摘 要

隨著人們對通信數(shù)據(jù)化、寬帶化、個(gè)人化和移動(dòng)化的需求，OFDM 技術(shù)在綜
合無線接入領(lǐng)域得到廣泛的應(yīng)用，它將是 4G 移動(dòng)通信的核心技術(shù)之一。
OFDM(Orthogonal Frequency Division Multiplexing)是一種特殊的多載波傳輸
方案，它將數(shù)字調(diào)制、數(shù)字信號處理、多載波傳輸?shù)燃夹g(shù)有機(jī)結(jié)合在一起，是目
前已知的頻譜利用率最高的一種通信系統(tǒng)，具有傳輸速率快、抗多徑干擾能力強(qiáng)
的優(yōu)點(diǎn)。目前，OFDM 技術(shù)在數(shù)字音頻廣播(DAB)、地面數(shù)字視頻廣播(DVB—T)、
無線局域網(wǎng)等領(lǐng)域得到廣泛應(yīng)用。
本文分析了無線信道的特點(diǎn)，簡要概述了 OFDM 技術(shù)的發(fā)展?fàn)顩r、原理、數(shù)
學(xué)表示、部分關(guān)鍵技術(shù)，采用 Matlab 仿真的方法，對由于高斯噪聲而產(chǎn)生碼間干
擾等問題進(jìn)行了仿真和討論,并對 QPSK 調(diào)制技術(shù)進(jìn)行了較為全面的仿真和分析。
文中通過仿真得出了在一定信噪比范圍內(nèi)的 BER性能曲線。

關(guān)鍵詞：正交頻分復(fù)用；調(diào)制； 解調(diào)


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 錄

第 1 章 緒論 ..................................................................................................................... 1
1.1 課題背景 ................................................................................................................ 1
1.2 無線通信 ................................................................................................................ 1
1.2.1 無線通信概述 ................................................................................................. 2
1.2.2 無線信道特性 ................................................................................................ 3
1.3 OFDM概述及應(yīng)用 .................................................................................................... 3
1.3.1 OFDM的應(yīng)用 .................................................................................................... 3
1.3.2 OFDM的發(fā)展 .................................................................................................... 5
1.3.3 OFDM的關(guān)鍵技術(shù) ............................................................................................ 6
1.3.4 OFDM的優(yōu)缺點(diǎn) ................................................................................................ 7
1.4 論文的結(jié)構(gòu) ............................................................................................................ 8
第 2 章 OFDM基本原理 ..................................................................................................... 9
2.1 原理及數(shù)學(xué)描述 .................................................................................................... 9
2.1.1 OFDM基本原理 ................................................................................................ 9
2.1.2 串并轉(zhuǎn)換 ...................................................................................................... 10
2.1.3 子載波調(diào)制 .................................................................................................. 11
2.1.4 DFT變換 ........................................................................................................ 13
2.1.5 傅立葉變換的過采樣 .................................................................................. 15
2.1.5 保護(hù)間隔、循環(huán)前綴和子載波數(shù)選擇 ...................................................... 15
2.2 調(diào)制方式 .............................................................................................................. 21
2.2.3 QPSK調(diào)制 ...................................................................................................... 21
2.2.4 QPSK信號的產(chǎn)生 .......................................................................................... 23
2.5 本章小結(jié) .................................................