Research Article One-to-Many Relationship Based Kullback Leibler Divergence against Malicious Users in Cooperative Spectrum Sensing Noor Gul , 1,2 Ijaz Mansoor Qureshi, 3 Sadiq Akbar, 2 Muhammad Kamran, 2 and Imtiaz Rasool 2 1 Department of Electrical Engineering, Faculty of Engineering and Technology, International Islamic University, Islamabad 44000, Pakistan 2 Department of Electronics, University of Peshawar, Peshawar 25000, Pakistan 3 Department of Electrical Engineering, Air University, Islamabad 44000, Pakistan Correspondence should be addressed to Noor Gul; noor.phdee51@iiu.edu.pk Received 21 April 2018; Revised 2 August 2018; Accepted 11 August 2018; Published 2 September 2018 Academic Editor: Sungchang Lee Copyright © 2018 Noor Gul et al. Tis 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. Te centralized cooperative spectrum sensing (CSS) allows unlicensed users to share their local sensing observations with the fusion center (FC) for sensing the licensed user spectrum. Although collaboration leads to better sensing, malicious user (MU) participation in CSS results in performance degradation. Te proposed technique is based on Kullback Leibler Divergence (KLD) algorithm for mitigating the MUs attack in CSS. Te secondary users (SUs) inform FC about the primary user (PU) spectrum availability by sending received energy statistics. Unlike the previous KLD algorithm where the individual SU sensing information is utilized for measuring the KLD, in this work MUs are identifed and separated based on the individual SU decision and the average sensing statistics received from all other users. Te proposed KLD assigns lower weights to the sensing information of MUs, while the normal SUs information receives higher weights. Te proposed method has been tested in the presence of always yes, always no, opposite, and random opposite MUs. Simulations confrm that the proposed KLD scheme has surpassed the existing sof combination schemes in estimating the PU activity. 1. Introduction Te rapid evolution in wireless communication demands new wireless services in both the used and unused parts of the radio spectrum [1]. Te Federal Communications Commis- sion (FCC) exclusively assigns spectrum bands to various services [2, 3]. Cognitive radio (CR) is a smart technique that gains knowledge from the environment and adjusts its parameters accordingly [4]. Te incumbent primary users (PUs) are free to transmit any time with no restrictions, while the secondary users (SUs) can get the beneft of the spectrum only when the licensee declares it free [5]. In cognitive radio network (CRN), sensing the incumbent user spectrum is vital. An ofensive detection on the PU channel due to false alarm reduces the SUs opportunity to utilize the free spectrum. Similarly, any misdetection in the PU transmission will produce interference in the transmis- sion of legitimate and opportunistic users. In case of the frequent usage of the spectrum by the PUs, the termination probability of SUs is not easy to ensure. Te proposed scheme in [6] uses channel reservation to improve the quality of service (QoS) for SUs. To confrm the status of the PU a number of detection schemes, such as energy detector (ED), feature detector (FD), and matched flter detector (MFD), are used in [3, 7]. Te use of multiple antennas for spectrum sensing is considered in [8], when noise and signal of the PU are considered as independent complex zero- mean Gaussian random variables. Detection results of the orthogonal frequency division multiplexing (OFDM) signals in the frequency selective fading channels are considered in [9, 10]. Optimal interference subcarriers are obtained based on Genetic Algorithm (GA) to suppress intercarrier interference of the unlicensed user to the licensee [11]. In [12], side-lobes reduction using generalized side-lobe canceller combined with GA and diferential evolution is proposed. Te GA and interior point method design schemes enhance Hindawi Wireless Communications and Mobile Computing Volume 2018, Article ID 3153915, 14 pages https://doi.org/10.1155/2018/3153915