Scalable Collocated Multi-User VR Through Virtual Environment User Spatial Coherence

This paper presents an approach to alleviating the server-client communication bottleneck in collocated multi-user virtual reality (VR). Instead of transmitting unique packets to each client, the system multicasts the same packets to all users, combining packetization, visibility-aware prioritization, and lightweight acknowledgments to ensure efficiency and fairness. To enable rapid scene completion, the environment is partitioned into independent fixed-size packets that can be decoded immediately upon arrival, and transmission order is guided by precomputed visibility footprints. Scalability is achieved through repeated multicast until compact bitmap acknowledgments confirm reception, keeping communication cost mostly independent of the number of clients. A controlled study with 23 participants in groups of 7 and 16 showed that this method reconstructs environments several times faster and with fewer missing parts than a conventional unicast TCP-based approach. These findings demonstrate that multicast transmission over commodity Wi-Fi can support large collocated VR groups.