FALLBACK OPERATION FOR A SEMI-STATIC HYBRID AUTOMATIC REPEAT REQUEST FEEDBACK CODEBOOK FOR MULTICAST

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, from a network entity, configuration information associated with a semi-static hybrid automatic repeat request (HARQ) feedback codebook for multicast messages. The UE may receive, from the network entity, a physical downlink control channel (PDCCH) message, associated with a radio network temporary identifier (RNTI), scheduling one or more multicast physical downlink shared channel (PDSCH) messages. The UE may transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI. Numerous other aspects are provided.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and specifically, to techniques and apparatuses associated with a fallback operation for a semi-static hybrid automatic repeat request (HARQ) feedback codebook for multicast.

BACKGROUND

In some examples, a multicast broadcast service architecture may be deployed in a wireless network to support multicast or broadcast services to simultaneously disseminate data, such as emergency alerts or audio or video content, among many other possibilities, to multiple user equipments (UEs) that may be located in the same or different cells. In general, because multicast broadcast operations enable multiple UEs to receive the same data at substantially the same time, multicast operations can significantly reduce network overhead relative to unicast operations in which a particular transmission is received by only one UE. In some cases, a UE may support hybrid automatic repeat request (HARQ) feedback codebook transmissions. A HARQ feedback codebook transmission may include a feedback message that the UE is to transmit to a network entity to provide feedback regarding, for example, downlink data transmission (for example, transmissions associated with a physical downlink shared channel (PDSCH)).

The UE may be configured with different types of codebooks, such as a Type-1 HARQ acknowledgement (ACK) codebook or a Type-2 HARQ ACK codebook. For example, the Type-1 HARQ ACK codebook may be associated with a fixed, or static, size (for example, that is configured by the network entity). The Type-2 HARQ ACK codebook may be associated with a dynamic size (for example, where the size of the Type-2 HARQ ACK codebook is based at least in part on, or otherwise associated with, scheduling received by the UE). Typically, if the UE is configured to transmit a Type-1 HARQ ACK codebook, the UE may collect feedback for PDSCH communications that are received by the UE during a feedback window (for example, k slots), and may transmit the Type-1 HARQ ACK codebook indicating feedback (for example, ACK/NACK feedback) associated with the PDSCH communications that are received by the UE during the feedback window. In some cases, if a small quantity of PDSCH communications are received during the feedback window, transmitting the Type-1 HARQ ACK codebook may consume significant resources (for example, time resources or frequency resources) because the Type-1 HARQ ACK codebook has a fixed sized regardless of the quantity of PDSCH communications that are received by the UE during the feedback window.

Therefore, in some cases, a fallback operation associated with Type-1 HARQ ACK codebooks may be supported by the UE. For example, in some cases, the UE may be enabled to transmit a fallback HARQ feedback indication (for example, that includes a single ACK/NACK indication or bit) that is associated with a smaller size than the Type-1 HARQ ACK codebook. In some cases, the fallback operation for Type-1 HARQ ACK codebook transmissions may be used for multicast or broadcast PDSCH receptions (for example, if the UE is configured to transmit HARQ ACK feedback). However, multicast or broadcast PDSCH receptions introduce additional problems and considerations that are not present for unicast PDSCH receptions, such as determining when to trigger or perform the fallback operation for Type-1 HARQ ACK codebook transmissions. For example, for multicast PDSCH receptions, multiple radio network temporary identifiers (RNTIs) may be configured, by one or more network entities, for the UE. Therefore, in a single feedback window for a Type-1 HARQ ACK codebook transmission, the UE may receive communications associated with different RNTIs. As another example, feedback configurations for different RNTIs may be different. For example, a given RNTI configured for the UE may be associated with dynamic enabling or disabling of feedback for communications associated with the given RNTI. Therefore, in some cases, a first RNTI may have feedback enabled for communications associated with the first RNTI and a second RNTI may have feedback disabled for communications associated with the second RNTI. As another example, some RNTIs may be associated with different feedback types than other RNTIs. For example, a first RNTI may be associated with negative ACK (NACK) only feedback (for example, where only NACK indications, and not ACK indications, are transmitted by the UE to the network entity) and a second RNTI may be associated with ACK/NACK feedback (for example, where both ACK indications and NACK indications are transmitted by the UE to the network entity). Therefore, handling of the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast or broadcast scenarios may be associated with additional considerations that are not currently addressed or defined by wireless communication standards. As a result, different UEs may handle the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast or broadcast scenarios differently, which may result in the network entity incorrectly interpreting feedback received from the different UEs.

SUMMARY

Some aspects described herein relate to a user equipment (UE) for wireless communication. The UE may include at least one memory and at least one processor communicatively coupled with the at least one memory. The at least one processor may be configured to cause the UE to receive, from a network entity, configuration information associated with a semi-static hybrid automatic repeat request (HARQ) feedback codebook for multicast messages. The at least one processor may be configured to cause the UE to receive, from the network entity, a physical downlink control channel (PDCCH) message, associated with a radio network temporary identifier (RNTI), scheduling one or more multicast physical downlink shared channel (PDSCH) messages. The at least one processor may be configured to cause the UE to transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to a network entity for wireless communication. The network entity may include at least one memory and at least one processor communicatively coupled with the at least one memory. The at least one processor may be configured to cause the network entity to transmit configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages. The at least one processor may be configured to cause the network entity to transmit a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages. The at least one processor may be configured to cause the network entity to receive one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to a method of wireless communication performed by a UE. The method may include receiving, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The method may include receiving, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The method may include transmitting, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to a method of wireless communication performed by a network entity. The method may include transmitting configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages. The method may include transmitting a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages. The method may include receiving one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a UE. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The set of instructions, when executed by one or more processors of the UE, may cause the UE to transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a network entity. The set of instructions, when executed by one or more processors of the network entity, may cause the network entity to transmit configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages. The set of instructions, when executed by one or more processors of the network entity, may cause the network entity to transmit a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages. The set of instructions, when executed by one or more processors of the network entity, may cause the network entity to receive one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for receiving, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The apparatus may include means for receiving, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The apparatus may include means for transmitting, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for transmitting configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages. The apparatus may include means for transmitting a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages. The apparatus may include means for receiving one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, or processing system as substantially described with reference to and as illustrated by the drawings and specification.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and are not to be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. One skilled in the art may appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any quantity of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. Any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Various aspects relate generally to a fallback operation for a semi-static hybrid automatic repeat request (HARQ) feedback codebook (for example, a Type-1 HARQ acknowledgement (ACK) codebook) for multicast communications. Some aspects more specifically relate to a user equipment (UE) transmitting a fallback HARQ feedback indication for one or more multicast communications (for example, a single ACK or negative ACK (NACK) feedback indication) associated with a semi-static HARQ feedback codebook (for example, a Type-1 HARQ ACK codebook) based at least in part on, or otherwise associated with, a radio network temporary identifier (RNTI) associated with the one or more multicast communications or a feedback configuration associated with the RNTI.

In some aspects, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the UE receiving only a single physical downlink shared channel (PDSCH) multicast communication (for example, a dynamic grant PDSCH communication or a semi-persistent scheduling (SPS) PDSCH communication) or a single multicast SPS PDSCH release communication (for example, a physical downlink control channel (PDCCH) communication that does not schedule any PDSCH communications) associated with any RNTI (for example, any group common RNTI (G-RNTI) or any group common configured scheduling RNTI (G-CS-RNTI)) during a feedback window associated with the Type-1 HARQ ACK codebook. In other words, if the UE receives multicast communications associated with different RNTIs during the feedback window, then the UE may transmit the semi-static HARQ feedback codebook (for example, a Type-1 HARQ ACK codebook), rather than transmitting the fallback HARQ feedback indication. In some other aspects, the UE may transmit a fallback HARQ feedback indication for each RNTI. For example, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the UE receiving only a single PDSCH multicast communication (for example, a dynamic grant PDSCH communication or an SPS PDSCH communication) or a single multicast SPS PDSCH release communication (for example, a PDCCH communication that does not schedule any PDSCH communications) associated with an RNTI (for example, a G-RNTI or a G-CS-RNTI) during a feedback window associated with the Type-1 HARQ ACK codebook. For example, the UE may transmit a first fallback HARQ feedback indication associated with a first RNTI and a second fallback HARQ feedback indication associated with a second RNTI.

Additionally or alternatively, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the feedback configuration associated with the RNTI indicating that feedback is enabled for the RNTI. In some examples, if the feedback configuration associated with the RNTI indicates that feedback is disabled for the RNTI, then the UE may not transmit the fallback HARQ feedback indication. Alternatively, in some other examples, if the feedback configuration associated with the RNTI indicates that feedback is disabled for the RNTI, then the UE may transmit a NACK indication regardless of whether the one or more multicast communications were successfully received.

Additionally or alternatively, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the feedback configuration associated with the RNTI indicating that the RNTI is associated with ACK/NACK-based feedback (rather than NACK-only-based feedback). In some examples, if the feedback configuration associated with the RNTI indicates that the RNTI is associated with NACK-only based feedback, then the UE may not transmit the fallback HARQ feedback indication. Alternatively, in some other examples, if the feedback configuration associated with the RNTI indicates that feedback is associated with NACK-only based feedback, then the UE may transform the NACK-only feedback to ACK/NACK-based feedback (for example, may transmit the fallback HARQ feedback indication indicating ACK feedback or NACK feedback based at least in part on, or otherwise associated with, whether the one or more multicast communications were successfully received by the UE).

Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some examples, the described techniques can be used to synchronize a fallback operation associated with semi-static HARQ feedback codebooks (for example, Type-1 HARQ ACK codebooks) in multicast scenarios. For example, the described techniques can be used to clarify when a UE is to transmit a fallback HARQ feedback indication associated with a Type-1 HARQ ACK codebook considering additional factors present in multicast scenarios, such as the UE being configured with multiple RNTIs, feedback being enabled or disabled for certain RNTIs of the configured RNTIs, or feedback reporting being different for certain RNTIs of the configured RNTIs, among other examples. As a result, multiple UEs may handle the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast scenarios in the same manner, which may enable a network entity to correctly interpret feedback received from the UEs.

A base station110may provide communication coverage for a macro cell, a pico cell, a femto cell, or another type of cell. A macro cell may cover a relatively large geographic area (for example, several kilometers in radius) and may allow unrestricted access by UEs120with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs120with service subscription. A femto cell may cover a relatively small geographic area (for example, a home) and may allow restricted access by UEs120having association with the femto cell (for example, UEs120in a closed subscriber group (CSG)). A base station110for a macro cell may be referred to as a macro base station. A base station110for a pico cell may be referred to as a pico base station. A base station110for a femto cell may be referred to as a femto base station or an in-home base station.

The wireless network100may be a heterogeneous network that includes base stations110of different types, such as macro base stations, pico base stations, femto base stations, or relay base stations. These different types of base stations110may have different transmit power levels, different coverage areas, or different impacts on interference in the wireless network100. For example, macro base stations may have a high transmit power level (for example, 5 to 40 watts) whereas pico base stations, femto base stations, and relay base stations may have lower transmit power levels (for example, 0.1 to 2 watts). In the example shown inFIG.1, the BS110amay be a macro base station for a macro cell102a, the BS110bmay be a pico base station for a pico cell102b, and the BS110cmay be a femto base station for a femto cell102c. A base station may support one or multiple (for example, three) cells. A network controller130may couple to or communicate with a set of base stations110and may provide coordination and control for these base stations110. The network controller130may communicate with the base stations110via a backhaul communication link. The base stations110may communicate with one another directly or indirectly via a wireless or wireline backhaul communication link.

In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move in accordance with the location of a base station110that is mobile (for example, a mobile base station). In some examples, the base stations110may be interconnected to one another or to one or more other base stations110or network nodes (not shown) in the wireless network100through various types of backhaul interfaces, such as a direct physical connection or a virtual network, using any suitable transport network.

The wireless network100may include one or more relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (for example, a base station110or a UE120) and send a transmission of the data to a downstream station (for example, a UE120or a base station110). A relay station may be a UE120that can relay transmissions for other UEs120. In the example shown inFIG.1, the BS110d(for example, a relay base station) may communicate with the BS110a(for example, a macro base station) and the UE120din order to facilitate communication between the BS110aand the UE120d. A base station110that relays communications may be referred to as a relay station, a relay base station, or a relay.

The UEs120may be dispersed throughout the wireless network100, and each UE120may be stationary or mobile. A UE120may include, for example, an access terminal, a terminal, a mobile station, or a subscriber unit. A UE120may be a cellular phone (for example, a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device, a biometric device, a wearable device (for example, a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (for example, a smart ring or a smart bracelet)), an entertainment device (for example, a music device, a video device, or a satellite radio), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium.

Some UEs120may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. An MTC UE or an eMTC UE may include, for example, a robot, a drone, a remote device, a sensor, a meter, a monitor, or a location tag, that may communicate with a base station, another device (for example, a remote device), or some other entity. Some UEs120may be considered Internet-of-Things (IoT) devices, or may be implemented as NB-IoT (narrowband IoT) devices. Some UEs120may be considered a Customer Premises Equipment. A UE120may be included inside a housing that houses components of the UE120, such as processor components or memory components. In some examples, the processor components and the memory components may be coupled together. For example, the processor components (for example, one or more processors) and the memory components (for example, a memory) may be operatively coupled, communicatively coupled, electronically coupled, or electrically coupled.

In general, any quantity of wireless networks100may be deployed in a given geographic area. Each wireless network100may support a particular RAT and may operate on one or more frequencies. A RAT may be referred to as a radio technology or an air interface. A frequency may be referred to as a carrier or a frequency channel. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some examples, two or more UEs120(for example, shown as UE120aand UE120e) may communicate directly using one or more sidelink channels (for example, without using a base station110as an intermediary to communicate with one another). For example, the UEs120may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (for example, which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, or a vehicle-to-pedestrian (V2P) protocol), or a mesh network. In such examples, a UE120may perform scheduling operations, resource selection operations, or other operations described elsewhere herein as being performed by the base station110.

In some aspects, the UE120may include a communication manager140. As described in more detail elsewhere herein, the communication manager140may receive, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages; receive, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages; and transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and based at least in part on, or otherwise associated with, at least one of the RNTI or a feedback configuration associated with the RNTI. Additionally or alternatively, the communication manager140may perform one or more other operations described herein.

In some aspects, a network entity (e.g., the base station110) may include a communication manager150. As described in more detail elsewhere herein, the communication manager150may transmit, to one or more UEs, configuration information associated with a semi-static HARQ feedback codebook for multicast messages; transmit, to the one or more UEs, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages; and receive, from a UE of the one or more UEs, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and based at least in part on, or otherwise associated with, at least one of the RNTI or a feedback configuration associated with the RNTI. Additionally or alternatively, the communication manager150may perform one or more other operations described herein.

FIG.2is a diagram illustrating an example base station in communication with a UE in a wireless network in accordance with the present disclosure. The base station may correspond to the base station110ofFIG.1. Similarly, the UE may correspond to the UE120ofFIG.1. The base station110may be equipped with a set of antennas234athrough234t, such as T antennas (T≥1). The UE120may be equipped with a set of antennas252athrough252r, such as R antennas (R≥1).

At the base station110, a transmit processor220may receive data, from a data source212, intended for the UE120(or a set of UEs120). The transmit processor220may select one or more modulation and coding schemes (MCSs) for the UE120based at least in part on, or otherwise associated with, one or more channel quality indicators (CQIs) received from that UE120. The base station110may process (for example, encode and modulate) the data for the UE120based at least in part on, or otherwise associated with, the MCS(s) selected for the UE120and may provide data symbols for the UE120. The transmit processor220may process system information (for example, for semi-static resource partitioning information (SRPI)) and control information (for example, CQI requests, grants, or upper layer signaling) and provide overhead symbols and control symbols. The transmit processor220may generate reference symbols for reference signals (for example, a cell-specific reference signal (CRS) or a demodulation reference signal (DMRS)) and synchronization signals (for example, a primary synchronization signal (PSS) or a secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor230may perform spatial processing (for example, precoding) on the data symbols, the control symbols, the overhead symbols, or the reference symbols, if applicable, and may provide a set of output symbol streams (for example, T output symbol streams) to a corresponding set of modems232(for example, T modems), shown as modems232athrough232t. For example, each output symbol stream may be provided to a modulator component (shown as MOD) of a modem232. Each modem232may use a respective modulator component to process a respective output symbol stream (for example, for OFDM) to obtain an output sample stream. Each modem232may further use a respective modulator component to process (for example, convert to analog, amplify, filter, or upconvert) the output sample stream to obtain a downlink signal. The modems232athrough232tmay transmit a set of downlink signals (for example, T downlink signals) via a corresponding set of antennas234(for example, T antennas), shown as antennas234athrough234t.

At the UE120, a set of antennas252(shown as antennas252athrough252r) may receive the downlink signals from the base station110or other base stations110and may provide a set of received signals (for example, R received signals) to a set of modems254(for example, R modems), shown as modems254athrough254r. For example, each received signal may be provided to a demodulator component (shown as DEMOD) of a modem254. Each modem254may use a respective demodulator component to condition (for example, filter, amplify, downconvert, or digitize) a received signal to obtain input samples. Each modem254may use a demodulator component to further process the input samples (for example, for OFDM) to obtain received symbols. A MIMO detector256may obtain received symbols from the modems254, may perform MIMO detection on the received symbols if applicable, and may provide detected symbols. A receive processor258may process (for example, demodulate and decode) the detected symbols, may provide decoded data for the UE120to a data sink260, and may provide decoded control information and system information to a controller/processor280. The term “controller/processor” may refer to one or more controllers, one or more processors, or a combination thereof. A channel processor may determine a reference signal received power (RSRP) parameter, a received signal strength indicator (RSSI) parameter, a reference signal received quality (RSRQ) parameter, or a CQI parameter, among other examples. In some examples, one or more components of the UE120may be included in a housing.

One or more antennas (for example, antennas234athrough234tor antennas252athrough252r) may include, or may be included within, one or more antenna panels, one or more antenna groups, one or more sets of antenna elements, or one or more antenna arrays, among other examples. An antenna panel, an antenna group, a set of antenna elements, or an antenna array may include one or more antenna elements (within a single housing or multiple housings), a set of coplanar antenna elements, a set of non-coplanar antenna elements, or one or more antenna elements coupled to one or more transmission or reception components, such as one or more components ofFIG.2.

On the uplink, at the UE120, a transmit processor264may receive and process data from a data source262and control information (for example, for reports that include RSRP, RSSI, RSRQ, or CQI) from the controller/processor280. The transmit processor264may generate reference symbols for one or more reference signals. The symbols from the transmit processor264may be precoded by a TX MIMO processor266if applicable, further processed by the modems254(for example, for DFT-s-OFDM or CP-OFDM), and transmitted to the base station110. In some examples, the modem254of the UE120may include a modulator and a demodulator. In some examples, the UE120includes a transceiver. The transceiver may include any combination of the antenna(s)252, the modem(s)254, the MIMO detector256, the receive processor258, the transmit processor264, or the TX MIMO processor266. The transceiver may be used by a processor (for example, the controller/processor280) and the memory282to perform aspects of any of the methods described herein.

The controller/processor240of the base station110, the controller/processor280of the UE120, or any other component(s) ofFIG.2may perform one or more techniques associated with a fallback operation for a semi-static HARQ feedback codebook for multicast, as described in more detail elsewhere herein. For example, the controller/processor240of the base station110, the controller/processor280of the UE120, or any other component(s) ofFIG.2may perform or direct operations of, for example, process700ofFIG.7, process800ofFIG.8, or other processes as described herein. The memory242and the memory282may store data and program codes for the base station110and the UE120, respectively. In some examples, the memory242or the memory282may include a non-transitory computer-readable medium storing one or more instructions (for example, code or program code) for wireless communication. For example, the one or more instructions, when executed (for example, directly, or after compiling, converting, or interpreting) by one or more processors of the base station110or the UE120, may cause the one or more processors, the UE120, or the base station110to perform or direct operations of, for example, process700ofFIG.7, process800ofFIG.8, or other processes as described herein. In some examples, executing instructions may include running the instructions, converting the instructions, compiling the instructions, or interpreting the instructions, among other examples.

In some aspects, the UE120includes means for receiving, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages; means for receiving, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages; or means for transmitting, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and based at least in part on, or otherwise associated with, at least one of the RNTI or a feedback configuration associated with the RNTI. The means for the UE120to perform operations described herein may include, for example, one or more of communication manager140, antenna252, modem254, MIMO detector256, receive processor258, transmit processor264, TX MIMO processor266, controller/processor280, or memory282.

In some aspects, a network entity includes means for transmitting configuration information associated with a semi-static HARQ feedback codebook for multicast messages; means for transmitting a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages; or means for receiving one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and based at least in part on, or otherwise associated with, at least one of the RNTI or a feedback configuration associated with the RNTI. In some aspects, the means for the network entity to perform operations described herein may include, for example, one or more of communication manager150, transmit processor220, TX MIMO processor230, modem232, antenna234, MIMO detector236, receive processor238, controller/processor240, memory242, or scheduler246.

Deployment of communication systems, such as 5G NR systems, may be arranged in multiple manners with various components or constituent parts. In a 5G NR system, or network, a network node, a network entity, a mobility element of a network, a RAN node, a core network node, a network element, a base station, or a network equipment may be implemented in an aggregated or disaggregated architecture. For example, a base station (such as a Node B (NB), an evolved NB (eNB), an NR BS, a 5G NB, an access point (AP), a TRP, or a cell, among other examples), or one or more units (or one or more components) performing base station functionality, may be implemented as an aggregated base station (also known as a standalone base station or a monolithic base station) or a disaggregated base station.

An aggregated base station may be configured to utilize a radio protocol stack that is physically or logically integrated within a single RAN node (for example, within a single device or unit). A disaggregated base station may be configured to utilize a protocol stack that is physically or logically distributed among two or more units (such as a CU, one or more DUs, or one or more RUs). In some examples, a CU may be implemented within a RAN node, and one or more DUs may be co-located with the CU, or alternatively, may be geographically or virtually distributed throughout one or multiple other RAN nodes. The DUs may be implemented to communicate with one or more RUs. Each of the CU, DU, and RU also can be implemented as virtual units, such as a virtual central unit (VCU), a virtual distributed unit (VDU), or a virtual radio unit (VRU), among other examples.

In some cases, a multicast communication may be a communication of information to a plurality (for example, a set) of UEs120. In some cases, each of the UEs120may need to join a multicast session prior to receiving information using the multicast communication. For example, the UEs120may join the multicast session using non-access stratum (NAS) based signaling. In some cases, the UEs120may need to be authorized, or authenticated, prior to joining the multicast session. For example, the base station may indicate to a UE120, of the set of UEs120, whether the UE120is authorized or authenticated prior to the UE120joining the multicast session and receiving information via a multicast communication. In some cases, not all of the UEs120within an area (for example, a multicast service area) may receive the information via the multicast communication. For example, the base station may transmit the information to a subset of the UEs120, of the set of UEs120, within the multicast service area. In some cases, a UE120in the multicast service area that has not been authorized or authenticated may not receive the information via the multicast communication. In some cases, the base station is aware of whether or not individual UEs120, of the set of UEs120, have received the information using the multicast communication. In some cases, the multicast communication may be referred to as a “one-to-many” communication.

In some cases, a broadcast communication may be a communication of information to all UEs120within an area (for example, a broadcast service area). The UEs120may not need to join a session prior to receiving the information using the broadcast communication. For example, the UEs120may not need to access a session using NAS based signaling prior to receiving the information using the broadcast communication. In some cases, the UEs120may not need to be authorized, or authenticated, prior to receiving information via a broadcast communication. In some cases, the base station may transmit the information to all of the UEs120within the broadcast service area. For example, the base station may not be able to broadcast the information to only a subset of the UEs120. In some cases, the base station may not be aware of whether or not individual UEs120, of the set of UEs120, have received the information using the broadcast communication. In some cases, the broadcast communication may be referred to as a “one-to-all” communication.

FIG.4is a diagram illustrating an example of an MBS architecture400in accordance with the present disclosure. In some examples, the multicast broadcast service architecture may be deployed in a wireless network (for example, wireless network100) to support multicast or broadcast services to simultaneously disseminate data, such as emergency alerts or audio or video content, among many other possibilities, to multiple UEs that may be located in the same or different cells. In general, because multicast broadcast operations enable multiple UEs to receive the same data at substantially the same time, multicast operations can significantly reduce network overhead relative to unicast operations in which a particular transmission is received by only one UE.

In a wireless network, MBS operations may be supported using enhanced multimedia broadcast/multicast service (eMBMS), single-cell point-to-multipoint (SC-PTM) services, multimedia broadcast multicast service over single frequency network (MBSFN), or enhanced TV (EnTV), among other examples. For example, in eMBMS, multicast data is transmitted in multiple cells to a group of UEs located in a particular area. In SC-PTM, multicast data is transmitted in a particular cell and the multicast data is received by a group of UEs that are located in the particular cell. In an NR network, a UE may receive multicast broadcast services in mixed mode or broadcast mode. For example, in mixed mode, a UE in an RRC connected mode may receive multicast broadcast service using a multicast broadcast radio bearer (MRB) or a dedicated radio bearer (DRB). In broadcast mode, a UE may receive multicast broadcast service using an MRB in an RRC connected mode, an RRC idle mode, or an RRC inactive mode.

As shown inFIG.4, the MBS architecture400may include a multicast broadcast user plane function (MB-UPF) that receives (for example, from an application server) a multicast broadcast (MB) flow including content to be multicasted or broadcasted. As further shown, the multicast broadcast service architecture may include a centralized base station unit (gNB-CU), such as a CU, that receives the MB flow and a temporary mobile group identity (TMGI) associated with the MB flow from the MB-UPF over an MB-N3 tunnel (for example, a user plane interface for delivering the MB flow and the corresponding TMGI using a general packet radio service tunneling protocol (GTP)). Furthermore, the gNB-CU may communicate with an AMF that manages UE network registration, manages mobility, maintains non-access stratum (NAS) signaling connections, or manages UE registration procedures, among other examples. For example, the gNB-CU may communicate with the AMF over an N2 interface that enables control signaling to establish or modify the MB flow or the TMGI.

In some examples, the gNB-CU may map the MB flow received from the MB-UPF to an MRB or a DRB based at least in part on, or otherwise associated with, the TMGI associated with the MB flow, and the gNB-CU may forward the MB flow to a DU that may include one or more TRPs, which may multicast or broadcast the content included in the MB flow to one or more UEs via an MRB. Additionally or alternatively, the DU may transmit the content included in the MB flow to one or more UEs via a DRB. In this way, the multicast broadcast service architecture may flexibly switch between transmitting content to UEs via a DRB (or a unicast bearer) and an MRB, and may provide unicast assistance to the MRB at lower layers to improve reliability or reduce service disruption.

FIG.5is a diagram illustrating an example of a channel mapping500for MBS communications in accordance with the present disclosure. As shown by MBS channels502, multicast or broadcast transmissions in an NR network may be supported using a multicast broadcast traffic channel (MTCH) and a multicast broadcast control channel (MCCH). The MTCH may carry multicast or broadcast data, while the MCCH may carry configuration information or control information for multicast or broadcast communications to be transmitted on the MTCH. An MBS communication on the MTCH may be addressed to a group of UEs using a group common radio network temporary identifier (G-RNTI).

In some examples, different MTCHs may be used to carry multicast broadcast traffic with different quality of service (QoS) requirements. A multicast broadcast traffic flow with associated QoS requirements or QoS parameters (for example, a group of related packets for the same multicast broadcast service) may be referred to as an MB-QoS flow. In some examples, there may be a one-to-one mapping between MB-QoS flows and MTCHs. A base station or a core network device may configure a multicast broadcast radio bearer (MRB) for an MB-QoS flow. In some examples, there may be a one-to-one mapping between MB-QoS flows and MRBs. Accordingly, each MTCH may correspond to an MRB for carrying an MB-QoS flow.

The MCCH may carry configuration information for configuring the MTCHs, and may be addressed to all UEs in a cell (for example, a physical cell or a virtual cell) using a single cell RNTI (SC-RNTI). In some examples, there may be a single MCCH per cell (physical cell or virtual cell), and the MCCH may carry MTCH configuration information for multiple multicast broadcast services with different MB-QoS flows. As shown by channel mapping504, the MCCH and the MTCH are logical channels, and may be mapped to a downlink shared channel (DL-SCH) transport channel, which may be mapped to a physical downlink shared channel (PDSCH).

In some cases, a UE may support HARQ feedback codebook transmissions (for example, at least for multicast services with a quality of service (QoS) requirement). A HARQ feedback codebook transmission may include a feedback message that the UE is to transmit to a network entity to provide feedback regarding, for example, downlink data transmission (for example, transmissions associated with a physical downlink shared channel (PDSCH)). For example, the UE may be configured to transmit HARQ codebook transmissions (for example, corresponding to one or more HARQ process identifiers).

The UE may be configured with different types of codebooks, such as a Type-1 HARQ acknowledgement (ACK) codebook or a Type-2 HARQ ACK codebook. The Type-1 HARQ ACK codebook may be referred to herein as a “semi-static HARQ feedback codebook.” The Type-2 HARQ ACK codebook may be referred to as a “dynamic HARQ feedback codebook.” For example, the Type-1 HARQ ACK codebook may be associated with a fixed, or static, size (for example, that is configured by the network entity). The Type-2 HARQ ACK codebook may be associated with a dynamic size (for example, where the size of the Type-2 HARQ ACK codebook is based at least in part on, or otherwise associated with, scheduling received by the UE). Additional details regarding some HARQ ACK codebooks can be found in, for example, 3GPP Technical Specification (TS) 38.213, Release (Rel.) 17, Version 17.0.0, such as in Section 9.1. Another type of HARQ ACK codebook that the UE may support is an enhanced Type-3 HARQ ACK Codebook, which may have a smaller size relative to other HARQ ACK codebooks defined for Rel. 16.

A codebook may be a sequence of bits, which may be constructed using ACK/NACK feedback associated with multiple PDSCH communications that are received by a UE during a feedback window. For Type-1 HARQ ACK codebooks, typically, if the UE is configured to transmit a Type-1 HARQ ACK codebook, the UE may collect feedback for PDSCH communications that are received by the UE during a feedback window (for example, k slots), and may transmit the Type-1 HARQ ACK codebook indicated feedback (for example, ACK/NACK feedback) associated with the PDSCH communications that are received by a UE during the feedback window. As described above, the Type-1 HARQ ACK codebook may have a static or fixed size. Therefore, in some cases, if a small quantity of PDSCH communications are received during the feedback window, transmitting the Type-1 HARQ ACK codebook may consume significant resources (for example, time resources or frequency resources) because the Type-1 HARQ ACK codebook has a fixed sized regardless of the quantity of PDSCH communications that are received by the UE during the feedback window.

Therefore, in some cases, a fallback operation associated with Type-1 HARQ ACK codebooks may be supported by the UE. For example, in some cases, the UE may be enabled to transmit a fallback HARQ feedback indication (for example, that includes a single ACK/NACK indication or bit) that is associated with a smaller size than the Type-1 HARQ ACK codebook. For example, if the UE is to report HARQ-ACK information via a physical uplink control channel (PUCCH), and the UE is configured to transmit Type-1 HARQ ACK codebooks, the UE may transmit a fallback HARQ feedback indication if, during a feedback window, the UE receives a single PDCCH communication scheduling one or more PDSCH communications. In some examples, the UE may transmit a fallback HARQ feedback indication if, during a feedback window, the UE receives a semi-persistent scheduling (SPS) PDSCH release (for example, a PDCCH communication with no scheduled PDSCH data) indicated by a downlink control information (DCI) format1_0(for example, with a counter downlink assignment index (DAI) field value of 1, thereby indicating that there is only 1 transmission of the PDCCH communication)), a PDSCH communication scheduled by a DCI format1_0with a counter DAI field value of 1 (for example, on a primary cell (PCell) associated with the UE), or one or more SPS PDSCH communications (for example, associated with a single PDCCH communication or no PDCCH communications). The network entity may perform a blind decoding to determine if the Type-1 HARQ ACK codebook or the fallback HARQ feedback indication is transmitted by the UE. The fallback operation may be defined, or otherwise fixed, for unicast communications by 3GPP TS 38.213, Rel. 17, Version 17.0.0, such as in Section 9.1.2.

In some cases, the fallback operation for Type-1 HARQ ACK codebook transmissions may be used for multicast or broadcast PDSCH receptions (for example, if the UE is configured to transmit HARQ-ACK feedback). However, multicast or broadcast PDSCH receptions introduce additional problems and considerations that are not present for unicast PDSCH receptions for determining, by a UE, when to trigger or perform the fallback operation for Type-1 HARQ ACK codebook transmissions. For example, for multicast or broadcast PDSCH receptions, multiple RNTIs (for example, multiple G-RNTIs or multiple group common configured scheduling (G-CS-RNTIs) may be configured, by one or more network entities, for the UE. Therefore, in a single feedback window for a Type-1 HARQ ACK codebook transmission, the UE may receive communications associated with different RNTIs. As another example, feedback configurations for different RNTIs may be different. For example, a given RNTI configured for the UE may be associated with dynamic enabling or disabling of feedback for communications associated with the given RNTI. Therefore, in some cases, a first RNTI may have feedback enabled for communications associated with the first RNTI and a second RNTI may have feedback disabled for communications associated with the second RNTI. As another example, some RNTIs may be associated with different feedback types than other RNTIs. For example, a first RNTI may be associated with NACK only feedback (for example, where only NACK indications, and not ACK indications, are transmitted by the UE to the network entity) and a second RNTI may be associated with ACK/NACK feedback (for example, where both ACK indications and NACK indications are transmitted by the UE to the network entity). Therefore, handling of the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast scenarios may be associated with additional considerations that are not currently addressed or defined by wireless communication standards. As a result, different UEs may handle the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast scenarios differently, which may result in the network entity incorrectly interpreting feedback received from the different UEs.

Various aspects relate generally to a fallback operation for a semi-static HARQ feedback codebook (for example, a Type-1 HARQ ACK codebook) for multicast communications. Some aspects more specifically relate to a UE transmitting a fallback HARQ feedback indication for one or more multicast communications (for example, a single ACK or NACK feedback indication) associated with a semi-static HARQ feedback codebook (for example, a Type-1 HARQ ACK codebook) based at least in part on, or otherwise associated with, an RNTI associated with the one or more multicast communications or a feedback configuration associated with the RNTI.

In some aspects, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the UE receiving only a single PDSCH multicast communication (for example, a dynamic grant PDSCH communication or an SPS PDSCH communication) or a single multicast SPS PDSCH release communication (for example, a PDCCH communication that does not schedule any PDSCH communications) associated with any RNTI (for example, any G-RNTI or any G-CS-RNTI) during a feedback window associated with the Type-1 HARQ ACK codebook. In other words, if the UE receives multicast communications associated with different RNTIs during the feedback window, then the UE may transmit the semi-static HARQ feedback codebook (for example, a Type-1 HARQ ACK codebook), rather than transmitting the fallback HARQ feedback indication. In some other aspects, the UE may transmit a fallback HARQ feedback indication for each RNTI. For example, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the UE receiving only a single PDSCH multicast communication (for example, a dynamic grant PDSCH communication or an SPS PDSCH communication) or a single multicast SPS PDSCH release communication (for example, a PDCCH communication that does not schedule any PDSCH communications) associated with an RNTI (for example, a G-RNTI or a G-CS-RNTI) during a feedback window associated with the Type-1 HARQ ACK codebook. For example, the UE may transmit a first fallback HARQ feedback indication associated with a first RNTI and a second fallback HARQ feedback indication associated with a second RNTI.

Additionally or alternatively, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the feedback configuration associated with the RNTI indicating that feedback is enabled for the RNTI. If the feedback configuration associated with the RNTI indicates that feedback is disabled for the RNTI, then the UE may not transmit the fallback HARQ feedback indication. Alternatively, if the feedback configuration associated with the RNTI indicates that feedback is disabled for the RNTI, then the UE may transmit a NACK indication regardless of whether the one or more multicast communications were successfully received. Additionally or alternatively, the transmission by the UE of the fallback HARQ feedback indication for the one or more multicast communications may be based at least in part on, or otherwise associated with, the feedback configuration associated with the RNTI indicating that the RNTI is associated with ACK/NACK-based feedback (rather than NACK-only-based feedback). For example, if the feedback configuration associated with the RNTI indicates that the RNTI is associated with NACK-only based feedback, then the UE may not transmit the fallback HARQ feedback indication. Alternatively, if the feedback configuration associated with the RNTI indicates that feedback is associated with NACK-only based feedback, then the UE may transform the NACK-only feedback to ACK/NACK-based feedback (for example, may transmit the fallback HARQ feedback indication indicating ACK feedback or NACK feedback based at least in part on, or otherwise associated with, whether the one or more multicast communications were successfully received by the UE).

Particular aspects of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. In some examples, the described techniques can be used to synchronize a fallback operation associated with semi-static HARQ feedback codebooks (for example, Type-1 HARQ ACK codebooks) in multicast scenarios. For example, the described techniques can be used to clarify when a UE is to transmit a fallback HARQ feedback indication associated with a Type-1 HARQ ACK codebook considering additional factors present in multicast scenarios, such as the UE being configured with multiple RNTIs, feedback being enabled or disabled for certain RNTIs of the configured RNTIs, or feedback reporting being different for certain RNTIs of the configured RNTIs, among other examples. As a result, UEs may handle the fallback operation for Type-1 HARQ ACK codebook transmissions in multicast scenarios in the same manner, which may enable a network entity to correctly interpret feedback received from the UEs.

FIG.6is a diagram of an example associated with a fallback operation600for a semi-static hybrid automatic repeat request feedback codebook for multicast in accordance with the present disclosure. As shown inFIG.6, a network entity605may communicate with a UE (for example, the UE120). The network entity605may be a base station, a CU, a DU, or an RU, among other examples. In some aspects, the network entity605and the UE120may be part of a wireless network (for example, the wireless network100). The UE120and the network entity605may have established a wireless connection prior to operations shown inFIG.6. Although examples of the fallback operation600are described herein in connection with multicast communications, the fallback operation600may be similarly applied to broadcast communications or any other group-based messaging where a first device is transmitting a communication to multiple devices.

In a first operation610, the network entity605may transmit, and the UE120may receive, configuration information. In some aspects, the UE120may receive the configuration information via one or more of RRC signaling, one or more MAC control elements (MAC-CEs), or downlink control information (DCI), among other examples. In some aspects, the configuration information may include an indication of one or more configuration parameters (for example, already known to the UE120or previously indicated by the network entity605or other network device) for selection by the UE120, or explicit configuration information for the UE120to use to configure the UE120, among other examples.

In some aspects, the configuration information may indicate information associated with a semi-static HARQ feedback codebook for multicast messages. For example, the configuration information may indicate that the UE120is to use a Type-1 HARQ-ACK feedback codebook for multicast messages transmitted by the network entity605. For example, the network entity605may transmit an indication of a PDSCH HARQ ACK codebook field with a value of semi-static (for example, the UE may be configured with an RRC parameter pdsch-HARQ-ACK-Codebook=semi-static) for multicast messages. In some aspects, the configuration information may indicate that the UE120is to transmit the feedback (for example, is to transmit the semi-static HARQ feedback codebook) via the PUCCH (for example, rather than a physical uplink shared channel (PUSCH)). For example, the network entity605may configure the UE120to transmit a Type-1 HARQ-ACK feedback codebook for multicast messages in a similar, or the same, manner as defined by 3GPP TS 38.213, Rel. 17, Version 17.0.0.

In some aspects, the configuration information may indicate a configuration for one or more RNTIs. For example, the RNTIs may be G-RNTIs, or G-CS-RNTIs, among other examples. For example, to facilitate multicast or broadcast messaging, the network entity605may configure the UE120with multiple RNTIs (for example, to identify different groups of UEs associated with the multicast or broadcast messaging). As described elsewhere herein, an RNTI may be an identifier that is associated with a value or a range of values. For example, an RNTI may be a 16-bit identifier. Different RNTIs may have different values or ranges of values. A G-RNTI may be used for dynamic scheduling of multicast messages. A G-CS-RNTI may be used for SPS associated with multicast messages.

In some aspects, the configuration information may indicate whether a field associated with enabling or disabling feedback (for example, HARQ-ACK feedback) is to be present in DCI scheduling the multicast messages. For example, the network entity605may use RRC signaling to indicate the presence of a field for enabling or disabling HARQ-ACK feedback in group-common DCI for scheduling dynamic grant multicast messages or for activating SPS multicast messages (for example, in a DCI format4_2, as defined or otherwise fixed by the 3GPP). As another example, the network entity605may use RRC signaling to indicate whether feedback (for example, HARQ-ACK feedback) is enabled or disabled for a given RNTI configured for the UE120. For example, the configuration information may indicate whether the HARQ-ACK feedback is enabled or disabled for a given G-RNTI or a given G-CS-RNTI, among other examples.

In some aspects, the configuration information may indicate respective feedback configurations for each RNTI configured for the UE120. For example, a feedback configuration may indicate whether feedback is enabled or disabled for the RNTI associated with the feedback configuration, or a type of feedback to be associated with the RNTI. The types of feedback may include ACK/NACK feedback (for example, where the UE120may transmit ACK indications or NACK indications), or NACK-only feedback (for example, where the UE120transmits only NACK indications and not ACK indications). For example, different RNTIs may have different feedback configurations. In other words, the network entity605may separately configure feedback configurations for each RNTI that is configured for the UE120.

The UE120may configure itself based at least in part on, or otherwise associated with, the configuration information. In some aspects, the UE120may be configured to perform one or more operations described herein based at least in part on, or otherwise associated with, the configuration information.

In a second operation615, the UE may transmit, and the network entity605may receive, a capability message. In some aspects, the capability message may indicate UE support for transmitting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook (for example, the Type-1 HARQ ACK codebook). For example, the UE120may transmit, and the network entity605may receive, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook. In some aspects, the UE supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook is based at least in part on, or otherwise associated with, a type of multicast messages associated with the fallback HARQ feedback indications (for example, dynamic grant versus SPS), a frequency band associated with the fallback HARQ feedback indications, or a feature set per component-carrier (FSPC) associated with the fallback HARQ feedback indications, among other examples. For example, the capability of the UE120to support a fallback operation for the Type-1 HARQ ACK codebook associated with multicast messages may be based at least in part on, or otherwise associated with, the type of multicast messages associated with the fallback operation, a frequency band, or a FSPC, among other examples.

For example, the capability message may indicate different capabilities of the UE120associated with supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook for dynamic grant multicast messages and SPS multicast messages (for example, the capability message may indicate separate capabilities or the UE120may transmit separate capability messages). Additionally or alternatively, the UE capability to support a fallback operation for the Type-1 HARQ ACK codebook associated with multicast messages may be different for different frequency bands or different FSPCs, among other examples. In some aspects, the UE120may transmit the capability message in the second operation615prior to receiving the configuration information in the first operation610. In some aspects, the network entity605may determine the configuration information based at least in part on, or otherwise associated with, the UE capability indicated by the capability message.

In some aspects, in a third operation620, the network entity605may transmit, and the UE120may receive, a PDCCH multicast communication. For example, the network entity605may transmit, and the UE120may receive, a PDCCH message, associated with an RNTI (for example, from the RNTIs configured for the UE120in the first operation610), scheduling one or more multicast PDSCH messages. In some other aspects, the PDCCH message may not schedule any PDSCH messages. In some aspects, the PDCCH message may include DCI. In some aspects, the DCI may have a DCI format4_1(for example, as defined, or otherwise fixed, by the 3GPP). In some aspects, the PDCCH message may schedule one or more dynamic grant multicast PDSCH messages. In some other aspects, the PDCCH message may be an SPS PDSCH release (for example, a PDCCH message that does not schedule any PDSCH messages or that deactivates configured SPS PDSCH messages).

In some aspects, in a fourth operation625, the network entity605may transmit, and the UE120may receive, one or more PDSCH multicast messages. For example, the one or more PDSCH multicast messages may be scheduled by the PDCCH message in the third operation620. In some other aspects, the one or more PDSCH multicast messages may be SPS multicast messages (for example, that are activated by a PDCCH message, such as the PDCCH message received by the UE120in the third operation620). For example, the one or more PDSCH multicast messages may be SPS multicast messages that may not be scheduled by a PDCCH message (for example, may not be scheduled by DCI). The one or more PDSCH messages may be associated with an RNTI (for example, the RNTI associated with the PDCCH message received by the UE120in the third operation620). For example, if the one or more PDSCH messages are dynamic grant PDSCH messages, then the RNTI may be a G-RNTI. If the one or more PDSCH messages are SPS multicast messages, then the RNTI may be a G-CS-RNTI.

In some aspects, the semi-static HARQ feedback codebook for multicast messages (for example, the Type-1 HARQ-ACK feedback codebook) may be associated with a feedback window. The feedback window may be a duration of time during which the UE is to collect feedback (for example, ACK/NACK feedback) for messages received by the UE. After the feedback window, the UE120may transmit the Type-1 HARQ-ACK feedback codebook indicating the feedback for the messages received by the UE during the feedback window. In some aspects, the feedback window may be based at least in part on, or otherwise associated with, DCI received by the UE (for example, in the PDCCH message received by the UE in the third operation620). For example, DCI may include a PDSCH-to-HARQ feedback timing indicator. The PDSCH-to-HARQ feedback timing indicator may indicate a value (for example, k). The value, k, may indicate HARQ feedback timing (in terms of a quantity of slots) to UE120. For example, the UE120may receive a PDSCH message in a slot n and DCI format1_0may be used by the network entity605to schedule the PDSCH message. In such examples, the Type-1 HARQ-ACK feedback codebook may indicate feedback associated with PDSCH messages received by the UE120during slots n through slot n+(k−1), where the Type-1 HARQ-ACK feedback codebook is transmitted by the UE120in slot n+k. In some other aspects, the PDSCH-to-HARQ feedback timing indicator may indicate multiple values, such as where the DCI format1_1is used by the network entity605to schedule a PDSCH message. For example, the PDSCH-to-HARQ feedback timing indicator may indicate values of (1,2,3,5, and7). In such examples, the Type-1 HARQ-ACK feedback codebook may indicate feedback associated with PDSCH messages received by the UE120during slots n+1, n+2, n+3, n+5, and n+7. The PDCCH message may be received by the UE120in the third operation620in the slot n. In some aspects, the PDCCH message may include the PDSCH-to-HARQ feedback timing indicator, as described above, indicating the feedback window associated with Type-1 HARQ-ACK feedback codebook reporting.

In a fifth operation630, the UE120may determine whether to perform a fallback operation for the semi-static HARQ feedback codebook (for example, for the Type-1 HARQ-ACK feedback codebook). For example, as described elsewhere herein, the fallback operation may include the UE120transmitting (for example, in a sixth operation635) a fallback HARQ feedback indication rather than the semi-static HARQ feedback codebook. The fallback HARQ feedback indication may be a single HARQ ACK indication (for example, a single ACK or NACK indication). For example, in some cases (as described in more detail elsewhere herein), the UE120may transmit the fallback HARQ feedback indication rather than the semi-static HARQ feedback codebook to conserve resources, such as where only a single PDCCH message or a single PDSCH message is received by the UE120during the feedback window associated with Type-1 HARQ-ACK feedback codebook reporting. For example, the semi-static HARQ feedback codebook may be associated with a first size (for example, that is static or fixed, such as by the configuration information received by the UE120in the first operation610), and a fallback HARQ feedback indication may be associated with a second size that is less than the first size. In some aspects, the second size may be 1 bit.

In some aspects, the UE120may determine whether to perform a fallback operation for the semi-static HARQ feedback codebook for multicast messages for all RNTIs together (for example, considering each RNTI). For example, the UE120may determine to transmit a fallback HARQ feedback indication based at least in part on, or otherwise associated with, not receiving another PDCCH message, associated with any RNTI (for example, any G-RNTI or any G-CS-RNTI), received during the feedback window. In other words, the UE120transmitting a fallback HARQ feedback indication (for example, in the sixth operation635) may be based at least in part on, or otherwise associated with, not receiving another PDCCH message associated with any other G-RNTI during a feedback window indicated by the configuration information. For example, the UE120may transmit a fallback HARQ feedback indication (for example, in the sixth operation635) based at least in part on, or otherwise associated with, determining that the UE120is to report HARQ-ACK information in a PUCCH only for a PDSCH reception scheduled by DCI format1_0with a counter DAI field value of 1 on a PCell of the UE120, or a PDSCH reception scheduled by DCI format4_1(for example, scheduled by DCI received by the UE120in the third operation620) with a counter DAI field value of 1 on the PCell, associated with any G-RNTI. For example, if the UE120receives a first multicast PDSCH message associated with a first G-RNTI and receives a second multicast PDSCH message associated with a second G-RNTI during the feedback window, then the UE120may determine that the fallback operation is not to be performed. In such examples, the UE120may transmit the semi-static HARQ feedback codebook (for example, the Type-1 HARQ ACK codebook) in the sixth operation635. The network entity605may perform a blind decoding to determine if the Type-1 HARQ ACK codebook or the fallback HARQ feedback indication is transmitted by the UE120.

As another example, the multicast messages received by the UE120in the third operation620or the fourth operation625may be SPS multicast messages. In such examples, the UE120may determine to transmit a single fallback HARQ feedback indication (for example, may determine to perform the fallback operation) based at least in part on, or otherwise associated with, determining that HARQ-ACK information to be reported by the UE120is associated only with one or more SPS PDSCH messages associated with any configured scheduling RNTI (CS-RNTI), only with a multicast SPS PDSCH release (for example, a PDCCH message associated with a DCI format4_1with a DAI counter field value of 1) associated with any G-CS-RNTI, or only with one or more SPS PDSCH messages received by the UE120associated with any G-CS-RNTI. For example, the UE120may determine to transmit a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages based at least in part on, or otherwise associated with, multicast messages, associated with any G-CS-RNTI, received during a feedback window indicated by the configuration information being only a single PDCCH message associated with any G-CS-RNTI (for example, received by the UE120in the third operation620) or being one or more SPS PDSCH messages (for example, received by the UE120in the fourth operation625) activated by a single PDCCH message that is associated with any G-CS-RNTI (for example, received by the UE120in the third operation620).

In other words, transmitting the one or more fallback HARQ feedback indications (for example, in the sixth operation635) may be based at least in part on, or otherwise associated with, not receiving another multicast message associated with any G-CS-RNTI during a feedback window. For example, if the UE120receives a first multicast SPS release or first one or more multicast SPS PDSCH messages associated with a first G-CS-RNTI and a second multicast SPS release or second one or more multicast SPS PDSCH messages associated with a second G-CS-RNTI during the feedback window, then the UE120may determine to not perform the fallback operation. In such examples, the UE120may transmit the semi-static HARQ feedback codebook (for example, the Type-1 HARQ ACK codebook) in the sixth operation635.

In some other aspects, the UE120may determine to transmit a fallback HARQ feedback indication based at least in part on, or otherwise associated with, PDCCH messages or PDSCH messages, associated with a given RNTI (for example, a given G-RNTI or a given G-CS-RNTI), received during the feedback window being only the PDCCH message or PDSCH message associated with the given RNTI (for example, received by the UE120in the third operation620). For example, the UE120may determine whether to transmit fallback HARQ feedback indications separately for different RNTIs. For example, the UE120may receive a first PDCCH message (for example, in the third operation620), associated with a first G-RNTI during the feedback window associated with the semi-static HARQ feedback codebook. Additionally, the UE120may receive a second PDCCH message (for example, in the third operation620), associated with a second G-RNTI during the feedback window associated with the semi-static HARQ feedback codebook. The UE120may determine to perform the fallback operation associated with the first G-RNTI so long as no other PDCCH messages (or PDSCH messages) associated with the first G-RNTI are received by the UE120during the feedback window. Similarly, the UE120may determine to perform the fallback operation associated with the second G-RNTI so long as no other PDCCH messages (or PDSCH messages) associated with the second G-RNTI are received by the UE120during the feedback window.

For example, the UE120may determine to perform the fallback operation based at least in part on, or otherwise associated with, determining that the UE120is to report HARQ-ACK information in a PUCCH only for a PDSCH reception scheduled by DCI format1_0with a counter DAI field value of 1 on the PCell, or only for a PDSCH reception scheduled by DCI format4_1with a counter DAI field value of 1 on the PCell, associated with a given G-RNTI. For example, in the sixth operation635, the UE120may transmit, and the network entity605may receive, a first fallback HARQ feedback indication associated with the first G-RNTI and a second fallback HARQ feedback indication associated with the second G-RNTI (for example, based at least in part on, or otherwise associated with, determining to perform the fallback operation for the first G-RNTI and the second G-RNTI separately). In other words, the UE120may transmit, and the network entity605may receive, a separate HARQ feedback indication associated with each G-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook (for example, based at least in part on, or otherwise associated with, the UE120determining to perform the fallback operation for each G-RNTI separately).

As another example, the multicast messages received by the UE120in the third operation620or the fourth operation625may be SPS multicast messages. In such examples, the UE120may determine to perform the fallback operation for each G-CS-RNTI separately. For example, the UE120may determine to perform the fallback operation based at least in part on, or otherwise associated with, determining that the UE120is to report HARQ-ACK information in a PUCCH only for a SPS PDSCH release indicated by DCI format1_0with a counter DAI field value of 1, only for SPS PDSCH reception(s) associated with a given CS-RNTI, only for an SPS PDSCH release indicated by DCI format4_1with a counter DAI field value of 1 and associated with a given G-CS-RNTI, or only for SPS PDSCH reception(s) associated with a given G-CS-RNTI. In other words, the UE120may determine whether conditions for transmitting a fallback HARQ feedback indication are met separately for each G-CS-RNTI.

For example, in the sixth operation635, the UE120may transmit, and the network entity605may receive, a first fallback HARQ feedback indication associated with a first G-CS-RNTI and a second fallback HARQ feedback indication associated with a second G-CS-RNTI (for example, based at least in part on, or otherwise associated with, determining to perform the fallback operation for the first G-CS-RNTI and the second G-CS-RNTI separately in the fifth operation630). In other words, the UE120may transmit, and the network entity605may receive, a separate HARQ feedback indication associated with each G-CS-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook (for example, based at least in part on, or otherwise associated with, the UE120determining to perform the fallback operation for each G-CS-RNTI separately in the fifth operation630).

In some aspects, in the fifth operation630, the UE120may determine whether to perform the fallback operation for a given RNTI based at least in part on, or otherwise associated with, whether feedback is enabled for the given RNTI. For example, a feedback configuration for a given RNTI may indicate whether feedback is enabled or disabled for the given RNTI. For example, an RRC configuration or a group-common DCI (for example, associated with DCI format4_2) may indicate whether feedback is enabled or disabled for a given RNTI (for example, for a given G-RNTI or a given G-CS-RNTI). In some aspects, the UE120may determine to perform the fallback operation associated with a given RNTI based at least in part on, or otherwise associated with, feedback being enabled for the given RNTI. In other words, if feedback is disabled for the given RNTI, then the UE120may determine that the fallback operation is not to be performed (for example, and may transmit the Type-1 HARQ ACK codebook in the sixth operation635). In some other aspects, if feedback is disabled for the given RNTI, then the UE120may determine that a fallback HARQ feedback indication is to be transmitted, but with a NACK indication regardless of whether multicast message(s) were successfully received by the UE120. In other words, the UE120may perform the fallback operation with a NACK indication (for example, a NACK bit) for the multicast RNTI (or multicast transport block) with feedback disabled. For example, in the sixth operation635, the UE120may transmit, and the network entity605may receive, a NACK indication regardless of whether the one or more multicast PDSCH messages are successfully received by the UE120when feedback is disabled for the one or more multicast PDSCH messages.

In some aspects, in the fifth operation630, the UE120may determine whether to perform the fallback operation for a given RNTI based at least in part on, or otherwise associated with, a feedback type associated with a given RNTI (for example, that is associated with the fallback operation). For example, a feedback configuration for a given RNTI may indicate the feedback type associated with the given RNTI. Feedback types may include ACK/NACK-based feedback (for example, where the UE120is to transmit ACK indications or NACK indications based at least in part on, or otherwise associated with, whether a message is successfully received by the UE120), or NACK-only-based feedback (for example, where the UE120does not transmit feedback if a message is successfully received and transmits NACK feedback if a message is not successfully received). For example, in some aspects, the UE120may determine to perform the fallback operation based at least in part on, or otherwise associated with, the RNTI, that is associated with the fallback operation, being associated with ACK/NACK feedback. In other words, the UE120may transmit (for example, in the sixth operation635) one or more fallback HARQ feedback indications based at least in part on, or otherwise associated with, the RNTI being associated with ACK/NACK feedback. For example, if the RNTI, that is associated with the fallback operation, is associated with NACK-only-based feedback, then the UE120may determine that the fallback operation is not to be performed. Alternatively, if the RNTI, that is associated with the fallback operation, is associated with NACK-only-based feedback, then the UE120may determine that the HARQ-ACK feedback information associated with the RNTI is to be transformed to ACK/NACK feedback (for example, from NACK-only feedback). For example, the UE120may transmit (for example, in the sixth operation635) an ACK or a NACK indication associated with the one or more multicast PDSCH messages based at least in part on, or otherwise associated with, whether the one or more multicast PDSCH messages are successfully received as part of the fallback operation (for example, even though the RNTI associated with the one or more multicast PDSCH messages is associated with NACK-only-based feedback).

As described above, in the sixth operation635, the UE120may transmit, and the network entity605may receive, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages (for example, received by the UE120in the fourth operation625), in accordance with the configuration information (for example, received by the UE120in the first operation610) and based at least in part on, or otherwise associated with, an RNTI associated with the one or more multicast PDSCH messages or multicast PDCCH message, or a feedback configuration associated with the RNTI, among other examples. For example, the UE120may transmit the one or more fallback HARQ feedback indications based at least in part on, or otherwise associated with, determining that the fallback operation is to be performed (for example, in the fifth operation630). If the UE120determines that the fallback operation is not to be performed (for example, in the fifth operation630), then the UE120may transmit, and the network entity605may receive, the Type-1 HARQ ACK codebook (for example, in the sixth operation635).

FIG.7is a flowchart illustrating an example process700performed, for example, by a UE in accordance with the present disclosure. Example process700is an example where the UE (for example, the UE120) performs operations associated with fallback operation for a semi-static HARQ feedback codebook for multicast.

As shown inFIG.7, in some aspects, process700may include receiving, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages (block710). For example, the UE (such as by using communication manager140or reception component902, depicted inFIG.9) may receive, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages, as described above.

As further shown inFIG.7, in some aspects, process700may include receiving, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages (block720). For example, the UE (such as by using communication manager140or reception component902, depicted inFIG.9) may receive, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages, as described above.

As further shown inFIG.7, in some aspects, process700may include transmitting, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI (block730). For example, the UE (such as by using communication manager140or transmission component904, depicted inFIG.9) may transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI, as described above.

Process700may include additional aspects, such as any single aspect or any combination of aspects described below or in connection with one or more other processes described elsewhere herein.

In a first additional aspect, the PDCCH message includes a DCI message having a DCI format4_1.

In a second additional aspect, alone or in combination with the first aspect, the semi-static HARQ feedback codebook is associated with a feedback window, wherein the PDCCH message is received during the feedback window, wherein the RNTI is a G-RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not receiving another PDCCH message, associated with any G-RNTI including the G-RNTI, during the feedback window.

In a third additional aspect, alone or in combination with one or more of the first and second aspects, the RNTI is a G-RNTI, and transmitting the one or more fallback HARQ feedback indications is associated with not receiving another PDCCH message associated with any G-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

In a fourth additional aspect, alone or in combination with one or more of the first through third aspects, the RNTI is a first G-RNTI, the PDCCH message is received during a feedback window associated with the semi-static HARQ feedback codebook, and process700includes receiving, during the feedback window, another PDCCH message, associated with a second G-RNTI, scheduling one or more other multicast PDSCH messages, and transmitting the one or more fallback HARQ feedback indications includes transmitting a first fallback HARQ feedback indication associated with the PDCCH message and the first G-RNTI, and transmitting a second fallback HARQ feedback indication associated with the other PDCCH message and the second G-RNTI.

In a fifth additional aspect, alone or in combination with one or more of the first through fourth aspects, the RNTI is a first G-RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a separate HARQ feedback indication associated with each G-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook.

In a sixth additional aspect, alone or in combination with one or more of the first through fifth aspects, the RNTI is a G-CS-RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not receiving another multicast message, associated with any G-CS-RNTI including the G-CS-RNTI, during a feedback window associated with the semi-static HARQ feedback codebook.

In a seventh additional aspect, alone or in combination with one or more of the first through sixth aspects, the one or more multicast PDSCH messages are SPS messages, the RNTI is a G-CS-RNTI, and transmitting the one or more fallback HARQ feedback indications is associated with not receiving another multicast message associated with any G-CS-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

In an eighth additional aspect, alone or in combination with one or more of the first through seventh aspects, the one or more multicast PDSCH messages are SPS messages, a first multicast PDSCH message, of the one or more PDSCH messages, is associated with a first G-CS-RNTI and a second multicast PDSCH message, of the one or more PDSCH messages, is associated with a second G-CS-RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a first fallback HARQ feedback indication associated with the first multicast PDSCH message and the first G-CS-RNTI, and transmitting a second fallback HARQ feedback indication associated with the second multicast PDSCH message and the second G-CS-RNTI.

In a ninth additional aspect, alone or in combination with one or more of the first through eighth aspects, the one or more multicast PDSCH messages are SPS messages, wherein the RNTI is a G-CS-RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a separate HARQ feedback indication associated with each G-CS-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook.

In a tenth additional aspect, alone or in combination with one or more of the first through ninth aspects, the feedback configuration indicates whether feedback is enabled or disabled for the RNTI, and transmitting the one or more fallback HARQ feedback indications is associated with feedback being enabled for the RNTI.

In an eleventh additional aspect, alone or in combination with one or more of the first through tenth aspects, the feedback configuration indicates that feedback is disabled for the RNTI, and transmitting the one or more fallback HARQ feedback indications includes transmitting a NACK indication regardless of whether the one or more multicast PDSCH messages are successfully received.

In a twelfth additional aspect, alone or in combination with one or more of the first through eleventh aspects, the feedback configuration indicates whether the RNTI is associated with ACK/NACK feedback or NACK only feedback, and transmitting the one or more fallback HARQ feedback indications is associated with the RNTI being associated with ACK/NACK feedback.

In a thirteenth additional aspect, alone or in combination with one or more of the first through twelfth aspects, the feedback configuration indicates that the RNTI is associated with NACK only feedback, and transmitting the one or more fallback HARQ feedback indications includes transmitting an ACK or NACK indication associated with the one or more multicast PDSCH messages associated with whether the one or more multicast PDSCH messages are successfully received.

In a fourteenth additional aspect, alone or in combination with one or more of the first through thirteenth aspects, process700includes transmitting, to the network entity, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook.

In a fifteenth additional aspect, alone or in combination with one or more of the first through fourteenth aspects, the UE supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook is associated with at least one of a type of multicast messages associated with the fallback HARQ feedback indications, a frequency band associated with the fallback HARQ feedback indications, or an FSPC associated with the fallback HARQ feedback indications.

In a sixteenth additional aspect, alone or in combination with one or more of the first through fifteenth aspects, the semi-static HARQ feedback codebook is a Type-1 HARQ-ACK codebook.

In a seventeenth additional aspect, alone or in combination with one or more of the first through sixteenth aspects, the one or more multicast PDSCH messages include dynamic grant multicast messages or SPS multicast messages.

In an eighteenth additional aspect, alone or in combination with one or more of the first through seventeenth aspects, the semi-static HARQ feedback codebook is associated with a first size, and a fallback HARQ feedback indication, of the one or more fallback HARQ feedback indications, is associated with a second size that is less than the first size.

In a nineteenth additional aspect, alone or in combination with one or more of the first through eighteenth aspects, the second size is 1 bit.

FIG.8is a flowchart illustrating an example process800performed, for example, by a network entity in accordance with the present disclosure. Example process800is an example where the network entity (for example, network entity605, the base station110, the CU310, a DU330, or an RU340, among other examples) performs operations associated with fallback operation for a semi-static HARQ feedback codebook for multicast.

As shown inFIG.8, in some aspects, process800may include transmitting configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages (block810). For example, the network entity (such as by using communication manager150, communication manager1008, or transmission component1004, depicted inFIG.10) may transmit configuration information, for one or more UEs, associated with a semi-static HARQ feedback codebook for multicast messages, as described above.

As further shown inFIG.8, in some aspects, process800may include transmitting a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages (block820). For example, the network entity (such as by using communication manager150, communication manager1008, or transmission component1004, depicted inFIG.10) may transmit a message, for the one or more UEs, associated with an RNTI, scheduling one or more multicast PDSCH messages, as described above.

As further shown inFIG.8, in some aspects, process800may include receiving one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI (block830). For example, the network entity (such as by using communication manager150, communication manager1008, or reception component1002, depicted inFIG.10) may receive one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI, as described above.

In a first additional aspect, the message includes a DCI message having a DCI format4_1.

In a second additional aspect, alone or in combination with the first aspect, the semi-static HARQ feedback codebook is associated with a feedback window, wherein the message is received during the feedback window, wherein the RNTI is a G-RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not transmitting another message, associated with any G-RNTI including the G-RNTI, during the feedback window.

In a third additional aspect, alone or in combination with one or more of the first and second aspects, the RNTI is a G-RNTI, and receiving the one or more fallback HARQ feedback indications is associated with not transmitting another message associated with any G-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

In a fourth additional aspect, alone or in combination with one or more of the first through third aspects, the RNTI is a first G-RNTI, the message is transmitted during a feedback window associated with the semi-static HARQ feedback codebook, and process800includes transmitting, during the feedback window, another message, associated with a second G-RNTI, scheduling one or more other multicast PDSCH messages, and receiving the one or more fallback HARQ feedback indications includes receiving a first fallback HARQ feedback indication associated with the message and the first G-RNTI, and receiving a second fallback HARQ feedback indication associated with the other message and the second G-RNTI.

In a fifth additional aspect, alone or in combination with one or more of the first through fourth aspects, the RNTI is a first G-RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a separate HARQ feedback indication associated with each G-RNTI associated with messages transmitted during a feedback window associated with the semi-static HARQ feedback codebook.

In a sixth additional aspect, alone or in combination with one or more of the first through fifth aspects, the RNTI is a G-CS-RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not transmitting another multicast message, associated with any G-CS-RNTI including the G-CS-RNTI, during a feedback window associated with the semi-static HARQ feedback codebook.

In a seventh additional aspect, alone or in combination with one or more of the first through sixth aspects, the one or more multicast PDSCH messages are SPS messages, the RNTI is a G-CS-RNTI, and receiving the one or more fallback HARQ feedback indications is associated with not transmitting another multicast message associated with any G-CS-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

In an eighth additional aspect, alone or in combination with one or more of the first through seventh aspects, the one or more multicast PDSCH messages are SPS messages, a first multicast PDSCH message, of the one or more PDSCH messages, is associated with a first G-CS-RNTI and a second multicast PDSCH message, of the one or more PDSCH messages, is associated with a second G-CS-RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a first fallback HARQ feedback indication associated with the first multicast PDSCH message and the first G-CS-RNTI, and receiving a second fallback HARQ feedback indication associated with the second multicast PDSCH message and the second G-CS-RNTI.

In a ninth additional aspect, alone or in combination with one or more of the first through eighth aspects, the one or more multicast PDSCH messages are SPS messages, the RNTI is a G-CS-RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a separate HARQ feedback indication associated with each G-CS-RNTI associated with messages during a feedback window associated with the semi-static HARQ feedback codebook.

In a tenth additional aspect, alone or in combination with one or more of the first through ninth aspects, the feedback configuration indicates whether feedback is enabled or disabled for the RNTI, and receiving the one or more fallback HARQ feedback indications is associated with feedback being enabled for the RNTI.

In an eleventh additional aspect, alone or in combination with one or more of the first through tenth aspects, the feedback configuration indicates that feedback is disabled for the RNTI, and receiving the one or more fallback HARQ feedback indications includes receiving a NACK indication regardless of whether the one or more multicast PDSCH messages are successfully received.

In a twelfth additional aspect, alone or in combination with one or more of the first through eleventh aspects, the feedback configuration indicates whether the RNTI is associated with ACK/NACK feedback or NACK only feedback, and receiving the one or more fallback HARQ feedback indications is associated with the RNTI being associated with ACK/NACK feedback.

In a thirteenth additional aspect, alone or in combination with one or more of the first through twelfth aspects, the feedback configuration indicates that the RNTI is associated with NACK only feedback, and receiving the one or more fallback HARQ feedback indications includes receiving an ACK or NACK indication associated with the one or more multicast PDSCH messages associated with whether the one or more multicast PDSCH messages are successfully received.

In a fourteenth additional aspect, alone or in combination with one or more of the first through thirteenth aspects, process800includes receiving, from the UE, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook.

In a fifteenth additional aspect, alone or in combination with one or more of the first through fourteenth aspects, the UE supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook is associated with at least one of a type of multicast messages associated with the fallback HARQ feedback indications, a frequency band associated with the fallback HARQ feedback indications, or an FSPC associated with the fallback HARQ feedback indications.

In a sixteenth additional aspect, alone or in combination with one or more of the first through fifteenth aspects, the semi-static HARQ feedback codebook is a Type-1 HARQ-ACK codebook.

In a seventeenth additional aspect, alone or in combination with one or more of the first through sixteenth aspects, the one or more multicast PDSCH messages include dynamic grant multicast messages or SPS multicast messages.

In an eighteenth additional aspect, alone or in combination with one or more of the first through seventeenth aspects, the semi-static HARQ feedback codebook is associated with a first size, and a fallback HARQ feedback indication, of the one or more fallback HARQ feedback indications, is associated with a second size that is less than the first size.

In a nineteenth additional aspect, alone or in combination with one or more of the first through eighteenth aspects, the second size is 1 bit.

In some aspects, the apparatus900may be configured to perform one or more operations described herein in connection withFIG.6. Additionally or alternatively, the apparatus900may be configured to perform one or more processes described herein, such as process700ofFIG.7, or a combination thereof. In some aspects, the apparatus900may include one or more components of the UE described above in connection withFIG.2.

The communication manager140may receive or may cause the reception component902to receive, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The communication manager140may receive or may cause the reception component902to receive, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The communication manager140may transmit or may cause the transmission component904to transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI. In some aspects, the communication manager140may perform one or more operations described elsewhere herein as being performed by one or more components of the communication manager140.

The communication manager140may include a controller/processor, a memory, or a combination thereof, of the UE described above in connection withFIG.2. In some aspects, the communication manager140includes a set of components, such as a fallback operation determination component908. Alternatively, the set of components may be separate and distinct from the communication manager140. In some aspects, one or more components of the set of components may include or may be implemented within a controller/processor, a memory, or a combination thereof, of the UE described above in connection withFIG.2. Additionally or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.

The reception component902may receive, from a network entity, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The reception component902may receive, from the network entity, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The transmission component904may transmit, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

The fallback operation determination component908may determine to perform a fallback operation associated with the semi-static HARQ feedback codebook. The transmission component904may transmit the one or more fallback HARQ feedback indications in lieu of transmitting the semi-static HARQ feedback codebook associated with determining to perform the fallback operation.

The transmission component904may transmit, to the network entity, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook.

FIG.10is a diagram of an example apparatus1000for wireless communication in accordance with the present disclosure. The apparatus1000may be a network entity, or a network entity may include the apparatus1000. In some aspects, the apparatus1000includes a reception component1002, a transmission component1004, and a communication manager1008, which may be in communication with one another (for example, via one or more buses). In some aspects, the communication manager1008may include one or more antennas, a modem, a controller/processor, a memory, or a combination thereof, of the base station described in connection withFIG.2. The communication manager1008may be, or be similar to, the communication manager150depicted inFIGS.1and2. For example, in some aspects, the communication manager1008may be configured to perform one or more of the functions described as being performed by the communication manager150. In some aspects, the communication manager1008may include the reception component1002or the transmission component1004. As shown, the apparatus1000may communicate with another apparatus1006(such as a UE, a base station, or another wireless communication device) using the reception component1002and the transmission component1004.

In some aspects, the apparatus1000may be configured to perform one or more operations described herein in connection withFIG.6. Additionally or alternatively, the apparatus1000may be configured to perform one or more processes described herein, such as process800ofFIG.8, or a combination thereof. In some aspects, the apparatus1000may include one or more components of the network entity described above in connection withFIG.2.

The communication manager1008may transmit or may cause the transmission component1004to transmit configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The communication manager1008may transmit or may cause the transmission component1004to transmit a message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The communication manager1008may receive or may cause the reception component1002to receive one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI. In some aspects, the communication manager1008may perform one or more operations described elsewhere herein as being performed by one or more components of the communication manager1008.

The communication manager1008may include a controller/processor, a memory, a scheduler, a communication unit, or a combination thereof, of the network entity described above in connection withFIG.2. In some aspects, the communication manager1008includes a set of components, such as a determination component1010, a decoding component1012, or a combination thereof. Alternatively, the set of components may be separate and distinct from the communication manager1008. In some aspects, one or more components of the set of components may include or may be implemented within a controller/processor, a memory, a scheduler, a communication unit, or a combination thereof, of the network entity described above in connection withFIG.2. Additionally or alternatively, one or more components of the set of components may be implemented at least in part as software stored in a memory. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by a controller or a processor to perform the functions or operations of the component.

The transmission component1004may transmit, to one or more UEs, configuration information associated with a semi-static HARQ feedback codebook for multicast messages. The transmission component1004may transmit, to the one or more UEs, a PDCCH message, associated with an RNTI, scheduling one or more multicast PDSCH messages. The reception component1002may receive, from a UE of the one or more UEs, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

The determination component1010may determine the configuration information. The decoding component1012may perform blind decoding to identify that the UE transmitted the one or more fallback HARQ feedback indications in lieu of receiving the semi-static HARQ feedback codebook.

The reception component1002may receive, from the UE, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook. The determination component1010may determine the configuration information associated with receiving the capability message.

Aspect 1: A method of wireless communication performed by a user equipment (UE), comprising: receiving, from a network entity, configuration information associated with a semi-static hybrid automatic repeat request (HARQ) feedback codebook for multicast messages; receiving, from the network entity, a physical downlink control channel (PDCCH) message, associated with a radio network temporary identifier (RNTI), scheduling one or more multicast physical downlink shared channel (PDSCH) messages; and transmitting, to the network entity, one or more fallback HARQ feedback indications, associated with the one or more multicast PDSCH messages, in lieu of transmitting the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Aspect 2: The method of Aspect 1, wherein the PDCCH message includes a downlink control information (DCI) message having a DCI format4_1.

Aspect 3: The method of any of Aspects 1-2, wherein the semi-static HARQ feedback codebook is associated with a feedback window, wherein the PDCCH message is received during the feedback window, wherein the RNTI is a group common RNTI (G-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not receiving another PDCCH message, associated with any G-RNTI including the G-RNTI, during the feedback window.

Aspect 4: The method of any of Aspects 1-3, wherein the RNTI is a group common RNTI (G-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications is associated with not receiving another PDCCH message associated with any G-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 5: The method of any of Aspects 1-2, wherein the RNTI is a first group common RNTI (G-RNTI), wherein the PDCCH message is received during a feedback window associated with the semi-static HARQ feedback codebook, the method further comprising: receiving, during the feedback window, another PDCCH message, associated with a second G-RNTI, scheduling one or more other multicast PDSCH messages, and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a first fallback HARQ feedback indication associated with the PDCCH message and the first G-RNTI; and transmitting a second fallback HARQ feedback indication associated with the other PDCCH message and the second G-RNTI.

Aspect 6: The method of any of Aspects 1-2, and 5, wherein the RNTI is a first group common RNTI (G-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a separate HARQ feedback indication associated with each G-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 7: The method of any of Aspects 1-2, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not receiving another multicast message, associated with any G-CS-RNTI including the G-CS-RNTI, during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 8: The method of any of Aspects 1-2 and 7, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications is associated with not receiving another multicast message associated with any G-CS-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 9: The method of any of Aspects 1-2, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein a first multicast PDSCH message, of the one or more PDSCH messages, is associated with a first group common configured scheduling RNTI (G-CS-RNTI) and a second multicast PDSCH message, of the one or more PDSCH messages, is associated with a second G-CS-RNTI, and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a first fallback HARQ feedback indication associated with the first multicast PDSCH message and the first G-CS-RNTI; and transmitting a second fallback HARQ feedback indication associated with the second multicast PDSCH message and the second G-CS-RNTI.

Aspect 10: The method of any of Aspects 1-2 and 9, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a separate HARQ feedback indication associated with each G-CS-RNTI detected during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 11: The method of any of Aspects 1-10, wherein the feedback configuration indicates whether feedback is enabled or disabled for the RNTI, and wherein transmitting the one or more fallback HARQ feedback indications is associated with feedback being enabled for the RNTI.

Aspect 12: The method of any of Aspects 1-11, wherein the feedback configuration indicates that feedback is disabled for the RNTI, and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting a negative acknowledgement (NACK) indication regardless of whether the one or more multicast PDSCH messages are successfully received.

Aspect 13: The method of any of Aspects 1-12, wherein the feedback configuration indicates whether the RNTI is associated with acknowledgement (ACK) and negative ACK (NACK) (ACK/NACK) feedback or NACK only feedback, and wherein transmitting the one or more fallback HARQ feedback indications is associated with the RNTI being associated with ACK/NACK feedback.

Aspect 14: The method of any of Aspects 1-13, wherein the feedback configuration indicates that the RNTI is associated with negative acknowledgement (NACK) only feedback, and wherein transmitting the one or more fallback HARQ feedback indications comprises: transmitting an acknowledgement (ACK) or NACK indication associated with the one or more multicast PDSCH messages associated with whether the one or more multicast PDSCH messages are successfully received.

Aspect 15: The method of any of Aspects 1-14, further comprising: transmitting, to the network entity, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook.

Aspect 16: The method of Aspect 15, wherein the UE supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook is associated with at least one of: a type of multicast messages associated with the fallback HARQ feedback indications, a frequency band associated with the fallback HARQ feedback indications, or a feature set per component-carrier (FSPC) associated with the fallback HARQ feedback indications.

Aspect 17: The method of any of Aspects 1-16, wherein the semi-static HARQ feedback codebook is a Type-1 HARQ-Acknowledgement (ACK) codebook.

Aspect 18: The method of any of Aspects 1-17, wherein the one or more multicast PDSCH messages include dynamic grant multicast messages or semi-persistent scheduling (SPS) multicast messages.

Aspect 19: The method of any of Aspects 1-18, wherein the semi-static HARQ feedback codebook is associated with a first size, and wherein a fallback HARQ feedback indication, of the one or more fallback HARQ feedback indications, is associated with a second size that is less than the first size.

Aspect 20: The method of Aspect 19, wherein the second size is 1 bit.

Aspect 21: The method of any of Aspects 1-20, wherein transmitting one or more fallback HARQ feedback indications is associated with the PDCCH message being associated with DCI format4_1, with a counter downlink assignment index (DAI) field value of 1 on a primary cell (PCell) associated with the UE, and with feedback being enabled for the RNTI.

Aspect 22: A method of wireless communication performed by a network entity, comprising: transmitting configuration information, for one or more user equipments (UEs), associated with a semi-static hybrid automatic repeat request (HARQ) feedback codebook for multicast messages; transmitting a message, for the one or more UEs, associated with a radio network temporary identifier (RNTI), scheduling one or more multicast physical downlink shared channel (PDSCH) messages; and receiving one or more fallback HARQ feedback indications, for a UE of the one or more UEs, associated with the one or more multicast PDSCH messages, in lieu of receiving the semi-static HARQ feedback codebook, in accordance with the configuration information and associated with at least one of the RNTI or a feedback configuration associated with the RNTI.

Aspect 23: The method of Aspect 22, wherein the message includes a downlink control information (DCI) message having a DCI format4_1.

Aspect 24: The method of any of Aspects 22-23, wherein the semi-static HARQ feedback codebook is associated with a feedback window, wherein the message is received during the feedback window, wherein the RNTI is a group common RNTI (G-RNTI), and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not transmitting another message, associated with any G-RNTI including the G-RNTI, during the feedback window.

Aspect 25: The method of any of Aspects 22-24, wherein the RNTI is a group common RNTI (G-RNTI), and wherein receiving the one or more fallback HARQ feedback indications is associated with not transmitting another message associated with any G-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 26: The method of any of Aspects 22-23, wherein the RNTI is a first group common RNTI (G-RNTI), wherein the message is transmitted during a feedback window associated with the semi-static HARQ feedback codebook, the method further comprising: transmitting, during the feedback window, another message, associated with a second G-RNTI, scheduling one or more other multicast PDSCH messages, and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a first fallback HARQ feedback indication associated with the message and the first G-RNTI; and receiving a second fallback HARQ feedback indication associated with the other message and the second G-RNTI.

Aspect 27: The method of any of Aspects 22-23 and 26, wherein the RNTI is a first group common RNTI (G-RNTI), and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a separate HARQ feedback indication associated with each G-RNTI associated with messages transmitted during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 28: The method of any of Aspects 22-23, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a single fallback HARQ feedback indication associated with the one or more multicast PDSCH messages associated with not transmitting another multicast message, associated with any G-CS-RNTI including the G-CS-RNTI, during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 29: The method of any of Aspects 22-23 and 28, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein receiving the one or more fallback HARQ feedback indications is associated with not transmitting another multicast message associated with any G-CS-RNTI during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 30: The method of any of Aspects 22-23, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein a first multicast PDSCH message, of the one or more PDSCH messages, is associated with a first group common configured scheduling RNTI (G-CS-RNTI) and a second multicast PDSCH message, of the one or more PDSCH messages, is associated with a second G-CS-RNTI, and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a first fallback HARQ feedback indication associated with the first multicast PDSCH message and the first G-CS-RNTI; and receiving a second fallback HARQ feedback indication associated with the second multicast PDSCH message and the second G-CS-RNTI.

Aspect 31: The method of any of Aspects 22-23 and 30, wherein the one or more multicast PDSCH messages are semi-persistent scheduling (SPS) messages, wherein the RNTI is a group common configured scheduling RNTI (G-CS-RNTI), and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a separate HARQ feedback indication associated with each G-CS-RNTI associated with messages during a feedback window associated with the semi-static HARQ feedback codebook.

Aspect 32: The method of any of Aspects 22-31, wherein the feedback configuration indicates whether feedback is enabled or disabled for the RNTI, and wherein receiving the one or more fallback HARQ feedback indications is associated with feedback being enabled for the RNTI.

Aspect 33: The method of any of Aspects 22-32, wherein the feedback configuration indicates that feedback is disabled for the RNTI, and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving a negative acknowledgement (NACK) indication regardless of whether the one or more multicast PDSCH messages are successfully received.

Aspect 34: The method of any of Aspects 22-33, wherein the feedback configuration indicates whether the RNTI is associated with acknowledgement (ACK) and negative ACK (NACK) (ACK/NACK) feedback or NACK only feedback, and wherein receiving the one or more fallback HARQ feedback indications is associated with the RNTI being associated with ACK/NACK feedback.

Aspect 35: The method of any of Aspects 22-34, wherein the feedback configuration indicates that the RNTI is associated with negative acknowledgement (NACK) only feedback, and wherein receiving the one or more fallback HARQ feedback indications comprises: receiving an acknowledgement (ACK) or NACK indication associated with the one or more multicast PDSCH messages associated with whether the one or more multicast PDSCH messages are successfully received.

Aspect 36: The method of any of Aspects 22-35, further comprising: receiving, from the UE, a capability message that indicates that the UE supports fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook.

Aspect 37: The method of Aspect 36, wherein the UE supporting fallback HARQ feedback indications associated with the semi-static HARQ feedback codebook is associated with at least one of: a type of multicast messages associated with the fallback HARQ feedback indications, a frequency band associated with the fallback HARQ feedback indications, or a feature set per component-carrier (FSPC) associated with the fallback HARQ feedback indications.

Aspect 38: The method of any of Aspects 22-37, wherein the semi-static HARQ feedback codebook is a Type-1 HARQ-Acknowledgement (ACK) codebook.

Aspect 39: The method of any of Aspects 22-38, wherein the one or more multicast PDSCH messages include dynamic grant multicast messages or semi-persistent scheduling (SPS) multicast messages.

Aspect 40: The method of any of Aspects 22-39, wherein the semi-static HARQ feedback codebook is associated with a first size, and wherein a fallback HARQ feedback indication, of the one or more fallback HARQ feedback indications, is associated with a second size that is less than the first size.

Aspect 41: The method of Aspect 40, wherein the second size is 1 bit.

Aspect 42: The method of any of Aspects 22-41, wherein receiving one or more fallback HARQ feedback indications is associated with the message being associated with DCI format4_1, with a counter downlink assignment index (DAI) field value of 1 on a primary cell (PCell) associated with the UE, and with feedback being enabled for the RNTI.

As used herein, the term “component” is intended to be broadly construed as hardware or a combination of hardware and software. “Software” shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, or functions, among other examples, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. As used herein, a “processor” is implemented in hardware or a combination of hardware and software. It will be apparent that systems or methods described herein may be implemented in different forms of hardware or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems or methods is not limiting of the aspects. Thus, the operation and behavior of the systems or methods are described herein without reference to specific software code, because those skilled in the art will understand that software and hardware can be designed to implement the systems or methods based, at least in part, on the description herein.