## 4 Measurements and Testing of the Measuring System
### Network Load Testing
#### 4.3.2 Transmission  
To test the network load in terms of the amount of transmitted data, the measuring station presented in Figure 2 was used. The WSS module transmitted data in accordance with the developed measurement procedure (26 measurement cases). During the system operation, Ethernet transmission frames, which use the UDP, were acquired on the PC server side using Wireshark. Then, the Wi-Fi frames captured by the Sniffer were also acquired. Only the data frames sent by the WSS were analysed. In the measurement cases (P1, P2, P8, P14, P19, and P24), for which the maximum frame transmission frequency\(f_{T}\) was 5 Hz or 15 Hz, Management frames were captured informing that the radio module goes to sleep or is woken up. These frames were not observed for the other measurement cases. Putting the radio module into the sleep mode allows to reduce power consumption, which was observed while testing the system energy efficiency (Section 4.2). In addition, the amount of data transferred was calculated (in kB/s), in which the Management and ACK frames captured by the Sniffer were omitted. The mean data rate during 1 s was calculated for both Ethernet and Wi-Fi frames. The graph of the amount of transmitted data versus time, taking into account the measurement cases (P1 to P26), is shown in Figure 11.  
In the case of Ethernet frames, the data include: data from the system, UDP, IP, and MAC 802.3 headers, whereas in the case of Wi-Fi frames, the total length of the frame sent by radio (including the radio interface configuration header, WPA2, MAC 802.11, LLC, SNAP, IP, and UDP). Due to the greater number of components and the fact that the 802.11 MAC header is longer than the 802.3 MAC, the total length of the Wi-Fi frame will be greater than for the Ethernet frame. Attention should be drawn to the difference in the amount of data captured by the Sniffer compared to the Ethernet transmission. The amount of data from the captured Wi-Fi frames should be greater than the amount of data from the Ethernet frames. In some measurement cases, the opposite is true because the Sniffer cyclically switches between Wi-Fi channels, which leads to partial data loss, but the shape of the curve remains intact.  
Reducing the maximum frequency with which data frames are transmitted, and possibly increasing the number of sensors for which data frames are transmitted at a frequency\(f_{T}\) of 5 Hz, allows for a significant reduction in the amount of data transmitted. This reduction does not have a significant impact on the quality of motion mapping on  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Transmission** & **5 Hz** & **15 Hz** & **30 Hz** & **60 Hz** \\
**Frequency** & & & & \\ \hline
**Difference (\%)** & \(-\)70.23\% & \(-\)38.05\% & \(-\)23.84\% & Reference \\ \hline \hline \end{tabular}
\end{table}
Table 4: Differences in the radio band occupancy depending on the frame transmission frequency.  
Figure 11: Changes in data rate for defined measurement cases: (**a**) for Ethernet frames and (**b**) for Wi-Fi frames.  
the PC server side, which is discussed later in the article. Most data are sent in the case of P26, whereas the least in P1. In the case of P1, the amount of data transferred is by approximately 91.6% lower than in the case of P26. The percentage differences between P26 and the other cases are presented in Table 5.