Elsevier

Ad Hoc Networks

Volume 8, Issue 8, November 2010, Pages 872-888
Ad Hoc Networks

Smart bridges, smart tunnels: Transforming wireless sensor networks from research prototypes into robust engineering infrastructure

https://doi.org/10.1016/j.adhoc.2010.04.002Get rights and content

Abstract

We instrumented large civil engineering infrastructure items, such as bridges and tunnels, with sensors that monitor their operational performance and deterioration. In so doing we discovered that commercial offerings of wireless sensor networks (WSNs) are still geared towards research prototypes and are currently not yet mature for deployment in practical scenarios.

We distill the experience gained during this 3-year interdisciplinary project into specific advice for researchers and developers. We discuss problems and solutions in a variety of areas including sensor hardware, radio propagation, node deployment, system security and data visualization. We also point out the problems that are still open and that the community needs to address to enable widespread adoption of WSNs outside the research lab.

Introduction

Large civil engineering infrastructure items such as bridges, highways, tunnels and water pipes are expected to last for decades or even centuries. Over the course of their lifetimes, these structures deteriorate and require timely maintenance in order to prevent further degradation that might lead to accidents, the need for replacement or, in the worst case, collapse. Traditionally, early detection of such deterioration is achieved by visual inspection, either during routine maintenance visits or when a maintenance team is sent to the site to investigate a known or suspected problem. But such inspections are time-consuming and costly and therefore infrequent. An alternative is to equip infrastructure with sensors that are permanently wired up to report back to a central system; but this solution is not adopted very extensively because of the difficulty and cost of running data and power cables to each individual sensor in challenging environments such as a subway tunnel or a long suspension bridge.

The purpose of our research project, which at the time of writing has been running for almost 3 years, is to develop a system for continuous monitoring of such infrastructure using wireless sensor networks which, compared to wired systems, are easier and cheaper to deploy and also offer the opportunity for straightforward expansion. Very few other groups, to our knowledge, have deployed wireless sensor networks (WSNs) with the goal of using them for long term monitoring of civil engineering infrastructure; among those few are Feltrin et al. [5] and there the main parameter being measured is vibration. Their system uses the limited processing power of the nodes in an efficient manner and their network feeds back only the most critical data.

Although many papers have been written about WSNs, experience papers reporting on real-world deployments are a minority: they include at least Mainwaring et al. [19] who monitor seabirds’ nesting environment and behaviour, Arora et al. [1] who deploy a perimeter control WSN and Werner-Allen et al. [23] who monitor an active volcano. Closer to our scenario are Krishnamurthy et al. [16] who monitor equipment for early signs of failure and especially Kim et al. [14] who monitor the structural health of the Golden Gate bridge. But our favourite is Barrenetxea et al. [2], which describes the authors’ experience in deploying several environmental monitoring networks over glaciers in the Alps: they offer a wealth of valuable insights on how to prepare for deployment and how to extract maximum value from the exercise. We adopted their “hitchhiker’s guide” structure of presenting our experience as advice to a reader who might wish to do something similar. Content-wise our papers are complementary, since we focus primarily on radio propagation and security issues which Barrenetxea et al. did not explore.

How nice it would be if we could just go out and buy a commercial off the shelf (COTS) WSN system and use it for monitoring our structures straight away. Unfortunately, though, the available commercial systems are typically only kits of building blocks and a non-trivial integration effort is required, together with the development of any missing parts, before arriving at a complete and usable monitoring solution.

This experience paper identifies some of the challenges and issues encountered when installing wireless sensor networks in the field, with specific but not exclusive reference to civil engineering deployments, and discusses how these challenges can be addressed. Inspired by the format of the instructive and well-presented paper by Barrenetxea et al. [2], we share our experience in the form of small independent vignettes, each accompanied by specific advice that tells you how to avoid falling into the same traps. These will hopefully be of use to both the application-oriented engineer working on a new deployment and the lab-based researcher developing an improved generation of WSN kit. Whilst we have made great strides in this area, much work still remains to be done and so we have also highlighted areas of ongoing and future research.

The structure of the rest of the paper is as follows. We first examine (Section 2) the main problems of WSN deployment and we present the contributions we offer. We then introduce the testbeds where we trialled, and continue to trial, our WSN systems (Section 3). In the main section of the paper (Section 4) we then look at the challenges of WSN deployment and the guidelines we distilled from our experience, with particular emphasis on installation planning, network optimization, radio propagation and security. As well as investigating issues of general applicability we also focus more specifically on the deployment of WSNs on civil infrastructure and on how to manage the data collected from such systems. Finally, in Section 5, we draw our conclusions and highlight the areas that still need further work. References and comparisons to related work are found throughout the paper, including earlier in this section. After most “Principles” we also point out the original papers in which we discussed the relevant issues in greater detail.

Section snippets

The problem and our contributions

Civil infrastructure in the UK ranges from masonry arch bridges constructed in Roman times2 to Victorian3 tunnels to modern structures that push the limits of materials and computer-based design. A similar situation exists around the world and all this infrastructure suffers from the common problem that it is deteriorating with time and in some cases is

Our three civil infrastructure testbeds

In order to gauge the effectiveness of COTS WSN hardware for use in civil infrastructure monitoring, the systems were deployed at three sites in the UK.

The first site, shown in Fig. 1b, is in the north anchorage chambers of the Humber Bridge—a major suspension bridge, shown in Fig. 1a, that crosses a river estuary in East Yorkshire. Each of the four underground anchorage chambers

Principles for successful WSN deployment

If WSNs are to be used pervasively on civil infrastructure, they will be deployed by maintenance crews, not by academics or their research students: they must therefore be straightforward to install (Section 4.1). Radio connectivity is not automatically guaranteed (Section 4.2) and neither is the security of the resulting installation (Section 4.3). Certain problems are typical of large civil engineering installations (Section 4.4) but also have relevance elsewhere. Finally, data interpretation

Conclusions and further work

In our experience, the WSN systems currently available on the market are still insufficiently mature for practical deployments: the basics are there but many problems, from radio propagation to deployment to security, are still left unaddressed. Domain experts such as bridge and tunnel engineers are still far from being able to buy a turn-key WSN system and apply it to their own problem: instead, they are forced to become co-developers of the WSN system and to build and sharpen their own tools.

Acknowledgements

We are grateful to EPSRC for funding this work as part of project EP/D076870/1 “WINES Smart Infrastructure”. We thank our civil infrastructure partners, both as individuals and as institutions, for their assistance and cooperation: Peter Hill (Humber Bridge Board), Peter Wright (Tubelines), Jim Moriarty (London Underground), Stephen Pottle (Transport for London). We gratefully acknowledge the essential contributions of other members of our team including, in alphabetical order, Dan Cvrcek

Frank Stajano is a Senior Lecturer at the University of Cambridge Computer Laboratory and the author of “Security for Ubiquitous Computing” (Wiley, 2002). He received a Ph.D. in computer security from the University of Cambridge. His principal research interests are systems security, ubiquitous computing and privacy in the electronic society. Besides his tenured academic appointment he also worked as a research scientist at leading IT corporations such as Google, Toshiba, AT&T and Oracle, and

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    Frank Stajano is a Senior Lecturer at the University of Cambridge Computer Laboratory and the author of “Security for Ubiquitous Computing” (Wiley, 2002). He received a Ph.D. in computer security from the University of Cambridge. His principal research interests are systems security, ubiquitous computing and privacy in the electronic society. Besides his tenured academic appointment he also worked as a research scientist at leading IT corporations such as Google, Toshiba, AT&T and Oracle, and he consults for industry on topics ranging from systems security to research planning and innovation; his research therefore retains a strong practical orientation. He has given over 40 invited and keynote talks in four continents. He was elected a Toshiba Fellow in 2000.

    Neil A. Hoult is an Assistant Professor in the Department of Civil Engineering, Queen’s University, Kingston, Canada. He received his B.A.Sc. and M.A.Sc. in civil engineering from the University of Toronto and his Ph.D. in engineering from the University of Cambridge. His research interests include the use of fibre reinforced polymers for reinforcing and retrofitting reinforced concrete structures as well as the use of structural health monitoring to assist in the evaluation of existing structures.

    Ian J. Wassell is a Senior Lecturer at the University of Cambridge Computer Laboratory. He received the Ph.D. degree from the University of Southampton in 1990 and the B.Sc., B.E. (Hons) Degrees (First Class) from the University of Loughborough in 1983. He has in excess of 15 years experience in the simulation and design of radio communication systems gained via a number of positions in industry and higher education. He has published in excess of 150 papers concerning wireless communication systems since joining the University of Cambridge in May 1990, and is also a fellow of Churchill College. His research interests include broadband fixed wireless (FWA) networks, wireless sensor networks (WSNs), radio propagation and modelling, coding and communication signal processing. He is a member of the Institution of Engineering and Technology (IET).

    Peter Bennett obtained his Ph.D. from the University of Southampton for research performed in the Laser Physics group. He subsequently held the post of research fellow in the EPSRC IRC, Optoelectronics Research Centre, University of Southampton, researching novel optical fibres. During the course of the research project described in this paper he was a Senior Research Associate in the Geotechnical and Environmental Research Group at Cambridge University. He has been researching new technologies for condition assessment and monitoring of ageing infrastructure, with a particular interest in the use of optical fibres for monitoring strain. He has a background in laser physics and optical fibres. He has also worked in an R&D role for the global telecommunications company Nortel Networks.

    Campbell Middleton is a Senior Lecturer in Structural Engineering at Cambridge University. He joined the staff in 1989 after nearly ten years experience in bridge and highway construction and design in Australia and with consultant Arup in London. He has a B.E. (Hons) from the University of Tasmania, an M.Sc. from Imperial College, London and a Ph.D. from Cambridge University. He is Chairman of the UK Bridge Owners Forum and a Fellow of the Transport Research Foundation. His research interests include computational collapse analysis, risk and reliability analysis, computer vision for bridge evaluation, non-destructive testing & inspection and wireless sensor networks for structural health monitoring of bridge performance.

    Kenichi Soga is Professor of Civil Engineering at the University of Cambridge. He studied Civil Engineering at Kyoto University and obtained B.E. and M.E. in 1987 and 1989, respectively. In 1989, he was awarded a 2-year scholarship from the Murata Overseas Scholarship Foundation to continue his study at the University of California at Berkeley. At Berkeley, he worked as a Research Assistant between 1991 and 1994 and was awarded a Ph.D. in 1994. His current research activities are modelling of geotechnical construction processes, development of innovative monitoring techniques and investigation of up-scaling from laboratory to field conditions. He has published more than 180 journal and conference papers. He is co-author of “Fundamentals of Soil Behavior, 3rd edition.” (John Wiley and Sons) with Professor James K. Mitchell. He is recipient of several awards including the George Stephenson Medal from the Institution of Civil Engineers (2006) and the Walter L. Huber Civil Engineering Research Prize from the American Society of Civil Engineers (2007).

    Revision 66 of 2010-02-03 18:30:09 +0100 (Wednesday, 03 Feb 2010).

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    Dr. Hoult, at Cambridge while this research was carried out, is now at Queen’s University, Department of Civil Engineering, Kingston, Ontario, Canada.

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