The digital revolution-whether it is video, voice or data-is shaking the cable industry down to its very roots…literally and figuratively. At the very heart of this revolution is the cable headend. With the addition of high-speed data, digital TV, a host of interactive services, and finally, lifeline telephony, old structures and old designs simply won't do.

Simply put, these ain't your daddy's headends anymore. As the industry veers off toward the digital world of tomorrow, the whole focus of what a headend does is shifting as well. As a result, headend design, like many of the services it provides, is getting more complex, more detailed, and quite frankly, more expensive.

Shifting the focus

This change in service offerings that's sweeping through the industry is not only having an impact on headend design and staffing, but on the very way cable professionals are having to think about their networks' functionality.


"I think headends of the future," says Fred Allegrezza, president and CEO of Vivid Technology Inc., "will certainly have more data-centric functions. In the past, headends were primarily involved in signal transmission. Now, with VOD, cable modems and telephony, there's a lot more network management, more sophisticated computer networking that's going to be taking place in the headend." Dave Grubb, vice president of marketing, transmission network systems at General Instrument, says the whole basis for headend design has undergone a major shift. "One way to look at this is the old model of the headend," explains Grubb, "where you had 80 channels of programming, so you had 80 channels worth of receivers, modulators, scramblers, etc. Now, you're moving to a model where you're going to have equipment on a per-subscriber basis.

"The fiber equipment is that way. You have transmitters per every 3,000 homes or whatever the architecture is. But now you're going to have signal processing in the headend that's proportional to homes instead of proportional to channels.

"I think the challenge for the headends is to be able to handle the processing of large volumes of targeted services and getting them routed out to the proper fiber nodes, and then to the home."

One of the biggest impacts on cable and its headends will come with the advent of circuit-switched and IP telephony services. Thought of as a pipe dream just a few years ago, with AT&T's move onto cable turf and its deep pockets and determination to crack into the local telephone loop, IP telephony is no longer a fantasy. By most accounts, it's just a matter of time. And that means new demands for cable's headends.

"I think the big change that's coming is the integration of voice capabilities into the cable plant," says Ed Morgan, executive director of research and development at Telogy Inc.

"What we see coming down the road, as far as headends go, is the ability to communicate with cable modems that are voice enabled and the integration in the headend of gateway functionality.

"Planning (headends) will be affected by the impact of being able to size and handle the amount of traffic you'll be predicting over the network. Today, it's much more of a data planning exercise for the people that are installing and configuring headends. That will grow to be a voice services planning exercise."

One house, many platforms

Multiple services can mean multiple headaches for those assigned the task of designing a new headend. A patchwork of platforms in a headend presents a whole host of problems. One of the most vexing, says Kevin Wilkes, vice president of network systems integration at Worldbridge Broadband Services Inc., is scalability.

"What operators need to do in the future, and I think the future is here already, is they have to be able to integrate many different platforms under one roof.

"The biggest thing operators are going to have to figure out, beyond just the obvious technical requirements and integrating all these different services, is scaling. That's because it's getting more and more difficult to predict size, power, and HVAC requirements for the future. Back in the old days, you just predicted channel growth and allowed for X number of racks. Today, you can deploy one service and suck up all your extra space."

According to Paul Connolly, vice president of marketing and network architectures at Scientific-Atlanta Inc., the complexities of a multi-platform network are causing many engineers to reconsider the very structure of their networks.

"Among operators," says Connolly, "there is a trade-off between what functionality is distributed out in hubs and what is centralized in headends. We see operators in both camps. In many cases, they're driven by whether or not they have existing hub sites. The cost of securing a hub site, getting the right-of-way, and building the building, etc., is really getting very expensive. So a lot of operators are looking at what I call hub elimination or minimization, to centralize a lot of the processing of the new services back in master or regional headends.

"A lot of that is really driven by the trade-off between the cost of the transport and the incremental cost of a distributed service. So operators are having to make a lot of traffic assumptions about how much bandwidth they need, how much processing capability they need for various kinds of service, whether it's video, voice or data."

Forging ahead

One would be hard pressed to tag Cox Communications as a conservative, don't-make-waves type of company. Program-ming, customer service, system consolidation, new service launches, you name it, and it's taken the lead. Headend design is no exception, either. It has seen the future, and according to Mark Davis, Cox's director of engineering, telephony technology, it decided to meet it head-on several years ago. "We started with a headend upgrade program about three years ago," says Davis, "and we looked at it as being the heart of the network. All your fiber, all your electronics, a significant investment has ended up in these buildings. So, the first thing we did was bring the issue of buildings and the critical nature of buildings to the highest level, to Jim Robbins, the president of the company.

"We put together a sales pitch that differentiated network buildings from office buildings. We then showed the impact as far as the critical revenue generating from such buildings and the investment impact if we were to lose a building to fire. We discussed a host of things that made it very easy to understand how badly we needed this program and to spend over $100 million on the buildings."

Davis says the process then evolved into a major system-wide assessment. Working with a core group of Cox personnel, they did detailed research on three things: how much space they would need to offer new services as well as expand their channel lineup; what type of space they would need to ensure reliable service; and what type of space they would need to protect their sizable investment in equipment.

Some of the issues that came up were quite predictable; others were less so. The Cox team looked at every "system" in its "headend of the future" and studied it exhaustively. This included such obvious things as the differing powering needs for the various services, as well as backup power systems to ensure a high degree of reliability. But other headend systems, says Davis, took on a whole new meaning and importance when seen through a multiple service provider's eyes.

"Grounding, for example, is a relatively new thing to cable TV," says Davis. "Traditionally, the RF gear was very robust, and you didn't need an elaborate grounding system. However, all of the silicon chips that are being deployed in headends these days to support data, voice and even digital video are very sensitive to static discharge, power surges and power loop currents coming through a ground system. So, we deployed an extremely elaborate grounding and surge protection system in these sites. It's a huge upgrade from where we used to be with a wire braid running through the floor.

"Another static discharge minimizing procedure is to maintain a constant 50 percent humidity inside the buildings. If you're running a lot of air conditioning, it dries out the air. If your finger touches a switch card that costs $30,000 and it fries the processor in it, you will have paid for a humidification system. So, we keep the temperature and humidity constant in all of our buildings." As a lifeline telephony provider, Davis says Cox has taken on a whole new approach to protect itself from disasters, both man-made and natural. "We have three stages of fire suppression. The first stage is just the detection of smoke and alarms so that people can take immediate action. That actually energizes what we call a pre-action dry pipe system. In this system, the pipes are actually filled with air. Water is not released into the pipes until the second alarm, which detects a certain amount of smoke in the air. And only after a sprinkler head is tripped will the water actually charge into the pipes.

"It's a very complicated and expensive system. But, again, if you imagine you have one headend or even the smallest hub site that can easily have $10 million worth of gear in it, much less the revenue hanging off of that gear, it was very easy to justify from that regard."

Davis notes that Cox facilities are built on a deliberate bunker-like system, featuring precast, reinforced concrete walls that have expansion functionality built in. "We tried to build for a five-year planning window," says Davis. "We buy enough land for a 10-year planning window, but we build enough building to last us five years based on the services we know about today. To do that, we've designed the buildings to expand on a what we call a 1,000-square-foot equipment bay design. It's a 32-foot by 32-foot module. So, we can add these modules as needed over time. The building is sized to handle a 10-year window."

For headends and hubs in special areas, Cox has made special adaptations. In California, Cox facilities are built to an earthquake "zone four" rating. In hurricane-prone tidal areas like New Orleans and Hampton Roads, Va. facilities feature concrete roof decks, four-foot metal floodgates at the doors and powerful ejector pumps.

The bottom line

Davis readily admits the headend project meant building bigger and more expensive facilities. But, says Davis, given the equipment investment and the revenue streams he's trying to protect, it's a cost well worth paying. "It depends on the number of homes passed out of a hub site or the number of homes served out of a given headend," says Davis, "but we have gone from a few hundred square feet in a headend, to on average, 7,000 square feet. And that would be a headend serving approximately 80,000 to 100,000 homes passed. And then you have sub-tending hub sites that would range anywhere from 2,000 square feet up to 10,000 square feet, depending on the number of homes passed per hub. Two thousand square feet would be about 20,000 homes.

"When we get through, it's $350 a square foot, excluding the land. In the past, it was usually a Butler building tin shed with no fire suppression, no generator and wood everywhere. You'd be lucky to be at $50 a square foot."

To get started on the road to the future, Davis suggests a few key points. "The most important thing," says Davis, "is to know the services you plan to offer and to do a long-range plan as to where you need to be.

"You have to standardize wherever possible. If you let every individual system do its own thing, you'd have 50 different flavors. So, we've set standards. If there's something that's not working right, we'll find out about it and make the changes so that we can incorporate those enhancements going forward. And, you have to have the flexibility to expand.

"Then, probably the biggest thing is to build in all the reliability insurance you can afford, because it is the heart of your network."