## 3 Concepts, Models and Technologies
### Wi-Fi Networks (5 and 6) and WSNs--Wireless Sensor Networks (WSNs)  
Wireless networking technologies, widely studied and popularly known as Wi-Fi, encompass standards such as the extensively used Wi-Fi 4 and 5 (or IEEE 802.11 b/n/g) as well as the latest implementations like Wi-Fi 6--IEEE 802.11 ax. These technologies culminate in a vital product that supports users' daily activities: WSNs in the IoT ecosystem--WSNs [15], along with relevant protocols and [19]--are designed to integrate seamlessly into use cases for Smart Buildings and, with the advent of 5G-IoT, into broader Smart City infrastructure.  
Moreover, considering the Smart Cities, there is a new field of research about distributed computation offloading for energy provision minimization in WP-MEC networks using multiple points obtaining the amount of energy available through radio-frequency of mobile devices [20].  
IoT Protocols: CoAP, MQTT in IoT and WSN and IoT Management  
Wireless networks that control and interact with IoT devices, including wireless sensors and actuators, are becoming increasingly common. WSNs are now widely adopted in Smart Factory, Smart Farm, Smart Grid and Smart Building implementations. These networks and infrastructures utilize various configurations, such as mesh and non-mesh, while advancing significantly in routing protocols tailored for WSNs. For further insights, refer to the studies in [2,21].  
The Constrained Application Protocol (CoAP) protocol of the IoT world, defined by the IETF in RFC 7252 [22] and with updates in subsequent RFC 7959 and RFC 8613, is a lightweight information transfer protocol designed for the Internet and integrates with the _http_ protocol using message exchange, supporting multicast traffic, as seen in Figure 4. These protocols are of particular interest in the case of SB use, being used in restricted environments of various types of IoT devices, that is, an inhospitable environment subject to interference, packet loss, noise, less CPU processing use and low transmission power.  
Figure 4: (**a**) Protocol stacks SIP(IP, RTP - VoIP) between a SIP Server and the client device, (**b**) Protocol stacks IoT—IoT devices and an associated IoT application server.  
Figure 3: Intelligent Edge Computing, SDN without the Fog layer, NFV and IoT devices [16].  
The CoAP protocol supports devices with a small amount of memory, high error rates and it is used in IoT and networks with low data transfer rates. The motivation for using CoAP is to bring the RESTful (Representational State Transfer) communication paradigm to smart objects, such as the IoT. Recalling the main idea of RESTful resource representations, they are exchanged between a server and an IoT device at the edge (client on the network).  
CoAP integrates with the HTTP protocol, with support for multimedia traffic and low additional overhead. This message exchange is very similar to those known from HTTP. It meets the requirements for M2M (Machine-to-Machine) Internet protocols, uses the UDP protocol with support for both multicast and optional unicast traffic, also allowing for the exchange of asynchronous messages. It has simple and low-complexity headers and allows stateless http; that is, without any state, allowing for a possible proxy to access CoAP resources through the HTTP protocol [23].