Martin-Escalona, I.; Barcelo, F.; Zola, E.; Ciurana, M. Recent Advances in Communications and Networking Technology Vol. 4, num. 2, p. 1-13 DOI: 10.2174/2215081103666141014212929 Date of publication: 2015-04-08 Journal article
Accuracy and scalability contribute to the quality of location solutions in wireless networks. While accuracy is a parameter addressed in all location technologies, scalability is often relegated. However, scalability becomes an actual issue in positioning solutions based message exchange (e.g. measuring ranges from beacons). The passive TDOA algorithm is a solution designed to localize terminals in a mobile ad hoc network in a passive way. It is achieved by computing time-differences of arrival from messages being exchanged by other network nodes (i.e. the active nodes), but just listening to the radio channel. In advanced stages of the passive TDOA algorithm (i.e. autonomous passive TDOA recently patented), it is able to compute the position of the unknown node (i.e. the passive node) and of the nodes which the listened location messages belong to (i.e. the active nodes). Thus, the requirement of active nodes informing about its own position to passive nodes is overcome. From the network perspective, the impact of this joint-position computation: it boosts the scalability since less information is transmitted and it helps to improve the accuracy of the active nodes, because passive nodes can report several positions regarding a single active node. However, the accuracy of the positions computed by means of the passive TDOA algorithm needs to be good enough to attend the user’s demands. The aim of this work is analyzing the accuracy achieved by the passive TDOA, focusing on the loss of precision due to passivity if compared with conventional two-way time-of-arrival active solutions, which passive TDOA is rely on.
Desde la Cátedra de Accesibilidad de la Universidad Politécnica de Cataluña se coordina el proyecto Easy Communicator con la doble finalidad de proporcionar a los estudiantes de ingeniería experiencia en el desarrollo de un proyecto real en e-learning y ofrecer a personas con dificultades en el aprendizaje una herramienta de comunicación alternativa y aumentativa. En el artículo se plantean la metodología de trabajo y las primeras conclusiones del desarrollo de la aplicación para tabletas Android.
Topics on network simulation are often offered as elective topics or short seminars of programs on computer sciences and telecommunications engineering. In other programs simulation is offered as part of a general core topic (e.g. probability and statistics, network performance, etc.). It is not frequent to find simulation as a core topic. At the Faculty of Telecommunications in Barcelona it was decided to include network simulation as a core topic in the former integrated master (5 academic years) on telecommunication engineering.
This paper deals with the reasons after that decision. The goal of
the paper is to present and discuss how the topic evolved through
the years and how it has been migrated to the new careers with
separated degree and master after the Bologna process.
El estudio que se presenta a continuación aporta las reflexiones necesarias
para empezar a trabajar en la consecución de un sistema de información que
permita recopilar los datos estadísticos necesarios para extraer el
conocimiento sobre la evolución del sistema universitario español. Demuestra
la viabilidad legal, académica y técnica del sistema sin dudas ni lagunas.
Aporta las especificaciones necesarias para su implementación. Y, finalmente,
pone en manos de la voluntad la necesidad de su creación.
Wireless networks of moving objects have drawn significant attention recently. These types of networks consist of a number of autonomous or semi-autonomous wireless nodes/objects moving with diverse patterns and speeds while communicating via several radio interfaces simultaneously. To overcome current shortcomings, a number of research challenges have to be addressed in this area, ranging from initial conceptualization and modelling, to protocols and architectures engineering, and development of suitable tools, applications and services, and to the elaboration of realistic use-case scenarios by taking into account corresponding societal and economic aspects. By applying a systematic approach the objective of this book is to assess the state of the art and consolidate the main research results achieved in this area. It was prepared as the Final Publication of the COST Action IC0906 “Wireless Networking for Moving Objects (WiNeMO)”. The book contains 15 chapters and is a show-case of the main outcomes of the action in line with its scientific goals. The book will serve as a valuable reference for undergraduate students, post-graduate students, educators, faculty members, researchers, engineers, and research strategists working in this field.
This paper analyses the difficulties found in some countries in Europe were the traditional integrated masters of five or six academic years were split into degree plus master after the Bologna process.
Often, the master years of the former integrated master are oriented to international students and the lecturers find a high degree of diversity not present in the degree (this latter in local language and
targeted to local students, close to the former first years of the integrated master). A case belonging to a master in computer networks is discussed together with some facts, difficulties found during the first years, discussion and possible ways to solve some of the detected issues.
Time-based multilateration in IEEE 802.11 networks usually involves custom hardware designs, which tend to slow down the implementation and deployment of the location system. This paper presents software for calculating time-based location observables. This software enhances the SoftMAC layer of the Linux operating system by adding location-related measuring capabilities. A plugin for calculating the round trip time between two network entities is included in the software definition. Real data have been collected to test the performance of the proposed system. Despite the relevant noise present in the measurements, the results prove that the round trip time measurements achieved are useful to estimate distances achieving estimates with RMS of the error close to 2 meters.
Several techniques have been proposed for
positioning nodes over IEEE 802.11 networks, but only few
consist in time-based multilateration, mainly due to the protocol
stack not supporting accurate timestamps. One frequent solution
is to develop the hardware required for providing accurate
timestamps. However, this approach tends to slow down the
research and the ulterior deployment of the location techniques,
since the performance of these techniques is bounded to a specific
hardware design. This paper presents a measuring system aimed
at providing location observables that can be used in time-based
multilateration techniques. The system, which follows a software
approach, is based on enhancing the SoftMAC layer of Linux
with location-measuring capabilities. The system is conceived for
supporting any kind of time-based measurements, by adding as
many plugins as measured observables. Two plugins have been
initially developed. The first one computes the round trip time of
a message from a station to an access point and back again to the
station. The second plugin calculates time-differences of arrival
suitable for being used in the passive TDOA technique. This
work provides the definition of the measuring system. Real data
has been collected to test the system. The results indicate that the
measurements provided by the system can be used for location
purposes, i.e. they follow the physical laws in which metrics are
based (e.g. they grow along with the distance between the nodes).
Positioning has been a hot topic in research for several years. GPS is
accepted as a global solution for positioning outdoors, but indoor positioning still remains an open issue. Time-based multilateration techniques are presented as a good trade-off between performance and complexity for indoor positioning. Although several proposals for time-based multilateration has been presented, only some of them has been really implemented and of them, only few can be reproduced by other researchers (mainly due to hardware customization). This work presents a system for measuring time-based location observables in IEEE 802.11 networks. This measuring system has been implemented in Linux, so it can be deployed easily by any researcher. The
current implementation supports the measurement of two kind of observables: round trip times (for two-way time-of-arrival techniques) and passive TDOAs (for the passive TDOA location technique). First experiments, presented in this paper, are focused on demonstrating the feasibility of the system for measuring these two location observables.
Positioning has been a hot topic in research for several years. GPS is
accepted as a global solution for positioning outdoors, but indoor positioning
still remains an open issue. Time-based multilateration techniques are presented
as a good trade-off between performance and complexity for indoor
positioning. Although several proposals for time-based multilateration has been
presented, only some of them has been really implemented and of them, only
few can be reproduced by other researchers (mainly due to hardware
customization). This work presents a system for measuring time-based location
observables in IEEE 802.11 networks. This measuring system has been
implemented in Linux, so it can be deployed easily by any researcher. The
current implementation supports the measurement of two kind of observables:
round trip times (for two-way time-of-arrival techniques) and passive TDOAs
(for the passive TDOA location technique). First experiments, presented in this
paper, are focused on demonstrating the feasibility of the system for measuring
these two location observables.
Indoor positioning has focused the interest of researchers for years. Although there are several techniques proposed, they are difficult to reproduce and consequently to contrast and improve. This paper presents a modular location platform, which enhances the SoftMAC implementation in Linux with positioning capabilities. This platform can be deployed in any device running Linux kernel 2.6 or higher. The core of the platform is its software-based measuring system. This measuring system supports the 2-way TOA technique, but any time-based multilateration technique (e.g. passive TDOA) can be incorporated with minimum changes. Real data have been gathered to assess the performance of the measuring system. The RTTs estimated grow with the distance, which demonstrates the feasibility of the system.
Together with the trend towards engineering designs
more accessible to handicapped people there is an increasing
concern at the engineering faculties to include topics related to
accessibility in their programs. Engineers must be aware that
handicapped people use technology and designs must take into
account this fact. This paper explains how a topic on accessibility
was started at a technical faculty as a cross topic to five different
engineering degrees: Electrical, Electronics and Automatic
Control, Industrial Product Design, Electronic Systems and
Computer Science. The introduction process is explained along
with the teaching methodology. Results after the first two courses
are good in general but present some issues. The main issue to be
corrected is that students from different branches achieve
different academic performances.
Together with the trend towards engineering designs more accessible to handicapped people there is an increasing concern at the engineering faculties to include topics related to accessibility in their programs. Engineers must be aware that handicapped people use technology and designs must take into account this fact. This paper explains how a topic on accessibility was started at a technical faculty as a cross topic to five different engineering degrees: Electrical, Electronics and Automatic Control, Industrial Product Design, Electronic Systems and Computer Science. The introduction process is explained along with the teaching methodology. Results after the first two courses are good in general but present some issues. The main issue to be corrected is that students from different branches achieve different academic performances.
Zola, E.; Barcelo, F.; Martin-Escalona, I. Eurasip journal on wireless communication and networking Vol. 2013, num. 16, p. 1-15 DOI: 10.1186/1687-1499-2013-16 Date of publication: 2013-01-25 Journal article
Users in a cellular network can move while their connections are handed off to different access points. Studies prove that the mobility pattern followed have a strong impact on performance metrics (i.e., handoff (HO) rate, cell residence time). Recently, some key aspects of the Random Waypoint mobility model have been studied in depth, but relating those studies with different cellular layouts has not been reported. Interest in forecasting the cell to which a device may be handed off depending on the movement pattern is twofold. First, it gives insight into properties and statistics of the mobility model. Second, and from a more practical perspective, it is useful to manage resource allocation and reservation strategies in order to smooth the HO process. The goal of this article is to provide an analytical framework for these predictions in a simple layout. Given a node's current location and the timestamp and location of the last waypoint, an approximation for HO during time Delta t is derived. The analysis is provided along with numerical examples and simulations for a symmetrical layout and uniform speed distribution. Results shed light on how useful more advanced strategies can be.
This paper presents a patent targeted to obtain distance measurements between nodes belonging to a wireless
network. The main motivation for this patent is the measurement of the distance between a user device and an access point
(or base station). After several distance measurements to different access points at sight and assuming the position of the
access points known, the device can compute its own position by trilateration. The main advantage in front of previously
existing methods to obtain distance measurements is that the method presented here involves only software modifications
to legacy terminals, thus allowing avoiding the need for hardware modifications at the user terminal.
Martin-Escalona, I.; Malpartida, M.; Barcelo, F. International Conference and Exhibition on Ubiquitous Positioning, Indoor Navigation and Location Based Services p. 1-8 DOI: 10.1109/UPINLBS.2012.6409767 Presentation's date: 2012-10-04 Presentation of work at congresses
Positioning in wireless networks has recently concentrated the interest of the research community. Outdoor positioning has been addressed successfully, but location indoors poses some open issues. Time-based ranging techniques, such as 2-way time-of-arrival (TOA), are promising for indoor positioning but present issues such as scalability and landmark dependency. Handling these problems separately makes it difficult to find solutions that can be implemented over communication networks on which positioning solutions rely. The passive TDOA algorithm was proposed for overcoming both issues together. Preliminary results indicate that scalability can be improved. This work assesses the performance of the passive TDOA in scenarios where there are not enough landmarks to run a regular 2-way TOA algorithm. Results show that the accuracy provided is worse than in scenarios with enough landmarks but, depending on the power of the ranging noise, good enough for most of the location-based services indoors.
Barcelo, F.; Martin-Escalona, I. Interactive Collaborative Learning: International Conference on Interactive Collaborative Learning and International Conference on Engineering Pedagogy p. 1-4 DOI: 10.1109/ICL.2012.6402201 Presentation's date: 2012-09-28 Presentation of work at congresses
This paper shows statistics of a group at the Faculty of Telecommunications Engineering in Barcelona (Spain). Due to the different origin and academic background of the students, planning the course is a challenging task. This work shows the features that characterize the group as heterogeneous. Statistics about the origin and the grades of a test before the course are shown along with the existing correlation between both. The paper also analyzes the grades obtained in the final exams and relates them to the origin and initial test. In the statistics some groups can be differentiated with students belonging to each group showing a similar degree of academic progress. The results allow drawing some conclusions on how a careful observation of the countries of origin, academic background and the results of a test before starting the course can help to plan a balanced course and evaluation.
This paper shows statistics of a group at the Faculty
of Telecommunications Engineering in Barcelona (Spain). Due to
the different origin and academic background of the students,
planning the course is a challenging task. This work shows the
features that characterize the group as heterogeneous. Statistics
about the origin and the grades of a test before the course are
shown along with the existing correlation between both. The
paper also analyzes the grades obtained in the final exams and
relates them to the origin and initial test. In the statistics some
groups can be differentiated with students belonging to each
group showing a similar degree of academic progress. The
results allow drawing some conclusions on how a careful
observation of the countries of origin, academic background and
the results of a test before starting the course can help to plan a
balanced course and evaluation.
Tappero, F.; Ciurana, M.; Batlle, J.; Uijt de Haag, M.; Martin-Escalona, I.; Fernández, D. International Conference on Space Applications p. 1-10 Presentation's date: 2012-06-25 Presentation of work at congresses
This paper discusses the implementation of a
modified IEEE 802.11 transceiver that is employed to enhance
the positioning capabilities of a traditional vehicle on-board
navigation unit (OBU). In this paper, we propose to use the
current wireless local access network (WLAN) as enhancing
infrastructure for ubiquitous localisation and positioning. We
describe the architecture of a localisation receiver built around a
FPGA that is capable of measuring the signal round trip time
and thus distance between itself and visible WiFi access points.
The proposed system has great potentials to enhance the
performance of traditional hardware solutions often based on
GNSS plus INS traditionally used as fundamental component in
an intelligent transportation system. The proposed system offers
vehicle-to-vehicle communication and ranging capabilities using
the current IEEE 802.11 standard. This paper describes the
details of the WLAN ranging estimation method, possible
integration approaches with a GPS plus INS system and an
analysis of the proposed system’s positioning performance in a
crowded urban environment.
Martin-Escalona, I.; Barcelo, F.; Zola, E. Annual Mediterranean Ad Hoc Networking Workshop p. 83-89 DOI: 10.1109/MedHocNet.2012.6257127 Presentation's date: 2012-06-22 Presentation of work at congresses
The positioning ability is essential in mobile networks.
Providing the position of entities is in general a complex task that
becomes especially hard in ad hoc networks. In these networks,
the topology cannot be planned and network nodes usually
present restrictions in terms of computation capabilities and
autonomy that constrain the network lifetime. Passive algorithms
have been proposed for minimizing the impact of location
services in the network, i.e. reducing the location traffic and
extending the network life. However, the accuracy of passive
algorithms tends to be worse than the accuracy for active
approaches. This paper studies the impact of several proposals
focused on improving the accuracy of the passive TDOA
algorithm. Results indicate that weighing the ordinary least
squares algorithm with the appropriate factors could be enough
for improving the accuracy of the algorithm in some scenarios.
Time of Arrival (TOA) based techniques are expected to overcome performance limitations of existing WLAN positioning approaches. The upcoming IEEE 802.11v standard is expected to play a key role because it will include new specific mechanisms for TOA-based positioning with WLAN. This article analyzes some of these new capabilities and evaluates the performance enhancement that they can provide in practice. To this end, a comparative assessment between an existing WLAN TOA-based approach that uses IEEE 802.11 b/g and an analogous solution employing IEEE 802.11v is performed.
Fernández, D.; Barcelo, F.; Martin-Escalona, I.; Ciurana, M.; Jofre, M.; Gutiérrez, E. IEEE Symposium on Computers and Communications p. 748-751 DOI: 10.1109/ISCC.2011.5983929 Presentation's date: 2011 Presentation of work at congresses
This paper proposes a positioning method that combines GPS pseudoranges and WLAN ranges when less than four GPS satellites are within sight. To enhance the positioning availability, a tight hybridization approach with both technologies is considered. Although the work has been performed considering WLAN and GPS, most of the presented ideas, procedures and results are also valid for generic tight non-synchronized fusion of GNSS with terrestrial signals. Special emphasis is placed on the phenomenon of positioning ambiguity that appears due to the combination of measurements with different characteristics. To solve this ambiguity, a method is proposed and studied. The availability and accuracy of the system are tested considering different satellite and terrestrial geometries. The results show that the proposed system is able to improve the availability while maintaining the accuracy of GPS as a standalone.
Fernández, D.; Ciurana, M.; Jofre, M.; Gutiérrez, E.; Chester, E.; Barcelo, F.; Martin-Escalona, I. European Navigation Conference on Global Navigation Satellite Systems Presentation's date: 2010-10-20 Presentation of work at congresses
This contribution proposes a positioning system that fuses GPS pseudoranges and WLAN ranges when fewer than four GPS satellites are available. In order to enhance as much as possible the positioning availability, a tight hybridization approach with both technologies is considered. Although the work has been performed considering WLAN and GPS, most of the presented ideas, procedures and results are also valid for generic tight non-synchronised fusion of GNSS with terrestrial signals.
Special emphasis is dedicated to the phenomenon of positioning ambiguity that appears due to the incorporation of the terrestrial measurements. In order to solve this ambiguity, a method is proposed and explained. Later, the method and the availability and the accuracy of the system are tested considering different satellite and terrestrial geometries. Results show that the proposed system is able to improve the availability while maintaining the accuracy of GPS alone.
Martin-Escalona, I.; Barcelo, F. International Conference on Ultra Modern Telecommunications p. 1218-1225 DOI: 10.1109/ICUMT.2010.5676674 Presentation's date: 2010-10 Presentation of work at congresses
Las redes inalámbricas han favorecido enormemente el interés de los usuarios, proveedores de servicio y operadores de red en el posicionamiento geográfico. Como consecuencia, se han propuesto mecanismos en la mayor parte de tecnologías de red inalámbrica con los que soportar la localización de usuarios. La evaluación de calidad ofrecida por dichas técnicas de localización, normalmente en términos de precisión, latencia y escalabilidad, recae en herramientas de simulación. Es esencial por tanto, que los modelos de error empleados en estas herramientas estén acordes a la realidad. Este hecho es si cabe más importante en el caso de emplear técnicas de localización basadas en medida de la distancia a partir de métricas temporales, como son el tiempo de llegada (TOA) o la diferencia entre tiempos de llegada (TDOA). Estas técnicas son especialmente sensibles a no disponer de visión directa entre los distintos elementos involucrados en la localización, por lo que la evaluación de sus capacidades suele hacerse bajo esas condiciones. El presente artículo compara bajo un mismo escenario, diversos modelos de error para las métricas empleadas en técnicas como TOA o TDOA. Los resultados concluyen que los modelos que no tienen en cuenta las distancias reales (que son los más habituales) tienden a proporcionar una estimación optimista el error de posicionamiento, cosa que no ocurre en el caso de modelos más complejos que sí tienen en cuenta esa información.
Ciurana, M.; Giustiniano, D.; Neira, A.; Barcelo, F.; Martin-Escalona, I. International Conference on Indoor Positioning and Indoor Navigation p. 1-8 DOI: 10.1109/IPIN.2010.5648117 Presentation's date: 2010-09 Presentation of work at congresses
This article proposes a set of strategies to improve the performance stability and reliability of purely software ToA-based ranging with off-the-shelf WLAN equipment. Taking as starting point the core design lines proposed in (1), where timing measurements were taken at OS level using the CPU clock of the client device, we optimize the OS configuration and the capture of the time-stamps. Results obtained with a prototype demonstrate that the proposed enhancements improve the performance stability by a factor four. The interest in this kind of ranging methods is because they enable cost-effective and accurate positioning in GNSSless environments.
This work studies the improvement in service coverage obtained by three different approaches to combining
two triangulation (terrestrial and satellite) location methods for cellular networks in an urban environment.
The paper assumes that the terrestrial cellular network uses enhanced observed time difference (E-OTD) in
2G or observed time difference of arrival (OTDOA) in 3G, while the satellite GNSS uses the assisted global
positioning system (A-GPS), but the analysis can be easily generalised to other triangulation methods. A
straightforward analytical model is presented to evaluate the service coverage resulting from each of the
three approaches. The model is fed with actual coverage figures, gathered from test measurements carried
out in Paris (France) for several urban scenarios. Numerical results show that the three approaches lead to
improvements in all the tested scenarios, and that the improvement obtained by the increasing complexity of
the fusion approach depends highly on the coverage of each individual method and on the joint probability
function of individual performances
Gete-Alonso, O.; Martin-Escalona, I.; Barcelo, F. International Conference on Computer Engineering and Applications p. 474-478 DOI: 10.1109/ICCEA.2010.241 Presentation's date: 2010-03-20 Presentation of work at congresses
This article presents a statistical study on the
availability of location sources. In particular, it rates the
availability of cellular network base stations and GPS satellites
in urban scenarios. Individual and joint availability density
functions have been obtained for both types of signal sources,
as well as statistical information that complements these
functions. This information is of great importance due to the
growing interest in fusion (i.e., combination) of location
techniques. The results indicate that the improvements in
coverage from fusion techniques depend both on the fusion
mechanism and the scenario, obtaining noticeable benefits in
Sistema y procedimiento de localización basados en medidas pasivas de diferencias temporales para el posicionamiento conjunto de nodos en redes colaborativas.
Procedimiento destinado a obtener la localización conjunta de nodos en una red colaborativa de forma pasiva, basado en la existencia de un nodo (pasivo) que se posiciona a partir de las peticiones de localización realizadas por un subconjunto de nodos de la misma red (nodos activos), que emplean una técnica de localización basada en la estimación del tiempo de ida y vuelta. El procedimiento permite la estimación de los tiempos de propagación de los nodos activos en el nodo pasivo, pudiéndose calcular la posición de los nodos activos y la del nodo pasivo de forma conjunta en éste último. El procedimiento está basado en "Sistema y procedimiento de localización basados en medidas pasivas de diferencias temporales tomadas a partir de escuchas de tiempo de llegada de otros nodos", donde se transforman las medidas de tiempo con las que operan los nodos activos, en diferencias temporales en los nodos pasivos.
Barcelo, F.; Martin-Escalona, I. International journal of business data communications and networking Vol. 5, num. 4, p. 1-15 DOI: 10.4018/jbdcn.2009091701 Date of publication: 2009-09-10 Journal article
Hybridization is a hot topic in the location field. Since
there is no universal location technique that is capable of
positioning in indoor and outdoor environments, two or more
techniques must be coupled to produce a complete location
solution. Accordingly, information on the availability of each of
the techniques being coupled is of great relevance in the design
and implementation stages of the location system. In public
cellular networks, this coupling usually involves a terrestrial
triangulation technique (e.g. E-OTD, OTDOA) and a GNSSbased
technique (e.g. A-GPS). The purpose of this paper is
twofold. Firstly, it presents a software tool developed for studying
the availability of location systems in certain environments,
which is able to capture and present information on the
availability of satellites in the NAVSTAR constellation (i.e. GPS)
and the GSM/GPRS base stations being received in the user
terminal. Secondly, it studies the coverage of these techniques
using the tool described. Availability data for three routes in an
urban environment are gathered and analyzed. In two of them,
GPS did not cover 100% of the route, which demonstrated the
need to couple the technique with another terrestrial technique to
cope with the “dark” areas.