卫星导航系统导航电文结构及广播星历分析与建议

Analysis and suggestions for GNSS Message Structure and Broadcast Ephemeris

导航电文是卫星导航系统顶层设计的重要组成部分，其结构设计直接决定了首次定位时间、通信效率和可扩展性等关键性能指标；而广播星历是导航电文的核心，其表示方式直接决定了卫星轨道表示精度和通信效率等。GPS和GLONASS作为当今世界在轨运行的两大卫星导航系统，其导航电文设计各具特点。GPSL1CA的电文采用帧结构，其中星历信息采用轨道根数及相应的摄动参数等16项参数来表示；GPS L2C／15的电文采用固定长度的信息类型结构，L1C采用信息内容可变的固定帧结构，其中星历信息采用18项参数表示。GLONASS Ll／12民用信号采用超帧结构形式，其中星历信息使用卫星的位置、速度以及日月摄动加速度等10项参数来表示。本文通过对GPS／GLONASS导航电．文结构和广播星历进行分析和计算，对未来全球导航系统导航电文的结构和广播星历设计给出了建议。

Navigation message is an important part of the top level design of GNSS. Its structure directly determines critical performance indexes, such as the TTFF, communication efficiency and expandability. Broadcast ephemeris is the core of the navigation massage, which determines the orbit representation accuracy and communication efficiency. The message designs of GPS and GLONASS have their own characteristics. GPS L1CA signal adopts frame structure and the broadcast ephemeris is represented by 16 parameters, like orbit elements and corresponding perturbation parameters; L2C/L5 signals adopt fixed length frame structure, while the L1 C adopts fixed frame structure with variable contents, and the ephemeris is represented by 18 parameters. GLONASS L1/L2 civil signal adopts superframe structure, and the broadcast ephemeris is represented by l0 parameters, including the satellite location, velocity, the perturbation acceleration of the Sun and the Moon, etc. After analyzing and calculating the message structure and broadcast ephemeris of GPS/GLONASS, some suggestions are presented for the future design of GNSS message structure and broadcast ephemeris.