On the trade-off between handover failure and small cell utilization in heterogeneous networks

To enhance the performance of a heterogeneous network, where many small cells are deployed in a macro cell, we consider two technical challenges. First, seamless handover between the same or different types of cells should be supported with a low handover failure rate. Second, small cells should use their radio resources as much as possible to maximize a cell splitting gain. It was well known that there is a trade-off between the low handover failure rate and the high small cell utilization. To find a better operation considering such a trade-off, we propose a state-dependent handover decision algorithm. In the proposed scheme, a user sets a “state” for each small cell, and performs a “state transition” to distinguish between macro-to-small and small-to-macro handovers, and then uses suitable handover parameters for each handover type. Through simulation, we observe that the proposed scheme can reduce the handover failure rate significantly without degrading the small cell utilization and the throughput experienced by the user.