electronics Article Multi-Objective Optimization of Joint Power and Admission Control in Cognitive Radio Networks Using Enhanced Swarm Intelligence Ayman A. El-Saleh 1 , Tareq M. Shami 2 , Rosdiadee Nordin 3, * , Mohamad Y. Alias 4 and Ibraheem Shayea 5   Citation: El-Saleh, A.A.; Shami, T.M.; Nordin, R.; Alias, M.Y.; Shayea, I. Multi-Objective Optimization of Joint Power and Admission Control in Cognitive Radio Networks Using Enhanced Swarm Intelligence. Electronics 2021, 10, 189. https://doi.org/10.3390/ electronics10020189 Received: 25 November 2020 Accepted: 9 January 2021 Published: 15 January 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Electronics and Communication Engineering, College of Engineering, A’Sharqiyah University (ASU), Ibra 400, Oman; ayman.elsaleh@asu.edu.om 2 Department of Electronic Engineering, University of York, York YO10 5DD, UK; tareq.al-shami@york.ac.uk 3 Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia 4 Faculty of Engineering, Multimedia University, Cyberjaya 63100, Malaysia; yusoff@mmu.edu.my 5 Department of Electronics and Communication Engineering, Faculty of Electrical and Electronics Engineering, Istanbul Technical University (ITU), 34467 Istanbul, Turkey; ibr.shayea@gmail.com * Correspondence: adee@ukm.edu.my; Tel.: +603-8911-8402 Abstract: The problem of joint power and admission control (JPAC) is a critical issue encountered in underlay cognitive radio networks (CRNs). Moving forward towards the realization of Fifth Generation (5G) and beyond, where optimization is envisioned to take place in multiple performance dimensions, it is crucially desirable to achieve high sum throughput with low power consump- tion. In this work, a multi-objective JPAC optimization problem that jointly maximizes the sum throughput and minimizes power consumption in underlay CRNs is formulated. An enhanced swarm intelligence algorithm has been developed by hybridizing two new enhanced Particle Swarm Optimization (PSO) variants, namely two-phase PSO (TPPSO) and diversity global position binary PSO (DGP-BPSO) variants employed to optimize the multi-objective JPAC problem. The perfor- mance of the enhanced swarm intelligence algorithm in terms of convergence speed and stability, while optimizing both the sum throughput and power consumption, is investigated under three different operational scenarios defined by their single objective priorities, which translate to sum throughput and power consumption preferences. Simulation results have proven the effectiveness of the enhanced swarm intelligence algorithm in achieving high sum throughput and low power consumption under the three operational scenarios when the network includes an arbitrary number of primary and secondary users. Comparing the hybrid SPSO approach and the proposed approach, the proposed scheme has shown its effectiveness in increasing the sum throughput to 7%, 16%, and 31% under the multimedia, balanced and power saving operational scenarios, respectively. In addition, the proposed approach is more power efficient as it can provide additional power savings of 3.58 W, 2.48 W, and 1.6741 W under the aforementioned operational scenarios, respectively. Keywords: cognitive radio; underlay channel access; power and admission control; multi-objective optimization; particle swarm optimization 1. Introduction Recently, there has been a tremendous increase in the number of wireless devices such as smartphones, notepads and laptops. This makes spectrum scarcity the essential dilemma when launching new wireless services. Another fundamental issue that contributes nega- tively to the spectrum scarcity problem is the static spectrum allocation policy regulated by each and every national spectrum regulatory authority, such as the Federal Commu- nications Commission (FCC) in the US, where a licensed user is assigned a fixed block of the spectrum on a long-term basis. This licensed user is typically known as a primary user (PU). The FCC conducted a study to figure out how the spectrum is being utilized Electronics 2021, 10, 189. https://doi.org/10.3390/electronics10020189 https://www.mdpi.com/journal/electronics