高速铁路移动通信系统

本文从高速铁路特点出发，提出了对高速铁路移动通信网的要求．以列车为主体的移动通信系统，是集话音和数据，控制和监测为一体的综合信息传输网；是以无线与有线相结合，控制与计算机和通信相结合的高质量、高可靠性的高速铁路综合业务通信网中的重要组成部分．文中简介了国外高速铁路移动通信网概况．并根据国情，提出了我国高速铁路移动通信网方案，包括两个系统：一、面向铁路公务人员和面向旅客的列车电话系统；二、提供调度员与机车司机间双向数据传输系统和列车定位系统．讨论了网络的特点和系统构成以及需要解决的有关关键技术问题．     

高速铁路移动通信系统性能研究

随着我国社会经济的快速发展,作为我国重要基础领域的交通运输领域,近年来也获得了蓬勃的发展,交通运输领域的不断发展,对于我国交通网络体系提出了更高的要求.在这样一个社会大环境下,高速铁路建设事业便应运而生,高速铁路不仅具有较高的运行速度,其还能为人们提供舒适便利的交通环境,而且其正点率也更高,因而高速铁路建设领域,已成为我国近年来重点发展的领域之一.随着移动通信技术手段的不断发展,移动通信系统在高速铁路中的应用也越来越广泛,其在提升人们快捷出行服务的同时,也为人们的提供高质量的信息通信服务.本文将就高速铁路移动通信系统的性能进行详细的探究.     

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。     

高速铁路移动通信系统性能分析

本文主要对人们比较关心的高速铁路移动通信系统性能进行分析,研究目前高速铁路移动通信系统的使用情况和目前使用中已经暴露出的一些不足,并针对高速铁路移动通信系统的现状提出相应的改进措施.     

高速铁路移动通信系统性能分析

对于高速铁路来说,移动通信系统对高速铁路具有更高的运营水平以及更良好的服务质量有重要的影响,应该强化分析高速铁路移动通信系统的性能,掌握其中的关键技术,为高速铁路的顺利发展打好基础。文章对移动通信系统在高速铁路中的发展情况进行分析,对移动通信系统的性能也进行探究。     

TDD-LTE移动通信系统高速铁路通信系统研究

本文介绍了高速铁路场景下移动通信系统的发展,阐述了TDD-LTE移动通信系统高速铁路通信系统的相关研究,其中分析了拓扑模型与天线模型,同时提出了干扰抑制方案,旨在不断提高高速铁路通信网络建设的高效性、科学性与合理性.     

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。     

蜂窝移动通信系统中的切换

切换是蜂窝移动通信系统中的一项关键技术。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蜂窝系统中的软切换方案。     

CDMA蜂窝移动通信系统的软切换

介绍了ＣＤＭＡ蜂窝系统采用的越区切换方式，详细分析软切换的原理及实现，突出了软切换在小区制通信体制中的作用。     

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。本文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。     

Quality of Service Improvement for High-Speed Railway Communications

With the fast development of highspeed railways, a call for fulfilling the notion of communication at ＂anytime, anywhere＂ for high-speed train passengers in the Train Operating Control System is on the way. In order to make a realization of that, new railway wireless communication networks are needed. The most promising one is the Long Term Evolution for Railway which will provide broadband access, fast handover, and reliable communication for high mobility users. However, with the increase of speed, the system is subjected to high bit error rate, Doppler frequency shift and handover failure just like other system does. This paper is trying to solve these problems by employing MIMO technique. Specifically, the goal is to provide higher data rate, higher reliability, less delay, and other relative quality of services for passengers. MIMO performance analysis, resource allocation, and access control for handover and various services in a two-hop model are proposed in this paper. Analytical results and simulation results show that the proposed model and schemes perform well in improving the system performances.     

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。     

基于位置的双播机制在高速铁路越区切换中的应用

提出了一种适用于高速铁路环境的LTE越区切换方案,该方案利用列车移动轨迹的固定性和列车运行的规律性,采用了基于位置的双播机制。和传统采用双播机制的越区切换方案相比,该方案能够降低切换中断时间,最小化双播带来的额外网络开销。     

一种适合高速铁路的宽带无线接入网络架构

快速发展的高速铁路是需要覆盖移动语音和数据业务的新热点场景,这使得高速铁路宽带无线接入系统成为研究重点。根据高速铁路的特定环境,本文提出了一种基于光载无线通信技术的新型高速铁路宽带无线接入网络架构,阐述了相对应的媒体接入控制方案,并对其移动性管理进行了说明。     

移动软交换中越区切换实现研究

软交换是下一代网络控制层中的核心实体,越区切换是移动软交换的重要功能之一。该文分析了越区切换的功能特点,研究了移动软交换中越区切换与呼叫控制和接入协议的关系。对越区切换进行了功能分解和分析,提出了一种可扩展性强、易于向3G演进的越区切换模块构建方式和越区切换状态机的实现方法。     

高速铁路宽带无线通信系统越区切换技术

我国现有的铁路移动通信系统已不能满足铁路信息化建设的要求,需要开展下一代高速铁路通信系统关键技术研究。越区切换是高速铁路宽带无线通信系统的关键技术,对保障列车的行车安全和通信可靠性具有重要意义。针对目前高速铁路通信系统中越区切换技术的研究现状和成果进行总结,分析存在的问题,并进一步探讨未来越区切换技术的发展方向。     

LTE中一种基于高速铁路场景的信道估计方法

LTE系统在下行采用了OFDM技术。OFDM技术将高速数据流调制到相互正交的N路子载波上,因此易受频偏的影响,尤其在多普勒频偏较大的高速环境下会受到严重的干扰。本文依托LTE系统,提出一种针对高速铁路场景的信道估计方法,在基于最小二乘(least squares,LS)估计的基础上,针对高速移动环境提出相应的处理方法,包括基于循环前缀(cyclic prefix,CP)的频偏估计和时域能量集中等处理,仿真分析结果表明,与传统方法相比更适合高速场景,在车速达到500 km/h时仍然保持良好的误码率,具有一定的实用价值。     

Link Synchronous Mobile IPv4 Handover Algorithms

The performance of the base Mobile IP handover algorithm for moving the Mobile Node’s network layer point of attachment from one subnet to another has been recognized as a potential performance bottleneck for some time. In this paper, we discuss a collection of algorithms that use a link synchronous approach to Mobile IP handover. In the link synchronous approach, information on the progress of switching the link is used to drive handover at the IP level. We present a comprehensive analysis of handover packet drop, and develop analytical models of how the link synchronous algorithms help to mitigate it. We use data from a handover emulator to test the analytical models, and to compare the performance of the different algorithms under a variety of link conditions. Data from implementations on IS-2000 and 802.11b show how the link synchronous algorithms behave on real radio protocols. The results indicate that the link synchronous algorithms can reduce packet loss substantially, with best results possible if the link layer provides information on the move prior to the link switch. James Kempf is a Research Fellow at DoCoMo USA Laboratories. He holds a Ph.D. from the University of Arizona, Tucson, AZ. Previously, James worked at Sun Microsystems for 13 years, and contributed to numerous research projects involving wireless networking, mobile computing, and service discovery. James is a former member of the Internet Architecture Board, and co-chaired the SEND and Seamoby IETF Working Groups. James continues to be an active contributor to Internet standards in the areas of security and mobility for next generation, Internet protocol-based mobile systems. Ajoy Singh is a Principal Staff Engineer at Motorola GTSS Division where he has led the development of radio network controllers and the various components of core networks for 3GPP-based HSDPA and 3GPP2-based CDMA prototype systems. He holds a Master’s degree from DePaul University, Chicago, IL. Ajoy is the co-developer of several pending patents on cellular radio technology, and has contributed to the standardization of seamless mobility protocols through the Seamoby and Mobile IP IETF Working Groups and through IEEE 802.21. Jonathan Wood is an independent contractor and has been working with DoCoMo Labs since 2001. He is currently contributing to research on next generation mobility and networking infrastructures. Previously at Sun Microsystems, Jonathan focused on Solaris networking and 4G wireless network research. Atsushi Takeshita is a Director at the NTT DoCoMo Multimedia Laboratories in Yokoska Research Park, Japan. Prior to that, he was Director of the Autonomous Communication Laboratory in DoCoMo USA Laboratories, and one of the founding members of DoCoMo USA Laboratories. Atsushi joined NTT DoCoMo in 1988 and has since been engaged in the research and development of multimedia information retreival and delivery, the mobile Internet, and mobile terminal architectures. He is a member of the Association for Computing Machinery (ACM) and Information Processing Society of Japan. Nat Natarajan joined Motorola in 1993, and is a Fellow of the Technical Staff at Motorola. He received his Ph.D. from Ohio State University in Columbus, OH. Prior to working at Motorola, Nat served as a research staff member for over 12 years with IBM Thomas J. Watson Research Center, Yorktown Heights, NY, working primarily on packet switched data, voice and integrated networks as well as wireless data and satellite networks, and he has been a major contributor to the IEEE 802.11 standard approved in 1997. Nat is a Motorola Distinguished Innovator, holding 30 patents, and is a Senior Member of IEEE. Nat’s current technical interests are Beyond 3G/4G mobile networking systems based on IP technologies.     

GSM数字移动通信系统的越区切换

切换技术是GSM数字移动通信系统保证移动中用户通信质量的一个重要手段。本文简要说明切换及其起因、启动标准和类型 ,并阐述基站决定切换启动的三个不同阶段的算法和要求 ,最后重点介绍网络系统中各种不同范围切换控制的信令关系及其实现过程。     

未来移动通信的展望

第三代移动通信系统虽然仍处于预商用阶段,但许多公司和组织早已对三代以后的移动通信系统及其关键技术开始前瞻性的预研工作了。本文首先分析了未来移动通信系统的发展趋势,认为未来的移动通信系统将具有更高的传输速率、更高的频谱利用率,同时支持与基于IP的其它数据网络的互联互通;最后,分别描述了在未来系统中可能采用的网络结构和多种无线传输技术。