On Supporting High-Quality 3D Geometry Multicasting over IEEE 802.11 Wireless Networks
With significant improvements in both wireless technologies and computational capabilities of mobile devices, it is now possible to exchange and render 3D graphics over wireless networks on mobile devices such as PDAs and laptops. In this paper, we consider a typical scenario where users holding mobile devices of different display resolutions and rendering capabilities request the same 3D object in an IEEE 802.11 wireless LAN. Several schemes are proposed. First, to support high-quality 3D content multicasting, we analyze the characteristics of 3D data and choose the minimum data set for unicast in order to avoid excessive bandwidth consumption. Then, a transcoding algorithm is proposed to address the issue of multiuser diversity. In addition, to take advantage of the nature of broadcast in wireless medium and further mitigate the issue of serious resource usage due to large data size, we propose to broadcast certain less important refinement data. With the proposed hybrid unicast/broadcast transmission scheme and a packet overhearing mechanism, good scalability can be achieved. Finally, we schedule the unicast according to users' experienced link condition to handle user mobility. Simulation results show that the proposed schemes in combination can efficiently achieve the dual objectives of low transmission delay and small distortion.