Fault Tolerance Events Ordering with Coverage and Connectivity Aware Clustering in Wireless Sensor and Actuator Networks

Fault Tolerance Events Ordering with Coverage and Connectivity Aware Clustering in Wireless Sensor and Actuator Networks

A network delay or a fail link is prone to be occurred in wireless sensor and actuator networks (WSAN). Since the events captured by sensors are related to others, events ordering is an vital issue in WSAN. However, it is hard to guarantee that no prior event is transmitted while the latter events arrive at actuator in network. While a fail link is occurred, it could be assumed as a special case that the delay is set to infinity. Event ordering by double confirmation (OBDC) was a typical events ordering while a network delay was occurred. Fault tolerance events ordering by aging learning (FTEOAL) was a typical events ordering mechanism while a fail link existed. However, both of them assumed that sensors were all covered by one actuator and none of them was the orphan sensor. Once a sensor was noncovered by an actuator or an orphan sensor existed, the rate of correct events ordering will decrease. Therefore, in this paper, we proposed a fault tolerance events ordering with coverage and connectivity aware clustering, FTEOCCAC. The simulation results demonstrated that events were treated in correct order even if the sensors are deployed randomly or an orphan sensor existed while a network delay or a fail link existed in network. The rate of correct events ordering could be closed to the expect value.