## 6 Use Case of One Smart Building and Its Applications  
This section aims to discuss a simplified real use case that applies the results from Section 5 and consolidates the research presented in Section 4. This provides a novel and comprehensive perspective on SBs, paving the way for future advancements considering emerging scientific developments in IoT, Fog and IEC. Section 1 examines SBs within the context of Smart Cities, highlighting their rapid growth internationally, including Europe -Fiware.org [29], the USA and some eastern countries. This growth introduces significant innovations in communication engineering, cloud computing and high-performance IoT devices. The proposed use case of just one SB with fifteen floors and sixty apartments is deemed suitable for this study due to the significant number of parameters involved in the decision-making process. The proposed SB solution utilizes VoIP and video equipment, typically embedded within IoT devices (as detailed in Section 4 and Table 1), offering a suitable number of interfaces for easy integration into the SB's wired and wireless local area networks. These IoT devices, connected by VIoT gateways, integrate IP phones (replacing traditional intercoms and potentially fixed-line phones), temperature and fire sensors, actuators, RFID and biometric readers, analog-to-digital converters for actuator control, IP cameras and other typical devices adopted in a SB [50]. Overall, the SB solution aims for secure, robust and reliable applications with consistent performance and the delivery of excellent QoS, resulting in a desirable QoE for users. Finally, this use case emphasizes high availability for edge solutions, parameters that should be regularly monitored within service contracts and their SLAs, long-term contracts spanning several years. To streamline the solution, the scope of the proposed SB is reduced to a single local server and an application running with less than five containers and a single CB, as suggested by Fiware. Only the most relevant applications, with direct connectivity to the chosen Fog or IEC architecture under discussion, and adding the recommended IoT devices category, are detailed here:  
1. IP telephony and VoIP [51], video recording and structured and unstructured database applications. 2. Directory applications with permissions for various user types, access levels, credentials, and a comprehensive identity and access management (IAM) system. [47]
3. Centralized control and monitoring dashboards via the Operational Control Center (CCO or CCC) operating on the selected cloud platform. 4. Visitor authentication applications: biometric authentication, facial recognition, QR code or physical token access [47; 52]. 5. Applications for SB access control and authorization, including a virtual concierge linked to the CCO or OCC. This may also include user-friendly applications such as smartphone apps, video communication [52] and intelligent chatbots, as well as internal IP telephony within the SB's commercial or residential areas [27]. These cloud services are integrated with the local SB desktop PC or local SB server to complement the solution. Alternative architectures could involve a centralized environment through the federation of SBs and Fog nodes, or SBs with internal IECs. The latter is generally suitable for a small number of towers in commercial or residential SBs. For simplification, this proposal and study limit the scope to one or two building towers to be exhaustive. This results in a comprehensive suite of applications, storage and high-capacity data analytics integrated via Fog or IEC with intelligent IoT devices at the SB's edge. These data are stored in the central cloud database, which interacts with the Fog or IEC [4]. In the single-tower scenario, an IEC infrastructure is deployed within the SB described in detail in this section. For security and high availability of data, voice and video communication (VIoT and VoIP), redundancy and a reliable fail-safe system are implemented.