一种新的卫星导航信号码跟踪误差下限

A New Code Tracking Error Lower Bound for Satellite Navigation Signals

卫星导航系统的精确定位是基于导航信号传输时延的精确估计,码跟踪误差是评估时延精度的重要参量之一。对信号的接收机码跟踪过程进行了理论研究,系统推导了相干延迟锁相环的跟踪误差。针对克拉美罗界(Cramer-RaoLower Bound,CRLB)只有在高信噪比时才能提供准确估计的问题,提出了一种新的码跟踪误差下限,称为MZZB(Modi-fied Ziv-Zakai Bound),该下限把码时延作为概率密度已知的随机变量,在更宽载噪比范围内提供更加紧密的下限。计算机仿真分析了BPSK-R(1)与BOC(1,1)信号的CRLB与MZZB异同,得出克拉美罗界只有在高信噪比时才能提供准确的估计,而MZZB在更宽范围信噪比下提供更加紧密的下限。

The accurate positioning of the global navigation satellite system（GNSS） is based on the accurate estimation of naviga- tion signal transmission delay. Code tracking error is an important parameter to estimate delay precision. A theoretical analysis of code tracking process is performed,and the DLL code tracking error is deduced. As for the problem of CRLB （Cramer-Rao Lower Bound） which provides accurate estimation only under high SNR,a new code tracking error lower bound named as MZZB （Modified Ziv-Zakai Bound） is proposed. It considers code delay as random variables of known probability density,and offers a closer limit in a wider range of C/No. Finally, the differences between CRLB and MZZB of BPSK-R （ 1 ） and BOC （ 1,1 ） are simulated, and the results show that CRLB only provides accurate estimation under high C/No ,and MZZB offeres a closer limit in a wider range of C/No.