VoIP Handoff Method Complemented with 802.11 BSS Network Table to Effectively Reduce the Handoff Delay on 802.11 Networks

In this paper, we propose a voice over IP (VoIP) handoff method on 802.11 networks to effectively reduce the handoff delay mainly caused by 802.1x authentication and IP acquisition time. The proposed method uses a basic service set (BSS) network information table which includes network layer (L3) information of APs in an extended service set (ESS) network. The table reduces the handoff delay by having 802.11i pre-authentication signaling made to only neighborhood APs and jointly using link layer (L2) events from the MAC driver to detect L3 movement. The table is created and renewed by SIP registration signaling that uses an extension header defined in this paper. Our experiment shows that L2 handoff takes at most 802.11i 4-way handshake delay and L3 handoff adds only DHCP signaling time to the L2 handoff delay.