  Interest in the integration of Terrestrial Networks (TN) and Non-Terrestrial
Networks (NTN); primarily satellites; has been rekindled due to the potential
of NTN to provide ubiquitous coverage. Especially with the peculiar and
flexible physical layer properties of 5G-NR, now direct access to 5G services
through satellites could become possible. However, the large Round-Trip Delays
(RTD) in NTNs require a re-evaluation of the design of RLC and PDCP layers
timers ( and associated buffers), in particular for the regenerative payload
satellites which have limited computational resources, and hence need to be
optimally utilized. Our aim in this work is to initiate a new line of research
for emerging NTNs with limited resources from a higher-layer perspective. To
this end, we propose a novel and efficient method for optimally designing the
RLC and PDCP layers' buffers and timers without the need for intensive
computations. This approach is relevant for low-cost satellites, which have
limited computational and energy resources. The simulation results show that
the proposed methods can significantly improve the performance in terms of
resource utilization and delays.
