Improvement of the Sum Rate and Energy Efficiency of IA-based Cognitive Radio Network by Successive Relaying and Power Allocation

In this paper, we propose an underlay cognitive radio network that consists of several secondary users and one successive relaying-aided primary user. Two half-duplex relays operate as full-duplex relays in the successive relaying technique. To improve spectral efficiency, the primary user utilizes the successive relaying technique. Inter relay interference and inter-user interference are challenges of the proposed network. For eliminating these interferences, the interference alignment method is utilized. Also, two power allocation algorithms are proposed to maximize the sum rate of secondary users and the energy efficiency of the network. In both power allocation algorithms, satisfying the quality of service of the primary user is considered. The closed-form solutions of these algorithms are obtained. We use the fractional programming approach to solve energy efficiency optimization in two steps.