5G and beyond 5G Non-Terrestrial Networks: Trends and research challenges

The evolution of 5G into beyond 5G and 6G networks aims at responding to the increasing need of our society of ubiquitous and continuous connectivity services in all areas of our life: from education to finance, from politics to health, from entertainment to environment protection. The next generation network communication infrastructure is called to support this increasing demand of connectivity by enforcing: energy-and costefficiency to guarantee environmental and economical sustainability; scalability, flexibility, and adaptability to ensure support to the heterogeneity of the service characteristics and constraints, as well as the variety of equipment; reliability and dependability to fulfil its role of critical infrastructure able to provide global connectivity no matter the social, political, or environmental situation. In this framework, non-terrestrial networks (NTN) are recognized to play a crucial role. It is in fact generally understood that the terrestrial network alone cannot provide the flexibility, scalability, adaptability, and coverage required to meet the above requirements, and the integration of the NTN component is a key enabler. In this framework, 3GPP has started to address the inclusion of technology enablers in the NR standard to support NTN. However, to fully exploit the potential of the NT component in an integrated terrestrial and NT architecture, several research and innovation challenges shall be addressed. In this paper, we first discuss the current development of NTN in 5G and then we present the vision of the role of NTN in B5G and 6G networks and we elaborate the corresponding research challenges.