Layered modulation for digital signals

• US 7,209,524 B2
• Filed: 04/27/2001
• Issued: 04/24/2007
• Est. Priority Date: 04/27/2001
• Status: Expired due to Fees

• Current Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Chen, Ernest C.
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US09/844,401
• Publication Number:
  US 20020181604A1
• Time in Patent Office: 2,188 Days
• Field of Search: 375/262, 375/265, 375/279, 375/281, 375/287, 375/298, 375/308, 375/341, 375/316, 375/329, 375/332, 375/295, 370/464, 370/201, 370/334
• US Class Current: 375/295
• 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 transmitting a transmitting signal having a legacy upper layer signal receivable by a plurality of legacy receivers and a plurality of layered modulation receivers and a lower layer signal non-coherently layered over the legacy upper layer signal, the lower layer signal receivable by the layered modulation receivers and not receivable by the legacy receivers, the method, comprising:

transmitting the legacy upper layer signal including a first carrier and first signal symbols; and

transmitting a lower layer signal including a second carrier and second signal symbols;

wherein the layered modulation receivers demodulate the legacy upper layer signal to produce the first signal symbols, remodulate the first signal symbols, and subtract the remodulated first signal symbols from she demodulated legacy upper layer signal to produce the second signal symbols.

2. 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).

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

4. The method of claim 1, wherein a code rate for at least one of the legacy upper layer signal and lower layer signal is 2/3.

5. The method of claim 1, wherein a code rate for at least one of the legacy upper layer signal and lower layer signal is 1/2.

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

7. 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 second signal layer.

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

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

10. A receiver for compatibly receiving a transmission signal having a legacy upper layer signal receivable by a plurality of legacy receivers and a plurality of layered modulation receivers and a lower layer signal non-coherently layered over the legacy upper layer signal, the lower layer signal receivable by the layered modulation receivers and not receivable by the legacy receivers, the receiver comprising:

a first demodulator for demodulating the legacy upper layer signal to produce a demodulated signal;

a first layer decoder, coupled to the first layer demodulator, for decoding the demodulated signal to produce legacy upper layer signal symbols;

a remodulator, coupled to the first layer decoder, for remodulating the first signal symbols to produce a remodulated legacy upper layer signal;

a subtracter, coupled to the first demodulator and the remodulator, for subtracting the remodulated legacy upper layer signal from the demodulated signal to produce the lower layer signal;

a second layer demodulator, coupled to the subtracter, the second layer demodulator for demodulating the lower layer signal to produce a second demodulator output; and

a second layer decoder, coupled to the second layer demodulator, the second layer decoder for decoding the second layer demodulated output to produce lower layer signal symbols.

11. The receiver system of claim 10, further comprising a non-linear distortion map for removing non-linear distortion effects from the remodulated legacy upper layer signal.

12. The receiver of claim 11, wherein the non-linear distortion map is estimated from the transmission signal.

13. The receiver of claim 11, wherein the non-linear distortion map is estimated from transmission signal transmitter characteristics.

14. The receiver of claim 13, wherein the transmission signal transmitter characteristics are downloaded to the receiver.

15. The receiver system of claim 10, wherein the legacy upper layer signal is a boosted legacy signal.

16. The receiver system of claim 10, wherein at least one of the legacy upper layer signal and lower layer signal are quadrature phase shift keyed (QPSK).

17. The receiver system of claim 10, wherein a code rate for at least one of the legacy upper layer signal and lower layer signal is 6/7.

18. The receiver system of claim 10, wherein a code rate for at least one of the legacy upper layer signal and lower layer signal is 2/3.

19. The receiver system of claim 10, wherein a code rate for at least one of the legacy upper layer signal and lower layer signal is 1/2.

20. The receives system of claim 10, wherein the second signal layer is generated by power boosting the legacy upper layer signal.

21. The receiver system of claim 10, 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.

22. The receiver system of claim 10, wherein at least one of the legacy upper layer signal and lower layer signal is coded using a turbo code.

23. The receiver system of claim 10, wherein both the legacy upper layer signal and lower layer signal are coded using a single turbo code.

24. The receiver system of claim 10, wherein the legacy upper layer signal and lower layer signal each have a carrier frequency that is substantially similar.

25. The receiver system of claim 10, wherein a carrier frequency of the legacy upper layer signal and a second carrier frequency of the lower layer signal are offset in frequency.

26. The receiver system of claim 10, wherein the the first layer decoder comprises a Viterbi decode.

27. The receiver system of claim 10, wherein the the first layer decoder comprises a Reed-Solomon decoder.

28. A method of receiving a transmission signal having a legacy upper layer signal compatibly receivable by a plurality of legacy receivers and a plurality of layered modulation receivers and a lower layer signal non-coherently layered over the upper layer signal, the lower layer signal receivable by the layered modulation receivers and not receivable by the legacy receivers, the method comprising:

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

decoding the demodulated signal to produce legacy upper layer symbols;

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.

29. The method of claim 28, 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.

30. The method of claim 29, wherein the non-linear distortion effects are estimated from the transmission signal.

31. The method of claim 29, wherein the non-linear distortion effects are estimated from transmission signal transmitter characteristics.

32. The method of claim 28, wherein the a frequency ω

_U of the legacy upper layer signal and a frequency ω

_L of the lower layer signal are offset.

33. The method of claim 28, wherein the legacy upper layer symbols are remodulated according to a pulse shaping filter p(t).

34. The method of claim 28, wherein at least one of the legacy upper layer signal and the lower layer signal are quadrature phase shift keyed (QPSK).

35. The method of claim 28, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is 6/7.

36. The method of claim 28, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is 2/3.

37. The method of claim 28, wherein a code rate for at least one of the legacy upper layer signal and the lower layer signal is 1/2.

38. The method of claim 28, wherein the lower layer signal is generated by power boosting legacy upper layer signal.

39. The method of claim 28, 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.

40. The method of claim 28, wherein at least one of the legacy upper layer signal and the lower layer signal is coded using a turbo code.

41. The method of claim 28, wherein both the legacy upper layer signal and the lower layer signal are coded using a single turbo code.

42. The method of claim 28, wherein the legacy upper layer signal and lower layer signal each have a carrier frequency that is substantially similar.

43. The method of claim 28, wherein a carrier frequency of the legacy upper layer signal and a second carrier frequency of the lower layer signal are offset in frequency.

44. The method of claim 28, wherein step of decoding the demodulated signal to produce legacy upper layer symbols comprises the step of Viterbi decoding the demodulated signal.

45. The method of claim 28, wherein the step of decoding the demodulated signal to produce upper layer symbols comprises the step of Reed-Solomon decoding the demodulated signal.