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Über dieses Buch

This edited book presents the results of the 5th Workshop on Real-world Wireless Sensor Networks (REALWSN). The purpose of this workshop was to bring together researchers and practitioners working in the area of sensor networks, with focus on real-world experiments or deployments of wireless sensor networks. Included were, nonetheless, emerging forms of sensing such as those that leverage smart phones, Internet of Things, RFIDs, and robots. Indeed, when working with real-world experiments or deployments, many new or unforeseen issues may arise: the network environment may be composed of a variety of different technologies, leading to very heterogeneous network structures; software development for large scale networks poses new types of problems; the performance of prototype networks may differ significantly from the deployed system; whereas actual sensor network deployments may need a complex combination of autonomous and manual configuration. Furthermore, results obtained through simulation are typically not directly applicable to operational networks; it is therefore imperative for the community to produce results from experimental research. The workshop collected the state of the art in emerging and current research trends dealing with Real-world Wireless Sensor Networks, with the aim of representing a stepping stone for future research in this field.

Inhaltsverzeichnis

Frontmatter

Applications

Frontmatter

Snowcloud: A Complete Data Gathering System for Snow Hydrology Research

Snowcloud is a data gathering system for snow hydrology field research campaigns conducted in harsh climates and remote areas. The system combines distributed wireless sensor network technology and computational techniques to provide data to researchers at lower cost and higher spatial resolution than ground-based systems using traditional “monolithic” technologies. Supporting the work of a variety of collaborators, Snowcloud has seen multiple Winter deployments in settings ranging from high desert to arctic, resulting in over a dozen node-years of practical experience. In this chapter, we discuss both the system design and deployment experiences.
Christian Skalka, Jeffrey Frolik

The Big Night Out: Experiences from Tracking Flying Foxes with Delay-Tolerant Wireless Networking

Long-term tracking of small-size animals with wireless sensor networks remains a challenge as only limited energy harvesting and storage is possible due to stringent size and weight constraints for animal collars. We present first experiences towards a perpetual monitoring system for free-living flying foxes. The high mobility of flying foxes requires a delay tolerant wireless network for data gathering: GPS positions and sensor data have to be stored locally until a wireless gateway deployed in bat congregation areas, so called roosting camps, comes within radio range. In this chapter, we present the system architecture and discuss our design decisions towards sustainable and reliable monitoring of flying foxes with a limited energy budget for sensing, storage and communication. Using empirical data from three free-living flying foxes, we characterize the overall system performance in terms of energy consumption and latency.
Philipp Sommer, Branislav Kusy, Adam McKeown, Raja Jurdak

On Rendezvous in Mobile Sensing Networks

A rendezvous is a temporal and spatial vicinity of two sensors. In this chapter, we investigate rendezvous in the context of mobile sensing systems. We use an air quality dataset obtained with the OpenSense monitoring network to explore rendezvous properties for carbon monoxide, ozone, temperature, and humidity processes. Temporal and spatial locality of a physical process impacts the number of rendezvous between sensors, their duration, and their frequency. We introduce a rendezvous connection graph and explore the trade-off between locality of a process and the amount of time needed for the graph to be connected. Rendezvous graph connectivity has many potential use cases, such as sensor fault detection. We successfully apply the proposed concepts to track down faulty sensors and to improve sensor calibration in our deployment.
Olga Saukh, David Hasenfratz, Christoph Walser, Lothar Thiele

Real-Life Deployment of Bluetooth Scatternets for Wireless Sensor Networks

Bluetooth scatternets are constructed from overlapping piconets, allowing any number of nodes to be connected into a multi-hop wireless network. Although the topic has been researched for 15 years, no deployments of self-organized scatternets have been published. Recently we have presented the SFX algorithm, which was implemented on commercial Bluetooth nodes and is an extension of SHAPER from 2003. Here measurements are presented for scatternet trees for a laboratory network of 24 nodes and for deployment in a photovoltaic power plant with 39 nodes. The results demonstrate the effectiveness of the SFX algorithm, which is evidently the only actually implemented scatternet contruction procedure which is distributed and does not assume full node-to-node visibility.
Michael Methfessel, Stefan Lange, Rolf Kraemer, Mario Zessack, Peter Kollermann, Steffen Peter

Poster and Demo Abstracts

Frontmatter

Poster Abstract: Velux-Lab—Monitoring a Nearly Zero Energy Building

Velux-Lab is the first Italian Nearly Zero Energy Building (NZEB) built inside a university campus; its main characteristic is the high energy efficiency. It constitutes an experimental module conceived as a laboratory to test new technologies and materials for energy efficiency in construction building. A Wireless Sensor Network collects data from several sensors monitoring the building and the HVAC system, and these data have been used to validate some properties of the building itself.
Alessandro Sivieri

Poster Abstract: Visualization and Monitoring Tool for Sensor Devices

The objective of this chapter is to present SensMap, a novel web-based interactive visualization, monitoring and managing tool which brings major advantages when compared with similar available solution. SensMap is built on the top of Xively web-cloud and it is not tied with any hardware platform. SensMap provides rich set of features, from real-time status observation of sensor devices to comprehensive historical data comparison among multiple devices.
Lubomir Mraz, Milan Simek

Demo Abstract: MakeSense—Managing Reproducible WSNs Experiments

Wireless Sensor Networks (WSN) users often use simulation campaigns before real deployment to evaluate performance and to fine-tune application and network parameters. This process requires repeating the same experiments under similar conditions and to collect, parse and present data efficiently. This chapter introduces MakeSense: a tool that automates this workflow and that allows reproducing simulations easily by defining the whole experiment and post-processing steps in a single JSON configuration file, easy to share and to modify. MakeSense also provides interfaces to interact with a running simulation, allowing to send external stimuli and to collect data in real time. MakeSense currently runs over the COOJA simulator, but has been built to be easily adapted to other architectures, including real testbeds.
Rémy Léone, Jérémie Leguay, Paolo Medagliani, Claude Chaudet

Demo Abstract: Cross Layer Design for Low Power, Low Delay, High Reliability Radio Duty-Cycled Multi-hop WSNs

We present a cross-layer approach for delivering low delay, low power and highly reliable sensor data transfer in radio duty-cycled multi-hop wireless sensor networks. We develop a novel routing metric that uses a number of weighted physical and logical parameters to enable better parent selection for routing data towards the sink. Trading latency against reliability, we demonstrate competitiveness with the state of the art, namely ORW and CTP, through direct comparison using real traces obtained from a 52 node deployment. We demonstrate reliability in excess of 99.9 % in all cases, improved energy efficiency over the state of the art, with minimal trade-offs in terms of end to end latency.
Eoin O’Connell, Brendan O’Flynn

Poster Abstract: Outdoors Range Measurements with Zolertia Z1 Motes and Contiki

Practically useful outdoor transmission ranges have been determined experimentally for Zolertia Z1 motes running Contiki. Both internal and external antennas were tested. The analog and digital quality of the received signal as well as the packet delivery rate have been measured. The influence of transmission power, bushes and weather conditions have been explored. Internal antennas were excessively sensitive to orientation, while external antennas allowed reliable and rather stable communications over distances between motes of up to 150 m. Radio duty cycling was responsible for some, still partially unexplained, packet losses.
Marie-Paule Uwase, Nguyen Thanh Long, Jacques Tiberghien, Kris Steenhaut, Jean-Michel Dricot

Poster Abstract: iBAST—Instantaneous Bridge Assessment Based on Sensor Network Technology

This poster presents the iBAST project, the goal of which is the continuous monitoring of highway bridges with sensor network technology. Currently working on a first individual solution, the long term goal of the project, though, is to move from individual case studies towards a comprehensive monitoring of bridges, by developing a monitoring system which can be easily and cost-effectively customized for every bridge. This poster abstract presents the system architecture and implementation as well as first results.
Richard Mietz, Carsten Buschmann, Dennis Boldt, Kay Römer, Stefan Fischer

Demo Abstract: SmartSync; When Toys Meet Wireless Sensor Networks

Since ancient times, toys have captured the imagination of children the world over with major roles in learning and entertainment. This chapter presents SmartSync, a platform for interactive toys using ultra low power Wireless Sensor/Actuation Network (WSN) technologies. These technologies are integrated into a number of off-the shelf micro-robots and colour LED arrays, making them fully autonomous. A demo system has been developed in which wireless micro-robots and the colour LED arrays interact with a wireless microphone to create an interactive concert scenario. The LED lights and dancing robots are synchronised with music through the WSN. In the final demonstration, the effectiveness of the dancing robots and lights are shown when they respond to traditional Irish music. The WSN interface added improves versatility and accessibility to such toys at a very low cost and low power overhead. This work represents a first step in the development of intelligent interfaces for enhanced interaction with toys for children, especially for those with disabilities.
Fiona Edwards-Murphy, Michele Magno, Aidan Frost, Amy Long, Naomi Corbett, Emanuel Popovici

Poster Abstract: Link Quality Estimation—A Case Study for On-line Supervised Learning in Wireless Sensor Networks

We focus on the implementation issues of on-line, batch supervised learning in computationally limited devices. As a case study, we consider the use of such techniques for link quality estimation. We compare three strategies for the on-line selection of the data samples to be kept in memory and used for learning. Results suggest that strategies that keep balanced the set of training samples in terms of ranges of target values provide better accuracy and faster convergence.
Eduardo Feo-Flushing, Michal Kudelski, Jawad Nagi, Luca M. Gambardella, Gianni A. Di Caro

Poster Abstract: An Experimental Study of Attacks on the Availability of Glossy

Glossy is a reliable and low latency flooding mechanism which makes use of constructive interference. Therefore, it is important to investigate what happens when attacks are mounted on Glossy that try to break constructive interference. In this chapter, we explore the effectiveness of different methods of breaking constructive interference in Glossy. Our results show that Glossy is quite robust to approaches where nodes do not respect the timing constraints necessary to create constructive interference. Changing the packet content, however, has a more tremendous effect on the packet reception rate.
Kasun Hewage, Thiemo Voigt

Low-level Components

Frontmatter

Node Identification Using Clock Skew

Clocks on wireless sensor nodes experience a natural drift. This clock skew is unique for each node as it depends on the clocks manufacturing characteristics. Clock skew can be used as unique node identifier which is, among other applications, useful for node authentication. We describe how clock skew of a node’s clock can be measured directly on a node by utilising the available high precision radio transceiver clock. We detail an implementation of this proposed local clock skew tracking method for the Zolertia Z1 platform. We determine the required sampling effort to accurately determine clock skew. We also discuss how clock skew measurements can be aligned with existing transceiver operations in order to avoid an increase in energy consumption.
Ibrahim Ethem Bagci, Utz Roedig

MagoNode: Advantages of RF Front-ends in Wireless Sensor Networks

This chapter introduces the MagoNode: a new low-power wireless device for Wireless Sensor Networks operating in the ISM 2.4 Ghz band. This platform is based on a highly efficient RF front-end that greatly improves RF performance, in terms of radio range and sensibility, still limiting energy consumption. Indeed, the device outperforms other existing amplified platforms available on the market and is comparable to most commonly known unamplified motes. Moreover, the MagoNode is tailored to operate in various countries with different wireless regulations. Our platform is also TinyOS-compatible and supports the Contiki operating system.
Mario Paoli, Antonio Lo Russo, Ugo Maria Colesanti, Andrea Vitaletti

MIMOSA, a Highly Sensitive and Accurate Power Measurement Technique for Low-Power Systems

In the area of wireless sensor networks, mobile computing systems and other battery-driven computing platforms it is an important task to reduce the system’s power consumption, as the usability of such a system is tightly coupled to the duration of a battery cycle. A basic task for reducing energy consumption is the creation of hardware and software energy models to find and understand existing power saving potentials. This often requires a most accurate measurement of both the energy and the timing behavior of such a system. In this chapter we will show that, especially for sub-milliampere applications such as sensor network nodes, commonly used power measurement techniques do not perform well. We introduce MIMOSA, a low-cost measurement device that uses a fast voltage regulator and analog integration circuits to overcome most of the issues existing in other approaches.
Markus Buschhoff, Christian Günter, Olaf Spinczyk

A Remotely Programmable Modular Testbed for Backscatter Sensor Network Research

The necessity of backscatter sensor networks (BSNs) has recently emerged due to the need for large-scale, ultra low-cost, ultra low-power, wireless sensing. Development of such networks requires tools for rapid prototyping and evaluation of key-enabling BSN technologies. Although tools for testing wireless sensor networks (WSNs) have been widely developed over the last few years in the form of testbeds, almost no significant testbed examples exist for BSNs. Throughout this work, a set of hardware, firmware and software components have been designed and implemented, creating a BSN research testbed. The latter employs a modular architecture and enables rapid prototyping of critical components for low-cost, large-scale BSNs. Testbed components enable microwave, detection, coding and multiple access research, tailored for backscatter radio and networking. The testbed offers dynamic reconfiguration through implementation of remote, over the air programming (OTAP), that reduced programming time per node by two orders of magnitude. An overview of the testbed is given, and its modular tools are described in terms of functionality and importance for BSN research.
Eleftherios Kampianakis , John Kimionis, Konstantinos Tountas, Aggelos Bletsas

Networking

Frontmatter

A Scalable Redundant TDMA Protocol for High-Density WSNs Inside an Aircraft

We present the results of a measurement campaign conducted with a wireless sensor network (WSN) deployment inside an aircraft. A robust and scalable TDMA protocol for mission-critical applications was developed, which exploits spatial diversity provided by redundant access points. The WSN, consisting of 500 sensor nodes organized in three cells with two redundant access points per cell, was installed in an Airbus A330–300. The link quality and the packet error rate with and without the redundant access points was evaluated. It was found that the packet error rate could be decreased more than four times by using the spatial diversity introduced by the dual access point approach.
Johannes Blanckenstein, Javier Garcia-Jimenez, Jirka Klaue, Holger Karl

Do We Really Need a Priori Link Quality Estimation?

Traditionally, link quality estimation (LQE) has been viewed as an a priori step in sensor network routing protocols because it filters out unreliable links before data transmission. Recent results, however, show that protocols can perform well without a priori LQE. Because getting rid of LQE seems rather counter-intuitive, the aim of this work is to look deeper into the behavior of LQE-free protocols. Our results, based on one of the state-of-the-art LQE-free protocols, show two interesting insights. First, LQE-free protocols manage to choose links that are slightly better than the ones obtained with a priori LQE methods. Second, in traditional protocols, the effort needed to identify good links accounts, on average, for roughly half of the energy consumption of nodes, depending on the nodes’ active period and on the inter-packet interval. By eliminating this overhead, LQE-free protocols can save a significant amount of energy compared to standard approaches.
Vasilis Vasilopoulos, Daniele Puccinelli, Marco Zúñiga

Redundant Border Routers for Mission-Critical 6LoWPAN Networks

Sensor networks are gradually moving towards full-IPv6 architectures and play an important role in the upcoming Internet of Things. Some mission-critical applications of sensor networks will require a level of reliability that excludes the presence of single points of failure, as it is often the case today for the gateways connecting sensor networks to the Internet. In this chapter, we introduce RPL-6LBR, a 6LoWPAN border router that addresses mission-critical deployments through redundancy. The chapter discusses how existing standards may be leveraged to enable redundant border router synchronization, while identifying certain of their shortcomings. We also propose innovative network architectures incorporating multiple border routers, which deal with redundancy and node mobility without requiring any synchronization among the border routers. We implement the proposed RPL-6LBR in the Contiki operating system and report on this implementation through trials on a small-scale testbed and simulator. Our results open new possibilities for real-world wireless sensor networks requiring reliable border routers, and guide further standardization efforts in emerging technologies in support of the Internet of Things.
Laurent Deru, Sébastien Dawans, Mathieu Ocaña, Bruno Quoitin, Olivier Bonaventure

Using Directional Transmissions and Receptions to Reduce Contention in Wireless Sensor Networks

Electronically Switched Directional (ESD) antennas allow software-based control of the direction of maximum antenna gain. ESD antennas are feasible for wireless sensor network. Existing studies with these antennas focus only on controllable directional transmissions. These studies demonstrate reduced contention and increased range of communication with no energy penalty. Unlike existing literature, in this chapter we experimentally explore controllable antenna directionality at both sender and receiver. One key outcome of our experiments is that directional transmissions and receptions together considerably reduce channel contention. As a result, we can significantly reduce intra-path interference.
Ambuj Varshney, Thiemo Voigt, Luca Mottola

Energy

Frontmatter

Energy Parameter Estimation in Solar Powered Wireless Sensor Networks

The operation of solar powered wireless sensor networks is associated with numerous challenges. One of the main challenges is the high variability of solar power input and battery capacity, due to factors such as weather, humidity, dust and temperature. In this article, we propose a set of tools that can be implemented onboard high power wireless sensor networks to estimate the battery condition and capacity as well as solar power availability. These parameters are very important to optimize sensing and communications operations and maximize the reliability of the complete system. Experimental results show that the performance of typical Lithium Ion batteries severely degrades outdoors in a matter of weeks or months, and that the availability of solar energy in an urban solar powered wireless sensor network is highly variable, which underlines the need for such power and energy estimation algorithms.
Mustafa Mousa, Christian Claudel

Experiences with Sensors for Energy Efficiency in Commercial Buildings

Buildings are amongst the largest consumers of electrical energy in developed countries. Building efficiency can be improved by adapting building systems to a change in the environment or user context. Appropriate action, however, can only be taken if the building control system has access to reliable real-time data. Sensors providing this data need to be ubiquitous, accurate, have low maintenance cost, and should not violate privacy of building occupants. We conducted a 3 year study in a mid-size office space with 15 offices and 25 people. Specifically, we focused on sensing modalities that can help improve energy efficiency of buildings. We have deployed 25 indoor climate sensor nodes and 41 wireless power meters, submetered 12 electric loads in circuit breaker boxes, logged data from our building control system and tracked activity on 40 desktop computers. We summarize our experiences with the cost, data yields, and user privacy concerns of the different sensing modalities and evaluate their accuracy using ground-truth experiments.
Branislav Kusy, Rajib Rana, Phil Valencia, Raja Jurdak, Josh Wall

Wireless Sensor Networks for Building Monitoring Deployment Challenges, Tools and Experience

As more large scale deployments of wireless solutions come on stream there is a real need for deployment support for system integrators to ensure a reliable infrastructure can be achieved. This chapter presents the experiences gained from a real deployment and discusses the process used by a designer in order to investigate what value the use of current support tools can offer a designer.
Alan McGibney, Suzanne Lesecq, Claire Guyon-Gardeux, Safietou R. Thior, Davide Pusceddu, Laurent-Frederic Ducreux, François Pacull, Dirk Pesch

Long Term WSN Monitoring for Energy Efficiency in EU Cultural Heritage Buildings

Historic buildings are a distinctive and invaluable characteristic of numerous European cities, and living symbols of Europe’s rich cultural heritage. However, today, EU cultural heritage buildings are contributing huge percentage to the greenhouse gas emissions. This has led to the increasing of wireless sensor network (WSN) deployments aimed at monitoring and improving the energy efficiency of these historic buildings. In this chapter we show a long term, low cost, passive distributed environmental monitoring system that promotes energy-efficient retrofitting in historic buildings. We focus on the design and implementation of an innovative technological framework, and on the hardware and software development of the solution. The presented system provides real-time feedback for the civil engineers for prompt intervention via remote interfaces.
Femi Aderohunmu, Domenico Balsamo, Giacomo Paci, Davide Brunelli
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