International Telecommunication Union   ITU
 
 
Site Map Contact us Print Version
 Thursday, December 07, 2006
Three new Recommendations from ITU-Ts Study Group 9 provide the first steps towards the next generation of cable modems. According to SG insiders new cable modems will boost bandwidth, increase security and provide greater flexibility overall for network operators to deploy data services.

Recommendations J.210-J.212 provide a basis for modularizing cable modem termination systems (CMTS) and were designed as an extension to the DOCSIS Recommendations to allow for flexibility and independent scaling of certain CMTS functions.

DOCSIS (data over cable service interface specifications) defined in Recommendations J.112 and J.122 - specifies transmission systems for interactive cable television services - IP cable modems. It defines the requirements for the two fundamental components that comprise a high-speed data-over-cable system: the cable modem (CM) and the CMTS.

The modular-CMTS (M-CMTS) architecture splits the CMTS function into three fundamental components: the M-CMTS Core, the EQAM (downstream modulator), and the Timing Server. Inasmuch as the modular components may be located on different chassis, and potentially at different physical locations, the new Recommendation J.211 (Timing Interface for CMTS) provides the robust and highly accurate transport of timing signals from the Timing Server to the other components of the M-CMTS network in order to ensure that the system components work in lock-step.

Recommendation J.212 defines the protocol used to tunnel downstream user data across an Ethernet network between the M-CMTS Core and EQAM. Finally, the new Recommendation J.210 defines the downstream physical layer modulator requirements for the EQAM. 

Another new Recommendation in the DOCSIS series, J.213, describes requirements on both CMTSs and CMs in order to implement a Layer-2 Virtual Private Network feature which allows operators to offer a Transparent LAN Service along the lines of Carrier Ethernet.