Abstract:
Narrowband Internet of Things (NB-IoT) is one of the most promising technologies for
enabling reliable communication among low-power, and low cost devices present in massive machine-type
communications (mMTC). In NB-IoT, random access (RA) is implemented in the medium access control
(MAC) layer to resolve access contention among massive IoT devices. Efficient network access techniques
are required to effectively solve the massive access issues in NB-IoT, guaranteeing increased throughput and
high spectrum utilization. In this paper, we present a comprehensive overview of NB-IoT towards supporting
mMTC, with focus on the NB-IoT coexistence with 5G, as well the design challenges and requirements of
RA in NB-IoT. Moreover, available literature is reviewed to highlight the RA congestion control schemes
proposed during the past few years to alleviate RA collisions. While existing RA approaches mainly focus
on conventional contention-based techniques for performing RA, intelligent learning based and grant-free
Non-Orthogonal Multiple Access (NOMA) have been identified as a potential candidates to increase the
transmission efficiency of mMTC applications.
