Chaotic carrier pulse position modulation communication system and method

• US 6,310,906 B1
• Filed: 08/18/1999
• Issued: 10/30/2001
• Est. Priority Date: 08/18/1999
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Volkovskii, Alexander R., Larson, Lawrence E., Tsimring, Lev S., Sushchik, Mikhail M., Abarbanel, Henry D. I., Rulkov, Nikolai F.
• Primary Examiner(s): Vo, Don N.
• Application Number:
  US09/376,440
• Time in Patent Office: 804 Days
• Field of Search: 375/239, 375/130, 380/262, 380/274, 380/46, 329/313, 332/112
• US Class Current: 375/130
• CPC Class Codes: H03K 7/04 Position modulation, i.e. PPM
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 14/026 using pulse time characteristics modulation, e.g. width, position, interval
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation
• CPC Class Codes: H04L 27/001 using chaotic signals for secret or secure communication H04L9/001

Abstract

A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

Claims

1. A communication system comprising:

a transmitter, said transmitter including

a transmission chaotic pulse regenerator which generates a carrier pulse train having chaotically variable interpulse intervals;

a data encoder which encodes data onto said carrier pulse train by selectively altering or not altering an interval between consecutive pulses to produce a pulse signal; and

a receiver which receives said pulse signal from said transmitter via a communication medium, said receiver including

a reception chaotic pulse regenerator matched to the transmission pulse regenerator, said reception chaotic pulse regenerator generating a synchronized replica of said carrier pulse train; and

a data decoder that receives said pulse signal and decodes said data based upon said synchronized replica of said carrier pulse train.

2. The system according to claim 1, wherein said data encoder comprises a delay circuit which delays a pulse in said carrier pulse train to alter an interpulse interval.

3. The system according to claim 1, wherein said data decoder only receives limited portions of said pulse signal in which data is expected.

4. The system according to claim 3, wherein said limited portions are determined by said synchronized replica of said carrier pulse train.

5. The system according to claim 1, wherein said decoder receives said pulse signal, commences an integration function each time the pulse signal exceeds a predetermined threshold and determines whether an interpulse interval has been altered by evaluating the difference between the value of the integration function and a nonlinear function used by said reception chaotic pulse regenerator to generate said synchronized replica of said carrier pulse train.

6. The system according to claim 5, wherein said decoder determines that an interpulse interval has been altered when the difference between the value of the integration function and the nonlinear function at the time coinciding with arrival of a pulse in said pulse signal exceeds a predetermined value.

7. The system according to claim 1, wherein said reception chaotic pulse regenerator receives said pulse signal as input for synchronization to said transmission chaotic pulse regenerator.

8. The system according to claim 7, wherein said data decoder comprises a subtractor and an integrator and said reception chaotic pulse regenerator comprises a nonlinear function generator, said subtractor determining the difference between a threshold value generated by said nonlinear function generator at a moment when the pulse signal exceeds a predetermined threshold to decode said data.

9. The system according to claim 8, wherein said receiver further comprises a window control unit which selectively blocks input of said pulse signal to said reception chaotic pulse regenerator outside windows of time when a pulse is expected in said pulse signal.

10. A method for communicating information comprising the steps of:

generating a pulse train carrier signal having adjacent pulses separated by a chaotically varying time;

pulse position modulating said pulse train carrier signal to produce a pulse signal;

transmitting said pulse signal over a communication medium to a receiver;

in the receiver, generating a synchronized replica of said pulse train carrier signal, and determining the modulation of said pulse train carrier performed in said modulating step based upon said synchronized replica of said pulse train carrier signal.

11. The method according to claim 10, further comprising:

in the receiver, predicting, based upon said synchronized replica of said pulse train carrier and a sample of said pulse signal, expected arrival times for pulses in said pulse signal; and

in the receiver, limiting said step of determining the modulation to windows of time corresponding to said expected arrival times for pulses.

12. The method according to claim 10, wherein spacing between adjacent (n−

1)-th and n-th pulses in said pulse signal is proportional to a threshold value x_n, the threshold value x_n being generated according to a map x_n+1=F(x_n)+s_n where F(x) is a nonlinear function and s_n is an information signal.