Method for use with analog FM cellular telephones

摘要

A method for determining the location of a mobile unit within a cellular system. A synchronized signal at a common phase is generated at each base station in a system. The mobile unit transmits a signal tone. Each base station compares the phase of the signal tone to the common phase of the synchronized signal to produce a phase offset. A system controller compares the difference between the phase offset of a first base station and the phase offset of a second base station and determines the difference in distance between the first base station and the mobile unit and the second base station and the mobile unit defining a hyperbolic curve of locations. The system controller determines the intersection of the first and second hyperbolic curves thus determining the location of the mobile unit. The mobile station transmits the signal tone on a second channel that is distinct from a first channel over which user information is transmitted. The mobile station switches to the second channel in response to a request by a base station to the mobile station.