Improving hybrid FSO/RF network reliability through transceiver reconfiguration

Despite the increasing popularity of Free-Space Optics (FSO) in wireless mesh networks, reliability is still a major concern. Due to the strong dependence of FSO link availability on weather conditions (e.g., fog, cloud, air turbulence) using RF links is inevitable, both for backup and signaling. In addition, reconfiguration of FSO transceivers could preserve network reliability when several connections suffer outages. In this paper, we find the optimal reconfiguration of transceivers and rerouting of traffic flows using an integer-linear program (ILP). The link availability prediction is used as an input and the overall throughput of the network is maximized while guaranteeing fairness to all traffic demands. To avoid the complexity of the ILP, an efficient probabilistic heuristic that computes a set of schedules for dynamic reconfiguration of FSO transceivers is proposed. We show that this heuristic achieves a high fraction of the optimal throughput, as verified by extensive simulations.