突发OFDM系统接收机同步算法设计及其FPGA实现

【作者】 杨晓；

【导师】 张朝阳；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2005， 硕士

【摘要】 目前，以互联网业务为代表的网络应用，正快速地向包括数据、语音、图像的综合宽带多媒体方向发展，构建宽带化、大容量、全业务、智能化的现代通信网络已成为大势所趋。宽带无线接入(BWA)凭借其组网快速灵活、运营维护方便及成本较低等竞争优势，迅速成为市场热点，各种微波、无线通信领域的先进手段和方法不断引入，各种宽带无线接入技术迅速涌现。 由于BWA要用于非视距传输，所以必须考虑无线信道的多经效应。而OFDM技术凭借着鲁棒的对抗频率选择性衰落能力和极高频谱效率引起了学术界和工业界的高度重视。其基本思想是把调制在单载波上的高速串行数据流，分成多路低速的数据流，调制到多个正交载波上并行传输，这样在传输时，虽然整个信道是频率选择性衰落，但是各个子信道却是平坦衰落，有效对抗了多经效应，同时由于各个子载波是正交的，极大提高了频谱效率。 可以预料的是，随着通信系统将向基于IPv6核心网的全IP包的传输方向发展，越来越多的通信系统将具有“突发模式”的特征。本文关注的正是突发OFDM系统接收机设计和实现。由于IEEE 802.11a无线局域网是OFDM技术第一次真正的应用于突发系统，实现了面向IP的无线宽带传输，所以基于IEEE 802.11a的突发OFDM系统有着重要的借鉴和研究价值，本文也正是围绕着这个中心而展开。 本文的各章节安排如下：在第一章中主要介绍OFDM的技术原理和在宽带无线接入中的应用，同时引出本文所关注的突发OFDM接收机设计。在第二章中先介绍了相干接收和信道估计的概念，重点分析了本文所采用的WLAN信道模型和信道估计算法，然后在得到同步误差表达式的基础上，先用星座图直观的表现OFDM系统中各种同步误差的影响，再从信噪比损失的角度对各种同步误差进行分析。第三章是本文的重点之一，在本章中对基于IEEE802.11a的各种同步算法包括帧检测和符号定时、载波同步和采样时钟同步进行仿真和比较，并针对适合FPGA实现的同步算法进行了重点的分析。第四章也是本文的重点之一，提出了整个OFDM系统平台的硬件结构和基于IEEE 802.11a的接收机FPGA设计方案，然后从整体上介绍了接收机的实现结构，并给出了接收机各个模块的具体设计，最后对整个系统调试过程和测试结果进行了分析。更多还原

【Abstract】 Nowadays, the wide application of networks, for instance, Internet, is developing fast in the direction of integrated broadband multimedia, which consists of data, voice, image and so on. Broadband Wireless Access (BWA) technology has become a hot spot of the market because of its many advantages. All kinds of advanced technologies in microwave and wireless communications are introduced to BWA and many lands of BWA technologies are coming out.BWA system must have the ability to support near-LOS and non-LOS (NLOS) because of wireless environment where multipath may be significant. The multicarrier transmission known as OFDM has recently received considerable attentiom for its robustness to multipath selective fading and high bandwidth efficiency. Its basic idea is to divide a given channel into many parallel subchannels or subcarriers, so that multiple symbols are in parrllel. Though the whole channel appears as frequency-selective fading channel, the subchannels appear as orthogonal, plat fading channels.With the development of IP technology, the "burst mode" transmission techniques have recently received considerable attention. This thesis cares about design and implementation of OFDM receiver based on "burst mode". IEEE 802.11a WLAN is the first burst system using OFDM and realizing the wireless broadband IP transmission., therefore it has great value in designing OFDM receiver based on "burst mode".The chapters are arranged as following: Chapter 1 introduces the basic principles of OFDM and its application in BWA. Chapter 2 takes consideration of WLAN channel model and channel estimation. The quantitative analysis of synchronization error is given then. Chapter 3 as one kernel part of the thesis, studies different synchronization algorithms such as Frame Synchronization, Symbol Timing Synchronization and Carrier Synchronization. Chapter 4 as another kernel part, focuses on FPGA implementation of OFDM receiver. Many different testing results are given finally.更多还原