Patent Publication Number: US-2023144165-A1

Title: Multi-user packet for user equipment assisted retransmission

Description:
FIELD OF THE DISCLOSURE 
     Aspects of the present disclosure generally relate to wireless communications, and more particularly to techniques and apparatuses for user equipment (UE) assisted retransmission of multi-user packets. 
     BACKGROUND 
     Wireless communications systems are widely deployed to provide various telecommunications services such as telephony, video, data, messaging, and broadcasts. Typical wireless communications systems may employ multiple-access technologies capable of supporting communications with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and long term evolution (LTE). LTE/LTE-Advanced is a set of enhancements to the universal mobile telecommunications system (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). 
     A wireless communications network may include a number of base stations (BSs) that can support communications for a number of user equipment (UEs). A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communications link from the BS to the UE, and the uplink (or reverse link) refers to the communications link from the UE to the BS. As will be described in more detail, a BS may be referred to as a Node B, a gNB, an access point (AP), a radio head, a transmit receive point (TRP), a New Radio (NR) BS, a 5G Node B, and/or the like. 
     The above multiple access technologies have been adopted in various telecommunications standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New Radio (NR), which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM)) on the uplink (UL), as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. 
     SUMMARY 
     According to an aspect of the present disclosure, a method for wireless communication performed by a user equipment (UE) includes receiving a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC) including a number of payloads. The method also includes transmitting an acknowledgement (ACK) in response to decoding the MUPC. The method also includes receiving a message requesting retransmission of at least one payload of the number of payloads. The method further includes transmitting the at least one payload in response to the message. 
     In another aspect of the present disclosure, a method for wireless communication performed by a base station (BS) includes transmitting a MUPC including a number of payloads to a number of UEs. The method also includes receiving a negative acknowledgement (NACK) from a first UE of the number of UEs in response to the MUPC. The method also includes receiving an ACK from a second UE of the number of UEs in response to the MUPC. The method further includes transmitting, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the number of payloads. 
     In another aspect of the present disclosure, a UE for wireless communications includes a memory and at least one processor operatively coupled to the memory. The memory and the processor(s) are configured to receive an MUPC including a number of payloads. The UE is configured to transmit an ACK in response to decoding the MUPC. The UE is also configured to receive a message requesting retransmission of at least one payload of the number of payloads. The UE is further configured to transmit the at least one payload in response to the message. 
     In another aspect of the present disclosure, a base station (BS) for wireless communications includes a memory and at least one processor operatively coupled to the memory. The memory and the processor(s) are configured to transmit an MUPC including a number of payloads to a number of UEs. The BS is configured to receive a NACK from a first UE of the number of UEs in response to the MUPC. The BS is also configured to receive an ACK from a second UE of the number of UEs in response to the MUPC. The BS is further configured to transmit, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the number of payloads. 
     In another aspect of the present disclosure, the UE includes means for receiving an MUPC including a number of payloads. The UE also includes means for transmitting an ACK in response to decoding the MUPC. The UE also includes means for receiving a message requesting retransmission of at least one payload of the number of payloads. The UE further includes means for transmitting the at least one payload in response to the message. 
     In another aspect of the present disclosure, the BS includes means for transmitting an MUPC including a number of payloads to a number of UEs. The BS also includes means for receiving a NACK from a first UE of the number of UEs in response to the MUPC. The BS also includes means for receiving an ACK from a second UE of the number of UEs in response to the MUPC. The BS further includes means for transmitting, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the number of payloads. 
     In another aspect of the present disclosure, a non-transitory computer-readable medium with program code recorded thereon is disclosed. The program code is executed by a UE and includes program code to receive an MUPC including a number of payloads. The UE also includes program code to transmit an ACK in response to decoding the MUPC. The UE also includes program code to receive a message requesting retransmission of at least one payload of the number of payloads. The UE further includes program code to transmit the at least one payload in response to the message. 
     In another aspect of the present disclosure, a non-transitory computer-readable medium with program code recorded thereon is disclosed. The program code is executed by a BS and includes program code to transmit an MUPC including a number of payloads to a number of UEs. The BS also includes program code to receive a NACK from a first UE of the number of UEs in response to the MUPC. The BS also includes program code to receive an ACK from a second UE of the number of UEs in response to the MUPC. The BS further includes program code to transmit, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the number of payloads. 
     The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that features of the present disclosure can be understood in detail, a particular description, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements. 
         FIG.  1    is a block diagram conceptually illustrating an example of a wireless communications network, in accordance with various aspects of the present disclosure. 
         FIG.  2    is a block diagram conceptually illustrating an example of a base station in communication with a user equipment (UE) in a wireless communications network, in accordance with various aspects of the present disclosure. 
         FIG.  3    is a diagram illustrating an example of multi-user packet design for New Radio, in accordance with various aspects of the present disclosure. 
         FIGS.  4 A and  4 B  are diagrams illustrating examples of UE-assisted full multi-user packet physical downlink shared channel communication retransmission, in accordance with various aspects of the present disclosure. 
         FIG.  5    is a diagram illustrating an example of UE-assisted partial multi-user packet physical downlink shared channel communication retransmission, in accordance with various aspects of the present disclosure. 
         FIG.  6    is a flow diagram illustrating an example process performed, for example, by a UE, in accordance with various aspects of the present disclosure. 
         FIG.  7    is a flow diagram illustrating an example process performed, for example, by a base station in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects of the disclosure are described more fully below with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not 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. Based on the teachings one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure, 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 number of the aspects set forth. 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. It should be understood that any aspect of the disclosure disclosed may be embodied by one or more elements of a claim. 
     Several aspects of telecommunications systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements”). These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     It should be noted that while aspects may be described using terminology commonly associated with 5G and later wireless technologies, aspects of the present disclosure can be applied in other generation-based communications systems, such as and including 3G and/or 4G technologies. 
     In new radio (NR), performance may be improved for some communication scenarios by using multi-user packets (MUPs), where data for multiple user equipments (UEs) may be multiplexed together in a single packet. For example, in scenarios where a small amount of data is communicated to the multiple UEs, such as a factory automation scenario, an Industrial Internet-of-Things (IIoT) scenario, a broadcast or multicast scenario, an evolved multimedia broadcast multicast service (eMBMS) scenario, a single-cell point-to-multipoint (SC-PTM) scenario, and/or the like, performance may be improved by aggregating the data in an MUP as opposed to transmitting the data via multiple packets. For example, such aggregation or concatenation of data in an MUP may improve coding gains as compared to the transmission of multiple packets. Additionally, or alternatively, downlink control overhead may be reduced because downlink control information (DCI) may be transmitted for the MUP instead of a DCI for multiple packets for different UEs. 
     Aspects of the present disclosure are directed to UE-assisted retransmission of MUPs. According to some aspects, multiple UEs receive an MUP from a base station. Each UE may transmit acknowledgment/negative acknowledgment (ACK/NACK) feedback in response to the received MUP. The base station may map the ACK/NACK feedback to the UEs. The base station may request one or more UEs associated with an ACK to retransmit at least a portion of the MUP. Aspects of the present disclosure may conserve network resources and computing resources of the base station and/or the UEs. 
       FIG.  1    is a diagram illustrating a network  100  in which aspects of the present disclosure may be practiced. The network  100  may be a 5G or NR network or some other wireless network, such as an LTE network. The wireless network  100  may include a number of BSs  110  (shown as BS  110   a , BS  110   b , BS  110   c , and BS  110   d ) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, an NR BS, a Node B, a gNB, a 5G node B (NB), an access point, a transmit and receive point (TRP), and/or the like. Each BS may provide communications coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used. 
     A BS may provide communications coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG)). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in  FIG.  1   , a BS  110   a  may be a macro BS for a macro cell  102   a , a BS  110   b  may be a pico BS for a pico cell  102   b , and a BS  110   c  may be a femto BS for a femto cell  102   c . ABS may support one or multiple (e.g., three) cells. The terms “eNB”, “base station”, “NR BS”, “gNB”, “TRP”, “AP”, “node B”, “5G NB”, and “cell” may be used interchangeably. 
     In some aspects, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network  100  through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network. 
     The wireless network  100  may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in  FIG.  1   , a relay station  110   d  may communicate with macro BS  110   a  and a UE  120   d  in order to facilitate communications between the BS  110   a  and UE  120   d . A relay station may also be referred to as a relay BS, a relay base station, a relay, and/or the like. 
     The wireless network  100  may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network  100 . For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts). 
     As an example, the BSs  110  (shown as BS  110   a , BS  110   b , BS  110   c , and BS  110   d ) and the core network  130  may exchange communications via backhaul links  132  (e.g., S1, etc.). Base stations  110  may communicate with one another over other backhaul links (e.g., X2, etc.) either directly or indirectly (e.g., through core network  130 ). The UEs  120  (e.g.,  120   a ,  120   b ,  120   c ) may communicate with the core network  130  through a communications link  135 . 
     The core network  130  may be an evolved packet core (EPC), which may include at least one mobility management entity (MME), at least one serving gateway (S-GW), and at least one packet data network (PDN) gateway (P-GW). The MME may be the control node that processes the signaling between the UEs  120  and the EPC. All user IP packets may be transferred through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the network operator&#39;s IP services. The operator&#39;s IP services may include the Internet, the Intranet, an IP multimedia subsystem (IMS), and a packet-switched (PS) streaming service. 
     The core network  130  may provide user authentication, access authorization, tracking, IP connectivity, and other access, routing, or mobility functions. One or more of the base stations  110  or access node controllers (ANCs) may interface with the core network  130  through backhaul links  132  (e.g., S1, S2, etc.) and may perform radio configuration and scheduling for communications with the UEs  120 . In some configurations, various functions of each access network entity or base station  110  may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station  110 ). 
     UEs  120  (e.g.,  120   a ,  120   b ,  120   c ) may be dispersed throughout the wireless network  100 , and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communications 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 or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. 
     One or more UEs  120  may establish a protocol data unit (PDU) session for a network slice. In some cases, the UE  120  may select a network slice based on an application or subscription service. By having different network slices serving different applications or subscriptions, the UE  120  may improve its resource utilization in the wireless communications system  100 , while also satisfying performance specifications of individual applications of the UE  120 . In some cases, the network slices used by UE  120  may be served by an AMF (not shown in  FIG.  1   ) associated with one or both of the base station  110  or core network  130 . In addition, session management of the network slices may be performed by a session management function (SMF). 
     The BSs  110  (e.g., BSs  110   a ,  110   b ,  110   c ,  110   d ) may include an MUP retransmission request module  138  for transmitting a message requesting an MUP retransmission. For ease of explanation, only one BS  110   a  is shown as including the MUP retransmission request module  138 . The MUP retransmission request module  138  may be a component of each BS  110 . The MUP retransmission request module  138  may transmit an MUP physical downlink shared channel (PDSCH) communication (MUP-PDSCH) including multiple payloads to multiple UEs  120 . The MUP retransmission request module  138  may receive a negative acknowledgment (NACK) from a first UE  120  of the multiple UEs  120  in response to the MUP-PDSCH communication. The MUP retransmission request module  138  may also receive an acknowledgment (ACK) from a second UE  120  of the multiple UEs  120  in response to the MUP-PDSCH communication. Additionally, the MUP retransmission request module  138  may transmit, to the second UE  120  in response to receiving the NACK from the first UE  120  and the ACK from the second UE  120 , a first message requesting the second UE  120  to retransmit one or more payload (e.g., one or more payload portions) of the multiple payloads. 
     The UEs  120  (e.g., UEs  120   a ,  120   b ,  120   c ,  120   d ,  120   e ) may include an MUP retransmission module  140 . For ease of explanation, only one UE  120   d  is shown as including the MUP retransmission module  140 . The MUP retransmission module  140  may be a component of each UE  120 . The MUP retransmission module  140  may be configured for receiving a multi-user physical (MUP) downlink shared channel (PDSCH) communication comprising multiple payloads (e.g., multiple payload portions). The MUP retransmission module  140  may transmit an ACK in response to decoding the MUP-PDSCH communication. The MUP retransmission module  140  may receive a message requesting retransmission of at least one payload of the multiple payloads. Additionally, the MUP retransmission module  140  may transmit the payload(s) in response to the message. 
     Some UEs may be considered machine-type communications (MTC) or evolved or enhanced machine-type communications (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communications link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband Internet-of-things) devices. Some UEs may be considered a customer premises equipment (CPE). UE  120  may be included inside a housing that houses components of UE  120 , such as processor components, memory components, and/or the like. 
     In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. 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 aspects, two or more UEs  120  (e.g., shown as UE  120   a  and UE  120   e ) may communicate directly using one or more sidelink channels (e.g., without using a base station  110  as an intermediary to communicate with one another). For example, the UEs  120  may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like), a mesh network, and/or the like. In this case, the UE  120  may perform scheduling operations, resource selection operations, and/or other operations described elsewhere as being performed by the base station  110 . For example, the base station  110  may configure a UE  120  via downlink control information (DCI), radio resource control (RRC) signaling, a media access control-control element (MAC-CE) or via system information (e.g., a system information block (SIB). 
     As indicated above,  FIG.  1    is provided merely as an example. Other examples may differ from what is described with regard to  FIG.  1   . 
       FIG.  2    shows a block diagram of a design  200  of the base station  110  and UE  120 , which may be one of the base stations and one of the UEs in  FIG.  1   . The base station  110  may be equipped with T antennas  234   a  through  234   t , and UE  120  may be equipped with R antennas  252   a  through  252   r , where in general T≥1 and R≥1. 
     At the base station  110 , a transmit processor  220  may receive data from a data source  212  for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS(s) selected for the UE, and provide data symbols for all UEs. Decreasing the MCS lowers throughput but increases reliability of the transmission. The transmit processor  220  may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., channel quality indicator (CQI) requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. The transmit processor  220  may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS)) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor  230  may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs)  232   a  through  232   t . Each modulator  232  may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator  232  may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators  232   a  through  232   t  may be transmitted via T antennas  234   a  through  234   t , respectively. According to various aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information. 
     At the UE  120 , antennas  252   a  through  252   r  may receive the downlink signals from the base station  110  and/or other base stations and may provide received signals to demodulators (DEMODs)  254   a  through  254   r , respectively. Each demodulator  254  may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator  254  may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector  256  may obtain received symbols from all R demodulators  254   a  through  254   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor  258  may process (e.g., demodulate and decode) the detected symbols, provide decoded data for the UE  120  to a data sink  260 , and provide decoded control information and system information to a controller/processor  280 . A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), and/or the like. In some aspects, one or more components of the UE  120  may be included in a housing. 
     On the uplink, at the UE  120 , a transmit processor  264  may receive and process data from a data source  262  and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from the controller/processor  280 . Transmit processor  264  may also generate reference symbols for one or more reference signals. The symbols from the transmit processor  264  may be precoded by a TX MIMO processor  266  if applicable, further processed by modulators  254   a  through  254   r  (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like), and transmitted to the base station  110 . At the base station  110 , the uplink signals from the UE  120  and other UEs may be received by the antennas  234 , processed by the demodulators  254 , detected by a MIMO detector  236  if applicable, and further processed by a receive processor  238  to obtain decoded data and control information sent by the UE  120 . The receive processor  238  may provide the decoded data to a data sink  239  and the decoded control information to a controller/processor  240 . The base station  110  may include communications unit  244  and communicate to the core network  130  via the communications unit  244 . The core network  130  may include a communications unit  294 , a controller/processor  290 , and a memory  292 . 
     The controller/processor  240  of the base station  110 , the controller/processor  280  of the UE  120 , and/or any other component(s) of  FIG.  2    may perform one or more techniques associated with MUP retransmission, as described in more detail elsewhere. For example, the controller/processor  240  of the base station  110 , the controller/processor  280  of the UE  120 , and/or any other component(s) of  FIG.  2    may perform or direct operations of, for example, the processes of  FIGS.  6 - 7    and/or other processes as described. Memories  242  and  282  may store data and program codes for the base station  110  and UE  120 , respectively. A scheduler  246  may schedule UEs for data transmission on the downlink and/or uplink. 
     In some aspects, the UEs  120  may include means for receiving a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC) including multiple payloads; transmitting an acknowledgement (ACK) in response to decoding the MUPC; receiving a message requesting retransmission of at least one payload of the multiple payloads; and transmitting the at least one payload in response to the message. 
     In some aspects, a BSs  110  may include means for transmitting an MUPC including multiple payloads to multiple UEs; receiving a negative acknowledgement (NACK) from a first UE of the multiple UEs in response to the MUPC; receiving an ACK from a second UE of the multiple UEs in response to the MUPC; and transmitting, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the multiple payloads. 
     As indicated above,  FIG.  2    is provided merely as an example. Other examples may differ from what is described with regard to  FIG.  2   . 
     In new radio (NR), performance may be improved for some communications scenarios by using multi-user packets (MUPs), where data for multiple UEs  120  is multiplexed together in the payload of a single packet. For example, in scenarios where a small amount of data is communicated to multiple UEs  120 , such as a factory automation scenario, an Industrial Internet-of-Things (IIoT) scenario, a broadcast or multicast scenario, an evolved multimedia broadcast multicast service (eMBMS) scenario, a single-cell point-to-multipoint (SC-PTM) scenario, and/or the like, performance may be improved by aggregating the data in an MUP. The aggregation of data in an MUP may improve coding gains and/or reduce downlink control overhead. 
     Aspects of the present disclosure are directed to UE-assisted retransmission for MUPs. According to some aspects, multiple UEs  120  receive an MUP from a base station  110 . Each UE  120  may transmit ACK/NACK feedback in response to the received MUP. The base station may map the ACK/NACK feedback to the UEs  120 . Additionally, the base station  110  may request one or more UEs  120  associated with an ACK to retransmit at least a portion of the MUP. Aspects of the present disclosure may conserve network resources and computing resources of the base station  110  and/or the UEs  120 . 
       FIG.  3    is a diagram illustrating an example  300  of an MUP design for NR, in accordance with various aspects of the present disclosure. In some cases, an MUP is referred to as a multi-user physical downlink shared channel (PDSCH) communication (MUPC). The MUPC may also be referred to as an MUP-PDSCH communication. 
     As shown in  FIG.  3   , an MUPC may include multiple sub-headers. Together, the multiple sub-headers form an MUPC header  305 . A sub-header may include a UE ID identifying a specific UE  120 , such as a cell radio network temporary identifier (C-RNTI). Different sub-headers may include different UE IDs identifying different UEs  120 . For example, a first sub-header (e.g., shown as sub-header A) may identify a first UE  120  (e.g., shown as UE A), a second sub-header (e.g., shown as sub-header B) may identify a second UE  120  (e.g., shown as UE B), and a third sub-header (e.g., shown as sub-header C) may identify a third UE  120  (e.g., shown as UE C). Aspects of the present disclosure are not limited to an MUPC for three UEs. The MUPC may aggregate data for any number of UEs (e.g., two or more UEs). 
     Additionally, the MUPC may include a payload  310  that is aggregated from multiple payload portions (e.g., payload portion a, payload portion b, and payload portion c) corresponding to the multiple UEs  120  (e.g., UE A, UE B, and UE C). Each payload portion may be referred to as a transport block (TB). The different payload portions may carry data intended for different UEs  120 . In one example, a first UE  120  (e.g., UE A) may identify a sub-header including a UE identifier for the first UE  120 . The first UE  120  may then identify a payload portion that corresponds to the identified sub-header (e.g., payload portion A). Furthermore, the first UE  120  may obtain the data included in the identified payload portion. In this way, data for multiple UEs  120  may be carried in a single MUPC. 
     In some aspects, as shown in  FIG.  3   , a sub-header may include a length field indicating a length (e.g., a size, a number of bits, a number of bytes, and/or the like) of a corresponding payload portion. Additionally, or alternatively, a sub-header may include a field indicating whether that sub-header is the last sub-header (shown as “Last SH Indicator”). One or more of these fields may identify an end of the sub-headers and a start of the payload portions. A UE  120  may identify a start of a payload portion intended for the UE  120  based on the start of the payload portions and a sum of all of the lengths indicated in sub-headers that occur before the sub-header that identifies the UE  120 . The UE  120  may identify an end of the payload portion intended for the UE  120  using the length indicated in the sub-header that identifies the UE  120 . 
     As further shown, a sub-header may include an acknowledgment or negative acknowledgment (ACK/NACK) resource indicator (ARI). The ARI may identify (e.g., by itself or in combination with other information) a physical uplink control channel (PUCCH) resource in which the UE  120 , identified in the sub-header, is to transmit ACK/NACK feedback for the MUPC (e.g., the payload portion, of the MUPC, that corresponds to the UE  120 ). A base station  110  may configure the ARIs included in different sub-headers to indicate different PUCCH resources, such that different UEs  120  transmit ACK/NACK feedback for the MUPC in different PUCCH resources (e.g., different time resources, different symbols, different slots, different subframes, different frequency resources, different resource blocks, and/or the like). In this way, the base station  110  may map ACK/NACK feedback to a UE  120  based on the PUCCH resource in which the ACK/NACK feedback is received. 
     In some aspects, the header  305  of the MUPC and the payload  310  of the MUPC may be included in a PDSCH payload. Additionally, or alternatively, the header of the MUPC (e.g., all of the sub-headers) may be included in a physical layer header (e.g., rather than a media access control (MAC) header), thereby allowing the header to be processed more quickly by the UEs  120  and reducing latency. In some aspects, each of the sub-headers may be the same size as one another. Additionally, or alternatively, the header may be a fixed or pre-configured size across multiple MUPCs. Thus, the sub-headers may include one or more reserved bits (e.g., filler bits) to achieve such alignment and reduce complexity. Alternatively, different sub-headers included in a header may have different sizes. Additionally, or alternatively, different headers included in different MUPCs may have different sizes. In this way, an MUPC may be flexibly configured (e.g., depending on a number of UEs  120  for which the MUPC is intended). 
     As shown by reference number  315 , in some aspects, an MUPC may have a first format where the sub-headers are grouped consecutively at the beginning of the MUPC. Additionally, or alternatively, if the MUPC is transmitted using multiple code blocks, the sub-headers may be included in a first code block (e.g., an initial code block or a first code block in time) of the MUPC. As such, the sub-headers may occur closer in time to a demodulation reference signal (DMRS), which may improve reliability of reception of the sub-headers. Furthermore, reducing a time between sub-headers and a DMRS may reduce an amount of data to be processed by UEs  120  because a UE  120  may process the sub-headers to determine whether there is a payload portion for the UE  120 . As shown by reference number  320 , in some aspects, an MUPC may have a second format where each sub-header is located immediately before a respective payload portion corresponding to that sub-header. 
     In some aspects, a DCI (not shown in  FIG.  3   ) may schedule and/or activate an MUPC. The DCI may be transmitted on a downlink control channel, such as a physical downlink control channel (PDCCH)). The DCI may include a group-radio network temporary identifier (RNTI) assigned to a group of UEs  120 . A UE  120  included in the group may determine that the DCI includes information for the UE  120  based on the group-RNTI. For example, the DCI may be descrambled based on the group-RNTI. Thus, the DCI may include the group-RNTI for the group of UEs  120  (e.g., a group-specific RNTI), and the MUPC sub-headers may include UE-specific RNTIs. Accordingly, each UE  120  configured with the group-RNTI may decode the PDSCH (e.g., the header  305  and payload  310  of the MUPC). As described above, by parsing the header  305 , a UE  120  may determine if it is being addressed and identify a corresponding payload portion (e.g., TB). 
     In some aspects, the DCI may include scheduling information and/or control information for the MUPC, which may indicate PDSCH resources that carry the MUPC, a modulation and coding scheme (MCS) for the MUPC, and/or the like. Additionally, or alternatively, the MUPC may be pre-scheduled using semi-persistent scheduling (SPS) (e.g., where scheduling information may be indicated in a radio resource control (RRC) message), and the UE  120  may activate and/or deactivate monitoring for the MUPC based at least in part on the DCI. In some aspects, the DCI may be a same format, size, and/or the like as unicast DCI, thereby reducing complexity. 
     In one configuration, a UE  120  configured to monitor a group-RNTI may decode data for other UEs  120  in the MUPC, when attempting to decode its own data. In some cases, the UE  120  may not be served by a particular MUPC. Still, the UE  120  is unaware of whether it is served by the particular MUPC until the UE  120  decodes the header  305 . In some aspects, a DCI piggyback design may separate the header  305  from the payload out of MUP-PDSCH. That is, the header  305  may be separately encoded from the payload  310 . Radio resource control (RRC) signaling may configure the UE  120  to decode the payload  310 . 
       FIG.  4 A  is a diagram illustrating an example  400  of UE-assisted full MUPC retransmission, in accordance with various aspects of the present disclosure. As shown in  FIG.  4 A , a first UE  120  (e.g., shown as UE 0 ), a second UE  120  (e.g., shown as UE 1 ), and a third UE  120  (e.g., shown as UE 2 ) may be configured as a mutual assisting group. Additionally, the first, second, and third UEs  120  may be configured with a group-RNTI. 
     In one example, at a first time period (T 1 ), a base station  110  (e.g., a gNB) may transmit a first DCI  402  for an MUPC  315 , in a similar manner as described in connection with  FIG.  3   . The first DCI  402  may correspond to the group-RNTI, such that each UE  120  configured with the group-RNTI may receive and decode the first DCI  402 . 
     Each UE  120  configured with the group-RNTI may determine, or attempt to determine, whether a sub-header of the MUPC  315  includes a UE-ID of the UE  120 . Additionally, each UE  120  configured with the group-RNTI may attempt to identify or decode a payload portion corresponding to the sub-header including the UE-ID. Such an attempt may be successful, or may fail, and the UE  120  may selectively transmit ACK/NACK feedback based on whether the attempt succeeded or failed. 
     In the example of  FIG.  4 A , the first, second, and third UEs  120  belong to the same group and are configured with a same group-RNTI. At a second time period (T 2 ), the base station  110  transmits the MUPC  315  to the first, second, and third UEs  120 . Additionally, at the second time period (T 2 ), the first, second, and third UEs  120  attempt to decode the MUPC  315  based on the first DCI  402 . In the current example, a payload  310  of the MUPC  315  includes a first payload portion (e.g., shown as TB to UE 0 ), a second payload portion (e.g., shown as TB to UE 1 ), and a third payload portion (e.g., shown as TB to UE 2 ). Each payload portion of the payload  310  may correspond to a different UE  120  configured with the group-RNTI. For example, the first payload portion (e.g., TB to UE 0 ) corresponds to the first UE (e.g., UE 0 ). 
     As described above, at the second time period (T 2 ), each UE  120  may receive and attempt to decode the MUPC  315 . As described, by parsing the header  305 , a UE  120  can identify a portion of the payload  310  designated for itself. In the example of  FIG.  4 A , the first UE  120  fails to decode or receive the MUPC  315 . Therefore, the first UE  120  transmits a NACK  410  to the base station  110  at a third time period (T 3 ). Additionally, the second and third UEs  120  successfully receive and decode the MUPC  315 . Therefore, each one of the second and third UEs  120  transmits an ACK  412  to the base station  110  (T 3 ). 
     In one configuration, the UEs  120  may identify a PUCCH resource, for acknowledging receipt (e.g., ACK/NACK) of the payload portion based on a UE-specific ARI included in the sub-header of the MUPC  315  that identifies the UE  120 . The PUCCH resource may also be identified based on a common ARI included in the first DCI  402 . For example, the UE  120  may determine the PUCCH resource as a function of the common ARI and the UE-specific ARI. 
     In one configuration, at time period T 3 , each UE  120  transmits an ACK  412  if the UE  120  has decoded the entire payload  310  (e.g., each payload portion) of the MUPC  315 , as opposed to only decoding a payload portion designated for the UE  120 . For example, in order to transmit the ACK  412 , the second UE  120  may be specified to successfully decode the payload portion designated for the first UE  120  (e.g., TB for UE 0 ), the payload portion designated for the second UE  120  (e.g., TB for UE 1 ), and the payload portion designation for the third UE  120  (e.g., TB for UE 2 ). 
     In another configuration, a payload portion may not be designated for a UE  120 . In this configuration, the header  305  may still include a sub-header for the UE  120 . The UE  120  may decode the sub-header to determine that a payload portion is not designated for the UE  120 . In this configuration, the UE  120  without a designated payload portion may be referred to as an assisting-only UE. Additionally, in this configuration, the assisting-only UE  120  transmits an ACK  412  if it has successfully decoded each payload portion of the payload  310 . 
     In the example of  FIG.  4 A , based on the NACK  410  received from the first UE  120 , the base station  110  determines the first UE  120  failed to receive or decode the MUPC  315 . Additionally, based on the ACK  412  received from the second and third UEs  120 , the base station  110  determines the second and third UEs  120  successfully received and decoded MUPC  315 . Therefore, the second and third UEs  120  have successfully received and decoded the payload portion of the first UE  120 . 
     In response to the ACKs  412  from the second and third UEs  120  and the NACK  410  from the first UE  120 , at a fourth time period (T 4 ), the base station  110  transmits a message to the second and/or third UEs  120  requesting retransmission of the MUPC  315 . In one configuration, the message is a second DCI  404  associated with the group-RNTI. The second DCI  404  may include a field to trigger the retransmission. The field may be an added field or a repurposed field. A downlink channel communication, such as a PDSCH, is not associated with the second DCI  404 . 
     The retransmission may be a full retransmission, where the entire MUPC  315  is retransmitted. Alternatively, the retransmission may be a partial retransmission, where only a portion of the MUPC is retransmitted. A hybrid automatic repeat request (HARQ) process ID and an NDI included in the second DCI  404  may indicate whether the retransmission is full or partial. That is, the HARQ process ID and the NDI may identify one or more payload portions for retransmission. Additionally, the second DCI identifies one or more resources for the retransmission. In one configuration, a time domain resource assignment (TDRA) or a frequency domain resource assignment (FDRA) in the second DCI  404  may be used for the retransmission. 
     As described above, in  FIG.  4 A , the base station  110  transmits the second DCI  404  to the first, second, and third UEs  120  at the fourth time period (T 4 ). As described,  FIG.  4 A  is an example of a full retransmission. Therefore, a format of the second DCI  404  matches a format of the first DCI  402 . For example, the HARQ process ID and the NDI of the second DCI  404  match the HARQ process ID and the NDI of the first DCI  402 . 
     In one configuration, a UE  120  that successfully decoded an initial MUPC performs a retransmission in response to receiving the second DCI  404  if a slot offset (K 0 ) is greater than zero (e.g., the PDSCH and the PDCCH are in different slots). 
     In the example of  FIG.  4 A , the second and/or third UEs  120  receive the second DCI  404  and determine that both the HARQ process ID and the NDI of the second DCI  404  match the HARQ process ID and the NDI of the first DCI  402 . As a result, the second and/or third UEs  120  determine the second DCI  404  is an assisted retransmission grant for a full retransmission. In the example of  FIG.  4 A , KO is greater than zero for the second and third UEs  120 . 
     In response to receiving the second DCI  404 , the second and/or third UEs  120  may retransmit the MUPC  315  at a fifth time period (T 5 ). The second and/or third UEs  120  are not specified to change the MUPC  315 , such that the first UE  120  may soft combine the retransmitted MUPC  315 . Still, this comes at a cost to the second and third UEs because both the second and third payload portions are retransmitted to each of the UEs  120 . In this example, none of the UEs  120  in the group-RNTI have a use for the second or third payload portions. 
     The second and/or third UEs  120  may retransmit the MUPC  315  via one or more resources indicated in the second DCI  404 . Additionally, the second and/or third UEs  120  may re-encode the MUPC  315  and rate match the re-encoded MUPC  315  to the one or more indicated resources. The redundancy version identifier (RVID) used to retransmit the MUPC  315  matches the RVID of the first DCI  402 . 
     As described, both the second and third UEs  120  may retransmit the MUPC  315 . In some examples, the second UE  120  may receive the MUPC  315  retransmission from the third UE  120 , and vice versa. In such examples, the second and third UEs  120  refrain from transmitting an ACK  412  or NACK  410  for the MUPC  315  retransmission. 
     The retransmissions from the second and/or third UEs  120  may follow a PDSCH waveform in a system frame number (SFN) fashion. 
     In the example of  FIG.  4 A , at the fifth time period (T 5 ), the first UE  120  receives the second DCI  404  and treats the second DCI  404  as a retransmission grant for itself. The first UE  120  may combine the retransmitted MUPC  315  with the initial MUPC  315  based on a log-likelihood ratio (LLR) method. That is, the first UE  120  may apply soft combining on the retransmitted MUPC  315  and the initial MUPC  315 . From the perspective of the first UE  120 , the source of the MUPC  315  retransmission is transparent. 
     In one configuration, the first UE  120  transmits an ACK  412  or a NACK  410  to the base station  110  in response to the MUPC retransmission. The second DCI  404  may provide an uplink grant for transmitting the ACK  412  or the NACK  410  at a sixth time period (T 6 ). In some aspects, multiple MUPC  315  retransmissions may be performed by one or more UEs  120  that successfully decoded an initial transmission of the MUPC  315 . 
     The example of  FIG.  4 A  is an example of macro diversity. In addition to, or as an alternate to, the aspects described in  FIG.  4 A , the second and/or third UEs  120  may detect the NACK  410  transmitted by the first UE  120 . A retransmission of the MUPC  315  may be triggered in response to detecting the NACK  410  transmitted by the first UE  120 . 
       FIG.  4 B  is a diagram illustrating another example  450  of UE-assisted full MUPC retransmission, in accordance with various aspects of the present disclosure. As shown in  FIG.  4 B , at time period T 1 , a base station  110  may transmit a first DCI  402  to a first UE  120 , second UE  120 , and third UE  120 , as described in  FIG.  4 A . Additionally, as described in  FIG.  4 A , at time period T 2 , the base station  110  may transmit the MUPC  315  to the first, second, and third UEs  120 . 
     In the example of  FIG.  4 B , at time period T 3 , the first and third UEs  120  transmit a NACK  410  in response to the MUPC  315  (e.g., an initial MUPC  315  transmission). Additionally, at time period T 3 , the second UE  120  transmits an ACK  412  in response to the initial MUPC  315  transmission. In response to the ACK  412  from the second UE  120  and the NACKs  410  from the first and third UEs  120 , at time period T 4 , the BS  110  transmits a second DCI  404  to the first, second, and third UEs  120 . 
     The second UE  120  identifies the second DCI  404  as a retransmission request and retransmits the MUPC  315 , in a similar manner as described in connection with  FIG.  4 A . Additionally, each one of the first and the third UEs  120  receives the second DCI  404  and treats the second DCI  404  as a retransmission grant itself. At time period T 5 , the first and third UEs  120  receive the MUPC  315  retransmission from the second UE  120 , in a similar manner as described in connection with  FIG.  4 A . 
     As described, the retransmission may be a partial retransmission (e.g., selective retransmission).  FIG.  5    is a diagram illustrating an example  500  of UE-assisted partial MUPC retransmission, in accordance with various aspects of the present disclosure. As shown in  FIG.  5   , at time period T 1 , a base station  110  may transmit a first DCI  402  to a first UE  120 , second UE  120 , and third UE  120 , in a similar manner as described in connection with  FIG.  4 A . Additionally, in a similar manner as described in connection with  FIG.  4 A , at time period T 2 , the base station  110  may transmit the MUPC  315  to the first, second, and third UEs  120 . 
     In the example of  FIG.  5   , at time period T 3 , the first UE  120  transmits a NACK  510  in response to the initial MUPC  315  transmission. Additionally, at time period T 3 , the second and third UEs  120  transmits an ACK  512  in response to the initial MUPC  315  transmission. In response to the ACKs  512  from the second and third UEs  120  and the NACK  410  from the first UE  120 , the BS  110  initiates a selective retransmission procedure. 
     In the example of  FIG.  5   , for the selective retransmission procedure, the BS  110  identifies the one or more payload portions that were not received by one or more UEs  120 . In this example, the first UE  120  did not receive the first payload portion (e.g., TB for UE 0 ). In response, the BS  110  transmits a message requesting the second and/or third UEs  120  to only retransmit the portion of the MUPC  315  corresponding to the first payload portion (e.g., the first payload portion and the corresponding sub-header). 
     In one configuration, at time period T 4 , the BS transmits a second DCI  502  to the second and/or third UEs  120  because the second and third UEs transmitted ACKs  510  in response to the initial MUPC  315 . The second DCI  502  may be associated with the group-RNTI of the first, second, and third UEs  120 . The content of the second DCI  502  distinguishes the second DCI  502  from an initial transmission grant (e.g., the first DCI  402 , as described in  FIG.  4 A ). That is, the content of the second DCI  502  identifies the second DCI  502  as a partial retransmission request. In one configuration, a HARQ process ID and NDI of the second DCI  502  identifies specific payload portions (e.g., specific TBs) for the retransmission. Additionally, or alternatively, a separate bit field of the second DCI  502  may identify specific payload portions (e.g., specific TBs) for the retransmission. 
     As shown in  FIG.  5   , at time period T 5 , the second and/or third UEs  120  may retransmit the payload portion identified in the second DCI  502  (e.g., the first payload portion) via resources identified in a third DCI  504 . The resources may include an RVID, a modulation coding scheme (MCS), and/or the like. The partial retransmissions from the second and/or third UEs  120  may follow a PDSCH waveform in a system frame number (SFN) fashion. 
     In one configuration, as shown in  FIG.  5   , at time period T 4 , the BS  110  transmits a third DCI  504  to the first UE  120  because the first UE  120  transmitted the NACK  512  in response to the initial MUPC  315  transmission. The NDI of the third DCI  504  may be flipped or the HARQ process ID of the third DCI  504  may be different from the HARQ process ID of the first DCI  402 . The first UE  120  may treat the third DCI  504  as a grant for a new transmission, where the new transmission is received according to the information in the third DCI  504 . 
     In the example of  FIG.  5   , at time period T 5 , the first UE  120  receives the retransmission from the second and or third UEs  120 . Because the second DCI  502  requests one or more specific payload portions, the first UE  120  may not perform soft combining on the retransmitted payload portion and the initial payload portion. From the perspective of the first UE  120 , the source of the retransmitted payload portion is transparent. At time period T 6 , the first UE  120  may transmit an ACK  510  or a NACK  512  to the BS  110  in response to receiving the retransmitted payload portion. 
     As indicated above,  FIGS.  3 ,  4 A,  4 B, and  5    are provided as examples. Other examples may differ from what is described with respect to  FIGS.  3 ,  4 A,  4 B , and  5 . 
       FIG.  6    is a diagram illustrating an example process  600  performed, for example, by a UE, in accordance with various aspects of the present disclosure. The example process  600  is an example of wireless communications, by a UE (user equipment), such as one of the UEs  120  described in  FIG.  1    or by a MUP retransmission module  140  as described in  FIG.  1   . The process  600  may include 
       FIG.  6    is a diagram illustrating an example process  600  performed, for example, by a UE, in accordance with various aspects of the present disclosure. The example process  600  is an example of a multi-user packet for user equipment assisted retransmission. 
     As shown in  FIG.  6   , in some aspects, the process  600  may include receiving a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC) comprising a plurality of payloads (block  602 ). For example, the UE (e.g., using the antenna  252 , DEMOD  254 , MIMO detector  256 , receive processor  258 , controller/processor  280 , memory  282 , and/or the like) can receive a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC). 
     As shown in  FIG.  6   , in some aspects, the process  600  may include transmitting an acknowledgement (ACK) in response to decoding the MUPC (block  604 ). For example, the UE (e.g., using the antenna  252 , MOD  254 , TX MIMO processor  266 , transmit processor  264 , controller/processor  280 , memory  282 , and/or the like) can transmit an acknowledgement (ACK). 
     As shown in  FIG.  6   , in some aspects, the process  600  may include receiving a message requesting retransmission of at least one payload of the plurality of payloads (block  606 ). For example, the UE (e.g., using the antenna  252 , DEMOD  254 , MIMO detector  256 , receive processor  258 , controller/processor  280 , memory  282 , and/or the like) can receive a message requesting retransmission. 
     As shown in  FIG.  6   , in some aspects, the process  600  may include transmitting the at least one payload in response to the message (block  608 ). For example, the UE (e.g., using the antenna  252 , MOD  254 , TX MIMO processor  266 , transmit processor  264 , controller/processor  280 , memory  282 , and/or the like) can transmit the at least one payload. 
       FIG.  7    is a diagram illustrating an example process  700  performed, for example, by a BS, in accordance with various aspects of the present disclosure. The example process  700  is an example of wireless communications, by a BS, such as the BS  110  as described in  FIG.  1    or by a MUP retransmission request module  138  as described in  FIG.  1   . The process  700  includes 
       FIG.  7    is a diagram illustrating an example process  700  performed, for example, by a base station, in accordance with various aspects of the present disclosure. The example process  700  is an example of a multi-user packet for user equipment assisted retransmission. 
     As shown in  FIG.  7   , in some aspects, the process  700  may include transmitting a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC) comprising a plurality of payloads to a plurality of UEs (block  702 ). For example, the base station (e.g., using the antenna  234 , MOD  232 , TX MIMO processor  230 , transmit processor  220 , controller/processor  240 , memory  242 , and/or the like) can transmit a multi-user physical (MUP) downlink shared channel (PDSCH) communication (MUPC). 
     As shown in  FIG.  7   , in some aspects, the process  700  may include receiving a negative acknowledgement (NACK) from a first UE of the plurality of UEs in response to the MUPC (block  704 ). For example, the base station (e.g., using the antenna  234 , DEMOD  232 , MIMO detector  236 , receive processor  238 , the controller/processor  240 , memory  242 , and/or the like) can receive a negative acknowledgement (NACK) from a first UE of the plurality of UEs in response to the MUPC. 
     As shown in  FIG.  7   , in some aspects, the process  700  may include receiving an acknowledgement (ACK) from a second UE of the plurality of UEs in response to the MUPC (block  706 ). For example, the base station (e.g., using the antenna  234 , DEMOD  232 , MIMO detector  236 , receive processor  238 , the controller/processor  240 , memory  242 , and/or the like) can receive an acknowledgement (ACK) from a second UE of the plurality of UEs in response to the MUPC. 
     As shown in  FIG.  7   , in some aspects, the process  700  may include transmitting, to the second UE in response to receiving the NACK from the first UE and the ACK from the second UE, a first message requesting the second UE to retransmit at least one payload of the plurality of payloads (block  708 ). For example, the base station (e.g., using the antenna  234 , MOD  232 , TX MIMO processor  230 , transmit processor  220 , controller/processor  240 , memory  242 , and/or the like) can transmit a first message requesting the second UE to retransmit at least one payload of the plurality of payloads. 
     The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. 
     As used, the term “component” is intended to be broadly construed as hardware, firmware, and/or a combination of hardware and software. As used, a processor is implemented in hardware, firmware, and/or a combination of hardware and software. 
     Some aspects are described in connection with thresholds. As used, satisfying a threshold may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like. 
     It will be apparent that systems and/or methods described may be implemented in different forms of hardware, firmware, and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described without reference to specific software code—it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description. 
     Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). 
     No element, act, or instruction used should be construed as critical or essential unless explicitly described as such. Also, as used, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like), and may be used interchangeably with “one or more.” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.