Interference reduction between SDD linear array antennas using end-fire arrangement

Experimental evaluation of interference reduction effect; Eigen-beamforming and digital subtraction by using MIMO-OFDM signals

“…This letter experimentally evaluates the interference cancellation performance of the method proposed in [7] by using real MIMO-OFDM signals. A signal frame-format is newly developed for this experiment, and the total performance of the self-interference reduction method including digital subtraction technique is investigated, where the remaining interference caused by the saturation of the RF frontend and imperfection of the antenna arrangement is evaluated.…”

“…Note that these methods cannot be directly applied to MIMO systems because the interference among all combinations of transmitting and receiving antennas must be considered and implementation is difficult. To resolve this problem, eigen-beamforming using linear array antennas in the end-fire arrangement was proposed for self-interference reduction in the MIMO full-duplex system [7]. This method offers very high interference reduction with the consumption of only one degree-of-freedom of the antenna array; this antenna arrangement degenerates the rank of the interference channel to 1.…”

“…Therefore, the self-interference needs to be suppressed before the RF front-end at the receiver. To combat this, three methods have been studied [5,6,7]. Antenna cancellation uses an additional transmitting antenna to form a null point at the receiving antenna [5].…”

Rotationally-symmetrical array for self-interference reduction in full-duplex MIMO

“…This is capable of multiple-input multiple-output (MIMO) transmission; however, it wastes many degrees of freedom (DoFs) for MIMO transmission because of making cancellation signals. To this end, the authors have proposed a combination technique of an end-fire array (EFA) and eigen-nullsteering, which reduces the interference by up to 75.2 dB while consuming only one DoF [5]. Since this technique relies on the characteristics of interference channel degenerated by the EFA, the defect in a rank-degeneracy causes a limited interference reduction performance because amplitude differences among the paths increase the rank of the channel.…”

“…Since this technique relies on the characteristics of interference channel degenerated by the EFA, the defect in a rank-degeneracy causes a limited interference reduction performance because amplitude differences among the paths increase the rank of the channel. In this letter, the authors propose a rotationallysymmetrical array (RSA) for [5]'s scenario, where geometrical symmetry of paths achieves a perfectly one-ranked channel and suppresses all of the self-interference in theory. A principle of the proposed technique is discussed; its interference reduction performance is calculated and compared with that of the EFA in order to clarify an effect of the symmetrical approach on the scenario.…”