Mobility support in IP cellular networks: a multicast based approach

Today’s cellular communication networks offer seamless mobility support but are based on a homogeneous networking technology and a complex voice-oriented networking infrastructure. The Internet technology is expected to cause a paradigm shift in cellular communication networks. Mobile IP is the classical solution to support host mobility, but faces a number of disadvantages, including triangular routing and its effect on protocol overhead and end-to-end delays, router ingress filtering, and handover performance. In the dissertation a different approach is pursued that solves the general mobility problem by means of group communication (multicast). In principle, it utilizes the capability of multicast for location-independent addressing and routing, but poses a number of challenges, including the fact that not all mobility functions are offered by the multicast, as well as the open problems of the multicast as it exists in today fixed networks, and problems that arise through the usage of multicast for mobility support, such as the scalability with the number of multicast groups. A few proposals in this area have already been made with different motivations, requirements, and assumptions about the networking architecture. In this dissertation the requirements for multicast-based support of host mobility are identified, as well as mobility functions and basic protocol options elaborated. The three components create a framework for the system and protocol design of multicast-based mobility support that is termed MOMBASA (Mobility Support – A Multicast-Based Approach). The framework is used to judge existing research approaches and serves as a basis to design new schemes and modify existing ones. Four case studies are derived from the framework based on the Any-Source Multicast, the current multicast standard in the Internet, as well as alternative service models. For these case studies a set of protocols are designed that augments the multicast schemes by mobility functions. The methodology of investigation is a combined approach of measurements, simulation, and analysis. For experimental investigation the MOMBASA Software Environment is developed – a generic software platform for experimentation with multicast-based mobility support in IP-based networks. The software environment offers an abstract interface to the multicast, and hence can be used for future investigations of different classes and types of multicast. The MOMBASA Software Environment is part of the evaluation environment that allows to investigate the selected case studies in a common experimental environment under comparable conditions. The results of the dissertation show the feasibility of a mobile communication system with multicast-based mobility support providing the full spectrum of IP services. Potential problems of multicast-based mobility support (e.g. lack of a reliable transport service for multicast, and others) can be avoided. The dissertation presents results of the performance evaluation for handover. Scalability issues are addressed, in particular the signaling costs in a system with multicast-based mobility support determined. All results are compared with the reference case Mobile IP and its hierarchical variant.