Dependency-aware quality-differentiated wireless video multicast

Video multicast exploits the wireless broadcast nature to transmit a video stream to multiple clients with a minimum bandwidth requirement. Assigning a suitable transmission bit-rate to each scalable coded block in a video stream is however a challenging problem because clients in a wireless network have heterogeneous channel quality and experience different packet loss probability. Prior work attempts to transmit the base-layer stream at a low transmission bit-rate to ensure a high reception probability, and hence the basic visual quality. Such methods however are over-simplified for a video stream that supports multiple quality levels in a video frame and needs explicit rate assignment for each block. We propose in this paper a dependency-aware rate scheduling scheme that assigns each block a rate according to dependency between blocks. With consideration of block dependency, we can better utilize limited wireless bandwidth to deliver important blocks, and minimize the number of undecodable blocks due to the loss of their reference blocks at the receivers. The simulation results show that since our scheme reduces the number of undecodable blocks, it achieves a higher overall video quality for a multicast group than the existing schemes under different client distributions.