  We study the problem of associating mobile terminals to base stations in a
linear interference network, with the goal of maximizing the average rate
achieved over both the uplink and downlink sessions. The cell association
decision is made at a centralized cloud level, with access to global network
topology information. More specifically, given the constraint that each mobile
terminal can be associated to a maximum of N base stations at once, we
characterize the maximum achievable pre-log factor (degrees of freedom) and the
corresponding cell association pattern. Interestingly, the result indicates
that for the case where N > 1, the optimal cell association guarantees the
achievability of the maximum uplink rate even when optimizing for the uplink
alone, and for the case where N=1, the optimal cell association is that of the
downlink. Hence, this work draws attention to the question of characterizing
network topologies for which the problem can be simplified by optimizing only
for the uplink or only for the downlink.
