移动蜂窝网络的无缝切换技术

蜂窝网络在通信过程中,由于移动台在通话过程中会随着距离基站的远近、信号强度、信号质量和通话质量等原因造成切换,为了能够让用户保持无感知通话状态,移动蜂窝网络需要采用无缝切换技术,有效的提高了移动蜂窝网络的通话质量。     

蜂窝网络和Ad Hoc网络综述

文章首先分别介绍了无线通信网络中的蜂窝网络及Ad Hoc网络的概念、发展及特点,分析了两者的不同及联系.之后又讨论了这两种网络中的信道分配问题:对于蜂窝网络介绍了基本的信道分配策略;对于Adhoc网络介绍了单频、双频和多频各自的频率分配特点.最后展望无线通信网络的发展方向和未来.     

移动Ad Hoc网络研究与发展现状

本文简要介绍移动ad hoc网络发展的历史、理论和技术上的一些热点问题，以及它的一些应用，从而给读者一个概括性的了解，为进一步学习和研究移动ad hoc网络奠定一些基础。为了便于读者跟踪国外先进的研究成果，本文最后介绍了一些在这一领域比较活跃的研究机构以及他们的主要工作。     

移动通信系统中的切换和切换算法

切换是蜂窝系统所独有的功能，也是移动通信系统的一个关键特征，它直接影响整个系统的性能。本对移动通信系统中切换和切换算法进行了深入细致的研究，包括切换的分类和功能、性能指标、各种切换方式及算法的优缺点，提出了自己的建议及需要继续研究的问题。     

Ad Hoc与蜂窝网络融合技术的讨论

蜂窝网络和AdHoc网络是两种不同结构的网络,前者是有中心的集中式网络结构,而后者是无中心的网络结构。为了有效地提高蜂窝网络的数据传输容量并改善网络覆盖,国外学者提出在蜂窝网络中引入AdHoc中继节点。分析了蜂窝网络和AdHoc网络各自的优缺点,二者融合带来的优势;并介绍了两种蜂窝网中引入AdHoc中继节点的实现方案,最后提出了融合网络中的重点和难点问题,对今后的研究具有一定的启示作用。     

移动Ad Hoc网络中的安全问题

移动自组网(Mobile Ad HoC Network)是一种无基础设施的无线网络由于它具有开放的媒质、分布式的合作、动态的拓扑结构和受限的网络能力等特点,所以特别容易受到攻击.为此文章结合移动Ad Hoc网络的特点分析了移动Ad Hoc网络面临的安全威胁,并对移动Ad Hoc网络的安全路由和安全报文传送问题进行了详细讨论.     

基于标签交换的Ad Hoc网络研究

研究基于标签交换的Ad Hoc网络，目的是提高网络的快速转发能力，减小数据包的转发时延，在功能上实现路由与交换功能的分离，本文研究通过在Ad Hoc网络中建立标签交换路径，实现数据包的标签交换，燕详细叙述了基于标签交换的Ad Hoc网络的基本架构和实现过程。     

一种适于波束切换移动自组网的邻居发现改进算法

基于多波束切换的移动自组网系统在未来通信中具有广阔的应用前景,邻居发现是基于多波束切换的移动自组网系统的关键技术之一。现有基于多波束切换的移动自组网邻居发现算法在波束交叠情况下无法选择最优通信波束,为了解决基于多波束切换的移动自组网邻居发现过程中的最优通信波束选择问题,提出一种改进算法,在邻居发现过程中增加接收信号质量评估机制,增强网络的稳定性,提高网络吞吐量,并通过仿真验证了在波束交叠的情况下系统的累计平均接收电平优于传统方法。     

蜂窝移动通信系统的中的切换

切换是蜂窝移动通信系统的中地一项关系技术。本文介绍了蜂窝移动通信系统 中不同的切换方案，分析了各种方案的优缺点，同时，着重讨论了ＣＤＭＡ蜂窝系统中的软件切换方案。     

移动Ad Hoc网络节能方案的分析

对Ad Hoc网络中节能机制进行了分层介绍,详细介绍了目前的路由节能机制,对节能算法进行了分析.但当前的协议在处理更复杂,拓扑变化频繁的的网络时表现不好.对当前协议进行跨层设计,以及随着仿生学的发展,将群集智能算法的思想加入到当前无线Ad Hoc网络中成了节能研究发展的新方向.对当前的蚁群算法进行了详细的研究,并对算法中的不足给出了修改意见.     

Handoff Algorithms for Integrated Ad Hoc and Mobile Cellular Systems

Multi-criteria handoff algorithms have been playing a more important role than the traditional handoff algorithms.In order to balance the satisfaction of users and the efficiency of networks,it is necessary to develop new technologies to improve the validity of handoff algorithms.Intelligent and optimized handoff algorithms in hybrid networks that integrate Ad hoc and mobile cellular systems are well-adaptive and robust.They are able to implement handoffs adaptively,according to specific multi-factors such as different Quality of Service(QoS)requirements,network states and mobile node conditions in the future hybrid networks.Therefore,these intelligent and optimized algorithms can make more effective handover decision,and accordingly improve the system’s performance.The future research will tackle intelligent or optimized vertical handoff algorithms for integrated Ad hoc and mobile cellular networks to improve their whole system performance.     

Performance Study of Proactive Flow Handoff for Mobile Ad Hoc Networks

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile computers forming a temporary network without any existing wire line infrastructure. Searching for feasible paths, or routing, is very challenging in mobile ad hoc networks because of frequent topology changes caused by users' mobility. Location information is required by some applications and can be used to facilitate routing implementation. In this paper, we propose a proactive flow handoff method based on nodes' location information. In summary, location information is utilised to reduce the control overhead in route discovery phase, to search quickly for a feasible path upon link breakage, and to hand off a flow to a stable path if the active one breaks based on predication. Keeping “always-on” end-to-end connectivity once a flow is established is the main advantage of this routing method. A thorough simulation study is performed to demonstrate the efficiency of this method. This research was supported by a grant from the Canadian Institute for Telecommunications Research under the NCE program of the Government of Canada. Kui Wu received his Ph.D in Computing Science from the University of Alberta, Canada, in 2002. He joined the Department of Computer Science at the University of Victoria, Canada in the same year and is currently an Assistant Professor there. His research interests include mobile and wireless networks, network performance evaluation, and network security. Janelle Harms received her Ph.D. in Computer Science from the University of Waterloo, Ontario, Canada working in the area of performance analysis of resource allocation mechanisms. She joined the Department of Computing Science at the University of Alberta in 1991 and is currently an Associate Professor there. Her research interests include performance aspects of network resource allocation, routing and design problems.     

An Adaptive Hard Handoff Algorithm for Mobile Cellular Communication Systems

In this letter, we propose an adaptive hard handoff algorithm with a dynamic hysteresis value based on the received signal strength from the serving base station, for mobile cellular communication systems. A discrete‐time method is presented to evaluate handoff algorithms analytically. Performance is evaluated in terms of the average number of handoffs, the probability of link degradation, and the average handoff delay. Numerical results and simulations demonstrate that the proposed algorithm outperforms the handoff algorithm with fixed hysteresis values and the handoff algorithm using both threshold and hysteresis.     

Ad hoc网络中的路由技术

Ad hoc网络是一些移动节点组成一个多跳的临时性无线自治系统，这种新型的通信网络具有动态变化的拓扑结构和分布控制的网络机制。文中针对Ad hoc网络作了简单的介绍并重点介绍了针对Ad hoc网络特性而提出的路由协议。     

基于网络编码的无线自组织网数据分发机制

 无线自组织网络中,移动台能量有限,为了延长生存期,需要减少中间节点之间的数据包交换次数,本文提出一种基于网络编码的数据分发机制CRNC,同基于泛洪的传统数据分发机制相比,CRNC在大幅度减少传输次数的同时,只增加了少量时延.理论分析及仿真试验,证明了采用网络编码的CRNC可以在传输时延和能量消耗上取得更好的均衡.     

移动自组网基于动态蜂窝的QoS路由协议

本文为移动自组网提出了一个基于动态蜂窝的QoS路由协议，它利用移动跟踪技术实现了一个分布式动态蜂窝生成协议；采用一个多Qos路由探测算法选择一条能够最大满足QoS要求的路由，并在这条路由上建立端．端主动资源预留；使用移动预测和被动资源预留技术预测源结点和目的结点可能进入的蜂窝集合，并在这些蜂窝集合与目的结点和源结点之间提前进行端．端被动资源预留；融合蜂窝动态检测技术与QoS路由修补技术自动发现和修补断裂的QoS路由．由于该路由协议模仿了固定蜂窝网络中的操作，所以，大大改善了QoS路由的性能．仿真结果表明：在满足QoS条件下，它明显提高了包传输率，减轻了路由负载．     

Energy-Efficient Routing Algorithms Using Directional Antennas for Mobile Ad Hoc Networks

Power consumption is an important issue in the wireless ad hoc networking environment. In this paper, we present several energy-efficient routing algorithms using directional antennas for wireless ad hoc networks. These algorithms are simple to implement and are distributed and can be applied to mobile environments. We evaluate how directional antennas improve system throughput. We study the influence of the battery recovery effect and mobility on the network throughput during a network lifetime. We also present an algorithm that exploits the broadcast nature of the wireless communication environment to improve end-to-end bit error performance for a Rayleigh fading channel.     

MANET实时传输的可靠性研究

以IDA算法的可逆"扩散-恢复"运算为基础,本中提出一个多径路由分布式网络环境的MANET信息扩散方案.该方案因MANET实时传输网络环境中无线信道质量和路由拓扑的持续变化,动态地调整IDA算法的两个主要参数,以实现自适应的冗余机制,在节约网络资源的同时保证实时传输的可靠性.该方案的实现只需在网络层和应用层做少量的修改,使得它在实际应用中更为方便、有效.     

无线传感器网络与自组织网络的研究现状

传感器网络综合了传感器技术、嵌入式计算技术、分布式信息处理技术和无线通信技术,是计算机科学技术的一个新的研究领域;自组织网络是一种移动、多跳、自律式系统,两者均具有十分广阔的应用前景.文章对传感器网络和自组织网络的概念、特征和发展动态等问题进行了介绍,重点分析了目前这两种网络的关键技术和研究现状.文章认为:传感器网络在特殊领域有着传统技术不可比拟的优势,而无线自组织网络通过临时组网的方式在恶劣环境中支持移动节点之间的无线传输,应用范围广阔.对这些网络的研究是中国未来高技术民用和军事发展的需要.