Tracking of mobile terminal equipment in a mobile communications system

This invention concerns a method for determination of the location of terminal equipment in a cellular mobile communications system including several base transceiver stations and wherein the terminal equipment may move from one cell to another and from one traffic area to another during the traffic connection. Drawbacks of known methods of location determination are that the location can be determined only when the mobile station is setting up a call and during the call. The invention utilises that characteristic feature of mobile telephone systems that the location of the terminal is always known to the system with location area precision and that the geographical network topology is known to the network planning system. The tracing system includes three functional parts: a first part provides the mobile telephone system with the connection number of the traced terminal as an enquiry input, and in response to the input it receives information on where the subscriber's location area should be enquired for. The second functional part asks for the subscriber's location area and receives in response a location area code, which identifies the location area unambiguously. The third functional part searches the location area table for information corresponding with the subscriber's location area and attends to reporting on the results. The location area table is formed on a basis of cell topology information which is available in advance from the network planning system, which converts the location area identity into an area name in plain language which is bound to a map. Enquiries may be made at desired intervals and the result may be stored in a tracing file. From this a report can be formed from which it is possible easy to find out the subscriber's movements with location area precision.