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Is Wideband's Upstream Ready to Go Mainstream?

Jeff Baumgartner
10/21/2009
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Docsis 3.0 downstream channel services that pump out shared speeds of 50 Mbit/s or more are starting to look routine rather than cutting edge, thanks to big deployments by domestic MSOs like Comcast Corp. (Nasdaq: CMCSA, CMCSK) and Cablevision Systems Corp. (NYSE: CVC). (See Cablevision Debuts 101-Mbit/s Wideband Service and Comcast Speeds Up '09 Wideband Goal .)

From a technical and operational standpoint, that component of wideband seems to be working, and working quite well, though MSOs have been reluctant to reveal what kind of pickup they've been getting from Docsis 3.0 service tiers so far.

But next on the Docsis 3.0 horizon is upstream channel bonding, a technique that will enable MSOs to fatten up the traditionally skinny upstream pipe to offer speed bursts of 100 Mbit/s or more if four or more channels are tied together as one, and give operators another weapon to wield against fiber-to-the-premises (FTTP) and advanced DSL competition.

But when will upstream channel bonding be ready for prime time?

Although there are some early deployments occurring in parts of Asia, Docsis 3.0 upstream channel bonding could become "commonplace" by 2011, according to Steven Krapp, director of product management at Arris Group Inc. (Nasdaq: ARRS). (See Japan Cablenet Swims Upstream .)

Krapp, a presenter during today's Light Reading Webinar, "Docsis 3.0: Taking Wideband to the Masses," said he expects that to be the case, not just among early adopting MSOs in Asia, but with North American cable operators as well.

But to get there, MSOs will need to do a decent job cleaning up their traditionally noisier upstream spectrum. And there's not that much there to start with, so getting the most bang out of that existing bandwidth is key.

Krapp noted that a four-bonded upstream will eat up about 25 MHz of spectrum. However, most operators only have about 35 MHz of upstream spectrum available. Not to get the cart too far ahead of the horse here, but that means MSOs could come up against quite a challenge if they intend to bond six or more upstream channels.

One way to get more channels for that purpose is to perform a "mid-split." Today, the upstream spectrum range for MSOs (at least those in North America) is 5 to 42 MHz. A mid-split would allow the operator to extend that upstream pool up to 108 MHz.

But that's easier said than done, since analog video services currently occupy that space in most cases. In addition to an "upgrade process" that would place a return path in that loftier spectrum range, the MSO in question would also have to do some juggling so the analog services that used to live there could find a home higher up in the spectrum. Of course, eliminating all analog video would help with a mid-split transition, but most U.S. MSOs intend to offer at least a small, "lifeline" analog video tier for the foreseeable future.

Still, channel bonding isn't the only option being touted as a way for cable operators to beef up upstream capacity. Another idea that has reemerged is the adoption of S-CDMA, an advanced physical layer scheme that's already supported by Docsis 2.0 gear. (See Moto Preaches Cable's Upstream Savior .)

— Jeff Baumgartner, Site Editor, Cable Digital News

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