Patent ID: 6249245
Filing Date: 2001-06-19
Classification: G01S

Abstract:
A method for determining a geographic position of a mobile terminal comprising the steps of:receiving global positioning system satellite signals having frequencies in a satellite frequency band at the mobile terminal from a plurality of global positioning system satellites that are in view of the mobile terminal;performing, by the mobile terminal, distance calculations using said global positioning system satellite signals to obtain distance measurements representing a pseudorange between the mobile terminal and each of the plurality of global positioning system satellites;transmitting a first signal from the mobile terminal to a cellular network base station, the first signal containing the distance measurements;receiving the first signal by the cellular network base station and forwarding the first signal to a mobile communications switching office;receiving, by the mobile communications switching office, the first signal from the cellular network base station and a second signal that contains differential global positioning satellite error correction data, the second signal being provided by a source;performing, by the mobile communications switching office, corrections on the distance measurements provided in the first signal based on the differential global positioning satellite error correction data, to create corrected pseudorange data;outputting, from the mobile communications switching office to the cellular network base station, a combined cellular signal that corresponds to the corrected pseudorange data combined with data that corresponds to at least one of voice data and data traffic for modems;receiving the combined cellular signal by the cellular network base station and outputting the combined cellular signal to the mobile terminal;receiving the combined cellular signal at the mobile terminal, wherein the combined cellular signal contains the corrected pseudorange data and the at least one of voice data and data traffic for modems;demodulating the combined cellular signal to extract the corrected pseudorange data therefrom, the demodulating being performed by the mobile terminal;determining, by the mobile terminal, a present position of the mobile terminal by using the corrected pseudorange data; andextracting, by the mobile terminal, the at least one of voice data and data traffic for modems from the combined cellular signal, for supplying to a corresponding one of a speaker and a modem coupled to the mobile terminal,wherein the mobile terminal is not capable of calculating the corrected pseudorange data but is capable of calculating the present position of the mobile terminal from the corrected pseudorange data provided to the mobile terminal.