Simulations of Low-Density Parity-Check Codes under high-order modulation

Improving the spectral efficiency as far as possible while guaranteeing communication quality by channel coding becomes the development direction of the communication system. This paper studies the application of Low-Density Parity-Check Codes under high-order modulation, which not only considers improving the reliability of communication through the LDPC channel coding, but also taking the effectiveness of communication by using high-order modulation. A detailed analysis is given for two methods of the calculation of initialization information for the LLR-BP algorithm under high-order modulation: component calculation and Euclidean distance calculation. The first method is deduced in detail by taking 16APSK modulation as an example. Finally, simulations are done to verify the decoding performance of LDPC code under high-order modulation. We do the simulations combining with QPSK, 8PSK, and 16APSK. The simulation results demonstrate the feasibility of the first method. The performance of two methods is similar.