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Building Big Bandwidth, Without Big Bucks

Both Verizon Communications Inc. and AT&T Inc. are building networks they say can deliver an infinite amount of channels — or communications services — to their subscribers.

And a July 31 research report produced by the CableLabs industry consortium and cited by The Wall Street Journal on its front page Thursday suggest that cable operators may have to make significant investments in their fiber and coaxial cable networks to keep pace. The Journal article indicates that industry may have to spend tens of billions of dollars to keep up.

The report, a copy of which has been reviewed by Multichannel News, indicates that existing cable technology will be competitive at least for the next three years. After that, improvements to cable’s infrastructure will be able to keep pace with broadband fiber-to-the-home rivals, if cable-modem termination systems become less expensive. If not, cable operators might have to consider building fiber-to-the-home networks, according to the report.

Cable’s Backup Bandwidth

The original article with the analysis on this page appeared as:

In a statement, CableLabs said, “the report shows that no major investment is needed for cable to compete’’ with fiber-to-the-premises networks.

A new generation of modular systems for cable modems handling Internet traffic will both increase capacity and cut costs tenfold, according to John Chapman, an engineer at Cisco Systems Inc. who wrote the specifications for the new generation of equipment.

Here’s how cable technologists believe they can counter any high-definition TV competition from direct-broadcast satellite providers — or infinite-channel services from telephone companies — without massive expenditures.

Digital simulcasts. Television programs are transmitted as digits to neighborhood distribution points, before they are converted back to analog channels that any TV can receive.

Fewer homes per fiber. Operators activate another fiber strand going into a neighborhood, or node. That splits nodes in half. In effect, each household is given twice as much bandwidth as before.

Sending signals only when needed. Not all channels are watched at the same time. With switched broadcast video, an operator will send a signal to a neighborhood only when someone asks for it. Then, if someone else wants to watch, the signal is already circulating.

Packing it in. Advanced compression techniques will allow cable systems to squeeze more programs into a given amount of bandwidth.

Gluing channels together. With channel capacity conserved by the other techniques, space is freed up to handle emerging uses. The available channels can be bonded to provide bandwidth for HDTV programming or Internet content at super-swift speeds.

“I think the cable operators are uniquely positioned to keep up,” Chapman said. “They have huge amounts of untapped bandwidth inside their existing coaxial cable and fiber-optic systems.”


Cable operators have begun to free up bandwidth by converting to digital signal transmission, said Cox Communications Inc. chief technology officer Chris Bowick.

In a typical 750-Megahertz cable plant, one analog signal uses a complete 6-MHz transmission “slot.” With digitization, eight to 10 signals can fit into the same space.

Digital simulcasting delivers signals digitally from the headend to the pedestal or node in a neighborhood. At the node, the signals are converted back to analog waves.

This allows TV sets without a set-top box to tune to ESPN, Cable News Network or their local ABC affiliate.

“Digital simulcast provides us with a competitive advantage going forward,” Bowick said, because consumers can still use their current TV sets.

Operators also are doubling the amount of data sent on a given video signal into the home. That effectively doubles the number of channels that can be delivered to a home.

Cable systems also are looking at switching video signals in headend or hub locations, Bowick said, further freeing up bandwidth in the network for more channels.

If the American consumer wants access to an unlimited number of “channels,” Bowick said, cable operators will be able to match that service using switched broadcast video technology.

Instead of broadcasting 200 channels from the headend to the home, the cable operator would broadcast only 120 channels to all subscribers. The other 80 channels could be used to deliver any one of hundreds or even thousands of channels, since the channel will get used only when a subscriber actually requests it.

Switched digital broadcasting does require upgrades to a cable system headend, but “upgrading the plant is more expensive than upgrading the headend equipment,” Chapman noted.


The cable industry is banking on the next generation of data-transmission techniques to deliver data at speeds up to 80 million bits per second, said Ralph Brown, chief technology officer at CableLabs.

This is possible with DOCSIS 3.0, the third generation of the Data Over Cable Service Interface Specification that CableLabs has developed.

Already, Bowick said, Cox is delivering 12 Megabits per second of data to homes in some markets, including Northern Virginia. “And we can go beyond that on the existing platform,” he said.

By comparison, AT&T plans to deliver 24 Mbps to the home, which would be shared between standard and high-definition TV channels, Internet access and voice services.

The new CableLabs specifications would “bond” two 6-Megahertz channels together. Cable operators use 6-MHz channel, capable of delivering about 40 Mbps of data, to deliver high-speed Internet service to the home. Bonding two channels together would double the speed. There is no theoretical limit, so operators could bond four channels together, offering speeds of 160 Mbps into neighborhoods, Brown said.

And not all homes need 40 Megabits at the same time, Brown said. Thus, operators can allocate bandwidth to homes in a neighborhood as necessary, depending on bandwidth requests.


Cable nodes are the last piece of physical hardware in a cable system, from which video, voice and data services are then sent to the home. Most cable operators build nodes to serve about 500 homes. At 60% video penetration, that’s 300 homes, each getting 16 Mbps of capacity at the same time.

Cable operators can split those nodes further, into 250-home increments, effectively doubling capacity again, Brown said. Instead of 300 homes getting 16 Mbps, 300 homes could get 32 Mbps.

“You just light up another fiber and connect the downstream coax at the node,” he said. “It’s a relatively straightforward process.”

“Most [operators] put plenty of dark fiber in their networks when they deployed it at the beginning,” Bowick said. To split a node requires some modulation upgrades, he said, “but that is an inexpensive thing.”

“We can even do virtual node splits,” said Bowick, by splitting data streams into different frequencies of light — colors — in a process called wave-division multiplexing. It multiplies the amount of channels or content that can be sent down a fiber.


Cisco Systems Inc., Arris and other equipment suppliers are tweaking cable modems and cable modem termination systems to handle the higher speeds of DOCSIS 3.0.

New “modular” architectures can allocate bandwidth more acutely to the kinds of traffic that need it at any given time, Brown said.

“Today, channels are dedicated. To change those today requires a lot of work,” Brown said. “You can’t reallocate bandwidth based on where the demand is.” With new software, “there is a flexible structure where you can shift demand as needed,” he said.

“The capacity can be dynamically allocated,” Brown said.

That means capacity can be used to handle, say, daytime data traffic for March Madness college-basketball tournament games. Later that evening, same capacity would handle video-on-demand requests.