The Open Challenge of Integrating Satellites into (Beyond-) 5G Cellular Networks

The 3rd Generation Partnership Program (3GPP) standardization has recognized the relevance of integrating a non-terrestrial (i.e., satellite-based) segment into the ubiquitous 5G (terrestrial) cellular network. But such integration has actually proven considerably slower than expected. This article starts with a review of the recent history of satellite mobile communications and surveys the current status of satellite networks and the related technologies, including high throughput satellites with large antenna arrays and mega constellations. Such discussion is used as the basis for the identification of technological gaps that are making the cited integration an open challenge. Since terrestrial networks are already targeting 6G, this article tries to project the current 5G gaps toward the beyond 5G horizon of 2030.