Roaming Free in the VR World with MP2

Free-roaming VR which allows a group of users to navigate in rooms and even buildings, enhances the VR experience by making it more immersive and interactive. Streaming VR videos over wireless enables unconstrained experiences but raises unprecedented requirements in mobility, efficiency, and scalability. Existing solutions fail in one or more of the following challenges: maintaining low latency during handover, balancing loads on different APs, and stabilizing bitrate for competing users, due to their decentralized nature where each user lacks information about others and makes locally optimal decisions. To address these problems, we present MP², a centralized VR streaming system that coordinates multiple Wi-Fi links and video bitrates among users for better QoE. A centralized controller collects cross-layer information from each user and makes better decisions based on global information. It achieves this in a timely manner through accurate modeling and the use of efficient pruning and partitioning algorithms. To our knowledge, MP² is the first centrally coordinated VR streaming system that supports multi-user free-roaming. Comprehensive benchmarks including real-world tests, large-scale emulation, and trace-driven user studies, confirm the effectiveness of MP² against state-of-the-art solutions. It achieves 35× improvement in tail latency, 1.56× in bitrate, and 1.86× in QoE over state-of-the-art baselines. MP² achieves up to a 99.1% improvement in mean opinion scores according to the user study.