Performance analysis of weighted nonbinary repeat multiple-accumulate codes

In this work, we consider weighted nonbinary repeat multiple-accumulate (WNRMA) code ensembles formed by the serial concatenation of a repetition code with multiple accumulators, where each encoder is followed by a nonbinary weighter. The WNRMA codes are assumed to be iteratively decoded using the turbo principle with maximum a posteriori constituent decoders. We give approximate weight enumerators for WNRMA code ensembles and show numerically that their symbol-wise minimum distance asymptotically grows linearly with the block length for the considered values of the repetition factor n and the field size q. Thus, WNRMA code ensembles are asymptotically good. Finally, we give iterative decoding thresholds, computed by an extrinsic information transfer chart analysis, and some simulation results on the q-ary symmetric channel to show the convergence properties.