VDES中ASM信号频偏估计算法研究

甚高频数据交换系统(VDES)是新一代船舶通信系统,由于卫星和船舶的移动,信号中存在多普勒频移,要完成信号的解调,必须对其多普勒频率进行精确地估计和抵消。为此,针对VDES中的特定应用消息(ASM)信号的频偏估计问题,基于M&M算法,提出了一种两步估计算法,先做范围较大,精度较低的粗频偏估计,再做范围较小,但精度较高的细频偏估计。仿真结果表明,两步估计算法的总估计范围为原始算法的两倍,并且具有较高的估计精度,在Eb/N0>4 dB后,归一化频偏估计的均方误差小于10^-4。

Research on ASM signal frequency estimation algorithm in VDES

VHF data exchange system(VDES) is a new-generation ship communication system. Due to the movement of satellites and ships, there is Doppler frequency offset in the signal. To demodulate the signal, the Doppler frequency must be accurately estimated and eliminated. Based on the M&M algorithm, a two-step estimation algorithm is proposed for the frequency offset estimation of the specific application message(ASM) signal in VDES. First, make a rough frequency offset estimation with a larger range and lower precision, and then make an accurate frequency offset estimation with a smaller range but higher precision. The simulation results show that its estimation range is twice that of the original algorithm and has high estimation precision. When Eb/N0>4 dB, the mean square error of the normalized frequency offset estimation is less than 10^-4.