正交频分复用（Orthogonal Frequency Division Multiplex，OFDM）是一种高效并行多载波传输技术，将所传送的高速串行数据分解并调制到多个并行的正交子信道中，从而使每个子信道的码元宽度大于信道时延扩展，再通过加入循环扩展，保证系统不受多径干扰引起的码间干扰（ISI）的影响。他可以有效对抗多径传播。
本文设计了一个基于卷积码的OFDM系统，并在计算机上进行了仿真和结果分析。全文主要由三部分构成：OFDM系统基本原理、基于卷积码的OFDM系统设计、仿真及结果分析。
本文完成了对一个完整的基带OFDM系统的设计与仿真，用MATLAB语言实现了整个系统的计算机仿真并给出参考设计程序。最后分别比较了在AWGN信道与瑞利衰落信道,16QAM调制与QPSK调制条件下，加入卷积码，加入交织对OFDM系统性能的影响,得出了较理想的结论。
关键词：正交频分复用，卷积编码，四相相移键控，正交幅度调制，通信系统仿真
ABSTRACT
Orthogonal Frequency Division Multiplexing is a highly efficient parallel multi-carrier transmission technology. It will decompose a high-speed serial data and modulate it to multiple parallel subchannels, so that the width of each subchannels Symbol is larger than the channel delay expansion .Than adds cycle of expansion to ensure that systems from multipath interference ,it will cause the interference between the Symbol (ISI) impact. It can be effective against multi-path transmission.
In this thesis, basing on convolutional code ,a OFDM system is analyzed, designed and simulated on a computer. The thesis mainly consists of three parts: the basic principles of OFDM system, the design of OFDM system witch based on convolutional code, the system simulation and the analysis of the results.
This paper has designed and simulated an intergrated baseband OFDM system, simulated the system with MATLAB language and given reference design process. Finally, in the conditions of AWGN channel and Rayleigh fading channel, 16 QAM modulation and QPSK modulation , adding convolution code, and by adding cutting , depicts the error rate OFDM system of comparison curve,and obtaines many satisfactory conclusion.
Keywords: OFDM, convolution encoding, QPSK, 16QAM, telecom system simulation
