In the Internet of Things (IoT), the interchange of data among sensors, devices, gateways, servers, and user applications is enabled by network protocols like WiFi, Bluetooth, ZigBee, and many others. End Application requirements of range, data, security, power, and battery life dictate network protocol choice. This article explores some of these communication technologies and protocols.

IoT Ecosystem

An IoT ecosystem typically consists of nodes, data, connectivity, and application layer. The node layer is a coalition of smart devices such as microcontrollers, microprocessors, sensors, actuators, connectivity, and gateways interacting with a network.

The data layer is concerned with the data collected, processed, sent, stored, analyzed, presented, and used in business contexts. The application or user layer is the component that allows humans to interact with IoT devices. We will discuss the connectivity layer which comprises of communication and IoT protocols. For more information about IoT products, please click here.

Protocol Network in an IoT Ecosystem
Figure1: Protocol Network in an IoT Ecosystem

IoT Protocol Types

The Internet Protocol's (IP) inherent adaptable and dependable nature makes it an acceptable medium for procedural transmission among IoT modules. The system architecture (through which the data must travel) determines the IoT protocol type. The Open Systems Interconnection (OSI) model delivers a map of the various layers that dispatch and accept data. Each protocol in the IoT system architecture enables device-to-device, device-to-gateway, gateway-to-data center, gateway-to-cloud communication, and communication between data centers. Figure 2 shows the IoT Protocol stack.

IoT Protocol stack
Figure2: IoT Protocol Stack

A few key IoT protocols used in the different layers of the IoT network are as follows

Advanced Message Queuing Protocol (AMQP)

AMQP is an application (software) layer protocol that offers route and queuing for a message-oriented middleware environment. It is used for reliable point-to-point connections and supports the seamless and secure interchange of data between the devices and the cloud. AMQP has three distinct components, namely Exchange, Message Queue, and Binding. These three ensure a dependable, successful exchange and message storage. They also denote the relationship between two messages. For more information about AMQP, please click here.

Constrained Application Protocol (CoAP)

CoAP is a constrained-bandwidth and constrained-network protocol for limited gadgets. This protocol enables the client to send the server a request, and the server sends a response in HTTP back to the client. It uses the User Datagram Protocol (UDP) for lightweight implementation and minimizes space use. The protocol employs binary data format EXL. CoAP protocol is primarily used in automation, microcontrollers, and mobiles. The protocol dispatches a request to the home's application endpoint and returns the application's response to services and resources. To learn more about CoAP, please click here.

Data Distribution Service (DDS)

DDS is a flexible peer-to-peer communication protocol. It does everything from running tiny devices to connecting high-performance networks. DDS streamlines deployment increases reliability and minimizes complexity.

Message Queue Telemetry Transport (MQTT)

MQTT, also known as subscribe/publish protocol, is a lightweight messaging protocol as well as the most preferable one for IoT devices. It collects data from various devices and supervises remote devices. It runs over Transmission Control Protocol (TCP) and supports event-driven message exchange through wireless networks. MQTT is mainly used in devices that require less power memory, for e.g., in-car sensors and smartwatches. To learn more about MQTT, please click here.

Machine-to-Machine (M2M) Communication Protocol

It refers to an open industry protocol. The M2M is created to manage IoT devices remotely. These cost-effective protocols use public networks. The M2M fashions an environment where two machines mutually communicate and swap data. Such a protocol reinforce machines to self-monitor and enable the systems to adapt as per the varying environment. It is mainly used for smart homes, vehicles, and ATMs. To learn more about M2M communication, please click here.

Extensible Messaging and Presence Protocol (XMPP)

The XMPP has a unique design. It was developed using open XML (Extensible Markup Language). It employs a push mechanism to swap synchronous messages. The flexible XMPP can seamlessly integrate with any changes. XMPP functions as a presence indicator. It displays the servers' availability status.

Other than WhatsApp, Google Talk, and other instant messaging apps, XMPP is also useful in online gaming, Voice over Internet Protocol (VoIP), and news websites. To learn more about XMPP, please click here.

Bluetooth

Bluetooth is widely used for short-range communication and is a standard IoT protocol for wireless data transmission. Its low-energy version is Bluetooth Low Energy (BLE). The latest version, BLE 5.0, supports low data rate applications and an extended range of up to 150 meters. Features like beaconing and location services have helped deploy it in a wide range of fitness and automotive applications. It can support star topology. The latest versions support mesh topology, stretching the network using many-to-many device networking suitable for home automation applications.

Zigbee

ZigBee uses IEEE 802.15.4 standard physical and link layer, operating at ISM 2.4 GHz band and provides a range of up to 300 feet. It supports mesh topology. Hence the network can be stretched over a longer distance using multi-hop operations. The protocol is highly interoperable and includes standard libraries of data models, security, and network management procedures. ZigBee has low power consumption, node discovery, duplicated packet detection, route discovery, sleep mode, and reliability. It is widely used in smart homes and building automation applications.

Z-Wave

Z-Wave is a low-power wireless technology designed for IoT Home Automation applications. It offers low-latency and reliable communication of small data packets with data rates up to 100kbit/s. It supports mesh topology with a maximum of 232 nodes in a single network. It works on 868 MHz for the Europe region and 915 MHz for North America and Australia, providing a 100-Kbps data rate. To learn more about Z-Wave, please click here.

6LowPAN

IPv6 Low-power Wireless Personal Area Network (6LowPAN) is an Internet Protocol-based technology. It is a network protocol that defines encapsulation and header compression mechanisms. It has the freedom of frequency band and physical layer, and can also be used across multiple communications platforms, including Ethernet, WiFi, 802.15.4, and sub-1GHz ISM. It is devised to dispatch IPv6 packets over the IEEE802.15.4-based networks and implement many open IP standards, including TCP, web sockets, UDP, HTTP, COAP, and MQTT. The standard provides end-to-end addressable nodes, permitting a router to link the network to IP. The 6LowPAN is a robust, scalable and self-healing mesh network.

Thread

Thread, based on various standards, including IEEE802.15.4, IPv6, and 6LoWPAN, is a fresh IP-based IPv6 networking protocol directed towards the home automation environment. It primarily complements WiFi and offers a resilient IP-based solution for IoT. Thread reinforces a mesh network utilizing IEEE802.15.4 radio transceivers. It manages up to 250 nodes with high authentication and encryption levels.

WiFi

WiFi is a wireless communication protocol. WiFi uses the star network topology, and the access point can be used as a gateway to the Internet. Each access point can connect to a maximum of 250 devices, and most commercially available solutions support up to 50 devices. The 802.11-b/g/n operates on 2.4GHZ and provides 150-200 Mbps data rate in the home or office environment, typically at a range of 50 meters. The latest 802.11-ac standard works on 5GHz and provides a 500Mbps-1Gbps data rate.

Cellular

Many IoT applications use existing cellular networks like 3G, 4G LTE, and 5G for data communication. 3G uses 2100 MHz and offers a 384 Kbps-10Mbps data rate, and the 4G LTE delivers a high data rate of 3Mbps-10 Mbps at 2700 MHz. They are unsuitable for most IoT applications due to their high power consumption and steep implementation costs. Cat-M1 and NB-IOT were introduced in the 3rd Generation Partnership Project (3GPP) for adoption to existing 4G LTE networks for IoT and M2M communication. 5G, with greater capacity than any 4G network, is under development to increase mobile broadband users and to support communication between devices. To do so, different techniques are applied to 5G, like massive multiple-input multiple-output (MIMO), full-duplex communication, heterogeneous networks (HetNet), millimeter wave (mmWave), and networking slicing. The entire 5G network services can be classified into three different categories as per The International Telecommunication Union (ITU): enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable and low latency communications (uRLLC).

NFC

Near Field Communication (NFC) is an Ultra-Short Range Radio communication protocol. It uses the ISO/IEC 18000-3 standard and the 13.56 MHz ISM frequency band. It provides a data rate of 100-420 Kbps and a range up to 20cm. Some NFC devices can read (ISO 15693 compliant) passive high-frequency RFID tags, which also works on 13.56 MHz. NFC provides full-duplex communication over the detection range from metallic and non-metallic substrates. It is used for contactless payment, fast synchronizing, and digital content access applications.

Sigfox

Sigfox is a private network provider similar to telephony or cellular service providers, focused on serving customers in IoT. It uses sub-GHz ISM bands (868 to 869 MHz or 902 to 928 MHz) and supports a long-range (up to 50km) using the star topology. Although Sigfox communication is bi-directional, the payload from the base station to the node is meager. It is used for remote sensing, where low amounts of data have to be transmitted sporadically with high battery life requirements. To learn more about Sigfox, please click here.

LoRaWAN

LoRaWAN is a Low Power Wireless WAN communication protocol in the sub-GHz frequency range (433/ 868/ 915 MHz). It has a typical data rate of 0.3-50 Kbps and can cover up to a 15km range. The higher distance is achieved by dynamically lowering data rates. It is designed to provide Low Power, low-cost, secure, and full-duplex communication for IoT, M2M, Smart City, and Industrial Applications. To learn more about LoRaWan, please click here.

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