Analytical Model for the Duty Cycle in Solar-Based EH-WSN for Environmental Monitoring

Abstract

A technology drift is currently taking place from traditional battery-powered sensor networks, which exhibit limited lifetime, to the new Energy-Harvesting Wireless Sensor Networks (EH-WSN), which open the way towards self-sustained operation. However, this emergent modality also brings up new challenges, especially due to the time-varying nature and unpredictability of ambient energy sources. Most proposals for implementing EH-WSN rely on heuristic approaches to redesign the duty-cycling mechanism at the MAC layer, with the ultimate goal of optimizing network performance while preserving self-sustained and continuous operation. In contrast to the common system-wide reduced duty cycle of battery-powered sensor networks, the duty cycle in EH-WSN is much larger and adapted to the energy harvesting rate and traffic load of each node in the network. In this paper, we focus on solar-based EH-WSN devoted to environmental monitoring. In contrast to current works, we follow an analytical approach, which results into closed-form expressions for the duty cycle and initial energy storage that guarantee self-sustained operation to any node in a solar-based EH-WSN. To center the analysis, we consider TinyOS sensor nodes, though we postulate that the essential components of the obtained formulation will contribute to further develop duty cycle adaptation schemes for TinyOS and other software platforms.

Optimal Routing for Time-Driven EH-WSN under Regular Energy Sources

“…For the sake of completeness, this subsection recalls the main results obtained in [ 14 ] about the energy consumed by the LPL mechanism implemented in TinyOS sensor nodes. Figure 2 describes this mechanism, where node A transmits a packet to node B, which receives and forwards such packet to the next hop (not shown).…”

“…On the basis of these assumptions, this paper demonstrates that the MHC criterion should be prioritized in the design of routing strategies and protocols for time-driven EH-WSN under regular energy sources. More specifically, the detailed contributions of this paper can be outlined as follows: Based on a previous result regarding the energy consumed by TinyOS sensor nodes [ 14 ], a comprehensive model is derived to characterize the energy consumption of nodes in generic time-driven duty-cycled wireless sensor networks. general formulation is then obtained which relates duty cycle and traffic load for time-driven duty-cycled EH-WSN.…”

“…Based on a previous result regarding the energy consumed by TinyOS sensor nodes [ 14 ], a comprehensive model is derived to characterize the energy consumption of nodes in generic time-driven duty-cycled wireless sensor networks.…”

“…The rest of this paper is organized as follows. In Section 2 , from the result obtained in [ 14 ], a generic energy consumption model for time-driven duty-cycled sensor networks is developed. Though the analysis performed in this paper is valid for any regular or quasi-periodic energy source, special attention is dedicated to solar radiation, as it is the most representative example.…”

An analytical model to estimate the state of charge and lifetime for batteries with energy harvesting capabilities

“…Energy harvesting is the process of extracting small amounts of energy that would be lost in the form of heat, light, sound, vibration, or movement . The collected energy can be used, for example, (a) to increase the efficiency of battery‐powered devices, because the energy initially wasted can be reused to maintain the operation of their electronic components; and (b) to enable the development of new technologies, such as WSN nodes equipped with energy harvesting devices …”