Abstract:
Narrowband Internet of Things (NB-IoT) is a type of low-power wide-area (LPWA) technology
standardized by the 3rd-Generation Partnership Project (3GPP) and based on long-term evolution (LTE)
functionalities. NB-IoT has attracted significant interest from the research community due to its support for
massive machine-type communication (mMTC) and various IoT use cases that have stringent specifications
in terms of connectivity, energy efficiency, reachability, reliability, and latency. However, as the capacity
requirements for different IoT use cases continue to grow, the various functionalities of the LTE evolved
packet core (EPC) system may become overladen and inevitably suboptimal. Several research efforts are
ongoing to meet these challenges; consequently, we present an overview of these efforts, mainly focusing on
the Open System Interconnection (OSI) layer of the NB-IoT framework. We present an optimized architecture of the LTE EPC functionalities, as well as further discussion about the 3GPP NB-IoT standardization
and its releases. Furthermore, the possible 5G architectural design for NB-IoT integration, the enabling
technologies required for 5G NB-IoT, the 5G NR coexistence with NB-IoT, and the potential architectural
deployment schemes of NB-IoT with cellular networks are introduced. In this article, a description of
cloud-assisted relay with backscatter communication, a comprehensive review of the technical performance
properties and channel communication characteristics from the perspective of the physical (PHY) and
medium-access control (MAC) layer of NB-IoT, with a focus on 5G, are presented. The different limitations
associated with simulating these systems are also discussed. The enabling market for NB-IoT, the benefits
for a few use cases, and possible critical challenges related to their deployment are also included. Finally,
present challenges and open research directions on the PHY and MAC properties, as well as the strengths,
weaknesses, opportunities, and threats (SWOT) analysis of NB-IoT, are presented to foster the prospective
research activities.
