PERMISSION-BASED SECURE MULTIPLE ACCESS COMMUNICATION SYSTEMS

• US 20110002360A1
• 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 8,385,385 B2
• Time in Patent Office: Days
• US Class Current: 375/132
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 2209/20 Manipulating the length of blocks of bits, e.g. padding or block truncation
• CPC Class Codes: H04L 27/001 using chaotic signals for secret or secure communication H04L9/001
• CPC Class Codes: H04L 27/36 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 9/001 using chaotic signals
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

Systems (100) and methods for selectively controlling access to multiple data streams which are communicated using a shared frequency spectrum and spreading code. The methods involve forming a global data communication signal (134) by amplitude modulating a global data signal (130) comprising global data symbols and forming a phase modulated signal (120) by phase modulating a protected data signal. The phase modulated signal represents protected data symbols. The methods also involve forming a protected data communication signal (126) by changing phase angles of the protected data symbols using a variable angle Ø determined by a random number source and combining the protected data signal with a spreading sequence (CSC). The methods further involve combining the global and protected data communication signals to form an output communication signal (140) having a spread spectrum format. The output communication signal is transmitted over a communications channel (104).

Claims

1. A method for selectively controlling access to multiple data streams which are communicated using a shared frequency spectrum and a shared spreading code, comprising the steps of:

forming a global data communication signal by amplitude modulating a global data signal comprising global data symbols;

forming a phase modulated signal by phase modulating a data signal including protected data symbols;

forming a protected data communication signal by changing phase angles of said protected data symbols by a variable angle Ø and

combining said phase modulated signal with a spreading sequence;

combining said global data communication signal and said protected data communication signal to form an output communication signal having a spread spectrum format; and

transmitting said output communication signal over a communications channel.

2. The method according to claim 1, further comprising the step of generating said global data communication signal using discrete time baseband modulation to form amplitude modulated symbols.

3. The method according to claim 1, further comprising the step of generating said protected data communication signal using discrete time baseband modulation to form phase modulated symbols.

4. The method according to claim 1, further comprising the step of generating a random number sequence.

5. The method according to claim 4, wherein the random number sequence is a pseudorandom number sequence or a digitally generated chaotic sequence.

6. The method according to claim 4, further comprising using a random number of said random number sequence to select said variable angle Ø

.

7. The method according to claim 6, further comprising the step of using different random numbers of said random number sequence to select said variable angle Ø

for changing said phase angles of said protected data symbols.

8. The method according to claim 6, further comprising the step of using at least one random number of said random number sequence for changing a phase angle of at least one protected data symbol of said protected data symbols.

9. The method according to claim 1, further comprising the step of selecting said spreading sequence to be a chaotic spreading sequence.

10. The method according to claim 9, wherein said chaotic spreading sequence has a non-Gaussian statistical amplitude characteristic.

11. The method according to claim 1, further comprising the steps of:

receiving said output communication signal at a partial permission receiver;

generating a de-spreading sequence which is identical to said spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence;

correlating said output communication signal with said de-spreading sequence to form a correlated signal; and

amplitude demodulating said correlated signal to recover said global data symbols.

12. The method according to claim 1, further comprising the steps of:

receiving said output communication signal at a full permission receiver;

generating a de-spreading sequence which is identical to said chaotic spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence;

correlating said output communication signal with said de-spreading sequence to obtain a correlated signal comprising a plurality of data symbols;

changing phase angles of said plurality of data symbols using said variable angle Ø

to form a phase de-rotated signal; and

phase demodulating said phase de-rotated signal to obtain said protected data symbols.

13. The method according to claim 12, further comprising the step of amplitude demodulating said phase de-rotated signal to obtain said global data symbols.

14. The method according to claim 1, further comprising the steps of:

receiving said output communication signal at a full permission receiver, said output communications signal comprising a plurality of data symbols;

changing phase angles of said plurality of data symbols using said variable angle Ø

to form a phase de-rotated signal;

generating a de-spreading sequence which is identical to said spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence;

correlating said phase de-rotated signal with said de-spreading sequence to obtain a correlated signal; and

phase demodulating said correlated signal to obtain said protected data symbols.

15. The method according to claim 14, further comprising the step of amplitude demodulating said phase de-rotated signal to obtain said global data symbols.

16. A communication system configured for selectively controlling access to multiple data streams which are communicated using a shared frequency spectrum, comprising:

an amplitude modulator configured for forming a global data communication signal by amplitude modulating a global data signal comprising global data symbols;

a phase modulator configured for forming a phase modulated signal by phase modulating a data signal including protected data symbols;

a phase rotating and signal combining (PRSC) device configured for forming a protected data communication signal by changing phase angles of said plurality of protected data symbols using a variable angle Ø and

combining said phase modulated signal with a spreading sequence;

a second combiner configured for combining said global data communication signal and said protected data communication signal to form an output communication signal having a spread spectrum format; and

a transceiver configured for transmitting said output communication signal over a communications channel.

17. The communication system according to claim 16, wherein said amplitude modulator is further configured for generating said global data communications signal using discrete time baseband modulation to form amplitude modulated symbols.

18. The communication system according to claim 16, wherein said phase modulator is further configured for generating said protected data signal using discrete time baseband modulation to form phase modulated symbols.

19. The communication system according to claim 16, further comprising a random number sequence generator configured for generating a random number sequence.

20. The communication system according to claim 19, wherein said random number sequence is a pseudorandom number sequence or a digitally generated chaotic sequence.

21. The communication system according to claim 19, wherein said PRSC device is further configured for using a random number of said random number sequence to select said variable angle Ø

.

22. The communication system according to claim 21, wherein said PRSC device is further configured for using different random numbers of said random number sequence for changing said phase angles of said protected data symbols.

23. The communication system according to claim 21, wherein said PRSC device is further configured for using at least one random number of said random number sequence for changing a phase angle of at least one protected data symbol of said protected data symbols.

24. The communication system according to claim 16, further comprising at least one partial permission receiver configured for

receiving said output communication signal,

generating a de-spreading sequence which is identical to said spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence,

correlating said output communication signal with said de-spreading sequence to form a correlated signal, and

amplitude demodulating said correlated signal to recover said global data symbols.

25. The communication system according to claim 16, further comprising at least one partial permission receiver configured to perform signal tracking operations on known data symbols.

26. The communication system according to claim 16, further comprising at least one full permission receiver configured for

receiving said output communication signal,

generating a de-spreading sequence which is identical to said spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence,

correlating said output communication signal with said de-spreading sequence to obtain a correlated signal comprising a plurality of data symbols,

changing phase angles of said plurality of data symbols using said variable phase rotating angle to form a phase de-rotated signal, and

phase demodulating said phase de-rotated signal to obtain said protected data symbols.

27. The communication system according to claim 26, wherein said full permission receiver is further configured for amplitude demodulating said phase de-rotated signal to obtain said global data symbols.

28. The communication system according to claim 16, further comprising at least one full permission receiver configured for

receiving said output communication signal comprising a plurality of data symbols,

changing phase angles of said plurality of data symbols using said variable angle Ø

to form a phase de-rotated signal,

generating a de-spreading sequence which is identical to said spreading sequence used to construct said output communication signal, said de-spreading sequence being synchronized in time and frequency with said spreading sequence,

correlating said phase de-rotated signal with said de-spreading sequence to obtain a correlated signal,

phase demodulating said correlated signal to obtain said protected data symbols, and amplitude demodulating said phase de-rotated signal to obtain said global data symbols.