AdaptiveScan: The Fast Layer-2 Handoff for WLAN

Recently, handoff is a critical issue for stations in IEEE 802.11-based wireless networks. In order to provide VoIP (Voice over IP) and real-time streaming applications for stations, handoff mechanism must be provided for reducing latency and seamless communication. However, the IEEE802.11 standards handoff is not appropriate to supply their QoS, because it is based on a full-scanning approach. Full-scanning spends too much time searching Access Point (AP). Therefore, the various pre-scan handoff protocols such as Sync Scan and Deuce Scan have been proposed. They perform scanning to find nearby APs before station is out of contact with AP, but they have much overhead for pre-scanning. Our handoff mechanism reduces the delay and overhead associated with link layer handoff by periodically scanning the channel groups. We prove that our per-scanning mechanism supports a faster handoff and has a lower overhead compared to the conventional schemes.