Implementation of split-radix FFT pruning for the reduction of computational complexity in OFDM based cognitive radio system

Abstract

It is necessary to devise the efficient IFFT/FFT algorithm which can reduce computational complexity due to multiplication in the butterfly structure with twiddle factors in the OFDM based Cognitive Radio, where zero valued inputs/outputs outnumber nonzero inputs/outputs. Transformed Decomposition is considered as more suitable candidate than FFT pruning method for OFDM based Cognitive Radio due to the feasibility of HW design about irregular position of zero inputs/outputs in spite of more computation complexity than normal FFT pruning. However, with the introduction of the efficient control circuit for the pruning matrix which selects the multiplication branch with regular design corresponding to nonzero outputs in OFDM based cognitive radio, the split-radix FFT pruning algorithm can be proposed for getting more reduction of computational complexity. Through analyzing and comparing the computation complexity of the split-radix FFT pruning algorithm with other algorithms, it is shown that the proposed method is more efficient than other conventional algorithms. Based on the above mentioned design idea, the ASIC chip with 64-point split-radix FFT pruning was implemented using Samsung STD150E library.