lte 系统的切换及高速铁路环境下的改进分析.docx

摘要
摘要
目前,无线通信呈现出移动化、宽带化、IP化的趋势,为了满足市场的需求同时保持3GPP无线接入技术的领先地位,3GPP组织启动了LTE项目。LTE主要以 OFDM和MIMO技术为基础,对3G系统进行长期演进。LTE对现有的3G系统网络架构和接入方式做了较大的调整,网络结构呈现扁平化和IP化,具有更高的数据传输速率,更低的系统时延。
另一方面,随着我国高速铁路的飞速发展,列车速度得到大幅提升的同时, 也造成旅客通信质量的大幅下降,存在频繁切换、掉话率高等现象。而LTE以其优越的性能,特别是其高传输速率,低延时的特点,能够更好的满足高速铁路的通信需求。切换作为移动性管理的重要部分,对于解决移动过程中的连续性有着重要意义,特别是在保障高速铁路环境下的通信质量。本论文研究了LTE的切换技术并针对高速铁路这一特殊环境提出改进的切换算法。
论文首先概述了LTE系统的网络架构、各个网元与接口的功能,介绍了切换的作用和分类,并对LTE系统的切换过程进行了详细说明。然后介绍了LTE A3切换算法,以及影响切换算法的影响因素,并搭建了LTE系统仿真平台,对A3切换算法的性能进行了研究。最后分析总结了高速铁路环境下通信中存在的问题以及现有的解决方法,并提出了改进的切换算法:基于TA变化率的切换参数自适应调整算法和改进的A3预触发切换算法。仿真结果表明改进的切换算法能够很好的提升高速用户的切换成功率。
关键字:LTE 切换高速铁路 TA变化率预触发
Abstract
Abstract
Currently, munication technology shows a trend of mobile, broadband, IP. To meet the requirement of the market and maintain the leading position of 3GPP radio access technology, anization starts the LTE project. LTE is the long term evolution of 3G system based on OFDM and MIMO technology and it has made a great
improvement work structure,with higher data transfer rate and lower system
latency.
On the other hand, with the rapid development of high speed railway in China, which gives the convenience to the passengers but at the same time results in munication problems, such as frequent handover and high dropped call rate. With its superior performance, especially high data transfer rate and low system latency, LTE meets the requirement of high speed railway better. As a basic function of mobile management, handover makes an important role especially in high speed railway environment. This paper mainly focuses on the handover technology of LTE and its improvement in high speed railway.
This paper firstly summarizes work structure, functions work nodes and interfaces of LTE, then introduces the role and classification of handover, and the handover procedure of LTE in detail. Secondly the A3 handover algorithm of LTE is introduced and its influence factor is discussed. By establishing a LTE system level simulation platform,