Improved reliability information for OFDM systems on time-varying frequency-selective fading channels

Recently, soft reliability information derived from the Channel State Information (CSI) using Distance Metric (DM) method was shown to improve the performance of rectangular M-ary Quadrature Amplitude Modulation (M-QAM) systems over flat Rayleigh fading channels. In this paper, we extend this method to Orthogonal Frequency Division Multiplexing (OFDM) systems on time-varying frequency-selective Rayleigh fading channels. In particular, we derive the soft reliability information from the frequency domain CSI. The performance of the OFDM system is verified using the Koetter and Vardy, Reed-Solomon (KV-RS) algebraic soft decision decoding algorithm. We compare the Codeword Error Rate (CER) performance of the OFDM system with 16-QAM as the modulation schemes. In addition, the OFDM system performance is documented for different values of normalized Doppler frequency, and frame length size. From the computer simulation results, the proposed method offers superior CER performance in comparison with the conventionally used DM method in the literature with no significant increase in computational time complexity.