  Massive Machine-Type Communications (MTC) over cellular networks is expected
to be an integral part of wireless "Smart City" applications. The Long Term
Evolution (LTE)/LTE-Advanced (LTE-A) technology is a major candidate for
provisioning of MTC applications. However, due to the diverse characteristics
of payload size, transmission periodicity, power efficiency, and quality of
service (QoS) requirement, MTC poses huge challenges to LTE/LTE-A technologies.
In particular, efficient management of massive random access is one of the most
critical challenges. In case of massive random access attempts, the probability
of preamble collision drastically increases, thus the performance of LTE/LTE-A
random access degrades sharply. In this context, this article reviews the
current state-of-the-art proposals to control massive random access of MTC
devices in LTE/LTE-A networks. The proposals are compared in terms of five
major metrics, namely, access delay, access success rate, power efficiency, QoS
guarantee, and the effect on Human-Type Communications (HTC). To this end, we
propose a novel collision resolution random access model for massive MTC over
LTE/LTE-A. Our proposed model basically resolves the preamble collisions
instead of avoidance, and targets to manage massive and bursty access attempts.
Simulations of our proposed model show huge improvements in random access
success rate compared to the standard slotted-Aloha-based models. The new model
can also coexist with existing LTE/LTE-A Medium Access Control (MAC) protocol,
and ensure high reliability and time-efficient network access.
