It has to preserve cell-splitting gains, in particular with the constraint of low power BSs.
The limitation caused by interference in such network has
to be carefully handled, and the techniques for interference
handling have to be adapted for the particular case of mmWave
channels. In addition, the users and BSs association in such
heterogeneous multi-RAT network has to be finely optimized,
using performance concepts such as game theory and models
for mobility support such as virtual cells. Needless to say
that the deployment of such dense network, with many small
low power BSs, involve a relatively high cost for installation,
maintenance and backhaul.