Abstract: In the current wireless sensor and actuator networks (WSANs),wireless sensor and its service types of transferring information tend to be diversified；at the same time,in the real-time industrial systems,packet drop under the wireless network environment will bring serious damage to the whole system.To improve the reliability of WSANs,this paper proposed an optimal design method for WSANs packet drop detector based on IEEE 802.11e.The method adopts IEEE 802.11e which provides quality of service (QoS) as data communication protocol,deduces WSANs packet drop probability matrix under the protocol,and uses the output of the Luenberger state observer based on the packet drop probability matrix as the decision threshold of packet drop,takes the packet drop in the network as a fault signal,thereby designs a WSANs packet drop detector.The packet drop detector mentioned in this paper not only can effectively determine whether there is a packet drop in the network,but also distinguish the cause of packet drop through the judgment of the fault signal waveform,that is,the sensor node fault,or random packet drop caused by unstable channel environment.Finally,the effectiveness of the proposed design is demonstrated by the results of MATLAB/OMNET+＋hybrid simulations.

Key words: Wireless sensor and actuator networks,IEEE 802.11e,Quality of service,Packet drop detector,Packet drop rate,Fault detection