Blind equalization and frequency offset estimation in OFDM systems exploiting guard interval redundancy

Abstract

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 intersymbol-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 equalizer is then adapted to take into account the frequency offset and hence allows the joint mitigation of the ISI and frequency offset effects.