摘要
近年来,无线通信技术迅速发展。CDMA作为实现第三代移动通信的关键技术,得到了广泛的应用。随着社会信息需求的急剧增加、个人移动通信的迅速普及,频谱已成为越来越宝贵的资源。为了在有限的频带上容纳更多的用户,有许多技术被提了出来,其中的一个研究热点就是智能天线。
智能天线采用空分多址,利用信号在传播方向上的差别,将同频率、同时隙的信号区分开来。它可以成倍地扩展通信容量,已经成为当今世界各国的重点研究对象。本文对无线通信系统主要是CDMA系统中的智能天线的技术特点做了详尽介绍,对智能天线对CDMA系统容量的影响做了细致分析。全文共分六章,安排如下:
第一章简述了无线通信的历史和三种CDMA标准,介绍了智能移动通信技术的一些内容。
第二章具体介绍了智能天线技术,包括两种类型的智能天线:切换波束系统和自适应天线系统。讨论了智能天线的空间处理接收机,介绍了几种典型的最优波束形成方案和自适应算法。
第三章分析了在基站使用智能天线来提高CDMA多小区系统的容量,给出了在更符合实际情况的模型下的计算公式。考虑了多径干扰、热噪声、路径损耗、处理增益和语音激活因子的影响;并介绍了与智能天线技术相结合的多用户检测技术。
第四章讨论了智能天线技术的一个重要组成部分:空时编码技术。将空时编码技术和盲自适应多用户检测技术相结合,进一步提高了系统容量。
第五章介绍了基于软件无线电的智能天线在CDMA通信系统中的应用。
第六章介绍了智能天线的研究现状,展望了智能天线的发展前景。
In recent years,the wireless communication technique has developed rapidly. CDMA becomes the key technique to realize the 3rd generation mobile communication,and has been widely used.With the rapid increase of social information demand and the fast popularization of individual mobile communication,frequency has become more and more valuable.In order to hold more users in a limited frequency,many technique is proposed,among which smart antenna is the research hotspot.
Smart antenna adopts SDMA, and in terms of the difference of transmission direction,it can distinguish signals of the same frequency and the same time interspace.Smart antenna can enlarge cacacity greatly ,and has become a key research topic of many countries nowdays.This dissertation makes a detailed introduction of smart antenna in the wireless communication system,mainly in the CDMA system,and the influence of smart antenna on CDMA system capacity is also analyzed.The dissertation is made up of six chapters:
Chapter 1 simply discusses the history of wireless communication and the three criteria of CDMA,and introduces smart mobile communication technique.
Chapter 2 embodies smart antenna technique.Two types of smart antenna are introduced:beam-switched system and adaptive antenna system.Then the spatial processor is discussed.Some classical optimization beamforming schemes and adaptive algorithms are also presented.
Chapter 3 investigates the capacity improvement in CDMA multi-cellular system with base-station smart antenna.We consider the effects of multipath interference, thermal noise, path loss, processing gain and voice activity factor.And introduces multiuser detection combined with smart antenna.
Chapter 4 discusses an important component of smart antenna technique: time-space coding.We combine time-space coding and blind adaptive multiuser detection to enhance system capacity further.
diaper 5 introduces the use of smart antenna based on software radio in CDMA communication system.
Chapter 6 narrates the status quo of smart antenna,and also expects its prospect.
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