Contradicting reports from two test equipment vendors on the quality of VoIP calls can be explained by the methods being used to conduct the tests.
In the first instance, Brix Networks caused a mild stir in VoIP circles when it issued a press release titled ‘Internet Phone Quality Drops Significantly and Steadily over Last 18 Months’. In it the company contended that one in five broadband Internet calls proved unacceptable on the Mean Opinion Score (MOS) scale, a subjective measurement of call quality long established in the telephony industry.
It turns out that Brix were apparently measuring VoIP calls made PC to PC – typically Skype type calls.
Meanwhile an announcement from test equipment vendor Minacom points out that “PC-PC VoIP quality is subject to many diverse impairments, including firewall settings, computer performance, antivirus installations, high-compression codecs, and Internet bandwidth shared with gaming, file downloads, web surfing, and email.”
By contrast, VoIP offered by service providers is switched using telecom grade equipment, uses lower-compression codecs, and is prioritised over regular Internet traffic using sophisticated, standards-based multimedia telephone adapters, maintained and monitored by the operator. It is over such managed broadband and cable lines—as well as the PSTN—that Minacom’s testing is run.
In any case, the latest Minacom results indicate—contrary to the Brix findings—only 1 in 10 VoIP calls worldwide—1 in 50 in North America—fall below the MOS acceptable threshold of 3.6, while 85 percent of VoIP calls exceeded the average MOS score for PSTN calls.
All this should be heartening for those seriously considering adopting IP-based or hybrid phone systems. Minacom’s findings certainly undercut one of the traditional barriers to VoIP adoption: the notion that VoIP call quality is not up to the telcos’ “toll” standards.