  Large-scale deployments of massive Machine Type Communications (mMTC) involve
several challenges on cellular networks. To address the challenges of mMTC, or
more generally, Internet of Things (IoT), the 3rd Generation Partnership
Project has developed NarrowBand IoT (NB-IoT) as part of Release 13. NB-IoT is
designed to provide better indoor coverage, support of a massive number of
low-throughput devices, with relaxed delay requirements, and lower-energy
consumption. NB-IoT reuses Long Term Evolution functionality with
simplifications and optimizations. Particularly for small data transmissions,
NB-IoT specifies two procedures to reduce the required signaling: one of them
based on the Control Plane (CP), and the other on the User Plane (UP). In this
work, we provide an overview of these procedures as well as an evaluation of
their performance. The results of the energy consumption show both
optimizations achieve a battery lifetime extension of more than 2 years for a
large range in the considered cases, and up to 8 years for CP with good
coverage. In terms of cell capacity relative to SR, CP achieves gains from 26%
to 224%, and UP ranges from 36% to 165%. The comparison of CP and UP
optimizations yields similar results, except for some specific configurations.
