Recently, a number of wireless communication technologies are migrating toward heterogeneous overlay networks. The integration of Mobile WIMAX and WLAN seems to be a promising approach due to their homogeneous nature and complementary characteristics. In this paper the investigation of several important issues for the interworking of Mobile WIMAX and WLAN networks are discussed by addressing a tightly coupled interworking architecture. A seamless and proactive vertical handoff scheme is

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... based on the architecture with aims to provide always the best quality of service (QOS) for users. In tightly coupled architecture WLAN works as a radio access network of cellular system, and loosely coupled where different networks which are independently deployed but integrated at network layer. Comparably, a more seamless VHO can be expected in the tightly coupled networks, where the handoff execution follows the protocols of cellular network conditions. A very simple evaluation algorithm is developed to estimate the conditions of both WIMAX and WLAN networks in terms of available bandwidth and packet delay. This scheme can keep stations always being best connected.