微弱信号下基于模糊度搜索的辅助式GPS定位算法研究

An algorithm for Assisted-GPS positioning based on ambiguous search in weak signal environment

针对微弱信号下GPS接收机无法测量得到完整信号发射时刻的问题,提出了一种基于模糊度搜索的辅助式GPS定位算法。基于该算法接收机不需要位同步、帧同步和解调导航电文,仅对GPS信号进行伪码相位测量,在获取卫星星历、卫星钟差参数等辅助信息的基础上完成定位解算。论文从数学上严格推导了消除信号发射时刻模糊度的条件,并对五颗以上的观测卫星建立了定位解算方程,给出了算法流程。利用实测数据仿真验证了该算法的有效性。比较表明,该算法的定位精度与常规GPS定位算法(信号发射时刻不存在模糊度)相当。

The GPS receiver in weak signal environment cant recover a full time of signal transmission. For overcoming this shortcoming, a new Assisted- GPS positioning algorithm is presented. Based on this algorithm, the receiver neednt accomplish the frame synchronization and navigation data demodulation, which are usually necessary for a conventional GPS receiver. The receiver position is estimated only through measuring the pseudo - code phase and synchronizing the bit data after the assistance data （ including ephemeris information and satellite clock corrections etc. ） is obtained. In this paper, the condition for resolving the ambiguity of time of signal transmission is derived strictly. Consequently, it provides an explicit solution equation for observing five satellites or more, and the computation flow is then summarized. The simulation results validated the proposed algorithm. Compared with conventional GPS positioning algorithm （unambiguous for time of signal transmission） , the positioning accuracy of proposed algorithm is exactly equal to that of the conventional algorithm.