摘要
在无线信道中,可靠、高速的传输数据是无线通信的目标和要求,而OFDM技术具有抗多径时延、抗信道衰落、频谱利用率高和硬件实现相对简单的特点,近年来获得了广泛的应用,并且有望成为4G的核心技术。同时,由于无线信道具有复杂、多变的特点,为了获得OFDM系统的最佳性能,对实际OFDM系统的设计起到帮助、指导作用,对该系统进行仿真模拟显得尤为重要。
首先,本文简述了OFDM技术的发展及应用;分析了OFDM系统的优缺点和研究热点;重点分析了无线信道的衰落特性及模型、OFDM的原理以及调制解调的模型,并作为系统仿真的理论基础。
其次,本文对OFDM系统的三个关键技术:信道估计、降低峰均功率比和同步技术作深入分析,重点分析了本文仿真所采用的基于导频估计信道算法。
最后,在以上工作的基础上,本文采用System View和MATLAB仿真软件对OFDM系统进行较为完整的仿真,在多径瑞利衰落信道和高斯白噪声信道情况下分别完成了OFDM调制解调工作。结果表明:OFDM技术可以大大降低系统的误码率;相比高斯白噪声信道,OFDM技术更适合于在多径瑞利衰落信道:仿真不仅证实了我们理论分析的结果,而且可以有效地消除实际系统设计、实现中潜在的不足,是对设计实际系统的一个有效补充,并具有一定的工程实用价值。
Data transmission in wireless channels with high speed and reliability is required in future wireless systems.OFDM,with the antvantage of high spectrum efficiency and easy realization, can strongly combat multi-path and dispersive channel interference, so its application is remarkable and it will be the key technology of 4G without question. At the same time, software simulation system is especially important for obtaining the best performance and playing a helpful and directive effort, because of the complexity and levity of wireless channel.
Firstly, in this paper, development and application of OFDM is brief analyzed. The advantage, disadvantage and hotspots of OFDM is analyzed. The main point that is the academic foundation to the simulation of OFDM is put on the awane speciality, model of wireless channel, the principles of OFDM and it's modulation/demodulation.
Secondly, the three key technology of OFDM that is the estimation of channel, reducing PAPR and synchronization of OFDM system is analyzed and studied, especially the arithmetics of baseing on guiding frequency in simulation of OFDM of the paper.
Finally, based on the research, the OFDM system fully simulated by System view and MATLAB softwares, it separately accomplished the modulation and demodulation of OFDM under the multipath Rayleigh channel and AWGN channel. It declared that the bit error rate can greatly reduced by OFDM and the OFDM in multipath Rayleigh channel is more adapted to AWGN channel. The simulation not only approved the academic result, but also could remove the shortages, optimize the capability of real system, and also is valuable for project.
引文
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