失锁重捕情况下的GPS接收机快速帧同步方法

A Fast Frame Synchronization Method of GPS Receiver After Signal Lost and Recapturing

普通帧同步需要耗费一个子帧周期的时间,接收机失锁后,需要6 s才能再次完成帧同步,再次定位时间较长。在卫星信号易受遮挡的应用环境中,会导致定位中断现象。针对这一问题,提出了一种快速的GPS接收机帧同步方法。该方法利用本地时、本地位置和有效星历反推卫星当前概略位置,进而计算卫星与接收机之间的伪距,并根据本地时反推电文发射时刻,进而推算出当前帧的帧计数和位计数,从而快速地完成帧同步。与普通帧同步相比,快速帧同步在保证定位精度的同时,大大缩短了接收机失锁后的再次定位时间。

In general, the common frame synchronization algorithm takes one sub-frame period of time for a deter- mination. That means the receiver will take 6 s to resynchronize the frames after the signal lost and recapturing, the repositioning takes much longer. That may cause the receiver positioning suspend in the environment of the satellite signal susceptible to block. To solve this problem, a fast frame synchronization method is proposed. This method uses local time, current general location and valid ephemeris to calculate the satellite position and range between satellite and the current location, and calculates the telegraph sending times backwards according to the local time and the range, finally, gets the current frame number and bit number, quickly determines the frame synchronization. Compared with the common frame synchronization algorithm, without losing the positioning accu- racy, a significant reduction of repositioning time is observed by using the proposed method.