Analysis of hard decision and soft decision decoding algorithms of LDPC codes in AWGN

Abstract

This article compares the Bit Error Rate (BER) performance of soft and hard decision decoding algorithms of LDPC codes on AWGN channel at different code rates and Signal to Noise Ratio (SNR) levels. Even though, hard decision decoding algorithm is computationally simple, its BER performance is not appreciable. Devising soft decision decoding algorithms which are simple and good in BER performance requires comparison of probabilistic and log domain methods. Towards this, a code word is generated through modulo(2) addition between message bits and generator matrix. After Binary Phase Shift Keying (BPSK) modulation the AWGN noise is introduced to the modulated code word. BER performance is computed by comparing the message decoded by soft and hard decision algorithms with the transmitted message. The experiment is conducted in MATLAB. Soft decision decoding algorithm in log domain provides better BER performance than hard decision decoding algorithm regardless of the SNR level.