Mobility and Capacity Offload for 3G UMTS Femtocells

Femtocells are low-power cellular base stations that are typically deployed indoors in residential, enterprise or hotspots settings. Femtocell deployments provide excellent user experience through better coverage for voice and very high data throughputs. In this paper, we focus on 3G UMTS femtocells and analyze the impact of femtocells on idle-mode mobility and UE battery life. Detailed dynamic simulations are presented to quantify the impact of femtocells on the number of cell searches, cell reselections and location area updates for both femtocell users and macro users. It is shown that femtocells reduce the number of intra-frequency and inter-frequency searches for femtocell users while increasing the number of searches for macro users. In addition, methods for facilitating capacity offload to femtocells are presented. In particular, cell reselection parameter optimization, use of beacons and enhancements of UE search algorithms are described as possible methods for facilitating capacity offload to femtocells. The tradeoffs between capacity offload and UE battery life are also evaluated.