  We propose the idea of extended networks, which is constructed by replicating
the users in the two-user deterministic interference channel (DIC) and
designing the interference structure among them, such that any rate that can be
achieved by each user in the original network can also be achieved
simultaneously by all replicas of that user in the extended network. We
demonstrate that by carefully designing extended networks and applying the
generalized cut-set (GCS) bound to them, we can derive a tight converse for the
two-user DIC. Furthermore, we generalize our techniques to the three-user DIC,
and demonstrate that the proposed approach also results in deriving a tight
converse for the three-user DIC in the symmetric case.
