Joint Time Domain Decoding and Equalization for Time Reversal-Space Time Block Coded Systems

We propose a practical adaptive equalizer structure for space-time block coded systems operating over frequency selective fading channels. Specifically, we develop a time domain block equalizer for time reversal-space time block coded transceivers, which eliminates the need for a separate decoding block requiring explicit channel estimation. The block equalizer length is also independent of the data block length, making it particularly suitable for short delay spread channels. We develop new normalized least mean square (NLMS) and recursive least squares (RLS) adaptive algorithms for this block structure. We use computer simulations to compare our new equalizer with an existing frequency domain equalizer. We show that our time domain equalizer requires far fewer equalizer taps, and our equalizer running the RLS algorithm outperforms in terms of both dynamic convergence behavior and symbol error rate performance. Using the flexibility of the new equalizer, we finally show that a frame structure evenly distributing the training among the blocks yields better performance for fast time-varying channels than frame structures that are constrained by frequency domain equalization.