Availability Modeling and Analysis of Autonomous In-Door WSNs

Availability analysis and modeling in autonomous and remotely administered systems that are composed of cheap and failure-prone components is vital to redundancy management, which includes the prediction of the required number of components and the way these components are scheduled ON and OFF. Targeting the application of wireless sensor networks for the monitoring of elder people living in their apartments, we use techniques from reliability theory to model the WSN as a kappa-out-of m system with independent components. In addition to predicting the required redundancy to meet the desired availability behavior early in the planning phase, we show that scheduling these nodes ON and OFF later on in the operational phase does indeed improve availability over the entire system lifetime. To validate our model, we design a simulator using nesC/TOSSIM. Our analytical and experimental results show that using node scheduling almost doubles the expected WSN total uptime.