Study on Multimedia Networking in ATM Networks

1实时视频传输的网络业务我们研究了适合实时视频传输的网络业务。通过对基于带宽预留业务（ATM网络中的CBR业务类）和统计复用业务（VBR业务类）的比较，表明基于带宽预留业务（CBR业务类）可以实现高质量、有效的视频传输。此外，为了在用户之间公平地共享带宽，我们提出了基于效用的带宽分配方案基于实时视频传输的MPEG编码系统，考虑到视频传输所需要的带宽不能保证，提出了一种在可用带宽上为用户提供尽可能高质量视频流的MPEG编码系统。此外，为了同时满足多个用户对QoS的要求，我们提出了分层编码算法，生成多层视频流在分布式多媒体系统中，由于用户所处环境的异构性，不同用户对QoS的要求不同。考虑到用户的QoS要求和可用带宽，提出了视频组播协议，为用户提供高质量的视频流具有QoS保证的多媒体应用系统分布式多媒体系统要求系统内每个实体都有QoS保证。介绍了一种将基于带宽预留的网络服务与实时Os相结合，实现资源有效利用和视频质量最大化的QoS控制方法。

1 Network service for real-time video transferWe investigate the network service suitable for the real-time video transfer. Comparing the band- width reservation based service (CBR service class in ATM networks) and the statistical multiplexing service (VBR service class), it is shown that the high quality and effective Video transfer can be achieved by the former class. Further, to fairly share the bandwidth among users, we propose the utility-based bandwidth allocation scheme.2 MPEG coding system for real-time video transferConsidering the fact that the required bandwidth cannot necessarily be reserved for the video transfer, we propose the MPEG coding system which provides a user with the video stream of as high quality as possible on the available bandwidth. Further, to satisfy the QoS requirements of a number of users simultaneously, we propose the hierarchical coding algorithm which produces the video stream of multiple layers.3 Video multicasting with consideration on various QoS requirementsIn the distributed multimedia system, the QoS requirement differs among users because of the heterogeneity of user's environment. We propose the video multicast protocol which provides users with the high quality video stream taking account of the user's QoS requirement and the available bandwidth.4 Multimedia application system with QoS guaranteesThe distributed multimedia system requires QoS guarantees in each entity within the system. We introduce the QoS control method which enables the effective resource usage and maximizes the provided video quality by combining the bandwidth reservation based network service and the real-time Os.