| To maximize the usage of optical resources, it is important to reduce the total bandwidth requirement for communication. Orthogonal Frequency Division Multiplexing (OFDM) has recently emerged as an encouraging competitor to Wavelength Division Multiplexing (WDM), which uses fixed capacity channels. A network using OFDM-based Spectrum-sliced Elastic Optical Path (SLICE) has a higher spectrum efficiency, due to the fine granularity of subcarrier frequencies used. To minimize the utilized spectrum in SLICE networks, the routing and spectrum allocation problem (RSA) has to be efficiently solved. We have solved the RSA problem using two Integer Linear Programming (ILP) formulations. Our first formulation provides an optimal solution, based on an exhaustive search and is useful as a benchmark. Our second approach reduces the time requirement by restricting the number of paths considered for each commodity, without significantly compromising on the solution quality. We have compared our approaches with another prominent formulation proposed recently. |
