Fast Hybrid DFT/DCT Architecture for OFDM in Cognitive Radio System

In this paper, the sparse matrix decompositions for DFT matrix and DCT matrix are proposed. Based on these propositions, we develop a fast hybrid DFT and DCT architecture for OFDM. In addition, we address the OFDM based on DFT or DCT in Cognitive Radio system. An adaptive OFDM based on DFT or DCT in Cognitive Radio system has the capacity to nullify individual carriers to avoid interference to the licensed users. Therefore, there could be a considerably large number of zero-valued inputs/outputs for the IDFT/DFT or IDCT/DCT on the OFDM transceiver. Hence, the standard methods of DFT and DCT are no longer efficient due to the wasted operations on zero. Based on this observation, we present a transform decomposition on two dimensional (2-D) systolic array for IDFT/DFT and IDCT/DCT, this algorithm can achieve an efficient computation for OFDM in Cognitive Radio system.