Femtocell Coverage Optimization Using Switched Multi-Element Antennas

Femtocells are low-cost, low-power cellular base stations that are deployed by the end user to supplement macro-cellular coverage and provide high data rates in the customer´s premises. 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. In this paper, a low cost multi-element antenna solution is proposed to reduce the core network mobility signalling over previously published results using a single antenna only. Antenna gain pattern measurements of a prototype with two patches and two inverted F antennas are presented and a corresponding feeder network is discussed. Self-optimization methods are proposed that jointly select an appropriate antenna pattern and optimize the pilot power. This allows to better match the femtocell coverage to the shape of each individual house and results in an improvement of both indoor coverage and core network signalling resulting from mobility events.