Full-duplex communication via adaptive nulling

Simultaneous communication in the same frequency band is gaining interest as an approach to increasing spectral efficiency. This functionality is usually prevented by the close proximity of the transmit and receive antennas, resulting in interference at, or saturation of, the receiver electronics. Furthermore, it is of interest to minimize complexity of mobile units; a worst case is to assume that the mobile units are unable to cooperate in the channel estimation and beamforming processes. In this paper, we develop an uncooperative wide-band MIMO adaptive channel estimation and nulling approach for simultaneous transmit and receive on the same channel. Low-power training waveforms are used to estimate the time-varying MIMO interference channel. Transmit beamforming weights that span the null space of the interference channel are then calculated via an algebraic approach. Results are reported, which show null depths at the receive antennas of greater than 40dB in simulation and 30dB in a slow-update wide-band experiment.