一种无线传感器网络实际环境测试系统

为实现无线传感器网络(WSNs)在实际环境下的综合性能测试,提出了一种无线传感器网络测试系统。系统采用全实物布置策略,以基于Linux操作系统的测试床为核心;支持多个节点和异构节点的通用测试,能够满足大规模、通用性和可扩展性需求;功能丰富,支持对节点的在线编程、电源控制以及状态监测。     

异构无线传感器网络中异构节点的部署与优化

在无线传感器网络中适当地部署少量的异构传感器节点能够有效地延长网络寿命,提高网络的可靠性.本文主要研究无线传感器网络中异构节点的部署问题,提出了基于选址问题的异构节点部署算法,以优化无线传感器网络中异构节点的数量和位置.与其它算法相比,该算法对无线传感器网络的拓扑结构没有特定的要求,可以支持随机部署或人工部署的各种传感器网络,最后还给出了该算法的仿真测试结果.     

基于零打扰测试背板的无线传感器网络测试平台

精确的网络运行状态监视和性能评估对于无线传感器网络的研究和实际部署具有极为关键的意义,而现有的测试技术和测试平台对无线传感器网络的自身运行存在一定的打扰,测试数据的精度也受限于传感器节点的硬件配置.针对现有测试技术和测试平台的缺陷,提出了内部侦听的测试方式,并进一步研发了基于零打扰测试背板的无线传感器网络测试平台.测试平台首先通过由额外的测试背板直接捕获传感器节点内部互连信号,产生测试数据;然后测试数据经由额外的传输网络传送到测试服务器,进行解析和预处理;最后,远程访问客户端通过订阅机制访问测试服务器上的测试数据,并对其分析和处理.测试平台在避免对无线传感器网络正常运行产生干扰的前提下,实现对运行时刻的无线传感器网络的高精度零打扰的透明测试.实验结果表明,基于零打扰测试背板的无线传感器网络测试平台可以对无线传感器网络进行信号分析、协议验证,并对性能进行精确的评估,     

基于Modbus协议的无线传感器网络网关设计

针对异构网络通信协议的融合问题,设计了一种无线传感器网络网关.网关通过Wi-Fi接入公共网络,采用ZigBee、蓝牙、Wi-Fi三种无线通信技术组建感知网络,以实现用户远程访问和控制传感器网络节点的功能.提出以Modbus协议规范作为不同类型网络间应用层协议转换的统一标准,屏蔽了异构网络通信协议数据格式的差异,改善了网关的可扩展性.在以ARM处理器为核心的硬件平台上,运用嵌入式编程实现网关功能.经测试,无线传感器网络网关运行稳定高效,满足多数应用场合的实时性要求.     

低功耗无线传感器网络节点的设计

在对无线传感器(WSNS)网络体系结构、传感器节点的特点、功能分析的基础上,给出了无线传感器网络节点的软硬件低功耗设计与实现方案.传感器节点以低功耗嵌入式处理器MSP430F1611为核心,TinyOS为嵌入式实时操作系统,配以基于IEEE 802.15.4的MAC层协议的无线传输模块作为网络数据出口以及CC2420无线收发器,可以实现高速的数据采集和可靠的数据传送,能够较好地达到低功耗和实时性的要求.测试结果证明:该平台适合节点的应用,具有易使用、低功耗特点.     

基于DS证据理论的无线传感器网络MAC层安全研究*

研究了无线传感器网络MAC层安全问题,分析了现有无线传感器网络MAC层协议安全体系的不足之处,针对无线传感器网络遭到非法入侵的情况,提出了一个基于D-S证据理论的MAC层入侵检测机制。该机制利用碰撞率、数据包平均等待时间、RTS包到达率以及邻居节点的报警作为证据,对网络的状态进行实时的分析检测,根据网络的状态作出响应。该算法能够应用于现有的MAC协议如S-MAC、IEEE 802.15.4中,仿真结果表明,该算法能够较好地抵御针对MAC层的攻击,保证网络的安全运行。     

无线传感器节点定位功能测试平台

建模测试对无线传感器网络的研究以及相关商用产品的开发起着至关重要的作用.描述了用于监控无线传感器节点定位功能的测试平台的工作过程,构建了基于ARM嵌入式系统的无线传感器网络.采用相对定位方法,确定网络内各节点的相对位置,降低误差,以符合精度要求.分析了在μC/OS-Ⅱ操作系统的调度下,传感器节点利用GPS模块进行相对定位的流程,并对网络状态的显示界面作了相应介绍.利用该平台对传感器网络进行测试,所得定位数据符合实际情况,获得了预期的结果.     

ZigBee 无线传感器网络节点能耗模型研究

针对当前无线传感器网络能耗模型计算复杂、通用性差及理论模型与实际相差较大等问题,提出一种 ZigBee 无线传感器网络节点的能耗模型。采用无线传感器网络节点工作电压、发送状态、接收状态中各阶段的时长和工作电流以及休眠状态的工作电压和工作电流等参数,建立无线传感器网络节点处于发送状态、接收状态和休眠状态的能耗数学模型,进而建立无线传感器网络节点的总能耗数学模型。实验结果表明,该模型能够准确预测无线传感器网络节点传输能耗代价和剩余工作寿命。     

能量异构的无线传感器网络分簇协议

无线传感器网络分簇协议通常假定网络是同构的,即网络中所有节点具有相同的初始能量,这些协议不能充分利用异构网的特点。提出了一种适合于异构网的分布式分簇协议(EHCP),该协议优先选择剩余能量较多的节点作为簇首以平衡节点的能量,并在簇间采用多跳通信以节省能量。仿真实验结果表明:与同类协议相比,EHCP协议能显著地延长网络稳定工作的时间,具有良好的性能。     

基于多蚁群算法的无线传感器网络路由的跨层设计

针对事件驱动型无线传感器网络对数据传输的强实时性和高可靠性的要求,将统计获得的节点接入效率和负载队列长度等MAC层状态信息作为路由度量参数。考虑到蚂蚁网络算法在重负荷网络中存在传输延迟大、聚合速度慢等缺陷,提出了一种基于多蚁群算法的负载感知和高效接入的跨层路由协议,该协议把节点的单跳延迟、负载及带宽接入效率等参数作为路径的启发值进行路由优化。仿真结果表明,基于多蚁群算法的路由协议能够保证数据传输的实时性,能够实现无线传感器网络的拥塞控制及负载平衡。     

Efficient allocation of resources in multiple heterogeneous Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are useful for a wide range of applications, from different domains. Recently, new features and design trends have emerged in the WSN field, making those networks appealing not only to the scientific community but also to the industry. One such trend is the running different applications on heterogeneous sensor nodes deployed in multiple WSNs in order to better exploit the expensive physical network infrastructure. Another trend deals with the capability of accessing sensor generated data from the Web, fitting WSNs in novel paradigms of Internet of Things (IoT) and Web of Things (WoT). Using well-known and broadly accepted Web standards and protocols enables the interoperation of heterogeneous WSNs and the integration of their data with other Web resources, in order to provide the final user with value-added information and applications. Such emergent scenarios where multiple networks and applications interoperate to meet high level requirements of the user will pose several changes in the design and execution of WSN systems. One of these challenges regards the fact that applications will probably compete for the resources offered by the underlying sensor nodes through the Web. Thus, it is crucial to design mechanisms that effectively and dynamically coordinate the sharing of the available resources to optimize resource utilization while meeting application requirements. However, it is likely that Quality of Service (QoS) requirements of different applications cannot be simultaneously met, while efficiently sharing the scarce networks resources, thus bringing the need of managing an inherent tradeoff. In this paper, we argue that a middleware platform is required to manage heterogeneous WSNs and efficiently share their resources while satisfying user needs in the emergent scenarios of WoT. Such middleware should provide several services to control running application as well as to distribute and coordinate nodes in the execution of submitted sensing tasks in an energy-efficient and QoS-enabled way. As part of the middleware provided services we present the Resource Allocation in Heterogeneous WSNs (SACHSEN) algorithm. SACHSEN is a new resource allocation heuristic for systems composed of heterogeneous WSNs that effectively deals with the tradeoff between possibly conflicting QoS requirements and exploits heterogeneity of multiple WSNs.     

一种异构传感器网络下的节能分簇路由算法

无线传感器网络存在着严重的能量约束,传统同构的传感网络路由协议和算法不适合异构网络,因此,设计异构传感网络下的节能路由算法具有现实意义。研究两种不同类型传感器节点构成的,具有不同的初始能量和不同感知数据能力的异构网络中基于簇头预测的节能分簇路由算法ECAH。根据簇内节点的剩余能量、能量消耗速率和跟上一轮簇头的距离预测出下一轮簇头,有效地减少了控制报文数量,降低了系统开销,节约了能量。仿真结果显示,在异构的网络中采用ECAH路由算法比LEACH算法网络生存时间大约提高了23%。     

A testbed for coverage control using mixed wireless sensor networks

Wireless sensor networks (WSNs) is a relatively new technology that has been proposed for several applications including wide area monitoring. Such applications may include stationary or mobile sensor platforms or they may include several stationary and some mobile-robotic sensor nodes that can move in the area in order to achieve certain objectives, e.g., monitor areas that are not adequately covered or assist in the transfer of data to prevent the energy depletion of certain critical nodes. Such networks that consist of both stationary and mobile nodes are referred to as mixed WSNs. This paper presents the development of an experimental testbed for mixed WSNs consisting of stationary and mobile sensor nodes that collaborate to improve the sensing coverage and event detection of the network in a given deployment area. The paper describes the hardware and infrastructure of the testbed as well as a case study for coverage control that was investigated using the testbed. We point out that the developed testbed can be used for the evaluation and validation of different algorithms for coverage control that involve collaboration between stationary and mobile sensors to improve the WSN's monitoring capabilities. In addition, it can also be used to investigate other objectives as well as other concepts (e.g., network control).     

On the effectiveness of Linux containers for network virtualization

This paper presents a novel approach to the study of multi-technological networks based on Linux containers and software emulators. We illustrate the architecture and implementation issues of a modular and flexible testbed (NetBoxIT) that supports the virtualization and the concurrent, real-time execution of several independent emulators on a single, multi-core hardware platform. Distinct virtual networks can be instantiated, and connected to synthesize heterogeneous networks configurations. NetBoxIT is also an open platform, which can be interfaced with external networks and nodes, enabling the evaluation of true users’ applications and protocols. We examine its performance under different viewpoints (scalability, computational load, timing overheads, and realism) and we show how the proposed testbed architecture leads to a general-purpose, reliable, and economical tool for assessing multipart networks with respect to real-world applications. Moreover, we discuss which are the current and future technologies that can be introduced to reduce the testbed timing overheads and to further improve performance.     

Object extraction scheme and protocol for energy efficient image communication over wireless sensor networks

To date, wireless sensor networks lack the most powerful human sense – vision. This is largely due to two main problems: (1) available wireless sensor nodes lack the processing capability and energy resource required to efficiently process and communicate large volume of image data and (2) the available protocols do not provide the queue control and error detection capabilities required to reduce packet error rate and retransmissions to a level suitable for wireless sensor networks. This paper presents an innovative architecture for object extraction and a robust application-layer protocol for energy efficient image communication over wireless sensor networks. The protocol incorporates packet queue control mechanism with built-in CRC to reduce packet error rate and thereby increase data throughput. Unlike other image transmission protocols, the proposed protocol offers flexibility to adjust the image packet size based on link conditions. The proposed processing architecture achieves high speed object extraction with minimum hardware requirement and low power consumption. The system was successfully designed and implemented on FPGA. Experimental results obtained from a network of sensor nodes utilizing the proposed architecture and the application-layer protocol reveal that this novel approach is suitable for effectively communicating multimedia data over wireless sensor networks.     

Kansei: a high-fidelity sensing testbed

Hardware and software testbeds are becoming the preferred basis for experimenting with embedded wireless sensor network applications. The Kansei testbed at the Ohio State University features a heterogeneous hardware infrastructure, with dedicated node resources for local computation, storage, data retrieval, and back-channel communication. Kansei includes a time-accurate hybrid simulation engine that uses testbed hardware resources to simulate large arrays. It supports high-fidelity sensor data generation as well as real-time data and event injection. The testbed also includes software components and an associated job-control language for complex multi-tier experiments.     

Efficient and accurate sensor network localization

Wireless sensor networks (WSN) have great potential in ubiquitous computing. However, the severe resource constraints of WSN rule out the use of many existing networking protocols and require careful design of systems that prioritizes energy conservation over performance optimization. A key infrastructural problem in WSN is localization—the problem of determining the geographical locations of nodes. WSN typically have some nodes called seeds that know their locations using global positioning systems or other means. Non-seed nodes compute their locations by exchanging messages with nodes within their radio range. Several algorithms have been proposed for localization in different scenarios. Algorithms have been designed for networks in which each node has ranging capabilities, i.e., can estimate distances to its neighbours. Other algorithms have been proposed for networks in which no node has such capabilities. Some algorithms only work when nodes are static. Some other algorithms are designed specifically for networks in which all nodes are mobile. We propose a very general, fully distributed localization algorithm called range-based Monte Carlo boxed (RMCB) for WSN. RMCB allows nodes to be static or mobile and that can work with nodes that can perform ranging as well as with nodes that lack ranging capabilities. RMCB uses a small fraction of seeds. It makes use of the received signal strength measurements that are available from the sensor hardware. We use RMCB to investigate the question: “When does range-based localization work better than range-free localization?” We demonstrate using empirical signal strength data from sensor hardware (Texas Instruments EZ430-RF2500) and simulations that RMCB outperforms a very good range-free algorithm called weighted Monte Carlo localization (WMCL) in terms of localization error in a number of scenarios and has a similar computational complexity to WMCL. We also implement WMCL and RMCB on sensor hardware and demonstrate that it outperforms WMCL. The performance of RMCB depends critically on the quality of range estimation. We describe the limitations of our range estimation approach and provide guidelines on when range-based localization is preferable.     

一种适用于无线传感器网络的拓扑控制算法

无线传感器网络拓扑控制算法对于延长网络的生存时间、减小通信干扰、提高路由协议和MAC协议的效率等具有重要的意义.在分析XTC(eXemplary Topology Control)算法的基础上,提出一种改进的基于局部网络信息的分布式拓扑控制算法M-XTC(M0dIfied-XTC).改进算法保持了XTC算法简单、实用,不需要节点位置信息,适用于普通节点、异构网络和三维空间等优点,并且更有利于延长网络的生存时间,具有更好的实时性和鲁棒性.     

Effective target tracking mechanism in a self-organizing wireless sensor network

Target tracking is an important sensing application of wireless sensor networks. In these networks, energy, computing power, and communication bandwidth are scarce. We have considered a random heterogeneous wireless sensor network, which has several powerful nodes for data aggregation/relay and large number of energy-constrained sensor nodes that are deployed randomly to cover a given target area. In this paper, a cooperative approach to detect and monitor the path of a moving object using a minimum subset of nodes while maintaining coverage and network connectivity is proposed. It is tested extensively in a simulation environment and compared with other existing methods. The results of our experiments clearly indicate the benefits of our new approach in terms of energy consumption.     

Efficient fault-tolerant collision-free data aggregation scheduling for wireless sensor networks

This paper investigates the design of fault-tolerant TDMA-based data aggregation scheduling (DAS) protocols for wireless sensor networks (WSNs). DAS is a fundamental pattern of communication in wireless sensor networks where sensor nodes aggregate and relay data to a sink node. However, any such DAS protocol needs to be cognisant of the fact that crash failures can occur. We make the following contributions: (i) we identify a necessary condition to solve the DAS problem, (ii) we introduce a strong and weak version of the DAS problem, (iii) we show several impossibility results due to the crash failures, (iv) we develop a modular local algorithm that solves stabilising weak DAS and (v) we show, through simulations and an actual deployment on a small testbed, how specific instantiations of parameters can lead to the algorithm achieving very efficient stabilisation.