By synergistically capitalizing emerging communication technologies from both
the RF and the optical domains, this paper proposes a hybrid system architecture by
leveraging the emerging programmable/cognitive radio technology and free space optical
communication. We identify some key research issues to enable such a system with high
data rate, mobility and ubiquitous coverage, and heterogeneous QoS support.
In a wavelength-routed WDM optical network, having regeneration and wavelength conversion at every node is not cost-effective. However, in a nation-wide backbone network, regeneration is required for some lightpaths. With shared-mesh protection, wavelength-conversion is helpful in increasing the wavelength sharing among protection paths therefore can improve resource-utilization. In this work we study the problem of selecting wavelength-conversion and regeneration sites in such a network. We show that the wavelength converter placement problem can be formulated as an integer linear program and propose several heuristics for solving the sparse wavelength conversion and regeneration problem.
In this paper we study an approach to Quality of Service that offers
end-users the choice between two classes of service defined according
to their level of transmission protection. The first class of service,
called Fully Protected (FP), offers end-users a guarantee of
survivability in the case of a single failure; all FP traffic is
protected using either a 1:1 or 1+1 protection scheme at the WDM
layer. The second class of service, called Best-Effort Protected
(BEP), is not protected; when a failure occurs, the network does the
best it can by restoring at the IP layer only as much BEP traffic as
possible. The FP service class mimics what Internet users receive
today. The motivation of this approach is to increase the amount of
bandwidth used on backbone networks by offering a lower quality of
service that does not affect the current QoS provided by the network.
We design an ILP model, for finding primary and backup paths at the
optical layer, that incorporates a number of carriers' common
practices. Namely we allow the FP demand to be specified via a traffic
matrix at the IP layer, we include an overprovisioning factor that
specifies the portion of each link that must be left unused, and we
incorporate a minimal fairness requirement on how the BEP traffic is
allocated. Our goal is thus to quantify how much BEP traffic can be
carried in addition to the FP traffic, without impacting the
protection quality of the FP traffic even in the case of failure, and
without impacting the FP load.
We show that by having two such classes of service, the load on a
network can be increased by a factor of 4 to 7 (depending upon the
network). Even if carriers want to overprovision their networks by
50%, we can still triple the total network load. We illustrate that
the location of the bottleneck can affect whether or not we see a
difference in performance between 1:1 or 1+1 protection schemes.
Finally we evaluate the tradeoff between the two carrier requirements
of overprovisioning and minimal f
This study investigates the problem of fault management in a wavelength-division multiplexing (WDM)-based optical mesh network in which failures occur due to fiber cuts. In reality, bundles of fibers often get cut at the same time due to construction or destructive natural events, such as earthquakes. Fibers laid down in the same duct have a significant probability to fail at the same time. If two fibers reside in the same cable (bundle of fibers) or the same duct, we say that these two fibers are in the same Shared Risk Group (SRG). When path protection is employed, we require the primary path and the backup path to be SRG-disjoint, so that the network is survivable under single-SRG failures. Moreover, if two primary paths go through any common SRG, their backup paths cannot share wavelengths on common links. This study addresses the routing and wavelength-assignment problem in a network with path protection under SRG constraints. Off-line algorithms for static traffic is developed to combat single-SRG failures. The objective is to minimize total number of wavelengths used on all the links in the network. Both Integer Linear Programs (ILPs) and heuristic algorithms are presented and their performances are compared through numerical examples.
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