一种基于移动速度和移动方向的CDMA软切换接入策略

由于传统的软切换技术是在理想化条件下的模型。在现实环境的一些特殊情况下，不利于高效的利用信道资源，本文针对这些特殊情况提出了基于移动台的移动方向和移动速率来进行用户软切换呼叫的接入策略，并建立数学模型进行分析。分析结果表明该策略在系统软切换呼叫到速率较高时，不仅扩在了系统容量而且从整体上提高了系统软切换的服务质量（QoS)。     

一种基于模糊逻辑的切换算法

针对蜂窝移动系统的越区切换,提出了一种基于模糊逻辑的切换判决算法.通过仿真与只以信号强度为指标的传统切换算法进行了性能比较,结果表明:采用多指标判决的模糊逻辑切换算法能够有效降低系统的掉话率和切换数量,提高服务等级.     

CDMA系统基于多业务的软切换优化算法

文中利用剩余容量的概念,提出了CDMA系统中基于多业务的软切换优化算法,并对其进行了仿真.此算法综合考虑了传播衰耗和负载均衡两个因素,达到了各小区之间负载平衡和资源合理利用的目的.通过仿真结果可以看出,相对于传统的软切换算法,新算法降低了切换中断率,提高了系统性能,显示出较大的优越性,具有一定的价值.     

CDMA软切换优先级的排队算法

简要介绍了移动通信中的一项关键技术——越区切换的发展过程,重点讨论了码分多址(CDMA)系统中的软切换,提出了CDMA软切换优先级排队算法的模型及根据移动台的移动方向、移动速率、业务类别进行软切换优先级排队的方法。认为目前初步的排队控制模型还有待于进一步分析和优化。     

基于RSS准则的CDMA软切换越区研究

硬切换技术中移动台在接收新基站信号之前中断与原基站的通信,通信中断的概率非常大。而软切换技术需要先建立与新基站之间的通信,等接收到原基站信号低于门限值时再切断与原基站的通信,故具有很高的可靠性。采用接收到的信号强度准则对软切换建立仿真模型,对两个小区之间的软切换进行了仿真,仿真结果表明,软切换的可靠性高于硬切换,采用软切换技术降低了系统的掉话率,提高了通信质量。然而,软切换也将使系统的复杂度和信道开销有所增加。     

CDMA软切换特性及其对系统性能的影响

本文对CDMA软切换增益、T-ADD和T-DROP等参数对软切换比例的影响等软切换特性进行了分析,在此基础上,分析了软切换对系统容量、覆盖范围等性能的影响情况,提出了软切换比例的合理取值范围.     

CDMA增强型软切换探讨

文章介绍了增强型软切换算法,并通过引用相关文献和分析商用网实验结果,证实该算法能够有效控制软切换比例,最后给出的参数设置方法可作为工程人员实用参考.     

A Study of Handoff in CDMA Systems

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Comparison of Downlink Power Allocation Mechanisms in Soft Handoff for the WCDMA System with Heterogeneous Cell Structures

Handoff in heterogeneous cellular networks is one of the hot topics for wireless networks beyond the third generation. We observe that a power exhausting issue may occur in a code division multiple access (CDMA) system with mixed-sized cells. During soft handoff in the downlink transmission, a number of base stations transmit signals to a user simultaneously. Usually, a microcell has a more stringent limitation on the total available power than a macrocell. Thus, ignoring the impact of various cell sizes, the traditional downlink power allocation techniques for soft handoff may easily consume excessive power to serve soft handoff users, while leaving insufficient power for serving other regular users.To resolve such an power exhausting issue in CDMA systems, we investigate different downlink power allocation techniques used in soft handoff subject to the impact of mixed-sized cells. For the single-site power allocation technique we consider the site selection diversity transmission (SSDT) technique, while for the multi-site power allocation we study the link proportional power allocation (LPPA), the quality balancing power allocation (QBPA), and the equal power allocation (EPA) techniques. We find that the multi-site LPPA technique can more efficiently allocate power to both handoff and non-handoff users than others. In an example with the ratio of the micrcocell radius/macrocell radius equal to 1/3, it is demonstrated that LPPA can improve the capacity over EPA, QBPA, and SSDT by 125, 30, and 5%, respectively. By taking account of measurement errors in the same case, the capacity improvements of LPPA over EPA, QBPA, and SSDT become 180, 41, and 23%, respectively.This work was supported jointly by the Lee and MTI Center for networking research, and the National Science Council, Taiwan under the contracts 90-2213-E-009-068 91-2219-E-009-016, and EX-91-E-FA06-4-4. Part of results in this paper were presented at the IEEE Globecom, Nov. 2002, and the Sixth ACM International Workshop on Modelling, Analysis and Simulation of Wireless and Mobile Systems, (MSWiM’03), Sep. 2003.Ching-Yu Liao received the B.S. and M.S. degrees in electrical engineering from Huafan Institute of Technology and National Central University (NCU), Taiwan, in 1995 and 1997, respectively. She is currently working toward the Ph.D degree in communication engineering at National Chiao Tung University (NCTU), Hsinchu, Taiwan. Also, she joins the program of Graduate Student Study Abroad (GSSA), which is sponsored by National Science Council, Taiwan, R.O.C., being a visiting graduate student in Dept. of Electrical Engineering at University of British Columbia, Vancouver, Canada, in 2004. Her research interests include handoff techniques, radio resource management, heterogeneous cellular networks, etc.Li-Chun Wang received the B.S. degree from National Chiao Tung University, Taiwan, in 1986, the M.S. degree from National Taiwan University in 1988, and the Ms. Sci. and Ph. D. degrees in electrical engineering from the Georgia Institute of Technology, Atlanta, in 1995, and 1996, respectively. From 1990 to 1992, he was with the Telecommunications Laboratories of the Ministry of Transportations and Communications in Taiwan (currently the Telecom Labs of Chunghwa Telecom Co.). In 1995, he was affiliated with Bell Northern Research of Northern Telecom, Inc., Richardson, TX. From 1996 to 2000, he was with AT&T Laboratories, New Jersey, USA, where he was a Senior Technical Staff Member in the Wireless Communications Research Department. Since August 2000, he has been an Associate Professor in the Department of Communication Engineering of National Chiao Tung University in Taiwan. His current research interests are in the areas of cellular architectures, radio network resource management, and cross-layer optimization for high speed wireless networks. Dr. Wang was a co-recipient of the Jack Neubauer Memorial Award in 1997 recognizing the best systems paper published in the IEEE Transactions on Vehicular Technology. He is holding three US patents and one more pending. Currently, he is the associate editor of the IEEE Transactions on Wireless Communications.Chung-Ju Chang was born in Taiwan, R.O.C., in August 1950. He received the B.E. and M.E. degrees in electronics engineering from National Chiao Tung University (NCTU), Hsinchu, Taiwan, in 1972 and 1976, respectively, and the Ph.D degree in electrical engineering from National Taiwan University (NTU), Taiwan, in 1985. From 1976 to 1988, he was with Telecommunication Laboratories, Directorate General of Telecommunications, Ministry of Communications, Taiwan, as a Design Engineer, Supervisor, Project Manager, and then Division Director. There, he was involved in designing digital switching system, RAX trunk tester, ISDN user-network interface, and ISDN service and technology trials in Science-Based Industrial Park. In the meantime, he also acted as a Science and Technical Advisor for the Minister of the Ministry of Communications from 1987 to 1989. In 1988, he joined the Faculty of the Department of Communication Engineering and Center for Telecommunications Research, College of Electrical Engineering and Computer Science, National Chiao Tung University, as an Associate Professor. He has been a Professor since 1993. He was Director of the Institute of Communication Engineering from August 1993 to July 1995 and Chairman of Department of Communication Engineering from August 1999 to July 2001. Now, he is the Dean of the Research and Development Office in NCTU. He was an Advisor for the Ministry of Education to promote the education of communication science and technologies for colleges and universities in Taiwan since 1995. He is also acting as a Committee Member of the Telecommunication Deliberate Body. His research interests include performance evaluation, wireless communication networks, and broadband networks. Dr. Chang is a member of the Chinese Institute of Engineers (CIE).E-mail:cjchang@cc.nctu.edu.tw     

三值CDMA移动通信系统容量分析

从编码理论和话务理论出发 ,分析了三值CDMA移动通信系统的系统容量。证明在信息传输速率一致的条件下 ,三值系统的无线容量约为二值系统的log2 3(约 1 6 )倍 ;在码元传输速率一致的条件下 ,三值系统的服务等级更高。可见 ,三值CDMA系统为解决现有移动通信系统容量不足的问题开辟了新的途径。     

一种新的CDMA软切换算法及其对软切换性能的改善

定义了残余容损比(RCLR)的概念,提出了一种新的基于最大RCLR的无线移动CDMA小区系统的软切换判决算法,称之为RCLR算法。区别通常的最小路径损耗(MPOL)算法,RCLR算法不仅考虑了呼叫业务的路径损耗,而且兼顾了小区负载平衡。最后,通过分别在单层小区系统和分层小区系统中进行仿真,比较了RCLR算法和MPOL算法的软切换性能,仿真结果表明RCLR算法显著地改善了呼叫业务的中断概率和分层小区系统的层间溢出概率,减少了软切换次数。     

基于双窗口测量的蜂窝移动通信系统越区切换算法性能分析

本文提出了一种新的蜂窝移动通信系统越区切换测量算法,该算法采用了两个长度不同的测量窗口,有利于在切换时延和切换平均次数这对矛盾之间取得更为有效的平衡,特别适用于需要对多个基站进行切换测量的情况.同时本文给出了基于矩形窗口的双窗口切换测量算法数学分析模型,及数值分析结果.     

软切换对CDMA无线子系统的影响及控制

章介绍了CDMA系统无线资源的软切换的管理与控制，包括切换类型，切换策略，无线网络设计对网络的影响，切换参数的设置，搜索窗参数设置，邻小区参数设置以及无线网络优化等内容。     

宽窄合用CDMA卫星移动通信系统容量的研究

本文分析了宽窄合用CDMA卫星移动通信系统中宽带CDMA信号和窄带CDMA信号之间的相互干扰,提出了最佳的宽窄合用频谱配置方案.研究表明宽窄CDMA信号适当合用后,卫星移动通信系统容量能够大幅度提高.     

MCIP: A 3G/IP Interworking System Supporting Inter-Cluster Soft Handoff

In this paper, a novel 3-tier Mobile Cellular IP (MCIP) access network is proposed for interworking between a third generation (3G) wireless cellular system and a wireline Internet Protocol (IP) based network. An inter-cluster hard handoff scheme and an inter-cluster soft handoff scheme are proposed, based on the 3-tier MCIP system model, the core network protocol stacks, and the underlying MCIP routing algorithm. The core network protocol stack is presented to integrate the 3G radio interface and the IP-based core network, and to provide the access network with capability to support soft handoff macroscopic space diversity. The MCIP hard and soft handoff schemes are compared with the hard handoff schemes used in the Cellular IP and HAWAII access networks. The MCIP access network is more efficient in terms of signaling cost, but has the same scalability as Cellular IP and HAWAII. Both MCIP hard and soft handoff schemes enable IP packets to be delivered within the MCIP access network in-order without loss and duplication, a highly desired attribute for real-time multimedia applications. The advantages of supporting soft handoffs and quality-of-service (QoS) provisioning for real-time services are achieved at slightly increased system complexity.This work was supported by a research grant from the Natural Science and Engineering Research Council (NSERC) of Canada. The authors wish to thank the anonymous reviewers for their helpful comments and suggestions which improve the presentation of this paper. Xin Liu received his B.E. and M.E. degrees in radio engineering from Harbin Institute of Technology (China), in 1990 and 1993, respectively, and his M.A.Sc degree in electrical engineering from the University of Waterloo in 2002. He joined Research In Motion in 2002 as a firmware developer. His current work involves GSM/GPRS and WCDMA firmware development. Weihua Zhuang received the B.Sc. and M.Sc. degrees from Dalian Maritime University (China) and the Ph.D. degree from the University of New Brunswick (Canada), all in electrical engineering. Since October 1993, she has been with the Department of Electrical and Computer Engineering, University of Waterloo, Canada, where she is a full professor. She is a co-author of the textbook Wireless Communications and Networking (Prentice Hall, 2003). Her current research interests include multimedia wireless communications, wireless networks, and radio positioning. Dr. Zhuang received the Premier's Research Excellence Award (PREA) in 2001 from the Ontario Government for demonstrated excellence of scientific and academic contributions. She is an Editor of IEEE Transactions on Wireless Communications, an Associate Editor of IEEE Transactions on Vehicular Technology, and an Editor of EURASIP Journal on Wireless Communications and Networking.     

CDMA系统软切换预测分析

在简要叙述了CDMA系统软切换过程的基础上,讨论了CDMA系统软切换的参数设置对系统的影响,给出了参数设置的建议值,并借助模拟软件给出了不同参数设置下某实际业务区的软切换区域预测图.     

WCDMA软切换中的下行功率控制方案

发射功率控制是CDMA系统的关键技术之一。在WCDMA的软切换中，传统下行链路功率控制方案的实现主要存在两个问题：基站发射功率的失衡和下行链路干扰的增大。为解决上述问题，本介绍三种新的下行功率控制方案：降低TPC频率功率控制、调整环功率控制和站选择分集发射功率控制。其中前两种方案用于恢复软切换中基站发射功率的平衡，而最后一种方案用于减小下行链路干扰。研究表明，利用上述方案能够有效减小软切换中基站发射功率的差异或下行链路干扰，从而提高了系统容量。     

下一代移动通信网络中的切换管理研究

本文概述了下一代移动通信网络中的切换管理研究框架结构,对切换管理研究涉及的领域加以介绍,并为下一代移动通信网络的切换管理系统性研究指引了方向.     

IS—95CDMA系统的容量分析

容量的需求是推动ＣＤＭＡ数字蜂窝移动通信开发的主要动力。系统的容量受许多因素的影响，本文针对ＩＳ－９５ＣＤＭＡ系统在采用了功率控制、话音激活和扇区划分技术的情况下，对系统的容量进行了分析，同时也分析了功率控制精度对容量的影响。     

浅谈蜂窝区移动通信系统中的频道切换

CDMA技术是未来全数字化移动通信系统最有希望的发展方向。本文围绕蜂窝区移动通信系统中的频道切换进行了较为详细的论述 ,包括越区切换、越局切换和漫游 ,并介绍了CDMA软切换技术的优越性及其切换原理。