在移动通信系统中的规划和设计中,无线资源的管理与控制居于中心地位,对系统的整体性能产生重要的影响。而切换是无线资源管理功能中的重要一部分,直接影响着系统的容量和服务质量,同时也是蜂窝系统所独有的功能和关键特征。用户终端在最初的小区与网络实现连接之后,由于各种原因有可能离开这个小区的服务范围。移动通信系统中的切换过程就是将用户终端的连接切换到其他小区,从而使得通信服务不中断。在WCDMA、CDMA2000系统中支持硬切换、软切换及更软切换;TD-SCDMA系统中支持硬切换、接力切换。快速、准确地切换能有效的保证呼叫的完整性。
切换过程的优化设计对于任何一个蜂窝通信系统都是十分重要的。因为从网络效率的角度出发,当用户终端处于不适合的服务小区进行通信时,不仅会影响自身的通信质量,同时也将增加整个网络的负荷,甚至增大对其他用户的干扰。移动用户应当使用网络中最优化的通信链路与相应的基站建立连接。
本文先介绍了切换的一些基本概念,然后分别介绍了不同系统中的切换技术,因为TD-SCDMA是我国唯一具有知识产权的标准,很有可能成为我国3G中所广泛使用的,所以本篇重点介绍了TD-SCDMA中的接力切换,并结合实际工作中接触到的切换的仿真更深入的了解了切换基本参数的设置等。
根据仿真结果得出以下结论:在TD-SCDMA规划工作中,需掌握合适的天线倾角,以取得最佳的接通率和基站下行资源利用率。综合比较分析知,城区环境下天线倾角选择7度最为合适,农村典型环境下天线倾角应选择3度最为合适。参数选择方面,根据仿真结果,建议切换过程中的滞后量取值4dB、滞后比较时间取值1000ms、切换测量启动门限取值-88dBm、\相邻小区检测门限取值-98dBm。
关键词:TD-SCDMA,接力切换,仿真,
In the programming and the design of the mobile communication systems, the management and the control of the radio resource occupies the central status, it has an important influence to overall performance of the system. Handoff technology is an important part in the function of the radio resource management, it directly affects the capacity and the quality of service of the system, simultaneously it is also the particular function and the essential characteristic in a cellular system. After the user equipment connects with the network in initial cell ,it may leave the range—serving of the cell because of each kind of reasons. The handoff process in mobile communication system means cut the connection of initial cell and connect with other cells,it can make communication without interrupting. In the system of WCDMA and CDMA2000,it support hard handoff、soft handoff . In the system of TD-SCDMA,it support hard handoff、relay handoff. Rapid and exact handoff can guarantee the integrity of calls effectively.
The optimum design for handoff process is very important to all cellular communication systems. From the aspect of the network efficiency, when the user equipment is not in the suitable serving-cell to carry on the communication,it will not only affect the quality of oneself ,simultaneously it will also increase the burden of the network, even worse ,it may increase the disturbance to other users. Mobile users should use the optimized communication link in the network and connect the corresponding basic state.
This article first introduced some basic concept of handoff technology ,then it introduced handoff technology in different systems. For TD-SCDMA is the only standard belong to China,and it will be used extensively in our country possibly. Therefore this article emphasis in the introducing of relay handoff in TD-SCDMA , and understand establishment of basic parameter in handoff ,contacting with simulation in practical work.
From the simulation results,the conclusion is given that in the programming in TD-SCDMA,the obliquity of antenna should be masterd appropriatly.In the aspect of parameter choice,here are some numbers suggested,4dB for RSCP_DL_COMP, 1000ms for time, -88dBm for RSCP_DL_DROP,-98dBm for RSCP_DL_ADD.