FlexVi: PHY Aided Flexible Multicast for Video Streaming over IEEE 802.11 WLANs

Wireless video multicast over IEEE 802.11 WLANs is a viable approach to bridging the gap between limited wireless resources and the ever-increasing mobile video traffic demand. However, existing wireless multicast mechanisms have several limitations, such as low spectral efficiency, high feedback overhead, and lack of consideration of the frame aggregation feature of current WLANs. In this paper, we propose FlexVi, a flexible wireless multicast solution for efficient video streaming over WLANs. Considering the frame aggregation of the current WLANs, FlexVi allows an access point to dynamically adjust the data rate on the basis of three factors: available wireless bandwidth, heterogeneity of the channel qualities among the clients, and the priorities among the video frames in terms of video quality. In addition, by harnessing the orthogonality of the subcarriers in the orthogonal frequency division multiplexing, FlexVi enables multiple clients to deliver their feedback to an access point simultaneously without collision, which results in very low feedback overhead. We verified the feasibility of FlexVi through experiments on a software defined radio platform. We also conducted an extensive simulation study and found that FlexVi outperforms the latest wireless multicast mechanisms.