正交頻分復用（Orthogonal Frequency Division Multiplex，OFDM）是一種高效并行多載波傳輸技術，是把高速的數據流通過串/并變換，分配到速率相對較低的若干個子信道中進行傳輸。OFDM技術很好的利用了控制方法，使頻譜利用率有所提高。在OFDM信號內的所有子載波都在時間和頻率上同步，使子載波之間的干擾被嚴格控制。這些復用的子載波在頻域中交錯重疊，但因為調制的正交性且采用循環前綴作為保護間隔，所以不會發生載波間干擾（ICI）。由于信道衰落特性的影響，傳輸的信息在某些區域往往會出現成片的差錯，即所謂的突發錯誤。交織是一種非常有效且簡單的對付突發差錯的技術。
本文分別介紹了OFDM和交織的原理，利用C語言在VC++環境搭建了一個OFDM系統，在瑞利衰落信道下，設計不同的交織器來對該OFDM系統進行仿真和分析。通過對比誤碼率曲線，得出了比較理想的結果。
關鍵詞：正交頻分復用，交織，通信系統仿真
ABSTRACT
OFDM(Orthogonal Frequency Division Multiplex) is an high efficient technique of Multi-Carrier parallel transmission. Through the Serial/Parallel transform, the high-speed data streams will be assigned to a number of sub-channels which have a relatively low rate for transmission. OFDM technology can improve the utilization of spectrum by a better use of the Control Methods. All the sub-carriers in OFDM signals are synchronized in time and frequency, so that the interference between the subcarriers can be strictly controlled. These multiplexing sub-carriers staggered overlap in the frequency domain, but because of the orthogonal modulation and the use of cyclic prefix as guard interval, there will be no inter-carrier interference (ICI). As a result of the channel asthenia characteristics, the information are errors in some areas always, the so-called burst errors. Intertleaver is a very effective and simple technique to deal with burst errors.
This paper introduced the principle of OFDM and intertleaver respectively, and structures a OFDM system in a VC++ environment by the C language, design the different interleavers to simulate and analyse the OFDM system over Rayleigh fading channel. Ideal results can be obtained by better the bit error rate curves.
Keywords: Orthogonal Frequency Division Multiplexing, Interleaver, Communication System Simulation
