1. Perception layer
The primary functions of the perception layer are object identification, information collection, and automatic control; it is the source for object identification and information collection in the Internet of Things (IoT). It consists of a data acquisition sublayer, short-range communication technology, and a collaborative information processing sublayer. The data acquisition sublayer acquires physical events and data information occurring in the physical world through various types of sensors, such as various physical quantities, identifiers, and audio/video multimedia data. IoT data acquisition involves technologies such as sensors, RFID, multimedia information acquisition, QR codes, and real-time positioning.
Short-range communication technology and the collaborative information processing sublayer collaboratively process the collected data within a local area to improve information accuracy and reduce redundancy. This data is then connected to a wide-area bearer network via a self-organizing short-range sensor network. The perception layer middleware technology aims to solve compatibility issues between perception layer data and various application platforms, including code management, service management, state management, device management, time synchronization, and positioning. In some applications, actuators or other intelligent terminals are needed to respond to the sensing results to achieve intelligent control. Besides relatively mature technologies such as RFID, short-range communication, and industrial bus, this part still requires the development of numerous IoT-specific technical standards.
The sensing layer consists of field devices and control devices, primarily responsible for sensing information from industrial machines and issuing control commands. Field devices mainly include temperature sensors, humidity sensors, pressure sensors, RFID tags, electric valves, and transmitters. These devices are directly connected to the industrial machines, acting as the final stages of the sensing and control process. Control devices mainly refer to controllers such as PLCs. In industrial systems, PLCs and similar controllers are used to implement high-speed, real-time control functions at a lower level, making them particularly important for industrial control.
Control devices and field devices form fieldbus control networks, such as commonly used CAN bus networks and PROFIBUS bus networks. It is worth mentioning that Industrial Wireless Sensor Networks (WISNs), as an important component of IoT technology, can coexist with existing fieldbus networks through gateways. WISNs, with their advantages of high reliability, low cost, and easy scalability, are widely used in the implementation of the sensing layer, playing a significant role in environmental data sensing, industrial process control, and other fields.
2. On-site management
The field management layer primarily refers to the factory's local dispatch and management center, i.e., the SCADA system mentioned above. The dispatch and management center acts as the local manager of the industrial system and the provider of external interfaces for industrial data. It typically includes equipment such as industrial database servers, monitoring servers, file servers, and web servers. As a layer distinct from traditional IoT system architectures, the field management layer plays a crucial role in industrial IoT systems.
The on-site management layer integrates with the existing industrial monitoring system. Its existence enables the timely recording and processing of key industrial data from the sensing layer. For lower-level process control commands requiring real-time performance, it can respond quickly and make timely control decisions. On the other hand, the on-site management layer provides external data interfaces. Through database servers and web servers, the dispatch management center can publish data from within the factory to the application layer via the network layer. The application layer can transparently access the sensing information from different industrial machines, playing a crucial role in further data analysis.
3. Network Layer
The network layer, composed of the internet, telecommunications networks, etc., is responsible for information transmission, routing, and control. It transmits various types of information from the perception layer to the application layer through the underlying bearer network, including mobile communication networks, the internet, satellite networks, broadcast networks, industry private networks, and converged networks. Depending on application needs, it can function as a transparent network layer or be upgraded to meet future requirements for different content transmission. After more than a decade of rapid development, mobile communication and internet technologies have matured considerably and are generally sufficient to meet the data transmission needs of the Internet of Things (IoT) in its early stages.
The network layer primarily focuses on the transmission of pre-processed data from the perception layer across various networks. This involves intelligent routers, interoperability between different network transmission protocols, self-organizing communication, and other network technologies. Global identifier resolution is performed at this layer. Except for global identifier resolution, the other technologies used in this part are relatively mature, and existing standards are primarily adopted.
