AGPS positioning principle and realization method

    AGPS (Assisted GPS, A-GPS, network assisted GPS) positioning technology combines the advantages of GPS positioning and cellular base station positioning. With the help of cellular network data transmission functions, it can achieve high positioning accuracy and fast positioning speed. Devices, especially mobile phones, are being used more and more widely.
    The problems with GPS positioning are: First, the hardware initialization (searching for satellites for the first time) takes a long time, which takes tens of seconds to ten minutes; second, the penetration of GPS satellite signals is likely to be blocked by buildings, trees, etc., and affect positioning. Accuracy. AGPS positioning technology successfully solves or alleviates these two problems through the assistance of the network. For the auxiliary network, there are many possibilities. Taking the GSM cellular network as an example, it is generally assisted by the GPRS network.
     AGPS implementation method
(1) The device obtains the current cell location from the cellular base station (ie a COO positioning)
(2) The device transmits the current cell location to the AGPS location server in the network through the cellular network
(3) APGS location server according to The current cell location queries the currently available satellite information in the area (including the satellite's frequency band, azimuth, elevation angle and other related information), and returns it to the device
(4) The GPS receiver can quickly find the currently available GPS satellites based on the obtained available satellite information
At this point, the GPS receiver can receive GPS signals normally, and the GPS initialization process ends. The improvement of AGPS positioning speed is mainly reflected in this process.
    Advantages of AGPS
(1) Fast star search for the first time
(2) Effectively reduce the power consumption of the device
    AGPS limitations
(1) Must have cellular network (GRRS/EDGE/CDMA, etc.) support for data transmission
(2) Must have AGPS location server support