Patent ID: 6741551
Filing Date: 2004-05-25
Classification: H04L

Abstract:
A digital transmission scheme for use in a multiple access communications network system with a system comprising an upstream channel with a bandwidth of 1/Tc Hz for transmission of information from remote stations to a head-end node, where a baseband signal is transmitted as passband signal employing a modulator, said baseband signal being generated by employing M subcarriers for transmission over M subchannels of blocks of M symbols, each taken from a symbol constellation, wherethe transmission over the i-th subchannel, with i=0, . . . , Mâˆ’1, takes place at a modulation rate of 1/(mi Tc) symbols/s, the i-th subchannel has a bandwidth of 1/(mi Tc) Hz, where the numbers mi satisfy the condition &Sum;i=0M-1&it;1mi=1at least one subchannel has spectral nulls at the bandedges, and at least one subchannel has zero guard bands.