移动无线传感器网络中一种新的路由算法

在节点采用RWP移动模型的移动无线传感器网络中,为了提高网络的综合性能,提出了一种新的路由算法LDM.LDM运用节点在RWP模型的运动特点及节点的运动方向与当前位置,推导出节点的传输概率,并使用传输概率来指导路由选择,同时对节点的消息队列进行了有效的管理,提高了网络的综合性能.通过在ONE仿真器上与Epidemic、DT、FAD算法进行比较,结果表明LDM在综合性能上得到了提升.     

基于半马尔科夫过程的DTN节点移动模型

节点移动模型对容延容断网络(Delay/Disruption Tolerant Networks,DTN)中路由算法性能有着重要影响.本文分析校园环境下学生所携带移动节点的运动特点,采用半马尔科夫过程模拟节点运动并建立相应的DTN节点移动模型,对模型进行仿真和分析,将仿真结果与随机路径点(RandomWay Point,RWP)模型及实际路径信息进行对比,可以看出半马尔科夫过程模型能够更准确地描述实际网络环境.     

一种基于热区的移动传感器网络的移动模型

移动模型在移动传感器网络的研究中起着非常重要的作用,因为几乎没有可以用于性能评估的大型真实网络环境.然而现在很多移动模型仅考虑了简单的地理位置移动性,在此的模型里强调人移动性的重要影响.在真实环境中,因为各地区对人移动的吸引力总是不同的,人的分布总是非均匀的,例如城市中的繁华地区会吸引更多的人过来.提出了一种基于热区的移动模型(HAM).在模型的设计中,整个区域被分成若干个子区域,每个子区域都有一个权重值用于表示对移动节点的吸引力.模型中,节点的移动是受周围所有子区域权重影响的.热区是拥有高权重的子区域,能够聚集更多的移动节点,就像城市中的繁华地区一样.利用仿真模拟显示提出的模型产生的节点移动轨迹,并比较其他的移动模型.     

Ad Hoc 网络中改善拓扑控制性能的移动控制算法

在无线Ad Hoc网络中,拓扑控制算法能够使节点的传输功率小于最大传输功率,从而可以节省网络能量,提高网络容量.由于节点分布的随机性,在节点较为稀疏的区域,拓扑控制算法存在着局限性,因而提出了移动控制算法来改善拓扑控制算法的性能.在保证网络连通性的前提下,算法首先根据收集到的信息,通过构造网络最小生成树确定较长的通信链路,并移动网络中的部分节点使这些链路缩短,从而显著减小网络中较大的通信半径,提高了拓扑控制的性能.仿真实现了PMST-P,PMST-UV和LMST-LUV这3种移动控制算法,并对它们的性能进行了讨论和相互比较.     

基于移动WSN目标追踪算法

水下移动无线传感器网络是追踪水下目标的重要手段,由于水下环境复杂,传感器节点会因为损坏或能量耗尽等问题脱离WSN网络,造成目标追踪困难。针对该问题,在拓扑熵理论基础上建立移动WSN目标追踪算法模型,利用拓扑熵对空间中点集拓扑关系描述移动WSN节点的部署情况。当有节点脱网后,通过不断计算拓扑熵值的变化合理调度节点移动,实现节点移动过程中的分布式自适应部署。仿真结果表明,在传感器节点损耗的情况下,提出算法和现有WSN目标追踪方法相比,在优化移动传感器网络的部署和目标追踪方面,具有更高的算法性能和效率。     

移动ZigBee节点无线传感器网络建模与性能仿真研究

在如智慧医疗等众多ZigBee无线传感器网络应用中,网络节点的移动常常不可避免,为保证移动节点在网络中的泛在通讯能力,研究节点移动引起的网络性能变化十分重要。论文首先对OPNET仿真开发平台的网络层进程域模型进行改进,利用状态转移过程模拟节点移动进程特性,优化节点路由协议,改善基于OPNET的ZigBee无线传感器网络模型组网能力及网络阻塞状况。其次,仿真研究移动节点数量、移动节点速度对三种拓扑结构ZigBee网络的MAC负载、MAC延迟、端到端延迟性能的影响。仿真结果表明,随着移动节点数量以及速度的增加,簇状ZigBee网络负载承受能力最好,星型ZigBee网络在延迟方面表现出更大优越性,综合考虑负载和延迟两方面性能,网状ZigBee网络具有更大的优势。     

无线传感器网络的生存性评估

当前无线传感器网络的生存性评估模型均假设网络的节点分布符合某种规律且在长期的运行中规律保持不变,但该种模型未考虑节点的移动性。针对以上问题进行了研究,通过引入节点的移动速率建立连续时间马尔科夫链表示的评估模型,该模型不依赖于网络的拓扑,能准确反映出节点的实际分布情况;其次研究不同攻击和故障对节点隔离的影响;稳态连通概率是刻画可生存性最为重要的指标,最后提出该指标的计算方法。仿真实验结果表明,本文提出的生存性评估模型能够对无线传感器网络的生存性进行有效的评估。     

基于NS2的规定轨迹的运动模型的实现与性能分析

该文基于仿真工具NS2在随机路点模型RWP(Random Waypoint Protocol)之上探讨了一种MANET环境下节点可沿规定轨迹移动的新的运动模型,对其主要思想及生成方法进行了较细致介绍,并通过仿真实验对其性能进行了评估和分析。     

WSN中基于多波束转换天线的网络拓扑控制算法

针对 WSN 中节点分布不均问题,提出采用区域划分策略基于多波束转换天线的网络拓扑控制算法SRADTC.算法通过关键邻居节点数将网络划分为若干个相互重叠的稀疏区域和稠密区域,稀疏区域按最小生成树算法进行拓扑控制,稠密区域按K邻居拓扑控制算法进行拓扑控制.用有边界的Pareto分布建模节点分布,仿真表明：SRADTC算法在保证网络连通性的同时,相比传统拓扑控制算法提高了网络的性能.     

可量化的移动Ad Hoc 网络时空动态特性评估方法

移动模型是Ad Hoc网络区别于其他形式网络的重要标志,对其产生的动态网络特性(简称动态特性)进行评估,是研究Ad Hoc网络的协议仿真和网络相关技术(如拓扑控制和网络性能测量等)的基础性问题.在已有研究的基础上,改进了网络的模型化描述,克服了以往模型无法很好地描述相关联的时空动态特性的缺陷,并在此基础上,提出了移动模型通用的可量化时空动态特性评估方法.通过构建节点空间位置分布,建立网络拓扑时空动态特性的分析模型,深入研究了几种移动模型的动态性.提出一种圆周曲线移动模型,弥补了以往移动模型难以描述现实的曲线移动场景.仿真实验结果表明,该方法能够有效地对现有移动模型的动态性进行评估.实验结果表明,圆周曲线移动模型与以往移动模型相比,具有良好的时空动态特性.     

A novel mobility model based on semi-random circular movement in mobile ad hoc networks

When simulating a mobile ad hoc network (MANET), it is important to use a realistic mobility model to reflect the actual performance of a mobile system. The spatial distribution of node locations in a mobile model plays a key role when investigating the characteristics of a MANET. However, most existing mobility models with random and simple straight line movement lead to unrealistic scenarios and non-uniform distributions, and can not describe the actual movement of Unmanned Aerial Vehicles (UAVs) connected via a MANET. To address this issue, a novel mobility model based on semi-random circular movement (SRCM) is presented. The approximate node distribution function in SRCM is derived within a 2D disk region. The relationship between application performance and node distribution is investigated for a UAV MANET, with focus on scan coverage and network connectivity. A simulation using the NS2 tool is conducted. It is shown that the presented model with a uniform distribution performs better than the popular Random Waypoint mobility model. The SRCM model with the NS2 simulator provides a realistic way for simulation and performance evaluation of UAV MANETs.     

An environment-aware mobility model for wireless ad hoc network

Simulation is a cost effective, fast and flexible alternative to test-beds or practical deployment for evaluating the characteristics and potential of mobile ad hoc networks. Since environmental context and mobility have a great impact on the accuracy and efficacy of performance measurement, it is of paramount importance how closely the mobility of a node resembles its movement pattern in a real-world scenario. The existing mobility models mostly assume either free space for deployment and random node movement or the movement pattern does not emulate real-world situation properly in the presence of obstacles because of their generation of restricted paths. This demands for the development of a node movement pattern with accurately representing any obstacle and existing path in a complex and realistic deployment scenario. In this paper, we propose a general mobility model capable of creating a more realistic node movement pattern by exploiting the concept of flexible positioning of anchors. Since the model places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, it is capable of representing any terrain realistically. Furthermore, obstacles of arbitrary shapes with or without doorways and any existing pathways in full or part of the terrain can be incorporated which makes the simulation environment more realistic. A detailed computational complexity has been analyzed and the characteristics of the proposed mobility model in the presence of obstacles in a university campus map with and without signal attenuation are presented which illustrates its significant impact on performance evaluation of wireless ad hoc networks.     

Applying location estimation for reliable routing in tactical unmanned ground vehicle networks

An unmanned ground vehicle (UGV) network operates as an ad hoc autonomous tactical network. In this paper, we study the deployment of a UGV network and its ability to use location estimation to provide reliable data forwarding. This analysis involves (1) location estimation to obtain realistic estimates of the node’s (UGV) spatial positions and (2) real-time path planning to obtain reliable routing among nodes using the estimates of the node positions. Conventional approaches commonly use the popular Random Waypoint (RWP) model (or its variants) as the mobility model. The RWP approach uses randomly selected node positions and has no way to cope with nodes moving in and out of transmission range. These deficiencies cause the route reliability to suffer. Our approach (1) uses an Extended Kalman Filter (EKF) for node mobility/location estimation and (2) uses a modified Ad Hoc On Demand Distance Vector (AODV) algorithm for route selection using a new routing parameter called contact time. We refer to this combined approach as the AODV-LocPred algorithm. We compare the AODV-LocPred algorithm with AODV using the RWP model. This is referred to as AODV-RWP. Our simulations show that the AODV-LocPred algorithm significantly outperforms the AODV-RWP algorithm in terms of packet delivery ratio (PDR), because it provides realistic node position estimates and it copes in a reasonable way with nodes moving in and out of transmission range. However, the AODV-LocPred incurs an increase in end-to-end delay. Nonetheless, we expect that in many real-world settings, this tradeoff is acceptable.     

基于圆周运动的自组网移动模型研究

自组网仿真研究大多基于特定的移动模型,而移动模型中节点空间概率分布是研究和评价自组网性能的理论基础.然而,现有的自组网移动模型存在诸多缺陷(如不现实的移动场景、节点的非均匀分布等).在分析和比较现有移动模型的基础上,提出一种基于圆周运动的移动模型,推导出移动节点的二维概率密度函数公式.理论分析和仿真实验表明,该模型能够克服现有移动模型的这些缺陷,为仿真和评估自组网的性能提供了精确的理论模型.     

Using mobile node speed changes for movement direction change prediction in a realistic category of mobility models

In order to evaluate performance of protocols for ad hoc networks, the protocols have to be tested under realistic conditions. These conditions may include a reasonable transmission range, a limited buffer size, and realistic movement of mobile users (mobility models). In this paper, we propose a new and realistic type of random mobility models in which the mobile node has to decelerate to reach the point of direction change and accelerates with a defined acceleration to reach its intended speed. This realistic mobility model is proposed based on random mobility models. In reality, mobile objects tend to change their speed when they are going to change their direction, i.e. decelerate when approaching a direction change point and accelerate when they start their movement in a new direction. Therefore, in this paper, we implement this behavior in random mobility models which lack such specification. In fact, this paper represents our effort to use this accelerated movement to anticipate a probable direction change of a mobile node with reasonable confidence. The simulation type of this paper is based on traces produced by a mobility trace generator tool. We use a data mining concept called association rule mining to find any possible correlations between accelerated movement of mobile node and the probability that mobile node wants to change its direction. We calculate confidence and lift parameters for this matter, and simulate this mobility model based on random mobility models. These simulations show a meaningful correlation between occurrence of an accelerated movement and event of mobile node's direction change.     

Mobility-sensitive topology control in mobile ad hoc networks

In most existing localized topology control protocols for mobile ad hoc networks (MANETs), each node selects a few logical neighbors based on location information and uses a small transmission range to cover those logical neighbors. Transmission range reduction conserves energy and bandwidth consumption, while still maintaining network connectivity. However, the majority of these approaches assume a static network without mobility. In a mobile environment network connectivity can be compromised by two types of "bad" location information: inconsistent information, which makes a node select too few logical neighbors, and outdated information, which makes a node use too small a transmission range. In this paper, we first show some issues in existing topology control. Then, we propose a mobility-sensitive topology control method that extends many existing mobility-insensitive protocols. Two mechanisms are introduced: consistent local views that avoid inconsistent information and delay and mobility management that tolerate outdated information. The effectiveness of the proposed approach is confirmed through an extensive simulation study.     

自组网Random Direction移动模型点空间概率分布的研究

在无线自组网的研究中，研究移动模型点的空间概率分布是研究自组网协议的仿真评价和分析移动自组网许多相关特性(例如网络连通性、最小生成树、平均路径长度、网络容量等)的重要的基础问题．针对自组网经常使用的Random Direction移动模型运动节点的空间分布进行了研究，给出了一维及二维情况下运动节点空间概率分布的精确公式．研究结果为基于Random Direction移动模型的证明、仿真与应用提供了严格的理论依据．     

高动态飞行器自组织网络组网研究

节点高速移动和网络拓扑变化迅速严重影响着高动态飞行器自组织网络性能。提出了一种适于高动态场景的移动自组织网络协议栈设计。该设计着重QoS需求,围绕网络拓扑高动态变化特征,合理配置不同层次的网络协议,适合高动态应用场景。以平面网络为例,分析评估了FANET网络在高动态环境下的性能。实验结果表明,该组网方式可行并能满足高动态飞行器自组织网络的功能和性能需求。还提出了节点在个体移动方式下保持网络高性能的最佳节点数目和网络各层次协议适应高动态拓扑变化的应对策略。     

A new wireless ad hoc multicast routing protocol

An ad hoc network is a multi-hop wireless network of mobile nodes without the intervention of fixed infrastructure. Limited bandwidth and mobility require that ad hoc routing protocols be robust, simple, and energy conserving. This paper proposes a new ad hoc multicast routing protocol called neighbor-supporting multicast protocol (NSMP). NSMP adopts a mesh structure to enhance resilience against mobility. And NSMP utilizes node locality to reduce the overhead of route maintenance. NSMP also attempts to improve route efficiency and reduce data transmissions. Our simulation results show that NSMP delivers packets efficiently while substantially reducing control overhead in various environments.     

车载自组织网络路由协议的仿真研究

本文简要介绍了车载自组织网络和移动自组织网络中两个典型的路由协议:表驱动路由协议DSDV和按需路由协议AODV;还介绍了一个实用的移动模型,使仿真实验更加接近现实。在Linux下使用网络仿真工具NS2对这两个典型协议进行仿真,并对仿真结果进行分析比较和性能评价,得出:AODV和DSDV协议都不太适用于车辆自组织网络,所以设计适合车辆网路的协议是急需解决的问题。