Multiple channel interference cancellation

• US 20060034162A1
• Filed: 10/13/2005
• Published: 02/16/2006
• Est. Priority Date: 04/28/2003
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: George A. Zimmerman, William W. Jones
• Inventors: Zimmerman, George A., Jones, William W.
• Granted Patent: US 7,742,386 B2
• Time in Patent Office: Days
• US Class Current: 370/201
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating

Abstract

A method and apparatus for reducing crosstalk in a multi-channel communication system is disclosed. In one embodiment, outgoing signals in a multi-channel environment are manipulated into a transform domain, such as the frequency domain. Thereafter, the signals may be combined and modified based on a weighting variable to create a cancellation signal. Combined processing greatly reduces system complexity and increases processing speed. After processing in the transform domain, the cancellation signal undergoes further processing to return the cancellation signal into the time domain. The cancellation signal may then be combined with received signals to cancel crosstalk or echo. A method and apparatus for crosstalk cancellation in the analog domain and digital domain is also disclosed. Cancellation at least partially in the analog domain reduces the dynamic range requirements for digital to analog converters within the front-end processing system of a receiver and thereby reducing clipping and increasing operating speed.

Claims

1. A method for reducing interference in an incoming signal received at a transceiver of a multi-channel communication device comprising:

receiving, in a serial format, a signal to be transmitted over a channel, the transmitted signal to be transmitted from the transceiver;

converting the signal to a parallel format;

performing overlap processing on the signal;

performing a Fourier transform on the signal to create a transform domain signal;

distributing the transform domain signal to two or more multipliers, at least one of which is associated with a different channel;

multiplying the transform domain signal by one or more weighting variables to create a weighted transform domain signal;

performing an inverse Fourier transform on the weighted transform domain signal to create a cancellation signal;

performing overlap processing on the cancellation signal;

converting the cancellation signal to a serial format; and

combining the cancellation signal with the incoming signal to reduce interference in the incoming signal.

2. The method of claim 1, wherein the signal comprises four signals and each signal is associated with a channel in the multi-channel communication device and each signal is subject to a single Fourier transform operation.

3. The method of claim 2, further comprising adding two or more weighted transform domain signals to generate a combined weighted transform signal that subsequently undergoes an inverse Fourier Transform to create a cancellation signal.

4. The method of claim 3, wherein distributing the transform domain signal to two or more multipliers comprises distributing the transform domain signal to one multiplier associated with each channel.

40. The method of claim 1, wherein the number of points in the Fourier transform is 512.

41. The method of claim 1, wherein the overlap processing comprises ⅝

overlap processing.

5. In a multi-channel environment, a method for canceling interference in one or more received signals comprising:

receiving two or more outgoing signals;

converting the two or more outgoing signal to a transform domain to create a transform domain signal for each channel;

distributing the transform domain signal for each channel to a multiplier associated with each channel;

processing, with the multiplier, the transform domain signal from each channel with weighting variables to generate two or more cancellation signals in the transform domain;

combining the two or more cancellation signals in the transform domain to create a combined transform domain cancellation signal;

converting the combined transform domain cancellation signal out of the transform domain to obtain a cancellation signal for each channel; and

combining the cancellation signal for each channel with the signal received on each the channel to cancel interference.

6. The method of claim 5, wherein the processing comprises multiplying the transform domain signal with the weighting variable.

7. The method of claim 6, wherein the multiplying comprises an element by element multiply operation.

8. The method of claim 5, wherein receiving one or more outgoing signals comprise receiving four outgoing signals and combining the cancellation signal with a received signal comprises combining a cancellation signals with each received signal.

9. The method of claim 8, further comprising combining two or more of the two or more cancellation signals in the transform domain prior to converting the two or more cancellation signals in the transform domain out of the transform domain.

10. The method of claim 5, wherein converting comprises performing a Fast Fourier Transform on the outgoing signal.

11. The method of claim 5, further comprising performing overlap processing on the one or more outgoing signals and the one or more cancellation signals.

12. A cancellation system for reducing interference in a received signal in a multi-channel communication device, wherein the cancellation system for each channel comprises:

an input for receiving an outgoing signal at a first transceiver, the outgoing signal in a first domain;

a transform unit configured to manipulate the outgoing signal into a second domain signal and distribute the second domain signal to at least one multiplier associated with each channel;

one or more a multipliers associated with each channel configured to receive the distributed second domain signal from each channel and multiply the second domain signal with one or more weighting variables to create a cancellation signal in the second domain;

an inverse transform unit configured to perform an inverse transform on the cancellation signals in the second domain to create a cancellation signal in the first domain; and

a subtractor configured to subtract the cancellation signal that is in the first domain from a received signal.

13. The system of claim 12, wherein the two or more multipliers comprise a processor.

14. The system of claim 12, further comprising one or more summing junctions configured to add the cancellation signals in the second domain from the multipliers to generate a combined cancellation signal in the second domain and output the combined cancellation signal in the second domain to the inverse transform unit.

15. The system of claim 12, further comprising an overlap processing module configured to perform overlap processing on the outgoing signal.

16. The system of claim 12, wherein the multi-channel communication device comprises a four channel communication device and each cancellation system generates a cancellation signal that accounts for the interference from each of the four channels.

17. The system of claim 12, further comprising an adaptation system configured to adaptively generate weighting variables.

18. The system of claim 17, wherein the adaptation system comprises a transform unit configured to convert an error signal to the second domain and an adaptation module configured to process the error signal in the second domain to generate the weighting variables.

19. A cancellation system for use in a multi-channel transceiver to cancel unwanted coupling comprising:

one or more inputs, wherein each input provides an outgoing signal to the cancellation system;

a transform unit associated with each channel, wherein each transform unit is configured to convert an outgoing signal from a channel to a transform domain;

one or more multipliers, wherein each multiplier is configured to receive the outgoing signal from each channel in the transform domain and multiply the outgoing signal from each channel in the transform domain with a weighting variable to create one or more cancellation signals in the transform domain;

one or more devices configured to combine two or more cancellation signals in the transform domain to create a combined cancellation signal in the transform domain for each channel; and

a inverse transform unit associated with each channel configured to receive the combined cancellation signal and reverse the processing of the transform units.

20. The system of claim 19, wherein the transform units and the inverse transform units perform overlap processing and transform processing.

21. The system of claim 19, wherein one transform unit and one inverse transform unit is associated with each channel.

22. The system of claim 19, wherein the weighting variables are generated based on least mean square adaptation.

23. The system of claim 19, wherein the transform units perform any type of Fourier transform and the inverse transform units perform any form of inverse Fourier transform.

24. The system of claim 19, wherein the one or more devices configured to combine comprise one or more adders.

25. The system of claim 19, wherein the weighting variables are generated by an adaptation system and the adaptation system is shared between two or more channels.

26. A method for generating a cancellation signal in a cancellation system, wherein said method occurs within a multi-channel communication system comprising:

receiving at a cancellation system two or more signals, wherein the two or more signals relate to one or more outgoing signals on the two or more channels in the multi-channel communication system;

performing a single transform operation on each of the two or more signals to convert each of the two or more signals into a transform domain;

distributing the two or more signals in the transform domain to a multipliers associated with each of the channels;

multiplying the two or more signals in the transform domain by one or more weighting variables to create one or more multiplier outputs;

combining the one or more multiplier outputs associated with each channel to create a combined transform domain cancellation signal, wherein the transform domain cancellation signal is associated with a channel; and

performing a single inverse transform operation on each of the transform domain cancellation signals to remove the cancellation signal from the transform domain and thereby create the cancellation signal for each channel.

27. The method of claim 26, wherein the cancellation signal is configured to cancel echo and crosstalk in the signal.

28. The method of claim 26, wherein the channel comprises a two conductor signal path.

29. The method of claim 26, wherein the transform domain comprises the frequency domain.

30. The method of claim 26, further comprising generating the one or more weighting variables based on a feedback error signal resulting from a combination of the cancellation signal and a received signal.

31. The method of claim 26, wherein the cancellation signal comprises components relating to each of the signals transmitted on other channels of the multi-channel communication device.

42. The method of claim 30, wherein the feedback error signal is generated based a decision device error signal.

32. A method of generating one or more weighting variables for use in a cancellation system comprising:

receiving one or more error signals, each of the one or more error signals associated with a channel in a multi-channel communication device;

receiving one or more data signals, the data signals in a transform domain and associated with a channel;

converting the one or more error signals to a transform domain;

performing adaptation processing on the one or more error signals in the transform domain and the one or more data signals in the transform domain to generate at least one weighting variables for each channel; and

outputting the weighting variable for each channel to a shared multiplier associated with each channel, wherein the weighting variable is configured to modify the data signals in a transform domain to generate a cancellation signal.

33. The method of claim 32, wherein receiving one or more error signals comprises selectively receiving one of one or more error signals and receiving one or more data signals comprises selectively receiving one of one or more data signals and outputting one or more weighting variables to a cancellation system comprises selectively outputting one or more weighting variables to a cancellation system and wherein the selectivity is controlled by a control signal.

34. The method of claim 32, wherein converting comprises performing a fast Fourier transform on the error signal and the method further comprises performing overlap processing on the error signal.

43. The method of claim 32, wherein the error signal comprises a decision device error.

44. The method of claim 32, wherein the error signal is selected from the group of error signals consisting of decision device error and the received signal.

45. The method of claim 32, wherein the method of generating is shared between two or more channels such that the method utilizes error signals and data signals associated with a first channel to generate the one or more first channel weighting variables and thereafter utilizes error signals and data signals associated with a second channel to generate the one or more second channel weighting variables.

46. The method of claim 45, wherein shared comprises shared on a round robin basis.

47. The method of claim 32, wherein the one or more weighting variables are shared utilizing a weighting variable switch.

35. A system for generating a two or more weighting variables for use by a transform domain processing module in an interference cancellation system comprising:

a first input configured to receive two or more a feedback signals;

a second input configured to receive a two or more data signals;

a transform unit configured to receive either or both of the feedback signal and the data signal and transform either or both of the feedback signal and the data signal into a transform domain, wherein the transform unit is shared between two or more channels; and

an adaptation module configured to process the feedback signal and the data signal to generate one or more weighting variables, wherein the adaptation module is shared by two or more channels.

36. The system of claim 35, wherein the transform domain processing module comprises one or more multipliers.

37. The system of claim 35, wherein the transform unit is configured to s perform a Fourier transform.

38. The system of claim 35, wherein the weighting variables are calculated to modify a transmitted signal to generate a cancellation signal.

39. The system of claim 35, wherein the transform domain is a domain in which multiplication between a data signal and one or more weighting variable is generally equivalent to convolution.