SWIPT-Enabled Cognitive Overlay-Based Non-Orthogonal Multi-User MIMO Cooperative Communication With Battery-Equipped Energy Harvesting Nodes

A simultaneous wireless information and power transfer (SWIPT)-assisted cognitive overlay-based multiple input multiple output (MIMO) downlink (DL) cooperative relaying system has been considered wherein a secondary network comprising of an energy harvesting (EH) base station (BS) and possibly multiple fully wireless powered secondary users (SUs) share the spectrum of a primary network for information transmission and energy harvesting. In exchange, the secondary BS acts as a relay for the primary network and aids in transmitting information from the primary BS to the primary users (PUs) along with its own information using non-orthogonal transmission and the harvested energy. Closed-form expressions for the end-to-end outage probability (OP) at all the PUs and SUs have been obtained considering Rayleigh fading channel links and also sensitivity and saturation impairments at the energy harvesting nodes. Moreover, all the energy harvesting nodes have been assumed to be equipped with a finite battery for storing the harvested energy and rely solely on this stored energy for running the transceiver circuitry. Closed-form expressions have also been obtained to characterize the degradation due to the energy harvesting impairments and finite battery on the end-to-end OP of all the users. Furthermore, closed-form expressions for the asymptotic outage floor and diversity order have been obtained to analyze the performance of the system at high transmit power. Finally, simulation results have been presented to validate the analytical results derived and provide further insights into the performance of the system.