Stochastic Geometry Based Handover Modelling in Two-tier Femtocell Networks

Background: In order to handle user demand the 4G mobile operators should install additional smaller cells to their traditional cellular structure for the sake of larger capacity, fewer call drops and for better network coverage. The result is a heterogeneous (two-tier) cellular network which contains smaller cells (like femtocells) under the macrocells. A femtocell usually provides coverage to a smaller area (e.g. flat or house) and transports the data to the femtocell gateway via wired technologies. Due to this wired background the handover between macro and femtocells might increases the number call drops. Method: The two-tier cellular structure includes open access femtocells. Femto base stations are deployed randomly and modeled with a two-dimensional homogeneous Poisson Point Process (PPP). The system model applies the fundaments of stochastic geometry and several parameters of the network are kept as random variable (such as slow fading, fast fading or the actual location of femtocells). Results: Relying on the forms presented in the paper we can discover the handover zones, where femtomacro or macro-femto handovers are expected. Since the femtocells are operating here in open access mode, so that the handover probability parameter becomes important concern. In this article, we declare the handover probability using the fundamentals of stochastic geometry. An analytical model has been proposed for handover modelling in two-tier femtocell environments based on stochastic geometrical tools. Conclusion: With this model the handover probability is easily calculable. The results show that the coverage area of the femtocells can be modelled with a circle and the radius of the circle extending while leaving the macro base station. Every femtocell has a concentric ring where the handover is probable.