  NarrowBand-IoT has just joined the LPWAN community. Unlike most of its
competitors, NB-IoT did not emerge from a blank slate. Indeed, it is closely
linked to LTE, from which it inherits many of the features that undoubtedly
determine its behavior. In this paper, we empirically explore the boundaries of
this technology, analyzing from a user's point of view critical characteristics
such as energy consumption, reliability and delays. The results show that its
performance in terms of energy is comparable and even outperforms, in some
cases, an LPWAN reference technology like LoRa, with the added benefit of
guaranteeing delivery. However, the high variability observed in both energy
expenditure and network delays call into question its suitability for some
applications, especially those subject to service-level agreements.
