基于simulink的ofdm通信系统的仿真.doc

摘 要
在无线信道环境中可靠、高速的传输数据是无线通信技术的目标和要求。OFDM技术能够大幅度的提高无线通信系统的信道容量和传输速率,并能有效地抵抗多径衰落、抑制干扰和噪声,有着广阔的应用前景。
本文在分析移动无线信道特性的基础上,基于OFDM系统的基本原理,研究了OFDM通信系统中同步实现和基于导频的信道估计问题,分析了几种经典信道估计算法以及相关的关键技术环节。
在此基础上,基于Simulink,讨论了如何构建完整的OFDM动态仿真系统,完成Simulink模块设置,确定搭建系统的主要参数,并对主要模块的构建方式进行了说明;就信道编码、多普勒频移及不同调制方式对OFDM系统性能的影响进行了全面的仿真分析和比较;参考COST-207多径信道模型,深入全面研究了瑞利衰落信道对OFDM通信系统性能的影响,对COST-207典型城市模型下OFDM系统性能仿真进行了有益的尝试;首次应用Simulink同时对不同导频方式、不同导频比、不同多普勒频移条件下的OFDM通信系统进行详细仿真分析。
研究结果表明,对于应用块状导频的OFDM通信系统,在Eb/N0较小时,加性高斯白噪声对性能起主导作用,Eb/N0较大时,ICI对性能起主导作用,形成了误比特率底限;仿真分析表明,OFDM通信系统采用块状导频方式时,适用的多普勒频移的范围为100Hz以下,对应的移动速度为静止或步行速度或较慢的汽车行驶速度;导频比为1/3或1/4时综合效果较好。对于应用梳状导频的OFDM通信系统,其系统性能不如块状导频,但这种导频插入方式对多普勒频移及时间选择性衰落不敏感,若将梳状导频与其他形式的导频综合使用,可用于改善OFDM通信系统性能,尤其是具有较高相对移动速度的OFDM系统。
论文所得结论可为进一步研究***数据,也可为OFDM系统的仿真与研究提供重要的参考。
关键词：OFDM；导频；衰落信道；信道估计；Simulink；多普勒频移；仿真分析
ABSTRACT
Data transmission in wireless channels with high speed and reliability is required in wireless communication technology. OFDM technology which has widely application prospects can not only increase the transmission rate and the capacity of the wireless communication system, but also effectively resist multi-path fading as well as restrain interference and noise.
In this paper, synchronization and channel estimation based on pilot are researched; several classic channel estimation algorithm and relative key technology are analysised on the basis of principles of OFDM.
Based on simulink, how to build a complete OFDM simulation systems is discussed; channel code, Doppler and different kinds of modulations influence on OFDM system performance is compared and analysised comprehensively; influence of Rayleigh fading channel which refer to COST-207 model is researched; a positive attempt on OFDM system performance simulation is made. It is the first time for OFDM communication system to be simulated and analysised in detail under condition of different pilot patterns, different pilot rate and different Doppler frequency shift at th