A Method to Improve Performance of Turbo Iterative Decoding in Low SNR Region

As far as a Turbo decoder is concerned, the lower Bit Err Rate (BER) at the expense of acceptable and feasible complexity, the better. In this paper, a method is proposed which employs additional redundant sequence added at the end of tail bits of an information sequence to improve performance of a Turbo decoder. Computer simulation results show that, when L=L´=1024, where L is the length of information sequence and L´ the length of redundant sequence, the method obtained about 0.45dB at BER=10^-3 and about 0.35dB at BER=10^-4 respectively compared to the case of L=1024 without redundancies, and also about 0.3dB at BER=10^-3 and about 0.1dB at BER=10-4 compared to the case of L=2048 without redundancies. It is superior to these two cases until Sinal to Noise Ratio (SNR)=0.9dB with moderate extra expenses.