A Novel Multiple Antennas Based Centralized Spectrum Sensing Technique

Abstract

In wireless communication, sensing failure, reliability, and fading affects the radio signals. Adaptive threshold and multiple antennas are one of the solutions of such problems. In this paper, authors introduced a novel multiple antennas based centralized spectrum sensing (SS) technique for cognitive radio networks (CRNs). This paper is divided into two parts: part A uses multiple antennas based improved sensing detector (MA_ISD), and part B uses multiple antennas based centralized spectrum sensing (MA_CSS) technique. Now, in the part A: the presented scheme uses two detectors (TD) concept, first one is an energy detector with a single adaptive threshold (ED-SAT) and the second one is an energy detector with two adaptive thresholds (ED-TAT). Both detectors imply multiple antennas, following selection combination to select best signals. The proposed model enhances the detection performance and takes less sensing or detection time. The thresholds are adaptive as they are dependent on noise variance ($\sigma_{\omega }^{2}$), and the value of this noise variance changes according to the noise signal. Both the detectors work simultaneously and their output is then fed to a decision device which takes the decision using an OR rule. Results confirm that the presented multiple antennas based improved sensing detector (MA_ISD) technique improves the detection performance by 24.6%, 53.4%, 37.9%, and 49.6%, as compared to existing schemes (i.e. EDT-ASS-2015 scheme, ED and cyclo-2010, adaptive SS-2012, and conventional-ED) scheme at −12 dB signal-to-noise ratio (SNR), respectively, while the number of antennas (N _r ) = 2. Meanwhile, proposed technique also decreases sensing time in the order of 47.0 ms, 49.0 ms, and 53.2 ms as compared to existing schemes (EDT-ASS-2015, Adaptive SS-2012, and ED and Cyclo-2010) scheme at −20 dB SNR respectively. Further, in the part B: cooperative SS (CSS) is introduced in which the local decisions from each cognitive radio are transferred to a fusion center (FC) that decides the final decision and shares the decision to every cognitive radio. It is also found that the proposed detection technique with CSS when a number of cognitive radio (CR) users (k) = 10, and N _r  = 2, achieves detection performance as per IEEE 802.22 at very low SNR i.e. −20 dB.