自组网路由协议的仿真与性能研究

在Ad Hoc网络中,如何针对实际的应用选择一个最佳的路由协议是一个难点问题.分析DSDV,OLSR,DSR,TORA和AODV五种常用的Ad HOC路由协议,基于网络节点暂停时间及最大移动速度变化两种情况,设计了针对平均端到端时延、数据包分组传送率、路由开销和平均跳数四个指标的仿真实验.仿真结果表明:在相同的网络环境下,与其他四种协议相比,OLSR协议的平均时延、路由开销和平均跳数都较小,分组传送率也较高,性能最好.通过对五种协议性能指标的综合比较,提出了一个通用的路由选择方案.     

Ad Hoc网路由协议在常规靶场中的应用及仿真

在试验通信系统IP化改造的要求下,建设基于多跳路由协议的无线移动自组织(Ad Hoc)试验通信网是必然的选择。传统的试验通信系统多采用集中控制的点对多点星状网,而移动自组网属于网状网,采用完全不同的组网方式,其对特定试验保障通信业务的承载能力,以及路由协议的适应性目前尚没有试验数据可供参考。对自组网路由协议在试验通信中的应用进行研究,根据想定试验场景对网络性能进行仿真分析,分别仿真了4种路由协议的数据包成功递交率、平均吞吐量以及平均时延等网络性能。仿真结果表明,4种路由协议中有3种协议综合性能完全可以满足试验通信保障任务。     

改进路由维护机制的动态源路由协议

目的是对Ad Hoc网络中按需路由协议DSR进行改进以提高网络的数据通信的实时性.通过对DSR协议中的路由维护和路由表存储机制进行改进来完成降低网络时延的目的,并在OPNET上进行仿真实验.分别比较了普通DSR协议,带多条备用路由的DSR协议和本文提出改进型路由维护的DSR协议进行仿真,比较三种协议下网络平均传输时廷.仿真实验证明,改进的路由协议对降低网络平均时延是行之有效的.     

一种基于AODV路由协议的分簇算法研究

基于距离向量的按需路由协议AODV是AdHoc网络研究的热点之一。该协议有效减少了建立和维护路由所需要的开支,但是随着网络节点发送数据量的增加,网络性能会迅速下降。为了提高AdHoc网络的路由效率和可靠性,文章提出了一种基于AODV路由协议的分簇算法。经仿真研究分析表明,该算法提高了网络节点的平均每跳吞吐率,减少了节点的平均每跳时延。     

基于路段连通性和方向转发策略的机会路由协议

文章针对车载自组织网络中由于道路拓扑的限制以及障碍物的存在导致车辆节点互相隐藏,造成的网络频繁连接中断的问题,综合考虑车辆位置、方向和速度、车辆密度信息,利用十字路口路段连通性和方向转发策略选择下一跳,提出了基于路段连通性和方向转发策略的车载机会路由协议。由仿真结果可知,在城市场景中,尤其当车辆节点比较稀疏时,本协议相比GPSR和GPCR协议具有更高的包投递率和较低的平均端到端传输时延。     

基于第一跳节点累积的AODV协议改进

利用DSR协议的源路由策略,对AODV协议进行修改——在其路由发现过程中,将第一跳节点的地址信息添加到路由消息中。中间节点接收路由消息后,建立或者更新到达第一跳节点的路由。将修改后的协议称为AODV-FA协议,并在ns2中模拟仿真其路由性能。结果表明:相较于AODV协议,AODV-FA在分组传输率、平均端到端时延和归一化路由负载3个路由性能上均有提升。     

城市场景下基于速度信息的VANET路由协议的改进

车载自组网络(Vehicular Ad Hoc Networks,VANET)是指道路上由车辆搭载的无线通信装置构成的一种特殊的多跳无线移动自组织网络。VANET在实现多种智能交通方面应用的同时,还能满足用户在乘车时的娱乐等舒适性的需求,近些年来已成为无线自组网络研究的新热点。总结了近些年来出现的主要VANET路由协议的核心路由机制及其优缺点,并分析了各种技术对路由协议性能的影响。其后给出了一种基于速度信息的VANET路由协议改进方法,并通过实验验证了将改进方法与GPSR协议结合可以提高路由路径的稳定性,减少了端到端的平均时延,降低了VANET网络中拓扑的高动态性对路由协议性能的影响。     

基于移动预测的VANETs广播路由协议

针对车载自组织网络（VANETs）的通信特点,基于移动预测的广播路由协议（MPBP）可以有效的提高网络的性能。MPBP的核心思想是根据车辆的位置信息和相对速度来预测节点和的链的路生存期,即连接的持续时间,由此来选择可靠高效的下一跳,即为选择了最稳定的路由路径,由此提高路由性能。仿真结果表明,无论在低速或高速场景下,MPBP协议能够实现可靠的数据递交率和较小的数据传榆时延。     

复杂网络环境下的DSR路由协议性能仿真

DSR是用于多跳无线Ad hoc网络的一个简单高效的路由协议,DSR协议由路由发现和路由维持两部分组成,允许节点在Ad hoc网络中发现、维持到任意节点的源路由.文章详细介绍了DSR协议的特点并利用Opnet Modeler 10.5构建了小规模(50节点)和大规模(100节点)复杂的(所有节点同时移动、所有节点既是源节点又是目的节点)移动自组网模型,通过改变节点移动速度及发送分组大小,对DSR路由算法的平均路由发现时间、平均路由长度、吞吐量、数据分组平均端到端的时延、及分组交付率在两种场景下进行了仿真分析和性能比较.     

车载自组织网中基于蚁群算法的延迟感知路由协议

针对城市道路环境下车载自组织网( VANETs)中通信性能下降以及数据传输失败的问题,提出了一种基于蚁群算法的延迟感知路由( ACDR)协议。首先,建立双向车道的数学延迟模型;然后,根据提出的端点十字路口( EI)的概念,ACDR利用蚁群优化( ACO)寻找最佳路线,其中前向蚂蚁根据本地路段延迟以及当前十字路口与目的节点的端点十字路口之间的全局时延来选择路径,后向蚂蚁则负责在返回路径时更新信息素,同时,相邻十字路口之间利用贪婪转发算法进行数据包的传递。最后仿真比较了ACDR协议与连通性感知路由( CAR)协议的性能,结果表明提出的ACDR协议的数据包的传输延迟小,丢包率低,通信性能好。     

A path selection based routing protocol for urban vehicular ad hoc network (UVAN) environment

Routing in urban environment is a challenging task due to high mobility of vehicles in the network. Many existing routing protocols only consider density, link connectivity, delay, and shortest path information to send the data to the destination. In this paper, a routing protocol is proposed which uses the urban road network information such as multi-lane and flyover to send the data to the destination with a minimum packet forwarding delay. The next path for data forwarding is selected based on a path value calculated by the Road Side Unit for each path connected to a junction. This protocol uses Ground Vehicle to Ground Vehicle (GV2GV) communication, Flyover Vehicle to Flyover Vehicle (FV2FV) communication, and Flyover Vehicle to Ground Vehicle/Ground Vehicle to Flyover Vehicle (FV2GV/GV2FV) communication to enhance the routing performance. Simulation results show that proposed protocol performs better than P-GEDIR, GyTAR, A-STAR, and GSR routing protocols in terms of end-to-end delay, number of network gaps, and number of hops.     

典型航空自组网路由协议仿真与性能评估

航空自组网是自组网在航空领域的典型应用.航空自组网的关键技术在于路由协议的选取和设计.基于场景用NS2软件仿真研究了3种适用于航空自组网的路由协议及其网络性能,并定义了4个性能评估准则.仿真结果表明,单跳距离一定时,3种路由协议的网络性能随着节点密度的增加而总体变差.同等条件下,AODV路由协议路由开销高于DSVD和GRID路由协议,端到端平均延时低于DSVD和GRID路由协议,而GRID协议分组投递率和平均跳数保持最高.     

Dynamic Relationship-Zone Routing Protocol for Ad Hoc Networks

A new dynamic relationship-zone routing protocol (DRZRP) for ad hoc networks is proposed. In this protocol, each node in the network establishes a neighboring-zone with a radius of ρ hops, and activates a relationship-zone according to the service request frequency and service hotspot condition. DRZRP establishes proactive routing for neighboring-zone and relationship-zone of the node, and the relationship-zone of the node can be dynamically maintained, including: initialization, relationship-zone activation, and relationship-zone inactivation. The simulation results are compared with LSR, ZRP and ZHLS protocols, and DRZRP greatly reduces the communication overhead of routing control messages and significantly improves the average delay of routing requests. The new protocol matches the service relationship among nodes in the network, and has comprehensive performance advantage in communication overhead and routing request delay, which improves the quality of network service.

     

紫外光无线传感器网络节能的研究与仿真

为了减少无线传感器网络节点的能量消耗,采用紫外光作为无线传感器网络的信息载体,研究了紫外光传感器节点的能量模型。理论分析了单跳节能和多跳节能,得出了计算最优跳数的数学表达式,并对单跳通信、多跳通信和最优跳通信的平均能量消耗进行了计算机仿真,仿真结果与理论分析一致;对于多跳通信带来的能量消耗不均匀的问题,利用移动sink节点来解决,通过仿真对比了sink节点不同移动速率对网络平均能量消耗、丢包率和端到端时延的影响。结果表明,借助移动sink节点可以降低网络的平均能量消耗,但要根据场景选择合适的移动速率。     

一种应急通信中业务感知的宽带自组网路由协议

随着科技进步,我国在应急通信系统建设上也正高速发展,当前应急通信网络对多媒体业务有着迫切需求,对网络带宽要求更高。而当网络存在多种不同业务时,传统通用的路由协议不再适用,它们大多以最小跳数为路由度量或者是某个单一度量,未能考虑不同业务的服务质量(Quality of Service, QoS)需求,因而无法同时兼顾不同业务流的传输要求。提出了一种应急通信中业务感知的宽带自组网路由策略,对不同类型业务在路由和转发优先级上进行区分。经多次仿真验证,该策略能使网络在满足应急语音业务QoS需求的同时,也能兼顾承载的视频、数据等其他业务的性能。     

基于城市道路的稳定车载网分簇路由策略

由于车载自组网具有节点高速运动、网络拓扑变化快、链路有效时间短等特点,使得传统移动自组网分簇路由协议在车载网中不再适用。基于此,提出了一种新的稳定的分簇路由策略,引入辅簇头的设计理念,并设计了一种高效的岔路口路由策略,通过岔路口二次选择,有效解决岔路口路由冗余问题。通过NS2模拟仿真表明,新的路由策略可有效避免簇结构变化导致的丢包率上升问题,能够以更少的跳数、更低的延时成功传递数据包,具有较好的性能。     

Reinforcement Learning Based Mobility Adaptive Routing for Vehicular Ad-Hoc Networks

Vehicular ad-hoc networks (VANETs) is drawing more and more attentions in intelligent transportation system to reduce road accidents and assist safe driving. However, due to the high mobility and uneven distribution of vehicles in VANETs, multi-hops communication between the vehicles is still particularly challenging. Considering the distinctive characteristics of VANETs, in this paper, an adaptive routing protocol based on reinforcement learning (ARPRL) is proposed. Through distributed Q-Learning algorithm, ARPRL constantly learns and obtains the fresh network link status proactively with the periodic HELLO packets in the form of Q table update. Therefore, ARPRL’s dynamic adaptability to network changes is improved. Novel Q value update functions which take into account the vehicle mobility related information are designed to reinforce the Q values of wireless links by exchange of HELLO packets between neighbor vehicles. In order to avoid the routing loops caused in Q learning process, the HELLO packet structure is redesigned. In addition, reactive routing probe strategy is applied in the process of learning to speed up the convergence of Q learning. Finally, the feedback from the MAC layer is used to further improve the adaptation of Q learning to the VANETs environment. Through simulation experiment result, we show that ARPRL performs better than existing protocols in the form of average packet delivery ratio, end-to-end delay and number hops of route path while network overhead remains within acceptable ranges.     

Characterizing Overlay Multicast Networks and Their Costs

Overlay networks among cooperating hosts have recently emerged as a viable solution to several challenging problems, including multicasting, routing, content distribution, and peer-to-peer services. Application-level overlays, however, incur a performance penalty over router-level solutions. This paper quantifies and explains this performance penalty for overlay multicast trees via: 1) Internet experimental data; 2) simulations; and 3) theoretical models. We compare a number of overlay multicast protocols with respect to overlay tree structure, and underlying network characteristics. Experimental data and simulations illustrate that the mean number of hops and mean per-hop delay between parent and child hosts in overlay trees generally decrease as the level of the host in the overlay tree increases. Overlay multicast routing strategies, overlay host distribution, and Internet topology characteristics are identified as three primary causes of the observed phenomenon. We show that this phenomenon yields overlay tree cost savings: Our results reveal that the normalized cost L(n)/U(n) is propn^0.9 for small n, where L(n) is the total number of hops in all overlay links, U(n) is the average number of hops on the source to receiver unicast paths, and n is the number of members in the overlay multicast session. This can be compared to an IP multicast cost proportional to n^0.6 to n^0.8     

用于VANET紧急消息传输的改进二元分割广播协议

摘要：针对车辆自组织网络（vehicular Ad Hoc network,VANET）中紧急消息的传输,提出一个改进的二元分割广播（MBPAB）协议。协议将通信范围迭代划分成小的区域,寻找离发送节点最远区域内的车辆,对紧急消息执行转发,通过减少转发跳数,提高消息传播速度。通过引入MAC（medium access control）子层的微型分布式帧间间隔（mini-DIFS）,赋予对紧急消息以更高的优先级接入通信信道。仿真结果表明,在VANET 中, MBPAB协议与现有的广播协议相比,在通信时延和消息传播速度方面有更好的性能表现。     

Reactive routing evaluation using modified 802.11a with realistic vehicular mobility

Realistic mobility dynamics and underlying PHY/MAC layer implementation affect real deployment of routing protocols in vehicular ad hoc network (VANET). Currently, dedicated short range communication devices are using wireless access in vehicular environment (WAVE) mode of operation, but now IEEE is standardizing 802.11p WAVE. This work presents an in-depth simulation-based analysis of two reactive routing protocols, i.e., dynamic source routing (DSR) and ad hoc on-demand distance vector (AODV) with modified IEEE 802.11a PHY/MAC layers (comparable to 802.11p) in modified VANET mobility models (freeway, stop sign, and traffic sign) in terms of load, throughput, delay, number of hops, and retransmission attempts. Results obtained using OPNET simulator show that in urban/highway mobility scenarios, AODV??s performance with forthcoming 802.11p at high bit rate would be better than DSR in terms of high throughput, less delay, and retransmission attempts. Moreover, this comprehensive evaluation will assist to address challenges associated with future deployment of routing protocols integrated upon devices with upcoming IEEE 802.11p, concerning specific macro-/micro-mobility scenarios.