Quality of Service for Voice on the Interop Show Floor

Published: May 3, 2006 - 9:17pm

A month ago, I was staging the Interop Labs, with a particular personal focus on VoIP on 802.11. A month ago, I promised to investigate what improvement Wi-Fi Multimedia (WMM) prioritization makes to voice quality. The Interop show floor is a terrible radio environment. From the Interop Labs booth, I can see between 40 and 70 access points. In this environment, WMM makes a huge difference.

We’re running the Interop Labs on Asterisk. To show off the difference in voice quality, I configured Asterisk to record the incoming voice stream from the 802.11 phone. You can listen to the results, and see what a difference WMM makes. Both recordings were made just before 2 pm today, when our corner of the show floor was fairly busy.

So, without further ado, here are the three recordings:

  • Introductory remarks. Before the show opened, I recorded a 5-minute introduction to the technology and the challenges we hoped to investigate. This recording was made from a wired phone about ten minutes before the expo floor opened.
  • Non-prioritized voice. This recording is a bit over one minute long, and was made between a phone and an access point that don’t support WMM. You can hear the effects of the heavy background traffic in the frequent dropouts.
  • WMM-prioritized voice. In the final 2-minute long recording, the voice is prioritized with WMM between the Unex WP2 phone and Trapeze wireless infrastructure. (This is one of the first, if not the first, public interoperable WMM demonstration.) There is only one dropout.

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