## 6 Discussion  
Reliable and seamless wireless communication is critical in industrial environments, so the effects of interference on IEEE 802.11 network performance should be understood in detail in order to allow the design of appropriate prevention and management measures [2]. In our laboratory set-up, interference from a wireless audio transmitter significantly reduced mean network throughput by 85%, based on measurements of down- and uploads. The strong reduction in throughput observed here reflects that the network and interferer were operating on the same frequency band (2.4 GHz) and that the interferer was operating continuously. As a result, the IEEE 802.11 station detected non-IEEE 802.11 radiofrequency energy from the interferer on the PHY layer, so the station either backed off from accessing the channel or it transmitted data but at higher probability of collision or frame corruption. The throughput reduction observed here is comparable to that reported for analogue wireless cameras or analogue cordless phones, which also transmit continuously [7]. The reduction observed here is greater than the 49% reported for a microwave oven placed 1 m from the IEEE 802.11 access point and the 9% reported for Bluetooth speakers [18]. Indeed, our results are consistent with that study and another one showing that wireless audio transmitters can reduce network throughput substantially more than Bluetooth handsets [22; 26]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Condition or** & & & & & \\
**Variable** & **n** & **Mean** & **Std. Err. ** & **Std. Dev. ** & **[95\% Conf. Interval]** \\ \hline No interference & 30 & 11.0786 & 1.0687 & 5.8539 & 8.8927 & 13.2645 \\ Interference & 30 & 1.6623 & 0.2053 & 1.1249 & 1.2422 & 2.0824 \\ Combined & 60 & 6.3705 & 0.8165 & 6.3252 & 4.7365 & 8.0044 \\ Difference * & 9.4163 & 1.0883 & 7.197 & 11.6356 \\ \(\mathrm{H_{null}}\): diff = 0 & \multicolumn{4}{c}{Satterthwaite’s degrees of freedom = 31.139} \\ \(\mathrm{H_{alternative}}\): diff \(<\) 0 & \multicolumn{4}{c}{Halbernative: diff \(!=0\)} & \multicolumn{4}{c}{Halbernative: diff \(>0\)} \\ \(\mathrm{Pr}\) (\(\mathrm{T}<\mathrm{t}\)) = 1.0000 & \multicolumn{4}{c}{\(\mathrm{Pr}\)(\(\mathrm{T}\)\(\mathrm{T}\)\(\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{    \mathrm{   }}}}}}}}}}}}}}}}\)\)\(\mathrm{1}\)\(\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{ \mathrm{ \mathrm{     }}}}}}}}}}}}}}}}}}\) \(\)\(\mathrm{0.0 Our results reveal several challenges that network professionals will need to resolve in order to optimize the functioning of IEEE 802.11 networks in Industry 4.0 environments. These challenges affect the four steps of site surveying, frequency planning, network testing, and troubleshooting [22]. First, sites should be surveyed before and after network deployment to ensure that specific network requirements are met. For example, some scenarios require rapid (millisecond) switching from one wireless network to another, such as when several automated guided vehicles must be coordinated as their positions change constantly [2; 3]. A network hampered by the interference in our experiment would likely be unable to support such roaming. Indeed, several other industrial applications require sustained high throughput, including video transmission for tracking and critical warning systems (6-48 Mbps), as well as high-resolution thermographic videos or videos that must be uploaded from smart glasses or helmet cameras (24-48 Mbps) [5].