I. Introduction
The Internet-of-Things (IoT) paradigm is rapidly maturing, with many massive deployments in areas such as smart cities, home automation, and agricultural monitoring. These massive IoT applications require scalable low-power connectivity over a long range. Recently, there has been a rising demand for IoT in more critical sectors, such as health care, security, energy and industrial automation. They are referred to as mission-critical IoT applications, and additionally require specific Quality-of-Service (QoS) guarantees in terms of latency, throughput or reliability.