# Impact of Latency on QoE, Performance, and Collaboration in Interactive Multi-User Virtual Reality
## 4 Results and Discussion
### Subjective Results
#### 4.4.1 Perception of the Network
Figure 12: Perceived de-synchronization between the participants own view of the virtual environment and the one of their collaborator, on a 1-to-5 Likert scale, where a higher score indicates more obvious desynchronization. Significant differences are indicated as * (\(p<0.05\)), *** (\(p<0.01\)) and *** (\(p<0.001\)), respectively, as obtained from Friedman tests followed by Dunn-Bonferroni post hoc tests. The full orange line indicates the median, the green dotted line the mean. The bullets indicate outliers, which are defined as samples laying outside the interval \([Q1-1.5\cdot IQR,Q3+1.5\cdot IQR]\), with IQR the Interquartile Range defined as IQR \(=Q3-Q1\). _(4) User preferences_: Post-session, we asked users to rank the four scenarios (\"Please order the network conditions of the playthroughs from most (1) to least (4) optimal to complete the given task.\"), without revealing the actual configuration, from the most (1) to least (4) optimal network configuration to complete the given task (Figure 13). The preference towards the undistorted scenario A was clear for user role B, with five out of six users (four subjects did not fill in or incorrectly filled in the post-session questionnaire and were, therefore, excluded) ranking it as most optimal and one out of six putting it in second rank. This was not reflected in the ranks of user role A, however, where a much more mixed view was observed. Only three out of nine users (one subject was excluded) ranked it in first place, while the same number of subjects even considered it as the worst scenario. Less consensus existed for the other three scenarios for both roles, again supporting the claim that distinguishing between latency, burst, or the combination of both was not straightforward. However, one can still observe a more convinced assessment from User B with half of the users ranking configurations C (latency) and D (burst + latency) in third and fourth place, respectively. In addition, distorted scenarios were selected only once as the most optimal one (configuration C). This is in contrast to User A, where all of the ranks were distributed more or less equally over the configurations, indicating that these users were experiencing much more difficulties in distinguishing between the configurations. One can assume that the nature and level of interactivity of the particular user role and its assigned tasks played an important role in this. As user B had to rotate more in the virtual environment (i.e., for operating the oven) and had more tasks and interactions to fulfill, they can be considered to have been more prone to distortions in the system than was the case for User A. _(5) Task difficulty_: The inability to make a distinction between distorted scenarios is also reflected in responses to the in-session question regarding the difficulty of the task given the current configuration (\"How difficult would you rate this task in the given network conditions?\"), as shown in Figure 14. Here as well, significant differences (Friedman, \(p<0.001\)) were observed between scenarios A (no distortions)-B (burst) ([PERSON] post hoc, \(p<0.05\)) and A (no distortions)-D (burst + latency) ([PERSON] post hoc, \(p<0.001\)), while the difference between A (no distortions) and C (burst) approached significance ([PERSON] post hoc, \(p=0.631\)). No pairwise significant differences were observed between any of the other scenarios, neither were there any significant differences in difficulty perception between user roles. Figure 13: Distribution of the different ranks assigned by subjects, split per user role, to each of the four scenarios with regard to the optimality of the network configuration (from most (1) to least (4)) to complete the given task. Note that some subjects did not fill in, or incorrectly filled in, the post-session questionnaire and are, therefore, excluded from these graphs.