Voice lessons: Agilent tunes quality for voice over IP

Sooner or later, great concepts must become reality. Voice over IP is a great concept, and it is becoming a more widespread reality. However, popular opinion says that to become a reality, voice over IP must meet the rigorous quality standards of traditional voice telecom service. Today, it falls short. But popular opinion among engineers is not always the same as it is among customers.

Users of wireless telecom service have learned to accept a lesser quality of service. Customers of these technologies tolerate noise, delay, echo and dropped connections largely because the convenience of wireless and novelty of the Web compensate for quality - for now.

"The end user has gone through a metamorphosis because of the wireless industry. The bar has been lowered on tolerance," said Carl Ford, community developer for Pulver.com.

In the long run, the novelty of conducting conversations over the Internet and the convenience and cost-savings benefits of wireless will dissipate, and people will expect quality once again.

"You won't see anybody spending money on moving facilities to [voice over IP] until the voice quality is there," said Dale Freelove, global business development manager for Agilent Technologies.

To help telecom equipment manufacturers design better IP-based voice and fax products and to provide network operators with the tools to monitor quality once those products have been deployed, Agilent has developed two test solutions: the Telegra Voice Quality Tester and the Internet Advisor, a voice- and fax-over-IP analysis software solution.

Telegra VQT measures the clarity and delay of voice in IP-based networks; it also can measure the effect of echo noise distortion on quality of service. It supports the perceptual speech quality measure (PSQM) and the perceptual analysis measurement system (PAMS). PAMs provides a repeatable, objective means for measuring perceived speech quality. VQT uses both measurement systems to identify quality impairment during the product development cycle and to verify end-to-end quality during system integration.

"Having an objective model that deals with the end user experience strikes me as a far better tool than looking at internal metrics like packet loss and such," Ford said.

Most IP-related test tools measure the parameters that relate to the proper functioning of network equipment such as routers and packet switches. Agilent's tools look at discarded packets, delay, congestion and other parameters related to network layer performance. VQT extracts the actual voice characteristics from the packet information to measure parameters that satisfy the end user experience, not the thresholds of a specific network element.

"There will always be some sort of impairment [with voice over IP]. We need to determine if it is perceptible," Freelove said.

Different types and numbers of network elements in a packet environment make it difficult to predict and pre-engineer voice quality. And telecom technicians who also understand the added complexity of packet networks are not easy to find.

"With any new technology, each company has a couple of gurus who get stretched thin. Companies need to have test tools to get more people involved," Freelove said.

VQT and Internet Advisor generally will be used in lab or implementation environments but also can be used by technicians, Ford said. Network operators now can determine how network configuration changes will affect quality.

"Enterprises have been slow to adopt voice-over-IP technology even though it's a no-brainer. The use of PSQM and PAMS reporting tools is valuable in putting those companies' fears to rest," Ford said.