Electronic Thesis/Dissertation


Reliability and Capacity Planning in Hybrid Optical Networks Open Access

RF-based wireless backhaul networks generally are a bottleneck in satisfying the ever-increasing demand for bandwidth. Enhancing the capacity of wireless backhauls can be done through boosting some strategically located links. The first part of this dissertation focuses on link augmentation via MIMO RF and Free Space Optics (FSO) technologies. Adopting a TDMA-based framework, we formulate the problem of transceiver placement and scheduling of the links to maximize the network capacity. To avoid the complexity of the ILP, we also propose a randomized greedy heuristic algorithm. We show by simulations that our heuristic achieves a high fraction of the network capacity.The second part of this dissertation is concentrated on planning reliability for FSO-based networks and providing reliability for partially disconnected networks through FSO technology. Due to the strong dependence of FSO link availability on weather conditions (e.g., fog, cloud, air turbulence), the use of RF links is still inevitable, both for backup and signaling. We use FSO link availability prediction as an input in the formulation of these problems. Especially, we take the reconfigurability of FSO links into account for added reliability. We also propose a method to recover a network that is partially disconnected due to natural disasters or terrorist attacks through FSO relays.Finally, we focus on reliability planning for high speed wireless backhaul based on high altitude platforms. High altitude balloons used as base stations appears to be an easy and cost-effective solution in remote and rural areas thanks to its infrastructure-less characteristics. Ease of deployment and low cost, however, come at the price of complicated issues introduced by dynamic and complex topology of such networks. Despite the possibility of moving the balloons vertically, their overall trajectories are greatly dependent on the stratospheric wind, which directly affects the availability of the wireless links. In the last part of this dissertation, we address the wireless backhaul reliability problem that arises due to limited control on horizontal mobility of the balloon transceivers. We show that using a few unmanned aerial vehicles as relays can drastically improve the reliability of such wireless backhaul networks.

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