A Simple Client Software Upgrade Enables Fast Handoff in IEEE 802.11 Wireless Networks

Handoff procedure in IEEE 802.11 wireless networks must be accomplished with as little interruption as possible to maintain the required quality of service (QoS). We have developed a fast handoff scheme, called AuthScan, to reduce the time-consuming channel scanning latency. AuthScan comprises two steps: First, a client caches its handoff history with beacon information. Second, when in need of handoff, a client transmits Authentication Request frames to the selected Access Points (APs) from the cache instead of broadcasting Probe Request frames like in active scan to discover the next AP. Our proposed method does not require any support from the infrastructure network and improve the efficiency of channel scanning. Furthermore, AuthScan requires neither hardware upgrades to the client, nor any modification to currently deployed APs. This paper presents the theoretical handoff latency of AuthScan, the effectiveness of our system through experiments, and the details of our demonstration.