Ericsson Gmbh

Daniel Wickstrom

Torbjorn Wilson Solve

Edward V Jolley

Methods and systems are provided for determining a position of a mobile terminal that includes a satellite radiotelephone and a global positioning system (GPS) receiver based on knowledge of the position of the communication satellite spot-beam in which the mobile terminal is located. Using knowledge of the location of the communication satellite spot-beam, the present invention can resolve the one-millisecond ambiguity, that typically arises from the code repeat length where relative code phase may be determined but absolute code phase (i.e. one millisecond increments) could be off by one or more code periods. The spot-beam identifier is obtained from the satellite communication system and used to determine the geographic location of the spot-beam. Trial positions, i.e., candidate mobile terminal positions, are then selected to cover the spot-beam area, with spacing between trial positions provided to account for the one-millisecond ambiguity. Pseudo-range measurements are generated for each trial position and used to generate position fixes. The best position fix, for example a fix selection based on a self-consistency check, is then selected as the mobile terminal's position. In an additional aspect of the present invention, the number of trial positions is reduced by selecting an arc of positions within the spot-beam as trial positions based on timing delay information from the satellite communication system.

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Daniel Wickstrom