A Hybrid Interference Alignment Scheme in Two-tiered MIMO Heterogeneous Network

Interference alignment (IA) is thought to be an effective technique on reducing interference in wireless communications. To mitigate the interference and improve the system performance, this paper proposes a two-stage hybrid interference alignment (THIA) scheme for the two-tiered multi-user multiple-input-multiple-output (MIMO) heterogeneous network (HetNet). Specifically, we focus on the downlink transmission of two-tiered HetNet. Firstly, we align the cross-tier interference from macro base station (MBS) to the users in the same small cell to a specific subspace, through which the first-stage transmit beamforming matrix at MBS is designed. Then, an equivalent virtual distributed method is applied to mitigate the co-tier interference among macro users. Numerical results demonstrate that the proposed THDIA scheme outperforms the conventional schemes in degrees of freedom and system sum rate.