基于SLM降低OFDM系统均峰比技术仿真

摘要

摘要

正交频分复用(OFDM，Orthogonal Frequency Division Multip1exing)是一种多载波调制技术，由于具有抗多径衰落能力强、频谱利用率高等优点，已广泛应用于数字音频(DAB)、数字视频广播(DVB)、无线局域网(WLAN)等技术领域。此外，正交频分复用技术(0FDM)被认为是第四代移动通信的核心技术之一。

但是OFDM技术存在传输过程中峰均比值(PAPR)较高的问题，高峰均比对功率放大器、A/D变换器等前端设备的线性范围提出更高的要求，影响着整个通信系统的运行成本和效率，所以，对降低峰均功率比技术的研究对于OFDM技术的更广泛应用有着一定的现实意义。

本论文的主要工作如下，通过查资料，了解OFDM原理，及存在的问题。介绍了OFDM高PAPR问题产生的原因和PAPR的分布，在此基础上了介绍了常用的几种限制OFDM系统高PAPR的算法如限幅法、编码法、概率类方法等，特别重点介绍了选择性映射(SLM，Selected mapping)算法，在传统的SLM方法基础上给出了改进型的SLM方法，并通过改进的SLM方法与限幅法有效结合来降低OFDM系统的均峰值，并做了降低OFDM系统PAPR的技术仿真，

关键词 正交频分复用；均峰比；选择性映射；

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燕山大学本科生毕业设计（论文）

Abstract

Orthogonal Frequency Division Multiplexing(OFDM)techniques have received a great deal of attention due to its data rate transmission capability with high bandwidth efficiency in coping with multipath fading and has been widely used in digital audio(DAB),Digital Video Broadcasting(DVB),wireless local area network(WLAN)and other technical fields. As a result, OFDM is considered as the key technologies of the 4G mobile communication.

However, one major drawback of OFDM is the high peak-to-average power ratio (PAPR) of the output signal. High PAPR at the transmitter can cause the high power amplifier (HPA) to go into non-linear regions and cause nonlinear output, and degrade the performance of OFDM system seriously.

The main work of this paper is as follows, through the search data, understand the OFDM principles and the paper introduced why the high PAPR happened and How the PAPR distribute. Then, paper introduced some kinds of algorithms to deal with the problem such as clipping algorithm, coding algorithm and probability algorithm, especially the clipping algorithm and SLM algorithm among and do the simulation of reducing the PAPR of OFDM system.

Keywords OFDM；PAPR；SLM

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目 录

摘要 ....................................................................................................................... I Abstract ................................................................................................................ II 第1章 绪论 ........................................................................................................ 1

1.1 课题研究的背景与意义 ..................................................................... 1 1.2 OFDM的研究现状 ............................................................................ 2 1.3 OFDM优缺点 .................................................................................... 4 1.4 PAPR抑制技术的国内外现状 .......................................................... 5 1.5 本论文的主要工作 ............................................................................. 8 第2章 OFDM系统基本原理及PAPR问题 .................................................... 9

2.1 OFDM系统的原理 ............................................................................ 9 2.1.1 OFDM的系统模型 ..................................................................... 9 2.1.2 离散傅立叶变换在OFDM系统中的应用 .............................. 12 2.1.3 傅里叶变换的过采样 ................................................................ 12 2.1.4 保护间隔和循环前缀 ................................................................ 13 2.2 OFDM的峰均功率比及其分布 ...................................................... 15 2.2.1 峰值平均功率比的定义 ............................................................ 15 2.2.2 OFDM系统内PAPR的分布 .................................................... 16 2.3 高PAPR带来的问题 ....................................................................... 17 2.4 降低峰均比常用方法 ....................................................................... 17 2.4.1 信号预畸变类算法 .................................................................... 18 2.4.2 概率类算法 ................................................................................ 19 2.4.3 编码类算法 ................................................................................ 19 2.5 本章小结 ........................................................................................... 20 第3章 基于SLM降低OFDM系统PAPR仿真 ........................................... 21

3.1 传统的SLM算法 ............................................................................. 21 3.2 改进的SLM算法 ............................................................................. 23 3.3 改进的SLM与限幅结合方法 ......................................................... 26 3.4 本章小结 ........................................................................................... 29 结论 .................................................................................................................... 31

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参考文献 ............................................................................................................ 32 致谢 .................................................................................................................... 34 附录1 ................................................................................. 错误！未定义书签。 附录2 ................................................................................. 错误！未定义书签。 附录3 ................................................................................. 错误！未定义书签。 附录4 ................................................................................. 错误！未定义书签。

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