초록 ▼

A system and method for unambiguously determining the position of a user terminal (for example, a mobile wireless telephone) in a low-Earth orbit satellite communications system. The system includes a user terminal, at least two satellites with known positions and known velocities, and a gateway (th

A system and method for unambiguously determining the position of a user terminal (for example, a mobile wireless telephone) in a low-Earth orbit satellite communications system. The system includes a user terminal, at least two satellites with known positions and known velocities, and a gateway (that is, a terrestrial base station) for communicating with the user terminal through the satellites. The method includes the steps of determining a range parameter, a range difference parameter, and either or both of a range-rate parameter and a range-rate difference parameter. A range parameter represents a distance between one of the satellites and the user terminal. A range difference parameter represents the difference between (1) the distance between a first one of the satellites and the user terminal and (2) the distance between a second one of the satellites and the user terminal. A range-rate parameter represents a relative radial velocity between one of the satellites and the user terminal. A range-rate difference parameter represents the difference between (a) a relative radial velocity between a first one of the satellites and the user terminal and (b) a relative radial velocity between a second one of the satellites and the user terminal. The position of the user terminal on the Earth's surface is then determined based on the known positions and known velocities of the satellites, the range parameter, the range difference parameter, and either or both of the range-rate parameter and the range-rate difference parameter.

대표청구항 ▼

[ What we claim as our invention is:] [29.]29. A position determining system for a satellite communications system, comprising:a user terminal;at least two satellites with known positions and known velocities;a gateway for communicating with said user terminal through said satellites;range parameter

[ What we claim as our invention is:] [29.]29. A position determining system for a satellite communications system, comprising:a user terminal;at least two satellites with known positions and known velocities;a gateway for communicating with said user terminal through said satellites;range parameter determining means for determining a range parameter;range difference parameter determining means for determining a range difference parameter;at least one of:range-rate parameter determining means for determining a range-rate parameter; andrange-rate difference parameter determining means for determining a range-rate difference parameter; andposition determining means in said gateway for determining a position of said user terminal on the Earth's surface based on said known positions and velocities of said satellites, said range parameter, said range difference parameter, and at least one of said range-rate parameter and said range-rate difference parameter, said position determining means comprisingmeans for generating a M.times.1 parameter vector z comprising said parameters, wherein M is the number of parameters determined;means for generating a position vector x representing an initial reference point;means for generating a partial derivative matrix H containing information regarding said known positions and velocities of said satellites and an Earth model describing the shape of the Earth wherein the relationship between x and H is given bymeans for generating a M.times.M weight matrix W to emphasize the influence of specific parameters; andmeans for executing the iterative equationwherein x.sub.i and x.sub.i+1 are the current and next position estimates, respectively, and i represents the iteration number, until the difference between x.sub.i and x.sub.i+1 falls below a first predetermined threshold.