How to Get Your Channels Bonded

Cable operators that have installed DOCSIS 2.0 gear and are looking to implement channel bonding will need to upgrade cable-modem termination system software and buy new modems, according to Arris Group Inc. chief technical officer Tom Cloonan.

Arris has been pitching to U.S. and international cable operators its FlexPath channel-bonding system, which will allow MSOs to offer high-speed Internet services at speeds up to 100 Mbps.

Cloonan said a handful of operators in Europe and Asia are serious about rolling out 100 Mbps service by early next year. So what does it take to get there?

“It’s not a terrible, difficult task,” Cloonan said. “You have to make sure your HFC [hybrid fiber coaxial] plant is wired up correctly. You might need new cabling to the CMTS [cable-modem termination system].”

Channel bonding, at least as it’s structured in the U.S., will require four downstream and four upstream channels, which can be “bonded” together to get 100 Mbps of throughput. Cloonan said current versions of Arris’ C4 CMTS that are Data Over Cable Service Interface Specification 2.0-capable have two downstream and 12 upstream paths.

New software can be added to those CMTS systems to create the four-down, four-up configuration needed for channel bonding, he said. That software upgrade is no more complex than a standard upgrade, Cloonan said.

“The hardware can be used without any existing changes,” he said. “You just grab the new software.”

In addition to the new software, channel bonding requires a new cable modem. “Today, we have sample quantities of the prototype,” Cloonan said. “It uses multiple DOCSIS 2.0 modems to create a wideband modem. We have trial customers around the world.”

Cloonan said Arris is working with Texas Instruments Inc., Broadcom Corp. and some startups to on their DOCSIS 3.0 chipset road maps.

“We expect to have commercially available modems in the first quarter,” he said.


The price will depend on volumes and the progress of integration, since early modem prices were in the $250 range. “We expect it will be much more tightly integrated, but some elements will still require discrete components.”

One challenge is to determine the right size modem, said Cloonan — is it 50 Mbps, 100 Mbps or more?

The CMTS can handle different sizes, but Cloonan said he thinks the sweet spot is between 50 and 100 Mbps.

“Some customers want 100 Megs,” he said. “The first modems will support 100 megabits symmetrical, which could also put them in line to be used in the commercial services market.”

Once the new modems are installed, they need to be configured with the file transfer protocol server.

“Operators need to install files in headend servers,” he said. “These modems operate with higher bandwidth.”

While the international market is active, U.S. MSOs are looking to do lab trials next year, Cloonan said, as they watch Verizon roll out 30 megabit service.

In addition to higher bandwidth speeds, Cloonan said DOCSIS 3.0 will provide other benefits. One is a segue to the IPv6 standard.

MSOs use IPv4 to assign IP addresses, but the well of addresses in that protocol is starting to run dry. As MSOs look to put DOCSIS signaling gateways into set-top boxes, each box will require a separate IP address. That’s tens of millions of new addresses.

Using IPv6 protocol will allow MSOs to use infinitely more addresses, Cloonan said. But IPv6 will require some wholesale changes in software and perhaps hardware, so CableLabs is looking at what smaller subsets of IPv6 features are most critical to MSOs.

Another benefit of channel bonding will be the separation of the MAC and PHY layers, required in the new modular CMTS specifications.

Operations like quality of service and packet flow occur on the MAC layer, Cloonan said, while PHY is an element that takes bit streams and converts them to RF streams on analog cable. “MSOs want to separate those because they hope they can start using edge QAMs used for VOD for CMTS services,” he said. Those edge QAMs could be configured for VOD or data or a mixture of both services, depending on traffic needs, he said.


And what of node-traffic issues? Cloonan said if a few 100 Mbps homes were along side a handful of homes receiving a different level of bandwidth, each would get the appropriate amount because of already implemented QOS procedures at the CMTS.

There is one other thing to think about, Cloonan said, educating the rest of the universe. Can Internet servers pump out traffic at 100 Mbps? Can all the connections and ports on the Net handle that load?

“Everyone needs to be educating everybody,” he said. “MSOs need to help users configure PCs correctly.”