移动WiMAX硬切换时延性能优化研究

介绍了约束移动WiMAX硬切换时延优化的理论解决方案,并提出一种新的结合关联2且利用R6信令进行参数协商的硬切换机制。最后模拟了真实实验环境用于测试新的硬切换机制,结果表明该机制可以有效减小硬切换时延,满足移动WiMAX较高服务质量的要求。     

移动IPv6切换时延优化新方法

移动IPv6中,移动节点(MN)在不同子网间移动时,既不中断与通信对端(CN)的通信,也不用改变其本身的IP地址.但是当MN与其家乡代理(HA)之间相距较远时,移动IPv6切换时延较大,对于实时性要求较高的业务无法适用.本文分析比较了目前移动IPv6常用的切换时延优化方法,提出了一种自适应快速层次移动IPv6切换时延优化方法,减小了移动IPv6切换时延,提高了网络的性能.     

移动IP中的S-MIP切换方法

有两种比较常用的减少切换时延的方法．第一种是通过分层管理的架构来减少家乡网络的注册时间，第二种是通过地址预先配置来减小地址长度的方法来解决延迟的快速切换机制。S-MIP切换方法是建立在分层和快速切换方法之上的。它能够实现与L2层相似的较少的数据包丢失和切换的时延。     

基于流的移动IPv6快速切换方法

文章介绍了一种基于流的移动IPv6快速切换方法．即路由器利用IPv6的业务流的信息把各个业务流重定向到移动节点的新转交地址上．这种重定向的方式是在MN绑定更新注册的过程中进行的．使得移动节点在向家乡代理的注册还未完成之前．便能与通信对端进行正常通信，这样大大减少了切换时延．提高了切换效率．另外．本文通过理论分析．将此方法与常规的移动IPv6和分层移动IPv6机制进行了比较．并利用NS-2网络模拟器的仿真数椐对在此方法下不同类型的业务流的传输进行了分析，验证其具有较为良好的性能。     

一种移动IPv6的切换优化方案

移动节点在两个不同子网之间移动时产生切换。移动节点的切换技术是保证实时业务服务质量的关键问题之一。目前比较经典的三种切换机制是快速移动IPv6、层次型移动IPv6和快速层次移动IPv6。在简单介绍了三种机制原理并分析了它们的不足后,提出了一种自适应移动IPv6切换时延优化方案。     

TD-SCDMA HSDPA切换和时延研究

HSDPA技术是TD-SCDMA的增强型技术,旨在提高下行信道传输数据的能力.引进HSDPIA技术的同时,对于TD-SCDMA系统的移动性管理提出了新的要求.TD-SCDMA HSDPA切换时延不同于引入新的DCH切换时延,对于业务质量和系统网络性能都产生了较大的影响.本文从理论和实际的角度分析了HSDPA切换过程中时延的产生,同时给出了TD-SCDMA系统中减小HSDPA切换时延、优化网络质量的一些措施,旨在进一步完善TD-SCDMA系统.     

使用EHN-HP机制提高移动切换中TCP性能

移动通讯技术的发展促使传统有线互联网向无线移动网络延伸.TCP协议是现在互联网上使用最为广泛的端到端可靠传输协议,但TCP协议是在有线链路基础上设计的,直接在无线移动网络上使用TCP协议会造成TCP性能的下降.本文详细分析了移动切换对TCP协议造成的影响,比较并分析现有的几种解决方案,针对切换对TCP造成的影响提出了EHN-HP机制.EHN-HP机制在现有的TCP协议上进行改进,增加了切换处理机制(Handoff Process),通过网络模拟器的模拟结果表明,EHN-HP机制有效的改善了TCP协议在切换过程中的性能.     

移动IPv6及其扩展协议性能分析

本文主要对这几种移动IP技术进行描述,然后在NS-2(一种开放源码的网络模拟工具)仿真平台下设定一定的切换场景进行仿真实现,对这几种协议进行切换时延和切换期间丢包数量的比较.     

基于动态分布结构的一种微观移动切换方法

提出了一种在动态分布结构下微观移动的切换方法,它可根据移动主机进入微观局网收到的首次注册信息,动态地选择微观移动的网关,调整微观局网结构,分布了网络负载。通过用比较分析的方法和仿真实验对切换时间进行了计算和验证,表明此方法减少了微观移动网关的切换时延。     

Impact of secondary user mobility on spectrum handoff under generalized residual time distributions in cognitive radio networks

Cognitive Radio is an emerging technology to accommodate the growing demand for wireless technology via dynamic spectrum access to enhance spectrum efficiency. Spectrum handoff is an important component of Cognitive Radio technology for practical implementation of radio frequency access strategy and better utilization of spectrum in both primary and secondary networks. The probability of spectrum handoff and expected number of spectrum handoffs are key parameters in performance analysis and design of the cognitive radio network. This work presents an analytical model to evaluate the impact of secondary users’ mobility on intra-cell spectrum handoff considering primary users’ activity model in a cognitive radio network. A standard form of intra-cell spectrum handoff probability and expected number of intra-cell spectrum handoffs are derived for complete call duration of a non-stationary secondary user. The probability and expected number of intra-cell spectrum handoffs of a post inter-cell handoff call are also derived for generalized residual time distributions of call holding time and spectrum holes. A detailed analysis of these performance measuring metrics is presented under the impact of departure rate and cell crossing rate of secondary users. The accuracy of the derived analytical result is validated by Monte-Carlo simulation of the model.     

基于预测的平滑切换机制及其性能评价

针对微观移动协议现有切换机制存在的问题,提出了基于预测的平滑切换机制,该机制利用移动预测技术,在切换发生前预测移动主机将要切换的下一蜂窝以及切换的时刻,为移动主机预先建立新路径;为了保证基于预测的平滑切换机制的实现,提出了一个易于实现的简单移动预测算法--SMPA算法;通过理论分析和系统仿真的方法对基于预测的平滑切换机制进行了性能评价,结果表明该切换机制以相对较小的代价获得了可观的性能改善.     

蜂窝重叠情况下移动IP切换延时分析

从理论上首次对移动 IP 切换过程中的切换延时和乱序分组进行了建模和分析,分别得到了各自的概率分布公式。并且根据这个结果,优化了重叠区域的半径。结果表明:本模型准确地描述了移动 IP 的切换行为,它对于评价移动 IP 的切换性能非常有用。     

认知频谱切换延时及用户容量的排队论分析

为了分析认知无线电系统中授权用户享有更高优先级对认知用户频谱切换造成的影响,提出了一种虚拟排队切换模型,对有强制中断率限制系统中的认知频谱切换延时进行了分析;并利用分段近似的方法给出了在切换超时概率较小环境下强制中断率和认知用户容量的解析表达. 仿真与数值计算验证了虚拟排队切换模型的有效性,同时也比较了不同授权用户行为对认知频谱切换延时及用户容量造成的影响。     

Optimal mobility control with energy constraint in delay tolerant networks

Owing to the uncertainty of transmission opportunities between mobile nodes, the routing in delay tolerant networks (DTNs) exploits the mechanism of store‐carry‐and‐forward. In this routing mechanism, mobility plays an important role, and we need to control the mobility of nodes around the network to help with carrying messages from the source to the destination. This is a difficult problem because the nodes in the network may move arbitrarily and it is difficult for us to determine when the nodes should move faster to help the data transmission while considering the complicated energy consumption in such a network. At the same time, for most DTNs, the system energy is limited, and energy efficient algorithms are crucial to maximizing the message delivery probability while reducing the delivery cost. In this paper, we investigate the problem of energy efficient mobility speed control in epidemic routing of DTN. We model the message dissemination process under variable mobility speed by a continuous‐time Markov model. With this model, we then formulate the optimization problem of the optimal mobility control for epidemic routing and obtain the optimal policy from the solution of this optimization problem. Furthermore, extensive numerical results demonstrate that the proposed optimal policy significantly outperforms the static policy with constant speed, in terms of energy saving. Copyright © 2012 John Wiley & Sons, Ltd.     

利用多目标PSO优化的累积时延和信道容量联合优化的频谱切换算法

目前频谱切换中多以单目标优化设计目标信道,为了满足大容量实时传输要求,需要综合考虑累积切换时延和有效信道容量。对此构建了目标信道设计的多目标函数,提出了求解离散多目标优化问题的粒子群算法（DMOPSO）,给出了种群编码、更新方式离散化设计。仿真结果表明,所提出的频谱切换算法得到的最优信道访问解集能够兼顾网络的实时性和高吞吐率,算法复杂度较低。     

A cross‐layer partner‐based fast handoff mechanism for IEEE 802.11 wireless networks

In wireless/mobile networks, users freely and frequently change their access points (APs) while they are communicating with other users. To support the mobility of mobile nodes (MNs), Mobile IPv6 (MIPv6) is used to inform the information of MN's home address and current care‐of‐address (CoA) to its home agent. MIPv6 suffers from a long delay latency and high packet losses (PLs) because MIPv6 does not support micromobility. A Hierarchical Mobile IPv6 (HMIPv6) is proposed which provides micromobility and macromobility to reduce handoff latency (HL) by employing a hierarchical network structure. In this paper, we propose a cross‐layer partner‐based fast handoff mechanism based on HMIPv6, called the PHMIPv6 protocol. Our PHMIPv6 protocol is a cross‐layer, layer‐2 + layer‐3, and cooperative approach. A cooperative node, called a partner node (PN), is adopted in the PHMIPv6 protocol. A new layer‐2 trigger scheme used in the PHMIPv6 protocol accurately predicts the next AP and then invites a cooperative PN in the area of the next AP. With the cooperation of the PN, the CoA can be pre‐acquired and duplicate address detection operation can be pre‐executed by the PN before the MN initializes the handoff request. The PHMIPv6 protocol significantly reduces the handoff delay time and PLs. In the mathematical analysis, we verified that our PHMIPv6 protocol offers a better HL than the MIPv6, HMIPv6, and SHMIPv6 protocols. Finally, the experimental results also illustrate that the PHMIPv6 protocol actually achieves performance improvements in the handoff delay time, PL rate, and handoff delay jitter. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance assessment of long‐range and Sigfox protocols with mobility support

Low‐power wide area networks (LP‐WANs) protocols are considered options to meet the requirements of Internet of Things (IoT) solutions that need long‐range communication with low power consumption. Few studies intended to evaluate the performance of the same class of protocols coexisting in the same environment and with mobility support. This paper explores the technical characteristics of Sigfox and long‐range (LoRa) protocols and presents a performance evaluation study considering mobility scenarios. The experiments were performed in real environments. Then, two prototypes for LoRa and Sigfox equipped with Global Positioning System (GPS) were created. Quantitative and qualitative performance metrics were also proposed for this study. The results showed that the coexistence between these protocols has soft impact on the performance presented. Because of the movement, the effects of Doppler, multipath, and signal fading hardly affect the performance of both protocols.     

The Effect of Handoff Dwell Time on the Mobile Network Performance

In this paper, we have studied the impact of the handoff dwell time (HDT) on the channel holding time (CHT) modeling and examined how it affects the mobile network performance evaluation. Realistic mobility model is constructed that includes the effect of HDT and we derive the important relationship between the critical parameters such as cell residence time (CRT), call holding time, CHT and HDT. Queueing priority scheme utilizing the HDT is applied to evaluate the HDT effect on performance indices in terms of the new call and handoff call blocking probabilities. It is observed that the relative error between the realistic new call blocking probability and conventional one can reach 70% and the conventional handoff blocking probability can even double the realistic one under the same specific practical condition. Next, we compare the new call and handoff call blocking probabilities when exponential handoff dwell time distribution is replaced by truncated Gaussian distribution with both the same mean and standard deviation in the discrete event simulation. A considerable gap between the handoff call blocking probabilities is shown, which indicates that the performance indices are sensitive to the handoff dwell time distribution.Zhang Yan received the B.S. degree in communication engineering from the Nanjing University of Post and Telecommunication, Peoples Republic of China, in 1997 and the M.S. degree in electrical engineering from the Beijing University of Aeronautics and Astronautics in 2000. After graduation, he worked as senior software engineer in Xinwei Telecom Technology Co., Datang Telecom Group, China, where he has been working on the CDMA base station software development. He is currently pursuing Ph.D. degree in School of Electrical and Electronics Engineering, Nanyang Technological University, Singapore. His research interests include call admission control and resource management in wireless multimedia systems, PCS network traffic load and performance evaluation.Dr. Soong Boon-Hee received his B. Eng. (Hons. I) degree in electrical and electronic engineering from University of Auckland, New Zealand, and the Ph.D. degree from the University of Newcastle, Australia, in 1984 and 1990, respectively. He is currently an associate professor with the School of Electrical and Electronic Engineering, Nanyang Technological University. From October 1999 to April 2000, he was a visiting research fellow at the Department of Electrical and Electronic Engineering, Imperial College, UK, under the Commonwealth Fellowship Award. He also served as a consultant for Mobile IP in a recent technical field trial of Next-Generation Wireless LAN initiated by InfoComm Development Authority (IDA), Singapore. He has supervised a number of postgraduate students in the area of optimization and planning of mobile communication networks. He has been teaching a number of subjects related to the field of network performance. His area of research interests includes ad-hoc networks, mobility issues, mobile IP, optimization of wireless networks, routing algorithms, queueing theory system theory, quality of service issues in high-speed networks, and signal processing. He has published a total of 60 international journals and conferences. He is a member of IEEE.     

异构网络垂直切换技术

下一代无线网络(Next Generation Wireless Networks,NGWN)将融合多种不同的网络体系结构与无线技术,NGWN的异构性要求向用户提供无缝切换。为此文章引入了异构无线网络垂直切换策略,并深入论述了其中的关键细节——网络发现、切换判决和切换信息交互流程等。