  In this paper, the energy efficiency of edge computing platforms for IoT
networks connected to a passive optical network (PON) is investigated. We have
developed a mixed integer linear programming (MILP) optimization model, which
optimizes the placement and number of the cloudlets and VMs and utilizes energy
efficient routes with the objective of minimizing the total IoT network and
processing power consumption. Our results show that the power consumption can
be reduced by consolidating the placement of these VMs at the PON Optical Line
Terminal (OLT) in cases where the traffic volume is still high after data
processing, ie at low traffic reduction percentages. On the other hand, at high
traffic reduction ratios, better power efficiency can be accomplished by
placing VMs in lower layer nodes (relays). Our results indicate that utilizing
PONs and serving heterogeneous VMs can save up to 19% of the total power. Based
on the MILP model insights, a heuristic is developed with very comparable
MILP-heuristic power consumption values. We considered three scenarios that
represent different levels of homogeneous and heterogeneous VM CPU demands.
Good agreement was observed between the heuristic results (17% power saving)
and the MILP which results in 19% power saving.
