Iterative detection for Walsh-Hadamard transformed OFDM

In this paper, an iterative detection method is proposed to reduce the noise enhancement in Walsh-Hadamard transformed (WHT)-OFDM system. The iterative detection starts with conventional detection. The estimation of the received signal at the weakest subcarrier is calculated based on the detection of all data symbols after the hard decision or a combination of hard decision with soft decision, such as utilizing a clipping function. Then the actual received signal at the weakest subcarrier is replaced by the estimated signal and the conventional detection is applied repeatedly to replace the next weakest signal until all subcarriers are replaced. Through replacing the real subcarrier signal with the less noisy estimated signal one by one, iteratively, we can reduce the noise amplification significantly and smoothly. It is seen in the simulations, the bit error rate performance of the iterative detection is much better than that of the conventional detection for either WHT-OFDM system or OFDM system.