正交频分复用同步技术研究

【作者】 吕淑静；

【导师】 张捷；

【作者基本信息】 西北工业大学 ， 通信与信息系统， 2005， 硕士

【摘要】 正交频分复用(OFDM:Orthgonal Frequency Division Multiplexing)技术是当今高速无线通信领域中的研究与应用热点。OFDM具有抗多径衰落,频谱利用率高,系统结构简单易于实现等优点,特别适合于无线环境中的高速数据传输。OFDM系统对频率偏移敏感,因此同步技术在OFDM系统中占有重要地位。本文重点研究了OFDM中的同步技术。 首先介绍了OFDM系统的原理,详细分析了其中关键技术对OFDM系统性能的影响,介绍了基于.IEEE802.11a标准的OFDM帧结构,并且建立了OFDM基带系统的Simulink模型;然后建立了具有同步偏差的OFDM系统数学模型,分析了载波同步、采样同步和符号定时同步对系统性能的影响,结果表明:载波频率偏差和采样间隔偏差破坏子载波正交性引起ICI,载波相位偏差、符号定时偏差和采样定时偏差只引起信号的相位旋转;最后详细介绍了分组检测、符号定时、载波频率同步和载波相位跟踪的算法,通过对各种同步方法进行比较,采用一种最优的方案对OFDM系统进行完整的同步偏差估计,计算机仿真表明该方案能有效的纠正同步偏差。更多还原

【Abstract】 In recent years, there has been a great interest in researching and applying Orthgonal Frequency Division Multiplexing (OFDM ) technology into high-speed wireless communications.OFDM based digital communication systems are robust in multipath environment. Moreover,OFDM can achieve high bandwidth efficiency and can be implemented with a simple structure.These advantages make OFDM technology particular suitable for high-rate data transmission in wireless environments.OFDM system is sensitive to frequency offset, so synchronization is one of the important technologies of OFDM .This thesis is mainly focus on the research of synchronization techniques in OFDM systems.The principle of OFDM system is presented in the beginning of this thesis ,and the effect of OFDM key technologies to its system performance is analyzed.After OFDM frame structure based on std IEEE 802.11a is presented, Simulations of OFDM baseband system model based on SINULINK are presented. Baesd on mathematical analysis of OFDM synchronization, the effects of OFDM synchronization errors,such as carrier offset,sample error and symbol timing error,are analyzed. The results show carrier frequency offset and sample interval error introduce Inter-Carrier-Interference (ICI), and carrier phase error, symbol timing error and sample timing error introduce signal phase circumvolution.At last, the algorithms of packet detecting,symbol timing, carrier frequency synchronization and carrier phase tracing are presented. All the algorithms are test against AWGN and multipath channel and analyzed,and then the better algorithms are chosed to compose a complete synchronization schemes. Results of sinulation and analysis show considerable performance using the synchronization scheme.更多还原