Impact of small cell deployments on mobility performance in LTE-Advanced systems

The use of small cell deployments in heterogeneous networks (HetNet) environments is considered a promising strategy to cope with the explosion in mobile traffic. In the deployments, there is a concern that the large number of small cells causes the signalling load on the network nodes to increase due to frequent handovers (HOs) and mobility robustness to be degraded due to increased handover failures (HOFs) and radio link failures (RLFs). To examine these impacts caused by the introduction of small cells, in this paper, we evaluate mobility performance on small cell deployments in LTE-Advanced systems. The simulation results show that the number of HOs occurs at most 3.5 times compared to a macro cell-only deployment even in the case where there are 20 small cells per macro cell and assuming a worst case scenario in which the small cells are located separately and their coverage does not overlap with each other. The results also show that the number of HOFs increases slightly compared to the macro-only case, but these HOFs can be eliminated by applying a handover optimization technique. Contrary to the fact that it is said that we have to deal with frequent HOs and HOFs in small cell deployments, it is concluded that mobility issues have little impact on small cell deployments in HetNet environments.