Regional Centralized Interference Alignment for Multi-cell Heterogeneous Networks

Aiming to mitigate interference and enhance the network capacity, we investigate the interference alignment (IA) for multiple-input-multiple-output (MIMO) multi-cell downlink in the two-layered heterogeneous networks (HetNet). In this paper, we propose a regional centralized IA algorithm (RCIA) by extending the grouping-based interference alignment (GIA) in single-layered network to our two-layered scenario. Furthermore, we design the two-cascade transmit beamforming matrices at macro base stations (MBS), so that interference from MBS to users can be mitigated. The receive beamforming matrices at pico users (PUEs) and macro users (MUEs) are obtained by using closed-form and distributed interference alignment algorithms respectively. Compared with the existing interference mitigation schemes, the proposed RCIA algorithm provides significantly higher spectrum efficiency.