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Oda T.,Fukuoka Institute of Technology | Sakamoto S.,Fukuoka Institute of Technology | Spaho E.,Fukuoka Institute of Technology | Barolli A.,Canadian Institute of Technology | And 2 more authors.
Proceedings - 2013 8th International Conference on Broadband, Wireless Computing, Communication and Applications, BWCCA 2013 | Year: 2013

In this paper, we deal with connectivity and coverage problems of Wireless Mesh Networks (WMNs). Because these problems are known to be NP-Hard, we propose and implement a system based on GA. We call the proposed system: WMN-GA. We evaluate the performance of WMN-GA considering Giant Component and Covered Mesh Clients metrics. We evaluate and compare the performance of different initial router node placement methods in a wireless mesh network considering different distributions of mesh clients. Our WMN-GA System have a good behavior and can find the best initial router node placement methods for every distribution of mesh clients. © 2013 IEEE. Source


Xhafa F.,Polytechnic University of Catalonia | Herrero X.,Polytechnic University of Catalonia | Barolli A.,Canadian Institute of Technology | Takizawa M.,Hosei University
Lecture Notes in Electrical Engineering | Year: 2013

Ground Station Scheduling arises in satellite mission planning and belongs to scheduling family with time windows. It is know for its high computational complexity and hardness to solve to optimality. In fact, in some cases it is even hard to find a feasible solution that satisfies all user requirements and resource constraints. In this paper we present a Hill Climbing (HC) algorithm for the problem, which is a fast local search algorithm. Despite of being a simple search method, HC showed a good performance for small size instance while could not cope with medium and large size instances. The Satellite Toolkit is used for its experimental study and performance evaluation. © 2013 Springer Science+Business Media Dordrecht. Source


Xhafa F.,University of Barcelona | Herrero X.,University of Barcelona | Barolli A.,Canadian Institute of Technology | Takizawa M.,Hosei University
Proceedings - 2013 7th International Conference on Complex, Intelligent, and Software Intensive Systems, CISIS 2013 | Year: 2013

The satellite scheduling and its version of ground station scheduling are increasingly attracting the attention of researchers from aerospace and optimization domain. While in the recent past satellite mission arise from large aero-spacial agencies, nowadays even smaller companies are interested in satellite missions for basic tasks such as telemetry, imaging, remote sensing, etc. The ground station scheduling problem consists in computing an optimal planning of communications between satellites or spacecraft (SC) and operations teams of Ground Station (GS). The problem is highly complex and multi-objective and in its general formulation has been shown NP-hard. Therefore, its resolution is tackled by heuristic and meta-heuristic methods. Although heuristic and meta-heuristic methods are well understood, their evaluation for specific problems, like ground station scheduling, remain a challenge. The design and development of benchmarks of instances is thus needful to evaluate such methods and also to provide the community with means to reproduce the experimental study for the same benchmark under the same or different parameter setting. In this paper, we present an XML-based benchmark of instances for the ground station scheduling generated with the STK simulation toolkit. Then we show the experimental evaluation of a Basic Genetic Algorithm using the benchmark. © 2013 IEEE. Source


Oda T.,Fukuoka Institute of Technology | Barolli A.,Canadian Institute of Technology | Spaho E.,Fukuoka Institute of Technology | Barolli L.,Fukuoka Institute of Technology | Xhafa F.,University of Barcelona
Proceedings - 2013 7th International Conference on Complex, Intelligent, and Software Intensive Systems, CISIS 2013 | Year: 2013

In this paper, we evaluate the performance of WMN-GA system for node placement problem in WMNs. For evaluation, we consider Normal and Uniform Distribution of mesh clients and different grid shapes. The simulation results shows that grid shape effects in the performance of WMN-GA. With the increasing of grid size, the mesh routers can not cover all mesh clients in the grid size and the performance of the system is decreased. The system performs better for Normal distribution of mesh clients. © 2013 IEEE. Source


Xhafa F.,Polytechnic University of Catalonia | Herrero X.,Polytechnic University of Catalonia | Barolli A.,Canadian Institute of Technology | Takizawa M.,Hosei University
Proceedings - 16th International Conference on Network-Based Information Systems, NBiS 2013 | Year: 2013

Among different versions of Satellite Scheduling, there is the Ground Station Scheduling, whose aim is mission allocation of ground stations to spacecrafts. This scheduling problem belongs to the family of scheduling with time windows, and besides complexities of classical scheduling problems, it has additional requirements that make it over-constrained and challenging to solve to optimality. In fact, in some cases it is even hard to find a feasible solution that satisfies all user requirements and resource constraints. As with other computationally hard combinatorial optimization problems, heuristic solutions are employed to find high quality solutions in reasonable amount of computation time. In this paper we present a Simulated Annealing (SA) algorithm for the problem, which is a local search based algorithm that simulates the cooling process by gradually lowering the temperature of the system until it converges to a stable state. The Satellite Toolkit is used for the experimental study and performance evaluation of the algorithm through a family of instances of small, medium and large sizes. Keywords: Ground station scheduling, Satellite scheduling, Simulated Annealing Algorithm, Constraint programming, Spacecrafts, Multi-objective Optimization, Satellite Simulation Toolkit. © 2013 IEEE. Source

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