A novel carrier estimation algorithm for OFDM communication systems

Abstract

A new pilot assisted (PA) carrier frequency offset (CFO) estimation algorithm for OFDM communication system is presented in this paper. This algorithm extends the principle of the discrete Fourier transform (DFT) based single carrier frequency estimation algorithm in S. Reisenfeld and E. Aboutanios (2003). The proposed algorithm comprises of two steps, first a coarse CFO estimator such as the one presented in M. Li and W. Zhang (2003) is employed to estimate the integer component of the CFO. Assuming frequency corresponding to the DFT bin number which is the integer component of the CFO has been estimated correctly, the residue CFO will be bounded between -0.5TU to 0.5TU, where TU is the OFDM symbol period. In this paper, a new fractional frequency estimation algorithm is presented. Unlike the fractional frequency estimation algorithm presented in M. Li and W. Zhang (2003) and P.H. Moose (1994), this estimator can estimate the frequency offset on a symbol by symbol bases which is ideal for environments where the channel characteristics change rapidly. It will be shown that under additive white Gaussian noise (AWGN), the proposed frequency estimation algorithm has a variance performance that approaches the Cramer Rao lower bound (CRLB) at high signal to noise ratio (SNR) and has an acquisition range of -0.5TU to 0.5T U Hz