  An Intelligent IoT Environment (iIoTe) is comprised of heterogeneous devices
that can collaboratively execute semi-autonomous IoT applications, examples of
which include highly automated manufacturing cells or autonomously interacting
harvesting machines. Energy efficiency is key in such edge environments, since
they are often based on an infrastructure that consists of wireless and
battery-run devices, e.g., e-tractors, drones, Automated Guided Vehicle (AGV)s
and robots. The total energy consumption draws contributions from multipleiIoTe
technologies that enable edge computing and communication, distributed
learning, as well as distributed ledgers and smart contracts. This paper
provides a state-of-the-art overview of these technologies and illustrates
their functionality and performance, with special attention to the tradeoff
among resources, latency, privacy and energy consumption. Finally, the paper
provides a vision for integrating these enabling technologies in
energy-efficient iIoTe and a roadmap to address the open research challenges
