Optimal Antenna Arrangement for Self-Interference Cancellation in Short-Range Full-Duplex MIMO

A self-interference cancellation (SIC) method is presented for short-range full-duplex multiple-input-multiple-output (MIMO) communication. The proposed SIC consists of the following steps. First, each peer has multiple transmitting (Tx) and receiving (Rx) antennas optimally arranged to form a one-rank self-interference (SI) matrix between Tx and Rx. The optimal antenna arrangement is derived using a geometric model. Second, null steering is performed by eigenmode beamforming excluding the primary eigenmode of the SI matrix. This realizes powerful SIC at the cost of processing just a single degree of freedom. The effectiveness of the proposed SIC is evaluated by electromagnetic simulations. The results confirm that it reduces the SI level by 22.76 dB. In addition, it is shown the proposal offers achievable rates 1.50 times those of the half-duplex scheme in line-of-sight (LOS).