Backhaul-aware Decoupled Uplink and Downlink User Association, and Power Control in Fi-Wi HetNets

Decoupling the uplink and downlink user association improves the throughput of heterogeneous networks (HetNets) and balances the traffic load of macro- and small- base stations. Recently, fiber-wireless HetNets (FiWi-HetNets) have been considered as viable solutions for access networks. To improve the accuracy of user association and resource allocation algorithms in FiWi-HetNets, the capacity limitation of various backhaul technologies must be considered. In this paper, we investigate the backhaul-aware decoupled uplink/downlink (UL/DL) user association, subcarrier allocation, and power control optimization problem in FiWi-HetNets. In our system model, fiber and millimeter wave (mmWave) links are used as backhaul of base stations, and the backhaul capacity limitation and minimum required transmission rate (R_min) are modeled in the optimization problem. As the formulated optimization problem is non-convex, we present a heuristic algorithm to divide the main problem into two sub-problems that are solved iteratively. The proposed algorithms are evaluated through exhaustive simulations. The results indicate that decoupling UL/DL user association improves the sum rate of FiWi-HetNets. Besides, we evaluate the effect of backhaul capacity limitation and R_min on the sum rate of FiWi-HetNets. The effect of upgrading fiber backhaul technology is also investigated to evaluate the role of fiber backhaul on the sum rate of the radio access network.