Eliminating handoff latencies in 802.11 WLANs using multiple radios

Abstract

Deployment of Voice-over IP (VoIP) and other real-time streaming applications have been somewhat limited in WLANs today, partially because of the high handoff latencies experienced by mobile users.Our goal in this work is to virtually eliminate this latency by exploiting the potential of multiple radios in WLAN devices and handsets.Our proposed approach, called MultiScan, is implemented entirely on the client-side.Unlike other prior work, MultiScan requires no changes in the Access Points (APs), nor does it require a priori knowledge of wireless network topology.Instead, Mul-tiScan relies on using its (potentially idle) second wireless interface to opportunistically scan and pre-associate with alternate APs and eventually seamlessly handoff ongoing connections.In this paper, we first describe our implementation of MultiScan, and then present detailed evaluations of its effect on handoff latency and evaluate performance gains for MultiScan-enhanced wireless clients running Skype, a popular commercial VoIP application.