An energy-efficient recovery algorithm for the free space optical communications network via reflections.

Free space optical (FSO) communication is a very attractive solution to substitute or complement radio frequency-based wireless technologies for providing high-speed wireless connections. FSO-based network consists of a lot of optical nodes, whose transmission power is concentrated in a narrow volume. Considering the directionality of FSO communications, the outage of a node in the network may result in reduced link connectivity and availability, thus causing coverage hole. Once the coverage hole, the accuracy of network monitoring data would not only be reduced, but much of the not-yet-used resource would also be abandoned in the network resulting in energy waste. In this paper, we propose an energy-efficient recovery algorithm for FSO network based on reflections. The proposed algorithm adopts the classified repair mode based on the communication conditions prior to dying of the node. If the dead node is a relay node, the mirror node is used as the repair node in order to reduce the energy consumption of data forwarding, and an evaluation model is established by combining the coverage and the energy to determine the repair location. However, if the dead node is not a relay node, the ordinary node is used as repair node. The location of the repair node is found based on the coverage and the geometric relationship to ensure the maximum coverage. The simulation results show that, the proposed algorithm not only sustains coverage but also reduces the network energy consumption and prolongs the network's lifetime. [ABSTRACT FROM AUTHOR]