Performance of Hard Decision Fusion based Cooperative and Clustered Spectrum Sensing with Multiple Transitions of Primary User under Static Channel Attenuation

In this paper, we present the case of multiple transitions of primary user in a real-time scenario. We assume static channel attenuation for a period of N symbols with additive impulsive Laplacian noise (AILN). Transitions of the PU from idle state to active state and vice-versa are modelled using transition probabilities (TrPs) which constitute Markov chain parameters such as ψ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> and ξ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf>. The K cognitive radios use improved absolute value cumulation detection (i-AVCD) scheme to obtain hard decisions in the forms of ‘0<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf>’ and ‘1<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf>’. The hard decisions are combined at the FC using CSS-OR rule. The TrPs modify the i-AVCD scheme which is referred to as ℳ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf>: i-AVCD. We derive closed-form expressions of the detection probability ${{\mathcal{Q}}_d}$ and false alarm probability ${{\mathcal{Q}}_f}$ at the fusion center (FC) using CSS-OR fusion scheme. We present the results using receiver operating characteristic and ${{\mathcal{Q}}_d}$ vs. average SNR (γ). We find that the CSS:OR fusion scheme outperforms conventional schemes. Further, we observe that the performance of modified schemes degrades with an increase in the value of M. Finally, we present cluster based spectrum sensing. We observe that the performance of the scheme degrades as the number of clusters decreases.