DOCSIS – Data over Cable Service Interface Specification

Abstract

Broadband cable networks, so-called CATV networks have been used since about the mid-1980s for distributing broadcast signals as an alternative to terrestrial or satellite transmissions. The end of the 1990s saw the appearance of the first data and telephony services on cable networks. For this purpose, the DVB-C return channel was defined early on in the DVB project as DVB-RCC and identified as DVB-RCC/DAVIC; however, this standard never caught on. At the same time, work on DOCSIS (Data Over Cable Service Interface Specification) was already in progress in the USA. The purpose of DOCSIS was to specify a bidirectional data connection between cable modems (CM) and a CMTS (Cable Modem Termination System) in order to be able to offer telephony over IP as well as Internet access. These days, such solutions are called “triple play”, i.e. three applications from a single connector: broadcasting (radio and TV), Internet, and telephony. In Europe, a slightly modified version of the system was rolled out as “EuroDOCSIS”, with only the downstream changed to use a DVB-C signal instead of the J83B signal in the original DOCSIS. Fast Internet access over broadband cable networks is highly attractive and is practically the only service where cable network operators really make money. It has thus been prioritized over the classic distribution of broadcasting services only.