Joint femtocell clustering and selective beamforming for interference mitigation in heterogeneous networks

A joint femtocell clustering and selective beamforming scheme is proposed to mitigate the severe interference at femtocell base stations (FBSs) caused by the uplink transmissions of macrocell users (MUs) within the heterogeneous networks (HetNets). Firstly, a number of adjacent FBSs are clustered according to a low complexity location-aware scheme, while their serving femtocell users (FUs) and some strongly interfering MUs are also enclosed in the cluster to perform uplink transmission. It is noted that the proposed clustering scheme actually splits the coverage of the considered HetNets, and further coarsely confines the dominating interference sources within each cluster. Then, both beamforming at the in-cluster FUs and MUs are designed with a strategy to minimize the generated interference (MinGI) toward some selected interference-vulnerable FBS(s) within each cluster. By employing such low-complexity selective beamforming, the in-cluster interference is significantly mitigated. In general, the proposed joint scheme notes the heterogeneous distribution of strong interference sources within the HetNets, and effectively mitigates the overall interference in a divide-and-conquer fashion with emphasis. Numerical results show that the proposed scheme outperforms the state-of-the-arts.