User terminal positioning system and method employing external signals
First Claim
1. A satellite communications system where an earth station is operative to exchange messages with a user terminal through a communications satellite in movement relative thereto, and to exchange messages with said communications satellite, to measure the position of the user terminal , said system being characterised by:
- said user terminal being operative to receive a signal, sent from a known position at a known time from a known autonomous source;
said user terminal being operative to note the time of arrival of said signal;
said user terminal being operative to communicate said time of arrival to said earth station via said communications satellite;
said earth station being operative to calculate the distance between said autonomous source and said user terminal; and
said earth station being operative to incorporate said calculated distance in the estimation of said position of said user terminal, otherwise derived by said exchanging messages between said earth station and said user terminal via said communications satellite.
4 Assignments
0 Petitions
Accused Products
Abstract
A communications satellite communications system and method, where a communications satellite 10 can pass messages between a user terminal 44 and an earth station 38, as the communications satellite moves in an orbit 12 12'"'"' as indicated by arrow 46, comprises means for estimating the position of the user terminal 44, on the surface of the earth 14, relative to the nadir 50, by means of doppler shift measurements and propagation delay measurements between the communications satellite 10 and the user terminal 44. Where more than one communications satellite 10 is visible to the user terminal 44, combination means are employed using propagation delays to plural communications satellites 10, and/or recordal of the receipt times, by the user terminal 44, of timed broadcasts from one or more communications satellites 10 to determine the propagation delay between the one or more communications satellites 10 and the user terminal 44. In addition, delay signals from navigational satellites 142 can be processed by the user terminal 44 measuring the time of arrival of signals from the navigational satellites 142 and conveying the identity of the navigational satellite and the arrival time of the signal to the earth station, which calculates the position of the user terminal 44 and can relay an idication thereof back to the user terminal 44.
60 Citations
27 Claims
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1. A satellite communications system where an earth station is operative to exchange messages with a user terminal through a communications satellite in movement relative thereto, and to exchange messages with said communications satellite, to measure the position of the user terminal , said system being characterised by:
- said user terminal being operative to receive a signal, sent from a known position at a known time from a known autonomous source;
said user terminal being operative to note the time of arrival of said signal;
said user terminal being operative to communicate said time of arrival to said earth station via said communications satellite;
said earth station being operative to calculate the distance between said autonomous source and said user terminal; and
said earth station being operative to incorporate said calculated distance in the estimation of said position of said user terminal, otherwise derived by said exchanging messages between said earth station and said user terminal via said communications satellite. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 23, 24)
- said user terminal being operative to receive a signal, sent from a known position at a known time from a known autonomous source;
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12. A method for operating a satellite communications system where an earth station is operative to exchange messages with a user terminal through a communications satellite in movement relative thereto, and to exchange messages with said communications satellite, to measure the position of the user terminal, said method including the steps of:
- said user terminal receiving a signal, sent from a known position at a known time from a known autonomous source;
said user terminal noting the time of arrival of said signal;
said user terminal communicating said time of arrival to said earth station via said communications satellite;
said earth station calculating the distance between said autonomous source and said user terminal; and
said earth station incorporating said calculated distance in the estimation of said position of said user terminal, otherwise derived by said exchange of messages between said earth station and said user terminal via said communications satellite. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 25, 26)
- said user terminal receiving a signal, sent from a known position at a known time from a known autonomous source;
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27. A user terminal for a satellite communications system in which an earth station is operative to exchange messages with the user terminal through a communications satellite in movement relative thereto, and to exchange messages with said communications satellite, in order to measure the position of the user terminal,
said user terminal being operative to receive a signal, sent from a known position at a known time from a known autonomous source; -
said user terminal being operative to note the time of arrival of said signal; and said user terminal being operative to communicate said time of arrival to said earth station via said communications satellite; whereby to permit said earth station to calculate the distance between said autonomous source and said user terminal; and
to incorporate said calculated distance in the estimation of said position of said user terminal, otherwise derived by said exchanging messages between said earth station and said user terminal via said communications satellite.
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Specification