A reliable and scalable groupCast block acknowledgement scheme for video multicast over IEEE 802.11aa

Reliable video delivery is one of the most important requirements to satisfy end user needs. With the proliferation of multimedia technologies there is a growing demand for video multicast, particularly in challenging wireless environments. Effective video multicast services need to meet the conflicting goals of assured data rate and reliability. The most used IEEE standards (802.11a/b/g/n) do not ensure reliable multicasts since throughput remained primary focus of research in recent past. The IEEE 802.11aa remains the only standard that attempts to handle the unreliability issue with multicasting. However, the block acknowledgement scheme of the IEEE 802.11aa standard suffers from scalability issue. As the number of receivers increases, the number of acknowledgement packets increases proportionally. This increasing acknowledgement storm eventually causes a decrease in the average peak signal-to-noise ratio (PSNR) of the video frames. Therefore, in order to overwhelm the scalability limitation of the IEEE 802.11aa block acknowledgment scheme, this paper proposes a modified block acknowledgment scheme for video multicast. Our scheme considers the impact of the loss of different frames on video quality under Moving Picture Expert Group 4 (MPEG-4) and H.264 video coding. We provide a Markov chain model and numerical analysis of our proposed protocol. Simulation results indicate that proposed scheme performs well in terms of PSNR.