Vergleich der Effizienz von Schutzstrategien in photonischen Transportnetzen


Christian Mauz


PhD Thesis, Technische Wissenschaften ETH Zürich, Nr. 15042, 2003, Series in Broadband Communications, Vol. 13, Hartung-Gorre Verlag Konstanz, ISBN 3-89649-848-0, pp. 159, 2003.

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The topic of this thesis is the systematical investigation of different protection schemes for photonic networks and the development of their efficient planning methods. Due to the high aggregation of large trarffic streams, protection against losses is of central importance. The direct routing of a light path results in an optical path layer (OPL). Efficient protection schemes apply directly to the OPL. As a comparison criterion between the protection schemes, the figure of the total required capacity for the network with respect to working and protection traffic is used. After a short introduction and motivation for the investigation at hand, important methods and terms for the network planning process are explained by illustrating the routing and wavelength assignment of light paths. It follows a description of the Pan-European networks which have been used for the comparison. First, protection schemes for mesh networks are considered. Such networks are based on optical cross connects (OXC) and enable the use of very flexible routing schemes. Span and path based methods for dedicated and shared protection have been investigated. For the case of dedicated protection, it is possible to find optimal solutions with simple and exact methods by the separation into sub-problems. For shared protection, a novel, unified integer linear programming (ILP) formulation has been used. For networks with wavelength conversion (virtual wavelength path, VWP), the corresponding system of equations may be solved directly. For larger networks or in the case where a light path uses the same wavelength throughout the whole network (wavelength path, WP), heuristics are required to solve the problem which reduce the complexity significantly. Corresponding approaches for shared path protection and protection with so called p-cycles are developed. Ring structures depend on simple optical add-drop multiplexers (OADM) and are simpler to realize than mesh networks from a technological point of view. On the other hand, the planning of multi-ring-networks with several interweaved rings is very complex. It is shown that an effective graph for ring-networks with dedicated protection rings (DPRing) and shared protection rings (SPRing) can be developed. For DPRing-networks, this allows to deduce an optimal ring-coverage. For SPRing-networks, the ring-identification may be formulated as an ILP-problem. For this case, a novel method for the ring-routing and -dimensioning based on the effective graph is proposed. This method has been used for the iterative ring-identification. Finally, the impact of uncertainties in the planning-process and the lack of knowledge of the exact traffic pattern on the required capacity is studied. A summary and outlook for further research work concludes the thesis.

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