600 research outputs found
Deterministic Leader Election in Anonymous Sensor Networks Without Common Coordinated System
National audienceDans ce papier, nous nous focalisons sur le problème qui consiste à élire un leader dans un réseau de n capteurs anonymes ne partageant aucun système commun de coordonnées. En supposant que lorsque les robots disposent de la propriété de latéralité, nous donnons une caractérisation complète sur les positions des capteurs permettant de distinguer un leader, et ce quelque soit n. Lorsqu'ils ne disposent pas de la propriété de latéralité, nous montrons que cette caractérisation reste vraie si et seulement si n est impair. Ces résultats sont vrais même si les capteurs possèdent une mémoire et une visibilité infinie, sont mobiles et peuvent communiquer entre eux
Gathering in Dynamic Rings
The gathering problem requires a set of mobile agents, arbitrarily positioned
at different nodes of a network to group within finite time at the same
location, not fixed in advanced.
The extensive existing literature on this problem shares the same fundamental
assumption: the topological structure does not change during the rendezvous or
the gathering; this is true also for those investigations that consider faulty
nodes. In other words, they only consider static graphs. In this paper we start
the investigation of gathering in dynamic graphs, that is networks where the
topology changes continuously and at unpredictable locations.
We study the feasibility of gathering mobile agents, identical and without
explicit communication capabilities, in a dynamic ring of anonymous nodes; the
class of dynamics we consider is the classic 1-interval-connectivity.
We focus on the impact that factors such as chirality (i.e., a common sense
of orientation) and cross detection (i.e., the ability to detect, when
traversing an edge, whether some agent is traversing it in the other
direction), have on the solvability of the problem. We provide a complete
characterization of the classes of initial configurations from which the
gathering problem is solvable in presence and in absence of cross detection and
of chirality. The feasibility results of the characterization are all
constructive: we provide distributed algorithms that allow the agents to
gather. In particular, the protocols for gathering with cross detection are
time optimal. We also show that cross detection is a powerful computational
element.
We prove that, without chirality, knowledge of the ring size is strictly more
powerful than knowledge of the number of agents; on the other hand, with
chirality, knowledge of n can be substituted by knowledge of k, yielding the
same classes of feasible initial configurations
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