Effect of Primary User Traffic on Largest Eigenvalue Based Spectrum Sensing Technique
In this paper, the effect of primary user (PU) traffic on the performance of largest eigenvalue based spectrum sensing technique (Roy’s Largest Root Test (RLRT)) is investigated. A simple and realistic discrete time modeling of PU traffic is considered wh
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itecnico di Torino, Turin, Italy {pawan.dhakal,daniel.riviello}@polito.it 2 University of Luxembourg, SnT, Kirchberg, Luxembourg {shree.sharma,symeon.chatzinotas,bjorn.ottersten}@uni.lu
Abstract. In this paper, the effect of primary user (PU) traffic on the performance of largest eigenvalue based spectrum sensing technique (Roy’s Largest Root Test (RLRT)) is investigated. A simple and realistic discrete time modeling of PU traffic is considered which is only based on the discrete time distribution of PU free and busy periods. Furthermore, in order to analyze the effect of PU traffic on the detection performance, analytical expressions for the probability density functions of the decision statistic are derived and validated by Monte-Carlo simulations. Numerical results demonstrate that the sensing performance of RLRT is no more monotonically increasing with the length of the sensing duration and also with SNR which contrasts with the common property of the spectrum sensing techniques under known PU traffic scenario. Furthermore, it is shown that the performance gain due to the multiple antennas in the sensing unit is significantly suppressed by the effect of the PU traffic when the frequency of the PU traffic transitions is higher. Keywords: Eigenvalue based detection sensing · RLRT · Primary user traffic
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Cognitive radio
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Spectrum
Introduction
By accessing the idle spectrum band of Primary User (PU) network (licensed user), Cognitive Radio (CR) based dynamic spectrum sharing is initially intended to alleviate one of the most challenging problems of future wireless communications, namely, spectrum scarcity. With the real-time perception of surroundings and bandwidth availability using spectrum sensing functionality of a CR, secondary users (unlicensed users) may dynamically use the vacant spectrum and perform opportunistic transmissions [1]. Thus, the domain of spectrum sensing techniques has long been investigated by many researchers: a detailed bibliography of the contributions in this area can be found in [2,3]. Despite the significant volume of available literature on spectrum sensing under ideal scenarios, investigation under practical constraints and imperfections are still lacking [3]. Thus, recent research efforts are devoted to improve the accuracy and efficiency of sensing techniques under practical constraints and imperfections. c ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2016 D. Noguet et al. (Eds.): CROWNCOM 2016, LNICST 172, pp. 67–78, 2016. DOI: 10.1007/978-3-319-40352-6 6
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Among many practical imperfections and constraints for spectrum sensing in CR scenarios mentioned in the literature, the unknown PU traffic is one of the important constraints which significantly limits the sensing performance of the secondary user. In the existing literature on spectrum sensing, the SUs are assumed to have a perfect knowledge of the exact time slot structure of PU transmissions providing a solid basis for guaranteeing that PU traffic transitions occur only
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