  A network consisting of a point-to-point (P2P) link and a multiple access
channel (MAC) sharing the same medium is considered. The resulting interference
network, with three transmitters and two receivers is studied from degrees of
freedom (DoF) perspective, with and without cognition. Several cognition
variants are examined. Namely, the setup is studied with (1) no cognitive
transmitters, (2) a cognitive P2P transmitter, (3) one cognitive MAC
transmitter, and (4) with two cognitive MAC transmitters. It is shown that
having a cognitive P2P transmitter does not bring any DoF gain to the network.
This is obtained by showing that the DoF of the two former cases (1) and (2) is
1. However, it is shown that a cognitive MAC transmitter is more beneficial
since the latter two cases (3) and (4) have 3/2 DoF. The achievability of 3/2
DoF is guaranteed by using a combination of interference neutralization and
interference alignment.
