Jan
13
2009

DOCSIS 3.0: Modems Over 300 Mbps

Cisco Systems is developing a cable modem that will use Broadcom’s recently announced DOCSIS 3.0 silicon to bond together eight downstream channels – letting cable providers, theoretically, pump Internet content down to subscribers at more than 300 Mbps.

According to Bekele, the idea with the eight-downstream-channel devices is to let cable operators future-proof their installed base of DOCSIS modems. So while a cable operator wouldn’t necessarily introduce a 300-Mbps Internet tier initially, that latent capacity would be available down the line.“As long as the cost is comparable, you’ll see a lot of operators gravitate toward 8 by 4,” he said, referring to a cable modem that provides eight downstream and four upstream channels.

He noted, however, that right now Cisco is not exactly sure how the cost of the DPC3212 cable modem would compare with current DOCSIS 3.0 models.

The forthcoming unit would be among the first to use Broadcom’s BCM3380 DOCSIS 3.0 modem chip. Cisco also plans to incorporate Broadcom’s DOCSIS 3.0 physical layer (PHY) component in its next-generation cable modem termination system (CMTS).

Cisco is currently shipping two DOCSIS 3.0 customer-premises products, the DPC3000 cable modem and DPC3202 eMTA, which both use Texas Instruments’ Puma 5 chip set.

The driving force in the future for higher-speed broadband will be video over DOCSIS — whether that’s managed video content or unmanaged content going over the top, Bekele said.

Cisco has predicted that the annual bandwidth demand on the world’s Internet networks will nearly double every two years — reaching 522 Exabytes annually in 2012 (the equivalent of 250 million DVDs) — and that half of that will be video traffic.

“That’s going to make it more likely that operators will push the tiers higher,” Bekele said. “That ability to leapfrog to eight channels definitely becomes an advantage.”

What is DOCSIS?
Data Over Cable Service Interface Specification (DOCSIS) is an international standard developed by CableLabs and contributing companies that include ARRIS, BigBand Networks, Broadcom, Cisco, Conexant, Correlant, Harmonic, Intel, Motorola, Netgear, Terayon, and Texas Instruments. DOCSIS defines the communications and operation support interface requirements for a data over cable system.

It 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 fibre coaxial (HFC) infrastructure.

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).

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