Adaptive Decoding and Equalization for Time Reversal-Space Time Block-Coded Cooperative Diversity Systems

We develop a practical adaptive equalizer structure for time reversal-space time block-coded amplify-and-forward relaying systems, which eliminates the need for a separate decoding block requiring explicit channel estimation. The adaptive equalizer length is also independent of the data block length, making it particularly suitable for frequency selective fading channels with short delay spreads. We derive the minimum mean square error (MMSE) solution and, using the resulting structure, we develop a block recursive least squares (RLS) adaptive algorithm. We use computer simulations to compare two new adaptive equalizer structures for an amplify-and-forward relay network based on Protocols I and III proposed by Nabar et al. We show that both adaptive equalizers work well, but the equalizer tailored for Protocol I outperforms that for Protocol III.