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University: "Sapienza" University of Rome
Name of Sponsoring Professors: Annalisa Massini
Department: Computer Science

At the University of Rome "La Sapienza", the Computer Networks group is presently using the simulation software OPNET mainly for teaching activities and educational purposes. Some research is in progress in a group of researchers, master students and Ph D students.

The tool has been used to study the problem of mobile sensor deployment and to simulate the behavior of the sensors under different algorithms and communication protocols.

Research

Mobile Sensor Networks

• Autonomous Deployment of Mobile Sensors
• Energy Saving Protocols
• Algorithms for Heterogeneous Sensors

Papers

Snap and Spread: a self-deployment algorithm for mobile sensor networks
N.Bartolini, T. Calamoneri, E. G. Fusco, A. Massini, S. Silvestri
in IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS-2008)

Abstract The use of mobile sensors is motivated by the necessity to monitor critical areas where sensor deployment cannot be performed manually.
In these working scenarios, sensors must adapt their initial position to reach a final deployment which meets some given performance objectives such as coverage extension and uniformity, total moving distance, number of message exchanges and convergence rate.
We propose an original algorithm for autonomous deployment of mobile sensors called Snap & Spread. Decisions regarding the behavior of each sensor are based on locally available information and do not require any prior knowledge of the operating conditions nor any manual tuning of key parameters. We conduct extensive simulations to evaluate the performance of our algorithm. This experimental study shows that, unlike previous solutions, our algorithm reaches a final stable deployment, uniformly covering even irregular target areas. Simulations also give insights on the choice of some algorithm variants that may be used under some different operative settings.

Autonomous deployment of self-organizing mobile sensors for a complete coverage N.Bartolini, T. Calamoneri, E. G. Fusco, A. Massini, S. Silvestri
in Proceedings of the International Workshop on Self-Organizing Systems (IWSOS-2008)

Abstract Mobile sensor networks are important for a number of strategic applications devoted to monitoring critical areas. Coverage completeness and uniformity determine the effectiveness of the sensor deployment. Despite the primary importance of such features, the initial sensor deployment of many applications is neither complete nor uniform, as sensors are sent from a safe location or dropped from an aircraft. The use of mobile sensors permits a dynamic reconfiguration of the sensor deployment. Sensors should coordinate their movements to quickly reach a more satisfactory deployment while minimizing the total traversed distance and the number of message exchanges. Existing distributed solutions either do not guarantee complete coverage or do not lead to a stable deployment. In this paper we propose a fully distributed algorithm for autonomous deployment of mobile sensors called PUSH&PULL, which is based on the interleaved execution of four basic activities. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions nor any manual tuning of key parameters. We prove that, unlike previous proposals, our approach guarantees a complete coverage, provided that a sufficient number of sensors are available. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations. Extensive simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between PUSH&PULL and one of the most acknowledged algorithms show how the former can reach a more uniform and complete coverage under a wide range of working scenarios, with lower energy consumption.

Push and Pull: autonomous deployment of mobile sensors for a complete coverage N. Bartolini, T. Calamoneri, E. G. Fusco, A. Massini, S. Silvestri
in ACM Wireless Networks, accepted for publication, (to appear).

Abstract Mobile sensor networks are important for several strategic applications devoted to monitoring critical areas. In such hostile scenarios, sensors cannot be deployed manually and are either sent from a safe location or dropped from an aircraft. Mobile devices permit a dynamic deployment reconfiguration that improves the coverage in terms of completeness and uniformity.
In this paper we propose a distributed algorithm for the autonomous deployment of mobile sensors called PUSH&PULL. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions or any manual tuning of key parameters.
We formally prove that, when a sufficient number of sensors are available, our approach guarantees a complete and uniform coverage. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations.
Numerous simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between PUSH&PULL and one of the most acknowledged algorithms show how the former one can efficiently reach a more uniform and complete coverage under a wide range of working scenarios.

Autonomous deployment of heterogeneous mobile sensors N.Bartolini, T. Calamoneri, T. La Porta, A. Massini, S. Silvestri
in Proceedings of the IEEE International Conference on Network Protocols (ICNP-2009), Best Paper

Abstract In this paper we address the problem of deploying heterogeneous mobile sensors over a target area. We show how traditional approaches designed for homogeneous networks fail when adopted in the heterogeneous operative setting. Unfortunately, network and device homogeneity is an unrealistic assumption in most practical deployments. In order to deal with realistic scenarios, we introduce Vor_Lag, a generalization of the Voronoi approach based on Laguerre geometry. We theoretically prove the appropriateness of our approach to the management of heterogeneous networks. In addition we demonstrate that Vor_Lag can be extended to deal with dynamically generated events or uneven energy depletion due to communications. Furthermore, by means of simulations, we show that Vor_Lag provides a very stable sensor behavior, with fast and guaranteed termination and moderate energy consumption. We also show that Vor_Lag performs better than other methods based on virtual forces.

On adaptive density deployment to mitigate the sink-hole problem in mobile sensor networks N. Bartolini, T. Calamoneri, A. Massini, S. Silvestri
in ACM/Springer Mobile Networks and Applications, (to appear).

The use of mobile sensors is of great relevance to monitor critical areas where sensors cannot be deployed manually. The presence of data collector sinks causes increased energy depletion in their proximity, due to the higher relay load under multi-hop communication schemes (sink-hole phenomenon). We propose a new approach towards the solution of this problem by means of an autonomous deployment algorithm that guarantees the adaptation of the sensor density to the sink proximity and enables their selective activation. The proposed algorithm also permits a fault tolerant and self-healing deployment, and allows the realization of an integrated solution for deployment, dynamic relocation and selective sensor activation. We formally prove the termination of our algorithm. Performance comparisons between our proposal and previous approaches show how the former can efficiently reach a deployment at the desired variable density with moderate energy consumption under a wide range of operative settings.

Teaching:

• Digital circuit design
• Computer architectures
• Scientific computation

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