Communication systems and methods employing receivers with estimators

• US 6,104,703 A
• Filed: 12/20/1996
• Issued: 08/15/2000
• Est. Priority Date: 12/20/1996
• Status: Expired due to Fees

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Sobiski, Donald J., Thorp, James S.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US08/770,115
• Time in Patent Office: 1,334 Days
• Field of Search: 370/252, 375/232, 375/233, 375/246, 375/285
• US Class Current: 370/252
• CPC Class Codes: H04L 27/001 using chaotic signals for secret or secure communication H04L9/001

Abstract

Communications systems and methods employ receivers which utilize estimators, such as extended Kalman filters, to estimate a transmitted information signal based only upon initial parameters in a transmitter and a single transmitted state of the transmitter. This arrangement facilitates the use of inherently secure chaotic modulation schemes in the transmitter. In one embodiment, one or more parameters of nonlinear transmitter elements are modulated with one or more information signals to generate a chaotically varying transmission signal. A communication scheme known as Parameter Division Multiple Access (PDMA) is thus created in which multiple information signals from multiple transmitters can be combined and transmitted to corresponding multiple receivers in a single transmission signal. A special Kalman filter known as a feedback Kalman filter is employed for separating each receiver'"'"'s corresponding portion of the transmitted signal.

Claims

1. A method for communicating at least one information signal from a transmitter to a receiver comprising the steps of:

a) providing a transmitter for generating a transmitter signal said transmitter being based on a chaotically varying system;

b) modulating at least one electrical parameter in said transmitter with an information signal to generate a chaotically varying modulated transmitter signal including a plurality of states;

c) transmitting only a selected portion of said modulated transmitter signal to a receiver, said selected portion including less than all of said states;

d) providing said receiver with initial parameter information for said transmitter;

e) applying said selected portion of said modulated transmitter signal to an Extended Kalman Filter (EKF) in said receiver; and

f) generating an estimate of said information signal with said EKF using only said selected portion of said modulated transmitter signal and said initial parameter information.

2. The method of claim 1, wherein said step of transmitting only a selected portion of said modulated transmitter signal further comprises transmitting only a single one of said states of said modulated transmitter signal to said receiver.

3. The method of claim 1, wherein said step of modulating further comprises modulating said transmitter signal with a first information signal by modulating a parameter in said transmitter with said first information signal, and simultaneously modulating said transmitter signal with a second information signal by modulating a second parameter in said transmitter with said second information signal to generate a modulated transmitter signal for communicating both of said first and second information signals to said receiver.

4. A method for communicating a plurality of information signals from a plurality of transmitters to a plurality of receivers comprising the steps of:

a) providing a plurality of transmitters for generating a plurality of corresponding transmitter signals;

b) modulating each said transmitter signal with a corresponding one of a plurality of information signals to generate a plurality of modulated transmitter signals;

c) combining said plurality of modulated transmitter signals to form a combined modulated transmitter signal;

d) transmitting a selected portion of said combined modulated transmitter signal to a means for separating each said modulated transmitter signal from said combined modulated transmitter signal;

e) separating said selected portion of said combined modulated transmitter signal into a plurality of received signals, each of which corresponds to one of said modulated transmitter signals; and

f) applying each of said received signals to a corresponding estimator in a corresponding one of said receivers for generating an estimate of each said corresponding information signal therefrom.

5. The method of claim 4, wherein said means for separating comprises a plurality of subtractors, one for each receiver, for subtracting all but a corresponding one of said received signals from said combined modulated transmitter signal.

6. The method of claim 5, wherein each of said received signals is generated as an estimate by a corresponding one of said estimators.

7. The method of claim 5, wherein each of said estimators comprises an extended Kalman filter.

8. A communication system comprising:

a) a transmitter for transmitting an information signal by modulating a transmitter signal with an information signal, said transmitter being based on a chaotically varying system and including;

1) means for modulating at least one electrical parameter in said transmitter with an information signal to generate a chaotically varying modulated transmitter signal including a plurality of states; and

2) means for transmitting only a selected portion of said modulated transmitter signal, said selected portion including less than all of said states; and

b) a receiver for receiving said selected portion of said modulated transmitter signal, said receiver including an Extended Kalman Filter (EKF) for generating an estimate of said information signal from said selected portion of said modulated transmitter signal and initial parameter information for said transmitter.

9. The system of claim 8, wherein said selected portion comprise only a single one of said states in said modulated transmitter signal.

10. The system of claim 8, wherein said transmitter further includes means for modulating said transmitter signal with a second information signal, whereby said EKF generates an estimate of both of said first and second information signals.

11. A communication system comprising:

a) a plurality of transmitters for transmitting a corresponding plurality of information signals, each of said transmitters including means for modulating a parameter in each of said transmitters with a corresponding one of said plurality of information signals, thereby generating a plurality of modulated transmitter signals;

b) means for selecting a portion of each of said modulated transmitter signals to be transmitted;

c) means for combining said portions of said plurality of modulated transmitter signals to form a combined modulated transmitter signal; and

d) a plurality of receivers, each for receiving a corresponding one of said information signals, each said receiver including means for generating an estimate of said corresponding information signal from said selected portion of said combined modulated transmitter signal.

12. The system of claim 11, wherein each means for estimating comprises an extended Kalman filter.

13. The system of claim 12, further comprising a plurality of subtractor means, one for each said extended Kalman filter, for subtracting from said combined modulated transmitter signal, estimates generated by each of said other extended Kalman filters, to generate said selected portion of said modulated transmitter signal corresponding to said information signal to be estimated by said extended Kalman filter.

14. The system of claim 11, wherein each parameter to be modulated in each of said transmitters is a parameter of a nonlinear device in a chaotically behaving system within said transmitter, whereby each said modulated transmitter signal is chaotically varying.

15. The system of claim 11, wherein each said modulated transmitter signal includes a plurality of states, and said means for selecting selects only a single one of said states.