Spectral Efficiency Optimization and Analysis of Time Switching-Based, Energy Harvesting Spectrum Sharing Cooperative Wireless System

Simultaneous wireless information and power transfer (SWIPT) has gained momentum as a novel and energy efficient technique to restore energy as well as transfer data in communication networks. In this paper, we consider an energy harvesting (EH) relay assisted collaborative wireless system which operates as a secondary network in underlay mode in a spectrum sharing environment. The collaborative system has a source node, a destination node, and multiple EH relays that are nonregenerative, interference-constrained, and use time-switching architecture to harvest energy and receive information from the source node. We select the relay with the maximum harvested energy for further transmission of data to the destination node. For the secondary cooperative EH system, we provide the average spectral efficiency analysis and propose an optimal time switching ratio policy for the selected EH relay that delivers superior performance than benchmark approaches, namely, the random selection and fixed time switching ratio approach. The proposed policy motivates its application in SWIPT based collaborative and spectrum sharing systems.