Patent ID: 6667963
Filing Date: 2003-12-23
Classification: H04J,H04W

Abstract:
A method of determining the position of a mobile communications device in a cellular telephone network and comprising the steps of:synchronising the mobile communications device to each of a plurality of neighboring base transceiver stations using the method comprising, in a Time Division Multiple Access (TDMA) cellular radio telephone system, synchronising a mobile communications device to a first radio channel transmitted from a first radio transmitter when the mobile communications device is currently synchronised to a second radio channel transmitted from a second radio transmitter, and wherein said first radio channel conveys at least one synchronization feature, the method further comprising: determining a real time difference between the operating clocks of said first and second radio transmitters; transmitting said determined real time difference, or a value or values derived therefrom, from said second transmitter to the mobile communications device, over said second radio channel; causing the mobile communications device to listen to said first radio channel for said synchronisation feature during a time window or windows derived from said determined real time difference or said value or values derived therefrom; and wherein said second transmitter belongs to a serving base transceiver station, and determining respective Observed Time Differences (OTDs); and determining the position of the mobile device using said OTDs and the respective RTDs.