Keynote Systems' study, based on the quality of calls made with voice over Internet Protocol and with standard phone lines, found thathas yet to reach the standards that consumers associate with traditional phone service.
The study tested calls from six providers:, Packet 8, Primus Lingo, ,Verizon Voicewing and .
Test calls between San Francisco and New York were placed from VoIP to standard telephone lines and vice versa; and between local loop VoIP to public switched telephone networks. Call quality over the "last mile" was also tested. A total of 163,000 calls were placed over five weeks in May and June, Internet performance monitor Keynote said.
The study evaluated service availability, daily outage time, average number of call attempts, dropped calls, audio delay, listening quality, audio delay consistency over time, and audio delay geographic uniformity. These factors were aggregated into reliability and audio clarity rankings, San Mateo, Calif.-based Keynote said.
Overall, Vonage ranked as the most reliable service provider, securing 80 points out of 100 points. But Keynote said it has to improve its performance in dropped calls.
AT&T's CallVantage had the best audio clarity, Keynote said, but needs to improve geographic variability on audio delay factor--a cause of call disruption. Overlapping sounds can confuse people and can result in missed information if someone is making a.
"VoIP reliability and audio clarity are important factors limiting the widespread adoption of VoIP in consumer markets," Dharmesh Thakker, senior product manager for service solutions at Keynote, said in a statement. "Consumers are unsure whether VoIP can live up to the dial-tone reliability and crystal-clear communication quality they have come to expect with traditional phone service over the years."