US 6,219,378 B1 · Digital subscriber line modem initialization

Abstract

A method of initializing the operation of a remote modem (10) and central office modem (20k) for asymmetric subscriber line modem communications over a twisted pair wire facility (TWP), using discrete multi-tone technology, is disclosed. The initialization process begins with the remote modem (10) issuing an initialization request, in response to which the central office modem (20k) issues an acknowledgment. The remote modem (10) includes a low-cost analog filter (21) for separating upstream communication echoes from downstream data. This analog filter (21) increases the duration of impulse response over the channel, and thus requires time-domain equalization (TEQ) process (31) performed by the remote modem (10) to filter relatively long circular prefixes, so that intersymbol interference is eliminated. Transceiver training processes (62R, 62C) are carried out, through the generation of a pseudo-random sequence of frames by the central office modem (20k), the receipt of which is used by the remote modem (10) to establish its TEQ coefficients and taps in an optimal manner.

Claims18

Dependent claims

A method of initializing modem communications between first and second modems over a communications facility, comprising the steps of:

operating the first modem to issue an activation signal to the second modem over the communications facility;
operating the second modem to issue an acknowledgment signal to the first modem over the communications facility;
operating the second modem to issue a time-domain equalizer training signal to the first modem over the communications facility, the time-domain equalizer training signal comprising a repeating sequence of pseudo-random blocks of data;
and
operating the first modem to set a plurality of time-domain equalizer tap values responsive to the received pseudo-random blocks of data in the time-domain equalizer training signal by, for each of the plurality of time-domain equalizer tap values:
generating a difference signal between a current pseudo-random block of data and a previously received pseudo-random block of data;
generating a current error value from a combination of the difference signal, a current value of the time-domain equalizer tap value, and a previous error value;
updating the time-domain equalizer tap value using the current error value;
and
repeating the generating and updating steps until the current error value falls below a convergence threshold.

7 more elements

A method of initializing a remote modem comprising a digital signal processor (DSP) to communicate with a central office modem over a communications facility, comprising the steps of:

issuing an activation signal to the central office modem over the communications facility;
receiving a time-domain equalizer training signal from the central office modem over the communications facility, the time-domain equalizer training signal comprising a repeating sequence of pseudo-random blocks of data;
and
operating the DSP according to an iterative convergence process and setting a plurality of time-domain equalizer tap values responsive to the received pseudo-random blocks of data in the time-domain equalizer training signal by, for:
each of the plurality of time-domain equalizer tap values:
generating a difference signal between a current pseudo-random block of data and a previously received pseudo-random block of data;
generating a current error value from a combination of the difference signal, a current value of the time-domain equalizer tap value, and a previous error value;
updating the time-domain equalizer tap value using the current error value;
and
repeating the generating and updating steps until the current error value falls below a convergence threshold.

7 more elements

A modem for communicating over a communications facility, comprising:

a host interface for coupling the modem to a host computer;
an analog interface for coupling the modem to the communications facility, the analog interface including an analog bandpass filter;
and
data processing circuitry, coupled to the host interface and to the analog interface, and programmed to perform the operations of:
issuing an activation signal over the communications facility;
receiving a time-domain equalizer training signal over the communications facility, the time-domain equalizer training signal comprising a repeating sequence of pseudo-random blocks of data;
and
setting a plurality of time-domain equalizer tap values responsive to the received pseudo-random blocks of data in the time-domain equalizer training signal by executing a sequence of steps comprising, for each of the plurality of time-domain equalizer tap values:
generating a difference signal between a current pseudo-random block of data and a previously received pseudo-random block of data;
generating a current error value from a combination of the difference signal, a current value of the time-domain equalizer tap value, and a previous error value;
updating the time-domain equalizer tap value using the current error value;
and
repeating the generating and updating steps until the current error value falls below a convergence threshold.

10 more elements

Dependencies are inferred from the claim text.

Digital subscriber line modem initialization

Life of this patent

Digital subscriber line modem initialization

Life of this patent

Abstract

Claims18