earticle

영어

Ubiquitous networks allow the co-existence of different wireless technologies (3GPP and non-3GPP) such as GSM (Global System for Mobile Communication), Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE). One of the challenging issues in Next Generation Wireless Systems (NGWS) is seamless Vertical Handover (VHO) during Mobile User (MU) mobility between these technologies therefore, the telecommunication operators will be required to develop a strategy for interoperability of these different types of existing networks to get the best connection anywhere anytime. In this survey, we overview two mechanisms which were proposed independently by IEEE and 3GPP, namely; Media Independent Handover (MIH) and Access Network Discovery and Selection Function (ANDSF), respectively that enable seamless VHO between the different types of technologies (3GPP and non-3GPP). We survey the VHO approaches proposed in the literature and classify them into three main categories based on these mechanisms for which we present their objectives, issues and evaluate their complexity of implementation. Finally, a conclusion about who will lead RATs through VHO is given.