Blind SOS subspace channel estimation and equalization techniques exploiting spatial diversity in OFDM systems

In this paper, we present second-order-statistics (SOS) subspace-based blind channel estimation techniques, which exploit the receive antenna diversity in each of the following situations: cyclic prefix-OFDM (CP-OFDM), zero padded-OFDM (ZP-OFDM), and bandwidth efficient-OFDM (BWE-OFDM) systems. We also propose a number of combinations of pre-FFT equalizer, post-FFT equalizer, zero-forcing (ZF) equalizer, and minimum-mean-square-error (MMSE) equalizer. For any number of receive antennas, the pre-FFT equalizers require only one FFT at the receiver. As a result, a considerable reduction in hardware complexity and power saving may be obtained especially for systems with higher number of sub-carriers. In contrast, post-FFT equalizers result in considerable reduction in processing complexity at the cost of one FFT for each antenna. Adaptive linear-complexity implementations of the proposed receivers are considered, along with some modifications in the presence of null side carriers. The effectiveness of the new techniques is demonstrated through simulations. [Copyright &y& Elsevier]