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，將所傳送的高速串行數據分解并調制到多個并行的正交子信道中，從而使每個子信道的碼元寬度大于信道時延擴展，再通過加入循環擴展，保證系統不受多徑干擾引起的碼間干擾（ISI）的影響。他可以有效對抗多徑傳播。
本文設計了一個基于卷積碼的OFDM系統，并在計算機上進行了仿真和結果分析。全文主要由三部分構成：OFDM系統基本原理、基于卷積碼的OFDM系統設計、仿真及結果分析。
本文完成了對一個完整的基帶OFDM系統的設計與仿真，用MATLAB語言實現了整個系統的計算機仿真并給出參考設計程序。最后分別比較了在AWGN信道與瑞利衰落信道,16QAM調制與QPSK調制條件下，加入卷積碼，加入交織對OFDM系統性能的影響,得出了較理想的結論。
關鍵詞：正交頻分復用，卷積編碼，四相相移鍵控，正交幅度調制，通信系統仿真
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
