Enhanced power headroom reporting based on power amplifer distortion compensation

Abstract

Embodiments include methods for a transmitter configured to generate transmissions to a receiver. Such methods include determining a backoff from a maximum allowed output power for a first transmission, which is to be amplified by a power amplifier (PA). The determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA. Such methods include selectively reducing the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter. Such methods include sending one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced. Other embodiments include complementary methods for a receiver, as well as transmitters and receivers configured to perform such methods.

Description

[0001] ENHANCED POWER HEADROOM REPORTING BASED ON POWER AMPLIFER DISTORTION COMPENSATION TECHNICAL FIELD The present disclosure relates generally to communication between a transmitter and a receiver, and more specifically to techniques for a transmitter to report remaining power headroom for its power amplifier in consideration of any techniques being used to compensate for any distortion of the transmitted signal by the power amplifier. BACKGROUND In general, the term “transmitter” may be used to refer to any device, apparatus, node, etc. that sends signals (e.g., including data) via a “channel” to a “receiver”, which is another device, apparatus, node, etc. that is compatible with the transmitter for communication-related purposes. The term “channel” may refer to any communication medium, such as a wireless channel, a copper (or other metallic) wire, an optical fiber, etc. The signals may be subject to distortion and / or impairments caused by the channel, the transmitter’s circuitry, and / or the receiver’s circuitry. The channel distortion may vary over time, space, and / or frequency but is generally unknown and needs to be estimated by the receiver in order to adapt its processing of the received signals to achieve optimal reception performance (e.g., to minimize bit or block error rate, to maximum throughput, etc.). For radio frequency (RF) wireless communications, the transmitter’s circuitry may introduce various impairments to the transmitted signal, including oscillator phase noise, digital- to-analog converter (DAC) quantization noise, and distortion due to power amplifier (PA) nonlinearity. The PA amplifies the signal to the necessary level so that the receiver can successfully detect and / or decode it at the other end of the channel. When generating relatively lower output signal power levels, a PA typically operates in a “linear” region whereby it introduces little or no distortion in its output signal. As the output signal power level increases, the PAs operation becomes more “non-linear” such that it introduces increasing levels of distortion in its output signal, making it more difficult for the receiver to detect and / or decode the signal received via the channel. For example, a more robust modulation and coding scheme (MCS) may be needed to combat the distortion, thereby reducing the amount of data that the transmitted signal can carry. Thus, from a distortion standpoint alone, it is desirable to operate the PA in the linear region, which may correspond to a “back-off” from a non-linear operating point. Even so, amplification of the signal requires significant energy, such that the PA usually dominates the energy consumption of the transmitter. Operating the PA in the non-linear region is one way to reduce energy consumption and / or improve energy efficiency of the transmitter. In other words, to generate an output signal of a given power level, a PA consumes less energy when operating in the non-linear region than when operating in the linear region. Thus, there is often a conflict between competing goals of transmitter energy efficiency and receiver performance / data throughput. Various techniques have been proposed to address this conflict. One class of techniques involves digital compensation for the distortion caused by PA operation in the non-linear region. In general, for a given level of receiver performance, these digital compensation techniques enable the transmitter PA to operate further into its non-linear region with increased distortion but less energy consumption. For example, digital pre-distortion (DPD) is a transmitter-based technique that applies “inverse distortion” to the signal input to the PA. DPD typically requires an accurate estimation of the PA’s non-linearity characteristics using a feedback loop from the PA’s output signal and extensive digital signal processing. As another example, digital post-distortion (DPoD) is a receiver-based technique that performs signal detection by reconstructing the distorted signal based on a PA non-linearity model known to the receiver. A specific DPoD technique based on an artificial intelligence (AI) neural network model is described in “A Deep Learning Receiver for Non-linear Transmitter” by Farhadi, et al., published in in IEEE Access, vol. 11, pp. 2796- 2803 (2023). In some communication systems, the receiver may use transmit power control (TPC) to regulate the power level that the PA of the transmitter applies to the transmitted signal so that the signal is received at a desired power level by the receiver. For example, the desired received power level should be high enough to support proper decoding of the information bits carried by the signal but low enough to avoid wasting transmitter energy and causing interference to signals from other transmitters. Using its TPC algorithm, the receiver determines an appropriate transmit power level to produce the desired received power level and sends an indication of that to the transmitter, which applies it for a subsequent transmission. To obtain the appropriate transmit power level, the TPC algorithm should consider channel path loss, noise, and interference at the receiver, and receiver decoding requirements of a MCS for data to be transmitted. Additionally, the TPC algorithm should consider any power limitations of the transmitter, so that the receiver does not instruct the transmitter to transmit at a power level above its maximum transmission power. However, this parameter may be unknown to the receiver. To get around this limitation, the transmitter may send the receiver an indication of how far below its maximum transmission power a previous transmission was or a current / next transmission will be, i.e., the additional transmission power (or “headroom”) available before reaching the maximum transmission power. This indication is often referred to as a power headroom report (PHR). SUMMARY However, conventional PHRs do not account for whether transmitter-based DPD and / or receiver-based DPoD is being used to compensate for PA non-linearities. For example, the transmitter reports the same remaining available transmission power regardless of whether compensation is being used, even though compensation allows the transmitter to operate closer to its maximum transmission power with increased energy efficiency. An object of embodiments of the present disclosure is to improve power headroom reporting by transmitters with non-linear PAs, thereby enabling such transmitters to operate with improved energy efficiency when transmitter- and / or receiver-based distortion compensation techniques such as DPD and DPoD are in use. Some embodiments include methods (e.g., procedures) for a transmitter configured to generate transmissions to a receiver. These exemplary methods include determining a backoff from a maximum allowed output power for a first transmission, which is to be amplified by a PA. The determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA. These exemplary methods also include selectively reducing the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter. These exemplary methods also include sending one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced. In some embodiments, selectively reducing the determined backoff includes the following operations: • reducing the determined backoff by the first amount when compensation for the distortion is available; and • refraining from reducing the determined backoff when compensation for the distortion is unavailable. In some embodiments, these exemplary methods also include transmitting the first transmission the first transmission at the maximum allowed output power minus the following: the determined backoff, when the determined backoff is not reduced; and the determined backoff minus the first amount, when the determined backoff is reduced. In some of these embodiments, transmitting the first transmission includes, when the determined backoff is reduced, causing the PA to amplify the first transmission using a more energy-efficient operating point (i.e., with greater non-linearity). Other embodiments include exemplary methods (e.g., procedures) for a receiver configured to receive transmissions from a transmitter. These embodiments are generally complementary to transmitter embodiments summarized above. These exemplary methods include receiving one or more of the following information from the transmitter: • a backoff from a maximum allowed output power for a first transmission by the transmitter, where the first transmission is to be amplified by a PA and the backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; • an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and • a first amount by which the transmitter reduced the backoff. These exemplary methods also include receiving the first transmission from the transmitter (e.g., via a channel). In some embodiments, these exemplary methods also include decoding the received first transmission using a model that selectively compensates for distortion in the first transmission based on the received information. In other embodiments, these exemplary methods also include, based on the received information and the received first transmission, training a model to compensate for distortion in received transmissions due to non-linearity of the PA. In some of these embodiments, the model is an artificial intelligence / machine learning (AI / ML) model. In various embodiments summarized above, the information is sent by the transmitter and received by the receiver in a power headroom report (PHR). In such case, the receiver is a base station or is included in a base station and one of the following applies: • the transmitter and the PA are included in a user equipment (UE); or • the transmitter is a UE that includes the PA. In some of these embodiments, the determined backoff is a maximum power reduction (MPR) and the first amount is a relaxation of the MPR. In some of these embodiments, the information sent to the base station also includes an indication of one or more of the following: the maximum allowed output power of the first transmission, and whether the first transmission is a real transmission or a hypothetical transmission. Other embodiments and variants of the exemplary methods summarized above are described herein. Other embodiments include transmitter apparatus (e.g., wireless devices, user equipment, base stations, etc.) and receiver apparatus (e.g., wireless devices, user equipment, base stations, etc.) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer-readable media storing program instructions that, when executed by processing circuitry, configure a transmitter apparatus or a receiver apparatus to perform operations corresponding to any of the exemplary methods described herein. These and other embodiments described herein may provide various benefits and / or advantages. For example, in the case of a UE transmitter and base station (e.g., gNB) receiver that selectively employs DPoD, embodiments may increase uplink (UL) coverage by increasing UE transmit power when there is capability to compensate for the increased PA distortion. Also, embodiments may increase UE energy efficiency by enabling the UE to operate its PA further into the non-linear region with reduced backoff, so long as DPoD compensation is available at the base station receiver. Similar benefits may be available for a UE transmitter that selectively employs DPD, either for UL transmission to a base station or for sidelink (SL) transmission to another UE. These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a high-level view of an exemplary 5G / NR network architecture. Figure 2 shows an exemplary configuration of 5G / NR user plane (UP) and control plane (CP) protocol stacks. Figure 3 shows an exemplary artificial neural network (NN). Figure 4 shows a block diagram of a gNB receiver that utilizes machine learning (ML)- based DPoD. Figure 5 shows an ML-based demapper used in the gNB receiver of Figure 4. Figure 6 illustrates block error rate (BLER) performance of the gNB receiver of Figure 4 in the presence of distortion due to non-linearity of the PA. Figure 7 shows a signaling diagram of a procedure that involves enhanced power headroom reporting according to some embodiments of the present disclosure. Figures 8-9 show exemplary ASN.1 data structures for an RRC PhysicalCellGroupConfig information element (IE), according to various embodiments of the present disclosure. Figures 10-12 show exemplary medium access control (MAC) control elements (CEs) for PHR, according to various embodiments of the present disclosure. Figure 13 shows a signaling diagram of a procedure for selective channel state information (CSI) reporting, according to some embodiments of the present disclosure. Figure 14 shows a flow diagram of an exemplary method for a transmitter (e.g., wireless device, UE), according to various embodiments of the present disclosure. Figure 15 shows a flow diagram of an exemplary method for a receiver (e.g., base station, eNB, gNB, ng-eNB, etc.), according to various embodiments of the present disclosure. Figure 16 shows a communication system according to various embodiments of the present disclosure. Figure 17 shows a UE according to various embodiments of the present disclosure. Figure 18 shows a network node according to various embodiments of the present disclosure. Figure 19 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized. DETAILED DESCRIPTION Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. In general, all terms used herein are to be interpreted according to their ordinary meaning to a person of ordinary skill in the relevant technical field, unless a different meaning is expressly defined and / or implied from the context of use. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise or clearly implied from the context of use. The operations of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless an operation is explicitly described as following or preceding another operation and / or where it is implicit that an operation must follow or precede another operation. Any feature of any embodiment disclosed herein can apply to any other disclosed embodiment, as appropriate. Likewise, any advantage of any embodiment described herein can apply to any other disclosed embodiment, as appropriate. Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system and can be applied to any communication system that may benefit from them. Currently the fifth generation (5G) of cellular systems is being standardized within the Third-Generation Partnership Project (3GPP). 5G is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases. NR was initially specified in 3GPP Release 15 (Rel-15) and continues to evolve through subsequent releases, including Rel-19 currently being specified. Figure 1 illustrates a high-level view of an exemplary 5G network architecture, consisting of a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). As shown in the figure, the NG-RAN can include gNBs (e.g., 110a,b) and ng-eNBs (e.g., 120a,b) that are interconnected with each other via respective Xn interfaces. The gNBs and ng-eNBs are also connected via NG interfaces to the 5GC, more specifically to AMFs ( e.g., 130a,b) via respective NG-C interfaces and to UPFs (e.g., 140a,b) via respective NG-U interfaces. Moreover, the AMFs can communicate with one or more policy control functions (PCFs, e.g., 150a,b) and network exposure functions (NEFs, e.g., 160a,b). The radio technology for the NG-RAN is often referred to as “New Radio” (NR). Each of the gNBs can support the NR radio interface including frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of ng-eNBs can support the fourth generation (4G) Long-Term Evolution (LTE) radio interface. Each of the gNBs and ng-eNBs can serve a geographic coverage area including one or more cells (e.g., 111a-b and 121a-b). Depending on the cell in which it is located, a user equipment (UE, e.g., 105) can communicate with the gNB or ng-eNB serving that cell via the NR or LTE radio interface, respectively. Although Figure 1 shows gNBs and ng-eNBs separately, it is also possible that a single NG-RAN node provides both LTE and NR functionality. NG RAN logical nodes (e.g., gNBs 110a-b) may include a Central Unit (CU) and one or more Distributed Units (DUs). CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are decentralized logical nodes that host lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. A CU connects to one or more associated DUs over respective F1 logical interfaces. Each CU and DU can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry. Figure 2 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks between a UE (210), a gNB (220), and an AMF (230), such as those shown in Figures 1-2. The Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between the UE and the gNB are common to UP and CP. PDCP provides ciphering / deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP. In addition, PDCP provides header compression and retransmission for UP data. On the UP side, Internet protocol (IP) packets arrive to PDCP as service data units (SDUs), and PDCP creates protocol data units (PDUs) to deliver to RLC. The Service Data Adaptation Protocol (SDAP) layer handles quality-of-service (QoS) including mapping between QoS flows and Data Radio Bearers (DRBs) and marking QoS flow identifiers (QFI) in UL and DL packets. When each IP packet arrives, PDCP starts a discard timer. When this timer expires, PDCP discards the associated SDU and the corresponding PDU. If the PDU was delivered to RLC, PDCP also indicates the discard to RLC. The RLC layer transfers PDCP PDUs to the MAC through logical channels (LCH). RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, reordering of data transferred to / from the upper layers. If RLC receives a discard indication from associated with a PDCP PDU, it will discard the corresponding RLC SDU (or any segment thereof) if it has not been sent to lower layers. MAC provides mapping between LCHs and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), hybrid ARQ (HARQ) error correction, and dynamic scheduling (in gNB). PHY provides transport channel services to MAC and handles transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming. On the CP side, the non-access stratum (NAS) layer between UE and AMF handles UE / gNB authentication, mobility management, and security control. RRC sits below NAS in the UE but terminates in the gNB rather than the AMF. RRC controls communications between UE and gNB at the radio interface as well as the mobility of a UE between cells in the NG-RAN. RRC also broadcasts system information (SI) and performs establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) and used by UEs. Additionally, RRC controls addition, modification, and release of carrier aggregation (CA) and dual-connectivity (DC) configurations for UEs, and performs various security functions such as key management. After a UE is powered ON it will be in the RRC_IDLE state until an RRC connection is established with the network, at which time the UE will transition to RRC_CONNECTED state (e.g., where data transfer can occur). The UE returns to RRC_IDLE after the connection with the network is released. In RRC_IDLE state, the UE’s radio is active on a discontinuous reception (DRX) schedule configured by upper layers. During DRX active periods (also referred to as “DRX On durations”), an RRC_IDLE UE receives SI broadcast in the cell where the UE is camping, performs measurements of neighbor cells to support cell reselection, and monitors a paging channel on PDCCH for pages from 5GC via gNB. An NR UE in RRC_IDLE state is not known to the gNB serving the cell where the UE is camping. However, NR RRC includes an RRC_INACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRC_INACTIVE has some properties similar to a “suspended” condition used in LTE. In addition to providing coverage via cells as in LTE, gNBs also provide coverage via “beams.” In general, a downlink (DL, i.e., network to UE) “beam” is a coverage area of a network- transmitted reference signal (RS) that may be measured or monitored by a UE. In NR, for example, RS can include any of the following: synchronization signal / PBCH block (SSB), channel state information RS (CSI-RS), tertiary reference signals (or any other sync signal), positioning RS (PRS), demodulation RS (DMRS), phase-tracking reference signals (PTRS), etc. In general, SSB is available to all UEs regardless of the state of their connection with the network, while other RS (e.g., CSI-RS, DM-RS, PTRS) are associated with specific UEs that have a network connection. To facilitate beam management operations such as beam switching, a serving gNB may configure a UE to measure and report layer one reference received signal power (L1-RSRP) or layer one signal to interference plus noise ratio (L1-SINR) for multiple SSB beams. Based on the report(s), the gNB can decide whether it is better to switch to a different SSB beam for serving the UE. Similarly, the serving RAN node may also be able to provide a set of narrower CSI-RS beams with higher gains. As such, the gNB may transmit and configured the UE to measure and report L1-RSRP or L1-SINR for multiple CSI-RS beams. Based on the report(s), the gNB can decide whether it is better to switch to a different CSI-RS beam for serving the UE. These UE measurements are often referred to as Channel State Information (CSI) measurements, which are configured by CSI measurement configurations typically provided via an RRCReconfiguration messages. Each CSI measurement configuration explicitly identifies a set of DL-RS (e.g., SSB, CSI-RS) to be measured by the UE in a serving cell. The gNB may also provide a CSI reporting configuration that explicitly configures the UE’s reporting of the CSI measurements. For example, the configured reporting can be periodic, semi-persistent, or aperiodic. CSI measurements are configured on a per-serving cell basis, but a UE may be configured to report CSI measurements of one serving cell via another serving cell.

[0002] As briefly mentioned above, in some communication systems, the receiver may use transmit power control (TPC) to regulate the power level the transmitter (i.e., the PA of the transmitter) applies to the transmitted signal so that it is received at a desired power level by the receiver. In 5G / NR, UL TPC is used by the gNB to set appropriate UE transmit power levels for different UL physical channels (e.g., PUSCH and PUCCH) and RS (e.g., SRS, DMRS, etc.) so that the gNB receives them at the desired signal level. For UL physical channels, the received signal level should be high enough to facilitate proper decoding of the carried information bits but to avoid excess UE energy consumption and interference to transmissions by other UEs. In general, UL TPC is needed for all UL transmissions including PUSCH, PUCCH, SRS, PRACH, etc. To obtain the appropriate transmit power level, the NR UL TPC algorithm should consider channel path loss, noise, and interference at the gNB receiver, and receiver decoding requirements for a target UL data rate for the UE. In general, as the target UL data rate increases (e.g., larger transmission bandwidth and / or less robust MCS), the received power level needed to decode the data also increases. For a given channel, the transmit power level must also increase. Decreasing target UL data rates (e.g., lower transmission bandwidth and / or more robust) produce a similar but opposite effect. Two types of UL TPC are used in 5G / NR. In open loop power control, the UE estimates its UL path loss based on DL measurements and sets its transmit power accordingly without receiving a TPC command from the gNB. This technique is used mainly for compensating long term pathloss and MCS change. In particular, the UE sets its transmit power based on parameters including normalized target received power (PO), Path loss compensation parameter (α), and MCS parameter (ΔTF). In general, the UE’s transmit power increases for higher MCS. In closed loop power control, the UE sets its UL transmit power based on explicit TPC command from the gNB, which generates these based on received power levels of previous UL transmissions by the UE. This technique is used mainly for following fast fading of the wireless channel. The TPC command is typically a power-up / power-down indicator sent to the UE in DL control information (DCI) on PDCCH. Consider the following illustrative example of PUSCH TPC. If a UE transmits PUSCH on active UL carrier bandwidth part (BWP) ^^^^ of carrier ^^^^ of serving cell ^^^^ using parameter set configuration with index ^^^^ and PUSCH power control adjustment state with index ^^^^, the UEdetermines the PUSCH transmission power ^^^^PUSCH,^^^^,^^^^,^^^^(^^^^, ^^^^, ^^^^^^^^, ^^^^) in PUSCH transmissionoccasion ^^^^ according to the following (in dBm): , Where: • ^^^^CMAX,^^^^,^^^^(^^^^) is the UE configured maximum output power for carrier ^^^^ of serving cell ^^^^ in PUSCH transmission occasion ^^^^. obtained from network-configured parameters, including the cell-specific value the UE-specific value ^^^^O_UE_PUSCH,^^^^,^^^^,^^^^(^^^^). ^^^^O_PUSCH,^^^^,^^^^,^^^^(^^^^)can be understood as a target received power for the UE. • ^^^^RPBU,S^^^^C,^^H^^,^^^^(^^^^) is the bandwidth of the PUSCH resource assignment expressed in number of resource blocks for PUSCH transmission occasion ^^^^ on active UL BWP ^^^^ of carrier ^^^^ of serving cell ^^^^. Parameter ^^^^ indicates subcarrier spacing. For example, μ of {0, 1, 2, 3} corresponds to subcarrier spacing of {15, 30, 60, 120} kHz. •^^^^^^^^,^^^^,^^^^(^^^^) ⋅ ^^^^^^^^^^^^,^^^^,^^^^(^^^^^^^^) is the pathloss factor which compensates for the path loss betweenthe UE and the base station. In particular, ^^^^^^^^,^^^^,^^^^(^^^^) is a network-configurable parameter, where ^^^^^^^^,^^^^,^^^^(^^^^) < 1 indicates fractional path-loss compensation and = 1indicates full path-loss compensation. Also, ^^^^^^^^^^^^,^^^^,^^^^(^^^^^^^^) is a downlink pathloss estimate in dB calculated by the UE using reference signal (RS) index ^^^^^^^^for the active DL BWP of carrier ^^^^ of serving cell ^^^^. • ∆TF,^^^^,^^^^,^^^^(^^^^)reflects the power adjustment considering the modulation scheme and channel coding rate used for the PUSCH transmission. ∆TF,^^^^,^^^^,^^^^(^^^^) = •^^^^^^^^,^^^^,^^^^(^^^^, ^^^^) is the PUSCH power control adjustment state for active UL BWP ^^^^ of carrier^^^^ of serving cell ^^^^ in PUSCH transmission occasion ^^^^. This is the accumulated power adjustment by the closed-loop power control. As briefly mentioned above, a TPC algorithm should consider any power limitations of the transmitter, so that the receiver does not instruct the transmitter to transmit at a power level above its maximum transmission power. For 5G UL TPC, the UE sends the gNB a power headroom report (PHR) that includes an indication of how far the current transmission will be below the UE’s maximum transmission power, i.e., the additional transmission power available before reaching the maximum transmission power. The UE’s PHR enables the gNB’s scheduler to make informed decisions about resource allocation and TPC for subsequent UL transmissions. Several types of UE PHRs are defined for various uplink transmissions. For example, Type 1 PHR is defined for PUSCH transmission occasion ^^^^ on active UL BWP ^^^^ of carrier ^^^^ of serving cell ^^^^. If a UE determines that a Type 1 PHR for an activated serving cell is based on an actual PUSCH transmission, then for PUSCH transmission occasion ^^^^ on active UL BWP ^^^^ of carrier ^^^^ of serving cell ^^^^, the UE computes the Type 1 PHR value (in dB) as: are as defined for PUSCH transmission power ^^^^PUSCH,^^^^,^^^^,^^^^(^^^^, ^^^^, ^^^^^^^^ , ^^^^).In essence, Type 1 PHR informs the gNB about the difference between the nominal UE maximum transmit power and the estimated power for Uplink Shared Channel (UL-SCH) transmission for the serving cell. A positive PHR value indicates that UE can increase its transmit power without exceeding the maximum allowed power, i.e., that the UE can support a higher UL data rate transmission if needed. Conversely, a negative PHR value indicates that the UE's transmit power was inadequate for the scheduled UL transmission associated with the PHR, i.e., that the UL scheduler has requested a higher data rate than the UE can support with its available transmission power. The gNB UL scheduler uses UE PHRs – along with other UE feedback such as channel quality indicator (CQI), buffer status report, etc. – to make decisions on resource allocation and power control for subsequent UE UL transmissions. The gNB scheduler can adjust the assigned resources and transmit power levels for each UE to maintain desired UL reception performance and interference level. Like other RF transmitters mentioned above, a UE may include a PA that amplifies the UL signal to the necessary level so that the gNB receiver can successfully detect and / or decode it at the other end of the wireless channel. Likewise, the UE’s PA may have a “linear” region in which it introduces little or no distortion and “non-linear” region where its distortion increases with output signal level. To generate a given UL transmit power according to gNB TPC commands, the UE’s PA consumes less energy but produces more signal distortion when operating in the non-linear region, as discussed previously. As also discussed above, transmitter- and receiver-based techniques are available to compensate for the distortion caused by PA operation in the non-linear region. In general, for a given level of receiver performance, these compensation techniques enable a UE’s PA to operate further into the non-linear region with increased distortion but less energy consumption. For example, digital post-distortion (DPoD) is a receiver-based technique that performs signal detection by reconstructing the distorted signal based on a PA non-linearity model known to the receiver. A specific DPoD technique based on an artificial intelligence (AI) and machine learning (ML) is described in “A Deep Learning Receiver for Non-linear Transmitter” by Farhadi, et al., published in in IEEE Access, vol.11, pp.2796-2803 (2023). In general, ML algorithms involve training models based on training data and using the trained models for inference, classification, and / or prediction. ML algorithms can be classified as offline (pre-trained model) or online (continuous model training as new data samples are received). ML algorithms can also be classified as supervised learning, unsupervised learning, or reinforcement learning. For example, in supervised learning, during the training phase each input data sample (feature) to the ML algorithm is paired with a corresponding output (label) of the ML algorithm. Artificial neural networks (NNs) are a type of ML algorithm that can approximate any general function based on training data sets. They are also amenable to parallel processing implementation on common accelerator hardware. In general, NNs are based on interconnected processing units called neurons, where each neuron receives weighted version of the other neuron’s outputs and computes its own output based on a nonlinear transformation of the aggregated inputs using an activation function. Figure 3 shows an exemplary artificial NN. Figure 4 shows a block diagram of a gNB receiver that utilizes the example ML-based DPoD mentioned above. The receiver includes an ML-based demapper that uses an artificial NN, which is further illustrated in Figure 5. The demapper performs soft symbol-by-symbol demapping using complex (I / Q) symbols from the DFT despreader, context information, and SNR estimate as inputs. The demapper generates log-likelihood ratios (also referred to as “soft bits”) as output. Figure 6 illustrates block error rate (BLER) performance of the receiver based on the ML-based demapper in the presence of distortion due to transmitter PA non-linearity. The line with the “square” data points represents conventional receiver performance with non-linear PA and 4dB PA backoff, while the line with the “triangle” data points represents ML-based receiver performance under the same transmitter conditions. In contrast, the line with the “circle” data points represents receiver performance with a linear PA. To summarize, the use of DPD and / or DPoD enables the transmitter (e.g., UE) to operate its PA in a more non-linear region (i.e., lower backoff) with increased distortion while maintaining a desired level of receiver performance (e.g., UL BLER). However, conventional PHRs do not account for whether transmitter-based DPD and / or receiver-based DPoD is being used to compensate for PA non-linearities. For example, a UE reports the same remaining available transmit power regardless of whether compensation is being used, even though this compensation allows the UE PA to operate with lower backoff and increased energy efficiency. As such, the gNB scheduler is unable to make informed decisions about resource allocation and power control for subsequent UE UL transmissions. Accordingly, embodiments of the present disclosure provide flexible and efficient techniques for transmitter PHR that consider whether compensation for transmitter PA non- linear distortion is being used. For example, the transmitter PHR can be substantially different depending on whether the PA distortion compensation is activated or deactivated. Embodiments include techniques for reporting compensation use / availability as well as techniques for triggering and / or constructing flexible PHRs. Embodiments are applicable to when the compensation is applied in the receiver (e.g., gNB DPoD) and / or in the transmitter (e.g., UE DPD). Embodiments are also applicable to both conventional and AI / ML-based compensation techniques. Embodiments may provide various benefits and / or advantages. For example, in the case of a UE transmitter and gNB receiver that selectively employs DPoD, embodiments may increase UL coverage by increasing UE transmit power when there is capability to compensate for the increased PA distortion. Also, embodiments may increase UE energy efficiency by enabling the UE to operate its PA further into the non-linear region with reduced backoff, so long as DPoD compensation is available at the gNB receiver. Similar benefits may be available for a UE transmitter that selectively employs DPD, either for UL transmission to a gNB or for sidelink (SL) transmission to another UE. Figure 7 shows a signaling diagram of a procedure that involves enhanced power headroom reporting according to some embodiments of the present disclosure. The procedure is between a DPoD-capable gNB (710) and a UE (720), In this procedure, the transmitter (721) is included in the UE and the receiver (711) is included in the gNB. The UE also includes a PA (722). Note that the gNB is only as an NR-specific example of more generic base stations that are DPoD-capable. The procedure may include an initial phase of capability reporting, where the gNB sends the UE a request for the UE’s capability to adapt UL transmit power in accordance with gNB- based DPoD and the UE reports this capability to the gNB. This phase is optional and if not performed, the gNB may assume or have knowledge of the UE’s capability. During network operation phase, the gNB activates its DPoD capability with respect to the UE’s UL transmissions, and sends the UE an indication of this activation. Subsequently, the UE determines its power headroom (PH) based on the indicated DPoD activation, which may be less than the PH that the UE would determine without knowing that the gNB had activated DPoD. The UE reports the determined PH (i.e., in an enhanced PHR) to the gNB. Based on this PHR from the UE, the gNB updates scheduling of the UE (and possibly other UEs) and sends a PUSCH scheduling configuration to the UE, which may include a TPC command. The TPC command may be based on the UE’s reduced PH reported based on the DPoD activated at the gNB. The UE updates its transmit configuration accordingly and transmits PUSCH as scheduled by the gNB. Put differently, the UE’s PA operation changes when informed of the DPoD activation at gNB. For example, when an AI / ML-based DPoD model is activated at gNB, then the UE’s PH increases. Alternately, this can be viewed as the UE decreasing the maximum power reduction (MPR) that it uses for the PA. In contrast, when the AI / ML-based DPoD model is not activated (or is later deactivated), the UE’s PH remains at (or returns to) its conventional setting. Alternately, this can be viewed as the UE’s MPR remaining at (or returning to) its conventional setting. In some embodiments, an indication of an activation, deactivation, or change in the AI / ML DPoD model used at the gNB causes (or triggers) a PHR by the UE. For example, this could be specified in the following modified text of a 3GPP specification: • A Power Headroom Report (PHR) shall be triggered if any of the following events occur: o phr-ProhibitTimer expires or has expired and the path loss has changed more than phr- Tx-PowerFactorChange dB for at least one RS used as pathloss reference for one activated Serving Cell of any MAC entity of which the active DL BWP is not dormant BWP since the last transmission of a PHR in this MAC entity when the MAC entity has UL resources for new transmission; o phr-PeriodicTimer expires; o upon configuration or reconfiguration of the power headroom reporting functionality by upper layers, which is not used to disable the function; o upon activation, or deactivation, or switching of a model (e.g., AI / ML model) that modifies the range of transmit power of the UE; o activation of an SCell of any MAC entity with configured uplink of which firstActiveDownlinkBWP-Id is not set to dormant BWP; … In the above text, the “model” refers to any type of model that may change the allowed transmission power level at the UE, including a DPD model at the UE, a DPoD model at the gNB, or a two-sided model at the UE and the gNB. As one example, an UE-side AI / ML model can learn the non-linearity and / or memory characteristics of the UE PA and perform DPD to remove the effects of these characteristics from the transmitted UL signal. As another example, a gNB-side AI / ML model (e.g., Figures 4-5) can learn the distortion in the received signal due to the UE PA characteristics, and remove the distortion prior to data detection or detect the data in the presence of the distortion. As such, even if the received signal has high Error Vector Magnitude (EVM) due to UE PA non-linear distortion, the gNB can still demodulate and detect the included data. As discussed above, when one or more non-linear distortion compensation models are active, the UE may reduce the power backoff of its PA so that the PA operates further into the non-linear region. In some embodiments, the gNB can send the UE an indication of a maximum decrease in (or “relaxation” of) the MPR the UE is allowed to apply. Put differently, the indication informs the UE to use a smaller transmit power backoff or an increased transmit power level. Figure 8 shows an ASN.1 data structure for an RRC PhysicalCellGroupConfig information element (IE), according to some embodiments of the present disclosure. This IE includes field maxRelaxedMPR-FR1 that indicates the maximum decrease in MPR that the UE is allowed to apply in frequency range 1 (FR1, e.g., below 6yGHz). Likewise, field maxRelaxedMPR-FR2 indicates the maximum decrease in MPR that the UE is allowed to apply in frequency range 2 (FR2, e.g., above 6 GHz). Both fields include one of the four enumerated values of {1 dB, 3 dB, 6 dB, 9 dB}, selected by the gNB. In conventional NR UL transmission, higher MPR values (i.e., lower transmit power level) are defined for higher order quadrature amplitude modulations (QAMs), so that the higher peak amplitudes present in these QAMs are more likely to be amplified in the UE PA’s linear region with less distortion. This is necessary because the neighboring points come closer together in higher-order QAM constellations, making detection performance more susceptible to distortion and noise. Thus, as QAM order increases, there is greater potential for decreasing MPR and operating the UE PA more non-linearly when DPoD and / or DPD are activated. Figure 9 shows an ASN.1 data structure for an RRC PhysicalCellGroupConfig information element (IE), according to other embodiments of the present disclosure. In these embodiments, maxRelaxedMPR-FR1 (for FR1) and maxRelaxedMPR-FR2 (for FR2) include a different set of enumerated values for maximum decrease in MPR for each of various QAM orders used for the UE’s UL transmission. For each of these FRs / fields, the gNB may select one set (corresponding to QAM used) and then include one MPR decrease value from the selected set in the message to the UE. In this example, the set of candidate MPR decreases for lower order 16-QAM includes {1 dB, 2 dB, 4 dB, 6 dB} while the set of candidate MPR decreases for higher order 1024-QAM includes {1 dB, 3 dB, 6 dB, 9 dB}. Even so, the specific values in these sets are only exemplary. In other embodiments, rather than a set of candidate MPR decreases for each QAM order, a field of an ASN.1 data structure can include a set of candidate MPR decreases for each of multiple MCS. As an example, the field can include a first set for {16-QAM, rate=1 / 3}, a second set for {16-QAM, rate=2 / 3}, a third set for{64-QM, rate 3 / 4}, etc. In any case, the UE receives from the gNB a value for maximum MPR decrease, which is also referred to as maximum MPR relaxation (denoted MPRrelax,max). The UE can then decrease (or relax) its MPR (or backoff) according to: MPR' = MPR - MPRrelax, (1) wherein 0 ≤ MPRrelax≤ MPRrelax,max, MPR is the conventional backoff without considering availability of DPD or DPoD, and MPR' is the adjusted backoff based on availability of DPD or DPoD. Subsequently, the UE uses MPR' instead of MPR when determining UL transmit power related values such as PCMAX,f,c, its configured maximum output power for carrier f of serving cell c in each slot. The configured maximum output power PCMAX,f,cis used for calculation of UL transmit power for various UL channels and signals (e.g., PUSCH transmission power^^^^PUSCH,^^^^,^^^^,^^^^(^^^^, ^^^^, ^^^^^^^^ , ^^^^)) as well as for calculation of various types of power headroom (e.g., Type1 power headroom In general, the gNB may only configure an allowed range of UE UL transmit power based on MPR, minimum peak equivalent isotropic radiated power (EIRP), maximum EIRP, maximum total radiated power for the UE power class, etc. As such, the gNB has no knowledge of the actual UL transmit power used by the UE for any given UL transmission. However, this information may be useful for training a gNB-side AI / ML model for DPoD. In some embodiments, the UE can report the actual MPR (or backoff) applied by the UE in association with a PHR report. For example, if the gNB configures a value for MPRrelax,max, the UE reports to the gNB the value 0 ≤ MPRrelax≤ MPRrelax,maxthat it actually used in (1) above. Figure 10 shows an exemplary MAC control element (CE) for a single-entry PHR, according to some embodiments of the present disclosure. This MAC CE includes the following fields related to UE UL transmit power: • A: indicates whether relaxed MPR is applied. If A=1, relaxed MPR is applied by the UE, i.e., MPR' is used instead of MPR in UE transmission power calculation. If A=0, relaxed MPR is not applied by the UE, i.e., MPR is used in UE transmission power calculation. • H: indicates whether a real (i.e., actual) or a hypothetical UL transmission is used for MPR' or MPR calculation. If H=1, a hypothetical UL transmission is used in the calculation of MPR', MPRrelax, or MPR. For example, a reference PUSCH transmission with predefined transmission parameters is used for, e.g., data collection for model / functionality monitoring / training purposes. The predefined parameters may include: the modulation and coding rate of PUSCH, the amount of time-frequency resources used (e.g., number of resource blocks), etc. On the other hand, if H=0, a real UL transmission is used in the calculation of MPR', MPRrelax, or MPR. The real UL transmission is typically the actual PUSCH transmission scheduled when the PHR is triggered. • R: Reserved bit, set to 0. • MPRrelax: provides information on the power backoff value used by the UE, possibly in conjunction with field A and a mapping table. For example: o If A=1, field 'MPRrelax' carries the value of MPRrelaxas mapped by Table 1 below; and o If A=0, field 'MPRrelax' carries the value of MPR as mapped by Table 1 below. Table 1. Reported value Measured quantity value Unit MPR_val_0000 0 ≤ MPR_value < 0.5 dB MPR_val_0001 0.5 ≤ MPR_value < 1.0 dB MPR_val_0002 1.0 ≤ MPR_value < 1.5 dB … … … MPR_val_1110 7.0 ≤ MPR_value < 7.5 dB MPR_val_1111 MPR_value ≥ 7.5 dB In some cases, a UE may be configured with multiple serving cells. Figure 11 shows an exemplary MAC CE for a multiple-entry PHR, according to some embodiments of the present disclosure. This MAC CE includes fields to report relaxed MPR for each of the serving cells, in ascending order according to each cell’s assigned ServCellIndex. In particular, the MAC CE includes fields to report PCMAX,f,cand MPRrelaxfor each serving cell. Note that the fields A, H, and MPRrelaxhave the same meaning as defined above in relation to Figure 10. In general, when a UE supports simultaneous UL transmission for multiple serving cells, it may divide its total UL transmission power among the serving cells and report MPR-related information for each serving cell independently. Even so, at each transmission time interval (TTI), the UE may or may not have an actual UL (e.g., PUSCH) transmission on each serving cell. For PH calculation, the UE uses a hypothetical PUSCH when there is no actual PUSCH for a serving cell. As an example, at a given TTI, the UE may have an actual PUSCH transmission for serving cell 1 but no PUSCH transmission for serving cell 2. The UE’s PHR may include parameters (e.g., actual MPRrelaxused) of the PUSCH transmission for serving cell 1 but hypothetical values (e.g., MPRrelax) of the hypothetical PUSCH transmission for serving cell 2. Alternatively, the PHR can omit parameters for cells with hypothetical PUSCH transmissions. In some cases, a UE may be configured to perform UL transmission to multiple transmission-reception points (TRPs) associated with a gNB. Figure 12 shows an exemplary MAC CE for a multi-TRP PHR, according to some embodiments of the present disclosure. Although the MAC CE in Figure 12 assumes the UE is connected to two TRPs, it can be extended in case the UE is connected to additional TRPs. The MAC CE in Figure 12 includes two sets of fields, with each set including the fields A, H, MPRrelax, and R for the corresponding TRP. Even so, at each TTI, the UE may or may not have an actual UL (e.g., PUSCH) transmission to each TRP. For PH calculation, the UE uses a hypothetical PUSCH when there is no actual PUSCH for a TRP. As an example, at a given TTI, the UE may have an actual PUSCH transmission for TRP1 but no PUSCH transmission for TRP2. The UE’s PHR may include parameters (e.g., actual MPRrelaxused) of the PUSCH transmission for TRP1 but hypothetical values (e.g., MPRrelax) of the hypothetical PUSCH transmission for TRP2. Alternatively, the PHR can omit parameters for TRPs with hypothetical PUSCH transmissions. In case a PHR is triggered (e.g., by indication that a compensation model is activated) but the UE does not have an actual UL transmission for either TRP, the UE’s PHR may include hypothetical values (e.g., MPRrelax) of hypothetical PUSCH transmissions for both TRPs. Conversely, when a PHR is triggered and the UE has actual UL transmissions for both TRPs, the UE’s PHR may include parameters (e.g., actual MPRrelaxused) of the actual PUSCH transmissions for both TRPs. Although the above examples are based on UE reporting of actual MPRrelaxused for an UL transmission, in some instances a UE vendor may consider such values proprietary and not want to report them. In such case, rather than a precise value (or small range), each reporting codepoint (e.g., Table 1) can correspond to a wider range of MPRrelaxvalues (e.g., 3 dB range). In some embodiments, the decrease (or relaxation) in MPR (or backoff) allowed or configured by the gNB may depend on UE PA characteristics, which may differ depending on chipset used. These differing characteristics may include non-linearity pattern and / or distortion model (e.g., EVM, cubic metric, intercept values), etc. For example, non-linearity patterns may differ based on amount of EVM as a function of transmit power level. Due to these UE differences, a gNB-side AI / ML DPoD model may be able to remove different amounts of the distortion present in a received signal for a given MPR used by the different UEs. Thus, the gNB receiver may experience different amounts of residual distortion from different UEs for the same MPR. However, it is desirable for the gNB-side AI / ML DPoD model to be sufficiently trained so that it can recognize and remove these differing distortions. Accordingly, in some embodiments, a UE may inform the gNB about its relevant PA characteristics. The UE may inform the gNB about its relevant PA characteristics as part of initial capability reporting (e.g., in Figure 7) and optionally provide updates when it changes the relevant PA characteristics (e.g., bias voltages, operating points, etc.). The gNB may adapt the UE’s PHR configuration based on the reported PA characteristics. In some situations, the gNB may determine that the UE’s PA characteristics are incompatible with the DPoD model being used, and thus deactivate (or refraining from activating) the model for UL transmissions by the UE. In some of these embodiments, the UE may indicate that its PA characteristics correspond to one of a predefined set of types, categories, or classes (e.g., a predefined PA type that is closest to the UE’s PA). One example PA characteristic that can be used to categorize UEs is relation between distortion (e.g., EVM) and transmit power. Another example PA characteristic that can be used to categorize UEs is amplifier class. In particular, amplifier classes A, B, AB, and C operate more linearly with less distortion at the expense of reduced energy efficiency, while amplifier classes D and E use switching architectures that cause higher distortion with increased energy efficiency. Another example PA characteristic that can be used to categorize UEs is amplifier bias voltage. In general, a higher bias voltage increases dynamic range (including linear operating region) and results in lower signal distortion. The amplifier bias voltage may be fixed or variable (e.g., for dynamic signal envelope tracking). In other of these embodiments, the UE may send the gNB more details of its relevant PA characteristics, such as a parametric or non-parametric representation of the PA input / output transfer function for one or more bias voltages, envelope tracking capability, and / or DPD capability. Same / compatible category or parameter info may be provided as a part of training data and during inference. Based on information about PA characteristics of different UEs, the gNB may train its DPoD model such that it can then recognize, mitigate, and / or remove distortions introduced by these PAs with different characteristics. In general, when a gNB configures the UE with a maximum MPR decrease (i.e., smaller backoff) due to an active distortion compensation model, the gNB may perform scheduling decisions similar to the conventional approach with no MPR decrease (i.e., standard backoff). One potential issue is that the smaller backoff results in more non-linear distortion, which creates out- of-band (OOB) spurious RF emissions. These may interfere with other UE UL transmissions in adjacent frequency resources (e.g., carriers, subcarriers, resource blocks, etc.). In such case, the gNB can make UL scheduling decisions to mitigate the impact of such interference. For example, the gNB may schedule concurrent UL transmissions from other UEs with sufficient separation in frequency domain to avoid or mitigate interference from the higher-power UE UL transmissions. Although the embodiments described above were based on a gNB’s DPoD compensation of a UE’s UL transmissions, similar techniques may be applied based on a UE’s DPoD compensation of a gNB’s DL transmissions. Typically, gNB DL transmission power is fixed. However, when a UE can apply DPoD compensation to the DL transmissions received from the gNB, the gNB is able to operate its PA in a more non-linear region that introduces more distortion into the transmitted signal. In other words, when a UE can apply DPoD compensation, the UE is capable of correctly receiving a DL transmission that includes more distortion. This capability can be reflected in the channel quality reporting from the UE to the gNB, such as more aggressive channel state information (CSI) indicated by the UE. For example, “more aggressive CSI” can include one or more of the following due to the availability of DPoD: • a higher MIMO rank for a given DL channel condition, e.g., 4-layer DL MIMO instead of 2-layer DL MIMO when DPoD is not available. • a higher channel quality indicator (CQI) that indicates the UE can support a less robust, more efficient DL MCS, e.g., {64-QAM, rate-2 / 3 coding} instead of {16-QAM, rate-1 / 2 coding } when DPoD is not available. • a smaller number of repetitions for the DL data. • a larger number of resource blocks to carry the DL data; and • a larger transport block (TB) size for the DL data. Figure 13 shows a signaling diagram of a procedure for selective CSI reporting, according to some embodiments of the present disclosure. The procedure is between a gNB (1310) and a DPoD-capable UE (1320). The procedure may include an initial phase of capability reporting, where the gNB sends the UE a request for the UE’s capability for DL DPoD and the UE reports this capability to the gNB. This phase is optional and if not performed, the gNB may assume or have knowledge of the UE’s capability. During network operation phase, the gNB transmits DL reference signals (RS) that the UE receives and uses to determine DL channel quality, which it then reports to the gNB as CSI. In this case, the UE determines and reports both conventional CSI for the DL channel (assuming no DL DPoD) as well as more aggressive CSI for the DL channel (assuming DL DPoD), according to any of the examples mentioned above. Based on the conventional and more aggressive CSI in the channel quality report from the UE, the gNB updates DL scheduling for the UE (and possibly other UEs) and sends a PDCCH with DCI that includes PDSCH scheduling information and an command for the UE to activate its DL DPoD. Based on this DCI, the UE prepares for receiving the scheduled PDSCH including activating the DL DPoD. Subsequently, the gNB performs the scheduled PDSCH to transmission to the UE, based on operating its PA in a more non-linear region that introduces more distortion to the transmitted signal. Using the activated DL DPoD, the UE can compensate for this distortion and successfully detect the data carried by the PDSCH. In other variants, the UE may report either conventional CSI (assuming no DL DPoD) or more aggressive CSI (assuming DL DPoD) in the channel quality report to the gNB. For example, the UE may include in the report a field (e.g., flag, Boolean variable, etc.) that indicates which type of CSI is carried in the report. Alternatively, the flag may be separate from the channel quality report, and may indicate that the type of CSI to be included in one or more subsequent channel quality reports. This alternative has the benefit of reduced signaling overhead, especially when a single flag relates to many subsequent channel quality reports. Various features of the embodiments described above correspond to various operations illustrated in Figures 14-15, which show exemplary methods (e.g., procedures) for a transmitter and a receiver, respectively. In other words, various features of the operations described below correspond to various embodiments described above. Furthermore, the exemplary methods shown in Figures 14-15 can be used cooperatively to provide various benefits, advantages, and / or solutions to problems described herein. Although Figures 14-15 show specific blocks in particular orders, the operations of the exemplary methods can be performed in different orders than shown and can be combined and / or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines. In particular, Figure 14 shows an exemplary method (e.g., procedure) for a transmitter configured to generate transmissions to a receiver, according to various embodiments of the present disclosure. The exemplary method can be performed by any appropriate transmitter (e.g., wireless device, UE etc.) such as described elsewhere herein. The exemplary method includes the operations of block 1430, where the transmitter determines a backoff from a maximum allowed output power for a first transmission. The first transmission is to be amplified by a power amplifier (PA, i.e., associated with the transmitter), and the determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA (i.e., more distortion for lower backoff and vice versa). The exemplary method also includes the operations of block 1450, where the transmitter selectively reduces the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter. The exemplary method also includes the operations of block 1460, where the transmitter sends one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced. In some embodiments, selectively reducing the determined backoff in block 1450 includes the following operations, labelled with corresponding sub-block numbers: • (1451) reducing the determined backoff by the first amount when compensation for the distortion is available; and • (1452) refraining from reducing the determined backoff when compensation for the distortion is unavailable. In some of these embodiments, the information sent to the receiver includes the following: • when the determined backoff is reduced, an indication that the determined backoff was reduced and the first amount by which the determined backoff was reduced; and • when the determined backoff is not reduced, the determined backoff and an indication that the determined backoff was not reduced. The MAC CEs shown in Figures 10-12 are examples of these embodiments, where field “A” corresponds to the indication and field “MPRrelax” corresponds to the determined backoff or the first amount, according to the value of field “A”. In some embodiments, the exemplary method also includes the operations of block 1420, where the transmitter receives from the receiver an indication of a maximum allowable reduction (e.g., MPRrelax,max) in backoff from a maximum allowed output power. The first amount is between zero and the maximum allowable reduction. In some of these embodiments, the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range, a serving cell, a transmission reception point (TRP) of the receiver, a modulation order, a modulation constellation, and an error-correcting code. In some embodiments, the exemplary method also includes the operations of block 1470, where the transmitter transmits the first transmission at the maximum allowed output power minus the following: the determined backoff, when the determined backoff is not reduced; and the determined backoff minus the first amount, when the determined backoff is reduced. In other words, the transmitter transmits the first transmission at the maximum allowed output power minus the selectively reduced backoff. In some of these embodiments, transmitting the first transmission in block 1470 includes the operations of sub-block 1471, where when the determined backoff is reduced, the transmitter causes the PA to amplify the first transmission using a more energy-efficient operating point (i.e., with greater non-linearity). In some embodiments, the exemplary method also includes the operations of block 1440, where the transmitter receives from the receiver a notification of activation, deactivation, or model change for receiver compensation for the distortion due to non-linearity of the PA. The backoff is selectively reduced in block 1450 in response to the notification. In some embodiments, the exemplary method also includes the operations of block 1410, where the transmitter sends to the receiver an indication of one or more of the following: • characteristics of the PA, • transmitter capability to compensate for the distortion due to non-linearity of the PA, and • transmitter capability for selective reduction of backoff from maximum allowed output power. In some of these embodiments, the indication is sent in response to one of the following: • a request by the receiver for transmitter capabilities; • transmitter adjustment or change to characteristics of the PA; or • transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to non-linearity of the PA. In some of these embodiments, the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types. In some embodiments, the backoff is determined in block 1430 based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation. In some embodiments, the information is sent to the receiver in a power headroom report (PHR), the receiver is a base station or included in a base station, and one of the following applies: • the transmitter and the PA are included in a UE; or • the transmitter is a UE that includes the PA. In some of these embodiments, the information sent to the base station also includes an indication of one or more of the following: the maximum allowed output power of the first transmission, and whether the first transmission is a real transmission or a hypothetical transmission. In some of these embodiments, the UE is served by a plurality of cells provided by the base station, the first transmission is associated with one or more of the plurality of cells, and the PHR includes the information for one of the following: each of the plurality of cells, or each of one or more the cells associated with the first transmission. The MAC CE shown in Figure 11 is an example of these embodiments. In other of these embodiments, the UE is connected to a plurality of TRPs associated with the base station, the first transmission is associated with one or more of the plurality of TRPs, and the PHR includes the information for one of the following: each of the plurality of TRPs, or each of the one or more TRPs associated with the first transmission. The MAC CE shown in Figure 12 is an example of these embodiments. In various embodiments, the determined backoff is a maximum power reduction (MPR) and the first amount is a relaxation of the MPR. In addition, Figure 15 shows an exemplary method (e.g., procedure) for a receiver configured to receive transmissions from a transmitter, according to various embodiments of the present disclosure. The exemplary method can be performed by any appropriate receiver (e.g., base station, eNB, gNB, ng-eNB, etc., or component thereof) such as described elsewhere herein. The exemplary method includes the operations of block 1540, where the receiver receives one or more of the following information from the transmitter: • a backoff from a maximum allowed output power for a first transmission by the transmitter, wherein the first transmission is to be amplified by a PA (i.e., associated with the transmitter) and the backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; • an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and • a first amount by which the transmitter reduced the backoff. The exemplary method also includes the operations of block 1550, where the receiver receives the first transmission from the transmitter (e.g., via a channel). In some embodiments, the exemplary method also includes the operations of block 1560, where the receiver decodes the received first transmission using a model that selectively compensates for distortion in the first transmission based on the received information. In other embodiments, the exemplary method also includes the operations of block 1570, where based on the received information and the received first transmission, the receiver trains a model to compensate for distortion in received transmissions due to non-linearity of the PA. In some of these embodiments, the model is an AI / ML model. In some embodiments, the backoff is reduced by the first amount when compensation for the distortion is available (i.e., at the receiver and / or at the transmitter) but the backoff is not reduced when compensation for the distortion is unavailable. In some of these embodiments, the information received from the transmitter includes the following: • when the backoff is reduced, an indication that the transmitter reduced the backoff and the first amount by which the transmitter reduced the backoff; and • when the backoff is not reduced, the backoff and an indication that the transmitter did not reduce the backoff. The MAC CEs shown in Figures 10-12 are examples of these embodiments, where field “A” corresponds to the indication and field “MPRrelax” corresponds to the backoff or the first amount, according to the value of field “A”. In some embodiments, the exemplary method also includes the operations of block 1520, where the receiver sends to the transmitter an indication of a maximum allowable reduction (e.g., MPRrelax,max) in backoff from a maximum allowed output power. The first amount is between zero and the maximum allowable reduction. In some of these embodiments, the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range, a serving cell, a TRP of the receiver, a modulation order, a modulation constellation, and an error-correcting code. In some embodiments, the exemplary method also includes the operations of block 1530, where the receiver sends to the transmitter a notification of activation, deactivation, or model change for receiver compensation of the distortion due to non-linearity of the PA. The information is received in block 1540 in response to the notification. In some embodiments, the exemplary method also includes the operations of block 1510, where the receiver receives from the transmitter an indication of one or more of the following: • characteristics of the PA, • transmitter capability to compensate for the distortion due to non-linearity of the PA, and • transmitter capability for selective reduction of backoff from maximum allowed output power. In some of these embodiments, the indication is received in response to one of the following: • a request by the receiver for transmitter capabilities; • transmitter adjustment or change to characteristics of the PA; or • transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to non-linearity of the PA. In some of these embodiments, the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types. In some embodiments, the backoff is based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation. In some embodiments, the information is received from the transmitter in a PHR, the receiver is a base station, and one of the following applies: • the transmitter and the PA are included in a UE; or • the transmitter is a UE that includes the PA. In some of these embodiments, the information received from the UE also includes an indication of one or more of the following: the maximum allowed output power of the first transmission, and whether the first transmission is a real transmission or a hypothetical transmission. In some of these embodiments, the base station serves the UE via a plurality of cells, the first transmission is associated with one or more of the plurality of cells, and the PHR includes the information for one of the following: each of the plurality of cells, or each of the one or more cells associated with the first transmission. The MAC CE shown in Figure 11 is an example of these embodiments. In other of these embodiments, the base station is connected to the UE via a plurality of TRPs, the first transmission is associated with one or more of the plurality of TRPs, and the PHR includes the information for one of the following: each of the plurality of TRPs, or each of the one or more TRPs associated with the first transmission. The MAC CE shown in Figure 12 is an example of these embodiments. In various embodiments, the backoff is an MPR and the first amount is a relaxation of the MPR. Although various embodiments are described above in terms of methods, techniques, and / or procedures, the person of ordinary skill will readily comprehend that such methods, techniques, and / or procedures can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, computer program products, etc. Figure 16 shows an example of a communication system 1600 in accordance with some embodiments. In this example, communication system 1600 includes a telecommunication network 1602 that includes an access network 1604 (e.g., RAN) and a core network 1606, which includes one or more core network nodes 1608. Access network 1604 includes one or more access network nodes, such as network nodes 1610a-b (one or more of which may be generally referred to as network nodes 1610), or any other similar 3GPP access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, telecommunication network 1602 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in telecommunication network 1602 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in telecommunication network 1602, including one or more network nodes 1610 and / or core network nodes 1608. Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1, F1, W1, E1, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. Network nodes 1610 facilitate direct or indirect connection of UEs, such as by connecting UEs 1612a-d (one or more of which may be generally referred to as UEs 1612) to core network 1606 over one or more wireless connections. Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 1600 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. Communication system 1600 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system. UEs 1612 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with network nodes 1610 and other communication devices. Similarly, network nodes 1610 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 1612 and / or with other network nodes or equipment in telecommunication network 1602 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 1602. In the depicted example, core network 1606 connects network nodes 1610 to one or more hosts, such as host 1616. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 1606 includes one or more core network nodes (e.g., 1608) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 1608. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF). Host 1616 may be under the ownership or control of a service provider other than an operator or provider of access network 1604 and / or telecommunication network 1602, and may be operated by the service provider or on behalf of the service provider. Host 1616 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. As a whole, communication system 1600 of Figure 16 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. In some examples, telecommunication network 1602 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 1602 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 1602. For example, telecommunication network 1602 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive IoT services to yet further UEs. In some examples, UEs 1612 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1604 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1604. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio – Dual Connectivity (EN-DC). In some embodiments, UE 1612 can be configured to perform the exemplary method (e.g., procedure) shown in Figure 14, while network node 1610 can be configured to perform the exemplary method (e.g., procedure) shown in Figure 15. In the example, hub 1614 communicates with access network 1604 to facilitate indirect communication between one or more UEs (e.g., UE 1612c and / or 1612d) and network nodes (e.g., network node 1610b). In some examples, hub 1614 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1614 may be a broadband router enabling access to core network 1606 for the UEs. As another example, hub 1614 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1610, or by executable code, script, process, or other instructions in hub 1614. As another example, hub 1614 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 1614 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 1614 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1614 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 1614 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy IoT devices. Hub 1614 may have a constant / persistent or intermittent connection to network node 1610b. Hub 1614 may also allow for a different communication scheme and / or schedule between hub 1614 and UEs (e.g., UE 1612c and / or 1612d), and between hub 1614 and core network 1606. In other examples, hub 1614 is connected to core network 1606 and / or one or more UEs via a wired connection. Moreover, hub 1614 may be configured to connect to an M2M service provider over access network 1604 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with network nodes 1610 while still connected via hub 1614 via a wired or wireless connection. In some embodiments, hub 1614 may be a dedicated hub – that is, a hub whose primary function is to route communications to / from the UEs from / to network node 1610b. In other embodiments, hub 1614 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and network node 1610b, but which is additionally capable of operating as a communication start and / or end point for certain data channels. In some embodiments, one or more network nodes 1610 may be configured to perform operations attributed to a receiver in various embodiments described above, including the exemplary method shown in Figure 15. In some embodiments, one or more UEs 1612 may be configured to perform operations attributed to a transmitter in various embodiments described above, including the exemplary method shown in Figure 14. Figure 17 shows a UE 1700 in accordance with some embodiments. Examples of UE 1700 include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by 3GPP, including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE. UE 1700 may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to- everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). UE 1700 includes processing circuitry 1702 that is operatively coupled via a bus 1704 to an input / output interface 1706, a power source 1708, a memory 1710, a communication interface 1712, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 17. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc. Processing circuitry 1702 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in memory 1710. Processing circuitry 1702 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, processing circuitry 1702 may include multiple central processing units (CPUs). In the example, input / output interface 1706 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into UE 1700. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device. In some embodiments, power source 1708 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. Power source 1708 may further include power circuitry for delivering power from power source 1708 itself, and / or an external power source, to the various parts of UE 1700 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of power source 1708. Power circuitry may perform any formatting, converting, or other modification to the power from power source 1708 to make the power suitable for the respective components of UE 1700 to which power is supplied. Memory 1710 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, memory 1710 includes one or more application programs 1714, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1716. Memory 1710 may store, for use by UE 1700, any of a variety of various operating systems or combinations of operating systems. Memory 1710 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ Memory 1710 may allow UE 1700 to access instructions, application programs and the like, stored on transitory or non- transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in memory 1710, which may be or comprise a device-readable storage medium. Processing circuitry 1702 may be configured to communicate with an access network or other network using communication interface 1712. Communication interface 1712 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1722. Communication interface 1712 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1718 and / or a receiver 1720 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, transmitter 1718 and receiver 1720 may be coupled to one or more antennas (e.g., antenna 1722) and may share circuit components, software, or firmware, or alternatively be implemented separately. In some embodiments, communication interface 1712 may include a power amplifier (PA) 1719 coupled to transmitter 1718. As discussed above in relation to other embodiments, PA 1719 may be configured to amplify transmissions (or signals) generated by transmitter 1718 to levels (or powers) necessary for a receiver to successfully detect and / or decode it at the other end of a channel. In the embodiments illustrated by Figure 17, communication functions of communication interface 1712 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth. Regardless of the type of sensor, UE 1700 may provide an output of data captured by its sensors, through its communication interface 1712, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., an alert is sent when moisture is detected), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient). As another example, UE 1700 may comprise an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, UE 1700 may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input. UE 1700, when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. When in the form of an IoT device, UE 1700 may include circuitry and / or software that facilitate an intended application of the IoT device, in addition to other components shown in Figure 17. As yet another specific example, in an IoT scenario, UE 1700 may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation. In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g., by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators. In some embodiments, UE 1700 may be configured to perform operations attributed to a transmitter in various embodiments described above, including the exemplary method shown in Figure 14. Figure 18 shows a network node 1800 in accordance with some embodiments. Examples of network node 1800 include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, Node Bs, eNBs, gNBs), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU). Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS). Other examples of network node 18000 include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs). Network node 1800 includes processing circuitry 1802, memory 1804, communication interface 1806, and power source 1808. Network node 1800 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 1800 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 1800 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1804 for different RATs) and some components may be reused (e.g., a same antenna 1810 may be shared by different RATs). Network node 1800 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1800, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1800. Processing circuitry 1802 may include a microprocessor, a controller, a microcontroller, a central processing unit, a digital signal processor, an application-specific integrated circuit, a field programmable gate array, and / or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 1800 components, such as memory 1804, to provide network node 1800 functionality. In some embodiments, processing circuitry 1802 includes a system on a chip (SOC). In some embodiments, processing circuitry 1802 includes one or more of radio frequency (RF) transceiver circuitry 1812 and baseband processing circuitry 1814. In some embodiments, RF transceiver circuitry 1812 and baseband processing circuitry 1814 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1812 and baseband processing circuitry 1814 may be on the same chip or set of chips, boards, or units. Memory 1804 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by processing circuitry 1802. Memory 1804 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions (collectively denoted computer program 1804a, which may be in the form of a computer program product) capable of being executed by processing circuitry 1802 and utilized by network node 1800. Memory 1804 may be used to store any calculations made by processing circuitry 1802 and / or any data received via communication interface 1806. In some embodiments, processing circuitry 1802 and memory 1804 are integrated. Communication interface 1806 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, communication interface 1806 comprises port(s) / terminal(s) 1816 to send and receive data, for example to and from a network over a wired connection. Communication interface 1806 also includes radio front- end circuitry 1818 that may be coupled to, or in certain embodiments a part of, antenna 1810. Radio front-end circuitry 1818 comprises filters 1820 and amplifiers 1822. Radio front-end circuitry 1818 may be connected to an antenna 1810 and processing circuitry 1802. The radio front-end circuitry may be configured to condition signals communicated between antenna 1810 and processing circuitry 1802. Radio front-end circuitry 1818 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1818 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1820 and / or amplifiers 1822. The radio signal may then be transmitted via antenna 1810. Similarly, when receiving data, antenna 1810 may collect radio signals which are then converted into digital data by radio front-end circuitry 1818. The digital data may be passed to processing circuitry 1802. In other embodiments, the communication interface may comprise different components and / or different combinations of components. In certain alternative embodiments, network node 1800 does not include separate radio front-end circuitry 1818, instead, processing circuitry 1802 includes radio front-end circuitry and is connected to antenna 1810. Similarly, in some embodiments, all or some of RF transceiver circuitry 1812 is part of communication interface 1806. In still other embodiments, communication interface 1806 includes one or more ports or terminals 1816, radio front-end circuitry 1818, and RF transceiver circuitry 1812, as part of a radio unit (not shown), and communication interface 1806 communicates with baseband processing circuitry 1814, which is part of a digital unit (not shown). Antenna 1810 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 1810 may be coupled to radio front-end circuitry 1818 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 1810 is separate from network node 1800 and connectable to network node 1800 through an interface or port. Antenna 1810, communication interface 1806, and / or processing circuitry 1802 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, antenna 1810, communication interface 1806, and / or processing circuitry 1802 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment. Power source 1808 provides power to the various components of network node 1800 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1808 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1800 with power for performing the functionality described herein. For example, network node 1800 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 1808. As a further example, power source 1808 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail. Embodiments of network node 1800 may include additional components beyond those shown in Figure 18 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, network node 1800 may include user interface equipment to allow input of information into network node 1800 and to allow output of information from network node 1800. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1800. In some embodiments, network node 1800 may be configured to perform operations attributed to a receiver in various embodiments described above, including the exemplary method shown in Figure 15. Figure 19 is a block diagram illustrating a virtualization environment 1900 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1900 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1900 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface. Applications 1902 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1900 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein. For example, a virtual node 1902 can be configured to perform operations attributed to a receiver in various embodiments described above, including the exemplary method shown in Figure 15. Hardware 1904 includes processing circuitry, memory that stores software and / or instructions (collectively denoted computer program 1904a, which may be in the form of a computer program product) executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1906 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1908a-1908b (one or more of which may be generally referred to as VMs 1908), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. Virtualization layer 1906 may present a virtual operating platform that appears like networking hardware to the VMs 1908. VMs 1908 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1906. Different embodiments of the instance of a virtual appliance 1902 may be implemented on one or more of VMs 1908, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment. In the context of NFV, each VM 1908 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1908, and that part of hardware 1904 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1908 on top of the hardware 1904 and corresponds to the application 1902. Hardware 1904 may be implemented in a standalone network node with generic or specific components. Hardware 1904 may implement some functions via virtualization. Alternatively, hardware 1904 may be part of a larger cluster of hardware (e.g., such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration function 1910, which, among others, oversees lifecycle management of applications 1902. In some embodiments, hardware 1904 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1912 which may alternatively be used for communication between hardware nodes and radio units. The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art. The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein. Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure. As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood that although such terms may be used synonymously herein, there may be instances when such terms are not intended to be used synonymously. Embodiments of the techniques and apparatus described herein also include, but are not limited to, the following enumerated examples: A1. A method for a transmitter coupled to a power amplifier (PA) arranged to amplify transmissions to a receiver via a channel, the method comprising: determining a backoff from a maximum allowed output power for a first transmission, wherein an amount of distortion in the first transmission due to PA non-linearity is inversely related to the determined backoff; selectively reducing the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or the transmitter; and sending one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced. A2. The method of embodiment A1, wherein selectively reducing the determined backoff comprises: reducing the determined backoff by the first amount when compensation for the distortion is available; and refraining from reducing the determined backoff when compensation for the distortion is unavailable. A2a. The method of embodiment A2, wherein the information sent to the receiver includes the following: when the determined backoff is reduced, an indication that the determined backoff was reduced and the first amount by which the determined backoff was reduced; and when the determined backoff is not reduced, the determined backoff and an indication that the determined backoff was not reduced. A3. The method of any of embodiments A1-A2a, further comprising receiving from the receiver an indication of a maximum allowable reduction in backoff from a maximum allowed output power, wherein the first amount is between zero and the maximum allowable reduction. A3a. The method of embodiment A3, wherein the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range, a serving cell, a transmission reception point (TRP) of the receiver, a modulation order, a modulation constellation, and an error-correcting code. A4. The method of any of embodiments A1-A3a, further comprising transmitting the first transmission at the maximum allowed output power minus the selectively reduced backoff. A4a. The method of embodiment A4, wherein transmitting the first transmission comprises, when the determined backoff is reduced, causing the PA to amplify the first transmission using a more energy-efficient operating point. A5. The method of any of embodiments A1-A4a, further comprising receiving, from the receiver, a notification of activation, deactivation, or model change for receiver compensation for the distortion due to PA non-linearity, wherein the backoff is selectively reduced in response to the notification. A6. The method of any of embodiments A1-A5, further comprising sending to the receiver an indication of one or more of the following: characteristics of the PA, transmitter capability to compensate for the distortion due to PA non-linearity, and transmitter capability for selective reduction of backoff from maximum allowed output power. A6a. The method of embodiment A6, wherein the indication is sent in response to one of the following: a request by the receiver for transmitter capabilities; transmitter adjustment or change to characteristics of the PA; or transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to PA non-linearity A6b. The method of any of embodiments A6-A6a, wherein the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types. A7. The method of any of embodiments A1-A6b, wherein the backoff is determined based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation. A8. The method of any of embodiments A1-A7, wherein the transmitter is a user equipment (UE), the receiver is a base station, and the information is sent to the base station in a power headroom report (PHR). A8a. The method of embodiment A8, wherein the information sent to the base station also includes an indication of one or more of the following: the maximum allowed output power of the first transmission; and whether the first transmission is a real transmission or a hypothetical transmission. A8b. The method of any of embodiments A8-A8a, wherein the UE is served by a plurality of cells provided by the base station, the first transmission is associated with one or more of the plurality of cells, and the PHR includes the information for one of the following: each of the plurality of cells, or each of the cells associated with the first transmission. A8c. The method of any of embodiments A8-A8a, wherein the UE is connected to a plurality of transmission reception points (TRPs) associated with the base station, the first transmission is associated with one or more of the plurality of TRPs, and the PHR includes the information for one of the following: each of the plurality of TRPs, or each of the TRPs associated with the first transmission. A8d. The method of any of embodiments A8-A8c, wherein the determined backoff is a maximum power reduction (MPR) and the first amount is a relaxation of the MPR. B1. A method for a receiver configured to receive transmissions, via a channel, from a transmitter coupled to a power amplifier (PA) arranged to amplify the transmissions, the method comprising: receiving one or more of the following information from the transmitter: a backoff from a maximum allowed output power for a first transmission by the transmitter, wherein an amount of distortion in the first transmission due to transmitter PA non-linearity is inversely related to the backoff; an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and a first amount by which the transmitter reduced the backoff; and receiving the first transmission from the transmitter. B1a. The method of embodiment B1, further comprising decoding the received first transmission using a model that selectively compensates for distortion in the first transmission based on the received information. B1b. The method of embodiment B1, further comprising, based on the received information and the received first transmission, training a model to compensate for distortion in received transmissions due to transmitter PA non-linearity. B1c. The method of any of embodiments B1a-B1b, wherein the model is an artificial intelligence (AI) / machine learning (ML) model. B2. The method of any of embodiments B1-B1c, wherein: the backoff is reduced by the first amount when compensation for the distortion is available; and the backoff is not reduced when compensation for the distortion is unavailable. B2a. The method of embodiment B2, wherein the information received from the transmitter includes the following: when the backoff is reduced, an indication that the transmitter reduced the backoff and the first amount by which the transmitter reduced the backoff; and when the backoff is not reduced, the backoff and an indication that the transmitter did not reduce the backoff. B3. The method of any of embodiments B1-B2a, further comprising sending to the transmitter an indication of a maximum allowable reduction in backoff from a maximum allowed output power, wherein the first amount is between zero and the maximum allowable reduction. B4. The method of embodiment B3, wherein the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range, a serving cell, a transmission reception point (TRP) of the receiver, a modulation order, a modulation constellation, and an error-correcting code. B5. The method of any of embodiments B1-B4, further comprising sending to the transmitter a notification of activation, deactivation, or model change for receiver compensation of the distortion due to transmitter PA non-linearity, wherein the information is received in response to the notification. B6. The method of any of embodiments B1-B5, further comprising receiving from the transmitter an indication of one or more of the following: characteristics of the PA; transmitter capability to compensate for the distortion due to PA non-linearity; and transmitter capability for selective reduction of backoff from maximum allowed output power. B6a. The method of embodiment B6, wherein the indication is received in response to one of the following: a request by the receiver for transmitter capabilities; transmitter adjustment or change to characteristics of the PA; or transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to PA non-linearity B6b. The method of any of embodiments B6-B6a, wherein the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types. B7. The method of any of embodiments B1-B6b, wherein the backoff is based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation. B8. The method of any of embodiments B1-B7, wherein the transmitter is a user equipment (UE), the receiver is a base station, and the information is received from the UE in a power headroom report (PHR). B8a. The method of embodiment B8, wherein the information received from the UE also includes an indication of one or more of the following: the maximum allowed output power of the first transmission; and whether the first transmission is a real transmission or a hypothetical transmission. B8b. The method of any of embodiments B8-B8a, wherein the base station serves the UE via a plurality of cells, the first transmission is associated with one or more of the plurality of cells, and the PHR includes the information for one of the following: each of the plurality of cells, or each of the cells associated with the first transmission. B8c. The method of any of embodiments B8-B8a, wherein the base station is connected to the UE via a plurality of transmission reception points (TRPs), the first transmission is associated with one or more of the plurality of TRPs, and the PHR includes the information for one of the following: each of the plurality of TRPs, or each of the TRPs associated with the first transmission. B8d. The method of any of embodiments B8-B8c, wherein the backoff is a maximum power reduction (MPR) and the first amount is a relaxation of the MPR. C1. A transmitter coupled to a power amplifier (PA) arranged to amplify transmissions to a receiver via a channel, the transmitter comprising: communication interface circuitry configured to generate the transmissions, to control PA amplification of the transmissions, and to receive information from the receiver; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the method of any of embodiments A1- A8d. C2. A transmitter coupled to a power amplifier (PA) arranged to amplify transmissions to a receiver via a channel, the transmitter being further configured to perform operations corresponding to the method of any of embodiments A1-A8d. C3. The transmitter of any of embodiments C1-C2, wherein the transmitter includes the PA. C4. A user equipment (UE) comprising the transmitter of any of embodiments C1-C3. C5. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a transmitter coupled to a power amplifier (PA) arranged to amplify transmissions to a receiver via a channel, configure the transmitter to perform operations corresponding to any of the methods of embodiments A1-A8d. C6. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a transmitter coupled to a power amplifier (PA) arranged to amplify transmissions to a receiver via a channel, configure the transmitter to perform operations corresponding to any of the methods of embodiments A1-A8d. D1. A receiver configured to receive transmissions, via a channel, from a transmitter coupled to a power amplifier (PA) arranged to amplify the transmissions, the receiver comprising: communication interface circuitry configured to receive the transmissions via the channel and to send information to the transmitter; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the method of any of embodiments B1- B8d. D2. A receiver configured to receive transmissions, via a channel, from a transmitter coupled to a power amplifier (PA) arranged to amplify the transmissions, the receiver being further configured to perform operations corresponding to the method of any of embodiments B1-B8d. D3. A base station comprising the receiver of any of embodiments D1-D2. D4. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a receiver configured to receive transmissions, via a channel, from a transmitter coupled to a power amplifier (PA) arranged to amplify the transmissions, configure the receiver to perform operations corresponding to any of the methods of embodiments B1-B8d. D5. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a receiver configured to receive transmissions, via a channel, from a transmitter coupled to a power amplifier (PA) arranged to amplify the transmissions, configure the receiver to perform operations corresponding to any of the methods of embodiments B1-B8d.

Claims

CLAIMS 1. A method for a transmitter configured to generate transmissions to a receiver, the method comprising: determining (1430) a backoff from a maximum allowed output power for a first transmission, wherein: the first transmission is to be amplified by a power amplifier, PA, and the determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; selectively reducing (1450) the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter; and sending (1460) one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced.

2. The method of claim 1, wherein selectively reducing (1450) the determined backoff comprises: reducing (1451) the determined backoff by the first amount when compensation for the distortion is available; and refraining (1452) from reducing the determined backoff when compensation for the distortion is unavailable.

3. The method of claim 2, wherein the information sent to the receiver includes the following: when the determined backoff is reduced, an indication that the determined backoff was reduced and the first amount by which the determined backoff was reduced; and when the determined backoff is not reduced, the determined backoff and an indication that the determined backoff was not reduced.

4. The method of any of claims 1-3, further comprising receiving (1420) from the receiver an indication of a maximum allowable reduction in backoff from a maximum allowed output power, wherein the first amount is between zero and the maximum allowable reduction.

5. The method of claim 4, wherein the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range; a serving cell; a transmission reception point, TRP, of the receiver; a modulation order; a modulation constellation; and an error-correcting code.

6. The method of claim 4, wherein the maximum allowable reduction is one of a plurality of candidate maximum allowable reductions, wherein the plurality are specific to one or more of the following associated with the first transmission: a frequency range; a serving cell; a transmission reception point, TRP, of the receiver; a modulation order; a modulation constellation; and an error-correcting code.

7. The method of any of claims 1-6, further comprising transmitting (1470) the first transmission at the maximum allowed output power minus the following: the determined backoff, when the determined backoff is not reduced; and the determined backoff minus the first amount, when the determined backoff is reduced.

8. The method of claim 7, wherein transmitting (1470) the first transmission comprises, when the determined backoff is reduced, causing (1471) the PA to amplify the first transmission using a more energy-efficient operating point.

9. The method of any of claims 1-8, further comprising receiving (1440) from the receiver a notification of activation, deactivation, or model change for receiver compensation for the distortion due to non-linearity of the PA, wherein the backoff is selectively reduced in response to the notification.

10. The method of any of claims 1-9, further comprising sending (1410) to the receiver an indication of one or more of the following: characteristics of the PA, transmitter capability to compensate for the distortion due to non-linearity of the PA, and transmitter capability for selective reduction of backoff from maximum allowed output power.

11. The method of claim 10, wherein the indication is sent in response to one of the following: a request by the receiver for transmitter capabilities;transmitter adjustment or change to characteristics of the PA; or transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to non-linearity of the PA.

12. The method of any of claims 10-11, wherein the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types.

13. The method of any of claims 1-12, wherein the backoff is determined based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation.

14. The method of any of claims 1-13, wherein: the information is sent to the receiver in a power headroom report, PHR; the receiver is a base station or is included in a base station; and one of the following applies: the transmitter and the PA are included in a user equipment, UE; or the transmitter is a UE that includes the PA.

15. The method of claim 14, wherein the information sent to the receiver also includes an indication of one or more of the following: the maximum allowed output power of the first transmission; and whether the first transmission is a real transmission or a hypothetical transmission.

16. The method of any of claims 14-15, wherein: the UE is served by a plurality of cells provided by the base station; the first transmission is associated with one or more of the plurality of cells; and the PHR includes the information for one of the following: each of the plurality of cells, or each of the one or more cells associated with the first transmission.

17. The method of any of claims 14-15, wherein: the UE is connected to a plurality of transmission reception points, TRPs, associated with the base station; the first transmission is associated with one or more of the plurality of TRPs; andthe PHR includes the information for one of the following: each of the plurality of TRPs, or each of the one or more TRPs associated with the first transmission.

18. The method of any of claims 14-17, wherein the determined backoff is a maximum power reduction, MPR, and the first amount is a relaxation of the MPR.

19. A method for a receiver configured to receive transmissions from a transmitter, the method comprising: receiving (1540) one or more of the following information from the transmitter: a backoff from a maximum allowed output power for a first transmission by the transmitter, wherein: the first transmission is to be amplified by a power amplifier, PA, and the backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and a first amount by which the transmitter reduced the backoff; and receiving (1550) the first transmission from the transmitter.

20. The method of claim 19, further comprising decoding (1560) the received first transmission using a model that selectively compensates for distortion in the first transmission based on the received information.

21. The method of claim 19, further comprising, based on the received information and the received first transmission, training (1570) a model to compensate for distortion in received transmissions due to non-linearity of the PA.

22. The method of any of claims 20-21, wherein the model is an artificial intelligence / machine learning, AI / ML, model.

23. The method of any of claims 19-22, wherein: the backoff is reduced by the first amount when compensation for the distortion is available; and the backoff is not reduced when compensation for the distortion is unavailable.

24. The method of claim 23, wherein the information received from the transmitter includes the following: when the backoff is reduced, an indication that the transmitter reduced the backoff and the first amount by which the transmitter reduced the backoff; and when the backoff is not reduced, the backoff and an indication that the transmitter did not reduce the backoff.

25. The method of any of claims 19-24, further comprising sending (1520) to the transmitter an indication of a maximum allowable reduction in backoff from a maximum allowed output power, wherein the first amount is between zero and the maximum allowable reduction.

26. The method of claim 25, wherein the maximum allowable reduction is specific to one or more of the following associated with the first transmission: a frequency range; a serving cell; a transmission reception point, TRP, of the receiver; a modulation order; a modulation constellation; and an error-correcting code.

27. The method of claim 25, wherein the maximum allowable reduction is one of a plurality of candidate maximum allowable reductions, wherein the plurality are specific to one or more of the following associated with the first transmission: a frequency range; a serving cell; a transmission reception point, TRP, of the receiver; a modulation order; a modulation constellation; and an error-correcting code.

28. The method of any of claims 19-27, further comprising sending (1530) to the transmitter a notification of activation, deactivation, or model change for receiver compensation of the distortion due to non-linearity of the PA, wherein the information is received in response to the notification.

29. The method of any of claims 19-28, further comprising receiving (1510) from the transmitter an indication of one or more of the following: characteristics of the PA; transmitter capability to compensate for the distortion due to non-linearity of the PA; and transmitter capability for selective reduction of backoff from maximum allowed output power.

30. The method of claim 29, wherein the indication is received in response to one of the following: a request by the receiver for transmitter capabilities; transmitter adjustment or change to characteristics of the PA; or transmitter activation, deactivation, or model change for transmitter compensation of the distortion due to non-linearity of the PA 31. The method of any of claims 29-30, wherein the indicated characteristics of the PA include one or more of the following: amplifier class, bias voltage, signal envelope tracking capability, input / output transfer function, distortion model, relation between output power and distortion, and one of a plurality of predefined PA types.

32. The method of any of claims 19-31, wherein the backoff is based on one or more of the following associated with the first transmission: a modulation order, and a modulation constellation.

33. The method of any of claims 19-32, wherein: the information is received from the transmitter in a power headroom report, PHR; the receiver is a base station or is included in a base station; and one of the following applies: the transmitter and the PA are included in a user equipment, UE; or the transmitter is a UE that includes the PA.

34. The method of claim 33, wherein the information received from the transmitter also includes an indication of one or more of the following: the maximum allowed output power of the first transmission; and whether the first transmission is a real transmission or a hypothetical transmission.

35. The method of any of claims 33-34, wherein: the base station serves the UE via a plurality of cells; the first transmission is associated with one or more of the plurality of cells; and the PHR includes the information for one of the following: each of the plurality of cells, or each of the one or more cells associated with the first transmission.

36. The method of any of claims 33-34, wherein:the base station is connected to the UE via a plurality of transmission reception points, TRPs; the first transmission is associated with one or more of the plurality of TRPs; and the PHR includes the information for one of the following: each of the plurality of TRPs, or each of the one or more TRPs associated with the first transmission.

37. The method of any of claims 33-36, wherein the backoff is a maximum power reduction, MPR, and the first amount is a relaxation of the MPR.

38. A transmitter (105, 210, 721, 1612, 1718) configured to generate transmissions to a receiver (110, 120, 220, 711, 1610, 1800, 1902), the transmitter comprising: communication interface circuitry (1712) configured to communicate with the receiver; and processing circuitry (1702) operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: determine a backoff from a maximum allowed output power for a first transmission, wherein: the first transmission is to be amplified by a power amplifier, PA (1719), and the determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; selectively reduce the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter; and send one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced.

39. The transmitter of claim 38, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the method of any of claims 2-18.

40. A transmitter (105, 210, 721, 1612, 1718) configured to generate transmissions to a receiver (110, 120, 220, 711, 1610, 1800, 1902), the transmitter being further configured to:determine a backoff from a maximum allowed output power for a first transmission, wherein: the first transmission is to be amplified by a power amplifier, PA (722, 1719), and the determined backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; selectively reduce the determined backoff by a first amount, based on whether compensation for the distortion is available at the receiver and / or at the transmitter; and send one or more of the following information to the receiver: the determined backoff, an indication of whether the determined backoff was reduced, and the first amount by which the determined backoff was reduced.

41. The transmitter of claim 39, being further configured to perform operations corresponding to the method of any of claims 2-18.

42. User equipment, UE (105, 210, 720, 1612, 1700) comprising: the transmitter (721, 1718) of any of claims 38-41, and the PA.

43. Non-transitory, computer-readable medium (1710) storing computer-executable instructions that, when executed by processing circuitry (1702) of a transmitter (105, 210, 721, 1612, 1718) configured to generate transmissions to a receiver (110, 120, 220, 711, 1610, 1800, 1902), configure the transmitter to perform operations corresponding to any of the methods of claims 1-19.

44. Computer program product (1714) comprising computer-executable instructions that, when executed by processing circuitry (1702) of a transmitter (105, 210, 721, 1612, 1718) configured to generate transmissions to a receiver (110, 120, 220, 711, 1610, 1800, 1902), configure the transmitter to perform operations corresponding to any of the methods of claims 1- 19.

45. A receiver (110, 120, 220, 711, 1610, 1800, 1902) configured to receive transmissions from a transmitter (105, 210, 721, 1612, 1718), the receiver comprising: communication interface circuitry (1806, 1904) configured to communicate with the transmitter; andprocessing circuitry (1802, 1904) operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: receive one or more of the following information from the transmitter: a backoff from a maximum allowed output power for a first transmission by the transmitter, wherein: the first transmission is to be amplified by a power amplifier, PA (722, 1719), and the backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and a first amount by which the transmitter reduced the backoff; and receive the first transmission from the transmitter.

46. The receiver of claim 45, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the method of any of claims 21-37.

47. A receiver (110, 120, 220, 711, 1610, 1800, 1902) configured to receive transmissions from a transmitter (105, 210, 721, 1612, 1718), the receiver being further configured to: receive one or more of the following information from the transmitter: a backoff from a maximum allowed output power for a first transmission by the transmitter, wherein: the first transmission is to be amplified by a power amplifier, PA (722, 1719), and the backoff is inversely related to an amount of distortion in the first transmission due to non-linearity of the PA; an indication of whether the transmitter reduced the backoff due to availability of compensation for the distortion; and a first amount by which the transmitter reduced the backoff; and receive the first transmission from the transmitter.

48. The receiver of claim 47, being further configured to perform operations corresponding to the method of any of claims 21-37.

49. A base station (710, 1610, 1800, 1902) comprising the receiver (711) of any of claims 45-48.

50. Non-transitory, computer-readable medium (1804, 1904) storing computer-executable instructions that, when executed by processing circuitry (1802, 1904) of a receiver (110, 120, 220, 711, 1610, 1800, 1902) configured to receive transmissions from a transmitter (105, 210, 721, 1612, 1718), configure the receiver to perform operations corresponding to any of the methods of claims 20-37.

51. Computer program product (1804a, 1904a) comprising computer-executable instructions that, when executed by processing circuitry (1802, 1904) of a receiver (110, 120, 220, 711, 1610, 1800, 1902) configured to receive transmissions from a transmitter (105, 210, 721, 1612, 1718), configure the receiver to perform operations corresponding to any of the methods of claims 20-37.

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