Lifetime and Buffer-Size Optimization for RF Powered Wireless Sensor Networks

Radio Frequency-Energy Harvesting (RF-EH) system usually incorporates ‘harvest-store-use’ mechanism, i.e. the harvested RF energy is first stored in an energy buffer and when the stored energy level is sufficient enough to power an application it is then supplied to the device. To improve the network’s performance in terms of lifetime and buffer capacity, it is crucial to develop a model for RF powered Wireless Sensor Networks (WSNs), which considers source-load relations, buffer size and ambient conditions within the context of Energy Neutral Operation (ENO) and minimum energy wastage. In this paper, we propose a model for RF powered WSNs that makes use of available RF energy with variations in maximum and minimum energy levels for two different worst case scenarios encompassing ENO and buffer requirements. We develop an algorithm based on the proposed model to find the optimum energy consumption rate of each sensor nodes that would ensure maximum lifetime of the WSN with minimum buffer capacity. We verified our approach by comparing the results with all other possible consumption rates. We also performed a comparative analysis to find the effect of available RF energy fluctuation in the individual sensor nodes’ lifetime.