On the Degrees of Freedom of Interference Broadcast Channels With Topological Interference Management

Topological interference management is the study of achievable rates within communication networks with no channel state information at the transmitter (CSIT) beyond knowledge of the network structure itself. In this work, we study the degrees of freedom (DoF) of a two-cell two-user-per-cell interference broadcast channel (IBC) with alternating connectivity and global topological interference management. The topological information allows transmitters to track the changing network topology and exploit the varying connectivity states to achieve a DoF gain. We derive novel DoF outer bounds for the two-cell two-user-per-cell IBC with alternating connectivity. This analysis is carried out for different system configurations, namely, single-input single-output (SISO), multiple-input single-output (MISO), and multiple-input multiple-output (MIMO) systems. While global channel knowledge is always restricted to topological information only, we introduce a mixed CSIT setting where varying degrees of local CSIT availability are considered depending on the system configuration. Additionally, we investigate the achievability of the derived bounds and propose new transmission schemes based on joint coding across states. Results show that DoF higher than those conventionally obtained without global topological information are achievable, indicating that even such a minimal level of global CSIT is still highly useful.