基于波形匹配的星载AIS信号检测

Detection of Satellite-Based AIS Signals Based on Waveform Matching

在星载船舶信号检测的研究中,针对星载AIS系统存在时延和较大多普勒频移问题,提出了基于波形匹配的AIS信号时延频偏联合估计及其译码算法。利用AIS信号序列中的先验信息构造样本信号,通过计算并比较样本信号在不同时延和频偏下与接收信号的相关系数,估计出AIS信号的时延和频偏值,进而估计出AIS信号的码元序列。方法不需要对信号进行解调,简单易于实现。仿真结果表明,上述算法比二比特差分解调具有更好的性能,在相同信噪比下优于二比特差分解调3 d B左右,适用于存在时延和较大多普勒频偏的情况,为星载船舶信号的准确检测提供了有效方法。

Aiming at resolving the problems of the exiting time delay and large Doppler shift,in satellite-based AIS system,this paper concentrates on the technique of symbol estimation of AIS signals and an algorithm based on waveform matching to realize joint estimation of time delay and frequency offset then decoding for AIS signals is proposed. With the symbols that are known and definitive in the sequence of AIS signals we can construct the sample signal,the time delay and the frequency offset of the received AIS signal can be estimated through calculating and comparing the correlation coefficients of the sample signal under different time delay and frequency offset and the received AIS signal,then we can estimate the symbols of the received AIS signal. This method is easy to be realized for the demodulating of the AIS signals. The simulation results show that this method has good performance,which is about3 d B better than the traditional two-bit differential decoding under the same SNR,and it can be applied to the conditions with time delay and large Doppler shift.