Architecture of IoT

Internet of Things involves multiple technologies which have different application needs and forms in different industries. In order to sort out the structure, the key technologies and application characteristics of IoT, it is necessary to establish a unified architecture and a standard technical system. In this book, the architecture of IoT is simply divided into four layers: perception & control layer, network layer, platform layer, and application layer.

Perception & Control Layer

As the most basic element of the IoT architecture, perception & control layer is the core to realise the comprehensive sensing of IoT. Its main function is to collect, identify and control information. It consists of a variety of devices with the ability of perception, identification, control and execution, and is responsible for retrieving and analysing data such as material properties, behavioural trends, and device status. In this way, IoT gets to recognise the real physical world. Besides, the layer is also able to control the status of the device.

The most common devices of this layer are various sensors, which play an important role in information collection and identification. Sensors are like human sensory organs, such as photosensitive sensors equalling to vision, acoustic sensors to hearing, gas sensors to smelling, and pressure- and temperature-sensitive sensors to touching. With all these “sensory organs”, objects become “alive” and capable of intelligent perception, recognition and manipulation of the physical world.

Network Layer

The main function of the network layer is to transmit information, including data obtained from the perception & control layer to specified target, as well as commands issued from the application layer back to the perception & control layer. It serves as an important communication bridge connecting different layers of an IoT system. To set up a basic model of Internet of Things, it involves two steps to integrate objects into a network: access to Internet and transmission through Internet.

Access to Internet

Internet enables interconnection between person and person, but fails to include things into the big family. Before the advent of IoT, most things were not “network-able”. Thanks to the continuous development of technology, IoT manages to connect things to the Internet, thus realizing interconnection between “people and things”, and “things and things”. There are two common ways to implement Internet connection: wired network access and wireless network access.

Wired network access methods include Ethernet, serial communication (e.g., RS-232, RS-485) and USB, while wireless network access depends on wireless communication, which can be further divided into short-range wireless communication and long-range wireless communication.

Short-range wireless communication includes ZigBee, Bluetooth®, Wi-Fi, Near-Field Communication (NFC), and Radio Frequency Identification (RFID). Long-range wireless communication includes Enhanced Machine Type Communication (eMTC), LoRa, Narrow Band Internet of Things (NB-IoT), 2G, 3G, 4G, 5G, etc.

Transmission through Internet

Different methods of Internet access lead to corresponding physical transmission link of data. The next thing is to decide which communication protocol to use to transmit the data. Compared with Internet terminals, most IoT terminals currently have fewer available resources, such as processing performance, storage capacity, network rate, etc., so it is necessary to choose a communication protocol that occupies fewer resources in IoT applications. There are two communication protocols that are widely used today: Message Queuing Telemetry Transport (MQTT) and Constrained Application Protocol (CoAP).

Platform Layer

The platform layer mainly refers to IoT cloud platforms. When all IoT terminals are networked, their data need to be aggregated on an IoT cloud platform to be calculated and stored. The platform layer mainly supports IoT applications in facilitating access and management of massive devices. It connects IoT terminals to the cloud platform, collects terminal data, and issues commands to terminals, so as to implement remote control. As an intermediate service to assign equipment to industry applications, the platform layer plays a connecting role in the entire IoT architecture, carrying abstract business logic and standardized core data model, which can not only realize rapid access of devices, but also provide powerful modular capabilities to meet various needs in industry application scenarios. The platform layer mainly includes functional modules such as device access, device management, security management, message communication, monitoring operation and maintenance, and data applications.

• Device access, realising the connection and communication between terminals and IoT cloud platforms.

• Device management, including functions such as device creation, device maintenance, data conversion, data synchronization, and device distribution.

• Security management, ensuring the security of IoT data transmission from the perspectives of security authentication and communication security.

• Message communication, including three transmission directions, that is, the terminal sends data to the IoT cloud platform, the IoT cloud platform sends data to the server side or other IoT cloud platforms, and the server side remotely controls IoT devices.

• Monitoring O&M, involving monitoring and diagnosis, firmware upgrade, online debugging, log services, etc.

• Data applications, involving the storage, analysis and application of data.

Application Layer

The application layer uses the data from the platform layer to manage the application, filtering and processing them with tools such as databases and analysis software. The resulting data can be used for real-world IoT applications such as smart healthcare, smart agriculture, smart homes, and smart cities.