On the degrees of freedom of partially-connected symmetrically-configured MIMO interference broadcast channels

In this paper, we study the degrees of freedom (DoF) of partially-connected symmetrically-configured multi-input-multi-output interference broadcast channel (MIMO-IBC) and the impact of partial connectivity on the DoF. We investigate the information theoretic maximal DoF and maximal DoF achieved by linear interference alignment (IA) for the symmetrically-connected symmetrically-configured MIMO-IBC, and prove that the DoF are achievable by asymptotic IA and linear IA for the asymmetrically-connected symmetrically-configured network when the maximal number of interfering cells seen at each BS and each user (denoted as the degrees of connectivity) is bounded. We find that for the symmetrically-connected symmetrically-configured MIMO-IBC, the maximal achievable DoF are independent of the number of total cells but depend on the degrees of connectivity. When the degrees of connectivity decrease, the maximal DoF achieved by linear IA are close to the information theoretic maximal DoF.