Introduction
Femtocell is a miniature basestation no larger than any DSL or WiFi access point. It is classified as the smallest basesetation available today following the Macrocell, Microcell and Picocell that have been deployed for many years. Back in the 2G and early 3G era, where voice communication is the main service category of a cellular network, the system capacity is not the greatest concern for the operators comparing to the coverage. Operators’ focus then has been on improving the signal coverage. There are many signal coverage enhancement techniques that were more cost affective than femtocell, for example: RF signal relay/booster and distributed antenna.
Hierarchical cell structure
Traditionally, due to the high cost associated with the acquisition of a suitable cell site, the installation of a basestation and the need for dedicated connections from the central office to the cell site, sectorization is used to achieve the same effect as adding new basestations. Sectorization of a cell means each cell site is (typically) divided into three sectors each overlooks one-third of the circumference. Another technique that has been thoroughly studied over the last decode is the adaptive beamforming. It is not widely adopted due to complexity and the need for multiple RF components.
Femtocell, recently, has surfaced as one of the most promising technologies that can improve the coverage and increase the capacity at the same time. The proliferation of broadband access and the explosion of the mobile Internet devices create the strong demand for femtocell.
Iu-h network architecture
For 3G femtocell, A new network element called femtocell gateway (FGW) is introduced between the core-network and the femtocell access point (FAP).
The purpose of the FGW is to handle the large amount of signalling traffic coming from thousands of FAPs in the field that might otherwise paralyze the core-network if allowed to connect to it directly. The interface between the FAP and FGW is the Iu-h interface.