UVOC-MAC: a MAC protocol for outdoor ultraviolet networks

As an alternative to radio-frequency (RF) communications, optical wireless communications can support high data rates and low power operations while providing good jamming resistance. Our focus in this paper is on deep ultraviolet (UV) outdoor communications (UVOC) where solar blind and non-line-of-sight operations are attractive. Light beams from UV light-emitting diode (LED) arrays serve as information carriers. In an abstract sense, this is similar to directional transmissions in RF; however, the physical (PHY) layer characteristics significantly differ due to atmospheric scattering. First, we perform extensive experiments on a UV testbed towards understanding signal propagation and the impact of the PHY on medium access. We find that UV propagation supports (a) fully duplex communications and (b) multiple data rate transmissions. Next, we propose a novel contention-based media access control (UVOC-MAC) protocol that inherently accounts for the UV PHY layer and fully exploits multi-fold spatial reuse opportunities. Evaluations via both simulations and analysis show that UVOC-MAC effectively mitigates collisions and achieves high throughput. In particular, up to a 4-fold increase in throughput and 50 % reduction in collision are possible compared to a MAC protocol agnostic to the UV PHY properties.