FFT and FIR Filter implementations for the DSL
MODEMS

Abstract

Broad band digital communication that operates over a standard copper wires. It requires
the DSL modems which splits the transmissions into 2 frequency bands. The lower frequencies for
voice and the higher frequencies for digital data (internet) in order to transmit the data to larger
distances through a copper cable we need modulation techniques. Generally in this DSL modems
modulation used is QAM technique. The output of the QAM is complex data this complex data we
cannot transfer directly through a copper cable because the data should be in time domain or
otherwise the phase of the data which is in frequency domain can be lost, in copper cable so this
data should be converted in time domain by using IDFT technique. As IDFT requires more
number of complex multiplications and more number of complex additions in comparison to IFFT
so to reduce the additions and multiplications IFFT technique is used. At the receiver side we can
retrieve the same data by using FFT technique. In this section the implemented FFT architecture is
fully efficient and this architecture will require less area. And before we have to transmit through
the copper line we have to do interpolation or decimation by using the Filtering operation. The
implemented poly phase architecture for the filtering is fully efficient, symmetrical and it requires
less number of multipliers.