【作者】 邓克波；

【导师】 刘中；

【作者基本信息】 南京理工大学 ， 通信与信息系统， 2009， 博士

【摘要】 无线传感器网络是由密集部署在监视区域内大量廉价微型的传感器节点通过无线通信方式自组织构成的多跳的网络系统,其中每个网络节点具备有限的电量、感知能力、计算能力和通信能力。作为一种新兴的信息获取技术,无线传感器网络在军用和民用领域具有广阔的应用前景,其中许多应用可以抽象成目标探测、定位或跟踪等问题。由于传感器节点的电池能量有限且在通常情况下不可充电或更换,高效使用网络节点的电池电量以延长整体网络的生存时间成为传感器网络的首要考虑。本论文研究能量有效的目标探测、定位与跟踪技术。首先研究了基于合理设定探测参数的能量有效的目标探测技术,然后研究了基于降低计算量、通信量以及参与节点数目的能量有效的目标定位技术,最后研究了基于动态簇的目标跟踪技术和基于跟踪链的目标查询技术。主要工作归纳如下:1.能量有效的目标探测技术研究无线传感器网络优化探测能耗的主要方式是调度网络节点的工作状态或者探测参数。本论文研究了如何合理设定网络节点的探测参数—探测间隔和探测距离,使得传感器网络在满足一定目标探测质量的基础上,消耗最少的能量。在设定探测间隔时,选用目标最小路径暴露作为网络探测质量的衡量指标,将能量有效的探测间隔的设定问题转化成带约束条件的优化问题—最小化网络能量消耗,同时满足目标最小路径暴露的要求。然后,给出了优化模型的求解方法,其中着重研究了目标最小路径暴露的改进的求解方法。最后,仿真分析了影响探测间隔设定的各种因素。在设定探测距离时,选用目标区域覆盖重数作为网络探测质量的衡量指标,将能量有效的探测距离的设定问题转化成带约束条件的优化问题—最小化网络能量消耗,同时满足目标区域覆盖重数的要求。然后,给出了优化模型的最优和次优求解方法,其中着重研究了目标区域覆盖重数的改进的求解方法。最后,仿真验证了本文方法的能量有效性。2.能量有效的目标定位技术研究无线传感器网络定位目标时的能量消耗分为数据采集、数据传输和数据处理等几个方面。本论文针对三种传统的目标定位算法,在不影响定位精度的前提下,研究了降低目标估计的计算量、网络节点的通信量以及参与目标定位的节点数目的方法。传统基于目标能量测量的定位算法是根据目标所在的球面或平面,利用最小二乘方法确定目标的位置。本论文根据测量噪声为目标球面或平面附上合理的权值,推出了目标位置估计的加权最小二乘求解算法。该算法可以根据权值选择少部分重要的目标球面或平面参与目标位置估计,从而在不影响定位精度的前提下,有效降低了目标定位的计算量。针对传统基于目标角度测量的定位算法,提出了节点坐标存在误差情况下的节点选择方案。该方案根据目标预测位置预测目标定位误差,并以此作为优化指标选择参与目标定位的节点组合,在不影响定位精度的前提下,减少了参与定位的节点数目。作为延伸工作,提出了基于目标定位的节点坐标校正算法。质心定位算法的本质是均值计算问题。本论文针对质心定位算法,提出了基于脉冲耦合振荡器模型的分布式均值计算的实现方案。该方案中,传感器节点按照脉冲耦合振荡器模型运行,节点坐标数据调制在振荡器的脉冲信号发射时间上,邻居节点通过脉冲耦合实现数据交换和本地运算。由于节点传输数据寄托于可由1比特0-1码表示的脉冲信号,该方案的通信量大大低于传统基于数据包通信的实现方案。3.能量有效的目标跟踪技术研究无线传感器网络应用于目标跟踪时,重点在于如何组建合理的目标跟踪结构,完成目标跟踪的同时,尽量降低能量消耗以延长网络的生存时间。从该角度出发,本论文研究了基于动态簇的目标跟踪结构和基于跟踪链的目标查询结构。首先,研究了基于动态簇的目标跟踪方法。在动态簇组建方面,提出了综合考虑节点感应信息和节点电量的簇头竞选方案;在目标状态估计方面,提出了基于最近点事件的新型估计算法。结合这两个关键环节,给出了基于动态簇的目标跟踪过程。仿真结果表明该跟踪方法具有失效概率低、网络寿命长和跟踪精度高等优点。然后,研究了基于跟踪链的目标查询方法。首次提出了目标跟踪链的概念;给出了目标跟踪链的构建方法和基于跟踪链的目标查询过程;理论分析了基于跟踪链的目标查询的能量消耗。仿真结果表明该查询方法在目标查询频率较低或目标运动频率较高时表现出能量有效。更多还原

【Abstract】 A wireless sensor network (WSN) is a multi-hop self-organized network system that consists of a large amount of low-cost and small-size sensor nodes with limited sensing, computing and communication capabilities. As a novel information acquisition technology, WSN has found a wide spectrum of both military and civilian applicalitons, among which lots of applications can be formulated into the target detection, localization or tracking problems. As the sensor nodes are powered by battery that is usually not rechargeable or replaceable, efficiently utilizing the node energy to improve the network liftime becomes the first consideration in the design of WSN.This dissertation studies the energy-efficient target detection, localization and tracking techniques with WSN. Firstly, the energy-efficient target detection techniques by setting optimal detection parameters are studied; Then, the energy-efficient target localization techniques by reducing the computation load, communication load and participant nodes are considered; Lastly, the energy-efficient target tracking techniques with dynamic cluster and tracking chain are investigated. The main works in the dissertation are summarized as follows:1. Study on the energy-efficient target detection techniquesTo reduce the energy consumption in target detection, the WSN can do node scheduling or detection parameter adjustment. This dissertation studies the approaches to set optimal detection parameters: detection interval and detection distance.For the setting of optimal detection interval, an improved method to solve the minimum path exposure is firstly proposed, and then the setting of detection interval is formulated as a constrained optimalization problem-minimization of the energy consumption with satisfactory minimum path exposure. A method to solve the optimalization problem is also presented. The influences of various factors on the setting of detection interval are theoretically analyzed and extensively simulated.For the setting of optimal detection distance, an improved method to solve the area coverage level is firstly proposed, and then the setting of detection distance is formulated to be a constrained optimalization problem-minimization of the energy consumption with satisfactory area coverage level. A method to solve the optimalization problem is also presented. Simulated results show that the proposed scheme consumes less energy than traditional methods.2. Study on the energy-efficient target localization techniquesTo localize a target, the WSN will consume energy in the target signal sensing, target information communication and target location estimation. This dissertation studies the approches to reduce the computation load, the communication load and the participant nodes of traditional localization methods.For the traditional energy-based target localization, this dissertation proposes two weighted least square solutions by assigning a weight to each hypersphere or hyperplane according to the noise. Only considering the large weighting hyperspheres or hyperplanes for the target location estimation, the proposed solutions can efficiently reduce the computation load with satisfactory localization accuracy. Simulated results confirm the advantages of the proposed methods.For the traditional bearing-only target localization, this dissertation proposes a node selection strategy for the case that node coordinates are imprecise. The covariance of target location estimation is firstly reduced with node coordinate error taken into account, and is then used as a metric to select the node set for target localization. Simulated results show that the proposed scheme can reduce participant sensor nodes for target localization with satisfactory localization accuracy. Furthermore, this dissertation proposes an approach to calibrate the node coordinate error with the target localization.Traditional centroid based localization is an average computation problem. This dissertation proposes a novel scheme to implement distributed average computation in WSN. In the scheme, the network of nodes operate as pulse-coupled oscillators; the data at each node is encoded into the firing time of the pulse; neighboring nodes use pulse coupling for data exchange and local computation. As the node data is reposed in a 1-bit pulse signal, the proposed scheme has much small communication load. The influences of various factors on the proposed scheme are extensively simulated.3. Study on the energy-efficient target tracking techniquesIt is expected in target tracking with WSN to arrange the sensor nodes into a tracking structure that is competent for target tracking and meanwhile consumes less energy. Motivated by this, the dissertation studies the approaches to track target with dynamic clusters and query target with tracking chain. A dynamic cluster is a tree structure consisting of the sensor nodes around the target. This dissertation emphatically studies the two key issues in target tracking with dynamic cluster, i.e. cluster construction and target estimation. For the former issue, a voting approach is developed for the cluster head selection. For the latter one, a new CPA (closest point of approach) event is defined and a target estimation algorithm is presented. Then, a dynamic cluster-based target-tracking process is presented. Simulated results show that the presented scheme has low failure probability, long network life and high tracking accuracy.A tracking chain is a bi-directional chain consisting of the sensor nodes on the target route and reserving the target spatio-temporal information. The dissertation defines the tracking chain for the first time, and proposes the approaches to construct the tracking train and to query the target with the tracking chain. The target query cost with the tracking chain is also analytically formulated. Simulated results show that the proposed scheme is energy-efficient for the cases that the target query frequency is low and the target mobility frequency is high.更多还原