Optimising QoE for Scalable Video multicast over WLAN

International audienceQuality of Experience (QoE) is the key to success for multimedia applications and perceptual video quality is one of the important component of QoE. A recent video encoding scheme called Scalable Video Coding (SVC) provides the flexibility and the capability to adapt the video quality to varying network conditions and heterogeneous users. In this paper, we focus on SVC multicast over IEEE 802.11 networks. Traditionally, multicast uses the lowest modulation resulting in a video with only base quality even for users with good channel conditions. To optimize QoE, we propose to use multiple multicast sessions with different transmission rates for different SVC layers. The goal is to provide at least the multicast session with acceptable quality to users with bad channel conditions and to provide additional multicast sessions having SVC enhancement layers to users with better channel conditions. The selection of modulation rate for each SVC layer and for each multicast session is achieved with binary integer linear programming depending on network conditions with a goal to maximize global QoE. Results show that our algorithm maximizes global QoE by providing highest quality videos to users with good channel conditions and by guaranteeing at least acceptable QoE for all users

Distributed Media-Aware Rate Allocation for Video Multicast over Wireless Networks

A unified optimization framework for rate allocation among multiple video multicast sessions sharing a wireless network is presented. Our framework applies to delivery of both scalable and non-scalable video streams. In both cases the optimization objective is to minimize the total video distortion of all peers without incurring excessive network utilization. Our system model explicitly accounts for heterogeneity in wireless link capacities, traffic contention among neighboring links, as well as different video rate-distortion (RD) characteristics. The proposed distributed rate allocation scheme leverages cross-layer information exchange between the MAC and application layers to achieve fast convergence at the optimal, media-aware allocation. Performance of the proposed media-aware rate allocation protocol is compared against a heuristic scheme based on TCP-Friendly Rate Control (TFRC). In network simulations of standard-definition (SD) video streaming over single or multiple multicast trees, the proposed scheme consistently achieves higher overall video quality than the TFRCbased heuristics. When delivering scalable streams, the flexibility of perpeer rate adaptation inside each multicast tree yields a further slight improvement in overall video quality over multicast of non-scalable streams