UCAM-CL-TR-656 - Technical Report Number 656 Computer...

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Unformatted text preview: Technical Report Number 656 Computer Laboratory UCAM-CL-TR-656 ISSN 1476-2986 Seamless mobility in 4G systems Pablo Vidales November 2005 15 JJ Thomson Avenue Cambridge CB3 0FD United Kingdom phone +44 1223 763500 http://www.cl.cam.ac.uk/ c circlecopyrt 2005 Pablo Vidales This technical report is based on a dissertation submitted May 2005 by the author for the degree of Doctor of Philosophy to the University of Cambridge, Girton College. Technical reports published by the University of Cambridge Computer Laboratory are freely available via the Internet: http://www.cl.cam.ac.uk/TechReports/ ISSN 1476-2986 Abstract 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 demand- ing 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 min- imise connection disruptions and support transparent mobility in future communication systems. Firstly, I show that repercussions on the link can be minimised by using the appro- priate architecture. Recently, it has been considered necessary to integrate commercially- available wireless networks into a universal access platform, also known as the fourth generation (4G) communication system. I present the design and deployment of an ex- perimental testbed that implements this 4G model, enabling roaming between the most popular wireless and wired technologies. In addition, the testbed is used to evaluate Mo- bile 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 implemen- tation 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. 4...
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UCAM-CL-TR-656 - Technical Report Number 656 Computer...

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