  Smart services based on Internet of everything (IoE) are prophesied to reap
notable attention by both academia and industry in the future. Although
fifth-generation (5G) is a promising communication technology, however it
cannot fulfill complete demands of novel applications. Sixth-generation (6G)
technology is envisaged to overcome limitations of 5G technology. The vision
and planning of future 6G network has been started with this aim to meet the
stringent requirements of mobile communication. Our aim is to explore recent
advances and potential challenges to enable 6G technology in this review. We
have devised a taxonomy based on computing technologies, networking
technologies, communication technologies, use cases, machine learning
algorithms and key enabler technologies. In this regard, we subsequently
highlight potential features and key areas of 6G. Key technological
breakthroughs which include quantum communication, tactile communication,
holographic communication, terahertz communication, visible light communication
(VLC) Internet of Bio Nano Things, which can put profound impact on wireless
communication, have been elaborated at length in this review. In this review,
our prime focus is to discuss potential enabling technologies which can develop
seamless and sustainable network, encompassing symbiotic radio, blockchain, new
communication paradigm, VLC and terahertz. In addition, we have investigated
open research challenges which can hamper the performance of 6G network.
Finally, we have outlined several practical considerations, 6G key projects and
future directions. We envision 6G undergoing unprecedented breakthroughs to
eliminate technical uncertainties and provide enlightening research directions
for subsequent future studies. Although it is impossible to envisage complete
details of 6G, we believe this study will pave the way for future research
work.
