Multilevel modulation codes for Rayleigh fading channels

Abstract

In this paper, new multilevel modulation codes with good error rate performance on the Rayleigh fading channel are presented. It has been demonstrated that the error performance of a multilevel block code is dominated by the minimum Hamming distance of the component codes when ideal interleaving is applied. BCH codes are often used in constructing multilevel codes due to their good Hamming distance properties. Since the error performances for various levels of the MPSK signals are different, component codes have to be chosen appropriately so that their error correcting capabilities suit the required error protection for each level. All the codes reported in this paper are 8-PSK modulation codes. The bit error rate performances of these codes obtained by Monte Carlo simulations are compared to those of Ungerboeck codes and the existing block modulation codes. They show a large bit error rate improvement at the same bandwidth efficiency and the same decoding complexity. Multistage soft decision decoding based on Viterbi algorithm is employed since it gives more options in code construction. Comparison results with the maximum likelihood Viterbi decoding based on full code trellis show only a slight degradation of multistage decoding.