Maximum-likelihood estimation of frequency and time offsets in OFDM systems with multiple sets of identical data

Abstract

This paper generalizes the existing algorithm for the maximum-likelihood (NIL) estimation of frequency and time offsets in orthogonal frequency-division multiplexing (OFDM) systems using from two sets to multiple sets of identical data. The algorithm is derived by the application of the matrix inversion lemma; the Cramer-Rao bound for estimation of the frequency offset is also obtained. For reducing realization complexity, a simplified algorithm is developed. Simulations using the ten sets of identical data in the preamble of IEEE 802.11a for estimation of frequency and time offsets have been performed to verify the effectiveness of the proposed algorithms.