Method and apparatus for layered modulation

• US 20060050805A1
• Filed: 07/03/2003
• Published: 03/09/2006
• Est. Priority Date: 07/03/2002
• Status: Active Grant

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Inventors: Santoru, Joseph, Chen, Ernest C
• Granted Patent: US 7,738,587 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04L 27/3488 Multiresolution systems

Abstract

Improvements to a layered modulation (LM) implementation are disclosed. The present invention discloses two implementations of LM, using single and multiple transponders per signal frequency, respectively. Layered hierarchical 8PSK (H-8PSK) is a special case of LM. By re-encoding the high-priority (HP) portion of an H-8PSK signal, LM can improve carrier-to-noise ratio (CNR) of a H-8PSK signal. LM can be computer-simulated and a two-layered signal can be sequentially demodulated with a predicted CNR performance. An LM signal can be simulated 10 using live signals for off-line processing. In addition, a signal processing apparatus can process in real time LM signals emulated from live satellite signals.

Claims

1. A method for simulating a layer modulated signal comprising the steps of:

providing an upper layer signal comprising a first modulated bit stream;

providing a lower layer signal comprising a second modulated bit stream;

attenuating the lower layer signal; and

combining the upper layer signal and the attenuated lower layer signal to produce the composite layer modulated signal;

wherein at least one directional coupler is used to tap the composite layer modulated signal.

2. The method of claim 1, further comprising:

adding noise to the upper layer signal; and

upconverting the composite layer modulated signal;

wherein providing the upper layer signal comprises modulating the first bit stream and providing the lower layer signal comprises modulating the second bit stream.

3. The method of claim 1, further comprising:

amplifying the upper layer signal; and

amplifying the lower layer signal;

wherein providing the upper layer signal comprises receiving the first modulated bit stream from a first satellite transponder and providing the lower layer signal comprises receiving the second modulated bit stream from a second satellite transponder.

4. The method of claim 1, wherein at least one directional coupler is used to tap the upper layer signal.

5. The method of claim 1, wherein at least one directional coupler is used to tap the attenuated lower layer signal.

6. The method of claim 1, further comprising:

tuning the composite layer modulated signal;

evaluating the composite layer modulated signal performance based upon the in-phase and quadrature components of the layer modulated signal.

7. (canceled)

8. A signal simulator for simulating a layer modulated signal having a first modulation of an upper layer and a second modulation of a lower layer, comprising:

a first modulator for modulating a bit stream of the upper layer to produce an upper layer signal;

a noise generator for adding noise to the upper layer signal;

a second modulator for modulating a bit stream of the lower layer to produce a lower layer signal;

an attenuator for attenuating the lower layer signal; and

a combiner for combining the noise-added upper layer signal and the attenuated lower layer signal to produce a composite layer modulated signal.

9. The receiver system of claim 8, wherein the attenuator comprises a variable attenuator.

10. The receiver system of any of claim 8, further comprising an upconverter for upconverting the composite layer modulated signal.

11. The receiver system of any of claim 8, further comprising an upconverter for upconverting the composite layer modulated signal.

12. The receiver system of any of claim 8, further comprising a tuner for tuning the composite layer modulated signal.

13. A receiver system for simulating a layer modulated signal, comprising:

a first antenna for receiving an upper layer signal from a first satellite transponder;

a first amplifier for amplifying the received upper layer signal;

a second antenna for receiving a lower layer signal from a second satellite transponder;

a second amplifier for amplifying the received lower layer signal;

an attenuator for attenuating the received lower layer signal; and

a combiner for combining the upper layer signal and the attenuated lower layer signal to produce a composite layer modulated signal.

14. The receiver system of claim 13, wherein the attenuator comprises a variable attenuator.

15. The receiver system of claim 13, further comprising a tuner for tuning the composite layer modulated signal.

16. A method for simulating a layer modulated signal having a first modulation of an upper layer and a second modulation of a lower layer, comprising the steps of:

providing an upper layer signal comprising a first modulated bit stream;

providing a lower layer signal comprising a second modulated bit stream;

attenuating the lower layer signal; and

combining the upper layer signal and the attenuated lower layer signal to produce the composite layer modulated signal;

tuning the composite layer modulated signal;

evaluating the composite layer modulated signal performance based upon the in-phase and quadrature components of the layer modulated signal.

17. The method of claim 16, further comprising:

adding noise to the upper layer signal; and

upconverting the composite layer modulated signal;

wherein providing the upper layer signal comprises modulating the first bit stream and providing the lower layer signal comprises modulating the second bit stream.

18. The method of claim 16, further comprising amplifying the upper layer signal;

and

amplifying the lower layer signal;

wherein providing the upper layer signal comprises receiving the first modulated bit stream from a first satellite transponder and providing the lower layer signal comprises receiving the second modulated bit stream from a second satellite transponder.

19. The method of claim 16, wherein at least one directional coupler is used to tap the upper layer signal.

20. The method of claim 16, wherein at least one directional coupler is used to tap the attenuated lower layer signal.

21. The method of claim 16, wherein at least one directional coupler is used to tap the composite layer modulated signal.

22. A signal simulator for simulating a layer modulated signal having a first modulation of an upper layer and a second modulation of a lower layer, comprising:

a first modulator for modulating a bit stream of the upper layer to produce an upper layer signal;

a noise generator for adding noise to the upper layer signal;

a second modulator for modulating a bit stream of a lower layer to produce a lower layer signal;

an attenuator for attenuating the lower layer signal;

a combiner for combining the noise-added upper layer signal and the attenuated lower layer signal to produce the composite layer modulated signal; and

a directional coupler, for tapping the composite layer modulated signal.

23. The receiver system of claim 22, wherein the attenuator comprises a variable attenuator.

24. The receiver system of any of claim 22, further comprising an upconverter for upconverting the composite layer modulated signal.

25. The receiver system of any of claim 22, further comprising an upconverter for upconverting the composite layer modulated signal.

26. The receiver system of any of claim 22, further comprising a tuner for tuning the composite layer modulated signal.

27. A signal simulator for simulating a layer modulated signal having a first modulation of an upper layer and a second modulation of a lower layer, comprising:

a first antenna for receiving the upper layer signal from a first satellite transponder;

a first amplifier for amplifying the received upper layer signal;

a second antenna for receiving the lower layer signal from a second satellite transponder;

a second amplifier for amplifying the received lower layer signal;

an attenuator for attenuating the received lower layer signal; and

a combiner for combining the upper layer signal and the attenuated lower layer signal to produce the composite layer modulated signal.

28. The receiver system of claim 27, wherein the attenuator comprises a variable attenuator.

29. The receiver system of any of claim 27, further comprising a tuner for tuning the composite layer modulated signal.