Research On White Light Optical Communication Technology Based On Multiprotection Transmission Method

With the explosion of information technology since the beginning of twenty first century, wireless network based on radio frequency communication system progresses extremely quickly. However, for the existing wireless network, there exists practical problems such as strong electromagnetic radiation, narrow frequency band, etc. A new wireless communication technology based on white LED can overcome the above shortage of the existing RF communication system. The communication system based on white LED has advantages of high capability of anti-electromagnetic interference,extreme wide frequency band, and zero electromagnetic radiation, etc. Thus the wireless communication system based on white LED is regarded as a new effective complementation with existing wireless network.However, the research on white LED communication is still in the initial stage of laboratory, there is a large extent disparity to be used practically. One of the existing problem is how to combine illumination and communication effectively, that is, how to ensure a high communication rate while illuminating effectively. The aim of this paper is to the question above. A white LED communication system is studied in this paper. A high power LED is used as the communication light source, A four-system modulation method based on Multiple Amplitude Shift Keying(MASK) is developed.Because the multi-system digital signal has a plurality of values in a signal pulse gap, it can improve the communication speed and the bandwidth utilization of the system effectively compared with the binary digital modulation system. Avisible white light communication system based on the 4ASK multi-system odulation technology is studied. A signal generator which can modulate the light intensity of the four LEDs is developed. A multi-amplitude signal detection circuit is developed and the received signal is restored from quaternary system to binary system. A communication systemhas been built and the feasibility and the transmission speed of the whole system have been tested. Experimental results show that communication rate can reach up to1.5Mbit/s in one meter range for the communication system.A small change in the distance and angle between the transmitter and the receiver can not cause distortions of the signal, when the transmission speed is less than 1Mbit/s, which shows certain stability and reliability.