The Wireless network, applications and devices have been dramatic changes in throughout the last decade. Several issues related to the heterogeneity of such wireless environment were handled, namely the mobility management, resource allocation, security, quality of service and transparent handover. In fact, to meet the increasing demands of mobile users, the next generation wireless systems form a relay of cooperatives of heterogeneous wireless technology that allows users to be connected anytime and anywhere. Wireless networks can integrate various heterogeneous radio access technologies as GSM, UMTS, WLAN, Wimax etc. . . The main promise of interconnecting these heterogeneous networks is to provide high performance in achieving a high data rate and support real time applications. In this Paper performance analysis of UMTS-WLAN integration network is performed and the vertical handover latency delay was improved by using the Network Simulator NS2 to model and simulate different scenarios by focusing on real-time traffic such as VoIP.

UMTS IEEE 802. 11 Mobility management