Direct-to-Satellite NB-IoT: the Contention-Based Early Data Transmission Advantage

Abstract

Direct-to-satellite narrowband Internet of Things (NB-IoT) is a prominent use case in non-terrestrial network (NTN) communications, rapidly approaching commercialization. The scalability of these systems relies heavily on the access procedures implemented by user equipments. While standardized access protocols perform well in terrestrial networks, their efficiency in NTN environments supporting massive machine-type communications remains uncertain. In this work, we analyze the latest access procedure features introduced in the 3GPP standard for IoT-NTN, specifically contention-based early data transmission (CB-EDT) in Release-19. We compare the solution with legacy procedures to assess its potential for future deployments. The results highlight substantial advantages when implementing CB-EDT in terms of energy savings, access completion time, and spectral efficiency, making it an optimal candidate for future massive IoT satellite deployments.