On Degrees of Freedom of the Cognitive MIMO Two-Interfering Multiple-Access Channels

This paper characterizes the exact spatial Degrees of Freedom (DoF) region of the two-user multiple-input–multiple-output two-interfering multiple-access channels (2-IMACs), which models the uplink transmission in cellular networks, for three scenarios. The first scenario is the 2-IMAC without cognition, for which the achievability is generalized for more than two transmitters in each multiple-access channel. The two-user 2-IMACs' DoF regions are also derived for two different genie-aided cognition scenarios. Here, zero forcing by transmitters and interference alignment are studied in a network with more than two transmitters, whereas previous works dealt with two-transmitter networks. We also perform a comparative analysis on the DoF of the three scenarios.