Patent ID: 7149243

Claim:
A method for establishing a data transfer link between an xDSL user modem and a xDSL modem within a central office wherein the xDSL modem within the central office comprises: demodulating means for demodulating a received analog pulse length modulated signal; storing means for a wake-up bit pattern which identifies the xDSL user modem; comparing means for comparing the demodulated received signal with the stored wake-up bit pattern; and wake-up command generating means for generating a wake-up command to switch the xDSL modem within the central office from a sleep mode to an operation mode, when the demodulated received signal is identical with the stored wake-up bit pattern; wherein the demodulating means of the xDSL modem within the central office comprises a gain sequencer for amplifying the received analog signal with an adjustable gain; rectifying means for rectifying the amplified signal; a low-pass filter for filtering the rectified signal; and a comparator for comparing the filtered signal with an adjustable threshold generating an asynchronous pulse train which is supplied to the comparing means within the central office comprising the following steps: (a) generating a wake-up bit pattern identifying the user xDSL modem; (b) pulse length modulating an upstream data signal with the generated wake-up bit pattern to generate a pulse length modulated wake-up signal; (c) transmitting the pulse length modulated wake-up signal from the user xDSL modem via a data transfer medium to the xDSL modem within the central office; wherein the xDSL modem within the central office performs the following steps (d) demodulating the transmitted wake-up signal; (e) comparing the demodulated wake-up signal with a stored wake-up bit pattern for the detection of a transmission of the wake-up bit pattern from the xDSL user modem; (f) generating a wake-up command signal, when the wake-up bit pattern is detected for switching the xDSL modem within the central office from the sleep mode to the operation mode for data transfer.