the transmitting device may determine to resend the message if the signal strength measured for the negative HARQ feedback meets a threshold, then the transmitting device may resend the message for the service group, as illustrated at <NUM>. The retransmission may be performed, e.g., by transmission component <NUM> of apparatus <NUM>. On the other hand, the transmitting device may determine to refrain from resending the message if the signal strength measured for the negative HARQ feedback is below the threshold, as illustrated at <NUM>.

For example, the transmitting device may determine the received strength of the NACK from receiving device(s). If the RSSI / RSRP of the NACK exceeds a threshold, then the transmitting device may decide to retransmit. In some aspects, the threshold may be based on at least one of an intended range for the message or a quality of service for the message.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a transmitting device or a component of a transmitting device that transmits wireless communication to a receiving device. The apparatus may comprise a UE <NUM> or a component of a UE, an RSU <NUM> or a component of an RSU, or a base station <NUM>, <NUM> or component of a base station engaged in PC5 communication. The wireless communication may comprise D2D communication, such as V2X communication, V2V communication, or other D2D communication, as described herein.

The apparatus includes a transmission component <NUM> configured to transmit (e.g., multicast) a message to a service group, e.g., as described in connection with <NUM> in <FIG>. The apparatus includes a reception component <NUM> that receives HARQ feedback from at least one receiving device. The apparatus includes a measurement component <NUM> configured to measure a signal strength for the HARQ feedback, e.g., as described in connection with <NUM> in <FIG>. The apparatus may include a range component <NUM> configured to determine whether the HARQ feedback is from a receiving device within the intended range based on the signal strength measured for the HARQ feedback. The apparatus includes a determination component <NUM> configured to determine whether to resend the message based on the signal strength measured for the HARQ feedback, e.g., as described in connection with <NUM> in <FIG>. In some aspects, the transmitting device may determine to resend the message if the signal strength measured for the negative HARQ feedback meets a second threshold, then the transmitting device may resend the message for the service group. On the other hand, the transmitting device may determine to refrain from resending the message if the signal strength measured for the negative HARQ feedback is below the second threshold. In some aspects, the second threshold may be based on at least one of an intended range for the message, or a quality of service for the message, or a combination of the intended range and the quality of service. The apparatus may include a parameter component <NUM> configured to provide a parameter for a signal strength threshold to receiving device(s) <NUM>.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the computer-readable medium/memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium/memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium/memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. In one configuration, the processing system <NUM> may be a component of the device <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for multicasting a message to a service group for an intended range. The apparatus may include means for receiving HARQ feedback from at least one RX UE. The apparatus may include means for measuring a signal strength for the HARQ feedback. The apparatus may include means for determining whether the HARQ feedback is from a receiving device within the intended range based on the signal strength measured for the HARQ feedback. The apparatus may include means for determining to resend the message based on the signal strength measured for the HARQ feedback.

Claim 1:
A method of wireless communication at a receiving device, comprising:
receiving, from a transmitting device, at least a portion of a message for a service group, wherein the message comprises a device-to-device, D2D, message (<NUM>);
measuring a signal strength for the received message (<NUM>);
determining whether the receiving device is within a range of the transmitting device based on the measured signal strength for the received message (<NUM>); and
determining to send HARQ feedback to the transmitting device when the receiving device is within the range of the transmitting device (<NUM>).