The demand for networked consumer systems and devices is large and growing rapidly.
At home, in a car or truck, at work, or at play, consumers want entertainment, information, and communication systems and devices to intercommunicate naturally and transparently. Connected multimedia terminals enable new and exciting applications but require existing laptops, palmtops, and cell phones to evolve into computing and information devices capable of supporting web-access, telephony, computation, data storage, and real-time media exchange using a variety of media formats over a variety of physical networks.
In other words, we are now in the midst of an accelerating trend towards converged services capable of delivering ubiquitous, personalized services across multiple domains.
This convergence involves all fields of computing and communications, wires and networks, middleware, applications, services, and has been fueled by more and more pervasive use of IP (Internet Protocol) in all facets of communication, media, entertainment, IT, and consumer-electronics industries.
We are very proud to open this issue with a keynote paper by one of the “fathers of the Internet,” Leonard Kleinrock. Starting with a little bit of history (his host computer at UCLA became the first node of the Internet in September 1969), he describes the next stages of development that will make “the Net” an invisible global infrastructure serving as a global nervous system for the peoples and processes of this planet.
From this foundation, we selected 11 authors from among the most recognized worldwide experts and ST researchers in the field. These experts present an outlook on the technical challenges that must be solved if the Internet is to displace the traditional audio, voice and video networks to become the universal network for all communications needs.
A first challenge is to solve the quality of service problems: in fact, the performance of video and voice over IP is impaired by packet loss and variable packet delay in the network. A paper by F. Tobagi et al. presents a global end-to-end approach to multimedia over IP quality of service, summarizing recent results pertaining to the handling of various traffic types (voice, video, real-time data) in various types of networks. Then, V. Roca et al. present INRIA’s approach to the large-scale multicast distribution of videos where robust and reliable layered transport protocols are used.
Four papers describe new techniques that can be used at the application level to increase the quality and robustness of video streaming over IP. B. Girod et al. present techniques recently developed by their research group at Stanford University to improve the performance of existing algorithms for rate-distortion optimized video streaming. Then, E. Piccinelli et al. describe a new algorithm that is able to transcode an MPEG2 stream into an H.264 one, with a visual quality equal to or better than that achieved by fully decoding/re-encoding the stream. The next two papers address the problem of error concealment and error resiliency of video streams: L. Celetto et al. propose an innovative algorithm for loss data recovery that greatly improves the quality of H.264/AVC incorrectly decoded images, while A. Vitali shows how to reduce the sensitivity to lost data using “multiple-description video coding,” in which several independent bitstreams are created from the original video source.
Three papers explore techniques aimed at increasing the audio/video quality using a cross-layer design approach. In cross-layer design, information available at the various levels of the protocol stack can be made available to other layers and exploited to create opportunities for performance improvement. In this section, R. L. Cruz describes a set of highly spectrum-efficient radio resource management algorithms developed at UCSD to support multimedia applications requiring high bandwidth over indoor wireless networks. L. Benini et al. use cross-layer optimization techniques to minimize power consumption at the wireless network adapter. G. Convertino et al. focus on the optimization of the link layer protocol and parameters to optimally support multimedia applications over WLAN.
The last section of this issue of the ST Journal of Research describes new end-to-end techniques in which each node involved in sending or receiving multimedia information must sense the network condition and adapt its behavior accordingly. In their adaptive MPEG4 video streaming work, M. Gerla et al. propose a new transport protocol with the unique feature of using receiver-side bandwidth estimation. A paper, by F. Rovati et al., develops a novel video-rate adaptation mechanism based on transmitter-side bandwidth estimation.
This issue of the ST Journal of Research offers a very brief introduction into the exciting field of IP-based multimedia systems, and some of the strategies the research community is establishing to achieve the Quality of Service level needed to match end-user expectations. Today, the marriage of digital media and IP networking is already fueling the growth of a new ubiquitous, converged, media delivery platform. In the next few years, we can expect that the full exploitation of the service and business potential of this marriage will change our lives at an even faster pace. |
