Hybrid Energy Resource Allocation for Simultaneous Wireless Information and Power Transfer for Green Communications

In this paper, we consider a simultaneous wireless information and hybrid power transfer system for cellular green networks. The small cells (SCs) use hybrid power of on-grid power and green energy harvested from environments, whilst the user equipments (UEs) are enabled by a power-splitting receiver. A quality-of-service (QoS) constrained problem is designed to maximize energy efficiency (EE) considering joint strategies of hybrid power allocation, resource block assignment, and power splitting ratio adjustment. We propose a joint wireless charging and hybrid power based resource allocation (J-WHA) algorithm by transforming the non-concave EE problem into a solvable one based on proved concavity property and Karush-Kuhn-Tucker (KKT) conditions. Moreover, a separated wireless charging and hybrid power based resource allocation (S-WHA) algorithm is proposed to obtain sub-optimal solutions with lower computational complexity. Simulation results demonstrate the convergence of both proposed algorithms in relation to transmission power utilization, wireless charging amount, and system EE. It is shown that the proposed J-WHA and S-WHA algorithms outperform existing schemes in terms of EE performance.