arXiv:2101.00225v1 [eess.SP] 1 Jan 2021 Energy-Efficient Resource Allocation for 5G Cognitive Radio NOMA Using Game Theory Shaima’ S. Abidrabbu * and H¨ useyin Arslan *† * Department of Electrical and Electronics Engineering, Istanbul Medipol University, Istanbul, 34810 Turkey † Department of Electrical Engineering, University of South Florida, Tampa, FL 33620 USA Email: sabidrabbu@st.medipol.edu.tr, huseyinarslan@medipol.edu.tr Abstract—Cognitive radio non-orthogonal multiple access (CR- NOMA) networks promise improved spectrum utilization and capacity in 5G networks. In this work, we aim to investigate efficient power allocation for the secondary users (SUs) in underlay CR-NOMA networks using a game-theoretic approach. We present a novel power allocation to CR-NOMA network from a game-theoretic perspective. First, we specify the utility function of the primary users (PUs) and SUs, and formulate the game as a non-cooperative game. Then, the existence and uniqueness of the Nash equilibrium (NE) are investigated. Finally, the sum utilities of SUs is maximized by optimal power allocation at the NE point. Simulation results provided that the proposed scheme outperforms the conventional method, providing up to 37.5% increase in sum utilities of the SUs. Index Terms—CR-NOMA, power allocation, game theory, spectrum utilization. I. I NTRODUCTION Increasing user requirements such as capacity and data rates have been the driving force behind evolving communication technologies. Cognitive radio (CR) and non-orthogonal mul- tiple access (NOMA) are two promising intended to improve spectral efficiency and consequently, system capacity [1], [2] in 5G communication. CR-NOMA networks are seen as a specific case of power-domain NOMA applied in CR, wherein the requirements of the secondary users (SUs) and primary users (PUs) are strictly met, resulting in improved system performance [3]. However, there are many critical challenges due to the severe interference caused by NOMA in CR networks, which are related to resource allocation (RA) and interference man- agement. Various efforts have been made to investigate and facilitate these challenges [3], [4]. RA and optimization aim for efficiently utilizing the resources in terms of different objectives like spectral and energy efficiency [5]. For example, the authors in [6] showed that the energy efficiency of underlay CR-NOMA can be higher than that of cognitive radio networks (CRNs) with orthogonal multiple access (OMA) using se- quential convex approximation method. In [7], the authors proposed a novel power allocation algorithm for CR-NOMA, where the characteristics of the NOMA-based system had totally exploited for designing the RA algorithm. RA in CR- NOMA studied also in the literature for simultaneous wireless information and power transfer (SWIPT) scheme. For example in [8], time sensing studied as a critical constraint in the optimization problem. In [9], the authors proposed a non-linear energy harvesting (EH) model to minimize the overall system power consumption. In [10], the multi-objective optimization problem based on EH and the quality of service (QoS) of the users in CR-NOMA considered. One of the biggest issues in CR-NOMA networks is the design of an optimal RA scheme, considering different (and often competing) objectives such as spectral efficiency, energy efficiency, and interference management [11]. Although the multi-objective optimization can be exploited to achieve sub- optimal solutions, the complexity of the designed algorithms may be very high. To cope with this complexity, we propose using game theory (GT) to design efficient RA in the proposed network. To the best of our knowledge, this is the first work to study RA in CR-NOMA using GT approach. In this paper, the power allocation of an underlying CR- NOMA network using the GT approach is investigated which introduces the GT to the RA in candidate 5G networks . More specifically, in this work, the game is represented as competition between the kth SU which is trying to predict the other players’ strategies to maximize his payoff and at the last find the Nash equilibrium (NE) of the game at the SU base station. As a result, the resource management mechanism of the proposed CR-NOMA-based GT approach will achieve high net utilities for all the SUs while maximizing the energy and spectrum efficiency by achieving their satisfactions. Our contributions are summarized as follows: • A novel non-cooperative power control framework for the CR-NOMA network is presented, where each SU selfishly optimizes its power allocation over the allocated resources to maximize its utility function. Moreover, we prove the existence, and provide the conditions for the uniqueness of the NE. The performance of the proposed approach is compared with OMA-based conventional non-cooperative GT power control. • Since the interference level to the PU is usually modeled as strict constraints for resource allocation optimization in the literature of CRNs. In this work, the interference to the PU is taken into the consideration by introducing the PUs as a part of the game where the number of PUs and their utilities are conducting in the overall system model.