Reliability, performance and signal quality aren't just routine, matter-of-fact cable functions anymore. The dawning of the digital age is seeing to that.

Intense competition and the critical need to serve a growing number of digital customers with highly reliable, picture-perfect quality services, including video, telephony, data, IP telephony and more to come, are elevating the big three system functions to mission critical status and sending a clear signal to test and measurement companies that their role in ensuring network reliability will be vital to the digital migration.


"With digital, a lot of people wonder why it needs to be tested in the field, since it's so robust. But operators are asking more and more for field testing of digital equipment, and it's happening at the headend, so we're addressing more digital signals at the headend," says Ralph Gerbasi, president of Avantron Technologies Inc., a Montreal-based test and measurement company.

The increased attention being paid to digital testing prompted Avantron to recently incorporate QAM functionality into its 2000 series of test instruments, including its spectrum analyzer. "Our spectrum analyzer is designed for FCC proof-of-performance measurements. Now, digital comes along with a different format, and we're doing bit error rates and constellation displays. You can't just use signal meters or analyzer tests anymore," Gerbasi says.

The migration to digital services by multi-service providers is spawning new test and measurement companies intent on filling the digital testing space, yet they have no illusions about the challenges that lie ahead in accurately testing digital service quality, reliability and performance.

"Network carriers are still analog carriers, but with all the new services, they're overlapping each other so quickly with digital TV, cable modems and now telephony, it's like three big waves crashing down at once," says Jim Boeddeker, president of Streamport Technologies, a fledgling digital test equipment company.

Those waves, Boeddeker admits, will continue pounding the digital shoreline. "We just began to understand digital TV, and now there are modems. We're not sure how we'll test for telephony," he says.

System test points: Speedy isolation of ingress noise is important because the first indication of a problem may be the subscriber's inability to use the service. Therefore, it's important to have monitor points near the output of each optical receiver and after signal combining. These allow the operator to quickly isolate a problem node and take corrective action. Source: ADC.

Most test equipment manufacturers are getting the message that as digital services expand to include video, telephony and data, the need for quality testing equipment and processes will follow, and are likely to generate strategic alliances such as ComSonics' and Trilithic's recent partnership, which is intended to combine key disciplines within the two test equipment and cable TV service companies. Other leading test equipment manufacturers such as Telecom Analysis Systems (TAS) are also developing test equipment for modems and related digital services.

Adding digital test and measurement capabilities to existing analog test equipment is pushing many test equipment companies to re-tool their traditional test products. Wavetek Wandel Goltermann (WWG) is a classic example, and though the process can be painful, it has to happen. "Our philosophy is a one-box solution with the capability of using our SDA 5000 (analyzer) to allow constellation displays and other digital functions such as Modulation Error Ratio (MER) and Bit Error Rate (BER). The project is very difficult with packaging, weight and heat issues, but when you think of how this will eliminate people (having to hang) meters from poles, it makes sense," says Mike Wright, principal software engineer for WWG.

Yet digital is so new, a big learning curve looms ahead, experts say. "There's not enough digital out there to see the problems. Operators have been hiding digital services in high-end frequencies, so there's not a full band of digital channels, and most operators don't yet feel the need to test digital services," says Brad Johnson, product marketing manager for Sencore Inc., an electronic test equipment provider which recently introduced its QAM B970 analysis meter, which estimates what the BER will be and what errors need to be corrected, among other functions.

As a result, Johnson says that operators are hesitant to purchase QAM analyzers and digital testing equipment. "It's difficult to sell a $4,000 QAM analyzer when an operator wants a $1,000 meter. But once a system is fully digital, more people will be using signals and more things can happen, like interference, ingress and noise in a system. And when there are enough errors, the 'cliff effect' occurs, and the signal is completely gone, without notice."

What is noticeable is the cost of digital test equipment. Adding a QAM analyzer to an existing spectrum analyzer will cost about $4,000, or 30 percent more than a traditional analyzer, and will bump the cost to about $15,000, on average. Yet costs can be much higher, depending on the quality of the equipment. "With digital testing, it's across the board, and equipment can range from a few thousand dollars to up to $50,000. And with the exponential growth of new services and equipment in customers' homes, installers must have sophisticated instruments to monitor installs," Gerbasi notes.

Most experts agree, however, that cutting corners with digital test equipment is not a good idea. "There are expected to be 25 million cable modems in the U.S. by 2004, so the cost of testing becomes insignificant when 20 percent of them don't work. That's a lot of truck rolls," says Rick Jaworski, vice president of marketing and sales for Hukk Engineering.

Hukk introduced its CM 1000 cable modem tester recently, which, along with its CR 1200R digital analyzer, gives the company two pieces of digital test equipment. Yet Jaworski admits that digital testing is in its infancy. "Some operators know what they need, but most don't. Digital testing just isn't their business. With the shortage of qualified technicians, testing new digital services can save truck rolls and installation costs."

Finding and training technicians skilled in the use of sophisticated digital testing equipment is an ongoing problem for both operators and digital test equipment companies. And the issue isn't likely to go away anytime soon. "Technicians with these skills are very hard to find, which makes our job much harder," says P.J. Kleffner, business development manager for Tektronix Inc.

Tektronix recently developed a "human interface" family of products designed to fit three levels of technicians, Kleffner says. The first is a low-skill, push-button, pass-fail device; the second is for more skilled technicians who can make adjustments and repairs on-site; and the third is designed for network engineers who can pre-set various limits right on the device. "We want information available to super-techs so they can repair and get the network back up and running, and we're getting the products into smaller, user-friendly packages," adds Kleffner.

Yet with digital and its subsequent testing and monitoring procedures, many technicians and engineers are learning its nuances through the "building the airplane while flying it" method, making training and the sharing of knowledge paramount. Says Johnson: "Digital is so new, there's a real lack of training and knowledge in the field. People just don't know where to go, and it's moving so fast, there's not much training getting done."

Despite the lack of digital training and expertise at most cable systems, however, the march to digital testing is likely to gain momentum. "Some operators are beginning to recognize the need to segment their networks and have test access points throughout the network. There's not much difference anymore between the competitors, and the telcos' reputation for reliability is far better than cable's. So, more test functionalities are needed, and not just for lifeline services, but all digital services," says Sara Manderfield, product manager for RF signal management products at ADC Telecommunications Inc.

Whether the cable industry fully embraces digital test equipment anytime soon is questionable. In the meantime, test equipment manufacturers are scrambling to not only design digital test functions into their existing products, but to develop new ones complete with the training and support crucial to their success.

Integrating these components is the test equipment manufacturers' next great challenge, and is forcing some to admit past failures. Concludes Boeddeker: "We don't do as good a job as we could in coordinating the different elements like analog, modulation quality and digital. Test equipment folks have to be involved early in the design stage and be fleet of foot with new platforms. More competition and network reliability will drive network measurement and testing, and with so much technology, it's a huge challenge."