Cable Operators

Cable Show 2011: Comcast Uses Cisco Gear In 1-Gig DOCSIS Demo

Vendor's 3G60 CMTS Card, Modems Used on Operator's Chicago Network 6/16/2011 2:51 PM Eastern

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Comcast used Cisco Systems' DOCSIS 3.0 cable modem termination system and modems to deliver more than 1 Gigabit per second downstream, running over a dedicated coax network segment in the operator's Chicago system.

Comcast chairman and CEO Brian Roberts highlighted the 1 Gbps demo in a video clip presented at Thursday's opening general session here. 

The operator is using Cisco's 3G60 CMTS line card to deliver 32 downstream channels, to two DOCSIS 3.0 prototype modems each with 16 downstream and four upstream channels. Originally Comcast was planning to show 300 Mbps upstream but ended up running just four up for about 100 Mbps.

In March, Cisco showed its CMTS delivering a 48-channel bonding group to hit nearly 1.6 Gbps at CableLabs' Winter Conference in Atlanta. In that demo, the operator bonded 48 downstream channels and 12 upstream channels, using 256 QAM in the downstream, and 64-QAM in the upstream.

According to John Chapman, chief technology officer for Cisco's cable access business unit, the demonstrations show that DOCSIS still has many years of life left.

"In short, it means that yes, DOCSIS does continue to scale -- in a big way, and for a long time," Chapman wrote in a blog post Thursday.

In a typical modern cable system there's total potential throughput of over 5 Gbps of capacity (figuring 134 digital 6-MHz channels downstream, modulated with 256 QAM). "Of course, this assumes that all of those channels are available for bonding (meaning they're not used by anything else), and that's a function of the long-term migration to IP," Chapman wrote. "But it's a powerful endorsement for full-spectrum bonding, as a catalyst for abundant levels of IP."

Separately at the Cable Show, Arris has a demo of a CMTS delivering 4.5 Gbps downstream and 575 Mbps upstream, using 16 DOCSIS 3.0 modems.

September