On the Design of Interference Alignment Scheme for Two-Cell MIMO Interfering Broadcast Channels

The interference alignment (IA) is a promising technique to effectively mitigate interferences in wireless communication systems. To show the potential benefits of such an IA scheme, this letter focuses on a two-cell multiple-input multiple-output (MIMO) Gaussian interfering broadcast channels (MIMO-IFBC) with M transmit antennas and N receive antennas. It corresponds to a downlink scenario for cellular networks with two base stations (BSs) with M transmit antennas per BS, and two users with N receive antennas per user, on the cell-boundary of each BS. In this scenario, we propose a novel IA technique jointly designing transmit and receive beamforming vectors in a closed-form expression without iterative computation. It is also analytically shown that the proposed IA algorithm achieves the optimal degrees of freedom (DoF) of 2N in the case of [¾N] ≤ M <; 2N. The simulations demonstrate that not only the analytical results are valid, but the sum-rate of our proposed scheme also outperforms those of conventional techniques, especially in the high signal-to-noise ratio (SNR) regime.