Spectrum sharing optimization based on joint user cluster pairing scheme in CRN-NOMA systems

This paper addresses the challenge of enhancing spectrum sharing in Cognitive Radio Networks (CRNs) while maintaining optimal data rates, energy efficiency, and interference thresholds. We introduce an innovative approach that integrates Non-Orthogonal Multiple Access (NOMA) into CRNs to accommodate a higher number of secondary users effectively. The core of this methodology is the development of a Joint User Cluster Pairing (J-UCP) scheme, which plays a pivotal role in balancing energy constraints against average interference power in the CRN-NOMA system. The J-UCP scheme operates by first arranging secondary users in ascending order of their channel gains relative to the secondary base station. These users are then divided into two groups: a ‘strong user group’ comprising the upper half and a ‘weak user group’ forming the lower half. In an innovative step, the weak user group is further split and reordered. Pairing within these groups follows a strategic protocol: a strong and a weak user are paired only if their channel gain difference exceeds a predefined threshold. This process effectively mitigates the formation of low-gain (near-gain) user pairs, which can impede system performance. Our research primarily investigates the energy efficiency of these user pairs in relation to average interference power, considering both peak and average energy efficiencies across Rayleigh and Rician channels. Additionally, we explore the ergodic capacity of user pairs under these parameters. The findings demonstrate the efficacy of the J-UCP scheme in optimizing the performance of CRN-NOMA systems, presenting a significant advancement in the field of wireless communication.