Modelling of Prioritised Vertical Handoff Scheme in Integrated UMTS/WLANs

The UMTS users have a relative low bandwidth requirement and arbitrary mobility feature, while the WLAN users have a high bandwidth requirement and limited mobility feature. Efficient sharing of resources between UMTS and WLANs can improve the capacity as well as quality of service (QoS) metrics. In this paper, prioritize vertical handoff scheme in integrated UMTS/WLAN network proposed. In this scheme the call residence times are modeled by general distribution to adapt the flexible mobility environments. The new originated and horizontal handoff call of UMTS users that are blocked in the UMTS-only coverage, can attempt a vertical handoff to the underlying WLANs. In the WLANs these call are given higher priority than the WLANs users call by reserving some channel for them plus they can share the rest of the channels with the WLANs users. The channel occupancy times and the blocking and dropping probabilities was derived and calculated. From analysis and numerical results, the performance of the UMTS network is improved with integration of WLANs, especially when the WLANs are in hot-spot areas.