Adaptive Multicast Transport of Realtime Video Over ATM Networks

虽然现有的研究表明，反应式拥塞控制机制能够为点对点实时视频提供高质量的视频质量和较高的信道利用率，但对于点对多点视频的反应式拥塞控制的研究相对较少，尤其是在ATM网络中。使基于反馈的多播实时视频服务的提供复杂化的问题包括(1)随着多播目的地的数量增加而内爆返回源的反馈，以及(2)多点连接中不同分支上的可用带宽量的变化。本文通过引入和研究一种新的实时组播视频服务来解决上述两个问题。多点反馈机制用于自适应地控制多层视频流的每一层的传输速率。所提出的服务依赖于视频源的自适应多层编码和来自网络的闭环反馈，以控制视频编码器的高优先级和低优先级视频生成率。它还支持最低带宽保证和对超过最低速率的视频流量的尽力支持。为了研究这些机制，采用了数学分析、模拟和使用可用于P.I.的ATM试验床网络的经验实验。

While existing research shows that reactive congestion control mechanisms are capable of providing high video quality and channel utilization for point-to-point real-time video, there has been relatively little study of the reactive congestion control of point-to-multipoint video, especially in ATM networks. Problems complicating the provision of multicast, feedback-based, real-time video service include (1) implosion of feedback returning to the source as the number of multicast destinations increases, and (2) variance in the amount of available bandwidth on different branches in the multipoint connection. The proposed research addresses and solves the two problems mentioned above by introducing and investigating a new service for real-time multicast video. Multipoint feedback mechanisms are used to adaptively control the transmission rates of each layer of a multi-layered video stream. The proposed service relies on adaptive, multi-layered coding at the video source and closed-loop feedback from the network in order to control the high and low priority video generation rates of the video encoder. It also supports a minimum bandwidth guarantee and the best effort support of video traffic exceeding the minimum rate. To study these mechanisms, mathematical analysis, simulations, and empirical experiments using the ATM testbed network available to the P.I. are employed.