Testing, testing, V...o...I...P

Sat, 07/31/2004 - 8:00pm
Joe Bant, Contributing Editor

The cable industry's continuing effort to roll out newer and more advanced services means different things to different people.

To customers, it signifies the potential to gain access to a comprehensive cable platform that offers more than ever before, and includes services such as IP telephony and video-on-demand.

Seeker Lite
Trilithic’s Seeker Lite
To MSOs, it represents broader streams of revenue and a more encompassing reach over consumers, and with VoIP in particular, a bridge to a service typically dominated by the telcos.

To companies specializing in broadband testing equipment, it represents the need for equipment with more advanced capabilities and functions to ensure that those new services don't fall on their face as they become available.

"As cable has become more things to more people, demand for quality has gone up, as well," says Jim Harris, marketing manager for test equipment-developer Trilithic Inc.'s Instrument division. "VoIP will only accelerate that trend. The number of dollars hanging per minute of outage is very high."

It's not difficult to see how testing has evolved in the industry. One only need look at requirements from the Federal Communications Commission that mandate testing for cable systems. They don't even mention digital services. All the required tests pertain to analog.

Today, digital is at the forefront, and VoIP is on the horizon, and IP-based video is following behind that. Operators and vendors, meanwhile, are continuing to evolve testing standards for embracing these new services.

Companies such as Trilithic are helping the MSOs do that. According to Harris, one of the necessities of the new testing environment is getting it right the first time, which means preventive maintenance during installations.

"It's the delivered quality of the content that's important," Harris says. The old way, he adds, was to fix problems when they happened. But with some new services, particularly VoIP, customer tolerance of inferior service isn't likely to be high. Traditional POTS (Plain Old Telephone Service) has such a high reliability standard, customers will want the same for VoIP–and if they don't get it, they could go elsewhere.

As Yankee Group Senior Analyst Lindsay Schroth explains: "People already have cell phones. They're not looking for another service that might or might not work."

Trilithic, for one, has a number of devices designed for installation testing, including the Seeker Lite and the 860 DSPi field analyzer. The Seeker Lite is specifically designed for detecting signal leakage during installations and displays numerical measurements of leaks on up to three selectable channels. It emits a tone signifying the strength of the leak and has a directional antenna to determine the leak's location.

The 860 DSPi verifies bi-directional service and uses a built-in DOCSIS modem to perform a range of forward level measurements and reverse level and data transmission tests.

But Harris says it's more than just the instruments that are important–it's the flexibility they provide in terms of being able to adapt and upgrade.

The 860 DSPi–along with a selection of other products from Trilithic and other companies–is software-based, which means many of its possible upgrades can be downloaded and installed via the Web.

Harris says this kind of customization is important because different MSOs have different needs and requirements, so it's an advantage to have flexible products with broad appeal, and comprehensive abilities.

Acterna’s DSAM
But adding advanced abilities doesn't mean much if cable technicians aren't capable of using them. Adding simplicity and consistency to the equation is another area in which installation testing must evolve to accommodate new services, explains Kevin Oliver, marketing director for Acterna.

In the past, the installation process has often been hampered by "no strategic management or training in installers, no real process control and inconsistency," Oliver adds.

When cable companies were simply broadcasting video and even data, the inconsistency wasn't a huge problem. But, with VoIP, any packet loss can mean diminished call quality or breaks in service that subscribers won't tolerate.

As a result, he adds, MSOs need to ramp up the consistency of their installations. To fuel that effort, Acterna is focusing on developing products that promote this kind of consistency with a recently released software platform called TechComplete. The software takes advantage of the DOCSIS network, allowing headend technicians to support workers in the field in real time, and interactive tests to be performed over the network. Headend techs can then monitor the field techs during installations to ensure that all the work is being done correctly.

The software also enables comparisons between different tests to ensure consistency in all the fieldwork.

Acterna's DSAM and SDA product lines, for instance, already communicate remotely to management systems. The SDA 5000 is a digital analyzer and sweep system. The DSAM 2500 is a digital service activation meter that verifies downstream and upstream signals, in addition to its other functions.

Sunrise Telecom’s CM-1000
But Acterna is not alone in this area. Sunrise Telecom also has installation tools that communicate with workforce management systems. The company's CM-1000 Cable Modem Network Analyzer is integrated with a Web browser that serves this purpose. Like Trilithic's 860 DSPi, the CM-1000 also comes equipped with a built-in cable modem to exercise the network's upstream and downstream paths. The device can test MER, BER, signal level and constellations on the downstream side, and Block Error Rate (BkER), power level, attenuation, ping time and lost packets on the upstream.

Eyeing the upstream

Upstream testing has gained new significance with the advent of new services. VoIP, in particular, will test the DOCSIS upstream as never before.

"It's not simply a pipe distributing services," says Gerard Terreault, Sunrise Telecom's CTO. "It's a bi-directional network with an optical side, a service side–a whole big system."

Testing the upstream can prove difficult, however, because most problems with it occur in the home, and it comprises signals from all the various modems in the network. But MSOs neglect it at their risk. Even one malfunctioning modem can cause problems for 500 or so others in an area of the network.

To get around the difficulties of testing upstream, many companies complement their testing gear with integrated cable modems. The modem plugs into the network like any other customer's modem and simulates the interaction between the customer's device and the cable modem termination system (CMTS). The instrument then monitors the signal running from the modem to the CMTS to verify the upstream connection is working properly.

ST-261 DOCSIS Analyzer
Filtronic Sigtek's ST-261 DOCSIS
Analyzer can test and monitor
upstream transmissions from any
individual cable modem in the network.
One testing device that takes the process a step further is the ST-261 DOCSIS Analyzer from Filtronic Sigtek. The company says its ST-261 platform does more than simulate the connection between a modem and the CMTS; it can actually measure the signals emitted by individual modems in the network.

"Many devices can act as cable modems," explains Brady Volpe, Filtronic Sigtek's director of technical marketing. "But the next-generation product can listen to all the cable modems. It's like a CMTS except it can look at both sides."

Deployed at the headend, the ST-261 can be used to prevent problems when it's not solving them–providing constant monitoring and archiving of signals coming to or from the CMTS.

Besides testing both directions of DOCSIS, new test equipment also focuses on testing the different layers of DOCSIS. Volpe divides DOCSIS into three layers: the physical layer, the DOCSIS protocol layer and the IP layer.

The IP layer consists of the content being distributed over the network and is where VoIP resides. Efforts in the testing industry today are focused on developing more effective ways to test the quality of the content, and not just the physical network.

For VoIP, this translates into testing call quality and making sure quality detractors, such as jitter and delay, are minimized.

Oliver says Acterna is in discussions with MSOs about appropriate standards for VoIP quality. That way, not only will tests be able to measure VoIP, but specific guidelines will be in place.

Oliver says VoIP deployment and testing is in a complicated state right now, but he's optimistic that MSOs and test manufacturers alike will grow uniform in their practices over the long haul.

Analysts, though, have mixed opinions about the MSOs' ability to deliver a service like VoIP. Schroth says the key will be progressing from a primary line-equivalent service to the advanced features that can be enabled by the softswitch connection. She admits it's a "different way of thinking" for MSOs but is confident they can establish their brand names and adjust to the scalability.

Patrick Kelly, founder and partner of the "OSS Observer," isn't quite as optimistic. "Historically, cable has not spent much on OSS systems," he says, adding that MSOs will need to increase their investment in test and measurement technology for VoIP.

"You really only get one shot, and if it's a bad service, people won't go back," Kelly says.

Meanwhile, test and measurement providers say they will be standing by, hoping to do their part in helping operators provide quality cable services.


Share This Story

You may login with either your assigned username or your e-mail address.
The password field is case sensitive.