辅助式GPS接收机信号发射时间恢复算法研究

当GPS接收机无法进行位同步、帧同步以及导航电文解调时, GPS接收机无法恢复卫星信号发射时间. 为解决该问题, 对基于迭代最小二乘的发射时间恢复算法进行了研究, 利用辅助GPS接收机中无线通信网络提供的卫星星历、卫星修正参数等辅助信息, 结合信号发射时间模糊度的遍历搜索, 完成了信号发射时间的恢复. 详细讨论了算法及其成立条件, 给出算法流程, 并推导出搜索因子的不同选取方案, 使该算法对接收机初始位置误差(150km)和初始时间误差(180s)没有限制. 通过仿真验证了算法的有效性. 

Method for Time-of-transmission Recovery Based on Assisted-GPS Positioning

As we all known, time-of-transmission cannot be worked out successfully when GPS receiver isn't able to accomplish the bit synchronization, frame synchronization and navigation data demodulation. In this proposed algorithm, the time-of-transmission was recovered through the iterative LMS equation and ambiguity search with the assistance data, including ephemeris information and satellite clock corrections etc. The algorithm was derived strictly and its main steps were introduced. Then, the selection of search factor ω was discussed and the restrictions for the initial errors of approximate location (150km) and receiver's clock bias (180s) were eliminated. The algorithm was proved to be valid using simulation results, which indicates that this method can be used in the real GPS application with poor received signal or partial signal.