Modulation Schemes For Indoor Visible Light Wireless Communication

Expected to serve in the next generation of environmental light sources, LED offers advantageous properties such as high brightness, reliability, lower power consumption and long life time, while be widely used in our daily life. Especially short response time can provide the high modulation frequency. Now the market is in grate need for wireless communication and the wireless light communication are widely concerned. Visible light communications technology is a new technology after the invention and development of white light LED. Compared with the traditional radio communication, LED VLCS has high transmission power, no elector-magnetic interference, no need for spectrum resources and in door no data leakage, and other advantages. Therefore, LED visible light communication possesses greater significance and development prospects, and it has also become an emerging transmission scheme for short-range and high-data-rate wireless communication.To study a suitable modulation schemes for indoor visible light wireless communication, in this paper, after the modulation structures of the typical modulation schemes OOK, PPM, DPPM and OPPM are analyzed with the characteristic of the communication channel and the photo-electricity receiver, a new modulation schemes-differential overlapping pulse-position modulation(DOPPM) is discussed. Then the lighting power and the information transmitting rate are analyzed and combined. The results show that DOPPM is a better choice of modulation scheme for the communication system.For testing the feasibility of DOPPM, designed a high speed indoor visible light wireless communications verification hardware system based on white light LED. Including the data encoder and light transmitter of sending part, and the photoelectric circuit, preprocessing circuit, automatic gain control circuit and signal demodulates decoder of receiving part.After mathematical calculation and analysis, we proved DOPPM's feasibility and more suitable for indoor visible wireless communications. Finally get the BER under the verification hardware system by calculating the test data. The study will offer theory support for the choice of modulation scheme, and show the example for the realization of this system.