Achievable spatial degrees of freedom for the MIMO interference channel with local CSIT

This paper discusses spatial degrees of freedom(DoFs) characterizations and achievable schemes for the 3-user symmetric MIMO interference channel without channel extensions over time and frequency dimensions. It is assumed that only the local channel state information (CSI) is available at the transmitters. We provide a constructive proof of achievability on the total spatial DoFs based on interference zero forcing for the 3-user MIMO interference channel. The DoFs and achievable scheme are presented by comparing the number of equations and the number of variables for 3-user interference channel with specific antenna configuration. Then we apply interference zero forcing scheme and signal subspace analysis approach to generalize the idea of interference management for this special case to the common 3-user symmetric MIMO interference channel and establish that the total spatial Dofs min(3 min(M_t, N_r), max(M_t, N_r)) is achievable in 3-user M_t ×N_r symmetric MIMO interference channel when only local CSI is available at each transmitter.