Analysis on the One-Way Communication Capability of GPS Satellites in Orbit Transmitting Non-navigational Information

The GPS system is capable of the one-way communication (OWC) transmitting non-navigational information if the reserved bits of L1C Nav message and the newly-added CNav message types for L2C signal are utilized. Excluding the potential communication protocol overheads, a single frequency with one satellite transmits data at 0.5B/s; with the dual frequency transmission by using L1C and L2C frequencies and the parallel transmission of multiple satellites, the transmission rate can be increased to approximately 4B/s. The one-way communication of GPS is covert due to the covertness of communication channels, the occasionality of one-way communication, the disorderly distribution of information and the difficulty in recognizing and understanding communication data when the communication protocol is unknown. This paper discusses the problems of satellite rise-and-fall, data packetization and data dropout and gives solutions for them. A design paradigm for the format of newly-added L2C CNav message types is given. The GPS one-way communication has the advantages of global coverage, day-and-night and all-weather operation, as well as low cost, thus it can meet the needs for special purposes, such as civilian emergency broadcast communication, military submarine command system and command of intelligence collection.