Spreading code derived from weil sequences

• US 20080219327A1
• Filed: 12/19/2007
• Published: 09/11/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Mitre Corporation
• Original Assignee: Mitre Corporation
• Inventors: Rushanan, Joseph J.
• Granted Patent: US 7,511,637 B2
• Time in Patent Office: Days
• US Class Current: 375/146
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/10 Code generation

Abstract

Methods and systems relating to Weil-based spreading codes are described herein. In an embodiment, a method includes generating a set of Weil sequences, adapting a plurality of sequences of the set of Weil sequences to form a first plurality of codes, and selecting a second plurality of codes from the first plurality of codes. A code of the first plurality of codes is selected based at least on a correlation associated with the code. Each code of the first plurality of codes has a predetermined length.

Claims

1. A method, comprising:

generating a set of Weil sequences;

adapting a plurality of sequences of the set of Weil sequences to form a first plurality of codes, wherein each code of the first plurality of codes has a predetermined length; and

selecting a second plurality of codes from the first plurality of codes, wherein a code of the first plurality of codes is selected based at least on a correlation associated with the code.

2. The method of claim 1, wherein a length of each sequence of the set of Weil sequences is 10223 or 10243.

3. The method of claim 1, wherein the adapting step comprises:

inserting a pad code into a sequence of the plurality of sequences at a defined location.

4. The method of claim 3, wherein the pad code is configured such that the sequence of the plurality of sequences has zero balance.

5. The method of claim 1, wherein the selecting step comprises:

selecting the code from the first plurality of codes if an autocorrelation of the code is below a threshold.

6. The method of claim 5, wherein the autocorrelation is an even autocorrelation or an odd autocorrelation.

7. The method of claim 1, wherein the selecting step comprises:

selecting the code from the first plurality of codes if a cross-correlation of the code with other codes of the first plurality of codes is below a threshold.

8. The method of claim 7, wherein the cross-correlation is an even cross-correlation or an odd cross-correlation.

9. The method of claim 1, wherein the predetermined length is a length of a global navigation satellite system (GNSS) spreading code.

10. The method of claim 1, further comprising:

forming a group of codes from the second plurality of codes, wherein each code of the group of codes has a relatively low cross-correlation with another code of the group.

11. The method of claim 1, further comprising:

designating a plurality of codes of the second plurality of codes as pilot spreading codes or data spreading codes.

12. The method of claim 1, wherein the generating step comprises:

multiplying a first Legendre sequence with a second Legendre sequence, wherein the second Legendre sequence is a shifted version of first Legendre sequence.

13. The method of claim 1, wherein at least one of the second plurality of codes is optimized for a BOC(1,1) spreading symbol.

14. The method of claim 1, wherein at least one of the second plurality of codes is optimized for a TMBOC spreading time series.

15. A method of generating a signal, comprising:

providing a sequence of symbols; and

modulating a sequence of symbols with a Weil-based spreading code, wherein the Weil-based spreading code includes at least a portion of a Weil sequence.

16. The method of claim 15, further comprising:

modulating the sequence of symbols with a sequence of spreading symbols.

17. The method of claim 16, wherein the sequence of spreading symbols comprises a BOC(1,1) spreading symbol.

18. The method of claim 17, wherein the sequence of spreading symbols further comprises a BOC(6,1) spreading symbol.

19. The method of claim 15, further comprising:

modulating a second sequence of symbols with a second Weil-based spreading code,

wherein the second Weil-based spreading code includes at least a portion of a second Weil code,

wherein the first sequence of symbols is a data sequence and the second sequence of symbols is an overlay sequence,

wherein the first sequence is used to form a data component of the signal and the second sequence is used to form a pilot component of the signal, and

wherein a greater portion of a total signal power is allocated to the pilot component compared to the data component.

20. The method of claim 15, further comprising:

retrieving the Weil-based spreading code from a memory.

21. The method of claim 15, further comprising:

generating the Weil-based spreading code.

22. The method of claim 21, wherein the generating step comprises:

multiplying a first Legendre sequence with a second Legendre sequence, wherein the second Legendre sequence is a shifted version of first Legendre sequence.

23. A system for generating a signal, comprising:

a sequence provider configured to provide a sequence of symbols; and

a modulator coupled to the sequence provider configured to modulate the sequence of symbols with a spreading code, wherein the spreading code is a Weil-based spreading code, wherein the Weil-based spreading code includes at least a portion of a Weil sequence.

24. The system of claim 23, further comprising:

a memory, wherein the memory is configured to store the spreading code, wherein the memory is coupled to the modulator.

25. The system of claim 23, further comprising:

a spreading code generator that generates the spreading code, wherein the spreading code generator is coupled to the modulator.