Methods and apparatuses for determining scrambling codes for signal transmission

• US 7,961,880 B2
• Filed: 08/25/2006
• Issued: 06/14/2011
• Est. Priority Date: 08/26/2005
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Lin, Tung-Sheng, Wang, Judith, Lai, Dennis, Zhou, Guangcai, Santoru, Joseph, Maitra, Shamik, Chen, Ernest C.
• Primary Examiner(s): GERGISO, TECHANE
• Application Number:
  US11/510,244
• Publication Number:
  US 20070074242A1
• Time in Patent Office: 1,754 Days
• Field of Search: 380/205, 375/148, 375/346
• US Class Current: 380/205
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0029 Gold
• CPC Class Codes: H04J 13/10 Code generation
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04N 21/6112 involving terrestrial transmission, e.g. DVB-T
• CPC Class Codes: H04N 21/6143 involving transmission via a satellite
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58

Abstract

Methods and apparatuses for determining scrambling codes for minimizing co-channel interference in a communication system. A method in accordance with the present invention comprises defining at least one initial default sequence, generating a scrambling code, scrambling a signal using the generated scrambling code, comparing the scrambled signal with all other scrambled signals meeting a specified criterion, and saving the scrambling code word if the comparison determines that the signal scrambled with the scrambling code also meets the specified criterion. The scrambling codes can be compared with each other for cross-correlation purposes to determine whether they meet the specified criterion based on laboratory testing.

Claims

1. A method for determining scrambling codes for reducing co-channel interference in a communication system, comprising:

defining at least one initial default sequence;

generating a scrambling code with a scrambling code generator;

scrambling a first signal in a plurality of signals with a scrambler apparatus using the generated scrambling code;

comparing the scrambled first signal with a remainder of the signals in the plurality of scrambled signals meeting a specified co-channel interference criterion with a computer device; and

saving the scrambling code word in the computer device if the comparison determines that the first signal scrambled with the scrambling code also meets the specified co-channel interference criterion, wherein the specified co-channel interference criterion comprises at least reducing co-channel interference between the first signal and the remainder of the signals in the plurality of scrambled signals.

2. The method of claim 1, wherein the scrambling code is applied to a header of the first signal.

3. The method of claim 1, wherein the scrambling code is applied to a payload portion of the first signal.

4. The method of claim 3, wherein the scrambling code is a Gold code.

5. The method of claim 1, wherein the specified co-channel interference criterion is a correlation threshold.

6. The method of claim 5, wherein the correlation threshold is set between 0 dB and −

12 dB.

7. The method of claim 6, further comprising:

setting a second co-channel interference criterion which is lower than the specified co-channel interference criterion; and

comparing the saved scrambling codes to determine a rank order of the saved scrambling codes.

17. A non-transitory computer-readable medium bearing instructions for minimizing co-channel interference in a communication system, said instruction, being arranged, upon execution, to cause one or more processors to perform the method of claim 1.

8. A method for determining scrambling codes for reducing co-channel interference in a communication system, comprising:

defining an initial seed;

generating a seeded scrambling code from the seed using a scrambling code generator;

scrambling a payload portion of a first signal of a plurality of signals with a scrambler apparatus using the generated seeded scrambling code;

comparing the scrambled payload portion of the first signal with a remainder of the signals in the plurality of signals having scrambled payload portions meeting a first specified criterion with a computer device;

saving the seeded scrambling code word in the computer device if the comparison determines that the payload portion of the first signal scrambled with the seeded scrambling code also meets the first specified criterion, wherein the first specified co-channel interference criterion comprises at least reducing co-channel interference between the first signal and the remainder of the signals in the plurality of scrambled signals;

generating a unique word (UW) scrambling code from an initial default sequence at the scrambling code generator;

scrambling a header portion of the first signal with the scrambler apparatus using the generated UW scrambling code;

comparing the scrambled header portion of the first signal with a remainder of the signals in the plurality of signals having scrambled header portions meeting a second specified criterion using a computer device;

saving the UW scrambling code word at the computer device if the comparison determines that the first signal scrambled with the scrambling code also meets the second specified criterion; and

pairing the saved UW scrambling codes with the saved seeded scrambling codes at the computer device.

9. The method of claim 8, wherein the first specified criterion is a correlation threshold.

10. The method of claim 9, wherein the correlation threshold is set between 0 dB and −

12 dB.

11. The method of claim 9, wherein the correlation threshold is set below −

12 dB.

12. The method of claim 8, wherein the second specified criterion is a correlation threshold.

13. The method of claim 12, wherein the correlation threshold is set between 0 dB and −

12 dB.

14. The method of claim 12, wherein the correlation threshold is set below −

12 dB.

15. The method of claim 8, wherein a number of saved UW scrambling codes and a number of seeded scrambling codes is determined based on a number of channels within the communication system.

16. The method of claim 8, further comprising the step of:

transmitting information associated with the seeded scrambling codes and the UW scrambling codes to a receiver within the communication system.

18. A non-transitory computer-readable medium bearing instructions for minimizing co-channel interference in a communication system, said instruction, being arranged, upon execution, to cause one or more processors to perform the method of claim 8.

19. A method for testing cross-correlation between two scrambling codes, comprising:

generating at least one wanted signal with a modulator, the wanted signal comprising a wanted header and a wanted payload, wherein the wanted payload is scrambled with a scrambler using a first seed and the wanted header is scrambled with the scrambler using a first header code;

generating an interfering signal with a modulator comprising an header and a payload, wherein the payload of the interfering signal is scrambled with the scrambler using a second seed and the header of the interfering signal is scrambled with the scrambler using a second header code;

comparing the at least one wanted signal with the interfering signal with a computer device;

determining the cross-correlation between the at least one wanted signal and the interfering signal based on the comparing of the at least one wanted signal with the interfering signal with the computer device; and

determining with the computer device if the cross-correlation between the at least one wanted signal and the interfering signal meets a specified criterion, wherein the specified criterion comprises at least reducing cross-correlation between the at least one wanted signal and the interfering signal.