1530-437X (c) 2015 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.2015.2393713, IEEE Sensors Journal IEEE SENSORS JOURNAL, VOL. XX, NO. X, JANUARY 2015 1 On Real-Time Performance Evaluation of Volcano Monitoring Systems with Wireless Sensor Networks Rom´ an Lara-Cueva, Member, IEEE, Diego Ben´ ıtez, Senior Member, IEEE, Antonio Caama˜ no, Member, IEEE, Marco Zennaro, Member, IEEE and Jos´ e Luis Rojo- ´ Alvarez, Senior Member, IEEE Abstract—Volcanic eruption early warning has to be launched with effectiveness and within the shortest time possible, which imposes the requirement of using real-time (RT) systems. In this setting, volcano monitoring systems using wireless sensor networks (WSN) may play a key role. Previous works did not report detailed enough performance evaluation, in order to identify their main constraints as RT systems, either in simulation tools or in test-bed scenarios. The aim of this work was to identify the optimum number of sensors to be deployed a posteriori, based on simulation results considering throughput, packet loss, and end-to-end delay, as metrics to satisfy RT requirements. We corroborated the simulation results obtained by a test-bed deployment within a controlled environment. We determined that optimal scenario for volcano monitoring is random topology, and the results show that twelve nodes should be deployed as maximum to satisfy the RT constraints. To test the system in a real scenario, ten sensors were deployed in a strategic area at Cotopaxi Volcano, and information was collected during three days of continuous monitoring. This information was sent to a remote surveillance laboratory located 45 km away from the station placed at the volcano using WiFi-based long distance technology. Our study shows that the coordinator node is the main bottleneck in the real application scenario, given that its processing rate provokes an excessive time delay near to 3s, which has to be solved to satisfy RT requirements. We conclude that a comprehensive study including simulation, test-bed, and in-situ deployment provides valuable information for the specifications to be accounted in permanent WSN RT volcano monitoring. Index Terms—WSN, 802.15.4, throughput, delay, packet loss, monitoring system, volcano. I. I NTRODUCTION A volcanic eruption may cause incalculable effects on the health and safety of humans, which has led to volcanoes monitoring systems, for the purpose of understanding their behavior and to provide, if possible, an early warning in case of an imminent volcanic eruption [1], [2]. In the long term, we are interested in developing a Real-Time Volcano Early Warning System (RT-VEWS) to safeguard human lives and resources, and in this setting we will need RT capabilities Manuscript received October 27, 2014; revised November 11, 2014; ac- cepted January 11, 2015. R.A. Lara is with Electrical and Electronic Department, Universidad de las Fuerzas Armadas ESPE, Quito-Ecuador, 171-5-231B e-mail: (see http://wicom.espe.edu.ec/contactos.html). D. Ben´ ıtez is with Prometeo Program, Electrical and Electronic Department, Universidad de las Fuerzas Armadas ESPE, Quito-Ecuador A. Caama˜ no and J.L. Rojo are with Department of Signal Theory and Communications, Rey Juan Carlos University, Fuenlabrada-Spain. M. Zennaro is with ICT for Development Laboratory, The Abdus Salam International Centre for Theorical Physics, Trieste-Italy for monitoring and for decision making in our system. The proposed system can be divided into 3 blocks: the first block performs the volcanic activity monitoring and sensing; since continuous monitoring produces a great amount of daily data; the second block corresponds to the feature extraction and event detection from the raw data; and the third block corresponds to the VEWS itself, in conformance with the Integrated Services Digital Broadcasting (ISDB-T), the stan- dard for digital terrestrial television, to alert people in case of an emergency. In this paper we focus on addressing the requirements of the first block for RT performance. Several of volcanoes monitoring systems have been de- ployed around the world in the past fifty years, allowing to understand these volcanoes in a better way [3]. There are several forms of volcanoes surveillance, for instance, visual observation, ground deformation monitoring, chemical analy- sis, and seismic monitoring [4]. Traditional systems are heavy, bulky, power-hungry, and complex, all of which are limitations in real volcano monitoring deployment scenarios. In the last decade, some works have reported deployments of volcano monitoring systems using wireless sensor networks (WSN), a non traditional monitoring system, as a new alternative to be considered [5]–[7]. WSN, with their low power consumption and ease of deployment, are a promising technology when considering volcano monitoring. As they can form networks independently, they can be provide with environmental infor- mation at low operational cost and without periodic main- tenance. For these reasons, Cyber-Physical Systems (CPS), Internet of Things (IoT), and Smart Cities, are new research topics based on WSN technologies. All of them are based in a similar infrastructure of heterogeneous networks, where data must be transmitted, processed, and finally enable people to use any application for monitoring or controlling objects [8]– [16]. Volcano monitoring using WSN still requires further re- search in order to present information in RT and to launch early emergency warnings. For example, South America lacks a sufficient number of monitoring systems, based on WSN, permanently deployed at active volcanoes. In previous works, such systems have been installed just for a couple of weeks, and they have not been reported with enough details about their performance in order to identify the main constraints for using them as RT systems, this issue is discussed in more detail later in Section II. Developing countries, such as Ecuador, can benefit from WSN used for volcano monitoring applications, since the WSN systems are much cheaper and easier to install than bulky and energy-hungry traditional systems. Copyright c  2013 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org.