Degrees of Freedom of Full-Duplex Multiantenna Cellular Networks

We study the degrees of freedom (DoF) of cellular networks in which a full duplex (FD) base station (BS) equipped with multiple transmit and receive antennas communicates with multiple mobile users. We consider two different scenarios. In the first scenario, we study the case when half duplex (HD) users, partitioned to either the uplink (UL) set or the downlink (DL) set, simultaneously communicate with the FD BS. In the second scenario, we study the case when FD users simultaneously communicate UL and DL data with the FD BS. For both network models, we completely characterize the sum DoFs by developing achievable schemes and obtaining matching upper bounds. The key idea of the proposed scheme is to carefully allocate UL and DL information streams using interference alignment and beamforming techniques. As a consequence of the result, we show that the DoF can approach the two-fold gain over the HD systems when the number of users becomes large enough as compared to the number of antennas at the BS.