Welcome to the Softspeak project! In this project we aim to make VoIP (Voice over IP) and WiFi (802.11) co-exist peacefully. We've developed a system that can do this using existing WiFi hardware and access points.

What's the basic problem we're addressing? By default, VoIP traffic is wasteful of WiFi airtime in the following ways. First, VoIP traffic consists of tightly spaced small packets, each of which is encumbered with large 802.11 and other headers. Second, when the channel gets busy, packets from multiple VoIP senders are increasingly likely to collide, rendering some or all of the packets indecipherable to the access point. These issues translate to a lot less bandwidth for other traffic (such as Web traffic) as well as degraded call quality. Softspeak addresses the problem by (a) aggregating many small packets into a few large packets, (b) imposing a TDMA schedule to avoid collisions. The details are in our NSDI 2009 paper.

We have implemented Softspeak on Linux for the Ralink and Madwifi WiFi chipsets and made recordings of voice traffic before and after applying Softspeak:


Softspeak: Making VoIP Play Well in Existing 802.11 Deployment [pdf] [html]
P. Verkaik, Y. Agarwal, R. Gupta, A. C. Snoeren
Proceedings of the 6th ACM/USENIX Symposium on Networked Systems Design and Implementation (NSDI), Boston, MA, April 2009.
Slides: [ppt] [pdf]

How to avoid killing the wireless internet with your phone [pdf] [ppt]
P. Verkaik, Y. Agarwal, A. C. Snoeren
Poster for Jacobs School of Engineering Research Expo, 2008.

Project members

This project is part of the Systems and Networking Wireless Research Group at UCSD.