Spectrum allocation and interference alignment for fractional frequency reuse based HetNets

In this paper, we focus on interference cancellation in multi-cell heterogeneous networks, where macrocells and femtocells coexist in the system and therefore incur significant interference. We propose an interference alignment(IA) scheme to support multi-macrocell heterogeneous networks(HetNets) with fractional frequency reuse(FFR). In order to let all the femtocells transmit simultaneously, we also propose a prioritized spectrum allocation scheme. The simulation results show that the proposed IA scheme can eliminate the interference for 3 macrocell, 3 femtocell system completely. Furthermore, combining the proposed IA scheme with the proposed spectrum allocation scheme will allow all the femtocells to transmit together and significantly increase the sum rate of HetNets.