Satellite-based communications networks can provide personal communications services to markets that are unable to be serviced by terrestrial wireless networks, such as maritime, aviation, military, developing countries and remote industry. Traditional Geostationary Earth Orbit (GEO) satellite communications suffer from high transmit power requirements and long delays. In comparison, Low Earth Orbit (LEO) satellite communications do not suffer these problems, and therefore promise to provide high-quality communications services to small handheld terminals. The convergence of traditional voice, data, fixed, and mobile communications networks, has prompted the extension of common terrestrial networking protocols into terrestrial wireless and satellite networks. The research presented in this thesis focuses on the Asynchronous Transfer Mode (ATM) extensions required to support the frequent satellite handovers that occur in LEO satellite networks. / During the late 1990s, the standards organisation known as the ATM Forum drafted a Wireless ATM (WATM) specification, which included the handover procedures for use in terrestrial WATM networks. It is advantageous to broaden the use of the terrestrial handover procedures to handover scenarios in a LEO satellite network, based on the Iridium constellation, and specifically focuses on the Quality of Service (QoS) provided during handover. / The first contribution of this thesis (Chapter 4) is the identification of a number of performance deficiencies within the ATM forum handover procedures when used in a typical LEO satellite network. The performance deficiencies were identified through analysis of the handover signalling and functionality used in the handover procedure, and were quantified through simulation of the handover procedure (Chapter 7) using the OPNET Modeler discrete event simulation tool. The performance deficiencies result in significant and unacceptable ATM cell loss and increases in ATM cell delays, which have the potential to cause a significant user perceived interruption in communications during handover. / The primary cause of poor performance in the ATM Forum handover procedure is the lack of ATM functionality to specifically control the handover of ATM cells from the existing ATM connection to the new ATM connection. The second contribution (Chapter 5) is the specification of novel ATM-attuned signalling and functionality to improve this aspect of the handover. The new functionality allows an incremental handover of ATM cells to be performed which, in combination with the new signalling messages to support this process, eliminates the potential for ATM cell loss and minimises the increases in ATM cell delay. / The third contribution of this thesis (Chapter 6) is the specification of two new handover procedures, which exploit the novel ATM signalling and functionality described above, to provide a lossless low-delay handover in a LEO satellite network. / The fourth and final contribution (Chapter 7) is the simulation and performance analysis of the ATM Forum handover procedure in a LEO satellite network based on the Iridium constellation. As far as I am aware, there are no other published attempts of its kind, thus making it a unique contribution amongst the literature. Iridium is currently the most sophisticated LEO satellite network in use today, and although it is a narrowband system, the constellation characteristics are suitable for use in a future broadband system. The OPNET Modeler discrete event simulation tool was used to create a satellite ATM simulation model, implementing the ATM Forum handover procedure, and the two new handover procedures specified in Chapter 6. Handover performance was methodically simulated using a comprehensive set of handover scenarios (i.e. handover geometries), ranging from single-user single-connection scenarios to scenarios involving hundreds of users and connections. The handover performance was analysed with respect to the ATM Cell Loss Ratio (CLR) and Cell Delay Variation (CDV) parameters, which are the primary indicators of handover performance, and with respect to the handover latency, which is a secondary indicator of performance. The performance of the ATM Forum handover procedure was shown to severely fail both the recommended ATM and WATM performance objectives in the majority of handover scenarios, rendering it unsuitable for use in a LEO satellite ATM network. Conversely, the new handover procedures suffer no ATM cell loss, and in the vast majority of handover scenarios minimise the increases in ATM cell delay. Hence, the new handover procedures are ideally suited for use in a future broadband LEO satellite ATM network. / Thesis (PhDTelecommunications)--University of South Australia, 2004.
| Identifer | oai:union.ndltd.org:ADTP/267429 |
| Creators | Grosser, Paul Matthew. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | copyright under review |
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