Channel, Deadline, and Distortion (CD2) Aware Scheduling for Video Streams over Wireless

We study scheduling of multimedia traffic on the downlink of a wireless communication system. We examine a scenario where multimedia packets are associated with strict deadlines and are equivalent to lost packets if they arrive after their associated deadlines. Lost packets result in degradation of playout quality at the receiver, which is quantified in terms of the "distortion cost" associated with each packet. Our goal is to design a scheduler which minimizes the aggregate distortion cost over all receivers. We study the scheduling problem in a dynamic programming (DP) framework. Under well justified modeling reductions, we extensively characterize structural properties of the optimal control associated with the DP problem. We leverage these properties to design a low-complexity Channel, Deadline, and Distortion (CD2) aware heuristic scheduling policy amenable to implementation in real wireless systems. We evaluate the performance of CD2 via trace-driven simulations using H. 264/MPEG-4 AVC coded video. Our experimental results show that CD2 comfortably outperforms benchmark schedulers like earliest deadline first (EDF) and best channel first (BCF). CD2 achieves these performance gains by using the knowledge of packet deadlines, wireless channel conditions, and application specific information (per-packet distortion costs) in a systematic and unified way for multimedia scheduling.