User association and routing in UAV-supported HetNets

Tezergil, Berke
With the introduction of millimeter waves in 5G, using wireless backhaul has become feasible with higher performance comparable to that of fiber cables. Using unmanned aerial vehicles as small cells enabled many use-cases by reducing the average link length and increasing the line-of-sight probability. In this work, a heterogeneous network with users, flying small cells on unmanned aerial vehicles, and macro base stations are considered. We introduce two main problems: establishing backhaul routes for small cells to maximize data capacity for users, and associating every user with a base station. The problem is named as the UAV-UAR problem. Initially, a mixed-integer linear programming formulation is given, which is optimal, but requires considerable time to find a solution. Using this formulation, a flow network definition is given for the heterogeneous network, and used to formulate relabel-to-front algorithm-based heuristics. While these heuristic methods do not guarantee optimality, they are significantly faster than the exact solution. The first developed heuristic, Relabel-to-Front-Eliminate, eliminates all edges that users allocate capacity except one. The second heuristic, Relabel-to-Front-Heuristic, uses a heuristic preflow initialization to associate users before execution. The final heuristic, Relabel-to-Front-Iterative, uses the second method, but iteratively changes user association until the result no longer improves. Monte Carlo Simulation results show that relabel-to-front-based heuristics have comparable, and usually the same throughput performance to that of linear programming optimization, but with a sliver of the execution time, outperforming by 20 to 1000 times depending on other parameters.


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Citation Formats
B. Tezergil, “User association and routing in UAV-supported HetNets,” M.S. - Master of Science, Middle East Technical University, 2022.