On the performance of concatenated space-frequency block coding for OFDM systems

In this paper, we analyze the performance of the optimal maximum likelihood (ML) receiver for a concatenated space-frequency block coded orthogonal frequency division multiplexing (CSFBC-OFDM) system over frequency-selective Rayleigh fading channels. First, we derive a simple expression to approximate the theoretical BER performance of the optimal ML receiver for CSFBC-OFDM systems. The accuracy of the derived theoretical BER expression is verified through performance comparisons with a Turbo-based maximum aposteriori (MAP) demodulator which is known to achieve near optimal performances. Next, we use the theoretical BER performance of the ML receiver to study the 'optimality' of a low complexity multi-stage iterative QR decomposition based successive interference cancellation (QR-SIC) receiver proposed previously. Our results show that the performance of the QR-SIC receiver can approach the optimal ML performance at high signal to noise ratios. In addition, we also demonstrate, via simulations, that the QR-SIC receiver performs reasonably close to the computationally more complex MAP demodulator at higher iterations.