OmniVoice: A Mobile Voice Solution for Small-scale Enterprises

We consider the problem of providing mobility support for Voic-eover-IP (VoIP) traffic in small-scale enterprises. There is considerable interest in providing on-the-go support for VoIP through the use of WiFi-enabled smart phones. However, existing solutions either do not support client mobility or require client modifications, making them difficult to deploy in practice. In this paper, we present OmniVoice, an 802.11 compliant solution that supports mobility for VoIP traffic without any client modifications. To effectively support such traffic, OmniVoice eliminates client handoff delays and manages interference from nonVoIP background traffic. It achieves this by using (a) a singlechannel WLAN design and (b) a lightweight central controller for scheduling non-interfering AP-to-client transmissions and dynamically associating clients. The controller minimizes interference with the help of an interference map that models potential exposed and hidden terminal conflicts in the WLAN, while allowing for the serialization of transmissions that would otherwise compete for medium access. We have implemented and extensively evaluated OmniVoice on a 40 node wireless testbed. OmniVoice meets the QoS requirements for VoIP in all operating scenarios and is unaffected by interference from non-VoIP traffic. In particular, OmniVoice provides 100% greater throughput and 130% greater uninterrupted connectivity time to mobile VoIP users as compared to an off-the-shelf 802.11 solution.