  In a multi-input multi-output (MIMO) full-duplex network, where an in-band
full-duplex infrastruc- ture node communicates with two half-duplex mobiles
supporting simultaneous up- and downlink flows, the inter-mobile interference
between the up- and downlink mobiles limits the system performance. We study
the impact of leveraging an out-of-band side-channel between mobiles in such
network under different channel models. For time-invariant channels, we aim to
characterize the generalized degrees- of-freedom (GDoF) of the side-channel
assisted MIMO full-duplex network. For slow-fading channels, we focus on the
diversity-multiplexing tradeoff (DMT) of the system with various assumptions as
to the availability of channel state information at the transmitter (CSIT). The
key to the optimal performance is a vector bin-and-cancel strategy leveraging
Han-Kobayashi message splitting, which is shown to achieve the system capacity
region to within a constant bit. We quantify how the side-channel improve the
GDoF and DMT compared to a system without the extra orthogonal spectrum. The
insights gained from our analysis reveal: i) the tradeoff between spatial
resources from multiple antennas at different nodes and spectral resources of
the side-channel, and ii) the interplay between the channel uncertainty at the
transmitter and use of the side-channel.
