Link Gain and Pulse Width Broadening Evaluation of Non-Line-of-Sight Optical Wireless Scattering Communication Over Broad Spectra

In addition to large path loss, non-line-of-sight (NLOS) optical wireless scattering communication suffers time dispersion due to the multipath nature of the NLOS scattering channel. In this paper, the channel pulse delay spreads over broad spectra $\left[ {0.2,1.6} \right]$ μm in polydisperse aerosols are investigated based on the Monte Carlo ray-tracing method. It is shown that the pulse delay spread first rises and then falls as the wavelength increases from deep ultraviolet to near-infrared spectrum. A comparison of pulse delay spread and path loss distributions over broad spectra is performed, which implies a tradeoff of channel bandwidth and power loss in the wavelength selection of NLOS optical scattering communication. The effects of relative humidity (RH) variations on NLOS optical scattering communication link are also studied, which indicate that RH variations do not significantly change the ultraviolet NLOS optical scattering communication link, but for near infrared spectrum, high RH condition can alleviate the large path loss and time dispersion and thus improve the NLOS optical scattering communication performance.