A frequency acquisition scheme for OFDM systems

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 by Moose (see IEEE Trans. Commun., vol.42, no.10, p.2908-14, 1994), 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 a multipath channel, 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