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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2006.12.004 Byline: Pablo Vidales (a), Carlos J. Bernardos (b), Ignacio Soto (b), David Cottingham (c), Javier Baliosian (d), Jon Crowcroft (c) Keywords: Mobile IPv6; 4G; Overlay networks; Handover optimisations Abstract: The commercial deployment of Mobile IPv6 has been hastened by the concepts of Integrated Wireless Networks and Overlay Networks, which are present in the notion of the forthcoming generation of wireless communications. Individual wireless access networks show limitations that can be overcome through the integration of different technologies into a single unified platform (i.e., 4G systems). This paper summarises practical experiments performed to evaluate the impact of inter-networking (i.e. vertical handovers) on the network and transport layers. Based on our observations, we propose and evaluate a number of inter-technology handover optimisation techniques, e.g., Router Advertisements frequency values, Binding Update simulcasting, Router Advertisements caching, and Soft Handovers. The paper concludes with the description of a policy-based mobility support middleware (PROTON) that hides 4G networking complexities from mobile users, provides informed handover-related decisions, and enables the application of different vertical handover methods and optimisations according to context. Author Affiliation: (a) Deutsche Telekom Laboratories, Ernst-Reuter-Platz 7, D-10587 Berlin, Germany (b) Universidad Carlos III de Madrid, Avda. Universidad 30, 28911 Leganes, Spain (c) Computer Laboratory, University of Cambridge, William Gates Building, 15 JJ Thomson Avenue, Cambridge CB3 0FD, UK (d) Network Management Research Centre, Ericsson R&D Ireland, Ericsson Software Campus, Athlone, Co Westmeath, Ireland Article History: Received 25 August 2005; Revised 8 September 2006; Accepted 7 December 2006 Article Note: (miscellaneous) Responsible Editor: M.M. Buddhikot

Individual wireless access networks show limitations that can be overcome through the integration of different technologies into a unified platform [i.e., fourth-generation (4G) system]. Nevertheless, the integration of heterogeneous networks poses many challenges such as adding complexity to the processes of deciding when to handoff, selecting the best network, and minimizing roaming effects using appropriate handover methods. This paper presents PROTON, a novel solution that supports decision-making processes related to roaming between heterogeneous technologies. PROTON deploys a formal policy representation model, based on finite-state transducers, that evaluates policies using information from the context to manage mobiles' behavior in a transparent manner, hiding 4G systems' complexities. We blend concepts of autonomic computing into the design of the solution and manage to improve user experience in typical 4G scenarios, while keeping transparency. [ABSTRACT FROM AUTHOR]