Time Difference of Arrival (TDoA), like Time of Arrival(ToA), is a time-based method for determining the position of mobile devices in cellular networks. The TDoA method works with difference times, in contrast to Time of Arrival (ToA), which works with absolute times.
Time Difference of Arrival is based on a time-of-arrival measurement, which measures the difference in propagation time of a timestamp that radio signals have from the mobile device, such as a smartphone, to different base stations in the cellular network. The distance between the mobile device and the base stations can be calculated directly from the signal propagation time. The propagation time differences are evaluated and compared in the Mobile Position Center( MPC), and the location of the mobile device is calculated from this.
The TDOA measurement is only meaningful if at least three base stations have received the time stamp. If there are two base stations, they would be somewhere on two circular perimeters. Only by the third base station the exact position can be determined. In practice, the TDoA method is used, among other things, in 5th generationmobile communications( 5G) with 5G Release 16 and achieves a positioning accuracy of 3 m indoors, while the resolution is 10 m outdoors. Since the mobile devices transmit in the direction of the transmitter, i.e., in the uplink, this method is also called uplink time of arrival( UL-ToA). Another method derived from Time Difference of Arrival (TDoA) is Observed Time Difference of Arrival( OTDoA).