Energy Harvest and Information Transmission algorithm in Wireless Internet-of-Things with Relay Cooperation

Wireless energy transmission is considered in the Internet-of-Things (IoT) dual-hop communication systems.In this paper, the energy collection and information transmission algorithms of the relay nodes using the collected energy by power shunting method are designed.The algorithms is formulated to maximize the energy efficiency defined as the ratio of the wireless information throughput of the first destination node over the power consumed by the whole IoT systems, which is subject to the required minimum energy harvested at the second destination node of the energy transfer.The relay node uses the signal sent by the source node for energy harvesting.Considering the actual power conversion efficiency and hardware circuit loss power factor in the EARTH plan, the analytical solution of the optimal power allocation scheme for the energy-collecting and information transmission of the wireless coordinated IoT system is derived.To tackle the non-convex problem, the exact expression of the wireless information throughput is approximated by the high signal to noise ratio (SNR) approximation method. Hence, the asymptotically optimal solution is derived in analytical expression by employing the Lagrangian method. Numerical simulations verify the performance of the proposed scheme.