【作者】 潘声勇；

【导师】 孙娇燕；

【作者基本信息】 大连海事大学 ， 通信与信息系统， 2002， 硕士

【摘要】 无线通信技术的发展给人们的生活带来了极大的方便。无线多媒体通信是无线技术的发展方向，而高速的无线数据传输是实现多媒体通信的基础。正交频分复用技术(OFDM)在无线环境下具有很高的频谱利用率和很强的抗多径干扰能力，其优良的特性已经使得OFDM成为各种高速无线接入的核心技术。 掌握无线信道传播特性是OFDM技术应用的基础；同时，OFDM采用IFFT来产生频谱正交的子载波，高速的数字信号处理技术是OFDM技术实用化的前提。另一方面，OFDM技术仍存在信号的峰均值功率比(PAR)过大导致对系统的非线性失真敏感；码元同步错误破坏载波间的正交性等问题，有必要进行深入的研究。 本文从OFDM系统的工作原理出发，阐述了OFDM的FFT实现方法和循环扩展的物理作用，接着对OFDM系统的基本性能进行仿真并分析了结果。本文重点分析了使用循环扩展实现码元同步的原理，并且指出了在多径环境下存在的问题，提出了改进方案；OFDM信号峰均值比(PAR)过大是其应用的主要缺点，现有的各种解决方案并没有以一种系统的观点来对待这个问题，本文对此进行了分类，指出不同方案优缺点。更多还原

【Abstract】 The development of wireless communication technology brings great facility to people’s life. Wireless multimedia communication is the future of wireless communications, and high data rate is the basement of wireless multimedia communication. Orthogonal Frequency Division Multiplexing (OFDM) has better bandwidth efficiency and increased robustness to multipath fading and to interference than single carrier adaptive equalization modulation techniques in wireless environment, OFDM has became the core technology of kinds of high speed wireless access due to its better characteristic.The properties of wireless access channel has great influence on OFDM systems performance, so it is the fundament knowledge of OFDM systems in application; on the other hand, OFDM use IFFT to produce orthogonal sub-carriers, high rate signal processing technology is very important. OFMD also have it disadvantages, for example, the big signal Peak-to-Average Power Ratio result in OFDM is very sensitive to system’s non-linearity; symbol synchronization error will destroy orthogonal between sub-carriers.This paper start from OFDM system work principle, describe the FFT realize method and Physical action of Cyclic Prefix of OFDM. Then simulating the OFDM basic property with simulate software and analysis the result. The emphasis of this paper is to analyze the principle of use Cycle Prefix to realize symbol synchronization, and point out it disadvantage in multipath propagation, we proposed a new schematic. The major drawback of OFDM is the large Peak-to-Average Power Ratio (PAR) of the transmit signal, Existing solutions do not attack this PAR issue in a systematic way however. We discuss and compare a broad range of such techniques and organize, andpoint out its advantages and disadvantages.更多还原