Hub location–allocation for combined fixed-wireless and wireline broadband access networks

This paper studies a telecommunications hub location model that includes the classical capacitated facility location problem on a wireline network, as well as a wireless network with technological constraints on crane-rain radius, line-of-sight, and capacity. There are multiple wireline and wireless hub types, differing in costs and capacities. We present a mathematical model to maximize network profit, build and test a quick greedy heuristic, and conduct sensitivity analysis using representative data. Solutions from the greedy heuristic are compared to the optimal solution for small instances, and the results indicate that the profit is on an average, within 98% of the optimal. For large instances that are intractable for the exact optimization approach, profit from the greedy solution is, on average, within 92% of that obtained from an upper-bounding linear programming relaxation. Sensitivity analysis shows that the optimal demand captured, revenue, and costs are not always monotone in input parameters: For a range of input values, profits improve by capturing more revenue with higher costs being incurred, in other cases, profits improve by reducing the costs of capturing demand while maintaining, or sometimes reducing revenue. Reducing hub installation costs or link transmission costs typically improves profit more than increasing hub capacity or link capacity by the same percentage. The combined network with both wireline and wireless technologies always delivers the highest profit, but in certain cases, depending on the demand, link capacity, and hub installation costs, either wireline-only or wireless-only networks can be quite competitive.