The system consists of three layers: a first layer, the perception layer, and an application layer. The first layer uses radio frequency identification (RFID), sensors, QR codes, and other technologies to acquire information about objects anytime and anywhere. The second layer is the network layer, which transmits information about objects accurately and in real time through the integration of telecommunications networks and the Internet. The third layer is the application layer, which processes the information obtained from the perception layer to achieve practical applications such as intelligent identification, positioning, tracking, monitoring, and management.
In industrial applications, the Industrial Internet of Things (IIoT) faces two main differences from traditional IoT system architectures: First, in the sensing layer, most industrial control commands and sensor data uploads require real-time processing. In traditional IoT architectures, data is transmitted from the network layer to the application layer, where it is processed before decision-making. Control commands are then transmitted back through the network layer to the sensing layer for execution. Since the network layer typically uses Ethernet or telecommunications networks, which lack real-time transmission guarantees, traditional IoT architectures are unsuitable for high-speed data acquisition or real-time control applications in industrial settings. Secondly, within existing industrial systems, different enterprises have their own supervisory control and data acquisition (SCADA) systems, which collect and monitor data within the factory. SCADA systems overlap with the application layer of the Internet of Things (IoT) in some functions. The challenge lies in integrating existing SCADA systems with IoT technology. For example, which data needs to be transmitted through the network layer to the application layer for analysis? Which data needs to be stored in the SCADA's local database? And which data should not be sent to the application layer, as it often involves critical sensor data or system information and should be processed only within the factory?
The system architecture of the Industrial Internet of Things (IIoT) requires the addition of a field management layer on top of the traditional IoT architecture. This layer functions similarly to an application sublayer, performing data preprocessing at a lower level. It is an indispensable layer for realizing real-time control, real-time alarms, and real-time data recording in industrial applications.
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. The short-range communication technology and collaborative information processing sublayers collaboratively process the collected data within a local area to improve information accuracy, reduce information redundancy, and connect to a wide-area bearer network through 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 also needed to respond to the perception 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 perception 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 perception 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, which is particularly important for industrial control. Control devices and field devices form a fieldbus control network, such as the commonly used CAN bus network and PROFIBUS bus network. 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 perception layer, playing a significant role in environmental data sensing and industrial process control.
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 the Industrial IoT system. It integrates existing industrial monitoring systems, enabling 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 field management layer provides external data interfaces. Through database servers and web servers, the dispatch and 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 vital 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 requirements, it can function as a transparent network layer or be upgraded to meet future content transmission needs. After more than a decade of rapid development, mobile communication and internet technologies are relatively mature and can basically 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 through various networks. This involves intelligent routers, interoperability of different network transmission protocols, self-organizing communication, and other network technologies. Global identifier resolution is completed at this layer. Except for global identifier resolution, other technologies in this part are relatively mature, primarily using existing standards.
4. Application Layer
The application layer provides application services for the perceived information, including technologies such as information processing, massive data storage, data mining and analysis, and artificial intelligence.
The application layer is the ultimate value embodiment of the Industrial Internet of Things (IIoT). Addressing the needs of industrial applications, the application layer deeply integrates with industry-specific technologies, utilizing big data processing techniques to analyze data from the perception layer. This primarily includes monitoring production processes and tracking and recording the operational status of industrial machines. Ultimately, it generates results that guide enterprise and industry development, such as optimizing production processes, guiding production management, improving operational efficiency, and predicting industry trends, thus achieving widespread intelligentization. Furthermore, different enterprises can share the results of big data analysis and processing, which plays a significant role in promoting collaborative production and overall productivity across enterprises.
The application layer mainly comprises a service support layer and an application subset layer. The core function of the Internet of Things (IoT) is the collection, development, and utilization of information resources; therefore, this part is crucial. The main function of the service support layer is to form a dynamic data resource library that adapts to business needs and is updated in real time based on the data collected from the lower layers. This part will employ various technologies such as metadata registration, metadata discovery, information resource catalogs, interoperability meta-models, classification coding, parallel computing, data mining, data harvesting, and intelligent search. It urgently requires the development of standards for IoT data models, metadata, ontology, and services, as well as the development of technologies for IoT data architecture, information resource planning, information resource library design, and maintenance. Various business scenarios can then conduct corresponding data resource management based on their specific business needs. The main function of the business architecture layer is to design the IoT business architecture, application architecture, IT architecture, data architecture, technical reference models, and business operation views based on IoT business requirements, using modeling, enterprise architecture, SOA, and other design methods. The Internet of Things (IoT) has a wide scope, encompassing various application systems with diverse business needs, operating models, application systems, technological frameworks, information requirements, and product forms. Therefore, a unified and systematic business architecture is essential to meet the IoT's demands for comprehensive real-time sensing, multi-target business operations, and the integration of heterogeneous technological frameworks. Each business application area can be further subdivided into different business types, including green agriculture, industrial monitoring, public safety, urban management, telemedicine, smart homes, intelligent transportation, and environmental monitoring. Based on different business needs, the technologies of the business, service, data resources, common support, network, and sensing layers can be tailored to form different solutions. This part can handle some presentation and human-computer interaction functions. The application layer will provide unified information resource support for various businesses. By establishing and updating reusable information resource libraries and application service resource libraries in real time, various business services can be combined on demand according to user needs, significantly improving the adaptability of IoT application systems to business requirements. This layer can enhance the reusability of application system resources, laying the foundation for rapidly building new IoT applications and meeting the complex and ever-changing network resource application needs and services in the IoT environment. This section covers areas such as data resources, system architecture, and business processes, which are crucial for the Internet of Things to function effectively. There are not many general information technology standards that can be adopted, so a large number of standards still need to be developed.
In addition to the above, the Internet of Things (IoT) also requires public technical support such as information security, IoT management, and service quality management, primarily adopting existing standards. Between each layer, information is not transmitted unidirectionally but involves interaction and control, and the transmitted information is diverse. The most crucial aspect is the handling of massive data collection, identification and resolution, transmission, and intelligent processing related to object information, integrating with various business applications to fulfill specific business functions. Therefore, the system architecture and standards framework of the IoT form a closely interconnected whole, guiding the direction and scope of IoT research.
