121 research outputs found
Optimization of WDM Optical Networks
Optical network, with its enormous data carrying capability, has become the obvious choice for today\u27s high speed communication networks. Wavelength Division Multiplexing (WDM) technology and Traffic Grooming techniques enable us to efficiently exploit the huge bandwidth capacity of optical fibers. Wide area translucent networks use sparse placement of regenerators to overcome the physical impairments and wavelength constraints introduced by all optical (transparent) networks, and achieve a performance level close to fully switched (opaque) networks at a much lesser network cost. In this dissertation we discuss our research on several issues on the optimal design of optical networks, including optimal traffic grooming in WDM optical networks, optimal regenerator placement problem (RRP) in translucent networks, dynamic lightpath allocation and dynamic survivable lightpath allocation in translucent networks and static lightpath allocation in translucent networks. With extensive simulation experiments, we have established the effectiveness and efficiencies of our proposed algorithms
IMPAIRMENT AWARE DYNAMIC ROUTING AND WAVELENGTH ASSIGNMENT IN WDM NETWORKS
Optical networks play a major role in supporting the traffic in backbone computer networks. Routing and Wavelength Assignment (RWA) is the technique used to establish a light-path from a source node to a destination node in a Wavelength Division Multiplexed (WDM) optical network. As an optical signal propagates through the network, the quality of the signal degrades due to physical layer impairments. To address this problem, in translucent WDM networks, the signal is regenerated at intervals. The main objective of this research is to propose a fast heuristic for dynamic lightpath allocation in translucent WDM networks and to compare the heuristic with an optimal algorithm that was proposed recently
Path Protection in Translucent WDM Optical Networks
Optical noise, chromatic dispersion, nonlinear effects, polarization mode dispersion (PMD) and cross-talk cause the quality of an optical signal to degrade as it propagates through the fibers in wavelength division multiplexed (WDM) optical networks. In a translucent network, regenerators are placed ay appropriate intervals to carry out 3R regeneration (re-amplify, re-shape and re-time). Translucent WDM networks are receiving attention as long-haul back bone networks. One important aspect of such networks that has not received attention is the possibility of cycles in the path of a translucent network. This research studies how we implement path protection in translucent networks, considering the possibility of cycles. We are developing a new scheme for dynamic lightpath allocation using the idea of shared path protection. We propose to study the performance of the scheme using a number of well known networks
A New Parametric Regenerator Allocation Scheme taking into account Inaccurate Physical Information
Regenerator allocation consists on selecting which of the already installed regenerators
in a translucent network may be used according to the dynamic traffic requests in order
to maximize the quality of the optical signal while minimizing the opaqueness of the
network. A recent study has shown that the performance of the regenerator allocation
techniques strongly depends on the accuracy of the physical-layer information. The
reason of this physical inaccuracy is the drift suffered by the physical-layer parameters
during the operation of the optical network. In these conditions, the performance of the
Impairment Aware-Routing and Wavelength Assignment (IA-RWA) process might drop
sharply when allocating regenerators inappropriately. In this paper, we propose new
regenerator allocation schemes taking into account the inherent and unavoidable
inaccuracy in the physical-layer informationPostprint (published version
The Effects of Optimized Regenerator Allocation in Trans-lucent Networks under Inaccurate Physical information
Optimized regenerator allocation techniques select
which of the already installed regenerators in a translucent
network must be used in order to maximize the quality of the
optical signal while minimizing the opaqueness of the network.
Unfortunately, the performance of an optimized regenerator
allocation strategy strongly depends on the accuracy of the
physical-layer information. In this paper, we investigate the
effects of optimized regenerator allocation techniques when the
physical-layer information is inaccurate. According to the performed
experiments, we conclude that mostly of the current
techniques of regenerator usage optimization are only possible
when perfect knowledge of physical information is available.
Hence, new regenerator allocation schemes taking into account
the inherent inaccuracy in the physical-layer information need
to be designed.Postprint (published version
Design of Disaster-Resilient Datacenter WDM Networks
Survivability of data in datacenters, when a fault occurs, is turning into an upcoming challenge in planning cloud-based applications. At the point when such a disaster happens, a particular geological range is disrupted, and units of transmission systems (e.g., nodes and fibers) within the disrupted region end up faulty, leading to the loss of one or more demands. To deal with such a circumstance, a resilient communication code is required, so arrangements can be made to accommodate an alternative disaster-free path when a fault upsets the path utilized for data requests before the failure happens. In this work, we have shown a new approach to deal with this issue, on account of the static Route and Wavelength Assignment (RWA) in Wavelength Division Multiplexing (WDM) systems. In our approach, a set of communication demands can be handled only if it is feasible to i) Find the datacenter node ii) a primary lightpath that minimizes the effect of disasters that may disrupt lightpaths and iii) (for every disaster that upsets the primary lightpath), a backup lightpath that handles the disaster. We have presented, implemented and examined an efficient heuristic to solve this issue
Optimal Regenerator Placement for Dedicated Path Protection in Impairment-Aware WDM Networks
Building resilient Wavelength Division Multiplexed (WDM) optical networks is an important area of research. This thesis deals with the design of reliable WDM networks where physical layer impairments are taken into account. This research addresses both the regenerator placement problem (RPP) and the routing with regenerator problem (RRP) in impairment-aware WDM networks, using dedicated path protection. Both the problems have been tackled using linear Integer formulations which can be implemented, using a solver such as the CPLEX. For solving RPP, two solutions have been proposed - i) a formulation that gives optimal solutions which works only for small networks, and ii) a highly effective heuristic which given an optimal solution in 97.5 to 99% of cases for networks having a size up to 60 nodes
Performance of translucent optical networks under dynamic traffic and uncertain physical-layer information
This paper investigates the performance of translucent
Optical Transport Networks (OTNs) under different traffic
and knowledge conditions, varying from perfect knowledge to
drifts and uncertainties in the physical-layer parameters. Our
focus is on the regular operation of a translucent OTN, i.e., after
the dimensioning and regenerator placement phase. Our contributions
can be summarized as follows. Based on the computation
of the Personick’s Q factor, we introduce a new methodology for
the assessment of the optical signal quality along a path, and
show its application on a realistic example. We analyze the performance
of both deterministic and predictive RWA techniques
integrating this signal quality factor Q in the lightpath computation
process. Our results confirm the effectiveness of predictive
techniques to deal with the typical drifts and uncertainties in the
physical-layer parameters, in contrast to the superior efficacy of
deterministic approaches in case of perfect knowledge. Conversely
to most previous works, where all wavelengths are assumed
to have the same characteristics, we examine the case
when the network is not perfectly compensated, so the Maximum
Transmission Distance (MTD) of the different wavelength channels
may vary. We show that blocking might increase dramatically
when the MTD of the different wavelength channels is overlooked.Postprint (published version
An Optimal Formulation for Handling SLD in Impairment Aware WDM Optical Networks
The effect of physical layer impairments in route and wavelength assignment in Wavelength Division Multiplexed optical networks has become an important research area. When the quality of an optical signal degrades to an unacceptable level, a regenerator must be used to recover the quality of the signal. Most research has focused on reducing the number of regenerators when handling static and ad-hoc lightpath demands in such networks. In networks handling scheduled lightpath demands (SLD), each request for communication has a known duration and start time. Handling SLD in impairment aware networks has not been investigated in depth yet. We propose to study the development of an optimal formulation for SLD, using a minimum number of regenerators. We will compare our optimal formulation with another formulation which has been proposed recently
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