Cable Modems—Using Cable TV Facilities for Data Communications

The cable TV plant is a strategic asset for Internet access, interactive television and telephone service. Cable modems provide high-speed connections from homes, schools and libraries to the Internet over the same coaxial cable and fiber optic cabling used in cable TV networks. See Table 7.2 for a comparison of download speeds between cable modems, standard modems and one channel of ISDN service.

Cable modems are different than standard modems that perform a "handshake," an agreement on how to transmit data, with a compatible modem outside of the provider's network. Cable modems need to "handshake" with modems located at the cable operator site. Complex signaling, use of frequencies and authentication need to be agreed upon between the two modems. If consumers purchase cable modems from retailers, they need to be certain that the modem is compatible with their provider's modem. To that end, the cable industry has set standards for modems, and modem manufacturers can have their modems tested and certified by Cable Labs, the research and development arm of the Cable TV industry.