Joint Interference Alignment and Power Allocation in Heterogeneous Networks

In the open subscriber group (OSG) mode of heterogeneous network (HetNet), the inter macro-user interference is the main interference to macro user equipments (UEs), and the inter cell interference (ICI), containing the inter picocell interference and the cross-layer interference from macro base station (BS), is the main interference to pico UEs. In this paper, we propose an interference alignment (IA) scheme for such HetNet. The transceiver is designed as follows. Firstly, the precoding matrix for macro BS and the interference suppression matrices for macro UEs are used to eliminate the inter macro-user interference. Secondly, the precoding matrices of pico BSs are designed to align the inter picocell interference onto the space of the strongest cross-layer interference produced by macro BS. Finally, the aligned interference is removed by the interference suppression matrices of pico UEs. In addition, we introduce a power allocation scheme for the macro BS to further reduce the interference to pico UEs. The simulation results and the complexity analysis show that the proposed scheme can reduce the requirement of the receive antennas number and improve the system throughput of HetNet with lower complexity.