Methods and apparatuses for minimizing co-channel interference

• US 8,571,480 B2
• Filed: 10/30/2008
• Issued: 10/29/2013
• 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: Lee, Lin-Nan, Sun, Feng-Wen, Von Ancken, Adam, Santoru, Joseph, Chen, Ernest C., Maitra, Shamik, Lai, Dennis, Zhou, Guangcai, Lin, Tung-Sheng
• Primary Examiner(s): Alam, Fayyaz
• Assistant Examiner(s): Bilodeau, David
• Application Number:
  US12/262,078
• Publication Number:
  US 20090068953A1
• Time in Patent Office: 1,825 Days
• Field of Search: 455/63.1
• US Class Current: 455/63.1
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/1858 Arrangements for data transmission on the physical system, i.e. for data bit transmission between network components
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/6143 involving transmission via a satellite
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence
• CPC Class Codes: H04N 7/16 Analogue secrecy systems; Analogue subscription systems
• CPC Class Codes: H04N 7/163 by receiver means only
• 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
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

Methods and apparatuses for minimizing co-channel interference in communications systems are disclosed. A method in accordance with the present invention comprises scrambling a first frame using a first scrambling code, attaching a first header to the first frame to create the first signal, scrambling a second frame using a second scrambling code, attaching a second header to the second frame to create the second signal, and transmitting the first signal and the second signal over different channels of the communication system.

Claims

1. A method for minimizing co-channel interference in a communication system transmitting a first signal having a first frame and a second signal having a second frame, the first signal and the second signal transmitted on different channels of the communication system, comprising:

determining a frame offset of the second frame from the first frame, the frame offset determined to mitigate expected co-channel interference between the first signal and the second signal; and

simultaneously transmitting the first signal having the first frame and the second signal having the second frame offset from the first frame by the determined frame offset from a transmitter over the different channels of the communication system.

2. The method of claim 1, wherein the frame offset is an offset in time.

3. The method of claim 2, wherein the frame offset is at least one symbol interval.

4. The method of claim 2, wherein the first frame comprises a first Start-Of-Frame (SOF) portion and the second frame contains a second SOF portion different than the first SOF portion.

5. The method of claim 4, wherein the first SOF portion and the second SOF portion are selected from a limited number of SOF portions.

6. The method of claim 4, wherein the first SOF portion is offset by at least one symbol interval from the second SOF portion.

7. The method of claim 6, wherein the first frame comprises a number of first pilot symbol blocks and the second frame comprises a number of second pilot symbol blocks.

8. The method of claim 7, wherein the first pilot symbol blocks are scrambled.

9. 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.

10. The method of claim 1, further comprising:

transmitting information associated with the frame offset to a receiver within the communication system.

11. In a system for transmitting data over a plurality of signals, each of the plurality of signals associated with one of a plurality of co-channels defined at least in part by a frequency band allocated to each respective co-channel,

a device for mitigating co-channel interference between

a first signal of the plurality of signals transmitting a first frame of a first plurality of frames on a first co-channel of the plurality of co-channels and

a second signal of the plurality of signals transmitting a second frame of a plurality of second frames on a second co-channel of the plurality of co-channels transmitted, wherein the first signal is transmitted at a first time and the second signal is transmitted at a second time equal to the first time,

the device comprising:

a transmitter for simultaneously transmitting at least one of the first signal and the second signal from an antenna, the transmitter comprising;

an encoder;

a modulator, communicatively coupled to the encoder;

wherein the modulator shifts a characteristic of the first signal with respect to a like characteristic of the second signal by an amount selected to mitigate c0-channel interference between the first signal and the second signal;

wherein the first frame comprises a first portion and the second frame comprises a second like portion and the characteristic comprises a start time of the first portion relative to a start time of the second portion.

12. The device of claim 11, wherein the first signal and the second signal are transmitted in the same frequency band.

13. The device of claim 11, wherein the transmitter transmits information associated with the shifted characteristic to a receiver within the communication system.

14. The device of claim 11, wherein the encoder is a Low Density Parity Check (LDPC) encoder.

15. The device of claim 14, wherein the encoder is also a Bose-Chaudhuri-Hocquenghem (BCH) encoder.

16. The device of claim 11, wherein the first portion of the first frame is identical to a like first portion for each of the first plurality of frames and the second portion of the second frame is identical to a like second portion of second plurality of frames.

17. The device of claim 16, wherein the first portion is the start of frame (SOF) of the first frame and the second portion is the start of frame (SOF) of the second frame.

18. The device of claim 11, wherein the first signal and the second signal are transmitted by different transmitters.

19. The device of claim 11, wherein the first signal and the second signal are transmitted by the same transmitter.