Ignacio Olabarrieta

Tecnalia · Digital

The estimation of the amount of uncertainty featured by predictive machine learning models has acquired a great momentum in recent years. Uncertainty estimation provides the user with augmented information about the model's confidence in its predicted outcome. Despite the inherent utility of this information for the trustworthiness of the user, the...

Vehicle flow forecasting is of crucial importance for the management of road traffic in complex urban networks, as well as a useful input for route planning algorithms. In general traffic predictive models rely on data gathered by different types of sensors placed on roads, which occasionally produce faulty readings due to several causes, such as m...

This paper describes a Big Data stream analytics platform developed within the DEWI project for processing upcoming events from wireless sensors installed in a truck. The platform consists of a Complex Event Processing (CEP) engine capable of triggering alarms from a predefined set of rules. In general these rules are characterized by multiple para...

This chapter outlines the reference architectures conceived for intelligent transportation systems (ITS) planning and deployment in Europe, their evolution through the inputs provided by major ITS projects and initiatives and some experiences from the authors when facing the definition of ITS architectures through their involvement in research proj...

Information about the position of entities is very valuable in many fields. People, animals, robots and sensors are some examples of entities that have been targeted as nodes of interest for localization purposes. Technical advances in ubiquitous computing and wireless communications properties are very valuable means to obtain localization informa...

One of the applications of wireless sensor networks currently undergoing active research focuses on the scenario where the information generated by a data source S is simultaneously sensed by N nodes and therefrom transmitted to a common receiver. Based on the received information from such N nodes, such receiver infers the original information fro...

In this paper we consider a network of distributed sensors which simultaneously measure a physical parameter of interest, subject to a certain sensing error probability. The sensed information at each of such nodes is forwarded to a central receiver through parallel independent AWGN channels. In this scenario the signals from different sensors can...

Recent contributions have shown that, by switching frequency bands at intermediate relay nodes, enhanced diversity can be attained in two-user wireless frequency division relay networks at a minimum computational cost. This paper elaborates on the design of frequency-switching patterns for more involved relay scenarios. We conclude that in general,...

In this paper we consider a network of distributed sensors which simultaneously measure a physical parameter of interest, subject to a certain probability of sensing error. The sensed information at each of such nodes is channel-encoded and forwarded to a central receiver through parallel independent AWGN channels. In this scenario, several recent...

This paper introduces a novel heuristic algorithm for N-user detection in synchronous CDMA multiple access networks. In such systems, the performance of the conventional single-user detection technique (i.e. a rake receiver compounded by a set of matched filters) is clearly bounded by the well-known multiple access interference (MAI). To avoid this...

Focusing on densely deployed wireless sensor networks, this paper presents a novel method for joint source-channel-network coding of distributed correlated sources through multiple access relay channels. In such networks, the role of intermediate sensors as relay nodes permits to achieve enhanced end-to-end error performance and increased spatial d...

We study the critical collapse of a massless scalar field with angular momentum in spherical symmetry. In order to mimic the effects of angular momentum we perform a sum of the stress-energy tensors for all the scalar fields with the same eigenvalue, l, of the angular momentum operator and calculate the equations of motion for the radial part of th...

We investigate the possibility of localizing scalar field configurations as a model for black hole accretion. We analyse and resolve difficulties encountered when localizing scalar fields in general relativity. We illustrate this ability with a simple spherically symmetric model which can be used to study features of accreting shells around a black...

We study head-on collisions of boson stars in three dimensions. We consider evolutions of two boson stars which may differ in their phase or have opposite frequencies but are otherwise identical. Our studies show that these phase differences result in different late time behavior and gravitational wave output.

The two body problem in General Relativity is studied in this work by solving numerically Einstein Equations. The approach chosen consists of modeling (at least) one of the compact object by means of a boson star, which is a self-graviting configuration of (complex) scalar field. We present studies of binary systems involving one of these boson sta...

We present a new numerical code (Flow-er) for calculating astrophysical flows in 1, 2 or 3 dimensions. We have implemented equations appropriate for the treatment of Newtonian gravity as well as the general relativistic formalism to treat flows with either a static or dynamic metric. The heart of the code is the recent non-oscillatory central diffe...

We present recent results from our efforts to evolve relativistic binaries composed of compact objects. We simultaneously solve the general relativistic hydrodynamics equations to evolve the material components of the binary and Einstein's equations to evolve the space-time. These two codes are coupled through an adaptive mesh refinement driver (ha...

``I numerically study general relativistic hydrodynamics in axisymmetric spacetimes. The hydrodynamic equations are solved using a high resolution shock capturing algorithm which uses the Roe method to compute the numerical fluxes. The equations for the geometry are solved using a variation of the general relativisitic axisymmetric code described i...

Black strings, one class of higher dimensional analogues of black holes, were shown to be unstable to long wavelength perturbations by Gregory and Laflamme in 1992, via a linear analysis. We revisit the problem through numerical solution of the full equations of motion, and focus on trying to determine the end-state of a perturbed, unstable black s...

We discuss the current status and results from our ongoing numerical effort to determine the end-state of a perturbed, unstable 5-dimensional black string. Our preliminary results show that such a spacetime evolves through a stage that resembles a sequence of spherical black holes connected by thin black strings. However, the coordinate system that...

In 1993 Gregory and Laflamme found (trhough linearized analysis and entropy considerations) that a black string (a higher dimensional analogue of a black hole) could bifurcate. This prompted the conjecture that these systems were examples of violations of cosmic censorship. Additionally, the bifurcation possibility was embraced in different investi...

We perform a numerical study of the critical regime at the threshold of black hole formation in the spherically symmetric, general relativistic collapse of collisionless matter. The coupled Einstein-Vlasov equations are solved using a particle-mesh method in which the evolution of the phase-space distribution function is approximated by a set of pa...

We perform a numerical study of the critical regime for the general relativistic collapse of collisionless matter in spherical symmetry. The evolution of the matter is given by the Vlasov equation (or Boltzmann equation) and the geometry by Einstein's equations. This system of coupled differential equations is solved using a particle-mesh (PM) meth...