Video Multicasting With Channel Diversity in Wireless OFDMA Networks

The demand for real-time video services coupled with the need for increased spectral efficiencies has brought a lot of attention to video multicasting in next generation OFDMA systems. Layered video provides an efficient solution to address the channel quality variation across users. However, the frequency selectivity across sub-channels introduced by OFDMA serves as a drawback for multicast scheduling. This significantly diminishes the benefits of video layering and can potentially degrade the system performance to worse than that without channel diversity. Layering the PHY with the help of multi-resolution modulation serves as an effective tool to help retain channel diversity and leverage the benefits of layered video. While layering the PHY provides benefits to multicast in general, we show that its benefits are much more significant in a system with channel diversity. The corresponding multicast scheduling problem now becomes all the more challenging with multi-resolution modulation. In addressing this problem, we provide efficient scheduling solutions both for systems with and without channel diversity. Our solutions have provable performance guarantees and are amenable to practical implementation. Further, evaluation in realistic scenarios reveals close to optimal performance of our proposed solutions as well as the large benefits obtained by layering the PHY in OFDMA systems with channel diversity.