OFDM的研究和仿真.doc

本科毕业设计论文题目正交频分复用( OFDM )的研究与仿真院系电子与电气学院班级电子 085 班姓名董方维指导教师郭建中日期 2012 年5月1日... ... 摘要正交频分复用(OFDM ) ,实际上是多载波调制(MCM ) 的一种。其主要思想是: 将信道分成若干正交子信道,将高速数据信号转换成并行的低速子数据流,调制到在每个子信道上进行传输。正交信号可以通过在接收端采用相关技术来分开, 这样可以减少子信道之间的相互干扰(ICI )。每个子信道上的信号带宽小于信道的相关带宽,因此每个子信道可以看成平坦性衰落信道,从而可以消除符号间干扰。论文首先介绍了无线通信的发展历程和 OFDM 的研究状况,接着讲述了 OFD M 和QAM 的基本原理,最后通过对 OFDM 和QAM 系统的输入输出信号波形及频谱比较分析得出结论。结论表明,多载波 OFDM 技术的传输性能优于单载波 QAM 技术。关键词: 正交频分复用;多载波调制; OFDM 和QAM 基本原理;波形及频谱分析... ... ABSTRACT Orthogonal frequency division multiplexing ( OFDM ), is actually a kind of multi-carrier modulation ( MCM ). The main idea contains that the channel is divided into a number of orthogonal sub-channels, the high speed data signal is convert into parallel low speed data streams which are modulat edon to sub-channels for transmission. Orthogonal signal s at the receiving end are separated from each other with correlation technologies, thus reducing the Inter-Channel Interference ( ICI ) .The signal bandwidth one ach sub- channel is less than on the relevant channel , so each sub- channel can be seen asa flat fading channel which can eliminate inter - symbol interference. T his thesis ,first ly introduces the development of munication course and the study status of OFDM, then describes the basic principle of OFDM and QAM, at last with analysis ing the OFDM and QAM system input and output signal of waveform and spread spectrum , comes toa conclusion that the performance of multiple carrier OFDM technology is better than the single carrier QAM technology .K eywords : OFDM ; MCM ; basic principle of OFDM and QAM ; the analysis of waveform and spread spectrum ... ... 目录 …………………………………………………………………… 5 无线通信的发展历史与现状…………………………………… 5 无线信道的传播特性…………………………………………… 6 快衰落…………………………………………………………… 6 慢衰落………………………………………………………… 7 OFDM 研究现状及前景………………………………………… 7 2. OFDM 系统的基本原理…………………………………………… 8 OFDM 基本原理…………………………………………………… 8 OFDM 信号的产生……………………………………………… 8 用 FFT 实现 OFDM …………………………………………… 9 OFDM 优缺点