GPS near-far resistant receiver

• US 6,771,214 B2
• Filed: 09/12/2002
• Issued: 08/03/2004
• Est. Priority Date: 09/12/2001
• Status: Active Grant

• Current Assignee: Data Fusion Corp.
• Original Assignee: Data Fusion Corp.
• Inventors: Kober, Wolfgang, Krumvieda, Robert K., Thomas, John K.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US10/243,301
• Publication Number:
  US 20030218568A1
• Time in Patent Office: 691 Days
• Field of Search: 342/357.12, 342/357.06, 701/213
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/215 issues related to spoofing
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04K 3/255 based on redundancy of transmitted data, transmission path or transmitting source
• CPC Class Codes: H04K 3/46 characterized in that the jamming signal is produced by retransmitting a received signal, after delay or processing
• 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

A method and receiver are disclosed for mitigating or substantially canceling signal interference between signals detected at the receiver. Once a presumed interfering signal(s) is acquired, parameters are determined that allow the interferer(s) to be modeled. An orthogonal projection (for projecting onto a subspace orthogonal to that spanned by the interferer(s)) is applied to the composite of all signals (y) for thereby projecting y onto this subspace, wherein the subspace is non-orthogonal to a representation of desired (but interfered) signal of the composite signals. With the receiver properly equipped to perform this projection operation, interfering signals, multipath, spoofing and/or meaconing can be effectively diminished.

Claims

1. A method for determining navigation information, comprising:

receiving a composite signal (y), wherein y includes, from each of a plurality of signaling sources, a corresponding wireless signal including navigation data;

obtaining, for each signal of one or more of said corresponding wireless signals, corresponding signal modeling data indicative of the signal;

performing a projection, of a representation of y, onto a subspace that is orthogonal to a space spanning a representation of at least one signal (s₀) of the one or more corresponding wireless signals, said space determined using said corresponding signal modeling data for s₀, and wherein said subspace is non-orthogonal to a representation of another signal (h₀) of said corresponding signals;

using a result from said step of performing for acquiring said another corresponding signal h₀;

first determining, after acquiring said another corresponding signal h₀, said navigation data from said another corresponding signal h₀; and

second determining navigation information using said navigation data from a plurality of said signaling sources including said signaling source for said another corresponding signal h₀.

2. The method of claim 1, wherein said receiving step includes receiving one or more of said corresponding signals from at least one of:

a satellite, a pseudolite, an aerial vehicle;

wherein said navigation data includes one or more of;

a telemetry word, hand-over word, clock corrections, SV health/accuracy, ephemeris parameters, almanac data, ionospheric model data and coordinated universal time data;

wherein said navigation information includes data identifying one or more of;

a position, a velocity and time for an antenna used in performing said step of receiving.

3. The method of claim 1, further including a step of:

first performing at least one of the following steps of acquiring and tracking said corresponding wireless signal s₀; and

performing said steps of claim 1 following said receiving step, wherein for at least one of said one or more corresponding wireless signals, said corresponding signal modeling data includes at least some of;

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate obtained from said step of first performing.

4. The method of claim 3, wherein said step of first performing includes performing only said step of acquiring.

5. The method of claim 3, wherein said corresponding signal modeling data for s_o includes at least most of:

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate.

6. The method of claim 1, wherein said step of obtaining includes at least one of acquiring and tracking each signal of the one or more of said corresponding wireless signals.

7. The method of claim 1 further including a step of creating, from said modeling data for s₀, additional signal data dependent upon a pseudorandom noise code for s₀, wherein said space is determined using said additional signal data.

8. The method of claim 1, further including a step of identifying the signal s₀ of said one or more corresponding wireless signals as an interfering signal.

9. The method of claim 1, wherein said corresponding signal modeling data for s₀ is dependent upon one or more of:

(a) coarse acquisition code and a carrier frequency, and (b) a coarse acquisition code, a precise positioning code and a carrier frequency.

10. The method of claim 1, wherein said step of receiving includes receiving the composite signal y at a single antenna element.

11. The method of claim 1, wherein said step of obtaining includes for each of said one or more corresponding wireless signals, a step of obtaining, as at least part of said corresponding signal modeling data, two or more of:

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate.

12. The method of claim 1 further including a step of accessing a threshold criteria for identifying the signal s₀ as an interfering signal, wherein said threshold criteria includes one of:

(a) a predetermined number of the strongest of said corresponding signals, (b) a predetermined decibel increase above a predetermined value, (c) a signal to noise ratio, (d) a signal to carrier ratio, (e) a carrier to noise ratio, (f) relative amplitude and (g) a weighted sum of two or more of (a) through (f).

13. The method of claim 12 further including a step of at least one of tracking and acquiring the signal s₀ prior to performing said step of accessing, wherein information from the at least one step of tracking and acquiring is used in said step of accessing.

14. The method of claim 1, further including a step of constructing an in-phase reference signal from said signal modeling data for s₀, wherein said in-phase reference signal is used to determine said space.

15. The method of claim 14, wherein said step of constructing includes using said corresponding signal modeling data for s_o to create an in phase interference reference signal having the following representation:

16. The method of claim 1, wherein said step of performing includes computing said projection for canceling a contribution of s₀ to said result, wherein the subspace is representable by a matrix G whose columns span the subspace, said subspace including a portion of said another corresponding signal h₀, wherein said portion is perpendicular to s₀.

17. The method of claim 16, wherein G=P_S^⊥

H such that H is a representation of said another corresponding signal h₀ and P_S^⊥

=I−

P_S is the orthogonal projection operator matrix that takes an input and projects the input onto a space spanned by the columns of the matrix perpendicular to the matrix S determined from a representation of a collection of one or more of the wireless signals of said composite signal, wherein said collection interferes with the signal h₀.

18. The method of claim 1, wherein said step of performing includes third determining said result as {tilde over (y)}=P_S^⊥

y, wherein (1) P_S^⊥

=I−

P_S is an orthogonal projection matrix operator for projecting an input onto the subspace orthogonal to the space, said space spanned by the columns of a matrix S, wherein S=[s₁ s₂ . . . s_N], such that for each s_i of S, s_i includes a representation of one of the corresponding wireless signals identified as an interfering signal i, and (2) P_S=S(S^TS)<sup>−

1</sup>S^T is a matrix operator for performing a projection that takes an input and projects the input onto a space spanned by the matrix S, where S includes a representation of s_o as a subspace.

19. The method of claim 18, wherein subsequent to said step of third determining a further step of determining

20. The method of claim 1, wherein said navigation data includes:

a telemetry word, hand-over word, clock corrections, SV health/accuracy, ephemeris parameters, almanac, ionospheric model and coordinated universal time data.

21. The method of claim 1, wherein said navigation information includes one or more of a position, velocity and time corresponding to a location of a device performing at least said step of receiving.

22. The method of claim 1, wherein said corresponding wireless signals includes GPS signals.

23. The method of claim 1, further including a step of coupling with an inertial navigation system.

26. The method of claim 23, wherein said step of providing includes incorporating into said navigation device a data store for storing said signal modeling data including one or more of:

(a) a pseudo-random number, (b) code offset data, (c) phase and Doppler data, (d) code offset rate, (e) phase rate, (f) Doppler rate, and (g) at least one bit that can be toggled between being set and being unset depending on whether s₀ has been labeled an interferer or not.

24. A method for determining navigation information, comprising:

providing a navigation device that performs (a) through (i) following;

(a) receives a composite signal (y), wherein y includes, from each of a plurality of signaling sources, a corresponding wireless signal including navigation data;

(b) obtains, for each signal of one or more of said corresponding wireless signals, corresponding signal modeling data indicative of the signal;

(c) performs projection, of a representation of y, onto a subspace that is orthogonal to a space spanning a representation for at least one signal (s₀) of the one or more corresponding wireless signals, wherein said space is determined using said signal modeling data for s₀, and wherein said subspace is non-orthogonal to a representation of another signal (h₀) of said corresponding signals;

(d) uses a result from (c) for acquiring the another corresponding signal h₀;

(e) first determines said navigation data from the another corresponding signal h₀; and

(f) second determines navigation information using said navigation data from a plurality of said signaling sources including said signaling source for the another corresponding signal h₀.

25. The method of claim 24, wherein said step of providing includes incorporating into said navigation device an analog to digital converter having a dynamic range effective for capturing a digital representation of each of said corresponding signals.

27. The method of claim 24, wherein said navigational device stores information indicative of the signal s₀ being an interfering signal.

28. The method of claim 24, wherein said navigation device performs (d) after previously acquiring said another corresponding signal s₀.

29. The method of claim 24, wherein said corresponding signal modeling data for each signal of said one or more corresponding wireless signals includes two or more data items of:

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate;

wherein said two or more data items for the signal s₀ are used in determining said subspace.

30. The method of claim 29, wherein said navigation device uses, for the signal s₀, said corresponding signal modeling data to create an in phase interference reference signal for so having the following representation:

31. The method of claim 24, wherein said navigational device includes only one antenna element for receiving the composite signal.

33. The method of claim 28, wherein said step of first performing must be performed prior to said step of obtaining.

34. The method of claim 28, further including a step of constructing an in-phase reference signal from said signal modeling data for s₀, wherein said in-phase reference signal is used to determine said space.

35. The method of claim 28, further including a step of counting a number of times that an evaluation relative to a threshold criteria identifies the signal s₀ as an interfering signal.

36. The method of claim 35 further including a step of accessing the threshold criteria, wherein said threshold criteria includes one of:

(a) a predetermined number of the strongest of said corresponding GPS signals, (b) a predetermined decibel value of s₀, (c) a signal to noise ratio, (d) a signal to carrier ratio, (e) a carrier to noise ratio, (f) relative amplitude and (g) a weighted sum of two or more of (a) through (f).

45. The navigation system of claim 36, further including a navigation processing component for determining one or more of:

a position, a velocity and time for said antenna.

32. A method for determining navigation information, comprising:

receiving a composite signal (y), wherein y includes, from each of a plurality of GPS signaling sources, a corresponding GPS signal;

for at least one of said GPS signaling sources, first performing at least one of the steps of acquiring and tracking the corresponding GPS signal(s₀) for the at least one GPS signaling source;

obtaining signal modeling data indicative of substantially only the GPS signal s₀;

second performing an orthogonal projection, of a representation of y, onto a subspace that is orthogonal to a space spanning a representation of the GPS signal, said space determined using said signal modeling data, and wherein said subspace is non-orthogonal to a representation of a second GPS signal of the corresponding GPS signals;

using a result from said step of second performing for acquiring the second GPS signal;

first determining said navigation data from the second GPS signal; and

second determining navigation information using said navigation data from a plurality of said signaling sources including said signaling source for the second GPS signal.

37. A navigational system, comprising:

an antenna for receiving a composite navigation signal (y); and

an interference processing channel for performing the following steps;

(a) obtaining, for at least one signal (s₀) of one or more of individual signals of y, signal modeling data indicative of the individual signal s₀;

(b) performing projection, of a representation of y, onto a subspace that is orthogonal to a space spanning a representation of s₀, wherein said subspace is non-orthogonal to a representation of a particular one of the individual signals for which s₀ is an interfering signal;

(c) using a result from (b) for acquiring the particular signal; and

(d) determining navigation data from the particular signal.

38. The navigation system of claim 37, wherein one or more of said individual signals are GPS signals.

39. The navigational system of claim 37, wherein said interference processing channel includes a data store for storing said modeling data, wherein said modeling data includes at least some of:

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate.

40. The navigational system of claim 37, wherein said space is determined using said signal modeling data.

41. The navigational system of claim 40, wherein said interference processing channel determines said result from said step (b) by performing computations representative of {tilde over (y)}=P_S^⊥

y, wherein;

(1) P_S^⊥

=I−

P_S is an orthogonal projection matrix operator for projecting an input onto a space orthogonal to a space spanned by the columns of a matrix S, wherein S=[s₁ s₂ . . . s_N], such that for each s_i of S, s_i includes a representation of one of the corresponding wireless signals identified as an interfering signal, and (2) P_S=S(S^TS)<sup>−

1</sup> S^T is a matrix operator for performing the orthogonal projection that takes an input and projects the input onto a space spanned by the matrix S, where S includes a representation of s₀ as a subspace.

42. The navigational system of claim 37, further including a single antenna element for receiving the navigation signal y.

43. The navigation system of claim 37, further including a counting component for determining a number of times that an evaluation relative to a threshold criteria identifies the signal s₀ as an interfering signal.

44. The navigation system of claim 37, wherein said interference processing channel includes a digital receiver channel and a receiver processing component for at least one of acquisition and tracking of s₀;

wherein said receiver processing component provides one or more of;

a loop discriminator and filter, a data demodulation, a meters, and a phase lock loop.

46. The navigational system of claim 37, further including one of a navigation augmentation system and a landing system for providing at least of ranging information and differential information to said interference processing channel.

47. A navigational receiver, comprising:

an antenna for receiving a composite navigation signal (y); and

an interference processing channel means for performing the following steps;

(a) obtaining, for each signal of one or more of individual signals of y, corresponding signal modeling data indicative of the individual signal;

(b) identifying at least one of the individual signals (s₀) as an interfering signal;

(c) performing projection, of a representation of y, onto a subspace that is orthogonal to a space spanning a representation of s₀, said subspace determined using said corresponding signal modeling data for s₀, and wherein said subspace is non-orthogonal to a representation of another one of the individual signals for which s₀ is an interfering signal;

(d) using a result from (c) for acquiring said another signal; and

(e) determining navigation data from said another signal.

48. The navigational receiver of claim 47, wherein:

said interference processing channel means includes a data store for storing said corresponding signal modeling data for s₀, wherein said corresponding signal modeling data for s₀ includes at least some of;

a pseudo-random number, code offset data, a phase, Doppler data, code offset rate, phase rate, and Doppler rate;

said interference processing channel means includes a counting component for determining a number of times that an evaluation relative to a threshold criteria identifies the signal s₀ as an interfering signal;

said interference processing channel means includes a digital receiver channel and a receiver processing component for at least one of acquisition and tracking of s₀; and

further including a navigation processing component for determining one or more of;

a position, a velocity and time for said antenna.

49. The navigational receiver of claim 47, wherein said antenna has a single antenna element for receiving the composite navigation signal.