Average interference analysis in two-tier wireless networks

The two-tier wireless network comprising a conventional cellular network overlaid with femtocells is considered as an economical network configuration to provide high quality indoor coverage. However, the cross-tier interference induced by femtocells will cause significant performance degradations to cellular users. In this paper, the closed-form expressions of the average cross-tier interference powers are derived, with the spacial distributions of home eNodeBs (HeNBs) and home user equipments (HUEs) modeled as a homogeneous spatial poisson point processes (SPPP). Considering the receiver sensitivity degradations of macro eNodeBs (MeNBs) and macro user equipments (MUEs), the acceptable cross-tier interference power can be obtained. Combining the acceptable power and the closed-form expressions of the average cross-tier interference, the constraints on the femto-tier configurations are given in terms of the transmit power and the density of femtocells as well as the required minimum distance between the aggressor and the victim. Analytical results of the required minimum distances between MUEs (resp. MeNBs) and HeNBs (resp. HUEs) are calculated when the transmit power and the density of femtocells are fixed. At last, simulation results validate our analysis.