PA-Aware Modulation and DPD for Nonlinear Distortion Compensation
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Solution Overview
Problem
Conventional modulation methods in wireless communication systems are impaired by distortion effects caused by power amplifier (PA) amplification due to the input-output PA characteristic, which introduces nonlinear and memory effects, leading to smearing of modulation symbols and erroneous demodulation.
Innovation Solution
Implementing a modulation scheme that adjusts symbol constellations and uses digital pre-distortion (DPD) to pre-compensate for PA distortion, where the adjusted symbol constellation and DPD work together to minimize the difference between transmission symbols and a scaled version of the target constellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional modulation methods are used with PA amplification, then signal transmission is achieved, but distortion effects occur due to nonlinear and memory effects of the PA
Solution Approach 1:
The patent applies preliminary anti-action by adjusting the symbol constellation before transmission to pre-compensate for the expected PA distortion effects. The constellation points are modified in advance based on the PA's nonlinear and memory characteristics, so that after passing through the PA, the distorted symbols still map correctly to the intended data bits, thereby counteracting the distortion before it degrades demodulation accuracy
Solution Approach 2:
The patent implements preliminary action by performing constellation adjustment prior to modulation and transmission. The system pre-calculates and applies compensation factors to the constellation points based on the PA's characteristics, ensuring that the transmitted symbols are already optimized to withstand the upcoming distortion, rather than attempting correction after distortion occurs
2Use of energy by moving object
If the PA operates in nonlinear region to increase power efficiency, then power consumption is reduced, but symbol smearing increases leading to demodulation errors
Solution Approach 1:
The patent applies parameter changes by modifying the constellation parameters (amplitude and phase of constellation points) based on the PA's operating characteristics. When the PA operates in nonlinear region for higher efficiency, the constellation parameters are adjusted to account for the resulting distortion, allowing the system to maintain both high power efficiency and reliable demodulation by adapting the modulation parameters to the PA's state
Data Source
AI summary
Methods and apparatuses for dynamically adjusting parameters of a modulation scheme and parameters of a digital pre-distorter (DPD) to pre-compensate for distortion effects of a power amplifier (PA). A user equipment (UE) comprises a modulator configured to generate modulation symbols from input bits according to an adjusted symbol constellation, a DPD operably configured to generate pre-distorted symbols, and a PA configured to amplify the pre-distorted symbols to generate transmission symbols that include distortion effects of the PA. The adjusted symbol constellation is adjusted from a target symbol constellation such that the generated modulation symbols pre-compensate for the distortion effects. The DPD is further configured to generate the pre-distorted symbols from the modulation symbols using a pre-distortion function to further pre-compensate for the distortion effects, and update the pre-distortion function such that a difference between the transmission symbols and a scaled version of the target symbol constellation is reduced.