The envisioned heterogeneous wireless systems are expected to integrate multiple access networks over a common IP platform. In such systems, since mobile users expect to achieve the Always Best Connected (ABC) experience, heterogeneous systems have to support the vertical handover of users among different access networks. On the other hand, the field of Multiple Attribute Decision Making (MADM) has proved to be a suitable tool to study the vertical handover process. This chapter presents a survey of MADM algorithms that have been proposed for vertical handover. First, the authors describe the procedures of methods such as SAW, MEW, TOPSIS, ELECTRE, and VIKOR. Then, the chapter compares them by mean of simulations and performance analysis for an heterogeneous system integrated by WLAN, UMTS, and WiMAX networks, when users conduct different applications. The chapter concludes with a summary of open issues and future research directions in the area of vertical handover.
