J. J. Astrain

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This paper presents three hierarchical algorithms for data aggregation in wireless sensor networks where sensors can crash and recover. The network is divided in several regions. The algorithms ensure (i) the selection of a common data aggregator sensor within each region, in charge of the collection of local data, and (ii) the selection of a unique(More)
This paper studies how the accuracy of the step detection algorithm of a pedestrian dead-reckoning (PDR) system is affected by the sampling frequency and the filtering of the data gathered from a wrist-worn inertial measurement unit (IMU). On the one hand, results show that sensors sampling rate can be reduced and a similar accuracy can still be obtained,(More)
For representing of digitized straight line segments (DSLS), each of the available research techniques has its advantages and appropriate applications considering the complexities of real world scenarios. Based on adaptive finite automaton (AFA), we propose an alternative paradigm that is convenient for problems modeled by a set of rules. The main objective(More)
The radio propagation for wireless systems embedded in surfboards has been characterized with the aim of testing the quality of a person to surfboard communication and person to infrastructure in aquatic environments, by means of wireless body area networks combined with an adequate transport technology. Wireless channel performance was analyzed using an in(More)
The increasing popularity of folksonomies has made them interesting as a tool to bridge the gap between Web 2.0 and the Semantic Web. This paper describes a modular and generic method (ACoAR) for the automatic classification of the resources tagged in a folksonomy, using semantic measures and a reduced number of relevant tags. Generic since it applies to(More)
Data gathering is one of the main issues to be faced in wireless sensor networks and is strongly dependent on sensor energy constrains. In this paper, we propose a chain-based distributed data gathering algorithm that provides a dynamic chain reconfiguration mechanism which dramatically improves the lifetime of the network. The key advantage of the(More)
A ray-tracing technique to predict the propagation channel parameters in indoor scenarios is presented. An analysis of the physical radio channel propagation inside a van full of buckets is presented. The propagation model is a deterministic technique, based on 3D ray launching. The results show the dependence of the scenario in the performance of the(More)
Railway transportation systems are gaining relevance in their adoption, driven by decreasing costs, higher interconnectivity options and timely operation. The Railway Transportation system is comprised by vehicular elements, as well as several infrastructure elements, which require constant interaction and communication, for tele-control and tele-command,(More)
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