Dedicated path protection for waveband switching in WDM networks

This paper considers the problem of dedicated path-protection in a wavelength-division multiplexing (WDM) mesh network with waveband switching (WBS) functionality under shared risk link group (SRLG) constraints. Two protection schemes are proposed, namely the Protecting-waveBand-At-waveBand-Level-only (PBABL) and the Mixed-Protection-At-waveBand-and-Wavelength-Level (MPABWL). The PBABL protects each working waveband-path by a backup waveband-path. While the MPABWL protects each working waveband-path by either a backup waveband-path or multiple backup lightpaths. The performances of the two protection schemes in terms of gained revenue and cost saving are studied and compared. Integer linear programming (ILP) formulations are presented to solve the problems for each protection scheme. Numerical results of the ILPs and the experimental results of previously proposed heuristics are presented, which show that both heuristics can obtain optimum solutions. According to the results, under heavy load traffic the MPABWL scheme provides solutions with higher revenues than the PBABL scheme does. Under light load traffic, where network resources are sufficient to accommodate all the traffics, the PBABL scheme leads to less switching and transmission costs than the MPABWL scheme does.