Patent ID: 9614660
Date: 2017-04-04
CPC Classifications: H04L

Claim:
1. A method comprising: modulating a plurality of synchronization signals (sync symbols) by a probe sequence (PS) to generate a plurality of modulated synchronization signals for a plurality of subscriber lines, wherein the PS comprises one or more zero element (0-element) columns that indicate a start or an end of the PS, and wherein a zero element (0-element) column is used to simultaneously modulate the plurality of synchronization signals by a zero element (0-element) for each corresponding subscriber line to indicate the start or the end of the modulated synchronization signal; and concurrently transmitting, using one or more transmitters, the plurality of modulated synchronization signals over the plurality of subscriber lines over a duration of a number of discrete multi-tone (DMT) symbols, wherein each of the plurality of modulated synchronization signals is intended for one of a plurality of receivers that are remotely coupled to the one or more transmitters via a vectored group of subscriber lines, and wherein the one or more 0-element columns cause all of the plurality of modulated synchronization signals to have a zero-amplitude during one or more corresponding DMT symbols, wherein the one or more 0-element columns are first columns or last columns of the PS, wherein the first columns containing only 0-elements indicate the start of the PS, wherein the last columns containing only 0-elements indicate the end of the PS, wherein the PS contains no 0-element in any other column except the first columns or the last columns, wherein the one or more 0-element columns comprise 0-elements, wherein the PS further comprises plus one (+1) elements and minus one (−1) elements located in other columns except the 0-element columns, wherein during the modulation of the sync symbols, each DMT symbol is multiplied by one of the +1 elements, the −1 elements' and the 0-elements that corresponds to the DMT symbol wherein either multiplication by the +1 element leaves the DMT symbol intact and multiplication by the −1 element reverses a phase of the DMT symbol during the modulation, or multiplication by the −1 element leaves the DMT symbol intact and multiplication by the +1 element reverses a phase of the DMT symbol during the modulation, and wherein multiplication by the 0-element, renders the DMT symbol to have the zero-amplitude.