Resource Allocation in Wireless Powered Sensor Networks With Circuit Energy Consumption Constraints

Wireless power transfer is able to provide sustainable and relatively stable energy supply for battery-powered wireless sensor networks. This paper investigates how to optimally design a wireless powered sensor network with minimal power requirements. To this end, we formulate an optimization problem to minimize the total energy consumption at two remote radio units (RRUs) by jointly optimizing energy beamforming and time assignment, where the circuit energy consumption including basic circuit and information processing energy consumption at sensors is taken into account in order to achieve a more practical and general system design. To solve this non-convex optimization problem, an efficient solution method is presented on the basis of variable substitutions and semidefinite relaxation technique. We analyze the optimality of our proposed solution method. When the number of sensors is not more than four, the rank-one constraint is always guaranteed. When it is larger than four, we show that with our proposed solution method via simulations, an approximate global optimal result can be achieved. Simulation results also show that by jointly optimizing the energy beamforming and time assignment, the system required power can be greatly reduced, while the energy beamforming has greater effect than time assignment on the proposed system. Moreover, it is shown that for fixed non-zero circuit energy consumption (including the static part and the dynamic part), the total energy consumption at the RRUs almost linearly increases with the increment of transmission rate requirement. Besides, the total energy consumption at two RRUs caused by different numbers of enjoyers and collaborators is also discussed.