Abstract
This study investigates the survivable traffic grooming problem for
elastic optical networks with flexible spectrum grid employing new transmission
technologies. In such networks, instead of following the traditional fixed
ITU-T wavelength grid, optical transponders are capable of properly tuning
their rates, and consequently their spectrum occupation, by introducing the
fine-granular spectrum unit, called a frequency
slot. The number of contiguous frequency slots allocated to an
optical path (i.e., lightpath) is adjusted to the current network flow. In
this study, we propose a novel shared protection specific to elastic networks,
namely, elastic separate-protection-at-connection (ESPAC). It not only provides
traditional backup sharing, but also offers a new opportunity of spectrum
sharing enabled by the elasticity of the transponders: 1) if the working paths
of two connections are link disjoint physically, and 2) if their backup paths
traverse two lightpaths which are adjacent on a fiber link, then the two backup
lightpaths can share spectrum. The new opportunity of spectrum sharing is
realized by using First-Fit to assign working traffic and Last-Fit to assign
backup traffic, and allowing spectrum overlap between adjacent backup wavelengths.
The elasticity of the transponder enables the expansion and contraction of
the lightpaths, thus when a single failure occurs in the network, lightpaths
carrying backup flows can be tuned to appropriate rates in such a way that
the overlap spectrum is used by only one of the adjacent lightpaths. The results
show ESPAC is very spectrum efficient in elastic network setting.
© 2012 IEEE
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