A Study on Interference Mitigation Framework Based on Interference Alignment for Femtocell-Macrocell Two Tier Cellular Systems

摘要

Femtocells have been considered as a promising technology to provide better indoor coverage and spatial reuse gains in the last few years. Additionally, it can be employed in mobile data offloading scenarios in order to decrease the overburden increasing traffic carried by ordinary macrocell basestations (MBSs). Unfortunately, the interference in such two tier cellular systems represent a great technical challenge that must be avoided. In this paper, we propose an interference mitigation approach that models the femtocell-macrocell two tier cellular system as a cognitive radio (CR) system, where spectrum resources of two systems are efficiently shared without affecting each other's operation. In addition, we propose a restricted waterfilling algorithm that makes the MBS to release part of its eigenmodes to its associated femtocell basestations (FBSs) to do their transmissions even at high signal to noise power ratio regimes. The simulation results show that the proposed approach provides an improved sum rate for the femtocell users compared to the conventional interference alignment techniques, like, the leakage minimization approach and the nuclear norm based rank constraint rank minimization approach.