García Manrubia, María Belén

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García Manrubia, María Belén

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García Manrubia, María Belén

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Universidad de Murcia. Departamento de Didáctica de las Ciencias Matemáticasy Sociales

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Open Access
Multi-hour network planning based on domination between sets of traffic matrices
(Elsevier, 2011-02-21) Pavon Marino, Pablo; García Manrubia, María Belén; Aparicio Pardo, Ramón; Didáctica de las Ciencias Matemáticas y Sociales
In multi-hour network design, periodic traffic variations along time are considered in the dimensioning process. Then, the non coincidence of traffic peaks along the day or the week can be exploited. This paper investigates the application of the traffic domination relation between sets of traffic matrices to multi-hour network planning. Two problem variants are considered: a network with a static, and with a dynamic traffic routing. We derive a set of techniques for, given a multi-hour traffic demand potentially composed of hundreds of matrices, obtaining a traffic series with a smaller number of matrices. The traffic domination relation guarantees that the network designed for the simplified series is suitable for the original one. Also, we apply the domination relation to derive lower bounds to the network cost, and upper bounds to the suboptimality incurred by simplifying the traffic demand. The algorithms proposed are tested in a case of study with the Abilene network. In our tests, a long traffic series could be reduced to a small number of traffic matrices, and be effective for network planning.
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Software tools and methods for research and education in optical networks
(Springer, 2009) Rumley, Sébastien; Gaumier, Christian; Aparicio Pardo, Ramón; Chang, Ching-Hung; Colitti, Walter; García Manrubia, María Belén; Kourtessis, Pandelis; Martínez León, Juan Antonio; Nowé, Ann; Pavón Mariño, Pablo; Scharf, J.; Steenhaut, K.; Didáctica de las Ciencias Matemáticas y Sociales
Recent advances in photonic communication networks require planning, modelling and simulation tools of ever increasing scope and complexity. Based on valid and credible models, simulators are used heavily to investigate and assess new solutions before implementing testbeds and field trials. On the other hand, tools relying on heuristics algorithms or analytical models are widely used for network planning and dimensioning. This chapter reviews some recent trends in conception and utilisation of tools for modelling and planning, and reports several developments performed with commercial or academic tools and frameworks within the COST action 291.
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(Non-)reconfigurable virtual topology design under multihour traffic in optical networks
(Institute of Electrical and Electronics Engineers, 2012-10) Aparicio Pardo, Ramón; Skorin Kapov, Nina; Pavon Marino, Pablo; García Manrubia, María Belén; Didáctica de las Ciencias Matemáticas y Sociales
This paper investigates offline virtual topology design in transparent optical networks under a multihour traffic demand. The main problem variant addressed here designs a reconfigurable virtual topology that evolves over time to more efficiently utilize network resources (the MH-VTD-R problem). The case of designing a static non-reconfigurable virtual topology that can accommodate the time-varying traffic (the MH-VTD-NR problem) is also considered. The objectives are to minimize: 1) the number of transceivers, which make up for the main network cost; and 2) the frequency of reconfiguration (for MH-VTD-R), which incurs additional overhead and potential service disruption. We formulate this multiobjective problem as an exact mixed integer linear program (MILP). Due to its high complexity, we propose a very efficient heuristic algorithm called Greedy Approach with Reconfiguration Flattening (GARF). GARF not only solves both (non-)reconfigurable problem variants, but it allows for tuning of the relative importance of the two objectives. Exhaustive experiments on real and synthetic traffic and comparison to previous proposals and bounds reveal the merits of GARF with respect to both solution quality and execution time. Furthermore, the obtained results indicate that the maximal transceiver cost savings achieved by the fully reconfigurable case may not be enough to justify the associated increase in reconfiguration cost. However, results show that an advantageous tradeoff between transceiver cost savings and reconfiguration cost can be achieved by a allowing a small number of virtual topology reconfigurations over time.
Open Access
Offline impairment-aware RWA and regenerator placement in translucent optical Networks
( Institute of Electrical and Electronics Engineers , 2011-02) García Manrubia, María Belén; Pavon Marino, Pablo; Aparicio Pardo, Ramón; Klinkowski, Miroslaw; Careglio, Davide; Didáctica de las Ciencias Matemáticas y Sociales
In translucent optical networks, the physical layer impairments degrading the optical signal are considered in the network planning. In this paper, we investigate the offline problem of routing and wavelength assignment (RWA) and regenerator placement (RP) in translucent networks, minimizing the lightpath blocking and regenerator equipment cost.We address two variants of the problem, which correspond to two different types of quality of transmission (QoT) estimators, called linear and nonlinear. In a nonlinear QoT, nonlinear impairments like crosstalk or cross-phase modulation, which account for the interferences from neighboring lightpaths in the network are explicitly computed. Then, the QoT estimated for a lightpath depends on the routes of other lightpaths in the network. In the linear QoT, the effects of the nonlinear impairments are overestimated and accumulated to the rest of the impairments in the QoT calculation. As a result, the QoT estimation of a lightpath solely depends on its route. For the linear case, we formulate an optimal integer linear programming model of the problem, to the best of the authors’ knowledge, for the first time in the literature. Its simplicity allows us to test it for small- and medium-size networks. Also, we propose two heuristic methods, namely, lightpath segmentation and three-step, and a tight lower bound for the regenerator equipment cost. For the nonlinear QoT case, we propose a new heuristic called iterative RP (IRP). Both the IRP and three-step algorithms are designed to guarantee that no lightpath blocking is produced by signal degradation. This is a relevant difference with respect to earlier proposals. The performance and the scalability of our proposals are then investigated by carrying out extensive tests. Results reveal that the solutions obtained by the heuristic algorithms are optimal or close to optimal, and outperform the earlier proposals in the literature.
Open Access
Heuristic approaches for periodic reconfiguration of lightpath-based networks under multi-hour traffic
(Academy Publisher, 2012-05) Aparicio Pardo, Ramón ; García Manrubia, María Belén; Skorin Kapov, Nina; Pavon Marino, Pablo; Didáctica de las Ciencias Matemáticas y Sociales
Periodic lightpath reconfiguration of virtual topologies in transparent optical networks has been recently investigated as a mechanism to more efficiently adapt the network to predictable periodic traffic variations along a day or week. Scheduling periodic reconfigurations involves tuning a trade-off between a lower network cost obtained through better resource allocation, and undesired traffic disruptions that these reconfigurations may cause. This paper presents and compares two algorithms for planning a reconfigurable virtual topology suitable for exploring this trade-off. The first is based on a Lagrangean Relaxation of the planning problem, and the second is based on a Tabu Search meta-heuristic. The merits of both algorithms are assessed for moderate network sizes through comparison with analytical lower bounds and exact solutions obtained by a MILP formulation.
Open Access
Profiles of intrinsic motivation and motivational learning strategies in Spanish University students
(Springer, 2025-02-13) Cecilia Ruiz-Esteban; Juan Pedro Martínez-Ramón; Belen García-Manrubia; José Manuel García-Fernández; Inmaculada Méndez; Méndez Mateo, Inmaculada; Ruiz Esteban, Cecilia; Martínez Ramón, Juan Pedro; García Manrubia, María Belén; García-Fernández, José Manuel; Psicología Evolutiva y de la Educación; Facultad de Educación
At the university stage, students must face new challenges and achieve necessary academic goals, with intrinsic motivation and the effective use of learning strategies playing a relevant role in not procrastinating. The objective of the study was to investigate the profiles of university students according to their levels of intrinsic motivation. It also sought to examine whether students with different intrinsic motivation profiles differ significantly in motivational learning strategies. The study participants were 719 university students in Spain (M = 21.31; SD = 4.43), being 64.8% women. The Educational Motivation Scale and the Questionnaire of Learning Strategies in University Students were used. During the completion of the instruments, anonymity and confidentiality of the data were ensured. Informed consent was requested from the participants, who participated voluntarily, without receiving any reward and were able to unsubscribe at any time. This was a cross-sectional study that used convenience sampling. The latent profile analysis was carried out. The results revelated that different intrinsic motivation profiles have been found among university students. Likewise, it was found that the different profiles differ significantly in motivational learning strategies. It was shown that those students with high values of intrinsic motivation are characterized by using motivational learning strategies to a high degree compared to students with low or intermediate values. The findings of the study can help personalize educational programs by providing prevention and intervention methods regarding inappropriate patterns in the use of students’ learning strategies as well as self-regulation in the learning process to ensure academic success.