Study On Dimming Control Technology Of Indoor Visible Light Communication System

With the development of the social informationization,the transmission capacity of information will exceed the capacity of the radio frequency spectrum.As a kind of high speed,high bandwidth and high security access method,visible light communication(VLC)is one of the next generation wireless communication technology with broad application prospect for its capacity of breaking through the severe shortage of radio spectrum resources effectively.The VLC system has both of the communication and illumination functions,therefore it should not only ensure the reliable transmission of information but also take the quality of illumination into account.For the reasons mentioned above,combining the VLC and dimming control technologies to achieve the VLC with the characteristics of green and energy saving,environmentally friendly and adapted to the requirements of different illumination conditions for different occasions has a potential development and application prospect.Firstly,the thesis gives an overview of VLC and dimming control technologies and illustrates the research status of dimming control for VLC.And then,the thesis proposes the frame model of the dimming control system for LED VLC and analyzes the link structure of indoor VLC.Moreover,the introduction about the key component characteristics of white light LED and Photo Detector(PD)for VLC system is made.Two kinds of technical proposals involving PPM-PAM and PPM-PWM are designed respectively in order to achieve the function of dimming control for VLC system and the design involves the communication protocol,the hardware circuit and the micro controller software programming in detail.The two designed proposals could ensure the quality of communication as well as the dimming control function.Four kinds of amplitude modulations for 100%,75%,50%,25%in PPM-PAM system and five kinds of duty cycle dimming modes for 100%,46%,43%,38%,33%in PPM-PWM system are achieved respectively.The experimental tests about the system performances of dimming and communication are made respectively to verify the feasibility and effectiveness of the designed system proposals.In addition,the dimming control system for VLC based on mobile phone camera is designed in this thesis and the system could transmit the text information correctly under different dimming modes through the test.In cater to the function requirements of dimming control for VLC system,the dimming control technologies based on PPM-PAM,PPM-PWM and mobile phone camera are achieved respectively in this thesis to provide theoretical basis and practical experience to further research about dimming control technology for VLC.