Interference Alignment for Heterogeneous Full-duplex Cellular Networks

In this paper, we consider a heterogeneous network composed of a full-duplex macrocell and a half-duplex femtocell. The macro-base station (BS) is equipped with L antennas where each antenna can be utilized either for downlink transmission or uplink reception. On the other hand, the femto-BS is equipped with M antennas that are used for downlink transmission. We assume that each user equipment has N antennas where L > M >= N. We investigate the benefit of using interference alignment for cross-tier and full-duplex interference management and present precoding schemes that are capable of achieving the total degrees of freedom of the network. We show that full-duplex operation of the macro-BS improves the degrees of freedom (DoF) of the system when M < 2N, otherwise half-duplex operation is optimal. Furthermore, the DoF of the system can be improved by 50% via full-duplex macro-BS operation when M=N.