  The Internet of Things (IoT) is seen as a novel technical paradigm aimed at
enabling connectivity between billions of interconnected devices all around the
world. This IoT is being served in various domains, such as smart healthcare,
traffic surveillance, smart homes, smart cities, and various industries. IoT's
main functionality includes sensing the surrounding environment, collecting
data from the surrounding, and transmitting those data to the remote data
centers or the cloud. This sharing of vast volumes of data between billions of
IoT devices generates a large energy demand and increases energy wastage in the
form of heat. The Green IoT envisages reducing the energy consumption of IoT
devices and keeping the environment safe and clean. Inspired by achieving a
sustainable next-generation IoT ecosystem and guiding us toward making a
healthy green planet, we first offer an overview of Green IoT (GIoT), and then
the challenges and the future directions regarding the GIoT are presented in
our study.
