  Since Facebook was renamed Meta, a lot of attention, debate, and exploration
have intensified about what the Metaverse is, how it works, and the possible
ways to exploit it. It is anticipated that Metaverse will be a continuum of
rapidly emerging technologies, usecases, capabilities, and experiences that
will make it up for the next evolution of the Internet. Several researchers
have already surveyed the literature on artificial intelligence (AI) and
wireless communications in realizing the Metaverse. However, due to the rapid
emergence and continuous evolution of technologies, there is a need for a
comprehensive and in-depth survey of the role of AI, 6G, and the nexus of both
in realizing the immersive experiences of Metaverse. Therefore, in this survey,
we first introduce the background and ongoing progress in augmented reality
(AR), virtual reality (VR), mixed reality (MR) and spatial computing, followed
by the technical aspects of AI and 6G. Then, we survey the role of AI in the
Metaverse by reviewing the state-of-the-art in deep learning, computer vision,
and Edge AI to extract the requirements of 6G in Metaverse. Next, we
investigate the promising services of B5G/6G towards Metaverse, followed by
identifying the role of AI in 6G networks and 6G networks for AI in support of
Metaverse applications, and the need for sustainability in Metaverse. Finally,
we enlist the existing and potential applications, usecases, and projects to
highlight the importance of progress in the Metaverse. Moreover, in order to
provide potential research directions to researchers, we underline the
challenges, research gaps, and lessons learned identified from the literature
review of the aforementioned technologies.
