Performance Research And Theoretical Design Of Visible Light LED Communication System

In the background of worldwide resources shortage, as a new kind of green lighting device, LED is considerd to take the place of traditional incandescent and fluorescent lights by more and more people. Then a kind of communication based on visible light LED comes in.Compared to radio communication, visible light LED communication(VLC) has the advantage of needing not apply for radio frequency spectrum, having no electromagnetic interference and safe communication. Compared to infrared communication, VLC has the advantage of needing not limit transmitting power. So it is researched at home and abroad. But up to now most researches are focused on experiments, others are focused on theory but specific to low power LEDs, which is not realistic nowadays. So this thesis is specific to the theory of high power visible light LED communication system, and use the theory to discuss the design of transmitter and receiver.The work of this thesis is:(1) The spectral and modulation characteristics of white LED are researched, two methods to increase the modulation bandwidth of white LED are discussed: using an blue optical filter and optimizing drive circuit. As to the latter, a drive circuit based on a pre-equalization technique is presented.(2) The indoor wireless optical communication channel confined by illumination conditions is modeled, the impulse responses of specific source, room and detector configurations are evaluated; several factors to influence system performance are analyzed, reducing system bandwidth, increasing transmitting power and centralizing light source can increase system signal to noise ratio.(3) The transmitting characteristics of white LED receiving system is analyzed, let it have a root raised cosine roll-off spectrum can eliminate intersymbol interference and realize matched filtering. The design of receiving filter with such spectrum using MATLAB is introduced.