Abstract: Based on experiments, the paper analyzed power-exhausting process of a node in event detection wireless sensor networks (WSN). It defined two states dead state and alive state of a node, according to node work limitation. What is more, it proposed a detection method of node sub-death state based on heartbeat mechanism, which employs neighbor node monitoring method to detect if a node is on silent state. With the method, sub-death state was determined by voltage value and restart of a node. A formula of node death was presented. Experiment results show that the method is effective,and the rate or incorrect state judgment is reduced. It supports the applications of event detection WSN.

Key words: Wireless sensor network, Event-detection, Node death, Node sub-death