第 1 页 共 45 页
摘 要
CDMA技术是当前无线电通信，尤其是移动通信的主要技术，不论是在中国已经建立的IS-95规范的中国联通CDMA网、各大移动通信运营商正准备实验及建立第三代（3G）系统还是大设备研发商已经在开发的三代以后（也称为4G）更宽带宽的移动通信系统，CDMA都是主要的选择。CDMA概念可以简单地解释为基于扩频通信的调制和多址接入方案。其反向链路有接入信道和反向业务信道组成。接入信道用于短信令消息交换、能提供呼叫来源、寻呼响应、指令和注册。
本设计选取CDMA通信系统中的接入信道部分进行仿真与分析。首先，通过学习相应的理论知识，熟悉接入信道实现的过程，对每一步的原理有了较深的理解，同时，也对MATALB软件进行熟悉和了解，对MATLAB软件中的SIMULINK部分及其内部的CDMA模块用法和参数设置进行熟悉，然后运用MATLAB软件对接入信道部分进行设计，并逐步地对各个模块进行分析、仿真与验证。目的是通过毕业设计工作熟悉现代无线通信系统的基本构成与基本工作原理，重点掌握卷积编码、块交织和码扩展等相关编码技术，并能将这些技术应用实际系统设计，提高自己对CDMA通信系统知识的认识。
关键字：CRC;卷积编码;块重复;交织;长码;沃尔什;PN序列
第 2 页 共 45 页
Abstract
CDMA is the major technology used in the wireless communication , especially in the mobile communication. Following the IS-95 standard set up in China ,CDMA is the mostly choice whether in China Uninet net ,in the third system (3G) that all kinds of mobile businessmen are to build or in the wider system than the third one(named 4G)that the large equipments researching businessmen have been researching.The concept of CDMA may be interpreted as the simulation that base on frequency spreading and the multiply address access project.Its reverse channel is composed of access channel and traffic channel.The access channel is used for brief information exchanging 、providing the source about the calling、the call responding 、the instruction and the enrollment.
This design choose the part of connect channel to simulate and analyse. First,we can familiar with the process of connect channel ,understand the principleof every step of the procedure about thre channel,after studying the relating knowledge .At the same time ,we an also have some acquaintance with the software about MATLAB and the part of SIMULINK and how to set the parameter of every klock in the soft.Then we can use the MATLAB software to design the part of the connect channel, to analyse , to simulate and to validate the design of every block gradually. This purpose is to be familiar with the basic structure and basic principle of the morden wireless communication system, to mastery the technology about the Convolutional Encoder,Interleaver ,Coder spread and so forth, then use those technology to design system in practice,so that to improve our knowledge about the CDMA communication system.
Key words:CRC;Convolutional Enconder;Block Repeat;Interleaver;Long code;Walsh;
PN sequence
第 3 页 共 45 页
目 录
中文摘要 关键字 …………………………………………………….……1 英文摘要 关键字 ………………………………………………….………2 目 录 ……………………………………………………………….……...3 前 言 ………………………………………………………………..……..4 1 设计总体框架 ……………………………………………………..……5 2 设计各个部分原理知识介绍 ………………………………………..…6 2.1 卷积编码……………………..………………………………………..…..7 2.2 交织技术介绍………………………..………….…………………………9 2.3 沃尔什函数说明………………………………..….………………………11 2.3.1 沃尔什函数特性说明………………………….…………………...……11
2.3.2 沃尔什函数的产生方法介绍……………………………………………..13 2.4 长码的实现……………………………………………………………….15 2.6 PSK和OQPSK调制…………………………………………………………18 2.7 短码的实现……………………………………………………….……….20
3 MTALAB软件中的SIMULINK的简介…………………………….………20 4 设计仿真、分析与验证……………..………………………….……….22 4.1 设计总体模块构造…………………………..…………………….……….22 4.2 对各个模块进行分析与验证 ………………………………….……………23 4.2.1 源中部分（subsystem1）设置、说明与分析……………………………...24 4.2.2 对卷积编码器和重复模块的设置、说明与分析 …………………………27 4.2.3 对子系统Subsystem2（块交织器）模块的设置、说明与分析 ……………30 4.2.4 沃尔什调制器输出与长码输出及其异或验证…..………………….………40 4.2.5 I路和Q路的输出验证与分析……………………………………………46 5.经验总结…………………………………………………………………..49 谢 辞………………………………………………………………………..50 参考文献……………………………………………………………………..51