Near-end, far-end and echo cancellers in a multi-channel transceiver system

• US 20040247022A1
• Filed: 06/03/2003
• Published: 12/09/2004
• Est. Priority Date: 06/03/2003
• Status: Active Grant

• Current Assignee: Entropic Communications Incorporated (Maxlinear Incorporated)
• Original Assignee: Entropic Communications Incorporated (Maxlinear Incorporated)
• Inventors: Sallaway, Peter J., Raghavan, Sreen A., Taylor, Gerard E., Manickam, Thulasinath G.
• Granted Patent: US 7,388,904 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H04B 3/20 Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04L 5/08 each combination of signals in different channels being represented by a fixed frequency

Abstract

A transceiver according to the present invention receives data from a plurality of frequency separated transmission channels from a complementary transmitter and includes an interference filter for correcting for interference from transmitters other than the complementary transmitter. The interference filter, for example, can correct for near-end cross-talk and echo interference filtering and/or far-end crosstalk interference filtering is presented. A transceiver can include a transmitter portion and a receiver portion with one or more receivers coupled to receives signals in the plurality of frequency separated transmission channels. A baseband transmitter can be combined with one or more transmitters that transmit data into one of the frequency separated transmission bands. Any combination of modulation systems can be utilized (e.g. PAM for the baseband and QAM for the frequency separated bands). In some embodiments, one baseband PAM transmitter is combined with one or more frequency separated QAM transmitters.

Claims

1. A transceiver, comprising:

a receiver portion including at least one receiver to receive signals from a complementary transmitter through a transmission medium, the at least one receiver including a plurality of demodulators to receive the signals from a corresponding plurality of frequency separated channels; and

an interference filter coupled to the receiver portion to substantially reduce interference in signals received by the receiver portion that result from transmission coupled to each of the plurality of corresponding frequency separated channels from transmitters other than the complementary transmitter.

2. The transceiver of claim 1, wherein the interference filter includes a far-end cross-talk filter.

3. The transceiver of claim 2, wherein the far-end cross-talk filter is combined with a cross-channel interference filter.

4. The transceiver of claim 2, wherein the far-end cross-talk filter receives input signals from each of the plurality of demodulators of each of the at least one receiver and removes interference from each of the signals in the receiver portion by subtracting a selected portion of each of the input signals from each of the signals in the receiver portion.

5. The transceiver of claim 4, wherein the far-end cross-talk filter further corrects for cross-channel interference by subtracting from each of the signals in the receiver portion a selected contribution from each of the other signals in the receiver portion.

6. The transceiver of claim 2, wherein parameters in the far-end cross-talk filter are adaptively chosen.

7. The transceiver of claim 1, wherein the transceiver further includes at least one transmitter and the interference filter includes a near-end cross talk and echo filter.

8. The transceiver of claim 7, wherein the near-end cross talk and echo filter subtracts from each of the signals received by the plurality of demodulators of each of the at least one receiver a selected portion of transmit signals transmitted by the at least one transmitter.

9. The transceiver of claim 8, wherein the at least one transmitter includes a plurality of modulators, each of the plurality of modulators transmitting into the corresponding plurality of frequency separated channels.

10. The transceiver of claim 8, wherein the selected portion is adaptively chosen.

11. The transceiver of claim 1, wherein the plurality of demodulators includes at least one down-converting demodulator, the down-converting demodulator comprising:

a down converter coupled to receiver an analog signal from the transmission medium and generate base-band signals corresponding to signals transmitted at a specific carrier frequency on the transmission medium;

an analog-to-digital converter coupled to the down converter to provide a digitized base-band signal; and

a decoder coupled to the analog-to-digital converter to provide data signals in response to the base-band signals.

12. The transceiver of claim 11, further including an analog filter coupled between the down converter and the analog-to-digital converter, the analog filter providing initial filtering and amplification to the base-band signals.

13. The transceiver of claim 12, wherein the analog filter includes an amplifier.

14. The transceiver of claim 11, wherein the analog filter includes a low pass filter.

15. The transceiver of claim 11, wherein the decoder includes a trellis decoder.

16. The transceiver of claim 15, wherein the trellis decoder decodes symbols from a QAM symbol set.

17. The transceiver of claim 11, wherein the plurality of demodulators includes a base-band demodulator, the base-band demodulator comprising:

an analog processor coupled to receive the analog signal from the transmission medium;

an analog-to-digital filter coupled to the analog processor, the analog-to-digital filter providing a digitized signal;

an equalizing filter coupled to the analog-to-digital filter; and

a data-recovery block coupled to receive signals from the equalizing filter.

18. The transceiver of claim 17, wherein the analog processor includes a low pass filter.

19. The transceiver of claim 17, wherein the equalizing filter includes an equalizer.

20. The transceiver of claim 17, wherein the data recovery block decodes data bits from a PAM symbol set.

21. The transceiver of claim 11, wherein the interference filter is coupled between the analog-to-digital converter and the decoder.

22. The transceiver of claim 21, further including a first digital filter coupled between the interference filter and the analog-to-digital converter.

23. The transceiver of claim 22, wherein the first digital filter includes phase and amplitude correction between in-phase and quadrature components of the digitized base-band signal output from the analog-to-digital filter.

24. The transceiver of claim 22, wherein the first digital filter includes an equalizer.

25. The transceiver of claim 22, further including a second digital filter coupled between the interference filter and the decoder.

26. The transceiver of claim 25, wherein the second digital filter includes phase and amplitude correction between in-phase and quadrature components of the base-band digital signal.

27. The transceiver of claim 25, wherein the second digital filter includes a digital offset.

28. The transceiver of claim 21, further including a cross-channel interference filter coupled between the digital filter and the interference filter.

29. The transceiver of claim 28, wherein the cross-channel interference is further coupled to a base-band demodulator to correct signals in the base-band demodulator from cross-channel interference.

30. The transceiver of claim 21, wherein the interference filter includes a far-end cross-talk filter.

31. The transceiver of claim 30, wherein the far-end cross-talk filter is coupled to receive input signals from each of the plurality of demodulators of each of the at least one receiver and corrects a signal related to the digitized base-band signals by subtraction a selected portion of each of the input signals from the signal related to the digitized base-band signals.

32. The transceiver of claim 31, wherein the selected portion of each of the input signals is adaptively chosen.

33. The transceiver of claim 31, wherein the far-end cross-talk filter includes cross-channel interference correction.

34. The transceiver of claim 31, wherein the transceiver further includes at least one transmitter, the at least one transmitter including a plurality of modulators coupled to transmit signals into a second plurality of frequency separated channels on the transmission medium.

35. The transceiver of claim 34, wherein the second plurality of frequency separated channels and the plurality of frequency separated channels are substantially identical.

36. The transceiver of claim 34, wherein the interference filter includes a near-end cross-talk filter.

37. The transceiver of claim 36, wherein a transmitter of the at least one transmitter and a receiver of the at least one receiver share a physical connection and the near-end cross-talk filter also corrects for echo interference.

38. The transceiver of claim 36, wherein the near-end cross-talk filter receives transmitted signals from each of the plurality of modulators from each of the at least one transmitter and subtracts a selected portion of each of the transmitted signals from a signal related to the digitized base-band signal.

39. A method of receiving data from a transmission medium, comprising:

receiving signals into a plurality of demodulators from a corresponding plurality of frequency separated channels transmitted on the transmission medium by a complementary transmitter;

digitizing signals related to the received signals to form a digitized signal in each of the plurality of demodulators;

correcting signals related to the digitized signals in each of the plurality of demodulators to remove interference resulting from transmitters other than the complementary transmitter transmitting signals through the transmission medium to form corrected signals; and

recovering data transmitted by the complementary transmitter from signals related to the corrected signals for each of the plurality of demodulators.

40. The method of claim 39, wherein receiving signals into a plurality of demodulators includes

receiving a transmitted signal from the transmission medium;

and

obtaining a base-band signal from the transmitted signal for each of the plurality of demodulators, the base-band signal corresponding to one of the plurality of demodulators corresponding to a transmission into the corresponding one of the plurality of frequency separated channels for that one of the plurality of demodulators.

41. The method of claim 40, wherein obtaining a base-band signal includes

down-converting the transmitted signal with a down converter;

and

filtering the output signal from the down converter.

42. The method of claim 40, wherein one of the plurality of demodulators receives signals transmitted on a base-band channel, the base-band channel being one of the plurality of frequency separated channels.

43. The method of claim 39, wherein correcting signals related to the digitized signals includes providing correction for far-end cross-talk interference.

44. The method of claim 43, wherein providing correction for far-end cross-talk interference includes subtracting a contribution of each signal in each of a second plurality of demodulators from the signals related to the digitized signal.

45. The method of claim 43, wherein providing correction for far-end cross-talk interference further includes correction for cross-channel interference, where a contribution from each of the plurality of demodulators is subtracted from the signals related to the digitized signal.

46. The method of claim 39, wherein correcting signals related to the digitized signals includes providing correction for near-end cross talk interference and echo interference.

47. The method of claim 46, where providing correction for near-end cross talk interference and echo interference includes subtracting a contribution from signals generated by at least one transmitter.

48. A transceiver system, comprising:

a transceiver comprising

a first transmitter including plurality of modulators, each of the plurality of modulators transmitting into one of a first plurality of frequency separated channels on a transmission medium, and

a first receiver including a plurality of demodulators, each of the plurality of demodulators receiving signals from one of a second plurality of frequency separated channels on the transmission medium; and

a complementary transceiver, the complementary transceiver including

a complementary first receiver coupled to receive signals corresponding to signals transmitted into one of the first plurality of frequency separated channels on the transmission medium, and

a complementary first transmitter coupled to transmit signals into the second plurality of frequency separated channels on the transmission medium; and

wherein the transceiver includes an interference filter coupled to the first receiver, the interference filter removing interference that result from transmitters other than the complementary first transmitter from signals in the first receiver.

49. The transceiver system of claim 48, wherein the interference filter includes a far-end cross-talk filter coupled to receive signals from at least one other transmitter in the transceiver and to correct signals in the first receiver.

50. The transceiver system of claim 48, wherein the interference filter includes a near-end cross-talk and echo filter coupled to receive signals from the first transmitter and correct signals in the first receiver.

51. The transceiver system of claim 50, wherein the near-end cross-talk and echo filter is further coupled to receive signals from at least one other transmitter in the transceiver.

52. The transceiver system of claim 48, wherein the transmission medium includes a first twisted copper pair coupling the first transmitter with the complementary first receiver and a second twisted copper pair coupling the first receiver with the complementary first transmitter.

53. The transceiver system of claim 52,

wherein the transceiver further includes a second transmitter and a second receiver, and the complementary transceiver further includes a complementary second receiver and a complementary second transmitter, and

wherein the transmission medium includes a third copper pair coupling the second transmitter with the complementary second receiver and a fourth copper pair coupling the second receiver and the complementary second transmitter.

54. The transceiver system of claim 53, wherein

the first plurality of frequency separated channels includes four channels at frequencies f₀, 2f₀, 3f₀ and 4f₀, where f₀ is about 312.5 MHz,

the second plurality of frequency separated channels is substantially the same as the first set of frequency separated channels,

each of the plurality of modulators transmits QAM 128 symbols with 6/7 trellis encoding at a baud rate of 208.333 Msymbols/sec, and each of the plurality of demodulators receives QAM 128 symbols with 6/7 trellis encoding at a baud rate of 208.333 Msymbols/sec.

55. The transceiver system of claim 48, wherein the transmission medium includes a first copper pair, the first transmitter and the complementary first receiver are coupled through the first copper pair and the first receiver and the complementary first transmitter are also coupled through the first copper pair.

56. The transceiver system of claim 55,

wherein the transceiver includes a second transmitter, a third transmitter and a fourth transmitter, a second receiver, a third receiver and a fourth receiver and the complementary transceiver includes a complementary second transmitter, a complementary third transmitter, a complementary fourth transmitter, a complementary second receiver, a complementary third receiver, and a complementary fourth receiver, and

wherein the transmission medium further comprises:

a second copper pair coupling the second transmitter, the second receiver, the complementary second transmitter and the complementary second receiver;

a third copper pair coupling the third transmitter, the third receiver, the complementary third transmitter and the complementary third receiver; and

a fourth copper pair coupling the fourth transmitter, the fourth receiver, the complementary fourth transmitter and the complementary fourth receiver.

57. The transceiver system of claim 56, wherein

the first plurality of frequency separated channels is at f₀ and 2f₀, where f₀ is about 312.5 MHz,

the second plurality of frequency separated channels is substantially the same as the first plurality of frequency separated channels, each of the plurality of modulators transmits a QAM 128 symbol set with 6/7 trellis encoding at a baud rate of about 208.333 Msymbols/sec, and

each of the plurality of demodulators receives QAM 128 symbols with 6/7 trellis encoding at a baud rate of 208.333 Msymbols/sec.

58. The transceiver system of claim 57, wherein the first plurality of frequency separated channels is at frequencies f₀ and 3f₀ and the second plurality of frequency separated channels is at frequencies 2f₀ and 4f₀.

59. The transceiver system of claim 57, wherein the interference filter includes a far-end cross-talk filter coupled to the receive signals from each of the first receiver, the second receiver, the third receiver and the fourth receiver and to correct signals in each of the first receiver, the second receiver, the third receiver and the fourth receiver.

60. The transceiver system of claim 57, wherein the interference filter includes a near-end cross-talk and echo filter coupled to receive signals from the first transmitter, the second transmitter, the third transmitter and the fourth transmitter and to correct signals in the first receiver, the second receiver, the third receiver and the fourth receiver.

61. The transceiver system of claim 48, wherein the transceiver includes a master phase-locked loop to provide timing signals and the complementary transceiver includes a frequency shift and a phase-locked loop to recover the timing signal of the transceiver.

62. The transceiver system of claim 48, wherein the complementary transceiver includes a master phase-locked loop to provide timing signals and the transceiver includes a frequency shift and a phase-locked loop to recover the timing signal of the transceiver.

63. A communication method, comprising receiving signals transmitted from a complementary transmitter on a set of frequency separated channels such that interference from non-complementary transmitters is corrected.

64. A communication device, comprising:

a receiver to receive signals on a set of frequency separated channels from a complementary transmitter; and

a filtering unit to correct for interference in the signals from a non-complementary transmitter.

65. A transceiver, comprising

means for receiving signals from a plurality of frequency separated channels transmitted from a complementary transmitter through a transmission medium;

and

means for correcting for interference from the effects of transmitters other than the complementary transmitter transmitting on the transmission medium.

66. The transceiver of claim 65, further including

means for transmitting signals into a second plurality of frequency separated channels on the transmission medium.

67. The transceiver of claim 65, wherein the means for correcting for interference includes means for correcting for far-end cross-talk interference.

68. The transceiver of claim 66, wherein the means for correcting for interference includes means for corrected for near-end cross-talk and echo interference.

69. The transceiver of claim 65, further including

means for performing timing recovery.