Delay-tolerant equalization for OFDM and other block-based systems

Orthogonal frequency division multiplex (OFDM) and other block-based systems have been widely used in wireless and wired communications. To combat frequency selectivity of channel, such systems usually adds a cyclic prefix (CP) or zero-padding (ZP) into every block. In conventional equalization, the receiver discards the CP first and then implements the fast Fourier transform (FFT) and divides the output by the frequency domain channel. In practice the received signals usually has timing errors, which makes the conventional equalization unreliable. In this paper, we propose a new equalization method called "delay-tolerant equalization", which either discarding the CP or discarding the last Ng symbols of every block, where Ng is the length of the CP. Furthermore, practical "tuning processes" are proposed that use the existing preambles. Theoretic analysis and simulation show that the new method is much better than the conventional method when random time synchronization error exists.