This paper reports the first results of the 5G-ALLSTAR project [1] aiming at providing solutions and enablers for spectrum sharing in a 5G cellular and satellite multi-connectivity context. First, we present an exhaustive study of the frequency bands eligible for these systems in the short and medium term. A ray-tracing based and a geometry-based stochastic channel models developed in the project are then described. These models can be used to simulate systems involving terrestrial and non-terrestrial networks. We then describe three different ways investigated in the project for managing interference: signal processing (hardware implementation of a 5G New Radio compatible physical layer), beamforming (steering and switching beams in order to avoid the interference while preserving the spectral efficiency) and radio resource management (tool designed for joint optimization of satellite and terrestrial resource sharing).

Harmonization of terrestrial standards such that they would support satellite elements would offer several benefits. This work has started at 3GPP relating to 5G new radio (NR). Downlink initial access is one of the topics that has to be evaluated in this respect among many others. This paper studies detection of the synchronization signals included in the synchronization (SS) block of the 5G NR signal in satellite channels that have large, up to 720 kHz, Doppler frequency shift at 30 GHz carrier frequency. Furthermore, the reception of system information data in the SS block is considered. It is shown that using dedicated large frequency shift aware detectors it is possible to meet the 5G NR requirements in the detection part. However, the data part cannot be reliably received using one-shot reception at low signalto-noise values. Some alternative solutions are considered and evaluated though some of them require changes to the standard in order to be efficient.

This paper provides an overview of recent research activities of the 5G AgiLe and fLexible integration of SaTellite And cellulaR (5G-ALLSTAR) project which aims to develop Multi-Connectivity technology that integrates the cellular and satellite accesses to provide seamless, reliable and ubiquitous broadband services. 5G-ALLSTAR also entails developing millimeter-wave (mmWave) 5G New Radio (NR)-based cellular access system and investigating the feasibility of NR-based satellite access for providing broadband and reliable 5G services. In addition, spectrum sharing between the cellular and satellite access is studied. With all these technologies developed in the project, the 5G-ALLSTAR will showcase the first fully integrated satellite/cellular prototype system for 5G and beyond 5G (B5G) services at a big event (e.g., sporting event like Roland-Garros) in 2021. This paper also provides a preliminary techno-economic analysis on potential use cases targeting vertical markets, and introduces recent standardization activities of relevance.

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