BIT ERROR RATE REDUCTION IN CHAOTIC COMMUNICATIONS

• US 20110004792A1
• Filed: 07/01/2009
• Published: 01/06/2011
• Est. Priority Date: 07/01/2009
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Michaels, Alan J., Chester, David B.
• Granted Patent: US 8,369,376 B2
• Time in Patent Office: Days
• US Class Current: 714/701
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04J 13/0018 Chaotic

Abstract

A system for chaotic sequence spread spectrum communications includes a transmitter (402) for transmitting information symbols using a chaotic sequence of chips generated at the transmitter, the information symbols having a duration of transmission based on a threshold symbol energy value and the chips. The system also includes a receiver (404) for extracting the information symbols from the transmitted signal using a chaotic sequence of chips generated at the receiver and the threshold symbol energy value. In the system, the chips generated at the transmitter and the receiver are identical and synchronized in time, where the duration of transmission of the information symbols in the carrier is a total duration of a selected number of the chips used for transmitting, and where the number of the chips is selected for the information symbols to provide a total chip energy greater than or equal to the threshold symbol energy value.

Claims

1. A method for communicating a sequence of information symbols between a transmitter and a receiver using a chaotic sequence spread spectrum signal, the method comprising:

generating identical sequences of chaotic chips at said transmitter and said receiver, said sequences of chips synchronized in time;

transmitting a sequence of information symbols in signal using said sequence of chips generated at said transmitter, each of said information symbols in said signal having a variable duration of transmission based on a threshold symbol energy value and said chips generated at said transmitter;

extracting said sequence of information symbols from said transmitted signal, each of said information symbols in said transmitted signal extracted using said chips generated at said receiver and said threshold symbol energy value;

wherein said duration of transmission of each of said information symbols in said signal is a total duration of a selected number of said chips used for transmitting each information symbols, and wherein said number of said chips is selected for each of said information symbols to provide a total chip energy that is greater than or equal to said threshold symbol energy value.

2. The method of claim 1, wherein said modulating further comprises:

selecting a first of said sequence of information data;

encoding a current portion of said information data using said selected one of said sequence of information encoding symbols;

modulating said current portion of said symbol using a current portion of said identical sequence of chips generated at said transmitter;

calculating a total energy of all of said chips used for modulating said selected one of said plurality of information symbols;

comparing said total energy for modulating to said threshold symbol energy value; and

based on said comparison, ascertaining whether to encode a next portion of said information data using a next of said sequence of information symbols.

3. The method of claim 2, said ascertaining further comprising:

if said total energy for modulating is greater than or equal to said threshold symbol energy value, selecting said next one of said plurality of information symbols, and repeating said encoding, said modulating, said calculating, said comparing, and said ascertaining.

4. The method of claim 2, said ascertaining further comprising:

if said total energy for modulating is less than said threshold symbol energy value associated with said selected one of said plurality of symbols, encoding a next portion of said carrier using said selected one of said plurality of information symbols and repeating said modulating, said calculating, said comparing, and said ascertaining.

5. The method of claim 2, said calculating further comprising:

obtaining conjugate pair product values for each of said chaotic chips in portions of said first of said identical sequences associated with said selected one of said symbols; and

obtaining a sum of said conjugate pair product values.

6. The method of claim 1, wherein said demodulating further comprises:

selecting a first portion of said transmitted signal;

associating said selected portion of said transmitted signal with one of said sequence of said information symbols;

demodulating said selected portion of said transmitted signal using a current portion of said identical sequence of chips generated at said receiver;

calculating a total energy of all of said chips used for demodulating said associated one of said sequence of information symbols;

comparing said total energy for demodulating to said threshold symbol energy value;

based on said comparison, ascertaining whether to associate a next portion of said transmitted signal with said associated one of said sequence of information symbols;

7. The method of claim 6, said ascertaining further comprising:

if said total energy for demodulating is greater than or equal to said selected threshold symbol energy value, decoding said one of said sequence of information symbols;

selecting a next portion of said transmitted signal;

associating said selected portion of said transmitted signal with a next one of said sequence of information symbols; and

repeating said demodulating, said calculating, said comparing, and said ascertaining.

8. The method of claim 6, said ascertaining further comprising:

if said total energy for demodulating is less than said selected threshold symbol energy value, selecting a next portion of said transmitted signal, and repeating said demodulating, said calculating, said comparing, and said ascertaining.

9. The method of claim 6, said calculating further comprising:

obtaining conjugate pair product values for each of said chips used for demodulating said associated one of said sequence of information symbols; and

obtaining a sum of said conjugate pair product values.

19. The method of claim 1, wherein said transmitter is further configured to dynamically modify or re-configure the symbol energy threshold.

20. The system of claim 1, wherein said receiver is further configured to dynamically modify or re-configure the symbol energy threshold.

10. A system for communicating a chaotic sequence spread spectrum signal, the system comprising:

a transmitter for transmitting a sequence of information symbols in a spread spectrum signal using a chaotic sequence of chips generated at said transmitter, each of said information symbols in said signal having a duration of transmission based on a threshold symbol energy value and said chips generated at said transmitter; and

a receiver for extracting said sequence of information symbols from said transmitted signal, each of said information symbols in said transmitted signal extracted using a chaotic sequence of chips generated at said receiver and said threshold symbol energy value;

wherein said chaotic sequences of chips generated at said transmitter and said receiver are identical and synchronized in time, wherein said duration of transmission of each of said information symbols in said carrier is a total duration of a selected number of said chips used for transmitting each information symbols, and wherein said number of said chips is selected for each of said information symbols to provide a total chip energy that is greater than or equal to said threshold symbol energy value.

11. The system of claim 10, wherein said transmitter is further configured for:

selecting a first of said sequence of information data;

encoding a current portion of said information data using said selected one of said sequence of information encoded symbols;

modulating said current portion of said symbol using a current portion of said identical sequence of chips generated at said transmitter;

calculating a total energy of all of said chips used for modulating said selected one of said plurality of information symbols;

comparing said total energy for modulating to said threshold symbol energy value; and

based on said comparison, ascertaining whether to encode a next portion of said signal using a next of said sequence of information symbols.

12. The system of claim 11, wherein said transmitter is further configured during said ascertaining for selecting said next one of said plurality of information symbols, and repeating said encoding, said modulating, said calculating, said comparing, and said ascertaining if said total energy for modulating is greater than or equal to said selected threshold symbol energy value.

13. The system of claim 12, wherein said transmitter is further configured during said ascertaining for encoding a next portion of said signal using said selected one of said plurality of information symbols and repeating said modulating, said calculating, said comparing, and said ascertaining if said total energy for modulating is less than said selected threshold symbol energy value associated with said selected one of said plurality of symbols.

14. The system of claim 11, wherein said transmitter is further configured during said calculating for:

obtaining conjugate pair product values for each of said chips used for modulating said selected one of said sequence of information symbols; and

obtaining a sum of said conjugate pair product values.

15. The system of claim 10, wherein said receiver is further configured for:

selecting a first portion of said transmitted signal;

associating said selected portion of said transmitted signal with one of said sequence of said information symbols;

demodulating said selected portion of said transmitted signal using a current portion of said identical sequence of chips generated at said receiver;

calculating a total energy of all of said chips used for demodulating said associated one of said sequence of information symbols;

comparing said total energy for demodulating to said threshold symbol energy value;

based on said comparison, ascertaining whether to associate a next portion of said transmitted signal with said associated one of said sequence of information symbols;

16. The system of claim 15, wherein said receiver is further configured during said ascertaining for:

decoding said one of said sequence of information symbols if said total energy for demodulating is greater than or equal to said threshold symbol energy value;

selecting a next portion of said transmitted signal;

associating said selected portion of said transmitted signal with a next one of said sequence of information symbols; and

repeating said demodulating, said calculating, said comparing, and said ascertaining.

17. The system of claim 16, wherein said receiver is further configured during said ascertaining for:

selecting a next portion of said transmitted signal, and repeating said demodulating, said calculating, said comparing, and said ascertaining if said calculated demodulation energy is less than said selected threshold symbol energy value.

18. The system of claim 16, wherein said receiver is further configured during said calculating to obtain conjugate pair product values for each of said chaotic chips in said second of said identical sequences associated with said one of said symbols and obtain a sum of said conjugate pair product values.