Joint Interference Alignment and Avoidance for Downlink Heterogeneous Networks

In this letter, a two-stage interference alignment (IA) scheme and a link scheduling scheme are proposed to cooperatively address both the cross-tier and co-tier interference for downlink heterogeneous networks (HetNets). The two-stage IA enables more small cells to transmit simultaneously by exploiting the characteristics of HetNets and the sacrificed signal dimensions of conventional IA. Then we propose a link scheduling scheme to address the interference that cannot be solved by the two-stage IA. Link scheduling is responsible for choosing the small cell links that can simultaneously transmit by using the two-stage IA and scheduling interfering small cell links to different time slots to avoid interference. Link scheduling is designed with the aims to minimize the number of time slots needed to schedule all links and then maximize the number of scheduled links in these time slots. The simulation results show that the proposed scheme can significantly increase the sum rate of HetNets.