Empowering User Capabilities via Non-Orthogonal Multiple Access in 3GPP Non-Terrestrial Networks

In this paper, we propose a novel technique for enhancing the initial access capacity of users in a 3GPP non-terrestrial network (NTN) by utilizing the non-orthogonal multiple access (NOMA) technique. The conventional initial access scheme standardized in 3GPP LTE or NR employs a contention-based approach, leading to frequent collisions among preambles transmitted by users in the 5G NTN. To overcome the drawbacks of the conventional approach and to enhance the user's initial access capacity in the future 6G NTN, we incorporate the NOMA scheme into the conventional initial access scheme. More specifically, we apply the NOMA scheme to Msg3 of the initial access procedure, thereby significantly reducing the collision probability. Simulation results verify the validity of our proposed scheme, and we also present potential directions for future research.