An Empirical Measurements-based Analysis of Public WLAN Handoff Operations

Recently, IEEE 802.11 wireless LAN (WLAN) has emerged as a widely accepted technology for broadband wireless networking. A WLAN handoff operation, which occurs when a wireless station (STA) changes its association from one access point (AP) to another, has not been well understood so far since the mobility has not been a major concern for typical WLAN environments. However, the mobility within WLAN is becoming more and more important as the portable WLAN devices, e.g., voice over WLAN (VoWLAN) devices, emerge today. In this paper, we introduce an empirical approach to evaluate the 802.11 handoff process in a public WLAN service network, i.e., KT (Korea Telecom) NESPOT. We analyze the handoff delay by characterizing individual delay components in terms of protocol-oriented delays and network configuration-dependent ones. From the analysis, we identify that the user authentication-related procedure, especially, with delay terms not rooted in the employed protocols, could become a major delay in a public service WLAN, and hence should be reduced in order to achieve a faster handoff