Digital Post-Distortion for Power Amplifier Non-Linearity
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Solution Overview
Problem
Wireless communication systems face inefficiencies due to power back-off (BO) to avoid distortion from high power amplifiers (HPAs) with limited linear dynamic range, leading to reduced transmit power and increased delays and latency.
Innovation Solution
Implementing high-order digital post-distortion (DPoD) procedures at user equipment (UE) using updated power amplifier (PA) models and non-linear equalizer functions signaled by the base station, allowing efficient estimation and removal of distortion components from received signals without violating error vector magnitude (EVM) limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power back-off is applied to avoid distortion from high power amplifiers, then transmit power is reduced, but system efficiency and throughput deteriorate
Solution Approach 1:
The patent converts the harmful distortion effect of operating HPAs in non-linear regions into a beneficial signal component that can be removed through digital post-distortion processing. By intentionally allowing the HPA to operate in non-linear regions and then compensating for the distortion digitally, the system achieves higher transmit power without sacrificing signal quality, thereby resolving the contradiction between reliability and productivity
2Reliability
If power back-off is applied to avoid distortion, then transmit power is reduced, but transmission speed and latency worsen
Solution Approach 1:
The digital post-distortion technique converts the harmful distortion into a removable artifact, allowing the system to operate at higher powers without compromising signal quality. This eliminates the need for conservative power back-off, thereby reducing transmission time and latency while maintaining reliability
3Measurement precision
If PA model parameters are updated frequently to adapt to temperature and beam changes, then distortion compensation accuracy is improved, but signaling overhead and processing complexity increase
Solution Approach 1:
The patent pre-calculates and stores multiple PA models corresponding to different operating conditions (temperature, beam) before actual transmission. When conditions change, the system simply selects the pre-prepared appropriate model rather than performing complex real-time calculations, thereby maintaining high distortion estimation accuracy while reducing processing complexity and signaling overhead
Solution Approach 2:
The system dynamically adapts to changing operating conditions by selecting from multiple pre-configured PA models based on current temperature and beam states. This dynamic model selection mechanism maintains accurate distortion compensation without requiring frequent complex model updates, thus resolving the contradiction between precision and complexity
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Generally, a base station may indicate, to a user equipment (UE), when it changes a power amplifier (PA) non-linearity model. The base station may transmit a set of parameters for the PA model, and a set of parameters for a non-linear equalizer function for the UE to use during a digital post-processing procedure (DPoD). The base station may indicate, to the UE, a lookup table, a vector of lookup tales, a set of kernels (e.g., from which the UE may estimate the coefficients of the PA model), or a set of both the kernels and the coefficients for the PA model. Similarly, for the non-linear equalizer function, the base station may indicate an explicit indication of the function, or may indicate a lookup table, or a kernels series (e.g., with or without corresponding coefficients).