A signal-space analysis of spatial self-interference isolation for full-duplex wireless

The challenge of full-duplex wireless communication is self-interference received directly from the transmit antennas and backscattered from nearby objects. Spatial isolation of the receive antennas from the transmit antennas can mitigate self-interference, but may cause the spatial resources of the channel to be under-utilized, sacrificing spatial multiplexing performance. We present an analysis of spatial isolation of self-interference for full-duplex base stations, which leverages the antenna-theory based channel model of Poon et. al.We characterize the scattering conditions under which spatial isolation can enable a degrees-of-freedom gain over half-duplex, and show that the gain is inversely proportional to the overlap between the backscattering intervals (set angles of departure/arrival of backscattered self-interference), and the forward scattering intervals (set of angles of departure/arrival to/from the intended users).