正交頻分復用（Orthogonal Frequency Division Multiplex，OFDM）是一種無線環境下的高速傳輸技術。OFDM技術的主要思想就是在頻域內將給定信道分成許多正交的子信道，在每個子信道上使用一個子載波調制，并且各個子載波并行輸出。是一種特殊的多載波傳輸方案，它可以被看作是一種調制技術，也可以被當作一種復用技術，正交頻分復用技術也是第四帶移動通信技術之一。由于OFDM系統能夠很好的對抗頻率選擇性衰落或窄帶干擾，它被越來越常用到現代移動通信中。
本文主要介紹了OFDM系統原理，以及用 C語言設計了一個OFDM系統，用C語言設計了一個卷積碼的編碼和譯碼程序。研究了在高斯信道和瑞利信道下，系統在使用卷積碼后的影響，得出誤碼率結果，最后得出結論。
關鍵詞：系統，正交頻分復用，卷積碼，BPSK，通信系統仿真 ,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++
