Patent ID: 7064706

Claim:
A method for maintaining the integrity of a mobile handset's location determination in a system comprising the mobile handset, radio communication infrastructure and a Differential Global Positioning System (DGPS) reference receiver coupled to the radio communication infrastructure and installed at a predetermined location, the DGPS reference receiver receiving GPS information from a plurality of GPS satellites, the method comprising: said radio communication infrastructure receiving DGPS information, from which differential correction data may be obtained, from the DGPS reference receiver; determining whether one or more of said plurality of GPS satellites have failed/are failing based on differential correction data within a specified time after failure; generating a failed satellite message when it is determined that one or more of said plurality of GPS satellites have failed/are failing, said failed satellite message identifying the one or more of said plurality of GPS satellites that have failed/are failing; and transmitting the failed satellite message identifying the one or more of said plurality of GPS satellites that have failed/are failing when it is determined that the one or more of said plurality of GPS satellites has failed/are failing.