IEEE 802.21 based seamless mobility in UMTS-WLAN heterogeneous network

The future generation of heterogeneous wireless network is expected to provide multimedia, multi class services any time anywhere with seamless mobility. In such environment, vertical handover (VHO) plays an important and challenging role to guarantee seamless mobility. Specially, in case when mobile nodes with multiple interfaces wants to be Always Best Connected (ABC), a smooth and seamless VHO is a key feature to accomplish requirement of users. Therefore, a well defined standard is required in order to facilitate seamless handover between such heterogeneous wireless networks. IEEE defines a standard IEEE 802.21 media independent handover (MIH), to coordinate between different layers of heterogeneous network and to provide optimize and seamless vertical handover. In this paper, we present comprehensive study of VHO based on 802.21 standards along with issues and challenges for achieving seamless mobility between UMTS and WLAN. Also, simulation of UMTS-WLAN integrated network performed using IEEE 802.21 standard to realize seamless vertical handover. The simulation is carried out using simulator ns-2.29 with NIST add on module.