@inproceedings{liu_rouskas_2012, title={A fast path-based ILP formulation for offline RWA in mesh optical networks}, DOI={10.1109/glocom.2012.6503572}, abstractNote={RWA is a fundamental problem in the design and control of optical networks. We introduce the concept of symmetric RWA solutions and present a new ILP formulation to construct optimally such solutions. The formulation scales to mesh topologies representative of backbone and regional networks. Numerical results demonstrate that the new formulation achieves a decrease of up to two orders of magnitude in running time compared to existing formulations. In particular, optimal solutions for topologies up to 20 nodes can be obtained within minutes using commodity CPUs, and larger networks can be solved in reasonable time. Our approach significantly lowers the barrier to entry in fully exploring the solution space of optical network design and in investigating the sensitivity of design decisions to forecast demands via extensive “what-if” analysis. Such analysis cannot be carried out currently without large investments in computational resources and time.}, booktitle={2012 ieee global communications conference (globecom)}, author={Liu, Z. Y. and Rouskas, George}, year={2012}, pages={2990–2995} }
 @article{yetginer_liu_rouskas_2011, title={Fast Exact ILP Decompositions for Ring RWA}, volume={3}, ISSN={["1943-0639"]}, DOI={10.1364/jocn.3.000577}, abstractNote={Wavelength division multiplexing rings are now capable of supporting more than 100 wavelengths over a single fiber. Conventional link and path formulations for the routing and wavelength assignment problem are inefficient due to the inherent symmetry in wavelength assignment and the fact that the problem size increases fast with the number of wavelengths. Although a formulation based on maximal independent sets (MIS) does not have these drawbacks, it suffers from exponential growth in the number of variables with increasing network size. We develop a new ILP (integer linear program) formulation based on the key idea of partitioning the path set and representing the MIS in the original network using the independent sets calculated in each of these partitions. This exact decomposition trades off the number of variables with the number of constraints and, as a result, achieves a much better scalability in terms of network dimension. Numerical results on ring networks of various sizes demonstrate that this new ILP decomposition achieves a decrease of several orders of magnitude in running time compared to existing formulations. Our main contribution is a novel and extremely fast technique for obtaining, in a few seconds using commodity CPUs, optimal solutions to instances of maximum size SONET rings with any number of wavelengths; such instances cannot be tackled with classical formulations without vast investments in computational resources and time.}, number={7}, journal={JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING}, author={Yetginer, Emre and Liu, Zeyu and Rouskas, George N.}, year={2011}, month={Jul}, pages={577–586} }
 @inproceedings{liu_rouskas, title={Link selection algorithms for link-based ilps and applications to RWA in mesh networks}, booktitle={2013 17th International Conference on Optical Networking Design and Modeling (ONDM)}, author={Liu, Z. Y. and Rouskas, G. N.}, pages={59–64} }