A Survey on NB-IoT Downlink Scheduling: Issues and Potential Solutions

The NarrowBand Internet of Things (NB-IoT) is one of the most promising technologies that fits the requirements of the low-power wide area networks (LPWAN). NB-IoT targets on supporting communications for small amount of data during a relatively long period of time (i.e., delay tolerant), which is one of the key features of IoT applications. Several studies have been conducted by some standard working groups to define the standards for NB-IoT. For example, the working group 3GPP aims to provide communication protocols with low energy consumption, good coverage penetration, and so on. Compared with the existing wireless communication protocols, less spectrum is allocated for NB-IoT. Thus, how to more efficiently use the resource/spectrum (i.e., resource allocation and scheduling) is one of the key issues. In this paper, we first describe the design of the physical layer for the downlink communication, especially the scheduling process. Secondly, we discuss the issues for resource allocation in NB-IoT while the delay requirement in the physical layer is satisfied. Thirdly, we discuss the open questions and possible solutions.