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摘要：越区切换是指将当前正在进行的移动用户与基站之间的通信链路从当前基站转移到另一基站而维持通信不中断的过程。在CDMA系统中，随着移动用户数量的增加，用户服务质量(QoS)的保证变得至关重要。越区切换技术是保证QoS的重要环节。
本文首先介绍了CDMA系统切换技术研究现状，并对越区切换策略、切换方式进行了分析，然后通过硬切换和软切换的比较选定软切换为本次仿真设计的重点。通过对软切换的分析，利用Hata传播模型和切换规则设置相关门限参数并在Visual C++平台上实现软切换的仿真设计，并通过相关实验，验证了CDMA系统中软切换各项参数取值对CDMA切换产生的影响，能够仿真CDMA切换功能。
关键词：CDMA；切换；门限；Hata模型
DMA Handoff Research and Simulation
Abstract： In CDMA system, the quality of service (QoS) of each MS becomes more important with the increase of the number of MS. To guarantee good QoS, Handoff is the key issue, which is also an important part of mobile management. CDMA Handoff is a process that the channel of MS can be switched to another Base station uninterrupted when mobile customer strides across one BS. Handoff can improve utilization ratio of system resources, also obtaining higher performance of system. Handoff is the most complicated and vital technique in CDMA system.
Firstly, this thesis introduces the principle research status of CDMA Handoff, then analyse the strategy and the mode of CDMA Handoff. By compared with Hard Handoff and Soft Handoff technique, this thesis focuses on Soft Handoff simulation. Secondly, this thesis simulates CDMA Soft Handoff by using Hata transmition model and the threshold parameters on Visual C++ platform. Then through relevant experiments, it validate the impact of CDMA system threshold parameters in switching.
At last, this design has been achieved the simulation of CDMA Soft Handoff, and complete the project.
Key words: CDMA, Handoff, Threshold, Hata transmition model
