Title of Thesis
UTILIZING ATM CONCEPTS IN MOBILE SATELLITE PERSONAL COMMUNICATION NETWORKS WITH INTERSATELLITE LINKS

Summary:
Low Earth and Medium Earth Orbit (LEO/MEO) satellite constellations are foreseen as appropriate alternatives to the geostationary satellite systems for providing global personal communications services (PCS). Compared to geostationary satellites, these constellations offer a significantly smaller round trip delay between earth and space segments. Furthermore, the use of inter-satellite links (ISLs) has been identified as a means to provide global connectivity in space, thereby, enhancing system autonomy and flexibility, and has been retained in the design of systems like Iridium and Teledesic. From a network point of view, a major benefit of a developed ISL subnetwork in space lies in the possibility to transport long distance traffic over reliable and high capacity connections, thus forming a good base for ATM (asynchronous transfer mode) operation. In this project, ATM concepts and routing algorithms for future mobile satellite based personal communication networks including ISLs will be examined and new handoff and routing schemes in order to achieve high quality of service will be proposed.

With the development of the 3G and 4G wireless networks, ATM is regarded as one of the potential promising candidates for providing QoS guaranteed broadband telecommunication services. The concept of WATM over LEO/MEO satellite networks is also strongly suggested recently because of several particular features of a LEO/MEO satellite network such as global coverage and flexible remote accessibility etc.  Handoff, as one of the most trouble issues in a wireless network system, is raised in such WATM based LEO/MEO satellite networks. How to keep the happening frequency of handoff as low as possible, and how to alleviate the by-effects of handoff events on the whole network are very important in providing QoS promised service. Here, based on the characters of both WATM and LEO/MEO satellite networks, we try to deal with the handoff issues from routing point of view because a good routing scheme is always high related to the happening of handoff events.

Apart from the well known Dijkastra and Bellman-ford routing scheme, we have introduced several feasible schemes, e.g. Modified Dijkstra Shortest Path (MDSP) Algorithm and Rerouting Nodes Handoff (RNH) Algorithm which are based on the network traffic detection, moving prediction and path reservation schemes. In order to best utilize the network resource and provide better network QoS service, we also introduce a brand new idea, dynamic channel allocation scheme (DCAS), which is based on the proposal of more reasonably allocating the network resource, to increase the network performance.

Overlay of IP over WATM is a very hot topic at the moment. However, routing and handoff issues are still very difficult with it and how to improve the efficiency and performance of IP network from the routing point of view still needs lots of research here. One of these examples is delay jitter issue in IP network [4]. Some feasible schemes are being proposed to deal with this topic.