Multi-carrier LAN adapter device using frequency domain equalizer

• US 6,507,585 B1
• Filed: 05/27/1998
• Issued: 01/14/2003
• Est. Priority Date: 05/27/1998
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Dobson, William Kurt
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): Pizarro, Ricardo M.
• Application Number:
  US09/085,653
• Time in Patent Office: 1,693 Days
• Field of Search: 370/401, 370/419, 370/421, 370/290, 370/307, 370/478, 370/352, 370/208, 370/203, 370/206, 370/210, 370/497, 370/494, 375/222, 375/223, 375/260, 375/219, 375/229, 375/231, 375/235, 375/269, 375/272, 375/316, 375/322
• US Class Current: 370/420
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03522 Frequency domain
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence

Abstract

A LAN Adapter device having a frequency domain equalizer. The LAN adapter device allows LAN computing devices to connect to the LAN medium. The adapter devices are internal or external to the LAN devices and provide a transceiver and protocol stacks for the LAN devices to communicate with each other. The physical layer of the transceivers includes transmitter having a DMT modulator and demodulator that is dynamically configurable with respect to data rate and spectrum usage. Within the receiver is an equalizer for equalizing the received signal with a simple yet effective equalizer training method, thereby obviating the need for extensive equalizer training and long-term coefficient storage. The equalizer trains on known symbols transmitted in one frame of a transmitted packet to determine an estimate of the channel response. The remaining frames that are modulated with data are equalized based on an estimate of the channel response determined from interpolating between the points previously determined from the known symbols.

Claims

1. A system for interconnecting a plurality of devices comprising:

a shared communication medium; and

a plurality of adapter devices having a first and second port, said first port for connection to one of the plurality of devices and said second port for connection to said shared communication medium, and each of said plurality of adapter devices having a multi-carrier transceiver for transmitting and receiving data on a plurality of predetermined carriers over said shared communication medium to at least one of said adapter devices;

wherein said multi-carrier transceiver further includes a signal transformer for generating a frequency domain signal from a received time domain signal, and a frequency domain equalizer for operating on said frequency domain signal, said equalizer comprising a single tap filter for each carrier of a multi-carrier signal received by said multi-carrier transceiver.

2. The system of claim 1 wherein said shared communication medium is standard POTS wiring.

3. The system of claim 1 wherein said first port is selected from the group consisting of internal parallel bus port, external parallel port, and external serial port.

4. The system of claim 1 wherein said transceiver transmits data in packet format, each said packet comprising a plurality of frames, at least one of said frames being an equalization frame consisting of predetermined equalization symbols, and said frequency domain equalizer is trained using said equalization frame.

5. The system of claim 4 wherein said equalization frame is the first frame of said packet.

6. The system of claim 4 wherein said frequency domain equalizer is updated by using decision feedback.

7. The system of claim 1 wherein said multi-carrier transceiver selectively transmits on less than all of said plurality of predetermined carriers.

8. A network adapter device for connecting a computing device to a shared electrical signaling medium comprising:

a first physical interface for connection to a computing device;

a second physical interface for connection to a shared electrical signaling medium; and

a transceiver connected to said first and second physical interfaces for transmitting and receiving data on said first interface and transmitting and receiving modulated multi-carrier data bursts over said second interface, wherein each said burst comprises a plurality of frames, said transceiver including a signal transformer for converting received time domain signals to frequency domain signals, and a frequency domain equalizer connected to said signal transformer for processing said frequency domain signals, said equalizer comprising a single tap filter for each carrier of said modulated multi-carrier data burst received by said transceiver.

9. The network adapter device of claim 8 wherein said first physical interface is a standard computer internal bus interface.

10. The network adapter device of claim 8 wherein said first physical interface is a standard external bus interface.

11. The network adapter device of claim 8 wherein said equalizer includes a decision feedback loop for updating said equalizer.

12. The network adapter device of claim 8 wherein said signal transformer performs a discrete Fourier transform.

13. The network adapter device of claim 8 wherein said transceiver operates in a frequency range above the frequency range of POTS services.

14. The network adapter device of claim 8 wherein said multi-carrier transceiver utilizes a plurality of predetermined carriers and selectively transmits on less than all of said plurality of predetermined carriers.

15. A method of transferring data among a plurality of computing devices connected to a shared communication medium comprising the steps of:

receiving data from a computing device;

mapping the data to a plurality of sets of signal points where each signal point is assigned a carrier frequency;

transforming each signal point set to a time domain signal;

transmitting the time domain signals to a plurality of computing devices over a shared communication medium;

receiving time domain signals from at least one of said plurality of computing devices;

converting said time domain signals to frequency domain signals; and

filtering said frequency domain signals using a frequency domain equalizer.

16. The method of claim 15 where the step of transforming includes performing a frequency domain to time domain transform.

17. The method of claim 15 further comprising the step of inserting at least one set of known symbols into the data stream.

18. The method of claim 17 further comprising the step of training the equalizer using the set of known symbols inserted into the data stream.

19. The method of claim 15 wherein the shared communication medium is standard POTS wiring.

20. The method of claim 15 further comprising the step of updating the frequency domain equalizer using decision feedback.