Copyright © 2008 Jianwei Huang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The advances of Internet
and wireless access technologies have opened up new opportunities to serve high
quality, on-demand multimedia applications. Applications like mobile TV, IPTV,
on-demand streaming, and peer-to-peer video sharing have fundamentally changed
the content distribution landscape, and have been accelerating a social and
engineering revolution in media distribution and consumption. To achieve the
ultimate goals of total freedom in self-expression, seamless mobile access, and
anytime anywhere media consumption, technology advances in various areas need
to be reexamined and jointly utilized under a coherent optimization framework
to reach an efficient end-to-end media delivery solution. New models, metrics,
and methodologies in source, and channel coding, distributed and
collaborative communications are needed to intelligently adapt the multimedia
content to suit user preferences, meet device and network constraints, and
achieve better communication resource utilization. The source coding and
adaptation decisions of media sources need to be reconciled with the limited
network resources, end-user preferences, and resource allocation schemes at
network nodes. Distributed optimization schemes like pricing and game
theoretical approaches are needed to improve resource allocation and management
efficiency. In this special issue on multimedia networking, we present several
papers that address such issues.
The
first paper of this special issue, “A collaborative wireless access to on-demand
services” by Z. Naor, presents a collaborative access scheme that exploits the
broadcast nature of the wireless communications in order to achieve better
multicast content delivery. The proposed method is particularly suitable for
sessions of long time durations, for applications where clients can
subscribe to ahead of time, and for applications in which the clients receive
the same information simultaneously.
The
second paper of this special issue, “A stream tapping protocol involving
clients in the distributions of videos on demand” by S. Kulkarni et al., presents
a stream tapping protocol that involves clients in the video distribution
process. Compared with the traditional taping protocol, the proposed one greatly
reduces the workload of the video server by delegating part of the content distribution
process to the clients who are watching the video.
The
third paper of this special issue, “Automatic bandwidth adjustment for content
distribution in MPLS networks” by D. Moltchanov, discusses a new algorithm for
dynamic resource adaptation to temporarily changing traffic conditions in multiprotocol label switching (MPLS)
networks. The major advantage of the proposed approach is that it is fully
autonomous, takes into account statistical characteristics of traffic patterns,
and is independent of the choice of the sampling interval of MPLS automatic
bandwidth adjustment capability.
The
fourth paper of this special issue, “Rate-distortion optimized frame dropping
for multiuser streaming and conversational video” by W. Tu et al., considers rate-distortion
optimized strategies for dropping frames from multiple conversational and
streaming videos sharing limited network node resources. Experimental results
show that a significant improvement in end-to-end performance is achieved
compared to priority-based random early dropping schemes.
The
fifth paper of this special issue, “A theoretical framework for quality-aware cross-layer
optimized wireless multimedia communications” by S. Ci et al., presents a theoretical framework for integrated cross-layer control and optimization in
wireless multimedia communications. The framework includes two essential parts:
a delay-distortion-driven optimization framework and a new approximate dynamic
programming technique based on significance measure and sensitivity analysis
for high-dimensional nonlinear cross-layer optimization.
The
sixth paper of this special issue, “Optimal multilayer adaptation of SVC video
over heterogeneous environments” by T. Thang et al., proposes an optimized
framework of controlling the SNR scalability across multiple spatial layers in scalable video coding format. The proposed framework has the
flexibility in allocating the resource (i.e., bitrate) among spatial layers,
where the overall quality is defined as a function of all spatial layers'
qualities and can be modified on the fly.
Acknowledgments
We
thank all the authors for their contributions to the special issues and wish
the readers a pleasant reading. We would also like to thank the reviewers for taking time to complete the reviews
promptly.
Jianwei Huang
Zhu Li
Qian Zhang