基于传输路径质量的无线mesh网络可靠多播

提出了一种可靠多播网(RM)模型,探讨了无线链路和节点可靠性对多播路径选择的影响。首先,建立了无线链路的相关性和多播路径的可靠性模型,并提出了多播传输的可靠性判据;同时,结合首树算法和多路径树算法提出了构造可靠多播网的算法。可靠多播网具有并行的多播路径,通过在多播源节点和目的节点之间选择多播链路和节点构成了可靠的多播路径,提供了多播路径的"负荷分担"和"热备份"功能,从而支持了多播业务可靠性。     

基于SimCT的多播路由及故障恢复研究

在数据交换网络中,颜色树是一种通过节点不相交的多路径路由数据报文的有效方法。这种方法中组建两棵以某一节点为根节点的颜色树,即Red树和Blue树,网络中各节点到根节点的路径是节点不相交的。本文在分析和研究SimCT算法的基础上,提出了一种基于颜色树的多播树生成方法及单节点/链路故障的多播通信恢复方案。该方法根据SimCT算法构造的颜色树来组建一棵多播转发树,在多播树中单节点或单链路故障后,故障检测节点本地执行故障恢复方案,将受影响的故障节点的下游子树重新连接到多播树。仿真实验表明,本文所提出的多播树生成方案相比现有方案可以减少网络资源的浪费,并且故障恢复后的代价与原多播通信树相当。     

多播群组通信中服务质量受限的Core Placement算法

与面向源节点的路由算法不同，Ｃｏｒｅ Ｂａｓｅｄ多播路由算法在网络中为一个多播组上 的多个多播连接只建立一棵共享树，从而实现了提高了网络资源利用率的目的。本文针对 Ｃｏｒｅ Ｂａｓｅｄ多播路由中 ｃｏｒｅ节点的定位问题，提出了一个同时最小化多播时延及目标节点间时延抖动的 ｃｏｒｅ节点定位算法 ＱＯＣＰ。由仿真结果可知，这里提出的方法在优化服务质量性能指标方面明显优 于文中涉及的其他算法。     

一种传感器网络的分布式多播路由优化算法

传感器感知的信息需要通过网络传送给感兴趣目标节点,传统网络中的多播技术往往能耗高、实时性不够理想,不利于在传感器网络中使用。针对 WSN中节点对网络拓扑未知,该文先将多播路由问题演化为最优多播路径问题,通过启发式算法求解分布式最优路径,并通过一种基于贪婪思想的裁剪合并策略优化多播路由树,直至整个网络得到最优路径,最后并结合了节点区域集中以及无线多播特性,提出了 DCast 路由算法。最后通过仿真实验与uCast, SenCast等经典的传感器网络的多播路由算法仿真比较,可以得出其算法在时延性以及能耗等方面性能有优势。     

KPP算法在城市地下管网中的应用

针对地下管网“一到多”的特点,利用多播路由的思想,在Maplnfo中实现KPP算法,开发出城市地下管网地理信息系统GIS（Geographic Information System）。仿真结果袁明,KPp算法在构造生成树的过程中动态调整路径的选取。尽可能共享网络中的链路,并对所构造的生成树进行进一步调整优化,从而得到一棵满足最短路径和较小的生成树。     

网络多播路由的改进编码软件设计与实现

传统网络多播路由编码方法采用多播分布树进行编码,但链路容量遭遇瓶颈,致使编码节点较多,导致浪费带宽资源的问题。在此提出基于Koetter指数时间的网络多播路由改进编码算法对编码软件进行设计,分析多播路由的总体设计,通过数据包编码转发模块在多播拓扑不相交路径上进行编码和转发多播数据包,利用输入模块实现网络多播路由和上游节点的信息交换,通过开关仲裁模块判断能够向特定输出端口传输信息的输入端口,利用死锁控制模块对出现死锁现象的路由节点进行检测,一段时间后使多播路由恢复正常的数据交换,通过输出模块对数据的输出进行管理。以降低带宽资源为目的,采用Koetter指数时间算法实现网络多播路由编码,并给出编码的详细代码。实验结果表明,所提方法不仅节省网络资源,而且显著降低多播路由时延,增强网络吞吐量。     

基于链路共享度的网络编码多播路由算法

针对网络编码中最小编码子图的构造问题,提出了一种基于链路共享度的网络编码多播路由算法.该算法利用各条链路的共享度不同,依次选择共享度最大的链路加入到多播传输路径中.实验仿真结果表明,该算法与传统的最短路径多播树算法相比,可节省网络资源约6%～15%,能更好地均衡网络负载,结合随机网络编码算法,能够有效提升多播传输的性能...     

Ad Hoc网络中基于粒子群优化的QoS多播路由研究

针对Ad Hoc网络中带QoS约束的多播路由问题，提出了一种新的结合MAODV多播路由发现方法和粒．子群优化算法的QoS多播路由发现算法。仿真试验显示该算法较好地改进了端到端传输的代价、延时和带宽利用率，能够找到一棵消耗趋于最小、状态稳定的多播路由树。     

传感器网络中基于最短路径树的低延时节能路由算法

借助图论中最短路径和最小生成树的原理,在无线传感器网络中构建若干棵以Sink节点为根的最短路径源路由树。与最小生成树相比,最短路径树能保证路径上大部分节点找到节点间RSSI较强的通讯路径并以较少的跳数把数据传输给Sink节点,而最小生成树中的节点则需较多跳数。因此,提出的算法在一定程度上降低了延时。算法通过事先设定最低RSSI和节点最大剩余能量MRE来构建路由树,并修改已存在的路由算法,从而保证节点通讯的可靠性和网络的节能。     

BowCast：一种适应非对称链路延时网络的P2P多播路由协议

虽然IP多播的性能优势无可否认,但是它却面临着部署上的困难。近年来,P2P多播作为提供多播服务的另一可行途径正不断为人们所认可。研究非对称链路延时网络环境下P2P多播的路由问题,提出一个新的P2P多播路由协议：BowCast.该协议采用基于树（tree-based）的分布式路由策略,使多播组成员之间能自组织地构建一棵基于源的最小延时P2P多播树。BowCast主要利用范围受限的单向探测技术（BOW）来实现路由优化算法。BOW能提供端系统节点间的单向相对延时,无需全局的同步时钟。仿真实验表明,BowCast能很好地适应非对称链路延时环境。通过调节BOW的探测范围,BowCast能灵活地在路由性能和控制开销之间进行折中。     

Rate-Diversity and Resource-Aware Broadcast and Multicast in Multi-rate Wireless Mesh Networks

This paper focuses on the problem of increasing the traffic capacity (volume of admissible traffic) of broadcast and multicast flows in a wireless mesh network (WMN). We study and suggest routing strategies where the process of constructing the forwarding tree considers three distinct features: (a) the ability of individual mesh nodes to perform link-layer broadcasts at multiple rates, (b) the wireless broadcast advantage, whereby a single broadcast transmission covers multiple neighboring receivers and (c) the residual transmission capacity at a WMN node, subject to intereference-based constraints from existing traffic flows in its neighborhood. Our metric of interest is the total number of broadcast and multicast flows that can be admitted into the network, without resulting in unacceptable degradation in metrics such as packet loss and dissemination latency. Our discrete event simulations show that the broadcast tree construction heuristic which takes both transmission rate and residual bandwidth into account out-performs those that do not. Building on our work on resource-aware broadcast tree construction, we propose a resource-aware multicast tree construction algorithm which exploits the multiple link-layer rates, the wireless broadcast advantage and the amount of resources available. Simulation results show that this algorithm performs better than heuristics based on pruning a broadcast tree or shortest path trees.     

QoS multicast routing by using multiple paths/trees in wireless ad hoc networks

In this paper, we investigate the issues of QoS multicast routing in wireless ad hoc networks. Due to limited bandwidth of a wireless node, a QoS multicast call could often be blocked if there does not exist a single multicast tree that has the requested bandwidth, even though there is enough bandwidth in the system to support the call. In this paper, we propose a new multicast routing scheme by using multiple paths or multiple trees to meet the bandwidth requirement of a call. Three multicast routing strategies are studied, SPT (shortest path tree) based multiple-paths (SPTM), least cost tree based multiple-paths (LCTM) and multiple least cost trees (MLCT). The final routing tree(s) can meet the user’s QoS requirements such that the delay from the source to any destination node shall not exceed the required bound and the aggregate bandwidth of the paths or trees shall meet the bandwidth requirement of the call. Extensive simulations have been conducted to evaluate the performance of our three multicast routing strategies. The simulation results show that the new scheme improves the call success ratio and makes a better use of network resources.     

Multicast Routing in Wireless Mesh Networks: Minimum Cost Trees or Shortest Path Trees?

There exist two fundamental approaches to multicast routing: shortest path trees (SPTs) and minimum cost trees (MCTs). The SPT algorithms minimize the distance (or cost) from the sender to each receiver, whereas the MCT algorithms minimize the overall cost of the multicast tree. Due to the very large scale and unknown topology of the Internet, computing MCTs for multicast routing in the Internet is a very complex problem. As a result, the SPT approach is the more commonly used method for multicast routing in the Internet, because it is easy to implement and gives minimum delay from the sender to each receiver, a property favored by many real-life applications. Unlike the Internet, a wireless mesh network (WMN) has a much smaller size, and its topology can be made known to all nodes in the network. This makes the MCT approach an equally viable candidate for multicast routing in WMNs. However, it is not clear how the two types of trees compare when used in WMNs. In this article we present a simulation-based performance comparison of SPTs and MCTs in WMNs, using performance metrics, such as packet delivery ratio, end-to-end delay, and traffic impacts on unicast flows in the same network.     

Dynamic agent-based hierarchical multicast for wireless mesh networks

We propose and analyze a multicast algorithm named Dynamic Agent-based Hierarchical Multicast (DAHM) for wireless mesh networks that supports user mobility and dynamic group membership. The objective of DAHM is to minimize the overall network cost incurred. DAHM dynamically selects multicast routers serving as multicast agents for integrated mobility and multicast service management, effectively combining backbone multicast routing and local unicast routing into an integrated algorithm. As the name suggests, DAHM employs a two-level hierarchical multicast structure. At the upper level is a backbone multicast tree consisting of mesh routers with multicast agents being the leaves. At the lower level, each multicast agent services those multicast group members within its service region. A multicast group member changes its multicast agent when it moves out of the service region of the current multicast agent. The optimal service region size of a multicast agent is a critical system parameter. We propose a model-based approach to dynamically determine the optimal service region size that achieves network cost minimization. Through a comparative performance study, we show that DAHM significantly outperforms two existing baseline multicast algorithms based on multicast tree structures with dynamic updates upon member movement and group membership changes.     

A cross‐layer optimization for maximum‐revenue‐based multicast in multichannel multiradio wireless mesh networks

Given a video/audio streaming system installed on a multichannel multiradio wireless mesh network, we are interested in a problem concerning about how to construct a delay‐constrained multicast tree to support concurrent interference‐free transmissions so that the number of serviced mesh clients is maximized. In this paper, we propose a heuristic approach called cross‐layer and load‐oriented (CLLO) algorithm for the problem. On the basis of the cross‐layer design paradigm, our CLLO algorithm can consider application demands, multicast routing, and channel assignment jointly during the formation of a channel‐allocated multicast tree. The experimental results show that the proposed CLLO outperforms the layered approaches in terms of the number of serviced mesh clients and throughputs. This superiority is due to information from higher layers can be used to guide routing selection and channel allocation at the same time. As a result, the CLLO algorithm can explore more solution spaces than the traditional layered approaches. In addition to that, we also propose a channel adjusting procedure to enhance the quality of channel‐allocated multicast trees. According to our simulations, it is proved to be an effective method for improving the performance of the proposed CLLO algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

A Multi-Objective Optimization Approach for Joint Channel Assignment and Multicast Routing in Multi-Radio Multi-Channel Wireless Mesh Networks

Multicast routing is an effective mechanism for delivering data to a group of receivers. Due to intrinsic property of air medium in wireless mesh networks (WMN), interference is an important issue in determining the data rate for multicast services. Interference reduction is handled by assigning multiple orthogonal channels to multiple radios in multi-radio multi-channel WMNs. Channel assignment is known to be a NP-complete problem. Most prior methods have solved multicast routing and channel assignment problems sequentially and have not considered the interplay between these two problems. Focusing on this issue, we address joint channel assignment and routing problem for multicast applications. In this paper, a novel technique based on a multi-objective genetic algorithm is proposed to build a delay constrained minimum cost multicast tree with minimum interference. We have examined the proposed algorithm on different network configurations. Experimental results demonstrate that our method finds better trees in terms of cost, delay, and interference compared to prior methods.     

An integrated routing and admission control mechanism for real‐time multicast connection establishment

There are two major difficulties in real‐time multicast connection setup. One is the design of an efficient distributed routing algorithm which optimizes the network cost of routing trees under the real‐time constraints. The other is the integration of routing with admission control into one single phase of operations. This paper presents a real‐time multicast connection setup mechanism, which integrates multicast routing with real‐time admission control. The proposed mechanism performs the real‐time admission tests on a cost optimal tree (COT) and a shortest path tree (SPT) in parallel, aiming at optimizing network cost of the routing tree under real‐time constraints. It has the following important features: (1) it is fully distributed; (2) it achieves sub‐optimal network cost of routing trees; (3) it takes less time and less network messages for a connection setup. Copyright © 2001 John Wiley & Sons, Ltd.     

一种基于排序蚁群算法的无线Mesh多径路由协议

无线Mesh网络因其较好的鲁棒性、可覆盖区域广、低成本、接入便利等优点,在临时布置通信网络逐渐得到了重用,在无线通信技术中扮演着越来越重要的角色。针对无线Mesh网络的特点,提出一种基于改进蚁群算法的多径路由协议Fortified Ant协议。与传统的蚁群算法路由协议相比,该协议对蚁群算法进行改进,在蚁群算法基础上加入排序算法,同时在该协议中加入多径传输,在主路由失效时马上启用备份路由,保证信息传输的时效性和可靠性。实验结果表明,与ADOV、DSR和ACO路由算法相比,该算法能迅速发现质量较优的多条路径,具有收敛快、开销少等优势。     

无线mesh网中最小编码代价低时延多播路由

提出了一种无线mesh网中最小网络编码代价低时延多播路由协议(MNCLDMR, minimal network coding and low delay multicast routing)。MNCLDMR的目标是选择合适的网络编码节点,最小化网络编码代价,降低网络时延。MNCLDMR主要思想是引入拓扑关键节点和网络编码关键节点的概念,以下一跳的节点是否是网络编码关键节点或拓扑关键节点作为路由判据,采用MNCLD算法构造多播树。仿真结果表明,MNCLDMR可以达到预定目标,合理形成网络编码机会,能实现最小网络编码代价低时延多播路由。