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Data Over Cable Service Interface specification (DOCSIS) is a family of specifications for the transmission of data over a cable network. DOCSIS is developed by the U.S. based company CableLabs. There is also a modified version for the European market. This version is called EURODOCSIS.

The first version of the Data Over Cable Service Interface Specification is DOCSIS 1.0. DOCSIS 1.0 defines the requirements for cable modems and cable modem termination systems that enable broadband Internet access.

DOCSIS 1.1 is the second version of the DOCSIS protocol specification. DOCSIS 1.1 adds quality of service (QoS) traffic management functions as well as cable modem authentication extensions. This version of DOCSIS support real-time communications due to the QoS. This makes Voice over IP services (VoIP) possible. CableLabs introduced a technology called PacketCable to build a telephony service on top of DOCSIS 1.1 based on VoIP.

DOCSIS 2.0 is the third version of the DOCSIS protocol specification. DOCSIS 2.0 is developed to significantly increase the upstream data carrying capacity and the robustness to noise and interference. DOCSIS 2.0 includes advanced technologies to divide the capacity between the different subscribers. These technologies are based on TDMA and S-CDMA.

In North-America the bandwidth from 50 - 750 or 860 MHz is used for downstream transport. The downstream spectrum is divided in channels with a bandwidth of 6 MHz. Usually, the lower part from 50 - 450 MHz is used for the analogue and digital television channels and the upper part for the advanced services. The bandwidth from 5 - 42 MHz is used for the uplink. The bandwidth is shared among all subscribers that are connected to the same street cabinet.

To comply with the European cable networks, which are based on 8 MHz broad channels, an addition to the DOCSIS standard was developed in mid-98. EuroDOCSIS is a modified version of DOCSIS which is based on an 8 MHz bandwidth downstream channel within a 100 to 860 MHz spectrum. On the upstream, the recommended upstream bandwidth has been increased to range from 5 to 65 MHz.

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