An adaptive rate control scheme for VBR video over ATM networks

A novel adaptive rate control scheme for MPEG-I video is developed in this paper. MPEG-I exploits varying compression techniques and produces variable-bit-rate (VER) and bursty traffic. Without rate control, the networks are prone to congestion and Cell Loss Rate (CLR) in a video source is so significant that the Quality of Service (QoS) will be poor. The objective of our adaptive rate control scheme is in two-fold: (1) protect the networks from congestion, and (2) maximize the network utilization for achieving high throughput. In this scheme, the traffic via a video source is adapted by controlling the traffic burstiness according to the occupancy of the multiplexing buffer at end of each frame interval. With this scheme, CLR is remarkably reduced, and the overall QoS is improved. Since the propagation delay between a video source and the network access node has significant impact on the effectiveness of the adaptive rate control scheme, our scheme is a function of the propagation delay to achieve a high efficiency. The adaptive rate control scheme is evaluated by both an analytical queueing model and simulations with actual video sequences under a variety of network loading scenarios and configurations. The CLR reduces in magnitude under high network utilization when our adaptive rate control scheme is applied. We find that the CLR of numerical simulation is close to that of the analytical calculation especially when network is highly utilized. Even though the adaptive rate control scheme results in some degradation due to the restricted traffic volume, it is not as much as if entire cells were to be discarded.