## 4 Experimental Setup and Procedures
### Discussion  
Regarding the first research question (RQ.1), we may conclude that each component has certain negative impact on the performance, in terms of both the frame rate and the client-server response time. The only exception was the E.ECA.1 experiment, where the ECA component has virtually zero influence on the frame rate. As shown in Tables 4 and 6 and scatter plots, linked in Figures 9 and 10, the performance was stable both with and without the corresponding components. In all cases but one, the values measured with the corresponding component followed the same trend as the values without it. The only exception was the response time in the E.6 DF.20 experiment (PH+19 PC) with the significant rise of the response time when 6-DoF SMC was involved. The ECA component has the lowest overall impact (4.03% on the frame rate and 6.08% on the response time on average). Based on this and its stable performance, we may conclude that ECA was implemented correctly and can be used without the risk of a significant performance loss. The 6-DoF SMC component was the most influential one. The primary reason for this is the resource-hungry motion tracking process, where the input from the phone primary camera has to be analyzed and the user motion calculated. This conclusion is based on two facts. First, the impact on the frame rate (36.07%) was almost the same as the impact on the response time (34.15%). Second, all the computations of the 6-DoF SMC happen in the phone and network communication is not involved in any way. The influence may be noticeably lower on a device better optimized for the motion tracking. On the mid-range device used (Redmi Note 7 with Android 10), the performance was still acceptable with 10 users sharing the scene (the E.6 DF.10 experiment). In E.6 DF.10, the minimal frame rate was 28 fps and the maximal response time was 27 ms. This means that the user of the phone still perceives the movements in the virtual scene (VS) as fluent and the information about the avatars of other users is up to date in each frame. The HoloGOM component has almost no impact on the response time (2.27%), while the frame rate drop is significant (29.1%). However, the performance on MS HoloLens is not good overall, with or without the component. Even with only one user in the scene, the average frame rate with the component was only 24.23 fps. With 5 and 10 users, the video output turned into a slideshow experience (11.87 fps for 5 and 6.75 fps for 10 users on average). Because of the performance drop being so significant, we decided not to carry out the experiments with 15 and 20 users on MS HoloLens. When interpreting the results with respect to the second research question (RQ.2), we have to be more careful. In the case of RQ.1, some generalizations have been possible as the experiments compared the performance with and without the components under the same conditions. The answer to RQ.2 is valid only for the used experimental setup, i.e. the virtual scene, the personal computers (PC) and the smartphone. According to their features and performance (see Table 1 in Section 4), the devices used belong to the middle \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & **E.6 DF.5** & **E.6 DF.10** & **E.6 DF.15** & **E.6 DF.20** & **E.HL.5** & **E.HL.10** \\ \hline \multirow{4}{*}{**F.6 DF.10**} & **max** & 21 & 27 & 35 & 55 & 85 & 115 \\  & **avg** & 19.35 & 26.14 & 34.04 & 51.29 & 59.22 & 81.87 \\  & **min** & 17 & 25 & 33 & 48 & 33 & 55 \\  & **std** & 1.36 & 0.82 & 0.76 & 2.20 & 14.91 & 18.11 \\ \hline \multirow{4}{*}{**F.6 DF.10**} & **max** & 17 & 24 & 29 & 32 & 73 & 94 \\  & **avg** & 16.00 & 22.02 & 27.65 & 29.51 & 58.85 & 78.79 \\  & **min** & 15 & 20 & 26 & 27 & 46 & 63 \\  & **std** & 0.80 & 1.37 & 1.10 & 1.77 & 8.18 & 9.02 \\ \hline \multicolumn{2}{c}{**RT.inc (\%)**} & 20.95 & 18.71 & 23.13 & 73.82 & 0.63 & 3.91 \\ \hline \hline \end{tabular}
\end{table}