Non-orthogonal Multiple Access Enhanced Scalable 360-degree Video Multicast

By providing an immersive experience with panoramic views, 360-degree video streaming has gained increasing popularity recently. In many cases, videos are transmitted to mobile users over cellular networks. However, due to the high bandwidth requirement of 360-degree videos and the growing number of users, it is challenging to provide high-quality live streaming services to all users with limited bandwidth. Improving spectral efficiency and reducing bandwidth consumption are two major approaches to address this issue, which can be achieved with non-orthogonal multiple access (NOMA) and scalable video coding (SVC), respectively. In this paper, we apply NOMA and SVC to 360-degree video streaming over a cellular network and propose a multicast scheme called SVCast, aiming to maximize the sum quality of experience of users served by a base station. Such a problem is formulated as an NP-hard problem, and we decompose it into two levels of subproblems. The lower-level subproblem is inter-group spectrum allocation, which is solved by a knapsack approach. The higher-level subproblem is intra-group multicast scheduling, and we propose a recursive algorithm to solve it. Simulation results demonstrate that SVCast improves the system utility by 31.9% on average. Furthermore, SVCast eliminates the need for viewport prediction by aggregating the contents from the viewports of multiple users.