  The efforts on the development, standardization and improvements to
communication systems towards 5G Advanced and 6G are on track to provide
benefits such as an unprecedented level of connectivity and performance,
enabling a diverse range of vertical services. The full integration of
non-terrestrial components into 6G plays a pivotal role in realizing this
paradigm shift towards ubiquitous communication and global coverage. However,
this integration into 6G brings forth a set of its own challenges, particularly
in Radio Access Technologies (RATs). To this end, this paper comprehensively
discusses those challenges at different levels of RATs and proposes the
corresponding potential emerging advancements in the realm of 6G NTN. In
particular, the focus is on advancing the prospective aspects of Radio Resource
Management (RRM), spectral coexistence in terrestrial and non-terrestrial
components and flexible waveform design solutions to combat the impediments.
This discussion with a specific focus on emerging advancements in 6G NTN RATs
is critical for shaping the next generation networks and potentially relevant
in contributing the part in standardization in forthcoming releases
