Satellite Direct-to-Device and Direct-to-Cell Technology for Broadband Connectivity From Satellite to IMT-UE: A Systematic Literature Review

Abstract

This Systematic Literature Review (SLR) examines the technical challenges and proposes solutions for implementing Satellite Direct-to-Device (DS2D) communication systems in non-terrestrial networks (NTNs), addressing two central research questions concerning technological challenges and existing approaches. Through a critical analysis of a corpus of works selected using a rigorous methodology, this review covers key themes such as developing an appropriate link budget, spectrum management and dynamic radio resource sharing, interference management, antenna technologies and adaptive beamforming, mobility and handover management, and the integration of artificial intelligence and machine learning techniques as optimization levers. The results highlight the central role of physical constraints in the design of DS2D solutions. Furthermore, the study underscores the importance of regulatory harmonization and ongoing work, particularly in identifying new frequency bands suitable for this technology. Finally, this review identifies the main gaps in the current literature and proposes directions for future work, particularly in terms of link budget optimization and interference management in multi-user multi-technology scenarios.