<P> Network simulators like OPNET, OMNET, NetSim, NS2 and NS3 can be used to simulate a wireless sensor network . </P> <P> Infrastructure-less architecture (i.e. no gateways are included, etc .) and inherent requirements (i.e. unattended working environment, etc .) of WSNs might pose several weak points that attract adversaries . Therefore, security is a big concern when WSNs are deployed for special applications such as military and healthcare . Owing to their unique characteristics, traditional security methods of computer networks would be useless (or less effective) for WSNs . Hence, lack of security mechanisms would cause intrusions towards those networks . These intrusions need to be detected and mitigation methods should be applied . More interested readers would refer to Butun et al.'s paper regarding intrusion detection systems devised for WSNs . </P> <P> If a centralized architecture is used in a sensor network and the central node fails, then the entire network will collapse, however the reliability of the sensor network can be increased by using a distributed control architecture . Distributed control is used in WSNs for the following reasons: </P> <Ol> <Li> Sensor nodes are prone to failure, </Li> <Li> For better collection of data, </Li> <Li> To provide nodes with backup in case of failure of the central node . </Li> </Ol>

Introduction to sensor network and parallel operating system