正交频分复用（Orthogonal Frequency Division Multiplex，OFDM）是一种无线环境下的高速传输技术。OFDM技术的主要思想就是在频域内将给定信道分成许多正交的子信道，在每个子信道上使用一个子载波调制，并且各个子载波并行输出。是一种特殊的多载波传输方案，它可以被看作是一种调制技术，也可以被当作一种复用技术，正交频分复用技术也是第四带移动通信技术之一。由于OFDM系统能够很好的对抗频率选择性衰落或窄带干扰，它被越来越常用到现代移动通信中。
本文主要介绍了OFDM系统原理，以及用 C语言设计了一个OFDM系统，用C语言设计了一个卷积码的编码和译码程序。研究了在高斯信道和瑞利信道下，系统在使用卷积码后的影响，得出误码率结果，最后得出结论。
关键词：系统，正交频分复用，卷积码，BPSK，通信系统仿真 ,visual c++
ABSTRACT
Orthogonal Frequency Division Multiplex is a kind of high-speed transmission technology in wireless environment. The main idea of OFDM technology is to divide the given route into a lot of orthogonal son route in frequency intra-area, modulating and outputting one by one on every son route by using subcarriers. It is a kind of special multi-carrier transmission scheme, which can be considered as a kind of modulation technique, or a multiplex technology. In the mean time, OFDM is also one of the fourth mobile communication technologies. Since OFDM system can resist and manage frequency-selective interference on the wane or narrow belt disturbs well, it becomes more and more common in the modern mobile communication.
The paper has introduced the principle of OFDM system, designed an OFDM system and encoding and decoding procedures with convolution codes by using C language. It has also studied the effect of the convolution codes on the system under the Gauss and Rayleigh channel, so as to get the result of BER and the final conclusion at last.
Keywords: System , OFDM , convolution encoding, BPSK , telecom system simulation, visual c++
