The Research of G-function Decoding Method for DFH System Based on State Trellis

Differential frequency hopping (DFH) was introduced as a new technology for reliable high data rate transmission in high frequency (HF) bands. However, traditional G-function decoding method is based on frequency trellis (FT-Viterbi) and its bit error rate (BER) performance depends on the minimum free distance (d_free) of frequency trellis. When reducing which is the number of available frequency choices, the (d_free) will reduce, causing a sharp decline in the system BER performance. In view of the disadvantage of the traditional G function decoding method, a G-function decoding method based on status trellis (ST-Viterbi) and a new general design method for G function are presented in this paper. The results of theoretical analysis and simulation show that when reducing, ST-Viterbi was better than FT-Viterbi in the system BER performance. At a BER of 9×10^-3, when M is 32, ST-Viterbi is more than FT-Viterbi 0.6dB SNR gain, when M is 16, ST-Viterbi is more than FT-Viterbi 1dB SNR gain.