Self-optimization of coverage for Femtocell Deployments

In femtocell deployments, leakage of the pilot signal to the outside of a house can result in a highly increased signalling load to the core network as a result of the increased number of handovers caused by passing users. This effect can be reduced by reducing the pilot power, however this could lead to insufficient indoor coverage, which also causes an increase in handovers. In this paper, coverage adaptation is proposed for femtocell deployments that use information on handover events of passing and indoor users to optimize the femtocell coverage in order to minimize the increase of core network mobility signalling. Different coverage adaptation methods are discussed and it is shown that handover based self-optimization of coverage can significantly outperform simpler methods that aim to achieve a constant cell radius.