Introduction to the Internet of Things (IoT)
The IoT refers to the paradigm of physical and virtual “things” that communicate and collaborate over the Internet, with or without human intervention. The spectra of things that may be connected within the IoT ranges from complex machines, such as aircraft and cars, to everyday appliances, such as consumer refrigerators, and very simple devices such as humidity sensors. The emphasis of the IoT is on services, which represent the primary driver for interconnecting things. Examples of IoT services include micro-climate monitoring of homes, asset tracking during transportation, and, on a larger scale, controlling the power consumption of all the refrigerators in a country depending on the load. Current and forecast market evaluations (such as Cisco's forecast of a $14.4 trillion global IoT market by 2022 ) show that the IoT has a huge revenue potential, to be shared between operators, service providers, hardware vendors, and testing-solutions vendors. Thus, it is not surprising that the IoT is currently one of the hottest topics in the telecommunications world, endorsed by both industry and academia.
A term closely related, but not identical to IoT is machine-to-machine (M2M) communications, or, in the Third Generation Partnership Project (3GPP) terminology, machine-type-communications (MTC). M2M communications refer to the concept in which machines (i.e., standalone devices) communicate with a remote server without human intervention. “M2M can be considered as the plumbing of IoT”  or, more formally stated, M2M communications are the key enabler of IoT services. A natural question that arises is how well the existing networking solutions and technologies can serve as the basis for M2M communications and, more broadly, IoT services and, when they cannot support them, how to design other, suitable connectivity solutions. These questions have in recent years instigated a significant body of research and development by industry, standardization bodies, and academia. The general conclusion is that the existing technologies, in their present form, cannot efficiently support M2M communications. The reason is that existing communication systems, particularly in the wireless domain, are designed to efficiently support human-type communications (HTC), such as web browsing, voice calls, and video streaming, where high data rates are essential but the volume of users that simultaneously require service is far beyond the expected number of interconnected devices.