## 3 Overview of IoT Technology
Although they have significant variances, MQTT, CoAP, XMPP, and HTTP are the primary IoT protocols. They are used to link IoT devices and IoT devices to the cloud. In terms of power consumption, ZigBee, (BLE), ZWave, and NFC are intended for portable devices with limited battery capacity [41]. Thus, it offers low power consumption. In terms of data rate, ZigBee, BLE, NFC, SigFox, and Z-Wave have data rates \(\leq\) 1 Mbps. However, RFID has the highest data rate of 4 Mbps. In terms of range, Sig Fox and Cellular have many kilometers of coverage. 6 LoWPAN, ZigBee, BLE, NFC, Z-Wave, and RFID have less than one-kilometer ranges [42]. The IEEE 802.15 working group handles the IEEE 802.15.4 short-range communication protocol, commonly used as the WSN communication  
Figure 6: IoT applications for smart building and the protocols. standard. Various correspondence conventions are defined for the application layer, as shown in Figure 7[43]. WiFi: The 2.4 GHz UHF and 5.8 GHz SHF ISM radio bands are the most widely utilized. One of the benefits of WiFi is that any device within the wireless modem's range can seek to connect to the network [44]. MQTT protocol: MQTT architecture employs a client/server approach, with each sensor acting as a client and connecting to a server. The MQTT protocol optimizes data transfer from sensor nodes to brokers over a WLAN. Customers may be required to enter a username and password to connect to MQTT brokers for security reasons [45]. CoAP protocol: CoAP is intended to meet the demands of limited-capacity devices. CoAP packets are significantly smaller than HTTP TCP streams. CoAP uses UDP rather than TCP. CoAP enables the use of Volatile Organic Compounds and multicast for addressing. CoAP uses the client/server paradigm. Clients send requests to servers, and servers respond [46]. (RFID): It is compliant with several standards, including ISO, IEC, ASTM International, the D7A, and EPC-Global. RFID systems may operate in a variety of frequency bands [41]. It works at 125-134.2 kHz for the Low-Frequency (LF) band and 13.56 MHz for the High-Frequency (HF) band. It operates at 850-960 MHz in Ultra-High-Frequency (UHF) bands where the EPC-GEN2 protocol is established [47]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**S.No** & **Tech** & **Medium** & **Max Coverage** \\ \hline
1 & WiFi & Wireless & Up To 100 M \\ \hline
2 & Ethernet & Copper Cable & Up To 50–70 M \\ \hline
3 & Wi Max & Wireless & Up To 50–70 M \\ \hline
4 & Cellular & Wireless & 10–100 M \\ \hline
5 & Xdsl & Twisted Pair Copper Cable & 1.3 km \\ \hline
6 & Plc & Electrical Power System & 1500 In 100 M Between Devices \\ \hline \hline \end{tabular}
\end{table} 
Table 2: IoT Communication Technology. Figure 7: IoT communication protocols. BLE: BLE, often known as Bluetooth smart, is essential for IoT applications. It is optimized for IoT applications with short-range, low bandwidth, and low latency. The features of standard Bluetooth BLE include lower battery usage, faster configuration, and support for star network topology with an infinite number of nodes. Bluetooth is appropriate for smaller devices such as phones, speakers, media players, and personal computers [48]. NFC: Mobile phones, industrial applications, and contactless payment systems all make considerable use of NFC technology. Similarly, NFC improves the connecting and operation processes. In addition, control of IoT devices in various settings such as the home, factory, and workplace. NFC supports P2P network topology [49]. XMPP protocol: The XMPP protocol is a real-time information transmission specification that combines IP technology and Extensible Markup Language (XML) to provide a publish/subscribe messaging system [50]. HTTP protocol: HTTP is the foundation of the Web's client-server paradigm. HTTP is intended for one-way communication between two systems. Most IoT applications have many sensors that generate data simultaneously [51].