Packet Scheduling for Scalable Video Streaming Over Lossy Packet Access Networks
Video streaming applications have gained in popularity in recent years. The quality of service offered by such applications is limited by the available transmission rates as well as time-varying conditions, such as, channel fading and network congestion, which lead to packet losses. Scalable video coding techniques that allow for the flexible adaptation of temporal resolution as well as quality of an encoded bitstream can be immensely useful in developing video streaming applications that can adapt to time-varying network and channel conditions. Scalable coding techniques, however, are generally designed to offer progressive refinement, which introduces dependencies between encoded video packets. Therefore, when determining a packet scheduling technique for scalable coded video, the possibility of random packet losses, which might affect the decodability of subsequent packets, must be taken into account. In this paper, we take into account the available transmission rate, possibly time-varying channel conditions, and the possibility of random packet losses, to design a scheduling technique for video packets in a scalable bit-stream. Since the optimal solution to the scheduling problem requires an exhaustive, and therefore, intractable computation, we propose a greedy algorithm that will schedule the optimal packet for transmission at a given transmission opportunity based on the encoded content and the available channel state information. Simulation results show significant gains in performance when the proposed technique is compared to content and channel independent packet scheduling techniques.