Communications system employing orthogonal chaotic spreading codes

• US 8,457,077 B2
• Filed: 03/03/2009
• Issued: 06/04/2013
• Est. Priority Date: 03/03/2009
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Michaels, Alan J., Chester, David B.
• Primary Examiner(s): Moore, Ian N
• Assistant Examiner(s): Alexander, Janee
• Application Number:
  US12/396,828
• Publication Number:
  US 20100226497A1
• Time in Patent Office: 1,554 Days
• Field of Search: 370208-210, 370/335, 370/342, 370/344, 370/441, 375/260, 375/130, 375132-141, 375/145, 375347-349
• US Class Current: 370/335
• CPC Class Codes: H04J 13/0018 Chaotic
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04L 2209/20 Manipulating the length of blocks of bits, e.g. padding or block truncation
• CPC Class Codes: H04L 9/001 using chaotic signals
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

Systems and methods for code-division multiplex communications. The methods involve forming orthogonal or statistically orthogonal chaotic spreading sequences (CSC_1,1, CSC_D,1), each comprising a different chaotic sequence. The methods also involve generating an offset chaotic spreading sequence (CSC_1,2, CSC_1,3, . . . , CSC_1,K(1), CSC_D,2, . . . , CSC_D,K(D)) which is the same as a first one of the orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset. Spread spectrum communications signals (SSCs) are each respectively generated using one of the orthogonal or statistically orthogonal chaotic spreading sequences. Another SSC is generated using the offset chaotic spreading sequence. The SSCs are concurrently transmitted over a common RF frequency band.

Claims

1. A method for code-division multiplex communications, comprising the steps of:

forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences, each comprising a different chaotic sequence;

generating at least one offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset by an amount defined by a remainder of division of a first number by a second number, where the remainder is computed via a modular division operation, the first number represents a number of cycles of a chaotic sequence generation offset from a reference time, and the second number represents a cycle in which each component of a chaotic sequence starts to repeat;

forming a plurality of first spread spectrum communications signals, each respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences;

forming at least one second spread spectrum communication signal using said at least one offset chaotic spreading sequence; and

concurrently transmitting said plurality of first spread spectrum communications signals and said second spread spectrum communication signal over a common RF frequency band.

2. The method according to claim 1, further comprising generating a plurality of said offset chaotic spreading sequences, each temporally offset to a different extent relative to said first one of said orthogonal or statistically orthogonal chaotic spreading sequences.

3. The method according to claim 1, further comprising, generating a plurality of said offset chaotic spreading sequences, each which is the same as a respective one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset.

4. The method according to claim 3, further comprising generating a plurality of said offset chaotic spreading sequences which are the same sequence, each temporally offset to a different extent relative to a common one of said orthogonal or statistically orthogonal chaotic spreading sequences.

5. The method according to claim 1, further comprising respectively forming each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different set of polynomial equations.

6. The method according to claim 1, further comprising respectively forming each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different value for each of N moduli comprising a respective moduli set in an RNS used for respectively solving a plurality of sets of polynomial equations.

7. The method according to claim 1, further comprising using residue number system (RNS) arithmetic operations to respectively determine a plurality of solutions to a plurality of sets of polynomial equations, said plurality of solutions iteratively computed and expressed as RNS residue values.

8. The method according to claim 7, further comprising respectively forming each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different value for each of N moduli comprising a respective moduli set in an RNS used for respectively solving each of said sets of polynomial equations.

9. A method for code-division multiplex communications, comprising:

forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences, each comprising a different chaotic sequence;

generating at least one offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset by an amount defined by a remainder of division of a first number by a second number, where the remainder is computed via a modular division operation;

forming a plurality of first spread spectrum communications signals, each respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences;

forming at least one second spread spectrum communication signal using said at least one offset chaotic spreading sequence; and

concurrently transmitting said plurality of first spread spectrum communications signals and said second spread spectrum communication signal over a common RF frequency band;

wherein each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences is respectively formed by using a different value for each of N moduli comprising a respective moduli set in an RNS used for respectively solving a plurality of sets of polynomial equations; and

wherein said generating steps further comprise determining a series of digits in a weighted number system based on respective values of said RNS residue values.

10. A method for code-division multiplex communications, comprising the steps of:

forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences, each comprising a different chaotic sequence;

generating at least one offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset;

forming a plurality of spread spectrum communications signals, each respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences;

forming at least one spread spectrum communication signal using said at least one offset chaotic spreading sequence;

concurrently transmitting said plurality of spread spectrum communications signals over a common RF frequency band; and

selecting an initial value for a variable “

x”

of a polynomial equation f(x(nT)), where n is an index of time, and T is a discrete time interval;

wherein said at least one offset chaotic spreading sequence has a static offset defined by said initial value for said variable “

x”

.

11. A method for code-division multiplex communications, comprising the steps of:

forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences, each comprising a different chaotic sequence;

generating at least one offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset;

forming a plurality of spread spectrum communications signals, each respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences;

forming at least one spread spectrum communication signal using said at least one offset chaotic spreading sequence;

concurrently transmitting said plurality of spread spectrum communications signals over a common RF frequency band; and

selecting a time offset value for a variable “

t”

of a polynomial equation f[x((n+v)T+t)], where n is an index of time, v is a variable having a value selected to accelerate or decelerate a chaotic sequence generation by at least one cycle, t is a variable representing an initial time offset, and T is a discrete time interval;

wherein said offset chaotic spreading sequence has a static offset defined by said time offset value for said variable “

t”

.

12. A code-division multiplex communications system, comprising:

a plurality of first transmitters configured to form a plurality of orthogonal or statistically orthogonal chaotic spreading sequences and to form a plurality of first spread spectrum communications signals, each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences comprising a different chaotic sequence and each of said plurality of first spread spectrum communications signals respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences; and

at least one second transmitter configured to

generate at least one temporally offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset by an amount defined by a remainder of division of a first number by a second number, where the remainder is computed via a modular division operation, the first number represents a number of cycles of a chaotic sequence generation offset from a reference time, and the second number represents a cycle in which each component of a chaotic sequence starts to repeat, and

form at least one second spread spectrum communication signal using said at least one offset chaotic spreading sequence;

wherein said plurality of first transmitters and said second transmitter are configured to concurrently transmit said plurality of first spread spectrum communications signals and said second spread spectrum communication signal over a common RF frequency band.

13. The system according to claim 12, further comprising a plurality of second transmitters configured for generating a plurality of said offset chaotic spreading sequences, each temporally offset to a different extent relative to said first one of said orthogonal or statistically orthogonal chaotic spreading sequences.

14. The system according to claim 12, further comprising a plurality of second transmitters configured for generating a plurality of said offset chaotic spreading sequences, each which is the same as a respective one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset.

15. The system according to claim 14, wherein said plurality of second transmitters are further configured for generating a plurality of said offset chaotic spreading sequences which are the same sequence, each temporally offset to a different extent relative to a common one of said orthogonal or statistically orthogonal chaotic spreading sequences.

16. The system according to claim 12, wherein each of said plurality of first transmitters is further configured for forming a respective one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different set of polynomial equations.

17. The system according to claim 12, wherein each of said plurality of first transmitters is further configured for using residue number system (RNS) arithmetic operations to determine a plurality of solutions to a set of polynomial equations, said plurality of solutions iteratively computed and expressed as RNS residue values.

18. A code-division multiplex communications system, comprising:

a plurality of first transmitters configured to form a plurality of orthogonal or statistically orthogonal chaotic spreading sequences and to form a plurality of first spread spectrum communications signals, each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences comprising a different chaotic sequence and each of said plurality of first spread spectrum communications signals respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences; and

at least one second transmitter configured to

generate at least one temporally offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset by an amount defined by a remainder of division of a first number by a second number, where the remainder is computed via a modular division operation, and

form at least one second spread spectrum communication signal using said at least one offset chaotic spreading sequence;

wherein said plurality of first transmitters and said second transmitter are configured to concurrently transmit said plurality of first spread spectrum communications signals and said second spread spectrum communication signal over a common RF frequency band; and

wherein each of said plurality of first transmitters is further configured for forming a respective one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different value for each of N moduli comprising a respective moduli set in an RNS used for respectively solving a set of polynomial equations.

19. A code-division multiplex communications system, comprising:

a plurality of first transmitters configured to form a plurality of orthogonal or statistically orthogonal chaotic spreading sequences and to form a plurality of first spread spectrum communications signals, each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences comprising a different chaotic sequence and each of said plurality of first spread spectrum communications signals respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences; and

at least one second transmitter configured to

generate at least one temporally offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset by an amount defined by a remainder of division of a first number by a second number, where the remainder is computed via a modular division operation, and

form at least one second spread spectrum communication signal using said at least one offset chaotic spreading sequence;

wherein said plurality of first transmitters and said second transmitter are configured to concurrently transmit said plurality of first spread spectrum communications signals and said second spread spectrum communication signal over a common RF frequency band;

wherein each of said plurality of first transmitters is further configured for using residue number system (RNS) arithmetic operations to determine a plurality of solutions to a set of polynomial equations, said plurality of solutions iteratively computed and expressed as RNS residue values; and

wherein each of said plurality of first transmitters is further configured for determining a series of digits in a weighted number system based on respective values of said RNS residue values.

20. The system according to claim 19, wherein each of said plurality of first transmitters is further configured for forming a respective one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences by using a different value for each of N moduli comprising a respective moduli set in an RNS used for respectively solving said set of polynomial equations.

21. A code-division multiplex communications system, comprising:

a plurality of first transmitters configured for forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences and for forming a plurality of spread spectrum communications signals, each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences comprising a different chaotic sequence and each of said plurality of spread spectrum communications signals respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences; and

at least one second transmitter configured for generating at least one temporally offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset, and for forming at least one spread spectrum communication signal using said at least one offset chaotic spreading sequence;

wherein said plurality of first transmitters and said second transmitter are configured for concurrently transmitting said plurality of spread spectrum communications signals over a common RF frequency band; and

wherein said at least one offset chaotic spreading sequence has a static offset defined by an initial value for a variable “

x”

of a polynomial equation f(x(nT)), where n is an index of time, and T is a discrete time interval.

22. A code-division multiplex communications system, comprising:

a plurality of first transmitters configured for forming a plurality of orthogonal or statistically orthogonal chaotic spreading sequences and for forming a plurality of spread spectrum communications signals, each of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences comprising a different chaotic sequence and each of said plurality of spread spectrum communications signals respectively generated using one of said plurality of orthogonal or statistically orthogonal chaotic spreading sequences; and

at least one second transmitter configured for generating at least one temporally offset chaotic spreading sequence which is the same as a first one of said orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset, and for forming at least one spread spectrum communication signal using said at least one offset chaotic spreading sequence;

wherein said plurality of first transmitters and said second transmitter are configured for concurrently transmitting said plurality of spread spectrum communications signals over a common RF frequency band; and

wherein said at least one offset chaotic spreading sequence has a static offset defined by a time offset value for a variable “

t”

of a polynomial equation f[x((n+v)T+t)], where n is an index of time, v is a variable having a value selected to accelerate or decelerate a chaotic sequence generation by at least one cycle, t is a variable representing an initial time offset, and T is a discrete time interval.