Cooperative schemes for path establishment in mobile ad-hoc networks under shadow-fading

The performance of routing protocols for multi-hop path-establishment in Mobile Ad-hoc NETworks (MANET) is examined when the individual radio links undergo shadow fading of parameterized severity. Such propagation modeling is typical of ground-level networking along with node mobility. The metrics of main interest are the probability of having a reliable multi-hop path plus the temporal statistics of such availability under a Markovian model. Such availability is an indicator for the suitability of the network to carry delay-sensitive applications (push-to-talk voice, streaming video) in uninterrupted manner. It is shown that high levels of diversity are necessary in such adverse environments, as obtained either by multiple independent paths or via concurrent cooperative transmission. Analytical and simulation comparisons of typical routing options are presented on the above metrics, plus on the required nodal engagement for supporting such diversity.     

Enabling off-the-grid telephony: An adaptive probabilistic model for broadcasting in ad-hoc mobile phone networks

Ad-hoc peer-to-peer mobile phone networks (phone-MANETs) can enable village level telephony for cash-strapped, off-the-grid communities in developing regions. Broadcasting is a fundamental operation in such MANETs (Mobile Ad-hoc Networks) and is used for route discovery. Cost and power consumption optimizations are critical for such systems. Hence, lightweight broadcast techniques which can operate on basic devices and incur low overheads are more pragmatic than their more complex counterparts. This paper proposes a new broadcast technique for rural phone-MANETS that is lightweight, efficient and incurs low latency. Using extensive simulations, the proposed technique is compared to existing lightweight broadcast protocols. The results show that the new technique is successful in outperforming existing lightweight techniques on multiple criteria that are important for a phone-MANET.     

MANET中IP地址自动配置算法设计

分析了具有全球连接的移动自组织网络中地址自动配置需要解决的地址唯一性、网络分裂与融合等关键问题,针对现有地址自动配置算法实现复杂、扩展性差、时延过长等不足,设计了一种自组织网络地址自动配置算法.该算法采用代理分配和自主分配相结合的方式,实现初始地址的快速分配,并在路由协议中引入虚拟地址概念,以维护本地地址的唯一性.算法...     

NS-2仿真系统TestSuite组件应用研究

应用NS-2技术进行网络仿真和协议算法研究,已广泛成为国内外学者和工程技术人员的首要选择。由于在NS-2网络仿真与模拟技术应用中常常对系统进行修改、移动和增减,相继产生的系统平台正确性与完整性问题也得到更多重视。重点对NS-2仿真系统Test Suite测试组件的应用进行研究,并以一个无线局域网测试组件为实例,较为全面地介绍Test Suite组件的测试原理、实现方法以及测试过程,希望对读者应用NS-2仿真系统Test Suite测试组件以及编写新的测试组件提供帮助。     

合作博弈论在MANET安全模型中的应用

本文介绍了MANET网络的一种安全机制模型及改进。由于MANET网络动态性、随机接入的特点，对于安全隐患的感知必须依赖成员节点的相互协作才能完成，而当前已有的理论模型均存在一些明显缺陷，比如不能有效检测到威胁，或者虚警率过高等，严重影响了这一类模型的实际应用价值。本文中通过引入安全分级，使用合作博弈论的算法来处理大量不同节点感测到的系统威胁的相关信息，给出合理的综合判断，并且对于各个节点本身也做出了一定的评估结果，有利于模型参数的优化。经过仿真验证，说明合作博弈论应用于该安全模型使得模型性能得到明显的改善。     

面向群组移动的轻型位置服务研究

针对现实应用中大规模MANET网络节点呈现的群组移动特性,提出了面向群组移动的轻型位置服务协议GHLLS。G-HLLS协议将HLLS协议框架与分簇机制相结合,从而保证位置更新及请求机制适应群组移动特性。基于OPNET的仿真实验,从负载、服务成功率、存储开销多个方面对G-HLLS协议性能进行了分析,验证了G-HLLS协议在大规模群组移动网络中表现出的优越性能。     

基于阈值判断的动态源路由协议算法优化设计

针对移动自组织网动态源路由协议(DSR)中旧路径中断至新路径建立期间存在的丢包和端到端时延问题,设计了一种基于阈值判断的路由发现和维护算法,以优化路由协议性能。该方法首先定义节点电池能量和节点接收信号能量双阈值等级,分别用于衡量节点和既存链路状态;然后修改路由发现和路由维护算法,使动态源路由具备阈值判断功能。分别对增强型动态源路由协议(EDSR)包传递率和端到端时延等性能随节点数目和移动速度等参数的变化规律进行了软件仿真。实验结果表明,节点数目超过150或者速度小于10 m/s时,EDSR端到端时延和包传递率优于DSR,其他性能基本相当,因此EDSR协议性能得到明显改善,为低速大规模移动自组网路由协议提供了重要参考。     

Improving MANET performance by a hop‐aware and energy‐based buffer management scheme

A hop‐aware and energy‐based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real‐time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real‐time and non‐real‐time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end‐to‐end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop‐aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end‐to‐end delays for real‐time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.     

基于发布/订阅中间件的移动计算

发布订阅(Pub/Sub)中间件以发布/订阅的通信模式实现分布式系统中的各参与者之间的交互,它的松耦合、异步、组播等特点,使它能够很好地适应移动计算动态变化的网络环境.分析Pub/Sub中间件系统的框架模型和集中式、分布式两种结构,并将其扩展到移动计算环境.     

移动自组网地址配置问题的研究

MANET（Mobile Ad hoc Network）中没有一个永久的中心机构，其网络拓扑结构不断变化，所以必须有一种能够对网络主机地址动态自配置和管理的协议。给出了在MANET中动态地址自配置与管理的方法，不同方案的特点及适应情况，最后对目前Ad hoc网络地址配置研究进行总结和展望。