OFDM Symbol Synchronization Using Frequency Domain Pilots in Time Domain

In this paper, we describe and evaluate a novel symbol synchronization algorithm for Orthogonal Frequency Division Multiplexing (OFDM) systems especially suited for channels with very long echoes. Most of the OFDM based standards provide known pilots in the frequency domain for channel estimation purposes. The basic idea of our contribution consists of interpreting the frequency domain pilots in the time domain to obtain a rough channel estimate before performing the discrete Fourier transform (DFT) and use it to properly position the DFT window. The proposed method aims to maximize the signal-to-inter-block-interference ratio after the DFT windowing. In short channels, where the channel length is shorter than the cyclic prefix length, the proposed method looks for an inter-block-interference free windowing of the OFDM symbol. In long channels, where the channel length is longer than the cyclic prefix of the OFDM symbol, the proposed method search for the minimum inter-block-interference power windowing of the OFDM symbol.