Patent Publication Number: US-2023163794-A1

Title: Power amplifier model estimation for digital post distortion in multi-antenna devices

Description:
FIELD OF TECHNOLOGY 
     The following relates to wireless communications, including power amplifier model estimation for digital post distortion in multi-antenna devices. 
     BACKGROUND 
     Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). 
     SUMMARY 
     The described techniques relate to improved methods, systems, devices, and apparatuses that support power amplifier model estimation for digital post distortion in multi-antenna devices. Generally, the described techniques provide for a base station determining a power amplifier response of one or more transmitter antennas, if not each transmitter antenna, of the base station and mapping one or more transmitter antennas, if not each transmitter antenna, to at least one of several antenna groups based on similar power amplifier responses. The base station may map a first set of one or more transmitter antennas with similar power amplifier responses to a first antenna group, and map a second set of one or more transmitter antennas with similar power amplifier responses to a second antenna group, etc. Based on the similar power amplifier responses, the base station may determine a first power amplifier model for the first antenna group, and determine a second power amplifier model for the second antenna group, etc. The base station may transmit an indication of the respective power amplifier models of one or more antenna groups, if not each antenna group, to a user equipment (UE). In some cases, the UE may determine a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the respective power amplifier models, where the transmitter antenna is associated with an antenna group of the multiple antenna groups and the power amplifier model for the transmitter antenna is associated with that same antenna group. In some cases, the UE and the base station may communicate with each other based on the power amplifier model for the one or more transmitter antennas. 
     A method for wireless communication at a user equipment (UE) is described. The method may include receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna, determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group, and communicating with the base station based on the power amplifier model for the transmitter antenna. 
     An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna, determine a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group, and communicate with the base station based on the power amplifier model for the transmitter antenna. 
     Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna, means for determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group, and means for communicating with the base station based on the power amplifier model for the transmitter antenna. 
     A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to receive, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna, determine a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group, and communicate with the base station based on the power amplifier model for the transmitter antenna. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the indication of the power amplifier model for each antenna group may include operations, features, means, or instructions for receiving a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the base station may be based on the receiving. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a first power amplifier model for the first antenna group based on the first reference signal and a second power amplifier model for the second antenna group based on the second reference signal and applying the first power amplifier model to each transmitter antenna mapped to the first antenna group and the second power amplifier model to each transmitter antenna mapped to the second antenna group, where communicating with the base station may be based on the applying. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first reference signal, or the second reference signal, or both include a respective demodulation reference signal. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the indication of the power amplifier model for each antenna group may include operations, features, means, or instructions for receiving, from the base station, each power amplifier model for each antenna group of the set of multiple antenna groups, where the indication of the power amplifier model may be received in a radio resource control message, and where communicating with the base station may be based on the receiving. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the indication of the power amplifier model indicates which transmitter antennas may be associated with each antenna group of the set of multiple antenna groups and which of the power amplifier models to use for each antenna group, or indicates which of the power amplifier models to use with each antenna group of the set of multiple antenna groups for a given temperature, or indicates both, where communicating with the base station may be based on the determining. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the indication of the power amplifier model indicates a link between a first power amplifier model of a first antenna group of the set of multiple antenna groups and a first set of one or more antenna rows of a precoding matrix, and indicates a link between a second power amplifier model of a second antenna group of the set of multiple antenna groups and a second set of one or more antenna rows of the precoding matrix, where communicating with the base station may be based on the determining. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the indication of the power amplifier model indicates, from a set of one or more linking patterns preconfigured on the UE, a preconfigured linking pattern that links a first power amplifier model of a first antenna group of the set of multiple antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the set of multiple antenna groups with a second set of one or more antenna rows of the precoding matrix, where communicating with the base station may be based on the determining. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the indication of the power amplifier model indicates a first list of kernels associated with a first power amplifier model of a first antenna group of the set of multiple antenna groups, and a second list of kernels associated with a second power amplifier model of a second antenna group of the set of multiple antenna groups, where communicating with the base station may be based on the determining. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the indication of the power amplifier model indicates a matrix of basis functions respectively associated with the set of multiple antenna groups, where communicating with the base station may be based on the determining. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, communicating with the base station may include operations, features, means, or instructions for implementing a digital post distortion model based on the power amplifier model of the transmitter antenna and performing digital post distortion processing on signals received from the base station based on the digital post distortion model. 
     A method for wireless communication at a base station is described. The method may include mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna, determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna, transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE, and communicating with the UE based on at least one of the power amplifier models. 
     An apparatus for wireless communication at a base station is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to map each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna, determine a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna, transmit an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE, and communicate with the UE based on at least one of the power amplifier models. 
     Another apparatus for wireless communication at a base station is described. The apparatus may include means for mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna, means for determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna, means for transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE, and means for communicating with the UE based on at least one of the power amplifier models. 
     A non-transitory computer-readable medium storing code for wireless communication at a base station is described. The code may include instructions executable by a processor to map each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna, determine a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna, transmit an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE, and communicate with the UE based on at least one of the power amplifier models. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the UE may be based on the transmitting. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, frequency domain multiplexing a first antenna port of the first reference signal with a second antenna port of the second reference signal, where communicating with the UE may be based on the frequency domain multiplexing. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for using each transmitter antenna of a first group of antennas of the set of multiple antenna groups to form a first beam associated with the first reference signal and using each transmitter antenna of a second group of antennas of the set of multiple antenna groups to form a second beam associated with the second reference signal, where communicating with the UE may be based on the forming the first beam and the forming the second beam. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first reference signal, or the second reference signal, or both include a respective demodulation reference signal. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to the UE, each power amplifier model for each antenna group of the set of multiple antenna groups, where the indication of the power amplifier model may be transmitted in a radio resource control message, and where communicating with the UE may be based on the transmitting. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for indicating in the indication of the power amplifier model which transmitter antennas may be associated with each antenna group of the set of multiple antenna groups and which of the power amplifier models to use for each antenna group, or which of the power amplifier models to use with each antenna group of the set of multiple antenna groups for a given temperature, or both. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for indicating in the indication of the power amplifier model a link between a first power amplifier model of a first antenna group of the set of multiple antenna groups and a first set of one or more antenna rows of a precoding matrix and a link between a second power amplifier model of a second antenna group of the set of multiple antenna groups and a second set of one or more antenna rows of the precoding matrix. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for indicating in the indication of the power amplifier model a preconfigured linking pattern, from a set of one or more linking patterns preconfigured on the UE, that links a first power amplifier model of a first antenna group of the set of multiple antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the set of multiple antenna groups with a second set of one or more antenna rows of the precoding matrix. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the power amplifier model of each antenna group may include operations, features, means, or instructions for converting a first power amplifier model of a first antenna group of the set of multiple antenna groups into a first list of kernels and converting a second power amplifier model of a second antenna group of the set of multiple antenna groups into a second list of kernels. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the indication of the power amplifier model of each antenna group may include operations, features, means, or instructions for transmitting at least the first list of kernels and the second list of kernels to the UE. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, determining the power amplifier model of each antenna group may include operations, features, means, or instructions for projecting coefficients of the power amplifier model of each transmitter antenna onto a reduced set of basis functions and determining a matrix of basis functions based on the projecting. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the indication of the power amplifier model of each antenna group may include operations, features, means, or instructions for transmitting the matrix of basis functions to the UE. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of a wireless communications system that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  2    illustrates an example of a wireless communications system that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  3    illustrates an example of a process flow that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIGS.  4  and  5    show block diagrams of devices that support power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  6    shows a block diagram of a communications manager that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  7    shows a diagram of a system including a device that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIGS.  8  and  9    show block diagrams of devices that support power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  10    shows a block diagram of a communications manager that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIG.  11    shows a diagram of a system including a device that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
         FIGS.  12  through  15    show flowcharts illustrating methods that support power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present techniques relate to power amplifier model estimation for digital post distortion in multi-antenna device. Some signals, such as wideband signals, are spectrally more efficient than others. However, these signals, such as the wideband signals, may be applied by power amplifiers (PAs), which are inherently nonlinear. The nonlinearity of PAs, in some examples, generates spectral re-growth, which leads to adjacent channel interference and violations of out-of-band emission constraints set by regulatory bodies, among other issues. The nonlinearity of the PAs also may cause in-band distortion, which degrades the bit error rate (BER) performance. In some cases, a receiver device (e.g., a user equipment (UE)) may perform digital post distortion processing to estimate the non-linearity and compensate accordingly. However, some base stations (e.g., 5G NR base stations) may include an antenna array that is configured with a relatively large number of antennas. In some cases, digital post distortion processing may be performed on each transmitter antenna, but performing digital post distortion processing on such relatively large transmit antenna arrays may result in relatively large numbers of operations, such as calculations. In some cases, the computational costs of the non-linearity estimation on such relatively large transmit antenna arrays may be impractical due to the adverse effects these computational costs could have on the performance of associated devices, quality of service, and user experience. 
     The techniques described herein enable a device, such as a base station, to efficiently transmit power amplifier models to a user equipment (UE) so that the UE may use the power amplifier models to compensate for power amplifier characteristics, such as non-linearity (e.g., non-linearity remaining after digital predistortion). The described techniques relate to combining transmitter antennas into groups of antennas based on a similarity between power amplifier models of the respective transmitter antennas. For example, in some cases, a power amplifier response (e.g., power amplifier output power relative to power amplifier input power) of a first transmitter antenna may be relatively similar to a power amplifier response of a second transmitter antenna, and a power amplifier response of a third transmitter antenna may be relatively similar to a power amplifier response of a fourth transmitter antenna. In some cases, the similarity between a first power amplifier response and a second power amplifier response may be based on the power amplifier output power levels of the second power amplifier response being within a set threshold of the power amplifier output power levels of the first power amplifier response for a set of power amplifier input power levels. Based on the described techniques, a base station may group the first transmitter antenna and second transmitter antenna in a first antenna group, and group the third transmitter antenna and fourth transmitter antenna in a second antenna group separate from the first antenna group. Accordingly, instead of transmitting a power amplifier model for each transmitter antenna based on the power amplifier response of each transmitter antenna, the base station may transmit a power amplifier model (e.g., an indication of a power amplifier model) for at least some antenna groups, if not each antenna group (e.g., transmit a first power amplifier model for the first antenna group of antennas and a second power amplifier model for the second antenna group of antennas). In some cases, a UE may perform digital post distortion processing on signals received from the base station based on the indicated power amplifier models. 
     Aspects of the subject matter described herein may be implemented to realize one or more advantages. The described techniques may support improvements in system efficiency in association with a device performing digital post distortion processing. Additionally, the described techniques may result in decreasing system latency, increasing device performance, increasing the reliability of digital post distortion processing, and thus improving quality of service and user experience, among other advantages. 
     Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are further illustrated by and described with reference to additional examples of the wireless communications systems as well as process flows that relate to power amplifier model estimation for digital post distortion in multi-antenna device. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to power amplifier model estimation for digital post distortion in multi-antenna device. 
       FIG.  1    illustrates an example of a wireless communications system  100  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The wireless communications system  100  may include one or more base stations  105 , one or more UEs  115 , and a core network  130 . In some examples, the wireless communications system  100  may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system  100  may support enhanced broadband communications, ultra-reliable communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof. 
     The base stations  105  may be dispersed throughout a geographic area to form the wireless communications system  100  and may be devices in different forms or having different capabilities. The base stations  105  and the UEs  115  may wirelessly communicate via one or more communication links  125 . Each base station  105  may provide a coverage area  110  over which the UEs  115  and the base station  105  may establish one or more communication links  125 . The coverage area  110  may be an example of a geographic area over which a base station  105  and a UE  115  may support the communication of signals according to one or more radio access technologies. 
     The UEs  115  may be dispersed throughout a coverage area  110  of the wireless communications system  100 , and each UE  115  may be stationary, or mobile, or both at different times. The UEs  115  may be devices in different forms or having different capabilities. Some example UEs  115  are illustrated in  FIG.  1   . The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115 , the base stations  105 , or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in  FIG.  1   . 
     In some examples, one or more components of the wireless communications system  100  may operate as or be referred to as a network node. As used herein, a network node may refer to any UE  115 , base station  105 , entity of a core network  130 , apparatus, device, or computing system configured to perform any techniques described herein. For example, a network node may be a UE  115 . As another example, a network node may be a base station  105 . As another example, a first network node may be configured to communicate with a second network node or a third network node. In one aspect of this example, the first network node may be a UE  115 , the second network node may be a base station  105 , and the third network node may be a UE  115 . In another aspect of this example, the first network node may be a UE  115 , the second network node may be a base station  105 , and the third network node may be a base station  105 . In yet other aspects of this example, the first, second, and third network nodes may be different. Similarly, reference to a UE  115 , a base station  105 , an apparatus, a device, or a computing system may include disclosure of the UE  115 , base station  105 , apparatus, device, or computing system being a network node. For example, disclosure that a UE  115  is configured to receive information from a base station  105  also discloses that a first network node is configured to receive information from a second network node. In this example, consistent with this disclosure, the first network node may refer to a first UE  115 , a first base station  105 , a first apparatus, a first device, or a first computing system configured to receive the information; and the second network node may refer to a second UE  115 , a second base station  105 , a second apparatus, a second device, or a second computing system 
     The base stations  105  may communicate with the core network  130 , or with one another, or both. For example, the base stations  105  may interface with the core network  130  through one or more backhaul links  120  (e.g., via an S 1 , N 2 , N 3 , or other interface). The base stations  105  may communicate with one another over the backhaul links  120  (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations  105 ), or indirectly (e.g., via core network  130 ), or both. In some examples, the backhaul links  120  may be or include one or more wireless links. 
     One or more of the base stations  105  described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology. 
     A UE  115  may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE  115  may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE  115  may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples. 
     The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115  that may sometimes act as relays as well as the base stations  105  and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in  FIG.  1   . 
     The UEs  115  and the base stations  105  may wirelessly communicate with one another via one or more communication links  125  over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links  125 . For example, a carrier used for a communication link  125  may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP)) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system  100  may support communication with a UE  115  using carrier aggregation or multi-carrier operation. A UE  115  may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. 
     Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements that a UE  115  receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE  115 . A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE  115 . 
     The time intervals for the base stations  105  or the UEs  115  may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T s =1/(Δ f   max ·N f ) seconds, where Δf max  may represent the maximum supported subcarrier spacing, and N f  may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023). 
     Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems  100 , a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N f ) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation. 
     A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system  100  and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system  100  may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)). 
     Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs  115 . For example, one or more of the UEs  115  may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs  115  and UE-specific search space sets for sending control information to a specific UE  115 . 
     In some examples, a base station  105  may be movable and therefore provide communication coverage for a moving geographic coverage area  110 . In some examples, different geographic coverage areas  110  associated with different technologies may overlap, but the different geographic coverage areas  110  may be supported by the same base station  105 . In other examples, the overlapping geographic coverage areas  110  associated with different technologies may be supported by different base stations  105 . The wireless communications system  100  may include, for example, a heterogeneous network in which different types of the base stations  105  provide coverage for various geographic coverage areas  110  using the same or different radio access technologies. 
     The wireless communications system  100  may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system  100  may be configured to support ultra-reliable low-latency communications (URLLC). The UEs  115  may be designed to support ultra-reliable, low-latency, or critical functions. Ultra-reliable communications may include private communication or group communication and may be supported by one or more services such as push-to-talk, video, or data. Support for ultra-reliable, low-latency functions may include prioritization of services, and such services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, and ultra-reliable low-latency may be used interchangeably herein. 
     In some examples, a UE  115  may also be able to communicate directly with other UEs  115  over a device-to-device (D2D) communication link  135  (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs  115  utilizing D2D communications may be within the geographic coverage area  110  of a base station  105 . Other UEs  115  in such a group may be outside the geographic coverage area  110  of a base station  105  or be otherwise unable to receive transmissions from a base station  105 . In some examples, groups of the UEs  115  communicating via D2D communications may utilize a one-to-many ( 1 :M) system in which each UE  115  transmits to every other UE  115  in the group. In some examples, a base station  105  facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs  115  without the involvement of a base station  105 . 
     The core network  130  may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network  130  may be an evolved packet core (EPC) or 5G core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs  115  served by the base stations  105  associated with the core network  130 . User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to IP services  150  for one or more network operators. The IP services  150  may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service. 
     Some of the network devices, such as a base station  105 , may include subcomponents such as an access network entity  140 , which may be an example of an access node controller (ANC). Each access network entity  140  may communicate with the UEs  115  through one or more other access network transmission entities  145 , which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). Each access network transmission entity  145  may include one or more antenna panels. In some configurations, various functions of each access network entity  140  or base station  105  may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station  105 ). 
     The wireless communications system  100  may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs  115  located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz. 
     The wireless communications system  100  may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system  100  may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations  105  and the UEs  115  may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples. 
     A base station  105  or a UE  115  may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station  105  or a UE  115  may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station  105  may be located in diverse geographic locations. A base station  105  may have an antenna array with a number of rows and columns of antenna ports that the base station  105  may use to support beamforming of communications with a UE  115 . Likewise, a UE  115  may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port. 
     The base stations  105  or the UEs  115  may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices. 
     Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station  105 , a UE  115 ) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation). 
     A base station  105  or a UE  115  may use beam sweeping techniques as part of beam forming operations. For example, a base station  105  may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE  115 . Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station  105  multiple times in different directions. For example, the base station  105  may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station  105 , or by a receiving device, such as a UE  115 ) a beam direction for later transmission or reception by the base station  105 . 
     Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station  105  in a single beam direction (e.g., a direction associated with the receiving device, such as a UE  115 ). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE  115  may receive one or more of the signals transmitted by the base station  105  in different directions and may report to the base station  105  an indication of the signal that the UE  115  received with a highest signal quality or an otherwise acceptable signal quality. 
     In some examples, transmissions by a device (e.g., by a base station  105  or a UE  115 ) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station  105  to a UE  115 ). The UE  115  may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station  105  may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)), which may be precoded or unprecoded. The UE  115  may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by a base station  105 , a UE  115  may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE  115 ) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device). 
     A receiving device (e.g., a UE  115 ) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station  105 , such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening according to multiple beam directions). 
     The wireless communications system  100  may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. 
     The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE  115  and a base station  105  or a core network  130  supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels. 
     The UEs  115  and the base stations  105  may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood that data is received correctly over a communication link  125 . HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., low signal-to-noise conditions). In some examples, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval. 
     In some examples, a base station  105  may determine a power amplifier response of each transmitter antenna of the base station  105 . The base station  105  may compare the power amplifier responses of each transmitter antenna. For example, the base station  105  may compare the power amplifier response of a first transmitter antenna to the power amplifier response of a second transmitter antenna, the power amplifier response of a third transmitter antenna, or the power amplifier response of a fourth transmitter antenna, of any combination thereof. In some cases, the base station  105  may compare the power amplifier response of the second transmitter antenna to the power amplifier response of the first transmitter antenna, the power amplifier response of the third transmitter antenna, or the power amplifier response of the fourth transmitter antenna, of any combination thereof. In some examples, the base station  105  may determine that the power amplifier response of the first transmitter antenna is relatively similar to the power amplifier response of the fourth transmitter antenna, and that the power amplifier response of the second transmitter antenna is relatively similar to the power amplifier response of the third transmitter antenna. 
     In some examples, the base station  105  may map each transmitter antenna to one of several antenna groups based on similarity between respective power amplifier responses. The base station  105  may map a first set of one or more transmitter antennas with similar power amplifier responses (e.g., the first transmitter antenna and the fourth transmitter antenna) to a first antenna group and map a second set of one or more transmitter antennas with similar power amplifier responses (e.g., the second transmitter antenna and the third transmitter antenna) to a second antenna group, etc. Based on the similar power amplifier responses, the base station  105  may determine a first power amplifier model for the first antenna group and determine a second power amplifier model for the second antenna group, and so on. In some cases, the first power amplifier model for the first antenna group may be based on an average of the power amplifier responses of the respective antennas of the first antenna group. In some cases, the second power amplifier model for the second antenna group may be based on an average of the power amplifier responses of the respective antennas of the second antenna group. 
     In some examples, the base station  105  may transmit an indication of the respective power amplifier models of each antenna group to a UE  115 . In some cases, the UE  115  may determine a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the respective power amplifier models, where the transmitter antenna is associated with an antenna group of the multiple antenna groups and the power amplifier model for the transmitter antenna is associated with that antenna group. In some examples, UE  115  may apply the first power amplifier model of the first antenna group to an antenna of the first antenna group (e.g., to fourth transmitter antenna, etc.). In some cases, the UE  115  and the base station  105  may communicate with each other based on the power amplifier model for the transmitter antenna (e.g., the first power amplifier model for the fourth transmitter antenna). 
       FIG.  2    illustrates an example of a wireless communications system  200  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. In some examples, some aspects of wireless communications system  200  may implement or be implemented by aspects of wireless communications system  100 . In the illustrated example, the wireless communications system  200  may include a base station  105 - a  and a UE  115 - a . The base station  105 - a  and the UE  115 - a  may be examples of corresponding devices described herein with reference to  FIG.  1   . 
     As illustrated, wireless communications system  200  may include downlink  205  and uplink  210 . Base station  105 - a  may use downlink  205  to convey control and/or data information to UE  115 - a . And UE  115 - a  may use uplink  210  to convey control and/or data information to base station  105 - a . In some cases, downlink  205  may use different time and/or frequency resources than uplink  210 . 
     In the illustrated example, UE  115 - a  may receive one or more transmissions from base station  105 - a . In some cases, the one or more transmissions may include an indication of a power amplifier model for each antenna group of base station  105 - a , where each antenna group includes one or more transmitter antennas of base station  105 - a.    
     In some examples, base station  105 - a  may analyze power amplifier responses of each transmitter antenna of base station  105 - a . In some cases, base station  105 - a  may compare the respective power amplifier responses to each other and identify which transmitter antennas have relatively similar power amplifier responses. The base station  105 - a  may map each transmitter antenna of the base station  105 - a  to one of a set of antenna groups based on a power amplifier response of each transmitter antenna. 
     In some examples, base station  105 - a  may determine a power amplifier model for each antenna group of the set of antenna groups based on the respective power amplifier responses associated with each antenna group (e.g., based on the averaged power amplifier response of each antenna group). As shown, base station  105 - a  may transmit the indication of the power amplifier models  215  for each antenna group of base station  105 - a  to UE  115 - a . In some cases, the indication of the power amplifier models  215  may be signaled via a radio resource control message. 
     In some examples, the indication of the power amplifier models  215  may be based on or include UE  115 - a  obtaining power amplifier response through estimation or explicit signaling per group of antennas. In some cases, the indication of the power amplifier models  215  may be based on or include one or more reference signals. In some cases, the one or more reference signals may be demodulation reference signals. 
     In some cases, base station  105 - a  may transmit to UE  115 - a  a first reference signal for a first antenna group of the set of antenna groups and a second reference signal for a second antenna group of the set of antenna groups. The first reference signal, or the second reference signal, or both may be based on or include a respective demodulation reference signal. In some cases, base station  105 - a  communicating with UE  115 - a  may be based on base station  105 - a  transmitting the one or more reference signals. 
     In some examples, an antenna port of each reference signal may be allocated per group of antennas (e.g., a first antenna port allocated for a first reference signal of a first power amplifier model of a first group of antennas, a second antenna port allocated for a second reference signal of a second power amplifier model of a second group of antennas, etc.). In some cases, UE  115 - a  may estimate the power amplifier model per group based on each respective reference signal. 
     In some examples, base station  105 - a  may multiplex (e.g., frequency domain multiplex) a first antenna port of the first reference signal with a second antenna port of the second reference signal. In some cases, base station  105 - a  communicating with UE  115 - a  may be based on the frequency domain multiplexing. In some cases, base station  105 - a  may frequency domain multiplex respective reference signal ports. In some examples, two reference signal resources on odd and even carriers may be frequency domain multiplexed such that the associated signals with their power amplifier non-linearity are orthogonal to each other. 
     In some examples, base station  105 - a  may use each transmitter antenna of a first group of antennas of the set of antenna groups to form a first beam associated with the first reference signal. In some cases, base station  105 - a  may use each transmitter antenna of a second group of antennas of the set of antenna groups to form a second beam associated with the second reference signal. In some cases, base station  105 - a  communicating with UE  115 - a  may be based on base station  105 - a  forming the first beam and the forming the second beam. 
     In some examples, base station  105 - a  may transmit, to the UE  115 - a , each power amplifier model for each antenna group of the set of antenna groups (e.g., transmit ten power amplifier models for a total of ten antenna groups). In some cases, the indication of the power amplifier model may be transmitted in a radio resource control message. In some cases, base station  105 - a  communicating with UE  115 - a  may be based on base station  105 - a  transmitting each power amplifier model. In some cases, base station  105 - a  may transmit explicit signaling to indicate the relevant power amplifier model for UE  115 - a  to use. In some cases, base station  105 - a  may transmit a temperature report to UE  115 - a , and UE  115 - a  may select the relevant power amplifier model to use based on the temperature report indicating a mapping between a current temperature and the relevant power amplifier model. 
     In some examples, base station  105 - a  may indicate in the indication of the power amplifier model which transmitter antennas are associated with which antenna group of the set of antenna groups and which of the power amplifier models to use for each antenna group, or which of the power amplifier models to use with each antenna group of the set of antenna groups for a given temperature, or a combination thereof. 
     In some examples, the indication of the power amplifier models  215  may be based on or include a set of links between power amplifier models and antenna groups, each link connecting a respective power amplifier model to an antenna group. Thus, base station  105 - a  may explicitly indicate relevant power amplifier models based on the set of links between power amplifier models and antenna groups. In some cases, the base station  105 - a  may indicate multiple sets of links for various operating conditions (e.g., various temperatures, etc.). Thus, the base station  105 - a  may transmit the indication of the power amplifier models  215  to UE  115 - a  (e.g., with the one or more sets of links), and UE  115 - a  may adapt to varying operating conditions by implementing or switching to the relevant power amplifier model per operating condition. 
     In some examples, base station  105 - a  may indicate in the indication of the power amplifier model a first link between a first power amplifier model of a first antenna group of the set of antenna groups and a first set of one or more antenna rows of a precoding matrix and a second link between a second power amplifier model of a second antenna group of the set of antenna groups and a second set of one or more antenna rows of the precoding matrix. In some cases, each precoding matrix row corresponds to a single transmitting antenna of base station  105 - a . When a power amplifier model applies to a group of antennas the same power amplifier model may correspond to a corresponding set of precoding matrix rows. Thus, a first group of three antennas may correspond to three precoding matrix rows, a second group of one antenna may correspond to one precoding matrix row, a third group of two antennas may correspond to two precoding matrix rows, etc. 
     In some examples, base station  105 - a  may indicate in the indication of the power amplifier model a preconfigured linking pattern, from a set of one or more linking patterns preconfigured on the UE  115 - a . In some cases, the base station  105 - a  may implicitly indicate relevant power amplifier models based on the preconfigured linking pattern. In some cases, the preconfigured linking pattern may link a first power amplifier model of a first antenna group of the set of antenna groups with a first set of one or more antenna rows of a precoding matrix, and link a second power amplifier model of a second antenna group of the set of antenna groups with a second set of one or more antenna rows of the precoding matrix. 
     In some examples, the indication of the power amplifier models  215  may be based on or include a list of kernels (e.g., coefficients) associated with a digital post distortion model (e.g., a digital post distortion model based on the respective power amplifier models indicated in the indication of the power amplifier models  215 ). In some cases, base station  105 - a  may convert a first power amplifier model of a first antenna group of the set of antenna groups into a first list of kernels, and convert a second power amplifier model of a second antenna group of the set of antenna groups into a second list of kernels. In some cases, base station  105 - a  may transmit at least the first list of kernels and the second list of kernels to the UE  115 - a.    
     In some examples, UE  115 - a  may receive the list of kernels and analyze the list of kernels. In some cases, UE  115 - a  may determine respective power amplifier models based on the list of kernels. In some cases, the base station  105 - a  may indicate multiple lists of kernels for various operating conditions (e.g., various temperatures, etc.). Thus, the base station  105 - a  may transmit the indication of the power amplifier models  215  to UE  115 - a  (e.g., with the one or more lists of kernels), and UE  115 - a  may adapt to varying operating conditions by implementing or switching to the relevant power amplifier model per operating condition according to which list of kernels applies to the given operating condition. 
     In some examples, the indication of the power amplifier models  215  may be based on or include a matrix of basis functions. The total number of reference signal resources for a set of transmitter antennas of base station  105 - a  may be linearly proportional to the product of the total number of transmitter antennas and the number of kernels per transmitter antenna. However, based on the similarity or correlation between power amplifier models, the kernels (e.g., power amplifier model coefficients) may be projected onto a reduced set of basis functions (e.g., reduced according to similar power amplifier responses) instead of the full set of basis functions for every power amplifier response of every transmitter antenna. In some cases, base station  105 - a  may generate an overall number of basis functions for the transmitter antennas. In some cases, the reduced set of basis functions may be a subset of the overall number of basis functions. In some cases, base station  105 - a  may select the reduced set of basis functions based on respective similarity of power amplifier responses of the transmitter antennas. 
     As described herein, a set of similar power amplifier responses may be mapped to a single representative power amplifier model, and the representative power amplifier model may be associated with one of the groups of antennas of the set of antenna groups. In some cases, the representative power amplifier model or the respective group of antennas may be associated with at least one basis function (e.g., instead of each antenna of the respective group of antennas being associated with at least one basis function). In some cases, base station  105 - a  may project the kernels (e.g., coefficients of the power amplifier model) of each transmitter antenna onto a reduced set of basis functions (e.g., instead of the kernels of each transmitter antenna being projected onto each basis function of each transmitter antenna). In some cases, base station  105 - a  may determine a matrix of basis functions based on the projecting. In some cases, base station  105 - a  may transmit the matrix of basis functions to the UE  115 - a.    
     In some examples, the basis functions may be based on the estimation of power amplifier models according to the following equation: 
     
       
         
           
             β 
             = 
             
               argmin 
               ⁢ 
               
                 
                    
                   
                     
                       [ 
                       
                         
                           
                             
                               p 
                               0 
                             
                           
                         
                         
                           
                             ⋮ 
                           
                         
                         
                           
                             
                               p 
                               
                                 Ntx 
                                 - 
                                 1 
                               
                             
                           
                         
                       
                       ] 
                     
                     - 
                     
                       
                         [ 
                         
                           
                             
                               
                                 A 
                                 0 
                               
                             
                             
                               … 
                             
                             
                               0 
                             
                           
                           
                             
                               ⋮ 
                             
                             
                               ⋱ 
                             
                             
                               ⋮ 
                             
                           
                           
                             
                               0 
                             
                             
                               … 
                             
                             
                               
                                 A 
                                 
                                   tx 
                                   - 
                                   1 
                                 
                               
                             
                           
                         
                         ] 
                       
                       ⁢ 
                       B 
                       ⁢ 
                       β 
                     
                   
                    
                 
                 2 
               
             
           
         
       
     
     where tx is the number of transmitter antennas of base station  105 - a  (e.g., the number of power amplifiers to estimate); B is the basis function matrix (e.g., (tx·K)·(L·K)) that projects, for each of the kernels, the tx power amplifier coefficients to L basis functions, where L is less than tx; β is the (LK) vector of basis functions coefficients; K is the number of kernels used per power amplifier model; f k  is the k-th kernel function; and p n,m  is a vector of received pilots around the m-th pilot element sent from the n-th power amplifier. 
     In some examples, the product B·β is equivalent to a single column matrix [α 0  to α tx−1 ] as indicated in the following: 
     
       
         
           
             
               B 
               ⁢ 
               β 
             
             ≡ 
             
               [ 
               
                 
                   
                     
                       α 
                       0 
                     
                   
                 
                 
                   
                     ⋮ 
                   
                 
                 
                   
                     
                       α 
                       
                         tx 
                         - 
                         1 
                       
                     
                   
                 
               
               ] 
             
           
         
       
     
     where the column matrix of α values represent the power amplifier response of the tx transmitter antennas. Thus, the product B·β replaces the power amplifier response of each antenna (e.g., from α 0  to α tx−1 ), such that the n-th power amplifier is modeled according to the following equation: 
     
       
         
           
             
               
                 PA 
                 n 
               
               ( 
               x 
               ) 
             
             = 
             
               
                 ∑ 
                 k 
               
               
                 
                   α 
                   
                     n 
                     , 
                     k 
                   
                 
                 ⁢ 
                 
                   
                     f 
                     k 
                   
                   ( 
                   x 
                   ) 
                 
               
             
           
         
       
     
     In some examples, UE  115 - a  is preconfigured with the basis functions of the respective power amplifier responses or are signaled by base station  105 - a  (e.g., via the indication of the power amplifier models  215 ). In some cases, UE  115 - a  determines how to combine the kernels for each transmitter antenna (e.g., coefficients of respective power amplifier models). Once base station  105 - a  determines the respective power amplifier responses of each transmitter antenna, base station  105 - a  may reduce the set of power amplifier responses down to two or more groups of power amplifier responses based on respective similarity between power amplifier responses. The base station  105 - a  may then determine a power amplifier model for each group of power amplifier responses. Thus,  13  represents a vector of coefficients of basis functions based on the group of power amplifier responses (e.g., based on each power amplifier model representative of each group of power amplifier responses), and B represents some known basis function matrix according to the correlation of transmitter antennas into groups of antennas (e.g., according to the similarity between power amplifier responses of each group of antennas). 
     As indicated, B may represent a matrix of basis functions that base station  105 - a  may signal to UE  115 - a  (e.g., signal to digital post distortion-capable UEs). In some cases, the a matrix of basis functions may be signaled via a radio resource control message. In some cases, UE  115 - a  may perform repeated estimations of power amplifier models per temperature per band, per transmitting power, etc., based on the same underlying basis functions matrix B. In some cases, UE  115 - a  may receive basis functions matrix B and adjust power amplifier models based on fluctuations in temperature per band, transmitting power per antenna, etc., based on the basis functions matrix B. 
     In some examples, UE  115 - a  may receive implicit (e.g., via the indication of the power amplifier models  215  or configured before the indication of the power amplifier models  215 , or a combination thereof) or explicit signaling (e.g., via the indication of the power amplifier models  215 ) regarding the mapping of power amplifiers among antenna groups and the relation between the power amplifier models and blind channel estimation in digital post distortion processing. In some cases, coefficients of a digital post distortion model used in digital post distortion processing may be equivalent to or referred to as coefficients of a power amplifier model. In some cases, a power amplifier model may be equivalent to or referred to as a digital post distortion model. In some cases, UE  115 - a  may select a power amplifier model and use the coefficients of the selected power amplifier model as coefficients of an associated digital post distortion model. 
     In some examples, base station  105 - a  and UE  115 - a  may communicate with each other based on at least one of the power amplifier models (e.g., based on the indication of the power amplifier models  215 ). In the illustrated example, the communication between base station  105 - a  and UE  115 - a  may include downlink signal  230 . In some cases, the base station  105 - a  may amplify the downlink signal  230  using a power amplifier. As the power amplifier nears saturation, this may result in a distortion that may generate non-linear noise according to a known model (e.g., power amplifier clipping), by directly affecting the mapped symbols of downlink signal  230 . Thus, aspects of the amplified downlink signal  230  may be distorted. In some cases, base station  105 - a  may remove non-linear noise from downlink signal  230 . In some other cases, UE  115 - a  may remove the non-linear noise from the downlink signal  230 . In some cases, UE  115 - a  may apply a digital post distortion algorithm  245  to the received downlink signal  230  to remove the non-linear noise from the downlink signal  230 . The digital post distortion algorithm  245  may be represented by Equation (1): 
         Y   k   =G ( X   k )+ N   k   =α·X   k   +D ( X   k )+ N   k    (1)
 
     where α may be a coefficient, such as a Bussgang coefficient, X k  may be the downlink signal  230 , and k may be a delay or time offset as a result of the distortion introduced by the power amplifier. The a X k  part of the Equation (1) may be a linear portion of the downlink signal  230  and may represent the downlink signal  230  before non-linear noise may have been introduced, for example, by the power amplifier at the base station  105 - a . The non-linear model that results from the downlink signal  230  may be represented by D (X k ) in the time domain. The non-linear model D (X k ) may include odd-order memoryless kernels, such as x*|x| 2  or x*|x| 4 , that may represent the power amplifier used at the base station  105 - a  to amplify the downlink signal  230 . As such, Y k  may represent the non-linearity of the signal X k , which may equate to the sum of the applied kernels, where each kernel has its own coefficient. In some cases, such as large bandwidth or high signal to noise ratio (SNR), memory kernels may also be applied, such as x[n]*|x[n−k]| M  where k may be a time delay and M may be an even integer. 
     The UE  115 - a  may apply the digital post distortion algorithm  245  to the downlink signal  230  one or more times, where each iteration includes performing a hard decision slicing operation  245 - a  to determine estimated constellation points (e.g., X_k) and estimating nonlinear noise  245 - c  (e.g., estimate D(X)). In some cases, the digital post distortion algorithm  245 , in conjunction with nonlinear noise  245 - c , may implement a nonlinear model of a power amplifier. In order to perform the hard decision slicing operation  245 - a , the UE  115 - a  may take the time domain signal  230 - a  (e.g., y_n) of the downlink signal  230  and apply demodulation operation  235  (e.g., a discrete Fourier transform (DFT)) in order to produce the demodulated downlink signal  230 - b  (e.g., frequency domain signal Y_k). The UE  115 - a  may perform the hard decision slicing operation  245 - a  on the demodulated downlink signal  230 - b  by comparing each symbol of the demodulated downlink signal  230 - b  to constellations in a constellation distribution that may be free of impairments and based on a modulation scheme used to modulate the downlink signal  230 . 
     In some examples, initial iterations of digital post distortion algorithm  245  may be distorted by relatively strong noise due to the non-linearity of the received signal that has not yet been processed (e.g., reduced) by the hard decision slicing performed by digital post distortion algorithm  245  in conjunction with hard slicer  245 - a . As shown, the digital post distortion algorithm  245  may provide the estimated nonlinear noise  245 - c  to adder  240 . In some cases, adder  240  may subtract the estimated nonlinear noise  245 - c  from the demodulated downlink signal  230 - b , where the adder  240  provides the difference to the digital post distortion algorithm  245  and the demapper  250 . As shown, the frequency-domain signal (e.g., the estimated nonlinear noise  245 - c  subtracted from the demodulated downlink signal  230 - b ) may be provided to demapper  250  to extract symbols from the frequency-domain signal. As shown, the demapper  250  may provide the extracted symbols (e.g., “LLR_b” based on log-likelihood ratio bits) to a decoder  260 . In some cases, the decoder  260  may extract bits (e.g., “b_k”) from the extracted symbols, and provide the extracted bits b_k as a result of the digital post distortion processing. 
     In some examples, the wireless communications system  200  may support multiple radio access technologies including 4G systems such as LTE systems, LTE-A systems, or LTE-A Pro systems, and 5G systems, which may be referred to as NR systems. The wireless communications system  200  may also support improvements to power consumption, spectral efficiency, higher data rates and, in some examples, may promote enhanced efficiency for higher reliability and lower latency wireless communications (e.g., uplink transmission, downlink transmission, uplink reception, and downlink reception), among other benefits. 
     The present techniques may reduce power consumption and free up processing cycles of one or more devices (e.g., battery-operated devices, a UE  115  of  FIG.  1   , etc.) by reducing system overhead associated with indication of power amplifier models of transmitter antennas. Additionally, described techniques may result in decreasing system latency, decreasing system computational load, and increasing resource utilization efficiency, while increasing spectrum efficiency and improving user experience. 
       FIG.  3    illustrates an example of a process flow  300  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. In some examples, some aspects of process flow  300  may implement or be implemented by aspects of wireless communications system  100 . For example, process flow  300  may include a base station  105 - b  and a UE  115 - b , which may be respective examples of a base station  105  or UE  115  described with reference to  FIG.  1   . 
     At  305 , base station  105 - b  may analyze power amplifier responses of each transmitter antenna of base station  105 - b . In some cases, the analysis of power amplifier responses may include determining a power amplifier response of each transmitter antenna of the base station  105 - b , comparing the power amplifier responses of each transmitter antenna, and grouping transmitter antennas based on similar power amplifier responses. 
     At  310 , base station  105 - b  may map each transmitter antenna to one of several antenna groups based on similarity between respective power amplifier responses. The base station  105 - b  may map a first set of one or more transmitter antennas with similar power amplifier responses to a first antenna group and map a second set of one or more transmitter antennas with similar power amplifier responses to a second antenna group, etc. 
     At  315 , base station  105 - b  may determine a power amplifier model for each group of antennas. In some cases, base station  105 - b  may determine a first amplifier model for a first group of antennas and a second amplifier model for a second group of antennas. The first amplifier model may be based on base station  105 - b  analyzing one or more respective power amplifier responses of transmitter antennas associated with the first group of antennas, and the second amplifier model may be based on base station  105 - b  analyzing one or more respective power amplifier responses of transmitter antennas associated with the second group of antennas. 
     At  320 , base station  105 - b  may transmit an indication of the respective power amplifier models of each antenna group to a UE  115 - b . In some cases, base station  105 - b  may transmit the indication of the respective power amplifier models via a radio resource control message. In some cases, base station  105 - b  may transmit the indication of the respective power amplifier models via a radio resource control message, a downlink control information message, or a media access control element message, or any combination thereof. 
     At  325 , UE  115 - b  may determine at least one power amplifier model of a transmitter antenna of base station  105 - b  based on the indication of the respective power amplifier models. In some cases, UE  115 - b  may analyze the indication of the respective power amplifier models and determine an indicated power amplifier model maps to a transmitter antenna based on the indicated power amplifier model and the transmitter antenna both mapping to a same group of antennas. 
     At  330 , UE  115 - b  may select and implement a selected power amplifier model. In some cases, UE  115 - b  may implement the selected power amplifier model based on one or more conditions (e.g., based on a current temperature, based on explicit signaling from base station  105 - b , etc.). In some cases, UE  115 - b  may implement the selected power amplifier model with digital post distortion processing. 
     At  335 , UE  115 - b  and base station  105 - b  may communicate with each other based on the implemented power amplifier model. In some cases, the communication between UE  115 - b  and base station  105 - b  may include control and/or data information communicated from UE  115 - b  to base station  105 - b , or from base station  105 - b  to UE  115 - b , or both. 
     At  340 , UE  115 - b  may apply digital post distortion processing to communications from base station  105 - b . In some cases, UE  115 - b  may apply digital post distortion processing based on the implemented power amplifier model. 
       FIG.  4    shows a block diagram  400  of a device  405  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  405  may be an example of aspects of a UE  115  as described herein. The device  405  may include a receiver  410 , a transmitter  415 , and a communications manager  420 . The device  405  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  410  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). Information may be passed on to other components of the device  405 . The receiver  410  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  415  may provide a means for transmitting signals generated by other components of the device  405 . For example, the transmitter  415  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). In some examples, the transmitter  415  may be co-located with a receiver  410  in a transceiver module. The transmitter  415  may utilize a single antenna or a set of multiple antennas. 
     The communications manager  420 , the receiver  410 , the transmitter  415 , or various combinations thereof or various components thereof may be examples of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  420 , the receiver  410 , the transmitter  415 , or various combinations or components thereof may support a method for performing one or more of the functions described herein. 
     In some examples, the communications manager  420 , the receiver  410 , the transmitter  415 , or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some examples, a processor and memory coupled with the processor may be configured to perform one or more of the functions described herein (e.g., by executing, by the processor, instructions stored in the memory). 
     Additionally or alternatively, in some examples, the communications manager  420 , the receiver  410 , the transmitter  415 , or various combinations or components thereof may be implemented in code (e.g., as communications management software or firmware) executed by a processor. If implemented in code executed by a processor, the functions of the communications manager  420 , the receiver  410 , the transmitter  415 , or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a central processing unit (CPU), an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in the present disclosure). 
     In some examples, the communications manager  420  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  410 , the transmitter  415 , or both. For example, the communications manager  420  may receive information from the receiver  410 , send information to the transmitter  415 , or be integrated in combination with the receiver  410 , the transmitter  415 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  420  may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager  420  may be configured as or otherwise support a means for receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The communications manager  420  may be configured as or otherwise support a means for determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The communications manager  420  may be configured as or otherwise support a means for communicating with the base station based on the power amplifier model for the transmitter antenna. 
     By including or configuring the communications manager  420  in accordance with examples as described herein, the device  405  (e.g., a processor controlling or otherwise coupled to the receiver  410 , the transmitter  415 , the communications manager  420 , or a combination thereof) may support techniques for improvements in system efficiency such that system latency associated with indication of power amplifier models is reduced. Additionally, described techniques may result in reduced processing, reduced power consumption, more efficient utilization of communication resources. 
       FIG.  5    shows a block diagram  500  of a device  505  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  505  may be an example of aspects of a device  405  or a UE  115  as described herein. The device  505  may include a receiver  510 , a transmitter  515 , and a communications manager  520 . The device  505  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  510  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). Information may be passed on to other components of the device  505 . The receiver  510  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  515  may provide a means for transmitting signals generated by other components of the device  505 . For example, the transmitter  515  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). In some examples, the transmitter  515  may be co-located with a receiver  510  in a transceiver module. The transmitter  515  may utilize a single antenna or a set of multiple antennas. 
     The device  505 , or various components thereof, may be an example of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  520  may include an indication manager  525 , a model manager  530 , a connection manager  535 , or any combination thereof. The communications manager  520  may be an example of aspects of a communications manager  420  as described herein. In some examples, the communications manager  520 , or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  510 , the transmitter  515 , or both. For example, the communications manager  520  may receive information from the receiver  510 , send information to the transmitter  515 , or be integrated in combination with the receiver  510 , the transmitter  515 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  520  may support wireless communication at a UE in accordance with examples as disclosed herein. The indication manager  525  may be configured as or otherwise support a means for receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The model manager  530  may be configured as or otherwise support a means for determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The connection manager  535  may be configured as or otherwise support a means for communicating with the base station based on the power amplifier model for the transmitter antenna. 
       FIG.  6    shows a block diagram  600  of a communications manager  620  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The communications manager  620  may be an example of aspects of a communications manager  420 , a communications manager  520 , or both, as described herein. The communications manager  620 , or various components thereof, may be an example of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  620  may include an indication manager  625 , a model manager  630 , a connection manager  635 , a reference manager  640 , or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The communications manager  620  may support wireless communication at a UE in accordance with examples as disclosed herein. The indication manager  625  may be configured as or otherwise support a means for receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The model manager  630  may be configured as or otherwise support a means for determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The connection manager  635  may be configured as or otherwise support a means for communicating with the base station based on the power amplifier model for the transmitter antenna. 
     In some examples, to support receiving the indication of the power amplifier model for each antenna group, the reference manager  640  may be configured as or otherwise support a means for receiving a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the base station is based on the receiving. 
     In some examples, the reference manager  640  may be configured as or otherwise support a means for determining a first power amplifier model for the first antenna group based on the first reference signal and a second power amplifier model for the second antenna group based on the second reference signal. In some examples, the reference manager  640  may be configured as or otherwise support a means for applying the first power amplifier model to each transmitter antenna mapped to the first antenna group and the second power amplifier model to each transmitter antenna mapped to the second antenna group, where communicating with the base station is based on the applying. 
     In some examples, the first reference signal, or the second reference signal, or both include a respective demodulation reference signal. 
     In some examples, to support receiving the indication of the power amplifier model for each antenna group, the indication manager  625  may be configured as or otherwise support a means for receiving, from the base station, each power amplifier model for each antenna group of the set of multiple antenna groups, where the indication of the power amplifier model is received in a radio resource control message, and where communicating with the base station is based on the receiving. 
     In some examples, the indication manager  625  may be configured as or otherwise support a means for determining that the indication of the power amplifier model indicates which transmitter antennas are associated with each antenna group of the set of multiple antenna groups and which of the power amplifier models to use for each antenna group, or indicates which of the power amplifier models to use with each antenna group of the set of multiple antenna groups for a given temperature, or indicates both, where communicating with the base station is based on the determining. 
     In some examples, the indication manager  625  may be configured as or otherwise support a means for determining that the indication of the power amplifier model indicates a link between a first power amplifier model of a first antenna group of the set of multiple antenna groups and a first set of one or more antenna rows of a precoding matrix, and indicates a link between a second power amplifier model of a second antenna group of the set of multiple antenna groups and a second set of one or more antenna rows of the precoding matrix, where communicating with the base station is based on the determining. 
     In some examples, the indication manager  625  may be configured as or otherwise support a means for determining that the indication of the power amplifier model indicates, from a set of one or more linking patterns preconfigured on the UE, a preconfigured linking pattern that links a first power amplifier model of a first antenna group of the set of multiple antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the set of multiple antenna groups with a second set of one or more antenna rows of the precoding matrix, where communicating with the base station is based on the determining. 
     In some examples, the indication manager  625  may be configured as or otherwise support a means for determining that the indication of the power amplifier model indicates a first list of kernels associated with a first power amplifier model of a first antenna group of the set of multiple antenna groups, and a second list of kernels associated with a second power amplifier model of a second antenna group of the set of multiple antenna groups, where communicating with the base station is based on the determining. 
     In some examples, the indication manager  625  may be configured as or otherwise support a means for determining that the indication of the power amplifier model indicates a matrix of basis functions respectively associated with the set of multiple antenna groups, where communicating with the base station is based on the determining. 
     In some examples, to support communicating with the base station, the connection manager  635  may be configured as or otherwise support a means for implementing a digital post distortion model based on the power amplifier model of the transmitter antenna. In some examples, to support communicating with the base station, the connection manager  635  may be configured as or otherwise support a means for performing digital post distortion processing on signals received from the base station based on the digital post distortion model. 
       FIG.  7    shows a diagram of a system  700  including a device  705  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  705  may be an example of or include the components of a device  405 , a device  505 , or a UE  115  as described herein. The device  705  may communicate wirelessly with one or more base stations  105 , UEs  115 , or any combination thereof. The device  705  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager  720 , an input/output (I/O) controller  710 , a transceiver  715 , an antenna  725 , a memory  730 , code  735 , and a processor  740 . These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus  745 ). 
     The I/O controller  710  may manage input and output signals for the device  705 . The I/O controller  710  may also manage peripherals not integrated into the device  705 . In some cases, the I/O controller  710  may represent a physical connection or port to an external peripheral. In some cases, the I/O controller  710  may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. Additionally or alternatively, the I/O controller  710  may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller  710  may be implemented as part of a processor, such as the processor  740 . In some cases, a user may interact with the device  705  via the I/O controller  710  or via hardware components controlled by the I/O controller  710 . 
     In some cases, the device  705  may include a single antenna  725 . However, in some other cases, the device  705  may have more than one antenna  725 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver  715  may communicate bi-directionally, via the one or more antennas  725 , wired, or wireless links as described herein. For example, the transceiver  715  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  715  may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas  725  for transmission, and to demodulate packets received from the one or more antennas  725 . The transceiver  715 , or the transceiver  715  and one or more antennas  725 , may be an example of a transmitter  415 , a transmitter  515 , a receiver  410 , a receiver  510 , or any combination thereof or component thereof, as described herein. 
     The memory  730  may include random access memory (RAM) and read-only memory (ROM). The memory  730  may store computer-readable, computer-executable code  735  including instructions that, when executed by the processor  740 , cause the device  705  to perform various functions described herein. The code  735  may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code  735  may not be directly executable by the processor  740  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some cases, the memory  730  may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  740  may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor  740  may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor  740 . The processor  740  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  730 ) to cause the device  705  to perform various functions (e.g., functions or tasks supporting power amplifier model estimation for digital post distortion in multi-antenna devices). For example, the device  705  or a component of the device  705  may include a processor  740  and memory  730  coupled to the processor  740 , the processor  740  and memory  730  configured to perform various functions described herein. 
     The communications manager  720  may support wireless communication at a UE in accordance with examples as disclosed herein. For example, the communications manager  720  may be configured as or otherwise support a means for receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The communications manager  720  may be configured as or otherwise support a means for determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The communications manager  720  may be configured as or otherwise support a means for communicating with the base station based on the power amplifier model for the transmitter antenna. 
     By including or configuring the communications manager  720  in accordance with examples as described herein, the device  705  may support techniques for improvements in system efficiency such that system latency associated with indication of power amplifier models is reduced. Additionally, described techniques may result in improved communication reliability, reduced latency, improved user experience related to reduced processing, reduced power consumption, more efficient utilization of communication resources, improved coordination between devices, longer battery life, improved utilization of processing capability. 
     In some examples, the communications manager  720  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver  715 , the one or more antennas  725 , or any combination thereof. Although the communications manager  720  is illustrated as a separate component, in some examples, one or more functions described with reference to the communications manager  720  may be supported by or performed by the processor  740 , the memory  730 , the code  735 , or any combination thereof. For example, the code  735  may include instructions executable by the processor  740  to cause the device  705  to perform various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein, or the processor  740  and the memory  730  may be otherwise configured to perform or support such operations. 
       FIG.  8    shows a block diagram  800  of a device  805  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  805  may be an example of aspects of a base station  105  as described herein. The device  805  may include a receiver  810 , a transmitter  815 , and a communications manager  820 . The device  805  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  810  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). Information may be passed on to other components of the device  805 . The receiver  810  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  815  may provide a means for transmitting signals generated by other components of the device  805 . For example, the transmitter  815  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). In some examples, the transmitter  815  may be co-located with a receiver  810  in a transceiver module. The transmitter  815  may utilize a single antenna or a set of multiple antennas. 
     The communications manager  820 , the receiver  810 , the transmitter  815 , or various combinations thereof or various components thereof may be examples of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  820 , the receiver  810 , the transmitter  815 , or various combinations or components thereof may support a method for performing one or more of the functions described herein. 
     In some examples, the communications manager  820 , the receiver  810 , the transmitter  815 , or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a DSP, an ASIC, an FPGA or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some examples, a processor and memory coupled with the processor may be configured to perform one or more of the functions described herein (e.g., by executing, by the processor, instructions stored in the memory). 
     Additionally or alternatively, in some examples, the communications manager  820 , the receiver  810 , the transmitter  815 , or various combinations or components thereof may be implemented in code (e.g., as communications management software or firmware) executed by a processor. If implemented in code executed by a processor, the functions of the communications manager  820 , the receiver  810 , the transmitter  815 , or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in the present disclosure). 
     In some examples, the communications manager  820  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  810 , the transmitter  815 , or both. For example, the communications manager  820  may receive information from the receiver  810 , send information to the transmitter  815 , or be integrated in combination with the receiver  810 , the transmitter  815 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  820  may support wireless communication at a base station in accordance with examples as disclosed herein. For example, the communications manager  820  may be configured as or otherwise support a means for mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The communications manager  820  may be configured as or otherwise support a means for determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The communications manager  820  may be configured as or otherwise support a means for transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The communications manager  820  may be configured as or otherwise support a means for communicating with the UE based on at least one of the power amplifier models. 
     By including or configuring the communications manager  820  in accordance with examples as described herein, the device  805  (e.g., a processor controlling or otherwise coupled to the receiver  810 , the transmitter  815 , the communications manager  820 , or a combination thereof) may support techniques for improvements in system efficiency such that system latency associated with indication of power amplifier models is reduced. Additionally, described techniques may result in reduced processing, reduced power consumption, more efficient utilization of communication resources. 
       FIG.  9    shows a block diagram  900  of a device  905  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  905  may be an example of aspects of a device  805  or a base station  105  as described herein. The device  905  may include a receiver  910 , a transmitter  915 , and a communications manager  920 . The device  905  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     The receiver  910  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). Information may be passed on to other components of the device  905 . The receiver  910  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  915  may provide a means for transmitting signals generated by other components of the device  905 . For example, the transmitter  915  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to power amplifier model estimation for digital post distortion in multi-antenna devices). In some examples, the transmitter  915  may be co-located with a receiver  910  in a transceiver module. The transmitter  915  may utilize a single antenna or a set of multiple antennas. 
     The device  905 , or various components thereof, may be an example of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  920  may include a mapping manager  925 , an amplifier manager  930 , a response manager  935 , a data control manager  940 , or any combination thereof. The communications manager  920  may be an example of aspects of a communications manager  820  as described herein. In some examples, the communications manager  920 , or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  910 , the transmitter  915 , or both. For example, the communications manager  920  may receive information from the receiver  910 , send information to the transmitter  915 , or be integrated in combination with the receiver  910 , the transmitter  915 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  920  may support wireless communication at a base station in accordance with examples as disclosed herein. The mapping manager  925  may be configured as or otherwise support a means for mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The amplifier manager  930  may be configured as or otherwise support a means for determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The response manager  935  may be configured as or otherwise support a means for transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The data control manager  940  may be configured as or otherwise support a means for communicating with the UE based on at least one of the power amplifier models. 
       FIG.  10    shows a block diagram  1000  of a communications manager  1020  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The communications manager  1020  may be an example of aspects of a communications manager  820 , a communications manager  920 , or both, as described herein. The communications manager  1020 , or various components thereof, may be an example of means for performing various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein. For example, the communications manager  1020  may include a mapping manager  1025 , an amplifier manager  1030 , a response manager  1035 , a data control manager  1040 , an estimation manager  1045 , a link manager  1050 , a conversion manager  1055 , a matrix manager  1060 , or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The communications manager  1020  may support wireless communication at a base station in accordance with examples as disclosed herein. The mapping manager  1025  may be configured as or otherwise support a means for mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The amplifier manager  1030  may be configured as or otherwise support a means for determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The response manager  1035  may be configured as or otherwise support a means for transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The data control manager  1040  may be configured as or otherwise support a means for communicating with the UE based on at least one of the power amplifier models. 
     In some examples, the estimation manager  1045  may be configured as or otherwise support a means for transmitting a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the UE is based on the transmitting. 
     In some examples, the estimation manager  1045  may be configured as or otherwise support a means for frequency domain multiplexing a first antenna port of the first reference signal with a second antenna port of the second reference signal, where communicating with the UE is based on the frequency domain multiplexing. In some examples, the first reference signal, or the second reference signal, or both include a respective demodulation reference signal. 
     In some examples, the estimation manager  1045  may be configured as or otherwise support a means for using each transmitter antenna of a first group of antennas of the set of multiple antenna groups to form a first beam associated with the first reference signal. In some examples, the estimation manager  1045  may be configured as or otherwise support a means for using each transmitter antenna of a second group of antennas of the set of multiple antenna groups to form a second beam associated with the second reference signal, where communicating with the UE is based on the forming the first beam and the forming the second beam. 
     In some examples, the response manager  1035  may be configured as or otherwise support a means for transmitting, to the UE, each power amplifier model for each antenna group of the set of multiple antenna groups, where the indication of the power amplifier model is transmitted in a radio resource control message, and where communicating with the UE is based on the transmitting. 
     In some examples, the response manager  1035  may be configured as or otherwise support a means for indicating in the indication of the power amplifier model which transmitter antennas are associated with each antenna group of the set of multiple antenna groups and which of the power amplifier models to use for each antenna group, or which of the power amplifier models to use with each antenna group of the set of multiple antenna groups for a given temperature, or both. 
     In some examples, the link manager  1050  may be configured as or otherwise support a means for indicating in the indication of the power amplifier model a link between a first power amplifier model of a first antenna group of the set of multiple antenna groups and a first set of one or more antenna rows of a precoding matrix and a link between a second power amplifier model of a second antenna group of the set of multiple antenna groups and a second set of one or more antenna rows of the precoding matrix. 
     In some examples, the link manager  1050  may be configured as or otherwise support a means for indicating in the indication of the power amplifier model a preconfigured linking pattern, from a set of one or more linking patterns preconfigured on the UE, that links a first power amplifier model of a first antenna group of the set of multiple antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the set of multiple antenna groups with a second set of one or more antenna rows of the precoding matrix. 
     In some examples, to support determining the power amplifier model of each antenna group, the conversion manager  1055  may be configured as or otherwise support a means for converting a first power amplifier model of a first antenna group of the set of multiple antenna groups into a first list of kernels. In some examples, to support determining the power amplifier model of each antenna group, the conversion manager  1055  may be configured as or otherwise support a means for converting a second power amplifier model of a second antenna group of the set of multiple antenna groups into a second list of kernels. 
     In some examples, to support transmitting the indication of the power amplifier model of each antenna group, the conversion manager  1055  may be configured as or otherwise support a means for transmitting at least the first list of kernels and the second list of kernels to the UE. 
     In some examples, to support determining the power amplifier model of each antenna group, the matrix manager  1060  may be configured as or otherwise support a means for projecting coefficients of the power amplifier model of each transmitter antenna onto a reduced set of basis functions. In some examples, to support determining the power amplifier model of each antenna group, the matrix manager  1060  may be configured as or otherwise support a means for determining a matrix of basis functions based on the projecting. 
     In some examples, to support transmitting the indication of the power amplifier model of each antenna group, the matrix manager  1060  may be configured as or otherwise support a means for transmitting the matrix of basis functions to the UE. 
       FIG.  11    shows a diagram of a system  1100  including a device  1105  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The device  1105  may be an example of or include the components of a device  805 , a device  905 , or a base station  105  as described herein. The device  1105  may communicate wirelessly with one or more base stations  105 , UEs  115 , or any combination thereof. The device  1105  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager  1120 , a network communications manager  1110 , a transceiver  1115 , an antenna  1125 , a memory  1130 , code  1135 , a processor  1140 , and an inter-station communications manager  1145 . These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus  1150 ). 
     The network communications manager  1110  may manage communications with a core network  130  (e.g., via one or more wired backhaul links). For example, the network communications manager  1110  may manage the transfer of data communications for client devices, such as one or more UEs  115 . 
     In some cases, the device  1105  may include a single antenna  1125 . However, in some other cases the device  1105  may have more than one antenna  1125 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver  1115  may communicate bi-directionally, via the one or more antennas  1125 , wired, or wireless links as described herein. For example, the transceiver  1115  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  1115  may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas  1125  for transmission, and to demodulate packets received from the one or more antennas  1125 . The transceiver  1115 , or the transceiver  1115  and one or more antennas  1125 , may be an example of a transmitter  815 , a transmitter  915 , a receiver  810 , a receiver  910 , or any combination thereof or component thereof, as described herein. 
     The memory  1130  may include RAM and ROM. The memory  1130  may store computer-readable, computer-executable code  1135  including instructions that, when executed by the processor  1140 , cause the device  1105  to perform various functions described herein. The code  1135  may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code  1135  may not be directly executable by the processor  1140  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some cases, the memory  1130  may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  1140  may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor  1140  may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor  1140 . The processor  1140  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  1130 ) to cause the device  1105  to perform various functions (e.g., functions or tasks supporting power amplifier model estimation for digital post distortion in multi-antenna devices). For example, the device  1105  or a component of the device  1105  may include a processor  1140  and memory  1130  coupled to the processor  1140 , the processor  1140  and memory  1130  configured to perform various functions described herein. 
     The inter-station communications manager  1145  may manage communications with other base stations  105 , and may include a controller or scheduler for controlling communications with UEs  115  in cooperation with other base stations  105 . For example, the inter-station communications manager  1145  may coordinate scheduling for transmissions to UEs  115  for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager  1145  may provide an X2 interface within an LTE/LTE-A wireless communications network technology to provide communication between base stations  105 . 
     The communications manager  1120  may support wireless communication at a base station in accordance with examples as disclosed herein. For example, the communications manager  1120  may be configured as or otherwise support a means for mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The communications manager  1120  may be configured as or otherwise support a means for determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The communications manager  1120  may be configured as or otherwise support a means for transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The communications manager  1120  may be configured as or otherwise support a means for communicating with the UE based on at least one of the power amplifier models. 
     By including or configuring the communications manager  1120  in accordance with examples as described herein, the device  1105  may support techniques for improvements in system efficiency such that system latency associated with indication of power amplifier models is reduced. Additionally, described techniques may result in improved communication reliability, reduced latency, improved user experience related to reduced processing, reduced power consumption, more efficient utilization of communication resources, improved coordination between devices, longer battery life, improved utilization of processing capability. 
     In some examples, the communications manager  1120  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver  1115 , the one or more antennas  1125 , or any combination thereof. Although the communications manager  1120  is illustrated as a separate component, in some examples, one or more functions described with reference to the communications manager  1120  may be supported by or performed by the processor  1140 , the memory  1130 , the code  1135 , or any combination thereof. For example, the code  1135  may include instructions executable by the processor  1140  to cause the device  1105  to perform various aspects of power amplifier model estimation for digital post distortion in multi-antenna devices as described herein, or the processor  1140  and the memory  1130  may be otherwise configured to perform or support such operations. 
       FIG.  12    shows a flowchart illustrating a method  1200  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The operations of the method  1200  may be implemented by a UE or its components as described herein. For example, the operations of the method  1200  may be performed by a UE  115  as described with reference to  FIGS.  1  through  7   . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1205 , the method may include receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The operations of  1205  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1205  may be performed by an indication manager  625  as described with reference to  FIG.  6   . 
     At  1210 , the method may include determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The operations of  1210  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1210  may be performed by a model manager  630  as described with reference to  FIG.  6   . 
     At  1215 , the method may include communicating with the base station based on the power amplifier model for the transmitter antenna. The operations of  1215  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1215  may be performed by a connection manager  635  as described with reference to  FIG.  6   . 
       FIG.  13    shows a flowchart illustrating a method  1300  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The operations of the method  1300  may be implemented by a UE or its components as described herein. For example, the operations of the method  1300  may be performed by a UE  115  as described with reference to  FIGS.  1  through  7   . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1305 , the method may include receiving, from a base station, an indication of a power amplifier model for each antenna group of a set of multiple antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna. The operations of  1305  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1305  may be performed by an indication manager  625  as described with reference to  FIG.  6   . 
     At  1310 , the method may include receiving a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the base station is based on the receiving of the first reference signal and the second reference signal. In some cases, the indication of the power amplifier model for each antenna group of the set of multiple antenna groups may include the first reference signal and the second reference signal. The operations of  1310  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1310  may be performed by a reference manager  640  as described with reference to  FIG.  6   . 
     At  1315 , the method may include determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based on the indication of the power amplifier model for an antenna group of the set of multiple antenna groups and the transmitter antenna being associated with the antenna group. The operations of  1315  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1315  may be performed by a model manager  630  as described with reference to  FIG.  6   . 
     At  1320 , the method may include communicating with the base station based on the power amplifier model for the transmitter antenna. The operations of  1320  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1320  may be performed by a connection manager  635  as described with reference to  FIG.  6   . 
       FIG.  14    shows a flowchart illustrating a method  1400  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The operations of the method  1400  may be implemented by a base station or its components as described herein. For example, the operations of the method  1400  may be performed by a base station  105  as described with reference to  FIGS.  1  through  3  and  8  through  11   . In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the described functions. Additionally or alternatively, the base station may perform aspects of the described functions using special-purpose hardware. 
     At  1405 , the method may include mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The operations of  1405  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1405  may be performed by a mapping manager  1025  as described with reference to  FIG.  10   . 
     At  1410 , the method may include determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The operations of  1410  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1410  may be performed by an amplifier manager  1030  as described with reference to  FIG.  10   . 
     At  1415 , the method may include transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The operations of  1415  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1415  may be performed by a response manager  1035  as described with reference to  FIG.  10   . 
     At  1420 , the method may include communicating with the UE based on at least one of the power amplifier models. The operations of  1420  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1420  may be performed by a data control manager  1040  as described with reference to  FIG.  10   . 
       FIG.  15    shows a flowchart illustrating a method  1500  that supports power amplifier model estimation for digital post distortion in multi-antenna devices in accordance with aspects of the present disclosure. The operations of the method  1500  may be implemented by a base station or its components as described herein. For example, the operations of the method  1500  may be performed by a base station  105  as described with reference to  FIGS.  1  through  3  and  8  through  11   . In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the described functions. Additionally or alternatively, the base station may perform aspects of the described functions using special-purpose hardware. 
     At  1505 , the method may include mapping each transmitter antenna of the base station to one of a set of multiple antenna groups based on a power amplifier response of each transmitter antenna. The operations of  1505  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1505  may be performed by a mapping manager  1025  as described with reference to  FIG.  10   . 
     At  1510 , the method may include determining a power amplifier model for each antenna group of the set of multiple antenna groups based on the power amplifier response of each transmitter antenna. The operations of  1510  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1510  may be performed by an amplifier manager  1030  as described with reference to  FIG.  10   . 
     At  1515 , the method may include transmitting an indication of the power amplifier model for each antenna group of the set of multiple antenna groups to a UE. The operations of  1515  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1515  may be performed by a response manager  1035  as described with reference to  FIG.  10   . 
     At  1520 , the method may include transmitting a first reference signal for a first antenna group of the set of multiple antenna groups and a second reference signal for a second antenna group of the set of multiple antenna groups, where communicating with the UE is based on the transmitting of the first reference signal and the second reference signal. In some cases, the indication of the power amplifier model for each antenna group of the set of multiple antenna groups may include the first reference signal and the second reference signal. The operations of  1520  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1520  may be performed by an estimation manager  1045  as described with reference to  FIG.  10   . 
     At  1525 , the method may include communicating with the UE based on at least one of the power amplifier models. The operations of  1525  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1525  may be performed by a data control manager  1040  as described with reference to  FIG.  10   . 
     The following provides an overview of aspects of the present disclosure: 
     Aspect 1: A method for wireless communication at a UE, comprising: receiving, from a base station, an indication of a power amplifier model for each antenna group of a plurality of antenna groups, each antenna group being associated with a respective set of transmitter antennas of the base station and a power amplifier response of each transmitter antenna; determining a power amplifier model for a transmitter antenna of the set of transmitter antennas based at least in part on the indication of the power amplifier model for an antenna group of the plurality of antenna groups and the transmitter antenna being associated with the antenna group; and communicating with the base station based at least in part on the power amplifier model for the transmitter antenna. 
     Aspect 2: The method of aspect 1, wherein receiving the indication of the power amplifier model for each antenna group comprises: receiving a first reference signal for a first antenna group of the plurality of antenna groups and a second reference signal for a second antenna group of the plurality of antenna groups, wherein communicating with the base station is based at least in part on the receiving. 
     Aspect 3: The method of aspect 2, further comprising: determining a first power amplifier model for the first antenna group based at least in part on the first reference signal and a second power amplifier model for the second antenna group based at least in part on the second reference signal; and applying the first power amplifier model to each transmitter antenna mapped to the first antenna group and the second power amplifier model to each transmitter antenna mapped to the second antenna group, wherein communicating with the base station is based at least in part on the applying. 
     Aspect 4: The method of any of aspects 2 through 3, wherein the first reference signal, or the second reference signal, or both comprise a respective demodulation reference signal. 
     Aspect 5: The method of any of aspects 1 through 4, wherein receiving the indication of the power amplifier model for each antenna group comprises: receiving, from the base station, each power amplifier model for each antenna group of the plurality of antenna groups, wherein the indication of the power amplifier model is received in a radio resource control message, and wherein communicating with the base station is based at least in part on the receiving. 
     Aspect 6: The method of aspect 5, further comprising: determining that the indication of the power amplifier model indicates which transmitter antennas are associated with each antenna group of the plurality of antenna groups and which of the power amplifier models to use for each antenna group, or indicates which of the power amplifier models to use with each antenna group of the plurality of antenna groups for a given temperature, or indicates both, wherein communicating with the base station is based at least in part on the determining. 
     Aspect 7: The method of any of aspects 1 through 6, further comprising: determining that the indication of the power amplifier model indicates a link between a first power amplifier model of a first antenna group of the plurality of antenna groups and a first set of one or more antenna rows of a precoding matrix, and indicates a link between a second power amplifier model of a second antenna group of the plurality of antenna groups and a second set of one or more antenna rows of the precoding matrix, wherein communicating with the base station is based at least in part on the determining. 
     Aspect 8: The method of any of aspects 1 through 7, further comprising: determining that the indication of the power amplifier model indicates, from a set of one or more linking patterns preconfigured on the UE, a preconfigured linking pattern that links a first power amplifier model of a first antenna group of the plurality of antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the plurality of antenna groups with a second set of one or more antenna rows of the precoding matrix, wherein communicating with the base station is based at least in part on the determining. 
     Aspect 9: The method of any of aspects 1 through 8, further comprising: determining that the indication of the power amplifier model indicates a first list of kernels associated with a first power amplifier model of a first antenna group of the plurality of antenna groups, and a second list of kernels associated with a second power amplifier model of a second antenna group of the plurality of antenna groups, wherein communicating with the base station is based at least in part on the determining. 
     Aspect 10: The method of any of aspects 1 through 9, further comprising: determining that the indication of the power amplifier model indicates a matrix of basis functions respectively associated with the plurality of antenna groups, wherein communicating with the base station is based at least in part on the determining. 
     Aspect 11: The method of any of aspects 1 through 10, wherein communicating with the base station comprises: implementing a digital post distortion model based at least in part on the power amplifier model of the transmitter antenna; 
     and performing digital post distortion processing on signals received from the base station based at least in part on the digital post distortion model. 
     Aspect 12: A method for wireless communication at a base station, comprising: mapping each transmitter antenna of the base station to one of a plurality of antenna groups based at least in part on a power amplifier response of each transmitter antenna; determining a power amplifier model for each antenna group of the plurality of antenna groups based at least in part on the power amplifier response of each transmitter antenna; transmitting an indication of the power amplifier model for each antenna group of the plurality of antenna groups to a UE; and communicating with the UE based at least in part on at least one of the power amplifier models. 
     Aspect 13: The method of aspect 12, further comprising: transmitting a first reference signal for a first antenna group of the plurality of antenna groups and a second reference signal for a second antenna group of the plurality of antenna groups, wherein communicating with the UE is based at least in part on the transmitting. 
     Aspect 14: The method of aspect 13, further comprising: frequency domain multiplexing a first antenna port of the first reference signal with a second antenna port of the second reference signal, wherein communicating with the UE is based at least in part on the frequency domain multiplexing. 
     Aspect 15: The method of any of aspects 13 through 14, further comprising: using each transmitter antenna of a first group of antennas of the plurality of antenna groups to form a first beam associated with the first reference signal; and using each transmitter antenna of a second group of antennas of the plurality of antenna groups to form a second beam associated with the second reference signal, wherein communicating with the UE is based at least in part on the forming the first beam and the forming the second beam. 
     Aspect 16: The method of any of aspects 13 through 15, wherein the first reference signal, or the second reference signal, or both comprise a respective demodulation reference signal. 
     Aspect 17: The method of any of aspects 12 through 16, further comprising: transmitting, to the UE, each power amplifier model for each antenna group of the plurality of antenna groups, wherein the indication of the power amplifier model is transmitted in a radio resource control message, and wherein communicating with the UE is based at least in part on the transmitting. 
     Aspect 18: The method of aspect 17, further comprising: indicating in the indication of the power amplifier model which transmitter antennas are associated with each antenna group of the plurality of antenna groups and which of the power amplifier models to use for each antenna group, or which of the power amplifier models to use with each antenna group of the plurality of antenna groups for a given temperature, or both. 
     Aspect 19: The method of any of aspects 12 through 18, further comprising: indicating in the indication of the power amplifier model a link between a first power amplifier model of a first antenna group of the plurality of antenna groups and a first set of one or more antenna rows of a precoding matrix and a link between a second power amplifier model of a second antenna group of the plurality of antenna groups and a second set of one or more antenna rows of the precoding matrix. 
     Aspect 20: The method of any of aspects 12 through 19, further comprising: indicating in the indication of the power amplifier model a preconfigured linking pattern, from a set of one or more linking patterns preconfigured on the UE, that links a first power amplifier model of a first antenna group of the plurality of antenna groups with a first set of one or more antenna rows of a precoding matrix, and links a second power amplifier model of a second antenna group of the plurality of antenna groups with a second set of one or more antenna rows of the precoding matrix. 
     Aspect 21: The method of any of aspects 12 through 20, wherein determining the power amplifier model of each antenna group comprises: converting a first power amplifier model of a first antenna group of the plurality of antenna groups into a first list of kernels; and converting a second power amplifier model of a second antenna group of the plurality of antenna groups into a second list of kernels. 
     Aspect 22: The method of aspect 21, wherein transmitting the indication of the power amplifier model of each antenna group comprises: transmitting at least the first list of kernels and the second list of kernels to the UE. 
     Aspect 23: The method of any of aspects 12 through 22, wherein determining the power amplifier model of each antenna group comprises: projecting coefficients of the power amplifier model of each transmitter antenna onto a reduced set of basis functions; and determining a matrix of basis functions based at least in part on the projecting. 
     Aspect 24: The method of aspect 23, wherein transmitting the indication of the power amplifier model of each antenna group comprises: transmitting the matrix of basis functions to the UE. 
     Aspect 25: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 1 through 11. 
     Aspect 26: An apparatus for wireless communication at a UE, comprising at least one means for performing a method of any of aspects 1 through 11. 
     Aspect 27: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform a method of any of aspects 1 through 11. 
     Aspect 28: An apparatus for wireless communication at a base station, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 12 through 24. 
     Aspect 29: An apparatus for wireless communication at a base station, comprising at least one means for performing a method of any of aspects 12 through 24. 
     Aspect 30: A non-transitory computer-readable medium storing code for wireless communication at a base station, the code comprising instructions executable by a processor to perform a method of any of aspects 12 through 24. 
     It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. 
     Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein. 
     Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. 
     Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media. 
     As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of”) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.” 
     The term “determine” or “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (such as via looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (such as receiving information), accessing (such as accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and other such similar actions. 
     In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label. 
     The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.