Continuous striving in the development of wireless mobile networks maximizes the possibility of user services and provides experience context rich and personalized services. In this way, for the development towards fully integrated 4G‐all IP network architecture, the interoperability between future generation wireless networks and seamless vertical handover (VHO) has become a crucially important issue. The proposed work is mainly focusing on exploring interoperability issues in heterogeneous networks considering development towards 4G and emphasizing on emerging IEEE 802.21 standard. Further, Simulation results were presented to showcase vertical handover (VHO) performance using IEEE 802.21. Simulation Analysis is done using Network Simulator (NS-2) with seamless mobility package extension.