Modeling and Assessing the Dependability of Wireless Sensor Networks

This paper proposes a flexible framework for dependability modeling and assessing of Wireless Sensor Networks (WSNs). The framework takes into account network related aspects (topology, routing, network traffic) as well as hardware/software characteristics of nodes (type of sensors, running applications, power consumption). It is composed of two basic elements: i) a parametric Stochastic Activity Networks (SAN) failure model, reproducing WSN failure behavior as inferred from a detailed Failure Mode Effect Analysis (FMEA), and ii) an external library reproducing network behavior on behalf of the SAN model. This library specializes the SAN model by feeding it with quantitative parameters obtained by simulation or by experimental campaigns; it is also in charge of updating the network state in response to failure events during the simulation (e.g., routing tree updated due to node failures). The framework is thus suited to evaluate the dependability of several WSNs, with different topologies, routing algorithms, hardware/software platforms, without requiring any changes to its structure. The use of the external library makes the model simpler, decoupling the network behavior from the failure behavior. Simulation experiments are discussed that provide a quantitative evaluation of WSN dependability for a sample scenario: results show how the proposed framework supports WSN developers to find proper cost-reliability trade-offs for the system being deployed.