MANET典型路由协议的性能分析与仿真

移动Ad Hoc网络(MANET)是由一组无线移动主机组成的一个没有任何事先建立好的基础设施或集中管理设备的临时网络,其特点是网络拓扑易变,带宽、能源有限及容易受到攻击等。该文对AODV, DSR, DSDV这几种典型的路由协议进行分析比较,指出它们的优缺点及适用场合。通过2个场景的配置,从路由开销、分组投递率、端到端的平均时延3个方面进行实验。仿真结果表明,按需路由协议在3个方面都表现出较好的性能。     

基于VBR业务模型的MANET DSR协议仿真性能分析

移动Ad Hoc网络(MANET)是由一组由移动节点组成的无线网络。MANET的性能已经被广泛的进行了研究,但是这些研究很多主要是针对节点的移动性和网络的规模来展开的。近年来,MANET在传输视频、音频、数据、图像等多媒体上的应用越来越多,因此对MANET在传输不同业务模型时的性能分析也引起了注意。本文中,我们主要研究分析了MANETDSR协议在传输VBR业务时的性能,并且将仿真结果和传输CBR业务时的结果进行了比较。通过进一步的分析,我们得出与传输VBR业务相比,在传输CBR业务时,MANET DSR协议性能明显提高。     

IEEE 802.11e协议HCCA机制下的QoS研究

分析了IEEE 802.11e协议HCCA信道接入机制下的简单带宽调度算法对多媒体业务的QoS支持情况,指出其不足并在其基础上进行了改进,提出了一种基于业务等级的带宽调度算法E-HCCA（Enhanced HCCA）。E-HCCA对不同优先等级业务的数据在带宽分配上采用不同的策略,在优先保证各个节点CBR业务的基础上,根据节点的VBR流量动态平均分配剩余带宽。相比较简单调度算法,E-HCCA算法更好地支持了多用户下的语音业务流和视频业务流,降低了分组时延,增加了系统吞吐率。     

针对逆向流的Reno和Vegas算法性能的仿真分析

网络拥塞已经成为制约网络发展和应用的一个瓶颈.在TCP中已经实现的Reno和Vegas均是基于端到端的拥塞控制算法,它们虽然减轻了前向路径上的拥塞程度,但不能改善后向路径上数据流拥塞所导致的诸如吞吐率、丢包率等网络性能降低这一状况.基于"包丢失是由于网络拥塞引起"的假定,利用OPNET网络仿真软件,建立了单个瓶颈网络,设定了吞吐量、丢包率以及拥塞窗口(cwnd)等参数,对Reno和Vegas两种算法在逆向流中的性能进行比较,分析影响网络吞吐量的因素.仿真结果表明,在非对称网络中,Reno比Vegas更灵活且更实用,后向路径上逆向流的拥塞会极大地降低Vegas的吞吐量,使得Vegas和Reno不能很好地兼容.     

A QoS Estimation-Based Scheduler for Real-Time Traffic in IEEE 802.11e Mobile Ad hoc Networks

ABSTRACT

For mobile ad hoc networks, the IEEE 802.11e standard specification provides Quality of Service (QoS) facility support in the MAC layer by Enhanced Distribution Channel Access (EDCA), which provides differentiated and distributed access to the wireless medium with four access categories (AC). It works efficiently for constant bit rate (CBR) types of traffic; however, for the case of variable bit rate (VBR) types of traffic, it shows poor performance due to the static nature of computing the number of packets and the time required to transmit these packets. In this paper, we present an EDCA scheduling algorithm that allocates transmission opportunities (TXOP) for fluctuating VBR traffic depending on their queue length estimations for mobile ad hoc networks. We classify the channel state as good or bad based on the channel error conditions. Then the scheduler determines the mean application data rate and estimates the TXOP for the next interval on the same Traffic Stream (TS). By simulation results, we show that the proposed scheduling scheme achieves good throughput and fairness with reduced delay for the VBR traffic class.     

分布式星群网络中基于蚁群算法的通信量分类路由

给出了一种分布式星群网络(Distributed Satellite Cluster Network,DSCN)体系架构,阐明了DSCN拓扑变化的特点。在分析网络状态获取方式和路由计算方法的基础上,提出了一种适用于DSCN的基于蚁群算法的通信量分类路由(Ant Colony Optimization Based Traffic Classified Routing,ATCR)算法。ATCR算法将通信量分为时延敏感型通信量A、带宽敏感型通信量B以及提供尽力而为服务的通信量C,并对蚁群算法(Ant Colony Optimization,ACO)收敛慢的缺点进行了改进。仿真实验表明,ATCR算法提高了收敛速度,可以有效平衡网络流量。通信量A和C的端到端时延要小于未采用通信量分类的改进ACO算法。由于减少了重负载链路的数量及拥塞引起的丢包,ATCR算法在分组递交率上的表现优于改进的ACO算法。     

Defending against Wormhole Attack in MANET Using an Artificial Immune System

MANETs are mobile networks that are spontaneously deployed over a geographically limited area without requiring any pre-existing infrastructure. Typically, nodes are both autonomous and self-organized without requiring a central administration or a fixed network infrastructure. Due to their distributed nature, MANET is vulnerable to a specific routing misbehavior, called wormhole attack. In a wormhole attack, one malicious node tunnels packets from its location to the other malicious node. Such wormhole attacks result in a false route with fewer hop count. If the source node follows this fake route, malicious nodes have the option of delivering the packets or dropping them. This article aims at removing these attacks. For this purpose, it investigates the use of an Artificial Immune System (AIS) to defend against wormhole attack. The proposed approach learns rapidly how to detect and bypass the wormhole nodes without affecting the overall performance of the network. The proposed approach is evaluated in comparison with other existing solutions in terms of dropped packet count, packet loss ratio, throughput, packet delivery ratio, and end-to-end delay. A simulation result shows that the proposed approach offers better performance than other schemes defending against the wormhole attack.     

IBFWA: Integrated Bloom Filter in Watchdog Algorithm for hybrid black hole attack detection in MANET

In recent days, the Mobile Ad-hoc Network (MANET) has gained more attention and popularity due to its dynamic nature. However, it is highly vulnerable to attacks due to its wireless nature and lack of central authority. This affects the overall performance of the network. To solve this problem, the Watchdog protocol was developed for attack detection. However, if it receives a false report from a misbehaving node, it fails to detect the attack. To overcome this problem, the Integrated Bloom Filter with Watchdog Algorithm (IBFWA) is proposed in this article to avoid packet loss. Here, the Certificate Authority (CA) validates the node through the process of key generation. Then, it checks whether the node is normal or attacker; if it is a black hole node, it will be blocked and communication through this node is avoided. If a node is compromised and revoked as a normal node, it is added to the network and communication through the node is enabled. The experimental results evaluate the performance of the proposed attack detection system in terms of lower node outage, residual energy, end-to-end delay, high detection probability, throughput, packet transfer rate and packet delivery ratio.     

避免路由断裂的优化AODV路由协议

移动自组网(MANET)中,节点的移动容易引起链路失效,传统的按需距离矢量(AODV)路由算法的本地修复机制局限于在链路断裂后进行,如果修复失败或者过慢,可能导致缓存的数据包丢失。针对这一问题,提出一种避免路由断裂的优化AODV路由算法ARB-AODV,该算法首先对即将断裂的链路进行预测,然后计算有关节点的相对稳定度,将稳定性较高的节点插入即将断裂的链路中,以消除节点的边缘效应来避免路由断裂。在NS-2平台下采用随机路点移动模型(RWM)和恒定比特率(CBR)数据源进行实验,在节点的移动速度大于10m/s时,ARB-AODV算法的分组投递率保持在80%以上,其平均端到端时延比AODV算法降低了40%,归一化路由开销比AODV算法降低了15%。仿真结果表明,ARB-AODV优于AODV,能有效提高网络性能。     

Fuzzy-Based Dynamic Distributed Queue Scheduling for Packet Switched Networks

Addressing the problem of queue scheduling for the packet-switched system is a vital aspect of congestion control. In this paper, the fuzzy logic based decision method is adopted for queue scheduling in order to enforce some level of control for traffic of different quality of service requirements using predetermined values. The fuzzy scheduler proposed in this paper takes into account the dynamic nature of the Internet traffic with respect to its time-varying packet arrival process that affects the network states and performance. Three queues are defined, viz low, medium and high priority queues. The choice of prioritizing packets influences how queues are served. The fuzzy scheduler not only utilizes queue priority in the queue scheduling scheme, but also considers packet drop susceptibility and queue limit. Through simulation it is shown that the fuzzy scheduler is more appropriate for the dynamic nature of Internet traffic in a packet-switched system as compared with some existing queue scheduling methods. Results show that the scheduling strategy of the proposed fuzzy scheduler reduces packet drop, provides good link utilization and minimizes queue delay as compared with the priority queuing (PQ), first-in-first-out (FIFO), and weighted fair queuing (WFQ).     

Swarm Intelligence Based Routing with Black Hole Attack Detection in MANET

Mobile Ad hoc Network (MANET) possesses unique characteristics which makes it vulnerable to security threats. In MANET, it is highly challenging to protect the nodes from cyberattacks. Power conservation improves both life time of nodes as well as the network. Computational capabilities and memory constraints are critical issues in the implementation of cryptographic techniques. Energy and security are two important factors that need to be considered for improving the performance of MANET. So, the incorporation of an energy efficient secure routing protocol becomes inevitable to ensure appropriate action upon the network. The nodes present in a network are limited due to energy constraints and secure communication protocols. Hence, the current study proposed an energy-efficient defense scheme using swarm intelligence approach. The functioning of the proposed method was validated under NS2 simulation. The experimental results confirmed that the proposed work outperformed existing methods in terms of packet delivery ratio, average end-to-end delay and throughput.     

Ad Hoc网络链路质量QoS多路径按需路由协议

传统的MANET路由协议是基于最小跳数的路由,没有考虑链路质量,不能适应网络拓扑的动态变化。针对这一问题,提出了一种Ad Hoc网络链路质量QoS多路径按需路由协议（QMORP）。QMORP采用移动预测来计算链路的生存时间,应用能量模型获得链路的剩余能量,综合链路生存时间和剩余能量两种因素来计算链路质量。选择链路质量大的路径转发分组。仿真实验表明,相比AOMDV协议,QMORP协议提高了网络的生命周期,降低了网络的平均端对端延迟、提高了网络的发包率和吞吐率。     

Design of a crossbar VOQ real-time switch with clock-driven scheduling for a guaranteed delay bound

Most commercial network switches are designed to achieve good average throughput and delay needed for Internet traffic, whereas hard real-time applications demand a bounded delay. Our real-time switch combines clearance-time-optimal switching with clock-based scheduling on a crossbar switching fabric. We use real-time virtual machine tasks to serve both periodic and aperiodic traffic, which simplifies analysis and provides isolation from other system operations. We can then show that any feasible traffic will be switched in two clock periods. This delay bound is enabled by introducing one-shot traffic, which can be constructed at the cost of a fixed delay of one clock period. We carry out simulation to compare our switch with the popular iSLIP crossbar switch scheduler. Our switch has a larger schedulability region, a bounded lower end-to-end switching delay, and a shorter clearance time which is the time required to serve every packet in the system.     

Ad Hoc网络中SWAN模型的改进研究

SWAN模型应用于Ad Hoc网络后,通过NS2仿真表明网络实时业务的分组递交率、业务吞吐量等性能可提高15%左右,平均端到端时延减少90%,但网络非实时业务的性能除业务吞吐量有较大幅度的提高,分组递交率和时延性能均有所下降,为此提出了一种增强的尢状态无线自组网速率控制方案:ESWAN.仿真表明ESWAN较SWAN而言不仪可以提高网络实时业务性能,而且网络非实时业务分组递交率可提高5%,时延减少38%.     

基于链路稳定度的车载网路由协议研究

针对车载网中节点移动速度快,拓扑结构变化速度快的特点,以及AODV协议广播式路由链路存活时间短、平均端到端时延大等问题,提出了一种通过计算链路稳定度的方式来改进AODV协议.在节点进行广播时,首先计算转发角度,然后,再将投影最长和链路生存时间最长作为综合选择条件,以此高效地选择路径相对较短以及链路相对稳定的路由.通过这种方式,改进后的AODV协议很好地解决了网络中链路易断裂的问题,提高了数据包的投递率,降低了平均端到端的时延.利用NS2仿真软件进行性能仿真,结果表明:改进后的AODV协议在包递率、平均时延和吞吐量方面优于传统模型.     

基于不同发送速率下移动自组网AODV路由协议的性能比较分析

人们一般只基于2kbps发送速率下研究移动自组网中路由协议的性能，基于对多媒体业务的支持，该文在144kbps发送速率下研究了，移动自组网中路由协议AODV(Ad Hoc按需距离矢量路由)的性能，并与2kbps发送速率下的性能进行了比较分析。研究结果表明，与2kbps发送速率下相比，144kbps发送速率的报文投递率要高，同时平均端到端的时延、路由负荷、MAC负荷也高。     

基于虚拟时钟的MANET端到端性能分析模型

在MANET中,节点移动对端到端性能产生消极影响。为了量化此影响,结合链路可用度的概念,将分组发送至下一跳的平均时间作为虚拟时钟节拍,提出一种基于虚拟时钟的MANET性能分析模型。通过此模型可以较准确地求出路径吞吐量和分组平均端到端时延等性能指标,并分析出节点速度、传输半径、分布密度等环境配置参数对这2个陛能指标的影响。     

AdHoc网络中考虑事件紧急度的跨层QoS保障机制

考虑Ad Hoc网络中事件紧急度,提出一种可以有效改善整体高优先级业务流时延和时延抖动性能的跨层QoS服务质量保障算法.根据时延要求及业务分组距离目的点的跳数信息,评估此业务的紧急度,并在调度传输时充分考虑各个事件的紧急度.在有实时要求的业务发生超时的情况下,通过合适的路由置换方法,改善业务流时延及网络吞吐量.本文重点讨论如何在IEEE802.11e协议基础上实现对指定优先级业务流的服务质量保障.GloMoSim仿真环境下的仿真结果显示该算法与原有IEEE802.11e协议相比,对于高优先级业务,在分组端到端时延、时延抖动以及网络吞吐量方面有较大的改善.     

Analysis of an access node multiplexer in a system serving CBR and VBR traffic

This paper considers a multiplexer at the access node of a system serving both CBR and VBR services in a B-ISDN environment. The CBR traffic component represents fixed bit rate services in an ATM network. Such services need to be allocated a fixed number of time slots in each output frame. The VBR traffic here represents connectionless and connection oriented variable bit rate services that are loss sensitive but delay insensitive. A mathematical model is developed for such a system and performance parameters are evaluated. These results are verified by simulation.