WO2020160709A1

WO2020160709A1 - Configured feedback techniques for wireless group cast

Info

Publication number: WO2020160709A1
Application number: PCT/CN2020/074428
Authority: WO
Inventors: Yiqing Cao; Yan Li; Wanshi Chen; Shuping Chen
Original assignee: Qualcomm Incorporated
Priority date: 2019-02-08
Filing date: 2020-02-06
Publication date: 2020-08-13
Also published as: WO2020160688A1

Abstract

Configured feedback techniques for wireless group cast provide fast and reliable sidelink group cast communications between a transmitting device and multiple receiving devices. For example, it may be desirable for a leader of a group of vehicles to transmit a message to all group members and be able to confirm that the message is received. The transmitting device may configure, via a sidelink control channel, sidelink acknowledgment resources for member receiving devices of a group. The transmitting device may transmit a sidelink group cast message to the member receiving devices of the group. The transmitting device may repeat the transmission of the sidelink group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the sidelink group cast message reaches a maximum number of transmissions. Accordingly, the transmitting device may confirm that the sidelink group cast message was correctly received.

Description

CONFIGURED FEEDBACK TECHNIQUES FOR WIRELESS GROUP CAST

CROSS REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority to International Application No. PCT/CN2019/074733 entitled “CONFIGURED FEEDBACK TECHNIQUES FOR WIRELESS GROUP CAST” filed February 8, 2019, which is assigned to the assignees hereof, and incorporated herein by reference in its entirety.

BACKGROUND

Technical Field

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

Introduction

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR) . 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT) ) , and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB) , massive machine type communications (mMTC) , and ultra reliable low latency communications (URLLC) . Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. Aspects of wireless communication may comprise direct communication between devices, such as in V2X, V2V, and/or other D2D communication. There exists a need for further improvements in V2X, V2V, and/or other D2D technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

Vehicle platooning may establish a convoy including a small group of vehicles that coordinate driving behavior. For example, in some implementations, truck platooning may utilize short range communications between 2-5 trucks. Due to the size of trucks, the number of vehicles in the convoy may be limited based on the distance between the first vehicle and last vehicle. Convoys may include larger numbers of small vehicles. In either case, existing group cast mechanisms may not be ideal for vehicle platooning scenarios. In particular, existing group cast mechanisms may not reliably and efficiently confirm that group members have received a transmission.

For example, in a first group cast mechanism, members may transmit a negative control channel transmission acknowledgment if a transmission is not received. While such a mechanism may efficiently conserve resources for large groups, there is no confirmation that a member has received the transmission. In a second group cast mechanism, members may use reserved resources for transmitting a positive acknowledgment or negative control channel transmission acknowledgment in response to each transmission. Such a mechanism may impose significant overhead. Additionally, waiting for each member to respond before retransmitting a message may extend the time until the message is received by the members.

The present disclosure provides configured feedback techniques for wireless group cast that provide fast and reliable group cast communications between a transmitting device and multiple receiving devices in a group. For example, it may be desirable for a leader of a group of vehicles to transmit a message to group members and be able to confirm that the message is received by the group members. The transmitting device may configure, via a control channel, acknowledgment resources for member receiving devices of a group. The transmitting device may transmit a group cast message to the member receiving devices of the group. A receiving device may receive the first transmission of the group cast message and attempt to decode the first transmission of the group cast message from the transmitting device based on the control channel. The receiving device may transmit a positive acknowledgment based on the configuration of acknowledgment resources in response to correctly decoding the group cast message. The receiving device does not transmit an acknowledgment in response to incorrectly decoding the transmission. The transmitting device may repeat the transmission of the group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the group cast message reaches a maximum number of transmissions. Accordingly, the transmitting device may confirm that the group cast message was correctly received or has timed out.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided for wireless communication, e.g., from a transmitting device. The apparatus may configure, via a control channel, acknowledgment resources for member receiving devices of a group. The apparatus may transmit a group cast message to the member receiving devices of the group and may repeat the transmission of the group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the group cast message reaches a maximum number of transmissions

In another aspect, a method, a computer-readable medium, and an apparatus are provided for wireless communication, e.g., at a receiving device. The apparatus may receive, as a member receiving device, via a control channel from a transmitting device, a configuration of acknowledgment resources for a group cast message. The apparatus may attempt to decode a first transmission of the group cast message from the transmitting device based on the control channel. The apparatus may transmit a positive acknowledgment based on the configuration of acknowledgment resources in response to correctly decoding the group cast message, wherein the member receiving device does not transmit an acknowledgment in response to incorrectly decoding the transmission.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIG. 2 illustrates an example of a sidelink slot structure.

FIG. 3 is a diagram illustrating an example of a first device and a second device involved in wireless communication based, e.g., on V2V, V2X, and/or device-to-device communication.

FIG. 4 is a diagram illustrating an example of vehicle platooning.

FIG. 5 is a call flow diagram illustrating an example communication flow between a transmitting device and multiple receiving devices.

FIG. 6 is a timing diagram illustrating various example control channel configurations.

FIG. 7 is a resource diagram showing various example configurations for acknowledgment resources.

FIG. 8 is a flowchart of an example method of wireless communication for a transmitting device.

FIG. 9 is a conceptual data flow diagram illustrating the data flow between different means/components in an example apparatus for a transmitting device.

FIG. 10 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system for a transmitting device.

FIG. 11 is a flowchart of an example method of wireless communication for a receiving device.

FIG. 12 is a conceptual data flow diagram illustrating the data flow between different means/components in an example apparatus for a receiving device.

FIG. 13 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system for a receiving device.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs) , central processing units (CPUs) , application processors, digital signal processors (DSPs) , reduced instruction set computing (RISC) processors, systems on a chip (SoC) , baseband processors, field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more example embodiments, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN) ) includes base stations 102, UEs 104, an Evolved Packet Core (EPC) 160, and a Core Network (e.g., 5GC) 190. The base stations 102 may include macro cells (high power cellular base station) and/or small cells (low power cellular base station) . The macro cells include base stations. The small cells include femtocells, picocells, and microcells.

The base stations 102 configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) ) may interface with the EPC 160 through backhaul links 132 (e.g., S1 interface) . The base stations 102 configured for NR (collectively referred to as Next Generation RAN (NG-RAN) ) may interface with Core Network 190 through backhaul links 184. In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160 or Core Network 190) with each other over backhaul links 134 (e.g., X2 interface) . The backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102' may have a coverage area 110' that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) . The communication links 120 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 /UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. 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) . The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell) .

Certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL/UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH) , a physical sidelink discovery channel (PSDCH) , a physical sidelink shared channel (PSSCH) , and a physical sidelink control channel (PSCCH) . D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 /AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

The small cell 102' may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102' may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cell 102', employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network.

A base station 102, whether a small cell 102' or a large cell (e.g., macro base station) , may include an eNB, gNodeB (gNB) , or other type of base station. Some base stations, such as gNB 180 may operate in a traditional sub 6 GHz spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies in communication with the UE 104. When the gNB 180 operates in mmW or near mmW frequencies, the gNB 180 may be referred to as an mmW base station. Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in the band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW /near mmW radio frequency band has extremely high path loss and a short range. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the extremely high path loss and short range.

The base station 180 may transmit a beamformed signal to the UE 104 in one or more transmit directions 182'. The UE 104 may receive the beamformed signal from the base station 180 in one or more receive directions 182″ . The UE 104 may also transmit a beamformed signal to the base station 180 in one or more transmit directions. The base station 180 may receive the beamformed signal from the UE 104 in one or more receive directions. The base station 180 /UE 104 may perform beam training to determine the best receive and transmit directions for each of the base station 180 /UE 104. The transmit and receive directions for the base station 180 may or may not be the same. The transmit and receive directions for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. User Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service, and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN) , and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The Core Network 190 may include an Access and Mobility Management Function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 may be in communication with a Unified Data Management (UDM) 196. The AMF 192 is the control node that processes the signaling between the UEs 104 and the Core Network 190. Generally, the AMF 192 provides QoS flow and session management. User Internet protocol (IP) packets are transferred through the UPF 195. The UPF 195 provides UE IP address allocation as well as other functions. The UPF 195 is connected to the IP Services 197. The IP Services 197 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service, and/or other IP services.

The base station may also 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 102 provides an access point to the EPC 160 or Core Network 190 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or any other similar functioning device. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc. ) . The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, a UE 104a, e.g., a transmitting Vehicle User Equipment (VUE) or other UE, may be configured to transmit messages directly to another UE 104, e.g., UE 104b. The communication may be based on V2V/V2X or other D2D communication, such as Proximity Services (ProSe) . Communication based on V2V, V2X, and/or other D2D may also be transmitted and received by other transmitting and receiving devices, such as Road Side Unit (RSU) 107, etc. Aspects of the communication may be based on PC5 or sidelink communication.

Referring again to FIG. 1, in certain aspects, a UE 104a or RSU 107 (e.g., a transmitting device) may comprise a group cast transmitter component 198 configured to configure, via a control channel, acknowledgment resources for member receiving devices (e.g. UE 104b) of a group. The group cast transmitter component 198 may be configured to transmit a group cast message to the member receiving devices of the group. The group cast transmitter component 198 may be configured to repeat the transmission of the group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the group cast message reaches a maximum number of transmissions.

In other aspects, a UE 104b (e.g., a receiving device) may comprise a group cast receiver component 140 configured to receive, at a member receiving device via a control channel from a transmitting device, a configuration of acknowledgment resources for a group cast message. The group cast receiver component 140 may be configured to attempt to decode a first transmission of the group cast message from the transmitting device based on the control channel. The group cast receiver component 140 configured to transmit a positive acknowledgment based on the configuration of acknowledgment resources in response to correctly decoding the group cast message, wherein the member receiving device does not transmit an acknowledgment in response to incorrectly decoding the transmission.

FIG. 2 illustrates example diagrams 200 and 210 illustrating examples slot structures that may be used for wireless communication between UE 104 and UE 104’, e.g., for sidelink communication. The slot structure may be within a 5G/NR frame structure. Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies. This is merely one example, and other wireless communication technologies may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms) . Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. Each slot may include 7 or 14 symbols, depending on the slot configuration. For slot configuration 0, each slot may include 14 symbols, and for slot configuration 1, each slot may include 7 symbols. Diagram 200 illustrates a single slot transmission, e.g., which may correspond to a 0.5 ms transmission time interval (TTI) . Diagram 210 illustrates an example two-slot aggregation, e.g., an aggregation of two 0.5 ms TTIs. Diagram 200 illustrates a single RB, whereas diagram 210 illustrates N RBs. In diagram 210, 10 RBs being used for control is merely one example. The number of RBs may differ.

A resource grid may be used to represent the frame structure. Each time slot may include a resource block (RB) (also referred to as physical RBs (PRBs) ) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs) . The number of bits carried by each RE depends on the modulation scheme. As illustrated in FIG. 2, some of the REs may comprise control information, e.g., along with demodulation RS (DMRS) . FIG. 2 also illustrates that symbol (s) may comprise CSI-RS. The symbols in FIG. 2 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 1 and a comb-2 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 1, 2, or 4 symbols depending on a configured number of ports. CSI-RS can be periodic, semi-persistent, or aperiodic (e.g., based on control information 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 12 is illustrated for data, it may instead be a gap symbol to enable turnaround for feedback in symbol 13. 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. 2. Multiple slots may be aggregated together. FIG. 2 also illustrates an example aggregation of two slot. 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. 3 is a block diagram 300 of a first wireless communication device 310 in communication with a second wireless communication device 350, e.g., via V2V/V2X/other D2D communication. The device 310 may comprise a transmitting device communicating with a receiving device, e.g., device 350, via V2V/V2X/other D2D communication. The communication may be based, e.g., on sidelink. The transmitting device 310 may comprise a UE, an RSU, etc. The receiving device may comprise a UE, an RSU, etc. Packets may be provided to a controller/processor 375 that implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the device 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the device 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the device 350. If multiple spatial streams are destined for the device 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by device 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by device 310 on the physical channel. The data and control signals are then provided to the controller/processor 359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. The controller/processor 359 may provide demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the transmission by device 310, the controller/processor 359 may provide RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression /decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ; RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by device 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

The transmission is processed at the device 310 in a manner similar to that described in connection with the receiver function at the device 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. The controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Vehicle platooning is an important use case for D2D communications. In particular, vehicle manufactures in different geographic regions may utilize D2D communications for vehicle platooning. One definition of platooning is the linking of multiple vehicles in a convoy, e.g., a communication group comprising two, three, or more vehicles. These vehicles may closely follow each other using a set, close distance by using connectivity technology and automated driving support systems. In an aspect, V2V, V2X, or other D2D communications may serve as the connectivity technology.

The vehicle platooning use cases may impose unique conditions on such V2X communications. For example, platooning may require a low latency, high reliability group cast mechanism among members. However, conventional group cast mechanisms in may not designed for small groups and high reliability. For example, two mechanisms include -1) negative acknowledgment (NAK) /discontinuous transmission (DTX) based –better for large group size; and 2) acknowledgment (ACK) /NAK/DTX based.

In a first group cast mechanism, members may transmit a negative acknowledgment (NACK) if a transmission is not received. While such a mechanism may efficiently conserve resources for large groups, there is no confirmation that a member has received the transmission. In a second group cast mechanism, members may use reserved resources for transmitting a positive acknowledgment (ACK) or NACK in response to each transmission. Such a mechanism may impose significant overhead. Additionally, waiting for each member to respond before retransmitting a message may extend the time until the message is received by the members.

The present disclosure provides configured feedback techniques for wireless group cast that provide fast and reliable group cast communications between a transmitting device and multiple receiving devices in a group. For example, aspects presented herein enable a transmitting device to ensure that the group members receive a message while reducing latency.

In an aspect, at a high level, the current disclosure includes an ACK/Discontinuous Transmission (DTX) based endless HARQ mechanism. The transmitter may keep on repeating the information (e.g., a group cast message) to members of a platooning group for up to a maximum number, N, times or until all the members send ACK. The ACK resources may be reserved and assigned by the transmitter for each individual member to avoid collision. For example, no NAK may be required from members.

FIG. 4 illustrates an example 400 of wireless communication between devices based on V2X/V2V/other D2D communication. Transmitting device 402 transmits a transmission 414, e.g., comprising a control channel and/or a corresponding data channel, that may be received by receiving

devices

404, 406, 408. The

devices

402, 404, 406, 408 may each be capable of operating as a transmitting device in addition to operating as a receiving device. In particular, the receiving

devices

404, 406, 408 may transmit positive acknowledgments of the transmission 414. Thus, device 406 is illustrated as transmitting a transmission 420 and device 408 is illustrated as transmitting a transmission 420. Device 404 is illustrated with no transmission, which may signify that the device 404 did not receive or correctly decode the transmission 414. The

transmissions

414, 416, 420 may be broadcast or multicast to nearby devices. In addition to receiving

devices

404, 406, 408, the transmitting device 402 may also transmit or receive communication from RSU 407 and other devices.

In an aspect, the transmitting device 402 may be the leader of a convoy or platoon 430. The platoon 430 may include the receiving

devices

404, 406, 408. For example the transmitting device 402 may be a first vehicle in a group of vehicles traveling together along a road 401. The transmission 414 may include information for the members of the platoon such as, for example, acceleration/deceleration commands, vehicle spacing, road conditions, or other information for controlling a vehicle associated with one of the receiving

devices

404, 406, 408. The transmitting device 402 may be configured with identifiers of each of the receiving

devices

404, 406, 408 in the platoon 430. The transmitting device 402 may broadcast or multicast the transmission 414 such that each of the receiving

devices

404, 406, 408 receive the transmission 414. For example, the transmitting device 402 may use beamforming to transmit the transmission 414 over a coverage area 440 including the platoon 430 The transmitting device 402 may receive the

transmissions

416, 420 as acknowledgments of the transmission 414. The transmitting device 402 may determine that the receiving device 404 did not correctly receive the transmission 414 by determining the number or sources of the

transmissions

416, 420 indicating acknowledgment. The transmitting device 402 may retransmit the transmission 414 until the members of the group, e.g., each of the members of the group. have acknowledged the transmission 414.

FIG. 5 illustrates an example communication flow 500 between a transmitting device 502 and multiple receiving

devices

504, 504, 508. The communication may be based on V2X, V2V, or other D2D based communication directly from a transmitting device to a receiving device. The communication transmitting from transmitting device 502 may be broadcast and received by multiple receiving devices within range of a particular transmitting device, as described in connection with FIG. 4.

The transmitting device 502 may be an example of the UE 104a and include the group cast transmitter component 198. The receiving

devices

504, 506, 508 may each be an example of the UE 104b and include an implementation of the group cast receiver component 140. Each of the receiving

devices

504, 506, 508 may be in a group with the transmitting device 502. The transmitting device 502 may act as a leader, at least for a current group cast message. In an aspect, each of the receiving

devices

504, 506, 508 may be a vehicle, be located within a vehicle, and/or be communicatively coupled to a vehicle. For example, the vehicles corresponding to the receiving

devices

504, 506, and 508 may form a convoy with the vehicle corresponding to the transmitting device 502 and use group cast messages to communicate among the members of the convoy. The present disclosure, however, is not limited to a vehicle platooning use case, and the disclosed techniques for group cast communications may be utilized for any purpose.

The transmitting device 502 may initiate a group cast message by transmitting a group control channel 510. The group control channel 510 may be transmitted to each of the receiving

devices

504, 506, 508. That is, the group control channel 510 may be transmitted in a manner that each of the receiving

devices

504, 506, 508 may receive the same transmission. For example, the group control channel 510 may be scrambled with a group identifier known to the group members. As discussed in further detail below, the group control channel 510 may schedule one or more transmissions of the group cast message. The group control channel may also indicate acknowledgment resources that may be used by the receiving

devices

504, 506, 508 to acknowledge successful receipt and decoding of the group cast message.

The transmitting device 502 may transmit a first transmission 512 of the group cast message. The first transmission 512 may be transmitted as indicated by the schedule of the group control channel 510. For example, the first transmission 512 may utilize time-frequency resources, sequences, redundancy version, and new data indicator indicated by the group control channel 510.

Each of the receiving

devices

504, 506, 508 may perform a

corresponding decode operation

514, 516, 518 on the first transmission 512. In an aspect, due to different channel conditions, each of the receiving

devices

504, 506, 508 may receive the first transmission 512 differently. Accordingly, the

decode operation

514, 516, 518 may or may not be successful for each receiving

devices

504, 506, 508. For example, as illustrated, the receiving device 504 may successfully decode the first transmission 512 in the decode operation 514, but the decode operations 516, 518 may be unsuccessful.

The receiving device 504 may transmit a positive acknowledgment 520 in response to the successful decode operation 514. The receiving device 504 may transmit the positive acknowledgment 520 using acknowledgment resources indicated by the group control channel 510. In an aspect, the receiving device 506 and receiving device 508, which performed unsuccessful decode operations 516 and 518, may not transmit any acknowledgment. That is, the receiving

devices

506, 508 may not transmit a negative acknowledgment.

The transmitting device 502 may optionally transmit a second group control channel 522. In some cases, the group control channel 510 may schedule transmissions and retransmissions, and the second group control channel 522 may not be transmitted. The second group control channel 522 may schedule a retransmission 524 of the group cast message. The second group control channel 522 may also specify acknowledgment resources for acknowledging the retransmission 524.

The transmitting device 502 may transmit the retransmission 524 to the receiving devices in the group, i.e., receiving

devices

504, 506, 508. The retransmission 524 may be the same message, or a different redundancy version of the first transmission 512, as indicated by the group control channel 510 and/or the second group control channel 522. In an aspect, the receiving device 504 may not receive the retransmission 524 because the receiving device 504 has already correctly decoded the group cast message. The receiving device 506 and receiving device 508, however, may attempt to decode the retransmission 524 in response to the previous unsuccessful decode operations 516, 518 by performing

decode operations

526, 528, respectively. If the retransmission 524 uses a different redundancy version than the first transmission 512, the

decode operations

526, 528 may combine the first transmission 512 and the retransmission 524. In this example, the

decode operations

526, 528 may both be unsuccessful. Accordingly, neither the receiving device 506 nor the receiving device 508 may transmit an acknowledgment in response to the unsuccessful decode operation.

The transmitting device 502 may optionally transmit a third group control channel 530 In some cases, the group control channel 510 may schedule transmissions and retransmissions, and the third group control channel 530 may not be transmitted. The third group control channel 530 may schedule a retransmission 532 of the group cast message. The third group control channel 530 may also specify acknowledgment resources for acknowledging the retransmission 532.

The transmitting device 502 may transmit the retransmission 532 to the receiving devices in the group, i.e., receiving

devices

504, 506, 508. The retransmission 524 may be the same message, or a different redundancy version of the first transmission 512 and the retransmission 524, as indicated by the group control channel 510 and/or the third group control channel 530. In an aspect, the receiving device 504 may not receive the retransmission 532 because the receiving device 504 has already correctly decoded the group cast message. The receiving device 506 and receiving device 508, however, may attempt to decode the retransmission 532 in response to the previous

unsuccessful decode operations

526, 528 by performing

decode operations

536, 538, respectively. If the retransmission 532 uses a different redundancy version than the first transmission 512 and/or the retransmission 524, the

decode operations

536, 538 may combine the first transmission 512 and/or the retransmission 524 with the retransmission 532. In this example, the

decode operations

536, 538 may both be successful. Accordingly, the receiving device 506 may transmit a positive acknowledgment 540 and the receiving device 508 may transmit a positive acknowledgment 542 in response to the respective successful decode operation. The transmitting device 502 may cease any additional retransmissions of the group case message once the transmitting device 502 has received an acknowledgment from each of the group

member receiving devices

504, 506, 508. In another aspect, the transmitting device 502 may continue retransmissions until a configured maximum number of transmissions has been transmitted.

Turning to FIG. 6, a diagram 600 shows several options for scheduling group cast transmissions and retransmissions. In a first option 610, one control channel may semi-persistently schedule multiple transmissions. The control channel may indicate, e.g., time-frequency resources, redundancy versions, NDI for 1st packet, and etc. for each of the multiple transmissions. The multiple transmissions may include a first transmission and retransmission (s) of the first transmission. As an example, the control channel may schedule the first transmission and the maximum number of retransmissions. For example, the control channel 612 may schedule a transmission 614 and

retransmissions

616, 618. The control channel 612 may also indicate the acknowledgment resources for each transmission and retransmission. In an aspect, the transmitting device 602 may check for acknowledgments following each transmission or retransmission at

feedback checkpoints

660, 662, 664. If the transmitting device 602 has received an acknowledgment from each member of the group by one of the

feedback checkpoints

660, 662, 664, the transmitting device 602 may omit subsequent retransmissions.

In a second option, 620, a control channel may indicate the resources for a next control channel and the scheduling information for the corresponding group cast transmission. (resources, NDI, RV, and etc. ) . For example, a first control channel 622 may indicate resources for the subsequent control channel 624. The first control channel 622 may also schedule a group cast transmission 632. The control channel may indicate the resources for a subsequent control channel 626 and schedule the retransmission 634. The control channel 626 may be a last control channel corresponding to the maximum number of transmissions. The control channel 626 may schedule the transmission 636, but may not indicate resources for a subsequent control channel

In a third option 640, a first control channel may semi-persistently schedule the maximum number of transmissions, and each retransmission may be associated with another control channel that repeats the scheduling information and/or provides additional information. For example, the third option 640 may allow the transmitting device 602 to change a redundancy version based on the received acknowledgments. For example, the first control channel 642 may schedule the transmission 652 and

retransmissions

654 and 656. The transmitting device 602 may also transmit a second control channel 644 for the retransmission 654 and a third control channel 646 for the retransmission 656.

Turning to FIG. 7, a diagram 700 shows options for acknowledgment resources. The options are illustrated with respect to the third option 740 of FIG. 7, but similar configurations of acknowledgment resources may be used with the other scheduling options.

In a first option 710, the feedback resources and transmission parameters (transmission power, Modulation and Coding Scheme (MCS) , beam information, etc. ) for each receiving device may be configured with a 1 to 1 mapping. That is, each receiving

device

504, 506, 508 may be configured with specific resources for transmitting an acknowledgment. Accordingly, the acknowledgments will not collide and the transmitting device 502 may determine which receiving devices have successfully decoded the group cast message.

In a second option 720, the feedback resource pool may be configured by the transmitter UE and receiving UEs may randomly pick resources for transmitting the acknowledgment. For example, the first control channel 642 may specify the resource pool 722. If the receiving device 504 successfully decodes the transmission 552, the receiving device 504 may transmit a positive acknowledgment using any of the resources in the resource pool 722. In one aspect, the receiving device 504 may include an identifier with the positive acknowledgment. The transmitting device 502 may use the identifier to determine which receiving devices have successfully received the group cast message. In another aspect, the receiving device 504 may not include an identifier. Instead, the transmitting device 502 may count a number of received acknowledgments.

FIG. 8 is a flowchart of a method 800 of wireless communication. The method may 800 be performed by a transmitting device or a component of a transmitting device (e.g., the UE 104a or RSU 107 including a group cast transmitter component 198, transmitting

device

402, 502, the apparatus 902/902'; the processing system 1014, which may include memory and which may be an entire UE or a component of a UE, such as the TX processor 368, the RX processor 356, and/or the controller/processor 359) . Optional aspects are illustrated with a dashed line. The method may improve the reliability, e.g., of communication in a platooning group, in a manner that improves latency.

At block 810, the transmitting device 104a may configure, via a sidelink control channel, sidelink acknowledgment resources for member receiving devices of a group. In an aspect, the resource component 908 may determine sidelink acknowledgment resources for the receiving devices. The resource component 908 may generate a sidelink control channel specifying the acknowledgment resources, and the transmission component 910 may transmit the sidelink control channel to the receiving devices (e.g., UE 104b, receiving

devices

404, 406, 408) . In an aspect, for example, at sub-block 812, the resource component 908 may specify transmission parameters for each receiving device of the group. The sidelink control channel may include, for example, resources associated with an identifier of each receiving device. As another example, at sub-block 814, the resource component 908 may configure a resource pool from which the member receiving devices of the group may select resources for transmitting the acknowledgment. The sidelink control channel may specify the resource pool.

The sidelink control channel may also schedule the sidelink group cast message. In an aspect, for example, the sidelink control channel may include a transmission prior to the group cast message that schedules the number of transmissions of the sidelink group cast message. For instance, the sidelink control channel may indicate time-frequency resources, sequences, redundancy version, and a new data indicator for each of the number of transmissions of the group cast message. In another aspect, the sidelink control channel may include a control channel transmission prior to each transmission of the sidelink group cast message. Each control channel transmission may schedule the corresponding transmission of the sidelink group cast message and a subsequent control channel transmission.

At block 820, the transmitting device 104a may transmit a sidelink group cast message to the member receiving devices of the group. For example, the message component 906 may generate the sidelink group cast message. The sidelink group cast message may include, for example, vehicle control commands to other members of a vehicle platoon. In an aspect, the sidelink group cast message may be valid for a limited period, and the message component 906 may determine a maximum number of transmissions based on the limited period. In another aspect, the maximum number of transmissions may be the same for each transmission and may be configured when forming the group. The message component 906 may provide the maximum number of transmissions to the retransmission component 914.

At block 830, the transmitting device 104a may optionally count a number of received acknowledgments. For example, the reception component 904 may receive the acknowledgments from the group member receiving devices and provide the acknowledgments to the acknowledgment component 912. The acknowledgment component 912 may count a number of received acknowledgments for the sidelink group cast message to determine whether the group member receiving devices have acknowledged the sidelink group cast message.

At block 840, the transmitting device 104a may repeat the transmission of the sidelink group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the sidelink group cast message reaches a maximum number of transmissions. For example, the retransmission component 914 may repeat the transmission of the sidelink group cast message. The retransmission component 914 may receive a number of and/or identifiers for remaining receiving devices from the acknowledgment component 912 that receives the acknowledgments from the group member receiving devices. The retransmission component 914 may also track the number of transmissions and compare the number of transmissions to the configured maximum number of transmissions. If there is at least one group member that has not acknowledged the transmission and the number of transmissions has not reached the maximum number of transmissions, the retransmission component 914 may send a retransmission to the transmission component 910.

In an aspect, at sub-block 842, the retransmission component 914 may transmit the sidelink group cast message with a different redundancy version. The retransmission component 914 may send the retransmission and the redundancy version to a redundancy component 916. The redundancy component 916 may generate an encoded transmission based on the redundancy version. The encoded transmission may allow combining the retransmission with one or more previous transmissions.

FIG. 9 is a conceptual data flow diagram 900 illustrating the data flow between different means/components in an example apparatus 902. The apparatus 902 may be a transmitting device or a component of a transmitting device, e.g., UE 104a. The apparatus 902 includes a reception component 904 that receives acknowledgments of sidelink group cast messages, a message component 906 that generates a sidelink group cast message, a resource component 908 that generates a sidelink control channel indicating resources for the sidelink group cast message and acknowledgments of the sidelink group cast message, a transmission component 910 that transmits the control channel and the sidelink group cast message, an acknowledgment component 912 that determines whether members of the group have received the sidelink group cast message, a retransmission component 914 that generates a retransmission, and a redundancy component 916 that generates an encoded transmission based on a retransmission and a redundancy version.

The apparatus 902 may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of FIG. 8, and/or aspects described in connection with FIGs. 4-7. As such, each block in the aforementioned flowchart of FIG. 8 and/or aspects described in connection with FIGs. 4-7 may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

FIG. 10 is a diagram 1000 illustrating an example of a hardware implementation for an apparatus 902' employing a processing system 1014. The processing system 1014 may be implemented with a bus architecture, represented generally by the bus 1024. The bus 1024 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1014 and the overall design constraints. The bus 1024 links together various circuits including one or more processors and/or hardware components, represented by the processor 1004, the

components

904, 906, 908, 910, 912, 914, 916 and the computer-readable medium /memory 1006. The bus 1024 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 1014 may be coupled to a transceiver 1010. The transceiver 1010 is coupled to one or more antennas 1020. The transceiver 1010 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1010 receives a signal from the one or more antennas 1020, extracts information from the received signal, and provides the extracted information to the processing system 1014, specifically the reception component 904. In addition, the transceiver 1010 receives information from the processing system 1014, specifically the transmission component 910, and based on the received information, generates a signal to be applied to the one or more antennas 1020. The processing system 1014 includes a processor 1004 coupled to a computer-readable medium /memory 1006. The processor 1004 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1006. The software, when executed by the processor 1004, causes the processing system 1014 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1006 may also be used for storing data that is manipulated by the processor 1004 when executing software. The processing system 1014 further includes at least one of the

components

904, 906, 908, 910, 912, 914, 916. The components may be software components running in the processor 1004, resident/stored in the computer readable medium /memory 1006, one or more hardware components coupled to the processor 1004, or some combination thereof. The processing system 1014 may be a component of the device 310 or the device 350 and may include the

memory

376, 360 and/or at least one of the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

375, 359. Alternately, the processing system 1014 may be the

entire device

310 or 350, such as an entire UE, and entire RSU, etc.

In one configuration, the apparatus 902/902' for wireless communication includes means for configuring, via a control channel, acknowledgment resources for member receiving devices of a group; means for transmitting a group cast message to the member receiving devices of the group; and means for repeating the transmission of the group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the group cast message reaches a maximum number of transmissions. The apparatus 902/902' may also include means for counting a number of received acknowledgments. The aforementioned means may be one or more of the aforementioned components of the apparatus 902 and/or the processing system 1014 of the apparatus 902' configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1014 may include the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

375, 359. As such, in one configuration, the aforementioned means may be the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

375, 359 configured to perform the functions recited by the aforementioned means.

FIG. 11 is a flowchart of a method 1100 of wireless communication. The method 1100 may be performed by a receiving device or a component of a receiving device (e.g., the UE 104b including a group cast receiver component 140, the receiving

device

404, 406, 408, 504, 506, 508, the apparatus 1202/1202'; the processing system 1314, which may include memory and which may be an entire UE or a component of a UE, such as the TX processor 368, the RX processor 356, and/or the controller/processor 359) . The method 1100 may be performed in combination with the method 800 being performed by a transmitting device (e.g., the UE 104a including the group cast transmitter component 198, or apparatus 902/902'. Optional aspects are illustrated with a dashed line. The method may improve the reliability, e.g., of communication in a platooning group, in a manner that improves latency.

At block 1110, the receiving device 104b may receive, via a sidelink control channel from a transmitting device, a configuration of sidelink acknowledgment resources for a sidelink group cast message. For example, the reception component 1204 may receive the control channel and send the control channel to a resource component 1208. The resource component 1208 may decode the control channel and extract the configuration of sidelink acknowledgment resources. The resource component 1208 may provide the configuration of sidelink acknowledgment resources to the transmission component 1210. The configuration of sidelink acknowledgment resources may specify transmission parameters for each receiving device of the group. The sidelink control channel may include, for example, resources associated with an identifier of each receiving device. As another example, the configuration of sidelink acknowledgment resources may specify a resource pool from which the member receiving devices of the group may select resources for transmitting the acknowledgment.

The sidelink control channel control may also schedule the sidelink group cast message. In an aspect, for example, the sidelink control channel may include a transmission prior to the group cast message that schedules the number of transmissions of the sidelink group cast message. For instance, the sidelink control channel may indicate time-frequency resources, sequences, redundancy version, and a new data indicator for each of the number of transmissions of the sidelink group cast message. In another aspect, the sidelink control channel may include a control channel transmission prior to each transmission of the sidelink group cast message. Each control channel transmission may schedule the corresponding transmission of the sidelink group cast message and a subsequent control channel transmission.

At block 1120, the receiving device 104b may attempt to decode a first transmission of the sidelink group cast message from the transmitting device based on the sidelink control channel. For example, the resource component 1208 may determine message resources based on the sidelink control channel and provide the message resources to the decoder component 1212. The message resources may include, for example, time-frequency resources, sequences, redundancy version, and new data indicator. The reception component 1204 may provide the received sidelink group cast message to the decoder component 1212. The decoder component 1212 may attempt to decode the sidelink group cast message according to the message resources. Due to, for example, interference or varying channel conditions, the decoder component 1212 may be successful or unsuccessful in decoding the received sidelink group cast message. If successful, the decoder component may indicate the success to an acknowledgment component 1214. If unsuccessful, the decoder component 1212 may indicate the failure to a combining component 1216.

At block 1130, the receiving device 104b may optionally receive a retransmission of the sidelink group cast message after incorrectly decoding the sidelink group cast message. For example, the reception component 1204 may receive the retransmission of the sidelink group cast message. The reception component 1204 may send the retransmission of the sidelink group cast message to the decoder component 1212. In an aspect, the retransmission of the sidelink group cast message may be scheduled by the initial sidelink control channel, or may be scheduled by a new sidelink control channel. In either case, the resource component 1208 may provide the message resources for the retransmission to the decoder component 1212.

In block 1140, the receiving device 104b may optionally combine the first transmission and the retransmission. For example, the combining component 1216 may provide the previous transmission to the decoder component 1212. Accordingly, if the transmission and retransmission use different redundancy versions (e.g., as indicated by the control channel) , the decoder component 1212 may combine the transmissions using known decoding techniques. The decoder component 1212 may then attempt to decode the retransmission, which may result in either success or failure. The

blocks

1120, 1130, 1140 may be repeated for each retransmission of the group cast message.

At block 1150, the receiving device 104b may transmit a positive acknowledgment based on the configuration of sidelink acknowledgment resources in response to correctly decoding the sidelink group cast message. The member receiving device (e.g., the UE 104b) may not transmit an acknowledgment in response to incorrectly decoding the transmission. For example, when the decoder component 1212 indicates success, the acknowledgment component 1214 may provide a positive acknowledgment to the transmission component 1210 for transmission on the ACK resources indicated by the resource component 1208 to the transmitting device (e.g., UE 104a or transmitting device 902/902'.

In an aspect, at sub-block 1152, the receiving device 104b may select resources for transmitting the positive acknowledgment from the resource pool. For example, in the case where the configuration of sidelink acknowledgment resources indicates a resource pool, the resource component 1208 may select the resources for transmitting the positive acknowledgment. For instance, the resource component 1208 may randomly or pseudo-randomly select the resources for transmitting the positive acknowledgment from the resource pool. In an aspect, the positive acknowledgment may include an identifier of the member receiving device. For example, the identifier may be included in the positive acknowledgment, or may be used to scramble the positive acknowledgment. Accordingly, the apparatus 902 may determine which member receiving devices have acknowledged the group cast message. If the identifier is not included, the apparatus 902 may count positive acknowledgments to determine whether each member of the group has acknowledged the sidelink group cast message.

FIG. 12 is a conceptual data flow diagram 1200 illustrating the data flow between different means/components in an example apparatus 1202. The apparatus 1202 may be a receiving device or a component of a receiving device, e.g., UE 104b. The apparatus 1202 includes a reception component 1204 that receives a sidelink control channel and sidelink group cast message from a transmitting device (e.g., apparatus 902) , a resource component 1208 that determines sidelink resources for the sidelink group cast message and acknowledgments of the sidelink group cast message based on the control channel, a transmission component 1210 that transmits the positive acknowledgment, a decoder component 1212 that decodes the sidelink group cast message based on the sidelink control channel, an acknowledgment component 1214 that generates a positive acknowledgment in response to successful decoding of the sidelink group cast message, and a combining component 1216 that combines a retransmission with one or more previous transmissions based on a redundancy version.

The apparatus 902 may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of FIG. 11. As such, each block in the aforementioned flowchart of FIG. 11 may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

FIG. 13 is a diagram 1300 illustrating an example of a hardware implementation for an apparatus 1202' employing a processing system 1314. The processing system 1314 may be implemented with a bus architecture, represented generally by the bus 1324. The bus 1324 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1314 and the overall design constraints. The bus 1324 links together various circuits including one or more processors and/or hardware components, represented by the processor 1304, the

components

1204, 1208, 1210, 1212, 1214, 1216 and the computer-readable medium /memory 1306. The bus 1324 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 1314 may be coupled to a transceiver 1310. The transceiver 1310 is coupled to one or more antennas 1320. The transceiver 1310 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1310 receives a signal from the one or more antennas 1320, extracts information from the received signal, and provides the extracted information to the processing system 1314, specifically the reception component 1204. In addition, the transceiver 1310 receives information from the processing system 1314, specifically the transmission component 1210, and based on the received information, generates a signal to be applied to the one or more antennas 1320. The processing system 1314 includes a processor 1304 coupled to a computer-readable medium /memory 1306. The processor 1304 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1306. The software, when executed by the processor 1304, causes the processing system 1314 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1306 may also be used for storing data that is manipulated by the processor 1304 when executing software. The processing system 1314 further includes at least one of the

components

1204, 1208, 1210, 1212, 1214, 1216. The components may be software components running in the processor 1304, resident/stored in the computer readable medium /memory 1306, one or more hardware components coupled to the processor 1304, or some combination thereof. The processing system 1314 may be a component of the device 310 or the device 350 and may include the

memory

376, 360 and/or at least one of the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

375, 359. Alternately, the processing system 1314 may be the

entire device

310 or 350, such as an entire UE, and entire RSU, etc.

In one configuration, the apparatus 1202/1202' for wireless communication includes means for receiving, at a member receiving device via a control channel from a transmitting device, a configuration of acknowledgment resources for a group cast message; means for attempting to decode a first transmission of the group cast message from the transmitting device based on the control channel; and means for transmitting a positive acknowledgment based on the configuration of acknowledgment resources in response to correctly decoding the group cast message. The apparatus 1202/1202' may also include means for receiving a retransmission of the group cast message after incorrectly decoding the group cast message, and means for combining the first transmission and the retransmission. The aforementioned means may be one or more of the aforementioned components of the apparatus 1202 and/or the processing system 1314 of the apparatus 1202' configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1014 may include the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

375, 359. As such, in one configuration, the aforementioned means may be the

TX processor

316, 368, the

RX processor

370, 356, and the controller/

processor

In view of the foregoing, the present disclosure provides configured feedback techniques for group cast communications. The transmitting device may utilize a continuous HARQ process, where retransmissions may occur until an acknowledgment is received from every receiving device in the group or a maximum number of transmissions is reached. The continuous HARQ process may allow rapid retransmissions, which may be useful in a vehicle platooning scenario where the receiving devices may benefit from low latency. Also, because the receiving devices transmit only positive acknowledgments when successfully decoding the group cast message, overhead for acknowledgments may be reduced compared to an ACK/NACK protocol, while the transmitting device may still confirm that each group member has received the group cast message.

In an aspect, a single control channel transmission may schedule the transmission as well as retransmissions of the group cast message. The single control channel transmission may conserve resources and/or reduce a time between retransmissions. In another aspect, a control channel may be transmitted with each retransmission, thereby providing redundancy in the event that the original control channel is not received correctly.

In another aspect, the transmitting device may specify acknowledgment resources for each receiving device, thereby preventing collisions between acknowledgments. In another aspect, the transmitting device may specify a pool of acknowledgment resources, which may reduce the number of required resources for larger groups.

It is understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

Claims

A method of wireless communication, comprising:

configuring, via a sidelink control channel, sidelink acknowledgment resources for member receiving devices of a group;

transmitting a sidelink group cast message to the member receiving devices of the group; and

repeating transmission of the sidelink group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the sidelink group cast message reaches a maximum number of transmissions.
The method of claim 1, wherein repeating the transmission of the sidelink group cast message comprises transmitting the sidelink group cast message with a different redundancy version, wherein the sidelink control channel specifies a corresponding redundancy version.
The method of claim 1, wherein the member receiving devices transmit only positive acknowledgments on the sidelink acknowledgment resources.
The method of claim 1, wherein the sidelink control channel comprises a control channel transmission prior to the sidelink group cast message that schedules the number of transmissions of the sidelink group cast message.
The method of claim 4, wherein the sidelink control channel indicates one or more of time-frequency resources, at least one sequence, a redundancy version, or a new data indicator for each of the number of transmissions of the sidelink group cast message.
The method of claim 1, wherein the sidelink control channel includes a control channel transmission prior to each transmission of the sidelink group cast message, each control channel transmission scheduling a corresponding transmission of the sidelink group cast message and a subsequent control channel transmission.
The method of claim 1, wherein configuring the sidelink acknowledgment resources for the member receiving devices of the group comprises specifying transmission parameters for each member receiving device of the group.
The method of claim 7, wherein the transmission parameters include one or more of:transmission power, time-frequency resources, modulation and coding scheme, and beam configuration.
The method of claim 1, wherein configuring the sidelink acknowledgment resources for the member receiving devices of the group comprises configuring a resource pool from which the member receiving devices of the group select resources for transmitting the acknowledgment.
The method of claim 9, wherein the acknowledgment comprises an ID, further comprising determining which member of the group transmitted the acknowledgment based on the ID.
The method of claim 9, further comprising counting a number of received acknowledgments.
The method of claim 1, wherein the sidelink acknowledgment resources are multiplexed using one or more of frequency division multiplexing, time division multiplexing, and code division multiplexing.
A method of wireless communication, comprising:

receiving, at a member receiving device via a sidelink control channel from a transmitting device, a configuration of sidelink acknowledgment resources for a sidelink group cast message for a group;

attempting to decode a first transmission of the sidelink group cast message from the transmitting device based on the sidelink control channel; and

transmitting a positive acknowledgment based on the configuration of sidelink acknowledgment resources in response to correctly decoding the sidelink group cast message, wherein the member receiving device does not transmit a negative acknowledgment (NAK) in response to incorrectly decoding the first transmission.
The method of claim 13, further comprising receiving a retransmission of the sidelink group cast message after incorrectly decoding the sidelink group cast message, wherein the positive acknowledgment is in response to correctly decoding the retransmission.
The method of claim 14, wherein the retransmission has a different redundancy version than the first transmission of the sidelink group cast message, wherein the sidelink control channel specifies a corresponding redundancy version, the method further comprising combining the first transmission and the retransmission.
The method of claim 13, wherein the sidelink control channel comprises a transmission prior to the sidelink group cast message that schedules a number of transmissions of the sidelink group cast message.
The method of claim 16, wherein the sidelink control channel indicates one or more of time-frequency resources, at least one sequence, a redundancy version, or a new data indicator for each of the number of transmissions of the sidelink group cast message.
The method of claim 13, wherein the sidelink control channel includes a control channel transmission prior to each transmission of the sidelink group cast message, each control channel transmission scheduling a corresponding transmission of the sidelink group cast message and a subsequent control channel transmission.
The method of claim 13, wherein the configuration of sidelink acknowledgment resources specifies transmission parameters for each member receiving device of the group.
The method of claim 19, wherein the transmission parameters include one or more of:transmission power, time-frequency resources, modulation and coding scheme, and beam configuration.
The method of claim 13, wherein the configuration of sidelink acknowledgment resources comprises a resource pool, wherein transmitting the positive acknowledgment comprises selecting resources for transmitting the positive acknowledgment from the resource pool.
The method of claim 21, wherein the positive acknowledgment comprises an ID of the member receiving device.
The method of claim 13, wherein the sidelink acknowledgment resources are multiplexed using one or more of frequency division multiplexing, time division multiplexing, and code division multiplexing.
An apparatus for wireless communication, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

configure, via a sidelink control channel, sidelink acknowledgment resources for member receiving devices of a group;

transmit a sidelink group cast message to the member receiving devices of the group; and

repeat transmission of the sidelink group cast message until an acknowledgment is received from each member of the group or a number of transmissions of the sidelink group cast message reaches a maximum number of transmissions.
The apparatus of claim 24, wherein the at least one processor is configured to transmit the sidelink group cast message with a different redundancy version, wherein the sidelink control channel specifies a corresponding redundancy version.
The apparatus of claim 24, wherein the member receiving devices transmit only positive acknowledgments on the sidelink acknowledgment resources.
The apparatus of claim 24, wherein the sidelink control channel comprises a control channel transmission prior to the sidelink group cast message that schedules the number of transmissions of the sidelink group cast message.
An apparatus for wireless communication, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

receive, via a sidelink control channel from a transmitting device, a configuration of sidelink acknowledgment resources for a sidelink group cast message for a group;

attempt to decode a first transmission of the sidelink group cast message from the transmitting device based on the sidelink control channel; and

transmit a positive acknowledgment based on the configuration of sidelink acknowledgment resources in response to correctly decoding the sidelink group cast message, wherein the apparatus does not transmit a negative acknowledgment (NAK) in response to incorrectly decoding the first transmission.
The apparatus of claim 28, wherein the at least one processor is configured to receive a retransmission of the sidelink group cast message after incorrectly decoding the sidelink group cast message, wherein the positive acknowledgment is in response to correctly decoding the retransmission.
The apparatus of claim 29, wherein the retransmission has a different redundancy version than the first transmission of the sidelink group cast message, wherein the sidelink control channel specifies a corresponding redundancy version, wherein the at least one processor is configured to combine the first transmission and the retransmission.