Degrees of Freedom and Interference Mitigation for MIMO Interfering Broadcast Channels

We provide lower and upper bounds on the degree of freedom of B multiple-input multiple-output (MIMO) interfering broadcast channels where each base station equipped with M antennas supports its corresponding K users each equipped with M antennas. It is observed that both bounds coincide using interference alignment with symbol extension when B > max(M, KM)/min(M, KM) = K. Iterative interference leakage minimization algorithm is proposed for MIMO interfering broadcast channels, and the numerical results show that interference leakage minimization is not the tightest approximation to the notion of degree of freedom. Alternatively, we present two linear transceiver optimization algorithms with (1) Minimum weighted SINR maximization, and (2) Weighted sum rate maximization using weighted sum-MSE. These algorithms are designed based on the iterative joint optimization of transmit and receive beamforming vectors. Numerical results show that the proposed schemes exhibit the linear sum rate scaling with respect to SNR and performs better than interference leakage minimization algorithm.