【作者】 车传强；

【导师】 李一兵；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2007， 硕士

【摘要】 正交频分复用(OFDM)是一种并行的多载波传输方案，它利用相互正交的多个子载波来传输信息，具有较高的频谱利用率和良好的抗多径干扰能力，适用于高速率和多媒体数据传输，被认为是未来第四代移动通信的核心技术之一。但是，其固有的高峰值平均功率比(PAPR)问题一直是将该技术实用化的一大阻碍。本论文就是围绕降低OFDM系统中的峰值平均功率比技术来展开研究的，并利用Matlab软件完成了对所有研究内容的仿真验证。论文介绍介绍了OFDM系统的基本原理和数学模型及OFDM系统的技术特点，分析了保护间隔和循环前缀对OFDM系统的影响，并对OFDM技术与单载波传输系统进行了系统的比较；然后从峰值平均功率比的定义出发，分析了OFDM系统PAPR值的定义，从理论上对OFDM信号包络以及OFDM系统PAPR的概率分布进行了详尽的分析。并从系统性能方面阐述了PAPR值对OFDM系统的影响。采用限幅法来降低OFDM系统中的PAPR值，将限幅引起的非线性失真等效为线路中其他的非线性失真，即可采用原有对抗非线性失真的方法，分析了该技术的降低OFDM信号PAPR值能力和影响系统误码性能这两个性能指标，并对限幅法进行计算机仿真；然后针对传统部分传输序列算法中计算量过大这一缺点，对其进行了改进，将输入的数据符号分为若干个互不重叠的子块，然后用相位因子去加权这些子块后再合并，以减小PAPR。并进行了大量仿真，结果证明：改进后的OFDM系统PAPR值得到了降低。最后，对全文进行总结，并展望了将所研究的技术实用化的进一步工作及方向。更多还原

【Abstract】 OFDM(orthogonal frequency division multiplexing)is a parallel transmission scheme of MCM(Multi-Carriers Modulation).It transmits information through orthogonal multiple sub-carriers and has high utilization of frequency spectrum, good capability of countering multi-path interference. It is also adaptive to high-rate data transmis sion and multimedia data transmission. This technology has been regarded as the core technology of 4G wireless communications system in the future. However, it has high peak-to-average power ratio (PAPR) , which is its inherent disadvantage. This disadvantage in OFDM systems has limited OFDM’S wide applications and has not been solved yet. This paper has mainly researched on the methods of PAPR reduction for OFDM and has obtained some results by MATLAB simulations.The fundamental principle of DFT-based OFDM system and its techniques are introduced in this thesis. Then, the distributions of PAPR are analyzed by simulation. In signal distortion techniques, clipping is analyzed in terms of two performance measures:complementary cumulative distribution function(CCDF) and bit error rate (BER). In order to reduce the large computation complexity of partial transmit sequence (PTS) an improved method has been analyzed and compared with customary PTS via computer simulation. The result of simulation shows that the PAPR is decreased..Finally, the relative research and simulation about the whole paper is summarizes, meanwhile, the further practically research in future is expected.更多还原