Method and apparatus for layered modulation

• US 7,738,587 B2
• Filed: 07/03/2003
• Issued: 06/15/2010
• Est. Priority Date: 07/03/2002
• Status: Expired due to Fees

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Santoru, Joseph, Chen, Ernest C.
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US10/519,375
• Publication Number:
  US 20060050805A1
• Time in Patent Office: 2,539 Days
• Field of Search: 375/295, 375/296, 375/297, 375/298, 375/308, 375/279, 375/299
• 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 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 bit stream modulated by a first carrier comprising modulating the first bit stream;

providing a lower layer signal comprising a second bit stream modulated by a second carrier not coherent with the first carrier comprising modulating the second bit stream;

adding noise to the upper layer signal;

attenuating the lower layer signal;

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

upconverting the composite layer modulation signal;

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

2. 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.

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

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

5. 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.

6. A signal simulator for simulating a layer modulated signal having a an upper layer and a lower layer not coherent with the upper layer, comprising:

a first modulator for modulating a bit stream of the upper layer according to a first carrier 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 according to a second carrier not coherent with the first carrier 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.

7. The signal simulator of claim 6, wherein the attenuator comprises a variable attenuator.

8. The signal simulator of claim 6, further comprising an upconverter for upconverting the composite layer modulated signal.

9. The signal simulator of claim 6, further comprising a tuner for tuning the composite layer modulated signal.

10. A method for simulating a layer modulated signal having an upper layer and a lower layer not coherent with the upper layer, comprising the steps of:

providing an upper layer signal comprising a first bit stream modulated according to a first carrier comprising modulating the first bit stream;

providing a lower layer signal comprising a second bit stream modulated according to a second carrier not coherent with the first carrier comprising modulating the second bit stream;

providing the upper layer signal to a noise generator to add noise to the upper layer signal;

attenuating the lower layer signal;

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

providing the composite layer modulated signal to an upconverter to upconvert the composite modulated signal;

communicating the composite layer modulated signal to a tuner to extract the composite layer modulated signal; and

evaluating the composite layer modulated signal performance based upon an in-phase component and a quadrature component of the extracted layer modulated signal.

11. The method of claim 10, 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.

12. The method of claim 10, wherein at least one directional coupler is used to tap the upper layer signal.

13. The method of claim 10, wherein at least one directional coupler is used to tap the attenuated lower layer signal.

14. The method of claim 10, wherein at least one directional coupler is used to tap the composite layer modulated signal.

15. 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 according to a first carrier 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 according to a second carrier not coherent with the first carrier 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.

16. The signal simulator of claim 15, wherein the attenuator comprises a variable attenuator.

17. The signal simulator of claim 15, further comprising an upconverter for upconverting the composite layer modulated signal.

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