GSM tracking

GSM positioning refers to the location determination of a switched-on and in a radio network is booked on the basis of Global System for Mobile Communications (GSM) -operated terminal ( cellular phone ) by the mobile network, Zip code locator .
The position of a mobile phone is known for the mobile operator through the permanent registration on the power in certain limits of accuracy. In standby mode, it is at least by the assignment to the currently used location area given. This information is updated periodically with movement of the mobile station and in a database, the Home Location Register (HLR) are stored. In conversation mode, the position of a mobile phone can be more accurately determined because at least this cell id is known to the active base station. Here there are several refinements.
GSM localization is, depending on the application, a simple alternative to the Global Positioning System (GPS) , since for the mobile device no additional infrastructure is required. The GSM positioning is, however, in comparison to determine location using GPS, most accurate, since the figures used for positioning signals include system-related tolerances and, due to the infrastructure used, factors such widely varying propagation conditions, topography of the underlying mobile network, geographical features and facilities of terminal used to accept the result of influence.
Variants
A GSM tracking can be done using different measurement methods, with the available options in terms of accuracy, the necessary hardware requirements differ in the mobile network and the requirements of the terminal complement.
Method without any additional equipment, neither network nor on the device side
Cell ID or Cell of Origin : This method is not in the 3GPP specified, was and is still used by network operators for coarse positioning. In this method, only the cell in which the terminal is located at the time of measurement, and determines the position of use. There are no changes to network or terminal side necessity, although the achieved accuracy is low and is directly related to the density of base stations.
Methods with power side, but without additional device-side equipment

Timing Advance (TA), the position of the terminal based on the position of the used In this method, radio cell and the parameter Timing Advance determined. The precision of the data depends on the accuracy of the parameter timing advance on what may be due to the system not more than 277 m. [2]
Uplink Time Difference of Arrival (U-TDOA): In this method, the position of the terminal based on the durations of the signals of the terminal to a specific place in the mobile network, the so-called Location Measurement Units (LMU) is determined.
Methods with network and device-side auxiliary equipment
Enhanced Observed Time Difference (E-OTD), the position of the terminal is based on time measurements of a plurality of adjacent In this method, base stations , performing the terminal is determined.
Global Navigation Satellite System (GNSS), the position of the terminal is determined and transmitted by the terminal itself to the cellular network during the procedure. The terminal determines its position using any satellite-based positioning system ( GPS , Zip code locator , GLONASS , QZSS ).
A special form of this method is assisted GNSS (A-GNSS), wherein the auxiliary data required for position determination are provided by the mobile network. In the name of this procedure is normally rather than the generic term GNSS the name of the satellite navigation system used in each case used, or about A-GPS .
The accuracy of the detected positions between several kilometers when using Cell ID under unfavorable circumstances, between 25 m for E-OTD and U-TDOA to less than 5 m using GNSS