11:00 AM -- As Broadcom Corp. worked on its next-gen Docsis 3.0 chipsets last summer, the chatter was that the company would try to leapfrog Intel Corp.'s Puma6 with silicon that could bond 32 downstream channels -- enough to push out max speeds of 1.2 Gbit/s.
That didn't happen. On Tuesday, Broadcom came out with two chipsets that mirror the capabilities of the Puma6 -- a high-end version that can bond 24 downstream channels and 8 upstreams, and one with a 16x4 configuration that can snap into Broadcom's widely deployed 8x4 D3 modem hardware designs. (See Broadcom Matches Intel With 1-Gig D3 Chipset.)
Of course, much has changed since last summer. The cable industry's Docsis 3.1 spec is pursuing faster speeds while doing away with the old 6MHz (North American Docsis) and 8MHz (EuroDocsis) channel spacing. Instead, Docsis 3.1 will favor the use of super-wide channels made up of small orthogonal frequency division multiplexing (OFDM) subcarriers. (See Docsis 3.1 Targets 10-Gig Downstream.)
The emergence of Docsis 3.1 could have contributed to Broadcom's decision, or perhaps the market told Broadcom that it didn't need 32-channel bonding capabilities just yet. But when it comes to a Docsis 3.0 chipset that goes beyond 24 downstreams, well, never say never.
"I wouldn’t rule out 32 [downstream channels] as the next step," says Jay Kirchoff, VP of marketing for Broadcom's cable broadband unit. "We're clearly looking at other things and the newest specs that are being developed." [Ed. note: several cable modem termination system (CMTS) vendors are working on software that enables the bonding of 32 downstream channels.]
He says Broadcom's Full-Band Capture (FBC) technology would certainly pave the way for the bonding of 32 channels. Rather than having to pluck channels out of a 100MHz-block, FBC lets operators grab and bond channels from anywhere on the spectrum, up to 1GHz.
"We don't have to add more tuners if we want more channels to bond. It's extremely scalable, should be want to go to 32 and even beyond in future generations of product," Kirchoff said.
So, 24 channels and about 1 Gbit/s is the current Docsis 3.0 downstream speed limit. But to go beyond it, Broadcom suggests all it has to do is press down a little harder on the gas pedal.
— Jeff Baumgartner, Site Editor, Light Reading Cable