Improved Reliability Information for Rectangular 16-QAM over Flat Rayleigh Fading Channels

Reliability information derived from the channel output in the form of a Log Likelihood Ratio or a Distance Metric (DM) have been proposed in literature for M-ary Quadrature Amplitude Modulation systems. Reliable soft information from the channel output improves the performance of the forward error correction decoding algorithm. This paper proposes an improved method of extracting reliability information in the form of a DM for rectangular 16-QAM over flat Rayleigh fading channels. The reliability information is obtained from the derived Scaled Channel State Information (CSI), and the estimated CSI which result due to variations in the Rayleigh fading channel gain. The Koetter and Vardy, Reed-Solomon (KV-RS) algebraic soft-decision decoding algorithm is used to verify the performance of this proposed method. The performance of this proposed method is documented through computer simulation. From the simulation results, the proposed method achieves significant improvement in Codeword Error Rate (CER) performance in comparison with the conventional DM method in literature with no additional computational time complexity.