A Scheduling Algorithm for Interactive Video Streaming in UMTS Systems

The importance of a Variable Bit Rate (VBR) video transmission on UMTS networks is increasing in time. The bursty nature of VBR traffic complicates the design of efficient mechanisms for video retrieval, transport, and provisioning to achieve a high bandwidth utilization and reduce the negative effects of bandwidth fluctuations in wireless channels. To this aim, several scheduling algorithms can be successfully implemented. They regulate data transmission to reduce the rate variability peculiar of VBR streams. At client side, scheduled data are temporarily stored in the client buffer before being decoded on the terminal. In this work, a novel scheduling algorithm, the Scheduling Algorithm for Interactive Video (SAIV) is presented and analyzed. It is an algorithm thought for VBR stream transmission in UMTS networks that takes into account the user interactivity. Scheduling is performed “online”, over relatively small video segments to reduce delays. SAIV dynamically varies the sampling frequency of the Real Time Control Protocol (RTCP) feedbacks that carry information on the client buffer status. The sampling frequency is modulated according to the difference between the calculated buffer fill level at server side and the real buffer fill level at client side. The latter is exploited to reschedule data with the updated information. Numerical results testify the SAIV effectiveness compared to the classical SLWIN online algorithm already known by literature, in some simulation scenarios of real interest.