Research On Sampling And Regconition Method In Optical Camera Communication

The last decade has witnessed the flourishing improvement of communication technique,with the requirement for high-speed service gaining as well.However,spectrum resource of conventional radio frequency has become inadequate at same time.Visible light communication(VLC)utilizing visible light for both communication and illumination,are widely researched due to capability of immunity to electromagnetic interference and sufficient light wave spectrum.Recently,optical camera communication(OCC)with light emit diode(LED)as transmitter and built-in complementary metal-oxide-semiconductor(CMOS)camera of smart device as receiver has been proposed.As the smart device with CMOS camera are so popularized,the installation cost of OCC system can be significantly reduced.In this paper,digital signal processing techniques based on OCC system are investigated and the main works are as follow:1.A sampling scheme based on estimation of the stripe length has been proposed and experimentally demonstrated in an OCC system with rolling shutter effect(RSE).And a hybrid threshold scheme is proposed to decrease the high extinct ratio in OCC system.The proposed sampling scheme can significantly mitigate the influence from sampling frequency offset(SFO)and has lower complexity.The experiment result shows that the proposed sampling scheme has strong tolerance against SFO over the conventional clock recovery(CR).With the proposed sampling scheme,the scale of SFO tolerance of OCC system can be increased from 0.8% to 3.2% with the data rate of 480 bits/frame;and a highest data rate of 672 bits/frame can be achieved.2.A pattern recognition and positioning scheme under moving situation in an OCC system with global shutter effect(GSE)has been proposed.With a 2*2 LED array in different lighting pattern,the proposed system can accomplish both illumination and marking.The system has been experimentally demonstrated and the experiment result shows that the adapting pattern recognition scheme can reduce the effect form the geometrical distortion in moving situation,and a recognition rate close to 90% can be achieved with a speed of 0.96 m/s.