LAYERED MODULATION FOR DIGITAL SIGNALS

• US 20090052590A1
• Filed: 10/28/2008
• Published: 02/26/2009
• Est. Priority Date: 04/27/2001
• Status: Abandoned Application

• Current Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Chen, Ernest C.
• Application Number:
  US12/259,744
• Publication Number:
  US 20090052590A1
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/393 A measuring circuit being coupled to the output of an amplifier
• CPC Class Codes: H03F 3/58 using travelling-wave tubes
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04H 20/103 Transmitter-side switching
• CPC Class Codes: H04H 20/42 Arrangements for resource management
• CPC Class Codes: H04H 60/07 characterised by processes or methods for the generation
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 2027/0061 remodulation
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04L 27/227 using coherent demodulation
• CPC Class Codes: H04L 27/3488 Multiresolution systems
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator

Abstract

Signals, systems and methods for transmitting and receiving layered modulation for digital signals are presented. A layered signal for transmitting data, comprises a first signal layer including a first carrier and first signal symbols for a first digital signal transmission and a second signal layer including a second carrier and second signal symbols for a second signal transmission disposed on the first signal layer, wherein the layered signal has the first carrier demodulated and first layer decoded to produce the first signal symbols for a first layer transport, the first signal symbols are remodulated and subtracted from the layered signal to produce the second signal layer, and the second signal layer has the second carrier demodulated and decoded to produce the second signal symbols for a second layer transport.

Claims

1. A method of receiving a legacy upper layer signal having first signal symbols and a lower layer signal having second signal symbols in a layered modulation receiver, the lower layer signal non-coherently layered over the legacy upper layer signal and receivable by the layered modulation receiver, but not receivable by a legacy receiver, comprising the steps of:

demodulating the legacy upper layer signal in the layered modulation receivers to produce first signal symbols;

remodulating the first signal symbols; and

subtracting the remodulated first signal symbols from the demodulated legacy upper layer signal to produce the second signal symbols.

2. The method of claim 1, wherein the plurality of legacy receivers demodulate the legacy upper layer signal to produce the first signal symbols and do not demodulate the lower layer signal to produce the second signal symbols

3. The method of claim 1, wherein the legacy upper layer signal includes non-linear distortion, and the method further comprises the step of:

removing non-linear distortion effects from the remodulated legacy upper layer symbols before subtracting the remodulated legacy upper layer symbols from the demodulated signal.

4. The method of claim 3, wherein the non-linear distortion effects are estimated from the transmission signal.

5. The method of claim 3, wherein the non-linear distortion effects are estimated from transmission signal transmitter characteristics.

6. The method of claim 1, wherein the a frequency ω

_U of the legacy upper layer signal and a frequency ω

_L of the lower layer signal are offset.

7. The method of claim 1, wherein the legacy upper layer symbols are remodulated according to a pulse shaping filter p(t).

8. The method of claim 1, wherein at least one of the legacy upper layer signal and the lower layer signal are quadrature phase shift keyed (QPSK).

9. The method of claim 1, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is 6/7.

10. The method of claim 1, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is ⅔

.

11. The method of claim 1, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is ½

.

12. The method of claim 1, wherein the lower layer signal is generated by power boosting legacy upper layer signal.

13. The method of claim 1, wherein a total code and noise level of the legacy upper layer signal is no greater than a noise floor of the lower layer signal.

14. The method of claim 1, wherein at least one of the legacy upper layer signal and the lower layer signal is coded using a turbo code.

15. The method of claim 1, wherein both the legacy upper layer signal and the lower layer signal are coded using a single turbo code.

16. The method of claim 1, wherein the legacy upper layer signal and lower layer signal each have a carrier frequency that is substantially similar.

17. The method of claim 1, wherein a carrier frequency of the legacy upper layer signal and a second carrier frequency of the lower layer signal are offset in frequency.

18. The method of claim 1, wherein step of decoding the demodulated signal to produce legacy upper layer symbols comprises the step of Viterbi decoding the demodulated signal.

19. The method of claim 1, wherein the step of decoding the demodulated signal to produce upper layer symbols comprises the step of Reed-Solomon decoding the demodulated signal.

20. A method of receiving a transmission signal having a legacy upper layer signal and a lower layer signal non-coherently added to the upper layer signal, the method comprising:

receiving the legacy upper layer signal and the lower layer signal in a plurality of layered modulation receivers, comprising the steps of;

demodulating the legacy upper layer signal of the transmission signal to produce a first demodulated signal;

decoding the demodulated signal to produce legacy upper layer symbols, and outputting the upper layer symbols to an upper layer transport;

remodulating the legacy upper layer symbols;

subtracting the remodulated legacy upper layer symbols from the demodulated signal to produce the lower layer signal;

demodulating the lower layer signal; and

decoding the demodulated lower layer signal to produce second decoded symbols, and outputting the lower layer signals to a lower layer transport; and

receiving the legacy upper layer signal and not the lower layer signal in a plurality of legacy receivers, comprising the steps of;

demodulating the legacy upper layer signal of the transmission signal to produce a second demodulated signal; and

decoding the second demodulated signal to produce legacy upper layer symbols and outputting the upper layer symbols.

21. The method of claim 20, wherein the legacy upper layer signal includes non-linear distortion, and the method further comprises the step of:

removing non-linear distortion effects from the remodulated legacy upper layer symbols before subtracting the remodulated legacy upper layer symbols from the demodulated signal.

22. The method of claim 21, wherein the non-linear distortion effects are estimated from the transmission signal.

23. The method of claim 21, wherein the non-linear distortion effects are estimated from transmission signal transmitter characteristics.

24. The method of claim 20, wherein the a frequency ω

_U of the legacy upper layer signal and a frequency ω

_L of the lower layer signal are offset.

25. The method of claim 20, wherein the legacy upper layer symbols are remodulated according to a pulse shaping filter p(t).