基于链路状态和节点状态信息的DSR增强算法

本文利用链路和节点发送缓存的状态信息对DSR协议进行优化和改进，提出了一种Performance—DSR（PDSR）协议。文中对PDSR协议的路由更新和路由选择机制进行了介绍，并对PDSR协议和DSR协议在节点不同移动速度下的性能进行了分析比较，结果表明PDSR协议比DSR协议更能适应网络拓扑变化快的MANET网络。     

基于DSR的移动自组网多路径路由协议的研究与分析

DSR动态源路由协议是一种典型的按需路由协议,它只在有需求的时候才启动路由发现过程,也是目前移动自组网网络的一种主要路由协议。本文阐述了DSR的工作原理并分析了多种基于DSR的移动自组网的多路径路由协议的工作原理与特点。     

基于稳定链路MANETs路由协议的研究现状

移动自组网(MANETs,mobile Ad Hoc networks)中节点随机移动,且无固定基础设施、节点能量受限等诸多的因素影响了链路的稳定性,给路由协议提出了挑战.目前,研究人员对基于稳定链路的路由协议进行了深入的研究,并提出不同的基于稳定链路的路由协议.为此,首先对现有的基于稳定链路的路由协议进行分类,然后,分析了每类的经典协议的性能,最后,讨论基于稳定链路的路由协议的未来发展方向.     

改进的最优链路状态路由协议算法

改进无线Mesh网中的最优链路状态路由协议的不足,设计OLSR路由协议的改进算法,仿真对比实验结果表明:随着节点速度的增加,改进后的算法在数据传输成功率、无线自组网的稳定性等方面具有明显的优势。在某工程实际应用中得出:改进后的协议在无线网带宽的稳定性、丢包率方面改善了系统的性能。     

支持移动自组网的柔性链路状态路由协议

在移动自组网(MANET)中,服务质量(QoS)路由的目标是要确定一种具有足够可用移动节点的有效路由路径来满足源点的需求,而且被选择的多点中继(MPR)节点是处在通过路由协议计算产生的最优路由路径上。为了能在较短时间内稳定地寻找到从源点到终点带有最大带宽和最小时延的最优QoS路由路径,提出一种新的柔性链路状态QoS路由协议FLSQR。该协议使用了一种新的链路状态方法——每个节点缓存中存储一张效用决策表(EDT)用作路由计算。FLSQR根据EDT中的效用距离(ED)使用MPR1和MPR2选项来选择最优和次优路由路径,进而通过提出的度量模型选择最优带宽和时延的路径。实验结果显示,FLSQR协议在MANET中的最优路由路径发现方面比OLSR和QOLSR-MPR协议性能更好。     

基于节点速度和能量的MPR节点集选择

考虑到无人机群在协同完成任务时对时延的高要求,选用先验式路由协议OLSR(Optimized Link State Routing)协议。但无人机自组网中无人机节点高速移动和能量有限的特性,使得OLSR选举出来的MPR(Multi-Point Relay)节点可能会因此而丧失MPR资格,从而导致时延增加,网络开销增大。针对该问题,提出一种基于节点速度和能量的MPR集选择算法,运用HELLO分组在邻居探测的过程中感知节点能量和速度,之后在MPR选举前根据节点速度和能量对一跳邻居进行预处理,从而使速度快能量低的节点永不成为MPR节点。排除掉节点后,在节点意愿值相同的情况下再次对节点的速度和能量进行加权计算,选出最优MPR节点。仿真结果表明,基于节点速度和能量的MPR集选择算法在时延、吞吐量、节点能量消耗三个指标都具有良好的特性。     

MANET的单向链路问题

在移动自组网络中,节点间存在单向链路。文章论述了单向链路的产生原因,其对现有网络结构的影响,而后介绍并分析国内外各高校、科研院所针对这一问题的解决方案。     

基于链路状态认知的无线Mesh网路由协议

在分析无线Mesh网路由协议所面临挑战的基础上,结合无线Mesh网络的性能要求,以优化链路状态路由(OLSR)协议为原型,采用跨层设计理论,提出了一种基于链路状态良好程度的路由协议LR-OLSR。该协议引入了认知无线网络中的环境感知推理思想,通过对节点负载、链路投递率和链路可用性等信息进行感知,并以此为依据对链路质量进行推理,获得网络中源节点和目的节点对之间各路径状态良好程度的评价,将其作为路由选择的依据,实现对路由的优化选择,提高网络的吞吐量,达到负载均衡。通过与OLSR及其典型改进协议P-OLSR、SC-OLSR的对比仿真结果表明,LR-OLSR能够提高网络中分组的递交率,降低平均端到端时延,在一定程度上达到负载均衡。     

移动自组网中基于预测机制的一种稳定路由算法设计

首先基于预测链路可保持时间,提出了链路在t0时刻存在并且在t0 Δt时刻仍然存在的概率预测方法.基于对链路保持连接的概率预测,提出了选择可保持至t0 Δt时刻稳定传输路径的路由协议.通过模拟和数据分析,该路由算法在链路断裂数目、丢失数据包数目以及数据包到达率等方面都有较大的改善,减少了网络拓扑结构的变化对于路由的影响,提高了网络运行性能.     

MANET节点移动模型仿真研究

移动自组网（MANET）节点移动特性对网络拓扑结构有重要影响,在合理的节点移动模型下对网络性能的评估才真实可靠。通过对网络仿真软件NS2进行拓展,实现个体、群体和具有地域限制的节点移动模型,提出物理链路和路由协议2个层面的评估准则,给出不同类节点模型对路由协议性能的影响程度。对研究和评估MANET的路由协议有重要的参考价值。     

移动自组网路由协议DSR性能评价

研究移动自组网的难点之一是开发能够跟随网络拓扑变化,在移动节点之间快速找到有效路径的路由协议。DSR协议作为一种简洁有效的按需机制路由协议,成为IETF的MANET工作组提出的草案之一。本文利用MANET工作小组推荐的Ns2仿真软件对DSR进行模拟,从源节点个数、分组发送频率、移动速度、节点密度、节点个数五个方面分析DSR的性能,指出对DSR性能影响最大的因素。分析随分组频率降低协议性能下降是由于它的路径缓存策略引起,提出将针对DSR路径缓存,搜索,抛弃策略进行改进。     

基于MANET的无线自组织网按需路由协议DSR的优化研究与实现

无线自组织网络由不需要任何基础设施的一组具有动态组网能力的节点组成,因此网络可以通过节点路由发现机制转发分组,并进行路由维护。这种网络适应了军事和商用中对网络和设备移动性的要求,而引起了人们的关注,并在20世纪90年代以后获得了广泛的研究和发展。文章对DSR(动态源路由协议)的路由发现过程进行了优化,并采用OPNET仿真软件对基于DSR协议的Ad Hoc网络的路由开销和时延等关键参数进行了仿真统计,分析了改进后的路由协议对网络质量的影响。     

移动自组网DSR协议路径缓存策略优化

移动自组网按需机制路由协议只是在有分组发送时,才启动路径发现机制搜索到达目的节点的路径。为了避免每发送一个分组都启动路由发现机制,必须利用路由保存机制将预先发现的路径缓存。对这些路径进行缓存、搜索、抛弃的管理策略极大地影响按需机制路由协议的性能。该文对多次性能测试中表现优越的DSR协议路由缓存策略进行分析,针对它的不足,提出改进算法。提出修正发送缓冲器的时限,根据最近路径失效时间和缓冲器中路径状况预测将来的路径失效时间,在缓存器中根据时间、能量参数搜索最佳路径、丢弃最差路径的策略。利用ns2对4组场景进行仿真,结果显示对DSR路径缓存策略进行优化后,比较明显改进了DSR协议性能。     

Backup path set selection in ad hoc wireless network using link expiration time

Topological changes in mobile ad hoc networks frequently render routing paths unusable. Such recurrent path failures have detrimental effects on quality of service. A suitable technique for eliminating this problem is to use multiple backup paths between the source and the destination in the network. Most of the proposed on-demand routing protocols however, build and rely on single route for each data session. Whenever there is a link disconnection on the active route, the routing protocol must perform a path recovery process. This paper proposes an effective and efficient protocol for backup and disjoint path set in an ad hoc wireless network. This protocol converges into a highly reliable path set very fast with no message exchange overhead. The paths selection according to this algorithm is beneficial for mobile ad hoc networks, since it produces a set of backup paths with much higher reliability. Simulations are conducted to evaluate the performance of our algorithm in terms of route numbers in the path set and its reliability. In order to acquire link reliability estimates, we use link expiration time (LET) between each two nodes.In another experiment, we save the LET of entire links in the ad hoc network during a specific time period, then use them as a data base for predicting the probability of proper operation of links.Links reliability obtains from LET. Prediction is done by using a multi-layer perceptron (MLP) network which is trained with error back-propagation error algorithm. Experimental results show that the MLP net can be a good choice to predict the reliability of the links between the mobile nodes with more accuracy.     

Discovering timely information in MANETs

Timely information refers to information whose ‘most recent’ or ‘latest’ instance is most valuable. In mobile ad hoc networks (MANETs), multiple instances of a piece of timely information may be produced by different nodes at different points in time. The problem is to discover the ‘latest’ instance among all existing instances. Within the context of MANETs, timely information discovery is fundamentally different from the existing resource/service discovery problem whose goal is to discover either any instance or a subset of instances which satisfy a local query constraint that can be specified and evaluated using only local attributes of each individual node. In contrast, the timely information discovery problem imposes the global (timeliness) constraint which should best be evaluated when all the instances are considered to determine the latest instance. The complication of discovering timely information arises from the existence of multiple instances of the information, which are produced at different points in time by different nodes in the network, and the need to collect all these instances to decide the latest instance. For MANETs, the lack of infrastructure supports, frequent topology changes, and potential packet loss in wireless communications further challenge the problem of timely information discovery. This paper describes a self-organizing, peer-to-peer based approach, termed ALADIN, to discovering timely information in MANETs. In ALADIN, nodes that produce instances of the timely information are peers who self-organize an adaptive and distributed ‘search infrastructure’ to facilitate the discovery of the latest instance. A simulation study shows that ALADIN is scalable without incurring network-wide flooding in the case of large-scale networks and popular timely information, and yields a high chance of discovering the latest instance in the presence of mobility.     

基于能量和链路状态的AODV路由请求转发机制研究

按需距离矢量路由算法(AODV)为移动无线自组织网络(Manet)提供了高效的、扩展性能良好的路由解决方案.然而AODV在选择路径时仅以最短路径和最快响应作为度量准则,并未考虑节点能量、负栽以及链路状态等因素,导致得到的路径并非为最优且节点能量消耗不均衡,降低了网络生存时间.在传统AODV算法基础上,提出了一个改进的路由算法,该算法在路由选择时充分考虑了节点的能量、负载以及节点间的链路状态,可以有效提高网络性能并延长网络生存时间.在NS2平台上的仿真实验结果也显示,所提算法在路由负荷、时延、分组传递率以及节能方面均优于传统AODV算法.     

Transmission scheduling algorithm for MIMO link ad hoc networks

Most reported works on transmission scheduling algorithm for multiple input multiple output (MIMO) link ad hoc networks do not fully exploit the spatial multiplexing potential inherent to multiple an-tennas system.In this paper,a novel transmission scheduling algorithm is proposed to further enhance the performance of MIMO link ad hoc networks.By utilizing the MIMO multi-stream reception capabilities and ordering the nodes’ allocation sequence,the proposed algorithm can dramatically shorten the scheduling frame length and more evenly distribute the data streams allocated to the network nodes.Meanwhile,allowing the nodes to transmit multiple streams in a slot,the algorithm can fully exploit the MIMO spatial multiplexing potential.Additionally,we give the theoretical analysis to quantify the throughput and delay performance with respect to this scheme.Numerical results demonstrate that the proposed algorithm can efficiently enhance the network throughput and reduce the average and maximum delay.     

基于位置信息的改进AODV路由算法

针对AODV协议路由开销较大的问题,提出一种基于位置信息的改进路由协议(GAODV).GAODV利用中间节点重新计算转发角度,保证转发角度内邻居节点数不小于预设门限值,同时还引入基于位置信息的计数器方案,使距离目的节点近的中间节点优先转发路由请求消息,有利于减少转发冗余路由请求信息和降低寻路失败概率.OPNET仿真实验结果表明,GAODV在数据分组投递率、路由开销、总丢包数、端到端时延和平均路由跳数等方面都优于已有算法.