Multi-Criteria Call Admission Control in IEEE 802.11 WLAN for Multi-Criteria Call Admission Control in IEEE 802.11 WLAN for Distributed Access Point Selection
陳建安 · 2004
Wireless local area networks (WLANs) are the predominant option for broadband wireless access network, and multiple access points (APs) will be much more available for wireless stations (WSTAs). Call admission control (CAC) on AP selection problem over 802.11 WLAN becomes a critical issue. In the existing architecture, Strongest-Signal-First (SSF) is the default AP selection mechanism in 802.11 WLAN which uses the single criterion, received signal strength indicator (RSSI), to select AP. However, this method suffers bandwidth deficiency and unbalanced load among APs due to the user load is often unevenly distributed, thus degrading the throughput in WLAN. We propose a semi-Markov model to predicate the system throughput, which is validated through simulation results. Two distributed multi-criteria AP selection algorithms are proposed based on this analytical model. The criteria considered in order are RSSI, required quality of service (QoS) level, estimated effective bandwidth (EEB), and AP-WSTA distance. The system performance is compared the proposed algorithms with the traditional algorithm SSF in terms of the balance index for AP and the average system throughput. The simulation results show that the proposed algorithms can improve the overall network throughput and achieve better load balancing among APs, especially when the users are distributed unevenly.