基于matlab的ofdm系统设计与仿真毕业论文.pdf

摘 要

随着人们对通信数据化、宽带化、个人化和移动化的需求，OFDM 技术在综
合无线接入领域得到广泛的应用，它将是 4G 移动通信的核心技术之一。
OFDM(Orthogonal Frequency Division Multiplexing)是一种特殊的多载波传输
方案，它将数字调制、数字信号处理、多载波传输等技术有机结合在一起，是目
前已知的频谱利用率最高的一种通信系统，具有传输速率快、抗多径干扰能力强
的优点。目前，OFDM 技术在数字音频广播(DAB)、地面数字视频广播(DVB—T)、
无线局域网等领域得到广泛应用。
本文分析了无线信道的特点，简要概述了 OFDM 技术的发展状况、原理、数
学表示、部分关键技术，采用 Matlab 仿真的方法，对由于高斯噪声而产生码间干
扰等问题进行了仿真和讨论,并对 QPSK 调制技术进行了较为全面的仿真和分析。
文中通过仿真得出了在一定信噪比范围内的 BER性能曲线。

关键词：正交频分复用；调制； 解调


Abstract

As people on the needs of data communication, broadband, individuals and mobile,
OFDM technology accesses a wide range of applications in the field of integrated
wireless , it will be one of the core technology of 4 G mobile communications. OFDM
(Orthogonal Frequency Division Multiplexing) is a special multi-carrier transmission
scheme , it combines some technologies such as figure modulation, digital signal
processing, multi-carrier transmission .It is the maximum utilization of the spectrum
communication system ,with the advantages of faster transfer rates ,anti-multipath
interference. Currently known at present, OFDM technology is widely used in the
digital audio broadcasting (DAB), terrestrial digital video broadcasting (DVB-T) and
wireless LAN.
The paper analyzes the features of wireless channel, and briefly summarizes the
development, principles, mathematics denotation, some key technology of the OFDM.
At the same time, imitate and discuss deeply about some problems, such as ISI and
QPSK modulation by using the method of matlab simulation. This paper simulates the
scope of BER performance curve within a certain signal to noise ratio.

Key words: OFDM; Modulation; Demodulation



目 录

第 1 章 绪论 ..................................................................................................................... 1
1.1 课题背景 ................................................................................................................ 1
1.2 无线通信 ................................................................................................................ 1
1.2.1 无线通信概述 ................................................................................................. 2
1.2.2 无线信道特性 ................................................................................................ 3
1.3 OFDM概述及应用 .................................................................................................... 3
1.3.1 OFDM的应用 .................................................................................................... 3
1.3.2 OFDM的发展 .................................................................................................... 5
1.3.3 OFDM的关键技术 ............................................................................................ 6
1.3.4 OFDM的优缺点 ................................................................................................ 7
1.4 论文的结构 ............................................................................................................ 8
第 2 章 OFDM基本原理 ..................................................................................................... 9
2.1 原理及数学描述 .................................................................................................... 9
2.1.1 OFDM基本原理 ................................................................................................ 9
2.1.2 串并转换 ...................................................................................................... 10
2.1.3 子载波调制 .................................................................................................. 11
2.1.4 DFT变换 ........................................................................................................ 13
2.1.5 傅立叶变换的过采样 .................................................................................. 15
2.1.5 保护间隔、循环前缀和子载波数选择 ...................................................... 15
2.2 调制方式 .............................................................................................................. 21
2.2.3 QPSK调制 ...................................................................................................... 21
2.2.4 QPSK信号的产生 .......................................................................................... 23
2.5 本章小结 .................................................