Combination Of Information Display And Visible Light Communication

Visible light communication(VLC)is a kind of communication manner.It uses visible light(wavelength 400 to 760nm)as information carrier to transmit light signal directly in the space.Similar to bluetooth,infrared and WIFI,VLC is a wireless communication technology.Recently,VLC has attracted great attention from academy and industry.It has so many good traits such as high secuity,easy connection,harmless to human beings,enough bandwidth and so on.As a result,it is of great significance in solving the current spectrum crisis and conducting communication in some special areas where RF signals are unsuitable to use(such as underwater,cabin,MRI room in hospital).So far,this thehnology has been applied to many fields,including indoor positioning,urban traffic and ZigBee.The conventional visible-light communication technique exploits a modulator to control an LED's on and off,which represents signal ‘0' and ‘1'.By converting transmitted information to bit stream consisting of signal ‘0' and ‘1',and controlling LED's on and off accordingly,people can make LED work as a signal source.As the LED flicker frequency is very fast,so the human eye can not detect its rapid light and dark jump.However,at the receiving end,a photodiode can be used to convert a rapidly changing optical signal,which is imperceptible to human eyes,into electrical signals of different levels.And then with the help of amplifiers,filters,A / D converters and demodulators,we can regain the signal emmited from the source.Thanks to the growing popularity of high-speed refresh rate display device and high-speed camera,it provides a possible and realistic soil to the new idea that combining information display and visible light communication.There is a well-known and important finding in the field of human visual system that the human eye usually can not distinguish objects with flicker frequencies above 60 Hz.However,the current mainstream 3D display screen can get at least120Hz;the LED screens we can easily find at shooping malls,stations and other public places can even provide several orders of magnitude higher than this refresh rate.With these popular and common display devices in our lives,we can modulate signals to achieve visible light communication without affecting their normal display function.At the receiving end,we can capture and decode the frames embedded with signals modulated in the display screen resorting to a high-speed camera.In this paper,we first put forward a complete set of technical solutions to combine information display and visible light communication together.The scheme uses a high-speed refresh display device as the transmitting end of the signal.Under the premise of avoid affecting its normal information display function,we design a practical codec solution to modulate every independent super pixel region in each atom frame,and make the display device as a 2D MIMO signal transmission array.At the same time,with the help of a high-speed camera,we can capture every atom frame of signal embedded and recover the hidden data signal in the two-dimensional plane.In addition,we have designed a set of effective synchronization scheme,to solve the synchronization problem between camera and displayed frame.Compared with the other existing schemes,the scheme proposed in this paper takes into account the aliasing problem of the captured signal frames caused by the smearing effect of LCD and the unsynchronization of the camera in the practical application.By analyzing and modeling the aliasing situation of captured frame,we can repair the contaminated and damaged data,thereby reducing the bit error rate of signal transmission and improving the robustness of the system.Besides,this paper also refers to the experience of other research in this field,and puts forward an effective signal hiding algorithm to minimize the visual disturbance to normal information display.