Statistical Multiplexing Of Vbr+ Video

The currently specified variable bit-rate (VER) service class for real-time traffic on broad-band networks [1] severely sacrifices network utilization to provide QoS support for multimedia traffic. A new service class, called VBR+, has been proposed to balance the goals of providing acceptable QoS and achieving high network utilization [2]. VBR+ is a flexible service class that extends the traditional VER service with bandwidth renegotiation. Bandwidth renegotiation is well suited for the dynamic traffic profiles of multimedia applications. Renegotiation allows a more efficient network capacity allocation and potentially allows the network to operate at more aggressive statistical multiplexing regimes while maintaining acceptable QoS. Some quality degradation is caused by source rate control when the network is congested and renegotiation requests cannot be fully satisfied. This paper quantifies the trade-off between video quality and network utilization for VBR+ transport. The multiplexing performance of VBR+ traffic is obtained via simulation using MPEG-2 video traces obtained using NEC's VisuaLink codec [3]. Results show that VBR+ transport can maintain acceptable video quality at 70-80% link utilization. This represents a 20-30% improvement on utilization over the currently specified VER service for comparable video quality.