New Feedback Topology Designs with Reduced CSI Overhead for MIMO Interference Alignment

This letter studies feedback topologies for interference alignment (IA) in a multiple-input multiple-output (MIMO) K-user interference channel with M = (K - 1)d antennas at each node, where d is the number of data streams per user. Under this antenna configuration, Cho et al. propose two two-hop centralized feedback topologies, as well as a channel state information (CSI) exchange structure which requires 2(K - 1) time slots to compute IA precoders. In order to reduce the CSI overhead or shorten the time delay for the existing feedback topologies, we propose three new ones: 1) a two-hop distributed one with reduced CSI overhead; 2) a modified CSI-exchange topology that has the same CSI overhead but shortened delay compared to its existing counterpart; and 3) a four-hop novel one with smaller CSI overhead rather than that of the conventional CSI-exchange topology.