Restless Video Bandits: Optimal SVC Streaming in a Multi-User Wireless Network

In this paper, we consider the problem of optimal scalable video delivery to mobile users in wireless networks given arbitrary Quality Adaptation (QA) mechanisms. In current practical systems, QA and wireless channel scheduling are performed independently by the content provider and network operator, respectively. While most research has been focused on jointly optimizing these two tasks, the high complexity that comes with a joint approach makes the implementation impractical. Therefore, we present a scheduling mechanism that takes the QA logic of each user as input and optimizes the scheduling accordingly. Hence, there is no need for centralized QA and cross-layer interactions are minimized. We model the QA-adaptive scheduling and the jointly optimal problem as a Restless Bandit and a Multi-user Semi Markov Decision Process, respectively, in order to compare the loss incurred by not employing a jointly optimal scheme. We then present heuristic algorithms in order to achieve the optimal outcome of the Restless Bandit solution, assuming the base station has knowledge of the underlying quality adaptation of each user (QA-Aware). We also present a simplified heuristic without the need for any knowledge of the QA logic at the base station (QA-Blind). We show that our QA-Aware strategy can achieve up to two times improvement in network utilization compared to popular baseline algorithms such as Proportional Fairness. We also show that the QA-Blind strategy performs very close to the QA-Aware scheme while providing significant reduction in complexity. Furthermore, we provide a testbed implementation of the QA-Blind scheme in order to compare it with baseline algorithms in a real network setting.