Designing Protograph LDPC Codes for Differential Chaotic Bit-Interleaved Coded Modulation System for Underwater Acoustic Communications

Underwater acoustic (UWA) communications face many challenges, such as large multipath delay, severe fading and the time-varying distortions. Chaotic modulations have shown advantages in UWA communications, but reliability of current chaotic is still not guaranteed. In this paper, a short-length protograph low-density parity-check (P-LDPC) code design framework for differential bit-interleaved coded modulation (DC-BICM) system communication proposed. This framework, considering requirements short codes integrates DC-BICM system, channel evolutionary searching algorithm. Through optimized P-LDPC can be obtained. Simulation results show that with proposed obtain more than 0.48 dB coding gain reduce 32.6%~69.5% average number iterations compared counterparts. Moreover, reconstructed underwater image clearest highest peak-signal-noise ratio value when