Propagation model for non-line-of-sight ultraviolet communication

Scattering deflects the ultraviolet ray, and makes it possible to bypass the obstacles between two blocked nodes. To investigate the channel characteristics of this kind of link, models have been developed, and most of them are based on coplanar geometry. Non-coplanar geometry, however, is unavoidable in most actual application. To make sure the influences of this factor, a universal model which describes the channel characteristics of Non-Line-Of-Sight (NLOS) Ultraviolet communication for non-coplanar geometry is developed in this paper. On the basis of classical single-scatter model, this model mainly estimates the impulse response and the pass loss with the transmitter and the receiver cone pointed in arbitrary directions. There are three major contributions in the paper. Firstly, classical single-scatter model and the differences effective scattering volume between coplanar geometry and non-coplanar geometry were described. Trigonometry and optimization techniques were proposed to overcome the restriction that the transmitter and the receiver cone axes lie in the same plane; secondly, a Monte-Carlo (MC) model was constructed to verify the single scatter model; finally numerical simulations and analysis were presented. Numerical simulation shows that the deflection of the transmission or the reception cones(alpha(t), alpha(r)) decreases the signal, this decrease is slight under small deflection, and becomes more serious as deflection increases, finally remarkable when the deflection reaches a threshold. The result shows that a positive correlation exists between the threshold and the source divergence, which means that large source divergence gives better tolerability of the off-axis angle, but worse pulse width. In addition, the influence of deflection can be reduced signally by deflecting the two cones in the same side. MC model draws the similar conclusion approximately. Compared with other models, this model releases the restriction that the transmitter and the receiver cone axes lie in the same plane, which making it more versatile.