Adaptive Hybrid Call Admission Control Policy for UMTS with Underlying Tunnel-WLANs Heterogeneous Networks

In this paper we evaluate the handoff performance of an UMTS network with underlying tunnel-WLANs at the cell periphery while developing an adaptive QoS oriented CAC function, proposed to limit the occurrence of hard IEEE 802.11 WLAN-UMTS handovers to mobiles using real time applications. The proposed protocol is hybrid and based on the service class differentiation, the location in the heterogeneous infrastructure and a vertical handoff decision function as well. The results show that our policy achieves significant performance and gains. It maximizes the utilization of the resources available at the WLAN cells, and meets as much as possible the QoS requirement of higher priority users.