Next, the fourth generation of mobile communication will have the capability to support the mobile users either they belong to any wireless network. In fourth generation integration of network technologies for better services to mobile users is done .For example, Universal Mobile Telecommunication System(UMTS) which provides a large coverage area with low bandwidth, while Wireless LAN (IEEE 802.11) provides a low coverage area with large bandwidth. So, by the combination of these two technologies,the mobile user can benefit from the best features of both technologies by roaming seamlessly and transparently between them. Switching among these different wireless technologies isknown as handover and it is a very important and burning issue.Every user wants to stay connected anywhere and anytime through whatever technology is available at the time. Providing connectivity by using integrated technologies is a difficult issue because every network has its own features and characteristics,such as data rate, geographical coverage area, latency, frequency and bandwidth.