80211a仿真链路系统.doc

802.11a仿真链路系统 摘要 IEEE 802.11a无线局域网，其物理层采用。本文了基于IEEE 802.11标准的物理层仿真平台的搭建，体现其对系统性能的提升。 本文首先介绍了IEEE 802.11a协议标准接着介绍了OFDM系统的基本原理及其实现基于协议标准进行了物理层仿真平台的搭建，形成发送端、信道、接收端三大部分在上述工作的基础上，本文还重点空时码，，通过仿真实现可以获得很可观的性能增益。 IEEE 802.11a，，802.11a Simulation Link System Abstract The physical layer of IEEE 802.11a WLAN adopts OFDM(Orthogonal Frequency Division Multiplexing). In this paper, the design of the physical layer simulator based on IEEE 802.11a standard is presented. Since the combination of MIMO (Multi-Input Multi-Output) with OFDM is regarded as a promising solution for the next generation mobile communication systems, the technology of antenna diversity is studied, which can improve the performance of the systems. The thesis firstly introduces the IEEE 802.11a standard, the basic principles and realization of OFDM. Then, based on the standard, the physical layer simulator which consists of transmitter, channel and receiver is designed. Emphasis is laid on synchronization, including packet detection, symbol timing, frequency estimation and phase tracking. Through simulation, we find that the simulator can detect the arrival of a packet correctly, and combining frequency estimation with phase tracking can improve the BER performance significantly. On the basis of above, we make research on Space-Time Block coding scheme and MRC(maximum ratio combining) receiver diversity. It is find through simulation that they can provide satisfactory diversity gain. Key Words: IEEE 802.11a, OFDM, Synchronization, Antenna diversity 目 录 1 绪论 1 1.1 无线局域网发展与现状 1 1.2 研究目的 2 1.3 研究方法及研究内容 2 2 IEEE802.11a的物理层规范 4 2.1 IEEE802.11a物理层包括的协议功能 4 2.2 PPDU帧结构 5 2.3 PPDU编码过程 6 2.4 802.11a的系统参数 8 3 OFDM系统的基本原理 9 3.1 OFDM的数学表示 9 3.2 OFDM信号的频谱 10 3.3 采用IDFT/DFT实现调制解调 10 3.4 循环前缀 11 4 802.11a协议物理层仿真平台的搭建 14 4.1 仿真模型和系统参数设置 14 4.1.1 根据802.11a协议规范设定仿真参数 14 4.1.2 插入导频 15 4.1.3 加循环前缀 16 4.1.4 前导的生成 17 4.2 18 4.2.1 分组检测 18 4.2.2 符号定时 21 4.2.3 频偏估计和载波相位跟踪 23 4.2.3.1 频偏估计 23 4.2.3.2 载波相位跟踪 24 4.2.3.3