Routing Wavelength And Timeslot Assignment Algorithm In WDM-TDM Optical Networks

Wavelength division multiplexing (WDM) technology tends to be the most promising candidate for next generation backbone networks for its high capacity and low cost. Low-rate session requests occupy the whole capacity of a wavelength in WDM optical networks, thus leading to a huge waste of resources. In order to fully exploit the bandwidth of wavelengths, time division multiplexing (TDM) is implemented on top of WDM optical networks to achieve WDM-TDM optical networks. By a TDM manner, wavelength channel is partitioned into multiple timeslot sub-channels and several session requests can share the bandwidth of a wavelength. Routing, wavelength and timeslot assignment (RWTA) problem is a key issue in WDM-TDM optical networks. Therefore, we will concentrate on solving the RWTA issue in this thesis.Firstly, topology aggregation in hierarchical multi-domain WDM-TDM optical networks is studied. With the idea that wavelength parameter takes precedence over timeslots parameter, a topology aggregation scheme called+Star is proposed.+Star scheme adopts aggregated star topology with bypasses and comprehensively considers the information of multiple paths between each border nodes pair. Simulation results show that+Star scheme obtains a better tradeoff between information reduction and information accuracy.Secondly, the RWTA issue in intra-domain WDM-TDM optical networks is researched. With the idea that assigned timeslots for a session request can be distributed on multiple different wavelengths, a dynamic RWTA scheme called MUMD algorithm and an adaptive RWTA scheme called LLR-MWLB algorithm are proposed. Compared to simulation performances of conventional RWTA schemes, MUMD and LLR-MWLB can effectively decrease the blocking probability and LLR-MWLB performs much better in blocking probability. In addition, simulation results show that routing policy have a greater impact on RWTA scheme than wavelength and timeslot assignment policy.Thirdly, we focus on the RWTA issue in inter-domain WDM-TDM optical networks. Based on the hierarchical PCE framework, four different RWTA algorithms are proposed. The simulation results of the four algorithms indicate that the RWTA algorithm called FM-FA which combines full-mesh (FM) topology aggregation scheme and firstfit resource assignment (FA) scheme achieves best performance. In addition, results show that performance of full-mesh is a litter bit better than+Star scheme. This validates that+Star scheme improves the information inaccuracy.Finally, a MATLAB-based network planning software named RwtaWDM is designed for WDM-TDM optical networks. RwtaWDM provides a simulation tool for topology designing, traffic model analysis and solving RWTA issue.