Method and apparatus for minimizing co-channel interference

• US 7,161,988 B2
• Filed: 12/10/2004
• Issued: 01/09/2007
• Est. Priority Date: 04/12/2004
• Status: Active Grant

• Current Assignee: DTVG Licensing, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Sun, Feng-Wen, Lee, Lin-Nan, Ancken, Adam Von
• Primary Examiner(s): BARRON JR, GILBERTO
• Application Number:
  US11/009,346
• Publication Number:
  US 20060153313A1
• Time in Patent Office: 760 Days
• Field of Search: 375/260, 375/130, 375/146, 375/140, 375/141, 375/285, 375/295, 375/296, 375/316, 375/346, 375/144, 375/147, 375/148, 370/335, 370/342, 370/441, 370/208, 725/31, 380/210, 380/268, 380/FOR.109
• US Class Current: 375/285
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04H 20/51 specially adapted for satellite broadcast systems
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence

Abstract

An approach is provided for minimizing co-channel interference in a communication system is disclosed. A header of a first frame is scrambled based on a first unique word. A header of a second frame is scrambled based on a second unique word. The first frame including the corresponding scrambled header and the second frame including the corresponding scrambled header are transmitted, respectively, over adjacent co-channels of the communication system. Each of the frames further includes a payload and a pilot block. The payload and the pilot block of the first frame are scrambled based on a first scrambling sequence. The payload and the pilot block of the second frame are scrambled based on a second scrambling sequence. The above arrangement is particularly suited to a digital satellite broadcast and interactive system.

Claims

1. A method for minimizing co-channel interference in a communication system, the method comprising the steps of:

scrambling a header of a first frame based on a first unique word;

scrambling a payload and a pilot block of the first frame based on a first scrambling sequence;

scrambling a header of a second frame based on a second unique word; and

scrambling a payload and a pilot block of the second frame based on a second scrambling sequence,

wherein the first frame including the corresponding scrambled header and the second frame including the corresponding scrambled header are transmitted, respectively, over adjacent co-channels of the communication system.

2. A method according to claim 1, further comprising the step of:

transmitting information associated with the unique words and the scrambling sequences over a default carrier to a receiver within the communication system.

3. A method according to claim 1, further comprising the step of:

generating a plurality of sets of unique words and scrambling sequences corresponding to carriers supported by the communication system.

4. A method according to claim 3, wherein the quantity of sets is a predetermined value.

5. A method according to claim 4, wherein a portion of the sets are stored at a receiver, the method further comprising the step of:

instructing the receiver about which of the stored sets to use.

6. A method according to claim 4, wherein a portion of the sets are stored at a receiver, and the receiver determines a valid set for a particular carrier from the stored sets.

7. A method according to claim 1, wherein the sets are stored in a database coupled to a receiver, and the receiver includes a cache configured to store a portion of the sets.

8. A method according to claim 7, wherein a portion of the sets are stored at a receiver, the method further comprising the step of:

instructing the receiver to update the cache.

9. A method according to claim 1, wherein the scrambling sequences are based on Gold sequences.

10. A method according to claim 1, wherein the communication system includes a satellite supporting digital broadcast and interactive applications.

11. A method according to claim 1, further comprising the step of:

transmitting each of the frames according to a modulation scheme including one of Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), BPSK, 16 Amplitude Phase Shift Keying (APSK), 32APSK, and a high order Quadrature Amplitude Modulation (QAM).

12. A method according to claim 1, wherein each of the frames includes information encoded according to Low Density Parity Check (LDPC) coding.

13. A 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.

14. An apparatus for minimizing co-channel interference in a communication system, comprising:

a scrambler configured to scramble a header of a first frame based on a first unique word, and to scramble a header of a second frame based on a second unique word, the scrambler being further configured to scramble a payload and a pilot block of the first frame based on a first scrambling sequence and to scramble a payload and a pilot block of the second frame based on a second scrambling sequence,

wherein the first frame including the corresponding scrambled header and the second frame including the corresponding scrambled header are transmitted, respectively, over adjacent co-channels of the communication system.

15. An apparatus according to claim 14, wherein information associated with the unique words and the scrambling sequences is transmitted over a default carrier to a receiver within the communication system.

16. An apparatus according to claim 14, wherein the scrambler generates a plurality of sets of unique words and scrambling sequences corresponding to carriers supported by the communication system.

17. An apparatus according to claim 16, wherein the quantity of sets is a predetermined value.

18. An apparatus according to claim 17, wherein a portion of the sets are stored at a receiver, and the receiver is instructed about which of the stored sets to use.

19. An apparatus according to claim 17, wherein a portion of the sets are stored at a receiver, and the receiver determines a valid set for a particular carrier from the stored sets.

20. An apparatus according to claim 14, wherein the sets are stored in a database coupled to a receiver, and the receiver includes a cache configured to store a portion of the sets.

21. An apparatus according to claim 20, wherein a portion of the sets are stored at a receiver, and the receiver is instructed to update the cache.

22. An apparatus according to claim 14, wherein the scrambling sequences are based on Gold sequences.

23. An apparatus according to claim 14, wherein the communication system includes a satellite supporting digital broadcast and interactive applications.

24. An apparatus according to claim 14, further comprising:

a modulator configured to modulate the frames according to a modulation scheme including one of Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 8PSK, 16 Amplitude Phase Shift Keying (APSK), 32APSK, and a high order Quadrature Amplitude Modulation (QAM).

25. An apparatus according to claim 14, wherein each of the frames includes information encoded according to Low Density Parity Check (LDPC) coding.

26. A method of communicating comprising the steps of:

tuning to a default carrier to receive scrambling information, wherein the scrambling information includes a unique word and a scrambling sequence corresponding to a particular carrier among a plurality of adjacent carriers, the unique word and the scrambling sequence being selected to minimize co-channel interference with respect to the adjacent carriers;

tuning to the particular carrier for receiving a scrambled frame including a header, a payload, and a pilot block;

descrambling the header with the unique word; and

descrambling the payload and the pilot block with the scrambling sequence.

27. A method according to claim 26, wherein the scrambling information is one of a plurality of sets of scrambling information corresponding to different ones of the adjacent carriers.

28. A method according to claim 27, wherein the quantity of sets is a predetermined value.

29. A method according to claim 27, further comprising:

receiving a portion of the sets of scrambling information; and

storing the portion of the sets of scrambling information in a cache.

30. A method according to claim 27, further comprising:

tuning to another one of the carriers; and

determining a valid set from the stored sets of scrambling information for the one carrier.

31. A method according to claim 27, further comprising:

receiving the sets of scrambling information; and

storing the sets of scrambling information in a database.

32. A method according to claim 31, further comprising:

storing a portion of the sets of scrambling information in a cache.

33. A method according to claim 32, further comprising:

receiving a command to update the cache.

34. A method according to claim 26, wherein the scrambling sequences are based on Gold sequences.

35. A method according to claim 26, wherein the communication system includes a satellite supporting digital broadcast and interactive applications.

36. A method according to claim 26, wherein the unique word has a length identical with the header, the scrambled header in the scrambled frame being determined based on an exclusive-OR function with the unique word.

37. A computer-readable medium bearing instructions for communicating in a communication system, said instruction, being arranged, upon execution, to cause one or more processors to perform the method of claim 26.