Psytechnics: Tracking the Voice Experience

Friday Sep 21st 2007 by Jeff Goldman

Experience Manager is designed to monitor the operation of a VoIP solution in a way that traditional IP QoS tools simply can't.

Psytechnics is the result of ten years of research on monitoring voice and video quality at British Telecom in the '90s. The company itself was founded in 2000 as a spin-off from BT, and now has venture capital backing from 3i, GIMV, NIF Ventures and NVP Brightstar.

Mike Hollier, Psytechnics' CTO, says the company differentiates itself by integrating a wide range of measurement capabilities into a single monitoring platform, the Psytechnics Experience Manager, which is designed to look beyond the basic metrics that an IP QoS tool would check.

When a hosted service provider deploys a huge IP telephony system and performance problems start cropping up, Hollier says, they're likely to turn to their IP QoS tools for the answer. "And they're in a world of pain, because they've got a green light from their service assurance or performance management system—and unhappy end users," he says.

Performance vs. experience
The point is that an IP QoS tool like HP OpenView or Computer Associates' eHealth, Hollier says, is designed to view performance specifically from a data perspective—and when you're trying to measure the quality of the voice experience, that's not enough. "You need to know a different set of things about the IP network to know if the IP network is service-affecting," he says.

That means being able to look at aspects of the voice application itself—"things like echo, noise level, speech level, speech distortion," Hollier says. "If any of those things are impaired, then quality of experience is impaired."

And according to Hollier, that's where Psytechnics is unique. "Even the people who are claiming to do voice quality measurement, they're looking at IP QoS quantities, packet loss, jitter, this kind of stuff," he says. "They're not measuring the voice application piece: whether there was echo, whether the speech levels were too cold or too hot and so on. It's not that they're doing a bad job of it—they're not doing it at all."

A deployment of Experience Manager (see image, below) consists of Linux appliances called IP Engines, which are placed at concentration points as monitoring probes. "You have a multiple number of those, which then get aggregated into an Experience Server—and that's where we do our analytics and diagnostics," Hollier says.

Prod interface

Subjective measures
The resulting data, Hollier says, can be viewed through Experience Manager's own user interface, and can also be integrated upwards into an IP QoS solution like HP OpenView. Within Experience Manager, he adds, "you can get summary views of all the call traffic that's going through your network, you can look at it on a per-site and per-end-user group basis—or you can divide the traffic up into performance categories."

Hollier says Psytechnics' solution has been validated through thousands of subjective tests. "We've brought hundreds and hundreds of real people through our laboratory, put them in soundproof rooms, and under properly controlled conditions we expose them to all kinds of voice distortions and network distortions and coding errors . . . so things like mean opinion score [MOS], voice quality type measurements, they are validated against hundreds of thousands of real, subjective judgments," Hollier says.

Putting it to work
As an example of the way that Experience Manager can resolve a problem, Hollier says one bank client had ongoing problems with speech distortion, but their network provider showed no issues with IP QoS. Using Experience Manager, he says, "we discovered that the third party WAN provider was actually transcoding the speech. He was having G.711 speech coming into his WAN and there was G.711 speech coming out of his WAN, but the speech quality was being ruined in the process—and when we inquired more closely, it turned out that he was transcoding to G.729 to save some money on the expensive international legs. And of course your IP QoS tool can never find that, whereas we spotted the distorted speech payload quickly."

The point, Hollier says, is that "the worst case scenario for any sort of service provider, or even an enterprise internally, is that you've got a problem and you can't find it . . . if you're going to have a real-time voice application, you have to know if the end user quality of experience is satisfactory within the business criteria you've set—and if it isn't, you have to be able to find that problem."

And so the value proposition for Experience Manager, Hollier says, is simple. "If you said, 'I want to know the performance of the voice application,' there are six things I've got to know, and something that's only measuring IP QoS is only measuring one of those six things," he says.

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