A Modified Fast FFT Algorithm for OFDM Based Future Wireless Communication System
Niladri Mandal1, Souragni Ghosh2 

1Niladri Mandal, Department of Electronics and Communication Engineering,West Bengal University of Technology, Kolkata, India.
2Souragni Ghosh, Department of Electronics and Communication Engineering, West Bengal University of Technology, Kolkata, India.
Manuscript received on December 05, 2011. | Revised Manuscript received on December 17, 2011. | Manuscript published on January 05, 2012. | PP: 179-184 | Volume-1 Issue-6, January 2012. | Retrieval Number: F0293111611/2012©BEIESP
Open Access | Ethics and Policies | Cite
© The Authors. Published By: Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Abstract: The limited available spectrum and the inefficiency in the spectrum usage in a fixed spectrum assignment policy, demands a new communication prototype to exploit the existing wireless spectrum opportunistically. This new networking paradigm is referred to as next generation networks as well as Dynamic Spectrum Access (DSA) and cognitive radio networks. The Fast Fourier Transform (FFT) and its inverse (IFFT) are very important algorithms in signal processing, software-defined radio, and the most promising modulation technique i.e. Orthogonal Frequency Division Multiplexing (OFDM). From the standard structure of OFDM we can find that IFFT/FFT modules play the vital role for any OFDM based transceiver. So when zero valued inputs/outputs outnumber nonzero inputs/outputs, then general IFFT/FFT algorithm for OFDM is no longer efficient in term of execution time. It is possible to reduce the execution time by “pruning” the FFT. In this paper we have implemented a novel and efficient input zero traced FFT pruning (IZTFFTP) algorithm based on DIF radix-2 technique. Compare to other algorithms, the results of IZFFTP shows that it is independent of the position of the zero valued input and also maintaining a good trade-off between time and space complexity of any system by not only reducing the number of complex multiplication as well as complex additions also. The proposed algorithm is implemented in high level computer program i.e. in C++and this is similar to the Cooley-Tukey radix-2 FFT algorithm, retaining all the key features such as simplicity and regularity, by making some alternation and programming modification.
Keywords: Cognitive radio, OFDM, FFT, Pruning Techniques, Execution time.