Downlink Interference Analysis in LTE-Femtocell Networks

Aiming to cope up with relentless wireless traffic and improving link quality against high wall penetration loss, Third Generation Partnership Project proposed the heterogeneous deployment of low power indoor hot spots such as Femtocell Access Points (FAPs) over the existing cellular network topology. In this two-tier heterogeneous network (HetNet) where femtocells coexist with macrocell, the FAPs may spatially reuse the spectrum assigned to macrocell base station in an unplanned way and the mitigation of the generated co-channel interference becomes a major challenge. The problem is more severe with FAPs operating in a closed access mode, particularly in urban and sub-urban environment. In this work, the impact of interference in downlink on quality of service to macro user and femto user is analyzed by modeling the Signal-to-Interference and Noise Ratio and achieved user throughput. Simulation results show significant reduction of achieved user throughput and creation of coverage holes because of interference. It is clear that the performance of restricted access FAPs under co-channel operation need to be explicitly accounted for and optimized against both cross-tier and co-tier interference.