Blind Equalization in OFDM Systems Exploiting Guard Interval Redundancy

We introduce a new low-complexity equalizer for OFDM systems, which in the presence of a guard interval, utilizes existing redundancy in the time domain to completely eliminate inter-symbol-interference. We prove that the usage of this guard interval redundancy is sufficient to obtain a zero-forcing time domain equalizer of the channel. The main advantage of this approach resides in its simplicity as the equalizer coefficients are estimated using a second-order least square fitting (LSF). In addition, to fully exploit the data information, we propose to use the previous LSF based equalizer in conjunction with a constant modulus algorithm (CMA). This would help to refine the equalizer estimation, especially for short data lengths, and to improve the system performance. Several implementations are proposed and compared through simulation experiments