Easy Communicator: una experiencia de aprendizaje-servicio para el aprendizaje de todos

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.Postprint (published version

Improving fingerprint-based positioning by using IEEE 802.11mc FTM/RTT observables

Received signal strength (RSS) has been one of the most used observables for location purposes due to its availability at almost every wireless device. However, the volatile nature of RSS tends to yield to non-reliable location solutions. IEEE 802.11mc enabled the use of the round trip time (RTT) for positioning, which is expected to be a more consistent observable for location purposes. This approach has been gaining support from several companies such as Google, which introduced that feature in the Android O.S. As a result, RTT estimation is now available in several recent off-the-shelf devices, opening a wide range of new approaches for computing location. However, RTT has been traditionally addressed to multilateration solutions. Few works exist that assess the feasibility of the RTT as an accurate feature in positioning methods based on classification algorithms. An attempt is made in this paper to fill this gap by investigating the performance of several classification models in terms of accuracy and positioning errors. The performance is assessed using different AP layouts, distinct AP vendors, and different frequency bands. The accuracy and precision of the RTT-based position estimation is always better than the one obtained with RSS in all the studied scenarios, and especially when few APs are available. In addition, all the considered ML algorithms perform pretty well. As a result, it is not necessary to use more complex solutions (e.g., SVM) when simpler ones (e.g., nearest neighbor classifiers) achieve similar results both in terms of accuracy and location error.This research was partially supported by MCIN/AEI/10.13039/ 501100011033 and ERDF “A way of making Europe” under grant PGC2018-099945-BI00, and by the European GNSS Agency (GSA) under grant GSA/GRANT/04/2019/BANSHEEPeer ReviewedPostprint (published version

Passive round-trip-time positioning in dense ieee 802.11 networks

The search for a unique and globally available location solution has attracted researchers for a long time. However, a solution for indoor scenarios, where high accuracy is needed, and Global Positioning System (GPS) is not available, has not been found yet. Despite the number of proposals in the literature, some require too long a calibration time for constructing the fingerprinting map, some rely on the periodic broadcast of positioning information that may downgrade the data communication channel, while others require specific hardware components that are not expected to be carried on commercial off-the-shelf (COTS) wireless devices. The scalability of the location solution is another key parameter for next-generation internet of things (IoT) and 5G scenarios. A passive solution for indoor positioning of WiFi devices is first introduced here, which merges a time-difference of arrival (TDOA) algorithm with the novel fine time measurements (FTM) introduced in IEEE 802.11mc. A proof of concept of the WiFi passive TDOA algorithm is detailed in this paper, together with a thorough discussion on the requirements of the proposed algorithmThis work was funded by the Spanish Government and European Regional Development Fund (ERDF) through Comisión Interministerial de Ciencia y Tecnología (CICYT) under Project PGC2018-099945-B-I00.Peer ReviewedPostprint (published version

IEEE 802.11mc ranging performance in a real NLOS environment

Since IEEE 802.11 defined a couple of enhancements that allow accurate time measurements in COTS Wi-Fi devices, the possibility of achieving precise low-cost distance estimations in Wi-Fi has become a reality. However, many sources of error, such as bandwidth limitations of the Wi-Fi signal, limited clock rate in the device, multipath propagation due to the obstacles in the indoor environment, etc., may add noise to the time measurements and therefore distort the estimated ranging. This study aims at covering the gap existing in the literature by assessing the performance of the ranging estimation in real IEEE 802.11mc stations in a typical NLOS environment. The impact on the accuracy is also explored when the station is held in different positions with respect to the floor.The Article Processing Charges were funded by the Spanish Government and ERDF through CICYT project under grant PGC2018-099945-B-I00. This research was partially supported by PGC2018-099945-BI00 and by the European GNSS Agency under grant GSA/GRANT/04/2019/BANSHEE.Postprint (published version

Coverage of Hybrid Terrestrial-Satellite Location in Mobile Communications

This work studies the improvement in service coverage obtained by three different ways of hybridising (terrestrial and satellite) triangulation location methods for cellular networks. Though the authors assume that terrestrial cellular networks use Enhanced Observed Time Difference (E-OTD) in 2G or Observed Time Difference Of Arrival (OTDOA) in 3G, and that the satellite GNSS uses Assisted Global Positioning System (A-GPS), their analysis can easily be generalized to address any other triangulation method. A simple analytical model is presented, which is used for evaluating the service coverage of each approach. The numerical results show how hybridisation leads to a high improvement and an easy balance between traffic and geographical coverage.Peer Reviewe

DYMO self forwarding: a simple way for reducing the routing overhead in MANETs

Current routing protocols in Mobile Ad hoc Networks tend to use information on the position of the nodes in order to improve their features. In fact, without this information, protocols are hardly scalable since they tend to overflow the radio media with control packets, most of them being useless at the end. This paper presents the assessment of a modification of the DYMO protocol in order to include and use positioning information. The evaluation is carried out through simulations in realistic environments and connectivity condition. The possible error in the position is seldom considered in this kind of studies but here taken into account to catch the impact of realistic GPS devices or other sources of location techniques.Peer ReviewedPostprint (published version

Discrete event simulation of wireless cellular networks

Postprint (published version

A user space implementation of the AODVv2 routing protocol

Ad hoc On Demand Distance Vector Routing (AODV) protocol is a reactive MANET routing protocol frequently used as reference for either developing new ad hoc routing protocols or performance assessment purposes. Although it is present in several general-purpose network simulators (e.g. ns2, omnetpp, etc.), there are few implementations that can be used under real conditions for on-field research or performance evaluation. This paper presents a user space implementation of the last version of this protocol, the AODVv2, that can be deployed in any device able to run the Linux O.S. The goal is developing a fresh, open source and easy-to-maintain implementation of the AODVv2 protocol that can be used by the research community for testing purposes. The paper provides a description of the main design and encoding decisions taken in order to implement the protocol, and explains the main testing actions carried out to prove its correctness.Postprint (published version

Implementation and analysis of the AODVv2 routing protocol in ARM devices

​© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.AODVv2 is a well-known routing protocol used in MANETs (Mobile Ad hoc Networks). Formerly known as DYMO (DYnamic MANET On-demand), it is frequently used as a reference for routing protocols assessment. However, implementations of these protocols are scarce and the few ones available are currently outdated, no longer maintained and hardly upgradeable. This paper provides the details of a new AODVv2 implementation to be used in embedded devices working with the ARM microprocessor architecture. A user-space approach has been followed so both the upgradability and platformindependence are favored. A WiFi ad hoc network, modeling representative real scenarios, has been deployed to verify the correctness of the developed AODVv2 code and assess the performance of the protocol under realistic traffic conditions. A virtual machine has been used to perform a cross-compilation of a the code that implements the DYMO protocol in the Intel x86 computer architecture. Once compiled for being used in ARMbased devices, the code has been tested in Raspberry Pi devices to verify the proper behaviour. Simple scenarios and scenarios with high density of nodes have been deployed and data have been collected and analysed.Postprint (author's final draft

Impacto del modelo de error en distancia en la simulación de sistemas de localización

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.Postprint (published version