Blind estimation of phase offset in OFDM subcarrier for coherent demodulation

Abstract

Abstract: An adaptive algorithm named low complexity phase off-set estimation (LC-POE) is proposed for orthogonal frequency divi-sion multiplexing (OFDM) signals. Depending on the requirement,the estimation procedure is divided into several scales to accel-erate the adaptive convergence speed and ensure the estimationaccuracy. The true phase offset is estimated through shrinking thedetection range and raising the resolution scale step by step. Boththe convergence performance and complexity are discussed in thepaper. Simulation results show the effectiveness of the proposedalgorithm. The LC-POE algorithm is promising in the application ofOFDM systems. Keywords: phase offset estimation (POE), coherent receiver,adaptive phase recovery, orthogonal frequency division multiplex-ing (OFDM). DOI: 10.1109/JSEE.2012.00060 1. Introduction Although orthogonal frequency division multiplexing(OFDM) has been extensively studied, its sensitivity tosynchronization errors is still a bottleneck in practicalOFDM systems [1, 2].Many algorithms have been proposed to estimate thecarrier phase offset in literature. Decision directedis a general method used in the phase offset estima-tion (POE), which utilizes the error signal between theoutput of equalizer and corresponding decision [3, 4].However, an inherent problem of this method is theconsiderable self-noise due to erroneous decisions, es-pecially in the low signal-to-noise ratio (SNR) situ-ation [5]. A blind estimation algorithm of carrier phaseoffsets in quadrature amplitude modulation (QAM) sig-nals was proposed in [6], which was based on the