移动Ad Hoc网路AODV路由协议的改进

针对移动Ad Hoc网络AODV路由协议的路由维护的缺点,提出了AODV-BR路由协议,即具有备份路由的AODV路由协议。新协议通过为网络中的连接链路增加一条备份路由提高了AODV路由维护的性能。仿真实验表明AODV-BR有效减少了网络中链路中断的数量,降低了丢包率。     

无线Ad Hoc网络中AODV路由算法的研究与改进

无线Ad Hoc网络是一个多跳的、临时的、对等的自治系统,它由一组带有无线收发信装置的移动节点组成.由于在军事通信、紧急救援、传感器网络等通信场合的广泛应用,无线Ad Hoc网络成为当前研究的热点之一.针对无线AdHoc网络中AODV路由协议算法在网络拓扑结构改变后出现的性能缺陷,提出了一种改进后的AODV路由协议M_EAODV,通过设置多条备份路由来减少链路修复.仿真结果表明,改进后的AODV在分组传送成功率、平均端到端时延、路由开销等性能方面都得到了有效改善,能够在链路中断后迅速启用备份路由,更适应于拓扑结构变化快的网络环境.     

移动Ad Hoc网络的可靠多播路由协议

在移动Ad Hoc网络环境中，分组的重传和路由的重构比有线网络更频繁。在网络多播树变化的情况下提供高的分组传输率是移动Ad Hoc网络多播路由的主要难题。文中提出了一种基于协议转接概念的移动Ad Hoc网络的可靠多播路由协议(RMRP)，该协议较好地减少了移动Ad Hoc网络中大量的路由重构和数据分组的重传。仿真实验显示RMRP具有较高的传输率和较低的端到端分组延迟。     

认知无线电网络备份路由协议研究

在认知无线电网络,由于非干扰性要求,次用户使用的频段会意外被主用户抢占.这种频段抢占可能频繁发生,它给可靠通信带来巨大的影响.提出一种面向可靠路由的备份路由协议,该协议将机会频谱、链路中断及节点失效考虑在内.仿真实验表明,所提出的新协议能有效地克服间歇连接、减小路由开销和提高数据传输的有效负载.     

基于GloMoSim的Ad Hoc网络路由协议仿真研究

针对24台移动终端在无线自组织网络中的联网通信需求,需要选择一种能够适应Ad Hoc网络拓扑结构不断变化的路由协议。文章对Ad Hoc网络的路由协议进行了分类和比较,并通过GloMoSim仿真平台,结合具体的网络仿真场景,着重对Ad Hoc网络中的AODV和DSR两种按需路由协议进行性能仿真测试,比较不同移动速度下两种协议的平均端到端时延、分组投递率和吞吐量性能优劣。实验表明,节点在GloMoSim平台中成功实现了通信互联,无论节点在静止状态还是高速移动情况下,AODV的性能都要优于DSR协议。     

Ad hoc网络中的抢先式路由算法

在无线Ad Hoc网络中，由于节点的频繁移动导致的路由失效引起了网络性能的严重下降。文中提出了一种针对无线Ad Hoc网络按需路由协议的抢先式路由算法。该算法以链路状态分析为基础，在路由发现时尽量保证新发现路由的可靠性；若节点接收信号强度小于危险阈值，则启动链路状态分析模块预测链路失效时间，如果预测结果小于反应时间，就提前进行路由维护。仿真结果表明，该算法能以可接受的开销有效地减少路由失效数、降低分组投递延迟，提高了网络性能。     

移动Ad Hoc网络基于路由协议的拥塞控制

为解决Ad Hoc网络的AODV路由协议在通信过程中存在的拥塞问题,提出了改进AODV路由协议的思想。根据网络链路拥塞度的大小采取不同措施和节点路由,建立不相关多径路由分流以避免拥塞。仿真结果表明,改进后的路由协议有效地减少了发生拥塞的几率,从而提高了移动Ad Hoc网络的性能。     

基于AODV协议的路由预测及预修复

针对移动Ad Hoc网络中节点链路断裂、路由需要不断进行维护的问题,在按需距离矢量路由(AODV)协议基础上结合链路质量指示器,添加对节点电池电量的监测功能,根据节点剩余能量进行路由预测及预修复,在对链路状况提前做出判断的基础上及时进行路由切换,避免路由频繁中断.仿真表明,改进协议提高了数据包投递率,降低了端到端延迟时间,使网络更加稳定高效.     

基于综合判据的无线Mesh网路由协议

为用户提供高质量、高性能的通信链路是无线Mesh网路由协议所面临的重要挑战,而当前从Ad Hoc网络沿袭下来的路由协议并不能够满足无线Mesh网的性能要求.文中以OLSR协议为原型,结合跨层优化理论,为基础设施架构的无线Mesh网提出了一种新颖的、基于综合判据的路由协议.该协议通过跨层操作机制综合考虑无线链接的长度及通信效率对链接性能的影响,从而达到优化路由选择的效果.仿真结果表明,所提出的路由协议能够有效地提高网络中分组的递交率,降低端到端的延时,并且能够在一定程度上达到负载均衡的路由效果.     

基于NS2的多机器人通信协议的研究与仿真北大核心CSCD

通信是多机器人之间交换信息和进行协作的基础,Ad Hoc无线网络作为一种典型的自组织网络,是解决多机器人通信问题的可行方案,而路由协议的研究一直都是Ad Hoc网络的研究热点,在分析了AODV协议存在的问题的基础上,提出一种改进的AODV路由协议,改进的AODV协议能够在一次路由发现过程中建立多条无重复中间节点的路由,并以NS2为平台进行了仿真分析,结果表明改进之后的AODVH协议在一定程度上提高了分组投递率,并且降低了归一化路由开销和平均端到端延时,有效提高了网络性能。     

A system for the design of packet-switched communication networks with economic tradeoffs

This paper studies the problem of designing a packet-switched communication network with tradeoffs between link costs and response time to users. It consists of assigning capacities to links in the network and determining the routes used by messages for all communicating node pairs in order to minimize total link fixed and variable costs. A tradeoff between link costs and response time to users is achieved by including a constraint that sets an upper limit on the average link queueing delay in the network. The topology of the network and the end-to-end traffic requirements are given. The problem is formulated as a nonlinear integer programming model. Unlike most of previous models, where the best route for a communicating node pair is restricted to a set of prespecified candidate routes, our model considers all possible routes for every communicating node pair. An efficient heuristic based on a Lagrangean relaxation of the problem is developed to generate feasible solutions. The results of extensive computational experiments across a variety of previously used networks are reported. These results indicate that the solution procedure is effective for a wide range of traffic loads and cost structures.     

MANET中一种新QoS路由技术的研究

移动AdHoc网络（MANET）支持QoS保证的能力,受限于无线介质的带宽和节点的移动特性。由于节点的移动,网络拓朴频繁发生变化,一旦节点移动,当前的路由就很容易失效,从而造成通讯中断,这种情况就是链路失效。QoS路由是MANET获得端到端QoS保证的第1步。然而,拓朴变化造成的链路失效状况的存在,使得路由的可靠性对于QoS路由而言非常重要。为使链路失效造成的影响最小,找到生存时间长并且可靠性高的路由就显得尤为重要。提出了一种在MANET中支持Oos路由,并能较好解决链路失效状况的方案。该方案定义了一种新机制,在执行时类似表驱路由协议,通过利用主路径上被共享的邻居节点信息,为主路径上各个独立的子路径预备了可替换的路径。     

改善BGP路由收敛的时间窗口机制

提出了一种时间窗口机制,能够基于路由抖动抑制中路由惩罚值的变化改善BGP(border gateway protocol)路由收敛.这种新机制把来自不同邻居的路由变化情况结合起来,利用BGP路由传播过程形成的路由相关性判断路由在网络中的稳定情况.时间窗口机制使BGP路由器能够更早地发现不稳定路由,优先将稳定路由选择为最优路由,终止路径搜索过程.模拟实验的结果表明,通过选择适当的参数,时间窗口机制能够大大缩短BGP路由收敛延时,减小收敛过程中的通信开销.而且,这种方法不需要在BGP的路由消息中增加额外的信息,因此容易在实际网络中逐步部署.     

多径路由在移动Ad hoc网络中的应用研究

在移动Ad hoc网中,多径路由因其能够更好地支持QoS而得到广泛的研究.从减少端到端延时、降低能耗、提高可靠度、有效利用链路带宽四个方面介绍多径路由在Ad hoc网中的应用.但是,现在大多数多径路由协议只考虑到网络层,而没有考虑到其它层和多径路由的相互关系,基于此,分析多径路由在链路层和传输层所面临的问题,并且提出解决这些问题的进一步的研究方法.     

Neighbor supported reliable multipath multicast routing in MANETs

The limited battery power, unpredictable mobility and large variation of received signal strength in nodes of Mobile Ad Hoc Networks (MANETs) create link and node vulnerability and instability. Multicast routing in MANETs for group communication requires the establishment of reliable links between neighboring nodes called as reliability pair beginning from the source and extending such reliability pairs enroute to the destination. We propose a scheme for Multipath Multicast Routing in MANETs using reliable Neighbor Selection (MMRNS) mechanism. A mesh of multipath routes are established from source to multicast destinations using neighbors that have high reliability pair factor. MMRNS operates in the following phases. (1) Computation of reliability pair factor based on node power level, received differential signal strength between the nodes and mobility. (2) Pruning neighbor nodes that have reliability pair factor smaller than a threshold. (3) Discovery of multipath multicast mesh routes with the help of request and reply packets. (4) Multipath priority assignment based on minimum value of reliability pair factor of a path and information transfer from source to the multicast destinations and (5) route maintenance against link/node failures. The scheme is simulated to evaluate the performance parameters like packet delivery ratio, memory overhead, message overhead, control overhead and packet delays in comparison to the mesh based multicast routing protocols such as On-demand Multicast Routing Protocol (ODMRP) and Enhanced ODMRP (EODMRP). MMRNS performs better than ODMRP and EODMRP as observed from the simulation results.     

A low-cost communication security scheme of UAV based on multi-round reverse auction model

In recent years, the security of wireless communication has received more and more attention. However, with the increasing requirements for security performance in the process of wireless communication, the cost of improving security also increases. Therefore, how to improve the security of wireless communication while reducing costs has become a serious challenge. Aiming at the security problems in the UAV-assisted wireless communication link based on the premise of low cost and high profit, this paper studies how to motivate non-offloading users to send jamming power to interfere with eavesdropping UAVs, so efficiently and economically to improve the security performance of wireless communication link. Firstly, the relationship between the security performance of the communication link and the interference power is revealed through the theoretical model. Then, we propose a scenario consisting of a legitimate UAV, a ground user group, and an eavesdrop UAV. In this scenario, we divide the ground users into offloading users and non-offloading users. At the same time, the cost functions for offloading users and utility functions for non-offloading users are defined, and non-offloading users are encouraged to help to offload users unload data safely to a legitimate UAV by obtaining rewards for offloading users. Considering the selfishness of users, a reverse auction algorithm based on multi-user groups is proposed to achieve the optimal mapping between non-offloading users and offloading users. Finally, the effectiveness of the proposed scheme is verified by a large number of simulations. The research results show that the scheme innovative designs a method for users to cooperate to interfere with eavesdroppers, which can reduce costs and improve utility while maximizing the improvement of wireless communication link security.     

有效的AODV路由协议改进方法

为了在路由请求时避免使用相对移动性很高的节点,在路由应答时选取更可靠的路由,提出一种AODV路由协议改进算法,该算法充分利用Ad hoc网络节点的移动性信息,与AODV相比,改进后的协议可发现更稳定的路径,并明显降低路径断裂的概率,且协议的延时小,包投递率高。仿真结果验证结论的正确性。     

Reduced GUI for an interactive geometry software: Does it affect students' performance?

PurposeThe purpose of this paper is to describe an experimental study to reduce cognitive load and enhance usability for interactive geometry software.Design/methodology/approachThe Graphical User Interface is the main mechanism of communication between user and system features. Educational software interfaces should provide useful features to assist learners without generate extra cognitive load. In this context, this research aims at analyzing a reduced and a complete interface of interactive geometry software, and verifies the educational benefits they provide. We investigated whether a reduced interface makes few cognitive demands of users in comparison to a complete interface. To this end, we designed the interfaces and carried out an experiment involving 69 undergraduate students.FindingsThe experimental results indicate that an interface that hides advanced and extraneous features helps novice users to perform slightly better than novice users using a complete interface. After receiving proper training, however, a complete interface makes users more productive than a reduced interface.Originality/valueIn educational software, successful user interface designs minimize the cognitive load on users; thereby users can direct their efforts to maximizing their understanding of the educational concepts being presented.     

无人机自组网按需寻路的可靠OLSR协议

无人机自组网应用场景中,针对OLSR(Optimized Link State Routing)协议在数据通信阶段,无人机快速移动可能引起通信链路中断,并且OLSR协议没有链路维护机制,导致发包成功率降低和时延增加.在节点入网阶段,无人机无法及时获取全网拓扑信息,导致通信失败.本文借鉴AODV(Ad Hoc On Demand Distance Vector)路由协议中按需寻路思想,提出一种按需寻路的可靠OLSR协议.该算法提出了两个优化思路:基于TC全网寻路机制和基于HELLO邻居寻路机制,通过增加路由获取途径,维护多跳链路的稳定性.通过仿真实验将该协议与现有协议进行比较,实验结果表明,该协议在不增加控制开销的前提下,提高网络的发包成功率,端到端时延和吞吐量.     

Uncovering the dual influence processes for click-through intention in the mobile social platform: An elaboration likelihood model perspective

The burgeoning growth of mobile social platforms has gained the attention of advertisers, and the way how to stimulate users’ click-through intention in the virtual social community is becoming a research focus of scholars. Drawing on the elaboration likelihood model (ELM), this study develops a theoretical framework to examine the mediation effects of cognitive vs. affective trust on the relationship between dual routes (central route vs. peripheral route) and users’ click-through intention in the context of mobile social platforms. Particularly, users’ prior product experience is incorporated in the research model to examine its moderating effect on the influence processes. A scenario-based survey is conducted in China, and the partial least square method is used to analyze the data. Empirical results suggest that perceived content personalization is positively associated with cognitive trust, and its influence is stronger for experienced users with the recommended product. Social recommendation is positively associated with affective trust, and its impact is higher for users without prior product experience. Advertiser reputation is positively associated with both cognitive trust and affective trust, and its effect on cognitive trust is stronger for users without prior product experience, while its impact on affective trust is higher for users with prior product experience. Moreover, cognitive trust is positively associated with affective trust, and the two trust mechanisms have positive influences on click-through intention toward the recommended product. We discuss theoretical and practical implications in the final section.