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Earth dams or embankments are susceptible to instability due to internal seepage, piping, and erosion, which can lead to catastrophic failure. Therefore, monitoring the seepage water level before the dam collapses is an important task for early warning of dam failure. Currently, there are hardly any monitoring methods that use wireless underground transmission to monitor the water content inside earth dams. Real-time monitoring of changes in the soil moisture content can more directly determine the water level of seepage. Wireless transmission of sensors buried underground requires signal transmission through the soil medium, which is more complex than traditional air transmission. Henceforth, this study establishes a wireless underground transmission sensor that overcomes the distance limitation of underground transmission through a hop network. A series of feasibility tests were conducted on the wireless underground transmission sensor, including peer-to-peer transmission tests, multi-hop underground transmission tests, power management tests, and soil moisture measurement tests. Finally, field seepage tests were conducted to apply wireless underground transmission sensors to monitor the internal seepage water level before an earth dam failure. The findings show that wireless underground transmission sensors can achieve the monitoring of seepage water levels inside earth dams. In addition, the results supersede those of a conventional water level gauge. This could be crucial in early warning systems during the era of climate change, which has caused unprecedented flooding events. [ABSTRACT FROM AUTHOR]

Replica attack is a critical concern in the security of wireless sensor networks. We employ mobile nodes as patrollers to detect replicas distributed in different zones in a network, in which a basic patrol detection protocol and two detection algorithms for stationary and mobile modes are presented. Then we perform security analysis to discuss the defense strategies against the possible attacks on the proposed detection protocol. Moreover, we show the advantages of the proposed protocol by discussing and comparing the communication cost and detection probability with some existing methods.

To solve the problems of limited energy of the nodes and security of routing in wireless sensor networks, load-balanced secure routing protocol (LSRP), a load-balanced secure routing protocol for wireless sensor networks, is proposed. Based on structured topology of hexagonal mesh, hops at different directions are calculated on the optimal route for transmitting data packets in LSRP. Depending on characters of hops, the nodes can rapidly find a route among multiple optimal routes by the policy of the twice probability routing selection. Data breach is prevented by data encryption, and data security is realized by one-way hash key chain and symmetric key authentication. LSRP offers preventions against usual attacks, and it also takes into account traffic load balance. Analysis and simulation results show that LSRP has better performance on traffic load balance and security. [ABSTRACT FROM AUTHOR]

Replica attack is a critical concern in the security of wireless sensor networks. We employ mobile nodes as patrollers to detect replicas distributed in different zones in a network, in which a basic patrol detection protocol and two detection algorithms for stationary and mobile modes are presented. Then we perform security analysis to discuss the defense strategies against the possible attacks on the proposed detection protocol. Moreover, we show the advantages of the proposed protocol by discussing and comparing the communication cost and detection probability with some existing methods. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are often deployed in hostile and unattended environments. The nodes will be failure by fault, intrusion, and the battery exhaustion. Node-failure tolerance is an acceptable method to improve the networks' lifetime. Then two key problems for topology control are presented: first, how to get a node-failure topology when there is intrusion from the nodes of hostile enemies? second, how to sustain this node-failure topology with all deployed nodes being exhausted ultimately? We propose a novel approach for topology control and prove that it is node-failure tolerant. The approach contains three phases: topology discovery, topology update, and topology regeneration. A tricolor-based method is proposed to build architecture with high tolerance ability and some security protocols are employed to preclude the hostile nodes in discovery phase. In update and regeneration phases, the newly deployed nodes are regarded as renewable resource to fill in the consumed energy, enhance the debased node-failure tolerance ability, and prolong network lifetime, and a security protocol with forward and backward secrecy is devised to adapt the topology changed by node failure and node joining. Some attributes of the presented method are shown by simulations, and differences are given by comparison with related work. [ABSTRACT FROM AUTHOR]

The advent of sensor-cloud technology alleviates the limitations of traditional wireless sensor networks (WSNs) in terms of energy, storage, and computing, which has tremendous potential in various agricultural internet of things (IoT) applications. In the sensor-cloud environment, virtual sensor provisioning is an essential task. It chooses physical sensors to create virtual sensors in response to the users' requests. Considering the capricious meteorological environment of the outdoors, this paper presents an measurements similarity-based virtual-sensor provisioning scheme by taking advantage of machine learning in data analysis. First, to distinguish the changing trends, we classified all the physical sensors into several categories using historical data. Then, the k-means clustering algorithm was exploited for each class to cluster the physical sensors with high similarity. Finally, one representative physical sensor from each cluster was selected to create the corresponding virtual sensors. The experimental results show the reformation of our scheme with respect to energy efficiency, network lifetime, and data accuracy compared with the benchmark schemes. [ABSTRACT FROM AUTHOR]