To provide seamless internet connectivity anywhere at any time to the mobile users, there is a strong demand for the integration of wireless access networks for all-IP based Next Generation Networks (NGNs). To support heterogeneous networking environment, a dual mode user terminal is required to support all access networks which are gathered to build the integrated unified network. Several research proposals build their integrated network on tight coupling mechanism and the treatment of the handover latency was taken as the prime factor. However, because of the flexibility and independence of deployment a loose coupling architecture has been preferred in this research effort. Moreover, this paper focuses on the design and evaluation of our Dual Mode Mobile Terminal (DMMT). The DMMT operates under the coverage of UMTS and WLAN radio access networks. The DMMT contains a software layer called Convergence Layer (CL) that provides the intelligence to switch the ongoing sessions between the UMTS and WLAN networks. The simulation results demonstrate that the straightforwardness of the proposed DMMT when using with a loosely coupled integrated network leads to the performance enhancements. Enhanced performance of data services such as low packet delay variation and download response time, high received traffic and downloaded objects make it an optimal choice for the NGN. © EuroJournals Publishing, Inc. 2012.