Research On Modulation Technology In Ultraviolet Turbulence Channel

Ultraviolet (UV) communication is a new type of wireless optical communication, since it is widely used in military field, it has attract experts attention at home and abroad. The wavelength 200 nm to 280 nm band of UV is strongly absorbed by the ozone layer, therefore UV reaches the earth's surface is very weak,and the band is called "solar blind". The wireless UV communication uses this band to transmit information. "Solar blind" UV communication not only has the traditional advantages of wireless optical communication but also has its unique advantages, such as non-line-of-sight (NLOS) communication, all-weather work, strong anti-interference ability, and it is very suitable for secure communication in complex environment.Current researches on wireless UV communication at home and abroad mostly focus on improving the performance of wireless UV communication, the simulation model of channel and the technology of wireless UV network, and some achievements are acquired. But there are few researches on the performance of UV communication channel in the atmospheric turbulence. In this paper , the characteristics of ultraviolet channel and modulation technology on the basis of the atmospheric transport theory are studied. The main work are as follows:(1)This article introduces wireless UV transmission theory, the model of wireless ultraviolet channel in the atmospheric turbulence was established based on two models of wireless UV Line-of-Sight (LOS) and NLOS communication and the probability density function of the signal intensity distribution at the receiver is also analyzed.(2) The geometric link model for ultraviolet slant path transmission is established The influence of distance between transmitter and receiver on UV signal intensity distribution of horizontal transmission, vertical transmission and slant path transmission under four different atmospheric turbulence models is studied. Finally, the influence of distance between transmitter and receiver on the received power under the three kinds of scenes is measured. The results show that the received power decreases with the increase of distance and the quality of the communication decreases as well.Aiming atthe performance of UV general modulations, the expressions for BER using on-off keying(OOK),pulse position modulation(PPM),pulse amplitude modulation (PAM),quadrature amplitude modulation (QAM) in lognormal distribution of wireless UV LOSand NLOScommunication are derived. Then, the BER performances of the four modulationsare simulatedand analyzed.The results show when the four modulation have the same signal-to-noise ratio(SNR), the PPM is best, the other is OOK, but QAM is the worst in the four methods.the advantage of PPM will be more obvious with the increase of modulation order. The BER of the four modulation modes in ultraviolet turbulence channel is much larger than other communication transmission channels.In summary, this paper mainly studies the signal intensity distribution of different atmosphericturbulencechannelsand the modulation technology in wireless UV communication.