摘要
随着信息技术不断的发展,人们对于无线通信系统的数据容量和传输速率的要求越来越高。与此同时,传统无线通信系统由于受到香农信息理论的限制很难有效提高系统容量。多输入多输出(MIMO)技术采用多天线系统,在不增加频谱资源和发送功率的前提,成倍地提高通信系统的容量,有效解决用户对于高质量通信的需求。因此,MIMO技术被认为是下一代移动通道的关键技术,并成为无线通信领域研究的新热点。
本文主要从理论和实际仿真两个方面研究MIMO信道模型和传播特性。本文介绍了MIMO室内多径信道模型,详细分析了典型的随机性统计模型及确定性模型。本文重点研究基于射线跟踪技术的镜像法的MIMO信道建模方法,通过对镜像法原理的研究建立室内多径MIMO信道的仿真平台,在高频窄带情况下仿真分析了视距(LOS)和非视距(NLOS)环境下的信道容量、功率、路径损耗等参数,结果验证了理论的正确性。本文建立了MIMO-UWB的仿真分析过程,重点分析了信道传输特性,通过理论验证了建模的正确性。
本文的主要工作具体如下:
(1)本文介绍了射线跟踪技术的原理,并分析比较了几种不同射线跟踪算法的性能。本文重点研究了镜像法射线跟踪技术,对使用镜像法如何求解镜像点和确定镜像点有效性进行详细分析,给出了镜像法仿真的详细流程并建立了室内多径信道仿真模型。
(2)本文在假设信号带宽为窄带的情况下,对MIMO室内LOS环境进行仿真,研究MIMO信号室内传播特性,估计各种参量包括:信道容量、接收功率、时延扩展、路径损耗等,并进行对比分析。再不停的深入,加入障碍物形成NLOS环境,对稍显复杂的环境进行仿真,并与LOS环境下的结果进行对比分析。
(3)将MIMO窄带扩展到MIMO-UWB,通过频带分割技术使用镜像法来仿真UWB信道,本文使用高斯脉冲信号作为发送波形建立UWB室内信道模型,仿真分析室内信道传输特性和信道输出,得到信道的输出状态响应r (t)、信道的冲激响应h (t)、信道冲激响应的功率时延分布P(t)、平均时延(?)、均方根时延扩展(?) rms、相干带宽Bc等UWB室内多径信道特征参数,并对仿真结果进行分析验证其准确性。
With the development of information theory, the demand for transfer rates and data capacity of wireless communication system is becoming higher and higher. At the same time, due to the limitations of Shannon information theory, it is difficult to improve capacity for traditional wireless communication systems. MIMO system using multiple transmit antennas and multiple receive antennas can exponentially improve the capacity of wireless communication system without increasing the spectral efficiency and transmit power, thereby effectively address the needs for high-quality communications. MIMO has become a hot spot of wireless communication research, and is considered to be one of the key technologies of next generation communications.
In this paper, it studies channel models and propagation characteristics of MIMO system from theoretical and practical aspects. This article describes the MIMO indoor multipath channel model and compares the advantages and disadvantages of the statistical channel models and deterministic models. On the basis of the research on the traditional ray tracing technique, the paper uses the image method to establish a simulation platform of indoor multipath MIMO channel, simulates and analyzes various parameters including the channel capacity, received power, path loss and so on in LOS and NLOS environments. The results verify the correctness of the theory. This paper establishes an analysis process of MIMO-UWB system simulation and focuses on channel transmission characteristics and verifies the correctness of modeling through theoretical.
The main work as follows:
(1) This paper introduces the principle of ray tracing techniques and compares several different ray tracing algorithms. It focuses on the image method and analyzes the use of image method to determine how to get the mirror points in detail. It gives a detailed image method simulation process and establishes a MIMO indoor multipath channel simulation model.
(2) In this paper, it simulates the indoor MIMO multipath channel in the LOS environment to study the propagation characteristics of indoor MIMO signal and estimates various parameters including the channel capacity, received power, delay spread, path loss and so on. And then obstacles are added to form the NLOS environment, in this case we simulate the channel and compare the results with LOS environment.
(3) The paper extends the narrowband MIMO to MIMO-UWB and simulates the indoor MIMO channel with a Gaussian pulse input signal to get UWB indoor multipath channel parameters including the channel impulse response, power delay distribution, mean excess delay, RMS delay, coherence bandwidth and so on. Finally, the accuracy of the simulation is verified.
引文
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