Importance

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Abstract

A radio telecommunications/location system includes a number of locator satellites in low earth orbits. The satellites include multibeam antennas. Locatable subscriber units communicate with the satellites. A single subscriber unit communicates with a single satellite using electromagnetic signals so that measurement processors can obtain Doppler component, and propagation duration measurements of the signals. A location processor converts these measurements into a two-position location solution. The two-position solution includes an actual position and an image position. The actual position may be detected in some situations by identifying a cell within which communications take place. In other situations, the actual position may be distinguished from the image position by comparing signals received at the subscriber unit through antenna beams projected to the left of the satellite's ground track with signals received at the subscriber unit through antenna beams projected to the right of the satellite's ground track.

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First Claim