Wireless sensor networks (WSNs) are envisioned for a number of application scenarios. Never- theless, the few in-the-field experiences typically focus on the features of a specific system, and rarely report about the characteristics of the target environment, especially with respect to the behavior and performance of low-power wireless communication. The TRITon project, funded by our local administration, aims to improve safety and reduce maintenance costs of road tunnels, using a WSN-based control infrastructure. The access to real tunnels within TRITon gives us the opportunity to experimentally assess the peculiarities of this environment, hitherto not in- vestigated in the WSN field. We report about three deployments: (i) an operational road tunnel, enabling us to assess the impact of vehicular traffic; (ii) a nonoperational tunnel, providing insights into analogous scenarios (e.g., underground mines) without vehicles; (iii) a vineyard, serving as a baseline representative of the existing literature. Our setup, replicated in each deployment, uses mainstream WSN hardware, and popular MAC and routing protocols. We analyze and compare the deployments with respect to reliability, stability, and asymmetry of links, the accuracy of link quality estimators, and the impact of these aspects on MAC and routing layers. Our analysis shows that a number of criteria commonly used in the design of WSN protocols do not hold in tunnels. Therefore, our results are useful for designing networking solutions operating efficiently in similar environments

Abstract. We study the characteristics of the communication links of a wireless sensor network in a tropical cloud forest in Ecuador, in the context of a wildlife monitoring application. Thick vegetation and high humidity are in principle a challenge for the IEEE 802.15.4 radio we employed. We performed experiments with stationary-only nodes as well as in combination with mobile ones. Due to logistics, all the experiments were performed in isolation by the biologists on our team. In addition to discussing the characteristics of links in this previously unstudied environment, we also discuss the lessons we learned from operating under peculiar constraints in a peculiar deployment scenario.

This paper describes the application of a wireless sensor network to a 31 meter-tall medieval tower located in the city of Trento, Italy. The effort is motivated by preservation of the integrity of a set of frescoes decorating the room on the second floor, representing one of most important International Gothic artworks in Europe. The specific application demanded development of customized hardware and software. The wireless module selected as the core platform allows reliable wireless communication at low cost with a long service life. Sensors include accelerometers, deformation gauges, and thermometers. A multi-hop data collection protocol was applied in the software to improve the system's flexibility and scalability. The system has been operating since September 2008, and in recent months the data loss ratio was estimated as less than 0.01%. The data acquired so far are in agreement with the prediction resulting a priori from the 3-dimensional FEM. Based on these data a Bayesian updating procedure is employed to real-time estimate the probability of abnormal condition states. This first period of operation demonstrated the stability and reliability of the system, and its ability to recognize any possible occurrence of abnormal conditions that could jeopardize the integrity of the frescos.

Modeling and prediction of Packet Loss Rate (PLR) of wireless links using hardware information is essential for the design of higher-layer protocols in Wireless Sensor Networks. While many previous studies revealed the spatio-temporal variation of various link quality metrics, how environment impacts on the mapping between PLR and hardware indicators still remains unclear. Without a comprehensive understanding of such environmental impact, the acquired empirical PLR models are severely limited to specific scenarios. In this paper, we present the results of indoor and outdoor experimental campaigns focusing on the impact of various environmental factors (e.g., obstacles, human activities, climate conditions) on the dependency between the link PLR, signal to noise ratio (SNR) and packet length. Rich observations are made on the spatio-temporal characteristics of the PLR-SNR relationship and our analysis shows that link PLR can be modeled, in all experimented scenarios, as an exponential function of SNR and packet length with two model parameters that may vary over space and time. Besides, implications of the observations are summarized, providing guidelines to construct and adapt PLR models in different environments.

One reasonable categorization of coordination models is into data sharing or message passing, based on whether the information necessary to coordination is persistently stored and shared, or instead is only transiently available during communication. Generally speaking, approaches based on data sharing are more expressive and provide full decoupling in space and time. The alternative approach requires the simultaneous presence of the coordinated parties, but is typically more scalable. Prominent examples are, respectively, tuple spaces and publish-subscribe.An open research question is whether it is possible to exploit in synergy the best of these two approaches, e.g. by implementing the more complex data sharing coordination on top of the more lightweight message passing one. In this paper, we seek an answer to this question in a pragmatic way: we analyze an implementation of the LIME tuple space middleware on top of REDS, an open source publish-subscribe system. Our implementation-driven style of investigation forces us to face details that do not surface when reasoning in the abstract about the nature and expressiveness of the models. We report about lessons we learned in this experience, and propose an extension to the publish-subscribe model that, albeit useful per se, constitutes a more effective foundation for data sharing coordination models.