Transport Layer Handover for Heterogenous Communication Systems

In the last few years we experienced a tremendous increase of available wireless network technologies and coverage. Most up-to-date devices, such as mobile phones, PDAs and laptops are equipped with at least one interface to connect to wireless networks like IEEE 802.11, Wimax, GPRS or Bluetooth.
Inter-technology seamless handovers enable mobile devices to switch to a network of another technology while preserving existing upper layer connections. A node moving in an environment of heterogeneous wireless infrastructure will continuously enter and leave the coverage area of different network technologies. The ability to perform seamless handovers therefore does not only improve connectivity, it also allows the user to choose a technology which is most appropriate to his requirements.
An interesting approach is to perform seamless handovers at the transport layer. This way, it is possible not only to switch between different networks, but also to use several communication systems at the same time for a single data transmission. Another advantage is that each application can use the communication path that fits best to its current requirements.
For realizing transport layer handovers, the transport protocol has to support functionalities like multihoming and dynamic reconfiguration. Unfortunately, today’s protocols like TCP and UDP do not support these features. However, newer transport protocols such as SCTP are able to handle several transmission paths and might provide a promising basis for integrating dynamic transport layer handovers.

Task Description

The goal of this thesis is to investigate the feasibility of transport layer handovers in heterogeneous mobile networks. The first assignment is to analyze current approaches for inter-system handovers and to determine a suitable transport protocol as basis for the integration of the handover mechanisms. Afterwards, these mechanisms have to be developed and implemented, in order to trigger handovers from the user space. Another assignment is to investigate the interaction of SIP-based location management with transport layer handovers. The performance of the implementation during handovers has to be analyzed under emulated conditions of packet loss and delay spikes, including influences on congestion control.