Joint LDPC-DQPSK iteration system for underwater acoustic communications

To reduce inter-symbol-interference (ISI) in underwater acoustic channels, a communication system based on joint LDPC-DQPSK iterative detection was proposed. Spread spectrum technology was adopted to increase communication distance and to combat multi-path effect. Joint LDPC-DQPSK iteration is essentially a joint demodulation and decoding iterative detection based on Turbo principle. To verify BER performance of proposed system, simulation experiments over typical underwater acoustic channels were carried out. Experiment results show that proposed system outperforms conventional systems. Proposed system with four rounds of joint iterations can obtain 3.5 dB SNR gains compared with conventional systems at BER of 10^-4.