北斗B1C信号及导航电文的特点分析与比较

我国北斗全球卫星导航系统工程建设已经启动,北斗互操作信号B1C的接口控制文件已经发布。本文重点对北斗B1C信号及导航电文进行介绍,并对其信号及导航电文的设计特点进行分析,同时与GPS L1C和Galileo E1OS互操作信号进行比较。分析显示,北斗B1C的信号和导航电文编排,在充分借鉴GPS L1C和Galileo E1OS信号特点的基础上,进行了优化设计。B1C信号具有与L1C信号和E1OS信号相同的中心频点和频谱结构,采用了数据导频支路、MBOC调制、分层码结构等设计方案,导航电文与GPS L1C也较为相近,实现与GPS L1C、Galileo E1OS信号的互操作。同时B1C也具有自身独有特点,如B1C导频支路采用QMBOC(6,1,4/33)调制方式、导航电文采用64进制LDPC编码,在实现互操作的基础上,也创新了自身特色。相对于北斗B1I信号,北斗B1C信号具有更好的弱信号跟踪、更短的首次定位时间等服务性能。

Characteristic Analysis and Comparison of Beidou B1C Signal

The third generation of BeiDou navigation satellite system (BDS) is under construction. The Interface Control Document of B1C interoperability signal has been released. This paper focuses on the analysis of B1C signal and its navigation messages features in comparison with GPS L1C and Galileo E1OS. Analysis shows that B1C has been optimized based on full reference to GPS L1C and Galileo E1OS characteristics. B1C interoperates with the GPS L1C and Galileo E1OS through a system of measures such as using the same center frequency and spectrum structure as L1C and E1OS, adopting the design scheme of the data pilot branches, MBOC modulation and hierarchical code structure, employing the similar navigation message structure to L1C and E1OS. At the same time, B1C also has its own unique features, such as employing QMBOC(6,1,4/33) modulation in pilot branch, using 64-ary LDPC encoding scheme in navigation message. Compared with B1I signal, B1C signal has better weak signal tracking performance, shorter initial positioning time.