An improved frequency offset estimator for SIMO-OFDM with maximum estimation range

We consider the problem of estimating the carrier frequency offset (CFO) for orthogonal frequency division multiplexing (OFDM) in single-input multiple-output (SIMO) systems. Most of the existing time-domain CFO estimators for SIMO-OFDM rely on the absolute phase of the correlation sum rather than the phase difference, hence their estimation ranges are generally limited. Extending the range simply by shortening the pilot symbols will degrade the accuracy. In this paper, we propose a new CFO estimator with the estimation range extended to its maximum without sacrificing the accuracy. The nonlinear least-squares (NLS) concept in conjunction with the summation-by-parts formula are used in the derivation. Simulation results show that the performance of the proposed estimator, in static channels, attains the Cramer-Rao Bound (CRB) even at a signal-to-noise ratio (SNR) as low as 0 dB with a large estimation range. In time-varying channels, the performance can be enhanced and be made close to the CRB by exploiting the receive antenna diversity.