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NB-IoT over Non-Terrestrial Networks: Link Budget Analysis

Machine Type Communications (MTC) and Internet of Things (IoT) applications are growing exponentially and are forecast to play an even more important role in Future Networks and Systems. The Third Generation Partnership Project (3GPP) introduced the Narrowband IoT (NB-IoT) air interface as a response to the IoT use case requirements. However, it is widely accepted that the terrestrial network alone is not able to serve the requirement of the IoT market of a truly ubiquitous coverage. To this aim, several initiatives are currently addressing the inclusion of a satellite component into the telecommunication infrastructure to extend its coverage to those areas that are unserved or underserved by the terrestrial network. The recently approved 3GPP study item on NB-IoT over Non-Terrestrial Network (NTN) is the most important of these initiatives. The study item, starting at the beginning of 2021, will assess the performance of the NB-IoT air interface over satellite and will identify which adaptations are needed to enable its use. In this context, our work provides an assessment of the system level performance, in terms of the link budget parameters, of the NB-IoT air interface in typical satellite scenarios. In particular, we provide a detailed discussion of the system architecture supporting the NB-IoT over NTN, a description of the link budget computation methodology, and the numerical results of the link budget analysis in both single-satellite and multi-satellite scenarios.