Seamless mobility in 4G systems

The proliferation of radio access technologies, wireless networking devices, and mobile services has encouraged intensive nomadic computing activity. When travelling, mobile users experience connectivity disturbances, particularly when they handoff between two access points that belong to the same wireless network and when they change from one access technology to another. Nowadays, an average mobile user might connect to many different wireless networks in the course of a day to obtain diverse services, whilst demanding transparent operation. Current protocols offer portability and transparent mobility, however, they fail to cope with huge delays caused by different link-layer characteristics when roaming between independent disparate networks. In this dissertation, I address this deficiency by introducing and evaluating practical methods and solutions that minimise connection disruptions and support transparent mobility in future communication systems. Firstly, I show that repercussions on the link can be minimised by using the appropriate architecture. Recently, it has been considered necessary to integrate commerciallyavailable wireless networks into a universal access platform, also known as the fourth generation (4G) communication system. I present the design and deployment of an experimental testbed that implements this 4G model, enabling roaming between the most popular wireless and wired technologies. In addition, the testbed is used to evaluate Mobile IPv6 performance in heterogeneous environments, and identify the weaknesses of this protocol to manage seamless roaming between different technologies. Secondly, I demonstrate that Mobile IPv6 can be optimised by modifying its current specification without altering the core functionality or adding significant overhead. My experimental results show the improvements in vertical handover latency, which varied between small time reductions and “zero” latency, for the case of soft handovers. Finally, I claim that minimising the latency is not enough to enable seamless roaming in highly-integrated and diverse networks. Therefore, I show the design and implementation of PROTON, a policy-based solution to assist nomadic users. To validate the strength of my proposal, I evaluate PROTON using the testbed, and demonstrate that it is possible to offer suitable mobility support in next generation systems, whilst handling the complexities and dynamic behaviour posed by the environment.