Comparison of FFT Approaches for Wireless OFDM Communication Systems

The FFT plays an important role in the modulation and demodulation of wireless OFDM systems. OFDM is a digital multi-carrier modulation method used for wide-band communications due its efficient computation of FFT components. The key techniques of FFT implementation based on FPGA should be analyzed in order to meet the requirements of FFT for OFDM systems. Recently, there is a need for longer length, high-speed and low power FFT processor for OFDM wireless applications. Various types of design architectures are available for implementing a FFT processor. But an efficient FFT algorithm is required to minimize the hardware complexity in order to implement the FFT architectures for wideband OFDM wireless applications. This paper compares the various types of FFT algorithms such as Radix 2, Radix 4, Split-radix, Pipeline FFT and Mixed radix with their hardware requirements for implementation. The design has been coded in Verilog and targeted into Xilinx Spartan3 FPGA‟s. The design has been parameterized in terms of complex multipliers, complex-adders, memory size and CLB slices. Finally the paper concludes that a compromise should be made between the block multipliers and CLB slices for selecting the appropriate FFT algorithm for implementation with reduced hardware complexity.