Patent ID: 6408178
Filing Date: 2002-06-18
Classification: G01S

Abstract:
A method for determining a position of a mobile terminal comprising the steps of:obtaining an identification of a spot-beam in which the mobile terminal is located from a satellite radiotelephone system communication; generating a plurality of trial positions within the spot-beam; determining candidate position fixes for the mobile terminal for at least two of the plurality of trial positions based on GPS signals received by the mobile terminal from a plurality of global positioning system (GPS) satellites; selecting one of the determined candidate position fixes as the position of the mobile terminal; and wherein the determining step further comprises the steps of: calculating a plurality of initial pseudo-range estimates corresponding to the plurality of GPS satellites for one of the plurality of trial positions based on the GPS signals received by the mobile terminal, the GPS signals having a code length, including determining fractional code periods from the received GPS signals; adjusting the initial pseudo-range estimates to produce a plurality of candidate pseudo-range estimates for the mobile terminal for the one of the plurality of trial positions; generating the candidate position fix for the mobile terminal for the one of the plurality of trial positions based on the plurality of candidate pseudo-range estimates, and repeating the calculating, adjusting and generating steps for a second one of the plurality of trial positions.