Modeling and topology design for free-space optical networks

To date, free-space optical (FSO) networks play an important role in current network construction to support large-capacity transmission, where randomly distributed FSO terminals desire to exchange a tremendous amount of information over atmospheric turbulence channels. However, in the presence of atmospheric turbulence and misalignment fading channels, FSO network topology can be dynamic and disconnected. To mitigate the impact of dynamic network environments, appropriate higher-layer protocols should be designed. We explore a practical terrestrial mobile ad-hoc FSO network based on the bundle protocol of disruption-tolerant network, and the theoretical cross-layer system model between physical layer and network layer is derived. To design the topology, at the bundle layer, the distributed routing scheme centrality and probability (CAP) is proposed, where contact probability, sociocentric measure, and message replication strategy are considered simultaneously, and the joint forwarding decision rule is given. Simulation results on the opportunistic networking environment simulator are presented, which show that CAP can be better compared with the conventional end-to-end protocol-based routing scheme.