Impact of Small Cells Overlapping on Mobility Management

The mobility management will be more complex and will have a great impact on the quality of service in the future cellular networks, as these networks will have to handle a huge number of user equipments (UEs) and their frequent hand offs due to very dense short-footage small cells. This paper presents a framework to model and derive the coverage of small cells, the cell sojourn time, and the hand off rate in multi-tier small cell networks. The distribution of the small cells around a reference UE’s path is studied by taking into consideration the overlaps among the small cells. Two types of hand off rates are introduced to estimate the load managed by different cells, where inter-frequency hand off rate and intra-frequency hand off rate represent the fraction of hand offs managed by the first tier and the other tiers, respectively. Our analysis shows that ignoring the overlaps among the small cells affects the accuracy of the results significantly. The simulation results validate the accuracy of the analytical results and also show the impact of different parameters, such as the small cell density, the number of tiers and the size of the small cells on the small cell sojourn time, the macro cell sojourn time, and the hand off rate.