Energy-Efficient Resource Allocation in SWIPT Cooperative Wireless Networks

In this article, energy-efficient resource allocation in simultaneous wireless information and power transfer (SWIPT) cooperative wireless networks is studied. With the transferred power, the SWIPT relays are adopted to improve the energy efficiency at the destination node. Two typical relay structures, decode-and-forward (DF) and amplify-and-forward (AF), are exploited for the optimal relay selection and power allocation with a power splitting SWIPT architecture. Nonconvex energy efficiency optimization problems are formulated for both DF and AF relay types. Based on the SNRs at the destination node, closed-form expressions of the optimal power splitting ratios are provided for DF and AF relays, respectively. With the optimal power splitting ratio, relay selection schemes based on full and partial knowledge of the channel state information are derived. Moreover, a novel power allocation scheme is proposed and illustrated based on the property of the simplified optimization problem with the power and quality of service constraints. Simulation results demonstrate that the proposed resource allocation scheme achieves the maximum energy efficiency with low computational complexity, in which the proposed relay selection outperforms the typical relay selection schemes in terms of energy efficiency.