On Degrees-of-Freedom of Multi-User MIMO Full-Duplex Network

When a multi-antenna (MIMO) base-station operates in full-duplex mode, multiple uplink and downlink streams can be supported simultaneously in the same frequency band. However, the inter-mobile interference from uplink streams to the downlink streams can limit the system performance. In this paper, we first characterize the degrees-of-freedom of a multiuser MIMO (MU-MIMO) full-duplex network with half-duplex mobile clients, and derive the regimes where the inter-mobile interference can be mitigated to yield significant gains over the half-duplex counterpart. The achievability is based on interference alignment and requires full channel-state information at the transmitter (CSIT). Next, we study the case with partial CSIT where only the base-station acquires downlink channel values to avoid collecting network-wide CSIT at all transmitters in the system. We show that the key to achieving the sum degrees-of-freedom upper bound with only partial CSIT is the ability of the base-station to switch antenna modes that can be realized via reconfigurable antennas.