Communications system employing chaotic spreading codes with static offsets

• US 8,351,484 B2
• Filed: 12/29/2008
• Issued: 01/08/2013
• Est. Priority Date: 12/29/2008
• 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): Payne, David C.
• Assistant Examiner(s): Cadeau, Wednel
• Application Number:
  US12/345,163
• Publication Number:
  US 20100165828A1
• Time in Patent Office: 1,471 Days
• Field of Search: 375/E7.126, 375/240.01, 375/140, 375/141, 375/146, 370/342, 370/441, 370/392, 370/208
• US Class Current: 375/141
• CPC Class Codes: G09C 1/00 Apparatus or methods whereby a given sequence of signs, e.g. an intelligible text, is transformed into an unintelligible sequence of signs by transposing the signs or groups of signs or by replacing them by others according to a predetermined system cryptographic typewriters G09C3/00
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/0018 Chaotic
• CPC Class Codes: H04J 13/12 Generation of orthogonal codes
• CPC Class Codes: H04K 1/025 using an analogue chaotic signal
• CPC Class Codes: H04K 1/10 by using two signals transmitted simultaneously or successively
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 9/001 using chaotic signals

Abstract

Methods for code-division multiplex communications. The method involve generating orthogonal or statistically orthogonal chaotic spreading codes (CSC₁, . . . , CSC_K) having different static offsets using a set of polynomial equations (f₀(x(nT)), . . . , f_N-1(x(nT)) and/or f₀[x((n+v)T+t)], . . . , f_N-1[x((n+v)T+t)]). The methods also involve forming spread spectrum communications signals respectively using the orthogonal or statistically orthogonal chaotic spreading codes. The methods further involve concurrently transmitting the spread spectrum communications signals over a common RF frequency band. The spreading codes are generated using different initial values for a variable “x” of a polynomial equation f(x(nT)) and/or different acc-dec values for a variable “v” of a polynomial equation f[x((n+v)T+t)]. The static offsets are defined by the different initial values for a variable “x” and/or different acc-dec values for a variable “v”.

Claims

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

generating a plurality of orthogonal or statistically orthogonal chaotic spreading codes having different static offsets using a set of modular polynomial equations of a third order or higher, where at least two polynomial equations of said set of modular polynomial equations differ with respect to polynomial degree;

forming a plurality of spread spectrum communications signals respectively using said plurality of orthogonal or statistically orthogonal chaotic spreading codes; and

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

wherein each spreading code of said plurality of orthogonal or statistically orthogonal chaotic spreading codes is generated using a different acc-dec value for a variable “

v”

of said modular polynomial equations, where v is a variable defined by a modular arithmetic equation and has a value selected to advance or regress a chaotic sequence generation by at least one cycle.

2. The method according to claim 1, wherein said generating step further comprises using residue number system (RNS) arithmetic operations to determine a plurality of solutions for said set of modular polynomial equations, said plurality of solutions iteratively computed and expressed as RNS residue values.

3. The method according to claim 2, wherein said generating step further comprises determining a series of digits in a weighted number system based on said RNS residue values.

4. The method according to claim 3, wherein said generating step further comprises selecting a value for each of N moduli in an RNS used for solving said set of modular polynomial equations.

5. The method according to claim 1, wherein said generating step further comprises selecting a plurality of relatively prime numbers to be used as moduli in solving said set of modular polynomial equations.

6. The method according to claim 1, further comprising:

receiving said plurality of spread spectrum communications signals at a receiver;

generating at least one chaotic de-spreading code; and

de-spreading at least one of said spread spectrum communications signals using said at least one chaotic de-spreading code.

7. The method according to claim 1, further comprising:

receiving said plurality of spread spectrum communications signals at a receiver;

generating a plurality of chaotic de-spreading codes; and

de-spreading said plurality of spread spectrum communications signals using said plurality of chaotic de-spreading codes.

8. The method according to claim 1, further comprising synchronizing a chaotic de-spreading code in time and frequency with at least one of said plurality of orthogonal chaotic spreading codes.

9. A code-division multiplex communication system, comprising:

a plurality of transmitters configured to

generate a plurality of orthogonal or statistically orthogonal chaotic spreading codes having different static offsets using a set of modular polynomial equations of a third order or higher, where at least two polynomial equations of said set of modular polynomial equations differ with respect to polynomial degree,

form a plurality of spread spectrum communications signals respectively using said plurality of orthogonal or statistically orthogonal chaotic spreading codes, and

concurrently transmit said plurality of spread spectrum communications signals over a common RE frequency band;

wherein each spreading code of said plurality of orthogonal or statistically orthogonal chaotic spreading codes is generated using a different acc-dec value for a variable “

v”

of said modular polynomial equations, where v is a variable defined by a modular arithmetic equations and has a value selected to advance or regress a chaotic sequence generation by at least one cycle.

10. The system according to claim 9, wherein said plurality of transmitters is further configured to use residue number system (RNS) arithmetic operations to determine a plurality of solutions for said set of modular polynomial equations, said plurality of solutions iteratively computed and expressed as RNS residue values.

11. The system according to claim 10, wherein said plurality of transmitters is further configured to determine a series of digits in a weighted number system based on said RNS residue values.

12. The system according to claim 11, wherein said plurality of transmitters is further configured to use a pre-selected value for each of N moduli in an RNS to solve said set of modular polynomial equations.

13. The system according to claim 9, wherein said plurality of transmitters is further configured to use a plurality of pre-selected relatively prime numbers as modulus to solve said set of modular polynomial equations.

14. The system according to claim 9, further comprising a receiver configured to

receive said plurality of spread spectrum communications signals,

generate at least one chaotic de-spreading code, and

de-spread at least one of said spread spectrum communications signals using said at least one chaotic de-spreading code.

15. The system according to claim 9, further comprising a receiver configured to

receive said plurality of spread spectrum communications signals,

generate a plurality of chaotic de-spreading codes, and

de-spread said plurality of spread spectrum communications signals using said plurality of chaotic de-spreading codes.

16. The system according to claim 9, further comprising a receiver configured to synchronize a chaotic de-spreading code in time and frequency with at least one of said plurality of orthogonal or statistically orthogonal chaotic spreading codes.