| Outdoor visible light communication is a communication method that uses visible light beams as the carrier for data transmission.The transmission of outdoor visible light communication signals is affected by the path loss of the atmospheric channel near the ground,resulting in a decline in communication performance,especially the impact of some special weather conditions is very serious.In this paper,an outdoor visible light communication path loss model is established through theoretical analysis and experimental measurement,and the attenuation under different weather conditions is analyzed.The main research contents are as follows:1.Through the analysis of the outdoor visible light system model,the relationship between the vertical and horizontal half-field angles of the system receiving end and the link span,lens focal length,and photodetector surface is studied,and the relationship between the half-power angle of the system transmitting end and the field of view of the transmitting end is studied.relation.2.The path loss model of the outdoor visible light communication system is established.The influence of different distances between vehicles and different weather conditions on the link received optical power and received signal bit error rate is studied through experimental data,and the change of system signal-to-noise ratio and bit error rate under different weather conditions is analyzed.3.According to the Mie theory and the distribution characteristics of different particles,the scattering effect of rain,fog,snow and dust particles with different diameters on visible light is simulated and analyzed.The attenuation of visible light under different weather conditions is studied,and the relationship between the attenuation coefficient and the wavelength of visible light is analyzed.4.Through experiments,the experimental data of different road sections and different weather conditions were analyzed,and the performance of outdoor visible light communication under different weather conditions was analyzed,and the single-layer and double-layer constellation diagrams of the measured received signals under different weather conditions were drawn.The research results show that the path loss model of the outdoor visible light communication system conforms to the Gaussian model.The photodetector surface area increases logarithmically.The half-power angle of the transmitter shows a logarithmic increase with the increase of the field of view of the transmitter.The loss of visible light communication is different in different weather,and the attenuation in rainy days is in descending order:heavy rain,light rain,heavy rain,and moderate rain.The loss in dense fog is greater than that in mist;the loss in dry snow is greater than that in wet snow when the snowfall is the same.The more severe the channel path loss,the greater the variance of the probability density function of the received optical power.The dispersion of constellation points in rainy days,snowy days,and foggy days gradually increases,and the impact on effective data transmission also gradually increases.When the visibility of foggy days is 500 meters,the dispersion of some constellation points has been connected.In the actual communication process,it is necessary to Receiving the constellation diagram for algorithm processing can achieve ideal communication performance. |
