Compander Design Using Constrained Optimization for OFDM PAPR Reduction

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Solution Overview

Problem

Current OFDM systems face challenges in reducing peak-to-average power ratio (PAPR) due to heavy-tailed Rayleigh distributed signal amplitudes, which lead to signal distortion and demodulation errors, and existing companders either introduce significant distortion or fail to minimize the original distribution.

Innovation Solution

A constrained optimization approach using Lagrange multipliers is employed to derive companders that compress and expand OFDM signals, minimizing distortion by decomposing the Rayleigh amplitude distribution into disjoint regions with piecewise linear amplitude weighting functions, ensuring minimal perturbation and maintaining constant power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If companders apply amplitude weighting to downweight large amplitude values, then PAPR is reduced, but signal distortion is introduced

Engineering Contradiction:

ImprovePAPRVSAvoidsignal distortion

Core Design Contradiction:

Loss of energyVSLoss of information

Solution Approach 1:

The amplitude distribution is decomposed into disjoint regions over which different amplitude weighting functions are used. This segmentation allows the compander to apply different weighting strategies to different parts of the signal distribution, reducing overall distortion while maintaining PAPR reduction benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different amplitude weighting functions are applied to different regions of the amplitude distribution. By tailoring the weighting function to local characteristics of the signal, the compander minimizes distortion in each region while collectively achieving PAPR reduction across the entire signal.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If existing companders transform the Rayleigh amplitude distribution, then PAPR is reduced, but the original distribution is significantly altered

Engineering Contradiction:

ImprovePAPRVSAvoidoriginal distribution

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The compander applies partial transformation to the Rayleigh amplitude distribution by using piecewise linear functions that only modify specific regions. This partial action approach reduces PAPR while minimizing perturbation to the overall distribution shape, preserving more of the original signal characteristics.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of manufacture

If piecewise linear transformations are used to compand the signal, then implementation is simplified, but distortion increases compared to optimal transformations

Engineering Contradiction:

Improveimplementation complexityVSAvoidsignal distortion

Core Design Contradiction:

Ease of manufactureVSLoss of information

Solution Approach 1:

The transformation function is divided into multiple linear segments that approximate the optimal transformation. By increasing the number of segments, the piecewise linear function can more closely follow the optimal curve, reducing distortion while maintaining the implementation simplicity of linear segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The parameters of the piecewise linear function (segment boundaries, slopes, and intercepts) are optimized to minimize distortion. By carefully selecting these parameters, the piecewise linear transformation achieves performance closer to optimal transformations while retaining implementation simplicity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9537697B2Constrained optimization approach to compander design for OFDM PAPR reduction

Publication Date: 2017.01.03 BAE SYSTEMS INFORMATION ANDELECTRONIC SYSTEMS INTEGRATION INC

AI summary

In the method for constrained optimization for compander design for OFDM PAPR, wherein the improvement comprises the step of converting a Rayleigh amplitude distribution from which superior performing companders are derived, whereby a constrained optimization problem may be solved using Lagrange multipliers.