On robust FSO network dimensioning

The presented work is motivated by Free Space Optics (FSO) communications. FSO is a well established wireless optical transmission technology considered as an alternative to radio communications for example in metropolitan wireless mesh networks. An FSO link is established by means of a laser beam between the transmitter and the receiver placed in the line of sight. A major disadvantage of FSO links (with respect to fiber links) is their sensitivity to weather conditions such as fog, rain and snow, causing substantial loss of the optical transmission power over the channel due mostly to absorption and scattering. Although the FSO technology allows for a fast and low-cost deployment of broadband networks, its operation will be affected by vulnerability of the link transmissions to weather conditions that can be manifested by substantial losses in links' transmission capacity with respect to the nominal capacity. Therefore, proper dimensioning of an FSO network should take such losses into account so that the level of carried traffic is satisfactory under all observed weather conditions. In the paper we introduce and study an optimization problem for such enhanced dimensioning using the robust optimization approach.