A Spectrum Handover Mechanism for Secondary Users in Cognitive Femtocell HetNets

This paper proposes a reserved channel based spectrum handover mechanism for cognitive heterogeneous networks (HetNet). To properly handover secondary users from Macro to Femto base stations and maintaining an acceptable protection on the primary users, we propose a priority-based scheme in which several channels are reserved only for handover of secondary users while the rest of channels can be shared by both the primary and the secondary users. The objective is to maximize the throughput of the secondary users meanwhile the throughput of the primary users is above a predefined value. To this end, we jointly optimize the number of the reserved channels and sensing time subject to constraints on false alarm and detection probability of the secondary users as well as throughput of the primary users. It is shown that the proposed optimization problem is convex and therefore can be solved efficiently by numerical methods. The simulation results show that, this method improves the throughput of the secondary users and in addition the achieved throughput is not sensitive to the arrival rate of the primary users. Moreover, it is found that the optimal number of the reserved channels keeps the blocking probability of the primary users below an acceptable level.