## 6 Use Case of One Smart Building and Its Applications
The network architecture, depicted in Figure 8, incorporates failover and fallback mechanisms. Failover utilizes a redundancy system, while fallback employs a secondary terrestrial communication link from a different provider (e.g., a fiber optic cable as the primary link and any available radio-link or satellite solution as failover), using 4G/5G and future 6G cellular networks in the SB's router. For SBs in medium and large cities, redundancy is achieved using two distinct carriers or at least a secondary local Internet service provider. In rural areas, a failover link using microwave radio/tower networks may be necessary, supplementing the primary connection (fiber optic or other technology). The proposed SB architecture in Figure 8 includes connections to cloud computing. For simplicity, the figure does not show all Fog components in detail, although they may be included in the deployment. Figure 8 shows a general example of the SB (left side of the figure), where the proposed edge (IEC) resides within the SB and is directly connected via router R1 to the cloud. This topology is applicable to one SB or, at most, two SBs. The SB's router or VoIP gateway connects to the two redundant Service Providers mentioned, adopting access lists and a firewall security layer to guarantee a robust solution \begin{table}
\begin{tabular}{c} \hline Classification of IoT and subtitles of Table 1 (IoT), \\ IoT devices: Category of the Embedded boards: \\ \hline (1) = _Low-end IoT device_ \\ (2) = _Middle-end IoT device_ \\ (3) = _High-end IoT device_ \\ ANY = any of 3 categories could be applied \\ \hline Acronyms for Architecture, Cloud architecture and Integration: \\ \hline FSN = Fog + SDN (or NFV) \\ FOG = Fog without SDN (or NFV) \\ ISN = IEC + SDN (or NFV) \\ IEC = IEC without SDN (or NFV) \\ ANY = any of above Cloud solution could be chosen \\ (—) = N/A Not applicable \\ \hline \end{tabular}
\end{table} 
Table 2: Classification of IoT devices categories and recommended Cloud architecture in Table 1.  
Figure 8: Smart Building: a simplified use case using Intelligent Edge Computing (IEC). for internal IoT devices and SB network against theses cyberattacks: DoS, DDoS, SQL injection, malware and Man-in-the-Middle. Only in the case of integration with a geographically proximate Fog node it provides access to that Fog and enables integration with federated SBs. However, in the second proposed IEC topology, computation and processing are handled by an IEC or Edge device deployed internally within the SB, as described in [2; 42]. In this case, the last-mile router R1 connects directly to the external network or the Internet, and to the central cloud solution. While a three-layer Cloud architecture is maintained, the IEC simplifies implementation by reducing the number of accesses to the central network. The adoption of SDN architecture with its switches, where feasible, is recommended to reduce costs through the use of open platforms for internal and external routers and switches. The manageability and administration of the solution are crucial; from security and technical point of view, billing and technical support are delegated to the local provider. Visitor registration and scheduling will be handled by mobile applications available in smartphone app stores and through readily available market APIs, facilitating easy authorization and registration of visitors and new residents by the building's residents. This SB context is managed by a CCO or OCC, at the top of Figure 8 of the solution provider, shared among one or multiple SBs. Furthermore, the central databases of actors and their credentials, obtained from Directory Services (Active Directory, AD), are implemented in the cloud Database, DB (see same Figure), connected by small local or remote replicas of the Fog or the IEC itself. Some of the SB's functionalities under study are summarized in Table 1, Figure 8 and described in this section as a use case for these SB applications.