Providing interoperability in heterogeneous environments towards 4G

Constant development of wireless and mobile networks and their capabilities enlarges the plethora of possible user services. It opens potentials for the operators to increase their service portfolio and for the users to experience context-rich and personalized services. In this manner, the interoperability between different wireless networks and the enabling of seamless vertical handovers (VHOs) become crucial cornerstones in the development towards a fully integrated 4G all-IP network architecture. This paper explores the development towards 4G exploring the benefits of the interoperability issues in heterogeneous networks and elaborating on the emerging IEEE 802.21 standard.