QoS based vertical handoff method between UMTS systems and wireless LAN networks

Future mobile telecom systems will most probably consist of various radio access networks to utilize various merits. A typical scenario of these network integrations is an interworking between UMTS networks and WLANs. The UMTS network is one of most prevalent networks that can cover wide areas, and wireless LAN (WLAN) is a good and cheap solution for local high speed data networks. Thus, the integration of these two networks enables users to be satisfied with an enhanced service coverage and quality. But, the different characteristics of these integrated networks, may degrade the service quality during the change of access networks, so called handoffs. To minimize service quality degradations, such as longer handoff delay, more packet losses, decreased throughput and network disconnection, we propose a QoS based vertical handoff scheme for UMTS and WLAN integrated networks. The main points of our proposed scheme are target cell searching through the connected access network and QoS based handoff. Simulation results show that our proposed scheme gives an increased QoS support during vertical handoffs.