Abstract— This paper considers two issues arising in an integrated IEEE 802.16e/802.11 network: 1) finding a possible network, which mobile station (MSTA) can switch to, and 2) making a decision whether to execute a vertical handoff (VHO). For this purpose, we propose that 802.16e Base Stations (BSs) periodically broadcast the information about the density of 802.11 access points (APs) within their cell coverage. Based on this information, we develop a novel model, which predicts the successful scan probability during a given scan time. Using this analytical model, we devise an energy-efficient scan policy (ESP) algorithm, which enables an MSTA to decide 1) whether to attempt to discover APs in the current 802.16e cell, and 2) if so, how to set the 802.11 active scan interval considering the energy consumption. For the VHO decision, we mainly consider the impact of the service charge. Especially, a practical service fee models, i.e., flat pricing for WLAN and partially-flat prici...