Sticking It Together

There was last week’s lead story on the Arris and Cisco Systems wideband demos from the National Show. That followed a CT Reports article on the DOCSIS 3.0 breakfast that we hosted with Texas Instruments in Las Vegas.

It’s almost enough to make us think about creating (with apologies to the late Reverend Falwell) our own "DOCSIS 3.0 Gospel Hour."

After all, this category is generating enough stories to fill up the electronic equivalent of 60 minutes. Moreover, DOCSIS 3.0 is billed as "good news" for cable operators; has its ranks of believers (even priesthood?) and is embodied in a document about as long as the Bible. It also has its share of controversies and skeptics.

For this week’s installment, we return to Motorola and its National Show demo and news. More bonding What Motorola announced in Vegas was that support for DOCSIS 3.0 will be integrated into the BSR 64000 cable modem termination system (CMTS) via software upgrade. The upshot is that come the third quarter of this year, existing BSR customers with 2-by-8 cards can expect to see the kinds of downstream speeds shown in Moto’s CableNet demo: more than 200 Mbps to a EuroDOCSIS modem, and up to 146 Mbps to a DOCSIS modem.

Motorola Senior Director of Marketing Jeff Walker noted that this demo was clocking transmission control protocol (TCP) traffic. "TCP is more real world. When you actually support applications across bonded channels, you’re going to have a mixture of traffic."

"It’s not just going to be UDP (user datagram protocol) video streaming downloads," he said. "It’s also going to be traffic requiring TCP acknowledgments. Like using file transfer protocol (FTP) that requires acknowledgements coming in the return path."

On the upstream, the BSR’s 2-by-8 card will support existing (and arguably underutilized) DOCSIS specs. By doubling the return path from 3.2 MHz to 6.4 MHz and supporting 64-QAM, for example, DOCSIS 2.0 enables upstream speeds of 30 Mbps, Walker noted.

The bottom line is that a migration path using a combination of DOCSIS 2.0 and early DOCSIS 3.0 could comfortably achieve downstream speeds of 50 Mbps or 100 Mbps and upstream of, say, 5 Mbps.

By leveraging dynamic channel change (DCC), Walker said the software upgrade also will allow BSR customers to do what Motorola calls dynamic load balancing, which is one way of giving DOCSIS 1.x and 2.0 modems their fair share of increased throughput. "Others have implemented DCC," he said, "but have to drop the modem session or voice call while they’re switching." Migration issues Motorola’s other channel-bonding news, which we covered in this CT Reports article involved a test using not only pre-DOCSIS 3.0 CMTS and modem technology from Motorola, but also spectrum overlay equipment from Vyyo.

One takeaway, frequently overlooked in these discussions, is that to get anywhere with the bonding of channels, you first need additional channels to bond.

Whether an operator exploits the range above 1 GHz or simply reclaims existing spectrum is only one of many questions surrounding this ongoing migration cycle. DOCSIS 2.0? Yes, 64-QAM upstream is commendable, but it’s been the rare operator who has actually deployed it, as Ron Hranac noted in his April column.

And software upgrades have tremendous cost advantages, and will work as an interim solution, but getting to full 3.0 capabilities will require new silicon. And that’s yet another story. – Jonathan Tombes