Arrangement With Means for Ensuring Bona Fide of Received Signals

Abstract

An arrangement including a receiver that receives a plurality of signals from different source that are modulated with a common carrier, where each signal of the signals experiences a transit delay and Doppler frequency shift before reaching the receiver. The receiver includes means, such as a directional antenna, to ensure that the received signals are bona fide, or at least not subject to the same bogus signal or signals to which a second receiver may be subjected. The arrangement further includes means for processing a signal derived from the signals received by the receiver with signals provided by a supplicant module to reach a conclusion about the bona fide of the signals provided by the supplicant module.

1 . A method for use by an apparatus in conjunction with a system of earth-orbiting satellites in which each satellite transmits a global positioning system signal containing data that is encoded using a first code, which is publicly known, and that is also encoded using a second code, which is not known to said server, the method comprising:
 accepting a commingled signal from a terrestrial supplicant system the commingled signal being a frequency-shifted version of a superposition of the satellite signals, as received by said supplicant system during one or more particular time intervals, the signals in said superposition including said first code and said second code;   a server of said apparatus receiving said particular ones of the signals that were transmitted from respective ones of the satellites, for said one or more particular time intervals, and storing in a memory signals related to the signals received by said server where said related signals include said first code and said second code; and   determining terrestrial locus of the supplicant system based on knowledge of the terrestrial location of the server and results of a correlation between a first signal that is a version of the accepted commingled signal and a second signal that is a version of at least three of said GPS signals received by the server.   
     
     
         2 . The method of  claim 1  wherein said accepting and said determining is performed in said server. 
     
     
         3 . The method of  claim 1  wherein said apparatus comprises said server and a processing device that is remote to said server, and said determining is performed in said processing device. 
     
     
         4 . The method of  claim 1  wherein
 each of said satellite signals occupies a particular frequency band about a carrier of a first frequency, and 
 the accepted commingled signal is a version of said transmitted satellite signals as received by said supplicant system at said particular time that occupies a frequency band that is substantially the same width as said particular frequency band, but shifted to a second carrier of a frequency that is significantly lower than said first frequency. 
 
     
     
         5 . The method of  claim 4  wherein the second frequency of said down-shifted carrier is close to zero. 
     
     
         6 . The method of  claim 1  wherein an indication of said one or more particular time intervals is received by the server from the supplicant system. 
     
     
         7 . The method of  claim 1  further comprising receiving an assertion regarding terrestrial position of said supplicant system, and said determining reaches a conclusion, based on the determined terrestrial locus, whether the assertion is to be confirmed. 
     
     
         8 . The method of  claim 7  further comprising acting on said conclusion. 
     
     
         9 . The method of  claim 8  where said acting comprises sending said conclusion to a remote apparatus. 
     
     
         10 . An arrangement employed in conjunction with a system of earth-orbiting satellites in which each satellite transmits a global positioning system signal containing data that is encoded using a first code, which is publicly known, and that is also encoded using a second code, which is not known to said server, comprising:
 a communications module for accepting a commingled signal transmitted from a terrestrial supplicant system over a communications channel, the commingled signal being a frequency-shifted version of a superposition of a plurality of the GPS signals transmitted from respective ones of the satellites, as received by said supplicant system during particular one or more time intervals, the signals in said superposition including said first code and said second code;   a receiver in a server of said arrangement for receiving said plurality of the GPS signals for said particular one or more time intervals;   a processor in said server for developing processed signals that correspond to the signals received by said server, wherein said processed signals contain said first code and said second code;   memory in said server for storing said processed signals; and   a computation module for determining terrestrial locus of the supplicant system based on knowledge of the terrestrial location of the server and results of a correlation between a first signal that is a version of the accepted commingled signal, and a second signal that is obtained from said memory.   
     
     
         11 . The arrangement of  claim 10  further comprising an antenna arrangement coupled to said receiver, where the antenna arrangement is constructed to enable it being directed to respond well to signals from certain spatial directions and to not respond well to signals from other spatial directions. 
     
     
         12 . The arrangement of  claim 10  where said communication module is within said server. 
     
     
         13 . The arrangement of  claim 10  wherein said communication modules and said computation module are within said server. 
     
     
         14 . The arrangement of  claim 13  further comprising a remote client apparatus to which said computation module sends information. 
     
     
         15 . The arrangement of  claim 10  further comprising a client apparatus that is remote to said server, and said computation modules is within said client apparatus. 
     
     
         16 . The arrangement of  claim 10  where said computation module reaches a conclusion, based on a received assertion regarding terrestrial position of said supplicant system, and said determined terrestrial locus, whether the assertion is to be confirmed.