Multi-constellation GNSS integrity check for detection of time signal manipulation
First Claim
1. A time distribution device for receiving and distributing a time signal, comprising:
- a Global Navigation Satellite System (GNSS) receiver suitable for receiving a GNSS time signal from a GNSS constellation;
a local time source suitable for providing a local time signal;
a time quality module configured to;
receive the GNSS time signal and local time signal;
maintain a counter based on the local time signal;
determine a rate of change of a number of counts of the counter between pulses of the GNSS time signal;
determine a profile using the rate of change; and
in response to detecting a change in the profile, determine that the GNSS time signal has been manipulated; and
a time output fordistributing a time signal to a receiving device; and
upon determination of the manipulation, distributing to the receiving device a manipulation indicator related to the determination of manipulation of the GNSS time signal.
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Accused Products
Abstract
The present application discloses detecting manipulation of GNSS signals using a second time source. If two or more GNSS constellation signals are being detected, the phase error between the GNSS constellation signals may be monitored. When the phase error drifts, then manipulation is determined. The integrity of a GNSS constellation signal may be monitored using an internal time source such as a crystal oscillator by monitoring a slope of the free running counter at the detected rising edges of a pulse-per-second signal from the GNSS constellation. If more than two GNSS constellations are monitored, a voting scheme may be used to determine the manipulated GNSS constellation.
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Citations
11 Claims
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1. A time distribution device for receiving and distributing a time signal, comprising:
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a Global Navigation Satellite System (GNSS) receiver suitable for receiving a GNSS time signal from a GNSS constellation; a local time source suitable for providing a local time signal; a time quality module configured to; receive the GNSS time signal and local time signal; maintain a counter based on the local time signal; determine a rate of change of a number of counts of the counter between pulses of the GNSS time signal; determine a profile using the rate of change; and in response to detecting a change in the profile, determine that the GNSS time signal has been manipulated; and a time output for distributing a time signal to a receiving device; and upon determination of the manipulation, distributing to the receiving device a manipulation indicator related to the determination of manipulation of the GNSS time signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method for receiving and distributing a time signal, comprising:
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receiving, by a time distribution device, a Global Navigation Satellite System (GNSS) time signal from a GNSS constellation; maintaining a counter based on a local time signal; determining a rate of change of a number of counts of the counter between pulses of the GNSS time signal; determine a profile using the rate of change; in response to detecting a change in the profile, transmitting an alert that the time signal may have been manipulated; distributing a time signal to a receiving device; and
,upon determination of manipulation, distribute to the receiving device a manipulation indicator related to the determination of manipulation of the GNSS time signal. - View Dependent Claims (7, 8, 9, 10)
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11. A system for distributing a time signal to a receiving device, comprising:
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a local time source configured to produce a counter signal; a Global Navigation Satellite System (GNSS) signal receiver configured to receive a GNSS time signal from a GNSS constellation; a time quality module in communication with the GNSS signal receiver and the local time source, configured to; receive the counter signal from the local time source; receive the GNSS time signal from the GNSS signal receiver; determine a time reference based on the GNSS signal receiver; determine a profile as a rate of change of the counter signal relative to the GNSS time signal; maintain a history of the profile; determine a change in the profile; and in response to determining a change in the profile, determining manipulation of the GNSS time signal; and a time output in communication with the time quality module, configured to; receive the time reference from the time quality module; distribute the time reference to a receiving device; and upon determination of manipulation, distribute to the receiving device a manipulation indicator related to the determination of manipulation of the GNSS time signal.
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Specification