  The logical separation of control signaling from data transmission in a
mobile cellular network has been shown to have significant energy saving
potential compared with the legacy systems. As a result, there has been a lot
of focus in recent years on development and realization of separation
architectures. Our study, however, shows that the energy savings of separation
architecture remain under 16-17% when compared with legacy systems and this
gain falls to a mere 7% when both architectures are realized under a CloudRAN
(CRAN) setting. Moreover, when we strategically place some small base-stations
(SBSs) to cover the area in a densely deployed scenario and allow all other
base-stations (BSs) to be used only on-demand, the system consumes much less
energy than the separation architecture. While we expected that most equipment
would be shut down during nights, our study shows that around 70% of the small
cells are required to be active to serve randomly distributed minimum data
load, i.e., active mobile equipment. Contemporary mobile traffic is
predominantly data which does not go to extremely low levels during nights. We
discuss, in detail, the assumptions, their implications, and the effects of
system parameter values on our conclusions.
