Background

With VoIP technology well past the early adopter phase, one might wonder:

"I thought we had voice quality figured out — are we worried about this again?"

Well, the answer is yes. As an industry over the last few years, we have been successful in creating VoIP applications and systems that provide excellent voice quality. But, in the past, VoIP carriers and enterprises did this in very controlled environments: private networks, enterprises, dedicated links and many times on highly over-engineered networks.

A new challenge

VoIP is entering a new phase, replacing traditional telephone service to both residential and commercial customers. The adoption rate has grown dramatically over the last two years and according to In-Stat, 8.8 million consumers in the U.S. are expected to subscribe to VoIP carrier services by 2008.

The VoIP carriers servicing this new wave of customers are facing a new frontier: delivering voice to residential and commercial users across existing broadband infrastructure. Based on geography and cost, customers have already chosen a broadband facility from a wide array of physical media: ATM, T1, cable, DSL, WiMax, satellite and other media. For the VoIP carriers to successfully deliver voice service to these new customers, they have to depend on the customer's existing infrastructure that brings broadband to their residence or place of business. Asking a customer to substantially upgrade their broadband service would cause a significant cost barrier that would wipe out much of the original incentive to use VoIP. In the end, VoIP carriers need to choose gateways and other equipment that can deal with the variability of a wide range of broadband infrastructure.

Is voice quality really that important?

Yes, from our discussions with a number of carriers and end customers, voice quality is the #1 post-installation operational and customer satisfaction issue.

"From our experience, voice quality is the most sensitive issue for business customers" Greg Schreiber, VP of Product Development - Vaspian (carrier customer, U.S.A.)

It seems that Murphy's Law comes to surface with many new VoIP installations. After many hours of testing and successful operations, as soon as the new customer's CEO picks up the phone, a technician elsewhere in the organization will start a huge file transfer over the broadband link, causing network congestion. With poor quality gateway equipment, the CEO's conversation will be plagued with broken and choppy speech.

Customers have told us that poor voice quality is definitely one of the items that will cause a "change in vendor".

How is AudioCodes different?

After many years of developing speech compression algorithms, AudioCodes has developed a number of standard and proprietary techniques to produce very high quality speech. Just a sampling of what makes AudioCodes voice quality tops in the industry:

1. Dynamic Jitter Buffer — dealing with network jitter is always a challenge, and it is especially difficult on shared broadband links. AudioCodes has developed a proprietary algorithm to manage the depth of the jitter buffering, maintaining a smooth stream of speech without unnecessary latency.
2. Echo Cancellation — starting with standard G.168 echo algorithms, AudioCodes has enhanced its technology with detection and acquisition algorithms, minimizing or eliminating annoying initial echo conditions
3. Packet Loss Concealment — packets get lost — it's a fact of real life — and AudioCodes has developed a number of algorithms to smooth the speech over the holes left by any missing packets.

How is voice quality tested?

Voice quality is tested on a range of performance attributes. The core of the testing is Listening Speech Quality Scoring using Mean Opinion Scoring (MOS). Modern MOS scoring is performed using a set of algorithms to measure what a bank of humans used to perform, scoring the quality of speech from 1 to 5. To perform this testing, gateways or other devices are put on a test bench that sends a range of pre-recorded human speech clips into the system; then the resulting output speech is analyzed, comparing it against the original. The tests are run to test a number of voice criteria and in a number of degraded network conditions.

What testing has AudioCodes done recently?

AudioCodes participated in the 3rd Annual European Telecommunications Standards Institute (ETSI) Speech Quality Test Event held in the UK and US. This year's ETSI testing pitted 10 different vendors against each other, testing the performance of supplied test gateways.

AudioCodes submitted a Mediant™ 2000 digital gateway for the testing. The Mediant 2000 shares core enabling technology with a wide range of AudioCodes gateway and media server platforms, testing the core of a large number of AudioCodes products.

The results of the testing are shown by a color-coded "Gateway Pie" chart, with the results of the AudioCodes Mediant 2000 shown below. Each segment of the pie represents one battery of tests. The size of the pie slice represents how well AudioCodes Mediant 2000 performed in each of the battery of tests. The color of the pie slices indicates whether the results were below standard (red), met the standard (yellow) or exceeded the standard (green). As you can see, there are no test results below standard, and a number of tests exceeded the standard significantly.

How did other vendors do in the testing?

ETSI performs their testing anonymously, releasing all the results to each vendor, but without indicating the identity of the competing vendors. Each vendor is then told which result is theirs and therefore the individual vendor can decide whether to publish their own results independently.

The results of all of the vendors are shown in the following set of "Gateway Pie" diagrams:

Summary:

AudioCodes has worked long and hard to distinguish itself with excellent voice quality and with the ETSI test results. After we released our results officially, we can now confirm what customers and colleagues have been telling us for some time. To quote from AudioCodes' press release of January 24, 2005:

"Voice quality is essential for VoIP to continue expanding and being deployed in the most demanding networks. Achieving the highest levels of voice quality requires technical expertise, commitment to quality, and also a critical mass of field deployments in many diverse conditions, networks and regions," said Jeremy Duke, President and CEO of Synergy Research. "In the ETSI test, AudioCodes proved it had the skill, quality, commitment and VoIP field-proven experience to achieve the leading voice quality offering. AudioCodes customers and the industry will benefit from this achievement."