《移动通信》期中论文
论文题目 智能天线在移动通信中的应用
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智能天线在移动通信中的应用
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摘 要 介绍了智能天线的基本原理、实现方法及其在移动通信中的应用。
近年发展起来的CDMA移动通信系统技术相对于FDMA、TDMA系统具
有较大的容量,但由于多径干扰、多址干扰的存在,其容量优势并没有得到充分的发挥,如果在基站上采用智能天线可以降低这些干扰的影响,提高系统的性能。本文通过对智能天线的认识、优势的阐述,从而引发智能天线在现代移动通信中的重要性。
最初的智能天线技术主要用于军事抗干扰通信和定位等。近年来,
随着移动通信的发展及对移动通信电波传播、组网技术、天线理论等方面的研究逐渐深入,智能天线开始用于具有复杂电波传播环境的移动通信。此外,随着移动用户数迅速增长和人们对通话质量要求的不断提高,要求移动通信网在大容量下仍具有较高的话音质量。经研究发现,在不增加系统复杂度的情况下,使用智能天线可满足服务质量和网络扩容的需要。 关键词 智能天线,移动通信,容量,覆盖
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ABSTRACT
Introduces the basic principle of smart antenna, method and its application in mobile communication.
Developed in recent years the CDMA system for mobile communications technology, TDMA system FDMA relative to have large capacity, but because the multipath interference, the existence of multiple access interference, its capacity advantage and didn't get sufficient play, if the base station on the smart antenna can reduce the influence of these interference, and improve the performance of the system. This article through to the understanding of the smart antenna, this advantage, and cause the smart antenna in modern mobile communication of importance.
The first smart antenna technology is mainly used for military anti-jamming communication and positioning, etc. In recent years, with the development of mobile communication and the mobile radio waves propagation, network technology, antenna theory of deep gradually, smart antenna started to use
with
complex
radio
waves
propagation
environment
mobile
communication.In addition, as mobile subscribers rapid growth and people to call the continuous improvement of the quality requirements for mobile communications network in the large capacity under the still has high voice quality. The study found that, without any increase in complexity system, by the use of smart antenna can meet the service quality and network expansion needs. Key Words: Smart Antenna Mobile Communication Capacity Cover
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目 录
1.引言............................................................................................................................................ 4
1.1发展历程 ........................................................................................................................... 4
1.2智能天线的基本思想 ......................................................................................................... 5 1.3空分多址的概念 ................................................................................................................ 5 1.4智能天线和自适应天线的区别 ........................................................................................... 5 2.智能天线的形式 .......................................................................................................................... 6
2.1根据工作方式的不同 ......................................................................................................... 6 2.2根据波束形成的不同 ......................................................................................................... 7 3.智能天线的结构 .......................................................................................................................... 7
3.1典型阵列 ........................................................................................................................... 7 3.2结构原理图 ....................................................................................................................... 8 3.3系统组成 ........................................................................................................................... 8
3.3.1天线阵列 ................................................................................................................ 8 3.3.2模数转换 ................................................................................................................ 8 3.3.3智能处理 ................................................................................................................ 9 4.智能天线的信号模型 ................................................................................................................... 9 5.智能天线的赋形 .........................................................................................................................10
5.1波束形成技术 ...................................................................................................................10 5.2零点技术 ..........................................................................................................................10 5.3空间谱估计技术 ...............................................................................................................10 6.智能天线的常用准则 ..................................................................................................................10
6.1最大信干噪比准则 ............................................................................................................10
6.2最小均方误差准则 ............................................................................................................10 6.3最小方差准则 ...................................................................................................................10 6.4最大似然准则 ...................................................................................................................10 7.智能天线在移动通信中的用途 ....................................................................................................10
7.1抗衰落 .............................................................................................................................10
7.2抗干扰 ............................................................................................................................. 11 7.3增加系统容量 ................................................................................................................... 11 7.4实现移动台定位 ...............................................................................................................12 8.智能天线的应用 .........................................................................................................................12
8.1用于FDMA系统 .................................................................................................................12 8.2用于TDMA系统 .................................................................................................................13 8.3用于CDMA系统 .................................................................................................................13 8.4用于无线本地环路系统 .....................................................................................................13 8.5用于DECT、PHS等系统 .....................................................................................................13 8.6用于第三代移动通信 ........................................................................................................14 9.智能天线技术的研究动向 ...........................................................................................................14 参考文献 .......................................................................................................................................16
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1. 引言
1.1发展历程
９０年代以来，阵列处理技术引入移动通信领域，很快形成了一个新的研究热点－智能天线（SmartAntennas）。智能天线应用广泛，它在提高系统通信质量、缓解无线通信日益发展与频谱资源不足的矛盾、以及降低系统整体造价和改善系统管理等方面，都具有独特的优点。
最初的智能天线技术主要用于雷达、声纳、军事抗干扰通信，用来完成空间滤波和定位等。近年来，随着移动通信的发展及对移动通信电波传播、组网技术、天线理论等方面的研究逐渐深入，现代数字信号处理技术发展迅速，数字信号处理芯片处理能力不断提高，利用数字技术在基带形成天线波束成为可能，提高了天线系统的可靠性与灵活程度。智能天线技术因此用于具有复杂电波传播环境的移动通信。此外，随着移动通信用户数迅速增长和人们对通话质量要求的不断提高，要求移动通信网在大容量下仍具有较高的话音质量。经研究发现，智能天线可将无线电的信号导向具体的方向，产生空间定向波束，使天线主波束对准用户信号到达方向DOA（direction of arrinal），旁瓣或零陷对准干扰信号到达方向，达到充分高效利用移动用户信号并删除或抑制干扰信号的目的。同时，利用各个移动用户间信号空间特征的差异，通过阵列天线技术在同一信道上接收和发射多个移动用户信号而不发生相互干扰，使无线电频谱的利用和信号的传输更为有效。在不增加系统复杂度的情况下，使用智能天线可满足服务质量和网络扩容的需要。实际上它使通信资源不再局限于时间域（TDMA）频率域（FDMA）或码域（CDMA）而拓展到了空间域，属于空分多
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