The Mobile Position Center(MPC) is a central component in determining the position of mobile devices in GSM networks. In general, position determination in mobile communications networks is based on various methods using time-of-arrival measurements.
Time of Arrival( ToA) is one time-based method for position determination, Time Difference of Arrival( TDoA) is another. In the latter, the propagation time differences of several time stamps that the radio signals of a mobile device have to different base stations of the mobile network are recorded and evaluated. Another time-based method is Roundtrip Time of Flight (RToF).
The Mobile Position Center evaluates the transit times and transit time differences between the mobile device and the base stations, compares them, and uses them to calculate the location of the mobile device.