An improved frequency offset estimator for OFDM applications

An efficient algorithm has been proposed by Schmidl and Cox (see IEEE Trans. Commun., p.1613-21, 1997) for carrier frequency estimation in orthogonal frequency division multiplexing systems. The scheme is based on the transmission of a training symbol composed of two identical halves in the time domain. Its accuracy is close to the Cramer-Rao bound and its estimation range, which is originally limited to the distance between two adjacent subcarriers, can be widened by exploiting a second training symbol containing some suitable pseudonoise sequence. In this paper we extend this algorithm by considering a training symbol composed of L>2 identical parts. This makes it possible to achieve a better accuracy at the cost of some increase in computational load. Furthermore, the estimation range can be widened in proportion to L without the need of a second training symbol