  We study in this paper optimal control strategy for Advanced Sleep Modes
(ASM) in 5G networks. ASM correspond to different levels of sleep modes ranging
from deactivation of some components of the base station for several
micro-seconds to switching off of almost all of them for one second or more.
ASMs are made possible in 5G networks thanks to the definition of so-called
lean carrier radio access which allows for configurable signaling
periodicities. We model such a system using Markov Decision Processes (MDP) and
find optimal sleep policy in terms of a trade-off between saved power
consumption versus additional incurred delay for user traffic which has to wait
for the network components to be woken-up and serve it. Eventually, for the
system not to oscillate between sleep levels, we add a switching component in
the cost function and show its impact on the energy reduction versus delay
trade-off.
