摘要正交频分复用(OFDM，Orthogonal Frequency Division Multiplexing)技术由于具有很好的抗多径效应性能和高频谱利用率等优点，已经成为4G的核心技术之一。OFDM 技 术 的 一 个 主 要 缺 点 就 是 会 出 现 比 较 高 的 峰 均 功 率 比 （PAPR ，peak-to-average power ratio)。过高的PAPR会使得发送端对相关的器件要求很高，从而增加了系统成本、功耗和实现难度，所以最好的方法是降低发送端信号自身的PAPR。65542

    本文介绍了目前主要的PAPR抑制技术：预畸变技术、信号编码技术和非预畸变技术。重点研究了限幅法和选择映射法，然后将上述两种算法结合，提出一种自适应算法，该算法首先采用SLM算法降低OFDM系统的峰均功率比，在不增加计算量的基础上如果SLM算法不能将PAPR降低到门限值以下时，则自动以牺牲误码率性能来选择采用限幅法降低PAPR，以达到降低OFDM系统峰均功率比，最后对算法进行了仿真，结果表明该算法可以很好的降低OFDM系统的PAPR。

毕业论文关键词 ：   正交分频复用  峰均功率比  限幅  选择映射  自适应

毕业设计说明书（论文）外文摘要

Title   Reduction of OFDM System’s PAPR Based on            

        Self-adaptive Algorithm                     

Abstract

  OFDM (Orthogonal Frequency Division Multiplexing) has become one of the core technology of 4G because it has advantages of excellent anti-multipart effect performance and good availability of frequency spectrum and etc. OFDM has one fatal weakness of high PAPR (peak-to-average power ratio). The high PAPR would promote the requirements of the relative devices, which increases system cost, power consumption and implement difficulty. So, the best solution to this problem is lowering the PAPR of the sending signal itself.

  This thesis introduces current main types of methods to suppress PAPR including distortion method, coding method and non-distortion method. In the paper, the limiting law and the selection mapping law are being highlighted. Then combine the two algorithms, and propose an adaptive algorithm, which uses the SLM algorithm to decrease the peak to average power ratio of the OFDM system. On the ground of decreasing the calculation amount, if the SLM algorithm can not decrease PAPR below the threshold, to sacrifice the BER performance, the limiting law will be used to reduce PAPR. Finally, the algorithm has been simulated, and the result shows the   algorithm can produce a good effect on reduce PAPR of the OFDM system.    

Keywords: Orthogonal Frequency Division Multiplexing    

           Peak-to-Average-Power-Ratio   Limiter    Select-Mapping    Adaptive

目   录

1  绪论 2

1. 1  移动通信的发展 2

1 .2  OFDM 技术概述 3

1 .3  本文的研究内容及工作安排 4

2  OFDM系统基本原理 5

2. 1  OFDM概述 5

2. 2  OFDM系统的原理框图 5

2. 3  OFDM系统发送端原理 6

2. 4  OFDM系统接收端原理 9

2. 5  FFT在正交频分复用（OFDM）中的应用