Georgios Mylonas

WISEBED: An Open Large-Scale Wireless Sensor Network Testbed

In this paper we present an overview of WISEBED, a large-scale wireless sensor network testbed, which is currently being built for research purposes. This project is led by a number of European Universities and Research Institutes, hoping to provide scientists, researchers and companies with an environment to conduct experiments with, in order to evaluate and validate their sensor network-related work. The initial planning of the project includes a large, heterogeneous testbed, consisting of at least 9 geographically disparate networks that include both sensor and actuator nodes, and scaling in the order of thousands (currently being in total 550 nodes). We present here the overall architecture of WISEBED, focusing on certain aspects of the software ecosystem surrounding the project, such as the Open Federation Alliance, which will enable a view of the whole testbed, or parts of it, as single entities, and the testbed’s tight integration with the Shawn network simulator. We also present examples of the actual hardware used currently in the testbed and outline the architecture of two of the testbed’s sites.

A new energy efficient and fault-tolerant protocol for data propagation in Smart Dust networks using varying transmission range

In this work we propose a new energy efficient and fault tolerant protocol for data propagation in wireless sensor networks, the variable transmission range protocol (VTRP). The basic idea of data propagation in VTRP is the varying range of data transmissions, i.e., we allow the transmission range to increase in various ways. Thus data propagation in our protocol exhibits high fault-tolerance (by bypassing obstacles or faulty sensors) and increases network lifetime (since critical sensors, i.e. close to the control center are not overused). As far as we know, it is the first time varying transmission range is used. We implement the protocol and perform an extensive experimental evaluation and comparison to a representative protocol (LTP) of several important performance measures with a focus on energy consumption. Our findings indeed demonstrate that our protocol achieves significant improvements in energy efficiency and network lifetime.

50 ways to build your application: A survey of middleware and systems for Wireless Sensor Networks

In this paper, we survey the current state-of-the-art in middleware and systems for Wireless Sensor Networks (WSN). We provide a discussion on the definition ofWSN middleware, design issues associated with it, and the taxonomies commonly used to categorize it. We also present a categorization of a number of such middleware platforms, using middleware functionalities and challenges which we think will play a crucial role in developing software for WSN in the near future. Finally, we provide a short discussion on WSN middleware trends.

Energy efficient protocols for sensing multiple events in Smart Dust networks

Wireless sensor networks are comprised of a vast number of ultra-small, autonomous computing and communication devices, with restricted energy, that cooperate to accomplish a large sensing task. In this work: a) we propose extended versions of two data propagation protocols for such networks: the sleep-awake probabilistic forwarding protocol (SW-PFR) and the hierarchical threshold sensitive energy efficient network protocol (H-TEEN). These non-trivial extensions improve the performance of the original protocols, by introducing sleep-awake periods in the PFR protocol to save energy, and introducing a hierarchy of clustering in the TEEN protocol to better cope with large networks; b) we implemented the two protocols and performed an extensive simulation comparison of various important measures of their performance with a focus on energy consumption; c) we investigate in detail the relative advantages and disadvantages of each protocol; and d) we discuss a possible hybrid combination of the two protocols towards optimizing certain goals.

Developing an IoT Smart City framework

In this paper, we discuss key findings, technological challenges and socioeconomic opportunities in Smart City era. Most of the conclusions were gathered during SmartSantander project, an EU project that is developing a city-scale testbed for IoT and Future Internet experimentation, providing an integrated framework for implementing Smart City services.

jWebDust: a Java-based generic application environment for wireless sensor networks

Wireless sensor networks can be very useful in applications that require the detection of crucial events, in physical environments subjected to critical conditions, and the propagation of data reporting their realization to a control center. In this paper we propose jWebDust, a generic and modular application environment for developing and managing applications that are based on wireless sensor networks. Our software architecture provides a range of services that allow to create customized applications with minimum implementation effort that are easy to administrate. We move beyond the ”networking-centric” view of sensor network research and focus on how the end user (administrator, control center supervisor, etc.) will visualize and interact with the system. We here present its open architecture, the most important design decisions, and discuss its distinct features and functionalities. jWebDust allows heterogeneous components to interoperate (real world sensor networks will rarely be homogeneous) and allows the integrated management and control of multiple such networks by also defining web-based mechanisms to visualize the network state, the results of queries, and a means to inject queries in the network. The architecture also illustrates how existing protocols for various services can interoperate in a bigger framework – such as the tree construction, query routing, etc.

Virtualising testbeds to support large-scale reconfigurable experimental facilities

Experimentally driven research for wireless sensor networks is invaluable to provide benchmarking and comparison of new ideas. An increasingly common tool in support of this is a testbed composed of real hardware devices which increases the realism of evaluation. However, due to hardware costs the size and heterogeneity of these testbeds is usually limited. In addition, a testbed typically has a relatively static configuration in terms of its network topology and its software support infrastructure, which limits the utility of that testbed to specific case-studies. We propose a novel approach that can be used to (i) interconnect a large number of small testbeds to provide a federated testbed of very large size, (ii) support the interconnection of heterogeneous hardware into a single testbed, and (iii) virtualise the physical testbed topology and thus minimise the need to relocate devices. We present the most important design issues of our approach and evaluate its performance. Our results indicate that testbed virtualisation can be achieved with high efficiency and without hindering the realism of experiments.

TRAILS, a Toolkit for Efficient, Realistic and Evolving Models of Mobility, Faults and Obstacles in Wireless Networks

We present a new simulation toolkit called TRAILS (Toolkit for Realism and Adaptivity In Large-scale Simulations), which extends the ns-2 simulator by adding important functionality and optimizing certain critical simulator operations. The added features provide the tools to study wireless networks of high dynamics. TRAILS facilitates the implementation of advanced mobility patterns, obstacle presence and disaster scenarios, and failures injection that can dynamically change throughout the execution of the simulation. Moreover, we define a set of utilities that enhance the use of ns-2. This functionality is implemented in a simple and flexible architecture, that follows design patterns, object oriented and generic programming principles, maintaining a proper balance between reusability, extendability and ease of use. We evaluate the performance of TRAILS and show that it offers significant speed-ups regarding the execution time of ns-2 in certain important, common wireless settings. Our results also show that this is achieved with minimum overhead in terms of memory usage.

Modeling and evaluation of the effect of obstacles on the performance of wireless sensor networks

In this work, we propose an obstacle model to be used while simulating wireless sensor networks. To the best of our knowledge, this is the first time such an integrated and systematic obstacle model appears. We define several types of obstacles that can be found inside the deployment area of a wireless sensor network and provide a categorization of these obstacles, based on their nature (physical and communication obstacles), their shape, as well as their nature to change over time. In light of this obstacle model, we conduct extensive simulations in order to study the effects of obstacles on the performance of representative data propagation protocols for wireless sensor networks. Our findings show that obstacle presence has a significant impact on protocol performance. Also, we demonstrate the effect of each obstacle type on different protocols, thus providing the network designer with advice on which protocol is best to use.

Implementing multiplayer pervasive installations based on mobile sensing devices: Field experience and user evaluation from a public showcase

In this work we discuss Fun in Numbers, a software platform for implementing multiplayer games and interactive installations, that are based on the use of ad hoc mobile sensing devices. We utilize a detailed log of a three-day long public showcase as a basis to discuss the implementation issues related to a set of games and installations, which are examples of this unique category of applications, utilizing a blend of technologies. We discuss their fundamental concepts and features, also arguing that they have many aspects and potential uses. The architecture of the platform and implementation details are highlighted in this work, along with detailed descriptions of the protocols used. Our experiments shed light on a number of key issues, such as network scaling and real-time performance, and we provide experiments regarding cross-layer software issues. We additionally provide data showing that such games and installations can be efficiently supported by our platform, with as many as 50 concurrent players in the same physical space. These results are backed up by a user evaluation study from a large sample of 136 visitors, which shows that such applications can be seriously fun.