Channel characteristics dependence of the performance of decoding algorithms for efficient error-control codes

In this paper we study the initialization step of decoding algorithms for efficient error-control coding techniques, and its dependence of the channel characteristics over which transmission is performed. LDPC and Polar codes are selected as efficient error-control codes operating over different channels. Channels under study are the classic Additive White Gaussian noise channel, the Rayleigh fading channel, and the Middleton's Class A impulsive noise channel. An efficient initialization step is performed when the initialization step uses estimates based on the corresponding probability density function of the channel, evaluated for the two possible transmitted signals of a binary transmission. However, real time evaluation of these estimates can be an operation of high complexity. A low complexity alternative decoding strategy is proposed, based on the estimation of square Euclidean distances propagated using antilog operations, in combination with a simple signal amplitude limiter. This low complexity strategy avoids the need of channel characteristics estimation, and results into a reasonable good BER performance, especially for decoding LDPC codes.