Introduction to the IoT Communication and Networking

There is no doubt that IoT is network-oriented: even the name IoT naturally relates to the Internet network. Communication is an essential part of IoT ideas. Every IoT device must somehow communicate, even the simplest, passive RFID tag – it responds with some data to the excitation.
Communication is always performed with some rules known for both communicating parties. People have different languages to use, and devices have protocols. Communication protocol describes how to address the information to the remote device, encode the data, and check the incoming message's correctness. The physical layer of the protocol description also tells how to transmit every bit of data, the frequency of radio waves, how fast we can send the data and the maximum range of the transmission. Those duties are pretty challenging to address in the context of the IoT, constrained devices.

Communication in IoT devices can be wired or wireless:

• End node (edge) devices mainly use wireless transmission.
• Fog-class devices use both, particularly as gateways or routers.
• The cloud segment of the IoT ecosystem extensively uses wired copper and optical (fibre).

IoT networking differs significantly from typical, multilayered, stack-oriented TCP/IP or similar communication models we know while using our PCs, MACs, servers or smartphones. Indeed, constrained IoT devices are usually unable to operate regularly – full time on ISO/OSI layered stack because of constrained resources. In detail, it primarily means IoT devices are limited by processor power, RAM and storage sizes, mainly because of limited power resources. IoT devices are expected to be energy efficient and thus low-powered, which usually excludes typical wireless connection standards, e.g., WiFi. On the other hand, IoT devices are expected to communicate over long distances – some couple or a dozen kilometres – where wired infrastructure like Ethernet cables and related infrastructure is non-existent and most of the wired technologies, copper-based, are out of range.

Also, the daily life-cycle of IoT devices is much different from that of PC life-cycles. We as humans used to switch on the notebook, work extensively on the web, then turn it to low power or off, making the machine sleep, hibernate or just shut it down. And we wake it up when needed. It barely makes network operation during sleep. IoT devices are expected to be sleeping, providing low power mode whenever possible, and on the other hand, they're supposed to be fully operable when only needed. Most performed IoT tasks related to sensing have a cyclical nature, e.g. measuring gases as a sensor-network node. In contrast, the period can be between seconds and months or even longer. They're usually expected to trigger themselves to be awake from sleep, perform some operation and connect to the network. Meanwhile, the network grid needs to be aware that those devices are still in their place, in good condition and able to awake (e.g. the battery is not being drained).

Because of the existence of different IoT devices, including those very constrained from 8-bit processors with some kB of the RAM to 32-bit multicore machines well-replacing PCs, IoT networking is very competitive on protocols, approaches and solutions. Standardisation organisations like IEEE indeed introduce some networking standards, yet they are competed by large manufacturers forcing their complex solutions, including dedicated hardware, software and protocols. The third force driving this market is open solutions and enthusiasts, usually working with cheap equipment, providing de-facto standards for many hobbyists and industries.

An interesting survey made by RS components ^[1] shows 11 wireless protocols used in IoT. Some of them you can use for free without having any license to purchase, while others are proprietary, and some need a subscription plan.

The following chapters explain some of the most popular concepts about organising networks, fulfilling the above constraints on communication between IoT devices (Machine-2-Machine) and how to let them communicate with the Internet, including hardware, software and human users. We focus on the de-facto standards existing on the web, usually as open-source libraries and somewhat low-cost devices.