室外可见光通信在弱湍流信道中的性能研究

发布时间：2019-03-06 08:46

【摘要】：可见光通信(Visible Light Communication,VLC)有效解决了无线电频谱紧缺的问题,同时具有抗电磁干扰能力强、保密性好、频段无需申请、设备简单以及易于安装等优点。可见光通信除了应用于室内高速通信,还被广泛应用于汽车间通信、路灯与行人间通信等室外场景。室外可见光通信(Outdoor Visible Light Communication,OVLC)受大气湍流、吸收等因素影响,造成光强随机变化,严重影响系统的传输性能。本文以室外可见光通信系统为研究对象,围绕抑制大气湍流产生的光强闪烁效应展开研究,主要研究内容和研究成果如下:(1)将强度调制技术引入到室外可见光通信系统中,在二进制相移键控子载波强度调制(Binary Phase Shift Keying Subcarrier Intensity Modulation,BPSK-SIM)中增加了一个直流分量,从而保证光信号强度幅值始终为正值;详细推导了开关键控(On-Off Keying,OOK)强度调制系统和BPSK-SIM系统的误码率理论表达式,同时给出其它四种预调制方式下子载波强度调制系统的误码率理论表达式;使用Matlab工具进行数值分析,得出BPSK-SIM系统能够更有效的缓解闪烁效应对信号强度的影响;然后对比分析了BPSK多子载波系统和单子载波系统误码性能,最后给出中断概率对系统性能的影响。(2)为了能够更好地抑制光强闪烁效应对光信号传输的影响,将空间分集接收技术引入到室外可见光通信系统中。分别推导了采用等增益合并(Equal Gain Combining,EGC)、最大比合并(Maximum Ratio Combing,MRC)和选择合并(Selection Combining,SC)三种线性合并技术的BPSK-SIM系统的误码率表达式;使用Matlab工具对上述系统进行信噪比、系统误码率以及大气湍流强度等多维度的数值分析。结果表明采用等增益合并技术能最有效地抑制光强闪烁效应。
[Abstract]:Visible light communication (Visible Light Communication,VLC (visible light communication) effectively solves the problem of the shortage of radio spectrum, and has the advantages of strong anti-electromagnetic interference ability, good confidentiality, no need to apply for frequency band, simple equipment and easy installation and so on. Visible light communication is not only used in indoor high-speed communication, but also widely used in outdoor scenes such as communication between cars, street lamps and pedestrians. Outdoor visible light communication (Outdoor Visible Light Communication,OVLC) is affected by atmospheric turbulence, absorption and other factors, resulting in random changes of light intensity, which seriously affects the transmission performance of the system. In this paper, the outdoor visible light communication system is taken as the research object, and the suppression of the light intensity flicker produced by atmospheric turbulence is studied. The main research contents and achievements are as follows: (1) the intensity modulation technology is introduced into the outdoor visible light communication system, and a DC component is added to the binary phase shift key controlled subcarrier intensity modulation (Binary Phase Shift Keying Subcarrier Intensity Modulation,BPSK-SIM). Thus, the amplitude of optical signal intensity is always positive. The theoretical expressions of BER for switching keying (On-Off Keying,OOK) intensity modulation system and BPSK-SIM system are derived in detail. At the same time, the theoretical expressions of BER for subcarrier intensity modulation systems with other four pre-modulation modes are given. Using the Matlab tool to carry on the numerical analysis, it is concluded that the BPSK-SIM system can alleviate the effect of flicker effect on the signal intensity more effectively. Then the error performance of BPSK multi-carrier system and single sub-carrier system is compared and analyzed. Finally, the effect of interrupt probability on the performance of the system is given. (2) in order to suppress the influence of light intensity flicker effect on optical signal transmission better, the performance of the system is analyzed. The spatial diversity receiving technology is introduced into the outdoor visible light communication system. The expressions of bit error rate (BER) for BPSK-SIM systems with equal gain combining (Equal Gain Combining,EGC), maximum ratio merging (Maximum Ratio Combing,MRC) and selective merge (Selection Combining,SC) are derived. The multi-dimensional numerical analysis of signal-to-noise ratio (SNR), system error rate (BER) and atmospheric turbulence intensity are carried out by using Matlab tool. The results show that the equal gain combination technique is the most effective method to suppress the flicker effect of light intensity.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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