  This paper first studies the homogeneous 3-user 2x1 broadcast channel (BC)
with no CSIT. We show a sufficient condition for it to achieve the optimal 3/2
degrees of freedom (DoF) by using Blind Interference Alignment (BIA). BIA
refers to the interference alignment method without the need of CSIT. It
further studies the 2x1 broadcast network in which there are K>=3 homogeneous
single-antenna users, and their coherence time offsets are independently and
uniformly distributed. We show that, if K>=11, the two-antenna transmitter can
find, with more than 95% certainty, three users to form a BIA-feasible 3-user
BC and achieve the optimal 3/2 DoF.
