Nonlinear Channel Estimation for OFDM System by Wavelet Transform Based Weighted TSVR

Lidong Wang,Xin Deng,Yang Cui,Xuebo Chen,Chuang Gao

doi:10.1109/access.2019.2962702

Abstract

An efficient nonlinear channel estimation method for pilot-aided orthogonal frequency division multiplexing system is proposed in this work. The considered channel is selective in time and frequency domain, that is doubly selective channel. Wavelet transform based weighted twin support vector regression is used for channel frequency response estimation, which is suitable for the regression of nonlinear system. Different from traditional support vector regression algorithm, the proposed algorithm gives samples different weights according to their variance calculated based on wavelet transform. The weights are added into both first and quadratic terms of the objective functions to reduce the impact of outliers, which is likely to appear in the received pilot signal polluted by noise. The proposed channel estimation algorithm has good generalization ability and can reduce the influence of overfitting problem. The results of computational tests show that the proposed algorithm is with better estimating performance compared to the classical pilot-aided channel estimation methods.

Highlights

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technology, which has high spectral efficiency and simple single tap equalizer structure
The improved twin SVR (TSVR) channel estimation method is proposed for the first time to estimate wireless channel parameters in OFDM system, performance of which is better than traditional estimation algorithm such as linear minimum mean square error (LMMSE), discrete Fourier transform (DFT)-based and basis expansion model (BEM)-based algorithms
EXPERIMENTAL RESULTS some simulation results of the proposed channel estimation algorithm based on the novel wavelet transform based weighted TSVR (WTWTSVR) will be shown

Summary

INTRODUCTION

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technology, which has high spectral efficiency and simple single tap equalizer structure. In 2010, the twin SVR (TSVR) was proposed by Peng [27] It is with high computational speed because it only solves two small-scale quadratic programming problems (QPPs). A novel nonlinear fading channel estimation in OFDM systems is proposed, which is based on wavelet transform based weighted TSVR (WTWTSVR). 1. The improved TSVR channel estimation method is proposed for the first time to estimate wireless channel parameters in OFDM system, performance of which is better than traditional estimation algorithm such as LMMSE, DFT-based and BEM-based algorithms. Due to the time-frequency characteristics of wavelet transform, the proposed algorithm is suitable for the processing of time sequence samples such as channel parameter estimation.

SYSTEM MODEL

CHANNEL ESTIMATION ALGORITHM-WAVELET

ACQUISITION OF TRAINING SAMPLES

SUMMARY OF THE ALGORITHM AND COMPUTATIONAL COMPLEXITY ANALYSIS

EXPERIMENTAL RESULTS

CONCLUSION