Study On The Performance Of Organic Device Based Visible Light Communication Systems

With the increasing demand of data rate and spectrum bandwidth,traditional wire-less communication is facing a critical issue of spectrum crunch.Meanwhile,with the widespread deployment and application of light-emitting diodes(LEDs),it is possible to popularize commercial visible light communication(VLC).VLC owns many advan-tages,including rich spectrum resources,immunity to wireless interference,and secu-rity,which have received considerable attention from researchers.The organic device based VLC is a promising technology due to the advantages of devices,such as thinness,flexibility,easy integration,and environmental friendliness,which can bring benefits to communication systems.However,this technology still remains in a research stage because of the limitation of devices and application scenarios,and there are many tech-nical difficulties to be solved.This dissertation mainly focuses on the performance of organic device based VLC systems.Specific characteristics of organic devices are explored from the communica-tion point of view,and their influence on communication links is studied.Then organic VLC systems are designed,and their communication performance is analyzed.First,the basic optoelectronic characteristics of an organic light-emitting diode(OLED)and an organic photodetector(OPD)are tested,and some specific device char-acteristics are explored,including linear dynamic transfer characteristics,flexibility,noise characteristics,etc.It is found through experiments that these organic devices have very small bandwidth,which significantly limits the communication system data rate.Meanwhile,their flexibility causes difficulties in accurately describing the spatial distribution of optical signals.These findings provide guidance to subsequent system design.Then,the impact of the characteristics of organic devices on the VLC links is inves-tigated.An improved radiation model over the traditional Lambertian model is proposed by testing the radiation pattern of a bent OLED panel under different curvatures.The influence of the developed bent OLED radiation model on VLC channel is further stud-ied.An organic VLC platform is built to test channel parameters and noise statistical distribution for subsequent communication system design and optimization.Finally,organic communication systems are designed and their performance is an-alyzed.Conventional one-dimensional(1D)constellation design methods can not sup-press noise effectively due to the existing signal-dependent shot noise(SDSN)which degrades the system performance.Thus constellation is designed in a 2-dimensional(2D)signal space.Two optimal orthonormal basis functions are chosen to build a max-imal 2D signal space.The optimal constellation is obtained by minimizing the maxi-mal symbol error rate(SER)among all constellation point pairs.Then we establish an OLED and OPD based all-organic VLC system,and test communication performance by off-line experiments.In order to tackle the bandwidth limitation,non-orthogonal multi-carrier modulation(OFDM-OQAM)with bit and power loading is applied at the transmitter,while a linear minimum mean-square-error(LMMSE)equalizer and a deci-sion feedback equalizer(DFE)are jointly implemented at the receiver.Finally a high-speed VLC system based on a monochromic OLED is established,achieving a data rate of 51.6 Mbps.