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Wireless Communications and Mobile Computing
Volume 2017, Article ID 1860134, 9 pages
Research Article

Suppression of Mutual Interference in Noncontiguous Orthogonal Frequency Division Multiplexing Based Cognitive Radio Systems

1Department of Electrical Engineering, Faculty of Engineering and Technology, International Islamic University, Islamabad, Pakistan
2Department of Electrical Engineering, Air University, Islamabad, Pakistan
3Department of Electrical Engineering, COMSATS Institute of Information Technology, Attock Campus, Attock, Pakistan

Correspondence should be addressed to Atif Elahi; kp.ude.uii@04eedhp.fita

Received 26 June 2016; Revised 9 November 2016; Accepted 16 November 2016; Published 16 January 2017

Academic Editor: Rafael Pérez-Jiménez

Copyright © 2017 Atif Elahi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Orthogonal frequency division multiplexing (OFDM) is a favourable technology for dynamic spectrum access (DSA) due to the flexibility in spectrum shaping. In spite of that, high sidelobes of OFDM subcarriers bring in considerable interference to the nearby users, particularly in OFDM based cognitive radio (CR) networks, where the secondary users (SUs) are capable of accessing the spectrum opportunistically. In this paper, two new techniques for the suppression of high sidelobes are proposed. The proposed techniques composed of an optimization scheme are followed by generalized sidelobe canceller. The proposed techniques can be considered as a two-level suppression technique in the sense that in the first level the sidelobe is reduced by using cancellation carriers (CCs), whose amplitudes are determined using genetic algorithm (GA) and differential evolution (DE), while in the second level further reduction of sidelobe is achieved using generalized sidelobe canceller (GSC). Simulation results show the power spectral density (PSD) performance of the proposed techniques in comparison with already existing techniques, demonstrating that the proposed techniques minimize the out-of-band radiation (OOBR) significantly, thus qualifying for more effective spectrum sharing.