Study on Multimedia Networking in ATM Networks

1实时视频传输的网络服务我们研究了适合实时视频传输的网络服务。对基于带宽预留的业务(ATM网络中的CBR业务类)和统计复用业务(VBR业务类)进行了比较，结果表明，基于带宽预留的业务可以实现高质量、高效率的视频传输。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。2.实时视频传输的MPEG编码系统考虑到所需的带宽不一定被预留用于视频传输的事实，我们提出了在可用带宽上为用户提供尽可能高质量的视频流的MPEG编码系统。此外，为了同时满足多个用户的服务质量要求，提出了分层编码算法，生成多个层次的视频流。3视频组播考虑了不同的服务质量要求。在分布式多媒体系统中，由于用户环境的异构性，不同用户的服务质量要求是不同的。提出了视频组播协议，该协议综合考虑了用户的服务质量要求和可用的带宽，为用户提供高质量的视频流。4具有服务质量保证的多媒体应用系统分布式多媒体系统要求系统内的每个实体都能提供服务质量保证。提出了基于带宽预留的网络服务与实时操作系统相结合的服务质量控制方法，实现了资源的有效利用和视频质量的最大化。

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.