Adaptive Multicast Transport of Realtime Video Over ATM Networks

虽然已有研究表明，响应式拥塞控制机制能够为点对点实时视频提供高视频质量和信道利用率，但对点对多点视频的响应式拥塞控制的研究相对较少，特别是在ATM网络中。使提供多播、基于反馈的实时视频服务复杂化的问题包括：(1)随着多播目的地数量的增加，反馈返回到源的内爆，以及(2)多点连接中不同分支上可用带宽的变化。本研究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。采用多点反馈机制自适应控制多层视频流中各层的传输速率。该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来控制视频编码器的高优先级和低优先级视频生成速率。它还支持最小带宽保证和最大限度地支持超过最小速率的视频流量。为了研究这些机制，采用了数学分析、模拟和经验实验，使用了pi可用的ATM测试平台网络。

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.