Adaptive RC QC-LDPC channel coding for frequency hopping shallow water acoustic communication

Shallow water acoustic (SWA) channels are fast varying spatially and temporarily according to environmental conditions. Adaptive coding is appealing for SWA communications to improve the system efficiency by matching transmission parameters to channel variations. In this paper, we construct rate-compatible QC-LDPC (RC QC-LDPC) codes by extending information bits in frequency hopping (FH) SWA communication system. Combining actual channel impulse response measurement in Quangang Xiaocuo harbor, Fujian and Wuyuan bay, Xiamen, we build two SWA channels, and analyze the performances of RC QC-LDPC codes under different channel environment in FH-SWA communication system. Simulation results show that RC QC-LDPC codes can greatly reduce the bit error rate (BER) of the communication system, improve the system performance; The lower the code rate, the better the BER; The harsher the channel (such as longer channel delay, more multipath, lower signal-to-noise ratio), the lower the code rate is needed to meet system communication indicators; And look-up table of RC QC-LDPC code rate to meet communication performance indicator in FH-SWA system under different signal-to-noise ratio is given. The look-up table also calculates the data saving rate of RC QC-LDPC codes relative to 1/2 code rate. RC QC-LDPC codes in FH-SWA communication system can improve channel utilization, with flexible encoding and decoding, has good prospects in SWA communication.