Patent ID: 8489122

Claim:
A method of estimating the location of a mobile device comprising the steps of: (a) determining the time of transmission of a first signal from a base station; (b) receiving the first signal at the mobile device; (c) transmitting a second signal from the mobile device, the second signal being a function of the first signal advanced by a timing parameter; (d) determining a time of receipt of the second signal at a first reference station; (e) determining a first range of the mobile device from the first reference station as a function of the determined time of transmission of the first signal and the determined time of receipt of the second signal; (f) providing a plurality of grid points in a geographic region, the plurality of grid points containing the first reference station; (g) determining a first relationship between the determined first range and a first range metric for each of the plurality of grid points; (h) determining a second relationship based on an ideal range from the first reference station to each of the plurality of grid points; (i) comparing the first and second relationships; and (j) determining a location of the mobile device as a function of the comparison of the first and second relationships.