  The impact of information and communication technologies on global energy
consumption is increasing every year, and mobile networks account for a
significant portion of it. More than 50% of the total energy consumption of
mobile networks is issued from radio access networks (RANs), due mainly to the
rapid penetration of data-intensive applications and the increasing
heterogeneity, dynamicity, and unpredictability of traffic. To tackle these
high-demanding problems, RAN densification through the installation of
additional base stations in high-demand areas is conventionally used. However,
this leads to inefficient energy use and over-provisioning issues. In this
context, high altitude platform stations (HAPS) may be used to complement RANs
and sustain their services in densely populated areas, where traffic can peak
unpredictably. Due to their wide coverage areas, substantial communication
payloads, and green energy model, HAPS super macro base stations (SMBSs) are
capable of handling the massive and dynamic mobile data traffic of ground
users. In this paper, we show how HAPS-SMBSs can complement RANs and serve the
dynamic and unpredictable traffic demands of users in an energy-efficient
manner. Through the simulation of a case study, we demonstrate the performance
of a HAPS-SMBS compared to the conventional RAN densification method and
analyze the two approaches in terms of sustainability.
