Energy Efficiency Maximization for MIMO enabled Multi Relay Cognitive Network

This paper presents a joint problem of relay selection and relay precoder designing for multi-input multi-output (MIMO) multi-relay cognitive networks (MRCNs), where a secondary network $(SN)$, consists of a secondary transmitter, receiver, and multiple half-duplex relays, transmits data simultaneously in the presence of a primary network $(PN)$. Here, three relay selection schemes are investigated and its impact on relay precoder designing is demonstrated in terms of achieved energy-efficiency (EE). An optimal solution is presented based on the Augmented Lagrangian method for designing a precoder at a selected relay. Simulation results are provided to validate the proposed schemes.