地基伪卫星系统多址测距误差的校正算法

相对于卫星导航，地基伪卫星与接收机距离较近，测距中不涉及电离层传播等误差，易实现高精度测距和定位。但由于地基伪卫星位置固定，在信号连续发射模式下伪卫星信号间的多址干扰(MAI)会引起相对恒定的测距误差，针对地基伪卫星系统这一特点，提出一种基于反馈串行干扰抵消(SIC)的测距算法。首先对全部伪卫星信号进行捕获跟踪和功率估计，然后通过串行干扰抵消算法降低强功率伪卫星信号对期望测距信号的干扰，通过反馈模式进一步提高干扰抵消算法的性能。仿真结果表明，该方法可有效改善地基伪卫星系统强远近效应区域内的测距性能，不考虑其他误差下在强远近效应区域内基于码环可将伪卫星测距性能从10 m以上降低到约0.3 m。

Ranging Error Caused by MAI in Terrestrial Pseudolites System and its Correction Method

The terrestrial pseudolites system is easy to realize high accuracy positioning comparing with the low transmit error in line of sight propagation link, while it has approximate constant ranging error under its multi access interferenc(MAI) for all terrestrial pseudolites having constant positions. A correction method based on feedback SIC (Serial Interference Cancellation)was given. First the receiver decide whether it is in strong near far effect area based on ranging and coarse positioning data; then restrain the interference of strong pseudolites′ signals on needed signals′ ranging by SIC; a feedback structure was adopted to enhance the cancellation performance. The simulation and hardware test results show that the method has an effective ranging correction performance which could reduce the error from tens of meters to 0.3 m in certain environment with high near-far effect.