K Pair of disjoint paths Algorithm for Protection in WDM Optical Networks

Survivable routing in wavelength division multiplexing (WDM) optical networks has been proven to be NP-hard problem. There is a trade-off between the computational time and the optimality of solutions in existing approaches to the problem. Existing heuristic approaches purely based the graph algorithms are efficient in computational time but do not offer optimal solutions and may fail in some cases even when a solution exists. Meanwhile, the integer linear programming (ILP) models offer optimal solutions but are intractable even with moderate scale networks. In this paper, we introduce a new algorithm for finding K pairs of disjoint paths which are employed as K candidate pairs for each connection in the ILP models. We introduce an ILP model for dedicated path protection in which the number of decision variables is mainly dependant on traffic requests and the constant K, not on the network siz

A Shared Backup Path Protection Scheme for Optical Mesh Networks

We propose a new heuristic ILP model for share backup path protection (SBPP) scheme of mesh networks, which used the sets of disjoint-joint primary-backup path candidates of using path-pair candidates. The solution of the model is near optimal and provides all the routing details of demands as well as the sharing information between backup paths, and also simplifies the wavelength assignment problem if the wavelength continuity is a consideration. The new entities are introduced into this model that allow to control the resource utilization as well as congestion level of the network for optimization purposes and the pre-processing of data offers more control in properties of the path candidate

Dynamic Wavelength routing in all optical mesh network

Wavelength-division multiplexing (WDM) offers the capability to handle the increasing demand of network traffic in a manner that takes advantage of already deployed optical fibers. Lightpaths are optical connections carried end-to-end over a wavelength on each intermediate link. Wavelengths are the main resource in WDM networks. Due to the inherent channel constraints, a dynamic control mechanism is required to efficiently utilize the resource to maximize lightpath connections. In this paper, we investigate a class of adaptive routing called dynamic wavelength routing (DWR), in which wavelength converters (WCs) are not utilized in the network. The objective is to maximize the wavelength utilization and reduces the blocking probability in an arbitrary network. This approach contains two sub-algorithms: least congestion with least nodal-degree routing algorithm (LCLNR) and dynamic two-end wavelength routing algorithm (DTWR). We demonstrate that DWR can significantly improve the blocking performance, and the results achieved as good as placing sparse WCs in the networ

Applications of Liquid Crystal Spatial Light Modulators in Optical Communications

Advances in liquid crystal (LC) materials and VLSI technology have enabled the development of multi-phase spatial light modulators (SLM) that can perform high-resolution, dynamic optical beam positioning as well as temporal and spatial beam shaping in the 1550 nm optical communication window. These attractive features can effectively be used to achieve optical switching, optical spectral equalization, tunable optical filtering and many other functions that are important for future reconfigurable optical telecommunication networks. We review potential optical telecommunication applications based on LC-SLMs

Capacity Utilization versus Congestion Levels in wavelength Routing for large scale WDM Networks

Wavelength routing (WR) has been a key issue in WDM optical networks which carry huge amount of traffic aggregated from Internet protocol (IP), asynchronous transfer mode (ATM) and SDH/SONET layers. The problem, however, has been proved NP-hard. The time complexity and the optimality of solutions are two conflicting metrics. In addition, for optimization purposes, capacity utilization and network congestion level can be compromised to reduce the blocking probability of future connections. In this paper, we propose a heuristic approach for WR in large scale networks based on a balanced model developed for the capacity utilization and the congestion level. This is a two step approach, i.e K shortest paths (KSP) algorithm and a path selection algorithm (PSA), and is applicable not only at network design phase but also for online provisioning where a number of traffic connections may be requested simultaneously. We investigate the time complexity and the optimality of solutions as metrics for comparing our approach and the ILP formulation for wavelength routing. Simulation results show that our approach yields very promising results in terms of the optimality of solutions whilst also applicable to very large scale networks, say 500 nodes or mor

Dynamic p-cycles selection in optical WDM Mesh networks

P-cycles have been recognized as a useful protection scheme in WDM mesh networks. This is a type of shared link protection that not only retains the mesh-like capacity efficiency, but also achieves the ring-like protection switching speed. However, finding the optimal set of p-cycles for protecting traffic demands is not a simple task and is an NP-hard problem. A general approach is to determine a set of candidate p-cycles and then determine optimal or near-optimal solutions by using integer linear programming (ILP) models or heuristics. In a dense mesh network, however, the number of candidate cycles is huge, and increases exponentially if the node number is increased. Thus, searching for a suitable set of efficient candidate cycles is crucial and imperative to balancing the computational time and the optimality of solutions. In this paper, we propose a dynamic P-cycles selection (DPS) algorithm that improves the efficiency of enumerating candidate p-cycles. The dynamic approach for cycle selection is based on the network state. In the DPS algorithm, all cycles are found and stored, then an efficient and sufficient set of p-cycles is extracted to achieve 100% working protection, minimize the spare capacity, and reduce time complexity

Efficient p-Cycle Design by Heuristic p-Cycle Selection and Refinement for Servivable WDM Mesh Networks

Using p-Cycles to protect against single span failures in Wavelength-Division Multiplexing (WDM) networks has been widely studied. p-Cycle retains not only the speed of ring-like restoration, but also achieves the capacity efficiency over mesh networks. However, in selecting an optimal set of p-cycles to achieve the minimum spare capacity and fast computational time is an NP-hard problem. To address this issue, we propose a heuristic approach to iteratively select and refine a set of p-cycles, which contains two algorithms: the Heuristic p-Cycle Selection (HPS) algorithm, and the Refine Selected Cycles (RSC) algorithm. Our simulation results show that the proposed approach is within 3.5% redundancy difference from the optimal solution with very fast computation time even for large networks

A Hybrid p-Cycle Search Algorithm for Protection in WDM Mesh Networks

p-Cycle is a type of shared link protection for survivable wavelength-division multiplexing (WDM) mesh networks. p-Cycle not only retains ring-like restoration speeds, but also achieves capacity efficiency in mesh networks. However, finding the optimal set of p-cycles to protect all traffic demands within a reasonable response time is difficult. This is particularity true with dense meshes or large networks, because the number of candidates is huge. Generally, p-cycles are determined by using either Integer Linear Programming (ILP) or specifically designed heuristic algorithms. However, both methods need a set of efficient candidate cycles to tradeoff between the computational time and the optimality of solutions. For this reason, constructing an efficient set of candidate p-cycles is crucial and imperative. In this paper, we propose the Span-weighted Cycle Searching (SCS) algorithm to generate and select an adequate number of p-cycles to minimize the spare capacity, while achieving 100% restorability, within low computational complexity

A Hybrid p-Cycle Search Algorithm for Protection in WDM Mesh Networks

p-Cycle is a type of shared link protection for survivable wavelength-division multiplexing (WDM) mesh networks. p-Cycle not only retains ring-like restoration speeds, but also achieves capacity efficiency in mesh networks. However, finding the optimal set of p-cycles to protect all traffic demands within a reasonable response time is difficult. This is particularity true with dense meshes or large networks, because the number of candidates is huge. Generally, p-cycles are determined by using either Integer Linear Programming (ILP) or specifically designed heuristic algorithms. However, both methods need a set of efficient candidate cycles to tradeoff between the computational time and the optimality of solutions. For this reason, constructing an efficient set of candidate p-cycles is crucial and imperative. In this paper, we propose the Span-weighted Cycle Searching (SCS) algorithm to generate and select an adequate number of p-cycles to minimize the spare capacity, while achieving 100% restorability, within low computational complexity

Identification des gènes impliqués dans l'autisme et les déficiences mentales

L'objectif de ce travail était d'apporter des éléments de réponse sur les causes de l'autisme et des déficiences mentales (DM) grâce à l'étude de remaniements chromosomiques apparus de novo chez des sujets autistes ou atteints de DM liées au sexe. Ainsi, l'étude d'une translocation chez un garçon autiste et DM nous a permis de montrer la déficience du gène KCNMA1 codant un canal K+ synaptique, et de voir que l'action d'une molécule ouvreuse de ce canal augmentait in vitro son activité, permettant d'envisager une approche thérapeutique pour les patients mutés pour KCNMA1. L'étude d'une inversion du chromosome X chez une fillette avec DM a abouti à l'implication du gène SOX3, codant un facteur de transcription, dans les DMX avec déficit en hormone de croissance. Enfin, nous avons montré que l'autisme et les DMX pouvaient avoir une cause génétique commune grâce à la présence d'une mutation du gène NLGN4 chez une famille où les garçons atteints ont une DM accompagnée ou non d'autisme.TOURS-BU Médecine (372612103) / SudocSudocFranceF