Performance of Iterative Soft Output Viterbi Algorithm (SOVA) Decoder on Turbo Coding under Fading Channel

Classical turbo coding base on Parallel Concatenated Convolutional Code has been used for forward error correcting (FEC). From some research reports [1,2,3,5] this technique show new hope to get the coding technique at near Shanon limitation. This paper explains how SOVA decoder works on classical turbo coding. Performance analysis of SOVA decoder is observed by measure the number of bit error (BER). The simulation is set up under Rayleigh Fading channel, where two types Rayleigh fading generation are considered, that are correlated and uncorrelated Rayleigh fading. Simulation parameters to evaluate the decoder performance are signal to noise ratio (Eb/No), frame size, code rate, and number of iteration. In this paper the effect of additional interleaver to interleave the code word on BER also discussed. From simulation, we found that increasing number of iteration not much helpful in the low region of Eb/No. In the middle to high region (Eb/No > 3 dB) the performance of SOVA decoder improve drastically. Increasing frame size it will produce larger distance by using an interleaver, and resulting a better decoder performance. Increasing the parity check bit also increases the decoder performance significantly, but consequently the requirement bandwidth also increases.