车载传感器网络的研究进展

车载传感器网络是一种建立在车载自组织网络基础上的以数据为中心的新型移动传感器网络。与传统传感器网络不同的是,车载传感器网络中的节点是高速移动的,从而导致网络间歇连通、拓扑结构变化频繁,网络中数据的传输只能依靠节点间机会性的传递,严重影响了这种以数据为中心的网络中的数据传输的性能。对目前车载传感器网络的研究现状进行了分析讨论,同时结合延迟容忍网络和机会网络思想,给出了车载传感器网络的研究方向。     

A token based distributed algorithm for supporting mutual exclusion in opportunistic networks

Opportunistic networks are essentially distributed networks with transient connectivity among nodes. Nodes in opportunistic networks are resource constrained, mobile and opportunistically come in contact with each other. In such a distributed network, nodes may require exclusive access to a shared object or resource. Ensuring freedom from starvation is a challenging problem in opportunistic networks due to limited pairwise connectivity and node failures. In this paper, we review mutual exclusion algorithms proposed for generic mobile ad hoc networks (MANETs) and discuss their applicability to opportunistic networks. Further, we propose a novel token based algorithm¹ and prove its correctness. Simulation results show that our algorithm is communication efficient as compared to other algorithms proposed for generic mobile ad hoc networks. We also propose a timeout based fault detection algorithm that exploits the intercontact time distributions.     

机会型网络研究综述

机会型网络是继移动自组网和无线传感器网络之后在无线网络领域中兴起的又一最新研究热点。机会型网络是移动自组网的演化,但机会型网络并不假设消息源和目标节点之间存在完整路径,而是通过节点的移动、相遇(Contact)和转发来实现在不连通的网络环境中通信,这种全新的组网模式引起了研究者极大的兴趣。介绍了机会型网络的概念、特点和典型应用,总结并详细阐述了机会型网络的路由机制、机会型网络的移动模型等主要研究热点问题,并对机会型网络的其他方向的研究作了简要介绍,对研究前景进行了展望。     

在操作系统中实现分布共享存储、存储管理和文件系统的集成

开发分布共享存储系统的目的是为了在分布式存储器的基础上构造逻辑上的共享存储器模型,对于如何在共享存储器模型的基础上为用户进程构造虚拟空间,传统的分布共享系统并未给予足够的重视。只有在操作系统中把分布共享存储技术、存储器管理和文件系统结合起来,才能充分发挥分布共享存储技术具有的能力。基于以上思想,在文中提出了一个实现了分布共享存储的操作系统模型,并分析了该模型一个实现原型,讨论该原型具有的优缺点。通过在操作系统中取消进程的逻辑空间,使进程直接在文件上运行,该模型不仅能够实现分布共享存储,而且和许多传统操作系统以及传统分布共享存储系统相比,具有许多优点。该操作系统实现了分布共享存储技术和操作系统中的存储管理以及文件系统的完美结合。     

一种基于移动Ad hoc网络的安全路由策略

移动Adhoc网是一种新兴的无线移动自组织网络,其路由安全机制与传统网络的路由安全机制有很大差异。在分析Adhoc网络的特点和局限性的基础上,从各网络节点易受攻击、俘获,各网络节点之间不可信赖的角度出发,引入了可信任第三方的信任分散策略,提出了一种新的移动Adhoc网络的安全路由策略,解决了节点之间身份的分布式认证,为节点之间的通信提供了极为安全的路由策略。     

An open and scalable architecture for delivering 3D shared visualization services to heterogeneous devices

Shared visualization environments represent an effective means to enhance collaborative work in engineering and scientific design tasks. The availability of high‐speed networks allows researchers to work together from geographically distributed locations, and mobile devices are able to carry out ubiquitous 3D visualization tasks through wireless network connections. This paper presents a scalable architecture for the delivery of shared 3D visualization services to heterogeneous terminals ranging from powerful workstations to mobile devices such as PDAs and smart‐phones. The framework design allows both desktop and mobile clients to simultaneously visualize the same model by sharing a common view. Remote‐rendering servers support effective visualization on thin clients, and a load balancing mechanism provides efficient resource usage. Copyright © 2011 John Wiley & Sons, Ltd.     

机会网络蓝牙设备唤醒调度机制研究

在以人为载体的机会网络中,移动蓝牙设备有电池能量有限的特点。同时,在机会网络中,节点经常处于较长时间的互不连通状态,如何设计有效的蓝牙节点唤醒调度模式来降低能耗并确保不破坏网络现有的连通性是一个重要问题。提出了一种机会网络蓝牙设备唤醒调度策略BWM。该策略分析蓝牙设备电池能耗问题,建立了涉及能耗的蓝牙数据传输模型,并对休眠唤醒机制中的参数内在联系进行研究,以确保数据成功传输量为前提来对唤醒周期间隔长度进行控制。仿真实验结果表明,BWM在保证节点有效数据发送性能前提下节省了节点消耗的能量。     

一种面向无线Ad Hoc网络的新型分布式哈希表

为了在无线ad hoc网络上构建各种应用系统,有必要提供一种高效的数据共享机制,使得网络中各节点之间能够方便地进行协同和交互。该文将分布式哈希表(DHT)的基本思想与无线ad hoc网络中的基于地理位置的路由技术结合起来,提出了一种新型的面向无线ad hoc网络的数据共享方案——基于位置的DHT(LDHT)。与传统的DHT方案相比,LDHT不是通过逻辑上的覆盖网络来实现,而是直接基于网络的物理拓扑结构来构建,有效地消除了传统DHT方案的拓扑结构不匹配问题,提高了在无线ad hoc网络中进行数据共享的效率。     

TreadMarks: shared memory computing on networks of workstations

Shared memory facilitates the transition from sequential to parallel processing. Since most data structures can be retained, simply adding synchronization achieves correct, efficient programs for many applications. We discuss our experience with parallel computing on networks of workstations using the TreadMarks distributed shared memory system. DSM allows processes to assume a globally shared virtual memory even though they execute on nodes that do not physically share memory. We illustrate a DSM system consisting of N networked workstations, each with its own memory. The DSM software provides the abstraction of a globally shared memory, in which each processor can access any data item without the programmer having to worry about where the data is or how to obtain its value     

基于分布式邻居发现机制的ZigBee网络能耗研究

ZigBee是一种基于IEEE 802.15.4标准的适用于短距离、低功耗和低数据传输率的无线网络技术。ZigBee网络的节点电池能量的有效利用能延长其网络生命周期。采用分布式邻居发现机制研究了ZigBee网络能耗。该机制使得ZigBee网络中的节点在其可访问的区域内及时发现邻居节点,通过分析和定义3种分布式邻居发现算法下ZigBee节点在整个发现过程中所需要的平均帧数,提出了ZigBee网络能耗模型,对ZigBee网络设备在3种分布式邻居发现算法下的能耗进行了详细分析并得出能耗表达式。在仿真实验中比较了ZigBee网络节点和邻居节点在不同算法下的工作循环模式和连续模式下设备的能耗,结果表明对于基于分布式邻居发现机制算法的ZigBee网络能耗,当帧时隙数较小时,选择争用树算法能获得较好的节能效果;当帧时隙数较大时,选择无反馈帧时隙算法或有反馈帧时隙算法则可减少节点能耗以延长ZigBee网络的生命周期。     

移动自组网的访问控制技术研究

网络资源的共享与保护是移动自组网需要解决的关键问题之一。运用Voronoi图模型和quorum系统的思想,提出了一种移动自组网的动态路径quorum系统,设计了动态路径quorum的生成算法。基于移动自组网的动态路径quorum系统,提出了基于quorum系统的移动自组网的分布式访问控制机制,详细描述了节点的身份认证、网络资源的访问控制和权限管理协议。与传统的基于单个节点自身的访问控制机制相比,该访问控制机制具有较强的抗攻击能力和较高的可靠性,能够有效地提高移动自组网的资源共享与保护水平。     

非合作信标条件下水下无线传感网可靠定位技术

传统假设水下无线传感器网络的传感器节点和信标节点都是合作的,但是在军事应用等特殊场合下,某些节点容易被敌方捕获或入侵,因而水下无线传感网络中有时会存在一些非合作的恶意节点。针对存在若干非合作信标的水下无线传感器网络定位应用,提出了一种非合作信标节点约束下水下无线传器网的可靠节点定位算法。本文算法利用一跳邻居范围内信标节点独自投票机制实现对非合作信标的判决与剔除,从而减少由于存在非合作信标节点对定位误差的影响,同时也分析了不同比例非合作信标下的定位误差界限。仿真结果验证了本文提出的算法相比传统定位算法,在平均定位精度和定位覆盖率等方面都有所提高。     

以SIP协定整合移动AD HOC网络

随着时代的演进,网络通讯科技的发展也从有线网络演进到无线网络。其中移动AdHoc网络,更是备受瞩目。它是由许多具有无线装置的移动节点所动态构成的网络,节点与节点之间的通讯是经由其邻近的节点所传送,其特色是不需预先建构相关网络基础设施。该论文是建立在集群路由方式的移动AdHoc网络平台上,整合IPv6自动组态设定和SIP协定,以提供移动节点所需的IP地址,与相关位置指信息。并提出一个分散式路由机制,使网络内的终端机可与移动网络节点互相通讯。     

Mobile data collection in sensor networks: The TinyLime middleware

In this paper we describe TinyLime, a novel middleware for wireless sensor networks that departs from the traditional setting where sensor data is collected by a central monitoring station, and enables instead multiple mobile monitoring stations to access the sensors in their proximity and share the collected data through wireless links. This intrinsically context-aware setting is demanded by applications where the sensors are sparse and possibly isolated, and where on-site, location-dependent data collection is required. An extension of the Lime middleware for mobile ad hoc networks, TinyLime makes sensor data available through a tuple space interface, providing the illusion of shared memory between applications and sensors. Data aggregation capabilities and a power-savvy architecture complete the middleware features. The paper presents the model and application programming interface of TinyLime, together with its implementation for the Crossbow MICA2 sensor platform.     

Multi-layer-based opportunistic data collection in mobile crowdsourcing networks

Along with the explosive popularity of wireless mobile devices and availability of high data rates, new crowdsourcing paradigms have emerged to leverage the power of problem-solving by crowds. A crucial challenge in crowdsourcing is data collection. With the increasing number of mobile users, device to device communication with opportunistic connections has become a real possibility, reducing the load on infrastructure based networks. Crowdsourcing over such opportunistic links presents with unique challenges. This paper proposes to exploit opportunistic transmission to collect data in crowdsourced networks, by using multiple layers of social graphs along with weight training for energy efficient data collection. We design two types of multi-layer-based opportunistic data collection methods by using different dimensions of data. Simulation experiments show that using these techniques, delivery ratio can be increased while reducing the load and energy consumption of the mobile network.     

Decentralized key generation scheme for cellular-based heterogeneous wireless ad hoc networks

With the support of cellular system a cellular-based mobile ad hoc network (MANET) offers promising communication scenarios while entails secure data exchange as other wireless systems. In this paper, we propose a novel decentralized key generation mechanism using shared symmetric polynomials in which the base stations (BSs) carry out an initial key generation by a symmetric polynomial in a distributed manner and then pass on the key material to mobile stations (MSs). Thereafter, our proposed key generation scheme enables each pair of MSs to establish a pairwise key without any intervention from the BS, thus reducing the management cost for the BS. The shared key between two MSs is computed without any interaction between them. In addition, the trust among MSs is derived from the cellular infrastructure, thus enjoying an equal security level as provided in the underlying cellular network. Simulations are done to observe the system performance and the results are very encouraging.     

一种基于混合社区的移动机会网络数据传输机制

由人携带或使用智能设备组成的移动机会网络采用"存储-携带-转发"的通信机制,通过中继转发来实现节点之间的数据传递。为了改善网络性能,往往需要借助节点的社会属性来进行中继选择和制定转发策略。然而,在已有的传输机制中,往往只是利用节点的部分社会属性,不能完全反映出节点之间的社会关系。为此,提出了一种新的基于混合社区的数据传输机制,并给出了混合社区的内涵、混合社区的构建方法和基于混合社区的数据传输算法。基于几种真实轨迹数据集的实验结果表明,与已有的几种经典路由算法相比,该方法传输成功率较高,传输延迟较短,性能更好。     

基于身份加密的机会网络安全路由架构

机会网络整合了容迟网络、移动自组织网络、社会网络等多种概念,可通过移动节点的相遇性机会实现消息的传输与共享,针对机会网络中目前较为流行的基于社会上下文的路由转发协议,设计了基于身份加密的安全架构来保证节点社会上下文的隐私性以及消息的机密性:通过可搜索的加密算法为每一个节点的社会属性设置相应的陷门,使得中继节点在可计算自...     

无线传感器网络密钥预分配与动态分配策略

为了实现无线传感器网络中的安全通讯,需要对传感器结点间传递的信息进行加密。由于受每个传感器结点自身资源的限制,传统网络中使用的密钥分配策略,并不适用于无线传感器网络。文章提出了一种基于结点位置对密钥进行预分配和动态分配相结合的密钥分配策略,通过构造一棵密钥管理树实现了分布式和集中式密钥管理的结合。应用这一策略构建的传感器网络其安全性和连通性有明显提高。