To delivery multimedia, especially video, the key issue of bandwidth must be addressed first. Bandwidth is communication power - the capacity of an information channel to transmit bits without error in the presence of noise. In fiber optics, in wireless communications, in new dumb switches, and in digital signal processors, bandwidth will expand from 5 to 100 times as fast as the rise of microprocessor speeds. With the rapid spread of national network of fiber and cable, the dribble of kilobits from twisted-pair telephone lines is about to become a firehouse of gigabits.
Broadband bandwidth and video compression are the important technologies to successfully transmit video information. Thus, the focus on this paper is digital video compression and broadband technology such as ADSL, hybrid network, ISDN, ATM, frame rely, and SMDS. In addition, according to Benton Foundation working paper, telephone and cable companies are currently testing delivery systems for video-on-demand and near-video-on demand services. Those interactive testbeds for video-on-demand service will be addressed as well.
MEG (Moving Picture Experts Group) is currently to generate standards for digital video (sequences of images in time) and audio compression. The MPEG format can support full-screen (640*480) 30 frames per second video with audio on computers equipped with hardware MPEG decoders.
In accord with the prevailing MPEG standards, digital compression can produce a bit stream running at between 1.5 and 6 Mbps. The complex and exacting of compressing bits - compensating for motion, comparing blocks of pixels for redundancy, smoothing out the flow of data - entails computer operations running 1,000 times as fast as the raw video bits. This means the video compression algorithm requires a processing speed between 150 and 600 gigabits per second- hundred of times faster than the Pentium. The real time compression process can save time and disk space, and speed transmission, allowing for longer and higher resolution video segments to be captured.
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ADSL is a multimedia modem which can transmit more than 6 Mbps over twisted pair copper and permits transmission of a single compressed, high- quality video signal, at a rate of 1.5 Megabits per second, in addition to an ordinary voice phone conversation. It is quick enough to bring remote multimedia - video, audio, graphics, and text - to millions of users. ADSL makes room for Plain Old Telephone Service (POTS) , so the phone line operates as it always did, for voice, facsimile, and computer services. Even if ADSL fails, the line still works for POTS. With ADSL, the following activities can be at the same time:
- Voice call (or send/ receive a fax).
- A selected video on demand or interactive education program.
- PC access to an office LAN at LAN speeds in one window, an Internet Video in a second window, and a video conference using a screen corner.
Since ADSL could convert copper lines to multimedia driveways based on customer request, some telephone companies already appreciate the truth of ADSL. Others have backed off because ADSL seems expensive and does not transmit analog video.
However, ADSL is not yet capable of providing a complete substitute for cable TV, because it can only send one channel at a time and will not serve households where more than one TV is in use at a time.
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Networks that reach into the home are hybrids of the fiber-optic cable, existing copper wire and coaxial cable used by telephone and cable television companies. Fiber-optic cables will be used in the major arteries and portions of the distribution system, while existing copper and coaxial cable will be used in the last hundred yards.
Hybrid networks can delivery a full range of high-bandwidth interactive service at a fraction of the cost of fiber to the home. Digital compression, storage, and transmission will reduce the cost of rewiring a neighborhood to a manageable burden. High-capacity video file servers capable of storing thousands of hours of programming will be attached at the regional level. Existing cable systems will be replaced by high-capacity, noiseless fiber-optic cable that will reach from the system's head into each neighborhood.
The "fiber-to-the-node" architecture will serve groups of 200 to 1500 homes. If the networks are engineered properly, every subscriber should be able to view a different program, even if all are watching at the same time. Over time, the network can be expanded to support full two-way communication applications like video telephony.
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ISDN is a technology designed for the public switched telephone network that allows low-cost communication in data, voice, graphics, and video. It is designed to run over the existing copper local loop that connects the telephone company's central office to the home. Some of the characteristics that distinguish ISDN are:
- It build on groups of standard transmission channels. Bearer channels (B channels) transmit user information at relatively high speeds, while separate data channels (D channels) carry call set-up, signaling and other information.
- It handle all type of information. They are all digitized and transmitted at high speeds in the same flow of data.
- It handle many devices and many telephone numbers on the same line.
- It supports up to 3 calls at the same time.
- It offers variable, responsive transmission speeds. Two or more channels can be combined into a single larger transmission "pipe." Channels can be assembled as needed for a specific application, and then broken down and reassembled into different groups for different applications.
- It uses switched digital connections. It offers inexpensive dialed digital access to the worldwide telecommunications network. It is no longer necessary to lease costly dedicated lines for high-speed transmission, or to limit data speed and accuracy by using modems to convert digital signals to analog pulses.
ISDN offers inexpensive dialed service, high-speed data transmission, and the ability to send and receive voice and images through the same fully digital connections. Therefore, it is especially useful for individual and those in smaller companies.
Charge of ISDN
- Usage is charged at standard business voice rates for voice or data transmission.
- Usage and distance sensitive pricing (same as business voice).
- Time of day and volume discounts available.
- Options and rates.
The following is three kinds of ISDN services:
- SDS ISDN
Monthly Service: $22.85
Installation: $70.75
Usage: usage is billed at regular business voice rates on a per B-Channel basis.
- Centrex ISDN
Monthly Service: $31.65
Installation: $70
Usage: usage is flat-rated within the centrex account. Outside the centrex, usage is billed at regular business rates.
- Home ISDN
Monthly Service: $22.95
Installation: $34.75
Usage: billed at regular business rates Mon - Fri, 8am- 5pm. All other time, zone 1 and 2 is flat-rated.
Some of the digitally stored information ISDN can make available includes X-rays, CAT-scans and other medical images, full color photographs and illustrations, general and specialized encyclopedias, film and television image and other visually intensive files.
ISDN, with its end-to-end digital connections, offers giant steps forward in speed-up to 112 Kbps today- with the quantum leap of digital compression still to come.
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ATM is the most important short-term contributor to the tides of bandwidth. It puts everything into same-sized boxes called cells and each one is 53 byes long, including a five-byte address. Small packets of a uniform 53 bytes can be switched at enormous speeds through an ATM network and dispatched to the end users on a fixed schedule that can accommodate voice, video and data, all at once. ATM also turns networks of small computers into scaleable supercomputers. It combines with fiber-optic links to provide a far simpler, more modular and more scaleable solution than the complex copper backplane buses that perform the same functions in large computers.
The basic principles of ATM:
- ATM is considered as a specific packet oriented transfer mode based on fixed length cells. Each cell consists of an information field and a head, which is mainly used to determine the virtual channel and to perform the appropriate routing.
- ATM is connection-oriented. The header values are assigned to each section of a connection for the complete duration of the connection. Signaling and user information are carried on separate virtual channels.
- The information field of ATM cells is carried transparently through the network. No processing like error control is performed on it inside the network.
- All service (voice, video, data) can be transported via ATM, including connectionless services.
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Frame Relay is a packet based on interface standard that has been optimized for the transport of protocol-oriented data. A frame relay network consists of user devices and network devices that implement the standard interface. The user device is responsible for delivering frames to the network in the prescribed format. The network in the prescribed format. The network is responsible for switching or routing the frames to the proper destination user device.
Benefits of Frame Relay
- Reduced internetworking costs.
- Increased performance with reduced network complexity.
- Increased interoperability via international standards.
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SMDS is a connectionless, cell-switched data transport service that offers total end-to-end application solutions. With SMDS, organizations have the flexibility they need for distributed computing and bandwidth-intensive applications. At the same time, because SMDS supports both existing and emerging technologies, it provides the scalability organizations need to support the application in the future. Because SMDS is able to coexist with dedicated facilities, it enables customers to create hybrid public/ private networks. SMDS also allows for the easy expansion of existing networks, since new sites can be quickly added to a SMDS net without totally reconfiguring the network. Flat rate tariffs for SMDS service range from $350 to $750 per mouth, plus a one-time installation charge per subscriber network interface of $700 to $1000.
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- Ameritech: Test of "think link"
Ameritech's thinklink is a video-on-demand test in Sterling Heighs, Michigan designed to provide nine-year-old children with access to education videos. Most of education video share 10 to 15 minutes long. Monthly charges run in the $5-7 range.
- Bell Atlantic: Video Dialtone Tests of ADSL
Bell Atlantic is testing an on-demand technology in northern Virginia & Unioncity, New Jersey, that allows full-motion video transmission over enhanced copper lines. ADSL would allow telephone companies to begin offering a primitive form video-on-demand over its copper-based network. 100 or more video selections are expected to provide. $1-5 per selections during a rollout will probably be offered.
- Bell Atlantic: Video Dialtone for Sammons
Bell Atlantic has signed a 10- year agreement with Pallas-based Sammons communications to provide regulated cable TV transport over its fiber optic network in the New Jersey Communities of Madison, Florham Park, and Chatham Borough. Services including video-on-demand, home banking and shopping, and education and heath care service will be offered.
- Bell Atlantic: Video Dialtone for Future Vision
Bell Atlantic has signed a ten-year, 60 channel video dialtone deal with Future Vision of America Corp. No video-on-demand is planned for the system launch in 1994, but the system will be "full interactive." In the future, the system could be capable of delivery movies and video programs to consumers on demand.
- Bell Atlantic: Interactive Cable TV Service
Bell Atlantic has proposed a cable-link video service in Alexandria, Virginia, to originate programming under its "Interactive Multimedia Television" label. The system can provide customers with up to 384 channels of regular and premium cable programming, including video-on-demand. The system would be built to serve 60,000 homes.
- GTE: Cerritos Testbed
The Cerritos testbed was designed to compare the transmission of voice, data and video services over a range of transmission networks, including fiber optics, coaxial cable, and twisted pair. Fiber optic services include Fiber Tone telephone service, integrated video and telephone service, and home shopping.
- GTE: Video Dialtone Trial (Manussas)
This GTE owned and operated network will consist of highly advanced fiber optics and coaxial cable, using AT&T's end-to-end video transport system. The network includes a video server from AT&T, a new
Pacific Bell will build an interactive video platform through California at a cost of $16 billion- 20 percent to 30 percent above current spending levels. Essentially, the upgrade will add ATM capabilities to its existing fiber-coaxial trunk, and transport broadband service to powerful 750 MHz digital nodes serving 500 home apiece. The system will provide a full state of interactive services, including movies on-demand, time-shifted TV, interactive news, tele-education, home shopping, video games, and electronic citizenship.
- Rochester Telephone: Video Dialtone with USA Video
The core of USA video's network is its patented store and forward video system, which allows movies to be compressed at a 160: 1 rate and transmitted in a fraction real time. The trial will use 3 Mbps ADSL technology. USA video intends to provide a 100 film video-on-demand library with "smart" selection by category, actor, director, and so on. Other services include home shopping, digital audio, and music videos.
- US WEST: Trail of Broadband Network
US WEST is launching a broadband testbed with hybrid fiber-coaxial-twisted pair network in Omaha that will serve as the first site of subscriber "1000" system capable of providing on-demand services including video-on-demand through its region. The network will cost roughly $1,000- $1,100 per subscriber to deploy.
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- TCI: Info Structure Network
TCI will create a multimedia "Info Structure Network" using new fiber facilities and data switched by ATM. The deployment of fiber trunks, together with the compressed data, will permit TCI to provide hundreds of transmission at an average through of 750 MHz. Services will include interactive education programming, multiplexed movie offerings, enhanced shop-at-home option, television services on demand, and so on.
- TCI, AT&T, US WEST: Test of View- Controlled TV
The viewer-controlled television(VCTV) remote control was designed so that customers could navigate between screens and complete all ordering tasks using only 5 color-coded buttons. Its purpose is to compare the buy rate and costs of video-on-demand and near-video-on-demand. VCTV is charging "Take One" customers from $3.99 for the most current movies to as little as 99 cents for documentaries, children's programming. "Hits at home" movies cost $2.99. Movies can be reserved up to one week in advance.
- Time Warner: Test of Quantum
Time Warner's "Quantum" system in Queens, New York provides near-video-on-demand services to about 10,000 customers. The Quantum service is based on a system upgrade from 550 MHz to 1 GHz, digital compression, fiber-to-the-feeder architecture, and a pioneer set-top converter. 10 to 15 pay-per-view movies a day are featured on the "Time Warner Home Theater." Time Warner prices less-recent hit movies at $2.95, children's movie at $1.95, artistic and foreign film at $3.95.
- Time Warner: Test of Full Service Network (FSN)
FSN is envisioned as providing a wide range of business and consumer services that would rely on fiber to the neighborhood and coaxial cable to the residence. True video-on-demand would be one of the many services on the system. The system would have room for about 60 channels devoted to analog video and 260 channels for digital video, plus an additional spectrum devoted to interactive and two-way communications. Services will include video-on-demand, near-video-on-demand, educational resources, high-speed data transmission, and so on.
- Viacom Cable: Test of Interactive TV
Viacom Cable is creating a testbed for advanced cable television services. The system will have 27 fiber nodes and 8 fibers per mode. One portion of the system will offer 77 channels and a second will have 155 channels. Some of these homes will be totally interactive. The server is provided by AT&T. The server can retrieve programs on-demand from a variety of storage formats. It will link with the cable system over a high-speed land line. Services will include near-video-on-demand, 22 channels of enhanced pay-per-view, home shopping by video browsing through retail catalogs. interactive games, and interactive advertising.
- Your Choice TV: Test of On-Demand Service
Discovery Communications is developing a Comcast's system for "Your Choice TV"
to help organize cable's future 500-channel environment. Your Choice TV will be configured for 80 channels during the test. Menu of up to 32 programs will be provided. Your Choice TV will provide services based on digital compression. Using 8:1 compression, Discovery will be able to put eight programs on the space of one channel. Services will include pay-per-view, home shopping. The costs of services to consumers are 69 cents for a repeat showing of television shows as "60 Minutes." Consumers can mimic their video store experience. The anticipates fees "north of $1" per TV show.
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