# Impact of Latency on QoE, Performance, and Collaboration in Interactive Multi-User Virtual Reality
## 5 Conclusions  
In this work, we have presented a networked multi-user and multi-device collaborative VR, which enables two simultaneous users to work together in a virtual environment to bake a virtual pizza. To this end, a multi-device server-based synchronizing architecture was presented and the most prominent network parameters (latency and throughput) were analysed. In addition, the results of a user study, evaluating the influence of multiple network distortions on end-user perception, performance and collaboration, subjective time perception, and the occurrence of cybersickness, were presented. The results show that users were able to easily distinguish between distorted and non-distorted network configurations, but that making a distinction between different types of distortions was much less straightforward. This suggests that for multi-user VR systems too a perception threshold for both latency and burst seems to exist. Nevertheless, the combination of both latency and burst has important repercussions in some cases, which may have both an objective and subjective underlying cause. As such, additional experiments to further explore the evaluation space and identify these perception thresholds are required and are, therefore, envisioned as an interesting direction for further research. Moreover, the user's role in the experience and their tasks, interactivity, and movement were shown to have an important influence on the subjective level of perception, the strength of preferences, and the occurrence of cybersickness symptoms, despite the absence of notable differences in the objective system and user performance. It would also be interesting to conduct additional, in-depth experiments in order to craft objective metrics of interactivity in VR and to investigate their relationship to subjective quality, time perception, and cybersickness with respect to the context of the task and use case at hand. As such, these objective metrics could be taken into account by VR designers to objectively, and optionally in real-time, monitor network and end-user characteristics and their influence on each other. Over time, this should lead to the creation of collective perception metrics that model the QoE of the group as a whole rather than at the individual level. This would create the possibility of dynamically counteracting any (expected) drops in group dynamics and performance by means of smart interventions in the transmission system and/or virtual environment. Figure 18: Distribution of the different ranks assigned by subjects to each of the four scenarios, split per user role, with regard to the level of cybersickness being induced (from most (1) to least (4)) for each scenario. Note that some subjects did not fill in or incorrectly filled in the post-session questionnaire and are, therefore, excluded from this graph. Some limitations of the presented study need to be mentioned. First of all, the pool of test subjects exhibits a bias towards academic environments, scientific backgrounds, and technological proficiency. Although the majority of the subjects indicated that they had little prior experience with VR, it is not implausible that the aforementioned factors exerted an influence on the obtained results. It is recommended, therefore, that further validation is undertaken to derive conclusions based on a more heterogeneous pool of test subjects. In addition, the required pace and movement from the end-user perspective is limited to the current collaborative use case. As different levels of interaction and movement could also affect end-user perception and valuation, repetition of the conducted evaluation in a more fast-paced environment with different interpretations of the user roles is desirable to gain more understanding of the influence of these contextual factors. Conceptualization, all authors; methodology, S.V.D., J.S. and M.T.V. ; software, S.V.D. and J.S. ; validation, S.V.D. and J.S. ; formal analysis, S.V.D. ; investigation, S.V.D. and J.S. ; resources, S.V.D., J.S., F.D.T. and M.T.V.