VRCast: Mobile streaming of live 360-degree videos

Live streaming of immersive multimedia content, e.g., 360-degree videos, is getting popular due to the recent availability of commercial devices that support interacting with such content such as smart phones, tablets, and head-mounted displays. Unicast streaming of immersive content on cellular networks consumes substantial network resources and does not scale to large number of users. Multicast, on the other hand, offers a scalable solution but it introduces multiple challenges, which include handling user interactivity, ensuring smooth quality, supporting user mobility, conserving the energy of mobile receivers, and ensuring fairness among users. We propose a comprehensive solution for the problem of live streaming of 360-degree videos to mobile users, which we refer to as VRCast. VRCast is designed for cellular networks that support multicast, such as LTE. It divides the 360-degree video into tiles and then solves the complex live streaming problem in two steps to maximize the viewport quality of users and ensure a smooth quality within the same viewport while saving the energy of mobile devices and achieving fairness across users. Extensive trace driven simulation and real LTE testbed results show that VRCast outperforms the closest algorithms in the literature by wide margins across several performance metrics. For example, compared to the state-of-the-art, VRCast enhances the median frame quality by up to 22% and reduces the variation in the spatial quality by up to 53% and improves the energy saving for mobile devices by up to 250%.