Implementation of Fft Algorithm Using Floating Point Numbers in Wimax Communication System

Mobile WiMAX (Worldwide Interoperability for Microwave Access) or 802.16e standard was ratified by the IEEE in late 2005 as a potential to emerge as a real viable competitor to existing 3G technologies. Mobile WiMAX uses an OFDMATM technology called 1K-FFT. Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user version of the popular Orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. In the widely used OFDM systems, the FFT and IFFT pairs are used to modulate and demodulate the data constellation on the subcarriers. This paper presents a high level implementation of a high performance FFT for OFDM Modulator and Demodulator. The design has been coded in Verilog and targeted into Xilinx vertex4 FPGAs. Radix-2^2 Algorithm is proposed and used for the OFDM communication system. This algorithm has the same multiplicative complexity as the radix-2^2 algorithm, but retains the butterfly structure of radix-2 algorithm. Increase in number of butterflies makes the system to work in efficiency mode and also computation of twiddle factors is very easy and it is implemented by using floating point multiplier. It reduces time complexity and increases computation speed. Here we implemented for 32 bit data length using number of desired clock cycles N/2 and required number of butterflies structures. Keywords—WIMAX, FFT,IFFT,FPGA,OFDMA,RADIX 2^2FFT, VERILOG HDL.