Analysis of handover failures in LTE femtocell systems

In this paper, we evaluate handover (HO) performance when user equipment (UE) moves between femto cell and macro cell in long term evolution (LTE) systems. The focus is on the HO performance for inbound and outbound mobility which corresponds to handoff between the femtocell and the macro cell. Due to the severe signal-to-interference noise ratio (SINR) degradation near the edge area of femtocell, HO triggering for inbound and outbound mobility needs to be carefully selected than that of the macro cell. Too late HO triggering leads to radio link failures (RLF), whereas too early HO triggering causes ping-pong HO. In this paper, we take the neighbouring cell configurations into account to keep the allowable RLF rate and low ping-pong rates. We propose a cell-types adaptive handover margins algorithm, which assigns different handover margins in line with neighbouring cell types. Simulation results indicate that the low ping-pong rate and the low RLF rate are achieved simultaneously by using the proposed algorithm.