VPAL: Video Packet Adaptation Layer for reliable video multicast over IEEE 802.11n WLAN

In this paper, we propose a scheme, called Video Packet Adaptation Layer (VPAL), for reliable video multicast over the IEEE 802.11n WLAN. VPAL is composed of (1) Raptor coding for reliable video transmission, (2) header compression and (3) packet aggregation, both for efficient video transmission. Most of the VPAL functionalities reside above the emerging IEEE 802.11n Medium Access Control (MAC) layer while the packet aggregation requires some changes in the MAC functionalities. The reliability of the video multicast under a strict delay requirement, is provided by achieving the target error probability of video packets, which is done by controlling both the Raptor code rate and the physical (PHY) layer transmission rate. This strategy can provide a satisfactory quality of multicast video service irrespective of the channel condition with a minimum bandwidth use. New features of the 802.11n MAC are utilized for the channel status feedback from the users. Redundant header fields in the video packets are compressed, and then these packets are aggregated to further reduce the protocol overheads. We also consider a reduced version of VPAL which does not require any change in the MAC functionalities and simply works with the IEEE 802.11n MAC. The performance of the proposed systems is comparatively evaluated in terms of the perceived video quality, i.e., peak signal-to-noise ratio (PSNR), as well as the amount of required resources via both numerical analysis and simulations.