自组网体系结构研究

CSCW系统目标是允许用户在任何地点任何时间可以方便地进行群体间的协同工作.目前大多数的CSCW用户都需要依靠现有的网络基础设施.自组网是一组带有无线收发装置的移动节点组成的一个多跳的临时性的自治系统.在这种环境中,由于节点无线通信覆盖范围的有限性,需要借助其他中间节点进行分组转发到达信宿.他可以在没有可用的网络基础设施的情况下提供一种通信支撑环境,从而拓宽了CSCW的应用环境.本文描述了自组网的概念和特点,并提出了自组网的体系结构.     

无线自组网(Ad Hoc Networks)体系结构研究

计算机支持协同工作(CSCW)目标是在计算机支持的环境中,一个群体协同工作完成一项共同的任务。现有的网络基础设施为大多数的CSCW用户提供通信保障。自组网(Ad Hoc Networks)是一组自治系统,它的组建时间是不确定的,由移动节点所组成,移动节点必须带有无线收发装置。节点通过无线通信覆盖有限的范围,若要到达信宿,需要借助其他中间节点进行分组转发。如果没有可用的网络,AHN可以提供一种通信支撑环境。文章描述了AHN的概念和特点,并提出了AHN的体系结构。     

基于CSD的WAP组网方案

针对承载网络,ＷＡＰ组网方式包括基于短消 息（ＳＭＳ）、电路交换数据（ＣＳＤ）和即将推出的通用分组无线业务（ＧＰＲＳ）等。本文具体介绍目前主要的基于ＣＳＤ的几种组网方案及系统构成。 一、 ＷＡＰ网关系统构成 一个ＷＡＰ网关系统可能由以下几个功能实体组成：ＷＡＰ网关、防火墙、接入服务器、ＤＮＳ服务器、各种应用（ＷＭＬ／ＷＷＷ、ＦＴＰ、Ｅ－ｍａｉｌ等）服务器。其中接入服务器中可能包括 ＡＡＡ服务、ＤＨＣＰ、计费数据产生等功能模块,而ＡＡＡ服务和计费信息产生等功能也可以由ＷＡＰ网关实现。具体系统构成见图１。其中接入服务器、ＤＮＳ服务器、各种应用服务器等均应根据需要设置。 二、基于电路交换方式（ＣＳＤ）的 ＷＡＰ业务组网方案 （一）利用移动网络组建ＷＡＰ业务网,ＷＡＰ网关集中设置 １接入服务器的设置 将接入服务器与本地网内ＧＳＭ网的ＧＭＳＣ相连。接入服务器与ＧＭＳＣ的接口信令采用ＩＳＵＰ。接入服务器接到ＩＰ网的骨干节点,如果本地没有ＩＰ网骨干节点,可就近接入ＩＰ网接入节点。图２给出了在这种情况下,ＧＳＭ网与接入服务器连接的示意图。 ２．ＷＡＰ业务的网络结构 ＷＡＰ网关的位置可以与接入服务器的位置 相同,也可以 不相同...     

无线自组网实现短消息业务的路由协议

运用无线自组网灵活、自治的网络特点也可以实现短消息的传递,这种网络架构改变了传统蜂窝网中对基础设施的需求,节省了一定的花费。充分利用多跳通信的特性,移动节点为固定节点提供转发数据包的服务,从而提高了网络的连通性,降低了网络节点密度,用无线自组网的形式实现短消息业务,不需要构建网络的基础设施,降低花费和复杂度。     

UT斯达康WACOS多用业务IP交换系统

ＷＡＣＯＳ 是面向未来的统一多业务ＩＰ交换系统。它不仅实现了通信网络从有线到无线、从窄带到宽带、从ＴＤＭ交换到ＩＰ交换的全方位转变,还兼顾到传统电信网络制造商和业务运营者利用现有基础设施提供新业务的需求。从而为通信网络平滑过渡到未来铺平了道路。ＷＡＣＯＳ系统采用灵活、性价比高、扩展性好的软交换体系结构,利用多协议网关,通过统一的ＩＰ网络向用户提供语音、数据、Ｉｎｔｅｒｎｅｔ接入及其它多种宽带业务。在未来的网络中,ＷＡＣＯＳ还支持 Ｆａｘ／ＶｏＩＰ、ＲＡＳ及高速ＩＰ交换和路由等功能。ＷＡＣＯＳ系统综合了交换、接入、运营支持等技术,为业务运营商提供了全面、有效、经济的解决方案。ＷＡＣＯＳ是构建下一代电信网络的理想体系。 一、系统特点 采用ＷＡＣＯＳ系统,网络运营者可以构建一个基于ＩＰ的、灵活、可靠、可扩展、性价比高的开放式多业务电信网络。在ＷＡＣＯＳ系统中,网络和业务均能适应未来发展的需求。对网络运营者来说,ＷＡＣＯＳ可以实现向未来网络的平稳过渡。 １．统一网络,多种服务 采用多协议接入网关,ＷＡＣＯＳ能够在一个网络中提供多种电信业务。如：基本业务、附加业务、移动业务、高级业务、管理业务、Ｉｎｔｅｒｎｅｔ接入业务...     

温室环境中的一种自组网路由算法研究

针对无线传感器网络中节点在温室场境中的自组网问题,文章介绍了一种自组网路由算法,每个节点都运行相同的程序。首先,上电后节点等待入网;然后,将入网信息上传至汇聚节点。节点的入网或退出,都是自动执行。在实验室环境下进行模拟实验,文章所讲述的算法可以应用于温室环境中。     

无人机自组网技术研究

在无人机系统中,编组和协同作战能力对提高无人机作站效能和生存能力具有重要意义。无线自组网是一种特殊结构的无线通信网络,其通信依靠节点之间的相互协作,以无线多跳方式完成,因此网络不依赖于任何固定设施,具有自组织和自管理的特性,这种特殊的组网方式使得无线自组网非常适用于无人机系统。介绍了无线自组网的原理,分析了无线自组网应用于无人机系统主要面临的关键技术:路由技术和安全问题。介绍了无线自组网的发展情况和在无人机领域的研究情况。     

一种适用于自组网的流媒体协议设计

本文基于自组网的应用背景,在分析了传统流媒体协议特性的基础上,进行了自组网应用层信令面及用户面的协议设计。该协议以SIP和RTP/RTCP协议为蓝本,针对自组网节点平等,移动性强及无线传输质量差的网络特性,对传统流媒体协议的架构及呼叫流程进行了更改,使其适用于自组织网络,是一种可行的自组网流媒体协议。     

无线自组网竞争类MAC协议分析及研究

无线自组织网络是一种无基础设施的移动网络,并且每个节点的业务多以突发业务为主,因此信道资源分配适用于采用竞争方式。本文在对无线自组网各种典型竞争类MAC协议进行分析及探讨的基础上,采用Opnet仿真建模环境,创建出各协议的状态分析模型,并在此基础上对各协议的性能优劣进行了比较总结。论文对无线自组网各协议仿真建模研究及选择高效适用的MAC技术方案具有实际参考价值。     

基于无线自组网的网络层交换软件设计与实现

研究了一种应用于无线自组网的网络层交换软件,通过系统模型的抽象和建立,将网络层需要实现的功能独立出来,进而制定了本地及全局路由的建立与维护、网络层数据交换等关键策略,综合运用了多线程设计、网络编程、驱动设计等多种编程技术,在高速ARM平台上,基于嵌入式Linux操作系统实现了网络层交换系统软件,使标准网络设备无需任何改变即可接入自组网节点设备,并能够通过无线自组网进行通信,解决了接入设备的数据寻路与数据交换问题。     

A study of a routing attack in OLSR‐based mobile ad hoc networks

A mobile ad hoc network (MANET) is a collection of mobile nodes which are able to communicate with each other without relying on predefined infrastructures or central administration. Due to their flexibilities and easy deployment, MANET can be applied in situation where network infrastructures are not available. However, due to their unique characteristics such as open medium and the lack of central administration, they are much more vulnerable to malicious attacks than a conventional infrastructured wireless network. MANET employs routing to provide connectivity for mobile nodes that are not within direct wireless transmission range. Existing routing protocols in MANET assume a trusted and cooperative environment. However, in hostile environment, mobile nodes are susceptible to various kinds of routing attacks. In this paper, we show that an OLSR MANET node is prone to be isolated by malicious attack called Node Isolation attack. After analysing the attack in detail, we present a technique to mitigate the impact of the attack and improve the performance of the network when the attack is launched. The results of our implementations illustrate that the proposed solution can mitigate the attack efficiently. Copyright © 2007 John Wiley & Sons, Ltd.     

Stable routing algorithm for mobile ad hoc networks using mobile agent

Wireless ad hoc networks are growing important because of their mobility, versatility, and ability to work with fewer infrastructures. The mobile ad hoc network is an autonomous system consisting of mobile nodes connected with wireless links. Establishing a path between two nodes is a complex task in wireless networks. It is still more complex in the wireless mobile ad hoc network because every node is no longer as an end node and an intermediate node. In this paper, it focuses on design of connectionless routing protocol for the wireless ad hoc networks based on the mobile agent concept. The proposed model tries to discover the best path taking into consideration some concerns like bandwidth, reliability, and congestion of the link. The proposed model has been simulated and tested under various wireless ad hoc network environments with the help of a different number of nodes. The results demonstrate that the proposed model is more feasible for providing reliable paths between the source and destination with the minimum control message packets over the network. It has delivered more number of packets to the destination over the network. Copyright © 2012 John Wiley & Sons, Ltd.     

A service level model and Internet mobility monitor

Mobility is gaining a tremendous interest among Internet users and wireless access networks are increasingly being installed to enable mobile usage. Internet mobility requires solutions to move between access networks with maintained network connectivity. Seamless mobility in turn means that the experience of using a service is unaffected while being mobile. Communication in next generation networks will use multiple access technologies, creating a heterogeneous network environment. Further, roaming between network service providers may take place. To enable mobile nodes to move between access networks within as well as between network service providers with minimal disruption, nodes should be able to maintain multiple active network connections. With the usage of multihomed nodes, seamless mobility can be achieved in already installed infrastructures, not providing mobility support. Mobility in heterogeneous access networks also requires network selections that scale for services. In this article we propose an architecture where application service providers and network service providers define service levels to be used by a mobile node and its user. The user selects a service and the service level from an application service provider. When performing access network selection, information received as part of an application service level will be used to find a network that supports the service required. The performance of available access networks will be monitored and considered when making the decision. Our proposed architecture provides solutions to move flows between interfaces in real-time based on network performance, quality of service signalling to correspondent nodes, and cancellation of flows to give way for more important traffic.     

Modeling epidemic data diffusion for wireless mobile networks

Data/content dissemination among the mobile devices is the fundamental building block for all the applications in wireless mobile collaborative computing, known as mobile peer‐to‐peer. Different parameters such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in a mobile peer‐to‐peer environment. In this paper, we develop analytical models for object diffusion time/delay in a wireless mobile network to apprehend the complex interrelationship among these different parameters. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in the wireless mobile network considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in the wireless mobile network. Copyright © 2012 John Wiley & Sons, Ltd.     

NonStop: continuous multimedia streaming in wireless ad hoc networks with node mobility

Guaranteeing continuous streaming of multimedia data from service providers to the users is a challenging task in wireless ad hoc networks, particularly when node mobility is considered. The topological dynamics introduced by node mobility are further exacerbated by the natural grouping behavior of mobile users, which leads to frequent network partitioning. Network partitioning poses significant challenges to the provisioning of continuous multimedia streaming services in wireless ad hoc networks, since the partitioning disconnects many mobile users from the centralized streaming service. In this paper, we propose NonStop, a collection of novel middleware-based run-time algorithms that ensures the continuous availability of such multimedia streaming services, while minimizing the overhead involved. The network-wide continuous streaming coverage is achieved by partition prediction and service replication on the streaming sources and assisted by distributed selection of streaming sources on regular mobile nodes and users. The proposed algorithms are validated by extensive results from performance evaluations.     

基于自组网的节能协作算法

自组网是兼做路由器的移动节点组成的移动无线网络，不依靠通信基础设施。本文提出了一个工作于物理层和MAC层之上、网络层之下的基于自组网的节能协作算法，其核心思想是构造虚拟主干网，使位于虚拟主干网外的节点工作于休眠状态，从而减少电源消耗。     

Performance evaluation of packet aggregation scheme for VoIP service in wireless multi-hop network

In a wireless multi-hop network environment, energy consumption of mobile nodes is an important factor for the performance evaluation of network life-time. In Voice over IP (VoIP) service, the redundant data size of a VoIP packet such as TCP/IP headers is much larger than the voice data size of a VoIP packet. Such an inefficient structure of VoIP packet causes heavy energy waste in mobile nodes. In order to alleviate the effect of VoIP packet transmission on energy consumption, a packet aggregation algorithm that transmits one large VoIP packet by combining multiple small VoIP packets has been studied. However, when excessively many VoIP packets are combined, it may cause deterioration of the QoS of VoIP service, especially for end-to-end delay. In this paper, we analyze the effect of the packet aggregation algorithm on both VoIP service quality and the energy consumption of mobile nodes in a wireless multi-hop environment. We build the cost function that describes the degree of trade-off between the QoS of VoIP services and the energy consumption of a mobile node. By using this cost function, we get the optimum number of VoIP packets to be combined in the packet aggregation scheme under various wireless channel conditions. We expect this study to contribute to providing guidance on balancing the QoS of VoIP service and energy consumption of a mobile node when the packet aggregation algorithm is applied to VoIP service in a wireless multi-hop networks.     

基于移动Agent的JPEG2000分布式编码算法研究

该文针对无线传感器网络节点处理能力、存储能力和能量供应均有限的特点,提出一种基于移动Agent的JPEG2000分布式编码算法。采用多个节点对图像进行分布式编码,通过引入移动Agent机制来实现网络节点间的信息交互,在保证图像编码性能不变的情况下,降低单个节点能耗,使系统不因单个节点能量耗尽而瘫痪,以延长系统的生命周期。仿真实验结果表明,该文所提出的基于移动Agent的分布式编码算法在无线传感器网络环境中可以保证编码后的图像质量没有下降,并能有效均衡系统能耗、延长网络工作寿命达3倍左右。     

Analysis of a Metropolitan-Area Wireless Network

We analyze a seven-week trace of the Metricom metropolitan-area packet radio wireless network to find how users take advantage of a mobile environment. Such understanding is critical for planning future large-scale mobile network infrastructures. Amongst other results, we find that users typically use the radios during the day and evening. Of the users who move around during the trace (over half), we find that the more locations a user visits on a daily basis, the closer together, on average, those locations are. While these results are only known to be valid for this particular network, we hope future analysis of other networks will add to a growing understanding of mobile network behavior.     

Novel service protocol for supporting remote and mobile users in wireless sensor networks with multiple static sinks

A wireless sensor network typically consists of users, a sink, and a number of sensor nodes. The users may be remotely connected to a wireless sensor network and via legacy networks such as Internet or Satellite the remote users obtain data collected by the sink that is statically located at a border of the wireless sensor network. However, in practical sensor network applications, there might be two types of users: the traditional remote users and mobile users such as firefighters and soldiers. The mobile users may move around sensor fields and they communicate with the static sink only via the wireless sensor networks in order to obtain data like location information of victims in disaster areas. For supporting the mobile users, existing studies consider temporary structures. However, the temporary structures are constructed per each mobile user or each source nodes so that it causes large energy consumption of sensor nodes. Moreover, since some of them establish the source-based structure, sinks in them cannot gather collective information like mean temperature and object detection. In this paper, to effectively support both the remote users and the mobile users, we propose a novel service protocol relying on the typical wireless sensor network. In the protocol, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed protocol is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing protocols.