路由特性对IEEE802．11 DCF多跳网络容量的影响

使用数学分析方法研究基于IEEE 802.11 DCF的Ad Hoc网络中节点传输半径和路由策略选择问题.在节点均匀分布的多跳网络中,使用四种路由策略以及不同的节点传榆半径设王,试图找出能够使网络容量最大化的方案组合.计算结果表明,在节点密度一定的情况下,减小网络节点的传输距离有利于增加网络的容量,而在传输半径一定的条件下,使用能够导致长跳路由的策略,有利于提高网络容量.     

基于缓存旁路和本地修复的多跳网络路由重建机制

该文针对多跳网络中现有AODV和AODV-BR按需路由算法的弊端,提出了基于缓存旁路和本地修复的AODV-CL路由重建机制。该机制利用空闲时间监听无线信道中传输的所有数据包和路由控制信令,用于维护有效的邻居节点列表及本地路由缓存,有效降低了周期性HELLO消息带来的信令负担,并增加了可用路由信息。中间节点在发现断链时,尝试采用局部修复,尽量避免由源节点广播RREQ消息发现路由。根据本地路由缓存及邻居节点的路由信息,实现了快速的路由发现及修复,能有效降低路由控制信令开销及丢包率。     

基于能量感知的Ad Hoc路由算法研究

针对移动adhoc网络终端能量资源受限对全网路由的影响,提出一种具有终端节点能量感知的路由协议(EARP,energy-awareroutingprotocol).该协议能够根据单个节点能量的使用情况以及全路径的能量消耗情况选择不同的传输路径,在路径断裂时,增加本地维护策略,有效减少了由此引起的发包重传情况,提高了路由效率.通过节点能级的设定,防止链路传输过程中由于能量耗尽而导致的路由断裂情况.经过NS2仿真实验与其他相关路由协议进行比较,结果表明在相同的实验环境下,该路由协议能够有效均衡负载,保护低能量节点,延长网络生存时间     

无线Mesh网中基于网络编码的多路径TCP研究

在无线多跳网络中,本地重传和网络编码已经被成功地应用到多路径技术上以增加吞吐量并减少丢包。然而,在提高UDP传输性能的同时,也产生了数据包重排序和延迟等副作用,严重影响了TCP性能。针对此问题,主要提出一种基于网络编码的多路径传输方案NC-MPTCP,即在无线mesh网络的多条路径中引入网络编码、执行拥塞控制以及使用一个基于信用的方法控制节点的传输速率,提高网络的吞吐量以及增加网络传输的可靠性。该方案使用一个简单的算法,评估丢包率以及发送线性组合数据包的速率,用来降低目的节点的数据包解码延迟和防止TCP的超时重传。仿真结果表明设计的NC-MPTCP有效。     

移动Adhoc网络中按需路由协议的安全性改进方案

在移动Adhoc网络中,安全性是保证其可用性的一个重要方面.文章提出了一种针对按需路由协议的安全性改进方案,这种方案采用了对邻居节点的身份即时认证、对远端节点按需认证、匿名寻找路由,逐跳加密传输的机制,能够有效地阻止恶意节点对网络的窃听、篡改等攻击,确保网络路由信息的安全.     

多约束主动路由协议及其性能分析

主动网络是一种新型的网络体系结构,能够快速地把新协议和新应用引入到正在运行的网络中。由于主动节点具有较高的计算能力,所以能够提供比传统网络更为有效的服务质量路由方案。该文尝试把服务质量路由引入到主动网络中,结合两者优点提出一种基于主动网络的多约束主动路由(MAR)协议。仿真结果表明MAR比目前其它的QoS路由机制更简洁、更灵活、更可控。     

面向目标态势感知的软件定义UAV网络

为解决无人机网络拓扑频繁变化导致数据传输不稳定而影响目标态势感知效果的问题,文中利用软件定义网络(SDN)能够获取全局链路状态信息的优势,综合考虑链路带宽、传输时延等因素,提出一种多链路状态感知的QoS(LSAQ)集中路由算法。同时考虑到UAV节点间通信故障问题,设计主动故障恢复策略将受影响数据流聚合后重新计算本地路由,并利用所提路由算法构建了面向目标态势感知的SDN UAV原型系统。仿真和实验结果表明,所提算法能够提高链路带宽利用率、降低传输时延和减少路由开销,有效保障SDN UAV网络实现目标态势感知任务。     

高动态无线自组网路由协议设计

针对节点快速移动过程中网络建立时间较长,数据端到端传输时延无法得到可靠保 障,并且由于维护动态网络连接性造成网络开销较大等方面的问题,提出了一种无线自组网 路由协议,通过分簇算法快速将网络分为多个簇,每个簇包括簇首节点、成员节点和簇间网 关节点。该协议能够应用于快速移动节点构成的高动态无线自组织网络中,实现了先应式和 反应式路由算法进行了有机结合,能够在快速变化的拓扑结构中为未知路由提供优化的路由 结果,利用较小的网络开销实现网络快速构建和数据端到端的实时传输。     

延迟容忍网络状态感知的路由策略研究

延迟容忍网络具有间歇连通的特点,这为数据传输提出了很大的挑战。目前的路由算法没有充分考虑节点的整个状态(位置、速度),该文提出了一种节点状态感知的路由策略SARM(Situation-Aware Routing Method)。SARM根据节点的状态估计它能把消息传送到汇聚节点的可能性,并把消息复制到那些比自身可能性大的节点上。该文根据消息的生存时间、剩余时间及复制次数提出了一种消息队列管理机制。仿真实验表明,SARM在不增加消息副本数量的情况下提高了传输成功率并降低了传输延迟。     

IMS重叠网络拓扑探测方法的研究

针对IMS重叠网络传输效率和网络资源利用率低下的问题,文章提出了一种拓扑探测方法。利用服务功能节点获取相关路由协议的路由表信息对网络拓扑结构进行探测,可以有效地避免远距离的、跨越多个AS的数据传输,改善网络的系统吞吐量,提高网络的资源利用率。仿真结果也表明使用了该文提出的探测方法的IMS重叠网络比普通的IMS重叠网络具有更好的传输性能和资源利用率。     

多速率移动Ad hoc网络路由策略研究

在多速率Ad hoc网络中，要充分利用多速率的优势，提高网络的整体性能，妊须设计一种适合网络特点以及满足用户需要的多速率路由策略。文中简要分析了多速率路由策略对网络性能的影响，重点介绍了现有的多速率路由策略。论文还给出了后续的工作——对在多频段和多模式的无线网络中采用改进的多速率路由算法的研究。     

A routing protocol using a reliable and high-throughput path metric for multi-hop multi-rate ad hoc networks

In this paper, a high-throughput routing protocol for multi-rate ad hoc networks using lower layer information is proposed. By choosing the route with the minimum value of the proposed “Route Assessment Index” metric which has the form of entropy function, the selected route is ensured to have high throughput and link reliability among route candidates. Link bottleneck is avoided in the chosen route; hence, the packet drop rate due to buffer overflow is alleviated. Furthermore, an effective route discovery strategy is also introduced along with new routing metric. The correctness of the proposal is proven, and the simulation results show that our new metric provides an accurate and efficient method for evaluating and selecting the best route in multi-rate ad hoc networks.     

High throughput route selection in multi-rate wireless mesh networks

Most existing Ad-hoc routing protocols use the shortest path algorithm with a hop count metric to select paths. It is appropriate in single-rate wireless networks, but has a tendency to select paths containing long-distance links that have low data rates and reduced reliability in multi-rate networks. This article introduces a high throughput routing algorithm utilizing the multi-rate capability and some mesh characteristics in wireless fidelity （WiFi） mesh networks. It uses the medium access control （MAC） transmission time as the routing metric, which is estimated by the information passed up from the physical layer. When the proposed algorithm is adopted, the Ad-hoc on-demand distance vector （AODV） routing can be improved as high throughput AODV （HT-AODV）. Simulation results show that HT-AODV is capable of establishing a route that has high data-rate, short end-to-end delay and great network throughput.     

An efficient handover decision method based on frame retransmission and data rate for multi-rate WLANs

To enhance the communication performance at handover between multi-rate WLANs, we propose a new handover decision method that can be applied to our previously reported handover management scheme, which handled a handover by utilizing two WLAN interfaces (IFs) through cross-layer collaboration between layer 2 and layer 4. It should be noted that we here propose a new handover decision scheme for traversing between multi-rate WLANs, while our previous decision scheme works only in fixed-rate WLANs. In this paper, to treat a handover between multi-rate WLANs, we employ two kinds of information: (1) the most frequently used data rate (MFDR) for assessing the stable communication performance of a multi-rate WLAN, and (2) the frame retransmission ratio (FRR) for assessing its exact communication performance. The MFDR enables us to estimate the area where we should start handover. If the MFDRs of two interfaces are same in the area, the FRR allows us to compare the wireless condition on the two interfaces precisely to give an optimal handover point. Through simulation experiments, we show that our proposed scheme certainly estimates an appropriate handover point as a result of multi-path transmission (s), thereby providing handover successfully. That is, the proposed method can determine handover at an optimal point depending on the various distances between access points, the mobile node (MN) velocity, and the MN moving pattern. Moreover, our proposed scheme prevents the redundant network load caused by multi-path transmission as much as possible, thereby providing the ideal TCP communication performance.     

Performance and fairness enhancement in IEEE 802.11 WLAN networks

The multi-rate transmission mechanism in IEEE 802.11 can improve its reliability and robustness. However, it causes a performance anomaly. After analyzing the reasons for the performance anomaly in multi-rate mechanism, we propose a new scheme to solve the performance anomaly. By adjusting packet size according to the transmission rate, this scheme guarantees that these nodes with different transmit rates can access wireless channel fairly. Theoretical analysis and performance evaluation show that the proposed scheme can well solve the performance anomaly problem.     

High throughput reactive routing in multi-rate ad hoc networks

A reactive routing algorithm for multi-rate ad hoc wireless networks is proposed. It enhances the AODV protocol and achieves higher throughput by utilising the multi-rate capability of the underlying wireless channel via the MAC delay routing metric. Simulations show that the protocol leads to a significant throughput increase over traditional ad hoc routing protocols.     

An integrated routing and rate adaptation framework for multi-rate multi-hop wireless networks

In this paper, we propose a new integrated framework for joint routing and rate adaptation in multi-rate multi-hop wireless networks. Unlike many previous efforts, our framework considers several factors that affect end-to-end performance. Among these factors, the framework takes into account the effect of the relative positions of the links on a path when choosing the rates of operation and the importance of avoiding congested areas. The key element of our framework is a new comprehensive path metric that we call ETM (for expected transmission cost in multi-rate wireless networks). We analytically derive the ETM metric. We show that the ETM metric can be used to determine the best end-to-end path with a greedy routing approach. We also show that the metric can be used to dynamically select the best transmission rate for each link on the path via a dynamic programming approach. We implement the ETM-framework on an indoor wireless mesh network and compare its performance with that of frameworks based on the popular ETT and the recently proposed ETOP metrics. Our experiments demonstrate that the ETM-framework can yield throughput improvements of up to 253 and 368 % as compared with the ETT and ETOP frameworks.     

Integrated dynamic distributed routing and admission control in ATM networks

A node-by-node admission control and routing scheme for ATM networks is devised. The scheme is based on the subdivision of traffic into a number of classes, characterized by different performance requirements. At each network node, for all outgoing links, link capacity partitions are periodically assigned to the traffic classes, as the result of an optimization problem over a fixed time interval. Local access control rules compute the maximum number of connections of each class that a link can accept within the assigned capacity. Incoming call connection requests are forwarded in a hop-by-hop fashion. Each node traversed, first checks the presence of resources needed to accept a new connection and guarantee all quality of service (QoS) requirements. This is done by using the local access control rule. Then, it chooses the next node along the path on the basis of a distributed routing strategy. This minimizes a cost function accounting for local instantaneous information, as well as for aggregate information that is passed periodically among adjacent nodes. Two routing strategies are introduced. In the first scheme, a new call is rejected if, at a certain node along the path, there are not enough resources to guarantee QoS requirements, and no recovery mechanism is implemented. In the second scheme, an alternative path is looked for after the first failure. Simulation results are presented which show a comparison between the two proposed routing strategies. Comparison is also made between the proposed scheme and the other approaches. © 1997 John Wiley & Sons, Ltd.     

Distributed Contention-Aware Call Admission Control for IEEE 802.11 Multi-Radio Multi-Rate Multi-Channel Wireless Mesh Networks

In this paper, we focus on call admission control (CAC) in IEEE 802.11 multi-radio multi-rate multi-channel (MR²-MC) wireless mesh networks (WMNs). CAC is the key component of QoS routing protocols. The goal of CAC is to protect existing flows from QoS violations and fully utilize available radio resource on channels. We propose a CAC mechanism, called Contention-Aware Multi-channel Call Admission Control (CMC), for MR²-MC WMNs based on IEEE 802.11 DCF. CMC is fully distributed, relies on local information to estimate the residual bandwidth of a path, and can be integrated into existing routing protocols for MR²-MC WMNs to provide QoS. We evaluate the performance of CMC via ns-2 simulations. The results show that CMC can precisely predict the end-to-end residual bandwidths of paths, successfully protects existing flows from QoS violations, and fully utilizes the bandwidths on channels.     

Interconnecting high-speed LANs and backbones

Transparent source routing, an algorithm that exploits the best features of the transparent spanning tree and source routing algorithms for medium-access-control (MAC) bridges used in local area network (LAN) interconnections, is presented. The scheme uses optimal routes, is transparent to end stations, and reduces bridge processing overheads. Aspects of the existing transparent spanning tree and source routing algorithms are described. A comparison of the new scheme with the two existing schemes is presented