摘要
正交频分复用（Orthogonal Frequency Division Multiplex，OFDM），即正交频分复用技术，实际上是多载波调制的一种。其主要思想是：将信道分成若干正交子信道，将高速数据流转换成并行的低速子数据流，调制到在每个子信道上进行传输。OFDM有抗多径衰落能力强、频谱利用率高等很多优秀的特性。OFDM也已经广泛应用于当今先进无线通信技术中。
本文介绍了OFDM的基本原理，分集技术的原理，分集技术应用和对通信系统性能的影响。本文利用C语言在VC++环境搭建了一个仿真OFDM系统，在其中加入不同的模块来分别在AWGN信道和瑞利信道环境下对该OFDM系统进行仿真和结果分析，对比了系统在不同信道环境、不同等增益合并分集方式时所获得的误码率曲线，得到了比较理想的结果。
关键字：正交频分复用，等增益合并，分集，C语言，通信系统仿真
ABSTRACT
OFDM（Orthogonal Frequency Division Multiplex）,actually is one of multi-carrier modulations. The main idea is that, it will divided channel into several orthogonal sub-channel, make the high-speed data stream into low-speed parallel data stream, and transmit them by modulated into each sub-channel. OFDM have many excellent features like that, it can reduce the multi-path fading, high spectrum efficiency and so on. Now OFDM is widely used in modern advanced wireless digital communication system.
This article introduced the basic principle of OFDM, the principle and effect of diversity, diversity technique in communication system and it’s effect on system’s performance. I set up a OFDM system simulation by C language in VC++ environment, and analyze the system with AWGN channel and Rayleigh channel, compared the result with different channel environment and different diversity model, get some great conclusion finally.
Keywords: OFDM, equal-gain combining, diversity, C language, communication system simulation
