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November 1999 Issue
Features

Headends Go Digital
Open The Door to the Future
By Arthur Cole

• Cram it in the headend
• Consolidation trade-offs
• Goodbye, "business as usual"
• New skills for a digital age
• Open vs. closed
• Bottom Line

Rick Glover, headend manager at Cable TV Arlington and Montgomery counties, outside of Washington, D.C., looks over the six racks of equipment that make up the system's new digital headend.

"We have 130 digital channels taking up one fifth of the space it takes to run our 78 analog channels," he says.

"We plugged it in and had digital pictures in the headend on the first day. We were able to get pictures in the field after a short series of tests."

Welcome to the era of the digital headend, where fewer devices in fewer headends will produce cleaner, more robust signals, and monitoring and repairs in the network can be done quickly and easily from a central computer.

But if you think digital technology is going to make your life easier, forget it. Digital is going to turn your once-simple TV operation into a telecommunications powerhouse, simultaneously carrying gigabits of data in dozens of formats and encoding schemes. That's going to mean more complexity, more racks of equipment and more demand placed on the headend.

Cram it in the headend

Probably the most significant impact that digital will have on your system will be the ability to consolidate active components in the headend. In large systems, this will offer an opportunity to run the network from what some are calling a "super headend" while converting the smaller headends to unmanned hubs. In short, the cable plant will mirror those of the telecommunications carriers, which are controlled from massive central offices.

"We started the process four years ago, and it hasn't changed," says Butch Robertson, manager of AT&T's Western Cable Division, consisting largely of former TCI systems in the San Francisco area.

Robertson said he is outfitting secondary hubs with simple optical regeneration equipment, moving the active gear into consolidated headends. This allows the company to remove a lot of redundant gear that was spread across multiple headends, reducing perhaps 20 racks of equipment for a typical 300-MHz system to just two. Not only is this a more efficient use of hardware, but people as well.

"It allows us to redirect our personnel so that the remaining headends can be staffed 24/7," Robertson says.

Although network management is simplified under this arrangement, these new headends will require a lot of expertise to run smoothly.

"Things are going to get much more complex than today," says Colin Boyd, vice president of North American and worldwide markets at Harmonic Inc. "In cable's past life, HITS (Headend In The Sky) and HBO (Home Box Office) were simply remodulated to a box in the home-it was a straightforward one-way broadcast. Now, with multiple services and interfaces with ISP (Internet service providers), satellite and telephone providers-not to mention two-way service-there's a lot more going on."

Consolidation trade-offs

However, bringing all the active components into the headend may be a temporary solution. As more subscribers come online, there eventually will be a need to push more active components back out into the field.

"It's a cost trade-off," says David Grubb, vice president of marketing for General Instrument's Transmission Network Systems business unit. "It's the cost of maintaining multiple locations vs. the cost of transporting signals to a master location."

Some of the benefits of a central location are quicker response times in case of outages or other problems, and you can share equipment over a large population of subscribers. But as more subscribers come online demanding data and telephony, the network is quickly maxed out. Take, for example, a return path of 5-40 MHz on a 1 Gbps fiber link. The actual data being carried is between 20 to 40 Mbps. The rest is overhead.

"Right now, it makes more sense to pay the cost of a more expensive transport because you can share headend costs and avoid having multiple CMTSs (cable modem termination systems)," Grubb says. "With more data, it may make sense to put multiple CMTSs in the node."

Some larger multiple systems operators (MSOs) already are planning for this eventuality. At Time Warner, new services such as Road Runner and video-on-demand (VOD) will begin with servers in the headend, according to Paul Gemme, vice president of plant engineering.

"As business picks up, we'll start to migrate (servers) to the hub sites," says Gemme. "Our architecture allows us to make decisions on a hub-by-hub basis, rather than ubiquitously across the entire system. It lets the business dictate where we spend the money."

Still, growing numbers of digital subscribers will have a direct impact on the headend, something most cable operators are not accustomed to. In the analog realm, new subscribers may have meant additions to the network, but the headend remained untouched as long as the channel count remained the same. With digital services, telephony and all the other goodies, new subscribers will mean more routers, muxes, lasers and the like.

Goodbye, "business as usual"

Reliability also will play a greater role in the headend and the field. Unlike the analog video days when loss of service produced little more than a few angry phone calls, an outage during a VOD event now means an immediate hit in revenues. As a result, the status monitoring and remote control side of the headend likely will grow.

All of this new gear will require a more suitable environment than traditional analog headends provide. Digital boxes are susceptible to heat, dust and moisture, so climate control will be a primary concern. You don't want all that fancy gear lost to fire, so new chemical fire suppression systems will be needed. Static electricity can cause digital circuits to fail, so you'll have to select the proper flooring, not only in the equipment room, but in reception areas, lounges and elsewhere. Clothing also will be a factor-absolutely no wool, even in winter.

New skills for a digital age

For cable engineers, the added complexity certainly will make the digital headend more difficult to operate. But it also will provide more opportunities and a greater ability to diversify. Getting tired of the video scene? Make a switch to broadband data or Internet protocol (IP) telephony. Specialists in every field will be in great demand, but it will be those with a well-rounded knowledge of digital communications who stand the best chance of breaking into upper management.

One key set of technologies to bone up on? Transcoding: converting signals from one data type or protocol to another.

"It used to be all you needed was someone who was something of an expert in television and AV (audio/visual) subcarriers," says Dean Rockwell, director and general manager of headend systems at Scientific-Atlanta. "In the future, we'll need database expertise and knowledge on converting between analog and digital modulation schemes, TCP/IP (transport control protocol/Internet protocol), ATM (asynchronous transfer mode), SONET (synchronous optical network), as well as formats on the optical side."

Open vs. closed

Still to be determined is whether open architectures or proprietary systems will reign in the headend. CableLab's OpenCable format will allow the consumer boxes to work across platforms, but that does not mean all systems in the plant have to be open.

"You're going to see several different formats in the headend," says Jim Lacey, director of sales for Blonder Tongue. "The headend will continue to have proprietary boxes because the manufacturers won't be forced into (open standards)."

An open architecture design certainly will afford a variety of lower-cost solutions from multiple vendors, but invariably, some killer applications will remain proprietary for the vendor to retain a competitive edge.

So this is how the digital world is shaping up: simplified but more complex; greater revenue potential, but more competition. Sure, the old analog way was fun and profitable, but the challenges awaiting us in the future are what make life worth living. CT

Arthur Cole is contributing editor to "Communications Technology."

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