【作者】 郑红党；

【导师】 徐钊；

【作者基本信息】 中国矿业大学 ， 通信与信息系统， 2010， 博士

【摘要】 电磁波在煤矿井巷的传输不仅会因巷道壁的吸收引起大的衰耗,更主要的是会频繁地发生反射和散射现象,形成多径效应。研究巷道电波的传播特性,一直是无线通信领域的难点。综合波模理论和几何光学方法的特点,提出运用多波模理论分析巷道内无线信道的大尺度衰落,几何光学方法分析巷道内的小尺度衰落,并建立了巷道内MIMO信道模型。在研究大尺度衰落过程中发展了波模理论,提出了多波模理论:(1)推导了高次模的介质波导损耗、散射损耗、倾斜损耗、分支损耗以及天线插入损耗的各个公式;(2)给出了波模数目的计算方法及公式;(3)考虑基模和各个高次模的共同作用,进一步推导了多波模作用下的介质波导、散射、倾斜、分支的损耗公式;(4)增大电磁波传输频率,介质波导损耗趋于收敛值;(5)考虑散射与倾斜损耗,给出最佳频率选择参考公式,以及参考表。通过仿真分析电磁波的传输衰落以及电波强度的分布情况,与文献所述实验数据基本相符。运用几何光学方法――帐篷定律,分析了无线信道的小尺度衰落。(1)定义了帐篷第三定律,把原先的标量建模发展成为矢量建模;(2)建立了巷道内MIMO信道模型。(3)对巷道内MIMO信道相关性进行了公式推导。通过仿真分析在巷道内信道的角度扩展较小,电波传输有较强的方向性,角度功率谱接近于拉普拉斯分布;巷道内的MIMO信道的相关性与天线阵列的布置密切相关,天线阵列最佳位置是垂直于轴心。天线间距达到10l时,可认为信道不相关。仿真结果与实验数据相吻合。MIMO要求天线阵列单元之间有足够的间距,使相关系数较小,才能够提供有效的子信道。矿井巷道横截面大小是否能够满足此空间要求,是一个关键性的问题。本文运用数学理论——本征模理论,研究分析在隧道受限空间本身(排除工程设计的因素)能够提供的空间自由度,给出了巷道内空间自由度的计算公式,得到了隧道空间能够提供的信道容量上限。通过仿真分析,只要合理的设计通信体,巷道内可提供一定的空间自由度,在距离300m处时,空间自由度为3。更多还原

【Abstract】 Electromagnetic waves will be attenuated greatly by the wall in mine tunnels, mostly come into multi-path because of continual reflections and dispersions. It is still a hard work to study the characteristics of Electromagnetic waves propagation in tunnels in the field of wireless communication. Wave-mode theory is going to study the large-scale fading and geometrical optics to the small-scale fading and build the MIMO channel model of wireless channel in tunnel in our work, considering their personal strongpoint.Medium-guide multi wave-mode theory is advanced from wave-mode theory during studying large-scale fading in our work.(1) Higher-mode loss formula owing to medium-guide, surface roughness, tilt, corner and antenna insertion are deduced.(2) Calculate the number of wave-modes in tunnels.(3)Various loss of above (1) covering overall modes is formularized because the fading is the result of not only fundamental mode but also every higher modes.(4) Medium-guide loss is converging to a value with increasing frequency. (5)Optimal frequency of propagation in tunnel is proposed by formula and tables according to the parameter of roughness and tilt. The simulation is well consistent with the experiment data of some conferences, about propagation fading and field strength distribution.The Tent Law theory part of geometrical optics is to analyze the small-scale fading of wireless channel. (1) Define the 3rd Tent Law to vector model from scalar model. (2)Build MIMO channel model in mine tunnel. (3) Formularize the correlation of MIMO channel of tunnel. By simulating according to above, azimuth spread is small, and power is close to the Laplacian distribution, in other words, propagation is directional strongly. Channel correlation has close relations with the placement of antenna array, which optimal placement is perpendicular to the axis of tunnel, and the correlation taken for zero with space between antennas to10l .Simulation of theory answers for the measured data.The effective sub channels are provided on condition of low correlation which requires enough space between antenna array elements of MIMO. Then it is a key that cross section of mine tunnel is large enough filled with antenna array. The eigen-mode theory is to analyze degrees of freedom provided by the tunnel space taking no account of engineering, thereby bring forward a formula calculating the degrees of freedom in tunnel which is the upper limit of MIMO capacity in tunnels. Tunnel space can provide some freedoms with designing communication volume reasonably. Degrees of freedom can reach to 3 with distance of 300 meters.更多还原