Heuristic Power Allocation in NOMA-based Overlay Cognitive Radio Networks

Spectral efficiency (SE) is crucial for wireless networks due to the scarcity of wireless spectrum and the ever increasing demand for high data rates. A prominent solution for SE is cognitive radio (CR) as it facilitates spectrum sharing between multiple users. Non-orthogonal multiple access (NOMA) is another technique for improving SE, which allows multiple users to access the same spectral resource at the same time. Together, NOMA and CRs have immense potential for enabling highly spectrally efficient communication. In this paper, NOMA in power domain has been considered in downlink for an overlay CR network. In power domain NOMA, power allocation (PA) for user signal multiplexing is a critical process. A novel heuristic PA method, called k-scaled PA, has been proposed and the symbol error rate (SER) performance of the users in the considered CR network for the proposed method has been extensively evaluated. This PA approach is robust against interference generated due to NOMA and reduces the information overhead for a network with a large number of users. Up to 5 users have been accommodated in the network using the proposed method.