Selected Areas in Communications, IEEE Journal on - IEEE Xplore

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 14, NO. 6, AUGUST 1996

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Guest Editorial Integrated Video-Based Services for the Hoime I. THEPROMISE OF BROADBAND SERVICES TO THE HOME

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HAT mankind should want to communicate by means of pictures should not surprise us, since images were used as a form of expression long before writing developed. Were the ancient cave paintings in the Lascaux cave used as a form of self-expression, or were they leaving instructions to other members of the tribe? To a large extent, progress in technology has determined when and how we have used still and moving images. It would appear that images and writing were closely interconnected, and the invention of the printing press did not change the balance; it increased the availability of information. Perhaps the biggest change to visual communication came in the 1890’s with the invention of cinematography. Suddenly a brand new form of telecommunication became available, and the balance between communicating to inform versus communicating to entertain veered sharply toward entertainment. The effect of television has been akin to the printing press-it greatly increased the ability to distribute a message. Have technologists been consistently dead wrong in their aspirations for the visual medium or just ahead of their time? The idea of being able to communicate visually is older ? than the concept of broadcast television for entertainment. A cartoon from Punch’s Almanac in 1879 shows Edison’s “telephonoscope” being used to connect grandparents with children and grandchildren in the antipodes. The idea of being able to see the other person at the same time as one could talk to them has captured the imagination of many an aspiring technologist. So when television was demonstrated at the World’s Fair in New York in 1939, it is little wonder that video conferencing was the application that was demonstrated.’ Regularly in the intervening period, interactive television has been proposed as the solution to some problem. Students of history might identify perhaps four different periods: the PicturephoneB period (let us see each other; late 1960’s),postPicturephone period (let us use still or moving images to solve useful problems; mid 1970’s), information period (let us use interactive television to access information; late 1970’s), and the electronic village period (let us use video to communicate, inform, entertain, and solve problems; early 1990’s). Publisher Item Identifier S 0733-8716(96)06646-2.

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The first demonstration of long-distance video-telephone service in the United States was between Washington DC and New York City in Aprilhlay,

1923.

At the end of each period, there was a time of reflection in which technologists and sociologists asked themselves why the promise of the technology was not fulfilled. I suspect that the answers to these questions are more complex and multidimensional than most of the studies admit. For the two early periods, the cost of the technology wa!j out of line with the value of the perceived benefits. In 1969, one could not conceive that the cost of Picturephone could ever be a marginal increment over the cost of regular telephone service, and yet it was hard to identify communication tasks where the visual channel added substantial value. The cost issue was solved in the France Telecom Minitel service by not charging for the terminal. In spite of having technology that is now showing its age, the service is still widely used for accessing a range of information services. The start-up probllem of having enough users to make the service viable was also solved by fiat. The vision of serving a range of perceived information, entertainment, and service needs by means of video-based services to the home is compelling for many, and it is easy for unrealistic expectations to develop. This leads to a scramble to develop the technology in order to fulfill the vision and to meet expectations. The downside is that when the technology inevitably fails to fulfill expectations (too expensive, poor user interface, insufficient functionality) we get another bump on the rollercoaster ride. There are a number of questions we could ask. about videobased services to the home. I do not claim any special knowledge except that of an eager participant in some of the above periods and a curious observer of others. With that warning here are some prognostications. Will we ever see broad penetration of video-based services to the home beyond the entertainment services that we now have? Technology is now invading the home at a rapid rate, in the form of personal computers, in order to perform a range of functions-work from home, desktop publishing, completing tax returns, and accessing the Internet. While most of these services are primarily text-based, image and video are being used increasingly to represent information and enrich communication. The multimedia capability to process and present the information within the home is growing rapidly, as fewer and fewer PC’s are being sold without multimedia capability. Real-time video capability will become standard on most new home comput-

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ers within the next few years. Supporting interactive video services will require a very small incremental investment over what the approximately 30 million households in the United States that already possess PC’s will have. We can, therefore, rule out the cost of the technology within the home as a barrier to wide deployment and acceptance. Except, perhaps, for the Minitel service this has never before been the case. More problematic is the communications link to the home, the access network. I expect that this will be the gating function. While there are a number of technical solutions-narrowband integrated services digital network (NISDN), asymmetric digital subscriber loop (ADSL), hybridfiber-coax (HFC), fiber-to-the-curb (FTTC)--each requires a very large capital investment by the service provider, with only the promise of an adequate return on that investment. Web frenzy has, and will continue, to stimulate the vision of what can be achieved and at the same time graphically demonstrate the inadequacy of the standard analog pair of wires to the home. The key to determining whether or not broadband services will widely penetrate the home market lies in the evolution of the communication link to the home. There are a number of performance/price points represented by the above-mentioned access loop technologies, any one of which may succeed. My prediction for the future is that ISDN will increase rapidly over the next few years and service providers will discover ways of providing relatively satisfying service for a large customer base. However, the greater speed provided by data-over-cable technology will permit hybridfiber-coax technology to chase ISDN technology and overtake it. But hybrid-fiber-coax technology will also be transitory and will, in time, evolve through various phases to an all-optical, largely passive network. A challenge will be to discover smooth, economic, migration strategies for each step along the way. We have plenty of time to address this migration, however, since the technology to do this cost-effectively will evolve over the next ten years. One clear, inevitable discontinuity will occur some time in the future when the leap is made to deliver all services to the home in a totally digital format. Speeding up this transition will be the desire to exploit the increased carrying capacity offered by the all-digital channel. Slowing down the transition will be the existence of some 300 million analog television sets that cannot decode digital television signals without the assistance of a converter, one for each television set! The speed of this transition could be greatly affected by regulation andor legislation and the desire to free up valuable pieces of the electromagnetic spectrum for new mobile uses. It has been over 30 years since the first serious attempt to deliver interactive video services to the home. I believe we will see ubiquitous broadband interactive services in the next ten to 15 years, but the path this evolution is taking is very different to that envisaged by the early pioneers. The sociological changes that will permit this to happen have been taking place over the last five years as technological trend setters absorb multimedia technology into their workaday lives

and instinctively look to Internet resources to solve routine daily problems. JOHN0. LIMB,Guest Editor

11. OVERVIEW OF THE ISSUE

This issue of the IEEE JOURNALON SELECTEDAREAS IN COMMUNICATIONS explores the open technical issues surrounding the challenge of delivering broadband video-based services to the home. Taken as a whole, the papers represent a snapshot of ongoing work in research laboratories around the world. But note that during the last two years a significant number of field trials have been mounted to understand both the technology and the user acceptance. None of that work is reported here. Many of these trials are only just finishing as this issue is going to press. In some cases, the business questions have been answered and resources have been directed to other problems; in other cases, we suspect that the findings represent valuable corporate information that may never be presented in great depth. Most of the papers in the issue address very fundamental problems and help emphasize the significant distance to be covered before we reach the maturity advisable for the wide deployment of a technology. It is hoped that these papers will stimulate further work that will continue to fill in many of the technological holes that remain. The contributions span a large technical area, all the way from the problem of transporting digital information over the physical link, to management, control, and economic issues. Let us briefly review the papers in the order of presentation. A. Physical Channel

Two papers discussing the physical channel look at the hybrid-fiber-coax channel in one case and at more robust modulation of the optical channel in the other. While cable TV technology is very mature, combining high-capacity digital transmission (64 QAM) with analog signals over a mixture of fiber and coax is less well understood. Joyce and Olshansky determine that the cable amplifiers limit performance rather than the optical link and measure a 3.5 dB CNR penalty for QAM reception when 63 AM channels are added to a digital-only system. The use of amplitude modulation of analog television requires very linear laser modulation and high CNR if signal quality is to be maintained. Kikushima et al. explore super wideband optical F M modulation which gives the advantage of greater power budget and the opportunity to deploy lower cost optical components. B. ATM Transport of video

Today, MPEG video streams are coded to yield a flow of information that is approximately constant. When there is little information to transmit because, for example, there may be little movement in the scene, the signal is coded more accurately so that the total number of bits transmitted in a “group of pictures” changes little. A small buffer is then


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needed to transmit the signal over a constant bit-rate channel. E. Management of Video TrafJic More efficient coding can be realized if only enough bits are That we are just beginning to lay the technological frameused in the encoding to produce the required image quality. work for video-based services is no more evideint than when The output bit-rate will then vary depending on the content of looking at network and service management. Fundamental the image sequence. A varying source rate is hard to handle issues are now starting to be addressed in this problem area. in any communication system, and ATM is no exception. One reason it is complex is that a number of distinct services, The approach of Reininger et al. is to request a change in each with a different quality-of-service requirement, must be the bandwidth of the ATM variable bit-rate channel as the managed simultaneously. Many entities need to communicate demands of the source go up and down. While this may at each step of the service delivery process. Cohen and seem trivial, what happens when an increase is requested and Chang explore an architecture for session manag:ement. Their there is no more channel capacity available? The approach of model breaks the control and management functions into three McManus and Ross to this problem is to play out the video parts: session management, call management, and connection at a rate that keeps a constant bit-rate channel full and to use management. A finite state machine is used to model a a large buffer at the receiver to produce a constant playback session. Balabanian et al. summarize a large body of work rate. One challenge is to ensure that the receive buffer neither now proceeding in the International Standards Organization underflows or overflows. to standardize the command and control (DSM-CC) of video services over broadband ATM networks. What began as a protocol for MPEG-2 video stream control now encompasses C. EfJicient Delivery of Video TrafJic We know very little about the statistical nature of video the protocols that enable a user to locate an integrated video services because there are just a few service trials in existence service, download application code, and play the video stream. and the range and combination of possible services is large. Further, this type of information is of great strategic value to a potential service provider and is rarely shared in any detail. This is just the situation where a flexible performance model of video service is useful. Li et al. develop such a model and incorporate the effect of batching user requests. Almeroth and Ammar explore the use of batching by means of the multicast mechanism to improve the scalability of videoon-demand service. One drawback that they address is the complication that batching introduces into the provision of interactive services where the service demands of members of a group might suddenly change. As video-based services increase, there will be many instances in which a group of video sessions is transmitted over a common channel. Statistical multiplexing can be effectively used to combine the sources over a fixed rate channel while the individual sources may be generating data at a variable rate. Liew and Tse study this scenario and show that it is preferable to combine the coding and multiplexing before packetizing the data rather than trying to combine separate transport (e.g., ATM) streams.

F. Economic Issues

The cost of memory to store digital video, even with the ever-decreasing cost of digital storage, can add significantly to the cost of providing service. Barnett and Anido explore ways of using distributed storage to reduce the overall cost of providing service. They conclude that a distributed approach costs no more than a centralized approach and offers considerable advantages in terms of bandwidth requirements and service quality. In their economic analysis, Olsen et al. focus on the access network. They report on extensive work done within the European RACE 2087 TITAN project. In one study, they compare optical and radio access to conventional copper pairs. In another study, they compare different upgrade strategies ranging from enhanced copper to hybrid-fiber-coax to broadband passive optical networks. Video-on-demand and Internet access upgrades have also been analyzed.

ACKNOWLEDGMENT D. Distribution Within the Home As homes become more high-tech, routing information around the home becomes more of a headache. Radio links and twisted pair wiring are being used for some purposes, but transmitting multiple video streams around the home will be technically and economically challenging. Deng et al. explore how well a very mature and economic technology may be applied to this problem. Ethernet is well characterized for the office but we know very little about traffic scenarios within the home. The authors constructed a residential network testbed using Ethernet over category 5 unshielded twisted pair wiring to collect traffic statistics. They conclude that Ethernet can be used as a cost-effective residential network for video and data communications.

The Guest Editors would like to acknowledge the conscientious work of the many reviewers who gave of their valuable time. As editors, we were able to see the significant improvements that were made to the manuscripts as a result of their suggestions and criticism. They also thank Valerie Johnson who worked hard to ensure that the whole editing process moved forward in a smooth, timely manner. JOHN0. LIMB, Guest Editor RICCARDO GUSELLA,Guest Editor GORDONKERR, Guest Editor TETSUYA MIKI. Guest Editor

W. D. SINCOSKIE, J-SAC Board filepresentative

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John 0. Limb (SM’72-F778) received the Ph.D. degree in electrical engineering from the University of Western Australia, Australia, in 1967. He joined Bell Laboratories, Holmdel, NJ, in 1967 and became Department Manager of the Visual Communications Research Department in 1971. He worked for a number of years on the coding of color and monochrome picture signals to reduce channel capacity requirements and has published widely in this area. He also worked and published in the areas of visual perception, office information systems, and local metropolitan-area networks. In 1984, he joined Bell Communications Research, and in 1986 he was appointed Director of the Networks and Communications Laboratory at Hewlett-Packard Laboratories, Bristol, U.K. In June 1989, he returned to the United States with Hewlett-Packard as Lab Manager, Technology Analysis, Cupertino, CA. In 1992, he returned to Hewlett-Packard Laboratories as Laboratory Director of the Media Technology Laboratory. In July 1994, he joined the Georgia Institute of Technology to accept the Eminent Scholar in Advanced Telecommunications Chair in the College of Computing. He is the former Editor-in-Chief of both the IEEE TRANSACTIONS ON COMMUNICATIONS and the IEEE JOURNAL ON SELECTED AREASIN COMMUNICATIONS. Dr. Limb received the 1990 IEEE Alexander Graham Bell Medal.

Kiccardo Gusella (S’8O-M’XI) received the lairca degree (cum laude) in electrical engineering from the University of Pndua, Italy. in 1984, and the M.S. and Ph.D. degrees from thc University of’ California, Berkeley. both in computer science, in I988 and 1990, respectivcly. He worked as a consultant for .4T&T Bell Labs, in 1987, and for Sun Microsystems. in 1988. He joined Hewlett-Packard Laboratories, Palo Alto, CA, in 1991, after a postdoctoral appointment at the International Computer Science Institute in Berkeley, CA. His primary research intercsts while :it Hewlett-Packard Laboratories have been in the arca of networking for digital audio and video. He served un the ATM Forum in 1993 and 1994. In 1994, he established and co-chaired the first IEEE International Workshop o n Community Networking. In 1995, he m o \ d to Beijing. China, where he currently resides, to direct HP Laboratories’ China research initiative, which is being carried out in partnership with the State Science and Technology Conirni5,ion of China.

Gordon Kerr received the B.A. and M.A. degrees in engineering and electrical sciences from

Cambridge University, Cambridge, U.K., in 1975 and 1977. He has worked for the R&D Labs of British Telecommunications PLC (and its legal predecessors) since 1975, starting on dial-up data modems. In 1981, he was asked to form a new team to design, develop, and deliver an on-demand video library system for the BT Westminster Cable-TV system in London. This was an early version of what is now known as video-on-demand. The considerable experience gained from this work was brought to bear when the technology drivers started to enable fully-digital video-on-demand to be considered; he was a major player behind the 1994 VoD technology trial, and the 1995/1996 current Market Trial of Interactive TV which BT recently has launched. His current focus of work is on technology options beyond the current trials. Dr. Kerr is a Fellow of the U.K. Institute of Electrical Engineers and the Society of Cable Telecommunications Engineers. He is also a Chartered Engineer.


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Tetsuya Miki (S’70-M’7&SM’95) received the B.E. degree from the University of ElectroCommunications, Tokyo, Japan, in 1965, and the M.E. and Ph.D. degrees from Tohoku University, Sendai, Japan, in 1967 and 1970, respectively. He is currently a Professor, Department of Electronic Engineering, University of ElectroCommunications, and a Senior Advisor for NTT Telecommunication Networks Laboratory Group. His research involves ATM networks, optical access networks, photonic networks, multimedia information communications, and network architectures. He joined the Electrical Communication Laboratories of NTT in 1970, where he was engaged in research and development of high speed digital transmission systems using coaxial cable, optical transmission systems, optical access networks, ATM and multimedia transpotrt networks, network management systems, and network architecture. He was the Executive Manager of the NTT Optical Network Systems Laboratories from 1992 to 1995. He is President of the IEICE Communications Society, Japan, Director of the Chapters Department {of the IEEE Communications Society, and a Technical Editor of the IEEE Communications Magazine. Dr. Miki received the IEICE Achievement Award for his contributions to the early development of optical transmission systems in 1978.