Abstract
One hypothesis of 5G cellular networks architecture is using three tiers: Macro BS, Wi-Fi Pico BS, and Wi-Gig Femtocell. The challenge addressed in this paper is to associate the user requirement (UE) to the best BS/tier to achieve the optimal operation for the network and maximum data rate for all UE. There are two proposed types of association in this paper; the first one is to find the best BS in the three tiers and then associate the UE to one of them based on the association algorithm, and the second proposed type is to decide the best tier for the UE and then associate the UE to one of the BS of this tier based on the association algorithm. The opportunistic user association problem is worked out as an optimization problem which is solved by the Nash bargaining solution (NBS). The proposed algorithms presented in this paper achieve optimality, 7% and 2% increase in total system data rate (SDR) for the first and second proposed algorithms respectively. They also achieved 6% and 2% increase in total Jain's fairness index (JFI) for the first and second proposed algorithms respectively.