Abstract
Cognitive radio (CR) is a regulated technique for opportunistic access of idle resources. In CR, spectrum sensing is one of the key functionalities. It is used to sense the unused spectrum in an opportunistic manner. In this paper, we have proposed two-stage detectors for spectrum sensing in cognitive radio networks (CRN). The first stage consists of multiple energy detectors (MED), where each energy detector (ED) is having single antenna with fixed threshold (MED_FT) for making a local binary decision, and if required, the second stage comprised of ED with adaptive double threshold (ED_ADT) is invoked. The detection performance of the proposed scheme is compared with cyclostationary-based sensing method and adaptive spectrum sensing scheme. Numerical results show that the proposed scheme improves detection performance and outperforms the cyclostationary-based sensing method and adaptive spectrum sensing by 12.3% and 14.4% at signal to noise ratio (SNR) setting of as low as −8 dB, respectively. Performance was also measured in terms of sensing time. It is shown that the proposed scheme yields smaller sensing time than cyclostationary detection and adaptive spectrum sensing scheme in the order of 4.3 ms and 0.1 ms at −20 dB SNR, respectively.
Highlights
In Cognitive radio (CR) systems, the unlicensed users can utilize the licensed frequencies while the primary user (PU) is not active
In the present system model, we have assumed total number of samples (N) as 1000, signal to noise ratio (SNR) range varies from −20 dB to 0 dB, probability of false alarm (Pf) = 0.1, number of energy detectors Nr = 2, and QPSK modulation is considered in Rayleigh fading channel
It is found that our scheme at Nr = 2 yields better results and the detection performance is improved by 12.3% and 14.4% as compared to cyclostationary based sensing method and adaptive spectrum sensing at −8 dB SNR, respectively
Summary
In CR systems, the unlicensed users can utilize the licensed frequencies while the primary user (PU) is not active. Further in [7], authors have proposed a “two-stage” spectrum sensing scheme to improve detection performance. This scheme consists of two detectors, energy detector in the first stage and cyclostationary detector in the second stage that provides better detection, but it is computationally more complex and needs longer sensing time. We focused on spectrum sensing failure problem and improved system detection performance. The second stage contains energy detector, with adaptive double threshold (ED ADT) scheme, and optimizes the detection performance at a fixed probability of false alarm (Pf), that is, 0.1, and overcomes sensing failure problem [9] as well.
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