无线Mesh网络路由协议研究

首先讨论了无线Mesh网络（WMN）路由协议的研究背景及其特点,阐述了WMN路由协议研究现状,介绍了其相关商业应用情况,并对其特性进行了简要分析。分别对多判据路由、QOS路由、分级路由、多信道路由、跨层路由等路由协议的设计原则和思路进行了详细讨论。最后。结合一些研究热点问题,展望了WMN路由协议的研发前景。     

无线Mesh网络路由协议研究

无线网状网络(WMN)的路由算法是Mesh领域的研究重点,采用何种路由协议使无线Mesh网络在需要的环境中性能达到最优,是目前WMN路由协议应用的实际问题.文中提出了设计无线网状网路由协议时需具备的特点,对目前提出WMN路由协议进行了分析研究,并比较了WMN路由协议优缺点,对WMN路由协议的选择提供了依据.     

无线Mesh网络路由协议研究

无线Mesh网络WMN（wireless mesh networks）是一种新型的无线网络，它融合了无线局域网（WLAN）和Ad Hoc网络的优势，成为宽带接入的一种有效手段。首先介绍了无线Mesh网的网络结构和特点．并在此基础上讨论了无线Mesh网络对路由协议的要求。无线Mesh网络的路由算法是Mesh领域的研究难点，通过分析比较4种针对WMN的路由协议，总结了现有的路由协议的优缺点，并对今后的研究方向做出了展望。     

基于无线Mesh网络跨层协议研究

介绍无线Mesh网络的基本概念和特点,基于Mesh网络的相关MAC协议和路由协议,从物理层、MAC层、路由协议层等层面介绍WMN跨层设计的一般原则和方法,对WMN的跨层设计方法和方案进行了阐述,对目前Mesh网络中的传统OSI分层结构参考模型存在的问题进行了分析,提出需要进一步研究的问题。     

无线Mesh网络跨层路由技术研究

无线Mesh网络(WMN:wireless mesh networks)作为一种新型的无线网络,成为近几年研究的热点。由于无线信道不稳定等特性,如何设计WMN的路由协议成为决定其性能的关键因素之一。近几年来的研究表明,通过跨层设计的方式综合其他层的重要参数来实现路由选择,能够很好地解决这一难题。介绍了几种先进的跨层路由设计方案,总结了现有的跨层路由协议的优缺点,并对如何设计并实现跨层路由协议进行了分析和总结。     

无线网状网中基于信道预留的多信道媒体接入控制方案

目前多信道无线Mesh网络WMN(Wireless Mesh Network)的MAC(Medium Access Contro)l仍然存在信道利用率低的问题,因此提出了具有控制信道和数据信道的多信道WMN的MAC方案。方案采用数据信道预留机制来提高系统的吞吐量,并降低接入时延。该方案通过减小控制信道上的碰撞概率可以有效降低系统接入时延并提高控制信道的利用率。理论分析和性能估计表明此方案具有高的吞吐量和低的接入时延,性能明显优于现有的公共信道控制方案CCC(Common Control Channel)。     

无线Mesh网络中路由算法的研究

无线Mesh网络(WMN)近年来受到了越来越多的关注,对其路由协议的研究一直是个热点问题。WMN是由移动自组织网络(MANET)发展起来,针对应用在MANET中的DSR、AODV、DSDV、CEDAR等4种路由协议算法,分析并总结它们的优缺点,并对上述4种算法在WMN中应用的可行性进行了分析。     

多信道无线Mesh网络的性能研究

在无线Mesh网络中使用多信道可以减少碰撞和干扰,提高系统吞吐量.本文先介绍无线Mesh网络,然后介绍多信道在无线Mesh网络中的应用,分析了几种常用的多信道MAC协议.接着着重阐述了多信道无线Mesh网络所面临的问题与挑战,对信道分配、路由选择和隐蔽终端这3个主要问题进行分析,并对其研究设计方向进行了展望.     

基于单射频的无线Mesh网多信道方法

无线网状网(Wireless Mesh Network,WMN)是一种新型的分布式宽带无线网络结构.典型的移动Ad Hoc网络具有节点移动性小、受电池动力限制和用户带宽需求大等特点,从而导致传统单信道的Ad Hoc结构不再满足WMN用户的需求.为了提供更大的带宽,多信道技术得到越来越多应用.探讨了WMN的网络结构与特点,对现有几种典型的多信道技术进行了比较,提出了一种基于单射频的无线Mesh网多信道的设计方案,不同网关节点所代理的节点使用不同的信道进行通信,从而避免了不同子网节点之间的信道干扰.通过NS2的仿真与分析表明,该方法在特定环境下的网络性能是传统单射频单信道方法的2倍.     

无线Mesh网络多信道MAC协议

分析了WMN多信道MAC协议设计所面临的问题;介绍了几种现有典型的多信道MAC协议,并对其进行了分析;对多信道MAC协议未来的发展作了简要的总结。期望文章使读者对WMN多信道MAC协议的关键技术,特别是协议的设计有一个概括性的了解。     

Algorithms for multicast traffic grooming in WDM mesh networks

Several of the new applications in high-performance networks are of the multicast traffic type. Since such networks employ an optical network infrastructure, and since most of these applications require subwavelength bandwidth, several streams are usually groomed on the same wavelength. This article presents an account of recent advances in the design of optical networks for multicast traffic grooming in WDM mesh networks. The article addresses network design and session provisioning under both static and dynamic multicast traffic. Under static traffic conditions, the objective is to accommodate a given set of multicast traffic demands, while minimizing the implementation cost. Optimal and heuristic solution techniques for mesh network topologies are presented. Under dynamic traffic conditions, techniques for dynamic routing and session provisioning of multicast sessions whose objective is to minimize session blocking probabilities are explained. The article also presents a number of open research issues     

The core-assisted mesh protocol

The core-assisted mesh protocol (CAMP) is introduced for multicast routing in ad hoc networks. CAMP generalizes the notion of core-based trees introduced for internet multicasting into multicast meshes that have much richer connectivity than trees. A shared multicast mesh is defined for each multicast group; the main goal of using such meshes is to maintain the connectivity of multicast groups even while network routers move frequently, CAMP consists of the maintenance of multicast meshes and loop-free packet forwarding over such meshes. Within the multicast mesh of a group, packets from any source in the group are forwarded along the reverse shortest path to the source, just as in traditional multicast protocols based on source-based trees. CAMP guarantees that within a finite time, every receiver of a multicast group has a reverse shortest path to each source of the multicast group. Multicast packets for a group are forwarded along the shortest paths front sources to receivers defined within the group's mesh. CAMP uses cores only to limit the traffic needed for a router to join a multicast group; the failure of cores does not stop packet forwarding or the process of maintaining the multicast meshes     

无线Mesh网络可靠多播路由

无线Mesh网络多播路由是无线路由必须解决的关键技术。部分研究者对网络资源和服务质量（QoS）进行研究,提出了建立最短路径树、最小开销树、负载感知、信道分配多播等多播算法;有的算法考虑链路可靠性,建立备用路径。将结合网络资源和可靠性对多播路由算法进行研究,提出了建立可靠多播树（RT,Reliable Tree）的多播路由算法：可靠多播树是一个多树结构,由一棵首选多播树和一棵多径树构成,多径树提供可靠多路径,以提高网络吞吐量。     

Overlay multicast for MANETs using dynamic virtual mesh

Overlay multicast protocol builds a virtual mesh spanning all member nodes of a multicast group. It employs standard unicast routing and forwarding to fulfill multicast functionality. The advantages of this approach are robustness and low overhead. However, efficiency is an issue since the generated multicast trees are normally not optimized in terms of total link cost and data delivery delay. In this paper, we propose an efficient overlay multicast protocol to tackle this problem in MANET environment. The virtual topology gradually adapts to the changes in underlying network topology in a fully distributed manner. To save control overhead, the participating nodes only keep a fisheye view of the dynamic mesh. The multicast tree is progressively adjusted according to the latest local topology information. Simulations are conducted to evaluate the tree quality. The results show that our approach solves the efficiency problem effectively. This research was supported in part by the National Science Foundation under the grants CCR-0296070 and ANI-0296034. The preliminary results of this work is presented in “Efficient Overlay Multicast in Mobile Ad Hoc Networks,” Proc. IEEE WCNC 2003. Chao Gui is a Technical Research Staff at Kiyon Inc (www.kiyon.com). His research interests include wireless networking and mobile computing. His current efforts are on industrial implementation of wireless mesh networks and embedded systems. Dr. Gui has received Ph.D. in Computer Science from University of California at Davis in 2005. Prasant Mohapatra is currently a Professor in the Department of Computer Science at the University of California, Davis. He has also held various positions at Iowa State University, Michigan State University, Intel Corporation, Panasonic Technologies, Institute of Infocomm Research, Singapore, and the National ICT, Australia. Dr. Mohapatra received his Ph.D. in Computer Engineering from the Pennsylvania State University in 1993. He was/is on the editorial boards of the IEEE Transactions on computers, ACM/Springer WINET, and Ad hoc Networks Journal. He has served on numerous technical program committees for international conferences, and served on several panels. He was the Program Vice-Chair of INFOCOM 2004, and the Program Co-Chair of the First IEEE International Conference on Sensor and Ad Hoc Communications and Networks, (SECON-2004). Dr. Mohapatra’s research interests are in the areas of wireless networks, sensor networks, Internet protocols and QoS.     

Adaptive Core Multicast Routing Protocol

The Adaptive Core Multicast Routing Protocol (ACMRP) is proposed for multicast routing in ad hoc networks. ACMRP is on demand core-based multicast routing protocol that is based on a multicast mesh. In ACMRP, a core is not well-known and it adapts to the current network topology and group membership. The enhanced adaptivity minimizes the core dependency and, accordingly, improves performance and robustness of ACMRP. A multicast mesh is created and maintained by the periodic flooding of the adaptive core. Since the flooding traffic is evenly maintained and a mesh provides rich connectivity among group members, ACMRP can achieve efficiency, scalability, and effectiveness. We evaluate scalability and performance of ACMRP via simulation.     

Multicast protection scheme based on Hamiltonian cycle in fault-tolerant optical mesh networks

The increase of multimedia service requirements results in the growing popularity of the multicast in Wavelength-Division Multiplexing (WDM) optical mesh networks. Multicast fault tolerance in WDM optical mesh networks is an important issue because failures caused by the traffic carried in WDM optical mesh networks may lead to huge data loss. Previous works have proposed multicast protection algorithms to address the single-fiber link failure dominant in current optical mesh networks. However, these existing algorithms are all mainly based on path protection or segment protection, which may lead to long restoration times and complicated protection switching procedures. This paper therefore proposes a new heuristic algorithm, called Enhanced Multicast Hamiltonian Cycle Protection (EMHCP), in which all working light-trees of multicast demands can be protected by a Hamiltonian cycle in the network. For each multicast demand, EMHCP computes a least-cost light-tree based on the presented link-cost function that considers load balancing and proper straddling link selection so that backup wavelengths on the Hamiltonian cycle can be reduced. Simulation results show that EMHCP can obtain significant performance improvement compared with the conventional algorithm.     

A ring-based multicast routing topology with QoS support in wireless mesh networks

Wireless mesh networking (WMN) is an emerging technology for future broadband wireless access. The proliferation of the mobile computing devices that are equipped with cameras and ad hoc communication mode creates the possibility of exchanging real-time data between mobile users in wireless mesh networks. In this paper, we argue for a ring-based multicast routing topology with support from infrastructure nodes for group communications in WMNs. We study the performance of multicast communication over a ring routing topology when 802.11 with RTS/CTS scheme is used at the MAC layer to enable reliable multicast services in WMNs. We propose an algorithm to enhance the IP multicast routing on the ring topology. We show that when mesh routers on a ring topology support group communications by employing our proposed algorithms, a significant performance enhancement is realized. We analytically compute the end-to-end delay on a ring multicast routing topology. Our results show that the end-to-end delay is reduced about 33 %, and the capacity of multicast network (i.e., maximum group size that the ring can serve with QoS guarantees) is increased about 50 % as compared to conventional schemes. We also use our analytical results to develop heuristic algorithms for constructing an efficient ring-based multicast routing topology with QoS guarantees. The proposed algorithms take into account all possible traffic interference when constructing the multicast ring topology. Thus, the constructed ring topology provides QoS guarantees for the multicast traffic and minimizes the cost of group communications in WMNs.     

ATM上多播技术的探讨

针对ＡＴＭ这种非广播的多址接系统,介绍了３种实现多播的方式。其中第１种和第２－多播ＶＣ网与多播服务器,是在ＡＴＭ上传送ＩＰ分组时,为实现ＩＰ层的多播而广泛认可的２种方式,而第３种连接服务器,则是在ＡＴＭ上进行域内无连接多播一种新型方式。重点介绍了第３种方式。     

A novel approach for multicast call acceptance in multi-channel multi-radio wireless mesh networks

Multicasting is an efficient data transmission approach for group communication applications in multi-channel multi-radio wireless mesh networks. In this paper we have studied the problem of accepting on-line multicast requests, which is quite important for supporting multimedia applications. Our proposed algorithm investigates the acceptance of an arrived call in two phases. In the first phase, a loop-free mesh backbone is constructed. In this mesh, the set of possible parents of each node is limited to the neighbors that are one hop closer to the source node. The neighbors with the same distance from the source node are also acceptable under the circumstance that two neighboring nodes cannot be the possible parents of each other. Next, a sub-optimal mathematical model has been proposed for tree construction over the obtained mesh. The derived multicast trees utilize the minimum amount of bandwidth; are load-balanced; and exploit wireless broadcast advantage. The results show that the proposed algorithm improves the rate of multicast call acceptance by 40% on average compared to previous algorithms in a short running time.     

Adaptive multicast on mobile ad hoc networks using tree-based meshes with variable density of redundant paths

Multicasting has been extensively studied for mobile ad hoc networks (MANETs) because it is fundamental to many ad hoc network applications requiring close collaboration of multiple nodes in a group. A general approach is to construct an overlay structure such as multicast tree or mesh and to deliver a multicast packet to multiple receivers over the overlay structure. However, it either incurs a lot of overhead (multicast mesh) or performs poorly in terms of delivery ratio (multicast tree). This paper proposes an adaptive multicast scheme, called tree-based mesh with k-hop redundant paths (TBM _k ), which constructs a multicast tree and adds some additional links/nodes to the multicast structure as needed to support redundancy. It is designed to make a prudent tradeoff between the overhead and the delivery efficiency by adaptively controlling the path redundancy depending on network traffic and mobility. In other words, when the network is unstable with high traffic and high mobility, a large k is chosen to provide more robust delivery of multicast packets. On the other hand, when the network traffic and the mobility are low, a small k is chosen to reduce the overhead. It is observed via simulation that TBM _k improves the packet delivery ratio as much as 35% compared to the multicast tree approach. On the other hand, it reduces control overhead by 23–87% depending on the value of k compared to the multicast mesh approach. In general, TBM _k with the small value of k offers more robust delivery mechanism but demands less overhead than multicast trees and multicast meshes, respectively.