Research Of Visible Light Communication System And Application Based On Mobile Phone Camera

With the increasing demand for communication,the problem of resource exhaustion and network interference in wireless communication spectrum is becoming more and more serious.Compared with the traditional wireless communication,visible light communication has the advantages of high speed,no electromagnetic interference,no occupation of radio frequency spectrum resources,but also has strong security and confidentiality.Therefore,the visible light communication develops rapidly and receives the attention of scholars from all over the world.At present,the receiver of visible light communication system includes photodiode and image sensor.The photodiode responds quickly but the processing circuit is complicated and it is not conductive to promote.The image sensor is an important part of the mobile phone camera.The mobile phones are widely used in daily lives.So using mobile phone camera as the receiver of visible light is proposed in this paper.We thoroughly research the visible light communication system based on mobile phone camera and propose a digital processing scheme of light and dark stripe image.We complete the whole system and the application program of receiving the visible light in mobile phone.In addition,the performance of the system is tested.The main contents of this paper are as follows:(1)By analysing the mobile phone camera imaging principle,the rolling shutter effect of CMOS image sensor is the basic principle of the camera to receive visible light in the processing of imaging.The camera can capture the information in the form of light and dark stripes by using this effect.The original bit sequence of the transmitter could be obtained through the data processing and judgement of the image.In this paper,a feasible digital image processing scheme for the application of visible light communication using mobile phone camera as receiver is proposed.The scheme includes grayscale correction,valid row selection,histogram equalization,high pass filter and the judgement.The valid row selection reduces the interference of LED facula and low grayscale area.The histogram equalization improves the extinction ratio of light and dark stripes.The image high pass filter reduces the blooming effect and the interference of background light.The judgement accuracy of light and dark stripes is improved by the digital image processing.(2)We complete the visible light communication system which bases on mobile phone camera.The transmitter of the system is achieved through the hardware circuit.Based on the Android mobile phone platform,the digital image processing algorithm is realized,and the application program of the reveiver is completed.This application can use the mobile phone camera to receive visible light and deal with data in real time.By testing the performance of the system,we analyse three factors affecting the performance of system,which include transmission distance,signal transmission rate,ambient illumination.The result of test also shows that the system has strong robustness and can effectively resist the interference.Compared with the existing research results,the transmission distance of the system is longer.(3)We analyse the application scenarios of the visible light communication.Combined with the transmission characteristics of this system and the high security of the visible light communication,we use visible light as a form of authorization and propose an identify verification and authorization system for indoor personnel.It is implemented in Android mobile phone,which provides an idea for the pratical application of visible light communication.