of length i equal to the length of the cyclic prefix the response energy output of filtering is monitored against a preset threshold value to adaptively position the window application_number US 99749197 A description general and additional details concerning digital subscriber loop modem telecommunications are given in copending patent application ser no 08 667 267 filed jun 20 1996 entitled u201c multi mode digital modem u201d the entirety of which is hereby incorporated by reference if the channel response is assumed to be given by h and the equalizer by w then the overall response will be given by b h w the objective is to make this effective channel overall response of length equal to the length of the cyclic prefix i sent as an overhead on each dmt frame in other words since achieving this exactly would probably be impractical computationally u2014 or even theoretically impossible u2014 with a finite length equalizer what is wanted is to have a window with size i with most of the energy of b inside this window or to decrease any energy outside that window now from the training sequence a pretty good estimate of h can be obtained this can then be convolved with the equalizer to get an estimate of b therefore if it can be known beforehand where the best place is to position the maximum energy window over the overall length.