Signal inconsistency detection of spoofing

• US 7,564,401 B1
• Filed: 08/10/2004
• Issued: 07/21/2009
• Est. Priority Date: 08/10/2004
• Status: Active Grant

• Current Assignee: Northrop Grumman Guidance And Electronics Company, Inc.
• Original Assignee: Northrop Grumman Corporation
• Inventors: Strachan, Victor F.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US10/916,075
• Publication Number:
  US 20090167597A1
• Time in Patent Office: 1,806 Days
• Field of Search: None
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/215 issues related to spoofing
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H04K 2203/22 for communication related to vehicles
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring
• CPC Class Codes: H04K 3/255 based on redundancy of transmitted data, transmission path or transmitting source
• CPC Class Codes: H04K 3/65 using deceptive jamming or spoofing, e.g. transmission of false signals for premature triggering of RCIED, for forced connection or disconnection to/from a network or for generation of dummy target signal
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

Methods and apparatus relating to signal inconsistency detection of spoofing (SIDS), i.e. the use of inconsistencies in signals received at a plurality of points in space to detect spoofing.

Claims

1. In a system having a GPS receiver, a plurality of antennas coupled to the GPS receiver, and knowledge of antenna orientation with respect to a frame of reference in which positions of satellites and the antennas are known, a method for detecting whether received signals are spoofing signals, the method comprising the steps of:

predicting a line-of-sight (LOS) from the antennas to a selected one of the satellites;

determining one or more vectors between the antennas;

measuring a LOS to a transmitter according to the one or more vectors and the phase differences between signals received at the antennas from the transmitter;

computing a difference between the predicted LOS and the measured LOS; and

comparing the computed difference to a statistical distribution of differences to establish a probability that the received signals are spoofing signals.

2. The method of claim 1 further comprising determining range and bearing of a spoofing source based on the phase differences.

3. The method of claim 1 further comprising determining, if the probability is greater than an acceptance criteria, that the received signals are spoofing signals.

4. The method of claim 1 further comprising repeating the steps a number of times to obtain a series of computed differences, and comparing the series of computed differences to the statistical distribution of differences until statistical uncertainty whether the received signals are spoofing signals is reduced to an acceptable point.

5. In a system having a GPS receiver, a movable antenna coupled to the GPS receiver, an inertial reference system (IRS) tracking movement of the antenna with respect to a frame of reference in which positions of satellites and the antenna are known, a method for detecting whether received signals are spoofing signals, the method comprising the steps of:

receiving a signal from a transmitter with the antenna at a first point in space and time;

moving the antenna to a second point in space and time;

receiving the signal from the transmitter with the antenna at the second point in space and time;

measuring a phase difference between the signal received at the first point in space and time and the signal received at the second point in space and time;

predicting a phase difference between the signal received at the first point in space and time and the signal received at the second point in space and time;

computing a difference between the predicted phase difference and the measured phase difference; and

comparing the computed difference to a statistical distribution of differences to establish a probability that the received signals are spoofing signals.

6. The method of claim 5 further comprising repeating the process with the antenna at subsequent points in space and time until statistical uncertainty in deciding whether the signal is a spoofing signal is reduced to an acceptable level.

7. The method of claim 5 wherein the predicting step accounts for motion of the antenna as measured by the IRS.

8. The method of claim 5 wherein the predicting step accounts for motion of the transmitter during a period between (i) time of transmission of the signal received at the first point in space and time and (ii) time of transmission of the signal received at the second point in space and time.

9. The method of claim 5 wherein the measuring step further comprises making independent redundant measurements to reduce noise effects in the measured phase difference used in the computing step.