Abstract | We consider the online impairment-aware routing
and wavelength assignment (IA-RWA) problem in transparent
WDM networks. To serve a new connection, the online algorithm,
in addition to finding a route and a free wavelength (a lightpath),
has to guarantee its transmission quality, which is affected by
physical-layer impairments. Due to interference effects, the establishment
of the new lightpath affects and is affected by the other
lightpaths. We present two multicost algorithms that account
for the actual current interference among lightpaths, as well as
for other physical effects, performing a cross-layer optimization
between the network and physical layers. In multicost routing,
a vector of cost parameters is assigned to each link, from which
the cost vectors of the paths are calculated. The first algorithm
utilizes cost vectors consisting of impairment-generating source
parameters, so as to be generic and applicable to different physical
settings. These parameters are combined into a scalar cost
that indirectly evaluates the quality of candidate lightpaths. The
second algorithm uses specific physical-layer models to define
noise variance-related cost parameters, so as to directly calculate
the -factor of candidate lightpaths. The algorithms find a set of
so-called nondominated paths to serve the connection in the sense
that no path is better in the set with respect to all cost parameters.
To select the lightpath, we propose various optimization functions
that correspond to different IA-RWA algorithms. The proposed
algorithms combine the strength of multicost optimization with
low execution times, making them appropriate for serving online
connections |