Scheduling Algorithms for Broadcasting Media with Multiple Distortion Measures

Carri W. Chan, Nicholas Bambos, Susie J. Wee, John G. Apostolopoulos

Abstract: The growing popularity of multimedia streaming applications brings a growth in diversity of media clients (laptops, PDAs, cellphones). Effectively serving this heterogeneous group of users is highly desirable. Scalable media codecs such as H.264/MPEG-4 SVC help make this adaptation possible. To account for the various capabilities and requests of each user, such as varying spatial or temporal resolutions, multiple distortion measures (MDM) are considered. Rather than consider a homogeneity in users, the MDM framework considers multiple different distortion values for each media packet for each user type. We consider the scenario of simultaneously broadcasting a video stream to multiple users over wireless links. The objective is to design a scheduling algorithm which achieves the highest aggregate quality-of-service, measured by distortion and delay, over all different user types. We cast the problem as a stochastic shortest path problem and use dynamic programming to find the optimal policy. For statistically static channels, the optimal policy is shown to be of threshold type. For time-varying channels, a quasi-static policy is introduced. Experimental results show that our policy reduces distortion by up to a factor of 2 over conventional approaches which do not consider MDM.