Patent ID: 6819719
Filing Date: 2004-11-16
Classification: H04L,H04M,Y02D

Abstract:
A method to transfer data from a digital data modulator device to a digital data demodulator device over a digital subscriber line, said method comprising:in said modulator device, the steps of modulating incoming groups of data bits into data symbols according to the trellis code modulation technique, and of mapping said data symbols on carriers associated to constellation points of a constellation scheme, and in said demodulator device, the steps of de-mapping received carriers into data symbols, and of de-modulating said data symbols into groups of data bits according to the trellis code de-modulation technique, wherein said method further comprises: in said modulator device, the step of detecting incoming idle data, and if idle data is detected, the step of generating null data cells derived from said idle data, and, after said steps of modulating and of mapping, the step of shifting constellation points corresponding to said null data cells towards constellation points having a low power, and in said demodulator device, the step of detecting received null data, and if null data is detected, the step of de-shifting constellation points having low power towards constellation points corresponding to null data cells, prior to said steps of de-mapping and of de-modulating.