Patent ID: 8150417

Claim:
A method of locating a mobile communications device on a known path, the mobile device communicating with a mobile communications network infrastructure including a plurality of base stations, communications between the mobile device and a base station to which it is attached having a timing advance to compensate for a time taken for a radio signal to reach the base station from the mobile device, the method comprising: reading a time ordered sequence of messages captured from said communications between the mobile device and said network infrastructure; reading timing advance information from said captured messages; identifying a step change in timing advance using said timing advance information; reading base station identification data from said captured messages, for identifying a base station to which the mobile device is attached at said time of said step change; reading base station location data for said identified base station; and determining a location of said mobile device on said known path at a time of said step change by determining an intersection of said path with a line having a position determined by said identified base station location and said timing advance immediately before or after said step change.