ing down all users on that line (this problem just needs network management attention, but it must be attended to). Amplifiers in CATV networks have been problems in the past. An ADSL modem failure only affects one subscriber, and telephone lines are legendary for reliability, rain or shine. Stability The first user of a cable modem on a given line will have excellent service. Each additional user creates noise, loads the channel, reduces reliability, and generally degrades the quality of service for everyone on the line. Quality of service will also degrade as Internet users on a line shift from text and low graphics to high graphics and multimedia, an inevitable trend if the Internet is in any way successful. ADSL itself suffers no degradation based on traffic or number of users in the access network. However, ADSL must work into an access concentrator of some sort, which will encounter congestion during peak hours. Indeed, if the concentrator output is not greater than the speed of a single cable modem, it will have identical degradation. However, it is probably easier to add concentrator capacity than split coax nodes. Home Wiring. Personal computers are seldom located in a home adjacent to the television, or television coaxial cabling. Personal computers, especially ones desiring Internet access, typically sit near a telephone line. Cable modems will usually require some new wiring in the home. ADSL for PC access may at some circumstances be installed without new wiring. The exact distribution of these circumstances will not be known until many units have been deployed. Several efforts are underway to standardize cable modems, particularly ones by IEEE 802.14 and Cable Labs (now joined by ADL in Cambridge). However, it is quite likely that quite a few will be deployed before a standard is agreed, and new transmission ideas still surface. It should be noted that CATV, as a business, has not history of standards development or enforc...
