Narrowband Internet of Things: A Comprehensive Study

Over the last decade, the number of Low-Power Wireless Access (LPWA) devices has increased remarkably. It has become crucial to introduce several LPWA technologies to share the burden of catering to the demands of these devices. Narrowband Internet of Things (NB-IoT) is one such new cellular LPWA technology which has been standardized by 3rd Generation Partnership Project (3GPP) in June, 2016. It was developed with the aim to support low-complexity and low-power devices serving areas of poor radio coverage. In this survey, we review NB-IoT technology in detail. NB-IoT's architecture is derived from that of Long Term Evolution (LTE) cellular technology, which is another 3GPP technology. We first discuss the architectural changes made to the design of LTE to derive the design of NB-IoT, including changes in physical layer and layer-2 architecture. Next, we describe the various features introduced for NB-IoT in 3GPP Rel-13 and follow it up to describe the enhancements made in subsequent 3GPP releases until 3GPP Rel-16. Then, we review, in depth, the research work done on various aspects of NB-IoT. We follow it up with a discussion on the combination of NB-IoT with other interesting cellular technologies like Device-to-Device communication (D2D), Non-Orthogonal Multiple Access (NOMA), social IoT, and 5th Generation New Radio (5G NR). We also look into a wide variety of real-world applications of NB-IoT. Finally, we point out a few open issues of NB-IoT and identify possible future research directions.