论文部分内容阅读
可见光大气传输系统面临的主要问题在于由大气湍流引起的光强闪烁和来自日光及其他照明设备的强背景光干扰,为了克服大气湍流造成的信道衰落效应及强背景光带来的噪声干扰问题,对室外可见光通信(VLC)强背景光大气湍流信道进行了建模。在接收端采用分集接收技术,在相同的发射功率下提高系统误码率(BER)性能。构建了在强背景光大气湍流信道模型下基于强度检测脉冲位置调制(PPM)方式的室外长距离可见光分集接收系统模型,在几十微瓦功率背景光噪声下,实现了800 Mb/s PPM信号的仿真系统传输。基于此系统分别研究对比了最大比合并(MRC)、等增益合并(EGC)、选择性合并(SC)3种分集合并方式的误码率性能。结果表明,在相同的发射功率下,误码率性能提升最大的是MRC,其次是EGC,SC最差。以7%前向纠错码(FEC)误码门限作为参考,MRC能显著降低对LED发射功率的要求,并且随着分集支路个数的增多,分集效果越好。
In order to overcome the channel fading caused by atmospheric turbulence and the noise interference caused by strong background light, the main problems that the visible light atmospheric transmission system faces are the flicker of light intensity caused by atmospheric turbulence and the strong background light interference from sunlight and other lighting devices. A strong background atmospheric atmospheric turbulence channel for outdoor visible light communication (VLC) was modeled. At the receiving end, diversity reception is used to improve system BER performance at the same transmit power. An outdoor long-distance visible light diversity receiver system model based on intensity detection pulse position modulation (PPM) under strong background atmospheric atmospheric turbulence channel model was constructed. Under the background noise of several tens of micro-watts, a 800 Mb / s PPM signal Simulation of system transmission. Based on this system, the bit error rate performance of three kinds of diversity combining methods, MRC, EGC and SC, respectively, are studied and compared. The results show that under the same transmit power, MRC is the most improved bit error rate performance, followed by EGC, SC is the worst. With a 7% FEC error threshold as a reference, MRC can significantly reduce the LED transmit power requirements, and as the number of diversity branches increases, the better the diversity effect.