## 2 Literature Review  
### Applications and Challenges of IEEE 802.11 Wireless Networks in Industry 4.0  
The general Industry 4.0 framework consists of two critical layers: (1) devices and (2) networks. The first layer comprises mobile devices, sensors, machines, automated guided vehicles, as well as people and other data-collecting entities that communicate with one another [2]. This communication is made possible by the second layer, which comprises wired and wireless communication technologies that allow real-time data transfer among devices in the first layer [2]. Regarding the second layer, Industry 4.0 already complements wired networks by making use of various wireless communication technologies (Table 1) which have to respond to various industrial requirements towards throughput, seamless connectivity, dynamic topologies, signal interference and path loss, real-time performance, and reliability. IEEE 802.11 networks are able to fulfill those requirements, as well as being widely available and easy and inexpensive to install, which makes them important wireless communication technology in Industry 4.0 [2; 4; 12]. For example, IEEE 802.11 networks have been used in various Industry 4.0 contexts, such as production planning, monitoring, data collection, navigation of moving devices, and transfer of multimedia content [3; 13]. Studies have examined IEEE 802.11 networks for monitoring steam flood and water flood pipelines in oil fields [14], monitoring a water pump control system [15], networking and managing automated guided vehicles in a warehouse [16], broadcasting multimedia \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name** & **Standard** & **Frequency Band** & \begin{tabular}{c} **Theoretical** \\ **Communication** \\ **Range** \\ \end{tabular} & \begin{tabular}{c} **Theoretical** \\ **Transfer Rates** \\ \end{tabular} \\ \hline \begin{tabular}{c} Advanced and \\ adaptive network \\ technology (ANT) \\ Bluetooth \\ (BLE) \\ \end{tabular} & Proprietary (Garmin) & 2.4 GHz & 30 m & 12.8, 20 or 60 Kbps \\ \begin{tabular}{c} \\ Bluetooth \\ \end{tabular} & IEEE 802.15.1 & 2.4/5 GHz & 10 m & 1, or 24 Mbps \\ \begin{tabular}{c} Bluetooth low energy \\ (BLE) \\ \end{tabular} & IEEE 802.15.1 & 2.4 GHz & 50 m & 125, 250, 500 Kbps; \\ \begin{tabular}{c} Long range (LoRa) \\ WAN \\ \end{tabular} & LoRaWAN TSI-1.0.4 & 868/900 MHz & 30 Km & 0.3–50 Kbps \\ \begin{tabular}{c} Narrowband Internet \\ of Things (NB-IoT) \\ \end{tabular} & \begin{tabular}{c} 3 GPP Release 13/14 \\ (LTE Advanced Pro) \\ \end{tabular} & 180 kHz & 10 Km & 26–159 Kbps \\ \begin{tabular}{c} Radio-frequency \\ identification (RFID) \\ \end{tabular} & ISO/IEC 24791 & 125 kHz/13.56 & 10 cm/1 m/20 m/100 m & 5/26.48/640 Kbps \\ \begin{tabular}{c} Wi-Fi \\ Worldwide \\ \end{tabular} & IEEE 802.11 & 2.4/5 GHz & 10–150 m & 54 Mbps to \textless{}1 Gbps \\ \begin{tabular}{c} interoperability for \\ microwave access \\ (WiMAX) \\ \end{tabular} & IEEE 802.16 & 2.4/5.1–66 GHz & 0.3–49 Km & 1 Mbps–1 Gbps (Fixed); 50–100 Mbps (mobile) \\ \begin{tabular}{c} ZigBee \\ \end{tabular} & IEEE 802.15.4 & 868/915 MHz/2.4 GHz & 10–300 m & 20, 40, or 250 Kbps \\ \
\begin{tabular}{c} Z-Wave \\ PHY/MAC \\ \end{tabular} &
\begin{tabular}{c} Proprietary/ITU.G9959 \\ 900 MHz \\ \end{tabular} & 900 MHz & 30 m & 100 Kbps \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of wireless communication technologies. Data from [2; 8; 9; 10; 11]. content in real time [1; 13; 17], and exchanging multimedia data between industrial PCs and monitoring devices in real time [13]. Thus, IEEE 802.11 networks can connect many devices in a heterogeneous industrial environment to support diverse applications, but they must fulfill certain minimum requirements to support the high demands of Industry 4.0, such as high throughput, including for a rapidly expanding range of multimedia applications [2; 3; 5], as well as dynamic topology that ensures uninterrupted communication in the presence of movement and large fluctuations in throughput [3].