OFDM系统中峰均功率比的研究－毕业设计论文模板3.docVIP

OFDM系统中峰均功率比的研究 PAGE PAGE 62 OFDM系统中峰均功率比的研究 摘 要 多载波传输系统已经应用于有线通信中，并且也是未来移动通信的候选方案。一般多载波调制技术的主要特性是将一定宽频信道分解成为一组多个窄频信道。在这些多载波传输系统中，最常使用的是正交频分复用(OFDM)系统，它以离散傅立叶转换(DFT)为基础，来构成一个可实现、高性能的系统。此项技术能够有效地抵抗多径效应现象，已经成功的应用于许多高速无线数据传输系统中，成为时下备受关注并且得到了广泛应用的技术。但是OFDM系统存在一个主要的缺点，那就是传输信号存在着潜在的高峰值平均功率比(PAPR)，在遇到射频功率放大器等非线性器件时，会发生严重的非线性畸变。 目前已有的降低OFDM信号PAPR的算法可以归纳为三大类：信号预畸变方法、信号扰码方法及编码方法。在本论文中对这三大类方法进行了理论分析和比较，得出各自方法的优缺点。对信号扰码技术进行了深入研究，对其代表性算法：选择性映射法（SLM）和部分传输序列法（PTS）进行了理论分析、仿真比较，得出两种算法的优缺点。 针对传统SLM的复杂度高，本论文引入了一种降低SLM-OFDM系统复杂度的方法。同时针对传统 PTS 算法的计算量很大，本论文提出了一种改进的 PTS 算法——迭代PTS 算法，该算法在降低 PAPR 的性能和计算复杂度之间取得了较好的折中。通过MATLAB仿真，针对传统 PTS 算法和迭PTS 算法就算法算术复杂度和 PAPR分布两方面进行了深入的理论分析和 MATLAB 仿真比较，验证得出各自的优缺点。 关键字：正交频分复用， 峰值平均功率比(峰平比)， 互补累积分布函数， 选择性映射，部分传输序列 PEAK-TO-AVERAGE POWER RATIO REDUCTION FOR ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING ABSTRACT Multicarrier communication has been employed for wire-line communications and has been adapted for use in the future mobile communication systems. The term multicarrier modulation includes a number of transmission schemes whose main characteristic is the decomposition of any wideband channel into a set of independent narrowband channels. With this family, the most commonly used schemes are Orthogonal Frequency Division Multiplexing (OFDM) which is based on the Discrete Fourier Transform, resulting in a realizable, high performance structure. Due to its robustness against multipath fading with certain implementation advantage over single-carrier system, OFDM has become a popular technique in various high-speed wireless data transmission system. Unfortunately, a central disadvantage of OFDM is potentially high peak-to-average power ratio (PAPR) values, which can result in significant distortion when transmitted through a nonlinear device, such as a transmitter power amplifier. A lot of literature on PAPR reduction for OFDM have been summarized and has been categorized into 3 classes . We analyse merit