可见光通信中的天线布局研究

发布时间：2018-03-18 06:41

本文选题：可见光通信　切入点：多输入多输出　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：为了提高系统容量,研究人员在可见光通信(VLC)中引入了多输入多输出(MIMO)技术。但是,MIMO技术在提高信道容量的同时,也带来了信道间干扰,使得MIMOVLC系统的性能严重恶化。信道间干扰易受信道传输矩阵的影响,而信道传输矩阵又与天线参数密切相关。因此,本文通过调整可见光通信中的天线参数优化了 MIMO VLC系统的性能。在已有的VLC天线布局研究中,仅考虑了接收端天线在室内中心处的情况。但在实际应用中,接收端天线可能遍布在房间的各个位置。因此,本文将接收端天线由室内中心处拓展到了整个室内平面,对比分析了几种圆形布局和格点型布局在整个室内平面上的信道容量分布特点。仿真结果表明,MIMOVLC系统的信道容量不仅与发光二极管(LED)之间的间距和光电检测器(PD)之间的间距有关,而且与天线摆放的位置有关。另外,在格点型布局中,信道容量的分布特性还与天线布局有关,而在圆形布局中与之无关。同时仿真结果也表明,室内中心处的MIMO信道中存在着较大的信道间干扰。为了减小或消除信道间的串扰,本文在发射端引入了两种功率分配方案。两种方案均基于保持总发射功率不变,调整各个天线之间的功率分配比例的思想。之后将两种方案分别应用于正方形9×9系统和三角形10×10系统,分析了功率分配对系统性能的影响。仿真结果表明,两种功率分配方案均能不同程度地抑制系统的性能缺陷。第一种方案能够减小信道容量曲线的波动程度,但是并不能完全抵制系统的恶化。相比之下,第二种方案优化之后的系统,其信道容量曲线更加平滑且系统容量值更大。Monte Carlo方法是一种计算精度非常高的数值计算方法,但是需要大量的样本来估计随机变量的期望值,因而计算量巨大。针对计算精度和计算量之间矛盾的问题,本文引入了 "解析法"来计算信道容量。该方法首先推导了互信息的渐近表达式,进而求解出互信息的最大值,即信道容量。然后为了验证解析法的可行性,本文利用解析法仿真计算了正方形8×8系统和三角形10×10系统的信道容量曲线并与MonteCarlo法加以比较。仿真结果表明,当SNR变化时,解析法能够计算出信道容量的变化趋势以及最大值,并且明显地减小系统的平均运行时间。从而为求解信道容量提供了一种新的并且计算量小的计算方法。
[Abstract]:In order to improve the capacity of the system, researchers have introduced the multi-input and multi-output MIMO-technology into VLC, but the MIMO technology not only improves the channel capacity, but also brings inter-channel interference. The performance of MIMOVLC system is seriously deteriorated. Interchannel interference is vulnerable to the influence of channel transmission matrix, which is closely related to antenna parameters. In this paper, the performance of MIMO VLC system is optimized by adjusting the antenna parameters in visible light communication. In the existing research of VLC antenna layout, only the situation of receiving antenna in the center of the room is considered. The receiver antenna may be located in all parts of the room. Therefore, this paper extends the receiver antenna from the center of the room to the whole indoor plane. The channel capacity distribution characteristics of several circular and lattice configurations on the whole indoor plane are compared and analyzed. The simulation results show that the channel capacity of the MIMOVLC system is not only the distance between the channel capacity and the LED and the PDD). The distance between them is related, In addition, in the lattice layout, the channel capacity distribution is also related to the antenna layout, but not in the circular layout. The simulation results also show that, In order to reduce or eliminate the crosstalk between channels, two power allocation schemes are introduced in this paper. Both schemes are based on keeping the total transmit power unchanged. The idea of adjusting the power distribution ratio between different antennas is presented. Then, two schemes are applied to square 9 脳 9 system and triangular 10 脳 10 system respectively. The influence of power allocation on system performance is analyzed. The simulation results show that, The first scheme can reduce the fluctuation of the channel capacity curve, but it can not resist the deterioration of the system completely. After the second scheme is optimized, the channel capacity curve is smoother and the system capacity is larger. The Monte Carlo method is a very accurate numerical method, but a large number of samples are needed to estimate the expected value of random variables. In this paper, the analytical method is introduced to calculate the channel capacity. In this method, the asymptotic expression of mutual information is derived, and the maximum value of mutual information is obtained. In order to verify the feasibility of the analytical method, the channel capacity curves of the square 8 脳 8 system and the triangular 10 脳 10 system are simulated and compared with the MonteCarlo method. The simulation results show that, when the SNR changes, The analytical method can calculate the variation trend and maximum value of channel capacity, and obviously reduce the average operating time of the system, thus providing a new and less computational method for solving the channel capacity.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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