Designing Protograph-Based LDPC Codes for Iterative Receivers on ${M}$ -ary DCSK Systems

In this brief, protograph-based low density parity check (P-LDPC) codes, which have simple structure and excellent error-correction capability, are designed for iterative receivers (IRs) on ${M}$ -ary differential chaos shift keying ( ${M}$ -ary DCSK) systems. Due to the non-periodic and random characteristics of chaos carriers and their interaction with soft information, the conventional optimal P-LDPC codes over Bi-AWGN channels in the tandem mode may not perform well in ${M}$ -ary DCSK systems with IR. With the help of a finite-length extrinsic information transfer (EXIT) algorithm, the convergence of IR is analyzed, by which a new design principle is proposed to construct new P-LDPC codes for the ${M}$ -ary DCSK systems. Both EXIT analysis and simulated results demonstrate the superiority of the proposed P-LDPC codes.