DOCSIS

This being my first project, should have been the first posting ! Nevertheless, here comes the brief intro of what is it all about.

Data Over Cable Service Interface Specification (DOCSIS) is an international telecommunications standard that permits the addition of high-speed data transfer to an existing Cable TV (CATV) system. It is employed by many cable television operators to provide Internet access (see cable internet) over their existing hybrid fiber coaxial (HFC) infrastructure.
DOCSIS was developed by CableLabs and contributing companies including ARRIS, BigBand Networks, Broadcom, Cisco, Conexant, Correlant, Harmonic, Intel, Motorola, Netgear, Terayon, and Texas Instruments.
The first DOCSIS specification was version 1.0, issued in March 1997, with revision 1.1 (adding quality of service (QoS) capabilities) following in April 1999. Because of increased demand for symmetric services such as IP telephony, DOCSIS was revised to enhance upstream transmission speeds; DOCSIS 2.0 was released in December 2001. Most recently, the specification was revised to significantly increase transmissions speeds (this time both upstream and downstream) and introduce support for Internet Protocol version 6 (IPv6). This version, DOCSIS 3.0, was released in August 2006. Cross-version compatibility has been maintained across all versions of DOCSIS, with the devices falling back to the highest supported version in common between both endpoints: cable modem and cable modem termination system (CMTS) The reciprocal is not true, however: if one has a cable modem that is, for example, only capable of handling DOCSIS 1.0, and the system is running 2.0, the end user will not be able to use the highest speeds the cable network is capable of delivering.

As frequency allocation band plans differ between U.S. and European CATV systems, DOCSIS standards have been modified for use in Europe. These changes were published under the name of "EuroDOCSIS". The main differences account for differing TV channel bandwidths; European cable channels conform to PAL TV standards and are 8 MHz wide, whereas in North American cable channels conform to ATSC standards which specify 6 MHz. The wider bandwidth in EuroDOCSIS architectures permits more bandwidth to be allocated to the downstream data path (toward the user). EuroDOCSIS certification testing is executed by Excentis (formerly known as tComLabs), while DOCSIS certification testing is executed by CableLabs. Typically, customer premises equipment receives "certification", while CMTS equipment receives "qualification".
Most cable systems in Japan utilize the North American version of DOCSIS, while some employ a variant of DOCSIS that uses upstream channels that are based on a 9.216 MHz master clock (as opposed to 10.24 MHz used in DOCSIS/EuroDOCSIS) resulting in upstream channel widths that are a power-of-two division of 6 MHz (as opposed to 6.4 MHz in DOCSIS/EuroDOCSIS).