TIME-RECURSIVE PARALLEL IIR FILTER STRUCTURES FOR THE IFFT/FFT IN DMT TRANSCEIVER SYSTEMS

Discrete multitone (DMT) is a line code which has been adopted as a standard for the asymmetric digital subscriber line (ADSL) systems by the American National Standards Institute (ANSI). The DMT uses the IFFT and FFT for modulation and demodulation, respectively. The large size of the IFFT/FFT results in a heavy computational load on the programmable DSP processors. It also proves that a costefficient hardware implementation of radix-2 IFFT/FFT butterfly structure is not feasible, since it requires a large number of multipliers and adders. For cost-efficient hardware implementation, we have proposed two schemes to develop the IFFT/FFT architecture based on the time-recursive approach. In fact, these methods require approximately a maximum of only 12.5% of the multipliers and 15.6% of the adders when compared to the conventional butterfly type of implementation.