  The stringent requirements of a 1,000 times increase in data traffic and one
millisecond round trip latency have made limiting the potentially tremendous
ensuing energy consumption one of the most challenging problems for the design
of the upcoming fifth-generation (5G) networks. To enable sustainable 5G
networks, new technologies have been proposed to improve the system energy
efficiency and alternative energy sources are introduced to reduce our
dependence on traditional fossil fuels. In particular, various 5G techniques
target the reduction of the energy consumption without sacrificing the
quality-of-service. Meanwhile, energy harvesting technologies, which enable
communication transceivers to harvest energy from various renewable resources
and ambient radio frequency signals for communi- cation, have drawn significant
interest from both academia and industry. In this article, we provide an
overview of the latest research on both green 5G techniques and energy
harvesting for communication. In addition, some technical challenges and
potential research topics for realizing sustainable green 5G networks are also
identified.
