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The evolution of cable television to interactive communications service provider
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Fiber optics also facilitate a larger broadcast spectrum and bi-directional communications. Recall that Figure 1.2 does specify a portion of the spectrum for upstream purposes. Two-way amplifiers can be incorporated into the cable distribution plant such that any signals falling into the range of downstream frequencies can be amplified downstream, while those that fit into the upstream range, can be amplified in the opposite direction.
A current state-of-the-art cable architecture is a hybrid fiber/coax (HFC) combination. Trunk cables can be upgraded to fiber optics without replacing existing feeder and drop lines. As cable franchises run fiber deeper into their network, they are capable of serving areas with custom programming and services tailored to individual neighborhoods. These service areas are usually in the range of 500 to 2,000 subscribers.11
Cablevision's Access Plaza
In the fall of 1995, Cablevision introduced a pilot program called Access Plaza and made it available to a subset of its Long Island subscribers. Access Plaza is a combination of hardware and software that lets users surf the Internet, get interactive news, and do home banking all through the coaxial drop cable that enters their homes. Although still in its early stages, it is Cablevision's plan to provide this service and perhaps additional ones for a flat monthly fee.
Cable modems
The key piece of terminal equipment that enables such access is the cable modem. Figure 1.3(a) shows how a generic cable modem might be incorporated into an existing home drop cable, and connected to a general-purpose computer. Figure 1.3(b) represents the implementation that was provided at the author's residence. Specifically, Cablevision installed a second drop cable, not for the reason that the data network is on a separate distinct distribution wire, but because they wanted to ensure sufficient signal strength to the cable modem. It is no mystery that cable TV subscribers will split the incoming signal several times to accommodate the various video devices, legal and illegal, in their homes. Each split contributes to a well-known reduction in signal power and quality.
The modem supplied by Cablevision is a Zenith HomeWorks model. The modem itself contains two physical connectors. One end is used to join the modem to the coaxial drop cable, the other is a proprietary high-speed interface including an IBM PC ISA card which must be installed into an IBM compatible personal computer. Already limiting hardware to IBM PC compatibles, network device drivers are available only for the MS-Windows 3.1 and 3.11 operating systems, further restricting choice. Clearly, the implementation does not take an open systems approach, but future-generation cable modems, discussed later, will address this shortcoming and much more. Cablevision's choice of the Zenith HomeWorks modem was a function of price and availability. At roughly 00, the HomeWorks model is the most affordable, and one of the few that is available in quantity.
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Resources
- The History of Cable Television, 1994:
http://www.pcta.com/histcabl.html - Deschler, Kenneth T., 1987, Cable Television Technology. McGraw-HillNew York, NY, pp. 1-2.
- Ciciora Walter S., 1994, Cable Television in the United States - An Overview, 1994:
http://www.cablelabs.com/CATV.pdf - How a Cable System Works, 1994:
http://www.continental.com/handbook/cablsys.html - Grant, William, 1983, Cable Television, Reston Publishing Co.Reston, VA, pp. 242-243.
- The Cable ConnectionThe Role of Cable Television in the National Information Infrastructure, 1994:
http://www.cablelabs.com/WPapers/cableNII.html - Bob's Cable Modems, 1994:
http://www.tezcat.com/~chicago/modem/ - For more information on @HOME, check out:
http://www.home.net
http://www.tcinc.com
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