Method to optimize hierarchical modulation for a diversity system
The present invention involves a method for transmitting data having primary and secondary data. A first transmit signal is transmitted from a first communication satellite wherein the first transmit signal is produced when the transmitter modulates the primary and secondary data on a first carrier wave associated with the first communication satellite, with secondary data having a first polarity. A second transmit signal is transmitted from a second communication satellite wherein said second transmit signal is produced when the transmitter modulates the primary and secondary data on a second carrier wave associated with the second communication satellite with secondary data having a second polarity opposite the first polarity.
1. A method for transmitting data having both primary and secondary data, said method comprising the steps of:
transmitting a first transmit signal in satellite based transmission to legacy and second generation receivers, wherein said first transmit signal is produced when the transmitter hierarchically modulates the secondary data on selected symbols of the primary data to provide first modified primary data and modulates the first modified primary data on a first carrier wave, wherein each of the selected symbols of the primary data is modified in a predetermined manner and in one of two opposing directions based on the value of the secondary data recoverably applied with a first polarity; and
transmitting a second transmit signal in satellite based transmission wherein said second transmit signal is produced when the transmitter hierarchically modulates the secondary data on the selected symbols of the primary data to provide second modified primary data and modulates the second modified primary data on a second carrier wave, wherein each of the selected symbols of the primary data is modified in the predetermined manner and in the other of the two opposing directions based on the value of the secondary data recoverably applied with a second polarity opposite the first polarity,
whereby the modification of each selected symbol of the primary data in the first transmit signal based on the secondary data is opposite in direction to the modification of the corresponding symbol of the primary data in the second transmit signal based on the same secondary data while the values of the secondary data are recoverably preserved in the first and second transmit signals.
2. The method of claim 1 wherein the first transmitting step and the second transmitting step have time diversity.
3. The method of claim 1 wherein the first transmitting step and the second transmitting step have spatial diversity.
4. The method of claim 1 wherein the first transmitting step and the second transmitting step have frequency diversity.
5. The method of claim 1 further comprising the step of receiving the first and second signals with a terrestrial repeater and re-broadcasting the first and second signals with the original diversity.
6. The method of claim 1 wherein the secondary data uses a different forward error correction technique than the primary data.
7. The method of claim 1 wherein the primary data is for a legacy system.
8. The method of claim 1 wherein the primary data is modulated on the carrier in a QPSK modulation and the secondary data is hierarchically modulated on the carrier wave by providing at least a phase offset in the QPSK modulation, with the polarity provided to the secondary data determining the phase offset direction.
9. The method of claim 8 wherein the hierarchical modulation of the secondary data is hierarchically modulated on the carrier wave entirely by the phase offset in the QPSK modulation.
10. The method of claim 1 wherein the first transmit signal is transmitted from a first communication satellite and the second transmit signal is transmitted from a second communication satellite.
11. The method of claim 10 wherein the primary data is modulated on the carrier in a QPSK modulation and the secondary data is hierarchically modulated on the carrier wave by providing at least a phase offset in the QPSK modulation, with the polarity provided to the secondary data determining the phase offset direction.
12. The method of claim 10 wherein the hierarchical modulation of the secondary data is hierarchically modulated on the carrier wave entirely by the phase offset in the QPSK modulation.
13. The method of claim 10 wherein the first transmitting step and the second transmitting step have time diversity.
14. The method of claim 10 wherein the first transmitting step and the second transmitting step have frequency diversity.
15. The method of claim 10 further comprising the step of receiving the first and second signals with a terrestrial repeater and re-broadcasting the first and second signals with the original diversity.
16. The method of claim 1 wherein the primary data is phase modulated on the carrier and the modification of the primary data by the secondary data in hierarchical modulation comprises at least a phase offset thereto, with the polarity provided to the secondary data determining the phase offset direction.
17. The method of claim 16 wherein the modification of the primary data by the secondary data in hierarchical modulation is entirely a phase offset thereto.