中文摘要：

在星载AIS接收机中，船舶信号在传输过程中产生的大范围时延和多普勒频移，给正确解码带来了困难。针对这一问题，基于AIS帧结构特点，提出一种差分相关帧同步算法。算法中将AIS帧结构中训练序列、开始标志和结束标志设计为间隔式特征序列作为同步码，通过差分相关函数来实现帧同步。仿真实验结果表明，该算法有较好的抗频偏特性，且在低信噪比下，性能要优于差分卷积法。

英文摘要：

Due to a wide range of time delay and Doppler frequency shift existing in transmission process of ships signal, it is difficult for satellite-based AIS （automatic identification system）receiver to decode correctly. To solve this problem, we present a differential correlation frame synchronisation algorithm based on the characteristics of AIS frame structure. In the algorithm, the training sequences, starting flag and ending flag in AIS frame structure are designed as the characteristics sequence with interval which is used as the synchronisation code, the frame synchronisation is achieved by the differential correlation function. Simulation experimental results show that the algorithm has good property in frequency shift resistance, and has better performance than the differential convolution at low SNR （signal to noise ratio）.