# System Architecture Design of IoT-Based Smart Cities
## 2 Background
### Internet of Things  
The Internet of Things (IoT) refers to the interconnectedness of devices through the internet. Historically, the internet was primarily used for connecting computers, requiring human interaction and monitoring. However, the IoT expands upon this concept by adding a new dimension to current information and communication technologies (ICTs), enabling 'anytime' and 'anyplace' connectivity for 'anything' by connecting physical and virtual objects in the real world. IoT encompasses various technologies, including wireless sensor networks, machine-to-machine communication, mobile computing, ubiquitous computing, and embedded systems. The International Telecommunication Union (ITU) defines IoT as \"the network of physical objects or things\" embedded with electronics, software, sensors, and network connectivity, which enables these objects to collect and exchange data [10]. IoT architecture is typically a layered structure, grouping modules offering cohesive services. Several reference architectures have been proposed in the literature, with common layers including the device, network, and application layer [1; 12; 13; 14]. The Internet of Things (IoT) architecture can be represented as a layered structure consisting of the following layers: device, network, session, application, business, management, and security (Figure 1). The device layer comprises sensors and physical devices that collect and identify data and information generated by sensors and physical devices. This data is then passed on to the network layer, which provides networking connectivity and transport capabilities, allowing for the secure transmission of data to the session layer. The session layer is responsible for service management, including setting up and breaking down associations between IoT connection points. Standards and protocols offered by different organizations can be used in this layer, most utilizing the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP) for transport. The application layer manages the IoT system using data from the session layer and contains IoT services such as smart farming, smart cities, and smart homes. The business layer defines business logic and workflows, manages all IoT systems, services, and applications within the domain, and analyzes data from the application layer to build required business models and strategies. Finally, the security layer provides security functionality, and the management layer supports capabilities such as device management, local network topology management, and traffic and congestion management. In fact, security mechanisms also need to be implemented at various layers of the architecture. For example, at the network layer, secure communication protocols can be implemented to ensure the confidentiality and integrity of data transmitted over the network. At the session layer, encryption techniques can be used to protect sensitive data, and access control mechanisms can be implemented to ensure that only authorized users are able to access the data. At the application layer, role-based access control can be used to ensure that users have access only to the data and services that they require for their specific roles. In addition to these measures, ongoing security monitoring and evaluation are crucial to identify and address security risks and vulnerabilities over time. This can include implementing regular security assessments and testing procedures, as well as developing incident response plans to ensure that security breaches are detected and addressed in a timely manner. A critical aspect of IoT systems is interoperability which enables different devices (e.g., sensors) and systems to communicate and exchange data effectively. The IoT reference architecture addresses interoperability in several ways, including the use of standardized protocols, a layered approach to system design, and the incorporation of middleware to enable data translation and communication between different systems.