Renewable solar energy harvesting systems have received considerable attention as a possible substitute for conventional chemical batteries in sensor networks. However, it is difficult to optimize the use of solar energy based only on empirical power acquisition patterns in sensor networks. We apply acquisition patterns from actual solar energy harvesting systems and build a framework to maximize the utilization of solar energy in general sensor networks. To achieve this goal, we develop a cross-layer optimization-based scheduling scheme called BUCKET (Binding optimization of dUty Cycling and net-worKing through Energy Tracking), which is formulated in fourstages: prediction of energy harvesting and arriving traffic, internode optimization at the transport and network layers, intranode optimization at the medium access control (MAC) layer, and flow control of generated communication task sets using a tokenbucket algorithm. Monitoring of the structural health of bridges is shown to be a potential application of an energy-harvesting sensor network. The example network deploys five sensor types: temperature, strain gauge, accelerometer, pressure, and humidity. In the simulations, the BUCKET algorithm displays performance enhancements of 12 ∼ 15% over those of conventional methods in terms of the average service rate.Index Terms-Binding optimization of duty cycling and networking through energy tracking (BUCKET), cross-layer optimization, equal duty cycle allocation (EDCA), energy-harvesting sensor network, inter-and intra-node optimization, maximization of the sum of the duty cycle (MSDC).1530-437X (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2014.2363900, IEEE Sensors Journal 2 harvesting sensor node networks. In Section III, the overall operation of our solar-powered cross-layer sensor network model is explained. Implementation of the BUCKET algorithm for real-time scheduling is discussed in Section IV. The core processes of the BUCKET algorithm: inter-and intra-node optimization are presented in Sections V and VI, respectively. Section VII demonstrates the performance enhancement attained through extensive simulation. Finally, we conclude the paper in Section VIII.
II. RELATED WORK
A. Optimization of Energy-Harvesting Sensor NodesPrevious studies have addressed the maximization of the efficiency of solar energy use via optimized hardware design, including the efforts in [5]-[7]. In each of these studies, a simple routing or scheduling algorithm for resource allocation is developed over a single layer, rather than over multiple layers [8,9]. The authors in [1,2] explore the design of an optimal duty cycle implemented at the MAC layer based on energyharvesting power m...