  Non-Terrestrial Networks (NTNs) can be used to provide ubiquitous 5G and
beyond services to un(der)served areas. To ensure reliable communication in
such networks, packet duplication (PD) through multi-connectivity is a
promising solution. However, the existing PD schemes developed for terrestrial
environments may not be reactive enough for the NTN environment where
propagation delays are significantly longer. This paper proposes a dynamic PD
activation scheme for NTNs based on hybrid automatic repeat request feedback.
The scheme aims to reduce the number of duplicated packets while maintaining
high reliability. To evaluate the proposed scheme, simulations are conducted in
a scenario with two transparent payload lowearth orbit satellites. The results
show a significant reduction of 87.2% in the number of duplicated packets
compared to blind duplication, with only marginal compromise in reliability.
