Proxy-Based Multi-Stream Scalable Video Adaptation Over Wireless Networks Using Subjective Quality and Rate Models
Despite growing maturity in broadband mobile networks, wireless video streaming remains a challenging task, especially in highly dynamic environments. Rapidly changing wireless link qualities, highly variable round trip delays, and unpredictable traffic contention patterns often hamper the performance of conventional end-to-end rate adaptation techniques such as TCP-friendly rate control (TFRC). Furthermore, existing approaches tend to treat all flows leaving the network edge equally, without accounting for heterogeneity in the underlying wireless link qualities or the different rate utilities of the video streams. In this paper, we present a proxy-based solution for adapting the scalable video streams at the edge of a wireless network, which can respond quickly to highly dynamic wireless links. Our design adopts the recently standardized scalable video coding (SVC) technique for lightweight rate adaptation at the edge. Leveraging previously developed rate and quality models of scalable video with both temporal and amplitude scalability, we derive the rate-quality model that relates the maximum quality under a given rate by choosing the optimal frame rate and quantization stepsize. The proxy iteratively allocates rates of different video streams to maximize a weighted sum of video qualities associated with different streams, based on the periodically observed link throughputs and the sending buffer status. The temporal and amplitude layers included in each video are determined to optimize the quality while satisfying the rate assignment. Simulation studies show that our scheme consistently outperforms TFRC in terms of agility to track link qualities and overall subjective quality of all streams. In addition, the proposed scheme supports differential services for different streams, and competes fairly with TCP flows.