Abstract: The advancements in VLSI technologies for Digital signal processing have opened many windows in past few years for designing real time applications, using efficient algorithms with custom chips. Multicarrier modulation techniques (OFDM) are rapidly moving in modern communication systems. Mobile WIMAX (Worldwide Interoperability for Microwave Access) or 802.16e standards uses this OFDM Technology. The FFT and IFFT pairs are most important blocks used to modulate and demodulate the data constellation on the subcarriers in the OFDM (Orthogonal Frequency-Division Multiple Access) system. In this paper we presented high level implementation of a FFT /IFFT to increase the speed and performance of OFDM Modulator and Demodulator. This paper presents the 256-point Radix-4 FFT algorithm. The design has been coded in VHDL and simulated in MODELSIM, targeted into Xilinx Spartan3 FPGAs.