A-GPS work theory introduction:
The basic idea of A-GPS is to set several reference GPS receivers at a position where the satellite signal reception effect is good, and use the AGPS server to obtain the rough position of the terminal through interaction with the terminal, and then use the ephemeris required by the terminal through the mobile network. Auxiliary data such as a clock and the like are sent to the terminal, and the terminal performs GPS positioning measurement. After the measurement is completed, the terminal can calculate the position result by itself or send the measurement result back to the AGPS server. The server calculates and sends the result back to the terminal. At the same time, the background SP can obtain location information for other service applications.