WO2021147117A1

WO2021147117A1 - Enhanced harq-ack bundling for cbg based retransmission

Info

Publication number: WO2021147117A1
Application number: PCT/CN2020/074047
Authority: WO
Inventors: Chao Wei; Jing Dai; Min Huang; Qiaoyu Li
Original assignee: Qualcomm Incorporated
Priority date: 2020-01-24
Filing date: 2020-01-24
Publication date: 2021-07-29

Abstract

A UE receives a physical downlink shared channel (PDSCH) transmission from a base station comprising one or more transport block (TB) that includes one or more code block groups (CBGs). The UE determines whether to apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission. The UE transmits bundled HARQ feedback or non-bundled HARQ feedback to the base station based on the determination.

Description

ENHANCED HARQ-ACK BUNDLING FOR CBG BASED RETRANSMISSION

BACKGROUND

Technical Field

The present disclosure relates generally to communication systems, and more particularly, to wireless communication including hybrid automatic repeat request (HARQ) feedback.

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. There exists a need for further improvements in 5G NR 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.

Aspects presented herein enable a user equipment (UE) to employ adaptive HARQ feedback bundling without ambiguity between the UE and the base station. Aspects may enable the UE to use HARQ feedback bundling without using dummy bits for code block groups (CBGs) that are not present in a physical downlink shared channel (PDSCH) transmission.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided for wireless communication at a UE. The apparatus receives a PDSCH transmission from a base station comprising one or more transport block (TB) that includes one or more CBGs. The apparatus determines whether to apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission. The UE transmits HARQ feedback to the base station based on the determination.

In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided for wireless communication at a base station. The apparatus a PDSCH transmission to a UE comprising one or more TB that includes one or CBGs. The apparatus determines whether the UE will apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission. Then, the bases station receives HARQ feedback from the UE based on the determination.

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.

FIGs. 2A, 2B, 2C, and 2D are diagrams illustrating examples of a first 5G/NR frame, DL channels within a 5G/NR subframe, a second 5G/NR frame, and UL channels within a 5G/NR subframe, respectively.

FIG. 3 is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

FIG. 4 illustrates an example of HARQ feedback multiplexing.

FIGs. 5A, 5B, and 5C illustrate examples of HARQ feedback bundling.

FIG. 6 illustrates an example of HARQ feedback bundling.

FIG. 7 illustrates an example of HARQ feedback bundling.

FIG. 8 illustrates an example of HARQ feedback bundling.

FIG. 9 is an example communication flow between a UE and a base station.

FIG. 10 is a flowchart of a method of wireless communication.

FIG. 11 is a conceptual data flow diagram illustrating the data flow between different means/components in an example apparatus.

FIG. 12 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

FIG. 13 is a flowchart of a method of wireless communication.

FIG. 14 is a conceptual data flow diagram illustrating the data flow between different means/components in an example apparatus.

FIG. 15 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

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 another core network 190 (e.g., a 5G Core (5GC) ) . The base stations 102 may include macrocells (high power cellular base station) and/or small cells (low power cellular base station) . The macrocells 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 first backhaul links 132 (e.g., S1 interface) . The base stations 102 configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN) ) may interface with core network 190 through second 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 third backhaul links 134 (e.g., X2 interface) . The third 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 macrocells 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 fewer 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, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and Electronics Engineers (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 and/or be referred to as an eNB, gNodeB (gNB) , or another type of base station. Some base stations 180, such as a gNB, 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 base station 180 operates in mmW or near mmW frequencies, the base station 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 (RF) band (e.g., 3 GHz –300 GHz) has extremely high path loss and a short range. The mmW base station, e.g., the 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 and the UE 104 may each include a plurality of antennas, such as antenna elements, antenna panels, and/or antenna arrays to facilitate the beamforming.

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. All 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 a 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. All 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 Packet Switch (PS) Streaming (PSS) Service, and/or other IP services.

The base station may include and/or be referred to as a gNB, 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.

The UE 104 may receive a PDSCH transmission from a base station 102/180 comprising one or more TB that includes one or more CBGs. The UE 104 may include a HARQ feedback component 198 configured to determine whether or not to apply HARQ feedback bundling when sending HARQ feedback for the PDSCH transmission. The HARQ feedback component may make the determination based on a number of HARQ bits per PDSCH transmission and a number of the scheduled CBGs across the TBs of the PDSCH transmission. The UE 104 may transmit bundled HARQ feedback or non-bundled HARQ feedback to the base station 102/180 based on the determination. The

base station

102 or 180 may include a HARQ feedback component 199 configured to determine whether the UE will apply HARQ feedback bundling in order to correctly receive the HARQ feedback. The HARQ feedback component 199 may make the determination based on the number of HARQ bits per PDSCH transmission and the number of scheduled CBGs across the TBs of the PDSCH transmission. Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as TE, LTE-A, CDMA, GSM, and other wireless technologies.

FIG. 2A is a diagram 200 illustrating an example of a first subframe within a 5G/NR frame structure. FIG. 2B is a diagram 230 illustrating an example of DL channels within a 5G/NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe within a 5G/NR frame structure. FIG. 2D is a diagram 280 illustrating an example of UL channels within a 5G/NR subframe. The 5G/NR frame structure may be frequency division duplexed (FDD) in which for a particular set of subcarriers (carrier system bandwidth) , subframes within the set of subcarriers are dedicated for either DL or UL, or may be time division duplexed (TDD) in which for a particular set of subcarriers (carrier system bandwidth) , subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by FIGs. 2A, 2C, the 5G/NR frame structure is assumed to be TDD, with subframe 4 being configured with slot format 28 (with mostly DL) , where D is DL, U is UL, and X is flexible for use between DL/UL, and subframe 3 being configured with slot format 34 (with mostly UL) . While

subframes

3, 4 are shown with slot formats 34, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI) , or semi-statically/statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI) . Note that the description infra applies also to a 5G/NR frame structure that is TDD.

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. The symbols on DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also referred to as single carrier frequency-division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to a single stream transmission) . The number of slots within a subframe is based on the slot configuration and the numerology. For slot configuration 0, different numerologies μ 0 to 5 allow for 1, 2, 4, 8, 16, and 32 slots, respectively, per subframe. For slot configuration 1, different numerologies 0 to 2 allow for 2, 4, and 8 slots, respectively, per subframe. Accordingly, for slot configuration 0 and numerology μ, there are 14 symbols/slot and 2 ^μ slots/subframe. The subcarrier spacing and symbol length/duration are a function of the numerology. The subcarrier spacing may be equal to 2 ^μ*15 kHz, where μ is the numerology 0 to 5. As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and the numerology μ=5 has a subcarrier spacing of 480 kHz. The symbol length/duration is inversely related to the subcarrier spacing. FIGs. 2A-2D provide an example of slot configuration 0 with 14 symbols per slot and numerology μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs.

A resource grid may be used to represent the frame structure. Each time slot includes 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. 2A, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include demodulation RS (DM-RS) (indicated as R _x for one particular configuration, where 100x is the port number, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS may also include beam measurement RS (BRS) , beam refinement RS (BRRS) , and phase tracking RS (PT-RS) .

FIG. 2B illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs) , each CCE including nine RE groups (REGs) , each REG including four consecutive REs in an OFDM symbol. A primary synchronization signal (PSS) may be within symbol 2 of particular subframes of a frame. The PSS is used by a UE 104 to determine subframe/symbol timing and a physical layer identity. A secondary synchronization signal (SSS) may be within symbol 4 of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI) . Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH) , which carries a master information block (MIB) , may be logically grouped with the PSS and SSS to form a synchronization signal (SS) /PBCH block. The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs) , and paging messages.

As illustrated in FIG. 2C, some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH) . The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE may transmit sounding reference signals (SRS) . The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by a base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

FIG. 2D illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI) , such as scheduling requests, a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a rank indicator (RI) , and hybrid automatic repeat request (HARQ) ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR) , a power headroom report (PHR) , and/or UCI.

FIG. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. In the DL, IP packets from the EPC 160 may be provided to a controller/processor 375. The controller/processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs) , RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release) , inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression /decompression, security (ciphering, deciphering, integrity protection, integrity verification) , and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs) , error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (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 transport blocks (TBs) , demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

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 UE 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 UE 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 UE 350. If multiple spatial streams are destined for the UE 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 the base station 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 the base station 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. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. 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 DL transmission by the base station 310, the controller/processor 359 provides 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 the base station 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 UL transmission is processed at the base station 310 in a manner similar to that described in connection with the receiver function at the UE 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. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from the controller/processor 375 may be provided to the EPC 160. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

At least one of the TX processor 368, the RX processor 356, and the controller/processor 359 may be configured to perform aspects in connection with 198 of FIG. 1.

At least one of the TX processor 316, the RX processor 370, and the controller/processor 375 may be configured to perform aspects in connection with 199 of FIG. 1.

A UE may receive downlink communication, such as PDSCH transmissions, from a base station. In response to receiving the downlink communication, the UE may provide HARQ feedback to the base station to indicate whether or not the UE correctly received the downlink communication. In the base station receives HARQ-ACK from the UE, the base station may determine that the UE correctly received the transmission and may not retransmit the downlink transmission. If the base station receives a NACK, the base station may respond by retransmitting the downlink transmission.

HARQ feedback for multiple PDSCH in time can be multiplexed and transmitted together in an uplink transmission. HARQ-ACK multiplexing may be based on a cell dimension, with HARQ-ACK for multiple carriers of downlink carrier aggregation for the UE being multiplexed together. HARQ-ACK multiplexing may be based on a time dimension, with HARQ-ACK for multiple downlink slots within a bundling window being multiplexed together. HARQ-ACK multiplexing may be based on a TB dimension, with HARQ-ACK for multiple TBs of a PDSCH being multiplexed together. HARQ-ACK multiplexing may be based on a CBG dimension, with HARQ-ACK for multiple CBGs within a TB being multiplexed together, such as when a 2-CW transmission or a CBG based transmission is configured.

The UE may determine the HARQ-ACK bundling window from a set of higher layer configured parameters, such as candidates for HARQ-ACK timing. For example, the set of higher layer configured timing candidates may be 2, 3, 4, and 6 slots. As shown in the slot diagram 400 in FIG. 4, the associated bundling window for an uplink slot 402 may include downlink slots #1, #3, #4, and #5 based on the set of higher layer configured timing candidates. K _x represents the time offset in a number of slots from the end of the PDSCH to the start of the associated HARQ-ACK transmission. For example, the timing candidates 2 may correspond to K ₄, the timing candidate 3 may correspond to k ₃, the timing candidate 4 may correspond to k ₂, and the timing candidate 6 may correspond to k ₁.

The number of bits and the meaning of the bits in the HARQ feedback may be based on a HARQ-ACK codebook. The codebook may be a semi-static HARQ-ACK codebook or a dynamic HARQ-ACK codebook.

In the semi-static HARQ-ACK codebook, the payload size for the HARQ feedback may be determined based on a configured number of component carriers (CCs) , a configured number of TBs per CC, a configured number of CBGs per CC, and/or a bundling window associated with a configured HARQ-ACK timing set. In some examples, a discontinuous transmission (DTX) /NACK bit may be transmitted for a non-scheduled PDSCH within a bundling set.

In the dynamic HARQ-ACK codebook, the payload size for the HARQ feedback may be based on a counter or a total downlink assignment index (DAI) in downlink control information (DCI) . For example, the HARQ feedback may be for the scheduled PDSCHs across the CCs configured for the UE and within a bundling window. The counter DAI may indicate the accumulated number of pairs of a serving cell and PDCCH monitoring occasion (e.g., {serving cell, PDCCH monitoring occasion} ) in which the UE receives PDSCH or SPS release is present. For example, the DAI may indicate an accumulated number of scheduled PDSCHs within the bundling window. The total DAI may indicate a total number of {serving cell, PDCCH} pairs in which PDSCH is received or SPS release is present up to a current slot. For example, the total DAI may indicate a total number of scheduled PDSCHs within a bundling window.

A UE may be configured for CBG based retransmission. The UE may provide HARQ feedback at a granularity of a CBG within a TB. If the UE does not receive one CBG within a TBs and receives the other CBGs in the TB, the UE may provide a NACK for the incorrectly received CBG and ACKs for the other CBGs. The base station may respond by retransmitting only the incorrectly received CBG without retransmitting the other CBGs in the TB that were correctly received by the UE. If CBG based retransmission is configured for the UE, the number of HARQ-ACK bits per PDSCH may be based on a maximum number of CBGs that is configured by the base station.

For a semi-static HARQ-ACK codebook,

HARQ-ACK bits may be reported per PDSCH in a serving cell c, where

represents a configured maximum number of codewords per PDSCH in the serving cell c and

represents the configured maximum number of CBGs per TB for the serving cell c.

For a dynamic HARQ-ACK codebook,

HARQ-ACK bits may be reported per PDSCH in each serving cell where

corresponds to the maximum value of

across all of the configured downlink serving cells for the UE.

As

can be configured to be 2, 4, 5, or 8, the payload can become large when HARQ-ACK bits for multiple PDSCHs are multiplexed together. For example, if a UE is configured for CBG based retransmission and with a maximum value of 8 for

for one serving cell for HARQ feedback based on a dynamic HARQ-ACK codebook, the HARQ-ACK payload may be up to 1024 ACK/NACK bits in an uplink slot. The number of ACK/NACK bits may be equal to Number of CCs *Number of slots in a bundling window *MIMO *Number of CBGs. For example:

1024 ACK/NACK bits = 16 CCs *8 slot bundling window *2 MIMO *4 CBGs

HARQ-ACK bundling may be used to reduce the size of an ACK/NACK payload. For example, the HARQ-ACK bundling may be based on a binary AND operation among multiple ACK/NACK bits. HARQ-ACK bundling may reduce the codebook size, e.g., in an example including an uplink coverage limitation.

Spatial domain HARQ-ACK bundling may include bundling across two TBs in a same PDSCH. Such bundling may be applied, e.g., for TB based retransmission. FIGs. 5A, 5B, and 5C illustrate examples of different types of HARQ-ACK bundling for CBG based retransmission.

FIG. 5A illustrates an example of inter-CBG bundling 500 in which HARQ-ACK for some CBGs within a same TB may be bundled. In FIG. 5A, the HARQ feedback for the CBG 506 and the CBG 508 in the TB 502 are bundled and the HARQ feedback for the CBG 510 and the CBG 512 in the TB 504 are bundled. Therefore, if both the CBG 506 and the CBG 508 in the TB 502 are received correctly, the UE may transmit an ACK for the bundled CBGs. Similarly, if both the CBG 510 and the CBG 512 in the TB 504 are received correctly, the UE may transmit an ACK for the bundled CBGs. If one of the bundled CBGs is not received correctly, the UE may transmit a NACK for the bundled CBGs. For example, if the UE does not correctly receive CBG 506, the UE may transmit a NACK for the bundled CBGs (e.g., CBG 506 and 508) regardless of whether the CBG 508 is correctly received. The bundling may reduce the HARQ-ACK payload similar to reducing or reconfiguring a maximum number of CBGs to a smaller value.

FIG. 5B illustrates an example of inter-TB bundling 550 in which HARQ-ACK bundling is applied across TBs within a PDSCH per CBG index. For example, HARQ feedback is bundled for CBGs having the same CBG index that are in different TBs. In FIG. 5B, HARQ feedback is bundled for the CBGs having CBG index 0 (e.g., CBG 506 and CBG 510) . Similarly, HARQ feedback is bundled for the CBGs having CBG index 1 (e.g., CBG 508 and CBG 512) . In this example, the bundled HARQ-ACK bits may be equal to the configured maximum number of CBGs for the TBs.

FIG. 5C illustrates an example showing a combination 575 of inter-CBG bundling and inter-TB bundling. In FIG. 5C, the HARQ feedback corresponding to multiple CBGs across multiple TBs are bundled. For example, the HARQ feedback is bundled for the CBG 506 and the CBG 508 in the TB 502 as well as for the CBG 510 and the CBG 512 in the TB 504.

In a first example, HARQ feedback payload for CBG based retransmission may be reduced by reducing the configured maximum number of CBGs per TB to a smaller value. However, reducing the maximum number of CBGs per TB also reduces some of the benefit provided by CBG based retransmission. For example,

for up to 2 TBs will provide a maximum HARQ feedback payload of 4 HARQ-ACK bits per PDSCH. Similarly,

for a single TB will provide a maximum HARQ feedback payload of 4 HARQ-ACK bits per PDSCH. In a second example, HARQ feedback payload for CBG based retransmission may be reduced through the use of inter-CBG bundling or inter-TB bundling for HARQ-ACK, such as described in connection with any of FIGs. 5A-5C.

Based on the first example, the bundled HARQ-ACK bits may include empty CBGs, such as when a single TB is scheduled and the maximum of 2 TBs is configured. For example, for 2 TBs with

if a first TB has 4 CBGs and a second TB has 0 CBGs, then the UE generates 2 HARQ-ACK bits for the 2 CBGs of TB1 and 2 bits of a dummy NACK for the second TB that is not scheduled. Based on the second example, the bundling schemes involve a fixed structure that could involve bundling of empty CBGs. FIG. 6 illustrates an example of HARQ feedback bundling 600 for a maximum of 4 CBGs per TB. CW1 has three non-empty CBGs (e.g.,

CBGs

602, 604, and 608) and one empty CBG (e.g., CBG 606) that is not present in the transmission. CW2 includes 2 non-empty CBGs (e.g., CBGs 610 and 618) and two empty CBGs (e.g., CBG 614 and 616) that are not present in the transmission. If inter-TB bundling is performed per CBG index, such as described in connection with FIG. 5B, the UE will generate 4 bits of HARQ feedback. As illustrated in FIG. 6, a first bit 620 will include bundled feedback for the CBG 602 and the CBG 610, a second bit 622 will include bundled feedback for the CBG 604 and the empty CBG 614, a third bit 624 will include a dummy NACK as bundled feedback for the empty CBGs 606 and 616, and a fourth bit 626 will include bundled feedback for the CBG 618 and the CBG 626. The UE transmits dummy bits for empty CBGs in order to avoid ambiguity between the base station and the UE about the number of HARQ feedback bits per PDSCH. For example, ambiguity may lead the base station to misinterpret the HARQ feedback and to unnecessarily retransmit CBGs that the UE has already received.

As presented herein, the UE may perform adaptive HARQ-ACK bundling. FIG. 9 illustrates an example communication flow 900 between a UE 902 and a base station 904, in which the UE determines, at 912, whether to bundle HARQ-ACK feedback for transmission to the base station 904. The UE may determine, at 912, whether to perform HARQ-ACK bundling based on a configured maximum number of HARQ-ACK bits per PDSCH and a number of scheduled CBGs across all of the TBs of a PDSCH 910. The maximum number of HARQ-ACK bits per PDSCH may be represented by M, which may have an integer value between M=1, ..., 8 bits. The number of scheduled CBGs across all of the TBs of a PDSCH may be represented by N, e.g., which may have an integer value between N = 1 , ..., 8, which may be determined by the bitmap based CBG transmission (CBGTI) field in a DCI. Thus, N may be indicated, at 908, based on a CBGTI value. The base station 904 that will receive the HARQ feedback may determine, at 913, whether the UE will perform HARQ-ACK bundling in the same manner so that there will not be ambiguity between the UE and the base station about the content of the HARQ feedback.

As an example, the UE may determine, at 912, not to use HARQ-ACK bundling to transmit HARQ feedback to the base station when N ≤ M (e.g., if the number of scheduled CBGs is less than or equal to the maximum number of HARQ-ACK bits per PDSCH) . The UE may then transmit HARQ-ACK feedback 918 without bundling. If N > M (e.g., if the number of scheduled CBGs is more than the maximum number of HARQ-ACK bits per PDSCH) , the UE may determine to use HARQ-ACK bundling for the scheduled CBGs. The UE may then transmit the bundled HARQ-ACK feedback 916. The UE may use transmit HARQ feedback with HARQ-ACK bundling only for the scheduled CBGs, which may enable the UE to avoid sending dummy bits for unscheduled CBGs.

The value of M (e.g., the maximum number of HARQ-ACK bits per PDSCH) can be configured for the UE, in configuration message 906, by the base station so that the value is known to both the UE and the base station. In some examples, the value of M may be configured semi-statically. In other examples, the value of M may be configured dynamically.

For a semi-static HARQ-ACK codebook, M may be cell specific. The cell specific value of M may be configured by RRC signaling to the UE or may be dynamically indicated by a DCI transmitted to the UE. For example, the value of M may be indicated by the last received DCI in the bundling window, e.g.the UE may implicitly determine the value of M based on a PUCCH resource such as an ACK/NACK resource indicator (ARI) field in the DCI.

For a dynamic HARQ-ACK codebook, M may be common to multiple cells. For example, M may be common to each configured downlink serving cell for the UE. The value of M may be configured by RRC signaling to the UE, or the UE may dynamically determine the value of N based on a total payload limitation or a coding rate of a given PUCCH resource. Thus, N may be indicated, at 908, based on a total payload limitation. For example, the UE may start from a maximum value for M and may reduce M to a smaller value when the HARQ-ACK payload size exceeds the maximum payload size supportable by a given PUCCH resource.

The UE may apply different HARQ-ACK bundling for a single TB than for multiple TBs. Therefore, the UE may determine, at 914, and the base station may determine, at 915, a bundling type based on whether the base station schedules a single TB or schedules multiple TBs.

If a single TB is scheduled for the PDSCH, the UE may apply inter-CBG bundling to the N scheduled CBGs. The UE may divide or group the N CBGs into M bundles. Each of the M bundles may include a set of consecutive CBGs based on the bundling size and the CBG index.

For example, P ₁=mod (N, M) , P ₂=M-P ₁,

and

where P ₁ represents the number of bundles with a size of K ₁, P ₂ represents the number of bundles with a size of K ₂, K ₁ represents one possible bundle size, and K ₂ represents another possible bundle size. If P ₁>0, the CBG-bundle m, m=0, 1, .., P ₁-1 may include CBGs with indices m·K ₁+k, k=0, 1, …, K ₁-1 , where m represents the index of the bundle, and the CBG-bundle m, m=P ₁, P ₁+1, .., M -1 may include the CBGs with indices P ₁·K ₁+ (m-P ₁) ·K ₂+k, k=0, 1, …, K ₂-1. The grouping of CBGs for HARQ-ACK bundling according to this example is shown in FIG. 7 as grouping example 702. The examples in FIG. 7 are for a single TB with 6 scheduled CBGs (e.g., N=6) and M = 4. In the grouping example 702, the smaller size group (e.g., of a single CBG) occurs at the beginning of a TB. Alternatively, the CBG-bundle m, m=0, 1, .., P ₂-1 may include the CBGs with indices m·K ₂+k, k=0, 1, …, K ₂-1 and the CBG-bundle m, m=P ₂, P ₂+1, .., M -1 may include the CBGs with indices P ₂·K ₂+ (m-P ₂) ·K ₁+k, k=0, 1, …, K ₁-1. The grouping of CBGs for HARQ-ACK bundling according to this example is shown in FIG. 7 as grouping example 704. In the grouping example 704, the smaller size group (e.g., of a single CBG) occurs at the end of a TB.

If multiple TBs are scheduled for the PDSCH, inter-CBG bundling, inter-TB bundling, or a combination of both inter-CBG bundling and inter-TB bundling may be applied to generate the HARQ feedback for the TBs. The determination of whether to use inter-CBG bundling, inter-TB bundling, or a combination of both inter-CBG bundling and inter-TB bundling may be based on a higher layer configuration from the base station. The determination may be based on a parameter (e.g., K) for a number of HARQ-ACK bits for inter-TB bundling.

If K is zero, the UE may determine to use inter-CBG bundling, e.g., without inter-TB bundling. If K is equal to M, the UE may determine to use inter-TB bundling, e.g., without using inter-CBG bundling. If K is a non-zero value other than M, both inter-CBG bundling and inter-TB bundling may be supported. Therefore, the UE may use both inter-CBG bundling and inter-TB bundling for the HARQ feedback.

If inter-TB bundling is configured, the first K CBGs of two TBs may be spatially bundled for the first K HARQ-ACK bits. The remaining CBGs in TB1 and TB2 may be represented as N ₁ and N ₂, where N ₁+N ₂+2K=N, and inter-CBG bundling may be applied separately for each TB.

In a first example, the number of CBG bundles may be based on equal splitting so that a number (M ₁) of bundles in a first TB is

and a number (M ₂) of bundles in a second TB is

As the same formula is used to determine M ₁ and M ₂, each TB will include an equal number of CBG bundles. The number of CBG bundles in each of TB may be different. For example, the number of CBGs bundles in each TB may be based on a non-equal splitting, e.g. scaled by the number of scheduled CBGs. Thus, for a first TB,

and for a second TB,

FIG. 8 illustrates an example for two TBs in which K=1, N=6, M=4, M ₁=2, and M ₂=1. As K=1, the UE applies inter-TB bundling for the first CBGs of the two TBs (e.g., a1 and b1, which are bundled in the first ACK/NACK bit 814) . The remaining CBGs in the two TBs are bundled based on inter-CBG bundling. As M ₁=2, the HARQ feedback for the remaining CBGs (e.g., a2 and a3) for the first TB are grouped into two CGB groups, each group corresponding to a single CBG. Thus, feedback for a2 is provided in the second ACK/NACK bit 816, and feedback for a3 is provided in the third ACK/NACK bit 818. As M ₂=1, the HARQ feedback for the remaining CBGs (e.g., b2 and b3) for the second TB are inter-CBG bundled in the fourth ACK/NACK bit 820.

The base station 904 may retransmit at least a portion of the PDSCH in response to

HARQ feedback

916 or 918.

FIG. 10 is a flowchart 1000 of a method of wireless communication. The method may be performed by a UE or a component of a UE (e.g., the

UE

104, 350, 902; the apparatus 1102/1102'; the processing system 1214, which may include the memory 360 and which may be the entire UE 350 or a component of the UE 350, 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 help the UE to apply adaptive HARQ-ACK bundling without the use of dummy bits.

At 1008, the UE receives a PDSCH transmission from a base station comprising one or more TBs that include one or more CBGs. The reception may be performed, e.g., by the PDSCH component 1108 of the apparatus 1102 in FIG. 11.

At 1010, the UE determines whether to apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission. The determination may be performed, e.g., by the determination component 1110 of the apparatus 1102 in FIG. 11. The determination may be based on aspects described in connection with the determination 912 in FIG. 9. If the first number of HARQ bits is greater than or equal to the second number of scheduled CBGs (e.g., if M ≥ N) , the UE may determine not to apply HARQ feedback bundling. If the first number of HARQ bits is less than the second number of scheduled CBGs (e.g., N > M) , the UE may determine to apply HARQ feedback bundling. The first number of HARQ bits may represent a maximum number of HARQ bits per PDSCH transmission (e.g., M) . The second number of scheduled CBGs (e.g., N) may be based on a CBGTI field in DCI from the base station.

The HARQ feedback may be based on a semi-static codebook, and the maximum number of HARQ bits per PDSCH transmission may be cell specific. As illustrated at 1004, the UE may receive a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling. Alternatively, the UE may determine the maximum number of HARQ bits per PDSCH transmission based on a last DCI received in a bundling window, as illustrated at 1006.

The HARQ feedback may be based on a dynamic codebook, and the maximum number of HARQ bits per PDSCH transmission may be common to each configured downlink serving cell for the UE. As illustrated at 1004, the UE may receive a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling. Alternatively, the UE may determine the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, as illustrated at 1002.

The UE may transmit the HARQ feedback to the base station based on the determination. For example, the UE may transmit the HARQ feedback without bundling, at 1012, if the UE determines, at 1010 not to bundle the HARQ feedback. The UE may transmit the HARQ feedback, at 1016, using bundling if the UE determines, at 1010, to bundle the HARQ feedback. The transmission may be performed, e.g., by the HARQ component 1112 and/or the transmission component 1106 of the apparatus 1102 in FIG. 11.

If the UE determines, at 1010 to bundle the HARQ feedback, the UE may further determine a type of bundling to use, such as described in connection with 914 in FIG. 9. If a single transport block is scheduled for the PDSCH transmission, the UE may use inter-CBG bundling. As illustrated at 1014, the UE may divide the scheduled CBGs into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index. The division may be performed, e.g., by the division component 1116 of the apparatus 1102 in FIG. 11.

If multiple TBs are scheduled for the PDSCH transmission, the UE may use at least one of inter-CBG bundling or inter-TB bundling. The UE may use at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling. For example, if the configured number has a zero value, the UE may use the inter-CBG bundling, e.g., as described in connection with FIG. 5A. If the configured number is equal to the first number of HARQ bits per PDSCH transmission, the UE may use the inter-TB bundling, e.g., as described in connection with FIG. 5B. If the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling are supported. Thus, the UE may use both inter-TB bundling and inter-CBG bundling, e.g., as described in connection with FIG. 5C, FIG. 8, etc.

Both the inter-CBG bundling and the inter-TB bundling may be used and the inter-TB bundling may be applied to a first plurality of CBG groups per TB, e.g., as described in connection with FIG. 8. The UE may apply the inter-CBG bundling using equal numbers of bundles of CBG groups per TB, where each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index. For each of the multiple TBs, the UE may apply the inter-CBG bundling using a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.

FIG. 11 is a conceptual data flow diagram 1100 illustrating the data flow between different means/components in an example apparatus 1102. The apparatus may be a UE or a component of a UE. The apparatus includes a reception component 1104 configured to receive downlink communication from the base station 1150 and a transmission component 1106 configured to transmit uplink communication to the base station 1150. The apparatus 1102 includes a PDSCH component 1108 configured to receive a PDSCH transmission from a base station comprising one or more TB that includes one or more CBGs, e.g., as described in connection with 1008 in FIG. 10. The apparatus 1102 includes a determination component 1110 configured to determine whether to apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission, e.g., as described in connection with 1014 in FIG. 10. The apparatus 1102 includes a HARQ component 1112 configured to transmit HARQ feedback to the base station based on the determination, e.g., as described in connection with 1016 and 1012 in FIG. 10. The apparatus 1102 includes a max HARQ bits component 1114 configured to receive a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, e.g., as described in connection with 1004 in FIG. 10. The max HARQ bits component 1114 may be configured to determine the maximum number of HARQ bits per PDSCH transmission based on a last DCI received in a bundling window, e.g., as described in connection with 1006 in FIG. 10. The max HARQ bits component 1114 may be configured to determine the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, e.g., as described in connection with 1002 in FIG. 10. The apparatus 1102 may include a CBG component 1118 configured to determine the number of scheduled CBGs for all of the TBs of the PDSCH. The apparatus 1102 includes a division component 1116 configured to divide the scheduled CBGs into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, where each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index, e.g., as described in connection with 1014 in FIG. 10.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of FIG. 10 and/or the aspects of the communication flow 900 that are performed by the UE 902. As such, each block in the aforementioned flowchart of FIG. 10 and/or the aspects of the communication flow 900 that are performed by the UE 902 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. 12 is a diagram 1200 illustrating an example of a hardware implementation for an apparatus 1102' employing a processing system 1214. The processing system 1214 may be implemented with a bus architecture, represented generally by the bus 1224. The bus 1224 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1214 and the overall design constraints. The bus 1224 links together various circuits including one or more processors and/or hardware components, represented by the processor 1204, the

components

1104, 1106, 1108, 1110, 1112, 1114, 1116 and the computer-readable medium /memory 1206. The bus 1224 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 1214 may be coupled to a transceiver 1210. The transceiver 1210 is coupled to one or more antennas 1220. The transceiver 1210 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1210 receives a signal from the one or more antennas 1220, extracts information from the received signal, and provides the extracted information to the processing system 1214, specifically the reception component 1104. In addition, the transceiver 1210 receives information from the processing system 1214, specifically the transmission component 1106, and based on the received information, generates a signal to be applied to the one or more antennas 1220. The processing system 1214 includes a processor 1204 coupled to a computer-readable medium /memory 1206. The processor 1204 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1206. The software, when executed by the processor 1204, causes the processing system 1214 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1206 may also be used for storing data that is manipulated by the processor 1204 when executing software. The processing system 1214 further includes at least one of the

components

1104, 1106, 1108, 1110, 1112, 1114, 1116. The components may be software components running in the processor 1204, resident/stored in the computer readable medium /memory 1206, one or more hardware components coupled to the processor 1204, or some combination thereof. The processing system 1214 may be a component of the UE 350 and may include the memory 360 and/or at least one of the TX processor 368, the RX processor 356, and the controller/processor 359. Alternatively, the processing system 1214 may be the entire UE (e.g., see 350 of FIG. 3) .

In one configuration, the apparatus 1102/1102' for wireless communication includes means for receiving a PDSCH transmission from a base station comprising one or more TB that includes one or more CBGs, e.g., as described in connection with 1008 in FIG 10. The apparatus may include means for determining whether to apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission, e.g., as described in connection with 1010 in FIG 10. The apparatus may include means for transmitting HARQ feedback to the base station based on the determination, e.g., as described in connection with 1012 and 1016 in FIG 10. The apparatus may further include means for receiving a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, e.g., as described in connection with 1004 in FIG 10. The apparatus may further include means for determining the maximum number of HARQ bits per PDSCH transmission based on a last DCI received in a bundling window, e.g., as described in connection with 1006 in FIG 10. The apparatus may further include means for determining the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, e.g., as described in connection with 1002 in FIG 10. The apparatus may further include means for dividing the scheduled CBGs into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index, e.g., as described in connection with 1014 in FIG 10. The aforementioned means may be one or more of the aforementioned components of the apparatus 1102 and/or the processing system 1214 of the apparatus 1102' configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1214 may include the TX Processor 368, the RX Processor 356, and the controller/processor 359. As such, in one configuration, the aforementioned means may be the TX Processor 368, the RX Processor 356, and the controller/processor 359 configured to perform the functions recited by the aforementioned means.

FIG. 13 is a flowchart 1300 of a method of wireless communication. The method may be performed by a base station or a component of a base station (e.g., the

base station

102, 180, 310, 904; the apparatus 1402/1402'; the processing system 1514, which may include the memory 376 and which may be the entire base station 310 or a component of the base station 310, such as the TX processor 316, the RX processor 370, and/or the controller/processor 375) . Optional aspects are illustrated with a dashed line. The method may help to enable a base station to receive HARQ-ACK feedback based on adaptive HARQ-ACK bundling without the use of dummy bits.

At 1308, the base station transmits a PDSCH transmission to a UE comprising one or more TBs that includes one or more CBGs. The transmission may be performed, e.g., by the PDSCH component 1408 and/or the transmission component 1406 of the apparatus 1402 in FIG. 14.

At 1310, the base station determines whether the UE will apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission. The determination may be performed, e.g., by the determination component 1410 of the apparatus 1402 in FIG. 14. The first number of HARQ bits may represent a maximum number of HARQ bits per PDSCH transmission (e.g., M) . The second number of scheduled CBGs (e.g., N) may be based on, or indicated in, a CBGTI field in DCI transmitted by the base station. If the first number of HARQ bits is greater than or equal to the second number of scheduled CBGs, the base station may determine that the UE will not apply HARQ feedback bundling. If the first number of HARQ bits is less than the second number of scheduled CBGs, the base station may determine that the UE will apply HARQ feedback bundling. The determination, at 1310, may include aspects described in connection with the determination 913 in FIG. 9 and may be made in a similar manner to the determination 912 made by the UE about whether to bundle the HARQ feedback.

The HARQ feedback may be based on a semi-static codebook, where the maximum number of HARQ bits per PDSCH transmission is cell specific. The base station may transmit a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, as illustrated at 1304. The base station may indicate the maximum number of HARQ bits per PDSCH transmission based on a last DCI transmitted in a bundling window, as illustrated at 1302.

The HARQ feedback may be based on a dynamic codebook, and where the maximum number of HARQ bits per PDSCH transmission is common to each configured cell for the UE. The base station may transmit a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, as illustrated at 1304. The base station may indicate the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, as illustrated at 1302.

The base station then receives HARQ feedback from the UE based on the determination. The reception may be performed, e.g., by the HARQ component 1412 and/or the reception component 1404 of the apparatus in FIG. 14. For example, at 1312, the base station may receive the HARQ feedback without bundling when the base station determines, at 1310, that the UE will not bundle the HARQ feedback. The base station may receive the HARQ feedback with bundling when the base station determines, at 1310, that the UE will bundle the HARQ feedback. The base station may further determine a type of bundling applied by the UE in order to receive the HARQ feedback. The determination may include aspects described in connection with 915 of FIG. 9.

If a single transport block is scheduled for the PDSCH transmission, the base station may receive the HARQ feedback based on inter-CBG bundling, e.g., such as described in connection with FIG. 5A. The scheduled CBGs may be divided into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.

If multiple TBs are scheduled for the PDSCH transmission, the base station may receive the HARQ feedback based on at least one of inter-CBG bundling or inter-TB bundling, e.g., as described in connection with FIG. 5B.

The base station may receive the HARQ feedback based on at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling. Therefore, the base station may determine a type of bundling that is applied by the UE. If the configured number has a zero value, the base station may receive the HARQ feedback based on the inter-CBG bundling. If the configured number is equal to the first number of HARQ bits per PDSCH transmission, the base station may receive the HARQ feedback based on the inter-TB bundling. If the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling may be supported. The base station may receive the HARQ feedback based on both inter-TB bundling and inter-CBG bundling, e.g., as described in connection with FIG. 5C or FIG. 8. The base station may receive the HARQ feedback based on both the inter-CBG bundling and the inter-TB bundling with the inter-TB bundling applied to a first plurality of CBG groups per TB, e.g., as described in connection with FIG. 8. The inter-CBG bundling may use equal numbers of bundles of CBG groups per TB, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index. For each of the multiple TBs, the inter-CBG bundling may use a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.

FIG. 14 is a conceptual data flow diagram 1400 illustrating the data flow between different means/components in an example apparatus 1402. The apparatus 1402 may be a base station or a component of a base station. The apparatus 1402 includes a reception component 1404 that receives uplink communication from the UE 1450 and a transmission component that transmits downlink communication to the UE 1450. The apparatus 1402 includes a PDSCH component 1408 configured to transmit a PDSCH transmission to a UE comprising one or more TB that includes one or more CBGs, e.g., as described in connection with 1308 in FIG. 13. The apparatus 1402 includes a determination component 1410 configured to determine whether the UE will apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission, e.g., as described in connection with 1310 in FIG. 13. The apparatus 1402 includes a HARQ component 1412 configured to receive HARQ feedback from the UE based on the determination, e.g., as described in connection with 1312 and 1314 in FIG. 13. The apparatus 1402 includes a max HARQ bits component 1414 configured to transmit a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, e.g., as described in connection with 1304 in FIG. 13. The max HARQ bits component 1414 may be configured to indicate the maximum number of HARQ bits per PDSCH transmission based on a last DCI transmitted in a bundling window, e.g., as described in connection with 1306 in FIG. 13. The max HARQ bits component 1414 may be configured to indicate the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, e.g., as described in connection with 1302 in FIG. 13.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of FIG. 13 and/or the aspects performed by the base station 904 in FIG. 9. As such, each block in the aforementioned flowchart of FIG. 13 and/or the aspects performed by the base station 904 in FIG. 9 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. 15 is a diagram 1500 illustrating an example of a hardware implementation for an apparatus 1402' employing a processing system 1514. The processing system 1514 may be implemented with a bus architecture, represented generally by the bus 1524. The bus 1524 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1514 and the overall design constraints. The bus 1524 links together various circuits including one or more processors and/or hardware components, represented by the processor 1504, the

components

1404, 1406, 1408, 1410, 1412, 1414, 1418, and the computer-readable medium /memory 1506. The bus 1524 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 1514 may be coupled to a transceiver 1510. The transceiver 1510 is coupled to one or more antennas 1520. The transceiver 1510 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1510 receives a signal from the one or more antennas 1520, extracts information from the received signal, and provides the extracted information to the processing system 1514, specifically the reception component 1404. In addition, the transceiver 1510 receives information from the processing system 1514, specifically the transmission component 1406, and based on the received information, generates a signal to be applied to the one or more antennas 1520. The processing system 1514 includes a processor 1504 coupled to a computer-readable medium /memory 1506. The processor 1504 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1506. The software, when executed by the processor 1504, causes the processing system 1514 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1506 may also be used for storing data that is manipulated by the processor 1504 when executing software. The processing system 1514 further includes at least one of the

components

1404, 1406, 1408, 1410, 1412, 1414, 1418. The components may be software components running in the processor 1504, resident/stored in the computer readable medium /memory 1506, one or more hardware components coupled to the processor 1504, or some combination thereof. The processing system 1514 may be a component of the base station 310 and may include the memory 376 and/or at least one of the TX processor 316, the RX processor 370, and the controller/processor 375. Alternatively, the processing system 1514 may be the entire base station (e.g., see 310 of FIG. 3) .

In one configuration, the apparatus 1402/1402' for wireless communication includes means for transmitting a PDSCH transmission to a UE comprising one or more TB that includes one or more CBGs, e.g., as described in connection with 1308 in FIG. 13. The apparatus may include means for determining whether the UE will apply HARQ feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission, e.g., as described in connection with 1310 in FIG. 13. The apparatus may include means for receiving HARQ feedback from the UE based on the determination, e.g., as described in connection with 1312 and 1314 in FIG. 13. The apparatus may further include means for transmitting a configuration of the maximum number of HARQ bits per PDSCH transmission in RRC signaling, e.g., as described in connection with 1304 in FIG. 13. The apparatus may further include means for indicating the maximum number of HARQ bits per PDSCH transmission based on a last DCI transmitted in a bundling window, e.g., as described in connection with 1306 in FIG. 13. The apparatus may further include means for indicating the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel, e.g., as described in connection with 1302 in FIG. 13. The aforementioned means may be one or more of the aforementioned components of the apparatus 1402 and/or the processing system 1514 of the apparatus 1402' configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1514 may include the TX Processor 316, the RX Processor 370, and the controller/processor 375. As such, in one configuration, the aforementioned means may be the TX Processor 316, the RX Processor 370, and the controller/processor 375 configured to perform the functions recited by the aforementioned means.

The following examples are illustrative only and aspects thereof may be combined with aspects of other embodiments or teaching described herein, without limitation.

Example 1 is a method of wireless communication at a UE comprising: receiving a physical downlink shared channel (PDSCH) transmission from a base station comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ; determining whether to apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and transmitting HARQ feedback to the base station based on the determination.

In Example 2, the method of Examples 1 further include that first number of HARQ bits is greater than or equal to the second number of scheduled CBGs, the UE determines not to apply HARQ feedback bundling.

In Example 3, the method of any Example 1 or Example 2 further include that if the first number of HARQ bits is less than the second number of scheduled CBGs, the UE determines to apply HARQ feedback bundling.

In Example 4, the method of any of Examples 1-3 further include that the first number of HARQ bits represents a maximum number of HARQ bits per PDSCH transmission, and wherein the second number of scheduled CBGs is based on a code block group transmission information (CBGTI) field in downlink control information (DCI) from the base station.

In Example 5, the method of any of Examples 1-4 further include that the HARQ feedback is based on a semi-static codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is cell specific.

In Example 6, the method of any of Examples 1-5 further include receiving a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or determining the maximum number of HARQ bits per PDSCH transmission based on a last DCI received in a bundling window.

In Example 7, the method of any of Examples 1-4 further include that the HARQ feedback is based on a dynamic codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is common to each configured downlink serving cell for the UE.

In Example 8, the method of any of Examples 1-7 further include receiving a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or determining the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel.

In Example 9, the method of any of Examples 1-8 further include that if a single transport block is scheduled for the PDSCH transmission, the UE uses inter-CBG bundling.

In Example 10, the method of any of Examples 1-9 further include dividing the scheduled CBGs into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.

In Example 11, the method of any of Examples 1-10 further include that multiple TBs are scheduled for the PDSCH transmission, the UE uses at least one of inter-CBG bundling or inter-TB bundling.

In Example 12, the method of any of Examples 1-11 further include that the UE uses at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling; wherein if the configured number has a zero value, the UE uses the inter-CBG bundling; wherein if the configured number is equal to the first number of HARQ bits per PDSCH transmission, the UE uses the inter-TB bundling; and wherein if the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling are supported.

In Example 13, the method of any of Examples 1-11 further include that both the inter-CBG bundling and the inter-TB bundling are used and the inter-TB bundling is applied to a first plurality of CBG groups per TB.

In Example 14, the method of any of Examples 1-11 further include that the UE applies the inter-CBG bundling using equal numbers of bundles of CBG groups per TB, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.

In Example 15, the method of any of Examples 1-11 further include that for each of the multiple TBs, the UE applies the inter-CBG bundling using a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.

Example 16 is a device including one or more processors and one or more memories in electronic communication with the one or more processors storing instructions executable by the one or more processors to cause the device to implement a method as in any of Examples 1-15.

Example 17 is a system or apparatus including means for implementing a method or realizing an apparatus as in any of Examples 1-15.

Example 18 is a non-transitory computer readable medium storing instructions executable by one or more processors to cause the one or more processors to implement a method as in any of Examples 1-15.

Example 19 is a method of wireless communication at a base station comprising: transmitting a physical downlink shared channel (PDSCH) transmission to a user equipment (UE) comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ; determining whether the UE will apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and receiving HARQ feedback from the UE based on the determination.

In Example 20, the method of Example 19 further includes that if the first number of HARQ bits is greater than or equal to the second number of scheduled CBGs, the base station determines that the UE will not apply HARQ feedback bundling.

In Example 21, the method of any of Example 19 or Example 20 further include that if the first number of HARQ bits is less than the second number of scheduled CBGs, the base station determines that the UE will apply HARQ feedback bundling.

In Example 22, the method of any of Examples 19-21 further include that the first number of HARQ bits represents a maximum number of HARQ bits per PDSCH transmission, and wherein the second number of scheduled CBGs is based on a code block group transmission information (CBGTI) field in downlink control information (DCI) transmitted by the base station.

In Example 23, the method of any of Examples 19-22 further include that the HARQ feedback is based on a semi-static codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is cell specific.

In Example 24, the method of any of Examples 19-23 further include that transmitting a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or indicating the maximum number of HARQ bits per PDSCH transmission based on a last DCI transmitted in a bundling window.

In Example 25, the method of any of Examples 19-24 further include that the HARQ feedback is based on a dynamic codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is common to each configured cell for the UE.

In Example 26, the method of any of Examples 19-25 further include that transmitting a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or indicating the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel.

In Example 27, the method of any of Examples 19-26 further include that if a single transport block is scheduled for the PDSCH transmission, the base station receives the HARQ feedback based on inter-CBG bundling.

In Example 28, the method of any of Examples 19-27 further include that the scheduled CBGs are divided into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.

In Example 29, the method of any of Examples 19-28 further include that if multiple TBs are scheduled for the PDSCH transmission, the base station receives the HARQ feedback based on at least one of inter-CBG bundling or inter-TB bundling.

In Example 30, the method of any of Examples 19-29 further include that the base station receives the HARQ feedback based on at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling; wherein if the configured number has a zero value, the base station receives the HARQ feedback based on the inter-CBG bundling; wherein if the configured number is equal to the first number of HARQ bits per PDSCH transmission, the base station receives the HARQ feedback based on the inter-TB bundling; and wherein if the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling are supported.

In Example 31, the method of any of Examples 19-30 further include that the base station receives the HARQ feedback based on both the inter-CBG bundling and the inter-TB bundling with the inter-TB bundling applied to a first plurality of CBG groups per TB.

In Example 32, the method of any of Examples 19-29 further include that the inter-CBG bundling uses equal numbers of bundles of CBG groups per TB, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.

In Example 33, the method of any of Examples 19-29 further include that for each of the multiple TBs, the inter-CBG bundling uses a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.

Example 34 is a device including one or more processors and one or more memories in electronic communication with the one or more processors storing instructions executable by the one or more processors to cause the device to implement a method as in any of Examples 19-33.

Example 35 is a system or apparatus including means for implementing a method or realizing an apparatus as in any of Examples 19-33.

Example 36 is a non-transitory computer readable medium storing instructions executable by one or more processors to cause the one or more processors to implement a method as in any of Examples 19-33.

Further disclosure is included in the Appendix.

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 at a user equipment (UE) , comprising:

receiving a physical downlink shared channel (PDSCH) transmission from a base station comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ;

determining whether to apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and

transmitting HARQ feedback to the base station based on the determination.
The method of claim 1, wherein if the first number of HARQ bits is greater than or equal to the second number of scheduled CBGs, the UE determines not to apply HARQ feedback bundling.
The method of claim 1, wherein if the first number of HARQ bits is less than the second number of scheduled CBGs, the UE determines to apply HARQ feedback bundling.
The method of claim 1, wherein the first number of HARQ bits represents a maximum number of HARQ bits per PDSCH transmission, and wherein the second number of scheduled CBGs is based on a code block group transmission information (CBGTI) field in downlink control information (DCI) from the base station.
The method of claim 4, wherein the HARQ feedback is based on a semi-static codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is cell specific.
The method of claim 5, further comprising:

receiving a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or

determining the maximum number of HARQ bits per PDSCH transmission based on a last DCI received in a bundling window.
The method of claim 4, wherein the HARQ feedback is based on a dynamic codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is common to each configured downlink serving cell for the UE.
The method of claim 7, further comprising:

receiving a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or

determining the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel.
The method of claim 1, wherein if a single transport block is scheduled for the PDSCH transmission, the UE uses inter-CBG bundling.
The method of claim 9, further comprising:

dividing the scheduled CBGs into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.
The method of claim 1, wherein if multiple TBs are scheduled for the PDSCH transmission, the UE uses at least one of inter-CBG bundling or inter-TB bundling.
The method of claim 11, wherein the UE uses at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling;

wherein if the configured number has a zero value, the UE uses the inter-CBG bundling;

wherein if the configured number is equal to the first number of HARQ bits per PDSCH transmission, the UE uses the inter-TB bundling; and

wherein if the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling are supported.
The method of claim 11, wherein both the inter-CBG bundling and the inter-TB bundling are used and the inter-TB bundling is applied to a first plurality of CBG groups per TB.
The method of claim 11, wherein the UE applies the inter-CBG bundling using equal numbers of bundles of CBG groups per TB, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.
The method of claim 11, wherein for each of the multiple TBs, the UE applies the inter-CBG bundling using a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.
An apparatus for wireless communication at a user equipment (UE) , comprising:

means for receiving a physical downlink shared channel (PDSCH) transmission from a base station comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ;

means for determining whether to apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and

means for transmitting HARQ feedback to the base station based on the determination.
The apparatus of claim 16, further comprising means for performing the method of any of claims 2-15.
An apparatus for wireless communication at a user equipment (UE) , comprising:

a memory; and

at least one processor coupled to the memory and configured to perform the method of any of claims 1-15.
A computer-readable medium storing computer executable code wireless communication at a user equipment (UE) , the code when executed by a processor cause the processor to perform the method of any of claims 1-15.
A method of wireless communication at a base station, comprising:

transmitting a physical downlink shared channel (PDSCH) transmission to a user equipment (UE) comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ;

determining whether the UE will apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and

receiving HARQ feedback from the UE based on the determination.
The method of claim 20, wherein if the first number of HARQ bits is greater than or equal to the second number of scheduled CBGs, the base station determines that the UE will not apply HARQ feedback bundling.
The method of claim 20, wherein if the first number of HARQ bits is less than the second number of scheduled CBGs, the base station determines that the UE will apply HARQ feedback bundling.
The method of claim 20, wherein the first number of HARQ bits represents a maximum number of HARQ bits per PDSCH transmission, and wherein the second number of scheduled CBGs is based on a code block group transmission information (CBGTI) field in downlink control information (DCI) transmitted by the base station.
The method of claim 23, wherein the HARQ feedback is based on a semi-static codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is cell specific.
The method of claim 24, further comprising:

transmitting a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or

indicating the maximum number of HARQ bits per PDSCH transmission based on a last DCI transmitted in a bundling window.
The method of claim 23, wherein the HARQ feedback is based on a dynamic codebook, and wherein the maximum number of HARQ bits per PDSCH transmission is common to each configured cell for the UE.
The method of claim 26, further comprising:

transmitting a configuration of the maximum number of HARQ bits per PDSCH transmission in radio resource control (RRC) signaling; or

indicating the maximum number of HARQ bits per PDSCH transmission based on a payload limitation or a coding rate for an uplink control channel.
The method of claim 20, wherein if a single transport block is scheduled for the PDSCH transmission, the base station receives the HARQ feedback based on inter-CBG bundling.
The method of claim 28, wherein the scheduled CBGs are divided into a plurality of bundles based on the first number of HARQ bits per PDSCH transmission, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.
The method of claim 20, wherein if multiple TBs are scheduled for the PDSCH transmission, the base station receives the HARQ feedback based on at least one of inter-CBG bundling or inter-TB bundling.
The method of claim 30, wherein the base station receives the HARQ feedback based on at least one of the inter-CBG bundling or the inter-TB bundling further based on a configured number of HARQ bits for the inter-TB bundling;

wherein if the configured number has a zero value, the base station receives the HARQ feedback based on the inter-CBG bundling;

wherein if the configured number is equal to the first number of HARQ bits per PDSCH transmission, the base station receives the HARQ feedback based on the inter-TB bundling; and

wherein if the configured number has a non-zero value that is smaller than the first number of HARQ bits per PDSCH transmission, both the inter-CBG bundling and the inter-TB bundling are supported.
The method of claim 31, wherein the base station receives the HARQ feedback based on both the inter-CBG bundling and the inter-TB bundling with the inter-TB bundling applied to a first plurality of CBG groups per TB.
The method of claim 30, wherein the inter-CBG bundling uses equal numbers of bundles of CBG groups per TB, wherein each bundle comprises a set of consecutive CBGs based on a bundling size and a CBG index.
The method of claim 30, wherein for each of the multiple TBs, the inter-CBG bundling uses a non-equal number of bundles of CBGs groups per TB that is scaled based on the second number of scheduled CBGs for a corresponding TB.
An apparatus for wireless communication at a at a base station, comprising:

means for transmitting a physical downlink shared channel (PDSCH) transmission to a user equipment (UE) comprising one or more transport block (TB) that includes one or more code block groups (CBGs) ;

means for determining whether the UE will apply hybrid automatic repeat request (HARQ) feedback bundling based on a first number of HARQ bits per PDSCH transmission and a second number of scheduled CBGs across the one or more TB of the PDSCH transmission; and

means for receiving HARQ feedback to the base station based on the determination.
The apparatus of claim 35, further comprising means for performing the method of any of claims 21-34.
An apparatus for wireless communication at a base station, comprising:

a memory; and

at least one processor coupled to the memory and configured to perform the method of any of claims 20-34.
A computer-readable medium storing computer executable code wireless communication at a base station, the code when executed by a processor cause the processor to perform the method of any of claims 20-34.