A frequency acquisition scheme for OFDM systems

Abstract

This paper derives a frequency acquisition algorithm for orthogonal frequency division multiplexing (OFDM) systems. This frequency acquisition algorithm is a modification of the frequency tracking algorithm introduced in [1], which uses a repeated data symbol and a maximum likelihood estimation (MLE) algorithm to estimate the frequency offset. The estimate is extremely accurate but the acquisition range is limited to +/-1/2 of the intercarrier spacing. With some modifications of the frequency tracking scheme and an assumption of the multipath channel introduced in this paper, the frequency acquisition can be converted to an analogous PN sequence acquisition problem. Therefore, a partial-sum correlator with an appropriate threshold can be used to acquire the frequency offset.