The creation of a sensors network for environmental monitoring, taking into account the functional and non-functional requirements, poses a series of problems that must be dealt with during the design phase. The main difficulties are related to the power of the nodes and their location so that the resulting network topology minimizes the overall energy consumption while guaranteeing the desired measurement accuracy. The adoption of a ''wireless'' communication model allows for greater flexibility during installation and allows creating remote connections more easily than the traditional wired pattern. Extension of the network topology by add ing new devices in the monitoring area or movement of devices already deployed are greatly simplified. But the requirements in terms of fault-tolerance and power consumption of a wireless network are in general more difficult to meet. In this chapter we propose two different solutions that improve performance in terms of power consumption of the main standard for communication in wireless sensor networks field (e.g. ZigBee) customizing it for monitoring applications in an open environment on geographical areas of several hectares. While the standard is intended to be as general as possible, optimizations have been included considering the special needs of our monitoring applications, in terms of number of nodes, topology density, nodes duty cycle and data-load. The first solution deals with the management of multi-hop communication and allows the use of devices that can be powered by batteries (and possibly small solar panels) for the relaying nodes. The second solution optimizes the management of faults (transient or permanent) in the network topology. It is rarely possible to develop and evaluate proposed solutions in the field prior to actual deployment, therefore simulation is an essential step in developing solutions for these applications. The simulation must be accurate and must provide an analysis of all issues related to communication and the behavioural dynamics of the single node in the network structure. For this reason the evaluation has been carried out by means of a modelling methodology developed expressly for wireless sensor networks.
MIARIA: Techologia e Conoscenza al Servizio della Sicurezza