A Case Study on the Power-Aware Protocol Framework for Wireless Sensor Networks

The proliferation of wireless sensor networks is one of the main hardware components enabling the creation of the Internet of Things. As sensor nodes are being deployed in a wide variety of indoor and outdoor environments, they are in general battery-powered devices. In fact, power provisioning is one of the main challenges faced by engineers when deploying IoT-based applications. This paper develops crosslayer architecture, integrating smart and power-aware protocols with a low-cost and high-efficiency power management module, which is the basis of long-lasting of self-powered WSNs. The main physical components of the proposed architecture are a wireless node comprising a set of small solar cells responsible for harvesting the energy and an ultracapacitor as storage device. Energy consumption is reduced significantly by varying the sleep/wake duty cycle of the radio module. For environments with only a few hours of sunlight per day we present the feasibility of ensuring long-lasting operation by means of adapting the duty cycle scheme according to the energy stored in the ultracapacitor. Our experiments prove the feasibility of a long-endurance outdoors operation with a low-complexity power management unit. This is an important advance towards the development of novel IoT-based applications. 1. Introduction The study of reliable and long-lasting power management systems for wireless sensor networks is nowadays the main subject of a large number of research efforts. Three main issues are being explored, namely, (1) energy harvesting, (2) energy storage, and (3) power-aware protocols. The former two mainly deal with the design and use of power generation and energy storage based on renewable energy systems and rechargeable energy storage devices, while the latter deals with the design of power-aware protocol mechanisms. Despite the advances in batteries and the reduction in energy requirements of electronics, the use of energy harvesting techniques needs to be considered in order to satisfy the requirements for low weight and volume, long life, and limited environmental impact [1]. The use of environmental energy is a feasible source for low-power wireless sensor networks [2, 3]. Among the various sources of renewable energy for outdoor applications, solar power is one of the most abundant and accessible energy sources to extend the operation of such networks. Several systems that have been designed to date aim to provide an efficient and reliable source of solar-based energy to WSNs, ranging from sophisticated adaptive power modules [4] to