Abstract
Previously, an optical code-division multiplexing (OCDM)-based
network architecture was proposed to improve the wavelength utilization and
to provide finer bandwidth granularities to users. By this technology, different
channels using distinct optical codes (OCs) can be multiplexed onto the same
wavelength, in which an OC is considered as the basic unit in lightpath provisioning.
In the ideal case, multiaccess interference (MAI) inherent to the OCDM technology
is assumed to be removed completely at intermediate nodes and cannot be propagated
or accumulated along the lightpath. However, since no optical–electrical
(O/E) or electrical–optical (E/O) conversion is allowed in transparent
OCDM-based optical networks, the MAI cannot be removed completely at intermediate
nodes with current all-optical regeneration techniques. As a result, the residual
MAI may be propagated and accumulated along the lightpath and affect other
active lightpaths carried by the same wavelength in the network. The affected
active lightpaths may build unintended cycles along which the MAI is accumulated.
Furthermore, this MAI keeps increasing when the lightpaths traversed by the
cycle are active, which deteriorates the lightpath signal quality. Since this
deterioration may eventually result in unacceptable signal quality and service
disruption, the phenomenon caused by the MAI is termed as cycle attack in
this paper. The explanations of the MAI propagation mechanism and the cycle
attack problem are given. A depth-first search (DFS)-based algorithm
is proposed to diagnose such cycle attacks under dynamic traffic conditions.
The numerical results show that our DFS-based cycle attack diagnostic algorithm
enables one to detect cycle attacks effectively, and the two-way resource
reservation method associated with heuristic wavelength assignment is shown
to mitigate the blocking performance degradation due to cycle attacks greatly
with some proper wavelength and OC configuration.
© 2008 IEEE
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