Relay-aided interference alignment for multiple partially connected subnetworks

In this paper, large partially connected wireless relay interference networks are considered. The entire network is made up of multiple disjoint groups of source-destination node pairs and relays called subnetworks. Each subnetwork is assumed to be fully connected. The different subnetworks are mutually connected by a few inter-subnetwork links. A two-hop relay-aided interference alignment scheme is applied to achieve interference-free communication in the whole network. The feasibility conditions for interference alignment in the considered networks are investigated. To this end, we extend the concept of external constraints, which was proposed in [1] for the two-subnetwork case, and characterize the proper relay antenna configurations in large networks with an arbitrary number of subnetworks.