Hard-Decision Aided Stopping Criterion Analysis in High Rate Modulation System

Hard-decision aided (HDA) method is used effectively as the stopping criterion in iterative turbo decoding. It inspects the sign of decoded bits between two successive iterations and stops the process when the sign does not change. Typically, a low rate modulation technique such as binary phase-shift keying is utilised to gauge the HDA performance. Thus, this paper investigates its average iteration number (AIN) and bit error rate (BER) performances under high rate quadrature amplitude modulation in an additive white Gaussian noise. HDA performance studies were simulated under four scenarios; a) varying turbo code generators, 2) varying turbo code rates, 3) varying modulation sizes, and 4) varying frame sizes. The results show that the HDA stopping criterion is well-performed at low SNR and high SNR, however, the criterion iterates to maximum iteration at medium SNR. Interestingly, its BER performances are maintained as the fixed stopping criterion.