Challenges of the always-best-connected enablers for user equipment in Evolved Packet System

Mobile Internet has rapidly evolved in the past years with an ever increasing number of novel technologies and services with a variety of access technologies. Indeed, today´s mobile devices often support multiple communication technologies for accessing Internet services. However, they all do not tap the full potential of these capabilities, as users often have to manually select each network, and only one network is used at a time. The concept of Always Best Connected (ABC) allows a person to connect applications using the devices and access technologies that best suit to his or her needs, thereby combining the features of access technologies to provide an enhanced user experience for future Internet. One of the key features for ABC in a heterogeneous network environment is the ability to make vertical handovers. These handovers are ones where the existing connection is changed from one technology to another. This handover has been considered to be complex and to generate a number of requirements.Over the resent years there have been techniques and standards to overcome the difficulties with vertical handovers. In this research the user equipment requirements of the most significant standards are examined and specification popularity in academic world and commercially is discussed. In addition, the performance of vertical handover with Android-based implementation is examined in real-life heterogeneous network environment. The presented standards are: Voice Call Continuity based on IP Multimedia Subsystem, Unlicensed Mobile Access, Media Independent Handover and The Third Generation Partnership Project Evolved Packet System. The research will show that existing mobile platforms such as Android environment is lacking some of the key requirements for vertical handover and current implementations cannot achieve seamless mobility by means that are currently defined by specifications.