OFDM Nonlinear Compensation Fusion for PA Distortion and Sampling Limits

Solution Overview

Problem

Existing OFDM systems face challenges in reducing the sampling rate requirement for ADC/DAC and improving DPD compensation for power amplifier nonlinearity, leading to increased hardware and algorithm complexity and cost due to the cascade arrangement of CFR and DPD modules.

Innovation Solution

A nonlinear compensation fusion model comprising a BL-DPD module, BL-CFR module, and error compensation module, connected in parallel, performs separate compensations to reduce nonlinear distortion, with parameter extraction and update mechanisms in offline and online modes using LNVSS-LMS and SEVSS-LMS algorithms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the power amplifier is placed near the saturation point to improve efficiency, then the efficiency of the power amplifier is improved, but serious in-band distortion is caused and the bit error rate increases

Engineering Contradiction:

Improvepower amplifier efficiencyVSAvoidbit error rate

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies digital pre-distortion technology to pre-compensate the OFDM signal before it enters the power amplifier. By introducing a distortion compensation model that predicts and corrects nonlinear distortion in advance, the system enables the power amplifier to operate near saturation while maintaining signal linearity and reducing bit error rate.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements an iterative feedback mechanism where the output signal from the power amplifier is fed back to update and refine the distortion compensation model parameters. This closed-loop approach continuously optimizes the pre-distortion coefficients to adapt to changing channel conditions and amplifier characteristics, improving both efficiency and reliability.

Inventive Principle:

Principle #23Feedback

2Use of energy by moving object

If the power amplifier is placed near the saturation point to improve efficiency, then the efficiency of the power amplifier is improved, but out-of-band spectrum spread occurs and adjacent channels are interfered with

Engineering Contradiction:

Improvepower amplifier efficiencyVSAvoidout-of-band spectrum spread

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies digital pre-distortion technology to pre-compensate the OFDM signal before it enters the power amplifier. By introducing a distortion compensation model that predicts and corrects nonlinear distortion in advance, the system enables the power amplifier to operate near saturation while maintaining signal linearity and reducing bit error rate.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements an iterative feedback mechanism where the output signal from the power amplifier is fed back to update and refine the distortion compensation model parameters. This closed-loop approach continuously optimizes the pre-distortion coefficients to adapt to changing channel conditions and amplifier characteristics, improving both efficiency and reliability.

Inventive Principle:

Principle #23Feedback

3Reliability

If the cascade mode of CFR module and DPD module is used, then the efficiency and linearity are improved, but the requirement for ADC/DAC sampling rate is raised and system implementation difficulty increases

Engineering Contradiction:

Improvelinearity indexVSAvoidsystem implementation difficulty

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the CFR (crest factor reduction) and DPD (digital pre-distortion) functions into a unified distortion compensation model. By combining these two separate modules into one integrated system, the patent reduces the overall complexity while maintaining the benefits of both peak power reduction and nonlinear distortion compensation, thereby lowering the ADC/DAC sampling rate requirement.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent creates a multi-functional distortion compensation model that simultaneously performs crest factor reduction and pre-distortion compensation. This universal model handles multiple functions within a single framework, reducing hardware requirements and simplifying system implementation while improving both efficiency and linearity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250343717A1Method for compensating for nonlinear distortion of signal, model, and communication system

Publication Date: 2025.11.06 CHONGQING SATELITE NETWORK SYSTEM CO LTD

AI summary

A method for compensating for nonlinear distortion of a signal, a model, and a communication system are disclosed. Based on a preset nonlinear compensation fusion model, digital pre-distortion (DPD), crest factor reduction (CFR) and error compensation are separately performed on an initial orthogonal frequency division multiplexing (OFDM) signal, and an initial OFDM signal after nonlinear distortion compensation is obtained accordingly. The nonlinear compensation fusion model may include a band limited-digital pre-distortion (BL-DPD) module, a band limited-crest factor reduction (BL-CFR) module and an error compensation module.