9 research outputs found

    Frequency assignment in a SDMA satellite communication system with beam decentring feature

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    International audienceIn satellite communication, Spatial Division Multiple Access (SDMA) has become one of the most promising techniques that can accommodate continuing increase in the number of users and traffic demands. The technology is based on radio resource sharing that separates communication channels in space. It relies on adaptive and dynamic beam-forming technology and well-designed algorithms for resource allocation among which frequency assignment is considered. This paper studies static Frequency Assignment Problem (FAP) in a satellite communication system involving a satellite and a number of users located in a service area. The objective is to maximize the number of users that the system can serve while maintaining the signal to interference plus noise ratio of each user under a predefined threshold. Traditionally, interference is treated as fixed (binary interferences or fixed minimal required separation between frequencies) . In this paper, the interference is cumulative and variable. To solve the problem, we work on both discrete and continuous optimizations. Integer linear programming formulations and greedy algorithms are proposed for solving the discrete frequency assignment problem. The solution is further improved by beam decentring algorithm which involves continuous adjustment of satellite beams and deals with non-linear change of interference

    Allocation de fréquences et coloration impropre des graphes hexagonaux pondérés

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    National audienceMotivés par un problème d'allocation de fréquences, nous étudions la coloration impropre des graphes pondérés et plus particulièrement des graphes hexagonaux pondérés. Nous donnons des algorithmes d'approximation pour trouver de telles colorations

    Improper colouring of weighted grid and hexagonal graphs

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    International audienceWe study a weighted improper colouring problem motivated by a frequency allocation problem. It consists of associating to each vertex a set of p(v) (weight) distinct colours (frequencies), such that the set of vertices having a given colour induces a graph of degree at most k (the case k = 0 corresponds to a proper coloring). The objective is to minimize the number of colors. We propose approximation algorithms to compute such colouring for general graphs. We apply these to obtain good approximation ratio for grid and hexagonal graphs. Furthermore we give exact results for the 2-dimensional grid and the triangular lattice when the weights are all the same

    Improper colouring of weighted grid and hexagonal graphs

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    We study a weighted improper colouring problem on graph, and in particular of triangular and hexagonal grid graphs. This problem is motivated by a frequency allocation problem. We propose approximation algorithms to compute such colouring

    Optimisation de la gestion des ressources voie retour

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    L'optimisation de l'utilisation des liens satellites est un enjeu majeur pour augmenter la rentabilité des systèmes satellites. L'augmentation de la réutilisation des fréquences est une des approches les plus prometteuses. La réutilisation des fréquences permet de transmettre plus d'informations sur une même fréquence, pour peu que les interférences entre les deux signaux ne soient pas trop importantes. Il est donc capital de contrôler l'impact de ces interférences, que ce soit via l'utilisation de schémas de réutilisation de fréquences, ou encore via des techniques de coordination dynamique des interférences, où la sélection des utilisateurs qui peuvent transmettre sur les mêmes fréquences est faite en prenant les interférences en compt

    Quasi-optimal bandwidth allocation for multi-spot MFTDMA satellites

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    Quasi-optimal bandwidth allocation for multi-spot MFTDMA satellites

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    International audienceThis paper presents an algorithm for resource allocation in satellite networks. It deals with planning a time/frequency plan for a set of terminals with a known geometric configuration under interference constraints. Our objective is to maximize the system throughput while guaranteeing that the different types of demands are satisfied, each type using a different amount of bandwidth. The proposed algorithm relies on two main techniques. The first generates admissible configurations for the interference constraints, whereas the second uses linear and integer programming with column generation. The obtained solution estimates a possible allocation plan with optimality guarantees, and highlights the frequency interferences which degrade the construction of good solutions

    Quasi-Optimal Bandwidth Allocation for Multi-Spot MFTDMA Satellites

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    This paper presents an algorithm for resource allocation in satellite networks . It deals with planning a time/frequency plan for a set of terminals with a known geometric configuration under interference constraints. Our objective is to maximize the system throughput while guaranteeing that the different types of demands are satisfied, each type using a different amount of bandwidth. The proposed algorithm relies on two main techniques. The first generates admissible configurations for the interference constraints, whereas the second uses linear and integer programming with column generation. The obtained solution estimates a possible allocation plan with optimality guarantees, and highlights the frequency interferences which degrade the construction of good solutions
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