One of the goals of next generation wireless networks (NGWNs) refers to the ability of supporting heterogeneous wireless access technologies. The objective is to provide a diverse range of seamlessly provide high-data rate multimedia services across different wireless networks. To achieve this, we must rely on seamless vertical handoff techniques. In this paper, we propose a distributed Simple Additive Weighting (SAW)-based vertical handoff mechanism. Our main goal is to reduce the processing overhead in the mobile terminal by delegating the calculation of handoff metrics for network selection to the Visiting Networks i.e. WiFi.