An Accelerated IEEE 802.11 Handoff Process Based on the Dynamic Cluster Chain Method

The latency of the IEEE 802.11 handoff process in wireless local area network (WLAN) is much higher than 50 ms. Since the bearable maximum delay is 50 ms in multimedia applications, e.g., voice over IP (VOIP), such large handoff gap may bring up excessive jitter. Therefore, many researches make much effort about how to fast handoff. In this paper, we propose an accelerated handoff mechanism in which three methods are involved: (1) dynamic cluster chain, (2) PMKSA caching, and (3) fast reassociation with the pairwise transient key security association (PTKSA) establishment. Access points (APs) are arranged as a cluster for each client station (STA). APs that are cluster members can cache PMKSA of STA in advance to reduce the extensible authentication protocol - transport Layer Security (EAP-TLS) authentication delay. The dynamic cluster chain, which is arranged by a dynamic cluster selection and transition method, is proposed to assure that STA stays within a cluster. Furthermore, the fast reassociation with the PTSA establishment process incorporates four-way handshake into the IEEE 802.11 reassociation process to further accelerate handoff process.