Method and apparatus for cross-talk cancellation in frequency division multiplexed transmission systems

• US 20030179766A1
• Filed: 08/15/2002
• Published: 09/25/2003
• Est. Priority Date: 03/22/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Azadet, Kameran
• Granted Patent: US 7,362,719 B2
• Time in Patent Office: Days
• US Class Current: 370/436
• CPC Class Codes: H04J 1/12 Arrangements for reducing cross-talk between channels in line transmission systems H04B3/32; in cables or lines H04B3/26 - H04B3/30
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A method and apparatus are disclosed for canceling cross-talk in a frequency-division multiplexed communication system. The disclosed frequency-division multiplexed communication system employs multiple carriers having overlapping channels and provides an improved cross-talk cancellation mechanism to address the resulting interference. Bandwidth compression is achieved using n level amplitude modulation in each frequency band. An FDM receiver is also disclosed that decomposes the received broadband signal into each of its respective frequency bands and returns the signal to baseband in the analog domain. Analog requirements are relaxed by removing cross-talk from adjacent RF channels, from image bands, and minimizing the performance degradation caused by In-phase and Quadrature-phase (I/Q) phase and gain mismatches in modulators and demodulators. The disclosed transmitter or receiver (or both) can be fabricated on a single integrated circuit.

Claims

1. A method for communicating one or more data signals, said method comprising the steps of:

modulating said one or more data signals onto a plurality of frequency bands to produce a frequency division multiplexed signal, wherein said frequency bands are overlapping; and

transmitting said frequency division multiplexed signal over a fiber channel.

2. The method of claim 1, wherein said overlapping frequency bands have a carrier spacing that approaches a Nyquist limit.

3. The method of claim 1, further comprising the step of employing a multiple level transmission scheme.

4. The method of claim 1, wherein said overlapping frequency bands have a non-uniform carrier spacing.

5. The method of claim 1, wherein said overlapping frequency bands have a uniform carrier spacing.

6. The method of claim 1, wherein said overlapping frequency bands use synchronous clocks.

7. The method of claim 1, wherein said overlapping frequency bands use asynchronous clocks.

8. The method of claim 1, further comprising the step of removing cross-talk at a receiver.

9. The method of claim 1, further comprising the step of removing cross-talk at a transmitter.

10. A method for receiving a frequency division multiplexed signal, said method comprising the steps of:

decomposing said frequency division multiplexed signal into a plurality of frequency bands;

returning said decomposed frequency bands to baseband signals; and

removing cross-talk from said baseband signals.

11. The method of claim 10, wherein said plurality of frequency bands are overlapping.

12. The method of claim 10, wherein said removing step further comprises the step of removing said cross-talk from a given baseband signal using said given baseband signal and at least one additional baseband signal.

13. The method of claim 10, wherein said removing step further comprises the steps of (i) applying time varying rotations to each received baseband signal to create rotated input signals;

(ii) applying digital filters to said rotated input signals;

(iii) combining outputs of said digital filters to create rotated output signals; and

(iv) derotating said rotated output signals.

14. The method of claim 13, wherein said digital filters are adaptive.

15. A method for receiving a frequency division multiplexed signal, said method comprising the steps of:

decomposing said frequency division multiplexed signal into a plurality of frequency bands;

returning said decomposed frequency bands to baseband signals;

removing cross-talk from said baseband signal; and

removing image bands from said baseband signal.

16. The method of claim 15, wherein said removing cross-talk step further comprises the steps of (i) applying time varying rotations to each received baseband signal to create rotated input signals;

(ii) applying digital filters to said rotated input signals;

(iii) combining outputs of said digital filters to create rotated output signals; and

(iv) derotating said rotated output signals.

17. The method of claim 15, wherein said removing image bands step further comprises the steps of (i) applying time varying rotations to each received baseband signal to create rotated input signals;

(ii) obtaining a complex conjugate of said rotated input signals;

(iii) applying digital filters to said complex conjugate of said rotated input signals;

(iii) combining outputs of said digital filters to create rotated output signals; and

(iv) derotating said rotated output signals.

18. The method of claim 15, wherein said cross-talk and image bands are removed using a single set of filters, wherein each complex filter tap realizes four independent real multiplications.

19. An integrated circuit, comprising:

RF carrier modulators for modulating one or more data signals onto a plurality of frequency bands to produce a frequency division multiplexed signal, wherein said frequency bands are overlapping; and

a driver for generating a signal that drives a light source that transmits said frequency division multiplexed signal over a fiber channel.

20. An integrated circuit, comprising:

RF carrier demodulators to decompose a frequency division multiplexed signal into a plurality of frequency bands and return said decomposed frequency bands to baseband signals; and

a cross-talk canceller for removing cross-talk in said baseband signals.

21. The integrated circuit of claim 20, wherein said cross-talk canceller is a digital signal processor.

22. A system for communicating one or more data signals, said system comprising:

a modulator for modulating said one or more data signals onto a plurality of frequency bands to produce a frequency division multiplexed signal, wherein said frequency bands are overlapping; and

a light source for transmitting said frequency division multiplexed signal over a fiber channel.

23. The system of claim 22, further comprising a cross-talk canceller at a receiver.

24. The system of claim 22, further comprising a cross-talk canceller at a transmitter.

25. A system for receiving a frequency division multiplexed signal, said system comprising:

a demodulator for decomposing said frequency division multiplexed signal into a plurality of frequency bands and returning said decomposed frequency bands to baseband signals; and

a cross-talk canceller for removing cross-talk from said baseband signals.

26. The system of claim 25, wherein said plurality of frequency bands are overlapping.

27. The system of claim 25, wherein said cross-talk canceller removes said cross-talk from a given baseband signal using said given baseband signal and at least one additional baseband signal.

28. The system of claim 25, wherein said cross-talk canceller (i) applies time varying rotations to each received baseband signal to create rotated input signals;

(ii) applies digital filters to said rotated input signals;

(iii) combines outputs of said digital filters to create rotated output signals; and

(iv) derotates said rotated output signals.

29. The system of claim 25, further comprising an image band canceller for removing image bands from said baseband signal.

30. The system of claim 29, wherein said image band canceller (i) applies time varying rotations to each received baseband signal to create rotated input signals;

(ii) obtains a complex conjugate of said rotated input signals;

(iii) applies digital filters to said complex conjugate of said rotated input signals;

combines outputs of said digital filters to create rotated output signals; and

(iv) derotates said rotated output signals.

31. The system of claim 29, wherein said image band canceller is at a receiver.

32. The system of claim 29, wherein said image band canceller is at a transmitter.