【作者】 易小龙；

【导师】 曾春年；

【作者基本信息】 武汉理工大学 ， 通信与信息系统， 2010， 硕士

【摘要】 随着无线通信技术的迅猛发展,当今人们对通信业务的需求不仅仅局限于语音业务上,对于图像、视频、数据、网络的需求也日益增长,这就对无信通信系统提出了更高的要求,高速率、大容量、高可靠性、多业务种类将是无线通信系统未来发展的趋势。MIMO-OFDM无线通信系统正好符合下一代通信系统的这类需求,而信道估计又是MIMO-OFDM无线通信系统中直接关系到通信质量的重要环节。本文对MIMO (Multiple Input and Multiple Output,多输入多输出)和OFDM (Orthogonal Frequency Division Multiplexing,正交频分复用)技术进行了相关介绍,MIMO技术通过多天线分集实现了大容量的无线通信,而OFDM技术通过多载波并行传输,同时对各路子载波信号进行严格的正交化,降低了系统的频谱带宽需求,这对目前越来越紧缺的频谱资源来说无疑是一个较大的进步,在抵抗噪声和干扰、抑制信号多径造成的衰落方面也具有良好的效果,二者的结合构成了MIMO-OFDM无线通信系统。然后对无线信道的特性与模型进行了相关研究,对其中的多径时延、多普勒频移、瑞利衰落展开了相关的讨论,对无线信道的模型进行了理论分析。最后对MIMO-OFDM无线通信系统中基于导频的非盲信道估计进行了研究和讨论,对于导频的形式与结构进行了介绍,主要讨论了最小平方误差信道估计算法、最小均方误差信道估计算法、线性最小均方误差信道估计算法,通过Matlab仿真对比了它们各自的优缺点和性能,针对算法的复杂度与应用性能展开了相关分析。对于信道估计的内插、滤波进行了一定的改进,通过小波去噪、加窗函数处理等方式,一方面尽量去除噪声信号,另一方面集中有用信号的能量,将系统的性能进一步提升,降低了系统的误码率。通过仿真表明改进后的内插滤波效果随着信噪比的增加在不断提高,这对于优化MIMO-OFDM无线通信系统的接收性能有很大帮助。对MIMO-OFDM无线通信系统信道估计的相关研究和仿真表明,MIMO-OFDM无线通信系统的信道估计是一个非常具有发展前景的研究领域。更多还原

【Abstract】 With the rapid development of wireless communication technology, the demand for communication services is not limited in voice area. Images, video, data, network services are also on the growth. This requires advanced capability for wireless communication system. High-speed, large capacity, high reliability, multi-service types will be the main features of the future wireless communication system. At the same time, the MIMO-OFDM wireless communication system greatly meets the needs of the next generation communication system. The channel estimation for MIMO-OFDM wireless communication system is a significant part which is directly related to communication quality.In this paper, we mainly introduced MIMO(Multiple Input and Multiple Output) and OFDM (Orthogonal Frequency Division Multiplexing) techniques. MIMO technique supplies high-capacity by multi-antennas, while OFDM technique generates multi-carrier signals by parallel transmission technology which is strictly orthogonal between each other. Through this, we weaken the needs for system’s wide spectral bandwidth, which is undoubtedly a big improvement under the circumstance of the rare spectrum resources. In this way, we resisted the noise, interference, signal fading effect. The two techniques constitute MIMO-OFDM wireless communication system. Then we discussed the features of the wireless channel, analyzed the model of it, including multi-path delay, Doppler frequency shift and Rayleigh fading. Finally, we made the research on non-blind channel estimation in MIMO-OFDM wireless communication system based on pilot signal, introduced the form and structure of pilot signal, mainly discussed the least square error channel estimation algorithm, minimum mean-square error channel estimation algorithm, linear minimum mean-square error channel estimation algorithm, compared the performance of the three ways through Matlab computer simulation and analyzed the complexity of the algorithms and application performance. We improved the interpolation and filter way in the channel estimation process to remove the noise as much as possible and concentrate the energy of the useful signal through wavelet denoising and adding window function. And in this way we lower down the bit error rate of the system. The computer simulation results show the performance is better and better as the signal to noise ratio has improved. This way provides great help to the optimization of MIMO-OFDM wireless communication system.The study and simulation of channel estimation in MIMO-OFDM wireless communication system indicates it is a very promising area.更多还原