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 higher number of mobility events caused by passing users. This effect can be minimized by reducing the pilot power. However this approach could lead to insufficient indoor coverage, which also causes an increase in mobility events. In this paper, coverage adaptation is proposed for femtocell deployments that uses information on mobility events of passing and indoor users to optimize the femtocell coverage in order to minimize the increase in core network mobility signalling. Different coverage adaptation methods are discussed and it is shown that the proposed mobility event based self-optimization can significantly outperform simpler methods that aim to achieve a constant cell radius.