Abstract
Physical impairments in optical fiber transmission necessitate the use
of regeneration at certain intermediate nodes, at least for certain lengthy
lightpaths. We design and implement impairment-aware algorithms for routing
and wavelength assignment (IA-RWA) in translucent optical networks. We focus
on the offline version of the problem, where we are given a network topology,
the number of available wavelengths and a traffic matrix. The proposed algorithm
selects the 3R regeneration sites and the number of regenerators that need
to be deployed on these sites, solving the regenerator placement problem for
the given set of requested connections. The problem can be also posed in a
slightly different setting, where a (sparse) placement of regenerators in
the network is given as input and the algorithm selects which of the available
regenerators to use, solving the regenerator assignment problem. We formulate
the problem of regenerator placement and regenerator assignment, as a virtual
topology design problem, and address it using various algorithms, ranging
from a series of integer linear programming (ILP) formulations to simple greedy
heuristic algorithms. Once the sequence of regenerators to be used by the
non-transparent connections has been determined, we transform the initial
traffic matrix by replacing non-transparent connections with a sequence of
transparent connections that terminate and begin at the specified 3R intermediate
nodes. Using the transformed matrix we then apply an IA-RWA algorithm designed
for transparent (as opposed to translucent) networks to route the traffic.
Blocked connections are re-routed using any remaining regenerator(s) in the
last phase of the algorithm.
© 2009 IEEE
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