IEEE 802.11s网络及其性能评估

无线局域网标准IEEE 802.11是一种较低成本的无线数据传输方案。无线网状网的产生解决了无线局域网覆盖范围小的问题。IEEE Task Group S早在2004年就开始策划制定关于无线网状网多跳通信,MAC层路由转发以及安全的标准——IEEE 802.11s。介绍了IEEE 802.11s最新的草案标准,并通过试验床的设计与试验评估了当前基于IEEE 802.11s无线网状网网络的整体性能。最后探讨了视频应用在IEEE 802.11s中的可行性。     

无线网状网及其在铁路应急通信中的应用

无线网状网融合了无线局域网和Ad Hoc络的优势,是一种大容量、高速率、覆盖范围广的网络。文章首先介绍了无线网状网的起源发展,其次研究了无线网状网的网络结构及特点,最后介绍了铁路应急通信的网络部署及无线网状网在铁路应急通信中的应用,并对目前无线网状网的研究热点和发展前景做了展望。     

新型宽带无线网络技术——无线网状网

无线网状网技术是一种具有良好市场应用前景的新型宽带无线网络技术.本文首先简要介绍了无线网状网的产生和发展,然后针对无线网状网的定义、特点、应用以及影响网络性能的关键因素等最核心的几个问题,进行了初步的探讨和总结.     

基于Mesh网络拓扑结构的无线城域网调度机制

基于IEEE802.16标准的无线城域网支持点对多点(PMP)和网状网(无线Mesh)两种网络拓扑结构,文章重点讨论了无线Mesh网络结构采用的关键技术——调度算法,首先介绍了适合无线Mesh的MAC层协议结构,重点分析和比较了3种不同调度机制的原理和特性,给出了相应的协议配置和算法解决方案,最后介绍了未来研究的重点。     

基于WMN的多信道物联网信息传输机制研究

多信道物联网是物联网技术未来发展的重要方向,文章基于多信道无线网状网（WMN）的应用特性,介绍了三种适用于多信道无线网状网的路由协议,对于发展基于无线网状网技术的物联网应用具有重要的实践指导意义,也为多信道物联网信息传输机制的发展提供了理论基础。     

无线网状网技术与应用

无线网状网(WMNs)由网状路由器节点和客户机节点组成,其中的网状路由器节点组成了无线网状网的网络骨干,其移动性很小。他们一起为无线网状网和其他常规无线网络的客户机节点提供网络的无线接入。WMNs技术结合了中心式控制的蜂窝网与分布式控制的无线自组织网的优点,可有效克服这两种技术的缺陷并显著提高无线网络的性能,已经成为下一代无线通信网络的研究热点之一。WMNs可为无线个域网、局域网、校园网、城域网的一系列应用提供高速无线宽带接入服务。虽然目前WMNs技术发展很快,但其协议栈各层仍存在许多有待研究的课题。首先简要介绍了无线网状网的结构与特点;随后重点分析了其主要的几个应用领域;最后探讨了WMNs各协议层的研究现状与关键技术,并分析了该技术存在的问题及未来的研究方向。     

无线网状网通信安全技术论述

随着近些年来我国通信技术的不断发展,人们对于通信安全也越来越重视,而无线网状网作为一种动态的自配置网络,它既具有无线网络的特征,同时也具备多跳、自组织和配置灵活等特征,虽然无线网络状网有着这些优势,但是在实际的应用过程中,由于其缺乏明确的网络边界防线,所以说无线网状网的安全一直以来都是人们较为关注的一个话题.因此本文就如何有效地保障无线网状网的通信安全进行了一定的论述,并介绍了相应的无线网状网通信安全技术.     

无线网状网与协作中继技术

无线网状网已经成为无线宽带通信领域的研究热点,但是基于交换技术的无线网状网因为其将整个网络看作是一个IP子网而无法适用于大范围的覆盖。在无线链路中采用协作中继,可以提高无线链路的传输速率及传输可靠性。同时采用基于网络层路由技术的无线网状网技术,可以实现整个无线网状网的频谱效率提升和厂域覆盖。不过,由于标准化、关键技术研究以及产业化推进方面还存在许多问题,使得协作中继技术在无线网状网中的应用面临着巨大挑战。     

北电构建无线校园服务中国教育信息化

近日，教育部科技发展中心主办的2005中国无线校园建设与发展论坛在北京国际会议中心隆重召开。来自教育部、全国各大高校和企业的业界专家和相关人士近1000人共聚一堂，围绕无线校园网的发展现状、部署实施和应用前景等多个话题展开讨论。北电为与会者介绍了新兴的校园无线网状网解决方案，并分享了无线网状网在全球校园网应用的成功案例。     

无线网状网技术分析

无线网状网是一种全新的无线接入技术。也是一种全新的增强型体系结构。它结合了无线和有线解决方案的最佳性能特点，可以为企业和公众终端用户提供可靠的无线接入。解决方案引入了对等网状拓扑的概念。可实现接入点之间的无线通信。这个概念解决了当今面临的许多部署问题。比如进行广泛的以太网布线。支持新的部署模式等。本文介绍了无线网状网的核心技术、安全性能、网络性能等及其与无线接入同类技术的比较。     

Experiences from the design, deployment, and usage of the UCSB MeshNet testbed

In this article we report on our effort and experience in designing, deploying, and using our 30-node wireless mesh testbed, the University of California at Santa Barbara (UCSB) MeshNet. Compared to simulation, the construction and utilization of a wireless mesh testbed poses many new challenges. We discuss the challenges with distributed testbed management, nonintrusive and distributed monitoring, and node status visualization. These are vital components in a sustainable wireless mesh testbed, but at the same time nontrivial to design and. realize. As a case study, we present the UCSB MeshNet architecture, including its management, monitoring, and visualization systems. We share our lessons learned from this effort and believe that they are valuable to other researchers who develop experimental wireless mesh networks.     

无线Mesh网络试验床的构建与应用

本文首先叙述了无线Mesh网络国内外研究和发展动态;接着描述了上海交通大学SJTU-Mesh网络试验床的体系结构,包括系统架构、硬件平台和软件结构;然后介绍了试验床的部署与应用情况;最后给出了对未来工作的展望.     

一种无线Mesh实验网络的构建

无线Mesh网络作为一种新型组网方式,已成为当前网络技术研究的热点。本文提出一种Mesh网络研究的实验测试平台,给出了整体的实现方案,并就实现细节做了详细的介绍。本方案主要采用当前流行的WLAN技术,结合PC机的灵活性和Linux操作系统的丰富功能和稳定性,实现Mesh网络的结构。经测试验证,网络性能稳定,功能良好。     

A Multi-radio 802.11 Mesh Network Architecture

The focus of this paper is to offer a practical multi-radio mesh network architecture that can realize the benefits of multiple radios. Our architecture provides solutions to challenges in three key areas. The first is the construction of a split wireless router that enables modular wireless mesh routers to be constructed from commodity hardware. The second is the design of a centralized channel assignment algorithm that considers the inter-dependence between channel assignment and routing in order to create high-throughput channel-diversified routes. Third is the design and implementation of several communication protocols that are necessary to make our architecture operational. Our system is comprehensively evaluated on a 20-node multi-radio wireless testbed. Results demonstrate that our architecture makes feasible the deployment of large-scale high-capacity multi-radio mesh networks built entirely with commodity hardware. Our implementation is available to the community for research and development purposes.     

Design and implementation of adaptive WLAN mesh networks for video surveillance

This paper presents a novel design and practical experiments of adaptive wireless mesh networks based on 802.11 based Wireless Local Area Networks for supporting public video surveillance. A network of video cameras and sensors can be equipped with wireless communication modules to form wireless surveillance at only a small expense of cost and labor. However, large and redundant multimedia data transmitted through the wireless medium pose challenging problems such as decrease in Quality of Service (QoS) and system reliability. To support seamless transmission of surveillance data through wireless means, we propose a wireless surveillance network design based on the protocols and functions of IEEE 802.11 mesh standard. One of the key functions of our adaptive mesh network is the “Multi-Gateway Routing with Congestion Avoidance”, which provides enhanced QoS support via adaptive congestion control. Network congestion is predicted in a distributed manner and amounts of data traffic transmitted to the congested path are redirected to multiple gateways. Redirection of traffic flows are made in such a way to provide quicker transmission for more time critical packets. Experimental studies via practical testbed implementation and simulation via NS-3 are conducted to prove the superiority of our proposed scheme.     

Mitigating the gateway bottleneck via transparent cooperative caching in wireless mesh networks

Wireless mesh networks (WMNs) have been proposed to provide cheap, easily deployable and robust Internet access. The dominant Internet-access traffic from clients causes a congestion bottleneck around the gateway, which can significantly limit the throughput of the WMN clients in accessing the Internet. In this paper, we present MeshCache, a transparent caching system for WMNs that exploits the locality in client Internet-access traffic to mitigate the bottleneck effect at the gateway, thereby improving client-perceived performance. MeshCache leverages the fact that a WMN typically spans a small geographic area and hence mesh routers are easily over-provisioned with CPU, memory, and disk storage, and extends the individual wireless mesh routers in a WMN with built-in content caching functionality. It then performs cooperative caching among the wireless mesh routers.We explore two architecture designs for MeshCache: (1) caching at every client access mesh router upon file download, and (2) caching at each mesh router along the route the Internet-access traffic travels, which requires breaking a single end-to-end transport connection into multiple single-hop transport connections along the route. We also leverage the abundant research results from cooperative web caching in the Internet in designing cache selection protocols for efficiently locating caches containing data objects for these two architectures. We further compare these two MeshCache designs with caching at the gateway router only.Through extensive simulations and evaluations using a prototype implementation on a testbed, we find that MeshCache can significantly improve the performance of client nodes in WMNs. In particular, our experiments with a Squid-based MeshCache implementation deployed on the MAP mesh network testbed with 15 routers show that compared to caching at the gateway only, the MeshCache architecture with hop-by-hop caching reduces the load at the gateway by 38%, improves the average client throughput by 170%, and increases the number of transfers that achieve a throughput greater than 1 Mbps by a factor of 3.     

QuRiNet: A wide-area wireless mesh testbed for research and experimental evaluations

Research in wireless mesh networks has been growing in recent years. Many testbeds have been created to study networking protocols in wireless mesh networks. In this work, we describe QuRiNet, an outdoor wide-area wireless mesh network deployed in a natural reserve. QuRiNet comprises of over 30 wireless nodes, spread over 2000 acres of wilderness. QuRiNet provides the backbone infrastructure for transporting ecological and environmental data from the natural reserve to the on-campus laboratories. Mesh nodes in QuRiNet are powered by solar energy, and comprise of multiple radios per node. Physical link distances in QuRiNet range from hundreds to thousands of meters. A parallel goal of deploying QuRiNet is to create a novel platform for advanced research in wireless mesh networks. In this report, we share our experiences in the deployment and maintenance of QuRiNet in its unique setting. We also describe various research efforts that have been leveraging the QuRiNet testbed. Several interesting measurement results are reported, along with the impact of various network configurations and technological variations on the functionality of the testbed. QuRiNet has been used for a variety of experimental studies including: channel assignment, network monitoring, and mobility studies. Current and future study plans include experimental evaluations of various security and reliability research.     

Understanding interference and carrier sensing in wireless mesh networks [Accepted from Open Call]

Wireless mesh networks aim to provide high-speed Internet service without costly network infrastructure deployment and maintenance. The main obstacle in achieving high-capacity wireless mesh networks is interference between the mesh links. In this article, we analyze the carrier sensing and interference relations between two wireless links and measure the impact of these relations on link capacity on an indoor 802.11a mesh network testbed. We show that asymmetric carrier sensing and/or interference relations commonly exist in wireless mesh networks, and we study their impact on the link capacity and fair-channel access. In addition, we investigate the effect of traffic rate on link capacity in the presence of interference.     

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a Simple Opportunistic Adaptive Routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.     

Wireless link prediction and triggering using modified Ornstein–Uhlenbeck jump diffusion process

Through time domain observation, typical wireless signal strength values seems to exhibit some forms of mean-reverting and discontinuous “jumps” behaviour. Motivated by this fact, we propose a wireless link prediction and triggering (LPT) technique using a modified mean-reverting Ornstein–Uhlenbeck (OU) jump diffusion process. The proposed technique which we refer as OU-LPT is an integral component of wireless mesh network monitoring system developed by ICT FP7 CARrier grade wireless MEsh Network project. In particular, we demonstrate how this technique can be applied in the context of wireless mesh networks to support link switching or handover in the event of predicted link degradation or failure. The proposed technique has also been implemented and evaluated in a real-time experimental testbed. The results show that OU-LPT technique can significantly enhance the reliability of wireless links by reducing the rate of false triggers compared to a conventional linear prediction technique and therefore offers a new direction on how wireless link prediction, triggering and switching process can be conducted in the future.