Study On Routing And Spectrum Assignment Of Elastic Optical Networks With Sub-band Virtual Concatenation

As Internet traffic keeps on increasing, how to improve the capacity efficiency of the optical transport network has become an important research problem in order to sustain the growth of traffic growth. Orthogonal Frequency Division Multiplexing(OFDM) has recently been proposed as a transmission technique for the optical network due to its higher spectral efficiency and superior impairment tolerance over the traditional Wavelength Division Multiplexing(WDM). For the OFDM-based elastic optical networks, we have seen extensive studies on the problem of routing and spectrum assignment(RSA), of which most focus on a single route for each lightpath service. In this thesis, we look into the RSA problem for the elastic optical network considering the multi-path sub-band virtual concatenation(VCAT) technique that allows the sub-bands of a VCAT lightpath to be transmitted over different routes. We develop integer linear programing(ILP) models to optimally solve the RSA problem. We evaluate the benefit of the multi-path sub-band VCAT technique for the RSA problem through comparing with the non-VCAT case. In addition, we also evaluate the various physical layer limitations of the VCAT transmission technique, which include the required guard band between VCAT sub-bands, the maximal distance difference among the sub-band paths of a VCAT service, and the limitation of sub-band size difference of a VCAT service. In addition, considering the evolution of the optical transport network from the traditional WDM technique to the elastic technique, we also apply the VCAT technique to an optical network with the co-existence of WDM and elastic ROADM nodes that switch WDM channels and elastic super-channels, respectively. Simulation studies show that the VCAT technique is an effective approach to enhance the spectrum utilization for an elastic optical network compared to the non-VCAT technique.