Efficient Sidelobe Reduction for OFDM Based Cognitive Radio Systems

This paper presents a problem of high out-of-band radiation problem in orthogonal frequency division multiplexing (OFDM) based cognitive radio system that results from the high sidelobes of the transmitted signal of OFDM. Reduction of these high out-of-band radiation in OFDM based cognitive radio systems allow a high spectral efficiency and a successful coexistence of licensed and un-licensed users in a spectrum sharing scenario. To reduce the high sidelobes of the transmitted OFDM signal, we propose an Eigenspace based generalized sidelobe canceler (ESGSC) technique. For finding the weight vector of our proposed ESGSC, the weight vector of a simple generalized sidelobe canceler (GSC) is projected onto a vector subspace that is constructed from the eigenstructure of the correlation matrix. Using this new weight vector instead of the simple GSC, leads to the better reduction of high sidelobes of the transmitted OFDM signal as compared to the simple GSC and existing techniques found in the literature.