Shifted channel characteristics for mitigating co-channel interference
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.
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.