Analysis of Spectral Efficiency and Management of Cross-Tier Interference in Femtocell Network

Femtocell is on the way of being extensively deployed in households to provide better indoor coverage and higher user capacity. However, as the coverage of femtocell is overlapped with that of conventional macrocell, the cross-tier interference may result in a considerable degradation of system performance in terms of spectral efficiency. This paper focuses on the improvement of cell spectral efficiency in two-tier network. We first derive the explicit expressions of cell spectral efficiency and average spectral efficiency of single user in each tier. Some remarks and observations are provided after analyzing numerical results of the expressions. Then based on the theoretical analysis, we propose a dynamic cross-tier interference coordination (D-CTIC) scheme. D-CTIC can provide high cell spectral efficiency by maximizing the number of coexistent femtocell base stations (FBSs) with macrocell base station (MBS) while still satisfying the QoS requirement of macrocell user (MUE) by restricting cross-tier interference under an acceptable level. Finally, simulation results verify the theoretical analysis and show that D-CTIC can enhance cell spectral efficiency significantly.