GG信道下MRC对直接通信链路误码率和多用户系统吞吐率的性能提升研究

发布时间：2018-06-27 16:33

本文选题：误码率 + 大气激光通信　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：自由空间光(Free Space Optical,FSO)通信被认为是一个低成本和高带宽的接入技术,引起了广泛的研究。但是,FSO通信链路的可靠性和稳定性容易受大气湍流的影响。其中影响最大的因子是大气的湍流。大气湍流会导致信号的衰落、扩展和闪烁,严重影响了通信系统的性能。因此,如何克服大气激光通信中由于光强闪烁引起的信道衰落是当前通信领域研究的热点课题之一。针对该科学问题,借鉴射频(Radio frequency,RF)通信,论文对基于双gamma衰落模型的多接收端最大比率合并(Maximal Ratio combing,MRC)技术进行了深入研究,具体内容如下:1)考虑到双gamma信道衰落模型,研究了二进制相位键控(Binary phase shift keying,BPSK)子载波强度调制(Subcarrier intensity modulation,SIM)的大气激光通信系统误码率性能。在等同或非等同信道条件下,通过将双gamma分布函数中的比较难处理的第二类修正贝塞尔函数表示成Meijer-G函数的形式,分别给出了双支和三支接收时关于信噪比(Signal-to-noise ratio,SNR)的误码率H-fox函数表达式,进而得到相对分集增益。以双支为例,仿真表明改变其中任意一支的信道条件,系统的误码率性能会随之改变。为了表明分集技术的优越性,在等同信道条件下比较了点对点、一发两收系统和一发三收系统性能。在同等衰落条件下,与等增益合并(Equal gain combing,EGC)等合并方式进行误码率特性的对比,表明了论文模型的优势。蒙特卡洛系统仿真的结果验证了论文误码率理论表达式的正确性。2)基于MRC技术,首次对有K个用户的中心结点的多用户下行链路系统进行了仿真研究。研究表明,引入MRC合并技术后,基于贪婪算法(Greedy scheduling,GS)、多用户选择算法(Selective multiuser diversity scheduling,SMDS)以及比例公平算法(Proportional fair scheduling,PFS)等多用户信道资源竞争方式得到的相对吞吐量都有了显著的提升,采用三支的MRC合并比双支的提升效果更加明显。在同等条件下,GS算法有最大的系统吞吐量,对于不同的滑动窗口参数值,PFS算法的系统吞吐量不同,随着滑动窗口取值增大时,系统吞吐量增大。论文研究成果对于大气激光通信光接收系统设计提供一定的参考。
[Abstract]:Free Space Optical Optical (FSO) communication is considered to be a low-cost and high-bandwidth access technology, which has attracted extensive research. However, the reliability and stability of FSO communication link are easily affected by atmospheric turbulence. The most influential factor is atmospheric turbulence. Atmospheric turbulence can cause signal fading, expansion and flicker, which seriously affects the performance of communication system. Therefore, how to overcome the channel fading caused by intensity scintillation in atmospheric laser communication is one of the hot topics in the field of communication. Aiming at this scientific problem and using radio frequency (RF) communication for reference, the maximum ratio combing (MRC) technique based on dual gamma fading model is studied in this paper. The main contents are as follows: 1) considering the dual gamma channel fading model, The bit error rate (BER) performance of binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in atmospheric laser communication systems is studied. Under the condition of equal or non-identical channel, the modified Bessel function of the second kind, which is difficult to deal with in the double gamma distribution function, is expressed in the form of Meijer-G function. The H-fox function expressions of signal-to-noise ratio (SNR) for two and three branches of receiver are given, respectively, and the relative diversity gain is obtained. Taking two branches as an example, the simulation results show that the BER performance of the system will change when the channel conditions of any one of them are changed. In order to demonstrate the superiority of diversity technique, the performance of point-to-point, one-send and two-receive systems and one-transmit three-receiver systems are compared under the same channel conditions. Under the same fading conditions, the BER characteristics of the model are compared with those of equal gain combination (EGC), which shows the advantages of the model. The simulation results of Monte Carlo system verify the correctness of the theoretical expression of bit error rate (BER) based on MRC technology, the simulation of multi-user downlink system with K central nodes is carried out for the first time. The results show that the relative throughput of multi-user channel resource competition based on greedy scheduling GS (greedy scheduling GS), selective multiuser diversity scheduling (SMDS) and proportional fair scheduling (PFS) has been significantly improved. The combination of MRC with three branches is more effective than that with two branches. Under the same conditions, the GS-algorithm has the maximum system throughput. For different sliding window parameter values and PFS algorithm, the system throughput is different, and the system throughput increases with the increase of sliding window value. The research results provide some reference for the design of optical receiving system for atmospheric laser communication.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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