HIDDEN MARKOV MODEL DETECTION FOR SPREAD SPECTRUM WAVEFORMS

• US 20110222584A1
• Filed: 03/11/2010
• Published: 09/15/2011
• Est. Priority Date: 03/11/2010
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Michaels, Alan J.
• Granted Patent: US 8,345,725 B2
• Time in Patent Office: Days
• US Class Current: 375/130
• CPC Class Codes: H04J 13/0018 Chaotic
• CPC Class Codes: H04J 13/10 Code generation

Abstract

Systems (100) and methods (700) for processing a data signal in a communications system. The methods involve generating a first chaotic sequence at a transmitter (102). The methods also involve performing first basis function algorithms using the first chaotic sequence to generate first statistically orthogonal chaotic sequences. At least one sequence is selected from the first statistically orthogonal chaotic sequences for combining with a first data signal. The selected sequence is combined with a second data signal to obtain a modulated chaotic communication signal. The modulated chaotic communication signal is transmitted to a receiver (104). At the receiver, the received modulated chaotic communication signal is processed to obtain data therefrom. Notably, the signal processing generally involves performing a deterministic process (e.g., a Hidden Markov Model deterministic process).

Claims

1. A method for processing a data signal in a communications system, comprising the steps of:

generating a first chaotic sequence at a transmitter of a first communication device;

performing at least two first basis function algorithms using said first chaotic sequence to generate at least two first statistically orthogonal chaotic sequences;

selecting at least one sequence from said first statistically orthogonal chaotic sequences for combining with a first data signal;

combining said selected sequence with a second data signal to obtain a modulated chaotic communication signal; and

transmitting said modulated chaotic communication signal to a receiver of a second communication device.

2. The method according to claim 1, further comprising selecting each of said first basis function algorithms from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm, an encryption algorithm, a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

3. The method according claim 1, wherein said sequence is selected from said first statistically orthogonal chaotic sequences based on at least one bit value of symbol formatted data contained in said first data signal.

4. The method according to claim 1, further comprising:

receiving said modulated chaotic communication signal at said receiver; and

processing said received modulated chaotic communication signal to obtain data therefrom.

5. The method according claim 4, wherein said processing step further comprises:

generating a second chaotic sequence which is a time synchronized replica of said first chaotic sequence generated at said transmitter;

performing at least two second basis function algorithms using said second chaotic sequence to generate at least two second statistically orthogonal chaotic sequences, each said second statistically orthogonal chaotic sequence being a time synchronized replica of a respective one of said first statistically orthogonal chaotic sequences generated at said transmitter; and

combining said received modulated chaotic communication signal with each of said second statistically orthogonal chaotic sequences to generate at least two observation signals each including a plurality of observations.

6. The method according to claim 5, further comprising selecting each of said second basis function algorithms from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm and an encryption algorithm.

7. The method according to claim 5, further comprising selecting each of said second basis function algorithms from the group consisting of a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

8. The method according to claim 5, wherein said processing step further comprises determining a plurality of correlation values for said observation symbols, each said correlation value associated with a respective one of said observation symbols.

9. The method according to claim 8, wherein each said correlation value is defined by at least one of a magnitude and a phase of said respective one of said observations.

10. The method according to claim 8, wherein said processing step further comprises:

selecting a first set of correlation values from said plurality of correlation values; and

identifying a largest correlation value from said first set of correlation values.

11. The method according to claim 10, wherein further comprising performing a deterministic process using at least said largest correlation value to determine if an observation associated with said largest correlation value represents a symbol of said first data signal.

12. The method according to claim 11, further comprising selecting said deterministic process to include a Hidden Markov Model deterministic process.

13. The method according to claim 11, further comprising selecting said deterministic process from the group consisting of a decision tree based deterministic process and a fractal evolutionary diagram based deterministic process.

14. The method according to claim 11, further comprising demodulating said observation associated with said largest correlation value if said observation associated with said largest correlation is determined to represent a symbol of said first data signal.

15. The method according to claim 11, further comprising adjusting a correlation window to increase a sequence length of said observation signal associated with said largest correlation value if said observation associated with said largest correlation is not determined to represent a symbol of said first data signal.

16. The method according to claim 11, further comprising adjusting said deterministic process in accordance with results of a comparison of said observation signals to an a priori known sequence of data symbols from said first data signal.

17. A method for processing a modulated chaotic communication signal at a receiver of a communications system, comprising the steps of:

receiving, at said receiver, said modulated chaotic communication signal transmitted from a transmitter;

generating a first chaotic sequence which is a time synchronized replica of a second chaotic sequence generated at said transmitter;

performing at least two basis function algorithms using said first chaotic sequence to generate at least two first statistically orthogonal chaotic sequences, each of said first statistically orthogonal chaotic sequence being a time synchronized replica of a respective one of a plurality of second statistically orthogonal chaotic sequences generated at said transmitter;

generating at least two observation signals by combining said received modulated chaotic communication signal with each of said first statistically orthogonal chaotic sequences including a plurality of observations;

determining a plurality of correlation values for said observations, each said correlation value associated with a respective one of said observations;

selecting a set of correlation values from said plurality of correlation values;

identifying a largest correlation value from said set of correlation values; and

performing a deterministic process using at least said largest correlation value to determine if an observation associated with said largest correlation value represents a symbol of said first data signal.

18. The method according to claim 17, further comprising selecting each of said basis function algorithms from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm, an encryption algorithm, a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

19. The method according to claim 17, wherein each said correlation value is defined by at least one of a magnitude and a phase of a respective observation.

20. The method according to claim 17, further comprising selecting said deterministic process to include a Hidden Markov Model deterministic process.

21. The method according to claim 17, further comprising selecting said deterministic process from the group consisting of a decision tree based deterministic process and a fractal evolutionary based deterministic process.

22. The method according to claim 17, further comprising demodulating said observation associated with said largest correlation value if said observation associated with said largest correlation is determined to represent a symbol of said first data signal.

23. The method according to claim 17, further comprising adjusting a correlation window to increase a sequence length of said observation signal associated with said largest correlation value if said observation associated with said largest correlation is not determined to represent a symbol of said first data signal.

24. The method according to claim 17, further comprising adjusting said deterministic process in accordance with results of a comparison of said observation signals to an a priori known sequence of data symbols from said first data signal.

31. The communication system according to claim 20, wherein said processing device is further configured for determining a plurality of correlation values for said observations, each said correlation value associated with a respective one of said observations.

32. The communication system according to claim 31, wherein each said correlation value is defined by at least one of a magnitude and a phase of said respective one of said observations.

33. The communication system according to claim 31, wherein said processing device is further configured for

selecting a first set of correlation values from said plurality of correlation values, and

identifying a largest correlation value from said first set of correlation values.

34. The communication system according to claim 33, wherein said processing device is further configured for performing a deterministic process using at least said largest correlation value to determine if an observation associated with said largest correlation value represents a symbol of said first data signal.

35. The communication system according to claim 34, wherein said deterministic process comprises a Hidden Markov Model deterministic process.

36. The communication system according to claim 34, wherein said deterministic process is selected from the group consisting of a decision tree based deterministic process and a fractal evolutionary diagram based deterministic process.

37. The communication system according to claim 34, wherein said processing device is further configured for demodulating said observation associated with said largest correlation value if said observation associated with said largest correlation is determined to represent a symbol of said first data signal.

38. The communication system according to claim 34, wherein said processing device is further configured for adjusting a correlation window to increase a sequence length of said observation signal associated with said largest correlation value if said observation associated with said largest correlation is not determined to represent a symbol of said first data signal.

39. The communication system according to claim 34, wherein said processing device is further configured for adjusting said deterministic process in accordance with results of a comparison of said observation signals to an a priori known sequence of data symbols from said first data signal.

25. A communication system, comprising:

a first chaos generator configured for generating a first chaotic sequence;

a plurality of first sequence generators configured for performing first basis function algorithms using said first chaotic sequence to generate first statistically orthogonal chaotic sequences;

a first sequence selector configured for selecting at least one sequence from said first statistically orthogonal chaotic sequences for combining with a first data signal;

a first complex multiplier configured for combining said selected sequence with a second data signal to obtain a modulated chaotic communication signal; and

a transmitter configured for transmitting said modulated chaotic communication signal to a receiver.

26. The communication system according to claim 25, wherein each of said first basis function algorithms is selected from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm, an encryption algorithm, a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

27. The communication system according claim 25, wherein said sequence is selected from said first statistically orthogonal chaotic sequences based on at least one bit value of symbol formatted data contained in said first data signal.

28. The communication system according to claim 25, further comprising:

a receiver configured for receiving said modulated chaotic communication signal at said receiver; and

at least one processing device configured for processing said received modulated chaotic communication signal to obtain data therefrom.

29. The communication system according claim 28, wherein said processing device is further configured for

generating a second chaotic sequence which is a time synchronized replica of said first chaotic sequence generated at said transmitter,

performing at least two second basis function algorithms using said second chaotic sequence to generate at least two second statistically orthogonal chaotic sequences, each said second statistically orthogonal chaotic sequence being a time synchronized replica of a respective one of said first statistically orthogonal chaotic sequences generated at said transmitter, and

combining said received modulated chaotic communication signal with each of said second statistically orthogonal chaotic sequences to generate at least two observation signals each including a plurality of observation symbols.

30. The communication system according to claim 29, wherein each of said second basis function algorithms is selected from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm, an encryption algorithm, a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

40. A communication system, comprising:

a receiver configured to receive a modulated chaotic spread spectrum communication signal transmitted from a transmitter; and

at least one processing device configured for

generating a first chaotic sequence which is a time synchronized replica of a second chaotic communication sequence generated at said transmitter,

performing at least two first basis function algorithms using said first chaotic sequence to generate at least two first statistically orthogonal chaotic sequences, each said first statistically orthogonal chaotic sequence being a time synchronized replica of a respective one of second statistically orthogonal chaotic sequences generated at said transmitter, and

combining said received modulated chaotic spread spectrum communication signal with each of said first statistically orthogonal chaotic sequences to generate at least two observation signals each including a plurality of observation symbols.

41. The communication system according to claim 40, wherein each of said first basis function algorithms is selected from the group consisting of a bijective function, a rotation algorithm, a scrambling algorithm, an XOR algorithm, an encryption algorithm, a uniform statistics preserving transformation, a statistical shaping transformation, a time-delayed statistical shaping transformation, and a fractal evolution statistical shaping transformation.

42. The communication system according to claim 40, wherein the processing device is further configured for determining a plurality of correlation values for said observations, each said correlation value associates with a respective one of said observations.

43. The communication system according to claim 42, wherein each said correlation value is defined by at least one of a magnitude and a phase of said respective one of said observations.

44. The communication system according to claim 42, wherein said processing device is further configured for

selecting a first set of correlation values from said plurality of correlation values, and

identifying a largest correlation value from said first set of correlation values.

45. The communication system according to claim 44, wherein said processing device is further configured for performing a deterministic process using at least said largest correlation value to determine if an observation associated with said largest correlation value represents a respective one of a plurality of possible transmitted data symbols.

46. The communication system according to claim 45, wherein said deterministic process comprises a Hidden Markov Model deterministic process.

47. The communication system according to claim 45, wherein said deterministic process is selected from the group consisting of a decision tree based deterministic process and a fractal evolutionary diagram based deterministic process.

48. The communication system according to claim 45, wherein said processing device is further configured for demodulating said observation associated with said largest correlation value if said observation associated with said largest correlation is determined to represent said respective one of a plurality of possible transmitted data symbols.

49. The communication system according to claim 45, wherein said processing device is further configured for adjusting a correlation window to increase a sequence length of said observation signal associated with said largest correlation value if said observation associated with said largest correlation is not determined to represent said respective one of a plurality of possible transmitted data symbols.