US 5,412,388 A · Position ambiguity resolution

Abstract

A radio telecommunications system includes a number of locator satellites in low earth orbits. Locatable subscriber units communicate with the satellites. A single subscriber unit communicates with a single satellite using electromagnetic signals so that a measurement processor can obtain Doppler component, propagation duration, and real time 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 detecting the eastward rotation of the earth. A service processor determines which qualifications to apply to communication services offered by the system. These qualifications are based on the subscriber unit's location.

Claims31

Dependent claims

A method of distinguishing an actual position from an image position in a location determination system, said method comprising the steps of:

obtaining a set of original location parameters, said original set describing a first position and a second position;
acquiring a set of subsequent location parameters;
and
selecting, as said actual position, the one of said first and second positions which, in response to said sets of original and subsequent location parameters, appears to move in a generally eastward direction over time.

1 more element

A method of operating a radio telecommunications system having a satellite moving in an orbit around the earth and having a subscriber unit located proximate the earth's surface, said method comprising the steps of:

obtaining a set of original location parameters, said original set describing first and second positions of said subscriber unit relative to said satellite;
acquiring a set of subsequent location parameters;
and
selecting, as an actual position for said subscriber unit, the one of said first and second positions which, in response to said sets of original and subsequent location parameters, appears to move in a generally eastward direction over time;
and
qualifying communication services provided for said subscriber unit in response to said actual position for said subscriber unit.

3 more elements

A location determination system comprising:

at least one locator unit moving in an orbit around the earth;
at least one locatable unit residing proximate the earth's surface;
a measurement processor residing in one of said locator and locatable units, said measurement processor being configured to determine a Doppler component of an electromagnetic signal traveling between said locator and locatable units;
a location processor in data communication with said measurement processor, said location processor being configured to determine two positions for said locatable unit in response to said Doppler component and to determine which of said two positions moves relative to said locator unit in a generally eastward direction, said eastward moving position corresponding to a location of said locatable unit.

1 more element

Dependencies are inferred from the claim text.

Position ambiguity resolution

Life of this patent

Position ambiguity resolution

Life of this patent

Abstract

Claims31