Jose Maranhao

Wavelength assignment in optical networks considering physical impairments

Several studies on the routing and wavelength assignment (RWA) problem have already incorporated the physical layer impairments in order to find the appropriate resources for establishing the lightpath. This approach has become known in the literature as impairment aware RWA (IA-RWA). Although it is a more realistic approach compared to the RWA, the conventional IA-RWA approach usually neglects the degradation caused by the establishment of a new lightpath in the others already established in the network. In this paper we adopted an IA-RWA approach that takes into account these degradations. From the perspective of this new approach, we conducted a performance evaluation study comparing some wavelength assignment algorithms known in the literature and a new algorithm proposed in this paper. Simulation results show that our algorithm outperforms all others evaluated.

Wavelength conversion architectures in OBS networks

Most studies about Optical Burst Switched (OBS) networks have assumed availability of full wavelength conversion throughout the network. In an optical network with full wavelength conversion capability, every output on each node is provided with a wavelength converter, resulting in the lowest bound for blocking probability. However, full wavelength conversion capability requires a large number of wavelength converters, which is, and will remain, quite expensive in the foreseeable future. Therefore, it is expected that conversion capability will be limited and only sparsely deployed. In this work we apply to OBS networks the main architectures for wavelength conversion proposed for circuit switched networks. These architectures operate with limited wavelength conversion capability. We also investigate the cost benefit and the gain factor related to full complete wavelength conversion for each architecture. In addition, we propose a new methodology to define the number of wavelength converters in order to achieve the best cost benefit, regardless of the traffic load.

Sparse partial optical Code and Wavelength Conversion architecture in hybrid WDM/OCDM OBS networks

The performance of Optical Code/Wavelength Conversion (OCWC) switch architectures are investigated in this work. We employed hybrid technologies within in Optical Burst Switching (OBS) networks, which include wavelength and optical code division multiplexing. The simulated results demonstrate the concomitant increase of optical codes per wavelength and the utilization of Sparse Partial Optical Code/Wavelength Conversion. Both lead to a considerable decrease of the Burst Blocking Probability (BBP). In addition, such hybrid approach also improves the utilization of network resources.

Cost Benefit Study of Sparse-PartialWavelength Conversion Architectures

In this paper, we propose a new wavelength converter placement scheme called Adaptive First Load Priority, useful for designing and planning of optical networks with sparse-partial wavelength conversion architecture. The adaptive FLP is an extension of the FLP (First Load Priority) placement scheme proposed by authors in a previous work [13]. Initially, we provide a performance evaluation of FLP. Comparing to others wavelength converter placement schemes proposed in the literature like XC scheme [5], our results show that FLP achieves the best performance at all scenarios studied, very close to that one achieved with a full-complete wavelength conversion architecture. However, we could observe that, after a certain threshold, just adding moreWavelength Converter Routers (WCR) with the FLP scheme may not have enough improvement in network performance that justifies a higherWCR cost. The Adaptive First Load Priority scheme was conceived in order to minimize the amount of WCRs used by FLP scheme, improving its cost benefit. A cost-benefit (ratio gain) study showing a superior performance of Adaptive FLP scheme is presented.

Evolution of hybrid WDM/OCDM technology in OBS networks with optical code and wavelength conversion

The performance of a hybrid WDM/OCDM technology is investigated under impairments of Multiple Access Interference. We employed analytical models of Optical Orthogonal Codes to evaluate the switching network resources, such as the number of optical codes carried on each wavelength. Moreover, we propose and analyze a few optical code and wavelength conversion switching architectures, in order to scale the number of codes and wavelength converters and obtain a minimum burst blocking probability. The results demonstrate that architectures comprising Sparse-Partial Optical Code Converters with Sparse-Partial Wavelength Converters provide better performance. The network resources utilization are improved with number of converters, hence reaching a better cost benefit.

Evaluation of hybrid WDM/OCDM technology with optical codes conversion in OBS networks

The performance of Sparse Optical Code Conversion (SOCC) architectures is investigated in Optical Burst Switching (OBS) networks using a hybrid technology, which apply optical code and wavelength division multiplexing. The simulation results indicate that the increase of the number of optical codes and the utilization of SOCC conversion, lead to considerable decrease of the Burst Blocking Probability and latency. In addition, this hybrid technology also improves the utilization of network resources.

Evolution of dynamic routing wavelength code assignment in WDM/OCDM OBS network

This paper proposes and investigates the performance of a dynamic routing and wavelength code assignment (RWCA) algorithm using hybrid technology with wavelength and optical code division multiplexing (WDM/OCDM) for Optical Burst Switching (OBS) network. An OCDM-based multigranularity optical cross-connect (MG-OXC) is used to enable the better granularity in optical path (wavelength and code) switching than the wavelength-based path. The results show that Random-Random heuristic has a better performance when the burst blocking probability as a function of traffic load is studied. In addition, show that WDM/OCDM technology increase the capacity and scalability in the optical network.

A solution to the MCSP problem considering physical layer degradations in transparent optical networks

In all-optical networks, the physical layer impairments cause a degradation in the transmitted signal. Sometimes, the degradation causes an inadmissible Optical Signal to Noise Ratio (OSNR), which is translated into blocking due to low quality of transmission. The Impairment Aware -- Routing and Wavelength Assignment (IA-RWA) should choose the route and wavelength considering the physical layer impairments. The Choice of the Best Combination among M Combinations of Shortest Paths (MCSP) problem consists of choosing the best of the shortest paths for a network topology aiming to reduce the blocking probability. This paper presents a pioneer study of the MCSPs problem assuming Amplified Spontaneous Emission (ASE), co-wavelength crosstalk, self-wavelength crosstalk, neighbor wavelength crosstalk, Polarization Mode Dispersion (PMD) and attenuations caused by fiber and devices. In this context, we propose a new routing algorithm that aims to resolve the MCSP problem considering the physical impairments.

Preventive Assignment of Regenerator in Translucent Optical Networks

In this paper we propose the APR algorithm to assignment regenerator (RA) in translucent optical networks. The aim of our propose to reduce the blocking probability cause by the degradation made by the establishment of a new light path in the others already established in the network. The APR is compared to other strategy that searches assign the minimal number of regenerator per light path (AMR). For the considered scenarios in this paper, the APR achieved a superior performance than AMR blocking probability terms.

ABOI: a novel strategy to mitigate the blocking due to outdated information in OCS/OBS network

The blocking probability in all-optical networks caused by out of date information from the network has been studied basically in the OCS paradigm. This paper presents a performance evaluation study that considers the problem of outdated information in hybrid optical networks (OCS/OBS). The ABOI is proposed to mitigate this problem. In our simulations, the ABOI strategy decreased the blocking probability due to outdated information from the network.