Over the past decade there is an explosive and parallel growth of the Internet and the mobile telephone services. Internet gives data communication benefits to the masses with email, E- Commerce and the Web, whereas mobile services provide "follow-me-anywhere/always on" telephony. Now, the two worlds (WLAN and 3G) are converging offering benefits of interactive multimedia services coupled to the flexibility and mobility of the wireless. The integration of different technologies with different capabilities and functionalities is an extremely complex task and involves issues at all the layers of the protocol stack. TCP is a major protocol among wireless access terminals supporting Web browsing and e-mail checking. Next Generation Wireless Systems (NGWS) integrate existing wireless networks such as wireless local area networks (WLANs), third generation (3G) cellular networks and satellite networks to realize a unified wireless communication system that has the best features of the individual networks to provide ubiquitous "always best connection" to mobile users.