Low complexity frequency domain equalizer having fast re-lock

• US 6,603,811 B1
• Filed: 05/29/1998
• Issued: 08/05/2003
• Est. Priority Date: 05/29/1998
• 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, Christiansen, Mark W.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Fan, Chieh M.
• Application Number:
  US09/087,835
• Time in Patent Office: 1,894 Days
• Field of Search: 375/229-236, 375/260, 370/480, 333/18, 333/28.R, 708/300, 708/322, 708/323, 708/400, 708/403, 708/404, 708/405
• US Class Current: 375/232
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03522 Frequency domain
• CPC Class Codes: H04L 2025/03668 to the value at the end of a previous adaptation period
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence

Abstract

A low-complexity frequency domain equalizer having fast re-lock capabilities for use in a DMT transceiver. The transceiver includes a modulator that utilizes DMT modulation methods for communication over the transmission medium, a demodulator for receiving DMT signals, and a channel equalizer that operates in the frequency domain. The equalizer models the channel characteristic as an FIR filter that distorts the signal transmitted over the channel. The channel distortion is removed at the receiver by performing a de-convolution of the channel response via a frequency domain multiplication. After a period of inactivity of the receiver, the equalizer taps are updated by the use of a fast re-lock method so that the previously trained equalizer may be utilized. An undetermined sampling time offset is determined and is used to update the equalizer coefficients such that a full retraining of the equalizer is not required.

Claims

1. A frequency domain equalization re-lock method for use in a DMT transceiver, where the equalizer has been previously trained to the channel, comprising the steps:

receiving a predetermined multi-carrier signal that includes channel distortion;

converting the received signal to the frequency domain;

equalizing the converted signal using the previously trained frequency domain equalizer;

comparing the equalized signal to a local copy of the frequency domain representation of the predetermined signal; and

updating the equalizer in response to the comparison

wherein the step of comparing the equalized signal to a local copy of the frequency domain representation of the predetermined signal includes forming the ratio of the equalized symbols to the known symbols on a bin-by-bin basis, and

wherein the step of updating the equalizer in response to the comparison including multiplying the taps of the previously trained equalizer by the ratio.

2. A frequency domain equalization re-lock method for use in a DMT transceiver, where the equalizer has been previously trained to the channel, comprising the steps:

receiving a predetermined multi-carrier signal that includes channel distortion;

converting the received signal to the frequency domain;

equalizing the converted signal using the previously trained frequency domain equalizer;

comparing the equalized signal to a local copy of the frequency domain representation of the predetermined signal;

updating the equalizer in response to the comparison; and

determining an average elemental phase rotation,

wherein the step of comparing the equalized signal to a local copy of the frequency domain representation of the predetermined signal includes forming the ratio of the equalized symbols to the known symbols on a bin-by-bin basis.

3. The frequency domain equalization re-lock method of claim 2, wherein the step of updating the equalizer in response to the comparison includes multiplying the taps of the previously trained equalizer by linear multiples of the elemental phase rotation.