Shifted channel characteristics for mitigating co-channel interference

• US 8,594,575 B2
• Filed: 04/14/2008
• Issued: 11/26/2013
• 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: Santoru, Joseph, Chen, Ernest C., Maitra, Shamik, Lai, Dennis, Zhou, Guangcai, Lin, Tung-Sheng
• Primary Examiner(s): Brown, Christopher
• Assistant Examiner(s): Baum, Ronald
• Application Number:
  US12/102,394
• Publication Number:
  US 20090052503A1
• Time in Patent Office: 2,052 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 shifting a characteristic of the first signal with respect to a like characteristic of the second signal to mitigate co-channel interference, and transmitting the first signal and the second signal over different channels of the communication system.

Claims

1. A system for minimizing co-channel interference comprising:

a television broadcast system, for transmitting data only to a subscribing plurality of receivers over a plurality of signals, each of the plurality of signals directly associated with a respective one of a plurality of co-channels defined at least in part by a frequency band allocated to each respective co-channel;

wherein the plurality of signals comprises;

a first signal having a first frame of a first plurality of frames on a first co-channel of the plurality of co-channels, the first signal transmitted at a first time; and

a second signal having a second frame of a second plurality of frames on a second co-channel of the plurality of co-channels, the second signal transmitted at a second time equal to the first time,

wherein the television broadcast system comprises;

an encoder;

a scrambler, coupled to the encoder; and

a modulator, coupled to the scrambler;

wherein the television broadcast system shifts a characteristic of the first signal with respect to a like characteristic of the second signal, wherein the shift is selected to mitigate co-channel interference between the first signal and the second signal, the characteristic comprising at least one of;

a transmission code schema of the first signal, wherein at least a portion of at least one of the first plurality of frames of the first signal are transmitted using a first transmission code schema and at least another portion of at least another one of the first plural of frames of the second signal are transmitted using a second transmission code schema different than the first transmission code schema; and

an in-phase (I) portion of the first signal and a quaternary (Q) portion of the first signal, wherein the first signal comprises an in-phase (I) first signal portion and a quaternary (Q) phase first signal portion, the second signal comprises an in-phase (I) second signal portion and a quaternary (Q) phase second signal portion, and the television broadcast system swaps the first signal in-phase (I) portion and the second signal quaternary (Q) first signal portion before transmission.

2. The system of claim 1, wherein the television broadcast system transmits information associated with the shifted characteristic to at least one of the plurality of receivers.

3. The system of claim 1, wherein the encoder is a Low Density Parity Check (LDPC) encoder.

4. The system of claim 3, wherein the encoder is also a Bose-Chaudhuri-Hocquenghem (BCH) encoder.

5. The system of claim 1, wherein;

the characteristic comprises the transmission code schema of the first signal;

the at least a portion of the at least one of the first plurality of frames of the first signal is transmitted using a different transmission code schema than another portion of the at least one of the first plurality of frames of the first signal.

6. The system of claim 5, wherein the transmission code schema is selected from a group comprising:

QPSK, 8PSK, and 16PSK.

7. The system of claim 1, wherein the television broadcast system comprises two transmitters and the first signal and the second signal are transmitted by different transmitters.

8. The system of claim 1, wherein the television broadcast system comprises two transmitters and the first signal and the second signal are transmitted by the same transmitter.

9. The method of claim 1, wherein the encoder is a Low Density Parity Check (LDPC) encoder.

10. The method of claim 9, wherein the encoder is also a Bose-Chaudhuri-Hocquenghem (BCH) encoder.

11. A method for minimizing co-channel interference, comprising:

transmitting encoded and scrambled data only to a subscribing plurality of receivers over a plurality of signals, each of the plurality of signals directly associated with a respective one of a plurality of co-channels defined at least in part by a frequency band allocated to each respective co-channel;

wherein the plurality of signals comprises;

a first signal having a first frame of a first plurality of frames on a first co-channel of the plurality of co-channels, the first signal transmitted at a first time; and

a second signal having a second frame of a second plurality of frames on a second co-channel of the plurality of co-channels, the second signal transmitted at a second time equal to the first time,

wherein a characteristic of the first signal is shifted with respect to a like characteristic of the second signal, wherein the shift is selected to mitigate co-channel interference between the first signal and the second signal, the characteristic comprising at least one of;

a transmission code schema of the first signal, wherein at least a portion of at least one of the first plurality of frames of the first signal are transmitted using a first transmission code schema and at least another portion of at least another one of the first plural of frames of the second signal are transmitted using a second transmission code schema different than the first transmission code schema; and

an in-phase (I) portion of the first signal and a quaternary (Q) portion of the first signal, wherein the first signal comprises an in-phase (I) first signal portion and a quaternary (Q) phase first signal portion, the second signal comprises an in-phase (I) second signal portion and a quaternary (Q) phase second signal portion, and the television broadcast system swaps the first signal in-phase (I) portion and the second signal quaternary (Q) first signal portion before transmission.

12. The method of claim 11, wherein further comprising the step of transmitting information associated with the shifted characteristic to at least one of the plurality of receivers.

13. The method of claim 11, wherein;

the characteristic comprises the transmission code schema of the first signal;

the at least a portion of the at least one of the first plurality of frames of the first signal is transmitted using a different transmission code schema than another portion of the at least one of the first plurality of frames of the first signal.

14. The method of claim 13, wherein the transmission code schema is selected from a group comprising:

QPSK, 8PSK, and 16PSK.

15. The method of claim 11, wherein the television broadcast system comprises two transmitters and the first signal and the second signal are transmitted by different transmitters.

16. The method of claim 11, wherein the television broadcast system comprises two transmitters and the first signal and the second signal are transmitted by the same transmitter.