Integrated approach to electrode and AlN depositions for bulk acoustic wave (BAW) devices

This paper investigates the (002) texture of AlN films deposited by reactive pulsed direct current sputtering on Al, Al–Cu, W and Mo metal electrodes. X-Ray diffraction and atomic force microscopy studies show that the AlN texture is dependent on the deposition conditions and nature of the underlayers. A smooth underlayer with a sharp texture represents the best combination of properties. AlN films with a full width at half maximum less than 1.5 have been deposited on the electrodes studied. It is also possible to deposit well-textured electrodes with a roughness less than 2.5 nm.     

Energy-efficient node deployment strategy for wireless sensor networks

To balancing energy consumption in wireless sensor networks, we proposed a fixed time interval node broadcasting scheme under variational acceleration straight-line movement model. Simulation results show that the approach proposed in this paper has a superior performance on energy consumption balance compared to uniform broadcasting methods.     

无线传感器网络节点应用的硬件设计

针对无线传感器网络技术引入到矿下安全监测中,首先分析了无线传感器网络的结构、特点及研究重点,提出了无线传感器网络节点的整体设计方案.介绍了传感器的选择和处理器、通信器件的选择,并将硬件分为数据采集单元、数据处理单元和数据传输单元进行详细的说明.     

基于RSSI的传感器网络节点安全定位机制

针对RSSI测距存在的脆弱性问题,提出了一种基于完整性编码和不间断占用信道的安全RSSI测距协议,该协议不仅可以抵抗伪造插入、重放/虫洞等常规攻击,而且可以防止信标信号被恶意干扰而削弱,即可抵抗虚增测距的外部攻击。在此基础上,设计了一种基于RSSI的传感器网络节点安全定位机制,该机制采用可校验的多边测量法来过滤虚减测距的外部攻击,实现安全定位,并对测距协议和定位机制的安全性进行了理论分析。     

距离辅助的无线传感器网络节点覆盖判别模型

提出了距离辅助的节点覆盖判别模型DANCI(distance-assistant node coverage identification model),通过邻居节点到本节点的距离信息,判别该节点被邻居节点覆盖的程度.理论分析与仿真结果表明,在节点随机部署情况下,计算所得的覆盖度与节点位置已知情况下,其覆盖度的最大误差仅为6.396 0%.相对于邻居节点个数与最近邻居距离覆盖判别方法,极大提高了覆盖判别的精确性.     

无线传感器网络节点定位技术综述

无线传感器网络在许多领域有着重要的科研和使用价值,网络中传感器节点自身定位可为无线传感器网络的很多应用提供基础信息,是重要研究方向之一.从无线传感器网络节点定位技术的研究意义与应用价值出发,介绍了节点定位技术的基本原理与方法,并讨论了定位算法的评价标准,最后对节点定位技术的发展方向进行了展望.     

无线传感器网络的中继节点自适应选择休眠机制

针对无线传感器网络节点能量有限的问题,设计一种中继节点自适应休眠方法,对网络节点的工作时间进行优化调度。在路由链路建立中,根据网络中节点的地理位置、剩余能量选择中继节点的方法进行节点休眠调度。网络工作时通过计算下一跳最佳节点位置,选取其附近区域内剩余能量多的节点作为下一跳的转发节点,设计出中继节点自适应选择的节点休眠机制。仿真结果表明,所设计的休眠机制提高了节点能量利用效率、延长了网络工作时间。     

Dynamic clustering for acoustic target tracking in wireless sensor networks

We devise and evaluate a fully decentralized, light-weight, dynamic clustering algorithm for target tracking. Instead of assuming the same role for all the sensors, we envision a hierarchical sensor network that is composed of 1) a static backbone of sparsely placed high-capability sensors which assume the role of a cluster head (CH) upon triggered by certain signal events and 2) moderately to densely populated low-end sensors whose function is to provide sensor information to CHs upon request. A cluster is formed and a CH becomes active, when the acoustic signal strength detected by the CH exceeds a predetermined threshold. The active CH then broadcasts an information solicitation packet, asking sensors in its vicinity to join the cluster and provide their sensing information. We address and devise solution approaches (with the use of Voronoi diagram) to realize dynamic clustering: (I1) how CHs operate with one another to ensure that only one CH (preferably the CH that is closes to the target) is active with high probability, (I2) when the active CH solicits for sensor information, instead of having all the sensors in its vicinity reply, only a sufficient number of sensors respond with nonredundant, essential information to determine the target location, and (I3) both the packets that sensors send to their CHs and packets that CHs report to subscribers do not incur significant collision. Through both probabilistic analysis and ns-2 simulation, we use with the use of Voronoi diagram, the CH that is usually closes to the target is (implicitly) selected as the leader and that the proposed dynamic clustering algorithm effectively eliminates contention among sensors and renders more accurate estimates of target locations as a result of better quality data collected and less collision incurred.     

Anchor node path planning for localization in wireless sensor networks

Wireless Networks - Localization is one of the most important challenges of wireless sensor networks because the location information is typically used in other domains such as coverage,...     

Efficient reporting node selection-based MAC protocol for wireless sensor networks

Wireless sensor networks rely on the cooperative effort of the densely deployed sensor nodes to report the detected events. As a result, sensor observations are highly correlated in the space domain. Typically, multiple sensor nodes may report the same event. Consequently, redundant information may be transmitted by the different sensor nodes, leading thus to unnecessary energy wastage. In this paper, we investigate the relationship between the spatial correlation and the number of reporting nodes by developing a new analytical model based on the theoretical framework of the CC-MAC (correlation-based collaborative medium access control) protocol (Vuran and Akyildiz in IEEE/ACM Trans Netw 14(2): 316–32912006). We show that the reporting task can be delegated to a small subset of sensor nodes without transgressing the distortion constraint. Building on this result, a simple spatial correlation medium access control protocol is then proposed to achieve further energy conservation and faster reporting latency than CC-MAC.     

无线传感器网络节点定位技术

无线传感器网络(Wireless Sensor Network,WSN)在许多领域有广泛的应用,无线传感器网络中节点位置对无线传感器网络的应用有重要的影响,没有位置属性的信息是无价值的,定位技术是无线传感器网络的重要研究方向之一。依据测距和非测距的分类方法,介绍节点定位技术的基本原理和方法及当前的发展状况,最后对节点定位技术的发展方向作展望。     

无线传感器网络节点定位技术

无线传感器网络（Wireless Sensor Network,WSN）在许多领域有广泛的应用,无线传感器网络中节点位置对无线传感器网络的应用有重要的影响,没有位置属性的信息是无价值的,定位技术是无线传感器网络的重要研究方向之一.依据测距和非测距的分类方法,介绍节点定位技术的基本原理和方法及当前的发展状况,最后对节点定位技术的发展方向作展望.     

Localization under anchor node uncertainty for underwater acoustic sensor networks

This paper deals with the problem of sensor node localization in the presence of uncertainty in anchor node location. Aqueous environments are prone to adverse effects of underwater currents. This adversity causes non‐negligible mobility to the anchor nodes deployed under water. Localization in the presence of uncertainty in the anchor node location is quite challenging. Also, the authors consider the ray‐bending property of underwater medium due to depth dependent sound speed, to furnish the accurate position estimate of the target node. Standard ray equations are used to model the path followed by acoustic rays in water. Maximum likelihood estimation is proposed to estimate the location of target node with uncertainty in anchor node positions and is compared with the scheme with exact knowledge of anchor node positions, and the results are reported. Monte Carlo simulation is used to assess the performance of the proposed method. Also, the Cramer‐Rao lower bound with uncertainty in anchor nodes is derived and described. Simulation results of the proposed algorithm outperform the existing algorithm with known anchor location by up to 49.4%, and hence, accuracy is improved in the proposed method.     

A collaborative node management scheme for energy-efficient monitoring in wireless multimedia sensor networks

Clustering in sensor networks provides energy conservation, network scalability, topology stability, reducing overhead and also allows data aggregation and cooperation in data sensing and processing. Wireless Multimedia Sensor Networks are characterized for directional sensing, the Field of View (FoV), in contrast to scalar sensors in which the sensing area usually is more uniform. In this paper, we first group multimedia sensor nodes in clusters with a novel cluster formation approach that associates nodes based on their common sensing area. The proposed cluster formation algorithm, called Multi-Cluster Membership (MCM), establishes clusters with nodes that their FoVs overlap at least in a minimum threshold area. The name of Multi-Cluster Membership comes from the fact that a node may belong to multiple clusters, if its FoV intersects more than one cluster-head and satisfies the threshold area. Comparing with Single-Cluster Membership (SCM) schemes, in which each node belongs to exactly one cluster, because of the capability of coordination between intersected clusters, MCM is more efficient in terms of energy conservation in sensing and processing subsystems at the cost of adding complexity in the node/cluster coordination. The main imposed difficulty by MCM, is the coordination of nodes and clusters for collaborative monitoring; SCMs usually assign tasks in a round-robin manner. Then, as second contribution, we define a node selection and scheduling algorithm for monitoring the environment that introduces intra and inter-cluster coordination and collaboration, showing how the network lifetime is prolonged with high lifetime prolongation factors particularly in dense deployments.     

A low‐cost node capture attack algorithm for wireless sensor networks

Wireless sensor networks (WSNs) have many micro devices that are easy to capture. In node capture attacks, the adversary physically captures sensors and extracts all information including key information from their memories, trying to compromise the system's security protection. However, the robust and random nature of many WSN security designs makes it difficult to compromise the system even with the capture of some sensors. In this paper, we approach WSN security from an adversarial point of view and investigate low‐cost and efficient algorithms to identify sensors in a WSN in the shortest time with the lowest cost. Instead of randomly capturing sensors, an intelligent attacker should choose the next target based on the known topology so far. Because the identification of such has been proven to be NP‐hard (non‐deterministic polynomial‐time hard), we propose to transform the problem into a set covering problem and develop a greedy minimum cost node capture attack algorithm (MCA) to lower cost of attack. Extensive simulations have been implemented to evaluate the performance of MCA and to compare it with several related schemes. It is shown that MCA lowers the cost of compromising WSNs by 16%. Copyright © 2015 John Wiley & Sons, Ltd.     

Strategies and techniques for node placement in wireless sensor networks: A survey

The major challenge in designing wireless sensor networks (WSNs) is the support of the functional, such as data latency, and the non-functional, such as data integrity, requirements while coping with the computation, energy and communication constraints. Careful node placement can be a very effective optimization means for achieving the desired design goals. In this paper, we report on the current state of the research on optimized node placement in WSNs. We highlight the issues, identify the various objectives and enumerate the different models and formulations. We categorize the placement strategies into static and dynamic depending on whether the optimization is performed at the time of deployment or while the network is operational, respectively. We further classify the published techniques based on the role that the node plays in the network and the primary performance objective considered. The paper also highlights open problems in this area of research.     

非均匀分布下无线传感器网络节点调度机制

针对传统依赖精确位置信息的计算复杂和无位置信息部署受限性等弊端,从理论上对节点部署方式进行分析,提出一种非均匀分布下的无线传感器网络节点调度NDNS(non-uniform distribution node scheduling)机制,该机制利用节点与邻居节点的距离信息,对节点覆盖冗余进行判别,适应于任意分布下的网络部署方式。通过实验对机制进行了性能分析和验证,结果表明该方案在保证网络覆盖的前提下,有效地延长了网络生存时间。     

声无线传感网络节点数据高速存储实现

无线传感网络是现代信息技术的融合,随着无线传感网络的广泛使用,以及每一个节点采集数据量的不断增大,为保证数据处理与传输速度的匹配,需要在一定时间内进行数据存储,同时也为后续数据分析提供了保证。通过流水线技术和交错双平面页编程技术实现了对NAND 型FLASH的高速存储。在理论分析下,最高可以达到40MB/s的数据存储。试验中增加冗余以30MB/s的速度进行存储,结果表明存储和读取数据正确,并且整个系统可靠、稳定。     

无线传感器网络恶意节点定位综述

无线传感器网络是近年来研究比较热门的课题,无线传感器网络的应用十分广阔,从军事到农业物联网,无线传感器网络起到了重要作用。但是网络中恶意节点行为也为其带来很大的风险,无论是外部恶意节点还是内部被俘节点都对无线传感器网络产生巨大危害,该文章从恶意节点定位的特点和研究现状出发,分析了目前国内外主要的恶意节点定位的方法和模型。为以后进一步改进定位提供参考。