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The Return Path More Traveled
Engineers Brave the Trenches for Two-Way Action
By Greta Durr

• Cables market changes form
• Clustering trend ignites
• Worth the effort
• At what cost?
• Ready, aim, fire
• A large upgrade
• Old ideas become new tricks
• A smaller upgrade
• The song remains the same
• The last word
• In the Two-Way Fast Lane
• Two-Way Survival Guide
• Bottom Line

In the more than two decades since cable TV officially began its evolutionary foray into the full-service cable telecommunications arena, there has been speculation about how two-way activation will take place and at what cost to operators. Market analysts have emitted numbers that illuminate the broadband landscape like particulate matter in the Los Angeles skyline.

Still, engineers in systems of all sizes are finding that two-ways inherent concerns remain unchanged.

Cables market changes form

According to Forrester Research, by 2002 cable companies will capture an estimated 80 percent of the residential broadband services market.

The firm also projects that cable data services will surge from 350,000 subscribers in mid-1998 to more than 2 million by the end of 2002, primarily because of falling cable modem prices and rising consumer awareness.

"Broadband will alter the Internet landscape, changing customers use and experience of online resources and forcing service providers to sharpen their broadband strategies," says Forrester research analyst Christopher Mines.

Clustering trend ignites

Vigorous deal-making indicates that the cable industry has come of age. A clustering pattern has emerged, as multiple systems operators (MSOs) become increasingly motivated to draw their lines in the system sand. This trend will forever change the way broadband services are delivered in the United States. (See Table 1.)

One such deal was Adelphias $2 billion purchase of FrontierVision that, upon its completion, will add 702,000 cable subscribers to Adelphias existing base of 2.36 million customers.

At the time of the announcement, approximately half of FrontierVisions customers were located adjacent to Adelphias existing operations in New England and Virginia.

"The FrontierVision systems represent the largest group of cable systems located within our Northeast region of operations that were likely to come up for sale," explains John Rigas, who founded Adelphia in 1952.

The deal, like many others taking place nationwide, will help the MSO to consolidate its efforts in offering enhanced services over two-way networks and insulate its holdings from formidable competition.

An agreement between leading contenders MediaOne and Cox indicates that the clustering trend shows no signs of slowing.

This swap, scheduled to be completed later in 1999 at an undisclosed price also covers systems in the Northeast.

Cox is trading its systems in Massachusetts, representing 54,000 customers, for access to 51,000 MediaOne customers in Connecticut and Rhode Island. This is not the first such deal for either MSO, nor is it likely to be the last.

Each companys efforts to consolidate operations into large clusters are aimed at better enabling new services such as digital TV (DTV), data, high-speed Internet access and telephony services.

"This transaction, our trade with Time Warner announced earlier this year and last years swap with TCI, which will increase our presence in South Florida, are part of our strategy to increase our strength in the areas we already serve," comments Jan Peters, an executive at MediaOne.

There is no doubt among cables engineers that deals such as these pose a new world of challenges to the people charged with bringing the new systems into the fold while working to upgrade and maintain existing plant.

Worth the effort

The industry is dealing and engineering so vigorously for good reason. According to the Strategis Group, the average monthly revenue per cable subscriber, estimated at $37.50 last year, will increase by 50 percent in 2003. (See Table 2 .) Combined with increased premium service offerings, analysts agree that the impact on revenue is bound to be significant.

At what cost?

According to a National Cable Television Association report, based on Paul Kagan Associates research, cable companies invested nearly $8 billion in infrastructure upgrades in 1998 to bring subscribers higher quality pictures and sound, more programming, and two-way capable systems.

The same study estimates that since the 1996 Telecommunications Act, cables infrastructure investments have totaled more than $20 billion.

At this point, the study estimates that 56 percent of all cable homes are passed by activated two-way plant, allowing the deployment of DTV, data, high-speed Internet access and telephony.

Ready, aim, fire ...

As the projections indicate, the chaotic broadband market has top guns and zip guns alike eyeing the same target: enhanced services deployment over whatever plant they can get their hands on.

In the meantime, engineers with systems of all sizes and upgrade status are working diligently to implement the changes. The work is no simple task for any of the operators making the transition.

A large upgrade

Cox Communications reports that two-way activation efforts are nearing the halfway mark throughout its rapidly expanding plant. Swaps and other dealings aside, the MSO anticipates that the majority of its two-way activation goals will be completed by 2000.

The huge upgrade effort has been nearly 10 years in the making, says Cox Telephony Technology Director Mark Davis.

In the planning process, the MSO decided that some of the elements of successful two-way activation would require additional downstream bandwidth coupled with useable upstream bandwidth for interactive services.

Davis says that by deploying ring-in-ring architecture and generator-backed power supplies in the outside plant, network reliability has been maximized.

Cox Vice President of Engineering Operations Dick Mueller says he can barely express the extent of what he has learned about activating the return path since the MSOs effort began. Headend design isnt the only thing thats changed, he says, or the only thing thats bound to change as two-way activation becomes more widespread.

"Early on, we looked at the available technologies," he says. "We did some market research relative to customers, and we decided that the best way to do powering on the NIUs (network interface units) on the side of the house was through network power."

At the time, he says, the only technology available was the very large and costly central power supplies. "You have to pick a penetration level when you do that design that you think youre going to hit. We picked 20 percent."

The market research didnt indicate they would reach the specified penetration level for years to come, he says. "We launched the service and started getting 20 percent in a few months rather than in several years, so we had to rethink our position."

Soon, he notes, Cox made the decision to move from centralized powering with generator backup back to distributed locations with generator backup.

"That gave us much higher penetration potential," says Mueller, "in some cases as much as 100 percent higher."

Currently, Cox has migrated about 40 percent of its system to distributed power from centralized power. It costs about the same, Mueller says, without being "the size of a Volkswagen bus." Another advantage to the turn in powering strategy, Mueller says, is avoiding the necessity of powering from subscribers front yards. "Thats always an issue."

Old ideas become new tricks

With the increasing demand for enhanced services and aggressive deployment schedules for two-way activation, Mueller says the industry is poised for changes in design and engineering strategies.

"Architectures will always evolve. They have to," he says. "As new technologies become available and the cost of existing technologies goes down, the design has to change."

Though multiplexing, in concept, is not new, dense wavelength division multiplexing (DWDM) is a technology many MSOs are looking to for expanding the capabilities of their broadband pipe without having to deploy as much additional fiber.

Comcast and TCI, for example, have been experimenting with Harmonics METROLink DWDM technology in a number of systems.

Among the reasons for the products emerging popularity, says Harmonic Transmitter Product Specialist Ketan Gadkari, are its offerings of a complete two-way, eight-wavelength solution that stands only 12 rack units tall. Efficient use of space in the hub is an important consideration for many operators seeking to deploy two-way and expand their service offerings.

As the technology becomes more pervasive, he says, prices for DWDM and associated equipment such as Erbium-doped fiber-optic amplifiers (EDFAs) will continue to drop.

Other vendors, such as ADC, ANTEC, Ciena, Philips, Scientific-Atlanta and Siemens, to name a few, also are working on it and are in various stages of ensuring a place for their DWDM products in the telecommunications marketplace.

"Were not deploying it at the moment," says Mueller, but Cox is regarding it as insurance for the future. "We have always planned that DWDM would be available to us going forward if we need to shrink node sizes. Weve got a standard on how many well place, and if we have to shrink the node sizes down over time, well do it through wavelength division multiplexing (WDM)," he says.

A smaller upgrade

Ohio cable system engineer Poge Smit also has learned a great deal from activating the return path in his system; moreover, he is never at a loss for words about it.

His system, the Oberlin Cable Co-op, is owned and operated by its 2,000 subscribers via an elected board of trustees. Oberlins traditional plant may be considered archaic by some standards.

For Smit, the challenge of going two-way and activating data services to bring connectivity to the city and its schools has been a two-year, in-the-trenches challenge that few engineers would dare to tackle.

"As a small, classic 450 MHz cable system contemplating two-way plant activation for data services, we faced many of the same obstacles and considerations as any larger operator," says Smit. "The biggest difference, other than the management logistics of a larger deployment, was the lack of fiber optics in our system.

"Without the convenience of multiple nodes combining at the headend, each with only five to seven actives representing several hundred drops, our noise battle was considerably more formidable than in a typical HFC (hybrid fiber/coax) design," he explains.

Bringing it all together with only a few people on staff and a similarly limited budget meant breaking a few rules, defying some conventions of modern broadband engineering and some experimentation, but its all starting to pay off, he says.

"We currently have a combination of nearly 120 trunk stations and line extenders representing approximately 1,600 service drops converging into one hub supernode with a consistent noise floor of 40 dBmV," Smit says. (See Figures 1 and 2 .)

"The keys to our success were meticulous attention to the initial reverse design considerations in a classic coax system, combined with a thorough understanding of the obstacles before us," Smit explains.

The song remains the same

Regardless of a systems architecture, size or enhanced service goals, ingress remains the top concern of operators seeking to activate and maintain a clean return path.

"We all know that ingress is the biggest problem in the return path," says Smit. "Despite the cleanroom engineering philosophy of those who proclaim high pass filtering of drops is the wrong way to eliminate return impairments, we chose to utilize high pass filters on all drops not receiving two-way services.

"As a small system, the cost was minimal, and 90 percent of the most likely sources of ingress inside the subscriber premises have been eliminated. This approach has been extremely effective in helping to isolate the occasional return aberrations in the cable plant itself.

"A very important element of any return path activation and two-way service deployment is having quality instrumentation for correct sweep/alignment and subsequent analysis/monitoring of the reverse spectrum on an ongoing basis. One must also understand what he is actually viewing on the instruments display and how to most effectively use test gear," says Smit.

Mueller agrees on the importance of monitoring for ingress. "Obviously, when we were a one-way downstream service, we didnt really pay attention to the upstream path and the ingress issues. Now that were a two-way service, we have a significant amount of preparation of the network to get it ready. Its a matter of fixing it and then keeping an eye on it going forward and having the tools in place for efficient monitoring. When things loosen up, you start getting ingress. Its a job of diligence more than anything else," he says.

Training is an issue initially, he says. "Its just a matter of taking the time to train people on the theory of return path operation, and when you see certain phenomena displayed on the scopewhat it means and how to find the problem. Its not a huge issue," he says, adding that the magnitude of the staff is more significant than the material that needs to be covered.

The last word

"Probably the most important aspect of establishing and maintaining a clean and efficient return path is to abandon some of the old ways of dealing with the forward path," says Smit. "The mindset of the pictures look OK is hardly appropriate for the strict requirements of two-way deployments.

"Use quality materials," he emphasizes. "Take installation procedures and general system maintenance and leakage detection practices to the highest possible level.

"Our entire project is nearly complete. It was accomplished by very careful study of the design considerations, seat-of-the-pants learning, aggressive pursuit of our objectives, and plenty of hard work by one engineer and one technician," Smit says.

Smits words of wisdom ring true for nearly any engineer working on return path activation in a system of any size, anywhere.

"Its not magic or rocket science," Smit concludes. "It all boils down to sound engineering and adherence to fundamental practices. Whether youre a monster MSO poised to conquer the world or a little popstand in the Midwest just having some fun, two-way is THE way." - CT

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