Wireless Sensor Networks (WSNs) are widely applied to monitor environments such as military surveillance and reconnaissance. However, individual sensor nodes are vulnerable to some types of attacks because they are usually deployed in open and unprotected environments. Once sensor nodes are compromised, malicious nodes can send erroneous data to the base station, and possibly mislead monitoring results and influence the whole networks' effectiveness. We need to find new mechanisms to protect the wireless networks from attacks. In this paper we develop a scheme for malicious node detection based on weighted-trust evaluation. A weight value is assigned to each sensor node initially. It updates every cycle if the node sends different report from the others. A malicious node will be detected when its weight value is lower than a threshold value. The simulation results show that our approach is more effective in detecting malicious nodes with lower misdetection ratio compared with existing schemes.

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Summary In wireless sensor networks, a lot of applications need the sensed information be transmitted to the sink node within a predefined time threshold. So end‐to‐end delay is an important performance metric in wireless sensor networks. Opportunistic routing protocols have been proposed to reduce the waiting delay. In the duty cycle networks, increasing the duty cycle ratio can also reduce the end‐to‐end delay. However, this method will consume more energy. It is obvious that there exists a trade‐off between delay and energy consumption. So adjusting the duty cycle ratio of each node can investigate this trade‐off. To the best of our knowledge, no existing work takes both of end‐to‐end delay and energy efficiency into consideration in the opportunistic routing networks. In this paper, we want to minimize the whole energy consumption while guaranteeing the expected end‐to‐end delay between the source nodes and the sink node is below the given threshold. To deal with this problem, we propose a dynamic duty cycle scheme which can significantly reduce the energy consumption and guarantee the expected end‐to‐end delay demand in the opportunistic routing network. To be specific, firstly, we formulate a new metric with the wake‐up time slots as the variable to measure the end‐to‐end delay. Secondly, for simplifying the complex problem, we decompose it into a set of single‐hop delay guarantee problems. Feedback controller has been used to solve the problem. We also analyze the influence of the multiple receivers in the same forwarding set. Finally, we conduct extensive simulations to evaluate the performance of the proposed algorithm. The experimental results reveal that our scheme can guarantee the delay requirement, meanwhile, significantly reduce the energy consumption compared with prior schemes.

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