DOCSIS 2.0 to Bolster Upstream, Mitigate Noise
Aiming to bolster cable return paths to 30 megabits per second in order to accommodate advanced applications like peer-to-peer and video conferencing, CableLabs said last month that it is creating a new version of the Data-Over-Cable Service Interface Specification that incorporates advanced PHY modulation techniques.
The new specification, dubbed DOCSIS 2.0, will employ two modulation methods: Terayon Communication Systems' proprietary synchronous code division multiple access (S-CDMA) and the standards-based advanced frequency agile time division multiple access (A-TDMA).
The selection of which mode to employ will fall to the cable operator's wishes, said CableLabs Executive Consultant and DOCSIS Project Leader Rouzbeh Yassini. "It's up to them to decide when they want to do it, or to select it," he said.
The move comes after CableLabs revealed earlier this year at a conference with reporters that it had placed advanced PHY on the front burner again. At the time, it was believed that advanced PHY would become merely an enhancement to existing DOCSIS specs and not a completely separate one.
CableLabs claimed the new spec and modulation techniques will be compatible with and use the same physical channel as existing 1.0 and 1.1-based cable modems and cable modem termination systems. It's expected that CableLabs will complete the spec before the end of 2001, and begin product interoperability and certification testing by mid-2002, Yassini said.
The upgrade to 2.0 will involve new chipsets for cable modems and CMTS blades, or new, full-blown chassis.
As a modem is registered on a given system, the CMTS will pick it up and treat it as a DOCSIS 2.0 operation, Yassini said. "But [already deployed] 1.0 and 1.1 modems can co-exist and work on the same channel," he added.
A CableLabs official said the R&D house was not considering a sub-set certification in which a product would be given a passing grade for adhering to just one of the two advanced PHY modulation techniques.