Maximizing power and spectral efficiencies for layered and conventional modulations
View Patent ↗Methods and apparatuses for maximizing power and spectral efficiencies in a wireless communication system are disclosed. The invention is particularly useful for layered modulation applications because power levels for such applications are relatively high. A layered modulation signal comprises an upper and a lower layer signal that interfere with each other within the same frequency band such that the upper layer signal can be demodulated directly from the layered modulation signal, and the lower layer signal can be demodulated after subtracting the first layer signal from the layered modulation signal. The invention applies one or more of the following four signal schemes in a communication signal including varying the symbol rate (rather than the code rate), reducing or eliminating the guard band, reducing excess signal bandwidth and employing layered modulation within the guard band of the legacy signal.
1. A method for increasing the transmission capacity of a legacy transmission system comprising at least one satellite having a first transponder, the first transponder configured to transmit a first legacy signal over a first legacy signal bandwidth within a first frequency band, and a second transponder, the second transponder configured to transmit a second legacy signal over a second legacy signal bandwidth within a second frequency band, wherein the first legacy signal bandwidth and the second legacy signal bandwidth are separated by a guard band, the method comprising the steps of:
augmenting the legacy transmission system with a third transponder and a fourth transponder; wherein
the third transponder is configured to transmit a first layer signal over a first layer signal bandwidth within the guard band; and
the fourth transponder is configured to transmit a second layer signal over a second layer signal bandwidth within the guard band.
2. The method of claim 1 , wherein the first layer signal and the second layer signal are non-coherent and wherein the first layer signal is of a higher power than the second layer signal.
3. The method of claim 1 , wherein the third transponder and fourth transponder are disposed on a second satellite.
4. The method of claim 3 , wherein the second satellite is a satellite new to the legacy transmission system.
5. The method of claim 1 , wherein the first layer signal and the second layer signal are transmitted over substantially all of the guard band.
6. The method of claim 1 , further comprising the steps of:
raising a power of the first legacy signal; and
expanding the second layer signal bandwidth to overlap the first legacy signal bandwidth.
7. The method of claim 6 , further comprising the steps of:
raising a power of the second layer signal; and
raising a power of the first layer guard band signal.
8. The method of claim 6 , wherein the third transponder and the fourth transponder are disposed on a second satellite new to the legacy transmission system, and wherein the method further comprises the steps of:
migrating the first legacy signal to be transmitted by a fifth transponder disposed on the new satellite;
migrating the second layer signal to be transmitted by a sixth transponder disposed on the new satellite; and
migrating the first legacy signal to be transmitted by a seventh transponder disposed on the new satellite.
9. The method of claim 8 , further comprising:
expanding the first layer signal bandwidth to substantially all of the first frequency band; and
expanding the second layer signal bandwidth to substantially all of the first frequency band.
10. A transmission system comprising:
at least one satellite having:
a first transponder, the first transponder configured to transmit a first legacy signal over a first legacy signal bandwidth within a first frequency band;
a second transponder the second transponder configured to transmit a second legacy signal over a second legacy signal bandwidth within a second frequency band, wherein the first legacy signal bandwidth and the second legacy signal bandwidth are separated by a guard band;
a third transponder and a fourth transponder, the third transponder configured to transmit a first layer signal over a first layer signal bandwidth within the guard band; and
a fourth transponder is configured to transmit a second layer signal over a second layer signal bandwidth within the guard band;
wherein the first layer signal and the second layer signal are non-coherent and wherein the first layer signal is of a higher power than the second layer signal.
11. The transmission system of claim 10 , wherein the third transponder and fourth transponder are disposed on a second satellite.
12. The transmission system of claim 10 , wherein the first layer signal and the second layer signal are transmitted over substantially all of the guard band.
13. The transmission system of claim 10 , wherein the carrier to noise ratio (CNR) of the first layer signal is 11.9 dB, the CNR of the second layer signal is 5.4 dB, and the CNR of the first legacy signal is 7.6 dB.